TW201616157A - Polarizing plate and method for producing the same - Google Patents

Abstract

The present invention provides a polarizing plate including a polarizer, an adhesive layer, and a brightness enhancement film in this order and the surface of the brightness enhancement film in the adhesive layer side is treated with surface activation treatment, and method for producing the polarizing plate. The surface active treatment is preferably a corona treatment.

Description

Polarizing plate and manufacturing method thereof

The present invention relates to a polarizing plate comprising a polarizer and a brightness enhancing film laminated thereon, and a method of manufacturing the same.

In recent years, with the increase in the size of the liquid crystal mobile terminal represented by the smart phone, in order to achieve long-term driving, the use of a brightness enhancement film can improve the utilization efficiency of the backlight. On the other hand, from the design and portability side, the demand for thinning of the liquid crystal mobile terminal is increasing, and even the polarizing plate used is required to be thinner and lighter.

The brightness enhancement film is a film which is a backlight of a liquid crystal display device and has a property of reflecting a linearly polarized light of a predetermined polarization axis or a circularly polarized light of a predetermined direction and transmitting other light when the reflected light is incident. For example, when the brightness enhancement film is disposed on the backlight side of the polarizer (absorbance type linear polarizer) disposed on the backlight side of the liquid crystal cell, the backlight is incident on the brightness enhancement film only through the specified polarization state (polarization through the polarizer) The light of the state is supplied to the polarizer, and on the other hand, light other than the specified polarization state is not transmitted and reflected. Provided on a reflective layer or the like on the backlight side of the brightness enhancement film, the light reflected on the brightness enhancement film surface is reversed by the reflection layer, and the brightness enhancement film can be re-injected. Part or all of the light that is emitted can be supplied to the polarizer by transmitting light in a polarized state through the brightness enhancement film.

Thus, when a brightness enhancement film is used, the polarized light absorbed by the polarizer is reflected not to pass through the polarizer side, and is repeatedly reflected and reversed between the brightness enhancement film-reflection layer, and the polarized light is converted into a transmissive polarizer. The polarized light can be supplied to the polarizer. In this way, since the use efficiency of the backlight can be improved, power consumption can be reduced, and when the same power consumption (backlight amount) is compared, the screen can be brighter than when the brightness enhancement film is not used (for example, Japanese Patent Laid-Open No. 11) Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei.

A polarizing plate having a brightness-increasing film having a thickness of 40 to 100 μm across the adhesive layer (pressure-sensitive adhesive layer) on the polarizer is disclosed in Japanese Patent No. 5332599.

A polarizing plate in which a brightness enhancing film is adhered to a polarizer via an adhesive layer is required to withstand the durability of a moist heat environment, and a conventional polarizing plate is subjected to a wet heat durability test such as 60 ° C and 90% RH, and is used in a polarizing plate. At the end, there is a problem of peeling at the interface between the brightness enhancing film and the adhesive layer. This problem is more pronounced as the thickness of the brightness enhancing film is smaller.

An object of the present invention is to provide a polarizing plate which is provided with a polarizer, an adhesive layer and a brightness enhancement film in sequence, which is less likely to cause peeling between the adhesive layer and the brightness enhancement film in a humid heat environment, and has excellent wet heat durability. Its manufacturing method.

The present invention provides a polarizing plate shown below, a method of manufacturing the same, and a liquid crystal display device.

[1] A polarizing plate comprising, in order, a polarizer, an adhesive layer, and a brightness enhancing film; wherein a surface of the brightness enhancing film on the side of the adhesive layer is surface-activated.

[2] The polarizing plate according to [1], wherein the adhesive layer is in contact with the brightness enhancing film.

[3] The polarizing plate according to [1] or [2] wherein the polarizer is in contact with the adhesive layer.

[4] The polarizing plate according to any one of [1] to [3] wherein the surface activation treatment is corona treatment.

[5] The polarizing plate according to any one of [1] to [4] wherein the brightness enhancing film has a thickness of 10 to 30 μm.

[6] The polarizing plate according to any one of [1] to [5] wherein the polarizer has a thickness of 15 μm or less.

[7] The polarizing plate according to any one of [1] to [6] wherein the adhesive layer has a storage elastic modulus of from 0.15 to 1 MPa in a temperature range of from 23 to 80 ° C and a thickness of from 3 to 20 μm.

[8] The polarizing plate according to any one of [1] to [7] further comprising a protective film laminated on a surface of the polarizer opposite to the adhesive layer.

[9] The polarizing plate according to [8], wherein the protective film is made of a polyolefin resin or a cellulose resin.

[10] A liquid crystal display device comprising: a liquid crystal cell The polarizing plate according to any one of [1] to [9].

[11] A method for producing a polarizing plate, comprising: a method of producing a polarizing plate, an adhesive layer, and a brightness enhancing film, comprising: forming a surface on a surface of the brightness enhancing film on the side of the adhesive layer side; a step of activating the treatment; and a step of laminating the pressure-sensitive adhesive layer on the surface after the surface activation treatment.

According to the present invention, it is possible to provide a polarizing plate which is excellent in wet heat durability even when the thickness of the brightness enhancing film is small and peeling between the adhesive layer and the brightness enhancing film is less likely to occur in a hot and humid environment. The polarizing plate of the present invention can be suitably applied to an image display device typified by a liquid crystal display device, and particularly to a liquid crystal display device for a small and medium-sized mobile terminal (a tablet computer, a smart phone, etc.).

