JP7144773B2 - Polyester-based pressure-sensitive adhesive composition, polyester-based pressure-sensitive adhesive, pressure-sensitive adhesive sheet for optical members, substrate-less double-sided pressure-sensitive adhesive sheet for optical members, optical member with pressure-sensitive adhesive layer, optical laminate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester-based pressure-sensitive adhesive composition, and more particularly, to a polyester-based pressure-sensitive adhesive composition containing a hydrolysis inhibitor, which is excellent in durability and blister resistance. be.

Conventionally, polyester resin has excellent heat resistance, chemical resistance, durability, and mechanical strength, so it has been used in a wide range of applications such as films, PET bottles, fibers, toners, electrical parts, and adhesives and pressure sensitive adhesives. It is

Regarding adhesives using polyester resin, when used for laminating optical components, the adhesive is exposed to high temperature and high humidity. I had a problem with the drop.

As a method for solving such problems, for example, in Patent Document 1, a polyester-based pressure-sensitive adhesive composition containing a polyester, a hydrolysis resistant agent, a tackifier, and a cross-linking agent, wherein the acid of the tackifier of 8 or less, the softening point of the tackifier is 80 to 170 ° C., and the tackifier is contained in an amount of 20 to 100 parts by weight with respect to 100 parts by weight of the polyester. system adhesive compositions have been proposed.

On the other hand, in recent years, a display device such as a liquid crystal display (LCD) and an input device such as a touch panel, which is a combination of the display device and a position input device, have been widely used in various fields. 2. Description of the Related Art A transparent adhesive sheet, for example, a substrateless double-sided adhesive sheet is used for laminating optical members such as optical films and substrates.

Here, transparent substrates are required for optical members that constitute optical devices such as touch panels, and glass substrates have been used for some time. Instead of glass substrates such as protective covers and glass substrates, plastic substrates such as polycarbonate resins, acrylic resins, and (cyclic) olefin resins have come to be used.
However, when such a plastic substrate is used, gas and moisture generated from the plastic substrate cause foaming and peeling between the plastic substrate and the pressure-sensitive adhesive layer, resulting in a problem of reduced visibility. rice field.

Therefore, pressure-sensitive adhesives used for bonding optical members are required to have a high level of blistering resistance that can suppress these problems.
In order to improve such blistering resistance, for example, in Patent Document 2, a pressure-sensitive adhesive containing an acrylic polymer and a cross-linking agent, a structural unit derived from an alkyl acrylate monomer having an alkyl group having 4 to 20 carbon atoms 30 to 77% by mass, 20 to 60% by mass of structural units derived from alicyclic group-containing (meth) acrylate monomers, and (meth) adhesive containing 0.1 to 10.0% by mass of structural units derived from acrylic acid agents have been proposed.

JP 2015-134906 A JP 2012-201877 A

However, in the technique disclosed in Patent Document 1, although hydrolysis of the polyester resin can be suppressed under high temperature and high humidity conditions because it contains a hydrolysis resistant agent, it also contains a tackifier, so it is colored at high temperatures. Therefore, it is difficult to use in applications where transparency is required for the pressure-sensitive adhesive layer.

In addition, although the technology disclosed in Patent Document 2 achieves blister resistance under certain conditions, it does not sufficiently satisfy the high level of blister resistance required in the market, and further improvement is desired. It was something.

Under such circumstances, the present invention proposes a highly durable polyester-based pressure-sensitive adhesive that has excellent adhesive physical properties (adhesive strength) and transparency even when the pressure-sensitive adhesive layer is exposed to high temperature and high humidity. It is an object of the present invention to provide a polyester-based pressure-sensitive adhesive composition capable of obtaining a polyester-based pressure-sensitive adhesive having excellent blister resistance.

However, as a result of extensive research in view of such circumstances, the present inventors have found that in a polyester-based pressure-sensitive adhesive composition containing a hydrolysis inhibitor, by using a polyester-based resin having a lower glass transition temperature than usual, Even without using a tackifier, you can obtain a polyester-based adhesive that has excellent adhesive properties, transparency, and blister resistance under conditions where durability is required (under high temperature and high humidity). We found that and completed the present invention.

That is, the gist of the present invention is a polyester pressure-sensitive adhesive containing a polyester resin (A) and a hydrolysis inhibitor (B), wherein the polyester resin (A) has a glass transition temperature of −10° C. or less. A polyester pressure-sensitive adhesive composition characterized by
Further, the present invention relates to a polyester-based pressure-sensitive adhesive, a pressure-sensitive adhesive sheet for optical members, a substrate-less double-sided pressure-sensitive adhesive sheet for optical members, an optical member with a pressure-sensitive adhesive layer, and an optical laminate.

The polyester-based pressure-sensitive adhesive composition of the present invention is excellent in both adhesive properties (adhesive strength) and transparency under conditions where durability is required (under high temperature and high humidity), and is resistant to blistering in harsh environments. It is possible to obtain a pressure-sensitive adhesive that is excellent in adhesiveness and has a moderate tackiness, so that it is excellent in workability and can be suitably used for bonding optical members, particularly for optical members made of plastic materials. It can be suitably used for bonding.

The configuration of the present invention will be described in detail below, but these are examples of preferred embodiments.
In the present invention, the term "carboxylic acid" includes not only carboxylic acid but also carboxylic acid derivatives such as carboxylic acid salts, carboxylic anhydrides, carboxylic acid halides and carboxylic acid esters.

<Polyester resin (A)>
The polyester resin (A) used in the present invention is characterized by having a glass transition temperature of -10°C or lower, preferably -80 to -10°C, particularly preferably -70 to -15°C. , more preferably -70 to -20°C.
When the glass transition temperature exceeds the upper limit, the flexibility is lost, the initial adhesiveness is lowered, it becomes difficult to exhibit sufficient adhesive strength with a pressure of about finger pressure, workability is deteriorated, and the object of the present invention is not achieved. cannot be achieved.
Here, the glass transition temperature (Tg) of the polyester resin (A) is a value measured using a differential scanning calorimeter DSC Q20 manufactured by TA Instruments.
The measurement temperature range is from -90°C to 100°C, and the temperature rise rate is 10°C/min.

