JP2021071550A - Polarizer protective resin composition and polarization plate equipped with protective layer formed from the composition - Google Patents

Abstract

To provide a polarizer protective resin composition excellent in adhesion with a polarizer and capable of preventing defects such as a color void from an end part, a reddish void, etc. and also to provide a polarization plate equipped with a protective layer formed from the resin composition.SOLUTION: A polarizer protective resin composition includes: a resin (A) with a weight average molecular weight of 3000 or more and having at least one epoxy group; a chemical compound (B) containing at least one kind of substituent group selected from a group composed of -NH2, -NHR and -NRR' (in which R and R' independently represent a methyl group or an ethyl group, the R and the R' may be the same or different) and a boronic acid group, in a molecule. The polarizer protective resin composition contains 0.3 to 5 pts.wt. of the chemical compound (B) based on 100 pts.wt. of the resin (A).SELECTED DRAWING: Figure 1

Description

The present invention relates to a resin composition for protecting a polarizer and a polarizing plate including a protective layer formed from the composition.

The polarizer is typically produced by dyeing a polyvinyl alcohol (PVA) -based resin film with a dichroic substance such as iodine (for example, Patent Documents 1 and 2). It is known that in a moist heat environment, the iodine complex is destroyed by moisture absorption, and iodine is eluted, so that the degree of polarization decreases and the transmittance increases (color loss). Since water penetrates from the end of the polarizing plate, color loss tends to be remarkable at the end of the polarizer.

The polarizer is typically used as a polarizing plate including the polarizer and protective layers provided on both sides of the polarizer. In recent years, due to the demand for thinning, thinning of a polarizing element and a protective layer, and a polarizing plate having a protective layer on only one side of the polarizing element have been proposed. In such a configuration, the absorption of water from the end portion becomes faster, and the color loss of the end portion may become more remarkable. Further, by thinning the housing of smartphones, tablets and the like, the display is fixed to the housing with an adhesive. Depending on the type of adhesive, the iodine complex contained in the polarizer can be selectively destroyed. Therefore, there is a new problem of color loss from the end to which the adhesive is applied.

Japanese Patent No. 5048120 Japanese Unexamined Patent Publication No. 2013-156391

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to have excellent adhesion to a polarizer, and even when an adhesive is used, problems such as color loss occur. It is an object of the present invention to provide a resin composition for protecting a polarizing element which can prevent

（式中、Ａは−ＮＨ^２、−ＮＨＲ、および、−ＮＲＲ´を表し、Ｒ^１は未置換の、あるいは、メチル基またはエチル基で置換された芳香族環、脂肪族環、または、炭素数１〜１０の直鎖または分岐を有する炭化水素を表す。Ａは単結合またはカルボニル基を介してＲ^１と結合している。ＲおよびＲ´は上記のとおりである）
１つの実施形態においては、上記Ｒ^１は置換されていない、あるいは、メチル基またはエチル基で置換された芳香族環である。
１つの実施形態においては、上記樹脂（Ａ）は主鎖に芳香族環を含む樹脂である。
本発明の別の局面においては、偏光板が提供される。この偏光板は、偏光子と、該偏光子の少なくとも一方の面に、上記偏光子保護用樹脂組成物から形成された保護層と、を備える。
１つの実施形態においては、上記保護層の厚みは０．１μｍ〜８μｍである。
１つの実施形態においては、上記偏光子のヨウ素含有量は２重量％〜２５重量％である。
１つの実施形態においては、上記偏光子の厚みは８μｍ以下である。 The resin composition for protecting a polarizer of the present invention comprises (A) a resin having a weight average molecular weight of 3000 or more and having at least one epoxy group, and (B) -NH ² , -NHR, and-in the molecule. At least one substituent selected from the group consisting of NRR'(R and R'represent a methyl group or an ethyl group, and R and R'may be the same or different), and Includes compounds having a boronic acid group. This resin composition for protecting a polarizer contains 0.3 parts by weight to 5 parts by weight of the compound (B) with respect to 100 parts by weight of the resin (A).
In one embodiment, the ratio of the epoxy equivalent of the resin (A) to the amine equivalent of the compound (B) is 0.1 or more and less than 4.0.
In one embodiment, the compound (B) is a compound represented by the following formula:

(In the formula, A represents -NH ² , -NHR, and -NRR', and R ¹ is an unsubstituted or methyl or ethyl group substituted aromatic ring, aliphatic ring, or carbon. .A representative of a hydrocarbon having a straight-chain or branched having 1 to 10 .R and R'is bonded to R ¹ through a single bond or a carbonyl group is as described above)
In one embodiment, R ¹ is an aromatic ring that is not substituted or is substituted with a methyl or ethyl group.
In one embodiment, the resin (A) is a resin containing an aromatic ring in the main chain.
In another aspect of the invention, a polarizing plate is provided. This polarizing plate includes a polarizing element and a protective layer formed from the above-mentioned resin composition for protecting a polarizing element on at least one surface of the polarizing element.
In one embodiment, the protective layer has a thickness of 0.1 μm to 8 μm.
In one embodiment, the polarizer has an iodine content of 2% to 25% by weight.
In one embodiment, the thickness of the polarizer is 8 μm or less.