1‧‧‧Polar plate

10‧‧‧ polarizer

20‧‧‧1st adhesive layer

30‧‧‧Brightening film

40‧‧‧Protective film

50‧‧‧2nd adhesive layer

60‧‧‧ partition members

70, 80‧‧‧ partition members

90‧‧‧Surface protection film

100, 200, 300‧‧‧ layered bodies

Fig. 1 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate of the present invention.

Fig. 2 (a) and (b) are schematic cross-sectional views showing an example of a method of producing a polarizing plate of the present invention.

Fig. 3 (a) and (b) are schematic cross-sectional views showing another example of the method for producing a polarizing plate of the present invention.

Hereinafter, the present invention will be described in detail while showing an embodiment.

<Polarizer>

(1) Composition of polarizing plate

Fig. 1 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate of the present invention. The polarizing plate of the present invention of the polarizing plate 1 shown in Fig. 1 includes the polarizer 10, the first adhesive layer 20, and the brightness enhancement film 30 in this order. The polarizing plate of the present invention may further include another film or layer, for example, the polarizing plate 1 shown in Fig. 1 and including a protective film 40 laminated on the surface of the polarizing plate 10 opposite to the first adhesive layer 20; The second adhesive layer 50 laminated on the outer surface of the protective film 40; and the partition member 60 laminated on the outer surface of the second adhesive layer 50. The second adhesive layer 50 is for attaching a polarizing plate to other members (for example, a liquid crystal cell or another optical film). The partition member 60 is a film that is temporarily attached to protect the surface of the second adhesive layer 50 before being bonded to other members.

The surface of the brightening film 30 on the side of the first adhesive layer 20 is subjected to a surface activation treatment. Thereby, peeling between the first adhesive layer 20 and the brightness enhancement film 30 is less likely to occur in a hot and humid environment, and the polarizing plate having excellent wet heat durability can be obtained. The surface activation treatment is preferably corona treatment.

(2) Polarizer

The polarizer 10 is provided with an absorptive polarizer that absorbs linear polarized light having a vibrating surface parallel to its absorption axis and penetrates a linearly polarized light having a vibrating surface perpendicular to the absorption axis (parallel to the transmission axis), and is suitable for use. The dichroic dye is adsorbed to a polarizing film of a polyvinyl alcohol-based resin film. The polarizer 10 can be produced, for example, by including the following steps: a polyvinyl alcohol-based resin film a step of performing one-axis stretching; a step of adsorbing a dichroic dye by a dichroic dye on a polyvinyl alcohol-based resin film; a step of treating the polyvinyl alcohol-based resin film having a dichroic dye adsorbed thereon with a boric acid aqueous solution; and borrowing A water washing step after treatment with an aqueous solution of boric acid.

As the polyvinyl alcohol-based resin, a polyvinyl acetate-based resin can be used for saponification. As the polyvinyl acetate-based resin, in addition to the polyvinyl acetate of the homopolymer of vinyl acetate, a copolymer of vinyl acetate and other monomers copolymerizable therewith can be used. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth) acrylamides having an ammonium group, and the like. In the present specification, the term "(meth)acrylic acid" means at least one selected from the group consisting of acrylic acid and methacrylic acid.

The degree of saponification of the polyvinyl alcohol-based resin is usually from about 85 to 100 mol%, more preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, an aldehyde-modified polyethylene formaldehyde or a polyvinyl acetal may be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually from about 1,000 to 10,000, more preferably from about 1,500 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726.

A film of the polyvinyl alcohol-based resin film can be used as a raw material film of the polarizer 10 (polarizing film). The method for forming a film of a polyvinyl alcohol-based resin is not particularly limited, and a conventional method can be employed. The thickness of the polyvinyl alcohol-based raw material film is not particularly limited, and is preferably from 5 to 35 μm in order to make the thickness of the polarizing plate 10 15 μm or less. More preferably, it is 20 μm or less. A polyvinyl alcohol-based raw material film having a thickness of more than 35 μm is stretched in order to obtain When the polarizer 10 having a thickness of 15 μm or less is required to have a stretch ratio, the dimensional shrinkage in a high-temperature environment is increased even when the thickness of the polarizer 10 is 15 μm or less. Further, when the thickness is less than 5 μm, the workability at the time of stretching is low, and when the polarizer is produced, the defects of cutting are likely to occur.

The one-axis extension of the polyvinyl alcohol-based resin film can be carried out before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. When the one-axis extension is performed after dyeing, the one-axis extension can be carried out before boric acid treatment or boric acid treatment. Moreover, one-axis extension can be performed at these plurality of stages.

When one shaft is extended, one shaft extension can be performed between the rollers of different rotational speeds, and one shaft extension can also be performed using the hot roller. Further, the one-axis extension may be a dry stretching in which stretching is performed in the air, or a wet stretching in which a polyvinyl alcohol-based resin film is stretched in a swelling state by using a solvent. The stretching ratio is usually about 3 to 8 times.

As a method of dyeing a polyvinyl alcohol-type resin film by a dichroic dye, the method of immersing this film in the aqueous solution containing a dichroic dye is used, for example. As the dichroic dye system, iodine or a dichroic organic dye is used. Further, the polyvinyl alcohol-based resin film is preferably subjected to immersion treatment of water before the dyeing treatment.

As a dyeing treatment by iodine, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing iodine and potassium iodide is usually used. The content of iodine in the aqueous solution is about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide may be from about 0.5 to 20 parts by weight per 100 parts by weight of water. Moreover, the temperature of the aqueous solution may be about 20 to 40 °C. On the other hand, as a dyeing treatment by a dichroic organic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic organic dye is usually employed. The aqueous solution containing a dichroic organic dye may contain an inorganic salt such as sodium sulfate as a dyeing auxiliary. Content of the aqueous solution of the dichroic organic dye, of water per 100 parts by weight of 1 × 10 ^-4 to 10 parts by weight. The temperature of the aqueous solution may be about 20 to 80 °C.

