JP4641616B2 - Method for producing acrylic polymer composition, and pressure-sensitive adhesive sheet for member processing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an acrylic polymer composition useful as an adhesive for an adhesive tape or sheet, an acrylic pressure-sensitive adhesive composition comprising the acrylic polymer composition, and production of various industrial members. The present invention relates to a member processing pressure-sensitive adhesive sheet used at the time.
[0002]
[Prior art]
Conventionally, acrylic pressure-sensitive adhesive compositions are industrially produced almost by solution polymerization. This polymerization is initiated thermally or radiationally by a radical initiator. In the solution polymerization method, the acrylic pressure-sensitive adhesive composition comprises (meth) acrylic acid alkyl ester in an organic solvent such as toluene together with a modifying monomer such as acrylic acid, styrene, or vinyl acetate as necessary. It is prepared by polymerizing with.
[0003]
However, solution polymerization using an organic solvent causes chain transfer of the grown polymer chain to the solvent, and generally it is difficult to obtain a high molecular weight polymer and high cohesive force is difficult to obtain. Moreover, since a large amount of organic solvent is used, it is not preferable from the viewpoints of resource saving, environmental hygiene and the like.
[0004]
On the other hand, semiconductor integrated circuits are usually manufactured by slicing a high-purity silicon single crystal or the like into a wafer, etching a predetermined circuit pattern such as an IC on the wafer surface, incorporating the integrated circuit, and then grinding the backside of the wafer It is performed by grinding with a machine to reduce the thickness of the wafer to about 100 to 600 μm, and finally dicing into chips. Here, at the time of the grinding, an adhesive sheet is attached to the wafer surface to prevent the wafer from being damaged and to facilitate the grinding process. At the time of dicing, an adhesive sheet is attached to the back side of the wafer, the wafer is bonded and fixed, and the formed chip is picked up by a needle from the film substrate side and picked up and fixed on the die pad. ing.
[0005]
Adhesive sheets used for this purpose need to have adhesive strength that does not peel during grinding or dicing, but can be easily peeled off after picking up after grinding or dicing, and damage the semiconductor wafer. It is required that the adhesive strength is as low as possible. Furthermore, it is desirable that the adhesive sheets do not cause adhesive residue on the wafer surface or the wafer back surface and do not contaminate these surfaces.
[0006]
[Problems to be solved by the invention]
Therefore, an object of the present invention is an acrylic polymer composition comprising a high molecular weight polymer, excellent in cohesion and adhesion, and less contaminating the adherend, and can be prepared without using an organic solvent. It is in providing the manufacturing method, the acrylic pressure-sensitive adhesive composition which consists of this acrylic polymer composition, and the adhesive sheet for member processing.
[0007]
[Means for Solving the Problems]
As a result of intensive investigations to achieve the above-mentioned object, the inventors of the present invention agglomerated by preparing a stable emulsion or dispersion from a high molecular weight polymer obtained by polymerization using carbon dioxide as a diluent. The present inventors have found that an adhesive composition that is excellent in strength and adhesive force and can be easily processed into a pressure-sensitive adhesive sheet for member processing is obtained, and the present invention has been completed.
[0008]
That is, this invention uses at least (meth) acrylic acid alkyl ester and cyclic or acyclic (meth) acrylamide as a monomer, uses carbon dioxide as a diluent, pressure 5.7-40 MPa, temperature 20-100. A polymer composition containing an acrylic polymer having a weight average molecular weight of 400,000 or more obtained by radical polymerization under the condition of ° C is changed from a pressure of 5.7 to 40 MPa containing carbon dioxide under atmospheric pressure. The method for producing an acrylic polymer composition is characterized in that an acrylic polymer emulsion or dispersion is prepared by jetting into a poor solvent of the acrylic polymer . Before SL polymer composition preferably comprises a molecular weight of 100,000 or less in the ratio of components is less than 10% by weight of the total polymer acrylic polymer is preferred.
