JP2019167440A - Acrylic copolymer, peeling agent composition and peeling sheet - Google Patents

Abstract

The present invention provides a (meth) acrylic copolymer capable of forming a release agent composition capable of forming a release layer having excellent release properties, a release agent composition capable of forming a release layer excellent in release properties, and a release sheet using the same. Offer. The composition has a structural unit (A) represented by the following formula 1, a structural unit (B) represented by the following formula 2, and a structural unit (C) represented by the following formula 3, and has a weight. An acrylic copolymer having an average molecular weight of 2,000 to 30,000. In the formula, R1, R3 and R5 each independently represent a hydrogen atom or a methyl group, R2 represents a linear or branched hydrocarbon group having 8 to 28 carbon atoms, and R4 represents a hydroxyl group, an amino group, a carboxyl group. Represents a hydrocarbon group having at least one functional group selected from the group consisting of a group and an epoxy group, or a hydrogen atom, and R6 represents a fluorocarbon group. [Selection diagram] None

Description

  The present invention relates to an acrylic copolymer, a release agent composition, and a release sheet.

Conventionally, pressure-sensitive adhesive sheets have been used in semiconductor device manufacturing processes and the like. In order to protect the adhesive layer, a release sheet having a release layer is usually laminated on the adhesive layer of the adhesive sheet.
As the release agent for forming the release layer, a silicone release agent containing a silicone compound is generally used from the viewpoint that the release force is light (small). However, the silicone-based release agent has a problem that the silicone-based compound easily moves to the adhesive layer and contaminates the adhesive layer. Therefore, a non-silicone release agent that does not contain a silicone compound is required.

As a non-silicone release agent, an acrylic release agent containing an acrylic resin having a long-chain alkyl group is known. However, acrylic release agents generally have a problem that the release force is heavier (larger) than silicone release agents.
Accordingly, the following release agent composition has been proposed.
(1) A poly (meth) acrylate containing a poly (meth) acrylic acid ester having a structural unit having a long-chain alkyl group having 12 to 28 carbon atoms, a liquid polymer, and a crosslinking agent, represented by a specific formula A release agent composition in which at least one of an acrylate ester and a liquid polymer has a reactive functional group (Patent Document 1).
(2) having a (meth) acrylic acid ester having a straight chain or branched aliphatic hydrocarbon group having 16 to 28 main chain carbon atoms and a linear or branched aliphatic hydrocarbon group having 4 to 14 main chain carbon atoms ( At least one selected from the group consisting of a prepolymer obtained by reacting a (meth) acrylic acid ester with at least one of (meth) acrylic acid and a (meth) acrylic acid ester having a reactive functional group, and a polyol compound. A release agent raw material composition containing two compounds (crosslinking agent) (Patent Document 2).

JP 2007-137940 A JP 2017-125091 A

  If the release agent composition of patent document 1 or 2 is used, the peeling force of a peeling layer will be reduced by introduce | transducing a crosslinked structure into a peeling layer. However, the peelability of the release layer formed from the release agent composition of Patent Document 1 or 2 is not yet sufficient.

  The present invention provides an acrylic copolymer from which a release agent composition capable of forming a release layer excellent in peelability is obtained, a release agent composition capable of forming a release layer excellent in peelability, and a release sheet using the same. With the goal.

The present invention has the following aspects.
[1] It has a structural unit (A) represented by the following formula 1, a structural unit (B) represented by the following formula 2, and a structural unit (C) represented by the following formula 3.
An acrylic copolymer having a weight average molecular weight of 2000 to 30000.

(Wherein R ¹ , R ³ and R ⁵ each independently represents a hydrogen atom or a methyl group, R ² represents a linear or branched hydrocarbon group having 8 to 28 carbon atoms, and R ⁴ represents This represents a hydrocarbon group having at least one functional group selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group and an epoxy group, or a hydrogen atom, and R ⁶ represents a fluorine group.
[2] When the total of all the structural units is 100% by mass, the proportion of the structural unit (A) is 60 to 99.4% by mass, and the proportion of the structural unit (B) is 0.5 to 20% by mass. The acrylic copolymer of [1], wherein the proportion of the structural unit (C) is 0.1 to 10% by mass.
[3] A release agent composition comprising the acrylic copolymer of [1] or [2] and a crosslinking agent.
[4] A release sheet having a release layer formed from the release agent composition of [3] on at least one surface of a substrate.

