Liquid crystal display apparatus

• US 4,556,880 A
• Filed: 11/01/1982
• Issued: 12/03/1985
• Est. Priority Date: 11/24/1981
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Hamada, Tatsuzo
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US06/438,257
• Time in Patent Office: 1,128 Days
• Field of Search: 340/713, 340/784, 340/805, 340/814
• US Class Current: 345/213
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3622 using a passive matrix G09G3/3674 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3681 suitable for passive matrices only
• CPC Class Codes: H04N 3/127 using liquid crystals

Abstract

The invention is concerned with a liquid crystal display apparatus which displays data by driving a liquid crystal panel in synchronism with horizontal synchronizing signals and vertical synchronizing signals. The driver for driving the liquid crystal panel is provided with timing signals maintaining a predetermined period, and with a voltage in synchronism therewith, irrespective of the horizontal and vertical synchronizing signals. Therefore, even when the horizontal and vertical synchronizing signals have not been applied, the liquid crystal panel is provided with an a-c voltage of which the polarity is alternatingly reversed by the timing signals. Therefore, electrolysis does not take place in the liquid crystal panel, and the quality of display is not degraded.

Claims

1. A liquid crystal display apparatus for displaying data on a liquid crystal panel, comprising:

a power source for supplying predetermined voltages;

electrodes arrayed in a predetermined manner in said liquid crystal panel;

synchronizing signal supplying means which produces synchronizing signals;

clock generating means which generates clock signals maintaining a predetermined period; and

driving means for generating an a-c voltage in accordance with said predetermined voltages from said power source and for driving said electrodes therewith, said driving means being responsive to said synchronizing signals from said synchronizing signal supplying means for driving said electrodes with an a-c voltage in synchronism with said synchronizing signals, said driving means being responsive to said clock signals from said clock generating means for driving said electrodes with an a-c voltage in accordance therewith in the absence of said synchronizing signals from said synchronizing signal supply means.

2. A liquid crystal display apparatus for displaying data on a liquid crystal panel according to claim 1, which further comprises:

a counter for counting clock signals produced by said clock generating means, the output of the counter being supplied to said driving means.

4. A liquid crystal display apparatus according to claim 1, wherein said driving means includes means for switching said predetermined voltages from said power source in response to clock signals from said clock generating means.

3. A liquid crystal display apparatus for displaying data on a liquid crystal panel by driving data electrodes and scanning electrodes that are arrayed in the form of a matrix, comprising:

a power source for supplying a plurality of voltage levels;

a first separator circuit which separates the data to be displayed from video signals that include the data to be displayed, horizontal synchronizing signals and vertical synchronizing signals;

a second separator circuit which separates horizontal synchronizing signals and vertical synchronizing signals from said video signals;

clock generating means which generates clock signals maintaining a predetermined period;

storing means which stores the data to be displayed in an amount of one horizontal period, which are successively sent from said first separator circuit, in synchronism with the clock signals from said clock generating means;

shift register means which is shifted by horizontal synchronizing signals produced by said second separator circuit, and which is reset by vertical synchronizing signals;

first drive means which drives data electrodes such that the data which is to be displayed and which is stored in said storing means, is displayed on the liquid crystal panel; and

second drive means for generating an a-c voltage in accordance with said plurality of voltage levels from said power source and for driving said scanning electrodes in accordance therewith, said second drive means being responsive to the outupts of said shift regiser means for driving said scanning electrodes with an a-c voltage in synchronism with the synchronizing signals applied to said shift register means said second drive means being responsive to said clock signals from said clock generating means for driving said scanning electrodes with an a-c voltage in synchronism with said clock signals at least in the absence of synchronizing signals being applied to said shift register means.

5. A liquid crystal display, in which at least one signal electrode and at least one scanning electrode are arranged in the form of a matrix or a liquid crystal panel and are driven to display data on the basis of display data and picture signals including a horizontal synchronizing signal and a vertical synchronizing signal, comprising:

power source means for applying a plurality of levels of voltages;

first separator means for separating said display data from said picture signals;

second separator means for separating said horizontal synchronizing signal and said vertical synchronizing signal from said picture signals;

first signal generating means for generating clock signals of a predetermined period;

means for storing one horizontal period portion of display data, which are successively supplied from said first separator means, in synchornism with a clock signal from said first signal generating means;

second signal generating means for shifting among the plurality of levels of voltages from said power source means in accordance with a clock signal from said first signal generating means for generating a switching signal enabling generation of first and second a-c voltages;

first driving means for controlling generation of said first a-c voltage in accordance with a switching signal from said second signal generating means and for applying said first a-c voltage to said at least one signal electrode in synchronism with a horizontal synchronizing signal wherein said horizontal synchronizing signal is present and for applying said first a-c voltage when said horizontal synchronizing signal is absent so as to enable display of said data stored in said storage means on said liquid crystal panel;

shift register means responsive to said horizontal synchronizing signal from said second separator means for effecting shifting and for being reset by said vertical synchronizing signal; and

second driving means for controlling generation of said second a-c voltage in accordance with a switching signal from said second signal generating means and for applying said second a-c voltage to said at least one electrode in synchronism with said horizontal synchronizing signal when said horizontal synchronizing signal is present and for applying said second a-c voltage when said horizontal synchronizing signal is absent so as to enable scanning of said at least one scanning electrode in accordance with the content of said shift register means.

6. A liquid crystal display apparatus according to claim 5, wherein said second signal generating means includes counter means for counting clock signals from said first signal generating means, said second signal generating means applying a switching signal to said second driving means each time the value of said counter means reaches a predetermined level.

7. A liquid crystal display apparatus according to claim 5, wherein said first driving means includes first and second transmission gate means, said first transmission gate means being enables in accordance with a switching signal from said second signal generating means and an inverted signal of said switching signal for controlling generation of said first a-c voltage, said second transmission gate means being enabled in accordance with the binary condition of said display data and for enabling application of said first a-c voltage to said at least one signal electrode, and said second driving means including third and fourth transmission gate means, said third transmission gate means being enabled in accordance with a switching signal from said second signal generating means and an inverted signal of said switching signal for generation of said second a-c votlage, said fourth transmission gate means being enabled in accordance with the binary condition of said horizontal synchronizing signal for enabling application of said second a-c voltage to said at least one scanning electrode.