JP5192302B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device with improved contrast.

  A liquid crystal display device capable of dot display in addition to segment display or segment display is used for an in-vehicle information display device, a car audio display unit, or the like. As one of liquid crystal display devices capable of performing color display on a segment display unit, there is a configuration in which white backlight light is irradiated to a liquid crystal display element on which a color filter is formed.

  Disadvantages of the liquid crystal display device using the color filter include that a process of forming a color filter on the glass substrate of the liquid crystal display element is necessary, and that the display color of each segment is limited to the color of the color filter. Can be mentioned.

  As another liquid crystal display device capable of performing color display on the segment display portion, there is one that performs so-called field sequential (FS) driving. In such a liquid crystal display device, instead of forming a color filter on the liquid crystal display element, for example, a multi-color backlight composed of a multi-color light-emitting diode (LED) light source capable of emitting red, green, and blue (RGB) light is used and turned on. Color display is performed by sequentially switching colors.

  A specific example of the conventional FS driving method will be described with reference to FIG. FIG. 8 is a timing chart showing an input signal of each segment and a backlight lighting state. As the liquid crystal display element, a normally black type is assumed.

  Three subframes SB1 to SB3 in which backlights are lit in R, G, and B are set in one frame, which is a time unit for displaying one image. For example, the length of one frame is 16.7 ms according to the NTSC standard, and the length of each subframe is 5.57 ms obtained by dividing one frame into three equal intervals.

  In general, a liquid crystal display element has a slower response to an applied voltage than that of a backlight, and therefore it takes a blank time to turn on the backlight until the liquid crystal display element responds to some extent.

  A blank time B is provided immediately after switching of each subframe. After the blank time B, the backlight lighting time L for lighting the backlight of the color corresponding to the subframe is from the end time of each subframe.

  If the sub-frame operation is driven at a speed that is not recognized by human eyes (for example, about 16.7 ms / frame, about 5.57 ms / sub-frame, about 3 ms / blank time), the flicker is suppressed as intended. Display is feasible. In the example shown in FIG. 8, segment 1 is recognized by human eyes as yellow, which is a mixed color of R and G, segment 2 is magenta, which is a mixed color of R and B, and segment n is displayed as green of G only.

  However, in the above-described FS driving method (when this FS driving method is distinguished from the color breakless FS driving method described later, it will be referred to as a normal FS driving method), particularly when the periphery of the observer is dark In addition, when the observer's line of sight moves away from the display element, or when vibration is applied to the element itself (for example, in an automobile environment), the images of each subframe that are not recognized by the human eye in a normal state are separated. A phenomenon called color break may appear. This phenomenon is not a preferable display state due to human psychological factors.

  Since the color break phenomenon appears clearly in the white display portion, in the normal FS driving method, when the lighting operation is performed in a plurality of subframes in one segment display portion, that is, white, yellow or magenta This is considered to be noticeable in the mixed color display state.

  As a method of reducing the color break phenomenon, a method of inserting a white display subframe in one frame has been proposed, but the color break phenomenon cannot be removed by such a method.

  The inventors of the present application have proposed an FS driving method (color breakless FS driving method) that can eliminate the color break phenomenon (see Patent Document 1). The basic idea of this driving method is that not only primary colors (R, G, B) but also mixed colors (white, orange, etc.) are used as backlight lighting colors within one subframe. By transmitting the backlight light only in one subframe, the color break phenomenon is not caused.

  A specific example of the color breakless FS driving method will be described with reference to FIG. FIG. 9 is a timing chart showing an input signal of each segment and a backlight lighting state. As the liquid crystal display element, a normally black type is assumed.

  In this example, one frame is 16.7 ms, and three equally spaced subframes are set. The backlight emission color is white in the first subframe, orange in the second subframe, and blue in the third subframe. In this driving method, the possible display colors in one frame are M + 1, where M is the number of subframes and black is added to the emission color M. Note that the interval between the sub-frames may be changed according to the emission color of the backlight. That is, the subframe can be operated even at unequal intervals.

  In this example, segment 1 is displayed in white, segment n is displayed in orange, and segment 2 remains dark (displayed in black). As for the lighting timing of the backlight, a blank time B of about 3 ms is provided immediately after subframe switching to wait for the electro-optical response of the liquid crystal display element, as in the normal FS driving method. After the blank time B, a backlight lighting time L for lighting the backlight of the color corresponding to the subframe is provided until the end of the subframe.

  Since the backlight lighting color can be made variable for each frame, when the operation of the liquid crystal display element is a binary operation of light and dark, the display color can be significantly increased as compared with the normal FS driving method. It will be clear that there is.

