JP2000276095A - Matrix type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a high-luminance image with nearly linear light emission characteristics for an original image by making inverse gamma corrections of a video signal and increasing the light emission intensity. SOLUTION: A display panel 10 has rows and columns of light emitting elements arrayed in matrix. A pulse-width modulating(PWM) circuit 4 and a shift register 7 supply a driving waveform corresponding to image data to be displayed by the light emitting elements to the display panel 10, thereby driving the respective light emitting elements. When the image data are smaller than a reference value, the lamp voltage generated by a waveform generating circuit 8 is cut with a pulse from the PWM circuit 4 to give a gradient to the driving waveform so that light emission characteristics of the respective light emitting elements will be nearly inverse gamma characteristics. When the image data are larger than the reference value, a constant voltage +Vd is supplied to the light emitting elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix for a display device using an electron emission source such as a cold cathode electron emission device (so-called field emission display device) and an electroluminescence (hereinafter abbreviated as EL) display device. The present invention relates to a type display device.

[0002]

2. Description of the Related Art As a matrix type display device, a field emission display device and an EL display device using a cold cathode electron-emitting device are known. FIG. 8 is a block diagram showing a conventional matrix type display device of this kind. 8, a display panel 10 is a display panel using, for example, cold cathode electron-emitting devices. As shown in FIG. 9, as an example, a plurality of row wirings connected to scan electrodes S1 to Sm;
The cells 10s forming the pixels are arranged in a matrix by a plurality of column wirings connected to the data electrodes D1 to Dn. The cell 10s includes an electron-emitting device that is an electron-emitting source and a phosphor that receives electron irradiation from the electron-emitting device.

A video signal input to a terminal 1 is written to a shift register 2. 1 in shift register 2
After the data for the row is written, the data is latched by the latch circuit 3. The data output from the latch circuit 3 is
The signal is input to a pulse width modulation (PWM) circuit 4. The PWM circuit 4 switches the switch Sd1 with a pulse corresponding to the magnitude of the data.
To Sdn. Switches Sd1 to Sdn are PW
It is turned on when the pulse input from the M circuit 4 is high, and a constant voltage + is applied to the data electrodes D1 to Dn of the display panel 10.
Vd.

On the other hand, the synchronization signal input to the terminal 5 is input to the timing control circuit 6. The timing control circuit 6 supplies a shift clock to the shift register 2 and a latch clock to the latch circuit 3. The timing control circuit 6 also supplies a one-line-width scan pulse to the shift register 7. The shift register 7 controls the switches Ss1 to Ssm with the pulse. The switches are turned on when the scan pulse input from the shift register 7 is high, and the scan electrodes S1 to Sm of the display panel 10 are turned on.
Is supplied with a constant voltage −Vs.

Further, the operation when driving the matrix type display device shown in FIG. 8 will be described in detail. As described above, the scan pulse is sequentially applied to the scan electrodes S1 to Sm of the display panel 10 by the shift register 7. Further, a pulse whose pulse width (PWM) is modulated by the PWM circuit 4 in accordance with data corresponding to the selected line is applied to the data electrodes D1 to Dn of the display panel 10. That is, a voltage is applied to the data electrode Dj for the data in the i-th row and the j-th column while the scanning electrode Si is selected. The intensity (gradation) of the light emission depends on the data electrode D1.
ＤDn is represented by the application time (pulse width) of the pulse applied to Dn.

FIGS. 10A to 10C are waveform diagrams showing the operation when displaying the j-th column as an example. FIGS. 10A to 10C show scan pulses applied to the scan electrodes, and FIG. 10D shows the scan pulses applied to the data electrodes. Pulses to be applied are shown in (E) to (G) in the element (cell 10).
The voltage applied to s) is shown. Here, the number of bits of the video signal is represented as 8 bits, perfect black is represented as 0, complete white is represented as 255, i-th row and j-column are black (0),
The (i + 1) th row and jth column are gray (128), and the (i + 2) th row and jth column are white (255). One horizontal scanning period is constituted by 255 unit times. The unit time is P
This is the clock cycle of the WM circuit 4, and the unit time is represented by T. The gradation expression is performed by changing the pulse width of the pulse applied to the data electrodes D1 to Dn from 0T to 255T. Actually, one horizontal scanning period is 2
The unit time may be 55 T or more.

