JP2016071378A - Manufacturing method of polarizing plate, set of polarizing plate, liquid crystal panel, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate including a polarizer, adhesive layer, and luminance improving film in this order, the polarizing plate suppressing the luminance improving film from being peeled off from the adhesive layer in a moist and hot environment and having excellent moist and heat resistance, and a manufacturing method of the same; and a set of polarizing plates, liquid crystal panel, and liquid crystal display device including the same.SOLUTION: There are provided a polarizing plate that includes a polarizer, adhesive layer, and luminance improving film in this order, where the luminance improving film has a surface on the adhesive layer side subjected to surface activation treatment, and a manufacturing method of the same; and a set of polarizing plates, liquid crystal panel, and liquid crystal display device including the same. The surface activation treatment is preferably corona treatment.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate including a polarizer and a brightness enhancement film laminated thereon, and a manufacturing method thereof. The present invention also relates to a set of polarizing plates including the polarizing plate, a liquid crystal panel, and a liquid crystal display device.

  In recent years, with the increase in the size of LCD mobile terminals represented by smartphones, in order to achieve long-term driving with a limited battery capacity, the use of backlight light has been improved using a brightness enhancement film. ing. On the other hand, there is an increasing demand for thinner liquid crystal mobile terminals in terms of design and portability, and further reduction in thickness and weight is required for polarizing plates used there.

  The brightness enhancement film is a film having a property of reflecting linearly polarized light having a predetermined polarization axis or circularly polarized light in a predetermined direction and transmitting other light when backlight light of the liquid crystal display device or reflected light thereof is incident. For example, by placing a brightness enhancement film on the backlight side of a polarizer (absorption type linear polarizer) placed on the backlight side of the liquid crystal cell, when the backlight light is incident on the brightness enhancement film, Only light in a predetermined polarization state (polarization state that can pass through the polarizer) is transmitted and supplied to the polarizer, while light other than the predetermined polarization state can be reflected without transmitting. If a reflective layer or the like is provided on the backlight side of the brightness enhancement film, the light reflected by the brightness enhancement film surface can be reversed by the reflection layer and re-incident on the brightness enhancement film. At this time, part or all of the re-incident light can be supplied to the polarizer through the brightness enhancement film as light having a predetermined polarization state.

  As described above, when the brightness enhancement film is used, the polarized light that is absorbed by the polarizer is reflected without being transmitted to the polarizer side, and the reflection and inversion between the brightness enhancement film and the reflection layer are repeated. The polarized light can be converted into polarized light that can be transmitted through the polarizer and supplied to the polarizer. As a result, it is possible to improve the use efficiency of the backlight light, so that it is possible to reduce the power consumption, and when compared with the same power consumption (backlight light amount), compared with the case where the brightness enhancement film is not used. The screen can be brightened (for example, Patent Documents 1 to 4).

  Patent Document 5 discloses a polarizing plate in which a luminance enhancement film having a thickness of 40 to 100 μm is laminated on a polarizer via a pressure-sensitive adhesive layer (pressure-sensitive adhesive layer).

Japanese Patent Laid-Open No. 11-248941 JP 11-248942 A Japanese Patent Laid-Open No. 11-64840 Japanese Patent Application Laid-Open No. 11-64841 Japanese Patent No. 5332599

  A polarizing plate in which a brightness enhancement film is bonded onto a polarizer via an adhesive layer is required to have durability that can withstand a humid heat environment. Conventional polarizing plates have a wet heat durability of, for example, 60 ° C. and 90% RH. When the property test was performed, there was a problem that peeling occurred at the interface between the brightness enhancement film and the pressure-sensitive adhesive layer at the end of the polarizing plate. This problem becomes more prominent as the thickness of the brightness enhancement film decreases.

  An object of the present invention is a polarizing plate including a polarizer, a pressure-sensitive adhesive layer, and a brightness enhancement film in this order, and does not easily peel off between the pressure-sensitive adhesive layer and the brightness enhancement film in a wet heat environment, and is resistant to heat and humidity. It is providing the polarizing plate excellent in property, and its manufacturing method. Another object of the present invention is to provide a set of polarizing plates including the polarizing plate, a liquid crystal panel, and a liquid crystal display device.

The present invention provides the following polarizing plate and method for producing the same, and a liquid crystal display device.
[1] A polarizer, an adhesive layer, and a brightness enhancement film are included in this order,
The polarizing plate by which the surface activation process is given to the surface at the side of the said adhesive layer in the said brightness improvement film.

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

  [3] The polarizing plate according to [1] or [2], wherein the polarizer and the pressure-sensitive adhesive layer are in contact with each other.

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

  [5] The polarizing plate according to any one of [1] to [4], wherein the brightness enhancement 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 pressure-sensitive adhesive layer according to any one of [1] to [6], wherein a storage elastic modulus in a temperature range of 23 to 80 ° C. is 0.15 to 1 MPa and a thickness is 3 to 20 μm. Polarizer.

  [8] The polarizing plate according to any one of [1] to [7], further including a protective film laminated on a surface of the polarizer opposite to the pressure-sensitive 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 set of a viewing side polarizing plate disposed on the viewing side of the liquid crystal cell and a back side polarizing plate disposed on the back side of the liquid crystal cell,
The back side polarizing plate is the polarizing plate according to any one of [1] to [9],
The back side polarizing plate has a distance from the surface in contact with the liquid crystal cell when it is disposed on the back side of the liquid crystal cell to the surface on the pressure-sensitive adhesive layer side in the brightness enhancement film is 100 μm or less,
The ratio between the dimensional change rate in the absorption axis direction when the viewing-side polarizing plate is heated at 85 ° C. for 100 hours and the dimensional change rate in the absorption axis direction when the back-side polarizing plate is heated at 85 ° C. for 100 hours is A set of polarizing plates that is more than 1 and less than 1.4.

[11] A liquid crystal cell, and a set of polarizing plates according to [10],
The liquid crystal panel, wherein the viewing side polarizing plate is disposed on the viewing side of the liquid crystal cell, and the back side polarizing plate is disposed on the back side of the liquid crystal cell.

  [12] A liquid crystal display device comprising a liquid crystal cell and the polarizing plate according to any one of [1] to [9] or the polarizing plate set according to [10].

[13] A method for producing a polarizing plate comprising a polarizer, an adhesive layer, and a brightness enhancement film in this order,
Applying a surface activation treatment to the surface of the pressure-sensitive adhesive layer in the brightness enhancement film;
Laminating the pressure-sensitive adhesive layer on the surface subjected to the surface activation treatment;
Manufacturing method.

