JP2009286142A - Release liner and pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a release liner which exhibits good release function without using silicon series material such as a silicon-based mold releasing agent, and also has heat resistance sufficient for not causing deformation such as curl even when heat is applied to the liner. <P>SOLUTION: The release liner is formed of only a plastic film having a laminated structure of at least three layers. As both surface layers, the release liner has (A) a mold releasing function layer composed of a polyethylene film having a density of 0.88 to 0.92 g/cm3, and a melt index of 10 g/10 min or less, and (B) a surface film layer having a thermal linear expansion coefficient similar to that of the mold releasing function layer, and also has (C) a reinforcement layer having a melting point of 120°C or higher as an intermediate layer. By forming a pressure-sensitive adhesive layer on the surface of the release functioning layer (A) of the release liner, a pressure-sensitive adhesive sheet can be obtained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a release liner and pressure-sensitive adhesive sheets using the release liner as constituent members, and more particularly to a release liner and a feeler suitably used for assembling an electronic apparatus that does not like silicone contamination such as a magnetic recording device (HDD). The present invention relates to pressure-sensitive adhesive sheets.

  In pressure-sensitive adhesive sheets such as double-sided adhesive tape used for joining various articles, a release liner is laminated on the surface of the pressure-sensitive adhesive layer for the purpose of protecting the pressure-sensitive adhesive layer until use. As such a release liner, a base material such as paper or plastic film is generally used in which a silicone release agent is applied as a release agent.

  On the other hand, in recent years, pressure-sensitive adhesive sheets have been used for assembling precision electronic parts (equipment) such as magnetic recording devices (HDD), and in such applications, contact failure and head crush failure on magnetic disks. In order to prevent this, it is required to exclude the silicone material from the constituent members of the pressure-sensitive adhesive sheets.

  Among the components of pressure-sensitive adhesive sheets, silicone materials are frequently used when silicone release agents are used as release agents for release liners, etc., in order to satisfy the aforementioned requirements. For this reason, the most effective solution is not to use a silicone release agent.

  In this case, as a method not using a silicone release agent, a release liner using a fluorine release agent or a long-chain alkyl release agent, or a polyolefin plastic film such as polyethylene or polypropylene having low adhesion is used as a release liner. The method of using as is conceivable. However, when a fluorine-based release agent is used, there is a problem that the cost of the release liner increases because the release agent is expensive. When a long-chain alkyl release agent is used, a silicone-type release agent is used. There is a problem that the peeling force when peeling the release liner is higher than that of the mold.

  On the other hand, when a polyolefin-based plastic film is used as a release liner, it has been found that depending on the composition of the plastic film, a product having a low peeling force (excellent mold release function) can be obtained. Problems are likely to occur. For example, when heat is applied to the release liner during the manufacturing process of pressure-sensitive adhesive sheets or the assembly process of parts, the release liner tends to curl, making it difficult to maintain the original sheet shape. There arises a problem that the appearance quality of the adhesive sheets cannot be maintained, or the pressure-sensitive adhesive sheets are deformed on a line such as an automatic assembly process, resulting in a process failure. Also, when a polyolefin-based plastic film is used as a release liner, the release liners adhere to each other (blocking) when the release liner or a pressure-sensitive adhesive sheet having a release liner is stored in a roll shape. In some cases, rewinding becomes difficult.

Accordingly, an object of the present invention is to have a good release function without using a silicone-based material such as a silicone-based release agent, and even when heat is applied, shape change such as curling is unlikely to occur. An object of the present invention is to provide a release liner having heat resistance and pressure-sensitive adhesive sheets having the release liner as a constituent member.
In addition to the above characteristics, another object of the present invention is to provide a release liner that does not easily block even when the release liner is stored in a rolled state, and a feeling that uses the release liner as a constituent member. It is to provide pressure-sensitive adhesive sheets.

  As a result of intensive investigations to achieve the above object, the present inventors have determined that the release liner has a laminated structure composed of at least three layers, and each layer is formed of a film layer having specific physical properties, without using a silicone material. The present invention was completed by finding that good release properties and high heat resistance can be obtained.

