JP2008304540A - Reflective liquid crystal display medium and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflective liquid crystal display medium in which excellent white balance is efficiently obtained in a white display even when a cholesteric liquid crystal is used for a liquid crystal layer, and further constructions of the display medium and of the device are simplified, and a display device using the reflective liquid crystal display medium. <P>SOLUTION: The reflective liquid crystal display medium is constructed by sequentially stacking respective light reflection panels respectively and selectively reflecting blue light, green light, and red light in this order from the observer's side, and further having a light reflection panel reflecting yellow light between these light reflection panels, wherein a pair of substrates of each light reflection panel has strip-shaped electrodes arranged on mutually opposing surfaces so as to vertically intersect each other, and an electrode width of the light reflection panel reflecting yellow light is larger than that of each of light reflection panel reflecting another color light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reflective liquid crystal display medium and a display device.

  Cholesteric liquid crystal has a helical structure composed of rod-like molecules, and selectively reflects visible light near a specific wavelength when the helical pitch is in the optical wavelength order. This phenomenon is known as selective reflection of cholesteric liquid crystals. The reflectivity of the selective reflection can be changed by controlling the direction of the helical axis by electricity, magnetism, light, heat, stress, etc., or by destroying / generating the helical structure itself. Thus, the reflective liquid crystal display medium controls the reflected light on and off.

  Since the reflective liquid crystal display medium is a display element that performs display using external light as illumination, it does not require illumination power and has low power consumption. In addition, it has a memory property that can hold a display without a power source, and therefore, an expensive active matrix substrate such as a thin film transistor is not required for driving, a flexible substrate such as a resin substrate can be used, and a clear display with high reflectivity is achieved. It has features such as being possible.

  The display driving of the cholesteric liquid crystal by electric field control is performed by applying an electric field between the opposing electrodes with the transparent electrodes facing each other and the cholesteric liquid crystal sandwiched therebetween. When an image is formed by passive matrix driving, a display medium is manufactured by forming electrodes in a strip shape on a substrate so that the upper and lower electrodes face each other orthogonally, and cholesteric liquid crystal is sealed in the gap.

Cholesteric liquid crystal displays either reflect light of a certain wavelength or transmit all wavelengths depending on the structure of the cholesteric liquid crystal, so each cholesteric liquid crystal that can display blue, green, and red colors can be displayed. It is known that a color can be displayed by laminating sealed single color panels (light reflecting panels).
In relation to the above, a yellow light reflecting panel is further added to the laminated structure of the blue, green and red light reflecting panels, and the direction of spiral twist of the cholesteric liquid crystal is alternately changed from the long wavelength side to 4 It has been clarified that, when the layer structure is used, a higher whiteness can be obtained than a three-layer structure of blue, green, and red (see, for example, Patent Documents 1 and 2).
Japanese Patent No. 3700756 Japanese Patent No. 3599089

  An object of the present invention is to provide a reflective liquid crystal display medium capable of efficiently obtaining a good white balance in white display even when cholesteric liquid crystal is used for the liquid crystal layer, and further simplifying the display medium configuration and device configuration, And providing a display device using the reflective liquid crystal display medium.

The above-mentioned subject is achieved by the following present invention.
That is, according to the first aspect of the present invention, each light reflecting panel that selectively reflects blue light, green light, and red light is laminated in this order from the observation side, and yellow light is further interposed between these light reflecting panels. It has a light reflecting panel that reflects light,
A pair of substrates in each of the light reflecting panels has strip-like electrodes arranged so that the surfaces facing each other are orthogonal to each other, and the electrode width in the light reflecting panel that reflects the yellow light reflects other color light. It is a reflective liquid crystal display medium that is larger than the electrode width in the light reflecting panel.

  In the invention according to claim 2, the electrode width in each light reflecting panel that selectively reflects blue light, green light, and red light is the same, and the electrode width in the light reflecting panel that reflects the yellow light is other than 2. The reflective liquid crystal display medium according to claim 1, wherein the reflective liquid crystal display medium is n times (n is an integer of 2 or more) the electrode width of the light reflecting panel that reflects colored light.

The invention according to claim 3 is a display device that performs display by applying a voltage to the reflective liquid crystal display medium according to claim 1,
In each light reflection panel of the reflective liquid crystal display medium, when each rectangular electrode action portion formed by the rectangular electrodes being orthogonal to each other is a pixel electrode,
For each pixel region in the light reflection panel that reflects yellow light, whether all of the pixel electrodes in the light reflection panel of the other color light corresponding to the pixels overlapping in the stacking direction of the pixel region and each light reflection panel are in a voltage application state. A judging means for judging;
In the light reflecting panel that reflects the yellow light, voltage applying means for applying a voltage to the pixel electrode corresponding to the pixel region in which all the pixel electrodes of the light reflecting panel for the other color light are determined to be in a voltage applied state;
It is a display apparatus which has.

