JP2002275440A - Adhesive tape/sheet for electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double-sided adhesive tape/sheet to be used in the adhesion of the covering material of electronic equipment or the various parts or the like inside electronic equipment, containing no silicone-based resin composition in the release layer while having good releasability of the release liner, thus reduced in the possibility of causing the corrosion and malfunction inside electronic equipment. SOLUTION: This double-sided adhesive tape/sheet is characterized by that the release layer of a release liner consists of a polyolefin resin consisting mainly of a polyethylene <=65 J/g in melting endothermic energy at its melting point and <=130 deg.C in melting peak temperature and the adhesive consists mainly of an acrylic ester copolymer >=40 mN/m(23 deg.C) in surface tension.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly used for bonding a cover material of an electronic device or various members inside the electronic device. The release layer of the release liner does not contain a silicone resin composition. The present invention relates to a double-sided pressure-sensitive adhesive tape and a pressure-sensitive adhesive sheet having good release properties.

[0002]

2. Description of the Related Art Double-sided adhesive tapes and adhesive sheets are
Due to its ease of handling and good adhesive properties, it is widely used in various industries. In the field of electronic devices, many double-sided pressure-sensitive adhesive tapes and pressure-sensitive adhesive sheets are used for bonding various members. Many conventional double-sided pressure-sensitive adhesive tapes and pressure-sensitive adhesive sheets, in order to obtain good release properties of the release liner,
For the release layer, a silicone resin composition having a small surface tension is used. In the field of electronic devices, with recent miniaturization of electronic devices, double-sided tapes and pressure-sensitive adhesive sheets that cause less generation of impurities that cause corrosion, malfunction, and malfunction are required.

[0003]

When a conventional double-sided pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet using a silicone-based resin composition for a release layer of a release liner is used for electronic equipment, the silicone-based resin composition becomes The phenomenon of transfer to the adhesive layer occurs, which is a factor of generating siloxane gas, which may cause corrosion, malfunction, and malfunction inside the electronic device.

[0004] Therefore, double-sided pressure-sensitive adhesive tapes and pressure-sensitive adhesive sheets used in electronic equipment applications do not contain a silicone-based resin composition in the pressure-sensitive adhesive composition, and also include a silicone-based resin in a release layer of a release liner. It is desirable not to use and contain the composition.

As a release layer other than the silicone resin composition, there are fluorine resin, alkyd resin, polyvinyl carbamate resin, polyolefin resin and the like. However, the fluorine-based resin has a relatively high elastic modulus although the surface tension is low similarly to the silicone-based resin composition.
When the anchoring to the base paper or base film is insufficient and it is easy to fall off, when the double-sided adhesive tape and adhesive sheets are manufactured, when the release liner passes through the roll,
It has a problem that it is likely to come off and cause a mold release failure. Alkyd resins and polyvinyl carbamate resins have relatively high surface tension as a resin used for the release layer, and when used for an acrylic pressure-sensitive adhesive, the release force is extremely heavy, which is not suitable for practical use. In addition, some alkyd resins control the release force by adding a silicone resin composition, which is not suitable for use in electronic parts. General polyolefin-based resins also have a problem that relatively high surface tension makes it difficult to obtain a suitable releasing force.

The present invention solves the above-mentioned problems, and does not include a silicone resin composition in a release layer of a release liner used for bonding a cover material of an electronic device or various members inside the electronic device. Another object of the present invention is to provide a double-sided pressure-sensitive adhesive tape and a pressure-sensitive adhesive sheet having good release properties.

[0007]

The inventor of the present invention has proposed that the release layer of the release liner has a melting endothermic energy of 65 ° C. at the melting point.
J / g or less and a melting peak temperature of 130 ° C. or less, comprising a polyolefin resin containing polyethylene as a main component,
The double-sided pressure-sensitive adhesive tapes and pressure-sensitive adhesive sheets, wherein the pressure-sensitive adhesive is mainly composed of an acrylate copolymer having a surface tension of 40 mN / m (23 ° C.) or more, the silicone resin composition in the release layer The present inventors have found that the above problem can be solved, that is, having good releasability without containing any substance, and have accomplished the present invention.