According to the acrylic copolymer of the present invention, a release agent composition capable of forming a release layer having excellent peelability is obtained.
According to the release agent composition of the present invention, a release layer excellent in peelability can be formed.
The release layer of the release sheet of the present invention is excellent in peelability.

[Acrylic copolymer]
The acrylic copolymer of the present invention includes a structural unit (A) represented by the following formula 1, a structural unit (B) represented by the following formula 2, and a structural unit (C) represented by the following formula 3. The weight average molecular weight is 2000-30000.

In formulas 1 to 3, R ¹ , R ³ and R ⁵ each independently represent a hydrogen atom or a methyl group. Each of R ¹ , R ³ and R ⁵ may be either a hydrogen atom or a methyl group, and a hydrogen atom is preferred in that the glass transition temperature of the acrylic copolymer is lowered and excellent flexibility can be imparted to the release layer. .

In Formula 1, ^{R 2} represents a straight-chain or branched hydrocarbon group having 8 to 28 carbon atoms. If the carbon number of R ² is within the above range, the layer formed from the release agent composition containing the acrylic copolymer of the present invention can function as a release layer.
The linear or branched hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, and a saturated hydrocarbon group, that is, an alkyl group is preferable from the viewpoint of polymerization stability, that is, gelation suppression.
Examples of R ² include 2-ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, isodecyl group, n-lauryl group, tridecyl group, hexadecyl group, isostearyl group, n-stearyl group, and behenyl group. It is done.

In Formula 2, R ⁴ is a hydrocarbon group having at least one functional group selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, and an epoxy group (hereinafter also referred to as “reactive functional group”), or Represents a hydrogen atom. An ester bond or an ether bond may be interposed between carbon atoms of the hydrocarbon group. R ⁴ is typically a hydrocarbon group having a hydroxyl group, a hydrocarbon group having an amino group, a hydrocarbon group having a carboxyl group, a hydrocarbon group having an epoxy group, or a hydrogen atom.

In Formula 3, R ⁶ represents a fluorocarbon group.
As the fluorocarbon group, a linear or branched fluorocarbon group is preferable. As for carbon number of a linear or branched fluorocarbon group, 2-8 are preferable. As the linear or branched fluorocarbon group, a fluoroalkyl group is preferable.
As the fluorocarbon group, 2,2,2-trifluoroethyl group, 2,2,3,3-tetrafluoropropyl group, 1H, 1H, 5H-octafluoropentyl group, 3,3,4,4,5 5,6,6,7,7,8,8,8-tridecafluorooctyl group and the like.

The structural unit (A) is typically a structural unit based on the monomer (a) represented by the following formula m1.
^{_{CH 2 = C (R 1)}} -COOR 2 Equation m1

As the monomer (a), 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate , N-lauryl (meth) acrylate, tridecyl (meth) acrylate, hexadecyl (meth) acrylate, isostearyl (meth) acrylate, n-stearyl (meth) acrylate, behenyl (meth) acrylate, etc. It is done. Any one of these monomers may be used alone, or two or more of these monomers may be used in combination.
In this specification, “(2-ethylhexyl) (meth) acrylate” refers to 2-ethylhexyl acrylate or 2-ethylhexyl methacrylate. The same applies to other (meth) acrylic acid esters.

The structural unit (B) is typically a structural unit based on the monomer (b) represented by the following formula m2.
^{_{CH 2 = C (R 3)}} -COOR 4 Formula m2

  As the monomer (b), 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, (meth) acrylic Diethylaminoethyl acid, acrylic acid, methacrylic acid, 2-methacryloyloxyethyl phthalate, 2-methacryloyloxyethyl hexahydrophthalate, 2-methacryloyloxyethyl succinate, glycidyl (meth) acrylate, 4- (meth) acrylic acid 4- Examples thereof include hydroxybutyl glycidyl ether. Any one of these monomers may be used alone, or two or more of these monomers may be used in combination.

