KR102034735B1 - Polarizer comprising optical film - Google Patents

Abstract

The polarizing plate according to the present invention, unlike the conventional cyclic PMMA, on one side or optionally both sides of an optical film made of polymethyl methacrylate containing a ring structure of 0% to 3% by weight in the polymer backbone It is possible to reduce the heat resistance and cause the dimensional change more easily, and to prevent bending of the panel due to temperature rise by setting the vertical bending force of the polarizer and to set the optimal point of curling and bending to improve the light leakage phenomenon of the polarizer. There is a characteristic.

Description

Polarizing plate containing film for optics {POLARIZER COMPRISING OPTICAL FILM}

The present invention relates to a polarizing plate including an optical film in which light leakage is improved.

The liquid crystal display uses polarized light, and for this purpose, a polarizing plate is used, and a PVA element is typically used. However, a polarizing plate such as a PVA device has a weak mechanical property and is easily affected by an external environment, for example, temperature or humidity, and thus requires a protective film to protect it.

Such protective films should be excellent in optical properties and in mechanical properties. Conventionally, a TAC film (Tri-Acetyl-cellulose Film) has been used as a protective film for a PVA device used in a polarizing plate, but recently, an acrylic film having better heat resistance and water absorption resistance than a TAC film has been used.

Such a polarizing plate protective acrylic film is manufactured through a stretching process, so that the acrylic resin having a glass transition temperature of 120 ° C. or more is generally used so that the dimensional change at a high temperature is small and the optical properties can be stably maintained. In addition, in order to further improve the dimensional stability and optical properties of the acrylic resin, a monomer having a cyclic structure for imparting heat resistance is introduced. However, when a monomer having a ring structure is introduced, not only the unit cost of the raw material increases but also a problem of processing at a higher temperature.

That is, conventionally, by applying a protective film having a high glass transition temperature as described above to prevent the deformation of the LCD display by applying a film of high heat resistance to the dimensional change of the polarization element by the temperature, through which the light of the LCD display This bird has been trying to stop the phenomenon. However, even in the case of the protective film having a high glass transition temperature of a certain level or more, it was not possible to properly suppress the shrinkage of the PVA device, and it was confirmed that a light leakage phenomenon occurred above a certain level.

The biggest cause of light leakage is due to the anisotropic nature of the polarizing element stretched in a single axis with high magnification, resulting in the collapse of the vertical balance of the LCD.

On the other hand, polymethyl methacrylate (PMMA) is excellent in transparency, there is a possibility to be a film for protecting the polarizing plate, but the glass transition temperature is low, and thus there is a problem that the draw history is released at high temperature, the dimensional stability worsens. In addition, in order to use as a polarizing plate protective film for the IPS mode, a separate phase difference regulator must be added in order to realize a low phase difference value. In this case, the phase difference regulator used must be excellent in compatibility with polymethyl methacrylate and also have a low phase difference. An appropriate content should be included for the realization of the value.

In addition, the polymethyl methacrylate has a negative birefringence characteristic that the refractive index increases in the direction perpendicular to the stretching direction when drawn into a film, so that the retardation agent used for the realization of a low phase difference value increases the refractive index in the stretching direction Must have positive birefringence properties. As a material having such positive birefringence properties, polycarbonate, polyester, phenoxy resin, and the like are known, and most have disadvantages of poor compatibility with polymethylmethacrylate.

Accordingly, the present inventors have made diligent efforts to manufacture an optical film and a polarizing plate including the same to improve light leakage by adjusting the vertical balance of the polarizing plate while using a general polymethyl methacrylate having almost no ring structure monomer in the polymer main chain. As a result, when using a polymethyl methacrylate containing a ring structure of 0% to 3% by weight in the polymer backbone as described below, it was confirmed that the above effects are achieved to complete the present invention.

The present invention provides an optical film made of PMMA containing a ring structure of 0 wt% to 3 wt% or less in the polymer main chain so as to reduce the heat resistance of the protective film, unlike the film applied to the existing polarizing plate to cause more dimensional change It is to.

In addition, the present invention is to provide a polarizing plate comprising the optical film on one side or both sides.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention is a polarizing plate containing an optical film in any one surface of a polarizing element, The optical film is an optical film which consists of polymethylmethacrylate, The said polymethylmethacrylate is a polymer It comprises a ring structure of 0% to 3% by weight in the main chain, the weight average molecular weight of the polymethyl methacrylate is 100,000 to 160,000, it provides a polarizing plate.

In addition, the present invention may provide a polarizing plate that selectively includes the optical film on both sides of the polarizing device according to another embodiment.

Polymethyl methacrylate (PMMA) is excellent in transparency and can be used as an optical film, especially a polarizing plate protective film. However, when the polymethyl methacrylate is produced as a film, a stretching process should be used to increase the mechanical strength. Since the polymethyl methacrylate has a low glass transition temperature, the optical film prepared using the same is stretched when used at a high temperature. There is a problem that the hysteresis is released and the dimensional stability worsens.