[0009]
Further, the present invention provides an acrylic polymer composition obtained by the above manufacturing method.
The present invention further provides a pressure-sensitive adhesive sheet for member processing having a pressure-sensitive adhesive layer composed of the acrylic polymer composition. The member processing adhesive sheet is used, for example, as a semiconductor wafer processing adhesive sheet.
In this specification, in addition to the above invention,
A polymer composition containing an acrylic polymer having a weight average molecular weight of 400,000 or more obtained by radical polymerization using carbon dioxide as a diluent is jetted into a poor solvent for the acrylic polymer, and then acrylic A method for producing an acrylic polymer composition, characterized by preparing an emulsion or dispersion of the polymer, will also be described .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, (meth) acrylic acid alkyl ester is preferably used as the monomer. (Meth) acrylic acid alkyl ester includes alkyl alkyl ester having 1 to 18 carbon atoms and alkyl methacrylate. Specific examples include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, butyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, and the like. . These (meth) acrylic acid alkyl esters can be used alone or in admixture of two or more.
[0011]
As the monomer, only the above (meth) acrylic acid alkyl ester may be used, but the above (meth) acrylic acid alkyl ester as a main component may be used in combination with another monomer copolymerizable therewith. . Representative examples of the copolymerizable monomer include carboxyl group-containing ethylenically unsaturated monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid. Among the carboxyl group-containing ethylenically unsaturated monomers, acrylic acid is particularly suitable.
[0012]
This ethylenically unsaturated monomer containing a carboxyl group is an important component for causing a cross-linking bond to the polymer. As other copolymerizable monomers, any of various monomers known as modifying monomers for acrylic pressure-sensitive adhesives such as vinyl acetate, styrene, acrylonitrile, cyclic (meth) acrylamide, and acyclic methacrylamide It can be used. The amount of these copolymerizable monomers used is preferably 50% by weight or less in the total monomer combined with the alkyl (meth) acrylate.
[0013]
The polymerization reaction can be carried out with the aid of an initiator that decomposes to generate radicals, and initiators usually used for radical polymerization can be used. Examples include organic peroxides such as dibenzoyl peroxide, di-tert-butyl peroxide, cumene hydroperoxide, and lauroyl peroxide, particularly when polymerizing at a temperature of 40 to 100 ° C. '-Azobisisobutyronitrile and azobisisovaleronitrile are used. Moreover, when superposing | polymerizing at the temperature of 20-40 degreeC, a binary initiator (Redox initiator) is used and the binary system of dibenzoyl peroxide and dimethylaniline etc. are mentioned as an example.
[0014]
The amount of the initiator used may be an amount usually used in the polymerization of the acrylic monomer. For example, about 0.005 to 10 parts by weight, preferably 0.1 to 100 parts by weight of the total amount of the monomers. About 5 parts by weight.
[0015]
The amount of carbon dioxide used as a diluent in the present invention is, for example, 5 to 2000 parts by weight, preferably 20 to 900 parts by weight with respect to 100 parts by weight of the total amount of the monomers. As the diluent, carbon dioxide alone is usually sufficient, but a small amount of an organic solvent may be included as necessary for improving the mixing property.
[0016]
Polymerization is performed in a temperature range of, for example, about 20 to 100 ° C. in carbon dioxide adjusted to a pressure of about 5.7 to 40 MPa, for example. For example, the polymerization can be performed in carbon dioxide in a supercritical state. The polymerization time is usually about 2 to 20 hours (for example, about 4 to 10 hours). The polymerization pressure and temperature may be set in several stages as required.
