JP2011237528A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device that performs highly contrasty displaying while securing the drive-responsiveness of a liquid crystal molecule and enabling a desired color to be recognized.SOLUTION: A liquid crystal display device comprising a displaying liquid crystal cell 30, a compensating liquid crystal cell 10 arranged by being joined to the undersurface of the displaying liquid crystal cell 30, an FSBL 50 radiating lights of different colors, and a drive circuit 70 to control voltage application to a lower transparent electrode and an upper transparent electrode and irradiation of the FSBL 50, causes a desired color to be displayed by controlling lights transmitted by the lower transparent electrode and the upper transparent electrode, wherein the twisted direction of the liquid crystal layer of the displaying liquid crystal cell 30 and the twisted direction of the liquid crystal layer of the compensating liquid crystal cell 10 are reverse to each other, the pretilt angle of the liquid crystal molecules of the displaying liquid crystal cell 30 and the pretilt angle of the liquid crystal molecules of the compensating liquid crystal cell 10 are reverse to each other and are substantially equal, and the orientative direction of the liquid crystal molecules in the vicinity of the lower end of the displaying liquid crystal cell 30 and the orientative direction of the liquid crystal molecules in the vicinity of the upper end of the compensating liquid crystal cell 10 are set to be reverse by 180 degrees to each other.

Description

The present invention relates to a liquid crystal display device capable of color display, and more particularly to a liquid crystal display device capable of displaying with high contrast.

2. Description of the Related Art Conventionally, a transmissive liquid crystal display device that includes a backlight and a color filter that transmits only light of a specific wavelength is known as a liquid crystal display device capable of color display. When segment display is performed by this liquid crystal display device, since a color filter of a desired color is arranged corresponding to each segment, each segment is a single color by a color filter arranged corresponding to the segment. Lights up.

When three color filters of red, green, and blue are used as the color filter, for example, a color filter that transmits light in the red wavelength band does not transmit light in the green or blue wavelength band. The segment corresponding to the filter can only be lit red. In addition, the light (light quantity) that actually passes through the color filter becomes 1/3 or less of the light irradiated to the color filter, and the quantity of light in the segment to be lit is likely to decrease, and the segment has a desired brightness. It is difficult to light up. In order to compensate for this decrease in the amount of light, for example, it was necessary to increase the power supply to the light source. As described above, in the liquid crystal display device that performs segment display, there are problems that the display color is limited to the color of the color filter and that it is difficult to express rich colors, and that the segment tends to be dark when lit.

In order to solve the above problem, field sequential backlight (
In the following, liquid crystal display devices using FSBL have been developed (see, for example, Patent Document 1). FIG. 12 shows a conventional configuration example of a liquid crystal display device using FSBL. The liquid crystal display device 500 includes a liquid crystal cell 510, an FSBL 520, a power supply circuit 530, and a drive circuit 600. The display liquid crystal cell 510 is configured by sandwiching liquid crystal molecules 514 between a pair of upper and lower glass substrates 512 and 512. Transparent electrodes 513 and 513 formed corresponding to the segment shape are disposed on the inner surfaces of the glass substrates 512 and 512, and the deflection plate 51 is disposed on the outer surface.
1,511 are disposed.

The FSBL 520 is configured to include a plurality of light sources 521, and light of a single color of red, green, or blue is emitted from each of the light sources 521. The light from the light source 521 is reflected by the light guide plate 522 and is incident on the display liquid crystal cell 510. Power supply circuit 530
Comprises a light source power source, a resistor, a changeover switch, and the like. The drive circuit 600 outputs a switching signal 610 to the power supply circuit 530 and outputs a voltage application signal 620 to the transparent electrode 513.

The liquid crystal display device 500 thus configured includes a switching signal 610 and a voltage application signal 62.
By controlling the timing of outputting 0, for example, eight colors can be displayed. For example, when the portions (segment portions) of the transparent electrodes 513 and 513 are displayed in yellow and the portions other than the transparent electrodes 513 and 513 (background portions) are displayed in black negative, the transparent electrodes 513 and 513 are red. In addition, the voltage application signal 620 is output in accordance with the timing at which the green light is incident, and control is performed so that the voltage application signal 620 is not always output to the transparent electrodes in the background portion other than the transparent electrodes 513 and 513. By doing so,
In the background portion, the light emitted from the light source 521 does not pass upward and is black, while the segment portion is visually recognized as yellow by mixing red and green.

Japanese Patent Laid-Open No. 5-19257

When negative display is performed in the configuration of the liquid crystal display device 500 described above, a clear display with high contrast becomes possible as the difference in brightness between the background portion and the segment portion increases. For this purpose, a configuration is desired in which light from the FSBL 520 is not transmitted as much as possible (low transmittance) in the background portion. In general, the light transmittance in a liquid crystal display device is closely related to the retardation Δn · d, which is the product of the birefringence Δn of the liquid crystal molecules used and the thickness d in the vertical direction of the liquid crystal layer. In general, as retardation Δn · d increases, the first portion where the transmittance becomes minimum is the 1st mode, the next portion where the transmittance becomes the minimum is the 2nd mode, and the next portion where the minimum becomes the next is the 3rd mode. , Respectively.

For example, when the thickness d is set to be as small as about 5 to 6 μm (1st mode), the drive response when changing the orientation of the liquid crystal molecules with respect to the voltage application signal 620 is improved, while R (red).
, G (green) and B (blue) are not sufficiently small in transmittance, it is difficult to completely block light by liquid crystal molecules, and the transmittance cannot be lowered sufficiently, and display with high contrast is difficult. It may become. On the other hand, when the thickness d is set large to about 10 to 15 μm (3rd mode), light can be completely blocked by the liquid crystal molecules, and the transmittance can be sufficiently lowered to display with high contrast, while applying voltage. The driving responsiveness of the liquid crystal molecules to the signal 620 is lowered, and the lighting is shifted to the light emission timing of the next color, so that it may be difficult to visually recognize a desired color. As described above, it is difficult to ensure both the driving responsiveness of the liquid crystal molecules with respect to the voltage application signal to make the desired color visible and the display with high contrast by sufficiently reducing the transmittance. There was a problem.