According to the first aspect of the present invention, even when cholesteric liquid crystal is used for the liquid crystal layer, a good white balance can be efficiently obtained in white display, and the display medium configuration and device configuration are simplified. A reflective liquid crystal display medium that can be provided can be provided.
According to the second aspect of the invention, it is possible to obtain a reflective liquid crystal display medium that can reproduce the image portion more clearly while maintaining the white balance.
According to the invention of claim 3, even when cholesteric liquid crystal is used for the liquid crystal layer, a good white balance can be efficiently obtained in white display with a simple configuration, and further, power saving can be achieved. Can be provided.

Hereinafter, the present invention will be described in detail.
<Reflective liquid crystal display medium>
In the reflective liquid crystal display medium of the present invention, each light reflecting panel that selectively reflects blue light, green light, and red light is sequentially laminated in this order from the observation side, and yellow light is further emitted between these light reflecting panels. A light reflection panel configured to have a light reflection panel that reflects, and has a strip-like electrode arranged so that a pair of substrates in each light reflection panel are orthogonal to each other on opposite surfaces, and reflects the yellow light The electrode width in the panel is larger than the electrode width in the light reflecting panel that reflects other color light.

  As described above, in the reflective liquid crystal display medium in which the light reflecting panels each having the respective liquid crystal layers that selectively reflect the blue light, the green light, and the red light are stacked, these are improved in order to improve the white display color. It is effective to provide a light reflection panel having a liquid crystal layer that reflects yellow light between the liquid crystal layers. The electrode configuration in these light reflecting panels is usually the same for the convenience of adjusting the display color for each pixel electrode (electrode working part formed by orthogonal strip electrodes) by laminating the light reflecting panels of the respective colors. In addition, when the electrodes have a simple matrix structure, the driving is the same for each panel in that each driving IC for driving each electrode is arranged.

However, when the yellow light reflecting panel is increased by one layer, the number of signal lines becomes 4/3 times both vertically and horizontally, so that there is a problem that a driving IC is required and the cost is increased. For example, when the A5 size (210 mm × 148 mm) and the resolution is 200 dpi (0.127 mm pitch), the number of signal lines per single color light reflection panel is (210 / 0.127) + (148/0. 127) = 1654 + 1166 = 2820. Therefore, in the case of the three-layer stack, 2820 × 3 = 8460, and in the case of the four-layer stack, the number is 11280.
When the resolution is increased and the screen size is increased, the number of lines is further increased, which raises the problem of higher costs.

  However, in actual image display, especially in the case of a character image, there are many white portions in the screen, so the white balance of the entire image has a white balance even if the white balance around the character portion is not adjusted. Often not a problem. Therefore, with respect to the yellow light reflection panel, it is possible to display yellow on a white portion having a certain area or more without matching yellow pixels at respective positions in correspondence with all pixels of blue, green, and red. The configuration is not a big problem on the image display, but rather the design of the display medium configuration and the display device configuration can be simplified.

In view of the above, the present invention relates to a yellow light reflecting panel that develops yellow, which is a color other than blue, green, and red, which is directly related to color expression. Improved.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a reflective liquid crystal display medium in which the light reflecting panels of the present embodiment are laminated.
The reflective liquid crystal display medium shown in FIG. 1 has a configuration in which a blue light reflecting panel 110, a yellow light reflecting panel 120, a green light reflecting panel 130, and a red light reflecting panel 140 are stacked in this order from the top. A black light shielding layer 135 is formed on the back surface (lower side of the drawing) of the red light reflecting panel 70.

  Here, the blue light, the green light, the yellow light, and the red light mean colored lights having peaks in wavelength ranges of 400 to 500 nm, 500 to 600 nm, 550 to 650 nm, and 600 to 700 nm, respectively. In the figure, reference numerals 111 to 118 are transparent substrates, reference numerals 121 to 128 are electrodes, reference numerals 131 to 134 are liquid crystal layers, and reference numeral 136 is a rib.

The blue light reflecting panel 110 is formed by forming a liquid crystal layer 131 made of right-twisted cholesteric liquid crystal that selectively reflects blue light between two transparent substrates 111 and 112 on which electrodes 121 and 122 that are orthogonal to each other are formed. The green light reflection panel 130 is formed by forming a liquid crystal layer 133 made of a left-handed cholesteric liquid crystal that selectively reflects green light between two transparent substrates 115 and 116 on which electrodes 125 and 126 that are orthogonal to each other are formed. In the red light reflection panel 140, a liquid crystal layer 134 made of a left-handed cholesteric liquid crystal that selectively reflects red light is formed between two transparent substrates 117 and 118 each having a transparent electrode.
A yellow light reflecting panel 120 disposed between the blue light reflecting panel 110 and the green light reflecting panel 130 is provided with yellow light between two transparent substrates 113 and 114 on which orthogonal electrodes 123 and 124 are formed. A liquid crystal layer 132 made of right-twisted cholesteric liquid crystal that selectively reflects is formed.

