JP2009036991A - Light-absorbing sheet for cholesteric liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-absorbing sheet whose reflectance is uniform, and in which a light-absorbing layer as a component of a cholesteric liquid crystal device is incorporated without causing physical damage to respective members. <P>SOLUTION: The light-absorbing sheet 20 is used for the cholesteric liquid crystal display device and includes a light-shielding double coated adhesive layer 22, a substrate 21a, and an electrode film 21 comprising a transparent electrode layer 21b formed on the upper face of the substrate 21a. A lower face of the substrate 21a is stuck to an upper face of the double coated adhesive layer 22. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light absorbing sheet for a cholesteric liquid crystal display element.

  In recent years, efforts to conserve resources, which are listed as environmental improvement measures, include limiting the amount of paper used and utilizing e-mails. Under such circumstances, development of an electronic paper that is thin and light, can record data, and has flexibility such as paper is underway.

  A part of electronic paper has been put into practical use, and there are electronic books, shelf label, etc. as its application. Among electronic papers, a display element using a cholesteric liquid crystal is currently used to realize colorization.

  FIG. 1 is a cross-sectional view schematically showing a configuration of a conventional cholesteric liquid crystal display element. The cholesteric liquid crystal display element 1 includes a light absorption layer 2, an electrode film 3, a cholesteric liquid crystal (R) layer 4, an electrode film 5, an electrode film 6, a cholesteric liquid crystal (G) layer 7, an electrode film 8, and an electrode film in order from the lower layer. 9, a cholesteric liquid crystal (B) layer 10 and an electrode film 11 are laminated. The electrode films 3 and 5 provided so as to sandwich the cholesteric liquid crystal (R) layer 4 are composed of substrates 3a and 5a and transparent electrode layers 3b and 5b, respectively, and the transparent electrode layers 3b and 5b are cholesteric liquid crystal (R). It arrange | positions so that the layer 4 may be contact | connected. The electrode films 6 and 8 provided so as to sandwich the cholesteric liquid crystal (G) layer 7 are composed of substrates 6a and 8a and transparent electrode layers 6b and 8b, respectively, and the transparent electrode layers 6b and 8b are cholesteric liquid crystal (G). It arrange | positions so that the layer 7 may be touched. The electrode films 9 and 11 provided so as to sandwich the cholesteric liquid crystal (B) layer 10 are composed of substrates 9a and 11a and transparent electrode layers 9b and 11b, respectively, and the transparent electrode layers 9b and 11b are cholesteric liquid crystal (B). It arrange | positions so that the layer 10 may be touched.

  Cholesteric liquid crystals have a property of selectively reflecting only visible light near a specific wavelength. When sunlight or fluorescent light enters the cholesteric liquid crystal, it selectively reflects colored light such as blue, green, and red. Sunlight or fluorescent light has various wavelengths, so it looks white when all the colored light is reflected, but the transparent electrode layers installed above and below each cholesteric liquid crystal layer 4, 7, 10 Switching between reflection and non-reflection by applying a voltage and changing the orientation of the liquid crystal molecules. The cholesteric liquid crystal (R) layer 4 can be controlled to selectively reflect red light. The cholesteric liquid crystal (G) layer 7 can be controlled to selectively reflect green light. The cholesteric liquid crystal (B) layer 10 can be controlled to selectively reflect blue light.

  A color cholesteric liquid crystal display element generally has a configuration in which cholesteric liquid crystal layers 4, 7, and 10 that selectively reflect are overlapped and a black light absorption layer 2 is provided in the lowermost layer as shown in FIG. 1. Sunlight or fluorescent light enters from the top layer. Incident light that is not reflected by any of the cholesteric liquid crystal layers 4, 7, 10 passes through the liquid crystal portion and reaches the light absorption layer 2, so that the black color of the light absorption layer 2 can be confirmed. The black light absorption layer 2 corresponds to an important part that determines contrast in recording display. In the light absorption layer 2, if the reflectance of incident light that has passed through the liquid crystal portion cannot be sufficiently reduced, the contrast becomes insufficient, the display is not clear, and a multicolor display cannot be obtained.

