JP2002196115A - Reflector and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflector, which reflects incident light concentrically in a specified direction by providing directivity to light reflected from the rugged surface of the reflector, and to provide a liquid crystal display with the reflector and a portable electronic information device with the liquid crystal display. SOLUTION: The reflector for a liquid crystal display has a random rugged and surface, diffusion angle θ of light reflected by the reflector has the relation θ(horizontal direction)<θ(vertical direction), and the reflector is formed by photolithography, in such a way that 30 times or higher than the intensity of the reflected light as the intensity of light reflected by a standard white board is obtained in a range of 10 deg.<=|θ|<=30 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflector for a liquid crystal display device, a liquid crystal display device provided with the reflector, and a portable electronic information device using this device.

[0002]

2. Description of the Related Art In recent years, in a so-called portable electronic information device such as a portable telephone, a reflective or semi-transmissive liquid crystal display device is provided on a display portion thereof so as to reduce power consumption and withstand long-time use. Widely used. The reflection type liquid crystal display device includes a reflector that reflects light incident from the display surface side. The transflective liquid crystal display device also includes a reflector, and when a sufficient amount of light is obtained, such as during the day, display is performed only by light reflected by the reflector, and a sufficient amount of light is obtained, such as at night. When it is not possible, light from a light source is transmitted to perform display. In such a reflector, it is possible to efficiently reflect the incident light over a wider range,
That is, there has been a demand for a proposal of a reflector having a wide viewing angle. To meet such demands, Japanese Patent Application Laid-Open Nos. 11-52110, 11-24070, and 11-38
In JP-A-213, JP-A-11-44804, etc., a reflector having a wide range of diffusion angles and good reflection efficiency and a reflection type liquid crystal display device using the reflector have been proposed. Further, in the reflector described in JP-A-11-52110, an uneven surface is formed on the surface of the reflector, and the inclination angle (differential value of a curve formed by the inner peripheral surface of the concave portion) is -18 to 18 degrees. By setting the range, the reflection efficiency is increased in all directions, and the viewing angle is widened.

[0003]

However, when a conventional reflector for a liquid crystal display device is used in a portable electronic information device such as a portable telephone which is often used facing a human body, Since the reflected light was diffused widely in an attempt to widen the viewing angle, sufficient brightness could not be obtained.

Accordingly, in the present invention, in order to solve the above-mentioned problems, the light reflected by the uneven surface of the reflector has directivity, so that the reflector reflects incident light in a specific direction. Another object of the present invention is to provide a liquid crystal display device including the reflector and a portable electronic information device including the liquid crystal display device.

[0005]

According to a first aspect of the present invention, there is provided a reflector for a liquid crystal display device having a random uneven surface on a surface thereof. The light diffusion angle θ has the following relationship: θ _{(left-right direction)} <θ _{(vertical direction)} , and in the range of 10 ° ≦ | θ | ≦ 30 °, the reflection intensity of the reflector is set to a standard white plate ratio of 30. It is characterized by being formed by photolithography so as to obtain a reflected light intensity twice or more. Also,
3. The reflector for a liquid crystal display device according to claim 2, wherein the surface of the reflector for a liquid crystal display device has a random uneven surface, and the diffusion angle θ of the light reflected by the reflector is θ _{(lateral direction)} ≦ θ. _{(Oblique direction)} ≦ θ _{(vertical direction)} , and the intensity of the reflected light beam of the reflector is θ
The integrated value of

(Equation 2) In the range of 10 ° ≦ | θ | ≦ 30 °, the reflector is formed by a photolithography method so as to obtain a reflected light intensity that is 30 times or more that of a standard white plate. Also,
The reflector for a liquid crystal display device according to claim 3 is the reflector for a liquid crystal display device according to claim 1 or 2, wherein the uneven surface has a change in exposure amount due to a proximity gap of an exposure machine. It is characterized by being formed by. The reflector for a liquid crystal display device according to claim 4 is
3. The reflector for a liquid crystal display device according to claim 1, wherein the uneven surface is formed with a change in exposure amount by using a negative or positive alignment photomask. According to a fifth aspect of the present invention, there is provided a liquid crystal display device including the liquid crystal display device reflector according to any one of the first to fourth aspects. According to a sixth aspect of the present invention, there is provided the portable electronic information device, wherein a vertical direction of the reflector of the liquid crystal display device according to the fifth aspect is aligned with a vertical direction as viewed from the portable electronic information device. And