According to the present invention, a resin composition for protecting a polarizing element, which has excellent adhesion to a polarizing element and can prevent problems such as color loss even when an adhesive is used, and the resin composition. A polarizing plate with a protective layer formed from is provided. The layer (protective layer) formed from the resin composition for protecting a polarizer of the present invention can sufficiently adhere to the polarizer and prevent the occurrence of appearance defects such as floating and peeling. Further, it is possible to prevent the intrusion of moisture from the end portion and prevent the color from coming off from the end portion of the polarizer. Further, even when it is fixed to the housing by using an adhesive, it is possible to prevent the occurrence of problems such as color loss, which can contribute to further thinning.

It is the schematic sectional drawing of the polarizing plate by one Embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Decoder-Protecting Resin Composition The polarizer-protecting resin composition of the present invention is referred to as (A) a resin having a weight average molecular weight of 3000 or more and having at least one epoxy group (hereinafter, also referred to as resin (A)). , (B) In the molecule -NH ² , -NHR, and -NRR'(R and R'represent a methyl or ethyl group, and R and R'may be the same or different. ), And a compound having a boronic acid group (hereinafter, also referred to as compound (B)). The resin composition for protecting a polarizer contains 0.3 parts by weight to 5 parts by weight of the compound (B) with respect to 100 parts by weight of the resin (A). By using the resin (A) and the compound (B), the epoxy group of the resin (A) is opened by ^{-NH 2, -NHR, and -NRR'in the molecule of the compound (B) in the composition.} It rings and an addition reaction with the epoxy group occurs. As a result, a resin (A') in which boronic acid is added to a portion of the resin (A) having an epoxy group is obtained. When the resin composition for protecting the polarizer contains this resin (A'), the adhesion of the formed protective layer to the polarizer can be improved. Further, even when a polarizing plate having a protective layer on one side is used, the polarizer can be sufficiently protected. Further, even when it is fixed to the housing by using an adhesive, it is possible to prevent the occurrence of problems such as color loss due to the adhesive.

The resin composition for protecting a polarizer contains 0.3 parts by weight to 5 parts by weight, preferably 0.4 parts by weight to 3 parts by weight, and more preferably 0 parts by weight of the compound (B) with respect to 100 parts by weight of the resin (A). Includes 5 to 2 parts by weight. If the content of the compound (B) is less than 0.3 parts by weight, sufficient adhesion to the polarizer may not be obtained. Further, when the content of the compound (B) exceeds 5 parts by weight, the compound (B) itself may adversely affect the characteristics of the polarizer.

The ratio of the epoxy equivalent of the resin (A) to the amine equivalent of the compound (B) (hereinafter, also referred to as an equivalent ratio) is preferably 0.1 or more and less than 4.0, and more preferably 0.3. It is ~ 3.0, more preferably 0.5 ~ 2.0. Since the ratio of the epoxy equivalent of the resin (A) to the amine equivalent of the compound (B) is within the above range, even when the resin (A) is fixed to the housing by using an adhesive, the color may be lost due to the adhesive. It is possible to prevent the occurrence of problems. When the equivalent ratio is less than 1.00, for example, when an adhesive containing a base is used, the epoxy group can also react with the base (for example, amine) contained in the adhesive. As a result, the adverse effect of this base on the characteristics of the polarizer can be prevented. In the present specification, the equivalent ratio means a value calculated by the following formula. When the equivalent ratio is 1.0, it means that the same number of epoxy groups and amino groups are contained. When the equivalent ratio is less than 1.0, the epoxy group is contained, and when the equivalent ratio is more than 1.0, the amino group is contained. Each means that they are in excess.

Equivalent ratio = {number of copies of compound (B) / amine equivalent} / {number of copies of resin (A) / epoxy equivalent}

A-1. Resin (A)
The resin (A) has a weight average molecular weight of 3000 or more and has at least one epoxy group. The epoxy group may be on the terminal portion of the resin or on the side chain. That is, the resin (A) may be a so-called epoxy resin, or may be an arbitrary suitable resin with an epoxy group added. The more epoxy groups the resin (A) has, the more boronic acid is added to the resin (A'), and the adhesion with the polarizer can be further improved. Only one type of resin (A) may be used, or two or more types may be used in combination.

As the epoxy resin, any suitable epoxy resin can be used. As the epoxy resin, an epoxy resin having an aromatic ring in the main chain is preferably used. By using an epoxy resin having an aromatic ring, a resin composition for protecting a polarizer, which is more excellent in heat resistance and can prevent color loss from the end of the polarizer, can be obtained. Further, when the pressure-sensitive adhesive layer is formed on the protective layer, the anchoring force of the pressure-sensitive adhesive layer can be improved. Examples of the epoxy resin having an aromatic ring include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin and other bisphenol type epoxy resins; phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde phenol novolac. Novolak type epoxy resin such as epoxy resin; polyfunctional epoxy resin such as tetrahydroxyphenylmethane glycidyl ether, tetrahydroxybenzophenone glycidyl ether, epoxidized polyvinylphenol, naphthol type epoxy resin, naphthalene type epoxy resin, biphenyl type Epoxy resin and the like can be mentioned. Preferably, a bisphenol A type epoxy resin, a biphenyl type epoxy resin, or a bisphenol F type epoxy resin is used. By using these epoxy resins, color loss from the end of the polarizer can be further prevented. Only one type of epoxy resin may be used, or two or more types may be used in combination.

In one embodiment, the epoxy resins include a bisphenol A type epoxy resin, an epoxy resin having a tetramethylbiphenyl unit and a 1,1,1-triphenylethane unit, and a tetramethylbiphenyl unit and 1,1,1-. An epoxy resin having a diphenyl-3,3,5-trimethylcyclohexylmethane unit can be preferably used.

