JP2013037102A - Antireflection article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection article capable of preventing light reflection by micro-asperities by dissolving and reducing or removing contamination stuck to the micro-asperities.SOLUTION: The antireflection article includes a micro-asperity layer having micro-asperities on the surface thereof. When the maximum wavelength in a visible-light wavelength range is λand a cycle in the apex of the micro-asperity surface is P, the micro-asperity satisfies the following relational expression: P≤λ. The micro-asperity has such a shape that the cross-section occupancy of a material portion of the micro-asperity layer in the cross section, when supposing that the micro-asperity is cut on a surface orthogonal to the asperity direction, continuously and gradually increases from the apex towards the deepest part of the micro-asperity, and photocatalyst is present on the surface and/or the inside of a protrusion of the micro-asperity.

Description

  The present invention relates to an antireflection article that prevents reflection of light on a surface and can be used in various applications such as protection of information display sections of equipment and exhibits.

  Information displays such as mobile phones and digital cameras, and exhibits such as works of art and merchandise are exposed to the outside and may become dirty or broken, protecting them from water, dust, external forces, etc. There is a need to. However, if a transparent plastic plate or the like is placed outside so that they are not exposed to the outside as they are, there is a problem that external light is reflected on both the front and back surfaces of the plate, which reduces the visibility of the display. Articles are being used.

  As a conventional antireflection treatment method, for example, an antireflection layer comprising a low refractive index layer single layer film or a multilayer film of a low refractive index layer and a high refractive index layer by a method such as vapor deposition, sputtering, or coating. Techniques such as providing are generally used. However, since the antireflection layer by vapor deposition, sputtering, etc. needs to form a thin film with a controlled refractive index and thickness by one or many batch processes, there is a problem in product stability, yield rate, etc. In addition, since batch production is used, productivity is low, and there is a problem that costs are increased.

  Another antireflection treatment is a technique that roughens the surface and reduces the specular reflection light by diffusing (disturbing) the reflection. However, this method diffuses the light so that the light utilization efficiency is improved. In addition, there is a problem that the resolution of the image seen through can not be improved.

  In view of this, a technique has been proposed in which surface reflectance is reduced by providing extremely fine irregularities with a repetition period equal to or less than the wavelength of light on the surface. For optical parts such as lenses that should reduce surface reflection, by applying photoresist, etc. on the surface, exposing, developing, etc., creating a resist pattern, and corroding the glass substrate with the pattern There is a method to form fine irregularities directly on the surface of the optical component for each product, but in the production of each product, the work efficiency is bad and the productivity (mass productivity) required for industrial products cannot be obtained. there were.

  In addition, there is a method of forming a fine uneven layer on a substrate by a so-called 2P method (Photo-polymerization method) while using a replication mold, but as long as the 2P method is used, the surface of the obtained antireflection article is used. Since the formed fine concavo-convex layer is made of an organic material called photocurable resin, it cannot be denied that heat resistance, weather resistance, and the like are limited as compared with the case of an inorganic material such as glass.

  In the method disclosed in Patent Document 1, when manufacturing an anti-reflection article having fine irregularities, as a process, (A) First, a prototype in which fine irregularities are shaped is prepared, and (B) then a shaping mold The above-mentioned prototype is used, or a fine rugged shape on the surface of the above-mentioned prototype is produced on one or two or more times by replicating by mold taking and reversal, and the replica mold is used to apply on the substrate. Each step of pressing the shaping mold against the formed sol-gel solution coating film containing the organometallic compound and then releasing the mold to form fine irregularities on the surface of the coating film to form a fine irregularity layer. As an arrangement for performing antireflection, an antireflection article is manufactured by a sol-gel method. When this method is used, the productivity can be improved because the replication type is used.

  However, dirt such as sebum may be attached by touching the anti-reflective article with a finger, or dust, dirt, or water may be attached because it is exposed to the external environment. Has a problem that it cannot be easily removed with alcohol or the like.

  Therefore, for applications where the outer surface (surface facing outward) of the anti-reflective article such as an anti-reflective article used in an information display unit of a mobile phone, digital camera, etc. is touched with a finger, the fine uneven surface of the anti-reflective article is on the inside. The fine irregularities are used in a closed internal space so that the fine irregular surface (moth eye surface) does not come into contact with fingers or be exposed to the external environment, such as being provided facing or inside the apparatus. However, in this case, although there is an effect of preventing reflection of external light on the inner surface, reflection of light on the outer surface is not prevented.

  When fine irregularities of anti-reflective articles are provided on the outer surface, it takes time to remove dirt. Applications of antireflection articles have been limited to cases and the like.

  However, in recent years, there has been a demand for a technology that can provide an antireflection function in a wider range of applications such as a convenience store, a department store or a mass retailer showcase, and a car navigation touch panel that is difficult to see in the evening.

Japanese Patent No. 4270806

  An object of the present invention is to provide an antireflection article that can decompose and reduce or remove dirt adhering to fine irregularities and prevent reflection of light by the fine irregularities.

Therefore, in order to solve the above problems, the antireflection article of the present invention is an antireflection article including a fine uneven layer having fine unevenness on the surface,
The fine unevenness has a maximum wavelength in the wavelength band of visible light as λ _MAX and a period at the top of the fine uneven surface as P _MAX .
P _MAX ≦ λ _MAX
The relationship
and,
The cross-sectional area occupancy of the material portion of the fine concavo-convex layer in the cross-section when the fine concavo-convex is assumed to be cut at a plane orthogonal to the concavo-convex direction is continuous as it goes from the top of the fine concavo-convex to the deepest part. Are fine irregularities having a shape that gradually increases,
A photocatalyst is present on the surface and / or inside of the convex portions of the fine irregularities.

Since the photocatalyst is present on the surface and / or the inside of the convex part of the fine unevenness, even if dirt is attached, it can be decomposed and removed or reduced by the photocatalyst.
In addition, the photocatalyst decomposes the moisture adsorbed on the surface of the fine irregularities to generate free radical hydrogen groups (OH), free oxygen (O), etc., and the surface wettability is promoted. There is also an effect that the film itself is covered with a thin film and the dirt itself is difficult to adhere.
It is to be noted that light reflection is prevented by the fine unevenness. Simply speaking, if a fine unevenness having a size equal to or smaller than the wavelength of the light to be prevented from reflection is provided on the material surface, the refractive index change between the surface and air This is because light reflection, which is a phenomenon that occurs when the refractive index changes rapidly and discontinuously, can be prevented. Moreover, the antireflection function of the antireflection article provided with such fine irregularities is not a light diffusive antireflection that reduces specular reflection due to irregular reflection such as a roughening treatment, but an antireflection article that is formed between the surface of the article and air. It is non-light diffusive because it is realized by mitigating the sudden change in refractive index at the interface, and the light transmittance is improved as much as the light reflectance is reduced.