In order to improve this, conventionally, there is a method of introducing a monomer having a ring structure in the polymethyl methacrylate polymer backbone, but the manufacturing process is complicated, the cost of the raw material is high, and processing at a higher temperature, This causes a problem in that the end groups of the polymer are decomposed or the low molecular weight additives are thermally decomposed.

In addition, even in the case of the protective film having a high glass transition temperature or more than a certain level, it was not possible to properly suppress the shrinkage of the PVA device, it was confirmed that the light leakage phenomenon occurs above a certain level. In general, in the case of the iodine dyeing type polarizing plate, the film is stretched at a magnification of 5 times or more in the MD direction, so that the force and dimensional change in the MD direction are large.

Thus, in the present invention, by using a polymethyl methacrylate, which will be described later, do not include a cyclic structure in the polymer backbone or by using a polymethyl methacrylate having a minimum content of the cyclic structure, heat resistance than conventional By reducing and inducing a dimensional change as much as the heat resistance is reduced, to match the vertical balance force of the polarizing plate, to provide an optical film and a polarizing plate including the same that can prevent the warping of the panel due to the temperature rise. As the structure of the present invention includes the ring structure in the polymer backbone, Tg rise and fall can be determined and controlled.

Hereinafter, the present invention will be described in more detail.

Polymethyl methacrylate

The term 'poly (methyl methacrylate) (PMMA)' used in the present invention refers to a polymer having methyl methacrylate (MMA) as a main monomer, and particularly, in the present invention, a polymer main chain It means that the cyclic structure to comprise from 0% to 3% by weight of the component.

In this case, when the cyclic structure in the polymethyl methacrylate exceeds 3% by weight, heat resistance according to the ring structure may be increased, but curling and bending characteristics are difficult to control, and thus the panel has a lot of warpage when applied to the polarizing plate. It is not possible to prevent light leakage by being generated.

When the cyclic structure is included in the polymethyl methacrylate, preferably the cyclic structure is more than 0% by weight, 0.1% by weight, 0.5% by weight or more, 1% by weight or more, 3% by weight or less, 2.9% by weight Up to 2.5 weight percent.

Such polymethyl methacrylate is preferably characterized by the following formula (1).

[Formula 1]

Where

A comprises a structure derived from phenyl maleimide or cyclohexyl maleimide,

l is an integer from 0 to 3,

m is an integer of 97 to 100,

n is an integer of 0-3.

In addition, the glass transition temperature of the polymethyl methacrylate is 125 degrees C or less, More preferably, it is 108-125 degreeC, Most preferably, it is 116 degreeC. If the glass transition temperature is less than 108 ° C, there is a problem that the thermal stability is too low when prepared as a film.

At this time, the polymethyl methacrylate of the present invention exhibits a general structure, but the glass transition temperature is lowered, but as the thermal change of the protective film causes more dimensional change, as described below, the optical film has one side of the polarizing element. When placed in, set the optimal point of curl and bending of the polarizer. Moreover, when the said optical film is arrange | positioned on both surfaces of a polarizing element, the optimal point of bending of a polarizing plate is set.

The polymethyl methacrylate may be prepared by a known method except that methyl acrylate monomer, phenylmaleimide, cyclohexyl maleimide, etc. are used in addition to methyl methacrylate, for example, emulsion polymerization method, It can be prepared by a method such as emulsion-suspension polymerization, suspension polymerization. In addition, methacrylic acid may be added if necessary. Preferably, the polymethylmethacrylate is a monomer comprising 97 to 100% by weight of methyl methacrylate monomer, 0 to 3% by weight of methyl acrylate monomer, and 0 to 3% by weight of phenylmaleimide or cyclohexyl maleimide monomer From the mixture can be prepared via polymerization. In the present invention, since the content of the cyclic monomer is minimized during PMMA polymerization, the repeating unit having a cyclic structure in the polymer main chain may be omitted or minimized. Therefore, the present invention further increases the dimensional change by further reducing the heat resistance of the optical film as compared to the conventional, so that the warpage of the panel can be well balanced when heat is applied to the protective film. Therefore, the present invention can improve the light leakage phenomenon in the polarizing plate than the prior art.

In addition, the weight average molecular weight of the polymethyl methacrylate is 100,000 to 160,000. When the weight average molecular weight is less than 100,000, there is a problem in that mechanical properties are poor when the film is manufactured, and when the weight average molecular weight is more than 160,000, stretching is difficult.

Optical film

The present invention also provides an optical film comprising the above-mentioned PMMA. The term "optical film" used in the present invention means a protective film prepared by stretching the above-mentioned PMMA.

