TWI715793B - Polarizing plate set, liquid crystal display panel and liquid crystal display device - Google Patents

Abstract

The present invention provides a polarizing plate set capable of suppressing warping occurring in a liquid crystal display panel.

The polarizing plate set 1 of the present invention comprises a first polarizing plate 2 disposed on the display surface side of the liquid crystal cell 20, and a second polarizing plate 3 and a reflective polarizer 6 disposed on the opposite side of the display surface of the liquid crystal cell 20; the first polarizing plate 2 includes a first polarizing film 4 having a polarizing absorption axis A in a short side direction, the second polarizing plate 3 includes a second polarizing film 5 having a polarizing absorption axis B in a long side direction, the reflective polarizer 6 has a polarizing reflection axis C in the long side direction.

Description

Polarizing plate group, liquid crystal display panel and liquid crystal display device

The present invention relates to a polarizing plate group, a liquid crystal display panel and a liquid crystal display device.

Conventionally, a liquid crystal display device is known as an image display device. In the liquid crystal display device, the illumination light emitted from the backlight is incident from the inner side of the liquid crystal display panel, and the modulated light is emitted from the surface side of the liquid crystal display panel through the liquid crystal display panel, thereby displaying images.

The liquid crystal display panel has a liquid crystal cell and a pair of polarizing plates arranged on both sides of the liquid crystal cell. A pair of polarizing plates generally uses a polarizing film (absorptive polarizer) in which dichroic dyes such as iodine are adsorbed and aligned on a stretched film of a polyvinyl alcohol (PVA) resin film. However, such a polarizing film penetrates the polarized light in the direction of the transmission axis, and absorbs almost all of the polarized light in the direction orthogonal to the transmission axis (the direction of the absorption axis), so the illumination light emitted by the backlight is about 50% cannot be used.

Therefore, recently, in order to improve the utilization efficiency of the illuminating light emitted from the backlight, the polarizing plate arranged on the inner side of the liquid crystal cell is used on the polarizing film with an adhesive layered reflective polarizer (for example, refer to the patent document Dedicated 1). The reflective polarizer is a reflective polarizer with a reflection axis in the direction orthogonal to the transmission axis of the above-mentioned polarizing film. It has the ability to transmit polarized light in the direction of the transmission axis and reflect the polarized light in the direction of the absorption axis to The function of the backlight side. Thereby, the light polarized in the absorption axis direction is reflected on the backlight side, converted into light polarized in the transmission axis direction and then incident on the polarizing film, so it can be reused without being absorbed by the polarizing film.

[Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Application Publication No. 2016-85444.

Moreover, in the above-mentioned liquid crystal display device, as the liquid crystal display panel becomes thinner, warping of the liquid crystal display panel caused by the shrinkage of the polarizing plate becomes a problem. In particular, in liquid crystal display devices for mobile devices, with the thinning of liquid crystal display panels, specifically the thinning of the glass substrate constituting the liquid crystal cell, such problems have become more prominent.

The present invention was proposed in view of the past, and aims to provide a polarizing plate group capable of suppressing warpage of a liquid crystal display panel, a liquid crystal display panel having such a polarizing plate group, and a liquid crystal display device having such a liquid crystal display panel.

As a means to solve the above problems, one aspect of the present invention is to provide a polarizing plate assembly, which has: a display arranged in a liquid crystal cell The first polarizing plate on the surface side, the second polarizing plate and the reflective polarizer arranged on the opposite side to the display surface of the liquid crystal cell, and the first polarizing plate includes a first polarizing plate having a polarization absorption axis in the short-side direction 1 Polarizing film, the second polarizing plate includes a second polarizing film having a polarization absorption axis in the longitudinal direction, and the reflective polarizer has a polarization reflection axis in the longitudinal direction.

In addition, in one aspect of the present invention, a configuration may be adopted in which the second polarizer and the reflective polarizer are laminated via an adhesive or an adhesive.

In addition, in one aspect of the present invention, the configuration may be such that when the reflective polarizer is heated at 85° C. for 100 hours, the dimensional change rate in the direction of the polarization reflection axis is -1.4% or more.

In addition, according to one aspect of the present invention, a liquid crystal display device can be provided, which includes a liquid crystal cell and any one of the aforementioned polarizing plate groups.

Furthermore, according to an aspect of the present invention, a liquid crystal display device can be provided, which includes the aforementioned liquid crystal display panel and a backlight.

As described above, according to one aspect of the present invention, it is possible to provide a polarizing plate group capable of suppressing warpage of a liquid crystal display panel in a high temperature environment, etc., a liquid crystal display panel having such a polarizing plate group, and a liquid crystal display panel having such a liquid crystal display panel. Liquid crystal display device.

1‧‧‧ Polarizing plate set

2‧‧‧The first polarizer

3‧‧‧Second Polarizing Plate

4‧‧‧The first polarizing film

5‧‧‧Second Polarizing Film

6‧‧‧Reflective polarizer

7‧‧‧The first protective film

8‧‧‧Second protective film

9‧‧‧The third protective film

10a、10b‧‧‧Adhesive layer

20‧‧‧LCD unit

30‧‧‧LCD Panel

40‧‧‧Backlight

50‧‧‧Light diffuser

A, B‧‧‧ Polarized absorption axis

C‧‧‧ Polarized reflection axis

Figure 1 is a schematic diagram illustrating the arrangement of polarizing plate groups in one embodiment of the present invention.

Fig. 2 shows the structure of the polarizing plate group shown in Fig. 1, (a) is a schematic cross-sectional view showing a configuration example of the first polarizing plate, and (b) is a schematic cross-sectional view showing a configuration example of the second polarizing plate.

Fig. 3 is a schematic cross-sectional view showing the structure of a liquid crystal display panel equipped with the polarizing plate group shown in Fig. 2.

