JP2003131197A - Liquid crystal display element, flicker adjustment method for liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it is hard to observe and adjust a flicker close to the optimum value due to that a proper transmittance such as that in periphery of a central gray scale among the whole gray scales is conventionally used as a halftone displayed for every column of a screen for adjustment to adjust the flicker to the minimum value. SOLUTION: The flicker value is adjusted so as to be the minimum value on a display screen of a liquid crystal display element to which a voltage minimizing transmittance and a voltage at a point where the slope of a voltage- transmittance characteristic curve is the steepest or a voltage nearly identical to that at the point where the slope of the voltage-transmittance characteristic curve is the steepest are applied per column in the longitudinal direction of the liquid crystal display element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device used in liquid crystal televisions, portable OA equipment and the like.

[0002]

2. Description of the Related Art At present, a liquid crystal element which is generally widely used is a TN (twisted nematic) type liquid crystal display element. Recently, various OCB (Optical Compensated Bend) type liquid crystal display elements (sometimes referred to as π cells) have been reported, but this mode is characterized by high-speed response and wide viewing angle. The OCB type liquid crystal display device is described in "Technical Report of the Institute of Electrical Communication, EDI 98-144 19".
Please refer to “Page 9”.

In an OCB type liquid crystal display device, nematic liquid crystal is injected inside the panel. FIG. 1 is a conceptual diagram showing a liquid crystal alignment state in an OCB type liquid crystal display element,
Reference numeral 11 is a substrate, and 12 is a liquid crystal molecule. The upper and lower substrate surfaces that sandwich the liquid crystal are rubbed in parallel, and when no voltage is applied, the liquid crystal is in a splay alignment state (Fig. 1).
(A)). By applying a relatively large voltage V to the liquid crystal layer when the power is turned on, the splay alignment is changed to the bend alignment (FIG. 1B). It is OC to display using this bend orientation state.
It is a feature of the B mode, and is an element that changes the transmittance of the panel by changing the magnitude of the voltage. In the TN mode, the transmittance of the panel is changed by using the optical rotatory power of the polarized light entering the liquid crystal cell, while in the OCB mode, the transmittance is changed due to the interference between the ordinary light and the extraordinary light of the polarized light entering the liquid crystal cell. Change. Therefore, the TN mode and the OCB mode differ in how the transmittance changes when the applied voltage is changed.

FIG. 2 is a conceptual diagram of a circuit per pixel for active matrix driving, in which 21 is a source electrode and 2 is a source electrode.
2 is a gate electrode, 23 is a liquid crystal, 24 is a storage capacitor, and 25 is a TFT element. In the current liquid crystal display element, a TFT is provided in each display pixel as shown in the circuit diagram of FIG. 2, and each pixel is driven. The mainstream is active matrix driving that holds a voltage. FIG. 3 shows a conceptual diagram of voltage waveforms in active matrix driving. In active matrix driving using this TFT, the pixel voltage differs between writing and holding due to capacitive coupling between the terminals of the TFT, and positive and negative asymmetry occurs in the voltage applied to the liquid crystal. This asymmetry appears as a difference in transmittance and is observed as flicker. The opposite voltage is adjusted to the optimum value as much as possible, and in an active matrix driving liquid crystal display element using TFTs, the polarity of the voltage applied to the liquid crystal is changed line by line in the scanning direction (usually the vertical direction), or the adjacent voltage is changed. For example, the polarity of the voltage applied to the liquid crystal is changed for each matching pixel to macroscopically cancel the positive and negative asymmetry of the voltage applied to the liquid crystal.

The flicker is adjusted by adjusting the counter voltage Vcom so that positive and negative asymmetries in the voltage applied to the liquid crystal are eliminated as much as possible.
Adjust the value of to minimize flicker. The adjustment screen for adjusting the flicker to the minimum is shown in FIG. 4 when the polarity of the voltage is inverted every column so that the flicker can be easily observed. Display alternately for each. Similarly, when the polarities of the voltages are inverted for each adjacent pixel, as shown in FIG.
The display with the minimum transmittance and the appropriate halftone display are alternately displayed for each adjacent pixel.

[0006] At this time, halftone display which is displayed for each column or for adjacent pixels is often a halftone near the central grayscale among the total grayscales, but flicker near the optimum value of the counter voltage Vcom occurs. Since it is difficult to observe, precise adjustment is difficult.

As described above, since the OCB type liquid crystal display element has a different voltage transmittance characteristic curve from the TN type liquid crystal display element, it is necessary to set the transmittance of the halftone display of the adjustment screen to what percentage. The best remained unclear.

[0008]

Heretofore, the halftone displayed for each row of the adjustment screen for adjusting the flicker to the minimum or for each adjacent pixel has an appropriate value such as near the central gradation in the total gradation. Since it was the transmittance, there was a problem that flicker near the optimum value was difficult to observe and adjustment was difficult. Further, in the above OCB type liquid crystal display element, the conventional T
Since the voltage transmittance characteristic curve is different from that of the N mode, if the transmittance is the same as that of the halftone display of the adjustment screen of the TN type liquid crystal display device, it is difficult to observe flicker near the optimum value of Vcom, and it is difficult to adjust. was there.

[0009]

In order to solve the above-mentioned problems, a liquid crystal display device of the present invention provides a liquid crystal sandwiched between a pair of substrates, a pair of polarizing plates sandwiching the pair of substrates, and a voltage applied to the liquid crystal. A liquid crystal display device comprising a voltage applying means for applying, wherein the transmittance is the ratio of the luminance value of light emitted from the other of the polarizing plates to the luminance value of light incident from one of the pair of polarizing plates, The transmittance is changed by changing the voltage applied to the liquid crystal.

Further, according to the present invention, the relationship between the voltage applied to the liquid crystal and the transmittance when the voltage is applied is defined as a voltage transmittance characteristic curve, and the change amount of the transmittance with respect to the minute change amount of the voltage is expressed as the voltage. The inclination of the transmittance characteristic curve is characterized in that the inclination of the voltage transmittance characteristic curve is not constant.

According to the present invention, the relationship between the voltage applied to the liquid crystal and the transmittance when the voltage is applied is defined as a voltage transmittance characteristic curve, and the change amount of the transmittance with respect to the minute change amount of the voltage is expressed by
The slope of the voltage transmittance characteristic curve is constant, where the slope of the voltage transmittance characteristic curve is constant.

Further, the present invention is characterized in that one of the substrates is an active matrix substrate, and the scanning direction of the active matrix is a vertical direction.

Further, the present invention is characterized in that the liquid crystal display element has a plurality of pixels in each of the vertical and horizontal directions, and the polarities of the voltages applied are reversed every vertical column.

According to the present invention, the voltage at which the transmittance is minimized and the voltage at the location where the slope of the voltage transmittance characteristic curve is the steepest or the voltage transmittance is vertical for each column of the liquid crystal display element. A flicker adjustment method for a liquid crystal display element, which adjusts so that the flicker value is minimized on the display screen of the liquid crystal display element to which a substantially equal voltage is applied to the location where the slope of the characteristic curve is the steepest.

The present invention is also a method of manufacturing a liquid crystal display device, which has a step of adjusting flicker by the above adjusting method.

The present invention also provides a liquid crystal display element inspection method for inspecting the degree of flicker on the display screen of the liquid crystal display element according to the flicker adjustment method.

In the present invention, the liquid crystal display element is an OCB.
Type liquid crystal display device.

According to the present invention, the voltage at which the transmittance is minimized and the voltage value at which the voltage transmittance value is maximized or the transmission modulation ratio value is minimized for each vertical column of the liquid crystal display element. A flicker adjustment method for a liquid crystal display device, which adjusts a flicker value to a minimum value on a display screen of the liquid crystal display device to which a voltage approximately equal to a larger voltage value is applied.

Further, the present invention is a method of manufacturing a liquid crystal display device, which has a step of performing flicker adjustment by the flicker adjustment method.

The present invention also provides a liquid crystal display element inspection method for inspecting the degree of flicker on the display screen of the liquid crystal display element according to the flicker adjustment method.

In the present invention, the liquid crystal display element is OCB.
Type liquid crystal display device.

Further, the present invention is characterized in that the liquid crystal display element has a plurality of pixels in each of a vertical direction and a horizontal direction, and polarities of voltages applied to adjacent pixels are opposite to each other.

According to the present invention, the voltage at which the transmittance is minimized and the voltage at the point where the slope of the voltage transmittance characteristic curve is the steepest, or the voltage transmittance is determined for each adjacent pixel of the liquid crystal display element. A method for adjusting flicker of a liquid crystal display element, in which a flicker value is adjusted to a minimum value on the display screen of the liquid crystal display element to which a substantially equal voltage is applied to a portion where the slope of the characteristic curve is the steepest.

The present invention is also a method of manufacturing a liquid crystal display device, which has a step of adjusting flicker by the above adjusting method.

The present invention also provides a liquid crystal display element inspection method for inspecting the degree of flicker on the display screen of the liquid crystal display element according to the flicker adjustment method.

In the present invention, the liquid crystal display element is OCB.
Type liquid crystal display device.

Further, according to the present invention, the voltage at which the transmittance is minimized, the voltage value at which the voltage transmittance value is maximized, or the transmittance value is maximized for each adjacent pixel of the liquid crystal display element. In the display screen of the liquid crystal display element to which a voltage substantially equal to the voltage value is applied, the flicker adjustment method of the liquid crystal display element is adjusted so as to minimize the flicker value.

The present invention is also a method of manufacturing a liquid crystal display device, which has a step of adjusting flicker by the above adjusting method.

The present invention is also the liquid crystal display element inspection method for inspecting the degree of flicker on the display screen of the liquid crystal display element according to the flicker adjustment method.

In the present invention, the liquid crystal display element is OCB.
Type liquid crystal display device.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) First, TF is formed on one substrate.
An active matrix substrate provided with T and coated with an aligning agent,
A nematic liquid crystal was sandwiched between substrates provided with a transparent electrode on the other side and coated with an aligning agent to manufacture a TN type liquid crystal display device. This liquid crystal display element was driven so that the polarity of the voltage applied every other row in the scanning direction of the TFT was reversed. The voltage transmittance curve of this liquid crystal display device is shown in FIG.

Display of minimum transmittance for each column (6 in FIG. 6)
Flicker was observed by alternately displaying 4) and an appropriate halftone display. At this time, the transmittance of the halftone displayed every other row was changed to 61, 62, and 63 in FIG. Then, when the steepest 62 of the voltage transmittance curve was displayed, the flicker was most visible. This is because the change amount of the transmittance with respect to the minute change of the voltage is the largest at the portion where the slope of the voltage transmittance curve is the steepest, and the positive / negative asymmetry of the voltage is most easily observed.

Further, even when 61 in FIG. 6 having a high transmittance is displayed, the flicker is relatively easy to see. this is,
This is because flicker is generally easier to observe as the brightness is higher.

On the other hand, when 63 in FIG. 6 was displayed, flicker was hard to see. This is because the slope of the voltage transmittance curve is not steep, the change amount of the transmittance with respect to a minute change of the voltage is small, and the positive / negative asymmetry is hardly observed in the voltage, and the observed brightness is low.

Next, as in the case of the TN type liquid crystal display element, an active matrix substrate is used, and a transparent electrode is used on the other side for O
A CB type liquid crystal display device was manufactured. This liquid crystal display element was driven so that the polarity of the voltage applied every other row in the scanning direction of the TFT was reversed. The voltage transmittance curve of this liquid crystal display device is shown in FIG.

Using this OCB type liquid crystal display element, a display with the minimum transmittance (74 in FIG. 7) and an appropriate halftone display were alternately displayed for each column, and flicker was observed. At this time, the transmissivity of the halftone displayed every other row is set to 7 in the figure.
It was changed to 1, 72, 73. Then, the same transmittance as the transmittance at which flicker of the TN type liquid crystal display element was most likely to be observed is 73 in FIG. 7 than when 72 in FIG. 7 is displayed.
When was displayed, flicker was easier to observe.
This is because, as described above, the slope in the vicinity of 73 in FIG. 7 is the steepest in the voltage transmittance curve.

From the above, by setting the halftone display voltage displayed in every other column of the flicker adjustment screen to the voltage value at which the slope of the voltage transmittance curve becomes the steepest, the flicker adjustment becomes much easier. . Further, if the display of every other row of the flicker adjustment screen is set near the voltage value where the brightness is highest, the flicker adjustment becomes easier to some extent.

(Embodiment 2) In Embodiment 1 described above, the TFTs are driven so that the polarity of the applied voltage is inverted every other column in the scanning direction of the TFT. However, the polarity of the applied voltage is changed between adjacent pixels. The same principle holds true when driving to invert. In this case, the flicker observation screen is shown in FIG.
As described above, the halftone display voltage to be displayed may be set to a voltage value at which the slope of the voltage transmittance curve becomes the steepest.

(Third Embodiment) In the first embodiment, the TFTs are driven so that the polarity of the applied voltage is inverted every other column in the scanning direction, but the polarity of the applied voltage is inverted every two columns. The same principle holds true when driven as described above. In this case, the flicker observation screen is as shown in FIG. 8, and the display voltage of the halftone to be displayed may be set to a voltage value at which the slope of the voltage transmittance curve becomes the steepest.

Although the TN type liquid crystal display element and the OCB type liquid crystal display element have been described in the first and second embodiments, the common problems in the element using liquid crystal for display can be solved. is there. In general, any element may be used as long as it is an element that drives a liquid crystal by a voltage to display.

[0042]

According to the present invention, it is possible to solve the problem that flicker of a liquid crystal display element is difficult to observe and adjustment is difficult. In addition, since the OCB type liquid crystal display element has a voltage transmittance characteristic curve different from that of the conventional TN mode, if the transmittance is the same as that of the halftone display of the adjustment screen of the TN type liquid crystal display element, it is close to the optimum value of Vcom. It is possible to solve the problem that flicker is hardly observed and adjustment is difficult.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a liquid crystal alignment state in an OCB type liquid crystal display device.

FIG. 2 is a conceptual diagram of a circuit per pixel for active matrix driving.

FIG. 3 is a conceptual diagram of a voltage waveform of active matrix driving.

FIG. 4 is a conceptual diagram of a flicker adjustment screen in which a minimum transmittance display and a halftone display are displayed for each column.

FIG. 5 is a conceptual diagram of a flicker adjustment screen in which a minimum transmittance display and a halftone display are displayed for each adjacent pixel.

FIG. 6 is a conceptual diagram of a voltage transmittance curve of a TN type liquid crystal display device.

FIG. 7 is a conceptual diagram of a voltage transmittance curve of an OCB type liquid crystal display device.

FIG. 8 is a conceptual diagram of a flicker adjustment screen in which a minimum transmittance display and a halftone display are displayed in two columns.

[Explanation of symbols]

11 substrate 12 liquid crystal molecule 21 source electrode 22 gate electrode 23 liquid crystal 24 storage capacitor 25 TFT element 31 voltage waveform applied to liquid crystal layer 32 Vcom before adjustment 33 Vcom after adjustment 34 asymmetric component of voltage applied to liquid crystal layer 51 halftone display 52 Display with minimum transmittance 61 Slightly bright halftone 62 Part where the slope of the voltage transmittance curve is the steepest 63 Slightly dark halftone 64 Minimum display of transmittance 71 Bright halftone 72 TN liquid crystal display device shows voltage transmittance curve The same transmittance as the transmittance with the steepest slope 73 73 The part with the steepest slope of the voltage transmittance curve 74 The minimum transmittance display 81 The halftone display 82 The minimum transmittance display

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ichiro Sato             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 2H093 NA16 NC12 NC13 NC18 NC34                       NC49 NC90 ND10 ND35 ND58                       NF04 NF05 NF09 NF28                 5C006 AB03 BA15 BB16 EB01 FA23                 5C080 AA10 BB05 DD06 EE02 EE26                       FF11 JJ01 JJ03 JJ04 JJ05

Claims (22)

[Claims] 1. A liquid crystal display device comprising a liquid crystal sandwiched between a pair of substrates, a pair of polarizing plates sandwiching the pair of substrates, and a voltage applying means for applying a voltage to the liquid crystal, The transmittance is defined as the ratio of the brightness value of the light emitted from one of the polarizing plates to the brightness value of the light incident from the other polarizing plate, and the transmittance is changed when the voltage applied to the liquid crystal is changed. Characteristic liquid crystal display element. 2. A voltage transmittance characteristic curve is a relationship between a voltage applied to the liquid crystal and the transmittance when the voltage is applied, and a change amount of the transmittance with respect to a minute change amount of the voltage is represented by the voltage transmittance. The liquid crystal display device according to claim 1, wherein the slope of the characteristic curve is not constant when the slope of the characteristic curve is defined. 3. A voltage transmittance characteristic curve is a relationship between the voltage applied to the liquid crystal and the transmittance when the voltage is applied, and a change amount of the transmittance with respect to a minute change amount of voltage is expressed by the voltage transmittance characteristic. The liquid crystal display device according to claim 1, wherein the slope of the curve is a constant slope of the voltage transmittance characteristic curve. 4. The liquid crystal display element according to claim 2, wherein one of the substrates is an active matrix substrate, and the scanning direction of the active matrix is the vertical direction. 5. The liquid crystal display according to claim 4, wherein the liquid crystal display element has a plurality of pixels in each of a vertical direction and a horizontal direction, and the polarities of the voltages applied are reversed every vertical line. element. 6. A flicker adjustment method for a liquid crystal display element, which adjusts flicker occurring in the liquid crystal display element according to claim 5, wherein a voltage at which the transmittance is minimized for each vertical row of the liquid crystal display element. 6. The liquid crystal display device according to claim 5, wherein a voltage at a position where the slope of the voltage transmittance characteristic curve is steepest or a substantially equal voltage is applied to a position where the slope of the voltage transmittance characteristic curve is steepest. A flicker adjustment method for a liquid crystal display element, which adjusts a flicker value to a minimum value on a display screen. 7. A method of manufacturing a liquid crystal display element, comprising the step of adjusting flicker by the method of adjusting flicker of a liquid crystal display element according to claim 6. 8. A liquid crystal display element inspection method for inspecting the degree of flicker on a display screen of a liquid crystal display element according to the method of adjusting flicker of a liquid crystal display element according to claim 6. 9. The liquid crystal display device according to claim 6, wherein the liquid crystal display device is an OCB type liquid crystal display device, a method for adjusting flicker of the liquid crystal display device, or manufacturing of the liquid crystal display device. Method or inspection method of liquid crystal display device. 10. A flicker adjusting method for a liquid crystal display element, which adjusts flicker occurring in the liquid crystal display element according to claim 5, wherein a voltage at which the transmittance is minimized for each vertical row of the liquid crystal display element. And a flicker value is minimized on the display screen of the liquid crystal display element to which a voltage value that maximizes the voltage transmittance value or a voltage that is approximately equal to the voltage value that maximizes the transmission modulation value is applied. Flicker adjustment method of liquid crystal display element to adjust. 11. A method of manufacturing a liquid crystal display device, comprising the step of adjusting flicker by the method of adjusting flicker of a liquid crystal display device according to claim 10. 12. A liquid crystal display element inspection method for inspecting the degree of flicker on a display screen of a liquid crystal display element according to the liquid crystal display element flicker adjustment method of claim 10. 13. The method for adjusting flicker of a liquid crystal display element, the method for manufacturing a liquid crystal display element, or the liquid crystal display according to claim 10, wherein the liquid crystal display element is an OCB type liquid crystal display element. Device inspection method. 14. The liquid crystal display according to claim 4, wherein the liquid crystal display element has a plurality of pixels in vertical and horizontal directions, and polarities of voltages applied to adjacent pixels are opposite to each other. element. 15. A method of adjusting flicker occurring in a liquid crystal display element according to claim 14, wherein the voltage at which the transmittance is minimized and the voltage transmittance characteristic are provided for each adjacent pixel of the liquid crystal display element. In the display screen of the liquid crystal display element, the flicker value is minimized on the display screen of the liquid crystal display element in which the voltage at the steepest curve or the voltage at which the voltage transmittance characteristic curve has the steepest slope is applied. How to adjust the flicker of the liquid crystal display device. 16. A method of manufacturing a liquid crystal display device, comprising the step of adjusting flicker by the method of adjusting flicker of a liquid crystal display device according to claim 15. 17. A liquid crystal display element inspection method for inspecting the degree of flicker on a display screen of a liquid crystal display element according to the method of adjusting flicker of a liquid crystal display element according to claim 15. 18. The liquid crystal display device according to claim 15, wherein the liquid crystal display device is an OCB type liquid crystal display device.
A method for adjusting flicker of a liquid crystal display device, a method for manufacturing a liquid crystal display device, or a method for inspecting a liquid crystal display device according to claim 17. 19. A method of adjusting flicker generated in a liquid crystal display element according to claim 14, wherein the voltage at which the transmittance is minimized and the voltage transmittance at the adjacent pixels of the liquid crystal display element are adjusted. In the display screen of the liquid crystal display element to which a voltage value that maximizes the value or a voltage that is substantially equal to the voltage value that maximizes the transmittance is applied, a liquid crystal display element that is adjusted to minimize the flicker value is displayed. How to adjust flicker. 20. A method of manufacturing a liquid crystal display device, which comprises the step of adjusting flicker by the method of adjusting flicker of a liquid crystal display device according to claim 19. 21. A liquid crystal display element inspection method for inspecting the degree of flicker on a display screen of a liquid crystal display element according to the liquid crystal display element flicker adjustment method of claim 19. 22. The liquid crystal display device according to claim 19, which is an OCB type liquid crystal display device.
22. A method for adjusting flicker of a liquid crystal display device according to claim 21, a method for manufacturing a liquid crystal display device, or a method for inspecting a liquid crystal display device.