WO2011148701A1

WO2011148701A1 - Color filter, and reflection-type display device equipped with same

Info

Publication number: WO2011148701A1
Application number: PCT/JP2011/056036
Authority: WO
Inventors: 博敏安永; 有史八代
Original assignee: シャープ株式会社
Priority date: 2010-05-28
Filing date: 2011-03-15
Publication date: 2011-12-01
Also published as: JP2013164429A

Abstract

A color filter (1A) comprising: a half-wave plate (3) which has a front surface and a rear surface; a front-surface-side photonic crystal layer (5) which has a two-dimensional photonic periodic structure and is formed on the front surface side of the half-wave plate (3); and a rear-surface-side photonic crystal layer (7) which has a two-dimensional photonic periodic structure and is formed on the rear surface side of the half-wave plate (3).

Description

Color filter and reflective display device having the same

The present invention relates to a color filter using a photonic crystal structure and a reflective display device including the color filter.

In recent years, the application range of display devices has continued to expand, and the use of display devices has become widespread in various devices such as mobile phones, portable music players, electronic advertisements, and electronic paper as well as televisions and personal computers. In general, display devices are roughly classified into a transmissive display device and a reflective display device based on the display method.

Usually, a transmissive display device is a display device in which a backlight as a light source is provided on the back side of the display unit, and an image displayed on the display unit can be visually recognized using light emitted from the backlight. It is to make. On the other hand, the reflective display device reflects external light incident from the display surface side of the display unit on the back surface side of the display unit, thereby making it possible to visually recognize an image displayed on the display unit using the reflected light. Is.

Therefore, the reflective display device has an advantage that it consumes less power than the transmissive display device in that it does not require a backlight. Therefore, the power consumption of the reflective display device is particularly low in mobile phones, portable music players, electronic paper, and the like. It is suitable for use in required equipment.

However, reflective display devices generally tend to darken the screen, and are inferior to transmissive display devices in terms of visibility, and so have not been widely used. In the reflective display device, the phenomenon that the screen becomes dark is partly due to the low utilization efficiency of incident light, and the improvement is strongly desired.

Conventionally, as color filters used for display devices, for example, those using pigments such as red, green and blue are used. In the color filter using this pigment, since the hue is determined by the light absorption spectrum exhibited by the pigment, it is necessary to configure the color filter to be thick to some extent. It tends to end up.

In the reflective display device, the amount of light that can be used for display is determined by the amount of incident external light, so when using a color filter using a pigment as described above in the reflective display device, If an attempt is made to reproduce high color purity, the light transmittance is lowered, resulting in a problem that the screen brightness is greatly lowered.

Therefore, in recent years, in order to solve the above-described problems, it has been proposed to employ a color filter using a photonic crystal structure. Photonic crystal structure is a general term for nanostructures whose refractive index changes periodically. By making the period of change of the refractive index below the wavelength of incident light, high wavelength selectivity can be realized. is there. Therefore, by adopting a color filter using a photonic crystal structure, it becomes possible to selectively reflect light of a specific wavelength and transmit light of other wavelengths in the color filter.

In a color filter using a photonic crystal structure, since the hue is determined by the light band of the photonic crystal structure, a high reflectance can be realized by using an appropriate structure. Therefore, in the reflective display device, if the color filter using the photonic crystal structure as described above is used, the screen brightness can be greatly improved as compared with the conventional case.

In addition, the photonic crystal structure has a one-dimensional photonic crystal structure based on whether the periodic change in refractive index is one-dimensional, two-dimensional, or three-dimensional. It is roughly classified into a two-dimensional photonic crystal structure and a three-dimensional photonic crystal structure. Conventionally, it has been studied that a one-dimensional photonic crystal structure is applied to a color filter, but the one-dimensional photonic crystal structure has sufficient wavelength selectivity due to the influence of polarization dependence and light incident angle dependence. There was a problem that the reflectance could not be obtained.

Therefore, Japanese Patent Application Laid-Open No. 2009-276766 (Patent Document 1) proposes to apply a two-dimensional photonic crystal structure to a color filter for the purpose of further improving wavelength selectivity and reflectance. In the said Unexamined-Japanese-Patent No. 2009-276766 (patent document 1), providing a two-dimensional photonic crystal structure on a transparent substrate, and comprising a color filter by these transparent substrates and a two-dimensional photonic crystal structure is disclosed. Has been.

Here, the two-dimensional photonic crystal structure has a smaller wavelength selectivity and lower reflectance due to the influence of polarization dependency and light incident angle dependency than the one-dimensional photonic crystal structure. For this reason, the reflective display device including the color filter using the two-dimensional photonic crystal structure can achieve both high color purity and improvement in screen luminance.

JP 2009-276766 A

However, although the two-dimensional photonic crystal structure has a smaller wavelength selectivity and lower reflectance due to the influence of polarization dependency and light incident angle dependency than the one-dimensional photonic crystal structure, the polarization dependency and light incident angle are small. There is a problem that the reflectance is still lowered due to the influence of dependency.

More specifically, in the two-dimensional photonic crystal structure, the electric field oscillates perpendicularly to the incident surface (that is, perpendicular to the reflecting surface that reflects the incident light beam and includes the incident light beam and the reflected light beam). As for the polarization, the influence of the light incident angle dependency is small, so that even when the light incident angle is large, the wavelength selectivity and the reflectance are hardly lowered, but the p-polarized light whose electric field oscillates parallel to the incident surface. As for, the influence of the light incident angle dependency is large, and as a result, as the light incident angle increases, the reflectance decreases significantly.

