JP4311925B2 - Diffuse reflector - Google Patents

Description

【００４３】
［視認性評価試験］
実施例１〜３及び比較例１〜４で得られた各拡散反射板にグリセリンを介してガラス基板を貼り合わせて視認性評価試料（液晶模擬セル）を作製した。
【００４４】
これらの液晶模擬セルについて、被験者が正面及び斜め４５°から観察し、各方向における視認性を評価した。評価は１（不良）、２（やや不良）、３（普通）、４（やや良好）、５（良好）の５段階とした。得られた結果を表２に示す。
【００４５】
【表２】

表２に示したように、実施例１〜３の拡散反射板を使用した場合、正面から見たときの視認性は十分に高く、その反面、斜めから見たときの視認性は十分に低いことが確認された。
【００４６】
【発明の効果】
以上説明した通り、本発明によれば、観察者が反射型液晶表示器を正面から見たときには明るく鮮明な表示を与え、且つ観察者以外の者が斜め方向から該液晶表示器を見たときの視認性を低下させることが可能な拡散反射板が提供される。
【図面の簡単な説明】
【図１】本発明の拡散反射板の一例を示す模式断面図である。
【図２】拡散反射板付きカラーフィルタの一例を示す模式断面図である。
【図３】拡散反射板付きカラーフィルタの製造方法の一例を示す説明図である。
【図４】拡散反射板が設けられたカラーフィルタを用いた反射型液晶表示器の一例を示す模式断面図である。
【符号の説明】
１…基板、２…凹凸層（フォトレジスト層）、２ａ…潜像濃度分布、３…反射膜、４Ｒ，４Ｇ，４Ｂ…着色樹脂領域、５…透明電極、６…保護層、７…フォトマスク、９…液晶層、１０…対向基板、１１…画素電極、１２…偏光板、１０１…光源、１０２ａ、１０２ｂ…光検出器。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diffuse reflector used in a liquid crystal display.
[0002]
[Prior art]
As a display that does not require a light source such as a backlight, light control means (electrodes, liquid crystal layer, etc.) for controlling the amount of light incident on the reflective plate and the display element and the light reflected by the reflective plate, a polarizing plate, A reflection type liquid crystal display that performs display in combination is known (for example, Patent Documents 1 and 2).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-337935 [Patent Document 2]
Japanese Patent Laid-Open No. 2000-180616
[Problems to be solved by the invention]
By the way, in the above-described conventional reflective liquid crystal display, it is generally preferable that a bright and clear display can be obtained from any angle. However, reflective liquid crystal displays, which have the advantages of low power consumption and a clearer background light, are often used for portable devices. There is a risk of peeping.
[0005]
The present invention has been made in view of such circumstances, and provides a bright and clear display when an observer views the reflective liquid crystal display from the front, and a person other than the observer can view the liquid crystal display from an oblique direction. An object of the present invention is to provide a diffusive reflector that can reduce the visibility when viewing the screen.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a diffusive reflector of the present invention is a diffusive reflector used in a reflective liquid crystal display, and includes a substrate and a concavo-convex layer formed on the substrate surface and having a concavo-convex surface on the side far from the substrate. A reflective film formed on the concave-convex surface of the concave-convex layer and including a metal film, and when the light is incident from the reflective film side at an incident angle of 30 ° with respect to the normal of the substrate surface, the reflective film from the regular reflection direction light intensity value of the reflected light reflected in the direction deviated 15 ° to the side is state, and are six times more light intensity value of the reflected light from the specular reflection direction is reflected in a direction deviated 25 ° to the reflective film side, After the concave / convex layer is coated on the substrate surface with a positive photoresist having a transmittance per unit thickness of 1 to 30% / μm with respect to the photosensitive wavelength region, a diffuse reflection region forming pattern is formed on the inner side, and a transparent pattern is formed on the outer side. The photo through each photomask formed It was subjected to proximity exposure to resist, characterized in that one formed by performing development and heat treatment.