The present invention has been made in view of the above problems, and ensures high-contrast display by reducing the light transmittance of the black display portion while ensuring the driving response of the liquid crystal molecules and visually recognizing a desired color. An object of the present invention is to provide a liquid crystal display device capable of performing the above.

In order to achieve the above object, a liquid crystal display device according to the present invention is encapsulated in a layer between a pair of transparent upper substrates (for example, the substrate 31 in the embodiment) arranged in parallel with each other and the pair of upper substrates. An upper liquid crystal cell (for example, the display liquid crystal cell 30 in the embodiment) composed of the upper liquid crystal layer (for example, the liquid crystal layer 40 in the embodiment), and a pair of transparent lower substrates (for example, implementation) A lower liquid crystal layer (for example, the liquid crystal layer 20 in the embodiment) sealed in layers between the pair of lower substrates, and the lower side bonded to the lower surface of the upper liquid crystal cell. A liquid crystal cell (for example, the compensation liquid crystal cell 10 in the embodiment) and a lower surface of the lower liquid crystal cell are arranged to irradiate light of different colors toward the lower liquid crystal cell. A pair of pattern electrodes (for example, the embodiment) formed in a desired pattern and arranged parallel to each other with respect to the source part (for example, FSBL50 in the embodiment) and one of the upper liquid crystal cell and the lower liquid crystal cell Lower transparent electrode 33 in
a, a drive control unit (for example, the drive circuit 70 in the embodiment) that performs voltage application control on the upper transparent electrode 33b) and irradiation control on the light source unit, and the light in the light source unit is controlled by the drive control unit. A liquid crystal display device for applying a voltage to the pattern electrode in accordance with the irradiation timing of the light source and controlling the light transmitted through the pattern electrode to display the pattern electrode portion in a desired color. The upper liquid crystal molecules are twisted in a first twist direction along a spiral axis parallel to the normal line of the upper substrate, and the lower liquid crystal molecules constituting the lower liquid crystal layer are normal lines of the lower substrate. The first twist direction and the second twist direction are opposite to each other, and are located in the vicinity of the upper end of the upper liquid crystal layer. And the pretilt angle of the liquid crystal molecules, the pretilt angle of the lower liquid crystal molecules located near the lower end of the lower liquid crystal layer is a reverse in and substantially the same angle,
The pretilt angle of the upper liquid crystal molecules located near the lower end of the upper liquid crystal layer and the pretilt angle of the lower liquid crystal molecules located near the upper end of the lower liquid crystal layer are opposite and substantially the same angle. The orientation direction of the upper liquid crystal molecules located near the lower end of the upper liquid crystal layer and the orientation direction of the lower liquid crystal molecules located near the upper end of the lower liquid crystal layer are set to be opposite to each other by 180 degrees. Is done.

In the above-described liquid crystal display device, the birefringence of the upper liquid crystal molecule is Δn1, the thickness of the upper liquid crystal layer is d1, the birefringence of the lower liquid crystal molecule is Δn2, and the thickness of the lower liquid crystal layer is d2. At this time, each of Δn1 · d1 and Δn2 · d2 is preferably set to about 500 to 600 nm.

Further, it is preferable that a plurality of the pattern electrodes are arranged in one of the upper liquid crystal cell and the lower liquid crystal cell, and voltage application control is performed on each of the pattern electrodes independently by the drive control unit. .

In the above-described liquid crystal display device, the pattern electrode is configured so that a capacitance changes according to a facing interval thereof, and is disposed in the upper liquid crystal cell, and the pattern electrode portion of the upper liquid crystal cell is downward. A capacitance change position detection unit (for example, the touch sensor circuit 1 in the embodiment) that detects the capacitance change position in the upper liquid crystal cell when pressed.
10).

The pattern electrode is disposed in the lower liquid crystal cell, and the upper liquid crystal cell is disposed with a touch sensor electrode capable of detecting that the pattern electrode is pressed due to a change in capacitance. A configuration may be provided that includes a capacitance change position detection unit that detects a capacitance change position in the upper liquid crystal cell when the touch sensor electrode portion of the cell is pressed downward.

Further, the light source unit includes a plurality of LEDs (for example, a red light source 53R, a green light source 53G, and a blue light source 53B in the embodiment) that emit light of different colors, and each of the plurality of LEDs is independent. It is preferable that a light emission control unit (for example, the drive circuit 70 in the embodiment) capable of controlling light emission is provided.

Further, the liquid crystal display device according to the present invention includes a pair of transparent upper substrates arranged in parallel to each other and an upper liquid crystal cell composed of an upper liquid crystal layer sealed in layers between the pair of upper substrates. A lower liquid crystal cell comprising a pair of transparent lower substrates disposed and a lower liquid crystal layer sealed in a layer between the pair of lower substrates, and being bonded to the lower surface of the upper liquid crystal cell;
A light source unit disposed on the lower surface side of the lower liquid crystal cell and irradiating light of different colors toward the lower liquid crystal cell, and a desired pattern for one of the upper liquid crystal cell and the lower liquid crystal cell And a drive control unit that performs voltage application control on a pair of pattern electrodes arranged in parallel to each other and irradiation control on the light source unit, and the drive control unit controls light of the light source unit. A liquid crystal display device that applies voltage to the pattern electrode in accordance with irradiation timing and controls light transmitted through the pattern electrode to display the pattern electrode portion in a desired color, near the upper end of the upper liquid crystal layer The pretilt angle of the liquid crystal molecules located at the same position and the pretilt angle of the liquid crystal molecules located near the lower end of the upper liquid crystal layer are in the same direction and substantially the same angle. The pretilt angle of the liquid crystal molecules located near the upper end of the lower liquid crystal layer and the pretilt angle of the liquid crystal molecules located near the lower end of the lower liquid crystal layer are in the same direction and substantially the same angle, The alignment direction of the liquid crystal molecules positioned near the lower end of the upper liquid crystal layer and the alignment direction of the liquid crystal molecules positioned near the upper end of the lower liquid crystal layer are set to be opposite to each other by 180 degrees.