That is, the present invention is a release liner composed only of a plastic film having a laminated structure composed of at least three layers, and both surface layers have a density of 0.88 to 0.92 g / cm ³ and a melt index of 10 g / 10. Reinforcement layer having a melting point of 120 ° C. or more as an intermediate layer, having a release functional layer (A) composed of a polyethylene film of less than or equal to a surface film layer (B) having a thermal linear expansion coefficient equivalent to that of the release functional layer A release liner having (C) is provided.

The present invention also relates to a release liner in which the surface film layer (B) of the release liner is formed of a material different from that of the release functional layer (A). Furthermore, the present invention provides a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on the surface of the release functional layer (A) of the release liner. The elastic modulus at 23 ° C. of the pressure-sensitive adhesive layer is, for example, about 1 × 10 ⁴ to 1 × 10 ⁶ dyn / cm ² . This pressure-sensitive adhesive sheet can be used as, for example, a pressure-sensitive adhesive sheet for a hard disk device of a computer.

  In the present invention, the release liner has a laminated structure composed of at least three layers, and each layer is composed of a film layer having specific physical properties, so that it has a good release function without using a silicone material. At the same time, it is excellent in workability and heat resistance, and even when heat is applied, shape changes such as curling are unlikely to occur. Therefore, it can be suitably used for joining electronic parts that dislike silicone contamination. Further, by forming the release functional layer and the surface film layer constituting both surface layers of the release liner with different materials, blocking when the release liner is wound in a roll shape can be effectively prevented. .

It is a schematic sectional drawing which shows an example of the peeling liner of this invention. It is a schematic sectional drawing which shows an example of the pressure sensitive adhesive sheet of this invention. It is a schematic sectional drawing which shows the other example of the pressure sensitive adhesive sheet of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as necessary.
[Peeling liner]
FIG. 1 is a schematic sectional view showing an example of a release liner of the present invention. In this example, the release liner 4 is composed of a plastic film having a three-layer structure in which a release functional layer 1 and a surface film layer 3 are provided as surface layers, and a reinforcing layer 2 is provided between both surface layers. ing.

The mold release functional layer 1 is made of a polyethylene film having a density of 0.88 to 0.92 g / cm ³ and a melt index of 10 g / 10 min or less. The density is preferably 0.89 to 0.90 g / cm ³ , and the melt index is preferably about 1 to 5 g / 10 minutes. When the density is less than 0.88 g / cm ³ , the heat resistance is remarkably lowered, while when it exceeds 0.92 g / cm ³ , heavy peeling occurs. On the other hand, when the melt index exceeds 10 g / 10 min, the sheet forming is hindered. In the present invention, the density of the release functional layer is a value measured based on JIS K 7112, and the melt index is a value measured based on JIS K 7210.

  The release functional layer 1 is preferably composed of a linear low density polyethylene film among polyethylene films. The thickness of the mold release functional layer 1 is 2-100 micrometers, for example, Preferably it is about 5-60 micrometers.

  The surface film layer 3 that is the other surface layer (outermost layer) has a thermal linear expansion coefficient equivalent to that of the mold release functional layer 1. “Equivalent” means, for example, that the thermal linear expansion coefficient of the surface film layer 3 is within about ± 50% of the thermal linear expansion coefficient of the release functional layer 1, preferably within ± 30%, more preferably ± Within 25%. When the thermal linear expansion coefficient of the surface film layer 3 and the thermal linear expansion coefficient of the release functional layer 1 are greatly different, curling becomes remarkable due to heat. In the present invention, the thermal linear expansion coefficient is a value measured based on JIS K 7197.

The plastic film constituting the surface film layer 3 is not particularly limited as long as the thermal expansion coefficient is the same as that of the mold release functional layer 1, but in particular, blocking when the release liner is wound into a roll shape is effectively prevented. From the viewpoint of doing, the surface film layer 3 is preferably formed of a material different from that of the mold release functional layer 1. Here, “formed from a material different from the release functional layer” means that the film forming the surface film layer 3 is different from the polyethylene film having the specific physical properties forming the release functional layer 1. Specifically, as a film for forming the surface film layer 3, for example, a polypropylene film, a polypropylene-SEBS copolymer film, a polyethylene terephthalate film, a polyimide film, a nylon film, a polystyrene film, An ethylene-vinyl acetate copolymer film, an ethylene- (meth) acrylic acid copolymer film, an ethylene- (meth) acrylic acid ester copolymer film, and the like can be used. As the film for forming the surface film layer 3, a film made of a single resin as described above, a film obtained by blending different resins, a film obtained by blending the above resin with a polyethylene resin, and the like can be used. The thickness of the surface film layer 3 is, for example, about 2 to 100 μm, preferably about 5 to 60 μm.
Further, the melting start temperature of the plastic film constituting the surface film layer 3 is preferably 5 ° C. or more, particularly 10 ° C. or more higher than the melting start temperature of the plastic film constituting the mold release functional layer 1.