The polyester-based resin (A) used in the present invention is obtained by copolymerizing copolymer components containing a polycarboxylic acid component (A1) and a polyol component (A2) as constituent raw materials.

[Polyvalent carboxylic acid component (A1)]
Examples of the polycarboxylic acid component (A1) used in the present invention include:
aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, benzylmalonic acid, diphenic acid, 4,4'-oxydibenzoic acid, and naphthalene dicarboxylic acid;
Malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, thiodipropionic acid , aliphatic dicarboxylic acids such as diglycolic acid;
Alicyclic groups such as 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, and adamantanedicarboxylic acid dicarboxylic acid;
and divalent carboxylic acids such as
These can be used alone or in combination of two or more.

Among these, it is preferable to contain an aromatic dicarboxylic acid, and it is particularly preferable to contain isophthalic acid from the viewpoint of imparting cohesive force.

The content of such aromatic dicarboxylic acid is preferably 50 mol% or less, particularly preferably 5 to 40 mol%, and still more preferably 10 to 30 mol%, based on the total polycarboxylic acid component (A1). %. If the content is too high, the glass transition temperature tends to be high, making it difficult to obtain sufficient adhesive performance.

From the viewpoint of imparting tackiness, it preferably contains an aliphatic dicarboxylic acid, particularly preferably an aliphatic dicarboxylic acid having 4 to 12 carbon atoms, and more preferably contains sebacic acid.

The content of such an aliphatic dicarboxylic acid is preferably 20 mol% or more, particularly preferably 50 mol% to 95 mol%, further preferably 70 to 90 mol%, based on the total polycarboxylic acid component (A1). in mol %. If the content is too low, the glass transition temperature tends to increase and sufficient adhesive strength cannot be obtained. tend to

In the present invention, it is preferable to use an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid in combination as the polyvalent carboxylic acid component (A1) from the viewpoint of the balance of adhesive properties. Dicarboxylic acid/aliphatic dicarboxylic acid = 1/99 to 90/10, particularly preferably aromatic dicarboxylic acid/aliphatic dicarboxylic acid = 5/95 to 49/51, more preferably aromatic dicarboxylic acid/ Aliphatic dicarboxylic acid = 10/90 to 30/70.

In order to increase the number of branch points in the polyester-based resin (A), a polyvalent carboxylic acid having a valence of 3 or more can also be used. , adamantanetricarboxylic acid, and trimesic acid. Among them, it is preferable to use trimellitic acid because gelation is relatively unlikely to occur.
The content of such trivalent or higher polyvalent carboxylic acid is preferably 10 mol % or less, particularly preferably 10 mol % or less, based on the total polyvalent carboxylic acid component (A1), in that the cohesive force of the adhesive can be increased. is 0.1 to 5 mol %, and if the content is too high, gelation tends to occur during the production of the polyester resin (A).

[Polyol component (A2)]
Examples of the polyol component (A2) used in the present invention include:
Ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol , 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1 ,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,6- aliphatic diols such as hexanediol;
1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecanedimethanol, adamantanediol, 2,2,4,4-tetramethyl-1,3 - cycloaliphatic diols such as cyclobutanediol;
4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-, m- and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol and their Aromatic diols such as ethylene oxide and propylene oxide adducts of
dihydric alcohols such as
These can be used alone or in combination of two or more.

Among these, aliphatic diols and alicyclic diols are preferable from the viewpoint of excellent reactivity. Particularly preferable aliphatic diols are ethylene glycol, 1,3-propanediol and 2-methyl-1,3-propane. diol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol; , 4 cyclohexanedimethanol.

A trihydric or higher polyhydric alcohol can also be used for the purpose of increasing the number of branch points in the polyester resin (A). Erythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, adamantanetriol and the like.
The content of such a trihydric or higher polyhydric alcohol is preferably 10 mol % or less, particularly preferably 0.1 to 5 mol %, relative to the entire polyol component (A2), and such a content is too high. and the production of the polyester resin (A) tends to be difficult.

The mixing ratio of the polycarboxylic acid component (A1) and the polyol component (A2) is preferably 1 to 2 equivalents of the polyol component (A2) per equivalent of the polycarboxylic acid component (A1), particularly preferably. is 1.1 to 1.7 equivalents. If the content of the polyol component (A2) is too low, the acid value tends to increase, making it difficult to increase the molecular weight.

The polyester-based resin (A) used in the present invention is produced by arbitrarily selecting the polyvalent carboxylic acid component (A1) and the polyol component (A2) and subjecting them to a polycondensation reaction by a known method in the presence of a catalyst. be done.

In the polycondensation reaction, the esterification reaction is first performed, and then the condensation reaction is performed.

In such an esterification reaction, catalysts are used, and specifically, catalysts such as titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate, antimony-based catalysts such as antimony trioxide, germanium-based catalysts such as germanium dioxide, Catalysts such as zinc acetate, manganese acetate, and dibutyltin oxide can be used, and one or more of these can be used. Among these, antimony trioxide, tetrabutyl titanate, and germanium dioxide are preferable from the viewpoint of balance between high catalytic activity and hue.

The blending amount of the catalyst is preferably 1 to 10,000 ppm, particularly preferably 10 to 5,000 ppm, more preferably 20 to 3,000 ppm, based on the total copolymerization components. If the compounding amount is too small, the polymerization reaction tends to be difficult to proceed sufficiently, and if it is too large, there is no advantage in shortening the reaction time, etc., and side reactions tend to occur easily.