The release liner used in the present invention is made of a polyolefin resin containing polyethylene as a main component and having a release layer having a melting endothermic energy of 65 J / g or less and a melting peak temperature of 130 ° C. or less. The release force of the release liner is greatly affected by the surface tension and the elastic modulus of the release layer, and the lower the value of both, the better the release force is not too heavy in the normal temperature range, which usually uses double-sided adhesive tapes. Value is obtained. In the polyolefin group whose surface tension is higher than that of the silicone resin composition, polyethylene having a relatively low surface tension and elastic modulus in the polyolefin group is advantageous as the release layer. However, when a general polyethylene is used as a main component, a sufficiently good release force cannot be obtained with respect to a pressure-sensitive adhesive containing an acrylic ester copolymer as a main component.
Therefore, the release layer is made of a polyolefin resin containing polyethylene having a low crystallinity as a main component and having a melting endothermic energy of 65 J / g or less and a melting peak temperature of 130 ° C. or less. It has been found that a great release force can be obtained.

Furthermore, since the crystallinity of polyethylene, which is the main component of the release layer, is low, the release layer contracts and the release liner curls when the release liner passes through a drying furnace during tape production. It was also found that there was no occurrence and that the workability was excellent.

The release agent layer used in the present invention has a melting endothermic energy of 65 J / g or less and a melting peak temperature of 130 ° C.
Although it is made of the following polyolefin resin containing polyethylene as a main component, another polyolefin resin may be blended. Examples include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-
1-pentene and the like, or a copolymer thereof,
Examples include ethylene-propylene copolymers. In the release agent layer used in the present invention, the polyethylene having a melting endothermic energy of 65 J / g or less and a melting peak temperature of 130 ° C. or less is preferably 80 parts by weight or more.

[0011] The molecular weight and density of the polyethylene used in the present invention are not particularly limited.
J / g or less and a melting peak temperature of 130 ° C. or less may be used as long as they have a sufficient film-forming property for forming a release layer.

The melting endothermic energy of polyethylene is 65
When it is larger than J / g, the crystallinity of polyethylene becomes high, and it becomes too rigid to be used as a release agent layer, and an acrylic ester copolymer having a surface tension of 40 mN / m (23 ° C.) or more as a main component. Even when a pressure-sensitive adhesive is used, a good release force in a normal temperature range cannot be obtained. Further, even when the melting peak temperature of polyethylene is higher than 130 ° C., when the polyethylene becomes tough and used as a release agent layer, the surface tension is similarly 40 mN / m (23 ° C.).
Even when the above-mentioned pressure-sensitive adhesive containing an acrylic ester copolymer as a main component is used, a good releasing force in a normal temperature range cannot be obtained.

The melting endothermic energy and the melting peak temperature can be measured by a differential scanning calorimeter (DSC).

The above-mentioned release layer is obtained by a known production method such as a film forming method using a T-die extruder, and is provided on a base paper or a base film of a release liner by extrusion lamination or the like. When using a T-die extruder, the extrusion temperature is suitably set in the range of 250 ° C to 350 ° C. Further, only these release layers can be used as a release liner. The surface of the release layer is mirror treated,
Surface treatment such as mat treatment may be appropriately performed as needed. The thickness of the release layer is set to a desired thickness, but is preferably set to a thickness of 5 to 150 μm. Alternatively, the thickness of the release liner is also set to a desired thickness.
Preferably, the thickness is set to 0 to 200 μm. Examples of the base paper used for the release liner include high quality paper, kraft paper, glassine paper, parchment paper, and the like.
Known papers can be used. Further, known plastic films such as a polyester film can be used as the base film.