[0017]
As described above, when an acrylic monomer is radically polymerized using carbon dioxide as a diluent, the chain transfer reaction of the grown polymer chain to the solvent does not occur. Therefore, a relatively high molecular weight polymer compared to solution polymerization, that is, an acrylic polymer having a polymerization average molecular weight of 400,000 or more (for example, 400,000 to 2,000,000) is obtained. Also, by this method, an acrylic polymer in which the ratio of components having a molecular weight of 100,000 or less is 10% by weight or less of the whole polymer can be obtained. An acrylic pressure-sensitive adhesive containing such a polymer exhibits high cohesive strength. The weight average molecular weight and molecular weight distribution can be adjusted by the type and ratio of the monomer, the type and ratio of the polymerization initiator, the polymerization temperature, the polymerization time, and the like. The content of the low molecular weight component in the polymer can be determined by a gel permeation chromatography method (GPC method).
[0018]
In the present invention, a polymer composition containing an acrylic polymer having a weight average molecular weight of 400,000 or more thus obtained is ejected into a poor solvent for the acrylic polymer to prepare an emulsion or dispersion of the acrylic polymer. To do. The poor solvent may be a solvent in which the polymer is insoluble, but water is particularly preferable.
[0019]
In order to obtain a stable emulsification or dispersion, an emulsifier is usually added to the solvent. Examples of the emulsifier include anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkylphenyl ether sulfate. Moreover, you may use the radically polymerizable emulsifier which has a propenyl group etc. The usage-amount of an emulsifier is 10 weight part or less (for example, 0.001 weight part-10 weight part) with respect to 100 weight part of acrylic polymers. If the amount of the emulsifier used exceeds 10 parts by weight, it is difficult to obtain good results in the water resistance of the pressure-sensitive adhesive, which is not preferable.
[0020]
The method for ejecting the polymer composition is not particularly limited, and examples thereof include a method in which the polymer composition is ejected from a high-pressure state containing carbon dioxide into the solvent insoluble in the polymer while being released at atmospheric pressure from the mouth of a die or the like.
[0021]
The acrylic polymer composition thus obtained can be used as an acrylic pressure-sensitive adhesive composition as it is or by adding various additives as required. For example, the acrylic polymer is used as a main adhesive component, and in order to adjust the adhesive properties thereof, a known or commonly used tackifier resin (for example, rosin resin, terpene resin, petroleum resin, coumarone indene resin, You may mix | blend a styrene-type resin etc.). As additives other than the tackifying resin, various known additives such as a plasticizer, a filler such as calcium carbonate and fine powder silica, a colorant, and an ultraviolet absorber can be blended. The amount of these additives used may be a normal amount applied to an acrylic pressure sensitive adhesive. The additive may be added together with the monomer before polymerization, or may be added to the polymer composition after polymerization or an emulsification or dispersion obtained by ejecting the polymer composition.
[0022]
Moreover, a crosslinking agent can be mix | blended with an acrylic pressure-sensitive adhesive composition, and cohesion force can further be enlarged as an adhesive agent by bridge | crosslinking the said acrylic polymer with this crosslinking agent.
[0023]
Conventionally known cross-linking agents are widely included in the crosslinking agent, and among them, polyfunctional melamine compounds such as methylated trimethylol melamine; polyfunctional epoxy compounds such as diglycidyl aniline and glycerin diglycidyl ether are particularly preferable. . A polyfunctional melamine compound and a polyfunctional epoxy compound can also be used in combination. The amount of the crosslinking agent used is, for example, in the range of 0.001 to 10 parts by weight, preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the acrylic polymer.
[0024]
In addition, the use of a polyfunctional isocyanate compound is also preferable. Examples of such a compound include tolylene diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, diphenylmethane diisocyanate, diphenylmethane diisocyanate duplex, trimethylolpropane and tolylene diene. The reaction product with isocyanate, the reaction product of trimethylolpropane and hexamethylene diisocyanate, polyether polyisocyanate, polyester polyisocyanate and the like can be mentioned. The amount of these compounds used is, for example, in the range of 0.01 to 20 parts by weight, preferably 0.05 to 15 parts by weight, with respect to 100 parts by weight of the acrylic polymer.
