JP2007065563A - Antireflective optical structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antireflective optical structure which can sufficiently suppress reflected light and can heighten visibility of a display section when used as a transparent panel of the display section in a display apparatus. <P>SOLUTION: The antireflective optical structure 1 is equipped with a reflection suppressing layer 3 which is made of a transparent material and which has minute ruggedness with a pitch between vertexes of convex parts 3A smaller than a wavelength of a visible ray and an antiglare layer 4 which intervenes between the transparent base material 2 and the reflection suppression layer 3 at least on one surface of the transparent base material 2. Reflected light of outdoor daylight is sufficiently suppressed by the reflection suppression layer 3 and the antiglare layer 4 and application of this structure to a display apparatus realizes improvement of visibility of the display section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an antireflection optical structure used for a transparent panel covering a display unit of a display device such as various displays including a vehicle instrument.

  FIG. 7 is a diagram illustrating the relationship between the display device 100 and the visual field A of the person. The display device 100 includes a display unit 101 and a transparent panel 102 covering the outside. In such a display device 100, external light is reflected by the transparent panel 102, and the reflected light Lr may enter the human field of view A, making it difficult to see the display unit 101. It is desirable to use a low one.

Therefore, conventionally, as shown in FIG. 8, for example, an antireflection optical structure used for the transparent panel 102 or the like has been proposed. The illustrated antireflection optical structure 110 is formed of a transparent material, and at least the outer surface (external light incident side) is formed with innumerable fine irregularities 111 having a pitch smaller than the wavelength of visible light. Therefore, the reflected light is suppressed by changing the refractive index of light in the thickness direction by the fine unevenness 111 (Patent Document 1).
JP 2002-267815 A

  By the way, the conventional antireflection optical structure as described above can theoretically make the reflectance as close to zero as possible, and if the theoretical value can be realized, the reflected light can be sufficiently suppressed. .

  However, in the conventional antireflection optical structure, it is actually very difficult to accurately form fine irregularities with a sub-wavelength size pitch smaller than the wavelength of visible light, thereby completely preventing reflected light. Therefore, when this is used for a transparent panel of a display device, the visibility of the display unit may be significantly reduced if the outline of the reflected image is clear even with a small amount of reflected light. In particular, when bright external light is received outdoors or the like, there is a problem in that the visibility of the display unit is significantly reduced, and it has been a problem to solve such a problem.

  The present invention has been made paying attention to the above-mentioned conventional problems, and can sufficiently suppress reflected light, and when used as a transparent panel of a display unit in a display device, the visibility of the display unit is improved. It is an object to provide an anti-reflection optical structure that can be enhanced.

  The antireflection optical structure of the present invention is a reflection suppressing layer made of a transparent material and having fine irregularities whose pitch between the vertices of the convex portions is smaller than the wavelength of visible light on at least one surface of the transparent substrate, It is set as the structure provided with the glare-proof layer interposed between a transparent base material and a reflection suppression layer, and is the means for solving the conventional subject with the said structure.

  Further, the antireflection optical structure of the present invention is characterized in that, as a more preferred embodiment, the vertex interval of the convex portions of the fine irregularities in the antireflection layer is constant, and the antiglare layer is made of a transparent material. The base material is characterized in that it contains light scattering particles having a particle diameter larger than the wavelength of visible light, and the particle diameter of the light scattering particles in the antiglare layer is 3 μm to 30 μm. Furthermore, the particle diameter of the light scattering particles in the antiglare layer is 3 μm to 5 μm, and the content of the light scattering particles in the base material in the antiglare layer is 0.1% to 10%. %.

  According to the antireflection optical structure of the present invention, by adopting the above configuration, reflected light can be sufficiently suppressed, and when used as a transparent panel of a display unit in a display device, it can be used outdoors. Even when bright external light is received, the visibility of the display portion can be remarkably improved.

