Color liquid crystal display unit

Abstract: A color liquid crystal display unit (D) comprises two liquid crystal cells (1-4, 1-5) formed by three glass substrates (1-1, 1-2, 1-3), a neutral polarizer (1-37) and color polarizer layers associated to each cell. Each color polarizer layer consists of at least two color polarizers with different absorption characteristics and absorption axes crossing at right angles. On substrate (1-2) there are the color polarizers (1-6, 1-7, 1-8) corresponding to the colors blue, red and green and (1-9, 1-10, 1-11) corresponding to red, green and blue in this sequence. Accordingly on substrate (1-3) there are the color polarizers (1-12, 1-13, 1-14) corresponding to the colors yellow, cyanogen and magenta and (1-15, 1-16, 1-17) corresponding to cyanogen, magenta and yellow, the color polarizers of the second all being complementary to the color polarizers of the first cell.

Description: Various types of color display units using liquid crystals have been presented. Among them, color liquid crystal display units which form a color filter layer comprising the inside surface of a liquid crystal cell. The characteristics of red, green and blue micropatterns are such that the cell structure is relatively simple and full color display is possible. This invention relates to improvements of color liquid crystal display units which have red, green and blue micropatterns and enable full color display. A former color liquid display unit Da is, as shown in Fig. 21, composed of a relief pattern comprising gelatin, glue or casein combining color filters 6-9a, 6-10a, and 6-11a dyed to red, green and blue, a twisted nematic liquid crystal layer 6-36a, and 2 photolithography type neutral polarizers 6-37a and 6-37b. Another former color liquid crystal display unit Dc is, as shown in Fig. 22, composed by combining color polarizers 6-9c, 6-10c, and 6-11c in which dichromatic dyes are lined up in one direction and a neutral polarizer 6-37c (see patent publication gazette No. SHO 58-7177 and 58-17420). In the color liquid crystal display unit Da, usually two neutral polarizers 6-37a and 6-37b are positioned so that their directions of polarization (arrow Fa and Fb) are in parallel, black is displayed when no voltage is applied to the transparent electrodes 6-24a, 6-18a, 6-19a, and 6-20a, and when voltage is applied, liquid crystal molecules rise in the direction of the electric field to display the colors of the color filters themselves. Therefore, by selecting the voltage to be applied to each picture element of red, green and blue independently and freely, the desired colors can be displayed on the black base. However, there was a problem in this color liquid crystal display unit Da that only one-third can contribute to the display in case of single-color display of red, green or red and the entire display is dark. In order to solve this problem, a light source may be placed on the back side for high contrast brighter display. This is undesirable, however, in that the general advantages of liquid crystal display units such as low power consumption and thinness are reduced because of the light source to be arranged on the back side. The problem with the color liquid crystal display unit Dc is that only one-third can contribute to the display in the case of single-color display of red, green or blue, as in the above color liquid crystal display unit Da. In addition, display in black is impossible. When there is no electric field, the direction of polarization of the linear polarization agrees with the absorption axis direction of the colour polarizers 6-9c, 6-10c, and 6-11c and they are seen as red, green and blue colours. When an electric field is applied, the linear polarization is not absorbed by the colour polarizers 6-9c, 6-10c, or 6-11c, and they are seen as colourless. In the colour liquid crystal unit DC, colours are displayed in white or no colour and therefore the entire display is brighter but, on the other hand, the display contrast is inferior. EP-A-0 127 374 describes a liquid crystal device having two cells, the first of which operates as a shutter to selectively pass incident light and the second of which provides a two layer colour polarizing plate. Voltages are selectively applied to the liquid crystal layer in the second cell in order to align the incoming light to be coloured by either layer of the colour polarizing plate. This invention was made in light of the above situation to provide a colour liquid crystal display unit with expanded display area, bright display, high display contrast, low power consumption and thinness. In accordance with a first aspect of this invention there is provided a colour liquid crystal display device having a plurality of picture elements each comprising a respective plurality of colour segments and comprising: first and second liquid crystal cells sharing a common substrate interposed between respective liquid crystal layers and each having a further substrate disposed on the other side of its liquid crystal layer to the common substrate, each of the display cells being provided with means for providing a predetermined voltage across the liquid crystal layer at areas corresponding to respective colour segments, the respective colour segments of the first and second cells being in register; a neutral polarizer disposed on the light incident face of one of the first and second cells; and first and second colour polarizers disposed between the outermost substrate and liquid crystal layer of the cell remote from neutral polarizer, the first and second colour polarizers having respectively orthogonal polarization axes one of which is parallel to the polarization axis of the neutral polarizer and having respectively different colour absorption characteristics corresponding to respective colours at regions in register, characterised in that, third and fourth colour polarizers are disposed between the liquid crystal layer of the cell closest to the neutral polarizer and the common substrate, the third and fourth colour polarizers having respectively orthogonal axes of polarization, one of which is parallel to the polarization axis of the neutral polarizer, regions of the third colour polarizer having colour absorption characteristics corresponding to a colour complementary to the colour corresponding to the absorption characteristics of regions of the fourth colour polarizer with which it is in register, and in that said respectively