The reaction temperature during the esterification reaction is preferably 160 to 260°C, particularly preferably 180 to 250°C, further preferably 200 to 250°C. If the reaction temperature is too low, the reaction tends not to proceed sufficiently, and if it is too high, side reactions such as decomposition tend to occur. Moreover, the pressure during the reaction may be normal pressure.

After the esterification reaction is performed, a condensation reaction is performed.
As for the reaction conditions of the polycondensation reaction, the same catalyst as used in the above esterification reaction is blended in the same amount, and the reaction temperature is preferably 220 to 280° C. (particularly preferably 230 to 270° C.), It is preferable to gradually depressurize the reaction system and finally carry out the reaction at 5 hPa or less.
If the reaction temperature is too low, the reaction tends not to proceed sufficiently, and if it is too high, side reactions such as decomposition tend to occur.

The polyester resin (A) used in the present invention preferably has a number average molecular weight of 5,000 or more, particularly preferably 10,000 to 100,000, and still more preferably 15,000 to 80,000.
If the number average molecular weight is too low, sufficient cohesion cannot be obtained as an adhesive, and heat resistance and mechanical strength tend to decrease. There is a tendency that it is difficult to exhibit sufficient adhesive strength with a pressure of finger pressure.

The above number average molecular weight is the number average molecular weight in terms of standard polystyrene molecular weight. × 10 ⁶ , theoretical plates: 16,000 plates/line, filler material: styrene-divinylbenzene copolymer, filler particle diameter: 4 µm).

The acid value of the polyether resin (A) is preferably 5 mgKOH/g or less, particularly preferably 1 mgKOH/g or less, still more preferably 0.5 mgKOH/g or less, and particularly preferably 0.2 mgKOH/g or less. be. If the acid value is too high, corrosion occurs when a metal oxide thin film layer is formed on one side of the pressure-sensitive adhesive layer made of the present polyester-based pressure-sensitive adhesive, and the conductivity of the metal oxide film tends to decrease. There is
The acid value of the polyester resin (A) is obtained by neutralization titration based on JIS K0070.

<Hydrolysis inhibitor (B)>
The polyester pressure-sensitive adhesive composition of the present invention contains a hydrolysis inhibitor (B) together with the polyester resin (A). By containing the hydrolysis inhibitor (B), the desired A pressure-sensitive adhesive layer having specific properties can be obtained, and improvement in durability especially under high temperature and high humidity conditions can be expected.

The hydrolysis inhibitor (B) is not particularly limited, and conventionally known ones can be used. For example, it reacts with the carboxylic acid terminal group of the polyester resin (A) to bond compounds, and specific examples include compounds having functional groups such as carbodiimide groups, epoxy groups, and oxazoline groups. Among these, carbodiimide group-containing compounds are preferred because they are highly effective in eliminating the catalytic activity of protons derived from carboxyl terminal groups.

As the carbodiimide group-containing compound, generally known polycarbodiimide having one or more carbodiimide groups (-N=C=N-) in the molecule may be used. In view of this, compounds containing 2 or more carbodiimide groups in the molecule are preferred, and compounds containing 3 or more, further 5 or more, particularly 7 or more carbodiimide groups are preferred. If 30 or more are contained, the molecular structure becomes too large, which tends to be undesirable. It is also preferable to use a high-molecular-weight polycarbodiimide produced by a decarboxylation condensation reaction of a diisocyanate in the presence of a carbodiimidation catalyst.

Examples of such high-molecular-weight polycarbodiimides include those obtained by subjecting the following diisocyanates to a decarboxylation condensation reaction.

Such diisocyanates include, for example, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'- diphenyl ether diisocyanate, 3,3′-dimethyl-4,4′-diphenyl ether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4, 4'-dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate and the like can be mentioned, and these can be used alone or in combination of two or more. Such high-molecular-weight polycarbodiimide may be synthesized or a commercially available product may be used.

Examples of commercially available carbodiimide group-containing compounds include the Carbodilite (registered trademark) series manufactured by Nisshinbo Chemical Co., Ltd. Among them, Carbodilite (registered trademark) V-01, V-03, V-05, V- 07 and V-09 are preferable because of their excellent compatibility with organic solvents.

As said epoxy compound, a glycidyl-ester compound, a glycidyl-ether compound, etc. are preferable, for example.

Specific examples of glycidyl ester compounds include glycidyl benzoate, t-Bu-glycidyl benzoate, glycidyl p-toluate, glycidyl cyclohexanecarboxylate, glycidyl pelargonate, glycyl stearate, and lauric acid. glycidyl ester, glycidyl palmitate, glycidyl behenate, glycidyl versatic acid, glycidyl oleate, glycidyl linoleate, glycidyl linoleate, glycidyl behenoleate, glycidyl stearate, diglycidyl terephthalate, Diglycidyl isophthalate, diglycidyl phthalate, diglycidyl naphthalene dicarboxylate, diglycidyl methyl terephthalate, diglycidyl hexahydrophthalate, diglycidyl tetrahydrophthalate, diglycidyl cyclohexanedicarboxylate, adipic acid diglycidyl ester, diglycidyl succinate, diglycidyl sebacate, diglycidyl dodecanedioate, diglycidyl octadecanedicarboxylate, triglycidyl trimellitate, tetraglycidyl pyromellitic acid, and the like. They can be used alone or in combination of two or more.

Specific examples of glycidyl ether compounds include phenylglycidyl ether, o-phenylglycidyl ether, 1,4-bis(β,γ-epoxypropoxy)butane, 1,6-bis(β,γ- epoxypropoxy)hexane, 1,4-bis(β,γ-epoxypropoxy)benzene, 1-(β,γ-epoxypropoxy)-2-ethoxyethane, 1-(β,γ-epoxypropoxy)-2- benzyloxyethane, 2,2-bis-[р-(β,γ-epoxypropoxy)phenyl]propane and 2,2-bis-(4-hydroxyphenyl)propane and 2,2-bis-(4-hydroxyphenyl ) bisglycidyl polyether obtained by reaction of bisphenol such as methane and epichlorohydrin, and the like, and these can be used alone or in combination of two or more.