[0025]
The pressure-sensitive adhesive sheet for member processing of the present invention has an adhesive layer composed of the above acrylic pressure-sensitive adhesive composition. This adhesive layer is formed, for example, by thinning the acrylic pressure-sensitive adhesive composition using a coating method using a conventional roll coater or the like. The member processing sheet is, for example, an adhesive tape in which an adhesive layer having a predetermined thickness is formed by coating the adhesive composition on one or both surfaces of various substrates such as paper, nonwoven fabric, plastic sheet, and foam sheet. Alternatively, it can take various forms such as a base-less adhesive tape in which the adhesive composition is coated on a release paper to form an adhesive layer having a predetermined thickness.
[0026]
The acrylic polymer that forms the adhesive layer coated on the adherend, substrate, or release paper is appropriately crosslinked in the drying step after coating, the light irradiation or electron beam irradiation step after this step, etc. It may be used.
[0027]
【The invention's effect】
According to the method for producing an acrylic polymer composition of the present invention, since carbon dioxide, which is a solvent without radical chain transfer, is used as a diluent, it has a low molecular weight compared to a polymer synthesized with a conventional organic solvent. An acrylic polymer composition containing a high molecular weight polymer with few components is obtained.
Since the acrylic pressure-sensitive adhesive composition of the present invention is composed of such an acrylic polymer composition, it has excellent cohesive strength and excellent adhesive strength. In addition, since the polymer composition is jetted into an acrylic polymer poor solvent and prepared as an emulsified or dispersed liquid, there is an advantage that it can be easily processed into a pressure-sensitive adhesive sheet for member processing, and there is no need to use an organic solvent. Therefore, it is preferable also in terms of environmental sanitation.
The pressure-sensitive adhesive sheet for processing members according to the present invention is low in contamination because the pressure-sensitive adhesive is composed of a high molecular weight polymer having a low low molecular weight component, and various industrial members, specifically semiconductors, circuits, various printed boards, various masks. It is extremely useful when manufacturing microfabricated parts such as lead frames.
[0028]
【Example】
Examples of the present invention will be described below in more detail. In the following, “parts” means parts by weight, and “%” means percent by weight.
[0029]
Reference example 1
100 parts of n-butyl acrylate and 0.1 part of 2,2′-azobisisobutyronitrile are placed in a stainless steel pressure vessel with an internal volume of 500 ml at 25 ° C. so that the total is 150 g. After mixing and charging, high purity carbon dioxide was gradually poured while stirring with a stirring blade, and the pressure was temporarily maintained at 2 MPa. After a few seconds, carbon dioxide was discharged from the outlet and the air remaining in the pressure vessel was replaced with carbon dioxide.
After the above operation, high-purity carbon dioxide was introduced in the same manner at 25 ° C., and once maintained at a pressure of 7 MPa.
Thereafter, the container was heated to raise the internal temperature to 65 ° C. When the temperature reached 65 ° C., high-purity carbon dioxide was introduced once again, and the internal pressure was adjusted to 20 MPa. In this state, the polymerization was carried out for about 6 hours to obtain a polymer composition of Reference Example 1. The weight average molecular weight of this polymer measured by the GPC method was 1.3 million, and the content of components having a molecular weight of 100,000 or less was 3.3%.
[0030]
Reference example 2
80 parts of 2-ethylhexyl acrylate, 20 parts of N-acryloylmorpholine, and 0.1 part of 2,2′-azobisisobutyronitrile were placed in a stainless steel pressure vessel having an internal volume of 500 ml at 25 ° C. The mixture was blended so that the whole became 150 g, and high-purity carbon dioxide was gradually poured while stirring with a stirring blade, and the pressure was temporarily maintained at 2 MPa. After a few seconds, carbon dioxide was discharged from the discharge port, and the air remaining in the pressure vessel was replaced with carbon dioxide.
After the above operation, high-purity carbon dioxide was introduced in the same manner at 25 ° C., and once maintained at a pressure of 7 MPa.