In the production of the optical film according to the present invention, any method known in the art, for example, a solution caster method or an extrusion method, may be used, and for example, a melt extrusion method may be used. Specifically, polymethyl methacrylate containing a ring structure of 0 wt% to 3 wt% or less in the polymer backbone as described above is vacuum dried to remove moisture and dissolved oxygen, and then the extruder is nitrogen from the raw material hopper. It was fed to a substituted single or twin extruder, melted at high temperature to obtain raw material pellets, and the obtained raw material pellets were vacuum dried and melted with a single extruder substituted with nitrogen from the raw material hopper to the extruder, followed by a coat hanger type T-die. It can pass through, and can manufacture a film through a chrome plating casting roll, a drying roll, etc. At this time, film forming temperature becomes like this. Preferably it is 150-350 degreeC, More preferably, it is 200-300 degreeC. On the other hand, when forming a film by the T-die method as mentioned above, a T-die is attached to the front-end | tip of a well-known single screw extruder or a twin screw extruder, the film extruded in film shape is wound up, and a roll-shaped film is obtained. Can be.

In addition, when preparing the optical film according to the present invention, one or more components such as antioxidants, UV absorbers, heat stabilizers, etc. may be added to polymethyl methacrylate as necessary. In addition, the content of the additionally added components is not particularly limited, and may be used in an amount of 0.1 to 1 parts by weight based on 100 parts by weight of polymethyl methacrylate, for example.

In particular, the optical film according to the present invention, including the above-described specific polymethyl methacrylate, may further cause a dimensional change due to the lowering of heat resistance, and thus the vertical bending force of the polarizing plate when the optical film is applied to the polarizing plate The panel can be warped by rising temperature. Specifically, in the case of the present invention, the optical film may be included on either side of the polarizing element, or may be optionally included on both sides.

Thus, according to the first preferred embodiment provides a polarizing plate comprising the optical film on one side of the polarizing element. In this case, when the temperature is applied to the optical film, after the expansion in the MD direction and the TD direction as the temperature increases, the curl in the MD direction measured according to the curl measurement method is 6 to 20mm, the curl in the TD direction is 7 to 20 mm, the bending in the MD direction measured according to the glass bending method is 6 to 10mm, the bending in the TD direction is characterized in that 5 to 10mm.

The present invention provides a polarizing plate, optionally comprising the optical film on both sides of the polarizing element, according to a second preferred embodiment. When including the optical film on both sides of the polarizing device, after the expansion in the MD direction and the TD direction with increasing temperature with respect to the optical film, the bending in the MD direction measured by the glass bending method is 6 to 10mm , TD bending is characterized in that 5 to 10mm.

On the other hand, the optical film according to the present invention is preferably produced by biaxially stretching the film made of the above-described PMMA 1.5 times to 2.5 times in the MD direction and 1.5 times to 3.0 times in the TD direction. The stretching is to align the molecules of the polymer contained in the composition for the optical material, affecting the properties of the optical film produced according to the degree of stretching. More preferably, the ratio (TD draw ratio / MD draw ratio) of the draw ratio in the said MD direction and the draw ratio in a TD direction is 1.05 or more and 1.70 or less. The optical film may have a bending difference in the MD direction and a bending difference (ΔMD · TD) in the TD direction from −1.5 to 1.5.

In addition, the stretching temperature is preferably carried out at a temperature of 10 ℃ to 30 ℃ higher than the glass transition temperature of the polymethyl methacrylate.

On the other hand, the thickness of the optical film according to the present invention can be appropriately adjusted as necessary, for example, it is preferably 10um to 100um. More preferably, the thickness of the optical film may be 30um to 80um, most preferably 40um to 60um.

In addition, the present invention is a polarizing plate comprising an optical film on one side or both sides of the polarizing element as described above, the optical film is an optical film made of polymethyl methacrylate, the polymethyl methacrylate is It comprises a ring structure of 0% to 3% by weight in the polymer backbone, the weight average molecular weight of the polymethyl methacrylate is 100,000 to 160,000, it provides a polarizing plate.

As described above, the optical film according to the present invention can be used as a protective film of the polarizing plate, thereby compensating for the mechanical properties of the polarizing plate and protecting the polarizing plate from the influence of the external environment, for example, temperature or humidity.

Figure 1 shows the action when heat is applied to the polarizing plate comprising the optical protective film according to the present invention on either side. As shown in FIG. 1, when heat is applied to a polarizing plate including an optical film, warpage occurs to cause shrinkage and stress. At this time, in addition, in the case of applying the protective film POL, there is a limit to reduction of shrinkage in order to minimize curl generation. In the present invention, the optimal point of curling and bending is set by applying the optical film as described above.

Specifically, the optical film according to the present invention may be attached to one surface of the polarizing plate and used as a polarizing plate protective film. In addition, when the optical film according to the present invention is applied to the liquid crystal display device, the optical film according to the present invention can be used between the polarizing plate and the liquid crystal cell, in this case it can protect the liquid crystal cell and the polarizing plate at the same time. Therefore, the liquid crystal display device may be configured in the order of a polarizing device / protective film / liquid crystal cell / protective film / polarizing device.

