JP4846527B2 - Liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display (LCD).

  In the segment type, dot matrix type, and liquid crystal display elements that combine both, the display color of the area other than the segment or dot used for display (non-display area) can be adjusted to improve display visibility and design. Improvements are being made.

  FIGS. 7A to 7C are schematic exploded perspective views showing an example of the internal configuration of a liquid crystal display element capable of adjusting the color tone of the non-display area.

  Reference is made to FIG. The liquid crystal display element is configured to include an upper substrate 50a and a lower substrate 50b disposed to face each other substantially in parallel, and a liquid crystal layer 55 sandwiched therebetween. The upper substrate 50a and the lower substrate 50b are formed of, for example, flat glass substrates (upper and lower glass substrates 51a and 51b) and transparent conductive materials such as ITO (indium tin oxide) on the opposing surfaces thereof, Electrodes having a pattern (upper and lower transparent electrodes 52a and 52b) and alignment films (upper and lower alignment films 53a and 53b) formed on the respective electrodes are provided. The liquid crystal layer 55 is a twisted nematic liquid crystal layer formed of, for example, nematic liquid crystal having a positive dielectric anisotropy (Δε> 0), and the twist angle determined by the rubbing directions of the upper and lower alignment films 53a and 53b is For example, 90 degrees.

  On the outside of the upper substrate 50a and the lower substrate 50b, a pair of upper and lower polarizing plates 54a and 54b are arranged in a crossed Nicols state along the rubbing direction. The upper and lower polarizing plates 54a and 54b each have a transmission axis in the in-plane direction, and transmit only light polarized in the direction of the transmission axis. With no voltage applied, the polarization direction of the incident light rotates according to the orientation of the liquid crystal molecules and transmits through the polarizing plate to perform normally white display. In FIG. 7A, the direction of the transmission axis is indicated by an arrow.

  A multi-color backlight 56 is disposed outside the lower polarizing plate 54b. The multi-color backlight 56 is a backlight that can emit light of a plurality of colors, and uses, for example, an RGB multi-color LED light source.

  The voltage application means connected between the upper and lower transparent electrodes 52a and 52b applies a voltage to the liquid crystal layer 55, so that the liquid crystal molecules rise from the horizontal direction to the vertical direction. It is not affected by the layer and is shielded by the cross polarizer.

  When the light emitted from the multi-color backlight 56 and passed through the liquid crystal layer 55 is transmitted through the upper polarizing plate 54a, “bright” is displayed by the color of the emitted light, and when the light is blocked by the upper polarizing plate 54a, “ A “dark” display is made.

  In a normally white type liquid crystal display element that displays the display area in black using “dark” display, the color tone of the non-display area can be obtained by using a multi-color backlight that can change the emission color of the backlight. Can be arbitrarily changed.

  Reference is made to FIG. The liquid crystal display element shown in FIG. 7B uses upper and lower color polarizing plates 54c and 54d instead of the upper and lower polarizing plates 54a and 54b when compared with that shown in FIG. 7A. And in that a white backlight 57 is used instead of the multi-color backlight 56.

  The white backlight 57 is configured by using, for example, a cold cathode fluorescent lamp (CCFL). In some cases, an inorganic white LED (light emitting diode), an organic white LED, or the like is used.

  The upper and lower color polarizing plates 54c and 54d are arranged in a crossed Nicols arrangement.

  The upper and lower polarizing plates 54a and 54b in FIG. 7A are neutral gray color polarizing plates, for example, while the upper and lower color polarizing plates 54c and 54d in FIG. 7B are dyed with a dye. It is a color polarizing plate. By transmitting the light emitted from the white backlight 57 through the upper and lower color polarizing plates 54c and 54d, the background color can be set to the color determined by the upper and lower color polarizing plates 54c and 54d. .

  Reference is made to FIG. The liquid crystal display element shown in FIG. 7C is different from that shown in FIG. 7A in that a retardation plate 58 is inserted between the upper polarizing plate 54a and the upper substrate 50a. By inserting the phase difference plate 58, the color tone of the non-display area can be adjusted.

  The color tone of the non-display area can be adjusted by adjusting the thickness of the liquid crystal layer, the twist degree of the liquid crystal molecules, a combination of a polarizing plate and a retardation plate, and the like.

  Note that in the liquid crystal display element shown in FIGS. 7B and 7C, the color of the non-display area cannot be changed after the element is completed.

  FIGS. 8A and 8B are schematic exploded perspective views showing an example of the internal configuration of a liquid crystal display element capable of adjusting the color tone of a dot portion or a segment portion.

  Reference is made to FIG. The liquid crystal display element shown in FIG. 8A is different from that shown in FIG. 7A in that an area color filter 60 and a black mask 59 are disposed between the upper and lower substrates 50a and 50b. Another difference is that a white backlight 57 is used instead of the multi-color backlight 56.

  The area color filter 60 includes, for example, a red part 60r, a green part 60g, a blue part 60b, and a white part 60w. In the illustrated liquid crystal display element, light emitted from the white backlight 57 passes through different color regions (each color portion 60 r, g, b, w) of the area color filter 60, thereby displaying a plurality of colors. It becomes possible.

  The black mask 59 covers the boundary of the color area and is arranged to increase contrast and color purity.

  Reference is made to FIG. The liquid crystal display element shown in FIG. 8B is different from that shown in FIG. 7A in that the upper and lower polarizing plates 54a and 54b are arranged in parallel Nicols. When light emitted from the multi-color backlight 56 is polarized by the lower polarizing plate 54b and rotated in accordance with the alignment state of the liquid crystal molecules when no voltage is applied, the polarization direction of the upper polarizing plate 54a is orthogonal. , Shielded from light. That is, the liquid crystal display element shown in this figure is a normally black type liquid crystal display element using a multi-color backlight. A plurality of colors can be displayed depending on the color of light emitted when a voltage is applied.

