TW202134044A - Polarizer and display apparatus using the same - Google Patents

Abstract

Provided are a polarizing plate having excellent durability under high temperatures and a display device using same. The polarizing plate includes a protective film A bonded together with one surface of a polarizer and a protective film B bonded together with the other surface, and the moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B at 40 DEG C and 90% RH simultaneously satisfy conditions (1) and (2) indicated below. Condition (1): 240 g/m2/day > TA > 70 g/m2/day. Condition (2): 70 g/m2/day ≥ TB.

Description

Polarizing plate and display device using the same

The present invention relates to a polarizing plate and a display device using the polarizing plate.

The polarizer used in the liquid crystal display device is equipped with the following polarizer: the iodine compound and organic dye are adsorbed on the polyvinyl alcohol (PVA) film, the PVA film is stretched, and the iodine compound and the organic dye are aligned. Polarizer. The polarizer formed by using PVA film has poor strength and water resistance, so a protective film is attached to both sides of the polarizer to protect the polarizer.

Conventionally, as a protective film for a polarizing plate, a hard coat film with a hard coat layer provided on one side of a triacetate cellulose (TAC) film is generally used (for example, refer to Patent Document 1). However, the moisture permeability of the hard-coated film made of TAC film as the substrate is ^{about 300-1000g/m 2} /day. Under high temperature and high humidity, the moisture absorption of the polarizer cannot be sufficiently suppressed, which may cause the polarizer. The problem of deterioration. Therefore, in order to improve the moisture resistance of the protective film using TAC film as the base material, various types of cyclic olefin polymer (COP) and polyethylene terephthalate (PET) as base materials have been developed. For the protective film used (for example, refer to Patent Document 2), the moisture permeability of the protective film is gradually reduced to ^{about 5-100 g/m 2} /day. [Prior Technical Documents] [Patent Documents]

[Patent Document 1] JP 2016-175991 A [Patent Document 2] JP 2006-30870 A

[The problem to be solved by the invention]

In recent years, the number of display devices mounted on vehicles is increasing. Since display devices for vehicles are used in extremely harsh environments with high temperatures, polarizers are also required to have durability in high-temperature environments.

By using the above-mentioned protective film using low moisture permeability substrates such as COP and PET, it is possible to sufficiently reduce the intrusion of moisture from the outside of the polarizer into the polarizer. However, it is known that when the polarizer is exposed to a high temperature environment such as in a car, the moisture contained in the base material of the protective film or the moisture contained in the adhesive used when the protective film is bonded to the polarizer will penetrate into the polarized light. The inside of the plate and continue to stay there, so the polarizer will be degraded due to the moisture.

Therefore, the purpose of the present invention is to provide a polarizing plate with excellent durability at high temperatures and a display device using the polarizing plate. [Means to solve the problem]

The polarizing plate of the present invention is a polarizing plate in which a protective film A is attached to one side of the polarizer and a protective film B is attached to the other side. The protective films A and B at 40°C and 90%RH The moisture permeability TA and TB satisfy the following conditions (1) and (2) at the same time: 240g/m ² /day＞TA＞70g/m ² /day (1) 70g/m ² /day≧TB (2).

Furthermore, the display device of the present invention includes the above-mentioned polarizing plate. [Effects of Invention]

According to the present invention, it is possible to provide a polarizing plate having excellent durability at high temperatures and a display device using the polarizing plate.

[Form to implement the invention]

Fig. 1 is a cross-sectional view showing the schematic configuration of the polarizing plate of the embodiment.

The polarizing plate 10 is provided with a polarizer 1, a protective film A laminated on one side of the polarizer 1, and a protective film B laminated on the other side of the polarizer 1. The polarizer 1 is formed by adsorbing and aligning iodine or dye on a polyvinyl alcohol (PVA) film. The PVA constituting the polarizer 1 is poor in strength and water resistance, so protective films A and B are attached to both sides of the polarizer 1.