For this reason, in the case of the color filter as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2009-276766, there is a problem that the reflectance is significantly reduced as the light incident angle is increased. It is necessary.

Accordingly, the present invention has been made to solve the above-described problems, and its object is to provide a color filter excellent in wavelength selectivity and reflectance, and using the color filter. Accordingly, an object of the present invention is to provide a reflective display device with excellent visibility.

A color filter according to the present invention includes a half-wave plate having a front surface and a back surface, a surface-side photonic crystal layer having a two-dimensional refractive index periodic structure and disposed on the front surface side of the half-wave plate, A back-side photonic crystal layer having a three-dimensional refractive index periodic structure and disposed on the back side of the half-wave plate.

In the color filter according to the present invention, the front-side photonic crystal layer includes a first photonic crystal region having a first periodic refractive index change, and the back-side photonic crystal. Preferably, the layer includes a second photonic crystal region having a periodic refractive index change substantially the same as the first periodic refractive index change. In that case, it is preferable that the first photonic crystal region and the second photonic crystal region are arranged corresponding to each other with the half-wave plate interposed therebetween.

In the color filter according to the present invention, the surface-side photonic crystal layer has a third periodic refractive index change different from the first periodic refractive index change. And the back-side photonic crystal layer further includes a fourth photonic crystal region having a periodic refractive index change substantially the same as the second periodic refractive index change. Also good. In that case, it is preferable that the third photonic crystal region and the fourth photonic crystal region are arranged corresponding to each other with the half-wave plate interposed therebetween.

In the color filter according to the present invention, the surface-side photonic crystal layer has a third period different from both the first periodic refractive index change and the second periodic refractive index change. A fifth photonic crystal region having a typical refractive index change, and the back-side photonic crystal layer has a periodic refractive index change substantially the same as the third periodic refractive index change. A sixth photonic crystal region having the following may be further included. In that case, it is preferable that the fifth photonic crystal region and the sixth photonic crystal region are arranged correspondingly with the half-wave plate interposed therebetween.

The color filter according to the present invention further includes a front-side light-transmitting substrate disposed on the front surface of the half-wave plate and a back-side light-transmitting substrate disposed on the back surface of the half-wave plate. Preferably it is. In that case, the surface-side photonic crystal layer is provided on the main surface of the surface-side translucent substrate opposite to the main surface on which the half-wave plate is located, and the back surface side. It is preferable that the photonic crystal layer is provided on the main surface on the side opposite to the main surface on the side where the half-wave plate of the back-side translucent substrate is located.

In the color filter according to the present invention, the front-side photonic crystal layer and the back-side photonic crystal layer are arranged in a two-dimensional lattice pattern, and the plurality of block structures. It is preferable that it is comprised by the space | gap part located between.

In the color filter according to the present invention, the front-side photonic crystal layer and the back-side photonic crystal layer are arranged in a two-dimensional lattice pattern, and the plurality of block structures. It is preferable that it is comprised with the translucent member filled between.

The reflection type display device according to the present invention includes any one of the color filters described above and an optical switching unit disposed to face the surface-side photonic crystal layer of the color filter.

In the reflective display device according to the present invention, it is preferable that the optical switching unit is composed of a liquid crystal layer.

In the reflective display device according to the present invention, it is preferable that the optical switching unit is configured by a MEMS (Micro Electro Mechanical Systems) shutter.

According to the present invention, a color filter having excellent wavelength selectivity and reflectance can be obtained, and a reflective display device having excellent visibility can be obtained by using the color filter.

It is sectional drawing of the color filter in Embodiment 1 of this invention. It is a top view of the color filter shown in FIG. It is a bottom view of the color filter shown in FIG. It is a schematic diagram for demonstrating the function of the color filter in Embodiment 1 of this invention. It is a schematic cross-sectional view showing a typical light path when white light is irradiated to a red filter portion of a conventional color filter using a photonic crystal structure. It is a schematic cross section which shows the path | route of a typical light when white light is irradiated to the red filter part of the color filter in this Embodiment. It is a graph which shows the light incident angle dependence (0 degree, 10 degrees, 20 degrees) of the reflective characteristic of the surface side photonic crystal layer of the red filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (30 degrees, 40 degrees, 50 degrees) of the reflective characteristic of the surface side photonic crystal layer of the red filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (0 degree, 10 degrees, 20 degrees) of the reflective characteristic of the surface side photonic crystal layer of the green filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (30 degrees, 40 degrees, 50 degrees) of the reflective characteristic of the surface side photonic crystal layer of the green filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (0 degree, 10 degrees, 20 degrees) of the reflective characteristic of the surface side photonic crystal layer of the blue filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (30 degrees, 40 degrees, 50 degrees) of the reflective characteristic of the surface side photonic crystal layer of the blue filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (0 degree, 10 degrees, 20 degrees) of the reflective characteristic of the back surface side photonic crystal layer of the red filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (30 degrees, 40 degrees, 50 degrees) of the reflective characteristic of the back surface side photonic crystal layer of the red filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (0 degree, 10 degrees, 20 degrees) of the reflective characteristic of the back surface side photonic crystal layer of the green filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (30 degrees, 40 degrees, 50 degrees) of the reflective characteristic of the back surface side photonic crystal layer of the green filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (0 degree, 10 degrees, 20 degrees) of the reflective characteristic of the back surface side photonic crystal layer of the blue filter part of the color filter which concerns on an Example. It is a graph which shows the light incident angle dependence (30 degrees, 40 degrees, 50 degrees) of the reflective characteristic of the back surface side photonic crystal layer of the blue filter part of the color filter which concerns on an Example. It is sectional drawing of the color filter in Embodiment 2 of this invention. It is a schematic cross section of the reflection type display apparatus in Embodiment 3 of this invention. It is a schematic cross section of the reflection type display apparatus in Embodiment 4 of this invention. It is a schematic cross section of the reflective display apparatus in Embodiment 5 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiments described below, a color filter to which the present invention is applied is illustrated and described in the first and second embodiments, and a reflective display device to which the present invention is applied is illustrated in the third to fifth embodiments. To explain.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a color filter according to Embodiment 1 of the present invention. 2 is a top view of the color filter shown in FIG. 1, and FIG. 3 is a bottom view of the color filter shown in FIG. FIG. 4 is a schematic diagram for explaining the function of the color filter in the present embodiment. First, the structure and function of the color filter in the present embodiment will be described with reference to FIGS.