The structural unit (C) is typically a structural unit based on the monomer (c) represented by the following formula m3.
^{_{CH 2 = C (R 5)}} -COOR 6 Formula m3

  As the monomer (c), 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate, 1H, 1H, 5H- (meth) acrylate Examples include octafluoropentyl, (meth) acrylic acid 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl and the like. Any one of these monomers may be used alone, or two or more of these monomers may be used in combination.

  When the total of all the structural units constituting the acrylic copolymer of the present invention is 100% by mass, the proportion of the structural unit (A) is preferably 60 to 99.4% by mass, more preferably 85 to 98% by mass. preferable. When the proportion of the structural unit (A) is not less than the lower limit of the above range, the release layer formed from the release agent composition containing the acrylic copolymer of the present invention tends to exhibit sufficient release force. When the proportion of the structural unit (A) is equal to or less than the upper limit of the above range, the effects of the structural units (B) and (C) are sufficiently exhibited.

When the total of all the structural units constituting the acrylic copolymer of the present invention is 100% by mass, the proportion of the structural unit (B) is preferably 0.5 to 20% by mass, and 1.0 to 10% by mass. Is more preferable. The COOR ⁴ of the structural unit (B) functions as a crosslinking point that reacts with the crosslinking agent. When the proportion of the structural unit (B) is less than the lower limit of the above range, the degree of cross-linking of the release layer is not sufficient, and therefore the release property of the release layer and the strength of the release layer may be deteriorated. When the proportion of the structural unit (B) exceeds the upper limit of the above range, the effects of the structural units (A) and (C) are not sufficiently exhibited.

When the total of all the structural units constituting the acrylic copolymer of the present invention is 100% by mass, the proportion of the structural unit (C) is preferably 0.1 to 10% by mass, and 1.0 to 5.0 The mass% is more preferable. When the proportion of the structural unit (C) is less than the lower limit of the above range, a sufficient amount of R ⁶ cannot be introduced into the release layer, and the peelability of the release layer may be inferior. When the proportion of the structural unit (C) exceeds the upper limit of the above range, the effects of the structural units (A) and (B) are not sufficiently exhibited.

The acrylic copolymer of the present invention may further contain other structural units other than the structural unit (A), the structural unit (B) and the structural unit (C) as long as the effects of the invention are not impaired.
As another structural unit, the structural unit based on the (meth) acrylic acid ester which has a C1-C7 hydrocarbon group is mentioned, for example.
The total proportion of the structural unit (A), the structural unit (B) and the structural unit (C) when the total of all the structural units is 100% by weight is preferably 70% by weight or more, more preferably 90% by weight or more. Preferably, 100 mass% is particularly preferable.

The weight average molecular weight (Mw) of the acrylic copolymer of this invention is 2000-30000, and 3000-20000 are preferable. If a weight average molecular weight is below the upper limit of the said range, it will be easy to lighten the peeling force of a peeling layer. If a weight average molecular weight is more than the lower limit of the said range, an acrylic copolymer will be easy to manufacture.
The weight average molecular weight of the acrylic copolymer is a standard polystyrene equivalent value measured by gel permeation chromatography (GPC).

The acrylic copolymer of the present invention described above has a structural unit (A), a structural unit (B), and a structural unit (C), and has a weight average molecular weight of 2000 to 30000. When a release agent composition is combined with the above, a release layer having excellent peelability can be formed. The peeling layer using the acrylic copolymer of the present invention has a light peeling force when peeled after being laminated on the pressure-sensitive adhesive layer, and hardly changes the pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer before and after the peeling layer is laminated.
Moreover, since the peeling layer formed from the said peeling agent composition is a crosslinked coating film which reacted with the crosslinking agent, it is excellent also in blocking resistance.
In view of the above effects, the acrylic copolymer of the present invention is preferably an acrylic copolymer for a release agent. However, the use of the acrylic copolymer of the present invention is not limited to a release agent, but a dispersant that improves dispersibility of an inorganic compound, a plasticizer that plasticizes a polymer compound, a polymer compound, etc. It can also be applied to uses such as compatibilizing agents that are compatibilized.

<Method for producing acrylic copolymer>
As a method for producing the acrylic copolymer of the present invention, for example, a monomer mixture containing the monomer (a), the monomer (b) and the monomer (c) is polymerized in the presence of a polymerization initiator and a solvent ( Solution polymerization).

The monomer mixture may further contain a monomer other than the monomer (a), the monomer (b) and the monomer (c).
When the total mass of the monomer mixture is 100% by mass, the preferable ratio of each of the monomer (a), the monomer (b) and the monomer (c) is when the total of all the structural units of the acrylic copolymer is 100% by mass. The preferred proportions of the structural unit (A), the structural unit (B), and the structural unit (C) are the same.

  As the polymerization initiator, a known polymerization initiator can be used, and examples thereof include 2,2'-azobisisobutyronitrile and benzoyl peroxide.

  Examples of the solvent include toluene, xylene, ethyl acetate, methyl ethyl ketone, tetrahydrofuran, isopropanol, dimethylformamide, N-methylpyrrolidone, methanol, ethanol, isopropyl alcohol, n-butanol, isobutanol, secondary butyl alcohol, 2-octanol, propylene glycol. Examples include monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, butylene glycol monomethyl ether, butylene glycol monoethyl ether and the like. Any one of these solvents may be used alone, or two or more thereof may be used in combination.

  When the monomer mixture is polymerized, a resin solution containing an acrylic copolymer having the structural unit (A), the structural unit (B), and the structural unit (C) and a solvent is obtained. If necessary, the solvent is distilled off from the obtained resin solution.

The polymerization of the monomer mixture can be performed, for example, by the following procedure.
A reaction vessel is charged with a monomer mixture, a polymerization initiator, and a solvent, and reacted at an arbitrary polymerization temperature for an arbitrary polymerization time.
The polymerization conditions are set so that the weight average molecular weight of the resulting acrylic copolymer is within the above range. The weight average molecular weight of the acrylic copolymer can be adjusted by the ratio of the polymerization initiator to 100 parts by mass of the monomer mixture, the polymerization time, the polymerization temperature, and the like.

  The ratio of the polymerization initiator with respect to 100 parts by mass of the monomer mixture is 0.1 to 5 parts by mass, preferably 0.3 to 4.0 parts by mass, and more preferably 0.5 to 3.0 parts by mass. It is easy to make the weight average molecular weight of an acrylic copolymer below the upper limit of the said range as the ratio of a polymerization initiator is more than the lower limit of the said range. When the ratio of the polymerization initiator is less than or equal to the upper limit of the above range, the content of the polymerization initiator remaining in the acrylic copolymer and its decomposition product is small, and the peelability of the release layer is more excellent.

The ratio of the solvent with respect to 100 parts by mass of the monomer mixture may be, for example, 40 to 900 parts by mass.
The polymerization temperature may be, for example, 60-130 ° C. The polymerization time may be, for example, 3 to 10 hours. The polymerization may be performed in the air or in an inert gas atmosphere such as nitrogen.

[Release agent composition]
The release agent composition of the present invention contains the above-mentioned acrylic copolymer of the present invention and a crosslinking agent.
The acrylic copolymer of the present invention contained in the release agent composition of the present invention may be one type or two or more types.

A crosslinking agent reacts with COOR ⁴ which a structural unit (B) has, and forms a crosslinked structure. Thereby, the peelability of a peeling layer improves.
The crosslinking agent is typically a polyfunctional compound having two or more functional groups capable of reacting with COOR ⁴ (hereinafter also referred to as “crosslinkable functional groups”). When COOR ⁴ contains a hydroxyl group, examples of the crosslinkable functional group include an isocyanate group. When COOR ⁴ contains an amino group, examples of the crosslinkable functional group include a carboxyl group and an epoxy group. When COOR ⁴ contains a carboxyl group, examples of the crosslinkable functional group include an amino group, an epoxy group, and a metal chelate compound. When COOR ⁴ contains an epoxy group, examples of the crosslinkable functional group include an amino group and a carboxyl group.

The crosslinking agent is at least one selected from the group consisting of a polyfunctional isocyanate compound, a polyfunctional carboxylic acid compound, and a polyfunctional amino compound from the viewpoint of reactivity with the functional group of the structural unit (B) of the acrylic copolymer. It is preferable that
Examples of the polyfunctional isocyanate compound include diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), xylene diisocyanate (XDI), and naphthalene. Examples thereof include diisocyanate (NDI), trimethylolpropane (TMP) adduct TDI, TMP adduct HDI, TMP adduct IPDI, and TMP adduct XDI.
Examples of the polyfunctional carboxylic acid compound include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, and suberic acid.
Examples of the polyfunctional amino compound include ethylenediamine, tetramethylenediamine, hexamethylenediamine, N, N′-diphenylethylenediamine, p-xylylenediamine, and the like.
A polyfunctional epoxy compound or a metal chelate compound may be used as the crosslinking agent.

The release agent composition of the present invention may further contain other components other than the acrylic copolymer and the cross-linking agent of the present invention as long as they do not impair the effects of the invention.
Examples of other components include solvents, resins other than the acrylic copolymer of the present invention, catalysts that promote the reaction between COOR ⁴ and a crosslinking agent, antistatic agents, surfactants, antioxidants, lubricants, flame retardants. , Colorants, light-resistant stabilizers, heat-resistant stabilizers, and the like.

  Examples of the solvent include toluene, xylene, methanol, ethanol, isobutanol, n-butanol, ethyl acetate, methyl ethyl ketone, acetone, tetrahydrofuran, isopropanol, dimethylformamide, N-methylpyrrolidone and the like.

  Examples of the other resin include polybutadiene, polyisoprene, polychloroprene, polypentadiene, polybutene, polyisobutylene, polystyrene, isoprene-butadiene copolymer, styrene-isoprene copolymer, polyolefin, and derivatives thereof. Other resins may have a functional group such as a hydroxyl group, an amino group, or a carboxyl group. Any one of these resins may be used alone, or two or more thereof may be used in combination.

  In the release agent composition of the present invention, the content of the crosslinking agent is preferably 0.5 to 10 parts by mass and more preferably 1.0 to 5.0 parts by mass with respect to 100 parts by mass of the acrylic copolymer of the present invention. preferable. If content of a crosslinking agent is more than the lower limit of the said range, the peelability of a peeling layer and the intensity | strength of a peeling layer will be more excellent. If content of a crosslinking agent is below the upper limit of the said range, peelability will be more excellent.

  The mass ratio of the other resin to the acrylic copolymer of the present invention (other resin / acrylic copolymer of the present invention) may be, for example, 0/100 to 90/10.

  The release agent composition of the present invention can be produced by mixing the acrylic copolymer of the present invention, a crosslinking agent, and other components as necessary.

In the release agent composition of this invention demonstrated above, since the acrylic copolymer of this invention and a crosslinking agent are included, the peeling layer excellent in peelability can be formed. The peeling layer formed from the release agent composition of the present invention has a light peeling force when peeled after being laminated on the pressure-sensitive adhesive layer, and hardly changes the pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer before and after the peeling layer is laminated.
The release layer formed from the release agent composition of the present invention is also excellent in blocking resistance.

[Peeling sheet]
The release sheet of the present invention has a release layer formed from the above-described release agent composition of the present invention on at least one surface of a substrate.
The release sheet may be a sheet-like sheet or a long sheet (tape or the like).

The release layer contains a reaction product of the acrylic copolymer of the present invention and a crosslinking agent.
The thickness of the release layer is usually about 0.1 to 5.0 μm, preferably about 0.1 to 1.0 μm.
The release layer may be provided on only one surface of the substrate, or may be provided on both surfaces.

  As the base material, those known as the base material of the release sheet can be used without particular limitation, for example, polyethylene, polypropylene, polybutene, polybutadiene, vinyl chloride, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyimide, Resins comprising resins such as polyetherimide, polyetherketone, polyetheretherketone, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, polycarbonate, polymethyl methacrylate, triacetyl cellulose, polynorbornene Film: Paper such as fine paper, dust-free paper, glassine paper, clay-coated paper, resin-coated paper, laminated paper (polyethylene laminated paper, polypropylene laminated paper, etc.); non-woven fabric, metal foil, etc.

