TW202018341A - Polarizing plate having adhesive layer - Google Patents

Abstract

In order to provide a thin polarizing plate having an adhesive layer and having extremely excellent thermal resistance, this polarizing plate having an adhesive layer has: a polarizer; a protective film arranged on one side of the polarizer; and an adhesive layer including lithium salt and arranged on the other side of the polarizer. The lithium content (LiPOL) in the polarizer is at least 0.3% by mass and the lithium content (LiPSA) in the adhesive layer is at least 0.0035% by mass.

Description

Polarizer with adhesive layer

The invention relates to a polarizing plate with an adhesive layer.

Background of the invention In a typical image display device, that is, a liquid crystal display device, due to its image forming method, polarizers (essentially, polarizers including polarizers) are arranged on both sides of the liquid crystal cell. The polarizer can be manufactured by dyeing a polyvinyl alcohol (PVA) resin film with a dichroic substance such as iodine. In recent years, the demand for thinner image display devices has greatly increased. Therefore, further thinning of the polarizer is also required. However, the thinner the polarizer is, the more likely it is that the optical characteristics tend to be reduced under high-temperature environments.

In addition, the polarizer is usually attached to other constituent members (such as a protective film) through an adhesive layer. In order to impart desired characteristics, various materials can be used for the adhesive layer-forming composition (adhesive composition). However, there is a problem that the material contained in the adhesive composition moves to the polarizer and the composition is damaged, and the desired characteristics cannot be maintained.

Prior technical literature Patent Literature Patent Literature 1: Japanese Patent Laid-Open No. 2012-247574 Patent Document 2: Japanese Patent Application Publication No. 2017-102476 Patent Document 3: Japanese Patent Laid-Open No. 2015-094906 Patent Document 4: Japanese Patent Laid-Open No. 2015-094907

Summary of the invention Problems to be solved by invention The present invention was made to solve the above-mentioned problems, and its main object is to provide a polarizing plate with an adhesive layer having very excellent heat resistance and small changes in the characteristics of the adhesive layer over time.

Means for Solving the Problem The polarizing plate with an adhesive layer of the present invention includes: a polarizer, a protective film disposed on one side of the polarizer, and an adhesive layer disposed on the other side of the polarizer, and the adhesive The agent layer contains a lithium salt. In the polarizer with an adhesive layer, the lithium content (Li _POL ) of the polarizer is 0.3% by weight or more, and the lithium content (Li _PSA ) of the adhesive layer is 0.0035% by weight or more. In one embodiment, the ratio of the lithium content of the polarizer (Li _POL ) to the lithium content of the adhesive layer (Li _PSA ) (Li _POL /Li _PSA ) is 100 or less. In one embodiment, the iodine content of the polarizer is 10% to 25% by weight. In one embodiment, the polarizer includes at least one selected from the group consisting of citric acid and citrate ions. In one embodiment, the thickness of the polarizer is 3 μm or less.

Effect of the Invention The present invention provides a polarizing plate with an adhesive layer that is thin but can achieve very excellent heat resistance. The polarizer with an adhesive layer of the present invention includes: a polarizer, a protective film disposed on one side of the polarizer, and an adhesive layer disposed on the other side of the polarizer, and the adhesive layer includes a lithium salt. By setting the lithium content (Li _POL ) of the polarizer of the polarizing plate to 0.3% by weight or more and the lithium content (Li _PSA ) of the adhesive layer to 0.0035% by weight or more, an additive with excellent heat resistance can be provided Polarizer with adhesive layer. Moreover, by containing the lithium in a specific content in the polarizer and the adhesive layer, it is possible to reduce the change over time in the characteristics (specifically, conductivity) of the adhesive layer.

Forms for carrying out the invention The embodiments of the present invention are described below, but the present invention is not limited by these embodiments.

A. Outline of polarizing plate with adhesive layer 1 is a schematic cross-sectional view of a polarizing plate with an adhesive layer according to an embodiment of the present invention. The polarizing plate 100 with an adhesive layer in the illustrated example includes a polarizer 10, a protective film 20 disposed on one side of the polarizer 10, and an adhesive layer 30 including a lithium salt disposed on the other side of the polarizer. The adhesive layer 30 is typically the outermost layer on the image display device side. In actual use, the separating member (not shown) on the adhesive layer 30 is temporarily adhered in a peelable state to protect the adhesive layer until it is actually used, and can be formed into a roll shape.

The polarizing plate with an adhesive layer of the invention is a combination of an adhesive layer and a polarizer, the adhesive layer contains a lithium salt that can function as a conductive agent, and the lithium content (Li _POL ) of the polarizer is 0.3% by weight the above. We believe that the lithium ions contained in the adhesive layer can stabilize the iodine complex more than other cations (such as potassium ions) contained in the polarizer. Therefore, while the lithium ions contained in the adhesive layer combine with the iodine complex in the polarizer to form a more stable iodine complex, lithium ions in the adhesive layer and other ions contained in the polarizer ( For example, potassium ion exchange reaction. By forming a more stable iodine complex, the reduction of iodine in the polarizer (especially poly iodide ions such as I ₃ ^- and I ₅ ^- ) can be suppressed. On the other hand, if the lithium contained in the adhesive layer moves too much to the polarizer, the lithium content (Li _POL ) of the adhesive layer itself will be reduced, and the desired characteristics (such as surface resistance value) may be damaged over time . This fact may also cause the characteristics of the polarizing plate to decrease over time in terms of results.

