KR20180118517A - Temperature sensitive adhesive - Google Patents

Abstract

The present invention provides a heat sensitive adhesive excellent in heat resistance and excellent peelability after being heated to a high temperature. The heat sensitive adhesive comprises a side chain crystalline polymer, is a thermosensitive pressure-sensitive adhesive whose adhesive strength is lowered at a temperature lower than a melting point of the side chain crystalline polymer. The side chain crystalline polymer includes (meth) acrylate, methyl (meth) acrylate and dicyclopentanyl (meth) acrylate having a linear alkyl group having at least 16 carbon atoms as a monomer component. The heat sensitive adhesive further contains a tackifier made of a styrene resin.

Description

{TEMPERATURE SENSITIVE ADHESIVE}

The present invention relates to a thermosensitive adhesive.

The thermosensitive pressure-sensitive adhesive contains a side chain crystalline polymer as a main component and, when cooled to a temperature lower than the melting point of the side chain crystalline polymer, crystallizes the side chain crystalline polymer, thereby lowering the adhesive strength. The thermosensitive pressure-sensitive adhesive is processed by a sheet, a tape, or the like to be used when temporarily fixing a substrate made of glass, plastic or the like in a manufacturing process of a flat panel display (FPD) or the like (see, for example, Patent Document 1). The thermosensitive adhesive used for such a purpose may be heated to a high temperature of 200 DEG C or higher, particularly 250 DEG C or higher depending on the process, and therefore heat resistance is required. Concretely, it is required to suppress lifting of the substrate at a high temperature of 250 DEG C or more. In addition, peelability after heating to a high temperature of 250 DEG C or more is also required.

Japanese Patent Laid-Open Publication No. 2012-102212

A problem to be solved by the present invention is to provide a thermosensitive pressure-sensitive adhesive excellent in heat resistance and peelability after being heated to a high temperature.

The thermosensitive pressure-sensitive adhesive of the present invention contains a side chain crystalline polymer, and the adhesive force is lowered at a temperature lower than the melting point of the side chain crystalline polymer. The side chain crystalline polymer is preferably a (meth) acrylate having a linear alkyl group having a carbon number of 16 or more , Methyl (meth) acrylate and dicyclopentanyl (meth) acrylate as a monomer component, and further contains a tackifier made of a styrene resin.

(Effects of the Invention)

According to the present invention, there is an effect that heat resistance and peelability after being heated to a high temperature are excellent.

Fig. 1 is a graph showing the results of thermogravimetric analysis in Examples. Fig.

≪ Temperature Sensitive Adhesive >

Hereinafter, the thermosensitive adhesive according to one embodiment of the present invention will be described in detail.

The thermosensitive adhesive of the present embodiment contains a side chain crystalline polymer. The side chain crystalline polymer is a polymer having a melting point. Melting point refers to the temperature at which a certain portion of the polymer that has been initially matched to the ordered arrangement by an equilibrium process becomes disordered and is measured using a differential scanning calorimeter (DSC) under the measurement conditions of 10 캜 / min And means a value obtained.

The side chain crystalline polymer is crystallized at a temperature lower than the above-mentioned melting point, and exhibits fluidity due to phase transition at a temperature higher than the melting point. That is, the side chain crystalline polymer has a thermosensitive property that reversibly causes a crystalline state and a flow state in response to a temperature change.

The pressure sensitive adhesive of the present embodiment is deteriorated in adhesion at a temperature lower than the melting point of the side chain crystalline polymer. In other words, the thermosensitive pressure-sensitive adhesive of the present embodiment contains the side chain crystalline polymer in such a ratio that the adhesive force is lowered when the side chain crystalline polymer is crystallized at a temperature lower than the melting point. That is, the thermosensitive adhesive of the present embodiment contains a side chain crystalline polymer as a main component. Therefore, when the adherend is peeled off from the thermosensitive pressure-sensitive adhesive, when the thermosensitive pressure-sensitive adhesive is cooled to a temperature lower than the melting point of the side chain crystalline polymer, the side chain crystalline polymer is crystallized and the adhesive force is lowered. Further, when the thermosensitive pressure-sensitive adhesive is heated to a temperature not lower than the melting point of the side chain crystalline polymer, the side chain crystalline polymer exhibits fluidity so that the adhesive force is restored.