FIG. 4 is a schematic cross-sectional view showing the structure of a liquid crystal display device equipped with the liquid crystal display panel shown in FIG. 3.

Figure 5 (a) is a schematic diagram showing the arrangement relationship of model A, and (b) is a schematic diagram showing the arrangement relationship of model B.

Fig. 6 (a) is a characteristic diagram showing the result of measuring the amount of warpage of model A, and (b) is a characteristic diagram showing the result of measuring the amount of warpage of model B.

Figure 7 is a characteristic diagram showing the measurement result of the change in the dimensional change rate (%) when the reflective polarizer is heated at 85°C.

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

In addition, in the drawings used in the following description, in order to make it easier to understand the constituent elements, the constituent elements may be schematically shown, and the dimensional ratio may be changed according to the constituent elements.

(Polarizer set)

First, an embodiment of the present invention will explain the arrangement of the polarizing plate group 1 shown in FIG. 1, for example. Moreover, FIG. 1 is a schematic diagram for explaining the arrangement relationship of the polarizing plate set 1.

As shown in Figure 1, the polarizing plate group 1 of this embodiment Equipped with: a first polarizing plate 2 arranged on the display surface (surface) side of the liquid crystal cell 20, and a second polarizing plate 3 and a reflective polarizer 6 arranged on the opposite (inside) side of the display surface of the liquid crystal cell 20 .

The first polarizing plate 2 includes a first polarizing film 4 having a polarization absorption axis A in the short-side direction. On the other hand, the second polarizing plate 3 includes a first polarizing film 5 having a polarization absorption axis B in the longitudinal direction.

On the other hand, the reflective polarizer 6 has a polarization reflection axis C in the longitudinal direction. In addition, the second polarizer 2 and the reflective polarizer 6 are laminated via an adhesive or an adhesive (not shown).

Using the polarizing plate set 1 of this embodiment, the first polarizing plate 2 is bonded to the surface side of the liquid crystal cell 20 via an adhesive layer, and the second polarizing plate 3 is bonded to the inner surface side of the liquid crystal cell 20 via an adhesive layer. , And set the reflective polarizer 6 to face the side opposite to the side opposite to the liquid crystal cell 20, thereby forming the liquid crystal display panel 30 of this embodiment.

In the liquid crystal display panel 30 of this embodiment, by using the above-mentioned polarizing plate group 1, the warpage caused by the shrinkage of the first polarizing plate 2, the second polarizing plate 3, and the reflective polarizer 6 can be suppressed. Seek to improve the display quality.

Next, the specific configuration of the above-mentioned polarizing plate group 1 will be described with reference to 2(a) and (b). In addition, FIG. 2(a) is a schematic cross-sectional view showing a configuration example of the first polarizing plate 2. FIG. 2(b) is a schematic cross-sectional view showing a configuration example of the second polarizing plate 3.

For example, as shown in Figure 2 (a), the first polarizing plate 2 has the following laminated structure: the first polarizing film 4, the first polarizing film 4 and the liquid crystal cell 20 The area layer first protective film 7 on the opposite side, and the area layer second protective film 8 on the side opposite to the liquid crystal cell 20 of the first polarizing film 4.

For example, as shown in FIG. 2(b), the second polarizing plate 3 has the following laminated structure: a second polarizing film 5, and a third protective film 9 is layered on an area of the second polarizing film 5 opposite to the liquid crystal cell 20. In addition, the reflective polarizer 6 is laminated on the surface of the second polarizing film 5 opposite to the liquid crystal cell 20. In addition, a protective film may be arranged between the second polarizing film 5 and the reflective polarizer 6.

The dimensional change rate of the reflection axis direction of the reflective polarizer 6 is preferably -1.4% or more.

In addition, the dimensional change rate of the first polarizer 2 and the dimensional change rate of the second polarizer 3 used in combination with the reflective polarizer are preferably -1.0 to 0% in the direction of the absorption axis, and preferably in the transmission The axis direction is -0.5~0%.

By adopting such a combination, the warpage of the liquid crystal panel 30 can be further reduced. In addition, the dimensional change rate can be controlled by, for example, adjusting the drying time or drying temperature after the protective film is attached to the polarizing film, the thickness of the polarizing film, and the stretching ratio of the polarizing film.

Here, the dimensional change rate of the polarizing plate when heated at 85°C for 100 hours refers to the value measured as follows. Specifically, the polarizing plate is first cut into a size of 100 mm in the absorption axis direction × 100 mm in the transmission axis direction, and after standing for 1 day in an environment with a temperature of 23°C and a relative humidity of 55%, the absorption axis direction (or transmission axis Direction) size (the size before heat treatment).

Next, the dimensions (dimensions after heat treatment) in the direction of the absorption axis (or the direction of the penetration axis) of the polarizing plate after being allowed to stand in a high temperature environment at a temperature of 85°C for 100 hours were measured. Substituting these measurement results into the following formula S ₀ , whereby the dimensional change rate in the direction of the absorption axis (or the dimensional change rate in the direction of the penetration axis) can be obtained.

S ₀ = ((size after heat treatment-size before heat treatment)×100)/size before heat treatment

(Polarizing film)

The first polarizing film 4 and the second polarizing film 5 are absorption-type polarizers, and a polyvinyl alcohol (PVA)-based resin film is usually used to adsorb or align dichroic dyes such as iodine. PVA resin is obtained by manufacturing polyvinyl acetate resin.

In addition to polyvinyl acetate which is a homopolymer of vinyl acetate, the polyvinyl acetate resin system includes, for example, copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate. Other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having ammonium groups, and the like.

The degree of saponification of the PVA-based resin is usually 85-100 mol%, preferably 98 mol% or more. PVA-based resins can be further modified, and polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used.

