KR101181951B1 - Color shift compensation filter and display device having the same - Google Patents

Abstract

The present invention is a color shift reduction optical filter provided in front of a display module of a display device to reduce color shift, and has a substrate and at least two refractive indices, and is dispersed in the substrate so that optical It provides a color shift reducing optical filter comprising an anisotropic material for scattering. Preferably, the optical axis of the anisotropic material is along the normal direction of the optical filter. Preferably, the normal refractive index of the anisotropic material is the same as the refractive index of the substrate. Preferably, the extraordinary refractive index of the anisotropic material is different from the refractive index of the base material, and when light enters at a greater angle with the normal direction, the base material and the extraordinary wave enter the extraordinary wave. The refractive index difference increases. Preferably, the light absorbing pattern may be provided to have a background and a depth in the background. Preferably, the light scattering pattern may be provided to have a background and a depth in the background. In addition, the present invention provides a display device comprising the color shift reduction optical filter.

Description

Color shift reduction optical filter and display device having same {COLOR SHIFT COMPENSATION FILTER AND DISPLAY DEVICE HAVING THE SAME}

The present invention relates to a color shift reducing optical filter and a display device having the same, and more particularly, to a color shift reducing optical filter for improving color shift using an anisotropic material and a display device having the same.

As the modern society is highly informationized, image display-related components and devices have been remarkably advanced and widespread. Among them, display apparatuses for displaying images are widely used as television apparatuses, monitor apparatuses for personal computers, and the like, and are being enlarged and thinned.

In general, a liquid crystal display is a flat panel display that displays an image using liquid crystal, and is thinner and lighter than other display devices, and has a low driving voltage and low power consumption. It is widely used throughout the industry.

1 is a conceptual diagram conceptually showing the basic structure and driving principle of an LCD. For example, the conventional VA mode LCD is attached so that the optical axes of the two polarizing films 110 and 120 are perpendicular to each other. The liquid crystal molecules 150 exhibiting birefringence are inserted and arranged between the two transparent substrates 130 coated with the transparent electrode 140. When the electric field is applied by the driving power supply unit 180, the liquid crystal molecules are arranged to move perpendicular to the electric field.

The light emitted from the backlight unit becomes linearly polarized light after passing through the first polarizing film 120. When the light is off, as shown in the left side of FIG. 1, the liquid crystal is vertically aligned with respect to the substrate. Is maintained as it is so as not to pass through the second polarizing film 110 perpendicular to the first polarizing film 120.

Meanwhile, in the on state as shown on the right side of FIG. 1, the liquid crystal is horizontally oriented between the optical axes of the two orthogonal polarizing films 110 and 120 in a direction parallel to the substrate by an electric field, and thus linearly polarized through the first polarizing film. While the light passes through the liquid crystal molecules, the light is changed to a linearly polarized, circularly or elliptically polarized state in which the polarization state is rotated by 90 degrees immediately before reaching the second polarizing film, thereby passing through the second polarizing film. By adjusting the intensity of the electric field, the alignment angle of the liquid crystal is gradually changed from the vertical alignment to the horizontal direction, and the intensity of light emitted from the liquid crystal can be adjusted.

2 is a conceptual diagram illustrating alignment states and light transmittances of liquid crystals according to viewing angles.

When the liquid crystal molecules are arranged in a predetermined direction in the pixel 220, the arrangement state is different depending on the viewing angle.

When viewed from the front side in the right direction 210, the arrangement state of the liquid crystal molecules appears to be almost horizontally aligned 212, and the screen appears relatively bright. When viewed from the front of the screen 230, the arrangement state of the liquid crystal molecules 232, it looks the same as the arrangement of the liquid crystal molecules in the pixel 220. When viewed from the front in the left direction 250, the arrangement state of the liquid crystal molecules appears in the vertical alignment 252, and the screen appears relatively dark.

Therefore, the LCD generates light intensity and color change according to the change in the viewing angle, and the viewing angle is greatly limited compared to the self-luminous display. Therefore, much research has been conducted for improving the viewing angle.

3 is a conceptual diagram illustrating an example of the prior art for improving the contrast ratio change and color shift according to the viewing angle.