The polarizer used in the present invention is treated with a treatment liquid containing lithium ions as described later. Therefore, we believe that the exchange reaction between lithium ions contained in the treatment liquid and other ions (such as potassium ions) of the polarizer will occur first. This exchange reaction causes the polarizer itself to contain lithium. Therefore, it is possible to suppress excessive exchange reaction with lithium ions contained in the adhesive layer, and it is possible to reduce the temporal change of the adhesive layer characteristics (such as conductivity).

The lithium content (Li _POL ) of the polarizer is 0.3% by weight or more, preferably 0.35% by weight or more. With the lithium content (Li _POL ) within the above range, excessive exchange reaction between lithium ions contained in the adhesive layer and other ions of the polarizer (such as potassium ions) can be suppressed, resulting in excellent heat resistance and reduced adhesion The characteristics of the agent layer change over time. The lithium content (Li _POL ) of the polarizer is, for example, 10% by weight or less. The lithium content (Li _POL ) can be measured using ICP-MS, for example.

Moreover, the lithium content (Li _PSA ) of the adhesive layer is 0.0035% by weight or more, preferably 0.0040% by weight or more, and preferably 0.0050% by weight or more. When the lithium content (Li _PSA ) of the adhesive layer is within the above range, the adhesive layer can exert desired conductive properties. The lithium content (Li _PSA ) of the adhesive layer can be measured by ICP-MS.

The ratio of the lithium content (Li _POL ) of the polarizer of the polarizer with an adhesive layer of the present invention to the lithium content (Li _PSA ) of the adhesive layer (Li _POL /Li _PSA , hereinafter also referred to as "lithium content ratio") is preferably Below 100, more preferably below 85. Since the lithium content ratio (Li _POL /Li _PSA ) of the polarizing plate is in the above range, even if it is thin, it can still achieve very excellent heat resistance, and it can reduce the temporal change of the characteristics of the adhesive layer. In addition, the lithium content ratio is, for example, 30 or more, preferably 60 or more.

The polarizer, the protective film and the adhesive layer constituting the polarizing plate with an adhesive layer will be described in detail below.

B. Polarizer B-1. Composition and characteristics of polarizer The polarizer is composed of a polyvinyl alcohol (PVA) resin film. Examples of the PVA-based resin forming the PVA-based resin film include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer can be 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 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be obtained in accordance with JIS K 6726-1994. By using the PVA-based resin with the degree of saponification, a polarizer with excellent durability can be obtained. When the degree of saponification is too high, there is a risk of gelation.

The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. In addition, the average degree of polymerization can be obtained in accordance with JIS K 6726-1994.

In one embodiment, the PVA-based resin film may be a PVA-based resin layer formed on the substrate. The laminate of the base material and the PVA-based resin layer can be produced by, for example, the following method: a method of applying the coating solution containing the above-mentioned PVA-based resin to the base material, and stacking the PVA-based resin film on the base material Methods, etc.

The lithium content (Li _POL ) of the polarizer is 0.3% by weight or more, preferably 0.35% by weight or more. The polarizer will contain lithium during its manufacturing process. For example, by treating a PVA-based resin film with a treatment liquid containing lithium, the polarizer produced will contain lithium. By containing lithium in the polarizer, it is possible to suppress the temporal change in the characteristics of the adhesive layer caused by excessive movement of the lithium contained in the adhesive layer to the polarizer. The lithium content (Li _POL ) of the polarizer is, for example, 10% by weight or less.

The iodine content of the polarizer can be appropriately set so as to have both sufficient polarizing performance and optimal monomer transmittance. The iodine content is preferably 10% by weight to 25% by weight, and preferably 15% by weight to 25% by weight. According to the polarizing plate with an adhesive layer of the present invention, even if it is a polarizing plate including the polarizer with an extremely high iodine content, by using a specific adhesive layer described later, it is possible to achieve a very excellent heat resistance which has been difficult to achieve in the past. The "iodine content" in this specification means the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, the iodine iodide ion (I ^-) is present in the form of a polarizer and the like, and the iodine content of the present specification is meant that molecular iodine (I _2), polyiodide ions _{^{(I 3 - -, I 5}} ) Contains the amount of iodine in all these forms. The iodine content can be calculated using a calibration curve method such as fluorescent X-ray analysis. In addition, the polyiodide ion exists in the state where the PVA-iodine complex is formed in the polarizer. By forming the complex, the absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, the complexes (PVA · I ₃ ^-) PVA and tri-iodide ions having a light absorption peak around 470nm; PVA complexes with five iodide ions (PVA · I ₅ ^-) having a light absorption near 600nm peak. As a result, the polyiodide ion can absorb light in a wide range of visible light according to its morphology. On the other hand, an iodide ion (I ^-) having a light absorption peak around 230nm, which absorption of visible light associated with insubstantial. Therefore, the polyiodide ion existing in the complex state with PVA is mainly related to the absorption performance of the polarizer.

The thickness of the polarizer is preferably 5 μm or less in one embodiment, 3 μm or less in another embodiment, and 2 μm or less in another embodiment. In addition, the thickness of the polarizer is preferably 0.5 μm or more in one embodiment, 0.6 μm or more in another embodiment, and 0.8 μm or more in another embodiment, and is suitable in another embodiment. It is 1 μm or more, and in another embodiment is preferably 2 μm or more. According to the embodiment of the present invention, even if it is a thin polarizer, the desired single transmittance and degree of polarization can still be achieved.