As a boric acid treatment by dyeing a dichroic dye, a method of immersing a dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid is usually employed. When iodine is used 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 from about 0.1 to 15 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be 50 ° C or higher, for example, 50 to 85 ° C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment can be carried out, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water to be washed is usually about 5 to 40 °C.

After washing with water, drying treatment was carried out to obtain a polarizing plate 10. The drying treatment can be carried out using a hot air dryer or a far infrared heater. The thickness of the polarizer 10 is preferably 15 μm or less, more preferably 10 μm or less. The thickness of the polarizer 10 is 15 μm or less, which is advantageous in the polarizing plate and the thin film formation of the liquid crystal display device. The thickness of the polarizer 10 is usually 4 μm or more.

(3) The first adhesive layer

The first adhesive layer 20 is a layer existing between the polarizer 10 and the brightness enhancement film 30. The first adhesive layer 20 is typically laminated directly on the polarizer 10 with the polarizer 10 and the first adhesive layer 20 being grounded. For example, when the protective film is bonded to the polarizer 10 and the first adhesive layer 20 is laminated thereon, it is found that peeling between the adhesive layer and the brightness enhancing film is less likely to occur even in a hot and humid environment. The first adhesive layer 20 may be composed of an adhesive composition containing a (meth)acrylic, rubber, urethane, ester, polyoxyn, or polyvinyl ether resin as a main component. . Among them, an adhesive composition having a (meth)acrylic resin excellent in transparency, weather resistance, and heat resistance as a matrix polymer is suitable. The adhesive composition may be an active energy ray hardening type or a thermosetting type.

As the (meth)acrylic matrix polymer, for example, butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate is suitably used. An ester (meth) acrylate-based matrix polymer and a copolymerization-based matrix polymer using two or more of these (meth) acrylates. Preferably, the matrix polymer is copolymerized with a polar monomer. As a polar monomer, for example, (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-di(meth)acrylate A monomer having a carboxyl group, a hydroxyl group, a decylamino group, an amine group, an epoxy group or the like of methylaminoethyl ester or glycidyl (meth)acrylate.

The adhesive composition usually contains a crosslinking agent. As a crosslinking agent, for example, a metal ion having a valence of two or more, a metal carboxylate is formed with a carboxyl group; a polyamine compound forms a guanamine bond with a carboxyl group; An oxygen compound or a polyhydric alcohol which forms an ester bond with a carboxyl group; a polyisocyanate compound which forms a guanamine bond with a carboxyl group. Among them, a polyisocyanate compound is preferred.

The active energy ray-curing type adhesive composition has a property of being cured by irradiation with an active energy ray such as an ultraviolet ray or an electron beam, and is also adhesive before irradiation of the active energy ray, and can be adhered to an adherend such as a film. An adhesive composition having a property of adjusting the adhesion force by curing by irradiation with an active energy ray. The active energy ray-curable adhesive composition is preferably an ultraviolet curing type. The active energy ray-curable adhesive composition may further contain an active energy ray-polymerizable compound in addition to the matrix polymer and the crosslinking agent. Further, a photopolymerization initiator, a photosensitizer, or the like may be contained as needed.

The adhesive composition may include: fine particles for imparting light scattering properties; beads; a resin other than the matrix polymer; an adhesion imparting agent; a filler; an antioxidant; a UV absorber; a pigment;

The first adhesive layer 20 can be formed by applying an organic solvent diluent of the above-described adhesive composition onto a substrate and drying it. The substrate may be a polarizer 10, a brightness enhancement film 30, a partition member, or the like. When the active energy ray-curable adhesive composition is used, the formed adhesive layer can be a desired cured product by irradiating the active energy ray.

The first adhesive layer 20 is preferably one having a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 °C. Thereby, in the hot and humid environment, the ruler which is easily generated accompanying the contraction of the polarizer 10 is suppressed. The change in inch can improve the durability of the polarizing plate. Further, when a liquid crystal display device (for example, a liquid crystal display device for a small-sized mobile terminal) equipped with a polarizing plate is placed in a hot and humid environment, the movement of the polarizing plate is suppressed, and the reliability of the liquid crystal display device can be improved.

The "storage elastic modulus of 0.15 to 1 MPa in the temperature range of 23 to 80 ° C" means a value at which the storage elastic modulus is within the above range at any temperature in the range. The storage elastic modulus generally decreases as the temperature rises, so that the storage elastic modulus at 23 ° C and 80 ° C is within the above range, and the storage elastic modulus in the above range can be displayed at the temperature in the range. The storage elastic modulus of the first adhesive layer 20 can be measured using a commercially available viscoelasticity measuring device, for example, a viscoelasticity measuring device "DYNAMIC ANALYZER RDA 11" manufactured by REOMETRIC Co., Ltd., which will be described later.

As a method of adjusting the storage elastic modulus to the above range, for example, an adhesive composition including an alkali polymer (meth)acrylate oligomer, It becomes an active energy ray-curable adhesive composition (preferably an ultraviolet curable adhesive composition). More preferably, the active energy ray is irradiated to moderately cure the adhesive layer.

The thickness of the first adhesive layer 20 may be 1 to 40 μm, and is preferably 3 to 25 μm (for example, 3 to 20 μm) from the viewpoint of suppressing dimensional change of the polarizing plate while maintaining good workability.

