JP2007009058A - Adhesive composition and adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition that gives sufficient adhesive force by press cure at a low temperature for a short time. <P>SOLUTION: The adhesive composition comprises an acrylic polymer and a resol-type phenolic resin, where the acrylic polymer is one obtained by copolymerizing a monomer mixture comprising (a) 45-85 wt% of an alkyl (meth)acrylate having a 2-12C alkyl group, (b) 10-50 wt% of (meth)acrylonitrile, (c) 0.1-10 wt% of a carboxy group-bearing vinyl monomer and (d) 0.01-5 wt% of an epoxy group-bearing vinyl monomer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an adhesive composition and an adhesive sheet, and more particularly to an adhesive composition that can be used for bonding a flexible printed circuit board (FPC) and the like and an adhesive sheet using the same.

In electronic devices, FPC is widely used for the purpose of downsizing, thinning, lightening, and high performance. The FPC is obtained by laminating a conductive metal foil such as copper or aluminum on a heat-resistant substrate such as polyimide or polyamide with an adhesive, and the FPC is further bonded to a reinforcing plate such as aluminum, SUS, or polyimide. As an adhesive, an adhesive including acrylonitrile butadiene rubber (NBR) and an epoxy resin (Patent Document 1), an adhesive including an acrylic resin and an epoxy resin (Patent Document 2), or an adhesive including an acrylic resin and a phenol resin. Many agents (Patent Document 3) have been used.
JP-A-61-211016 JP 2000-256635 A JP 05-171126 A

However, the adhesive containing NBR and epoxy resin, and the adhesive containing acrylic resin and epoxy resin are satisfactory in terms of adhesive strength and reliability, but amine-based and acid-based curing agents to cure the epoxy resin. Therefore, there is a problem that gas generated by the reaction between the epoxy resin and the curing agent in the bonding process is included in the bonding layer as bubbles. In order to suppress the generation of bubbles, high-temperature and long-time press cure is required.
In addition, an adhesive containing an acrylic resin and a phenol resin can be bonded by low-temperature and short-time press cure because there are few bubbles, but there is a problem that it is difficult to obtain sufficient reliability due to low adhesive force. there were.
In recent years, in the manufacture of FPC, in order to increase production efficiency, there is a strong demand for realizing a low-temperature and short-time press cure, and development of an adhesive that can meet this demand is eagerly desired.
Therefore, the present invention has been made in view of such circumstances, and the problem to be solved is an adhesive composition capable of obtaining a sufficient adhesive force at a low temperature in a short time and using the same. It is to provide an adhesive sheet.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by using an adhesive composition combining an acrylic polymer composed of a specific component and a resol type phenol resin. The headline and the present invention were completed.

That is, the present invention is as follows.
[1] (a) 45 to 85% by weight of an alkyl (meth) acrylate having an alkyl group having 2 to 12 carbon atoms, (b) 10 to 50% by weight of (meth) acrylonitrile, and (c) a carboxyl group-containing vinyl monomer Containing an acrylic polymer obtained by copolymerizing a monomer mixture containing 0.1 to 10% by weight and (d) 0.01 to 5% by weight of an epoxy group-containing vinyl monomer, and a resol type phenol resin, Adhesive composition.
[2] The adhesive composition according to the above [1], containing an epoxy resin.
[3] The adhesive composition according to [1] or [2], wherein the content of the resol type phenol resin is 1 to 20 parts by weight with respect to 100 parts by weight of the acrylic polymer.
[4] The adhesive composition according to [2] or [3], wherein the content of the epoxy resin is 20 parts by weight or less with respect to 100 parts by weight of the acrylic polymer.
[5] The adhesive composition according to any one of [1] to [4], wherein the adhesive strength after the curing treatment is greater than 15 N / cm.
[6] An adhesive sheet comprising the adhesive composition according to any one of [1] to [5].
[7] The adhesive sheet according to [6], wherein the adhesive strength after the curing treatment is greater than 15 N / cm.
[8] An adhesive sheet in which an adhesive layer made of the adhesive composition according to any one of [1] to [5] is provided on at least one surface of the substrate.
[9] The adhesive sheet according to [8], wherein the adhesive strength of the adhesive layer after the curing treatment is greater than 15 N / cm.

