Color display device having filterless areas

A color display device comprises a substrate, pixel structure demarcating a multiplicity of light-transmissive unit display regions formed on said substrate and color filters configured to cover only a part of area of respective unit display regions and not to cover the remaining are of the unit display region. A color display device which can be easily designed and is capable of producing desired color reproducibility and light transmissivity is provided.

This application is based on Japanese patent application No. Hei 10-372789,
 filed on Dec. 28, 1998, the entire contents of which are incorporated
 herein by reference.
 BACKGROUND OF THE INVENTION
 a) Field of the Invention
 This invention relates to a color display device and more particularly to a
 color display device comprising a multiplicity of display areas.
 b) Description of the Related Art
 A flat panel such as a liquid crystal display (LCD), a plasma display panel
 (PDP) and the like is widely used as a display device.
 Recently, color LCDs and color PDPs that have a variety of abilities in
 color display are commonly used Usually color filters are used to perform
 color display while utilizing the advantages of a flat panel, such as
 thinness, lightweight and the like.
 A color filter is a filter that transmits only such visible light that has
 a selected wavelength range. Corresponding to the principles of light
 mixing and separating, there are three-primary-color filters, which are
 red (R), green (G) and blue (B) filters, and complementary-color filters,
 which are cyan (C), magenta (M) and yellow (Y) filters.
 A color display device for performing optional color display comprises a
 multiplicity of unit display regions on which predetermined color filters
 are disposed. The color display device performs desired color display by
 controlling transmission or reflection of each unit display. In order to
 make a display image vivid by preventing color mixing, it is widely
 performed that an area of each unit display region is demarcated by
 covering the periphery thereof with a black matrix (BM) such as metal,
 opaque resin and the like. In that case, an opening of the BM will be the
 unit display region that will be also a light transmissive region.
 A liquid crystal display (LCD) will be described hereinbelow, as an example
 of the color display. An LCD controls an optical characteristic of a
 liquid crystal layer sandwiched between a pair of substrates with
 respective electrodes by impressing voltage across the liquid crystal
 layer. Transmissivity of light as a whole is controlled, if necessary, by
 combining a polarizer or polarizers. A pair of transparent substrates such
 as glass or the like is used for a transmissive-type display device. For a
 reflective-type display device, at least one of two substrates through
 which light transmits is a transparent substrate.
 There are known systems for driving a display region; one is the simple
 matrix system in which a plurality of electrodes (common electrodes and
 segment electrodes) crossing each other are formed on a pair of facing
 substrates, and another is the active matrix system in which a whole
 surface electrode (a common electrode) is formed on one substrate, and a
 picture-element (pixel) electrode and a switching transistor are formed in
 each unit display region on the other substrate in order to store desired
 voltage in each pixel.
 To realize the active matrix display with glass substrates, a thin film
 transistor (TFT) made of amorphous silicon (a-Si) or polycrystallized
 silicon (poly-Si) is used as material for forming a switching transistor.
 One current electrode (hereinafter, referred to as a source electrode) of
 TFT is connected to a pixel electrode, and the other (hereinafter,
 referred to as a drain electrode) is connected to a data line. A control
 electrode (a gate electrode) is connected to a scanning line, and the data
 and the scanning lines are configured to cross each other on the
 substrate.
 It is preferable for a color display to have high color reproducibility and
 a high transmissivity of light. The color reproducibility depends on the
 coordinates of chromaticity. In case of RGB-type, a wider area of a
 triangle formed on the coordinates of chromaticity with each of color
 filters (red, green and blue) makes higher color reproducibility. The
 transmissivity of light depends on the output-light intensity when white
 light is irradiated on each color filter and on an aperture ratio of the
 BM.
 A high transmissivity of light is desired to get a bright color display,
 especially in a color LCD for a notebook computer and in a reflective-type
 LCD. In such a case, it is desired to increase the aperture ratio of the
 BM by narrowing a width of the BM between the light transmissive regions,
 and to increase the transmissivity of color filters by thinning the color
 filters or changing their material.
 The color filters cover a whole surface of each light transmissive region,
 which is referred to as the unit display region, and are configured to
 overlap the BM surrounding the light transmissive regions. Narrowing the
 width of the BM might risk adjacent color filters overlap each other,
 which may cause aberrant thickness and lower a yield of the production
 process. It requires new experiments to determine new conditions to change
 a film thickness of color filters or material for changing a design of an
 LCD, and causes lowering in throughput and productivity in a mass
 production.