The single transmittance (Ts) of the polarizer is preferably 30.0%~43.0%, more preferably 35.0%~41.0%. The polarization degree of the polarizer is preferably 99.9% or more, preferably 99.95% or more, and more preferably 99.98% or more. By setting the transmittance of the monomer lower and the degree of polarization higher, the contrast can be improved and the black display can be displayed more black. Therefore, an image display device with excellent image quality can be realized. In addition, the unit transmittance is the value measured by a spectrophotometer with an integrating sphere. The unit transmittance is the Y value measured with a 2 degree field of view (C light source) of JIS Z 8701 and corrected by the optical performance. : V7100).

For the polarizer with an adhesive layer of the present invention, even if the iodine content of the polarizer is extremely high as described above, the change of the optical characteristics under a high temperature environment can still be significantly suppressed. Moreover, the hue change under high temperature environment is also suppressed. As described above, the excellent effect can be achieved by using an adhesive layer containing a lithium salt that functions as a conductive agent in combination with the polarizer as described above.

The polarizer should preferably contain citric acid and/or citrate ions. The polarizer preferably contains citrate ions. This is due to the treatment with the treatment liquid (Item B-2-2) in the manufacturing method (Item B) described later. The polarizer contains the compound (in other words, the polarizer is manufactured by the manufacturing method including the treatment described in item B-2-2), and the discoloration of the polarizer in a high-temperature environment can be significantly suppressed. I think this is because the protons in the PVA-based resin can be suppressed by the buffering effect of the treatment liquid in a predetermined pH region, and as a result, the generation of multiple double bonds (polyalkylation) in the PVA-based resin under high-temperature environment can be suppressed, thereby It can suppress discoloration. In addition, by suppressing polyalkylation, cracks and warpage can be suppressed. Regarding this part, I think the following: once the double bond is formed in the PVA resin molecule due to polyalkylation, the distance between the monomer units near the double bond will be reduced. As a result, the PVA-based resin molecule (chain) partially shrinks, which may cause warpage or cracks. Therefore, by inhibiting polyalkylation, the formation of the double bond can be suppressed, and as a result, warpage and cracks can be suppressed.

B-2. Manufacturing method of polarized parts B-2-1. Outline of manufacturing method The polarizer can be produced by a manufacturing method including at least stretching and dyeing a PVA-based resin film. Representatively, the manufacturing method includes a step of preparing a PVA-based resin film, an extension step, a swelling step, a dyeing step, a cross-linking step, a washing step, and a drying step. Each step of supplying the PVA-based resin film can be performed in an arbitrary and appropriate order and timing. Therefore, each step may be performed in the above order, or may be performed in an order different from the above. One step can also be carried out multiple times according to needs. In addition, the steps other than the above (for example, the insolubilization step) can be performed at an arbitrary and appropriate timing, and steps other than the dyeing step can be omitted. In addition, if the PVA-based resin film is a PVA-based resin layer formed on the substrate, the laminate of the substrate and the PVA-based resin layer may be used in the above step.

As described above, the polarizing member included in the polarizing plate of the present invention contains lithium. Therefore, the manufacturing method of the polarizer preferably includes a processing step using a processing liquid containing lithium. The treatment liquid containing lithium is specifically a treatment liquid obtained by containing lithium iodide and/or lithium hydroxide in any suitable solvent other than water or water. The polarizer will contain lithium through a processing step performed using a processing liquid containing lithium. The treatment step using the treatment liquid can be performed at any appropriate time point after the above dyeing.

Each step is described below, but as described above, each step can be performed in an arbitrary and appropriate order, and is not limited by the described order.

B-2-2. Treatment with treatment liquid As described above, the manufacturing method of the polarizer used in the present invention includes: after dyeing, the PVA-based resin film is treated with a treatment solution containing lithium. The treatment using the treatment liquid may be performed at any appropriate timing as long as it is after dyeing. The treatment using the treatment liquid may be performed before the crosslinking step or may be performed after the crosslinking step; may be performed before the washing step or may be performed after the washing step. When the stretching step is performed after the dyeing step, the treatment with the treatment liquid may be performed before the stretching step or may be performed after the stretching step. When the swelling step is performed after the dyeing step, the treatment with the treatment liquid may be performed before the swelling step or may be performed after the swelling step. When the insolubilization step is performed after the dyeing step, the treatment with the treatment liquid may be performed before the insolubilization step or may be performed after the insolubilization step. Representatively, the treatment with the treatment liquid may be performed after the washing step and before the drying step, or may be performed between the first drying step and the second drying step when the drying step is performed in two stages.

The pH of the treatment liquid is preferably 2.5 to 6.0, and preferably 3.0 to 5.7, more preferably 3.5 to 4.8. In addition, the treatment liquid should preferably have a buffering effect in this pH range (that is, a pH range of 2.5 to 6.0). The treatment liquid may be, for example, an aqueous solution containing sodium bicarbonate, potassium bicarbonate, disodium hydrogen phosphate, potassium carbonate, sodium carbonate, and citric acid. Compared with treatment liquids containing, for example, acetic acid-based compounds, the treatment liquids containing these compounds have a buffering effect in a high pH region, and as a result, can have a more excellent discoloration prevention effect under high-temperature environments. The aqueous solution may contain these compounds alone, or two or more kinds. The treatment liquid is preferably an aqueous solution of citric acid. Therefore, the polarizer used in the present invention will contain citric acid and/or citrate ions. The concentration of the aqueous solution can be appropriately set according to the desired pH and buffering effect. For example, the concentration of the citric acid aqueous solution may be preferably 0.10% to 3.0% by weight. And the aqueous solution preferably contains a pH adjusting agent. Examples of the pH adjuster include lithium hydroxide. By using a treatment liquid containing lithium hydroxide as a pH adjusting agent, the polarizer produced will contain lithium.

