TW201843275A - Temperature-sensitive adhesive - Google Patents

Abstract

The present invention provides a temperature-sensitive adhesive having excellent heat resistance and release-ability after being heated to high temperature. The temperature-sensitive adhesive of the present invention comprises a side chain crystalline polymer, and having reduced adhesive strength at a temperature lower than the melting point of the side chain crystalline polymer; wherein, the side chain crystalline polymer comprises (meth)acrylate having a linear alkyl group of 16 or more carbon atoms, methyl(meth)acrylate and dicyclopentanyl(meth)acrylate as monomer components; and the temperature-sensitive adhesive further comprises a tackifier composed of a styrene resin.

Description

   Thermosensitive adhesive   

The present invention relates to a thermosensitive adhesive.

The temperature-sensitive adhesive contains a side chain crystalline polymer as a main component, and if it is cooled to a temperature below the melting point of the side chain crystalline polymer, the side chain crystalline polymer is crystallized and the adhesion is reduced. Adhesive. Thermosensitive adhesives are processed into sheets, tapes, etc., and are used in the manufacturing steps of flat panel displays (FPDs) to temporarily fix substrates made of glass, plastic, etc. (see, for example, patent documents 1). The temperature-sensitive adhesive used for such applications may be heated to a high temperature of 200 ° C. or higher, particularly 250 ° C. or higher depending on the procedure, and therefore requires heat resistance. Specifically, it is required to suppress the substrate from floating at a high temperature of 250 ° C or higher. In addition, peelability after heating to a high temperature of 250 ° C. or higher is also required.

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent Application Publication No. 2012-102212

An object of the present invention is to provide a temperature-sensitive adhesive excellent in heat resistance and releasability after heating to a high temperature.

The temperature-sensitive adhesive of the present invention contains a side-chain crystalline polymer, and its adhesion decreases at a temperature lower than the melting point of the side-chain crystalline polymer; wherein the side-chain crystalline polymer contains a carbon number 16 or more linear alkyl (meth) acrylates, methyl (meth) acrylates, and dicyclopentyl (meth) acrylates as monomer components; the temperature-sensitive adhesive further contains styrene Resin tackifier.

According to the present invention, there is an effect that the so-called heat resistance and peelability after heating to a high temperature are excellent.

FIG. 1 is a graph showing the results of thermogravimetric analysis in the examples.

    <Thermal adhesive>    

Hereinafter, a temperature-sensitive adhesive according to an embodiment of the present invention will be described in detail.

The temperature-sensitive adhesive of the present embodiment contains a side chain crystalline polymer. The side chain crystalline polymer is a polymer having a melting point. The so-called melting point means the temperature at which a specific part of a polymer that has been originally integrated into an ordered array becomes disordered due to some equilibrium process. It is measured at 10 ° C / min using a differential scanning calorimeter (DSC). Measured value.

The side chain crystalline polymer crystallizes at a temperature lower than the melting point described above, and undergoes a phase change at a temperature higher than the melting point to exhibit fluidity. That is, the side chain crystalline polymer has a temperature sensitivity that reversibly produces a crystalline state and a flowing state in response to a temperature change.

The temperature-sensitive adhesive of the present embodiment decreases the adhesive force at a temperature not reaching the melting point of the side chain crystalline polymer. In other words, the temperature-sensitive adhesive of the present embodiment contains the side chain crystalline polymer at a ratio at which the adhesion force decreases when the side chain crystalline polymer is crystallized at a temperature below the melting point. That is, the temperature-sensitive adhesive of this embodiment contains a side chain crystalline polymer as a main component. Therefore, when the adherend is peeled from the temperature-sensitive adhesive, if the temperature-sensitive adhesive is cooled to a temperature that does not reach the melting point of the side-chain crystalline polymer, the side-chain crystalline polymer will crystallize and cause adhesion. reduce. In addition, if the temperature-sensitive adhesive is heated to a temperature equal to or higher than the melting point of the side chain crystalline polymer, the side chain crystalline polymer exhibits fluidity and recovers the adhesive force, so it can be reused.

