JP5540383B2 - Tin-doped indium oxide film adhesive and double-sided adhesive sheet - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive and a double-sided pressure-sensitive adhesive sheet used when various optical members are bonded to a tin-doped indium oxide film.

In a flat panel display, a touch panel, an electromagnetic wave shielding material, and the like, a transparent conductive film having conductivity while having visible light permeability is provided. As the transparent conductive film, a tin-doped indium oxide film (hereinafter referred to as “ITO film”) is widely used.
Various optical members (for example, a liquid crystal panel, a front plate, an antireflection body, etc.) may be disposed adjacent to the ITO film. Conventionally, the ITO film and various optical members have been arranged with a space between them, but in recent years, the optical member may be directly bonded to the ITO film via an adhesive for the purpose of reducing the thickness and improving the image quality. is there. As the pressure-sensitive adhesive, acrylic pressure-sensitive adhesive is often used from the viewpoint of cost and durability, and the pressure-sensitive adhesive is a release sheet on both sides of the pressure-sensitive adhesive layer in order to improve the workability of the bonding process. Is often provided in the form of a double-sided pressure-sensitive adhesive sheet laminated (see, for example, Patent Document 1).

JP 2010-90344 A

However, when an optical member is bonded to the ITO film using a conventionally known acrylic pressure-sensitive adhesive, the conductivity of the ITO film tends to decrease with time.
Then, an object of this invention is to provide the adhesive for ITO films | membranes and double-sided adhesive sheet which can fully suppress the electroconductive fall of an ITO film | membrane.

  The present inventors presumed that when the acrylic adhesive has a carboxy group, the ITO film was corroded and the conductivity decreased, and verification was performed using an acrylic adhesive without a carboxy group. It was not possible to sufficiently suppress the deterioration of the properties. Therefore, as a result of studying other methods for further preventing the corrosion of the ITO film, the following pressure-sensitive adhesive and double-sided pressure-sensitive adhesive sheet have been invented.

That is, this invention has the following aspects.
[1] An adhesive for a tin-doped indium oxide film used when an optical member is bonded to a tin-doped indium oxide film, the acrylic pressure-sensitive adhesive having a (meth) acrylic acid alkyl ester unit, and the acrylic A cross-linking agent that crosslinks the base adhesive main agent, a hindered phenol antioxidant, and a phosphorus antioxidant, and the acrylic adhesive main agent has a carboxy group content of 0 to 1% by mass. A pressure-sensitive adhesive for tin-doped indium oxide films.
[2] The adhesive for tin-doped indium oxide films according to [1], wherein the acrylic adhesive main component has a (meth) acrylic acid hydroxyalkyl ester unit represented by the following formula (1).
(In the formula, R ¹ is a hydrogen atom or a methyl group, and n is an integer of 4 or more.)

[3] Double-sided pressure-sensitive adhesive comprising a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive for tin-doped indium oxide film according to [1] or [2], and a release sheet laminated on both sides of the pressure-sensitive adhesive layer. Sheet.

  The pressure-sensitive adhesive for ITO film and the double-sided pressure-sensitive adhesive sheet of the present invention can sufficiently suppress the decrease in conductivity of the ITO film.

It is sectional drawing which shows one Embodiment of the double-sided adhesive sheet of this invention.

<ITO film adhesive>
The adhesive for ITO film of the present invention is used when sticking an optical member to a tin-doped indium oxide film, and is an acrylic adhesive main agent, a crosslinking agent, a hindered phenol antioxidant, and a phosphorous oxidation. Containing an inhibitor.

(Acrylic adhesive main agent)
The acrylic adhesive main agent consists of an acrylic polymer having a (meth) acrylic acid alkyl ester unit.
The (meth) acrylic acid alkyl ester unit is derived from a (meth) acrylic acid alkyl ester unit.
Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, (meth) Isobutyl acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, ( Iso-octyl acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, (meth) N-dodecyl acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, (meth ) Ethoxyethyl acrylate, cyclohexyl (meth) acrylate include benzyl (meth) acrylate. These may be used individually by 1 type and may use 2 or more types together.
Among the above (meth) acrylic acid alkyl esters, methyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are preferable because of high tackiness.
In the present invention, “(meth) acrylic acid” means containing both “acrylic acid” and “methacrylic acid”.