The treatment with the treatment liquid typically includes the treatment of bringing the treatment liquid into contact with the PVA-based resin film. The contact method may be any appropriate method. Specific examples include immersing the PVA-based resin film in the treatment liquid, or coating or spraying the PVA-based resin film. And the coating or spraying treatment liquid is suitable. Since the problem of changes in the absorption spectrum of the polarizer before and after the immersion can be prevented during the immersion, the PVA polyalkylation can be further well prevented. As for the method (means) of applying or spraying the treatment liquid to the PVA-based resin film, any appropriate method (means) can be adopted. Examples of the coating mechanism include a reverse coater, a gravure coater (direct, reverse, or indirect), a bar reverse coater, a roll coater, a die coater, a bar coater, and a bar coater. The spraying mechanism may be, for example, any appropriate spraying device (for example, a pressure nozzle type or a rotating disc type).

B-2-3. Extension steps In the stretching step, the PVA-based resin film is uniaxially stretched or biaxially stretched 3 to 7 times on behalf of the upper system. The extending direction may be the long-side direction (MD direction) of the film, the width direction (TD direction) of the film, or both the long-side direction and the width direction. The stretching method may be dry stretching, wet stretching, or a combination of these. In addition, the PVA-based resin film may be stretched during the cross-linking step, swelling step, dyeing step, and the like. In addition, the extending direction may correspond to the direction of the absorption axis of the obtained polarizer.

B-2-4. Swelling steps The swelling step is usually carried out before the dyeing step. The swelling step can be performed, for example, by immersing the PVA-based resin film in a swelling bath. The swelling bath can usually use distilled water, pure water and other water. The swelling bath may also contain any suitable other ingredients than water. Other components include solvents such as alcohols, additives such as surfactants, and iodides. Examples of the 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. Potassium iodide should be used. The temperature of the swelling bath is, for example, 20°C to 45°C. In addition, the immersion time is, for example, 10 seconds to 300 seconds.

B-2-5. Dyeing procedure The dyeing step is a step of dyeing the PVA-based resin film with a dichroic substance. It should be carried out by making it absorb dichroic substances. Examples of the adsorption method include a method of immersing the PVA-based resin film in a dyeing solution containing a dichroic substance, a method of applying the dyeing solution to the PVA-based resin film, and spraying the dyeing solution to the PVA-based resin Resin film method, etc. It is desirable to immerse the PVA-based resin film in the dyeing solution. Because it can absorb dichroic substances well.

Examples of the dichroic substance include iodine and dichroic dyes. And iodine is appropriate. When iodine is used as the dichroic substance, an aqueous iodine solution is preferably used as the dyeing solution. The iodine content of the iodine aqueous solution is preferably 0.04 to 5.0 parts by weight relative to 100 parts by weight of water. In order to improve the solubility of iodine in water, it is appropriate to mix iodide in the iodine aqueous solution. Potassium iodide should be used as iodide. The content of iodide is preferably 0.3 to 15 parts by weight relative to 100 parts by weight of water.

The liquid temperature of the dyeing liquid during dyeing can be set to an arbitrary and appropriate value, for example, 20°C to 50°C. When the PVA-based resin film is immersed in the dyeing liquid, the immersion time is, for example, 5 seconds to 5 minutes.

B-2-6. Crosslinking procedure In the cross-linking step, a boron compound is usually used as a cross-linking agent. Examples of boron compounds include boric acid and borax. And boric acid is suitable. In the cross-linking step, the boron compound is usually used in the form of an aqueous solution.

When using a boric acid aqueous solution, the boric acid concentration of the boric acid aqueous solution is, for example, 1% by weight to 15% by weight, preferably 1% by weight to 10% by weight. The aqueous solution of boric acid can also contain iodides such as potassium iodide, zinc compounds such as zinc sulfate and zinc chloride.

The cross-linking step can be carried out 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 of a boron-containing compound to the PVA-based resin film, or spraying an aqueous solution of a boron-containing compound onto the PVA-based resin film Methods. It is suitable to be immersed in the aqueous solution containing boron compound.

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

B-2-7. Washing steps The washing step means that the upper part is carried out after the cross-linking step. The washing step is representatively performed by immersing the PVA-based resin film in the washing solution. A representative example of the cleaning solution can be pure water. Potassium iodide can also be added in pure water.

The temperature of the cleaning solution is, for example, 5°C to 50°C. The dipping time is, for example, 1 second to 300 seconds.

B-2-8. Drying step The drying step can be performed by any appropriate method. Examples of drying methods include natural drying, air drying, reduced-pressure drying, and heating drying. And it should be heated and dried. When heating and drying, the heating temperature is, for example, 30°C to 100°C. In addition, the drying time is, for example, 20 seconds to 10 minutes.

C. Protective film The protective film (and, if present, another protective film) uses any suitable resin film. Examples of resin film forming materials include (meth)acrylic resins, cellulose resins such as diacetyl cellulose and triethyl cellulose, cycloolefin resins such as norbornene resins, and olefin resins such as polypropylene. , Ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins and copolymer resins thereof. In addition, "(meth)acrylic resin" means acrylic resin and/or methacrylic resin.

In one embodiment, the (meth)acrylic resin is a (meth)acrylic resin having a glutarimide structure. (Meth)acrylic resins having a glutarimide structure (hereinafter also referred to as glutarimide resins) are described, for example, in the following documents: Japanese Patent Laid-Open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560 Gazette, Japanese Unexamined Patent Publication No. 2006-328329, Japanese Unexamined Patent Publication No. 2006-328334, Japanese Unexamined Patent Publication No. 2006-337491, Japanese Unexamined Patent Publication No. 2006-337492, Japanese Unexamined Patent Publication No. 2006-337493, Japanese Unexamined Patent Publication 2006-337569, JP 2007-009182, JP 2009-161744, and JP 2010-284840. These descriptions are cited as references in this specification.

