KR100861957B1 - Liquid crystal display device - Google Patents

Abstract

The gray scale display of the liquid crystal display changes the transmittance of the liquid crystal by the applied voltage applied to the liquid crystal element to display the halftone, but for generating the applied voltage applied to the liquid crystal to display the halftone. By providing a plurality of gradation reference voltage generating circuits as a basis, a gradation reference voltage having a? Characteristic according to the display color is generated for each display color, and an applied voltage according to the display color is further generated from the generated gradation reference voltage, and the display color The gray scale display according to the present invention was enabled, and excellent image display was made possible.

Ferroelectric liquid crystal, antiferroelectric liquid crystal, liquid crystal display device, portable terminal

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method of driving a liquid crystal display device and a liquid crystal display device, and more particularly, to a liquid crystal display device using ferroelectric liquid crystal (FLC) or anti-ferroelectric liquid crystal (AFLC) having spontaneous polarization. It is about.

In general, TN (Twisted Nematic) liquid crystals have been widely used, and the response speed with respect to an applied voltage is 10 to 10 Hz, and the rise time until the transmittance of the liquid crystal element reaches 0% to 95% after applying the voltage is The smaller the applied voltage difference is, the longer it may be to 100 kHz (Patent Document 1). Therefore, in the case of performing halftone display with different numbers of gray scales, the response speed is drastically slowed down. Therefore, when a moving image is displayed at 60 images / second in a liquid crystal display device using a TN liquid crystal, the liquid crystal molecules operate completely. Since the image is blurred due to failure, the TN liquid crystal is not suitable for moving image display applications such as multimedia.

In addition, since the liquid crystal material has a wavelength dependency, the gamma characteristic curve differs for each display color. Therefore, when gradation by monochromatic color is displayed on a liquid crystal display device, coloring is seen somewhat. Moreover, in the conventional liquid crystal display device, a white cold cathode tube is provided on the rear side of the liquid crystal panel, and color filters of respective RGB colors are provided on the liquid crystal element on the front side of the liquid crystal panel, respectively, and the voltage applied to each liquid crystal element. By changing the transmittance | permeability of a liquid crystal element, the color display by mixing of three primary colors is performed.

It is necessary to perform gamma correction with respect to each RGB color by wavelength dependence of this liquid crystal material itself, a color filter characteristic, and the visibility of a person, and in a conventional liquid crystal display device, it applies to a liquid crystal pixel according to the gradation. The display data is corrected so that the? Characteristic curve is the same for each display color by making the number of applied voltages about 4 times the number of gray levels of the input image data.

With reference to FIG. 1 and FIG. 2, the specific example regarding the gray scale display of the said conventional liquid crystal display device is demonstrated. In FIG. 1, voltages V0 and V8 are applied to the gray scale reference voltage generation circuit 200 from an LCD power supply circuit (not shown) to divide the voltages applied by the resistors R1 to R8 connected in series. This divided voltage was used as a gradation reference voltage applied to the liquid crystal element. The gradation reference voltages V0, V1, ..., V7, V8 generated by the gradation reference voltage generation circuit 200 are further divided by the gradation voltage generation circuit 220 in the source driver 210, and the respective liquid crystals are divided. The number of gradation voltages applied to the device is set to 64.

In such a conventional liquid crystal display device, since there is only one type of gradation voltage, as described above, the display data is converted by the LUT 230 and the data latched by the LUT 230 in order to match different gamma characteristics by respective RGB colors. The circuit 240 is held, and then the held data is D / A converted and amplified at the D / A conversion + amplifier stage 250, and then at each level from the gradation voltage circuit. Converted to analog voltage based on the reference voltage. The converted analog voltages are 001 pixels (R), 001 pixels (G), 001 pixels (B),... And 800 pixels (R), 800 pixels (G), and 800 pixels (B) are sent out at predetermined timings. Here, one display pixel is composed of one set of three pixels of 001 pixels R, 001 pixels G, and 001 pixels indicated by reference numeral 260, and all pixels indicated by reference numeral 270 indicate one line. The display pixel is comprised.

Details of the LUT 230 described above will be described with reference to FIG. 2. Fig. 2 shows the input gradation and output with the horizontal axis as the input gradation corresponding to the gradation data for a certain color of the image data, and the output voltage from the source driver 210 applied to the liquid crystal element corresponding to the input gradation as the vertical axis. It is a figure which shows the relationship of a voltage.

2 indicates the correspondence relationship between the gradation voltage generated by the gradation voltage generation circuit 220 and the gradation data. The gamma characteristic represented by this black spot needs to be corrected for each of the RGB colors by the wavelength dependence of the liquid crystal material itself, the characteristics of the color filter, and the visibility of the human eye. In order to obtain appropriate gamma characteristics, the LUT 230 converts the tone data n of the image data into n ', m into m', and the like as illustrated.