In addition, the degree of polymerization of the PVA-based resin is usually 1,000 to 10,000, and preferably 1,500 to 5,000. Specific examples of PVA-based resins and dichroic dyes include PVA-based resins and dichroic dyes exemplified in JP 2012-159778 A.

The manufacturing method of a polarizing film is not specifically limited, It can manufacture by a well-known method. Specifically, the polarizing film is stretched through a step of uniaxially stretching the PVA-based resin film, and then the PVA-based resin film is stretched by two It is produced by the step of dyeing the chromatic pigment and adsorbing the dichroic pigment, the step of treating the PVA resin film with the dichroic pigment adsorbed with the boric acid aqueous solution, the step of washing with the boric acid aqueous solution and the drying step. The polarizing film can be continuously manufactured by moving the long PVA-based resin film in the production line.

In addition, the polarizing film can be manufactured, for example, by the method described in JP 2012-159778 A. In this method, a PVA-based resin film can be formed as an absorption-type polarizer by coating a PVA-based resin on a base film.

The thickness of the embryo membrane made of PVA-based resin is not particularly limited, but is, for example, 150 μm or less. In consideration of ease of extension, etc., the film thickness is preferably 3 μm or more and more preferably 75 μm or less.

In addition, the first polarizing film 4 and the second polarizing film 5 may be the same polarizing film or different polarizing films.

(Protective film)

The first protective film 7, the second protective film 8, and the third protective film 9 are preferably composed of thermoplastic resin films having excellent transparency or uniform optical properties, mechanical strength, and thermal stability. The thermoplastic resin film can use cellulose-based resins such as cellulose triacetate and cellulose diacetate; polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate. Ester resins; (meth)acrylic resins such as polymethyl (meth)acrylate and poly(meth)ethyl acrylate; polycarbonate resins; polyether turquoise resins; poly turquoise resins; polyamides Imine resins; polyolefin resins such as polyethylene and polypropylene; polynorbornene resins, etc. Among them, it is preferable to use cellulose resins, polyester resins, (meth)acrylic resins, and polycarbonate resins. Thermoplastic resin film formed of acid ester resin or polyolefin resin. In addition, the (meth)acrylate referred to herein refers to methacrylate or acrylate, and the same applies to the "(meth)" when referring to (meth)acrylic acid.

In addition, commercially available products can be suitably used for the thermoplastic resin film. Commercially available cellulose resin films include "Fujitac (registered trademark) TD80", "Fujitac (registered trademark) TD80UF" and "Fujitac (registered trademark) TD80UZ" manufactured by Fujifilm Co., Ltd., and KONICA MINOLTA Co., Ltd. "KC2UAW", "KC8UX2M", "KC8UY" and so on.

Commercially available polyester resin films include "DIAFOIL (registered trademark)" manufactured by Mitsubishi Plastics Corporation, "lumirror (registered trademark)" manufactured by Toray Co., Ltd., and "COSMOSHINE (registered trademark) manufactured by Toyobo Co., Ltd. "Wait.

Commercial products of the (meth)acrylic resin film include "TECHNOLLOY (registered trademark)" manufactured by Sumitomo Chemical Co., Ltd., "ACRYPLEN (registered trademark)" manufactured by Mitsubishi Rayon Co., Ltd., and the like.

Examples of commercially available polycarbonate resin films include "PANLIGHT (registered trademark)" manufactured by Teijin Co., Ltd. and the like.

Commercial products of polyolefin resins include "Topas" manufactured by Topas Advanced Polymers GmbH and sold by Polyplastics Co., Ltd., "ARTON" (registered trademark) sold by JSR Co., Ltd., and Japan ZEON Co., Ltd. "ZEONOR (registered trademark)", "ZEONEX (registered trademark)" sold by the company, "apel" (registered trademark) sold by Mitsui Chemicals Co., Ltd. (all the above are trade names), etc., and The film can be made from the above resin.

In addition, commercially available polyolefin resin films can be used, such as "ARTON film" sold by JSR Co., Ltd. ("ARTON" is a registered trademark of the same company), "Esushina" sold by Sekisui Chemical Industry Co., Ltd. (Registered trademark), "ZEONOR FILM" (registered trademark) sold by ZEON Co., Ltd., etc.

The thickness of the thermoplastic resin film is usually 5 to 100 μm, preferably 10 to 50 μm, and more preferably 10 to 30 μm.

In addition, the first protective film 7 and the second protective film 8 and the third protective film 9 may be the same protective film or different protective light films.

The first polarizing film 4 and the second polarizing film 5 may have the same thickness or different thicknesses. The thickness of the first polarizing film 4 is preferably 15 μm or less, and the thickness of the second polarizing film 5 is preferably 12 μm or less.

In addition, the thickness of the polarizing film is usually 3 μm or more.

(Hard coating)

In addition, the structure of the first protective film 7 may be such that a hard coat layer (not shown) is provided on the surface opposite to the side facing the liquid crystal cell 20. The hard coat layer can prevent scratches and the like generated on the first polarizer 2.

Since the dimensional change of the hard coat layer is small, the dimensional change of the first polarizing plate 2 can be further suppressed by providing the hard coat layer. In addition, the main factor causing the dimensional change rate of the first polarizer 2 is the first polarizing film 4. Therefore, in terms of more effectively suppressing the dimensional change of the first polarizer 2, the hard coat layer is preferably provided close to The position of the first polarizing film 4. Specifically, the first bias The distance between the optical film 4 and the hard coat layer is preferably 30 μm or less, more preferably 25 μm or less.

In addition, in terms of suppressing the dimensional change of the first polarizing plate 2, it is preferable that there is no adhesive layer between the first polarizing film 4 and the hard coat layer. When there is no layer with a low elastic modulus such as an adhesive layer between the first polarizing film 4 and the hard coating layer, the hard coating layer can effectively suppress the dimensional change of the first polarizing film 4.