Referring to FIG. 3, the pixel is divided into two partial pixels, that is, the first pixel portion 320 and the second pixel portion 340 so that the liquid crystal arrangement of each pixel portion is symmetrical to each other. According to the viewing direction, the arrangement of the liquid crystals in the first pixel unit 320 and the arrangement of the liquid crystals in the second pixel unit 340 are simultaneously seen, and the intensity of light visible to the viewer is determined by the light of each pixel unit. It is the sum of the strengths of.

That is, when viewed from the front side in the right direction 310, the liquid crystal of the first pixel portion 320 is shown as the horizontal alignment 312 and the liquid crystal of the second pixel portion 340 is shown as the vertical alignment 314. The screen may be made bright by the one pixel unit 320. Similarly, when viewed from the front in the left direction 350, the liquid crystal of the first pixel portion 320 is shown in the vertical alignment 352, and the liquid crystal of the second pixel portion 340 is shown in the horizontal alignment 354. By the two pixel unit 340, the screen can be seen brightly. When viewed from the front (330) is the same as the arrangement state of each pixel portion. Accordingly, the brightness of the screen when viewed by the viewer becomes the same or similar as the viewing angle changes, and becomes symmetric about the vertical direction with respect to the screen. Therefore, the change in contrast ratio and the degree of color change according to the change of viewing angle can be improved.

4 is a conceptual diagram illustrating another example of the related art for improving the contrast ratio change and color shift according to the viewing angle.

Referring to FIG. 4, an optical film 420 having a birefringence characteristic, the characteristic of which is the same as that of the liquid crystal molecules in the pixel 440 in the LCD panel, and which is symmetric with the arrangement state of the liquid crystal molecules, is added. Due to the arrangement state of the liquid crystal in the pixel 440 and the birefringence characteristic of the optical film 420 according to the viewing direction, the light intensity seen by the viewer is the sum of the light intensities.

That is, when viewed from the front to the right direction 410, the liquid crystal in the pixel 440 is shown in the horizontal alignment 414, the virtual liquid crystal by the optical film 420 is shown in the vertical alignment 412, the light intensity is Each sum. Similarly, when viewed from the front in the left direction 450, the liquid crystal in the pixel 440 is shown in the vertical alignment 454 and the virtual liquid crystal by the optical film 420 is shown in the horizontal alignment 452, the light intensity is Each sum. In the front view 430, the arrangement state of the liquid crystal molecules in the pixel 440 and the birefringent arrangement state of the optical film 420 appear to be the same (432 and 434).

However, even with the above technique, as shown in FIG. 5, there is still a color shift according to the viewing angle, and thus there is a problem that a color change occurs as the viewing angle increases.

SUMMARY OF THE INVENTION The present invention has been made under the above-described background, and an object of the present invention is to provide an optical filter and a display device having the same that can improve a color shift phenomenon caused by an increase in viewing angle.

In addition, another object of the present invention is to provide a color shift reducing optical filter and a display device which provide excellent luminance characteristics by minimizing transmission loss.

In order to achieve the above object, the present invention is a color shift reduction optical filter provided in front of the display module of the display device to reduce the color shift, a substrate, having a refractive index of at least two or more, and dispersed in the substrate The present invention provides a color shift reducing optical filter comprising an anisotropic material that scatters light due to a difference in refractive index from a substrate.

Preferably, the optical axis of the anisotropic material is along the normal direction of the optical filter.

Preferably, the normal refractive index of the anisotropic material is the same as the refractive index of the substrate.

Preferably, the extraordinary refractive index of the anisotropic material is different from the refractive index of the substrate, and when light enters at a greater angle with the normal direction of the optical filter, the substrate and the extraordinary wave are incident. The difference in refractive index of the anisotropic material increases.

Preferably, the light absorbing pattern may be provided to have a background and a depth in the background.

Preferably, the light scattering pattern may be provided to have a background and a depth in the background.

In addition, the present invention provides a display device comprising the color shift reduction optical filter.

According to the above configuration, the present invention has the effect of securing the viewing angle of the display device and improving the image quality by minimizing the color shift phenomenon caused by the viewing angle increase.

In addition, there is an effect that can provide excellent luminance characteristics by minimizing the front transmittance loss.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

6 is a cross-sectional view illustrating an optical filter according to a first embodiment of the present invention, and FIGS. 7 and 8 are enlarged cross-sectional views showing examples of the anisotropic material 20 usable for the optical filter of FIG. 6, respectively.