The light absorption layer of the prior art is formed as follows, for example.
a) A flexible substrate made of a polyester film having a transparent electrode layer formed by vapor deposition or the like, or a paint such as black dye or pigment is applied to the back side of glass or the like by a spin coat method or a silk printing method. B) A polyester film or the like coated with a black dye or pigment paint by spin coating or silk printing, etc., and a transparent electrode is formed on the opposite side by vapor deposition or the like. A transparent electrode is formed by vapor deposition or the like on a film sheet kneaded into a film d) A paint such as a black dye or pigment is applied to a film sheet or a polyester film kneaded with a dye in advance into a polyester film or the like by spin coating or silk A light-absorbing sheet that has been applied by a printing method, etc. and a polyester film with a transparent electrode layer bonded with a transparent adhesive. Patent Document 1 describes that a transparent electrode is formed on each side of two substrates, a cholesteric liquid crystal is injected between the substrates, and then a light absorption layer is formed on the back surface of the lower substrate. . As a material of the light absorption layer, it is described that a paint containing a dye or a pigment or a vapor deposition film such as a metal or a metal oxide film can be used. That is, the light absorption layer formed by the method a) is described.
Japanese Patent Laid-Open No. 2002-62540

  In the method a), there is a possibility that the transparent electrode layer provided in advance may be scratched when the light absorption layer is formed by coating the paint. Further, coating unevenness is likely to occur in the coating, and the reflectance becomes non-uniform due to the influence. Concerning the method b), contrary to the a), the coat is easily peeled off during the transparent electrode layer forming step, and there is a possibility that the incident light is leaked to the outside. As for the above methods c) and d), the process of kneading the dye into the base material is costly in production and goes against the cost reduction based on the future popularization. Furthermore, when the light absorbing sheet is bonded with an adhesive, a drying step of the adhesive is necessary after the adhesive is applied. At that time, the sheet on which the light absorbing sheet and the transparent electrode layer are formed is shrunk by heat, causing curling and distortion. Cause.

  The conventional light absorption layer formed by any one of the above methods may not be able to obtain a sufficient reflectance reduction effect. In this case, there is a problem that the contrast is insufficient and the display is not clear.

  The present invention provides a light-absorbing sheet that includes a light-absorbing layer having a uniform reflectance and that can incorporate such a light-absorbing layer as a component of a cholesteric liquid crystal display element without causing physical damage to each member. The purpose is to provide. Furthermore, it aims at providing the light absorption sheet in which the reflectance in the said light absorption layer was fully reduced.

  In order to achieve the above object, the light absorbing sheet of the present invention comprises a light-shielding double-sided pressure-sensitive adhesive layer and an electrode film comprising a substrate and a transparent electrode layer formed on the upper surface of the substrate, and the lower surface of the substrate is It is the light absorption sheet for cholesteric liquid crystal display elements stuck on the upper surface of the said double-sided adhesive layer. In the above light-absorbing sheet, the L * value (luminance) measured above the transparent electrode layer is preferably 0.01 to 1.0.

  According to the light-absorbing sheet of the present invention, a light-absorbing layer can be incorporated as a component of a cholesteric liquid crystal display element without causing physical damage to each member, and a uniform reflectance is realized throughout the light-absorbing sheet. it can. Furthermore, other components can be easily incorporated using the surface of the double-sided pressure-sensitive adhesive layer on which the electrode film is not attached.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1. Light Absorbing Sheet FIG. 2 is a cross-sectional view schematically showing the configuration of the light absorbing sheet according to the embodiment of the present invention. The light absorbing sheet 20 includes a light-shielding double-sided pressure-sensitive adhesive layer 22, an electrode film 21 attached to the upper surface of the double-sided adhesive layer 22, and a functional film layer 23 attached to the lower surface of the double-sided adhesive layer 22. Consists of. The electrode film 21 includes a substrate 21 a and a transparent electrode layer 21 b formed on the upper surface of the substrate 21 a, and the lower surface of the substrate 21 a is adhered to the upper surface of the double-sided adhesive layer 22. The light absorption sheet of the present invention preferably has an L * value (luminance) measured from above the transparent electrode layer 21b of 0.01 to 1.0 or less. Because the L * value (luminance) is within this range, the reflectivity can be suppressed to a low level, and when the cholesteric liquid crystal display element is used, a clear contrast display can be obtained. is there. Note that the L * value represents the luminance, and the smaller the numerical value, the less the reflected light and the more black the index.