(4) Brightening film

The brightness enhancement film 30, also referred to as a reflection type polarization film, can use a polarization conversion element having a function of separating emitted light from a light source (backlight) into a function of transmitting polarized light, reflecting polarized light, or scattering polarized light. As described above, by arranging the brightness enhancement film 30 on the polarizer 10, it is possible to increase the emission efficiency of the linearly polarized light emitted from the polarizer 10 by the reflected light of the reflected polarization or the scattered polarization. The brightness enhancement film 30 is usually laminated on the first adhesive layer 20.

The brightness enhancement film 30 may be, for example, an anisotropic reflective polarizer. An example of the anisotropic reflective polarizer is an anisotropic multiple film that transmits linearly polarized light in the direction of vibration and reflects linearly polarized light in the other direction of vibration. A specific example is DBEF manufactured by 3M (Japanese Patent Laid-Open No. 4-268505, etc.) ). The other example of the anisotropic reflective polarizer is a composite of a cholesteric liquid crystal layer and a λ/4 plate, and a specific example thereof is PCF manufactured by Nitto Denko Corporation (Japanese Patent Laid-Open Publication No. Hei 11-231130, etc.). Another example of the anisotropic reflective polarizer is a reflective grating polarizer, and a specific example thereof is a fine processing of a metal, and a reflective metal polarized reflective polarizer is also emitted in the visible light region (US Patent No. 6288840, etc.) A film in which metal fine particles are added to a polymer matrix and stretched (JP-A-H8-184701).

The surface of the brightness enhancement film 30 on the opposite side to the first adhesive layer 20 may be provided with an optical layer such as a hard coat layer, an antiglare layer, a light diffusion layer, and a retardation layer having a phase difference of 1/4 wavelength. By the formation of the optical layer, the adhesion to the backlight tape and the uniformity of the displayed image can be improved. The thickness of the brightness enhancement film 30 may be about 10 to 100 μm, and more preferably 10 to 50 μm, more preferably 10 to 30 μm from the viewpoint of film formation of the polarizing plate.

In the polarizing plate of the present invention, the first stick of the brightness enhancing film 30 The surface on the side of the agent layer 20 is subjected to a surface activation treatment. This surface activation treatment is performed before the bonding of the brightness enhancement film 30 and the first adhesive layer 20. Thereby, peeling between the brightness enhancement film 30 and the first adhesive layer 20 is less likely to occur in a hot and humid environment, and the polarizing plate 1 having excellent wet heat durability can be obtained.

The surface activation treatment may be a hydrophilization treatment of the surface, and may be a dry treatment or a wet treatment. As dry treatment, for example, corona treatment, plasma treatment, discharge treatment such as glow discharge; flame treatment; ozone treatment; UV ozone treatment; ionization active line treatment such as ultraviolet treatment, electron beam treatment, and the like. As the wet treatment, for example, ultrasonic treatment using a solvent such as water or acetone, alkali treatment, anchor coating treatment, or the like is used. These treatments may be carried out singly or in combination of two or more.

Among them, from the viewpoint of the peeling suppressing effect of the brightness enhancing film 30 and the productivity of the polarizing plate in a hot and humid environment, the surface activation treatment is preferably corona treatment and/or plasma treatment. As long as the surface activation treatment is performed, even when the thickness of the brightness enhancement film 30 is as small as 30 μm or less in a hot and humid environment, peeling between the first adhesive layer 20 and the brightness enhancement film 30 can be effectively suppressed. Further, the surface of the first adhesive layer 20 on the side of the brightness enhancement film 30 may be subjected to a surface activation treatment, and a sufficient effect can be obtained even if the surface of the brightness enhancement film 30 is surface-activated. . Conversely, when the surface of the first adhesive layer 20 on the side of the brightness enhancement film 30 is reversely surface-treated, the effect is lacking.

(5) Protective film

The protective film 40 is arbitrarily laminated on the polarizer 10 and the first adhesive A film of the face on the opposite side of layer 20. However, the polarizing plate is preferably included in the protective polarizing film 10 from the viewpoint of protecting the polarizing film 10. The protective film 40 is a thermoplastic resin having translucency (preferably optically transparent), for example, a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a decene-based resin). a polyolefin resin; a cellulose ester resin such as cellulose triacetate or cellulose diacetate; a polyester resin such as polyethylene terephthalate or polybutylene terephthalate; Polycarbonate resin; (meth)acrylic resin; polystyrene resin; polyvinyl chloride resin; acrylonitrile/butadiene/styrene resin; acrylonitrile/styrene resin; polyvinyl acetate Resin; polyvinylidene chloride resin; polyamido resin; polyacetal resin; modified polyphenylene ether resin; polyfluorene resin; polyether oxime resin; polyarylate resin; A film composed of a quinone imine resin or a polyimine resin. Among them, a polyolefin resin or a cellulose resin is preferably used.

The chain-like polyolefin resin is a copolymer of two or more kinds of chain olefins, in addition to a homopolymer of a chain olefin of a polyethylene resin or a polypropylene resin.

The cyclic polyolefin resin is a general term for a resin in which a cyclic olefin is a polymerization unit. Specific examples of the cyclic polyolefin-based resin include a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene ( Representative of a random copolymer) and such graft polymers modified with unsaturated carboxylic acids and derivatives thereof, and such hydrides. Among them, a norbornene-based monomer using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer as a cyclic olefin The fat is ideal.