[0007]
According to the diffusive reflector of the present invention, when a photoresist having a concavo-convex surface and a reflective film are formed on a substrate and light is incident from the reflective film side at an incident angle of 30 ° with respect to the normal of the substrate surface, The light intensity value of the reflected light reflected in the direction deviated by 15 ° from the reflection direction to the reflection film side is 6 times the light intensity value of the reflected light reflected in the direction deviated by 25 ° from the regular reflection direction to the reflection film side. By doing so, a bright and clear display is given when the observer sees the reflective liquid crystal display from the front, and visibility when a person other than the observer sees the liquid crystal display from an oblique direction is lowered. It becomes possible to make it. In addition, after applying the above-mentioned specific positive type photoresist on the substrate surface, the uneven layer is exposed to the photoresist through a photomask having a diffuse reflection area forming pattern on the inside and a transparent pattern on the outside. After performing the above, it is possible to easily and reliably form a concavo-convex layer for the light intensity value of the reflected light to satisfy the above-described conditions. If the transmittance of the positive resist is less than 1% / μm, the processability becomes insufficient and a lot of exposure energy tends to be required. Further, when the transmittance exceeds 30% / μm, the processing depth changes rapidly with respect to the exposure conditions and the development conditions, so that it is difficult to stably form an uneven surface with a predetermined shape. is there.
[0009]
In the diffusive reflector of the present invention, the concavo-convex layer may be made of a positive photoresist containing a light-shielding material having a light-shielding property with respect to the photosensitive wavelength region. By using a positive photoresist containing a light-shielding material, the specific concavo-convex layer can be easily and reliably formed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.
[0011]
FIG. 1 is a schematic cross-sectional view showing an example of the diffuse reflector of the present invention. In FIG. 1, an uneven layer 2 having a fine uneven curved surface is provided on the surface of the transparent substrate 1 on the side far from the substrate 1. A reflective film 3 including a highly reflective metal film such as aluminum is formed on the surface of the uneven layer 2 by a method such as vapor deposition.
[0012]
The uneven layer 2 is made of an organic material such as a photoresist (photosensitive resin). The photoresist has a property of being cured in a heating process after the exposure process and the development process. The photoresist has a property that it melts and softens with hardening in the heating step, and the film surface becomes smooth. The heating process here includes a softening process for heating to a temperature at which the photoresist softens, and a baking process for curing the photoresist.
[0013]
The reflective film 3 is made of a material such as pure aluminum, an aluminum alloy (such as an Al—Nd alloy), or a silver alloy (such as an Ag—Pd—Cu alloy).
[0014]
The shapes of the concavo-convex layer 2 and the reflective film 3 are reflected light at a position deviated by 15 ° from the regular reflection direction when light is incident from the reflective film 3 side at an incident angle of 30 ° with respect to the normal line l ₁ of the substrate 1 surface. the light intensity value I ₁₅ is 6 times more light intensity value I ₂₅ of the reflected light at 25 ° shifted position from the specular reflection direction (preferably 14 times or more, more preferably 60 times or more) is set to be .
[0015]
Here, the concept of the light intensity values I ₁₅ and I ₂₅ will be further described with reference to FIG. In FIG. 1, l ₁ indicates a normal line of the surface of the substrate 1 and l ₂ indicates a direction inclined by 30 ° with respect to the normal line l ₁ . Further, l ₃ indicates a regular reflection direction when light is incident along l ₂ (that is, at an incident angle of 30 ° with respect to the normal l ₁ ), and l ₄ and l ₅ are diffuse reflectors from l3, respectively. The direction which shifted 15 degrees and 25 degrees to the side is shown.