As shown, the optical filter of FIG. 6 includes a substrate 10 and an anisotropic material 20.

The substrate may be made of a resin that transmits light. The substrate may be formed of a polymer resin or, for example, an ultraviolet curable resin, but the present invention is not limited thereto.

The anisotropic material is formed by being dispersed in the substrate. The anisotropic material has at least two refractive indices. The anisotropic material scatters light by the difference in refractive index with the substrate, thereby compensating for the color shift according to the viewing angle.

Preferably the optical axis of the anisotropic material follows the normal direction of the optical filter. Normal refractive index n _⊥ of the anisotropic material is preferably the same as the refractive index of the substrate.

The abnormal refractive index n _// of the anisotropic material is different from the refractive index of the substrate.

7 shows an optical axis in the normal direction of an optical filter in a structure in which a positive uniaxial anisotropic material (or liquid crystal molecules) is spherical in a film in which the normal refractive index is the same as the refractive index of the substrate and the abnormal refractive index is larger than the refractive index of the substrate. If arranged as

8 shows an optical axis in the normal direction of an optical filter in a structure in which a negative uniaxial anisotropic material (or liquid crystal molecules) is spherical in a film, in which the normal refractive index is the same as the refractive index of the substrate and the abnormal refractive index is smaller than the refractive index of the substrate. If arranged as

The refractive index of the optical filter in the normal direction, that is, at an angle θ with the optical axis of the anisotropic material, and when the normal wave is incident is n _⊥ , which is the same as the refractive index of the substrate. The refractive index n (θ) when an extraordinary wave is incident is as follows.

n (θ) = n _⊥ n _// / (n _// ² cos ² θ + n _⊥ ² sin ² θ) ^1/2

The refractive index n (θ) of the anisotropic material when the extraordinary ray is incident is larger than the refractive index of the substrate as light enters at a larger angle with the normal line direction of the optical filter, that is, as the incident angle θ becomes larger. Have When light is incident on the optical filter plane horizontally, that is, when the incident angle θ = 90 degrees, the refractive index n (θ) is maximum and has a value of n _// .

Since the screen light incident from the display module perpendicularly to the optical filter of FIG. 6 (incident angle θ = 0 degrees) is incident in the optical axis direction, the refractive index of the substrate and the refractive index of the normal light and the refractive index of the abnormal light are the same, This does not happen. Therefore, the front transmittance loss can be minimized.

On the other hand, in the screen light incident obliquely to the optical filter, the refractive index of the abnormal light is different from the refractive index of the substrate and the refractive index of the normal light, so that scattering occurs. As the viewing angle increases, the refractive index difference becomes larger to diffuse more light evenly from the display module, thereby inducing color mixing and reducing color shift.

The larger the refractive index of the extraordinary ray at the incident angle of 90 degrees and the larger the refractive index of the substrate is, the more preferable it is. The refractive index difference is preferably at least 0.01 or more, but the present invention is not limited thereto.

In addition, the anisotropic material preferably forms a spherical fine particle structure of 0.01 μm or more, but the present invention is not limited thereto.

As shown in FIGS. 7 and 8, the fine particle structure of the anisotropic material may be formed in a structure in which the liquid crystal molecules 21 in which the optical axis is arranged in the normal direction of the optical filter are spherical in the film.

9 is a schematic cross-sectional view of an optical filter according to a second exemplary embodiment of the present invention.

As shown, the optical filter of the present invention may include a backing 30 for supporting the substrate. As for backing, the transparent resin film which has ultraviolet permeability is preferable. As the material of the backing, polyethylene terephthalate, polycarbonate, polyvinyl chloride, or the like can be used. The refractive index of the backing preferably matches the refractive index of the substrate, but the present invention is not limited thereto.

The method of dispersing and forming fine particles of anisotropic materials on a substrate may be completed by first dispersing an ultraviolet curable resin and anisotropic material on one surface of the backing, and then irradiating and curing ultraviolet rays while arranging the anisotropic material through an electric field. have.

In this case, when the liquid crystal is used as the anisotropic material, the UV curable resin and the liquid crystal may be phase-separated and mixed at an appropriate ratio to form a spherical fine particle structure, and the temperature may be adjusted as necessary. However, the present invention is not limited thereto.

10 is a schematic cross-sectional view of an optical filter according to a third exemplary embodiment of the present invention.

FIG. 10 shows that the optical filter of FIG. 9 may have other functional layers 40 such as transparent substrates (eg, glass substrates), antireflective layers, anti-glare layers, hard coating layers, anti-fog layers, and the like.

Each component layer constituting the optical filter of the present invention may be adhered or adhered using an adhesive or an adhesive. Specific examples of the material include acrylic adhesives, silicone adhesives, urethane adhesives, polyvinyl butyral adhesives (PMB), ethylene-vinyl acetate adhesives (EVA), polyvinyl ethers, saturated amorphous polyesters, melamine resins, and the like.

11 is a schematic cross-sectional view of an optical filter according to a fourth exemplary embodiment of the present invention.

As shown, the optical filter of FIG. 11 includes a background 50 and a light absorption pattern 60.

The background is formed by layering materials that transmit light. The background may be formed of an ultraviolet curable resin.

The light absorption pattern is formed in the background to absorb light. The light absorption pattern is formed to have a depth in the background, thereby absorbing a specific wavelength region of obliquely incident incident light to reduce color shift.

The substrate 10 and the anisotropic material 20 are formed to be included in both the background 50 and the light absorption pattern 60.

In addition, the light absorption pattern 60 may include the following light absorbing materials. i) comprising a white light absorbing material, such as carbon black, ii) comprising a green wavelength range absorbing material, or iii) comprising a cyan wavelength range absorbing material and an orange wavelength range absorbing material together with the green wavelength range absorbing material, or iv) Along with the green wavelength range absorbing material, it may include a white light absorbing material such as carbon black.

Light absorption pattern including white light absorbing material

The color shift may be improved by including a white light absorbing material (visible light field absorbing material) such as carbon black in the light absorbing pattern.

At higher gray levels, the luminance decreases as the viewing angle increases, but at low gray levels, the luminance increases as the viewing angle increases, which causes the color shift to worsen. Therefore, as the viewing angle increases, the color shift can be improved by allowing more light to be emitted from the display panel to be absorbed so that the luminance decreases according to the viewing angle regardless of the gray level.

When carbon black is added to form a light absorption pattern, since it appears achromatic in front, there is no need for color correction to achromatic color separately, so that the structure is simple and the production cost is reduced.

Light absorption pattern including green wavelength region absorbing material

In general, the display industry evaluates 13 mixed colors (White, Red, Blue, Green, Skin, Sony Red, Sony Blue, Sony Green, Cyan, Purple, Yellow, Moderate Red, and Purplish Blue). .

When the white light emitted from the display panel is emitted at high gradation, the luminance decreases in all wavelength ranges and the blue wavelength range decreases most rapidly as the viewing angle increases. The luminance increases in the wavelength region and the green wavelength region increases relatively quickly.

Therefore, the light absorption pattern is filled with the green wavelength region absorbing material, so that the absorption of light from the display panel increases gradually as the viewing angle of the light emitted from the display panel increases and the green wavelength region of 510 to 560 nm is increased. The absorption of light is relatively increased, thereby minimizing mixed color change due to an increase in viewing angle.

Here, the green wavelength region absorbing material may be any one of an inorganic material and an organic material capable of absorbing light of the green wavelength of 510 ~ 560nm, it is preferable that a pink pigment is used. In addition to the pink dye, any material capable of absorbing green wavelength light may be used as the green wavelength region absorbing material.

Light absorption pattern including green wavelength region absorbent material, cyan wavelength region absorbent material and orange wavelength region absorbent material

Unlike the LED, the CCFL backlight has strong peaks in the cyan wavelength region near 490 nm and orange wavelength region near 590 nm.

These peaks in the cyan and orange wavelength ranges cause color reproduction areas and worsen color shift.

The color shift results of the LCD, which consists of LEDs and the backlight of the CCFL, show that the CCFL is not good.

Therefore, when the peaks of the cyan wavelength region and the orange wavelength region which adversely affect the color shift according to the viewing angle are absorbed more as the viewing angle increases, the mixed color change according to the viewing angle may be further minimized.

To this end, the light absorption pattern includes not only the green wavelength region absorbing material capable of absorbing the green wavelength region of 510-560 nm, but also the cyan wavelength region absorbing substance of 480-510 nm and the orange wavelength region absorbing substance of 570-600 nm. Can be. As a result, the green wavelength region of the light emitted from the display panel is absorbed more as the viewing angle increases, and the peak angles of the cyan wavelength region and the orange wavelength region which increase the viewing angle adversely affect the color shift according to the viewing angle in the spectrum of the LCD are increased. Absorbs more along. Through this, it is possible to further increase the viewing angle improvement effect by minimizing the color change according to the increase of the viewing angle and minimizing the color change in all the mixed colors including the blue mixed color series and the red mixed color series.

The background or backing may include color correction pigments that change or adjust the color balance by reducing or adjusting the amount of red (R), green (G), and blue (G).

When the light from the front of the display passes through the optical filter for display device, the image color of the display is changed by the light absorption pattern. Therefore, wavelengths other than the wavelength region, orange wavelength region, and cyan wavelength region drawn with color correction dye in the background or backing are changed. A color absorbing region, for example, a red wavelength range absorbing dye and a blue wavelength range absorbing dye may be appropriately included and color corrected close to the original color from the front. It is not provided as a separate layer or film, it is formed by adding a color correction pigment to the background or the backing can simplify the structure of the optical filter and shorten the manufacturing process.

Of course, the color correction pigment may be included in the adhesive layer in addition to the background or backing, and may also be included in other functional films.

The light absorption pattern may be any one of a wedge cross-section stripe pattern, a wedge cross-section wave pattern, a wedge cross-section matrix pattern, a wedge cross-section honeycomb pattern, a cross-section stripe pattern, a cross-section wave pattern, a cross-section matrix pattern and a cross-section honeycomb pattern. Also, for example, the stripe pattern may have various patterns such as a horizontal stripe pattern, a vertical stripe pattern, and the like.

The light absorption pattern is preferably arranged in parallel with the wedge end surface portion spaced at regular intervals on one surface of the background.

The light absorption pattern may be formed so that the bottom surface thereof faces the viewer, may be formed to face the display panel, or may be formed on both sides of the ground.

11 illustrates an embodiment in which the light absorption pattern is engraved with respect to the background, but is not necessarily limited thereto and may be embossed.

In the method of manufacturing the optical filter, after applying the ultraviolet curable resin on one surface of the backing, it is contacted with the roll for forming the light absorption pattern to form a negative groove in the ultraviolet curable resin. Thereafter, the ultraviolet curable resin is irradiated with ultraviolet rays to complete the background on which the wedge cross-sectional recesses are finally formed. The engraved groove is filled with, for example, an ultraviolet curable resin in which the green wavelength region absorbing material and the anisotropic material are mixed. In the state where the electric field is applied, ultraviolet light is irradiated to complete the light absorption pattern.

However, the present invention is not limited to this, and the intaglio groove of the second background can be obtained by various methods such as a heat press method using a thermoplastic resin, an injection molding method of filling a thermoplastic resin or a thermosetting resin by molding.

The optical filter of FIG. 11 simultaneously obtains the color shift reduction effect by the anisotropic material and the color shift reduction effect by the light absorption pattern, thereby greatly reducing the color shift.

12 is a schematic cross-sectional view of an optical filter according to a fifth exemplary embodiment of the present invention.

6 to 11 illustrate embodiments in which a substrate and an anisotropic material are included over the entire area of the optical filter.

In contrast, FIG. 12 shows that the anisotropic material is not included in the light absorption pattern but may be included only in the background.

13 is a schematic cross-sectional view of an optical filter according to a sixth exemplary embodiment of the present invention.

The optical filter of FIG. 13 includes a background 50 and a light scattering pattern 70. As shown, the anisotropic material can be included only in the light scattering pattern.

Here, the light scattering pattern 70 is similar to the light absorption pattern 60 described above, except that the light scattering pattern 70 may not include the light absorbing material instead of necessarily including the anisotropic material. Of course, as another embodiment, the light scattering pattern may include both an anisotropic material and a light absorbing material.

14 is a schematic cross-sectional view of an optical filter according to a seventh exemplary embodiment of the present invention.

FIG. 14 shows that the optical filter of FIG. 13 may include other functional layers, such as transparent substrate 80 and antireflective layer 90.

15 is a schematic cross-sectional view of a display apparatus according to an eighth exemplary embodiment of the present invention.

As shown, the display device includes a backlight 600, a display module 100, and an optical filter 700.

The optical filter is provided in front of the display module.

In the above, for convenience of description, the LCD of the display device of the present invention was described as an example, but the display device of the present invention is not necessarily limited thereto. The display device of the present invention can be variously applied to a large display device such as PDP, OLED, FED, etc. that implements RGB, a small mobile display device such as a PDA, a small game machine display window, a mobile phone display window, and a soft display device.

1 is a conceptual diagram conceptually showing the basic structure and driving principle of an LCD.

2 is a conceptual diagram illustrating alignment states and light transmittances of liquid crystals according to viewing angles.

3 is a conceptual diagram illustrating an example of the prior art for improving the contrast ratio change and color shift according to the viewing angle.

4 is a conceptual diagram illustrating another example of the related art for improving the contrast ratio change and color shift according to the viewing angle.

5 is a graph showing a color shift according to the viewing angle of the LCD without the optical filter of the present invention.

6 is a cross-sectional view showing an optical filter according to a first embodiment of the present invention.

7 is an enlarged cross-sectional view illustrating an example of an anisotropic material usable in the optical filter of FIG. 6.

8 is an enlarged cross-sectional view illustrating another example of the anisotropic material usable in the optical filter of FIG. 6.

9 to 14 are cross-sectional views schematically showing optical filters according to second to seventh embodiments of the present invention.

15 is an exploded perspective view schematically illustrating a display device according to an eighth embodiment of the present invention.

Claims (15)

A color shift reducing optical filter provided in front of a display module of a display device to reduce color shift, Materials and An anisotropic material having at least two refractive indices and dispersed in the substrate and scattering light by a difference in refractive index with the substrate, The extraordinary refractive index of the anisotropic material is different from the refractive index of the substrate, and when light enters at a greater angle with the normal direction of the optical filter, the substrate and the extraordinary wave enter the extraordinary wave. Color shift reduction optical filter, characterized in that the difference in refractive index increases. The method of claim 1, The optical axis of the anisotropic material is a color shift reduction optical filter, characterized in that along the normal direction of the optical filter. The method according to claim 1 or 2, The normal refractive index of the anisotropic material (ordinary refractive index), color shift reduction optical filter, characterized in that the same as the refractive index of the substrate. delete delete The method of claim 1, The anisotropic material is a color shift reduction optical filter, characterized in that dispersed in the substrate in the form of particles. The method of claim 1, The anisotropic material is a liquid crystal, color shift reduction optical filter, characterized in that dispersed in phase with the substrate. The method of claim 1, The substrate is a color shift reducing optical filter, characterized in that the polymer resin. The method of claim 1, Color shift reducing optical filter comprising the substrate and the anisotropic material over the entire area. The method of claim 1, A light absorption pattern formed to have a background and a depth in the background, The substrate and the anisotropic material are filled in the background, The light absorption pattern, the color shift reduction optical filter, characterized in that it comprises a green wavelength region absorbing material for absorbing the green wavelength region of 510 ~ 560nm. The method of claim 1, A light scattering pattern formed to have a background and a depth in the background, And the substrate and the anisotropic material are filled in the light scattering pattern. 12. The method of claim 11, The light scattering pattern is a wedge section-stripe pattern, wedge section-wavy pattern, wedge section-matrix pattern, wedge section-honeycomb pattern, rectangle section-stripe pattern, rectangle section-wave pattern, rectangle section-matrix pattern or rectangle section-honeycomb Color shift reduction optical filter characterized by having a pattern. 12. The method of claim 11, The light scattering pattern, the color shift reduction optical filter, characterized in that it comprises a green wavelength region absorbing material absorbing the green wavelength region of 510 ~ 560nm. 12. The method of claim 11, The substrate is a color shift reduction optical filter, characterized in that the ultraviolet curable resin. A display apparatus comprising the color shift reducing optical filter of claim 1.

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