  By performing such an operation, it is possible to realize flicker-free color display as intended in appearance without color breaks.

Japanese Patent No. 3894323

  In the color breakless FS driving method, the display portion is brought into a bright state only during one subframe period per frame, and it is difficult to increase the display luminance. For example, a technique for reducing the light transmittance of the dark display portion of the display background and improving the contrast is desired.

  In the color breakless FS driving method, the backlight lighting color can be varied for each frame. If the light transmittance of the dark display portion of the background is high, when the lighting color of the backlight changes, the background color changes and is observed, which is not preferable for display.

  An object of the present invention is to provide a liquid crystal display device capable of color breakless FS driving and improved in contrast by reducing light transmittance in a dark display portion.

  According to one aspect of the present invention, a first polarizing plate, a second polarizing plate disposed above the first polarizing plate, and arranged in a crossed Nicol arrangement with respect to the first polarizing plate, A third polarizing plate disposed above the second polarizing plate and arranged in a crossed Nicols arrangement with respect to the second polarizing plate; between the first and second polarizing plates; and the second and third polarizing plates A vertical alignment type liquid crystal cell disposed on one side between the plates, displaying at least one of a segment display and a dot matrix display, and displaying a display pattern including a plurality of display portions; and the first and second A vertical alignment type liquid crystal cell disposed between the polarizing plates and the other between the second and third polarizing plates, an area designation cell for performing dot matrix display, a backlight for lighting a plurality of colors, and the display Cell display pattern tables The display cell is controlled so that the portion is in a translucent state only in one subframe per frame, and the backlight is controlled so that the color corresponding to the display portion is lit in each subframe. In the dot matrix display portion of the area designating cell, the area designating cell is set so that a light transmissive region including the display pattern of the display cell is in a translucent state and an outside of the light transmissive region is in a light shielding state. There is provided a liquid crystal display device having a driving device for controlling and performing color breakless field sequential driving.

  The display pattern of the display cell is included in the light transmission region of the area designation cell and is brightly displayed to the observer. When considering a first liquid crystal display element composed of a display cell and an upper and lower polarizing plate sandwiching the display cell, and a second liquid crystal display element composed of an area designation cell and an upper and lower polarizing plate sandwiching the cell, the display cell The area outside the display pattern and in the light-shielded state of the area-designated cell is low estimated by the product of the light transmittance of the first liquid crystal display element in the light-shielded state and the light transmittance of the second liquid crystal display element in the light-shielded state. The light transmittance is darkly displayed, and a high contrast is obtained with respect to the display pattern.

  The light transmission area of the area designation cell is set to a size that includes the display pattern of the display cell. The area inside the light transmission area of the area designation cell and the outside of the display pattern of the display cell are in the light transmission state in the area designation cell but in the light shielding state in the display cell, and are therefore darkly displayed to the observer. Therefore, the edge of the display pattern of the display cell defines the edge of the display observed by the observer.

  Considering a liquid crystal display device in which the light transmission area of the area designation cell matches the display pattern of the display cell, in such a liquid crystal display device, both the edge of the light transmission area and the edge of the display pattern are observed by the observer. Defines the edges of the display to be observed. In such a liquid crystal display device, for example, a problem such that the edge of the display looks double due to parallax during oblique observation is likely to occur. Since the light transmission area of the area designation cell is set to a size including the display pattern of the display cell, such a problem is suppressed, for example.

  With reference to FIG. 1, the structure of the liquid crystal display device of the Example of this invention is demonstrated. FIG. 1 is a schematic perspective view of a liquid crystal display device of an embodiment.

  The liquid crystal display device of the embodiment has a structure in which upper and lower vertical alignment type liquid crystal cells CU and CL are stacked. An electrode pattern 4 (24) is formed on the upper transparent substrate 3 (23), and a vertical alignment film 5 (25) is formed so as to cover the electrode pattern 4 (24). An electrode pattern 14 (34) is formed on the lower transparent substrate 13 (33), and a vertical alignment film 15 (35) is formed to cover the electrode pattern 14 (34). The transparent substrate is, for example, a glass substrate, and the electrode pattern is made of, for example, an indium tin oxide (ITO) film.

  A liquid crystal layer 6 (26) made of a liquid crystal material having a negative dielectric anisotropy Δε is sandwiched between the upper transparent substrate 3 (23) and the lower transparent substrate 13 (33) facing each other, and the upper (lower) Side) Vertical alignment type liquid crystal cell CU (CL) is formed.