As the oxazoline compound, a bisoxazoline compound or the like is preferable. Specifically, for example, 2,2′-bis(2-oxazoline), 2,2′-bis(4-methyl-2-oxazoline), 2,2′-bis(4,4-dimethyl-2- oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4,4'-diethyl-2-oxazoline), 2,2'-bis(4-propyl-2 -oxazoline), 2,2′-bis(4-butyl-2-oxazoline), 2,2′-bis(4-hexyl-2-oxazoline), 2,2′-bis(4-phenyl-2-oxazoline) ), 2,2′-bis(4-cyclohexyl-2-oxazoline), 2,2′-bis(4-benzyl-2-oxazoline), 2,2′-p-phenylenebis(2-oxazoline), 2 , 2′-m-phenylenebis(2-oxazoline), 2,2′-o-phenylenebis(2-oxazoline), 2,2′-p-phenylenebis(4-methyl-2-oxazoline), 2, 2′-p-phenylenebis(4,4-dimethyl-2-oxazoline), 2,2′-m-phenylenebis(4-methyl-2-oxazoline), 2,2′-m-phenylenebis(4, 4-dimethyl-2-oxazoline), 2,2′-ethylenebis(2-oxazoline), 2,2′-tetramethylenebis(2-oxazoline), 2,2′-hexamethylenebis(2-oxazoline), 2,2'-octamethylenebis(2-oxazoline), 2,2'-decamethylenebis(2-oxazoline), 2,2'-ethylenebis(4-methyl-2-oxazoline), 2,2'- Tetramethylenebis(4,4-dimethyl-2-oxazoline), 2,2'-9,9'-diphenoxyethanebis(2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline), 2 ,2'-diphenylenebis(2-oxazoline) and the like can be exemplified, and among these, 2,2'-bis(2-oxazoline) is most preferable from the viewpoint of reactivity with polyester. Further, the above-mentioned bisoxazoline compounds may be used alone or in combination of two or more as long as the objects of the present invention are achieved.

As these hydrolysis inhibitors (B), those with low volatility are preferable, and therefore those with high molecular weight are preferably used.

The content of the hydrolysis inhibitor (B) is preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight, with respect to 100 parts by weight of the polyester resin (A). , more preferably 0.2 to 3 parts by weight. If the amount is too large, turbidity tends to occur due to poor compatibility with the polyester resin (A), and if it is too small, it tends to be difficult to obtain sufficient durability.

In addition, the amount of the hydrolysis inhibitor (B) is preferably optimized according to the acid value of the polyester resin (A), and the polyester resin in the polyester resin composition ( The molar ratio ((b)/(a)) of the total (a) of the acid values of A) and the total (b) of the functional group amount of the hydrolysis inhibitor (B) in the polyester resin composition is 0 .5 ≤ (b)/(a) is preferred, 1 ≤ (b)/(a) ≤ 1,000 is particularly preferred, and 1.5 ≤ (b)/(a) ≤ 100 is more preferred. be.
If the content ratio of (b) to (a) is too high, the compatibility with the polyester resin (A) tends to decrease, and the adhesive strength, cohesive strength, and durability tend to decrease. When the content of b) is low, the moist heat resistance tends to be low.

<Polyester adhesive composition>
The polyester-based pressure-sensitive adhesive composition of the present invention contains the polyester-based resin (A) and the hydrolysis inhibitor (B). Generally, the polyester-based resin (A) is crosslinked using a cross-linking agent (C). It becomes excellent in cohesive strength and exhibits performance as an adhesive. Examples of the cross-linking agent (C) include compounds having functional groups that react with hydroxyl groups and/or carboxyl groups contained in the polyester resin (A), such as polyisocyanate compounds and polyepoxy compounds. Among these, polyisocyanate compounds are particularly preferred because they can achieve a good balance of initial tackiness, mechanical strength, and heat resistance.

Examples of such polyisocyanate compounds include polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate. , tolylene diisocyanate adducts of trimethylolpropane, isocyanate adducts such as hexamethylene diisocyanate adducts and isophorone diisocyanate adducts. The above polyisocyanate compound may also be one whose isocyanate portion is blocked with phenol, lactam, or the like. These crosslinking agents (C) may be used singly or in combination of two or more.

The amount of the cross-linking agent (C) to be blended can be appropriately selected depending on the molecular weight of the polyester resin (A) and the purpose of use. On the other hand, the reactive group contained in the cross-linking agent (C) preferably contains the cross-linking agent (C) in a proportion of 0.2 to 10 equivalents, particularly preferably 0.5 to 5 equivalents, and more preferably is 0.5 to 3 equivalents.
If the number of equivalents of the reactive groups contained in the cross-linking agent (C) is too small, the cohesive force tends to decrease and sufficient heat resistance tends not to be obtained. There is a tendency that sufficient adhesive strength cannot be exhibited with a pressure equivalent to finger pressure.

The polyester-based pressure-sensitive adhesive of the present invention preferably contains substantially no acidic groups, specifically, preferably has an acid value of 10 mgKOH/g or less, particularly preferably 1 mgKOH/g or less, and Preferably, it is 0.1 mgKOH/g or less.
The acid value of the polyester-based pressure-sensitive adhesive can be obtained by the same method as for the acid value of the polyether-based resin (A).

The polyester-based pressure-sensitive adhesive composition of the present invention contains additives such as conventionally known softeners, ultraviolet absorbers, stabilizers, antistatic agents, tackifiers, and other inorganic additives, as long as the effects of the present invention are not impaired. Alternatively, additives such as organic fillers, metal powders, powders such as pigments, and particulates can be added.
In addition, it is preferable not to substantially contain the said tackifier from the viewpoint of durability and transparency.

