JPH09198005A - Plasma display - Google Patents

Abstract

(57) Abstract: To prevent the PDP panel part from being destroyed due to high temperature, brightness adjustment is performed. SOLUTION: A transparent heat conductive sheet 3 is provided on a front surface 1 of a PDP panel, and a heat conductive sheet 4 is provided on a back surface 2 thereof.
In addition to improving the heat radiation effect of the P panel, the temperature of the PDP panel is detected by providing the temperature detector in the heat conductive sheet 4, and the temperature rise prevention circuit to the PDP panel destruction temperature detects the signal from the temperature detector. Then, the brightness can be adjusted by adjusting the gain and the clamp level of the image signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas discharge type image signal display device (International Patent Classification G09G 3/28).

[0002]

2. Description of the Related Art In recent years, a color cathode ray tube (hereinafter referred to as CRT) has been widely used as an image display device.
The RT requires a certain depth because of a driving method in which a set of three electron beams is deflected to scan on the phosphor.
The depth increases in proportion to the size of the screen. On the other hand, there is a demand for a gas discharge type image display device (plasma display) having a memory function as a display device which can be made significantly thin while having a large screen. The gas discharge type image display device having this kind of memory function is roughly classified into an AC type and a DC type, but the basic concept of obtaining light emission by discharge is the same.

In a gas discharge type image display device, a plurality of electrodes are arranged in a space surrounded by a barrier of an insulator, and discharge gas is sealed in the space to form a discharge cell. A desired number of the discharge cells arranged in the vertical and horizontal directions is called a plasma display panel (hereinafter referred to as PDP). When a voltage required for discharge is applied to a plurality of electrodes in the discharge cell of the PDP, discharge light emission occurs and is recognized as visual information. When displaying in color with this method,
By disposing a phosphor in each discharge cell and enclosing a discharge gas that emits ultraviolet rays by discharge, for example, a discharge gas such as helium-xenon, the fluorescent substances are caused to emit light by ultraviolet rays and recognized as visual information.

The brightness of the gas discharge type image display device is adjusted by adjusting the light emission time. A typical example of such a technique is the brightness adjustment method by the subfield method. In this method, one vertical period is divided into a plurality of subfields, the number of times of light emission is determined for each subfield, and the brightness is adjusted by combining the subfields. For example, when expressing the brightness with 256 gradations, eight subfields are used, 128 times in the eighth subfield, and 64 times in the seventh subfield.
The number of times of light emission is 32 times in the sixth subfield, 16 times in the fifth field, 8 times in the fourth field, 4 times in the third field, 2 times in the second subfield, 1 time in the first subfield. decide.

The brightness adjustment is performed in the excited state of each sub-field. When no light is emitted, all the sub-fields are not excited. When the brightness is maximum, all the sub-fields are excited. In the case of displaying the 67th gray level, the 7th, 2nd and 1st subfields are excited. In this way, the brightness adjustment is performed digitally. Therefore, simply limiting the maximum value of the light emission brightness of the gas discharge type image display device causes a deterioration in gradation.

In the gas discharge type image display device equipped with such a PDP, the temperature of the PDP rises in proportion to the increase in luminance because of the operating principle of generating visual information by light emission by gas discharge. The PDP has a structure in which a discharge cell is formed between two glass plates. Therefore, when the temperature of the PDP continues to rise, thermal expansion of the glass causes the PDP to self-destruct. Therefore, as a countermeasure against this, a method of extracting the luminance level from the image signal (for example, calculating the average luminance of the entire screen) is used. If the level is above a certain level, adjust the brightness,
A method to reduce the overall brightness level below a certain value, or P
It is possible to prevent the temperature of the PDP from reaching the destruction temperature by measuring the DP or the ambient temperature and using the obtained temperature data to adjust the brightness (Japanese Patent Laid-Open No. 4-284).
492 publication).

[0007]

However, in the above-mentioned conventional example, since the heat dissipation effect of the PDP itself is low, the limit of the brightness level becomes a low value, and the brightness gradation is deteriorated. Furthermore, when there is an image signal in which only the temperature of a certain area of the PDP rises and such an image signal is input for a long time,
The above method cannot handle it.