  The photocatalyst is preferably present on the surface and / or inside of a region including at least the top of the fine irregularities. Since the photocatalyst is present in a wide area including the top that is most likely to be touched by fingers and easily contaminated, it is possible to efficiently decompose the adhered dirt.

  In the antireflection article according to the present invention, the fine uneven layer is preferably provided on the surface of the transparent substrate. Thereby, when the antireflection article of the present invention is attached to glass, external light reflection can be extremely reduced so that the presence of glass is not known.

The photocatalyst is preferably photocatalyst fine particles having an average primary particle size of less than the height of the fine irregularities and less than the period P _{MAX at the} top.

  The photocatalyst is preferably a photocatalyst containing titanium oxide.

  The fine irregularities can be formed using a material selected from the group consisting of a material containing an organic structure and an inorganic structure and a latex binder.

  The fine irregularities are preferably made of a cured product obtained by a sol-gel reaction of a sol-gel reactive composition containing an organometallic compound. Since the fine concavo-convex layer formed on the surface of the antireflection article is formed by a sol-gel method using an organometallic compound as a starting material, an inorganic layer is obtained. For example, a resin by a 2P method (Photo-polymerization method) or the like Compared with the case where it is formed as a layer, an antireflection article having excellent heat resistance, weather resistance and the like can be obtained. Further, the hardness of the fine irregularities can be obtained, and the washing resistance is improved.

According to the present invention, when the surface has fine irregularities and the photocatalyst is present on the surface and / or inside of the convexes of the fine irregularities, the dirt containing organic matter adheres to the surface of the fine irregularities. The dirt can be decomposed and removed or reduced.
In addition, the photocatalyst decomposes the moisture adsorbed on the surface of the fine irregularities, generates OH, O, etc., promotes the wettability of the surface, covers the surface with a thin film of water, and makes it difficult for the dirt itself to adhere. There is also an effect.

Sectional drawing which illustrates notionally one form of the anti-reflective article of this invention. The figure for demonstrating notionally the distribution of the effective refractive index obtained by a fine unevenness | corrugation. The figure for demonstrating notionally the distribution of the effective refractive index obtained by a fine unevenness | corrugation. The figure for demonstrating notionally the distribution of the effective refractive index obtained by a fine unevenness | corrugation. Sectional drawing which illustrates some of vertical cross-sectional shapes of a fine unevenness | corrugation. Sectional drawing which illustrates some arrangement | positioning in the horizontal surface of a fine unevenness | corrugation.

Hereinafter, the antireflection article according to the present invention will be described with reference to the drawings. However, the drawings illustrate the present invention by way of example for ease of explanation, and the present invention is not limited thereto.
As shown in FIG. 1, the antireflection article 1 of the present invention is an antireflection article 1 including a fine uneven layer 3 having fine unevenness 2 on the surface,
The fine unevenness 2 has a maximum wavelength in the wavelength band of visible light as λ _MAX and a period at the top 4 of the surface of the fine unevenness 2 as P _MAX .
P _MAX ≦ λ _MAX
The relationship
and,
The cross-sectional area occupation ratio of the material portion of the fine concavo-convex layer 3 in the cross section when it is assumed that the fine concavo-convex 2 is cut along a plane orthogonal to the concavo-convex direction is the deepest part from the top 2t of the fine concavo-convex 2 It is a fine unevenness having a shape that gradually increases gradually as going to 2b,
A photocatalyst is present on the surface and / or inside of the convex and concave portion 4 having fine irregularities.

The antireflection article 1 of the present invention exhibits an antireflection effect by the fine irregularities 2 having a shape satisfying the above conditions on the surface, and a photocatalyst is present on the surface and / or inside of the convex portions 4 of the fine irregularities 2. By doing so, when dirt containing organic matter adheres to the surface of the fine irregularities 2, the dirt can be decomposed and removed or reduced.
In addition, the photocatalyst decomposes the moisture adsorbed on the surface of the fine irregularities, generates OH, O, etc., promotes the wettability of the surface, covers the surface with a thin film of water, and makes it difficult for the dirt itself to adhere. There is also an effect.

  “The photocatalyst is present on the surface and / or the inside of the convex portion of the fine unevenness” means that the photocatalyst is attached to the surface of the top portion 2t of the fine unevenness 2, and the photocatalyst is formed on the material constituting the top portion 2t of the fine unevenness 2 Is included, or includes both. The photocatalyst is preferably present on the surface and / or inside the region including at least the top 2t of the fine irregularities 2. This is because the dirt is most likely to adhere to the top 2t and the dirt needs to be decomposed by the photocatalyst, so that the photocatalyst can act effectively. “A region including the top 2t” means ¼ from the top of the height of the fine irregularities. Moreover, the convex part 4 means the whole upper side (top part side) from the deepest part 2b of the fine uneven | corrugated layer 2. As shown in FIG.

  When the photocatalyst is present at least on the surface of the region including the top 2t of the fine unevenness 2, the photocatalyst adheres continuously to the surface of the region including the top 2t of the fine unevenness 2, and the surface of the fine unevenness is the photocatalyst layer ( Preferably, it is coated with a photocatalyst layer).

  When the photocatalyst is present at least inside the region including the top 2t of the fine irregularities 2, the photocatalyst is preferably present in the vicinity of the surface of the fine irregularities. For example, there is an embodiment in which photocatalyst particles (photocatalyst particles) are dispersed in the material constituting the fine irregularities, but the photocatalyst particles may be spread and dispersed throughout the convex portion 4, but the fine irregularities 2 May be unevenly distributed only in the vicinity of the surface. Or the fine unevenness | corrugation may be formed with the photocatalyst itself. This is because even if the photocatalyst is present inside the convex portion, the photocatalyst at a position far from the surface of the fine irregularities 2 cannot come into contact with the attached dirt and cannot exert its effect, so the added photocatalyst is effective. It is for use in.

  The photocatalyst is preferably attached over a wide range near the surface of the fine irregularities 2. Thereby, the effect of the photocatalyst superior to the antireflection article having a flat surface of the same area and having the photocatalyst on the surface can be realized. If the photocatalyst is present on the surface and / or inside of the top 2t of the fine irregularities 2, the photocatalyst may also be present on the surface and / or inside of the deepest part 2b (here, the inside of the deepest part 2b) In the case where the bottom of the deepest part 2b (the deepest concave part) is in the form of fine unevenness that does not reach the support 5, it means a fine uneven material part having a thickness existing between the deepest part 2b and the support 5. Therefore, when the photocatalyst is present at least on the surface of the region including the top 2t of the fine unevenness 2, it is preferable that the entire surface of the fine unevenness 2 is covered with the photocatalyst layer (photocatalyst layer). 2 is present in the region including the top 2t of the photocatalyst, the photocatalyst continuously forms a layer near the inside of the fine irregularities 2, or the fine irregularities 2 are formed of the photocatalyst itself. It is preferable.

