JP2008038103A - Heat-resistant pressure-sensitive adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant pressure-sensitive adhesive composition having an initial adhesive strength in a degree of not allowing easy dropping, and capable of holding the adhesive strength in a degree of allowing easy peeling even after heated to a high temperature in the pressure-sensitive adhesive composition usable for a pressure-sensitive adhesive sheet having an adhesive layer formed on a base material sheet; and to provide the heat-resistant pressure-sensitive adhesive sheet obtained by coating the heat-resistant pressure-sensitive adhesive composition on the base material sheet, and drying the coated product. <P>SOLUTION: The heat-resistant pressure-sensitive adhesive composition contains 85-15 mass% high-molecular weight acrylic copolymer having ≥600,000 mass-average molecular weight and ≤20 mg/mgKOH acid value, and 15-85 mass% low-molecular weight acrylic copolymer having ≤500,000 mass-average molecular weight and ≥25 mg/mgKOH acid value as essential components, and is obtained by using alkyl (meth)acrylates in which the difference of the numbers of carbons of the alkyl parts of the alkyl (meth)acrylates of the main component monomers constituting both of the copolymers is ≤2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet obtained by applying and drying the pressure-sensitive adhesive composition. More specifically, the pressure-sensitive adhesive composition having excellent heat resistance and the surface of a base sheet are coated with the same. The present invention relates to a heat-resistant adhesive sheet obtained by drying.

  In recent years, electronic devices and the like have been miniaturized, and the components constituting them have also been increasingly light, thin and small. Among them, for example, an electronic circuit board which is a brain part of an electronic device is also miniaturized, and in the manufacturing site, for example, a substrate is provided on a carrier sheet having a fixing adhesive layer formed on the surface for the purpose of stable processing. Processing such as adhesive fixing of materials and mounting of each part is performed. After the processing is completed, each substrate is peeled and separated from the carrier sheet, and proceeds to the next processing process, inspection process or packaging process . When exposed to a high-temperature environment or heating condition atmosphere in the section through the processing process, the adhesive strength increases, peeling becomes difficult and the work efficiency decreases, or in the case of remarkable pressure-sensitive adhesive on the back side of the substrate May remain (so-called adhesive residue), hinder the next process, or may impair the performance of the product.

  As a method for improving such a problem, for example, an acrylic resin obtained by polymerizing an acrylic monomer in the presence of a specific silane compound, a curing agent, preferably a polyol compound and / or melamine as a curing aid. A pressure-sensitive adhesive composition obtained by blending a system compound is disclosed. (See Patent Document 1) According to the description of the effect column of the invention, this adhesive has little change over time in cohesive force and adhesive force even under high temperature or high temperature and high humidity, and is excellent in curved surface adhesive force. In addition, the adhesive between various optical films and various substrates such as glass is not only excellent in durability such as not causing foaming or peeling of the adhesive, but also left for a long time in a high temperature and high humidity environment. However, it is described that there is an effect that the optical characteristics are not deteriorated.

However, the adhesive film thus obtained has an adhesive strength (adhesive strength) of 1.7 to 1.9 kg / 25 mm (_0.68 to 0.76 N / cm), and is a thin film for electronic circuits. Adhesive strength is excessive as compared with 0.05 to 0.3 N / cm, which is suitable for use, while the adhesive having a relatively low level of adhesive force shown as a comparative example has an adhesive strength of 0. Although it is a low level of 5 to 0.8 kg / 25 mm (0.2 to 0.32 N / cm), the cohesive force is inferior, and it is evaluated that foaming and peeling occur after a 50 ° C. × 48 hour durability test. . That is, it is suggested that adhesive residue is likely to occur.

In addition, as a pressure-sensitive adhesive composition with little increase in adhesive strength even after heat treatment, a releasable pressure-sensitive adhesive comprising a hydroxyl group-containing acrylic polymer, an amine compound containing a plurality of hydroxyl groups, and a polyisocyanate compound. An adhesive composition and a re-peeling pressure-sensitive adhesive sheet are known (see Patent Document 2). This adhesive sheet for re-peeling has an initial adhesive force of 1.8 to 2.4 N / 20 mm (0.9 to 1.2 N / cm) by a 180-degree peeling method for a melamine resin-coated steel sheet, and is 50 ° C. × 48 hours. The adhesive strength after heat treatment is 1.2 times or less of the initial adhesive strength. As in the case of the pressure-sensitive adhesive film described in Patent Document 1, the re-peeling pressure-sensitive adhesive sheet also has a high initial level of adhesive strength itself, that is, excessive weight.
Japanese Patent Application Laid-Open No. 08-199144. JP 2002-356562 A.

