KR102508186B1 - Optical sheet and display apparatus comprising same - Google Patents

Abstract

In the optical sheet according to an embodiment, by adding one or more types of organic dyes that absorb light in a specific wavelength band to the prism pattern layer, the color gamut is improved with a simpler manufacturing process than the prior art while minimizing luminance degradation due to light absorption. can In addition, by controlling the composition of the prism pattern layer, it is possible to secure optical and mechanical properties while preventing deterioration of organic dyes due to UV curing.

Description

Optical sheet and display device including the same {OPTICAL SHEET AND DISPLAY APPARATUS COMPRISING SAME}

Embodiments relate to an optical sheet having improved color gamut and luminance, and a display device including the same.

In the past, 40-inch (") TVs were the mainstream, but now many consumers are purchasing 50" and even 60" TVs. When this size competition is over, the resolution competition has begun. Just a year ago, FHD (Full High Definition) level belonged to the high-end model, but now UHD (Ultra High Definition) has rapidly spread in the market.

Recently, the field of display devices is evolving from large-area, high-resolution competition to color competition. For this reason, competition for the manufacture of display devices having excellent colors has recently emerged.

A liquid crystal display (LCD) displays an image using the optical properties of liquid crystal. Since a liquid crystal display panel displaying an image is a non-emission type device that does not emit light itself, it is disposed on the rear surface of the liquid crystal display panel together with the liquid crystal display panel to display the liquid crystal. It has a structure including a back-light unit supplying light to the display panel. While the liquid crystal display has advantages of being thinner, lighter in weight, less power consumption, and lower driving voltage than other display devices, it is somewhat inferior to other display devices in terms of color.

In addition, in the case of cathode ray tube display (CRT), which is now disappearing, the color gamut reaches 80% based on NTSC (National Television Standards Committee), and plasma display device (PDP) also has products at the NTSC 90% level. released until recently. In addition, in the case of an organic light emitting display (OLED), which is in the spotlight as a next-generation display device, it is possible to achieve up to 100% of NTSC. However, LCD TVs are at the level of NTSC 72%.

Accordingly, in order to activate the display device market, there is a demand for a technology that improves the conventional color gamut and does not lower luminance by improving the disadvantages of the liquid crystal display device.

Korean Patent Publication No. 2012-0072194

An optical sheet applied to a backlight unit of a display device performs functions such as condensing, diffusing, reflecting, and the like, and when two or more functions are combined, individual optical functions can be complemented and maximized. In addition, the color gamut may be improved by combining the optical sheet with a filter layer that blocks unnecessary wavelengths other than RGB. However, conventionally, in the process of introducing such an additional filter layer, there have been problems in that the manufacturing process is complicated, the total thickness is increased, or the luminance is lowered.

Accordingly, as a result of research by the present inventors, by adding one or more types of organic dyes that selectively absorb light in a specific wavelength band to the prism pattern layer, the color gamut is improved with a simpler manufacturing process than before, while reducing the luminance due to light absorption. could be minimized. In addition, the present inventors were able to secure optical and mechanical properties while preventing deterioration of organic dyes due to UV curing by adjusting the composition of the prism pattern layer.

Accordingly, an object of embodiments is to provide an optical sheet having excellent luminance and processability while improving a color gamut, a method for manufacturing the same, and a display device including the same.

According to one embodiment, a base layer; and a prism sheet including a prism pattern layer disposed on the substrate layer, wherein the prism pattern layer includes a light absorber that selectively absorbs light in a specific wavelength band, and wherein the light absorber includes one or more organic dyes. Including, an optical sheet is provided.

According to another embodiment, a step of coating a composition for forming a prism pattern on an upper surface of a base layer, transferring the pattern, and curing the pattern by UV to form a prism pattern layer, wherein the composition for forming a prism pattern includes a binder resin and a light absorber , a UV blocker, an antioxidant, and a light stabilizer, and the light absorber includes one or more organic dyes that selectively absorb light in a specific wavelength band.

According to another embodiment, a light source; a display panel receiving light from the light source and displaying an image; and an optical sheet disposed in a light path from the light source to the display panel, the optical sheet comprising: a substrate layer; and a prism sheet including a prism pattern layer disposed on the substrate layer, wherein the prism pattern layer includes a light absorber that selectively absorbs light in a specific wavelength band, and wherein the light absorber includes one or more organic dyes. Including, a display device is provided.

In the optical sheet according to the embodiment, by adding one or more types of organic dyes that selectively absorb light in a specific wavelength band to the prism pattern layer, the color gamut is improved with a simpler manufacturing process than the prior art while reducing luminance due to light absorption. It is possible to provide an optical sheet in which is minimized.

In addition, according to a preferred embodiment, it is possible to secure optical and mechanical properties while preventing deterioration of organic dyes due to UV curing by adjusting the composition of the prism pattern layer.

Accordingly, the optical sheet according to the embodiment may be applied to a backlight unit of a display device such as an LCD to improve performance.

1 illustrates a display device and a traveling direction of light according to an exemplary embodiment.
2 is a method of calculating a color gamut from CIE 1976 chromaticity coordinates u'v'.
3 is an exploded perspective view of a display device according to an exemplary embodiment.
4 is a cross-sectional view of a backlight unit according to an exemplary embodiment.
5A to 5E show cross-sectional views of the optical sheets of Examples 1 to 5.
6 is a cross-sectional view of an optical sheet of Comparative Example 1;
7 shows a process of forming a first prism pattern layer and laminating with a second substrate layer.
8 illustrates a method of manufacturing an optical sheet according to an embodiment.
9A to 9C show a method of manufacturing an optical sheet according to another embodiment.
10A to 10C are cross-sectional views of a prism sheet included in an optical sheet according to an embodiment.
11A and 11B are cross-sectional views of a first functional coating layer and a second functional coating layer included in an optical sheet according to an embodiment.
12 is a cross-sectional view of a reflective polarizing film included in an optical sheet according to an embodiment.
13 shows transmission spectra of the optical sheets of Example 5 and Comparative Example 2.
14 shows a net absorbance spectrum of the optical sheet of Example 5.

In the following description of the implementation, one component is described as being formed on or under another component, one component directly on or under another component, or intervening with another component. It includes everything that is formed indirectly by doing so.

In addition, the criteria for the top/bottom of each component will be described based on the drawings. The size of each component in the drawing may be exaggerated for description, and may differ from the actually applied size.

"Including" a component in this specification means that other components may be further included, not excluding other components, unless otherwise stated.

In addition, it should be understood that all numerical ranges representing physical property values, dimensions, etc. of components described in this specification are modified by the term "about" in all cases unless otherwise specified.

In this specification, singular expressions should be interpreted as meaning including the singular or plural interpreted in context unless otherwise specified.

display device

A display device according to an exemplary embodiment includes a light source, a display panel, and an optical sheet. The display panel displays an image by receiving light from the light source. The optical sheet is disposed in a light path from the light source to the display panel. Accordingly, the display device includes a light source; an optical sheet into which the light from the light source is incident; and a display panel into which light from the optical sheet is incident. Light from the light source is improved in characteristics while passing through the optical sheet, and the display panel displays an image using the light having the improved characteristics. As a result, referring to FIG. 1 , an image displayed through the light L emitted from the screen of the display device 1 can be perceived with excellent color.

Specifically, referring to FIG. 3 , the display device 1 includes a backlight unit 10; and a display panel 20 disposed on the backlight unit 10 . The backlight unit 10 includes an optical sheet 11; and a diffusion plate or a light guide plate 700, and may further include a light source 900.

The light source may be disposed on a side of the light guide plate or below the diffusion plate. The diffusion plate or light guide plate 700 is disposed below the optical sheet 11 and serves to transmit light generated from the light source 900 to the display panel 20 . The light guide plate 700 is used in the case of an edge type light source, and at this time, the reflector 800 is disposed under the light guide plate 700 to reduce light loss. The diffusion plate is used in the case of a direct light source, and light efficiency can be improved by using an LED planar light source.

Referring to FIG. 3 , light generated from the light source 900 is incident on the side surface of the light guide plate 700 , is reflected by the reflector plate 800 , and then enters the lower portion of the optical sheet 11 . The incident light passes vertically through the optical sheet 11 and exits upward. The light emitted from the top of the optical sheet 11 is incident on the display panel 20 , and as a result, an image may be displayed on the screen of the display panel.