Figure 2 shows the action when heat is applied to the polarizing plate comprising the optical protective film according to the invention on both sides. As shown in FIG. 2, when heat is applied to a polarizing plate including an optical film, warpage occurs to cause shrinkage and stress. At this time, in addition, in the case of POL applied to a protective film, there is a limit to reduction of shrinkage in order to minimize curl generation. In the present invention, curling is prevented by applying the optical film as described above, and the optimal point of bending is set. It is characterized by.

Specifically, the optical film according to the present invention is attached to both sides of the polarizing plate may be used as a polarizing plate protective film. In addition, when the optical film according to the present invention is applied to the liquid crystal display device, the optical film according to the present invention can be used between the polarizing plate and the liquid crystal cell, in this case it can protect the liquid crystal cell and the polarizing plate at the same time. Therefore, the liquid crystal display device may be configured in the order of a polarizing device / protective film / liquid crystal cell / protective film / polarizing device.

In addition, the other surface of the polarizing device of the present invention may further include a protective film, an adhesive layer, and the like, for example, a TAC film, or an acrylic film can be used without limitation. The material of the polarizer is not particularly limited since all materials well known in the art may be used.

An example in which the optical film of the present invention is applied to one surface is shown in FIG. 1. As illustrated in FIG. 1, the above-described protective film may be attached to one surface of the polarizer, and a hard coat layer and an adhesive layer may be formed on a lower portion thereof. Therefore, the polarizing plate of the present invention may be configured in the order of the adhesive layer (PSA) / hard coating layer (HC layer) / polarizing element (PVA) / protective film. In this case, the thickness of the optical film (protective film) applied to either side of the polarizing element may be applied in the range of 40 to 60 μm, and the thickness of the hard coating layer may be 3 to 8 μm.

An example in which the optical film of the present invention is applied to both surfaces is shown in FIG. 2. As illustrated in FIG. 2, the above-described protective film may be attached to both surfaces of the polarizer, and an adhesive layer may be formed on the lower portion of the protective film. Therefore, the polarizing plate of the present invention may be configured in the order of the adhesive layer (PSA) / protective film / polarizing element (PVA) / protective film.

In this case, the thickness of the optical film (protective film) applied to both surfaces of the polarizing element can be applied within the same range. For example, the thickness of the double-sided optical film (protective film) may be applied in the range of 40 to 60 μm, and optionally, the thickness of the bottom optical film may be 40 μm.

As described above, the optical film according to the present invention, by using a polymethyl methacrylate having a low glass transition temperature but does not have a ring structure in the polymer backbone or contains almost no ring structure at 3% by weight or less, By using this to reduce the heat resistance of the protective film when manufacturing an optical film is characterized by improving the light leakage phenomenon by adjusting the vertical balance of the polarizing plate through the dimensional change.

Figure 1 schematically shows an example in which the optical protective film according to the present invention is applied to either side.
Figure 2 schematically shows an example in which the optical protective film according to the present invention is applied to both sides.
Figure 3 shows the action when heat is applied to the polarizing plate comprising an optical protective film according to the present invention.
4 is a view showing an operation when heat is applied to a liquid crystal device including a polarizing plate using a polarizing plate using an optical protective film according to the present invention, and a polarizing plate using a protective film using an existing cyclic PMM. will be.

Hereinafter, preferred examples are provided to aid in understanding the present invention. However, the following examples are merely provided to more easily understand the present invention, and the contents of the present invention are not limited thereto.

Production Example  One

In a 5 liter reactor, 1000 g of a mixture of 98 wt% methyl methacrylate and 2 wt% methyl acrylate was added, 2000 g of distilled water, 8.4 g of 5% polyvinyl alcohol solution (POVAL PVA217, kuraray), and dispersion aid 0.1 g of zero boric acid was added and dissolved. To this, 2.5 g of n-octyl mercaptan as a chain transfer agent and 1.5 g of 2,2'-azobisisobutyronitrile as a polymerization initiator were added and dispersed in an aqueous phase while stirring at 400 rpm to prepare a suspension. It heated up to 80 degreeC and superposed | polymerized for 90 minutes, and then cooled to 30 degreeC. The obtained beads were washed with distilled water, dehydrated, and dried to prepare a polymethylmethacrylate resin. The glass transition temperature and molecular weight of the prepared resin were measured, and the glass transition temperature was 116 ° C. and the weight average molecular weight was 120,000. The glass transition temperature was measured under a temperature rising condition of 10 ° C./min using a differential scanning calorimeter (DSC) manufactured by Mettler Toledo.