  The antireflection optical structure 1 shown in FIG. 1 is made of a transparent material on one surface (upper surface) of a transparent substrate 2 and the pitch P1 between the vertices of the convex portions 3A is smaller than the minimum wavelength of visible light 370 nm. The antireflection layer 3 having fine unevenness and the antiglare layer 4 interposed between the transparent base material 2 and the antireflection layer 3 are provided, and the other surface (lower surface) of the transparent base material 2 also has fine unevenness. The antireflection layer 3 is provided, for example, for a transparent panel that covers a display unit in a display device such as a vehicle instrument.

  As shown in FIGS. 2 and 3, the reflection suppressing layer 3 is formed by arranging innumerable convex portions 3 </ b> A vertically and horizontally to form fine irregularities, and the refractive index of light is changed in the thickness direction by the fine irregularities. Thus, it functions to suppress reflected light, and more desirably, by making the vertex interval of the convex portions 3A, that is, the pitch P1, constant, the degree of change in the refractive index is made uniform over the entire surface.

  When the optical structure 1 is used as a transparent panel of a display device, the reflection suppressing layer 3 is provided on at least the outer surface, that is, the surface on the incident side of external light, with respect to the transparent substrate 2. Moreover, although the quadrangular pyramid-shaped convex portion 3A is illustrated in the drawing, the shape is not particularly limited, and for example, a conical shape or a shape having a spherical tip portion may be used.

  Similar to the antireflection layer 3, the antiglare layer 4 is provided on at least the outer surface with respect to the transparent substrate 2, that is, the surface on the incident side of external light. Light scattering particles having a particle diameter larger than the wavelength of 780 nm are contained, and the light that has passed through the reflection suppressing layer 3 is scattered by the light scattering particles.

  That is, in the optical structure 1, most of the reflected light can be suppressed by the reflection suppression layer 3, but it is difficult to completely prevent the reflected light unless a theoretical value is realized. When used for the transparent panel of the apparatus, even if it is a slight amount of reflected light, the visibility of the display unit is lowered if the outline of the reflected image is clear, so that the light is scattered by the antiglare layer 4. Thus, the outline of the reflected image is made unclear and the visibility of the display unit is improved.

  As described above, the optical structure 1 suppresses most of the reflected light by the reflection suppression layer 3 and scatters the light that has passed through the reflection suppression layer 3 by the anti-glare layer 4, thereby reflecting the reflected light as a whole. It can be sufficiently suppressed. Therefore, in a display device using the optical structure 1 as a transparent panel, the visibility of the display unit is remarkably good.

  Here, the material of the transparent substrate 2 may be any material that is transparent and can be polymerized and cured by thermoforming or active energy rays. For example, polyethylene, polypropylene, polyvinyl alcohol, polyvinylidene chloride, polyethylene terephthalate, Polyvinyl chloride, polystyrene, ABS resin, AS resin, acrylic resin, polyamide, polyacetal, polybutylene terephthalate, glass reinforced polyethylene terephthalate, polycarbonate, modified polyphenylene ether, polyphenylene sulfide, polyether ether ketone, liquid crystalline polymer, fluorine resin, polyarate , Thermoplastic resins such as polysulfone, polyethersulfone, polyamideimide, polyetherimide and thermoplastic polyimide, phenol resin, melamine Use thermosetting resins such as fats, urea resins, epoxy resins, unsaturated polyester resins, alkyd resins, silicone resins, diallyl phthalate resins, polyamide bismaleimides and polybisamide triazoles, and blends of these materials. It is possible. These materials can also be used for the base material of the antiglare layer 4.

  As a material of the light scattering particles in the antiglare layer 4, each of silica, talc, clay, alumina white, calcium carbonate, polyacrylic acid esters, polymethacrylic acid esters, polystyrene, and melamine resin may be used alone or in combination of two or more. Can be used.

  The shape of the light scattering particles is not particularly limited, but may be, for example, spherical, substantially spherical, fibrous, or needle-like.

  The particle diameter (average particle diameter) of the light scattering particles is desirably in the range of 3 μm to 30 μm, and more desirably in the range of 3 μm to 5 μm. This is because if the particle diameter of the light scattering particles is smaller than 3 μm, the function of scattering the light may be impaired, and if the particle diameter of the light scattering particles is larger than 30 μm, the size becomes visible. This is because the transparency of the optical structure 1 may be impaired. Therefore, the light scattering function and the transparency can be favorably obtained by setting the particle diameter of the light scattering particles in the above range.

