JPH064047A - Display device - Google Patents

Abstract

PURPOSE:To attain a smooth rise without an odd feel in appearance by detecting the turn off of a power source and initializing display contents. CONSTITUTION:A back light 267 is first turned off when a request for turning off the power source is generated. The display is thereafter initialized by making the entire screen of the display panel black. Namely, the output voltages from a segment driving section 262 and a common driving section 263 are maintained at Vc. The output voltage from the segment driving section 262 and the common driving section 263 are grounded. The power source is thereafter tuned off. Namely, the display screen of an FLCD(ferroelectric liquid crystal display) 261 is rewritten to a full-black surface or full-white surface before the power source is turned off and, therefore, the display free from the odd feel is obtd. in spite of the generation of such things that the display contents at the time of the turning off of the power source are stored by the bistability of the FLCD 261, that the previous screen at the time of the turning off of the power source is displayed instantaneously before the turning on that power source and that the screen stored at the time of the turning off of the power source is visible by irradiating the display surface of the FLCD262 with a outside light when the power source is turned off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly, to a display device capable of holding a display state updated by applying an electric field using, for example, a ferroelectric liquid crystal as an operating medium for display update. The present invention relates to a display device.

[0002]

2. Description of the Related Art Generally, a display device is connected to an information processing system or the like as an information display means having a function of visually displaying information. As such a display device, a CRT
However, since the CRT requires a certain length in the thickness direction of the display screen, the CRT has a large volume as a whole, and it is difficult to reduce the size of the entire display device. Further, this impairs the degree of freedom in using the information processing system using such a CRT as a display, that is, the degree of freedom in installation location, formality and the like.

A liquid crystal display (hereinafter referred to as an LCD) can be used to supplement this point. That is,
According to LCD, downsizing of the entire display device (especially thinness)
Can be achieved. Among such LCDs, ferroelectric liquid crystal (hereinafter, referred to as FLC: Ferroelectric Liquid Cryst
Display using a liquid crystal cell (hereinafter referred to as al) (hereinafter, FLCD:
There is a FLC display), and one of its features is the preservation of the display state of the liquid crystal cell. Therefore, when driving the FLCD, unlike the CRT and other liquid crystal displays, there is a time margin in the cycle of continuous refresh driving of the display screen, and the display can be displayed separately from the continuous refresh driving. Partial rewriting drive that updates the display state of only the part corresponding to the change on the screen becomes possible.
Therefore, such an FLCD can be used as a large-screen display as compared with other liquid crystal displays.

Here, in the FLCD, the liquid crystal cell is sufficiently thin, and the elongated FLC molecules therein are oriented in the first stable state or the second stable state depending on the direction of application of the electric field. , The respective alignment state is maintained even when the electric field is cut off. Due to the bistability of the FLC molecule, F
The LCD has a memory property. Such FLC and FL
Details of the CD are described, for example, in JP-A-63-243919.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Since has the above-mentioned features, it causes the following drawbacks. For example, when the power is turned on, the screen at the time of the previous power-off is stored, it is displayed for a moment, and then the startup screen is displayed. Also,
When the display surface of the liquid crystal is irradiated with external light even when the power is turned off, the screen stored when the power is turned off may be seen even though the liquid crystal display is not operating.

[0006]

Therefore, according to the present invention,
In a display device having a display screen in which a plurality of display elements capable of holding the updated display state are arranged and updating the display based on the display data on the display screen, regardless of the display data when the power is turned off. It is characterized in that it has means for forcibly initializing the display contents.

[0007]

In the present invention, when the power-off is detected, the data for forcibly initializing the display content is given to the display device to initialize the display content. By performing such processing, even if the display contents when the power is turned off, which is stored due to the bistability which is a feature of the FLCD, is displayed when the power is turned on next time, the initialized contents are displayed. Because
You can achieve a smooth start-up that does not look strange.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows an FLC according to an embodiment of the present invention.
It is a block diagram of an information processing system using a display device as a display device of various characters, image information and the like.

In the figure, 11 is a CPU that executes control of the entire information processing system, 13 is a main memory that stores a program executed by the CPU 11 and is used as a work area during this execution, and 14 is control of the CPU 11. It is a DMA controller (Direct Memory Access Controller, hereinafter referred to as DMAC) that transfers data between the main memory 13 and various devices constituting the present system without intervention. 15 is a LAN interface between a LAN (local area network) 16 such as Ethernet (by XEROX) and this system, and 17 is RO
It is an input / output device (hereinafter referred to as I / O) having an M, SRAM, RS232C system interface and the like. I / O
Various external devices can be connected to 17. 18 and 1
Reference numeral 9 is a hard disk device and a floppy disk device as external storage devices, respectively, and 20 is a disk interface for signal connection between the hard disk device 18 and the floppy disk device 19 and this system. Reference numeral 21 is a printer which can be constituted by an ink jet printer, laser beam printer or the like capable of recording at a relatively high resolution, and 22 is a printer interface for making a signal connection between the printer 21 and this system. . Reference numeral 23 denotes a keyboard for inputting character information such as various characters, control information, and the like.
Reference numeral 4 is a mouse as a pointing device, and 25 is a key interface for making a signal connection between the keyboard 23 and the mouse 24 and this system. Reference numeral 26 is an FLC display device (hereinafter referred to as FLCD) whose display is controlled by the FLCD interface 27, and has a display screen using the above-mentioned ferroelectric liquid crystal as its display operation medium. The FLCD interface 27 has a power control register 271. Reference numeral 12 is a system bus including a data bus, a control bus, and an address bus for connecting signals among the above-mentioned devices. Two
Reference numeral 8 denotes a power supply, which supplies a predetermined power to each device. The hard switch 281 performs connection / disconnection, and the switch detection unit 282 detects the operation of the hard switch 281 and supplies it to the CPU 11.

In the information processing system in which the various devices described above are connected, the user of the system is generally F
The operation is performed in correspondence with various information displayed on the display screen of the LCD 26. That is, LAN16, I / O17
The external device connected to the computer, the hard disk 18, the floppy disk 19, the keyboard 23, the characters supplied from the mouse 24, the image information, and the operation information related to the user's system operation stored in the main memory 13 are F
Displayed on the display screen of the LCD 26, the user collects information and gives an instruction operation to the system while watching this display. Here, the above-mentioned various devices are
A display information supply means.

(First Embodiment) FIG. 2 is a block diagram showing details of the FLCD 26 according to the present embodiment. here,
261 is an FLC panel, for example, JP-A-63-24.
As disclosed in Japanese Patent No. 3919, it is composed of a transparent electrode wiring group and the like provided on a pair of upper and lower glass substrates with a deflector in which FLC is enclosed. The wiring directions of the wiring group on the upper glass substrate and the wiring group on the lower glass substrate are orthogonal to each other, and the number of wirings can be appropriately determined according to the size and resolution of the display screen. 4 pels in this example
At a density of 960 in the horizontal scanning direction and 1 in the vertical scanning direction
There are 312 wires, and the FLC in that part depends on the polarity and strength of the electric field generated at the intersection.
Since the orientation state of can be changed, the number of display pixels of the FLC panel of this example is 1312 × 960.

In this example, a group of 1312 wirings in the vertical scanning direction is called a common side wiring, and the above-mentioned sequential line addresses are assigned to these wirings. Also, 9 in the horizontal scanning direction
The 60 wiring group is referred to as a segment side wiring group, and when a certain common side wiring (line) is selected and driven, the segment side wiring group is driven to display, erase, or update the line.

Reference numerals 262 and 263 denote drive units (respectively referred to as a segment drive unit and a common drive unit) for driving the segment side wiring group and the common side wiring, respectively, and generate a voltage signal having an appropriate waveform according to display data. Drive each wiring. The waveform and the like are disclosed, for example, in JP-A-63-243919. The display data signal is a serial signal Address / Data composed of a portion indicating the line address and a data group (data for 960 dots) following the portion indicating the line address, based on the horizontal synchronizing signal HSYNC transmitted from the data conversion unit 265. Input is made line-sequentially via the FLCD interface 27. Further, in order to distinguish the address portion and the data group portion of the signal, an identification signal AH / DL that is High in the address portion and Low in the data group portion is supplied. In the data conversion unit 265, the address (line address) Address and the data group Data are separated from the display data signal Address / Data based on the identification signal AH / DL and are input to the address / data selector 264. The address / data selector 264 receives the Address input from the data conversion unit 265 when the power-off request is not detected.
And Data are set in the common drive unit 263 and the segment drive unit 262, respectively. The initial data generation unit 266 generates an address and a data group for initializing the display contents when the POFF signal, which is a signal indicating power off, is generated.

Reference numeral 267 denotes F to obtain the brightness of the display screen.
A backlight 268 formed of a plurality of cold cathode fluorescent lamps provided on the back surface of the LC panel 261 is for obtaining a desired DC power supply (hereinafter referred to as DC power supply) from a commercial AC power supply (hereinafter referred to as AC power supply). It is a switching power supply. The DC power supply obtained by the switching power supply is
It is supplied as a power source for the data conversion unit 265, the initial data generation unit 266, and the like that configure the FLCD 26. 26
A backlight control unit 9 controls turning on / off of power supplied to the backlight 267.