The light source may be a white light source. For example, the light source may have a continuous emission spectrum. Specifically, the light source may be a white LED. More specifically, the light source may include a blue GaN (Gallium Nitride) light emitting chip and a yellow YAG (Yttrium Aluminum Garnet, Y ₃ Al ₅ O ₁₂ ) phosphor. In addition, the light source may include a blue GaN (Gallium Nitride) light emitting chip and r, g phosphor, or may include an r phosphor and a red KSF (K ₂ SiF ₆ :Mn) phosphor.

The display panel 20 may include a liquid crystal cell and one or more polarizing plates, and as a specific example, may have a structure in which a first polarizing plate, a liquid crystal cell, and a second polarizing plate are stacked, and an adhesive layer is provided between the polarizing plate and the liquid crystal cell. can be formed.

The display device 1 may further include a cover window 30 disposed on the display panel 20 , and the cover window may be made of a transparent polyimide film or ultra-thin glass (UTG). Also, the display device 1 may further include an electrode and a substrate connected to the display panel 20 . In addition, the liquid crystal display device 1 may include frames 51 and 52 that surround and protect these components.

Components of an optical sheet

An optical sheet according to an embodiment base layer; and a prism sheet including a prism pattern layer disposed on the substrate layer, wherein the prism pattern layer includes a light absorber that selectively absorbs light in a specific wavelength band, and wherein the light absorber includes one or more organic dyes. includes

As such, the optical sheet includes at least one prism sheet. In addition, the optical sheet includes a light absorber in a prism pattern layer of at least one prism sheet. The prism sheet may be disposed in a light path from the light source to the display panel.

The optical sheet may further include a base film, a reflective polarizing film, a buffer film, a functional coating layer, and an adhesive layer.

Hereinafter, each component will be described in detail.

prism sheet

The prism sheet serves to improve luminance by condensing light due to a difference in refractive index at the interface of the prism pattern.

Referring to FIG. 10A , the prism sheet 200 includes a substrate layer 201 and a prism pattern layer 202 formed on the substrate layer. The pattern shape of the pattern layer is not particularly limited, and for example, light may be refracted at the interface by having a long triangular prism shape.

The prism sheet may include a plurality of prism patterns having different heights. Referring to FIG. 10B , the prism pattern may include a first pattern 202a and a second pattern 202b having different heights. A ratio (Tb/Ta) of the height Tb of the second pattern to the height Ta of the first pattern may be 0.5 to 0.99 or 0.8 to 0.95.

Referring to FIG. 10C , the apex of the top of the first pattern 202a penetrates into the adhesive layer 600 and is bonded. At this time, a meniscus 601 is generated, degrading the light condensing performance. Therefore, by making the height of the second pattern 202b different from that of the first pattern to preserve the shape of the upper end, degradation of light condensing performance can be suppressed.

The base layer and the pattern layer may be made of the same material, and for example, the base layer and the pattern layer may be integrally manufactured. Alternatively, the base layer and the pattern layer may be made of different materials, and for example, a pattern layer may be formed thereon after manufacturing the base layer.

Specifically, as the material of the base layer, polyester resin, polyethersulfone resin, acrylic resin, polyetherimide resin, polyphenylene sulfide resin, polyarylate resin, polyimide resin, polycarbonate resin, cellulose triacetate resin , Cellulose acetate propionate resin, etc. are mentioned. More specifically, the material of the base layer may be a polyester resin, particularly a polyethylene terephthalate resin or a polyethylene naphthalate resin.

In addition, the material of the pattern layer may be a UV curable resin, and may be, for example, an acrylate-based resin such as epoxy acrylate or urethane acrylate, a methacrylate-based resin, or an epoxy resin.

Referring to FIG. 10A, the thickness T1 of the base layer of the prism sheet may be 30 μm to 300 μm, specifically 50 μm to 200 μm, and the thickness T2 of the pattern layer may be 10 μm to 100 μm. It may be ㎛, specifically, it may be 20 ㎛ to 60 ㎛.

Composition and characteristics of the prism pattern layer

8(c) is a cross-sectional view of a prism pattern layer included in an optical sheet according to an embodiment. Referring to (c) of FIG. 8, the prism pattern layer 202 includes a light absorber and a binder resin.

The light absorber selectively absorbs light in a specific wavelength band. The light absorber may have a main absorption wavelength within a visible light wavelength band. However, the main absorption wavelength of the light absorber may belong to a band excluding pure RGB wavelength within the visible light wavelength band. For example, the main absorption wavelength of the light absorber may fall within 470 nm to 520 nm or 550 nm to 620 nm. Specifically, the main absorption wavelength of the light absorber may fall within 480 nm to 510 nm, 560 nm to 610 nm, or 580 nm to 620 nm.

The light absorber includes one or more organic dyes. The organic dye selectively absorbs light in a specific wavelength band. Specifically, the organic dye may have a chromophore that selectively absorbs light in a specific wavelength band. In particular, the organic dye has an unsaturated bond (eg, a conjugated bond) such as a double bond, and thus can selectively absorb light in a specific wavelength band.

As a specific example, the light absorber may include at least one organic dye selected from the group consisting of pyrrolmethines, rhodamines, borondipyrromethenes, tetraazaporphyrins, squarines, and cyanines.

Organic dyes having an unsaturated bond as described above are easily added to a conventional coating layer or a thermosetting resin layer because a radical reaction occurs due to UV light and the activity is easily reduced. On the other hand, in order to form a prism pattern and maintain the pattern shape even when adhered to an adjacent layer, a certain level of strength through UV curing is required, so it is conventionally difficult to add a light absorber to the prism pattern layer. However, according to the present invention, it is possible to form a prism pattern layer having optical/mechanical properties while preventing deterioration in the activity of the light absorber due to UV curing by adjusting the composition and content of components added to the prism pattern layer. Accordingly, it is not necessary to manufacture a separate coating layer for introducing the light absorption layer, and an additional aging step is not required accordingly, thereby simplifying the process and improving productivity.

For example, the content of the light absorber is 0.01 wt% to 10 wt%, for example, 0.01 wt% to 7 wt%, 0.01 wt% to 5 wt%, or 0.01 wt% based on the total weight of the prism pattern layer. to 3% by weight. Specifically, the light absorber may be included in an amount of 0.01 wt % to 1 wt % based on the total weight of the prism pattern layer. In addition, the content of the light absorber is 0.01 parts by weight or more, 0.015 parts by weight or more, 0.02 parts by weight or more, 0.025 parts by weight or more, 0.03 parts by weight or more, 0.035 parts by weight based on 100 parts by weight of the binder resin included in the prism pattern layer. or more, or 0.04 parts by weight or more, and may be 1 part by weight or less, 0.5 parts by weight or less, 0.1 parts by weight or less, 0.05 parts by weight or less, 0.045 parts by weight or less, 0.04 parts by weight or less, 0.035 parts by weight or less, 0.03 parts by weight or less. , or 0.025 parts by weight or less.

The binder resin may be composed of components suitable for coating and pattern formation, and may be, for example, a UV curable resin as exemplified above. Specifically, the binder resin is from the group consisting of epoxy acrylate, urethane acrylate, polyester acrylate, acrylic acrylate, silicone acrylate, polybutadiene acrylate, melamine acrylate, epoxy-modified acrylate and urethane-modified acrylate It may be one or more selected species.

The prism pattern layer may further include at least one of a UV blocker, an antioxidant, and a light stabilizer.

For example, the UV blocker may be at least one selected from the group consisting of a hydroxybenzotriazole-based UV blocker, a tris-resorcinol-triazine chromophore-based UV blocker, and a hydroxyphenyl-benzotriazole chromophore-based UV blocker.

In addition, the antioxidant may be at least one selected from the group consisting of amine-based, phenol-based, sulfur-based, phosphine-based, phosphite-based, and thioester-based antioxidants.

In addition, the light stabilizer may be at least one selected from the group consisting of a hindered amine light stabilizer (HALS)-based light stabilizer, a benzotriazole-based light stabilizer, and a benzophenol-based light stabilizer.

The weight of the UV blocker included in the prism pattern layer may be 10 times, 20 times, or 30 times greater than the weight of the light absorber, and may be 100 times less, 70 times less, or 50 times less than the weight of the light absorber. Specifically, the weight of the UV blocker may be 10 to 100 times the weight of the light absorber.

