JP2010285524A - Adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive sheet including an adhesive inhibiting progress of corrosion of an ITO film. <P>SOLUTION: An adhesive layer 6 of the adhesive sheet is used when a substrate 4 on which an ITO film 3 is formed is attached to a film 1. The adhesive layer 6 at least includes: an adhesive at least including one or more acrylic acid derivatives and an acrylic acid hydroxyl ester; a crosslinking agent; and a phenolic antioxidant. The acrylic acid derivatives are preferably methyl acrylate and n-butyl acrylate, and the acrylic acid hydroxyl ester is preferably 2-hydroxyethyl acrylate. The crosslinking agent is preferably an isocyanate-based crosslinking agent. The adhesive layer 6 with such structure suppresses a resistance value of the ITO film 3 below 20 kΩ even after being left for 1,000 hours while attached to the ITO film 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an adhesive sheet that suppresses corrosion of an ITO (Idium Thin Oxide) film.

  Liquid crystal displays are widely used in various application fields such as flat-screen liquid crystal televisions, touch panels, car navigation systems, and mobile phones. A transparent conductive film such as ITO (Idium Thin Oxide) is commonly used in liquid crystal televisions, car navigation systems, touch panels, and the like. The ITO film is formed on a film or glass by vacuum deposition or the like.

  Usually, when an ITO film is used for the various display elements described above, a protective film is bonded to the surface of the ITO film (see, for example, Patent Document 1). For example, in a capacitive touch panel, a protective film is bonded to the surface of an ITO film formed by vacuum deposition on the surface of an insulating substrate (plastic, glass, etc.). When a human finger contacts the touch panel surface through the protective film, the electric field value at the contact portion changes. By recognizing the coordinates of the portion where the electric field value has changed, the position of the portion in contact with the human finger is specified.

JP 2008-63433 A

  However, the pressure-sensitive adhesive used when the ITO film and the protective film are bonded causes the corrosion of the ITO film to progress when used for a long time. Since the ITO film has an increased electrical resistance value due to corrosion, as described above, when the ITO film is used in a capacitive touch panel, there is a problem in that malfunction such as poor sensing is likely to occur. .

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive capable of preventing the progress of corrosion of an ITO film.

  In order to solve the above-mentioned problems, the pressure-sensitive adhesive sheet of the invention according to claim 1 includes a pressure-sensitive adhesive layer containing at least a pressure-sensitive adhesive, and a release sheet that is releasably attached to at least one surface of the pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet is characterized in that the pressure-sensitive adhesive layer contains at least a pressure-sensitive adhesive containing at least one acrylic acid-modified product and acrylic acid hydroxy ester, a crosslinking agent, and a phenolic antioxidant. To do.

  The pressure-sensitive adhesive sheet of the invention according to claim 2 is characterized in that, in addition to the configuration of the invention according to claim 1, the one or more acrylic acid-modified products are composed of methyl acrylate and n-butyl acrylate. And

  The pressure-sensitive adhesive sheet of the invention according to claim 3 is characterized in that, in addition to the structure of the invention according to claim 2, the hydroxy ester of acrylic acid is 2-hydroxyethyl acrylate.

  The pressure-sensitive adhesive sheet according to a fourth aspect of the invention includes the composition according to the third aspect of the invention, wherein the proportion of the methyl acrylate in the pressure-sensitive adhesive is 10% to 50%, and the acrylic acid n The ratio of butyl is 45% or more and 85% or less, and the ratio of 2-hydroxyethyl acrylate is 1% or more and 10% or less.

  The pressure-sensitive adhesive sheet of the invention according to claim 5 is characterized in that, in addition to the configuration of the invention according to any one of claims 1 to 4, the phenolic antioxidant is butylated hydroxytoluene. .

  The pressure-sensitive adhesive sheet according to claim 6 is characterized in that, in addition to the configuration of the invention according to any one of claims 1 to 5, the crosslinking agent is an isocyanate-based crosslinking agent.

  The pressure-sensitive adhesive sheet of the invention according to claim 7 is the structure according to any one of claims 1 to 6, wherein the adhesive layer is attached to the ITO film and then 1000 hours have passed. The ITO film has a resistance value of less than 20 kΩ.

  When the pressure-sensitive adhesive sheet of the present invention is used for the purpose of bonding a protective film or the like to the ITO film, the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet suppresses the progress of corrosion of the ITO film. For this reason, the ITO film can be maintained at a low resistance.

2 is a cross-sectional view showing a physical configuration of the pressure-sensitive adhesive sheet 10. FIG. 2 is a cross-sectional view showing a physical configuration of a touch panel 11. FIG.