As shown in FIG. 10, during the horizontal scanning period of the i-th row, the voltage -Vs is applied to the scanning electrodes Si of the i-th row, and no voltage is applied to the other scanning electrodes.
At this time, since the signal in the i-th row and the j-th column is 0, the data electrode Dj in the j-th column is always at the 0 potential. When the horizontal scanning period for the i-th row ends, the process proceeds to the horizontal scanning period for the (i + 1) -th row.

In the horizontal scanning period of the (i + 1) th row, i +
A voltage -Vs is applied to one row of scan electrodes S (i + 1), and no voltage is applied to the other scan electrodes. At this time, since the signal of the (i + 1) -th row and the j-th column is 128, the voltage + Vd is applied to the data electrode Dj of the j-th column only for about half (128T) of the horizontal scanning period (255T). It becomes 0 potential. When the horizontal scanning period of the (i + 1) -th row ends, the process proceeds to the horizontal scanning period of the (i + 2) -th row.

In the horizontal scanning period of the i + 2 row, i +
The voltage -Vs is applied to the scanning electrodes S (i + 2) in two rows, and no voltage is applied to the other scanning electrodes. At this time, since the signal of the (i + 2) th row and the jth column is 255, the data electrode Dj of the jth column is supplied to the entire horizontal scanning period (255T).
, A voltage + Vd is applied.

Meanwhile, in the case of the display panel 10 using the cold cathode electron emitting device, the electron emitting device has a threshold value for emitting electrons. In FIG. 11, the solid line is
Shows the characteristic of emission current i _e to the applied voltage v _a of the cold cathode electron emission element. Voltage Vth is a threshold for the emission current i _e is generated. During the scanning period, the scanning electrodes S1 to S1
Voltage (absolute value) Vs applied to Sm and data electrode D
The voltages Vd applied to 1 to Dn are both set to be equal to or lower than the voltage Vth, and the voltage (Vd + Vs) is set to be higher than the voltage Vth.

The voltage applied to the cold cathode electron-emitting device (cell 10s) includes the potentials of the data electrodes D1 to Dn and the scanning electrodes S
In this case, when a voltage (Vd or Vs) is applied to only one of the data electrodes D1 to Dn and the scan electrodes S1 to Sm, the cold cathode electron-emitting device emits electrons. No data electrode D1 to Dn and scan electrode S1
Only when a voltage is applied to both Sm to Sm, the cold cathode electron-emitting device emits electrons, and the cell 10s emits light.

In the example of FIG. 10, the voltage applied to the cell 10s in the i-th row and the j-th column is always equal to or lower than the voltage Vth, so that the cell 10s does not emit light. The voltage applied to the cell 10s in the (i + 1) -th row and the j-th column is the voltage Vt only for a period of 128T indicated by hatching.
h, the cell 10s emits light only for a period of 128T. Since the voltage applied to the cell 10s in the (i + 2) row and j column exceeds the voltage Vth in the hatched period of 255T, the cell 10s emits light in the period of 255T.

Here, only the display process from the i-th row to the (i + 2) -th row has been described.
0 scanning electrodes S1 to Sm are sequentially arranged from row 1 to row M.
A scan pulse is applied, and a PWM-modulated pulse is applied to the data electrodes D1 to Dn in accordance with the scan timing. In the case of displaying 480 rows × 640 columns of effective pixels, 480 scanning electrodes and 6 data electrodes are used.
There are 40 data electrodes and 1920 data electrodes in the case of color display of the RGB stripe structure.