different colour absorption characteristics of the first and second colour polarizers comprise colour absorption characteristics corresponding to complementary colours. In accordance with a second aspect of the invention there is provided a colour liquid crystal display device having a plurality of picture elements each comprising a respective plurality of colour segments and comprising: first and second liquid crystal cells sharing a common substrate interposed between respective liquid crystal layers and each having a further substrate disposed on the other side of its liquid crystal layer to the common substrate, each of the display cells being provided with means for providing a predetermined voltage across the liquid crystal layer at areas corresponding to respective colour segments, the respective colour segments of the first and second cells being in register; a neutral polarizer disposed on the light incident face of one of the first and second cells; and first and second colour polarizers disposed between the outermost substrate and liquid crystal layer of the cell remote from neutral polarizer, the first and second colour polarizers having respectively orthogonal polarization axes one of which is parallel to the polarization axis of the neutral polarizer and having respectively different colour absorption characteristics corresponding to respective colours at regions in register, characterised in that, third and fourth colour polarizers are disposed between the liquid crystal layer of the cell closest to the neutral polarizer and the common substrate, the third and fourth polarizers having respectively orthogonal axes of polarization, one of which is parallel to the polarization axis of the neutral polarizer, and having respectively different absorption characteristics at regions in register, each of the first, second, third and fourth colour polarizers comprising a plurality of said regions having respective colour absorption characteristics corresponding to each picture element, the regions of the third and fourth colour polarizers having respective absorption characteristics corresponding to colours complementary to the colours corresponding to the absorption characteristics of the regions in register therewith in respective ones of the first and second colour polarizers. This invention relates to a colour liquid crystal display unit which can selectively display either one of the colour polarizers laid upon one another or black. Referring to the detailed composition, this is a colour liquid display unit in which at least 2 colour polarizers with different absorption characteristics and absorption axes crossing at right angles to each other are arranged so as to lie upon each other at corresponding positions on each substrate interposing the first and second liquid crystal layers respectively arranged so as to lie upon each other to rotate the direction of polarization of the incidence polarized light selectively by 90° in response to the application of voltage; a neutral polarizer with a direction of polarization in parallel with, or crossing the above absorption axis direction on the light incidence or outgoing side is arranged; and the directions of the absorption axes of the above color polarizers arranged so as to correspond to each other on the upper and lower layers are in almost the same direction. This invention is a color liquid display unit comprising a first liquid crystal layer using the twisted nematic mode to selectively set up such conditions where the direction of polarization of the incident polarized light is rotated by 90° and such conditions where the incident polarized light is allowed to pass through as it is when voltage is applied or not applied. A second liquid crystal layer making use of the guest host mode to selectively set up such conditions so that the incident polarized light is absorbed by dichromatic dye added to the liquid crystal and such conditions where the incident polarized light is allowed to pass through as it is; circuit boards to interpose the said first and second liquid crystal layers respectively; two color polarizers laid upon each other on the circuit board on one side interposing the said first liquid crystal layer so that the absorption spectrum is different from each other and the directions of the absorption axes cross at right angles; and a neutral polarizer the direction of polarization which is in parallel with the direction of the absorption axis of either one of the said color polarizers. According to this invention, 2/3 or 3/3 of picture elements can contribute to display in case of single color display and, in addition, black display is possible. As a result, the display is bright and color display with excellent display contrast can be realized. By using the guest host mode, color liquid crystal display with less reduction of the display contrast can be realized even when viewed in a wide range. The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: Fig. 1 is an explanatory drawing of the configuration showing an embodiment of this invention, Figs. 2 through 4 are explanatory drawings of the configuration showing the operation of the embodiment. Fig. 9 is a sectional view showing the structure of a liquid crystal display cell of an embodiment according to this invention. Figs. 10 through 12 are explanatory drawings of the operation of the liquid crystal display cell shown in Fig. 9; Fig. 10 shows black display, Fig. 11 red display, and Fig. 12 white display. Fig. 5 is a block diagram of a former color liquid crystal display cell using a color filter. Fig. 13 is a sectional view showing the cell structure of the embodiment according to this invention, Figs. 14 through 16 are explanatory drawings of the operation of the same embodiment, Fig. 14 shows the display condition of black display, Fig. 15 red single color display, and Fig. 16 white display condition. The numerals 4-17 show a liquid crystal molecule, 4-11, 4-16 1 and 4-16 2 are glass substrate, 4-22, 4-23, and 4-24 are cyanogen, magenta, and yellow color polarizers, 4-19, 4-20, and 4-21 are red, green, and blue color polarizers, and R, G and B show red, green and blue color light. Fig. 17 is a sectional view showing the cell structure of the embodiment according to this invention, Figs. 18 through 20 are explanatory drawings of the operation according to this invention. Fig. 18 shows black display, Fig. 19 red single color display, and Fig. 20 white