Reflection preventing film

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a film for preventing reflection of light on the surface of a base material, and more particularly to an antireflection film applied for antireflection on a transparent base material surface such as a front plate of a display device.

【0002】

[Conventional technology]

When viewing the display through a transparent front plate (hereinafter referred to as the base material) such as the display part of a television or computer, if the reflected light on the base material surface is strong, it not only causes discomfort to the eyes, but also causes discomfort to the eyes. The displayed contents are difficult to see. Further, in the case of a lens for spectacles, if the reflected light is strong, a reflected image called ghost, flare, etc. is generated, and in the case of a looking glass, the contents are not clear.

【0003】

Therefore, an antireflection film is provided on the surface of the transparent base material. For example, glass having a reflectance of about 4.5% is used for the base material of the display unit, but the reflectance can be reduced to about 1.0% by providing an antireflection film on the surface of the base material. Can be done.

【0004】

The antireflection film is made of a substance having a refractive index close to that of air, and has a film thickness set so as to obtain a higher antireflection effect. When the antireflection film has a single-layer structure, the highest antireflection effect can be obtained by setting the optical film thickness t of the antireflection film to t = (1/4) λ (2n-1). Can be obtained. However, the optical film thickness t is a value given by the product of the refractive index and the film thickness of the film-forming material, λ is the wavelength of light to be reflected, and n is an integer of 1 or more. ..

【0005】

Further, the antireflection film is not limited to a single layer, but also has a multilayer structure composed of a plurality of layers. In the case of a multi-layer structure, a material having a higher refractive index than the upper layer should be placed in the lower layer as described in "Engineering Technology Contact, vol.9, No. 8, (1971) p.17". Therefore, it is possible to further enhance the antireflection effect of the antireflection layer. Further, as described in JP-A-58-46301, JP-A-59-49501, and JP-A-59-50401, a plurality of layers satisfying the above-mentioned optical film thickness t condition. A method of forming an antireflection film made of a liquid composition using a liquid composition has also been proposed.

【0006】

In the display unit, an antireflection film made of an inorganic oxide or an inorganic halide film formed by a vacuum vapor deposition method or a sputtering method is used. Such an antireflection film has a high surface hardness. Further, in the above publication, in order to further increase the surface hardness of the antireflection film, it is also proposed that the outermost surface film contains an inorganic substance such as silica fine particles in an amount of 30% by weight or more.

【0007】

[Problems to be Solved by the Invention]

However, while the antireflection film has a high surface hardness, it has a problem that stains due to fingerprints, sweat, hair liquid, hair spray and the like are easily noticeable and difficult to remove. Therefore, as described in Japanese Patent Application Laid-Open No. 1-204130, an antireflection film having a polysiloxane-based polymer on the outermost surface has been proposed. Further, as described in Japanese Patent Application Laid-Open No. 3-266801, an antireflection film having a water-repellent fluorine-based resin layer on the outermost surface has been proposed. In these antireflection films, a substance having a low surface energy is provided on the outermost surface to prevent dirt and moisture from adhering to the outermost surface.

【0008】

However, even with such an antireflection film, there is a problem that the dirt once adhered must be removed by wiping or the like.

【0009】

[Means for solving problems]

The antireflection film of the present invention for solving the above problems is composed of an antireflection layer covering the surface of the base material and a photocatalyst layer provided on the antireflection layer. The photocatalyst layer has a film thickness within a range in which the antireflection effect of the antireflection layer can be obtained.

【0010】

In the antireflection film having the above structure, when irradiated with light, an oxidizing active surface is formed on the surface composed of the photocatalyst layer, and acts as a catalyst for decomposition of organic compounds and the like. Therefore, the organic compound-based stains adhering to the surface of the antireflection film are decomposed and removed by the catalytic action of the photocatalyst layer. Moreover, since the photocatalyst layer has a film thickness within a range in which the antireflection effect of the lower antireflection layer can be obtained, the antireflection effect is ensured even if the photocatalyst layer covers the antireflection layer.

【0011】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to FIG. First, as shown in FIG. 1 (1), a transparent base material 11 made of glass or other resin material is prepared. Next, as shown in FIG. 1 (2), the antireflection layer 12 is formed on the upper surface of the base material 11. The antireflection layer 12 has a single-layer or multi-layer structure. In the figure, the antireflection layer 12 having a two-layer structure consisting of the lower layer 12a and the upper layer 12b is shown. As the material constituting the uppermost layer (upper layer 12b in the figure) of the antireflection layer 12, a material whose refractive index difference from air is smaller than that between the base material 11 and air is used. To do. When the antireflection layer 12 has a single-layer structure, the antireflection layer 12 is made of a material in which the difference in the refractive index between the base material and the air is smaller than the difference in the refractive index between the base material and the air.