Moreover, the acrylic adhesive main agent has a crosslinkable acrylic monomer unit. Examples of the crosslinkable acrylic unit include a hydroxy group-containing monomer unit, an amino group-containing monomer unit, a glycidyl group-containing monomer unit, and a carboxy group-containing monomer unit. These monomer units may be one kind or two or more kinds.
The hydroxy group-containing monomer unit is derived from a hydroxy group-containing monomer. Examples of the hydroxy group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate, (Meth) acrylic acid lactones such as (meth) acrylic acid mono (diethylene glycol) (meth) acrylic acid [(mono, di or poly) alkylene glycol] and (meth) acrylic acid monocaprolactone.
Examples of the amino group-containing monomer unit include those derived from amino group-containing monomers such as (meth) acrylamide and allylamide.
Examples of the glycidyl group-containing monomer unit include those derived from glycidyl group-containing monomers such as glycidyl (meth) acrylate.
Carboxy group-containing monomer units are derived from α, β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, grataconic acid, or anhydrides thereof. Is mentioned.
Among these, since it is hard to corrode ITO film | membrane and can suppress electroconductivity fall more, a hydroxyl-group containing monomer unit is preferable, and the (meth) acrylic-acid hydroxyalkyl unit represented by the said Formula (1) is more. Preferably, 4-hydroxybutyl (meth) acrylate is particularly preferable.

  The content of the crosslinkable acrylic monomer unit in the acrylic adhesive main agent is preferably 0.01 to 20% by mass, and more preferably 0.5 to 10% by mass. If the content of the crosslinkable acrylic monomer unit is not less than the lower limit, the cohesive force can be sufficiently increased, and if the content is not more than the upper limit, sufficient adhesive strength can be ensured.

Moreover, since the acidity will become strong when the adhesive for ITO films has many carboxy groups, it will become easy to corrode an ITO film. Therefore, the content rate of the carboxy group in the adhesive for ITO films is 0 to 1% by mass, preferably 0 to 0.5% by mass, and more preferably not contained at all. If the content ratio of the carboxy group is 1% by mass or less, it is almost consumed when the acrylic pressure-sensitive adhesive main agent is crosslinked with a crosslinking agent. Absent.
In order to make the content ratio of the carboxy group in the adhesive for ITO film within the above range, the content of the carboxy group-containing monomer unit should be as small as possible or not have the carboxy group-containing monomer unit. .

(Crosslinking agent)
A crosslinking agent crosslinks the said acrylic adhesive main ingredient.
Examples of the crosslinking agent include isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds.
Here, the isocyanate compound is a crosslinking agent that reacts with a hydroxy group, an amino group, or a carboxy group.
Epoxy compounds are crosslinking agents that react with hydroxy groups, amino groups, glycidyl groups, and carboxy groups.
Oxazoline compounds are crosslinkers that react with carboxy groups.
The aziridine compound is a crosslinking agent that reacts with a hydroxy group or a carboxy group.
The metal chelate compound is a crosslinking agent that reacts with a hydroxy group or a carboxy group.
A butylated melamine compound is a cross-linking agent that reacts with a hydroxy group or a carboxy group.

When the acrylic pressure-sensitive adhesive only has a hydroxy group-containing monomer unit, among the above-mentioned crosslinking agents, the acrylic pressure-sensitive adhesive can be easily cross-linked, so that isocyanate compounds, epoxy compounds, aziridine compounds, metal chelate compounds, butylated melamine Compounds are preferred, and isocyanate compounds are particularly preferred because of their high reactivity with hydroxy groups.
Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.
A crosslinking agent may be used individually by 1 type, and may use 2 or more types together. It is preferable that the content of the crosslinking agent is appropriately selected according to the desired pressure-sensitive adhesive properties.

  In the case where the adhesive for ITO film is a combination of a hydroxyl group-containing monomer unit and an isocyanate compound-based crosslinking agent such as hexamethylene diisocyanate, it is preferable to contain a catalyst in order to promote the reaction of the crosslinking agent. . Examples of the catalyst include amine catalysts (for example, triethylenediamine, normal ethyl morpholine, ethylenediamine), and organic tin catalysts (for example, dibutyltin dilaurate).

