TW201506102A - Adhesive composition and composite polarization plate using the same - Google Patents

Abstract

Disclosed are an adhesive composition and a composite polarizing plate using the same. The adhesive composition includes: a water-soluble resin that includes a polyvinylalcohol resin having a benzene ring at a side chain; and a cross-linking agent, thereby when the composite polarizing plate is fabricated by combining the polarizer with the patterned retardation layer using the adhesive composition of the present invention, adhesion between the polarizer and the patterned retardation layer is remarkably improved, and the adhesive composition has excellent thermal resistance and moist heat resistance, and is easily bound to a display panel when it is applicable to an image display device.

Description

Adhesive composition and composite polarizing plate using the same

The present invention relates to a binder composition and a composite polarizing plate using the same.

In general, display devices, such as liquid crystal display devices for obtaining stereoscopic images, typically include a patterned retardation layer. Such a patterned retardation layer has a technical configuration in which optical axes of separate pattern regions are formed from respective different directions to transmit separate images to the right and left eyes of a viewer wearing polarized glasses, thereby embodying three dimensions. Image (ie stereo) image.

The patterned retardation layer is usually prepared by forming an alignment layer on a glass substrate and applying a liquid crystal to the alignment film to obtain an alignment effect. The photosensitive liquid crystal material is crosslinked on the alignment layer and then crosslinked by optical radiation such as UV light to form a polymer liquid crystal layer. The polymer liquid crystal layer thus formed can function as a retardation pattern depending on the alignment direction of the liquid crystal accompanying the surface alignment of the alignment layer.

The patterned retardation layer is usually adhered to one side of the polarizing plate by a binder or a binder, and in recent years, the patterned retardation layer is adhered to one side of the polyvinyl alcohol polarizer to reduce the thickness and weight of the display device.

When the adhesion between such a patterned retardation layer and a polarizing plate or polarizer is reduced, deformation may occur during control or use during manufacturing. In addition, when exposed to a hot and humid environment for a long time, there may be peeling or pushing out. In addition, a typical polyethylene polarizer is reduced in the direction of extension, so that the position of the retardation film affects different delays, which in turn causes deterioration of the 3D stereoscopic effect.

For this reason, it is still necessary to develop improved adhesives with different properties (such as resistance to hot water or heat and humidity) and excellent adhesion.

A film patterning retarder preparation method, a film patterning retarder, and a polarizing plate and an image display device including the polarizing plate are disclosed in Korean Patent Publication No. 2013-0028881.

Accordingly, it is an object of the present invention to provide a binder composition which, when used to fabricate a composite polarizing plate by combining a polarizer and a patterned retardation layer, can significantly improve the relationship between the polarizer and the patterned retardation layer. Bonding.

Another object of the present invention is to provide a composite polarizing plate manufactured by bonding the adhesive composition.

The above objects of the present invention are achieved by the following features:

(1) A binder composition comprising: a water-soluble resin comprising a polyvinyl alcohol resin having a benzene ring in a side chain; and a crosslinking agent.

(2) The composition according to the above item (1), wherein the polyvinyl alcohol resin has a hydroxyl group which is modified to a substituent containing a benzene ring.

(3) The composition according to the above item (2), wherein the substituent is a benzamidineoxy group which is or is not substituted with a halogen element, a hydroxyl group, a carboxyl group, an amine group or a nitro group.

(4) The composition according to the above item (2), wherein the degree of modification from the hydroxyl group to the substituent containing the benzene ring ranges from 10% to 30%.

(5) The composition according to the above (1), wherein the polyvinyl alcohol resin having a benzene ring in a side chain is obtained by condensing a benzene ring-containing sulfhydryl chloride or an acid anhydride with a polyvinyl alcohol resin.

(6) The composition according to the above item (1), wherein the polyvinyl alcohol resin having a benzene ring in the side chain is contained in an amount of 10% by weight or more with respect to the total weight of the water-soluble resin.

(7) The composition according to the above item (1), wherein the crosslinking agent is selected from the group consisting of monoaldehyde, dialdehyde, amine formaldehyde resin, glyoxal, acetal compound, divalent metal, trivalent metal, tetravalent metal At least one of the group consisting of a metal chelate compound, an oxazoline, a melamine, an aziridine, and a polymineral acid.

(8) The composition according to the above item (1), wherein, in terms of solid content, the crosslinking agent is contained in an amount of from 0.5 to 20 parts by weight based on 100 parts by weight of the water-soluble resin.

(9) A composite polarizing plate comprising: a polarizer; and a patterned retardation layer adhered to the polarizer using the adhesive composition according to any one of the above items (1) to (8) one side.

(10) The polarizing plate according to the above item (9), wherein the polarizer comprises a film having a function of a protective film or a film having a function of a retardation film adhered to a face opposed to the surface of the patterned retardation layer.

(11) The polarizing plate of the above item (9), wherein the patterned retardation layer comprises a liquid crystal coating layer, and the liquid crystal coating layer contains a reactive liquid crystal monomer having a benzene ring.

(12) The polarizing plate of the above item (9), wherein the patterned retardation layer does not include the alignment layer.

(13) The polarizing plate according to the above item (9), wherein the edge portion is bent from the polarizer side toward the patterned retardation layer side.

(14) The polarizing plate according to the above (9), wherein a difference in height between a center of balance of the polarizer and a highest point at a distance of 5 cm from the center of balance is 3 mm or more.

(15) The polarizing plate according to the above item (9), wherein a peeling strength between the polarizer and the patterned retardation layer is 2 N/25 mm or more.

(16) An image display device comprising the composite polarizing plate of the above item (9).

When the composite polarizer is fabricated by using the binder composition of the present invention in combination with the polarizer and the patterned retardation layer, the adhesion between the polarizer and the patterned retardation layer is remarkably improved.

The composite polarizing plate produced by the adhesion of the adhesive composition of the present invention has good thermal resistance and moist heat resistance even when exposed to a hot and humid environment for a long period of time, thereby suppressing occurrence of peeling and ejection.

The composite polarizing plate manufactured by bonding using the adhesive composition of the present invention can simultaneously have polarization properties and improved 3D stereoscopic effects.

When a composite polarizing plate manufactured by bonding the adhesive composition of the present invention is used for an image display device, it can be easily attached to the display panel.

The present invention discloses a binder composition and a composite polarizing plate using the same, the binder composition comprising: a water-soluble resin comprising a polyvinyl alcohol resin having a benzene ring in a side chain; and a crosslinking agent, whereby When the composite polarizing plate is fabricated by using the adhesive composition of the present invention in combination with the polarizer and the patterned retardation layer, the adhesion between the polarizer and the patterned retardation layer is remarkably improved, and the adhesive composition is excellent. The thermal resistance and the moist heat resistance, and when applied to an image display device, the adhesive composition can be easily attached to the display panel.

The invention will be explained in more detail below.

Adhesive composition

The binder composition of the present invention may be a water-based binder composition including a water-soluble resin.

The water-soluble resin according to the present invention may include a polyvinyl alcohol resin having a benzene ring in its side chain.

When the adhesive composition of the present invention is used to bond a polarizer and a patterned retardation layer to thereby produce a composite polarizing plate, the polyvinyl alcohol resin having a benzene ring in its side chain can significantly improve the polarizer and the patterned retardation layer. Bonding between. The reason for this result can be considered because the above resin reacts with the benzene ring of the liquid crystal coating layer of the patterned retardation layer to cause a π bond interaction. This improved adhesion increases thermal resistance and damp heat resistance.

Further, it can be assumed that a hydroxyl group in the polyvinyl alcohol resin forms a hydrogen bond together with a polar group contained on the surface of the polarizer and the liquid crystal coating layer, thereby further improving the adhesion.

The polyvinyl alcohol resin having a benzene ring in its side chain according to the present invention has a structure in which a hydroxyl group of polyvinyl alcohol is modified to a substituent containing a benzene ring.

The substituent is not particularly limited as long as it contains a benzene ring and may be or is not, for example, a halogen element, a hydroxyl group, a carboxyl group, an amine group, a nitro group, an alkyl group having 1 to 12 carbon atoms or a carbon having 6 to 8 carbon atoms. An aryl substituted benzyl methoxy group of an atom.

In the polyvinyl alcohol resin according to the present invention, the degree of modification from the hydroxyl group to the substituent containing a benzene ring is not particularly limited but may be suitably selected within a range in which the solubility of the resin in the solvent is not improved when the adhesion is improved. It will decrease and, for example, be in the range of 10% to 30%. If the degree of modification is less than 10%, the effect of improving the adhesion of the patterned retardation layer may be negligible. Likewise, when the degree of modification exceeds 30%, the solubility of the resin in the solvent is lowered to obtain a very small improvement in adhesion. The degree of modification described above can be calculated using chemical shifts of adjacent hydrogen during nuclear magnetic resonance (NMR) measurements.

The average degree of polymerization of the polyvinyl alcohol resin used in the preparation of the polyvinyl alcohol resin having a benzene ring in the side chain according to the present invention is not particularly limited but may be considered in the range of from 100 to 5,000, preferably from 1,000 to 4,000. Further, the average degree of saponification may range from 85 to 100 mole percent, preferably from 90 to 100 mole percent.

The polyvinyl alcohol resin may be reacted with a compound containing a benzene ring according to any method known in the related art to prepare a polyvinyl alcohol resin having a benzene ring in a side chain according to the present invention. For example, condensation of a polyvinyl alcohol resin with a fluorenyl chloride or anhydride containing a benzene ring can form a polyvinyl alcohol resin having a benzene ring in a side chain according to the present invention.

The water-soluble resin according to the present invention may further include a water-soluble resin which is often used in the related art.

The water-soluble resin includes, but is not particularly limited, but may include, for example, a partially saponified polyvinyl alcohol resin, a wholly saponified polyvinyl alcohol resin, a carboxyl group-modified polyvinyl alcohol resin, an ethyl acetate-modified polyvinyl alcohol resin, and hydroxy group. A methyl modified polyvinyl alcohol resin, an amine modified polyvinyl alcohol resin, a water-dispersible polyacrylic resin or the like.

The content of the polyvinyl alcohol resin having a benzene ring in the side chain according to the present invention is not particularly limited as long as it sufficiently exhibits its intended properties, for example, it may be 10% by weight or more based on the total weight of the water-soluble resin. If the content is less than 10% by weight, the effect of improving the adhesion may be negligible, causing problems such as a decrease in durability.

The binder composition of the present invention may further comprise a crosslinking agent.

The crosslinking agent is not particularly limited but may include any conventional crosslinking agent used in the related art. For example, it can be used, such as formaldehyde, acetaldehyde, propionaldehyde, butanal, etc.; such as glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, maleic aldehyde, phthalaldehyde, etc. An amine formaldehyde resin such as a carbamide of methylol urea, a methylol melamine, a methylol urea alkylate, a methylol melamine alkylate, a methylguanamine or a benzoguanamine condensate; Such as glyoxylate metal salts (metals include, for example, alkali metals such as lithium, sodium, potassium, alkaline earth metals such as magnesium, calcium, etc., such as titanium, zirconium, chromium, manganese, iron, cobalt, nickel, copper Glyoxylic acid esters such as transition metal, zinc, aluminum or the like), glyoxylate amine salts (amines including, for example, ammonia, methylamine, dimethylamine, trimethylamine, etc.); such as dimethoxyacetaldehyde, An acetal compound such as diethoxy acetaldehyde or dialkoxy acetaldehyde; a divalent metal such as magnesium, calcium, aluminum, iron or nickel; a trivalent metal; a tetravalent metal; a metal chelate compound; Melamine; aziridine; poly mineral acid such as boric acid, phosphoric acid, sulfuric acid or the like.

In terms of solid content, the content of the crosslinking agent is not particularly limited for 100 parts by weight of the water-soluble resin but may be, for example, from 0.5 to 20% by weight. If the content of the crosslinking agent is in the above range, the effect of improving the adhesion between the polarizer and the patterned retardation layer is good.

Composite polarizer

Further, the present invention provides a composite polarizing plate made using the above binder composition.

The composite polarizing plate of the present invention comprises a polarizer and a patterned retardation layer adhered to one side of the polarizer by a binder composition.

Since the polarizer is bonded to the patterned retardation layer using the above binder composition, the composite polarizing plate of the present invention can have high adhesion. As such, as described above, the binder composition layer can form a hydrogen bond with the polarizer, and together with the patterned retardation layer, cause a π bond interaction.

The polarizer is not particularly limited as long as it is generally used in the display field and can polarize incident light. For example, a product made by dyeing a polyvinyl alcohol (PVA)-based film with iodine or a dichroic dye and then extending the dyed film in a desired direction can be used. A film having a protective film function or an additional film having a function of a retardation film can be adhered to one side of the face to which the patterned retardation layer is adhered.

The configuration of the patterned retardation layer is not particularly limited but may include any configuration commonly used in the related art. For example, the substrate, the alignment film, and the liquid crystal coating layer may be stacked in this order to form a laminated structure. Furthermore, the structure may not include an alignment film.

The patterned retardation layer may be adhered such that the liquid crystal coating layer faces the polarizer.

The substrate is not particularly limited as long as it is made of a material having good properties such as transparency, mechanical strength, thermal stability, moisture barrier property, retardation uniformity, isotropic property or the like. For example, a polyolefin resin, a polyester resin, a cellulose resin, a polycarbonate resin, an acrylic resin, a styrene resin, a vinyl chloride resin, a guanamine resin, a quinone imine resin, a polyether oxime resin, or the like may be used. An epoxy resin, a polyether ether oxime resin, a polyetheretherketone resin, a polyphenylene sulfide resin, a vinyl alcohol resin, a vinyl chloride resin, an ethylene butyral resin, an acrylic resin, a polyacetal resin, and an epoxy resin. A substrate made of at least one of the groups.

When the patterned retardation layer includes an alignment layer, the composition for forming an alignment layer (which is often used in the related art) can be applied to the substrate to provide alignment properties, and then the plating film is patterned to have different alignment directions. An alignment layer is formed.

Methods for providing alignment properties can include, for example, grinding, aligning light, etc., while the patterning process can include multiple exposure procedures using a reticle. However, the method and/or the patterning method for providing the alignment property is not particularly limited.

The light for exposure is not particularly limited but may include, for example, polarized UV light radiation, ion beam or plasma beam radiation at a desired angle, irradiation, or the like. For example, polarized UV light radiation is preferably used.

The liquid crystal layer can be formed by applying a composition for forming a liquid crystal coating layer to an alignment layer and then crosslinking it, the liquid crystal coating layer including a reactive liquid crystal monomer (RM) and is often used in the related art.

The RM is not particularly limited but may include any monomer which is often used in the related art, and is preferably a monomer having a benzene ring.

When the patterned retardation layer does not include the alignment layer, the patterned retardation layer can be formed by applying a composition for forming a liquid crystal coating layer to a substrate having no alignment layer, and then exposing it to simultaneously perform patterning and alignment. .

In this example, the composition for forming the liquid crystal coating layer may further include any compound that may be aligned by polarized UV light to produce an alignment, such as a linear photopolymerization polymer.

Compared to the example including the alignment layer, if the patterned retardation layer does not include the alignment layer, a thin film display having a thin thickness can be obtained.

Generally, the polarizing plate is bonded to the display panel through bonding, so it can be used in an image display device. The composite polarizing plate of the present invention can easily perform the above bonding.

More specifically, the bonding using a water-based binder is usually performed by compounding, adhering, and drying. Since the polarizer and the protective film have a high moisture absorption effect, they can absorb moisture and expand after drying. In such an example, as shown in Fig. 1, the edge portion of the composite polarizing plate can be bent from the polarizer side toward the side of the patterned retardation layer, thereby facilitating simple bonding.

The degree of bending is not particularly limited as long as it does not affect the physical properties such as durability in bending. For example, the height difference between the balance center of the polarizer and the highest point 5 cm away from the balance center of the polarizer may be 3 mm or more. If the degree of bending is within the above range, the ease of bonding can be maximized. The degree of bending is preferably from 3 to 5 mm in terms of excellent physical properties and adhesion.

A composite polarizing plate made using the above binder composition exhibits excellent adhesion between the polarizer and the patterned retardation layer. For example, the peel strength between the polarizer and the patterned retardation layer may be 2 N/25 mm or more, preferably from 2.5 to 5 N/25 mm or more.

Image display device

Further, the present invention provides an image display apparatus including the above composite polarizing plate.

The image display device is not particularly limited but may include, for example, a liquid crystal display device or a semi-transmissive liquid crystal display device, a plasma display device, an organic EL display device, or the like for obtaining a stereoscopic image.

The composite polarizing plate of the present invention can be provided at a position where the polarizing plate and the patterned retardation layer are usually stacked.

Hereinafter, preferred embodiments will be described with reference to examples to more specifically understand the present invention. However, it will be apparent to those skilled in the art that the present invention is not limited to the scope of the accompanying claims, and various modifications and alternatives are possible without departing from the invention. The scope and spirit of the invention, and such modifications and substitutions are included in the invention as appropriate, as defined by the scope of the appended claims.

Preparatory example 1

After heating 10 g of polyvinyl alcohol resin (P2000, Nippon Synthetic Co., Ltd.) and then dissolving it in 100 ml of dimethyl hydrazine (DMSO), gently drip 10 g of the solution through a dropping funnel over 30 minutes. Benzoquinone chloride while stirring the solution. Next, the solution was stirred at the same temperature for 5 hours, and then cooled at room temperature, and the reaction mixture was successively dropped into 300 ml of acetone to form a precipitate. The precipitate was filtered with a glass filter and then dried with hot air at 100 ° C for 1 hour.

A part of the resulting product was dissolved in DMSO-d6 solvent and analyzed by NMR to compare the intensity of the CH-OH peak and the CH-OBz peak. As a result of the comparison, the product was found to be a polyvinyl alcohol having a degree of modification of 25%. Then, 10 g of the reaction mixture was placed in 500 ml of distilled water, heated to 50 ° C to dissolve in distilled water, to prepare a 2% water-soluble solution.

Preparatory example 2

A 2% water-soluble polyvinyl alcohol solution having a 15% degree of modification was prepared by the same procedure as described in Preparation Example 1, except that 7 g of benzamidine chloride was used.

Preparatory example 3

A 2% water-soluble polyvinyl alcohol solution having an 8% modification degree was prepared by the same procedure as described in Preparation Example 1, except that 2 g of benzamidine chloride was used.

Preparatory example 4

A 2% water-soluble polyvinyl alcohol solution having a 32% degree of modification was prepared by the same procedure as described in Preparative Example 1, except that 15 g of benzamidine chloride was used.

Examples and comparative examples

Table 1 below lists the binder compositions prepared with different compositions of the compound and content (in terms of solids content).

Comparative example 3

A photopolymerizable binder composition was prepared by adding 1 part by weight of Irgacure-184 (BASF Co.) as a starter to 100 parts by weight of 2-hydroxy-3-phenoxy propyl acrylate.

Experimental example

(1) Measurement of peel strength

A polyvinyl alcohol polarizer was placed by a roll laminator using the adhesive composition prepared in each of the examples and comparative examples to contact and adhere to the liquid crystal coating layer, wherein the polyvinyl alcohol polarizer includes a pattern The retardation layer (MPR32, DNP Co.) and a cellulose triacetate protective film adhered to one side thereof. For evaluation, the end portion of the laminate was not coated with a binder composition.

Next, the treated product was dried at 100 ° C for 3 minutes and then left at room temperature for 48 hours until solidified.

After the composite polarizing plate manufactured as described above was cut into a sample having a width of 25 mm, the sample was peeled off at a peeling rate of 180 ° in a peeling direction of 180 °, and then the peeling strength was measured.

(2) Evaluation of thermal resistance and damp heat resistance

A composite polarizing plate was prepared according to the same procedure as described in Experimental Example (1). After the acrylic adhesive was applied to the protective film and cured, the cured layer was adhered to the soda glass and subjected to autoclaving.

Next, after the treated film was placed at 80 ° C for 500 hours and at 60 ° C, 90% RH for 500 hours, it was examined whether or not bubble generation occurred or the adhesion surface between the polarizer and the liquid crystal coating layer occurred. Peel off. The results of the tests were used to evaluate thermal resistance and damp heat resistance according to the following criteria for evaluation.

○: No bubbles or peeling were observed.

△: Bubbles or peeling were observed in a very small area.

X: Bubbles or peeling can be easily observed.

In the case of ○, ○ is evaluated only when the thermal resistance and the moist heat resistance are both up to the above criteria. For Δ and X, even when one of the thermal resistance and the moist heat resistance reaches the above criteria, it is evaluated as Δ or X.

(3) Measurement of the degree of bending

A composite polarizing plate was prepared according to the same procedure as described in Experimental Example (1). After cutting the center of balance of the polarizing plate to a size of 10 cm by 10 cm, the cut sample is placed on the table so that the surface of the patterned retardation layer faces upward.

Next, the height from the center of the table to the maximum bending side of the polarizer side is measured.

Referring to Table 2, it can be seen that the composite polarizing plate produced by bonding each of the adhesive compositions prepared in Examples 1, 2, and 5 to 7 has a very high peeling strength of 2.8 N/25 mm without bubbles or It is exfoliation, which results in excellent thermal resistance and damp heat resistance. In addition, the polarizing plate is bent by 3.5 mm or more, thus demonstrating the possibility of simple bonding.

For the example 3 and 4 adhesive compositions where the degree of modification of the water-soluble resin is outside the desired range, those exhibit good performance despite a slight decrease in performance.

For the Example 8 adhesive composition comprising a polyvinyl alcohol resin in excess of the desired range, and the Example 9 adhesive composition comprising an excess of crosslinker, those exhibited good performance despite a slight decrease in performance.

However, the binder compositions prepared in Comparative Examples 1-3 have a considerable reduction in peel strength. Further, Comparative Examples 1 and 2 showed a decrease in thermal resistance and moist heat resistance, while Comparative Example 3 did not show a bending effect to cause a difficult adhesion.

100‧‧‧Polarizer
200‧‧‧ adhesive layer
300‧‧‧patterned retardation layer
400‧‧‧Protective layer

The above and other objects, features and other advantages of the present invention will become more <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; The state immediately after bonding, and another state of the composite polarizing plate bent by moisture absorption.

100‧‧‧Polarizer

200‧‧‧ adhesive layer

300‧‧‧patterned retardation layer

400‧‧‧Protective layer

Claims (16)

A binder composition comprising: a water-soluble resin comprising a polyvinyl alcohol resin having a benzene ring in one side chain; and a crosslinking agent. The composition of claim 1, wherein the polyvinyl alcohol resin has a hydroxyl group modified to a monocyclic group containing a benzene ring. The composition of claim 2, wherein the substituent is a benzhydryloxy group substituted with or without a halogen element, a monohydroxy group, a monocarboxy group, an amine group or a mononitro group. The composition of claim 2, wherein a degree of modification from the hydroxyl group to the substituent containing a benzene ring ranges from 10% to 30%. The composition of claim 1, wherein the polyvinyl alcohol resin having a benzene ring in one side chain is a mono- toluene chloride or monoanhydride containing a benzene ring and a polyvinyl alcohol resin. Obtained by condensation. The composition according to claim 1, wherein the polyvinyl alcohol resin having a benzene ring in one side chain is contained in 10% by weight or more with respect to a total weight of the water-soluble resin. In the content. The composition of claim 1, wherein the crosslinking agent is selected from the group consisting of a monoaldehyde, a dialdehyde, an amine formaldehyde resin, a glyoxal, an acetal compound, a divalent metal, a trivalent metal, and a tetravalent metal. At least one of the group consisting of a metal chelate compound, an oxazoline, a melamine, an aziridine, and a polymineral acid. The composition according to claim 1, wherein the crosslinking agent is contained in an amount of from 0.5 to 20 parts by weight based on 100 parts by weight of the water-soluble resin in terms of solid content. A composite polarizing plate comprising: a polarizer; and a patterned retardation layer adhered to one side of the polarizer using the adhesive composition according to any one of claims 1 to 8 . The polarizing plate of claim 9, wherein the polarizer comprises a film having a protective film function or a film having a function of a retardation film adhered to a side opposite to the surface to which the patterned retardation layer adheres. The polarizing plate of claim 9, wherein the patterned retardation layer comprises a liquid crystal coating layer, and the liquid crystal coating layer comprises a reactive liquid crystal monomer having a benzene ring. The polarizing plate of claim 9, wherein the patterned retardation layer does not include the alignment layer. The polarizing plate of claim 9, wherein an edge portion is bent from the polarizer side toward the patterned retardation layer side. The polarizing plate of claim 9, wherein a height difference between a balance center of the polarizer and a highest point 5 cm away from the balance center is 3 mm or more. The polarizing plate of claim 9, wherein a peeling strength between the polarizer and the patterned retardation layer is 2 N/25 mm or more. An image display device comprising the composite polarizing plate according to claim 9 of the patent application.