The polyester pressure-sensitive adhesive composition of the present invention is preferably used as an optical member pressure-sensitive adhesive for bonding optical members, and a pressure-sensitive adhesive layer comprising such a polyester pressure-sensitive adhesive composition is laminated on an optical member. Thus, the pressure-sensitive adhesive layer-attached optical member can be obtained.

Examples of such optical members include ITO electrode films, transparent electrode films such as inorganic or organic conductive films such as polythiophene, polarizing plates, retardation plates, elliptically polarizing plates, optical compensation films, brightness enhancement films, electromagnetic wave shielding films, An infrared absorbing film, an AR (anti-reflection) film, and the like are included. Among these, when the optical member is a transparent electrode film, the effect of the present invention can be remarkably exhibited, and high adhesive strength can be obtained, and the ITO electrode film is particularly preferable. The ITO electrode film is often formed as a thin film on a substrate such as glass or PET. Especially preferred.

It is preferable to further provide a release sheet on the surface of the pressure-sensitive adhesive layer opposite to the optical member surface of the pressure-sensitive adhesive layer-attached optical member. The pressure-sensitive adhesive layer and the adherend are laminated. As such a release sheet, it is preferable to use a silicon-based release sheet.

In addition, the polyester-based adhesive of the present invention can be used as a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive of the present invention on one or both sides of a supporting substrate, and in particular, an optical sheet used for laminating optical members. It is suitable as an adhesive sheet for members.
It is also preferable to use a substrate-less double-sided pressure-sensitive adhesive sheet that does not have a supporting substrate, in terms of excellent transparency and high adhesive strength relative to the thickness of the composition.
In the present invention, the term "sheet" includes "film" and "tape".
The adhesive sheet can be produced, for example, as follows.

<Adhesive sheet>
As a method for producing such a pressure-sensitive adhesive sheet, it can be produced according to a known general method for producing a pressure-sensitive adhesive sheet. Furthermore, the pressure-sensitive adhesive sheet of the present invention having a pressure-sensitive adhesive layer comprising the polyester-based pressure-sensitive adhesive of the present invention on a substrate by applying a polyester-based pressure-sensitive adhesive composition containing a crosslinking agent (C), drying, and curing as necessary. is obtained.
Also, a substrate-less double-sided PSA sheet can be produced by forming a PSA layer on a release sheet and laminating the release sheet on the opposite side of the PSA layer.
When using the obtained pressure-sensitive adhesive sheet or substrate-less double-sided pressure-sensitive adhesive sheet, the release sheet is peeled off from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer and the adherend are bonded together.

Examples of the base material include polyester resins such as polyethylene naphtate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate/isophthalate copolymer; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyvinyl fluoride; Polyethylene fluoride resins such as polyvinylidene fluoride and polyethylene fluoride; polyamides such as nylon 6 and nylon 6,6; polyvinyl chloride, polyvinyl chloride/vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl Vinyl polymers such as alcohol copolymers, polyvinyl alcohol and vinylon; Cellulose resins such as cellulose triacetate and cellophane; Acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate and polybutyl acrylate. polystyrene; polycarbonate; polyarylate; synthetic resin sheets such as polyimide; metal foils of aluminum, copper and iron; paper such as woodfree paper and glassine paper; . These base sheets can be used as a single-layer body or as a multi-layer body in which two or more types are laminated.
Among these, a substrate sheet made of polyethylene phthalate or polyimide is particularly preferable, and polyethylene terephthalate is particularly preferable in that it has excellent adhesion to the pressure-sensitive adhesive. It is preferable in that the adhesion between the material and the adhesive is excellent, the base material can be stably maintained without corroding the metal thin film layer, and the effect of the polyester pressure-sensitive adhesive of the present invention can be exhibited remarkably.
In the present invention, the film in which the ITO electrode film is formed as a thin film on the PET substrate has an adhesive layer on the PET side, and the PET substrate and the polycarbonate film are laminated via the adhesive layer, Furthermore, it is most preferable to form an optical laminate in which an acrylic film is laminated (layer structure: ITO electrode film/PET substrate/adhesive layer/PC film/acrylic film).

As the release sheet, for example, the various synthetic resin sheets, paper, cloth, non-woven fabric, etc. exemplified in the above substrates, which have undergone a release treatment, can be used. As the release sheet, it is preferable to use a silicon-based release sheet.

The thickness of the substrate is, for example, preferably 1 to 1000 μm, particularly preferably 2 to 500 μm, still more preferably 3 to 300 μm.

As the coating method of the pressure-sensitive adhesive composition, for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater and the like may be used.

The conditions for the curing treatment are usually room temperature to 70° C., and the time is usually 1 day to 30 days. Specifically, for example, 23° C. for 1 day to 20 days, preferably 23° C. for 3 days. 14 days, 1 day to 10 days at 40° C., and the like.

As for the drying conditions, the drying temperature is preferably 60 to 140° C., particularly preferably 80 to 120° C., and the drying time is preferably 1 to 30 minutes, particularly preferably 2 to 5 minutes.

The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet and the substrate-less double-sided pressure-sensitive adhesive sheet is preferably 2 to 500 μm, particularly preferably 5 to 200 μm, and still more preferably 10 to 100 μm. If the thickness of the pressure-sensitive adhesive layer is too thin, the adhesive strength tends to decrease. be. In addition, it is preferable to make it 50 micrometers or more when considering impact absorption.

The thickness of the pressure-sensitive adhesive layer is obtained by subtracting the thickness of the constituent members other than the pressure-sensitive adhesive layer from the measured thickness of the entire pressure-sensitive adhesive sheet using "ID-C112B" manufactured by Mitutoyo. value.