The protective film A is a hard coat film with a hard coat layer laminated on one surface of the TAC film. The hard coat layer is a functional layer that covers the soft TAC film and imparts hardness to the protective film A, and can be formed by applying and curing a coating liquid containing an ultraviolet curable material. The pencil hardness of the protective film A (hard-coated film) is preferably 3H or more. In addition, the TAC film has low water vapor barrier properties (high moisture permeability), and the moisture permeability of the protective film can be adjusted by the hard coat layer. Specifically, by blending a hydrophobic material on the hard coat layer, the moisture permeability of the protective film A can fall within the range described later. As the hydrophobic material contained in the hard coat layer, for example, a cycloolefin polymer can be used. The TAC film of the protective film A can be attached to the polarizer 1 using a water paste (PVA aqueous solution).

The thickness of the TAC film used on the protective film A is not particularly limited, and it is preferably 25-100 μm. In addition, the thickness of the hard coat layer is not particularly limited, but it is preferably 2 to 15 μm. Among them, as long as the moisture permeability of the protective film A is in the range described later, the thickness of the TAC film and the film thickness of the hard coat layer can be appropriately changed.

The protective film B is a low-moisture-permeable film, and can be composed of any of a cycloolefin polymer, polyethylene terephthalate, and polymethyl methacrylate. The protective film B is bonded to the polarizer 1 with an ultraviolet curable adhesive. The thickness of the protective film B is not particularly limited, but is preferably 10 to 100 μm.

In addition, in a display device equipped with a display panel and a polarizing plate, the protective film B is arranged on the display panel side, and the hard coat layer of the protective film A is arranged on the visual recognition side (the opposite side of the display panel).

The polarizer 1 and the TAC film of the protective film A can be bonded together using water paste as an adhesive. Therefore, even after the drying step, moisture can still be contained in the adhesive layer and the TAC film. If it is assumed that both protective films A and B are made of films with low moisture permeability, although the intrusion of moisture from the outside can be suppressed, but in the extremely high temperature environment such as the car interior in summer, due to the adhesive layer and/or The moisture contained in the TAC film continues to stay in the polarizer 10, which will cause the polarizer 1 to deteriorate. Therefore, for the polarizing plate 10 of this embodiment, the moisture permeability of the protective film A and the moisture permeability of the protective film B are different, and the moisture permeability of the protective film A and the moisture permeability of the protective film B are respectively set at The specific range suppresses the deterioration of the polarizer 1 caused by moisture from the adhesive and/or TAC film.

Specifically, when the moisture permeability of the protective films A and B at 40° C. and 90% RH are set to TA and TB, respectively, TA and TB satisfy the following conditions (1) and (2) at the same time. In addition, the water vapor permeability TA and TB are the values measured based on JIS Z 0208:1976. 240g/m ² /day＞TA＞70g/m ² /day (1) 70g/m ² /day≧TB (2)

By satisfying the above conditions (1) and (2) at the same time, the intrusion of water from the outside into the inside of the polarizing plate can be suppressed. The moisture generated by the TAC film of the protective film A is discharged to the outside.

The moisture permeability TA of the protective film A is preferably 180g/m ² /day. At this time, in order to adjust the moisture permeability of the protective film A, the amount of hydrophobic material contained in the hard coat layer can be reduced, so the surface hardness of the hard coat layer is excellent. In addition, since the protective film B is used to completely isolate water from entering and exiting, the moisture permeability TB of the protective film B is preferably small.

As described above, the polarizing plate 10 of the present embodiment includes the protective film A having the moisture permeability satisfying the above condition (1) and the protective film B having the moisture permeability satisfying the above condition (2) as the protective film of the polarizer 1. With this configuration, the protective film B arranged on the display panel side almost blocks the entry and exit of moisture. On the other hand, although the protective film A arranged on the visual recognition side suppresses the intrusion of moisture from the outside into the inside of the polarizing plate 10, it may release the moisture generated inside the polarizing plate 10. Therefore, when the polarizing plate 10 of this embodiment is used in a high-temperature environment, the moisture generated inside the polarizing plate 10 will not be retained, so the deterioration of the polarizing plate can be suppressed, and the polarizing plate 10 can be maintained for a longer period of time. Optical performance.