The weight of the antioxidant included in the prism pattern layer may be 0.5 times or more, 1 time or more, 2 times or more, 10 times or more, or 30 times or more, and 100 times or less, 10 times or less, It may be 7 times or less, or 5 times or less. Specifically, the weight of the antioxidant may be 1 to 10 times the weight of the light absorber.

The weight of the light stabilizer included in the prism pattern layer may be 0.2 times or more, 0.5 times or more, 1 time or more, 5 times or more, or 10 times or more, and also 50 times or less, 30 times or less, based on the weight of the light absorber. , 20 times or less, 10 times or less, or 5 times or less. Specifically, the weight of the light stabilizer may be 10 to 50 times the weight of the light absorber.

In addition, the prism pattern layer may further include a photoinitiator, specifically at least one selected from the group consisting of (2,4,6-trimethylbenzoyl)diphenylphosphine, hydroxydimethylacetophenone, and methylbenzoylformate. can be all day The weight of the photoinitiator included in the prism pattern layer may be 0.1 part by weight to 1 part by weight based on 100 parts by weight of the binder resin.

Characteristics of the prism pattern layer

The prism pattern layer selectively absorbs light in a specific wavelength band due to a light absorber included therein.

The prism pattern layer may have a main absorption wavelength within a visible light wavelength band. However, the main absorption wavelength of the prism pattern layer may belong to a band excluding pure RGB wavelength within the visible light wavelength band. Accordingly, the prism pattern layer may improve a color gamut by blocking unnecessary wavelengths other than pure RGB wavelengths emitted from a light source. For example, the main absorption wavelength of the prism pattern layer may fall within 470 nm to 520 nm or 550 nm to 620 nm. Specifically, the main absorption wavelength of the prism pattern layer may fall within 480 nm to 510 nm, 560 nm to 610 nm, or 580 nm to 620 nm.

In addition, the prism pattern layer may additionally have a sub-absorption wavelength having a lower absorption rate than the main absorption wavelength, and the sub-absorption wavelength may also belong to a visible light wavelength band. For example, the sub-absorption wavelength may also belong to a band excluding pure RGB wavelengths within the visible light wavelength band. Alternatively, the sub absorption wavelength may belong to a pure RGB wavelength band unlike the main absorption wavelength, and for example, the sub absorption wavelength may belong to 510 nm to 560 nm or 530 nm to 570 nm.

As a specific example, the prism pattern layer may have a main absorption wavelength at 580 nm to 620 nm and a sub absorption wavelength at 530 nm to 570 nm. When within the above range, the color gamut can be more effectively improved.

The prism pattern layer may have UV transmittance within a certain range. For example, the UV-A light transmittance of the prism pattern layer may be 10% or more, 20% or more, or 30% or more, and may be 80% or less, 70% or less, 60% or less, or 50% or less. . As a specific example, the prism pattern layer may have transmittance of 10% to 70% with respect to UV-A light.

In addition, the prism pattern layer may have a visible light transmittance of at least a certain level. For example, the prism pattern layer may have a light transmittance of 30% or more, 45% or more, 50% or more, or 70% or more, specifically 30% to 90%, or 50% to 90% for a wavelength of 590 nm. can

Types and compositions of functional coating layers

The optical sheet may further include one or more functional coating layers.

The functional coating layer may be, for example, a light diffusion layer, a split prevention layer, a hard coating layer, or a heat-resistant coating layer.

Referring to FIG. 4 , a first functional coating layer 310 may be formed on the lower portion of the optical sheet 11 and a second functional coating layer 320 may be formed on the upper portion of the optical sheet 11 . The first functional coating layer and the second functional coating layer may be the same or different types of functional coating layers.

As an example, the optical sheet may further include a functional coating layer disposed under the prism sheet, and the functional coating layer may be selected from the group consisting of a light diffusion layer, an anti-split layer, and a heat resistant coating layer.

The light diffusion layer may conceal a prism pattern or the like by diffusing light. The optical sheet may include one or more light diffusion layers. Specifically, a first light diffusion layer and a second light diffusion layer may be formed on a lower portion of the optical sheet. The first light diffusion layer may have a haze of 3% to 30%, and more specifically, a haze of 7% to 17%. The second light diffusion layer may have a haze of 60% to 99%, more specifically, a haze of 60% to 98%. When within the above preferred haze range, there is an advantage of high luminance while having sufficient hiding power.

The anti-grinding layer may prevent interfacial grinding from occurring due to a dot print pattern on the lower part of the light guide plate or a concave-convex pattern by laser processing or frictional wear caused by vibration on the upper part of the optical sheet after the optical sheet and the light guide plate are laminated. can The anti-galling layer may include beads dispersed in a polymer resin. The beads serve to prevent cracking with the light guide plate by forming roughness on the surface.

The heat-resistant coating layer serves to increase the heat resistance of the optical sheet by including a heat-resistant polymer resin. The heat-resistant polymer resin may include, for example, a phenyl silicone-based resin.

The hard coating layer may be provided on the outermost surface of the optical sheet to improve surface hardness. The surface hardness of the hard coating layer may be 2H or more, specifically 3H or more, or 4H or more.

Referring to FIGS. 11A and 11B , the first functional coating layer 310 may include a bead 311 and a binder resin 312 . In addition, the second functional coating layer 320 may also include beads 321 and a binder resin 322 .

The bead may be an organic bead, and the specific material may be at least one selected from the group consisting of an acrylate-based resin, a polystyrene resin, a nylon resin, and a silicone resin, and more specifically, may be a hard acrylate-based resin. The shape of the bead is not particularly limited, but may be spherical, for example. In addition, the average particle diameter of the beads is advantageous in terms of hiding power, brightness and prevention of splitting with adjacent layers to have an average particle diameter of 5 μm to 20 μm, and more specifically, 0.5 μm to 10 μm, or 0.8 to 6 μm. there is.

The binder resin may be at least one of a thermoplastic resin, a thermosetting resin, and a UV curable resin.

Specific examples of the thermoplastic resin and the thermosetting resin include acrylic resins, urethane resins, epoxy resins, urethane acrylate resins, epoxy acrylate resins, cellulose resins, acetal resins, melamine resins, phenolic resins, and silicone resins. resins, polyester resins, polycarbonate resins, polyethylene resins, polystyrene resins, polyamide resins, polyimide resins, mixtures thereof, and the like.

As the UV curable resin, a photopolymerizable prepolymer that is crosslinked and cured by UV light irradiation may be used, and the photopolymerizable prepolymer may include a cationic polymerization type and a radical polymerization type photopolymerizable prepolymer. Examples of the cationically polymerized photopolymerizable prepolymer include epoxy-based resins and vinyl ester-based resins, and examples of the epoxy-based resins include bisphenol-based epoxy resins, novolac-type epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, and mixtures thereof; and the like.

The functional coating layer may further include a heat stabilizer, a UV photoinitiator, a coupling agent, an antioxidant, a surfactant, a silicone additive, a UV absorber, and the like, if necessary.

The UV curing agent is not particularly limited as long as it can be used to cure a UV curing type resin in general. α-hydroxyketone, phenylglyoxylate, benzyldimethyl-ketal, α-aminoketone, triarylsulfonium hexafluoroantimonate ), cationic photoinitiators such as triarylsulfonium hexafluorophosphate and diaryliodonium salt.

The coupling agent may include a silane coupling agent, a titanate-based coupling agent, an aluminate-based coupling agent, a silicone compound, and the like, and these coupling agents may be used alone or in combination.

The antioxidant may include a phenol-based, sulfur-based or phosphorus-based antioxidant, and the antioxidant may be used to improve heat resistance stability of a cured product by preventing deterioration due to oxidation of the thermosetting resin composition.

The surfactant is a compound having a hydrocarbon hydrophobic group of a certain length in the molecule and a hydrophilic group such as -COONa and -OSO ₃ Na in the molecule, anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, sulfonic acid salts, sulfates, sulfate ester salts, ethoxylates, and the like, and these surfactants may be used alone or in combination.

base film

The optical sheet according to the embodiment may further include a base film on which the functional coating layer is coated. That is, the functional coating layer may be coated on the base film.