The problem to be solved by the present invention is that a pressure-sensitive adhesive composition that can be used for a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on a base material sheet has an adhesive strength that does not easily fall off as an initial adhesive strength, and is heated at a high temperature. It is to provide a heat-resistant pressure-sensitive adhesive composition that can maintain a light adhesive strength that can be easily peeled even after being applied, and further, the heat-resistant pressure-sensitive adhesive composition is applied onto a substrate sheet and dried. It is providing the heat resistant adhesive sheet obtained by this.

The first gist of the present invention is that 97.5 to 99% by mass of an alkyl (meth) acrylate having 3 to 12 carbon atoms in the alkyl group portion as a main component monomer and 2.5 to 1 mass of a functional group-containing acrylic monomer. 85 to 15% by mass of an acrylic high molecular weight copolymer having a mass average molecular weight of 600,000 or more and an acid value of 20 mg / mg KOH or less, and an alkyl group part having 3 to 12 carbon atoms as a main component monomer. An acrylic low molecular weight copolymer containing 90 to 98% by mass of an alkyl (meth) acrylate and 10 to 2% by mass of a functional group-containing acrylic monomer, having a mass average molecular weight of 500,000 or less and an acid value of 25 mg / mg KOH or more. The main component monomer of the acrylic high molecular weight copolymer, comprising 100 parts by mass of a copolymer composition having 15 to 85% by mass as a main component and 1 to 15 parts by mass of a crosslinking agent. In the heat-resistant pressure-sensitive adhesive composition in which the difference between the carbon number of the alkyl group moiety and the carbon number of the alkyl group moiety of the main component monomer of the acrylic low molecular weight copolymer is 2 or less, The gist lies in a heat-resistant pressure-sensitive adhesive sheet obtained by applying a coating solution containing the above heat-resistant pressure-sensitive adhesive composition on a substrate sheet and drying it. In the present invention, (meth) acrylate means acrylate and / or methacrylate.

The heat-resistant pressure-sensitive adhesive composition of the present invention has a mass average molecular weight as large as 600,000 or more, an acrylic high molecular weight copolymer having a low acid value of 20 mg / mg KOH or less, a mass average molecular weight as small as 500,000 or less, an acid By blending as a main component an acrylic low molecular weight copolymer having a value of 25 mg / mg KOH or higher and a crosslinking agent, the adhesive strength before heating is not too low, and adhesion is possible even after high temperature heating. The increase in strength is small, and at this time, the difference in carbon number of the alkyl group part of the main component monomer constituting both copolymers is 2 or less, so the compatibility between both copolymers is excellent, and these are blended The pressure-sensitive adhesive thus obtained has no risk of phase separation, and since there is no adhesive residue even after peeling after use as an adhesive, it can provide an adhesive having heat resistance and excellent removability. .

The heat-resistant pressure-sensitive adhesive composition of the present invention comprises an acrylic high molecular weight copolymer and an acrylic low molecular weight copolymer as main components and a crosslinking agent added thereto.

Said acrylic high molecular weight copolymer has 97.5 to 99% by mass of an alkyl (meth) acrylate having 3 to 12 carbon atoms in the alkyl group as a main component monomer and 2.5 to 2.5 functional group-containing acrylic monomer. 1.0 mass% is included. The polymerization molecular weight is 600,000-3 million normally, Preferably it is 800,000-1 million.

  Examples of the alkyl (meth) acrylate as the main component include, for example, (meth) acrylic acid alkyl esters such as propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and isobutyl (meth). Alkyl (meta) such as acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate ) Acrylates and the like. Among them, those having 7 or more carbon atoms in the alkyl group are preferably 50% by mass or more, for example, 2-ethylhexyl acrylate is preferably 50% by mass or more, and 90% by mass. More preferably from above, still more preferably at least 95 mass%.

Examples of the functional group-containing acrylic monomer include a carboxyl group-containing acrylic monomer and a hydroxyl group-containing acrylic monomer.

Examples of the carboxyl group-containing acrylic monomer include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and the like.
Examples of the hydroxyl group-containing acrylic monomer include hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4 -Hydroxyalkyl (meth) acrylate such as hydroxybutyl (meth) acrylate and 6-hydroxyhexyl (meth) acrylate. The amount of the functional group-containing acrylic monomer is relatively small so that the acid value of the copolymer is 20 mg / mg KOH or less, and is usually 1 to 2.5% by mass. Among them, the carboxyl group-containing acrylic monomer is preferably 1% by mass or more.