[0016]
In diffuse reflector of the present invention, the photodetector 102a, 102b were arranged on the light source 101, l ₄ and l ₅ on l _2, the light from the reflective film 3 side at an incident angle of 30 ° relative to the normal l ₁ The light intensity value of the reflected light detected by the photodetector 102a (the light intensity value of the reflected light reflected in a direction shifted by 15 ° from the regular reflection direction toward the reflective film 3) I ₁₅ is The light intensity value of the reflected light detected by the photodetector 102b (the light intensity value of the reflected light reflected in a direction shifted by 25 ° from the regular reflection direction to the reflective film 3 side) I ₂₅ or more. Set to By setting I ₁₅ / I ₂₅ ≧ 5, a bright and clear display is given when an observer views the reflective liquid crystal display from the front, and a person other than the observer views the liquid crystal display from an oblique direction. It becomes possible to reduce the visibility at the time. The light detector 102a, 102b, each light receiving surface is disposed equidistant from the intersection of the reflective film 3 and the normal l _1.
[0017]
FIG. 2 is a schematic cross-sectional view showing a color filter with a diffuse reflector according to an embodiment of the present invention. The diffusive reflector provided in the color filter shown in FIG. 2 has the same configuration as that of the diffusive reflector shown in FIG. 1, and the concavo-convex layer 2 and the reflective film 3 have a function as a light scattering layer.
[0018]
When the light scattering layer is formed on the color filter substrate and used, the colored resin regions 4R, 4G, and 4B are provided on the light scattering layer. A transparent protective film 6 is provided on the colored resin regions 4R, 4G, and 4B as necessary, and a transparent electrode 5 for driving the liquid crystal is formed.
[0019]
The colored resin regions 4R, 4G, and 4B may be made of any material as long as impurities that cause display defects are not eluted in the liquid crystal. Specific examples of the material include an inorganic film whose film thickness is controlled so as to transmit only arbitrary light, and a dyed, dye-dispersed or pigment-dispersed resin.
[0020]
Although there is no restriction | limiting in particular in the kind of this resin, Acrylic, polyvinyl alcohol, a polyimide, etc. can be used. In view of simplicity of the manufacturing process and weather resistance, it is preferable to use a pigment-dispersed resin film for the colored resin regions 4R, 4G, and 4B.
[0021]
FIG. 3 is an explanatory diagram for explaining a method of manufacturing a color filter including the above-described diffuse reflector. This color filter is manufactured by sequentially executing the following steps (a) to (e).
[0022]
Step (a)
A positive resist is applied on the transparent substrate 1 to form a photoresist layer (intermediate body of the concavo-convex layer 2) 2 (FIG. 3A). A positive type photoresist is used.
[0023]
Here, the transmittance per unit thickness with respect to the photosensitive wavelength region of the photoresist is preferably 1 to 30% / μm. When the transmittance is less than 1% / μm, processability is insufficient and a lot of exposure energy tends to be required. Further, when the transmittance exceeds 30% / μm, the processing depth changes rapidly with respect to the exposure conditions and the development conditions, so that it is difficult to stably form an uneven surface with a predetermined shape. is there.
[0024]
Step (b)
Collective exposure (proximity exposure) is performed through the photomask 7 (FIG. 3B). Polygonal, circular, and ring-shaped transmission portions T are regularly or randomly arranged on the photomask 7. In this example, a ring-shaped transmission part T is used. A plurality of transmission portions T are arranged at equal intervals. Therefore, a latent image density distribution 2a is formed in the photoresist by exposure.
[0025]
Let L (μm) be the distance between the photomask 7 and the photoresist 2 during proximity exposure, and let D (μm) be the outer dimension of the transmission portion T of the photomask 7 during proximity exposure. Here, the external dimension means the dimension (diameter) of the outer diameter when the transmission part is circular or annular, and the average distance from the center of gravity position to the outer periphery when the transmission part is elliptical or polygonal. Means twice as much.
[0026]
The transmission part T on the photomask 7 has an outer diameter D of 20 μm or less, more preferably 15 μm or less, and preferably 3 μm or more.
[0027]
Step (c)
Patterning is performed by developing the photoresist 2 (FIG. 3C). The development can be performed by selecting conditions suitable for the photoresist. The developer is a solution of an inorganic alkali such as sodium or potassium hydroxide, carbonate or hydrogencarbonate, or an organic alkali such as organic ammonium. Is carried out by dipping or showering at 20 ° C. to 40 ° C. The substrate after development is thoroughly washed with pure water and then heat-treated.
[0028]
In the heat treatment step, the photoresist pattern is melted and softened before being cured, and a smooth uneven surface is formed on the surface of the photoresist. The heat treatment temperature is preferably 120 to 250 ° C, more preferably 150 to 230 ° C. Further, the heat treatment time is preferably 10 to 60 minutes.
[0029]
The shape of the concavo-convex layer formed by the above steps (a) to (c) is such that when light is incident from the reflective film 3 side at an incident angle of 30 ° with respect to the normal of the surface of the substrate 1, the reflective film is reflected from the regular reflection direction. The light intensity value of the reflected light reflected in the direction shifted by 15 ° to the 3 side is 6 times or more than the light intensity value of the reflected light reflected in the direction shifted by 25 ° from the regular reflection direction to the reflective film side. Is set.
[0030]
Step (d)
A metal film reflective film 3 is formed (FIG. 2D). For this formation, vapor deposition or sputtering can be used. The thickness of the reflective film 3 is preferably in the range of 0.1 to 0.3 μm, more preferably in the range of 0.15 to 0.25 μm. A dielectric multilayer film can also be used for the reflective film 3. Further, when the reflective film 3 includes a metal film, a high reflectance can be achieved. The metal film preferably contains metal aluminum, aluminum alloy or silver alloy, but of course may contain other elements which do not adversely affect the properties.
[0031]
The metal reflective film 3 removes unnecessary portions by etching or the like as necessary to form a light transmission portion and marks.
[0032]
Step (e)
If necessary, colored layers of red, green, and blue are formed, and subsequently, a protective layer 6 and a transparent electrode 5 are deposited on the formed product to complete a color filter substrate with a diffuse reflector (FIG. 2 (e)). )).
[0033]
FIG. 3 is a cross-sectional view of a reflective liquid crystal display using a color filter provided with the above-described diffuse reflector.
[0034]
This liquid crystal display is a reflection type color liquid crystal display of a single polarizer type. A predetermined gap is provided between the glass substrate 1 and the counter substrate 10, and a liquid crystal layer 9 filled with liquid crystal and a pixel electrode 11 are provided in the gap. A polarizing plate 12 is provided outside the counter substrate 10.
Moreover, it is also possible to form a wiring or a driving element on a light scattering layer formed by the same method and use it as an element substrate.
[0035]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.
[0036]
[Example 1]
First, carbon black is added to a positive photoresist (PR-13, Tokyo Ohka Kogyo Co., Ltd.) to prepare a light-absorbing photoresist, which is then coated on a glass substrate and pre-baked at 100 ° C. for 90 seconds. Thus, a photoresist layer was formed. The film thickness of the photoresist layer was 1.25 μm, and the transmittance with respect to the main sensitivity wavelength (405 nm) was 7% / μm.
[0037]
Next, this photoresist layer was subjected to proximity exposure through a photomask in which transmission portions having an outer diameter of 11 μm and an inner diameter of 5 μm were randomly arranged. The exposure amount was 400 mJ / cm ² and the exposure gap was 150 μm.
[0038]
The exposed photoresist layer was developed in a 0.5% KOH solution for 70 seconds, and then heat treated for 20 minutes in a clean oven maintained at 200 ° C. to form an uneven layer.
[0039]
Furthermore, an aluminum film was vapor-deposited on the concavo-convex layer to obtain a target diffuse reflector.