When a resin to which an epoxy group is added is used as the resin (A), any suitable resin can be used as the resin. For example, a resin used for forming a protective layer for a polarizer can be used. Specifically, cellulose-based resins such as triacetyl cellulose (TAC), polyester-based resins, polyvinyl alcohol-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyether sulfone-based resins, polysulfone-based resins, and polystyrene-based resins. Transparent resins such as resins, polynorbornene resins, polyolefin resins, (meth) acrylic resins, acetate resins; (meth) acrylic resins, urethane resins, (meth) acrylic urethane resins, epoxy resins, silicones Heat-curable resins such as based resins or ultraviolet curable resins; glassy polymers such as siloxane-based polymers can be mentioned.

The resin (A) preferably has a weight average molecular weight (Mw) of 3000 or more, more preferably 5000 or more, and further preferably 10000 or more. When the weight average molecular weight of the resin (A) is in the above range, color loss from the end of the polarizer can be further prevented. The weight average molecular weight of the resin (A) is, for example, 300,000 or less. The weight average molecular weight can be measured, for example, by GPC.

The epoxy equivalent of the resin (A) can be set to any suitable value. For example, it is preferable that the equivalent ratio of the compound (B) to be used with the amine equivalent is set to a value of 0.1 or more and less than 4.0. The epoxy equivalent of the resin (A) is, for example, 5000 or more, more preferably 6000 or more. The epoxy equivalent is, for example, 50,000 or less.

A-2. Compound (B)
Compound (B) is -NH ² , -NHR, and -NRR'(R and R'represent a methyl or ethyl group, and R and R'may be the same or different). It has at least one substituent selected from the group consisting of, and a boronic acid group. As described above, the resin (A') is formed by the compound (B) having -NH ² , -NHR, and -NRR', and a boronic acid group. Only one type of compound (B) may be used, or two or more types may be used in combination.

Compound (B) is preferably ^{a compound having -NH 2} and / or -NHR, and more preferably a compound having ^{-NH 2.}

（式中、Ａは−ＮＨ^２、−ＮＨＲ、または、−ＮＲＲ´を表し、Ｒ^１は未置換の、あるいは、メチル基またはエチル基で置換された芳香族環、脂肪族環、または、炭素数１〜１０の直鎖または分岐を有する炭化水素を表す。Ａは単結合またはカルボニル基を介してＲ^１と結合している。ＲおよびＲ´は上記のとおりである）。 In one embodiment, compound (B) is a compound represented by the following formula.

(In the formula, A represents -NH ² , -NHR, or -NRR', and R ¹ is an unsubstituted or methyl or ethyl group substituted aromatic ring, aliphatic ring, or carbon. .A representative of a hydrocarbon having a straight-chain or branched having 1 to 10 .R and R'is bonded to R ¹ through a single bond or a carbonyl group is as previously described).

The above A represents -NH ² , -NHR, or -NRR'. A is attached to R ¹ through a single bond or a carbonyl group. R ¹ represents an unsubstituted or methyl or ethyl group-substituted aromatic ring, aliphatic ring, or hydrocarbon having a linear or branched carbon number of 1 to 10. R ¹ is preferably an unsubstituted or methyl or ethyl group substituted aromatic ring or aliphatic ring, and more preferably an unsubstituted or methyl or ethyl group substituted aromatic ring. It is a ring.

Specific examples of the compound (B) include the following compounds.

The amine equivalent of compound (B) can be set to any suitable value. For example, the equivalent ratio of the resin (A) to the epoxy equivalent can be set to a value of 0.1 or more and less than 4.0. The amine equivalent of compound (B) is, for example, 100 or more, preferably 120 or more. The amine equivalent of compound (B) is, for example, 300 or less.

A-3. Other Ingredients In addition to the above resin (A) and compound (B), the resin composition for protecting a polarizer may contain any suitable other ingredient. Other components include, for example, solvents and additives. As the solvent, ethyl acetate, toluene, methyl ethyl ketone and cyclopentanone are preferably used. Only one of these solvents may be used, or two or more of these solvents may be used in combination.

As the additive, any suitable additive can be used. For example, surfactants, ultraviolet absorbers, antioxidants, tackifiers and the like can be mentioned. Only one type of additive may be used, or two or more types may be used in combination. These additives can be used in any suitable amount.

A-4. Method for Preparing Resin Composition for Protecting Polarizer The resin composition for protecting a polarizer can be prepared by any suitable method. For example, it can be prepared by mixing the resin (A), the compound (B), and optionally any suitable additive in any suitable solvent.

B. Polarizing plate The polarizing plate of the present invention includes a polarizing element and a protective layer formed from the resin composition for protecting the polarizer on at least one surface of the polarizing element. The protective layer formed from the resin composition for protecting the polarizer is excellent in adhesion to the polarizer. Therefore, even when the thickness of the polarizer is thin, it is possible to prevent appearance defects such as floating and peeling of the protective layer from the polarizer. In addition, color loss from the end of the polarizer can be prevented. Further, even when it comes into contact with the adhesive, it is possible to prevent the occurrence of problems such as color loss.