display. Fig. 21 shows a cell structure of a former color liquid crystal display unit using a color filter, and Fig. 22 shows a cell structure of a former color liquid crystal display unit using a color polarizer. Numerals 5-7 shows liquid crystal, 5-11, 5-16 1, and 5-16 2 glass substrate, 5-17 liquid crystal, 5-18 neutral polarizer, 5-19 color polarizer (cyanogen), 5-20 color polarizer (red), 5-22 color polarizer (green), 5-21 2 electrode, 5-24 1 electrode, and R, G and B show the red, green and blue color light. [Embodiment 1] This invention will be described below in detail according to the embodiment as shown in Figs. 1 to 4 but not limited to this one. Fig. 1 shows the composition of the color liquid crystal display unit D. Two cells 1-4 and 1-5 are formed by glass substrates 1-1 and 1-2, and 1-2 and 1-3 arranged in parallel. Blue, red and green color polarizers 1-6, 1-7, and 1-8 are laid upon one another respectively on the glass substrate 1-2. The direction of the absorption axes of the color polarizers 1-6, 1-7, and 1-8 is shown by arrow A. The color polarizers 1-6, 1-7, and 1-8 are formed by applying single-shaft drawn polyvinyl alcohol film (not illustrated) onto the glass substrate 1-2 in the direction of arrow A and dying using blue, red and green dichromatic dyes respectively to specified patterns. The second layer color polarizers 1-9, 1-10, and 1-11 which are red, green and blue respectively have been laid upon one another on the color polarizers 1-6, 1-7, and 1-8. The absorption axis direction of the color polarizers 1-9, 1-10, and 1-11 is in the direction of arrow B, crossing the direction of the absorption axis of the color polarizers 1-6, 1-7, and 1-8 at right angles. The color polarisers 1-9, 1-10, and 1-11 are formed by applying one-shaft drawn polyvinyl alcohol film (not illustrated) onto the color polarizers 1-6, 1-7, and 1-8 in the direction of arrow B and dying to specified patterns using red, green and blue --- dichromatic dyes respectively. At the positions on the glass substrate 1-3 corresponding to the color polarizers 1-6, 1-7, and 1-8, color polarizers 1-12, 1-13, and 1-14 of yellow, cyanogen, and magenta which are complementary colors respectively of blue, red and green which are the colors of the color polarizers 1-6, 1-7, and 1-8 are laid upon each other. Arrow C shows the direction of absorption of the color polarizers 1-12, 1-13, and 1-14 which is the same as that of the color polarizers 1-6, 1-7, and 1-8. The color polarizers 1-12, 1-13, and 1-14 are formed by attaching one-shaft drawn polyvinyl film (not illustrated) to the glass substrate 1-3 in the direction of arrow C and dying with the specified pattern with yellow, cyanogen and magenta respectively. On the color polarizers 1-12, 1-13, and 1-14, the second layer color polarizers 1-15, 1-16, and 1-17 of cyanogen, magenta, and yellow, which are complementary colors of red, green and blue which are colors of the color polarizers 1-9, 1-10, and 1-11 respectively, are laid upon each other. The direction of the absorption axis of the color polarizers 1-15, 1-16, and 1-17 is in the direction of arrow E crossing the direction of the absorption axis of the color polarizers 1-12, 1-13, and 1-14 at right angles. The color polarizers 1-15, 1-16, and 1-17 are formed by attaching single-shaft drawn polyvinyl alcohol film (not illustrated) onto the color polarizers 1-12, 1-13, and 1-14 in the direction of arrow E and dying them with specified patterns using cyanogen, magenta, and yellow dyes. The colors of the first layer color polarizers 1-6, 1-7, and 1-8 and the colors of the second layer color polarizers 1-9, 1-10, and 1-11 on the glass substrate 1-2 are shifted by one pitch respectively. In the same way, the colors of the first layer color polarizers 1-12, 1-13, and 1-14 and those of the second layer color polarizers 1-15, 1-16, and 1-17 on the glass substrate 1-3 are shifted by one pitch respectively. 1-18, 1-19, 1-20, and 1-21, 1-22, and 1-23 show transparent electrodes. The transparent electrodes 1-18, 1-19, 1-20, and 1-21, 1-22, and 1-23 are formed by forming transparent conductive film by the low temperature sputtering method and then etching with the specified patterns. 1-24 and 1-25 are transparent electrodes corresponding to transparent electrodes 1-18, 1-19, and 1-20 and 1-21, 1-22, and 1-23 respectively. 1-26, 1-27, 1-28, 1-29, 1-30, and 1-31 show power sources to supply voltage between the transparent electrodes 1-24 and 1-18, 1-19, 1-20, and 1-25 and 1-21, 1-22, and 1-23 respectively. 1-32, 1-33, 1-34, and 1-35 are liquid crystal molecule orientation films. Twisted nematic liquid crystal 1-36 has been injected into the cells 1-4 and 1-5 and sealed with seal (not illustrated). 1-37 shows a neutral polarizer arranged on the incident light side of the cell 1-4. The direction of polarization of the neutral polarizer 1-37 is in the direction of arrow F. That is, the direction of polarization of the neutral polarizer 1-37 crosses the direction of the absorption axis of the color polarizers 1-9, 1-10, 1-11, 1-15, 1-16, and 1-17 with right angles and in parallel with the direction of the absorption axis of the color polarizers 1-6, 1-7, 1-8, 1-12, 1-13, and 1-14. The color liquid crystal display unit D is composed as described above. Its operation is described below. Fig. 2 shows an example of a single color display of red. Voltage is applied between the transparent electrodes 1-19, 1-24, and 1-23 and 1-25. The incident light (arrow L) is polarized in the direction of arrow F with the neutral polarizer 1-37, transmits the glass substrate 1-1, transparent electrode 1-24, and liquid crystal molecule orientation film 1-32 and enters the layer of the liquid crystal 1-36 of the cell 1-4. The light is twisted by 90° only between the transparent electrodes 1-18 and 1-24, and 1-20 and 1-24 and reaches the transparent electrodes 1-18 and 1-20 respectively. The light is not twisted between the transparent electrodes 1-19 and 1-24 and reaches straight the transparent electrode 1-19. The light which reaches the transparent electrode 1-18 enters the color polarizer 1-9 and is colored red. In the lower layer color polarizer 1-6, the direction of polarization of the light which was changed red by the color polarizer 1-9 crosses the direction of the absorption axis of the color polarizer 1-6 at right angles and therefore transmits straight free from any influence. The red light after transmitting the color polarizer 1-6 transmits the glass substrate 1-2, transparent electrode 1-25, and liquid crystal molecule orientation film 1-34, advances to the cell 1-5, is bent by 90° and reaches the transparent electrode 1-21. The light after reaching the transparent electrode 1-21 advances to the color polarizer 1-15. At this time, since the direction of polarization of the light crosses direction of the absorption axis of the color polarizer 1-15 at right angles, the light transmits the color polarizer 1-15 as red without being absorbed by the cyanogen color and advances to the color polarizer 1-12. The direction of polarization of the light advancing to the color polarizer 1-12 is in parallel with the direction of the absorption axis of the color polarizer 1-12. However, since the color polarizer 1-12 yellow, the red light transmits it as red and is seen as red below the glass substrate 1-3. The light after having reached the transparent electrode 1-20 enters the color polarizer 1-11, is colored blue, transmits the color polarizer 1-18 straight and advances to the cell 1-5. Then the light reaches the transparent electrode 1-23 without being twisted since electricity is applied between the transparent electrodes 1-23 and 1-25 and advances to the color polarizer 1-17. In the color polarizer 1-17, since the color polarizer 1-17 is yellow which is a complementary color of blue, the blue light is absorbed and cut off, and therefore seen as black below the glass substrate 1-3. The light after having reached the transparent electrode 1-19 advances to the color polarizers 1-10 and 1-17, colored red by the color polarizer 1-7 with the same direction of polarization and direction of the absorption axis, and advances to the cell 1-5. The red light from the color polarizer 1-7 is twisted by 90° by the cell 1-5 and only transmits the magenta color polarization 1-16 straight. Then, the light transmits the color polarizer 1-13 of the cyanogen, the complementary color of red, straight without being absorbed since the direction of polarization crosses is at a right angle, and is seen as red below the glass substrate 1-13. As described above, in the color liquid crystal display unit D, the red display extends over 2/3 of the display area. The display area is large, the picture is bright and contrast is high. Therefore, no light source is specifically provided and low power consumption and thinness are still ensured. In the example of Fig. 3, red display is observed on the left side, green display in the middle and black display on the right side. Voltage is applied between the transparent electrodes 1-23 and 1-25 and light (arrow L) is applied from above the neutral polarizer 1-37. On the left side, red light is observed under the glass substrate 1-3 as in Fig. 2. In the middle, the light is colored green in the color polarizer 1-10 since its direction of polarization is the same as the direction of the absorption axis of the color polarizer 1-10 and in the color polarizer 1-7, it transmits straight since its direction of polarization is different from the absorption axis direction of the color polarizer 1-7. The light advances to the cell 1-5. The direction of polarization of the light is twisted by 90° by the liquid crystal 1-36 of the cell 1-5. The direction of polarization obtained through twisting crosses the direction of the absorption axis of the color polarizer 1-16 at right angles and therefore the green light transmits the color polarizer 1-16 straight without being absorbed and advances to the color polarizer 1-13. In the color polarizer 1-13, green light transmits it straight since green is not a complementary color for cyanogen and green light is observed below the glass substrate 1-3. On the right side, black display is observed as in Fig. 2. Here, by making the color polarizers 1-9, 1-10, and 1-11 very small, yellow can be observed below the glass substrate 1-3 by adding color stimuli. In Fig. 4, the red display is shown on the left side, green display in the middle and blue display on the right side. While no voltage is applied, light (arrow L) is applied from above the central polarizer 1-37. Red and green are observed respectively below the glass substrate 1-3 as in Fig. 3. On the right side, the light is colored blue in the color polarizer 1-11 since the light direction of polarization and the direction of the absorption axis of the color polarizer 1-11 are the same. The direction of the absorption axis of the color polarizer 1-8 and direction of polarization of the blue light differ, and therefore the blue light is transmitted straight and advances to the cell 1-5, is twisted by 90° by the liquid crystal 1-36 and reaches the color polarizer 1-17. Since the polarization of blue color and color polarizer 1-17 differ from each other, the blue light transmits is straight without it being absorbed by the color polarizer 1-17 and blue light is seen below the glass substrate 1-3. Here by making the color polarizers 1-9, 1-10, and 1-11 very small, white can be seen below the glass substrate 1-3 by additing color stimuli. Additionally, by applying or not applying voltage between the transparent electrodes 1-24 and 1-18, 1-19 and 1-20, and 1-25 and 1-21, 1-22, and 1-23, full color display is possible. [Embodiment 2] Fig. 9 is a sectional view showing the cell structure of the color liquid crystal display unit which is an embodiment of this invention. The liquid crystal cell has a 2-layer structure and opposing clearances of the 3 glass substrates 3-18₁, 3-11, and 3-18₂ are filled with liquid crystal. The cyanogen, magenta and yellow color polarizers 3-12₁, 3-12₂, and 3-12₃ are formed by attaching one-shaft drawn polyvinyl alcohol (PVA) film onto the upper surface of the glass substrate 11 in the middle of the cell and dying them with the specified patterns using cyanogen, magenta, and yellow dichromatic dyes. On these first layer color polarizers 3-12₁, 3-12₂, and 3-12₃, one-shaft drawn PVA film is polymerized and attached. At this time, the PVA film should be attached so that its directions of drawing on the first and second layers cross at right angles. Next, the second layer color polarizers 3-13₁, 3-13₂, and 3-13₃ are formed by dying the second layer PVA film with the specified patterns using red, green and blue dichromatic dyes as in the first layer. Here, the second layer PVA film should be dyed so that the colors of the first layer color polarizers 3-12₁, 3-12₂, and 3-12₃ and the second layer color polarizers 3-13₁, 3-13₂, and 3-13₃ are complementary colors to each other at the areas where they overlap each other. Then, the first layer color polarizers 3-14₁, 3-14₂, and 3-14₃ are formed by attaching the one-shaft drawn PVA film onto the lower grass substrate 3-18₂ and dyeing them with the specified patterns. It is necessary that the color arrangement of the color polarizers formed on the lower glass substrate 3-18₂ should be same combination as and deviated by one pitch from the color arrangement of the first and second layer color polarizers formed on the middle glass substrate 3-11. In this embodiment, colors of the first (and second) layer colour polarizers are arranged as cyanogen (red), magenta (green) and yellow (blue) from the left on the middle glass substrate 3-11 and yellow (blue), cyanogen (red), and magenta (green) on the lower glass substrate 3-18₂. Therefore, on the lower glass substrate 3-18₂, yellow cyanogen and magenta colour polarizers 3-14₁, 3-14₂, and 3-14₃ are formed first, by dyeing the first layer PVA film with the specified patterns using yellow, cyanogen and magenta, dichromatic dyes. Then, one-shaft drawn PVA film is attached to this first layer colour polarizer so as to cross the first layer at right angles, and then the second layer colour polarisers 3-15₁, 3-15₂, and 3-15₃ are formed by dying the second layer PVA film into specified patterns as in the first layer using the blue, red and green dichromatic dyes. In₂0₃ or other transparent conductive film is formed on the obtained colour polarizer 3-13 and 3-15 by low temperature sputtering or other methods and then transparent electrode 3-16₁ is formed by etching them with the specified patterns. After the transparent electrode 3-16₁ is formed, liquid crystal molecule orientation film 3-17₁ is formed in the display region. Opposing the middle glass substrate 11, the upper glass substrate 3-18₁ is arranged and first and second layer liquid crystal layers are packed in the clearance between the glass substrates 3-18₁, 3-11, and 3-18 to form twist oriented liquid crystal cells 3-9 and 3-10. On the inside surface of the glass substrate opposing the color polarizer, the transparent electrode 3-16₂ and liquid crystal molecule orientation film 3-17₂ are formed and placed upon each other. The above glass substrates are attached to each other and sealed, twisted nematic liquid crystal 3-20 is poured, and then the neutral polarizer 3-19 is provided. When the glass substrates are attached to each other, the first and second layer should be laid upon each other so that their display picture elements match each other and the said neutral polarizer 3-19 should be provided on the incidence said of the outside of the 2 liquid crystal cells laid upon each other. In the figure, D is the direction of polarization of the neutral polarizer 3-19. E1, E2, E3 and E4 are directions of the absorption axis of the color polarizers 3-12, 3-13, 3-14, and 3-15. The direction of polarization of the neutral polarizer 3-19 crosses at right angles, or in parallel with the directions of absorption axes of the color polarizers respectively. The operation principle of this embodiment is described below. Fig. 10 is an explanatory drawing of the operation showing a case of black display. The linearly polarized light after passing through the neutral polarizer 3-19 is twisted by 90° in the direction of polarization according to the arrangement of the liquid crystal molecules of the first liquid crystal cell 3-9. It is colored red, green, or blue respectively by the second layer color polarizers 3-13₁, 3-13₂, and 3-13₃ but in the cyanogen, magenta and yellow color polarizers 3-12₁, 3-12₂, and 3-12₃ immediately below it, it is not affected because of the different direction of the absorption axis and direction of polarization of the linear polarization and passes through the first liquid crystal cell 3-9 as red, green and blue color light. In the second liquid crystal cell 3-10, the liquid crystal molecules are oriented vertically and therefore, the light reaches the second layer color polarizer 3-15₁, 3-15₂, and 3-15₃ formed on the glass substrate 3-18 a, without turning in the direction of polarization. Here, since the direction of polarization and direction of the absorption axis of the color polarizer match, red, green, and blue color light is absorbed by the color polarizers 3-15₁, 3-15₂, and 3-15₃, and thus, all the picture elements are observed as black. Then, a case to display red by all picture elements will be described referring to Fig. 11. In the picture element on the left side in Fig. 11, the liquid crystal molecule has been twisted by the first liquid crystal layer 9 and therefore, the light is colored red by the second layer color polarizer 3-13₁, enters the second liquid crystal layer 3-10 as it is, and the direction of polarization is twisted by 90°. In the first layer color polarizer 3-14₃, colors other than yellow (red, green) are absorbed and the red color passes through it as it is. In the middle picture element, since the liquid crystal molecule is vertically arranged, the light is colored magenta by the first layer color polarizer 3-12₂, enters the second liquid crystal layer 10 as it is, and the direction of polarization is twisted by 90°. In the second layer color polarizer 3-15₁, light other than red is cut off and only the red light passes through. In the right side picture element, the liquid crystal molecule is oriented vertically and therefore, the light is colored yellow in the first layer color polarizer 3-12₃, and enters the second liquid crystal layer 3-10 as it is. Here the direction of polarization is unchanged, colors other than magenta (red, blue) are absorbed in the first layer color polarizer 3-14₂, and only the red light passes through. As described above, by changing the arrangement of the liquid crystal molecules and selecting either one of the color polarizers laid upon each other, red display is possible for all the picture elements. Next, display of each red, green and blue of the three picture elements will be described referring to Fig. 12. The liquid crystal molecule is twisted by 90° in the first liquid crystal layer 3-9 and therefore the incident light is colored red, green and blue respectively by the second layer color polarizers 3-13₁, 3-13₂, and 3-13₃ and enters the liquid crystal layer 3-10 as it is. Here, since the liquid crystal molecule is twisted by 90°, the direction of polarization of the light passing through