As described above, in order to obtain gamma characteristics suitable for each color, in the conventional liquid crystal display device, the source driver 210 generates a gradation voltage corresponding to about four times the number of gradations displayed on the liquid crystal panel. In addition, in order to accurately match the gamma characteristic of each color, the number of gradation voltages had to be increased. In other words, even if the number of gradation voltages is large, correcting the image data to correct the? Characteristic for each display color reduces the number of gradations that can be expressed.

Regarding the generation of the gray scale voltage described above, in the circuit corresponding to the gray scale reference voltage generating circuit 200 of FIG. 1, the divided voltage ratio by the resistance is determined based on the data previously stored in the nonvolatile memory. It is known to correct the γ characteristic by using a γ correction adjusting circuit composed of a constant flux and a resistance and a buffer amplifier (Patent Document 2). However, when the γ characteristic is largely different, such as blue and green, color reproduction is always required. This is not good.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2000-137809

[Patent Document 2] Japanese Unexamined Patent Publication No. 2004-080615

In addition to the drawback that the above-mentioned TN liquid crystals have a slow rise time and use of RGB color filters, the TN liquid crystal is corrected to gamma characteristics of each color by using one type of gray reference voltage, corresponding to gray data. It also has the drawback that the color purity is bad because it generates an applied voltage to the liquid crystal.

On the disadvantage that the rise time of conventional TN liquid crystals is slow, as a liquid crystal material having spontaneous polarization, a liquid crystal display device using FLC or AFLC, which has a high response speed with respect to an applied voltage of several tens to several hundred microseconds, has been put to practical use. By using these high-speed responsive liquid crystals in a liquid crystal display device, a voltage applied to each pixel is controlled by a switching element such as a thin film transistor (TFT) or a metal insulator metal (MIM) to complete polarization of liquid crystal molecules in a short time. This enables time-division color system using a backlight which enables excellent moving picture display and emits light in red, green, and blue time division using an LED light source instead of a white backlight without using a color filter. As a result, a liquid crystal display device in which a gradation reference voltage and a gradation voltage are generated for each display color and the color reproducibility is very excellent is provided.

The present invention provides a liquid crystal display device having a liquid crystal element, characterized by having a plurality of gray level reference voltage circuits for generating a gray level reference voltage applied to the liquid crystal element corresponding to a plurality of gray levels of emission colors from the liquid crystal element. A liquid crystal display device is provided.

According to the present invention, there is provided a liquid crystal display device, wherein the light emission color is plural, and the gray reference voltage circuit generates a gray reference voltage corresponding to each of the plurality of light emission colors. .

In addition, the present invention provides a liquid crystal display device having a liquid crystal element, comprising: a source driver having a digital-analog conversion circuit for converting display data, which is digital data input to the liquid crystal display device, into an analog voltage applied to the liquid crystal element; The digital-analog conversion circuit has a gradation reference voltage generator that generates a plurality of sets of combinations of the plurality of analog voltages to convert the display data into corresponding analog voltages, and the source driver is included in the display data. A liquid crystal display device is provided which converts the digital data into an analog voltage based on any one of a plurality of sets of the analog voltages according to the display color.

In addition, the present invention provides a liquid crystal display device having a liquid crystal element, comprising: a source driver having a digital-analog conversion circuit for converting display data, which is digital data input to the liquid crystal display device, into an analog voltage applied to the liquid crystal element; The digital-analog conversion circuit has a gradation reference voltage generation section for generating a plurality of sets of combinations of the plurality of analog voltages in order to convert the display data into a corresponding analog voltage, and a γ correction circuit for correcting the gradation of the display data. In accordance with the display color data of the display data, the display color corresponding to the display data is synchronized with the display on the liquid crystal element, and the gray scale correction by the gamma correction circuit corresponds to the display color. Selecting the set of combinations of the analog voltages to It provides a liquid crystal display device characterized in that to display.

In addition, the present invention provides a liquid crystal display device having a liquid crystal element, comprising: a source driver having a digital-analog conversion circuit for converting display data, which is digital data input to the liquid crystal display device, into an analog voltage applied to the liquid crystal element; The digital-analog converting circuit has a gradation reference voltage generator for generating a plurality of sets of combinations of the plurality of analog voltages in order to convert the display data into a corresponding analog voltage, and a γ correction circuit for correcting the gradation of the display data. And a backlight capable of emitting light by switching a plurality of emission colors arranged on the back side of the liquid crystal element, and selecting a set of combinations of the analog voltages corresponding to the display colors according to the display color data among the display data. And controlling the light emission luminance of the backlight. A liquid crystal display device is provided.