The pressure-sensitive adhesive layer used in the present invention is characterized by comprising a pressure-sensitive adhesive mainly composed of an acrylate copolymer having a surface tension of 40 mN / m (23 ° C.) or more. When the surface tension is lower than 40 mN / m (23 ° C.), even when the above-described release layer is used, the release force is increased and workability is impaired. The acrylate copolymer is composed of a (meth) acrylate copolymer and an unsaturated monomer copolymerizable therewith.

The acrylate copolymer used for the pressure-sensitive adhesive in the present invention is obtained by a known polymerization method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a suspension polymerization method, and is not limited to a production method.

Examples of (meth) acrylates include n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, Isopentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, Examples include isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and tridecyl (meth) acrylate.

Examples of the unsaturated monomer copolymerizable with the (meth) acrylate used in the present invention include alkyl (meth) acrylates other than those exemplified above as the alkyl (meth) acrylate;
(Meth) acrylates having an ether group and the like; aliphatic unsaturated (di) carboxylic acids such as (meth) acrylic acid and fumaric acid; aliphatic unsaturated hydrocarbons such as ethylene and butadiene; styrene, α-methylstyrene Aromatic unsaturated hydrocarbons such as vinyl acetate; vinyl esters such as vinyl acetate; vinyl ethers; (meth) acrylates having an amino group or an amide group; halogen-substituted aliphatic unsaturated hydrocarbons such as vinyl chloride; Cyanide compounds such as acrylonitrile and the like can be mentioned.

The pressure-sensitive adhesive of the present invention contains an acrylate copolymer as a main component, but is generally one crosslinked with a crosslinking agent. Examples of the crosslinking agent include an isocyanate compound, an epoxy resin, and a metal chelate. Various additives such as a tackifying resin, an antioxidant, and a filler may be appropriately added to the pressure-sensitive adhesive within a range in which the surface tension of the pressure-sensitive adhesive is within the range described in the claims.

The weight average molecular weight of the acrylate copolymer used in the present invention is not particularly limited, but is preferably 300,000 to 1.2 million. If the weight average molecular weight of the acrylate copolymer is less than 300,000,
When an ordinary amount of the crosslinking agent is added, the cohesive strength of the pressure-sensitive adhesive is insufficient and is often unsuitable for practical use. When the amount of the cross-linking agent is increased, the adhesive properties are impaired. Also, when the weight average molecular weight of the acrylate copolymer is larger than 1.2 million, the adhesive properties are impaired.

The pressure-sensitive adhesive of the present invention has a surface tension of 40 mN /
m (23 ° C.) or higher, but the above-mentioned (meth) acrylates having a hydroxyl group, an ether group and the like; aliphatic unsaturated (di) carboxylic acids such as (meth) acrylic acid and fumaric acid By increasing the copolymerization amount of a polar functional group-containing monomer that can be used in the present invention, a high surface tension can be obtained. The copolymerization amount of the functional group-containing monomer is not particularly limited, and is appropriately set within a range where the surface tension of the pressure-sensitive adhesive is 40 mN / m (23 ° C.) or more and the adhesive property is not impaired. Preferably, the surface tension is 40 mN / m (23 ° C.) or more and 60 mN / m (23
° C). Surface tension is 40mN / m (23 ℃)
If it is less than 1, as described above, even when the polyethylene of the present invention is used as the main component in the release layer, the release force becomes heavy and the workability becomes difficult. If it is 60 mN / m (23 ° C.) or higher, the copolymerization amount of the functional group-containing monomer increases, and the adhesive properties tend to be impaired. As the copolymerization amount of the functional group-containing monomer, (meth) acrylate copolymer 1
It is preferable to copolymerize the functional group-containing monomer in an amount of 3 to 50 parts by weight with respect to 00 parts by weight. If the copolymerization amount of the functional group-containing monomer is less than 3 parts by weight, the surface tension of the pressure-sensitive adhesive is 4%.
It is less than 0 mN / m (23 ° C.), which is unsuitable for the present invention. When the copolymerization amount of the functional group-containing monomer is more than 50 parts by weight, the tackiness of the pressure-sensitive adhesive is impaired, and the adhesive properties are deteriorated.

The surface tension of the pressure-sensitive adhesive may be adjusted not only by the amount of the functional group-containing monomer in the (meth) acrylate copolymer but also by the addition of a tackifier resin or a filler. .

The thickness of the pressure-sensitive adhesive used in the present invention is not particularly limited, but is preferably from 5 to 150 μm. When the thickness of the pressure-sensitive adhesive is less than 5 μm, the adhesive properties are often insufficient, and when the thickness is more than 150 μm, workability and the like are deteriorated when punching a product.

The present invention is not limited to the constitution of the double-sided pressure-sensitive adhesive tape and the pressure-sensitive adhesive sheet. In the double-sided pressure-sensitive adhesive tape, a release layer is provided on both sides of the release liner, and a single release liner is used to form a roll. Specifications and specifications in which a release liner is provided for each of the adhesive surfaces can be used. Also, the base material used for the double-sided adhesive tape is also a plastic film such as a polyester film, rayon, hemp, various nonwoven fabrics made of fibers such as polyester, polyurethane foam, various foams such as polyethylene foam, various rubber sheets, etc. Known ones can be used. In the pressure-sensitive adhesive sheets, a pressure-sensitive adhesive layer is provided on various known substrates such as polyester films, papers, and foams, and the release liner of the present invention is provided on a surface opposite to the substrate.

The method for producing a double-sided pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet in the present invention is not particularly limited, and can be obtained by a known method. As an example, a release method in which an adhesive solution is applied to a release liner and dried, and a transfer method in which the adhesive solution is applied to a nonwoven fabric or a polyester film or the like, or an adhesive solution is directly applied to a nonwoven fabric or a polyester film and dried. There is a direct method of bonding.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The release layer according to the present invention has a melting endothermic energy of 65 J / g or less and a melting peak temperature of 130 ° C.
Using a release liner made of a polyolefin resin containing polyethylene as a main component, the surface tension of which is 40 m
By using a pressure-sensitive adhesive mainly composed of an acrylate ester copolymer having an N / m (23 ° C.) or higher, it is used for bonding a cover material of an electronic device and various members inside the electronic device. Since there is no cause for the occurrence of such problems, a double-sided pressure-sensitive adhesive tape and a pressure-sensitive adhesive sheet having a very low possibility of causing corrosion, operation failure, and malfunction inside the electronic device and having good release properties can be obtained.

[0027]

Next, the present invention will be described with reference to examples.

(Example 1) As a release liner, the melting endothermic energy was 59.9 J / g, and the melting peak temperature was 1
Exelen VL100 polyethylene at 13 ° C
A product obtained by providing a release layer having a thickness of 20 μm (manufactured by Sumitomo Chemical Co., Ltd.) on a polyester film having a thickness of 50 μm by an extrusion lamination method was used. As an adhesive, 90 parts by weight of n-butyl acrylate, 10 parts by weight of acrylic acid, and 0.2 parts by weight of 2-droxyethyl methacrylate were polymerized by a solution polymerization method using benzoyl peroxide as a thermal polymerization initiator. An acrylate copolymer having a weight average molecular weight of 600,000 was used. 0.5 part by weight of an isocyanate compound as a cross-linking agent was added to 100 parts by weight of the pressure-sensitive adhesive, coated on the release liner, dried at 100 ° C. for 5 minutes, and provided with a pressure-sensitive adhesive having a thickness of 50 μm. It was adhered to a polyester film having a thickness of 100 μm as a material to obtain an adhesive tape.

Example 2 Example 1 was applied to a release liner.
The same one was used. As the pressure-sensitive adhesive, 88 parts by weight of 2-ethylhexyl acrylate, 12 parts by weight of acrylic acid, and 0.2 parts by weight of 2-hydroxyethyl methacrylate were added by a solution polymerization method to 2,2′-azobisisobutyrate as a thermal polymerization initiator. An acrylate copolymer having a weight average molecular weight of 700,000 polymerized using lonitrile was used. 100 parts by weight of the pressure-sensitive adhesive was mixed with 0.3 parts of an epoxy resin as a crosslinking agent.
It was added in parts by weight to obtain an adhesive tape in the same manner as in Example 1.