  In the upper liquid crystal cell CU, for example, the layer thickness d of the liquid crystal layer 6 is about 2 μm, and the thickness cross-sectional retardation (product Δnd of refractive index anisotropy Δn and layer thickness d) is about 300 nm. In the lower liquid crystal cell CL, for example, the layer thickness of the liquid crystal layer 26 is approximately 4 μm, and the thickness cross section retardation is approximately 600 nm.

  Considering a display surface parallel to the transparent substrate 3 (13, 23, or 33), an azimuth angle is defined in the display surface. When the liquid crystal display device is viewed from the front (normal direction of the display surface), the right direction is 0 ° direction (3 o'clock direction), the upper direction is 90 ° direction (12 o'clock direction), and the left direction is 180 ° direction ( 9 o'clock direction), and the downward direction is the 270 ° direction (6 o'clock direction).

  The upper vertical alignment film 5 (25) and the lower vertical alignment film 15 (35) are rubbed so as to be anti-parallel alignment. The in-plane orientation direction of the center molecule in the thickness direction of the liquid crystal layer 6 (26) is set to the 90 ° direction.

  Above the upper liquid crystal cell CU, the upper polarizing plate 1 with the absorption axis Ab1 in the 135 ° to 315 ° direction is disposed, and the absorption axis Ab11 is set to 45 ° − between the upper liquid crystal cell CU and the lower liquid crystal cell CL. An intermediate polarizing plate 11 having a 225 ° direction is disposed, and a lower polarizing plate 31 having an absorption axis Ab31 in the 135 ° to 315 ° direction is disposed below the lower liquid crystal cell CL. That is, the upper polarizing plate 1, the intermediate polarizing plate 11, the intermediate polarizing plate 11, and the lower polarizing plate 31 are arranged in crossed Nicols with an absorption axis direction of 90 °. As the polarizing plates 1, 11, and 31, iodine-based polarizing plates (for example, manufactured by Sumitomo Chemical) can be used.

  As described above, the upper liquid crystal display element DU having the upper vertical alignment type liquid crystal cell CU sandwiched between the upper polarizing plate 1 and the intermediate polarizing plate 11 arranged in crossed Nicols, and the intermediate polarizing plate 11 and the lower polarizing plate arranged in crossed Nicols. A structure is formed in which the lower liquid crystal display element DL is stacked with the lower vertical alignment type liquid crystal cell CL interposed therebetween. The intermediate polarizing plate 11 is shared by the upper and lower liquid crystal display elements DU and DL.

  Further, viewing angle compensation members 2 and 12 having negative biaxial optical anisotropy are inserted above and below the upper liquid crystal cell CU and between the upper polarizing plate 1 and the intermediate polarizing plate 11, respectively. Each of the viewing angle compensation members 2 and 12 has, for example, an in-plane retardation of about 45 nm and a thickness cross-section retardation of about 120 nm. The in-plane slow axis S12 of the viewing angle compensation member 2 and the in-plane slow axis S112 of the viewing angle compensation member 12 are substantially the same as the absorption axis Ab1 of the adjacent upper polarizing plate 1 and the absorption axis Ab11 of the intermediate polarizing plate 11, respectively. They are arranged in parallel.

  Further, from the lower side between the lower liquid crystal cell CL and the lower polarizing plate 31, a viewing angle compensation member 32b having negative biaxial optical anisotropy and a viewing angle compensation member having negative uniaxial optical anisotropy. A viewing angle compensation member 32a is inserted. The viewing angle compensation member 32b has, for example, an in-plane retardation of about 50 nm and a thickness cross section of about 220 nm, and the viewing angle compensation member 32a has, for example, a thickness cross section of about 220 nm. The in-plane slow axis Sl32b of the viewing angle compensation member 32b is disposed in a direction substantially orthogonal to the absorption axis Ab31 of the adjacent lower polarizing plate 31.

  A multicolor backlight 8 including light sources (for example, light emitting diodes) 9 of a plurality of colors (for example, red, green, and blue) is disposed below the lower polarizing plate 31 and emits light upward.

  The driving devices 7 and 27 control the voltage applied to the upper and lower electrodes 4 and 14 of the upper liquid crystal cell CU and the voltage applied to the upper and lower electrodes 24 and 34 of the lower liquid crystal cell CL, respectively. The driving device 40 controls the light emission state of the backlight 8 so that color breakless field sequential (FS) driving is performed, and the backlight 8, the driving device 7 of the upper liquid crystal cell CU, and the lower liquid crystal cell. The CL drive device 27 is synchronously controlled. The driving devices 7, 27, and 40 can be collectively regarded as a driving device for a liquid crystal display device.