In addition, in the gray scale reference voltage generation circuit which generates the gray scale reference voltage required when the LCD source driver IC which ICizes the source driver of a liquid crystal display device converts display data into digital-analog, supplies it to a LCD source driver IC. There are two or more types of gradation reference voltage combinations, the gradation reference voltage generating circuit for switching the combination of the gradation reference voltages in synchronization with the display color, and a γ correction circuit for correcting the gradation of the display data input to the display device. By synchronizing the gradation reference voltage generating circuit and the γ correction circuit in synchronization with each display color, the combination of the voltages output from the gradation reference voltage generating circuit and the correction method in the γ correction circuit can be changed for each color. There is provided a liquid crystal display device.

In addition, in the gray scale reference voltage generation circuit which generates the gray scale reference voltage required when the LCD source driver IC which ICizes the source driver of a liquid crystal display device converts display data into digital-analog, supplies it to a LCD source driver IC. The gradation reference voltage generating circuit having two or more kinds of gradation reference voltage combinations and switching the combination of the gradation reference voltages in synchronization with a display color, and a γ correction circuit for correcting the gradation of display data input to the liquid crystal display device; And a backlight control circuit for adjusting the emission luminance of the backlight disposed on the rear side of the liquid crystal element for each display color, and interlocking the gradation reference voltage generation circuit, the γ correction circuit and the backlight control circuit in synchronization with each display color. To adjust the voltage output from the gradation reference voltage generating circuit for each color. And, provides a liquid crystal display device, characterized in that the correction method in the γ correction circuit, being able to change the degree of light-emission luminance of the backlight according to the backlight control circuit.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a conventional example of a liquid crystal source driver and a gradation reference voltage generation circuit.

2 shows an example of gamma correction.

3 is a diagram showing a schematic block configuration of a liquid crystal display of the present invention.

4 is a diagram schematically illustrating a cross section of a liquid crystal panel used in the present invention.

Fig. 5 is a schematic perspective view showing an example of the configuration of a liquid crystal panel, a backlight and a deflection plate used in the present invention.

It is a figure which shows the schematic top view of the structure of the back side glass substrate side of the liquid crystal panel of the liquid crystal display device of this invention.

Fig. 7 is a diagram showing an outline of a source driver and a gradation reference voltage generating circuit of the present invention.

8 shows an example of display characteristics according to the present invention;

9 shows an example of display characteristics according to the present invention;

10 shows an example of display characteristics according to the present invention;

11 is a diagram showing an example of a circuit configuration of a second embodiment of the present invention.

In FIG. 12, FIG. 12A is a diagram for explaining display characteristics according to the second embodiment of the present invention, and FIG. 12B is for explaining display characteristics according to the second embodiment of the present invention. 12C is a diagram illustrating display characteristics according to the second embodiment of the present invention, and FIG. 12D is a diagram illustrating display characteristics according to the second embodiment of the present invention.

Fig. 13 shows the circuit construction of the third embodiment of the present invention.

In FIG. 14, FIG. 14A is a diagram for explaining display characteristics according to the third embodiment of the present invention, and FIG. 14B is for explaining display characteristics according to the third embodiment of the present invention. FIG. 14C is a diagram illustrating display characteristics according to the third embodiment of the present invention, and FIG. 14D is a diagram illustrating display characteristics according to the third embodiment of the present invention.

Fig. 15 is a diagram showing a configuration example using a digital potentiometer in the gradation reference voltage generating circuit of the present invention.

16 is a diagram illustrating an example of the configuration of a digital potentiometer.

It is a figure which shows an example of the portable terminal which registered the liquid crystal display device of this invention.

Explanation of symbols for the main parts of the drawings

1: liquid crystal panel 2: counter electrode

4: front side glass substrate 5: pixel electrode

6: back side glass substrate 9: liquid crystal layer

21: TFT 30: LCD control circuit

32: control unit 34: display data analysis unit

36: gamma correction unit 40: frame memory

50: LCD power supply circuit 52: gradation reference voltage generation circuit

54: gradation reference voltage generating circuit 60: backlight power supply circuit

62: backlight 64: luminance control unit

70: source driver 72: gradation voltage generating circuit

74: data latch circuit 76: D / A conversion + amplifier stage

80: gate driver

90: digital potentiometer control unit

92: digital potentiometer 100: portable terminal

104: liquid crystal display device

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on drawing which showed the Example.

FIG. 3 is a diagram showing a schematic block configuration of a liquid crystal display device according to the present invention, FIG. 4 schematically shows a cross section of a liquid crystal panel used in the present invention, and FIG. 5 is a configuration of a liquid crystal panel, a backlight, and a deflection plate. It is a figure which shows an example typically, and FIG. 6: is a top view which showed typically the structure of the back side glass substrate side of the liquid crystal panel of the liquid crystal display device of this invention.

In addition, this invention is not limited to a following example.