When the hard coat layer is provided, the thickness of the hard coat layer is preferably 1 to 8 μm, more preferably 1 to 6 μm from the viewpoint of having both protection and flexibility. When the thickness of the hard coat layer exceeds 8 μm, the flexibility is low and tends to break easily when bent. On the other hand, when the thickness of the hard coat layer is less than 1 μm, the flexibility is good, but from the viewpoint of in-plane uniformity, there is a tendency that sufficient characteristics cannot be obtained in many cases.

The hard coat layer may be formed of a resin coating layer. Among the resins forming the resin coating layer, a resin having sufficient strength and transparency after the resin coating layer is formed can be used. Examples of the aforementioned resin include active energy ray-curable resins such as thermosetting resins, thermoplastic resins, ultraviolet-curable resins, and electron beam-curing resins, and two-component hybrid resins. Among them, the resin can be cured by irradiating ultraviolet rays, and the resin coating layer can be efficiently formed by simple processing operations. In addition, a light diffusion layer such as an anti-glare treatment layer can also be formed. Therefore, an ultraviolet curable resin is preferred. Examples of ultraviolet curable resins include polyester-based, acrylic-based, urethane-based, amide-based, silicone-based, and epoxy-based resins. The wettability (water drop contact angle) of the hard coat layer can be adjusted by a known method such as adding an additive to the aforementioned resin (coating liquid).

The method of forming the hard coat layer can be a suitable known method, For example, a method of drying after coating the aforementioned resin (coating liquid) can be mentioned. When a curable resin is used as the resin forming the resin coating layer, the curing process is performed after coating. The coating method of the coating liquid can be injection method, die slit coater, casting, spin coating, fountain metalling, gravure etc. methods. In addition, the coating liquid may be diluted with general solvents such as toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, isopropanol, ethanol, etc., or may not be diluted.

(Reflective polarizer)

The reflective polarizer 6 has a function of transmitting polarized light in the direction of the transmission axis of the second polarizing film 5 and reflecting the polarized light in the direction of the absorption axis.

The reflective polarizer 6 can include: a grid-type polarizing film; a multilayer film laminate of two or more layers formed of two or more materials with a difference in refractive index; used in a beam splitter and other vapor-deposited multilayer films with different refractive indexes; A birefringent multilayer film laminate with two or more layers formed by two or more materials of birefringence; a stretched film of two or more resin laminates using two or more resins with birefringence; and by direct contact with linearly polarized light A film that reflects/transmits in the axial direction and separates the polarization direction.

The multilayer thin film laminate system constituting the reflective polarizer 6 has a configuration in which a first optical material layer and a second optical material layer are alternately laminated in the thickness direction.

The specific materials of the first optical material layer and the second optical material layer include, for example, polyethylene naphthalate (PEN) and its isomers (e.g., 1,4-PEN, 1,5-PEN, 2,7-PEN). PEN and 2,3-PEN, etc.), and polyterephthalene Alkyl formate (e.g. polyethylene terephthalate (PET), polybutylene terephthalate, poly(1,4-cyclohexane dimethyl terephthalate)), methacrylic resin (e.g. Polymethyl methacrylate (PMMA), etc.), polycarbonate resin, polystyrene resin, polyolefin resin (polystyrene, polypropylene, etc.), cyclic polyolefin resin, etc.

In addition, the specific materials of the first optical material layer and the second optical material layer may be a copolymer of PEN, a copolymer of polyalkylene terephthalate, or a styrene copolymer. Specific examples of PEN copolymers can include 2,6-, 1,4-, 1,5-, 2,7- and 2,3-naphthalenedicarboxylic acid or its ester and a) terephthalic acid or its Esters, b) isophthalic acid or its esters, c) phthalic acid or its esters, d) alkanediol, e) cycloalkanediol (e.g. cyclohexane dimethanol), or f) alkane dicarboxylic acid (Such as cyclohexane dicarboxylic acid) copolymer.

Specific examples of copolymers of polyalkylene terephthalate include terephthalic acid or its esters and a) naphthalene dicarboxylic acid or its ester, b) isophthalic acid or its ester, and c) phthalic acid Or its ester, d) alkanediol, e) cycloalkanediol (e.g. cyclohexane dimethanol), f) alkane dicarboxylic acid, and/or g) cycloalkene dicarboxylic acid (e.g. cyclohexane dicarboxylic acid) ) Of the copolymer.

Specific examples of styrene copolymers are styrene/butadiene copolymers and styrene/acrylonitrile copolymers. In addition, the materials of the first and second optical material layers include ABS resin (acrylonitrile/styrene/butadiene copolymer resin) and MS resin (methyl methacrylate/styrene copolymer resin). Commercially available reflective polarizers include "DBEF" (registered trademark), "APF-V3" (product name), and "APF-V2" (product name) manufactured by 3M.

Also, each of the first optical material layer and the second optical material layer The layer can be a mixture of two or more of the exemplified polymers or polymer copolymers. In addition, from the viewpoint of low absorption coefficient and small loss due to absorption, the exemplified materials are preferable.

The thickness of the reflective polarizer 6 is usually 5-100 μm, preferably 10-50 μm, and more preferably 10-30 μm.

When the reflective polarizer 6 is heated at 85°C for 100 hours, the dimensional change rate in the direction (long side direction) along the polarization reflection axis C is preferably -1.4 to 0%, more preferably -1.2 to 0%, and More preferably, it is -0.5~0%.

The reflective polarizer 6 having the above-mentioned dimensional change rate can be obtained, for example, by adjusting the stretching ratio when manufacturing the reflective polarizer 6, or adjusting the time of annealing treatment.