B-1. Outline of Polarizing Plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. The polarizing plate 100 of the illustrated example includes a polarizing element 10 and a protective layer 20 formed on at least one surface of the polarizing element. The protective layer 20 is a layer formed from the above resin composition for protecting a polarizer. By forming the protective layer from the resin composition for protecting the polarizer, the adhesion between the protective layer and the polarizer is improved. Therefore, it is possible to prevent the intrusion of moisture from the end portion of the polarizing plate and prevent the color from coming off from the end portion. Further, since the protective layer 20 is also excellent in crack resistance, the polarizer 10 can be appropriately protected. Further, the protective layer 20 can prevent color loss of the polarizer from the end portion even when the protective layer 20 is formed on only one side of the polarizer 10. Therefore, it can also contribute to reducing the thickness of the polarizing plate 100. In the illustrated example, the protective layer 20 is formed only on one surface of the polarizer 10, but the protective layers 20 may be formed on both sides of the polarizer 10. Further, the protective layer 20 may be formed on one surface of the polarizer 10, and another protective layer may be formed on the other surface of the polarizer 10. The protective layer 20 is typically formed directly on the polarizer 10 (without an adhesive layer or an adhesive layer). By forming the protective layer directly on the polarizer, it can contribute to the thinning of the polarizing plate. Further, by directly forming the protective layer, the adhesion between the polarizer and the protective layer can be improved.

The polarizing plate 100 may further include any suitable functional layer other than the protective layer 20 depending on the purpose. Examples of the functional layer include a retardation layer, a light diffusion layer, an antireflection layer, and a reflection type polarizer. The functional layer may be laminated on the side of the polarizer 10 or may be laminated on the side of the protective layer 20. It may also include a plurality of functional layers.

B-2. Polarizer Polarizer is typically a resin film containing a dichroic substance. Examples of the dichroic substance include iodine and organic dyes. Only one kind of dichroic substance may be used, or two or more kinds may be used in combination. It preferably contains iodine.

In one embodiment, the polarizer 10 preferably has an iodine content of 2% to 25% by weight. In another embodiment of the invention, the polarizer 10 preferably has an iodine content of 10% to 25% by weight, more preferably 15% to 25% by weight. Polarizers with a high iodine content can be more prominent in color loss in a moist heat environment. Therefore, the effect of forming the protective layer using the above-mentioned resin composition for protecting a polarizer can be more exerted. As used herein, the term "iodine content" means the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, in the polarizer, iodine exists in the form of ^{iodine ion (I −} ), iodine molecule (I ₂ ), polyiodine ion (I ₃ ⁻ , I ₅ ^{−) and the like.} Iodine content means the amount of iodine that includes all of these forms. The iodine content can be calculated, for example, by the calibration curve method of fluorescent X-ray analysis. The polyiodine ion exists in a state in which a PVA-iodine complex is formed in the polarizer. By forming such a complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, a complex of PVA and tri-iodide ion (PVA · _{I 3} ^-) has a light absorption peak around 470 nm, a complex of PVA and five iodide ion (PVA · _{I 5} ^-) is 600nm near Has an absorptive peak. As a result, polyiodine ions can absorb light in a wide range of visible light, depending on their morphology. On the other hand, iodine ion (I ⁻ ) has an absorption peak near 230 nm and is not substantially involved in the absorption of visible light. Therefore, polyiodine ions present in the form of a complex with PVA may be mainly involved in the absorption performance of the polarizer.

The thickness of the polarizer is preferably 8 μm or less, more preferably 0.6 μm or more and less than 8 μm. In one embodiment, the thickness of the polarizer is preferably 5 μm or less.

The simple substance transmittance of the polarizer is, for example, 30% or more. The theoretical upper limit of the simple substance transmittance is 50%, and the practical upper limit is 46%. The single transmittance (Ts) is a Y value measured by a two-degree field of view (C light source) of JIS Z8701 and corrected for luminosity factor. For example, a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation). It can be measured using the product name: V7100).

The degree of polarization of the polarizer is, for example, 99.0% or more, preferably 99.5% or more, and more preferably 99.9% or more. As described above, the polarizing plate of the present invention can prevent color loss from the end portion. Therefore, even when the degree of polarization of the polarizer is high, the degree of polarization can be maintained satisfactorily.

B-2-1. Method for Producing Polarizer The polarizer can be manufactured by any suitable method. For example, it can be produced by subjecting a PVA-based resin film to a swelling step, a dyeing step, a cross-linking step, a stretching step, a washing step, and a drying step. In one embodiment, the PVA-based resin film may be a PVA-based resin layer formed on a base material. The laminate of the base material and the resin layer can be obtained, for example, by a method of applying the coating liquid containing the PVA-based resin to the base material, a method of laminating a PVA-based resin film on the base material, or the like. As the base material, any suitable resin base material can be used, and for example, a thermoplastic resin base material can be used.

B-2-1-1. PVA-based resin film Examples of the PVA-based resin forming the PVA-based resin film include polyvinyl alcohol and an ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% or more and less than 100 mol%, preferably 95.0 mol% to 99.99 mol%, and more preferably 99.0 mol% to 99.99 mol%. is there. The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a saponification degree, a polarizer having excellent durability can be obtained.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the intended purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined according to JIS K 6726-1994.

The thickness of the PVA-based resin film can be set according to the desired thickness of the polarizer. The thickness of the PVA-based resin film is, for example, 0.5 μm to 200 μm. By using the dyeing solution described later, for example, even if the PVA-based resin film is less than 10 μm, it can be sufficiently dyed in a short time, and the property of being able to sufficiently function as a polarizer can be imparted.

As described above, the polarizer can be produced, for example, by subjecting a PVA-based resin film to a swelling step, a dyeing step, a cross-linking step, a stretching step, a washing step, and a drying step. Each step is performed at an arbitrary appropriate timing. Further, if necessary, any step other than the dyeing step may be omitted, a plurality of steps may be performed at the same time, and each step may be performed a plurality of times. Hereinafter, each step will be described.