As described above, the reflector of the present invention has a number of uneven surfaces formed on the surface by photolithography. The range of the diffusion angle θ at which a reflected light intensity of 30 times or more of the standard white plate ratio of such a reflector is obtained is 10 ° ≦ | θ.
By limiting | ≦ 30 °, the reflected light is efficiently concentrated and reflected within the range of the diffusion angle. Thereby, the incident light can be effectively used on the display surface of the liquid crystal display device of the portable electronic information device which does not require a wide viewing angle. By making the vertical diffusion angle of the reflector wider than the horizontal diffusion angle in the range of the diffusion angle, the reflected light can be diffused in the vertical direction wider than the horizontal direction. Further, a value obtained by integrating the reflected light intensity with respect to the diffusion angle in the range of the diffusion angle is set such that the vertical integration value of the reflector is equal to or greater than the diagonal integration value, and the diagonal integration value is equal to or greater than the horizontal integration value. Thus, the reflected light intensity in the vertical direction of the reflector can be equal to or higher than the reflected light intensity in the horizontal direction. By providing the reflecting plate having the above configuration in the vertical direction of the visual direction with respect to the portable electronic information device, the portable type has a wide range of viewing angles when used in the vertical direction, and has a strong white intensity and is easy to see. The display surface of the electronic information device can be configured.

[0007] The "diffusion angle" refers to the angle between the normal of the reflecting surface and the reflected light, assuming that the entire reflecting surface of the reflector forms a horizontal plane. Is the maximum value of the angle from the normal to the display surface of the liquid crystal display device, at which a predetermined contrast ratio can be obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the reflector and the liquid crystal display device of the present invention will be described below with reference to the drawings as necessary. 1 to 3 show an embodiment of the reflector of the present invention, in which a photosensitive resist thin film is provided on a substrate surface of a glass plate, and the resist thin film is provided with an uneven surface by photolithography. It was made. In detail, acrylic resist, polystyrene resist, azide rubber resist,
Spin coating a photosensitive resin liquid such as an imide-based resist,
It is applied by a coating method such as a screen printing method or a spraying method. Then, after the coating is completed, the photosensitive resin liquid in the form of a substrate is applied to a heating device such as a heating furnace or a hot plate for 8 hours.
Pre-baking is performed in a temperature range of 0 to 120 ° C. for 1 minute or more to form a photosensitive resin layer on the substrate. Since the pre-bake conditions vary depending on the type of the photosensitive resin used, it is needless to say that the treatment may be performed at a temperature and time outside the above range. Further, the film thickness of the photosensitive resin layer formed here is preferably in the range of 2 to 4 μm. Then, exposure is performed using a photomask drawn with high definition as shown in FIG. At this time, the proximity gap at the time of exposure is set in the range of 80 μm to 200 μm, and light of different intensity is introduced into the light shielding portion by utilizing the diffraction phenomenon when ultraviolet rays pass through the light transmitting portion of the photomask. So that it fits. By performing the exposure in this manner, in the resist immediately below the light-transmitting portion, the intensity of incident light in the wavelength band necessary for the resist to be exposed becomes the weakest, and conversely, the resist immediately below the light-transmitting portion Will be the strongest. Thereby, the residual ratio of the resist immediately below the light transmitting portion during development becomes higher, and the residual ratio of the resist immediately below the light transmitting portion becomes lower, so that an uneven surface can be formed. Although the case where a negative type resist is used as the resist has been described, when a positive type resist is used, if the pattern of the light transmitting part and the light shielding part of the photomask is reversed, a positive type resist is used. A concave / convex surface can be formed in the same manner even with a mold resist. The ultraviolet rays include i-line, g-line, h-line and the like, and they are appropriately selected and used according to the type of the photosensitive resin. Thereafter, the same heating furnace as that used in the pre-bake, using a heating device such as a hot plate, post-baking by heating the photosensitive resin layer in the form of a glass substrate at, for example, about 240 ° C. for 60 minutes or more, and performing the glass substrate-like Baking the photosensitive resin layer;
Finally, for example, aluminum is formed on the surface of the photosensitive resin layer by a sputtering method to form a reflection film along the surface of the uneven surface.