  As shown in FIG. 1, the antireflection article 1 of the present invention is provided with a fine uneven layer 3 having the fine unevenness 2 on the surface of a support 5.

[Shape of fine irregularities]
The first condition of the shape of the fine unevenness of the present invention “P _MAX ≦ λ _MAX when the maximum wavelength in the wavelength band of visible light is λ _MAX and the period at the top of the fine uneven surface is P _MAX. "Relationship" will be explained. The antireflection article of the present invention exhibits an antireflection effect due to its fine unevenness, and the reason why the fine unevenness 2 has an antireflection effect is as follows.
The fine unevenness 2 makes the fine unevenness layer 3 constituting the surface of the antireflective article and the outside ( usually air. However, depending on the portable use of the antireflective article 1, water, vacuum, or resin such as an adhesive, etc. This is because a sudden and discontinuous change in refractive index between the change and the change in refractive index can be changed into a continuous and gradually changing refractive index change. Since light reflection is a phenomenon caused by a sudden and rapid change in the refractive index of the material interface, the refractive index change on the surface of the article is changed spatially and continuously. Light reflection on the surface of the article is reduced. The fine uneven layer 3 is normally transparent and allows light to pass therethrough, but even if it is opaque, an antireflection effect that reduces surface reflection can be obtained.

Hereinafter, the reason why the antireflection effect is obtained by the fine unevenness 2 formed on the surface of the fine unevenness layer 3 is that the fine unevenness layer 3 (and the support (base material) 5) is transparent, and the microresponse 2 It will be described in detail on the assumption that the medium constituting the air is air.
FIG. 2 is a conceptual diagram for conceptually explaining the refractive index distribution obtained by the fine unevenness 2 formed on the surface of the fine uneven layer 3. First, FIG. 2 shows the height of the fine unevenness 2 on the Z-axis for the fine unevenness layer 3 which is laminated on the support 5 (not shown) as the antireflection article and the surface is provided with the fine unevenness 2. When the height including the deepest portion tb of the fine concavo-convex layer 3 is 0 and the height (thickness) including the top 2t of the fine concavo-convex layer 3 is 1, a portion of the fine concavo-convex layer 3 that does not include the fine concavo-convex ( The portion other than the convex portion 4 occupies the space of the portion of Z ≦ 0, and on the surface of the fine concavo-convex layer 3, that is, on the XY plane at Z = 0, a large number of fine portions having the Z-axis direction as the concavo-convex direction The state where the unevenness 2 is arranged is shown.

In the present invention, as shown in FIG. 2, when the period at the top 2t is P _MAX as shown in FIG. 2, this P _MAX is equal to or less than the maximum wavelength λ _MAX of the visible light wavelength band. For the light reaching the surface with fine irregularities, even if there is a spatial distribution in the refractive index of the medium (fine irregularities layer 3 and air), it is the wavelength of at least some components included in the wavelength band. Since the distribution has the following size, the distribution does not act directly on the light, but acts as an average. Therefore, if the distribution is such that the averaged refractive index (effective refractive index) changes continuously as the light travels, reflection of light can be prevented.

In the present invention, the period P _MAX at the top 2t is the maximum distance between the tops 2t of the adjacent fine irregularities 2, and each periodic irregularity is regularly arranged. May have a characteristic (all the distances between adjacent fine irregularities are the same), but may have a periodicity (the distances between adjacent fine irregularities are not uniform), or the fine irregularities 2 have periodicity. A configuration having a distribution (spatial frequency spectrum) in the period may be used. In the latter case, the period P _MAX is defined as the maximum value in the period distribution of the top 2t. However, in order to exclude peculiar values due to defects, defects, etc., usually a large number (usually about 10 to 100) of the period between adjacent two apexes was measured, and “average value of these values + (3 × standard deviation) "Is taken as the maximum value.

Further, in the case where “P _MAX is equal to or less than the maximum wavelength λ _MAX of the visible light wavelength band”, when the wavelength of visible light is single (a line spectrum like a laser), the wavelength becomes the maximum wavelength λ _MAX . When the wavelength of visible light is two or more or has a spectrum (wavelength distribution or wavelength band), the maximum wavelength among the two or more wavelengths or wavelength bands of the spectrum is the maximum wavelength λ _MAX .
When the visible light has two or more wavelengths or has a spectrum, and P _MAX ≦ λ _MAX , the fine irregularities having a size smaller than the wavelength of the light can prevent reflection of the light as described above. _from when the _{P MAX} = _{λ MAX,} fine irregularities of _{P MAX} is prevented reflection maximum wavelength lambda _MAX, can not be prevented reflects _{P MAX} smaller wavelength. P _MAX = λ _MAX is a minimum condition for exhibiting the antireflection effect.
If it is desired to exhibit the antireflection effect, P _MAX <λ _MAX , more preferably P _MAX <λ _MIN . Here, _λMIN is the shortest wavelength in the wavelength band of visible light. Thereby, even when the wavelength of visible light has two or more types or a spectrum, the size of the fine irregularities becomes not more than all wavelengths, and light of all wavelengths can be prevented from being reflected.

  In FIG. 2, as an orthogonal coordinate system, the Z-axis is taken in the normal direction standing on the envelope surface of the surface of the fine concavo-convex layer 3, and the X-axis and Y-axis are taken in a plane orthogonal to the Z-axis. And now, light enters the fine concavo-convex layer from the outside of the fine concavo-convex layer, proceeds inside the fine concavo-convex layer, and is proceeding near the surface of the fine concavo-convex layer in the negative direction of the Z-axis, It is assumed that the Z-axis coordinate exists at z.

Then, for the light at Z = z here, the refractive index of the medium is such that the surface of the fine concavo-convex layer 3 forms specific fine concavo-convex 2, strictly speaking, the XY plane perpendicular to the Z axis at Z = z. In (cross section: horizontal section), it appears to have a distribution f (x, y, z). That, in the XY plane, cross section has a refractive index nb (about 1.5) of the fine uneven layer 3, its other parts, part of the air a is specifically a refractive index n _{a (=} 1. 0 (see FIG. 3).
However, in practice, for light, the wavelength (if the wavelength of the light to be prevented from being reflected has a distribution, the maximum wavelength λ _MAX of the wavelength band, preferably the minimum wavelength λ _MIN of the wavelength band is considered. The spatial refractive index distribution smaller than (good) acts as an average, so that the averaged effective refractive index is the refractive index distribution f (x, y, z) integrated in the XY plane,

It becomes. As a result, the distribution of the effective refractive index (n _ef ) becomes a function n _eff (z) of only z (see FIG. 4).

Therefore, if the cross-sectional area of the convex portion of the fine concavo-convex layer 3 in the fine concavo-convex portion 2 is a shape that continuously increases toward the concave portion, the fine concavo-convex layer portion (in the XY plane) Since the area ratio with the air portion continuously changes in the Z-axis direction, the effective refractive index n _ef (z) is a continuous function with respect to z.

On the other hand, a case where light is generally incident on a medium having a refractive index n ₁ from a medium having a refractive index n ₀ is considered. Here, for simplicity, an incident angle θ = 0 ° (perpendicular incidence) is considered. However, the incident angle is an angle with respect to the normal of the incident surface. In this case, the reflectance R at the medium interface does not depend on the polarization and the incident angle, and is expressed by the following formula (2).

Therefore, the change in the effective refractive index in the Z direction is a continuous function means that the refractive index n _ef (z) at Z = z, two points separated by a small distance Δz in the Z direction (light traveling direction). Is n ₀ , and the refractive index n _ef (z + Δz) at Z = z + Δz is n ₁ ,
If Δz → 0, then n ₁ → n ₀
(From the definition of the continuous function), so from equation (2)
R → 0.

Strictly speaking, the wavelength of light in the object is λ / n where λ is the wavelength in the vacuum and n is the refractive index of the object. Become small. However, since the refractive index when the object is air is n≈1, it can be considered that λ / n≈λ. However, materials used in the fine uneven layer, since the refractive index before and after the normal 1.5, the wavelength in the substrate of refractive index n _b (λ / n _b) becomes about 0.7Ramuda. Considering this point, in the portion of the fine unevenness 2, when looking at the air side portion (the concave portion of the fine unevenness 2),
P _MAX ≦ λ _MAX , preferably P _MAX ≦ λ _MIN
When the above condition is satisfied, the effect of reducing the reflectance by averaging the refractive index can be expected.
However, λ _MIN / n _b ≦ P _MAX ≦ λ _MIN
In this case, if the contribution of the portion of the fine concavo-convex layer (the convex portion 4 of the fine concavo-convex 2) is observed, the reflectance reduction effect by the refractive index averaging cannot be expected at least completely. However, it still has an anti-reflection effect as a whole because of its contribution in the air portion.
And
P _MAX ≦ λ _MIN / n _b , more preferably P _MAX <λ _MIN / n _b
If the above condition is also satisfied, the condition that the period P _MAX is smaller than the shortest wavelength as well as the maximum wavelength in both the air portion and the fine uneven layer portion is completely satisfied. The prevention effect is more complete.
Specifically, the upper limit 780nm visible light wavelength band lambda _MAX, if the tentatively and 1.5 _{n b,} the lambda _MAX / _{n b} if 520nm, i.e. _{P MAX} and 520nm or less, a minimum visible light In this case, a sufficient antireflection effect is exhibited with respect to light having the maximum wavelength λ _MAX in the entire wavelength band. lower 380nm visible light wavelength band lambda _MIN, if tentatively 1.5 _{n b,} λ _MIN / _{n b} is 250nm, that is, if _{P MAX} and 250nm or less, with respect to light in the entire wavelength range of visible light Sufficient anti-reflective effect.

Next, the second condition of the shape of the fine unevenness “the cross-sectional area occupancy of the material portion of the fine unevenness layer in the cross section when it is assumed that the surface is cut in a plane orthogonal to the unevenness direction is the top of the fine unevenness The fine unevenness having a shape that gradually increases gradually from the deepest to the deepest part will be described.
The shape of the fine irregularities 2 is the cross-sectional area occupancy ratio of the material portion of the fine irregularities layer in the cross section (horizontal cross section) when the fine irregularities 2 are assumed to be cut by a plane (XY plane) perpendicular to the irregular direction. However, it is set as the shape which increases gradually gradually as it goes to the deepest part 2b (valley bottom) from the top part 2t (top) of this fine unevenness | corrugation. For this purpose, it is sufficient that at least a part of the ridges of the fine irregularities 2 have an inclined slope. However, as shown in FIG. But it ’s okay. In particular, it is preferable that the cross-sectional area occupancy is completely converged to 0 at the top 2t and the cross-sectional area occupancy is completely converged to 1 at the deepest part. Specifically, for example, shapes as shown in FIGS. 5B and 5C can be given. However, as shown in FIG. 5 (D) or FIG. 5 (E), at the top, the shape where the cross-sectional area occupancy asymptotically approaches 0, or at the deepest portion, asymptotically approaches 1 If so, a certain degree of effect can be obtained. The shape of the fine irregularities may be any shape as long as these conditions are satisfied.

For example, the vertical cross-sectional shape of each fine unevenness 2 is a wave-like shape only by a curve such as a sine wave as shown in FIG. 5 (A) (see also FIG. 2), as shown in FIG. 5 (B) and FIG. 5 (C). A shape only by a straight line such as a triangle, or a trapezoidal shape in which the top of a triangle forms a flat surface as shown in FIG. 5D, and a deepest portion between adjacent triangles as shown in FIG. And the like. However, as shown in FIG. 5D and FIG. 5E, in the shape having a flat surface at the top or deepest part, the larger the area ratio of the flat surface in the flat part of the top or deepest part, The change in effective refractive index is larger and discontinuous. In that respect, performance is inferior. However, even in this case, the effective refractive index can be continuously changed from the top of the fine unevenness to the deepest part. Therefore, in terms of antireflection performance, the area ratio of the flat surface at the top or deepest portion is preferably as small as possible. 5A, 5B, or 5C in which the cross-sectional area occupation ratio of the fine unevenness layer converges to 0 at the top of the fine unevenness (that is, a sharp shape). In addition, a shape in which the cross-sectional area occupancy continuously converges to 1 in the deepest part is most preferable.
Note that the vertical cross-sectional shape of the fine unevenness 2 (the convex portion 4) is such that the shape in which the vicinity of the top becomes a smooth curve convex outward (upward in the drawing) as shown in FIG. The thickness direction of the effective refractive index n _ef at the top or the deepest part of the fine uneven layer as compared with the shape in which the vicinity of the top becomes a discontinuous point (point) in the outer direction as shown in FIG. 5 (B). This is preferable because there is less discontinuity of change with respect to (the vertical direction in FIG. 5B) and the light reflectance is further reduced.

  Next, the horizontal sectional shape of each fine unevenness is arbitrary such as a circle (for example, FIG. 2), an ellipse, a triangle, a quadrangle, a rectangle, a hexagon, and other polygons. The horizontal cross-sectional shape need not be the same from the top to the deepest part of the fine irregularities. Therefore, the three-dimensional shape of the fine unevenness is, for example, a fine three-dimensional shape of the fine unevenness when the horizontal cross-sectional shape is circular and the vertical cross-sectional shape is equilateral triangle, and the fine shape when the horizontal cross-sectional shape is circular and the vertical cross-sectional shape is triangular. The three-dimensional shape of the unevenness is an oblique cone, the three-dimensional shape of the fine unevenness is a triangular pyramid when the horizontal cross-sectional shape is triangular and the vertical cross-sectional shape is an equilateral triangle, and the fine unevenness when the horizontal cross-sectional shape is quadrilateral and the vertical cross-sectional shape is a triangular shape The three-dimensional shape becomes a quadrangular pyramid.

  Further, the arrangement of the fine irregularities in the horizontal plane is not limited to the two-dimensional arrangement as illustrated in FIG. 2, but also as the linear groove-shaped fine irregularities 2 illustrated in the perspective view of FIG. The original arrangement may be used, and both are effective. However, in the case of the one-dimensional arrangement, anisotropy occurs in which a direction in which an antireflection effect is obtained and a direction in which the antireflection effect is not obtained are generated in relation to the amplitude direction of the light wave. Accordingly, the two-dimensional arrangement illustrated in the perspective view of FIG. 2 and the plan views of FIGS. 6B and 6C is preferable in that there is no directivity.

  In addition, although all the solid shapes of each fine unevenness | corrugation may be the same, it does not need to be all the same. In addition, when the individual fine irregularities 2 are two-dimensionally arranged, the period may be the same in each fine irregularity or not all.

Further, the height H of the fine unevenness is determined according to the desired reflectance reduction effect and the maximum wavelength of the visible light band incident on the surface of the fine uneven layer. For example, when designing based on the relationship described in Japanese Patent Laid-Open No. 50-70040 (particularly, FIG. 3 thereof) with the reflectance, the height of fine irregularities, and the light wavelength, for example, the reflectance in the visible light band If the goal is to reduce the H2 to less than 2% (half of the untreated glass), the minimum height H _MIN is 0.2λ _MAX or more,
That is,
H _MIN ≧ 0.2λ _MAX

If the goal is to reduce the reflectance in the visible light band to 0.5% or less,
H _MIN ≧ 0.4λ _MAX
Is preferable.
Here, λ _MAX is the maximum wavelength in the visible light wavelength band. Although the reflectance decreases as the height H of the fine irregularities increases from zero, a significant effect can be obtained when the height reaches a height that satisfies the above inequality condition. Specifically, for example, if a fluorescent lamp having a maximum emission spectrum wavelength of λ _MAX = 640 nm is used, H _MIN ≧ 0.2λ _MAX = 128 nm. That is, H _MIN may be 128 nm or more. Further, when considering a solar ray having a maximum wavelength of λ _MAX = 780 nm, H _MIN ≧ 0.2λ _MAX = 156 nm, that is, H _MIN may be set to 156 nm or more. The minimum in the relationship between the height _{H MIN} and the period _{P MAX,} the ratio of the minimum height _{H MIN} / period _{P MAX,} and about 1 / 2-4 / 1.
In addition, at least the convex part 4 should just exist in the fine uneven | corrugated layer 3 on the support body 5 at the minimum. However, in reality, in order to firmly and firmly fix the convex portion 4 on the support 5, and when the fine irregularities 2 are formed by a stamping process, the convex portion 4 to be pushed into the shaping layer. Therefore, a layer made of the same material as that of the protrusion 4 having a thickness of about 1 to 5 μm is usually provided between the protrusion 4 of the fine uneven layer 3 and the support 5 (see FIG. 1). ).

Here, if the specific shape and size of the fine unevenness are illustrated, the shape is as follows: (1) The vertical cross section cut along the plane including the normal of the envelope surface of the fine uneven layer 3 is sinusoidal and the horizontal cross section is An assembly of many circular conical shapes arranged two-dimensionally regularly. (2) The vertical cross section is a shape obtained by rounding the vicinity of the apex of a triangle into an arc shape, and the horizontal cross section is a circle or an ellipse. An assembly having a shape in which the vicinity of the top of the cone is a spherical curved surface can be given. Further, the size of the fine irregularities can be one in which the period P _MAX is 50 to 250 nm and the minimum height H _MIN is 1.5 times the period P _MAX .

Hereinafter, the photocatalyst, the support, and the fine uneven material of the present invention will be described in detail.
〔photocatalyst〕
As the photocatalyst in the present invention, those capable of decomposing organic substances such as sebum and dirt, dust, water and the like are used. For example, anatase type titanium oxide, rutile type titanium oxide, tin oxide, zinc oxide, dioxide trioxide. Examples thereof include bismuth, tungsten trioxide, ferric oxide, and strontium titanate. In particular, the photocatalyst in the present invention is preferably a photocatalyst containing titanium oxide. Examples of the photocatalyst containing titanium oxide include anatase type titanium dioxide (TiO ₂ ) and rutile type titanium dioxide (TiO ₂ ), and a photocatalyst made of anatase type titanium oxide is preferable. This is because mass production technology has been established industrially, is readily available at an appropriate price in the market, and has a high and stable photocatalytic function.

There are various specific forms in which the photocatalyst is present on the surface and / or inside of the convex part 4 of the fine irregularities 2 as described above, but a typical form is a form in which fine particles of the photocatalyst are added to the convex part. It is done. In this case, the shape of the photocatalyst fine particles is not particularly limited, such as a spherical shape, a polyhedral shape, a needle shape, or an amorphous powder shape, but the photocatalyst having an average primary particle size less than the height of the fine irregularities and less than the period P _{MAX at the} top. Fine particles are preferred. This is because particles larger than this cannot be contained in the fine uneven layer. Further, in order to make it possible to faithfully reproduce the fine uneven shape, the photocatalyst particles preferably have an average primary particle size of 100 nm or less.
In the present invention, the average particle size of the fine particles means a value measured using a Microtrac particle size analyzer manufactured by Nikkiso Co., Ltd. in the case of fine particles in the composition, and in the case of fine particles in a cured film. The average value of 10 particles observed by a transmission electron microscope (TEM) photograph of the cross section of the cured film.

  As the photocatalyst, those described above may be used alone or in combination of two or more.

When making a photocatalyst exist on the surface of the convex part of a fine unevenness | corrugation, the quantity should just be 10-90 mass% with respect to 100 mass% of total solid of a fine unevenness formation composition. Here, solid content means the part remove | excluding the solvent from the fine uneven | corrugated formation composition.
When making a photocatalyst exist inside the convex part of a fine unevenness | corrugation, the quantity should just be 70-97 mass% with respect to 100 mass% of total solid content of a fine unevenness | corrugation formation composition.

[Support]
Although it does not specifically limit as the support body 5, Synthetic resins, such as inorganic materials, such as glass (including ceramics), a thermoplastic resin, and a thermosetting resin, can be used. In addition, when baking a coating film, an inorganic material is preferable as a support body at the point of the heat resistance at the time of baking. What is necessary is just to use the material according to the use of an antireflective article for the material of a support body. The antireflection article of the present invention is preferably one in which a fine uneven layer is provided on the surface of a transparent substrate. In this case, it is preferable that the fine uneven layer is also transparent, and when the antireflection article is attached to the glass, an effect as if the glass is not present is exhibited.

Examples of the support of the inorganic material include glass such as soda glass, lead glass, and quartz glass, ceramics such as PLZT, quartz, and fluorite.
As the support of the organic material, a thermoplastic resin is typically used. For example, poly (meth) methyl acrylate, poly (meth) ethyl acrylate, methyl (meth) acrylate-butyl (meth) acrylate copolymer Acrylic resin such as coalescence (however, (meth) acryl means acryl or methacryl), polycarbonate resin, polypropylene, polymethylpentene, cyclic olefin polymer (typically norbornene resin, etc. For example, polyolefin resin such as “ZEONOR” manufactured by Nippon Zeon Co., Ltd. and “ARTON” manufactured by JSR Co., Ltd.), thermoplastic polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyamide resins, polystyrene, Acrylonitrile-styrene copolymer, polyethers , Polysulfone, cellulose resins, vinyl chloride resins, polyether ether ketone, polyurethane, and the like.

[Fine unevenness]
The constituent material of the fine unevenness is preferably a material having excellent resistance to the decomposition action of the photocatalyst in addition to the workability capable of forming the fine unevenness.
In particular, with regard to the workability that can form fine irregularities, the fine irregularities are formed by a forming process using a fine irregularity mold such as stamping (pressing, embossing), casting (casting, casting), and injection molding. It is preferable that the molding material be capable of forming

  As a molding material applicable to a shaping process and having excellent resistance to the decomposition action of a photocatalyst, a sol-gel reactive composition containing an organometallic compound, an organic containing an organic structure and an inorganic structure in a polymer molecule— This includes materials containing an organic structure and an inorganic structure, such as a composition containing an inorganic hybrid polymer, a composition containing an inorganic material and an organic binder, and other organic binders such as latex binders. . In particular, the fine irregularities in the present invention are preferably formed using a material selected from the group consisting of a material containing an organic structure and an inorganic structure and a latex binder.

As the sol-gel reactive composition containing an organometallic compound, a compound whose viscosity is increased by a polycondensation reaction or a crosslinking reaction can be used. Examples of the organometallic compound include a metal alkoxide compound represented by the general formula RnM (OR ′) m, a hydrolyzate thereof, and the like. In the above formula, M represents a metal such as Si, Ti, Zr, Al, Ca, Na, Pb, B, Sn, Ge, etc., and R and R ′ are a methyl group, an ethyl group, a propyl group, and a butyl group. N and m each represents an integer such that n + m is the valence of the metal M. Therefore, for example, when the metal M is silicon Si, the above general formula is RnSi (OR ′) _n−4 .

Further, specific examples of the metal alkoxy compound as described above include silicon-based alkoxide compounds such as Si (OCH ₃ ) ₄ and Si (OC ₂ H ₅ ) ₄ , Ti (OC ₃ H ₇ ) ₄ , and Ti (OC _4). Titanium alkoxide compounds such as H ₉ ) ₄ , zirconium alkoxide compounds such as Zr (OC ₃ H ₇ ) ₄ and Zr (OC ₄ H ₉ ) ₄ , Al (OC ₃ H ₇ ) ₄ , Al (OC ₄ H ₉ ) Aluminum-based alkoxide compounds such as ₄ , sodium-based alkoxide compounds such as NaOC ₂ H _{5 and the} like.
Furthermore, specific examples of the silicon-based alkoxide compound include methyltriethoxysilane [(CH ₃ ) Si (OC ₂ H ₅ ) ₃ ], methyltripropoxysilane [(CH ₃ ) Si (OC ₃ H ₇ ) ₃ ]. , Dimethyldiethoxysilane [(CH ₃ ) ₂ Si (OC ₂ H ₅ ) ₂ ] and the like.

  In addition, 4, 3, and bifunctional alkoxysilanes, and condensates, hydrolysates, silicone varnishes, and the like of these alkoxysilanes can be used. The trifunctional or bifunctional alkoxysilane is generally often referred to as a silane coupling agent, but in the present invention, a compound in which one or more alkoxy groups are bonded to one silicon molecule is referred to as an alkoxysilane. Specifically, tetramitoxysilane, tetraethoxysilane and tetrapropoxysilane as pentafunctional alkoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane vinyltrimethoxy as trifunctional alkoxysilane. Silane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane, glycidpropoxytrimethoxysilane, glyciropropylmethyldiethoxysilane, aminopropyltriethoxysilane, aminoethylaminopropyltrimethoxysilane and mercaptopropyltrimethoxysilane, 2 Examples of functional alkoxysilanes include dimethylmethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane. Examples of the condensate include condensates of tetrafunctional alkoxysilanes such as ethyl silicate 40, ethyl silicate 48, and methyl silicate 51, but are not limited thereto. As a hydrolyzate, what hydrolyzed the alkoxysilane using the organic solvent, water, and a catalyst can be used. Among these silica compounds, in particular, totramethoxysilane, tetraethoxysilane, ethyl silicate 40, ethyl silicate 48, methyl silicate 51, and alcoholic silica sol as a hydrolysis product thereof can firmly fix the film, and are compared. It is particularly good because it is inexpensive.

  In addition, as the organometallic compound, a metal alkoxide compound represented by the general formula XnM (OR ′) m (wherein X is an amino group, a carboxyl group, a glycidyl group, an acryloyloxy group, a methacryloyloxy group, etc.) For example, when the metal is silicon, a so-called silane coupling agent can be used.

In addition, as a resin or a low molecular compound to be added to improve the plasticity at the time of shaping to a sol-gel reactive composition containing an organometallic compound, for example, an acrylic resin, a thermoplastic resin such as polyvinyl alcohol, polyethylene glycol, Low molecular organic compounds such as polyether compounds such as polypropylene glycol and polytetraethylene glycol can be used.
For the sol-gel solution, water or a solvent such as alcohol such as methanol or ethanol, a ketone such as methyl ethyl ketone or methyl isobutyl ketone, or an ester such as ethyl acetate or butyl acetate is appropriately used. In the sol-gel solution, an acid such as hydrochloric acid or an alkali is appropriately used as a catalyst for promoting a hydrolysis reaction such as an organometallic compound or a hydrolyzate thereof.

  Since the sol-gel reactive composition containing an organometallic compound is cured by a polycondensation reaction and then further baked, it becomes an inorganic material that does not substantially contain an organic component. It has excellent resistance and is extremely preferable.

  Examples of the organic-inorganic hybrid polymer having an organic structure and an inorganic structure in the polymer molecule include a silicone-based binder mainly composed of organopolysiloxane. For example, it may be a polyorganosiloxane including polydialkylsiloxane, polydiarylsiloxane, polyalkylarylsiloxane, polyalkylalkoxysiloxane, or the like.

  Examples of the composition in which an inorganic material and an organic binder are mixed include a mixture of a pure inorganic material such as silica and a thermoplastic, photocurable or thermosetting organic binder. As the organic binder, a latex binder described later is used. It is preferable to use a photocatalyst having excellent resistance to the decomposition action.

  Examples of the latex binder include natural latex, neoprene latex, nitrile latex, acrylic latex, vinyl acrylic latex, nitrile latex, styrene butadiene latex, and the like. The latex binder may be combined with the silicone-based binder described above.

  In addition, although the material which consists only of the inorganic substance which does not contain an organic structure substantially is excellent in the resistance with respect to the decomposition | disassembly effect | action of a photocatalyst, it is generally difficult to form a fine unevenness | corrugation by a shaping process. However, it is possible to form a coating film made of an inorganic substance. Therefore, a fine unevenness | corrugation can be formed by forming a fine resist pattern in an inorganic coating film by a photo process, and performing an etching process.

〔Production method〕
Next, the manufacturing method of the antireflective article of this invention is demonstrated.
The antireflective article of the present invention is prepared by providing a support, providing a fine irregularity forming material thereon, forming fine irregularities, and then providing a photocatalyst on the surface of the fine irregularities, or providing a support. Then, after providing a fine unevenness forming material containing a photocatalyst thereon, it can be produced by a method of forming fine unevenness.

  As a method for forming fine irregularities, there are methods such as a stamping process and injection molding for forming fine irregularities using a mold as a material for forming fine irregularities, and a fine resist by a photo process on a coating film of the fine irregularities forming material. Fine irregularities can be formed by forming a pattern and etching.

  For example, in the method disclosed in Japanese Patent No. 4406553, (a) anodized porous alumina having pores on the surface where irregularities can be formed by structure transfer, the pore diameter formed by anodization and corrosion By alternately repeating the enlargement process, the anodized porous alumina with the pores having a tapered shape whose pore diameter changes in the depth direction is used as a mold, or (b) the anodized porous alumina is used as a mold. Using the produced stamper as a mold, irregularities are formed on the surface of the polymer film.

  Further, for example, in the method disclosed in Patent Document 1, when manufacturing an antireflection article having fine irregularities, as a process, (A) First, a prototype having a fine irregular shape formed on the surface is prepared, and (B ) Then, the above-mentioned prototype is used as a shaping mold, or a replica mold is produced by replicating the surface of the above-mentioned prototype with fine irregularities one or more times by mold taking and reversal. The sol-gel solution is dehydrated and polymerized after pressing the shaping mold against a coating film composed of a sol-gel reactive composition solution (also referred to as a sol-gel solution) containing an organometallic compound formed on a substrate. After the gelation, an antireflection article is produced by a sol-gel method as a configuration in which each step is performed by releasing the mold to form a fine unevenness on the surface of the solidified coating film to form a fine uneven layer.

  Here, the sol-gel method is a coating film in which a sol-gel solution containing a metal oxide precursor obtained by hydrolyzing and dissolving an organometallic compound such as alkoxysilane in water and an alcohol mixed solution is coated on a substrate. Therefore, it is known as a method of forming an inorganic coating film made of a metal oxide by dehydration by heating. Recently, it is also known as a method for forming an organic-inorganic composite film. In these sol-gel methods, when the base material is a resin sheet, etc., a baking process is not included, in which the coating film is heat-treated at a high temperature to burn / disappear organic components, but when the base material is an inorganic material such as glass In addition, since the substrate can withstand high heat, the coating film can be further baked to form a complete inorganic film.

  In particular, the fine irregularities of the present invention are preferably made of a cured product obtained by a sol-gel reaction of a sol-gel reactive composition containing an organometallic compound. The fine concavo-convex layer formed on the surface of the anti-reflective article is an inorganic layer because it is formed by the sol-gel method. For example, compared to the case where it is formed as a resin layer by the 2P method, etc., it has heat resistance, weather resistance, etc. It can be excellent. Further, the hardness of the fine irregularities can be obtained, and the washing resistance and the like are improved. In addition, when the fine uneven layer after shaping is not fired, the substrate can be an organic material having poor heat resistance such as a resin other than an inorganic material such as glass. Moreover, the productivity is good because there is no time-consuming baking step, and it is possible to further improve the productivity by continuous processing for a continuous belt-like substrate such as a resin sheet.

As a method of applying a photocatalyst to the surface and / or the inside of the fine irregularities,
(1) A method for forming fine irregularities by incorporating fine particles of a photocatalyst into the fine irregularities forming material as described above,
(2) A method of forming a fine unevenness using a material for forming fine unevenness, and then depositing a photocatalyst component on the surface of the fine unevenness by a dry process such as vapor deposition or CVD,
(3) A method for forming a fine unevenness by forming a coating film by adding photocatalyst fine particles to the material for forming fine unevenness, forming a fine resist pattern on the coating film by a photo process, and etching.
(4) A method of forming a fine unevenness by forming a fine resist pattern on a coating film made of the photocatalyst itself by a photo process and performing an etching process.

In the above, as a method of forming a coating film of the photocatalyst itself by a method other than the dry process,
(A) A solution in which a titanium alkoxide such as titanate tetraethoxide or the like is dissolved in an alcohol such as ethyl alcohol disclosed in Japanese Utility Model Laid-Open No. 5-7394, JP-A-8-108075, JP-A-8-182019, or the like. A method of firing amorphous titanium oxide fine particles (particle size of about 3 to 150 nm) generated by a dehydration condensation reaction during drying at room temperature to 500 ° C. (a kind of sol-gel method),
(B) Titanium oxide having an average particle diameter of 0.001 to 0.5 μm disclosed in Japanese Patent No. 3732247, general formula Si _n O _n-1 (OR) _{2n + 2} (where n is 2 to 6, R is a method of applying a hydrolyzate of a lower alkyl silicate condensate represented by C ₁ -C ₄ alkyl group) and drying or baking at 100 to 300 ° C.,
(C) Spray coating, flow coating, spin coating, dip coating, an acidic aqueous solution of TiCl ₄ or Ti (SO ₄ ) ₂ disclosed as an embodiment different from the above (a) in JP-A-8-182019 Examples of the method include forming by applying by roll coating, and then drying the inorganic titanium compound at a temperature of about 100 ° C. to 200 ° C. and subjecting it to hydrolysis and dehydration condensation polymerization.

Examples of the fine unevenness in which the photocatalyst of the present invention finally obtained is present include the following.
(1) A mode in which photocatalyst particles are dispersed inside fine irregularities.
(2) A mode in which the surface of the fine irregularities is coated with a photocatalyst layer.
(3) A mode in which fine irregularities are formed by the photocatalyst itself.
Among these, the form (1) is preferable because the production process is easy and mass productivity is high.

[Use of anti-reflective articles]
In the antireflection article according to the present invention, the shape is arbitrary such as a three-dimensional shape, a plate, a sheet, and the use is not particularly limited. In addition, the use which this invention can apply is not limited to the use illustrated from now on.

  For example, the window material of the information display part in various apparatuses, such as a mobile phone and a clock, is mentioned. In these display units, a resin or glass window material that is a plate or a molded product is disposed on the front surface of a display panel such as an LCD. In addition to the display panel such as an LCD, the information display unit may be displayed by a mechanical means such as a mechanical analog meter represented by a watch, or may be a window material of these. Note that the window material has a flat plate shape, but some have a projection or the like around it from the viewpoint of assembly or design.

  As a device having an information display unit with a window as described above, besides a mobile phone and a watch, a PDA such as a television receiver, a personal computer, a digital game machine, an electronic notebook, a portable information terminal, a calculator, or , CD players, DVD players, MD players, various portable music players such as semiconductor memory music players, video tape recorders, IC recorders, video cameras, digital cameras, label printers, and other electronic devices, or electric rice cookers There are electronic products such as electronic pots and washing machines.

  In the case of a plate-like or sheet-like antireflection article, a transparent substrate such as a transparent plate used for a transparent touch panel or the like can be used. The transparent touch panel adds an input function to the display unit. However, because the product is assembled as a separate part from the display panel such as LCD and CRT, a gap remains between the display panel and the transparent touch panel. Furthermore, interference fringes (Newton ring) resulting from this occur. Then, if the transparent base material which comprises the back surface side of a transparent touch panel is made into the antireflection article which provided the fine unevenness | corrugation peculiar to this invention on the back surface, light reflection can be prevented.

The transparent touch panel is, for example, a PDA such as an electronic notebook or a portable information terminal (equipment), or a car navigation system, a POS (point-of-sale information management) terminal, a portable order input terminal, or an ATM (automatic cash deposit payment combined use machine). , Facsimiles, landline telephones, mobile phones, digital cameras, video cameras, personal computers, PC displays, television receivers, digital game machines, TV monitor displays, ticket machines, measuring instruments, calculators, electronic musical instruments, and other electronic devices It is used for office machines such as copiers and ECRs (cash register machines), or electrical products such as washing machines and microwave ovens.
The antireflection article of the present invention can also be used as various optical components. For example, a camera lens, a finder window material of a camera, a spectacle lens, a Fresnel lens of an overhead projector, an output extraction window of a laser device, an optical input window of an optical sensor, a telescope lens, and the like.
In addition, there are applications such as showcases for high-priced products, protective plates for artworks, and the like.
In particular, the present invention can decompose or reduce or remove dirt adhering to fine irregularities, so that it can be used for store windows such as department stores, large windows, and general merchandise showcases. In that case, it is preferable to use a transparent substrate as the support because of high visibility.

As described above, the antireflection article of the present invention has fine irregularities on the surface, and a photocatalyst is present on the surface and / or inside of the convex portions of the fine irregularities. Thereby, when dirt containing an organic substance adheres to the surface of fine irregularities, the dirt can be decomposed and removed or reduced. For this reason, it is possible to arrange and use fine irregularities on the outer surface (toward the outside) where the fingers come into contact.
In addition, the photocatalyst decomposes the moisture adsorbed on the surface of the fine irregularities, generates OH, O, etc., promotes the wettability of the surface, covers the surface with a thin film of water, and makes it difficult for the dirt itself to adhere. There is also an effect.

1 ... antireflection article 2 ... fine irregularities 2t ... (fine concavo-convex 2) top 2b ... (fine concavo-convex 2) deepest 3 ... fine uneven layer 4 ... protrusion 5 ... support n ... refractive index n a _... refractive index (air)
n _b ... refractive index (support)
n ₀ ... Refractive index n ₁ ... Refractive index n _ef (Z) ... Effective refractive index P _MAX ... Period

Claims (7)

An antireflective article comprising a fine uneven layer having fine unevenness on the surface,
The fine unevenness has a maximum wavelength in the wavelength band of visible light as λ _MAX and a period at the top of the fine uneven surface as P _MAX .
P _MAX ≦ λ _MAX
The relationship
and,
The cross-sectional area occupancy of the material portion of the fine concavo-convex layer in the cross-section when the fine concavo-convex is assumed to be cut at a plane orthogonal to the concavo-convex direction is continuous as it goes from the top of the fine concavo-convex to the deepest part. Are fine irregularities having a shape that gradually increases,
An antireflective article, wherein a photocatalyst is present on the surface and / or inside of the convex portions of the fine irregularities.   The antireflective article according to claim 1, wherein the photocatalyst is present on the surface and / or inside of a region including at least the top of the fine irregularities.   The antireflection article according to claim 1 or 2, wherein the fine uneven layer is provided on a surface of a transparent substrate.   The antireflective article according to claim 1, wherein the photocatalyst is a photocatalyst fine particle having an average primary particle size less than the height of the fine irregularities and less than a period PMAX at the top.   The antireflection article according to claim 1, wherein the photocatalyst is a photocatalyst containing titanium oxide.   The antireflection article according to claim 1, wherein the fine unevenness is formed using a material selected from the group consisting of a material including an organic structure and an inorganic structure and a latex binder.   The antireflection article according to claim 6, wherein the fine irregularities are made of a cured product obtained by a sol-gel reaction of a sol-gel reactive composition containing an organometallic compound.

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