  In the reflective liquid crystal display medium, only the liquid crystal layers 131, 133, or 134 that reflect blue light, green light, or red light are reflected in blue, green, or red, respectively, and blue light and green are displayed in cyan. The liquid crystal layers 131 and 133 that reflect light are set to a reflective state, and the liquid crystal layers 131 and 134 that reflect blue light and red light are set to a reflective state during magenta display. During yellow display, (1) only the liquid crystal layer 132 that reflects yellow light, or (2) the liquid crystal layers 133 and 134 that reflect green light and red light, or (3) yellow light, green light, and red light are displayed. The liquid crystal layers 132, 133, and 134 to be reflected are brought into a reflective state, and (3) is desirable for obtaining a high reflectance.

  Further, at the time of white display, all of the liquid crystal layers 131, 132, 133, and 134 that reflect blue light, yellow light, green light, and red light are brought into a reflective state. Further, if all of the liquid crystal layers are made colorless, a black display can be obtained by the light shielding layer 35.

  The blue light reflection panel 110, the green light reflection panel 130, and the red light reflection panel 140 have the same electrode and rib configuration. For example, in the blue light reflection panel 110, the surfaces of the substrate 111 and the substrate 112 are arranged on the surface. Strip-shaped electrodes 121 and 122 are formed in parallel so as to be orthogonal to the x-direction (for example, the left-right direction in the figure) and the y-direction (the vertical direction in the figure), respectively, and the strip-shaped electrode 122 on the substrate 112 is formed. The rib 136 is provided for every two electrodes. In the configuration shown in FIG. 1, the arrangement of these electrodes and ribs is the same in each of the blue, green, and red light reflecting panels, and the positions of the electrodes and ribs on each panel are from the top to the bottom in the figure. It is laminated so that it is uniform (lamination direction).

  In the configuration shown in the figure, the shape and the arrangement position of the electrodes in each light reflecting panel match as described above. Blue, green, and red are essential primary colors for color reproduction. In the method of forming an image with each pixel and controlling the color for each pixel, this is the configuration. Is preferable. Therefore, the electrode configuration of each of the blue light, green light, and red light reflecting panels and the stacked configuration of each panel are the same as those in the prior art.

On the other hand, regarding the yellow light reflection panel 120, as shown as the electrode 123 of FIG. 1, the electrode width is larger than the electrode width in other light reflection panels. Although not obvious in the figure, the electrode 124 arranged linearly in the left-right direction in the figure is also wider than the electrode width in other light reflecting panels. Here, the electrode width refers to the width in the short side direction of the strip-shaped electrode.
By adopting such an electrode configuration, the number of electrodes in the yellow light reflecting panel 120 is obviously smaller than that of other light reflecting panels, and the number of driving ICs arranged at the ends of these electrodes at the time of display is also different. This is less than the driving IC for the light reflecting panel.

For comparison, FIG. 2 shows an example (schematic cross-sectional view) in which electrodes are configured and arranged according to a conventional method for a yellow light reflecting panel.
In the configuration shown in FIG. 2, the strip-shaped electrodes 123 ′ and 124 ′ in the yellow light reflecting panel 120 ′ are both the same as the electrode width in the other light reflecting panels, and the positions where the electrodes 123 ′ and 124 ′ are arranged are also shown. It corresponds with the electrode in other light reflection panels. For this reason, the pixel electrodes (electrode working portions) corresponding to the respective pixels in the yellow light reflecting panel 120 ′ are rectangular electrodes each having a side indicated by S1 to S6 (all having the same width) in the drawing, This pixel electrode has the same size and position as the pixel electrode in the other light reflecting panels.

  On the other hand, in the reflective liquid crystal display medium of this embodiment shown in FIG. 1, the pixel electrodes in the yellow light reflecting panel 120 are rectangular electrodes each having a width indicated by T1 and T2, respectively. The size does not match the pixel electrode in the light reflecting panel. Therefore, for example, when a pixel electrode having one side with the width indicated by T1 in the yellow light reflection panel 120 is turned on, yellow display is performed across a plurality of pixel electrodes in another light reflection panel. .