The gel fraction of the adhesive layer of the adhesive sheet is preferably 50% or more, particularly preferably 60 to 100%, further preferably 70 to 85%, from the viewpoint of durability and adhesive strength. If the gel fraction is too low, cohesive strength tends to decrease, resulting in a decrease in durability. In addition, if the gel fraction is too high, there is a concern that the cohesive force will increase and the adhesive force will decrease.

The gel fraction is a measure of the degree of cross-linking, and is calculated, for example, by the following method. That is, a pressure-sensitive adhesive sheet (not provided with a separator) in which a pressure-sensitive adhesive layer is formed on a polymer sheet (for example, polyethylene terephthalate film, etc.) serving as a base material is wrapped in a 200-mesh SUS wire mesh, and then immersed in toluene. ℃×24 hours, the weight percentage of the undissolved pressure-sensitive adhesive component remaining in the wire mesh is defined as the gel fraction. However, the weight of the base material is subtracted.

Furthermore, such a pressure-sensitive adhesive sheet may be protected by providing a release sheet outside the pressure-sensitive adhesive layer, if necessary. Further, in a pressure-sensitive adhesive sheet in which an adhesive layer is formed on one side of a base material, the surface of the base material opposite to the pressure-sensitive adhesive layer is subjected to a release treatment so that the pressure-sensitive adhesive layer can be removed using the release-treated surface. can also be protected.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In addition, "parts" and "%" in the examples are based on weight.
The number average molecular weight and glass transition temperature of the polyester resin (A) in the following examples were measured according to the methods described above. The acid value of the polyester resin (A) was measured by neutralization titration according to JIS K0070 after dissolving 0.5 g of the polyester resin in a mixed solvent of 7/3 (weight ratio) (toluene/methanol).

<Production of polyester resin (A)>
[Production Example 1: Production of polyester resin (A-1)]
9.6 parts (0.2 mol) of isophthalic acid and 46.8 parts of sebacic acid as the polyvalent carboxylic acid component (A1) were placed in a reactor equipped with a thermometer, a stirrer, a rectifying column, a nitrogen inlet tube and a vacuum device. (0.8 mol), 27.1 parts (0.9 mol) of neopentyl glycol as the polyol component (A2), 13 parts (0.5 mol) of 1,4-butanediol, 3 parts of 1,6-hexanediol (0.09 mol), 0.5 part (0.01 mol) of trimethylolpropane, and 0.01 part of tetrabutyl titanate as a catalyst are charged, and the internal temperature is gradually raised to 250° C., and the mixture is esterified over 4 hours. reacted. Thereafter, the inner temperature was raised to 260° C., 0.01 part of tetrabutyl titanate was charged as a catalyst, the pressure was reduced to 1.33 hPa, and polymerization was carried out over 3 hours to produce a polyester resin (A-1). The resulting polyester resin (A-1) had a number average molecular weight of 25,000, a glass transition temperature of -50°C and an acid value of 0.4 (mgKOH/g).

[Production Example 2: Production of polyester resin (A-2)]
9.2 parts (0.2 mol) of isophthalic acid and 22.3 parts of sebacic acid as the polyvalent carboxylic acid component (A1) were placed in a reactor equipped with a thermometer, a stirrer, a rectifying column, a nitrogen inlet tube and a vacuum device. (0.4 mol), 20.7 parts (0.4 mol) of azelaic acid, 8.9 parts (0.52 mol) of ethylene glycol as the polyol component (A2), 38.9 parts (0.98 mol) of cyclohexanedimethanol mol), and 0.02 part of germanium dioxide as a catalyst were charged, and the temperature was gradually raised to 250° C., and the esterification reaction was carried out over 4 hours. Thereafter, the internal temperature was raised to 270° C. and the pressure was reduced to 1.33 hPa, and polycondensation reaction was carried out over 3 hours to produce a polyester resin (A-2). The resulting polyester resin (A-2) had a number average molecular weight of 30,000, a glass transition temperature of -25°C and an acid value of 0.7 (mgKOH/g).

[Comparative Production Example 1: Production of polyester resin (A'-1)]
A reactor equipped with a thermometer, a stirrer, a rectifying column, a nitrogen inlet tube and a vacuum device was charged with 21 parts (0.33 mol) of terephthalic acid and 16.6 parts (0 .26 mol), 23 parts (0.41 mol) of adipic acid, 18.4 parts (0.78 mol) of ethylene glycol as the polyol component (A2), 21 parts (0.53 mol) of neopentyl glycol, tetra 0.02 part of butyl titanate was charged, the internal temperature was gradually raised to 250° C., and the esterification reaction was carried out over 4 hours. Thereafter, the inner temperature was raised to 260° C., 0.02 part of tetrabutyl titanate was charged as a catalyst, the pressure was reduced to 1.33 hPa, and polycondensation reaction was carried out over 3 hours to produce a polyester resin (A'-1). The obtained polyester resin (A'-1) had a number average molecular weight of 20,000 and a glass transition temperature of 11.degree. The acid value was 0.6 (mgKOH/g).

<Hydrolysis inhibitor (B)>
The following was prepared as a hydrolysis inhibitor (B).
- (B-1) Carbodiimide group-containing hydrolysis inhibitor (manufactured by Nisshinbo Chemical Co., Ltd.; trade name "Carbodilite V-07")
- (B-2) Carbodiimide group-containing hydrolysis inhibitor (manufactured by Nisshinbo Chemical Co., Ltd.; trade name "Carbodilite V-05")

(Example 1)
The polyester resin (A-1) obtained above is diluted with ethyl acetate to a solid content concentration of 50%, and 100 parts of this polyester resin (A-1) solution (solid content) is added with a hydrolysis inhibitor ( B-1) 2 parts and 6 parts of trimethylolpropane/tolylene diisocyanate adduct (manufactured by Nippon Polyurethane Industry Co., Ltd.; product name "Coronate L55E") as a cross-linking agent (C) are blended, stirred and mixed to obtain A polyester adhesive was obtained.