Production Example  2

In a 5 liter reactor, 1000 g of a monomer mixture of 99.5 wt% methyl methacrylate and 0.5 wt% methyl acrylate were added, 2000 g of distilled water, 8.4 g of 5% polyvinyl alcohol solution (POVAL PVA217, kuraray), and dispersion aid 0.1 g of zero boric acid was added and dissolved. To this, 2.5 g of n-octyl mercaptan as a chain transfer agent and 1.5 g of 2,2'-azobisisobutyronitrile as a polymerization initiator were added and dispersed in an aqueous phase while stirring at 400 rpm to prepare a suspension. It heated up to 80 degreeC and superposed | polymerized for 90 minutes, and then cooled to 30 degreeC. The obtained beads were washed with distilled water, dehydrated, and dried to prepare a polymethylmethacrylate resin. The glass transition temperature and molecular weight of the prepared resin were measured, and the glass transition temperature was 116 ° C. and the weight average molecular weight was 120,000. The glass transition temperature was measured under a temperature rising condition of 10 ° C./min using a differential scanning calorimeter (DSC) manufactured by Mettler Toledo.

Production Example  3

In a 5 liter reactor, 1000 g of a monomer mixture of 98 wt% methyl methacrylate and 2 wt% phenyl maleimide were added, 2000 g of distilled water, 8.4 g of 5% polyvinyl alcohol solution (POVAL PVA217, kuraray), and dispersion aid 0.1 g of zero boric acid was added and dissolved. To this, 2.5 g of n-octyl mercaptan as a chain transfer agent and 1.5 g of 2,2'-azobisisobutyronitrile as a polymerization initiator were added and dispersed in an aqueous phase while stirring at 400 rpm to prepare a suspension. It heated up to 80 degreeC and superposed | polymerized for 90 minutes, and then cooled to 30 degreeC. The obtained beads were washed with distilled water, dehydrated, and dried to prepare a polymethylmethacrylate resin. The glass transition temperature and molecular weight of the prepared resin were measured, and the glass transition temperature was 118 ° C. and the weight average molecular weight was 130,000. The glass transition temperature was measured under a temperature rising condition of 10 ° C./min using a differential scanning calorimeter (DSC) manufactured by Mettler Toledo.

Production Example  4

In a 5 liter reactor, 1000 g of a mixture of 92 wt% of methyl methacrylate, 6 wt% of phenyl maleimide, and 2 wt% of alpha methylstyrene were added, and 2000 g of distilled water and 8.4 g of a 5% polyvinyl alcohol solution (POVAL PVA217). , kuraray)), and 0.1 g of boric acid were added as a dispersing aid and dissolved. To this, 2.5 g of n-octyl mercaptan as a chain transfer agent and 1.5 g of 2,2'-azobisisobutyronitrile as a polymerization initiator were added and dispersed in an aqueous phase while stirring at 400 rpm to prepare a suspension. It heated up to 80 degreeC and superposed | polymerized for 90 minutes, and then cooled to 30 degreeC. The obtained beads were washed with distilled water, dehydrated, and dried to prepare a polymethylmethacrylate resin. The glass transition temperature and molecular weight of the prepared resin were measured, and the glass transition temperature was 125 ° C. and the weight average molecular weight was 114,000. The glass transition temperature was measured under a temperature rising condition of 10 ° C./min using a differential scanning calorimeter (DSC) manufactured by Mettler Toledo.

Example  1 to 7

As shown in Table 1 below, in the polymethyl methacrylate prepared in Preparation Example 1, Preparation Example 2, or Preparation Example 3, the UV absorber (Tinuvin 360, BASF Co., Ltd.) 1.5 wt%, based on the solid content, antioxidant ( The final resin composition was prepared by compounding 1.5 wt% of Irganox 1010, BASF Co.). This was melted at 265 ° C. and extrusion cast in the form of a sheet through T-Die, and then biaxially stretched at a stretching temperature and a draw ratio as shown in Table 1 to prepare an optical film.

Comparative example  1 to 5

In the polymethyl methacrylate prepared in Preparation Example 4, 1.5 wt% of a UV absorber (Tinuvin 360, BASF) based on solids and 1.5 wt% of an antioxidant (Irganox 1010, BASF) based on solids Resin compositions were prepared. This was melted at 265 ° C. and extrusion cast in the form of a sheet through T-Die, and then biaxially stretched at a stretching temperature and a draw ratio as shown in Table 1 to prepare an optical film.

Experimental Example  One

The characteristics were evaluated as follows using the optical film prepared in Examples 1 to 7 and Comparative Examples 1 to 5.

1) Thermal Shrinkage: After the optical film was prepared with a sample having a size of 20 × 200 mm, the length of change in the MD direction and the TD direction relative to the initial length was measured after 12 hours in an oven at 80 ° C.

2) Polarizer Curl Measurement Method: Prepare a polarizer specimen cut to MD 200mm × TD 200mm, store the specimen with the concave side facing up on a horizontal table at 24 ° C and 50% RH for 1 hour, and then store the specimen. The height of four corners of the table lifted from the table was measured using a ruler, and the maximum value was defined as the amount of curl.