Specifically, the dimensional change rate refers to a value measured in the following manner. First, the reflective polarizer 6 is cut into a size of 100 mm in the direction of the polarization reflection axis × 100 mm in the direction of the transmission axis, and after standing for 1 day in an environment with a temperature of 23°C and a relative humidity of 55%, the direction of the polarization reflection axis is measured The size is the size before heat treatment. Next, the size in the direction of the polarization reflection axis after the reflection-type polarizer 6 is allowed to stand in a high temperature environment at a temperature of 85° C. for 100 hours is measured, that is, the size after the heat treatment. By substituting these measurement results into the following formula S ₁ , the dimensional change rate in the direction of the polarization reflection axis can be obtained.

S ₁ = ((size after heat treatment-size before heat treatment)×100)/size before heat treatment

(Adhesive or adhesive)

Laminating method of each film constituting the first polarizing plate 2 and the second polarizing plate 3 The method of bonding with adhesive or adhesive is usually adopted. In addition, the method of laminating the second polarizer 3 and the reflective polarizer 6 is usually a method of bonding with an adhesive or an adhesive.

When laminating each film, the same type of adhesive or adhesive can be used, or a different type of adhesive or adhesive can be used.

Examples of the adhesive include water-based adhesives, photocurable adhesives, and the like. A water-based adhesive is an adhesive that dissolves adhesive components in water or an adhesive that disperses adhesive components in water, so that the adhesive layer can be thinned. The water-based adhesive is preferably a water-based adhesive in which the main component of the adhesive (composition) is PVA-based resin or urethane resin.

In addition to partially saponified polyvinyl alcohol or fully saponified polyvinyl alcohol, PVA-based resins can be modified by carboxyl groups, modified with acetyl acetone groups, modified with polyvinyl alcohol, methylol groups, and modified with amine groups. Modified PVA resins such as polyvinyl alcohol. When PVA-based resin is contained as an adhesive component, the adhesive is often prepared as an aqueous solution of PVA-based resin. The concentration of the PVA-based resin in the adhesive is usually about 1 to 10 parts by weight, preferably 1 to 5 parts by weight relative to 100 parts by weight of water.

In an adhesive containing a PVA-based resin as a main component, in order to improve adhesiveness, it is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent. Water-soluble epoxy resins include: polyalkylene polyamines such as diethylenetriamine or triethylenetetramine and dicarboxylic acid of adipic acid are polyamide polyamines, and the polyalkylene polyamines Polyamide polyamine epoxy resin obtained by the reaction of amide polyamine and epichlorohydrin.

The commercial products of polyamide polyamine epoxy resin are Sumika "Sumirez Resin (registered trademark) 650(30)", "Sumirez Resin (registered trademark) 675" sold by Chemtex Co., Ltd., and "WS-525" sold by Starlight PMC Co., Ltd., etc., can be used appropriately These commercially available products.

The addition amount of the curable component or the crosslinking agent is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight with respect to 100 parts by weight of the PVA-based resin. If the addition amount is small, the adhesiveness improvement effect becomes small. On the other hand, if the addition amount is large, the adhesive layer tends to become fragile.

The layered body joined via an aqueous adhesive is usually dried. The adhesive is dried and hardened. The drying treatment can be performed by spraying hot air, for example. The drying temperature is generally 40-100°C, preferably 60-100°C. The drying time is, for example, about 20 to 1,200 seconds. The thickness of the adhesive layer after drying is usually about 0.001 to 5 μm, preferably 0.01 μm or more, more preferably 2 μm or less, and more preferably 1 μm or less. If the thickness of the adhesive is too large, the appearance of the polarizing plate is likely to be poor.

After the drying treatment, it can be aged at a temperature above room temperature for at least half a day, usually for more than one day to obtain sufficient adhesive strength. Typically, this maturation is carried out in a state wound into a roll. The preferred aging temperature is usually 30-50°C, and more preferably 35°C or more and 45°C or less. If the aging temperature exceeds 50°C, the state of being wound into a roll is likely to cause the so-called "overtight winding". In addition, the humidity at the time of aging is preferably selected appropriately so that the relative humidity becomes 70% or less, for example. The maturation time is usually about 1 to 10 days, preferably about 2 to 7 days.

Light-curing adhesives include light-curing epoxy resins and Mixtures of photocationic polymerization initiators, etc. Examples of the photocurable epoxy resin include alicyclic epoxy resins, epoxy resins that do not have an alicyclic structure, and mixtures of these. In addition, photocurable adhesives can also be used in epoxy resins, acrylic resins, oxetane resins, urethane resins, polyvinyl alcohol resins, etc. with radical polymerization initiators and/or cationic polymerization types. Adhesive of starter.

The layered system joined through the photocurable adhesive is irradiated with active energy rays after the layer is laminated, thereby curing the photocurable adhesive. The light source of the active energy line is preferably an active energy line with a luminescence distribution below the wavelength of 400nm. Specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, and microwave excitation are preferably used. Mercury lamps, metal halide lamps, etc.

According to the composition of the photo-curable adhesive, it is appropriate to determine the light intensity of the photo-curable adhesive, but the radiation intensity in the wavelength range effective for the activation of the photocationic polymerization initiator is preferably 0.1 to 6,000 mW /cm ² . When the irradiation intensity is 0.1mW/cm ² or more, the reaction time will not be too long. When it is 6,000mW/cm ² or less, the yellowing or yellowing of the epoxy resin caused by the radiant heat from the light source and the heat generated when the photo-curable adhesive is cured There is less risk of deterioration of the polarizing plate, which is preferable in this regard.

The light irradiation time to the photo-curable adhesive is controlled by the entire photo-curable adhesive, but it is preferable that the cumulative light amount shown by the product of the above-mentioned irradiation intensity and irradiation time becomes 10~10,000mJ/cm ² way to set. When the cumulative amount of light for the photocurable adhesive is 10 mJ/cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated and the curing reaction can proceed more reliably. When it is 10,000 mJ/cm ² or less, The irradiation time is not too long, and it is preferable in terms of maintaining good productivity. The thickness of the adhesive layer after active energy ray irradiation is usually 0.001 to 5 μm, preferably 0.01 μm to 3 μm.

