JP2001158642A - Formed product having antifogging thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a formed product having antifogging thin film capable of maintaining antifogging properties for a long time. SOLUTION: In a formed product comprising a base material and an antifogging thin film on the outermost surface of the base material, the antifogging thin film is characterized in that it has an assemblage of fine asperity having 20-500 Å RMS value on the whole surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antifogging thin film which is widely and effectively used for articles requiring an antifogging property such as mirrors, window glasses, automobile glasses, spectacle lenses, sunglasses and other optical parts. And a molded article having:

[0002]

2. Description of the Related Art Transparent materials such as glass and plastic
Exposure to environments with different temperatures and humidities results in fogging and loss of transparency. This is because moist air comes into contact with the surface of the transparent material whose temperature has dropped to a temperature lower than the dew point, and dew condensation occurs. As a conventional means for imparting anti-fogging property to the surface of a transparent material such as an optical component, an anti-fogging film is formed on the outermost layer of the transparent material.
As the material, for example, a surfactant or an organic compound having a hydrophilic functional group such as hydroxyethyl methacrylate, polyether, or polyvinyl alcohol has been used.
As a method of forming a film, there is a method of forming an antifogging thin film by applying or spraying the organic compound on the substrate surface as described above.

Further, there is a method in which a material obtained by combining a hydrophilic vinyl compound and an organic silane compound is used, and this material is applied to the substrate surface. Further, a method has been performed in which a surfactant is added in advance to a liquid plastic to be a plastic molded body, kneaded, and then molded.

[0004]

SUMMARY OF THE INVENTION The present inventors have used a surfactant or an organic compound having a hydrophilic functional group such as hydroxyethyl methacrylate, polyether, polyvinyl alcohol, etc. On a plastic substrate to form an antifogging thin film. Further, an attempt was made to form an antifogging thin film by spraying the organic compound onto a plastic substrate using a spray.

When the durability of the formed antifogging thin film was examined, the antifogging effect was not long-lasting, and a thin film having satisfactory durability could not be obtained. Further, if an antifogging thin film is formed by a conventional material and a film forming method after forming an antireflection film on a substrate, the antireflection effect may be adversely affected. The present inventors have tried to improve the durability of the thin film by forming the anti-fogging thin film by changing the material. The present inventors have decided to use a combination of a hydrophilic vinyl compound and an organic silane compound as the antifogging material. Then, this material was applied on the surface of a plastic substrate by an application method to form an antifogging thin film. However, improvement in durability of the antifogging thin film could not be realized.

Further, the present inventors have tried to impart an antifogging property to a molded plastic substrate by adding a surfactant to a liquid plastic material, kneading the surfactant, and molding. Was. However, even this method could not improve the durability of the antifogging thin film. In particular, in this method, the combination of a plastic material and a surfactant that can be used is limited, the versatility is poor, and since the amount of the surfactant that can be kneaded is limited, it is not practical, and the method is inefficient. Met.

Accordingly, an object of the present invention is to provide a practically useful antifogging thin film that has a long lasting sufficient antifogging property and does not adversely affect antireflection performance and the like.
Another object is to provide an antifogging thin film having improved durability.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that if an aggregate of fine irregularities having a specific depth is formed on the surface of a film, an excellent antifogging effect can be maintained for a long time. I found to do. Further, it has been found that when the roughness of the film surface is represented by an RMS value, when the value is not less than a certain value, a particularly excellent antifogging effect is maintained for a long time.

It has also been found that the cross-sectional structure of the thin film exhibiting excellent anti-fogging properties as described above is preferably one having a columnar structure. Further, it has been found that when the substance constituting the anti-fogging thin film is an inorganic oxide, the durability is further improved, and particularly excellent anti-fogging property is maintained for a long time. Therefore, the present invention firstly provides a molded article comprising a substrate and an antifogging thin film on the outermost surface of the substrate, wherein the antifogging thin film has an RMS value of 20 ° or more and 500 ° or less on the entire surface. A molded article provided with an antifogging thin film, characterized by having an aggregate of fine irregularities having a depth of (1). Secondly, there is provided "a molded article provided with an anti-fogging thin film according to claim 1, wherein the surface of the anti-fogging thin film has a hydrophilic group (claim 2)." Thirdly, there is provided "a molded article provided with an anti-fogging thin film according to claim 1 or 2, wherein the anti-fogging thin film contains an inorganic oxide as a main component." . Fourthly, there is provided "a molded article provided with an anti-fogging thin film according to claim 1 or 2 or 3, wherein the anti-fogging thin film is formed by a dry method". .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The antifogging thin film of the present invention is a thin film exhibiting a property of reducing the contact angle of water, that is, a hydrophilic property.
Due to the hydrophilicity, water spreads over the entire surface of the thin film without adhering to the surface of the thin film in the form of water droplets. As a result, light scattering does not occur, and fogging can be prevented.

Conventionally, there have been many thin films showing hydrophilicity immediately after the formation of the antifogging thin film. However, the effect usually does not last long, and in one to several days, the contact angle of water becomes 30 degrees or more, and it becomes easily clouded by exhalation. The anti-fogging thin film of the present invention is capable of maintaining high hydrophilicity as high as that at the time of film formation for several months or more. In the past, when discussing hydrophilicity and anti-fog properties, only the measured value of the contact angle at a certain point in time has often been discussed. But,
From a practical point of view, it was considered more appropriate to use the time-dependent change in antifogging property as a guideline for evaluation.

In the present invention, in addition to the measured value immediately after the formation of the antifogging thin film, the contact angle of water after a certain period of time has elapsed since the film formation was measured, and these were compared to obtain the antifogging thin film. Sustainability was assessed. The hydrophilicity required to develop anti-fog properties is
Depending on the conditions of use of the anti-fog thin film, etc., generally,
If the contact angle of water is not more than 20 degrees, it can be said that there is anti-fog performance.

The surface roughness of the antifogging thin film of the present invention is determined by RMS.
When expressed in terms of (Root-Mean-Square) value, it is not less than 20 ° and not more than 500 °. With such a surface, particularly excellent antifogging property is maintained for a long time. The RMS value indicates the depth of the concave portion on the surface, and is not the number. Therefore, it can be said that a film having a large RMS value is a film having a deep concave portion. The measurement of the surface roughness was performed by AFM (atomic force microscope). It is necessary to form such an unevenness on the outermost surface countlessly over the entire surface to form an aggregate of the unevenness.

The distance between the peaks of the irregularities is approximately 1 mm to
Preferably, it is about 1000 °. The antifogging thin film can be formed by a dry method such as sputtering, vacuum evaporation, or CVD, or a wet method such as a sol-gel method, and there is no particular limitation. In order to form irregularities on the surface of the anti-fogging thin film, a method of controlling film forming conditions such as a pressure setting in a vacuum chamber, a substrate position, a substrate temperature, and a film forming rate in sputtering or vacuum deposition, or an etching treatment after film formation ( For example, various methods such as a method of performing plasma treatment and immersion in an acid solution or an alkali solution can be employed. Alternatively, irregularities may be formed in advance on the base on which the antifogging thin film is formed, and the antifogging thin film may be formed thereon. Even in this case, irregularities are formed on the surface of the antifogging thin film.

As described above, the irregularities on the surface of the thin film can be formed at the same time as the film formation, and the treatment for forming the irregularities can be separately performed after the film formation. Further, the RMS value of the irregularities on the outermost surface of the antifogging thin film in the present invention is preferably about 20 ° or more and about 500 ° or less, more preferably about 20 ° or more and about 100 ° or less.

Although the reason why the antifogging thin film having the irregularities having the RMS values as described above maintains the excellent antifogging property is not necessarily clear, the RM of the present invention is not always clear.
Since the concave portion having the S value has a depth suitable for holding moisture for a long period of time, it is considered that the antifogging property is maintained. The substance constituting the anti-fogging thin film of the present invention is not particularly limited, but preferably has a hydrophilic group on the outermost surface.

When an inorganic oxide is used, if an inorganic oxide such as silicon oxide, titanium oxide, zirconium oxide, zinc oxide, tantalum oxide, or tungsten oxide is used, a film having an OH group on the surface is used. Can be These inorganic oxides have a large number of hydrophilic groups such as silanol groups on the surface. In addition, an inorganic oxide layer formed using a metal alkoxide as a raw material can also be used.

It is also possible to use an organic compound having a hydrophilic group. For example, polymer compounds such as polyacrylic acid, polyvinyl alcohol, and polyvinylpyrrolidone can be used. Further, a compound having ethyleneoxy in the molecule can also be used. As described above, the antifogging thin film according to the present invention preferably has a hydrophilic group on the outermost surface, but may not be the inorganic oxide as described above.

The thickness of the antifogging thin film of the present invention is preferably about 200 ° or more and about 100 μm or less.
More preferably, the thickness is not less than about 10 μm. If the film thickness is less than about 200 °, the duration of the anti-fog performance will be short. The substrate on which the antifogging thin film is formed is not particularly limited, and any substrate such as various kinds of glass, plastic, or silicon wafer can be used.

The antifogging thin film may be provided on one side of the substrate or on both sides. If necessary, a thin film such as an antireflection film or a hard coat may be formed on the surface on which the antifogging thin film is not provided. Further, the antifogging thin film of the present invention needs to be formed on the outermost surface,
It is also possible to provide another layer between the substrate and the antifogging thin film to form a multilayer. For example, a hard coat is provided to improve abrasion resistance, a layer made of a material having a high refractive index is provided to provide anti-reflection properties, or a shock absorbing layer is provided to improve impact resistance. can do.

[0021]

Embodiment 1 A silicon oxide film was formed on a substrate by RF sputtering using a white plate glass of 2 mm in thickness and 5 cm on a side as a substrate and SiO ₂ as a target. The pressure in the vacuum chamber during film formation was 1.5 Pa, and argon gas was
00 sccm was introduced. RF power is 800W,
The film formation time was 1 hour.

In the present embodiment, the RMS value of the irregularities on the outermost surface is controlled by adjusting the pressure in the vacuum chamber. (If the pressure in the vacuum chamber is about 0.5 Pa, the RMS value is about 10 ° C.)
The RMS value can be changed by changing other conditions. The thickness of the silicon oxide film formed under such conditions was measured by a stylus-type film thickness meter and found to be 3000 °.

The contact angle of water of the anti-fogging thin film was 5 ° immediately after the film formation, and was again measured after leaving it in the room for 2 months. It was found that the hydrophilicity was maintained for a long time. In addition, even when sprayed, no fogging occurred even after being left for two months. Further, the glass substrate was placed in a constant temperature bath set at 5 ° C. for 1 hour, and then immediately transferred to a constant temperature / humidity bath set at 25 ° C. and 85% RH. As a result, a thin water film was formed on the surface. However, the transparency of the glass was not impaired at all, and excellent antifogging performance was confirmed.

The surface roughness of the antifogging thin film of this embodiment was measured by AFM.
As a result, the RMS value was 27 °, which revealed that fine irregularities were formed on the surface. SE of cross section of molded article having antifogging thin film obtained in this example
An M photograph is shown in FIG. From this, it was clarified that the anti-fogging thin film of this example had a columnar structure, and deep concave portions (holes) existed deeply. In the figure, about 0.2 mm in the thickness direction from the outermost surface (the dimension (length x width) of the photograph is 8.3 cm x 1
Area (for 1.1 cm) corresponds to a depth with an RMS value of about 27 °.

[0025]

Example 2 A silicon oxide film was formed on the surface of a plastic spectacle lens substrate having a diameter of 80 mm by a vacuum evaporation method. For film formation, oxygen was introduced into a vacuum chamber having a vacuum degree of 6 × 10 ⁻⁶ Torr, the pressure was set to 5 × 10 ⁻⁵ Torr, and Si was formed.
This was performed by an electron beam heating evaporation method using O ₂ granules as an evaporation source. The power of the electron beam was about 90 mA, and a 1500 ° -thick SiO ₂ film was formed.

Next, the film obtained above was subjected to oxygen plasma treatment to form fine irregularities on the surface. The oxygen flow rate was 100 sccm, the RF power was 500 W, the pressure was 0.2 Torr, and the processing time was 300 seconds. When the contact angle of water on the thin film surface was measured after the oxygen plasma treatment, it was 7 degrees. Then, when this was left in a room for two months and re-measured, it was again 7 °, and it became clear that excellent hydrophilicity was maintained. In addition, no fogging was observed even after spraying, even after being left for two months.

Further, the plastic lens substrate was heated at 5 ° C.
1 hour in a thermostat set at 25 ° C, 85%
When the glass was immediately transferred to a constant temperature and humidity chamber at RH, a thin water film was formed on the surface, but the transparency of the glass was not impaired at all, and excellent antifogging performance was confirmed. When the surface roughness of the anti-fogging thin film of this example was measured by AFM, the RMS value was 25 °, and it became clear that fine irregularities were formed on the surface.

[0028]

COMPARATIVE EXAMPLE The same operation as in Example 2 was performed except that the oxygen plasma treatment was not performed after the formation of the antifogging thin film. When the contact angle of water was measured after the formation of the antifogging thin film, it was 8 degrees. However, when it was re-measured after being left indoors for two months, it was found to have risen significantly to 40 degrees. When spraying was performed, no fogging was observed immediately after the film formation, but one that had been left for two months easily turned white and cloudy by exhalation.

Further, the plastic lens substrate was heated at 5 ° C.
1 hour in a thermostat set at 25 ° C, 85%
Immediately after being transferred to a constant temperature and humidity chamber at RH, immediately after film formation, although a thin water film was formed on the surface, transparency was not impaired at all, and excellent antifogging performance was confirmed. . However, when the plastic substrate was left for two months, it was fogged the moment it was transferred to a thermo-hygrostat set at 25 ° C. and 85% RH, and the anti-fog performance was lost.

The surface roughness of the antifogging thin film of this embodiment was measured by AFM.
Was measured. As a result, the RMS value was 8 °, and it was found that the film had recesses having a smaller depth than the surfaces of the films of Examples 1 and 2, and was more flat.

[0031]

According to the present invention, the antifogging property is maintained for a long period of time as compared with a conventional molded article having an antifogging thin film. When a material having a hydrophilic group is used, the anti-fogging property can be further improved, and the high anti-fogging property can be continued for a long time.

When the anti-fogging thin film of the present invention is formed using an inorganic compound having high hardness, the anti-fogging film becomes excellent in scratch resistance and durability. Thus, a molded article having properties can be obtained. In addition, when formed using a dry method such as a vacuum evaporation method, a material having excellent adhesion can be obtained. Further, the film can be formed irrespective of the type of the substrate such as glass and plastic.

As described above, the molded article provided with the anti-fogging thin film of the present invention has a prolonged product life, so that a product having excellent anti-fogging properties can be used for a long period of time. In addition, those having an antifogging thin film made of an inorganic oxide exhibit high durability, so that they can be used in various environments, and the range of use of products having antifogging properties should be widened. Can be. Therefore, the anti-fogging thin film of the present invention is used for applications other than optical devices, such as for preventing fogging of various optical devices such as glasses, cameras, microscopes, telescopes, and binoculars, and for preventing fogging of car windows and bathroom mirrors. Widely applicable.

[Brief description of the drawings]

FIG. 1 is an electron micrograph showing a cross-sectional structure of a molded article having an antifogging thin film according to the present example.

[Explanation of Signs] 11: Silicon substrate 12: Anti-fog thin film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09K 3/18 C09K 3/18 G02B 1/10 G02B 1/10 Z (72) Inventor Kazuki Ohashi Tokyo 3-2-3 Marunouchi, Chiyoda-ku Nikon Corporation (72) Inventor Nobuyuki Nakagiri 3-2-3 Marunouchi, Chiyoda-ku, Tokyo Nikon Corporation F term (reference) 2K009 BB01 BB02 BB11 CC03 CC21 DD01 DD03 DD04 DD12 DD15 EE02 4F100 AA17B AA20B AG00A AR00B AT00A BA02 BA10A BA10B DD07B EH66 GB07 GB32 GB90 JB05B JB20B JM02B YY00B 4G059 AA01 AA11 AC01 AC21 EA01 EA04 EA05 A01 A04 EB03 A01 A04A04

Claims (4)

[Claims] 1. A molded article comprising a base material and an antifogging thin film on the outermost surface of the base material, wherein the antifogging thin film has an RMS
A molded article provided with an antifogging thin film, comprising an aggregate of fine irregularities having a value of not less than 20 ° and not more than 500 °. 2. The molded article provided with the anti-fogging thin film according to claim 1, wherein the surface of the anti-fogging thin film has a hydrophilic group. 3. The molded article provided with the anti-fogging thin film according to claim 1, wherein the anti-fogging thin film contains an inorganic oxide as a main component. 4. The molded article provided with the anti-fogging thin film according to claim 1, wherein the anti-fogging thin film is formed by a dry method.