As shown in FIGS. 1 to 3, the color filter 1A according to the present embodiment is a so-called RGB color filter including a red filter portion 2R, a green filter portion 2G, and a blue filter portion 2B. The color filter 1A is configured to have a flat outer shape as a whole, and usually includes a plurality of red filter portions 2R, green filter portions 2G, and blue filter portions 2B as shown in the drawing as unit units. Configured as follows.

More specifically, the color filter 1A includes a half-wave plate 3, a front-side translucent substrate 4, a front-side photonic crystal layer 5, a back-side translucent substrate 6, and a back-side photonic crystal layer 7. It is comprised as a laminated body of these. Each of the red filter portion 2R, the green filter portion 2G, and the blue filter portion 2B described above includes a front-side photonic crystal layer 5, a half-wave plate 3 and a back surface that are mainly located at portions corresponding to the

filter portions

2R, 2G, and 2B. The side photonic crystal layer 7 is constituted.

The half-wave plate 3 is an optical system that generates a phase difference of ½ wavelength in light, and has a function of rotating the incident light beam by rotating it by 90 °. The half-wave plate 3 is made of natural crystals such as quartz, mica, and karsite. The half-wave plate 3 is composed of a flat member having a front surface and a back surface as a pair of main surfaces, and the thickness thereof is uniquely determined by the material.

The front-side light-transmitting substrate 4 is made of a flat plate member that can transmit light, and is disposed on the surface of the half-wave plate 3 described above. The surface side light-transmitting substrate 4 is made of, for example, a glass substrate or a transparent plastic substrate, and the thickness is not particularly limited, but is preferably about 780 nm to 900 μm.

The surface-side photonic crystal layer 5 has a two-dimensional refractive index periodic structure, and more specifically, a plurality of block structures 5a arranged in a two-dimensional lattice, and the plurality of block structures 5a. And a gap portion located between the two. The surface-side photonic crystal layer 5 is provided on the main surface opposite to the main surface on the side where the half-wave plate 3 is located, of the pair of main surfaces of the surface-side light-transmitting substrate 4. The plurality of block structures 5a described above are composed of, for example, Si, SiC, ZnS, AlN, BN, GaTe, AgI, TiO ₂ , SiON, GaP, or a composite thereof.

The surface-side photonic crystal layer 5 has a first photonic crystal region having a first periodic refractive index change, and a second periodic refractive index change different from the first periodic refractive index change. A third photonic crystal region having a third periodic refractive index change different from the first periodic refractive index change and the second periodic refractive index change; Is included. Among these, the first photonic crystal region is disposed in a portion corresponding to the red filter portion 2R, the third photonic crystal region is disposed in a portion corresponding to the green filter portion 2G, and the fifth photonic crystal region is , And is disposed at a portion corresponding to the blue filter portion 2B.

The back-side light-transmitting substrate 6 is made of a flat plate member that can transmit light, and is disposed on the back surface of the half-wave plate 3 described above. The back side light-transmitting substrate 6 is made of, for example, a glass substrate or a transparent plastic substrate, and the thickness is not particularly limited, but is preferably about 780 nm to 900 μm.

The back-side photonic crystal layer 7 has a two-dimensional refractive index periodic structure, and more specifically, a plurality of block structures 7a arranged in a two-dimensional lattice, and the plurality of block structures 7a. And a gap portion located between the two. The back-side photonic crystal layer 7 is provided on the main surface opposite to the main surface on the side where the half-wave plate 3 is located, of the pair of main surfaces of the back-side light-transmitting substrate 6. The plurality of block structures 7a described above are composed of, for example, Si, SiC, ZnS, AlN, BN, GaTe, AgI, TiO ₂ , SiON, GaP, or a composite thereof.

The back-side photonic crystal layer 7 includes a second photonic crystal region having substantially the same periodic refractive index change as the above-described first periodic refractive index change, and the above-described second periodic refraction. A fourth photonic crystal region having a periodic refractive index change substantially the same as the refractive index change, and a sixth photo having a periodic refractive index change substantially the same as the third periodic refractive index change described above. And a nick crystal region. Among these, the second photonic crystal region is disposed in a portion corresponding to the red filter portion 2R, the fourth photonic crystal region is disposed in a portion corresponding to the green filter portion 2G, and the sixth photonic crystal region is , And is disposed at a portion corresponding to the blue filter portion 2B.

Here, in the front surface side photonic crystal layer 5 and the back surface side photonic crystal layer 7 (that is, the first photonic crystal region and the second photonic crystal region) constituting the red filter portion 2R. The arrangement pitch D _R (that is, the period of the first periodic refractive index change) of the plurality of

block structures

5a and 7a arranged in a two-dimensional lattice is about 300 nm, and each

block structure

5a , 7a has a width L _R of about 150 nm, and each of the

block structures

5a, 7a has a height H _R of about 250 nm.

