JPH07772B2 - Pressure sensitive adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure-sensitive adhesive composition. For more details,
The present invention relates to a pressure-sensitive adhesive composition capable of reducing the adhesive force by irradiation with ultraviolet rays.

[Problems to be Solved by Conventional Techniques and Inventions] Generally, pressure-sensitive adhesive sheets or pressure-sensitive adhesive sheets obtained by coating a pressure-sensitive adhesive on a base sheet are used for various purposes in general households and various industrial fields. ing. Therefore, the required characteristics of the pressure-sensitive adhesive sheet have been diversified, and various functions have been required according to various uses.

For example, in manufacturing an integrated circuit, in order to obtain a dice by cutting the silicon wafer into a predetermined size (by dicing), the silicon wafer is placed on a pressure-sensitive adhesive sheet called a dicing film,
After fixing by pressure-sensitive adhesion and cutting, this is peeled off from the dicing film and picked up. Therefore, in order to accurately dice a silicon wafer, the dicing film has a strong adhesive force to the silicon wafer during dicing, while the dicing film has an adhesive force when picking up the obtained dice from the dicing film. Need to be weak. For example, when dicing a silicon wafer, the dicing film generally has an adhesive force of about 100 to 800 g / 25 mm, while when picking up a dice, the dicing film has an adhesive force of about several tens g / 25 mm or less. It is said that it is desirable.

Also, a technique has recently been adopted in which the pressure-sensitive adhesive sheet is stretched (expanded) before being picked up to increase the distance between the cut silicon wafers to facilitate picking up. In this case, the property of withstanding the stretching of the sheet as the base material of the adhesive is also important.

In this way, when it is necessary to reduce the adhesive force after application to the adherend, a pressure-sensitive adhesive composition having such characteristics is used, and when it is necessary to expand the pressure-sensitive adhesive sheet before pickup. Requires a pressure-sensitive adhesive sheet having such characteristics, and various studies have been made on these.

For example, Japanese Unexamined Patent Publication (Kokai) No. 62-153376 discloses a method using a urethane acrylate oligomer. However, since the urethane acrylate oligomer has a high molecular weight, it is necessary to irradiate it for a long time in order to reduce the adhesive strength by ultraviolet irradiation. In addition, the adhesive strength is not significantly reduced, and artificial peeling may be necessary. Further, when the adhesive is peeled off from the adherend, the adhesive may remain (adhesive residue) on the adherend, and a cleaning operation or the like is required to remove the adhesive. In particular, if the adhesive layer after curing does not have flexibility, the phenomenon of cracking occurs, and adhesive residue on the adherend easily occurs.

As described above, when it is necessary to reduce the adhesive force after application to the adherend, a pressure-sensitive adhesive composition having such characteristics is required, but one having sufficient performance is required. The reality is that it is not known yet.

[Means for Solving the Problems] The inventors of the present invention have conducted intensive studies to obtain a pressure-sensitive adhesive that initially has a strong adhesive force and can reduce the adhesive force as needed. Unexpectedly, a pressure-sensitive adhesive composition comprising a mixture containing an elastic polymer and an ultraviolet-crosslinkable acrylic ester as a main component, when the composition is irradiated with ultraviolet rays, its adhesive force is significantly reduced. I found it. Further, when a pressure-sensitive adhesive composition using a polyisocyanate is used, the initial adhesive force is strong, but when it is irradiated with ultraviolet rays, the adhesive force is more significantly reduced or substantially disappears. By using a urethane group-containing (meth) acrylic acid ester having a specific structure as the UV-crosslinkable acrylic acid ester contained in the composition, the formed adhesive layer has flexibility and is immediately expandable. The present invention has been completed, and the present invention has been completed.

That is, the present invention provides (a) an elastic polymer, (b) a UV-crosslinkable (meth) acrylic acid ester, (c) a polyisocyanate, and (d) a general formula (1): (Bn ₁ U-AmUB) n ₂ (1) (In the formula, A is (Each of R ¹ and R ² is a saturated hydrocarbon group, an unsaturated hydrocarbon group, a divalent aromatic group or a divalent group obtained by adding an oxyalkylene group thereto, and p is 1 to Ten)
Polyester group-containing diol residue or -OR
An alkylenediol residue represented by ¹ O- (R ¹ is the same as above), and B is (R ³ is H or CH ₃ , R ⁴ is a (q + 1) -valent hydrocarbon group having 1 to 5 carbon atoms, q is 1 to 5, and q R ^{3 s} are not necessarily the same). (Meth) acrylic acid ester-containing group, U is (R ¹ is the same as above), m is 1 to 1
0, n ₁ and n ₂ are each 1 or more and represented by the general formula (1)
Urethane compound-containing UV-crosslinkable compound represented by the formula (average number of 700 to 2500) (urethane group-containing UV-crosslinkable compound which contains (meth) acrylic acid ester as a main component and is (d) component) (Meth) acrylic acid ester
The present invention relates to a pressure-sensitive adhesive composition capable of reducing the adhesive force by ultraviolet irradiation, which is used in an amount of 1 to 150 parts with respect to 100 parts (part by weight) of the elastic polymer (a).