In the liquid crystal display device according to the present invention, in the upper liquid crystal cell and the lower liquid crystal cell, the twist directions of the liquid crystal molecules are opposite to each other, and the pretilt angles are opposite to each other and are set to substantially the same angle. In addition, the alignment direction of the liquid crystal molecules positioned near the lower end of the upper liquid crystal cell and the alignment direction of the liquid crystal molecules positioned near the upper end of the lower liquid crystal cell are set to be opposite to each other by 180 degrees. That is, the upper liquid crystal cell and the lower liquid crystal cell are configured to have a mirror image isomerism relationship with respect to optical characteristics. With this configuration, for example, even if one of the upper liquid crystal cell and the lower liquid crystal cell has a phase difference in the transmitted light, the other liquid crystal cell can compensate (cancel) the phase difference. For example, the transmittance of the black display portion can be sufficiently reduced. Therefore, it is possible to perform display with high contrast by reducing the light transmittance of the black display portion while visually recognizing a desired color.

In each of the upper liquid crystal cell and the lower liquid crystal cell, the product of the birefringence of the liquid crystal molecules and the thickness of the liquid crystal layer is preferably set to about 500 to 600 nm. For example, birefringence Δn is set to 0.
. 1. By setting the thickness d of the liquid crystal layer to 5 μm, Δn · d can be set to 500 nm. In this case, since the thickness d of the liquid crystal layer is thin, the voltage application signal On the other hand, the time required for the liquid crystal molecules to change their orientation can be shortened, and the drive response of the liquid crystal molecules can be improved. Therefore, it is possible to perform display with high contrast by reducing the light transmittance of the black display portion while visually recognizing a desired color.

In addition, it is preferable that the voltage application is controlled independently for each of the plurality of pattern electrodes.
An example of such a control method is a static drive method. When voltage application is controlled by this method, the voltage ratio between when voltage is applied and when voltage is not applied can be set large.
The drive response of the liquid crystal molecules to the voltage application signal can be further improved.

In the above-described liquid crystal display device, when the pattern electrode is disposed in the upper liquid crystal cell and the pattern electrode portion of the upper liquid crystal cell is pressed downward, the capacitance for detecting the position where the electrostatic capacitance has changed, that is, the pressed position. It is preferable that a change position detection unit is provided. Thus, when the pattern electrode has a configuration having two functions of the display electrode and the touch sensor electrode,
An easy-to-use and thin liquid crystal display device capable of touch operation can be realized without adding a separate touch sensor electrode.

In addition, the structure by which the pattern sensor is arrange | positioned at a lower side liquid crystal cell, and the touch sensor electrode which can detect that the upper side liquid crystal cell was touched to the upper side liquid crystal cell may be arrange | positioned. When configured in this way, since the pattern electrode and the touch sensor electrode are arranged in separate liquid crystal cells, for example, each liquid crystal is compared with a configuration in which the pattern electrode and the touch sensor electrode are mixed in one liquid crystal cell. An easy-to-use liquid crystal display device can be realized with a simple cell configuration.

Furthermore, it is preferable that the light source unit includes a plurality of LEDs that emit light of different colors. When configured in this manner, the light emission timing of each color (each LED) can be controlled with high accuracy, so that, for example, the light emission timing is shifted and two or more colors are not mixed and visually recognized.
It is possible to visually recognize the desired color.

In the liquid crystal display device according to the present invention, in each of the upper liquid crystal cell and the lower liquid crystal cell, the pretilt angle of the liquid crystal molecules located near the upper end and the pretilt angle of the liquid crystal molecules located near the lower end are in the same direction and At substantially the same angle, the alignment direction of the liquid crystal molecules positioned near the lower end of the upper liquid crystal layer and the alignment direction of the liquid crystal molecules positioned near the upper end of the lower liquid crystal layer are set to be opposite to each other by 180 degrees. That is, the liquid crystal molecules of the upper liquid crystal cell and the lower liquid crystal cell are set to π cells. With this configuration, the liquid crystal molecules in the central portion are always positioned with one of the major axes thereof obliquely up and down regardless of whether or not voltage is applied. For this reason, it is possible to perform display with high contrast by reducing the light transmittance of the portion to be displayed in black.

It is the schematic of the liquid crystal display device to which this invention is applied. It is principal part sectional drawing of the said liquid crystal display device. It is the schematic diagram which showed the orientation direction. It is the figure which showed the control with respect to a segment and a light source. It is the graph which showed the relationship between the transmittance | permeability and retardation. It is a top view of the said liquid crystal display device. 6 is a schematic diagram of a liquid crystal display device according to Embodiment 2. FIG. (A) is a side view of the compensation liquid crystal cell according to the second embodiment, and (b) is a plan view of the compensation liquid crystal cell according to the second embodiment. FIG. 6 is a schematic diagram illustrating an alignment direction of a liquid crystal display device according to Example 2. 6 is a plan view of a liquid crystal display device according to Embodiment 2. FIG. (A) is a side view of a compensation liquid crystal cell having another configuration, and (b) is a plan view of the compensation liquid crystal cell having another configuration. It is the schematic of the conventional liquid crystal display device.

Hereinafter, embodiments of the present invention will be described with reference to Examples 1 and 2 with reference to the drawings. For convenience of explanation, front and rear, left and right, and up and down directions are shown in the directions of the arrows in each drawing, and description will be made using these directions.

First, referring to FIGS. 1 and 2, a liquid crystal display device 1 according to a first embodiment to which the present invention is applied.
The basic configuration will be described. As shown in FIG. 1, the liquid crystal display device 1 includes a compensation liquid crystal cell 1.
0, the liquid crystal cell 30 for display disposed above the compensation liquid crystal cell 10, and the compensation liquid crystal cell 1
FSBL 50 disposed below 0, power supply circuit 60 electrically connected to FSBL 50,
And a drive circuit 70.

As shown in FIG. 2, the compensation liquid crystal cell 10 includes a pair of upper and lower transparent substrates 11, 11 disposed with a predetermined gap, and an alignment film disposed on the inner surface side of each substrate 11, 11. 12 a, 12 b, a sealing member 14 provided to surround the peripheral portions of the substrates 11, 11, and a liquid crystal layer 20 sealed in the gap between the substrates 11, 11. A lower polarizing plate 3 that transmits only linearly polarized light that vibrates in a specific direction is disposed on the lower surface side of the compensation liquid crystal cell 10.

The liquid crystal layer 20 is formed using a twisted nematic liquid crystal material, and is configured by laminating liquid crystal molecules having aligned alignment directions in layers. The liquid crystal molecules constituting the liquid crystal layer 20 are optically uniaxial birefringent crystals having birefringence in the minor axis direction and no birefringence in the major axis direction, and the birefringence Δn is about It is 0.08-0.30. Further, the thickness d in the vertical direction of the liquid crystal layer 20 is set to about 2 to 6 μm, and the retardation Δ of the liquid crystal layer 20 is set.
n · d is about 500 to 600 nm. Details of the retardation Δn · d will be described later.

A twisted nematic liquid crystal material used for the liquid crystal layer 20 is added with a chiral material for controlling the twist pitch of liquid crystal molecules with respect to the nematic liquid crystal. As this chiral material, for example, chiral nematic liquid crystal or cholesteric liquid crystal can be used.

An alignment process (rubbing process) is performed on the inner surfaces of the alignment films 12a and 12b, and minute grooves arranged in a certain direction are formed. The liquid crystal molecules of the liquid crystal layer 20 are arranged and sealed so that the major axis is aligned in the groove direction (alignment direction). In addition, the alignment films 12a and 12
The liquid crystal molecules in contact with b are arranged in a state of rising by a pretilt angle of 2 to 10 degrees with respect to the surfaces of the alignment films 12a and 12b. The pretilt angle is determined by the alignment films 12a and 12a.
It is determined by the material of b and the characteristics of liquid crystal molecules.

The display liquid crystal cell 30 includes a pair of upper and lower transparent substrates 31 and 31 disposed with a predetermined gap.
And lower transparent electrodes 33a and 35a made of a transparent conductive film disposed on the upper surface side of the lower substrate 31.
And upper transparent electrodes 33b and 35b made of a transparent conductive film disposed on the lower surface side of the upper substrate 31.
An alignment film 32a disposed on the upper surface side of the lower transparent electrodes 33a, 35a, and the upper transparent electrode 33a
, 35 a, an alignment film 32 b disposed on the lower surface side, a sealing member 34 provided to surround the peripheral portions of the substrates 31, 31, and a liquid crystal layer 40 enclosed in a gap between the substrates 31, 31. The On the upper surface side of the liquid crystal cell 30 for display, an upper polarizing plate 4 that transmits only linearly polarized light that vibrates in a specific direction is disposed.

The liquid crystal layer 40 is configured using a twisted nematic liquid crystal material in the same manner as the liquid crystal layer 20, and a chiral material is added to the twisted nematic liquid crystal material. In the liquid crystal layers 20 and 40, the twist pitch of the liquid crystal molecules changes according to the temperature change, and the chiral material to be added is selected and added so that the change is equal between the liquid crystal layer 20 and the liquid crystal layer 40. The amount has been adjusted. As the liquid crystal molecules of the liquid crystal layer 40, the birefringence Δn is about 0.08-0.
30 are used. The vertical thickness d of the liquid crystal layer 40 is set to about 2 to 6 μm, and the retardation Δn · d of the liquid crystal layer 40 is about 500 to 600 nm. Details of the retardation Δn · d will be described later.

The alignment films 32a and 32b are rubbed on the inner surfaces in the same manner as the alignment films 12a and 12b. The lower transparent electrode 33a and the upper transparent electrode 33b are formed in a desired pattern in a pair of upper and lower sides and correspond to a segment S1 portion described later (see FIG. 6). The lower transparent electrode 35a and the upper transparent electrode 35b are disposed around the transparent electrode formed in a desired pattern, and correspond to a segment W portion described later (see FIG. 6). FIG. 2 shows only a pair of lower transparent electrode 33a and upper transparent electrode 33b as transparent electrodes formed in a desired pattern, but in actuality, a pair of upper and lower electrodes formed in a desired pattern is shown. A plurality of transparent electrodes are provided.

In this liquid crystal display device 1, the voltage application control to the transparent electrodes is performed by switching the voltage application state and the non-application state independently for each pair of upper and lower transparent electrodes. The difference is set by static drive that can be set large.
Therefore, the direction of the liquid crystal molecules in the portion sandwiched between the transparent electrodes can be instantaneously changed according to the application or non-application of voltage.

As shown in FIG. 1, the FSBL 50 has a red light source 53R that emits red light, a green light source 53G that emits green light, and a blue light source 53B that emits blue light.
Is configured. Inside the light main body 51, a light guide plate 52 capable of surface emitting incident light is disposed. With this configuration, each light source 53R, 53G,
The light emitted from 53B toward the light guide plate 52 is uniformly surface-emitted on the light guide plate 52 and irradiated to the lower polarizing plate 3. In addition, as each light source 53R, 53G, 53B, the structure using the LED light source with a high on-off switching response is preferable.

The power supply circuit 60 includes a light source power supply 61, a ballast resistor 62, and a changeover switch 63. The ballast resistor 62 is attached to an electric circuit that connects each of the light sources 53R, 53G, and 53B and the light source power supply 61. By adjusting the current supplied to each of the light sources 53R, 53G, and 53B, variation in luminance can be achieved. It is for preventing. The changeover switch 63 is a switch for electrically connecting any one of the light sources 53R, 53G, and 53B to the light source power supply 61, and is switch-controlled by a switch signal 71 described later.

