JP2017171867A - Pressure sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensitive adhesive sheet having high weatherproofness.SOLUTION: A pressure sensitive adhesive sheet 1 includes a film layer 3, an adhesive layer 4 disposed on one side of the film layer 3, and a surface protective layer 2 disposed on the other side of the film layer 3. The film layer 3 contains a first ultraviolet light absorber and a PET-G resin as a resin material. The adhesive layer 4 contains a second ultraviolet light absorber. The surface protective layer 2 contains a triazine-type ultraviolet light absorber as a third ultraviolet light absorber and a mixed resin of an acrylic resin and a urethane resin as a resin material. The pressure sensitive adhesive sheet 1 has a mixedly existing area in which a PET-G resin and the mixed resin exist in a mixed manner at an interface between the film layer 3 and the surface protective layer 2. The mixed amount of the acrylic resin in the mixed resin is preferably 25-75 mass%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure-sensitive adhesive sheet that can be bonded to an adherend.

2. Description of the Related Art Conventionally, a marking film that is used by being attached to the surface of a railway vehicle, an automobile, a vending machine or the like has been used. An overlay film for the purpose of surface protection, glossy factory, fading / deterioration prevention and the like may be attached to the surface of the marking film. Such an overlay film and a pressure-sensitive adhesive sheet used as a surface protecting film for an exterior signboard are required to have high weather resistance.
For example, in the following Patent Document 1 and Patent Document 2, a decorative sheet or a resin film is prepared by adding a weather stabilizer such as an ultraviolet absorber to the resin layer in order to achieve high weather resistance. It is described that a weathering stabilizer such as an ultraviolet absorber or a light stabilizer is added to the resin layer.

JP 2008-114560 A JP 2005-015557 A

However, in the above-described pressure-sensitive adhesive sheet or the like, there are cases where the followability to a non-flat adherend such as a curved surface is not sufficient while maintaining high weather resistance.
The present invention has been made paying attention to the above-described points, and an object thereof is to provide a pressure-sensitive adhesive sheet having high followability to an adherend while maintaining high weather resistance.

  In order to solve the problem, an adhesive sheet according to one embodiment of the present invention includes a film layer, an adhesive layer formed on one surface of the film layer, and a surface protective layer formed on the other surface of the film layer. The film layer includes a first ultraviolet absorber and PET-G resin as a resin material, the adhesive layer includes a second ultraviolet absorber, and the surface protective layer serves as a third ultraviolet absorber. It contains a triazine ultraviolet absorber and a mixed resin of an acrylic resin and a urethane resin as a resin material.

  According to one embodiment of the present invention, it is possible to obtain a pressure-sensitive adhesive sheet having high followability to an adherend while maintaining high weather resistance.

It is sectional drawing explaining the structure of the adhesive sheet which concerns on embodiment based on this invention. FIG. It is an expanded sectional view explaining the composition of the adhesive sheet concerning the embodiment based on the present invention in detail.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing the pressure-sensitive adhesive sheet 1 according to this embodiment, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Further, the embodiment described below exemplifies a configuration for embodying the technical idea of the present invention, and the technical idea of the present invention is that the material, shape, structure, etc. of the component parts are as follows. It is not something specific. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

FIG. 1 is a cross-sectional view of an adhesive sheet 1 according to this embodiment. As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 of this embodiment includes a film layer 3, a pressure-sensitive adhesive layer 4 formed on one surface of the film layer 3, and the other surface of the film layer 3 (pressure-sensitive adhesive layer 4 And a surface protective layer 2 formed on a surface opposite to the formation surface.
FIG. 2 is an enlarged cross-sectional view of the interface between the film layer 3 and the surface protective layer 2. As shown in FIG. 2, the pressure-sensitive adhesive sheet 1 of the present embodiment includes a PET-G resin contained in the film layer 3 and a mixed resin contained in the surface protective layer 2 at the interface between the film layer 3 and the surface protective layer 2. The mixed region 5 is provided. The mixed resin and the mixed region 5 will be described in detail later.
Hereinafter, with reference to FIG.1 and FIG.2, each layer of the adhesive sheet 1 is demonstrated in detail.