For each of the upper and lower vertical alignment type liquid crystal display elements DU and DL, at the time of dark display, the light transmittance is almost the same as that of a polarizing plate arranged in crossed Nicols (for example, about 1 × 10 ⁻³ % with an iodine polarizing plate) ) Is obtained. In the liquid crystal display device of the embodiment, since the vertical alignment type liquid crystal display elements DU and DL are laminated, a very low light transmittance (for example, iodine) estimated by a product of low light transmittance at the time of dark display of both elements. (1 × 10 ⁻³ %) × (1 × 10 ⁻³ %) = 1 × 10 ⁻⁶ %) is obtained with the system polarizing plate.

  Further, since the upper and lower vertical alignment type liquid crystal display elements DU and DL share the intermediate polarizing plate 11, the light transmitted through the lower liquid crystal display element DL at the time of bright display has little loss and the upper liquid crystal display element DU. Is incident on. For example, when the light transmittance of the lower liquid crystal display element DL is about 25%, the light transmittance of the stacked upper and lower liquid crystal display elements DU and DL can be secured about 20%.

  As described above, the liquid crystal display device according to the embodiment can extremely reduce the light transmittance of the dark display while ensuring the light transmittance of the bright display, and a display with high contrast can be obtained. Furthermore, for example, in color breakless FS driving, when the lighting color of the backlight changes, it is suppressed that the color of the dark display portion of the display background changes and is observed.

  Next, a display pattern of the liquid crystal display device according to the embodiment will be described. In the liquid crystal display device according to the embodiment, the upper liquid crystal display element DU displays a desired display pattern to the observer, and the lower liquid crystal display element DL sets a light transmission region that is slightly larger than the desired display pattern.

  The upper liquid crystal cell CU that displays a desired display pattern is called a display cell, and the lower liquid crystal cell CL that sets a light transmission region that is slightly larger than the desired display pattern is called an area designation cell. .

  FIG. 2A is a schematic plan view showing a display portion which is a displayable area of the display cell. In the display surface, a one-segment display unit 50 “STANLEY” displayed in red, a one-segment display unit 51 “R & D” displayed in blue, and a two-digit seven-segment display unit 52 displayed in green Is arranged. The upper and lower electrodes of the display cell are designed in a pattern in which the overlapping portions constitute these segment display portions 50 to 52.

  FIG. 2B is a schematic plan view showing a display portion that is a displayable area of the area designated cell. Square dot-shaped display portions (pixels) are arranged in a matrix in a region having a size including the display portions 50 to 52 of the display cells in the display surface. That is, the upper and lower electrodes of the area designation cell are designed in a pattern in which the overlapping portion forms a dot matrix display portion. In the example of FIG. 2B, 1444 pixels (seg1 to seg1444) of 38 rows × 38 columns are arranged.

  FIG. 3A is a schematic plan view illustrating an example of a display pattern that is a portion that is brightly displayed (light transmission state) in the display portion of the display cell. The display portion 50 “STANLEY” shown in FIG. 2A is left dark, the display portion 51 “R & D” is displayed in blue, and the two-digit 7-segment display portion 52 has a portion “24”. Displayed in green.

  That is, in this example, a display pattern composed of blue “R & D” and green “24” is a desired display pattern provided to the observer. The outside of the display units 50 to 52 is always dark display (light-shielded state) without voltage being applied.

  FIG. 3B is a schematic plan view showing an example of a display pattern that is a bright display portion of the display portion of the area designated cell. In order to distinguish the display pattern of the area designation cell from the desired display pattern of the display cell, it is referred to as a light transmission region of the area designation cell. A desired display pattern of the display cell is simply referred to as a display pattern.

  The pixels in the region 60 that is slightly larger than the “R & D” portion of the display pattern of the display cell and the pixels in the region 61 that is slightly larger than the “24” portion of the display pattern are brightly displayed. That is, the areas 60 and 61 including the display pattern in the display surface are the light transmission areas of the area designated cell. The outside of the light transmission region remains dark.

  The area inside the display pattern of the display cell is brightly displayed, and this area is also inside the light transmission area of the area designation cell, so that a desired display pattern is clearly displayed to the observer.

  Since the area outside the light transmission area of the area designation cell is darkly displayed, it is darkly displayed to the observer. Since this area is also a dark display area in the display cell, the product of the light transmittance in the dark display of the liquid crystal display element including the area designation cell and the light transmittance in the dark display of the liquid crystal display element including the display cell. It shows a very low light transmittance estimated by A very high contrast can be obtained for the display pattern.