  According to the present invention, there is provided a polarizing plate excellent in wet heat durability in which even when the thickness of the brightness enhancement film is small, peeling between the pressure-sensitive adhesive layer and the brightness enhancement film hardly occurs in a humid heat environment. can do. The polarizing plate according to the present invention can be suitably applied to an image display device typified by a liquid crystal display device, particularly a liquid crystal display device for a small and medium mobile terminal (tablet, smartphone, etc.).

It is a schematic sectional drawing which shows an example of the laminated constitution of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows an example of the manufacturing method of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows another example of the manufacturing method of the polarizing plate which concerns on this invention. It is a schematic sectional drawing for demonstrating the structure of the set of the polarizing plate which concerns on this invention, a liquid crystal panel, and a liquid crystal display device.

Hereinafter, the present invention will be described in detail with reference to embodiments.
<Polarizing plate>
(1) Configuration of Polarizing Plate FIG. 1 is a schematic sectional view showing an example of a layer configuration of a polarizing plate according to the present invention. Like the polarizing plate 1 shown in FIG. 1, the polarizing plate of this invention contains the polarizer 10, the 1st adhesive layer 20, and the brightness enhancement film 30 in this order. The polarizing plate of the present invention can further include other films and layers. For example, the polarizing plate 1 shown in FIG. 1 is laminated on the surface of the polarizer 10 opposite to the first pressure-sensitive adhesive layer 20. Protective film 40; second adhesive layer 50 laminated on the outer surface of protective film 40; separator 60 laminated on the outer surface of second adhesive layer 50. The 2nd adhesive layer 50 is for sticking a polarizing plate to other members (for example, a liquid crystal cell or other optical films). The separator 60 is a film that is temporarily attached to protect the surface of the second pressure-sensitive adhesive layer 50 until it is bonded to another member.

  A surface activation treatment is performed on the surface of the brightness enhancement film 30 on the first pressure-sensitive adhesive layer 20 side. Thereby, it can be set as the polarizing plate excellent in wet heat durability which the peeling between the 1st adhesive layer 20 and the brightness improvement film 30 does not produce easily in a wet heat environment. The surface activation treatment is preferably a corona treatment.

(2) Polarizer The polarizer 10 has the property of absorbing linearly polarized light having a vibration surface parallel to the absorption axis and transmitting linearly polarized light having a vibration surface orthogonal to the absorption axis (parallel to the transmission axis). An absorptive polarizer, and a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be suitably used. The polarizer 10 is, for example, a step of uniaxially stretching a polyvinyl alcohol resin film; a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye; a dichroic dye being adsorbed It can be produced by a method comprising a step of treating a polyvinyl alcohol resin film with an aqueous boric acid solution; and a step of washing with water after the treatment with the boric acid aqueous solution.

  As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth) acrylamides having ammonium groups, and the like. In the present specification, “(meth) acryl” means at least one selected from acryl and methacryl.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol resin is usually about 1000 to 10000, preferably about 1500 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can be determined according to JIS K 6726.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of the polarizer 10 (polarizing film). The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol-based raw film is not particularly limited, but in order to make the thickness of the polarizer 10 15 μm or less, it is preferable to use a film having a thickness of about 5 to 35 μm. More preferably, it is 20 μm or less. If an attempt is made to stretch a polyvinyl alcohol-based raw film having a thickness of more than 35 μm to obtain a polarizer 10 having a thickness of 15 μm or less, it is necessary to increase the stretching ratio. Even when the thickness of the polarizer 10 is set to 15 μm or less, the temperature is high. Dimensional shrinkage under the environment increases. Moreover, when thickness is less than 5 micrometers, the handleability at the time of extending | stretching falls and it becomes easy to produce malfunctions, such as a cutting | disconnection at the time of polarizer manufacture.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps.

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

  As a method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing the dichroic dye is employed. As the dichroic dye, iodine or a dichroic organic dye is used. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

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 usually employed. The iodine content in the aqueous solution can be about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide can be about 0.5 to 20 parts by weight per 100 parts by weight of water. Moreover, the temperature of this aqueous solution can be about 20-40 degreeC. On the other hand, as a dyeing treatment with 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 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 this aqueous solution can be about 1 × 10 ⁻⁴ to 10 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution can be about 20 to 80 ° C.

  As boric acid treatment after dyeing with a dichroic dye, a method of immersing a dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution is usually employed. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of boric acid in the boric acid-containing aqueous solution can be about 2 to 15 parts by weight per 100 parts by weight of water. The amount of potassium iodide in this aqueous solution can be about 0.1 to 15 parts by weight per 100 parts by weight of water. The temperature of this aqueous solution can be 50 ° C. or higher, for example, 50 to 85 ° C.

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

  The polarizer 10 is obtained by performing a drying process after washing with water. The drying process can be performed using a hot air dryer or a far infrared heater. The thickness of the polarizer 10 is preferably 15 μm or less, and more preferably 10 μm or less. Setting the thickness of the polarizer 10 to 15 μm or less is advantageous for reducing the thickness of the polarizing plate, and thus the liquid crystal panel and the liquid crystal display device. The thickness of the polarizer 10 is usually 4 μm or more.

(3) First pressure-sensitive adhesive layer The first pressure-sensitive adhesive layer 20 is a layer interposed between the polarizer 10 and the brightness enhancement film 30. The first pressure-sensitive adhesive layer 20 is typically directly laminated on the polarizer 10 so that the polarizer 10 and the first pressure-sensitive adhesive layer 20 are in contact with each other. For example, when a protective film is bonded onto the polarizer 10 and the first pressure-sensitive adhesive layer 20 is laminated thereon, peeling occurs between the pressure-sensitive adhesive layer and the brightness enhancement film even in a humid heat environment. It has become clear that it is difficult. The first pressure-sensitive adhesive layer 20 can be composed of a pressure-sensitive adhesive composition containing as a main component a resin such as (meth) acrylic, rubber-based, urethane-based, ester-based, silicone-based, or polyvinylether-based. Especially, the adhesive composition which uses (meth) acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is suitable. The pressure-sensitive adhesive composition may be an active energy ray curable type or a thermosetting type.

  Examples of the (meth) acrylic base polymer include (meth) acrylic acid such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Ester base polymers and copolymer base polymers using two or more of these (meth) acrylic esters are preferably used. The base polymer is preferably copolymerized with a polar monomer. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, glycidyl ( Mention may be made of monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as (meth) acrylate.

  The pressure-sensitive adhesive composition usually further contains a crosslinking agent. As a crosslinking agent, a metal ion having a valence of 2 or more, which forms a carboxylic acid metal salt with a carboxyl group; a polyamine compound, which forms an amide bond with a carboxyl group; Examples thereof include epoxy compounds and polyols that form ester bonds with carboxyl groups; polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are preferred.

  The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by irradiation with active energy rays such as ultraviolet rays and electron beams, and has an adhesive property even before irradiation with active energy rays. It is a pressure-sensitive adhesive composition having such a property that it can be adhered to an adherend such as the like and can be cured by irradiation with active energy rays to adjust the adhesion. The active energy ray-curable pressure-sensitive adhesive composition is preferably ultraviolet curable. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent. Further, if necessary, a photopolymerization initiator, a photosensitizer and the like may be contained.

  The pressure-sensitive adhesive composition contains fine particles for imparting light scattering properties; beads; resins other than the base polymer; tackifiers; fillers; antioxidants; ultraviolet absorbers; pigments; be able to.

  The 1st adhesive layer 20 can be formed by apply | coating the organic solvent dilution liquid of the said adhesive composition on a base material, and making it dry. The substrate can be a polarizer 10, a brightness enhancement film 30, a separator, or the like. When the active energy ray-curable pressure-sensitive adhesive composition is used, a desired cured product can be obtained by irradiating the formed pressure-sensitive adhesive layer with active energy rays.

  It is preferable that the 1st adhesive layer 20 shows the storage elastic modulus of 0.15-1 MPa in the temperature range of 23-80 degreeC. Thereby, the dimensional change which is easy to generate | occur | produce with shrinkage | contraction of the polarizer 10 in a humid heat environment can be suppressed, and durability of a polarizing plate can be improved. Further, even when a liquid crystal panel or a liquid crystal display device (for example, a liquid crystal display device for a small-to-medium-sized mobile terminal) equipped with a polarizing plate is placed in a humid heat environment, the movement of the polarizing plate is suppressed. The reliability of the liquid crystal display device can be increased.

  “Showing a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C.” means that the storage elastic modulus is a value within the above range at any temperature within this range. Since the storage elastic modulus usually decreases gradually as the temperature rises, if both the storage elastic modulus at 23 ° C. and 80 ° C. are within the above range, the storage elastic modulus within the above range is exhibited at the temperature in this range. Can be seen. The storage elastic modulus of the first pressure-sensitive adhesive layer 20 should be measured using a commercially available viscoelasticity measuring device, for example, a viscoelasticity measuring device “DYNAMIC ANALYZER RDA II” manufactured by REOMETRIC as shown in the examples below. Can do.

  As a method for adjusting the storage elastic modulus to the above range, an active energy is obtained by further adding an oligomer, specifically, a urethane (meth) acrylate oligomer, to a pressure-sensitive adhesive composition containing a base polymer and a crosslinking agent. Examples thereof include a line curable pressure-sensitive adhesive composition (preferably an ultraviolet curable pressure-sensitive adhesive composition). More preferably, the adhesive layer is appropriately cured by irradiating active energy rays.

  Although the thickness of the 1st adhesive layer 20 can be 1-40 micrometers, it shall be 3-25 micrometers (for example, 3-20 micrometers) from a viewpoint which suppresses the dimensional change of a polarizing plate, maintaining favorable workability. Is preferred.

(4) Brightness-enhancing film The brightness-enhancing film 30 is also called a reflective polarizing film, and has a function of separating the emitted light from the light source (backlight) into transmitted polarized light and reflected polarized light or scattered polarized light. An element is used. As described above, by arranging the brightness enhancement film 30 on the polarizer 10, it is possible to improve the emission efficiency of linearly polarized light emitted from the polarizer 10 using retroreflected light that is reflected polarized light or scattered polarized light. Can do. The brightness enhancement film 30 is usually laminated in contact with the first pressure-sensitive adhesive layer 20.

  The brightness enhancement film 30 can be, for example, an anisotropic reflective polarizer. An example of an anisotropic reflective polarizer is an anisotropic multiple thin film that 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 made of 3M ( JP-A-4-268505). Another 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 a PCF manufactured by Nitto Denko (JP-A-11-231130, etc.). Yet another example of an anisotropic reflective polarizer is a reflective grid polarizer, a specific example of which is a metal grid reflective polarizer (US) that emits reflected polarized light even in the visible light region by finely processing the metal. Patent No. 6288840, etc.), a film (JP-A-8-184701) obtained by adding metal fine particles into a polymer matrix and stretching.

  An optical layer such as a hard coat layer, an antiglare layer, a light diffusion layer, or a retardation layer having a retardation value of ¼ wavelength is provided on the surface of the brightness enhancement film 30 opposite to the first pressure-sensitive adhesive layer 20. It may be provided. By forming the optical layer, the adhesion to the backlight tape and the uniformity of the display image can be improved. Although the thickness of the brightness enhancement film 30 can be about 10 to 100 μm, it is preferably 10 to 50 μm, more preferably 10 to 30 μm from the viewpoint of thinning the polarizing plate.

  In the polarizing plate according to the present invention, the surface of the brightness enhancement film 30 on the first pressure-sensitive adhesive layer 20 side is subjected to a surface activation treatment. This surface activation treatment is performed prior to bonding of the brightness enhancement film 30 and the first pressure-sensitive adhesive layer 20. Thereby, it can be set as the polarizing plate 1 excellent in wet heat durability which does not produce peeling easily between the 1st adhesive layer 20 and the brightness improvement film 30 in a wet heat environment.

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

  Especially, from a viewpoint of the peeling suppression effect of the brightness enhancement film 30 in a wet heat environment and the productivity of a polarizing plate, the surface activation treatment is preferably a corona treatment and / or a plasma treatment. According to these surface activation treatments, even if the thickness of the brightness enhancement film 30 is small and 30 μm or less, the peeling between the first pressure-sensitive adhesive layer 20 and the brightness enhancement film 30 in a wet heat environment is effective. Can be suppressed. The surface of the first pressure-sensitive adhesive layer 20 on the brightness enhancement film 30 side may also be subjected to a surface activation treatment. However, even if the surface activation treatment is performed on the surface of the brightness enhancement film 30, a sufficient effect can be obtained. Can be obtained. Surprisingly, when the surface activation treatment is performed only on the surface of the first pressure-sensitive adhesive layer 20 on the brightness enhancement film 30 side, the effect is poor.

(5) Protective film The protective film 40 is a film arbitrarily laminated on the surface of the polarizer 10 opposite to the first pressure-sensitive adhesive layer 20. However, the polarizing plate preferably includes the protective film 40 from the viewpoint of protecting the polarizer 10. The protective film 40 is a light-transmitting (preferably optically transparent) thermoplastic resin such as a chain polyolefin resin (polypropylene resin, etc.) or a cyclic polyolefin resin (norbornene resin, etc.). Polyolefin resins; Cellulosic resins such as triacetyl cellulose and diacetyl cellulose; Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate resins; (Meth) acrylic resins; Polystyrene resins; Polyvinyl chloride resins Acrylonitrile butadiene styrene resin; acrylonitrile styrene resin; polyvinyl acetate resin; polyvinylidene chloride resin; polyamide resin; polyacetal resin; modified polyphenylene ether resin; Emissions-based resins; poly (ether sulfone) resins; polyarylate resin; polyamideimide resin; can be a film made of polyimide resin or the like. Among these, it is preferable to use a polyolefin resin or a cellulose resin.

  Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins.

  Cyclic polyolefin resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.

  Cellulosic resins are those in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linter and wood pulp (hardwood pulp, conifer pulp) are substituted with acetyl groups, propionyl groups and / or butyryl groups. Further, it refers to a cellulose organic acid ester or a cellulose mixed organic acid ester. For example, cellulose acetate, propionate, butyrate, and mixed esters thereof can be used. Among these, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferable.

  It is also useful to control the retardation value of the protective film 40 to a value suitable for a liquid crystal display device. For example, it is preferable to use a film having a substantially zero retardation value for an in-plane switching (IPS) mode liquid crystal display device. A retardation value of substantially zero means that the in-plane retardation value at a wavelength of 590 nm is 10 nm or less, the absolute value of the thickness direction retardation value at a wavelength of 590 nm is 10 nm or less, and the thickness direction position at a wavelength of 480 to 750 nm. The absolute value of the phase difference value is 15 nm or less.

  Depending on the mode of the liquid crystal display device, the protective film 40 may be stretched and / or contracted to give a suitable retardation value.

  Although the thickness of the protective film 40 can be about 1-100 micrometers, 5-60 micrometers is preferable from viewpoints, such as intensity | strength and handleability, and 5-50 micrometers is more preferable. When the thickness is within this range, the polarizer 10 is mechanically protected, and the polarizer 10 does not contract even when exposed to a humid heat environment, and stable optical characteristics can be maintained.

  The protective film 40 can be bonded to the polarizer 10 through an adhesive layer. As the adhesive forming the adhesive layer, a water-based adhesive or an active energy ray-curable adhesive can be used.

  Examples of the water-based adhesive include an adhesive made of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component urethane emulsion adhesive, and the like. Among these, a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is preferably used. Polyvinyl alcohol resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol copolymer obtained by saponifying a polymer, or a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group thereof can be used. The water-based adhesive can 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 using a water-based adhesive, it is preferable to carry out a drying step in order to remove water contained in the water-based adhesive after the polarizer 10 and the protective film 40 are bonded together. After the drying process, for example, a curing process for curing at a temperature of about 20 to 45 ° C. may be provided.

  The active energy ray-curable adhesive refers to an adhesive that cures when irradiated with active energy rays such as ultraviolet rays. For example, the active energy ray-curable adhesive includes a polymerizable compound and a photopolymerization initiator, and includes a photoreactive resin. And those containing a binder resin and a photoreactive cross-linking agent. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable (meth) acrylic monomers, and photocurable urethane monomers, and oligomers derived from the photopolymerizable monomers. it can. Examples of the photopolymerization initiator include those containing substances that generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, those containing a photocurable epoxy monomer and a cationic photopolymerization initiator can be preferably used.

  When using an active energy ray-curable adhesive, after bonding the polarizer 10 and the protective film 40, a drying process is performed as necessary, and then the active energy ray-curable adhesive is irradiated by irradiating active energy rays. A curing step for curing the agent is performed. The light source of the active energy ray is not particularly limited, but ultraviolet light having a light emission distribution at a wavelength of 400 nm or less is preferable. A wave excitation mercury lamp, a metal halide lamp, etc. can be used.

  In bonding the polarizer 10 and the protective film 40, saponification treatment, corona treatment, plasma treatment, or the like can be performed on at least one of these bonding surfaces.

(6) 2nd adhesive layer and separator The 2nd adhesive layer 50 laminated | stacked on the outer surface of the protective film 40 is provided in order to stick a polarizing plate to other members (for example, a liquid crystal cell or another optical film). Any layer that can. About the composition of the adhesive composition which comprises the 2nd adhesive layer 50, the above description about the 1st adhesive layer 20 is quoted. The storage elastic modulus of the 2nd adhesive layer 50 may be the same as that of the 1st adhesive layer 20, and may differ.

  The separator 60 is a film that is temporarily attached to protect the surface of the second pressure-sensitive adhesive layer 50 until it is bonded to another member. For example, a silicone-based film made of a transparent resin such as polyethylene terephthalate is used. Those treated with a release agent such as In order to temporarily protect the surface of the first pressure-sensitive adhesive layer 20 until the brightness enhancement film 30 is pasted, a separator similar to the above can be pasted.

<Production method of polarizing plate>
The manufacturing method of the polarizing plate which concerns on this invention is a manufacturing method of the polarizing plate which contains a polarizer, a 1st adhesive layer, and a brightness enhancement film in this order, Comprising:
A first step of performing a surface activation treatment on the surface of the brightness enhancement film on the first pressure-sensitive adhesive layer side; and a second step of laminating the first pressure-sensitive adhesive layer on the surface subjected to the surface activation treatment.

  With reference to FIG. 2, one embodiment of a method for producing the polarizing plate 1 shown in FIG. 1 will be described as follows. First, the protective film 40 is bonded to one surface of the polarizer 10 via an adhesive layer, the second pressure-sensitive adhesive layer 50 is laminated thereon, and the first pressure-sensitive adhesive layer 20 is formed on the other surface of the polarizer 10. The laminated body 100 of the layer structure shown by Fig.2 (a) is obtained by bonding. As illustrated, the separator 60 may be temporarily attached to the outer surface of the second pressure-sensitive adhesive layer 50, and the separator 70 may be temporarily attached to the outer surface of the first pressure-sensitive adhesive layer 20.

  Next, after the separator 70 was peeled and removed from the first pressure-sensitive adhesive layer 20 of the laminate 100, a surface activation treatment was previously applied to the peeling surface on the bonding surface (lamination surface) in the first step. The brightness enhancement film 30 is laminated to obtain the polarizing plate 1 (FIG. 2B, second step). A surface activation treatment may also be performed on the bonding surface of the first pressure-sensitive adhesive layer 20 with the brightness enhancement film 30.

  In the production of the laminate 100, the order of lamination is not limited to the above example as long as a layer configuration including the second pressure-sensitive adhesive layer 50 / protective film 40 / polarizer 10 / first pressure-sensitive adhesive layer 20 in this order is obtained. . For example, the protective film 40 may be laminated on one side of the polarizer 10, the second pressure-sensitive adhesive layer 50 may be provided thereon, and then the first pressure-sensitive adhesive layer 20 may be laminated on the other side of the polarizer 10. The protective film 40 is laminated on one side of the polarizer 10, the first adhesive layer 20 is laminated on the other side of the polarizer 10, and then the second adhesive layer 50 is provided on the protective film 40. Good.

  The method for bonding the brightness enhancement film 30 to the first pressure-sensitive adhesive layer 20 of the laminate 100 may be a sheet-fed bonding method, or a sheet / roll composite as described in JP-A-2004-262071. It may be a bonding method. In addition, when it can be produced in a long length and the required quantity is large, a film that is stretched so that its transmission axis is in the width direction is selected as the brightness enhancement film, and its transmission axis is in the width direction as a polarizer. By selecting what has been stretched so as to become, it is possible to apply a roll-to-roll bonding method (the same applies to the following embodiments).

  Next, with reference to FIG. 3, it will be as follows when other embodiment of the manufacturing method of the polarizing plate 1 shown by FIG. 1 is described. First, the protective film 40 is bonded to one surface of the polarizer 10 via an adhesive layer, and the second pressure-sensitive adhesive layer 50 is laminated thereon, and the laminate 200 having a layer configuration shown in FIG. Get. As illustrated, a separator 60 may be temporarily attached to the outer surface of the second pressure-sensitive adhesive layer 50, and a surface protective film 90 may be temporarily attached to the outer surface of the polarizer 10. At least one of the bonding surface with the 2nd adhesive layer 50 in the protective film 40, the bonding surface with the protective film 40 in the 2nd adhesive layer 50, and the surface protection film 90 in the polarizer 10 Surface activation treatment such as corona treatment or plasma treatment may be performed on at least one of the bonding surface and the bonding surface with the polarizer 10 in the surface protective film 90.

  On the other hand, after surface activation treatment is performed on the surface of the brightness enhancement film 30 in the first step, the first pressure-sensitive adhesive layer 20 is laminated on the surface to obtain a laminate 300. The bonding surface of the first pressure-sensitive adhesive layer 20 with the brightness enhancement film 30 may be subjected to a surface activation treatment such as corona treatment or plasma treatment. As illustrated, a separator 80 may be temporarily attached to the outer surface of the first pressure-sensitive adhesive layer 20.

  Next, after removing the separator 80 from the first pressure-sensitive adhesive layer 20 of the laminate 300 and the surface protection film 90 from the polarizer 10 of the laminate 200, the first pressure-sensitive adhesive layer 20 is bonded onto the polarizer 10. Thus, the polarizing plate 1 is obtained (FIG. 3B, the second step).

  In the production of the laminate 200 provided with the surface protective film 90, the order of lamination is as long as the layer configuration including the second pressure-sensitive adhesive layer 50 / protective film 40 / polarizer 10 / surface protective film 90 in this order is obtained. It is not limited to the example. For example, the protective film 40 may be laminated on one side of the polarizer 10, the second adhesive layer 50 may be provided thereon, and then the surface protective film 90 may be laminated on the other side of the polarizer 10. The protective film 40 may be laminated on one side of the child 10, the surface protective film 90 may be laminated on the other surface of the polarizer 10, and then the second pressure-sensitive adhesive layer 50 may be provided on the protective film 40.

<Polarizing plate set, liquid crystal panel and liquid crystal display device>
FIG. 4 is a schematic cross-sectional view for explaining the configuration of a set of polarizing plates, a liquid crystal panel, and a liquid crystal display device according to the present invention. The polarizing plate according to the present invention described above can be preferably applied to a set of polarizing plates, a liquid crystal panel, and a liquid crystal display device. If it demonstrates with reference to FIG. 4, the set of polarizing plates is the visual recognition side polarizing plate 4 arrange | positioned at the visual recognition side of the liquid crystal cell 2, and the back side polarizing plate 5 arrange | positioned at the back side of the liquid crystal cell 2. Means a combination. The viewing side polarizing plate 4 is a polarizing plate disposed on the viewing side of the liquid crystal cell 2, and the back side polarizing plate 5 is a polarizing plate disposed on the back side of the liquid crystal cell 2, that is, on the backlight 3 side. In the example of FIG. 4, the polarizing plate shown in FIG. 1 (with the separator 60 removed) is used as the back side polarizing plate 5. The liquid crystal panel 6 is a combination of the liquid crystal cell 2 and the above polarizing plate set. Specifically, the viewing side polarizing plate 4 is disposed on the viewing side of the liquid crystal cell 2, and the back side of the liquid crystal cell 2. The back side polarizing plate 5 is an optical member. In the liquid crystal panel 6, the viewing-side polarizing plate 4 and the back-side polarizing plate 5 are bonded to the viewing-side surface and the back-side surface of the liquid crystal cell 2, respectively. Bonding of each polarizing plate to the liquid crystal cell 2 can be performed via an adhesive layer (the second adhesive layer 50 and the third adhesive layer 51 shown in FIG. 4). The liquid crystal display device 7 is an image display device including a combination of the liquid crystal cell 2 and a polarizing plate (usually the set of polarizing plates), that is, a liquid crystal panel 6. The liquid crystal display device 7 further includes a backlight 3 disposed on the back side of the liquid crystal panel 6. The driving method of the liquid crystal cell 2 may be any conventionally known method, but is preferably the IPS mode. The liquid crystal panel 6 and the liquid crystal display device 7 using the polarizing plate according to the present invention are excellent in wet heat durability.

  The polarizing plate according to the present invention is usually used as the back side polarizing plate 5. When the polarizing plate which concerns on this invention is arrange | positioned as the back side polarizing plate 5, as the visual recognition side polarizing plate 4, it does not restrict | limit in particular, Arbitrary polarizing plates can be selected. The viewing side polarizing plate 4 may be a polarizing plate having a protective film on one surface of the polarizer or a polarizing plate having a protective film on both surfaces of the polarizer. As the viewing-side polarizing plate 4, it is preferable to set the thickness of the polarizer to 15 μm or less in the same manner as the back-side polarizing plate 5 in order to suppress the shrinkage force. The thickness of the polarizer is usually 3 μm or more in that good optical characteristics (polarization characteristics, etc.) can be imparted.

  Regarding the back side polarizing plate 5 (polarizing plate according to the present invention), the surface that contacts the liquid crystal cell 2 when it is disposed on the back side of the liquid crystal cell 2 (in the example of FIG. 4, the liquid crystal cell of the second pressure-sensitive adhesive layer 50) The distance H (see FIG. 4) from the side surface) to the surface on the first pressure-sensitive adhesive layer 20 side (surface on the polarizer 10 side) in the brightness enhancement film 30 enhances the effect of introducing the brightness enhancement film 30. In view of the above, it is preferably 100 μm or less, more preferably 80 μm or less, and further preferably 60 μm or less. The distance H is usually 5 μm or more, and more typically 10 μm or more.

  In the liquid crystal panel 6 according to the present invention, the dimensional change rate A in the absorption axis direction when the viewing-side polarizing plate 5 is heated at 85 ° C. for 100 hours and the back-side polarizing plate 4 are heated at 85 ° C. for 100 hours. It is preferable to use a set of polarizing plates having a ratio A / B with a dimensional change rate B in the absorption axis direction of more than 1 and not more than 1.4. By adopting such a set of polarizing plates, the absolute amount of warpage of the liquid crystal panel 6 can be reduced to 0.5 mm or less. The ratio A / B of the dimensional change rate is more preferably 1.05 or more and 1.3 or less. In this case, the absolute amount of warpage can be reduced to 0.3 mm or less.

  From the viewpoint of reducing the absolute amount of warpage of the liquid crystal panel 6, the dimensional change rate A in the absorption axis direction when the viewing-side polarizing plate 5 is heated at 85 ° C. for 100 hours is preferably 1.0% or more. It is more preferable that it is 1.1% or more. The dimensional change rate A is preferably 1.4% or less, and more preferably 1.3% or less. From the viewpoint of reducing the absolute amount of warping of the liquid crystal panel 6, the dimensional change rate B in the absorption axis direction when the back-side polarizing plate 4 is heated at 85 ° C. for 100 hours is preferably 1.1% or less. % Or less is more preferable. Further, the dimensional change rate B is preferably 0.5% or more, and more preferably 0.8% or more.

The dimensional change rates A and B in the absorption axis direction when the polarizing plate is heated at 85 ° C. for 100 hours are measured as follows. First, the polarizing plate is cut into a size of 100 mm in the long direction (absorption axis direction) × 100 mm in the width direction, and left still in an environment of a temperature of 23 ° C. and a relative humidity of 55% for one day, and the long direction (absorption axis direction). The dimension (L ₀ ) is measured. Next, the dimension (L ₁ ) in the longitudinal direction (absorption axis direction) after standing for 100 hours in a high temperature environment of 85 ° C. is measured. From these measurement results, the following formula:
Dimensional change rate (%) = [(L ₀ −L ₁ ) / L ₀ ] × 100
To obtain the dimensional change rate (%).

From the dimensional change rate A of the viewing side polarizing plate 4 and the dimensional change rate B of the back side polarizing plate 5, the following formula:
Ratio of dimensional change rate = A / B
Thus, the ratio of the dimensional change rate can be obtained.

  In the liquid crystal panel 6 according to the present invention, the absorption axis direction of the polarizer of the viewing side polarizing plate 4 is parallel to the short side direction of the rectangular liquid crystal cell 2 having a long side direction and a short side direction, When the absorption axis direction of the polarizer of the back-side polarizing plate 5 is parallel to the long side direction of the liquid crystal cell 2, the effect of suppressing the amount of warpage is great and preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In addition, the thickness of the film, the retardation value, the storage elastic modulus, the dimensional change rate of the polarizing plate, and the warpage amount of the liquid crystal panel were measured according to the following.

(1) Thickness The thickness was measured using a digital micrometer “MH-15M” manufactured by Nikon Corporation.

(2) In-plane retardation value and thickness direction retardation value “KOBRA-ADH” manufactured by Oji Scientific Instruments, which is a phase difference meter based on the parallel Nicol rotation method, is used at 23 ° C. and at wavelengths of 590 nm and 483 nm. Or it measured with the light of 755 nm.

(3) Storage elastic modulus The storage elastic modulus G 'of the pressure-sensitive adhesive layer was measured according to the following (I) to (III).
(I) Two samples of 25 ± 1 mg are taken out from the pressure-sensitive adhesive layer, and each is formed into a substantially ball shape. (II) The obtained approximately ball-shaped sample is attached to the upper and lower surfaces of the I-shaped jig, and the upper and lower surfaces are sandwiched between the L-shaped jig. The configuration of the measurement sample is L-shaped jig / adhesive / I-shaped jig / adhesive / L-shaped jig.
(III) The storage elastic modulus G ′ of the thus prepared sample was measured using a dynamic viscoelasticity measuring device “DVA-220” manufactured by IT Measurement Control Co., Ltd., at a temperature of 23 ° C., a frequency of 1 Hz, and an initial strain of 1 N. The measurement was performed under the following conditions.

(4) Dimensional change rate of polarizing plate It measured using the Nikon Corporation two-dimensional measuring instrument "NEXIV VMR-1207" according to the above-mentioned measurement procedure.

(5) Warpage amount of liquid crystal panel After the prepared liquid crystal panel was allowed to stand in an environment of 85 ° C. for 240 hours, the two-dimensional measuring instrument “NEXIV VMR-1207” manufactured by Nikon Corporation with the viewing side polarizing plate facing upward was used. Placed on a measuring table. Next, after focusing on the surface of the measuring table and using that as a reference, focusing on each of the four corners, four sides of the liquid crystal panel and the center of the liquid crystal panel surface, and measuring the distance from the reference focus The longest distance in absolute value from the measuring table was taken as the amount of warpage of the liquid crystal panel.

(Preparation of polarizer A having a thickness of 7 μm)
A 20 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched about 5 times by dry stretching and further kept in a pure water at 60 ° C. while maintaining tension. After being immersed for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with 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 in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

(Preparation of polarizer B having a thickness of 12 μm)
A thickness of 12 μm in which iodine is adsorbed and oriented on the polyvinyl alcohol film in the same manner as in the polarizer A, except that a polyvinyl alcohol film having a thickness of 30 μm (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is used. A polarizer B was obtained.

(Preparation of brightness enhancement films C and D)
Two types of brightness enhancement films:
-Brightness enhancement film C having a thickness of 26 μm; “Advanced Polarized Film, Version 3” made by 3M,
・ Brightness enhancement film D with a thickness of 17 μm; “Advanced Polarized Film, Version 4” made by 3M
Prepared.

(Preparation of protective films E, F and G)
Three types of protective films:
Protective film E: Cyclic polyolefin resin film (thickness 23 μm, in-plane retardation value at wavelength 590 nm = 2.1 nm, thickness direction retardation value at wavelength 590 nm = 2.8 nm, wavelength, manufactured by Nippon Zeon Co., Ltd. Thickness direction retardation value at 483 nm = 2.5 nm, thickness direction retardation value at wavelength 755 nm = −4.2 nm),
Protective film F: cyclic polyolefin resin film (thickness 13 μm, in-plane retardation value at wavelength 590 nm = 0.8 nm, thickness direction retardation value at wavelength 590 nm = 3.4 nm, wavelength manufactured by Nippon Zeon Co., Ltd. Thickness direction retardation value at 483 nm = 3.5 nm, thickness direction retardation value at wavelength 755 nm = 2.8 nm),
-Protective film G: Triacetyl cellulose film “25KCHCN-TC” with a hard coat layer manufactured by Konica Minolta Co., Ltd. (thickness: 32 μm)
Prepared.

(Preparation or preparation of adhesive layer)
・ The following three types of adhesive layers:
A first pressure-sensitive adhesive layer; an organic solvent solution obtained by adding a urethane acrylate oligomer and an isocyanate-based cross-linking agent to a copolymer of butyl acrylate and acrylic acid, and a separator made of polyethylene terephthalate having a thickness of 38 μm. The pressure-sensitive adhesive layer with a separator obtained by coating the mold release surface with a die coater so that the thickness after drying becomes 15 μm and drying (the storage elastic modulus of this pressure-sensitive adhesive layer is 0.00 at 23 ° C.). 40 MPa, 0.18 MPa at 80 ° C.)
Second pressure-sensitive adhesive layer; a commercially available pressure-sensitive adhesive layer with a separator (urethane having a 25 μm-thick acrylic pressure-sensitive adhesive layer provided on a release-treated surface of a separator made of polyethylene terephthalate having a thickness of 38 μm that has been subjected to a release treatment No acrylate oligomer was blended, and the storage modulus of this pressure-sensitive adhesive layer was 0.05 MPa at 23 ° C. and 0.04 MPa at 80 ° C.).
Third adhesive layer: 20 μm thick sheet adhesive (“NCF #KT, manufactured by Lintec Corporation)
Was prepared or prepared.

(Preparation of aqueous adhesive)
3 parts by weight of carboxyl group-modified polyvinyl alcohol [“KL-318” manufactured by Kuraray Co., Ltd.] was dissolved in 100 parts by weight of water to prepare an aqueous polyvinyl alcohol solution. To the obtained aqueous solution, 1.5 parts by weight of water-soluble polyamide epoxy resin (“Smile Resin 650 (30) manufactured by Taoka Chemical Industry Co., Ltd., solid content concentration: 30% by weight)” per 100 parts by weight of water. The aqueous adhesive was obtained by mixing at a ratio of

[Preparation of polarizing plate]
<Example 1>
A polarizing plate was produced in the same procedure as shown in FIG. First, the protective film E was bonded to one side of the polarizer A using the aqueous adhesive. Prior to the bonding, the bonding surface of the protective film E with the polarizer A was subjected to a corona treatment of 15.9 kJ / m ² . Then, it was dried at 80 ° C. for 5 minutes and cured at 40 ° C. for 168 hours. Subsequently, the 1st adhesive layer was bonded to the surface on the opposite side to the protective film E in the polarizer A. FIG. Prior to the bonding, a corona treatment of 15.9 kJ / m ² was performed on both the bonding surface of the polarizer A and the bonding surface of the first pressure-sensitive adhesive layer.

Next, the second pressure-sensitive adhesive layer was bonded to the outer surface of the protective film E. Prior to bonding, 15.9 kJ / m ² of corona treatment was performed on both the bonding surface of the protective film E and the bonding surface of the second pressure-sensitive adhesive layer. Finally, the separator of the first pressure-sensitive adhesive layer is peeled off, and 15.9 kJ / m ² of corona treatment is performed on one side of the brightness enhancement film C, and then the brightness enhancement film C is disposed on the corona-treated surface side of the first pressure-sensitive adhesive. A polarizing plate was obtained by bonding to the outer surface of the layer.

<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 procedure as shown in FIG. First, the protective film E was bonded to one side of the polarizer A using the aqueous adhesive. Prior to the bonding, the bonding surface of the protective film E with the polarizer A was subjected to a corona treatment of 15.9 kJ / m ² . Then, it was dried at 80 ° C. for 5 minutes and cured at 40 ° C. for 168 hours. Next, a surface protective film (“Tretec 7332” manufactured by Toray Film Processing Co., Ltd.) was bonded to the surface of the polarizer A opposite to the protective film E. Prior to pasting, a corona treatment of 15.9 kJ / m ² was performed on the pasting surface of the polarizer A. Furthermore, the second pressure-sensitive adhesive layer was bonded to the outer surface of the protective film E. Prior to bonding, 15.9 kJ / m ² of corona treatment was performed on both the bonding surface of the protective film E and the bonding surface of the second pressure-sensitive adhesive layer.

Next, the 1st adhesive layer (with a separator) was bonded to the single side | surface of the brightness enhancement film C. FIG. Prior to bonding, 15.9 kJ / m ² of corona treatment was performed on both the bonding surface of the brightness enhancement film C and the bonding surface of the first pressure-sensitive adhesive layer. Finally, after peeling off the surface protective film of the polarizer A and the separator of the first pressure-sensitive adhesive layer, the exposed surface (outer surface) of the polarizer A exposed by peeling off the surface protective film is 15.9 kJ / m ² of corona treatment. Then, the 1st adhesive layer was bonded to the corona treatment surface, and the polarizing plate was obtained.

<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>
Example 6 except that the corona treatment on the exposed surface of the polarizer A was not performed when the first pressure-sensitive adhesive layer was bonded to the exposed surface of the polarizer A (the surface exposed by peeling off the surface protective film). A polarizing plate was produced in the same manner as described above.

<Example 12>
A polarizing plate was produced in the same manner as in Example 2 except that the third pressure-sensitive adhesive layer was used instead of the second pressure-sensitive adhesive layer.

<Comparative Examples 1-11>
A polarizing plate was produced in the same manner as in Examples 1 to 11 except that the corona treatment was not performed on the bonding surface of the brightness enhancement film C or D to the first pressure-sensitive adhesive layer. In Comparative Examples 6 to 11, the corona treatment was not performed on the bonding surface of the brightness enhancement film C or D prior to the bonding of the brightness enhancement film C or D and the first pressure-sensitive adhesive layer. The bonding surface of the pressure-sensitive adhesive layer was subjected to corona treatment.

[Evaluation of wet heat durability]
A sample of 111 mm × 65 mm size was cut out from the obtained polarizing plate, and non-alkali glass (“Eagle XG” manufactured by Corning) through the second pressure-sensitive adhesive layer (the third pressure-sensitive adhesive layer for the polarizing plate of Example 12). ). About this glass bonding sample, the wet heat durability test put into oven of 60 degreeC90% RH for 500 hours was implemented, and the external appearance of the sample after a test was visually evaluated according to the following reference | standard. The results are shown in Table 1. In addition, the column of "surface activation process" in Table 1 has shown the presence or absence of the surface activation process with respect to the bonding surface of a brightness improvement film.

A: Peeling at the interface between the brightness enhancement film and the pressure-sensitive adhesive layer is not recognized at the edge of the polarizing plate, and the appearance is good.
B: The above peeling is observed only at the end of the polarizing plate.
C: The above-described peeling is observed not only at the end of the polarizing plate but also at the center.

[Production of liquid crystal panel]
(Preparation of viewing-side polarizing plate 1)
The protective film G was subjected to saponification treatment, and one surface of the protective film E was subjected to corona treatment. The protective film G is laminated on one surface of the polarizer B via an aqueous adhesive so that the triacetyl cellulose surface of the protective film G and the corona-treated surface of the protective film E are bonded to the polarizer B, respectively. In addition, after the protective film E was laminated on the other surface via a water-based adhesive, a drying treatment was performed to obtain the viewing-side polarizing plate 1. The dimensional change rate A in the MD direction (absorption axis direction) of the viewing-side polarizing plate 1 was 1.02%. The dimensional change rate A was adjusted by adjusting the drying time in the drying process. Furthermore, the 3rd adhesive layer was bonded to the outer surface of the protective film E of the visual recognition side polarizing plate 1, and it was set as the polarizing plate with an adhesive layer. When laminating the third pressure-sensitive adhesive layer, corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive layer surface.

(Preparation of viewing side polarizing plates 2 to 6)
The viewing side polarizing plates 2 to 6 were prepared in the same manner as the viewing side polarizing plate 1 except that the dimensional change rate A in the MD direction (absorption axis direction) was different by adjusting the drying time in the drying treatment. Then, the 3rd adhesive layer was bonded on the outer surface of the protective film E, and it was set as the polarizing plate with an adhesive layer. The dimensional change rate A of the viewing-side polarizing plates 2 to 6 was as follows.

Viewing side polarizing plate 2: 1.09%,
Viewing side polarizing plate 3: 1.23%,
Viewing side polarizing plate 4: 1.30%,
Viewing side polarizing plate 5: 1.41%,
Viewing side polarizing plate 6: 0.95%.

(Preparation of the back side polarizing plate 1)
A polarizing plate was produced in the same manner as in Example 2 except that the second pressure-sensitive adhesive layer was not bonded, and this was used as the back-side polarizing plate 1. The dimensional change rate B in the MD direction (absorption axis direction) of the back-side polarizing plate 1 was 0.98%. Next, the 3rd adhesive layer was bonded to the outer surface of the protective film F of the back side polarizing plate 1. FIG. Prior to bonding, a corona treatment of 15.9 kJ / m ² was performed on both the bonding surface of the protective film F and the bonding surface of the third pressure-sensitive adhesive layer.

(Preparation of liquid crystal cell)
Google Inc. The viewing side polarizing plate and the back side polarizing plate were peeled off from the manufactured Nexus 7 liquid crystal panel to obtain a liquid crystal cell.

<Example 13>
The viewing side polarizing plate 1 is cut into a 7-inch diagonal size so that the absorption axis of the polarizer is parallel to the short side of the liquid crystal cell, and the absorption axis of the polarizer is parallel to the long side of the liquid crystal cell. Thus, the back side polarizing plate 1 was cut into a 7-inch diagonal size. Each polarizing plate thus produced was attached to a liquid crystal cell via an adhesive layer (the third adhesive layer was used for the viewing-side polarizing plate. The same applies to Examples 14 to 16 and Comparative Examples 12 to 13). In addition, a liquid crystal panel was produced. In the back side polarizing plate 1, the distance H from the surface in contact with the liquid crystal cell to the surface on the first pressure-sensitive adhesive layer side (polarizer side) in the brightness enhancement film was 55 μm.

<Examples 14-16, Comparative Examples 12-13>
A liquid crystal panel was produced in the same manner as in Example 13 except that the viewing side polarizing plate shown in Table 2 was used.

  The dimensional change rate A in the absorption axis direction of the viewing side polarizing plate used in Examples 13 to 16 and Comparative Examples 12 to 13, the dimensional change rate B in the absorption axis direction of the back side polarizing plate, and the ratio A / B of the dimensional change rate The amount of warpage of the liquid crystal panel is summarized in Table 2.

  DESCRIPTION OF SYMBOLS 1 Polarizing plate, 2 Liquid crystal cell, 3 Backlight, 4 Viewing side polarizing plate, 5 Back side polarizing plate, 6 Liquid crystal panel, 7 Liquid crystal display device, 10 Polarizer, 20 1st adhesive layer, 30 Brightness improvement film, 40 Protective film, 50 2nd pressure-sensitive adhesive layer, 51 3rd pressure-sensitive adhesive layer, 60, 70, 80 separator, 90 surface protective film, 100, 200, 300 laminate.

Claims (13)

A polarizer, an adhesive layer, and a brightness enhancement film are included in this order,
The polarizing plate by which the surface activation process is given to the surface at the side of the said adhesive layer in the said brightness improvement film.   The polarizing plate according to claim 1, wherein the pressure-sensitive adhesive layer is in contact with the brightness enhancement film.   The polarizing plate according to claim 1, wherein the polarizer and the pressure-sensitive adhesive layer are in contact with each other.   The polarizing plate according to claim 1, wherein the surface activation treatment is a corona treatment.   The polarizing plate according to claim 1, wherein the brightness enhancement film has a thickness of 10 to 30 μm.   The polarizing plate according to claim 1, wherein the polarizer has a thickness of 15 μm or less.   The polarizing plate according to claim 1, wherein the pressure-sensitive adhesive layer has a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C. and a thickness of 3 to 20 μm.   The polarizing plate of any one of Claims 1-7 which further contains the protective film laminated | stacked on the surface on the opposite side to the said adhesive layer in the said polarizer.   The polarizing plate according to claim 8, wherein the protective film is composed of a polyolefin resin or a cellulose resin. A set of a viewing side polarizing plate disposed on the viewing side of the liquid crystal cell and a back side polarizing plate disposed on the back side of the liquid crystal cell,
The back side polarizing plate is the polarizing plate according to any one of claims 1 to 9,
The back side polarizing plate has a distance from the surface in contact with the liquid crystal cell when it is disposed on the back side of the liquid crystal cell to the surface on the pressure-sensitive adhesive layer side in the brightness enhancement film is 100 μm or less,
The ratio between the dimensional change rate in the absorption axis direction when the viewing-side polarizing plate is heated at 85 ° C. for 100 hours and the dimensional change rate in the absorption axis direction when the back-side polarizing plate is heated at 85 ° C. for 100 hours is A set of polarizing plates that is more than 1 and less than 1.4. A liquid crystal cell and a set of polarizing plates according to claim 10,
The liquid crystal panel, wherein the viewing side polarizing plate is disposed on the viewing side of the liquid crystal cell, and the back side polarizing plate is disposed on the back side of the liquid crystal cell.   The liquid crystal display device containing a liquid crystal cell and the polarizing plate of any one of Claims 1-9, or the set of the polarizing plate of Claim 10. A method for producing a polarizing plate comprising a polarizer, a pressure-sensitive adhesive layer, and a brightness enhancement film in this order,
Applying a surface activation treatment to the surface of the pressure-sensitive adhesive layer in the brightness enhancement film;
Laminating the pressure-sensitive adhesive layer on the surface subjected to the surface activation treatment;
Manufacturing method.

Images