<Film layer>
The film layer 3 is a film formed of a resin material such as a thermoplastic resin containing a first ultraviolet absorber for improving weather resistance. The film layer 3 may be transparent or opaque. The film layer 3 may be colored or uncolored. A light stabilizer may be added to the film layer 3 in order to prevent the resin material itself from being deteriorated by light, heat, water, or the like.

The film layer 3 contains PET-G resin as a resin material. PET (PolyEthylene Terephthalate) -G is a glycol-modified polyester in which a part of the ethylene glycol of PET is replaced with cyclohexanedimethanol (CHDM) in order to prevent crystallization. For this reason, PET-G has excellent flexibility, impact strength, transparency, and the like. The PET-G resin has high flexibility, and when used for the film layer 3, the film layer 3 tends to extend isotropically. For this reason, the film layer 3 can easily follow a non-flat adherend such as a curved surface.
The film layer 3 may be made of a thermoplastic resin such as polypropylene, polyethylene, polyethylene terephthalate, or a mixture, modified product, or polymer thereof, together with the PET-G resin.

As a 1st ultraviolet absorber added to the film layer 3, the material which has an ultraviolet absorption wavelength range different from the ultraviolet absorption wavelength range of the 2nd ultraviolet absorber added to the adhesive layer 4 is mentioned. The 1st ultraviolet absorber added to the film layer 3 absorbs the ultraviolet-ray of a different wavelength range (wavelength range which is hard to be absorbed with the adhesive layer 4) from the 2nd ultraviolet absorber added to the adhesive layer 4. be able to.
The first ultraviolet absorber is preferably a material that absorbs ultraviolet rays having a wavelength longer than that of the second ultraviolet absorber. The first ultraviolet absorber preferably absorbs ultraviolet rays having a wavelength of 350 nm or more and 370 nm or less.

  As such a first ultraviolet absorber, for example, a benzotriazole ultraviolet absorber is preferably used. Examples of the benzotriazole ultraviolet absorber include 2- (2-hydroxy-5-tert-butylphenyl) -2H-benzotriazole, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy −3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2- (3-t- Butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5- Di-t-amyl-2-hydroxyphenyl) benzotriazole, 2- (2′-hydroxy-5′-octylphenyl) benzotriazole And mixtures thereof, modified products, polymers, and derivatives.

  The number of added parts of the first ultraviolet absorber is 0.1% by mass or more and 50% by mass or less, preferably 0.5% by mass or more and 30% by mass or less with respect to the resin material that is the material of the film layer 3. This is because the ultraviolet absorbing effect is sufficiently exhibited and bleeding out of the ultraviolet absorbent can be suppressed.

Further, as the light stabilizer added to the film layer 3, a hindered amine light stabilizer is preferably used.
As the hindered amine light stabilizer, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl Malonate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, methyl (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis [2,2] decanoic acid 2,6,6-tetramethyl-1-octyloxy) -4-piperidinyl] ester and the like, mixtures thereof, modified products, polymers, derivatives and the like.

The film layer 3 can be formed to have a desired thickness. For example, the thickness is preferably 60 μm or more and 100 μm or less. This is because the adhesive film 1 has particularly high strength and weather resistance, and the productivity at the time of manufacturing the film layer 3 is better.
Such a film layer 3 has a light transmittance of 0.5% or less in an ultraviolet region having a wavelength region of 310 nm to 370 nm. Therefore, deterioration of the film layer 3 due to ultraviolet rays can be suppressed.

<Adhesive layer>
The pressure-sensitive adhesive layer 4 is formed of an adhesive containing a second ultraviolet absorber for improving weather resistance. Further, a light stabilizer may be added to the pressure-sensitive adhesive layer 4 in order to prevent the adhesive itself from being deteriorated by light, heat, water or the like. Examples of the adhesive include acrylic adhesives, rubber adhesives, epoxy adhesives, and isocyanate adhesives, but acrylic adhesives are preferably used.

  Examples of the acrylic adhesive include n-butyl (meth) acrylate, hexyl (meth) acrylate, 2-diethylbutyl (meth) acrylate, isooctyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, (Meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid decyl, (meth) acrylic acid dodecyl, (meth) acrylic acid tridecyl ester, etc. (Meth) acrylic acid, itaconic acid, maleic acid, maleic anhydride, hydroxyethyl acrylate, hydroxypropyl acrylate, acrylamide, dimethylacrylamide, methylaminoethyl methacrylate, (meth) acrylic acid, copolymerizable with acrylic ester Copolymers with functional monomers such as methoxyethyl And the like.