  Hereinafter, an adhesive sheet 10 according to an embodiment of the present invention will be described with reference to the drawings. These drawings are used for explaining the technical features that can be adopted by the present invention, and the configuration of the apparatus described is not intended to be limited to this, but is merely an illustrative example. .

  With reference to FIG. 1, the physical structure of the adhesive sheet 10 is demonstrated. As shown in FIG. 1, the adhesive sheet 10 includes an adhesive layer 6, and a release sheet 5 and a release sheet 7 that are bonded to the adhesive layer 6 so as to sandwich the adhesive layer 6. The pressure-sensitive adhesive layer 6 contains at least a pressure-sensitive adhesive, a crosslinking agent, and an antioxidant. In the example shown in FIG. 1, the adhesive layer 6 is laminated on the upper side of the release sheet 7, and the release sheet 5 is arranged on the upper side of the adhesive layer 6.

  With reference to FIG. 2, an example of the application example of the adhesive sheet 10 (refer FIG. 1) is shown. In FIG. 2, the case where the adhesive sheet 10 is applied to the capacitive touch panel 11 is shown. The touch panel 11 is a substrate 4 such as transparent plastic, glass, or film, an ITO film 3 formed on the surface of the substrate 4, and an adhesive bonded to a surface of the ITO film 3 opposite to the surface in contact with the substrate 4. The adhesive layer 6 of the sheet 10 and the film 1 having a function such as surface protection bonded to the substrate 4 by the adhesive layer 6 are provided. The touch panel 11 is used in a state in which the surface of the substrate 4 opposite to the surface on which the ITO film 3 is formed (the lower surface of the paper) is close to a display element (LCD, EL element, etc.).

  A method for creating the touch panel 11 will be outlined. The release sheet 5 is peeled from the pressure-sensitive adhesive sheet 10 in FIG. The pressure-sensitive adhesive layer 6 in the dew state is bonded to the surface of the ITO film 3 formed on the substrate 4. Thereafter, the release sheet 7 is peeled off. The film 1 is bonded to the adhesive layer 6 in a dew state. The touch panel 11 is created as described above.

  The pressure-sensitive adhesive, the crosslinking agent, and the antioxidant constituting the pressure-sensitive adhesive layer 6 will be described in detail. In the present embodiment, (1) the functional group in the pressure-sensitive adhesive considered to be a corrosion factor of the ITO film 3 is changed from a carboxyl group-based to a hydroxyl group-based, and (2) an unreacted hydroxyl group remains in the pressure-sensitive adhesive. In order to prevent the corrosion of the ITO film 3, an antioxidant is added to the pressure-sensitive adhesive.

  First, the adhesive will be described. As an adhesive, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid have been used. In the present embodiment, an acrylic acid-modified product is used as an adhesive, not an acrylic acid-based adhesive that contains an acid component that is considered to cause corrosion of the ITO film and increase the resistance value. Examples of acrylic acid-modified products include acrylamides such as (meth) acrylamide, N-methyl (meth) acrylamide, and N-methylol (meth) acrylamide; monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate , (Meth) acrylic acid monomethylaminopropyl, (meth) acrylic acid monoethylaminopropyl and other (meth) acrylic acid monoalkylamino esters; methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid Propyl, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, (meth) acryl Decyl acid, (meth) a Dodecyl acrylic acid, (meth) acrylic acid myristyl, palmityl (meth) acrylate, and stearyl (meth) acrylate. Among these, it is preferable to use methyl acrylate and n-butyl acrylate because the adhesiveness is improved.

  In addition to the above acrylic acid-modified product, acrylic acid hydroxy ester is used in combination for the reasons of preventing corrosion of the ITO film, adhesive properties, moldability, workability, and the like. Examples of the hydroxy ester of acrylic acid include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth) Examples include (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. Among these, it is preferable to use 2-hydroxyethyl acrylate because adhesion is improved.

In the following,% notation represents weight%.
When the acrylic acid modified product and the acrylic acid hydroxy ester are used in combination, the ratio of the acrylic acid modified product is preferably 90% or more and 99% or less of the pressure-sensitive adhesive. The proportion of acrylic acid hydroxy ester is preferably 1% or more and 10% or less of the pressure-sensitive adhesive. More preferably, methyl acrylate and n-butyl acrylate are used in combination as the acrylic acid-modified product. As the acrylic acid hydroxy ester, 2-hydroxyethyl acrylate is preferably used. As for the ratio of methyl acrylate, butyl acrylate, and 2-hydroxyethyl acrylate, methyl acrylate is preferably 10% or more and 50% or less. It is preferable that n-butyl acrylate is 45% or more and 85% or less. It is preferable that 2-hydroxyethyl acrylate is 1% or more and 10% or less. More preferably, methyl acrylate is 20% or more and 40% or less. It is preferable that n-butyl acrylate is 55% or more and 75% or less. It is preferable that 2-hydroxyethyl acrylate is 3% or more and 8% or less.

  By setting the acrylic acid modified product to 90% to 99% and the acrylic acid hydroxy ester to 1% to 10%, it is easy to prevent corrosion of the ITO film while having sufficient adhesive strength. Further, when methyl acrylate is 10% to 50%, n-butyl acrylate is 45% to 85%, and 2-hydroxyethyl acrylate is 1% to 10%, methyl acrylate is further added. 20% to 40%, n-butyl acrylate 55% to 75%, 2-hydroxyethyl acrylate 3% to 8%, and even better adhesion and prevention of ITO film corrosion It is preferable because it can be achieved.

  As a polymerization method for obtaining an acrylic polymer such as an acrylic acid modified product and / or an acrylic acid hydroxy ester, any polymerization method such as solution polymerization, emulsion polymerization, bulk polymerization and the like can be used. As the polymerization initiator in the present embodiment, radical polymerization that generates radicals in a solution is preferably used, and known polymerization initiators such as benzoyl peroxide and azodiisobutyronitrile can be used. In the present embodiment, an azo polymerization initiator such as azodiisobutyronitrile is preferably used.

  The amount of the azo polymerization initiator used in the radical polymerization is preferably 0.005 to 1.0 part by weight with respect to 100 parts by weight of the monomer. The weight average molecular weight of the obtained acrylic polymer is preferably 500,000 to 1,500,000, and more preferably 800,000 to 1,300,000. This is because when the weight average molecular weight is set within this range, an appropriate coagulation effect can be obtained by reaction with the crosslinking agent.

  The crosslinking agent will be described. As the crosslinking agent, generally used crosslinking agents can be used. For example, isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, trimethylolpropane tolylene diisocyanate, diphenylmethane triisocyanate; epoxy resins such as epichlorohydrin type epoxy resin, ethylene glycol glycidyl ether, polyethylene diglycidyl ether, glycerin diglycidyl ether Compounds; amine compounds such as hexamethylenediamine, triethyldiamine, polyethyleneamine; polyvalent metals and metal chelate compounds typified by aluminum; N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxide) , N, N′-toluene-2,4-bis (1-aziridinecarboxide), tri-1-aziridinylphosphine oxide, etc. Compounds. Among these, one type or a mixture of two or more types can be used. Among these, isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, trimethylolpropane tolylene diisocyanate, and diphenylmethane triisocyanate are preferable, and trimethylolpropane tolylene diisocyanate is more preferable. By cross-linking the pressure-sensitive adhesive polymer mainly composed of an acrylic polymer with a crosslinking agent, it is possible to improve durability under high temperature, wet heat and low temperature environments while maintaining sufficient adhesiveness. Therefore, it is preferable.

  The amount of the crosslinking agent added is preferably 0.1 parts by weight or more and 20 parts by weight or less in terms of solid content with respect to 100 parts by weight of the pressure-sensitive adhesive polymer. More preferably, it is 1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the pressure-sensitive adhesive polymer. If it is less than 0.1 part by weight, an unreacted hydroxyl group remains in the pressure-sensitive adhesive polymer, which causes the corrosion of the ITO film to be accelerated. In addition, the adhesiveness decreases due to insufficient cohesive force, and problems such as floating and peeling occur. Further, when the pressure-sensitive adhesive sheet is laminated on the touch panel, the pressure-sensitive adhesive tends to protrude. Moreover, since the adhesive is soft, workability may be greatly reduced, such as adhesion of the adhesive to the blade during slitting, which is not preferable. If the amount exceeds 20 parts by weight, corrosion of the ITO film will be prevented and durability will be improved, but the adhesive strength will decrease and it may be difficult to laminate the functional film.

  Acrylic acid-modified product and acrylic acid hydroxy ester are used as the pressure-sensitive adhesive, an isocyanate compound is used as the cross-linking agent, methyl acrylate and n-butyl acrylate are used as the acrylic acid-modified material, and acrylic acid hydroxy ester is used as the acrylic acid hydroxy ester. When the acid 2-hydroxyethyl is used, the adhesiveness is further improved. In addition, the addition amount of the crosslinking agent is 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight in terms of solid content with respect to 100 parts by weight of the pressure-sensitive adhesive polymer. Thereby, sufficient adhesiveness is maintained. Moreover, it becomes easier to prevent corrosion of the ITO film, and an increase in resistance value can be suppressed.

  The antioxidant will be described. Examples of the antioxidant include a phenol compound, a salicylic acid compound, a thioether compound, a hydrazine compound, a phosphorus compound, and a sulfur compound. Specific compounds include ascorbic acid, ascorbyl palmitate, propyl gallate mixture, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), propyl gallate, and citric acid, butylated There are hydroxytoluene, t-butylhydroquinone, natural tocopherol, butylated hydroxyanisole, dodecyl gallate, and the like. In this embodiment, a phenol compound is used as an antioxidant. By adding a phenolic antioxidant, an increase in the resistance value of the ITO film can be suppressed. One type of phenolic antioxidant or a mixture of two or more types can be used.

  In particular, salicylic acid compounds, thioether compounds, hydrazine compounds, and sulfur compounds have poor solubility in toluene, ethyl acetate, and MEK (methyl ethyl ketone) used as solvents for adhesives. Phosphorus compounds have poor solubility in ethyl acetate and MEK. From this, since the addition amount to an adhesive is limited, the corrosion prevention function of an ITO film | membrane falls. If the amount added is large, the undissolved material aggregates and inhibits the formation of a uniform adhesive layer, or precipitates and affects the quality such as transparency, durability, and adhesive physical properties. For this reason, a phenolic compound having good solubility and a large effect of suppressing increase in resistance value due to corrosion of the ITO film is used. More preferred is BHT. Use of BHT is most effective in suppressing an increase in resistance value caused by ITO corrosion. The addition amount of the antioxidant is preferably 0.004 parts by weight or more and 0.4 parts by weight or less in terms of solid content with respect to 100 parts by weight of the pressure-sensitive adhesive polymer. More preferably, they are 0.04 weight part or more and 0.35 weight part or less. When the amount is less than 0.004 parts by weight, it is difficult to obtain an effect of suppressing an increase in resistance value due to corrosion of the ITO film. Exceeding 0.4 parts by weight, after forming the adhesive layer, excessive antioxidant bleeds out on the surface of the adhesive layer over time, causing peeling and turning, and the ITO film comes into contact with air, and the ITO film May corrode.

  The resistance value of the ITO film is suppressed to less than 20 KΩ by using a modified acrylic acid and an acrylic acid hydroxy ester as an adhesive, using a crosslinking agent, and using a phenolic compound, preferably butylated hydroxytoluene as an antioxidant. This is preferable because the pressure-sensitive adhesive sheet prevents corrosion of the ITO film. Furthermore, an isocyanate compound is used as a crosslinking agent, the amount of crosslinking agent added is 0.1 to 20 parts by weight in terms of solid content with respect to 100 parts by weight of the pressure-sensitive adhesive polymer, and the amount of antioxidant added is the pressure-sensitive adhesive polymer. It is 0.004 parts by weight or more and 0.4 parts by weight or less in terms of solid content with respect to 100 parts by weight, and the acrylic acid hydroxy ester component of the adhesive, particularly 2-hydroxyethyl acrylate, 10 parts by weight or less. This is preferable because the resistance value of the ITO film can be suppressed to 15 KΩ or less while maintaining high adhesiveness, and the corrosion of the ITO film is further easily prevented. In addition, if the addition amount of the crosslinking agent is 1 part by weight or more and 10 parts by weight or less in terms of solid content with respect to 100 parts by weight of the adhesive polymer, the tackiness can be further improved. In addition, the resistance value of the ITO film is obtained by setting the addition amount of the antioxidant in terms of solid content with respect to 100 parts by weight of the pressure-sensitive adhesive polymer, more preferably 0.04 parts by weight or more and 0.35 parts by weight or less. Can be suppressed to 10 KΩ or less. In particular, the pressure-sensitive adhesive sheet is particularly preferable for preventing corrosion of the ITO film.

  Moreover, 90% or more and 99% or less of the acrylic acid modified product, 1% or more and 10% or less of the acrylic acid hydroxy ester, and 0.1 to 20 parts by weight, more preferably 1 part by weight of the isocyanate compound as a crosslinking agent. More than 10 parts by weight, and the phenolic compound as an antioxidant is 0.004 parts by weight or more and 0.4 parts by weight or less, more preferably 0.04 parts by weight or more and 0.35 parts by weight or less. It is easy to further suppress an increase in resistance value due to corrosion of the ITO film while maintaining the properties. Particularly preferably, methyl acrylate is 10% to 50%, most preferably 20% to 40%, and n-butyl acrylate is 45% to 85%, most preferably 55% to 75 as the acrylic acid-modified product. % Or less, 2-hydroxyethyl acrylate as 1% to 10%, most preferably 3% to 8% as the hydroxy ester of acrylic acid, and butylated hydroxytoluene as the antioxidant. This makes it easy to maintain high adhesiveness and to suppress the increase in resistance value due to corrosion of the ITO film. However, if the acrylic acid hydroxy ester (2-hydroxyethyl acrylate) is 15 parts by mass or more with respect to 100 parts by mass of the adhesive, the ITO film is corroded by the hydroxyl group in the acrylic acid hydroxy ester (2-hydroxyethyl acrylate). There is a possibility that the resistance value of the ITO film is lowered.

  A method for forming the adhesive layer 6 will be described. The pressure-sensitive adhesive layer 6 is prepared by applying a mixture of a pressure-sensitive adhesive, a crosslinking agent, and an antioxidant to a release sheet 7 that has been subjected to a peeling treatment, drying and crosslinking, and then providing the pressure-sensitive adhesive layer 6. A separate release sheet 5 is pasted on top. At this time, the method for forming the adhesive layer 6 is not particularly limited, and a known method such as a gravure printing method, a spray method, a roll coater method, a die coater method or the like can be used.

  The thickness of the adhesive layer is not particularly limited, but is preferably 10 μm or more, particularly preferably 15 μm or more. When the thickness is less than 10 μm, peeling between the substrates tends to occur due to insufficient adhesive force. On the other hand, when the thickness exceeds 50 μm, the cutting area of the adhesive layer at the time of processing increases, and the adhesive may adhere to the slit blade, or the end face may be deformed by the blade pressure of the slit blade.

  The release sheets 5 and 7 of the pressure-sensitive adhesive sheet 10 in the present embodiment are not particularly limited as long as they can be peeled off without being bonded to the pressure-sensitive adhesive composition. For example, what applied the release agent to paper and a synthetic resin film can be mentioned. The use of a release agent is preferable because it appropriately adjusts the release force and prevents delamination of the adhesive layer.

  As described above, in the pressure-sensitive adhesive sheet 10 of the present embodiment, the pressure-sensitive adhesive layer 6 includes a pressure-sensitive adhesive containing one or more acrylic acid-modified products and acrylic acid hydroxy ester, a crosslinking agent, and a phenol-based antioxidant. At least. By setting it as such a structure, when the film 1 is bonded on the surface of the ITO film | membrane 3 using the adhesion layer 6, the progress of corrosion of the ITO film | membrane 3 can be suppressed. Therefore, for example, when applied to the ITO film 3 used in the capacitive touch panel 11, the resistance value can be suppressed to less than 20 KΩ, further to 15 KΩ or less, and particularly to 10 KΩ or less. The touch panel 11 can be supplied with stable quality.

  In addition, this invention is not limited to the said embodiment, A various change is possible. In the above-described embodiment, the case where the pressure-sensitive adhesive sheet 10 is applied to the touch panel 11 has been described. However, the present invention is not limited to this example. Therefore, the adhesive sheet 10 may be applied to other application examples.

The pressure-sensitive adhesive sheet of the present invention will be specifically described below according to examples. However, the present invention is not limited to these examples. Hereinafter, (1) sample preparation, (2) evaluation contents, and (3) evaluation results will be described in this order.
(1) Sample preparation

  The adhesive sheet 10 which consists of the adhesive layer 6 of 40 types (Examples 1-25, Comparative Examples 1-15) from which a composition differs was created. An acrylic polymer (methyl acrylate (MA), butyl acrylate (BA), acrylic acid (AA), 2-hydroxyethyl acrylate (2HEA)) was used as an adhesive. These pressure-sensitive adhesives were mixed and used at the composition ratios shown in Tables 1 and 2. 25 parts by weight of acrylic polymer was dissolved in 75 parts by weight of solvent (a solvent in which 22 parts by weight of toluene, 42 parts by weight of ethyl acetate and 11 parts by weight of MEK were mixed) to obtain an acrylic polymer having a solid content of 25% by weight. As the crosslinking agent, an isocyanate or epoxy crosslinking agent described in Tables 1 and 2 was dissolved in a solvent (ethyl acetate) and the solid content was adjusted to 45% by weight. The adjusted cross-linking agent was added to the pressure-sensitive adhesive in the proportions shown in Tables 1 and 2. As antioxidant, what melt | dissolved the compound of Table 1 and Table 2 in the solvent (ethyl acetate), and adjusted to solid content 10-20 weight% was used. The adjusted antioxidant was added to the pressure-sensitive adhesive in the proportions shown in Tables 1 and 2. All the stated ratios are weight percentages in terms of solid content.