Further, in the front surface side photonic crystal layer 5 and the back surface side photonic crystal layer 7 (that is, the third photonic crystal region and the fourth photonic crystal region) constituting the green filter part 2G, The arrangement pitch D _G (that is, the period of the second periodic refractive index change) of the plurality of

block structures

5a and 7a arranged in a two-dimensional lattice is about 240 nm, and each block structure 5a, is the width L _G of about 120nm of 7a, each block structure 5a, the height HG of 7a is about 190 nm.

Further, in the surface side photonic crystal layer 5 and the back side photonic crystal layer 7 (that is, the fifth photonic crystal region and the sixth photonic crystal region) constituting the blue filter portion 2B, The arrangement pitch D _B (that is, the period of the third periodic refractive index change) of the plurality of

block structures

5a and 7a arranged in a two-dimensional lattice is set to about 210 nm, and each block structure 5a, is a 7a width L _B of about 105nm of each of the block structure 5a, the height HB of 7a is about 170 nm.

As shown in FIG. 4, in the color filter 1A in the present embodiment, when white light is irradiated to the main surface on the side where the surface-side photonic crystal layer 5 of the color filter 1A is disposed, In the red filter portion 2R, only light in a wavelength range mainly exhibiting red color (light in a wavelength of 620 nm to 750 nm) is selectively reflected, light in other wavelength ranges is transmitted, and green color is mainly displayed in the green filter portion 2G. Only light in the wavelength band (light having a wavelength of 495 nm to 570 nm) is selectively reflected, light in other wavelength bands is transmitted, and light in a wavelength band mainly exhibiting blue (wavelength of 450 nm to 495 nm) is transmitted in the blue filter portion 2B. Only light) is selectively reflected, and light in other wavelength ranges is transmitted. Thereby, the wavelength selectivity as a color filter is implement | achieved because the light of a specific wavelength range is reflected in each

filter part

2R, 2G, 2B of the color filter 1A.

FIG. 5 is a schematic cross-sectional view showing a typical light path when white light is irradiated on a red filter portion of a conventional color filter using a photonic crystal structure, and FIG. 6 shows the present embodiment. It is a schematic cross section which shows the path | route of a typical light when white light is irradiated to the red filter part of the color filter. Next, referring to FIG. 5 and FIG. 6, the color filter according to the present embodiment is superior in wavelength selectivity and reflectivity compared to the conventional color filter using a photonic crystal structure. A mechanism that can be used as a color filter will be described.

As shown in FIG. 5, in the conventional color filter 1 ′ using the photonic crystal structure, a two-dimensional surface is formed on the surface which is one of the main surfaces of the pair of translucent substrates 4 ′. A photonic crystal layer 5 'having a refractive index periodic structure is provided. The photonic crystal layer 5 'includes a plurality of block structures 5a' arranged in a two-dimensional lattice.

In the conventional color filter 1 ′, when white light such as natural light is applied to the red filter portion 2R ′, light other than red light 100R such as green light 100G and blue light 100B included in the white light is selected. Thus, the light passes through the photonic crystal layer 5 'and further passes through the light transmitting substrate 4'. On the other hand, at least a part of the red light 100R included in the white light is selectively reflected in the photonic crystal layer 5 ′.

Here, since the photonic crystal layer 5 ′ has a so-called two-dimensional photonic crystal structure having a two-dimensional refractive index periodic structure as described above, the photonic crystal layer 5 ′ is perpendicular to the incident surface (that is, the reflection surface that reflects incident light). In addition, the s-polarized light whose electric field oscillates perpendicularly to the plane including the incident light and the reflected light) has little influence on the light incident angle, so that even when the light incident angle is large, wavelength selectivity and reflection On the other hand, the p-polarized light whose electric field oscillates in parallel to the incident surface has a large influence on the light incident angle, so that the decrease in the reflectivity becomes remarkable as the light incident angle increases. Become.

Therefore, as shown in FIG. 5, when the light incident angle θ has a certain large value, the p-polarized component 100R (p) of the red light 100R is transmitted without being reflected by the photonic crystal layer 5 ′. Only the s-polarized component 100R (s) of the red light 100R is reflected by the photonic crystal layer 5 ′, and the reflectance of the red filter portion 2R ′ is significantly reduced. Although illustration and explanation thereof are omitted, the above phenomenon also occurs in the filter portions of other colors.

On the other hand, as shown in FIG. 6, in the color filter 1A in the present embodiment, as described above, the front-side light-transmitting substrate 4 and the back-side light-transmitting substrate 6 are arranged so as to sandwich the half-wave plate 3 therebetween. The photonic crystal layer 5 having a two-dimensional refractive index periodic structure is provided on the main surface of the front surface side transparent substrate 4, and the two-dimensional refractive index periodic structure is provided on the main surface of the rear surface side transparent substrate 6. A photonic crystal layer 7 is provided.

In the color filter 1A in the present embodiment, when white light such as natural light is irradiated to the red filter portion 2R, light other than red light 100R such as green light 100G and blue light 100B included in white light is emitted. The light is selectively transmitted through the surface-side photonic crystal layer 5 and further sequentially transmitted through the surface-side translucent substrate 4, the half-wave plate 3, the back-side translucent substrate 6, and the back-side photonic crystal layer 7. On the other hand, at least a part of the red light 100R included in the white light is selectively reflected by the front surface side photonic crystal layer 5, and at least a part of the red light 100R is also selectively reflected by the back surface side photonic crystal layer 7. Will be reflected.