The term "cellulosic resin" means a part or all of the hydrogen atom of the hydroxyl group of the cellulose obtained from the raw material cellulose such as cotton linter, wood pulp (broadwood pulp, and conifer pulp), and is acetylated, propylidene and/or Or a cellulose organic acid ester or a cellulose mixed organic acid ester substituted with a butyl group. For example, cellulose acetate, propionate, butyrate, and such mixed esters are used. Among them, preferred is triethyl fluorenyl cellulose, diethyl acetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

The phase difference value of the protective film 40 is controlled to be a value suitable for the liquid crystal display device. For example, in a liquid crystal display device of a horizontal alignment (IPS) mode, it is preferable to use a film having a substantially phase difference value of zero. The substantially phase difference value is 0, which means that the in-plane retardation value of the wavelength 590 nm is 10 nm or less, the absolute value of the thickness direction phase difference of the wavelength 590 nm is 10 nm or less, and the absolute value of the thickness direction of the wavelength direction of 480 to 750 nm is absolute. The value is 15 nm or less.

According to the mode of the liquid crystal display device, the protective film 40 is stretched and/or shrunk to impart a suitable phase difference value.

The thickness of the protective film 40 may be about 1 to 100 μm, and more preferably 5 to 60 μm, and more preferably 5 to 50 μm from the viewpoint of strength, workability, and the like. The polarizer 10 can be mechanically protected as long as it is in the range, and the polarizer 10 does not shrink even when exposed to a moist heat environment, and the stable optical characteristics can be maintained.

The protective film 40 can be bonded to the polarizer 10 via an adhesive layer. As an adhesive for forming an adhesive layer, a water-based adhesive or a live solution can be used. Performance line sclerosing adhesive.

The water-based adhesive is, for example, an adhesive composed of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component urethane-based emulsion adhesive, or the like. Among them, an adhesive composed of a polyvinyl alcohol-based resin aqueous solution is suitably used. As the polyvinyl alcohol-based resin, in addition to the vinyl alcohol homopolymer obtained by saponification of polyvinyl acetate of a homopolymer of vinyl acetate, a copolymer of vinyl acetate and other monomers copolymerizable therewith may be used. The polyvinyl alcohol-based copolymer obtained by the saponification treatment or the modified polyvinyl alcohol-based polymer partially modified by the hydroxyl group. The aqueous binder may include 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 the water-based adhesive is used, after the polarizer 10 and the protective film 40 are bonded together, it is preferred to carry out the drying step in order to remove the water contained in the aqueous binder. After the drying step, a curing step of, for example, curing at a temperature of about 20 to 45 ° C may be provided.

The active energy ray-curable adhesive refers to an adhesive which is cured by irradiation with an active energy ray such as ultraviolet rays, and includes, for example, a polymerizable compound and a photopolymerization initiator, including a photoreactive resin, including a binder. Resin and photoreactive crosslinker, etc. The polymerizable compound is, for example, a photopolymerizable monomer such as a photocurable epoxy monomer, a photocurable (meth)acrylic monomer, or a photocurable amine ester monomer, and a photopolymerizable monomer. Oligomers and the like. The photopolymerization initiator includes, for example, a substance which generates an active species of a neutral radical, an anionic radical, or a cationic radical by irradiation with an active energy ray such as ultraviolet rays. As included As the active energy ray-curable adhesive of the polymerizable compound and the photopolymerization initiator, for example, a photocurable epoxy monomer and a photocationic polymerization initiator are preferably used.

When the active energy ray-curable adhesive is used, after the polarizer 10 and the protective film 40 are bonded together, a drying step is performed as needed, and then the active energy ray-curable adhesive is hardened by irradiation of the active energy ray. step. The light source of the active energy ray is not particularly limited, and is preferably an ultraviolet ray having a light-emitting distribution of a wavelength of 400 nm or less. Specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black lamp, and a microwave-excited mercury lamp can be used. , metal halide lamps, etc.

When the polarizer 10 and the protective film 40 are bonded together, saponification treatment, corona treatment, plasma treatment, or the like may be performed on at least one of the bonding surfaces.

(6) 2nd adhesive layer and partition member

The second adhesive layer 50 laminated on the outer surface of the protective film 40 is an optional layer provided for the polarizing plate to be attached to another member (for example, a liquid crystal cell or another optical film). The composition of the adhesive composition constituting the second adhesive layer 50 is described on the first adhesive layer 20. The storage elastic modulus of the second adhesive layer 50 may be the same as or different from that of the first adhesive layer 20.

The separator member 60 is a film which is temporarily attached to protect the surface of the second adhesive layer 50 before being bonded to another member, and can be formed, for example, by using a film made of a transparent resin of polyethylene terephthalate. borrow Treated by a release agent such as polyfluorene. The same partition member as described above can be attached to the surface of the first adhesive layer 20 in order to protect the surface thereof before bonding to the brightness enhancing film.

<Method of Manufacturing Polarizing Plate>

A method for producing a polarizing plate according to the present invention is a method for producing a polarizing plate comprising a polarizer, a first adhesive layer and a brightness enhancing film, comprising the steps of: surface of the first adhesive layer side of the brightness enhancing film; The first step of performing the surface activation treatment; and the second step of laminating the first adhesive layer on the surface on which the surface activation treatment is performed.

Referring to Fig. 2, an embodiment of a method of manufacturing the polarizing plate 1 shown in Fig. 1 will be described below. First, the protective film 40 is bonded to the single surface of the polarizer 10 via the adhesive layer, and the second adhesive layer 50 is laminated thereon, and the first adhesive is bonded to the other surface of the polarizer 10 In the layer 20, the layered body 100 having the layer structure shown in Fig. 2(a) is obtained. As shown in the figure, the partition member 60 is temporarily attached to the outer surface of the second adhesive layer 50, and the partition member 70 is temporarily attached to the outer surface of the first adhesive layer 20.