  As the monomer constituting the acrylic high molecular weight copolymer, in addition to the main component monomer, other copolymerizable monomers may be used as long as they do not impair the purpose of the present invention. As a part, Preferably it is 10 mass% or less, More preferably, the quantity of 5 mass% or less can be mix | blended.

Examples of the other copolymerizable monomers include alkyl (meth) acrylates having 1 or 2 alkyl groups, (meth) acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth And vinyl monomers such as acrylamide, (meth) acrylic acid dimethylaminoethyl ester, (meth) acrylic acid diethylaminoethyl ester, dimethylaminopropylacrylamide, and vinyl acetate.

  The acrylic high molecular weight copolymer used in the present invention is a reaction solution obtained by dissolving each of the above monomer components in a solvent, and after adding a polymerization initiator and a chain transfer agent as necessary to this, usually, It can be produced by heat polymerization. In order to achieve the target mass average molecular weight of 600,000 to 3,000,000, the above concentration is set to a relatively high monomer concentration in the reaction solution, for example, 40 to 50% by mass at the beginning of polymerization. It is preferable to add a solvent and dilute to a practical concentration, for example, 30 to 40% by mass.

  Examples of the solvent used for dissolving the above components include n-pentane, toluene, benzene, n-hexane, dioxane, methyl ethyl ketone, methyl isobutyl ketone, methyl acetate, ethyl acetate, butyl acetate, and mixtures thereof. In general, ethyl acetate, toluene or a mixture thereof is generally used. As the above solvent, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and butyl alcohol can be mixed in a range of about 10% by mass or less as long as the purpose of the present invention is not hindered.

  Examples of the polymerization initiator include peroxides such as benzoyl peroxide (BPO), lauryl peroxide, cumene peroxide, and azo compounds such as azobisisobutyronitrile. Such a polymerization initiator is usually 0.05 to 2.0 parts by mass, and practically 0.1 to 0.5 parts by mass with respect to 100 parts by mass of all copolymerization monomers.

  As the chain transfer agent, thiols are usually used, and specific examples include n-dodecanethiol and the like. Such a chain transfer agent is usually 0.01 to 0.5 parts by mass, and practically 0.1 to 0.5 parts by mass with respect to 100 parts by mass of all copolymerization monomers.

  The conditions for the above copolymerization reaction are not particularly limited. Usually, the inside of the reaction system is replaced with an inert gas, and refluxed using a cooler. The reaction is continued for about 10 hours. Moreover, as said inert gas, nitrogen gas is generally used from an economical viewpoint. In the reaction, the mass average molecular weight of the polymer component is usually controlled by monitoring the reaction liquid component at any time and adjusting the solution concentration, polymerization initiator addition amount, chain transfer agent addition amount, reaction temperature, reaction time, etc. The

The acrylic low molecular weight copolymer comprises 90 to 98% by mass of an alkyl (meth) acrylate having 3 to 12 carbon atoms in the alkyl group and 2 to 10% by mass of a functional group-containing acrylic monomer as a main component monomer. Including. The polymerization molecular weight is usually 200,000 to 500,000, preferably 300,000 to 400,000.

Examples of the alkyl (meth) acrylate that is a main component constituting the acrylic low molecular weight copolymer include those used in the acrylic high molecular weight copolymer. Those having 7 or more carbon atoms are preferably 50% by mass or more, for example, 2-ethylhexyl acrylate is preferably 50% by mass or more, and more preferably 90% by mass or more.

In addition, the functional group-containing acrylic monomer constituting the acrylic low molecular weight copolymer may be one used for the acrylic high molecular weight copolymer. The blending amount is relatively large so that the acid value of the copolymer is 25 mg / mg KOH or more, usually 2 to 10% by mass, and practically 3 to 6% by mass. The group-containing acrylic monomer is preferably 3% by mass or more.

As the monomer constituting the acrylic low molecular weight copolymer, in the same manner as in the case of the acrylic high molecular weight copolymer, in addition to the main component monomer, other copolymerizable monomers may be used. As a part of the alkyl (meth) acrylate, an amount of preferably 10% by mass or less, more preferably 5% by mass or less can be blended. Examples of such other copolymerizable monomers include those exemplified in the case of the acrylic high molecular weight copolymer.

In addition, the adhesive in the copolymer composition obtained by blending both of the above acrylic high molecular weight copolymer and the above acrylic low molecular weight copolymer is the main application. From the viewpoints of suppressing phase separation when used as an agent, suppressing adhesive residue after peeling, and improving the transparency of the adhesive layer, the main component monomers of both copolymers are mutually structured. Are preferably used at a higher content, for example, the difference in the carbon number of the alkyl group portion of the alkyl (meth) acrylate, which is the main component monomer constituting both copolymers, is 2 or less. And it is more preferred that both alkyl groups are the same. Such an alkyl (meth) acrylate is preferably contained in each copolymer in an amount of 50% by mass or more, and more preferably 90% by mass or more. Among the alkyl (meth) acrylates having 3 to 12 carbon atoms in the alkyl group portion, 2-ethylhexyl acrylate (2EHA) can be cited as a more preferable one.

The acrylic low molecular weight copolymer used in the present invention is prepared by dissolving a monomer component in a solvent to prepare a reaction solution in the same manner as in the case of the acrylic high molecular weight copolymer. In this case, the concentration of the initial reaction solution is determined in view of the fact that the target copolymer has a relatively small mass average molecular weight of 200,000 to 500,000. However, it is not necessary to make it particularly high, and it can be generally 30 to 45% by mass, and practically about 35 to 45% by mass.

  The heat-resistant pressure-sensitive adhesive composition of the present invention is prepared by blending the acrylic high molecular weight copolymer and acrylic low molecular weight copolymer obtained as described above, and adding a crosslinking agent thereto. Usually, it is obtained as a solution containing a reaction solvent. The blending ratio of the acrylic high molecular weight copolymer and the acrylic low molecular weight copolymer is 85:15 to 15:85, preferably 75:25 to 25:85, as a solid content ratio. When it exceeds 85:15, the heat resistance is insufficient, and the peel strength becomes too high when exposed to a high temperature environment. Moreover, when it is less than 15:85, since the adhesive strength at the beginning of application is small, there is a risk of peeling and dropping at the handling stage after application. The solid content in the above composition, that is, the concentration of the acrylic copolymer is usually 30 to 50% by mass, but practically the copolymer solution prepared by the above procedure is used for the acrylic high molecular weight copolymer. What is necessary is just to mix according to the predetermined | prescribed compounding ratio of a compound and an acrylic low molecular weight copolymer, and it is not necessary to adjust a density | concentration except the case where it is necessary to make the density | concentration as a product constant.

As said crosslinking agent, an isocyanate type compound and an epoxy-type compound are mentioned normally. The isocyanate compounds are roughly classified into aliphatic and aromatic compounds, and aromatic compounds include those that are partially hydrogenated. Can be used. Examples of the isocyanate-based crosslinking agent include TDI-TMP (tolylene diisocyanate-trimethylpropane adduct), HMDI-burette type, HMDI-isocyanurate, HMDI-TMP adduct (hexamethylene diisocyanate-trimethylpropane adduct), XDI- Isocyanate compounds such as TMP adducts (xylylene diisocyanate-trimethylpropane adduct).

Examples of the epoxy compound include epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, diglycidyl aniline, trimethylolpropane triglycidyl ether, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, and the like. Can be mentioned.

  The amount of the crosslinking agent added to the heat-resistant pressure-sensitive adhesive composition is an amount that can sufficiently crosslink between functional groups contained in the acrylic copolymer contained in the composition. Specifically, the copolymer is a copolymer. It is about 1-15 mass% with respect to the mass of.

  The heat-resistant pressure-sensitive adhesive sheet of the present invention can be obtained by applying the above heat-resistant pressure-sensitive adhesive composition solution to a substrate sheet and drying it.

  The base sheet is not particularly limited. For example, a sheet made of polyester resin such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyolefin, polyamide, polycarbonate, acrylic resin, polyvinyl chloride, or the like or Examples include papers. Among them, a PET sheet can be preferably cited from the viewpoint of price, waist strength, and the like. These base sheets have other additives such as pigments, dyes, antioxidants, deterioration inhibitors, fillers, ultraviolet absorbers, antistatic agents, and / or other additives, as long as the effects of the present invention are not adversely affected. Alternatively, it may contain an electromagnetic wave preventing agent. The thickness of the substrate sheet is not particularly limited, but is appropriately adjusted depending on the purpose and is usually 20 μm to 10 mm. However, when used as a carrier sheet, it is usually 25 μm to 1 mm, and is practically 50 μm to 50 μm. It is about 200 μm. In addition, the above base sheet can be subjected to an easy adhesion treatment such as a corona treatment, a plasma treatment, and a blast treatment on the coating surface of the base sheet, if necessary. Moreover, what has the anchor coat layer or the easily bonding layer provided on the surface can also be used suitably.

  The amount of the heat-resistant pressure-sensitive adhesive composition solution applied to the substrate sheet is appropriately set depending on the application of the heat-resistant pressure-sensitive adhesive sheet, but is usually 1 to 50 μm as a solid content. A known method can be applied as the coating method, and examples thereof include a roller coating method, a brush coating method, a spray coating method, a die coater, a bar coater, a knife coater, and the like. And said coating layer forms an adhesive layer by drying for 30 to 120 second in 80-150 degreeC warm air normally, Preferably it is 40-120 second in 100-130 degreeC warm air. The heat resistant pressure-sensitive adhesive sheet of the present invention can be obtained.

  A release sheet can be laminated on the surface of the pressure-sensitive adhesive layer of the heat-resistant pressure-sensitive adhesive sheet for convenience in handling. As such a releasable sheet, a known sheet can be used. For example, a sheet obtained by applying a silicone release agent to the surface of a plastic sheet can be used. Since it is at a low level, a film with low adhesiveness such as a polyolefin film may be used as it is.

The heat-resistant pressure-sensitive adhesive sheet obtained as described above is preferably cured to promote the crosslinking of the pressure-sensitive adhesive layer. Such curing conditions are not particularly limited, but are usually 5 to 10 days at 30 to 50 ° C, preferably 5 to 7 days at 40 to 50 ° C.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.
In this example, the evaluation method and mass average molecular weight of the heat-resistant pressure-sensitive adhesive sheet were based on the following evaluation methods.

(Measurement method of mass average molecular weight)
It was measured by the following GPC method.
Shodex GPC KF-806L was used as the column, the system column temperature was 40 ° C., and the eluent was 1.0 ml / min. And was detected by an RI detector and measured as a polystyrene equivalent value.

(Adhesive strength before and after heating)
A strip-shaped test piece having a width of 25 mm and a length of 250 mm is cut from the heat-resistant adhesive sheet on which the release sheet is laminated, and the release sheet is peeled off. Then, according to the adhesive strength test method of JIS Z 0237, A polyimide sheet (Kapton 100H, manufactured by Toray DuPont Co., Ltd.) having a thickness of 25 μm as an adherend was subjected to pressure bonding with the surface of the pressure-sensitive adhesive layer of the heat-resistant pressure-sensitive adhesive sheet being left as a terminal and leaving a peeling portion. In this way, a plurality of test pieces were prepared, and the test piece left for 30 minutes at 30 ° C. (before heating) and the test piece heated for 60 minutes at 180 ° C. (after heating) were subjected to the AUTOGRAPH AGS-50D manufactured by Shimadzu Corporation. Each of the pressure-sensitive adhesive layer and the PET sheet layer as a base material sheet was gripped and peeled together at a peeling rate of 300 mm per minute using a peeling angle 180 degree method for each of the pressure-sensitive adhesive layer and a polyimide sheet having a thickness of 25 μm. The adhesive strength between them was measured, and the average value of the measured values of each of the three test pieces was taken as the adhesive strength.

(Evaluation of initial bond strength and post-heat bond strength)
About the result of said each Example and a comparative example, when adhesive strength is less than 0.05 N / cm, it evaluates as "x" as insufficient adhesive force, 0.05-0.3N / cm is made into a preferable range, and it is "(circle)". It was evaluated. Moreover, the thing exceeding 0.3 N / cm was evaluated as "x" as excess weight.

(Transparency of adhesive solution)
Acrylic high molecular weight copolymer solution and an acrylic low molecular weight copolymer were mixed, and the transparency of the mixed coating solution stirred for 60 minutes with a magnetic stirrer was visually observed to be “transparent”, “slightly cloudy”, Evaluation was made by classifying into "white turbidity".

(Turbidity of adhesive layer (1), (2))
An acrylic high molecular weight copolymer solution and an acrylic low molecular weight copolymer were mixed and mixed and mixed with the same magnetic stirrer for 5 minutes (1) and 60 minutes (2), respectively, with a thickness of 50 μm. After applying the polyester film (trade name: Lumirror 50S10, manufactured by Toray Industries, Inc.) to a thickness of about 10 μm using a Mayer bar and drying it using a 100 ° C. ventilation dryer The appearance on the coated surface was visually observed and evaluated by classifying as “×” (cloudy), “Δ” (slightly cloudy), or “◯” (transparent and no problem).

(Comprehensive evaluation)
The above-mentioned initial adhesive strength, adhesive strength after heating, transparency of the coating solution, and turbidity (1) and (2) of the pressure-sensitive adhesive layer were comprehensively evaluated.

(Preparation of acrylic high molecular weight copolymer (1))
Into a 1 L three-necked reaction vessel, 40 g of ethyl acetate and 60 g of acetone are added as reaction solvents, and 60 g of 2-ethylhexyl acrylate (2EHA), 37.9 g of butyl acrylate (BA), and acrylic acid (AA) 2. 1 g was added and dissolved, and 0.05 g of AIBN as a polymerization initiator and 0.01 g of n-dodecanethiol as a chain transfer agent were added, and a condenser, a thermometer and a stirrer were attached. The temperature was raised at 0.5 ° C / min in a water bath, and after raising the temperature to the boiling point, after 3.5 hours while refluxing with a refluxing apparatus, 50 g of ethyl acetate alone was added to dilute the monomer concentration to about 40% by mass. Then, continue the reaction for 10 hours from the start of the reaction while heating in a water bath and refluxing, and then remove the reaction vessel from the water bath. Allowed to cool Te to obtain a solution of acrylic high molecular weight copolymer (1). With respect to the obtained acrylic high molecular weight copolymer solution, the mass average molecular weight was measured by the above-described method for measuring the mass average molecular weight. The acid value of this copolymer was 16.3 mg / mg KOH. These results are shown in Table 1 together with the monomer composition.

(Preparation of acrylic high molecular weight copolymer (2))
In the preparation of the acrylic high molecular weight copolymer (1), the monomer composition was changed to 98 g of 2-ethylhexyl acrylate (2EHA), 0 g of butyl acrylate (BA), and 2 g of acrylic acid (AA). A solution of the acrylic high molecular weight copolymer (2) was obtained in the same manner as in the preparation of the acrylic high molecular weight copolymer (1). With respect to the obtained acrylic high molecular weight copolymer solution, the mass average molecular weight was measured by the above-described method for measuring the mass average molecular weight, and it was about 890,000. The acid value of this copolymer was 15.6 mg / mg KOH. These results are shown in Table 1 together with the monomer composition.

(Preparation of acrylic low molecular weight copolymer (1))
In a 1 L three-necked reaction vessel, 150 g of ethyl acetate as a reaction solvent is added, and 96 g of 2-ethylhexyl acrylate (2EHA) and 4.0 g of acrylic acid (AA) are added and dissolved in this solvent. Add 0.05g of AIBN as an agent and 0.1g of n-dodecanethiol as a chain transfer agent, attach a cooler, thermometer and stirrer, raise the temperature at 0.5 ° C / min in a water bath, After the temperature is raised to 80 ° C., the reaction is continued for 10 hours from the start of the reaction while refluxing with a reflux apparatus, and then the reaction vessel is taken out of the water bath and allowed to cool to obtain a solution of the acrylic low molecular weight copolymer (1). It was. With respect to the solution of the obtained acrylic low molecular weight copolymer (1), the mass average molecular weight was measured by the above-described method for measuring the mass average molecular weight, and it was about 400,000. The acid value of this copolymer was 31.1 mg / mg KOH. These results are shown in Table 1 together with the monomer composition.

(Preparation of acrylic low molecular weight copolymer (2))
In the preparation method of the above acrylic low molecular weight copolymer (1), except that 96 g of charged 2-ethylhexyl acrylate (2EHA) and 4.0 g of acrylic acid (AA) were changed to 99 g and 1 g, respectively. Copolymerization was carried out in the same manner as the preparation method of the acrylic low molecular weight copolymer 1 to obtain a solution of the acrylic low molecular weight copolymer (2). With respect to the solution of the obtained acrylic low molecular weight copolymer (2), the mass average molecular weight was measured by the above-described method for measuring the mass average molecular weight, and it was about 400,000. The acid value of this copolymer was 7.1 mg / mg KOH. These results are shown in Table 1 together with the monomer composition.

(Preparation of acrylic low molecular weight copolymer (3))
In the method for preparing the acrylic low molecular weight copolymer (1), the solvent composition is 100 parts by mass of ethyl acetate: 50 parts by mass of toluene, and butyl acrylate (BA) is used instead of 2-ethylhexyl acrylate (2EHA). ) And 90.0 g of acrylic acid (AA) and 10.0 g of acrylic acid (AA), and copolymerization was carried out in the same manner as the preparation method of the acrylic low molecular weight copolymer (1). A solution of the low molecular weight copolymer (3) was obtained. With respect to the solution of the obtained acrylic low molecular weight copolymer (3), the mass average molecular weight was measured by the above-described method for measuring the mass average molecular weight, and it was about 410,000. The acid value of this copolymer was 77.9 mg / mg KOH. These results are shown in Table 1 together with the monomer composition.

[Example 1]
10 g of the acrylic high molecular weight copolymer solution (1) and 30 g of the acrylic low molecular weight copolymer (1) solution are mixed, and TETRAD-C (manufactured by Mitsubishi Gas Chemical Co., Ltd.) is used as a crosslinking agent. .5 g was added to form a pressure-sensitive adhesive coating solution, and the thickness after drying using a Mayer bar was 10 μm on the surface of a 50 μm-thick polyester sheet (trade name: Lumirror 50S10, manufactured by Toray Industries, Inc.). It applied so that it might become, and it dried for 60 second with the hot air dryer adjusted to 100 degreeC, and the heat resistant adhesive sheet was obtained.
About the obtained heat-resistant sheet, the adhesive strength before heating and the adhesive strength after heating were measured by the above-mentioned methods, and the transparency of the pressure-sensitive adhesive coating solution and the turbidity of the pressure-sensitive adhesive layer were evaluated. It was shown in 1.

[Example 2] to [Example 3]
Example 2 and Example 3 except that the mixing amounts of the acrylic high molecular weight copolymer (1) solution and the acrylic low molecular weight copolymer (1) solution were 20 g and 20 g, and 30 g and 10 g, respectively. Obtained a heat-resistant adhesive sheet in exactly the same manner as in Example 1.
About the obtained heat-resistant sheet, the adhesive strength before heating and the adhesive strength after heating were measured by the above-mentioned methods, and the transparency of the pressure-sensitive adhesive coating solution and the turbidity of the pressure-sensitive adhesive layer were evaluated. It was shown in 1.

[Comparative Example 1]
A heat-resistant pressure-sensitive adhesive sheet was obtained in exactly the same manner as in Example 1, except that only the acrylic low molecular weight copolymer (1) solution was used as the copolymer solution, and the amount used was 40 g. . About the obtained heat-resistant sheet, the adhesive strength before heating and the adhesive strength after heating were measured by the above-mentioned methods, and the transparency of the pressure-sensitive adhesive coating solution and the turbidity of the pressure-sensitive adhesive layer were evaluated. It was shown in 1.

[Comparative Example 2]
A heat-resistant adhesive sheet was used in exactly the same manner as in Example 1, except that only the acrylic high molecular weight copolymer (1) solution was used as the copolymer solution used, and the amount used was 40 g. Obtained. About the obtained heat-resistant sheet, the adhesive strength before heating and the adhesive strength after heating were measured by the above-mentioned methods, and the transparency of the pressure-sensitive adhesive coating solution and the turbidity of the pressure-sensitive adhesive layer were evaluated. It was shown in 1.

[Comparative Example 3] to [Comparative Example 6]
As the copolymer solution used, a solution of acrylic high molecular weight copolymer (1) and a solution of acrylic low molecular weight copolymer (2) were respectively 0 g and 40 g, 10 g and 30 g, 20 g and 20 g, and 30 g. A heat resistant pressure-sensitive adhesive sheet was obtained in exactly the same manner as in Example 1 except that the combination was 10 g. About the obtained heat-resistant sheet, the adhesive strength before heating and the adhesive strength after heating were measured by the above-mentioned methods, and the transparency of the pressure-sensitive adhesive coating solution and the turbidity of the pressure-sensitive adhesive layer were evaluated. It was shown in 1.

[Example 4]
Except that the copolymer solution used was a combination of 20 g and 20 g of the acrylic copolymer (2) solution and the acrylic low molecular weight copolymer (1) solution, respectively, exactly the same as in Example 1. Thus, a heat-resistant adhesive sheet was obtained. About the obtained heat-resistant sheet, the adhesive strength before heating and the adhesive strength after heating were measured by the above-mentioned methods, and the transparency of the pressure-sensitive adhesive coating solution and the turbidity of the pressure-sensitive adhesive layer were evaluated. It was shown in 1.

[Comparative Example 7] to [Comparative Example 11]
As [Comparative Example 7] to [Comparative Example 11], only 40 g of the acrylic high molecular weight copolymer (2) as the copolymer solution used, respectively, the acrylic high molecular weight copolymer (2) solution and acrylic Example, except that the solution of the low molecular weight copolymer (3) was a combination of 30 g and 10 g, 20 g and 20 g, 10 g and 30 g, respectively, and only 40 g of the acrylic low molecular weight copolymer (3) solution was used. A heat-resistant adhesive sheet was obtained in exactly the same manner as in 1. Among the obtained heat-resistant pressure-sensitive adhesive sheets, the adhesive strength before heating and the adhesive strength after heating were measured for Comparative Examples 7 and 11 by the above-mentioned method, and the results are shown in Table 1. In Comparative Examples 8 to 10, since the adhesive coating solution and the pressure-sensitive adhesive layer were poor in compatibility from the results of turbidity, none of the adhesive strength was measured.

(Consideration of results)
As can be seen from the results of Table 1, the mass ratio of the copolymer having a high molecular weight and relatively few functional groups to the copolymer having a low molecular weight and a large amount of functional groups is 85:15 to 15:85. The adhesive strength of the pressure-sensitive adhesive sheet formed from the composition included in the range of 0.05 to 0.3 N / cm both before heating and after heating at 180 ° C. for 60 minutes, can be easily peeled off even before heating. Moreover, it was a pressure-sensitive adhesive sheet that can be easily peeled after heating. Furthermore, since the compatibility between the high molecular weight copolymer component and the low molecular weight copolymer component is excellent, each adhesive solution and the adhesive layer formed by coating and drying are not turbid and transparent. It was excellent.

The heat-resistant pressure-sensitive adhesive sheet of the present invention has an adhesive strength of 0.05 to 0 when applied to an article, both before heating, that is, at the time of application, and after heating, that is, after being exposed to a high temperature heating environment. .3 N / cm, it does not easily fall off and can be easily reattached, and because the compatibility between the high molecular weight copolymer component and the low molecular weight copolymer component constituting the adhesive is excellent, Since the coating solution and the pressure-sensitive adhesive layer formed by applying and drying are excellent, and there is no adhesive residue even after re-peeling after heating, for example, it was used as a carrier sheet for articles in manufacturing processes including heating processes Even in this case, it can be easily peeled off from the carrier sheet without contaminating the article after processing, and the industrial utilization effect is great.

Claims (5)

It includes 97.5 to 99% by mass of an alkyl (meth) acrylate having 3 to 12 carbon atoms in the alkyl group portion as a main component monomer and 2.5 to 1% by mass of a functional group-containing acrylic monomer, and has a mass average molecular weight. 85 to 15% by mass of an acrylic high molecular weight copolymer having an acid value of 60 mg or more and an acid value of 20 mg / mg KOH or less, and an alkyl (meth) acrylate 90 to 98 having 3 to 12 carbon atoms in the alkyl group portion as a main component monomer 15% to 85% by mass of an acrylic low molecular weight copolymer having a mass average molecular weight of 500,000 or less and an acid value of 25 mg / mg KOH or more, including 10% by mass and 10 to 2% by mass of a functional group-containing acrylic monomer. Comprising 100 parts by mass of the copolymer composition as a component and 1 to 15 parts by mass of a cross-linking agent; Heat-resistant pressure-sensitive adhesive composition difference between the number of carbon atoms in the alkyl moiety of the principal component monomer of the number and the acrylic low molecular weight copolymer of 2 or less.
2. The heat-resistant pressure-sensitive adhesive composition according to claim 1, wherein the initial adhesive strength and the adhesive strength after heating at 180 ° C. for 60 minutes are both 0.05 to 0.3 N / cm.
The monomer composition ratio of the acrylic high molecular weight copolymer is 97.5 to 99% by mass of an alkyl (meth) acrylate having 3 to 12 carbon atoms in the alkyl group part containing 90% by mass or more of 2-ethylhexyl acrylate and functional. The heat-resistant pressure-sensitive adhesive composition according to claim 1 or 2, comprising 2.5 to 1% by mass of acrylic acid as a group-containing acrylic monomer.
The monomer blending ratio constituting the acrylic low molecular weight copolymer is 90 to 98 masses of alkyl (meth) acrylates having 3 to 12 carbon atoms in the alkyl group portion containing 90 mass% or more of 2-ethylhexyl acrylate as the main component monomer. % And 2-10 mass% of acrylic acid as a functional group containing acrylic monomer, The heat-resistant adhesive composition as described in any one of Claim 1 to 3 characterized by the above-mentioned.
The heat resistant adhesive sheet obtained by apply | coating the coating liquid containing the heat resistant adhesive composition any one of Claim 1 to 4 to a base material sheet, and drying.