The yellow display as described above is a configuration that cannot be applied to the conventional method that considers the white balance for each pixel as shown in FIG. 2, but the white portion in the image as described above. It is possible to sufficiently cope with a method in which a wide area is judged and yellow display is selectively performed only in the area to adjust the white balance.
In addition, in the case of the above method, since the number of electrodes is reduced for the yellow light reflecting panel 120 as described above, not only the driving IC corresponding to this is reduced, but also the control for driving is simplified, Furthermore, since the display pixel area is reduced as compared with the case where each pixel electrode shown in FIG. 2 is turned ON / OFF as a whole, power saving can be achieved.

In the configuration of the present embodiment, the electrode width (here, “T”) in the yellow light reflection panel 120 only needs to be larger than the electrode width (here, “S”) in the other light reflection panel, and the width is There is no particular limitation. In addition, although the electrode width may be the same or different in one yellow light reflection panel, it is desirable from the viewpoint of control to be the same. Moreover, when the electrode width in light reflection panels other than the yellow light reflection panel 120 differs, it should just be larger than the largest electrode width of them.
Furthermore, when the area ratio between the white portion and the non-white portion (portion including characters other than white) in the image is actually considered, the width ratio (T / S) of both is 1.5 to 25. Desirably, the range is preferably 2 to 10.

  Further, in the present embodiment, the configuration is simplified by reducing the number of component types by unifying the relationship between the pixel display positions in other light reflecting panels when performing yellow display by the yellow light reflecting panel 120 and the driving chip. Therefore, the electrode widths in the blue light reflection panel 110, the green light reflection panel 130, and the red light reflection panel 140 are the same, and the electrode width in the yellow light reflection panel 120 is n times the electrode width in other light reflection panels ( n is preferably an integer of 2 or more. The configuration shown in FIG. 1 shows an example in which the electrode width T1 in the yellow light reflection panel 120 is three times (n = 3) the electrode width of other light reflection panels (the electrode widths are equal).

  However, even in this case, for the same reason as described above, the upper limit of n is preferably about 25, and more specifically, n is more preferably in the range of 2 to 10.

Next, each member, material, etc. constituting the reflective liquid crystal display medium of this embodiment will be described.
As the substrate, a light-transmitting insulating material such as glass such as borosilicate glass or quartz glass, or a resin such as polyester, polycarbonate, or polyether sulfone can be used. The thickness of the substrate is preferably in the range of 50 to 500 μm.

For the electrode formed over the substrate, a light-transmitting conductive material such as indium tin oxide, tin oxide, or aluminum-added zinc oxide is used. These materials are formed into a thin film on a substrate by a sputtering method, a vapor deposition method, a sol-gel method, or the like, and processed into a strip shape by a photoetching method or the like to form an electrode. The electrodes are strip-shaped, and a plurality of the strip-shaped electrodes are formed in parallel at a constant width on one substrate. The width of the electrode is not particularly limited, but it is desirable that the width is the same for each strip, and it is also desirable that the substrates facing each other in one light reflection panel have the same width (that is, the electrode pattern having the same shape).
In this embodiment, it is desirable that the width of the strip-shaped electrodes in the blue light reflecting panel, the green light reflecting panel, and the red light reflecting panel is in the range of 117 to 122 μm, and the gap width between the electrodes is in the range of 5 to 10 μm. It is preferable to do.

The substrate is provided with ribs for forming cells. The rib width is preferably adjusted in the range of 5 to 20 μm, more preferably in the range of 5 to 10 μm, and the height of the rib is preferably adjusted in the range of 5 to 6 μm. The rib is provided in a straight line in the gap between the strip-shaped electrodes. The gap between the electrodes is orthogonal due to the orthogonal arrangement of the electrodes, and the ribs provided in the gap are also orthogonal, resulting in the formation of square cells between the substrates. The square cell may be square or rectangular.
In the present embodiment, it is desirable to provide linear ribs every ten strip-shaped electrodes, and more preferably every three. Further, the ribs may not have the same spacing in the x and y directions on the substrate surface.
In addition, as a method of providing the ribs on the display medium, there are a both-rib method in which ribs are formed after forming the ribs on both opposing substrate surfaces, and a single-rib method in which ribs are formed only on one substrate.

  Examples of the method for forming ribs on the substrate surface include a screen printing method, a sand blasting method, a photolithography method, and an additive method. Among these, a photolithography method using a resist film is preferably used.

  As the light shielding layer 135 formed on the back side of the substrate 118 as shown in FIG. 1, a black colorant that absorbs the entire visible wavelength range (400 to 700 nm), for example, a black pigment such as carbon black or aniline black, A paint containing a black dye or an inorganic material such as chromium oxide is used. For example, in the case of a reflective liquid crystal display medium that reflects four color lights shown in FIG. 1, the light shielding layer 35 may be provided below the liquid crystal layer 134 that reflects red light. It may also serve as an electrode or a substrate.