The side chain crystalline polymer contains, as a monomer component, a (meth) acrylate having a linear alkyl group having 16 or more carbon atoms. In the (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, the linear alkyl group having 16 or more carbon atoms functions as a side chain crystalline portion of the side chain crystalline polymer. That is, the side chain crystalline polymer is a comb-shaped polymer having a linear alkyl group having 16 or more carbon atoms in a side chain, and the side chain is crystallized by being integrated into an ordered arrangement by an intermolecular force or the like .

Examples of the (meth) acrylate having a linear alkyl group having 16 or more carbon atoms include cetyl (meth) acrylate, stearyl (meth) acrylate, and icos (meth) acrylate. (Meth) acrylic acid esters having a linear alkyl group having 16 to 22 carbon atoms such as behenyl (meth) acrylate and behenyl (meth) acrylate. The exemplified (meth) acrylates may be used alone or in combination of two or more. The (meth) acrylate means an acrylate or a methacrylate.

The proportion of the (meth) acrylate having a linear alkyl group of 16 or more in the monomer component, that is, in all the monomer components constituting the side chain crystalline polymer, is, for example, 10 to 55 wt%.

Here, the side chain crystalline polymer according to the present embodiment includes (meth) acrylate and (meth) acrylic acid in addition to the (meth) acrylate having a linear alkyl group having 16 or more carbon atoms. Dicyclopentyl ester is used as a monomer component. In other words, the side chain crystalline polymer of the present embodiment is (meth) acrylate, methyl (meth) acrylate, and dicyclopentyl (meth) acrylate having at least a linear alkyl group having 16 or more carbon atoms. Ester copolymer. In addition, the temperature-sensitive adhesive of the present embodiment contains a tackifier containing a styrene resin in addition to the side chain crystalline polymer.

If it is the said structure, the outstanding heat resistance can be exhibited, and the effect excellent in peelability after heating to high temperature can also be acquired. Specifically, even if the adherend such as a substrate is fixed to a high temperature of 250 ° C. or higher, the adherend can be prevented from floating or the like. The 180 ° peel strength of the polyimide film at 5 ° C after 1 hour at 250 ° C measured by the measurement method described in the examples described below is preferably 0.15N / 25mm or less. It is 0.1N / 25mm or less. Therefore, the temperature-sensitive adhesive of the present embodiment can be suitably used for temporary fixing of a substrate in a manufacturing process of FPD.

The reason why the effect of being excellent in heat resistance and peelability after heating to high temperature can be obtained is presumably as described below. Generally, when heated to a high temperature, the cohesive force decreases and the fluidity increases. Therefore, the heat resistance tends to decrease, and the anchoring effect exhibited when the side chain crystalline polymer is crystallized becomes stronger, and the peelability is also easily reduced. When the temperature-sensitive adhesive has the above-mentioned configuration, it is less likely to be deteriorated by heat at a high temperature of 200 ° C or higher, particularly 250 ° C or higher. If it is hard to be deteriorated by heat at high temperatures, cohesion is not easily reduced at high temperatures, and therefore excellent heat resistance can be exhibited. In addition, even when heated to a high temperature, there is little increase in fluidity, and it is difficult to exhibit an extreme anchoring effect when the side chain crystalline polymer is crystallized. As a result, excellent peelability can be exhibited even after heating to a high temperature.

Among the above monomer components, the methyl (meth) acrylate system functions as a main component that imparts cohesive force to the thermosensitive adhesive. The proportion of methyl (meth) acrylate in the monomer component is, for example, 10 to 85% by weight. When methyl (meth) acrylate is contained in the monomer component in the largest proportion, the heat resistance tends to be improved.

The dicyclopentyl (meth) acrylate system functions as a main component for improving the heat resistance of a thermosensitive adhesive. The proportion of the dicyclopentyl (meth) acrylate in the monomer component is, for example, 5 to 35% by weight.

As the thickener, a commercially available product can be used. Examples of commercially available tackifiers include "YS resin SX100" manufactured by Yasuhara Chemical Co., and the like.

The content of the tackifier is, for example, 1 part by weight or more, preferably 20 to 100 parts by weight, and more preferably 20 to 50 parts by weight with respect to 100 parts by weight of the side chain crystalline polymer.

The softening point of the tackifier is, for example, 90 to 110 ° C, preferably 95 to 105 ° C. The softening point is a value measured according to the ring and ball method specified in JIS K 5902.