  The melting point of the reinforcing layer 2 is 120 ° C. or higher, preferably 130 ° C. or higher, more preferably 140 ° C. or higher. The plastic material constituting the reinforcing layer 2 is not particularly limited as long as the melting point is 120 ° C. or higher. For example, polyesters; olefins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer Resin etc. are mentioned. The reinforcing layer 2 may be blended with various additives such as a filler such as titanium white and silica, and a deterioration preventing agent, if necessary. In the present invention, the melting point of the reinforcing layer 2 refers to a value measured based on JIS K7121.

  When the reinforcing layer 2 is not provided, or even when the reinforcing layer 2 is provided, if the melting point is less than 120 ° C., the release liner is easily stretched by heat and curling is likely to occur.

The release liner of the present invention may have a laminated structure composed of at least three layers, and may have a layer structure of four or more layers. For example, the reinforcing layer (intermediate layer) may be composed of a plurality of layers. The elastic modulus of the release liner (23 ° C.), from the viewpoint of strength, 100 kgf / cm ² or more, preferably 150 kgf / cm ² or more. The total thickness of the release liner can be appropriately selected within a range that does not impair the strength, handleability, etc., but is generally about 20 to 200 μm.

  The method for producing the release liner of the present invention is not particularly limited, and a conventional plastic film laminating method can be adopted. For example, the release liner can be manufactured by an inflation method or a T-die extrusion method.

  According to the release liner of the present invention, since the density and melt index of the polyethylene film constituting the release functional layer which is one surface layer are in a specific range, the release property is excellent without using a silicone material. Moreover, since heat resistance and workability are excellent, and the thermal linear expansion coefficients of both surface layers are equal, the occurrence of curling due to heat is extremely small. Furthermore, blocking when the release liner is wound into a roll can be effectively prevented by forming the release functional layer and the surface film layer constituting both surface layers with different materials. Therefore, the release liner of the present invention can be suitably used as a release layer for a silicone-free pressure-sensitive adhesive sheet in the field of electronic materials.

[Pressure-sensitive adhesive sheet]
FIG. 2 is a schematic sectional view showing an example of the pressure-sensitive adhesive sheet of the present invention. FIG. 3 is a schematic cross-sectional view showing another example of the pressure-sensitive adhesive sheet of the present invention.

  In the example of FIG. 2, the surfaces of the release functional layers 1 of the two release liners 4 composed of the release functional layer 1, the reinforcing layer 2, and the surface film layer 3 are both surfaces of the pressure-sensitive adhesive layer 5. Are attached to each other. In the example of FIG. 3, the surfaces of the release functional layers 1 of the two release liners 4 composed of the release functional layer 1, the reinforcing layer 2, and the surface film layer 3 are on both sides of the substrate 6. It is bonded to each surface of the pressure-sensitive adhesive layer 5 formed on the surface. These pressure-sensitive adhesive sheets are used as double-sided pressure-sensitive adhesive tapes or sheets, and are used after the release liner 4 is peeled off.

  The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 5 is not particularly limited, and various types of pressure-sensitive adhesives such as rubber and acrylic can be used, but the amount of impurity ions contained in the pressure-sensitive adhesive is small. In particular, an acrylic adhesive is preferable.

  The acrylic pressure-sensitive adhesive is mainly composed of an acrylic polymer obtained by a conventional polymerization method. If necessary, various additives such as a crosslinking agent, a tackifier, a softening agent, an anti-aging agent and a filler are added. Can be prepared.

  As the acrylic polymer, for example, a copolymer of a monomer mixture in which (meth) acrylic acid alkyl ester is a main component and a copolymerizable monoethylenically unsaturated monomer is added as necessary is used. . When a monoethylenically unsaturated monomer is used as a comonomer, a functional group or a polar group is introduced, and heat resistance and adhesiveness can be improved and modified.