The uneven surface formed as described above has a diffusion angle | θ without deteriorating the performance of the liquid crystal display device.
In order to satisfy | ≦ 30 °, the top of the uneven surface is required.
The period between the tops is 30 μm or less (more preferably 10 to 30 μm), or the distance between the top and bottom of the uneven surface is 2.5.
It is preferable that the thickness be not more than μm. This is because, if an irregular surface having a period exceeding 30 μm is to be formed, the concave bottom will be formed on a substantially flat surface unless the film thickness is increased, and the proportion of light in the regular reflection direction will increase. . Also, if an attempt is made to form an uneven surface of less than 10 μm, the performance of the exposure apparatus and the photosensitive resist is affected, and the entire surface of the photosensitive resin layer is exposed, and the desired uneven surface cannot be formed. It is.

It is preferable that the distance between the top and bottom of the uneven surface is 2.5 μm or less. If the thickness exceeds 2.5 μm, the thickness of the flattening film needs to be increased, and the reflectance is reduced, the distribution of the color filter on the reflector surface is uneven, or the reliability near the sealing material is reduced at the time of assembling the liquid crystal panel. It is because there is. Further, when the reflector under this condition is used in a transflective liquid crystal display device, it is necessary to increase the thickness of the diffusion film and the flattening film, so that the transmittance and the brightness at the time of transmission are reduced. And the top of the uneven surface-
This is because it becomes impossible to form an uneven surface such that | θ | ≦ 30 ° in the range of the period between the tops.

Next, an embodiment of a liquid crystal display device using the reflector will be described. FIG. 5 shows an embodiment of a reflection type liquid crystal display device, and a case where the reflector of the present invention is used in an STN type reflection type liquid crystal display device will be described. This reflection type liquid crystal display device has a pair of glass substrates 1 and 2 vertically arranged opposite to each other, a liquid crystal layer 4 sealed between them by a sealing agent 3, and an upper surface of the upper glass substrate 1. , And a retardation plate 7,
8 is provided. And the glass substrate 2
The upper surface side of the resin layer 10 has an uneven surface, and a metal thin film 11 such as an aluminum thin film is formed on the surface. The reflector 12 includes the glass substrate 2 and the resin layer 1
0 and the metal thin film 11. An electrode layer 15 made of ITO (indium tin oxide) and the like, a top coat layer 16 and an alignment film 17 are laminated on the lower surface of the glass substrate 1, and the upper surface of the metal thin film 11 is required for a color display structure. The overcoat layer 19, the electrode layer 20, and the alignment film 21 are laminated via the color filter 18.

[0012]

Next, a more specific embodiment will be described. (Example 1) In this example, a photosensitive resist thin film was provided on the substrate surface of a glass plate, and this resist thin film was provided with an uneven surface. Specifically, first, a photosensitive resin liquid of an acrylic resist was applied to a substrate surface of a glass substrate by a spin coating method. After completion of the coating, the substrate-shaped photosensitive resin liquid was prebaked in a heating furnace at a temperature of 80 to 120 ° C. for 60 minutes or more to form a photosensitive resin layer on the substrate. Incidentally, the film thickness of the photosensitive resin layer formed here is preferably in the range of 2 to 4 μm. Then, a random uneven surface was formed on the substrate surface of the glass substrate by a photolithography method. In order to form a random uneven surface by a photolithography method, in this embodiment, a circular pattern as shown in FIG.
2 μm was used so that it was adjacent in the horizontal direction and the same pattern was formed in the vertical direction so as to be adjacent at intervals of t2 = 22 μm. Then, the proximity gap at the time of exposure is set to 80 to 200 μm, and by utilizing the diffraction phenomenon when ultraviolet rays pass through the light-transmitting portion of the photomask, light of different intensity is introduced into the light-shielding portion, In the resist immediately below the adjacent light-transmitting portion, the intensity of incident light in the wavelength band necessary for the resist to be exposed is the strongest,
Conversely, by making the incident light immediately below the translucent part the weakest, an uneven surface was formed on the resist surface during development. Although the case where a negative type resist is used as the resist has been described, when a positive type resist is used, if the pattern of the light transmitting part and the light shielding part of the photomask is reversed, a positive type resist is used. A concave / convex surface can be formed in the same manner even with a mold resist. After that, the glass substrate-shaped photosensitive resin layer was baked by heating the glass substrate-shaped photosensitive resin layer at about 240 ° C. for 60 minutes or more using a heating furnace. Finally, aluminum was formed on the surface of the photosensitive resin layer by a sputtering method or the like to form a reflective film along the surface of the uneven surface to obtain a reflector having a random uneven surface. As shown in FIGS. 1B to 1D, the concave-convex surface of this reflector has an average period of 21.5 μm between the top and the bottom (aa) in the left-right direction and the top and bottom (b) in the vertical direction. -B) with an average period of 22 μm,
The average distance between the top and bottom (ac and bd) is 1.7
μm.

(Embodiment 2) Using the same glass substrate and resist as in Embodiment 1 above, and adjusting the proximity gap between 80 and 200 μm for the photomask pattern using the same mask as in Embodiment 1. A reflector 2 was obtained in the same manner as in Example 1 except that the uneven surface was formed. As shown in FIGS. 2B to 2D, the uneven surface of the reflector has a top-to-top (aa) in the left-right direction of the uneven surface.
The average period between them is 15 μm, and the top-to-top (b-
The average period between b) was 14.5 μm, and the average interval between the top and bottom (ac and bd) was 0.7 μm.

Example 3 A reflector 3 was obtained in the same manner as in Example 1 except that the same glass substrate and resist as in Example 1 were used and the photomask pattern was changed. As shown in FIGS. 3 (b) to 3 (d), the uneven period of the reflector has an average period between the top and bottom (aa) in the left-right direction of the uneven surface is 14.5 μm, and the top in the vertical direction. The average period between the top (bb) is 27 μm, and the average interval between the top and bottom (ac and bd) is 0.8 μm.
m.

Next, using the reflector according to the above embodiment,
Irradiation was performed at an angle of 30 ° with respect to the normal direction of the reflector, and the reflection intensity was measured at diffusion angles of 0 °, 45 °, and 90 ° of the reflected light. The results are shown in Tables 1 and 2, and FIGS. 6 to 8.

[0016]

[Table 1]

[0017]

[Table 2]

The effective angle of the reflected light is 30 times that of the standard white plate, and the diffusion angle at which the intensity of the reflected light is obtained is measured. In this measurement method, a laser having a wavelength of 543.5 nm and a beam diameter of φ3 mm is incident using a light source of a semiconductor laser of 0.7 mV, and light diffusely reflected by a reflector is received by a light receiver (diameter of φ5 mm). The reflection intensity was measured.

As is clear from Tables 1 and 2, according to the reflector of this embodiment, reflected light having high directivity was obtained in the vertical direction. Further, if the liquid crystal display device including the reflector of the above embodiment is provided so as to be vertically aligned with the portable electronic information device in the viewing direction, the liquid crystal display device is strong in the direction directly facing the human body when using the portable electronic information device. Since reflected light is obtained, a portable electronic information device having an extremely bright display surface can be obtained.

[0020]

As described above, according to the reflector for a liquid crystal display device of the present invention, limited incident light can be efficiently used by giving directivity to reflected light. This allows
A reflector for a liquid crystal display device having excellent viewing angle whiteness can be obtained. Further, such a reflector can be very easily manufactured by a photolithography method. Also,
The pattern shape and arrangement can be varied by photolithography. Further, compared to conventional press molding, a pattern having a controlled diffusion angle can be formed with high definition and high density, so that the uneven surface per unit area becomes denser, which results in a light utilization efficiency of several times. It will be step up, brighter,
A reflector having whiter characteristics is obtained. Further, if the vertical direction of the reflector of the present invention is provided so as to be aligned with the vertical direction of the viewing direction with respect to the portable electronic information device, reflected light is reduced in the horizontal direction with respect to the viewing direction, and Strong reflected light can be obtained, and incident light can be more effectively utilized.

[Brief description of the drawings]

FIG. 1 (a) AFM of a reflector according to one embodiment of the present invention
(B) A photograph of the reflector of the embodiment from the top view by AFM (c) X in the horizontal direction of the reflector of the embodiment
-X-ray sectional view (d) Y- in the vertical direction of the reflector of the embodiment
Y-line sectional view

FIG. 2 (a) AF of reflector according to another embodiment of the present invention
(B) A photograph of the reflector of the embodiment from the top view by AFM (c) Cross-sectional view of the reflector of the embodiment in the left-right direction (d) Top and bottom of the reflector of the embodiment Direction Y
-Y line sectional view

FIG. 3 (a) AF of reflector according to another embodiment of the present invention
(B) A photograph of the reflector of the embodiment from the top view by AFM (c) Cross-sectional view of the reflector of the embodiment in the left-right direction (d) Top and bottom of the reflector of the embodiment Direction Y
-Y line sectional view

FIG. 4 is an explanatory diagram illustrating a photomask.

FIG. 5 is an explanatory sectional view of a reflection type liquid crystal display device.

FIG. 6 is an explanatory diagram for explaining a relationship between a diffusion angle and a reflection intensity of the reflector described in the first embodiment.

FIG. 7 is an explanatory diagram for explaining the relationship between the diffusion angle and the reflection intensity of the reflector described in Example 2.

FIG. 8 is an explanatory diagram for explaining a relationship between a diffusion angle and a reflection intensity of the reflector described in the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Glass substrate 3 Sealant 4 Liquid crystal layer 6 Polarizer 7 Retardation plate 8 Retardation plate 10 Resin layer 11 Metal thin film 12 Reflector 15 Electrode layer 16 Top coat layer 17 Orientation film 18 Color filter 19 Overcoat layer Reference Signs List 20 electrode layer 21 alignment film 22 photomask 23 circular pattern t1 distance between centers of circular patterns t2 distance between centers of circular patterns a top (in the vertical direction of the uneven surface) b top (in the horizontal direction of the uneven surface) c ( The bottom d (in the vertical direction of the uneven surface) d the bottom (in the horizontal direction of the uneven surface)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideharu Watanabe No. 145, Yokatakida, Kosaka-cho, Iwaki City, Fukushima Prefecture 1 Inside Andes Intec Co., Ltd. (72) Daisuke Chihiro No. 145, Yokatakita, Takasaka-cho, Iwaki City, Fukushima Prefecture 1 Andean Intec Co., Ltd. (72) Inventor Hiromi Kikuchi No. 145, Yokatagida, Kosaka-cho, Iwaki City, Fukushima Prefecture 1 Andean Intec Co., Ltd. F-term (reference) 2H042 BA03 BA14 BA20 DA02 DC02 DE04 2H091 FA14Z GA01 MA10 5C094 AA07 BA43 CA19 EB04 ED11 ED13 HA08 JA09 JA11

Claims (6)

[Claims] 1. A reflector for a liquid crystal display device having a random uneven surface on the surface, wherein a diffusion angle θ of light reflected by the reflector has a relationship of θ _{(left-right direction)} <θ _{(vertical direction)} . A liquid crystal formed by a photolithography method such that the reflection intensity of the reflector is 30 times or more that of a standard white plate in the range of 10 ° ≦ | θ | ≦ 30 °. Reflectors for display devices. 2. A reflector for a liquid crystal display device having a random uneven surface on its surface, wherein a diffusion angle θ of light reflected by the reflector is θ _{(lateral direction)} ≦ θ _{(oblique direction)} ≦ θ _{(up and down ) Direction)} , and the intensity of the reflected light beam of the reflector is θ
The value integrated with respect to A liquid crystal display formed by a photolithography method so that the reflection intensity of the reflector is 30 times or more that of a standard white plate in a range of 10 ° ≦ | θ | ≦ 30 °. Reflector for equipment. 3. The liquid crystal display device according to claim 1, wherein the uneven surface is formed by changing an exposure amount by a proximity gap of an exposure machine. Reflector. 4. The liquid crystal display device according to claim 1, wherein the uneven surface is formed by changing the exposure amount by using a negative or positive alignment photomask. Reflector. 5. A liquid crystal display device comprising the reflector for a liquid crystal display device according to claim 1. 6. A portable electronic information device according to claim 5, wherein a vertical direction of the reflector of the liquid crystal display device according to claim 5 is aligned with a vertical direction as viewed from the portable electronic information device.