The brightness level of the image signal, or P
In the method of limiting the maximum brightness by the temperature around the DP,
Even if the brightness level is not limited, the maximum brightness is limited even when the temperature of the PDP is maintained or drops because the brightness level of the subsequent image signal becomes low, and the brightness gradation is degraded. The deterioration in gradation deteriorates the delicate light and dark expression of the image signal, generates a pseudo contour, and deteriorates the image quality of the image signal.

[0009]

In order to solve the above problems, the present invention firstly comprises a transparent heat conductive sheet or a transparent heat conductive plate on the front surface of a PDP and a heat conductive sheet on the rear surface thereof. Alternatively, it is provided with a heat conduction plate.

According to the present invention, it is possible to make the temperature of the surface of the panel uniform, prevent destruction or deterioration of the panel, and provide a high-definition image.

Further, the present invention detects the case where the PDP temperature decreases without the brightness limitation depending on the temporal transition of the image signal, that is, it detects the high brightness signal for a short time and does not suppress the brightness. The present invention relates to a plasma display that executes optimum brightness control by detecting a case where brightness control is unnecessary in terms of time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first invention relates to a plasma display characterized in that a transparent heat conducting means is provided on the front surface of a panel for displaying an image and a heat conducting means is provided on the rear surface of the panel. By providing the heat conducting sheet or the heat conducting plate, the heat distribution of the PDP can be made uniform, a part of the heat generation can be prevented, and the heat dissipation efficiency can be increased.

A second aspect of the invention is to transmit a light beam having a desired wavelength at a desired transmittance by using a technique such as metal film deposition or coloring on a transparent heat conducting means such as a transparent heat conducting sheet or a transparent heat conducting plate. In order to obtain the effect of preventing reflection of external light and improving the contrast ratio by providing the transparent heat conducting sheet or the heat conducting plate provided on the front surface with the function of an optical filter. By removing the optical filter provided in the display device, the effect of reducing the cost can be obtained.

According to a third aspect of the invention, the heat conducting sheet or the heat conducting means of the heat conducting plate is provided with a plurality of temperature detecting means, and the first signal processing circuit for processing an output signal of the temperature detecting means is provided. A second signal processing circuit for performing signal processing of the image signal according to the calculation result of the signal processing circuit, and storing the relationship between the PDP temperature, the brightness level of the image signal and the temperature change due to the brightness limitation in the storage means, The second signal processing circuit realizes a configuration in which the corresponding brightness limiting level is obtained from the storage means by the output from the temperature detecting means, and the effect of alleviating the deterioration of the gradation of the image as compared with the conventional technique can be obtained.

According to a fourth aspect of the present invention, the heat conducting means has a shape including a heat conducting portion and a heat disconnecting portion. Further, each of the heat conducting parts is equipped with a temperature detecting means so that the PDP can be oriented in a desired direction
With this, it is possible to detect the temperature change of the PDP in the vertical or horizontal direction. As a result, when an image signal in which the temperature of a certain region of the PDP rises is input, it is possible to detect the state, and it is possible to prevent the PDP from being destroyed because the temperature of only a certain region becomes high. Is obtained.

A fifth aspect of the present invention comprises an image signal recognition circuit for recognizing the luminance level from the luminance data of the image signal used for light emission.
The brightness data of the image signal used for the light emission of is compared with the brightness data of the input image signal, that is, by comparing the brightness of the preceding and following image signals in time, the result is sent to the signal processing circuit. It is configured to output and adjust the brightness.
According to the present invention, it is possible to detect the image signal in which the PDP temperature is lowered without suppressing the brightness by comparing the brightness data before and after temporally, and perform the brightness suppression determination, thereby preventing the deterioration of the gradation. Is obtained.

(First Embodiment) The first invention of the present invention will be described below. An example is a case of a heat conductive sheet, but a heat conductive member such as a heat conductive plate can achieve the purpose by the same use method.

