JP2003066436A - Semi-transmission type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semi-transmission type liquid crystal display device in which color purity of a panel display in a transmission mode is made almost equal to that of the panel display in a reflection mode and whose optical characteristics are enhanced. SOLUTION: One member is prepared by forming a first color filter 12, a transparent resin layer 11 on which a projection-arrayed group is formed, a translucent film 10, a second color filter 9, an overcoat layer 8, a transparent electrode 5 and an alignment layer 6 on a glass substrate 4 in this order. The other member is prepared by forming another transparent electrode 5 and another alignment layer 6 on another glass substrate 4 successively. This semi- transmission type liquid crystal display device is obtained by sticking the one member to the other member while interposing a liquid crystal 7 between them.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transflective liquid crystal display device. 2. Description of the Related Art In recent years, liquid crystal display devices have been used for large and high-definition monitors in addition to small or medium-sized portable information terminals and notebook personal computers. Further, a technology of a reflective liquid crystal display device that does not use a backlight has been developed, and is excellent in thinness, light weight, and low power consumption. A reflection type liquid crystal display device includes a scattering reflection type in which a light reflection layer having an uneven shape is formed on the inner surface of a substrate provided behind, but the use of a backlight makes it possible to effectively use ambient light. I use it. In addition, a transflective liquid crystal display device has been developed in which a transflective film is formed instead of the light reflecting layer, a backlight is provided, and the transflective mode is selectively used in a reflective mode or a transmissive mode. According to this transflective liquid crystal display device, it is used as a device in a reflection mode by external illumination such as sunlight or a fluorescent lamp, or used as a device in a transmission mode by mounting a backlight as internal illumination. In order to have both functions together, a semi-permeable membrane is used (see JP-A-8-292413). Further, it has been proposed to use a transflective film for the same purpose in an active matrix type transflective liquid crystal display device (see Japanese Patent Application Laid-Open No. Hei 7-318929). However, in the above-mentioned proposed transflective liquid crystal display device, according to the structure in which the color filter is provided inside, in the reflection mode, the incident light passes through the color filter twice, whereas the transmission mode. In this case, the incident light passes through only once, and the thickness of the color filter (colored layer) is constant in both the reflection region and the transmission region, so that the color purity of the panel display in the transmission mode is lower than that in the reflection mode. , Had a pale hue. To solve this problem, a transflective liquid crystal display device using two layers of color filters has been proposed (see Japanese Patent Application Laid-Open No. 2000-47192). According to the proposed liquid crystal display device, one member formed by sequentially laminating a transparent electrode and an alignment layer on a transparent substrate, and a color filter, an overcoat layer, a semi-transmissive film, and the like on a transparent substrate. The other member formed by sequentially laminating a color filter, a transparent electrode, and an alignment layer is attached to the outside of one member of a liquid crystal panel in which pixels are arranged in a matrix by laminating through a nematic liquid crystal. When the phase difference plate and the polarizing plate are sequentially stacked, when used in the reflection mode, the irradiation light from the external illumination sequentially passes through the polarizing plate, the phase difference plate, and the liquid crystal panel, and is further reflected by the semi-transmissive film. The reflected light passes through the liquid crystal panel,
It does not pass through the other polarizing plate, thereby increasing the brightness.On the other hand, when used in the transmission mode, the irradiation light of the backlight sequentially passes through the polarizing plate, the phase difference plate, and the semi-transmissive film, and Through the panel, this allows the panel used in the above reflection mode to be used in the transmission mode under the same conditions, and enables stable and clear color display in either the reflection mode or the transmission mode, As a result, a high-performance semi-transmissive liquid crystal display device whose characteristics are enhanced to such an extent that both functions of the reflection mode and the transmission mode can be satisfied can be provided. Further, by interposing the forward scattering film between one of the members and the phase difference plate, the light reflected by the semi-transmissive film is more reflected in a direction other than the regular reflection direction, thereby displaying an image. Has a large viewing angle, and the recognition area for image display has been widened. [0010] However, by providing such a transflective liquid crystal display device having a two-layer structure of color filters, the panel display in the transmissive mode could be improved. Because of the external scattering structure, the display performance of the reflection mode was deteriorated due to the back scattering of the forward scattering film. It is therefore an object of the present invention to provide a transflective liquid crystal display device in which the color purity of a panel display in a transmissive mode is substantially equal to that in a reflective mode and the optical characteristics are improved. In the transflective liquid crystal display device of the present invention, a first color filter is formed on a main surface of a substrate, and a convex portion is formed on the surface of the first color filter. A transparent resin layer which is randomly arranged to form a convex arrangement group, and a member formed by sequentially laminating a light semi-transmissive film, a second color filter, a smooth film, a transparent electrode, and an alignment layer on the transparent resin layer And a pixel arranged in a matrix with a nematic liquid crystal interposed between the transparent member and the other member formed by sequentially laminating a transparent electrode and an alignment layer on a transparent substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a transflective liquid crystal display device of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view of an STN type transflective liquid crystal display device for color display, and FIG. 2 is a schematic sectional view of a main part of one member. 3 and 4 show a process for manufacturing one member. According to FIG. 1, reference numeral 4 denotes a glass substrate on the segment side or a glass substrate on the common side. On one side, a first color filter 12 arranged for each pixel is formed on the glass substrate 4. ing. The first color filter 12 is formed by a pigment dispersion method, that is, a method in which a photosensitive resist prepared in advance with a pigment is applied on a substrate and photolithography is performed. As a typical example, three colors of red, green, and blue are colored. A plurality of substantially hemispherical convex portions (diameter: 10 to 15 μm) are arranged on the surface of the first color filter 12 to form a transparent resin layer 11 having a convex arrangement group. The semi-permeable membrane 10 is applied on the layer 11, that is, on the convex array. Further, a second color filter 9 arranged for each pixel is formed on the semi-transmissive film 10. Similarly to the first color filter 12, the second color filter 9 is formed into three colored layers of red, green, and blue by photolithography using a pigment dispersion method. A chromium metal or a black matrix of a photosensitive resist may or may not be formed between the color filters 9 for each pixel of the second color filter 9. Then, an overcoat layer 8 made of an acrylic resin and a plurality of transparent electrodes 5 made of ITO arranged in parallel are formed on the second color filter 9. On this transparent electrode 5, an alignment film 6 made of a polyimide resin rubbed in a certain direction is formed. Further, in order to easily form the second color filter 9 and the like, the color filter 9 may be provided on the semi-transmissive film 10 via an SiO ₂ layer. It should be noted that the position of the second red color filter 9 is substantially the same as the position of the second red color filter 9 above the first red color filter 12. Similarly, the first green color filter 12 and the second green color filter 9 and the first blue color filter 12 and the second blue color filter 9 are substantially matched in terms of positional relationship. On the other member, on the glass substrate 4, a large number of transparent electrodes 5 made of ITO and an alignment film 6 made of polyimide resin rubbed in a certain direction are sequentially formed. Si between the transparent electrode 5 and the alignment film 6
An insulating film layer made of O ₂ may be interposed. A structure in which one member and the other member are bonded together via a nematic liquid crystal 7 as described above,
For example, they are bonded with a sealant via a liquid crystal 7 made of a chiral nematic liquid crystal twisted at an angle of 200 to 270 °. Furthermore, a liquid crystal 7 is provided between the two members.
A large number of spacers are arranged in order to keep the thickness of the spacer constant. A retardation plate 13 made of polycarbonate or the like and an iodine-based polarizing plate 14 are sequentially stacked on the outer main surface of one member, and a retardation plate 3 made of polycarbonate or the like and another on the outer main surface of the other member. The retardation plate 2 and the iodine polarizing plate 1 are sequentially stacked. In these arrangements, the adhesive is applied by applying an adhesive made of an acrylic material. Further, a backlight (not shown) is provided outside the polarizing plate 14. In this embodiment, the retardation plate 2 and the retardation plate 3 are combined, but a single retardation plate may be used instead. The semi-permeable film 10 is formed of a metal layer or a dielectric layer. Al, C when using a metal layer
r, SUS, Ag or the like, and the film thickness is preferably 50 to 700 ° to satisfy both the light transmittance and the light reflectivity.
