JP5301223B2 - Ferroelectric liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce burning defects caused by a lateral electric field. <P>SOLUTION: In the ferroelectric display device with a ferroelectric liquid crystal display panel which holds a ferroelectric liquid crystal by a first electrode substrate having a plurality of pixel electrodes and a second electrode substrate stuck at a prescribed position and at an interval facing the first electrode substrate and performs display on the basis of the change of optical characteristics of the ferroelectric liquid crystal generated by applying an electric field to the ferroelectric liquid crystal by the first electrode substrate and the second electrode substrate, a non-display field is provided for every two or more fields and drive for dispersing the bias of an electric field to the entire surface of the ferroelectric liquid crystal display panel is executed during the non-display field. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a ferroelectric liquid crystal display device that prevents seizure defects.

  In an LCOS type liquid crystal display device using a ferroelectric liquid crystal, a glass substrate in which a plurality of pixel electrodes are formed on a first electrode substrate which is a Si substrate and a transparent electrode is formed on one surface is used as a second electrode substrate. When driving the LCOS type liquid crystal display device using the electrode potential of the second electrode substrate as a reference potential, when white display is performed, a positive voltage is applied to the pixel electrode of the first electrode substrate, while black display is performed. A voltage having a negative potential is applied to the pixel electrode of the first electrode substrate. The voltage of each pixel electrode is held for a period according to the gradation of each pixel, and this is called time-division gradation driving. (See Patent Document 1)

  When the total time of the potential difference (vertical electric field) between the first electrode substrate and the second electrode substrate is not zero, that is, when there is a DC component of voltage, the internal ions of the ferroelectric liquid crystal are reduced by the bias of the DC component. It is said that poor seizure occurs when attracted in the direction. In the case of still image display, since the images in the respective fields are the same, the bias of the DC component on the same pixel (same location) is superimposed, and the image sticking failure becomes noticeable.

  The seizure failure due to the vertical electric field between the substrates is determined by the DC component of the voltage applied between the electrodes, and can be prevented by applying a reverse voltage so as to cancel the DC component. Called drive. (See Patent Document 2)

  FIG. 1 is a timing chart of voltages applied to the first electrode in the field sequential mode. FIG. 6 is a diagram for explaining the DC balance driving, in which one display cycle (field) is divided into a display period and a non-display period, and the voltage applied to the display period in the non-display period is the same as the reverse voltage. Is applied to cancel the DC component of the voltage applied to the liquid crystal during the display period, thereby preventing burn-in failure.

  FIG. 2 shows an image (a) and a reverse image (b). When the image shown in FIG. 2 (a) is displayed, a voltage corresponding to the image of FIG. 2 (a) is applied to each pixel during the display period, and during the non-display period in order to cancel the DC component of the voltage. As shown in FIG. 2B, a voltage corresponding to the reverse image of the display image in FIG. 2A is applied to each pixel by DC balance driving.

  One display cycle is T, which consists of a display period and a non-display period of T / 2, and the voltage applied to the first electrode is ± V1, and the voltage applied to the second electrode is the voltage applied to the first electrode. The intermediate potential (reference potential) of ± V1 is 0 V in the figure. By switching the voltage of the first electrode to + V1 higher than the voltage of the second electrode or -V1 lower than the voltage of the second electrode, the electric field applied to the liquid crystal is inverted in the first electrode direction or the second electrode direction opposite to the first electrode. The optical characteristics of the liquid crystal are reversed. For example, in the case of black and white display, white display is obtained when the voltage of the first electrode is + V1, and black display is obtained when -V1.

  FIG. 1 shows an example of 75% white display. In order to perform white display, + V1 is applied to the first electrode during t1 corresponding to 75% of T / 2, and 25% of T / 2 for black display. -V1 is applied to the first electrode during t2. In order to obtain the balance of the electric field applied to the liquid crystal during this period, −V1 is applied to the first electrode so that the electric field is opposite to the t1 period during t3 which is the same length as t1 in the non-display period. The electric field is canceled by applying + V1 to the first electrode at t4 corresponding to t2.

JP 2005-99712 A JP 2006-522372 A

  The prior art pays attention to the vertical electric field between the substrates as prevention of burn-in failure, but a horizontal electric field is also generated in an actual panel, and in the above DC balance driving method, the horizontal electric field generated between adjacent pixel electrodes is generated. There is no effect of preventing seizure due to an electric field.

  When displaying white and black with adjacent pixels, a vertical electric field is generated between the first electrode substrate and the second electrode substrate, but a horizontal electric field is generated between the pixels at the same time. FIG. 3 is a schematic diagram for explaining a lateral electric field generated between pixels. Since + V1 is applied to the pixel electrode for white display on the first electrode substrate, −V1 is applied to the pixel electrode for black display, and 0 V is applied to the second electrode substrate, the potential difference between the upper and lower electrode substrates is V1. The potential difference between the pixel electrodes is 2V1. In a small high-resolution liquid crystal display device, the distance between pixel electrodes (for example, 0.5 μm) is narrower than the distance between upper and lower electrode substrates (for example, 1 μm), and as a result, the strength of the horizontal electric field is much stronger than the strength of the vertical electric field. become.

  This seizure due to the transverse electric field cannot be solved by canceling the DC component by applying the reverse voltage. The cause is considered to be the complexity of the electric field distribution and the liquid crystal layer structure and asymmetry. Considering the asymmetric characteristics of the liquid crystal, it is difficult to calculate the DC component of the transverse electric field distributed in-plane for each image and to balance the electric field in two dimensions.

  An object of the present invention is to reduce seizure defects caused by a transverse electric field.

A ferroelectric liquid crystal is sandwiched between a first electrode substrate having a plurality of pixel electrodes and a second electrode substrate bonded to the first electrode substrate at a predetermined position and interval, and the first electrode substrate and the second electrode substrate are sandwiched between the first electrode substrate and the second electrode substrate. In a ferroelectric liquid crystal display device having a ferroelectric liquid crystal display panel for performing display based on a change in optical characteristics of the ferroelectric liquid crystal generated by applying an electric field to the ferroelectric liquid crystal by an electrode substrate, a non-display field for each of a plurality of fields In the non-display field, the ferroelectric liquid crystal display device is driven to disperse the bias of the horizontal electric field over the entire surface of the ferroelectric liquid crystal display panel.

  A non-display field is provided once in multiple fields, and when the non-display field is driven, the bias of the electric field is scattered over the entire surface of the ferroelectric liquid crystal display panel, so that even when a still image is displayed, ions are not fixed and seizure defects occur. do not do.

  A ferroelectric liquid crystal is sandwiched between a first electrode substrate having a plurality of pixel electrodes and a second electrode substrate bonded to the first electrode substrate at a predetermined position and interval, and the first electrode substrate and the second electrode substrate are sandwiched between the first electrode substrate and the second electrode substrate. In a ferroelectric liquid crystal display device having a ferroelectric liquid crystal display panel for performing display based on a change in optical characteristics of the ferroelectric liquid crystal generated by applying an electric field to the ferroelectric liquid crystal by an electrode substrate, a non-display field for each of a plurality of fields And a ferroelectric liquid crystal display device which is driven to disperse the electric field bias over the entire surface of the ferroelectric liquid crystal display panel in the non-display field.

  FIG. 4 shows a cross hatch image, in which black and white display is arranged every other pixel, and black and white are reversed in (a) and (b). By applying and driving such a cross hatch image signal to the ferroelectric liquid crystal display panel, ions are dispersed. FIG. 5 is a schematic diagram for explaining a driving method in which a transverse electric field is dispersed by applying a cross hatch pattern every nine fields. Numbers from 1 to 10 indicate one display period, that is, one field. Each of the first to ninth fields shows a state where an image “image A” is repeatedly displayed, that is, a ferroelectric liquid crystal display display of a still image. In the tenth field where the horizontal electric field is dispersed, a cross hatch image signal is applied to the panel.

  The first to ninth fields have a display period and a non-display period, and the DC balance of the vertical electric field is taken in the non-display period. It is hidden. In the case of color image display with a frame frequency of 60 Hz, one field is 180 Hz, which is three times the frame frequency.

Driving example of 75% white display in the timing diagram of the voltage applied to the first electrode in the field sequential mode Image (a) and inverted image (b) Schematic diagram explaining the lateral electric field generated between pixels Cross hatch Schematic diagram illustrating a driving method for dispersing a horizontal electric field by applying a cross hatch pattern every nine fields

Claims (1)

A ferroelectric liquid crystal is sandwiched between a first electrode substrate having a plurality of pixel electrodes and a second electrode substrate bonded to the first electrode substrate at a predetermined position and interval, and the first electrode substrate and the second electrode substrate are sandwiched between the first electrode substrate and the second electrode substrate. In a ferroelectric liquid crystal display device having a ferroelectric liquid crystal display panel for performing display based on a change in optical characteristics of the ferroelectric liquid crystal generated by applying an electric field to the ferroelectric liquid crystal by an electrode substrate, a non-display field for each of a plurality of fields A ferroelectric liquid crystal display device, characterized in that a drive is performed to disperse the bias of the lateral electric field over the entire surface of the ferroelectric liquid crystal display panel in the non-display field.

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