More specifically, when the light incident angle θ has a certain large value, the s-polarized component 100R (s) of the red light 100R is reflected by the surface-side photonic crystal layer 5 and the p-polarized component of the red light 100R. 100R (p) is transmitted without being reflected by the surface-side photonic crystal layer 5, but the p-polarized component 100R (p) of the transmitted red light 100R is transmitted through the surface-side light-transmitting substrate 4 and is a half-wave plate. 3 is incident. The p-polarized component 100R (p) of the red light 100R incident on the half-wave plate 3 is converted into the s-polarized component 100R (s) because the vibration direction is rotated by 90 ° when passing through the half-wave plate 3. The light enters the back side translucent substrate 6.

The converted s-polarized component 100R (s) incident on the back-side translucent substrate 6 passes through the back-side translucent substrate 6 and is irradiated on the back-side photonic crystal layer 7. Since the converted s-polarized component 100R (s) irradiated to the back-side photonic crystal layer 7 is s-polarized light whose electric field oscillates perpendicularly to the incident surface, the influence of the light incident angle dependency is small. Therefore, even when the light incident angle θ is large, the light is reflected with a high reflectance.

The s-polarized component 100R (s) reflected by the back-side photonic crystal layer 7 passes through the back-side translucent substrate 6 and enters the half-wave plate 3 again. The reflected s-polarized component 100R (s) incident on the half-wave plate 3 is rotated by 90 ° when passing through the half-wave plate 3, so that it is converted into the p-polarized component 100R (p) and the surface. The light enters the side translucent substrate 4.

The converted p-polarized component 100R (p) incident on the surface-side translucent substrate 4 is transmitted through the surface-side translucent substrate 4 and irradiated on the surface-side photonic crystal layer 5. The converted p-polarized component 100R (p) irradiated to the surface-side photonic crystal layer 5 is p-polarized light whose electric field oscillates perpendicularly to the incident surface, and therefore has a large influence on the light incident angle dependency. Therefore, when the light incident angle θ is large, the light passes through the surface side photonic crystal layer 5.

Therefore, in the color filter 1A according to the present embodiment, even when the light incident angle θ has a certain large value, the red light 100R included in the white light irradiated on the red filter portion 2R is reflected on the surface side photo. At least a part of the nick crystal layer 5 is selectively reflected, and at least a part of the nick crystal layer 5 is also selectively reflected by the back-side photonic crystal layer 7. Therefore, by using the color filter 1A in the present embodiment, not only the red light reflected on the front-side photonic crystal layer 5 but also the back-side photonic crystal, compared to the conventional color filter 1 ′ described above. Even the red light reflected in the layer 7 is obtained as the reflected light in the red filter portion 2R of the color filter 1A, and the reflectance in the red filter portion 2R as a whole is greatly improved. Although illustration and description thereof are omitted, the improvement in the reflectance can be similarly obtained in the filter portions of other colors.

That is, by using the color filter 1A in the present embodiment, the p-polarized component of incident light that could not be used in the conventional color filter 1 ′ described above is reflected in the back-side photonic crystal layer 7. It can be used after being reflected and emitted from the surface side of the color filter 1A. Therefore, by using the color filter 1A in the present embodiment, a decrease in wavelength selectivity and reflectance due to the influence of polarization dependency and incident angle dependency can be greatly reduced. As a result, wavelength selectivity and A color filter having excellent reflectance can be obtained.

7 to 18 specifically design the color filter according to the example based on the present embodiment, and show the reflection characteristics in the front-side photonic crystal layer and the back-side photonic crystal layer of the designed color filter. It is a graph which shows the result computed based on RCWA (Rigorous Coupled Wave Analysis) method. More specifically, FIG. 7 and FIG. 8 are graphs showing the light incident angle dependence of the reflection characteristics of the surface-side photonic crystal layer of the red filter portion of the color filter according to the example. FIG. 11 is a graph showing the light incident angle dependence of the reflection characteristics of the surface-side photonic crystal layer of the green filter portion of the color filter according to the embodiment. FIGS. 11 and 12 are blue filter portions of the color filter according to the embodiment. It is a graph which shows the light incident angle dependence of the reflection characteristic of the surface side photonic crystal layer. 13 and 14 are graphs showing the light incident angle dependency of the reflection characteristics of the back side photonic crystal layer of the red filter portion of the color filter according to the example. FIGS. 15 and 16 are graphs showing the example. FIG. 17 and FIG. 18 are graphs showing the light incident angle dependence of the reflection characteristics of the back side photonic crystal layer of the green filter part of the color filter according to FIG. It is a graph which shows the light incident angle dependence of the reflection characteristic of a photonic crystal layer.

As shown in FIGS. 7 to 12, the surface-side photonic crystal layer has generally good reflection characteristics when the light incident angle θ is 0 °, 10 °, and 20 ° (that is, the reflectance is approximately 0.6). In contrast, as the light incident angle θ takes a large value of 30 °, 40 °, or 50 °, the reflection characteristics greatly decrease (that is, the reflectivity becomes less than about 0.6). It can be confirmed that there is a tendency to decrease). Here, the light incident on the surface-side photonic crystal layer is white light including an s-polarized component and a p-polarized component, and the decrease in the reflection characteristics described above is based on the light incident angle dependency. This is because the proportion of the p-polarized component transmitted through the surface-side photonic crystal layer increases as the number increases. In addition, since the conventional color filter described above is configured such that incident light is reflected only by the surface-side photonic crystal layer as described above, the result is the same as the conventional color filter described above. It also shows the reflection characteristics of the filter.