FIG. 3 is a cross-sectional view schematically showing the configuration of the pressure-sensitive adhesive sheet 24 used for configuring the light absorbing sheet 20. The pressure-sensitive adhesive sheet 24 includes a light-shielding double-sided pressure-sensitive adhesive layer 22 and two release films 25a and 25b that are attached so as to protect both surfaces thereof. The light absorption sheet 20 adheres the base material 21a to the upper surface of the double-sided pressure-sensitive adhesive layer 22 that is exposed after peeling off one release film 25a of the pressure-sensitive adhesive sheet 24. Thereafter, the other release film 25 b is peeled off, and the functional film 23 is adhered to the exposed lower surface of the double-sided adhesive layer 22. In this way, the light absorbing sheet 20 is configured. The functional film 23 is not essential, and the lower surface of the double-sided pressure-sensitive adhesive layer 22 may be used for attaching other components when the light-absorbing sheet is incorporated into a cholesteric liquid crystal display element.
2. Adhesive sheet (adhesive)
As the pressure-sensitive adhesive for forming the double-sided pressure-sensitive adhesive layer, one containing an acrylic polymer and a crosslinking agent is preferably used. As the acrylic polymer, a polymer having a monomer unit selected from the group consisting of acrylic acid ester, methacrylic acid ester, and a combination thereof as a main component of the skeleton is preferably used. For example, methyl acrylate, ethyl acrylate, n-butyl It is selected from the group consisting of acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl acrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, and combinations thereof. In particular, n-butyl acrylate (Tg = −55 ° C.) and 2-ethylhexyl acrylate (Tg = −70 ° C.) having a low glass transition point (Tg) having adhesive force even at low temperatures are preferable.

  The acrylic polymer is preferably a copolymer of a monomer that is a main component of the skeleton and a monomer having a functional group that can react with the crosslinking agent. The monomer having a functional group is preferably selected from the group consisting of hydroxyalkyl esters of acrylic acid, hydroxyalkyl esters of methacrylic acid, unsaturated aliphatic carboxylic acids, and combinations thereof, such as hydroxyalkyl esters of acrylic acid. 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate, which are hydroxyalkyl esters of methacrylic acid, unsaturated aliphatic carvone The acid is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and combinations thereof. In particular, it is preferable to use one or more of 2-hydroxyethyl acrylate, acrylic acid, and methacrylic acid because the aggregation effect by polymerization with n-butyl acrylate and 2-ethylhexyl acrylate is high.

  When the acrylic polymer is a copolymer, the monomer corresponding to the main component of the skeleton is 90 to 99.5% by weight as the monomer unit of the copolymer, and the monomer having a functional group capable of reacting with the crosslinking agent is 0.5 to It is preferably 10% by weight. This is because if the total amount of the monomers is less than 0.5% by weight, the cohesiveness of the pressure-sensitive adhesive is low, and if it exceeds 10% by weight, the cohesiveness is strong and it is difficult to form an adhesive layer. The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, but is preferably 300,000 to 2,000,000, particularly preferably 800,000 to 1,300,000. In the present specification, the weight average molecular weight (Mw) is a value in terms of polystyrene measured by gel permeation chromatography (GPC method).

  By using the above-mentioned pressure-sensitive adhesive, heat resistance and moisture resistance are excellent, and adhesive strength is reduced due to a significant increase in cohesiveness when L * preparation components are added. It is possible to suppress a change in reflectance when distorted.