The TAC film of the protective film A can be attached to the PVA film of the polarizer 1 using a water paste (PVA aqueous solution) as an adhesive. In order to ensure the adhesion between the TAC film and the PVA film, the protective film A can be saponified before bonding. Among them, when the saponification treatment is performed, not only the surface of the TAC film, but also the contact angle of the surface on the opposite side also becomes smaller, which causes the moisture permeability of the protective film A to increase. The increase in the moisture permeability of the protective film A is considered to be due to the decrease in the contact angle of the surface opposite to the TAC film, which makes it difficult to bounce off water, that is, it presents a state in which water can easily pass through. After review by the inventor of this case, it was found that if the contact angle of the protective film A on the opposite side (the surface of the TAC film) to the polarizer (the surface of the TAC film) after saponification is above the predetermined value, it can be Fully reduce the moisture permeability of the protective film A.

Specifically, the contact angle CA after saponification of the surface opposite to the bonding surface in the protective film A satisfies the following condition (3). In addition, the contact angle CA after saponification is after the protective film A is immersed in a 2.0N sodium hydroxide aqueous solution at 50°C for 60 seconds, washed with pure water for 30 seconds, and dried in an oven at 100°C for 60 seconds. , The value measured in accordance with JIS R 3257: 1999. 70°≦CA≦120° (3)

When the saponified contact angle CA of the surface opposite to the bonding surface of the protective film A is less than 70°, the water vapor transmission rate of the protective film A becomes higher (moisture becomes easier to penetrate). The higher the contact angle CA after saponification of the surface opposite to the bonding surface, the more the moisture permeability of the protective film A can be reduced. However, when the protective film A with a hard coat layer is provided on the TAC film, the The contact angle of the hard coat surface on the opposite side is 120° or less. In addition, the saponified contact angle CA of the surface opposite to the bonding surface can be based on the blending ratio of the hydrophobic compound in the adhesive component used to form the coating film laminated in the form of a TAC film and the coating solution. The type of leveling agent used can be adjusted. When the saponified contact angle CA of the surface of the protective film A on the opposite side to the bonding surface satisfies the above condition (1), the adhesion between the protective film A and the polarizer 1 can be ensured, and the moisture permeability of the protective film A can be reduced. . [Example]

Hereinafter, examples of concretely implementing the present invention will be described.

A. Examples 1 to 7 and Comparative Examples 1 to 4 (Example 1) The composition 1 described in Table 1 as a coating liquid for forming a hard coat layer was coated on a TAC film ( Trade name: TJ40UL manufactured by Fuji Film Co., Ltd.). After drying, ^{ultraviolet rays were irradiated on the coating film at an exposure amount of 100 mJ/cm 2} to harden the protective film A (hard coating film) of Example 1. The film thickness of the hard coat layer after hardening is the value described in Table 2. In addition, a COP film with a thickness of 5 μm is regarded as the protective film B.

Paste the polarizer on the TAC film surface of the protective film A using a water paste, and after drying, bond the protective film to the polarizer using an ultraviolet curable adhesive, and cure the ultraviolet curable adhesive by irradiating ultraviolet rays. The polarizing plate of Example 1 was obtained.

[Table 1] Substrate HC coating Main material Hydrophobic material Photopolymerization initiator Solvent Material name Blending amount (parts by weight) Material name Blending amount (parts by weight) Material name Blending amount (parts by weight) Solvent 1 Blending amount (parts by weight) Solvent 2 Blending amount (parts by weight) Composition 1 TAC Neopentyl erythritol triacrylate 39.9 Cycloolefin polymer 0.1 Irgacure184 5 Dimethyl carbonate 32.5 MIBK 17.5 Composition 2 39.7 0.3 Composition 3 39.5 0.5 Composition 4 39.0 1.0 Composition 5 39.8 2.0 Composition 6 Composition 7 Composition 8 40.0 - - TPO Irgacure184 3 7 Composition 9 40.0 - - Irgacure184 5

(Examples 2-7) Except having used the composition 2-7 described in Table 1 as the coating liquid for hard-coat layer formation, it carried out similarly to Example 1, and produced the polarizing plate of Examples 2-7.