<First Embodiment>

3 is a diagram showing a schematic block configuration of a liquid crystal display of the present invention. As shown in FIG. 6, the liquid crystal panel 1 of FIG. 3 has a detailed structure in which the pixel electrodes 5 and the TFTs 21 are 1024 in the transverse direction in a matrix shape on the rear glass substrate 6 in the longitudinal direction. 768 and a total of 1024 x 768 are arranged, and each pixel electrode 5 is connected to the drain terminal of the TFT 21, respectively. The gate terminal of the TFT 21 is connected to the scanning line Li (i = 1, 2, 3, ..., 768) from the gate driver 80, and the source terminal of the TFT 21 is a source driver ( Data line Dj (j = 1, 2, 3, ..., 1024) from 70 is connected.

By inputting the scanning signals supplied from the gate driver 80 in line order to the scanning line Li, the TFT 21 whose gate is connected to the scanning line Li is controlled on / off, and the source driver in the on period. A data voltage input from 70 to each data line Dj is applied to the pixel electrode 5, and the data voltage up to that time is held by a capacitor (not shown) or the like in the off period. Then, the image is displayed by controlling the light transmittance of the liquid crystal determined by the VT characteristic indicating the relationship between the applied voltage which is the electro-optical characteristic of the liquid crystal and the transmittance of the liquid crystal element by the data voltage applied through the TFT 21. do.

In addition to the source driver 70 and the gate driver 80 as described above, the liquid crystal display device according to the present embodiment has an LCD control circuit 30, a frame memory 40, and an LCD as shown in FIG. The power supply circuit 50 and the peripheral circuit of the backlight power supply circuit 60 are provided.

The image control data and the synchronization signal Sync are input to the LCD control circuit 30 from a host device such as a personal computer. The LCD control circuit 30 writes and reads display data DATA in the frame memory 40. A RAM control signal RAM-CS for controlling the input / output timing for the control unit; a control signal SD-CS for controlling the operation of the source driver 70; a control signal GD-CS for controlling the operation of the gate driver 80; A control signal LP-CS necessary for controlling the LCD power supply circuit 50 and a control signal BP-CS necessary for controlling the backlight power supply circuit 60 are generated, and the generated control signals are transmitted to the frame memory 40. And output to the source driver 70, the gate driver 80, the LCD power supply circuit 50, and the backlight power supply circuit 60, respectively.

The LCD control circuit 30 writes the input display data DATA in synchronization with the input synchronization signal Sync, accumulates the data in the frame memory 40, and displays the display data DATA to be displayed on the liquid crystal panel 1. It receives from the frame memory 40 and outputs it to the source driver 70 as image data PD.

The synchronization signal Sync and the display data DATA input to the LCD control circuit 30 are signals after A / D conversion of the CRT output signal of the personal computer, signals restored by a DVI (Digital Video Interface) receiver IC, or DVI. Signal, a signal restored by a Low Voltage Differential Signaling (LVDS) receiver IC, or an LVDS signal, a signal created by a dedicated Peripheral Component Interconnect (PCI) card, a CPU mounted in a personal digital assistant (PDA) or a mobile phone, The LCD signal output from the LCD control IC or the video RAM on a device such as a PDA or a PC may be a signal obtained by directly controlling the LCD control circuit.

The frame memory 40 accumulates the display data DATA received by the LCD control circuit 30 in synchronization with the control signal RAM-CS generated by the LCD control circuit 30, and stores the accumulated display data DATA in the LCD control circuit ( 30) Input and output as RAM-DATA.

The LCD power supply circuit 50 is a drive voltage for the source driver 70, a drive voltage for the gate driver 80, and a liquid crystal panel 1 in synchronization with the control signal LP-CS generated by the LCD control circuit 30. A voltage Vcom to be applied to the counter electrode 2 (see FIG. 4) of the substrate, and the drive voltage for the source driver 70, the drive voltage for the gate driver 80, and the counter electrode 2 of the liquid crystal panel 1, respectively. Prints to

In response to the control signal BP-CS generated by the LCD control circuit 30, the backlight power supply circuit 60 generates a voltage for lighting the backlight and simultaneously performs on / off control of the backlight.

The source driver 70 receives the image data PD output by the LCD control circuit 30 in synchronization with the control signal SD-CS generated by the LCD control circuit 30, and also supplies a voltage corresponding to the image data PD. It is applied to the data line Dj of the liquid crystal panel 1.

The gate driver 80 applies the on / off control voltage to the scanning lines Li in line order in synchronization with the control signal GD-CS generated by the LCD control circuit 30.

7, an embodiment of the LCD power supply circuit 50 having a plurality of gradation reference voltage generating circuits 52 and 54 in the driving voltage for the source driver is shown. There are two or more types of gray reference voltage generating circuits 52 and 54, and the gray level reference voltages &quot; V0, V1,... , V8 &quot; are different for each gradation reference voltage generating circuit, and the generated gradation reference voltages &quot; V0, V1,... , V8 &quot; is switched by the switch 56 controlled by the selection signal SEL-CS from the LCD control circuit 30 for each display color. In addition, although the case where there are two types of gradation reference voltage generation circuits in FIG. 7 was shown, it respond | corresponds to R, G, and B, and the three kinds of gradation reference voltages "V0, V1,... , V8 &quot;, and the gradation reference voltages are set to &quot; V0, V1,... , V8, V9,... , V15, V16 "can be produced by partial dividing.