On the other hand, as shown in FIGS. 13 to 18, in the back side photonic crystal layer, not only when the light incident angle θ is 0 °, 10 °, 20 °, but also as large as 30 °, 40 °, 50 °. Even when the value is taken, it can be confirmed that generally good reflection characteristics (that is, the reflectance is approximately 0.6 to 0.95) can be obtained. Here, the light incident on the back-side photonic crystal layer is mainly light of the s-polarized component generated by converting the p-polarized component transmitted through the front-side photonic crystal layer by the action of the latter half wave plate. The above-described reflection characteristics generally mean the reflectance of the s-polarized component.

From the above results, by using the color filter in the present embodiment, in addition to the light reflected by the surface-side photonic crystal layer based on the reflection characteristics shown in FIGS. 7 to 12, FIGS. Based on the reflection characteristics shown in Fig. 1, the light reflected by the back-side photonic crystal layer is emitted from the front side of the color filter. As a result, wavelength selection is affected by the influence of polarization dependence and incident angle dependence. As a result, it was confirmed that the decrease in the property and reflectance can be greatly reduced.

(Embodiment 2)
FIG. 19 is a cross-sectional view of the color filter according to Embodiment 2 of the present invention. Hereinafter, the structure of the color filter in the present embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected in the figure about the part similar to the color filter in Embodiment 1 mentioned above, and the description is not repeated here.

As shown in FIG. 19, the color filter 1B according to the present embodiment is a so-called RGB including a red filter portion 2R, a green filter portion 2G, and a blue filter portion 2B, similarly to the color filter 1A according to the first embodiment. It is a color filter. The color filter 1B includes a half-wave plate 3, a front-side translucent substrate 4, a front-side photonic crystal layer 5, a back-side translucent substrate 6, and a back-side photonic crystal layer 7, which are laminated. It is structured as a body. Each of the red filter portion 2R, the green filter portion 2G, and the blue filter portion 2B described above includes a front-side photonic crystal layer 5, a half-wave plate 3 and a back surface that are mainly located at portions corresponding to the

filter portions

2R, 2G, and 2B. The side photonic crystal layer 7 is constituted.

Here, in the color filter 1B, the surface-side translucent member 8 is formed on the main surface of the surface-side translucent substrate 4 so as to seal the plurality of block structures 5a included in the surface-side photonic crystal layer 5. Is provided, and a back surface side light transmissive member 9 is provided on the main surface of the back surface side light transmissive substrate 6 so as to seal a plurality of block structures 7a included in the back surface side photonic crystal layer 7. That is, on the main surface of the front surface side transparent substrate 4, the space between the plurality of block structures 5a is filled with the front surface side transparent member 8, and on the main surface of the rear surface side transparent substrate 6, A space between the plurality of block structures 7 a is filled with the back surface side light transmissive member 9.

Thereby, the surface side photonic crystal layer 5 is comprised by the several block structure 5a arranged in the two-dimensional lattice form, and the surface side translucent member 8 with which the space between these several block structures 5a is filled. Thus, the back-side photonic crystal layer 7 is composed of a plurality of block structures 7a arranged in a two-dimensional lattice, and a back-side translucent member 9 filling between the plurality of block structures 7a. Will be composed. In addition, the surface side translucent member 8 and the back surface side translucent member 9 are comprised, for example with a transparent organic substance, and the thickness is not specifically limited.

In the case of the color filter 1B according to the present embodiment described above, the wavelength selectivity or the wavelength selectivity due to the influence of the polarization dependency or the incident angle dependency is similar to the case of the color filter 1A according to the first embodiment. A decrease in reflectance can be greatly reduced. Therefore, by using the color filter 1B having the configuration, a color filter having excellent wavelength selectivity and reflectance can be obtained.

(Embodiment 3)
FIG. 20 is a schematic cross-sectional view of a reflective display device according to Embodiment 3 of the present invention. Hereinafter, the structure of the reflective display device according to the present embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected in the figure about the part similar to Embodiment 1 mentioned above, and the description is not repeated here.

As shown in FIG. 20, the reflective display device 10A in the present embodiment includes the color filter 1A in the first embodiment described above. The reflective display device 10A mainly includes a color filter 1A, a TFT (Thin Film Transistor) substrate 12, a liquid crystal layer 13, a counter substrate 14, a polarizing plate 15, a light shielding substrate 16, and a support member 17. Yes.

The TFT substrate 12 mainly includes a translucent substrate 12a provided with TFTs (not shown), a transparent electrode layer 12b, and an alignment film (not shown), and the surface-side photonic crystal layer of the color filter 1A. 5 is arranged opposite to the main surface provided. The transparent electrode layer 12b is provided on the upper surface of the transparent substrate 12a, and the alignment film is provided on the upper surface of the transparent substrate 12a so as to cover the transparent electrode layer 12b and the TFT. The translucent substrate 12a is made of, for example, a glass substrate or a transparent plastic substrate having a sufficiently low refractive index, and the transparent electrode layer 12b is made of, for example, an ITO (Indium Thin Oxide) film or the like. The alignment film is composed of, for example, a polyimide film.