  Since the area outside the display pattern of the display cell and inside the light transmission area of the area designation cell is a dark display area of the display cell, the light transmittance is higher than that outside the light transmission area of the area designation cell. , Darkly displayed to the observer.

  In order to widen the dark display region where a very high contrast can be obtained with respect to the display pattern, it is preferable that the light transmission region of the area designated cell has a shape close to the display pattern of the display cell. However, if the light transmission region of the area designation cell and the desired display pattern of the display cell are matched, it is difficult to align the upper and lower cells, or double display due to parallax occurs.

  In the liquid crystal display device of the example, the shortest distance from the edge of the light transmission region of the area designation cell to the edge of the display pattern of the display cell is 1.0 mm or more, more preferably 1.5 mm to 2.5 mm within the display surface. Secure within the range of

  Since it is only necessary to align the display cells so that the display pattern is arranged in the light transmission region of the area designation cell, it is easy to align the upper and lower cells. In addition, since one cell (display cell) demarcates the edge of the desired display pattern, double display due to parallax during oblique observation is also suppressed.

  In addition, in order to make the light transmissive area close to the display pattern, the shortest distance from the edge of the light transmissive area of the area designation cell to the edge of the display pattern of the display cell is set to 3.0 mm or less in the display surface. It is preferable.

  Further, by adopting a dot matrix display as the area designation cell, the shape of the light transmission region can be set with a high degree of freedom. When the display pattern of the display cell is changed, it is possible to easily set a light transmission region corresponding to the change. When a plurality of correspondence relationships between a desired display pattern and the light transmission region are stored in the driving device and the display pattern is switched to another one, the light transmission region can be switched to correspond.

  The display patterns (referred to as second display patterns) shown in FIGS. 3C and 3D are the same as the display patterns shown in FIGS. 3A and 3B (first display patterns and An example of a display pattern switched from “to be called” is shown.

  FIG. 3C shows the display pattern of the switched display cell. The display portion 50 “STANLEY” is switched from dark display to red display, and the display portion 51 “R & D” is switched from blue display to dark display. In addition, the display portion “24” of the 2-digit 7-segment display section 52 remains green.

  FIG. 3D shows the display pattern of the switched area designation cell. The area 60A that is slightly larger than the “STANLEY” part is switched to the light transmission state, and the area 60 corresponding to “R & D” is darkly displayed. The area 61 corresponding to “24” is in a light transmission state as it is.

  Next, a color breakless FS driving method for switching and displaying from the first display pattern to the second display pattern will be described.

  4A and 4B are timing charts of the color breakless FS driving method for the first display pattern and the second display pattern, respectively. The ON / OFF state of the display portions “STANLEY”, “R & D”, and “24” of the display cell, the ON / OFF state of the area designation cell, and the backlight lighting state are shown.

  As shown in FIG. 4A, in the frame F1 that displays the first display pattern, a color breakless FS drive having two subframes SB11 and SB12 that turn on blue (B) and green (G) as backlights. Has been done. The display portion “R & D” is turned on (bright) only in the sub-frame SB11 when lighted in blue, and the display portion “24” is turned on only in the sub-frame SB12 when lighted in green. The display portion “STANLEY” is turned off (dark) in any subframe. The light transmission region of the area designated cell is turned on in any subframe.

  In order to display the second display pattern, the color breakless FS drive having two sub-frames for lighting red (R) and green (G) is switched. Further, the light transmission area of the area designated cell is also switched for the second display pattern.

  As shown in FIG. 4B, in the frame F2 displaying the second display pattern, the display portion “STANLEY” is turned on only in the sub-frame SB21 when red is lit, and only in the sub-frame SB22 when green is lit. The display portion “24” is turned on. The display portion “R & D” is turned off in any subframe. The light transmission region of the area designated cell is turned on in any subframe.

  As described above, in the color breakless FS drive, each display portion of the display pattern corresponding to the frame (“R & D” and “24” in the first display pattern, so that only one subframe per frame is displayed brightly) In the second display pattern, “STANDLEY” and “24”) are controlled, and in each subframe, the backlight is controlled so that the color corresponding to the displayed display portion is lit.

  When switching from the first display pattern to the second display pattern, the backlight lighting color (lighting pattern in the frame) changes. In the liquid crystal display device of the embodiment, in particular, the light transmittance outside the light transmission region of the area designated cell can be very low, so when the lighting color of the backlight changes, the color of the dark display portion of the display background changes. To be observed.

  Next, a display pattern according to a modification of the above embodiment will be described. The point of using the display cell and the area designation cell is the same as the display pattern example described with reference to FIGS. 2 (A) to 3 (D).

  FIG. 5A is a schematic plan view showing a display portion that is a displayable area of a display cell according to a modification. In the same manner as in the embodiment, a one-segment display unit 50 “STANLEY” displayed in red, a one-segment display unit 51 “R & D” displayed in blue, and a two-digit display unit displayed in green. A seven-segment display unit 52 is arranged, and in the modified example, a dot matrix display unit 53 that is displayed in white is added next to the segment display units 50 to 52. The upper and lower electrodes of the display cell are designed in a pattern in which the overlapping portions constitute the segment display units 50 to 52 and the dot matrix display unit 53.

  FIG. 5B is a schematic plan view showing a display unit that is a displayable area of the area designation cell according to the modification. Similar to the embodiment, the area designating cell has a dot matrix display portion, and the upper and lower electrodes are designed in a pattern in which the overlapping portion forms the dot matrix display portion. The dot matrix display part of the area designation cell of the modified example is arranged so as to include the segment display parts 50 to 52 and the dot matrix display part 53 of the display cell.

  FIG. 6A is a schematic plan view illustrating an example of a display pattern which is a portion that is brightly displayed among the display portions of the display cell according to the modification. The display portion 50 “STANLEY” is displayed in red, the display portion 51 “R & D” is left dark, and the two-digit 7-segment display portion 52 is green in “33”.

  Further, the pixel of the character portion “STANLEY” in the dot matrix display portion 53 is displayed in white. In the dot matrix display unit 53, pixels other than the character portion “STANLEY” remain darkly displayed. That is, in this example, a display pattern composed of the characters “STANLEY” and “33” in the segment display and the characters “STANLEY” in the dot matrix display is a desired display pattern. Outside the display units 50 to 53, no voltage is applied and the display is always dark.

  FIG. 6B is a schematic plan view showing an example of a light transmission region which is a portion of the display portion of the area designated cell that is brightly displayed. Pixels in the region 62 that is slightly larger than the “STANLEY” portion of the segment display in the display pattern of the display cell, pixels in the regions 63l and 63r that are slightly larger than the “33” portion of the segment display of the display pattern, and display Pixels in the region 64 that is slightly larger than the “STANLEY” portion of the dot matrix display of the pattern are brightly displayed. That is, the regions 62, 63l, 63r, and 64 that include the display pattern in the display surface are light transmissive regions of the modified example. The outside of the light transmission region remains dark.

  When displaying this display pattern, color breakless FS driving having three sub-frames of red lighting, green lighting, and white lighting is performed. The display part “STANLEY” is turned on only in the sub-frame when red is lit, the display part “33” is turned on only in the sub-frame when green is lit, and the dot matrix is displayed only in the sub-frame when white is lit. The display part “STANLEY” is turned on. The display portion “R & D” is turned off in any subframe. The light transmission region of the area designated cell is turned on in any subframe.

  Also in the modified example, the contrast between the area darkly displayed in both the display cell and the area designation cell and the display pattern can be very high. In the display surface, the shortest distance from the edge of the light transmission region of the area designation cell to the edge of the display pattern of the display cell is preferably set to 1.0 mm or more and 3.0 mm or less. It is more preferable to ensure within a range of 5 mm.

  In the modification, the display cell includes a dot matrix display unit. The dot matrix display section can set the display shape with a higher degree of freedom than the segment display section. Each pixel in the dot matrix display section of the area designation cell is displayed in order to facilitate the setting of a light transmission area that is a shape close to that of the display pattern displayed in the dot matrix display section of the display cell. It is preferable to have a fine shape included in each pixel of the dot matrix display portion of the cell. That is, it is preferable that the pitch in the row and column directions of the pixels of the dot matrix display portion of the area designation cell is smaller than that of the dot matrix display portion of the display cell. For example, it is more preferable that the area of each pixel in the dot matrix display portion of the area designation cell is ½ or less (pitch ½ or less) of the area of each pixel in the dot matrix display portion of the display cell.

  In the example described above, the upper liquid crystal cell CU is a display cell and the lower liquid crystal cell CL is an area designation cell. In the color breakless FS drive, the display cell is required to perform fast display control in which the display portion can be switched for each subframe, while the area designation cell only needs to perform slow display control for each display pattern switching. For this reason, it is preferable that the switching performance on the display cell side is high.

  Next, a preferred range of angles formed by the absorption axes of the polarizing plates arranged in crossed Nicols will be described.

  In the above description, the angle formed by the absorption axis directions of the upper and lower polarizing plates 1 and 11 of the upper liquid crystal display element DU is 90 °, and the absorption axis direction of the upper and lower polarizing plates 11 and 31 of the lower liquid crystal display element DL is formed. Although the angle is also 90 °, as described below, the angle formed by the absorption axis directions of the upper and lower polarizing plates may be shifted from 90 ° to about 5 °. A case where the angle formed by the absorption axis directions of the upper and lower polarizing plates is in the range of 85 ° to 95 ° is referred to as a crossed Nicol arrangement.

  FIG. 7 shows that the left / right observation angle (polar angle) dependence of the light transmittance when no voltage is applied in the liquid crystal display device of the example is absorbed by the upper polarizing plate 1, the intermediate polarizing plate 11, and the lower polarizing plate 31. It is a graph which shows the result of having investigated how it changes when the angle which axial azimuths make is changed. The polarizing plate uses an iodine type.

  A curve C1 is a case where the absorption axis direction of the upper polarizing plate 1 and the absorption axis direction of the lower polarizing plate 31 are 135 ° -315 ° directions and the absorption axis direction of the intermediate polarizing plate 11 is 45 ° -225 ° directions. That is, the light transmittance when the absorption axis directions of the upper polarizing plate 1 and the intermediate polarizing plate 11 form 90 ° and the absorption axis directions of the intermediate polarizing plate 11 and the lower polarizing plate 31 also form 90 ° is shown. . This case is referred to as “when the angle is 90 °”.

  A curve C2 indicates that the absorption axis direction of the upper polarizing plate 1 and the absorption axis direction of the lower polarizing plate 31 are in the direction of 136 ° -316 °, and the absorption axis direction of the intermediate polarizing plate 11 is in the direction of 44 ° -224 °. That is, the absorption axis directions of the upper polarizing plate 1 and the intermediate polarizing plate 11 are 92 ° (or 88 °), and the absorption axis directions of the intermediate polarizing plate 11 and the lower polarizing plate 31 are also 92 ° (or 88 °). ) Shows the light transmittance. This case will be referred to as “when the angle is 92 °”.

  A curve C3 is a case where the absorption axis direction of the upper polarizing plate 1 and the absorption axis direction of the lower polarizing plate 31 are 137 ° -317 ° direction, and the absorption axis direction of the intermediate polarizing plate 11 is 43 ° -223 ° direction. That is, the absorption axis directions of the upper polarizing plate 1 and the intermediate polarizing plate 11 are 94 ° (or 86 °), and the absorption axis directions of the intermediate polarizing plate 11 and the lower polarizing plate 31 are also 94 ° (or 86 °). ) Shows the light transmittance. This case is referred to as “when the angle is 94 °”.

In the case of an angle of 90 °, a very low light transmittance of about 5 × 10 ⁻⁵ % is obtained during frontal observation (left-right observation angle 0 °). However, as the observation angle increases, the light transmittance rapidly increases. For example, both the left and right reach about 0.01% at an observation angle of about 50 °. The width of the light transmittance change with respect to the observation angle change is large.

  When the formed angle is 92 °, the light transmittance during frontal observation is as high as 0.01%, but the light transmittance does not change much even if the observation angle changes. For example, a substantially constant light transmittance of about 0.01% is obtained on both the left and right sides up to an observation angle of about 50 °.

  When the formed angle is 94 °, the light transmittance at the time of frontal observation is as high as close to 0.1%. However, as in the case of the formed angle of 92 °, the light transmittance is maintained even when the observation angle is changed. Does not change much. For example, a substantially constant light transmittance of about 0.1% is obtained on both the left and right sides up to an observation angle of about 60 °.

  In this way, by setting the upper and lower polarizing plates of the liquid crystal display element to a crossed Nicol arrangement in which the angle between the absorption axis directions is deviated from 90 °, the width of the light transmittance change with respect to the observation angle change can be suppressed. . By reducing the difference in contrast between frontal observation and oblique observation, the difference in display quality can be reduced.

  When the angle between the absorption axis orientations deviates from 90 °, the light transmittance of the upper and lower polarizing plates arranged in crossed Nicols increases, but by laminating two layers of the structure in which the upper and lower polarizing plates are arranged in crossed Nicols, 1 A light transmittance significantly lower than that of the layer can be obtained.

  Based on the above results, when the contrast at the time of front observation is emphasized, the angle formed by the absorption axis directions of the upper and lower polarizing plates is preferably 90 °. Further, from the viewpoint of reducing the contrast difference between the front observation and the oblique observation, the angle formed by the absorption axis directions of the upper and lower polarizing plates for each of the upper and lower liquid crystal display elements is 91 ° to 95 ° (or 85 ° to 85 °). 89 °), and more preferably 91 ° to 93 ° (or 87 ° to 89 °) in order to obtain low light transmittance.

  In the case where the angle formed by the absorption axis is shifted from 90 °, the angle formed by the absorption axis is smaller than 90 ° when viewed from the left and right directions in the above-described left and right observations. Therefore, it is preferable to make the angle formed by the absorption axis smaller than 90 °.

  Examples of products to which the technology of the above embodiments can be applied include general information display devices. For example, an in-vehicle information display device, a car audio display unit, an operation panel display unit of office equipment such as a copy machine, and the like. Note that display control may be performed by a thin film transistor (TFT).

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

FIG. 1 is a schematic perspective view of a liquid crystal display device according to an embodiment of the present invention. FIG. 2A is a schematic plan view showing a display portion of a display cell of the liquid crystal display device of the embodiment, and FIG. 2B is a schematic view showing a display portion of an area designation cell of the liquid crystal display device of the embodiment. It is a top view. 3A and 3C are schematic plan views showing examples of display patterns of the display cells of the liquid crystal display device of the example. FIGS. 3B and 3D are examples of the display pattern. It is a schematic plan view which shows the example of the light transmissive area | region of the area designation | designated cell of the liquid crystal display device. FIGS. 4A and 4B are timing chart examples of color breakless FS driving for displaying a display pattern of the liquid crystal display device of the embodiment. FIG. 5A is a schematic plan view showing a display unit of a display cell of a liquid crystal display device according to a modification, and FIG. It is a top view. FIG. 6A is a schematic plan view showing an example of a display pattern of a display cell of a liquid crystal display device according to a modified example, and FIG. It is a schematic plan view which shows the example of. FIG. 7 is a graph showing the results of examining how the left-right observation angle dependency of the light transmittance changes depending on the angle formed by the polarizing plate absorption axis orientations. FIG. 8 is a timing chart example of normal FS driving. FIG. 9 is a timing chart example of color breakless FS driving.

Explanation of symbols

1, 11, 31 Polarizing plate 2, 12, 32a, 32b Viewing angle compensation member 3, 13, 23, 33 Glass substrate 4, 14, 24, 34 Electrode 5, 15, 25, 35 Vertical alignment film
6, 26 Liquid crystal layer CU Upper vertical alignment liquid crystal cell CL Lower vertical alignment liquid crystal cell DU Upper liquid crystal display element DL Lower liquid crystal display element 7, 27, 40 Driving device 8, multi-color backlight 9 Light source

Claims (4)

A first polarizing plate;
A second polarizing plate disposed above the first polarizing plate and arranged in a crossed Nicol arrangement with respect to the first polarizing plate;
A third polarizing plate disposed above the second polarizing plate and arranged in a crossed Nicol arrangement with respect to the second polarizing plate;
A vertical alignment type liquid crystal cell disposed between the first and second polarizing plates and between the second and third polarizing plates, and displays at least one of segment display and dot matrix display, and displays a plurality of displays. A display cell for displaying a display pattern including a portion;
An area-designated cell that is a vertical alignment type liquid crystal cell disposed between the first and second polarizing plates and between the second and third polarizing plates and that performs dot matrix display;
A backlight to light multiple colors,
The display cell is controlled so that each display portion of the display pattern of the display cell is in a translucent state only in one subframe per frame, and the color corresponding to the display portion is lit in each subframe. Further, the backlight is controlled, and in the dot matrix display portion of the area designation cell, the light transmission region including the display pattern of the display cell is set in a light-transmitting state, and the outside of the light transmission region is shielded from light A liquid crystal display device comprising: a drive device that controls the area-designated cells to perform color breakless field sequential drive.   2. The liquid crystal display device according to claim 1, wherein a shortest distance from an edge of the light transmission region to an edge of the display pattern is ensured to be 1.0 mm or more in a plane where display is performed.   The display cell includes a dot matrix display unit, and the pitch in the row and column directions of the pixels of the dot matrix display unit of the area designation cell is smaller than that of the dot matrix display unit of the display cell. The liquid crystal display device described.   In the plane where the display is performed, the angle of the absorption axis direction of the second polarizing plate with respect to the absorption axis direction of the first polarizing plate, and the third polarization with respect to the absorption axis direction of the second polarizing plate The liquid crystal display device according to any one of claims 1 to 3, wherein an angle in the absorption axis direction of the plate is in a range of 91 ° to 95 ° or 85 ° to 89 °.

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