The thickness of a base material can be suitably selected according to a use, the material of a base material, etc. When the substrate is a resin film, the thickness of the substrate is usually 5 to 300 μm, preferably about 20 to 200 μm. When the substrate is paper, the thickness of the substrate is usually about ²⁰ to 450 g / m ² , preferably about 40 to 220 g / m ² as basis weight.

The release sheet of the present invention can be produced by forming a layer composed of the release agent composition of the present invention on at least one surface of a substrate and reacting the acrylic copolymer of the present invention with a crosslinking agent. By reacting them, a crosslinked structure is formed, and a release layer is formed.
The layer comprising the release agent composition of the present invention can be formed by a conventional method. For example, when the release agent composition of the present invention contains a solvent, the release agent composition may be a known wet method such as a gravure coating method, a roll coating method, a blade coating method, a knife coating method, a bar coating method, or a spray coating method. The said layer can be formed by apply | coating on a base material by the coating method.
The acrylic copolymer and the crosslinking agent of the present invention can be reacted, for example, by heating the layer. As a heating condition, the conditions for 1 to 60 minutes are mentioned at 50-200 degreeC, for example.
When the layer contains a solvent, the solvent may be removed by heating when the acrylic copolymer of the present invention is reacted with the crosslinking agent, or the acrylic copolymer of the present invention is reacted with the crosslinking agent. Before the treatment, the layer may be dried at a temperature at which the acrylic copolymer of the present invention and the crosslinking agent do not react to remove the solvent.

There is no restriction | limiting in particular in the use of the peeling sheet of this invention, It may be the same as that of a well-known release agent.
For example, the release sheet of the present invention may be laminated such that the surface on the release layer side is in contact with an adhesive layer such as an adhesive sheet having an adhesive layer.
You may use the peeling sheet of this invention for manufacture of an adhesive sheet. For example, a pressure-sensitive adhesive is applied to the surface on the release layer side of the release sheet of the present invention to form an adhesive layer, and a base material of the adhesive sheet or another release sheet of the present invention is laminated thereon. Thereby, the double-sided adhesive sheet (adhesion layer) by which the peeling sheet of this invention was laminated | stacked on the adhesive sheet which has an adhesive layer in the one surface of a base material, or both surfaces is obtained.
When the release sheet of the present invention has a release layer on one surface of the substrate, an adhesive layer may be formed on the other surface of the substrate to provide an adhesive sheet with a release layer. Such a pressure-sensitive adhesive sheet can be stored in a state of being wound in a roll shape.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these. Hereinafter, “part” means “part by mass”. “%” Indicates “mass%” unless otherwise specified.

Example 1
<Manufacture of acrylic copolymer>
In a separable flask equipped with a stirring bar equipped with a stirring blade for polymerization, a stirrer, a thermometer, and a glass tube for nitrogen purge, 233 parts of propylene glycol monomethyl ether, 93.0 parts of n-lauryl acrylate, acrylic Acid 2-hydroxyethyl 5.0 parts, acrylic acid 2,2,2-trifluoroethyl 2.0 parts, polymerization initiator (2,2'-azobisisobutyronitrile) 2.0 parts In addition, solution polymerization was carried out by maintaining at 90 ° C. for 8 hours under stirring in a nitrogen atmosphere to obtain a resin solution containing 30% of an acrylic copolymer.
From the obtained resin solution, the solvent described above was distilled off under reduced pressure at 130 ° C. to obtain an acrylic copolymer having a weight average molecular weight (Mw) of 5000.
The Mw of the acrylic copolymer was determined by measuring a standard polystyrene equivalent value by gel permeation chromatography (GPC).

<Manufacture of release agent composition>
To 100 parts of the acrylic copolymer, 350 parts of toluene and a solution prepared by dissolving 2.66 parts of trifunctional isocyanate (Coronate L, manufactured by Tosoh Corporation) in 7.34 parts of toluene are stirred and peeled at room temperature. An agent composition was obtained.

<Manufacture of release sheet>
The release agent composition was applied onto a polyethylene terephthalate film having a film thickness of 50 μm (manufactured by Panac Corporation, Lumirror 50S10) using a bar coater so that the film thickness after drying was 1 μm or less. Heat at 5 ° C. for 5 minutes. Thereby, while drying the coating film, the acrylic copolymer and the trifunctional isocyanate were reacted to form a cured coating film (release layer) to obtain a release sheet.

<Evaluation of peelability>
To 100 parts of an acrylic pressure-sensitive adhesive (manufactured by Fujikura Kasei Co., Ltd., Acrybase LKG-1413), a solution obtained by dissolving 1.33 parts of trifunctional isocyanate (manufactured by Tosoh Corporation, Coronate L) in 8.67 parts of toluene was added. The mixture was stirred at room temperature to obtain a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition was applied onto the release layer of the release sheet using a doctor blade so that the film thickness after drying was 30 μm, and the coating film was heated at 100 ° C. for 5 minutes. Thereby, while the coating film was dried, the acrylic adhesive and the trifunctional isocyanate were reacted to form an adhesive layer. Next, a 50 μm-thick polyethylene terephthalate film (Panac Lumirror 50S10) is bonded onto the adhesive layer, reciprocated with a 2 kg rubber roller, and left to stand at 40 ° C. for 72 hours. The laminate was obtained by allowing to stand for a period of time.
The obtained laminate was cut to a width of 25 mm, and then peeled off at a tensile speed of 300 mm / min using a tensile tester (STROGRAPG VG1-E manufactured by Toyo Seiki Seisakusyo Co., Ltd.) at a temperature of 23 ° C. and a humidity of 50%. The sheet was peeled 180 ° to determine the peel force (mN / 25 mm).
The obtained peeling force was determined according to the following criteria.
A: Peeling force is 200 mN / 25 mm or less.
X: Peeling force is over 200 mN / 25 mm.

(Examples 2-4, 8-10, Comparative Examples 1-4)
Except having changed the material added to a separable flask in manufacture of an acrylic copolymer as shown in Tables 1-2, the same operation as Example 1 is performed, and an acrylic copolymer, a release agent composition, and a release sheet are used. The peelability of the release layer was evaluated. In Tables 1 and 2, the unit of the blending amount of each material is “parts” (the same applies hereinafter). The Mw and evaluation results of the acrylic copolymer are shown in Tables 1-2.

(Examples 5-7)
Example 1 except that the materials added to the separable flask in the production of the acrylic copolymer were changed as shown in Table 1 and that the following crosslinking agent was used instead of 1.33 parts of the trifunctional isocyanate. The same operation was performed to produce an acrylic copolymer, a release agent composition and a release sheet, and the peelability of the release layer was evaluated. The Mw and evaluation results of the acrylic copolymer are also shown in Table 1.
Example 5: 1.0 part adipic acid.
Example 6: 1.0 part of hexamethylenediamine.
Example 7: 1.0 part of succinic acid.

  As shown in the above results, the release layers of the release sheets obtained in Examples 1 to 10 were less peelable and excellent in peelability than the release layers of the release sheets obtained in Comparative Examples 1 to 4. It was.

Claims (4)

A structural unit (A) represented by the following formula 1, a structural unit (B) represented by the following formula 2, and a structural unit (C) represented by the following formula 3;
An acrylic copolymer having a weight average molecular weight of 2000 to 30000.

(Wherein R ¹ , R ³ and R ⁵ each independently represents a hydrogen atom or a methyl group, R ² represents a linear or branched hydrocarbon group having 8 to 28 carbon atoms, and R ⁴ represents This represents a hydrocarbon group having at least one functional group selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group and an epoxy group, or a hydrogen atom, and R ⁶ represents a fluorine group.   When the total of all the structural units is 100% by mass, the proportion of the structural unit (A) is 60 to 99.4% by mass, the proportion of the structural unit (B) is 0.5 to 20% by mass, The acrylic copolymer according to claim 1, wherein the proportion of the unit (C) is 0.1 to 10% by mass.   A release agent composition comprising the acrylic copolymer according to claim 1 or 2 and a crosslinking agent.   A release sheet having a release layer formed from the release agent composition according to claim 3 on at least one surface of a substrate.