(Example 2)
A polyester adhesive was obtained in the same manner as in Example 1, except that 2 parts of the hydrolysis inhibitor (B-1) in Example 1 was changed to 2.5 parts of the hydrolysis inhibitor (B-2). rice field.

(Example 3)
In Example 1, the polyester resin (A-1) was changed to the polyester resin (A-2) and the hydrolysis inhibitor (B-1) was changed to 1 part in the same manner as in Example 1. A system adhesive was obtained.

(Comparative example 1)
A polyester-based adhesive was obtained in the same manner as in Example 1, except that the polyester-based resin (A-1) was changed to the polyester-based resin (A'-1).

(Comparative example 2)
A polyester pressure-sensitive adhesive was obtained in the same manner as in Example 1, except that no hydrolysis inhibitor was added.

<Production of PET film with adhesive layer>
Each of the polyester adhesives obtained in Examples 1 to 3 and Comparative Examples 1 and 2 was applied to a polyethylene terephthalate (PET) film having a thickness of 38 μm using an applicator, dried at 100 ° C. for 3 minutes, and adhered. A pressure-sensitive adhesive sheet having an agent layer thickness of 25 μm was obtained. Then, the obtained pressure-sensitive adhesive layer surface was covered with a release-treated PET film (release film), and aging treatment was performed at 40° C. for 5 days to obtain a release film-attached pressure-sensitive adhesive layer-attached PET film.

Initial adhesive strength, durability, and transparency were evaluated using the release film-attached PET film with an adhesive layer. The results are summarized in Table 1.

[Initial adhesive strength]
After cutting the PET film with the adhesive layer with the release film obtained above to 25 × 200 mm in an environment of 23 ° C. and 50% RH, the release film was peeled off, and the adhesive layer side was placed on a SUS plate with a 2 kg roller. After reciprocating and pressing and pasting, leaving it for 10 seconds in the same atmosphere, using an autograph (manufactured by Shimadzu Corporation "Autograph AGS-H 500N"), 180 degree peel strength (N /25 mm) was measured and evaluated according to the following criteria.
(Evaluation criteria)
○: 1 N / 25 mm or more ×: less than 1 N / 25 mm

[durability]
As shown below, the adhesive strength under normal conditions (adhesive strength before wet heat test) and the adhesive strength after being exposed to high temperature and high humidity for a long time (adhesive strength after wet heat test) are measured, (adhesive strength after wet heat test / before wet heat test Adhesive force)×100 (%) value (adhesive force change) was calculated, and durability was evaluated according to the following criteria.
(Evaluation criteria)
○: 50% or more ×: less than 50%

<Adhesive strength before wet heat test>
After cutting the PET film with the adhesive layer with the release film obtained above to 25 × 200 mm in an environment of 23 ° C. and 50% RH, the release film was peeled off, and the adhesive layer side was placed on a SUS plate with a 2 kg roller. After reciprocating and pressing and pasting, leaving it for 30 minutes in the same atmosphere, using an autograph (manufactured by Shimadzu Corporation "Autograph AGS-H 500N"), 180 degree peeling degree (N /25 mm) was measured.

<Adhesive strength after wet heat test>
After cutting the PET film with the adhesive layer with the release film obtained above to 25 × 200 mm in an environment of 23 ° C. and 50% RH, the release film was peeled off, and the adhesive layer side was placed on a SUS plate with a 2 kg roller. was reciprocated and pressure-bonded, and left for 500 hours in an environment of temperature: 85°C and relative humidity of 85%. After returning to room temperature and leaving for 24 hours, using an autograph ("Autograph GS-H 500N" manufactured by Shimadzu Corporation) in an environment of temperature: 23 ° C. and relative humidity of 50%, at a peeling speed of 300 mm / min. 180 degree peel strength (N/25mm) was measured.

[transparency]
The PET film with the pressure-sensitive adhesive layer was left in an environment of 80° C. for 5 days. After that, the temperature was returned to room temperature, and the degree of yellowness b* was measured with a color difference meter and evaluated according to the following criteria.
(Evaluation criteria)
○・・・Less than 1 ×・・・1 or more

From the results of Examples 1 to 3, the polyester-based adhesive obtained by using a polyester-based resin having a glass transition temperature within the desired range and a hydrolysis inhibitor has an adhesive layer exposed to high temperature and high humidity. It can be seen that the adhesive physical properties and transparency are excellent even in the case where the adhesive is applied.
On the other hand, the polyester-based adhesive of Comparative Example 1, which uses a polyester-based resin whose glass transition temperature is higher than the range specified in claim 1 of the present application, has a low initial adhesive strength, and sufficient adhesive strength can be obtained with a pressure of about finger pressure. It can be seen that this is not the case.
In addition, the polyester-based adhesive of Comparative Example 2, which does not contain a hydrolysis inhibitor, causes hydrolysis of the adhesive after being exposed to high temperature and high humidity, resulting in a decrease in cohesive strength, resulting in insufficient adhesive strength. is not obtained.

(Example 4)
The polyester resin (A-1) obtained above is diluted with ethyl acetate to a solid content concentration of 50% by weight, and 100 parts of this polyester resin (A-1) solution (solid content) is added with a hydrolysis inhibitor. (B-1) 1 part and 3 parts of trimethylolpropane/tolylene diisocyanate adduct (manufactured by Nippon Polyurethane Industry Co., Ltd.; product name "Coronate L55E") as a cross-linking agent (C) are blended, stirred and mixed. , to obtain a polyester adhesive.

(Example 5)
A polyester-based adhesive was obtained in the same manner as in Example 4, except that the polyester-based resin (A-1) was changed to the polyester-based resin (A-2).

(Comparative Example 3)
A polyester adhesive was obtained in the same manner as in Example 4, except that the hydrolysis inhibitor (B-1) was not added.