  In addition, when AA was used as an adhesive (Comparative Examples 8 to 15), an epoxy-based crosslinking agent that easily reacts with AA was used in combination with an isocyanate-based crosslinking agent. The reason is that the isocyanate-based cross-linking agent is yellowed by mixing with AA and has a characteristic that performance variation is likely to occur due to the influence of moisture. On the other hand, when AA is not used (Examples 1 to 25 and Comparative Examples 1 to 7), the adhesive and the epoxy-based crosslinking agent hardly react with each other, so that only the isocyanate-based crosslinking agent is used.

  After preparing the pressure-sensitive adhesive, the crosslinking agent, and the antioxidant, the mixture was allowed to stand for 2 hours. Next, the release sheet 7 subjected to the release treatment was coated with a die coater so as to have a thickness of 25 μm, and dried and crosslinked at 80 to 110 ° C. for 2 minutes. As a result, the adhesive layer 6 was formed on the release sheet 7. Next, another release sheet 5 was stuck on the adhesive layer 6 to prepare an adhesive sheet 10. It shows in Table 1 and Table 2 about the composition of the adhesive which comprises the adhesion layer 6 of the produced adhesive sheet 10. FIG.

（２）評価内容 In Tables 1 and 2, trimethylolpropane tolylene diisocyanate was used as the isocyanate-based crosslinking agent. As the isocyanate / epoxy crosslinking agent, trimethylolpropane tolylene diisocyanate / glycerin diglycidyl ether was used. Butylated hydroxytoluene was used as a phenolic antioxidant. As the phosphorus antioxidant, 3,9-bis (octadecyloxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane was used. 3- (Salicyloylamino) -1H-1,2,4-triazole was used as a salicylic acid antioxidant. Bis [3- (dodecylthio) propionic acid] 2,2-bis [[3- (dodecylthio) -1-oxopropyloxy] methyl] -1,3-propanediyl was used as the thioether-based antioxidant. 3,3′-thiobis (dodecyl propionate) was used as a sulfur-based antioxidant. 1,2-bis [3- [4-hydroxy-3,5-bis (1,1-dimethylethyl) phenyl] propionyl] hydrazine was used as a hydrazine antioxidant.

(2) Evaluation contents

  The prepared pressure-sensitive adhesive sheet 10 was used to evaluate adhesiveness. Adhesiveness evaluated the adhesiveness with respect to a to-be-adhered body combining evaluation of adhesive force and durability. Adhesive strength evaluation used the adhesive sheet 10 bonded together to A4100 by Toyobo Co., Ltd. as a support body. The pressure-sensitive adhesive sheet 10 was adhered to an adherend (glass) and left in a 23 ° C., 50% environment for 20 minutes. Thereafter, the adhesive strength to the adherend when the pressure-sensitive adhesive sheet 10 was peeled off from the adherend was evaluated. Durability evaluation uses the prepared pressure-sensitive adhesive sheet 10 to adhere the adherend to a high temperature environment (80 ° C. dry), a moist heat environment (60 ° C./95%), and a low temperature environment (−40 ° C.). After leaving for 1000 hours, it was performed by observing the presence or absence of floating or foaming. Tables 3 and 4 show the results for the samples where the most peeling and foaming occurred in each environment.

  In Tables 3 and 4, “◎” indicates that the adhesive strength is sufficient as a result of the adhesive strength evaluation, and the durability evaluation results in no occurrence of defects that impair the appearance such as peeling off and foaming. Indicates a level. “◯” indicates that the adhesive strength evaluation and durability evaluation are slightly inferior to “◎”, but it is a level usable as a product. “Δ” indicates that the adhesive strength evaluation and durability evaluation are further inferior to those of “◯”, and it is difficult to use as a product. “X” indicates that the result of the adhesive strength evaluation and the durability evaluation is a level at which the product cannot be used.

（３）評価結果 The resistance value of the ITO film 3 was measured after the adhesive layer 6 was attached to the ITO film 3 using the prepared adhesive sheet 10. Using the prepared pressure-sensitive adhesive sheet 10, A4100 manufactured by Toyobo Co., Ltd. was used as the base material 1, and the pressure-sensitive adhesive layer 6 was attached to the easy adhesion treatment surface. Next, the entire surface of the film 4 (40 mm × 40 mm) in which the ITO film 3 is formed is bonded to the surface of the pressure-sensitive adhesive layer 6 in the state where the dew on the side opposite to the side on which the substrate 1 is bonded. . Then, it was put in an environment of 60 ° C. and 95% RH and left for 1000 hours. Thereafter, the substrate 1 and the adhesive layer 6 were peeled off to expose the ITO film 3. Then, the resistance value between two corners on the diagonal line of the film 4 on which the ITO film 3 was formed was measured using an insulation resistance meter “SK-300” manufactured by Kaise Corporation. The initial resistance value of the ITO film is 700 to 1,000Ω. The results are shown in Tables 3 and 4.

(3) Evaluation results

  As a result of the adhesive evaluation, in the case of Example 10 (crosslinking agent: 0.02 parts by weight) and Example 11 (crosslinking agent: 30 parts by weight), the adhesiveness was lowered (Δ). On the other hand, in the case of Example 8 (crosslinking agent: 0.1 parts by weight) and Example 9 (crosslinking agent: 20 parts by weight), the adhesiveness was good (◯). In Example 12 (crosslinking agent: 1 part by weight) and Example 13 (crosslinking agent: 10 parts by weight), good adhesiveness was indicated (◎). From the above results, the pressure-sensitive adhesive layer 6 of the pressure-sensitive adhesive sheet 10 is good when the pressure-sensitive adhesive contains the isocyanate-based crosslinking agent in a proportion of at least 0.02 parts by weight and not more than 30 parts by weight. It was found that it showed excellent adhesiveness.

  In addition, in Example 18 (MA composition ratio: 5%, BA composition ratio: 90%) and Example 19 (MA composition ratio: 55%, BA composition ratio: 40%), the adhesiveness was lowered ( Δ). On the other hand, in Example 14 (MA composition ratio: 10%, BA composition ratio: 85%) and Example 15 (MA composition ratio: 50%, BA composition ratio: 45%), the adhesiveness was good. (○). Further, in Example 16 (MA composition ratio: 20%, BA composition ratio: 75%) and Example 17 (MA composition ratio: 40%, BA composition ratio: 55%), good adhesiveness was exhibited. (◎). From the above results, it was found that the pressure-sensitive adhesive layer 6 of the pressure-sensitive adhesive sheet 10 exhibits good adhesiveness when the MA composition ratio is at least 5% to 55%. Further, it was found that the pressure-sensitive adhesive layer 6 of the pressure-sensitive adhesive sheet 10 exhibits good adhesiveness by setting the composition ratio of BA to at least 40% to 90%.

  Moreover, in Example 24 (2HEA composition ratio: 0.5%) and Example 25 (2HEA composition ratio: 15%), adhesiveness fell ((triangle | delta)). In addition, in Example 25, the resistance value increased (18 KΩ). On the other hand, in Example 22 (2HEA composition ratio: 1%) and Example 23 (2HEA composition ratio: 10%), the adhesiveness was good (◯). Further, when the composition ratio of 2HEA was 3% (Example 20) and 8% (Example 21), good adhesiveness was shown (（). From the above results, it was found that the pressure-sensitive adhesive layer 6 of the pressure-sensitive adhesive sheet 10 exhibits good adhesiveness by setting the composition ratio of 2HEA to 0.5% or more and 15% or less. It was also found that by setting the composition ratio of 2HEA to 10% or less, the resistance value can be 15 KΩ or less, and corrosion of the ITO film can be prevented.

  Moreover, in the case of the comparative example 1 (without a crosslinking agent), adhesiveness deteriorated (x). On the other hand, in the case of other examples (Examples 1 to 7) containing a crosslinking agent, the adhesive layer 6 of the pressure-sensitive adhesive sheet 10 is good by containing an isocyanate-based crosslinking agent because it shows good adhesiveness. It was found to show adhesiveness. In Comparative Example 2 (without antioxidant), the resistance value deteriorated (20 KΩ). Therefore, it was found that the corrosion of the ITO film can be prevented by adding the antioxidant.

  In addition, as shown in Examples 1 to 5, when left in a high temperature environment (80 ° C. dry), a moist heat environment (60 ° C./95%), and a low temperature environment (−40 ° C.) for 1000 hours, respectively. Even so, it showed good adhesion. From this result, it became clear that the pressure-sensitive adhesive sheet 10 of the present embodiment does not depend on temperature and humidity and exhibits good adhesiveness.