Thereafter, the container was heated to raise the internal temperature to 65 ° C. When the temperature reached 65 ° C., high-purity carbon dioxide was introduced again to adjust the internal pressure to 20 MPa. Thereafter, the internal temperature was set to 65 ° C. in this state, and the polymerization was carried out while maintaining this state for about 6 hours to obtain a polymer composition of Reference Example 2. The weight average molecular weight of this polymer measured by the GPC method was 900,000, and the content of components having a molecular weight of 100,000 or less was 6.2%.
[0031]
Example 1
The polymer composition obtained in Reference Example 1 is released from the pressure vessel into the atmosphere in ion-exchanged water that is premixed with polyoxynonyl phenyl ether sulfate sodium salt so as to be 3 parts with respect to 100 parts of the polymer solid content. The mixture was discharged while being emulsified while stirring with a homogenizer to prepare a stable emulsion.
[0032]
Example 2
The polymer composition obtained in Reference Example 2 was released from the pressure vessel into the atmosphere in ion-exchanged water previously blended with polyoxynonylphenyl ether sulfate sodium salt so as to be 3 parts with respect to 100 parts of the polymer solid content. The mixture was discharged while being emulsified while stirring with a homogenizer to prepare a stable emulsion.
[0033]
Comparative Example 1
In a three-necked flask type reactor having an internal volume of 500 ml equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, n-butyl acrylate 100 parts, 2,2'-azobisisobutyronitrile 0.1 part and 200 parts of toluene were blended in a total amount of 300 g, stirred while introducing nitrogen gas for about 1 hour, and the air inside was replaced with nitrogen.
Thereafter, the internal temperature was set to 65 ° C., and the polymerization was carried out in this state for about 6 hours to obtain a polymer composition of Comparative Example 1. The weight average molecular weight of this polymer measured by the GPC method was 270,000, and the content of components having a molecular weight of 100,000 or less was 33.2%.
[0034]
As described above, in the examples, since a high molecular weight acrylic polymer with a small amount of low molecular weight component is included as a polymer component, a high cohesive force can be obtained when used as a pressure sensitive adhesive constituting the pressure sensitive adhesive layer of the pressure sensitive adhesive sheet. At the same time, there is very little contamination on the adherend. Moreover, since the polymer composition is ejected to adjust the emulsion of the acrylic polymer, coating is easy, and it is not necessary to use an organic solvent, which is advantageous in terms of environmental hygiene.
On the other hand, in the comparative example, only a low molecular weight acrylic polymer can be obtained. Therefore, when used as a pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, a high cohesive force cannot be obtained. Moreover, since an organic solvent is used, it is not preferable in terms of environmental hygiene.

Claims (5)

Using at least (meth) acrylic acid alkyl ester and cyclic or acyclic (meth) acrylamide as the monomer, and using carbon dioxide as the diluent, the pressure is 5.7 to 40 MPa and the temperature is 20 to 100 ° C. The acrylic polymer obtained by polymerizing a polymer composition containing an acrylic polymer having a weight average molecular weight of 400,000 or more from a pressure of 5.7 to 40 MPa containing carbon dioxide under atmospheric pressure. A method for producing an acrylic polymer composition, which comprises jetting into a poor solvent and preparing an emulsion or dispersion of an acrylic polymer. And jetting a polymer composition ratio of molecular weight of 100,000 or less components containing an acrylic polymer is 10 wt% or less of the total polymer, according to claim 1 Symbol for preparing an emulsion or dispersion of acrylic polymer The manufacturing method of the acrylic polymer composition of mounting. Acrylic polymer composition obtained by the production method according to claim 1 or 2. The adhesive sheet for member processing which has an adhesive layer comprised with the acrylic polymer composition of Claim 3 . The pressure-sensitive adhesive sheet for member processing according to claim 4, which is used for processing a semiconductor wafer.