Further, when the layer structure as shown in FIG. 1 is adopted, a yellow or red filter can be provided between the panels as required.
These filters can be formed by a known method such as applying a colored paint containing a pigment or a dye on a substrate, or providing an acrylic resin or gelatin film on the substrate and dyeing with a dye.

  In the case of the configuration shown in FIG. 1, examples of the cholesteric liquid crystal used for the liquid crystal layers 131 to 134 include liquid crystalline asymmetric carbon compounds such as cholesterol derivatives such as cholesteryl chloride and cholesteryl nonanoate, benzylidene aniline, Known including chemical structures such as azobenzene, azoxybenzene, cyanobiphenyl, cyanoterphenyl, phenylcyclohexane, phenylbenzoate, cyclohexylcyclohexane, cyclohexylcarboxylic acid ester, phenylpyrimidine, phenyldioxane, cyclohexylcyclohexaneester, cyclohexylethane, cyclohexene, and tolane An asymmetric carbon compound called a chiral agent such as 2-methyl-n-butylcyanobiphenyl is added to the nematic liquid crystalline compound. The compositions were, can be used. These compounds may be low molecular compounds or high molecular compounds.

  In the present embodiment, it is desirable that the spiral twist direction of the liquid crystal layers 131 to 134 be such that the selective reflection wavelength range uses reverse rotation for each light of adjacent colors. That is, from the low wavelength side, the liquid crystal layer 131 that reflects blue light and the liquid crystal layer 133 that reflects green light, the liquid crystal layer 133 that reflects green light, the liquid crystal layer 132 that reflects yellow light, and the yellow light are reflected. It is desirable that the liquid crystal layer 132 and the liquid crystal layer 134 that reflects red light have opposite spiral twist directions.

  This is because the cholesteric liquid crystal has circular dichroism that reflects only the circularly polarized light component in the same direction as the helical twist direction, and the rotation direction of the circularly polarized light is different in the wavelength band where the reflection spectra overlap. This is because the reflectance is higher than when the directions are the same.

  The liquid crystal layers 131 to 134 may contain components other than those described above, for example, a polymer or an inorganic compound dispersed in a cholesteric liquid crystal in a gel, matrix, or fine particle form, or conversely in a polymer matrix. A so-called polymer having a functional group called mesogen that induces liquid crystallinity in the main chain or side chain of the polymer may be used, in which cholesteric liquid crystal is dispersed in the form of droplets or in the form of microcapsules. It may be a liquid crystal.

  In order to improve the display characteristics and display uniformity of the display medium, an alignment film may be provided at the interface between the electrode formed on each substrate surface and the liquid crystal layers 131, 132, 133, and 134. Good. As the alignment film, resins such as polyimide and polyvinyl alcohol, low molecular surface modifiers such as alkyl ammonium compounds and alkyl silane compounds, inorganic thin films such as SiO, and the like can be used. As the alignment film, a vertical alignment film is particularly preferable.

  It should be noted that members provided between adjacent liquid crystal layers, such as a substrate, an electrode, and an alignment film, need not disturb the polarization state, and therefore the retardation of these members is preferably close to zero.

First, an adhesive is applied to the end portion of one substrate on which an electrode is formed, and the other substrate on which an electrode is similarly formed is connected to the light reflecting panel via the ribs arranged as described above. Adhering at regular intervals so that both electrodes face each other. This is produced for each required color.
Next, in the case of a laminated structure like the display medium shown in FIG. 1, cholesteric liquid crystal capable of reflecting blue light, yellow light, green light, and red light is injected between a pair of substrates in each panel. Then, the blue light reflection panel 110, the yellow light reflection panel 120, the green light reflection panel 130, and the red light reflection panel 140 are manufactured by sealing the edge of the substrate. The thickness of the liquid crystal layers 131, 132, 133, and 134 in each panel is set to a range of 2 to 20 μm.

In the production of the reflective liquid crystal display medium of the present embodiment, it is desirable to provide an adhesive layer when the light reflecting panels produced as described above are laminated.
For the adhesive layer, UV curable or thermosetting adhesives such as acrylic resin and epoxy resin, hot melt adhesives such as polyester and polyethylene-polyvinyl alcohol copolymer, adhesives such as polyvinyl acetate, etc. A known optical adhesive or pressure-sensitive adhesive can be used. However, the adhesive layer needs to have translucency. The adhesive layer not only adheres the panels to each other but also has an effect of increasing the contrast by reducing the surface reflection of the substrate.

The layers for obtaining the reflective liquid crystal display medium as shown in FIG. 1 are laminated as follows, for example. First, the yellow filter is formed on the upper surface of the yellow light reflecting panel 120, the red filter is formed on the upper surface of the red light reflecting panel 140, and the light shielding layer 35 is formed on the lower surface. Finally, the blue light reflection panel 110, the yellow light reflection panel 120 formed with a yellow filter, the green light reflection panel 130, and the red light reflection panel 140 formed with a red filter and a light shielding layer 35 are respectively connected via an adhesive layer. Glue.
In FIG. 1, the yellow light reflection panel 120 is an upper layer of the green light reflection panel 130, but the green light reflection panel 130 may be replaced with the upper layer of the yellow light reflection panel 120.