B-2-1-2. Stretching In the stretching treatment, the PVA-based resin film is typically uniaxially stretched 3 to 7 times the original length. In one embodiment, the PVA-based resin film is subjected to dry stretching. Dry stretching is preferable because the stretching treatment can be performed in a wider temperature range. The temperature at which the dry stretching is performed is, for example, 50 ° C. to 200 ° C., preferably 80 ° C. to 180 ° C., and more preferably 90 ° C. to 160 ° C. The stretching direction may be the longitudinal direction of the film (MD direction) or the width direction of the film (TD direction). The stretching direction can correspond to the absorption axis direction of the obtained polarizer.

B2-1-3. Dyeing The dyeing step is a step of dyeing a PVA-based resin film with a dichroic substance. It is preferably carried out by adsorbing a dichroic substance. Examples of the adsorption method include a method of immersing a PVA-based resin film in a dyeing solution containing a bicolor substance, a method of applying the dyeing solution to the PVA-based resin film, and a method of spraying the dyeing solution onto the PVA-based resin film. The method of doing this can be mentioned. A method of immersing the PVA-based resin film in the dyeing solution is preferable. This is because the dichroic substance can be adsorbed well.

Examples of the dichroic substance include iodine and a dichroic dye as described above. Iodine is preferred. When iodine is used as the dichroic substance, an aqueous iodine solution is preferably used as the staining solution. The iodine content of the iodine aqueous solution is preferably 0.04 parts by weight to 5.0 parts by weight with respect to 100 parts by weight of water. In one embodiment, the iodine content in the iodine aqueous solution is preferably 0.3 parts by weight or more with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to the aqueous iodine solution. Potassium iodide is preferably used as the iodide. The content of iodide is preferably 0.3 to 15 parts by weight with respect to 100 parts by weight of water.

The liquid temperature at the time of dyeing the dyeing solution can be set to any appropriate value. For example, it is 20 ° C to 50 ° C. When the PVA-based resin film is immersed in the dyeing solution, the immersion time is, for example, 1 second to 1 minute.

The content of the iodide contained in the dyeing solution is preferably 1 part by weight to 40 parts by weight, and more preferably 3 parts by weight to 30 parts by weight with respect to 100 parts by weight of the solvent. When the content of iodide is in the above range, sufficient polyiodine ions can be formed in the dyeing solution. 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. And so on. Potassium iodide is preferred.

As the solvent of the dyeing solution, any suitable solvent can be used, and water is usually used.

B2-1-4. Swelling The swelling step is usually performed before the dyeing step. In one embodiment, the swelling step may be performed with the dyeing step in the same immersion bath. The swelling step is performed, for example, by immersing a PVA-based resin film in a swelling bath. As the swelling bath, any suitable liquid can be used, and for example, water such as distilled water or pure water is used. The swelling bath may contain any suitable other ingredients other than water. Examples of other components include solvents such as alcohol, additives such as surfactants, and iodides. Examples of the iodide include those exemplified above. Preferably, potassium iodide is used. The temperature of the swelling bath is, for example, 20 ° C to 45 ° C. The immersion time is, for example, 10 seconds to 300 seconds.

B2-1-1-5. Cross-linking In the cross-linking step, a boron compound is usually used as a cross-linking agent. Examples of the boron compound include boric acid and borax. Preferably, it is boric acid. In the cross-linking step, the boron compound is usually used in the form of an aqueous solution.

When an aqueous boric acid solution is used, the boric acid concentration of the aqueous boric acid solution is, for example, 2% by weight to 15% by weight, preferably 3% by weight to 13% by weight. The boric acid aqueous solution may further contain an iodide such as potassium iodide and a zinc compound such as zinc sulfate and zinc chloride.

The cross-linking step can be performed by any suitable method. For example, a method of immersing a PVA-based resin film in an aqueous solution containing a boron compound, a method of applying an aqueous solution containing a boron compound to a PVA-based resin film, or a method of spraying an aqueous solution containing a boron compound onto a PVA-based resin film can be mentioned. Be done. It is preferable to immerse in an aqueous solution containing a boron compound.

The temperature of the solution used for crosslinking is, for example, 25 ° C. or higher, preferably 30 ° C. to 85 ° C., and more preferably 40 ° C. to 70 ° C. The immersion time is, for example, 5 seconds to 800 seconds, preferably 8 seconds to 500 seconds.

B2-1-1-6. Cleaning The cleaning step is performed using water or an aqueous solution containing the above iodide. Typically, this is done by immersing a PVA-based resin film in an aqueous potassium iodide solution. The temperature of the aqueous solution in the washing step is, for example, 5 ° C to 50 ° C. The immersion time is, for example, 1 second to 300 seconds.

B2-1-1-7. Drying The drying step can be performed by any suitable method. For example, natural drying, blast drying, vacuum drying, heat drying and the like can be mentioned, and heat drying is preferably used. When heat drying is performed, the heating temperature is, for example, 30 ° C. to 100 ° C. The drying time is, for example, 10 seconds to 10 minutes.

B-3. Protective layer The protective layer 20 is formed on at least one surface of the polarizer 10. The protective layer 20 is formed by using the above resin composition for protecting a polarizer.