  It is difficult to control the display area and the non-display area independently of each other and in any color tone after the liquid crystal display element is manufactured. If it is a full dot matrix liquid crystal display element using a micro color filter, it is possible to make it possible to adjust the color of the non-display area and the display area independently, but the micro color filter The use of increases the cost.

  In particular, in the case of a segment type or a segment and dot composite type liquid crystal display element, low cost is required, so it is preferable not to use a color filter such as a micro color filter. (For example, see Patent Document 1.)

Japanese Patent Laid-Open No. 49-074438

  An object of the present invention is to provide a liquid crystal display element capable of displaying various colors.

According to one aspect of the present invention, a first substrate having a transparent electrode having a predetermined pattern are arranged in parallel the first substrate and substantially, a second substrate having a transparent electrode having a predetermined pattern A display unit provided corresponding to the transparent electrode of the first substrate and the transparent electrode of the second substrate, and a liquid crystal layer formed between the first substrate and the second substrate; The first polarizing plate disposed on the opposite side of the first substrate from the side on which the liquid crystal layer is formed, and the opposite side of the first polarizing plate on the side on which the first substrate is disposed. A front light disposed on the side, and a transmission / reflection plate disposed on the side opposite to the side on which the liquid crystal layer of the second substrate is formed, which transmits or reflects incident light according to the polarization state , Second disposed on the opposite side of the transmission / reflection plate from the side on which the second substrate is disposed. And a polarizing plate, wherein and a backlight disposed on the side opposite to the second of the side where transmission and reflection plates are disposed polarizing plates, the transmission and reflection plate, the first polarizing plate Both the light emitted from the front light and the light emitted from the backlight are reflected by reflecting the light in the polarized state that is transmitted and transmitting the light in the polarized state that is transmitted through the second polarizing plate. A liquid crystal display element that performs display on the front light side using the above light is provided.

  According to the present invention, a liquid crystal display element capable of displaying various colors can be provided.

  FIGS. 1A and 1B are a plan view showing a display unit and a schematic exploded perspective view showing an example of the internal structure of a liquid crystal display device according to an embodiment described in detail with reference to FIG. .

  Reference is made to FIG. The liquid crystal display element is displayed on, for example, a 7-segment display unit 30. The display unit 30 includes display units (each segment) 31 to 37 and a background region 38. Each of the display units 31 to 37 is provided with electrodes that can be driven independently. By selectively applying a voltage to these electrodes, the alignment state of the liquid crystal molecules in the liquid crystal layer corresponding to the electrodes can be changed, and for example, numbers “0” to “9” can be displayed.

  In this specification, for example, a display unit used for displaying numbers is called a display area, and other display units and background areas are called non-display areas. For example, when the number “7” is displayed, the display area means display units 31 to 33, and the non-display area means display units 34 to 37 and the background area 38.

  Reference is made to FIG. The liquid crystal display device according to the embodiment includes an upper substrate 50a and a lower substrate 50b that are arranged to face each other substantially in parallel, and a liquid crystal layer 55 that is sandwiched therebetween. The upper substrate 50a and the lower substrate 50b are, for example, flat glass substrates (upper and lower glass substrates 51a, 51b), electrodes formed on a transparent surface such as ITO on opposite surfaces thereof, and having predetermined patterns ( Upper and lower transparent electrodes 52a, 52b) and alignment films (upper and lower alignment films 53a, 53b) formed on the respective electrodes.

  A pair of upper and lower polarizing plates 54a and 54b are disposed outside the upper substrate 50a and the lower substrate 50b. The upper and lower polarizing plates 54a and 54b are, for example, linearly polarizing plates, circularly polarizing plates, or elliptically polarizing plates. The upper and lower polarizing plates 54a and 54b each have a transmission axis in the in-plane direction, and transmit only light polarized in the direction of the transmission axis. In the case of a circularly polarizing plate and an elliptically polarizing plate, a retardation plate is further provided inside.

  A voltage applying means 68 is connected between the upper transparent electrode 52a and the lower transparent electrode 52b. The voltage applying means 68 can apply an arbitrary voltage between the electrodes 52 a and 52 b to change the alignment state of the liquid crystal molecules in the liquid crystal layer 55.

  A polarized light separating / transmitting / reflecting plate 67 is disposed between the lower substrate 50b and the lower polarizing plate 54b. The polarized light separating / transmitting / reflecting plate 67 transmits or reflects incident light according to its polarization state. As the polarized light separating transmission / reflection plate 67, for example, broadband cholesteric used in D-BEF (brightness enhance film) manufactured by 3M, Inc., brightness enhancement film PCF (polarization conversion film) manufactured by Nitto Denko Corporation, etc. A film can be used.

  A multi-color front light 66 and a multi-color backlight 56 are disposed outside the upper polarizing plate 54a and the lower polarizing plate 54b, respectively. The multi-color front light 66 and the multi-color backlight 56 are lights that can selectively emit light of a plurality of colors. For example, the multi-color front light 66 and the multi-color backlight 56 have RGB multi-color LED light sources on the side, Irradiate toward the liquid crystal layer. As the color light source, an organic LED, an inorganic LED, a CCFL, an FE lamp, or the like can be used. The change of the emitted light color may be realized by a configuration using a plurality of monochromatic light sources having different emission colors, or may be realized by a configuration using a single light source capable of changing the emission color. The multi-color front light 66 transmits light from the liquid crystal layer.