On the other hand, when importance is attached to the light reflectivity, the angle is preferably set to 100 to 700 °. When a dielectric layer is used, for example, a film in which a TiO ₂ film of a high refractive index material and a SiO ₂ film of a low refractive index material are alternately laminated may be used.
It may be formed with a thickness of 10,000 °. Note that the formation with a metal layer is low in cost in that a single material is used, and is also advantageous in that a high-quality film can be easily and stably formed by a sputtering method. Thus, when the liquid crystal display device having the above-described configuration is used in the reflection mode, the irradiation light from the external illumination such as sunlight or a fluorescent lamp is applied to the polarizing plate 1, the phase difference plates 2 and 3, the other member, the liquid crystal 7, and the like. Are sequentially reflected at that time, are reflected by the semi-transmissive film 10 provided on one member, and the reflected light passes through the other member and passes through the retardation plates 2 and 3 and the polarizing plate 1. Since the light does not pass through the other polarizing plate 14, the luminance increases. In order to obtain a higher luminance, the second color filter 9 may be made of a material having a high transmittance. Regarding the transmittance, the first color filter 12
By not providing a substantial difference between the second color filter 9 and the second color filter 9, the cost can be reduced in that the same material is used as compared with the case where the difference is provided.
A transmittance characteristic may be appropriately selected between the first color filter 12 and the second color filter 9 according to each required characteristic of luminance and color purity. When the liquid crystal display device having such a configuration is used in the transmission mode, the light emitted from the backlight is applied to the polarizing plate 1.
4, the phase difference plate 13, the first color filter 12, the semi-transmissive film 10, and the second color filter 9, thus passing through one member, the liquid crystal 7, and the other member. , 3 and the polarizing plate 1 sequentially, whereby the light passing through the polarizing plate 14 changes the polarization state by the phase difference plate 13. With such a configuration, the light used as the reflection mode is used as it is. High brightness was obtained. Regarding the color display characteristics in the transmissive mode, the second color filter 9 is made of a material having a high transmittance (the color purity is reduced as a material) in order to achieve high luminance when used in the reflective mode. ), The first color filter 12 in addition to the second color filter 9.
Also, the passage of the irradiation light prevented deterioration of color display and achieved excellent color purity. As described above, according to the liquid crystal display device of the present invention, a clear color display (color purity) as well as high luminance was obtained in both the reflection mode and the transmission mode. In addition, in one member, the glass substrate 4
, The light does not pass through the glass substrate 4 even when it is used in the reflection mode, whereby the incident light and the reflected light due to the refractive index of the glass substrate 4 There is also an advantage that there is no longer any difference between them, and there is no longer a phenomenon in which both lights appear double. Further, according to the liquid crystal display device of the present invention, the transparent resin layer 11 composed of the convex arrangement group is formed on the first color filter 12, and the semi-transmissive film 10 is coated on the convex arrangement group. When the device is used in the reflection mode, a scattering layer is formed inside the panel, so that the back scattering caused by forming the scattering layer outside the panel can be eliminated, thereby improving the contrast. When used in the transmission mode, the transparent acrylic convex array group has a refractive index substantially equal to that of the upper and lower color filters, so that light incident from the lower side of the panel is refracted by the convex array group. This does not occur and the effect of emitting light at the same angle is achieved. Next, a method for manufacturing one member will be described. FIG.
And each of the steps (a) to (i) as shown in FIG. Step (a): A photosensitive resist prepared with a red pigment by a pigment dispersion method is applied on a glass substrate 4 to a thickness of 1.0 ± 0.5 μm, and then applied to a predetermined portion by photolithography. And a red color filter 12 is provided. Similarly, a photosensitive resist prepared with green and blue pigments is formed at a predetermined portion to form a blue or green color filter 12. Step (b): A transparent photosensitive resist 15 (positive resist) having a thickness of 1.
