TW201811951A - Substrate-less double-sided adhesive sheet - Google Patents

Abstract

The present invention provides a substrate-less double-sided adhesive sheet having a first release film, an adhesive layer provided on the first release film, and a second release film on the adhesive layer. The first release film has a first biaxially stretched polyester film and a first release layer provided on the adhesive layer side of the first biaxially stretched polyester film. The second release film has a second biaxially-oriented polyester film and a second release layer on the adhesive layer side of the second biaxially oriented polyester film. Both the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film are 19 to 50 [mu]m. The inclination of the orientation major axis of the substrate-less double-sided adhesive sheet is -12 degrees to 12 degrees.

Description

   Adhesive sheet on both sides without substrate   

The present invention relates to an adhesive sheet on both sides without a substrate.

In the past, there have been known various adhesive sheets for adhering surfaces between objects. As one of the adhesive sheets, it is known whether there is an adhesive sheet on both sides of a substrate. The substrate-free two-sided adhesive sheet is formed by laminating a relatively light peeling sheet having a relatively low peeling force on both sides of the adhesive layer and a heavy peeling sheet having a relatively high peeling force. The substrate-free two-sided adhesive sheet is firstly peeled off the light release sheet, so that one side of the exposed adhesive layer is adhered to the surface of the object, and then, the heavy release sheet is further peeled, so that the other side of the exposed adhesive layer is adhered to The surfaces of dissimilar objects, by which the surfaces of the objects adhere.

For example, Patent Document 1 discloses a release film for bonding a protective film having a hard coating layer to a substrate-free double-sided adhesive sheet for a panel substrate. This release film has a release layer on one side of a polyester film substrate having an orientation angle of 12 degrees or less and a thickness of 50 to 150 μm.

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent Laid-Open No. 2015-199265

As the application of the adhesive sheet on both sides of the substrate, there are optical films such as polarizing films (polarizing plates) and retardation films. When an adhesive is bonded to an optical film such as a polarizing plate, if there is a defect such as a tiny foreign body or a flaw in the adhesive, the defect will eventually appear as a bright spot that can be seen on the display.

Therefore, in the field of optical films, the inspection criteria for defects are strict, and it is extremely important to improve the accuracy of inspection. The same inspection standard and improved inspection accuracy are also required in the adhesive sheet on both sides without a substrate.

For example, as a defect inspection in a polarizing plate, inspection is generally carried out by emphasizing defects by a cross-Nicol method. The crossed Nicol method is used to make two mating polarizers overlap and orthogonally intersect with the main axis of orientation to make them dull. If there are defects, bright spots will appear here. Disadvantages can still be inspected.

The present invention has been made in view of such facts, and an object thereof is to provide a substrate-free two-faced adhesive sheet having excellent inspection properties based on the orthogonal Nicol method.

As a result of careful discussions by the present inventors in order to solve the above-mentioned problems, it has been found that by setting the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film to a specific range, the orientation If the inclination of the main shaft is set to a specific range, the above problems can be solved.

The present invention has been completed based on this knowledge.

That is, the present invention provides the following [1] to [6].

[1] A substrate-free two-sided adhesive sheet comprising a substrate-free two surfaces including a first release film, an adhesive layer provided on the first release film, and a second release film provided on the adhesive layer. The adhesive sheet, wherein the first release film has a first biaxially stretched polyester film, a first release layer provided on the adhesive layer side of the first biaxially stretched polyester film, and the second release film It has a second biaxially stretched polyester film and a second release layer provided on the side of the adhesive layer of the second biaxially stretched polyester film. The thickness of the first biaxially stretched polyester film is the same as that described above. The thickness of the second biaxially stretched polyester film is 19 to 50 μm, and the inclination of the orientation main axis of the aforementioned substrate-free two-sided adhesive sheet is -12 degrees or more and 12 degrees or less.

[2] The substrate-free two-sided adhesive sheet according to the above [1], wherein the thickness of the aforementioned adhesive layer is 1 to 250 μm.

[3] The substrate-free two-sided adhesive sheet according to the above [1] or [2], wherein the first biaxially stretched polyester film and the second biaxially stretched polyester film are both polyethylene terephthalate Diester film.

[4] The substrate-free two-sided adhesive sheet according to any one of the above [1] to [3], wherein the first peeling layer and the second peeling layer are layers formed of a silicone resin.

[5] The substrate-free two-sided adhesive sheet according to any one of the above [1] to [4], wherein the haze value is 25% or less.

[6] The substrate-free two-sided adhesive sheet according to any one of the above [1] to [5], wherein a difference in a peeling force between the first release film and the second release film is 5 mN / 25 mm or more.

According to the present invention, it is possible to provide a substrate-free double-sided adhesive sheet having excellent checkability by the cross-Nicol method.

1‧‧‧adhesive layer

2‧‧‧The first biaxially stretched polyester film

3‧‧‧ the first peeling layer

4‧‧‧Second biaxially stretched polyester film

5‧‧‧Second release layer

10‧‧‧ Adhesive sheet on both sides without substrate

11‧‧‧The first release film

12‧‧‧Second release film

[Fig. 1] A cross-sectional view showing one embodiment of the substrate-free double-sided adhesive sheet of the present invention.

    [Adhesive sheet on both sides without substrate]    

The substrate-free two-sided adhesive sheet of the present invention has a first release film, an adhesive layer provided on the first release film, and a second release film provided on the adhesive layer. The first release film has a first biaxially stretched polyester film and a first release layer provided on the adhesive layer side of the first biaxially stretched polyester film, and the second release film has a second biaxially stretched film. The stretched polyester film and a second release layer provided on the adhesive layer side of the second biaxially stretched polyester film.

In addition, the substrate-free two-sided adhesive sheet of the present invention is characterized in that the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially-stretched polyester film are both 19 to 50 μm. The inclination of the main axis of the sheet is -12 degrees or more and 12 degrees or less.

FIG. 1 is a cross-sectional view showing one embodiment of the substrate-free double-sided adhesive sheet of the present invention. The substrate-free two-sided adhesive sheet 10 of FIG. 1 is provided with an adhesive layer 1 on a first release film 11, and a second release film 12 is provided on the adhesive layer 1. The first release film 11 has a first biaxially stretched polyester film 2 and a first release layer 3 provided on the adhesive layer side of the first biaxially stretched polyester film 2, and the first release layer 3 It is in contact with the adhesive layer 1. In addition, the second release film 12 includes a second biaxially stretched polyester film 4 and a second release layer 5 provided on the adhesive layer side of the second biaxially stretched polyester film 4, and the second release layer The 5 series is connected to the adhesive layer 1.

The inclination of the orientation main axis of the substrate-free two-sided adhesive sheet of the present invention is -12 degrees or more and 12 degrees or less.

Here, the "inclination of the orientation main axis" is also referred to as the orientation angle, which means the inclination of the major axis with respect to the width direction or the longitudinal direction of the sheet. If the tilt of the directional spindle is less than -12 degrees and more than 12 degrees, there will be anxiety that the light leakage will increase during the inspection by the orthogonal Nicoll method, and it will prevent the detection of defects such as foreign objects or scars. .

The tilt of the directional main axis is preferably -10 ° to 10 °, and more preferably -8 ° to 8 °.

(First release film and second release film)

The first release film includes a first biaxially stretched polyester film and a first release layer disposed on the first biaxially stretched polyester film. The second release film includes a second biaxially stretched polyester film and a second release layer provided on the second biaxially stretched polyester film.

In the present invention, the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film are both 19-50 μm. If it is less than 19 μm, there is a concern that dents such as deformation, unevenness, and distortion are generated on the surface of the adhesive layer. Moreover, the stiffness as a release film becomes weak, and it becomes difficult to handle. If it exceeds 50 μm, the orientation angle of the biaxially stretched polyester film becomes large, and it is impossible to uniformly reduce the orientation angle in the width direction of the biaxially stretched polyester film that has been filmed, which not only has a large impact on cost, There is also the concern of reducing the testability based on the cross Nicolson method.

The thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film are both preferably 25 to 48 μm.

The inclination (orientation angle) of the orientation main axis of the first biaxially stretched polyester film and the second biaxially stretched polyester film is adjusted so that the inclination (orientation) of the orientation main axis of the substrate-free two-sided adhesive sheet of the invention Angle) to the desired range.

In the present invention, the orientation angle is defined as 0 degrees when parallel to the width direction of the film, + for a clockwise inclination with respect to the film width direction, and-for a counterclockwise inclination. When the orientation angles of the first biaxially stretched polyester film and the second biaxially stretched polyester film are +, the orientation of the first biaxially stretched polyester film and the second biaxially stretched polyester film is The angles are preferably made from 0 to 12 degrees, more preferably from 0 to 10 degrees, more preferably from 0 to 8 degrees, the first biaxially stretched polyester film, and the second biaxial When the orientation angle of the stretched polyester film is-, the orientation angles of the first biaxially stretched polyester film and the second biaxially stretched polyester film are both preferably -12 degrees or more and 0 degrees or less. A range of -10 ° to 0 ° is preferable, and a range of -8 ° to 0 ° is more preferable. When the signs of the orientation angles of the first biaxially stretched polyester film and the second biaxially stretched polyester film are different, the orientation angle is not particularly limited. For example, the first biaxially stretched polyester film The orientation angle of the ester film is preferably in a range of -40 ° to 0 °, and the orientation angle of the second biaxially stretched polyester film is preferably in a range of 0 ° to 40 °.

The haze of the first biaxially stretched polyester film and the second biaxially stretched polyester film is preferably 12% or less, and more preferably 10% or less. By making it 12% or less, it is possible to adjust the haze of the adhesive sheet on both sides without a substrate to a desired value or less.

In addition, the above-mentioned haze can be measured by a method according to JIS K-7136 using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH-5000).

Examples of the first biaxially stretched polyester film and the second biaxially stretched polyester film include polyethylene terephthalate film, polybutylene terephthalate film, and polynaphthalene Ethylene formate film.

The first biaxially stretched polyester film and the second biaxially stretched polyester film may be the same film or different films. Among them, from the viewpoint of optical characteristics, it is preferable that both the first biaxially stretched polyester film and the second biaxially stretched polyester film are polyethylene terephthalate films.

Examples of a method for biaxially stretching a polyester film include a method of stretching in a length direction and a width direction, a method of stretching in a width direction and a length direction, and a combination thereof. A known method such as a method in which the stretching in the longitudinal direction and the stretching in the width direction are performed a plurality of times, or a method called simultaneous biaxial stretching, in which simultaneous stretching is performed.

The first release layer and the second release layer have a function of imparting releasability to a release film. The first release layer and the second release layer are formed of, for example, a cured product of a composition for forming a release layer containing a release agent.

The release agent is not particularly limited, and examples thereof include a silicone resin, an alkyd resin, an acrylic resin, and a long-chain alkyl resin, and it is preferably formed using a silicone resin.

Examples of the silicone resin include a silicone resin having dimethylpolysiloxane as a basic skeleton. Examples of the silicone resin include addition reaction type, condensation reaction type, ultraviolet curing type, and electron beam curing type. Among them, the addition reaction type polysiloxane resin is not only highly reactive and excellent in productivity, but also has the advantages of less change in peeling force after production and no hardening shrinkage when compared with the condensation reaction type. Better to use.

Specific examples of the above-mentioned addition-reaction type silicone resin include, for example, those having 2 to 10 or more carbon atoms such as vinyl, allyl, propenyl, and hexenyl at the molecular end and / or side chain. Alkenyl organic polysiloxane. When using such an addition reaction type silicone resin, it is preferable to use a crosslinking agent and a catalyst together.

As the above-mentioned crosslinking agent, for example, an organopolysiloxane having at least two hydrogen atoms bonded to a silicon atom in one molecule may be specifically exemplified by dimethylhydrosiloxy-terminated dimethylsiloxy. Alkane-methylhydrosilane copolymer, trimethylsiloxy-terminated dimethylsiloxane-methylhydrosiloxane copolymer, trimethylsiloxy-terminated chain methylhydrogen polysiloxane Oxane, poly (hydrosiloxanes), etc.

Examples of the catalyst include fine particulate platinum, fine particulate platinum adsorbed on a carbon powder carrier, platinum chloride, alcohol-denatured platinum chloride, olefin complexes of platinum chloride, palladium, rhodium, etc. Platinum is a metal-based compound. By using such a catalyst, the curing reaction of the composition for forming a peeling layer can be performed more efficiently.

When using a silicone resin as a release agent, a peeling adjuster such as MQ resin is preferably added.

Further, additives may be appropriately blended in the composition for forming a release layer. Examples of the additives include dyes and dispersants. Furthermore, in order to make the viscosity at the time of coating into an appropriate range, a dispersing medium or a solvent may be appropriately contained in the composition for forming a release layer.

Examples of the dispersing medium or solvent include organic solvents such as aromatic hydrocarbons such as toluene, fatty acid esters such as ethyl acetate, ketones such as methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and heptane. Wait.

The content of the release agent contained in the release layer-forming composition is not particularly limited, but is preferably 0.3 to 10% by mass.

Examples of the method for applying the composition for forming a release layer to the first or second biaxially stretched polyester film include, for example, a gravure coating method, a bar coating method, a spray coating method, a spin coating method, and a gas coating method. A knife coating method, a roll coating method, a doctor blade coating method, a horizontal roll coating method, a die coating method, and the like. Among these, a gravure coating method and a bar coating method are preferable, and a bar coating method is preferable.

In addition, as a method of heating and drying the composition for forming a peeling layer, 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 preferably, for example, 10 seconds to 5 minutes.

The thickness of the first release layer (when dry) and the thickness of the second release layer (when dry) are both preferably 40 nm to 1 μm, both 50 nm to 0.5 μm are preferred, and 60 nm to 0.3 μm are more preferred. . By making it 40 nm or more, uneven peeling force due to deviation of the coating amount can be suppressed, and by making it 1 μm or less, blocking can be suppressed.

In the present invention, the difference in peeling force between the first release film and the second release film is preferably 5 mN / 25 mm or more, more preferably 10 mN / 25 mm or more, and more preferably 20 mN / 25 mm or more. By making it 5mN / 25mm or more, when the peeling film is peeled off, the so-called peeling defect which can make the adhesive stick to the peeled film is not easy to occur.

When the first release film is on the heavy release side, the peel force of the first release film to the adhesive layer is preferably 30 to 300 mN / 25 mm, more preferably 50 to 200 mN / 25 mm, and more preferably 50 to 100 mN / 25 mm. . By making it into the said range, when peeling a 1st peeling film, the so-called peeling defect which can make an adhesive transfer to the peeled 1st peeling film is hard to produce.

When the second release film is on the light release side, the peel force of the second release film to the adhesive layer is preferably 10 to 200 mN / 25 mm, more preferably 15 to 100 mN / 25 mm, and more preferably 20 to 80 mN. / 25mm. By making it within the said range, even if the peeling force of a 1st peeling film is reduced, the difference of the peeling force of a 1st peeling film and a 2nd peeling film can be made large.

(Adhesive layer)

The adhesive layer is formed using an adhesive. Examples of the adhesive include acrylics, rubbers, polyesters, urethanes, and silicones. In the present invention, as the adhesive, it is particularly preferable to include an acrylic adhesive, and from the viewpoint of durability, it is preferable to include a (meth) acrylate copolymer.

Examples of the form of the adhesive include a solvent type, an emulsion type, and a solventless type.

When the adhesive is a solvent-based or emulsion-type acrylic adhesive, the adhesive may be composed of a main monomer component that imparts adhesion, a comonomer component that imparts adhesion or cohesion, and contains an improved crosslinking point or adhesion. The functional monomer is mainly composed of a polymer or copolymer. By including these components, the cohesive force and adhesive force of the obtained adhesive layer can be improved.

Examples of the main monomer component include alkyl groups such as butyl acrylate, pentyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate, benzyl acrylate, and methoxyethyl acrylate. Alkyl acrylate having a carbon number of 1 to 20, or alkyl carbon number of butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, etc. ~ 20 alkyl methacrylate, etc.

Examples of the comonomer component include methyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acetate, styrene, and acrylonitrile.

As the functional group-containing monomer component, the functional group preferably contains at least one of a hydroxyl group, a carboxyl group, and an amine group. Specific examples include 2-hydroxyethyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate. Hydroxyalkyl (meth) acrylates such as hydroxypropyl esters; monomethyl (meth) acrylates such as monomethylaminoethyl (meth) acrylate and monoethylaminoethyl (meth) acrylate Amino alkyl esters; ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and maleic acid.

The copolymerization form of the (meth) acrylate copolymer is not particularly limited, and may be any of random, block, and graft copolymers.

As the (meth) acrylate copolymer, it is preferable to use a mass average molecular weight of 300,000 or more, it is more preferable to use 400,000 to 2,000,000, and it is more preferable to use 500,000 to 1.8 million. Thereby, the adhesiveness or adhesion durability to an adherend can be made sufficient, and the occurrence of floating or peeling can be prevented more effectively.

In addition, in this specification, a mass average molecular weight is a polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

In the (meth) acrylic acid ester copolymer, the unit content derived from the functional group-containing monomer component is preferably from 0.01% by mass to 10% by mass, more preferably from 0.05% by mass to 7.0% by mass, and 0.2 is preferred. It is more preferably 6.0% by mass or more. When the content is within the above-mentioned range, the crosslinking with the crosslinking agent described later becomes sufficient. As a result, the adhesive layer becomes more flexible or more excellent in durability.

In addition, such a (meth) acrylate copolymer may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of the organic solvent used to prepare the solvent-based acrylic adhesive composition include toluene, stubble, t-butanol, acetone, methyl ethyl ketone, tetrahydrofuran, and ethyl acetate.

The solvent-based acrylic adhesive composition may be either a cross-linked type to which a cross-linking treatment is applied and a non-cross-linking type to which no cross-linking treatment is applied, but a cross-linked type is preferred. In the case of a composition for forming a cross-linked adhesive layer, an adhesive layer having more excellent cohesive force can be formed.

Examples of the cross-linking agent used as the cross-linking type acrylic adhesive composition include isocyanate compounds, epoxy compounds, metal chelate compounds, metal alkoxides, metal salts, amine compounds, amidine compounds, and aldehyde compounds. Wait.

In addition, when the adhesive layer in the substrate-free double-sided adhesive sheet of the present invention is formed of a solvent-free acrylic adhesive, it may be selected from those containing a radically polymerizable unsaturated double bond group having a radically polymerizable unsaturated bond in a side chain. At least one of (meth) acrylate polymer (A1), (meth) acrylate oligomer (A2), and (meth) acrylate monomer (A3), and a photopolymerization initiator (B ) (I).

From the viewpoint of improving the strength or cohesiveness of the adhesive layer, the (meth) acrylate polymer (A1) and the (meth) acrylate oligomer (A2) have radical polymerizable unsaturated double bonds The number of sexual bases is preferably two or more.

The polymer (A1) of the (meth) acrylic acid ester means a polymer structure having a (meth) acrylic acid ester, and a side chain of the polymer structure has a radical polymerizable unsaturated double bond. Specifically, preferred examples include the main monomer component disclosed in the solvent-based acrylic adhesive composition, the comonomer component disclosed in the solvent-based acrylic adhesive composition, and a compound having active hydrogen. In the copolymer of a functional monomer, the functional group having an active hydrogen described above is introduced with a radical polymerizable unsaturated double bond.

Examples of the monomer having a functional group holding an active hydrogen include monomers having a functional group such as a hydroxyl group, an amine group, and a carboxyl group. Specific examples include the compounds exemplified in the item containing a functional group-containing monomer disclosed in the solvent-based acrylic adhesive composition.

A copolymer is prepared by polymerizing each of the monomers according to a conventional method. The copolymers of the (meth) acrylates may be used alone or in combination of two or more.

In the above-mentioned copolymer, a radical polymerizable unsaturated double bond group is introduced into a functional group holding an active hydrogen, for example, by adding a compound having both a radical polymerizable unsaturated double bond and an active hydrogen reactive group. The reaction proceeds. Examples of the active hydrogen-reactive group include an isocyanate group and an epoxypropyl group.

As a compound having both a radically polymerizable unsaturated double bond and an active hydrogen reactive group, specifically, preferred examples include acryloxyethyl isocyanate, acryloxypropyl isocyanate, and methacrylium Oxyethyl isocyanate, methacryloxypropyl isocyanate, allyl isocyanate, glycidyl (meth) acrylate, and the like.

The above-mentioned addition reaction system is preferably performed at a temperature of 25 to 60 ° C. for about 6 to 48 hours. In the above-mentioned addition reaction, an organic tin compound such as dibutyltin dilaurate or a substituted amine compound is preferably used as a catalyst as necessary.

Examples of the (meth) acrylate oligomer (A2) include urethane (meth) acrylate oligomer, epoxy (meth) acrylate oligomer, and polyester Various (meth) acrylate-based oligomers such as (meth) acrylate oligomers and polyether (meth) acrylate oligomers. Among these, a urethane (meth) acrylate oligomer can be preferably used. The urethane (meth) acrylate oligomer is, for example, a polyurethane oligomer obtained by reacting a polyether polyol or polyester polyol with a polyisocyanate, and then (Meth) acrylic acid is obtained by esterification.

The (meth) acrylate oligomer (A2) is used singly or in combination of two or more kinds. A (meth) acrylate polymer (A1) and a (meth) acrylate oligomer (A2) may be used in combination.

The weight average molecular weight of the (meth) acrylate polymer (A1) and the (meth) acrylate oligomer (A2) are 20,000 or more, preferably 25,000 to 80,000, and more preferably 30,000 to 60,000. .

Moreover, the weight average molecular weight is a polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

As said (meth) acrylate monomer (A3), the monomer which comprises the (meth) acrylate polymer (A1) as mentioned above, or the reaction which has 2 or more such as a carbon-carbon double bond can be illustrated preferably Multifunctional acrylates for sexual sites.

Specific examples of the polyfunctional acrylate include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and caprolactone-modified dicyclopentane. Bifunctional types such as alkenyl di (meth) acrylate, ethylene oxide modified phosphate di (meth) acrylate, etc .; trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylic acid 3-functional types such as esters; 4-functional types such as diglycerol tetra (meth) acrylate and pentaerythritol tetra (meth) acrylate; 5-functional types such as propionic acid-modified dipentaerythritol penta (meth) acrylate ; 6-functional types such as dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, and the like.

The (meth) acrylate polymer (A1) or (meth) acrylate oligomer (A2) is used as a main raw material. When the composition (i) for forming an adhesive layer has a high viscosity, the above The (meth) acrylic acid ester monomer (A3) may be added in order to reduce the viscosity of the composition (i) for forming an adhesive layer and improve the coating properties. The (meth) acrylic acid ester monomers (A3) are (meth) acrylic acid ester monomers (A3) each other, or the (meth) acrylic acid ester polymer (A1) and / or the (methacrylic acid ester) Since the base) acrylate oligomer (A2) forms a crosslinked structure, the cohesive force of the obtained adhesive layer can be improved, and problems such as bleeding can be effectively prevented.

By including the photopolymerization initiator (B) in the above-mentioned composition (i) for forming an adhesive layer, the ultraviolet-curable component in the composition (i) for forming an adhesive layer can be efficiently cured and reduced. Polymerization hardening time and ultraviolet radiation.

Examples of the photopolymerization initiator (B) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, acetophenone, dimethylaminoacetophenone, 2,2- Dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone , Dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, benzyldimethylketal, acetophenone Methyl ketal, p-dimethylamino benzoate, 2,4,6-trimethylbenzylfluorenyl-diphenyl-phosphine oxide, and the like. These can be used alone or in combination of two or more.

The content of the photopolymerization initiator (B) contained in the adhesive layer-forming composition (i) is based on the (meth) acrylate polymer (A1) and (meth) acrylate oligomer ( The total of 100 parts by mass of A2) and (meth) acrylate monomer (A3) is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.2 to 2 parts by mass.

In addition, the composition for forming an adhesive layer may contain various additives commonly used in adhesives, such as a silane coupling agent, an antistatic agent, an adhesion-imparting agent, an antioxidant, an ultraviolet absorber, a light stabilizer, and a softening agent, as desired. , Filler, refractive index adjuster, colorant, etc.

From the viewpoint of productivity and cost, the thickness of the 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 applying the adhesive layer of the present invention to an optical film, it is preferable that orange peel (a plurality of minute irregularities) does not occur on the surface of the adhesive layer. From such a viewpoint, the proportion of the unevenness on the surface of the adhesive layer from the reference plane to the range of ± 0.2 μm is preferably 20% or less. By making it into the said range, when sticking an adhesive layer to an to-be-adhered body, the appearance defect can be prevented effectively.

In addition, the ratio of the unevenness on the surface of the adhesive layer from the reference surface to the range of ± 0.2 μm can be calculated using, for example, an optical interference type surface shape observation device. Specifically, using an optical interference type surface shape observation device, based on a surface shape image in the 4 × 4 mm range obtained by stitching at a magnification of 2.5 times in the VSI mode, from a reference plane to ± 0.2 μm The part outside the range and the part within the range of ± 0.2 μm are binarized to the image. Thereby, it can be obtained by calculating the area ratio occupied by the unevenness of the portion outside the range from the reference plane to ± 0.2 μm.

The haze of the substrate-free two-sided adhesive sheet of the present invention is preferably 25% or less, more preferably 20% or less, and even more preferably 10% or less. The above-mentioned haze can be measured by a method according to JIS K-7136 by using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH-5000).

The substrate-free two-faced adhesive sheet of the present invention is excellent in checkability according to the crossed Nicols method, and can therefore be suitably used in optical films such as polarizing plates.

(Manufacturing method of two sides without substrate)

There is no particular limitation on the manufacturing method of the substrate-free two-sided adhesive sheet. For example, first a first release film having a first release layer formed on a first biaxially stretched polyester film, and a second biaxially stretched film are prepared. A second release film having a second release layer formed on the stretched polyester film. Next, when the solvent-based adhesive composition is used, the adhesive composition is coated on the first release layer of the first release film by a known method, and then heated and dried to form a coating film. Next, the second release layer side surface of the second release film is bonded to the coating film and the curing process is performed to obtain an adhesive-free sheet on both sides of the substrate.

Examples of the coating method of the adhesive composition include a spin coating method, a spray coating method, a bar coating method, a blade coating method, a roll coating method, a knife-roll coating method, and a blade coating method. , Die coating method, gravure coating method, etc.

When the above-mentioned solventless adhesive composition is used, the adhesive composition is coated on the first release layer of the first release film by a known method, and then activated energy rays such as ultraviolet rays and electron rays are irradiated to form adhesion.剂 层。 The agent layer. In addition, the irradiation of the active energy ray can semi-harden the adhesive composition or sufficiently harden the adhesive composition. Secondly, by bonding the surface on the second release layer side of the second release film to the adhesive layer, an adhesive sheet without substrate on both sides can be obtained.

    [Example]    

Hereinafter, the present invention will be specifically described with examples and comparative examples. The present invention is not limited by the forms described in the examples.

1. orthogonal nico test

Two polarizing plates were used to hold the polarizing axis orthogonal to each other, and the substrate-free two-sided adhesive sheet (20cm × 20cm) produced in the examples and comparative examples was held, and installed in a flat panel illuminator (manufactured by Dentsu Industry Co., Ltd., trade name) : HF-SL-A312LC, illuminance: 26,000 Lux, brightness: 10,000 cd), and evaluated visually based on the following criteria.

<Evaluation Criteria>

G: Fully crossed Nicolas (Dark Vision), and those with sufficient inspection degree

F: Insufficient orthodox nicols (light leakage), as those with insufficient inspection degree

2. Foreign body inspection

The second release film (light release film) of the substrate-free double-sided adhesive sheet (20 cm × 20 cm) produced in the examples and comparative examples was peeled off, and the size was about 20 μm between the second release film and the adhesive layer. After the black metal powder (foreign matter) was mixed in about 50 degrees, the second release film was attached again. From the side of the second release film, the adhesive-bonded sheet on both sides of the base material without foreign matter mixed therein obtained by visual observation was evaluated, and the detection status of the foreign matter mixed was evaluated according to the following criteria.

<Evaluation Criteria>

G: Good foreign body recognition, sufficient inspection for optical use

F: Foreign matter cannot be found, inappropriate inspection degree for optical use

3.Inclination of orientation spindle (orientation angle)

Using a phase difference measuring device (KOBRA-WR, manufactured by Oji Measurement Co., Ltd.), the orientation of the biaxially stretched polyethylene terephthalate (PET) film used in the examples and comparative examples was observed, and the in-plane of the PET film was measured. The direction of the main orientation axis is inclined with respect to the width direction of the PET film by several degrees and set as an orientation angle. Moreover, the orientation angle is set to 0 degrees when it is parallel to the film width direction, the inclination clockwise with respect to the film width direction is set to +, and the inclination counterclockwise is set to-.

4.Haze

The biaxially stretched polyethylene terephthalate (PET) used in the examples and comparative examples was measured by a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH-5000) by a method in accordance with JIS K-7136. ) Haze of the film and the substrate-free two-sided adhesive sheet produced in the examples and comparative examples.

    [Preparation of Adhesive Composition a]    

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, and 2 parts were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux cooler, a dropping device, and a nitrogen introduction tube. 0.08 parts by mass of 2'-azobisisobutyronitrile. The air in the reaction vessel was replaced with nitrogen. While stirring in this nitrogen environment, the reaction solution was heated to 60 ° C. and allowed to react for 16 hours, and then cooled to room temperature. Here, GPC measurement was performed on a part of the obtained solution, and it was confirmed that a polymer (A) having a mass average molecular weight of 1.6 million was produced. To 100 parts by mass (solid content) of the polymer (A), 4 parts by mass of a mixed polyisocyanate-based crosslinking agent (manufactured by Japan Polyurethane Industry Co., Ltd., trade name: Coronate L), and 0.1 parts by mass of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KBM-403), toluene was added as a solvent, and the solid content was adjusted to 15% by mass to prepare a solvent-based acrylic adhesive adhesive composition. a.

    [Preparation of Adhesive Composition b]    

40 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of isofluorenyl acrylate, 10 parts by mass of 2-hydroxyethyl acrylate, 30 parts by mass of urethane acrylate oligomer, and 1-hydroxyl 1 mass part of cyclohexyl phenyl ketones and 0.2 mass parts of 3-glycidoxypropyltrimethoxysilane were prepared into the adhesive composition b of a solventless acrylic adhesive.

The urethane acrylate oligomer silicon is synthesized by the following procedure. First, 4 parts by mass of hexamethylene diisocyanate was added to 100 parts by mass of polypropylene glycol having a weight average molecular weight of 3,000, and 0.02 parts by mass of dioctyltin dilaurate was stirred at 80 ° C. for 6 hours to obtain a first reaction. Thing. Next, it was confirmed from the IR spectrum of the obtained first reactant that the isocyanate group almost disappeared. Then, 1 part by mass of 2-isocyanatoethylacrylate was added, and the mixture was stirred at 80 ° C for 3 hours to obtain a second reactant. Next, it was confirmed from the IR spectrum of the obtained second reactant that the isocyanate almost disappeared, and then a urethane acrylate oligomer having a weight average molecular weight of 25,000 was obtained.

(Example 1)

1. Preparation of Composition (A) for Peeling Layer Formation

A polysiloxane resin solution (manufactured by Toray Dow Corning Corporation, trade name: BY24-561, solid content 30% by mass) containing an organopolysiloxane having a vinyl group and an organopolysiloxane having a hydrogen silicon group was used as a solid The composition was converted into 30 parts by mass, and the MQ resin having a vinyl group (manufactured by Toray Dow Corning, trade name: SD7292, solid content 71% by mass) was converted to 15 parts by mass based on solid content, and diluted and mixed in a toluene solvent to form a solid The component concentration was 1.0% by mass. To this solution was added 2 parts by mass of a platinum-based catalyst (manufactured by Toray Dow Corning, trade name: SRX-212, solid content 100% by mass) to prepare a release layer forming composition (A).

2. Production of the first release film

A biaxially stretched polyethylene terephthalate (PET) film having a thickness of 38 μm, an orientation angle of 6 degrees, and a haze of 10% was prepared.

Next, on one side of the biaxially stretched PET film (first biaxially stretched PET film), the composition (A) for forming a release layer obtained as described above was used so that the thickness after drying became 0.1 μm, and a rod was used. The applicator was applied and dried at 120 ° C. for 1 minute to form a release layer (first release layer) to obtain a first release film.

3. Preparation of composition (B) for release layer formation

A polysiloxane resin solution (manufactured by Toray Dow Corning Corporation, trade name: BY24-561, solid content 30% by mass) containing an organopolysiloxane having a vinyl group and an organopolysiloxane having a hydrogen silicon group was used as a solid The component was converted into 30 parts by mass, and the solid content was diluted and mixed in a toluene solvent to a concentration of 1.0% by mass. To this solution was added 2 parts by mass of a platinum-based catalyst (manufactured by Toray Dow Corning, trade name: SRX-212, solid content 100% by mass) to prepare a composition (B) for forming a release layer.

4. Production of the second release film

A biaxially stretched polyethylene terephthalate (PET) film having a thickness of 38 μm, an orientation angle of 6 degrees, and a haze of 10% was prepared.

Next, on one side of the biaxially stretched PET film (second biaxially stretched PET film), the composition (B) for forming the release layer obtained above was used so that the thickness after drying became 0.1 μm, and a rod was used. The coater was applied and dried at 120 ° C. for 1 minute to form a release layer (second release layer) to obtain a second release film.

5. Production of adhesive sheet on both sides without substrate

On the surface of the first release layer side of the first release film, the adhesive composition a was applied with a coater so that the film thickness after drying became 20 m, and dried at 105 ° C for 2 minutes. Thereafter, the surface on the second release layer side of the second release film was bonded, and it was aged at 23 ° C. and 50 RH for one week to prepare a substrate-free double-sided adhesive sheet.

(Example 2)

1. Production of the first release film and the second release film

It carried out similarly to Example 1, and produced the 1st release film and the 2nd release film.

2. Production of adhesive sheet on both sides without substrate

On the surface of the first release layer side of the first release film, the adhesive composition b was applied using a coater so that the film thickness became 125 μm to form a coating layer. Next, under the following conditions, ultraviolet rays were irradiated from the exposed surface side of the obtained coating layer to pre-harden the coating layer to prepare a pre-hardened coating layer.

    [UV irradiation conditions]    

‧ Lamp: High-pressure mercury lamp

‧ Cumulative light quantity (wavelength 365nm): 40mJ / cm ²

Next, the exposed surface of the obtained pre-cured coating layer is bonded to the surface on the second release layer side of the second release film. Thereafter, the pre-hardened coating layer in a state where the second release film is laminated is irradiated with ultraviolet rays from the biaxially stretched PET film side of the second release film under the following conditions, so that the pre-hardened coating layer is mainly cured. An adhesive layer having a thickness of 125 μm was prepared, and then a substrate-free two-sided adhesive sheet composed of a layer of the first release film / adhesive layer / second release film was obtained.

    [UV irradiation conditions]    

‧ Lamp: High-pressure mercury lamp

‧ Cumulative light quantity (wavelength 365nm): 1200mJ / cm ²

(Example 3)

Except that the thickness of the first biaxially stretched PET film was set to 50 μm, the same operation as in Example 1 was performed to obtain a substrate-free double-sided adhesive sheet.

(Example 4)

Except that the thickness of the second biaxially stretched PET film was 25 μm, the same procedure as in Example 1 was performed to obtain a substrate-free double-sided adhesive sheet.

(Example 5)

Except that the haze of the first biaxially stretched PET film and the second biaxially stretched PET film were both 3%, the same operation as in Example 1 was performed to obtain a substrate-free double-sided adhesive sheet.

(Example 6)

Except that the orientation angle of the first biaxially stretched PET film was set to 12 degrees, and the orientation angle of the second biaxially stretched PET film was set to 0 degrees, the same operation as in Example 1 was performed to obtain both sides without a substrate. Adhesive flakes.

(Example 7)

Except that the orientation angles of the first biaxially stretched PET film and the second biaxially stretched PET film were all 0 degrees, the same operation as in Example 1 was performed to obtain a substrate-free double-sided adhesive sheet.

(Example 8)

Except that the orientation angle of the first biaxially stretched PET film was 36 degrees and the orientation angle of the second biaxially stretched PET film was -12 degrees, the same operation as in Example 1 was performed to obtain a substrate-free material. Thin flakes on both sides.

(Comparative example 1)

Except that the orientation angle of the first biaxially stretched PET film was -12 degrees and the orientation angle of the second biaxially stretched PET film was -18 degrees, the same operation as in Example 1 was performed to obtain a baselessness. Sheets on both sides of the wood.

(Comparative example 2)

Except that the orientation angles of the first biaxially stretched PET film and the second biaxially stretched PET film were each 15 degrees, the same operation as in Example 1 was performed to obtain a substrate-free double-sided adhesive sheet.

(Summary of results)

Examples 1 to 8 using the substrate-free two-sided adhesive sheet of the present invention are excellent in cross-nicole inspection and foreign object inspection.

Claims (6)

    A substrate-free double-sided adhesive sheet comprising a first release film, an adhesive layer provided on the first release film, and a substrate-free double-sided adhesive sheet provided on the second release film on the adhesive layer. The first release film has a first biaxially stretched polyester film and a first release layer disposed on the adhesive layer side of the first biaxially stretched polyester film, and the second release film has a second The biaxially stretched polyester film and the second release layer disposed on the adhesive layer side of the second biaxially stretched polyester film, the thickness of the first biaxially stretched polyester film and the second biaxially stretched polyester film The thickness of the axially stretched polyester film is 19-50 μm, and the inclination of the orientation main axis of the aforementioned substrate-free two-sided adhesive sheet is -12 degrees or more and 12 degrees or less.         For example, if there is an adhesive sheet on both sides without a substrate in claim 1, wherein the thickness of the aforementioned adhesive layer is 1 to 250 μm.         For example, if the substrate-free two-sided adhesive sheet of claim 1 or 2 is used, both the first biaxially stretched polyester film and the second biaxially stretched polyester film are polyethylene terephthalate films.         For example, the substrate-free two-sided adhesive sheet according to any one of claims 1 to 3, wherein the first peeling layer and the second peeling layer are both layers formed of a silicone resin.         For example, the substrate-free two-sided adhesive sheet according to any one of claims 1 to 4, wherein the haze value is 25% or less.         For example, the substrate-free two-sided adhesive sheet according to any one of claims 1 to 5, wherein the difference in peeling force between the first release film and the second release film is 5 mN / 25 mm or more.