On the other hand, the monomer component constituting the side chain crystalline polymer may include other monomers other than the above-mentioned monomers. Examples of the other monomer include a polar monomer and a reactive fluorine compound.

When a polar monomer is contained as a monomer component, the adhesive physical property of a thermosensitive adhesive can be adjusted. Examples of the polar monomer include acrylic monomers, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid having carboxyethylenically unsaturated monomers such as (meth) acrylic 2- An ethylenically unsaturated monomer having a hydroxyl group, such as hydroxyethyl ester, 2-hydroxypropyl (meth) acrylate, 2-hydroxyhexyl (meth) acrylate, and the like. The exemplified polar monomers may be used alone or in combination of two or more. The proportion of the polar monomer in the monomer component is, for example, 1 to 10% by weight.

When a polar monomer is further included as the monomer component, the proportion of each monomer in the monomer component is, for example, 9 to 45% by weight of a (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, ( The methyl (meth) acrylate is 10 to 85% by weight, the dicyclopentyl (meth) acrylate is 5 to 35% by weight, and the polar monomer is 1 to 10% by weight.

When a reactive fluorine compound is included as a monomer component, when the temperature-sensitive adhesive is cooled to a temperature lower than the melting point of the side chain crystalline polymer, the adhesive force due to the crystallization of the side chain crystalline polymer is reduced. In addition to the reduction, in addition to the mold releasability caused by the fluorine compound, the adhesion can be greatly reduced.

The reactive fluorine compound means a fluorine compound having a functional group exhibiting reactivity. Examples of the functional group exhibiting reactivity include an epoxy group (including glycidyl group and epoxy cycloalkyl group), a mercapto group, a methanol group (hydroxymethyl), a carboxyl group, a silanol group, a phenol group, and an amine group , A hydroxyl group, a group having an ethylenically unsaturated double bond, and the like. Examples of the group having an ethylenically unsaturated double bond include vinyl, allyl, (meth) acryl group, (meth) acryl group ((meth) acryloyl group), (meth) acryloxy group, and the like.

Specific examples of the reactive fluorine compound include a compound represented by the following general formula (I).

R ₁ -CF ₃ (I) [wherein R ₁ represents a group: CH ₂ = CHCOOR ² -or CH ₂ = C (CH ₃ ) COOR ^2- (wherein, R ² represents an alkylene group). A

Examples of the alkylene group represented by R ² include those having 1 to 6 carbon atoms, such as methylene, ethylene, trimethylene, propylene, tetramethylene, pentamethylene, and hexamethylene. Linear or branched alkylene etc.

Specific examples of the compound represented by the general formula (I) include acrylic acid 2,2,2-trifluoroethyl ester represented by the following formula (Ia), and methacrylic acid 2, represented by the formula (Ib). 2,2-trifluoroethyl and the like.

As the reactive fluorine compound, a commercially available product can be used. Examples of commercially available reactive fluorine compounds include "Viscoat 3F", "Viscoat 3FM", "Viscoat 4F", "Viscoat 8F", and "Viscoat 8FM" all manufactured by Osaka Organic Chemical Industry Co., Ltd. "Light ester M-3F" manufactured by Soka Chemical Co., Ltd.

The reactive fluorine compound may be used singly or in combination of two or more kinds. The proportion of the reactive fluorine compound in the monomer component is, for example, 1 to 10% by weight.

When the polar monomer and the reactive fluorine compound are further included as monomer components, the ratio of each monomer in the monomer component is, for example, that the (meth) acrylate having a linear alkyl group having 16 or more carbon atoms is 8 To 35% by weight, 10 to 85% by weight of methyl (meth) acrylate, 5 to 35% by weight of dicyclopentyl (meth) acrylate, 1 to 10% by weight of polar monomers, and 1 to 10% by weight.

Examples of the polymerization method of the monomer include a solution polymerization method, a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method. In the case of a solution polymerization method, it is sufficient to mix a monomer with a solvent, add a polymerization initiator, a chain transfer agent, and the like as necessary, and allow it to react at about 40 to 90 ° C. for about 2 to 10 hours while stirring.