(Hindered phenolic antioxidant)
A hindered phenolic antioxidant consists of a compound which has a substituent in the ortho position of the hydroxyl group of phenol.
Specific examples of the hindered phenol antioxidant include pentaerythritol-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate), thiodiethylene-bis (3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N′-hexane-1,6-diylbis ( 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide), diethyl ((3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl) methyl) phosphate, 3,3 ', 3 ″, 5,5 ′, 5 ″ -hexa-t-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl) tri-p-cresol, ethyl Renbis (oxyethylene) bis (3- (5-t-butyl-4-hydroxy-m-tolyl) propionate), hexamethylene-bis (3- (3,5-di-t-butyl-4-hydroxyphenyl) Propionate), 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 1,3,5-tris ((4-tert-butyl-3-hydroxy-2,6-xylyl) methyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione 2,6-di-t-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol, 3,9-bis (2- (3- (3 -T-butyl-4-hydroxy-5-methylphenyl Propionyloxy) -1,1-dimethylethyl) -2,4,8,10-spiro (5,5) undecane. These may be used individually by 1 type and may use 2 or more types together.
Among the hindered phenol-based antioxidants, pentaerythritol-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) is preferable because the decrease in the conductivity of the ITO film can be further suppressed.

  The content of the hindered phenol-based antioxidant is preferably 0.01 to 5.0 parts by mass, and 0.05 to 1.0 parts by mass with respect to 100 parts by mass of the acrylic adhesive main agent. More preferred. If the content of the hindered phenol-based antioxidant is equal to or higher than the lower limit value, it is possible to further suppress the decrease in the conductivity of the ITO film, and if the content is equal to or lower than the upper limit value, the adhesive force can be easily adjusted. On the other hand, if the content of the hindered phenolic antioxidant in the pressure-sensitive adhesive layer is large, the hindered phenolic antioxidant may recrystallize and precipitate. Precipitation due to crystallization does not occur.

(Phosphorus antioxidant)
Phosphorus antioxidant consists of phosphoric acid, phosphorous acid, or these ester (phosphite, phosphonite).
Examples of phosphorus antioxidants include tris (2,4-di-t-butylphenyl) phosphite, bis (2,4-bis (1,1-dimethylethyl) -6-methylphenyl) ethyl ester Phosphoric acid, tetrakis (2,4-di-t-butylphenyl) (1,1-biphenyl) -4,4′-diylbisphosphonite, bis (2,4-di-t-butylphenyl) pentaerythritol Diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,4-dicumylphenyl) pentaerythritol-diphosphite, tetrakis (2,4-t- Butylphenyl) (1,1-biphenyl) -4,4′-diylbisphosphonite, di-t-butyl-m-cresyl-phosphonite, etc. . These may be used individually by 1 type and may use 2 or more types together.
Among phosphorus-based antioxidants, tris (2,4-di-t-butylphenyl) phosphite is preferable because it can further suppress the decrease in conductivity of the ITO film.

  The content of the phosphorus antioxidant is preferably 0.01 to 5.0 parts by mass, more preferably 0.05 to 1.0 parts by mass with respect to 100 parts by mass of the acrylic adhesive main agent. If the content of the phosphorus-based antioxidant is equal to or higher than the lower limit value, it is possible to further suppress the decrease in the conductivity of the ITO film, and if the content is equal to or lower than the upper limit value, it is easy to adjust the adhesive strength. On the other hand, if the content of the phosphorus-based antioxidant in the pressure-sensitive adhesive layer is large, the phosphorus-based antioxidant may recrystallize and precipitate. Does not occur.

  The mass ratio of the hindered phenolic antioxidant to the phosphorus antioxidant is preferably 1: 1 to 1: 3. If the mass ratio of the hindered phenolic antioxidant and the phosphorus antioxidant is within the above range, the synergistic effect by combining the hindered phenolic antioxidant and the phosphorus antioxidant is sufficiently exhibited. Further, it is possible to further suppress the decrease in the conductivity of the ITO film.

