JP7036488B2 - Substrate-less double-sided adhesive sheet - Google Patents

Description

The present invention relates to a base material-less double-sided adhesive sheet.

Various adhesive sheets for surface-bonding between objects have been conventionally known, and a base material-less double-sided adhesive sheet is known as one of the adhesive sheets.
In the base material-less double-sided pressure-sensitive adhesive sheet, the light peeling film having a relatively low peeling force against the pressure-sensitive adhesive layer and the peeling power against the pressure-sensitive adhesive layer are relative to both sides of the pressure-sensitive adhesive layer having no base material as a core material. It is configured by laminating each of a high-weight release film.
In the base material-less double-sided adhesive sheet, the light release film is first peeled off, and one surface of the exposed adhesive layer is adhered to the object surface. The heavy release film is then peeled off and the other surface of the exposed pressure-sensitive adhesive layer is adhered to different object surfaces, thereby surface-adhering between the objects.

By the way, as a problem of the base material-less double-sided adhesive sheet, when the light release film is peeled off, the adhesive layer is stretched and pulled between the heavy release film and the light release film following the light release film. It is possible that the stretched adhesive breaks and the adhesive layer that should originally remain on the heavy release film side is transferred to the light release film side in a planar manner, resulting in peeling failure.
Poor peeling due to such surface transfer is caused by the peeling force of the heavy-release film against the pressure-sensitive adhesive layer (hereinafter, also referred to as "peeling force of the heavy-release film") and the peeling force of the light-release film against the pressure-sensitive adhesive layer (hereinafter referred to as "peeling force"). , Also referred to as "peeling force of light release film"), which tends to occur when the difference is small.
Therefore, it has been conventionally practiced to increase the difference between the peeling force of the heavy release film and the peeling force of the light release film (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 07-041736

However, in the base material-less double-sided adhesive sheet, peeling defects different from peeling defects due to planar transfer may occur.
As a result of various studies on a substrate-less 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, the present inventors have made light peeling. It has been found that when the film is peeled off, minute spot-like transfer (hereinafter, also referred to as "spot transfer"), which is a peeling defect different from the above-mentioned transfer, may occur.
Spot transfer is a factor that causes minute defects in the pressure-sensitive adhesive layer. Since the base material-less double-sided pressure-sensitive adhesive sheet is used for applications such as bonding of optical films, it is desired to suppress the generation of minute defects in the pressure-sensitive adhesive layer as much as possible.

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

The present inventors have solved the above problems by using a biaxially stretched polyester film in which the peak temperature of the minute heat of melting is equal to or lower than a specific temperature as the polymer film constituting the light release film of the base material-less double-sided pressure-sensitive adhesive sheet. I found that it could be done.

That is, the present invention relates to the following [1] to [5].
[1] A substrate-less 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-weight 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 the bonding surface of the first biaxially stretched polyester film with the adhesive layer.
The heavy release film has a second biaxially stretched polyester film and a second silicone resin layer provided on the bonding surface of the second biaxially stretched polyester film with the adhesive layer.
A substrate-less double-sided pressure-sensitive adhesive sheet in which the peak temperature of the minute heat of fusion 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 base material-less double-sided pressure-sensitive adhesive sheet according to the above [1], wherein the peak temperature of the minute heat of fusion of the first biaxially stretched polyester film is less than 220 ° C.
[3] The absolute value of the difference between the peeling force of the light release film with respect to the pressure-sensitive adhesive layer and the peeling force of the heavy-release film with respect to the pressure-sensitive adhesive layer is 5 mN / 25 mm or more, the above [1] or [2]. Substrate-less double-sided adhesive sheet described in.
[4] The base material-less double-sided pressure-sensitive adhesive sheet according to any one of the above [1] to [3], wherein the pressure-sensitive adhesive layer has a thickness of 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 both 19 to 188 μm. The base material-less double-sided adhesive sheet described.

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

It is sectional drawing which shows one Embodiment of the base material-less double-sided adhesive sheet of this invention. It is a conceptual diagram of the spot transfer which can occur in the base material-less double-sided adhesive sheet. It is a figure which shows an example of the measurement result of the minute heat-for-melting peak of a biaxially stretched polyethylene terephthalate film. FIG. 3 is an enlarged view of the minute heat of melting peak in FIG.

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

Further, in the present specification, for example, "(meth) acrylic acid" means both "acrylic acid" and "methacrylic acid", and other similar terms are also used.

[Structure of double-sided adhesive sheet without base material]
The base material-less double-sided adhesive sheet of the present invention has a light release film, an adhesive layer provided on the light release film, and a heavy release film provided on the adhesive layer.
The light release film has a first biaxially stretched polyester film and a first silicone resin layer provided on the bonding surface of the first biaxially stretched polyester film with an adhesive layer.
The double-release film has a second biaxially stretched polyester film and a second silicone resin layer provided on the bonding surface of the second biaxially stretched polyester film with an adhesive layer.
The pressure-sensitive adhesive layer does not have a base material as a core material.