 SUMMARY OF THE INVENTION
 An object of this invention is to provide a color display device that is
 easily designed and is capable of producing desired color reproducibility
 and light transmissivity.
 According to one aspect of this invention, there is provided a color
 display device comprising a substrate, a pixel structure demarcating a
 multiplicity of light-transmissive unit display regions formed on said
 substrate and color filters configured to cover only a part of area of
 respective unit display regions and not to cover the remaining of the unit
 display region.
 Because the color filter is configured only on a part of the unit display
 region that is the light transmissive region, the unit display region is
 divided into regions one of which has the color filter and the other not.
 Bright color display is obtained by expanding the region having no color
 filter within the unit display region. By adjusting an areal ratio of the
 regions with and without a color filter, it is possible to realize a
 variety of color reproducibility with the same material and the same film
 thickness for the color filters.
 As explained above, it is possible to get desired color reproducibility and
 brightness by adjusting areas occupied by the color filters in the unit
 display regions of the color display device. Moreover, it becomes easier
 to keep up with a change in the design, and to increase a throughput of a
 mass production. A bright color display device can be provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The preferred embodiments of this invention will be explained in the
 following with reference to the drawings. Although an LCD is used to
 describe the embodiments as an example, this invention is in no way
 limited to an LCD. For example, the invention can be applied to a PDP and
 the like.
 FIGS. 1A to 1C show the structure of the transmissive-type LCD according to
 an embodiment of this invention, and FIGS. 1D and 1E show that of the
 conventional liquid crystal display device. FIG. 1A is a plan view of a
 color filter substrate. FIG. 1B is a cross-sectional view of the color
 filter substrate of FIG. 1A. FIG. 1C is a cross-sectional structural view
 of the LCD. FIG. 1D is a plan view of a color filter substrate according
 to the conventional technique. FIG. 1E is a cross-sectional view of the
 color filter substrate according to the conventional technique of FIG. 1D.
 First, a structure of the conventional color filter substrate is described
 with reference to FIGS. 1D and 1E. A BM 2 is formed on a glass substrate
 1, and it demarcates light transmissive regions. On the light transmissive
 regions, color filters 3 are formed to overlap edges of the BM 2. Color
 filters 3R, 3G and 3B of three colors are formed in different process. A
 planarizing layer 4 is formed to cover the color filters 3, and forms the
 leveled or planarized surface. A transparent electrode 5 and an
 orientation layer 6 are formed on the leveled surface of the planarizing
 layer 4.
 Narrowing the width of the BM 2 might risk the color filters 3 overlapping
 with adjacent color filters 3, which may cause aberrant thickness and
 lower a yield of the production process.
 An LCD according to the embodiment of this invention is described with
 reference to FIGS. 1A, 1B and 1C.
 As shown in FIGS. 1A and 1B, a color filter substrate 10 comprises a glass
 substrate 1 on which a BM 2 is formed thereon. The BM 2 can be formed, for
 example, by forming a single chromium layer, a laminate of chromium oxide
 film and a chromium film or a laminate of a chromium oxide film, a
 chromium nitride film and a chromium film by sputtering. A chromium
 oxynitride film can substitute the chromium nitride film.
 Reflectance of the BM viewing from the side of the substrate 1 can be
 lowered by the above-mentioned laminate structure. A plan shape of the BM
 is same as in the conventional color substrate illustrated in FIG. 1D. The
 BM comprises a multiplicity of openings configured in a matrix shape, and
 each opening demarcates a unit display region that is a light transmissive
 region.
 Color filters 3R, 3G and 3B in three colors are formed on the substrate on
 which the BM is formed by the way described above. The three color filters
 are formed individually. For example, a colored resin of a desired color
 is applied to coat the whole surface of the substrate by the spin-coater,
 the roll-coater, the slit-coater or the like. As the colored resin, for
 example CR-7001, CG-7001 and CB-7001 of Fuji Hunt, JAPAN, can be used.