(Crosslinking agent)
It is preferable to add a crosslinking agent to the adhesive solution. Examples of the crosslinking agent added to the adhesive solution include isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, trimethylolpropane tolylene diisocyanate, diphenylmethane triisocyanate; bisphenol A, epichlorohydrin type epoxy resin, ethylene glycol glycidyl ether , Epoxy compounds such as polyethylene glycol diglycidyl ether and glycerin diglycidyl ether; amine compounds such as hexamethylenediamine, triethyldiamine and polyethyleneimine; polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium and nickel Chelate compound coordinated to acetylacetone or ethyl acetoacetate; N, N′-diphenylmethane-4,4′-bis (1-aziridine Ruboxide), N, N′-toluene-2,4-bis (1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tri-1-aziridinylphosphine oxide, etc. Among these aziridine compounds, one kind or a mixture of two or more kinds can be used.

  A predetermined pressure-sensitive adhesive performance can be obtained by cross-linking the pressure-sensitive adhesive polymer mainly composed of an acrylic polymer with a crosslinking agent. The addition amount to the crosslinking agent solution is preferably 0.05 to 15 parts by weight in terms of solid content with respect to 100 parts by weight of the pressure-sensitive adhesive. If the adhesive layer is less than 0.05 parts by weight, the adhesive layer is soft, and the adhesive inside the electronic display is likely to protrude, and the adhesive layer is soft. Or the distortion changes the reflectivity and the like, which greatly affects the contrast. When it exceeds 15 parts by weight, it is difficult to laminate functional films due to insufficient adhesive strength.

(L * value adjustment component)
A colorant is added to the pressure-sensitive adhesive solution as an L * adjusting component to impart light shielding properties to the pressure-sensitive adhesive layer. As the colorant, iron oxide black, carbon black, or the like can be used. The addition amount of the colorant is preferably 15 to 25 parts by weight, more preferably 17 to 20 parts by weight, based on 100 parts by weight of the pressure-sensitive adhesive, in terms of solid content. Similarly, when an acrylic polymer is used as an adhesive and a master batch in which iron oxide black, carbon black, or the like is added as a colorant to the paste is prepared to prepare an adhesive solution, the same applies to 100 parts by weight of the acrylic polymer. The added amount of the colorant is preferably 15 to 25 parts by weight, more preferably 17 to 20 parts by weight in terms of solid content. This is because if the addition amount is less than 15 parts by weight, sufficient light shielding performance cannot be obtained, and if it is added more than 30 parts by weight, the adhesion performance such as adhesive force, tack force, and holding force is lowered.

   In the preparation of the L * value adjusting component paste masterbatch, it is more preferable to use an acrylic ester resin, which is the main component of the adhesive, because the compatibility with the adhesive is good.

(Adhesive additive)
Furthermore, the pressure-sensitive adhesive solution has a cross-linking accelerator, a tackifier, a plasticizer, a filler, an ultraviolet absorber, an antioxidant, a flame retardant, as necessary, as long as it does not impair the light shielding property, reflectivity, adhesive properties, etc. In addition, various additives such as an antistatic agent and a light stabilizer can be appropriately added to obtain a light-shielding pressure-sensitive adhesive solution.

(Adhesive layer)
The pressure-sensitive adhesive layer 22 of the pressure-sensitive adhesive sheet 24 obtained by applying the pressure-sensitive adhesive solution has an extension of the pressure-sensitive adhesive layer of 1 mm or less when a load of 1 g is applied to the pressure-sensitive adhesive layer, and extends the pressure-sensitive adhesive layer until it breaks. It is preferable that the adhesive layer has an elongation of 0.8 mm to 200 mm. By setting the value within this range, when a cholesteric liquid crystal display element for electronic paper is configured using the light-absorbing sheet of the present invention, even if it is curved during use, the L * value due to the bias of the adhesive layer due to strain is obtained. The influence of can be suppressed.