The plasma display of the first invention of the present invention comprises, as transparent heat conducting means, for example, the transparent heat conducting sheet 3 on the front surface of the PDP 10 and the heat conducting sheet 4 on the back surface. Since the front surface is a display surface of an image recognized by humans, the heat conductive sheet needs to transmit visible light, so the transparent heat conductive sheet 3 is used. On the other hand, the back surface determines whether or not the heat conductive sheet 4 is made transparent if necessary to transmit visible light. Transparent heat conducting sheet 3 and heat conducting sheet 4
Adopts a glass substrate (front plate 1 and back plate 2) used for the PDP 10 that has a high heat radiation efficiency to the air, thereby increasing the heat radiation efficiency of the PDP 10 to the air and emitting light. Since it has the effect of reducing the temperature rise rate of the PDP 10 and making the heat distribution on the surface of the PDP 10 uniform, the effect of reducing the reaching coefficient to the destruction temperature of the PDP 10 by light emission can be obtained.

The transparent heat-conducting sheet 3 or the heat-conducting sheet 4 may be made of, for example, silicon rubber or the like, and preferably has a thickness of 1 mm or less, and its effect is great.

Further, since the entire surface of the PDP 10 is covered with the heat conductive sheet, it serves as a protective film of the PDP 10 to improve the breaking strength by external impact and to prevent the scattering of fragments when the PDP 10 is broken. To be

(Second Embodiment) A plasma display according to a second invention of the present invention will be described with reference to FIG. When the transparent heat conducting sheet 3 is used as the transparent heat conducting means provided on the front surface of the PDP 10, a metal thin film 6 such as a dichroic mirror is deposited on the transparent heat conducting sheet 3 to obtain a desired wavelength. By providing the function of a filter that transmits visible light with a desired transmittance, the black-and-white contrast ratio can be increased and the color temperature of the white screen can be set to a desired value.

Further, for example, an AR coating process is performed to reduce the reflection of external light on the PDP 10. By providing the transparent heat conductive sheet 3 with such an action, it is not necessary to add a filter to the transparent heat conductive sheet 3, and the cost can be reduced, and the heat dissipation efficiency of the transparent heat conductive sheet is not lowered by adding the filter. Therefore, the effect of the transparent heat conductive sheet 3 can be maximized.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to FIG.

In the PDP 10, the transparent heat conducting means provided on the front plate and the heat conducting means provided on the back plate include one or a plurality of temperature detecting means 11, such as a thermocouple.
Stick it to a position that does not interfere with the image. By sticking the temperature detecting means 11 to the heat conducting means, only the front and back surface temperatures of the PDP 10 are measured. Although it may be singular or plural, by sticking a plurality of them, the amount of heat generation on the surface of the PDP 10 changes depending on the site depending on the image signal, so that the temperature change in the entire region can be captured for one-point measurement. Further, the temperature detecting means is attached to the front plate and the back plate because the front plate and the back plate differ in heat radiation efficiency depending on the contact area with air, the presence of a drive circuit, the presence of a cooling device, etc. Since a temperature difference occurs between the front plate and the back plate, the temperature difference is detected, and the PDP has a function of preventing the PDP from being destroyed due to the large temperature difference.

PDP 1 output from the temperature detecting means 11
The temperature signal of 0 is input to the signal processing circuit 12. Further, the storage means 13 stores the brightness suppression data corresponding to the temperature difference between the front plate and the back plate of the PDP 10 and the temperature of the PDP 10, and the desired data can be input by inputting the necessary data without using an arithmetic circuit. The luminance suppression data of is obtained.

The first signal processing circuit 12 has a function of detecting the peak temperature of each of the front plate and the back plate, and a function of detecting the peak of the temperature difference between the front plate and the back plate. The peak temperature obtained from these is given to the storage means 13, and the brightness suppression data is output.

Here, an example of a configuration that fulfills the function of the storage means 13 will be given. The peak temperature that requires luminance suppression is represented by, for example, 8-bit data. That is, PDP1
If 8-bit data is used for the peak temperature of 0 and 8-bit data is used for the peak temperature difference, a total of 16-bit data is required. For example, when a storage element such as a flash memory having a 16-bit address is used as the storage unit 13, by using this 16-bit data as the address of the storage unit 13, the data output corresponding to the address is uniquely associated. Therefore, a configuration sufficiently satisfying the function of the storage unit 13 is realized.

