JPWO2016006384A1 - Polarizer - Google Patents

Abstract

A polarizer and a first protective film laminated on one surface of the polarizer via a first adhesive layer, the first adhesive layer having a refractive index of 1 made of a cured product of an active energy ray-curable adhesive There is provided a polarizing plate which is a layer of .47 or more and less than 1.57 and is laminated in contact with the one surface of the polarizer. The polarizing plate may further include a second protective film that is laminated on the other surface of the polarizer via a second adhesive layer.

Description

  The present invention relates to a polarizing plate, and more particularly to a polarizing plate in which a protective film is bonded to at least one surface of a polarizer via an adhesive layer.

  The polarizing plate is widely used in display devices such as a liquid crystal display device, especially in various mobile devices such as smartphones in recent years. As a polarizing plate, the thing of the structure which bonded the protective film on the single side | surface or both surfaces of the polarizer using the adhesive agent is common.

  Active adhesives such as water-based adhesives and UV curable adhesives are known as the above adhesives. However, when a protective film with low moisture permeability is to be bonded, a protective film is used. Since it is difficult to volatilize and remove moisture from the adhesive layer after joining, active energy ray-curable adhesives are frequently used (for example, Patent Documents 1 to 4).

JP2013-205741A JP2012-203205A JP2012-203108A JP 2004-245925 A

  When the polarizer and the protective film are bonded using an active energy ray-curable adhesive, a fine surface irregularity of a yuzu skin shape is generated on the surface of the polarizer. Hereinafter, in this specification, the surface irregularities of the Yuzu skin shape are referred to as “skin defect”. Skin defects are due to curing shrinkage of the adhesive layer accompanying rapid curing by irradiation of active energy rays, and distortion of the surface of the polarizer caused by sudden application of heat from the active energy ray light source. Skin irregularities occur as a result of the microscopic irregularities originally present on the child surface being emphasized by curing shrinkage and heat distortion. When a protective film is bonded to one side of the polarizer using an active energy ray-curable adhesive, skin failure occurs on the adhesive layer side, but the opposite side (the surface of the polarizer on which the protective film is not bonded) ) Is also observed due to the distortion of the polarizer. A polarizing plate having a skin defect on the surface of the polarizer is not only undesirable in appearance because the skin defect is visible even through a protective film, but when incorporated in an image display device, the display is distorted. There is a risk of adversely affecting the visibility.

  In a form such as a smartphone in which a transparent member (substrate) such as a touch input element is further bonded to the outer surface of the protective film using an adhesive, the problem of poor skin on the polarizer surface is particularly noticeable. May be. This is because when the outermost surface of the polarizing plate (the outer surface of the translucent member) that reflects most of the external light is smooth, the reflected light from there hardly contains the scattered light, This is because the light reflected from the interface with the adhesive layer hardly mixes and the light reflected from the interface may be more clearly visible.

  As a means for suppressing poor skin due to curing shrinkage, etc., when thickening the polarizer or protective film to be bonded, or when curing the adhesive layer, the support substrate for reinforcement to the polarizer or protective film It is conceivable to increase the rigidity (resistance to curing shrinkage) by attaching the. However, increasing the thickness of the polarizer and the protective film goes against the recent trend of thinning image display devices. Moreover, when using a support base material, it is necessary to attach a support base material to a polarizer or a protective film, such as attaching through an adhesive layer. In this case, a sufficient rigidity improvement effect can be obtained. Can not.

  Moreover, a polarizer may have surface unevenness | corrugation extended in stripe shape along the extending | stretching direction, and visually recognized as a brown line. Hereinafter, in the present specification, the surface irregularities are referred to as “tea stripes”. Tea stripes are easily visible when a protective film or the like is placed on the surface. Similar to the skin defect, such a brown stripe can adversely affect the appearance of the polarizing plate and the visibility of the image display device.

  Therefore, the present invention is a polarizing plate in which a protective film is bonded onto a polarizer using an active energy ray-curable adhesive, and the polarizer has surface irregularities such as poor skin and brown stripes. Even if it exists, it cannot be visually recognized through a protective film, it is excellent in an external appearance, and when applied to an image display apparatus, there is no distortion of a display, and the polarizing plate which can give favorable visibility The purpose is to provide.

The present invention provides the following polarizing plates.
[1] A polarizer and a first protective film laminated on one surface of the polarizer via a first adhesive layer,
The first adhesive layer is a layer made of a cured product of an active energy ray-curable adhesive and having a refractive index of 1.47 or more and less than 1.57, and is laminated in contact with the one surface of the polarizer. ,Polarizer.

[2] The polarizing plate according to [1], wherein the polarizer has a thickness of 10 μm or less.
[3] The polarizing plate according to [1] or [2], wherein the first protective film has a thickness of 30 μm or less.

  [4] The polarizing plate according to any one of [1] to [3], further including a second protective film laminated on the other surface of the polarizer via a second adhesive layer.

  [5] The polarizing plate according to any one of [1] to [4], further including a translucent member laminated on the outer surface of the first protective film via a third adhesive layer.

  [6] The polarizing plate according to [5], wherein the translucent member is a touch input element.

  According to the polarizing plate of the present invention, even if surface irregularities such as poor skin and brown stripes exist on the surface of the polarizer, the surface irregularities are optically transparent by the adhesive layer having a predetermined refractive index. And can have an excellent appearance. The polarizing plate of the present invention is less likely to cause problems such as display distortion even when applied to an image display device.

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 another example of the laminated constitution of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows another example of the laminated constitution of the polarizing plate which concerns on this invention. It is a flowchart which shows a preferable example of the manufacturing method of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the laminated | multilayer film obtained at a resin layer formation process. It is a schematic sectional drawing which shows an example of the laminated constitution of the stretched film obtained at a extending process. It is a schematic sectional drawing which shows an example of the laminated constitution of the light-polarizing laminated film obtained at a dyeing process. It is a schematic sectional drawing which shows an example of the laminated constitution of the bonding film obtained at a 1st bonding process.

<Polarizing plate>
(1) Layer Configuration of Polarizing Plate FIG. 1 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate according to the present invention. A polarizing plate of the present invention like the polarizing plate 1 shown in FIG. 1 includes a polarizer 5 and a single-side protection provided with a first protective film 10 laminated on one surface of the polarizing plate 1 with a first adhesive layer 15 interposed therebetween. It can be a polarizing plate with a film. The first adhesive layer 15 is a layer made of a cured product of an active energy ray-curable adhesive, and is laminated on the polarizer 5 in contact with the one surface of the polarizer 5 as shown in FIG. The

  In addition, the polarizing plate according to the present invention may be obtained by further bonding a protective film to the other surface of the polarizer 5, and specifically, the polarizing plate 2 as shown in the polarizing plate 2 shown in FIG. 2. 5, a first protective film 10 laminated on one surface thereof via a first adhesive layer 15, and a second protective film 20 laminated on the other surface via a second adhesive layer 25. It can also be a polarizing plate with a double-sided protective film.

  The polarizing plate according to the present invention is a polarizing plate disposed on the visual (front) side of an image display element such as a liquid crystal cell when incorporated in an image display device such as a liquid crystal display device. The protective film 10 is disposed closer to the visual recognition (front surface) side of the image display device than the polarizer 5.