<Display device>
Next, the display device of the present invention will be described.
The display device of the present invention is a display device that performs display by applying a voltage to the reflective liquid crystal display medium of the present invention. In each light reflection panel of the reflective liquid crystal display medium, strip-like electrodes are provided. When each pixel electrode is a rectangular electrode action part formed by orthogonality, each pixel area in the light reflection panel that reflects yellow light corresponds to a pixel that overlaps in the stacking direction of the pixel area and each light reflection panel Means for judging whether all the pixel electrodes of the light reflection panel for other color light are in a voltage application state, and in the light reflection panel for reflecting the yellow light, all the pixel electrodes of the light reflection panel for the other color light are voltages. Means for applying a voltage to the pixel electrode corresponding to the pixel region determined to be in the applied state.

The display device of the present invention uses the reflective liquid crystal display medium of the present invention and performs yellow display based on a yellow light reflecting panel on a white display pixel by selecting only a region having a large white area in the image. It is. Thereby, not only the configuration of the display medium can be simplified, but also the configuration of the display device can be simplified, and the power consumption in the display can be reduced.
In this case, in the reflective liquid crystal display medium of the present invention described in the above embodiment, the electrode configuration of the yellow light reflecting panel is different from that of the other light reflecting panels. The applied voltage must be controlled for an electrode different from the light reflecting panel.

That is, in the other light reflecting panels other than the yellow light reflecting panel, the electrode configurations are all the same and their positions are aligned in the stacking direction of the panels, so that each light formed by the rectangular electrodes being orthogonal to each other. Each pixel electrode of the reflection panel is also aligned in the stacking direction. For the display of blue, green, and red, since the color of each pixel in the display image is determined, ON / OFF to each electrode in the blue light reflection panel, the green light reflection panel, and the red light reflection panel is determined. OFF control is performed synchronously.
On the other hand, regarding the yellow display based on the yellow light reflection panel, the pixel electrode area in the yellow light reflection panel is larger than that in the other light reflection panels as described above, and therefore, synchronized with the electrodes in the other light reflection panels. Can not be controlled.

For this reason, in the display device of the present invention, a region having a large white area in the entire display image is determined in advance, and ON / OFF of the pixel electrode in the yellow light reflecting panel is controlled based on the information.
Specifically, when each rectangular electrode action portion formed by orthogonal strip-shaped electrodes is used as each pixel electrode, first, from the image data, for each pixel region in the yellow light reflecting panel, the pixel region and It is determined whether all the pixel electrodes in the light reflecting panel of the other color light overlapping in the stacking direction of each light reflecting panel are in the voltage application state, and the light reflecting panel for the other color light in the yellow light reflecting panel based on this data A voltage is applied to the pixel electrode corresponding to the pixel region in which all the pixel electrodes are determined to be in the voltage application state.

The embodiment will be specifically described with reference to the drawings.
FIG. 3 is an enlarged view schematically showing an image in a state where a character image is displayed. In the figure, 60 is a white display pixel, 62 is a black display pixel, 64 is a magenta display pixel, 66 is a green display pixel, 68 is a blue display pixel, and 70 is a red display pixel. In addition, the code | symbol is abbreviate | omitted about the other pixel of the same color. On the other hand, for example, ranges indicated by Y1 to Y4 indicate pixel areas corresponding to the pixel electrodes in the yellow light reflecting panel. FIG. 3 shows a case where the electrode width in the yellow light reflecting panel shown in FIG. 1 is three times (n = 3) the electrode width in the other light reflecting panels. The pixel, that is, the pixel electrode in the other light reflection panel is included in a total of nine pixels in three rows and columns (a total of 27 in the three light reflection panels).

  Each of these pixels corresponds to each pixel electrode formed by orthogonal electrodes in the light reflecting panel other than the yellow light reflecting panel. For example, the white display pixel 60 reflects blue light according to each color. All the corresponding pixel electrodes in the panel, the green light reflecting panel, and the red light reflecting panel are applied with voltage, and in the black display pixel 62, all the corresponding pixel electrodes in the three light reflecting panels are not applied with voltage. Yes.

  As is clear from the image shown in the figure, the upper left area of the image has many white display pixels 60, whereas the upper right area of the image has more pixels of colors other than white. Therefore, when adjusting the white balance by adding yellow display to the white display pixel 60, it is efficient to select only an area with many white display pixels 60 such as the upper left area in the image and add yellow display. Is.