When using a laminate of a substrate and a PVA-based resin layer to manufacture a polarizer, it can be used directly as a protective film without peeling off the substrate. Furthermore, after the base material is peeled off, the polarizer can be attached to the protective film.

It is also possible to use any appropriate optical functional film as the protective film (and, another protective film in the presence of it) according to the purpose. Examples of optically functional films include phase difference films and reflective polarizers (brightness enhancing films).

D. Adhesive layer The polarizing plate with an adhesive layer according to an embodiment of the present invention is representatively as described above, a protective film is disposed on one side of the polarizer, and an adhesive layer is disposed on the other side of the polarizer. That is, in this embodiment, the protective film is not disposed on the other side of the polarizer, and the adhesive layer is directly disposed on the polarizer.

As described above, the lithium content (Li _PSA ) of the adhesive layer is 0.0035 wt% or more, preferably 0.0040 wt% or more, and preferably 0.0050 wt% or more. When the lithium content (Li _PSA ) of the adhesive layer is within the above range, the adhesive layer can exert desired conductive properties.

D-1. Adhesive composition The adhesive composition constituting the adhesive layer includes a base polymer and a lithium salt.

D-1-1. Base polymer Representative examples of the base polymer include (meth)acrylic polymers ((meth)acrylic resins). The (meth)acrylic polymer represents a monomer unit derived from an alkyl (meth)acrylate as a main component. (Meth)acrylic acid alkyl esters are (meth)acrylic acid alkyl esters. Examples of the alkyl group forming the alkyl ester include straight-chain or branched-chain alkyl groups having 1 to 18 carbon atoms. Specific examples of alkyl include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl , Decyl, isodecyl, dodecyl, isomyristyl, lauryl, thirteen, fifteen, sixteen, seventeen, and eighteen. These can be used alone or in combination. The average carbon number of the alkyl group contained in the alkyl (meth)acrylate is preferably 3-9.

The base polymer may also contain monomer units derived from any appropriate copolymerization components depending on the purpose. Examples of the copolymerization component include hydroxyl group-containing monomers, carboxyl group-containing monomers, acid anhydride group-containing monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, (N-substituted) amide-based monomers, (Meth)acrylic acid alkylaminoalkyl-based monomer, (meth)acrylic acid alkoxyalkyl-based monomer, succinimide-based monomer, maleimide-based monomer, Iconamide Amine monomer, vinyl monomer, cyano (meth)acrylate monomer, epoxy-containing (meth)acrylic monomer, diol (meth)acrylate monomer, silane Series monomer, multifunctional monomer. By adjusting the type, quantity, combination, and copolymerization ratio (weight ratio) of the copolymerization components, a base polymer (finally an adhesive layer) having desired characteristics can be prepared. Relative to 100% by weight of the total monomer component, the ratio of the copolymerization component in the total monomer component is preferably 0% by weight to 20% by weight, preferably 0.1% by weight to 15% by weight, more preferably 0.1% by weight to 10% by weight .

The weight average molecular weight of the base polymer is typically 500,000 to 3 million, preferably 700,000 to 2.7 million, and more preferably 800,000 to 2.5 million. If the weight average molecular weight is too small, heat resistance may be insufficient. If the weight average molecular weight is too large, the handleability may deteriorate. In addition, for coating, viscosity adjustment requires a large amount of dilution solvent, which may increase the cost. In addition, the weight average molecular weight refers to a value measured by GPC (gel permeation chromatography; Gel Permeation Chromatography) and calculated in terms of polystyrene.

D-1-2. Lithium salt The above-mentioned adhesive layer contains a lithium salt (lithium-anion salt). As mentioned above, the lithium salt can function as a conductive agent. Constituting the anion of the ionic portion of the can for example such as ^{Cl -, Br -, I -} , AlCl 4 -, Al 2 Cl 7 -, BF 4 -, PF 6 -, ClO 4 -, NO 3 -, CH 3 COO -, CF 3 _{^{COO -, CH 3 SO 3 -}} , CF 3 SO 3 -, (CF 3 SO 2) 3 C -, AsF 6 -, SbF 6 -, NbF 6 -, TaF 6 -, (CN) 2 N -, C 4 _{^{F 9 SO 3 -, C 3}} F 7 COO -, (CF 3 SO 2) (CF 3 CO) N -, - O 3 S (CF 2) 3 SO 3 -, and the following formula (1) - ( 4) _{anion: (1) :( C n F} 2n +1 SO 2) 2 N - (n is an integer of 1 to _{10), (2): CF 2} (C m F 2m SO 2) 2 N - ( m is an integer of 1 to ^{10), (3): - O} 3 S (CF 2) l SO 3 - (l is an integer of 1 to _{10), (4) :( C p} F 2p +1 SO 2) N - (C _q F _{2q +1} SO ₂ ), (p, q are integers from 1 to 10). Fluoride-containing anions are preferred, and fluoride-containing imide anions are more preferred.