  The polarizing plate according to the present invention can further include a translucent member laminated on the outer surface (viewing side) of the first protective film 10. Like the polarizing plate 3 shown in FIG. 3, the translucent member 30 can be bonded onto the first protective film 10 via the third adhesive layer 35. The translucent member 30 is, for example, a translucent plate or sheet material for protecting the surface of the image display device, or a touch input element when the image display device is a touch panel device.

(2) Polarizer The polarizer 5 can be obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin layer (or film). The thickness of the polarizer 5 can be, for example, 30 μm or less, and further 20 μm or less. In particular, in a polarizing plate for a mobile device, the thickness is preferably 10 μm or less from the viewpoint of thinning the polarizing plate, and is 8 μm or less. More preferably. The thickness of the polarizer 5 is usually 2 μm or more.

  As the polyvinyl alcohol resin constituting the polyvinyl alcohol resin layer, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

  In the present specification, “(meth) acryl” means at least one selected from acryl and methacryl.

  A film obtained by forming the polyvinyl alcohol-based resin constitutes the polarizer 5. The method for forming the polyvinyl alcohol-based resin is not particularly limited and can be formed by a known method. However, it is easy to obtain a polarizer 5 having a small thickness, and the thin-film polarizer 5 is handled in the process. In view of excellent properties, it is preferable to form a film by coating a solution of a polyvinyl alcohol-based resin on a base film.

  The degree of saponification of the polyvinyl alcohol-based resin can be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 99.5 mol%, more preferably 94.0. It is in the range of ˜99.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and heat-and-moisture resistance of the resulting polarizing plate are lowered. When a polyvinyl alcohol-based resin having a saponification degree exceeding 99.5 mol% is used, the dyeing speed becomes slow, the productivity decreases, and the polarizer 5 having sufficient polarization performance may not be obtained.

The degree of saponification is the unit ratio (mol%) of the proportion of acetate groups (acetoxy groups: —OCOCH ₃ ) contained in polyvinyl acetate resin, which is a raw material for polyvinyl alcohol resins, changed to hydroxyl groups by the saponification step. The following formula:
Saponification degree (mol%) = 100 × (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups)
Defined by The saponification degree can be determined according to JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and thus the lower the proportion of acetate groups that inhibit crystallization.

  The polyvinyl alcohol-based resin may be a modified polyvinyl alcohol partially modified. For example, polyvinyl alcohol resins modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; alkyl esters of unsaturated carboxylic acids, acrylamide, and the like can be used. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10%. When the modification exceeding 30 mol% is performed, it is difficult to adsorb the dichroic dye, and it is difficult to obtain the polarizer 5 having sufficient polarization performance.

  The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can also be determined according to JIS K 6726 (1994).

  The dichroic dye contained (adsorption orientation) in the polarizer 5 can be iodine or a dichroic organic dye. Specific examples of the dichroic organic dye include: Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Includes Sky Blue, Direct First Orange S and First Black. A dichroic dye may be used individually by 1 type, and may use 2 or more types together.

(3) 1st protective film The 1st protective film 10 is a thermoplastic resin which has translucency (preferably optically transparent), for example, chain polyolefin resin (polypropylene resin etc.), cyclic polyolefin resin Polyolefin resins such as (norbornene resins); cellulose ester resins such as cellulose triacetate and cellulose diacetate; polyester resins; polycarbonate resins; (meth) acrylic resins; polystyrene resins; or a mixture thereof And a film made of a copolymer or the like. Among them, the first protective film 10 preferably used in the present invention is a protective film having low moisture permeability that is difficult to adhere with an aqueous adhesive, such as polyolefin resin, polyester resin, (meth) acrylic resin, polystyrene resin, and the like. It is a protective film.

  The first protective film 10 can also be a protective film having an optical function such as a retardation film and a brightness enhancement film. For example, a retardation film provided with an arbitrary retardation value by stretching a film made of the thermoplastic resin (uniaxial stretching or biaxial stretching) or by forming a liquid crystal layer or the like on the film. It can be.

  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 cyclic olefins as polymerization units. 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.

  The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and those in which a part of the hydroxyl group is modified with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable.

  The polyester-based resin is a resin having an ester bond other than the cellulose ester-based resin, and generally includes a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. A diol can be used as the polyhydric alcohol, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

  Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, and polycyclohexanedimethyl naphthalate.

  The polycarbonate resin is composed of a polymer in which monomer units are bonded via a carbonate group. The polycarbonate-based resin may be a resin called a modified polycarbonate having a modified polymer skeleton, a copolymer polycarbonate, or the like.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of (meth) acrylic resins include, for example, poly (meth) acrylic acid esters such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylic acid Ester copolymer; methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin etc.); methyl methacrylate and alicyclic hydrocarbon group And a copolymer (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, a polymer based on a poly (meth) acrylic acid C _1-6 alkyl ester such as poly (meth) acrylic acid methyl is used, and more preferably methyl methacrylate is the main component (50-100). % Methyl methacrylate resin is used.

  A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer is formed on the surface of the first protective film 10 opposite to the polarizer 5. You can also. The method for forming the surface treatment layer is not particularly limited, and a known method can be used.

  The first protective film 10 may contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant. it can.

  The thickness of the first protective film 10 is preferably 90 μm or less, more preferably 50 μm or less, and still more preferably 30 μm or less, from the viewpoint of thinning the polarizing plate. The thickness of the 1st protective film 10 is 5 micrometers or more normally from a viewpoint of intensity | strength and a handleability.

(4) First Adhesive Layer The first adhesive layer 15 is a layer for bonding and fixing the first protective film 10 to one surface of the polarizer 5, and the polarizer is directly bonded to the polarizer 5. 5 are laminated in contact with the one surface. The first adhesive layer 15 is usually also in contact with the bonding surface (the surface on the polarizer 5 side) of the first protective film 10.

  The first adhesive layer 15 is formed by applying an active energy ray-curable adhesive that is cured by irradiation of active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays to the polarizer 5 and / or the first protective film 10. After coating on the mating surface, the polarizer 5 and the first protective film 10 are overlapped via the coating layer of the adhesive, and cured by irradiating the coating layer with active energy rays. It is a cured product layer of an active energy ray-curable adhesive, and its refractive index (refractive index as a cured product) is 1.47 or more and less than 1.57. The active energy ray curable adhesive forming the first adhesive layer 15 is preferably an ultraviolet curable adhesive.

  By directly bonding the first adhesive layer 15 having a refractive index of 1.47 or more and less than 1.57 to the surface (bonding surface) of the polarizer 5, the polarizer 5 has surface irregularities such as skin defects and brown stripes. Even if it has a surface, the said surface unevenness | corrugation is filled with the 1st adhesive bond layer 15 which has the same refractive index as the polarizer 5, or the same grade, and the surface (bonding surface) of the polarizer 5 and the 1st Since the reflection at the interface with the adhesive layer 15 can be made extremely small, the surface irregularities can be made optically transparent or almost transparent, whereby the polarizing plate passes through the first protective film 10. The surface irregularities can be made completely or almost completely invisible. In addition, since the polarizing plate according to the present invention optically has no or almost no surface irregularities, the polarizing plate according to the present invention can be applied to an image display device such as a liquid crystal display device. Display distortion due to surface irregularities can be effectively prevented or suppressed.