(Comparative Example 4)
A polyester adhesive was obtained in the same manner as in Example 4, except that the hydrolysis inhibitor (B-1) was not added.

<Production of substrate-less double-sided pressure-sensitive adhesive sheet>
The polyester pressure-sensitive adhesives obtained in Examples 4 and 5 and Comparative Examples 3 and 4 were each applied onto a release-treated polyethylene terephthalate (PET) film (release film) having a thickness of 38 μm using an applicator. and dried at 100° C. for 3 minutes to obtain an adhesive sheet having an adhesive layer thickness of 50 μm. Then, the surface of the obtained PSA composition layer was covered with a release-treated PET film and subjected to aging treatment at 40° C. for 5 days to obtain a substrate-less double-sided PSA sheet with a double-sided release film.

One release film of the substrate-less double-sided pressure-sensitive adhesive sheet with a release film on both sides was peeled off, transferred to a polyethylene terephthalate (PET) film with an easy-adhesion layer having a thickness of 100 μm, and PET with a pressure-sensitive adhesive layer with a release film. got the film.
The blister resistance was evaluated using the obtained PET film with a release film and an adhesive layer. Table 2 shows the results.

[Blister resistance]
The PET film with a release film and a pressure-sensitive adhesive layer obtained above is cut into a width of 50 mm × length of 40 mm, the release film is peeled off, and the pressure-sensitive adhesive layer side is placed on a polycarbonate plate at 23 ° C. and a relative humidity of 50%. After applying pressure with a 2 kg rubber roller 2 reciprocations in an atmosphere of , autoclave treatment at 0.5 MPa x 50 ° C. for 20 minutes, then left under conditions of temperature: 85 ° C. and relative humidity of 85% for 3 hours. The generation of air bubbles was confirmed by post-visual observation. Evaluation criteria are as follows.
(Evaluation criteria)
○…No air bubbles exceeding φ0.2 mm △… Air bubbles exceeding φ0.2 mm were generated on less than 1/3 of the entire sticking surface ×… Air bubbles exceeding φ0.2 mm were generated on 1/3 or more of the entire sticking surface or the adhesive layer melted and eluted

From the results of Examples 4 and 5, it can be seen that the polyester pressure-sensitive adhesive of the present invention does not foam even when exposed to high-temperature and high-humidity conditions and is extremely excellent in blistering resistance.
On the other hand, in Comparative Examples 3 and 4, in which a polyester resin having a glass transition temperature within the desired range was used, but a polyester pressure-sensitive adhesive containing no hydrolysis inhibitor was used, exposure to high temperature and high humidity conditions was performed. As a result, foaming occurs and the adhesive layer is eluted, and the blister resistance is not satisfied.

The polyester-based pressure-sensitive adhesive of the present invention can be used as a pressure-sensitive adhesive for electronic parts, a pressure-sensitive adhesive for bonding optical members, a pressure-sensitive adhesive for soft vinyl chloride, and the like.
In particular, the polyester-based pressure-sensitive adhesive of the present invention is excellent in both adhesive physical properties (adhesive strength) and transparency under conditions where durability (under high temperature and high humidity) is required, and is also extremely resistant to blistering. Because of its excellent properties, it can be suitably used for bonding optical members, and in particular, it can be suitably used for bonding optical members made of plastic materials.

Claims (13)

A polyester- based pressure-sensitive adhesive composition containing a polyester-based resin (A) and a hydrolysis inhibitor (B), wherein the glass transition temperature of the polyester-based resin (A) is −10° C. or lower. Yes, the total (a) of the acid value of the polyester resin (A) in the polyester pressure-sensitive adhesive composition and the total (b) of the functional group amount of the hydrolysis inhibitor (B) in the polyester pressure-sensitive adhesive composition A polyester pressure-sensitive adhesive composition characterized in that the molar ratio ((b)/(a)) of is 0.5 or more . 2. The polyester pressure-sensitive adhesive composition according to claim 1, wherein the polyester resin (A) has an acid value of 5 mgKOH/g or less. 3. The polyester pressure-sensitive adhesive composition according to claim 1, wherein the polyester resin (A) has a number average molecular weight of 5,000 to 100,000. 4. The polyester-based pressure-sensitive adhesive composition according to any one of claims 1 to 3 , wherein the polycarboxylic acid component (A1), which is a constituent raw material of the polyester-based resin (A), contains isophthalic acid. 5. The polyester pressure-sensitive adhesive composition according to any one of claims 1 to 4 , wherein the hydrolysis inhibitor (B) is a carbodiimide hydrolysis inhibitor. The polyester adhesive according to any one of claims 1 to 5 , wherein the content of the hydrolysis inhibitor (B) is 0.01 to 10 parts by weight with respect to 100 parts by weight of the polyester resin (A). agent composition. 7. The polyester pressure-sensitive adhesive composition according to any one of claims 1 to 6 , further comprising a cross-linking agent (C). 8. The polyester pressure-sensitive adhesive composition according to any one of claims 1 to 7 , which does not contain a tackifier . A polyester pressure-sensitive adhesive comprising the polyester pressure-sensitive adhesive composition according to any one of claims 1 to 8 crosslinked with a crosslinking agent (C). A pressure-sensitive adhesive sheet for optical members, comprising a pressure-sensitive adhesive layer comprising the polyester-based pressure-sensitive adhesive according to claim 9 . A substrate-less double-sided pressure-sensitive adhesive sheet for optical members, comprising a release sheet on both sides of the pressure-sensitive adhesive layer comprising the polyester-based pressure-sensitive adhesive according to claim 9 . An optical member with a pressure-sensitive adhesive layer, which is obtained by laminating a pressure-sensitive adhesive layer comprising the polyester-based pressure-sensitive adhesive according to claim 9 and an optical member. 10. An optical layered body comprising a metal oxide thin film layer on at least one side of an adhesive layer comprising the polyester-based adhesive according to claim 9 .