The composition of the present invention has a strong adhesive force when it is not irradiated with ultraviolet rays, and by irradiating it with ultraviolet rays, the adhesive force can be remarkably reduced, and the pressure-sensitive property exhibiting excellent expandability is exhibited. It is an adhesive composition.

[Examples] Conventionally, for example, "Adhesion Handbook (2nd Edition)" (edited by Japan Adhesive Association, published by Nikkan Kogyo Shimbun, 1980) Nos. 398-4
Various pressure sensitive adhesive compositions are known, as described on page 14.

A typical pressure sensitive adhesive composition is mainly composed of an elastic polymer,
Tackifiers and plasticizers with good compatibility with this, further,
A composition in which a filler, an antiaging agent, a colorant, and the like are blended as necessary and the components are uniformly mixed.

In the present invention, as the elastic polymer as the component (a), for example, a saturated copolyester resin, a homopolymer of (meth) acrylic acid ester, a copolymer of (meth) acrylic acid ester and the like are preferable. However, it is not limited thereto. These may be used alone or in combination of two or more.

Specific examples of the saturated copolyester resin are usually two or more kinds of different saturated divalent carboxylic acids, as described in "Industrial Materials", Vol. 25, No. 11, pp. 101-106. And a saturated copolymer resin having a relatively low glass transition point obtained by polycondensation of a saturated dihydric alcohol with a saturated dihydric alcohol. Usually, an aromatic divalent carboxylic acid and an aliphatic divalent carboxylic acid are used in combination as the saturated divalent carboxylic acid, and an aliphatic or alicyclic dihydric alcohol is used as the saturated dihydric alcohol.
That is, glycol is used, but is not limited thereto. In particular, the saturated copolyester resin used in the present invention includes aromatic divalent carboxylic acid /
Saturated obtained by polycondensation of a saturated divalent carboxylic acid mixture in which the aliphatic divalent carboxylic acid is in a molar ratio of 80/20 to 20/80, preferably 70/30 to 50/50 in an equimolar amount. Copolymerized polyester resin is preferably used.

Examples of the aromatic divalent carboxylic acid include terephthalic acid, examples of the aliphatic divalent carboxylic acid include sebacic acid and adipic acid, and examples of the glycol include ethylene glycol, 1,4-butanediol and propylene glycol. The saturated copolymerized polyester resin obtained by using these is preferably used.
In addition, when producing a saturated copolyester resin, a trivalent or more saturated polyvalent carboxylic acid or a trivalent or more saturated polyhydric alcohol may be partially used as a carboxylic acid component, if necessary.

Specific examples of the (meth) acrylic acid ester homopolymer or (meth) acrylic acid ester copolymer include, but are not particularly limited to, pressure-sensitive adhesives conventionally known as (meth) acrylic acid ester-based pressure-sensitive adhesives. Can be used.
As the polymer used as the elastic polymer in the (meth) acrylic ester-based pressure-sensitive adhesive, a homopolymer or a copolymer can be usually used, but a copolymer of a (meth) acrylic ester is used. There are many cases. This copolymer usually contains an acrylic acid alkyl ester such as ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, which forms a polymer having a low glass transition point for imparting tackiness, as a main monomer. , Comonomers that form hard polymers with a high glass transition point to impart cohesiveness, such as vinyl acetate, acrylonitrile, styrene, methyl acrylate, methyl methacrylate, etc., and for improving crosslinkability and adhesion. Monomers having functional groups such as carboxylic acid group, hydroxyl group, amide group, glycidyl group, and hydroxylmethyl group, such as monomers such as acrylic acid, methacrylic acid, itaconic acid, hydroxylethyl methacrylate, hydroxylpropyl methacrylate, acrylamide, glycidyl methacrylate. Which is a copolymer comprising copolymerized.