  In recent years, image display devices including liquid crystal display devices and polarizing plates constituting the same have been required to be significantly thinned. In order to meet this requirement, the thickness of the polarizer and protective film constituting the polarizing plate. If the rigidity of the polarizer and the protective film is lowered along with this, the problem of poor skin becomes more obvious. Therefore, the present invention capable of preventing or suppressing the appearance defect due to the skin defect being visually recognized through the first protective film 10 and the display distortion in the image display device due to the skin defect is the first protection in the polarizer 5. When skin defects are present on the surface of the film 10 and the thickness of the polarizer 5 and / or the first protective film 10 is small, for example, the thickness of the polarizer 5 is 10 μm or less and / or the first protective film 10 It is particularly advantageous when the thickness is 30 μm or less.

  Moreover, when the transparent member 30 like a touch input element is further laminated | stacked through the 3rd adhesive bond layer 35 on the outer surface of the 1st protective film 10, a skin defect and the surface of the polarizer 5, for example, If there are surface irregularities such as brown stripes, the surface irregularities may be emphasized and visually recognized as described above. Therefore, in the present invention, surface irregularities such as skin defects and brown stripes are present on the surface of the polarizer 5 on the first protective film 10 side, and the translucent member 30 is laminated on the outer surface of the first protective film 10. It is particularly advantageous in some cases.

  From the viewpoint of more effectively preventing or suppressing appearance defects due to skin irregularities and surface irregularities such as brown stripes being visually recognized through the first protective film 10, and display distortion in the image display device associated with the surface irregularities, The refractive index of the first adhesive layer 15 is preferably 1.49 or more and 1.55 or less, and more preferably 1.50 or more and 1.53 or less. For the same reason, the absolute value of the difference between the refractive index of the polarizer 5 and the refractive index of the first adhesive layer 15 is preferably 0.07 or less, and more preferably 0.05 or less. .

  In addition, the refractive index of the 1st adhesive bond layer 15 here refers to the refractive index as a hardened | cured material after the active energy ray hardening adhesive hardens | cures as mentioned above, and before hardening in a liquid state It does not refer to the active energy ray-curable adhesive itself. Usually, an active energy ray-curable adhesive has a different refractive index before and after curing. This is because the molecular structure itself changes because a chemical bond is newly formed by the curing reaction, and the density of the molecule changes due to the chemical bond. The extent of these changes depends on the type and combination of the curable compounds (monomers) used in the active energy ray curable adhesive, the reaction rate, the presence or absence of additives, and so on. The refractive index of the curable adhesive usually changes by 0.02 or more before and after curing, and often changes by 0.05 or more. In particular, an adhesive containing a component that volatilizes at the time of curing and does not remain in the adhesive layer after curing, or an adhesive containing a curable compound whose structure is largely changed by a curing reaction, has a refractive index change before and after curing. There is a big tendency. Further, the kind and content of additives such as a polymerization initiator and a leveling agent contained in the adhesive can greatly affect the degree of refractive index change. In order to obtain the above-described effect, it is important to set the refractive index of the first adhesive layer 15 after curing within the above range, not the refractive index of the adhesive itself before curing.

  In Patent Documents 1 to 3, there is a reference to the refractive index of the active energy ray-curable adhesive itself before curing, but there is no reference to the refractive index of the adhesive layer after curing, as described above. In light of the fact that the refractive index can change significantly before and after, the descriptions of Patent Documents 1-3 do not anticipate or teach any refractive index after curing.

  The refractive index of the first adhesive layer 15 after curing contained in the polarizing plate is measured by removing either the first protective film 10 or the polarizer 5 and exposing the first adhesive layer 15. Can do. When removing the 1st protective film 10, what is necessary is just to melt | dissolve and remove using the organic solvent of a suitable kind according to the kind of resin which comprises this. For example, when the 1st protective film 10 consists of cyclic polyolefin resin, cyclohexane etc. can be used suitably. When the first protective film 10 is made of a cellulose ester resin or a (meth) acrylic resin, methylene chloride or the like can be suitably used. On the other hand, when removing the polarizer 5, it can be dissolved and removed by warm water. In order to make dissolution and removal with warm water easier, wet heat treatment (for example, storing in an environment of 80 ° C. and 90% RH for about one week) may be performed in advance. Even with treatment with an organic solvent, treatment with warm water, and wet heat treatment, the first adhesive layer 15 having a crosslinked structure is not structurally changed, and therefore the refractive index is not changed. It is preferable to measure the refractive index of a sample treated with warm water after drying the water adhering to the adhesive layer. For example, it is measured after air-drying for 12 hours or more in a normal temperature environment (25 ° C., 50% RH, etc.). Used for.

  The refractive index of the exposed first adhesive layer 15 is measured according to JIS K 0062: 1992 “Refractive Index Measurement Method for Chemical Products”, and Abbe refractometer (for example, “NAR manufactured by Atago Co., Ltd.”). -4T ", measurement wavelength 589 nm).

  The refractive index can also be measured using a spectroscopic ellipsometer. Examples of the spectroscopic ellipsometer include HORIBA, Ltd .: UVISE2, JA Woollam Japan: alpha-SE, JASCO Corporation: M550, Otsuka Electronics Co., Ltd .: FE-5000, and the like. However, other devices can be used as long as they can measure at a wavelength of 589 nm.

  The active energy ray-curable adhesive forming the first adhesive layer 15 is not particularly limited as long as it can form a cured product exhibiting a refractive index within the above range. An active energy ray-curable adhesive composition containing a polymerizable curable compound and / or a radical polymerizable curable compound can be preferably used. The active energy ray-curable adhesive usually further includes a cationic polymerization initiator and / or a radical polymerization initiator for initiating a curing reaction of the curable compound.

  Examples of the cationic polymerizable curable compound include an epoxy compound (a compound having one or more epoxy groups in the molecule) and an oxetane compound (one or two or more oxetane rings in the molecule). Or a combination thereof. Examples of the radical polymerizable curable compound include (meth) acrylic compounds (compounds having one or more (meth) acryloyloxy groups in the molecule) and radical polymerizable double bonds. Other vinyl compounds or combinations thereof can be mentioned, and (meth) acrylic compounds that can easily introduce a functional group by esterification are particularly preferable. A cationic polymerizable curable compound and a radical polymerizable curable compound may be used in combination.

  Regardless of the polymerization type of the curable compound, the refractive index of the first adhesive layer 15 can be controlled by appropriately selecting the type (molecular structure) of the curable compound. For example, when it is desired to lower the refractive index, it is effective to introduce a linear, branched or cyclic saturated alkyl group or a fluorine atom into the curable compound. It is also preferable to introduce a saturated alkyl group containing a fluorine atom into the curable compound. On the other hand, in order to increase the refractive index, it is effective to introduce an unsaturated group such as a cyclohexene ring, a benzene ring, a biphenyl ring, or a naphthalene ring into the curable compound. However, if an unsaturated group having a conjugated length longer than the anthracene ring is introduced, the first adhesive layer 15 may exhibit an undesirable coloration.