Next, the gradation voltage generation circuit 72 inside the source driver 70 includes the gradation reference voltages "V0, V1, ..." generated by the gradation reference voltage generation circuits 52, 54 input from the outside. , V8 &quot;, to generate gradation voltages for all gradation data. The voltage generated by the gray voltage generator circuit 72 is output to each pixel as a gray voltage by the D / A conversion + amplifier terminal circuit.

In addition, when there are two types of gradation reference voltage generating circuits, for example, red and green are generated in the same gradation reference voltage generation circuit, and gradation voltages in blue are generated in another gradation reference voltage generation circuit, and red For green and green, the display data may be corrected. In this manner, even in the two types of gradation reference voltage generating circuits, the amount of correction is minimized, so that color reproducibility can be improved as compared with the prior art.

With reference to FIG. 4, the liquid crystal panel 1 used for this invention is demonstrated. The liquid crystal panel 1 includes a pixel electrode 5 having excellent light transmittance made of indium tin oxide (ITO) disposed on a rear glass substrate 6 in a matrix form, and each of the pixel electrodes 5. Connected TFTs (not shown) are provided, and these are covered by the alignment film 7.

In the front side glass substrate 4, the counter electrode 2 made of ITO which is a transparent electrode, and the oriented film 8 are provided. An alignment film 7 and an alignment film 8 are provided on the pixel electrode 5 and the counter electrode 2, respectively, and the front side glass substrate 4 and the back side glass substrate 6 are each of the alignment layer 7 and the alignment layer ( 8 are disposed so as to face each other, and a spherical spacer (for example, 1.6 µm) is maintained between the alignment film 7 and the alignment film 8 to maintain an in-plane uniform gap (for example, 1.6 µm). 10) is scattered, and the liquid crystal layer 9 is formed by filling the FLC in this in-plane uniform gap. In this embodiment, the pixel electrodes 5 arranged in a matrix on the back side glass substrate 6 are 0.24 mm × 0.24 mm, and the number of pixels is 1024 in the transverse direction, 768 in the longitudinal direction, and 12.1 inches diagonal. The panel is taken as an example.

As shown in FIG. 5, the said liquid crystal panel 1 is inserted between two polarizing plates 11 and 12, and the backlight 62 is arrange | positioned at the back side glass substrate 6 side. One end of the backlight 62 is provided with a light source 64 having a red, green, and blue monochromatic surface-emission switchable LED array, and the backlight 62 has light emitted from each light source 64. A light diffuser plate for guiding light and diffusing the emitted light toward the rear glass substrate 6 is provided.

6 is a schematic plan view of the liquid crystal panel of the liquid crystal display device according to the first embodiment of the present invention, wherein the pixel electrodes 5 and the TFTs 21 are arranged in a matrix on the rear glass substrate 6. (Total of 1024 x 768 total of 1024 in the transverse direction and 768 in the longitudinal direction), each pixel electrode 5 is connected to the drain terminal of the TFT 21, respectively. The gate terminal of the TFT 21 is connected to the scanning lines Li (i = 1, 2, 3, ..., 768) from the gate driver 80, and the source terminal of the TFT 21 is data from the source driver 70. It is connected to the line Dj (j = 1, 2, 3, ..., 1024). The scanning line Li is connected in order to the output terminal of the gate driver 80, and the data line Dj is connected in order to the output terminal of the source driver 70.

The TFT 21 is controlled on / off by inputting the scanning signals supplied from the gate driver 80 in line order to the scanning lines Li, and during the on period, the TFTs 21 input data voltages input from the source driver 70 to the respective data lines Dj. It applies to the pixel electrode 5, and maintains the data voltage up to that time in an off period. The light transmittance of the liquid crystal determined by the V-T characteristic (applied voltage-transmittance characteristic), which is the electro-optical characteristic of the liquid crystal, is controlled by the data voltage applied through the TFT 21 to display an image.

According to the first embodiment of the present invention described above, in the case of the red display in FIG. 8, the green display in FIG. 9, and the blue display in FIG. 10, the horizontal axis represents the input gray scale of the image data, and the source driver is applied to the liquid crystal element in the vertical axis. A characteristic showing the output voltage of 70 is obtained. In this manner, an image can be displayed with a desirable gamma characteristic for each display color, and gamma characteristics can be adjusted without reducing the number of gray levels that the source driver 70 can express. In addition, the black spot in the figure indicates the gradation reference voltages "V0, V1,... , V8 ”.

As described above, in the present invention, the gamma characteristic can be adjusted for each display color, so that the display characteristics are good, and the liquid crystal display device of the present invention is a desktop liquid crystal display, which is used for a liquid crystal display, a PDA, or a mobile phone mounted in a notebook PC. In addition to the liquid crystal display on board, liquid crystal display mounted on game consoles, liquid crystal displays for home or portable televisions, video cameras and digital cameras facing the viewfinder or monitor, car navigation systems, point of sales terminals, etc. Application to a display device is possible.

In addition, in the above description, the source driver is illustrated with a plurality of functional blocks, but it is advantageous to make the IC in terms of reliability, miniaturization, and the like.

In addition, for example, in FIG. , V8 may be divided into a plurality of voltages, and the gray level reference voltage may be further divided to further divide the voltage into 64 gray levels including V0.

According to the first embodiment, the liquid crystal display device has two or more types of gradation reference voltages supplied to the source driver, and switches the combinations of the gradation display reference voltages for each color in synchronism with the display color, thereby γ characteristic. The curve can be changed for each display color.

Second Embodiment

Next, with reference to FIGS. 11 and 12 (a) to 12 (d), a second embodiment of the present invention will be described. In Fig. 11 showing the second embodiment, the same functional units as the first embodiment are denoted by the same reference numerals.

The second embodiment has a configuration substantially the same as that of the first embodiment shown in FIG. 3, but the internal configuration of the LCD control unit 30 is different. In FIG. 11, the display data DATA is stored in the frame memory 40 via the display data analyzer 34 provided inside the LCD control circuit 30. As shown in Fig. 12A, the display data analysis unit 34 analyzes the gradation frequency of each color of the display data in the display data in one frame. This result is transmitted to the control unit 32 inside the LCD control circuit 30, so that when reading display data stored in the frame memory 40, the less frequent grayscales can be displayed and the more frequent grayscales can be displayed. The gamma correction unit 36 and the gradation reference voltage generation circuit 52 are adjusted as shown in Figs. 12B and 12C, and the frequency as shown in Fig. 12D. The display is centered around many gradations.

That is, for each display color of the image data DATA, the number of pixels having each gray scale between 0 and 255 gray scales in one frame is interpreted by the display data analyzing section 34, and the display colors are shown in FIG. As shown, the gradation number and the frequency relationship are analyzed, and the γ correction which makes the distribution near 0 to 63 gradations centered on the distribution with a high frequency is performed by the γ correction unit 36, while the display data analysis unit The control signal LP-CS is transmitted from the control unit 32 to the gradation reference voltage generation circuit 52 to generate a gradation voltage of 0 to 63 gradations in the vicinity of the frequent distribution analyzed by (34). The gradation voltage having the characteristic of the gradation number-output voltage showing the γ characteristic shown in 12 (c) is generated by the gradation voltage generating circuit 72, and the display shown in Fig. 12 (d) is generated by this gradation voltage. In the vicinity of gradation with many gradations An image is displayed on a liquid crystal display device. Here, in FIG. 11, one type of the gradation reference generation circuit 52 is provided, but a plurality of types may be provided as in the first embodiment.

By performing the above operation for each display color, the gradation expression more than the gradation number that can be expressed by the source driver 70 can be realized by the liquid crystal element, resulting in a color display device of smooth color expression.

The display device with improved display characteristics is a desktop liquid crystal display, such as a liquid crystal display mounted on a notebook PC, a liquid crystal display mounted on a PDA or a mobile phone, a liquid crystal display mounted on a game machine, or a liquid crystal display for a home or portable television. The present invention can be applied to display devices such as video cameras, digital cameras, car navigation devices, and POS terminals that face the viewfinder or monitor.

According to the second embodiment, the combination of the gradation reference voltage supplied to the LCD source driver and the γ correction circuit for correcting the gradation of the display data input to the liquid crystal display device are linked to subtract gradations of the less frequently displayed data. It is possible to express multi-gradation even by using an LCD source driver with a small number of gradations that can be expressed by expressing gradations with a high frequency.

Third Embodiment

Next, a third embodiment of the present invention will be described with reference to FIGS. 13 and 14A to 14D. In Fig. 13 showing the third embodiment, the same functional units as the first and second embodiments are denoted by the same reference numerals.

The display data DATA is stored in the frame memory 40 via the display data analysis circuit 34. In the display data analysis circuit 34, as shown in FIG. In the display data in the frame, the frequency of each gradation of display data and the number of gradations which become the maximum gradation among the display data are analyzed. This result is transmitted to the LCD control circuit 32 to read display data for each color stored in the frame memory 40, and the gamma correction unit 36 transmits the maximum number of gray levels of the display data to the source driver 70. The image of the color in one frame is removed for each color as shown in Fig. 14B by subtracting the less frequent grayscale so that it can be converted to the maximum number of grayscales that can be expressed. The gradation reference voltage output from the gradation reference generation circuit 52 is performed via the control signal LP-CS from the control unit 32 as shown in Fig. 14C so that the gradation vicinity included in the data can be displayed. . In addition, the control unit 32 controls the luminance control unit 64 in the backlight power supply circuit 60 via the control signal BP-CS, and controls the current to the LED 64 (see FIG. 5) of the backlight 62. By adjusting the luminance of the backlight 62 to the luminance proportional to the maximum number of gray scales of the display data, as shown in FIG. 13, one type of gradation reference generation circuit 52 is provided, but a plurality of types may be provided as in the first embodiment.

By performing the above operation for each display color, it becomes a color display device of a smooth color expression.

The display device with improved display characteristics is a desktop liquid crystal display, which is a liquid crystal display mounted on a notebook PC, a liquid crystal display mounted on a PDA or a mobile phone, a liquid crystal display mounted on a game machine, or a liquid crystal display for a home or portable television. In addition, the present invention can be applied to display devices such as a video camera, a digital camera, a car navigation device, a POS terminal, and the like which face the viewfinder or monitor.

According to the third embodiment, the combination of the gradation reference voltage supplied to the LCD source driver, the? Correction circuit for correcting the gradation of the display data input to the liquid crystal display device, and the emission luminance can be adjusted for each color of the backlight. Multi-gradation can be expressed even by using an LCD source driver having a low number of gradations that can be expressed by the backlight control circuit.

Fourth Embodiment

In the gradation reference voltage generation circuit 52 in the first to third embodiments, the gradation reference voltages "V0, V1,... , V8 &quot;, but the gradation reference voltage generation circuit 52 can be simplified by using an element that can electronically change the resistance value, such as a digital potentiometer. Similarly, the gray scale reference voltage generator circuit 52 is configured in the gray voltage generator circuit 72 inside the source driver 70 to realize the simplification of the circuit.

In Fig. 15, a plurality of digital potentiometers 92 are used for the gradation reference voltage generation circuit 52 in the LCD power supply circuit, and the gradation reference voltages V0, V1, V2,... The digital potentiometer control unit 90 receives a digital potentiometer control signal DPM-CS from an LCD control circuit (not shown) (see Fig. 3). According to this digital potentiometer control signal DPM-CS, the digital potentiometer control part 90 connects the predetermined switch 94 of the multiple switch 94 in the digital potentiometer shown in FIG. 16 according to the display color. do. In FIG. 16, for example, when the switch 94 'of the plurality of switches 94 is connected, the resistance value between VL and VW is set to (r1 + r2 + r3) to be divided.

By using the digital potentiometer which can select a predetermined resistance value by the selection signal from the digital potentiometer control part 90, the gradation reference voltage according to the emission color can be set easily, and the apparatus can be miniaturized. Done.

In addition, by integrally configuring the gradation reference generation circuit in the gradation voltage generation circuit 72, the device can be further miniaturized. Also in this fourth embodiment, a plurality of types of reference gradation voltage circuits 52 may be provided.

Fifth Embodiment

A fifth embodiment in which the liquid crystal display device of the present invention is used in a portable terminal will be described with reference to FIG. In FIG. 17, the portable terminal 100 has a liquid crystal display device 104 according to the present invention in a housing 102 made of a resin, and a plurality of keys 106 are disposed below the liquid crystal display device 104. The key 106 is configured such that a desired character input, an icon displayed on the liquid crystal display 104 and the like can be selected. Compared to the conventional liquid crystal display device, the liquid crystal display device 104 according to the present invention has one pixel for one display pixel, and enables high-definition display and color display of high-quality image data even in a small display area. do.

In the first to fifth embodiments, the liquid crystal material is described as a ferroelectric liquid crystal and an anti-ferroelectric liquid crystal, using a time division color scheme in which the backlight color is converted to RGB. A filter can be arrange | positioned and it can use suitably also for the color system which irradiates white light from the back of a liquid crystal element.

As described above, according to the present invention, the gradation reference voltage generated in the gradation reference voltage generation circuit can be adjusted for each display color, and the γ curve can be adjusted for each display color without gamma correction of the display data. The liquid crystal display device excellent in the gray scale display characteristics can be realized.

Claims (11)