The side chain crystalline polymer includes (meth) acrylate having a linear alkyl group having at least 16 carbon atoms as a monomer component. (Meth) acrylate having a straight chain alkyl group having a carbon number of 16 or more functions as a side chain crystalline site in the branched chain crystalline polymer. That is, the side chain crystalline polymer is a comb-like polymer having a linear alkyl group having at least 16 carbon atoms in its side chain, and the side chains are crystallized by aligning them in an ordered arrangement due to the intermolecular force or the like.

Examples of the (meth) acrylate having a straight chain alkyl group having a carbon number of 16 or more include cetyl (meth) acrylate, stearyl (meth) acrylate, eicosyl (meth) acrylate and behenyl (Meth) acrylates having a linear alkyl group having from 16 to 22 carbon atoms. The exemplified (meth) acrylates may be used alone or in combination of two or more. Further, (meth) acrylate means acrylate or methacrylate.

The proportion of the (meth) acrylate having a straight chain alkyl group having at least 16 carbon atoms in the entire monomer component constituting the side chain crystalline polymer is, for example, 10 to 55% by weight.

Herein, the side chain crystalline polymer of the present embodiment includes, as monomer components, methyl (meth) acrylate and dicyclopentanyl (meth) acrylate in addition to (meth) acrylate having a straight chain alkyl group having 16 or more carbon atoms . In other words, the side chain crystalline polymer of the present embodiment is at least a copolymer of (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, methyl (meth) acrylate, and dicyclopentanyl (meth) acrylate. The thermosensitive pressure-sensitive adhesive of the present embodiment further contains a tackifier made of a styrene resin in addition to the side chain crystalline polymer.

According to the above-described constitution, an excellent heat resistance can be exhibited and an effect of being excellent in peeling property after being heated to a high temperature is also obtained. Specifically, even if an adherend such as a substrate is fixed and heated to a high temperature of 250 캜 or higher, it is possible to suppress the occurrence of floating of the adherend. Further, the 180 占 peel strength to the polyimide film at 5 占 폚 after 1 hour at 250 占 폚 as measured by the measuring method described in the following Examples is 0.15 N / 25 mm or less, preferably 0.1 N / 25 mm or less . Therefore, the thermosensitive adhesive of the present embodiment can be suitably used for temporarily fixing the substrate in the process of manufacturing the FPD.

The reasons for the heat resistance and the excellent peelability after being heated at a high temperature are considered as follows. Generally, when heated at a high temperature, the cohesive force is lowered and the fluidity is increased, so that the heat resistance tends to be lowered, and the anchoring effect to be exhibited when the side chain crystalline polymer is crystallized becomes strong, When the thermosensitive pressure-sensitive adhesive has the above-described constitution, heat deterioration becomes difficult at a high temperature of 200 DEG C or higher, particularly 250 DEG C or higher. When heat deterioration hardly occurs at a high temperature, excellent cohesiveness is not easily lowered at a high temperature, and excellent heat resistance can be exhibited. Further, even when heated to a high temperature, an increase in fluidity is small, and when the side chain crystalline polymer is crystallized, an extreme anchoring effect is difficult to manifest. As a result, excellent peelability can be exhibited even after being heated to a high temperature.

Among the above-mentioned monomer components, methyl (meth) acrylate mainly functions as a component imparting 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 the methyl (meth) acrylate is contained in the largest proportion of the monomer components, the heat resistance tends to be improved.

Dicyclopentanyl (meth) acrylate mainly functions as a component for increasing the heat resistance of the thermosensitive pressure-sensitive adhesive. The proportion of dicyclopentanyl (meth) acrylate in the monomer component is, for example, 5 to 35% by weight.

Commercially available products can be used as the tackifier described above. As a commercially available tackifier, for example, "YS Resin SX100" manufactured by Yasuhara Chemical Co., Ltd. and the like can be mentioned.

The tackifier is contained in an amount of, for example, 1 part by weight or more, preferably 20 to 100 parts by weight, more preferably 20 to 50 parts by weight, based on 100 parts by weight of the side chain crystalline polymer.

The softening point of the tackifier is, for example, 90 to 110 占 폚, preferably 95 to 105 占 폚. The softening point is a value measured according to the ring method defined in JIS K 5902.

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

When the polar monomer is included as a monomer component, the adhesive property of the thermosensitive adhesive can be adjusted. Examples of the polar monomer include an ethylenic unsaturated monomer having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid; And ethylenically unsaturated monomers having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and 2-hydroxyhexyl (meth) acrylate. The illustrated 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 the polar monomer is further contained as a 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 rate is 10 to 85% by weight, the dicyclopentanyl (meth) acrylate is 5 to 35% by weight, and the polar monomer is 1 to 10% by weight.

