JP2018016781A - Adhesive composition and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition capable of forming an adhesive layer which enables a re-sticking work at ordinary temperature, satisfactorily holds an adherend, is surely brought into close contact with the adherend at the time of film working in heating (for instance, 60°C) and conveyance, and is easily peeled from the adherend even after treatment on high temperature condition (for instance, at 150°C for one hour), and to provide an adhesive sheet having an adhesive layer formed from the adhesive composition.SOLUTION: An adhesive sheet has an adhesive layer formed from an adhesive composition having the following structure on a base material film. The adhesive composition has such physical properties that a peeling force at 23°C in an initial period is 0.05 (N/25 mm) or more, a peeling force at 60°C in heating is 0.05 (N/25 mm) or more and a peeling force after heating at ordinary temperature after heating at 150°C for one hour is 0.7 (N/25 mm) or less, and has a resin component (A) blended with two kinds of specific acrylic resins in a specific ratio and a crosslinking agent (B).SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition suitable for forming a re-peelable pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the composition.

  In various processes for processing a thin adherend, such as an insulating substrate of a flexible printed circuit board (FPC), a reinforcing sheet is attached to the adherend to improve handling at work. . Since the reinforcing sheet needs to be peeled off after the processing is completed, a releasable pressure-sensitive adhesive sheet is usually used as the reinforcing sheet. As a releasable pressure-sensitive adhesive sheet, a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer containing a pressure-sensitive polymer whose main chain and / or side chain is a crystalline polymer is provided on a substrate is known (Patent Document 1).

JP-A-9-251923

  The pressure-sensitive adhesive sheet disclosed in Patent Document 1 has a sufficient pressure-sensitive adhesive force at the time of use, and the pressure-sensitive adhesive force decreases by cooling to room temperature (23 ° C.) or lower, thereby facilitating peeling of the adherend. . In addition, there is an advantage that the adhesive can be reused even after the adherence is peeled off and the adherend is peeled off.

However, although the pressure-sensitive adhesive sheet disclosed in Patent Document 1 can be securely adhered to the adherend during film processing or transportation under a heating condition (for example, 60 ° C.), the tack during heating is sufficient. The peelability is good), and the initial peel force is small, so it is difficult to hold the adherend at room temperature (small initial tack, poor initial peelability at room temperature), and high temperature conditions (for example, 150 ° C., 1 hour) When it is required to peel off the adherend from the pressure-sensitive adhesive layer after the treatment in step), adhesive residue or the like tends to be easily generated on the adherend at the time of peeling after the purpose of use has become unnecessary. Poor peelability).
Such a problem becomes a particularly serious problem in processing a film having a very thin adherend.

  The object of the present invention is to allow re-working at normal temperature, to hold the adherend well, and to adhere firmly to the adherend during film processing or transportation under heating conditions (for example, 60 ° C.). A pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that can be easily peeled off from an adherend even after treatment at a high temperature condition (for example, 150 ° C., 1 hour), and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition Is to provide.

  The inventors of the present invention have made extensive studies in order to solve the above problems, and have completed the present invention. That is, according to this invention, the adhesive composition of the structure shown below is provided. Moreover, according to this invention, the adhesive sheet which formed the adhesion layer by the adhesive composition of the structure shown below on the base film is provided.

  The pressure-sensitive adhesive composition of the present invention includes the following resin component (A) containing A1 and A2 and a crosslinking agent (B), and the mixing ratio (A1: A2) of A1 and A2 in A is mass. Conversion is 95: 5 to 65:35, the initial peel force at 23 ° C. (normal temperature) is 0.05 (N / 25 mm) or more, and the peel force when heated at 60 ° C. is 0.05 (N / 25 mm) or more and used for forming an adhesive layer having a peel strength after heating at 23 ° C. (room temperature) after heating for 1 hour at 150 ° C. of 0.7 (N / 25 mm) or less. .

A1 (first acrylic resin) has a glass transition temperature (Tg1) and a mass average molecular weight (Mw1), and A2 (second acrylic resin) has a glass transition temperature (Tg2) and a mass average molecular weight (Mw2). )have.
The relationship between Tg1 and Tg2 is Tg1 <Tg2 (Tg2 is higher than Tg1).
Both Mw1 and Mw2 are 100,000 or more.

  In the pressure-sensitive adhesive composition of the present invention, the blending ratio (A1: A2) of A1 and A2 in A is preferably 90:10 to 80:20 in terms of mass.