The material of the base film may be, for example, a polyester resin, and specifically, a polyethylene terephthalate resin.

reflective polarizing film

The optical sheet according to the embodiment may include a reflective polarizing film to improve luminance. For example, the reflective polarizing film may be disposed on the prism sheet.

The reflective polarizing film refers to a film that produces a desired optical effect by a plurality of thin films stacked therein, and may include, for example, a dual luminance enhancement film (DBEF).

Specifically, the reflective polarizing film may include two or more types of thin films having different optical properties in a stacked form.

As shown in FIG. 12 , the reflective polarizing film may have a stack M of a plurality of thin films between two skin layers S. At this time, the optical properties different from each other of the thin films may be refractive index or phase difference.

As a specific example, the reflective polarizing film may be one in which first resin layers and second resin layers having different optical properties are alternately laminated in 100 to 2000 layers, specifically, 800 to 1000 layers.

buffer film

The optical sheet may further include a buffer film to protect the skin layer of the reflective polarizing film. Specifically, as shown in FIG. 4 , when the prism sheet 220 is disposed under the reflective polarizing film 400, the pattern of the prism sheet 210 may affect the thin film of the reflective polarizing film to deteriorate performance. there is. Accordingly, by disposing the buffer film 500 between the reflective polarizing film 400 and the prism sheet 220, such degradation in performance can be prevented.

The material of the buffer film may be, for example, a polyester resin, and specifically, a polyethylene terephthalate resin.

adhesive layer

The optical sheet may include an adhesive layer between components thereof (prism sheet, base film, reflective polarizing film, buffer film, etc.).

Commonly used thermosetting resins and UV curable resins may be used as materials for the adhesive layer, and for example, acrylic, urethane, epoxy, vinyl, polyester, polyamide, or mixtures thereof may be used. . Examples of the acrylic resin include methyl methacryl, methacryl, ethyl acryl, butyl acryl, aryl acryl, hexyl acryl, isopropyl methacryl, benzyl acryl, vinyl acryl, or a single polymer of 2-methoxyethyl acryl resin or copolymers thereof. synthetic or blended resins.

Preferred examples of the material of the adhesive layer are (meth) acrylate-based resins, unsaturated polyester resins, polyester (meth) acrylate resins, silicone urethane (meth) acrylate resins, silicone polyester (meth) acrylate resins, fluorine urethane (meth)acrylate resins, and mixtures thereof.

Component-specific thickness of the optical sheet

Thicknesses of the components of the optical sheet described above may be adjusted within a certain range.

The thickness of the prism sheet may be 50 μm or more or 80 μm or more, and may be 300 μm or less or 200 μm or less.

The functional coating layer may have a thickness of 3 μm or more or 5 μm or more, and may be 30 μm or less or 20 μm or less.

The thickness of the base film may be 50 μm or more or 70 μm or more, and may be 200 μm or less or 150 μm or less.

The reflective polarizing film may have a thickness of 50 μm or more or 70 μm or more, and may be 200 μm or less or 150 μm or less.

The thickness of the buffer film may be 50 μm or more or 70 μm or more, and may be 200 μm or less or 150 μm or less.

As a specific example, the reflective polarizing film may have a thickness of 50 μm to 200 μm, the buffer film may have a thickness of 50 μm to 200 μm, and the prism sheet may have a thickness of 50 μm to 350 μm. The functional coating layer may have a thickness of 3 μm to 30 μm.

Laminated structure of optical sheet

Components of the optical sheet described above (prism sheet, functional coating layer, reflective polarizing film, buffer film, etc.) may be disposed in the optical path.

Also, components of the optical sheet may be coupled to each other. The bonding may be direct bonding or indirect bonding through an adhesive layer or the like. Accordingly, the optical sheet may include a laminate in which the components are directly or indirectly coupled.

As an example, the optical sheet may include a prism sheet; and a functional coating layer disposed under the prism sheet, wherein the prism sheet and the functional coating layer may be directly or indirectly coupled to each other.

In addition, the optical sheet may include a reflective polarizing film disposed on the prism sheet; and a functional coating layer disposed on the reflective polarizing film, wherein the reflective polarizing film may include two or more types of thin films having different optical properties in a stacked form. The optical sheet may further include a buffer film between the reflective polarizing film and the prism sheet, and the reflective polarizing film, the buffer film, the prism sheet, and the functional coating layer may be directly or indirectly coupled to each other.

The optical sheet may include two or more prism sheets, and specifically, the prism sheet may include a first prism sheet and a second prism sheet. Patterns of the first prism sheet and the second prism sheet may be identical to or different from each other. For example, the prism sheet may include a first prism sheet including a first prism pattern extending in a first direction in a plane; and a second prism sheet including a second prism pattern extending in a second direction within a plane crossing the first direction. Specifically, grain directions of the patterns of the first prism sheet and the second prism sheet may be orthogonal to each other. More specifically, the first prism sheet may be a horizontal prism sheet, and the second prism sheet may be a vertical prism sheet, or vice versa. In addition, the pattern layer of the first prism sheet and the pattern layer of the second prism sheet may both face the same direction or face different directions.

Optical performance may be improved by adjusting a position of the prism sheet in the optical sheet (in particular, a relative position between the prism pattern layer and other components).

For example, the prism sheet may include a first prism sheet; and a second prism sheet disposed on the first prism sheet, wherein the first prism sheet includes a first substrate layer and a first prism pattern layer disposed on the first substrate layer, 2 The prism sheet may include a second substrate layer and a second prism pattern layer disposed on the second substrate layer. Accordingly, the first prism sheet may be disposed rearward than the second prism sheet based on a front side from which incident light is emitted from the optical sheet. In this case, the first prism pattern layer may extend in a first in-plane direction, and the second prism pattern layer may extend in a second in-plane direction crossing the first direction. In addition, at least one of the first prism pattern layer and the second prism pattern layer may include a light absorber that selectively absorbs light in a specific wavelength band, and the light absorber may include one or more organic dyes.

In addition, the optical sheet further includes a first functional coating layer disposed under the first prism sheet and a second functional coating layer disposed on the second prism sheet, wherein the first functional coating layer and the second functional coating layer are Each is selected from the group consisting of a light diffusion layer, an anti-split layer, a heat-resistant coating layer, and a hard coating layer, and the first functional coating layer, the first prism sheet, the second prism sheet, and the second functional coating layer are directly or indirectly bonded to each other. It can be.

In addition, the optical sheet further includes a reflective polarizing film disposed between the second prism sheet and the second functional coating layer, and a buffer film disposed between the second prism sheet and the reflective polarizing film, wherein the reflective polarizing film may have a structure in which a first resin layer and a second resin layer having different optical properties are alternately stacked in 100 to 2000 layers.

Referring to FIG. 4 , light is incident from the lower portion of the optical sheet 11 and emitted upward, and the first prism sheet 210 including the light absorber may be disposed below the second prism sheet 220 . there is. According to this arrangement, light incident from the light source passes through the first prism pattern layer including the light absorber before passing through the second prism sheet, and thus color deviation according to viewing angles can be minimized.

Specifically, the prism sheet includes a first prism sheet including a light absorber and a first prism pattern extending in a first direction; and a second prism sheet including a second prism pattern extending in a second direction crossing the first direction, wherein the first prism sheet is disposed under the second prism sheet, and the first prism sheet is disposed below the second prism sheet. A first functional coating layer may be disposed under the sheet.

As a specific example, as shown in FIG. 5A , the optical sheet 11 may include a first prism sheet 210 including a light absorber.

As another specific example, as shown in FIG. 5B , the optical sheet 11 may include a first prism sheet 210 including a light absorber and a first functional coating layer 310 stacked in this order.

As another specific example, as shown in FIG. 5C , the optical sheet 11 includes a second functional coating layer 320, a reflective polarizing film 400, a buffer film 500, a second prism sheet 220, and a light absorber. The first prism sheet 210 including the first prism sheet 210 and the first functional coating layer 310 may be sequentially stacked, and adhesive layers 610 , 620 , and 630 may be formed between them.

As another specific example, as shown in FIG. 5D , the optical sheet 11 includes a first prism sheet including a second functional coating layer 320, a base film 350, a second prism sheet 220, and a light absorber. 210, and the first functional coating layer 310 may be laminated in this order, and adhesive layers 610 and 620 may be formed between them.