(Comparative Example 1) Except that the composition 8 described in Table 1 was used as the coating liquid for forming a hard coat layer, and the ultraviolet exposure amount was set to 75 mJ/cm ² , it was produced in the same manner as in Example 1 The polarizing plate of Comparative Example 1 was produced.

(Comparative example 2) The polarizing plate of Comparative Example 2 was produced in the same manner as in Example 1 except that the composition 9 described in Table 1 was used as the coating liquid for forming a hard coat layer.

(Comparative example 3) Except for using a PMMA film with a thickness of 40 μm as the protective film A, the operation was performed in the same manner as in Example 1, and a polarizing plate of Comparative Example 3 was produced.

(Comparative Example 4) A polarizing plate of Comparative Example 4 was produced in the same manner as in Example 1 except that a COP film with a thickness of 5 μm was used as the protective film A.

(Water permeability) According to JIS Z 0208:1976, the moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B attached to the polarizer are measured under the conditions of 40°C and 90%RH.

(Polarization after high temperature and high humidity endurance test) The polarizing plates of Examples 1 to 7 and Comparative Examples 1 to 4 were put into a thermostat at 85° C. and 85% RH, and the degree of polarization was measured after 240 hours and 500 hours from the start of the input. In addition, the degree of polarization is a value measured through an absorbance photometer ("V7100" manufactured by JASCO Corporation) with an integrating sphere, and the visual sensitivity is corrected with a 2 degree field of view (light source C) of "JIS Z 8701". And calculated.

Table 2 shows the moisture permeability TA of the protective film A, the moisture permeability TB of the protective film B, and the degree of polarization of the polarizing plate (initial value, high temperature and high humidity endurance test) used in Examples 1-7 and Comparative Examples 1-4 Before and after) the measured value.

[Table 2] Protective film A characteristics Protective film B characteristics Polarizer characteristics constitute HC composition <Refer to Table 1> HC film thickness (μm) Moisture permeability: TA ＜g/m ² /day＞ (40℃-90%RH) constitute Moisture permeability: TB ＜g/m ² /day＞ ＜40℃-90%RH＞ Polarization After high temperature and high humidity endurance test (85℃, 85%RH) Early 240hrs. after input 500hrs. After putting in Example 1 Hard-coated multilayer TAC film Composition 1 7 215 Cycloolefin polymer 5 99.510 99.502 99.459 Example 2 Composition 2 7 204 99.505 99.480 Example 3 Composition 3 7 179 99.505 99.482 Example 4 Composition 4 7 155 99.506 99.481 Example 5 Composition 5 7 102 99.507 99.481 Example 6 Composition 6 9 91 99.507 99.466 Example 7 Composition 7 12 80 99.496 99.461 Comparative example 1 Composition 8 7 295 99.388 Unable to determine Comparative example 2 Composition 9 7 270 99.406 Unable to determine Comparative example 3 PMMA film - - 40 99.407 Unable to determine Comparative example 4 COP film - - 5 99.396 Unable to determine

The moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B of the polarizing plate of Examples 1-7 meet the above conditions (1) and (2), even if they are put in a constant temperature bath at 85°C and 85%RH In the case of 500 hours, the value of high degree of polarization is also displayed. The test results after the high-temperature and high-humidity endurance test of Examples 1-7 show that even if exposed to high-temperature and high-humidity, the deterioration of the polarizer due to moisture intruding into the polarizer from the outside and the protective film A and/or used No deterioration of the polarizer due to moisture contained in the adhesive to which the protective film A was attached did not occur.

The polarizing plate protective film A of Comparative Examples 1 and 2 has a high moisture permeability TA, which exceeds the upper limit of the above condition (1). The polarizing plates of Comparative Examples 1 and 2 were placed in a thermostat at 85° C. and 85% RH for 240 hours. The degree of polarization was lower than those of Examples 1-7. In addition, when the polarizing plates of Comparative Examples 1 and 2 are placed in a constant temperature bath at 85°C and 85%RH for 500 hours, the polarizers are excessively deteriorated, and the amount of light passing through the polarizing plates (that is, the amount of light leaking) becomes Too much to measure the degree of polarization. From the comparison between Comparative Examples 1 and 2 and Examples 1-7, it can be seen that in the polarizing plates of Comparative Examples 1 and 2, moisture invades from the protective film A into the inside of the polarizing plate under high temperature and high humidity, resulting in deterioration of the polarizer.