Apply at 5 ± 0.5 μm, then pre-bake at 105 ± 10 ° C. for 3 minutes. Step (c): Proximity exposure is performed on the photosensitive resist 15 using a photomask 16 at an exposure amount of 80 mj / cm ² . As shown in FIG. 6, the photomask 16 uses a light-shielding pattern 17 in which innumerable circular patterns are formed in random arrangement with Cr or the like. The photomask 16 in FIG. 6 is made of a metal such as Cr metal or iron oxide on a glass substrate. A large number of circular spots 17 (for example, 15 μm in diameter) are arranged in a random state, and when the image display surface is 5.7 inches in size, about 10 million pieces are formed on a glass substrate corresponding to one display surface. Spots are arranged. This spot may be, for example, a square, pentagon, hexagon, or even a polygonal spot other than a circle. However, it is preferable that the spot is formed in a circular shape so that there is no difference in scattering characteristics depending on the viewing direction. Good. Then, a projection having substantially the same shape as the spot shape is formed. Further, it is desirable to define the spot diameter and the spot interval. That is, the spot diameter is 1 to 50 μm.
By setting m to preferably 3 to 15 μm, many irregularities can be formed with the same resist film thickness, and good scattering characteristics can be obtained. Moreover, the distance between the spots is 0.1 to 20 μm,
When the thickness is preferably 4 to 7 μm, the irregularities are continuously connected after exposure and development, whereby good scattering characteristics can be obtained. Step (d): Next, development was performed, thereby forming a convex array group. According to this development, the corner of the pattern is removed and a smooth curved surface is obtained using the wraparound of the light of the proximity exposure. In the developer,
Using PD523AD (0.25 ± 0.1%) (manufactured by JSR), development was performed for 50 ± 10 seconds (20 ° C.). Step (e): The entire surface is exposed to remove unreacted components of the photosensitive resin, and decoloring is performed. Further, the surface shape is smoothed by the first post-baking at 150 ± 10 ° C. (2 minutes), and the resin is cured by performing the second post-baking at 220 ± 10 ° C. (15 minutes). Transparent resin layer 11 in this step
To form a convex array group. Step (f): In this step, the semi-permeable film 10 is applied. This film 10 is made of Al, Al alloy (AlNd, AlCA).
g, etc.), Ag, Ag alloy (AgCuAu, AgPd, AgPdCu, AgRuCu
And the like, or a dielectric layer having a thickness of 100 to 10000 is laminated. In addition, in order to improve the adhesion between the convex array group and the metal film, an oxide such as SiO ₂ , ITO, In ₂ O ₃ , and TiO ₂ is formed in a thickness of about 100 mm on the base of the metal film. Is also good. Step (g): A second color filter 9 is formed. According to this example, a photosensitive resist prepared with a black pigment by a pigment dispersion method on a glass substrate is applied to the substrate at a thickness of 1.0 ± 0.5 μm, and then formed on a predetermined portion by photolithography. To form a black matrix 9a. Then, similarly to the step (a), red, green,
A photosensitive resist prepared with a blue pigment is formed at a predetermined site. Step (h): 2.2 ± 0.2 μm of acrylic resin
m to form an overcoat layer 8. Step (i): ITO is used to form a transparent electrode.
The film is formed with a thickness of 1000-3700 °. here,
In order to improve the adhesion between the overcoat layer and the ITO film, an intermediate layer such as SiO ₂ may be formed under the ITO film. According to the present invention, a liquid crystal display device of the present invention as shown in FIG. 1 is obtained by using the color filter substrate obtained by the above steps. Next, the behavior of incident light in the liquid crystal display device of the present invention will be described with reference to FIG. 2 for a reflection mode and a transmission mode. (Reflection Mode) The incidence of light from the upper side of the liquid crystal display device will be described separately, and how the light rays travel will be described in order. Is light incident between pixels of the color filter. This portion is absorbed by the black resist (black matrix 9a) and has no reflected light. In this case, in the reflection mode, since there is no reflected light from between the pixels of the color filter, high contrast is obtained. Is light incident on the pixel. This portion is reflected by the semi-transmissive film 10 and becomes reflected light. (Transmission Mode) The incidence of light from the lower side of the liquid crystal display device will be separately described, and how the light rays travel will be described in order with reference to FIG. Reference numeral denotes light incident between pixels of the color filter. Since this portion is formed with a black resist, it is absorbed by the resist and has no transmitted light. In this case, in the transmission mode, there is no transmitted light from between the pixels of the color filter, so that high contrast is obtained. Is light incident on the pixel. This portion passes through the semi-transmissive film 10 and becomes transmitted light. In this example, the reflected light in the reflection mode is 1
The light passes through the μm color filter twice, and the transmitted light in the transmission mode also passes through the 1 μm color filter twice. According to the present invention, it is preferable that the second color filter 9 is provided with the black matrix 9a and the other first color filter 12 is not provided with such a black matrix. . Hereinafter, this point will be described. When a black matrix is provided on the first color filter 12, the black matrix rides on the end of each color filter, and an overlapping portion is formed on both sides. Thus, even when the transparent resin 11 is applied and formed, the overlapping portion is formed. In some cases, it is difficult to flatten the difference in height of the color filters, which may affect the scattering characteristics of the convex array group. On the other hand, when the black matrix 9a is provided only in the second color filter 9, such a problem can be solved. To eliminate. When used in the transmission mode,
It is sufficient that a black matrix is formed on one of the first color filter and the second color filter. However, when used in the reflection mode, it is necessary to form a black matrix above the reflective film, and thus it can be seen that it is sufficient to form the black matrix only on the second color filter. By providing the black matrix 9a only in the second color filter 9, the coloring of each color filter becomes clear in both the reflection mode and the transmission mode. Further, the first color filter 12 and the second
When a black matrix is provided for both of the color filters 9, high-precision alignment is required for both black matrices, which causes a reduction in manufacturing yield. Next, the optical characteristics of the liquid crystal display device of the present invention were measured. In the case of the reflection mode, as shown in FIG. 5A, light (C light source) was incident from an obliquely upper 15 ° of the liquid crystal display device, and the liquid crystal display device was driven (white display, black display,
(Red display, green display, blue display), and the reflectance, contrast, and color gamut area of the reflected light in the vertical direction were measured. In the case of the transmission mode, as shown in FIG. 5B, light (C light source) was incident from the lower part of the liquid crystal display device, and the liquid crystal display device was driven (white display, black display, (Red display, Green display, Blue display), and the transmittance, contrast, and color gamut area for the transmitted light in the vertical direction were measured. The results shown in Tables 1 and 2 were obtained. The results of the optical characteristics of the conventional transflective liquid crystal display device shown in FIG. 7 are also shown. In the figure, the same parts as those shown in FIG. 1 are denoted by the same reference numerals. The liquid crystal display device shown in FIG. 7 has a structure in which the first color filter 12 is not provided. Other configurations are exactly the same as those of the liquid crystal display device of FIG. [Table 1] [Table 2] FIG. 8 shows a definition diagram of the color gamut area. The color gamut area indicates an area surrounding each RGB chromaticity point. The larger the area, the higher the color reproducibility and the higher the color purity of the panel display. In Table 1, Ron and Ton are the reflectance and the transmittance when displaying white, and Roff and Toff are the reflectance and the transmittance when displaying black. CR (contrast) is Ron / R
off, Ton / Toff. As is clear from the results shown in Tables 1 and 2, in the reflection mode, the conventional example and the liquid crystal display device of the present invention have almost the same characteristics. On the other hand, in the transmission mode, the liquid crystal display device of the present invention has a lower transmittance than the conventional example, but has a color gamut area of 0.85 to 1.82.
Up to 2.14 times. Therefore, in a conventional structure in which a single color filter is formed on a semi-transmissive film, when the color in the transmission mode is improved, the color purity in the reflection mode is also improved.