The UV-crosslinkable (meth) acrylic acid ester, which is the component (b) used in the present invention, means an acrylic acid ester or a methacrylic acid ester as an oligomer or a monomer which is crosslinked by irradiation of ultraviolet rays, and has at least two acryloyl groups in the molecule. Or it has a methacryloyl group. Specifically, as such an oligomer,
For example, oligoester acrylate and the like, and as the monomer, for example, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, dipentaerythritol hexaacrylate, and other polyhydric alcohol esters of acrylic acid, Alternatively, there may be mentioned esters of methacrylic acid with polyhydric alcohols such as 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, and dipentaerythritol pentamethacrylate.

The amount of the UV-crosslinkable (meth) acrylic acid ester which is the component (b) is generally preferably about 15 to 200 parts, more preferably about 50 to 150 parts per 100 parts of the elastic polymer of the component (a). preferable. When the amount of the component (b) used is less than 15 parts, the adhesive strength of the adhesive composition is not substantially changed by irradiating the adhesive composition with ultraviolet rays. Can be reduced,
For example, the adhesive may remain on the dice when picking up the dice after dicing a silicone wafer, which is not preferable.

The polyisocyanate which is the component (c) used in the present invention is not particularly limited and any polyisocyanate can be used, but diisocyanates and triisocyanates are industrially readily available and used.

Specific examples of the diisocyanate include 2,4-
Examples thereof include toluene diisocyanate, m-phenylene diisocyanate, m-xylylene diisocyanate, 4,4'-diphenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

Various triisocyanates are also commercially available, for example, trimethylolpropane toluentisocyanate commercially available as "Sumijour L" from Sumitomo Chemical Co., Ltd. is a preferred specific example of the triisocyanate used in the present invention. Can be given as an example.

Further, a terminal isocyanate compound obtained by reacting a diisocyanate and a polyol in the presence of an excessive amount of diisocyanate, for example, a urethane oligomer obtained as an intermediate of a compound represented by the general formula (1) can also be used as the polyisocyanate. .

The amount of the polyisocyanate used as the component (c) is preferably 0.1 to 20 parts, more preferably 1 to 15 parts, per 100 parts of the elastic polymer of the component (a).

In the present invention, as the component (d), the general formula (1): (Bn ₁ U-AmUB) n ₂ (1) (wherein A is (Each of R ¹ and R ² is a saturated hydrocarbon group, an unsaturated hydrocarbon group, a divalent aromatic group or a divalent group obtained by adding an oxyalkylene group thereto, and p is 1 to Ten)
Polyester group-containing diol residue or -OR
An alkylenediol residue represented by ¹ O- (R ¹ is the same as above), and B is (R ³ is H or CH ₃ , R ⁴ is a (q + 1) -valent hydrocarbon group having 1 to 5 carbon atoms, q is 1 to 5, and when q is 2 or more, q
R ³ does not have to be the same), a (meth) acrylic acid ester-containing group represented by (R ¹ is the same as above), m is 1 to 1
0, n ₁ and n ₂ are each 1 or more and represented by the general formula (1)
The urethane group-containing UV-crosslinkable (meth) acrylic acid ester represented by the formula (7), which has an average molecular weight of 700 to 2500, is used.

The component (d) is a component used to improve the flexibility and expandability of the adhesive layer after UV curing, and the portion A in the general formula (1) mainly improves the compatibility with other components. , The physical properties of the cured product are improved, the B part is mainly UV curable, and the U part is mainly the flexibility and expandability of the resin.

A in the general formula (1) is Polyester group-containing diol residue or -OR
¹ O- is an alkylene diol residue, wherein R ¹ and R ² in the residue are both saturated hydrocarbon group, unsaturated hydrocarbon group, divalent aromatic group and oxyalkylene group It is a group selected from divalent groups in which one or more, preferably about 2 to 10 are added, and p is 1 to 10, and has the formula (1)
The molecular weight can be changed to be in the range of 700 to 2500, and in practice, the larger the molecular weight, the greater flexibility,
The expandability is improved, but if it is too large, the ultraviolet curing speed becomes slow, which causes the adhesive strength after the irradiation of ultraviolet rays not to decrease.

B in the general formula (1) is Is a (meth) acrylic acid ester group, wherein R ³ is H or CH ₃ , and R ⁴ has 1 to 5 carbon atoms (q + 1)
Since it is a valent hydrocarbon group and q is 1 to 5, the curing at the time of ultraviolet curing is fast and the adhesive residue is small.

Furthermore, U in the general formula (1) is Since it is a urethane group represented by, it contributes to the improvement of flexibility and expandability of the adhesive layer after ultraviolet curing.