(Antistatic agent)
The adhesive may contain an antistatic agent. If an antistatic agent is included in the adhesive, it can be applied to bonding of optical members that dislike static electricity.
The antistatic agent may be an inorganic compound or an organic compound. For example, inorganic compounds such as sodium sulfate, sodium carbonate, lithium carbonate, sodium metasilicate, sodium tripolyphosphate, sodium metaphosphate, anionic surfactants such as sulfonate, sulfate, carboxylate, phosphate, Examples include cationic surfactants, nonionic surfactants such as polyethylene glycol, glycerin, and sorbit, amphoteric surfactants, polymer electrolytes, and conductive resins.
As the antistatic agent for the inorganic compound, sodium hydrogen carbonate or sodium chloride is preferable, and sodium hydrogen carbonate is preferable from the viewpoint of durability of the antistatic effect.
Among the organic compound antistatic agents, examples of the cationic surfactant include quaternary ammonium chloride, quaternary ammonium nitrate, and quaternary ammonium sulfate. Examples of amphoteric surfactants include alkyl betaine type, alkyl imidazoline type, and alkyl alanine type compounds. Examples of the conductive resin include polyvinyl benzyl type cations and polyacrylic acid type cations.
The content of the antistatic agent in the pressure-sensitive adhesive is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the acrylic adhesive main agent. . If the content of the antistatic agent is equal to or higher than the lower limit value, the antistatic property can be sufficiently exerted, and if the content is equal to or lower than the upper limit value, a decrease in adhesiveness can be prevented.

(Additive)
Further, the ITO film pressure-sensitive adhesive may contain other additives such as a tackifier, a silane coupling agent, a UV absorber, a light stabilizer such as a hindered amine compound, and a filler as necessary. Good.
Examples of the tackifier include rosin resin, terpene resin, terpene phenol resin, coumarone indene resin, styrene resin, xylene resin, phenol resin, and petroleum resin.
Examples of the silane coupling agent include mercaptoalkoxysilane compounds (for example, mercapto group-substituted alkoxy oligomers).
Examples of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds.

<Double-sided adhesive sheet>
One embodiment of the double-sided pressure-sensitive adhesive sheet of the present invention will be described.
In FIG. 1, sectional drawing of the double-sided adhesive sheet of this embodiment is shown. The double-sided pressure-sensitive adhesive sheet 10 of the present embodiment includes a pressure-sensitive adhesive layer 11, a first release sheet 12 laminated on one surface of the pressure-sensitive adhesive layer 11, and a second layer laminated on the other surface of the pressure-sensitive adhesive layer 11. The release sheet 13 is provided.

(Adhesive layer)
The pressure-sensitive adhesive layer 11 is a layer made of the pressure-sensitive adhesive for ITO film.
The thickness of the pressure-sensitive adhesive layer 11 is preferably 10 to 500 μm, and more preferably 20 to 400 μm. If the thickness of the pressure-sensitive adhesive layer 11 is not less than the lower limit value, sufficient adhesive force can be secured, and if the thickness is not more than the upper limit value, the pressure-sensitive adhesive layer 11 can be easily formed.

(First release sheet and second release sheet)
The first release sheet 12 and the second release sheet 13 are sheets having releasability on at least one side.
As the first release sheet 12 and the second release sheet 13, a peelable laminated sheet having a release sheet substrate and a release agent layer provided on one side of the release sheet substrate, or a polyethylene film, Examples thereof include polyolefin films such as polypropylene films.
Papers and polymer films are used as the release sheet substrate in the peelable laminate sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition type or condensation type silicone release agent or a long-chain alkyl group-containing compound is used. In particular, an addition type silicone release agent having high reactivity is preferably used.
Specific examples of silicone release agents include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone, KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Is mentioned. Further, the silicone-based release agent may contain a silicone resin that is an organosilicon compound having a SiO ₂ unit and (CH ₃ ) ₃ SiO _1/2 unit or CH ₂ ═CH (CH ₃ ) SiO _1/2 unit. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone, KS-3800, X92-183, manufactured by Shin-Etsu Chemical Co., Ltd., and the like.
The first release sheet 12 and the second release sheet 13 are preferably different in peelability. If the peelability between the first release sheet 12 and the second release sheet 13 is different, it can be easily peeled off from one of the release sheets, so that the work of attaching the adhesive layer 11 to the ITO film can be facilitated. In addition, peelability is adjusted with the kind of release agent.