  According to the present invention, it is possible to obtain an adhesive composition having sufficient adhesive force even with a low temperature and short time press cure. Moreover, if the adhesive sheet comprised from this adhesive composition is used, FPC can be manufactured efficiently.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. For the convenience of illustration, the dimensional ratios in the drawings do not necessarily match those described.

First, the adhesive composition of the present invention will be described.
The adhesive composition of the present invention contains an acrylic polymer and a resol type phenol resin, and the acrylic polymer is a copolymer of a mixture containing the following components (a) to (d): And
(A) alkyl (meth) acrylate having an alkyl group having 2 to 12 carbon atoms (b) (meth) acrylonitrile (c) carboxyl group-containing vinyl monomer (d) epoxy group-containing vinyl monomer

  The component (a) has a function of imparting flexibility to the adhesive composition. As long as the alkyl group which (a) component has is a C2-C12, any form of a linear form, a branched form, and cyclic | annular form may be sufficient. As the component (a), ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are preferable.

  (A) Content of a component is 45 to 85 weight% normally with respect to the total weight of the monomer mixture which comprises an acrylic polymer, Preferably it is 50 to 80 weight%. When the content is less than 45% by weight, flexibility tends to be lacking, and when it exceeds 85% by weight, adhesion tends to be inferior. In addition, (a) component can be used individually or in combination of 2 or more types. In the present specification, (meth) acrylate means acrylate or a corresponding methacrylate, and the same applies to (meth) acrylonitrile.

  The component (b) has a function of imparting heat resistance and adhesiveness to the adhesive composition. As the component (b), acrylonitrile and methacrylonitrile can be used alone or as a mixture thereof. The content of component (b) is usually 10 to 50% by weight, preferably 20 to 40% by weight, based on the total weight of the monomer mixture constituting the acrylic polymer. When the content is less than 10% by weight, the heat resistance tends to be inferior, and when it exceeds 50% by weight, the flexibility tends to decrease.

  The component (c) imparts adhesiveness to the adhesive composition and has a function of increasing the crosslinking density by crosslinking with, for example, an epoxy group of the component (d) described later. As the component (c), any compound having a carboxyl group and an ethylenically unsaturated double bond can be used without particular limitation. Specific examples include (meth) acrylic acid, itaconic acid, etc. Among them, (meth) acrylic acid is preferable, and acrylic acid is more preferable. In addition, (c) component can be used individually or in combination of 2 or more types. The content of the component (c) is usually 0.1 to 10% by weight, preferably 0.5 to 8% by weight, based on the total weight of the monomer mixture constituting the acrylic polymer. When the content is less than 0.1% by weight, the crosslinking density becomes insufficient. On the other hand, when the content exceeds 10% by weight, the crosslinking density is too high and the adhesive composition is hardly dissolved in the solvent.

  The component (d) imparts adhesiveness to the adhesive composition and has a function of increasing the crosslinking density by crosslinking with, for example, the carboxyl group of the component (c) and the hydroxyl group of a resol type phenol resin described later. As the component (d), any compound having an epoxy group and an ethylenically unsaturated double bond can be used without particular limitation. Specific examples include glycidyl (meth) acrylate, glycidylmethyl (meth) acrylate, epoxycyclohexyl (meth) acrylate and the like. Among them, glycidyl (meth) acrylate is preferable, and glycidyl methacrylate is more preferable. In addition, (d) component can be used individually or in combination of 2 or more types. The content of the component (d) is usually 0.01 to 5% by weight, preferably 0.01 to 3% by weight, based on the total weight of the monomer mixture constituting the acrylic polymer. If the content is less than 0.01% by weight, the adhesiveness becomes insufficient. On the other hand, if it exceeds 5% by weight, the crosslinking reaction may proceed excessively during the polymerization, making it difficult to form a sheet.

