JP2693500B2 - 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] It is well known to provide a multilayer antireflection film on a plastic substrate in order to improve the reflection characteristics of the surface of the plastic substrate. , Titanium dioxide has been used recently by taking advantage of its high refractive index. And as a method of providing a titanium dioxide film on a plastic substrate,
For example, in JP-A-55-65239, a plastic substrate is first irradiated with an oxygen ion beam in a low temperature state without heating at a high temperature to perform surface modification of the substrate, and then titanium is irradiated while being irradiated with an oxygen ion beam. Alternatively, a method of forming a titanium dioxide film on a base material by flying titanium oxide on the base material and reactively depositing titanium dioxide on the base material is described.

[Problems to be Solved by the Invention] However, in the method described in JP-A-55-65239, low-temperature vapor deposition is performed in order to prevent the plastic base material from being surface-altered by heat. The formed titanium dioxide film has the drawbacks of low surface hardness and poor wear resistance.

Accordingly, an object of the present invention is to provide an antireflection film which has excellent antireflection function and excellent wear resistance despite using titanium dioxide, and which is suitable to be provided on a plastic lens substrate. is there.

[Means for Solving the Problems] The present invention has been made in order to solve the above-mentioned problems, and the antireflection film of the present invention provided on a plastic substrate is a silicon dioxide counted from the substrate side. A first layer having a film thickness of λ / 2 to 5λ, and a second layer having a film thickness of λ / 4 made of a two-layer equivalent film of zirconium oxide and silicon dioxide,
It has a third layer made of titanium dioxide having a thickness of λ / 2 and a fourth layer made of silicon dioxide having a thickness of λ / 4, and the third layer is a plastic substrate at 50 to 120 ° C. It is characterized in that the substrate is not irradiated with an oxygen ion beam in the state of being heated, and titanium or an oxide thereof is blown toward the substrate to deposit titanium dioxide.

 Hereinafter, the antireflection film of the present invention will be described in detail.

The antireflection film of the present invention is composed of four layers, the first of which is counted from the plastic substrate on which the antireflection film is provided.
The layer is made of silicon dioxide and has a thickness of λ / 2 to 5λ. The reason why silicon dioxide is selected as the material forming the first layer is that plastic generally has a large expansion coefficient and differs by about two orders of magnitude compared with quartz, but a vapor-deposited film of silicon dioxide is a relatively porous film. This is because, compared with other vapor-deposited films, the adhesive force to plastic is stronger and the hardness is high, so that excellent wear resistance is obtained, and even plastics having a large expansion coefficient can withstand well and cracks are less likely to occur. The reason for limiting the film thickness to λ / 2 to 5λ is that silicon dioxide has the above-mentioned advantages, but if the film thickness is less than λ / 2, the hardness cannot be increased and sufficient wear resistance is obtained. On the other hand, on the other hand, when the film thickness exceeds 5λ, cracks are likely to occur due to the internal stress of the film. A particularly preferable thickness of the first layer is 3 / 2λ.

Next, the second layer formed on the first layer is composed of a two-layer multi-equivalent film of zirconium oxide and silicon dioxide, and its film thickness is λ / 4. In the second layer, a film made of zirconium oxide is formed on the side of the first layer described above, and a film made of silicon dioxide is formed on the film made of zirconium oxide. Zirconium oxide and silicon dioxide were selected as the materials constituting the second layer to form a two-layer equivalent film because (a) by using these two materials, the refractive index of the second layer was set to a desired value. It can be adjusted to (1.70 to 1.85), whereby an excellent antireflection effect can be obtained by the combination of this second layer with the below-mentioned third layer and fourth layer. This is because the layer-equivalent film has high film strength and has adhesiveness to the silicon dioxide film of the first layer and the titanium dioxide film of the third layer described later. The thickness of this second layer is λ
The reason for limiting the thickness to / 4 is that the thickness of the second layer is λ / 4 in relation to the thickness λ / 2 of the third layer and the thickness λ / 4 of the fourth layer described later.
This is because the desired antireflection effect cannot be obtained unless it is set.

Next, the third layer formed on the second layer is made of titanium dioxide and has a film thickness of λ / 2. The reason why titanium dioxide was selected as the material constituting the third layer is as follows: (a) titanium dioxide is a high refractive index material having a refractive index of 2.40, and this third layer composed of a titanium dioxide film having a high refractive index is A desired antireflection effect can be obtained by disposing the zirconium oxide-silicon dioxide film having a low refractive index and the fourth layer including a silicon dioxide film having a low refractive index described below. b) This is because titanium dioxide has an adhesive force to the second and fourth layers. Also, the reason why the thickness of the third layer is limited to λ / 2 is that the desired antireflection effect is obtained unless the values are set to this value in relation to the thicknesses of the second layer and the fourth layer as described above. Because I can't.

Next, the fourth layer formed on the third layer is made of silicon dioxide and has a film thickness of λ / 4. Silicon dioxide was selected as the material for the third layer because silicon dioxide is a low refractive index material with a refractive index of 1.47. A desired antireflection effect can be obtained by providing it on the third layer having a high refractive index provided on the layer.

This is because the silicon dioxide film has a strong film strength and a strong adhesion to the third layer made of titanium dioxide. The reason why the thickness of the fourth layer is limited to λ / 4 is that the desired antireflection effect is obtained unless the values are set to this value in relation to the thicknesses of the second layer and the fourth layer as described above. Because there is no.

As described above, the antireflection film of the present invention comprises four layers.
The reason for limiting the number of layers 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 eyeglass lenses, since they are used as a pair, there is a large error in the film thickness of the left and right lenses, and the reproducibility of interference colors deteriorates.

According to the study of the present invention, it has been clarified that the deterioration of the reproducibility of the film thickness and the deterioration of the reproducibility of the interference color due to the decrease are unlikely to occur in the case of up to 4 layers.

(Ii) Of the four layers constituting the antireflection film of the present invention, the first
The layer enhances the adhesion between the antireflection film and the plastic substrate,
In addition, the hardness of the antireflection film is improved to improve wear resistance,
It has a function as a so-called cured film, and it is the remaining second, third and fourth layers that are responsible for the antireflection effect, but by limiting the materials and film thickness of these three layers as described above. A sufficient antireflection effect can be obtained.

(Iii) When the number of layers constituting the antireflection film is increased,
Generally, cracks tend to occur in the antireflection film, but 4
Cracks are unlikely to occur in the antireflection film of the present invention composed of layers.

The antireflection film of the present invention is characterized in that the third layer made of titanium dioxide is formed by an oxygen ion beam irradiation vapor deposition method while the substrate is heated. That is, the third layer is a plastic base material of 50 to 120.
It is formed by a method in which titanium or its oxides (titanium monoxide, titanium dioxide, etc.) is blown toward the base material while irradiating the base material with an oxygen ion beam in a state of being heated to ° C, and titanium dioxide is deposited. The reason for heating the plastic substrate to 50 to 120 ° C. in this oxygen ion beam irradiation vapor deposition method is that the hardness of the titanium dioxide film formed is not sufficient when the temperature is lower than 50 ° C., while the plastic substrate is heated when the temperature exceeds 120 ° C. This is because the base material may be thermally deformed to cause distortion. Other conditions in this oxygen ion beam irradiation vapor deposition method (for example, a method of irradiating a substrate with an oxygen ion beam, a method of vaporizing titanium or its oxide as a raw material, etc.)
Is appropriately selected from the conditions usually adopted.

Although the third layer is formed by the oxygen ion beam irradiation vapor deposition method as described above, the remaining first layer, second layer and fourth layer are vacuum vapor deposition method, ion plating method, sputtering method, It is formed by an ordinary film forming means such as 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 cellulose plastic lens, a polycarbonate plastic lens containing a diethylene glycol bisallyl carbonate polymer, a polystyrene plastic lens, Examples thereof include polyurethane plastic lenses and polyvinyl chloride plastic lenses.

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.

As described above, the third layer made of titanium dioxide is formed by the oxygen ion beam irradiation vapor deposition method while the plastic substrate is heated to 50 to 120 ° C. When the third layer is formed, the third layer is already formed on the plastic substrate. , A first layer of silicon dioxide and a second layer of zirconium oxide-silicon dioxide
Since the layers have already been formed and these serve as one kind of protective film to prevent deformation of the plastic substrate due to heating, problems such as distortion of the plastic lens do not easily occur.

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

Example 1 (1) Formation of Antireflection Film on Plastic Lens A polyurethane plastic lens (Hi-LuxEXC manufactured by HOYA Co., Ltd.) was used as a plastic lens, and a vacuum deposition method (vacuum degree 2) was used on the plastic lens. × 10 ^-5 Torr)
Thus, a first layer [refractive index 1.47, film thickness 3 / 2λ (λ is 550 nm)] made of a silicon dioxide film was formed.

Next, on this first layer, a vacuum deposition method (vacuum degree 2 × 10 ⁻⁵
The second layer (refractive index 1.80, film thickness λ / 4) composed of a two-layer equivalent film of zirconium oxide and silicon dioxide was formed by Torr).

Next, while the plastic lens is being heated, titanium dioxide is evaporated while irradiating the lens with an oxygen ion beam, and this is vapor-deposited on the second layer to form a third layer (refractive index 2.40) composed of a titanium dioxide film. Then, a film thickness λ / 2) was formed. When forming the third layer by this oxidation ion beam irradiation vapor deposition method, the heating temperature of the plastic lens is set to 40,5.
Five levels were changed at 0, 80, 120 and 130 ° C.

Next, a fourth layer (refractive index 1.47, film thickness λ / 4) made of silicon dioxide was formed on the third layer obtained above by a vacuum evaporation method (vacuum degree 2 × 10 ⁻⁵ Torr). Five types of antireflection films having different substrate temperatures during the formation of the third layer were obtained.

(2) Performance Test of Obtained Antireflection Film The five types of antireflection films obtained were tested for wear resistance, adhesion, luminous transmittance, luminous reflectance and lens distortion. The test method is as follows.

(A) Abrasion resistance The abrasion resistance was determined as follows by rubbing the surface 10 times (reciprocating) with # 0000 steel wool.

A: Slightly scratched B: A lot of scratches C: Film peeling occurs (b) Adhesion 10 × 10 goggles are made according to JIS-Z-1522, and a peeling test is performed 3 times with cellophane adhesive tape. I checked how many gobang eyes remained.

(C) Luminous transmittance and luminous reflectance The luminous transmittance and luminous reflectance were measured using a 340 type self-recording spectrophotometer.

(D) Lens distortion Visual inspection was performed using a strain gauge.

The test results are shown in Table-1. According to Table-1, when forming the titanium dioxide film by the oxygen ion beam irradiation vapor deposition method, setting the plastic lens substrate temperature to 50 to 120 ° C., wear resistance, adhesion, luminous transmittance, luminous reflectance In addition to excellent anti-reflection coatings for all items of lens distortion and lens distortion, abrasion resistance deteriorates below 50 ° C (40 ° C) and above 120 ° C (130 ° C) It is clear that distortion will occur.

Comparative Example 1 The third layer made of titanium dioxide was formed by vacuum deposition (vacuum degree 2 × 10 5) while heating the plastic lens substrate at 80 ° C.
^-5 Torr), an antireflection film was formed in the same manner as in Example 1, and various performances were tested. Table 1 shows the results.
It was revealed that the wear resistance was remarkably inferior as shown in FIG.

Comparative Example 2 Instead of forming a two-layer equivalent film made of zirconium oxide and silicon dioxide by the vacuum evaporation method (vacuum degree 2 × 10 ⁻⁵ Torr) as the second layer, a magnesium oxide film was formed in a vacuum of the same vacuum degree. A film is formed by the vapor deposition method, and the second layer (refractive index 1.
74, film thickness λ / 4), except that the thickness is λ / 4) (the third layer made of titanium dioxide was also formed by oxygen ion beam irradiation vapor deposition at a substrate temperature of 80 ° C.), and plastic lens An antireflection film was formed on the upper surface, but it was revealed that the obtained antireflection film having the second layer made of magnesium oxide had poor wear resistance as shown in Table 1.

[Effects of the Invention] As described in detail above, the antireflection film of the present invention is excellent in the original antireflection function and also excellent in abrasion resistance, so that it is preferably provided, for example, on a plastic lens. Further, the antireflection film of the present invention has an advantage that the plastic base material is not deformed despite the step of forming titanium dioxide under high temperature in the forming process.

Claims (1)

(57) [Claims] 1. An antireflection film provided on a plastic substrate, the first layer comprising silicon dioxide having a thickness of λ / 2 to 5λ, counted from the substrate side, and two layers of zirconium oxide and silicon dioxide. Second film with equivalent thickness of λ / 4
A layer, a third layer of titanium dioxide having a thickness of λ / 2 and a fourth layer of silicon dioxide having a thickness of λ / 4,
The third layer is obtained by vapor-depositing titanium dioxide by flying titanium or its oxide toward the base material while irradiating the base material with an oxygen ion beam while heating the plastic base material at 50 to 120 ° C. Is an antireflection film.