Examples of fluorine-containing amide imide anions include amide imide anions having a perfluoroalkyl group. Specific examples may be cited as described above _{(CF 3 SO 2) (CF} 3 CO) N -, and the general formula (1), (2) and (4) _{anion: (1) :( C n F} 2n + 1 SO _{2) 2} N ^- (n is an integer of 1 to _{10), (2): CF 2} (C m F 2m SO 2) 2 N - (m is an integer of 1 to _{10), (4) :( C p} F ^{_{2p + 1 SO 2) N -}} (C q F 2q + 1 SO 2), (p, q is an integer of 1 to 10). And Yi is _{(CF 3 SO 2) 2 N} -, (C 2 F 5 SO 2) 2 N - like the formula (1) (perfluoroalkyl sulfonic acyl) (PEI), but also to (CF ₃ SO ₂ ) ₂ N ^- preferably bis(trifluoromethanesulfonyl) amide imide. Therefore, the preferred lithium salt that can be used in the embodiments of the present invention is lithium bis(trifluoromethanesulfonyl)amideimide.

The content of the lithium salt in the adhesive composition (resulting in the adhesive layer) is preferably 0.01 to 5 parts by weight, preferably 0.5 to 3 parts by weight, 0.7 parts by weight relative to 100 parts by weight of the base polymer Parts ~ 1.5 parts by weight is better. As long as the content of the lithium salt is within the range, the heat resistance of a thin polarizer with a high iodine content (the result is a polarizing plate containing the polarizer) can be significantly improved.

D-1-3. Organic cationic salt The adhesive composition may also contain organic cationic salts as needed. By using lithium salt in combination with organic cation salt, the surface resistance value can be lowered without causing the lithium salt to overflow.

The organic cation salt is specifically an organic cation-anion salt. The cation constituting the cation portion of the organic cation salt can be exemplified by organic onium in which an onium ion is formed by substitution with an organic group. Examples of the onium in the organic onium include nitrogen-containing onium, sulfur-containing onium, and phosphorus-containing onium. Nitrogen-containing and sulfur-containing onium are preferred. Examples of the nitrogen-containing onium include ammonium cations, piperidinium cations, pyrrolidinium cations, pyridinium cations, cations having a dihydropyrrole skeleton, cations having a pyrrole skeleton, imidazolium cations, tetrahydropyrimidinium cations, dihydropyrimidine Onium cation, pyrazolium cation, pyrazolinium cation. Ammonium cations, piperidinium cations, and pyrrolidinium cations are preferred, and pyrrolidinium cations are more preferred. The sulfur-containing onium may, for example, be a cation. Examples of the phosphonium-containing phosphonium include phosphonium cations. Examples of the organic group in the organic onium include alkyl groups, alkoxy groups, and alkenyl groups. Specific examples of preferred organic oniums include tetraalkylammonium cations, alkylpiperidinium cations, and alkylpyrrolidinium cations. And ethyl methyl pyrrolidinium cation is better. The anions constituting the anion portion of the organic cation salt are as described for the anions constituting the anion portion of the lithium salt. Therefore, a preferred organic cationic salt that can be used in the embodiment of the present invention is a pyrrolidinium salt, and more preferably ethylmethylpyrrolidinium bis(trifluoromethanesulfonyl)amideimide.

For 100 parts by weight of the base polymer, the content of the organic cationic salt in the adhesive composition (adhesive layer in the result) is preferably 0.1 to 10 parts by weight, preferably 0.3 to 3 parts by weight, 0.5 parts by weight Parts ~ 1.5 parts by weight is better. If the content of the organic cationic salt is within the above range, the combined effect of the organic cationic salt and the lithium salt is remarkable.

D-1-4. Silane coupling agent The adhesive composition may further contain a silane coupling agent. The durability can be improved by using silane coupling agent. The silane coupling agent may use any functional group that is suitable. Specific examples of the functional group include a vinyl group, an epoxy group, an amine group, a mercapto group, a (meth)acryl oxy group, an acetyl acetyl group, an isocyanate group, a styryl group, and a polysulfide group. Specific examples include vinyl-containing silane coupling agents such as vinyl triethoxy silane, vinyl tripropoxy silane, vinyl triisopropoxy silane, and vinyl tributoxy silane; γ-ring Oxypropyloxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyl diethoxysilane, 2-(3,4- Epoxy cyclohexyl) ethyl trimethoxy silane and other epoxy-containing silane coupling agent; γ-aminopropyl trimethoxy silane, N-β-(aminoethyl)-γ-aminopropyl methyl dimethyl Oxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, γ-triethoxysilyl-N-(1,3-dimethylbutylene)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane and other amine-containing silane coupling agents; γ-mercaptopropylmethyldimethoxysilane and other thiol-containing silane coupling agents; p-styrene trimethoxysilane Silane coupling agent containing styrene group; silane coupling with (meth)acryloyl group containing γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, etc. Agents; 3-isocyanate propyl triethoxysilane and other silane coupling agents containing isocyanate groups; bis (triethoxysilyl propyl) tetrasulfide and other polysulfide groups containing silane coupling agents.

D-1-5. Other The adhesive composition (as a result, the adhesive layer) may further contain arbitrary and appropriate additives. Specific examples of additives include crosslinking agents, silane coupling agents, heavy industry lifters, antioxidants, antistatic agents, crosslinking retarders, emulsifiers, colorants, pigments and other powders, dyes, surfactants, and plasticizers , Tackifier, surface lubricant, leveling agent, softener, anti-aging agent, light stabilizer, ultraviolet absorber, polymerization inhibitor, inorganic filler, organic filler, metal powder, granular, foil, etc. . The quantity, type, amount and combination of additives can be set appropriately according to the purpose.

Any appropriate method can be used for the method of forming the adhesive layer. Representative examples of the forming method include the following method: applying the above-mentioned adhesive composition to a separation member subjected to peeling treatment, etc., and drying and removing the polymerization solvent, etc. to form an adhesive layer, and transferring it to the polarizer Method; or, a method of applying the adhesive composition to the polarizer, drying and removing the polymerization solvent, etc. to form an adhesive layer on the polarizer. In addition, when applying the adhesive, one or more solvents other than the polymerization solvent may be additionally added according to needs.