  The multi-color backlight 56 controls display of display areas such as dots and segments. The multi-color front light 66 is used to realize color display in a non-display area. Both lights 56 and 66 may be continuously lit or intermittently lit in response to a cell response.

  In the display of the liquid crystal display element, both the multi-color front light 66 and the multi-color backlight 56 are turned on, and operations for displaying these and the display unit of the liquid crystal cell (electrical switching of the liquid crystal cell) Do not need to be synchronized.

  The liquid crystal cell composed of the upper and lower substrates 50 a and 50 b, the liquid crystal layer 55, the upper and lower polarizing plates 54 a and 54 b, and the polarization separation / transmission / reflection plate 67 is light emitted from the multicolor backlight 56. On the other hand, it is a normally black type liquid crystal cell.

  In such a liquid crystal display element, by controlling the emission colors of the multi-color front light 66 and the multi-color backlight 56, the display area and the non-display area can be expressed separately with different color tones.

  Specific examples will be described below. In the liquid crystal display elements according to the first to third embodiments, D-BEF manufactured by 3M Co., Ltd. was used as the polarization separation transmission / reflection plate 67 in FIG. The D-BEF has a reflection axis in the in-plane direction and reflects light polarized in the reflection axis direction. In the liquid crystal display elements according to the fourth and fifth embodiments, the broadband cholesteric film used in the brightness enhancement film PCF manufactured by Nitto Denko Corporation is used as the polarization separation transmission / reflection plate 67 in FIG. did. The broadband cholesteric film reflects, for example, right circularly polarized light and transmits left circularly polarized light. Some broadband cholesteric films do the reverse.

  FIG. 2 is a schematic exploded perspective view showing an example of the internal configuration of the liquid crystal display element according to the first embodiment.

  The liquid crystal layer 55 is formed using a liquid crystal material having a negative dielectric anisotropy (Δε <0) to form a vertical alignment type liquid crystal display element. This figure shows the alignment state of liquid crystal molecules when no voltage is applied. Further, linearly polarizing plates were used as the upper and lower polarizing plates 54a and 54b. In the figure, the directions of the transmission axes of the upper and lower polarizing plates 54a and 54b are indicated by arrows.

  The upper and lower polarizing plates 54a and 54b are arranged in a crossed Nicols arrangement. Furthermore, both were arranged so that the reflection axis of the D-BEF 69 and the transmission axis of the lower polarizing plate 54b were orthogonal to each other (so that light from the lower side transmitted through the D-BEF 69). The liquid crystal cell composed of the upper and lower substrates 50a and 50b, the liquid crystal layer 55, the upper and lower polarizing plates 54a and 54b, and the D-BEF 69 allows light emitted from the multicolor backlight 56 to be applied with no voltage applied. Thus, the liquid crystal cell is a normally black liquid crystal cell that transmits light without changing its polarization state and shields it with the upper polarizing plate 54a.

  The operation of the liquid crystal display device according to the first embodiment will be described. As described above, the liquid crystal molecules of the liquid crystal display element according to the first embodiment are aligned substantially perpendicularly to the upper and lower substrates 50a and 50b when no voltage is applied. For this reason, the light incident on the liquid crystal layer is transmitted through the liquid crystal layer without changing the polarization direction.

  On the other hand, when a voltage is applied, the alignment state of the liquid crystal molecules in the non-display area is not different from that when no voltage is applied. In contrast, the light that is inclined toward the in-plane direction of 45 ° and incident on the liquid crystal layer is given a birefringence effect. The liquid crystal layer has the same effect as the half-wave plate, and incident light is emitted from the liquid crystal layer with the polarization direction changed by 90 °.

  First, the operation when no voltage is applied will be described.

  The light emitted from the multicolor front light 66 enters the liquid crystal layer 55 as linearly polarized light having a polarization direction in the transmission axis direction of the upper polarizing plate 54a. The light passes through the liquid crystal layer 55 without changing the polarization state, and enters the D-BEF 69. The reflection axis direction of the D-BEF 69 is parallel to the transmission axis direction of the upper polarizing plate 54a. For this reason, the light of the multi-color front light 66 that has passed through the liquid crystal layer 55 is reflected almost 100% by the D-BEF 69 and again passes through the liquid crystal layer 55 and the upper polarizing plate 54a. The transmitted light is visually recognized by an observer.

  The light emitted from the multi-color backlight 56 becomes linearly polarized light having a polarization direction in the transmission axis direction of the lower polarizing plate 54 b and enters the D-BEF 69. Since the reflection axis direction of the D-BEF 69 and the transmission axis direction of the lower polarizing plate 54 b are orthogonal to each other, the linearly polarized light passes through the D-BEF 69 and enters the liquid crystal layer 55. In the liquid crystal layer 55, the polarization direction does not change. For this reason, the light emitted from the liquid crystal layer 55 is absorbed by the upper polarizing plate 54a arranged in a crossed Nicols manner with respect to the lower polarizing plate 54b.

  Therefore, when no voltage is applied, the light emitted from the multicolor front light 66 is visually recognized by the observer in the entire area of the display unit.

  Next, the operation at the time of voltage application will be described.

  The light emitted from the multi-color front light 66 is visually recognized by the observer in the non-display area for the same reason as when no voltage is applied.