From the viewpoint of improving flexibility and expandability, m in the general formula (1) is preferably as large as possible.
If it is too large, the ultraviolet curing rate is slow like p and it becomes difficult to reduce the adhesive strength, so that 1 to 10, preferably 1
˜2, both n ₁ and n ₂ are 1 or more, and n ₁ + n ₂ ≧
2, preferably 4 ≧ n ₁ + n ₂ ≧ 1, the average molecular weight of the urethane group-containing (meth) acrylic acid ester represented by the general formula (1) is 700 to 2500, preferably 1000 to 250.
It is also preferable that 0 is used.
The urethane group-containing (meth) represented by the general formula (1)
If the average molecular weight of the acrylic ester is less than 700, the adhesive residue will be large, and if it is more than 2500, the adhesive strength after ultraviolet irradiation will not decrease, which is not preferable.

The compound represented by the general formula (1) is a terminal (meth) acryl obtained by reacting a terminal isocyanate isocyanate urethane synthesized by a reaction between a diol component and an isocyanate component with a (meth) acryloyloxy group-containing hydroxyl compound. It is an acid esterified urethane compound.

The diol component used in the synthesis of the compound represented by the general formula (1) may be an alkylene diol as described above, a polyester group-containing diol, a polyoxyalkylene group-containing diol, or the like. For example, 1,4-butanediol, 1,6-hexanediol and other aliphatic diols, polyethylene glycol, polypropylene glycol, polytetraethylene glycol and other polyoxyalkylene glycols, aliphatic diol alkylene oxide adducts, bisphenol A alkylene oxides. Both ends hydroxy compound such as an aromatic group-containing polyoxyalkylene glycol such as an adduct, and further both ends obtained by esterification of the hydroxy compound with a dicarboxylic acid compound such as succinic acid, fumaric acid, adipic acid or phthalic acid Examples thereof include hydroxypolyester compounds.

The isocyanate component is preferably diisocyanate or triisocyanate, and examples of the diisocyanate include 2,4-toluene diisocyanate and m-
Phenylene diisocyanate, m-xylylene diisocyanate, 4,4'-diphenyl diisocyanate, 4,4'-
Examples thereof include diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, dianisidine diisocyanate and hexamethylene diisocyanate.

Examples of triisocyanates include triphenylmethane triisocyanate and tolylene triisocyanate adducts of trimethylolpropane (for example, Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.).

Specific examples of the (meth) acryloyloxy group-containing hydroxyl compound include, for example, hydroxyethyl acrylate, hydroxypropyl acrylate, trimethylolpropane diacrylate, glycerin diacrylate, pentaerythritol triacrylate, and methacrylates obtained by converting these acrylates into methacrylates. Kind and the like.

Specific examples of the urethane group-containing UV-crosslinkable (meth) acrylic acid ester represented by the general formula (1) include, for example, 4 mol of ethylene oxide adduct of bisphenol A (1 mol), xylene diisocyanate (2 mol) and hydroxyethyl acrylate. (2 mol) reactant;
Bisphenol A ethylene oxide 4 mol reaction product (2
Reaction product of isophorone diisocyanate (3 mol) and hydroxyethyl acrylate (2 mol); 1,6
-Hexanediol (5 mol) and adipic acid (4 mol)
Reaction product of polyester diol (1 mol) formed by esterification with 2,4-toluene diisocyanate (2 mol), glycerin diacrylate (1 mol), hydroxypropyl acrylate (1 mol); diethylene glycol (6 mol) and amber Reaction product of polyester diol (1 mol) formed by esterification with acid (5 mol), xylylene diisocyanate (2 mol) and hydroxypropyl acrylate (2 mol); 4 mol ethylene oxide adduct of bisphenol A (2 mol) And a reaction product of xylylene diisocyanate (3 mol), hydroxyethyl acrylate (1 mol), pentaerythritol triacrylate (1 mol), and the like.

The urethane group-containing UV-crosslinkable (meth) acrylic acid ester represented by the general formula (1), which is the component (d), is (a)
Using 5 to 150 parts per 100 parts of the elastic polymer of the component, the initial adhesive strength is strong, the adhesive strength is greatly reduced by UV irradiation, the adhesive residue when picked up after UV irradiation is small, and the expandability is high. It is preferable in terms of goodness, and more preferably 10 to 130 parts.

The pressure-sensitive adhesive composition according to the present invention usually contains a photopolymerization initiator, and may further contain a photosensitizer and may also contain a polymerization inhibitor.

The photopolymerization initiator is used for cross-linking polymerization of the UV-crosslinkable acrylic ester by UV irradiation.
Such a photopolymerization initiator is generally well known in the technical field of ultraviolet crosslinking polymerization, and in the present invention, a photopolymerization initiator generally well known from the past can be used. Specific examples of such a polymerization initiator include benzoin alkyl ethers such as benzoin methyl ether and benzoin isopropyl ether, and aromatic oxyketones and aromatic ketones such as benzoin, benzyl and benzophenone.
It is not limited to these.

As the polymerization inhibitor, the compound represented by the general formula (1) which is the component (d) and the UV-crosslinkable (meth) acrylic acid ester which is the component (b) are polymerized by, for example, heat without being irradiated with UV rays. It is added in order to prevent this, and a conventional polymerization inhibitor conventionally known as such a polymerization inhibitor can be used. Examples of such a polymerization inhibitor include hydroquinone,
Examples thereof include hydroquinone monomethyl ether.

The photopolymerization initiator and the polymerization inhibitor may be blended in the amounts generally used in the technical field of ultraviolet polymerization. For example, in the case of a polymerization initiator, the total amount of the components (b) and (d) may be used. About 1 to 20 parts is preferable with respect to 100 parts, and in the case of a polymerization inhibitor, it is used in the range of 0.01 to 1 part if necessary.

The pressure-sensitive adhesive composition of the present invention comprises an elastic polymer, a UV-crosslinkable (meth) acrylic acid ester, a urethane group-containing UV-crosslinkable acrylic acid ester represented by the general formula (1) and a polyisocyanate in the above-mentioned blending amount. A polymerization initiator, an acrylic acid ester-based tackifier, a polymerization inhibitor, a filler, an antioxidant, a colorant, etc., if necessary, and a suitable organic solvent that dissolves these, for example, an aromatic hydrocarbon, A homogeneous solution composition can be obtained by dissolving it in a ketone, a mixed solvent thereof, or the like. As a specific solvent, for example, a mixed solvent of toluene and methyl ethyl ketone is preferably used, but the solvent is not limited thereto.

The content of the elastic polymer in the pressure-sensitive adhesive composition may be appropriately selected depending on the application etc., but is usually 10 to
It is in the range of 50% (% by weight, the same applies hereinafter). However, it is not limited to this range.

There is no limitation on the method for preparing the pressure-sensitive adhesive composition of the present invention, but normally, the elastic polymer and the tackifier are commercially available in the form of a solution, and it is convenient to use these. For example, a mixture of these solutions is added thereto, and an ultraviolet crosslinkable (meth) acrylic acid ester, a urethane group-containing ultraviolet crosslinkable acrylic acid ester represented by the general formula (1) and a polyisocyanate, and, if necessary, a polymerization initiator The acrylic ester polymerization inhibitor, the filler, the antiaging agent, the colorant and the like may be added and mixed and dissolved.

Further, the pressure-sensitive adhesive composition of the present invention may optionally contain a plasticizer such as liquid polyacrylic acid ester, liquid polyphthene, mineral oil, lanolin, and the like.

The pressure-sensitive adhesive composition of the present invention is used, for example, as a pressure-sensitive adhesive sheet by forming a layer of the pressure-sensitive adhesive composition on a base sheet that allows transmission of ultraviolet rays. Therefore,
For example, the pressure-sensitive adhesive sheet is produced by applying the liquid pressure-sensitive adhesive composition as described above onto the substrate sheet and drying it.

The base sheet is not particularly limited as long as it is a sheet that can transmit ultraviolet rays, and various sheets can be used, but normally a transparent to translucent synthetic resin sheet is used. Specific examples of such synthetic resin sheet include, for example, vinyl chloride resin, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate copolymer, vinylidene chloride resin, polyolefin, acetyl cellulose, polyvinyl alcohol, polyamide, polyester. A resin sheet having a thickness of about 50 to 300 μm and made of polycarbonate or the like is preferably used.

Among the resin sheets used as the base sheet, polyvinyl chloride or vinyl chloride copolymers such as vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-acrylic acid ester copolymer, etc. The resin sheet made of is particularly preferable because it is flexible and inexpensive.

In addition to the vinyl chloride resin sheet, as a flexible base sheet, for example, a sheet made of polyvinylidene chloride, acetyl cellulose, or the like can be preferably used.

When a resin sheet containing a plasticizer is used as the base resin sheet of the pressure-sensitive adhesive sheet, the plasticizer migrates from this resin sheet into the pressure-sensitive adhesive composition, and, depending on the resin sheet, ultraviolet rays Since it has good compatibility with the crosslinkable acrylic ester, the UV crosslinkable acrylic ester contained in the pressure-sensitive adhesive composition migrates into the resin sheet, and by such mutual migration, the pressure-sensitive adhesive sheet The effect of reducing the adhesive strength after ultraviolet irradiation is significantly reduced.

Therefore, in the present invention, as the base material sheet of the pressure-sensitive adhesive sheet, a barrier layer made of a resin layer that does not allow the plasticizer and the UV-crosslinkable acrylic ester to pass between the base material sheet and the pressure-sensitive adhesive sheet. Is preferably interposed. However, this barrier layer must not prevent the transmission of ultraviolet rays.

That is, this barrier layer does not hinder the transmission of ultraviolet rays at all, but prevents the plasticizer contained in the base resin sheet from migrating into the pressure-sensitive adhesive composition, and at the same time, the pressure-sensitive adhesive composition. The UV-crosslinkable acrylic acid ester contained in the base resin sheet is prevented from migrating to the base resin sheet, and thus, the plasticizer contained in the base resin sheet is retained in the base material, The UV-crosslinkable acrylic ester contained in the pressure-sensitive adhesive composition is retained in the adhesive composition.

As the barrier layer, a film of poly-α-olefin such as polyethylene or polypropylene, a polyalkylene terephthalate such as polyethylene terephthalate, or a resin coating film such as a modified polyacrylic resin coating film layer is preferably used. Therefore, the barrier layer is obtained by pressure-bonding a film made of the above-exemplified resin on the base resin sheet, or by applying a melt of the resin and cooling, or by applying a solution of the above resin and drying, Can be formed. The barrier layer can also be obtained by, for example, applying a modified polyacrylic resin solution and heating and drying it as necessary to form a coating film.

As the modified polyacrylic resin, various kinds have been conventionally known, but in the present invention, generally, they are excellent in solvent resistance, and therefore, a plasticizer contained in the ultraviolet-crosslinkable acrylic ester or the base resin sheet. An alkyd-modified polyacrylic resin that does not dissolve and swell in water and a thermosetting polyacrylic resin are preferable. As the thermosetting polyacrylic resin, for example, acid type, hydroxyl type, epoxy type, amide type and the like are preferably used.

However, in the present invention, as long as the barrier layer does not substantially permeate the UV-crosslinkable acrylic acid ester contained in the pressure-sensitive adhesive composition and the plasticizer contained in the base resin sheet as described above, the barrier layer is particularly preferable. It will be readily understood that the materials are not limiting and will be selected according to the particular UV-crosslinkable acrylic ester ester and plasticizer used in the present invention.

Next, the composition of the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Synthesis Example 1 (Synthesis Example of Urethane Acrylate A) 116 g (1 mol) of 2-hydroxyethyl acrylate and hydroquinone monomethyl ether which is a polymerization inhibitor.
25 g was put into a 1-volume four-necked flask and stirred. Inner temperature 6
After heating to 0 ℃, xylylene diisocyanate 188g
(1 mol) was added. Since it generates heat, it was cooled as necessary to keep the internal temperature below 80 ° C. After addition 2
The exotherm subsided over time, but stirring was continued at 75-80 ° C for 1 hour.

Next, glycerin diacrylate (hydroxyl value 28
200 g (1 mol) of 0, saponification number 562, and bromine number 160) were added, and the mixture was stirred at 75 to 80 ° C. After 4 hours, 1 g of dibutyltin dilaurate was added, and after 1 hour, 11.6 g (0.1 mol) of 2-hydroxyethyl acrylate was added. The reaction was continued until the amount of free isocyanate was 0.2% (% by weight, the same applies below), and the reaction was terminated.

When the reaction product was analyzed by gel chromatography, the width of the molecular weight distribution was relatively narrow and the average molecular weight was 500.

Synthesis Example 2 (Synthesis Example of Urethane Acrylate B) 232 g (2 mol) of 2-hydroxyethyl acrylate and hydroquinone monomethyl ether which is a polymerization inhibitor.
50 g was placed in a 1-volume four-necked flask and stirred. Inner temperature 6
Heat to 0 ° C, and xylylene diisocyanate 376g (2
Mol) was added. The reaction was performed under the same reaction conditions as in Synthesis Example 1. Three hours after the addition of xylylene diisocyanate, 405 g (1 mol) of a 4 mol adduct of bisphenol A ethylene oxide (hydroxyl number 277) was added, and the mixture was stirred at 75 to 80 ° C. Thereafter, the reaction was carried out in the same manner as in Synthesis Example 1, and the reaction was terminated when the amount of free isocyanate was 0.2% or less.