In the pressure-sensitive adhesive composition of the present invention, Tg1 is preferably −70 to −25 ° C., Tg2 is −15 to 30 ° C., and the difference between Tg2 and Tg1 (Tg2−Tg1) is preferably 10 ° C. or more.
In the pressure-sensitive adhesive composition of the present invention, the ratio of Mw2 and Mw1 (Mw2 / Mw1) is preferably 0.5-2.

  In the pressure-sensitive adhesive composition of the present invention, the composition of A1 and A2 is not particularly limited. A2 as an example may be formed of at least a copolymer of A11, A12 and A13 shown below. A1 as an example may be formed of at least a copolymer of A12 and A13 shown below.

A11: ethyl methacrylate or methyl methacrylate,
A12: (meth) acrylate having a functional group capable of reacting with B and an alkyl group having 2 to 8 carbon atoms,
A13: A monomer having an ethylenically unsaturated double bond (excluding ethyl methacrylate and methyl methacrylate).

  The pressure-sensitive adhesive composition of the present invention contains, in the resin component (A), a plurality of acrylic resins (at least A1 and A2) having a specific relationship between the glass transition temperature (Tg) and the mass average molecular weight (Mw), Furthermore, a crosslinking agent (B) is contained in an appropriate amount range. Therefore, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition has an initial peel strength at 23 ° C. of 0.05 (N / 25 mm) or more, and a peel strength when heated at 60 ° C. is 0.05 (N / 25 mm). ) As described above, the peel strength at room temperature after heating at 150 ° C. for 1 hour can exhibit physical properties of 0.7 (N / 25 mm) or less.

  By including A1 and A2 in which Tg and Mw are in a specific relationship in A, re-working at normal temperature (23 ° C.) becomes possible. Since the initial peel strength at 23 ° C. is 0.05 (N / 25 mm) or more, the adherend is well held at room temperature, and the peel strength when heated at 60 ° C. is 0.05 (N / 25 mm) or more, the film is securely adhered to the adherend during film processing or transportation under heating conditions (for example, 60 ° C.), and the peel strength at normal temperature after heating at 150 ° C. for 1 hour is 0. Since it is 0.7 (N / 25 mm) or less, peeling from the adherend can be facilitated even after the treatment under the conditions.

  That is, according to the present invention, it is possible to perform a re-sticking operation at room temperature, the holding of the adherend is good, and the film adheres securely to the adherend during film processing or transportation under heating conditions (for example, 60 ° C.). A pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that can be easily peeled off from an adherend even after treatment at a high temperature condition (for example, 150 ° C., 1 hour), and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition Can be provided.

  The pressure-sensitive adhesive composition of the present invention is characterized by being formed to exhibit the following performance with respect to an adherend.

  First, the initial peel force at 23 ° C. (initial peel force (X1) at normal temperature) is 0.05 (N / 25 mm) or more. If X1 is less than 0.05 (N / 25 mm), the bonding with the adherend is deteriorated, which may cause inconveniences such as a decrease in workability, thereby preventing this. In this example, X1 is preferably 0.15 (N / 25 mm) or more. The upper limit of X1 is, for example, about 1 (N / 25 mm).

  Secondly, the peeling force (heating peeling force (X2)) in a heated atmosphere at 60 ° C. is 0.05 (N / 25 mm) or more. If X2 is less than 0.05 (N / 25 mm), the adhesion with the adherend is deteriorated during the heating step, which may cause inconveniences such as floating and peeling from the adherend, and this is prevented. . In this example, X2 is preferably 0.07 (N / 25 mm) or more. The upper limit of X2 is, for example, about 1 (N / 25 mm).

  Thirdly, the peel strength at normal temperature after heating at 150 ° C. (1 hour) (post-heat peel strength (X3)) is 0.7 (N / 25 mm) or less. When X3 exceeds 0.7 (N / 25 mm), it becomes difficult to peel off when the adhesive body is peeled off from the adherend, which may cause curling or adhesive residue on the adherend or cause cohesive failure. This is to prevent this. In this example, X3 is preferably 0.3 (N / 25 mm) or less. The lower limit of X3 is theoretically 0 (N / 25 mm).

  Although the composition of the pressure-sensitive adhesive composition of the present invention that exhibits the above performance (physical properties) is not particularly limited, it can be composed of, for example, the pressure-sensitive adhesive composition shown below.

  The pressure-sensitive adhesive composition according to an example contains a resin component (A) and a crosslinking agent (B) as essential components.