 After applying the colored resin, a colored resin film is exposed in the
 shape shown in FIGS. 1A and 1B. An exposed region is configured to retain
 the left and the right portions of each light transmissive region. The
 exposure intensity is, for example, 300 mJ/cm.sup.2. After the exposure,
 the exposed colored resin is developed with an alkaline developing
 solution (for example CD of Fuji Hunt). After development, the colored
 resin film is post-baked in an oven at 230.degree. C. for about an hour to
 harden the colored resin and thereby forms the color filter. In the above
 process, a color filter for one color is formed. These processes are
 repeated to make three of them.
 By the repeated process described above, color filter stripes 3R, 3G and 3B
 of three colors are lined up in a transverse direction as shown in FIGS.
 1A and 1B. Each color filter stripe extends in a longitudinal direction in
 the drawings, overlaps the BM and has a width narrower than that of the
 light transmissive regions. Therefore, within the light transmissive
 regions, regions T having no color filter are formed.
 After forming the color filters, a transparent planarizing resin, for
 example HP-1009 of Hitachi Kasei, JAPAN, is applied to coat the substrate
 by the spin-coater to have a thickness of about 1.5 .mu.m and post-baked
 at a temperature of 230.degree. C. for about an hour in an oven. The
 asperity of the substrate surface made by the formation of the color
 filters 3 and the BM 2 is leveled by the planarizing resin layer 4, and
 thereby a leveled surface is provided.
 On the leveled surface, an indium tin oxide (ITO) film is formed as a
 transparent electrode by sputtering. In this manner, a transparent common
 electrode 5 is formed on a whole surface of the substrate. A polyimide
 layer or the like is formed on the transparent common electrode 5 as an
 orientation film 6. After forming the orientation film, an orientation
 structure is formed by performing orientation treatment such as rubbing
 treatment or the like to the orientation film 6. In this manner, the color
 filter substrate 10 is formed, which comprises the BM which defines the
 openings as the unit display regions demarcating the light transmissive
 region, and the color filters formed on part of the aperture regions in
 the openings of the BM.
 When characteristic of a light source is colored in a way deviating from
 the design, an optical characteristic of a liquid crystal display device
 as a whole is deviated from the design. In such a case, the optical
 characteristic of the liquid crystal display device as a whole can be
 compensated for by coloring the transparent planarizing resin layer 4.
 As shown in FIG. 1C, the color filter substrate 10 is facing toward a TFT
 substrate 20 with a predetermined interval, and liquid crystal 24 is
 injected into a space between both substrates. A first polarizer P1 is
 formed on an outside surface of the color filter substrate 10, and a
 second polarizer P2 is formed on an outside surface of the TFT substrate
 20.
 The TFT substrate 20 is formed by the following steps. An SiO.sub.2 layer
 is formed, depending on the necessity, on a surface of a glass substrate
 11 by plasma enhanced CVD or the like, and thereon a gate electrode 13 is
 formed by depositing a Cr layer, a Ti/Al layer, a Mo layer or the like,
 and patterning the deposited layer with photolithography. A gate
 insulating film 15 is formed with an insulating film such as SiN.sub.x,
 SiO.sub.2 or the like to cover the gate electrode 13. On the gate
 insulating film 15, a semiconductor layer such as a-Si, poly-Si or the
 like is formed by chemical vapor deposition (CVD) or the like, and is
 patterned with photolithography, to form an active layer 17.
 On the active layer 17, an n.sup.+ -Si layer and an Al layer or a Ti/Al/Ti
 layer is formed as a source and drain electrode layer, and patterned to
 form a source electrode 18S and a drain electrode 18D. A thin film
 transistor 19 is formed with the gate electrode 13, the gate insulating
 film 15, the active layer 17, the source electrode 18S and the drain
 electrode 18D.
 After forming the source electrode 18S and the drain electrode 18D, an
 SiO.sub.2 layer, a phosphosilicate glass (PSG) layer, a
 borophosphosilicate glass (BPSG) layer, an SiN layer or the like is
 deposited on a whole surface of the substrate as an inter-layer insulating
 film 21. A photo-resist layer is formed on the inter-layer insulating film
 21, and openings are formed in a region where contact holes are formed.
 Then, openings are formed in a desired region of the inter-layer
 insulating film 21 by etching with a photo-resist pattern.
