JP7125462B2 - adhesive film - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having an anti-clouding performance, which prevents the pressure-sensitive adhesive film coated with a thick pressure-sensitive adhesive layer from becoming cloudy even when left in a high-temperature, high-humidity atmosphere for a long period of time. . More specifically, regarding a pressure-sensitive adhesive composition containing a nitrogen-containing vinyl monomer or an alkoxy group-containing (meth)acrylic acid ester monomer that does not contain a hydroxyl group, transparency is impaired even when the thickness of the pressure-sensitive adhesive layer is increased. The present invention relates to a pressure-sensitive adhesive composition which is excellent in anti-whitening performance even after being left in a high-temperature, high-humidity atmosphere for a long period of time, and to provide a pressure-sensitive adhesive film using the same.

2. Description of the Related Art In recent years, in various displays such as PDPs (plasma displays), liquid crystal panels, and organic EL panels, various optical films and protective plates are attached to the front surfaces of the displays.
For example, in PDPs, in addition to shielding films for electromagnetic waves, near-infrared absorbing films for preventing malfunction of various remote control switches using the near-infrared wavelength region, near-infrared absorbing films used for the near-infrared absorbing films Ultraviolet absorption film to prevent deterioration of infrared absorbers over time, neon light cut film to adjust color tone in the visible light region, antireflection film to prevent external light from reflecting on the surface of optical filters, etc. , is attached to the front of the display. By using these films as optical filters for displays, the quality of images is improved.

Also, in a mobile phone in which a liquid crystal panel is used as a display, a protective plate for shock absorption is attached to the front surface of the liquid crystal panel via an air layer to prevent cracking of the liquid crystal panel. However, in recent years, in order to reduce weight and thickness and improve visibility, it has become possible to attach a thin protective plate directly to the front surface of the liquid crystal panel of a mobile phone using an adhesive layer without providing an air layer. is being carried out.
In the case of PDPs as well, in order to reduce the weight and thickness of the PDP and to improve the visibility, bonding a film for an optical filter directly to the PDP panel is being studied as a direct color filter method.

The above optical films and protective plates are attached to the front surface of the display using an adhesive layer. There is a problem that microbubbles are generated in the pressure-sensitive adhesive layer.
In addition, in the display performance test performed before shipment of the display device, it is necessary to pass the endurance test under environmental conditions of high temperature and high humidity using an oven. However, in the case of an optical film using a pressure-sensitive adhesive layer with unimproved anti-clouding performance, there is a problem that the pressure-sensitive adhesive layer becomes cloudy after being taken out of the oven, impairing the commercial value of the display.

In this way, when an optical film is attached to a display using an adhesive tape, there is a problem that microbubbles are generated in the adhesive layer. Various efforts have been made in the past to solve the problem that the pressure-sensitive adhesive layer becomes cloudy when the durability test is performed under the pressure and after it is removed from the oven.

For example, Patent Literature 1 discloses a pressure-sensitive adhesive optical film using a pressure-sensitive adhesive layer that improves repair performance when dents are formed on the surface of the pressure-sensitive adhesive layer and prevents inclusion of air bubbles.
Specifically, a polymer containing an alkyl (meth)acrylate having an alkyl group having 7 to 18 carbon atoms and a hydroxyl group-containing monomer at a weight ratio of 100:0.01 to 5, and a functional group that reacts with a hydroxyl group It is a pressure-sensitive adhesive layer formed by a crosslinked product of a composition containing two or more compounds. After the optical film using this adhesive layer (thickness 20 μm) was attached to the glass, it was allowed to stand in an atmosphere of 50° C.×0.05 MPa for 5 minutes, and the presence or absence of microbubbles in the adhesive layer was visually observed. The presence or absence of air bubbles is inspected by a method of confirming by

Further, Patent Document 2 discloses a resin composition containing an acrylic acid derivative, an acrylic acid derivative polymer, and a high-molecular-weight cross-linking agent for absorbing impact necessary for protecting an image display device and the like. . It is useful for preventing cracking of image display panels and for relieving stress and impact, and is said to have excellent transparency.
As a moisture absorption test, a resin sheet molded in a frame with a depth of 0.5 mm was placed in a high temperature and high humidity test chamber at 60 ° C. and 90% RH for 50 hours. It is said that this resin composition has little foaming and is excellent in transparency.