As long as the adhesive meets the required properties of the optical film (transparency, durability, reworkability, etc.), an acrylic adhesive containing an acrylic resin with a glass transition temperature (Tg) below 0°C and a crosslinking agent can be used The acrylic resin is formed by radically polymerizing an acrylic monomer composition in the presence of a polymerization initiator, and the acrylic monomer composition contains (meth)acrylate as the main component and further contains A small amount of (meth)acrylic monomers with functional groups.

(LCD panel)

Next, the structure of the liquid crystal display panel 30 of this embodiment will be described with reference to FIG. 3. In addition, FIG. 3 shows a schematic cross-sectional configuration of the liquid crystal display panel 30.

The liquid crystal display panel 30 of this embodiment has the following structure: the first polarizer 2 is bonded to the surface of the liquid crystal cell 20 via an adhesive layer 10a, and the reflective polarizer 6 is placed on the inner surface of the liquid crystal cell 20 In a state facing the side opposite to the side facing the liquid crystal cell 20, the second polarizer 3 and the reflective polarizer 6 are bonded via the adhesive layer 10b.

The adhesives forming the adhesive layers 10a and 10b only need to satisfy the properties (transparency, durability, reworkability, etc.) required by the optical film, and acrylic resins containing glass transition temperature (Tg) below 0°C and Crosslinking agent, acrylic adhesive, etc., the acrylic resin is formed by radical polymerization of an acrylic monomer composition in the presence of a polymerization initiator, and the acrylic monomer composition is formed by (meth) Acrylate is a main component and further contains a small amount of (meth)acrylic monomers having functional groups.

The liquid crystal cell 20 can be any of the conventionally known modes such as VA (Vertical Alignment) mode, IPS (In Plane Switching) mode, TN mode (Twisted Nematic) mode, ECB (Electrically Controlled Birefringence) mode, OCB (Optically Compensated Birefringence) mode, etc. Liquid crystal cell.

According to the polarizing plate set of the present invention, even if the thickness of the liquid crystal cell 20 is 0.4 mm or less, the warpage of the liquid crystal display panel 30 in a high temperature environment can be significantly suppressed.

(Liquid crystal display device)

Next, the structure of the liquid crystal display device of this embodiment will be described with reference to FIG. 4. In addition, Fig. 4 shows a schematic cross-sectional configuration of the liquid crystal display device.

The liquid crystal display device shown in FIG. 4 includes the liquid crystal display panel 30 and the backlight 40 shown in FIG. 3. The backlight 40 is arranged on the side of the liquid crystal display panel 30 opposite to the second polarizing plate 3. Furthermore, a light diffusion plate 50 is arranged between the liquid crystal display panel 30 and the backlight 40, and the light diffusion plate 50 diffuses the light emitted from the backlight 50.

In the liquid crystal display device, the illumination light emitted by the backlight 50 is incident from the inner side of the liquid crystal display panel 30, and passes through the liquid crystal display surface. The light modulated by the panel 30 is emitted from the surface side of the liquid crystal display panel 30, whereby images can be displayed.

In addition, the backlight 40 is not limited to the direct type, and an edge type may also be used. The direct type irradiates light toward the liquid crystal display panel 30 from a position opposite to the liquid crystal display panel 30 via the light diffusion plate 50. The light system irradiates the light that is arranged on the side edge of the liquid crystal display panel 30 and guided through the light guide plate facing the liquid crystal display panel 30 toward the liquid crystal display panel 30.

As described above, in the liquid crystal display panel 30 equipped with the polarizing plate set 1 of this embodiment, the warpage caused by the shrinkage of the first polarizing plate 2, the second polarizing plate 3, and the reflective polarizer 6 can be suppressed, so Can seek to improve the display quality.

Here, Fig. 5(a) shows the arrangement relationship of the polarizing plate group 1 (hereinafter referred to as model A) of this embodiment. In addition, Fig. 5(b) shows the arrangement relationship of the polarizing plate group (hereinafter referred to as model B) of the comparative example. In the model B, the same parts as those of the above-mentioned polarizing plate group 1 are omitted from the description, and the same reference numerals are attached in the figure.

In the model A shown in FIG. 5(a), the first polarizing film 4 constituting the first polarizing plate 2 has a polarization absorption axis A in the short-side direction. In addition, the first polarizing film 5 constituting the second polarizing plate 3 has a polarization absorption axis B in the longitudinal direction, and the reflective polarizer 6 has a polarization reflection axis C in the longitudinal direction.

In contrast, in the model B shown in Fig. 5(b), the first polarizing film 4 constituting the first polarizing plate 2 has a polarization absorption axis in the longitudinal direction A. In addition, the second polarizing film 5 constituting the second polarizing plate 3 has a polarization absorption axis B in the short-side direction, and the reflective polarizer 6 has a polarization reflection axis C in the short-side direction.

After attaching the polarizing plate sets of these models A and B to a 5-inch diagonal glass substrate imitating the liquid crystal cell 20, the warpage in the long-side and short-side directions when heated at 85°C for 24 hours was measured量(mm). The measurement results are shown in Figure 6 (a) and (b). In addition, Fig. 6(a) is a characteristic diagram showing the measurement result of model A, and Fig. 6(b) is a characteristic diagram showing the measurement result of model B.

As shown in Figure 6(a), the warped shape of model A is that the warping amount of the center in the long side direction is larger than that of both ends (convex shape), and the warping amount of both ends in the short side direction is larger than the center Large (concave shape).

