JPH09156015A - Hard coat film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the static prevention performance without lowering the hardness of a surface and retain the static prevention effect for a long period of time by incorporating a needle-shaped crystal structure conductive material in a hard coat layer. SOLUTION: A hard coat layer can be formed of a polymer binder composed mainly of thermosetting resin or ionization radiation curing resin and a conductive material of needle-shaped crystal structure. As the polymer binder, ionization radiation curing resin is preferred from the viewpoint of providing easily the high hardness. As the shape of the conductive material of needle-shaped crystal is of needle shape, a large charge prevention effect can be provided by a small content. As for the conductive material, tin oxide of needle-shaped crystal structure formed doped with antimony oxide is most preferable. The needle-shaped crystal tin oxide is not only of high static prevention performance, but also improves transparency.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hard coat film having excellent antistatic properties.

[0002]

2. Description of the Related Art In recent years, hard coat films have been used for display parts of various home electric appliances and decorative plates for membrane switches.

Since such a hard coat film contains an insulating resin as a main component, it is apt to be charged with static electricity due to its nature and problems such as stains are likely to occur.

In order to solve this, an antistatic layer is provided on the surface of the hard coat layer, or an antistatic agent is contained in the hard coat layer.

However, when the antistatic layer is provided on the surface, the antistatic layer is scraped off during use,
The antistatic effect is lost.

Further, when an antistatic agent is contained in the hard coat layer, the hardness of the hard coat layer itself is considerably lowered, and problems such as scratches occur.

[0007]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a hard coat film which imparts antistatic performance without lowering the hardness of the surface and can maintain the antistatic effect for a long period of time. .

[0008]

The present invention provides a hard coat film having a hard coat layer on a plastic film, wherein the hard coat layer contains a conductive material having an acicular crystal structure.

Further, in a hard coat film having a hard coat layer on a plastic film, the hard coat layer contains tin oxide having an acicular crystal structure doped with antimony oxide.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

As the plastic film, a film or plate of polyethylene terephthalate, polybutylene terephthalate, polycarbonate, acrylic, triacetate or the like can be used. When used for a decorative plate such as a membrane switch, a stretched film, particularly a biaxially stretched film is preferable because mechanical strength and dimensional stability are improved. The thickness can be appropriately selected depending on the use, but in the above use, it is generally 25 to 500 μm.
Film is preferred.

The specific hard coat layer formed on the plastic film has a function relating to surface hardness such as scratch resistance and a function of antistatic property.

Such a hard coat layer can be formed by a polymer binder mainly composed of a thermosetting resin or an ionizing radiation curing resin, and a conductive material having a needle crystal structure.

As the polymer binder, an ionizing radiation curable resin is preferable in that high hardness can be easily obtained.

The ionizing radiation curable resin is formed from a coating material containing at least a resin which is cured by irradiation with electron beams or ultraviolet rays. Specifically, it contains a photopolymerizable prepolymer, a photopolymerizable monomer, a photopolymerization initiator, and further contains a sensitizer, a non-reactive resin, an additive such as a leveling agent, and a solvent, if necessary. Is.

The structure and molecular weight of the photopolymerizable prepolymer are related to the curing of the ionizing radiation-curable coating material and determine the properties such as adhesion, hardness and crack resistance of the ionizing radiation-curable resin. The photopolymerizable prepolymer undergoes radical polymerization when the acryloyl group introduced into the skeleton is irradiated with ionizing radiation. Those that cure by radical polymerization have a fast curing speed and a large degree of freedom in resin design.
Particularly preferred.

As the photopolymerizable prepolymer, an acrylic prepolymer having an acryloyl group is particularly preferable, which has two or more acryloyl groups in one molecule and has a three-dimensional network structure. As the acrylic prepolymer, urethane acrylate, epoxy acrylate, melamine acrylate, polyester acrylate and the like can be used.

The photopolymerizable monomer is used for diluting the high-viscosity photopolymerizable prepolymer, lowering the viscosity, improving workability, and imparting coating strength as a crosslinking agent. .

As the photopolymerizable monomer, monofunctional acrylic monomers such as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and butoxyethyl acrylate, 1,6
-Bifunctional acrylic monomers such as hexadiol acrylate, neopentyl glycol diacrylate, hydroxypavirin ester neopentyl glycol acrylate, dipentaerythritol hexaacrylate,
One or more of polyfunctional acrylic monomers such as trimethylpropane triacrylate and pentaerythritol triacrylate are used.

Further, since the coating film becomes harder than necessary when the amount of the photopolymerizable monomer mixed is increased, the mixing ratio may be appropriately selected so as to obtain a desired hardness or a desired flexibility. For example, when the hard coat film of the present invention is used for bending, the hardness is adjusted by mixing a non-reactive resin such as a thermosetting, thermoplastic acrylic resin or epoxy resin having excellent flexibility. be able to.

The photopolymerization initiator is added in order to start the reaction of the acryloyl group by irradiation of ionizing radiation in a short time and accelerate the reaction, and has a catalytic action. The photopolymerization initiator is required particularly when curing is performed by ultraviolet irradiation, and may not be required when irradiating a high energy electron beam. As the kind of the photopolymerization initiator, there are radical polymerization by cleavage, radical polymerization by abstracting hydrogen, and cationic polymerization by generating ions.

The photopolymerization initiator can be appropriately selected.
Examples thereof include benzoin ether-based, ketal-based, acetophenone-based, thioxanthone-based and other radical-type photopolymerization initiators, diazonium salts, diaryl iodonium salts, triarylsulfonium salts, and complex-type cationic photopolymerization initiators. 1 type or 2 or more types can be used. The photopolymerization initiator is 2 to 10 relative to the resin solid content.
%, Preferably 3 to 6% by weight is used as a mixture.

To cure the ionizing radiation curable paint,
Irradiate with electron beam or ultraviolet ray.

When irradiating with an electron beam, a scanning type or curtain type electron beam accelerator is used, and an accelerating voltage of 1000 ke
It can be performed by irradiating with an electron beam having an energy of V or less, preferably 100 to 300 keV and having a wavelength region of 100 nm or less.

When irradiating with ultraviolet rays, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a metal halide lamp or the like is used, and the wavelength is 100 to 400 nm, preferably 2 nm.
50 to 300 kcal in the wavelength region of 00 to 400 nm
Irradiate with ultraviolet light having an energy of / mol.

The conductive material having a needle crystal structure in the hard coat layer of the present invention imparts antistatic property, that is, functions as an antistatic agent.

Since such a needle-shaped crystal conductive material is needle-shaped, it can impart a large antistatic effect with a small content. The ion-conducting conductive material used conventionally has a small antistatic effect even if it is added in a considerably large amount. Further, although the spherical electron conductive type conductive material used conventionally has a larger antistatic effect than the ion conductive type conductive material, the antistatic effect cannot be obtained unless it is contained in a considerably large amount. In the present invention, by using such a needle-shaped conductive material, the content of the conductive material in the hard coat layer can be suppressed to a very small amount as compared with the spherical conductive material, and as a result, the hard coat layer It is possible to obtain high hardness.

As such a conductive material, tin oxide having an acicular crystal structure doped with antimony oxide (hereinafter referred to as acicular tin oxide) is most preferable.

The acicular crystal tin oxide has not only high antistatic ability, but also can greatly improve transparency.
That is, since the content of the antistatic agent can be suppressed as described above, the transparency of the hard coat film itself becomes very high. Therefore, it is particularly suitable for applications requiring transparency, such as a transparent touch panel.

The acicular crystalline tin oxide has a major axis diameter in the length direction of 0.1 to 5 μm, preferably 0.2 to 2 μm, and a minor axis diameter in the width direction of 0.01 to 1 μm, preferably 0. .01
Those having a thickness of up to 0.02 μm are particularly preferable because high transparency and antistatic property can be obtained.

The blending ratio of the polymer binder and the acicular crystal tin oxide is preferably 5 to 50 parts by weight, more preferably 10 to 40 parts by weight, relative to 100 parts by weight of the polymer binder. .

The hard coat layer may contain additives such as an inorganic pigment, an organic pigment and a leveling agent, if necessary.

To form a hard coat layer having such a composition, when an ionizing radiation curable resin is used, an ionizing radiation curable resin coating material containing a needle-shaped crystal conductive material is applied to a plastic film, and an electron It is formed by irradiating rays or ultraviolet rays.

The ionizing radiation curable coating composition can be applied to a plastic film by a conventional coating method such as bar, blade, gravure, spin or spray coating.

When the ionizing radiation-curable coating material is cured by irradiating it with an electron beam or an ultraviolet ray, the presence of oxygen and the thickness of the coating film are closely related to the curing. Radicals generated by irradiation with ionizing radiation supplement oxygen, thereby suppressing curing. Therefore, when the thickness of the coating film is small, the surface area occupying the volume of the coating film becomes large, and the coating is easily affected by curing in air. Further, if the coating film is thick, it is difficult for ionizing radiation to penetrate to the inside, and even if the surface is cured, internal curing is not sufficient, and the uncured portion of the coating interface exists, so that the hard coating layer and Poor adhesion with the transparent substrate will occur.
In order to prevent such curing inhibition and uncuring, particularly in the case of electron beam irradiation, irradiation can be performed under an inert gas such as N ₂ gas. Further, the inhibition of curing can be prevented by adjusting the thickness of the coating film, selecting a photopolymerizable prepolymer or a photopolymerizable monomer having a fast curing rate, and increasing the mixing amount of the photopolymerization initiator.

[0036]

The present invention will be described in more detail with reference to the following examples.

[Example 1] 25.0 parts by weight of an ultraviolet-curable acrylic resin (Aronix UV-3700: Toagosei Kagaku) on a 125 μm thick polyester film, and oxidation of an acicular crystal structure doped with antimony oxide Tin (major axis diameter: 0.2-2.0 μm, minor axis diameter 0.01
~ 0.02 μm) 8.0 parts by weight, methyl ethyl ketone 2
A coating material for a hard coat layer consisting of 4.0 parts by weight and 33.0 parts by weight of toluene was applied with a Meyer bar and irradiated with ultraviolet rays for 1 to 2 seconds by a high pressure mercury lamp to obtain a hard coat film.

Comparative Example 1 8.0 parts by weight of tin oxide doped with antimony oxide and having a needle-shaped crystal structure of Example 1 was changed to 8.0 parts by weight of tin oxide doped with spherical antimony oxide. In the same manner as in Example 1,
A hard coat film was obtained.

[Comparative Example 2] 8.0 parts by weight of tin oxide having a needle-like crystal structure doped with antimony oxide of Example 1 was replaced with tin oxide 1 doped with spherical antimony oxide.
In the same manner as in Example 1 except that the amount was changed to 5.0 parts by weight,
A hard coat film was obtained.

The hard coat films of Examples and Comparative Examples were evaluated as follows.

Antistatic property: After rubbing the hard coat layer and the untreated polyester film 20 times so as to face each other, tobacco ash was adhered, and what was not adhered at all was adhered as "○". The thing was designated as "x".

Surface hardness: The hard coat layer was rubbed 10 times with steel wool # 000, and the one with little scratches on the surface was marked with "O", and the one with many scratches was marked with "X".

[0043]

[Table 1]

[0044]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a hard coat film capable of imparting antistatic performance without lowering the hardness of the surface and maintaining the antistatic effect even after long-term use. Furthermore, a hard coat film having very good transparency can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C08J 7/06 C08J 7/06 A

Claims (2)

[Claims] 1. A hard coat film having a hard coat layer on a plastic film, wherein the hard coat layer contains a conductive material having an acicular crystal structure. 2. A hard coat film having a hard coat layer on a plastic film, wherein the hard coat layer contains tin oxide having a needle-like crystal structure doped with antimony oxide.