CN109313306B

CN109313306B - Polarizing plate assembly

Info

Publication number: CN109313306B
Application number: CN201780038092.4A
Authority: CN
Inventors: 白石贵志
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2016-06-21
Filing date: 2017-05-29
Publication date: 2021-08-31
Anticipated expiration: 2037-05-29
Also published as: JP6887222B2; JP2017227731A; TWI726116B; KR20190020732A; KR102412245B1; TW201804182A; CN109313306A; WO2017221638A1

Abstract

The invention provides a polarizing plate assembly, which has small warpage when being arranged in a damp-heat resistant/heat resistant environment and can reduce display unevenness caused by possibly generated warpage. The invention provides a polarizing plate assembly comprising a back side polarizing plate disposed on one side of a liquid crystal cell and a front side polarizing plate disposed on the other side, the back-side polarizing plate has a reflective polarizing plate, a first adhesive layer, a first polarizer, a first protective film, and a second adhesive layer, the front-side polarizing plate has a third adhesive layer, a second polarizing plate, and a second protective film, when a difference dF-dR obtained by subtracting a thickness dR (μm) of the first polarizer of the rear polarizing plate from a thickness dF (μm) of the second polarizer of the front polarizing plate is defined as Δ d (μm), 0 μm < Δ d < 5 μm, an angle formed by the absorption axis of the second polarizer of the front-side polarizing plate and the absorption axis of the first polarizer of the rear-side polarizing plate is 90 ° ± 1 °.

Description

Polarizing plate assembly

Technical Field

The present invention relates to a polarizing plate assembly that can be used in various optical applications.

Background

Polarizing plates are disposed on both sides of the liquid crystal cell for reasons of an image forming method of the liquid crystal display device.

For example, patent document 1 discloses a liquid crystal panel in which polarizing plates are disposed on the front surface side and the back surface side of a liquid crystal cell. Patent document 2 discloses an optical laminate disposed on the front and back sides of a liquid crystal cell.

According to the liquid crystal panel disclosed in patent document 1 and the optical laminate disclosed in patent document 2, it has been attempted to reduce the warpage of the liquid crystal panel by defining the relationship between the thicknesses of the polarizing film disposed on the front surface side and the polarizing film disposed on the back surface side.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2012-58429

Patent document 2: japanese patent laid-open publication No. 2013-37115

Disclosure of Invention

Problems to be solved by the invention

Conventionally, although the warpage of a liquid crystal panel has not been a problem if only the warpage in a high-temperature environment is focused on and controlled, it has been found that the warpage of a liquid crystal cell can be significantly observed due to stress of a polarizer caused by a slight dimensional change amount generated in a hot and humid environment (e.g., 60 ℃ and 90% humidity) as the thickness of the liquid crystal cell becomes thinner (e.g., the thickness of a glass substrate constituting the liquid crystal cell is 0.5mm or less).

The inventions disclosed in patent documents 1 and 2 have problems that the liquid crystal panel is peeled off from the touch panel or the backlight unit is peeled off due to the warping of the liquid crystal panel under a wet heat condition depending on conditions such as the structure of the protective film and the polarizing plate used.

Accordingly, an object of the present invention is to provide a polarizing plate assembly capable of suppressing the warpage of a liquid crystal panel in a high-temperature environment and also in a moist-heat environment.

Means for solving the problems

The present invention includes the following.

[1] A polarizing plate assembly is provided which includes a polarizing plate,

the polarizing plate assembly comprises a back-side polarizing plate disposed on one side of a liquid crystal cell and a front-side polarizing plate disposed on the other side,

the back-side polarizing plate has a reflective polarizing plate, a first adhesive layer, a first polarizer, a first protective film, and a second adhesive layer,

the front-side polarizing plate has a third adhesive layer, a second polarizing plate, and a second protective film,

when a difference dF-dR obtained by subtracting a thickness dR (μm) of the first polarizer of the rear polarizing plate from a thickness dF (μm) of the second polarizer of the front polarizing plate is defined as Δ d (μm), 0 μm < Δ d < 5 μm,

an angle formed by the absorption axis of the second polarizer of the front-side polarizing plate and the absorption axis of the first polarizer of the rear-side polarizing plate is 90 ° ± 1 °.

[2] The polarizing plate assembly according to [1], wherein an angle formed by an absorption axis of the first polarizer of the back-side polarizing plate and a long side of the back-side polarizing plate is 0 ° ± 0.5 °.

[3] The polarizing plate assembly according to [1] or [2], wherein the reflective polarizing plate has at least 2 films, and the refractive index anisotropy of the at least 2 films is different.

[4] A liquid crystal panel has a liquid crystal cell and a pair of polarizing plates disposed on both sides of the liquid crystal cell,

the pair of polarizing plates is the polarizing plate assembly according to any one of [1] to [3],

a second protective film, a second polarizer, a third adhesive layer, a liquid crystal cell, a second adhesive layer, a first protective film, a first polarizer, a first adhesive layer, and a reflective polarizing plate are sequentially stacked.

Effects of the invention

According to the present invention, a polarizing plate assembly capable of reducing warpage of a liquid crystal panel when exposed to a moist heat environment and a high temperature environment can be obtained.

Drawings

Fig. 1 is a schematic cross-sectional view illustrating one embodiment of a polarizing plate assembly of the present invention.

Fig. 2 is a schematic diagram illustrating an angle formed by the absorption axis of the front-side polarizing plate and the absorption axis of the rear-side polarizing plate.

Fig. 3 is a diagram illustrating measurement of the warpage amount.

Detailed Description

Hereinafter, the polarizing plate assembly of the present invention will be described with reference to the drawings as appropriate, but the present invention is not limited to these embodiments.

The invention provides a polarizing plate assembly comprising a back side polarizing plate disposed on one side of a liquid crystal cell and a front side polarizing plate disposed on the other side,

For example, according to the liquid crystal panel including the polarizing plate assembly of the present invention, it is possible to suppress peeling of the liquid crystal panel from the touch panel or dropping of the backlight assembly, and to obtain a display device with less display unevenness.

As shown in fig. 1, the polarizing plate assembly of the present invention includes a back-side polarizing plate 10 disposed on one surface side of a liquid crystal cell 30 and a front-side polarizing plate 20 disposed on the other surface side. The back-side polarizing plate 10 has a reflective polarizing plate 11, a first adhesive layer 12, a first polarizer 13, a first protective film 14, and a second adhesive layer 15. In one embodiment, the back-side polarizing plate 10 may have other layers as necessary.

In another embodiment, the rear-side polarizing plate 10 is a polarizing plate in which a reflective polarizing plate 11, a first adhesive layer 12, a first polarizer 13, a first protective film 14, and a second adhesive layer 15 are stacked in this order. The rear-side polarizing plate 10 may further include a protective film (not shown) between the first adhesive layer 12 and the first polarizer 13. That is, the back-side polarizing plate 10 may have protective films on both sides of the first polarizer 13.