is twisted by 90°. In the second layer color polarizers 3-15₁, 3-15₂, and 3-15₃, since the direction of absorption axis and the direction of polarization of the linear polarization differ, the light passes straight through unabsorbed. The first layer color polarizers 3-14₁, 3-14₂, and 3-14₃ allow yellow (red, green), cyanogen (green, blue), and magenta (blue, red) and therefore, red, green, and blue color lights after passing through the second layer color polarizers pass through the first layer color polarizers straight. When these picture elements are sufficiently small, they are seen by adding color stimuli. In Figs. 10 to 12, the arrow shows the path of the light. The light is colored by the color polarizers shown by black circle. (R), (G), and (B) show red, green and blue lights respectively. [Embodiment 3] An embodiment according to this invention is described in detail below. Fig. 13 is a sectional view showing the cell structure of an embodiment according to this invention. The red and green color polarizers 4-19 and 4-20 are formed by attaching one-shaft drawn polyvinyl alcohol (PVA) onto the one glass substrate 4-11 composing the first liquid crystal layer 4-9 of the liquid crystal cell, and dyeing them with the specified patterns using red and green dichromatic dyes. In this embodiment, 2 picture elements of 3 composing one group are the red color polarizer 4-19 and the remaining 1 picture element is the green color polarizer 4-20. One-shaft drawn PVA film is attached to the first layer color polarizer. At this time, the film should be attached so that the directions of drawing of the first and second layers cross each other at right angles. Then, the second layer color polarizers 4-22 and 4-23 are formed by dying the second layer PVA film with the specified pattern as in the first layer using cyanogen and magenta dichromatic dyes. At this time, the second layer PVA film should be dyed so that the colors of the first and second polarizers are complementary colors to each other. Then, one-shaft drawn PVA film is attached to the other glass substrate 4-16₂ of the second liquid crystal layer 4-10 and dyed with the specified pattern. First, the first layer PVA film is dyed with the specified pattern using green and blow dischromatic dyes to form green and blue color polarizers 4-20 and 4-21. Here, the blue color polarizer 4-21 is made a picture element and the two picture elements are formed to correspond with the red end green picture elements in the above described first liquid crystal layer 4, 9. On that first layer color polarizer, one-shaft drawn PVA film is attached. The second layer PVA film is dyed to a specified pattern as in the first layer using the magenta and yellow dichromatic dyes to form the second layer color polarizers 4-23 and 4-24. After a transparent conductive film is formed on each color polarizer of the said first and second liquid crystal layer by low temperature sputtering or other methods, transparent electrodes 4-25₁, 4-25₂, 4-25₃, 4-28₁, 4-28₂, and 4-28₃ are formed by etching with the specified patterns. Then after a transparent electrode is formed, liquid crystal molecule orientation films 4-27₁ and 4-30₁ are formed respectively. Another substrate opposing the color polarizer in the first and second liquid crystal layer 4-9 and 4-10 is the transparent electrode 4-26 and 4-29 and liquid crystal molecule orientation film 4-27₂ and 4-31₂ formed on the glass substrate. After the above substrates are attached to each other and sealed, twisted nematic liquid crystal is poured. When the first and second liquid crystal layer glass substrates 4-11, 4-16₁, and 4-16₂ are attached to each other, they should be laid upon each other so that their display picture elements match and a neutral polarizer 4-18 is provided on the outside of the liquid crystal layer laid upon each other and on the incident light side. D in the figure is the direction of polarization of the neutral polarizer and E1 and D2 are directions of the first and second layer color polarizer absorption axes of the first liquid crystal layer 4-9, and E3 and E4 are direction of the absorption axis of the first and second layer color polarizers of the second liquid crystal layer 4-10. The direction of polarization of the neutral polarizer 4-18 crosses the direction of the absorption axis of each color polarizer at right angles or in parallel with it. The operation principle of this embodiment is described below. Fig. 14 shows a case of black display. The linearly polarized light after passing through the neutral polarizer 4-18 is colored red and green in the first layer color polarizers 4-19 and 4-20 without altering the direction of polarization since the liquid molecule of the first liquid crystal layer 4-9 is oriented verfically. In the second liquid crystal layer 4-10 also, the liquid crystal molecule is oriented vertically and the light is absorbed by the first green and blue color polarizers 4-20 and 4-21. Therefore, all the picture elements are observed as black. A case to display red by all the picture elements will be described next. As for the left side picture element in Fig. 15, since the liquid crystal molecule of the first liquid crystal layer 4-9 is oriented vertically, the light is colored red by the first layer color polarizer 4-19 because the liquid crystal molecule oriented vertically enters the second liquid crystal layer 4-10 as it is. The liquid crystal molecule is twisted 90° there, the direction of polarization is also twisted 90° and the light is absorbed by the color polarizer 4-23 of the second layer of 90° twisting. However, the red light passes through as it is. For the central picture element, since the liquid crystal molecule of the first liquid crystal layer 4-9 is oriented vertically, the light is colored red by the first layer collar polarizer 4-19, enters the second liquid crystal 4-10 straight, and the direction of polarization is twisted by 90° according to the liquid crystal molecule twisted 90°. The light is absorbed by the second layer yellow color polarizer 4-24 but the red light passes through as it is. For the right side picture element, the liquid crystal molecule is twisted by 90° by the first liquid crystal layer 4-9, and the direction of polarization is also twisted 90°. The light is absorbed by the second layer magenta color polarizer 4-23 and enters the second liquid crystal layer 4-10. The liquid crystal molecule of the second liquid crystal layer is oriented vertically and therefore, the light is absorbed by the second layer yellow color polarizer 4-24 and only the red light passes through. As described above, by changing the orientation of the liquid crystal molecule and selecting either one of the color polarizers laid upon each other, red display is possible for all the picture elements. It is the same for green and blue single color display. Next, display of red, green or blue of the three picture elements is described. As shown in Fig. 16, with respect to the left side picture element, the light is colored red by the first liquid crystal layer 4-9. Other elements than the green one transmit the magenta color polarizer of the second liquid crystal layer 4-10 and the red light passes through it. For the central picture element, the light is colored cyanogen by the first liquid crystal layer. In the second liquid crystal layer, the light is absorbed by the yellow color polarizer 4-24 and only the green light passes through. For the right side picture element, the light is colored magenta by the second layer color polarizer 4-23 of the first liquid crystal layer and only blue light passes through the first layer color polarizer 4-21 of the second liquid crystal layer. By making those picture elements sufficiently small, they are seen as a whole by additing column stimuli. the arrow maks in Figs. 14 to Fig. 16 shows the path of the light. The light is colored various colors by the color polarizers shown by black circles. [Embodiment 4] The embodiment will be described in detail below according to this invention. Fig. 17 is a sectional view showing the cell structure of this invention. The first color polarizer 5-19 is formed by attaching single-shaft drawn polyvinyl alcohol (PVA) film onto one of the glass substrate 5-11 of the liquid crystal cell and dying the entire surface of the PVA film using cyanogen dichromatic dye. Single-shaft drawn PVA film is attached to the first layer color polarizer 5-19. In this case, the films should be attached so that the directions of drawing of the first and second layers crosss each other at right angles. Then the entire surface of the PVA film is dyed using red dichromatic dye to form the second layer color polarizer 5-20. Next, single-shaft drawn PVA film is attached to the other glass substrate 5-16₂ and dyes the PVA film using magenta dichromatic dye to form the first layer color polarizer 5-22. Moreover, single-shaft drawn PVA film is attached to the first layer color polarizer 5-22, the PVA film is dyed using green dichromatic dye to form the second layer color polarizer 5-23. Transparent conductive film is formed on those color polarizers 5-20 and 5-23 by low temperature sputtering or other methods and then transparent electrodes 5-21₁ and 5-24₁ are formed by etching with the specified patterns. After transparent electrode is formed, liquid crystal molecule orientation film 5-25₁ is formed on the transparent electrode 5-21₁ and 5-24₁ in the first and second liquid crystal cell 5-9 and 5-10, another substrate opposing to the color polarizer is the transparent electrodes 5-21₂ and 5-24₂ and liquid crystal molecule orientation film 5-25₂ formed on the glass substrates 5-16₁ and 5-11. After the above substrates are attached to each other and sealed, nematic liquid crystal 5-17 is poured. When the first and second liquid crystal cells 5-9 and 5-10 are sticked together, they are laid upon each other so that their display picture elements agree and one neutral polarizer 5-18 is provided on the incident light side of the 2 layers of liquid crystal sells laid upon each other. In the figure, D indicates the direction of polarization of the neutral polarizer. E1, E2, E3, and E4 are the directions of the absorption axes of the neutral polarizers 5-19, 5-20, 5-22, 5-23 respectively. The directions of polarization of the neutral polarizers cross the directions of absorption axes of the color polarizers at right angles or in parallel with them respectively. The operation principle of this embodiment is described below. Fig. 18 shows a case of black display. In this case, voltage is not applied to the first layer liquid crystal layer 5-9 but only to the second liquid crystal layer 5-10. The linear polarization after passing through the neutral polarizer is twisted 90° in the direction of polarization according to the arrangement of the liquid crystal molecules of the first liquid crystal cell 5-9. It is colored red by the second layer color polarizer 5-20. Since the direction of polarization and direction of absorption axis of the color polarizer cross each other at right angles in the first layer color polarizer 5-19 provided just below it, the light passes through the first liquid crystal cell 5-9 as red color light unaffected. In the second liquid crystal cell 5-10, the liquid crystal molecules are oriented vertically under voltage and the light reaches the second layer color polarizer 5-23 with no rotation of the direction of polarization. Here, since the direction of polarization and the direction of the absorption axis of the color polarizer coincide, the red color light is absorbed in the second layer color polarizer 5-22 and therefore, all the picture elements are observed as black. Next, a case to display red with all the picture elements is described referring to Fig. 19. In this case, no voltage is applied to any of the first and second layer liquid crystal layers 5-9 or 5-10. Since the liquid crystal molecule has been twisted 90° by the first liquid crystal layer 5-9, the light is colored red by the second layer color polarizer 5-20, enters the second liquid crystal layer 5-10 as it is and the direction of polarization is twisted by 90°. Colors other than magenta (red, blue) are absorbed in the second color polarizer 5-22 and the red light passes through as it is. Next, case of display of red, green, or blue of the three picture elements is described. For the left picture element in Fig. 20, since voltage is applied to neither the first nor the second liquid crystal layers, the liquid crystal molecule is twisted by 90° in the first liquid crystal layer 5-9, the light is colored red in the second layer color polarizer 5-19 and enters the second liquid crystal layer 5-10 as it is, and direction of polarization is twisted 90°. In the first layer color polarizer 5-22, colors other than magenta (red, blue) are absorbed but the red light passes through as it is. then, in the central picture element, voltage is applied to the liquid crystal layer of the first layer only. In this case, since the liquid crystal molecule of the first liquid crystal layer 5-9 is oriented vertically, the light is colored by the first layer cyanogen color polarizer 5-19. The light enters the second liquid crystal layer 5-10, the direction of polarization is twisted by 90°, and only the green light passes through the second layer green color polarizer 5-23. Next, for the right side picture element, voltage is applied to both the first and second layer liquid crystal layers. Since the liquid crystal molecule is oriented vertically in the first liquid crystal layer 5-9, the light is colored by the first layer cyanogen (green, blue) color polarizer 5-19. The light enters the second liquid crystal layer 5-10 and reaches the color polarizer without the direction of polarization being turned, the green light is absorbed by the color polarizer 5-22 of the first layer magenta (red, blue) and only the blue light passes through. When these picture elements are sufficiently small and the rate of the color elements proper, they are seen as white by additing color stimuli. In Figs. 18 through 20, the arrow indicates the path of the light and the light is colored various colors by the color polarizers shown by black circles.

Claims: A colour liquid crystal display device having a plurality of picture elements each comprising a respective plurality of colour segments and comprising: first and second liquid crystal cells sharing a common substrate interposed between respective liquid crystal layers and each having a further substrate disposed on the other side of its liquid crystal layer to the common substrate, each of the display cells being provided with means for providing a predetermined voltage across the liquid crystal layer at areas corresponding to respective colour segments, the respective colour segments of the first and second cells being in register; a neutral polarizer disposed on the light incident face of one of the first and second cells; and first and second colour polarizers disposed between the outermost substrate and liquid crystal layer of the cell remote from neutral polarizer, the first and second colour polarizers having respectively orthogonal polarization axes one of which is parallel to the polarization axis of the neutral polarizer and having respectively different colour absorption characteristics corresponding to respective colours at regions in register, characterised in that, third and fourth colour polarizers are disposed between the liquid crystal layer of the cell closest to the neutral polarizer and the common substrate, the third and fourth colour polarizers having respectively orthogonal axes of polarization, one of which is parallel to the polarization axis of the neutral polarizer, regions of the third colour polarizer having colour absorption characteristics corresponding to a colour complementary to the colour corresponding to the absorption characteristics of regions of the fourth colour polarizer with which it is in register. and in that said respectively different colour absorption characteristics of the first and second colour polarizers comprise colour absorption characteristics corresponding to complementary colours. The colour liquid crystal display device of claim 1, wherein said first through fourth colour polarizers each comprises two regions corresponding to each picture element and having respective colour absorption characteristics. The colour liquid crystal display device of claim 1, wherein said first through fourth colour polarizers each comprises three regions corresponding to each picture element and having respective colour absorption characteristics. The colour liquid crystal display device of claim 1, wherein said first through fourth colour polarizers each comprises a single region. A colour liquid crystal display device having a plurality of picture elements each comprising a respective plurality of colour segments and comprising: first and second liquid crystal cells sharing a common substrate interposed between respective liquid crystal layers and each having a further substrate disposed on the other side of its liquid crystal layer to the common substrate, each of the display cells being provided with means for providing a predetermined voltage across the liquid crystal layer at areas corresponding to respective colour segments, the respective colour segments of the first and second cells being in register; a neutral polarizer disposed on the light incident face of one of the first and second cells; and first and second colour polarizers disposed between the outermost substrate and liquid crystal layer of the cell remote from neutral polarizer, the first and second colour polarizers having respectively orthogonal polarization axes one of which is parallel to the polarization axis of the neutral polarizer and having respectively different colour absorption characteristics corresponding to respective colours at regions in register, characterised in that, third and fourth colour polarizers are disposed between the liquid crystal layer of the cell closest to the neutral polarizer and the common substrate, the third and fourth polarizers having respectively orthogonal axes of polarization, one of which is parallel to the polarization axis of the neutral polarizer, and having respectively different absorption characteristics at regions in register, each of the first, second, third and fourth colour polarizers comprising a plurality of said regions having respective colour absorption characteristics corresponding to each picture element, the regions of the third and fourth colour polarizers having respective absorption characteristics corresponding to colours complementary to the colours corresponding to the absorption characteristics of the regions in register therewith in respective ones of the first and second colour polarizers. The colour liquid crystal display device of claim 5, wherein the first and second colour polarizers comprise three said regions having colour absorption characteristics corresponding respectively to red, green and blue and the third and fourth colour polarizers comprise three said regions having colour absorption characteristics corresponding respectively to cyan, magenta and yellow.

Inventors: TAKAMATSU TOSHIAKI, TAKAMATSU, TOSHIAKI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1987
Main classification: G02F1
IPC codes: G02F1