[0014]

According to the gradation expression by the PWM modulation, it is possible to exhibit a substantially linear light emission characteristic with respect to the image data. However, in an actual video signal, the relationship between the brightness of the original image (original image) and the amplitude of the image data is not linear but has a gamma characteristic. Therefore, in a matrix type display device having linear characteristics, it is necessary to perform inverse gamma correction on a video signal. Although it is conceivable to perform inverse gamma correction on the input video signal in advance, the configuration becomes complicated.

The present applicant has previously filed Japanese Patent Application No. 10-3157.
No. 42, the voltage waveform applied to the element is made into a ramp shape, and according to Japanese Patent Application No. 10-349662,
We have proposed a matrix type display device in which inverse gamma correction is performed by making the voltage waveform applied to the element into a step shape. However, when the voltage waveform applied to the element is ramp-shaped or step-shaped, there is a problem that the light emission intensity when the pulse width of the pulse output from the PWM circuit 4 is maximized is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. A matrix type display device capable of performing inverse gamma correction and improving the light emission intensity by improving a driving method is provided. The purpose is to provide.

[0017]

According to the present invention, there is provided a display panel (10) in which light emitting elements (10s) are arranged in a matrix by a plurality of rows and a plurality of columns. In the matrix type display device that drives the light emitting elements, the driving circuits (2 to 4, 6, 7, Sd1 to Sdn, and Sx) that drive the light emitting elements by a driving waveform corresponding to the image data displayed by the light emitting elements.
d1 to Sxdn, Ss1 to Ssm), and when the image data is smaller than a predetermined reference value, a gradient forming means (G) for forming a gradient in the drive waveform so that the light emission characteristics of each of the light emitting elements become substantially inverse gamma characteristics. 8) and a supply unit (4) for supplying a substantially constant voltage or current to the light emitting element when the image data is equal to or more than the predetermined reference value.
0, 41, Sxd1 to Sxdn) are provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a matrix type display device according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a first embodiment of the matrix type display device of the present invention. FIGS. 2 and 3 are waveform diagrams for explaining the operation of the first embodiment of the matrix type display device of the present invention. FIG. 5 is a characteristic diagram for explaining a first embodiment of the matrix type display device of the present invention, and FIG. 5 is a second diagram of the matrix type display device of the present invention.
FIG. 6 is a block diagram showing an embodiment, FIG. 6 is a waveform diagram for explaining the operation of the second embodiment of the matrix type display device of the present invention,
FIG. 7 is a characteristic diagram for explaining a second embodiment of the matrix type display device of the present invention. 1 and 5, the same parts as those in FIG. 8 are denoted by the same reference numerals.

<First Embodiment> In FIG. 1, a display panel 10 is, for example, a display panel using cold cathode electron-emitting devices, and the specific configuration is as described with reference to FIG. The video signal input to the terminal 1 is transmitted to the shift register 2
Is written to. After one row of data is written in the shift register 2, the data is latched by the latch circuit 3. The data output from the latch circuit 3 is input to the PWM circuit 4 and the comparison circuit 40. The PWM4 circuit is
Switches Sd1 to Sdn with pulses corresponding to the magnitude of data
Control. The switches Sd1 to Sdn are connected to the PWM circuit 4
It is turned on when the input pulse is high. To the switches Sd1 to Sdn, a ramp-shaped voltage described later after the waveform generation circuit 8 is input.

The switches Sd1 to Sdn are respectively
Switches Sxd1 to Sxdn are connected in cascade. The outputs of the switches Sd1 to Sdn are input to one terminal of the switches Sxd1 to Sxdn, and the constant voltage + Vd is input to the other terminal. Switches Sxd1 to Sx
The switching of dn is controlled in accordance with the output of the comparison circuit 40. When the pulse input from the PWM circuit 4 is high, the switches Sd1 to Sdn are turned on, and the switch Sxd1
When Sxdn is connected to the terminal on the left side in the figure, a ramp-shaped voltage is supplied to the data electrodes D1 to Dn of the display panel 10. When the switches Sxd1 to Sxdn are connected to the terminals on the right side in the drawing, a constant voltage + Vd is supplied to the data electrodes D1 to Dn of the display panel 10.