As another specific example, as shown in FIG. 5E, the optical sheet 11 includes a second prism sheet 220, a first prism sheet 210 including a light absorber, and a first functional coating layer 310 in that order. It may be laminated, and an adhesive layer 610 may be formed between the second prism sheet 220 and the first prism sheet 210 .

As another specific example, in the stacked structure of FIGS. 5A to 5E, the second prism pattern layer 222 instead of the first prism pattern layer 212 includes a light absorber, or the first prism pattern layer 212 and All of the second prism pattern layer 222 may include a light absorber.

color gamut

The color gamut of the display device including the optical sheet according to the exemplary embodiment may be improved compared to the conventional one.

A color gamut means a color gamut that can be reproduced by each medium in the entire light gamut. In general, color gamut evaluation of any medium obtains a triangle composed of RGB three points from CIE (Commission Internationale de L'eclairage) chromaticity coordinates, and obtains a triangle composed of RGB three points, This is done by comparing

Chromaticity means a property of color other than brightness, and the CIE 1976 chromaticity coordinate u'v' is a method that can be expressed closest to the color perceived by humans.

2 illustrates a method of calculating a color gamut from CIE 1976 chromaticity coordinates u'v'. As shown in FIG. 2, the first color gamut (CG1) as a reference within the entire color gamut (CG) of chromaticity coordinates is drawn, and the coordinates of red (R), green (G), and blue (B) measured from the sample. After constructing the second color region CG2, which is a triangle having as a vertex, the area of the overlapping color region CG0 between them is obtained. Then, the color gamut of the sample can be measured by calculating the ratio between the areas of these regions. For example, within the chromaticity coordinates (CIE 1931 chromaticity coordinates xy or CIE 1976 chromaticity coordinates u'v'), a triangle of the reference DCI color gamut (first color gamut) is drawn, and the color gamut measured from the sample (second color gamut) is drawn. The DCI area ratio may be calculated by drawing a triangle of the color gamut and calculating the percentage (%) of the area of the second color gamut to the area of the first color gamut. In addition, after obtaining an overlapping color gamut of the two color gamuts, a DCI overlapping ratio may be obtained by calculating a percentage (%) of an area of the overlapping color gamut with respect to an area of the first color gamut.

For example, a display device including the optical sheet may have a DCI area ratio of 80% or more in CIE 1931 chromaticity coordinates xy, and specifically, 85% or more, 90% or more, or 95% or more.

In addition, the display device including the optical sheet may have a DCI overlap ratio of 80% or more, specifically, 85% or more, 90% or more, or 95% or more in CIE 1976 chromaticity coordinates u'v'.

As an example, a display device including the optical sheet has a DCI overlap ratio of 90% or more in CIE 1976 chromaticity coordinates u'v', and has a white light of 250 cd/m ² or more, 260 cd/m ² or more, or 270 cd/m 2 or more. It may represent a luminance of cd/m ² or more.

In addition, the display device including the optical sheet has little change in chromaticity coordinate values according to a viewing angle, so that color deviation according to a viewing angle can be effectively reduced.

Specifically, the display device including the optical sheet may have a value of Δu'v'(60D) of 0.015 or less, more specifically 0.012 or less, 0.01 or less, or 0.007 or less according to the equation below:

Δu'v'(60D) = [ (u'0 - u'60) ² + (v'0 - v'60) ² ] ^1/2

In the above equation, u'0 and u'60 are CIE 1976 chromaticity coordinates u' values measured from the front of the display device and at an angle of 60°, respectively, and v'0 and v'60 are measured from the front of the display device and at an angle of 60°, respectively. A CIE 1976 chromaticity coordinate v' value.

In addition, in the display device including the optical sheet, the value of Δu'v'(-60D) obtained by measuring the display device from the front side and at an angle of -60 ° in the same manner as above is also 0.015 or less, 0.012 or less, 0.01 or less, or 0.007 or less.

Wavelength absorption selectivity

The optical sheet has excellent absorption selectivity for light in a specific wavelength band by including a light absorber, specifically, an organic dye, in a prism pattern. Accordingly, the transmission spectrum curve of the optical sheet may exhibit a narrow and deep valley at a specific wavelength in the visible light band (see FIG. 13 ).

On the other hand, when a pigment or phosphor other than an organic dye is used as the light absorber, it is difficult to achieve such selective absorption of light of a specific wavelength. Specifically, according to the embodiment, since the organic dye is uniformly dissolved in a solvent and added to the prism pattern, wavelength absorption selectivity may be very excellent, and luminance deterioration may be minimized because it hardly absorbs other wavelengths. On the other hand, when a pigment or phosphor is used as a light absorber, since it is dispersed without being dissolved in a solvent, absorption selectivity for a specific wavelength is low, so it is not suitable for use in improving a color gamut.

The net absorbance obtained by subtracting the transmittance for each wavelength measured in the optical sheet from the transmittance for each wavelength measured after removing only the light absorber from the optical sheet is obtained, and then this is obtained as a spectrum curve (that is, a graph in which the horizontal axis is the wavelength and the vertical axis is the net absorbance). ), the main absorption peak may appear very sharp and narrow (see FIG. 14).

For example, the optical sheet may satisfy Equation (1) below:

FWHM ≤ 50 nm... (1)

In Equation (1), FWHM is the full width at half maximum (nm) of the maximum peak in the spectral curve of the net absorbance according to the wavelength, and a light source is prepared to measure the net absorbance, and light from the light source is transmitted to the optical sheet first transmittance T1 is measured, a reference sheet in which only the light absorber is removed from the optical sheet is prepared, and light from the light source is passed through the reference sheet to measure second transmittance T0 , The net absorbance is a value obtained by subtracting the first transmittance T1 from the second transmittance T0.

Specifically, the FWHM value of Equation (1) may be 0 nm to 50 nm, or 10 nm to 40 nm.

More specifically, the maximum peak in the net absorbance spectrum may appear in a first absorption wavelength band, where the first absorption wavelength band may be 500 nm to 700 nm, specifically 550 nm to 650 nm. . In addition, the height of the maximum peak in the spectral curve of the net absorbance may be 5% or more, for example, 10% or more, specifically 5% to 50%, or 10% to 30%.

Also, the light source used to measure the net absorbance may be a light source emitting white light having a continuous emission spectrum.

Manufacturing method of optical sheet

A method of manufacturing an optical sheet according to an embodiment includes the steps of coating a composition for forming a prism pattern on an upper surface of a substrate layer, transferring the pattern, and UV-curing to form a prism pattern layer, wherein the composition for forming a prism pattern is It includes a binder resin, a light absorber, a UV blocker, an antioxidant and a light stabilizer, and the light absorber includes at least one organic dye that selectively absorbs light in a specific wavelength band.

8 illustrates a manufacturing method of an optical sheet, specifically, a prism sheet including a light absorber, according to an embodiment. Referring to FIG. 8, (a) preparing a base layer 201, (b) on the base layer 201, a light absorber, a binder resin, and other additives (UV blocker, antioxidant, light stabilizer, etc.) After applying the prism pattern layer composition 202 ′ including (c), a prism pattern is formed and cured with UV light to obtain a prism sheet 200 having a prism pattern layer 202 formed thereon.

The type and content of each component included in the composition for forming the prism pattern is the same as exemplified in the type and content of each component included in the prism pattern layer. For example, the composition for forming a prism pattern includes 0.01 to 1 part by weight of the light absorber based on 100 parts by weight of the binder resin, and includes the UV blocker in an amount of 10 to 100 times the weight of the light absorber, The antioxidant may be included in an amount of 1 to 10 times the weight of the light absorber, and the light stabilizer may be included in an amount of 10 to 50 times the weight of the light absorber.

The composition for forming the prism pattern may further include an organic solvent to adjust viscosity for coating. For example, the solvent may be included such that the solid content of the composition is 10% to 50% by weight. Specific examples of the organic solvent include toluene, methyl ethyl ketone, ethyl acetate, and the like, and other solvents are also possible. According to the above embodiment, since the light absorber includes an organic dye, it is uniformly dissolved in an organic solvent to improve light absorption characteristics after coating.

The prism pattern may be formed by transferring a pattern formed on a cylindrical master roll to a coating layer by a roll to roll method. First, a pattern may be engraved on the master roll by cutting the outer circumferential surface (circumferential surface of a cylinder) of the master roll with a bite, laser, or the like. Thereafter, the composition for forming a pattern may be coated on the base film, and the pattern of the master roll may be transferred to the coating layer to form a prism pattern. Alternatively, the prism pattern may be formed by melting the plastic raw material as heat by extrusion and transferring the pattern of the master roll while the liquid plastic flat plate is solidified.