  On the other hand, in the display area, the light emitted from the multi-color front light 66 enters the liquid crystal layer 55 as linearly polarized light having a polarization direction in the transmission axis direction of the upper polarizing plate 54a. Since the alignment state of the liquid crystal molecules has changed since no voltage was applied, the light incident on the liquid crystal layer 55 is emitted from the liquid crystal layer 55 with the polarization direction changed by 90 °. The polarization direction of the linearly polarized light emitted from the liquid crystal layer 55 and the reflection axis direction of the D-BEF 69 are orthogonal (parallel to the transmission axis direction of the D-BEF 69). Therefore, the linearly polarized light emitted from the liquid crystal layer 55 passes through the D-BEF 69 and then the lower polarizing plate 54b, propagates to the multi-color backlight 56 side, and disappears due to scattering or the like. For this reason, the light emitted from the multi-color front light 66 is not visually recognized by the observer.

  The light emitted from the multi-color backlight 56 is not visually recognized by the observer in the non-display area for the same reason as when no voltage is applied.

  On the other hand, in the display area, the light emitted from the multi-color backlight 56 becomes linearly polarized light having a polarization direction in the transmission axis direction of the lower polarizing plate 54b, passes through the D-BEF 69, and enters the liquid crystal layer 55. To do. In the liquid crystal layer 55, the polarization direction is changed by 90 °. For this reason, the light emitted from the liquid crystal layer 55 passes through the upper polarizing plate 54a and is visually recognized by the observer.

  Therefore, when a voltage is applied, the light emitted from the multi-color front light 66 is visually recognized by the observer in the non-display area, and the light emitted from the multi-color backlight 56 is visually recognized by the observer in the display area. Will be.

  As described above, the liquid crystal display element according to the first embodiment can independently express the color tone of the non-display area by the multi-color front light 66 and the color tone of the display area by the multi-color backlight 56. Further, by selecting the color of light emitted from the lights 56 and 66, the display colors of the display area and the non-display area can be selected, respectively.

  As described above, in the liquid crystal display element according to the first embodiment, even when the multi-color front light 66 and the multi-color backlight 56 are lit at the same time, only one light is emitted at any one place. Is visually recognized by an observer. If the liquid crystal display element performs an on / off binary operation such as simple matrix driving, simultaneous lighting of the two hardly causes color mixing.

  The inventors of the present invention turned on the multi-color front light 66 of the liquid crystal display element according to the first embodiment in blue and the multi-color backlight 56 in yellow. A voltage was applied only to the electrodes corresponding to the display units 31 to 33 in FIG. As a result, it was confirmed that the number “7” was displayed in yellow on a blue background.

  A viewing angle compensation film or the like may be inserted between the polarizing plate and the liquid crystal cell.

  FIG. 3 is a schematic exploded perspective view showing an example of the internal configuration of the liquid crystal display element according to the second embodiment. In the first embodiment, a vertical alignment type liquid crystal cell is used. In the second embodiment, a liquid crystal cell having a two-layer structure including a compensation cell (upper cell) 70 and a drive cell (lower cell) 71 disposed on the upper and lower polarizing plates 54a and 54b, respectively. Is different from the liquid crystal display device according to the first embodiment in that

  The liquid crystal layer 55 of the compensation cell 70 and the drive cell 71 are both formed using the same liquid crystal material having a positive dielectric anisotropy (Δε> 0), and each of the cells 70 and 71 has a left twist angle of 90 °. A horizontal alignment type liquid crystal display element having a right twist angle of 90 ° was obtained. The liquid crystal molecule alignment directions at the centers of the liquid crystal layers 55 of the cells 70 and 71 are orthogonal to each other, and the thicknesses of the liquid crystal layers 55 of the cells 70 and 71 are equal. This figure shows the alignment state of liquid crystal molecules when no voltage is applied.

  The display operation was performed only by applying a voltage to the drive cell (lower cell) 71, and no power was supplied to the compensation cell (upper cell) 70.

  The liquid crystal cell including the compensation cell 70, the drive cell 71, the upper and lower polarizing plates 54a and 54b, and the D-BEF 69 is a normally black type liquid crystal cell with respect to the light emitted from the multi-color backlight 56. It is.

  The operation of the liquid crystal display device according to the second embodiment will be described. As described above, since no power is supplied to the compensation cell 70, the liquid crystal molecules in the compensation cell 70 always maintain a left twist angle of 90 °. Therefore, the light incident on the compensation cell 70 is emitted from the compensation cell 70 with the polarization direction changed by 90 ° to the left.

  When no voltage is applied, the drive cell 71 emits incident light with the polarization direction changed 90 ° to the right. That is, in the driving cell 71, the polarization direction of light is changed by 90 ° in the opposite direction to that in the compensation cell. Therefore, the light exits the two-layer liquid crystal cell with the same polarization direction as that incident on the two-layer liquid crystal cell.

However, when a voltage is applied, the alignment state of the liquid crystal molecules in the non-display area is not different from that when no voltage is applied, but in the display area, the alignment state of the liquid crystal molecules of the drive cell 71 changes from when no voltage is applied (upper side). And light that is incident on the drive cell 71 and is emitted from the drive cell 71 without changing the polarization direction. Therefore, the light is emitted from the liquid crystal cell having a two-layer structure with a polarization direction different by 90 ° from that incident on the liquid crystal cell having a two-layer structure.
Therefore, the polarization direction of light is not changed by the two-layer liquid crystal cell (compensation cell 70 and drive cell 71) in the non-display region even when no voltage is applied and even when the voltage is applied. On the other hand, when a voltage is applied, in the display region, light is emitted from a liquid crystal cell having a two-layer structure with the polarization direction changed by 90 °.

  Therefore, the liquid crystal display element according to the second embodiment operates in the same manner as the liquid crystal display element according to the first embodiment. When no voltage is applied, the liquid crystal display element is emitted from the multi-color front light 66 in the entire area of the display unit. When the voltage is applied, the light emitted from the multi-color front light 66 is visible to the observer in the non-display area, and from the multi-color backlight 56 in the display area. The light will be visually recognized by the observer.

  The inventor of the present application turned on the multi-color front light 66 of the liquid crystal display element according to the second embodiment in blue, and turned on the multi-color backlight 56 in yellow. A voltage was applied only to the electrodes corresponding to the display units 31 to 33 in FIG. As a result, it was confirmed that the number “7” was displayed in yellow on a blue background.

  As a result of studying liquid crystal cells having various twist angles by the inventor of the present application, when the twist angles of the compensation cell 70 and the drive cell 71 are 70 ° to 240 °, the liquid crystal display element according to the second embodiment is practically effective. It was found to act on.

  The same effect was obtained when the compensation cell (upper cell) 70 was replaced with Twistar manufactured by Polatechno Co., Ltd., which is a liquid crystalline polymer alignment phase difference plate having an optical function equivalent to this.

  FIG. 4 is a schematic exploded perspective view showing an example of the internal configuration of the liquid crystal display element according to the third embodiment.

  The liquid crystal display device according to the third embodiment is a liquid crystal display device including a retardation plate 72 between the upper substrate 50a and the upper polarizing plate 54a.

  By appropriately determining the twist angle of the liquid crystal molecules, the thickness of the liquid crystal layer, the retardation value of the retardation plate, and the direction of the slow axis, the upper and lower substrates 50a and 50b, the liquid crystal layer 55, the upper and lower sides The liquid crystal cell composed of the polarizing plates 54a and 54b, the D-BEF 69, and the retardation plate 72 was a normally black liquid crystal cell for the light emitted from the multi-color backlight 56. Here, the phase difference plate 72 plays a role of adjusting the color tone.

  Details of the configuration are as follows.

  The thickness of the liquid crystal layer 55 was 6 μm, and RDP00333 manufactured by Dainippon Ink Co., Ltd. was used as the liquid crystal material. The liquid crystal molecules had a twisted horizontal orientation with a twist angle of 240 ° to the left. As the retardation plate 72, a uniaxial optically anisotropic retardation plate having a retardation value of 600 nm was used. In addition, the angle between the slow axis of the retardation plate 72, the transmission axis of the upper polarizing plate 54a, the transmission axis of the D-BEF 69, and the transmission axis of the lower polarizing plate 54b is respectively the center molecular alignment direction of the liquid crystal layer 55. It was set to 140 °, 95 °, 70 °, and 70 °.

  This figure shows the alignment state of liquid crystal molecules when no voltage is applied. The directions of the transmission axes of the upper and lower polarizing plates 54a and 54b, the direction of the slow axis of the phase difference plate 72, and the direction of the transmission axis of the D-BEF 69 are indicated by arrows.

  The inventors of the present invention turned on the multi-color front light 66 of the liquid crystal display device according to the third embodiment in blue and the multi-color backlight 56 in yellow. A voltage was applied only to the electrodes corresponding to the display units 31 to 33 in FIG. As a result, it was confirmed that the number “7” was displayed in yellow on a blue background.

  In the third embodiment, one retardation plate 72 is used, but a plurality of retardation plates can also be used. Further, not only a uniaxial optically anisotropic phase difference plate, but also a biaxial optically anisotropic phase difference plate may be used.

  The twist angle of the liquid crystal molecules is preferably 180 ° to 240 °.

  FIG. 5 is a schematic exploded perspective view showing an example of the internal configuration of the liquid crystal display device according to the fourth embodiment.

  The liquid crystal display element according to the fourth embodiment is similar to the liquid crystal display element according to the first embodiment shown in FIG. In the liquid crystal display device according to the first embodiment, upper and lower polarizing plates 54a and 54b are arranged on the outer sides of the upper and lower substrates 50a and 50b sandwiching the liquid crystal layer 55, respectively. A color front light 66 and a multi-color backlight 56 were arranged. Then, D-BEF was inserted between the lower substrate 50b and the lower polarizing plate 54b as a polarization separation transmission / reflection plate that transmits or reflects incident light according to its polarization state.

  The liquid crystal display device according to the fourth example is that, in the first place, a broadband cholesteric film instead of D-BEF is disposed between the lower substrate 50b and the lower polarizing plate 54b as the polarization separating / transmitting / reflecting plate 67. This is different from the liquid crystal display device according to the first embodiment.

  In the liquid crystal display device according to the first embodiment, linearly polarizing plates are used as the upper and lower polarizing plates 54a and 54b. However, in the liquid crystal display device according to the fourth embodiment, as the upper polarizing plate 54a, In addition, a circularly polarizing plate for light from above, which is a combination of the upper linear polarizing plate 54e and the upper quarter-wave plate 54g, is employed. As the lower polarizing plate 54b, the lower linear polarizing plate 54f and the lower 1 / A circularly polarizing plate for light from below, which is combined with a four-wave plate 54h, was employed. The upper and lower polarizing plates 54a and 54b are both formed by arranging a linear polarizing plate on the lights 66 and 56 side and a quarter-wave plate on the liquid crystal cell side, and the transmission axis of the linear polarizing plate 1 / The angle formed by the slow axis of the 4-wavelength plate was ± 45 °. The transmission axes of the upper and lower linearly polarizing plates 54e and 54f were orthogonal to each other. However, the orientation of the transmission axis of the linearly polarizing plates 54e and 54f may be arbitrary with respect to the upper and lower substrates 50a and 50b.

  Further, the functions of the quarter wavelength plates 54g and 54h may be realized by using a combination of a plurality of wavelength plates (for example, a combination of a quarter wavelength plate and a half wavelength plate).

  In the liquid crystal display device according to the fourth embodiment, the upper polarizing plate 54a is a right circular polarizing plate, and the lower polarizing plate 54b is a left circular polarizing plate. The broadband cholesteric film 73 reflects right circularly polarized light and transmits left circularly polarized light.

  Hereinafter, circularly polarized light whose x component is retarded with respect to the y component is right-circularly polarized light, and circularly polarized light whose phase is fast is left-polarized light.

  On the contrary, the upper polarizing plate 54a may be a left circular polarizing plate, the lower polarizing plate 54b may be a right circular polarizing plate, and the broadband cholesteric film 73 may reflect left circular polarized light and transmit right circular polarized light. . The circular polarization directions of the upper polarizing plate 54a and the lower polarizing plate 54b are reversed, and the circular polarization direction transmitted through the broadband cholesteric film 73 is matched with the circular polarization direction of the lower polarizing plate 54b.

  In addition, NITOCS manufactured by Nitto Denko Corporation and TRANSMAX manufactured by Merck Co., Ltd., which adopt a configuration in which a broadband cholesteric film and a circularly polarizing plate are bonded together, are usually bonded to the backlight or the lower side of the liquid crystal cell. Used. In this case, a broadband cholesteric film is disposed on the light side. This embodiment is different from this in that the polarizing plate is disposed on the light side.

  The liquid crystal layer 55 is formed using a liquid crystal material having a negative dielectric anisotropy (Δε <0) to form a vertical alignment type liquid crystal display element. This figure shows the alignment state of liquid crystal molecules when no voltage is applied. Further, the retardation of the liquid crystal layer 55 at the time of voltage application was set to ½ wavelength (for example, the x component was ½ wavelength delayed phase).

  The light emitted from the multi-color front light 66 is polarized in the transmission axis direction of the upper linear polarizing plate 54e and enters the upper quarter wavelength plate 54g, and the x component is delayed by a quarter wavelength. Becomes right circularly polarized light.

  When no voltage is applied, the light incident on the liquid crystal layer 55 exits the liquid crystal layer 55 without changing the polarization state. The right circularly polarized light emitted from the multi-color front light 66 and emitted from the upper quarter-wave plate 54 g is emitted from the liquid crystal layer 55 as right circularly polarized light and reflected by the broadband cholesteric film 73. The reflected light is transmitted through the liquid crystal layer as right circularly polarized light, and the y component undergoes a quarter wavelength retardation by the upper quarter wavelength plate 54g. For this reason, it becomes linearly polarized light having the same polarization direction as that at the time of incidence, passes through the upper linear polarizing plate 54e, and is visually recognized by an observer. On the contrary, the light emitted from the multi-color backlight 56 is subjected to the ¼ wavelength phase advance of the x component by the lower ¼ wavelength plate 54h, passes through the liquid crystal layer while being left circularly polarized, and is transmitted to the upper ¼. Since the wavelength plate 54g receives the quarter wavelength retardation, the lower polarizing plate 54f is linearly polarized light whose polarization axis is rotated by 90 °, is shielded by the upper linear polarizing plate 54e, and is not visually recognized by the observer.

  When a voltage is applied, the alignment state of the liquid crystal molecules in the liquid crystal layer 55 changes, so that the right circularly polarized light incident on the liquid crystal layer 55 in the display region becomes left circularly polarized light and exits the liquid crystal layer 55. The left circularly polarized light becomes right circularly polarized light and exits the liquid crystal layer 55.

  The light emitted from the multi-color front light 66 is visually recognized by the observer in the non-display area in the same manner as when no voltage is applied. In the display area, the x component is delayed by 1/4 wavelength and 1/2 wavelength, and becomes left circularly polarized light, transmitted through the broadband cholesteric film 73, and 1/4 wavelength by the lower 1/4 wavelength plate 54h. The phase is advanced and transmitted through the lower linear polarizing plate 54f, so that it is not visually recognized by an observer.

  On the other hand, the light emitted from the multi-color backlight 56 is a quarter-wave phase advance, a half-wave retardation, respectively, at the lower quarter-wave plate 54h, the liquid crystal layer 55, and the upper quarter-wave plate 54g. Since it receives the 1/4 wavelength retardation phase and enters the upper linear polarizing plate 54e, it is transmitted therethrough and visually recognized by the observer.

  The liquid crystal cell composed of the upper and lower substrates 50 a and 50 b, the liquid crystal layer 55, the upper and lower polarizing plates 54 a and 54 b, and the broadband cholesteric film 73 is free of light emitted from the multicolor backlight 56. This is a liquid crystal cell of the mari black type. In addition, although a retardation plate (retardation film) such as a viewing angle compensation plate was not used between the liquid crystal cell and the upper or lower polarizing plates 54a and 54b, it can be used as needed. It is.

  The operation of the liquid crystal display element according to the fourth embodiment is the same as that of the liquid crystal display element according to the first embodiment. Therefore, when no voltage is applied, the light emitted from the multi-color front light 66 is visually recognized by the observer in the entire area of the display unit, and when no voltage is applied, the light is emitted from the multi-color front light 66 in the non-display area. The observed light is visually recognized by the observer, and in the display area, the light emitted from the multi-color backlight 56 is visually recognized by the observer.

  The liquid crystal display element according to the fourth embodiment can achieve the same effects as the liquid crystal display element according to the first embodiment.

  The inventors of the present invention turned on the multi-color front light 66 of the liquid crystal display device according to the fourth embodiment in blue and the multi-color backlight 56 in yellow. A voltage was applied only to the electrodes corresponding to the display units 31 to 33 in FIG. As a result, it was confirmed that the number “7” was displayed in yellow on a blue background.

  A viewing angle compensation film or the like may be inserted between the polarizing plate and the liquid crystal cell.

  FIG. 6 is a schematic exploded perspective view showing an example of the internal configuration of the liquid crystal display element according to the fifth embodiment. In the fourth embodiment, a vertical alignment type liquid crystal cell is used. In the fifth embodiment, a two-layer structure including a twisted nematic compensation cell (upper cell) 70 and a twisted nematic drive cell (lower cell) 71 disposed on the upper and lower polarizing plates 54a and 54b, respectively. The difference from the liquid crystal display element according to the fourth embodiment is that a twisted nematic liquid crystal cell having a structure is used.

  The liquid crystal layer 55 of the compensation cell 70 and the drive cell 71 are both formed using the same liquid crystal material having a positive dielectric anisotropy (Δε> 0), and each of the cells 70 and 71 has a left twist angle of 90 °. A horizontal alignment type liquid crystal display element having a right twist angle of 90 ° was obtained. The liquid crystal molecule alignment directions at the centers of the liquid crystal layers 55 of the cells 70 and 71 are orthogonal to each other, and the thicknesses of the liquid crystal layers 55 of the cells 70 and 71 are equal. This figure shows the alignment state of liquid crystal molecules when no voltage is applied. The retardation of the liquid crystal layer 55 of both cells 70 and 71 is set to one wavelength.

  The display operation was performed only by applying a voltage to the drive cell (lower cell) 71, and no power was supplied to the compensation cell (upper cell) 70.

  The liquid crystal cell composed of the compensation cell 70, the drive cell 71, the upper and lower polarizing plates 54a and 54b, and the broadband cholesteric film 73 is a normally black type liquid crystal with respect to the light emitted from the multi-color backlight 56. It is a cell.

  The operation of the liquid crystal display device according to the fifth embodiment will be described. As described above, since the compensation cell 70 is not energized, the compensation cell 70 functions as a polarization rotator. Accordingly, the right circularly polarized light incident on the compensation cell 70 becomes left circularly polarized light and exits from the compensation cell 70. The left circularly polarized light becomes right circularly polarized light and exits from the compensation cell 70.

  The drive cell 71 functions as a polarization rotator that exhibits a rotation direction opposite to that of the compensation cell when no voltage is applied. The same applies to the non-display area even when the voltage is applied. However, in the display region, the alignment state of the liquid crystal molecules of the driving cell 71 changes from when no voltage is applied (aligned substantially perpendicularly to the upper and lower substrates 50a and 50b), and the light incident on the driving cell 71 is in the polarization state. The light is emitted from the drive cell 71 without changing.

  Accordingly, when no voltage is applied and in the non-display region even when a voltage is applied, the light incident on the liquid crystal cell having the two-layer structure (compensation cell 70 and drive cell 71) is right circularly polarized light if it is right circularly polarized light. If left circularly polarized, the liquid crystal cell having a two-layer structure is emitted as left circularly polarized. On the other hand, when a voltage is applied, in the display region, the right circularly polarized light becomes left circularly polarized light, and the left circularly polarized light becomes right circularly polarized light and is emitted from the liquid crystal cell having a two-layer structure.

  Therefore, the liquid crystal display element according to the fifth embodiment operates in the same manner as the liquid crystal display element according to the fourth embodiment. When no voltage is applied, the liquid crystal display element is emitted from the multi-color front light 66 in the entire area of the display unit. When the voltage is applied, the light emitted from the multi-color front light 66 is visible to the observer in the non-display area, and from the multi-color backlight 56 in the display area. The light will be visually recognized by the observer.

  The inventors of the present invention turned on the multi-color front light 66 of the liquid crystal display device according to the fifth embodiment in blue and the multi-color backlight 56 in yellow. A voltage was applied only to the electrodes corresponding to the display units 31 to 33 in FIG. As a result, it was confirmed that the number “7” was displayed in yellow on a blue background.

  As a result of studying liquid crystal cells having various twist angles by the inventor of the present application, when the twist angles of the compensation cell 70 and the drive cell 71 are 70 ° to 240 °, the liquid crystal display element according to the fifth embodiment is practically effective. It was found to act on.

  The same effect was obtained when the compensation cell (upper cell) 70 was replaced with Twistar manufactured by Polatechno Co., Ltd., which is a liquid crystalline polymer alignment phase difference plate having an optical function equivalent to this.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these. For example, FIG. 3 and FIG. 6 illustrate liquid crystal display elements in which the upper and lower substrates 50a and 50b of the compensation cell 70 include upper and lower transparent electrodes 52a and 52b, respectively, but no voltage is applied to the compensation cell 70. If these are not necessary. In the embodiment, the compensation cell 70 is arranged on the upper side and the driving cell 71 is arranged on the lower side. However, these arrangements may be reversed.

  In all the examples, a normally black type liquid crystal cell was used, the display area was displayed with a multi-color backlight, and the non-display area was displayed with a multi-color front light. A normally white liquid crystal cell may be used to display a non-display area with a multi-color backlight and display a display area with a multi-color front light.

  Furthermore, although the segment type liquid crystal display element has been described in the embodiments, a liquid crystal display element capable of performing both segment display and dot display, or a full dot type liquid crystal display element may be used.

  The retardation plate (retardation film) can be inserted between the upper substrate 50a and the upper polarizing plate 54a or between one or both of the lower substrate 50b and the lower polarizing plate 54b.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like are possible.

  It can be used for a segment type, a combined type of segment display and dot display, and a full dot type liquid crystal display element. The driving method may be simple matrix driving or active matrix driving.

FIGS. 2A and 2B are a plan view showing a display unit and a schematic exploded perspective view showing an example of an internal configuration of a liquid crystal display device according to an embodiment described in detail with reference to FIG. It is a schematic exploded perspective view which shows the example of an internal structure of the liquid crystal display element by a 1st Example. It is a schematic exploded perspective view which shows the internal structural example of the liquid crystal display element by a 2nd Example. It is a schematic exploded perspective view which shows the internal structural example of the liquid crystal display element by a 3rd Example. It is a schematic exploded perspective view which shows the internal structural example of the liquid crystal display element by a 4th Example. It is a schematic exploded perspective view which shows the internal structural example of the liquid crystal display element by a 5th Example. (A)-(C) are schematic exploded perspective views which show the example of an internal structure of the liquid crystal display element which can adjust the color tone of a non-display area | region. (A) And (B) is a schematic exploded perspective view which shows the internal structural example of the liquid crystal display element which can adjust the color tone of a dot part or a segment part.

Explanation of symbols

30 Display unit 31 to 37 Display unit 38 Background region 50a Upper substrate 50b Lower substrate 51a Upper glass substrate 51b Lower glass substrate 52a Upper transparent electrode 52b Lower transparent electrode 53a Upper alignment film 53b Lower alignment film 54a Upper polarizer 54b Lower polarizer 54c Upper color polarizer 54d Lower color polarizer 54e Upper linear polarizer 54f Lower linear polarizer 54g Upper quarter wavelength plate 54h Lower quarter wavelength plate 55 Liquid crystal layer 56 Multicolor backlight 57 White backlight 58 Phase difference plate 59 Black mask 60 Area color filter 60r Red part 60g Green part 60b Blue part 60w White part 66 Multi-color front light 67 Polarization separation transmission / reflection plate 68 Voltage application means 69 D-BEF
70 Compensation cell 71 Drive cell 72 Phase difference plate 73 Broadband cholesteric film

Claims (10)

A first substrate comprising a transparent electrode having a predetermined pattern ;
A second substrate provided with a transparent electrode disposed substantially parallel to the first substrate and having a predetermined pattern ;
Display units provided corresponding to the transparent electrode of the first substrate and the transparent electrode of the second substrate;
A liquid crystal layer formed between the first substrate and the second substrate;
A first polarizing plate disposed on a side of the first substrate opposite to the side on which the liquid crystal layer is formed;
A front light disposed on the opposite side of the first polarizing plate from the side on which the first substrate is disposed;
A transmission / reflection plate that transmits or reflects incident light according to a polarization state, disposed on a side opposite to the side on which the liquid crystal layer is formed of the second substrate;
A second polarizing plate disposed on a side opposite to the side on which the second substrate of the transmission / reflection plate is disposed;
A backlight disposed on the side opposite to the side on which the transmission / reflection plate is disposed of the second polarizing plate;
The transmitting / reflecting plate reflects light in a polarized state that transmits the first polarizing plate, transmits light in a polarized state that transmits the second polarizing plate ,
A liquid crystal display element that performs display on the front light side by using both the light emitted from the front light and the light emitted from the backlight using the display unit . The liquid crystal display element according to claim 1, wherein the front light or the backlight can selectively emit light of a plurality of colors. The first polarizing plate and the second polarizing plate are linear polarizing plates each having a transmission axis in a first direction and in a second direction orthogonal to the first direction. A liquid crystal display element according to 1. The liquid crystal display element according to claim 3, wherein the direction of the reflection axis of the transmission / reflection plate is parallel to the first direction. The first polarizing plate is a circularly polarizing plate that transmits right circularly polarized light, and the second polarizing plate is a circularly polarizing plate that transmits left circularly polarized light, or the first polarizing plate is left circularly polarized light. The liquid crystal display element according to claim 1, wherein the second polarizing plate is a circularly polarizing plate that transmits right-handed circularly polarized light. The liquid crystal display element according to claim 5, wherein each of the first and second polarizing plates includes a linear polarizing plate and a quarter-wave plate. The liquid crystal display element according to claim 1, wherein the liquid crystal layer is sandwiched vertically between the first substrate and the second substrate. The liquid crystal layer includes a first liquid crystal layer, a second liquid crystal layer, and a third substrate formed between the first liquid crystal layer and the second liquid crystal layer,
The first and second liquid crystal layers include liquid crystal molecules that are twisted in opposite directions and horizontally aligned.
The alignment direction of the liquid crystal molecules located at the center of the thickness direction of the first liquid crystal layer is orthogonal to the alignment direction of the liquid crystal molecules located at the center of the thickness direction of the second liquid crystal layer,
The liquid crystal display element according to claim 1, wherein the retardations of the first and second liquid crystal layers are equal. The liquid crystal display element according to claim 8, wherein a twist angle of liquid crystal molecules of the first and second liquid crystal layers is 70 ° to 240 °. Furthermore, it contains the phase difference plate arrange | positioned between the said 1st board | substrate and the said 1st polarizing plate, or between the said 2nd board | substrate and the said 2nd polarizing plate. The liquid crystal display element according to any one of the above.

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