  The active energy ray curable adhesive may be a cationic polymerization accelerator, an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow modifier, a plasticizer, Additives such as foaming agents, antistatic agents, leveling agents and solvents can be contained.

  The thickness of the 1st adhesive bond layer 15 is about 0.001-5 micrometers normally, Preferably it is 0.01-3 micrometers.

(5) 2nd protective film The 2nd protective film 20 which the polarizing plate 2 with a double-sided protective film shown by FIG. 2 has is a film which consists of a thermoplastic resin illustrated above similarly to the 1st protective film 10. FIG. And a protective film having both optical functions such as a retardation film and a brightness enhancement film. Regarding the surface treatment layer that the second protective film 20 may have, the thickness of the film, and the like, the above description of the first protective film 10 is cited. The first protective film 10 and the second protective film 20 may be protective films made of the same kind of resin or may be protective films made of different kinds of resins. When the polarizing plate 2 with double-sided protective film is incorporated in an image display device such as a liquid crystal display device, the second protective film 20 is disposed on the image display element side with respect to the polarizer 5.

(6) Second Adhesive Layer The second adhesive layer 25 is a layer for adhering and fixing the second protective film 20 to the other surface of the polarizer 5. Like the first adhesive layer 15, the polarizer In general, the polarizer 5 is laminated so as to be in direct contact with the other surface of the polarizer 5. Moreover, the 2nd adhesive bond layer 25 is also in contact also with the bonding surface (surface by the side of the polarizer 5) of the 2nd protective film 20 normally.

  The adhesive forming the second adhesive layer 25 can be an active energy ray-curable adhesive, or an aqueous adhesive in which an adhesive component such as a polyvinyl alcohol resin is dissolved or dispersed in water. From the viewpoint of production efficiency, it is preferably an active energy ray-curable adhesive like the first adhesive layer 15. In particular, when the moisture permeability of the second protective film 20 is low, an active energy ray-curable adhesive is preferably used. The active energy ray curable adhesive forming the second adhesive layer 25 is preferably an ultraviolet curable adhesive.

  When surface irregularities such as skin defects and brown stripes are present on the surface of the polarizer 5 on the second protective film 20 side, the surface is not as great as when surface irregularities are present on the surface of the first protective film 10 side. The unevenness may be visually recognized through the first protective film 10. Therefore, the appearance irregularity due to the surface irregularities present on the surface of the polarizer 5 on the second protective film 20 side being viewed through the first protective film 10 and the display distortion in the image display device due to the surface irregularities are prevented or suppressed. In view of the above, the refractive index of the second adhesive layer 25 (refractive index as a cured product) is preferably 1.47 or more and less than 1.57. The refractive index is more preferably 1.49 to 1.55, and still more preferably 1.50 to 1.53. Further, the difference between the refractive index of the polarizer 5 and the refractive index of the second adhesive layer 25 is an absolute value, preferably 0.07 or less, and more preferably 0.05 or less.

  Regarding the method of measuring the refractive index of the second adhesive layer 25, the composition of the active energy ray-curable adhesive (type of curable compound, etc.), the thickness of the second adhesive layer 25, etc., the first adhesive layer 15 The above statement is cited. The active energy ray-curable adhesive forming the second adhesive layer 25 may have the same composition as the active energy ray-curable adhesive forming the first adhesive layer 15 or a different composition. It may be.

(7) Translucent Member and Third Adhesive Layer The translucent member 30 provided in the polarizing plate 3 shown in FIG. 3 is, for example, a translucent plate or sheet material for protecting the surface of the image display device. When the image display device is a touch panel device, it can be a touch input element for detecting touch position information. The light-transmitting plate material or sheet material is preferably optically transparent, and examples thereof include a glass plate and a thermoplastic resin sheet. The touch input element is also usually made of a glass plate, a thermoplastic resin sheet, or the like.

  The third adhesive layer 35 can be an active energy ray-curable adhesive, or an aqueous adhesive in which an adhesive component such as a polyvinyl alcohol resin is dissolved or dispersed in water. Therefore, like the first adhesive layer 15, it is preferably an active energy ray-curable adhesive. The active energy ray-curable adhesive that forms the third adhesive layer 35 may have the same composition as the active energy ray-curable adhesive that forms the first adhesive layer 15 or the second adhesive layer 25. It may have a different composition.

(8) Adhesive layer On the polarizer 5 in the polarizing plates 1 and 3 with single-sided protective film shown in FIGS. 1 and 3, or on the second protective film 20 in the polarizing plate 2 with double-sided protective film shown in FIG. A pressure-sensitive adhesive layer for bonding the polarizing plate to another member (for example, a liquid crystal cell when applied to a liquid crystal display device) may be laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is usually based on a (meth) acrylic resin, styrene resin, silicone resin or the like, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. It consists of an adhesive composition. Furthermore, it can also be set as the adhesive layer which contains microparticles | fine-particles and shows light-scattering property. The thickness of an adhesive layer is 1-40 micrometers normally, Preferably it is 3-25 micrometers.

(9) Other Optical Layer The polarizing plate according to the present invention can further include another optical layer laminated on the protective films 10 and 20 and the polarizer 5. As another optical layer, a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light that exhibits the opposite properties; a film with an antiglare function having a concavo-convex shape on the surface; a film with a surface antireflection function A reflective film having a reflective function on the surface; a transflective film having both a reflective function and a transmissive function; and a viewing angle compensation film.

<Production method of polarizing plate>
The polarizing plate of the present invention is preferably manufactured by the method shown in FIG. 4 because a thin film polarizer 5 can be easily obtained and the film is easily handled during the manufacturing process. The manufacturing method shown in FIG. 4 includes the following steps:
(1) Resin layer forming step S10 in which a coating liquid containing a polyvinyl alcohol-based resin is applied to at least one surface of a base film and then dried to form a polyvinyl alcohol-based resin layer to obtain a laminated film. ,
(2) Stretching step S20 to stretch the laminated film to obtain a stretched film,
(3) Dyeing step S30 to obtain a polarizing laminated film by dyeing the polyvinyl alcohol resin layer of the stretched film with a dichroic dye to form a polarizer,
(4) 1st bonding process S40 which bonds a protective film on the polarizer of a light-polarizing laminated film, and obtains a bonding film,
(5) Peeling step S50 to peel and remove the base film from the laminated film to obtain a polarizing plate with a single-sided protective film
Are included in this order.

When manufacturing the polarizing plate 2 with a double-sided protective film as shown in FIG. 2, after the peeling step S50, (6) a second method of bonding a protective film to the polarizer surface of the polarizing plate with a single-sided protective film. Pasting step S60,
including.

  Hereinafter, each step will be described with reference to FIGS. In the resin layer forming step S10, the polyvinyl alcohol-based resin layer may be formed on both surfaces of the base film, but the case where it is mainly formed on one surface will be described below.