(how to use)
In the double-sided pressure-sensitive adhesive sheet 10, the first release sheet 12 is peeled to expose one surface of the pressure-sensitive adhesive layer 11, and then an ITO film is bonded to the pressure-sensitive adhesive layer 11. In general, the ITO film is not a single layer and is provided on one side of a base material such as a polyethylene terephthalate film.
Next, the second release sheet 13 is peeled to expose the other surface of the pressure-sensitive adhesive layer 11, and an optical member (for example, a liquid crystal panel, a front plate, an antireflection body, etc.) is bonded to the pressure-sensitive adhesive layer 11. Thereby, the ITO film and the optical member are bonded.
Moreover, after peeling the 1st peeling sheet 12 and bonding the optical member which does not have an ITO film | membrane to the surface which exposed one side of the adhesive layer 11, the 2nd peeling sheet 13 is peeled. Then, the other surface of the pressure-sensitive adhesive layer 11 may be exposed, and an ITO film may be bonded to the pressure-sensitive adhesive layer 11.
Depending on the configuration of the touch panel or the like, the ITO layer may be bonded to both sides of the pressure-sensitive adhesive layer 11.

(Production method)
The double-sided pressure-sensitive adhesive sheet 10 is manufactured by the following manufacturing method, for example.
That is, first, the pressure-sensitive adhesive layer-forming coating solution containing the ITO film pressure-sensitive adhesive and solvent is applied to the surface of the first release sheet 12 having releasability. Here, examples of the solvent include methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, toluene, n-hexane, n-butyl alcohol, methyl isobutyl ketone, methyl butyl ketone, ethyl butyl ketone, cyclohexanone, ethyl acetate, butyl acetate, Propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, N-methyl-2-pyrrolidone and the like are used. These may be used alone or in combination of two or more.
The coating method for the adhesive layer forming coating solution can be appropriately selected from knife coaters, micro bar coaters, air knife coaters, reverse roll coaters, reverse gravure coaters, vario gravure coaters, die coaters, curtain coaters and the like. .
Next, the applied pressure-sensitive adhesive layer forming coating solution is heated to evaporate the solvent of the pressure-sensitive adhesive layer forming coating solution, thereby forming the pressure-sensitive adhesive layer 11.
Subsequently, the 2nd peeling sheet 13 is laminated | stacked on the surface on the opposite side to the 1st peeling sheet 12 of the adhesive layer 11, and the double-sided adhesive sheet 10 is obtained.

(Function and effect)
As a result of investigation by the present inventors, even when the pressure-sensitive adhesive layer 11 made of the above-mentioned pressure-sensitive adhesive for ITO film is brought into contact with the ITO film, the ITO film is hardly corroded, and the decrease in conductivity is suppressed.

Example 1
As a crosslinking agent, 100 parts by mass of an acrylic adhesive main agent having 4.5% by mass of 4-hydroxybutyl acrylate unit (4-HBA), 60% by mass of butyl acrylate unit and 35.5% by mass of methyl acrylate unit. 0.3 parts by mass of a tolylene diisocyanate compound (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L), pentaerythritol-tetrakis (3- (3,5-di-t-butyl-) as a hindered phenol antioxidant 0.7 parts by mass of 4-hydroxyphenyl) propionate (BASF Japan Ltd., IRGANOX1010), and tris (2,4-di-t-butylphenyl) phosphite (BASF Japan Ltd.) as a phosphorus-based antioxidant , IRGAFOS168) is blended in an amount of 0.5 parts by mass, and the adhesive for ITO film (carboxy group) The content ratio was 0% by mass).
The above-mentioned adhesive for ITO film was coated with a knife coater on the first release sheet [Oji Special Paper Co., Ltd., 38 μRL-07 (2)] provided with a release agent layer on one side of a polyethylene terephthalate film, A pressure-sensitive adhesive layer was formed by heating at 100 ° C. for 3 minutes.
A second release sheet [manufactured by Oji Specialty Paper Co., Ltd., 38 μRL-07 (L)] provided with a release agent layer having a higher release property than the first release sheet on one side of the polyethylene terephthalate film. Were laminated to obtain a double-sided PSA sheet.

(Example 2)
A double-sided pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the amount of hindered phenolic antioxidant was changed to 0.05 parts by mass and the amount of phosphorus antioxidant was changed to 0.1 parts by mass. Obtained.

(Example 3)
A double-sided PSA sheet was obtained in the same manner as in Example 1 except that the 4-hydroxybutyl acrylate unit was changed to 2-hydroxyethyl acrylate unit (2-HEA).

