JP2846887B2 - Transparent conductive laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention forms a transparent conductive thin film on one surface of a transparent film substrate and a transparent dielectric thin film thereon further,
The present invention relates to a transparent conductive laminate obtained by bonding a transparent substrate to the other surface via a transparent pressure-sensitive adhesive layer.

[Conventional technology]

In general, thin films that are transparent in the visible light region and have electrical conductivity are used in new displays such as liquid crystal displays and electroluminescence displays, as well as in transparent electrodes in touch panels, etc. Used for

Conventionally, as such a transparent conductive thin film, a so-called conductive glass in which an indium oxide thin film is formed on glass is well known. However, since the base material is glass, flexibility and workability are poor. However, it may not be preferable depending on the use.

For this reason, in recent years, in addition to flexibility and workability, it has excellent impact resistance and is lightweight, so that it has advantages such as polyethylene terephthalate film and various kinds of plastic films as base materials. Has been awarded.

[Problems to be Solved by the Invention] However, the conventional transparent conductive thin film using such a film substrate has a problem that the transparency is inferior because the light reflectance of the thin film surface is large, The abrasion resistance was poor, and there was a problem that the electrical resistance increased due to scratches during use, or the disconnection occurred.

In particular, in the case of a conductive thin film for a touch panel, a pair of thin films opposed to each other via a spacer come into strong contact at a pressing point from one of the base material sides. It is desired that the transparent conductive thin film has characteristics, that is, hitting characteristics. However, the above-described conventional transparent conductive thin film is inferior in such characteristics, and there is a problem that the life of the touch panel is shortened.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to improve the transparency, abrasion resistance and hitting characteristics of a transparent conductive thin film using a film base such as a polyethylene terephthalate film.

[Means for solving the problem]

The present inventors have conducted intensive studies to achieve the above object, and as a result, using a film base having a specific film thickness, sequentially forming a transparent conductive thin film and a transparent dielectric thin film on one surface thereof. While forming, by attaching another transparent substrate to the other surface via a transparent adhesive layer, transparency,
The inventors have found that the present invention can greatly improve the scratch resistance and the hitting point characteristics, and have completed the present invention.

That is, according to the present invention, a transparent conductive thin film is formed on one surface of a transparent film base material having a thickness of 2 to 120 μm and a transparent dielectric thin film is further formed thereon, and an elastic coefficient of 1 is formed on the other surface. The present invention relates to a transparent conductive laminate in which a transparent substrate is bonded via a transparent pressure-sensitive adhesive layer having a thickness of × 10 ⁵ to 1 × 10 ⁷ dyn / cm ² and a thickness of 1 μm or more.

[Structure and operation of the invention]

Various plastic films having transparency can be used as the film substrate used in the present invention,
Specifically, polyethylene terephthalate, polyimide,
Polyethersulfone, polyetheretherketone, polycarbonate, polypropylene, polyamide,
Examples include polyacryl and cellulose propionate. The thickness of these film base materials needs to be in the range of 2 to 120 μm, and particularly preferably in the range of 6 to 100 μm. If the thickness is less than 2 μm, the mechanical strength of the base material is insufficient, and it is difficult to continuously form a conductive thin film, a dielectric thin film, and an adhesive layer by forming the base material into a roll. On the other hand, if it exceeds 120 μm, it will not be possible to improve the abrasion resistance and hitting point characteristics based on the cushioning effect of the pressure-sensitive adhesive layer described later.

This film substrate is pre-sputtered on its surface,
An etching treatment such as corona discharge, flame, ultraviolet irradiation, electron beam irradiation, chemical conversion, oxidation or the like, or an undercoating treatment may be applied to improve the adhesion of the conductive thin film provided thereon to the base material. Before providing the conductive thin film, dust removal and cleaning may be performed by solvent cleaning or ultrasonic cleaning as necessary.

In the present invention, a transparent conductive thin film is formed on one surface of such a film substrate. As a method for forming the conductive thin film, any of conventionally known techniques such as a vacuum deposition method, a sputtering method, and an ion plating method can be adopted. The thin film material to be used is not particularly limited. For example, indium oxide containing tin oxide, tin oxide containing antimony, and the like are preferably used.

The thickness of the conductive thin film is preferably 50 ° or more, and if it is thinner, it is difficult to form a continuous film having good conductivity with a surface resistance of 10 ³ Ω / □ or less. Further, if the thickness is too large, the transparency is lowered. Therefore, a particularly preferable thickness is preferably about 100 to 2,000 mm.

In the present invention, after forming a transparent conductive thin film as described above, a transparent dielectric thin film is further formed on this thin film. By the formation of this dielectric thin film, mainly the transparency and the scratch resistance are greatly improved, and the dot characteristics are also improved. From this viewpoint, those having a refractive index smaller than the refractive index of the conductive thin film, usually from 1.3 to 2.0, preferably from 1.3 to 1.6 are good, for example, CaF ₂ , MgF ₂ , NaAlF ₆ ,
Al ₂ O ₃ , SiOx (1 ≦ x ≦ 2), ThF _{4 and the} like are preferable, and among them, SiOx (1 ≦ x ≦ 2) is most preferable. In addition,
These materials are not limited to one kind, and two or more kinds may be used in combination.

The thickness of the dielectric thin film is preferably 100 mm or more, usually 100 to 3,000 mm, particularly preferably 200 to 1,500 mm.
It is good to be in the range of. If it is less than 100 mm, it is difficult to form a continuous film, and the improvement in transparency and scratch resistance cannot be expected much. On the other hand, if the thickness is too large, the conductivity and transparency of the film surface may be degraded or cracks may occur, which is also not preferable.

Examples of the method for forming the dielectric include a vacuum deposition method, a sputtering method, an ion plating method, and a coating method. An appropriate method can be employed depending on the type of the above-described material and the required film thickness. .

A transparent substrate is attached to the other surface of the film substrate on which such a transparent conductive thin film and a transparent dielectric thin film are sequentially formed via a transparent adhesive layer. For this bonding, the pressure-sensitive adhesive layer is provided on the transparent substrate,
The above-mentioned film substrate may be bonded to this, or conversely, the above-mentioned pressure-sensitive adhesive layer may be provided on the film substrate, and the transparent substrate may be bonded to this. The latter method is more advantageous in terms of productivity because the pressure-sensitive adhesive layer can be formed continuously by making the film base into a roll.

The pressure-sensitive adhesive layer can be used without any particular limitation as long as it has transparency. For example, an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, or the like is used. The pressure-sensitive adhesive layer has a function of improving the abrasion resistance and hitting characteristics of the conductive thin film provided on one surface of the film substrate by the cushioning effect after the adhesion of the transparent substrate. From the point of view of better performance,
It is desirable to set the elastic modulus in the range of 1 × 10 ⁵ to 1 × 10 ⁷ dyn / cm ² and the thickness in the range of 1 μm or more, usually ⁵ to 100 μm.

When the above elastic coefficient is less than 1 × 10 ⁵ dyn / cm ² , the pressure-sensitive adhesive layer becomes inelastic, so that it is easily deformed by pressurization to cause irregularities in the film base material and, consequently, the conductive thin film. The adhesive tends to protrude from the cut surface, and the effect of improving the scratch resistance and the hitting point characteristics is reduced. On the other hand, if the elastic modulus exceeds 1 × 10 ⁷ dyn / cm ² , the pressure-sensitive adhesive layer becomes hard and the cushioning effect cannot be expected, so that the abrasion resistance and hitting point characteristics cannot be improved.

When the thickness of the pressure-sensitive adhesive layer is less than 1 μm, the cushioning effect cannot be expected, so that it is impossible to improve the scratch resistance and the hitting point characteristics. If the thickness is too large, transparency is impaired, and it is difficult to obtain good results in terms of workability of forming an adhesive layer, bonding a transparent substrate, and cost.

The transparent substrate bonded via such an adhesive layer imparts good mechanical strength to the film substrate,
In particular, it contributes to the prevention of curl and the like, and when it is required to be flexible even after lamination, a plastic film of about 6 to 300 μm is usually required. If not, usually 0.05
A glass plate having a thickness of about 1 mm or a plastic film or plate is used. Examples of the material of the plastic include those similar to the above-mentioned film substrate.

If necessary, an anti-glare treatment layer or an anti-reflection treatment layer for improving visibility may be provided on the outer surface of the transparent substrate (the surface opposite to the pressure-sensitive adhesive layer). May be provided with a hard coat layer for the purpose of protection.

〔The invention's effect〕

As described above, in the present invention, a transparent film base having a specific thickness is used, and a transparent conductive thin film is formed on one surface thereof and a transparent dielectric thin film is further formed thereon, while the other is formed. With a configuration in which a transparent substrate is adhered to the surface of the substrate via a transparent pressure-sensitive adhesive layer, the abrasion resistance and hitting characteristics are improved based on the cushioning effect of the pressure-sensitive adhesive layer and the protective effect of the dielectric thin film, Further, it is possible to provide a transparent conductive laminate whose transparency is greatly improved by an antireflection effect of the dielectric thin film.

〔Example〕

Hereinafter, embodiments of the present invention will be described in more detail.

Example 1 PET (polyethylene terephthalate) having a thickness of 12 μm
On one surface of a film substrate made of a film, a thickness is formed by a reactive sputtering method using an indium-tin alloy in an atmosphere of 4 × 10 ⁻³ Torr containing 80% of argon gas and 20% of oxygen gas. A transparent conductive thin film (hereinafter referred to as IT) consisting of a composite oxide of 400 mm2 indium oxide and tin oxide
O film).

Next, on the above-mentioned ITO film by a SiO ₂ electron-beam heating method, (1-2) was vacuum deposited at × 10 ^-4 Torr in vacuum, transparent dielectric made of SiO ₂ having a thickness of about 400Å A body thin film (hereinafter, referred to as a SiO ₂ thin film) was formed.

Then, on the other surface of the PET film, an acrylic transparent pressure-sensitive adhesive layer (elastic coefficient adjusted to 1 × 10 ⁶ dyn / cm ² ) (weight ratio of butyl acrylate, acrylic acid and vinyl acetate of 100: 100 parts by weight of a 2: 5 acrylic copolymer and 1 part by weight of an isocyanate-based cross-linking agent) are added to about 20 parts by weight.
A transparent conductive laminated film of the present invention having a structure shown in the figure was produced by bonding a transparent substrate made of a PET film having a thickness of 75 μm thereon.

In the drawing, 1 is a transparent film base made of a PET film having a thickness of 12 μm, 2 is a transparent conductive thin film made of an ITO thin film, 3 is a transparent dielectric thin film made of a SiO ₂ thin film,
Is a transparent acrylic adhesive layer, 5 is PE with a thickness of 75 μm
It is a transparent substrate made of T film.

Examples 2 to 3 Two types of the present invention having the structure shown in the drawing in the same manner as in Example 1 except that the thickness of the SiO ₂ thin film was changed to 200 ° (Example 2) and 1,400 ° (Example 3). Was produced.

Examples 4 to 6 As a film substrate, a transparent PES (polyethersulfon) film having a thickness of 25 μm (Example 4) was used.
The same procedure as in Example 1 was carried out except that a transparent PI (polyimide) film of 12.5 μm (Example 5) and a transparent PC (polycarbonate) film of 80 μm in thickness (Example 6) were used, respectively. The three kinds of transparent conductive laminated films of the present invention having the structures shown in the following were produced.

Comparative Example 1 A transparent conductive film was produced in the same manner as in Example 1 except that the formation of the SiO ₂ thin film and the pressure-sensitive adhesive layer and the bonding of the transparent substrate were not performed.

Comparative Example 2 A transparent conductive laminated film was produced in the same manner as in Example 1 except that a SiO ₂ thin film was not formed.

Comparative Example 3 A transparent conductive film was produced in the same manner as in Example 1, except that the formation of the pressure-sensitive adhesive layer and the bonding of the transparent substrate were not performed.

Comparative Example 4 A transparent conductive laminated film was produced in the same manner as in Example 1 except that a PET film having a thickness of 125 μm was used as a film substrate.

Comparative Example 5 A transparent conductive laminated film was produced in the same manner as in Example 1, except that a PC film having a thickness of 140 μm was used as a film substrate.

Next, with respect to the transparent conductive laminated films of Examples 1 to 6 and Comparative Examples 2, 4 and 5 and the transparent conductive films of Comparative Examples 1 and 3, film resistance, transmittance, abrasion resistance and spotting were evaluated. Characteristics were measured and evaluated in the following manner.

<Film resistance> Using the two-terminal method, the surface electrical resistance of the film (Ω /
□) was measured.

<Transmittance> The visible light transmittance at a light wavelength of 550 nm was measured using a spectrophotometer UV-240 manufactured by Shimadzu Corporation.

<Scratch resistance> Haydon surface type measuring instrument TYPE-HEIDON14 manufactured by Shinto Kagaku
Scratches: gauze (Japanese Pharmacopoeia Type I)
Load: 100 g / cm ² , Scratch speed: 30 cm / min, Scratch frequency: 10
Under the condition of 0 times (50 round trips), the film resistance (Rs) is measured after rubbing the thin film surface, and the initial film resistance (Ro)
The rate of change (Rs / Ro) with respect to was determined, and the scratch resistance was evaluated.

<Rotation Characteristics> Two transparent conductive laminated films (or transparent conductive films) are arranged so that conductive thin films (or dielectric thin films) face each other via a spacer having a thickness of 100 μm, and one of the films ( Transparent substrate or film substrate)
From the side, a rod made of urethane rubber with a luminous intensity of 40 degrees (key tip
7R), the center spot of 1 million times with a load of 100 g is measured, the film resistance (Rd) is measured, and the rate of change (Rd / Ro) with respect to the initial film resistance (Ro) is determined, and the dot characteristics are determined. evaluated.

The measurement of the film resistance described above was carried out by using the two oppositely arranged films.
The contact resistance at the time of hitting a sheet of the transparent conductive laminated film (or the transparent conductive film) is expressed as an average value.

As is clear from the results in the above table, the transparent conductive laminated film of the present invention has excellent transparency and conductivity, and is also extremely excellent in scratch resistance and hitting point characteristics.

[Brief description of the drawings]

The drawing is a sectional view showing an example of the transparent conductive laminate of the present invention. DESCRIPTION OF SYMBOLS 1 ... Film base material 2 ... Conductive thin film 3 ... Dielectric thin film 4 ... Adhesive layer 5 ... Transparent base

Claims (1)

(57) [Claims] 1. A transparent film base material having a thickness of 2 to 120 .mu.m, a transparent conductive thin film is formed on one surface and a transparent dielectric thin film is further formed thereon, and the other surface has an elastic coefficient of 1.times. 10 ⁵ 〜
A transparent conductive laminate obtained by laminating a transparent substrate via a transparent pressure-sensitive adhesive layer having a thickness of 1 × 10 ⁷ dyn / cm ² and a thickness of 1 μm or more.