  The average particle diameter of the light-scattering particles is a volume average particle diameter, that is, a sphere diameter when converted to a sphere having the same volume. As a volume average particle diameter measuring apparatus, there is Multisizer II manufactured by Beckman Coulter.

  Furthermore, the content of the light scattering particles in the base material in the antiglare layer 4 is preferably in the range of 0.1% to 10%. This is because if the content of light scattering particles is less than 0.1%, the light scattering function may be impaired, and if the content of light scattering particles is greater than 10%, the optical structure This is because the transparency of the body 1 may be impaired. Therefore, by setting the content of the light scattering particles in the above range, the light scattering function and transparency can be obtained satisfactorily.

  Furthermore, as a method of molding the antireflection optical structure 1, for example, a transparent base film, an antiglare film containing light scattering particles, and a transparent base film in a first mold having a fine uneven structure Are stacked in order, and a second die having a fine concavo-convex structure is combined thereon, and the whole is subjected to hot press molding.

  In addition, the said optical structure 1 may make it form the reflection suppression layer 3 and the glare-proof layer 4 by making the panel main body of the transparent panel in a display apparatus into the transparent base material 2, or the transparent base material 2, reflection suppression. It is also possible to form the entire layer 3 and the antiglare layer 4 into a flexible film and affix them to another transparent plate.

  FIG. 4 is a diagram showing the relationship between the display device 50 that is an instrument panel of an automobile and the visual field A of the driver. The display device 50 includes a display unit 51 and a transparent panel 52 covering the outside thereof, and has a configuration without a meter hood. In such a display device 50, by applying the antireflection optical structure 1 described with reference to FIG. 1 to the transparent panel 52, the reflected light of the transparent panel 52 is sufficiently reflected even in a configuration without a meter hood. Therefore, good visibility of the display unit 51 can be obtained.

  However, in order to ensure the visibility of the display unit 51 at night or the like, the display device 50, which is an instrument panel of an automobile, is illuminated by a self-luminous type that causes the display unit 51 to emit light, or the display unit 51 is illuminated. It is well known that there is an indirect illumination method. When the illumination is turned on, the display light Ld from the display device 50 is reflected by the front window FW to form a virtual image Vi, which may enter the driver's visual field A.

  Therefore, the antireflection optical structure of the present invention includes the transparent base material 2, the antireflection layer 3 and the antiglare layer 4 as shown in FIG. The transparent substrate 2 includes a light shielding layer 5 having a light shielding plate 5A.

  More specifically, the illustrated antireflection optical structure 11 is made of a transparent material on one surface (outer surface) of the transparent substrate 2 and the pitch between the vertices of the convex portions is the minimum of visible light. The antireflection layer 3 having fine irregularities smaller than a wavelength of 370 nm, the antiglare layer 4 interposed between the transparent base material 2 and the antireflection layer 3 and containing light scattering particles, and the other of the transparent base material 2 Is provided with a reflection suppressing layer 3 having fine irregularities on the surface (inner surface which is the display portion side), and is longer than the maximum wavelength of visible light of 780 nm in the middle of the thickness direction of the transparent substrate 2. A light shielding layer 5 in which light shielding plates 5A are arranged at intervals P2 is provided.

  As shown in FIG. 6, the light shielding layer 5 shown in FIG. 6 has a louver shape in a cross section perpendicular to the thickness direction of the layer by alternately arranging the light shielding plates 5A and the transparent portions 5B. The interval P2 between the adjacent light shielding plates 5A is longer than the maximum visible light wavelength of 780 nm. For example, the light shielding layer 5 is interposed in the transparent base material 2 by being sandwiched by the transparent base material 2 divided into two in the thickness direction.

  In the light shielding layer 5, the material of the light shielding plate 5 </ b> A is not particularly limited as long as it has light shielding properties. In addition to the illustrated example, the shape of the light shielding plate 5A may be a honeycomb shape or a rectangular mesh shape in a cross section perpendicular to the thickness direction of the layer. Further, the material of the transparent portion 5B is not particularly limited, and for example, a transparent acrylic resin is used.

  Here, as shown in FIG. 5, when the emission angle formed by the display light Ld from the self-luminous display 51 and the normal of the surface of the antireflection optical structure 11 is θ, the light shielding layer 5 is When there is no light, the maximum value of the emission angle θ is 180 °. However, when the light shielding layer 5 is provided, the emission angle θ of the display light Ld from the display unit 51 is limited by the light shielding plate 5A of the light shielding layer 5. Therefore, the maximum value of the emission angle θ can be controlled to be less than 180 °.

  In FIG. 4, as described above, the display light Ld from the display unit 51 is reflected by the front window FW to form a virtual image Vi, which enters the driver's visual field A.

  At this time, when the locus of the display light Ld from the portion closest to the front window FW of the display unit 51 is viewed, if the emission angle of the display light Ld is smaller than θ1, the reflected light from the front window FW is reflected by the driver. It can be seen that the portion closest to the front window FW of the display unit 51 does not appear in the window FW.

  When the locus of the display light Ld from the portion farthest from the front window FW of the display unit 51 is viewed, if the emission angle of the display light Ld is smaller than θ2, the reflected light from the front window FW is reflected by the driver. It can be seen that the portion farthest from the front window FW of the display unit 51 does not appear in the window FW without entering the field of view A.

  Further, when the emission angles θ1 and θ2 of the display light Ld are defined as the critical emission angles, it can be seen that the critical emission angles at other parts of the display unit 51 are larger than θ1 or θ2. Therefore, when the critical emission angle at an arbitrary position of the display unit 51 is smaller than θ1 and θ2, not all of the display unit 51 is reflected in the front window FW.

  Therefore, the optical structure 11 includes the transparent base material 2, the reflection suppressing layer 3, and the antiglare layer 4, and the light shielding plate 5A is provided in the transparent base material 2 at an interval P2 longer than the maximum visible light wavelength of 780 nm. The meter hood has a configuration including the arranged light shielding layers 5 and sets the arrangement interval P2 of the light shielding plates 5A and the thickness of the light shielding layer 5 so that the emission angle θ of the display light Ld is smaller than θ1 and θ2. Even if it is the structure without this, it can prevent that the display part 51 reflects in the front window FW, can eliminate formation of the virtual image Vi which obstructs a driver | operator's visual field, and can obtain a favorable visual field. .

Example 1
On one surface of the transparent substrate (2), a reflection suppressing layer (3) made of a transparent material and having fine irregularities in which the pitch (P1) between the vertices of the convex portion (3A) is smaller than the wavelength of visible light, An anti-glare layer (4) interposed between the transparent substrate (2) and the antireflection layer (3) is provided, and the antireflection layer (3) also has fine irregularities on the other surface of the transparent substrate (2). ) And a light shielding layer (5) in which light shielding plates (5A) are arranged at intervals (P2) longer than the wavelength of visible light are provided in the transparent substrate (2), and the antireflection shown in FIG. Optical structure 11 was produced.

  The transparent substrate 2 is made of a transparent acrylic resin, and the thickness t1 on one side (upper side) of the light shielding layer 5 is 0.5 mm, and the thickness t2 on the other side of the light shielding layer 5 is 1.5 mm. .

  The reflection suppressing layers 3 on both sides are made of a transparent acrylic resin, and as shown in FIGS. 2 and 3, square-convex convex portions 3 </ b> A are arranged vertically and horizontally to form fine concave portions, and adjacent to each other. The pitch P1 between the convex portions 3A is 250 nm, which is smaller than the minimum visible light wavelength of 370 nm, the height (the height difference of the concave and convex portions) H of the convex portion 3A is 500 nm, and the base a × b of the convex portion 3A is 250 nm × 250 nm. It was.

  The antiglare layer 4 is a transparent acrylic resin base material containing 3% of silica light scattering particles having a volume average particle diameter of 5 μm, and has a thickness t3 of 50 μm.

  As shown in FIG. 6, the light shielding layer 5 has an opaque light shielding plate 5A having a thickness t4 of 5 μm and a width W of 170 μm, and a transparent portion 5B made of a transparent acrylic resin. The light shielding plate 5A is provided in a louver shape in a cross section perpendicular to the thickness direction, and the interval (thickness of the transparent portion 5B) P2 between the light shielding plates 5A is 80 μm, which is larger than the maximum wavelength of visible light 780 nm, The layer thickness t5 was set to 170 μm.

  Then, in the display device 50 that is an instrument panel of the automobile shown in FIG. 4, the antireflection optical structure 11 is used as the transparent panel 52, and the visibility of the display unit 51 and the visibility of the front view are visible in a vehicle traveling outdoors in fine weather. The sensory evaluation was performed on the sex. The results are shown in Table 1 below.

  The sensory evaluation related to the visibility of the display unit 51 is performed when eight or more panelists judge the anti-reflection performance of the external light on the transparent panel 52, and when there are seven or more persons who have judged that the reflected light does not matter at all. Indicates that the visibility of the display unit 51 is good (◯), and when there are two or more persons who are determined to be concerned about the reflected light, the visibility of the display unit 51 is insufficient (Δ). It was supposed to be.

  The sensory evaluation related to the visibility of the front field of view is the same for eight panelists who judged the anti-reflection performance of the display unit 51 in the front window FW and judged that the reflection was completely unnoticeable. In this case, the visibility of the front view is good (◯), and if there are two or more persons who are judged to be interested in even a slight reflection, the visibility of the front view is insufficient (△). It was supposed to be.

  Here, the evaluation that the visibility is insufficient is a case where there are two or more people who are determined to be worried even slightly. Absent.

  Further, in the antireflection optical structure 11 of this embodiment, in the light shielding layer 5, since the interval between the light shielding plates 5A is 80 μm and the width W is 170 μm, the emission angle θ of the display light Ld is about 39 °. . The inclination angle of the front window FW is 30 °, which is applied to most commercial vehicles, and there is no meter hood.

  Furthermore, the reflected image contrast ratio of the transparent panel 52 was measured with a luminance meter as a physical quantity related to visibility. The reflected image contrast ratio is a value obtained by dividing the brightness of the bright part of the reflected image by the brightness of the dark part. If the value is about 1.8 or less, the reflected light is hardly noticed.

  Furthermore, in Table 1, the haze value Th is a measure of transparency in which the smaller the value, the higher the transparency, Rv is the vertical reflectance, and Tt is the vertical transmittance.

(Example 2)
The antireflection optical structure 11 shown in FIG. 5 is assumed to have no antireflection layer 3 on the other surface of the transparent substrate 2, and otherwise the same as in Example 1.

(Example 3)
With respect to the antireflection optical structure 11 shown in FIG. 5, the reflection suppressing layer 3 on the other surface of the transparent substrate 2 was used as a two-layer interference antireflection film, and the others were the same as in Example 1. The two-layer interference antireflection film includes, from the outside, a first layer having a thickness of 10 μm and a refractive index of 1.1, and a second layer having a thickness of 10 μm and a refractive index of 1.3.

Example 4
In contrast to the antireflection optical structure 11 shown in FIG.

(Example 5)
With respect to the antireflection optical structure 11 shown in FIG. 5, the reflection suppressing layer 3 and the light shielding layer 5 on the other surface of the transparent base material 2 are not provided, and the others are the same as in Example 1.

(Example 6)
For the antireflection optical structure 11 shown in FIG. 5, the antireflection layer 3 on the other surface of the transparent substrate 2 is a two-layer interference antireflection film similar to that of Example 3, and the light shielding layer 5 is Otherwise, it was the same as in Example 1.

(Comparative Example 1)
With respect to the antireflection optical structure 11 shown in FIG. 5, it was assumed that the antiglare layer 4 and the light shielding layer 5 were not present, and the others were the same as in Example 1.

(Comparative Example 2)
In contrast to the antireflection optical structure 11 shown in FIG. 5, the antiglare layer 4 and the light shielding layer 5 are not provided, and the antireflection layer 3 on the other surface of the transparent substrate 2 is the same as in Example 3. The other two-layer interference antireflection film is the same as in Example 1.

(Comparative Example 3)
It is assumed that the antireflection optical structure 11 shown in FIG. 5 does not have the antireflection layer 3, the antiglare layer 4, and the light shielding layer 5 on the other surface of the transparent substrate 2, and otherwise the embodiment 1 And so on.

  As is clear from Table 1, since Comparative Examples 1 to 3 do not have the anti-glare layer 4 and the light shielding layer 5, the reflected light of the external light on the transparent panel 52 and the reflection of the display unit 51 on the front window FW. The sensory evaluation of both the visibility of the display unit 51 and the visibility of the front field of view was insufficient (Δ).

  On the other hand, Examples 1-6 of this invention are set as the structure provided with the glare-proof layer 4, and the reflection light of the external light in the transparent panel 52 is not confirmed at all, and visual recognition of the display part 51 is carried out. The sensory evaluation of the property was good (◯).

  In Examples 2 and 5, since there is no reflection suppression layer 3 on the other surface of the transparent substrate 2, light is reflected at the interface between the back surface of the optical structure and the air, so that the vertical reflectance Rv is slightly Further, in Examples 4 to 6, since the light shielding layer 5 was not provided, the reflection of the display unit 51 in the front window FW was confirmed, but the light shielding layer 5 was provided as in Examples 1 to 3. By adopting the configuration, no reflection of the display unit 51 in the front window FW was confirmed, and the sensory evaluation of the visibility of the front view was good (◯).

  The anti-reflection optical structure of the present invention is very suitable for a vehicle instrument panel as described above, but in addition, it can be applied to transparent panels of various display devices such as personal computers and mobile phones. Thus, good visibility of the display portion of the display device can be realized even in bright outdoors.

It is sectional drawing explaining one Example of the antireflection optical structure of this invention. It is sectional drawing explaining a reflection suppression layer. It is a perspective view explaining a reflection suppression layer. It is explanatory drawing which shows the relationship between the display apparatus which is an instrument panel of a motor vehicle, and a driver | operator's visual field. It is sectional drawing explaining the other Example of the antireflection optical structure of this invention. It is the perspective view (a), top view (b), and sectional view (c) explaining a light shielding layer. It is explanatory drawing which shows the relationship between a display apparatus and a human visual field. It is sectional drawing explaining the conventional antireflection optical structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 11 Antireflection optical structure 2 Transparent base material 3 Antireflection layer 3A Convex part 4 Anti-glare layer 5 Light-shielding layer 5A Light-shielding plate 50 Display apparatus 51 Display part 52 Transparent panel

Claims (9)

  A reflection suppressing layer made of a transparent material and having fine irregularities whose pitch between the vertices of the convex portions is smaller than the wavelength of visible light on at least one surface of the transparent substrate, and interposed between the transparent substrate and the reflection suppressing layer An anti-reflection optical structure comprising an anti-glare layer.   The antireflection optical structure according to claim 1, wherein the vertex interval of the convex portions of the fine irregularities in the antireflection layer is constant.   The antireflection optical structure according to claim 1 or 2, wherein the antiglare layer contains light scattering particles having a particle diameter larger than the wavelength of visible light in a base material made of a transparent material. .   The antireflection optical structure according to claim 3, wherein the particle size of the light scattering particles in the antiglare layer is 3 μm to 30 μm.   The antireflection optical structure according to claim 4, wherein the particle diameter of the light scattering particles in the antiglare layer is 3 μm to 5 μm.   The antireflection optical structure according to any one of claims 1 to 5, wherein the content of the light scattering particles in the base material in the antiglare layer is 0.1% to 10%.   The antireflection optical structure according to any one of claims 1 to 6, further comprising a light shielding layer in which a light shielding plate is arranged at an interval longer than the wavelength of visible light in the transparent substrate.   The shape of the light shielding plate in the light shielding layer is at least one of a honeycomb shape, a rectangular mesh shape, and a louver shape in a cross section perpendicular to the thickness direction of the layer. Antireflective optical structure. A display device comprising the antireflection optical structure according to claim 1 for a transparent panel of a display unit.

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