【0012】

As a material constituting the antireflection layer 12, SiO₂, SiO, Al₂O₃, ZrO₂, TiO₂, TiO, Ti₂O₃, Y₂O₃, Yb₂O₃, MgO, CeO₂, ITO (Indium Tin Oxide) and other oxides and TaHf₂Etc. are used. The antireflection layer 12 has a good film thickness controllability by a PVD (Physical Vapor Deposition) method represented by a vacuum deposition method, an ion plating method, a sputtering method, etc., or a CVD (Chemical Vapor Deposition) method. It shall be formed by. The antireflection layer 12 may be formed by using a liquid composition.

【0013】

The film thickness of the antireflection layer 12 is set to a value such that the reflectance of the light emitted from the surface side of the photocatalyst layer is the lowest when the photocatalyst layer is next provided on the upper surface of the antireflection layer 12. To. This film thickness is obtained by, for example, simulation.

【0014】

Next, as shown in FIG. 1 (3), the photocatalyst layer 13 is formed on the upper surface of the antireflection layer 12. As a material constituting the photocatalyst layer 13, TiO₂, ZnO, etc. are used. The photocatalyst layer 13 has a good film thickness controllability by a PVD (Physical Vapor Deposition) method represented by a vacuum deposition method, an ion plating method, a sputtering method, etc., or a CVD (Chemical Vapor Deposition) method. The film will be deposited.

【0015】

The film thickness T of the photocatalyst layer 13 is a range in which the antireflection effect of the antireflection layer 12 can be obtained, that is, a range in which the photocatalytic effect of the photocatalyst layer 13 can be obtained and a range in which the antireflection effect of the antireflection layer 12 is not hindered. It shall be set to.

【0016】

As described above, the antireflection film 14 composed of the antireflection layer 12 and the photocatalyst layer 13 above the antireflection layer 12 is obtained.

【0017】

In the antireflection film 14 having the above configuration, when the antireflection film 14 covering the surface of the base material 11 is irradiated with light, an oxidizing active surface is formed on the surface of the antireflection film 14 by the photocatalyst layer 13 to decompose organic compounds. Etc. will act as a catalyst. Therefore, the organic compound-based stains adhering to the surface of the antireflection film 14 are decomposed and removed by the catalytic action of the photocatalyst layer 13. Moreover, the photocatalyst layer 13 has a film thickness T within a range in which the antireflection effect of the antireflection layer 12 can be obtained. Therefore, TiO has a large difference in refractive index from air and a large reflectance.₂Even if the photocatalyst layer 13 made of or ZnO is provided on the outermost surface, the antireflection effect is not impaired.

【0018】

Further, in the antireflection film 14, the surface of the antireflection layer 12 under the photocatalyst layer 13 is made of SiO.₂When composed of (silicon dioxide), that is, in the figure, the upper layer 12b is SiO₂When configured with, SiO₂Acts as a barrier between the antireflection layer (that is, the lower layer 12a in the figure) and the base material 11 and the photocatalyst layer 13 below it. Therefore, the catalytic action of the photocatalyst layer 13 is not hindered by the antireflection layer (lower layer 12b) or the base material 11.

【0019】

[Example]

Hereinafter, examples of the present invention will be described with reference to FIG.

【0020】

First, as shown in FIG. 1 (1), a polyethylene terephthalate film having a film thickness of 100 μm (hereinafter referred to as PET) was prepared as the base material 11. Then, as shown in FIG. 1 (2), an ITO film (lower layer) 12a is formed on the substrate 11 with a film thickness of 96 nm by a sputtering method, and further, SiO is formed on the ITO film 12a.₂A film (upper layer) 12b was formed with a film thickness of 62 nm. These ITO films 12a and SiO₂The film 12b gave an antireflection layer 12 having a two-layer structure.

【0021】

Next, as shown in FIG. 1 (3), on the antireflection layer 12, TiO by the CVD method.₂(Titanium dioxide) was formed with a film thickness T of 5 nm, and this TiO₂A photocatalyst layer 13 composed of the same was formed. As described above, an antireflection film 14 composed of an antireflection layer 12 having a two-layer structure and a photocatalyst layer 13 was obtained. The antireflection film 14 shown in FIG. 1 (3) is used as a sample of the example.

【0022】

The ITO film 12a and SiO that constitute the antireflection layer 12₂The film thickness of the film 12b is TiO with a film thickness of 5 nm.₂It is a value obtained by simulation as a value having the lowest reflectance in the antireflection film 14 having the above configuration provided with the photocatalyst layer 13 made of the above.

【0023】

A performance test was conducted on the antireflection effect and the decontamination effect of the antireflection film 14. In order to compare the results of the performance test, the following samples of Comparative Examples 1 to 3 were prepared.

【0024】

As shown in FIG. 2, the sample of Comparative Example 1 has an antireflection layer 12 and a TiO with a film thickness of 20 nm on the base material 11.₂It is provided with a photocatalyst layer 13a made of the same material. The antireflection film 12 is the ITO film 12a and SiO as in the sample of the above example.₂It has a two-layer structure with the membrane 12b. However, in Comparative Example 1, the film thickness of the ITO film 12a constituting the antireflection layer 12 is 69 nm, SiO.₂The film thickness of the film 12b is 40 nm. These film thicknesses are 20 nm film thickness TiO₂It is a value obtained by simulation as a value having the lowest reflectance when the photocatalyst layer 13a made of the above is provided in the upper layer.

【0025】

As shown in FIG. 3, the sample of Comparative Example 2 is a TiO having a film thickness of 5 nm on the base material 11.₂Only the photocatalyst layer 13 made of the material is provided.

【0026】

As shown in FIG. 4, the sample of Comparative Example 3 has only the antireflection layer 12 provided on the base material 11. The antireflection film 12 is the ITO film 12a and SiO as in the sample of the above example.₂It has a two-layer structure with the membrane 12b. However, in Comparative Example 3, the film thickness of the ITO film 12a constituting the antireflection layer 12 is 103 nm, SiO.₂The film thickness of the film 12b is 78 nm. These film thicknesses are values obtained by simulation so that the reflectance is the lowest.

【0027】

The performance test regarding the antireflection effect was performed by measuring the reflectance when the sample was irradiated with light (wavelength 380 nm to wavelength 780 nm). In addition, the performance test on the decontamination effect was carried out by using an ultraviolet lamp on the salad oil dropped on the surface of each film at 5 mW / cm.²This was done by irradiating with UV light for 2 weeks and observing a decrease in salad oil on the membrane.

【0028】

FIG. 5 shows a wavelength-reflectance curve showing the measurement result of the reflectance. The table below shows the average reflectance of each sample (the average spectral reflectance for light with a wavelength of 450 nm to 650 nm) and the results of performance tests related to the decontamination effect.

【0029】

[table 1]

<img file="JPH11109104A_D0001.tif" />【0030】

As shown in FIG. 5 and Table 1, the sample of Example (FIG. 1) has almost the same reflection as the sample of Comparative Example 3 (FIG. 4) with only the antireflection layer 12 in the wavelength range of 450 nm to 650 nm. A rate curve was drawn and similar average reflectance was obtained. Therefore, in the wavelength range of 450 nm to 650 nm, TiO with a film thickness of 5 nm.₂It was confirmed that the antireflection effect was obtained without being hindered by the photocatalyst layer 13 made of the material.

【0031】

Further, in the sample having only the photocatalyst layer 13 of Comparative Example 2 (FIG. 3), the reflectance curve and the average reflectance in the wavelength range of 450 nm to 650 nm were higher than those of Examples and Comparative Example 3. From this, it was confirmed that the antireflection effect of the sample of the above-mentioned example was obtained by the antireflection layer 12.

【0032】

Moreover, the antireflection layer 12 of Comparative Example 1 (Fig. 2) and TiO with a film thickness of 20 nm₂Since the reflectance curve of the sample provided with the photocatalyst layer 13a composed of the same is higher than the reflectance curve of Examples and Comparative Example 3, TiO having a film thickness of 20 nm.₂It was confirmed that the photocatalyst layer 13a composed of the antireflection layer 12 hindered the antireflection effect.

【0033】

Furthermore, from the above table, it was confirmed that the sample of Example (Fig. 1) had a decontamination effect as good as that of the sample of Comparative Example 1 (Fig. 2) provided with the photocatalyst layer 13a having a thicker film thickness. Was done.

【0034】

Further, SiO of the embodiment (Fig. 1)₂The sample provided with the photocatalyst layer 13 on the surface of the antireflection layer 12 made of the film 12b has a better decontamination effect than the sample having only the photocatalyst layer 13 of Comparative Example 2 (FIG. 3). From this, SiO₂It was confirmed that the decontamination effect of the photocatalyst layer 13 was further enhanced by providing the photocatalyst layer 13 on the surface of the antireflection layer 12 made of the material.

【0035】

From the above, the antireflection film 14 in the sample of the example (FIG. 1) does not have the antireflection effect of the antireflection layer 12 extremely impaired by the photocatalyst layer 13, and has a decontamination effect. It was confirmed that there was.

【0036】

[Effect of the invention]

As described above, according to the antireflection film of the present invention, the antireflection effect is ensured by providing a photocatalyst layer having a thickness within the range in which the antireflection effect can be obtained by the antireflection layer on the upper surface thereof. However, organic compound-based stains such as fingerprints and hand stains adhering to the film surface can be naturally decomposed and removed by a photocatalytic reaction. Therefore, an antireflection film having excellent antifouling properties can be obtained.

[Simple explanation of drawings]

[Figure 1]

It is sectional drawing which explains the manufacturing of the antireflection film of a real form and Example.

[Figure 2]

It is sectional drawing which shows the structure of the sample of the comparative example 1. FIG.

[Fig. 3]

It is sectional drawing which shows the structure of the sample of the comparative example 2.

[Fig. 4]

It is sectional drawing which shows the structure of the sample of the comparative example 3. FIG.

[Fig. 5]

It is a figure which shows the wavelength-reflectance curve of each sample.

[Explanation of symbols]

11 ... base material, 12 ... antireflection layer, 13 ... photocatalytic layer, 14 ... antireflection film