The comparison circuit 40 compares the input data with a predetermined reference value, and when the input data is smaller than the reference value, sets the switches Sxd1 to Sxdn to select the outputs of the switches Sd1 to Sdn. When the input data is equal to or higher than the reference value, the switches Sxd1 to Sxdn are controlled to select the constant voltage + Vd. As an example, when the reference value is 255, when the input data is 0 to 254, the switches Sxd1 to Sxdn select the outputs of the switches Sd1 to Sdn. When the input data is 255, the switches Sxd1 to Sxdn are Select the constant voltage + Vd. The reference value is not limited to 255.

The synchronization signal input to the terminal 5 is input to the timing control circuit 6. The timing control circuit 6 supplies a shift clock to the shift register 2 and a latch clock to the latch circuit 3. Timing control circuit 6
Supplies a pulse of one line width to the shift register 7. The shift register 7 uses the pulse to switch Ss
1 to Ssm are controlled. The switches Ss1 to Ssm are turned on when the scan pulse input from the shift register 7 is high, and the scan electrodes S1 to Sm of the display panel 10 are turned on.
Is supplied with a constant voltage −Vs. The timing control circuit 6
Further, the timing at which the waveform generating circuit 8 generates the ramp voltage is controlled.

Here, the operation of the drive circuit shown in FIG.
This will be described in detail with reference to FIG. FIG. 2 also shows the operation when displaying the j-th column as an example, and (A) to (C)
Shows a scan pulse applied to the scan electrode, (D) shows a ramp-like voltage generated by the waveform generating circuit 8, (E) shows a pulse applied to the data electrode, and (F) to (H) show a pulse. The voltage applied to the element (cell 10s) is shown. The ramp voltage generated by the waveform generating circuit 8 is a waveform having a predetermined gradient of one horizontal scanning period cycle as shown in FIG. Minimum voltage of ramp voltage (start voltage of ramp)
Is + Vd1, and the highest voltage (end voltage of the slope) is + Vd1.
d2.

Here, the number of bits of the video signal is 8 bits, perfect black is represented as 0, and perfect white is represented as 255, i-th row and j-th column is black (0), and i + 1-th row and j-th column are gray ( 128), the case where the (i + 2) th row and the jth column are white (255). In the first embodiment, the reference value is 255, and one horizontal scanning period is constituted by 254 units.
The unit time is a clock cycle, and the unit time is represented by T. In the gradation expression of data 0 to 254, the pulse width of the pulse applied to the data electrodes D1 to Dn is set to 0T to
This is done by changing at 254T. The unit time T of the pulse width can be changed by changing the clock frequency.

As shown in FIG. 2, during the horizontal scanning period of the i-th row, the voltage -Vs is applied to the scanning electrodes Si of the i-th row, and no voltage is applied to the other scanning electrodes. At this time, since the signal in the i-th row and the j-th column is 0, the data electrode Dj in the j-th column is always at the 0 potential. When the horizontal scanning period for the i-th row ends, the process proceeds to the horizontal scanning period for the (i + 1) -th row.

In the horizontal scanning period of the (i + 1) th row, i +
A voltage -Vs is applied to one row of scan electrodes S (i + 1), and no voltage is applied to the other scan electrodes. At this time, since the signal of the (i + 1) -th row and the j-th column is 128, a voltage is applied to the data electrode Dj of the j-th column for about a half (128T) of the horizontal scanning period (254T). Potential. The voltage applied to the data electrode Dj has a ramp-shaped waveform obtained by cutting off the ramp-shaped voltage shown in FIG. When the horizontal scanning period of the (i + 1) -th row ends, the process proceeds to the horizontal scanning period of the (i + 2) -th row.

In the horizontal scanning period of the i + 2 row, i +
The voltage −Vs is applied to the scanning electrodes S (i + 2) of the two rows, and no voltage is applied to the other scanning electrodes. At this time, since the signal of the (i + 2) th row and the jth column is 255, the switches Sxd1 to Sxdn are controlled by the comparison circuit 40.
Selects the constant voltage + Vd. Therefore, the constant voltage + Vd is applied to the data electrodes Dj in the j-th column in the entire period (254T) of the horizontal scanning period. Note that the constant voltage + Vd is an arbitrary voltage higher than the minimum voltage + Vd1 of the ramp voltage.
The voltage applied to the data electrode Dj has a rectangular waveform instead of a ramp waveform.

During the scanning period, the voltage (absolute value) Vs applied to the scanning electrodes S1 to Sm and the data electrodes D1 to Dn
The voltages Vd1 to Vd2 and Vd applied to
Are set to be equal to or lower than the voltage Vth which is the threshold for the electron-emitting device of the display panel 10 to emit electrons, and the sum of the voltages Vd1 to Vd2, Vd and the voltage Vs is equal to the voltage Vt.
Set larger than h. Therefore, the data electrodes D1 to Dn
Only when a voltage is applied to both the scan electrodes S1 to Sm, the cold cathode electron-emitting device emits electrons, and the cell 10
s emits light.

In the example of FIG. 2, the element (cell 10
Since the voltage applied to s) is always equal to or lower than the voltage Vth, the cell 10s does not emit light. Cell 10 at i + 1 row and j column
Since the voltage applied to s exceeds the voltage Vth only for a period of 128T indicated by hatching, the cell 10s emits light only for a period of 128T. The voltage applied to the cell 10s in the (i + 2) row and j column is 254, which is the entire period of one hatched horizontal scanning period.
Since the voltage exceeds the voltage Vth during the period T, the cell 10s emits light during the period 254T. In this embodiment, when the data is 254 or less, a ramp voltage is applied, and in the data 255, a constant rectangular voltage is applied for one horizontal scanning period.

Here, only the display process from the i-th row to the (i + 2) -th row has been described.
0 scanning electrodes S1 to Sm are sequentially arranged from row 1 to row M.
A scan pulse is applied, and a PWM-modulated pulse is applied to the data electrodes D1 to Dn in accordance with the scan timing. At this time, the voltage applied to the data electrodes D1 to Dn is different from the conventional flat waveform, and the PWM circuit 4 generates the ramp voltage generated by the waveform generating circuit 8 when the data is in the range up to 254. It becomes a waveform cut out according to the pulse width of the pulse to be generated. When the data is 255, the voltage applied to the data electrodes D1 to Dn has a flat rectangular waveform.

The light emission characteristics when driven with the above-described waveforms will be specifically described. Note that, to simplify the calculation,
It is assumed that the voltage-emission current characteristics of the electron-emitting device described with reference to FIG. 11 are approximated not by actual characteristics shown by solid lines but by straight lines shown by broken lines. When this straight line is expressed by an equation, the following equation (1) is obtained. Incidentally, i _e is the emission current, v _a is the applied voltage, g is the slope of the straight line (conductance).

[0032]

(Equation 1)

Further, the voltage v _a is applied to each element of the display panel 10, as shown in FIG. 3 (A) as an example, time t
= Given voltage of 0 v _1, t = the voltage of the t _w is linearly boosted so as to be v _2, an electronic volume q to be emitted from the elements in the pulse width from time zero up to the t _p follows (2) can be calculated. Note that the voltage v ₁
Is the voltage (Vd1 + Vs), the voltage v ₂ is the voltage (Vd
2 + Vs).