  As a result of measuring the resistance value, when Comparative Examples 8 to 15 (using MA, BA, and AA as pressure-sensitive adhesives) were used, the resistance value of the ITO film 3 was increased (from 100 kΩ). On the other hand, when another example (Example etc.) containing MA, BA, and 2HEA was used as the adhesive, the resistance value of the ITO film 3 was reduced. From the above results, it was found that the pressure-sensitive adhesive layer 6 of the pressure-sensitive adhesive sheet 10 can suppress the corrosion of the ITO film 3 by using at least MA, BA, and 2HEA as the pressure-sensitive adhesive.

  When Example 6 (antioxidant: 0.0004 parts by weight) and Example 7 (antioxidant: 0.8 parts by weight) were used, the resistance value of the ITO film 3 tended to increase ( 18 kΩ). On the other hand, when Example 4 (antioxidant: 0.004 part by weight) and Example 5 (antioxidant 0.4 part by weight) were used, the resistance value of the ITO film 3 was improved (15 kΩ). Furthermore, when Example 2 (antioxidant: 0.04 part by weight) and Example 3 (antioxidant: 0.35 part by weight) were used, the resistance value of the ITO film 3 was further improved (10 kΩ). . In particular, when Example 1 (antioxidant: 0.2 part by weight) was used, the resistance value of the ITO film 3 was particularly improved (8 kΩ). From the above results, it was found that the pressure-sensitive adhesive layer 6 of the pressure-sensitive adhesive sheet 10 can suppress the corrosion of the ITO film 3 by setting the antioxidant (BHT) to at least 0.0004 parts by weight and not more than 0.8 parts by weight.

  In addition, when Comparative Examples 3 to 7 (using an antioxidant other than BHT) were used, the resistance value of the ITO film 3 increased (50 k to 80 kΩ). On the other hand, the resistance value of the ITO film 3 became small in the case of other examples (Example etc.) which used BHT as antioxidant. From the above results, it was found that the adhesive layer 6 of the adhesive sheet 10 can suppress the corrosion of the ITO film 3 by using BHT as an antioxidant. In Comparative Examples 3 to 7, the antioxidant bleeded out, and the resistance value varied greatly depending on the sample. Therefore, Table 3 and Table 4 list the variation range of 50 KΩ to 80 KΩ.

  In particular, when Examples 1 to 5, 8 to 9, and 12 to 24 are used, the resistance of the ITO film 3 is maintained even when the sample is left in an environment of 60 ° C. and 95% RH and left for 1000 hours. The value was 15 kΩ or less. From this result, it is clear that when the adhesive layer 6 of the adhesive sheet 10 of the present embodiment is affixed to the ITO film 3, corrosion of the ITO film 3 can be satisfactorily suppressed and increase in resistance of the ITO film 3 can be suppressed. became. In addition, when Examples 1 to 5, 12, 13, 16, 17, 20, and 21 were used, the tackiness was further improved. In particular, when Examples 1 to 3 were used, the pressure-sensitive adhesive sheet had excellent adhesiveness (◎) and a low resistance value (10 KΩ or less), and the adhesive sheet was able to most prevent corrosion of the ITO film.

1 Film 3 ITO Film 4 Substrate 5, 7 Release Sheet 6 Adhesive Layer 10 Adhesive Sheet

Claims (7)

  A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer containing at least a pressure-sensitive adhesive and a release sheet that is releasably attached to at least one surface of the pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer includes one or more acrylic acid-modified products, A pressure-sensitive adhesive sheet comprising at least a pressure-sensitive adhesive containing at least acrylic acid hydroxy ester, a crosslinking agent, and a phenolic antioxidant.   The pressure-sensitive adhesive sheet according to claim 1, wherein the one or more acrylic acid-modified products are composed of methyl acrylate and n-butyl acrylate.   The pressure-sensitive adhesive sheet according to claim 2, wherein the acrylic acid hydroxy ester is 2-hydroxyethyl acrylate.   The proportion of the methyl acrylate in the pressure-sensitive adhesive is 10% to 50%, the proportion of the n-butyl acrylate is 45% to 85%, and the proportion of the 2-hydroxyethyl acrylate is 1% to 10%. It is the following, The adhesive sheet of Claim 3 characterized by the above-mentioned.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the phenolic antioxidant is butylated hydroxytoluene.   The pressure-sensitive adhesive sheet according to claim 1, wherein the crosslinking agent is an isocyanate-based crosslinking agent.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the ITO film has a resistance value of less than 20 kΩ after 1000 hours have elapsed after the pressure-sensitive adhesive layer is attached to the ITO film.

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