Although the reflectance was also reduced, according to the apparatus configuration of the present invention, since the reflection mode and the transmission mode can independently control the color purity, without reducing the brightness of the reflection mode, The color in the transmission mode could be improved. The present invention is not limited to the above embodiment, and various changes and improvements may be made without departing from the spirit of the present invention. For example, in the above embodiment, S
The description is given using a TN type simple matrix type color liquid crystal display device. In addition, a twisted nematic type color liquid crystal display device such as a TN type simple matrix type liquid crystal display device and a TN type active matrix type, and a bistable type simple liquid crystal display device. Similar effects can be obtained even in a matrix type color liquid crystal display device. As described above, according to the present invention, the first color filter, the transparent resin layer having the convex arrangement group, the light semi-transmissive film, and the second color filter are provided on the main surface of the substrate. A matrix in which a nematic liquid crystal is interposed between one member formed by sequentially laminating a smooth electrode, a transparent electrode and an alignment layer, and the other member formed by sequentially laminating a transparent electrode and an alignment layer on a transparent substrate. By using a semi-transmissive device configuration in which pixels are arranged in a shape, when used in a reflective mode, it does not pass through the other polarizing plate, thereby increasing the luminance, while using it in a transmissive mode. In this case, the irradiation light of the backlight sequentially passes through the polarizing plate, the phase difference plate, and the semi-transmissive film, passes through the liquid crystal panel, and thereby passes through the panel used in the above-described reflection mode under the same conditions. Mode Can be used, and stable and clear color display can be performed in either the reflection mode or the transmission mode.
Sufficient color compensation, and as a result, the color purity of the panel display in the transmissive mode is equivalent to that of the reflective mode, and the high-performance transflective type whose characteristics have been enhanced to the extent that it can satisfy both the functions of the reflective mode and the transmissive mode A liquid crystal display device could be provided. In the present invention, when the color filter is used in the reflection mode, the color filter can be made of a material having a high transmittance (the color purity is reduced as a material) to obtain higher luminance. Even when used in the transmission mode, the irradiation light passes through the color filter twice, preventing deterioration of the color display and achieving excellent color purity.
As a result, a clear color display (color purity) with high brightness in both the reflective mode and the transmissive mode
was gotten. Furthermore, according to the present invention, even when used in the reflection mode, the optical path difference between the incident light and the reflected light caused by the refractive index of the glass substrate does not occur, thereby eliminating the phenomenon that appears double. Was.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a transflective liquid crystal display device of the present invention. FIG. 2 is a cross-sectional view of one member of the transflective liquid crystal display device of the present invention. FIGS. 3A to 3F are process diagrams showing a method for manufacturing one member. FIGS. 4A to 4G are process diagrams showing a method for manufacturing one member. 5A is an explanatory diagram illustrating a reflection optical characteristic evaluation method, and FIG. 5B is an explanatory diagram illustrating a transmission optical characteristic evaluation method. FIG. 6 is a plan view of a photomask. 7 is a cross-sectional view of a conventional liquid crystal display device. FIG. 8 is an explanatory diagram showing a color gamut area. [Description of References] 1, 14,..., Polarizing plates 2, 3, 13,. Phase difference plate 4 ... Glass substrate 5 ... Transparent electrode 6 ... Alignment film 7 ... Liquid crystal 8 ... Overcoat layer 9 ... Second color filter 10 ... Semi-transmissive film 11 ... ..Transparent resin layer 12: first color filter

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Claims (1)

Claims: 1. A transparent resin in which a first color filter is formed on a main surface of a substrate, and convex portions are randomly arranged on the surface of the first color filter to form a convex array. A member formed by sequentially laminating a light translucent film, a second color filter, a smoothing film, a transparent electrode, and an alignment layer on the transparent resin layer, and a transparent electrode and an alignment layer on a transparent substrate. A transflective liquid crystal display device in which pixels are arranged in a matrix with a nematic liquid crystal interposed between the other member and a member formed by sequentially laminating the layers.