[0034]

(Equation 2)

When the data is in the range of 0 to 254, the display panel
Voltage v applied to each element of _aIs shown in FIG.
As shown in FIG._pAgainst
The emitted electron quantity q indicates a quadratic function. On the other hand, if the data is 255
, The voltage v applied to each element of the display panel 10_a
Is a constant voltage v as shown in FIG._ThreeIt is. What
Contact, voltage v_ThreeIs the voltage (Vd + Vs). Voltage v
_ThreeIs the voltage v_TwoMay or may not be the same. At this time
Is larger than the electron quantity q when the data is 254.
It can be much larger.

Since the light emission of the display panel 10 is caused by the irradiation of electrons from the electron-emitting device, according to the first embodiment, the light emission characteristics for the image data are as shown by the solid line in FIG. In the range of 0 to 254, the curve is a quadratic curve. Accordingly, Japanese Patent Application Nos. 10-315742 and 10-349662.
The emission intensity can be made higher than that of the prior application indicated by the symbol. Moreover, data by indicates that the amount of emitted electrons q is a quadratic function with respect to the pulse width t _p in the range of 0 to 254, similar to the above prior application, may be subjected to inverse gamma correction. As a result, in a matrix type display device,
It is possible to display with substantially linear light emission characteristics with respect to the original image. In FIG. 4, a broken line indicates a light emission characteristic according to a conventional example.

<Second Embodiment> A second embodiment shown in FIG.
A PWM circuit 41 is provided instead of the comparison circuit 40, and the pulse width is controlled according to image data even for a constant voltage + Vd. In FIG. 5, FIG.
The same parts as those described above are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

The data output from the latch circuit 3 is P
It is input to the WM circuits 4 and 41. In the second embodiment, the reference value is set to 252 as an example. If the data output from the latch circuit 3 is smaller than the reference value 252 (up to 251), the switches Sxd1 to Sxdn switch the outputs of the switches Sd1 to Sdn. select. Then, the operation is performed in the same manner as in the first embodiment. If the data output from the latch circuit 3 is equal to or more than the reference value 252, the PWM circuit 41 supplies the switches Sxd1 to Sxdn with pulses whose pulse width gradually increases from 252 to 255. The switches Sxd1 to Sxdn are connected to the terminal on the right side in the figure and supply a constant voltage + Vd to the data electrodes D1 to Dn of the display panel 10 while the pulse is supplied from the PWM circuit 41.

In the second embodiment, since the reference value is 252, the gradation expression for the data output from the latch circuit 3 up to 251 is performed by setting the pulse width of the pulse applied to the data electrodes D1 to Dn to 0T to This is performed by changing at 251T.

When the data is in the range of 0 to 251, the display panel
Voltage v applied to each element of _aIs shown in FIG.
As shown in FIG._pAgainst
The emitted electron quantity q indicates a quadratic function. For example, if the data is 252
, The voltage v applied to each element of the display panel 10_a
Are from 0 to t, as shown in FIG._aUp to ramp
Waveform, t_aThe constant voltage v_ThreeBecomes And the data
In 253 and 254, the constant voltage v_ThreePeriod of FIG. 6 (B)
Spread to the left of. When the data is 255, FIG.
As shown in FIG._ThreeBecomes

Also in the second embodiment, the quantity of emitted electrons q (that is, the emission intensity) can be made much larger than that described in the prior application. In addition, the constant voltage v ₃
The gradation characteristic can be smoothed by making the transition to stepwise. Incidentally, the reference value of shifting from the ramp-like waveform to a constant voltage v ₃ is not limited to 252. If the reference value is set to a smaller value, the unit time T of the pulse width of the pulse generated by the PWM circuit 4 increases. When the unit time T is increased, the frequency of the clock supplied to the PWM circuit 4 can be reduced.