Further, Patent Document 3 discloses a pressure-sensitive adhesive layer for electronic displays having excellent moist heat resistance. Specifically, an electronic display pressure-sensitive adhesive composition comprising a copolymer and/or mixture of a (meth)acrylic acid alkyl ester monomer and a carboxyl group-containing monomer, further comprising a monomer having an alkyleneoxy group, and a hydroxyl group-containing (meth)acrylic acid ester monomer.
As a moisture absorption test, a laminate laminated to a glass plate via an adhesive layer (thickness of 200 μm) laminated on a resin film was left in an environment of 60 ° C. and 90% RH for 120 hours. ) for 30 minutes, the haze value is measured to determine the transparency of the laminate. According to this adhesive composition, it is possible to maintain high transparency with little foaming even after being left under high temperature and high humidity conditions.

JP-A-2003-262729 JP 2008-248221 A JP 2008-001739 A

The requirements for optical adhesive films in recent years are to ensure high transparency even when the adhesive layer is thickly applied, and to leave it for a long time in an atmosphere of high temperature and high humidity. It should not become cloudy even after it is taken out to a room temperature environment.
However, even if high transparency can be achieved when the thickness of the pressure-sensitive adhesive layer is increased, it has often been difficult to achieve cloudiness prevention performance at high temperature and high humidity. In addition, in order to improve the anti-clouding performance, attempts have been made to increase the amount of hydroxyl group-containing monomer added, and the anti-clouding performance has been improved. It had many shortcomings. There is a need for an adhesive that can simultaneously overcome these drawbacks.

That is, the object of the present invention is to provide a pressure-sensitive adhesive composition having anti-whitening performance, which does not cause whitening even when a pressure-sensitive adhesive film coated with a thick pressure-sensitive adhesive layer is left for a long period of time in an atmosphere of high temperature and high humidity. and to provide an adhesive film.

In order to solve the above problems, the present invention provides a pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer is laminated on one side of a base film, wherein the acrylic polymer However, (A) the total of at least one alkyl (meth)acrylate monomer having an alkyl group of C1 to C14 carbon atoms and at least one phenoxy group-containing alkyl (meth)acrylate monomer is 50 to 95 parts by weight. , (B) 5 to 50 parts by weight of at least one nitrogen-containing vinyl monomer or alkoxy group-containing alkyl (meth)acrylate containing no hydroxyl group or carboxyl group, and (C) a hydroxyl group containing no carboxyl group in the functional group At least one of the copolymerizable vinyl monomers containing 0.5 to 10 parts by weight and a weight average molecular weight of 200,000 to 2,000,000 obtained by copolymerizing without containing a copolymerizable vinyl monomer containing a carboxyl group It is a copolymer, the total of (A) and (B) is contained in a proportion of 100 parts by weight, and the pressure-sensitive adhesive layer is crosslinked with a crosslinking agent, or light by ultraviolet rays When the pressure-sensitive adhesive layer is cross-linked by cross-linking and the pressure-sensitive adhesive layer is cross-linked with a cross-linking agent, the pressure-sensitive adhesive composition contains, with respect to 100 parts by weight of the total of (A) and (B), The (D) crosslinking agent is contained in a proportion of 0.01 to 5 parts by weight, and the (B) nitrogen-containing vinyl monomer containing no hydroxyl group or carboxyl group is an acrylic having an N,N-dialkyl-substituted amino group. a compound selected from the group of compounds consisting of a system monomer, an acrylic monomer having an N,N-dialkyl-substituted amide group, N-vinyl-substituted lactams, and N-(meth)acryloyl-substituted cyclic amines, and the above (C) Copolymerizable vinyl monomers containing hydroxyl groups but not carboxyl groups in functional groups are 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxy from butyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, N-hydroxy (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide Provided is an adhesive film characterized by containing one or more compounds selected from the group consisting of:
A pressure-sensitive adhesive layer having a coating thickness of 250 μm formed from the pressure-sensitive adhesive composition was allowed to stand in an atmosphere of 60° C. and 90% RH for 240 hours, and then taken out to a room temperature environment. The haze value was 4.0%. The following are preferable.
Moreover, this invention provides the film for touchscreens using the said adhesive film.
The present invention also provides an electronic paper film using the pressure-sensitive adhesive film.
The present invention also provides an organic EL film using the pressure-sensitive adhesive film.

According to the present invention, when the pressure-sensitive adhesive layer is thickly coated with a thickness of 250 μm or more, not only is the transparency excellent, but it is also possible to improve the cloudiness prevention performance at high temperature and high humidity.

5 is a graph showing changes in haze values of Example 1 and Comparative Example 1 immediately after being removed from a high-temperature, high-humidity environment.

The present invention will be described below based on preferred embodiments.
The pressure-sensitive adhesive composition of the present invention comprises (B) at least one nitrogen-containing vinyl monomer or alkoxy group-containing alkyl (meth)acrylate monomer, and (C) a copolymer containing no carboxyl group but a hydroxyl group in the functional group. and vinyl monomers.

The adhesive polymer used in the present invention is preferably an acrylic polymer, and in particular, (A) a copolymer composition containing as a main component at least one alkyl (meth)acrylate monomer having an alkyl group with a carbon number of C1 to C14. is preferred.

(A) Alkyl (meth)acrylate monomers having C1 to C14 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and isobutyl (meth)acrylate. Acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth) Acrylate, decyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate and the like. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched or cyclic.
(A) A phenoxy group-containing alkyl (meth)acrylate monomer such as 2-phenoxyethyl (meth)acrylate may be used in combination instead of a part of the alkyl (meth)acrylate monomer having an alkyl group having C1 to C14 carbon atoms. can.

Among (B), nitrogen-containing vinyl monomers include cyclic nitrogen vinyl compounds such as N-vinyl-2-pyrrolidone, N-vinylcaprolactam and N-acryloylmorpholine; N,N-dimethyl(meth)acrylamide, N,N -diethyl (meth)acrylamide, N,N-dipropylacrylamide, N,N-diisopropyl (meth)acrylamide, N,N-dibutyl (meth)acrylamide, N-ethyl-N-methyl (meth)acrylamide, N-methyl -N-propyl (meth)acrylamide, dialkyl-substituted (meth)acrylamide such as N-methyl-N-isopropyl (meth)acrylamide; N,N-dimethylaminomethyl (meth)acrylate, N,N-dimethylaminoethyl (meth) ) acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-dimethylaminoisopropyl (meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate, N-ethyl-N-methylaminoethyl (meth) ) acrylate, dialkylamino (meth)acrylates such as N-methyl-N-propylaminoethyl (meth)acrylate, N-methyl-N-isopropylaminoethyl (meth)acrylate, N,N-dibutylaminoethyl (meth)acrylate ; N,N-dimethylaminopropyl (meth)acrylamide, N,N-diethylaminopropyl (meth)acrylamide, N,N-dipropylaminopropyl (meth)acrylamide, N,N-diisopropylaminopropyl (meth)acrylamide, N -N,N-dialkyl-substituted aminopropyls such as ethyl-N-methylaminopropyl(meth)acrylamide, N-methyl-N-propylaminopropyl(meth)acrylamide, N-methyl-N-isopropylaminopropyl(meth)acrylamide (Meth)acrylamide and the like.
As the nitrogen-containing vinyl monomer (B), those containing no hydroxyl group are preferable, and those containing neither hydroxyl group nor carboxyl group are more preferable. Such monomers include the monomers exemplified above, for example, acrylic monomers containing N,N-dialkyl-substituted amino groups and N,N-dialkyl-substituted amide groups; N-vinyl-2-pyrrolidone, N-vinyl N-vinyl-substituted lactams such as caprolactam and N-vinyl-2-piperidone; N-(meth)acryloyl-substituted cyclic amines such as N-(meth)acryloylmorpholine and N-(meth)acryloylpyrrolidine are preferred.

Among (B), alkoxy group-containing alkyl (meth)acrylate monomers include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, and 2-isopropoxyethyl (Meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, 2-ethoxypropyl (meth) acrylate, 2-propoxypropyl (meth) acrylate, 2-isopropoxypropyl (meth) acrylate , 2-butoxypropyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 3-propoxypropyl (meth)acrylate, 3-isopropoxypropyl (meth)acrylate, 3-butoxy Propyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, 4-ethoxybutyl (meth) acrylate, 4-propoxybutyl (meth) acrylate, 4-isopropoxybutyl (meth) acrylate, 4-butoxybutyl (meth) acrylates and the like.
These alkoxy group-containing alkyl(meth)acrylate monomers have a structure in which the alkyl group atoms in the alkyl(meth)acrylate are substituted with alkoxy groups.

(C) Examples of copolymerizable vinyl monomers containing hydroxyl groups but not carboxyl groups in functional groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate. , 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, hydroxyl group-containing (meth) acrylic acid esters such as 8-hydroxyoctyl (meth) acrylate, N- hydroxy (meth) acrylamide, N- Examples include hydroxyl group-containing (meth)acrylamides such as hydroxymethyl (meth)acrylamide and N-hydroxyethyl (meth)acrylamide, and at least one compound selected from these compound groups is preferred.
Incidentally, hydroxyl-containing (meth)acrylamides contain nitrogen, but in the present invention, they belong to group (C) instead of group (B).

Copolymerizable vinyl monomers other than the above include copolymers containing carboxyl groups such as (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate. Examples include polymerizable vinyl monomers, aromatic group-containing (meth)acrylic acid esters such as benzyl (meth)acrylate, and various vinyl monomers such as styrene, acrylamide, acrylonitrile, methyl vinyl ether, ethyl vinyl ether, vinyl acetate, and vinyl chloride.

The above monomers (A), (B) and (C) constitute, as an acrylic copolymer, a pressure-sensitive adhesive polymer that is the main ingredient of the pressure-sensitive adhesive. The polymerization method of the copolymer is not particularly limited, and suitable polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization and emulsion polymerization can be used.
Although the average molecular weight of the pressure-sensitive adhesive polymer is not particularly limited, for example, the weight average molecular weight is in the range of 200,000 to 2,000,000.

The pressure-sensitive adhesive polymer used in the present invention contains (A) 50 to 95 parts by weight of at least one alkyl (meth)acrylate monomer having an alkyl group having C1 to C14 carbon atoms or an alkyl (meth)acrylate monomer containing a phenoxy group; (B) 5 to 50 parts by weight of at least one of nitrogen-containing vinyl monomers containing no hydroxyl groups or alkyl (meth)acrylate monomers containing alkoxy groups; It is preferably a copolymer containing 0.5 to 10 parts by weight of at least one of the vinyl monomers. Here, the parts by weight of (A) to (C) are defined so that the total of (A) and (B) is 100 parts by weight.

In the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive polymer is preferably crosslinked when forming the pressure-sensitive adhesive layer. For cross-linking, the pressure-sensitive adhesive composition may contain a known cross-linking agent, or may be cross-linked by photo-crosslinking such as ultraviolet (UV) light. Examples of cross-linking agents include di- or more functional isocyanate compounds, bi- or more functional epoxy compounds, bi- or more functional acrylate compounds, metal chelate compounds, and the like. The content of the cross-linking agent is not particularly limited, but may be 0.01 to 5 parts by weight.

(D) The cross-linking agent is preferably one capable of cross-linking the acrylic copolymer by reacting with the hydroxyl group contained in the monomer (C). Examples of such a cross-linking agent include burette modified products and isocyanurates of diisocyanates (compounds having two NCO groups in one molecule) such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate. Modified products, polyisocyanate compounds such as adducts (polyol modified products) with trivalent or higher polyols (compounds having at least 3 or more OH groups in one molecule) such as trimethylolpropane and glycerin. Moreover, you may bridge|crosslink by photocrosslinking, such as an ultraviolet-ray (UV).
Since the copolymer used in the present invention contains the hydroxyl group-containing vinyl monomer (C) as a functional group monomer that reacts with the cross-linking agent, it can be free of the carboxyl group-containing vinyl monomer. .

The pressure-sensitive adhesive composition of the present invention contains (A) 50 to 95 parts by weight of at least one alkyl (meth)acrylate monomer having an alkyl group having a carbon number of C1 to C14 or a phenoxy group-containing alkyl (meth)acrylate monomer, ( B) 5 to 50 parts by weight of at least one of nitrogen-containing vinyl monomers containing no hydroxyl groups or alkyl (meth)acrylate monomers containing alkoxy groups; A copolymer having a weight average molecular weight of 200,000 to 2,000,000, comprising at least one vinyl monomer of 0.5 to 10 parts by weight, and (D) a crosslinking agent of 0.01 to 5 parts by weight, It is preferable to contain (A) and the above (B) in such a proportion that the total is 100 parts by weight.

The pressure-sensitive adhesive composition of the present invention further contains other components such as silane coupling agents, antioxidants, surfactants, curing accelerators, plasticizers, fillers, curing retarders, processing aids, and anti-aging agents. Known additives can be blended as appropriate. These can be used alone or in combination of two or more.

According to the pressure-sensitive adhesive composition of the present invention, when the thickness of the pressure-sensitive adhesive layer is thick, not only is it excellent in transparency, but it is also possible to improve the cloudiness prevention performance at high temperature and high humidity. . It is preferable that the pressure-sensitive adhesive layer having a coating thickness of 250 μm formed from the pressure-sensitive adhesive composition has a total light transmittance of 90% or more and a haze value of 1.0% or less. In addition, the haze value when the pressure-sensitive adhesive layer with a coating thickness of 250 μm formed by the pressure-sensitive adhesive composition was left in an atmosphere of 60° C. and 90% RH for 240 hours and then taken out to a room temperature environment was 4.0. % or less.

The pressure-sensitive adhesive film of the present invention is obtained by laminating a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition of the present invention on one side of a base film. The pressure-sensitive adhesive film of the present invention can be used for various applications such as touch panels, electronic paper, organic EL, optical members, and surface protection. Although the thickness of the pressure-sensitive adhesive layer is not particularly limited, it is, for example, 100 to 2000 μm. If the thickness of the pressure-sensitive adhesive layer is too thin, the impact absorption performance will deteriorate, but if the thickness of the pressure-sensitive adhesive layer is too thick, there is a disadvantage in that the cost increases. In particular, it is preferable that the pressure-sensitive adhesive layer is thickly coated with a thickness of 250 μm or more, because the effect of the present invention is high.

A resin film such as a polyester film can be used as the base film of the pressure-sensitive adhesive layer and the release film (separator) that protects the pressure-sensitive adhesive surface.
On the side of the base film opposite to the side of the resin film on which the pressure-sensitive adhesive layer is formed, silicone-based or fluorine-based release agents or coating agents, antifouling treatment with silica fine particles, etc., antistatic agent coating, Antistatic treatment such as kneading can be applied.
The release film is subjected to release treatment with a silicone-based or fluorine-based release agent or the like on the side of the release film that is to be matched with the adhesive surface of the adhesive layer.
In the case of an optical surface protective film such as a polarizing plate surface protective film, it is preferable that the substrate film and the pressure-sensitive adhesive layer have sufficient transparency.
Moreover, it can use for the laminated|multilayer film which laminated|stacked various films through an adhesive layer. Examples of such films include touch panel films, electronic paper films, organic EL films, and optical films.

Moreover, the pressure-sensitive adhesive composition of the present invention can also be used for an optical film with a pressure-sensitive adhesive, in which a pressure-sensitive adhesive layer is laminated on at least one surface of an optical film.
In the adhesive-attached optical film, optical films such as a polarizing plate film, a retardation plate film, a lens film, a polarizing plate film also used as a retardation plate, and a polarizing plate film also used as a lens film can be used as the base film. .
The adhesive-attached optical film is obtained by laminating an adhesive layer on one side or both sides of an optical film, and can be used for lamination with a glass plate or the like of an image display device. These adhesive-attached optical films can be attached to a glass substrate or the like via an adhesive layer and incorporated into an image display device or the like. The pressure-sensitive adhesive layer used in the pressure-sensitive adhesive optical film such as the pressure-sensitive adhesive polarizing plate preferably has sufficient transparency.
A polarizing plate used as a base film generally has a three-layer structure in which a polyvinyl alcohol-based polarizer is sandwiched between triacetylcellulose-based protective films on both sides.
A polarizing plate in which a discotic liquid crystal is coated on the surface of a protective film, or a stretched triacetylcellulose film, a stretched polycycloolefin film, or a stretched cellulose acetate propionate film instead of a triacetylcellulose film It has a structure in which it is pasted together by etc. Furthermore, these polarizing plate films are attached to a glass substrate, which is a surface base material of a liquid crystal display panel, via an adhesive layer.

EXAMPLES The present invention will be specifically described below with reference to Examples.

<Production of acrylic copolymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube to replace the air in the reactor with nitrogen gas. Then, 95 parts by weight of 2-ethylhexyl acrylate, 5 parts by weight of N-vinyl-2-pyrrolidone, 1.0 parts by weight of 6-hydroxyhexyl acrylate, and 100 parts of solvent (ethyl acetate) were added to the reactor. Thereafter, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and reacted at 65° C. for 8 hours to obtain the acrylic copolymer solution of Example 1 having a weight average molecular weight of 800,000. got 1.
[Examples 2-7 and Comparative Examples 1-2]
Examples 2 to 7 and Comparative Examples 1 and 2 were prepared in the same manner as the acrylic copolymer solution 1 used in Example 1 above, except that the composition of each monomer was as described in Table 1. An acrylic copolymer solution to be used was obtained.

<Production of adhesive composition and adhesive film>
[Example 1]
0.5 parts by weight of Coronate HX (an isocyanurate of a hexamethylene diisocyanate compound) is added to the acrylic copolymer solution 1 (of which 100 parts by weight are group (A) + group (B)) produced as described above. In addition, they were stirred and mixed to obtain a pressure-sensitive adhesive composition of Example 1. After applying this adhesive composition onto a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, the solvent was removed by drying at 90° C., and the thickness of the adhesive layer was 250 μm. A sticky film was obtained.
After that, the adhesive sheet was transferred to a polyethylene terephthalate (PET) film to obtain an adhesive film of Example 1 having a laminated structure of "PET film/adhesive layer/release film (silicone resin-coated PET film)". .
[Examples 2-7 and Comparative Examples 1-2]
Adhesives of Examples 2 to 7 and Comparative Examples 1 and 2 were prepared in the same manner as the surface protective film of Example 1 above, except that the composition of the cross-linking agent was as described in Table 1 (D). got the film.

In Table 1, the compounding ratio of each component is shown by enclosing the numerical value of parts by weight in parentheses, based on the total of Group (A) + Group (B) being 100 parts by weight. Mw in Table 1 means weight average molecular weight.
In addition, Table 2 shows the compound names of the abbreviations of the respective components used in Table 1. Moreover, in the (D) group of Table 2, HDI means hexamethylene diisocyanate and XDI means xylylene diisocyanate.
Coronate (registered trademark) HX, HL and L-45 are trade names of Nippon Polyurethane Industry Co., Ltd. Duranate (registered trademark) 24A-100 is a trade name of Asahi Kasei Chemicals Co., Ltd. Takenate (Registered Trademark) D-110N is a trade name of Mitsui Chemicals, Inc.

<Test method and evaluation>
After aging the adhesive films of Examples 1 to 7 and Comparative Examples 1 and 2 in an atmosphere of 23 ° C. and 50% RH for 7 days, the release film (silicone resin-coated PET film) was peeled off to form an adhesive layer. was used as a measurement sample for the total light transmittance.
In addition, after aging the adhesive films of Examples 1 to 7 and Comparative Examples 1 and 2 in an atmosphere of 23° C. and 50% RH for 7 days, the adhesive layer was removed with a release film (silicone resin-coated PET film). A sample with both sides covered was used as a sample for haze value measurement.
Further, the adhesive films of Examples 1 to 7 and Comparative Examples 1 and 2 were aged in an atmosphere of 23° C. and 50% RH for 7 days, and then left in an oven at 60° C. and 90% RH for 240 hours. After being removed from the oven to a room temperature environment (23 ° C., 50% RH), both sides of the adhesive layer covered with a release film (silicone resin-coated PET film) were used as a measurement sample for the haze value after moist heat. did.
In addition, the adhesive film with the adhesive layer exposed is attached to the surface of the non-alkali glass plate via the adhesive layer, left to stand for one day, and then autoclaved at 50 ° C., 5 atmospheres for 20 minutes, and heated at room temperature. The sample was left for another 12 hours and used as a test sample for adhesive strength.
Also, the adhesive film with the adhesive layer exposed was attached to the surface of an alkali-free glass plate via the adhesive layer to obtain a durability measurement sample.

<Total light transmittance>
For the measurement sample of the total light transmittance obtained above, a haze meter (manufacturer: Nippon Denshoku Co., Ltd., model: Haze Meter, NDH2000) is used to measure the total light transmittance of the pressure-sensitive adhesive layer according to JISK7105. was measured.

<Haze value and haze value after moist heat>
Using a haze meter (manufacturer: Nippon Denshoku Co., Ltd., model: Haze Meter, NDH2000), the haze value of the pressure-sensitive adhesive layer was measured for the samples obtained above for measuring the haze value and the post-wet heat haze value.
In the above measurement sample, the release film (silicone resin-coated PET film) covering both sides of the adhesive layer was used as the measurement sample for the haze value and the haze value after moist heat, but the release film itself was confirmed to be negligibly small.

<Adhesive strength to glass plate>
The adhesive force measurement sample obtained above (a 25 mm wide adhesive film laminated on the surface of a non-alkali glass plate) was subjected to 0.3 m / min tension using a tensile tester in the 180 ° direction. The adhesive strength was determined by peeling at a speed and measuring the peel strength.

<Durability>
The durability measurement sample obtained above was allowed to stand in an atmosphere of 80° C. (dry) for 250 hours, then taken out to room temperature, and peeling from the adherend, foaming, etc. were visually observed. The evaluation criteria were "○" when no peeling/foaming was observed at all, "△" when peeling/foaming was slightly observed, and "×" when peeling/foaming was clearly observed.

Table 3 shows measurement results and evaluation results.

The pressure-sensitive adhesive films of Examples 1 to 7 have not only transparency (total light transmittance of 90% or more, haze value of 1.0% or less) when the pressure-sensitive adhesive layer is thickly coated (250 μm), but also It has little cloudiness even when left in a humid atmosphere for a long period of time, and has cloudiness prevention performance (haze value is 4.0% or less after being left for 240 hours at 60°C, 90% RH), and improves cloudiness prevention performance. I was able to Furthermore, even when left in a high-temperature atmosphere for a long period of time, neither peeling nor foaming occurred.
When the pressure-sensitive adhesive films of Comparative Examples 1 and 2 were left in a high-temperature, high-humidity atmosphere for a long period of time, an increase in haze value was observed, indicating a problem in cloudiness prevention performance. In addition, when left in a high-temperature atmosphere for a long period of time, peeling and foaming were observed, resulting in a problem of durability. Furthermore, in Comparative Example 1, the results of measurement of transparency (total light transmittance/haze value) were poor even before being left in an atmosphere of high temperature and high humidity.

<Change in haze value after removal from high-temperature and high-humidity environment>
In addition, the adhesive films of Example 1 and Comparative Example 1 were aged in an atmosphere of 23°C and 50% RH for 7 days, and then left in an oven at 60°C and 90% RH for 240 hours. It was taken out to the environment (23° C., 50% RH), and the haze value was measured for 60 minutes from immediately after taking it out. FIG. 1 shows the obtained change in haze value after removal from the environment of high temperature and high humidity.
In FIG. 1, in Example 1 according to the present invention, the haze value reached the maximum value (3.5%) about 1 minute after it was taken out of the oven. The haze value does not exceed 4.0%, demonstrating excellent anti-whitening performance. On the other hand, in Comparative Example 1, the haze value increased to a maximum value of about 25% within a few minutes immediately after being taken out of the oven, and then the haze value tended to decrease gradually with the lapse of the standing time, but cloudiness was observed. It can be seen that this remarkable state continues for 60 minutes or longer.
In addition, in both Example 1 and Comparative Example 1, the cloudiness that occurred in a high-temperature and high-humidity environment gradually disappeared by leaving it at room temperature for several hours, and finally the adhesive film became transparent (haze value was 1.0% or less).
This evaluation is a change that occurs when both sides of the pressure-sensitive adhesive layer are covered between release films. In the case of samples laminated to each other or acrylic plate and glass, the timing of cloudiness is the same, but it may take several days for the cloudiness to disappear.

Claims (5)

A pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer is laminated on one side of a base film,
The acrylic polymer is
(A) a total of 50 to 95 parts by weight of at least one alkyl (meth)acrylate monomer having an alkyl group having C1 to C14 carbon atoms or a phenoxy group-containing alkyl (meth)acrylate monomer;
(B) 5 to 40 parts by weight of at least one nitrogen-containing vinyl monomer containing no hydroxyl group or carboxyl group;
(C) 0.5 to 10 parts by weight of at least one copolymerizable vinyl monomer containing a hydroxyl group but not a carboxyl group in the functional group;
is a copolymer having a weight average molecular weight of 450,000 to 2,000,000 obtained by copolymerizing without containing a copolymerizable vinyl monomer containing a carboxyl group,
The total of (A) and (B) is contained at a rate of 100 parts by weight,
The pressure-sensitive adhesive layer is crosslinked by a crosslinking agent or by photocrosslinking by ultraviolet light,
When the pressure-sensitive adhesive layer is crosslinked with a crosslinking agent, the pressure-sensitive adhesive composition contains the (D) crosslinking agent with respect to 100 parts by weight of the total of the (A) and the (B). Containing at a rate of 0.01 to 5 parts by weight,
The (C) functional group containing a hydroxyl group-free copolymerizable vinyl monomer is 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, or 3-hydroxypropyl (meth)acrylate. , 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl ( One or more selected from the group of compounds consisting of meth)acrylamide, and 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, N-hydroxymethyl An adhesive film comprising at least one compound selected from the group of compounds consisting of (meth)acrylamide and N-hydroxyethyl(meth)acrylamide. A pressure-sensitive adhesive layer having a coating thickness of 250 μm formed from the pressure-sensitive adhesive composition was allowed to stand in an atmosphere of 60° C. and 90% RH for 240 hours, and then taken out to a room temperature environment. The haze value was 4.0%. The pressure-sensitive adhesive film according to claim 1, wherein: A touch panel film using the adhesive film according to claim 1 or 2. An electronic paper film using the adhesive film according to claim 1 or 2. An organic EL film using the adhesive film according to claim 1 or 2.

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