Example 4
A double-sided PSA sheet was obtained in the same manner as in Example 2 except that the 4-hydroxybutyl acrylate unit was changed to a 2-hydroxyethyl acrylate unit (2-HEA) part.

(Comparative Example 1)
A double-sided PSA sheet was obtained in the same manner as in Example 1 except that the hindered phenol antioxidant and the phosphorus antioxidant were not blended.

(Comparative Example 2)
A double-sided PSA sheet was obtained in the same manner as in Example 1 except that the amount of the hindered phenol-based antioxidant was 1.0 part by mass and no phosphorus-based antioxidant was added.

(Comparative Example 3)
A double-sided PSA sheet was obtained in the same manner as in Example 1 except that the amount of the phosphorus-based antioxidant was 1.0 part by mass and the hindered phenol-based antioxidant was not blended.

(Comparative Example 4)
A double-sided PSA sheet was obtained in the same manner as in Example 1 except that the 4-hydroxybutyl acrylate unit was changed to an acrylic acid unit (AA).

[Evaluation]
By the adhesive layer of the obtained double-sided pressure-sensitive adhesive sheet, a laminate having an ITO film provided on one side of a polyethylene terephthalate film and polyethylene terephthalate were bonded together to obtain a transparent laminate. In that case, it arrange | positioned so that an adhesive layer and an ITO film | membrane may contact | connect.
Next, after measuring the resistance value of the ITO film of the obtained transparent laminate, it was left in a moist heat environment at a temperature of 60 ° C. and a relative humidity of 90%, and was heated and humidified. Then, the resistance value of the ITO film was measured at processing times of 240 hours, 500 hours, and 1000 hours, and the rate of increase in the ITO film resistance value was calculated from the formula of (resistance value after processing / resistance value before processing) × 100. Asked. The obtained results are shown in Table 1.

The double-sided pressure-sensitive adhesive sheets of Examples 1 to 4 containing both a hindered phenol-based antioxidant and a phosphorus-based antioxidant had a small increase in the resistance value of the ITO film, and a decrease in conductivity was suppressed.
On the other hand, the double-sided pressure-sensitive adhesive sheet of Comparative Example 1 that did not contain both the hindered phenol-based antioxidant and the phosphorus-based antioxidant had a large increase in the resistance value of the ITO film, and the decrease in conductivity was suppressed. There wasn't.
Moreover, Example 3 containing both a hindered phenolic antioxidant and a phosphorus antioxidant is Comparative Example 2 which is only a hindered phenolic antioxidant and has a high content of hindered phenolic antioxidants. The rate of increase in resistance value was smaller than that of Comparative Example 3 in which only the phosphorus-based antioxidant and the content of the phosphorus-based antioxidant were large. From this, it was found that the decrease in the conductivity of the ITO film was suppressed by the synergistic effect of the hindered phenol-based antioxidant and the phosphorus-based antioxidant.
Further, in comparison with Example 1 and Example 3 and Example 2 and Example 4, when 4-hydroxybutyl acrylate unit was used as the crosslinkable acrylic monomer unit, 2-hydroxyethyl acrylate unit It turned out that the electroconductive fall of the ITO film | membrane is suppressed rather than the case where is used.

DESCRIPTION OF SYMBOLS 10 Double-sided adhesive sheet 11 Adhesive layer 12 1st peeling sheet 13 2nd peeling sheet

Claims (3)

An adhesive for tin-doped indium oxide film used when sticking an optical member to a tin-doped indium oxide film,
Containing an acrylic pressure-sensitive adhesive having a (meth) acrylic acid alkyl ester unit, a crosslinking agent for crosslinking the acrylic pressure-sensitive adhesive, a hindered phenol-based antioxidant, and a phosphorus-based antioxidant; The adhesive agent for tin-doped indium oxide films, wherein the adhesive main agent is an adhesive having a carboxy group content of 0 to 1% by mass. The adhesive for tin-doped indium oxide films according to claim 1, wherein the acrylic adhesive main component has a (meth) acrylic acid hydroxyalkyl ester unit represented by the following formula (1).

(In the formula, R ¹ is a hydrogen atom or a methyl group, and n is an integer of 4 or more.)   A double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive for tin-doped indium oxide film according to claim 1 and a release sheet laminated on both surfaces of the pressure-sensitive adhesive layer.

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