  As the resin component (A), at least two (two or more) acrylic resins are used. As the two or more kinds of acrylic resins, at least the component (A1) that maintains X1 (that is, maintains adhesion when bonded to the adherend) and X2 (that is, heating with the adherend). It is desirable to include the component (A2) for suppressing the increase of X3 and improving the removability at room temperature while maintaining the close contact with time).

  In order to suppress the increase in X3 while maintaining X2 together with X1, both A1 and A2 have moderately high mass average molecular weights (Mw1, Mw2) (Mw1 and Mw2 are 100,000 or more), and A2 is glass of A1. Those having a glass transition temperature (Tg2) higher than the transition temperature (Tg1) are used (Tg1 <Tg2).

  As A1 (first acrylic resin), one having a mass average molecular weight (Mw1) of 100,000 or more and a glass transition temperature (Tg1) of −25 ° C. or less is used. If Mw1 is less than 100,000, the peeling force after heating tends to increase, which is not preferable. The reason why Tg1 becomes −25 ° C. or less is that the adhesive strength starts to appear around 30 ° C. (Tg + 30 ° C.) plus the glass transition temperature (Tg) of the adhesive. If Mw1 is too high, the compatibility with A2 is deteriorated, and it is difficult to adjust the initial peeling force at room temperature and the peeling force after heating. If Tg1 is too low, it is difficult to adjust the peeling force during heating. For this reason, as A1, in addition to satisfying the above conditions (Mw1 is 100,000 or more and Tg1 is −25 ° C. or less), Mw1 is 1 million or less, preferably 800,000 or less, and / or Tg1 is − What becomes 70 degreeC or more is desirable.

  A1 is, for example, a (meth) acrylate (A12) having an alkyl group having 2 to 8 carbon atoms together with a functional group capable of reacting with a crosslinking agent (B) described later, and a monomer having an ethylenically unsaturated double bond ( A copolymer with A13).

  A12 is a component for improving the cohesive force of the pressure-sensitive adhesive layer by the pressure-sensitive adhesive composition of the present invention and preventing adhesive residue from being generated on the adherend. Examples of the functional group include a hydroxyl group, a carboxyl group, an amino group, an acetoacetoxyethyl group, and an epoxy group, but at least one selected from a hydroxyl group and an amino group is preferable from the viewpoint of versatility. Examples of A12 having such a functional group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, diethylene glycol mono (meta) as a monomer having a hydroxyl group. ) Acrylate, N-methylolacrylamide, allyl alcohol, p-hydroxystyrene and the like. Examples of the monomer having a carboxyl group include β-carboxyethyl (meth) acrylate, (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, and maleic anhydride. Examples of the monomer containing an amino group include aminomethyl (meth) acrylate, methylaminomethyl (meth) acrylate, methylaminoethyl (meth) acrylate, methylaminopropyl (meth) acrylate, and acrylamide. Examples of the monomer containing an acetoacetoxyethyl group include acetoacetoxyethyl (meth) acrylate. Examples of the monomer containing an epoxy group include glycidyl (meth) acrylate. Among these, by using at least one selected from 2-hydroxyethyl methacrylate (HEMA) and 2-hydroxyethyl acrylate (HEA), which are monomers having a hydroxyl group, the cohesive force of the adhesive layer can be further improved, and the adherend can be further adhered. It is possible to prevent the adhesive residue from being generated.

  A13 is a component for adjusting the peeling force from the adherend and making it easy to adjust the Tg of the entire pressure-sensitive adhesive layer of the pressure-sensitive adhesive composition of the present invention to an appropriate range. As A13, a (meth) acrylate having 2 to 8 carbon atoms (excluding ethyl methacrylate and methyl methacrylate), for example, ethyl acrylate (EA), methyl acrylate, butyl (meth) acrylate (BA, BMA), 2-ethylhexyl (meth) acrylate (2-EHA, 2-EHMA), propyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, vinyl acetate (VA), vinyl propionate, vinyl ether, Examples include styrene and (meth) acrylonitrile. Above all, by using at least one selected from ethyl acrylate, butyl (meth) acrylate, acrylonitrile (AN), methyl acrylate, 2-ethylhexyl (meth) acrylate and vinyl acetate, the peel strength from the adherend is further adjusted. This makes it easier to adjust the Tg of the entire adhesive layer to an appropriate range.

  Preferred mass ratios of A12 and A13 that can constitute A1 are as follows. A12 is 0.5% by mass or more, further 1% by mass or more as a lower limit, 10% by mass or less, further 5% by mass or less as an upper limit, and A13 is 30% by mass or more, further 50% by mass as a lower limit. %, And the upper limit is preferably 99.5% by mass or less, and more preferably 70% by mass or less.