The details of the adhesive composition are described in Japanese Patent Laid-Open No. 2014-48497, for example. In this specification, the description of this publication is used as a reference.

D-2. Composition and characteristics of adhesive layer The thickness of the adhesive layer is preferably 10 μm to 200 μm, more preferably 10 μm to 100 μm. As long as the thickness of the adhesive layer is within the above range, the heat resistance improvement effect brought by the lithium salt is remarkable.

The surface resistance value (initial) of the adhesive layer is preferably 1.0×10 ¹¹ Ω·□ or less, and preferably 8.0×10 ¹⁰ Ω·□ or less, more preferably 5.0×10 ¹⁰ Ω·□ or less. The surface resistance value of the adhesive layer may be, for example, 5.0×10 ⁹ Ω·□ or more. As long as the surface resistance of the adhesive layer is within the above range, it has the advantage of easily suppressing the unevenness of static electricity. Examples

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. The measuring method of each characteristic is as follows. In addition, as long as there is no special note, "parts" and "%" in the examples are based on weight.

(1) Iodine content For the polarizer of the polarizing plate with an adhesive layer obtained in Examples and Comparative Examples, the fluorescence was measured using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, trade name "ZSX-PRIMUS II", measuring diameter: ψ20 mm) Light X-ray intensity (kcps). On the other hand, the thickness (μm) of the polarizer was measured using a spectroscopic film thickness meter (manufactured by Otsuka Electronics Co., Ltd., trade name "MCPD-3000"). From the obtained fluorescent X-ray intensity and thickness, the iodine content (wt%) was determined by the following formula. (Iodine content)=20.5×(fluorescence X-ray intensity)/(polarizer thickness) In addition, the coefficient when calculating the iodine content will vary depending on the measuring device, and this coefficient can be obtained using an appropriate calibration curve. (2) Lithium content The polarizer with an adhesive layer prepared in the examples and comparative examples was peeled off, and 20 mg was taken as a sample and weighed in a Teflon (registered trademark) container. Next, the acid is added and capped tightly, and then a whole batch of microwave irradiation system (manufactured by CEM, product name: MARS5) is used to irradiate the microwave, and pressurized acid hydrolysis is performed at a maximum of 220°C. After the acid hydrolysis, ultrapure water was added and the volume was adjusted to 25 mL, then diluted appropriately, and then ELAN DRC II (manufactured by PerkinElmer) was used to perform quantitative analysis of Li by ICP-MS. In addition, the measurement conditions are as follows. Nebulizer: Teflon (registered trademark) coaxial nebulizer m/z: Li(7) DRC mode: OFF In addition, the material after the adhesive composition has been removed from the polarizing plate with the adhesive layer is prepared and measured in the same manner as above, and the lithium content in the polarizer is measured. The lithium content of the polarizer is subtracted from the lithium content of the polarizer with an adhesive layer, thereby calculating the lithium content of the adhesive layer (the following formula). (Lithium content of adhesive layer) = (Lithium content of polarizer with adhesive layer)-(Lithium content of polarizer) (3) Surface resistance The polarizing plate with an adhesive layer prepared in the examples and comparative examples was placed in an environment of 23° C. and 55% RH for more than 30 days. After that, the separation film was peeled off, and the surface resistance value (Ω·□) on the surface of the adhesive was measured using a resistivity meter (manufactured by Mitsubishi Chemical Analytech, product name: Hiresta-UP MCP-HT450). (4) Heating reliability After peeling off the separator from the polarizing plate with an adhesive layer prepared in each of Examples and Comparative Examples, it was attached to a non-alkali glass with a thickness of 1.3 mm. After that, after putting it in an oven at 105°C for 60 hours, the heating reliability was evaluated. Visually compare the polarizing plate before and after the input, and check whether the polarizing plate has become red due to polyalkylation.

[Example 1] (Base polymer for preparing adhesive composition) A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was fed into a 4-neck flask equipped with a stirring blade, a thermometer, a nitrogen introduction tube, and a cooler. And with respect to 100 parts of the above monomer mixture (solid content), 0.12 parts of 2,2´-azobisisobutyronitrile as a polymerization initiator was fed together with ethyl acetate, and nitrogen was introduced while stirring slowly After the substitution, the temperature of the liquid in the flask was maintained at about 60°C, and a polymerization reaction was carried out for 7 hours. Then, ethyl acetate was added to the prepared reaction liquid to adjust the solid content concentration to 30%. In the above manner, a solution of acrylic polymer (A-1) (base polymer) having a weight average molecular weight of 1.4 million was prepared.

(Preparation of adhesive composition) Relative to 100 parts of the solid content of the acrylic polymer (A-1) solution, lithium bis(trifluoromethanesulfonyl)amideimide (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) 1.0 is mixed as a conductive agent Parts and ethyl methyl pyrrolidinium bis(trifluoromethanesulfonyl) amide imide (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.7 parts, trimethylolpropane diisocyanate sucralate as a crosslinking agent (Mitsui Chemical Company Manufacture: TAKENATE D110N) 0.095 parts and 0.3 parts of dibenzoyl peroxide, 0.2 parts of organic silane (manufactured by Kken Chemical Co., Ltd.: A100) as a silane coupling agent and silane coupling agent (manufactured by Shin-Etsu Chemical Industry Co., Ltd.: X41-1810) 0.2 parts, heavy industry lifter (manufactured by KANEKA CORPORATION, Silyl SAT10) 0.03 parts, and antioxidant (manufactured by BASF, Irganox 1010) 0.3 parts, to prepare an adhesive composition (solution).