  The acrylic polymer according to the present invention can be obtained by ordinary solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. The weight average molecular weight (Mw) of the obtained acrylic polymer is preferably 200,000 to 1,000,000, more preferably 300,000 to 900,000. If it is less than 200,000, the viscosity tends to be too low and tends to flow during bonding, while if it exceeds 1,000,000, the viscosity tends to be too high and it tends to be difficult to form a sheet smoothly. In addition, Mw means the weight average molecular weight of standard polystyrene conversion by GPC.

  In addition, the resol type phenol resin has a function of imparting thermosetting property and heat resistance to the adhesive composition. Resole-type phenolic resins are commercially available, for example, those obtained by condensation reaction of phenolic compounds such as phenol, cresol, xylenol, resorcinol, alkylphenol, and modified phenol with aldehyde compounds such as formalin and paraformaldehyde Is mentioned. In addition, these can be used individually or in combination of 2 or more types. The compounding amount of the resol type phenol resin is usually 1 to 20 parts by weight, preferably 1 to 15 parts by weight with respect to 100 parts by weight of the acrylic polymer. If the amount is less than 1 part by weight, the thermosetting property is insufficient and the desired properties tend to be difficult to obtain. On the other hand, if the amount exceeds 20 parts by weight, the adhesiveness tends to decrease.

  Furthermore, in this invention, in order to improve adhesiveness further, an epoxy resin can be contained in an adhesive composition as needed. Epoxy resins generally used in the field of adhesives, such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, glycidylamine type epoxy resins, etc. Among them, bisphenol A type epoxy resin and glycidylamine type epoxy resin are preferably used. In addition, these can be used individually or in combination of 2 or more types. The compounding quantity of an epoxy resin is 20 parts weight or less normally with respect to 100 weight part of acrylic polymers, Preferably it is 15 parts weight or less. If it exceeds 20 parts by weight, bubbles may be generated when press-cured, and the adhesiveness tends to decrease. In addition, in order to obtain more reliable adhesive force, it is desirable that the amount of the epoxy resin is 1 part by weight or more.

  In the present invention, additives generally used in the field of adhesives, such as various fillers such as inorganic fillers and flame retardants, anti-aging agents, pigments, etc., do not affect the properties of the adhesive composition. It can mix | blend within the range.

  In addition, the adhesive composition of the present invention can have an adhesive force greater than 15 N / cm by the curing treatment. Here, the “adhesive strength” means that a 25 μm thick sheet-like adhesive composition is sandwiched between a 100 μm thick FPC and a 0.5 μm thick aluminum plate, at 150 ° C. for 60 seconds, 0.5 MPa This was measured by thermocompression bonding at a pressure of 150 ° C., further heat-cured at 150 ° C. for 1 hour, and then measured at 23 ° C. and a pulling speed of 50 mm / min.

  As described above, the adhesive composition of the present invention is a resol-type phenol resin in an acrylic polymer further containing (d) component in addition to (a), (b) and (c) components as monomer components. As a result of modifying the acrylic polymer by combining the above, sufficient adhesive force can be exhibited even if the press cure is carried out at a relatively low temperature and in a short time.

Next, the adhesive sheet of the present invention will be described.
FIG. 1 is a cross-sectional view showing an embodiment of the adhesive sheet of the present invention. The adhesive sheet 10 itself has adhesiveness and is composed of the adhesive composition described above. Moreover, FIG. 2 is sectional drawing which shows other embodiment of the adhesive sheet of this invention. The adhesive sheet 20 includes a base material 1 and an adhesive layer 3 laminated on one side of the base material 1. The adhesive layer 3 itself has adhesiveness, and is composed of the adhesive composition described above. The form of the adhesive sheets 10 and 20 is not limited to a sheet shape, and may be a tape shape.

  The adhesive layer 3 of the adhesive sheet 10 and the adhesive sheet 20 is characterized in that the adhesive force after the curing treatment is greater than 15 N / cm. Here, the “adhesive strength” means that the adhesive sheet 10 having a thickness of 25 μm or the adhesive layer 3 peeled from the adhesive sheet 20 is sandwiched between an FPC having a thickness of 100 μm and an aluminum plate having a thickness of 0.5 μm. This is one measured by thermocompression bonding at a temperature of 60 ° C. for 60 seconds and a pressure of 0.5 MPa, and further heated and cured at 150 ° C. for 1 hour, and then measured at 23 ° C. and a pulling speed of 50 mm / min.

  The adhesive sheet 20 is obtained by dissolving the above-described adhesive composition in an organic solvent, applying the solution onto the substrate 1, and then removing the organic solvent. The adhesive sheet 10 is obtained by peeling the base material 1 from the adhesive sheet 20. Although it does not specifically limit as a coating method, A comma coater, a reverse roll coater, etc. are mentioned. The thickness of the adhesive layer 3 is usually 10 to 100 μm, preferably 15 to 80 μm. If the thickness is less than 10 μm, the adhesive strength tends to be low, and if it exceeds 100 μm, it tends to flow out during heating. A drying temperature is 40-120 degreeC normally, Preferably it is 50-100 degreeC. The drying time is a time until the solvent is removed and the reaction of the composition does not occur, and is usually 30 to 180 seconds.

  Examples of the substrate 1 include papers (eg, Japanese paper, craft paper, etc.), fabrics (eg, fabric, non-woven fabric, etc.), plastics (eg, polyimide, polyamideimide, polyetherimide, polyamide, polytetrafluoro). (Ethylene, polyester, polyvinyl chloride) or a laminate of the above-described plastics can be appropriately used depending on the purpose. Although the thickness of the base material 1 can be suitably determined according to the kind and use, it is 25-300 mm normally, Preferably it is 50-200 mm. A release liner can also be used as the substrate 1. Examples of release liners include olefin films such as polyethylene (PE) and polypropylene (PP), films such as paper and polyester laminated with PE or PP, or those obtained by applying silicone treatment to the film or laminate. Is mentioned.

  The adhesive sheet 20 may be used as it is without peeling off the substrate 1 by peeling off the substrate 1 and using only the adhesive layer 3. The adhesive sheets 10 and 20 are particularly suitable as an FPC adhesive material.

  Although the adhesive sheet 20 of the said embodiment has the adhesive layer 3 formed in the single side | surface of the base material 1, the base material 1 may be formed in both surfaces of the adhesive layer 3, as shown in FIG. In addition, as for the adhesive sheet 30, at least one of the base materials 1 is comprised with the peeling liner.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but these examples do not limit the present invention.

Example 1
(A) butyl acrylate (BA) as component, (b) acrylonitrile (AN) as component, (c) acrylic acid (AA) as component, and (d) glycidyl methacrylate (GMA) as component Was polymerized at a ratio of BA / AN / AA / GMA = 68/30 / 1.8 / 0.2 (weight ratio) to obtain an acrylic polymer. The Mw of this acrylic polymer was 600,000. Next, 100 parts by weight of the obtained acrylic polymer and 10 parts by weight of resol-type phenol (trade name: Sumilite PR51283, manufactured by Sumitomo Bakelite Co., Ltd.) were dissolved in MEK so as to have a solid content of 20%. And this solution was apply | coated to release paper so that the film thickness of the contact bonding layer after drying might be set to 25 micrometers, and it dried and obtained the adhesive sheet.