(Peeling film)
An appropriate thin leaf made of a synthetic resin film such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyethylene terephthalate, rubber sheet, or a laminate thereof can be used. The surface is preferably subjected to a release treatment such as a silicone treatment, a long-chain alkyl treatment, a fluorine treatment or the like as necessary in order to improve the peelability from the adhesive layer 22. Further, a release agent may be applied. The release agent is preferably prepared by appropriately adjusting the peeling force so as not to cry when peeling. The release film is preferably used on both sides of the adhesive layer in order to protect the adhesive layer.

(Coating method / conditions)
The method for forming the pressure-sensitive adhesive layer 22 is not particularly limited, and the pressure-sensitive adhesive solution is applied to the release film by a known method such as a gravure printing method, a spray method, a dipping method, a roll coater method, or a die coater method. The pressure-sensitive adhesive layer 22 can be formed by processing and drying. The thickness of the pressure-sensitive adhesive layer 22 is not particularly limited, but an acrylic polymer is used as a pressure-sensitive adhesive, and 15 to 25 parts by weight of iron oxide black is added as an L * value adjusting component to 100 parts by weight of the acrylic polymer in terms of solid content. When the adhesive layer 22 is formed using the adhesive solution thus prepared, the thickness of the adhesive layer 22 is preferably 20 to 30 μm. If the thickness is less than 20 μm, it is difficult to obtain the desired light-shielding property, and peeling due to insufficient adhesive force is likely to occur. If the thickness exceeds 30 μm, the adhesive is likely to protrude during processing of the adhesive sheet.
3. Electrode film (substrate)
As the substrate 21a of the electrode film 21, a dielectric made of glass, a resin such as polycarbonate, polyethylene terephthalate, or polyether sulfone is used. The substrate 21a is preferably transparent. This is because the electrode film made of the transparent substrate 21a is used for other than the lowermost layer of the cholesteric liquid crystal display element, and therefore has high versatility and contributes to cost reduction.

(Transparent electrode layer)
The transparent electrode layer 21b is formed of a light-transmitting conductive oxide such as ITO (indium tin oxide), SnO ₂ , or ZnO: Al. These materials are deposited on the substrate 21a by vapor deposition, sputtering, ion plating, or the like to form the transparent electrode layer 21b.

In addition, as the electrode film 21, the well-known electrode film used for the cholesteric liquid crystal display element can be used.
4). Application The light absorbing sheet 20 of the present invention is used as a component of a cholesteric liquid crystal display element. FIG. 4 is a cross-sectional view schematically showing a configuration of a color cholesteric liquid crystal display element in the present embodiment.

  The cholesteric liquid crystal display element 26 includes, in order from the lower layer, a light absorbing sheet 20, a cholesteric liquid crystal (R) layer 34, an electrode film 35, an electrode film 36, a cholesteric liquid crystal (G) layer 37, an electrode film 38, an electrode film 39, and a cholesteric liquid crystal. (B) The layer 40 and the electrode film 41 are laminated. A transparent electrode layer 21 b is provided on the uppermost surface of the light absorbing sheet 20 and is in contact with the lower surface of the cholesteric liquid crystal (R) layer 34. The electrode film 35 provided on the upper surface of the cholesteric liquid crystal (R) layer 34 includes a substrate 35 a and a transparent electrode layer 35 b, and the transparent electrode layer 35 b is disposed so as to be in contact with the upper surface of the cholesteric liquid crystal (R) layer 34. ing. The electrode films 36 and 38 provided so as to sandwich the cholesteric liquid crystal (G) layer 37 are composed of substrates 36a and 38a and transparent electrode layers 36b and 38b, respectively. The transparent electrode layers 36b and 38b are cholesteric liquid crystal (G). It arrange | positions so that the layer 37 may be touched. The electrode films 39 and 41 provided so as to sandwich the cholesteric liquid crystal (B) layer 40 are respectively composed of substrates 39a and 41a and transparent electrode layers 39b and 41b, and the transparent electrode layers 39b and 41b are formed of the cholesteric liquid crystal (B). It arrange | positions so that the layer 40 may be contact | connected.