[0040]
With respect to the diffuse reflector thus obtained, light is incident from the reflective film side at an incident angle of 30 ° with respect to the normal of the substrate surface, and reflected in a direction shifted by 15 ° and 25 ° from the regular reflection direction to the reflective film side. The light intensity values I ₁₅ and I ₂₅ of the reflected light were measured. As a result, I ₁₅ was 254, I ₂₅ was 4, and I ₁₅ / I ₂₅ was 63.
[Examples 2 to 3 and Comparative Examples 1 to 4]
In Examples 2 to 3 and Comparative Examples 1 to 4, diffusion was performed in the same manner as in Example 1 except that the thickness and transmittance of the photoresist layer, the exposure amount, and the exposure gap were as shown in Table 1. A reflector was produced. Table 1 shows I ₁₅ , I ₂₅ and I ₁₅ / I ₂₅ of the obtained diffuse reflector.
[0042]
[Table 1]

[0043]
[Visibility evaluation test]
A glass substrate was bonded to each of the diffuse reflectors obtained in Examples 1 to 3 and Comparative Examples 1 to 4 via glycerin to prepare a visibility evaluation sample (liquid crystal simulation cell).
[0044]
About these liquid crystal simulation cells, the test subject observed from the front and 45 degrees diagonally, and the visibility in each direction was evaluated. Evaluation was made into 5 grades, 1 (bad), 2 (slightly bad), 3 (normal), 4 (slightly good), and 5 (good). The obtained results are shown in Table 2.
[0045]
[Table 2]

As shown in Table 2, when the diffusive reflectors of Examples 1 to 3 are used, the visibility when viewed from the front is sufficiently high, while the visibility when viewed from the diagonal is sufficiently low. It was confirmed.
[0046]
【The invention's effect】
As described above, according to the present invention, when an observer views the reflective liquid crystal display from the front, a bright and clear display is given, and when a person other than the observer views the liquid crystal display from an oblique direction. There is provided a diffusive reflector that can reduce the visibility.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a diffuse reflector of the present invention.
FIG. 2 is a schematic cross-sectional view showing an example of a color filter with a diffuse reflector.
FIG. 3 is an explanatory diagram showing an example of a method for producing a color filter with a diffuse reflector.
FIG. 4 is a schematic cross-sectional view showing an example of a reflective liquid crystal display using a color filter provided with a diffuse reflector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Uneven layer (photoresist layer), 2a ... Latent image density distribution, 3 ... Reflective film, 4R, 4G, 4B ... Colored resin region, 5 ... Transparent electrode, 6 ... Protective layer, 7 ... Photomask DESCRIPTION OF SYMBOLS 9 ... Liquid crystal layer, 10 ... Counter substrate, 11 ... Pixel electrode, 12 ... Polarizing plate, 101 ... Light source, 102a, 102b ... Photodetector.

Claims (2)

In the diffuse reflector used in the reflective liquid crystal display,
A substrate, a concavo-convex layer having a concavo-convex surface on a side far from the substrate formed on the substrate surface, and a reflective film including a metal film formed on the concavo-convex surface of the concavo-convex layer,
When light is incident from the reflective film side at an incident angle of 30 ° with respect to the normal of the substrate surface, the light intensity value of the reflected light reflected in a direction shifted by 15 ° from the regular reflection direction to the reflective film side is , der 6 times more light intensity value of the reflected light from the specular reflection direction is reflected in a direction deviated 25 ° to the reflective film side is,
The concavo-convex layer is coated with a positive photoresist having a transmittance per unit thickness of 1 to 30% / μm with respect to the photosensitive wavelength region on the substrate surface, and then a diffuse reflection region forming pattern on the inside and transparent on the outside A diffusive reflector formed by subjecting the photoresist to proximity exposure through a photomask on which a pattern is formed, followed by development and heat treatment . The diffusive reflector according to claim 1, wherein the concavo-convex layer is made of a positive photoresist containing a light shielding material having a light shielding property with respect to a photosensitive wavelength region .

Images