The weight average molecular weight of the side chain crystalline polymer is, for example, 100,000 or more, preferably 300,000 to 900,000, and more preferably 400,000 to 700,000. The weight average molecular weight is a value measured by gel permeation chromatography (GPC), and the obtained measurement value is converted into polystyrene.

The melting point of the side chain crystalline polymer is, for example, 0 ° C or higher, and preferably 10 to 60 ° C. The melting point can be adjusted by changing the composition of the side chain crystalline polymer and the like.

The temperature-sensitive adhesive of this embodiment may further contain a crosslinking agent. Examples of the crosslinking agent include metal chelate compounds, aziridine compounds, isocyanate compounds, and epoxy compounds. When the metal chelate compound in the illustrated crosslinking agent is used, heat resistance can be improved.

Examples of the metal chelate compound include a polyvalent metal acetoacetone complex, a polyvalent metal acetoacetate complex, and the like. Examples of the polyvalent metal include aluminum, nickel, chromium, iron, titanium, zinc, cobalt, manganese, and zirconium. The metal chelate compound may be used singly or in combination of two or more kinds. Among these, an aluminum acetoacetone complex or an acetoacetate complex is preferred, and aluminum triacetamate acetone is more preferred.

The content of the crosslinking agent is, for example, 0.1 to 10 parts by weight based on 100 parts by weight of the side chain crystalline polymer.

The cross-linking reaction can be performed by adding a cross-linking agent to a thermosensitive adhesive and then heating it. Specifically, the temperature is about 90 to 110 ° C, and the time is about 1 minute to 20 minutes.

The use form of the said thermosensitive adhesive agent is not specifically limited, For example, it can be used as it is, and it can also be used in the form of an adhesive sheet, an adhesive tape, etc. as demonstrated below.

    <Thermal adhesive sheet>    

The temperature-sensitive adhesive sheet of the present embodiment is a sheet containing no substrate, as long as it includes the above-mentioned temperature-sensitive adhesive. The thickness of the temperature-sensitive adhesive sheet is, for example, 5 to 100 μm, and preferably 5 to 50 μm.

A release film may be laminated on the surface of the thermosensitive adhesive sheet. Examples of the release film include those coated with a release agent such as silicone on the surface of a film containing polyethylene terephthalate or the like. The thickness of the release film is, for example, 5 to 500 μm , and preferably 25 to 250 μm . The release film is peeled off when the temperature-sensitive adhesive sheet is used.

    <Thermal adhesive tape>    

The temperature-sensitive adhesive tape of the present embodiment includes a film-shaped substrate and an adhesive layer laminated on at least one side of the substrate. The film shape is not limited to a film shape, but means a concept including a film shape or a sheet shape without impairing the effects of the present embodiment.

Examples of constituent materials of the substrate include polyethylene, polyethylene terephthalate, polypropylene, polyester, polyamide, polyimide, polycarbonate, and ethylene-vinyl acetate copolymer. , Ethylene-ethyl acrylate copolymer, ethylene-polypropylene copolymer, polyvinyl chloride and other synthetic resins.

The structure of the substrate may be either a single-layer structure or a multilayer structure. The thickness of the substrate is, for example, 5 to 500 μm, and preferably 25 to 250 μm. In order to improve the adhesion to the adhesive layer, the substrate may be surface-treated. Examples of the surface treatment include corona discharge treatment, plasma treatment, sandblasting treatment, chemical etching treatment, and primer treatment.

The adhesive layer laminated on at least one side of the substrate contains the above-mentioned thermosensitive adhesive. In the case where the adhesive is laminated on at least one side of the substrate, for example, a solvent is added to the thermosensitive adhesive to prepare a coating liquid, and the obtained coating liquid is applied to the substrate using a coating machine or the like. Just dry one or both sides. Examples of the coater include a blade coater, a roll coater, a calender coater, a comma coater, a gravure coater, and a rod coater.

The thickness of the adhesive layer is, for example, 5 to 100 μm, and preferably 5 to 50 μm.

In the case of the two-layer adhesive layer on the base material, the thickness and composition of the adhesive layer on one side and the adhesive layer on the other side may be the same or different from each other. In addition, as long as the adhesive layer on one side contains the above-mentioned thermosensitive adhesive, the adhesive layer on the other side is not particularly limited. The other side of the adhesive layer may be made of, for example, a pressure-sensitive adhesive. Examples of the pressure-sensitive adhesive include natural rubber adhesives, synthetic rubber adhesives, styrene-butadiene latex-based adhesives, and acrylic adhesives.