When the reactive fluorine compound is contained as a monomer component, if the thermosensitive adhesive is cooled to a temperature lower than the melting point of the side chain crystalline polymer, in addition to the deterioration of the adhesion due to crystallization of the side chain crystalline polymer, The adhesive strength can be greatly reduced.

The reactive fluorine compound means a fluorine compound having a functional group showing reactivity. Examples of the functional group which exhibits reactivity include epoxy groups (including glycidyl and epoxycycloalkyl groups), mercapto groups, carbinol groups (methylol groups), carboxyl groups, silanol groups, phenol groups, amino groups, A group having an unsaturated double bond, and the like. Examples of the group having an ethylenically unsaturated double bond include a vinyl group, an allyl group, a (meth) acryl group, a (meth) acryloyl group, and a (meth) acryloyloxy group.

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

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

Specific examples of the compound represented by the general formula (I) include 2,2,2-trifluoroethyl acrylate represented by the following formula (Ia), 2,2,2-trifluoroacetic acid represented by the formula (Ib) Ethyl methacrylate and the like.

Commercially available products can be used for the above-mentioned reactive fluorine compounds. Examples of commercially available reactive fluorine compounds include "Viscot 3F", "Viscot 3FM", "Viscot 4F", "Viscot 8F", "Viscot 8FM" manufactured by Osaka Yuki Kagaku Kogyo Co., &Quot; Light Ester M-3F "

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

When the above-mentioned polar monomer and the reactive fluorine compound are further contained as monomer components, the proportion of each monomer in the monomer component is, for example, 8 to 35 wt% (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, 10 to 85% by weight of methyl (meth) acrylate, 5 to 35% by weight of dicyclopentanyl (meth) acrylate, 1 to 10% by weight of polar monomer, and 1 to 10% by weight of reactive fluorine compound.

As the polymerization method of the monomer, for example, a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method and the like can be given. When the solution polymerization is adopted, the monomer and the solvent are mixed, and if necessary, a polymerization initiator, a chain transfer agent and the like are added, and the mixture is reacted 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, 100000 or more, preferably 300000 to 900000, and more preferably 400000 to 700000. The weight average molecular weight is a value measured by gel permeation chromatography (GPC) and a value obtained by converting the measured value into polystyrene.

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

The thermosensitive adhesive of the present 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 exemplified metal chelate compound is used in the crosslinking agent, the heat resistance can be improved.

Examples of the metal chelate compound include an acetylacetone coordination compound of a polyvalent metal, an acetoacetic acid ester coordination compound of a polyvalent metal, 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 alone or in combination of two or more. Among them, an acetylacetone coordination compound or acetoacetic acid ester coordination compound of aluminum is preferable, and aluminum trisacetylacetonate is more preferable.

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

The crosslinking reaction can be carried out by adding a crosslinking agent to the thermosensitive adhesive, followed by heating. Specifically, the temperature is about 90 to 110 DEG C and the time is about 1 to 20 minutes.

The mode of use of the above-described thermosensitive adhesive is not particularly limited and may be used as it is or may be used in the form of a pressure-sensitive adhesive sheet or an adhesive tape as described below.

<Temperature Sensitive Adhesive Sheet>

The thermosensitive adhesive sheet of the present embodiment includes the above-mentioned thermosensitive adhesive, and is a sheet-like base-less sheet. The thickness of the thermosensitive adhesive sheet is, for example, 5 to 100 占 퐉, preferably 5 to 50 占 퐉.

A releasing film may be laminated on the surface of the thermosensitive adhesive sheet. Examples of the release film include those obtained by applying a releasing agent such as silicone to the surface of a film made of, for example, polyethylene terephthalate. The thickness of the release film is, for example, 5 to 500 占 퐉, preferably 25 to 250 占 퐉. The releasing film is peeled off when the heat sensitive adhesive sheet is used.

<Temperature Sensitive Adhesive Tape>

The thermosensitive adhesive tape of the present embodiment includes a base material film and a pressure-sensitive adhesive layer laminated on at least one side of the base material. The term "film phase" is not limited to a film phase but is a concept including film phase and sheet phase as long as the effect of the present embodiment is not impaired.