In a liquid crystal display device having a liquid crystal element, A plurality of gradation reference voltage circuits for generating gradation reference voltages applied to the liquid crystal elements in correspondence with a plurality of gradations of emission colors from the liquid crystal element, and gradations of the gradations of respective colors of display data in one frame. And a gradation reference voltage having a display data analysis section for analyzing the frequency, the gradation reference voltage having the gradation frequency near the gradation frequency analyzed by the display data analysis section as the center of the gradation voltage in the plurality of gradation reference voltage circuits. Display device. The method of claim 1, And the gradation reference voltage circuit generates a gradation reference voltage corresponding to each of the plurality of luminescence colors. In a liquid crystal display device having a liquid crystal element, A data driver having a digital-analog conversion circuit for converting display data, which is digital data input to the liquid crystal display device, into an analog voltage applied to the liquid crystal element; A gradation reference voltage generator for generating a plurality of sets of a plurality of combinations of the analog voltages in order to convert the display data into corresponding analog voltages, and a digital analog conversion circuit of the gradation of each color of the display data in one frame. Has a display data analysis section for analyzing the frequency, The data driver converts the digital data into an analog voltage based on any one of a plurality of sets of analog voltages at the gradation reference voltage having the frequency of the gradation voltage near the gradation voltage as interpreted by the display data analysis unit. A liquid crystal display, characterized in that the conversion. In a liquid crystal display device having a liquid crystal element, A data driver having a digital-analog conversion circuit for converting display data, which is digital data input to the liquid crystal display device, into an analog voltage applied to the liquid crystal element; A gradation reference voltage generator for generating a plurality of sets of combinations of the plurality of analog voltages in order to convert the display data into corresponding analog voltages, Has a gamma correction circuit for correcting the gradation of the display data, It has a display data analysis part which analyzes the frequency of the gradation of each color of display data in one frame, At the gradation reference voltage having the gradation near the gradation frequency as the center of the gradation voltage synchronized with the display on the liquid crystal element of the display color corresponding to the display data, And a set of a combination of the correction of the gradation by the correction circuit and the analog voltage corresponding to the display color to display the display data. In a liquid crystal display device having a liquid crystal element, A data driver having a digital-analog conversion circuit for converting display data, which is digital data input to the liquid crystal display device, into an analog voltage applied to the liquid crystal element; A gradation reference voltage generator for generating a plurality of sets of combinations of the plurality of analog voltages so that the digital-analog conversion circuit converts the display data into a corresponding analog voltage; A gamma correction circuit for correcting the gradation of the display data; A display data analysis unit for analyzing the frequency of the gradation of each color of the display data in one frame; It has a backlight capable of emitting light by switching a plurality of emission colors arranged on the back side of the liquid crystal element, From the gradation reference voltage having the gradation voltage near the gradation voltage as the center of the gradation voltage, a set of combinations of the analog voltages corresponding to the display color is selected to control the luminance of the backlight. A liquid crystal display device characterized in that. The method according to any one of claims 1 to 5, The said liquid crystal element has a liquid crystal material which has spontaneous polarization, The liquid crystal display device characterized by the above-mentioned. The method of claim 6, The liquid crystal material is a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal. In the gradation reference voltage generation circuit which generates the gradation display reference voltage required when the LCD source driver IC which ICizes the source driver of a liquid crystal display device converts display data into digital-analog conversion, the gradation reference | standard supplied to an LCD source driver IC. Two or more kinds of combinations of voltages are generated and analyzed by a display data analysis unit that analyzes the frequency of gradation of each color of the display data in one frame, and the vicinity of the gradation voltage having a high frequency analyzed by the display data analysis unit And a gradation reference voltage generating circuit for switching a combination for each of the colors in synchronization with the gradation reference voltage at the center of the display color. In the gradation reference voltage generation circuit which generates the gradation display reference voltage required when the LCD source driver IC which ICizes the source driver of a liquid crystal display device converts display data into digital-analog conversion, the gradation reference | standard supplied to an LCD source driver IC. A gradation reference voltage generating circuit for generating two or more kinds of voltage combinations and switching the combination of the gradation reference voltages in synchronization with a display color, a γ correction circuit for correcting the gradation of display data input to a display device, 1 A display data analysis section for analyzing the frequency of the gradation of each color of the display data in a frame, and interlocking the gradation reference voltage generating circuit and the γ correction circuit in synchronization with each display color to generate the gradation reference voltage for each display color. The combination of the voltage output from the circuit and the correction method in the γ correction circuit are changed, and the gradation A gray voltage based on the voltage outputted from the standard voltage generation circuit to the liquid crystal display device with a number of gray levels near the frequency analysis in the display data analyzer characterized in that the center of the gradation voltages. In the gradation reference voltage generation circuit which generates the gradation display reference voltage required when the LCD source driver IC which ICizes the source driver of a liquid crystal display device converts display data into digital-analog conversion, the gradation reference | standard supplied to an LCD source driver IC. The gradation reference voltage generation circuit having two or more kinds of voltage combinations and switching the combination of the gradation display reference voltages in synchronization with the display color, and a γ correction circuit for correcting the gradation of display data input to the liquid crystal display device. And a display data analysis section for analyzing the frequency of the gradation of each color of the display data in one frame, and a backlight control circuit for adjusting the emission luminance of the backlight disposed on the back side of the liquid crystal element for each display color. The gradation reference voltage generating circuit, the γ correction circuit and the backlight control in synchronization with A combination of voltages in which the gradation voltage is interpreted based on the gradation reference voltage generation circuit in the display color analysis unit, and the voltage is set around the gradation voltage near the frequency of the gradation voltage for each display color, and the γ correction circuit And a degree of correction of the light emission luminance of the backlight by the backlight control circuit. delete

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