The operation when the power-off request is generated on the information processing system side will be described below.

FIG. 3 is a timing chart when a power-off request is generated in this embodiment. Hard switch 2
A request to turn off the power is generated by pressing 81, etc.
When notified to the PU 11, the CPU 11 causes the power control register 27 in the FLCD interface 27 to operate.
Set the POFF bit of 1 to 1. FIG. 10 shows the configuration of the power control register 271. In this example, it is assumed that the power control register 271 has an 8-bit configuration, bit 0 is filled with a POFF bit, and when this bit is set to 1, it becomes active. The POFF bit is input to the address / data selector 264 and the initial data generator 266 in the FLCD 26 as a POFF signal which is a display screen initialization request signal,
When the POFF signal is generated, first, a signal for turning off the backlight by turning off the power supplied to the backlight 267 is sent from the initial data generation unit 266 to the backlight control unit 269. After the backlight is turned off, the address / data selector 264 forcibly switches the address and data group given to the common drive section and the segment drive section from the output from the data conversion section 265 to the output from the initial data generation section 266. . Next, in the initial data generation unit 266, the number of lines from the address 0 to the vertical scanning direction (1311 in this example)
The same data of, for example, "1" (or, for example, "0" as data for turning white) is output as data for turning the display state to black as a data group at that time. This data is previously stored in the initial data generator 26.
This is the data set in 6. When the rewriting of all 1312 lines is completed, all black (or all white) is displayed on the display screen of the FLCD 26. On the information processing system side, FLCD 2 is issued after the power-off request is generated.
If the power is turned off after a sufficient time for rewriting the entire display screen of No. 6, the FLCD 26 is turned off while the entire black (or all white) state is stored.

The power supply can be cut off, for example, by providing a capacitor having a sufficient capacity in the power supply 28 or connecting / disconnecting the power supply by software.

(Second Embodiment) In the first embodiment, as a means for the FLCD 26 to detect a power-off request, the FLCD is used.
P requesting initialization of display contents in interface 27
A register having an OFF bit is provided, and when the CPU 11 detects a power-off request by means such as a hard switch, the POFF bit is set to "1" and the PO
The configuration for inputting the FF bit signal to the FLCD 26 to detect that the FLCD 26 has issued a power-off request and to initialize the display contents has been described. In this example, a voltage monitoring circuit is provided in the FLCD 26,
A structure for recognizing that the AC power supplied to the FLCD 26 is cut off when the DC monitoring voltage output from the switching power supply 268 becomes equal to or less than a predetermined value and initializing the display content will be described.

FIG. 4 is a block diagram showing the details of the FLCD 26 according to the present embodiment, and FIG. 5 is a timing diagram when the power is cut off in the configuration of FIG.

In FIG. 4, 270 is a voltage monitoring circuit for detecting that the DC monitoring voltage obtained by the switching power supply 268 has dropped below a predetermined voltage. FIG. 6 shows a circuit diagram of the voltage monitoring circuit 270.

In FIG. 6, reference numeral 2701 denotes a comparator for detecting that the DC monitoring voltage has become equal to or lower than the reference voltage, 2
Reference numeral 702 is a Zener diode, and 2703 is a resistor, which creates a reference voltage.

In the above configuration, the operation when the power is turned off will be described below.

When the AC power supplied to the FLCD 26 is cut off, the DC monitoring voltage (24 V in this example) of the switching power supply 268 drops before the logic control voltage, and the reference voltage (20 V in this example). Voltage), the comparator 2701 in the voltage monitoring circuit 270 detects that the AC power is cut off and generates a POWDOWN signal. The POWDOWN signal is input to the address / data selector 264 and the initial data generation unit 266, and the display screen is initialized after the backlight 267 is turned off under the control of the initial data generation unit 266. Regarding the initialization processing of the display screen, POFF which is a display screen initialization request signal in the first embodiment.
The operation is the same as when a signal is generated. If the logic control voltage is cut off and the operation of the FLCD 26 is stopped after a sufficient time for initializing the display screen,
The FLCD 26 is turned off while the entire black (or all white) state is stored.

(Third Embodiment) In the first and second embodiments, the initial data generating unit 266 generates an address and a data group for initializing the display screen when a power-off request is generated. The means for rewriting the display screen according to the address given from the initial data generation unit 266 and the same data group of "1" (or "0") has been described. In this example, application of the means disclosed in JP-A-3-141321 as means for initializing the display screen will be described.