The counter substrate 14 mainly includes a translucent substrate 14 a, a transparent electrode layer 14 b, and an alignment film (not shown), and is disposed to face the upper surface of the TFT substrate 12. The transparent electrode layer 14b is provided on the lower surface of the translucent substrate 14a, and the alignment film is provided on the lower surface of the translucent substrate 14a so as to cover the transparent electrode layer 14b. The translucent substrate 14a is composed of, for example, a glass substrate or a transparent plastic substrate having a sufficiently low refractive index, and the transparent electrode layer 14b is composed of, for example, an ITO film. The alignment film is composed of, for example, a polyimide film.

The liquid crystal layer 13 functions as an optical switching unit, and is configured by filling a liquid crystal in the space between the TFT substrate 12 and the counter substrate 14 described above. As the liquid crystal, nematic, smectic, cholesteric, or a mixture thereof can be applied. As the alignment state of the liquid crystal molecules, homogeneous, homeotropic, twist, hybrid, bend and the like are preferable. The thickness of the liquid crystal layer 13 is preferably 10 μm or less.

The polarizing plate 15 is formed by laminating a protective film, a polarizing portion, a protective film, and an adhesive in this order from the top, and is disposed on the upper surface of the counter substrate 14 described above. As the protective film, triacetyl cellulose is suitably used, and the thickness thereof is preferably 40 μm or less. As the polarizing part, a material obtained by adsorbing and dispersing a material such as iodine or a dye on a polyvinyl alcohol film and stretching it in one direction is preferably used, and the thickness is preferably 25 μm to 30 μm.

The light shielding substrate 16 is, for example, a substrate whose surface is coated with a black matrix, and is disposed so as to face the main surface on which the back surface side photonic crystal layer 7 of the color filter 1A is provided.

The support member 17 functions as a spacer and holder for holding the color filter 1A, the TFT substrate 12, the liquid crystal layer 13, the counter substrate 14, the polarizing plate 15, and the light shielding substrate 16 in a stacked state. A substrate coated with a black matrix is used.

The distance g between the surface-side photonic crystal layer 5 and the liquid crystal layer 13 is preferably 780 nm or more, which is the longest wavelength of visible light. This is to prevent unintended light interference between the photonic crystal layer 7 and the liquid crystal layer 13, and if there is no interference within the range of visible light, the function as a reflective display device is achieved. It is because it is not inhibited.

By adopting the reflective display device 10A in the present embodiment described above, a wide viewing angle is ensured, and both high color purity and improvement in screen luminance are achieved within the wide viewing angle range. A reflective display device can be obtained. This is because the reflective display device 10 </ b> A includes the color filter 1 </ b> A according to Embodiment 1 described above, which is excellent in wavelength selectivity and reflectance. Therefore, by using the reflective display device 10A having the above configuration, a reflective display device with excellent visibility can be obtained.

(Embodiment 4)
FIG. 21 is a schematic cross-sectional view of a reflective display device according to Embodiment 4 of the present invention. Hereinafter, the structure of the reflective display device according to the present embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected in the figure about the part similar to Embodiment 1 thru | or 3 mentioned above, and the description is not repeated here.

As shown in FIG. 21, the reflective display device 10B according to the present embodiment includes the color filter 1B according to the second embodiment described above, and the configuration thereof is the reflection according to the third embodiment described above. It conforms to the type display device 10A. The reflective display device 10B mainly includes a color filter 1B, a transparent electrode layer 8a, a liquid crystal layer 13, a counter substrate 14, a polarizing plate 15, a light shielding substrate 16, and a support member 17.

The transparent electrode layer 8a is provided on the upper surface of the surface side light transmitting member 8 of the color filter 1B, and a TFT (not shown) is further provided on the upper surface of the surface side light transmitting member 8. In addition, an alignment film (not shown) is provided on the upper surface of the surface-side translucent member 8 so as to cover the transparent electrode layer 8a and the TFT. That is, in the reflective display device 10B in the present embodiment, the translucent substrate 12a of the TFT substrate 12 included in the reflective display device 10A in the above-described third embodiment is used as the surface-side translucent member 8 of the color filter 1B. The other configuration is the same as that of the reflective display device 10A according to the third embodiment described above.

Even in the case of the reflective display device 10B in the present embodiment described above, a wide viewing angle is secured and the wide display as in the case of the reflective display device 10A in the third embodiment described above. A reflective display device that achieves both high color purity and improved screen brightness within the viewing angle range can be obtained. Therefore, by using the reflective display device 10B having the above configuration, a reflective display device with excellent visibility can be obtained.

(Embodiment 5)
FIG. 22 is a schematic cross-sectional view of a reflective display device according to Embodiment 5 of the present invention. Hereinafter, the structure of the reflective display device according to the present embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected in the figure about the part similar to Embodiment 1 thru | or 4 mentioned above, and the description is not repeated here.

As shown in FIG. 22, the reflective display device 10C according to the present embodiment includes the color filter 1A according to the first embodiment described above, and the configuration thereof is the reflection according to the third embodiment described above. It conforms to the type display device 10A. The reflective display device 10 </ b> C mainly includes a color filter 1 </ b> A, a MEMS shutter 18, a translucent substrate 19, a polarizing plate 15, a light shielding substrate 16, and a support member 17. The reflective display device 10C in the present embodiment is different from the reflective display device 10A in the third embodiment described above in the configuration of the optical switching unit, and the other configurations are the reflection in the third embodiment described above. This is the same as the type display device 10A.

The translucent substrate 19 is disposed to face the main surface of the color filter 1A on which the surface-side photonic crystal layer 5 is provided, and is composed of, for example, a glass substrate or a transparent plastic substrate having a sufficiently low refractive index. The The translucent substrate 19 corresponds to a base material on which the MEMS shutter 18 is formed, and the MEMS shutter 18 is provided on the lower surface of the translucent substrate 19.

The MEMS shutter 18 is an optical switching unit formed by applying MEMS technology, and serves as an alternative to the liquid crystal layer 13 in the third embodiment described above. Specifically, the MEMS shutter 18 is an element having a shutter structure capable of mechanically controlling the passage / shielding of light, and, for example, a MEMS shutter element manufactured by PIXTRONIX can be suitably used. As the MEMS shutter 18, for example, a shutter as disclosed in JP-T-2008-533510 can be used.

Even in the case of the reflective display device 10C in the present embodiment described above, a wide viewing angle is secured and the wide display as in the case of the reflective display device 10A in the third embodiment described above. A reflective display device that achieves both high color purity and improved screen brightness within the viewing angle range can be obtained. Therefore, by using the reflective display device 10C having the above configuration, a reflective display device with excellent visibility can be obtained.

In the first to fifth embodiments of the present invention described above, the color filter is described by exemplifying a so-called RGB color filter including a red filter portion, a green filter portion, and a blue filter portion. However, the number of filter units is not particularly limited, and includes a color filter that includes only one type of filter unit, a color filter that includes only two types of filter units, and four or more types of filter units. Naturally, it is possible to apply the present invention to a color filter or the like.

In Embodiments 1 to 5 of the present invention described above, the block structure provided in the photonic crystal structure provided in the color filter is exemplified as a rectangular parallelepiped, but the block structure The shape of the body is not limited to this, and block structures having various shapes such as a columnar shape and a polygonal column shape can be used.

Thus, the above-described embodiments and examples disclosed this time are examples in all respects and are not restrictive. The technical scope of the present invention is defined by the scope of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1A, 1B color filter, 2R red filter section, 2G green filter section, 2B blue filter section, 3 half-wave plate, 4 surface side translucent substrate, 5 surface side photonic crystal layer, 5a block structure, 6 back side translucent Optical substrate, 7 Back side photonic crystal layer, 7a Block structure, 8 Front side translucent member, 9 Back side translucent member, 10A to 10C reflective display device, 12 TFT substrate, 12a translucent substrate, 12b transparent electrode Layer, 13 liquid crystal layer, 14 counter substrate, 14a translucent substrate, 14b transparent electrode layer, 15 polarizing plate, 16 light shielding substrate, 17 support member, 18 MEMS shutter, 19 translucent substrate.

Claims

A half-wave plate (3) having a front surface and a back surface;
A surface-side photonic crystal layer (5) having a two-dimensional refractive index periodic structure and disposed on the surface side of the half-wave plate (3);
A color filter having a two-dimensional refractive index periodic structure and comprising a back side photonic crystal layer (7) disposed on the back side of the half wave plate (3).
The surface-side photonic crystal layer (5) includes a first photonic crystal region having a first periodic refractive index change;
The back-side photonic crystal layer (7) includes a second photonic crystal region having a periodic refractive index change substantially the same as the first periodic refractive index change;
2. The color filter according to claim 1, wherein the first photonic crystal region and the second photonic crystal region are arranged so as to sandwich the half-wave plate (3).
The surface-side photonic crystal layer (5) further includes a third photonic crystal region having a second periodic refractive index change different from the first periodic refractive index change,
The back-side photonic crystal layer (7) further includes a fourth photonic crystal region having a periodic refractive index change substantially the same as the second periodic refractive index change,
3. The color filter according to claim 2, wherein the third photonic crystal region and the fourth photonic crystal region are arranged to correspond to each other with the half-wave plate (3) interposed therebetween.
The surface-side photonic crystal layer (5) has a third periodic refractive index change different from both the first periodic refractive index change and the second periodic refractive index change. Further comprising a photonic crystal region,
The back side photonic crystal layer (7) further includes a sixth photonic crystal region having a periodic refractive index change substantially the same as the third periodic refractive index change,
4. The color filter according to claim 3, wherein the fifth photonic crystal region and the sixth photonic crystal region are arranged so as to sandwich the half-wave plate (3).
A surface-side translucent substrate (4) disposed on the surface of the half-wave plate (3);
A back-side light-transmitting substrate (6) disposed on the back surface of the half-wave plate (3);
The surface-side photonic crystal layer (5) is provided on the main surface opposite to the main surface on the side on which the half-wave plate (3) of the surface-side translucent substrate (4) is located,
The back-side photonic crystal layer (7) is provided on the main surface opposite to the main surface on the side where the half-wave plate (3) is located of the back-side translucent substrate (6). The color filter according to claim 1.
A plurality of block structures (5a, 7a) in which the front-side photonic crystal layer (5) and the back-side photonic crystal layer (7) are arranged in a two-dimensional lattice, and the plurality of block structures ( The color filter according to any one of claims 1 to 5, wherein the color filter is formed by a gap portion located between 5a and 7a).
A plurality of block structures (5a, 7a) in which the front-side photonic crystal layer (5) and the back-side photonic crystal layer (7) are arranged in a two-dimensional lattice, and the plurality of block structures ( The color filter according to any one of claims 1 to 5, wherein the color filter is configured by a translucent member (8, 9) filling a space between 5a and 7a).
A color filter according to any one of claims 1 to 7;
A reflective display device comprising: an optical switching portion disposed to face the surface-side photonic crystal layer (5) of the color filter.
The reflective display device according to claim 8, wherein the optical switching unit is configured by a liquid crystal layer (13).
The reflective display device according to claim 8, wherein the optical switching unit is configured by a MEMS shutter (18).