(Example 3) As a release liner, the melting endothermic energy was 62.2 J / g, and the melting peak temperature was 1
Exelen VL700 polyethylene at 02 ° C
(Released by Sumitomo Chemical Co., Ltd.) having a thickness of 20 μm.
What was obtained by providing on a 50-micrometer-thick polyester film by extrusion lamination was used. Using the above release liner, a pressure-sensitive adhesive tape was obtained by the same pressure-sensitive adhesive and production method as in Example 1.

(Comparative Example 1) A 20 μm-thick release liner made of polyethylene “Sumikacene L” (manufactured by Sumitomo Chemical Co., Ltd.) having a melting endothermic energy of 108.1 J / g and a melting peak temperature of 120 ° C. as a release liner. A layer obtained by providing a layer on a polyester film having a thickness of 50 μm by an extrusion lamination method was used. Using the above release liner, a pressure-sensitive adhesive tape was obtained by the same pressure-sensitive adhesive and production method as in Example 1.

(Comparative Example 2) Example 1 was applied to a release liner.
The same one was used. As the adhesive, 99 parts by weight of n-butyl acrylate and acrylic acid 1 were prepared by a solution polymerization method.
Parts by weight, 2-hydroxyethyl methacrylate 0.2
90 parts by weight of an acrylic ester copolymer having a weight average molecular weight of 600,000 polymerized by using benzoyl peroxide as a thermal polymerization initiator and rosin ester 10 having a softening point of 110 ° C.
A mixture with parts by weight was used. 0.5 part by weight of an isocyanate compound as a crosslinking agent was added to 100 parts by weight of the above-mentioned pressure-sensitive adhesive, and a pressure-sensitive adhesive tape was obtained in the same manner as in Example 1.

Comparative Example 3 Comparative Example 1 was applied to a release liner.
The same one was used. Using the above release liner, an adhesive tape was obtained by the same adhesive and production method as in Example 2.

(Surface Tension of Adhesive) The method of measuring the surface tension of the adhesive is as follows. A smooth adhesive film having no foaming or the like is provided on a film such as a polyester film, and a known pressure is applied to this adhesive surface at 23 ° C. Were dropped, and the contact angles were measured. From the proportional relationship between the surface tension of the liquid and the contact angle, the critical surface tension when the contact angle becomes 0 °
Obtained as the surface tension of the adhesive.

(Release Force of Release Liner) The prepared pressure-sensitive adhesive tape was cut into a width of 50 mm, and the stress when the release liner was peeled from the pressure-sensitive adhesive tape in a T-shape at a pulling speed of 300 mm / min was measured by a tensile tester. It measured using. The releasing force range in which the workability in the normal temperature range is good is 1.30 N / 50.
mm, and when it is larger than 1.30 N / 50 mm, workability is impaired. ○: Release force is 1.30 N / 50 mm or less ×: Release force is greater than 1.30 N / 50 mm

The above evaluation was performed using the pressure-sensitive adhesive tapes of Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Tables 1 and 2.

[0037]

[0038]

[0039]

According to the present invention, a cover material for electronic equipment,
Used for bonding various components inside electronic equipment.The release layer does not contain a silicone resin composition while maintaining good release properties of the release liner.Corrosion inside the electronic equipment, malfunction, malfunction It is possible to provide a double-sided pressure-sensitive adhesive tape and a pressure-sensitive adhesive sheet with reduced possibility of causing the pressure-sensitive adhesive sheet.

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Claims (1)

[Claims] The release layer of the release liner is made of a polyolefin resin containing polyethylene as a main component and having a melting endothermic energy of 65 J / g or less at a melting point and a melting peak temperature of 130 ° C. or less, and the pressure-sensitive adhesive has a surface tension of 40 mN.
/ M (23 ° C.) or more, a double-sided pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet containing an acrylate copolymer as a main component.