The brightness suppression data output from the storage means 13 is input to the second signal processing circuit 14. The second signal processing circuit 14 is a circuit that performs signal processing such as gamma correction, white balance adjustment, and noise removal, and suppresses the luminance level of the input image signal by the luminance suppression data from the storage unit 13. Examples of the method of suppressing the brightness include a method of adjusting the YP and ABL levels of the brightness suppression data, and a method of adjusting the brightness level by using the brightness suppression data as a coefficient by which the brightness level of the image signal is multiplied.

The image signal subjected to signal processing and brightness suppression by the second signal processing circuit 14 is input to the signal converting means 5.
The signal converting means 15 has a function of converting an image signal into data corresponding to the subfield shown in the conventional technique. That is, for example, when there are 8 subfields, the luminance can be expressed by 8 bits. This time,
It is necessary to convert the image signal into 8-bit data and convert the data array into data corresponding to each subfield.
The signal converting means 15 has a function of converting the image signal into subfield data. The image signal converted into subfield data by the signal conversion means 15 is input to the drive circuit control means 16.

The drive circuit control means 16 outputs drive signals necessary for the operation of each drive circuit to the drive circuit 17 for controlling the horizontal electrodes and the drive circuit 18 for driving the vertical electrodes.

With the above circuit configuration, the temperature of the PDP 10 is measured in real time on both the front and back sides, and a circuit configuration for suppressing the brightness corresponding to the data is realized.
Prevention of reaching the P breakdown temperature can be realized.

(Embodiment 4) A light emitting region and a non-light emitting region are clearly divided depending on an input image signal, and there is a signal in which only half or less of the entire screen emits light. For example, when displaying a pattern such as a square or triangle,
There are those that satisfy the above conditions. An automatic brightness suppression mechanism (hereinafter referred to as ABL: auto) that is mainly used in image display devices.
(abbreviation of bright limit) applies brightness suppression to the image signal in proportion to the average value of the brightness level of the input image, but in the case of an image that emits light in only half or less of the screen,
The average value of the brightness levels of the input image may be less than or equal to the ABL operation value, and the ABL may not operate. If the ABL does not operate and a signal that clearly distinguishes the light emitting region and the non-light emitting region is input for a long time, the temperature difference between the cells existing at the boundary between the light emitting region and the non-light emitting region of the PDP increases, Reach the breaking temperature.

An embodiment of the present invention for this problem will be described with reference to FIG. The present invention includes a heat conducting section 32 and a heat disconnecting section 31.
By mounting a heat conductive sheet, which is an example of the heat conductive means in which the above are alternately woven, on the PDP, it becomes possible to finely detect the temperature difference between the adjacent cells in the horizontal or vertical direction. In the case of a DC type PDP, for example, in the case of a DC type PDP, this heat conduction sheet is attached to the PDP such that the width of the heat conduction section is equal to the width of the discharge cell of the anode section and the width of the heat insulation section is equal to the width of the sub-anode. . The completed heat conductive sheet is attached to the PDP so that the heat conductive portion is located at the anode. With this configuration, when an image signal for vertically dividing the PDP is input, the temperature difference caused by the light emission of the discharge cell can be detected.

For example, with the heat conductive sheet shown in FIG. 3A, the temperature difference in the horizontal direction can be detected. FIG. 3 (b)
With the heat conductive sheet having the above structure, it is possible to detect the temperature difference of the PDP in the vertical direction. In the heat conductive sheet of FIG. 3C, the area of the heat conductive portion 32 is formed in the area of the heat insulation 31,
It is possible to detect a temperature difference in an arbitrary area.

3 (a) and 3 (b), if the intervals of the heat conducting portion 32 and the heat insulating portion 31 are equal over the entire surface, the temperature can be accurately detected and the brightness can be adjusted without degrading the image quality. Further, it becomes possible to protect the PDP.

Each heat conducting section is provided with temperature detecting means 1, a signal processing circuit 2 for receiving the output thereof is added with a peak detecting circuit for temperature difference between adjacent heat conducting sections, and a memory means 3 is adapted to cope with temperature difference between adjacent cells. With such a configuration, it is possible to realize a configuration in which the PDP is prevented from being destroyed by the temperature difference between the adjacent cells.

