JP4770805B2 - 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 using a polymer dispersed liquid crystal.

  A liquid crystal display device using a polymer dispersed liquid crystal is known as a device that uses a liquid crystal display element formed by dispersing a polymer resin and a liquid crystal, and performs predetermined display by controlling transmission and non-transmission of light by an applied voltage. is there. Here, the polymer-dispersed liquid crystal becomes light transmissive when a voltage is applied.

  When a translucent electrode is patterned on a glass substrate corresponding to a display pattern in order to perform a predetermined display in a conventional liquid crystal display device using a polymer dispersed liquid crystal, the following problems occur. As shown in FIG. 9, when a polymer dispersed liquid crystal layer 91 is formed on the entire surface of a glass substrate and a closed region 92 indicated by a solid line in FIG. The transparent electrode 93 patterned as shown by the broken line is formed on the glass substrate, and a terminal portion 93a is formed continuously from the electrode 93, and a voltage is applied from the outside through the terminal portion 93a.

  As shown in FIG. 9, when displaying the closed region 92, when a voltage is applied from the terminal portion 93a, the light transmittance of the closed region 92 corresponding to the electrode 93 increases, and the light transmittance of the closed region 92 is different from the surroundings. For this reason, the closed region 92 is displayed, but at this time, the region corresponding to the terminal portion 93a is also displayed because its light transmittance changes. As described above, when a closed region is displayed in a conventional liquid crystal display device using a polymer dispersed liquid crystal, an unnecessary region such as a terminal portion is displayed, which is not preferable in terms of liquid crystal display quality.

  An object of the present invention is to provide a liquid crystal display device capable of displaying a closed region with a simple electrode configuration.

In order to achieve the above object, the present invention provides a liquid crystal display device that displays a closed region with a liquid crystal whose light transmittance changes according to an applied voltage, and a pair of light-transmitting substrates facing each other and the pair of light-transmitting substrates. A first liquid crystal region corresponding to the closed region, wherein the first liquid crystal region is disposed between the conductive substrates with a flat and uniform thickness, and the light transmittance and the applied voltage change in a first relationship; A second liquid crystal region disposed around the liquid crystal region and having a light transmittance and an applied voltage that change in a second relationship different from the first relationship, and the entire surface of the pair of translucent substrates. And a translucent electrode for applying a common voltage to the first liquid crystal region and the second liquid crystal region , wherein the first liquid crystal region and the second liquid crystal region are made of a polymer. The first liquid crystal region and the second liquid crystal region are composed of dispersed liquid crystal. LCD said different mixing ratio of the polymer dispersed liquid crystal liquid crystal and the polymer resin of each other, and displaying the closed region of the first liquid crystal region and the transmittance difference of the second liquid crystal region A display device is provided .

  According to the present invention, since the relationship between the light transmittance and the applied voltage is different between the first liquid crystal region and the second liquid crystal region, when the applied voltage is in a predetermined state, each light transmittance in both regions is Since they are different, the first and second liquid crystal regions can be distinguished and visually recognized. Thereby, a predetermined display can be performed without particularly patterning the electrode, and the problem that the terminal portion of the electrode is displayed does not occur.

  Further, the closed voltage cannot be visually recognized by changing the applied voltage so that the light transmittances of the first liquid crystal region and the second liquid crystal region are the same or approximate.

  Thereby, while performing a predetermined display by the difference in light transmittance between the two liquid crystal regions, by controlling to a predetermined voltage determined by the first relationship and the second relationship, the both light transmittance is the same or approximate, The first and second liquid crystal regions are made indistinguishable from being visually recognized. In this way, predetermined display can be performed and non-display can be performed.

  Further, the first liquid crystal region and the second liquid crystal region are made of polymer dispersed liquid crystal.

  Further, the first liquid crystal region and the second liquid crystal region are different from each other in a mixing ratio of the liquid crystal of the polymer dispersed liquid crystal and the polymer resin.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device which can display a closed area | region with a simple electrode structure, without displaying the terminal part of an electrode, etc. can be provided.

  Hereinafter, first to third embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a plan view of a liquid crystal display device using a polymer dispersed liquid crystal according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, and FIG. It is line sectional drawing. The liquid crystal display device 1 shown in FIG. 1 includes polymer dispersed liquid crystals 10 and 11 having different voltage-light transmittance characteristics, and the polymer dispersed liquid crystal 11 can display the number “8888”.

  As shown in the cross-sectional views of FIGS. 2 and 3, the liquid crystal display device 1 includes polymer dispersed liquid crystals 10 and 11 formed between a pair of glass substrates 13 and 13, and the periphery thereof is a sealing material 14. It is sealed by. Translucent electrodes 12 and 12 are formed on the entire surface of the glass substrates 13 and 13 on the side in contact with the liquid crystals 10 and 11, respectively. The translucent electrodes 12 and 12 can be formed from, for example, ITO (Indium Tin Oxide) or the like by vapor deposition.

FIG. 4 shows the relationship between the voltage applied to each of the liquid crystals 10 and 11 and the light transmittance in the first embodiment. The voltage light transmittance characteristic curve 101 shown in FIG. 4 indicates the characteristics of the liquid crystal 10, and the voltage light transmittance curve 102 indicates the characteristics of the liquid crystal 11. As can be seen from FIG. 4, when the applied voltage is V1, the light transmittance T1 (V1) of the liquid crystal 10 is equal to the light transmittance T2 (V1) of the liquid crystal 11, and the light transmittance of both the liquid crystals 10 and 11 is reduced. Since there is no difference, the number “8888” by the liquid crystal 11 is not visible. However, when the applied voltage is reduced to V2, the light transmittance T1 (V2) of the liquid crystal 10 becomes larger than the light transmittance T2 (V2) of the liquid crystal 11, so that there is a difference between the light transmittances of both the liquid crystals 10 and 11. Therefore, the number “8888” by the liquid crystal 11 can be visually recognized. The light transmittance difference DT (V) when the applied voltage is V can be expressed by the following equation (1).
DT (V) = abs (T1 (V) −T2 (V)) (1)
Here, abs () is a function for obtaining an absolute value, T 1 (V) is a light transmittance when the applied voltage of the liquid crystal 10 is V, and T 2 (V) is a value obtained when the applied voltage of the liquid crystal 11 is also V. Light transmittance.

  In this way, by changing the voltage applied to the liquid crystal, it is possible to change the contrast of the display numbers of the liquid crystal display device 1. When such a liquid crystal display device 1 is backlit, each region of the liquid crystal 10 and the liquid crystal 11 appears white (high luminance) at the applied voltage V1, and the liquid crystal 10 appears white (high luminance) at the applied voltage V2. At the same time, the liquid crystal 11 appears gray (low luminance). Further, when the voltage is lowered and no voltage is applied, the liquid crystal 10 looks gray (high luminance) and the liquid crystal 11 looks black (low luminance).

  As described above, when a voltage is not applied, numbers and the like are displayed. On the other hand, when the applied voltage is increased, the numbers and the like become invisible at a certain voltage or higher. Since the liquid crystal display device having such a configuration can display in a state where no voltage is applied, it can be used, for example, to display a warning lamp that warns when the voltage drops.

  In this case, the voltage V may be a DC voltage, but may be an AC voltage, and the liquid crystal display device is driven by duty driving.

  In addition, to produce a polymer-dispersed liquid crystal so as to have a difference in voltage light transmittance characteristics as shown in FIG. 4, for example, it can be realized by changing the mixing ratio of the liquid crystal and the polymer resin, In the case of using an ultraviolet light curable polymer resin, it can be realized by changing the network temperature of the cured resin by changing the temperature at the time of curing.

<Second Embodiment>
The liquid crystal display device in the second embodiment has the same configuration as that shown in FIGS. 1 to 3, but the relationship between the applied voltage and the light transmittance in each of the liquid crystals 10 and 11 is as shown in FIG. Is.

The voltage light transmittance characteristic curve 103 shown in FIG. 5 indicates the characteristics of the liquid crystal 10, and the voltage light transmittance curve 104 indicates the characteristics of the liquid crystal 11. As can be seen from FIG. 4, when the applied voltage is V3, the light transmittance T3 (V3) of the liquid crystal 10 is equal to the light transmittance T4 (V3) of the liquid crystal 11, and the light transmittance of both the liquid crystals 10 and 11 is reduced. Since there is no difference, the number “8888” by the liquid crystal 11 is not visible. However, when the applied voltage rises to V4, the light transmittance T3 (V4) of the liquid crystal 10 becomes smaller than the light transmittance T4 (V4) of the liquid crystal 11, so that there is a difference between the light transmittances of the two liquid crystals 10 and 11. Therefore, the number “8888” by the liquid crystal 11 can be visually recognized. The light transmittance difference DT (V) at the applied voltage V can be expressed by the following equation (2) as in the equation (1).
DT (V) = abs (T3 (V) −T4 (V)) (2)

<Third Embodiment>
FIG. 6 is an exploded perspective view of a more specific liquid crystal display device according to the third embodiment of the present invention. A liquid crystal display device 19 shown in FIG. 6 includes polymer-dispersed liquid crystal layers 16a and 16b having different voltage-light transmittance characteristics, and translucent electrodes 15a and 15b disposed so as to sandwich the liquid crystal layers 16a and 16b. An AC power supply 17 for applying an AC voltage to these electrodes 15a and 15b, and a switch 18 for ON / OFF control of the power supply 17 are provided. The switch 18 controls the light transmittance and light diffusion state of the polymer dispersed liquid crystal layers 16a and 16b.

  FIG. 7 shows the voltage-light transmittance characteristics of the polymer dispersed liquid crystal layers 16a and 16b. The voltage / light transmittance characteristic curve 105a represents the characteristics of the liquid crystal layer 16a, and the voltage / light transmittance curve 105b represents the characteristics of the liquid crystal layer 16b. Respectively. As can be seen from FIG. 7, the polymer-dispersed liquid crystal layer 16b exhibits a large light transmittance when no voltage is applied.

  FIG. 8 is a plan view showing a display state of the liquid crystal display device 19 of FIG. Now, when the voltage of the AC power supply 17 is set to V5 and the switch 18 is turned on, as shown in FIG. 7, the liquid crystal layer 16a sandwiched between the electrodes 15a and 15b in FIG. It becomes substantially equal to the light transmittance of the liquid crystal layer 16b not sandwiched by 15b. The region 20 in FIG. 8 corresponds to the liquid crystal layer 16a, and the region 21 corresponds to the liquid crystal layer 16b. Therefore, the region 20 and the region 21 are indistinguishable in FIG. The terminals for connecting the electrodes 15a and 15b to the AC power source are provided on the upper side of the figure for the electrode 15a and on the lower side of the figure for the electrode 15b so as not to overlap each other as shown in FIG. Therefore, no voltage is applied to the liquid crystal layer 16b when the switch 18 is on.

  Next, when the switch 18 is turned off, the liquid crystal layer 16a in FIG. 6 is in a light diffusing state (white turbid state) and the light transmittance is almost zero, while the liquid crystal layer 16b is in the same light transmitting state as before the switch is turned off. In FIG. 8, the region 20 and the region 21 can be clearly distinguished. In this way, the dark region 20 that is a light-transmissive and bright region 21 and that is a closed region that is not light-transmissive can be displayed. Such a configuration can be realized by a simple electrode arrangement without complicated electrode arrangement.

  As described above, according to each embodiment, even if a translucent electrode is arranged on the entire surface (or the electrode) by varying each voltage-light transmittance characteristic of the polymer dispersed liquid crystal for each region. The closed area can be displayed / hidden (with a simple arrangement). Therefore, unlike the conventional liquid crystal display device shown in FIG. 9, there is no problem of deterioration in display quality such as display of the electrode terminal portion that inevitably occurs for displaying the closed region.

  In addition, when the translucent electrode is divided and formed, and the first liquid crystal region and the second liquid crystal region of the polymer dispersed liquid crystal are controlled independently, the applied voltages can be set independently. Thus, for example, the difference in light transmittance between the first liquid crystal region and the second liquid crystal region can be increased, the contrast difference can be increased, and display visibility can be improved. In addition, it is possible to make the display invisible by making the respective light transmittances substantially equal at any light transmittance.

  For example, when the voltage light transmittance characteristic shown in FIG. 4 has temperature dependence, the temperature appears as a difference between the light transmittances of the two liquid crystal regions, so that it can also be used as a thermometer. In this case, temperature calibration can be performed by adjusting the driving voltage of the liquid crystal applied to the electrode.

1 is a plan view of a liquid crystal display device using a polymer-dispersed liquid crystal according to a first embodiment of the present invention. It is the II-II sectional view taken on the line of FIG. It is the III-III sectional view taken on the line of FIG. It is a figure which shows the relationship between the applied voltage and light transmittance of each polymer dispersion type liquid crystal of FIG. It is a figure which shows the relationship between the applied voltage and light transmittance of each polymer dispersion type liquid crystal in 2nd Embodiment. It is a disassembled perspective view of the liquid crystal display device by 3rd Embodiment. It is a figure which shows the relationship between the applied voltage and light transmittance of each polymer dispersion type liquid crystal layer of FIG. It is a top view of the liquid crystal display device of FIG. It is a top view for demonstrating the conventional liquid crystal display element.

Explanation of symbols

1,19 Liquid crystal display device 10 Polymer dispersion type liquid crystal (first liquid crystal region)
11 Polymer dispersed liquid crystal (second liquid crystal region)
101, 103, 105a Voltage light transmittance characteristic curve of the first liquid crystal region 102, 104, 105b Voltage light transmittance characteristic curve of the second liquid crystal region 12 Translucent electrode 13 Glass substrate 14 Sealing material 16a Polymer dispersion type Liquid crystal layer (first liquid crystal region)
16b Polymer dispersed liquid crystal layer (second liquid crystal region)
15a, 15b Translucent electrode

Claims (2)

In a liquid crystal display device that displays a closed region with a liquid crystal whose light transmittance changes according to an applied voltage,
A pair of opposing translucent substrates;
A first liquid crystal region corresponding to the closed region, wherein the first liquid crystal region is disposed between the pair of translucent substrates with a flat and uniform thickness, and the light transmittance and the applied voltage change in a first relationship; ,
A second liquid crystal region disposed around the first liquid crystal region, wherein the light transmittance and the applied voltage change in a second relationship different from the first relationship;
Each provided on the entire surface of the pair of translucent substrates, and having a translucent electrode for applying a common voltage to the first liquid crystal region and the second liquid crystal region,
The first liquid crystal region and the second liquid crystal region are composed of polymer dispersed liquid crystal, and the first liquid crystal region and the second liquid crystal region are higher than the liquid crystal of the polymer dispersed liquid crystal. The mixing ratio with molecular resin is different from each other,
The liquid crystal display device, wherein the closed region is displayed by a difference in transmittance between the first liquid crystal region and the second liquid crystal region.   2. The closed region cannot be visually recognized by changing the applied voltage so that light transmittances of the first liquid crystal region and the second liquid crystal region are the same or approximate. The liquid crystal display device described.

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