 A transparent electrode 22 such as an ITO layer is formed on the interlayer
 insulating film 21 having the openings. A multiplicity of pixel electrodes
 disposed in a two-dimentional matrix are formed by patterning the ITO
 layer with photolithography and etching. A polyimide layer or the like is
 formed as an orientation film 23 to cover the pixel electrodes and the
 inter-layer insulating film. An orientation treatment such as rubbing or
 the like is applied to the orientation film 23 to get a desired
 orientation for liquid crystal molecules. On the other surface of the
 substrate 11, another polarizer P2 is formed.
 When the color substrate 10 is changed to the substrate shown in FIGS. 1C
 and ID, an LCD produced will be a conventional one. That is to say, only
 difference between the LCD according to the embodiment of this invention
 and the conventional LCD is that the color filter 3 covers whether a whole
 surface of the light transmissive region or just a part of it at a
 predetermined ratio.
 According to this embodiment, the color filter 3 is configured on a part of
 the light transmissive region. Visible light having all range of
 wavelengths can penetrate through the remaining area of the light
 transmissive region. Therefore, the brightness of the LCD is remarkably
 increased by the region without the color filter. On the other hand, color
 reproducibility of color display is decreased because the color filter 3
 is not configured on the whole surface, and all light having any
 wavelengths is transmitted through the area without the color filter.
 However, in a specific use of a color display device, an increase in the
 light transmissivity has priority over the color reproducibility. In such
 a case, it is very effective for an increase in the light transmissivity
 to have the region T not having a color filter within the light
 transmissive region.
 According to the embodiment, the transmissivity can be increased by
 adjusting the area of the region having no color filter within the light
 transmissive region. A change in desired light transmissivity requires
 only a change in the areal ratio of the region T to the other region, but
 does not require a change in the filme thickness and material of the color
 filter.
 FIGS. 2A and 2B are graphs showing the characteristic of the
 high-transmissive LCD according to the embodiment of this invention in
 comparison to that of the conventional art. FIG. 2A shows the
 transmissivity of each light transmissive region according to the
 embodiment of this invention. FIG. 2B shows the transmissivity of each
 light transmissive region according to the conventional technique.
 In FIG. 2A, the minimum light transmissivity can be obtained at all
 wavelengths because there is a region having no color filter. The case
 shown in FIG. 2A is a case in which the 50% of the transmissive regions
 have color filters, and the remaining 50% have no color filter. Because
 the 50% of the light transmissive region has no color filters, at least
 about 50% transmissivity can be obtained. Each color filter has the
 desired characteristic of color selectivity in that each color filter
 transmits only light of the desired wavelength and shields light of the
 other wavelength.
 FIG. 2B show the transmissivity of each light transmissive region according
 to the conventional technique. A thickness of the color filter is
 decreased to get higher light transmissivity, and color concentration is
 decreased to get the desired light transmissivity. Each color filter's
 ability of shading undesired light is degraded thereby, and so almost 50%
 of undesired light at all wavelengths is transmitted through the color
 filters. That is to say, each color filter transmits light at a specified
 wavelength, but also transmits 50% of light at other wavelengths.
 Comparing FIGS. 2A and 2B, their performances as a whole are almost the
 same. Therefore, the same performance as the conventional color display
 device can be obtained by the color display device according to this
 embodiment of the invention. According to the conventional technique,
 changing material and the film thickness of the color filter is necessary
 for new designing conditions which require new experiments, whereas the
 device according to the embodiment of this invention requires only a
 change in the occupying area of the color filters within the light
 transmissive region. Therefore, preparation of design changes can be
 simplified.
 There is an additional feature of the device according to this embodiment.
 The color reproducibility and a light transmissive characteristic are
 easily calculated based on the areal ratio (%) of the color filter to the
 light transmissive region when well known material is used for forming the
 color filter having a predetermined film thickness.
 FIG. 3 is a schematic plan view showing a structure of a modification of
 the embodiment illustrated in FIG. 1A to 1C. Materials that have well
 known characteristics are selected for color filters 3R, 3G and 3B formed
 on the light transmissive region. An occupying area of each color filter
 within the respective light transmissive region is controlled to get the
 desired color reproducibility and the light transmissivity. The occupying
 area of the color filters 3R, 3G and 3B differ from each other. It is
 possible to control the light transmissivity and the color reproducibility
 by adjusting the area having no color filter within each light
 transmissive region for each color filter.
 FIGS. 4A to 4E are graphs explaining functions of the embodiment shown in
 FIGS. 1A to 1C and 3. FIGS. 4A and 4C are chromaticity coordinates graphs
 which are plots of chromaticity coordinates of three primary colors and
 plots of chromaticity coordinates illustrating the possible color
 reproducibility of the color filter substrate as a whole. FIGS. 4B and 4D
 are graphs illustrating the visible light transmissivity. FIGS. 4A and 4B
 illustrate characteristics of the region having the color filters, and
 FIGS. 4C and 4D illustrate characteristics of whole pixel including three
 primary colors.
 For evaluating the characteristics, three kinds of samples are examined.
 Sample S0 is a sample device according to the conventional technique
 having the color filters all over the surface of the light transmissive
 region, and the film thickness of the color filters is thinned to increase
 the light transmissivity. Sample S1 is a sample device according to the
 embodiment of this invention having the color filters only on a part of
 the light transmissive region. Sample S2 is a sample device having the
 color filters only on a part of the light transmissive region according to
 the embodiment of the invention and the film thickness of the color
 filters is further thinned, in the same way as the sample S0, to increase
 the light transmissivity. FIG. 4E is a table illustrating conditions and
 characteristics of each sample together.
 "The expression colored resin part above openings" in the table refers to
 the region having the color filters. Numerical values under the visible
 transmissivity Y, the chromaticity coordinates x and y are measured
 values. The color filters of sample S0 and S2 are the same, and therefore
 yield same numerical values. "The expression as a CF substrate" shows a
 characteristic of the light transmissive regions including the regions
 having the color filters and the regions without color filters. Areal
 ratios of the regions with the color filters to the light transmissive
 area are shown in percentage (%).
 The sample S0 according to the conventional technique has the color filters
 all over the light transmissive region, and so the characteristic of the
 colored resin part above the openings and the characteristic as the CF
 substrate are the same. On the other hand, because the samples S1 and S2
 both comprise the region not having the color filters, they have the
 increased characteristic in the transmissivity Y as the CF substrates,
 compared to the characteristic of the colored resin part, and also the
 characteristic in the chromaticity coordinates x and y changes. Here, the
 optical characteristics of the samples S1 and S2 as the CF substrates are
 calculated by simulation.
 FIG. 4A is a graph showing the chromaticity coordinates on the color
 filters of each sample. The samples S0 and S2 have the same chromaticity
 coordinates because they use the same material as the color filters. The
 sample S1 has the outer plot on the chromaticity coordinates than that of
 the sample S0 by using the color filters having the better color
 selectivity. Therefore, the sample S1 has the best color reproducibility
 on the color filters.
 As shown in FIG. 4B, in the visible light transmissivity, the sample S1
 that has the better color reproducibility has the lower light
 transmissivity than the sample S0 and S2 that have the thinner color
 filter thickness.
 FIG. 4C is a graph showing the chromaticity coordinates of each light
 transmissive region as a whole. In the sample S1 and S2, because there are
 the regions having the color filters on the light transmissive regions and
 the regions having no color filter, the characteristics of the light
 transmissive regions as a whole are different from those of the light
 transmissive regions having the color filters.
 By adjusting the areal ratio of the region having no color filter within
 the light transmissive region, the sample S1 is selected to have the same
 chromaticity coordinates as the sample S0 having the color filters all
 over the surface of the light transmissive region according to the
 conventional technique. Therefore, the chromaticity coordinates of the
 samples S0 and S1 are the same.
 In the sample S2, the material used as the color filter is similar to that
 in the sample S0, and the area having the color filters is limited to 20%
 of the light transmissive region. Thereby the color reproducibility is
 lowered compared to the case where the color filters are formed all over
 the light transmissive region.
 FIG. 4D is a graph showing the visual light transmissivity. By adjusting
 the size of the area having no color filters, the sample S1 is adjusted to
 have the equivalent visual transmissivity to the sample S0 which has the
 color filters all over the light transmissive regions. The sample S2 has
 the same color filters as the sample S0 and has a wide area having no
 color filters over the light transmissive region. The visual light
 transmissivity is improved by adjusting the size of the area having no
 color filters.
 Thin color filters that are hard to be produced may be needed to brighten
 an LCD by thinning film thickness of the color filters. There is no
 technical difficulty in this embodiment to brighten an LCD by making the
 occupying area of the color filter small.
 FIGS. 5A to 5G are plan views showing examples of configurations of the
 color filters over the light transmissive region. Relationship between
 opening area OA of the black matrix and regions CF where the color filters
 are configured is shown schematically in the figures.
 As shown in FIG. 5A, pluralities of the color filter regions CF are
 configured to form transverse stripes within each light transmissive
 region. Each color filter region CF is configured abreast in a
 longitudinal direction and has the larger size than a transverse size of
 the opening area (a light transmissive region) OA of the black matrix, and
 so extends onto the black matrix BM.
 FIG. 5B shows a structure in which the color filter regions CF extend
 inward from the outside of the opening area OA of the black matrix in a
 predetermined direction. For example, in case that 90% of the light
 transmissive region is covered by the color filters, certain level of
 technique is needed to configure the whole area having the color filters
 inside the openings OA. Forming the color filter regions from the outside
 (right-hand side) of each light transmissive region to an intermediate
 position (predetermined point in the transverse direction) of the light
 transmissive region, as shown in this example of a structure, decrease a
 precision requirement of forming the color filters CF because the precise
 placement of the color filters CF is required only at one side (left-hand
 side) in a transverse position.
 By making a study of the relationship between the edges of the color
 filters which are long in the longitudinal direction and are adjacent to
 each other in the transverse direction, it is seen that the first color
 filter CF extends to the outside of the light transmissive region and
 extends onto the BM, but the second color filter CF has the edge drawn
 inside the light transmissive region. Therefore, the risk that the
 adjacent color filter regions CF on the light transmissive region OA might
 overlap each other on the BM is decreases.
 FIGS. 5C and 5D are examples of structures in which contiguous single-unit
 color filter regions CF are formed. In FIG. 5C, the color filter regions
 CF each being formed inside a light transmissive region OA are shaped
 almost similar to the shape of the light transmissive region OA.
 FIG. 5D shows a case that the regions CF where the color filters are formed
 are shaped to be a rectangular region disposed at the center of the light
 transmissive region. As shown in FIGS. 5C and 5D, by separating the color
 filter CF from the edge of adjacent color filter on the light transmissive
 region at a distance larger than a positioning error, the light
 transmissivity will not be affected by the positioning error.
 FIGS. 5E, 5F and 5G show cases where the plurality of the regions where the
 color filters are formed are configured inside each light transmissive
 region OA. As shown in FIG. 5E, six color filter regions are configured in
 each light transmissive region OA.
 In FIG. 5F, the number of the color filter regions configured in each light
 transmissive region is decreased to three regions.
 FIG. 5G shows an example in which regions where the color filters are
 configured are divided into sub areas in a matrix shape within each light
 transmissive region, and the color filters are configured at the sub
 areas.
 In FIG. 5G, the regions where the color filters are configured are formed
 in the matrix shape of the plurality of rows and columns.
 Visibility when an area of pixels is wider can be increased by increasing
 the number of the color filter regions configured in each light
 transmissive region and dispersing the color filter regions configured in
 each light transmissive region.
 FIGS. 6A to 6C are schematic cross-sectional views of the other example of
 a structure of an LCD device according to the embodiments of this
 invention.
 In FIG. 6A, a black matrix BM is formed with a resin. Therefore, it is
 possible to make the height (film thickness) of the black matrix similar
 to that of the color filter CF. For example, with an adoption of the
 configurations shown in FIGS. 5C to 5G, the black matrix is formed with
 opaque insulating organic resin layers and is configured adjacent to the
 color filters CF.
 Because both of the black matrix BM and the color filters CF are formed
 with an organic material and have the equivalent film thickness,
 difference in the film thickness at the surface of the substrate is
 decreased. By covering the black matrix BM 2 and the color filters CF 3,
 an ITO layer 22 as a transparent electrode 5 is formed on the substrate.
 An orientation film 4 is formed on the surface of the ITO layer 22. By
 using a resin layer having the equivalent thickness to the CF layer 3 for
 the BM layer 2, unevenness of the surface of the substrate after the color
 filters are formed can be lowered.
 FIG. 6B shows a structure of a device formed by the following process. A
 black matrix 2 is formed with metal such as Cr and the like on a glass
 substrate 1. Then, after color filters 3 are formed with a colored resin,
 transparent electrodes 5 are formed by being placed onto the black matrix
 2 all over the surface of the substrate. The black matrix is formed with
 metal and has a high electroconductivity. The transparent electrodes are
 formed with ITO or the like, and thereby have the lower
 electroconductivity than metal. By electrically connecting the black
 matrix 2 and the transparent electrodes 5, effective resistance of the
 transparent electrodes 5 formed with ITO or the like can be lowered.
 FIG. 6C shows a case of forming a planarizing layer 4 at first instead of
 forming it over the color filters. In the case, the planarizing layer 4 is
 formed at first, reentrant parts are formed thereon, and therein color
 filters 3 are formed as being embedded The surfaces of the color filters 3
 and the planarizing layer 4 are formed to have a flush surface. Etching
 back and abrading can be employed to form the leveled surface. After the
 formation of the leveled surface, the transparent electrodes and the
 orientation layer are formed similar to the above-mentioned embodiments.
 In the above-mentioned embodiments, are formed the color filters on the
 common electrode substrate forming a transparent electrode all over the
 substrate surface. The color filters can also be formed on a TFT substrate
 on which TFT are formed.
 FIGS. 7A and 7B show a case where the color filters are formed on a TFT
 substrate. FIG. 7A is a cross-sectional view of an LCD, and FIG. 7B is a
 plan view of a structure of one pixel in the TFT substrate.
 A TFT substrate 20a is formed by the following process. After an SiO.sub.2
 film is formed on the surface of a glass substrate 11, gate electrodes 13
 are formed with metal such as Cr or the like. A gate insulating film 15 is
 formed to cover the gate electrodes 13. The gate insulating film 15 can be
 formed with, for example, an SiO.sub.2 film, an SiN film or the like.
 Semiconductor layers of amorphous silicon (a-Si) or poly-crystalline
 silicon (poly-Si) are formed on the gate insulating film to form active
 layers 17 by patterning.
 At both portions of each active layer 17, a drain electrode 18D and a
 source electrode 18S are formed by depositing an Si layer having a high
 impurity concentration and a Ti/Al/Ti layer or the like. After that, the
 surface of the substrate is covered by an inter-layer insulating film 21.
 The inter-layer insulating film 21 can be formed, for example, with
 SiO.sub.2, SiN or the like.
 On the inter-layer insulating film 21, color filters 3 are configured.
 Then, a planarizing film 25 is formed thereon. To form transparent
 electrodes 22, contact halls are bored through the planarizing film 25 and
 the inter-layer insulating layer 21. After patterning of the transparent
 electrodes 22, an orientation film 23 is formed on the surface and an
 orientation treatment is done thereon.
 A common electrode substrate 10a opposing to the TFT substrate is formed by
 forming a common electrode 5 and an orientation film 6 on the surface of
 the glass substrate 1 and performing the orientation treatment to the
 orientation film 6. The common electrode substrate 10a has neither a black
 matrix nor a color filter and so it has a very simple structure. In such a
 case, the pixel electrodes (transparent electrodes), except the part
 overlapped with the source electrode, demarcate the light transmissive
 regions which are the unit display regions. Moreover, a black matrix as
 shown in FIG. 1B may be formed on the common electrode substrate 10a.
 A polarizer P1 is formed on the outer surface of the common electrode
 substrate 10a, and another polarizer P2 is formed on the outer surface of
 the TFT substrate 20a.
 FIG. 7B is a plan view of one light transmissive region showing a
 configuration of a TFT, color filters and a transparent electrode. The
 drawing also shows a storing capacity SC configured to overlap the lower
 side of the transparent electrode 22.
 By the way, the color filter and the TFT can be overlapped, and the contact
 hall can be bored through the color filter 3.
 FIG. 7C is a plan view of the configuration in that way. The color filter 3
 is overlapped with a part of the TFT, and the contact hall CH is bored
 through the color filter. In addition, in this configuration, the device
 is a top-gate type in which a gate electrode is configured on an active
 layer.