The drive circuit 70 is electrically connected to the pair of upper and lower transparent electrodes in the display liquid crystal cell 30 and the changeover switch 63. The drive circuit 70 outputs a voltage application signal 72 for applying a voltage to a pair of upper and lower transparent electrodes, and switches for switching a light source electrically connected to the light source power supply 61 to the changeover switch 63. A signal is output.

Up to this point, the basic configuration of the liquid crystal display device 1 has been described. In the following, the assembly configuration of the compensation liquid crystal cell 10 and the display liquid crystal cell 30, particularly the alignment direction, will be described with reference to FIG.

First, the assembly configuration of the compensation liquid crystal cell 10 will be described. In the state where the compensation liquid crystal cell 10 is assembled, the direction of the rubbing process for the alignment film 12a is the direction indicated by the arrow 13a shown in FIG. 3, while the direction of the rubbing process for the alignment film 12b is relative to the arrow 13a. 9
The direction is indicated by the arrow 13b rotated by 0 degrees. Therefore, among the liquid crystal molecules of the liquid crystal layer 20, the liquid crystal molecules located at the lower end and in contact with the alignment film 12 a are oriented so that the long axis is in the direction of the arrow 13 a and the liquid crystal molecules located at the upper end and in contact with the alignment film 12 b are With its long axis pointing in the direction of arrow 13b,
The liquid crystal molecules located in the intermediate portion are sealed with the major axis gradually twisted from the direction of the arrow 13a to the direction of the arrow 13b.

Among the liquid crystal molecules of the liquid crystal layer 20, the liquid crystal molecules located at the lower end and in contact with the alignment film 12 a and the liquid crystal molecules located at the upper end and in contact with the alignment film 12 b are formed in minute grooves formed by rubbing treatment. It is accommodated and tilted by a predetermined angle (pretilt angle) with respect to the alignment films 12a and 12b (see FIG. 2).

Next, an assembly configuration of the display liquid crystal cell 30 will be described. In the assembled state of the display liquid crystal cell 30, the direction of the rubbing process for the alignment film 32a is the direction indicated by the arrow 39a, while the direction of the rubbing process for the alignment film 32b is rotated 90 degrees with respect to the arrow 39a. The direction indicated by the arrow 39b. Therefore, among the liquid crystal molecules of the liquid crystal layer 40, the liquid crystal molecules located at the lower end and in contact with the alignment film 32a have their major axes directed in the direction of the arrow 39a, and the liquid crystal molecules located at the upper end and in contact with the alignment film 32b are The major axis is directed in the direction of the arrow 39b, and the liquid crystal molecules located in the middle portion are sealed with the major axis gradually twisted from the direction of the arrow 39a to the direction of the arrow 39b.

Among the liquid crystal molecules of the liquid crystal layer 40, the liquid crystal molecules located at the lower end and in contact with the alignment film 32a and the liquid crystal molecules located at the upper end and in contact with the alignment film 32b are formed in minute grooves formed by rubbing treatment. It is accommodated and tilted by a predetermined angle (pretilt angle) with respect to the alignment films 32a and 32b (see FIG. 2).

So far, the assembly configuration of the compensation liquid crystal cell 10 and the display liquid crystal cell 30 has been described. Below, the assembly structure of the liquid crystal display device 1 is demonstrated.

The display liquid crystal cell 30 is placed and fixed on the upper surface side of the compensation liquid crystal cell 10, and the lower polarizing plate 3 and the upper polarizing plate 4 are sandwiched from above and below the fixed and integrated liquid crystal cell. To fix. At this time, as shown in FIG. 3, the transmission axis direction 3a of the lower polarizing plate 3 and the arrow 13a indicating the rubbing treatment direction of the alignment film 12a are adjusted to be in the same direction. In addition, the transmission axis direction 4a of the upper polarizing plate 4 and the arrow 39b indicating the rubbing treatment direction of the alignment film 32b are adjusted so as to be rotated by 90 degrees.

An arrow 13b indicating the direction of the rubbing treatment of the alignment film 12b and an arrow 39a indicating the direction of the rubbing treatment of the alignment film 32a are parallel to each other and rotated by 180 degrees (a state facing the opposite direction). . Further, an arrow 13a indicating the direction of the rubbing treatment of the alignment film 12a,
The arrows 39b indicating the direction of the rubbing treatment of the alignment film 32b are parallel to each other and rotated by 180 degrees (a state facing the opposite direction).

As can be seen from FIG. 3, the twist direction of the liquid crystal molecules in the compensation liquid crystal cell 10 and the twist direction of the liquid crystal molecules in the display liquid crystal cell 30 are reversed. That is, the liquid crystal molecules in the compensation liquid crystal cell 10 are twisted clockwise as they go from bottom to top,
Liquid crystal molecules in the display liquid crystal cell 30 are sealed in a state of being twisted counterclockwise from the bottom to the top. Further, the pretilt angle of the liquid crystal molecules in contact with the alignment film 12a and the alignment film 3
The pretilt angle of the liquid crystal molecules in contact with 2b is the same, and the pretilt angle of the liquid crystal molecules in contact with the alignment film 12b and the pretilt angle of the liquid crystal molecules in contact with the alignment film 32a are the same.

Thus, the compensation liquid crystal cell 10 and the display liquid crystal cell 30 are mutually connected to the liquid crystal cells 20 and 4.
The retardation Δn · d of 0 is the same, the optical rotation (twisting direction) of the liquid crystal molecules is reversed, and the optical properties are enantiomeric.

So far, the assembly configuration of the liquid crystal display device 1 has been described. Hereinafter, the liquid crystal display device 1
As shown in FIG. 6, in the liquid crystal display device 1 configured to be able to display, for example, two digits, the segment S1 is red, the segment S2 is yellow, and the segment S3 is
Is displayed in white and the segment W corresponding to the background portion is negatively displayed in black.

The liquid crystal display device 1 emits light of each color of red, green, and blue from the FSBL 50 at a predetermined light emission timing, and performs voltage application control on the transparent electrode in accordance with the light emission timing, whereby each segment has a desired color. It is comprised so that it can be displayed on. As shown in FIG. 4, each of the light sources 53R, 53G, and 53B of the FSBL 50 emits the green light source 53G and the green light source 53G after the red light source 53R is emitted by the switching signal 71 from the drive circuit 70. The light emission timing is controlled so that blue 53B is emitted later.
That is, the light emission timing is controlled so that two or more light sources do not emit light simultaneously.

The segment S1 will be described. A voltage application signal 72 is output to the pair of lower transparent electrode 33a and upper transparent electrode 33b corresponding thereto in accordance with the light emission timing of the red light source 53R (see FIG. 4). At this time, of the circularly polarized light 59 emitted from the red light source 53R, only linearly polarized light parallel to the transmission axis direction 3a of the lower polarizing plate 3 is incident on the compensation liquid crystal cell 10. The illumination light incident on the compensation liquid crystal cell 10 advances upward while changing the polarization direction due to the optical rotation of the liquid crystal molecules in the liquid crystal layer 20, and the direction of the arrow 13b rotated 90 degrees clockwise is taken as the polarization direction. The compensation liquid crystal cell 10 exits and enters the display liquid crystal cell 30.

Among the liquid crystal molecules in the liquid crystal layer 40, the portion of the liquid crystal molecules sandwiched between the lower transparent electrode 33a and the upper transparent electrode 33b is in a state in which the major axis is directed vertically by voltage application. Therefore, red light traveling in the liquid crystal layer 40 travels along the major axis direction of the liquid crystal molecules without being affected by the birefringence of the liquid crystal molecules, and reaches the upper polarizing plate 4 without changing the polarization direction. To do. The polarization direction of the red light reaching the upper polarizing plate 4 is the direction indicated by the arrow 39b, and the arrow 39b and the transmission axis direction 4a of the upper polarizing plate 4 are parallel, so that the red light is transmitted from the segment S1 portion. In this way, the segment S1 portion can be displayed in red.

The segment S2 will be described. The voltage application signal 72 is output to the corresponding transparent electrode in accordance with the light emission timing of the red light source 53R and the green light source 53G. By doing so, red and green light is transmitted upward from the segment S2 portion, and red and green are mixed and visually recognized as yellow.

The segment S3 will be described. The voltage application signal 72 is output to the corresponding transparent electrode in accordance with the light emission timings of the red light source 53R, the green light source 53G, and the blue light source 53B.
By doing so, red, green, and blue light are transmitted upward from the segment S3 portion, and these colors are mixed and visually recognized as white.

The segment W will be described. Since the voltage application signal 72 is not always outputted to the pair of lower transparent electrode 35a and upper transparent electrode 35b corresponding to the segment W, black is displayed without transmitting light upward.

In a liquid crystal display device, it is an important quality item to make a segment visually visible without blinking (flickering). In order to satisfy this quality item, when it is defined that one light source 53R, 53G, 53B emits light once in order as one frame, it is necessary to emit 60 frames or more per second, and this light emission timing is delayed. It is necessary to change the orientation of the liquid crystal molecules with good responsiveness according to the voltage application signal 72. In addition, when performing negative display, it is also an important quality item to perform display with high contrast by reducing the light transmittance of the background portion (black display portion) as much as possible. In order to satisfy the above two quality items, in the liquid crystal display device 1 according to the present invention, the display liquid crystal cell 30 is combined with the compensation liquid crystal cell 10 having an enantiomeric relationship with respect to the optical characteristics, and these The retardation Δn · d of the liquid crystal cells 10 and 30 is set to the 1st mode of about 500 to 600 nm.

The graph of FIG. 5 shows the relationship between retardation Δn · d and transmittance for each color of light. A solid line, a dotted line, and a two-dot chain line in FIG. 5 indicate blue light, green light, and red light, respectively. The 1st mode is a portion where the average value of retardation Δn · d of blue, green and red light is first minimized when the thickness d is gradually increased. That is, the 1st mode is a portion where the thickness d is set to be the smallest in relation to the transmittance.

Thus, since the thickness d is set to be as small as about 2 to 6 μm, the driving response of the liquid crystal molecules in the display liquid crystal cell 30 can be improved, and the light sources 53R and 53 can be improved.
The direction of the liquid crystal molecules can be changed without delaying the emission timing of G and 53B. Specifically, the orientation of the liquid crystal molecules can be changed based on the voltage application signal 72 at a time interval shorter than 16.7 / 3 ms. Therefore, the segment S1 ~ displayed in color
It can be visually recognized that S3 is clearly displayed in a desired color without blinking.

Further, by setting the thickness d to be small, it is possible to reduce the path difference between the light that is transmitted obliquely upward through the liquid crystal display device 1 and the light that is transmitted straight and vertically. Therefore, for example, even when the liquid crystal display device 1 is viewed obliquely from above, the display content can be clearly seen and the viewing angle can be enlarged.

In a configuration that does not include a conventional liquid crystal cell for compensation, if the thickness d is set to about 2 to 6 μm, it is difficult to completely block light by liquid crystal molecules in a black display portion, and a display with high contrast is achieved. It was difficult. In contrast, the liquid crystal display device 1 according to the present invention.
The liquid crystal cell 30 for compensation and the liquid crystal cell 10 for compensation compensate for each other by combining the liquid crystal cell for compensation 10 which has an enantiomeric relationship with respect to the optical characteristics with respect to the liquid crystal cell for display 30. It has become. Therefore, for example, in the background portion to be displayed in black, the light transmitted through the display liquid crystal cell 30 due to the phase difference can be reduced, so that high-quality display with enhanced contrast between the segment portion and the background portion can be achieved. It becomes possible.

The liquid crystal display device 1 described above can be used as, for example, a display device that displays a power usage state provided in a home. In this case, a positive display that displays the segment in a desired color on a white background during bright days and a negative display that automatically switches to a black background during the night will respond to changes in ambient brightness. An easy-to-see display device can be obtained. Further, for example, by displaying all the segments in red at the time of abnormality, it is possible to visually inform the user that the abnormality is occurring.

A liquid crystal display device 100 according to a second embodiment to which the present invention is applied will be described with reference to FIGS. First, the configuration of the liquid crystal display device 100 will be described.

The liquid crystal display device 100 is obtained by partially changing the configuration of the compensation liquid crystal cell 10 in the liquid crystal display device 1 described above. Therefore, the same members as those of the liquid crystal display device 1 are denoted by the same reference numerals, and the description thereof will be omitted.

The compensation liquid crystal cell 10 ′ is provided on the upper surface side of the display liquid crystal cell 30 as shown in FIG. As shown in FIGS. 8A and 8B, the plurality of transparent touch sensor electrodes 101, 102, 103 disposed on the lower surface side of the alignment film 12 b are electrically connected to the touch sensor circuit 110. In the display liquid crystal cell 30, the touch sensor electrodes 101, 102,
Segments S4, S5, and S6 made up of a pair of upper and lower transparent electrodes are disposed at positions corresponding to 103 (see FIG. 10).

Referring to FIG. 9, the rubbing treatment direction of each alignment film will be described. The alignment film 32a
The rubbing process direction (arrow 39 a) is set to be parallel to the transmission axis direction 3 a of the lower polarizing plate 3. The rubbing direction (arrow 39b) of the alignment film 32b is set to a direction rotated 90 degrees clockwise with respect to the arrow 39a. The rubbing treatment direction of the alignment film 12a (
Arrow 13a) is set in the opposite direction parallel to arrow 39a and rotated 180 degrees. The rubbing treatment direction (arrow 13b) of the alignment film 12b is set to a direction rotated 90 degrees counterclockwise with respect to the arrow 13a, and is parallel to the transmission axis direction 4a of the upper polarizing plate 4.

From such a configuration, similarly to the liquid crystal display device 1 described above, the switching control for the switching switch 63 is performed by the switching signal 71 and the voltage application control for the transparent electrode is performed by the voltage application signal 72. W can be displayed in a desired color. Further, for example, when the user touches the segment S4 portion in a state where the segments S1 to S6 are displayed, distortion in micrometer units is generated in the portion, and the distortion is detected by the touch sensor electrode 101. By outputting a capacitance change signal 111 indicating that the capacitance has changed from the touch sensor electrode 101 to the touch sensor circuit 110, the segment S4 corresponding to the touch sensor electrode 101 is touched in the touch sensor circuit 110. Can be detected. As described above, by incorporating the touch sensor electrodes 101 to 103 into the compensation liquid crystal cell 10, the compensation liquid crystal cell 10 'can be provided with a phase difference compensation function and a function as a touch panel. An easy-to-use liquid crystal display device 100 that can be touch-operated on the screen without increasing the overall size can be realized.

The liquid crystal display device 100 can be used, for example, as a multi-information display by being mounted on an automobile. At this time, for example, the segment S4 is a button for switching between the outside air temperature and the vehicle interior temperature, the segment S5 is a button for switching between a negative display with a black background and a positive display with a white background, and the segment S6 is turned on / off. Easy-to-use liquid crystal display device 10 according to the purpose of use by setting each switch button.
0 can be realized.

In the first embodiment described above, the pair of upper and lower transparent electrodes disposed in the display liquid crystal cell 30 is electrically connected to a touch sensor circuit (not shown), so that the pair of upper and lower transparent electrodes function as a segment display. In addition, it can have a function as a touch sensor. With this configuration, it is possible to realize an easy-to-use liquid crystal display device that can be touch-operated using a pair of upper and lower transparent electrodes without newly adding a touch sensor.

In the above-described second embodiment, the single touch configuration example in which the button-like touch sensor electrodes 101 to 103 are arranged on one surface (alignment film 12b) of the compensation liquid crystal cell 10 is shown. It is not limited to this configuration. For example, the configuration of the compensation liquid crystal cell 150 shown in FIG. 11 is also possible. As shown in FIG. 11A, the compensation liquid crystal cell 150 has
A plurality of Y touch sensor electrodes 152 are disposed on the alignment film 12a, and a plurality of X touch electrodes are disposed on the alignment film 12b.
A touch sensor electrode 151 is provided. As can be seen from FIG. 11B, the X touch sensor electrode 151 and the Y touch sensor electrode 152 are arranged in a lattice pattern so as not to overlap each other. Also, the X touch sensor electrode 151 and the Y touch sensor electrode 1
52 is arranged on the entire surface of the display area, so that multi-touch can be supported. That is, by detecting a touch sensor electrode whose capacitance has changed, it is possible to recognize that the position where the touch sensor electrode is disposed has been touched.

In the first and second embodiments described above, the alignment film 12a and the alignment film 12b are disposed so that the rubbing treatment directions are rotated by 90 degrees, and the alignment film 32a and the alignment film 32b are similarly configured. The configuration in which the rubbing process is disposed so that the directions of the rubbing process are rotated by 90 degrees has been described. However, the configuration is not limited to such a configuration. For example, the alignment film 12a
And the alignment film 12b are arranged so that the rubbing treatment directions are aligned with each other, so that the compensation liquid crystal cell 10
A configuration in which (10 ′) liquid crystal molecules are set in a π cell may be employed. At this time, the alignment film 32a and the alignment film 32b are arranged so that the rubbing treatment directions are aligned with each other, the liquid crystal molecules of the display liquid crystal cell 30 are set to π cells, and the compensation liquid crystal cell 10 (10 ′) ) And the liquid crystal cell 30 for display are set so that the rubbing process direction is in a mirror image relation. In this way, liquid crystal molecules
When the cell is set, since the liquid crystal molecules in the upper and lower central portions always have the long axis directed vertically, the drive response to the on / off of the voltage application signal 72 can be further improved.

In the first and second embodiments described above, as a light source of the FSBL 50, a small cold cathode fluorescent tube having a relatively short drive response time can be used instead of the LED.

In the above-described first and second embodiments, the case where the segments are displayed in red, yellow, white, and black has been exemplified. However, in addition to these colors, blue and green are naturally magenta by mixing red and blue. In addition, it is possible to perform a display in which green and blue are mixed and visually recognized as cyan.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 10 Compensation liquid crystal cell (lower liquid crystal cell)
11 Substrate (lower substrate)
20 Liquid crystal layer (lower liquid crystal layer)
30 Liquid crystal cell for display (upper liquid crystal cell)
33a, 33b Lower transparent electrode, upper transparent electrode (pattern electrode)
31 substrate (upper substrate)
40 Liquid crystal layer (upper liquid crystal layer)
50 FSBL (light source)
53R, 53G, 53B Red light source, green light source, blue light source (LED)
70 Drive circuit (drive control unit, light emission control unit)
101, 102, 103 Touch sensor electrode 110 Touch sensor circuit (press detection unit)

Claims (7)

An upper liquid crystal cell comprising a pair of transparent upper substrates disposed in parallel to each other and an upper liquid crystal layer sealed in a layer between the pair of upper substrates;
A lower liquid crystal cell comprising a pair of transparent lower substrates arranged in parallel to each other and a lower liquid crystal layer sealed in layers between the pair of lower substrates, and being bonded to the lower surface of the upper liquid crystal cell When,
A light source unit disposed on the lower surface side of the lower liquid crystal cell and irradiating light of different colors toward the lower liquid crystal cell;
A drive control unit that performs voltage application control on a pair of pattern electrodes formed in a desired pattern and arranged in parallel to each other and irradiation control on the light source unit with respect to one of the upper liquid crystal cell and the lower liquid crystal cell And
A liquid crystal display for applying a voltage to the pattern electrode according to the light irradiation timing of the light source unit by the drive control unit and controlling the light transmitted through the pattern electrode to display the pattern electrode portion in a desired color A device,
The upper liquid crystal molecules constituting the upper liquid crystal layer are twisted in a first twist direction along a helical axis parallel to the normal line of the upper substrate, and the lower liquid crystal molecules constituting the lower liquid crystal layer are The first torsional direction and the second torsional direction are opposite to each other, being located in a second torsional direction along a spiral axis parallel to the normal of the lower substrate;
The pretilt angle of the upper liquid crystal molecules located near the upper end of the upper liquid crystal layer and the pretilt angle of the lower liquid crystal molecules located near the lower end of the lower liquid crystal layer are opposite and substantially the same angle. And
The pretilt angle of the upper liquid crystal molecules located near the lower end of the upper liquid crystal layer and the pretilt angle of the lower liquid crystal molecules located near the upper end of the lower liquid crystal layer are opposite and substantially the same angle. And
The orientation direction of the upper liquid crystal molecules located near the lower end of the upper liquid crystal layer and the orientation direction of the lower liquid crystal molecules located near the upper end of the lower liquid crystal layer are opposite to each other by 180 degrees. A liquid crystal display device. When the birefringence of the upper liquid crystal molecule is Δn1, the thickness of the upper liquid crystal layer is d1, the birefringence of the lower liquid crystal molecule is Δn2, and the thickness of the lower liquid crystal layer is d2.
2. The liquid crystal display device according to claim 1, wherein each of Δn1 · d1 and Δn2 · d2 is set to approximately 500 to 600 nm. A plurality of the pattern electrodes are disposed on one of the upper liquid crystal cell and the lower liquid crystal cell,
The liquid crystal display device according to claim 1, wherein each of the pattern electrodes is independently controlled in voltage application by the drive control unit. The pattern electrode is configured in such a manner that the capacitance changes according to the facing interval, and is arranged in the upper liquid crystal cell,
The capacitance change position detection part which detects the capacitance change position in the said upper side liquid crystal cell when the said pattern electrode part of the said upper side liquid crystal cell is pressed downward is provided. The liquid crystal display device according to any one of the above. The pattern electrode is disposed in the lower liquid crystal cell;
A touch sensor electrode that can detect that the upper liquid crystal cell is pressed by changing the electrostatic capacitance is disposed,
4. A capacitance change position detection unit that detects a capacitance change position in the upper liquid crystal cell when the touch sensor electrode portion of the upper liquid crystal cell is pressed downward. A liquid crystal display device according to any one of the above. The light source unit includes a plurality of LEDs that emit light of different colors,
The liquid crystal display device according to claim 1, further comprising a light emission control unit capable of independently controlling light emission of each of the plurality of LEDs. An upper liquid crystal cell comprising a pair of transparent upper substrates disposed in parallel to each other and an upper liquid crystal layer sealed in a layer between the pair of upper substrates;
A lower liquid crystal cell comprising a pair of transparent lower substrates arranged in parallel to each other and a lower liquid crystal layer sealed in layers between the pair of lower substrates, and being bonded to the lower surface of the upper liquid crystal cell When,
A light source unit disposed on the lower surface side of the lower liquid crystal cell and irradiating light of different colors toward the lower liquid crystal cell;
A drive control unit that performs voltage application control on a pair of pattern electrodes formed in a desired pattern and arranged in parallel to each other and irradiation control on the light source unit with respect to one of the upper liquid crystal cell and the lower liquid crystal cell And
A liquid crystal display for applying a voltage to the pattern electrode according to the light irradiation timing of the light source unit by the drive control unit and controlling the light transmitted through the pattern electrode to display the pattern electrode portion in a desired color A device,
The pretilt angle of the liquid crystal molecules located near the upper end of the upper liquid crystal layer and the pretilt angle of the liquid crystal molecules located near the lower end of the upper liquid crystal layer are in the same direction and substantially the same angle,
The pretilt angle of the liquid crystal molecules located near the upper end of the lower liquid crystal layer and the pretilt angle of the liquid crystal molecules located near the lower end of the lower liquid crystal layer are in the same direction and substantially the same angle,
An alignment direction of liquid crystal molecules positioned near the lower end of the upper liquid crystal layer and an alignment direction of liquid crystal molecules positioned near the upper end of the lower liquid crystal layer are opposite to each other by 180 degrees. .

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