The surface of the thermosensitive adhesive tape can be laminated with a release film. Examples of the release film include the same release films as those exemplified above for the temperature-sensitive adhesive sheet. The release film is peeled off when the temperature-sensitive adhesive tape is used.

Hereinafter, the present invention will be described in detail by listing synthesis examples and examples, but the present invention is not limited to the following synthesis examples and examples.

    (Synthesis Examples 1 to 3 and Comparative Synthesis Example: Side-chain crystalline polymer)    

First, the monomer shown in Table 1 was added to the reaction vessel at the ratio shown in Table 1. The monomers shown in Table 1 are shown below.

C18A: stearyl acrylate

C22A: behenyl acrylate

C1A: methyl acrylate

FA513AS: Dicyclopentyl acrylate "FA-513AS" manufactured by Hitachi Chemical Co., Ltd.

AA: Acrylic

V3F: Reactive fluorine compound "Viscoat 3F" manufactured by Osaka Organic Chemical Industry Co., Ltd. of 2,2,2-trifluoroethyl acrylate represented by the above formula (Ia)

Next, a mixed solvent of ethyl acetate: toluene = 75: 25 (weight ratio) was added to the reaction container so that the solid content concentration became 30% by weight to obtain a mixed solution. Each monomer was copolymerized by stirring the obtained mixed liquid at 55 ° C for 4 hours to obtain a side chain crystalline polymer.

Table 1 shows the weight average molecular weight and melting point of each of the side chain crystalline polymers obtained in Synthesis Examples 1 to 3 and Comparative Synthesis Examples. The weight average molecular weight is a value obtained by GPC measurement and converting the obtained measurement value into polystyrene. The melting point is a value measured under measurement conditions of 10 ° C / min using DSC.

1) C18A: stearyl acrylate, C22A: behenyl acrylate, C1A: methyl acrylate FA513AS: dicyclopentyl acrylate, AA: acrylic acid, V3F: 2,2,2-trifluoroethyl acrylate

    [Examples 1 to 5 and Comparative Examples 1 to 3]         <Production of Thermosensitive Adhesive Sheet>    

First, with respect to 100 parts by weight of each of the side chain crystalline polymers obtained in Synthesis Examples 1 to 3 and Comparative Synthesis Examples, the tackifiers shown in Table 2 were mixed in the proportions shown in Table 2. The tackifiers shown in Table 2 are shown below.

Styrene resin: "YS resin SX100" manufactured by Yasuhara Chemical Co., Ltd. with a softening point of 95 to 105 ° C

Rosin: Rosin ester "D-160" manufactured by Arakawa Chemical Industries, Ltd. with a softening point of 150 to 170 ° C

Next, a cross-linking agent was mixed at a ratio of 3 parts by weight to 100 parts by weight of the side chain crystalline polymer to obtain a thermosensitive adhesive. The crosslinking agent used is shown below.

Crosslinking agent: aluminum triacetamone acetone manufactured by Kawaken Fine Chemical Co., Ltd. which is a metal chelate compound

Next, the obtained thermosensitive adhesive was adjusted with ethyl acetate so that solid content concentration might become 30 weight%, and the coating liquid was obtained. Then, the obtained coating solution was applied to a release film, and a crosslinking reaction was performed under the conditions of 100 ° C. × 10 minutes to obtain a temperature-sensitive adhesive sheet having a thickness of 25 μm. In addition, the release film was a polyethylene terephthalate film having a thickness of 50 μm coated with polysiloxane on the surface.

    <Evaluation>    

For each of the temperature-sensitive adhesive sheets obtained in Examples 1 to 5 and Comparative Examples 1 to 3, 180 ° peel strength and heat resistance were evaluated. In addition, each thermosensitive adhesive sheet obtained in Example 3 and Comparative Examples 1 to 3 was evaluated by thermogravimetric analysis (TGA). Each evaluation method is shown below. The results of 180 ° peel strength and heat resistance are shown in Table 2, and the results of thermogravimetric analysis are shown in FIG. 1.