The moisture permeability TA of the polarizing plate-based protective film A of Comparative Examples 3 and 4 is lower than the lower limit of the above condition (1). The polarizing plates of Comparative Examples 3 and 4 also had a degree of polarization lower than those of Examples 1-7 after being placed in a thermostat at 85° C. and 85% RH for 240 hours. In addition, when the polarizing plates of Comparative Examples 3 and 4 were placed in a constant temperature chamber at 85°C and 85%RH for 500 hours, the polarizers were excessively deteriorated, and the amount of light passing through the polarizing plates (that is, the amount of light leakage) changed Too much to measure the degree of polarization. From the comparison between Comparative Examples 3 and 4 and Examples 1-7, it can be seen that the polarizing plates of Comparative Examples 3 and 4 can suppress the intrusion of moisture into the polarizing plate under high temperature and humidity, but because of the protective film A And/or the moisture contained in the adhesive used to bond the protective film A and the polarizer deteriorates.

B. Examples 8 to 10 and Comparative Example 5 A coating solution for forming a hard coat layer containing a polymerizable compound, a solvent, a leveling agent, and a photopolymerization initiator, which is a binder component, was prepared, and a wire bar coater was used to When the thickness after curing becomes 7 μm, the prepared coating solution for forming a hard coat layer is applied on a TAC film (trade name: TJ40 manufactured by Fuji Film Co., Ltd.) having a thickness of 40 μm. After drying the coating film, ^{ultraviolet rays were irradiated with an exposure amount of 100 mJ/cm 2 to} harden the coating film to form a protective film A (hard coating film). For each of Examples 8 to 10 and Comparative Example 5, by blending a hydrophobic compound (a polymerizable compound having a hydrophobic functional group) in a polymerizable compound used in the coating liquid for forming a hard coat layer The ratio is different, and adjusted to the contact angle after saponification shown in Table 1. In addition, a COP film with a thickness of 5 μm is regarded as the protective film B.

After the protective film A was immersed in a 2.0N sodium hydroxide aqueous solution at 50°C for 60 seconds, the protective film A was washed with pure water for 30 seconds and dried in an oven at 100°C for 60 seconds. According to JIS R 3257:9999, the contact angle of the hard coat surface of the protective film A after the saponification treatment was measured using a contact angle meter ("LSE-B100" manufactured by NiCK). The solvent used in the contact angle measurement is pure water.

Use water paste to bond the TAC film surface (bonding surface) of the protective film A to the polarizer, and after drying, use an ultraviolet curable adhesive to bond the protective film to the polarizer, and irradiate ultraviolet rays to make the ultraviolet rays The curable adhesive is cured to obtain a polarizing plate.

The moisture permeability of the protective film A and the protective film B of Examples 8-10 and Comparative Example 5, and the degree of polarization of the polarizing plate after the constant temperature and humidity endurance test were measured by the same method as in Example 1. Table 3 shows the saponification contact angle CA, moisture permeability TA, moisture permeability TB of the protective film B, and the degree of polarization (initial value, The measured value before and after the high temperature and high humidity endurance test.

[table 3] Protective film A characteristics Protective film B characteristics Polarizer characteristics HC film thickness (μm) Contact angle (°) Moisture permeability: TA ＜g/m ² /day＞ (40℃-90%RH) constitute Moisture permeability: TB ＜g/m ² /day＞ ＜40℃-90%RH＞ Polarization After high temperature and high humidity endurance test (85℃, 85%RH) Early After saponification: CA Early 240hrs. after input 500hrs. After putting in Example 8 7 80.1 73.1 214 Cycloolefin polymer 5 99.510 99.505 99.455 Example 9 7 80.3 77.0 198 99.501 99.480 Example 10 7 81.2 77.2 180 99.502 99.485 Comparative example 5 7 81.0 56.0 320 99.250 Unable to determine

The saponified contact angle CA of the hard coat surface of the polarizing plate of Examples 8 to 10 was 70° or more and 120° or less. In addition, the moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B satisfy the above-mentioned conditions (1) and (2). Therefore, the polarizing plates of Examples 8 to 10 showed high polarization values even after being placed in a thermostat at 85° C. and 85% RH for 500 hours. The test results of the degree of polarization after the high temperature and high humidity endurance test of Examples 8 to 10 show that even if exposed to high temperature and high humidity, the deterioration of the polarizer due to moisture intruding into the polarizer from the outside and the protective film A and/ Or the deterioration of the polarizer due to the moisture contained in the adhesive (water paste) used to attach the protective film A did not occur.

The saponified contact angle CA of the polarizing plate hard coat surface of Comparative Example 5 is less than the lower limit of the above condition (1), so the moisture permeability TA of the protective film A exceeds the upper limit of the above condition (2) and becomes higher. Therefore, the polarization degree of the polarizing plate of Comparative Example 5 after being placed in a thermostat at 85° C. and 85% RH for 240 hours became lower than that of Examples 8-10. In addition, when the polarizing plate of Comparative Example 5 was placed in a constant temperature chamber at 85°C and 85% RH for 500 hours, the polarizing plate was excessively deteriorated, and the amount of light passing through the polarizing plate (that is, the amount of light leaking) became excessive , And the degree of polarization cannot be measured. From the comparison between Comparative Example 5 and Examples 8 to 10, it can be seen that for the polarizing plate of Comparative Example 5, moisture invades from the protective film A into the inside of the polarizing plate under high temperature and high humidity, as a result of the deterioration of the polarizer.

As described above, according to the present invention, even in the case of long-term exposure to extremely harsh environments of high temperature and high humidity, it can be confirmed that the deterioration of the polarizer can be suppressed and the optical performance of the polarizer can be maintained. [Possibility of Industrial Use]

The present invention can be used as a polarizing plate used in a display device, and is particularly suitable for use as a polarizing plate of a display device used in a high-temperature environment such as in-vehicle use.

1: Polarizer 10: Polarizing plate A: Protective film B: Protective film

Fig. 1 is a cross-sectional view showing the schematic configuration of the polarizing plate of the embodiment.

1: Polarizer

10: Polarizing plate

A: Protective film

B: Protective film

Claims (7)

A polarizing plate, which is a polarizing plate with a protective film A attached to one side of the polarizer and a protective film B attached to the other side, characterized by the protection at 40°C and 90%RH The moisture permeability TA and TB of film A and B meet the following conditions (1) and (2) at the same time: 240g/m ² /day＞TA＞70g/m ² /day (1) 70g/m ² /day≧TB (2 ). Such as the polarizing plate of claim 1, wherein the saponified contact angle CA of the surface opposite to the bonding surface of the polarizer in the protective film A satisfies the following condition (3): 70°≦CA≦120° (3). The polarizing plate of claim 1, wherein the protective film A is a hard coat film in which a hard coat layer is laminated on one side of a cellulose triacetate film. Such as the polarizing plate of claim 3, wherein the pencil hardness of the hard-coated film is 3H or more. The polarizing plate according to any one of claims 1 to 4, wherein the protective film B is a film containing any one of cycloolefin polymer, polyethylene terephthalate, and polymethyl methacrylate. A display device, which is a display device provided with a polarizing plate, characterized in that the polarizing plate is composed of a protective film A attached to one side of the polarizer and a protective film B attached to the other side, The moisture permeability TA and TB of the protective films A and B at 40°C and 90%RH satisfy the following conditions (1) and (2): 240g/m ² /day＞TA＞70g/m ² /day (1 ) 70g/m ² /day≧TB (2). Such as the display device of claim 6, wherein the saponified contact angle CA of the surface of the protective film A opposite to the bonding surface facing the polarizer satisfies the following condition (3): 70°≦CA≦120° (3).

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