The thickness of the protective layer 20 can be set to an arbitrary appropriate value depending on the thickness of the polarizer and the like. In one embodiment, the thickness of the protective layer is preferably 0.1 μm to 8 μm, more preferably 0.2 μm to 5.0 μm, and even more preferably 0.3 μm to 3.0 μm. When the thickness of the protective layer is within the above range, it can contribute to the thinning of the polarizing plate. As described above, even when the protective layer 20 is thin, it can appropriately protect the polarizer 10 and prevent color loss from the end portion. If the thickness of the protective layer 20 exceeds 8 μm, the adhesion between the polarizer and the protective layer may decrease.

Moisture permeability of the protective layer is preferably ^{10g / m 2 · 24h~2000g / m} 2 · 24h, more preferably from ^{100g / m 2 · 24h~1800g / m} 2 · 24h, more preferably 150 g / m a ^{2 · 24h~1500g / m 2 · 24h} . When the moisture permeability is in the above range, it is possible to prevent moisture from entering and causing color loss in the polarizer.

The protective layer can be formed by any suitable method. For example, it can be formed by applying the resin composition for protecting a polarizer to the polarizer. Various coating methods include bar coater coating, air knife coating, gravure coating, gravure reverse coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexographic printing, screen printing, etc. Method can be adopted. Further, any appropriate surface modification treatment may be applied to the surface to which the resin composition for protecting the polarizer of the polarizer is applied.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[Production Example 1] Preparation of UV-curable adhesive 40 parts by weight of N-hydroxyethylacrylamide (HEAA), 60 parts by weight of acryloyl morpholine (ACMO), and photoinitiator (manufactured by BASF, trade name: IRGACURE 819) 3 A part by weight was mixed to prepare an ultraviolet curable adhesive.

[Production Example 2] Preparation of Polarizer Laminated Body 1 As a base material, an amorphous isophthalic acid copolymer polyethylene terephthalate (IPA copolymer PET) film (thickness) having a long shape, a water absorption rate of 0.75%, and a Tg of 75 ° C. : 100 μm) was used. One side of the base material is subjected to corona treatment, and polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6) are treated on this corona-treated surface. %, Saponification degree 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: Gosefimer Z200) is applied at 25 ° C. and dried, and PVA having a thickness of 13 μm is applied. A based resin layer was formed to prepare a laminate.
The obtained laminate was uniaxially stretched at the free end 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, the laminate was mixed with a staining solution at 30 ° C. (an aqueous solution obtained by adding 7.0 parts by weight of potassium iodide and 1.0 part by weight of solid iodine to 100 parts by weight of water) to obtain the transmittance of the polarizer. Was dyed by immersing it so that the content was 42% or more (dyeing treatment).
Next, it was immersed in a cross-linked bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 35 seconds. (Crossing treatment).
Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration: 4.0% by weight) having a liquid temperature of 70 ° C., the total draw ratio was 5. The uniaxial stretching was performed so as to be 5 times (stretching in water).
Then, the laminate was immersed in a washing bath at a liquid temperature of 20 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) for 3 seconds (cleaning treatment).
Then, it was dried in an oven at 60 ° C. for 60 seconds to obtain a laminate 1 having a PVA-based resin layer (polarizer) having a thickness of 5 μm.
The ultraviolet curable adhesive is applied to the surface of the obtained laminate 1 on the polarizer side so that the thickness after curing is 1 μm, and the (meth) acrylic resin film A having a lactone ring structure is applied to the coated surface. The corona-treated surfaces (thickness 40 μm) were bonded together to cure the ultraviolet curable adhesive. Then, the PET film was peeled off from the laminate to obtain a single protective polarizer laminate 1 (protective layer (40 μm) / adhesive layer (1 μm) / polarizer (5 μm)).

[Production Example 3] Preparation of Polymer (A) Methyl methacrylate (MMA, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name: methyl methacrylate monomer) 99.0 parts by weight, monomer of the following formula (1e) 1. 0 parts by weight and 0.2 parts by weight of a polymerization initiator (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name: 2,2'-azobis (isobutyronitrile)) were dissolved in 100 parts by weight of toluene. Next, a polymerization reaction was carried out for 5 hours while heating at 70 ° C. in a nitrogen atmosphere to obtain a polymer (A) (solid content concentration: 50% by weight). The weight average molecular weight of the obtained polymer (A) was 50,000.

[Production Example 4] Preparation of Acrylic Adhesive In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler, 99 parts by weight of butyl acrylate and 1 part by weight of 4-hydroxybutyl acrylate. A monomer mixture containing the above was charged. Further, with respect to 100 parts by weight of the above-mentioned monomer mixture (solid content), 0.1 part by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with ethyl acetate, and nitrogen gas was added while gently stirring. After the introduction and substitution with nitrogen, the liquid temperature in the flask was maintained at around 60 ° C. and the polymerization reaction was carried out for 7 hours. Then, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30%. In this way, a solution of an acrylic polymer (base polymer) having a weight average molecular weight of 1.4 million was prepared.
With respect to 100 parts by weight of the solid content of the above acrylic polymer solution, 0.095 parts by weight of trimethylolpropane xylylene diisocyanate (manufactured by Mitsui Chemicals, trade name: Takenate D110N) and 0.3 by weight of dibenzoyl peroxide as a cross-linking agent. 0.2 parts by weight of organosilane (manufactured by Soken Kagaku Co., Ltd., trade name: A100) and thiol group-containing silane coupling agent (manufactured by Shinetsu Kagaku Kogyo Co., Ltd., trade name: X41-1810) 0. An acrylic pressure-sensitive adhesive (solution) was obtained by blending 2 parts by weight and 0.3 parts by weight of an antioxidant (manufactured by BASF, trade name: Irganox1010).

[Example 1] Preparation of polarizing plate 1 100 parts by weight of epoxy resin E1 (manufactured by Mitsubishi Chemical Co., Ltd., trade name: jER (registered trademark) 1256B40, weight average molecular weight: 40,000) and m-aminophenylboronic acid 0.90 A resin composition for protecting a polarizer was prepared by mixing with parts by weight. The obtained resin composition for protecting a polarizer was applied to the surface of the polarizing element laminate 1 on the polarizer side so that the thickness after drying was 0.3 μm to form a protective layer, and a polarizing plate 1 was obtained.

[Example 2] Preparation of polarizing plate 2 Polarizing plate 2 was obtained in the same manner as in Example 1 except that a resin composition for protecting a polarizer was prepared using 1.86 parts by weight of m-aminophenylboronic acid. ..

[Example 3] Preparation of polarizing plate 3 A polarizing plate 3 was obtained in the same manner as in Example 1 except that a resin composition for protecting a polarizer was prepared using 2.90 parts by weight of m-aminophenylboronic acid. ..

[Example 4] Preparation of polarizing plate 4 Instead of epoxy resin E1, epoxy resin E2 (manufactured by Mitsubishi Chemical Co., Ltd., trade name: jER® YX6954BH30, weight average molecular weight: 36000) was used, and A resin composition for protecting a polarizer was prepared in the same manner as in Example 1 except that 0.50 parts by weight of m-aminophenylboronic acid was used. A polarizing plate 4 was obtained in the same manner as in Example 1 except that the obtained resin composition for protecting a polarizer was used.

[Example 5] Preparation of polarizing plate 5 A polarizing plate 5 was obtained in the same manner as in Example 4 except that a resin composition for protecting a polarizer was prepared using 1.05 parts by weight of m-aminophenylboronic acid. ..

[Example 6] Preparation of polarizing plate 6 Epoxy resin E3 (manufactured by Mitsubishi Chemical Co., Ltd., trade name: jER® YX7200B35, weight average molecular weight: 29000) was used instead of the epoxy resin E1. A resin composition for protecting a polarizer was prepared in the same manner as in Example 1 except that 0.70 parts by weight of m-aminophenylboronic acid was used. A polarizing plate 6 was obtained in the same manner as in Example 1 except that the obtained resin composition for protecting a polarizer was used.

[Example 7] Preparation of polarizing plate 7 A polarizing plate 7 was obtained in the same manner as in Example 6 except that a resin composition for protecting a polarizer was prepared using 1.44 parts by weight of m-aminophenylboronic acid. ..

(Comparative Example 1) Preparation of Polarizing Plate C1 A polarizing plate C1 was obtained in the same manner as in Example 1 except that a resin composition for protecting a polarizer was not applied to form a protective layer.

(Comparative Example 2) Preparation of polarizing plate C2 80 parts by weight of epoxy resin E1 (manufactured by Mitsubishi Chemical Co., Ltd., trade name: jER (registered trademark) 1256B40) and 20 parts by weight of polymer (A) are mixed, and a polarizer A protective resin composition was prepared. The obtained resin composition for protecting a polarizer was applied to the surface of the polarizing element laminate 1 on the polarizer side so that the thickness after drying was 0.3 μm to form a protective layer, and a polarizing plate C2 was obtained.

(Comparative Example 3) Preparation of Polarizing Plate C3 A polarizing plate C3 was obtained in the same manner as in Example 1 except that a resin composition for protecting a polarizer was prepared without adding m-aminophenylboronic acid.

(Comparative Example 4) Preparation of Polarizing Plate C4 A polarizing plate C4 was obtained in the same manner as in Example 1 except that a resin composition for protecting a polarizer was prepared using 9.0 parts by weight of m-aminophenylboronic acid. It was.

[Evaluation]
(Preparation of polarizing plate with adhesive layer)
The acrylic pressure-sensitive adhesive composition obtained in Production Example 4 is uniformly coated on the surface of a polyethylene terephthalate film (separator) treated with a silicone-based release agent with a fountain coater, and then air-circulated constant temperature at 155 ° C. It was dried in an oven for 2 minutes to form a 20 μm thick pressure-sensitive adhesive layer on the surface of the separator. Next, this pressure-sensitive adhesive layer was transferred to the surface side of the polarizing element protective layer (the surface coated with the resin composition for protecting the polarizer) of the polarizing plate obtained in Examples or Comparative Examples to obtain a polarizing plate with a pressure-sensitive adhesive layer. In Comparative Example 1, the pressure-sensitive adhesive layer was transferred to the surface of the polarizer to obtain a polarizing plate with a pressure-sensitive adhesive layer. The following evaluation was performed using the obtained polarizing plate with an adhesive layer. Until the evaluation, the separator was stored in a state of being laminated on the pressure-sensitive adhesive layer. The results are shown in Table 1.

1. 1. PVA Adhesive Strength The polarizing plate with an adhesive layer (protective film / adhesive / polarizer / protective layer / adhesive / separator) was cut out to a size of 25 mm × 150 mm. Next, the separator was peeled off and bonded so that the pressure-sensitive adhesive layer surface and the vapor-deposited surface of the vapor-deposited film in which indium-tin oxide was vapor-deposited on the surface of a 50 μm-thick polyethylene terephthalate (PET) film were in contact with each other. After that, the end of the PET film is peeled off by hand, and after confirming that the adhesive layer is attached to the PET film side, a tensile tester (manufactured by Shimadzu Corporation, product name: AG-1) is used. It peeled off at a rate of 300 mm / min in the 180 ° direction. The peeling of the PET film was measured within 24 hours after the pressure-sensitive adhesive was applied to the polarizing plate and the pressure-sensitive adhesive layer was formed. For each polarizing plate after the PET film was peeled off, the presence or absence of peeling between the protective layer and the polarizer was visually observed. Those in which no peeling was observed between the protective layer and the protector were marked with 〇, and those in which the polarizer and the protective layer were peeled off were marked with x.

2. Color loss at the end The above-mentioned polarizing plate with an adhesive layer (protective film / adhesive / polarizer / protective layer / adhesive / separator) was cut out into a square of 50 mm × 50 mm. Then, the separator was peeled off and bonded to non-alkali glass via an adhesive layer. Then, it was left for 72 hours under the conditions of a temperature of 65 degrees and a humidity of 90%. Then, the four corners of the sample were confirmed with an optical microscope (manufactured by Olympus, product name: MX61L), and the average value of the color loss lengths of the four corners was taken as the length of the color loss portion of the sample. Those having a length of 200 μm or less were evaluated as 〇, and those having a length of more than 200 μm were evaluated as ×.

3. 3. Red spot The above-mentioned polarizing plate with an adhesive layer (protective film / adhesive / polarizer / protective layer / adhesive / separator) was cut out into a square of 50 mm × 50 mm. Then, the separator was peeled off and bonded to non-alkali glass via an adhesive layer. An adhesive (manufactured by ThreeBond Co., Ltd., trade name: 2082C (epoxy two-component curable adhesive, adhesive containing a base)) is applied so as to cover the entire end (side surface) of the polarizing plate with an adhesive layer, and the temperature is 60 ° C. It was put into the oven for 1 hour and cured. Then, it was left for 72 hours under the conditions of a temperature of 65 degrees and a humidity of 90%. Next, the adhesive was peeled off, the presence or absence of red spots on the four corners of the polarizing plate was confirmed with an optical microscope (manufactured by Olympus, product name: MX61L), and the average value of the lengths of the red spots on the four corners was the red spot of the sample. The length of the part. Those having a length of 550 μm or less were evaluated as 〇, those having a length of more than 550 μm and 600 μm or less were evaluated as Δ, and those having a length of more than 600 μm were evaluated as ×.

The polarizing plate obtained in Examples 1 to 7 loses color from the end of the polarizer even when the protective layer (protective layer formed by applying the resin composition for protecting the polarizer) is thin. Was prevented. In addition, the adhesion between the polarizer and the protective layer was also excellent, and it was possible to protect the polarizer without peeling. Further, even when the adhesive comes into contact with the end portion, the red spot of the polarizer is prevented.

The resin composition for protecting a polarizer of the present invention has excellent adhesion to a polarizer, and even if it is thin, it is possible to provide a polarizing plate in which color loss at an end is prevented. The polarizing plate of the present invention can be widely applied to liquid crystal panels of liquid crystal televisions, liquid crystal displays, mobile phones, digital cameras, video cameras, portable game machines, car navigation systems, copiers, printers, fax machines, watches, microwave ovens, and the like. it can.

10 Polarizer 20 Protective layer 100 Polarizer

Claims (9)

(A) A resin having a weight average molecular weight of 3000 or more and having at least one epoxy group,
(B) -NH ² , -NHR, and -NRR'in the molecule (R and R'represent a methyl or ethyl group, and R and R'may be the same or different). Containing at least one substituent selected from the group consisting of, and a compound having a phenylboronic acid group.
A resin composition for protecting a polarizer containing 0.3 to 5 parts by weight of the compound (B) with respect to 100 parts by weight of the resin (A). The polarizer protective resin according to claim 1, wherein the equivalent ratio of the epoxy equivalent of the resin (A) to the amine equivalent of the compound (B) calculated from the following formula is 0.1 or more and less than 4.0. Composition:
Equivalent ratio = {number of copies of compound (B) / amine equivalent} / {number of copies of resin (A) / epoxy equivalent}. The resin composition for protecting a polarizer according to claim 1 or 2, wherein the compound (B) is a compound represented by the following formula:

(In the formula, A represents -NH ² , -NHR, and -NRR', and R ¹ is an unsubstituted or methyl or ethyl group substituted aromatic ring, aliphatic ring, or carbon. .A representative of a hydrocarbon having a straight-chain or branched having 1 to 10 .R and R'is bonded to R ¹ through a single bond or carbonyl groups are as described above). The resin composition for protecting a polarizer according to claim 3, wherein R ¹ is an unsaturated or methyl or ethyl group-substituted aromatic ring. The resin composition for protecting a polarizer according to any one of claims 1 to 4, wherein the resin (A) is a resin containing an aromatic ring in the main chain. Polarizer and
A polarizing plate comprising, on at least one surface of the polarizing element, a protective layer formed from the resin composition for protecting a polarizing element according to any one of claims 1 to 5. The polarizing plate according to claim 6, wherein the protective layer has a thickness of 0.1 μm to 8 μm. The polarizing plate according to claim 6 or 7, wherein the polarizing element has an iodine content of 2% by weight to 25% by weight. The polarizing plate according to any one of claims 6 to 8, wherein the thickness of the polarizer is 8 μm or less.

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