(180 ° peel strength)

The 180 ° peel strength of the polyimide film at 50 ° C, 200 ° C, 250 ° C, and 5 ° C was measured in accordance with JIS Z0237. Specifically, first, a thermosensitive adhesive sheet was attached to a glass plate using a 2 kg rubber roller at an ambient temperature of 50 ° C. Next, the temperature-sensitive adhesive sheet was degassed under the conditions of 200 ° C. × 10 minutes. Then, the ambient temperature was lowered to 50 ° C., and a polyimide film was attached to the thermosensitive adhesive sheet at the ambient temperature to obtain a test piece.

After setting the obtained test piece under the following conditions, the polyimide film was peeled from the thermosensitive adhesive sheet at 180 ° (n = 3) at a speed of 300 mm / min using a load cell.

[50 ° C]

The test piece was allowed to stand at an ambient temperature of 50 ° C for 20 minutes, and then peeled at 180 °.

[200 ° C]

The test piece was placed on a hot plate at 200 ° C for 20 minutes, and then peeled at 180 °.

[250 ° C]

The test piece was placed on a hot plate at 250 ° C for 20 minutes, and then peeled at 180 °.

[5 ° C]

The test piece was left on a hot plate at 250 ° C for 1 hour, and then left on a cold plate at 5 ° C for 20 minutes, and then peeled at 180 °.

(Heat resistance)

First, a test piece was obtained in the same manner as in the evaluation of the 180 ° peel strength. Next, the obtained test piece was left to stand at 50 ° C for 3 minutes, and then heated in a hot air circulation oven at 250 ° C for 30 minutes. Then, the heat resistance was evaluated by visually observing the state of the test piece at room temperature (23 ° C). The evaluation criteria are set as follows.

○: No swell was observed on the polyimide film.

X: Floating was observed in the polyimide film.

(Thermogravimetric analysis)

With respect to each of the temperature-sensitive adhesive sheets obtained in Example 3 and Comparative Examples 1 to 3, a change in weight accompanying a change in temperature was measured. The measurement conditions are shown below.

Measuring instrument: "TG / DTA6200" manufactured by Hitachi High-Technologies Corporation

Heating range: 30 to 300 ° C

Heating rate: 10 ° C / min

Other: 250ml / min under nitrogen

As is clear from Table 2, in Examples 1 to 5, the 180 ° peel strength value at 50 to 250 ° C. was high, and the 180 ° peel strength value at 5 ° C. after 250 ° C. was low, and the heat resistance was also excellent. In addition, it is clear from the first figure that Example 3 can suppress thermal degradation when heated to a temperature of 200 ° C or higher, particularly 250 ° C or higher.

Claims (7)

    A temperature-sensitive adhesive, which contains a side chain crystalline polymer, and the adhesive force decreases at a temperature lower than the melting point of the side chain crystalline polymer; the side chain crystalline polymer contains a carbon number of 16 The above linear alkyl (meth) acrylate, methyl (meth) acrylate, and dicyclopentyl (meth) acrylate are used as monomer components; the temperature-sensitive adhesive further contains a styrene resin Thickener.         The temperature-sensitive adhesive according to item 1 of the scope of patent application, wherein the dicyclopentyl (meth) acrylate is contained in a monomer component in a proportion of 5 to 35% by weight.         The temperature-sensitive adhesive according to item 1 of the patent application scope, wherein the tackifier is contained in a proportion of 20 to 50 parts by weight based on 100 parts by weight of the side chain crystalline polymer.         The temperature-sensitive adhesive according to item 1 of the scope of patent application, wherein the 180 ° peel strength of the polyimide film at 5 ° C. after 1 hour at 250 ° C. is 0.15 N / 25 mm or less.         The temperature-sensitive adhesive according to item 1 of the scope of patent application is used for temporary fixing of a substrate in a manufacturing process of a flat panel display.         The invention relates to a temperature-sensitive adhesive sheet, which comprises the temperature-sensitive adhesive described in item 1 of the patent application scope.         A temperature-sensitive adhesive tape comprising: a film-shaped substrate; and an adhesive layer, which is laminated on at least one side of the substrate and includes the temperature-sensitive adhesive described in Item 1 of the scope of patent application.