Examples of the rubber-based adhesive include natural rubber-based, isoprene rubber-based, styrene-butadiene-based, recycled rubber-based, polyisobutylene-based, and blocks including rubbers such as styrene-isoprene-styrene and styrene-butadiene-styrene. Examples thereof include an adhesive mainly comprising a copolymer.
Examples of the epoxy adhesive include aliphatic chain-modified epoxy resins, hydrocarbon-modified epoxy resins such as cyclopentadiene-modified epoxy resins and naphthalene-modified epoxy resins, elastomer-modified epoxy resins, and silicone-modified epoxy resins.
Examples of the isocyanate-based adhesive include caprolactam-based blocked isocyanate, phenol-based blocked isocyanate, and toluene diisocyanate-based.

  As the above-mentioned adhesive, any of non-crosslinked type and crosslinked type can be used. In the latter case, a crosslinking agent can be added as necessary. As the crosslinking agent, for example, an epoxy compound, an isocyanate compound, a metal chelate compound, a metal alkoxide, a metal salt, an amine compound, a hydrazine compound, an aldehyde compound, or the like can be used alone or in admixture of two or more. .

Examples of the second ultraviolet absorber added to the pressure-sensitive adhesive layer 4 include a material having an ultraviolet absorption wavelength region different from the ultraviolet absorption wavelength region of the first ultraviolet absorber added to the film layer 3. The second ultraviolet absorber added to the pressure-sensitive adhesive layer 4 absorbs ultraviolet rays in a wavelength region different from that of the first ultraviolet absorber added to the film layer 3 (wavelength region difficult to be absorbed by the film layer 3). Can do.
The second ultraviolet absorber is preferably a material that absorbs ultraviolet rays having a shorter wavelength than the first ultraviolet absorber. The second ultraviolet absorber preferably absorbs ultraviolet rays having a wavelength of at least 310 nm and not more than 350 nm.

  As such a second ultraviolet absorber, for example, a triazine-based ultraviolet absorber is preferably used. Examples of the triazine ultraviolet absorber include 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol, 2- [4-[(2- Hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2- [4-[(2-hydroxy- 3-tridecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2,4-bis (2,4-dimethylphenyl) ) -6- (2-hydroxy-4-iso-octyloxyphenyl) -s-triazine, mixtures thereof, modified products, polymers, derivatives, and the like.

  The added number of the second ultraviolet absorber is 0.1% by mass or more and 50% by mass or less, and preferably 0.5% by mass or more and 30% by mass or less with respect to the adhesive which is the material of the pressure-sensitive adhesive layer 4. This is because the ultraviolet absorbing effect is sufficiently exhibited and bleeding out of the ultraviolet absorbent can be suppressed.

  Further, as the light stabilizer added to the pressure-sensitive adhesive layer 4, it is preferable to use the same hindered amine light stabilizer as the light stabilizer added to the film layer 3.

The pressure-sensitive adhesive layer 4 can be formed to a desired thickness, and for example, the thickness is preferably 20 μm or more and 40 μm or less. This is because the pressure-sensitive adhesive film 1 has higher strength and weather resistance, and the productivity during production of the pressure-sensitive adhesive layer 4 is better.
Such an adhesive layer 4 has a light transmittance of 0.5% or less in an ultraviolet region having a wavelength region of 310 nm or more and 370 nm or less. Therefore, deterioration of the film layer 3 due to ultraviolet rays can be suppressed.

<Surface protective layer>
The surface protective layer 2 is formed of a resin material such as a thermoplastic resin containing a third ultraviolet absorber for improving weather resistance. The surface protective layer 2 is a layer transparent to the extent that the film layer 3 can be visually recognized. In addition, a light stabilizer may be added to the surface protective layer 2. By providing the surface protective layer 2, bleeding out of the plasticizer contained in the PET-G resin of the film layer 3 can be suppressed, and stickiness on the surface of the pressure-sensitive adhesive sheet 1 can be suppressed.
Examples of the resin material used for the surface protective layer 2 include a mixed resin of an acrylic resin and a urethane resin. Here, the “mixed resin of acrylic resin and urethane resin” refers to a resin obtained by further mixing a urethane resin by melt kneading or the like with an acrylic urethane resin obtained by reacting an acrylic polyol compound and an isocyanate compound as a curing agent. .
Further, the surface protective layer 2 is selected in consideration of the adhesion to the film layer 3 as long as the mixed amount does not impair the flexibility of the mixed resin, and is selected from polyolefin resins such as polypropylene and polyethylene, and acrylic resins. And other thermoplastic resins such as a mixture, a modified product and a polymer thereof.
The mixing amount of the acrylic resin in the mixed resin in which the acrylic resin and the urethane resin are mixed is preferably 25% by mass or more and 75% by mass or less. When the mixing amount of the acrylic resin is within the above range, the water resistance and weather resistance of the surface protective layer 2 are improved as compared with the case where the acrylic resin is less outside this range. Moreover, when the mixing amount of the acrylic resin is within the above-mentioned range, the flexibility of the surface protective layer 2 is improved as compared with the case where there are many acrylic resins outside this range, and the pressure-sensitive adhesive sheet 1 is applied to the non-adhesive body. Followability is improved.

When the surface protective layer 2 contains a mixed resin of an acrylic resin and a urethane resin, the flexibility of the surface protective layer 2 is improved, and the surface protective layer 2 easily follows the film layer 3. Moreover, the adhesiveness of the surface protective layer 2 and the film layer 3 improves because the surface protective layer 2 contains the mixed resin mentioned above.
This is because when the surface protective layer 2 is formed on the surface of the film layer 3, if the mixed resin is dissolved in a solvent and applied to the surface of the film layer 3, the surface of the film layer 3 is dissolved. As a result, a mixed region 5 in which the PET-G resin contained in the film layer 3 and the mixed resin contained in the surface protective layer 2 are mixed is formed at the interface between the surface protective layer 2 and the film layer 3. 2 and the film layer 3 are improved in adhesion.
Furthermore, for example, when a polyolefin resin is used as the main material of the surface protective layer 2, the surface of the film layer 3 may be subjected to a surface treatment in order to improve the adhesion between the film layer 3 and the surface protective layer 2. is there. On the other hand, when the surface protective layer 2 contains the above-described mixed resin, the surface treatment of the film layer 3 becomes unnecessary.

  As a 3rd ultraviolet absorber added to the surface protective layer 2, the triazine type ultraviolet absorber similar to a 2nd ultraviolet absorber is used, for example. When the surface protective layer 2 contains the triazine-based ultraviolet absorber in the pressure-sensitive adhesive sheet 1, the surface protective layer 2 that first receives the ultraviolet light can efficiently absorb the ultraviolet light and improve the weather resistance of the pressure-sensitive adhesive sheet 1. Moreover, the quantity of the ultraviolet-ray which the film layer 3 and the adhesion layer 4 receive can be reduced, the stability of the film layer 3 and the adhesion layer 4 improves dramatically, and the weather resistance of the adhesive sheet 1 improves. The third ultraviolet absorber is a material that absorbs ultraviolet rays having a wavelength different from that of the first ultraviolet absorber. Specifically, the third ultraviolet absorber is a material that absorbs ultraviolet rays having a shorter wavelength than the first ultraviolet absorber. Therefore, a wide range of ultraviolet rays can be absorbed by the film layer 3 containing the first ultraviolet absorber and the surface protective layer 2 containing the third ultraviolet absorber.

The number of added parts of the third ultraviolet absorber is 0.05% by mass or more and 30% by mass or less, preferably 0.05% by mass or more and 25% by mass with respect to the resin material containing the acrylic urethane resin that is the material of the surface protective layer 3. % Or less. This is because the ultraviolet absorbing effect is sufficiently exhibited and bleeding out of the ultraviolet absorbent can be suppressed. When a triazine-based ultraviolet absorber is used as the third ultraviolet absorber, the number of added ultraviolet absorbers can be reduced as compared with the case where a benzotriazole-based ultraviolet absorber is used. For this reason, it becomes easy to mix a 3rd ultraviolet absorber with acrylic urethane resin, and the productivity of an adhesive sheet improves. Moreover, since the addition property of the 3rd ultraviolet absorber with respect to acrylic urethane resin improves, the quality of the surface protective layer 2 improves and the stability of the adhesive sheet 1 improves. Moreover, when using a triazine type ultraviolet absorber as a 3rd ultraviolet absorber, the surface protection layer 2 can be made thin compared with the case where the benzotriazole type ultraviolet absorber of the same amount addition part is used. For this reason, since formation of the surface protective layer 2 becomes easy and manufacturing time is shortened, productivity of the pressure-sensitive adhesive sheet is improved.
Further, as the light stabilizer added to the surface protective layer 2, it is preferable to use the same hindered amine light stabilizer as the light stabilizer added to the film layer 3.

  The surface protective layer 2 can be formed to a desired thickness, and for example, the thickness is preferably 6 μm to 15 μm. When the thickness of the surface protective layer 2 is in the above range, the weather resistance and water resistance of the pressure-sensitive adhesive sheet 1 are sufficiently high, and the surface protective layer 2 is not too thick. Is prevented and blocking is prevented. Thereby, the fall of the production speed at the time of adhesive sheet manufacture and the fall of a yield can be suppressed, and the productivity of the adhesive sheet 1 can be improved.

<Mixed area>
As shown in FIG. 2, the mixed region 5 is interposed at the interface between the film layer 3 and the surface protective layer 2, and the PET-G resin contained in the film layer 3 and the mixed resin contained in the surface protective layer 2 are mixed. This is the area. In the mixed region 5, when the surface protective layer 2 is formed on the surface of the film layer 3, the surface of the film layer 3 is dissolved and dried by applying a solvent in which the mixed resin is dissolved to the surface of the film layer 3. Thus, the PET-G resin in the film layer 3 and the mixed resin in the surface protective layer 2 are mixedly formed. For this reason, the adhesion between the surface protective layer 2 and the film layer 3 is improved by forming the mixed region 5.
The ratio of the PET-G resin and the mixed resin acrylic resin and urethane resin in the mixed region 5 varies depending on the manufacturing conditions and the configurations of the film layer 3 and the surface protective layer.

<Effect>
The adhesive layer according to the present embodiment as described above has the following effects.
(1) The surface protective layer contains a triazine ultraviolet absorber as an ultraviolet absorber, and the film layer contains a PET-G resin as a resin material, so that the surface protective layer that first receives ultraviolet rays efficiently absorbs ultraviolet rays. While improving a weather resistance, a film layer tends to extend isotropically and a film layer becomes easy to follow the to-be-adhered bodies, such as a curved surface.
(2) When the surface protective layer contains an acrylic resin (acrylic urethane resin), the water resistance of the surface protective layer is sufficiently increased, which contributes to an improvement in weather resistance.
(3) The surface protective layer contains a mixed resin of an acrylic resin and a urethane resin as a resin material, so that the flexibility of the surface protective layer is improved while maintaining the water resistance and weather resistance of the surface protective layer. The followability to a non-adhesive body is improved.
(4) A mixed region in which the PET-G resin contained in the film layer and the mixed resin contained in the surface protective layer are mixed is formed at the interface between the surface protective layer and the film layer. Adhesion is improved.
(5) Since the thickness of the surface protective layer can be reduced, the amount of resin material used (the amount of molten resin applied) can be reduced, and the surface protective layer can be easily formed.
(6) When the pressure-sensitive adhesive sheet 1 is used, discoloration of the surface protective layer 2 due to the surface protective layer being exposed to moisture is suppressed.
(7) By adding an ultraviolet absorber to each of the film layer, the pressure-sensitive adhesive layer and the surface protective layer, the absorption wavelength of ultraviolet rays can be made different in each layer, and ultraviolet rays in a wavelength region that are difficult to be absorbed by any layer Can be absorbed by other layers. That is, each layer can mutually compensate for the ultraviolet absorption wavelength.
(8) Not only one layer (for example, the surface protective layer) but also other layers (for example, the film layer and the pressure-sensitive adhesive layer) are added with an ultraviolet absorber to suppress the bleeding out of the ultraviolet absorber. Connected.
(9) Since the ultraviolet absorption wavelength region of the first ultraviolet absorber and the ultraviolet absorption wavelength region of the second ultraviolet absorber are different, the film layer and the pressure-sensitive adhesive layer can supplement each other with the ultraviolet absorption wavelength. .
(10) The third ultraviolet absorber overlaps with both the ultraviolet absorption wavelength region of the first ultraviolet absorber and the ultraviolet absorption wavelength region of the second ultraviolet absorber. Thereby, in the surface protective layer that is likely to be an ultraviolet incident surface of the pressure-sensitive adhesive sheet, ultraviolet rays having a wide range of wavelengths can be absorbed, and the ultraviolet rays incident on the film layer and the pressure-sensitive adhesive layer can be reduced. Thereby, deterioration of the film layer and the pressure-sensitive adhesive layer is further suppressed, the pressure-sensitive adhesive layer is deteriorated and peeled off from the adherend such as an outer wall or a window, or the film layer and the pressure-sensitive adhesive layer are deteriorated due to deterioration of at least one of Peeling of the pressure-sensitive adhesive layer can be further prevented.
(11) By including a thermoplastic resin in the film, deterioration of the pressure-sensitive adhesive sheet when the outer wall, the window, or the like becomes high temperature is suppressed.
(12) When the thickness of the surface protective layer is 6 μm or more and 15 μm or less, the weather resistance of the pressure-sensitive adhesive sheet becomes sufficiently high, and the occurrence of blocking during production is prevented, thereby improving the productivity of the pressure-sensitive adhesive sheet. Can be made.

Hereinafter, the adhesive sheet in the present embodiment will be described with specific examples and comparative examples. In addition, this embodiment is not restrict | limited by the following examples and comparative examples. <Example 1>
(Formation of film)
A benzotriazole ultraviolet absorber and a hindered amine light stabilizer that absorb ultraviolet rays having a wavelength of 350 nm or more and 370 nm or less were added to kneaded PET-G resin (manufactured by Riken Technos Co., Ltd.) and kneaded. Subsequently, the molten resin kneaded with the ultraviolet absorber and the light stabilizer was extruded at a thickness of 100 μm using an extruder to form a transparent film (hereinafter referred to as a transparent film).

(Formation of adhesive layer)
A triazine-based ultraviolet absorber that absorbs ultraviolet rays on a shorter wavelength side, which is different from the benzotriazole-based ultraviolet absorber added to the transparent film, in a two-component cross-linking acrylic adhesive (Arivine BPS 6316, manufactured by Toyo Ink Co., Ltd.) And a hindered amine light stabilizer was added and kneaded. Subsequently, the acrylic adhesive kneaded with the above-described ultraviolet absorber and light stabilizer is dried on the other surface of the transparent film (a surface different from the surface protective layer forming surface) to a thickness of 30 μm. The coating amount was adjusted to be applied. Finally, the coated acrylic adhesive was dried to form an adhesive layer having a thickness of 30 μm.

(Formation of surface protective layer)
UV light of the same wavelength as that of the benzotriazole UV absorber added to the transparent film and the triazine UV absorption added to the adhesive layer in a molten thermosetting acrylic resin and urethane resin (made by DIC Graphics Co., Ltd.) A triazine-based ultraviolet absorber and a hindered amine-based light stabilizer that absorb ultraviolet rays having the same wavelength as the agent were added and kneaded. At this time, the mixing amount of the acrylic resin in the mixed resin was 25% by mass.
Subsequently, a mixed resin obtained by kneading the above-described ultraviolet absorber and light stabilizer was applied onto one surface of the transparent film by adjusting the coating amount so that the thickness after drying was 9 μm. Finally, the coated mixed resin was dried to form a surface protective layer having a thickness of 9 μm.
As described above, a pressure-sensitive adhesive sheet was produced in which the surface protective layer was formed on one surface of the transparent film and the pressure-sensitive adhesive layer was formed on the other surface of the transparent film.

<Example 2>
A pressure-sensitive adhesive sheet of Example 2 in which the surface protective layer and the pressure-sensitive adhesive layer were formed on both surfaces of the transparent film was produced in the same manner as in Example 1 except that the thickness of the surface protective layer after curing was changed to 6 μm.

<Example 3>
A pressure-sensitive adhesive sheet of Example 3 in which the surface protective layer and the pressure-sensitive adhesive layer were formed on both surfaces of the transparent film was produced in the same manner as in Example 1 except that the thickness of the surface protective layer after curing was 15 μm.

<Example 4>
As a mixed resin of acrylic resin and urethane resin used for the surface protective layer, a mixed resin (manufactured by DIC Graphics Co., Ltd.) in which the mixed amount of the acrylic resin in the mixed resin is 75% by mass was used. Except this, it carried out similarly to Example 1, and produced the adhesive sheet of Example 3 in which the surface protection layer and the adhesion layer were each formed in both surfaces of the transparent film.

<Comparative Example 1>
When forming the film layer, a polypropylene resin (manufactured by Prime Polymer Co., Ltd., Prime TPO F-3900 (registered trademark)) was used instead of the PET-G resin, and the thickness of the film layer was 80 μm. Except this, it carried out similarly to Example 1, and produced the adhesive sheet of the comparative example 1 by which the surface protective layer and the adhesion layer were each formed on both surfaces of the transparent film.

<Comparative example 2>
A pressure-sensitive adhesive sheet of Comparative Example 2 in which the surface protective layer and the pressure-sensitive adhesive layer were formed on both sides of the transparent film was prepared in the same manner as in Example 1 except that the thickness of the film layer was 80 μm and the surface protective layer was not provided. did.

[Evaluation]
The following evaluation was performed on the pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 2 described above.

(Accelerated weather resistance test)
The accelerated weather resistance test was performed on the pressure-sensitive adhesive sheets of each Example and each Comparative Example under the following conditions, and the surface of each pressure-sensitive adhesive sheet was confirmed for cracks / cracks.

(conditions)
Testing machine: Metal weather testing machine (Daipura Metal Weather KU-R5DC1-A manufactured by Daipura Wintes Co., Ltd.)
Condition: Illuminance 65 mW / cm ² , Light (53 ° C., 50% RH) 20 hours, Dew (30 ° C., 95% RH) 4 hours Watering condition: 30 s before and after Dew
The above process was made into 1 cycle, and the accelerated weather resistance test was implemented with respect to each adhesive sheet of an Example and a comparative example for 144 hours.
After the test, the surface of the adhesive sheet was checked for cracks / cracks.

  In the accelerated weather resistance test, regarding the cracks / cracks on the surface of the pressure-sensitive adhesive sheet, “◎” indicates that no cracks or cracks were generated on the surface, and “○” indicates that cracks or cracks were generated. The case where occurrence occurred was evaluated as “×”.

(Evaluation of followability of adhesive sheet)
The followability was evaluated for the pressure-sensitive adhesive sheets of each Example and each Comparative Example.
The follow-up property of the pressure-sensitive adhesive sheet is affixed with a pressure-sensitive adhesive sheet on a curved adherend, observe the presence or absence of the peel-off of the pressure-sensitive adhesive sheet, and when the follow-up property to a non-adhesive body is high, The case where there was peeling and the followability to a non-adhesive body was low was evaluated as “x”.

(Evaluation of productivity of adhesive sheet)
Productivity was evaluated about the adhesive sheet of each Example and each comparative example.
Regarding the evaluation of productivity, “◎” indicates that productivity is very good, “◯” indicates that productivity is good, and productivity is inferior (for example, production of an adhesive sheet is impossible) ) Was marked with “x”.

  Table 1 below shows the configurations of Examples and Comparative Examples. The evaluation results are shown in Table 2 below.

(Discussion)
As can be seen from Table 1, the pressure-sensitive adhesive sheets of Examples 1 to 4 have significantly improved followability and improved weather resistance as compared with the pressure-sensitive adhesive sheet of Comparative Example 1. This is because the pressure-sensitive adhesive sheets of Examples 1 to 4 use PET-G resin as the resin material of the transparent film, and use a mixed resin of acrylic resin and urethane resin as the resin material of the surface protective layer. This is thought to be because the flexibility of the surface protective layer has increased. In addition, it is considered that the surface protective layer and the film layer on the ultraviolet incident side contain different ultraviolet absorbers and absorbed ultraviolet rays having different wavelengths, so that deterioration of each layer of the adhesive layer was efficiently suppressed.
Moreover, as can be seen from Table 1, the pressure-sensitive adhesive sheets of Example 1 to Example 4 provided with the surface protective layer have cracks and cracks on the surface as compared with the pressure-sensitive adhesive sheet of Comparative Example 2 provided with no surface protective layer. It did not occur and the weather resistance was improved. As described above, this is considered to be due to absorption of ultraviolet absorbers having different wavelengths between the surface protective layer and the film layer.

  In addition, it can be seen from Comparative Example 2 that although the followability is improved by forming the transparent film using the PET-G resin, the weather resistance is lowered because the surface protective layer is not formed. Therefore, it was found that the pressure-sensitive adhesive sheet can achieve both weather resistance and followability when the transparent film is formed using the PET-G resin and the surface protective layer is formed.

In addition, according to the comparison between Example 1 and Example 4, in the mixed resin, the case where the acrylic resin content is 25% by mass and 75% by mass can be evaluated in the same degree in terms of weather resistance and followability. I understood.
Furthermore, as shown in Example 1, Example 2 and Example 3, when the thickness of the surface protective layer is 9 μm or more, the pressure-sensitive adhesive sheet is compared with the case where the thickness of the surface protective layer is 6 μm. The surface was hard to crack or crack. This is considered to be because when the thickness of the surface protective layer becomes equal to or greater than a certain level, the amount of ultraviolet absorber contained in the surface protective layer increases and the ultraviolet absorbing effect is enhanced.
Moreover, as shown in Example 1, Example 2, and Example 3, when the thickness of the surface protective layer is 6 μm, the productivity is higher than when the thickness of the surface protective layer is 9 μm or more. Became high. This is considered to be because the drying at the time of forming the surface protective layer is accelerated when the thickness of the surface protective layer is below a certain value.

  As described above, in the pressure-sensitive adhesive sheet of this embodiment, as in the pressure-sensitive adhesive sheets of Examples 1 to 4, the transparent film (film layer) includes a PET-G resin as a resin material, and the surface protective layer is a resin material. As a mixed resin of an acrylic resin and a urethane resin and a triazine ultraviolet absorber. Moreover, as for the adhesive sheet of this embodiment, it is preferable that the mixing amount of the acrylic resin in mixed resin is 25 mass% or more and 75 mass% or less like the adhesive sheet of Example 1- Example 4. Furthermore, as for the adhesive sheet of this embodiment, it is preferable that the thickness of a surface protective layer is 6 micrometers or more and 15 micrometers or less like the adhesive sheet of Example 1- Example 3.

[Others]
The scope of the present invention is not limited to the illustrated and described exemplary embodiments, but also includes all embodiments that provide equivalent effects to those intended by the present invention. Further, the scope of the invention is not limited to the combinations of features of the invention defined by the claims, but can be defined by any desired combination of specific features among all the disclosed features.

1 Adhesive sheet 2 Surface protective layer 3 Film layer 4 Adhesive layer 5 Mixed area

Claims (8)

A film layer;
An adhesive layer formed on one surface of the film layer;
A surface protective layer formed on the other surface of the film layer;
With
The film layer includes a first ultraviolet absorber and a PET-G resin as a resin material,
The pressure-sensitive adhesive layer contains a second ultraviolet absorber,
The pressure-sensitive adhesive sheet, wherein the surface protective layer includes a triazine ultraviolet absorber as a third ultraviolet absorber and a mixed resin of an acrylic resin and a urethane resin as a resin material. The pressure-sensitive adhesive sheet according to claim 1, further comprising a mixed region in which the PET-G resin and the mixed resin are mixed at an interface between the film layer and the surface protective layer. The pressure-sensitive adhesive sheet according to claim 1, wherein the mixed amount of the acrylic resin in the mixed resin is 25% by mass or more and 75% by mass or less.   The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein an ultraviolet absorption wavelength region of the first ultraviolet absorber is different from an ultraviolet absorption wavelength region of the second ultraviolet absorber.   5. The pressure-sensitive adhesive sheet according to claim 4, wherein the first ultraviolet absorber absorbs ultraviolet rays having a wavelength longer than that of the second ultraviolet absorber. The third ultraviolet absorber has an ultraviolet absorption wavelength region that overlaps with both the ultraviolet absorption wavelength region of the first ultraviolet absorber and the ultraviolet absorption wavelength region of the second ultraviolet absorber. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5.   The pressure-sensitive adhesive sheet according to claim 1, wherein the film contains a thermoplastic resin.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the thickness of the surface protective layer is 6 µm or more and 15 µm or less.

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