3) Bending: An optical film was used as a protective film of a PVA polarizing element, and on the opposite side, a hard coating layer was coated to prepare a polarizing plate. After the polarizing plate was cut to 140 × 20 mm in the MD and TD directions, the PSA was laminated on the hard coating layer, and the hard coating layer was laminated on 0.7 t glass having a size of 150 × 30 mm. The polarizing plate laminated on the glass was kept in an oven at 80 ° C. for 24 hours, and then aged at room temperature for 24 hours. After fixing one side of the curved polarizing plate to the ground, the other height of the floating polarizing plate was measured to set this as the Pol Bending value.

4) ΔMD · TD: The difference between the bending value in the MD direction and the bending value in the TD direction of the polarizing plate measured above.

5) Light leakage Lv .: After the display was manufactured by a conventional method using a polarizer manufactured in actual manner, the light leakage phenomenon was visually observed after driving for 72 hours in an oven at 60 ° C., and then divided into Lv.

(O Lv: No light leakage ~ 5 Lv: Light leakage occurs considerably (90% more than light leakage))

The results are shown in Tables 1 and 2 below.

unit Example One 2 3 4 5 6 7 PMMA Preparation Example 1 Preparation Example 1 Preparation Example 1 Preparation Example 1 Preparation Example 1 Preparation Example 2 Preparation Example 3 Ring structure weight% 0 0 0 0 0 0 2 Tg ℃ 116 116 116 116 116 116 118 Elongation ratio MD stomach × 2 × 2 × 2 × 2 × 2 × 2 × 2 TD stomach × 2 × 1.8 × 2.3 × 2.3 × 2.3 × 2.3 × 2 Drawing temperature MD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 10 Tg + 20 Tg + 20 Tg + 20 TD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 20 Tg + 10 Tg + 10 Tg + 20 Heat shrinkage MD % 0.052 0.048 0.04 0.072 0.059 0.071 0.030 TD % 0.041 0.055 0.082 0.077 0.087 0.148 0.021 Curl MD [mm] 7 7 10 12 10 14 6 TD [mm] 8 8 8 9 8 16 5 Bending MD [mm] 6.3 6.1 6 7.2 6.9 6.6 6.3 TD [mm] 5.2 5.5 6.2 6 6.3 8 4.1 ΔMD, TD [mm] 1.1 0.6 -0.2 1.2 0.6 -1.4 2.2 Light Fountain Lv. Visually 2 0.5 0.5 One 0.5 One 2

unit Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 PMMA Preparation Example 4 Preparation Example 4 Preparation Example 4 Preparation Example 4 Preparation Example 4 Ring structure weight% 6 6 6 6 6 Tg ℃ 125 125 125 125 125 Elongation ratio MD stomach × 2 × 2 × 2 × 2 × 2 TD stomach × 2 × 1.8 × 2.3 × 2.3 × 2.3 Drawing temperature MD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 10 Tg + 20 TD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 20 Tg + 10 Heat shrinkage MD % 0.001 0.004 0.003 0.004 0.003 TD % 0.001 0.003 0.004 0.003 0.002 Curl MD [mm] 4 4 4 4 4 TD [mm] 6 6 6 6 6 Bending [mm] MD [mm] 5.5 5.4 5.2 5.2 5.6 TD [mm] 2.3 2.1 2.1 2 2.2 ΔMD, TD [mm] 3.2 3.3 3.1 3.2 3.4 Light Fountain Lv. Visually 2 2 2 2 2

As shown in Tables 1 and 2, in the case of Examples 1 to 7, since the optical film to be applied to any one side of the polarizing device using PMMA having a ring structure ratio of 0% to 3% by weight, any stretching Even under the conditions, the shrinkage rate, curling property, and bending property were remarkably superior to Comparative Examples 1 to 5, and light leakage was improved.

On the other hand, Comparative Examples 1 to 5 used the optical film made of PMMA having a ring structure of 6% by weight under the same drawing temperature conditions, and thus a lot of light leakage occurred due to poor heat shrinkage, curl and bending characteristics. Therefore, the optical film made of PMMA including the ring structure in the range of 4% by weight to 10% by weight can not prevent the leakage of light of the LCD display, and thus can not suppress the shrinkage of the PVA device.

Experimental Example  2

After using the optical film of Example 1 and Comparative Example 1 in the usual manner to prepare a polarizing plate of the structure of the structure in which the optical film is applied to one side as shown in Figure 2, the polarizing plate is sandwiched between the liquid crystal cell It arrange | positioned and manufactured the liquid crystal display element like FIG. Then, the state was confirmed after applying 80 degreeC heat with respect to the said liquid crystal display element.

