JP2776553B2 - Anti-reflective coating - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an antireflection film provided on a plastic substrate such as a plastic lens.

[Prior Art] In order to improve the reflection characteristics of the surface of a plastic substrate such as diethylene glycol bisallyl carbonate resin (generally called CR-39 resin), a multilayer antireflection film is provided on the plastic substrate. It is well known. As such an antireflection film, for example,
Japanese Patent No. 56-116003 discloses that a total thickness of a two-layer equivalent film composed of a silicon dioxide layer and a zirconium dioxide layer and a base layer having a thickness of 3 / 2λ, which is made of silicon dioxide, counted from the substrate side. A first layer of about λ / 4, a second layer of zirconium dioxide having a thickness of about λ / 2, and a third layer of silicon dioxide having a thickness of about λ / 4, It has been disclosed.

[Problem to be disclosed by the invention] The antireflection film disclosed in Japanese Patent Application Laid-Open No. 56-116003 has sufficient scratch resistance and adhesion, but has insufficient heat resistance. When the plastic lens provided with is heated and framed in, for example, a spectacle frame made of cellulose, there is a problem that cracks easily occur in the antireflection film. The luminous reflectance of the plastic lens provided with the anti-reflection film is about 1.5%. When the plastic lens with the anti-reflection film is used as a spectacle lens,
There is a problem that the ghost phenomenon cannot be completely eliminated. Therefore, from the viewpoint of fashion, there has been a demand for the development of an antireflection film that does not easily cause a ghost phenomenon when a plastic lens is used as a substrate.

Accordingly, the object of the present invention is to not only satisfy the basic properties such as scratch resistance and adhesion, but also, when the substrate is made of a plastic lens, is superior in heat resistance to the conventional antireflection film,
An object of the present invention is to provide an antireflection film which does not crack when heated, has an excellent antireflection effect, and hardly causes a ghost phenomenon.

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and in an antireflection film provided on a plastic substrate, a film made of silicon dioxide counted from the substrate side Thickness 0.
An underlayer having a thickness of 45 to 0.55λ; a film thickness of 0.22 to 0.2 constituted by a titanium dioxide layer, a silicon dioxide layer and a titanium dioxide layer.
A first layer comprising a three-layer equivalent film having a wavelength of 28λ and a refractive index of 1.65 to 1.80;
Titanium dioxide film thickness 0.45-0.55λ, refractive index 2.40-
A second layer of 2.45; and a film thickness of 0.22-0.
A third layer having a wavelength of 28λ and a refractive index of 1.45 to 1.47,
An anti-reflection film, wherein the titanium dioxide layer in the first layer and the titanium dioxide layer as the second layer are layer-evaporated while irradiating the substrate with an oxygen ion beam. It is the gist.

 Hereinafter, the present invention will be described in detail.

The antireflection film of the present invention is obtained by providing a base layer on a plastic base material, and then sequentially providing a first layer, a second layer, and a third layer having an antireflection effect. The anti-reflection film preferably has an anti-reflection layer having a substantially λ / 4 film-λ / 2 film-λ / 4 film as a basic film design.

First, the underlayer is made of silicon dioxide, and its thickness is practically preferably in the range of 0.45 to 0.55λ. The reason for providing the underlayer is to increase the adhesion between the base material and the antireflection film, and to improve the hardness of the antireflection film to increase the wear resistance.

The reason that silicon dioxide was selected as a material constituting the underlayer is that plastic generally has a large expansion coefficient and differs from quartz by about two orders of magnitude, but the deposited film of silicon dioxide is a relatively porous film. This is because, compared to other vapor-deposited films, the adhesiveness to plastic is higher and the hardness is higher, so that excellent abrasion resistance can be obtained. In addition, it can well withstand plastic having a large expansion coefficient and is less likely to crack. A practically preferable range of the film thickness is 0.45 to 0.55λ.
The reason is that when the film thickness is in this range, the adhesion between the base material and the antireflection film is increased, and the hardness of the antireflection film is also improved, so that the wear resistance is increased, and the first layer, which will be described later, This is because the antireflection effect of the antireflection layer composed of the combination of the second layer and the third layer can be maximized.

Next, the first layer formed on the underlayer is a three-layer equivalent film composed of a titanium dioxide layer, a silicon dioxide layer and a titanium dioxide layer. This three-layer equivalent film corresponds to the first λ / 4 film in the basic film design including the λ / 4 film-λ / 2 film-λ / 4 film. Its film thickness is practically 0.
The range of 22 to 0.28λ is preferred. The reason for selecting titanium dioxide and silicon dioxide as the material constituting the first layer and forming a three-layer equivalent film formed in the order of a titanium dioxide layer, a silicon dioxide layer and a titanium dioxide layer, counting from the underlayer, is as follows. This is as described in (a) and (b) below.

(A) By forming a three-layer equivalent film composed of these two substances, the refractive index of the first layer can be adjusted to, for example, 1.65 to 1.80, and the film thickness can be adjusted to, for example, 0.22 to 0.28λ, to desired values. An excellent antireflection effect can be obtained by a combination of the first layer, the underlayer, the second layer, and the third layer.

(B) The three-layer equivalent film formed by the titanium dioxide layer and the silicon dioxide layer has high heat resistance, and has an adhesive force to the silicon dioxide of the underlayer and the titanium dioxide of the second layer described later. .

Next, the second layer formed on the first layer is made of titanium dioxide. In the basic film design consisting of the λ / 4 film-λ / 2 film-λ / 4 film, the λ / 2 film is used. And the thickness is practically in the range of 0.45 to 0.55λ. The reason why titanium dioxide was selected as the material constituting the second layer is as described below.

(A) Titanium dioxide is a high-refractive-index substance having a refractive index of about 2.40, and is made of high-refractive-index titanium dioxide. By disposing between the first layer made of the layer equivalent film and the third layer made of silicon dioxide having a low refractive index described later, a desired antireflection effect can be obtained.

(B) Titanium dioxide is adhesive to the first and third layers.

Incidentally, the refractive index of the second layer is practically in the range of 2.40 to 2.45.

Next, the third layer formed on the second layer is made of silicon dioxide. In the basic film design consisting of the λ / 4 film-λ / 2 film-λ / 4 film, the last λ / This corresponds to four films, and the film thickness is practically in the range of 0.22 to 0.28λ. The reason why silicon dioxide was selected as the substance constituting the third layer is as described below.

Silicon dioxide is a low-refractive-index substance having a refractive index of about 1.46, and a third layer made of silicon dioxide having this refractive index is formed on a high-refractive-index second layer provided on a low-refractive-index first layer. By providing such a layer, a desired anti-reflection effect can be obtained.

The silicon dioxide film has high film strength and strong adhesion to the second layer made of titanium dioxide.

Incidentally, the refractive index of the third layer is practically in the range of 1.45 to 1.47.

As described above, the antireflection film of the present invention has three layers having an antireflection effect. The reason why the number of layers is limited to three is as follows.

(I) As the number of layers of the anti-reflection film increases, the anti-reflection area generally increases, but as the number of layers increases, the reproducibility of the thickness of the anti-reflection film for each product decreases, and the reproduction of interference colors The nature also worsens.
For example, in the case of a pair of spectacle lenses, the use of a pair of lenses causes a large error in the film thickness of the left and right lenses.

(Ii) When the number of layers constituting the antireflection film is increased, cracks generally tend to occur in the antireflection film, but cracks are less likely to occur in the three-layer antireflection film of the present invention.

(Iii) If the material and the film thickness are set as described above, a sufficient antireflection effect can be obtained even with three layers.

In the antireflection film of the present invention, the method of depositing the titanium dioxide layer in the first layer and the titanium dioxide layer in the second layer, which is composed of the three-layer equivalent film, comprises the steps of: Limited to the assist method. The reason is that without this ion beam assist method,
A titanium dioxide layer with sufficient hardness cannot be formed,
Also, the refractive index of titanium dioxide does not become 2.40 or more. Conditions in the ion beam assist method (for example, a method of irradiating the substrate with an oxygen ion beam, a method of evaporating titanium dioxide as a raw material, and the like) are appropriately selected from conditions generally employed.

As described above, the titanium dioxide layer in the first layer and the titanium dioxide in the second layer are deposited by an ion beam assist method. Silicon dioxide layer, the third layer of silicon dioxide is a vacuum deposition method, an ion plating method,
It is formed by ordinary film forming means such as a sputtering method and a CVD method.

As the plastic substrate on which the antireflection film of the present invention is formed, it is preferable to use a plastic lens, for example, a cellulosic plastic lens, diethylene glycol bisallyl carbonate homopolymer or diethylene glycol bisallyl carbonate and one or more other materials. Plastic lenses, polycarbonate plastic lenses, polystyrene plastic lenses, polyurethane plastic lenses, polyvinyl chloride plastic lenses, etc. made of a copolymer with the above monomer.

These plastic lens substrates may be subjected to a surface treatment. Specific examples of the surface treatment include a surface made of an organic substance (for example, an organosilicon compound), an inorganic substance (for example, colloidal silica), or a mixture thereof on the plastic lens substrate. Forming a treatment film may be mentioned.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to these examples.

The physical properties of the antireflection films obtained in Examples and Comparative Examples were measured by the following test methods.

(A) Scratch resistance Scratch resistance was determined as follows by rubbing the surface 10 times with # 0000 steel wool in a reciprocating manner.

A: Slightly scratched B: Many scratches C: Peeling of the film occurs (b) Adhesion According to JIS-Z-1522, make 10 × 10 squares and perform the peeling test three times with cellophane adhesive tape. The number of remaining Goban eyes was counted.

(C) Luminous transmittance and luminous reflectance The luminous transmittance and luminous reflectance were measured using a Hitachi 340 automatic recording spectrophotometer.

(D) Heat resistance Heating was performed at 80 ° C. for 10 minutes in an electric furnace, and the occurrence of cracks was examined.

：: no cracks generated ×: cracks generated Example 1 As a plastic lens, a diethylene glycol bisallyl carbonate polymer-based plastic lens (HO
Using a Hi-Lux manufactured by YA Corporation (refractive index: 1.499), a vacuum evaporation method (degree of vacuum: 2 × 10 ⁻⁵ Tor) was first formed on this plastic lens.
r) an underlayer consisting of silicon dioxide [refractive index 1.46,
0.5λ (λ is 550 nm)].

Next, on this underlayer, a layer (thickness 0.06λ) of titanium dioxide is formed by an ion beam assist method in which the plastic lens is irradiated with an oxygen ion beam while the plastic lens is heated, and silicon dioxide is formed by a vacuum evaporation method. Layer (thickness 0.12λ) and a first layer [refractive index 1.70, thickness 0.24λ] which is a three-layer equivalent film composed of a layer (thickness 0.06λ) of titanium dioxide by an ion beam assist method. Formed.

Next, a second layer (refractive index: 2.40, thickness: 0.5λ) made of titanium dioxide is formed on the first layer by an ion beam assist method in which the plastic lens is irradiated with an oxygen ion beam while the plastic lens is heated. did.

Next, on this second layer, a vacuum deposition method (degree of vacuum 2 × 10 ⁻⁵⁾
Torr) to form a third layer of silicon dioxide (refractive index 1.4
6, and a film thickness of 0.25λ) to obtain a plastic lens with an antireflection film.

Table 1 shows the test results of the obtained plastic lens with an antireflection film. As shown in the table, the plastic lens with an antireflection film obtained in Example 1 not only has good scratch resistance and adhesion, but also has excellent heat resistance and a luminous reflectance of 0.4%. It was excellent in prevention effect. FIG. 1 shows the reflectance curve of the plastic lens with an antireflection film obtained in Example 1.

Example 2 As a plastic lens, a diethylene glycol bisallyl carbonate copolymer plastic lens (HO
Using YA Corporation Hi-Lux II, refractive index 1.56), a plastic lens with an antireflection film having the film configuration shown in Table 1 was obtained. As shown in Table 1, the plastic lens with an antireflection film obtained in Example 2 not only has good scratch resistance and adhesion, but also has excellent heat resistance and a luminous reflectance of 0.4%. It was excellent in prevention effect. FIG. 2 shows the reflectance curve of the plastic lens with an antireflection film obtained in Example 2.

Comparative Example 1 As a plastic lens, a diethylene glycol bisallyl carbonate polymer-based plastic lens (HOYA
(Hi-Lux, Inc.) was used. On this plastic lens, as in the case of the antireflection film described in JP-A-56-116003, an underlayer made of silicon dioxide (thickness: 1.5λ) is provided, and then a zirconium dioxide layer (thickness: 0.06λ) A first layer (total thickness 0.14λ) composed of a two-layer equivalent film of silicon and a silicon dioxide layer (thickness 0.08λ), and a second layer composed of zirconium dioxide.
A layer (thickness 0.5λ) and a third layer (thickness 0.25λ) made of silicon dioxide were sequentially provided to obtain a plastic lens with an antireflection film of this comparative example.

The plastic lens with an antireflection film obtained in this comparative example had good scratch resistance and good adhesion, but had insufficient heat resistance and a luminous reflectance of 1.5%, which was the antireflection of Example 1. The antireflection effect was inferior to that of the plastic lens with a film. FIG. 3 shows a reflectance curve of the plastic lens with an antireflection film obtained in Comparative Example 1.

Comparative Example 2 As a plastic lens, a diethylene glycol bisallyl carbonate polymer-based plastic lens (HO
A plastic lens with an antireflection film in the same manner as in Comparative Example 1 except that a diethylene glycol bisallyl carbonate copolymer plastic lens (Hi-Lux II manufactured by HOYA Corporation) was used instead of the Hi-Lux manufactured by YA Corporation. I got
The plastic lens with an anti-reflection film obtained in this comparative example had good scratch resistance and adhesion, but had insufficient heat resistance and a luminous reflectance of 1.5%, which was the anti-reflection property of Example 2. The antireflection effect was inferior to that of the plastic lens with a film. FIG. 4 shows the reflectance curve of the plastic lens with the antireflection film obtained in Comparative Example 4.

[Effects of the Invention] As described in detail above, the antireflection film of the present invention not only has good scratch resistance and adhesion when provided on a plastic substrate, but also has good heat resistance. Since cracks are hardly generated, luminous reflectance is extremely low, excellent antireflection effect is obtained, and ghost phenomenon is eliminated, the lens can be particularly suitably used as a spectacle lens having antireflection ability.

[Brief description of the drawings]

FIG. 1 is a reflectance curve diagram of a plastic lens with an antireflection film of Example 1, FIG. 2 is a reflectance curve diagram of a plastic lens with an antireflection film of Example 2, and FIG. FIG. 4 is a reflectance curve diagram of a plastic lens with an antireflection film of Comparative Example 2 and FIG. 4 is a reflectance curve diagram of a plastic lens with a film.

Claims (1)

(57) [Claims] 1. An anti-reflection film provided on a plastic substrate, comprising, as counted from the substrate side, an underlayer of silicon dioxide having a thickness of 0.45 to 0.55λ; a titanium dioxide layer, a silicon dioxide layer and a titanium dioxide layer. Constructed film thickness 0.
First layer consisting of a three-layer equivalent film having a refractive index of 22 to 0.28λ and 1.65 to 1.80; thickness of 0.45 to 0.55λ made of titanium dioxide, refractive index
A second layer of 2.40 to 2.45;
22 to 0.28 λ, having a third layer with a refractive index of 1.45 to 1.47,
The reflection, wherein the titanium dioxide layer in the first layer and the titanium dioxide layer as the second layer, each of which is composed of the three-layer equivalent film, are deposited while irradiating the substrate with an oxygen ion beam. Prevention film.