In addition, the prism patterns may be manufactured to have different heights, and master rolls for this may be manufactured by cutting using a diamond tool, for example. As a specific example, a continuous groove pattern may be formed by thread cutting along the circumference of the roll while moving a diamond tool in a transverse direction while rotating a cylindrical roll made of a material such as hard copper. At this time, the pitch of the prism pattern can be changed by adjusting the moving speed of the diamond tool, and the prism can be adjusted by adjusting the penetration depth of the diamond tool into the cylindrical roll, the horizontal/vertical angle between the tool and the surface of the roll, and the rotational speed of the cylindrical roll. The specifications of the pattern can be changed more diversely and in detail.

The formed prism pattern may be cured by UV light irradiation to form a prism pattern layer. Specifically, the UV curing may be performed with a UV irradiation amount of about 100 to 200 mJ/cm ² .

Since the prism pattern manufactured according to the above method includes at least one organic dye that selectively absorbs light in a specific wavelength band, an optical sheet that minimizes luminance degradation due to light absorption while improving color gamut through a simple manufacturing process. can provide

A method of manufacturing an optical sheet according to another embodiment includes (1) forming a functional coating layer on a lower surface of a base layer; and (2) forming a prism pattern layer by coating a composition for forming a prism pattern on the upper surface of the base layer, transferring the pattern, and curing the pattern by UV, wherein the composition for forming a prism pattern includes a binder resin, a light absorber, It includes a UV blocker, an antioxidant and a light stabilizer, and the light absorber includes one or more organic dyes that selectively absorb light in a specific wavelength band.

A method of manufacturing an optical sheet according to another embodiment includes (1) forming a first functional coating layer on a lower surface of a first base layer; (2a) forming a first prism pattern layer by coating a composition for forming a first prism pattern on the upper surface of the first base layer, transferring the pattern, and curing the pattern by UV; (2b) laminating a second substrate layer on an upper surface of the first prism pattern layer; and (3) forming a second prism pattern layer on the upper surface of the second substrate layer, wherein the composition for forming the first prism pattern includes a binder resin, a light absorber, a UV blocker, an antioxidant and a light stabilizer. And, the light absorber includes at least one organic dye that selectively absorbs light in a specific wavelength band.

In the method according to the above embodiment, steps (2a) and (2b) may be performed in separate process lines or simultaneously in one process line.

9A to 9C show a method of manufacturing an optical sheet according to the embodiment. 9A to 9C , the manufacturing method of the optical sheet includes (1) forming a first functional coating layer 310 on the lower surface of the first base layer 211; (2) A composition for forming a first prism pattern is coated on the upper surface of the first substrate layer 211, the pattern is transferred, and UV cured to form the first prism pattern layer 212 and the first prism pattern. laminating a second substrate layer 221 on the upper surface of the layer 212; and (3) forming a second prism pattern layer 222 on the upper surface of the second base layer 221, wherein the composition for forming the first prism pattern includes a binder resin, a light absorber, a UV blocker, and an oxidizing agent. It includes an inhibitor and a light stabilizer, and the light absorber includes at least one organic dye that selectively absorbs light in a specific wavelength band.

In addition, in the method according to the embodiment, the composition for preparing the second prism pattern layer 222 instead of the first prism pattern layer 212 includes a binder resin, a light absorber, a UV blocker, an antioxidant and a light stabilizer A composition is used, or a composition including a binder resin, a light absorber, a UV blocker, an antioxidant and a light stabilizer is used as a composition for preparing the first prism pattern layer 212 and the second prism pattern layer 222. It can also be manufactured.

7 illustrates a process of forming a first prism pattern layer using a pattern roll and laminating the second substrate layer. Referring to FIG. 7 , the first base layer on which the first functional coating layer is formed on the back side is unwound from the first unwinding roll 2-1, and the first base layer is coated on the first base layer by the first coating device 3-1. 1 A prism pattern layer composition is applied. Thereafter, a prism pattern is formed by the pattern roll 4 and at the same time UV cured by the first curing device 5-1 to manufacture a first prism pattern layer. Separately from this, the second substrate layer is unwound from the second unwinding roll 2-2, and the UV curable adhesive composition is applied on the second substrate layer by the second coating device 3-2. Then, it is laminated to the surface of the first prism pattern layer while passing between the two pressure rolls 6, and then UV cured by the second curing device 5-2, so that the second substrate layer, the first prism pattern layer, A composite sheet having a first base layer and a first functional coating layer can be obtained. Thereafter, a final optical sheet may be obtained by forming a second prism pattern layer on the surface of the second substrate layer of the composite sheet.

Hereinafter, the embodiment will be described with more specific examples, but the scope of the embodiment is not limited to these ranges.

Preparation Example 1

A light absorption pattern layer composition was prepared by mixing the following components.

- Epoxy-modified acrylate resin (solid content 100%, SHPR-HV200, SMS Co., Ltd.) 100 parts by weight

- Light absorber: 0.02 parts by weight of organic dye (C590B, KISCO)

- UV blocker (Tinuvin-928, BASF) 1 part by weight

- Antioxidant (Irganox-1010, BASF) 0.1 parts by weight

- Light stabilizer (Tinuvin-292, BASF) 0.5 parts by weight

- Photoinitiator (TPO, BASF) 0.5 parts by weight

- Solvent (methyl ethyl ketone / toluene = 1: 1) blended so that the solid content in the composition is 80% by weight

Preparation Example 2

A light absorption pattern layer composition was prepared by changing the content of the light absorber in the composition of Preparation Example 1 to 0.03 parts by weight.

Preparation Example 3

A light absorption pattern layer composition was prepared by changing the content of the light absorber in the composition of Preparation Example 1 to 0.04 parts by weight.

Production Example 4

In the composition of Preparation Example 1, a light absorption pattern layer composition was prepared without adding a light absorber.

Example 1

While coating the composition of Preparation Example 1 on one side of the first base layer (PET) having a thickness of 188 μm and forming a prism pattern using a master roll having a pattern on the surface, UV irradiation (100 ~ 200 mJ / cm ² ) Cured by a thickness of about 40 ㎛ to prepare a first prism pattern layer. As a result, an optical sheet composed of the first prism sheet was obtained (see FIG. 5A).

Example 2

Step 1) After preparing a composition in which 15 parts by weight of polybutyl methacrylate (PBMA) beads, 35 parts by weight of a urethane acrylate resin, and 50 parts by weight of methyl ethyl ketone (MEK) as a solvent are mixed, a first layer having a thickness of 188 μm is prepared. A first light diffusion layer having a thickness of 5 μm was formed by coating and drying one surface of the substrate layer (PET).

Step 2) Coating the composition of Preparation Example 1 on the other surface of the first base layer and curing by UV irradiation (100 to 200 mJ/cm ² ) while forming a prism pattern using a master roll having a pattern on the surface A first prism pattern layer having a thickness of about 40 μm was prepared. As a result, an optical sheet having a first prism sheet and a first light diffusion layer was obtained (see Fig. 5B).

Example 3

Step 1) After preparing a composition in which 15 parts by weight of polybutyl methacrylate (PBMA) beads, 35 parts by weight of a urethane acrylate resin, and 50 parts by weight of methyl ethyl ketone (MEK) as a solvent are mixed, a first layer having a thickness of 100 μm is prepared. A first light diffusion layer having a thickness of 5 μm was formed by coating and drying one surface of the substrate layer (PET).

Step 2) Coating the composition of Preparation Example 1 on the other surface of the first base layer and curing by UV irradiation (100 to 200 mJ/cm ² ) while forming a prism pattern using a master roll having a pattern on the surface A first prism pattern layer having a thickness of about 40 μm was prepared. A UV curable adhesive resin is micro-gravure coated to a thickness of 0.5 to 1.0 μm on the surface of the second substrate layer (PET) having a thickness of 100 μm, and then laminated on the surface of the first prism pattern layer, UV light of about 1000 mJ / cm ² was cured by irradiation.

Step 3) A second prism pattern layer having a thickness of about 40 μm was formed on the surface of the second substrate layer using a UV curable resin and UV cured to prepare a second prism sheet.

Step 4) Coat a UV curable adhesive resin on one side of a buffer film (PET) having a thickness of 100 μm to a thickness of 0.5 to 1.0 μm using a Mayer bar, and adhere to the surface of the prism pattern layer of the previously prepared second prism sheet, UV cured.

Step 5) After preparing a composition in which 15 parts by weight of polymethyl methacrylate (PMMA) beads, 35 parts by weight of acrylic binder resin, and 50 parts by weight of methyl ethyl ketone (MEK) as a solvent are mixed, 95 ㎛ thick dual brightness enhancement The composition was coated on one surface of a film (DBEF, Qv2, 3M) and dried to form a second light diffusion layer having a thickness of 10 μm. The other surface of the dual brightness enhancement film was coated with a UV curable adhesive resin to a thickness of 10 μm using a Mayer bar, adhered to the surface of the previously prepared buffer film, and UV cured to obtain an optical sheet (see FIG. 5C).

Example 4

Steps 1) to 3) of Example 3 were repeated to obtain an optical sheet having a first light diffusion layer, a first prism sheet, and a second prism sheet.

After preparing a composition in which 15 parts by weight of polymethyl methacrylate (PMMA) beads, 35 parts by weight of acrylic binder resin, and 50 parts by weight of methyl ethyl ketone (MEK) as a solvent were mixed, a base film (PET) having a thickness of 100 μm was prepared. The composition was coated on one surface and dried to form a second light diffusion layer having a thickness of 15 μm. A UV curable adhesive resin was coated on the other surface of the base film to a thickness of 0.5 to 1.0 μm using a Mayer bar, adhered to the surface of the prism pattern layer of the previously prepared second prism sheet, and UV cured to obtain an optical sheet ( see Fig. 5d).

Example 5

Step 1) After preparing a composition in which 15 parts by weight of polybutyl methacrylate (PBMA) beads, 35 parts by weight of a urethane acrylate resin, and 50 parts by weight of methyl ethyl ketone (MEK) as a solvent are mixed, a first layer having a thickness of 125 μm is prepared. A first light diffusion layer having a thickness of 5 μm was formed by microgravure coating and drying on one surface of the substrate layer (PET).

Step 2) Coating the composition of Preparation Example 1 on the other surface of the first base layer and curing by UV irradiation (100 to 200 mJ/cm ² ) while forming a prism pattern using a master roll having a pattern on the surface A first prism pattern layer having a thickness of about 40 μm was prepared. At the same time, a UV curable adhesive resin is coated with micro gravure to a thickness of 0.5 to 1.0 μm on the surface of the second substrate layer (PET) having a thickness of 125 μm, and after laminating on the surface of the first prism pattern layer, UV light is applied to about It was cured by irradiation with an amount of 1000 mJ/cm ² .

Step 3) A second prism pattern layer having a thickness of about 40 μm was formed on the surface of the second substrate layer using a UV curable resin and UV cured to prepare a second prism sheet. As a result, an optical sheet having a first light diffusion layer, a first prism sheet, and a second prism sheet was obtained (see Fig. 5E).

Example 6

Steps 1) to 3) of Example 5 were repeated, but an optical sheet was manufactured using the composition of Preparation Example 2 as a composition for preparing the first prism pattern layer in step 2).

Example 7

Steps 1) to 3) of Example 5 were repeated, but an optical sheet was prepared using the composition of Preparation Example 3 as a composition for preparing the first prism pattern layer in Step 2).

Comparative Example 1

Step 1) Light absorbing layer composition (100 parts by weight of a solution in which acrylic binder resin (AOF-2914, Aekyung) and propylene glycol methyl ether (PGME) are mixed in a weight ratio of 30:70, light absorber (PANAX NEC 584, Woosung Chemical) 0.05 parts by weight of the composition) was coated on one surface of the first substrate layer (PET) having a thickness of 125 μm and dried to form a light absorption coating layer having a thickness of 3 μm.

Step 2) After preparing a composition in which 15 parts by weight of polybutyl methacrylate (PBMA) beads, 35 parts by weight of a urethane acrylate resin, and 50 parts by weight of methyl ethyl ketone (MEK) as a solvent are mixed, the surface of the light absorbing coating layer A first light diffusion layer having a thickness of 5 μm was formed by microgravure coating and drying.

Step 3) UV curable resin was coated on the other surface of the first base layer and UV cured while forming a prism pattern using a master roll having a pattern on the surface to prepare a first prism pattern layer having a thickness of about 40 μm. A UV curable adhesive resin is micro-gravure coated to a thickness of 0.5 to 1.0 μm on the surface of the second substrate layer (PET) having a thickness of 125 μm, and then laminated on the surface of the first prism pattern layer, UV light of about 1000 mJ / cm ² was cured by irradiation.

Step 4) A second prism pattern layer having a thickness of about 40 μm was formed on the surface of the second substrate layer using a UV curable resin and UV cured to prepare a second prism sheet. As a result, an optical sheet having a first light diffusion layer, a light absorbing coating layer, a first prism sheet, and a second prism sheet was obtained (see FIG. 6).

Comparative Example 2

Steps 1) to 3) of Example 5 were repeated, but an optical sheet was prepared using the composition of Preparation Example 4 (no light absorber added) as a composition for preparing the first prism pattern layer in Step 2). did

Example of application to display devices

In the liquid crystal display (55-inch LED direct type, 220V, LG Electronics), the optical film (reflective polarizing film, prism sheet, etc.) located on the back of the liquid crystal display panel was removed, and an optical sheet was placed there.

Test Example 1

Apply the optical sheet to the display device and measure luminance, CIE 1931 chromaticity coordinates xy, CIE 1976 chromaticity using a spectroradiometer (Spectroradiometer, SR-3, TOPCON, Working Distance: 660 mm, Field Spec.: 0.2D) Coordinates u'v' and the like were measured, and based on this, the area of the color gamut and the DCI overlapping ratio were calculated.

In addition, the color was observed from the front of the display device and at an angle of 60 °, and Δu'v' (60D) was calculated according to the following equation, and is shown in the table below.

Δu'v'(60D) = [ (u'0 - u'60) ² + (v'0 - v'60) ² ] ^1/2

In the above equation, u'0 and u'60 are CIE 1976 chromaticity coordinates u' values measured from the front of the display device and at an angle of 60°, respectively, and v'0 and v'60 are measured from the front of the display device and at an angle of 60°, respectively. A CIE 1976 chromaticity coordinate v' value.

Also, in the same manner, the color was observed from the front of the display device and at an angle of -60°, and Δu'v' (-60D) was calculated. The results are shown in the table below.

division Comparative Example 1 Example 5 Example 6 Example 7 floor
nine
castle 2nd prism sheet O O O O 1st prism sheet O light absorber
0.02 parts by weight light absorber
0.03 parts by weight light absorber
0.04 part by weight light absorbing coating layer light absorber
0.05 parts by weight X X X 1st light diffusion layer O O O O test
result Luminance (cd/m ² ) 257.2 277.3 264.6 253.8 color x 0.2647 0.2624 0.2577 0.2538 color y 0.2708 0.2701 0.2647 0.2593 gain 100.0% 107.8% 102.9% 98.7% △x 0.0000 -0.0023 -0.0070 -0.0109 △y 0.0000 -0.0007 -0.0061 -0.0115 Peak Point -5 -5 0 0 left and right viewing angle 52.7° 50.4° 50.3° 50.4° spectral luminance 100.0% 107.1% 101.8% 97.9% area ratio 89.4% 90.6% 92.7% 94.3% DCI overlap ratio 90.8% 91.6% 92.6% 93.7% Δu'v'(60D) 0.0077 0.0065 0.0066 0.0057 Δu'v'(-60D) 0.0153 0.0095 0.0077 0.0067

As shown in the table above, compared to the optical sheet of Comparative Example 1 in which the light absorbing coating layer was separately formed, the optical sheets of Examples 5 to 7 in which a light absorber was appropriately added to the prism pattern layer had better luminance when applied to a display device. , viewing angle and color.

In particular, the optical sheet of Comparative Example 1 requires a separate process of forming a light absorbing coating layer, whereas the optical sheets of Examples 5 to 7 do not require such a separate process, so production efficiency can be improved. In addition, compared to the optical sheet of Comparative Example 1, the optical display device to which the optical sheet of Examples 5 to 7 is applied has a small change in chromaticity coordinate values according to a viewing angle, so that color deviation according to a viewing angle can be effectively reduced.

