JP2022111238A - Polyester-based adhesive, adhesive sheet for optical member and polyester-based adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester-based adhesive having excellent adhesiveness to an adherend, especially a polycarbonate base material and having a high refractive index, to provide an adhesive sheet for an optical member and to provide a polyester-based adhesive composition.

SOLUTION: A polyester-based adhesive, which is composed of [I] an adhesive composition containing (A) a polyester-based resin, has an adhesive strength (α) as given below of 10 N/25 mm or more and a refractive index of 1.530 or more. The adhesive strength (α): when a polyester-based adhesive is formed on a base material into an adhesive sheet, 180 degree peeling strength (N/25 mm) at a peeling speed of 300 mm per minute for an adherend in a measurement after the lapse of 24 hours after attaching the adhesive sheet to an adherend of a polycarbonate plate and subjecting the same to autoclave treatment at 50°C and 0.5 MPa for 20 minutes.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a polyester-based pressure-sensitive adhesive, more specifically, a polyester-based pressure-sensitive adhesive having a high refractive index and excellent adhesive strength to various adherends, particularly polycarbonate materials, furthermore, a pressure-sensitive adhesive sheet for optical members, and a polyester pressure-sensitive adhesive composition for obtaining these.

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

In recent years, display devices such as liquid crystal displays (LCDs) and input devices such as touch panels that are used in combination with the display devices have become widely used. A transparent adhesive sheet is used for laminating optical members such as films and substrates.

Furthermore, a light diffusion sheet is used to improve the visibility of the liquid crystal display device. The light diffusing sheet is made of a transparent resin material and a filler, and uses a difference in refractive index between the resin material and the filler to develop diffusibility. The optical member of the liquid crystal display device is incorporated into the liquid crystal display device using an adhesive, and it is desired that the refractive index of the adhesive layer is higher for light diffusion.
In addition, since the refractive index of the optical film is generally higher than that of the pressure-sensitive adhesive, there is a problem that reflection occurs at the interface and the light extraction property of the display device is lowered. Therefore, from the viewpoint of light extraction efficiency, it is desired that the refractive index of the pressure-sensitive adhesive is higher.

Acrylic resin pressure-sensitive adhesives are generally used for bonding optical members as described above. It does not have a high refractive index.
Therefore, Patent Document 1 proposes a polyester-based pressure-sensitive adhesive instead of the acrylic resin pressure-sensitive adhesive.

JP 2009-25575 A

However, in the technique disclosed in Patent Document 1, the adhesive composition contains a polyester-based resin having a high refractive index to some extent. There is a demand for a polyester resin with a high refractive index.

Therefore, in the present invention, in such a background, a polyester-based pressure-sensitive adhesive having excellent adhesive strength to an adherend, particularly a polycarbonate material, and a high refractive index, a pressure-sensitive adhesive sheet for optical members, and a method for obtaining these The object of the present invention is to provide a polyester pressure-sensitive adhesive composition.

However, as a result of extensive research in view of such circumstances, the present inventors have found that in a pressure-sensitive adhesive composed of a pressure-sensitive adhesive composition containing a polyester resin, it has been difficult to achieve both high adhesiveness and high The present invention was completed by discovering a polyester pressure-sensitive adhesive that also has a refractive index.

That is, the present invention provides a polyester-based pressure-sensitive adhesive comprising a pressure-sensitive adhesive composition [I] containing a polyester-based resin (A), wherein the following adhesive strength (α) is 10 N/25 mm or more and the refractive index is 1 The first gist of the invention is a polyester pressure-sensitive adhesive having a viscosity of 0.530 or more.
Adhesive strength (α): When a polyester-based adhesive is formed on a substrate to form an adhesive sheet, it is attached to an adherend of a polycarbonate plate and autoclaved at 50 ° C. and 0.5 MPa for 20 minutes, followed by 24 hours. 180 degree peel strength (N/25 mm) at a peel rate of 300 mm/min to the adherend afterward.

Furthermore, the second aspect of the present invention is a pressure-sensitive adhesive sheet for optical members having a pressure-sensitive adhesive layer comprising the polyester-based pressure-sensitive adhesive.

Further, the present invention contains a polyester resin (A), a hydrolysis inhibitor (B) and a cross-linking agent (C), and the polyester resin (A) is a structural site derived from an aliphatic polycarboxylic acid and a polyester-based pressure-sensitive adhesive composition containing a structural moiety derived from an aromatic polyhydric alcohol.

Further, the present invention provides a polyester-based pressure-sensitive adhesive comprising a pressure-sensitive adhesive composition containing a polyester-based resin (A) and an inorganic oxide (E), wherein the following adhesive strength (β) is 5 N/25 mm or more, and A fourth aspect is a polyester pressure-sensitive adhesive having a refractive index of 1.530 or more.
Adhesive strength (β): When a polyester-based adhesive is formed on a substrate to form an adhesive sheet, it is attached to an adherend of a glass plate and left at 23 ° C. and 50% RH for 30 minutes. 180 degree peel strength (N/25 mm) at a peel speed of 300 mm/min to the body.

In the present invention, when applying a polyester resin with a high glass transition temperature to an adhesive, rigid structures such as aromatics are eliminated as much as possible, and by introducing an alkyl group-derived component, the glass transition temperature is lowered and a soft adhesive is used. It is necessary to convert Further, fine adjustment of the glass transition temperature is generally performed by adjusting an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid, and introduction of an aromatic diol is hesitant. On the other hand, in order to increase the refractive index, it is effective to introduce a structure with a high electron density, that is, an aromatic ring, etc., but as described above, the introduction of an aromatic ring is not suitable for application to adhesives. However, in the present invention, by selecting the acid component and the alcohol component that constitute the polyester resin, it is possible to achieve both a high refractive index and adhesive performance, which have been contradictory in the past.

The polyester-based pressure-sensitive adhesive of the present invention has excellent adhesion to adherends, particularly polycarbonate materials, and has a high refractive index, and is useful as a pressure-sensitive adhesive sheet for optical members.

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 acids" includes not only carboxylic acids but also carboxylic acid derivatives such as carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides and carboxylic acid esters.

The polyester-based pressure-sensitive adhesive of the present invention comprises the pressure-sensitive adhesive composition [I] containing the polyester-based resin (A), that is, the pressure-sensitive adhesive composition [I] is cured.
The polyester-based pressure-sensitive adhesive has an adhesive strength (α) of 10 N/25 mm or more and a refractive index of 1.530 or more as measured below.
Adhesive strength (α): When a polyester-based adhesive is formed on a substrate to form an adhesive sheet, it is attached to an adherend of a polycarbonate plate and autoclaved at 50 ° C. and 0.5 MPa for 20 minutes, followed by 24 hours. 180 degree peel strength (N/25 mm) at a peel rate of 300 mm/min to the adherend afterward.

Specifically, the adhesive strength (α) can be measured in the following manner, for example.

That is, the adhesive composition [I] was applied to a polyethylene terephthalate (PET) film having a thickness of 50 μm using an applicator and dried at 100° C. for 3 minutes to form an adhesive composition layer (thickness of 25 μm). Then, the surface of the obtained pressure-sensitive adhesive composition layer is covered with a release-treated PET film (release film) and subjected to aging treatment at 40 ° C. for 10 days to obtain a pressure-sensitive adhesive sheet with a release film. The release film was peeled off, and a 2 kg roller was reciprocated twice to adhere to the adherend of the polycarbonate plate, and after autoclaving at 50 ° C. and 0.5 MPa for 20 minutes, after 24 hours, the peel speed was 300 mm / Adhesive strength (α) is obtained by measuring 180 degree peel strength (N/25 mm) at min.

In the present invention, the adhesive strength (α) of the polyester adhesive is 10 N/25 mm or more, preferably 15 N/25 mm or more, and particularly preferably 20 N/25 mm or more. If the adhesive strength (α) is too smaller than the above range, the adhesiveness will be poor and the adhesion reliability will be lowered. The upper limit of the adhesive strength (α) is usually 200 N/25 mm, preferably 100 N/25 mm, particularly preferably 80 N/25 mm.

Further, in the present invention, the refractive index of the polyester adhesive is 1.530 or more, preferably 1.530 to 1.650, more preferably 1.540 to 1.640, particularly preferably 1.550. to 1.630, particularly preferably 1.560 to 1.620. If the refractive index is too smaller than the above range, the effect of the present invention cannot be exhibited, and interface reflection may occur when laminated with an optical film, which may cause problems such as a decrease in brightness. If it is too large, the refractive index becomes higher than that of the optical film, and interface reflection occurs when laminated with the optical film, which tends to cause problems such as a decrease in brightness.

The refractive index in the present invention is the refractive index for the D line (589 nm) at 23° C., and is measured using an Abbe refractometer DR-M4 manufactured by Atago.

In the polyester-based pressure-sensitive adhesive of the present invention, in order to satisfy the above adhesive strength and refractive index, it is preferable to form the pressure-sensitive adhesive using the pressure-sensitive adhesive composition [I] containing the polyester-based resin (A). , The adhesive composition [I] preferably contains the following polyester resin (A), hydrolysis inhibitor (B) and cross-linking agent (C) from the viewpoint of adhesive strength and durability, It is preferable to further contain a plasticizer (D) from the viewpoint of increasing initial adhesion, and it is preferable to further contain an inorganic oxide (E) from the viewpoint of improving the refractive index.
Hereinafter, each component will be described in order.

<Polyester resin (A)>
The polyester-based resin (A) used in the present invention is obtained by copolymerizing copolymerization components containing polyhydric carboxylic acids (A1) and polyhydric alcohols (A2) as constituent raw materials. Among them, those containing a structural site derived from an aliphatic polycarboxylic acid and a structural site derived from an aromatic polyhydric alcohol are preferable from the viewpoint of the balance between adhesive strength and refractive index.

[Polyvalent carboxylic acids (A1)]
Examples of polyvalent carboxylic acids (A1) used in the present invention include:
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 , diglycolic acid, or aliphatic dicarboxylic acids such as these carboxylic acids;
Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, benzylmalonic acid, diphenic acid, 4,4′-oxydibenzoic acid, naphthalene dicarboxylic acid, or these carboxylic acids;
1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, adamantanedicarboxylic acid, or carboxylic acids thereof Alicyclic dicarboxylic acids such as acids;
and divalent carboxylic acids such as
These can be used alone or in combination of two or more.

Among these, from the viewpoint of imparting tackiness, it preferably contains aliphatic dicarboxylic acids, particularly preferably aliphatic dicarboxylic acids having 4 to 12 carbon atoms, and more preferably contains sebacic acids. .

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

In addition, among the above, aromatic dicarboxylic acids, such as isophthalic acids, can be included from the viewpoint of imparting cohesive force.

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

In the present invention, aromatic dicarboxylic acids and aliphatic dicarboxylic acids can be used in combination as polyvalent carboxylic acids (A1) from the viewpoint of the balance of adhesive physical properties. Acids/aliphatic dicarboxylic acids = 0/100 to 90/10, particularly preferably aromatic dicarboxylic acids/aliphatic dicarboxylic acids = 1/99 to 49/51, more preferably aromatic dicarboxylic acids/fatty Group dicarboxylic acids = 10/90 to 30/70.

[Sulfonic Acid Group-Containing Dicarboxylic Acids (A1-1)]
In the present invention, sulfonic acid group-containing dicarboxylic acids (A1-1) can be used as the polyvalent carboxylic acids (A1) from the viewpoint of improving compatibility when adding the inorganic oxide (E) described later. preferable. Such a sulfonate group-containing dicarboxylic acid (A1-1) is not particularly limited as long as it is a monomer component having both carboxyl groups and a sulfonate group in the molecule. Phthalic acid containing an alkali metal sulfonate such as potassium sulfonate, isophthalic acid, terephthalic acid, and mono- or diesters thereof are preferably used. These sulfonate group-containing dicarboxylic acids (A1-1) can be used alone or in combination of two or more.

Specific examples of the sulfonate group-containing dicarboxylic acids (A1-1) include, for example, 4-dimethylsodium sulfoisophthalate, 5-sodium sulfoisophthalate, 5-dimethylsodium sulfoisophthalate, and dimethyl 4-sulfoisophthalate. potassium, dimethyl potassium 5-sulfoisophthalate, sodium 2-sulfoterephthalate, potassium 2-sulfoterephthalate, dimethyl sodium 2-sulfoterephthalate, dimethyl potassium 2-sulfoterephthalate, etc., diethylene glycol sodium 2-sulfoterephthalate etc. Among these, sodium 5-dimethylsulfoisophthalate is preferably used.

In addition, the proportion of the sulfonic acid group-containing dicarboxylic acid (A1-1) in the polycarboxylic acid (A1) is 0.001 to 20 mol% with respect to the total polycarboxylic acid (A1). is preferred, particularly preferably 0.01 to 10 mol %, more preferably 0.03 to 5 mol %, particularly preferably 0.05 to 2 mol %. If the sulfonate group-containing dicarboxylic acid (A1-1) is too small, the compatibility with the inorganic oxide (E) tends to decrease when the inorganic oxide (E) described later is added, resulting in large haze. (transparency decreases), and if it is too large, durability tends to decrease.

In order to increase the number of branch points in the polyester resin (A), trivalent or higher polyvalent carboxylic acids may be used. Such trivalent or higher carboxylic acids include, for example, trimellitic acid and pyromellitic acid. , adamantanetricarboxylic acid, trimesic acid, or these carboxylic acids. Among them, it is preferable to use trimellitic acids because gelation is relatively unlikely to occur.

The content of such trivalent or higher polyvalent carboxylic acids is preferably 10 mol% or less, particularly preferably 10 mol% or less, based on the total polyvalent carboxylic acids (A1), in that the cohesive force of the pressure-sensitive adhesive can be increased. It 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).

[Polyhydric alcohol (A2)]
Examples of the polyhydric alcohol (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, bisphenol S, bisphenol A, bisphenolfluorene, 4,4'-dihydroxybiphenyl, o-, m- and p-dihydroxybenzene, 2,5- aromatic diols such as naphthalene diol and p-xylene diol;
and ethylene oxide and propylene oxide adducts thereof;
aromatic diols such as; dihydric alcohols such as;

Furthermore, in the present invention, it is preferable to contain a fluorene-based diol represented by the following general formula (1) as the aromatic diol.

In formula (1), R ₁ is an alkylene group having 1 to 5 carbon atoms, such as methylene, ethylene, propylene, butylene, and pentylene. R ₂ , R ₃ , R ₄ and R ₅ are a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group or an aralkyl group, and they may be the same or different.

Examples of alkyl groups having 1 to 5 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, neopentyl group and isopentyl group.
Aryl groups include those having 6 to 10 carbon atoms, such as phenyl, tolyl and o-xylyl groups.
Aralkyl groups include those having 7 to 20 carbon atoms, such as benzyl and phenethyl groups.

In the fluorene diol represented by the general formula (1), R ₁ preferably includes a methylene group and an ethylene group. R ₂ , R ₃ , R ₄ and R ₅ are preferably a hydrogen atom, a methyl group and an ethyl group, with a hydrogen atom being particularly preferred. As the fluorene compound, bisphenoxyethanol fluorene and bis(4-(2-hydroxyethoxy)phenyl)fluorene are preferably used from the viewpoint of availability. One or more fluorene compounds can be used.
These dihydric alcohols may be used alone or in combination of two or more.

In the present invention, among the polyhydric alcohols (A2), it is preferable to contain an aromatic diol from the viewpoint of being able to exhibit a high refractive index. It is preferable to contain the fluorene-based diol, and it is particularly preferable to contain the fluorene-based diol from the viewpoint of increasing the refractive index while maintaining adhesiveness.

The content of the aromatic diol in the polyhydric alcohol (A2) is preferably 10 to 100 mol%, particularly 15 to 80 mol%, and further 20 to 70 mol% relative to the total polyhydric alcohol (A2). %, especially 25 to 60 mol %. If the content is too low, it tends to be difficult to obtain a sufficient refractive index, and if it is too high, the adhesive performance tends to decrease.

The content of the aromatic diol is preferably 10% by weight or more, more preferably 15 to 85% by weight, particularly 20 to 65% by weight, particularly 25 to 60% by weight, based on the total polyester resin. % by weight is preferred. If the content is too low, it tends to be difficult to obtain a sufficient refractive index, and if it is too high, the adhesive performance tends to decrease.

Furthermore, the content of the fluorene-based diol is preferably 10 to 90 mol%, particularly 15 to 80 mol%, further 20 to 70 mol%, particularly is preferably 25 to 60 mol %. If the content is too low, it tends to be difficult to obtain a sufficient refractive index, and if it is too high, the adhesive performance tends to decrease.

Further, the content of the fluorene diol relative to the entire aromatic diol is 50 mol% or more, particularly 60 mol% or more, further 70 mol% or more, particularly 90 mol%, from the viewpoint of obtaining a sufficient refractive index. % or more. Among them, it is particularly preferable that all of them are fluorene diols.

Furthermore, in the present invention, among the above-mentioned polyhydric alcohols (A2), aliphatic diols and alicyclic diols are preferably included from the viewpoint of excellent reactivity, and particularly preferably aliphatic diols such as ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and alicyclic Diols include, for example, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol. It is particularly preferable to contain an aliphatic diol from the viewpoint of balancing flexibility and expressing adhesive performance.

The content of the aliphatic diol is preferably 1 to 90 mol%, particularly 10 to 85 mol%, further 20 to 80 mol%, particularly 30 mol%, relative to the total polyhydric alcohol (A2). It is preferably ~75 mol%. If the content is too low, the adhesive performance tends to decrease, and if it is too high, the refractive index tends to decrease.

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%, based on the total polyhydric alcohol (A2). If the content is too high, it tends to be difficult to produce the polyester resin (A).

The mixing ratio of the polyhydric carboxylic acid (A1) and the polyhydric alcohol (A2) is preferably 1 to 2.5 equivalents of the polyhydric alcohol (A2) per equivalent of the polyhydric carboxylic acid (A1). Especially preferred is 1.1 to 2.0 equivalents. If the content of the polyhydric alcohol (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 polyhydric carboxylic acid (A1) and the polyhydric alcohol (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 specific examples include titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate, antimony-based catalysts such as antimony trioxide, and 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, germanium dioxide, and zinc acetate 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 280°C, particularly preferably 180 to 250°C, further preferably 200 to 240°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 is usually normal pressure.

After the esterification reaction is performed, a condensation reaction is performed.
As the reaction conditions for 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° C.
It is preferable to set the temperature to 270° C., gradually reduce the pressure in 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.

Thus, the polyester resin (A) used in the present invention is obtained.
The glass transition temperature of the polyester resin (A) is preferably 40° C. or lower, more preferably 30° C. or lower, and further preferably 20° C. or lower from the viewpoint of the balance between adhesive properties and refractive index. If the glass transition temperature is too high, flexibility will be lost, initial adhesiveness will be lowered, and it will be difficult to exhibit sufficient adhesive strength with a pressure of about finger pressure, and workability will tend to be lowered. The lower limit of the glass transition temperature is usually -40°C, preferably -30°C, more preferably -20°C.

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.

In addition, the weight average molecular weight of the polyester resin (A) is preferably 8,000 to 200,000, particularly 10,000 to 180,000, further 20, 000 to 150,000 is preferred. If the weight-average molecular weight is too small, sufficient cohesive force as an adhesive cannot be obtained, and the 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 the order of finger pressure.

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

The acid value of the polyether resin (A) is preferably 10 mgKOH/g or less, particularly preferably 3 mgKOH/g or less, more preferably 1 mgKOH/g or less, and particularly preferably 0.5 mgKOH/g or less. If the acid value is too high, there is a concern that when a layer of metal or the like comes to one side of the pressure-sensitive adhesive layer made of the present polyester-based pressure-sensitive adhesive, it may corrode. For example, when a metal oxide thin film layer is formed, corrosion tends to occur and the electrical conductivity of the metal oxide film tends to decrease.

The acid value of the polyester resin (A) is obtained by neutralization titration based on JIS K 0070.

Moreover, in the present invention, the refractive index of the polyester-based resin (A) alone is preferably 1.530 or more.

<Hydrolysis inhibitor (B)>
The polyester-based pressure-sensitive adhesive composition [I] in the present invention preferably contains a hydrolysis inhibitor (B) together with the polyester-based resin (A). The hydrolysis inhibitor (B) is contained to ensure long-term durability.

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 thereof include compounds having functional groups such as carbodiimide groups, epoxy groups, oxazoline groups, and the like. 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 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 benzoic acid glycidyl ester, t-Bu-benzoic acid glycidyl ester, p-toluic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycyl ester, 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. Moreover, these can be used individually or in combination of 2 or more types.

These hydrolysis inhibitors (B) preferably have low volatility, and for that reason, it is preferable to use those having a high number average molecular weight, usually 300 to 10,000, preferably 1,000 to 5,000. Use the one from

Among the hydrolysis inhibitors (B), it is preferable to use a carbodiimide group-containing compound. At that time, the carbodiimide equivalent is preferably 50 to 10,000, particularly 100 to 1,000, further preferably 150 to 500. The carbodiimide equivalent is the chemical formula weight per carbodiimide group.

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 content 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.

Further, the content of the hydrolysis inhibitor (B) is preferably optimized according to the acid value of the polyester resin (A). The molar ratio ((b)/(a)) of the total amount of functional groups (b) of the hydrolysis inhibitor (B) in the pressure-sensitive adhesive composition to the total (a) of the acid value of the resin (A) is 0.5≤(b)/(a) is preferable, 1≤(b)/(a)≤1,000 is particularly preferable, and 1.5≤(b)/(a)≤100 is more preferable. is.
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. If the content of b) is too low, the moist heat resistance tends to decrease.

<Crosslinking agent (C)>
The polyester-based pressure-sensitive adhesive composition [I] in the present invention contains the polyester-based resin (A) and preferably further contains a hydrolysis inhibitor (B), but usually a cross-linking agent (C). By containing the cross-linking agent (C), the polyester resin (A) is cross-linked with the cross-linking agent (C) and has excellent cohesive strength, improving the performance as a pressure-sensitive 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, it is particularly preferable to use a polyisocyanate-based compound from the viewpoint of achieving a good balance between initial tackiness, mechanical strength, and heat resistance.

Examples of such polyisocyanate compounds include tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, tetramethylxylylene diisocyanate, 1 , 5-naphthalene diisocyanate, triphenylmethane triisocyanate, and the like, and adducts of the above polyisocyanates with polyol compounds such as trimethylolpropane, burettes of these polyisocyanate compounds, and isocyanurates. body, etc. The above polyisocyanate-based compound may also be one in which the 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 content of the cross-linking agent (C) can be appropriately selected depending on the molecular weight of the polyester resin (A) and the purpose of use, but usually it is 1 equivalent of the hydroxyl group and / or carboxyl group contained in the polyester resin (A). 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.

In addition, when blending the cross-linking agent (C), it is preferable to contain a catalyst at the same time.
Such catalysts include metal catalysts such as tin, lead, and bismuth compounds; transition metal compounds such as iron, copper, titanium, zirconium, nickel, cobalt, and manganese; acetylacetonate complexes; amine compounds and the like. From the viewpoint of catalytic activity, organic tin, organic titanium, and organic zirconium are preferred.

<Plasticizer (D)>
Thus, a pressure-sensitive adhesive composition [I] containing a polyester resin (A), preferably further a hydrolysis inhibitor (B), and a cross-linking agent (C) is obtained. In the present invention, a plasticizer ( D) is preferably contained. The plasticizer (D) is contained to ensure adhesiveness even when the glass transition temperature of the resin is excessively increased due to the high refractive index.

Examples of the plasticizer (D) include alkyl esters of aromatic polycarboxylic acids and alkyl esters of aliphatic polycarboxylic acids. Among them, alkyl esters of aromatic polyvalent carboxylic acids are preferable, and alkyl esters of trivalent or higher aromatic polyvalent carboxylic acids are more preferable, since they can exhibit a plasticizing effect without a large decrease in refractive index.

The content of the plasticizer (D) is preferably 2 to 30 parts by weight, particularly preferably 3 to 20 parts by weight, more preferably 4 to 30 parts by weight, based on 100 parts by weight of the polyester resin (A). 10 parts by weight. If the content is too high, the plasticizer will bleed out, resulting in a decrease in adhesive strength.

<Inorganic oxide (E)>
In the present invention, it is preferable to further contain an inorganic oxide (E), and since the inorganic oxide (E) has a relatively high refractive index, it should be contained for the purpose of increasing the refractive index of the pressure-sensitive adhesive layer. is preferred. Furthermore, by blending the inorganic oxide (E), it is possible to improve the adhesive strength as a polyester-based adhesive.

That is, in a polyester-based pressure-sensitive adhesive composed of a pressure-sensitive adhesive composition containing a polyester-based resin (A) and an inorganic oxide (E), the following adhesive strength (β) is 5 N / 25 mm or more, and the refractive index is 1 0.530 or more can be a polyester pressure-sensitive adhesive.
Adhesive strength (β): When a polyester-based adhesive is formed on a substrate to form an adhesive sheet, it is attached to an adherend of a glass plate and left at 23 ° C. and 50% RH for 30 minutes. 180 degree peel strength (N/25 mm) at a peel speed of 300 mm/min to the body.

When the inorganic oxide (E) is contained, the refractive index can be further increased, and the refractive index is 1.530 or more, preferably 1.560 or more, more preferably 1.530 or more. 0.600 or more, particularly preferably 1.620 or more. The upper limit is usually 1.700, preferably 1.680. More preferably, it is 1.660.

The inorganic oxide (E) is not particularly limited, but is preferably a metal oxide. Among them, a particle containing a metal oxide and an organic substance having a reactive functional group that modifies the surface thereof, more specifically, a metal oxide particle and a reactive functional group that modifies the surface of the particle Coated particles (hereinafter also referred to as reactive modified metal oxide particles) containing an organic substance having The reactive functional group may be in a state of having an interaction such as a hydrogen bond with the metal oxide, or may be in a state of being able to interact with another substance without such a state. The inorganic oxide (E) is preferably inorganic oxide fine particles in a fine particle state, and examples of inorganic oxide fine particles include fine particle powder, paste, and sol, which are preferred. is a sol.

As metal oxides, metal oxides generally used as fillers in resins are preferably used. Examples of such metal oxides include zirconium oxide (ZrO ₂ : zirconia), titanium oxide (TiO ₂ titania), aluminum oxide ( _Al2O3 : alumina), iron oxides _{( Fe2O3 , Fe3O4} ), copper oxide ₍ CuO), zinc oxide ₍ ZnO), yttrium oxide ( _Y2O3 : yttria) , niobium oxide _{( Nb2O5} ) _, molybdenum oxide _{( MoO3} , _MoO2 ), indium oxide ₍ In2O3), tin oxide ₍ SnO2), tantalum oxide ( _Ta2O5 , _TaO2 ), tungsten oxide (WO3 _{, WO2} ), lead oxide (PbO), bismuth oxide ₍ Bi2O3), cerium oxide ₍ CeO2: ceria), antimony oxide _{( Sb2O3 , Sb2O5} ), tin _- doped indium oxide (ITO), antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), phosphorus-doped tin oxide (PTO), zinc antimonate (AZO), indium-doped zinc oxide (IZO), aluminum-doped zinc oxide, gallium-doped oxide Zinc etc. are mentioned. Examples of the non-metal oxides include silicon oxide (SiO ₂ : silica) and boron oxide (B ₂ O ₃ ), which are generally used as fillers in resins. These metal oxides and non-metal oxides may be used alone or in combination. Among these, zirconium oxide (ZrO ₂ : zirconia) and titanium oxide (TiO ₂ : titania) are preferable from the viewpoint of easily obtaining a pressure-sensitive adhesive with a high refractive index.