Examples of the constituent material of the base material include polyethylene, polyethylene terephthalate, polypropylene, polyester, polyamide, polyimide, polycarbonate, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene polypropylene copolymer, poly And synthetic resins such as vinyl chloride.

The structure of the substrate may be a single layer structure or a multilayer structure. The thickness of the substrate is, for example, 5 to 500 mu m, preferably 25 to 250 mu m. The substrate may be surface-treated after the adhesion to the pressure-sensitive adhesive layer is enhanced. Examples of the surface treatment include a corona discharge treatment, a plasma treatment, a blast treatment, a chemical etching treatment, a primer treatment, and the like.

The pressure-sensitive adhesive layer laminated on at least one side of the base material includes the above-mentioned pressure-sensitive adhesive. In order to laminate the pressure-sensitive adhesive layer on at least one side of the substrate, for example, a solvent may be added to the thermosensitive pressure-sensitive adhesive to prepare a coating liquid, and the resulting coating liquid may be coated on one side or both sides of the substrate with a coater and dried. Examples of the coater include a knife coater, a roll coater, a calendar coater, a comma coater, a gravure coater, and a rod coater.

The thickness of the pressure-sensitive adhesive layer is, for example, 5 to 100 占 퐉, preferably 5 to 50 占 퐉.

When the pressure-sensitive adhesive layer is laminated on both sides of the substrate, the thickness of the pressure-sensitive adhesive layer on one side and the pressure-sensitive adhesive layer on the other side may be the same or different from each other. Further, the pressure-sensitive adhesive layer on the other surface is not particularly limited as long as the pressure-sensitive adhesive layer on one side is composed of the above-mentioned pressure-sensitive adhesive. The pressure-sensitive adhesive layer on the other surface may be constituted by, for example, a pressure-sensitive adhesive. Examples of the pressure-sensitive adhesive include natural rubber adhesives, synthetic rubber adhesives, styrene-butadiene latex base adhesives, acrylic adhesives, and the like.

A release film may be laminated on the surface of the thermosensitive adhesive tape. Examples of the release film include those exemplified in the above-mentioned pressure sensitive adhesive sheet. The releasing film is peeled off when the heat sensitive adhesive tape is used.

Hereinafter, the present invention will be described in detail with reference to 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 Examples: side chain crystalline polymer)

First, the monomers shown in Table 1 were added to the reaction vessel at the ratios shown in Table 1. The monomers shown in Table 1 are as follows.

C18A: stearyl acrylate

C22A: Behenyl acrylate

C1A: methyl acrylate

FA513AS: dicyclopentanyl acrylate &quot; FA-513AS &quot; manufactured by Hitachi Chemical Co.,

AA: Acrylic acid

V3F: The reactive fluorine compound "Viscot 3F" manufactured by Osaka Yuki Kagaku Kogyo Co., Ltd., which is 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 vessel so that the solid concentration became 30% by weight, to obtain a mixed solution. The obtained mixed solution was stirred at 55 占 폚 for 4 hours to copolymerize the respective monomers 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 converting the measured value obtained by GPC measurement into polystyrene. The melting point is a value measured at 10 ° C / minute using DSC.

[Examples 1 to 5 and Comparative Examples 1 to 3]

<Production of a thermosensitive pressure-sensitive adhesive sheet>

First, to 100 parts by weight of each of the side chain crystalline polymers obtained in Synthesis Examples 1 to 3 and Comparative Synthesis Example, the tackifiers shown in Table 2 were mixed at the ratios shown in Table 2. The tackifier shown in Table 2 is as follows.

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

Rosin: Rosin ester "D-160" manufactured by Arakawa Kagaku Kogyo Co., Ltd. having a softening point of 150 to 170 ° C

Next, 100 parts by weight of the side chain crystalline polymer was mixed with 3 parts by weight of a cross-linking agent to obtain a thermosensitive pressure-sensitive adhesive. The crosslinking agent used is as follows.

Crosslinking agent: Aluminum trisacetylacetonate manufactured by Kawaken Fine Chemical Co., which is a metal chelate compound

Next, the thermosensitive adhesive obtained was adjusted with ethyl acetate to a solid concentration of 30% by weight to obtain a coating liquid. The obtained coating liquid was coated on a release film and subjected to a crosslinking reaction under the conditions of 100 占 폚 for 10 minutes to obtain a pressure sensitive adhesive sheet having a thickness of 25 占 퐉. The release film used was a polyethylene terephthalate film having a thickness of 50 占 퐉 in which the surface was coated with silicon.

<Evaluation>

Each of the thermosensitive adhesive sheets obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was evaluated for 180 ° peel strength and heat resistance. Further, thermogravimetric analysis (TGA) of each of the thermosensitive pressure-sensitive adhesive sheets obtained in Example 3 and Comparative Examples 1 to 3 was evaluated. Each evaluation method is shown below. The results of the 180 占 peel strength and the heat resistance are shown in Table 2, and the results of the thermogravimetric analysis are shown in Fig.

(180 DEG peel strength)

180 占 peel strength of the polyimide film at 50 占 폚, 200 占 폚, 250 占 폚 and 5 占 폚 was measured according to JIS Z0237. Specifically, first, the thermosensitive adhesive sheet was adhered to a glass plate using a 2 kg rubber roller at an ambient temperature of 50 캜. Next, the temperature sensitive adhesive sheet was degassed under the conditions of 200 DEG C x 10 minutes. Thereafter, the ambient temperature was lowered to 50 占 폚, and a polyimide film was adhered to the thermosensitive adhesive sheet at this ambient temperature to obtain a test piece.

The obtained test piece was subjected to the following conditions, and then the polyimide film was peeled off at 180 ° from the thermosensitive adhesive sheet at a rate of 300 mm / min using a load cell (n = 3).

[50 DEG C]

The test piece was allowed to stand at an atmospheric temperature of 50 캜 for 20 minutes, and then peeled off at 180 캜.

[200 DEG C]

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

[250 DEG C]

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

[5 ° C]

The test piece was placed on a hot plate at 250 DEG C for 1 hour, then placed on a cool plate at 5 DEG C for 20 minutes, and then peeled at 180 DEG.

(Heat resistance)

First, a test piece was obtained in the same manner as in the evaluation of the 180 ° peel strength described above. Next, the obtained test piece was allowed to stand at 50 캜 for 3 minutes, and then heated in a hot air circulating oven at 250 캜 for 30 minutes. Then, the state of the test piece was visually observed at room temperature (23 DEG C) to evaluate the heat resistance. The evaluation criteria were set as follows.

○: No peeling was observed on the polyimide film.

X: The polyimide film was peeled off.

(Thermogravimetric analysis)

Each of the thermosensitive pressure-sensitive adhesive sheets obtained in Example 3 and Comparative Examples 1 to 3 was measured for change in weight with changes in temperature. The measurement conditions are as follows.

Measuring instrument: "TG / DTA6200" manufactured by Hitachi High Tech

Temperature range: 30 ~ 300 ℃

Heating rate: 10 ° C / min

Other: Under a nitrogen atmosphere of 250 ml / min

As apparent from Table 2, in Examples 1 to 5, the value of the 180 占 peeling strength at 50 占 폚 to 250 占 폚 was high, the value of 180 占 peeling strength at 5 占 폚 after passing through 250 占 폚 was low, . Further, as apparent from Fig. 1, it can be seen that Example 3 can suppress thermal deterioration when heated to a high temperature of 200 DEG C or higher, particularly 250 DEG C or higher.

Claims (7)

Sensitive adhesive which contains a side chain crystalline polymer and whose adhesive strength is lowered at a temperature lower than the melting point of the side chain crystalline polymer,
The side chain crystalline polymer includes (meth) acrylate, methyl (meth) acrylate and dicyclopentanyl (meth) acrylate having a linear alkyl group having a carbon number of 16 or more as a monomer component,
Sensitive adhesive comprising a styrene resin. The method according to claim 1,
Wherein the dicyclopentanyl (meth) acrylate is contained in the monomer component in a proportion of 5 to 35% by weight. The method according to claim 1,
Sensitive adhesive is contained in an amount of 20 to 50 parts by weight based on 100 parts by weight of the side chain crystalline polymer. The method according to claim 1,
Wherein the 180 ° peel strength to the polyimide film at 5 占 폚 after 1 hour at 250 占 폚 is 0.15 N / 25 mm or less. The method according to claim 1,
A thermosensitive pressure-sensitive adhesive for temporarily fixing a substrate in a manufacturing process of a flat panel display. Sensitive adhesive sheet comprising the thermosensitive adhesive according to claim 1. A film substrate,
Sensitive adhesive tape comprising a pressure-sensitive adhesive layer laminated on at least one side of the substrate and comprising the thermosensitive adhesive according to claim 1.

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