On the other hand, as shown in Fig. 6(b), the warped shape of model B is that the warping amount of both ends in the long side direction is larger than that in the center (concave shape), and the center is farther in the short side direction. The warpage is large (convex shape).

In addition, it can be seen that compared with model B, model A suppresses the amount of warpage that occurs in the long-side direction and the short-side direction. In particular, it can be seen that compared with model B, model A greatly suppresses the amount of warpage generated in the longitudinal direction.

As described above, in the liquid crystal display panel 30 of the liquid crystal cell 20 where the polarizing plate assembly 1 of this embodiment is bonded, the shrinkage of the first polarizing plate 2, the second polarizing plate 3, and the reflective polarizing film 6 can be suppressed. Since warpage occurs, it is possible to improve the display quality of the liquid crystal display device.

[Example]

The following examples further illustrate the effects of the present invention. In addition, the present invention is not limited to the following examples, and can be implemented with appropriate changes within a range that does not change its gist.

In this embodiment, the polarizing plate group of model A (Examples 1 to 5) and the polarizing plate group of model B (comparative examples 1 to 5) with reflective polarizers with different dimensional change rates were produced as follows ).

(Production of the first polarizing film)

A polyvinyl alcohol film with a thickness of 30μm (average degree of polymerization is about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched to about 4 times by dry stretching, and then immersed in pure water at 40°C for 40 seconds while maintaining the tension. , Dyeing is performed by immersing in an aqueous solution with a weight ratio of iodine/potassium iodide/water of 0.04/5.7/100 at 28°C for 30 seconds. Thereafter, it was immersed in an aqueous solution with a weight ratio of potassium iodide/boric acid/water of 11.0/6.2/100 at 70°C for 120 seconds. Next, after washing with 8°C pure water for 15 seconds, it was dried at 60°C to obtain a polarizing film with a thickness of 12 μm in which iodine was adsorbed and aligned on the polyvinyl alcohol film.

(Production of the second polarizing film)

A polyvinyl alcohol film with a thickness of 20μm (average degree of polymerization is about 2400, saponification degree of 99.9 mol% or more) is stretched in a longitudinal uniaxial manner to about 5 times by dry stretching, and then immersed in pure water at 60°C while maintaining the tension. 1 Minutes later, immerse for 60 seconds in a 28°C aqueous solution with a weight ratio of iodine/potassium iodide/water of 0.05/5/100. Thereafter, it was immersed in a 72°C aqueous solution with a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 for 300 seconds. Then, after washing with pure water at 26°C for 20 seconds, it was dried at 65°C to obtain polyethylene The alcohol film absorbs and aligns iodine to a polarizing film with a thickness of 7 μm.

(Production of reflective polarizer)

First, prepare the following as thermoplastic resins A and B.

Thermoplastic resin A: polyethylene naphthalate (refractive index 1.65) obtained by polycondensation of dimethyl naphthalene 2,6-dicarboxylate and ethylene glycol in a conventional method.

Thermoplastic resin B: polyethylene naphthalate copolymerized with 30 mol% terephthalic acid (refractive index 1.65).

In addition, prior to the thermal measurement of the polymer using a thermal differential scanner, it was confirmed that the thermoplastic resin A was crystalline and the thermoplastic resin B was amorphous.

Next, the thermoplastic resins A and B were put into two single-screw extruders, respectively, and kneaded while being melted at 300°C. After that, after passing through 5 leaf disc filters of the FSS type, a gear pump is used to measure the thickness of the thick film layer to remove the film so that the lamination ratio of the film is thermoplastic resin A/thermoplastic resin B = 1/1. The stacking devices are merged to form a stack of 903 layers alternately stacked in the thickness direction. The 903 layer is composed of 2 slit plates with 301 slits and 1 slit plate with 303 slits, totaling 3 pieces .

Next, after supplying the laminate to a T mold and forming it into a sheet shape, while applying an electrostatic voltage of 8 kV with a steel wire, it was quenched and solidified on a casting drum whose surface temperature was maintained at 25° C. to obtain an unstretched film. After the unstretched film was longitudinally stretched 5.0 times at 140°C by a longitudinal stretcher, it was cooled at 70°C and heat-treated at 160°C to obtain a laminate film with a thickness of 34 μm.

(Polyvinyl alcohol adhesive)

The polyvinyl alcohol-based adhesive is dissolved in 100 parts by weight of water, acetyl acetyl modified polyvinyl alcohol [product name "GOHSEFIMERTM (registered trademark) Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] 2 parts by weight, ethyl acetate Sodium aldehyde [trade name "SPM-01" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] 2 parts by weight was prepared.

(Production of the first polarizing plate (front side polarizing plate))

A protective film with a thickness of 23μm (trade name "ZEONOR FILM (registered trademark) ZF14-023" manufactured by ZEON Co., Ltd., Japan) is attached with a polyvinyl alcohol-based adhesive on one side of the first polarizing film on the other side of the first polarizing film A polyvinyl alcohol-based adhesive is attached to the TAC side of a cellulose triacetate (TAC) film with a hard coat layer ("25KCHCN-TC" manufactured by Toppan Printing Co., Ltd., thickness 32μm). Next, a 20 μm thick adhesive [product name "NCF#KT" manufactured by LINTEC Co., Ltd.] was attached to the ZEONOR FILM side.

(Production of the second polarizer and reflective polarizer (rear side polarizer))

A cellulose ester film (KC2CT) made by KONICA MINOLTA Co., Ltd. (KC2CT) with a thickness of 20μm was adhered to one side of the second polarizing film with a polyvinyl alcohol-based adhesive, and then a 20μm-thick adhesive [LINTEC] was attached to the side of the cellulose ester film Co., Ltd. product name "NCF#KT"]. Also, an adhesive with a thickness of 5μm is interposed on the other side of the second polarizing film [LINTEC Corporation Co., Ltd. product name "NCF#L2"] and a reflective polarizer is attached.

Next, a measurement sample was prepared in the following manner, and the measurement sample was made by bonding the polarizing plate groups of Examples 1 to 5 and Comparative Examples 1 to 5 to a glass substrate imitating a liquid crystal cell.

(Production of measurement samples)

The 5.2-inch (116mm×67mm) glass with a thickness of 0.3mm is cut into a 4.3-inch (96mm×48mm) polarizing plate in order to form the configuration relationship of model A and B.

Next, regarding each measurement sample of the polarizing plate set of Examples 1 to 5 and Comparative Examples 1 to 5, the amount of warpage generated in the long side direction and the short side direction when heated at 85°C for 24 hours was measured as follows ( mm). The measurement results are summarized in Table 1.

(Measurement of warpage)

First, the measurement sample with polarizing plates attached to both sides is allowed to stand at 85°C for 100 hours, and the front polarizing plate is placed on the upper side and placed on the Nikon Co., Ltd. two-dimensional measuring device "NEXIV VMR-12072" for measurement. On stage. Next, align the focal point on the surface of the measuring table, use it as a reference, and measure the distance to the focal point with a total of 5 points on the long side and 5 points on the short side of the measurement sample as the basis, and then use the distance from the measuring table In absolute value, the difference between the longest distance and the shortest distance is used as the warpage amount.

(Measurement of dimensional change rate)

The dimensional change rate when heated at 85°C for 100 hours was measured as follows using a two-dimensional measuring device "NEXIV VMR-12072" manufactured by Nikon Co., Ltd. First, cut each film into a size of (absorption axis direction (or reflection axis direction)) 100mm×(transmission axis direction) 100mm, and let stand for 1 day in an environment with a temperature of 23°C and a relative humidity of 55%, and measure the absorption The dimension in the axis direction (L ₀ ). Next, the dimension (L ₁ ) in the direction of the absorption axis after being allowed to stand in a high-temperature environment at a temperature of 85°C for 100 hours was measured. From these measurement results, the dimensional change rate (%) in the direction of the absorption axis is obtained from the following equation.

Size change rate (%)=[(L ₁ -L ₀ )/L ₀ ]×100

The dimensional change rate in the direction of the reflection axis or the transmission axis is also calculated in the same way.

In Table 1, the polarizing plate groups of Examples 1 to 5 (model A) and Comparative Examples 1 to 5 (model B) indicate the dimensional change rate in the reflection axis direction and the transmission axis direction of the reflective polarizer ( %), the rate of dimensional change in the direction of the absorption axis and transmission axis of the first polarizer (%), and the rate of dimensional change in the direction of the absorption axis and transmission axis of the second polarizer (%). In addition, regarding Examples 1 to 5 (model A) and Comparative Examples 1 to 5 (model B), the amount of warpage generated and the judgment result of its quality (○/×) are shown. In addition, the degree of warpage is judged as "○" when the amount of warpage is 0.55 mm or less, and judged as "×" when the amount of warpage exceeds 0.55 mm.

Furthermore, in this embodiment, by adjusting the time of the heating treatment (annealing treatment), reflective polarizers with different dimensional change rates are obtained. Specifically, the reflective polarizers of Example 5 and Comparative Example 5 were prepared. The reflective polarizers of Example 1 and Comparative Example 1 were prepared by setting the reflective polarizers of Example 5 and Comparative Example 5 at 85°C. It is obtained by heating for 2500 minutes. The reflective polarizers of Example 2 and Comparative Example 2 were obtained by heating the reflective polarizers of Example 5 and Comparative Example 5 at 85°C for 240 minutes. The reflective polarizers of Example 3 and Comparative Example 3 were obtained by heating the reflective polarizers of Example 5 and Comparative Example 5 at 85°C for 30 minutes. The reflective polarizers of Example 4 and Comparative Example 4 were obtained by heating the reflective polarizers of Example 5 and Comparative Example 5 at 85°C for 10 minutes. In addition, the dimensional change rate of the reflective polarizer was measured with respect to the heat treatment (annealing treatment) described above.

In addition, Figure 7 shows the change in the dimensional change rate (%) of the reflective polarizers of Example 5 and Comparative Example 5 when heated at 85°C. The result.

As shown in Table 1, it can be seen that, compared with Comparative Examples 1 to 5 (Model B), Examples 1 to 5 (Model A) can suppress the amount of warpage generated in a high-temperature environment.

1‧‧‧ Polarizing plate set

2‧‧‧The first polarizer

3‧‧‧Second Polarizing Plate

4‧‧‧The first polarizing film

5‧‧‧Second Polarizing Film

6‧‧‧Reflective polarizer

20‧‧‧LCD unit

30‧‧‧LCD Panel

A, B‧‧‧ Polarized absorption axis

C‧‧‧ Polarized reflection axis

Claims (4)

A polarizing plate set is provided with a first polarizing plate arranged on the display surface side of a liquid crystal cell, and a second polarizing plate and a reflective polarizer arranged on the opposite side to the display surface of the liquid crystal cell; the first polarizing plate It contains a first polarizing film with a polarization absorption axis in the short side direction; the second polarizer contains a second polarizing film with a polarization absorption axis in the long side direction; the reflective polarizer has a polarization reflection in the long side direction When heated at 85°C for 100 hours, the dimensional change rate along the aforementioned polarization reflection axis was -1.4% or more. The polarizing plate set described in the first item of the scope of patent application, wherein the second polarizing plate and the reflective polarizing film are laminated via an adhesive or an adhesive. A liquid crystal display panel is provided with a liquid crystal cell and a polarizing plate group described in item 1 or 2 of the scope of patent application. A liquid crystal display device is provided with a liquid crystal display panel described in item 3 of the scope of patent application, and a backlight.

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