  Examples of (meth) acrylic acid alkyl esters include, for example, ethyl (meth) acrylate, butyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isooctyl (meth) acrylate. (Meth) acrylic acid alkyl esters having about 2 to 12 carbon atoms in the alkyl moiety such as isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and the like. These (meth) acrylic acid alkyl esters can be used alone or in combination of two or more.

  Examples of the monoethylenically unsaturated monomer include carboxyl group-containing monomers such as acrylic acid and itaconic acid; sulfo group-containing monomers such as sulfopropyl (meth) acrylate; hydroxyalkyl (meth) acrylate and the like Hydroxyl group-containing monomers; cyano group-containing monomers such as cyanoalkyl (meth) acrylate and acrylonitrile; amide group-containing monomers such as acrylamide, substituted acrylamide and N-vinylcaprolactam; glycidyl groups such as glycidyl acrylate Containing monomers; alkoxyalkyl (meth) acrylates such as 2-methoxyethyl acrylate; vinyl esters such as vinyl acetate; styrene monomers such as styrene. These monomers can be used alone or in combination of two or more depending on the purpose.

  The polymerization method of the acrylic polymer is arbitrary, and for example, an appropriate method such as an addition polymerization method such as a solution polymerization method, an emulsion polymerization method, a photopolymerization method using an electron beam or ultraviolet rays, or a combination method thereof can be adopted. .

In the present invention, the elastic modulus at 23 ° C. of the pressure-sensitive adhesive layer 5 is in the range of 1 × 10 ⁴ to 1 × 10 ⁶ dyn / cm ² , particularly in the range of 1 × 10 ^{5 to} 7 × 10 ⁵ dyn / cm ² . It is preferable that it exists in. When the elastic modulus exceeds 1 × 10 ⁶ dyn / cm ² , the peeling becomes light and the peeling liner 4 easily falls off. When the elastic modulus is less than 1 × 10 ⁴ dyn / cm ² , the peeling becomes heavy. Therefore, the release liner 4 is difficult to peel off. In the present invention, the elastic modulus of the pressure-sensitive adhesive layer is a value determined according to JIS K 7127.

  The thickness of the pressure-sensitive adhesive layer 5 can be appropriately selected in consideration of tackiness and the like, and is, for example, about 1 to 200 μm, preferably about 30 to 150 μm.

  Examples of the base material 6 include plastic films such as polyester, polypropylene, polystyrene, and polyvinyl chloride; metal foils such as aluminum foil and stainless steel foil; and papers such as kraft paper, high-quality paper, and crepe paper. Although the thickness of the base material 6 can be suitably selected in consideration of handling properties and the like, it is generally about 5 to 300 μm, preferably about 30 to 200 μm.

  The pressure-sensitive adhesive sheet of the present invention can be produced by a conventional film lamination method (for example, a coating method).

  For example, in the pressure-sensitive adhesive sheet of FIG. 2, a pressure-sensitive adhesive is applied to the surface of the release functional layer 1 of one release liner 4, dried, and cross-linked as necessary, thereby pressure-sensitive adhesive layer 5. And the surface of the pressure-sensitive adhesive layer 5 is bonded to the surface of the release liner 4 on the release functional layer 1 side.

  In addition, the pressure-sensitive adhesive sheet of FIG. 2 is, for example, a pressure-sensitive adhesive that is coated with a pressure-sensitive adhesive on a film (separator) such as a polyethylene terephthalate film whose surface is silicone-treated, dried, and cross-linked as necessary. After the layer 5 is formed and the release functional layer 1 surface of one release liner 4 is bonded to the surface of the pressure sensitive adhesive layer 5, the separator is peeled off to expose the exposed pressure sensitive adhesive layer 5 surface. It can also be manufactured by bonding the surface of the release liner 4 on the release functional layer 1 side. The pressure-sensitive adhesive sheet thus obtained is used as a substrate-less pressure-sensitive adhesive sheet using a single-side siliconeless release liner. This method can be used to prevent the gas generated when the pressure-sensitive adhesive layer 5 is heated and dried from adhering to the release liner and remaining on the pressure-sensitive adhesive sheet as it is, or to apply excessive heat to the release liner. Useful when you don't want to.

  In the pressure-sensitive adhesive sheet of FIG. 3, for example, a pressure-sensitive adhesive is applied to one surface of the substrate 6 and dried, and then crosslinked as necessary to form the pressure-sensitive adhesive layer 5. After bonding the surface of the release liner 4 on the release functional layer 1 side to the surface of the agent layer 5, the pressure-sensitive adhesive layer 5 is formed on the other surface of the substrate 6 in the same manner. It can be produced by bonding the surface of the release liner 4 on the surface of the pressure-sensitive adhesive layer 5 to the release functional layer 1 side.

  The pressure-sensitive adhesive sheet of the present invention may be a single-sided pressure-sensitive adhesive tape or sheet having a pressure-sensitive adhesive layer only on one side. Such a single-sided pressure-sensitive adhesive tape or sheet is formed by, for example, applying a pressure-sensitive adhesive to one surface of the substrate 6, drying, and cross-linking as necessary to form the pressure-sensitive adhesive layer 5. It can be manufactured by bonding the surface of the release liner 4 on the release functional layer 1 side to the surface of the adhesive layer 5.

  According to the pressure-sensitive adhesive sheet of the present invention, as described above, a release liner that has excellent releasability without using a silicone-based material, has high heat resistance, and is difficult to curl is used. The release liner can be easily peeled off and the handleability is excellent, and no silicone compound remains in the pressure-sensitive adhesive layer after the release liner is peeled off. Therefore, it is suitable as a silicone-free pressure-sensitive adhesive sheet or tape for the electronic material field, particularly for computer hard disk devices.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. In the following, “parts” means parts by weight.

Preparation Example 1
Using 70 parts of isooctyl acrylate, 20 parts of butyl acrylate, 10 parts of acrylic acid and 0.5 part of 2,2-dimethoxyphenylacetophenone (trade name: Irgacure 651, manufactured by Ciba Geigy Corporation) as a photoinitiator, Prepared. This was partially polymerized by exposure to ultraviolet light under a nitrogen atmosphere to obtain a coatable syrup having a viscosity of about 5000 centipoise. To 100 parts of this partially polymerized syrup, 1 part of tetrabismethylene-3- (3'-5'-di-t-butyl-4'-hydroxyphenyl) propionate methane as a radical chain inhibitor and a crosslinking agent 0.2 parts of trimethylolpropane triacrylate was added and mixed to obtain a pressure-sensitive adhesive composition.

Preparation Example 2
After 90 parts of 2-ethylhexyl acrylate, 10 parts of acrylic acid, 210 parts of ethyl acetate and 0.4 part of 2,2′-azobisisobutyronitrile were charged into the flask and the system was sufficiently replaced with nitrogen gas, Solution polymerization was performed by stirring at a temperature of -80 ° C. to obtain a polymer solution having a viscosity of about 120 poise and a polymerization rate of 99.0% by weight. To 100 parts of this solution, 2 parts of a polyfunctional isocyanate compound as a crosslinking agent was added and mixed to obtain a pressure-sensitive adhesive composition.

Example 1
By a T-die extrusion method, a linear low-density polyethylene layer (density 0.89 g / cm ³ , melt index 5 g) having a thickness of 15 μm as a release functional layer (surface to be bonded to the pressure-sensitive adhesive layer) under the condition of 180 ° C. / 10 minutes, thermal linear expansion coefficient 18 × 10 ⁻⁵ / ° C., melting start temperature 65 ° C. (measured according to JIS K 7121)), 50 μm thick polypropylene layer (melting point 140 ° C.) as outer layer (intermediate layer), outer layer As a (surface film layer), a release liner (laminated plastic sheet) consisting of three layers of a linear low-density polyethylene layer (thermal linear expansion coefficient 18 × 10 ⁻⁵ / ° C.) having a thickness of 15 μm was obtained.
On the other hand, the pressure-sensitive adhesive composition obtained in Preparation Example 1 was applied onto a 50 μm-thick silicone-treated polyethylene terephthalate film (separator), and a high-pressure mercury lamp with a light intensity of 5 mW / cm ² in a nitrogen gas atmosphere. A 50 μm-thick pressure-sensitive adhesive layer (photopolymer layer) (elastic modulus 6 × 10 ⁵ dyn / cm ^{2 at} 23 ° C.) is formed by photopolymerization by irradiating with 900 mJ / cm ² ultraviolet rays. Then, it was dried at 120 ° C. for 7 minutes in a hot air circulating dryer. The surface of the release functional layer of the release liner obtained above was bonded to the surface of this pressure-sensitive adhesive layer, then the separator was peeled off, and another surface of the pressure-sensitive adhesive layer was exposed. A release liner was bonded to produce a pressure sensitive double-sided adhesive tape.

Example 2
By a T-die extrusion method, a linear low-density polyethylene layer (density 0.91 g / cm ³ , melt index 2 g) having a thickness of 30 μm as a release functional layer (surface to be bonded to the pressure-sensitive adhesive layer) under the condition of 180 ° C. / 10 minutes, thermal linear expansion coefficient 14 × 10 ⁻⁵ / ° C.), melting start temperature 74 ° C. (measured according to JIS K 7121)), and a 50 μm thick polyethylene-propylene copolymer layer (intermediate layer) ( Melting point 125 ° C.), 20 μm thick polypropylene-SEBS copolymer layer (thermal expansion coefficient 11 × 10 ⁻⁵ / ° C., melting start temperature 83 ° C. (measured according to JIS K 7121)) as an outer layer (surface film layer) A three-layer release liner (laminated plastic sheet) was obtained. Even when this release liner was stored for a long time in the state of being wound in a roll, blocking did not occur and rewindability was good.
On the other hand, the pressure-sensitive adhesive composition obtained in Preparation Example 1 was applied onto a 75 μm-thick base polyethylene terephthalate film, and 900 mJ / cm from a high-pressure mercury lamp having a light intensity of 5 mW / cm ² in a nitrogen gas atmosphere. By irradiating with ultraviolet ray ² and photopolymerizing, a pressure-sensitive adhesive layer (photopolymerized layer) having a total thickness of 100 μm is formed, and the above obtained release is formed on the surface of the pressure-sensitive adhesive layer. The liner release functional layer surfaces were bonded together. Furthermore, the pressure-sensitive adhesive composition obtained in Preparation Example 1 was applied to the other surface of the base polyethylene terephthalate film in the same manner and photopolymerized, whereby a pressure-sensitive adhesive layer having a total thickness of 125 μm. (Photopolymerized layer) is formed, and the surface of the release sensitive layer of the release liner obtained above is bonded to the surface of the pressure-sensitive adhesive layer in the same manner. A pressure-sensitive double-sided adhesive tape as a material was produced.

Example 3
The pressure-sensitive adhesive composition obtained in Preparation Example 1 was applied to the surface of the release functional layer of the release liner (laminated plastic sheet) obtained in Example 2, and the light intensity was 5 mW / cm in a nitrogen gas atmosphere. by by ultraviolet irradiation of 900 mJ / cm ² photopolymerizing than ² of the high-pressure mercury lamp, (a layer of photopolymerized) pressure-sensitive adhesive layer having a thickness of 50 [mu] m (elastic modulus 6 × 10 at 23 ° C. ⁵ dyn / cm ² ) and dried in a hot air circulating dryer at 120 ° C. for 7 minutes, and then the release functional layer surface of the release liner (laminated plastic sheet) obtained in Example 1 was formed on the surface of the pressure-sensitive adhesive layer. A pressure-sensitive double-sided adhesive tape was prepared by bonding.

Example 4
The pressure-sensitive adhesive composition obtained in Preparation Example 2 was applied onto a 50 μm thick silicone-treated polyethylene terephthalate film (separator), dried in a hot air circulating dryer at 40 ° C. for 5 minutes, and then at 120 ° C. for 7 minutes. The film was dried to form a pressure-sensitive adhesive layer (solution polymer layer) (elastic modulus 2 × 10 ⁵ dyn / cm ² ) having a thickness of 50 μm. The surface of the release functional layer of the release liner obtained in Example 2 was bonded to the surface of this pressure-sensitive adhesive layer, then the separator was peeled off, and the surface of the exposed pressure-sensitive adhesive layer was The other release liner obtained in 2 was bonded to prepare a pressure-sensitive double-sided adhesive tape.

Comparative Example 1
A pressure-sensitive double-sided adhesive tape was prepared in the same manner as in Example 1 except that a silicone-treated polyethylene terephthalate separator was used instead of the release liner (laminated plastic sheet).

Comparative Example 2
Except for changing the release functional layer of the release liner (laminated plastic sheet) to a high-density polyethylene layer (density 0.95 g / cm ³ , melt index 1 g / 10 min) having a thickness of 25 μm, the same as in Example 1. A pressure sensitive double-sided adhesive tape was prepared.

Comparative Example 3
Example 1 except that the release functional layer of the release liner (laminated plastic sheet) was changed to a linear low density polyethylene layer (density 0.86 g / cm ³ , melt index 12 g / 10 min) having a thickness of 50 μm. In the same manner, an attempt was made to produce a pressure-sensitive double-sided adhesive tape, but the film could not be formed and a pressure-sensitive double-sided adhesive tape could not be produced.

Comparative Example 4
Pressure sensitive as in Example 1, except that the outer layer (surface film layer) of the release liner (laminated plastic sheet) was composed of a 15 μm thick polypropylene film having a thermal linear expansion coefficient of 6 × 10 ⁻⁵ / ° C. A double-sided adhesive tape was prepared.

Comparative Example 5
A pressure-sensitive double-sided adhesive tape was produced in the same manner as in Example 1 except that the reinforcing layer (intermediate layer) of the release liner (laminated plastic sheet) was composed of a polyethylene film having a melting point of 95 ° C. and a thickness of 50 μm.

Evaluation Test For each pressure-sensitive double-sided adhesive tape of Examples and Comparative Examples, the amount of silicone transferred to the pressure-sensitive adhesive layer, the release property of the release liner, and the presence or absence of curling were measured and evaluated by the following methods. The results are shown in Table 1.
(Amount of silicone transferred to pressure-sensitive adhesive layer)
The pressure-sensitive double-sided adhesive tape was left in an atmosphere of 40 ° C. for 24 hours, then the release liners on both sides were peeled off, and the amount of silicone contained on both sides of the pressure-sensitive adhesive layer was measured with fluorescent X-rays. Table 1 shows the total amount on both sides.
(Peelability of release liner)
After peeling off one release liner by hand with a pressure-sensitive double-sided adhesive tape, sticking it to the AL plate with a hand roller, and observing the release condition of the release liner when peeling the other release liner by hand, Evaluation based on the criteria.
○: Good ×: The release liner was heavily peeled.
(Presence or absence of curling)
The A4 size pressure-sensitive double-sided adhesive tape was allowed to stand in an atmosphere at 70 ° C. for 12 hours.
○: Curling was hardly observed. ×: Curling was remarkably generated.

  As is apparent from the results in Table 1, the pressure-sensitive double-sided adhesive tapes of Examples 1 to 4 were excellent in that the amount of silicone transferred to the pressure-sensitive adhesive layer was small, the peelability was good, and the occurrence of curling was small. Has quality characteristics. In Comparative Example 5, the elongation of the release liner was significant.

DESCRIPTION OF SYMBOLS 1 Mold release functional layer 2 Reinforcement layer 3 Surface film layer 4 Release liner 5 Pressure sensitive adhesive layer 6 Base material

Claims (5)

A release liner composed only of a plastic film having a laminated structure composed of at least three layers, and as both surface layers, from a polyethylene film having a density of 0.88 to 0.92 g / cm ³ and a melt index of 10 g / 10 min or less. A release functional layer (A) and a surface film layer (B) having a thermal expansion coefficient equivalent to that of the release functional layer, and a reinforcing layer (C) having a melting point of 120 ° C. or more as an intermediate layer Liner.   The release liner according to claim 1, wherein the surface film layer (B) is formed of a material different from that of the release functional layer (A).   A pressure-sensitive adhesive sheet, wherein a pressure-sensitive adhesive layer is formed on the surface of the release functional layer (A) of the release liner according to claim 1 or 2. The pressure-sensitive adhesive sheet according to claim 3, wherein the pressure-sensitive adhesive layer has an elastic modulus at 23 ° C. in the range of 1 × 10 ⁴ to 1 × 10 ⁶ dyn / cm ² .   The pressure-sensitive adhesive sheet according to claim 3 or 4, which is used for a hard disk device.

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