(Example 2)
(A) butyl acrylate (BA) as component, (b) acrylonitrile (AN) as component, (c) acrylic acid (AA) as component, and (d) glycidyl methacrylate (GMA) as component Was polymerized at a ratio of BA / AN / AA / GMA = 68/30 / 1.8 / 0.2 (weight ratio) to obtain an acrylic polymer. The Mw of this acrylic polymer was 600,000. Next, 100 parts by weight of the obtained acrylic polymer, 5 parts by weight of resol type phenol (trade name: Sumilite PR51283, manufactured by Sumitomo Bakelite Co., Ltd.), and epoxy resin (trade name: Epicoat # 1001, Japan Epoxy Resin Co., Ltd.) 5) parts by weight were dissolved in MEK to a solid content of 20%. And this solution was apply | coated to release paper so that the film thickness of the contact bonding layer after drying might be set to 25 micrometers, and it dried and obtained the adhesive sheet.

(Comparative Example 1)
Butyl acrylate (BA), acrylonitrile (AN), and acrylic acid (AA) were polymerized at a ratio of BA / AN / AA = 68/30/2 (weight ratio) to obtain an acrylic polymer. The acrylic polymer had a Mw of 700,000. Next, 100 parts by weight of the obtained acrylic polymer and 10 parts by weight of resol-type phenol (trade name: Sumilite PR51283, manufactured by Sumitomo Bakelite Co., Ltd.) were dissolved in MEK so as to have a solid content of 20%. And this solution was apply | coated to release paper so that the film thickness of the contact bonding layer after drying might be set to 25 micrometers, and it dried and obtained the adhesive sheet.

<Adhesion test>
The adhesive sheets obtained in Examples 1 and 2 and Comparative Example 1 were sandwiched between an FPC having a thickness of 100 μm and an aluminum plate having a thickness of 0.5 μm, and heated at 150 ° C. for 60 seconds and a pressure of 0.5 MPa. After pressure bonding, the test piece was obtained by heat curing at 150 ° C. for 1 hour. Then, the adhesive strength of the adhesive layer was measured using Tensilon at 23 ° C. and a pulling speed of 50 mm / min. The test results are shown in Table 1.

It is sectional drawing which shows one Embodiment of the adhesive sheet of this invention. It is sectional drawing which shows other embodiment of the adhesive sheet of this invention. It is sectional drawing which shows other embodiment of the adhesive sheet of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base material, 3 ... Adhesive layer, 10 ... Adhesive sheet, 20 ... Adhesive sheet, 30 ... Adhesive sheet.

Claims (9)

(A) 45 to 85% by weight of an alkyl (meth) acrylate having an alkyl group having 2 to 12 carbon atoms;
(B) 10-50% by weight of (meth) acrylonitrile,
(C) 0.1 to 10% by weight of a carboxyl group-containing vinyl monomer;
(D) An adhesive composition containing an acrylic polymer obtained by copolymerizing a monomer mixture containing 0.01 to 5% by weight of an epoxy group-containing vinyl monomer and a resol type phenol resin.   The adhesive composition according to claim 1, comprising an epoxy resin.   The adhesive composition of Claim 1 or 2 whose content of a resol type phenol resin is 1-20 weight part with respect to 100 weight part of acrylic polymers.   The adhesive composition according to claim 2 or 3, wherein the content of the epoxy resin is 20 parts by weight or less with respect to 100 parts by weight of the acrylic polymer.   The adhesive composition according to any one of claims 1 to 4, wherein the adhesive strength after the curing treatment is greater than 15 N / cm.   The adhesive sheet which consists of an adhesive composition as described in any one of Claims 1-5.   The adhesive sheet according to claim 6, wherein the adhesive strength after the curing treatment is greater than 15 N / cm.   The adhesive sheet in which the contact bonding layer which consists of the contact bonding composition as described in any one of Claims 1-5 is provided in the at least one surface of the base material.   The adhesive sheet according to claim 8, wherein the adhesive strength of the adhesive layer after the curing treatment is greater than 15 N / cm.

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