From the above viewpoint, in the present embodiment, the pixel in the stacking direction of the light reflecting panel for each pixel region in the yellow light reflecting panel (in the figure, the region including nine pixel electrodes in another light reflecting panel such as Y1). The voltage application state is confirmed for all the pixel electrodes in the other light reflection panel overlapping the region, and all of those pixel electrodes (all 27 in one pixel region in the figure) are determined to be the voltage application state (that is, the white display state). When this is done, a voltage is applied to the pixel electrode on the yellow light reflecting panel corresponding to the pixel region to cause yellow display.
In the above description, “overlap with the pixel area” means not only a state where all pixels of the other light reflection panel are included in the pixel area but also a state where a part of the pixels is included.

  Specifically, in FIG. 3, in the pixel region of the yellow light reflecting panel divided by nine pixels, the pixel electrodes in all the light reflecting panels are in a voltage application state (ie, white) at Y1 to Y4. A voltage is applied to the pixel electrode of the yellow light reflecting panel corresponding to this area, and a yellow display is applied to these areas. On the other hand, in other pixel regions, there is always at least one colored pixel (at least one of the pixel electrodes in the light reflection panel other than the yellow light reflection panel is a pixel in which no voltage is applied). No voltage is applied to the pixel electrode of the corresponding yellow light reflecting panel, and yellow display is not performed.

  As described above, when yellow display by the yellow light reflection panel is selectively performed in an area where there are many white display pixels 60, white is formed around the pixels 62 to 70 forming the character portion as shown in the figure. Although the display pixels 60 are present, it is the Y1 to Y4 region that is easy to be visually recognized as a white portion as a whole image. If these white balances are improved, the white pixels 60 around the pixels 62 to 70 are improved. Even if the white balance is not improved, there is no problem.

FIG. 4 is a block diagram showing a schematic configuration of an example of the display device of the present invention that performs display by applying a voltage to the reflective liquid crystal display medium of the present invention as described above.
FIG. 4 illustrates the case where voltage is applied to one of the four light reflecting panels based on the image data.

The display device 40 includes a scanning electrode drive circuit 42, a data electrode drive circuit 44, power supply circuits 46 and 48 (which constitute voltage applying means with the above elements), and a control device (determination means) 50. .
The scan electrode drive circuit 42 is connected to each scan electrode 14 in the yellow light reflection panel, and is supplied with various voltages supplied from the power supply circuit 46, that is, the first scan electrode ON voltage and the second scan electrode ON. A voltage, an OFF voltage, or the like is applied to each scanning electrode 14 according to an instruction from the control device 50.

  The data electrode drive circuit 44 is connected to each data electrode 20 and is supplied with various voltages supplied from the power supply circuit 48, that is, the first data electrode ON voltage, the second data electrode ON voltage, the OFF voltage, and the like. Is applied to each data electrode 20 in accordance with an instruction from the control device 50.

The scan electrode driving circuit 42 is connected to each scan electrode 14 (strip-shaped electrode), and applies various voltages supplied from the power supply circuit 46 to each scan electrode 14 according to instructions from the control device 50.
The data electrode drive circuit 44 is connected to each data electrode 20 (strip-shaped electrode) and applies various voltages supplied from the power supply circuit 48 to each data electrode 20 in accordance with instructions from the control device 50.

  Image data corresponding to an image to be displayed on the image display medium 10 is input to the control device 50. Based on the input image data, the control device 50 scans a row number designation signal for designating the row number of the scan electrode 14 to be scanned and a scan electrode voltage designation signal for designating the type of applied voltage. A column number designation for designating the column number of the data electrode 20 to which a predetermined voltage is to be applied based on the line image corresponding to the scanning electrode 14 designated by the row number designation signal while being output to the electrode drive circuit 42 A data electrode voltage specifying signal for specifying the signal and the type of the predetermined voltage is output to the data electrode driving circuit 44.

Here, image data processing and conversion to display data in the control device 50 will be briefly described.
The image data input to the control device 50 is first decomposed into display data for each panel of blue, green and red according to the color of each pixel. Since the display data on each color panel is driven by simple matrix drive, for example, when the number of electrodes on the substrate is m and n in the vertical and horizontal directions, the display data is composed of m × n bit data, The order in which the voltage is applied to the scan electrodes is designated by m bits in the vertical direction, and the order in which the voltage is applied to the data electrodes is designated by n bits in the horizontal direction.

  From these data, display data for turning on / off the voltage to the electrodes of the yellow light reflecting panel is determined as follows. For example, in the image shown in FIG. 3, nine pixels are included in one yellow pixel region, but regarding the ON / OFF of the pixel electrode in the yellow light reflecting panel, this range is included in all pixel regions. Judgment is made based on the ON / OFF states of a total of 27 pixel electrodes of the light reflecting panel.

