JP2019065218A - Substrate-less double-sided adhesive sheet - Google Patents

Abstract

To provide a substrate-less double-sided adhesive sheet capable of suppressing spot transfer when a light peeling film is peeled.SOLUTION: A substrate-less double-sided adhesive sheet 10 which has a light-to-release film 11, an adhesive layer 1 provided on the light-to-release film and a heavy-to-release film 12 provided on the adhesive layer, where the light-to-release film 11 has a first biaxially oriented polyester film 2 and a first silicone resin layer 3 provided on a stuck surface of the first biaxially oriented polyester film and the adhesive layer, the heavy-to-release film 12 has a second biaxially oriented polyester film 4 and a second silicone resin layer 5 provided on a stuck surface of the second biaxially oriented polyester film and the adhesive layer, and a small melting heat quantity peal temperature of the first biaxially oriented polyester film 2 is lower than [Tmp-40]°C (Tmp: melting point of polyester).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a substrateless double-sided pressure-sensitive adhesive sheet.

Various pressure-sensitive adhesive sheets for surface bonding between objects are conventionally known, and a substrateless double-sided pressure-sensitive adhesive sheet is known as one of the pressure-sensitive adhesive sheets.
The substrate-less double-sided pressure-sensitive adhesive sheet has a light-peelable film having a relatively low peel strength to the pressure-sensitive adhesive layer and a peel strength to the pressure-sensitive adhesive layer relative to both sides of the pressure-sensitive adhesive layer having no base material as a core material. And the heavy peeling films are respectively laminated.
In the substrate-less double-sided pressure-sensitive adhesive sheet, first, the light release film is peeled off, and one surface of the exposed pressure-sensitive adhesive layer is adhered to the object surface. Then, the heavy release film is peeled off, and the other side of the exposed pressure-sensitive adhesive layer is adhered to a different object surface, thereby surface-adhering between the objects.

By the way, as a problem of the substrate-less double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer follows the light release film and is stretched between the heavy release film and the light release film when peeling the light release film. It may be mentioned that the stretched adhesive is broken to cause peeling failure in which the pressure-sensitive adhesive layer, which should originally remain on the heavy peel film side, is surface-transferred to the light peel film side.
Peeling defects due to such planar transfer are due to the peeling force of the heavy release film to the pressure-sensitive adhesive layer (hereinafter also referred to as "the peel force of the heavy release film") and the peeling force of the light release film to the pressure-sensitive adhesive layer , It is easy to produce when the difference with "the exfoliation power of light exfoliation film" is small.
Then, making large the difference of the exfoliation power of a heavy exfoliation film, and the exfoliation power of a light exfoliation film is performed conventionally (for example, refer to patent documents 1).

Japanese Patent Application Laid-Open No. 07-041736

However, in the substrate-less double-sided pressure-sensitive adhesive sheet, peeling defects different from peeling defects due to planar transfer may also occur.
The present inventors variously examined a substrateless double-sided pressure-sensitive adhesive sheet having a light release film in which a silicone resin layer is formed as a release layer on the bonding surface of the biaxially stretched polyester film with the pressure-sensitive adhesive layer. When peeling the film, it has been found out that minute spot-like transfer (hereinafter also referred to as "spot transfer") which is a peeling failure different from the above-described transfer can occur.
Spot transfer is a factor that causes minute defects in the pressure-sensitive adhesive layer. Since a substrate-less double-sided pressure-sensitive adhesive sheet is used for applications such as bonding of optical films, it is desirable to suppress the occurrence of minute defects in the pressure-sensitive adhesive layer as much as possible.

  An object of the present invention is to provide a substrateless double-sided pressure-sensitive adhesive sheet capable of suppressing spot transfer when peeling off a light release film.

  The present inventors solved the above-mentioned subject by using a biaxially stretched polyester film whose micro melting calorie peak temperature is below a specific temperature as a polymer film which constitutes a light release film of a substrate-less double-sided pressure-sensitive adhesive sheet. I found that I could do it.

That is, the present invention relates to the following [1] to [5].
[1] A substrateless double-sided pressure-sensitive adhesive sheet comprising a light release film, a pressure-sensitive adhesive layer provided on the light release film, and a heavy release film provided on the pressure-sensitive adhesive layer,
The light release film has a first biaxially stretched polyester film, and a first silicone resin layer provided on a bonding surface of the first biaxially stretched polyester film with the pressure-sensitive adhesive layer,
The heavy release film has a second biaxially oriented polyester film, and a second silicone resin layer provided on the bonding surface of the pressure sensitive adhesive layer of the second biaxially oriented polyester film,
The substrate-less double-sided pressure-sensitive adhesive sheet, wherein the micro melting calorie peak temperature of the first biaxially stretched polyester film is less than [Tmp-40] ° C (Tmp: melting point of polyester).
[2] Both the first biaxially stretched polyester film and the second biaxially stretched polyester film are biaxially stretched polyethylene terephthalate films,
The substrate-less double-sided pressure-sensitive adhesive sheet as described in the above [1], wherein the micro melting calorie peak temperature of the first biaxially stretched polyester film is less than 220 ° C.
[3] The above [1] or [2], wherein the absolute value of the difference between the peel strength of the light release film to the pressure-sensitive adhesive layer and the peel strength of the heavy release film to the pressure-sensitive adhesive layer is 5 mN / 25 mm or more The substrateless double-sided pressure-sensitive adhesive sheet as described in.
[4] The substrate-less double-sided pressure-sensitive adhesive sheet according to any one of the above [1] to [3], wherein the thickness of the pressure-sensitive adhesive layer is 1 to 250 μm.
[5] In any one of the above [1] to [4], the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film are each 19 to 188 μm. The substrate-less double-sided pressure-sensitive adhesive sheet described above.

  According to the present invention, it is possible to provide a substrateless double-sided pressure-sensitive adhesive sheet capable of suppressing spot transfer when peeling off a light release film.

FIG. 1 is a cross-sectional view showing an embodiment of a substrateless double-sided pressure-sensitive adhesive sheet of the present invention. It is a conceptual diagram of the spot transfer which may arise in a substrate-less double-sided adhesive sheet. It is a figure which shows an example of the measurement result of the micro melting calorie peak of a biaxially stretched polyethylene terephthalate film. It is the figure which expanded the micro fusion | melting thermal energy peak in FIG.

  In the present specification, the mass average molecular weight (Mw) is a value in terms of standard polystyrene measured by gel permeation chromatography (GPC), and specifically, a value measured based on the method described in the examples. It is.

  Moreover, in the present specification, for example, “(meth) acrylic acid” indicates both “acrylic acid” and “methacrylic acid”, and the other similar terms are also the same.

[Composition of a substrate-less double-sided adhesive sheet]
The substrate-less double-sided pressure-sensitive adhesive sheet of the present invention has a light release film, a pressure-sensitive adhesive layer provided on the light release film, and a heavy release film provided on the pressure-sensitive adhesive layer.
The light release film has a first biaxially oriented polyester film and a first silicone resin layer provided on the bonding surface of the pressure sensitive adhesive layer of the first biaxially oriented polyester film.
The heavy release film has a second biaxially oriented polyester film and a second silicone resin layer provided on the bonding surface of the pressure-sensitive adhesive layer of the second biaxially oriented polyester film.
In addition, an adhesive layer does not have a base material used as a core material.

Examples of the substrateless double-sided pressure-sensitive adhesive sheet according to one embodiment of the present invention include a substrateless double-sided pressure-sensitive adhesive sheet 10 shown in FIG.
A substrate-less double-sided pressure-sensitive adhesive sheet 10 shown in FIG. 1 has a light release film 11, an adhesive layer 1 provided on the light release film 11, and a heavy release film 12 provided on the pressure-sensitive adhesive layer 1. .
The light release film 11 has a first biaxially stretched polyester film 2 and a first silicone resin layer 3 provided on the bonding surface of the first biaxially stretched polyester film 2 with the pressure-sensitive adhesive layer 1. . The first biaxially stretched polyester film 2 and the pressure-sensitive adhesive layer 1 are bonded without another layer.
The heavy release film 12 has a second biaxially oriented polyester film 4 and a second silicone resin layer 5 provided on the bonding surface of the pressure sensitive adhesive layer 1 of the second biaxially oriented polyester film 4. . The second biaxially stretched polyester film 4 and the pressure-sensitive adhesive layer 1 are bonded without another layer.
In the substrate-less double-sided pressure-sensitive adhesive sheet according to one aspect of the present invention, the space between the first biaxially stretched polyester film 2 and the first silicone resin layer 3 and the second biaxially stretched polyester film 4 and the second Another layer may be provided between the second silicone resin layer 5. As another layer, an antistatic layer, an anchor layer, etc. are mentioned, for example.

  In one aspect of the present invention, the thickness of the pressure-sensitive adhesive layer is preferably 1 to 250 μm, more preferably 5 to 200 μm, and still more preferably 10 to 175 μm from the viewpoint of productivity and cost. .

In one aspect of the present invention, the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film cause dents such as deformation, unevenness, and distortion on the surface of the pressure-sensitive adhesive layer. Of making it easy to suppress the occurrence of light, and uniformly reduce the orientation angle in the width direction of the biaxially stretched polyester film, thereby suppressing the occurrence of light leakage during the inspection by the cross nicol method, and the inspection property by the cross nicol method Is preferably 19 μm or more, more preferably 25 μm or more, and still more preferably 30 μm or more. In any case, it is preferably 188 μm or less, more preferably 125 μm or less, still more preferably 100 μm or less, still more preferably 50 μm or less, and still more preferably 48 μm or less.
In one embodiment of the present invention, when the substrate-less double-sided pressure-sensitive adhesive sheet is used for a polarizing plate, the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film are both 19 to The thickness is preferably 50 μm, and more preferably 25 to 48 μm.
In one embodiment of the present invention, when using a substrate-less double-sided pressure-sensitive adhesive sheet for touch panel applications, the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film are both 38 to 188 μm Is preferred, and 38 to 125 μm is more preferred.

  Further, in one aspect of the present invention, the thickness of the first silicone resin layer when dried and the thickness of the second silicone resin layer when dried are different in the peeling force due to the fluctuation of the applied amount of the composition for forming a silicone resin layer. From the viewpoint of suppressing and from the viewpoint of suppressing blocking, the thickness is preferably 40 nm to 1 μm, more preferably 50 nm to 0.5 μm, and still more preferably 60 nm to 0.3 μm.

  The thickness of the pressure-sensitive adhesive layer, the thickness of the biaxially oriented polyester film, and the thickness of the silicone resin layer can be measured, for example, using the methods described in the examples described later.

The shape of the substrate-less double-sided pressure-sensitive adhesive sheet according to one embodiment of the present invention includes, for example, a square, a rectangle, a polygon, a circle, and an annular shape, but is not limited to these shapes. It selects suitably according to the use of a double-sided adhesive sheet.
In addition, the substrate-less double-sided pressure-sensitive adhesive sheet according to one embodiment of the present invention may be, for example, a wound body obtained by winding a long substrate-less double-sided pressure-sensitive adhesive sheet in a roll shape or a core.

  Hereinafter, the light release film, the heavy release film, and the pressure-sensitive adhesive layer, which constitute the substrate-less double-sided pressure-sensitive adhesive sheet of the present invention, will be described in detail.

[Light release film and heavy release film]
The light release film has a first biaxially oriented polyester film and a first silicone resin layer provided on the bonding surface of the pressure sensitive adhesive layer of the first biaxially oriented polyester film.
In addition, the heavy release film has a second silicone resin layer provided on the bonding surface of the second biaxially stretched polyester film and the pressure-sensitive adhesive layer of the second biaxially stretched polyester film.

<First biaxially stretched polyester film>
The first biaxially stretched polyester film is a biaxially stretched polyester film having a micro melting calorie peak temperature of less than [Tmp-40] ° C. (Tmp: melting point of polyester).
The biaxially stretched polyester film is produced by subjecting the polyester film to biaxial stretching and then heat setting.
As a method of biaxially stretching a polyester film, for example, a method of stretching in the longitudinal direction and then stretching in the width direction, a method of stretching in the width direction and then stretching in the longitudinal direction, stretching in the longitudinal direction and stretching in the width direction Examples include a method of combining a plurality of times, and a method called simultaneous biaxial stretching in which stretching in the longitudinal direction and stretching in the width direction are simultaneously performed.
The heat setting treatment is performed by heating at a temperature below the melting point of polyester using an oven or the like. By performing the heat setting process, the shrinkage of the biaxially stretched polyester film can be suppressed, and the dimensional stability can be made favorable.
In addition, as a 1st biaxially-stretched polyester film, a biaxially-stretched polyethylene terephthalate film, a biaxially-stretched polybutylene terephthalate film, a biaxially-stretched polyethylene naphthalate film etc. are mentioned, for example. Among these, a biaxially stretched polyethylene terephthalate film is preferable from the viewpoint of transparency and smoothness.
In the following description, "polyethylene terephthalate" may be abbreviated as "PET".

As a result of variously examining a substrate-less double-sided pressure-sensitive adhesive sheet having a light release film in which a silicone resin layer is formed on a bonding surface of a biaxially stretched polyester film with a pressure-sensitive adhesive layer, the present inventors release the light release film. In this case, it was found that spot transfer, which is a peeling failure different from the planar transfer, which occurs when the difference between the peel force of the heavy release film and the peel force of the light release film is small, may occur.
A conceptual view of a substrateless double-sided pressure-sensitive adhesive sheet in which spot transfer occurs is shown in FIG. When the light release film 21 of the substrate-less double-sided pressure-sensitive adhesive sheet 20 is peeled off from the pressure-sensitive adhesive layer 23, a part of minute portions of the pressure-sensitive adhesive layer 1 follows the light release film 21, and the light release film 21 and the heavy release film 22 Be stretched between. A part of the stretched adhesive 23 a does not peel off at the interface between the light release film 21 and the adhesive layer 23, and the stretched adhesive 23 a is broken and the stretched adhesive The adhesive located on the side of the light release film 21 with respect to the broken portion among the portions 23a remains on the light release film 21 and becomes a spot-like residual adhesive 23b. Moreover, a micro defect may also be produced on the adhesive layer 23 by the adhesive located in the adhesive layer 23 side rather than the fracture | rupture part among the extended adhesive 23a.
Such spot transfer does not occur in the double-sided pressure-sensitive adhesive tape in which a substrate serving as a core material is present in the pressure-sensitive adhesive layer. Moreover, when peeling off the heavy release film of the substrate-less double-sided pressure-sensitive adhesive sheet, an adherend is attached to the exposed surface of the pressure-sensitive adhesive layer after peeling off the light release film, and the adherend is a support Because it functions as a spot transfer problem does not occur. That is, the problem of spot transfer is a problem unique to peeling of a light release film, which occurs because the substrate-less double-sided pressure-sensitive adhesive sheet does not have a core material.

As a result of examining the cause of the spot transfer, the present inventors rarely generate repelling when the composition for forming a silicone resin layer containing a silicone-based mold release agent is applied to a biaxially stretched polyester film, It was found that the pressure-sensitive adhesive layer and the biaxially oriented polyester film were in contact with each other without the silicone resin layer at the micro site where the a. And in the minute part where the pressure sensitive adhesive layer and the biaxially stretched polyester film are in contact, when peeling the light peeling film, the pressure sensitive adhesive layer follows the light peeling film without being peeled from the light peeling film in the minute part. As a result of stretching, we came to find out that spot transfer could occur.
That is, regardless of the peeling force of the light peeling film and the peeling force of the heavy peeling film, spot transfer may be caused due to coating abnormality such as repelling of the composition for forming the silicone resin layer which occurs rarely. It came to

Also, as a result of various investigations, the inventors of the present invention found that if the heat setting treatment temperature of the biaxially oriented polyester film is high, the monomer component, the oligomer component, etc. constituting the polyester film sublime during the heat setting treatment. It has been found that they adhere to the inside and can fall on the biaxially oriented polyester film during the heat setting process or after the heat setting process to become an attached foreign matter.
For example, when the polyester film is a PET film, terephthalic acid or an oligomer component may be present as an attached foreign matter on the surface of the PET film when the heat setting treatment temperature of the biaxially oriented polyester film is high.
The present inventors considered that these adhering foreign substances are the cause of repelling when applying the composition for forming a silicone resin layer to a biaxially stretched polyester film. Therefore, by setting the heat setting temperature to a low temperature, it is suppressed that the monomer component, the oligomer component and the like constituting the polyester film sublime and adhere to the inside of the oven, and the foreign matter on the biaxially stretched polyester film is reduced. , I thought to suppress the above repelling.
Here, the heat setting temperature has a correlation with the micro melting heat peak temperature, and the higher the temperature when heat setting is performed, the higher the micro melting heat peak temperature, and the lower temperature when heat setting is performed. The lower the heat of fusion peak temperature, the lower the temperature. Then, as a result of conducting various examinations focusing on the minute melting calorie peak temperature, the present inventors conducted a biaxial drawing polyester having a minute melting calorie peak temperature less than [Tmp-40] ° C. (Tmp: melting point of polyester) By using the film, it is possible to significantly reduce adhesion foreign matter on the biaxially stretched polyester film, and to suppress repelling when applying the composition for forming a silicone resin layer to the biaxially stretched polyester film, and light peeling It has been found that it is possible to suppress spot transfer when peeling off the film.

  In the present specification, the micro melting calorie peak temperature is the temperature at the top of the micro melting calorie peak of the biaxially stretched polyester film measured using a differential scanning calorimeter according to JIS K7121 (1999). Specifically, it can be measured and determined using the method described in the examples described later.

Here, the micro melting calorie peak temperature of the first biaxially stretched polyester film is preferably [Tmp-45] ° C. or less, from the viewpoint of better suppressing spot adhesion at the time of peeling the light release film. Preferably [Tmp-50] ° C. or less, more preferably [Tmp-60] ° C. or less, still more preferably [Tmp-70] ° C. or less, still more preferably [Tmp-80] ° C. or less, particularly preferably [Tmp] -90] ° C or less.
The lower limit value of the micro melting calorie peak temperature of the first biaxially stretched polyester film corresponds to the lower limit value of the heat setting treatment temperature capable of suppressing the contraction of the first biaxial stretched polyester film It is sufficient if it is a temperature, and usually it is [Tmp-100] ° C.

When the first biaxially stretched polyester film is a biaxially stretched PET film, the micromelting heat peak temperature is less than 220 ° C., preferably 215 ° C. or less, more preferably 210 ° C. or less, still more preferably 200. C. or less, still more preferably 190 ° C. or less, still more preferably 180 ° C. or less, particularly preferably 170 ° C. or less.
The lower limit value of the micro melting calorie peak temperature of the biaxially stretched PET film is usually 160 ° C.

<Second biaxially oriented polyester film>
The second biaxially stretched polyester film is not particularly limited, and the biaxially stretched polyester film used for the substrateless double-sided pressure-sensitive adhesive sheet can be appropriately selected and used, but from the viewpoint of transparency and smoothness, It is preferred to use a biaxially oriented PET film.
Therefore, it is more preferable that both the first biaxially stretched polyester film and the second biaxially stretched polyester film be biaxially stretched PET films.
In addition, as the second biaxially stretched polyester film, one similar to the above-mentioned biaxially stretched polyester film mentioned as the first biaxially stretched polyester film is selected independently from the first biaxially stretched polyester film You may
The second biaxially stretched polyester film is the same as the first biaxially stretched polyester film from the viewpoint of making the dimensional stability better when used for laminating optical materials such as optical films or the like. It is preferable to use one of

<First silicone resin layer>
The first silicone resin layer has a function of imparting releasability from the pressure-sensitive adhesive layer to the light release film.
Although the first silicone resin layer is a release layer containing a silicone resin, it may contain an additive for release layer, if necessary, as long as the effects of the present invention are not impaired.
The first silicone resin layer can be formed by curing a silicone resin layer-forming composition (A) containing a silicone-based release agent.
Hereinafter, each component contained in the composition for silicone resin layer formation (A) which is a formation material of a 1st silicone resin layer is demonstrated.

(Silicone-based mold release agent)
As the silicone-based release agent, a silicone release agent blended with a silicone resin having dimethylpolysiloxane as a basic skeleton can be used.
The silicone resin may be any of an addition reaction type, a condensation reaction type, and an energy ray curing type such as an ultraviolet ray curing type and an electron beam curing type, but is preferably an addition reaction type silicone resin.
The addition reaction type silicone resin has high reactivity and is excellent in productivity, and has merits such as small change in peel force after production and no curing shrinkage as compared with the condensation reaction type.

Specific examples of the addition reaction type silicone resin include an organo-functional silicone having two or more alkenyl groups having 2 to 10 carbon atoms such as vinyl group, allyl group, propenyl group, and hexenyl group at the terminal and / or side chain of the molecule. Polysiloxane is mentioned.
When using such an addition reaction type silicone resin, it is preferable to use a crosslinking agent and a catalyst in combination.

(Crosslinking agent)
Examples of the crosslinking agent include organopolysiloxanes having hydrogen atoms bonded to at least two silicon atoms in one molecule.
Specific examples of the crosslinking agent include dimethylhydrogensiloxy end-capped dimethylsiloxane-methyl hydrogen siloxane copolymer, trimethylsiloxy end-capped dimethylsiloxane-methyl hydrogen siloxane copolymer, trimethylsiloxy end-capped methyl hydrogen Polysiloxane, poly (hydrogen silsesquioxane), etc. are mentioned.

(catalyst)
As the catalyst, particulate platinum, particulate platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, palladium, platinum group metal compounds such as rhodium, etc. It can be mentioned.
By using such a catalyst, the curing reaction of the composition (A) for forming a silicone resin layer can be advanced more efficiently.

(Other additives)
The composition (A) for forming a silicone resin layer may contain an additive generally used in a release layer as long as the effects of the present invention are not impaired.
Examples of such additives include dyes and dispersants.

(Dilution solvent)
The composition for forming a silicone resin layer (A) may contain a dilution solvent together with the various active ingredients described above from the viewpoint of adjusting the viscosity to improve the coating property on the first biaxially stretched polyester film. .
In the present specification, the "active ingredient" refers to the ingredient contained in the composition of interest excluding the diluent solvent.
In addition, the solvent contained in a silicone type mold release agent is also contained in the said dilution solvent.

Examples of the dilution solvent include aromatic hydrocarbons such as toluene, fatty acid esters such as ethyl acetate, ketones such as methyl ethyl ketone, and organic solvents such as aliphatic hydrocarbons such as hexane and heptane.
One of these dilution solvents may be used alone, or two or more thereof may be used in combination.

  The concentration of the active ingredient (solid content) of the solution of the composition (A) for forming a silicone resin layer is preferably 0.3 to 10% by mass, more preferably 0.5 to 5% by mass, and still more preferably 0.5. It is -3 mass%.

<Second silicone resin layer>
The second silicone resin layer has a function of imparting releasability from the pressure-sensitive adhesive layer to the light release film.
The second silicone resin layer is a release layer containing a silicone resin, but may contain an additive for release layer as needed, as long as the effects of the present invention are not impaired.
The second silicone resin layer can be formed by curing the silicone resin layer-forming composition (B) containing a silicone-based release agent.

  The composition (B) for forming a silicone resin layer is prepared such that the peel strength of the heavy peel film having the second silicone resin layer is larger than the peel force of the light peel film having the first silicone resin layer. Ru. Specifically, for example, the silicone-based release agent, the crosslinking agent, the catalyst, and the other additives of the composition (A) for forming a silicone resin layer described above are appropriately selected and prepared.

Moreover, it is preferable that the composition for silicone resin layer formation (B) contains a heavy release additive.
The heavy release additive includes, for example, silicone resins and organosilanes such as silane coupling agents. Among these, silicone resins are preferably used.
As the silicone resin, it is preferable to use, for example, an MQ resin containing an M unit which is a monofunctional siloxane unit [R ₃ SiO _1/2 ] and a Q unit which is a tetrafunctional siloxane unit [SiO _4/2 ]. In addition, three R in M unit respectively independently represent a hydrogen atom, a hydroxyl group, or an organic group. From the viewpoint of facilitating inhibition of silicone migration, one or more of the three R's in the M unit is preferably a hydroxyl group or a vinyl group, and more preferably a vinyl group.

[Pressure-sensitive adhesive layer]
The pressure-sensitive adhesive layer included in the substrate-less double-sided pressure-sensitive adhesive sheet of the present invention is a layer containing a pressure-sensitive adhesive resin, but if necessary, an additive for pressure-sensitive adhesive is contained as long as the effects of the present invention are not impaired. It is also good.
An adhesive layer is formed using the adhesive composition containing adhesive resin.
The form of the pressure-sensitive adhesive composition may be any of a solvent type, an emulsion type, and a solventless type.

<Adhesive resin>
The adhesive resin is a polymer having adhesiveness by itself and having a mass average molecular weight (Mw) of 10,000 or more, preferably a polymer having a mass average molecular weight (Mw) of 10,000 to 2,000,000.

Specific examples of the adhesive resin include acrylic resins, rubber resins such as polyisobutylene resins, polyester resins, urethane resins, and silicone resins.
These tackifying resins may be used alone or in combination of two or more.
Moreover, when these adhesive resins are copolymers which have 2 or more types of structural units, the form of the said copolymer is not specifically limited, A block copolymer, a random copolymer, and a graft co It may be any of polymers.
In one aspect of the present invention, the pressure-sensitive adhesive composition preferably contains an acrylic resin, and from the viewpoint of adhesion durability, more preferably contains a (meth) acrylic acid ester copolymer among the acrylic resins.
Hereinafter, the case where the solvent-type or emulsion-type pressure-sensitive adhesive composition contains an acrylic resin as the adhesive resin and the case where the solvent-free adhesive composition contains an acrylic resin as the adhesive resin will be described as an example. .

<Solvent-type or emulsion-type pressure-sensitive adhesive composition>
When the pressure-sensitive adhesive composition is a solvent type or an emulsion type, the acrylic resin contained in the pressure-sensitive adhesive composition is a polymer or copolymer mainly composed of a main monomer component giving tackiness, or the main monomer component In addition to the above, it may be composed of a copolymer further including a functional group-containing monomer component for improving the crosslinking point and adhesion.
In addition, from the viewpoint of further improving cohesion and adhesion, the polymer or copolymer may further contain a comonomer component.
In one aspect of the present invention, the acrylic resin is preferably a (meth) acrylic acid ester copolymer which is a copolymer of a main monomer component and a functional group-containing monomer component, and the pressure-sensitive adhesive composition It is preferable to include a crosslinking agent together with the (meth) acrylic acid ester copolymer.

(Acrylic resin)
The main monomer component is, for example, an acrylic having 1 to 20 carbon atoms having an alkyl group such as butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate, benzyl acrylate, methoxyethyl acrylate and the like And alkyl esters of alkyl groups such as alkyl methacrylates, alkyl methacrylates such as butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate.
As the main monomer component, one type may be used alone, or two or more types may be used in combination.
Also, butyl acrylate and 2-ethylhexyl acrylate, which are monomers having an alkyl group having 4 to 8 carbon atoms, are preferable as the main monomer component, and butyl acrylate is more preferable.
The content of the constituent unit derived from the main monomer component is preferably 70 to 100% by mass, more preferably 80 to 99.9% by mass, based on the total constituent units (100% by mass) of the acrylic polymer or the acrylic copolymer. More preferably, it is 90-99.5 mass%.

The functional group-containing monomer component preferably contains at least one of a hydroxyl group, a carboxyl group, and an amino group as a functional group, and more preferably contains a hydroxyl group.
Specific examples include (meth) acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth) acrylic acid and 2-hydroxypropyl (meth) acrylic acid; monomethyl aminoethyl (meth) acrylic acid, (meth) acrylic acid mono Examples include monoalkylaminoalkyl (meth) acrylates such as ethylaminoethyl; and ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and maleic acid.
The functional group-containing monomer component is preferably 2-hydroxyethyl (meth) acrylate.
The content of the structural unit derived from the functional group-containing monomer component with respect to the total structural unit (100% by mass) of the acrylic copolymer is the viewpoint of the reactivity with the crosslinking agent, and the flexibility and adhesion durability of the pressure-sensitive adhesive layer. From the viewpoint of improvement, it is preferably 0.01 to 10% by mass, more preferably 0.05 to 7.0% by mass, and still more preferably 0.2 to 6.0% by mass.

Comonomer components are, for example, methyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acetate, styrene and acrylonitrile.
A comonomer component may be used individually by 1 type, and may use 2 or more types together.

  In one aspect of the present invention, a constituent unit derived from a main monomer component and a constituent unit derived from a functional group-containing monomer component with respect to all constituent units (100% by mass) of a (meth) acrylic acid ester copolymer preferable as an acrylic resin The total content of is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass, still more preferably 95 to 100% by mass.

  There is no restriction | limiting in particular about the copolymerization form of acrylic copolymers, such as an acrylic acid ester copolymer contained in an adhesive composition, It is any of a random copolymer, a block copolymer, and a graft copolymer. May be

  The mass average molecular weight (Mw) of the acrylic polymer and acrylic copolymer such as acrylic ester copolymer contained in the pressure-sensitive adhesive composition has sufficient adhesion and adhesion durability to the adherend, and Are preferably 300,000 or more, more preferably 400,000 to 2,000,000, and even more preferably 500,000 to 1,800,000, from the viewpoints of preventing the generation of floating and peeling more effectively. Is more preferred.

  The acrylic polymer may be used in combination of two or more kinds, and two or more kinds of acrylic copolymers such as acrylic acid ester copolymer may be used in combination. In addition, two or more types of acrylic copolymers such as an acrylic polymer and an acrylic ester copolymer may be used in combination.

(Crosslinking agent)
In one aspect of the present invention, when the pressure-sensitive adhesive composition has a functional group-containing monomer component as a constituent unit, as in the above-mentioned acrylic acid ester copolymer, it is preferable that the pressure-sensitive adhesive composition contains a crosslinking agent.
As a crosslinking agent, an isocyanate compound, an epoxy-type compound, a metal chelate compound, a metal alkoxide, a metal salt, an amine compound, a hydrazine compound, an aldehyde compound etc. are mentioned.
One of these crosslinking agents may be used alone, or two or more thereof may be used in combination.
Moreover, as a crosslinking agent, an isocyanate compound is preferable.
Content of a crosslinking agent is suitably adjusted with the number of the functional groups which the said acrylic acid ester copolymer has. For example, the amount is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 8 parts by mass, still more preferably 1 to 6 parts by mass with respect to 100 parts by mass of the acrylic acid ester copolymer having the functional group-containing monomer component. It is a mass part.

(Other additives)
In one aspect of the present invention, the pressure-sensitive adhesive composition may contain, in addition to the crosslinking agent, an additive for a pressure-sensitive adhesive used in a general pressure-sensitive adhesive, as long as the effects of the present invention are not impaired. .
Such an additive for an adhesive may be appropriately selected according to the type of adhesive resin to be used, and for example, a silane coupling agent, an antistatic agent, a tackifier, an antioxidant, an ultraviolet absorber, A light stabilizer, a softener, a filler, a refractive index modifier, a colorant and the like may be contained.

(Dilution solvent)
Examples of the dilution solvent used to prepare the solvent type pressure-sensitive adhesive composition include toluene, xylene, t-butanol, acetone, methyl ethyl ketone, tetrahydrofuran, ethyl acetate and the like.
One of these dilution solvents may be used alone, or two or more thereof may be used in combination.
As the organic solvent used as the dilution solvent, the organic solvent used in the synthesis of the adhesive resin may be used as it is, or the organic solvent used in the synthesis of the adhesive resin can be uniformly applied. A solvent and / or one or more other organic solvents may be added.

In addition, an azo compound, an organic peroxide, etc. are mentioned as a polymerization initiator used when superposing | polymerizing an acryl-type polymer and an acryl-type copolymer.
The polymerization initiator may be used alone or in combination of two or more.
As an azo compound which can be used as a polymerization initiator, for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (2) Cyclohexane 1-carbonitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2′-azobis (2-methyl propionate), 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2- ( 2-Imidazolin-2-yl) propane] etc. are mentioned.
Among these, 2,2'-azobisisobutyronitrile is preferable.

<Solvent-free type pressure-sensitive adhesive composition>
When the pressure-sensitive adhesive composition is solventless, the pressure-sensitive adhesive composition is a polymer (X1) of (meth) acrylic acid ester having a radically polymerizable unsaturated double bond group at a side chain, (meth) acrylate oligomer It is preferable to contain at least one selected from (X2) and (meth) acrylic acid ester monomers (X3), and a photopolymerization initiator (Y).

(Acrylic resin)
As a polymer (X1) of (meth) acrylic acid ester, what has a polymer structure of (meth) acrylic acid ester and has a radically polymerizable unsaturated double bond in the side chain of this polymer structure is mentioned.
Specifically, in the copolymer (X1a) of the main monomer component and the comonomer component mentioned in the section of the solvent-type pressure-sensitive adhesive composition and the monomer having a functional group having active hydrogen, the functional having the active hydrogen It is preferable that a radically polymerizable unsaturated double bond is introduced to the group.
The number of the radically polymerizable unsaturated double bond groups is preferably 2 or more from the viewpoint of enhancing the strength and cohesion of the pressure-sensitive adhesive layer.

  As a monomer which has a functional group which has active hydrogen, the monomer which has functional groups, such as a hydroxyl group, an amino group, a carboxyl group, is mentioned, for example. Specifically, the same compounds as the functional group-containing monomer components listed in the section of the solvent-based pressure-sensitive adhesive composition can be used.

  A copolymer is obtained by polymerizing each of the above-mentioned monomer components according to a conventional method. As the copolymer (X1a), one type may be used alone, or two or more types may be used in combination.

  The introduction of the radically polymerizable unsaturated double bondable group into the functional group having active hydrogen for the copolymer (X1a) has, for example, both a radically polymerizable unsaturated double bond and an active hydrogen reactive group It can be carried out by subjecting the compound to an addition reaction. As said active hydrogen reactive group, an isocyanate group, glycidyl group etc. are mentioned, for example.

  Specific examples of the compound having both a radically polymerizable unsaturated double bond and an active hydrogen reactive group include acryloyloxyethyl isocyanate, acryloyloxypropyl isocyanate, methacryloyloxyethyl isocyanate, methacryloyloxypropyl isocyanate, allyl isocyanate, Glycidyl (meth) acrylate etc. are mentioned preferably.

  The above addition reaction is preferably performed, for example, at a temperature of 25 to 60 ° C. for about 6 to 48 hours. In the above addition reaction, it is also preferable to use, as a catalyst, an organic tin compound such as dibutyltin dilaurate, a substituted amine compound, or the like, as necessary.

Examples of the (meth) acrylate oligomer (X2) include various (meth) acrylate oligomers such as urethane (meth) acrylate oligomers, epoxy (meth) acrylate oligomers, polyester (meth) acrylate oligomers, and polyether (meth) acrylate oligomers. Etc.
Among these, urethane (meth) acrylate oligomers can be preferably used. The urethane (meth) acrylate oligomer can be obtained, for example, by esterifying a polyurethane oligomer obtained by the reaction of a polyether polyol or a polyester polyol with a polyisocyanate by a reaction with (meth) acrylic acid.
As the (meth) acrylate oligomer (X2), one type may be used alone, or two or more types may be used in combination.
Moreover, the polymer (X1) of (meth) acrylic acid ester and the (meth) acrylate oligomer (X2) can also be used together.

  The mass average molecular weight (Mw) of the (meth) acrylic acid ester polymer (X1) and the (meth) acrylate oligomer (X2) is respectively 20,000 or more, preferably 25,000 to 80,000, More preferably, it is 30,000 to 60,000.

  As the (meth) acrylic acid ester monomer (X3), for example, a monomer constituting the polymer (X1) of the (meth) acrylic acid ester, or a multiple having two or more reactive sites such as a carbon-carbon double bond And functional acrylates.

  Specific examples of the polyfunctional acrylate include, for example, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene Bifunctional types such as oxide-modified phosphoric acid di (meth) acrylate; trifunctional types such as trimethylolpropane tri (meth) acrylate and dipentaerythritol tri (meth) acrylate; diglycerin tetra (meth) acrylate, pentaerythritol tetra ( 4-functional type such as meta) acrylate; 5-functional type such as propionic acid modified dipentaerythritol penta (meth) acrylate; dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate Hexafunctional type such as bets and the like.

When a polymer (X1) of a (meth) acrylic acid ester or a (meth) acrylate oligomer (X2) is used as a main raw material and the non-solvent type pressure-sensitive adhesive composition has a high viscosity, (meth) acrylic acid The ester monomer (X3) may be added to reduce the viscosity of the solventless pressure-sensitive adhesive composition and to improve the coatability.
The (meth) acrylic acid ester monomer (X3) is a mixture of (meth) acrylic acid ester monomers (X3) with each other by ultraviolet irradiation, or the polymer (X1) of the above (meth) acrylic acid ester and / or the above (meth) acrylate oligomer ( In order to form a crosslinked structure with X2), the cohesive force of the obtained pressure-sensitive adhesive layer can be enhanced, and the occurrence of problems such as exudation can be effectively prevented.

(Photopolymerization initiator)
The non-solvent type pressure-sensitive adhesive composition can efficiently cure the ultraviolet curable component in the non-solvent type pressure-sensitive adhesive composition by containing the photopolymerization initiator (Y), and the polymerization curing time and the ultraviolet light The radiation dose of can be reduced.

As the photopolymerization initiator (Y), for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, Benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylamino Examples thereof include benzoic acid ester and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide.
One of these may be used alone, or two or more of these may be used in combination.

  The content of the photopolymerization initiator (Y) contained in the solventless pressure-sensitive adhesive composition is the polymer (X1) of (meth) acrylic acid ester, the (meth) acrylate oligomer (X2) and the (meth) acrylic acid ester It is preferable that it is 0.01-10 mass parts with respect to a total of 100 mass parts of a monomer (X3), It is more preferable that it is 0.1-5 mass parts, It is 0.2-2 mass parts Is more preferred.

(Other additives)
In one aspect of the present invention, the solventless pressure-sensitive adhesive composition contains an additive for pressure-sensitive adhesive used in a general pressure-sensitive adhesive, in addition to the crosslinking agent, as long as the effects of the present invention are not impaired. May be
Examples of such additives for pressure-sensitive adhesives include the additives exemplified in the section of solvent-type or emulsion-type pressure-sensitive adhesive composition.

[Physical Properties of Substrateless Double-sided Adhesive Sheet]
<Peeling force of light peeling film and heavy peeling film>
In the substrate-less double-sided pressure-sensitive adhesive sheet of the present invention, the peelability of the light release film is smaller than the peel force of the heavy release film.
Here, in one aspect of the present invention, the peeling force and the weight of the light peeling film are more preferable from the viewpoint of better suppressing the transfer which occurs when the difference between the peeling force of the heavy peeling film and the peeling force of the light peeling film is small. The absolute value of the difference in peel force of the release film is preferably 5 m / 25 mm or more, more preferably 10 mN / 25 mm or more, and still more preferably 20 mN / 25 mm or more.

In addition, in one aspect of the present invention, the peeling power of the heavy peeling film is preferably from the viewpoint of suppressing transfer adhesion which occurs when the difference between the peeling power of the heavy peeling film and the peeling power of the light peeling film is small. Of 30 to 300 mN / 25 mm, more preferably 50 to 200 mN / 25 mm, still more preferably 50 to 100 mN / 25 mm.
The peeling force of the heavy release film can be adjusted by the selection of the forming material of the composition (B) for forming a silicone resin layer and the compounding amount of the heavy release additive.

Further, in one aspect of the present invention, also from the viewpoint of increasing the absolute value of the difference between the peeling force of the light peeling film and the peeling force of the heavy peeling film even when the peeling force of the heavy peeling film to the pressure-sensitive adhesive layer is suppressed. The peel strength of the light release film is preferably 10 to 200 mN / 25 mm, more preferably 15 to 100 mN / 25 mm, and still more preferably 20 to 80 mN / 25 mm.
The peel strength of the light release film can be adjusted by the selection of the forming material of the composition (A) for forming a silicone resin layer.
In addition, said peeling force is a value measured by the normal area | region in which spot transfer does not arise in all.

[Production method of substrateless double-sided pressure-sensitive adhesive sheet]
The method for producing the substrate-less double-sided pressure-sensitive adhesive sheet of the present invention is not particularly limited. For example, first, a light release film in which a first silicone resin layer is formed on a first biaxially stretched polyester film, and a second A heavy release film in which a second silicone resin layer is formed on a biaxially stretched polyester film is prepared. Next, when using the above-mentioned solvent type pressure-sensitive adhesive composition, the solvent type pressure-sensitive adhesive composition is applied on the first silicone resin layer of the light release film by a known method, and then heated and dried. Form a coating. Next, the surface of the second release film on the second silicone resin layer side is bonded onto the coating film, and subjected to an aging treatment, whereby a substrateless double-sided pressure-sensitive adhesive sheet can be obtained.
Examples of the method for applying the pressure-sensitive adhesive composition include spin coating, spray coating, bar coating, knife coating, roll coating, roll knife coating, blade coating, die coating, and gravure coating. It can be mentioned.

The light release film is formed by applying the composition for forming a silicone resin layer (A) on the bonding surface of the first biaxially stretched polyester film with the pressure-sensitive adhesive layer, heating and drying.
Similarly, the heavy release film is formed by applying the composition for forming a silicone resin layer (B) on the bonding surface of the second biaxially oriented polyester film to the pressure-sensitive adhesive layer, heating and drying.
As a method of applying the composition (A) or (B) for forming a silicone resin layer to the first or second biaxially oriented polyester film, for example, a gravure coating method, a bar coating method, a spray coating method, a spin coating method, Examples thereof include an air knife coating method, a roll coating method, a blade coating method, a gate roll coating method, and a die coating method. Among these, the gravure coating method and the bar coating method are preferable, and the bar coating method is more preferable.
Moreover, as a heating method and drying method of composition (A) or (B) for silicone resin layer formation, the method of heat-drying etc. in a hot air drying furnace etc. is mentioned, for example.
The drying temperature is, for example, 50 ° C. or more and 150 ° C. or less.
The drying time is, for example, 10 seconds to 5 minutes.

  The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

  Physical property values in the following Examples and Comparative Examples are values measured by the following methods.

[Micro-melting heat peak]
In accordance with JIS K 7121 (1999), the peak of the heat of fine melting was measured by the following method using a differential scanning calorimeter (Model DSC Q2000, manufactured by TA Instruments Japan).
5 mg of the sample was weighed into a sample pan, and the sample was heated from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min. At this time, it is observed on the lower end side of the temperature of the endothermic peak attributed to the melting of the sample and at the top of the micropeak existing in the vicinity of the endothermic peak or in the endothermic peak The peak of the micro shoulder was taken as the micro melting heat peak (° C.).
An example of the measurement result (peak temperature: 210 ° C.) of the micro melting calorimetry peak of the biaxially stretched PET film is shown in FIG. Further, FIG. 4 shows an enlarged view of the minute melting heat energy peak portion in FIG.
In addition, in FIG. 3, Tmp is melting | fusing point (260 degreeC) of a biaxially stretched PET film, and Tmeta is a micro melting calorie peak.

[Measurement of thickness of each layer]
The thickness of the silicone resin layer was measured using a spectral ellipsometer (manufactured by JA Woollam Japan Co., Ltd., product name “Spectroscopic Ellipsometry 2000 U”).
The thickness of the other layer was measured using a constant pressure thickness measuring instrument (model number: “PG-02J”, standard standard: in accordance with JIS K6783, Z1702, Z1709) manufactured by Teclock Co., Ltd.

[Mass average molecular weight]
It measured on condition of the following using the gel permeation chromatograph apparatus (Tosoh Corp. make, product name "HLC-8020"), and the value measured by standard polystyrene conversion was used.
(Measurement condition)
・ Column: “TSK guard column HXL-L”, “TSK gel G2500 HXL”, “TSK gel G2000 HXL”, “TSK gel G1000 HXL” (all manufactured by Tosoh Corporation) • Column temperature: 40 ° C.
-Developing solvent: tetrahydrofuran-Flow rate: 1.0 mL / min

  The pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer, the composition for forming a silicone resin layer (A) for forming a first silicone resin layer, and the second used in the following Examples and Comparative Examples The composition (B) for silicone resin layer formation for forming a silicone resin layer was prepared by the following method.

[Adhesive composition]
95.0 parts by mass of n-butyl acrylate, 5.0 parts by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen introducing pipe And 0.08 parts by mass of 2,2′-azobisisobutyronitrile were charged, and the air in the reaction vessel was replaced with nitrogen gas. The reaction solution was heated to 60 ° C. with stirring under the nitrogen atmosphere, reacted for 16 hours, and cooled to room temperature. Here, a part of the obtained solution was subjected to GPC measurement to confirm the formation of a polymer (A) having a mass average molecular weight of 1,600,000. 100 parts by mass (solid content) of the polymer (A): 4 parts by mass of a polyisocyanate crosslinking agent (Nippon Polyurethane Industry Co., Ltd., trade name: Coronate L), and a silane coupling agent (Shin-Etsu Chemical Co., Ltd.) Brand name: KBM-403) What was further added and mixed with 0.1 mass part, toluene was further added as a solvent, solid content was adjusted to 15 mass%, and the adhesive composition was prepared.

[Composition for forming a silicone resin layer (A)]
100 parts by mass of a silicone-based mold release agent (Shin-Etsu Chemical Co., Ltd., KS 847H, solid content 30 mass%) containing an organopolysiloxane having a vinyl group and an organopolysiloxane having a hydrosilyl group and a platinum (Pt) catalyst A mixed solvent of toluene and methyl ethyl ketone (toluene / methyl ethyl ketone = 1/1 (mass ratio)) is added to 2 parts by mass of Shin-Etsu Chemical Co., Ltd. (PL-50T, solid content 2 mass%) to make the solid content 1 mass% The composition (A) for forming a silicone resin layer was prepared.

[Composition for forming silicone resin layer (B)]
100 parts by weight of a silicone-based mold release agent containing an organopolysiloxane having a vinyl group and an organopolysiloxane having a hydrosilyl group (by Toray Dow Corning, BY24-561, solid content: 30% by mass), heavy peeling 10 parts by mass of MQ resin (Toray Dow Corning, SD-7292, solid content 71% by mass) having a vinyl group as an additive, and a platinum (Pt) catalyst (Toray Dow Corning, SRX-212) A mixed solvent of toluene and methyl ethyl ketone (toluene / methyl ethyl ketone = 1/1 (mass ratio)) is added to 2 parts by mass of the solid content to adjust the solid content to 1 mass%, and a composition for forming a silicone resin layer The product (B) was prepared.

[Examples 1 to 3 and Comparative Examples 1 to 3]
The substrate-less double-sided pressure-sensitive adhesive sheets of Examples 1 to 3 and Comparative Examples 1 to 3 were produced by the following procedure.

Example 1
(Preparation of a light release film)
The composition (A) for forming a silicone resin layer is applied to a PET film A1 (micro melting heat peak: 170 ° C.) so that the film thickness after drying becomes 0.1 μm, and the first composition is formed on the PET film A1. The silicone resin layer was formed to prepare a light release film.

(Preparation of heavy release film)
The composition (B) for forming a silicone resin layer was coated on a PET film B (PET 38R-64, manufactured by Toray Industries, Inc.) so that the film thickness after drying would be 0.1 μm. A second silicone resin layer was formed to make a heavy release film.

(Production of substrate-less double-sided adhesive sheet)
The pressure-sensitive adhesive composition was applied onto the second silicone resin layer of the heavy release film so that the film thickness after drying was 20 μm, and dried to form a pressure-sensitive adhesive layer. Then, on the pressure-sensitive adhesive layer formed, a light release film was bonded such that the first silicone resin layer was in contact with the pressure-sensitive adhesive layer. Thereafter, it was aged for 7 days under conditions of a temperature of 23 ° C. and a relative humidity of 50% to prepare a substrateless double-sided pressure-sensitive adhesive sheet.

Example 2
A substrate-less double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the PET film A1 of the light release film was changed to a PET film A2 (micro melting calorie peak: 180 ° C.).

Example 3
A substrateless double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the PET film A1 of the light release film was changed to a PET film A3 (with a minute melting heat peak: 210 ° C.).

Comparative Example 1
A substrate-less double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the PET film A1 of the light release film was changed to a PET film A4 (micro melting calorific peak: 220 ° C.).

Comparative Example 2
A substrate-less double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the PET film A1 of the light release film was changed to a PET film A5 (micro melting heat peak: 230 ° C.).

Comparative Example 3
A substrate-less double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the heavy release film PET film B was changed to a light release film PET film A1.

  The following tests were implemented about the light exfoliation film and substrate-less double-sided adhesive sheet which comprise the substrate-less double-sided adhesive sheet of Examples 1-3 and Comparative Examples 1-3.

[Peeling force difference]
The peeling force X of the light peeling film and the peeling force Y of the heavy peeling film were measured by the following method in accordance with JIS-Z0237.
And the absolute value of the difference of the peeling force X and the peeling force Y was computed, and it was set as the peeling force difference (N / 25 mm).

<Peeling Force of Light Release Film X>
The substrate-less double-sided pressure-sensitive adhesive sheet was cut into a width of 25 mm and a length of 200 mm to prepare a test piece.
The heavy release film side of the test piece is fixed to a stainless steel (SUS) plate with a double-sided adhesive tape, and the light release film is pulled in a 180 ° direction at a peeling speed of 300 mm / min using a tensile tester. Peeling force X was measured.

<Peel force Y of heavy release film>
A 50 μm-thick PET film (“Lumirror T60” manufactured by Toray Industries, Inc.) is laminated to the adhesive layer exposed by peeling the light release film from the substrate-less double-sided adhesive sheet, and then cut into a width of 25 mm and a length of 200 mm. The test piece was made.
The heavy peel film side of the test piece is fixed to a stainless steel (SUS) plate with a double-sided adhesive tape, and the PET film and the pressure-sensitive adhesive layer are pulled in a 180 ° direction at a peel speed of 300 mm / min using a tensile tester. The peel force Y of the heavy release film was measured.

[Evaluation of the number of defects of repelling]
The number of repelling defects (number of repellings) of the light release films constituting the substrate-less double-sided pressure-sensitive adhesive sheets of Examples 1 to 3 and Comparative Examples 1 to 3 was calculated.
Specifically, the first silicone resin layer is formed by repelling when the first composition for forming a silicone resin layer (A) is applied to the PET films A1 to A5 and B constituting the light release film. the disadvantage of the compositions were counted by visual inspection, was calculated repelling number drawback per 1 m ^2.

[Evaluation of spot transfer]
The spot transfer produced by peeling the light release film of the substrate-less double-sided pressure-sensitive adhesive sheet of Examples 1 to 3 and Comparative Examples 1 to 3 was counted by visual inspection, and the number of spot transfers per 1 m ² was calculated. . And three-step evaluation was performed according to the following criteria.
:: The number of spot adhesions is less than 0.010 pieces / m ² ○: The number of spot adhesions is 0.010 pieces / m ² or more and 0.030 pieces / m ² or less ×: The number of spot adhesions is 0.030 / m ² Also, before the spot transfer evaluation, it is examined whether there is a planar transfer that occurs when the difference between the peel force of the heavy release film and the peel force of the light release film is small. The sample in which the planar transfer did not occur was rated as ○, and the sample in which the planar transfer occurred was ×. The evaluation of the spot transfer was not performed for the sample in which the planar transfer occurred.

  The results are shown in Table 1.

From Table 1, the following can be seen.
It can be seen that the number of spot adhesions matches the number of repelling defects. From this, it is understood that repelling that occurs when the composition for forming a silicone resin layer is applied on a PET film is a factor of spot transfer.
Further, from Comparative Examples 1 and 2 in Table 1, it is understood that the number of repelling defects increases and the spot transfer also increases when the micro melting heat energy peak of the PET film constituting the light release film is 220 ° C. or higher.
On the other hand, it is understood from Examples 1 to 3 that the number of repelling defects decreases and the spot transfer also decreases if the micro-melting calorific peak of the PET film constituting the light release film is less than 220 ° C.
In particular, it is understood from Examples 1 and 2 that the number of repelling defects is significantly reduced and the spot transfer is also significantly reduced when the micro melting heat energy peak of the PET film constituting the light release film is 180 ° C. or less. .

10, 20 substrate-less double-sided pressure-sensitive adhesive sheet 11, 21 light release film 12, 22 double release film 1, 23 pressure-sensitive adhesive layer 2 first biaxially stretched polyester film 3 first silicone resin layer 4 second biaxially stretched Polyester film 5 Second silicone resin layer 23a Stretched adhesive 23b Spot-like residual adhesive

Claims (5)

A substrateless double-sided pressure-sensitive adhesive sheet comprising a light release film, a pressure-sensitive adhesive layer provided on the light release film, and a heavy release film provided on the pressure-sensitive adhesive layer,
The light release film has a first biaxially stretched polyester film, and a first silicone resin layer provided on a bonding surface of the first biaxially stretched polyester film with the pressure-sensitive adhesive layer,
The heavy release film has a second biaxially oriented polyester film, and a second silicone resin layer provided on the bonding surface of the pressure sensitive adhesive layer of the second biaxially oriented polyester film,
The substrate-less double-sided pressure-sensitive adhesive sheet, wherein the micro melting calorie peak temperature of the first biaxially stretched polyester film is less than [Tmp-40] ° C (Tmp: melting point of polyester). Both the first biaxially oriented polyester film and the second biaxially oriented polyester film are biaxially oriented polyethylene terephthalate films,
The substrate-less double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the micro melting calorie peak temperature of the first biaxially stretched polyester film is less than 220 ° C.   3. The substrate-less according to claim 1, wherein an absolute value of a difference between the peeling force of the light release film to the pressure-sensitive adhesive layer and the peel force of the heavy release film to the pressure-sensitive adhesive layer is 5 mN / 25 mm or more. Double-sided adhesive sheet.   The substrate-less double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer has a thickness of 1 to 250 μm.   The substrate-less double-sided according to any one of claims 1 to 4, wherein the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film are both 19 to 188 μm. Adhesive sheet.