  As A2 (second acrylic resin), one having a mass average molecular weight (Mw2) of 100,000 or more and a glass transition temperature (Tg2) higher than Tg1 is used. When Mw2 is less than 100,000, the peel strength after heating tends to increase. On the other hand, when Tg2 is Tg1 or less (Tg2 ≦ Tg1), the peel strength during heating tends to be insufficient, which is not preferable. If Mw2 is too high, the compatibility with A1 deteriorates, and it becomes difficult to adjust the initial peeling force at room temperature and the peeling force after heating. On the other hand, if Tg2 is too high, it is difficult to adjust the peeling force at room temperature after heating. Therefore, as A2, in addition to satisfying the above conditions (Mw2 is 100,000 or more and Tg2 is higher than Tg1 (Tg2> Tg1)), Mw2 is 1,000,000 or less, preferably 600,000 or less, and It is desirable that Tg2 is 30 ° C. or lower.

A2 can be composed of, for example, a copolymer of A12 and A13 and A11 (ethyl methacrylate or methyl methacrylate).
A11 is a component for preventing adhesive residue from being produced on the adherend even after being applied to the adherend and heated at high temperature without reducing the thickness of the adhesive layer of the pressure-sensitive adhesive composition of the present invention. is there.

  Preferred mass ratios of A11, A12, and A13 that can constitute A2 are as follows. A11 has a lower limit of 20% by mass or more, preferably 30% by mass or more, more preferably 50% by mass or more, and an upper limit of 80% by mass or less, preferably 70% by mass or less, more preferably 65% by mass. The lower limit is 0.5% by mass or more, preferably 1% by mass or more, the upper limit is 10% by mass or less, preferably 5% by mass or less, and A13 is 10% by mass or more, preferably 25% by mass as the lower limit. More preferably, the content is 30% by mass or more, and the upper limit is 79.5% by mass or less, preferably 69% by mass or less, and more preferably 49% by mass or less.

  In the present invention, the blending ratio (A1: A2) of A1 and A2 is in the range of 95: 5 to 65:35 (preferably 90:10 to 80:20) in terms of mass. When the blending ratio of A2 is less than 95: 5, the peeling force during heating is insufficient, and the peeling force after heating tends to increase. On the other hand, when the blending ratio of A2 exceeds 65:35, the initial peeling force This is not preferable because the compatibility is likely to deteriorate.

  In the present invention, it is further preferable that A1 and A2 are selected so that the difference between Tg2 and Tg1 (Tg2−Tg1) is 10 ° C. or more from the viewpoint of increasing the peeling force during heating. In addition to or separately from this, it is preferable to select A1 and A2 so that the ratio of Mw2 to Mw1 (Mw2 / Mw1) is 0.5-2. By making Mw2 / Mw1 0.5 or more, it is possible to make it easier to suppress an increase in peel force after heating, and by making Mw2 / Mw1 2 or less, compatibility can be further improved, so that desired A pressure-sensitive adhesive layer can be easily obtained.

A crosslinking agent (B) means the substance which can bridge | crosslink A1 and / or A2 which were demonstrated previously, and can form a crosslinked polymer. By forming the crosslinked polymer, it becomes easy to exhibit sufficient adhesive force during film processing and excellent peelability after cooling.
As B, an isocyanate crosslinking agent, a metal chelate crosslinking agent, an epoxy crosslinking agent, or the like is generally known. In the present invention, an isocyanate crosslinking agent can be preferably used.

  As an isocyanate type crosslinking agent, a conventionally well-known isocyanate type crosslinking agent, for example, a polyvalent isocyanate compound, its oligomer, a prepolymer, etc. can be used conveniently. Examples of the polyvalent isocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4′-diisocyanate, and diphenylmethane. -2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate and the like. . Among these, alicyclic diisocyanates such as isophorone diisocyanate can be preferably used. This cross-linking agent is preferable in that it has the effect of imparting excellent removability and heat resistance. In addition, a "crosslinking agent" may be used independently and may be used in combination of 2 or more type.

  The blending ratio of B is not particularly limited because it varies depending on the type of crosslinking agent, the number of functional groups, and the like, but is 1 to 8 parts by mass with respect to 100 parts by mass of A (for example, the sum of A1 and A2). The range is preferable, and the range of 1.5 to 6 parts by mass is more preferable. By setting the blending ratio of B to 1 part by mass or more, it is possible to further suppress the increase in peeling force after heating and to easily peel without remaining, and by setting it to 8 parts by mass or less, the initial peeling at room temperature can be performed more easily. The decrease in power can be suppressed.

  The pressure-sensitive adhesive composition of this example can be obtained by adding the above-described (A) and (B), and various conventionally used additives as necessary, in any order, and dissolving or dispersing them. . The raw materials can be mixed using a mixer or a kneader such as a dissolver, planetary mixer, butterfly mixer.

Examples of the various additives include crosslinking accelerators, antioxidants, stabilizers, viscosity modifiers, tackifier resins, organic or inorganic fillers, and light absorbers such as ultraviolet rays. Examples of the crosslinking accelerator include triethylamine, cobalt naphthenate, tin, zinc, titanium, zirconium, and the like. When the crosslinking agent is an isocyanate-based crosslinking agent, in particular, zinc-based, titanium-based and zirconium-based accelerators such as alkoxides, acylates, complexes, stannous chloride, tetra-n-butyltin, stannic chloride, trimethyltin hydroxide It is preferable to use a tin accelerator such as dimethyltin dichloride or di-n-butyltin dilaurate. Moreover, when using an epoxy resin as a crosslinking agent, phenols containing three tertiary amines known as trade name TMP-30 in one molecule are particularly effective. Examples of the light absorber include benzotriazole ultraviolet absorbers and triazine ultraviolet absorbers.
Moreover, phenolic antioxidant etc. are mentioned as antioxidant. By containing an appropriate amount of an antioxidant in the pressure-sensitive adhesive composition of this example, an increase in peel strength after heating can be further suppressed when the pressure-sensitive adhesive layer is formed.
The addition amount of the antioxidant is preferably 10 parts by mass or less, more preferably 1 part by mass or less with respect to 100 parts by mass of A (for example, the sum of A1 and A2). In addition, even if it adds antioxidant excessively, since the effect acquired is constant, it is preferable that antioxidant is the said range from a viewpoint of economical efficiency. Moreover, since the antioxidant added excessively tends to precipitate from the pressure-sensitive adhesive layer with time and may adversely affect the peel strength after heating, the above range is preferable from this point of view.

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer. This pressure-sensitive adhesive layer can be obtained by applying the above-described pressure-sensitive adhesive composition on a substrate film and drying it as necessary.
The substrate film used in the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but those having heat resistance are good. For example, in addition to polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyimide resin, polycarbonate Examples include films made of resin, polystyrene resin, polyamide resin, polyetherimide resin, polyetherketone resin, polyphenylene sulfide resin, polyacrylate resin, polyester ether resin, polyamideimide resin, polymethyl methacrylate resin, fluorine resin, etc. Polyethylene terephthalate is a particularly preferable base material in terms of properties and performance. The base film can be used regardless of whether it is transparent or opaque, and may be colored.

  The thickness of the base film is a thickness of what is conventionally used as the base film as long as it can protect the adherend and can be supported with the necessary strength, for example, about 10 to 125 μm. The thickness is used.

  The surface of the base film can be subjected to a surface treatment as desired. Examples of the surface treatment at this time include (1) discharge treatment such as corona discharge treatment and glow discharge treatment, (2) plasma treatment, (3) flame treatment, (4) ozone treatment, (5) ultraviolet treatment and electron beam. Ionizing active ray treatment such as radiation treatment, (6) surface roughening treatment such as sand mat treatment and hairline treatment, (7) chemical treatment, (8) anchor layer formation, and the like. As the anchor layer, polyurethane resin, polyester resin, acrylic resin, polyester polyurethane resin, or the like is used. The thickness of this anchor layer is usually in the range of 0.01 to 1.5 μm.

  The thickness of the adhesive layer is not particularly limited as long as it has predetermined peeling performance (X1 to X3), and is generally about 2 to 50 μm, preferably about 3 to 20 μm. If it is thinner than this thickness, X1 becomes small and X2 is difficult to satisfy 0.05 (N / 25 mm) or more, and as a result, the adherend may float or peel off during the process. Moreover, when this range is exceeded, X1 becomes high and X3 also becomes large, which is unfavorable because it impairs removability.

  In order to facilitate the handling of the pressure-sensitive adhesive sheet of the present invention, a peelable separator is preferably bonded to the surface of the pressure-sensitive adhesive layer until it is bonded to the adherend. Any known separator can be used, and its thickness is preferably about 15 to 200 μm.

The pressure-sensitive adhesive sheet of the present invention can be used for a wide range of applications such as formation of a fine pattern on a substrate (production of a fine pattern substrate in which the fine pattern is arranged on the substrate).
Examples of the fine pattern include a decorative pattern of a decorative film and a wiring pattern for transmitting a signal. A wiring pattern substrate on which a wiring pattern is arranged on a substrate is used by being incorporated into various electronic components such as a touch panel, a liquid crystal display, an organic EL display, a solar cell module, and a printed wiring board. The decoration pattern board | substrate with which the decoration pattern has been arrange | positioned on a base material is used for an electronic device, a vehicle interior, an exterior, etc., for example.

  Therefore, the adherend referred to in this example means a laminate that is the basis of the above-described formation of a fine pattern (production of a fine pattern substrate). Such a laminate is, for example, a photosensitive material comprising a laminate of a pattern forming layer (a layer on which a fine pattern is formed. For example, a wiring pattern forming layer or a decorative pattern forming layer) and a photosensitive resin layer on a substrate. And a laminate of a photosensitive film provided with a layer, a base material having a pattern-forming layer formed on the entire surface of one side, and a dry film resist corresponding to the photosensitive resin layer. In this example, a pattern formation layer is provided on a base material, and a photosensitive resin layer is provided on a pattern formation layer.

  Hereinafter, the present invention will be specifically described based on experimental examples (including examples and comparative examples), but the present invention is not limited to these examples.

1. Preparation of adhesive sheet [Experimental Examples 1 to 14]
On one side of a heat-resistant substrate film (50 μm, polyethylene terephthalate), adhesive layer forming coating liquids a to p prepared by uniformly mixing and dissolving the following components at a solid content ratio (in terms of mass) shown in Table 2 are prepared. Each was applied by a Baker type applicator so that the dry film thickness was about 7 μm. The total solid content in each coating solution was adjusted to 30% by mass. Then, after forming an adhesive layer by drying at 160 ° C. for 1 minute, after bonding a PET film (separator) having a thickness of 25 μm, one surface of which was subjected to silicone release treatment, to the surface of this adhesive layer Then, curing was performed at room temperature to obtain a pressure-sensitive adhesive sheet of each example.

<< Constituent Components of Adhesive Layer Forming Coating Liquids a to p >>
First acrylic resin (A1, A1 ′): type / composition described in Table 1 and solid content ratio described in Table 2 Second acrylic resin (A2, A2 ′): type / composition described in Table 1 And solid content ratio / crosslinking agent (B) described in Table 2: Solid content ratio described in Table 2 (Takenate D-140N, alicyclic diisocyanate, manufactured by Mitsui Chemicals, Inc.)
・ Solvent (mixed solvent of toluene and methyl isobutyl ketone): appropriate amount

2. Evaluation About the adhesive sheet obtained by each example, the physical property of the adhesion layer was measured and evaluated by the following method.
(2-1) Initial peeling force X1 (N / 25mm)
The pressure-sensitive adhesive sheet obtained in an experimental example of 2 cm × 10 cm was prepared under the conditions of 23 ° C. and 65% RH, and the pressure-sensitive adhesive layer was peeled off and exposed to a PET film (thickness 50 μm, Lumirror T-60, Toray Industries, Inc.) was reciprocated once at a speed of 300 mm / min using a 2 kg rubber roller and bonded together. Next, for a test piece that was left for 20 minutes under the same conditions (23 ° C., 65% RH), the PET film was peeled off in a 180 ° direction at a pulling speed of 300 mm / min using a tensile tester under the same conditions. The peel force (initial peel force X1) was measured (Table 2) and evaluated according to the following criteria. The results are shown in Table 3.

“AA”: 0.15 (N / 25 mm) or more (excellent bonding properties).
“A”: 0.05 (N / 25 mm) or more and less than 0.15 (N / 25 mm) (adhesiveness is good).
“B”: Less than 0.05 (N / 25 mm) (bonding property is poor).

(2-2) Peeling force during heating X2 (N / 25mm)
The PET film and pressure-sensitive adhesive sheet were pressure-bonded in the same manner as in (2-1) above, and the test piece that was allowed to stand for 20 minutes was peeled in the same manner as in (2-1) in a 60 ° C. atmosphere (peeling force when heated) X2) was measured (Table 2) and evaluated according to the following criteria. The results are shown in Table 3.

“AA”: 0.07 N / 25 mm) or more (excellent adhesion).
“A”: 0.05 (N / 25 mm) or more and less than 0.07 (N / 25 mm) (adhesion is good).
“B”: Less than 0.05 (N / 25 mm) (adhesion is poor).

(2-3) Peeling force after heating X3 (N / 25mm)
In the same manner as in (2-1) above, the PET film and the pressure-sensitive adhesive sheet were pressure-bonded, and the test piece that was allowed to stand for 20 minutes was heated in an atmosphere of 150 ° C. for 1 hour, and then cooled under conditions of 23 ° C. and 65% RH. The peel strength (post-heat peel strength X3) was measured in the same manner as in (2-1) above (Table 2), and evaluated according to the following criteria. The results are shown in Table 3.

“AA”: 0.3 (N / 25 mm) or less (excellent peelability).
“A”: More than 0.3 (N / 25 mm) and 0.7 (N / 25 mm) or less (good peelability).
“B”: 0.7 (N / 25 mm) exceeded (peelability is poor).

(2-4) Compatibility of acrylic resin (A1) and acrylic resin (A2) in coating solution First acrylic resin (A1) and second acrylic resin in adhesive layer-forming coating solution ( Whether the compatibility with A2) is good or not was evaluated by visual observation of the coating liquid and the state of the adhesive layer surface. The results are shown in Table 3.

“AA”: The coating solution is transparent without white turbidity, and there is no whitening on the surface of the adhesive layer (excellent compatibility)
"A": The coating solution becomes slightly cloudy, but there is no whitening on the adhesive layer surface (good compatibility)
“B”: The coating solution becomes cloudy and the adhesive layer surface is whitened (poor compatibility)

3. Consideration
Experimental Examples 2-4, 4a, 4b, 5, 6, 8, 9, 12, 13, 14 have Aw and Mw (Mw1, Mw2) of 100,000 or more (A1a, A2a, A2b, A2c) is used, and those used as A2 (A2a, A2b, A2c) have a glass transition temperature Tg2 higher than the glass transition temperature Tg1 of A1, and further, the compounding ratio (A1) of A1 and A2 : A2) was an adhesive sheet having an adhesive layer made of an adhesive composition satisfying 95: 5 to 65:35 in terms of mass (Tables 1 and 2). These pressure-sensitive adhesive sheets had a sufficient initial tack and good bonding properties (X1 is A or AA). Moreover, it had sufficient adhesiveness at the time of heating (X2 is A or AA), and there was no residue after heat treatment, and the peelability was good (X3 was A or AA). Moreover, the compatibility of A1 and A2 in the coating solution was also good (compatibility A or AA) (Table 3).
In particular, in Experimental Examples 3, 4, and 5, both Mw1 and Mw2 are 100,000 or more, Mw1 is 800,000 or less, Mw2 is 600,000 or less, and the mixing ratio of A1 and A2 (A1: A2) is converted into mass. However, X1, X2, X3 and compatibility were all excellent.

  On the other hand, although Experimental example 1 contained what belongs to A1 (A1a) as an adhesive composition, it did not contain what belongs to A2 (Table 2). As a result, compared with Experimental Examples 2-4, 4a, 4b, 5, 6, 8, 9, 12, 13, 14, X2 was low and X3 was high (Table 3). From this, it is understood that the pressure-sensitive adhesive composition must contain, as A, together with A1, those belonging to A2.

  Experimental Example 7 is a pressure-sensitive adhesive sheet in which the blending ratio of A1 and A2 (A1: A2) is 64:36 (not satisfying 95: 5 to 65:35) in terms of mass and the amount of A2 is large. (Table 2). As a result, compared with Experimental Examples 2-4, 4a, 4b, 5, 6, 8, 9, 12, 13, 14, X1 was low. Further, the compatibility of A1 and A2 in the coating solution was poor (Table 3). This shows that the pressure-sensitive adhesive composition must contain A1 and A2 in an appropriate amount.

  Experimental Example 10 contains A1 as the pressure-sensitive adhesive composition, but does not contain any material belonging to A2, and instead contains one having Mw2 of 24,000 (less than 100,000) (A2d) (Table 1, Table 2). As a result, X3 became high compared with Experimental Examples 2-4, 4a, 4b, 5, 6, 8, 9, 12, 13, and 14 (Table 3). From this, it can be seen that the pressure-sensitive adhesive composition must contain A as well as A1 with Mw2 belonging to A2 of 100,000 or more.

  Moreover, although Experimental example 11 contains A1 as an adhesive composition, it does not contain what belongs to A2, A11 is not contained instead, and Mw1 is 27,000 (less than 100,000) ( A1b) was used (Table 1, Table 2). As a result, X3 became high compared with Experimental Examples 2-4, 4a, 4b, 5, 6, 8, 9, 12, 13, and 14 (Table 3). From this, it can be seen that the pressure-sensitive adhesive composition must contain A as well as A1, which belongs to A2, that is, contains A11 and has Mw of 100,000 or more.

  Subsequently, the effect of adding an antioxidant was examined as follows.

1. Preparation of pressure-sensitive adhesive sheet [Experimental Examples 15 to 18]
A pressure-sensitive adhesive sheet was prepared in the same manner as in Experimental Examples 1 to 14 except that the pressure-sensitive adhesive layer-forming coating solution used was added with an antioxidant as follows.
<< Constituent Components of Adhesive Layer Forming Coating Liquid q to t >>
First acrylic resin (A1, A1 ′): type / composition described in Table 1 and solid content ratio described in Table 4. Second acrylic resin (A2, A2 ′): type / composition described in Table 1 And solid content ratio / crosslinking agent (B) described in Table 4: Solid content ratio described in Table 4 (Takenate D-140N, alicyclic diisocyanate, manufactured by Mitsui Chemicals, Inc.)
Antioxidant: solid content ratio described in Table 4 (IRGANOX3114, phenolic antioxidant, BASF)
・ Solvent (mixed solvent of toluene and methyl isobutyl ketone): appropriate amount

2. Evaluation Regarding the pressure-sensitive adhesive sheet obtained in each example, the initial peel force X1 (N / 25 mm), the peel force during heating X2 (N / 25 mm), and the peel force after heating X3 (N / 25 mm) were the same as above. ) Was measured. The results are shown in Table 4. In Table 4, the results of Experimental Example 4 are also shown for comparison.

3. Discussion In each of Experimental Examples 15 to 18, X1 is 0.15 (N / 25 mm) or more, X2 is 0.07 (N / 25 mm) or more, and X3 is 0.3 (N / 25 mm) or less. Met.
Compared with Experimental Example 4, Experimental Examples 15 to 17 have the same initial peel force X1 (N / 25 mm) and warm peel force X2 (N / 25 mm), and post-heating peel force X3 (N / 25 mm). Was better.
Experimental Example 18 is superior to Experimental Example 4 in initial peel force X1 (N / 25 mm) and warming peel force X2 (N / 25 mm), and the post-heating peel force X3 (N / 25 mm) is It was almost the same.
As described above, any of the initial peeling force X1 (N / 25 mm), the heating peeling force X2 (N / 25 mm), and the post-heating peeling force X3 (N / 25 mm) can be achieved by adding an antioxidant. It turned out that it can do better. In particular, by setting the addition amount of the antioxidant to 10 parts by mass or less with respect to 100 parts by mass of A, the increase in the post-heating peel force X3 is suppressed while maintaining the initial peel force X1 and the warming peel force X2. I found out that I could do it.

Claims (7)

A first acrylic resin (A1) and a second acrylic resin (A2) having a glass transition temperature (Tg2) higher than the glass transition temperature (Tg1) of the A1, and the mass average molecular weight of the A1 ( A resin component (A) in which both Mw1) and A2 have a mass average molecular weight (Mw2) of 100,000 or more;
A crosslinking agent (B);
Including
The blending ratio (A1: A2) of A1 and A2 in A is 95: 5-65: 35 in terms of mass,
The initial peel force at 23 ° C. is 0.05 (N / 25 mm) or higher, and the peel strength when heated at 60 ° C. is 0.05 (N / 25 mm) or higher, after heating at 150 ° C. for 1 hour. Used to form an adhesive layer having a peel strength of 0.7 (N / 25 mm) or less after heating at
Adhesive composition.   The pressure-sensitive adhesive composition according to claim 1, wherein Tg1 is -70 to -25 ° C, Tg2 is -15 to 30 ° C, and a difference between Tg2 and Tg1 (Tg2-Tg1) is 10 ° C or more.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the ratio (Mw2 / Mw1) of Mw2 and Mw1 is 0.5 to 2.   A2 includes at least ethyl methacrylate or methyl methacrylate (A11), (meth) acrylate (A12) having a functional group capable of reacting with B and an alkyl group having 2 to 8 carbon atoms, and an ethylenically unsaturated double bond. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive composition is formed from a copolymer with a monomer (excluding ethyl methacrylate and methyl methacrylate) (A13).   The pressure-sensitive adhesive composition according to claim 4, wherein A1 is formed of at least a copolymer of A12 and A13.   The pressure-sensitive adhesive composition according to any one of claims 1 to 5, further comprising an antioxidant.   The adhesive sheet which has the adhesion layer which consists of an adhesive composition in any one of Claims 1-6 on a base film.