When the reaction product was analyzed by gel chromatography, it had a relatively narrow molecular weight distribution range and the average molecular weight was 1010.

Synthesis Example 3 (Synthesis Example of Urethane Acrylate C) 603.5 g (0.5 mol) of polyester diol (hydroxyl number 93) having hydroxyl groups at both ends synthesized by esterification of diethylene glycol and adipic acid
Was placed in a 1-volume four-necked flask, heated to 60 ° C., and 188 g (1 mol) of xylylene diisocyanate was added. Since it generates heat, it was cooled as necessary to keep the internal temperature below 80 ° C. The exotherm subsided 2 hours after the addition,
Stirring was continued for another 2 hours at 75-80 ° C.

Next, 2-hydroxyethyl acrylate 63.8 g (0.55
Mol), trimethylolpropane diacrylate (purity by gas chromatography is 60%, others are trimethylolpropane triacrylate, hydroxyl number 139) 202
g, add hydroquinone monomethyl ether 0.53g,
Stir at 75-80 ° C. After 4 hours, 1.0 g of dibutyltin dilaurate was added, and the mixture was further stirred with heating, and the reaction was terminated when the amount of free isocyanate was 0.2% or less.

When the reaction product was analyzed by gel chromatography, the average molecular weight excluding trimethylolpropane triacrylate contained as an impurity was 1950.

Synthesis Example 4 (Synthesis Example of Urethane Acrylate D) 482.7 g (0.4 mol) of the polyester diol (hydroxyl number 93) used in Synthesis Example 3 was placed in a one-volume four-necked flask and heated to 60 ° C. and stirred. 112.8 g (0.6 mol) of xylylene diisocyanate was added, and the mixture was cooled if necessary to keep the internal temperature at 80 ° C or lower. After adding and stirring at 75-80 ° C for 3 hours, add 2-hydroxyethyl acrylate.
25.6 g (0.22 mol), trimethylolpropane diacrylate (gas chromatographic analysis purity 60%, hydroxyl number 139) 80.8 g, hydroquinone monomethyl ether 0.
35 g was added, and the mixture was maintained at 75 to 80 ° C and stirred.

After 4 hours, 1.0 g of dibutyltin dilaurate was added, and the mixture was further stirred with heating, and the reaction was terminated when the amount of free isocyanate was 0.2% or less.

Gel chromatography analysis of the reaction product revealed that the average molecular weight was 3,300.

Examples 1 to 4 and Comparative Examples 1 to 6 In the formulations shown in Table 1, urethane acrylates shown in Table 2 were added, and with 100 parts of the elastic polymer shown in Table 1, urethane acrylates shown in Table 2 were added. The pressure-sensitive adhesive composition was prepared by blending so as to have the number of parts shown in Table 2. The obtained composition was applied onto a release paper and dried at 120 ° C. for 1 minute to form a layer of the pressure-sensitive adhesive composition having a solid content of 10 μm.

Next, 100 parts of polyvinyl chloride having an average degree of polymerization of 1300, 35 parts of dioctyl phthalate as a plasticizer and a thickness of 0.1 m formed from a vinyl chloride resin composition comprising an appropriate amount of a stabilizer.
The modified acrylic resin solution was applied onto the sheet of m and dried to form a barrier layer. After that, the pressure-sensitive adhesive layer formed on the release paper was laminated on the surface of the barrier layer of the base resin sheet and laminated to obtain a pressure-sensitive adhesive sheet.

Each pressure-sensitive adhesive sheet thus obtained was allowed to stand at room temperature for 20 minutes, the release paper was peeled off, and the adhesive strength was measured as it was. Separately, ultraviolet rays were irradiated from the vinyl chloride resin sheet side at a main wavelength of 365 mμ and 120 W / cm for 7 seconds, and then the adhesive strength was measured. In addition, the adhesive residue property and the expandability were evaluated by the following methods. The results are shown in Table 2.

(Adhesive strength) A pressure-sensitive adhesive sheet is cut into a width of 25 mm and a length of 100 mm to form a test piece, which is an adherend stainless steel plate (SUS-304)
After stacking it on top and pressing it back and forth 5 times with a 3 kg roller,
A 180 ° peel test was performed using a shopper at a pulling speed of 300 mm / min.

The higher the adhesive strength, the better before irradiation with ultraviolet rays. However, when the adhesive layer was cohesively broken and did not function as an adhesive, X was marked as a judgment.

After UV irradiation, it can be used if it is 100g / 25mm or less, but 5
Less than 0 g / 25 mm was evaluated as O, 50-100 g / 25 mm as Δ, and 100 g / 25 mm as ×.

(Adhesive residue) The wafer is cut using a dicing machine (manufactured by DISCO), and after UV irradiation, the wafer chip is picked up by a pickup machine (manufactured by Nichiden Machinery Co., Ltd.) and the back surface of the obtained wafer chip is observed. The case where no paste remained on the back surface was evaluated as ◯, the case where the paste remained slightly was evaluated as Δ, and the case where a large amount remained on the entire back surface was evaluated as x.

(Expandability) A wafer is attached to a pressure-sensitive adhesive sheet, cut with a dicing machine (manufactured by DISCO), irradiated with UV, and then expanded by about 25% with an expand machine (manufactured by Nichiden Machine Co., Ltd.). When the chips were not distorted, the tape was not broken, and the chips were opened at regular intervals, the chip was evaluated as ◯, and the other was evaluated as x.

The pressure-sensitive adhesive sheet produced using the pressure-sensitive adhesive composition of the present invention is particularly remarkable in the reduction of the adhesive force due to ultraviolet irradiation even after storage for a long period of time. It has an adhesive strength of 25 mm, and after irradiation with ultraviolet rays it is several tens of g /
Since the adhesive strength can be reduced or substantially eliminated to about 25 mm, it can be suitably used for dicing a silicon wafer as described above.

From the results shown in Table 2, the performance greatly varies depending on the type of urethane acrylate to be added. For urethane acrylate A having an average molecular weight of less than 700 and urethane acrylate D having an average molecular weight of more than 2500, the adhesive strength and adhesive residue after ultraviolet irradiation , The expandability is remarkably inferior.

It should be noted that if the amount of urethane acrylate added is too large or too small, the adhesive strength will be poor and this is not preferable.

[Effect of the Invention] The pressure-sensitive adhesive composition of the present invention initially has a strong adhesive force, but when it is irradiated with ultraviolet rays, the adhesive force is significantly reduced. Therefore, when the pressure-sensitive adhesive composition is applied onto a base sheet which can transmit ultraviolet rays to produce a pressure-sensitive adhesive sheet, the adhesive force is remarkably reduced by the irradiation of ultraviolet rays, and the pressure-sensitive adhesive sheet is covered. It can be easily peeled off from the surface to be adhered, the amount of adhesive residue (remaining adhesive layer on the surface to be adhered) is small, and the washing operation after the separation of the surface to be adhered becomes unnecessary.

Therefore, the pressure-sensitive adhesive sheet as described above produced by using the composition of the present invention can be suitably used as a dicing film for a silicone wafer as described above.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-54779 (JP, A) JP 62-54778 (JP, A) JP 62-153376 (JP, A) JP 63- 210182 (JP, A) JP-A 1-271408 (JP, A) JP-A-62-138572 (JP, A)

Claims (2)

[Claims] 1. An elastic polymer (a) (b) UV-crosslinkable (meth) acrylic acid ester (c) polyisocyanate and (d) general formula (1): (Bn ₁ U-AmUB) n ₂ (1) (In the formula, A is (Each of R ¹ and R ² is a saturated hydrocarbon group, an unsaturated hydrocarbon group, a divalent aromatic group or a divalent group obtained by adding an oxyalkylene group thereto, and p is 1 to Ten)
Polyester group-containing diol residue or -OR
An alkylenediol residue represented by ¹ O- (R ¹ is the same as above), and B is (R ³ is H or CH ₃ , R ⁴ is a (q + 1) -valent hydrocarbon group having 1 to 5 carbon atoms, q is 1 to 5, and q R ^{3 s} are not necessarily the same). (Meth) acrylic acid ester-containing group, U is (R ¹ is the same as above), m is 1 to 1
0, n ₁ and n ₂ are each 1 or more and represented by the general formula (1)
Urethane compound-containing UV-crosslinkable compound represented by the formula (average number of 700 to 2500) (urethane group-containing UV-crosslinkable compound which contains (meth) acrylic acid ester as a main component and is (d) component) (Meth) acrylic acid ester
A pressure-sensitive adhesive composition, which is used in an amount of 5 to 150 parts by weight, based on 100 parts by weight of the elastic polymer as the component (a), to reduce the adhesive force by ultraviolet irradiation. 2. The elastic polymer as the component (a) is a polymer selected from saturated copolymerized polyester resins, homopolymers of (meth) acrylic acid esters and copolymers of (meth) acrylic acid esters. 2. The composition of claim 1, which is: