JP2003205567A - Surface protecting film for transparent conductive film, and transparent conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protecting film for a transparent conductive film which can be smoothly released in a later stage, even when the film is laminated on a transparent conductive film as an adherend and disposed under heating environments. <P>SOLUTION: The surface protecting film protects an opposite side to a conductive thin film of the transparent conductive film and has a pressure-sensitive adhesive layer formed on one side of a base material film. In addition, the surface protecting film shows that the tack strength measured under conditions of a rate of pulling of 0.3 m/min. and the tack strength measured under conditions of a rate of pulling of 10 m/min., after the heating of the pressure- sensitive adhesive layer at 150°C for one hour, in such a state that the layer is laminated on the adherend face, are equally 2.8 N/20 mm or less. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a surface protective film used for a transparent conductive film which is widely used in the fields of liquid crystal displays, touch panels, sensors, transparent electrodes in solar cells, and the like, and a transparent film using the same. The present invention relates to a conductive film.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 3, a transparent conductive film is a base film 2a made of polyester or the like.
1 has a structure in which a conductive thin film 2b made of ITO or the like is formed on one surface and a hard coat layer 2c (or an antiglare layer) is formed on the other surface. In such a transparent conductive film 2, conventionally, a surface protective film is used for the hard coat layer 2c or the anti-glare layer on the side opposite to the conductive thin film 2b in order to prevent the adhesion of foreign matters and dirt. Examples of the surface protective film include polyethylene / ethylene-vinyl acetate copolymer (P
E / EVA) double-layer tape is used.

When the transparent conductive film to be adhered to the surface protection film is used, for example, in the manufacture of a touch panel, silver ink is printed in order to form electrodes in the manufacturing process, and in a plurality of steps. It is subjected to heat drying. The heating conditions are in the temperature range of 90 to 150 ° C., the time is 10 to 30 minutes in each drying step, and the total time is about 1 hour. However, in such a heating and drying step, the surface protective film has a markedly increased adhesive force, making it impossible to peel it from the transparent conductive film.

Acrylic pressure-sensitive adhesives have been investigated for forming the pressure-sensitive adhesive layer of the surface protective film. However, the acrylic pressure-sensitive adhesive has a problem that it has a high pressure-sensitive adhesive force after being dried by heat, and it is difficult to perform the peeling work, and eventually destroys the transparent conductive film.

As described above, since the conventional surface protection film has the above problems, the surface protection film is used before and after the heating step, but it is difficult to use it during the heating step. Therefore, the adherend cannot be protected from scratches and dirt during the heating process.

[0006]

DISCLOSURE OF THE INVENTION The present invention makes it possible to favorably carry out the subsequent peeling work even when placed in a heating environment in the state of being stuck to a transparent conductive film which is an adherend. It is an object of the present invention to provide a surface protection film for a transparent conductive film that can be obtained. Another object of the present invention is to provide a transparent conductive film using the same.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and found that the above-mentioned problems can be solved by providing the following pressure-sensitive adhesive layer as a pressure-sensitive adhesive layer of a surface protective film. Heading The present invention has been completed.

That is, the surface protective film for a transparent conductive film of the present invention is a film for protecting the surface of the transparent conductive film opposite to the conductive thin film, and an adhesive layer on one side of the base film. Is provided, and after the adhesive layer is attached to the adherend surface and heated at 150 ° C. for 1 hour, the adhesive force measured under the condition of a tensile speed of 0.3 m / min,
And the adhesive force measured under the condition of a pulling speed of 10 m / min,
Both are characterized by being 2.8 N / 20 mm or less. Here, the adhesive force is a value specifically measured by the measuring method described in Examples.

On the other hand, the transparent conductive film of the present invention is provided with a conductive thin film on one side of the substrate film and a hard coat layer or an anti-glare layer on the other side of the base film, The pressure-sensitive adhesive layer is attached to the surface of the hard coat layer or the anti-glare layer.

Further, another transparent conductive film of the present invention is provided with a conductive thin film on one side of a base film, and the pressure-sensitive adhesive layer of the surface protective film for a transparent conductive film is added to the base film. It is attached to the other surface.

[Effects] The surface protective film for a transparent conductive film of the present invention (hereinafter, abbreviated as "surface protective film") has a small increase in the adhesive force of the adhesive layer even under a heating environment. The peeling work can be performed well. Therefore, the surface protection film can be subjected to the heating step in a state of being bonded to the adherend (the surface opposite to the conductive surface of the transparent conductive film), and the adherend is protected from scratches and dirt during the heating step. be able to. Further, conventionally, it took a lot of time to replace the surface protective film before and after the heating step, but the surface protective film of the present invention can be provided during the heating step in a state of being attached to an adherend,
The labor of replacing the surface protection film can be saved and the workability can be remarkably improved.

The surface protective film of the present invention, after being bonded to an adherend, is heated at 150 ° C. for 1 hour,
The adhesive force measured under the conditions of a pulling speed of 0.3 m / min and 10 m / min are both 2.8 N / 20 mm or less, preferably 2
N / 20 mm or less, more preferably 1.5 N / 20 mm
It is the following. The pulling speed varies from a slow peeling speed (0.3 m / min) to a relatively high peeling speed (10 m / min) because the speed at which a person actually peels the surface protective film from the adherend is not constant. It shows that the adhesive force is light in the peeling speed range that is actually specified. Therefore, if the adhesive force at either one of the pulling speeds exceeds 2.8 N / 20 mm, the peeling work may be inconvenient. From the viewpoint of maintaining the protective function of the surface protective film with respect to the adherend, the initial adhesive force of the surface protective film with respect to the adherend (adhesive force at a pulling speed of 0.3 m / min after 30 minutes after bonding) is: It is preferably 0.01 N / 20 mm or more, and more preferably 0.03 N / 20 mm or more.

On the other hand, according to the transparent conductive film of the present invention, the surface protective film as described above is adhered to the surface of the hard coat layer or the antiglare layer or the base film, so that the adherend is adhered during the heating step. The workability can be remarkably improved because the work can be protected and the work of replacing the surface protection film can be omitted.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a usage state of the surface protective film of the present invention,
FIG. 2 is a cross-sectional view showing another example of the usage state.

In the surface protective film of the present invention, as shown in FIG. 1, an adhesive layer 1b is provided on one side of a base film 1a. The surface protection film of the present invention protects the surface of the transparent conductive film opposite to the conductive thin film. The embodiment shown in FIG. 1 is an example in which the surface protective film 1 is attached to the surface of the hard coat layer 2c (or the anti-glare layer) of the transparent conductive film 2, and the embodiment shown in FIG. This is an example in which the surface protection film 1 is attached to the surface of the base film 2a of the film 2.

The base film 1a is not particularly limited, and for example, polyethylene terephthalate (PE
T), polyester such as polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polycarbonate, polymethylmethacrylate, polystyrene, polyvinyl chloride, polyethylene, polypropylene, polyethylene / polypropylene blend, polyamide, polyimide, cellulose acetate, polysulfone, Examples include polyether sulfone. Above all, if transparency and heat resistance are required, PET,
PEN and PPS are preferred.

The thickness of the substrate film 1a is not particularly limited, but it is preferably 10 to 200 μm, preferably 15 to 100 μm, and more preferably 20 to 70 μm. If the thickness is too thin, the strength for peeling the surface protection film 1 and the surface protection function tend to be insufficient. If the thickness is too thick, it tends to be disadvantageous in terms of handleability and cost. Considering the anchoring property with the pressure-sensitive adhesive layer 1b, the surface of the base film 1a is preferably subjected to a treatment such as corona discharge, electron beam irradiation, sputtering, or an easy adhesion treatment.

As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 1b,
Removable pressure-sensitive adhesives (acrylic type, rubber type, synthetic rubber type, etc.) capable of forming the pressure-sensitive adhesive layer having the above-mentioned adhesive force can be used without particular limitation. Above all, an acrylic pressure-sensitive adhesive whose adhesive strength is easily controlled by its composition is preferable. In order to obtain an adhesive layer having the above-mentioned adhesive strength, it is preferable that the adhesive layer is crosslinked at high density.

As the acrylic pressure-sensitive adhesive, the base polymer preferably has a weight average molecular weight of about 300,000 to 2,500,000. As the monomer used for the acrylic polymer that is the base polymer of the acrylic pressure-sensitive adhesive, various alkyl (meth) acrylates can be used. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Can be used alone or in combination.

As the acrylic pressure-sensitive adhesive, a copolymer obtained by copolymerizing the above-mentioned acrylic polymer with a functional group-containing monomer as a base polymer and blending a cross-linking agent capable of undergoing a cross-linking reaction with the functional group of the functional group-containing monomer is used. preferable.

Examples of the monomer having a functional group include a monomer containing a carboxyl group, a hydroxyl group, an epoxy group, amino and the like. Examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, fumaric acid, maleic acid and itaconic acid. As the monomer having a hydroxyl group, 2-hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, N-methylol (meth) acrylamide, and the like, and as the monomer having an epoxy group, glycidyl ( Examples thereof include (meth) acrylate.

Further, an N element-containing monomer can be copolymerized with the acrylic polymer. Examples of the N element-containing monomer include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, (meth) acryloylmorpholine, and (meth).
Acetonitrile, vinylpyrrolidone, N-cyclohexylmaleimide, itacone imide, N, N-dimethylaminoethyl (meth) acrylamide and the like can be mentioned. In addition, vinyl acetate, styrene, etc. may be used as the acrylic polymer as long as the performance of the pressure-sensitive adhesive is not impaired. These monomers can be used alone or in combination of two or more.

The proportion of the copolymerizable monomer in the acrylic polymer is not particularly limited, but the copolymerizable monomer may be added to 100 parts by weight of the alkyl (meth) acrylate.
It is preferably about 0.1 to 12 parts by weight, more preferably 0.5 to 10 parts by weight.

Examples of the crosslinking agent include epoxy type crosslinking agents, isocyanate type crosslinking agents, imine type crosslinking agents and metal chelate type crosslinking agents. Examples of the cross-linking agent include polyamine compounds, melamine resins, urea resins and epoxy resins. Among the crosslinking agents, the epoxy-based crosslinking agent is suitable. The mixing ratio of the cross-linking agent to the acrylic polymer is not particularly limited, but normally, the cross-linking agent (solid content) is 0.0 to 100 parts by weight of the acrylic polymer (solid content).
About 1 to 10 parts by weight is preferable. In order to crosslink with high density, it is preferable that the mixing ratio of the crosslinking agent is 3 parts by weight or more.

Further, if necessary, the above-mentioned pressure-sensitive adhesives include tackifiers, plasticizers, fillers, antioxidants, ultraviolet absorbers,
A silane coupling agent or the like can also be used appropriately.

As the pressure-sensitive adhesive layer of the present invention, it is more preferable to use one that is crosslinked with high density as described above. For example, it is possible to crosslink the acrylic pressure-sensitive adhesive at a higher density than that of a commonly used acrylic pressure-sensitive adhesive by blending the above-mentioned cross-linking agent with the acrylic pressure-sensitive adhesive or irradiating with an electron beam or the like. For example, in the acrylic pressure-sensitive adhesive, the gel content is preferably 90% by weight or more as a standard for high-density crosslinking. The gel fraction can be calculated by the following method.

(Gel Fraction) Adhesive Bulk 10 cm × 10
After taking out cm and measuring the weight (w1), Nitto Denko Fluororesin membrane NTF-1122 (average pore diameter 0.2 μm)
m) It was put in 10 cm × 10 cm, tied with a string and sealed. This sample was left to stand in 40 ml of ethyl acetate for 7 days, and the ethyl acetate in the sample was volatilized under the atmosphere of 130 ° C. for 2 hours. Then, the weight (w2) of the residual adhesive in the fluororesin film was measured and calculated from the following formula. Gel fraction (% by weight) = (w2 / w1) ×
100.

The method for forming the pressure-sensitive adhesive layer 1b is not particularly limited, and a method in which a pressure-sensitive adhesive is applied to a silicone-treated polyester film, dried and then transferred to the base film 1a (transfer method), the base film 1a is formed. Examples thereof include a method of directly applying and drying the pressure-sensitive adhesive composition (direct copying method) and a method of coextrusion.

The thickness of the pressure-sensitive adhesive layer 1b is not particularly limited, but is preferably about 3 to 100 μm, more preferably about 5 to 40 μm. When the thickness of the pressure-sensitive adhesive layer 1b is too thin, it tends to be difficult to form the coating, and the adhesive force tends to be insufficient. If the thickness is too thick, the adhesive strength tends to be too high, which is disadvantageous in terms of cost.

The surface protective film 1 of the present invention can be wound in a roll shape if the pressure-sensitive adhesive layer 1b is protected by a separator or if the base film 1a has good releasability. . Further, the surface protection film 1 may be subjected to an antistatic treatment by a usual means in order to prevent dust adhesion and the like.

On the other hand, the transparent conductive film 2 protected by the surface protective film 1 of the present invention is, for example, as shown in FIG. 1 or 2. That is, as shown in FIG. 1, the transparent conductive film of the present invention is provided with a conductive thin film 2b on one side of the base film 2a and a hard coat layer 2c (or an anti-glare layer) on the other side thereof, and has surface protection. Film 1
The pressure-sensitive adhesive layer 1b is adhered to the surface of the hard coat layer 2c (or antiglare layer). Alternatively,
A conductive thin film 2b is provided on one side of the base film 2a, and the pressure-sensitive adhesive layer 1b of the surface protection film 1 is attached to the other surface of the base film 2a.

The conductive thin film 2b is made of ITO (indium.
It is formed by a thin film of a metal oxide such as tin oxide), tin / antimony, zinc, tin oxide, or an ultrathin film of a metal such as gold, silver, palladium or aluminum. These are formed by a vacuum vapor deposition method, an ion beam vapor deposition method, a sputtering method, an ion plating method, or the like. Conductive thin film 2b
The thickness of is not particularly limited, but generally 50 Å or more,
It is preferably 100 to 2000Å.

As the base film 2a, a film made of a transparent material is usually used. As such a transparent material,
Examples thereof include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polymethyl methacrylate, styrene polymers such as polystyrene and acrylonitrile / styrene copolymer (AS resin), and polycarbonate. Further, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefins such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers, poly Ether sulfone-based polymer, polyether ether ketone-based polymer, polyphenylene sulfide-based polymer, vinyl alcohol-based polymer, vinylidene chloride-based polymer, vinyl butyral-based polymer, arylate-based polymer, polyoxymethylene-based polymer, epoxy-based polymer, or the above-mentioned polymer Blended products are also included.

The thickness of the base film 2a is not particularly limited, but is generally about 20 to 130 μm, preferably 3
It is 0 to 80 μm.

The hard coat layer 2c may have not only a hard coat function, but also an antiglare function at the same time, or a hard coat layer 2c provided with an antiglare layer on its surface.

Usable hard coating agents include ordinary ultraviolet (UV) and electron beam curable coatings, silicone type hard coating agents, phosphazene resin type hard coating agents, etc., but they are easy in terms of material cost and process.・
A UV-curable coating is preferable in terms of the degree of freedom in composition. U
V-curing type paints include vinyl polymerization type, polythiol / polyene type, epoxy type, amino alkyd type, and prepolymer types are classified into alkyd, polyester, polyether, acrylic, urethane and epoxy types. However, any type can be used.

The antiglare layer refers to a layer having functions such as glare prevention and antireflection. Specifically, for example, one utilizing the difference in refractive index between layers, one utilizing the difference in refractive index with the contained fine particles, and one having a surface with fine irregularities are mentioned.

The transparent conductive film 2 of the present invention is used not only for new display systems such as liquid crystal displays and electroluminescence displays, transparent electrodes for touch panels, sensors, solar cells, etc., but also for preventing electrostatic charge of transparent articles and electromagnetic wave shielding. be able to.

[0039]

EXAMPLES Examples and the like specifically showing the constitution and effects of the present invention will be described below.

Example 1 Polyester film (Mitsubishi Chemical Polyester Co., Ltd.)
(Diafoil T100C), thickness 38 μm), the thickness after drying the following acrylic adhesive on one side is 20 μm
To obtain a surface protective film. <Acrylic pressure-sensitive adhesive> By a normal solution polymerization, an acrylic polymer having a weight average molecular weight of 600,000 was obtained with butyl acrylate / acrylic acid = 100/6 (weight ratio). To 100 parts by weight of this acrylic polymer, 6 parts by weight of an epoxy crosslinking agent (“Tetrad C” manufactured by Mitsubishi Gas Chemical Co., Ltd.) was added to obtain a pressure-sensitive adhesive composition. The gel fraction of the pressure-sensitive adhesive layer was 95% by weight.

Example 2 Surface protection was carried out in the same manner as in Example 1 except that as the acrylic pressure-sensitive adhesive, a pressure-sensitive adhesive composition in which the amount of the epoxy-based crosslinking agent used was changed to 4 parts by weight was used. I got a film. The gel fraction of the pressure-sensitive adhesive layer was 94% by weight.

Comparative Example 1 A surface protective film was obtained in the same manner as in Example 1 except that the following acrylic adhesive was used.

<Acrylic Adhesive> An acrylic polymer having a weight average molecular weight of 600,000 was obtained by ordinary solution polymerization with 2-ethylhexyl acrylate / 2-hydroxyethyl acrylate = 100/4 (weight ratio). To 100 parts by weight of this acrylic polymer, 3 parts by weight of an isocyanate crosslinking agent (“Coronate L” manufactured by Nippon Polyurethane) was added to prepare an adhesive composition. The gel fraction of the pressure-sensitive adhesive layer was 89% by weight.

Comparative Example 2 As the surface protective film, a two-layer structure film of polyethylene (base material) / ethylene-vinyl acetate copolymer (adhesive) (“SPV-300” manufactured by Nitto Denko) was used.

Comparative Example 3 As a surface protective film, a film obtained by coating a polyisobutylene adhesive on a blend film of polypropylene and polyethylene (“SPV-3643F” manufactured by Nitto Denko).
Was used.

[Evaluation Test] (1) Initial Adhesion Strength Adhesion of the surface protective films of Examples and Comparative Examples to the hard coat surface of the transparent conductive film (“Electrista G400L-TMP” manufactured by Nitto Denko) which is the adherend. After bonding the agent layers, after 30 minutes have passed, at 23 ° C., the tensile speed was 0.3 m / min and the tensile speed was 10 m / min.
The adhesive force (N / 20 mm) at 80 ° (peel angle) was measured. The results are shown in Table 1.

(2) Adhesive force after heating On the hard coat surface of the transparent conductive film (“Electrista G400L-TMP” manufactured by Nitto Denko), which is the adherend, the pressure-sensitive adhesive layer of the surface protective film of Examples and Comparative Examples. After bonding, the mixture was heated at 150 ° C. for 1 hour. After cooling, 23 ℃
At a pulling speed of 0.3 m / min and a pulling speed of 10 m
Adhesive force (N
/ 20 mm) was measured. The results are shown in Table 1.

[0048]

[Table 1] As the results of Table 1 show, the surface protection films of Examples had tensile speeds of 0.3 m / min and 1 even after heating.
Adhesive strength is 2.8 N / m under any condition of 0 m / min.
It was 20 mm or less, and the peeling workability was good. On the other hand, in the comparative example, the adhesive strength after heating exceeded 2.8 N / 20 mm, and the peeling workability was poor.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a usage state of a surface protective film for a transparent conductive film of the present invention.

FIG. 2 is a cross-sectional view showing another example of a usage state of the surface protective film for a transparent conductive film of the present invention.

FIG. 3 is a cross-sectional view showing an example of a transparent conductive film that does not use a surface protection film.

[Explanation of symbols]

1 Surface protection film 1a Base film 1b adhesive layer 2 Transparent conductive film 2a Base film 2b conductive thin film 2c hard coat layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsushi Yamamoto             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Masatake Hayashi             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. F term (reference) 4F100 AK25G AK41 AT00A AT00D                       BA02 BA05 BA07 BA10A                       BA10E CA02 GB41 JG01E                       JK12C JL13B JL14B JM02E                       JN30C YY00B                 4J004 AA05 AA10 AB01 CA03 CA05                       CA06 CB03 CC02 FA04 FA05                 4J040 DF011 DF041 DF051 DF081                       DF091 DG001 DH031 GA05                       GA11 GA13

Claims (3)

[Claims] 1. A film for protecting the surface of a transparent conductive film on the side opposite to the conductive thin film, wherein a pressure-sensitive adhesive layer is provided on one side of a base film, and the pressure-sensitive adhesive layer is applied. After being heated at 150 ° C. for 1 hour in a state of being bonded to the surface, the adhesive force measured under the condition of a tensile speed of 0.3 m / min and the adhesive force measured under the condition of a tensile speed of 10 m / min are both 2.8 N. / 20 mm or less, a surface protective film for a transparent conductive film. 2. The substrate film is provided with a conductive thin film on one side and a hard coat layer or an antiglare layer on the other side, and the pressure-sensitive adhesive layer of the surface protective film for a transparent conductive film according to claim 1, A transparent conductive film which is attached to the surface of the hard coat layer or the anti-glare layer. 3. A conductive thin film is provided on one side of a base film, and the pressure-sensitive adhesive layer of the surface protective film for a transparent conductive film according to claim 1 is attached to the surface of the other side of the base film. A transparent conductive film formed by.