  The light absorption sheet 20 is provided in the lowermost layer of the cholesteric liquid crystal display element 26, and has a function as an electrode for controlling the cholesteric liquid crystal layer 34 laminated at the position farthest from the light incident surface, and all the liquid crystal layers. It has a light absorption function of absorbing light that has passed through 40, 37, and 34.

  As described above, in the light-absorbing sheet 20 of the present invention, the layer having the light-absorbing function is composed of the double-sided adhesive layer 22, whereby the lower surface of the substrate 21 a on which the electrode layer 21 b is formed in advance is pasted on the double-sided adhesive layer 22. It can be manufactured simply by being attached, and physical damage to the electrode layer 21b can be prevented in the manufacturing process. Furthermore, in the double-sided pressure-sensitive adhesive layer 22, the functional film 23 can be attached to the surface on which the substrate 21a is not attached. For example, a film coated with a hard coat agent for preventing scratches, a drive circuit, and the like Or a metal foil film that diffuses and dissipates heat generated from the control circuit.

  In the light-absorbing sheet 20 of the present invention, the layer having a light-absorbing function is composed of an adhesive layer 22 formed of an adhesive solution. It can be set as the light absorption sheet which has a rate. Moreover, the light absorption sheet which has desired L * value is comprised by adjusting the kind of L * value adjustment component added to the adhesive solution which forms the double-sided adhesive layer 22 as mentioned above, addition amount, etc. Is possible. Therefore, an L * value measured from above the transparent electrode layer is 0.01 to 1.0, and a light absorbing sheet with reduced reflectance can be provided.

  Hereafter, the adhesive sheet and light absorption sheet of Examples 1-9 and the comparative example 1 were produced, the light absorption sheet of the comparative example 2 was further prepared, and each evaluation was performed.

Example 1
The pressure-sensitive adhesive sheet of Example 1 was produced as follows. Acrylic polymer having a weight average molecular weight (Mw) of 1,000,000 (n-butyl acrylate 74.5% by weight, methyl acrylate 20% by weight, acrylic acid 5.0% by weight, and 2-hydroxyethyl acrylate 0.5% 30 parts by weight of a copolymer (by weight%) was dissolved in 70 parts by weight of a solvent (a solvent obtained by mixing 30 parts by weight of toluene and 40 parts by weight of ethyl acetate) to obtain an acrylic polymer solution having a solid content of 30% by weight. When the solid content of the acrylic polymer solution is 100 parts by weight, 0.15 part by weight of trimethylolpropane tolylene diisocyanate as a cross-linking agent in terms of solid content and 1,3-bis (N, N-diglycidyl) are added to this solution. A pressure-sensitive adhesive solution was prepared by adding 0.1 part by weight of aminomethyl) cyclohexane in terms of solid content.

  100 parts by weight of the solid content of the acrylic polymer solution is added to the pressure-sensitive adhesive solution, 17 parts by weight of OT6414 (manufactured by Resino Color Industries) is added as an L * value adjusting component, stirred, and the pressure-sensitive adhesive solution is applied onto the release film by an applicator Was applied to form an adhesive layer. At this time, the pressure-sensitive adhesive solution was applied so that the thickness of the pressure-sensitive adhesive layer after drying was 25 μm. And the water-repellent surface of a peeling film was bonded together to the surface which the adhesion layer has exposed, and the adhesive sheet of Example 1 was produced.

  Remove one release film of the pressure-sensitive adhesive sheet, and expose the exposed surface, and the surface opposite to the surface on which the transparent electrode layer of the polyester sheet is formed. Bonding, peeling off the other release film attached to the adhesive sheet and attaching a transparent polyester film (A4100, manufactured by Toyobo Co., Ltd.), followed by autoclave at 5 atm and 50 ° C. The light absorption sheet of Example 1 was produced by treating for 15 minutes.

(Example 2)
The pressure-sensitive adhesive sheet and the light-absorbing sheet of Example 2 were produced in the same manner as the pressure-sensitive adhesive sheet and the light-absorbing sheet of Example 1, except that the thickness of the pressure-sensitive adhesive layer was changed to 20 μm instead of 25 μm.

(Example 3)
The pressure-sensitive adhesive sheet and the light-absorbing sheet of Example 2 were produced in the same manner as the pressure-sensitive adhesive sheet and the light-absorbing sheet of Example 1, except that the thickness of the pressure-sensitive adhesive layer was changed to 30 μm instead of 25 μm.

Example 4
Except for the point that OT6414 (manufactured by Resinocolor Kogyo Co., Ltd.), which is an L * value adjusting component added to the adhesive solution, is changed to 15 parts by weight instead of 17 parts by weight, and the thickness of the adhesive layer is changed to 20 μm instead of 25 μm. The pressure-sensitive adhesive sheet and the light-absorbing sheet of Example 4 were produced in the same manner as the pressure-sensitive adhesive sheet and the light-absorbing sheet of Example 1.

(Example 5)
Except that OT6414 (manufactured by Resino Color Kogyo Co., Ltd.), which is an L * value adjusting component added to the adhesive solution, was changed to 15 parts by weight instead of 17 parts by weight, it was the same method as the adhesive sheet and light absorbing sheet of Example 1. The pressure-sensitive adhesive sheet and light absorption sheet of Example 5 were produced.

(Example 6)
Except for the point that OT6414 (manufactured by Resino Color Kogyo Co., Ltd.), which is an L * value adjusting component added to the adhesive solution, is changed to 15 parts by weight instead of 17 parts by weight, and the thickness of the adhesive layer is changed to 30 μm instead of 25 μm. The pressure-sensitive adhesive sheet and light absorption sheet of Example 6 were produced in the same manner as the pressure-sensitive adhesive sheet and light absorption sheet of Example 1.

(Example 7)
Except for the point that OT6414 (manufactured by Resinocolor Kogyo Co., Ltd.), which is an L * value adjusting component added to the adhesive solution, is changed to 25 parts by weight instead of 17 parts by weight, and the thickness of the adhesive layer is changed to 20 μm instead of 25 μm. The pressure-sensitive adhesive sheet and light absorption sheet of Example 7 were produced in the same manner as the pressure-sensitive adhesive sheet and light absorption sheet of Example 1.

(Example 8)
Except that OT6414 (manufactured by Resino Color Kogyo Co., Ltd.), which is an L * value adjusting component added to the adhesive solution, was changed to 25 parts by weight instead of 17 parts by weight, it was the same method as the adhesive sheet and light absorbing sheet of Example 1. The pressure-sensitive adhesive sheet and light absorption sheet of Example 8 were produced.

Example 9
Except for the point that OT6414 (manufactured by Resinocolor Kogyo Co., Ltd.), which is an L * value adjusting component added to the adhesive solution, was changed to 25 parts by weight instead of 17 parts by weight, and the thickness of the adhesive layer was changed to 30 μm instead of 25 μm. The pressure-sensitive adhesive sheet and the light-absorbing sheet of Example 9 were produced in the same manner as the pressure-sensitive adhesive sheet and the light-absorbing sheet of Example 1.

(Comparative Example 1)
A pressure-sensitive adhesive sheet of Comparative Example 1 was produced in the same manner except that the L * value adjusting component was not added to the pressure-sensitive adhesive solution and a transparent pressure-sensitive adhesive layer was formed. In addition, in the light absorbing sheet, for the polyester film attached to one surface of the adhesive layer, a black paint is applied to the surface opposite to the surface attached to the adhesive layer by a silk printing method to transmit light. A light-absorbing sheet of Comparative Example 1 was produced in the same manner as in Example 1 except that a light-shielding polyester film having a rate of 1.0% or less was used.