Then, the partition member 70 is peeled off from the first adhesive layer 20 of the laminated body 100, and then the surface is subjected to surface activation treatment on the bonding surface (product layer) in the first step on the peeling surface. The bright film 30 is obtained, and the polarizing plate 1 is obtained (Fig. 2 (b), second step). The surface of the first adhesive layer 20 and the brightness enhancement film 30 may be surface-activated. Reason.

In the production of the laminated body 100, in the layer configuration in which the second adhesive layer 50/protective film 40/polarizing sheet 10/first adhesive layer 20 are sequentially provided, the order of lamination is not limited to the above example. For example, the protective film 40 may be laminated on one surface of the polarizer 10, and the second adhesive layer 50 may be provided thereon, and then the first adhesive layer 20 may be laminated on the other surface of the polarizer 10; On the one surface of the polarizer 10, the protective film 40 is laminated, and the first adhesive layer 20 is laminated on the other surface of the polarizer 10, and then the second adhesive layer 50 is placed on the protective film 40.

The bonding method of the brightness enhancement film 30 to the first adhesive layer 20 of the laminated body 100 may be a single sheet bonding method, or may be a sheet ‧ roller composite bonding method as described in JP-A-2004-262071. Moreover, it can be produced in a long strip shape, and when the required amount is large, the method of attaching the roller to the roller is also useful (the same applies to the following embodiments).

Next, another embodiment of the method of manufacturing the polarizing plate 1 shown in Fig. 1 will be described with reference to Fig. 3 as follows. First, the protective film 40 is bonded to the single surface of the polarizer 10 via the adhesive layer, and the second adhesive layer 50 is laminated thereon to obtain the layered body 200 having the layer structure shown in Fig. 3(a). . As shown in the figure, the partition member 60 may be temporarily attached to the outer surface of the second adhesive layer 50, or the surface protective film 90 may be temporarily attached to the outer surface of the polarizer 10. At least one of the bonding surface of the protective film 40 with the second adhesive layer 50 and the bonding surface of the second adhesive layer 50 with the protective film 40, and the surface of the polarizing film 10 with the surface protective film 90 The bonding surface and at least one of the bonding surface of the surface protective film 90 and the polarizer 10 can be performed Surface activation treatment such as corona treatment, plasma treatment, and the like.

On the other hand, in the first step, after the surface of the brightness enhancement film 30 is subjected to a surface activation treatment, the layered body 300 is obtained on the surface layer first adhesive layer 20. The bonding surface of the first adhesive layer 20 and the brightness enhancing film 30 may be subjected to surface activation treatment such as corona treatment or plasma treatment. As shown in the figure, the partition member 80 can be temporarily attached to the outer surface of the first adhesive layer 20.

Then, the partition member 80 is peeled off from the first adhesive layer 20 of the laminated body 300, and the surface protective film 90 is peeled off from the polarizing plate 10 of the laminated body 200, and then the first adhesive layer is bonded to the polarizing plate 10. 20, the polarizing plate 1 is obtained (Fig. 3 (b), second step).

In the production of the laminated body 200 including the surface protective film 90, the order of laminating is not limited to the above, in the layer configuration in which the second adhesive layer 50/protective film 40/polarizing sheet 10/surface protective film 90 are sequentially provided. example. For example, the protective film 40 may be laminated on one side of the polarizer 10, and the second adhesive layer 50 may be disposed thereon, and then the surface protective film 90 may be laminated on the other side of the polarizer 10; or may be polarized. On one side of the sheet 10, the protective film 40 is laminated on the other surface of the polarizer 10, and the surface protective film 90 is laminated, and then the second adhesive layer 50 is placed on the protective film 40.

<Liquid crystal display device>

The polarizing plate of the present invention can be applied to a liquid crystal display device. The liquid crystal display device includes a liquid crystal cell and a polarizing plate of the present invention attached to the surface thereof. The polarizing plate is attached to the liquid crystal cell, and the adhesive layer can be separated (Fig. 1) The second adhesive layer 50 of the polarizing plate 1 shown is carried out. The polarizing plate of the present invention can be generally used as a polarizing plate disposed on the backlight side of the liquid crystal cell. The driving mode of the liquid crystal cell can be any conventionally known method, and is preferably an IPS mode. The liquid crystal display device using the polarizing plate of the present invention has excellent wet heat durability.

Example

Hereinafter, the present invention will be more specifically described by showing examples and comparative examples, but the present invention is not limited to the examples. Further, the thickness of the film, the retardation value, and the storage elastic modulus of the adhesive layer were measured in accordance with the following.

(1) Thickness

It was measured using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

(2) In-plane phase difference and thickness direction phase difference

"KOBRA-ADH" manufactured by Oji Scientific Instruments Co., Ltd., which uses a parallel Nicols rotation method as a principle, was measured at 23 ° C with light having a wavelength of 590 nm, 483 nm or 755 nm.

(3) Storage elastic modulus

The storage elastic modulus G' of the adhesive layer was measured in accordance with the following (I) to (III).

(I) Two 25 ± 1 mg samples were taken out from the adhesive layer and each formed into a spherical shape.

(II) The obtained approximately spherical sample is attached to the upper and lower surfaces of the type I jig. Next, use the L-shaped fixture together. The composition of the measurement sample was an L-shaped jig/adhesive/I-type jig/adhesive/L-type jig.

(III) The storage elastic modulus G' of the sample thus produced was measured under the conditions of a temperature of 23 ° C, a frequency of 1 Hz, and an initial deformation of 1 N using a dynamic viscoelasticity measuring apparatus "DVA-220" manufactured by IT Measurement Control Co., Ltd.