4 is a view showing an operation when heat is applied to a liquid crystal device including a polarizing plate using a polarizing plate using an optical protective film according to the present invention, and a polarizing plate using a protective film using an existing cyclic PMM. will be.

As shown in Figure 4, in the case of the present invention by using the above-described specific polymethyl methacrylate as the material of the optical film, it is possible to appropriately adjust the bending force of the upper and lower sides of the polarizing plate, to catch the warpage of the panel according to the temperature rise. Therefore, the present invention was found to include the optical film on either side of the polarizer to minimize the occurrence of curl to set the optimum point of bending.

Example  8 to 12

As shown in Table 3 below, 1.5 wt% of the UV absorber (Tinuvin 360, BASF Co., Ltd.) and the antioxidant (Irganox 1010, BASF Co., Ltd.) were added to the polymethylmethacrylate prepared in Preparation Example 1, based on solid content. 1.5 wt% was compounded to prepare a final resin composition. This was melted at 265 ° C. and extrusion cast in the form of a sheet through T-Die, and then biaxially stretched at a stretching temperature and a draw ratio as described in Table 3 below to prepare an optical film.

Example  13 to 17

As shown in Table 4 below, 1.5 wt% of the UV absorber (Tinuvin 360, BASF) and the antioxidant (Irganox 1010, BASF) based on the solid content in the polymethyl methacrylate prepared in Preparation Example 3 1.5 wt% was compounded to prepare a final resin composition. This was melted at 265 ° C. and extrusion cast in the form of a sheet through T-Die, and then biaxially stretched at a stretching temperature and a draw ratio as described in Table 3 below to prepare an optical film.

Comparative example  6 to 10

As shown in Table 5 below, 1.5 wt% of the UV absorber (Tinuvin 360, BASF Co., Ltd.) and the antioxidant (Irganox 1010, BASF Co., Ltd.) were added to the polymethylmethacrylate prepared in Preparation Example 4, based on solid content. 1.5 wt% was compounded to prepare a final resin composition. This was melted at 265 ° C. and extrusion cast in the form of a sheet through T-Die, and then biaxially stretched at a stretching temperature and a draw ratio as described in Table 3 below to prepare an optical film.

Experimental Example  3

The characteristics were evaluated as follows using the optical film prepared in Examples 8 to 17 and Comparative Examples 6 to 10.

1) Bending: The optical film was made into the protective film of a PVA polarizing element, and it laminated on both surfaces, and manufactured the polarizing plate. After the polarizing plate was cut to 140 × 20 mm in the MD and TD directions, PSA was laminated on one side of the protective film, and one side of the protective layer was laminated on 0.7 t glass having a size of 150 × 30 mm. The polarizing plate laminated on the glass was kept in an oven at 80 ° C. for 24 hours, and then aged at room temperature for 24 hours. After fixing one side of the curved polarizing plate to the ground, the other height of the floating polarizing plate was measured to set this as the Pol Bending value.

2) ΔMD · TD: The difference between the bending value in the MD direction and the bending value in the TD direction of the polarizing plate measured above.

3) Light leakage Lv .: After the display was manufactured by a conventional method using a polarizer manufactured in real time, the light leakage phenomenon was visually observed after driving for 72 hours in an oven at 60 ° C., and the Lv was divided.

(O Lv: No light leakage ~ 5 Lv: Light leakage occurs considerably (90% more than light leakage))

The results are shown in Tables 3 to 5 below.

unit Example 8 Example 9 Example 10 Example 11 Example 12 PMMA Preparation Example 1 Preparation Example 1 Preparation Example 1 Preparation Example 1 Preparation Example 1 Ring structure weight% 0 0 0 0 0 Tg ℃ 116 116 116 116 116 Elongation ratio MD stomach × 2 × 2 × 2 × 2 × 2 TD stomach × 2 × 1.8 × 2.3 × 2.3 × 2.3 Drawing temperature MD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 10 Tg + 20 TD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 20 Tg + 10 Bending MD [mm] 8.2 8.2 8.3 9.2 9 TD [mm] 7.5 6.8 8 8.3 88 ΔMD, TD [mm] 0.7 1.4 0.3 0.9 0.2 Light Fountain Lv. Visually One 2 One 2 2

unit Example 13 Example 14 Example 15 Example 16 Example 17 PMMA Preparation Example 3 Preparation Example 3 Preparation Example 3 Preparation Example 3 Preparation Example 3 Ring structure weight% 2 2 2 2 2 Tg ℃ 118 118 118 118 118 Elongation ratio MD stomach × 2 × 2 × 2 × 2 × 2 TD stomach × 2 × 1.8 × 2.3 × 2.3 × 2.3 Drawing temperature MD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 10 Tg + 20 TD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 20 Tg + 10 Bending MD [mm] 9.2 8.3 8.3 9.2 8.3 TD [mm] 7.5 7.5 8.1 7.7 9.1 ΔMD, TD [mm] 1.7 0.8 0.2 1.5 -0.8 Light Fountain Lv. Visually 2 One 2 2 2