(Comparative Example 2)
The light-shielding polyester sheet described in Comparative Example 1 was evaluated for the L * value of Comparative Example 2.

(Evaluation method and evaluation)
1. About L * value evaluation Examples 1-9 and the light absorption sheet of Comparative Examples 1 and 2, above the transparent electrode layer with a C light source and a viewing angle of 2 ° using a spectrophotometer “SD5000” manufactured by Nippon Denka Co., Ltd. The L * value of the reflected light was measured. Table 1 shows the results.
2. Evaluation of adhesive strength For the adhesive sheets of Examples 1 to 9 and Comparative Examples 1 and 2, the surface exposed by peeling one of the release films was transferred to the easy adhesion treatment surface of a polyester film (A4100, manufactured by Toyobo Co., Ltd.). After the other release film was peeled off and pasted on soda lime glass for 30 minutes, a polyester film was used at a pulling angle of 180 ° and a pulling speed of 300 mm / min using an autograph “AGS-500NG” manufactured by Shimadzu Corporation. The value obtained by converting the value of the force at the time of pulling up to 25 mm width was defined as the adhesive strength. Table 1 shows the results.

表１より、実施例１〜９の光吸収シートはＬ＊値が１．０以下であり、低い反射率を実現できることがわかる。比較例１，２の光吸収シートでは、１．０以下のＬ＊値が実現されなかった。さらに、実施例１〜９の粘着シートでは、適度な対ガラス粘着力が得られることがわかった。上記方法により測定する対ガラス粘着力は、好ましくは１Ｎ／２５ｍｍ以上であり、いずれの実施例もかかる範囲の値であった。１Ｎ／２５ｍｍ未満であると、意図しない剥離、ハガレが発生しやすいからである。

From Table 1, it can be seen that the light absorption sheets of Examples 1 to 9 have an L * value of 1.0 or less and can realize a low reflectance. In the light absorbing sheets of Comparative Examples 1 and 2, an L * value of 1.0 or less was not realized. Furthermore, in the adhesive sheet of Examples 1-9, it turned out that moderate adhesive force with respect to glass is obtained. The adhesion to glass measured by the above method was preferably 1 N / 25 mm or more, and all the examples were in this range. This is because if it is less than 1 N / 25 mm, unintended peeling and peeling are likely to occur.

  Moreover, the light absorption sheet | seat of Examples 1-9 could be produced only by sticking an electrode film to an adhesive sheet, and the transparent electrode layer provided in the electrode film was not damaged.

  The cholesteric liquid crystal display element using the light-absorbing sheet of the present invention is useful as a display element for electronic paper such as an electronic newspaper or an electronic book because it can display bright light with a clear contrast using reflection of external light. .

It is sectional drawing which shows typically the structure of the conventional multicolor cholesteric liquid crystal display element. It is sectional drawing which shows typically the structure of the light absorption sheet of this embodiment. It is sectional drawing which shows typically the structure of the adhesive sheet of this embodiment. It is sectional drawing which shows typically the structure of the multicolor cholesteric liquid crystal display element of this embodiment.

Explanation of symbols

1,26 Cholesteric liquid crystal display element 4,34 Cholesteric liquid crystal (R) layer 7,37 Cholesteric liquid crystal (G) layer 10,40 Cholesteric liquid crystal (B) layer 20 Light absorbing sheet 21 Electrode sheet 21a Substrate 21b Transparent electrode layer 22 Double-sided adhesive Layer 24 Adhesive sheet 25a, 25b Release sheet

Claims (2)

A light-shielding double-sided adhesive layer, and an electrode film comprising a substrate and a transparent electrode layer formed on the upper surface of the substrate;
A light-absorbing sheet for a cholesteric liquid crystal display element, wherein the lower surface of the substrate is attached to the upper surface of the double-sided adhesive layer.   The light absorption sheet according to claim 1 whose L * value (luminance) measured above said transparent electrode layer is 0.01-1.0.

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