Specifically, all nine pixel electrodes (a total of 27 in three panels) in each of the blue, green, and red color panels corresponding to one yellow pixel area at the time of a specific determination are in the ON state. If a voltage is applied to all of the scanning electrodes and data electrodes corresponding to the electrodes, the yellow pixel electrode is turned ON. On the other hand, among the nine pixel electrodes in the blue, green, and red color panels, at least one of the pixel electrodes is in an OFF state (that is, at least one of the scan electrode and the data electrode is not applied with a voltage with one or more electrodes). ), The yellow pixel electrode is turned off.
Display data for the yellow light reflection panel is input to the control device 50, and is determined as described above from the display data decomposed for each of the blue, green, and red panels, and is supplied to a circuit that drives the scan electrode and the data electrode. Sent.

  The scan electrode drive circuit 42 applies a voltage of the type designated by the scan electrode voltage designation signal to the scan electrode 14 of the row designated by the row electrode designation signal from the control device 50, and the row number designation signal. An OFF voltage is applied to the scan electrodes 14 other than the scan electrode 14 designated by the above.

  The data electrode drive circuit 44 applies a voltage of the type specified by the data electrode voltage specification signal to the data electrode 20 of the column specified by the control device 50 by the column number specification signal, and also supplies a column number specification signal. An OFF voltage is applied to the data electrodes 20 other than the data electrode 20 designated by the above.

  After the image data conversion process is performed as described above, the control device 50 controls the scan electrode drive circuit 42 and the data electrode drive circuit 44 to reflect each color light based on the image data converted by the conversion process. The panel is driven. As a result, image display corresponding to the input image data is performed. In this display device, since the yellow display for selecting the white display portion in the image and adjusting the white balance is performed, an image having excellent saturation in the white display can be obtained without greatly changing the device as compared with the conventional device. Obtainable.

  In the present embodiment, the case where the reflective liquid crystal display medium is configured to be detachable from the display device 40 has been described. However, the present invention is not limited thereto, and the reflective liquid crystal display medium, the scan electrode driving circuit 42, and the data electrode driving circuit are used. It is good also as a structure which can integrate 44, and this can be attached or detached with the display apparatus 40, changing the vertical and horizontal direction.

It is a schematic cross section which shows an example of the reflection type liquid crystal display medium of this invention. It is a schematic cross section which shows the conventional reflection type liquid crystal display medium. It is a model enlarged view which shows the display state of an image. It is a block diagram which shows schematic structure of an example of the display medium of this invention.

Explanation of symbols

14 Scan electrode 20 Data electrode 40 Display device 42 Scan electrode drive circuit 44 Data electrode drive circuit 46 Power supply circuit 50 Control device 60 White display pixel 62 Black display pixel 64 Magenta display pixel 66 Green display pixel 68 Blue display pixel Pixel 70 Pixel for red display 110 Blue light reflection panel 111 to 118 Transparent substrate 120 Yellow light reflection panel 121 to 128, 123 ′, 124 ′ Electrode 130 Green light reflection panel 131 to 134 Liquid crystal layer 135 Light shielding layer 140 Red light reflection panel

Claims (3)

Each light reflection panel that selectively reflects blue light, green light, and red light is laminated in this order from the observation side, and a light reflection panel that reflects yellow light is provided between these light reflection panels. And
A pair of substrates in each of the light reflecting panels has strip-like electrodes arranged so that the surfaces facing each other are orthogonal to each other, and the electrode width in the light reflecting panel that reflects the yellow light reflects other color light. A reflection-type liquid crystal display medium characterized by being larger than an electrode width in a light reflection panel.   The electrode width in each light reflection panel that selectively reflects blue light, green light, and red light is the same, and the electrode width in the light reflection panel that reflects yellow light is the same in the light reflection panel that reflects other color light. 2. The reflection type liquid crystal display medium according to claim 1, wherein the reflection type liquid crystal display medium is n times the electrode width (n is an integer of 2 or more). A display device that performs display by applying a voltage to the reflective liquid crystal display medium according to claim 1,
In each light reflection panel of the reflective liquid crystal display medium, when each rectangular electrode action portion formed by the rectangular electrodes being orthogonal to each other is a pixel electrode,
For each pixel region in the light reflection panel that reflects yellow light, whether all of the pixel electrodes in the light reflection panel of the other color light corresponding to the pixels overlapping in the stacking direction of the pixel region and each light reflection panel are in a voltage application state. A judging means for judging;
In the light reflecting panel that reflects the yellow light, voltage applying means for applying a voltage to the pixel electrode corresponding to the pixel region in which all the pixel electrodes of the light reflecting panel for the other color light are determined to be in a voltage applied state;
A display device comprising: