JPH07159753A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a color liquid crystal display device applicable to a reflection type without using a color filter and automatically changing a display color corresponding to a lapse of time. CONSTITUTION:This device is provided with a liquid crystal display body 3 displaying different colors according to driving voltages VR, VB, VG and a drive control circuit 5 alternately switching the driving voltages VR, VB at every prescribed time. Transfer gates 53a, 53b, 53c connected to respective signal electrodes Y three pieces each are turned on/off corresponding to the display data outputted from a control part 56, and the drive voltages VR, VB, VG are applied selectively to the signal electrodes Y. Either one side of PMOSs 60, 62 or NMOSs 61, 63 are turned on alternately synchronizing with an output signal with a prescribed frequency of a frequency division circuit 58. When the PMOSs 60, 62 are turned on, respective pixels whose transfer gates 53a and 53b are turned on become a red color and a blue color respectively. When the NMOSs 61, 63 are turned on, respective pixels displayed in the red color and the blue color change to the blue color and the red color respectively. When the PMOSs 60, 62 are turned on again, respective pixels return to original colors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal display device, and more particularly, to a color liquid crystal display device which performs color display by utilizing the birefringence of liquid crystal.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display device has been known as a display device for a television, a personal computer, a wristwatch and the like, and in recent years, it has been possible to display a chromatic color like a liquid crystal color television or a color display of a computer terminal. Color liquid crystal display devices that can be used are also becoming popular.

In a color liquid crystal display device, in general,
The display is a transmissive type in which a liquid crystal cell is sandwiched between a pair of polarizing plates and a backlight (illumination light source) is arranged outside one polarizing plate. In that case, the liquid crystal cell is formed by sandwiching liquid crystal between a pair of transparent electrodes facing each other, and a color filter that selectively transmits light of a specific wavelength is provided on the side of one of the transparent electrodes.

By turning on / off the drive voltage applied between the pair of transparent electrodes, the light of the backlight may or may not pass through the liquid crystal display. The light of the backlight is colored with a specific color that is selectively transmitted by the color filter when passing through the color filter in the liquid crystal display. The colored transmitted light is emitted from the liquid crystal display, and a display colored with the color of the color filter is obtained.

That is, in the conventional liquid crystal display, the liquid crystal cell merely functions as an optical switch, and the coloring of light is performed by the color filter.

[0006]

However, the conventional color liquid crystal display device described above has a drawback in that a loss occurs when light passes through the color filter and the display becomes dark. Therefore, it has been extremely difficult to add a color filter to a reflective liquid crystal display having a reflective plate on the back surface of the liquid crystal cell to display the entire display including the background in chromatic colors.

That is, in the conventional color liquid crystal display device and the device of the multi-color or full-color matrix display system, it is inevitable to provide a backlight in the device, which not only makes the display device expensive. However, there is a problem in that it leads to higher power consumption and hinders further thinning. In particular, those problems have been obstacles to the use of the color liquid crystal display device in a simple display section that does not require a very fine display, such as a calculator, a wristwatch, and an instrument.

Further, the color filter, like other optical elements such as a polarizing plate, is required to have high accuracy in dimensions such as thickness and its assembly, which causes an increase in cost of the liquid crystal display device.

Further, conventionally, the same color is continuously displayed unless a command for changing the display color is inputted by key input or the like, so that there is a drawback that the display is poor in change and does not look good.

The present invention has been made in view of the above circumstances, and an object thereof is to obtain a bright color display without using a color filter and without providing a dedicated light source, which is suitable for the reflection type. An object of the present invention is to provide a color liquid crystal display device whose display color automatically changes in response to the passage of time.

[0011]

In order to achieve the above object, the present invention provides a liquid crystal cell in which a liquid crystal layer is interposed between a pair of electrodes facing each other, directly on at least the surface on which light is incident. Alternatively, it is provided with a liquid crystal display in which a polarizing plate is arranged via a retardation plate, and the light transmitted through the liquid crystal layer is elliptically polarized by the birefringence action of the liquid crystal, and the liquid crystal drive voltage applied to the liquid crystal layer is changed. A color liquid crystal display device that changes the polarization state of elliptically polarized light by changing the retardation of a liquid crystal layer to change the color of transmitted light, and a drive voltage generation circuit that generates a plurality of drive voltages of different magnitudes,
A voltage switching unit that selects two or more driving voltages from a plurality of the driving voltages and switches one output driving voltage from the selected driving voltages at predetermined times, and the driving voltage and the voltage switching unit, respectively. From the output drive voltage, a voltage selection means for selecting a drive voltage corresponding to display data including color information to be displayed, and a liquid crystal drive voltage composed of the drive voltage selected by the voltage selection means between the pair of electrodes. And a liquid crystal driving circuit for applying a voltage.

[0012]

According to the color liquid crystal display device described above, the electrodes of the liquid crystal display that display different colors corresponding to the applied drive voltage value contain color information to be displayed from a plurality of different drive voltages. However, since two or more drive voltages corresponding to the display data are selected and the selected two or more drive voltages are applied alternately by switching at a predetermined time, the elliptically polarized transmitted light corresponding to the selected drive voltage is applied. Thus, it is possible to perform color display with the number of colors corresponding to the number of types of drive voltage applied to the electrodes without using a color filter.

Therefore, as compared with the case where a color filter is used, light transmission loss due to the color filter is eliminated, so that a bright color display can be obtained, and in a transmissive type as well as a reflective type liquid crystal display which does not require a backlight. In addition, color display is possible, and the liquid crystal display device can be inexpensive, thin, and consume less power.

Further, since the selected two or more drive voltages are switched to each other at every predetermined time, the colors of the pixels to which the two or more drive voltages are applied are automatically switched at every predetermined time. , A variety of displays can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the color liquid crystal display device according to the present invention will be described below with reference to FIGS.

FIG. 1 schematically shows a cross section of an example of a color liquid crystal display device according to the present invention. As shown in FIG. 1, the color liquid crystal display device 1 includes a liquid crystal display body 3 and a drive control circuit 5 for driving the liquid crystal display body 3, and different colors are used depending on the drive voltage value applied to the liquid crystal display body 3. The display is performed.

In the liquid crystal display 3, the liquid crystal cell 30 is sandwiched between a pair of upper polarizing plate 40 and lower polarizing plate 41, and the liquid crystal cell 3 is further provided.
0 and the upper polarization plate 40, a retardation plate 42 is interposed, and a reflection plate 43 is provided on the lower surface of the lower polarization plate 41 (the back surface of the liquid crystal display 3).

The liquid crystal cell 30 comprises a pair of transparent substrates 31, 3
2 are bonded together via a sealant 33, and the liquid crystal layer 3 is provided inside thereof.
4 is enclosed. Transparent electrodes 36 and 38 are formed in advance on the surfaces of the transparent substrates 31 and 32 facing each other, and alignment films 37 and 39 are formed so as to cover the transparent electrodes 36 and 38, respectively.

The alignment films 37 and 39 are provided to control the alignment direction of the liquid crystal molecules. For example, the alignment films 37 and 39 are subjected to an alignment treatment such as rubbing with a cloth,
The alignment direction of the liquid crystal molecules adjacent to each other is regulated so that the long axis direction of the liquid crystal molecules is along the alignment processing direction. Accordingly, the alignment state of the liquid crystal molecules 34a of the liquid crystal layer 34 is 180 ° to 27 ° from the one transparent substrate 31 toward the other transparent substrate 32.
It becomes a state that it is lined up so as to be twisted at an angle of 0 °. That is, the liquid crystal cell 30 is a super twisted nematic (STN) type liquid crystal cell.

The retardation plate 42 elliptically polarizes the linearly polarized light transmitted through the upper polarizing plate 40, and its optical axis (fast axis or slow axis) is adjacent to the retardation plate 42. They are arranged in a state of being slanted by a predetermined angle with respect to the transmission axis 40a of 40.

In FIG. 2, the alignment treatment direction in the liquid crystal cell 30, the optical axis of the retardation plate 42 and the polarizing plate 4 are shown.
An example of a combination of 0 and 41 transmission axes is shown in a schematic plan view for each component. In the figure, straight lines 31a and 32a with single arrows indicate the alignment treatment directions applied to the lower alignment film 37 and the upper alignment film 39 in the liquid crystal cell 30, and straight lines 40a and 41a with double arrows respectively indicate the upper polarizing plate 40. And the transmission axis of the lower polarizing plate 41, and the straight line 42a is the optical axis of the retardation plate 42. The straight line S is a reference line extending in the left-right direction of the display surface and is provided for convenience of explanation.

As shown in FIG. 2, the alignment treatment directions 31a and 32a of the liquid crystal cell 30 are set in directions opposite to each other with respect to the reference line S by a predetermined angle θ, whereby liquid crystal molecules 34a are formed. The alignment state of the lower transparent substrate 3
The orientation is twisted in the angle and direction indicated by arrow T from the first side toward the upper transparent substrate 32 side.

Further, the optical axis 42a of the retardation plate 42 is a slow axis here, and a predetermined tilt angle ψ with respect to the reference line S.
It crosses at an angle. Further, in this embodiment, the transmission axes 40a, 41 of the pair of upper and lower polarizing plates 40, 41 are arranged.
a is substantially parallel to each other, and the optical axis 42a of the retardation plate 42
The tilt angle φ is deviated from the diagonal direction.

In the color liquid crystal display device 1 having the liquid crystal display body 3 having the above structure, the polarization effect of the retardation plate 42 and the polarization effect of the liquid crystal cell 30 cause the liquid crystal display element 3 to enter and be reflected by the reflection plate 43. Light emitted outside the liquid crystal display body 3 is colored. At this time, the display color can be arbitrarily changed by changing the magnitude of the voltage applied to the liquid crystal cell 30 by the drive control circuit 5. It is like this.

The coloring mechanism will be described below. Light from the outside becomes linearly polarized light as it passes through the upper polarizing plate 40, and further passes through the retardation plate 42 in the process of passing through the retardation plate 4.
It becomes elliptically polarized light by being subjected to a polarization action according to the optical arrangement conditions such as the position of the second optical axis 42a and the retardation value.
While passing through the liquid crystal cell 30, the elliptically polarized light is further subjected to a polarization action according to the optical arrangement condition of the liquid crystal cell 30 and the value of retardation, and its polarization state changes.

When the elliptically polarized light that has been polarized by the retardation plate 42 and the liquid crystal cell 30 is incident on the lower polarizing plate 41, of the elliptically polarized light, the transmission axis 41 of the lower polarizing plate 41 is included.
Only the wavelength light of the polarization component along a passes through the lower polarizing plate 41. Therefore, the light (linearly polarized light) emitted from the lower polarizing plate 41 is in a colored state. The hue is mainly determined by the retardation of the retardation plate 42 and the retardation of the liquid crystal cell 30.

Further, the light that has passed through the lower polarizing plate 41 is reflected by the reflection plate 43 and is emitted to the upper surface side of the liquid crystal display body 3 through a route opposite to the above-mentioned optical route, so that depending on the color of this emitted light. Display is obtained.

The retardation of the retardation plate 42 is
The product Δn of the refractive index anisotropy Δn of the retardation plate 42 and the plate thickness d
d, and the retardation of the liquid crystal cell 30 is determined by the alignment state of the liquid crystal molecules 34a. Therefore, by changing the voltage value applied to the liquid crystal cell 30, the liquid crystal molecules 3 are changed.
By changing the alignment state of 4a, the liquid crystal cell 30
Retardation changes and the polarization effect in the liquid crystal cell 30 changes.

Specifically, when no voltage is applied to the liquid crystal cell 30, the light incident on the liquid crystal display body 3 depends on the polarization effect of the retardation plate 42 and the initial twist angle T of the liquid crystal molecules 34a. The polarized light is changed to elliptically polarized light. Then, the light passes through the lower polarizing plate 41, is reflected by the reflecting plate 43, passes through the opposite path, and is emitted to the upper surface side of the liquid crystal display body 3. The display color at that time is a color corresponding to the retardation of both the retardation plate 42 and the liquid crystal layer 34 oriented at the initial twist angle T.

Further, the transparent electrodes 36 and 38 of the liquid crystal cell 30.
When a voltage is applied in the meantime, the liquid crystal molecules 34a gradually rise from the initial twisted state as the voltage value increases. The retardation of the liquid crystal cell 30 changes according to the raised alignment state, and the light incident on the liquid crystal display 3 has a polarization effect of the retardation plate 42 and a polarization effect according to the changed retardation of the liquid crystal cell 30. It is received and becomes elliptically polarized light accordingly. Therefore, the display color at that time is different from the color when no voltage is applied to the liquid crystal cell 30 described above.

Further, in the liquid crystal cell 30, liquid crystal molecules 34a are formed.
When a voltage is applied that causes the liquid crystal to rise and align almost vertically, the retardation of the liquid crystal cell 30 also becomes substantially “0”. Therefore, the polarization effect of the liquid crystal cell 30 disappears,
The light incident on the liquid crystal display body 3 becomes elliptically polarized light only by the polarization effect of the retardation plate 42. And the elliptically polarized light is
The light is emitted from the liquid crystal display 3 through the lower polarization plate 41, the reflection plate 43, and the reverse path, and is colored in a color corresponding to the retardation of the retardation plate 42.

Regarding the angles θ, T, ψ, and φ described above, for example, θ is 30 °, T is 240 °, and ψ is 45 °.
φ is preferably about 45 °. Further, the retardation of the retardation plate 42 is about 1240 nm, and Δn of the liquid crystal cell 30 is
Is 0.1238, d is 6.8 μm, and Δn · d at that time is preferably about 842 nm. In that case, in the liquid crystal display body 3 having the above configuration, when the effective drive voltage applied to the liquid crystal cell 30 is about 1.0 V, 1.3 V, and 2.3 V, blue, green, and red displays are obtained, respectively. .

Next, an example of the drive control circuit 5 configured to display three colors in the liquid crystal display 3 will be described.

FIG. 3 shows an example of the circuit configuration. As shown in the figure, the drive control circuit 5 includes a shift register 50, a first latch circuit 51A, a second latch circuit 51B, a decoder 52, and a plurality of transfer gates (TG) 53a, 53b, 53c. A drive circuit, a drive voltage generation circuit 54, a scan electrode drive circuit 55,
It has a control unit 56, an oscillation circuit 57, and a frequency dividing circuit 58. Incidentally, in FIG. 3, the display unit MD of the liquid crystal display 3 is shown.
Has a simple matrix display configuration with a plurality of scanning electrodes X and a plurality of signal electrodes Y, and is driven by the drive control circuit 5 in a time division manner.

Transfer gates 53a, 53b, 53
Three sets of c are arranged for each signal electrode Y. In each set, the output terminals of the transfer gates 53a, 53b, 53c are commonly connected and connected to the corresponding signal electrode Y.

Further, the transfer gates 53a, 53
The non-control terminals of b and 53c are connected to the power lines L4, L5,
It is connected to L2. The power supply lines L4 and L5 are both branched into power supply lines L0 and L1, and a PMOS 60 is provided between the power supply line L4 and the power supply line L0 and an NMOS is provided between the power supply line L4 and the power supply line L1.
61, a PMOS 62 is provided between the power supply line L5 and the power supply line L1, and an NMOS 63 is provided between the power supply line L5 and the power supply line L0.

PMOS 60, 62 and NMOS 61, 6
An enhancement type FET 3 functions as a switching element. That is, by switching the FETs, the power supply lines L4 and L5 are connected to opposite power supply lines L0 and L1, respectively.

Here, the power supply lines L0 and L1 are connected to the drive voltage V
R, VB output lines, and transfer gates 53a, 5
The opposite ones of the drive voltages VR and VB are applied to the respective non-control terminals of 3b. The power supply line L2 has a drive voltage VG
Drive voltage VG is applied to the non-control terminal of the transfer gate 53c.

Further, the transfer gates 53a, 53
The control terminals b, 53c are connected to the signal lines La, Lb, Lc.
Is connected to the decoder 52 via
The transfer gates 53a, 53b, and 53c are turned on / off in response to the control signals output from the respective bits. Then, the transfer gates 53a, 53
The gate which is turned on among b and 53c outputs the input (that is, the drive voltages VR, VB and VG) of its non-control terminal from the output terminal.

That is, the decoder 52 and the transfer gates 53a, 53b, 53c constitute a voltage selecting means. The voltage selecting means selectively selects which one of the set of three transfer gates 53a, 53b, 53c connected to each signal electrode Y to turn on, in accordance with the display data. The voltage applied to the signal electrode Y is selected from the drive voltages VR, VB and VG.

Here, the display data is data composed of, for example, 2 bits. The combination of the first bit data (“0” or “1”) and the second bit data (“0” or “1”) causes the decoder 52 to be a set of three connected to one signal electrode Y. Transfer gate 53
Control signals of different combinations are generated for a, 53b, and 53c.

By the way, the shift register 50 fetches the display data corresponding to each signal electrode Y from the data line DL and outputs it to the first latch circuit 51A in synchronization with the synchronization control signal inputted from the control section 56. To do.

The first latch circuit 51A latches the display data output from the shift register 50 and outputs it to the second latch circuit 51B in synchronization with the synchronization control signal input from the control unit 56. The second latch circuit 51B latches the display data output from the first latch circuit 51A and outputs the display data to the decoder 52 in synchronization with the synchronization control signal input from the control unit 56.

The decoder 52 includes a second latch circuit 51B.
Of the display data output by each of the signal lines L
A control signal (specifically, a high / low signal) for turning on / off each of the transfer gates 53a, 53b, 53c corresponding to display data is output to a, Lb, Lc.

The drive voltage generating circuit 54 uses the power supply voltage or a voltage of a predetermined value obtained by boosting the power supply voltage by a DC-DC converter if necessary, and outputs the drive voltages VR, VB, VG is generated to generate power lines L0,
In addition to outputting to L1 and L2, a scan voltage for the scan electrode X is generated and supplied to the scan electrode drive circuit 55 via the power supply line L3. Further, the drive voltage generation circuit 54 supplies the power supply voltage to the oscillation circuit 57 via the power supply line L6.

The oscillation circuit 57 operates a crystal oscillator or the like by the power supply voltage supplied from the drive voltage generation circuit 54 to generate a predetermined clock signal and outputs it to the frequency dividing circuit 58.

The frequency dividing circuit 58 generates an output signal of a predetermined frequency synchronized with the clock frequency output from the oscillating circuit 57, for example, a one second clock signal, and outputs the above-mentioned PMOS 60, 62 and NMOS 61, 63 via the signal line Lt. Output to the gate electrode.

The output signal of the frequency dividing circuit 58 is "0 (low)".
At this time, the PMOS 60 and 62 are turned on, while the NMOS 6
1, 63 turn off. As a result, the power supply line L4 is separated from the power supply line L1 and connected to the power supply line L0, and the drive voltage VR is applied to the non-control terminal of the transfer gate 53a. On the other hand, the power supply line L5 is separated from the power supply line L0 and connected to the power supply line L1, and the drive voltage VB is applied to the non-control terminal of the transfer gate 53b.

The output signal of the frequency dividing circuit 58 is "1 (high)".
At the time of, the PMOS 60 and 62 are turned off, while the NMOS 6 is
1, 63 turn on. As a result, the power supply line L4 is disconnected from the power supply line L0 and connected to the power supply line L1, and the drive voltage VB is applied to the non-control terminal of the transfer gate 53a. On the other hand, the power supply line L5 is separated from the power supply line L1 and connected to the power supply line L0, and the drive voltage VR is applied to the non-control terminal of the transfer gate 53b.

That is, the frequency dividing circuit 58, the PMOSs 60 and 6
2 and the NMOSs 61 and 63 constitute a voltage switching means, and the voltage switching means 58 divides the frequency divider circuit 58.
The drive voltage applied to the non-control terminals of the transfer gates 53a and 53b is alternately changed at every predetermined time in response to the output signal of, and the display color is changed.

The scan electrode drive circuit 55 generates a scan signal in synchronization with the synchronization control signal from the controller 56. Then, the scan electrode drive circuit 55 line-sequentially scans each scan electrode X based on the scan signal, and applies the applied voltage (scan voltage) supplied from the drive voltage generation circuit 54.

The controller 56 generates a synchronization control signal and outputs it to the shift register 50, the first latch circuit 51A, the second latch circuit 51B and the scan electrode drive circuit 55.

The operation of the drive control circuit 5 having the above configuration will be specifically described below. Here, as shown in FIG.
As an example, a case of displaying the time on the display unit MD of the liquid crystal display body 3 described above will be described. In the example of FIG. 4, a frame 9 is displayed around the “hour: minute” display portion 8 displayed in green, and the frame 9 is formed by alternately arranging blue pixels and red pixels, The color of each pixel of the frame 9 is set at a predetermined time, for example, 1
It alternates between blue and red every second.

In the liquid crystal display 3, the angle θ,
The values of T, ψ, φ, retardation of the retardation plate 42, and Δn · d of the liquid crystal cell 30 are the values exemplified above. Then, the drive voltage VR output from the drive voltage generation circuit 54,
Both VB and VG are effective values of 2.3V, 1.0V,
It is set to 1.3V. In that case, the display data and each transfer gate (T
G) Table 1 shows the relationship between the combination of control signals of 53a, 53b, 53c, the applied voltage value (effective value), and the display color.

[Table 1]

When the display data corresponding to the signal electrode Y is input to the shift register 50, the shift register 50 fetches the display data in synchronization with the synchronization control signal from the control unit 56 and the first latch circuit 51A. Output to.

The first latch circuit 51A latches each display data output from the shift register 50 in synchronization with the synchronization control signal from the control unit 56, and the second latch circuit 51B.
The second latch circuit 51B latches each display data output from the first latch circuit 51A and outputs the latched display data to the decoder 52 in synchronization with the synchronization control signal from the control unit 56.

The decoder 52 includes a second latch circuit 51B.
Each of the display data output by is decoded to generate a control signal for turning on / off the transfer gates 53a, 53b, 53c.

For example, the scan electrode drive circuit 55 selects the scan electrode X corresponding to the "hour: minute" display section 8 in FIG. 4 in synchronization with the synchronization control signal input from the control section 56.
When the pixels of the "hour: minute" display unit 8 are displayed in green, the display data input to the shift register 50 is "0, 1 (the left is the first bit data and the right is the second bit data. The same shall apply hereinafter.) ”.

Then, the decoder 52 decodes the display data "0, 1" and transfers it to the transfer gate 53.
a, 53b, 53c control signal "0, 0, 1 (each control signal of transfer gates 53a, 53b, 53c from the left. The same applies to the following)".

As a result, the transfer gate 53c
Only the signal electrode Y of the pixel of the "hour: minute" display section 8 is turned on.
Then, a drive voltage VG having an applied effective voltage of 1.3 V is applied, and the corresponding pixel of the "hour: minute" display portion 8 is displayed in green.

Further, in synchronization with the synchronization control signal input from the control unit 56, the scan electrode driving circuit 55 selects the scan electrode X corresponding to the frame display unit 9 in FIG. When displaying, the display data input to the shift register 50 is “1,0” or “1,1”.

When the display data is "1,0", the transfer gates 53a, 53b generated by the decoder 52,
The control signal of 53c is "0, 1, 0", and only the transfer gate 53b is turned on. At this time, the frequency dividing circuit 58
If the output signal is 0, the PMOSs 60 and 62 are turned on and the drive voltage VB with an applied effective voltage of 1.0 V is applied to the non-control terminal of the transfer gate 53b, and the corresponding pixel of the frame display unit 9 is applied. 90 (see FIG. 4) is displayed in blue.

Then, the output signal of the frequency dividing circuit 58 is "1".
Then, the NMOSs 61 and 63 are turned on and the applied effective voltage is 2.3V to the non-control terminal of the transfer gate 53b.
Driving voltage VR is applied, and the corresponding pixel 90 changes from blue to red. When the output signal of the frequency dividing circuit 58 becomes “0” again, the PMOSs 60 and 62 are turned on and the drive voltage VB having the applied effective voltage of 1.0 V is applied to the non-control terminal of the transfer gate 53b, which is applicable. The pixel 90 of the frame display portion 9 changes from red to blue.

When the display data is "1,1", the transfer gates 53a, 53b generated by the decoder 52,
The control signal of 53c is "1, 0, 0", and only the transfer gate 53a is turned on. At this time, the frequency dividing circuit 58
If the output signal is 0, the PMOSs 60 and 62 are turned on, and the drive voltage VR which makes the applied effective voltage 2.3V is applied to the non-control terminal of the transfer gate 53a, and the pixel of the corresponding frame display unit 9 is applied. 91 (pixel next to the pixel 90,
(See FIG. 4) is displayed in red.

Then, the output signal of the frequency dividing circuit 58 is "1".
Then, the NMOSs 61 and 63 are turned on and the effective voltage applied to the non-control terminal of the transfer gate 53a is 1.0V.
Driving voltage VB is applied, and the pixel 91 of the corresponding frame display portion 9 changes from red to blue. Again, the frequency divider circuit 58
When the output signal of “0” becomes “0”, the PMOSs 60 and 62 are turned on, and the drive voltage VR having an applied effective voltage of 2.3 V is applied to the non-control terminal of the transfer gate 53a, and the pixel of the corresponding frame display unit 9 is applied. 91 changes from blue to red.

When the display data input to the shift register 50 is "0, 0", the decoder 52 controls the transfer gates 53a, 53b, 53c to "0, 0".
0, 0 "is generated. The decoder 52 outputs the control signal" 0, 0, 0 "to a set of transfer gates 53a, 5a.
When output to 3b and 53c, the transfer gates 53a, 53b and 53c of the set are all turned off. Therefore,
None of the drive voltages VR, VB, and VG are applied to the corresponding signal electrode Y, and the corresponding pixel is displayed in a background color different from red, blue, and green.

The above processing is continuously performed during the scanning of each scan electrode X by the scan electrode drive circuit 55. Also,
Color change by the output signal of the frequency dividing circuit 58 is performed by each scan electrode X.
It may or may not be synchronized with a cycle (frame cycle) in which one scan is completed and display of one frame ends.

As described above in detail, according to the color liquid crystal display device 1 of the present embodiment, unlike the conventional color liquid crystal display device, the magnitude of the drive voltage applied to the liquid crystal cell 30 without using the color filter. Different colors can be displayed by simply changing the height. In this case, since the color filter is not used, the loss of the amount of transmitted light is significantly reduced,
The display brightness can be made sufficiently high. Therefore, the brightness of the display is sufficient even if it is a reflective display body that does not use a backlight like the liquid crystal display body 3 in the above-mentioned embodiment, and practically no inconvenience occurs.

Therefore, the cost reduction, the thickness reduction and the power consumption reduction of the color liquid crystal display device can be achieved. The reflective type is particularly suitable for simple color display on a calculator or wristwatch.

Further, like the pixels 90 and 91 of the frame 9, the display color is automatically switched at every predetermined time,
A variety of displays can be obtained.

Although the liquid crystal displays 3 and 103 are of the reflective type in the above embodiment, they may be of the transmissive type without the reflector 43.

Further, in the above embodiment, the liquid crystal cell 3
Although 0 is an STN type cell, it is not limited thereto. For example, the twist angle of liquid crystal molecule alignment is 90.
A twisted nematic (TN) type cell having a degree of about ° or a homogeneous cell in which the twist orientation is not performed and the cells are oriented in one direction along the substrate may be used.

Further, although the retardation plate 42 is provided in the above embodiment, the retardation plate may be omitted. Also,
The transmission axes of the upper polarizing plate 40 and the lower polarizing plate 41 are not limited to parallel,
It may be orthogonal. Even in such a case, the display color changes by changing the voltage value applied to the signal electrode Y as in each of the above-described embodiments, color display is possible, and the display color changes at every predetermined time.

Furthermore, in the above embodiment, the case where the display colors are three colors has been described, but it is also possible to use two colors.
Of course, four or more colors may be used. Also, by providing an appropriate number of NMOSs and PMOSs and arranging them appropriately, 2
It is possible to switch not only between colors but also between three or more colors.

Further, in the above embodiment, the color switching of the frame display section 9 has been described, but the color of the "hour: minute" display section 8 may be switched, or the "hour: minute" display section may be switched. 8 and the frame display section 9 may be switched at the same time.