Examples of the base material-less double-sided pressure-sensitive adhesive sheet according to one aspect of the present invention include the base material-less double-sided pressure-sensitive adhesive sheet 10 shown in FIG.
The base material-less double-sided 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 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 together without interposing another layer.
The double-release film 12 has a second biaxially stretched polyester film 4 and a second silicone resin layer 5 provided on the bonding surface of the second biaxially stretched polyester film 4 with the pressure-sensitive adhesive layer 1. .. The second biaxially stretched polyester film 4 and the pressure-sensitive adhesive layer 1 are bonded together without interposing another layer.
In the base material-less double-sided pressure-sensitive adhesive sheet of one aspect of the present invention, between the first biaxially stretched polyester film 2 and the first silicone resin layer 3, and between the second biaxially stretched polyester film 4 and the second. Another layer may be provided between the second silicone resin layer 5. Examples of the other layer include an antistatic layer and an anchor layer.

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 even more preferably 10 to 175 μm from the viewpoint of productivity and cost. ..

Further, 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. From the viewpoint of facilitating the suppression of light leakage, the orientation angle is uniformly lowered over the width direction of the biaxially stretched polyester film to prevent light leakage during inspection by the cross Nicol method, and the inspection property by the Cross Nicol method. From the viewpoint of making the above-mentioned better, it is preferably 19 μm or more, more preferably 25 μm or more, and further preferably 30 μm or more. Further, all of them are preferably 188 μm or less, more preferably 125 μm or less, further preferably 100 μm or less, further preferably 50 μm or less, still more preferably 48 μm or less.
In one aspect of the present invention, when the base material-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 19. It is preferably 50 μm, more preferably 25 to 48 μm.
Further, in one aspect of the present invention, when the base material-less double-sided adhesive sheet is used for a touch panel, 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. It is preferably 38 to 125 μm, and more preferably 38 to 125 μm.

Further, in one aspect of the present invention, the thickness of the first silicone resin layer at the time of drying and the thickness of the second silicone resin layer at the time of drying have variations in the peeling force due to fluctuations in the coating amount of the composition for forming the silicone resin layer. From the viewpoint of suppressing and suppressing blocking, both are preferably 40 nm to 1 μm, more preferably 50 nm to 0.5 μm, and even more preferably 60 nm to 0.3 μm.

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

The shape of the base material-less double-sided pressure-sensitive adhesive sheet according to one aspect of the present invention includes, for example, a square, a rectangle, a polygon, a circle, an annular shape, and the like, but the shape is not limited to these shapes, and the base material is not used. It is appropriately selected according to the use of the double-sided adhesive sheet.
Further, the base material-less double-sided pressure-sensitive adhesive sheet according to one aspect of the present invention may be, for example, a wound body obtained by winding a long base material-less double-sided pressure-sensitive adhesive sheet in a roll shape or a winding body wound around a core material.

Hereinafter, the light release film, the heavy release film, and the pressure-sensitive adhesive layer constituting the base material-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 stretched polyester film and a first silicone resin layer provided on the bonding surface of the first biaxially stretched polyester film with an adhesive layer.
Further, the heavy release film has a second biaxially stretched polyester film and a second silicone resin layer provided on the bonding surface of the second biaxially stretched polyester film with the pressure-sensitive adhesive layer.

<First biaxially stretched polyester film>
The first biaxially stretched polyester film is a biaxially stretched polyester film having a micro-melting calorific value peak temperature of less than [Tmp-40] ° C. (Tmp: melting point of polyester).
The biaxially stretched polyester film is produced by subjecting a polyester film to a biaxially stretched treatment and then a heat fixing treatment.
Examples of the method of biaxially stretching the polyester film include 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, and a method of stretching in the longitudinal direction and stretching in the width direction. Examples thereof include a method in which stretching is performed a plurality of times in combination, and a method called simultaneous biaxial stretching in which stretching in the longitudinal direction and stretching in the width direction are performed at the same time.
The heat fixing treatment is performed by heating at a temperature lower than the melting point of polyester using an oven or the like. By performing the heat fixing treatment, the shrinkage of the biaxially stretched polyester film can be suppressed, and the dimensional stability can be improved.
Examples of the first biaxially stretched polyester film include biaxially stretched polyethylene terephthalate film, biaxially stretched polybutylene terephthalate film, and biaxially stretched polyethylene naphthalate film. 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 various studies on a substrate-less double-sided pressure-sensitive adhesive sheet having a light-release film having a silicone resin layer formed on the bonding surface of the biaxially stretched polyester film with the pressure-sensitive adhesive layer, the present inventors peel off the light-release film. At that time, it was found that spot transfer, which is a peeling defect different from the planar transfer that occurs when the difference between the peeling force of the heavy release film and the peeling force of the light release film is small, may occur.
FIG. 2 shows a conceptual diagram of a base material-less double-sided adhesive sheet in which spot transfer occurs. When the light release film 21 of the base material-less double-sided adhesive sheet 20 is peeled off from the pressure-sensitive adhesive layer 23, some minute portions of the pressure-sensitive adhesive layer 1 follow the light release film 21, and the light release film 21 and the heavy release film 22 Is stretched between and. A part of the stretched pressure-sensitive adhesive 23a did not peel off at the interface between the light release film 21 and the pressure-sensitive adhesive layer 23, and the stretched pressure-sensitive adhesive 23a broke, resulting in the stretched pressure-sensitive adhesive. Of the 23a, the pressure-sensitive adhesive located on the light release film 21 side of the broken portion remains on the light release film 21 and becomes a spot-shaped residual pressure-sensitive adhesive 23b. Further, the pressure-sensitive adhesive located on the pressure-sensitive adhesive layer 23 side of the stretched pressure-sensitive adhesive 23a may cause minute defects on the pressure-sensitive adhesive layer 23.
It should be noted that such spot transfer does not occur in the double-sided adhesive tape in which the base material serving as the core material is present in the adhesive layer. Further, when the heavy release film of the base material-less double-sided adhesive sheet is peeled off, the adherend is attached to the exposed surface of the pressure-sensitive adhesive layer after the light release film is peeled off, and the adherend is a support. As it functions as, the problem of spot transfer does not occur. That is, the problem of spot transfer is a problem peculiar to peeling the light release film, which occurs because the base material-less double-sided adhesive sheet does not have a core material.

As a result of investigating the cause of the spot transfer, the present inventors rarely generate repellent 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 stretched polyester film were in contact with each other without interposing the silicone resin layer at the minute portion where the above occurred. Then, in the minute portion where the pressure-sensitive adhesive layer and the biaxially stretched polyester film are in contact with each other, when the light release film is peeled off, the pressure-sensitive adhesive layer does not peel off from the light release film at the minute portion and follows the light release film. As a result of the stretching, we have found that spot transfer can occur.
That is, regardless of the peeling force of the light peeling film or the peeling force of the heavy peeling film, it is found that spot transfer may occur due to a rare application abnormality such as repelling of the silicone resin layer forming composition. It came to.

Further, as a result of various studies, the present inventors found that when the heat fixing treatment temperature of the biaxially stretched polyester film was high, the monomer components and oligomer components constituting the polyester film sublimated during the heat fixing treatment and the oven. It was found that these adhered to the inside and could fall on the biaxially stretched polyester film during the heat-fixing treatment or after the heat-fixing treatment to become adhered foreign matter.
For example, when the polyester film is a PET film, if the heat fixing treatment temperature of the biaxially stretched polyester film is high, terephthalic acid or an oligomer component may be present as adhered foreign matter on the surface of the PET film.
The present inventors considered that these adhered foreign substances are the cause of repelling when the composition for forming a silicone resin layer is applied to a biaxially stretched polyester film. Therefore, by lowering the heat fixing treatment temperature, the monomer components and oligomer components constituting the polyester film are suppressed from sublimating and adhering to the oven, and the adhering foreign matter on the biaxially stretched polyester film is reduced. , I thought about suppressing the above-mentioned repellent.
Here, the heat fixing treatment temperature has a correlation with the micromelt heat quantity peak temperature, and the higher the temperature at the time of performing the heat fixing treatment, the higher the micromelt calorific value peak temperature, and the lower the temperature at the time of performing the heat fixing treatment. The smaller the temperature of the minute heat of fusion peak, the lower the temperature. Therefore, as a result of various studies focusing on the peak temperature of the minute heat of melting, the present inventors have conducted biaxially stretched polyester having the peak temperature of the minute heat of melting less than [Tmp-40] ° C. (Tmp: melting point of polyester). By using the film, foreign matter adhering to the biaxially stretched polyester film can be significantly reduced, and repelling when the composition for forming a silicone resin layer is applied to the biaxially stretched polyester film can be suppressed, and light peeling can be performed. It has been found that spot transfer can be suppressed when the film is peeled off.

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

Here, the peak temperature of the minute heat of fusion of the first biaxially stretched polyester film is preferably [Tmp-45] ° C. or lower, from the viewpoint of better suppressing spot transfer when peeling the light release film. It is preferably [Tmp-50] ° C. or lower, more preferably [Tmp-60] ° C. or lower, even more preferably [Tmp-70] ° C. or lower, still more preferably [Tmp-80] ° C. or lower, and particularly preferably [Tmp-80] ° C. or lower. -90] ° C or lower.
The lower limit of the micromelt heat peak temperature of the first biaxially stretched polyester film corresponds to the lower limit of the heat fixing treatment temperature capable of suppressing the shrinkage of the first biaxially stretched polyester film. Any temperature may be sufficient, and it is usually [Tmp-100] ° C.

When the first biaxially stretched polyester film is a biaxially stretched PET film, the micromelt heat peak temperature is less than 220 ° C., preferably 215 ° C. or lower, more preferably 210 ° C. or lower, still more preferably 200 ° C. ° C. or lower, more preferably 190 ° C. or lower, even more preferably 180 ° C. or lower, and particularly preferably 170 ° C. or lower.
The lower limit of the peak temperature of the minute heat of fusion of the biaxially stretched PET film is usually 160 ° C.

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

<First silicone resin layer>
The first silicone resin layer has a function of imparting peelability from the pressure-sensitive adhesive layer to the light release film.
The first silicone resin layer is a release layer containing a silicone resin, but may contain an additive for a 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 the silicone resin layer forming composition (A) containing a silicone-based mold release agent.
Hereinafter, each component contained in the silicone resin layer forming composition (A), which is a material for forming the first silicone resin layer, will be described.

(Silicone mold release agent)
As the silicone release agent, a silicone release agent containing 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 curable type such as an ultraviolet curable type and an electron beam curable type, but an addition reaction type silicone resin is preferable.
The addition reaction type silicone resin has merits such as high reactivity and excellent productivity, a small change in peeling force after production, and no curing shrinkage as compared with the condensation reaction type.

As a specific example of the addition reaction type silicone resin, an organon having two or more alkenyl groups having 2 to 10 carbon atoms such as a vinyl group, an allyl group, a propenyl group, and a hexenyl group at the terminal and / or side chain of the molecule. Examples include polysiloxane.
When using such an addition reaction type silicone resin, it is preferable to use a cross-linking agent and a catalyst in combination.

(Crosslinking agent)
Examples of the cross-linking agent include organopolysiloxane having a hydrogen atom bonded to at least two silicon atoms in one molecule.
Specific examples of the cross-linking agent include dimethylhydrogensiloxy group-terminated closure dimethylsiloxane-methylhydrogensiloxane copolymer, trimethylsiloxy group-terminated closure dimethylsiloxane-methylhydrogensiloxane copolymer, and trimethylsiloxy group-terminated closure methylhydrogen. Examples thereof include polysiloxane and poly (hydrogencil sesquioxane).

(catalyst)
Examples of the catalyst include fine particle platinum, fine particle platinum adsorbed on a carbon powder carrier, platinum chloride acid, alcohol-modified platinum chloride acid, an olefin complex of platinum chloride acid, palladium, and platinum group metal compounds such as rhodium. Can be mentioned.
By using such a catalyst, the curing reaction of the silicone resin layer forming composition (A) can proceed 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 effect of the present invention is not impaired.
Examples of such additives include dyes and dispersants.

(Diluting solvent)
The composition (A) for forming a silicone resin layer may contain a diluting solvent together with the above-mentioned various active ingredients from the viewpoint of adjusting the viscosity and improving the coatability on the first biaxially stretched polyester film. ..
As used herein, the term "active ingredient" refers to a component contained in a target composition excluding a diluting solvent.
The diluting solvent also includes the solvent contained in the silicone-based mold release agent.

Examples of the diluting 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.
These diluting solvents may be used alone or in combination of two or more.

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

<Second silicone resin layer>
The second silicone resin layer has a function of imparting peelability 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 a release layer, if necessary, 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 mold release agent.

The composition (B) for forming a silicone resin layer is prepared so that the peeling force of the heavy release film having the second silicone resin layer is larger than the peeling force of the light release film having the first silicone resin layer. To. Specifically, for example, the silicone-based mold release agent, the cross-linking agent, the catalyst, and other additives of the above-mentioned silicone resin layer forming composition (A) are appropriately selected and prepared.

Moreover, it is preferable that the composition (B) for forming a silicone resin layer contains a heavy release additive.
Examples of the heavy peeling additive include organosilanes such as silicone resin and silane coupling agent, and among these, silicone resin is preferably used.
As the silicone resin, for example, it is preferable to use 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 ]. The three Rs in the M unit independently represent a hydrogen atom, a hydroxyl group, or an organic group. From the viewpoint of facilitating the suppression of silicone migration, one or more of the three Rs in the M unit is preferably a hydroxyl group or a vinyl group, and more preferably a vinyl group.

[Adhesive layer]
The pressure-sensitive adhesive layer of the base-less double-sided pressure-sensitive adhesive sheet of the present invention is a layer containing a pressure-sensitive adhesive resin, but contains an additive for a pressure-sensitive adhesive as necessary within a range that does not impair the effects of the present invention. May be good.
The pressure-sensitive adhesive layer is formed by using a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive resin.
The form of the pressure-sensitive adhesive composition may be any of a solvent type, an emulsion type, and a solvent-free 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 million.

Specific examples of the adhesive resin include rubber resins such as acrylic resins and polyisobutylene resins, polyester resins, urethane resins, and silicone resins.
These adhesive resins may be used alone or in combination of two or more.
Further, when these adhesive resins are copolymers having two or more kinds of structural units, the form of the copolymer is not particularly limited, and the block copolymer, the random copolymer, and the graft can be used together. It may be any of the polymers.
In one aspect of the present invention, the pressure-sensitive adhesive composition preferably contains an acrylic resin, and from the viewpoint of adhesive durability, it is more preferable to contain a (meth) acrylic acid ester copolymer among the acrylic resins.
Hereinafter, a case where the solvent type or emulsion type pressure-sensitive adhesive composition contains an acrylic resin as an adhesive resin and a case where the solvent-free type pressure-sensitive adhesive composition contains an acrylic resin as an 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 that imparts tackiness, or the main monomer component. In addition, it can be composed of a copolymer further containing a cross-linking point and a functional group-containing monomer component for improving adhesiveness.
Further, from the viewpoint of further improving the cohesive force and the adhesive force, the above-mentioned 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 tacky composition is the (meth) acrylic acid ester copolymer. It is preferable to include a cross-linking agent together with the meta) acrylic acid ester copolymer.

(Acrylic resin)
The main monomer component is acrylic having 1 to 20 carbon atoms of an alkyl group such as butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate, benzyl acrylate, and methoxyethyl acrylate. An acid alkyl ester, an alkyl methacrylic acid ester having 1 to 20 carbon atoms of an alkyl group such as butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate and the like.
As the main monomer component, one type may be used alone, or two or more types may be used in combination.
Further, as the main monomer component, butyl acrylate and 2-ethylhexyl acrylate, which are monomers having an alkyl group having 4 to 8 carbon atoms, are preferable, and butyl acrylate is more preferable.
The content of the structural unit derived from the main monomer component with respect to the total structural unit (100% by mass) of the acrylic polymer or the acrylic copolymer is preferably 70 to 100% by mass, more preferably 80 to 99.9% by mass. , More preferably 90-99.5% by mass.

The functional group-containing monomer component preferably contains at least one of a hydroxyl group, a carboxyl group, and an amino group as the functional group, and more preferably contains a hydroxyl group.
Specific examples include (meth) acrylic acid hydroxyalkyl esters such as (meth) acrylic acid 2-hydroxyethyl and (meth) acrylic acid 2-hydroxypropyl; (meth) acrylic acid monomethylaminoethyl and (meth) acrylic acid mono. Monoalkylaminoalkyl (meth) acrylic acid such as ethylaminoethyl; ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and the like.
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 from the viewpoint of reactivity with the cross-linking agent, as well as the flexibility and adhesive 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 further preferably 0.2 to 6.0% by mass.

The comonomer components are, for example, methyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acetate, styrene, and acrylonitrile.
One type of comonomer component may be used alone, or two or more types may be used in combination.

In one aspect of the present invention, a structural unit derived from the main monomer component and a structural unit derived from the functional group-containing monomer component with respect to the total structural unit (100% by mass) of the (meth) acrylic acid ester copolymer preferable as the acrylic resin. The total content of the above 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.

The copolymerization form of the acrylic copolymer such as the acrylic acid ester copolymer contained in the pressure-sensitive adhesive composition is not particularly limited, and may be any of a random copolymer, a block copolymer, and a graft copolymer. You may.

The mass average molecular weight (Mw) of the acrylic polymer such as the acrylic polymer and the acrylic acid ester copolymer contained in the pressure-sensitive adhesive composition is such that the adhesion to the adherend and the adhesive durability are sufficient. From the viewpoint of preventing the occurrence of floating and peeling, the amount is preferably 300,000 or more, more preferably 400,000 to 2 million, and more preferably 500,000 to 1.8 million. Is even more preferable.

Two or more kinds of acrylic polymers may be used in combination, or two or more kinds of acrylic copolymers such as an acrylic acid ester copolymer may be used in combination. Further, two or more kinds of acrylic copolymers such as an acrylic polymer and an acrylic acid ester copolymer may be used in combination.

(Crosslinking agent)
In one aspect of the present invention, the pressure-sensitive adhesive composition preferably contains a cross-linking agent when it has a functional group-containing monomer component as a constituent unit, such as the acrylic acid ester copolymer.
Examples of the cross-linking agent include isocyanate compounds, epoxy compounds, metal chelate compounds, metal alkoxides, metal salts, amine compounds, hydrazine compounds, aldehyde compounds and the like.
These cross-linking agents may be used alone or in combination of two or more.
Further, as the cross-linking agent, an isocyanate compound is preferable.
The content of the cross-linking agent is appropriately adjusted by the number of functional groups of the acrylic acid ester copolymer. For example, with respect to 100 parts by mass of the acrylic acid ester copolymer having the functional group-containing monomer component, it is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 8 parts by mass, and further preferably 1 to 6 parts by mass. It is a mass part.

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

(Diluting solvent)
Examples of the diluting solvent used for preparing the solvent-type pressure-sensitive adhesive composition include toluene, xylene, t-butanol, acetone, methyl ethyl ketone, tetrahydrofuran, ethyl acetate and the like.
These diluting solvents may be used alone or in combination of two or more.
As the organic solvent used as the diluting solvent, the organic solvent used at the time of synthesizing the adhesive resin may be used as it is, or the organic used at the time of synthesizing the adhesive resin may be used so that the pressure-sensitive adhesive composition can be uniformly applied. A solvent and / or one or more other organic solvents may be added.

Examples of the polymerization initiator used when polymerizing the acrylic polymer and the acrylic copolymer include azo compounds and organic peroxides.
As the polymerization initiator, one type may be used alone, or two or more types may be used in combination.
Examples of the azo compound that can be used as the polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), and 1,1'-azobis ( Cyclohexane 1-carbonitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis (2-Methylpropionate), 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2-( 2-imidazolin-2-yl) propane] and the like.
Of these, 2,2'-azobisisobutyronitrile is preferable.

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

(Acrylic resin)
Examples of the polymer (X1) of the (meth) acrylic acid ester include those having a polymer structure of the (meth) acrylic acid ester and having a radically polymerizable unsaturated double bond in the side chain of the polymer structure.
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 functionality having the active hydrogen. Those having a radically polymerizable unsaturated double bond introduced into the group are preferable.
The number of the radically polymerizable unsaturated double bond groups is preferably 2 or more from the viewpoint of increasing the strength and cohesive force of the pressure-sensitive adhesive layer.

Examples of the monomer having a functional group having active hydrogen include a monomer having a functional group such as a hydroxyl group, an amino group and a carboxyl group. Specifically, the same compounds as the functional group-containing monomer components mentioned 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 by 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 a radically polymerizable unsaturated double-binding group into a 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. This can be done by subjecting the compound to an addition reaction. Examples of the active hydrogen reactive group include an isocyanate group and a glycidyl group.

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, and allyl isocyanate. Glycidyl (meth) acrylate and the like are preferably mentioned.

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

Examples of the (meth) acrylate oligomer (X2) include various (meth) acrylate-based oligomers such as urethane (meth) acrylate oligomer, epoxy (meth) acrylate oligomer, polyester (meth) acrylate oligomer, and polyether (meth) acrylate oligomer. And so on.
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 reacting a polyether polyol or a polyester polyol with a polyisocyanate by a reaction with (meth) acrylic acid.
The (meth) acrylate oligomer (X2) may be used alone or in combination of two or more.
Further, the polymer (X1) of the (meth) acrylic acid ester and the (meth) acrylate oligomer (X2) can also be used in combination.

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

The (meth) acrylic acid ester monomer (X3) includes, for example, a monomer constituting the polymer (X1) of the (meth) acrylic acid ester, or a polymer having two or more reactive sites such as carbon-carbon double bonds. Examples include functional acrylates.

Specific examples of the polyfunctional acrylate include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, caprolactone-modified dicyclopentenyldi (meth) acrylate, and ethylene. Bifunctional types such as oxide-modified di (meth) acrylate phosphates; trifunctional types such as trimethylolpropanetri (meth) acrylates and dipentaerythritol tri (meth) acrylates; diglycerintetra (meth) acrylates and pentaerythritol tetras ( 4-functional type such as meta) acrylate; 5-functional type such as propionic acid-modified dipentaerythritol penta (meth) acrylate; 6-functional type such as dipentaerythritol hexa (meth) acrylate and caprolactone-modified dipentaerythritol hexa (meth) acrylate. Can be mentioned.

Further, when the polymer (X1) or the (meth) acrylate oligomer (X2) of the (meth) acrylic acid ester is used as the main raw material and the solvent-free pressure-sensitive adhesive composition has a high viscosity, the (meth) acrylic acid is used. The ester monomer (X3) may be added in order to reduce the viscosity of the solvent-free pressure-sensitive adhesive composition and improve the coatability.
The (meth) acrylic acid ester monomer (X3) is irradiated with ultraviolet rays to each other (meth) acrylic acid ester monomers (X3), or the polymer (X1) of the above (meth) acrylic acid ester and / or the above (meth) acrylate oligomer ( Since the crosslinked structure is formed with X2), the cohesive force of the obtained pressure-sensitive adhesive layer can be enhanced, and problems such as seepage can be effectively prevented.

(Photopolymerization initiator)
By containing the photopolymerization initiator (Y), the solvent-free pressure-sensitive adhesive composition can efficiently cure the ultraviolet curable component in the solvent-free pressure-sensitive adhesive composition, and also has a polymerization curing time and ultraviolet rays. The amount of irradiation can be reduced.

Examples of the photopolymerization initiator (Y) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, and the like. Benzophenone, p-Phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, benzyldimethylketal, acetphenone dimethylketal, p-dimethylamino Examples include benzoic acid esters, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide.
These may be used individually by 1 type, or may be used in combination of 2 or more type.

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

(Other additives)
In one aspect of the present invention, the solvent-free pressure-sensitive adhesive composition contains, in addition to the cross-linking agent, an additive for a pressure-sensitive adhesive used for a general pressure-sensitive adhesive, as long as the effect of the present invention is not impaired. You may.
Examples of such additives for pressure-sensitive adhesives include the additives exemplified in the section of solvent-type or emulsion-type pressure-sensitive adhesive compositions.

[Physical characteristics of base-less double-sided adhesive sheet]
<Peeling power of light release film and heavy release film>
In the base material-less double-sided pressure-sensitive adhesive sheet of the present invention, the peeling force of the light release film is smaller than the peeling force of the heavy release film.
Here, in one aspect of the present invention, from the viewpoint of better suppressing the transfer that occurs when the difference between the peeling force of the heavy release film and the peeling force of the light release film is small, the peeling force and weight of the light release film are heavy. The absolute value of the difference in the peeling force of the release film is preferably 5 m / 25 mm or more, more preferably 10 mN / 25 mm or more, and further preferably 20 mN / 25 mm or more.

Further, in one aspect of the present invention, the peeling force of the heavy release film is preferable from the viewpoint of better suppressing the transfer that occurs when the difference between the peeling force of the heavy release film and the peeling force of the light release film is small. Is 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 peeling film can be adjusted by selecting the forming material of the silicone resin layer forming composition (B) and the blending amount of the heavy peeling additive.

Further, in one aspect of the present invention, even when the peeling force of the heavy-release film against the pressure-sensitive adhesive layer is suppressed, the absolute value of the difference between the peeling force of the light-release film and the peeling force of the heavy-release film is increased. The peeling force of the light release film is preferably 10 to 200 mN / 25 mm, more preferably 15 to 100 mN / 25 mm, and further preferably 20 to 80 mN / 25 mm.
The peeling force of the light release film can be adjusted by selecting the forming material of the silicone resin layer forming composition (A).
The peeling force is a value measured in a normal region where spot transfer does not occur.

[Manufacturing method of base-less double-sided adhesive sheet]
The method for producing the base material-less double-sided pressure-sensitive adhesive sheet of the present invention is not particularly limited, and 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 having a second silicone resin layer formed on the biaxially stretched polyester film is prepared. Next, when the above-mentioned solvent-type pressure-sensitive adhesive composition is used, the solvent-type pressure-sensitive adhesive composition is applied onto the first silicone resin layer of the light release film by a known method, and then heated and dried. Form a coating film. Next, the surface of the second release film on the side of the second silicone resin layer is bonded onto the coating film and subjected to aging treatment to obtain a base material-less double-sided pressure-sensitive adhesive sheet.
Examples of the method for applying the pressure-sensitive adhesive composition include a spin coating method, a spray coating method, a bar coating method, a knife coating method, a roll coating method, a roll knife coating method, a blade coating method, a die coating method, and a gravure coating method. Can be mentioned.

The light release film is formed by applying the silicone resin layer forming composition (A) to 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 silicone resin layer forming composition (B) to the bonding surface of the second biaxially stretched polyester film with the pressure-sensitive adhesive layer, heating and drying.
Examples of the method for applying the silicone resin layer forming composition (A) or (B) to the first or second biaxially stretched polyester film include a gravure coating method, a bar coating method, a spray coating method, and 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 coat method and the bar coat method are preferable, and the bar coat method is more preferable.
Further, as a heating method and a drying method of the silicone resin layer forming composition (A) or (B), for example, a method of heat-drying in a hot air drying furnace or the like can be mentioned.
The drying temperature is, for example, 50 ° C. or higher and 150 ° C. or lower.
The drying time is, for example, 10 seconds to 5 minutes.

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

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

[Minute heat peak]
In accordance with JIS K7121 (1999), the minute heat calorie peak was measured by the following method using a differential scanning calorimetry device (manufactured by TA Instrument Japan, model DSC Q2000).
A sample of 5 mg was weighed in a sample pan, and the sample was heated from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min. Observed at this time, at the apex of a minute peak existing on the lower temperature side than the temperature of the apex of the endothermic peak attributed to melting of the sample and in the vicinity of the endothermic peak, or during the endothermic peak. The apex of the minute shoulder was defined as the minute heat endothermic peak (° C).
FIG. 3 shows an example of the measurement result (peak temperature: 210 ° C.) of the minute heat of fusion peak of the biaxially stretched PET film. Further, FIG. 4 shows an enlarged portion of the minute heat of melting peak in FIG.
In FIG. 3, Tmp is the melting point (260 ° C.) of the biaxially stretched PET film, and Tmeta is the peak of the amount of heat of minute melting.

[Measurement of thickness of each layer]
The thickness of the silicone resin layer was measured using a spectroscopic ellipsometer (manufactured by JA Woolam Japan Co., Ltd., product name "spectral ellipsometry 2000U").
The thickness of the other layers was measured using a constant pressure thickness measuring instrument manufactured by Teclock Co., Ltd. (model number: "PG-02J", standard: JIS K6783, Z1702, Z1709).

[Mass average molecular weight]
It was measured under the following conditions using a gel permeation chromatograph device (manufactured by Tosoh Corporation, product name "HLC-8020"), and the value measured in terms of standard polystyrene was used.
(Measurement condition)
-Column: "TSK guard volume HXL-L""TSK gel G2500HXL""TSK gel G2000HXL""TSK gel G1000HXL" (all manufactured by Tosoh Corporation) are connected in sequence.-Column temperature: 40 ° C.
・ Developing solvent: Tetrahydrofuran ・ Flow rate: 1.0 mL / min

The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, the silicone resin layer-forming composition (A) for forming the first silicone resin layer, and the second silicone resin layer-forming composition used in the following Examples and Comparative Examples. The silicone resin layer forming composition (B) for forming the 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, thermometer, reflux condenser, dropping device and nitrogen introduction tube. , And 0.08 parts by mass of 2,2'-azobisisobutyronitrile were charged, and the air in the reaction vessel was replaced with nitrogen gas. While stirring in this nitrogen atmosphere, the reaction solution was heated to 60 ° C., reacted for 16 hours, and then cooled to room temperature. Here, a part of the obtained solution was measured by GPC, and the formation of the polymer (A) having a mass average molecular weight of 1.6 million was confirmed. 100 parts by mass (solid content) of the polymer (A), 4 parts by mass of a polyisocyanate-based cross-linking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate L), and a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., Trade name: KBM-403) 0.1 parts by mass of KBM-403) was added and mixed, and toluene was further added as a solvent to adjust the solid content to 15% by mass to prepare a pressure-sensitive adhesive composition.

[Composition for Forming Silicone Resin Layer (A)]
100 parts by mass of a silicone-based mold release agent (KS847H, solid content 30% by mass) containing an organopolysiloxane having a vinyl group and an organopolysiloxane having a hydrosilyl group, and a platinum (Pt) catalyst. (Manufactured by Shin-Etsu Chemical Co., Ltd., PL-50T, solid content 2% by mass) Add a mixed solvent of toluene and methyl ethyl ketone (toluene / methyl ethyl ketone = 1/1 (mass ratio)) to 2 parts by mass to add 1% by mass of solid content. The composition (A) for forming a silicone resin layer was prepared.

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

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

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

(Preparation of heavy release film)
The composition for forming a silicone resin layer (B) is applied to PET film B (PET38R-64 manufactured by Toray Industries, Inc.) so that the dried film thickness is 0.1 μm, and the first film is formed on PET film B. A second silicone resin layer was formed to prepare a heavy release film.

(Making a baseless 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. Next, a light release film was attached onto the formed pressure-sensitive adhesive layer so that the first silicone resin layer was in contact with the pressure-sensitive adhesive layer. Then, it was cured for 7 days under the conditions of a temperature of 23 ° C. and a relative humidity of 50% to prepare a base material-less 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 the PET film A2 (micro heat heat peak: 180 ° C.).

<Example 3>
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 the PET film A3 (micro heat 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 the PET film A4 (micro heat heat 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 the PET film A5 (micro heat 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 PET film B of the heavy release film was changed to the PET film A1 of the light release film.

The following tests were carried out on the light release film and the base material-less double-sided pressure-sensitive adhesive sheet constituting the base material-less double-sided pressure-sensitive adhesive sheets of Examples 1 to 3 and Comparative Examples 1 to 3.

[Difference in peeling force]
The peeling force X of the light peeling film and the peeling force Y of the heavy peeling film were measured by the following methods in accordance with JIS-Z0237.
Then, the absolute value of the difference between the peeling force X and the peeling force Y was calculated and used as the peeling force difference (N / 25 mm).

<Peeling force X of light peeling film>
A substrate-less double-sided 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 double-sided adhesive tape, and the light release film is pulled in the 180 ° direction at a release speed of 300 mm / min using a tensile tester. The peeling force X of was measured.

<Peeling force Y of heavy peeling film>
A PET film with a thickness of 50 μm (“Lumilar T60” manufactured by Toray Industries, Inc.) is laminated on the exposed adhesive layer by peeling the light release film from the baseless double-sided adhesive sheet, and then cut to a width of 25 mm and a length of 200 mm. Then, a test piece was prepared.
The heavy release film side of the test piece is fixed to a stainless steel (SUS) plate with double-sided adhesive tape, and the PET film and the adhesive layer are pulled in the 180 ° direction at a release rate of 300 mm / min using a tensile tester. , The peeling force Y of the heavy release film was measured.

[Evaluation of the number of repellent defects]
The number of repellent defects (number of repellents) of the light release films constituting the base material-less double-sided adhesive sheets of Examples 1 to 3 and Comparative Examples 1 to 3 was calculated.
Specifically, for forming the first silicone resin layer generated by repelling when the composition (A) for forming the first silicone resin layer is applied to PET films A1 to A5 and B constituting the light release film. The defects of the composition were counted by visual inspection, and the number of repellent defects per 1 m ² was calculated.

[Evaluation of spot transfer]
The spot transfer caused by peeling the light release film of the base material-less double-sided adhesive sheet of Examples 1 to 3 and Comparative Examples 1 to 3 was visually inspected, and the number of spot transfer per 1 m ² was calculated. .. Then, a three-stage evaluation was performed according to the following criteria.
⊚: Number of spot transfer is 0.010 / m ² or less ○: Number of spot transfer is 0.010 / m ² or more and 0.030 / m ² or less ×: Number of spot transfer is 0.030 / m More than m ² Before evaluating spot transfer, it is also examined whether or not planar transfer occurs when the difference between the release force of the heavy release film and the release force of the light release film is small. The sample in which the planar transfer did not occur was marked with ◯, and the sample in which the planar transfer occurred was marked with x. The spot transfer was not evaluated 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 transfer is consistent with the number of repellent defects. From this, it can be seen that the cissing generated when the composition for forming the silicone resin layer is applied onto the PET film is a factor of spot transfer.
Further, from Comparative Examples 1 and 2 in Table 1, it can be seen that when the peak of the amount of heat of minute melting of the PET film constituting the light release film is 220 ° C. or higher, the number of repellent defects increases and the spot transfer also increases.
On the other hand, from Examples 1 to 3, it can be seen that when the peak of the amount of heat of minute melting of the PET film constituting the light release film is less than 220 ° C., the number of repellent defects is reduced and the spot transfer is also reduced.
In particular, from Examples 1 and 2, it can be seen that when the peak amount of heat of minute melting of the PET film constituting the light release film is 180 ° C. or lower, the number of repellent defects is remarkably reduced and the spot transfer is also remarkably reduced. ..

10, 20 Substrate-less double-sided adhesive sheet 11, 21 Light release film 12, 22 Double release film 1, 23 Adhesive layer 2 First biaxially stretched polyester film 3 First silicone resin layer 4 Second biaxial stretch Polyester film 5 Second silicone resin layer 23a Stretched adhesive 23b Spot-like residual adhesive

Claims (4)

A substrate-less 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-weight 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 the bonding surface of the first biaxially stretched polyester film with the adhesive layer.
The heavy release film has a second biaxially stretched polyester film and a second silicone resin layer provided on the bonding surface of the second biaxially stretched polyester film with the adhesive layer.
A substrate-less double-sided pressure-sensitive adhesive sheet in which the peak temperature of the minute heat of fusion of the first biaxially stretched polyester film is less than [Tmp-40] ° C. (Tmp: melting point of polyester) and 200 ° C. or less . The base material-less double-sided adhesive according to claim 1, wherein the absolute value of the difference between the peeling force of the light release film with respect to the pressure-sensitive adhesive layer and the peeling force of the heavy-release film with respect to the pressure-sensitive adhesive layer is 5 mN / 25 mm or more. Sheet. The base material-less double-sided pressure-sensitive adhesive sheet according to claim 1 or 2 , wherein the pressure-sensitive adhesive layer has a thickness of 1 to 250 μm. The substrate-less double-sided surface according to any one of claims 1 to 3 , 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.

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