Examples of reactive functional groups in organic substances having reactive functional groups include hydroxyl groups, phosphoric acid groups, carboxyl groups, amino groups, alkoxy groups, isocyanate groups, acid halides, acid anhydride groups, glycidyl groups, chlorosilane groups, and alkoxy groups. A silane group is mentioned. As the organic substance having a reactive functional group, an organic substance having an isocyanate group is particularly preferable because it can improve the stability between the metal oxide and surrounding substances. Examples of organic substances having an isocyanate group include acryloxymethyl isocyanate, methacryloxymethyl isocyanate, acryloxyethyl isocyanate, methacryloxyethyl isocyanate, acryloxypropyl isocyanate, methacryloxypropyl isocyanate, 1,1-bis(acryloxymethyl) Ethyl isocyanate may be mentioned.

In the reactive modified metal oxide particles, the content of the organic matter having a reactive functional group is preferably 1 to 40 parts by weight per 100 parts by weight of the metal oxide.

Reactive modified metal oxide particles are prepared by mixing metal oxide particles, an organic substance having a reactive functional group, an organic solvent, and optional additives that can be added as necessary, and further adding A suspension in which the particles are dispersed in an organic solvent can be obtained by subjecting the particles to treatment such as ultrasonic treatment.

Examples of organic solvents include ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetone and cyclohexanone, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, methanol, ethanol, isopropyl alcohol, n-butanol and iso-butanol. alcohols, ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethyl acetate, butyl acetate, ethyl lactate, γ-butyrolactone, propylene glycol monomethyl ether Examples include esters such as acetate and propylene glycol monoethyl ether acetate, and amides such as dimethylformamide, N,N-dimethylacetoacetamide and N-methylpyrrolidone. As the organic solvent, one of these may be used alone, or two or more may be used in combination. Examples of optional additives that may be added to the mixture include metal chelating agents.

When reactively modified metal oxide particles are obtained as a suspension in which particles are dispersed in an organic solvent, conditions such as the amount of solvent are adjusted so that one reactively modified metal oxide particle is included in the suspension. From the standpoint of ease of production, etc., it is preferable to adjust the content to 50% by weight and use it as it is for the production of the pressure-sensitive adhesive composition.

When preparing the mixture, it is preferable to mix each component with a bead mill or the like. By such mixing, secondary particles or higher order particles can be pulverized to the level of primary particles, and the surface can be treated in the state of primary particles, resulting in uniform surface treatment.

The mixture can be further sonicated if desired. Ultrasonic treatment can be performed using an apparatus such as an ultrasonic cleaner, an ultrasonic homogenizer, an ultrasonic disperser, or the like. A good suspension can be obtained by such treatment.

As the reactive modified metal oxide particles, commercially available particles may be used as they are. The commercially available particles may be provided as a slurry containing components such as a solvent and additives, but can be used as a material for the pressure-sensitive adhesive composition of the present invention in a slurry state containing such components as they are.
An example of a slurry of reactively modified metal oxide particles containing ZrO ₂ as a metal oxide is the product name “NANON5 ZR-010” (manufactured by Solar Co., Ltd., solvent: methyl ethyl ketone, particle content rate of 30%, surface modification Organic matter having a reactive functional group: isocyanate having a polymerizable functional group, volume average particle size 15 nm). An example of a slurry of reactively modified metal oxide particles containing TiO ₂ as a metal oxide is the product name "NOD-742GTF" (manufactured by Nagase ChemteX Corporation, solvent: polyethylene glycol monomethyl ether, particle content of 30%, volume average particle diameter of 48 nm).

The volume average particle size of the inorganic oxide (E) is preferably 5 nm or more, more preferably 10 nm or more, and particularly preferably 20 nm or more, while it is preferably 50 nm or less, more preferably 40 nm or less. It is preferably 30 nm or less. By setting the particle size within the above numerical range, it is possible to obtain an adhesive layer with little coloration and high light transmittance, and the particles are easily dispersed. When the reactively modified metal oxide aggregates to form secondary particles or higher-order particles, the particle size range may be the primary particle size range. The particle size can be measured by using a dynamic light scattering particle size distribution analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.) based on the volume of the particle size.

The lower limit of the content of the inorganic oxide (E) in the pressure-sensitive adhesive composition is preferably 10 parts by weight or more, particularly preferably 40 parts by weight or more, relative to 100 parts by weight of the polyester resin (A). , more preferably 90 parts by weight or more. On the other hand, the upper limit of the content of the inorganic oxide (B) is 500 parts by weight or less, preferably 400 parts by weight or less, more preferably 300 parts by weight, relative to 100 parts by weight of the polyester resin (A). It is below. If the content of the inorganic oxide (B) is too low, the desired refractive index tends to be unobtainable, and if it is too high, the adhesive strength tends to decrease.

In the present invention, in addition to the polyester resin (A), the hydrolysis inhibitor (B), the cross-linking agent (C), the plasticizer (D), and the inorganic oxide (E), the effects of the present invention are obtained. Additives such as conventionally known antioxidants, softeners, ultraviolet absorbers, stabilizers, antistatic agents, tackifiers, etc., inorganic or organic fillers, metal powders, pigments, etc. Additives such as powders and particles can be added.
In addition, it is preferable not to substantially contain the said tackifier from the viewpoint of durability and transparency.

The polyester-based pressure-sensitive adhesive of the present invention comprises the pressure-sensitive adhesive composition [I], that is, the pressure-sensitive adhesive composition [I] is cured.
In the polyester-based pressure-sensitive adhesive of the present invention, when adjusting the adhesive strength (α) to 10 N/25 mm or more and the refractive index to 1.530 or more, for example, (1) the raw material of the polyester-based resin (A) In the composition, a method of blending many raw materials having an aromatic ring among polyhydric carboxylic acids and / or polyhydric alcohols, (2) In the raw material composition of the polyester resin (A), polycarboxylic acids and / or polyhydric alcohols A method of adding a plasticizer to a polyester resin (A) having a glass transition temperature of −20° C. to 40° C. by blending many raw materials having an aromatic ring among the functional alcohols, (3) a polyester resin ( A) includes a method of adding an inorganic oxide (E) with a high refractive index, (4) and a combination of (1) to (3), etc., and the cost, refractive index and adhesive performance are well balanced. The methods (1) and (2) are preferable, and the method (2) is particularly preferable, because they are easy.
As a method of increasing the refractive index, a method of combining (2) and (3) is preferable.

Such a polyester-based pressure-sensitive adhesive preferably contains substantially no acidic groups, and specifically, preferably has an acid value of 10 mgKOH/g or less, particularly preferably 5 mgKOH/g or less, more preferably 5 mgKOH/g or less. 1 mg KOH/g or less, particularly preferably 0.5 mg KOH/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 [I] of the present invention can be used for laminating various members. By laminating a pressure-sensitive adhesive layer of a polyester-based pressure-sensitive adhesive comprising the pressure-sensitive adhesive composition [I] on an optical member, the above 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, the ITO electrode film is particularly preferable because it is effective when the optical member is a transparent electrode film and high adhesive strength can be obtained. The ITO electrode film is often formed as a thin film on a substrate such as glass or PET. Especially preferred.
It is also suitable for use as a light extraction film provided on the light emitting surface of a surface light emitter of an organic EL device, or as a light diffusion sheet for a liquid crystal display.

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. 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".

<Adhesive sheet>
The adhesive sheet can be produced, for example, as follows.
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. The adhesive sheet of the present invention having the adhesive layer comprising the polyester-based adhesive of the present invention on the substrate is obtained by laminating a release sheet on the adhesive layer surface and curing as necessary.

Alternatively, the pressure-sensitive adhesive sheet of the present invention can be obtained by coating the pressure-sensitive adhesive composition [I] on a release sheet, drying it, laminating a substrate sheet on the opposite side of the pressure-sensitive adhesive layer, and curing if 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 naphthalate, 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; Polyimide; Synthetic resin sheets such as cycloolefin polymers; A nonwoven fabric is mentioned. 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 base sheet made of polyethylene terephthalate 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 substrate can be kept stable without corroding the metal thin film layer, and the effect of the polyester adhesive of the present invention can be remarkably exhibited.

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, Further, it is preferable to use an optical laminate in which acrylic films are laminated (layer structure: ITO electrode film/PET substrate/adhesive layer/PC film/acrylic film).
Further, it is preferable that the base film adjacent to the pressure-sensitive adhesive layer has a refractive index of 1.52 to 1.63 in terms of good light extraction property when the pressure-sensitive adhesive of the present invention is laminated.

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 adhesive composition [I], 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, etc. 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, 1 day to 20 days at 23° C. The conditions may be 14 days, 40° C. for 1 to 10 days, 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 0.5 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, further 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 a value obtained by subtracting the measured thickness of the constituent members other than the pressure-sensitive adhesive layer from the measured value of the thickness of the entire pressure-sensitive adhesive sheet using "ID-C112B" manufactured by Mitutoyo. is.

The gel fraction of the adhesive layer of the adhesive sheet is preferably 20% or more, particularly preferably 30 to 90%, and still more preferably 40 to 70%, 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. In the case of a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed on one side of a substrate, the surface of the substrate 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 weight-average molecular weight and glass transition temperature of the polyester-based resins in the following examples were measured according to the methods described above. The acid value of the polyester resin was measured by neutralization titration according to JIS K0070 by dissolving 1 g of the polyester resin in 30 g of a mixed solvent of 7/3 (weight ratio) (toluene/methanol).

<Production of polyester resin (A)>
The mol described in the following production examples indicates the molar ratio when the total amount of polycarboxylic acid components is 1.0 mol.

[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 42.9 parts (1.0 mol) of sebacic acid as the polycarboxylic acid component (A1) and the polyol component (A2). As, 15.5 parts (0.7 mol) of neopentyl glycol, 13.4 parts (0.7 mol) of 1,4-butanediol, and 0.4 parts (0.013 mol) of trimethylolpropane, bisphenoxyethanol 27.9 parts (0.3 mol) of fluorene and 0.01 part of tetrabutyl titanate as a catalyst were charged, the internal temperature was gradually raised to 250° C., and an esterification reaction was carried out over 4 hours. Thereafter, the internal 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 obtained polyester resin (A-1) had a weight average molecular weight of 65,000, a glass transition temperature of -18°C, an acid value of 0.7 mgKOH/g, and a refractive index of 1.537.
Also, the ratio of finished components was as follows: Sebacic acid = 100 mol% as the polycarboxylic acid component, and neopentyl glycol/1.4-butanediol/trimethylolpropane/bisphenoxyethanol fluorene = 33 as the polyhydric alcohol component. 4 mol %/36.5 mol %/0.8 mol %/29.3 mol %.

[Production Example 2: Production of polyester resin (A-2)]
A reactor equipped with a thermometer, a stirrer, a rectifying column, a nitrogen inlet tube and a vacuum device was charged with 40.1 parts (1.0 mol) of sebacic acid as the polycarboxylic acid component (A1) and the polyol component (A2). as 12.4 parts (0.6 mol) of neopentyl glycol, 12.4 parts (0.7 mol) of 1,4-butanediol, and 0.3 parts (0.013 mol) of trimethylolpropane, bisphenoxyethanol 34.7 parts (0.4 mol) of fluorene and 0.01 part of tetrabutyl titanate as a catalyst were charged, the internal temperature was gradually raised to 250° C., and an esterification reaction was carried out over 4 hours. Thereafter, the internal 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-2).
The obtained polyester resin (A-2) had a weight average molecular weight of 36,000, a glass transition temperature of −4° C., an acid value of 1.0 mgKOH/g, and a refractive index of 1.553.
Also, the ratio of finished components was as follows: sebacic acid = 100 mol% as the polycarboxylic acid component, and neopentyl glycol/1.4-butanediol/trimethylolpropane/bisphenoxyethanol fluorene = 26 as the polyhydric alcohol component. 3 mol %/33.9 mol %/0.8 mol %/39.0 mol %.

[Production Example 3: Production of polyester resin (A-3)]
A reactor equipped with a thermometer, a stirrer, a rectifying column, a nitrogen inlet tube and a vacuum device was charged with 37.6 parts (1.0 mol) of sebacic acid as the polycarboxylic acid component (A1) and the polyol component (A2). As, 9.7 parts (0.5 mol) of neopentyl glycol, 11.7 parts (0.7 mol) of 1,4-butanediol, and 0.3 parts (0.013 mol) of trimethylolpropane, bisphenoxyethanol 40.7 parts (0.5 mol) of fluorene and 0.01 part of tetrabutyl titanate as a catalyst were charged, the internal temperature was gradually raised to 250° C., and an esterification reaction was carried out over 4 hours. Thereafter, the inner temperature was raised to 260° C., 0.01 part of tetrabutyl titanate was added 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-3).
The obtained polyester resin (A-3) had a weight average molecular weight of 41,000, a glass transition temperature of 14° C., an acid value of 1.2 mgKOH/g, and a refractive index of 1.566.
Also, the finished component ratio was as follows: sebacic acid = 100 mol% as the polycarboxylic acid component, and neopentyl glycol/1.4-butanediol/trimethylolpropane/bisphenoxyethanol fluorene = 19.0% as the polyhydric alcohol component. 6 mol %/31.0 mol %/0.7 mol %/48.7 mol %.
Met.

[Production Example 4: Production of polyester resin (A-4)]
40.3 parts (0.95 mol) of sebacic acid and dimethylsodium sulfonylisophthalate as the polyvalent carboxylic acid component (A1) were placed in a reaction vessel equipped with a thermometer, a stirrer, a rectifying column, a nitrogen inlet tube and a vacuum device. 3.1 parts (0.05 mol), and as the polyol component (A2), 15.3 parts (0.7 mol) of neopentyl glycol, 13.2 parts (0.7 mol) of 1,4-butanediol and tri 0.4 parts (0.013 mol) of methylolpropane, 27.6 parts (0.3 mol) of bisphenoxyethanol fluorene, and 0.01 part of tetrabutyl titanate as a catalyst were charged, and the internal temperature was gradually raised to 250°C. , the esterification reaction was carried out over 4 hours. Thereafter, the inner temperature was raised to 260° C., 0.01 part of tetrabutyl titanate was added 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-4).
The resulting polyester resin (A-4) had a weight average molecular weight of 46,000, a glass transition temperature of -27°C, an acid value of 1.0 mgKOH/g, and a refractive index of 1.537.
In addition, the finished component ratio is as follows: Sebacic acid/sodium sulfonylisophthalate = 95 mol%/5 mol% as the polyvalent carboxylic acid component, and neopentyl glycol/1.4-butanediol/tri Methylolpropane/bisphenoxyethanol fluorene = 33.4 mol%/36.5 mol%/0.8 mol%/29.3 mol%.

[Production Example 5: Production of polyester resin (A-5)]
45.9 parts (0.8 mol) of sebacic acid and 7.1 parts of isophthalic 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. parts (0.15 mol), 4.2 parts (0.05 mol) of sodium dimethyl sulfonylisophthalate, 26.6 parts (0.9 mol) of neopentyl glycol as the polyol component (A2), 1,4-butane 12.8 parts (0.5 mol) of diol, 2.9 parts (0.087 mol) of 1.6-hexanediol and 0.5 parts (0.013 mol) of trimethylolpropane, 0 part of tetrabutyl titanate as a catalyst 0.01 part was charged, and the internal temperature was gradually raised to 250° C., and the esterification reaction was carried out over 4 hours. Thereafter, the internal temperature was raised to 260° C., 0.01 part of tetrabutyl titanate was added 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-5).
The obtained polyester resin (A-5) had a weight average molecular weight of 51,000, a glass transition temperature of -49°C, an acid value of 0.8 mgKOH/g, and a refractive index of 1.489.
Also, the finished component ratio is as follows: sebacic acid/isophthalic acid/sodium sulfonylisophthalate = 80 mol%/15 mol%/5 mol% as the polycarboxylic acid component, and neopentyl glycol/1 as the polyhydric alcohol component. .4-butanediol/1.6-hexanediol/trimethylolpropane=58.7 mol %/34.1 mol %/6.2 mol %/1.0 mol %.

[Production Example 6: 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. part (0.8 mol), as the polyol component (A2), neopentyl glycol 27.1 parts (0.9 mol), 1,4-butanediol 13.0 parts (0.5 mol), 1,6- 3.0 parts (0.09 mol) of hexanediol, 0.5 parts (0.013 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. , the esterification reaction was carried out over 4 hours. Thereafter, the internal 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 performed over 3 hours to produce a polyester resin (A′-1). .
The obtained polyester resin (A'-1) had a weight average molecular weight of 70,000, a glass transition temperature of -50°C, an acid value of 0.4 mgKOH/g, and a refractive index of 1.486.
In addition, the finished composition is as follows: Sebacic acid/isophthalic acid = 80 mol%/20 mol% as polyvalent carboxylic acid components, and neopentyl glycol/1.4-butanediol/1.6-hexane as polyhydric alcohol components. Diol/trimethylolpropane = 54.8 mol%/38.4 mol%/0.9 mol%/5.9 mol%.
Met.

[Production Example 7: Production of polyester resin (A'-2)]
22.9 parts (0.64 mol) of naphthalenedicarboxylic acid dimethyl ester (NDCM) as a polyvalent carboxylic acid component (A1) was placed in a reactor equipped with a thermometer, a stirrer, a rectifying column, a nitrogen inlet tube and a vacuum device. , 65.8 parts (1.0 mol) of bisphenoxyethanol fluorene (BPEF) as a polyol component (A2) and 0.01 part of tetrabutyl titanate as a catalyst were charged, and the internal temperature was gradually increased to 250 ° C. The esterification reaction was carried out over a period of time. Subsequently, after cooling to 200° C., 11.3 parts (0.36 mol) of pyromellitic anhydride (PMAn) as a carboxylic acid anhydride was added and reacted at 170° C. for 2 hours while dissolving. A polyester resin (A'-2) was produced.
The obtained polyester resin (A'-2) had a weight average molecular weight of 2000, a glass transition temperature of 173° C., an acid value of 32 mgKOH/g and a refractive index of 1.652.

<Hydrolysis inhibitor (B)>
The following was prepared as a hydrolysis inhibitor (B).
(B-1) Carbodiimide group-containing hydrolysis inhibitor (manufactured by Nisshinbo Chemical; trade name “Carbodilite V-07”)

<Crosslinking agent (C)>
The following were prepared as a crosslinking agent (C).
(C-1) Trimethylolpropane/tolylene diisocyanate adduct (manufactured by Nippon Polyurethane Industry Co., Ltd.; product name “Coronate L55E”)

<Plasticizer (D)>
The following was prepared as a plasticizer (D).
(D-1) Trioctyl trimellitate (TOTM)
(D-2) Dioctyl phthalate (DOP)

<Inorganic oxide (E)>
The following were prepared as inorganic oxides (E).
(E-1) AX-ZP-158-A (zirconium oxide dispersion manufactured by Nippon Shokubai Co., Ltd.)
(E-2) NANON5 ZR-010 (zirconium oxide dispersion manufactured by Solar Co., Ltd.)
(E-3) ZIRCOSTAR ZP-153 (zirconium oxide dispersion manufactured by Nippon Shokubai Co., Ltd.)

<Catalyst>
The following catalysts were prepared.
・Dibutyl tin dilaurate (DBTL)

<Antioxidant>
The following were prepared as antioxidants.
・ Hindered phenolic antioxidant / Irganox 1010 (manufactured by BASF)

(Examples 1 to 14, Comparative Examples 1 to 3)
The polyester resin obtained above was diluted with ethyl acetate to a solid content concentration of 50%, and 200 parts of this polyester resin solution (solid content: 100 parts) was blended with each component as shown in Table 1 and stirred. , to obtain a polyester adhesive composition.
Using the obtained polyester-based pressure-sensitive adhesive composition, evaluation was performed as follows.

<Production of adhesive sheet with release film>
Each of the polyester pressure-sensitive adhesive compositions obtained in Examples 1 to 14 and Comparative Examples 1 to 3 was applied onto a polyethylene terephthalate (PET) film having a thickness of 50 μm using an applicator and dried at 100° C. for 3 minutes. , A pressure-sensitive adhesive composition layer (25 μm thick) is formed, and then the surface of the pressure-sensitive adhesive composition layer obtained is covered with a release-treated PET film (release film) and aged at 40 ° C. for 10 days. to obtain a pressure-sensitive adhesive sheet with a release film.

Using such a release film-attached pressure-sensitive adhesive sheet, the gel fraction, adhesive strength, and optical performance (refractive index, transparency) were evaluated as follows. The results are summarized in Table 1.

[Gel fraction (%)]
The release film of the pressure-sensitive adhesive sheet with a release film obtained above was peeled off, wrapped with a 200-mesh SUS wire mesh, immersed in toluene at 23 ° C. for 24 hours, and the insoluble adhesive component remaining in the wire mesh. was determined as the gel fraction. However, the weight of the substrate was subtracted.

[Adhesive strength (N/25 mm)]
The release film of the pressure-sensitive adhesive sheet with a release film obtained above was peeled off, and a 2 kg roller was reciprocated twice to adhere to a polycarbonate plate adherend, and autoclaved at 50 ° C. and 0.5 MPa for 20 minutes. , 24 hours later, the adhesive force was determined by measuring the 180 degree peel strength (N/25 mm) at a peel rate of 300 mm/min. An Autograph ("Autograph AGS-H 500N" manufactured by Shimadzu Corporation) was used to measure the adhesive strength.
The evaluation criteria for adhesive strength are as follows.
(Evaluation criteria)
○: 20 N / 25 mm or more ×: less than 20 N / 25 mm

[Refractive index]
The pressure-sensitive adhesive sheet with a release film obtained above is left at 23 ° C. for 3 hours, the release film is peeled off, and the pressure-sensitive adhesive layer side is treated with an Abbe refractive system DR-M4 manufactured by Atago Co., Ltd. D line (589 nm ) was measured.

[transparency]
The transparency of the pressure-sensitive adhesive sheet with a release film obtained above was visually observed.
○・・・transparent △・・・slightly cloudy ×・・・cloudy

From the above results, in Examples 1 to 14, a pressure-sensitive adhesive having excellent adhesive strength and a very high refractive index was obtained, whereas Comparative Examples 1 and 2 had a low refractive index. In Comparative Example 3, since the glass transition point was too high, although the refractive index was high, adhesive properties were not obtained, and both the refractive index and the adhesive strength were not satisfied.

In Examples 10 to 14 above, the initial adhesive strength was also evaluated as follows. Table 2 shows the results.

[Initial adhesive strength (N/25mm)]
The release film of the pressure-sensitive adhesive sheet with a release film obtained above was peeled off, and the glass plate adherend was coated with a 23° C. 50% R.I. H. 30 minutes after pasting by reciprocating a 2 kg roller twice, the adhesive strength was determined by measuring the 180 degree peel strength (N/25 mm) at a peel rate of 300 mm/min. An Autograph ("Autograph AGS-H 500N" manufactured by Shimadzu Corporation) was used to measure the adhesive strength. The evaluation criteria for adhesive strength are as follows.
(Evaluation criteria)
○: 5 N / 25 mm or more △: 0.5 N / 25 mm or more, less than 5 N / 25 mm ×: less than 0.1 N / 25 mm

From the above results, in Examples 10 to 14, the addition of the inorganic oxide resulted in an improvement in the refractive index as well as good initial adhesive strength.

(Reference examples 1 to 6)
The polyester resin obtained above was diluted with ethyl acetate to a solid content concentration of 50%, and 200 parts of this polyester resin solution (solid content: 100 parts) was blended with an inorganic oxide as shown in Table 3, A polyester-based resin composition was obtained by stirring and mixing.
Using the obtained polyester-based resin composition, the refractive index and transparency were evaluated as follows. Table 3 shows the results.

[Refractive index]
The refractive index of the polyester-based resin composition obtained above was measured for the D line (589 nm) using an Abbe refractive system DR-M4 manufactured by Atago Co., Ltd.

[transparency]
The transparency of the polyester-based resin composition obtained above was visually observed.
○・・・transparent △・・・slightly cloudy ×・・・cloudy

From the above results, in Reference Examples 1 to 5, when blending inorganic oxides, by including sulfonic acid group-containing dicarboxylic acids as a copolymerization component of the polyester resin, compatibility in addition to the refractive index is good. and had excellent transparency. Reference Example 6 had a good refractive index due to the addition of the inorganic oxide, but was slightly inferior in transparency because it contained no sulfonate group-containing dicarboxylic acid as a copolymerization component.

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 has excellent adhesive strength to adherends, particularly polycarbonate materials, and has a high refractive index, so that it can be suitably used for laminating optical members.

Claims (11)

In the polyester-based pressure-sensitive adhesive composed of the pressure-sensitive adhesive composition [I] containing the polyester-based resin (A), the following adhesive strength (α) is 10 N/25 mm or more and the refractive index is 1.530 or more. A polyester adhesive characterized by:
Adhesive strength (α): When a polyester-based adhesive is formed on a substrate to form an adhesive sheet, it is attached to an adherend of a polycarbonate plate and autoclaved at 50 ° C. and 0.5 MPa for 20 minutes, followed by 24 hours. 180 degree peel strength (N/25 mm) at a peel rate of 300 mm/min to the adherend afterward. The adhesive composition [I] contains a polyester resin (A), a hydrolysis inhibitor (B) and a cross-linking agent (C), and the polyester resin (A) is derived from aliphatic polycarboxylic acids 2. The polyester-based pressure-sensitive adhesive according to claim 1, comprising a structural site of and a structural site derived from an aromatic polyhydric alcohol. 3. The polyester pressure-sensitive adhesive according to claim 1, wherein the pressure-sensitive adhesive composition [I] further contains a plasticizer (D). 4. The polyester-based pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the polyvalent carboxylic acid (A1), which is a constituent raw material of the polyester-based resin (A), contains an aliphatic polyvalent carboxylic acid. 5. The polyester-based pressure-sensitive adhesive according to any one of claims 1 to 4, wherein the polyhydric alcohol (A2), which is a constituent raw material of the polyester-based resin (A), contains an aromatic polyhydric alcohol. The polyester pressure-sensitive adhesive according to any one of claims 1 to 5, wherein the polyester resin (A) has a glass transition temperature of 40°C or less. The polyester pressure-sensitive adhesive according to any one of claims 1 to 6, wherein the polyester resin (A) has a weight average molecular weight of 8,000 to 200,000. The polyester adhesive according to any one of claims 2 to 7, 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. The polyester pressure-sensitive adhesive according to any one of claims 3 to 8, wherein the content of the plasticizer (D) is 2 to 30 parts by weight per 100 parts by weight of the polyester resin (A). The polyester pressure-sensitive adhesive according to any one of claims 1 to 9, further comprising an inorganic oxide (E). 11. A pressure-sensitive adhesive sheet for an optical member, comprising the polyester-based pressure-sensitive adhesive according to any one of claims 1 to 10 formed on a substrate.