In the first and second embodiments described above, the voltage waveform applied to the electron-emitting device is a ramp waveform.
Reverse gamma correction may be performed by using a step-like waveform. What is necessary is just to form a gradient in the drive waveform so that the light emission characteristics become substantially inverse gamma characteristics. Note that a waveform that changes with time, such as a ramp-shaped waveform, may not be a waveform that increases linearly, and may be a curve. According to the present invention, the emission current from the electron-emitting device based on the pulse width corresponding to the image data is changed with time in a certain range of the image data, and is set to a constant voltage in a range beyond the range. Can be made to be a substantially inverse gamma characteristic, and the emission intensity can be increased.

Further, the scanning electrodes S1 to S1 of the display panel 10
A ramp voltage or a step voltage may be supplied to both the Sm and the data electrodes D1 to Dn. Also, the scanning electrodes S1 to S1
The drive signal (drive waveform) supplied to Sm and the data electrodes D1 to Dn may be a current source instead of a voltage source, and the polarity of the drive waveforms of the scan electrodes S1 to Sm and the data electrodes D1 to Dn is reversed. It may be. The present invention is not limited to a field emission display device or an EL display device, but can be applied to any matrix type display device in which a light emitting element is driven by a pulse having a pulse width corresponding to image data.

[0044]

As described above in detail, in the matrix type display device of the present invention, a driving circuit for driving each of the light emitting elements by a driving waveform corresponding to the image data to be displayed by each of the light emitting elements; Is smaller than a predetermined reference value, a gradient forming means for forming a gradient in the drive waveform so that the light emission characteristics of each light emitting element become substantially inverse gamma characteristics, and a light emitting element when the image data is equal to or more than a predetermined reference value. Since the apparatus is provided with the supply means for supplying a substantially constant voltage or current, it is possible to perform inverse gamma correction on the video signal and increase the light emission intensity. As a result, in the matrix type display device, it is possible to display a high-brightness image with almost linear emission characteristics with respect to the original image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the first embodiment of the present invention.

FIG. 3 is a waveform chart for explaining the operation of the first embodiment of the present invention.

FIG. 4 is a characteristic diagram for explaining the first embodiment of the present invention.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a waveform chart for explaining the operation of the second embodiment of the present invention.

FIG. 7 is a characteristic diagram for explaining a second embodiment of the present invention.

FIG. 8 is a block diagram showing a conventional example.

FIG. 9 is a diagram illustrating a configuration of a display panel of a matrix display device.

FIG. 10 is a waveform chart for explaining the operation of the conventional example.

FIG. 11 is a characteristic diagram showing a relationship between a voltage applied to a cold cathode electron-emitting device and an emission current.

[Explanation of symbols]

1, 5 terminal 2 shift register 3 latch circuit 4, 41 pulse width modulation circuit 6 timing control circuit 7 shift register 8 waveform generation circuit 10 display panel 10s cell (light emitting element) 40 comparison circuit Sd1-Sdn, Sxd1-Sxdn, Ss1- Ssm
switch

Claims (3)

[Claims] 1. A matrix-type display device for driving a display panel in which light-emitting elements are arranged in a matrix by a plurality of rows and a plurality of columns, wherein a driving waveform corresponding to image data displayed by each of the light-emitting elements is used. A drive circuit for driving each of the light emitting elements; and a gradient forming means for forming a gradient in the drive waveform so that when the image data is smaller than a predetermined reference value, the light emitting characteristics of each of the light emitting elements are substantially inverse gamma characteristics. A supply unit configured to supply a substantially constant voltage or current to the light emitting element when the image data is equal to or greater than the predetermined reference value. 2. The apparatus according to claim 1, wherein said supply means includes a pulse width modulation circuit for supplying a pulse having a pulse width modulated according to the image data to said light emitting element when said image data is equal to or greater than said predetermined reference value. The matrix type display device according to claim 1, wherein 3. The matrix type display device according to claim 1, wherein said matrix type display device is a field emission display device or an electroluminescence display device.