Needless to say, the present invention is not limited to displaying the time as in the above embodiment.

The switching elements for switching the drive voltages VR and VB are the PMOSs 60 and 62 of the above embodiment.
It is not limited to the NMOSs 61 and 63, and any type may be used as long as the drive voltages VR and VB can be switched according to the output signal of the frequency dividing circuit 58.

Furthermore, the present invention is not limited to the simple matrix system as in the above embodiment, but can be applied to the active matrix system and the segment display system, and further to the static drive system other than the time division drive system. Similarly, it is applicable.

Furthermore, if the drive voltage applied to the signal electrode Y can be set to a predetermined effective value, the pulse width of the pulse for applying the ON voltage can be changed or the number of times the ON voltage is applied among a plurality of frames. May be changed, and the driving form does not matter.

[0080]

According to the color liquid crystal display device of the present invention, a plurality of different driving voltages are applied to the electrodes of the liquid crystal display that display different colors according to the applied driving voltage value. The two or more drive voltages corresponding to the display data including the color information to be selected are selected, and the selected two or more drive voltages are applied by switching each other at a predetermined time. Therefore, an ellipse corresponding to the selected drive voltage is selected. Polarized transmitted light is obtained, and it is possible to perform color display of the number of colors corresponding to the number of types of drive voltage applied to the electrodes without using a color filter, and the display color is automatically changed at predetermined times. The display is switched and a variety of displays are obtained.

Accordingly, bright color display is possible not only in the transmissive type but also in the reflective type liquid crystal display body which does not require a backlight, and the liquid crystal display device can be made inexpensive, thin and consume less power.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of a color liquid crystal display device according to the present invention.

FIG. 2 is a schematic diagram showing, for each component, an example of a combination of an alignment direction of liquid crystal molecules, an optical axis of a retardation plate, and a transmission axis of a polarizing plate in a liquid crystal cell of the color liquid crystal display device.

FIG. 3 is a block diagram showing a configuration example of a drive circuit in the color liquid crystal display device.

FIG. 4 is a schematic view showing one display example in the color liquid crystal display device.

[Explanation of symbols]

MD display section VR, VB, VG drive voltage X scanning electrode Y signal electrode 1 color liquid crystal display device 3 liquid crystal display body 5 drive control circuit 30 liquid crystal cell 31, 32 transparent substrate 33 sealing material 34 liquid crystal layer 36, 38 transparent electrode 37, 39 Alignment Film 40 Upper Polarizing Plate 41 Lower Polarizing Plate 42 Phase Difference Plate 43 Reflecting Plate 50 Shift Register 51A First Latch Circuit 51B Second Latch Circuit 52 Decoder (Voltage Selector) 53a, 53b, 53c Transfer Gate (Voltage Selector) 54) Driving voltage generating circuit 55 Scan electrode driving circuit 56 Control unit 57 Oscillation circuit 58 Dividing circuit (voltage switching means) 60, 62 PMOS (voltage switching means) 61, 63 NMOS (voltage switching means)

Claims (1)

[Claims] 1. A liquid crystal comprising a liquid crystal cell having a liquid crystal layer interposed between a pair of opposing electrodes, and a polarizing plate disposed on at least a surface on which light is incident, directly or through a retardation plate. Equipped with a display body, the light transmitted through the liquid crystal layer is elliptically polarized by the birefringence effect of liquid crystal, and the polarization state of the elliptically polarized light is changed by changing the retardation of the liquid crystal layer by changing the liquid crystal driving voltage applied to the liquid crystal layer. A color liquid crystal display device that changes the color of transmitted light by changing the color of transmitted light, wherein a drive voltage generation circuit that generates drive voltages of different magnitudes and two or more drive voltages are selected from the plurality of drive voltages. Then, display is made from the voltage switching means for switching one output drive voltage from these selected drive voltages at predetermined time intervals, and the drive voltage output from each of the drive voltage and the voltage switch means. Voltage selection means for selecting a drive voltage corresponding to display data including information; and a liquid crystal drive circuit for applying a liquid crystal drive voltage composed of the drive voltage selected by the voltage selection means between the pair of electrodes. A color liquid crystal display device characterized by.