(1) Resin layer forming step S10
Referring to FIG. 5, this step is a step of obtaining laminated film 100 by forming polyvinyl alcohol-based resin layer 6 on at least one surface of base film 40. The polyvinyl alcohol-based resin layer 6 is a layer that becomes the polarizer 5 through the stretching step S20 and the dyeing step S30. The polyvinyl alcohol-based resin layer 6 can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one or both surfaces of the base film 40 and drying it. The method of forming a polyvinyl alcohol-based resin layer by such coating is advantageous in that a thin film polarizer 5 can be easily obtained.

  The base film 40 can be composed of a thermoplastic resin, and is preferably composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability and the like. Specific examples of such thermoplastic resins include, for example, polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins (norbornene resins, etc.); polyester resins; (meth) acrylic resins; cellulose triacetate, Cellulose ester resins such as cellulose diacetate; Polycarbonate resins; Polyvinyl alcohol resins; Polyvinyl acetate resins; Polyarylate resins; Polystyrene resins; Polyethersulfone resins; Polysulfone resins; Polyamide resins; System resins; and mixtures and copolymers thereof.

  The base film 40 may have a single-layer structure made of one resin layer made of one kind or two or more kinds of thermoplastic resins, or a plurality of resin layers made of one kind or two or more kinds of thermoplastic resins. A laminated multilayer structure may be used. The base film 40 is preferably made of a resin that can be stretched at a stretching temperature suitable for stretching the polyvinyl alcohol-based resin layer 6 when the laminated film 100 is stretched in the stretching step S20 described later.

  The base film 40 can contain an additive. Specific examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, an anti-coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent.

  The thickness of the base film 40 is usually 1 to 500 μm, preferably 1 to 300 μm, more preferably 5 to 200 μm, and still more preferably 5 to 150 μm from the viewpoints of strength and handleability.

  The coating liquid applied to the base film 40 is preferably a polyvinyl alcohol resin solution obtained by dissolving a polyvinyl alcohol resin powder in a good solvent (for example, water). The details of the polyvinyl alcohol resin are as described above. The coating liquid may contain additives such as a plasticizer and a surfactant as necessary.

  The coating liquid is applied to the base film 40 by a wire bar coating method; a roll coating method such as reverse coating or gravure coating; a die coating method; a comma coating method; a lip coating method; a spin coating method; The method can be appropriately selected from a method such as a fountain coating method, a dipping method, and a spray method.

  The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set according to the type of solvent contained in the coating solution. A drying temperature is 50-200 degreeC, for example, Preferably it is 60-150 degreeC. When the solvent contains water, the drying temperature is preferably 80 ° C. or higher.

  The polyvinyl alcohol-based resin layer 6 may be formed only on one side of the base film 40 or on both sides. When formed on both sides, curling of the film that may occur during the production of the polarizing laminated film 300 (see FIG. 7) can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film 300. It is also advantageous in terms of plate production efficiency.

  The thickness of the polyvinyl alcohol-based resin layer 6 in the laminated film 100 is preferably 3 to 30 μm, more preferably 5 to 20 μm. If the polyvinyl alcohol-based resin layer 6 has a thickness within this range, the dichroic dye has good dyeability and excellent polarization performance through a stretching step S20 and a dyeing step S30 described later, and is sufficiently thin (for example, A polarizer 5 (thickness of 10 μm or less) can be obtained.

  Prior to the application of the coating liquid, in order to improve the adhesion between the base film 40 and the polyvinyl alcohol resin layer 6, at least the surface of the base film 40 on the side where the polyvinyl alcohol resin layer 6 is formed is provided. Corona treatment, plasma treatment, flame (flame) treatment or the like may be performed. For the same reason, the polyvinyl alcohol-based resin layer 6 may be formed on the base film 40 via a primer layer or the like.

  The primer layer can be formed by applying a primer layer forming coating solution onto the surface of the substrate film 40 and then drying it. This coating liquid includes a component that exhibits a certain degree of strong adhesion to both the base film 40 and the polyvinyl alcohol-based resin layer 6, and usually includes a resin component that imparts such adhesion and a solvent. . As the resin component, a thermoplastic resin excellent in transparency, thermal stability, stretchability and the like is preferably used, and examples thereof include (meth) acrylic resins and polyvinyl alcohol resins. Among these, polyvinyl alcohol resins that give good adhesion are preferably used. More preferably, it is a polyvinyl alcohol resin. As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component is usually used, but it is preferable to form the primer layer from a coating solution containing water as a solvent.

  In the peeling step S50 described later, the primer layer may be peeled off from the polarizer together with the base film, or may be peeled off from the base film together with the polarizer. If it is the former, a primer layer can be formed with the arbitrary thermoplastic resins which are easy to peel from the polyvinyl alcohol-type resin layer as mentioned above. On the other hand, in the latter case, the primer layer is dyed together with the polyvinyl alcohol-based resin layer in the dyeing step S30 to be described later, and after the base film is peeled off in the peeling step S50, the primer layer is combined with the dyed layer. It becomes necessary to become a polarizer. If the primer layer is formed of the polyvinyl alcohol resin, the primer layer is dyed together with the polyvinyl alcohol resin layer in the subsequent dyeing step S30, and peeled off from the base film together with the polarizer in the peeling step S50. Become part of the child.

  In order to increase the strength of the primer layer, a crosslinking agent may be added to the primer layer forming coating solution. Specific examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, metal salts, metal oxides, metal hydroxides, organometallic compounds), and polymer-based crosslinking agents. When a polyvinyl alcohol resin is used as the resin component for forming the primer layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde crosslinking agent, a metal chelate compound crosslinking agent, or the like is preferably used.

  The thickness of the primer layer is preferably about 0.05 to 1 μm, more preferably 0.1 to 0.4 μm. When the thickness is less than 0.05 μm, the effect of improving the adhesion between the base film 40 and the polyvinyl alcohol resin layer 6 is small, and when the thickness is more than 1 μm, it is disadvantageous for making the polarizing plate thin.

  The method of applying the primer layer forming coating solution to the base film 40 can be the same as the coating solution for forming the polyvinyl alcohol-based resin layer. The drying temperature of the coating layer made of the primer layer forming coating solution is, for example, 50 to 200 ° C, and preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C. or higher.

(2) Stretching step S20
With reference to FIG. 6, this process extends | stretches the laminated | multilayer film 100 which consists of the base film 40 and the polyvinyl alcohol-type resin layer 6, and is extended | stretched which consists of the extended base film 40 'and the polyvinyl alcohol-type resin layer 6'. In this step, the film 200 is obtained. The stretching process is usually uniaxial stretching.

  The stretching ratio of the laminated film 100 can be appropriately selected depending on the desired polarization characteristics, but is preferably more than 5 times and not more than 17 times, more preferably more than 5 times the original length of the laminated film 100. 8 times or less. If the draw ratio is 5 times or less, the polyvinyl alcohol resin layer 6 ′ is not sufficiently oriented, and the degree of polarization of the polarizer 5 may not be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, the film is likely to be broken during stretching, and the thickness of the stretched film 200 becomes unnecessarily thin, and the workability and handleability in subsequent processes may be reduced.

  The stretching process is not limited to stretching in one stage, and can be performed in multiple stages. In this case, all of the multistage stretching processes may be performed continuously before the dyeing process S30, or the second and subsequent stretching processes may be performed simultaneously with the dyeing process and / or the crosslinking process in the dyeing process S30. Good. Thus, when performing a extending | stretching process in multistage, it is preferable to perform an extending | stretching process so that it may become a draw ratio exceeding 5 times combining all the stages of an extending | stretching process.

  The stretching treatment may be longitudinal stretching that extends in the film longitudinal direction (film transport direction), and may be lateral stretching or oblique stretching that extends in the film width direction. Examples of the longitudinal stretching method include inter-roll stretching using a roll, compression stretching, stretching using a chuck (clip), and the like, and examples of the lateral stretching method include a tenter method. As the stretching treatment, either a wet stretching method or a dry stretching method can be adopted.

  The stretching temperature is set to be equal to or higher than the temperature at which the polyvinyl alcohol-based resin layer 6 and the entire base film 40 can be stretched, and preferably the phase transition temperature (melting point or glass transition temperature) of the base film 40. It is in the range of −30 ° C. to + 30 ° C., more preferably in the range of −30 ° C. to + 5 ° C., and still more preferably in the range of −25 ° C. to + 0 ° C. When the base film 40 consists of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.

  If the stretching temperature is lower than the phase transition temperature of −30 ° C., high-strength stretching exceeding 5 times is difficult to achieve, or the fluidity of the base film 40 is too low and the stretching process tends to be difficult. If the stretching temperature exceeds + 30 ° C. of the phase transition temperature, the fluidity of the base film 40 is too large and stretching tends to be difficult. Since it is easier to achieve a high draw ratio of more than 5 times, the drawing temperature is within the above range, and more preferably 120 ° C. or higher.

  As a heating method of the laminated film 100 in the stretching process, a zone heating method (for example, a method in which hot air is blown and heated in a stretching zone such as a heating furnace adjusted to a predetermined temperature); There is a method of heating the roll itself; a heater heating method (a method in which infrared heaters, halogen heaters, panel heaters, etc. are installed above and below the laminated film 100 and heated by radiant heat). In the inter-roll stretching method, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature.

  Prior to the stretching step S20, a preheat treatment step for preheating the laminated film 100 may be provided. As the preheating method, the same method as the heating method in the stretching process can be used. The preheating temperature is preferably in the range of −50 ° C. to ± 0 ° C. of the stretching temperature, and more preferably in the range of −40 ° C. to −10 ° C. of the stretching temperature.

  Moreover, you may provide a heat setting process process after the extending | stretching process in extending process S20. The heat setting process is a process in which heat treatment is performed at a temperature equal to or higher than the crystallization temperature while maintaining the tensioned state with the end of the stretched film 200 held by a clip. The crystallization of the polyvinyl alcohol-based resin layer 6 'is promoted by this heat setting treatment. The temperature of the heat setting treatment is preferably in the range of −0 ° C. to −80 ° C. of the stretching temperature, and more preferably in the range of −0 ° C. to −50 ° C. of the stretching temperature.

(3) Dyeing step S30
With reference to FIG. 7, this step is a step of making the polarizer 5 by dyeing the polyvinyl alcohol resin layer 6 ′ of the stretched film 200 with a dichroic dye and adsorbing and orienting it. Through this step, the polarizing laminated film 300 in which the polarizer 5 is laminated on one side or both sides of the base film 40 ′ is obtained.

  The dyeing step can be performed by immersing the entire stretched film 200 in a solution (dyeing solution) containing a dichroic dye. As the staining solution, a solution in which a dichroic dye is dissolved in a solvent can be used. As the solvent, water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight.

  When iodine is used as the dichroic dye, it is preferable to further add iodide to the dyeing solution because dyeing efficiency can be improved. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Is mentioned. The concentration of iodide in the dyeing solution is preferably 0.01 to 20% by weight. Of the iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is, by weight, preferably 1: 5 to 1: 100, more preferably 1: 6 to 1:80. The temperature of the dyeing solution is preferably 10 to 60 ° C, more preferably 20 to 40 ° C.

  In addition, although it is possible to perform dyeing process S30 before extending process S20, or to perform these processes simultaneously, the dichroic dye adsorb | sucked to a polyvinyl alcohol-type resin layer can be orientated favorably. As described above, it is preferable that the dyeing step S30 is performed after the laminated film 100 is subjected to at least some stretching treatment.

  The dyeing step S30 may include a crosslinking treatment step that is performed subsequent to the dyeing treatment. The crosslinking treatment can be performed by immersing a dyed film in a solution (crosslinking solution) in which a crosslinking agent is dissolved in a solvent. Examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. Only 1 type may be used for a crosslinking agent and it may use 2 or more types together. As a solvent for the crosslinking solution, water can be used, but it may further contain an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution is preferably 1 to 20% by weight, more preferably 6 to 15% by weight.

  The crosslinking solution can further comprise iodide. By adding the iodide, the polarization performance in the plane of the polarizer 5 can be made more uniform. Specific examples of iodide are the same as described above. The concentration of iodide in the crosslinking solution is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. The temperature of the crosslinking solution is preferably 10 to 90 ° C.

  In addition, a crosslinking process can also be performed simultaneously with a dyeing | staining process by mix | blending a crosslinking agent in a dyeing solution. Moreover, you may perform the process immersed in a crosslinking solution 2 or more times using 2 or more types of crosslinking solutions from which a composition differs.

  It is preferable to perform a washing | cleaning process and a drying process after dyeing process S30 and before 1st bonding process S40 mentioned later. The washing process usually includes a water washing process. The water washing treatment can be performed by immersing the film after the dyeing treatment or after the crosslinking treatment in pure water such as ion exchange water or distilled water. The water washing temperature is usually 3 to 50 ° C, preferably 4 to 20 ° C. The washing step may be a combination of a water washing step and a washing step with an iodide solution. As a drying process performed after the washing process, any appropriate method such as natural drying, blow drying, and heat drying can be adopted. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C.

(4) 1st bonding process S40
Referring to FIG. 8, in this step, a protective film is applied on the polarizer 5 of the polarizing laminated film 300, that is, on the surface opposite to the base film 40 ′ side of the polarizer 5 via an adhesive layer. It is the process of obtaining the bonding film 400 by combining. Although the example which bonds the 1st protective film 10 through the 1st adhesive bond layer 15 is shown in FIG. 8, when manufacturing the polarizing plate 2 with a double-sided protective film, the 2nd adhesive bond layer 25 is shown. You may make it bond the 2nd protective film 20 through. The adhesive forming the first adhesive layer 15 and the second adhesive layer 25 is as described above.

  In addition, when the polarizing laminated film 300 has the polarizer 5 on both surfaces of the base film 40 ′, usually, a protective film is bonded onto each of the polarizers 5 on both surfaces. In this case, these protective films may be the same type of protective film or different types of protective films.

  Using an active energy ray-curable adhesive as an example, the protective film bonding method will be described with reference to the case where the first protective film 10 is bonded. The active energy ray-curable adhesive that becomes the first adhesive layer 15 will be described. After laminating the first protective film 10 on the polarizer 5 via the agent, the adhesive layer is cured by irradiating active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. Among them, ultraviolet rays are preferable, and as a light source in this case, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, or the like can be used.

  In bonding a protective film to the polarizer 5, a plasma treatment, a corona treatment, an ultraviolet irradiation treatment, and a bonding surface of the protective film and / or the polarizer 5, in order to improve adhesiveness with the polarizer 5, Surface treatment (easily adhesion treatment) such as flame (flame) treatment or saponification treatment can be performed, and among them, plasma treatment, corona treatment or saponification treatment is preferable.

(5) Peeling step S50
This step is a step of peeling and removing the base film 40 ′ from the bonding film 400. Through this step, a polarizing plate with a single-sided protective film similar to that shown in FIG. 1 is obtained, but when the target polarizing plate is a polarizing plate with a single-sided protective film, the first protective film in the first bonding step S40. 10 is bonded. When the polarizing laminated film 300 has the polarizer 5 on both surfaces of the base film 40 ′ and the protective film is bonded to both the polarizers 5, one polarizing laminated film is obtained by the peeling step S50. Two polarizing plates with a single-side protective film are obtained from the film 300.

  The method for peeling and removing the base film 40 ′ is not particularly limited, and can be peeled by the same method as the separator (peeling film) peeling step performed by a normal pressure-sensitive adhesive polarizing plate. Substrate film 40 'may peel immediately as it is after 1st bonding process S40, and after 1st bonding process S40, it winds up in the shape of a roll once, and peels off while unwinding in the subsequent process. May be.

(6) 2nd bonding process S60
In this step, a protective film is further bonded on the polarizer 5 of the polarizing plate with a single-side protective film, that is, on the surface opposite to the protective film bonded in the first bonding step S40, and is shown in FIG. It is the process of obtaining the polarizing plate 2 with a double-sided protective film of the structure which is made. When the 1st protective film 10 is bonded in 1st bonding process S40, the 2nd protective film 20 is bonded in this process, and the 2nd protective film 20 is bonded in 1st bonding process S40. In the case of being bonded, the first protective film 10 is bonded in this step. The bonding of the second protective film 20 via the second adhesive layer 25 can be performed in the same manner as the bonding of the first protective film 10.

  As mentioned above, although the polarizer was formed from the polyvinyl alcohol-type resin layer coated on the base film, and the method of manufacturing a polarizing plate was explained in full detail next, it is not restrict | limited to this, From a simple substance (single) film The polarizing plate may be manufactured by bonding the first protective film 10 or the first and second protective films 10 and 20 to the polarizer 5.

  The polarizer 5 composed of a single (single) film is prepared by, for example, a step of producing a polyvinyl alcohol-based resin film by a known method such as a melt extrusion method or a solvent casting method; a step of uniaxially stretching a polyvinyl alcohol-based resin film; A step of dyeing a resin film with a dichroic dye and adsorbing it; a step of treating a polyvinyl alcohol resin film adsorbed with a dichroic dye with an aqueous boric acid solution; and washing with water after the treatment with an aqueous boric acid solution It can manufacture by the method including a process. Uniaxial stretching can be performed before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. 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 the case where both the first and second protective films 10 and 20 are bonded to produce a polarizing plate with a double-sided protective film, these protective films may be sequentially bonded via an adhesive layer, It may be pasted at the same time.

  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 the following examples and comparative examples, the refractive index was measured at a measurement wavelength of 589 nm using an Abbe refractometer “NAR-4T” manufactured by Atago Co., Ltd.

<Example 1>
(1) Primer layer forming step Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, saponification degree 99.5 mol%) is dissolved in 95 ° C. hot water, A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared. The resulting aqueous solution was mixed with a crosslinking agent (“Smiles Resin 650” manufactured by Taoka Chemical Co., Ltd.) at a ratio of 5 parts by weight to 6 parts by weight of the polyvinyl alcohol powder to form a primer layer forming coating solution. Got.

  Next, after applying a corona treatment to one side of a 90 μm-thick base film made of polypropylene (melting point: 163 ° C.), the primer layer forming coating solution is applied to the corona treatment surface using a small-diameter gravure coater. The primer layer having a thickness of 0.2 μm was formed by drying at 80 ° C. for 10 minutes.

(2) Production of laminated film (resin layer forming step)
Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C., and a polyvinyl alcohol aqueous solution having a concentration of 8% by weight. This was used as a coating liquid for forming a polyvinyl alcohol resin layer.

  By applying the polyvinyl alcohol-based resin layer forming coating solution to the surface of the primer layer of the base film having the primer layer prepared in (1) above using a die coater, and then drying at 80 ° C. for 20 minutes. Then, a polyvinyl alcohol-based resin layer was formed on the primer layer to obtain a laminated film composed of base film / primer layer / polyvinyl alcohol-based resin layer.

(3) Production of stretched film (stretching process)
The laminated film produced in the above (2) was subjected to 5.3 times free end uniaxial stretching at 160 ° C. using a floating longitudinal uniaxial stretching apparatus to obtain a stretched film. The thickness of the stretched polyvinyl alcohol resin layer was 5.0 μm.

(4) Production of polarizing laminated film (dyeing process)
The stretched film prepared in the above (3) is added to a dyeing aqueous solution at 30 ° C. containing iodine and potassium iodide (containing 0.6 parts by weight of iodine and 10 parts by weight of potassium iodide per 100 parts by weight of water). After immersing for 2 seconds, the polyvinyl alcohol-based resin layer was dyed, and the excess dyeing aqueous solution was washed away with pure water at 10 ° C.

  Next, it is immersed for 120 seconds in a first aqueous crosslinked solution at 78 ° C. containing boric acid (containing 10.4 parts by weight boric acid per 100 parts by weight of water), and then a 70 ° C. aqueous solution containing boric acid and potassium iodide. 2 A crosslinking treatment was performed by immersing in a crosslinking aqueous solution (containing 5.7 parts by weight of boric acid and 12 parts by weight of potassium iodide per 100 parts by weight of water) for 60 seconds. Thereafter, the film was washed with pure water at 10 ° C. for 10 seconds, and finally dried at 80 ° C. for 300 seconds to obtain a polarizing laminated film comprising a base film / polarizer.

(5) Production of polarizing plate with single-sided protective film (first bonding step and peeling step)
Prepare a protective film A made of triacetylcellulose having a thickness of 25 μm (“KC2UAW” manufactured by Konica Minolta Co., Ltd.), and having a small diameter so that the thickness after curing the ultraviolet curable adhesive on one side is about 1.0 μm. After coating using a gravure coater, this was bonded to the polarizer surface of the polarizing laminate film prepared in (4) above using a bonding roll. Thereafter, the adhesive layer is cured by irradiating ultraviolet rays from the base film side with an integrated light amount of 200 mJ / cm ² using a high-pressure mercury lamp, and the protective film A / adhesive layer / polarizer / base film The bonding film which consists of a layer structure was obtained (1st bonding process).

  Next, the base film was peeled and removed from the obtained laminated film to obtain a polarizing plate with a single-side protective film having a layer structure of protective film A / adhesive layer / polarizer (peeling step). The thickness of the polarizer was 5.4 μm.

  A black acrylic plate was prepared, and the polarizing plate with a single-sided protective film was bonded to the black acrylic plate using an adhesive layer on the protective film A side. When the surface of the polarizer (the surface opposite to the surface on which the protective film A is bonded) of the obtained polarizing plate with a single-side protective film was visually observed under a fluorescent lamp, surface irregularities, specifically, In addition, skin defects caused by curing shrinkage of the UV curable adhesive were remarkably recognized.

  An organic solvent layer coated with xylene (refractive index 1.50) is provided as a simulated layer of an adhesive layer made of a cured product of an active energy ray-curable adhesive on the surface of a polarizer having surface irregularities, and further A protective film B having a thickness of 25 μm (“KC2UAW” manufactured by Konica Minolta Co., Ltd.) is laminated on the simulated layer, and the protective film A / adhesive layer / polarizer / simulated layer / protective film B Thus, a simulated polarizing plate with a double-sided protective film was obtained.

<Examples 2-3 and Comparative Examples 1-3>
A simulated polarizing plate with a double-sided protective film was produced in the same manner as in Example 1 except that the type of organic solvent (and hence the refractive index) of the simulated layer was changed as shown in Table 1 below.

[Evaluation of appearance of polarizing plate with double-sided protective film]
(1) Effect of suppressing skin defects and tea streak visibility (no glass plate)
Under the fluorescent lamp, the polarizer surface of the obtained polarizing plate with a protective film on both sides (surface opposite to the surface on which the protective film A is bonded) was visually observed through the protective film B, and the following: According to the evaluation criteria, it was evaluated how much skin defects and tea streaks that were actually present were not visible. The results are shown in Table 1. In Examples 1 to 3 and Comparative Examples 1 to 3, an organic solvent layer is used as a simulation layer instead of an adhesive layer made of a cured product of an active energy ray-curable adhesive. The reason why skin defects and tea streaks on the surface are visible through the protective film is based on the interface reflection at the interface between the polarizer and the layer to be bonded on top of it. The effect of the present invention can be sufficiently confirmed.

A: Skin defects and tea streaks are not visible at all.
B: Slightly poor skin or brown streaks can be visually recognized, but at a level that does not cause any practical problems.
C: Skin defects or tea streaks are clearly visible than B,
D: Skin defects or brown stripes are noticeable visually.

(2) Effect of suppressing visual failure of skin defects and tea streaks when a glass plate is further laminated on the protective film B (with glass plate)
On the protective film B of the polarizing plate with a double-sided protective film obtained in each Example and Comparative Example, an organic solvent layer composed of the same organic solvent as that used in each Example and Comparative Example was provided, and further thereon Glass plates were laminated. In this state, visually observe over the protective film B, the organic solvent layer and the glass plate, and evaluate how much skin defects and tea streaks are not visible in the same manner as in (1) according to the above evaluation criteria. did. The results are shown in Table 1.

  In Comparative Example 3, in the case of “with glass plate”, both the skin defect and the tea streak were more clearly visible than in the case of “without glass plate”.

<Example 4>
A polarizing laminate film comprising a base film / polarizer was obtained according to (1) to (4) of Example 1. Thereafter, a protective film A made of triacetylcellulose having a thickness of 25 μm (“KC2UAW” manufactured by Konica Minolta Co., Ltd.) was prepared, and an ultraviolet curable adhesive (“Optodyne UV3200” manufactured by Daikin Industries, Ltd.) The refractive index after curing: 1.51) was applied using a small-diameter gravure coater so that the thickness after curing was about 1.0 μm, and this was applied to the polarizing laminated film using a bonding roll. Bonded to the polarizer surface. Thereafter, the adhesive layer is cured by irradiating ultraviolet rays from the base film side with an integrated light amount of 200 mJ / cm ² using a high-pressure mercury lamp, and the protective film A / adhesive layer / polarizer / base film A laminated film having a layer structure was obtained.

  Next, the base film was peeled and removed from the obtained laminated film to obtain a polarizing plate with a single-side protective film having a layer configuration of protective film A / adhesive layer / polarizer. The thickness of the polarizer was 5.4 μm.

<Example 5>
A polarizing plate with a single-sided protective film was prepared in the same manner as in Example 4 except that “Optodyne UV3100” (refractive index after curing: 1.49) manufactured by Daikin Industries, Ltd. was used as the ultraviolet curable adhesive. did.

<Example 6>
Same as Example 4 except that “Optodyne UV2100” (refractive index before curing: 1.45, refractive index after curing: 1.48) manufactured by Daikin Industries, Ltd. was used as the ultraviolet curable adhesive. The polarizing plate with a single-sided protective film was produced by the method.

<Comparative example 4>
A polarizing plate with a single-sided protective film was produced in the same manner as in Example 4 except that “Optodyne UV1000” (refractive index after curing: 1.45) manufactured by Daikin Industries, Ltd. was used as the ultraviolet curable adhesive. did.

  About the polarizing plate with the single-sided protective film of Examples 4-6 and the comparative example 4, (1) Visibility inhibitory effect (no glass plate) of a skin defect and a tea stripe, and (2) Further laminating | stacking a glass plate on the protective film A In the same manner as in Example 1, the skin defect and the effect of suppressing visual recognition of tea streaks (with glass plate) were evaluated. In addition, in the case of evaluation, the protective film A side was turned up, and it observed over the protective film A (in the evaluation of said (2), over the protective film A and a glass plate). The results are shown in Table 2.

  In the evaluation of the above (2), the same ultraviolet curable adhesive as that used for bonding the protective film A and the polarizer is used for bonding the protective film A and the glass plate, and cured under the same conditions. Thus, an adhesive layer having a thickness after curing of about 1.0 μm was formed.

  1, 2, 3 Polarizing plate, 5 Polarizer, 6 Polyvinyl alcohol resin layer, 6 ′ stretched polyvinyl alcohol resin layer, 10 First protective film, 15 First adhesive layer, 20 Second protective film, 25 2nd adhesive bond layer, 30 Translucent member, 35 3rd adhesive bond layer, 40 base film, 40 'stretched base film, 100 laminated film, 200 stretched film, 300 polarizing laminated film, 400 bonding the film.

Claims (6)

Including a polarizer and a first protective film laminated on one surface of the polarizer via a first adhesive layer;
The first adhesive layer is a layer made of a cured product of an active energy ray-curable adhesive and having a refractive index of 1.47 or more and less than 1.57, and is laminated in contact with the one surface of the polarizer. ,Polarizer.   The polarizing plate according to claim 1, wherein the polarizer has a thickness of 10 μm or less.   The polarizing plate according to claim 1, wherein the first protective film has a thickness of 30 μm or less.   The polarizing plate of any one of Claims 1-3 which further contains the 2nd protective film laminated | stacked through the 2nd adhesive bond layer on the other surface of the said polarizer.   The polarizing plate according to any one of claims 1 to 4, further comprising a translucent member laminated on an outer surface of the first protective film via a third adhesive layer.   The polarizing plate according to claim 5, wherein the translucent member is a touch input element.

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