In the ferroelectric liquid crystal panel, when the voltage supply to the common drive section and the segment drive section is cut off during writing by refresh scanning or the like, a few seconds (1-2 seconds) immediately after that. ), It has been found that the image disturbance occurs due to the DC voltage irregularly applied to the liquid crystal due to the difference in time constant between the common drive section and the segment drive section. Further, it has been known that a strong DC voltage is applied to the liquid crystal along the write scan line immediately before the power is turned off, and the uniform alignment state of the liquid crystal along the scan line is destroyed. As measures against this, for example, the means disclosed in Japanese Patent Laid-Open No. 3-141321 has been proposed. This is a few μsec after the power-off request is issued
After that, the output voltage of the common drive unit 263 and the segment drive unit 262 is set to a certain constant voltage Vc, and then the output voltage of the segment drive unit is set to black over the entire screen of the display panel 261 for a period of several tens to several hundreds of μsec. the voltage V _4, then a constant voltage Vc with the output voltage of the common driver and the segment driver for several .mu.sec, then power down the output voltage of the common driver and the segment driver to the ground potential It is intended to suppress the occurrence of image disturbance that is sometimes seen and to cancel the application of a strong DC voltage to the pixel.

FIG. 7 is a block diagram when the means disclosed in Japanese Patent Laid-Open No. 3-141321 is applied as means for initializing the display screen, and FIG. 8 shows a power-off request in the configuration of FIG. FIG. 9 is a flowchart showing a flow of initialization processing of the display screen at this time, and FIG. 9 is a timing chart when a power-off request is generated in the configuration of FIG. In FIG. 7, reference numeral 271 denotes a drive voltage generation circuit for supplying V ₁ , V ₂ and Vc to the common drive unit 263 and V ₃ , V ₄ and Vc to the segment drive unit 262.
272 is a common drive unit 263 and a segment drive unit 262
And a control circuit for controlling the drive voltage generation circuit 271.

When a power-off request is generated (801)
First, the backlight 267 is turned off (802).
After that, the entire screen of the display panel is set to black and the display is initialized according to the means disclosed in JP-A-3-141321. That is, the output voltage from the segment drive unit 262 and the common drive unit 263 is set to Vc (80
3). The output voltage of the common drive unit 263 is set to Vc, the output of the segment drive unit 262 is set to V4, and the entire display panel screen is rewritten to black (804). The output voltage from the segment drive unit 262 and the common drive unit 263 is set to Vc (805). Segment drive unit 262, common drive unit 2
Set the output voltage from 63 to ground (80
6). After that, the power is turned off (807).

As described above, according to this embodiment,
Before the power is turned off, the display screen of the FLCD 26 is completely black or white, so the display contents at the time of power off are stored for the bistability, which is a feature of the FLCD. Even if the screen is displayed for a moment or the FLCD display surface is exposed to external light even when the power is turned off, and the screen that was stored when the power is turned off appears, it is uncomfortable. It can be displayed not.

[0030]

As described above, according to the present invention, the contents of the display screen are cleared before the power supply to the display device is stopped.

[Brief description of drawings]

FIG. 1 is a block diagram of an information processing system incorporating a display control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of the FLCD according to the first embodiment of the present invention.

FIG. 3 is a timing chart when a power-off request is generated in the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of an FLCD according to a second embodiment of the present invention.

FIG. 5 is a timing diagram when the power is cut off in the second embodiment of the present invention.

FIG. 6 is a voltage monitoring circuit 27 used in the second embodiment of the present invention.
Circuit diagram of 0

FIG. 7 is a block diagram showing a configuration of an FLCD according to a third embodiment of the present invention.

FIG. 8 is a flow chart diagram when a power-off request is generated in the third embodiment of the present invention.

FIG. 9 is a timing chart when a power-off request is generated in the third embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a power control register.

[Explanation of symbols]

 11 CPU 12 System Bus 13 Main Memory 14 DMA Controller 15 LAN Interface 16 LAN 17 I / O Device 18 Hard Disk Device 19 Floppy Disk Device 20 Disk Interface 21 Printer 22 Printer Interface 23 Keyboard 24 Mouse 25 Key Interface 26 FLCD (FLCD Display) 27 FLCD interface 28 power supply 261 FLC panel 262 segment driver 263 common driver 264 address / data selector 265 data converter 266 initial data generator 267 backlight 268 switching power supply 269 backlight controller 270 voltage monitoring circuit 2701 comparator 2702 20 volt Zener Diode 271 drive voltage Generation circuit 272 Control circuit

Claims (1)

[Claims] 1. A display device comprising a display screen in which display elements capable of holding a display state are arranged, and updating the display based on display data on the display screen, and an initialization means for initializing display contents. A detection means for detecting the disconnection of the power source, the detection means detects the disconnection of the power source,
A display device, wherein display contents are initialized by the initialization means.