The front-side polarizing plate 20 has a third adhesive layer 21, a second polarizing plate 22, and a second protective film 23. The front-side polarizing plate 20 may have other layers as needed.

In another embodiment, the front side polarizing plate 20 is a polarizing plate in which a third adhesive layer 21, a second polarizing plate 22, and a second protective film 23 are laminated in this order. The front-side polarizing plate 20 may further include a protective film (not shown) between the third adhesive layer 21 and the second polarizing plate 22. That is, the front-side polarizing plate 20 may have protective films on both sides of the second polarizing plate 22.

The back-side polarizing plate of the present invention is bonded to, for example, the surface of the liquid crystal cell opposite to the surface on the viewing side. In one embodiment, the back-side polarizing plate may be bonded to the liquid crystal cell so as to be adjacent to a light source provided in the liquid crystal panel, for example, a backlight. Further, a double-sided tape having a narrow width may be attached to the edge of the rear polarizing plate to attach the backlight assembly.

On the other hand, the front surface side polarizing plate of the present invention is bonded to, for example, the surface of the liquid crystal cell on the viewing side.

Although not shown in fig. 1, for example, layers other than the above-described layers may be provided on the rear-side polarizing plate 10 and the front-side polarizing plate 20, which are the polarizing plate assembly shown in fig. 1. The polarizing plates 13 and 22 and the

protective films

14 and 23 are usually bonded to each other with an adhesive layer interposed therebetween.

As shown in fig. 1, the polarizing plate assembly of the present invention has a relationship of 0 μm < Δ d < 5 μm, and more preferably a relationship of 1 μm < Δ d < 5 μm, where dF is the thickness of the second polarizer of the front polarizing plate 20, dR is the thickness of the first polarizer of the back polarizing plate 10, and Δ d (μm) is the difference dF-dR obtained by subtracting the thickness dR (μm) of the first polarizer of the back polarizing plate 10 from the thickness dF (μm) of the second polarizer of the front polarizing plate 20.

When Δ d (μm), which is a difference obtained by subtracting the thickness dR from the thickness dF, is set in such a range, the amount of warpage of the laminate is small even when the laminate (liquid crystal panel) of the front-side polarizing plate, the glass (liquid crystal cell), and the back-side polarizing plate is exposed to high temperature (for example, 85 ℃ c, humidity 5%) for a long time. Further, even when the laminate of the front-side polarizing plate, the glass, and the back-side polarizing plate is placed in a hot and humid environment (for example, 60 ℃ C., humidity 90%), the warpage of the laminate can be suppressed.

As described above, since the laminate including the polarizing plate assembly of the present invention has a small amount of warpage when it is disposed in a hot and humid environment or a high-temperature environment, it is considered that it has heat and humidity resistance and does not peel off from the touch panel or fall off from the backlight assembly in the hot and humid environment.

In addition, the display unevenness due to warpage after the high-temperature environment and the damp-heat environment test is reduced.

By making Δ d (μm) have such a relationship, the polarizing plate assembly of the present invention can be applied to liquid crystal panels having various sizes and thicknesses.

In this specification, a temperature of 85 ℃ will be described as an example of a high-temperature environment. In the present invention, the high temperature environment may mean an environment in which a polarizing plate or the like is exposed to a temperature of 70 to 95 ℃ and a humidity of 0 to 20% for at least 30 to 60 minutes, for example.

Further, as an example of the moist heat environment, a condition of a temperature of 60 ℃ and a humidity of 90% will be described. In the present invention, the moist heat environment may be an environment in which a polarizing plate or the like is exposed to a temperature of 50 to 80 ℃ and a humidity of 60 to 95% for at least 30 to 60 minutes, for example.

In one embodiment, the thickness dR of the first polarizer of the rear-side polarizing plate is 15 μm or less, and more preferably 0.1 μm or more and 13 μm or less.

Since the rear-side polarizing plate includes the reflective polarizing plate, the rear-side polarizing plate can be made thinner as the thickness of the first polarizer is thinner.

The thickness of the polarizing plate assembly of the present invention can be measured by a measurement method known in the art.

In the present invention, the angle formed by the absorption axis of the second polarizer of the front-side polarizing plate and the absorption axis of the first polarizer of the back-side polarizing plate is 90 ° ± 1 °, and more preferably 90 ° ± 0.5 °.

For example, fig. 2 is a diagram illustrating a relationship between absorption axes of a polarizing plate according to an embodiment of the present invention. In fig. 2, the absorption axis of the first polarizer of the back-side polarizing plate 10 is denoted by 10a, and the transmission axis of the first polarizer is denoted by 10 b. The long side of the back-side polarizing plate is denoted by 10 c.

On the other hand, in fig. 2, the absorption axis of the second polarizing plate of the front-side polarizing plate 20 is denoted by 20a, and the transmission axis of the second polarizing plate is denoted by 20 b.

In the present invention, the angle formed by the absorption axis 10a of the first polarizer and the absorption axis 20a of the second polarizer is 90 ° ± 1 ° as described above. This angle can be represented, for example, as angle α in fig. 2.

In one embodiment, the angle formed by the absorption axis of the first polarizer of the back-side polarizing plate and the long side of the back-side polarizing plate (first polarizer) is 0 ° ± 1 °, and in another embodiment, the angle is 0 ° ± 0.5 °.

In the present invention, the absorption axis of the second polarizer of the front-side polarizing plate may be referred to as the absorption axis of the front-side polarizing plate, and the absorption axis of the first polarizer of the back-side polarizing plate may be referred to as the absorption axis of the back-side polarizing plate.

In the polarizing plate assembly of the present invention, when a difference dF-dR obtained by subtracting a thickness dR (μm) of a first polarizing plate of a rear-side polarizing plate from a thickness dF (μm) of a second polarizing plate of a front-side polarizing plate is defined as Δ d (μm),

by setting 0 μm < Δ d < 5 μm, even when a liquid crystal panel having, for example, a front-side polarizing plate, a glass plate, and a back-side polarizing plate is exposed to a high-temperature condition and a hot and humid environment, warping thereof can be suppressed.

In the case where the polarizing plate of the present invention is exposed to a high temperature condition, slight warpage may occur in the polarizing plate, and for example, the reflective polarizing plate, the first adhesive layer, the first polarizer, the first protective film, and the second adhesive layer may be integrally warped. Likewise, the third adhesive layer, the second polarizing plate, and the second protective film may be integrally warped.

Therefore, the back-side polarizing plate and the front-side polarizing plate of the present invention can generally prevent interlayer peeling between at least one of these layers.

In some cases, either the rear-side polarizing plate or the front-side polarizing plate may be warped, and both the rear-side polarizing plate and the front-side polarizing plate may be warped.

Such warpage can be evaluated by measuring the amount of warpage in the present invention. For example, the warpage amount can be evaluated by measuring the warpage amount under a moist heat condition, or by measuring the warpage amount under a high temperature condition.

For example, in the case of measuring the amount of warpage under a moist heat condition, the third adhesive agent of the front-side polarizing plate and the second adhesive layer of the back-side polarizing plate were bonded to the front and back surfaces of the glass panel, and left to stand for 250 hours in an environment of 60 ℃ and 90% humidity, and then the glass panel was set so that the back-side polarizing plate was located below, and the relative height of warpage from the horizontal surface of the measurement table was measured.

For example, when the amount of warpage in a high temperature state is measured, the third adhesive of the front-side polarizing plate and the second adhesive layer of the back-side polarizing plate are bonded to the front and back surfaces of the glass panel, and the glass panel is left standing at 85 ℃ and 5% humidity for 250 hours, and then the glass panel is placed so that the back-side polarizing plate is located below the glass panel, and the relative height of warpage from the horizontal surface of the measurement table is measured.

[ reflection type polarizing plate ]

A reflective polarizing plate is also called a brightness enhancement film, and uses a polarization conversion element having a function of separating light emitted from a light source (backlight) into transmission polarized light and reflection polarized light or scattering polarized light. By disposing the reflective polarizing plate and the polarizing plate in a predetermined relationship as described above, the emission efficiency of the linearly polarized light emitted from the polarizing plate can be improved by using the return light which is the reflected polarized light or the scattered polarized light. For example, a reflective polarizing plate is laminated in contact with the first adhesive layer.

The reflective polarizing plate may be, for example, an anisotropic reflective polarizer. An example of the anisotropic reflective polarizing plate is an anisotropic multiple film which transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, and a specific example thereof is DBEF manufactured by 3M corporation (japanese patent application laid-open No. 4-268505, etc.). Such a reflective polarizing plate is obtained by stretching a multilayer laminate comprising at least 2 films having different refractive index anisotropy. Accordingly, this reflective polarizing plate has at least 2 films, and at least 2 films stretched are films having different refractive index anisotropy.

Another example of the anisotropic reflective polarizing plate is a composite of a cholesteric liquid crystal layer and a λ/4 plate, and a specific example thereof is PCF (Japanese patent application laid-open No. 11-231130, etc.) manufactured by Nindon electric Co. Another example of the anisotropic reflective polarizing plate is a reflective grating polarizing plate, and specific examples thereof include a metal lattice reflective polarizing plate (see, for example, U.S. Pat. No. 6288840) in which a metal is finely processed and a film obtained by adding metal fine particles to a polymer matrix and stretching the polymer matrix (see, for example, japanese patent laid-open No. 8-184701).

On the surface of the reflective polarizing plate opposite to the first pressure-sensitive adhesive layer, an optical layer such as a hard coat layer, an antiglare layer, a light diffusion layer, or a retardation layer having a phase difference value of 1/4 wavelength may be provided. By forming the optical layer, the adhesion to the backlight tape and the uniformity of the displayed image can be improved. The thickness of the reflective polarizer may be about 5 to 100 μm, but is preferably 10 to 40 μm, and more preferably 10 to 30 μm, from the viewpoint of reducing warpage of the liquid crystal panel.

In the polarizing plate assembly of the present invention, the surface of the reflective polarizing plate on the first adhesive layer side may be subjected to a surface activation treatment. The surface activation treatment may be performed before the reflective polarizing plate is attached to the first adhesive layer. Thus, a polarizing plate excellent in moisture and heat durability in which peeling between the first adhesive layer and the reflective polarizing plate is less likely to occur in a moist heat environment can be obtained.

The surface activation treatment may be a hydrophilization treatment of the surface, and may be either a dry treatment or a wet treatment. Examples of the dry treatment include discharge treatments such as corona treatment, plasma treatment, and glow discharge treatment; flame treatment; carrying out ozone treatment; carrying out UV ozone treatment; ionizing active ray treatment such as ultraviolet ray treatment and electron beam treatment. Examples of the wet treatment include ultrasonic treatment, alkali treatment, anchor coat treatment, and the like using a solvent such as water or acetone. These treatments may be performed alone or in combination of two or more.

Among them, the surface activation treatment is preferably corona treatment and/or plasma treatment in view of the peeling prevention effect of the reflective polarizing plate in a moist heat environment and the productivity of the polarizing plate. According to these surface activation treatments, even when the thickness of the reflective polarizer is thin, for example, 30 μm or less, peeling between the first adhesive layer and the reflective polarizer in a moist heat environment can be effectively suppressed. The surface of the first adhesive layer on the side of the brightness reflection type polarizing plate may be also subjected to surface activation treatment.

[ first adhesive layer ]

The first adhesive layer is a layer interposed between the first polarizer and the reflective polarizing plate. The first adhesive layer is typically directly laminated to the polarizer in such a manner that the first polarizer is in contact with the first adhesive layer.

The first pressure-sensitive adhesive layer may be formed of a pressure-sensitive adhesive composition containing a resin such as an acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin as a main component. Among them, the pressure-sensitive adhesive composition is suitable for use as a base polymer, which is an acrylic resin having excellent transparency, weather resistance, heat resistance and the like. The adhesive composition may be an active energy ray-curable type or a thermosetting type.

As the acrylic base polymer, for example, (meth) acrylate base polymers such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, and copolymer base polymers using two or more of these (meth) acrylates can be suitably used. It is preferred to copolymerize the polar monomer with the base polymer. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.

The adhesive composition typically also contains a crosslinking agent. Examples of the crosslinking agent include a crosslinking agent which is a metal ion having a valence of 2 or more and forms a metal carboxylate salt with a carboxyl group; a crosslinking agent which is a polyamine compound and forms an amide bond with a carboxyl group; a crosslinking agent which is a polyepoxy compound or a polyol and forms an ester bond between the polyepoxy compound or the polyol and a carboxyl group; a crosslinking agent which is a polyisocyanate compound and forms an amide bond between the polyisocyanate compound and a carboxyl group. Among them, polyisocyanate compounds are preferable.

The active energy ray-curable pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition which is cured after being irradiated with an active energy ray such as ultraviolet ray or electron beam, has adhesive properties even before irradiation with the active energy ray, can be adhered to an adherend such as a film, and can be cured by irradiation with the active energy ray to adjust the adhesion force. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition. The active energy ray-curable adhesive composition contains an active energy ray-polymerizable compound in addition to a base polymer and a crosslinking agent. Further, a photopolymerization initiator, a photosensitizer and the like may be contained as necessary.

The adhesive composition may comprise particles for imparting light scattering properties; beads; a resin other than the base polymer; a tackifier; a filler; an antioxidant; an ultraviolet absorber; a pigment; colorants, and the like.

The first pressure-sensitive adhesive layer can be formed by applying a diluted solution of the above-mentioned pressure-sensitive adhesive composition in an organic solvent to a substrate and drying it. The substrate may be a polarizer, a reflective polarizing plate, a spacer, or the like. When an active energy ray-curable pressure-sensitive adhesive composition is used, the pressure-sensitive adhesive layer formed can be irradiated with an active energy ray to produce a desired cured product.

The first adhesive layer is preferably a material exhibiting a storage modulus of 0.15 to 1.2MPa in a temperature range of 23 to 80 ℃. This can suppress the dimensional change that tends to occur due to the shrinkage of the polarizer in a high-temperature and humid environment, and can improve the durability of the polarizing plate. In addition, when a liquid crystal panel (for example, a liquid crystal panel for a small-to-medium-sized mobile terminal) having a polarizing plate mounted thereon is placed in a high-temperature and hot-humid environment, the movement of the polarizing plate can be suppressed, and therefore, the reliability of the liquid crystal panel can be improved.

The phrase "exhibits a storage modulus of 0.15 to 1.2MPa in a temperature range of 23 to 80 ℃ means that the storage modulus is a value within the above range at any temperature in the range. The storage modulus generally decreases gradually with increasing temperature, and therefore if the storage modulus at 23 ℃ and 80 ℃ both fall within the above range, it can be considered that the storage modulus in the above range is exhibited at a temperature in this range. The storage modulus of the first pressure-sensitive adhesive layer can be measured using a commercially available viscoelasticity measuring apparatus, for example, a viscoelasticity measuring apparatus "DYNAMICs ANALYZER RDA II" manufactured by reomeric corporation as shown in examples described later.

As a method for adjusting the storage modulus to the above range, an active energy ray-curable pressure-sensitive adhesive composition (preferably, an ultraviolet-curable pressure-sensitive adhesive composition) can be obtained by further adding an oligomer, specifically, a urethane acrylate oligomer, to a pressure-sensitive adhesive composition containing a base polymer and a crosslinking agent. More preferably, the adhesive layer is moderately cured by irradiation with active energy rays.

The thickness of the first adhesive layer may be 30 μm or less. Preferably 25 μm or less, particularly preferably 20 μm or less, and particularly preferably 15 μm or less. By making the thickness of the first adhesive layer in such a range, dimensional changes of the polarizing plate can be suppressed while maintaining good workability. The thickness of the first pressure-sensitive adhesive layer may be appropriately adjusted so that the interlayer thickness is within a predetermined range.

[ polarizing plate ]

The polarizing plate is an absorption type polarizing plate having a property of absorbing linearly polarized light having a vibration plane parallel to an absorption axis thereof and transmitting linearly polarized light having a vibration plane orthogonal to the absorption axis (parallel to a transmission axis). The first polarizing plate and the second polarizing plate used in the polarizing plate assembly of the present invention may be the same polarizing plate or different polarizing plates as long as the thicknesses thereof have a predetermined relationship. For example, a polarizing film in which a polyvinyl alcohol resin film is aligned by adsorbing a dichroic dye can be suitably used. Examples of the polarizing plate include a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing the polyvinyl alcohol resin film with a dichroic dye to thereby adsorb the dichroic dye; treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereon with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.

As the polyvinyl alcohol resin, a resin obtained by saponifying a polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other copolymerizable monomers. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The polyvinyl alcohol resin has an average polymerization degree of usually about 1000 to 10000, preferably about 1500 to 5000. The average polymerization degree of the polyvinyl alcohol resin can be determined in accordance with JIS K6726.

A film obtained by forming such a polyvinyl alcohol resin film is used as a raw material film of a polarizing plate (polarizing film). The method for forming the film from the polyvinyl alcohol resin is not particularly limited, and a known method can be used. The thickness of the polyvinyl alcohol-based material film is not particularly limited, but for setting the thickness of the polarizing plate to, for example, 15 μm or less, it is preferable to use a material film of about 5 to 35 μm.

The uniaxial stretching of the polyvinyl alcohol resin film may be performed before, simultaneously with, or after the dyeing of the dichroic dye. In the case where the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before boric acid treatment or in boric acid treatment. In addition, uniaxial stretching may be performed in a plurality of stages of these.

In the case of uniaxial stretching, the stretching may be performed uniaxially between rolls having different peripheral speeds, or may be performed uniaxially using a heat roll. The uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which stretching is performed in a state where the polyvinyl alcohol resin film is swollen with a solvent. The draw ratio is usually about 3 to 8 times.

As a method for dyeing the polyvinyl alcohol resin film with the dichroic dye, for example, a method of immersing the film in an aqueous solution containing the dichroic dye can be employed. Iodine or a dichroic organic dye is used as the dichroic dye. The polyvinyl alcohol resin film is preferably subjected to an immersion treatment in water before the dyeing treatment.

As the dyeing treatment with iodine, a method of immersing a polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide is generally employed. The iodine content in the aqueous solution may be about 0.01 to 1 part by weight per 100 parts by weight of water. The potassium iodide may be contained in an amount of about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be about 20 to 40 ℃. On the other hand, as the dyeing treatment using the dichroic organic dye, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic organic dye is generally employed. The aqueous solution containing the dichroic organic dye may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The content of the dichroic organic dye in the aqueous solution may be 1 × 10 per 100 parts by weight of water^－4About 10 parts by weight. The temperature of the aqueous solution can be about 20-80 ℃.

As the boric acid treatment after dyeing with the dichroic dye, a method of immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid is generally employed. In the case of using iodine as the dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide.

The amount of boric acid in the aqueous solution containing boric acid may be about 2 to 15 parts by weight per 100 parts by weight of water. The amount of potassium iodide in the aqueous solution may be about 0.1 to 15 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be 50 ℃ or higher, for example, 50 to 85 ℃.

The polyvinyl alcohol resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment can be performed by, for example, immersing the boric acid-treated polyvinyl alcohol resin film in water. The water washing treatment may be performed using water containing potassium iodide. The temperature of water in the water washing treatment is usually about 5 to 40 ℃.

After washing with water, drying treatment was performed to obtain a polarizing plate. The drying treatment may be performed using a hot air dryer or a far infrared heater. The thickness of the polarizing plate is preferably 15 μm or less, and more preferably 13 μm or less. The thickness of the polarizing plate is usually 4 μm or more. In one embodiment, the thickness dR of the first polarizer of the rear-side polarizing plate is 15 μm or less. In one embodiment, the thickness dF of the second polarizer of the front-side polarizer is 15 μm or less, and more preferably 0.1 μm or more and 13 μm or less.

The thickness of the polarizing plate may be appropriately adjusted within a range not departing from the scope of the present invention.

[ protective film ]

The first protective film is a film laminated on a surface of the first polarizing plate opposite to the first adhesive layer. The second protective film is a film laminated on the surface of the second polarizing plate opposite to the third adhesive layer. The first protective film and the second protective film may be the same film or different films.

The protective film may be a polyolefin-based resin including a light-transmitting (preferably optically transparent) thermoplastic resin, for example, a chain polyolefin-based resin (such as a polypropylene-based resin) or a cyclic polyolefin-based resin (such as a norbornene-based resin); cellulose resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; a polycarbonate-based resin; acrylic resins such as (meth) acrylic resins; a polystyrene-based resin; a polyvinyl chloride resin; acrylonitrile/butadiene/styrene resins; acrylonitrile/styrene resins; polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; modified polyphenylene ether resin; a polysulfone-based resin; a polyether sulfone-based resin; a polyarylate-based resin; a polyamide imide resin; a film of a polyimide resin or the like. Among them, a polyolefin-based resin or an acrylic resin is preferably used, and a cyclic polyolefin-based resin is particularly preferably used.

Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, and copolymers of two or more kinds of chain olefins.

The cyclic polyolefin resin is a general term for resins obtained by polymerizing cyclic olefins as polymerization units. Specific examples of the cyclic polyolefin resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with linear olefins such as ethylene and propylene (typically random copolymers), graft polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrogenated products thereof. Among these, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers are preferably used as the cyclic olefin. In a preferred embodiment, the protective film of the present invention contains a cyclic polyolefin resin.

The cellulose resin refers to a cellulose organic acid ester or a cellulose mixed organic acid ester in which some or all of hydrogen atoms of hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linters and wood pulp (hardwood pulp and softwood pulp) are substituted with acetyl groups, propionyl groups and/or butyryl groups. Examples of the resin include cellulose acetate, cellulose propionate, cellulose butyrate, and mixed esters thereof.

A preferable specific example of the acrylic resin film is a film containing a methyl methacrylate resin. The methyl methacrylate resin is a polymer containing 50% by weight or more of methyl methacrylate units. The content of the methyl methacrylate unit is preferably 70% by weight or more, and may be 100% by weight. The polymer having a methyl methacrylate unit of 100% by weight is a methyl methacrylate homopolymer obtained by polymerizing methyl methacrylate alone.

The methyl methacrylate resin can be obtained by polymerizing a monofunctional monomer containing methyl methacrylate as a main component and a polyfunctional monomer used as needed in the coexistence of a radical polymerization initiator and a chain transfer agent used as needed.

Examples of the monofunctional monomer copolymerizable with methyl methacrylate include methacrylic acid esters other than methyl methacrylate such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate; acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate; hydroxyacrylates such as methyl 2- (hydroxymethyl) acrylate, methyl 3- (hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, and butyl 2- (hydroxymethyl) acrylate; unsaturated acids such as methacrylic acid and acrylic acid; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyl toluene and alpha-methyl styrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; and unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. These monomers may be used alone or in combination of two or more.

Examples of the polyfunctional monomer copolymerizable with methyl methacrylate include those obtained by esterifying both terminal hydroxyl groups of ethylene glycol or an oligomer thereof with acrylic acid or methacrylic acid, such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, nonaethylene glycol di (meth) acrylate, and tetradecylene glycol (meth) acrylate; a substance obtained by esterifying both terminal hydroxyl groups of propylene glycol or an oligomer thereof with acrylic acid or methacrylic acid; a product obtained by esterifying a hydroxyl group of a diol with acrylic acid or methacrylic acid, such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, or butanediol di (meth) acrylate; a bisphenol A, an alkylene oxide adduct of bisphenol A, or a halogen-substituted product thereof, wherein both terminal hydroxyl groups are esterified with acrylic acid or methacrylic acid; a polyol such as trimethylolpropane and pentaerythritol esterified with acrylic acid or methacrylic acid, and a polyol obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate to the terminal hydroxyl group; a compound obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate to a dibasic acid such as succinic acid, adipic acid, terephthalic acid, phthalic acid or a halogen-substituted compound thereof or an alkylene oxide adduct thereof; aryl (meth) acrylates; and diaryl compounds such as divinylbenzene. Among them, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate and neopentyl glycol dimethacrylate are preferably used.

The methyl methacrylate resin may be a modified methyl methacrylate resin modified by a reaction between functional groups of the resin. Examples of the reaction include an intrachain demethanol condensation reaction of a methyl ester group of methyl acrylate and a hydroxyl group of methyl 2- (hydroxymethyl) acrylate, and an intrachain dehydration condensation reaction of a carboxyl group of acrylic acid and a hydroxyl group of methyl 2- (hydroxymethyl) acrylate.

It is also useful to control the phase difference value of the protective film to a value suitable for the liquid crystal panel. For example, in a liquid crystal panel of an in-plane switching (IPS) mode, a film having a substantially zero retardation value is preferably used. The phrase "substantially zero in phase difference" means that the in-plane phase difference value at a wavelength of 590nm is 10nm or less, the absolute value of the phase difference value in the thickness direction at a wavelength of 590nm is 10nm or less, and the absolute value of the phase difference value in the thickness direction at a wavelength of 480 to 750nm is 15nm or less.

Depending on the mode of the liquid crystal panel, the protective film may be subjected to stretching and/or shrinking processing to provide an appropriate phase difference value.

The thickness of the protective film may be about 1 to 30 μm, but is preferably 5 to 25 μm, and more preferably 5 to 20 μm from the viewpoint of strength, handling property, and the like. If the thickness is within this range, the polarizing plate is physically protected, and even when exposed to a moist heat environment, the polarizing plate does not shrink, and stable optical characteristics can be maintained. The thickness of the protective film may be appropriately adjusted so that the interlayer thickness is within a predetermined range.

The protective film may be bonded to the polarizing plate with an adhesive layer interposed therebetween. As the adhesive for forming the adhesive layer, an aqueous adhesive or an active energy ray-curable adhesive can be used.

Examples of the aqueous adhesive include an adhesive comprising a polyvinyl alcohol resin aqueous solution, and an aqueous two-pack type urethane emulsion adhesive. Among these, an aqueous adhesive comprising a polyvinyl alcohol resin aqueous solution can be suitably used. As the polyvinyl alcohol resin, not only a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate as a homopolymer of vinyl acetate, but also a polyvinyl alcohol copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith, a modified polyvinyl alcohol polymer obtained by partially modifying hydroxyl groups thereof, and the like can be used. The aqueous adhesive may contain a crosslinking agent such as an aldehyde compound, an epoxy compound, a melamine compound, a methylol compound, an isocyanate compound, an amine compound, or a polyvalent metal salt.

When an aqueous adhesive is used, it is preferable to perform a step of drying the polarizing plate after the polarizing plate and the protective film are bonded to each other in order to remove water contained in the aqueous adhesive. After the drying step, a curing step of curing at a temperature of, for example, about 20 to 45 ℃ may be provided.

The active energy ray-curable adhesive is an adhesive that is cured by irradiation with an active energy ray such as ultraviolet light, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and an adhesive containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and oligomers derived from the photopolymerizable monomers. Examples of the photopolymerization initiator include those containing active species such as neutral radicals, anionic radicals, and cationic radicals generated by irradiation with active energy rays such as ultraviolet rays. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.

In the case of using an active energy ray-curable adhesive, after the polarizing plate and the protective film are bonded, a drying step is performed as necessary, and then a curing step of curing the active energy ray-curable adhesive by irradiation with an active energy ray is performed. The light source of the active energy ray is not particularly limited, but ultraviolet rays having a light emission distribution at a wavelength of 400nm or less are preferable, and specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used.

When the polarizing plate and the protective film are bonded, at least one of the bonding surfaces may be subjected to saponification treatment, corona treatment, plasma treatment, or the like.

[ second and third adhesive layers ]

The adhesive for forming the second adhesive layer and the third adhesive layer may be any adhesive that is selected as appropriate and has adhesion to such an extent that peeling or the like does not occur in a high-temperature environment, a moist-heat environment, or an environment where high and low temperatures are repeated, to which the polarizing plate is exposed. Specifically, an acrylic adhesive, a silicone adhesive, a rubber adhesive, and the like are mentioned, and an acrylic adhesive is particularly preferable in view of transparency, weather resistance, heat resistance, and processability.

The first pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer, and/or the third pressure-sensitive adhesive layer may use the same type of pressure-sensitive adhesive or may use different types of pressure-sensitive adhesives.

In a preferred embodiment, the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer are formed of an acrylic pressure-sensitive adhesive.

If necessary, various additives such as a tackifier, a plasticizer, glass fibers, glass beads, metal powder, a filler containing other inorganic powder, a pigment, a colorant, a filler, an antioxidant, an ultraviolet absorber, an antistatic agent, and a silane coupling agent may be appropriately blended in the adhesive.

The adhesive layer is generally formed by applying a solution of the adhesive to a release sheet and drying. The coating on the release sheet may be performed by, for example, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a spray coating method, a dipping method, a spraying method, or the like. The release sheet provided with the adhesive layer is applied by a method of transferring the release sheet, or the like. The thickness of the adhesive layer is usually about 3 to 30 μm, preferably 10 to 30 μm, and more preferably 10 to 25 μm. In a preferred embodiment, the second adhesive layer and the third adhesive layer have such thicknesses, whereby breakage of the polarizing plate can be suppressed, and light leakage at the end of the liquid crystal panel can be suppressed when the liquid crystal display device is incorporated. The thicknesses of the second adhesive layer and the third adhesive layer may be appropriately adjusted so that the interlayer thickness is within a predetermined range.

The storage modulus at 80 ℃ of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer is preferably 0.025MPa or more, and more preferably 0.07MPa or more. If the storage modulus of the pressure-sensitive adhesive layer is less than 0.025MPa, aggregation failure of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer may occur, and if aggregation failure is significant, not only may the appearance of the polarizing plate be adversely affected, but also light leakage may occur at the end of the liquid crystal panel when the liquid crystal display device is incorporated, thereby adversely affecting display. The storage modulus at 80 ℃ of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer is preferably 1.1MPa or less, and more preferably 0.9MPa or less. If the storage modulus of the adhesive layer at 80 ℃ is more than 1.1MPa, the heat resistance and durability of the second adhesive layer, the third adhesive layer, and the glass or panel become poor, and bubbles are liable to be generated between the layers.

The spacer may be provided to protect the surface of the second and third adhesive layers before the second and third adhesive layers are attached to other members. For example, a film obtained by treating a film made of a transparent resin such as polyethylene terephthalate with a release agent such as silicone resin is used.

[ method for producing backside polarizing plate ]

The back-side polarizing plate of the present invention is produced, for example, by performing a step of subjecting the surface of the reflective polarizing plate on the side closer to the first pressure-sensitive adhesive layer to a surface activation treatment, and a step of laminating the first pressure-sensitive adhesive layer on the surface subjected to the surface activation treatment.

The back-side polarizing plate of the present invention includes, for example: a first protective film is bonded to one surface of a polarizer with an adhesive layer interposed therebetween, a second adhesive layer is laminated to the surface of the first protective film on the side opposite to the first polarizer, a first adhesive layer is bonded to the surface of the first polarizer on the side opposite to the first protective film, and a reflective polarizing plate is laminated to the surface of the first adhesive layer on the side opposite to the first polarizer. Through these steps, the back-side polarizing plate of the present invention can be obtained. The spacer may be temporarily attached to the outer surface of the second adhesive layer, or the surface of the first adhesive layer that is bonded to the reflective polarizing plate may be subjected to surface activation treatment.

The method of bonding the reflective polarizing plate to the first adhesive layer may be a single-sheet bonding method or a sheet-roll composite bonding method as described in japanese patent application laid-open No. 2004-262071. Further, when the tape can be produced in a long size and the required number is large, a method of bonding by roll-to-roll is also useful.

As described above, the method for manufacturing the rear-side polarizing plate of the present invention can be manufactured by a method known in the art.

[ method for producing front surface side polarizing plate ]

The method for producing the rear-side polarizing plate of the present invention can be produced by a method known in the art. For example, the front-side polarizing plate can be obtained through the same steps as the above-described method for producing the back-side polarizing plate.

[ liquid Crystal Panel ]

The polarizing plate assembly of the present invention may be preferably applied to a liquid crystal panel. The liquid crystal panel includes a liquid crystal cell and the polarizing plate of the present invention attached to the surface thereof. The back-side polarizing plate may be bonded to the liquid crystal cell with a second adhesive layer interposed therebetween. The backside polarizing plate of the present invention is generally used as a polarizing plate disposed on the backlight side of a liquid crystal cell.

On the other hand, the front surface side polarizing plate may be bonded to the liquid crystal cell via a third adhesive layer. The front-side polarizing plate of the present invention is generally used as a polarizing plate disposed on the viewing side of a liquid crystal cell.

In one embodiment, there is provided a liquid crystal panel including a liquid crystal cell and a pair of polarizing plates disposed on both surfaces of the liquid crystal cell,

the pair of polarizing plates is the above-described polarizing plate assembly,

the liquid crystal panel is laminated with a second protective film, a second polarizer, a third adhesive layer, a liquid crystal cell, a second adhesive layer, a first protective film, a first polarizer, a first adhesive layer, and a reflective polarizing plate in this order.

The liquid crystal cell may be driven in any conventionally known manner, but the IPS mode is preferable. The liquid crystal panel using the polarizing plate of the present invention has excellent moisture and heat durability.

In the present invention, the organic electroluminescent display device can be obtained by bonding the respective polarizing plates to the organic electroluminescent display with the second adhesive layer and the third adhesive layer interposed therebetween.

[ examples ]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, the% and parts indicating the content or amount used are based on the weight unless otherwise specified.

The thickness of the film was measured by the following method.

(1) Measurement of film thickness

The measurement was carried out using a digital micrometer "MH-15M" manufactured by Nikon K.K.

[ production of polarizing plate ]

Production example P1

A60 μm thick polyvinyl alcohol film (average degree of polymerization: 2400, degree of saponification: 99.9 mol% or more) was uniaxially stretched in the machine direction by dry stretching to about 5 times, immersed in pure water at 60 ℃ for 1 minute while maintaining the tension, and then immersed in an aqueous solution at 28 ℃ for 60 seconds, wherein the weight ratio of iodine/potassium iodide/water was 0.05/5/100. Thereafter, the plate was immersed in an aqueous solution at 72 ℃ having a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 for 300 seconds. Subsequently, the substrate was washed with pure water at 26 ℃ for 20 seconds and then dried at 65 ℃ to obtain a polarizing plate having a thickness of 23 μm, in which iodine was adsorbed on a polyvinyl alcohol film and oriented. Hereinafter, this polarizing plate may be referred to as a polarizing plate (23 μm).

Production example P2

A30 μm thick polyvinyl alcohol film (average degree of polymerization: 2400, degree of saponification: 99.9 mol% or more) was uniaxially stretched in the machine direction by dry stretching to about 5 times, immersed in pure water at 60 ℃ for 1 minute while maintaining the tension, and then immersed in an aqueous solution at 28 ℃ for 60 seconds, wherein the weight ratio of iodine/potassium iodide/water was 0.05/5/100. Thereafter, the plate was immersed in an aqueous solution at 72 ℃ having a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 for 300 seconds. Subsequently, the substrate was washed with pure water at 26 ℃ for 20 seconds and then dried at 65 ℃ to obtain a 12 μm-thick polarizing plate in which iodine was adsorbed on a polyvinyl alcohol film and oriented. Hereinafter, this polarizing plate may be referred to as a polarizing plate (12 μm).

Production example P3

A polarizing plate 11 μm thick, in which iodine was adsorbed on a polyvinyl alcohol film and was oriented, was obtained in the same manner as in preparation example P2, except that the stretch ratio was adjusted. Hereinafter, this polarizing plate may be referred to as a polarizing plate (11 μm).

Production example P4

A polyvinyl alcohol film having a thickness of 20 μm (average degree of polymerization of about 2400, degree of saponification of 99.9 mol% or more) was uniaxially stretched about 5 times in the longitudinal direction by dry stretching, immersed in pure water at 60 ℃ for 1 minute while maintaining the state of tension, and then immersed in an aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.05/5/100 at 28 ℃ for 60 seconds. Thereafter, the plate was immersed in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 at 72 ℃ for 300 seconds. Subsequently, the substrate was washed with pure water at 26 ℃ for 20 seconds and then dried at 65 ℃ to obtain a polarizing plate having a thickness of 7 μm, in which iodine was adsorbed and oriented on a polyvinyl alcohol film. Hereinafter, this polarizing plate may be referred to as a polarizing plate (7 μm).

Production example P5

A polarizing plate having a thickness of 8 μm and formed by adsorbing iodine on a polyvinyl alcohol film and orienting the film was obtained in the same manner except that the stretching ratio in production example P4 was adjusted. Hereinafter, this polarizing plate may be referred to as a polarizing plate (8 μm).

[ preparation example of first adhesive layer ]

An organic solvent solution obtained by adding a urethane acrylate oligomer and an isocyanate-based crosslinking agent to a copolymer of butyl acrylate and acrylic acid was applied to a release-treated surface of a 38 μm-thick polyethylene terephthalate film (release film) subjected to release treatment by a die coater so that the thickness after drying was 5 μm, and dried to obtain an adhesive sheet.

[ production examples of the second adhesive layer and the third adhesive layer ]

A commercially available pressure-sensitive adhesive sheet was provided with an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm on the release-treated surface of a polyethylene terephthalate film (release film) having a thickness of 38 μm and subjected to release treatment. No urethane acrylate oligomer was incorporated.

[ reflection type polarizing plate ]

As the reflective polarizing plate-1, "Advanced Polarizer Film, Version 3" (thickness 26 μ M) manufactured by 3M was used.

[ protective film ]

The following protective films were used.

HC-TAC: a triacetyl cellulose film (25 KCHC-TC, manufactured by TOPPAN TOMOEGAWA OPTICAL FILMS, Inc.) having a thickness of 32 μm and a hard-coated surface,

TAC: triacetyl cellulose film (TAC) having a thickness of 25 μm (trade name "KC 2 UA" manufactured by Konica Minolta K.K.)

COP-1: not stretched norbornene resin film having a thickness of 23 μm (trade name "ZEONOR" manufactured by ZEON K.K.)

COP-2: nontitruded norbornene resin film having a thickness of 13 μm (trade name "ZEONOR" available from ZEON corporation)

[ preparation of aqueous adhesive ]

An aqueous polyvinyl alcohol solution was prepared by dissolving 3 parts by weight of a carboxyl-modified polyvinyl alcohol ("KL-318" manufactured by Kuraray Co., Ltd.) in 100 parts by weight of water. To the obtained aqueous solution, a water-soluble polyamide-epoxy Resin ("Sumirez Resin 650(30) manufactured by takaki chemical corporation, having a solid content concentration of 30% by weight) was mixed in a proportion of 1.5 parts by weight relative to 100 parts by weight of water to obtain an aqueous adhesive.

[ production example of front surface side polarizing plate ]

(preparation of front polarizing plate A)

An aqueous adhesive was applied to one side of the polarizing plate (12 μm), HC-TAC was bonded as a second protective film, and COP-1 was laminated on the opposite side thereof using the above adhesive, and dried at 80 ℃ for 5 minutes, thereby bonding the protective film to the polarizing plate. After the application, the resultant was aged at 40 ℃ for 168 hours. Then, a third adhesive layer was attached to the surface of COP-1 opposite to the polarizing plate. This laminate was set as a front surface side polarizing plate a. The laminate was rectangular in shape with a long side of 155.25mm and a short side of 95.90 mm.

(preparation of front polarizing plate B)

The polarizing plate was produced in the same manner as the front polarizing plate a except that the polarizing plate of the front polarizing plate a was changed to a polarizing plate (11 μm). This laminated body was set as a front surface side polarizing plate B.

(preparation of front polarizing plate C)

The polarizing plate was produced in the same manner as the front polarizing plate a except that the polarizing plate of the front polarizing plate a was changed to a polarizing plate (23 μm). This laminated body was set as a front surface side polarizing plate C.

[ production example of backside polarizing plate ]

(production example of Back-side polarizing plate A)

TAC was attached as a protective film by applying an aqueous adhesive to one side of a polarizing plate (11 μm), and COP-2 was laminated on the opposite side using the adhesive as a first protective film, and dried at 80 ℃ for 5 minutes, thereby attaching the protective film to the polarizing plate. After the application, the resultant was aged at 40 ℃ for 168 hours. Then, a second adhesive layer was attached to the surface of COP-2 opposite to the polarizing plate. Then, the reflective polarizing plate is bonded to the surface of the TAC opposite to the polarizer with a first adhesive interposed therebetween. This laminate was used as a rear-side polarizing plate a. The laminate was rectangular in shape with a long side of 155.25mm and a short side of 95.90 mm.

(production example of Back side polarizing plate B)

An aqueous adhesive was applied to one side of the polarizing plate (8 μm), COP-2 was laminated as a first protective film, and the protective film was bonded to the polarizing plate by drying at 80 ℃ for 5 minutes. Then, a second adhesive layer was attached to the surface of COP-2 opposite to the polarizing plate. Then, the reflective polarizing plate is bonded to the surface of the polarizer opposite to the first protective film with a first adhesive interposed therebetween. This laminate was set as a rear-side polarizing plate B. The laminate was rectangular in shape with a long side of 155.25mm and a short side of 95.90 mm.

(production example of Back side polarizing plate C)

The polarizing plate B was produced in the same manner as the rear polarizing plate B except that the polarizing plate of the rear polarizing plate B was changed to a polarizing plate (7 μm). This laminated body was set as a front surface side polarizing plate C.

(production example of Back-side polarizing plate D)

The polarizing plate a was produced in the same manner as the rear polarizing plate a except that the polarizing plate of the rear polarizing plate a was changed to a polarizing plate (12 μm). This laminate was set as a front surface side polarizing plate D.

The structures of the polarizing plates of examples and comparative examples thus obtained are shown in table 1. The physical properties of each of the obtained polarizing plates were evaluated in accordance with the following descriptions. The results are shown in table 1.

[ measurement of amount of warpage ]

(preparation of laminate)

The amount of warpage of the polarizing plate produced in the above procedure was measured in the following manner. First, in the produced backside polarizing plate, the surface of the second adhesive layer opposite to the first protective film was bonded to glass (model: EAGLE XG, manufactured by Corning corporation) having a thickness of 0.4mm^{(registered trademark)}) The above.

Then, the surface of the third pressure-sensitive adhesive layer of the front surface-side polarizing plate opposite to the second polarizing plate was bonded to the surface of the glass opposite to the second pressure-sensitive adhesive layer side.

The laminated body was prepared so that the angle formed by the absorption axis of the second polarizer of the front-side polarizer and the absorption axis of the first polarizer of the back-side polarizer was 90 °, and the angle formed by the absorption axis of the first polarizer of the back-side polarizer and the long side of the back-side polarizer was 0 °.

(warpage in a moist Heat Environment)

The laminate having the structure of the back-side polarizing plate/glass/front-side polarizing plate was left to stand at 60 ℃ for 250 hours under an atmosphere having a humidity of 90%. The laminate was taken out of the test chamber and placed on a measurement table of a two-dimensional measuring instrument (NEXIV (registered trademark) MR-12072, manufactured by Nikon K.K.) with the front surface side polarizing plate facing upward.

Then, the surface of the measurement stage was brought into focus, and the height of the focal point with respect to the reference position was measured by bringing the surface into focus at 25 points on the glass sample surface. The difference between the maximum value and the minimum value of the height at the 25-point measurement point was defined as the warpage amount. Specifically, the point 40 shown in fig. 3 is set as a measurement point. The 25 dots shown in fig. 3 are dots in a region 7mm inside from the end portion of the polarizing plate, and are disposed at intervals of about 20mm in the short side direction and about 35mm in the long side direction. In fig. 3, reference numeral 50 denotes a polarizing plate, and 60 denotes a glass plate.

The determination is performed as follows. The results are shown in table 1.

In the examples, the lifting and peeling of the entire laminate, and the lifting and peeling between the layers were not observed in any of the samples.

< decision >

The glass sample left standing in a hot and humid environment was evaluated as "O" when the warpage amount was less than 0.6 mm.

The warpage amount of a glass sample left standing in a humid and hot environment was 0.6mm or more and was defined as "x".

(warpage in high temperature Environment)

In the laminate having the structure of the rear-side polarizing plate/glass/front-side polarizing plate, the laminate was left to stand in an environment of 85 ℃ and a humidity of 5% for 250 hours so that the front-side polarizing plate was positioned on the upper side. The laminate was taken out of the test chamber, and the warped laminate was placed on a measurement table of a two-dimensional measuring instrument (NEXIV (registered trademark) MR-12072, manufactured by Nikon K.K.) so that the front surface side polarizing plate was on the upper side. The amount of warpage was measured in the same manner as in the above-described method.

< decision >

The glass sample left in a high-temperature environment had a warpage of 0.6mm or less and was evaluated as "o".

The case where the warp amount of the glass sample left standing in a high temperature environment was larger than 0.6mm was set as "x".

[ Table 1]

According to the above results, the polarizing plate assembly of the present invention can suppress the warping of the liquid crystal panel even when the polarizing plate is exposed to a high temperature condition or a humid and hot environment. Further, the cohesive failure of the second adhesive layer and the third adhesive layer can be suppressed. In addition, the polarizing plate of the present invention has excellent visibility even when exposed to high temperature conditions or humid and hot environments, and does not cause light leakage of the polarizing plate.

As described above, the polarizing plate assembly of the present invention has a small amount of warpage when disposed in a hot and humid environment or a high-temperature environment, and thus can reduce or prevent peeling from the touch panel and dropping of the backlight assembly. In addition, reduction of display unevenness caused by warping that may occur due to exposure to a high-temperature environment and a damp-heat environment is promoted.

Industrial applicability

According to the present invention, a polarizing plate assembly in which warpage due to shrinkage of a polarizer and a reflective polarizing plate, for example, is suppressed can be provided. Further, according to the present invention, it is possible to provide a polarizing plate assembly in which aggregation breakdown of an adhesive layer attached to a glass substrate of a liquid crystal cell is also suppressed.

Description of the symbols

A back-surface side polarizing plate 10, a reflective polarizing plate 11, a first adhesive layer 12, a first polarizer 13, a first protective film 14, a second adhesive layer 15, a front-surface side polarizing plate 20, a third adhesive layer 21, a second polarizer 22, a second protective film 23, a liquid crystal cell 30, a measurement point 40, a polarizing plate 50, and a glass plate 60.

Claims

1. A polarizing plate assembly includes a back-side polarizing plate disposed on one side of a liquid crystal cell and a front-side polarizing plate disposed on the other side,

the front-side polarizing plate has a third adhesive layer, a second polarizing plate and a second protective film,

when a difference dF-dR obtained by subtracting the thickness dR of the first polarizer of the rear-side polarizing plate from the thickness dF of the second polarizer of the front-side polarizing plate is represented by Δ d, Δ d is 3 to 4 μm,

the angle formed by the absorption axis of the second polarizer of the front-side polarizing plate and the absorption axis of the first polarizer of the rear-side polarizing plate is 90 ° ± 1 °,

dF. The unit of dR, Δ d is μm.

2. The polarizer assembly of claim 1,

an angle formed by the absorption axis of the first polarizer of the back-side polarizing plate and the long side of the back-side polarizing plate is 0 ° ± 0.5 °.

3. The polarizing plate assembly of claim 1 or 2,

the reflective polarizing plate has at least 2 films, and refractive index anisotropy of the at least 2 films is different.

4. A kind of liquid crystal panel is disclosed,

which comprises a liquid crystal cell and a pair of polarizing plates disposed on both sides of the liquid crystal cell,

the pair of polarizing plates is the polarizing plate assembly of any one of claims 1 to 3,

the liquid crystal panel includes the second protective film, the second polarizer, the third adhesive layer, the liquid crystal cell, the second adhesive layer, the first protective film, the first polarizer, the first adhesive layer, and the reflective polarizing plate stacked in this order.