unit Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 PMMA Preparation Example 4 Preparation Example 4 Preparation Example 4 Preparation Example 4 Preparation Example 4 Ring structure weight% 6 6 6 6 6 Tg ℃ 125 125 125 125 125 Elongation ratio MD stomach × 2 × 2 × 2 × 2 × 2 TD stomach × 2 × 1.8 × 2.3 × 2.3 × 2.3 Drawing temperature MD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 10 Tg + 20 TD ℃ Tg + 20 Tg + 20 Tg + 20 Tg + 20 Tg + 10 Bending [mm] MD [mm] 7.7 7.7 7.8 8.2 8.2 TD [mm] 4.5 4.5 4.6 4 4.3 ΔMD, TD [mm] 3.2 3.2 3.2 4.2 3.9 Light Fountain Lv. Visually 4 4 4 4.5 4

As shown in Tables 3 to 5, in Examples 8 to 17, since the optical film is applied to both sides of the polarizing device using a PMMA having a ring structure ratio of 0 wt% to 3 wt% or less, any stretching conditions Also in the shrinkage, bending properties were significantly better than Comparative Examples 6 to 10 and it was confirmed that the light leakage was improved.

On the other hand, Comparative Examples 6 to 10 in the same stretching temperature conditions using the optical film made of PMMA having a ring structure of 6% by weight, a lot of light leakage occurs due to poor heat shrinkage and bending characteristics. Therefore, the optical film made of PMMA including the ring structure in the range of 4% by weight to 10% by weight can not prevent the leakage of light of the LCD display, and thus can not suppress the shrinkage of the PVA device.

Experimental Example  4

After using the optical film of Example 8 and Comparative Example 6 in the usual manner to prepare a polarizing plate having a structure in which the optical film is applied to both sides as shown in Figure 2, the polarizing plate is disposed between the liquid crystal cell between The liquid crystal display element like 4 was manufactured. Then, the state was confirmed after applying 80 degreeC heat with respect to the said liquid crystal display element.

As a result, in the case of the present invention, by using the above-described specific polymethyl methacrylate as the material of the optical film, it is possible to appropriately adjust the vertical bending force of the polarizing plate, to catch the warpage of the panel due to the temperature rise. Therefore, it was confirmed that the present invention can set the optimum point of bending.

Claims (10)

As a polarizing plate containing an optical film in any one surface of a polarizing element,
The optical film is an optical film made of polymethyl methacrylate, the polymethyl methacrylate comprises a ring structure of 0% to 3% by weight in the polymer backbone,
The weight average molecular weight of the polymethyl methacrylate is 100,000 to 160,000,
After the expansion in the MD direction and the TD direction with increasing temperature with respect to the optical film, the curl in the MD direction measured according to the curl measurement method is 6 to 20mm, the curl in the TD direction is 7 to 20mm, Glass bending method It is characterized in that the bending in the MD direction of 6 to 10mm, the bending in the TD direction of 5 to 10mm,
Polarizer.
delete The method of claim 1,
To include the optical film on both sides of the polarizing element,
Polarizer.
The method of claim 3,
When including the optical film on both sides of the polarizing device, after the expansion in the MD direction and the TD direction with increasing temperature with respect to the optical film, the bending in the MD direction measured by the glass bending method is 6 to 10mm , The bending in the TD direction is 5 to 10 mm,
Polarizer.
The method of claim 1,
The polymethyl methacrylate is characterized in that represented by the following formula (1),
Polarizer.
[Formula 1]

Where
A comprises a structure derived from phenyl maleimide or cyclohexyl maleimide,
l is an integer from 0 to 3,
m is an integer of 97 to 100,
n is an integer of 0-3.
The method of claim 1,
The polymethylmethacrylate is prepared from a monomer mixture comprising from 97 to 100% by weight of methyl methacrylate monomer, from 0 to 3% by weight of methyl acrylate monomer, and from 0 to 3% by weight of phenylmaleimide or cyclohexyl maleimide monomer. felled,
Polarizer.
The method of claim 1,
Characterized in that the glass transition temperature of the polymethyl methacrylate is 108 to 125 ℃,
Polarizer.
The method of claim 1,
The optical film is produced by biaxially stretching the polymethyl methacrylate 1.5 times to 2.5 times in the MD direction and 1.5 times to 3.0 times in the TD direction,
Polarizer.
The method of claim 1,
The optical film is characterized in that the bending difference in the MD direction and the bending direction (ΔMD · TD) in the TD direction is -1.5 or more and 1.5 or less,
Polarizer.
The method of claim 8,
The stretching is characterized in that carried out at a temperature of 10 ℃ to 30 ℃ higher than the glass transition temperature of the polymethyl methacrylate,
Polarizer.

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