Test Example 2

The optical sheets of Example 5 and Comparative Example 2 were put into a spectrophotometer (CM-3700A, Konica Minolta Co., Ltd., light source D65), and transmission spectra were measured, respectively, and the results are shown in FIG. 13 .

As shown in FIG. 13, Comparative Example 2 in which no organic dye was added to the prism pattern appeared flat in all wavelengths of the visible light band in the transmission spectrum curve.

On the other hand, the transmission spectrum curve of Example 5 showed a narrow and deep valley at a specific wavelength in the visible light band, and it was confirmed that the optical sheet of Example 5 selectively absorbed light of a specific wavelength by the organic dye.

Such a characteristic of selective absorption of light of a specific wavelength is difficult to achieve when a pigment or phosphor other than an organic dye is used as a light absorber. In Example 5, since the organic dye is uniformly dissolved in a solvent and added to the prism pattern, wavelength absorption selectivity may be very excellent, and luminance deterioration may be minimized because it hardly absorbs other wavelengths. On the other hand, when a pigment or phosphor is used as a light absorber, since it is dispersed without being dissolved in a solvent, absorption selectivity for a specific wavelength is low, so it is not suitable for use in improving a color gamut.

14 shows a value obtained by subtracting the transmittance of Example 5 from the transmittance of Comparative Example 2 for each wavelength, that is, the net absorbance by the organic dye, and then shows it as a spectrum curve. In FIG. 14, the highest height (h) of the peak (pointed peak) of the net absorbance is about 11%, and the height corresponding to 1/2 of this (1/2 h) is about 5.5%, and the peak width at that height (w), that is, the full width at half maximum (FWHM) was measured to be about 32 nm. As such, since the full width at half maximum of the peak in the net absorbance spectrum of Example 5 is very narrow, less than 50 nm, it can be confirmed that the absorption selectivity of the wavelength is very high.

1: display device;
2-1: 1st unwinding roll, 2-2: 2nd unwinding roll,
3-1: 1st curing device, 3-2: 2nd curing device,
4: pattern roll, 6: pressure roll,
5-1: 1st curing device, 5-2: 2nd curing device,
10: backlight unit, 11: optical sheet,
20: display panel, 30: cover window,
51: upper frame, 52: lower frame,
200: prism sheet, 201: base layer,
202: prism pattern layer, 202': prism pattern layer composition,
202a: first pattern, 202b: second pattern,
210: first prism sheet, 220: second prism sheet,
211: first substrate layer, 212: first prism pattern layer,
221: second substrate layer, 222: second prism pattern layer,
310: first functional coating layer, 320: second functional coating layer,
311: bead, 312: binder resin,
321: bead, 322: binder resin,
350: base film,
400: reflective polarizing film, 500: buffer film,
600, 610, 620, 630: adhesive layer, 601: meniscus,
700: light guide plate, 800: reflector,
L: outgoing light, UV: UV light
M: laminate, S1, S2: skin layer,
T1: the thickness of the substrate layer, T2: the thickness of the pattern layer,
Ta: height of the first pattern, Tb: height of the second pattern,
CG: full color gamut, CG0: overlapping color gamut,
CG1: first color gamut, CG2: second color gamut,
R: red, G: green, B: blue.

Claims (11)

base layer; And a prism sheet comprising a UV curable prism pattern layer disposed on the base layer, and
Including a functional coating layer disposed under the prism sheet,
The prism pattern layer includes a light absorber that selectively absorbs light in a specific wavelength band, a UV blocker, a photoinitiator, and a binder resin, the light absorber includes one or more organic dyes, and the light absorber includes the binder. 0.01 to 0.1 part by weight based on 100 parts by weight of the solid content of the resin, the optical sheet.
According to claim 1,
Applying the optical sheet to a liquid crystal display device of a direct-type LED light source,
When measured at a distance of 660 mm with a spectroradiometer,
An optical sheet wherein the DCI overlap ratio in the CIE 1976 chromaticity coordinates u'v' is measured to be 91.6% or more.
According to claim 1,
The light absorber includes at least one organic dye selected from the group consisting of pyrrolmethines, rhodamines, borondipyrromethenes, tetraazaporphyrins, squarines, and cyanines,
The optical sheet, wherein the prism pattern layer has a transmittance of 10% to 70% with respect to UV-A light.
According to claim 1,
An optical sheet in which the optical sheet satisfies the following formula (1):
FWHM ≤ 50 nm... (1)
In the above equation (1)
FWHM is the full width at half maximum (nm) of the maximum peak in the spectral curve of the net absorbance according to the wavelength, and a light source is prepared to measure the net absorbance, and light from the light source is passed through the optical sheet to obtain a first transmittance ( T1) is measured,
A reference sheet in which only the light absorber is removed from the optical sheet is prepared, and a second transmittance T0 is measured by passing light from the light source through the reference sheet;
The net absorbance is a value obtained by subtracting the first transmittance T1 from the second transmittance T0.
According to claim 1,
The prism pattern layer further includes at least one of an antioxidant and a light stabilizer,
The UV blocking agent is at least one selected from the group consisting of hydroxybenzotriazole-based, tris-resorcinol-triazine chromophore-based and hydroxyphenyl-benzotriazole chromophore-based UV blocking agents,
The antioxidant is at least one selected from the group consisting of amine-based, phenol-based, sulfur-based, phosphine-based, phosphite-based and thioester-based antioxidants,
The light stabilizer is at least one selected from the group consisting of HALS-based, benzotriazole-based, and benzophenol-based light stabilizers,
The weight of the UV blocker included in the prism pattern layer is 10 to 100 times the weight of the light absorber, the weight of the antioxidant included in the prism pattern layer is 1 time to 10 times the weight of the light absorber, and the prism The optical sheet wherein the weight of the light stabilizer included in the pattern layer is 10 to 50 times the weight of the light absorber.
According to claim 1,
The optical sheet, wherein the functional coating layer is selected from the group consisting of a light diffusion layer, an anti-split layer, and a heat-resistant coating layer.
According to claim 1,
the optical sheet
a first prism sheet;
a first functional coating layer disposed under the first prism sheet; and
A second prism sheet disposed on the first prism sheet;
The first functional coating layer is selected from the group consisting of a light diffusion layer, an anti-split layer, a heat-resistant coating layer, and a hard coating layer,
The first prism sheet includes a first base layer and a first prism pattern layer disposed on the first base layer,
The second prism sheet includes a second base layer and a second prism pattern layer disposed on the second base layer,
The first prism pattern layer extends in a first in-plane direction,
The second prism pattern layer extends in an in-plane second direction crossing the first direction,
At least one of the first prism pattern layer and the second prism pattern layer includes a light absorber that selectively absorbs light in a specific wavelength band, and the light absorber includes one or more organic dyes.
According to claim 7,
the optical sheet
Further comprising a second functional coating layer disposed on the second prism sheet,
The second functional coating layer is selected from the group consisting of a light diffusion layer, an anti-split layer, a heat-resistant coating layer, and a hard coating layer,
The optical sheet, wherein the first functional coating layer, the first prism sheet, the second prism sheet, and the second functional coating layer are directly or indirectly bonded to each other.
According to claim 8,
the optical sheet
A reflective polarizing film disposed between the second prism sheet and the second functional coating layer, and
Further comprising a buffer film disposed between the second prism sheet and the reflective polarizing film,
The reflective polarizing film has a structure in which first resin layers and second resin layers having different optical properties are alternately stacked in 100 to 2000 layers.
According to claim 1,
An optical sheet in which light is incident on a lower portion of the optical sheet and emitted upward.
light source;
a display panel receiving light from the light source and displaying an image; and
an optical sheet disposed in a light path from the light source to the display panel;
The optical sheet may include a substrate layer; And a prism sheet including a UV curable prism pattern layer disposed on the base layer, and a functional coating layer disposed under the prism sheet,
The prism pattern layer includes a light absorber that selectively absorbs light in a specific wavelength band, a UV blocker, a photoinitiator, and a binder resin, the light absorber includes one or more organic dyes, and the light absorber includes the binder. 0.01 to 0.1 parts by weight based on 100 parts by weight of the solid content of the resin, the display device.

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