(Production of polarizer A having a thickness of 7 μm)

a polyvinyl alcohol film having a thickness of 20 μm (having an average degree of polymerization of about 2,400 and a degree of saponification of 99.9 mol% or more), and stretching by about 5 times by dry stretching, and further immersing at 60 ° C while maintaining tension. After 1 minute of pure water, it was immersed in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.05/5/100 at 28 ° C for 60 seconds. Then, it was immersed at 72 ° C for 300 seconds in an aqueous solution of potassium iodide / boric acid / water in a weight ratio of 8.5 / 8.5 / 100. Subsequently, the mixture was washed in pure water at 26 ° C for 20 seconds, and then dried at 65 ° C to obtain a polarizer A having a thickness of 7 μm which was iodine-adsorbed to a polyvinyl alcohol film.

(Production of polarizer B having a thickness of 12 μm)

In the same manner as the polarizer A, a polarizing film having a thickness of 12 μm in which the iodine was adsorbed and aligned to the polyvinyl alcohol film was obtained, except that a polyvinyl alcohol film having a thickness of 30 μm (having an average degree of polymerization of about 2,400 and a degree of saponification of 99.9 mol% or more) was used. Slice B.

(Preparation of brightness enhancement film C and D)

The following two brightness enhancement films:

‧26μm thickening film C; 3M system "Advanced Polarized Film, Version 3"

‧17μm thickening film D; 3M "Advanced Polarized Film, Version 4"

(Preparation of protective film E and F)

The following two protective films:

‧Protective film E; a cyclic polyolefin resin film made by Japan ZEON Co., Ltd. (thickness 23 μm, in-plane retardation value of wavelength 590 nm = 2.1 nm, thickness direction phase difference of wavelength 590 nm = 2.8 nm, wavelength of 483 nm) Thickness direction phase difference = 2.5 nm, wavelength direction 755 nm thickness direction phase difference = -4.2 nm)

‧Protective film F; a cyclic polyolefin resin film made by Japan ZEON Co., Ltd. (thickness: 13 μm, in-plane retardation value of wavelength 590 nm = 0.8 nm, thickness direction phase difference of wavelength 590 nm = 3.4 nm, wavelength of 483 nm) Thickness direction phase difference = 3.5 nm, wavelength direction 755 nm thickness direction phase difference = 2.8 nm)

(modulation or preparation of the adhesive layer)

‧The following two adhesive layers

‧ a first adhesive layer; an organic solvent solution in which a copolymer of butyl acrylate and acrylic acid is added with an amine ester acrylate oligomer and an isocyanate crosslinking agent, and applied to a release treatment by a slit coater The release-treated surface of the partition member made of polyethylene terephthalate having a thickness of 38 μm was dried to a thickness of 15 μm, and dried to obtain a portion. Adhesive layer of the spacer member (the storage elastic modulus of the adhesive layer is 0.40 MPa at 23 ° C and 0.18 MPa at 80 ° C)

‧Second adhesive layer; commercially available attachment of a 25 μm thick acrylic adhesive layer on a release treatment surface of a separator made of polyethylene terephthalate having a thickness of 38 μm which has been subjected to release treatment Adhesive layer with partition member (no urethane acrylate oligomer. The storage modulus of the adhesive layer is 0.05 MPa at 23 ° C and 0.04 MPa at 80 ° C)

(modulation of water-based adhesive)

To 100 parts by weight of water, 3 parts by weight of a carboxyl group-modified polyvinyl alcohol [KL-318" manufactured by Kuraray Co., Ltd. was dissolved to prepare a polyvinyl alcohol aqueous solution. In the obtained aqueous solution, a water-soluble polyamine epoxy resin ("SUMIREZ RESIN 650 (30)", manufactured by Tanaoka Chemical Industry Co., Ltd., solid content: 30% by weight) was mixed with 1.5 parts by weight of 100 parts by weight of water. In proportion, a water-based adhesive is obtained.

<Example 1>

A polarizing plate was produced in the same order as shown in Fig. 2 . First, the protective film E is bonded to one surface of the polarizer A by using the above-described water-based adhesive. Before the bonding, a corona treatment of 15.9 kJ/m ^{2 was performed} on the bonding surface of the protective film E and the polarizing plate A. Then, it was dried at 80 ° C for 5 minutes and cured at 40 ° C for 168 hours. Then, the first adhesive layer is bonded to the surface of the polarizer A on the side opposite to the protective film E. Before the bonding, corona treatment of 15.9 kJ/m ^{2 was performed} on both the bonding surface of the polarizing plate A and the bonding surface of the first adhesive layer.

Then, the second adhesive layer is bonded to the outer surface of the protective film E. Before the bonding, corona treatment of 15.9 kJ/m ^{2 was performed} on both the bonding surface of the protective film E and the bonding surface of the second adhesive layer. Finally, the partition member of the first adhesive layer was peeled off, and after the corona treatment of 15.9 kJ/m ^{2 was performed} on one surface of the brightness enhancement film C, the brightness enhancement film C was bonded to the first adhesive with the corona-treated surface side. The outer surface of the layer gives a polarizing plate.

<Example 2>

A polarizing plate was produced in the same manner as in Example 1 except that the protective film F was used instead of the protective film E.

<Example 3>

A polarizing plate was produced in the same manner as in Example 1 except that the brightness enhancement film D was used instead of the brightness enhancement film C.

<Example 4>

A polarizing plate was produced in the same manner as in Example 1 except that the polarizer B was used instead of the polarizer A.