 Although a transparent-type LCD is described in the above-mentioned
 embodiments, same configurations can be applied to a reflective-type LCD.
 FIGS. 8A to 8D are schematic cross-sectional views showing a configuration
 of a reflective-type LCD according to the other embodiment of this
 invention.
 FIG. 8A shows basic configuration of the reflective-type LCD In FIG. 8A, a
 linear polarizer 31, a liquid crystal display device 33 and a reflector 35
 are stacked. Light is first irradiated to the linear polarizer 31 and then
 to a liquid crystal layer of the liquid crystal display device 33. The
 liquid crystal layer is designed to perform the function of a .lambda./4
 plate. By transmitting through the .lambda./4 plate, linear polarized
 light is converted into circular polarized light. Moreover, if the liquid
 crystal display device is turned either on or off, the liquid crystal
 layer looses its function of the .lambda./4 plate, and thereby incident
 linear polarized light exits as linear polarized light.
 The reflected light is reflected by the reflector 35 and irradiated into
 the linear polarizer 31 through the liquid crystal display device 33
 again. In a case that circular polarized light irradiates onto the liquid
 crystal display device 33, the liquid crystal layer again performs the
 function of the .lambda./4 plate. Thereby circular polarized light becomes
 linear polarized light of different polarizing direction from incident
 linear polarized light at 90 degree and is cut by the linear polarizer 31.
 In a case where linear polarized light irradiates onto the liquid crystal
 layer, because the liquid crystal layer does not have the function of the
 .lambda./4 plate, the linear polarized light transmits through the linear
 polarizer 31.
 FIG. 8B shows a modified example of the reflective-type LCD. In this
 configuration, a .lambda./4 plate 32 is configured between a linear
 polarizer 31 and a liquid crystal display device 33 as an optical
 compensator. Therefore, linearly polarized light transmitted through the
 linear polarizer 31 is converted to circularly polarized light by passing
 through the .lambda./4 plate 32. The liquid crystal layer of the liquid
 crystal display device 33 functions as a .lambda./4 plate or a light
 transmissive plate, and thereby incident light exits after being converted
 into either linear polarized light or circular polarized light. Either of
 linear polarized or circular polarized light which is reflected by the
 reflector 35 changes into either of linear polarized or circular polarized
 light by transmitting through the liquid crystal display device 33. Then,
 it changes to linear polarized light by transmitting through the
 .lambda./4 plate 32, and transmits through the polarizer 31 or is blocked
 by the polarizer 31.
 As a liquid crystal display device 33 shown in FIGS. 8A and 8B, an
 equivalent configuration to the above-mentioned embodiments can be used.
 More particularly, it is possible to use the configuration in which the
 polarizers P1 and P2 are taken away and the thickness of the liquid
 crystal layer is adjusted to function as the .lambda./4 plate. In
 addition, the liquid crystal display device can include the reflector 35
 therein.
 FIG. 8C shows an example of the configuration of the TFT substrate
 including the reflector 35 therein. Description will be made mainly on
 different portions of the TFT substrate from those of the liquid crystal
 display device illustrated in FIG. 1C.
 One of the source/drain electrodes 18 formed on each active layer 17 is
 extended to the whole surface of the light transmissive region. These
 electrode layers 18 function as reflectors. After color filters 3 are
 formed on the reflectors 18, an interlayer insulating film 37 is formed.
 Contact holes are bored through the interlayer insulating film 37 and the
 color filters 3, and thereon a transparent electrode layer 22 is formed
 and connected to the respective reflection electrodes 18. The transparent
 electrode layer 22 is patterned to form pixel electrodes. By this
 configuration, light incident from the upper side of the drawing transmits
 through the transparent electrode 22, the interlayer insulating film 37
 and the color filter 3, and then returns to the upper side by being
 reflected at the reflector electrode 18.
 It is preferable that a reflection-type LCD comprises a light diffusing
 mechanism. FIG. 8D shows an example of color filter formed ruggedly on a
 surface. By forming a rugged distribution on the surface, light
 transmitting through the CF is refracted. By these refractions, the light
 diffusing mechanism is obtained.
 This invention has been described in connection with the preferred
 embodiments. The invention is not limited only to the above embodiments.
 It will be apparent to those skilled in the art that various
 modifications, improvements, combinations and the like can be made.