(Making polarizer) As the thermoplastic resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) with a water absorption of 0.75% and a Tg of 75°C is used. Corona treatment was applied on one side of the substrate, and the corona treatment surface was coated with polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetonitrile at a ratio of 9:1 at 25°C. Acetoyl modified PVA (degree of polymerization 1200, degree of modification of acetylacetal 4.6%, saponification degree of 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z200") and dried. A PVA-based resin layer with a thickness of 11 μm was formed to produce a laminate. Using a tenter stretching machine, the obtained laminate was stretched in air at a temperature of 140° C. in the direction orthogonal to the longitudinal direction of the laminate by 4.5 times (stretching treatment). Next, the laminate was immersed in a dyeing bath (aqueous solution with an iodine concentration of 1.4% by weight and a potassium iodide concentration of 9.8% by weight) at a liquid temperature of 25° C. for 12 seconds to perform dyeing (dyeing treatment). Next, the laminate was immersed in a washing bath (pure water) at a liquid temperature of 25°C for 6 seconds (first washing treatment). Then, it was immersed in a cross-linking bath (aqueous solution with a boron concentration of 1% by weight and a potassium iodide concentration of 1% by weight) at a liquid temperature of 60°C for 16 seconds (cross-linking treatment). Next, the laminate was immersed in a washing bath (aqueous solution of potassium iodide concentration of 1% by weight) at a liquid temperature of 25°C for 3 seconds (second washing treatment). Then, the laminate was dried in an oven at 60°C for 21 seconds (drying treatment). Next, using a bar coater, the treatment liquid (0.15 parts by weight of citric acid and 0.04 parts by weight of lithium hydroxide was added to 50 parts by weight of water, and the pH was measured after stirring for 10 minutes, followed by the addition of 50 parts by weight of ethanol to prepare , PH=4.2) applied to the PVA-based resin layer of the laminate, and applied so that the film thickness in the wet state is 8 μm. Finally, the laminate was dried in an oven at 60°C for 60 seconds to obtain a laminate (polarizer) having a PVA-based resin layer (polarizer) with a thickness of 1.2 μm. The polarizer of the obtained polarizer had an iodine content of 20.9% by weight and a monomer transmittance of 40.3%.

(Making polarizer with adhesive layer) Apply the above adhesive composition uniformly to the surface of the polyethylene terephthalate film (separator) treated by the silicone release agent with a spray coater, and circulate with air at 155℃ In a constant temperature oven for 2 minutes, an adhesive layer with a thickness of 20 μm was formed on the surface of the separator. Then, the adhesive layer is transferred to the surface of the polarizer of the polarizing plate to prepare a polarizing plate with an adhesive layer.

The prepared polarizing plate with an adhesive layer was subjected to the above evaluations (3) to (4). The results are listed in Table 1.

[Example 2] A polarizing plate with an adhesive layer was prepared in the same manner as in Example 1 except that the treatment liquid was applied to a film thickness of 5 μm in a wet state. The obtained polarizing plate with an adhesive layer was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

(Comparative example 1) A polarizing plate with an adhesive layer was prepared in the same manner as in Example 1, except that the treatment liquid was not coated. The obtained polarizing plate with an adhesive layer was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

(Comparative example 2) The treatment liquid was treated with sodium hydroxide instead of lithium hydroxide and the pH was adjusted, and the treatment liquid was applied to a film thickness of 7 μm in a wet state, except that it was prepared in the same manner as in Example 1. Polarizing plate with adhesive layer. The obtained polarizing plate with an adhesive layer was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

[Table 1]

It is clear from Table 1 that the polarizing plate with an adhesive layer according to an embodiment of the present invention is one in which the increase in the surface resistance value of the adhesive layer is suppressed and the reliability of humidification is also excellent.

Industrial availability The polarizing plate with adhesive layer of the present invention can be widely used in LCD TVs, LCD monitors, mobile phones, digital cameras, video cameras, handheld game consoles, car navigation, photocopiers, printers, fax machines, clocks, microwave ovens, etc. On the LCD panel.

10: polarizer 20: Protective film 30: Adhesive layer 100: polarized light with adhesive layer

FIG. 1 is a schematic cross-sectional view for explaining a polarizing plate with an adhesive layer according to an embodiment of the present invention.

10: polarizer

20: Protective film

30: Adhesive layer

100: polarizer with adhesive layer

Claims (5)

A polarizer with an adhesive layer, comprising: a polarizer, a protective film disposed on one side of the polarizer, and an adhesive layer disposed on the other side of the polarizer, and the adhesive layer includes a lithium salt; The lithium content (Li _POL ) of the polarizer is 0.3% by weight or more, and the lithium content (Li _PSA ) of the adhesive layer is 0.0035% by weight or more. The polarizing plate with an adhesive layer according to claim 1, wherein the ratio of the lithium content (Li _POL ) of the polarizer to the lithium content (Li _PSA ) of the adhesive layer (Li _POL /Li _PSA ) is 100 or less. The polarizing plate with an adhesive layer according to claim 1 or 2, wherein the iodine content of the polarizer is 10% by weight to 25% by weight. The polarizing plate with an adhesive layer according to any one of claims 1 to 3, wherein the polarizer includes at least one selected from the group consisting of citric acid and citrate ions. The polarizing plate with an adhesive layer according to any one of claims 1 to 4, wherein the thickness of the polarizer is 3 μm or less.

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