<Example 5>

A polarizing plate was produced in the same manner as in Example 3 except that the polarizer B was used instead of the polarizer A.

<Example 6>

A polarizing plate was produced in the same order as shown in Fig. 3. First, the protective film E is bonded to one surface of the polarizer A using the above-described water-based adhesive. Before the bonding, a corona treatment of 15.9 kJ/m ^{2 was performed} on the bonding surface of the protective film E and the polarizing plate A. Then, it was dried at 80 ° C for 5 minutes and cured at 40 ° C for 168 hours. Then, a surface protective film ("TORETEC 7332" manufactured by Toray Processing Co., Ltd.) was bonded to the surface of the polarizer A on the side opposite to the protective film E. Before the bonding, a corona treatment of 15.9 kJ/m ^{2 was performed} on the bonding surface of the polarizer A. Further, the second adhesive layer is bonded to the outer surface of the protective film E. Before the bonding, both the bonding surface of the protective film E and the bonding surface of the second adhesive layer were subjected to a corona treatment of 15.9 kJ/m ² .

Then, the first adhesive layer (with a partition member) is bonded to one side of the brightness enhancement film C. Before the bonding, both the bonding surface of the brightness enhancement film C and the bonding surface of the first adhesive layer were subjected to a corona treatment of 15.9 kJ/m ² . Finally, after peeling off the surface protective film of the polarizer A and the partition member of the first adhesive layer, the exposed surface (outer surface) of the polarizer A exposed by the peeling of the surface protective film was 15.9 kJ/m ² . After corona treatment, the first adhesive layer was bonded to the corona-treated surface to obtain a polarizing plate.

<Example 7>

A polarizing plate was produced in the same manner as in Example 6 except that the protective film F was used instead of the protective film E.

<Example 8>

A polarizing plate was produced in the same manner as in Example 6 except that the brightness enhancement film D was used instead of the brightness enhancement film C.

<Example 9>

A polarizing plate was produced in the same manner as in Example 6 except that the polarizer B was used instead of the polarizer A.

<Example 10>

A polarizing plate was produced in the same manner as in Example 8 except that the polarizer B was used instead of the polarizer A.

<Example 11>

When the first adhesive layer of the exposed surface of the polarizer A (the surface exposed by the peeling of the surface protective film) is bonded, the corona treatment is not performed on the exposed surface of the polarizer A, and Example 6 A polarizing plate was produced in the same manner.

<Comparative Examples 1 to 11>

A polarizing plate was produced in the same manner as in Examples 1 to 11, except that the bonding surface of the brightness enhancing film C or D and the first adhesive layer was not subjected to corona treatment. Further, in Comparative Examples 6 to 11, before the bonding of the brightness enhancement film C or D to the first adhesive layer, the bonding surface of the brightness enhancement film C or D was not subjected to corona treatment, but the first adhesion was performed. The bonding surface of the agent layer is subjected to corona treatment.

[Evaluation of wet heat durability]

From the obtained polarizing plate, a sample having a size of 111 mm × 65 mm was cut out, and bonded to an alkali-free glass ("Eagle XG" manufactured by Corning Co., Ltd.) via a second adhesive layer. The glass-bonded sample was subjected to a wet heat durability test in an oven of 60° C. and 90% RH for 500 hours, and the appearance of the sample after the test was visually evaluated based on the following criteria. The results are shown in Table 1. In addition, the column of "surface activation treatment" of Table 1 shows whether or not the bonding surface of the brightness enhancement film is surface-activated.

A: At the end of the polarizing plate, no peeling of the interface between the brightness enhancing film and the adhesive layer was observed, and the appearance was good.

B: The above peeling was observed only at the end of the polarizing plate.

C: Not only the end portion of the polarizing plate but also the peeling progress was observed up to the center portion

1‧‧‧Polar plate

10‧‧‧ polarizer

20‧‧‧1st adhesive layer

30‧‧‧Brightening film

40‧‧‧Protective film

50‧‧‧2nd adhesive layer

60‧‧‧ partition members

Claims (11)

A polarizing plate comprising a polarizer, an adhesive layer and a brightness enhancing film in sequence; wherein a surface of the brightness enhancing film on the side of the adhesive layer is surface-activated. The polarizing plate of claim 1, wherein the adhesive layer is in contact with the brightness enhancing film. The polarizing plate of claim 1, wherein the polarizer is in contact with the adhesive layer. The polarizing plate of claim 1, wherein the surface activation treatment is corona treatment. The polarizing plate of claim 1, wherein the brightness enhancing film has a thickness of 10 to 30 μm. The polarizing plate according to claim 1, wherein the polarizing plate has a thickness of 15 μm or less. The polarizing plate according to claim 1, wherein the adhesive layer has a storage elastic modulus of from 0.15 to 1 MPa in a temperature range of from 23 to 80 ° C and a thickness of from 3 to 20 μm. The polarizing plate according to claim 1, further comprising: a protective film laminated on a surface of the polarizer opposite to the adhesive layer. The polarizing plate according to claim 8, wherein the protective film is made of a polyolefin resin or a cellulose resin. A liquid crystal display device comprising: a liquid crystal cell and a polarizing plate according to any one of claims 1 to 9. A method for manufacturing a polarizing plate, the polarizing plate sequentially comprising a polarizing plate and a sticky film a coating layer and a brightness enhancement film, the method for producing the polarizing plate comprising: performing a surface activation treatment on a surface of the brightness enhancement film on the side of the adhesive layer; and performing the surface after the surface activation treatment The step of laminating the aforementioned adhesive layer.