(Fifth Embodiment) In the present invention, since the brightness adjustment of the PDP is digitally performed, merely suppressing the brightness deteriorates the gradation of the image signal, and the image is This will deteriorate the expressiveness of the signal.
In addition, for example, for image signals such as television broadcasting,
There are few image signals in which the high-intensity part continues at the same display location for a long time, and the PDP temperature may not reach the destruction temperature without executing the brightness suppression. The luminance suppression for such an image signal is the surplus luminance suppression in consideration of the deterioration of the image expression capability.

That is, when the brightness is suppressed for a pixel (cell) which has a high brightness for a moment and does not emit any light thereafter, the brightness of the pixel is lowered and the gradation is deteriorated. There is a problem that it will end up.

Therefore, the PDP is currently displayed on the PDP in consideration of the characteristic that a certain time elapses until the input image signal is displayed on the PDP because various data conversions are included in the image signal processing. The brightness data of the existing image signal and the brightness data of the image signal currently input to the signal processing circuit are compared, and the result is used for brightness suppression. The above problems can be solved by adjusting the brightness in consideration of the state. The structure for that is shown in FIG.

The first signal processing circuit 22 judges the future brightness state from the signal of the temperature information of the PDP panel section given from the temperature detecting means 21 and the signal outputted from the signal recognizing circuit 29, and the storing means. 3 is a circuit for determining the output value to 3. The storage unit 23 holds the brightness suppression amount (data) for various conditions, and outputs the brightness suppression amount corresponding to the output value of the signal processing circuit 22 to the signal processing circuit 24.

The second signal processing circuit 24 is a circuit that applies brightness suppression to the input image signal, and performs brightness suppression with the brightness suppression amount provided from the storage means 23. The signal conversion means 25 converts the image signal sent from the signal processing circuit 24 into the data corresponding to the subfield. The drive circuit control means 26 sends a drive signal corresponding to data (hereinafter referred to as output image data) for displaying an image on the PDP to the drive circuits 27 and 28, and at the same time outputs the average luminance of the output image data as a signal. Output to the recognition circuit 29.

The signal recognition circuit 29 includes means for making a comparison, and the average luminance of the input image signal just input from the second signal processing circuit 24 and the drive circuit control means 26 to the drive circuit 27. The average brightness of the output image data currently sent to 28 is compared, and a signal corresponding to the comparison result is output to the first signal processing circuit 22. For example, when the average luminance of the output image data is high and the input image data is also high, it is determined that the state of the high average luminance continues, and the first signal processing circuit 22 suppresses the luminance to protect the PDP. Is output to the storage means 23 to prevent the temperature from becoming high. If the signal recognition circuit 29 determines that the average luminance of the output image data is high but that of the input image data is lower than that, it is determined that the temperature of the PDP does not become high because the luminance of the next image decreases. Therefore, the brightness is not suppressed.

With the above circuit, the average luminance data of the current input image signal and the image signal being displayed are recognized by the signal recognition circuit 29.
And the result is given to the second signal processing circuit 22, so that from the storage means 23 of the second signal processing circuit 22,
A configuration that outputs the brightness suppression amount in consideration of the change in brightness with time becomes possible.

With this structure, the brightness is not uniformly suppressed for all image signals, but the brightness is suppressed only when the PDP is prevented from being damaged due to a temperature rise (due to a continuous high brightness). It is possible to
It is possible to minimize the gradation deterioration of the input image due to the surplus brightness suppression.

[0045]

According to the present invention, it is possible to increase the heat radiation efficiency of the PDP and realize a structure in which the heat distribution of the PDP is uniform, and it is possible to reduce the temperature at which the PDP is destroyed by light emission.

Further, a structure is obtained in which the effect of reducing the reflection of external light on the PDP and the effect of increasing the contrast ratio can be obtained without lowering the effect of claim 1, and it is not necessary to add a new filter mechanism. We were able to reduce costs.

Further, it has been possible to realize a structure in which the temperature of the PDP is detected and the brightness is prevented from reaching the breakdown temperature of the PDP.

Further, it was possible to realize a structure in which it was found and prevented that the PDP reached the destruction temperature by heating only one region.

Further, it is possible to realize a structure in which the image signal in which the brightness suppression is excessively executed is detected and the brightness suppression is controlled, and it is possible to realize the structure in which the deterioration of the expression capability of the image signal is suppressed to the minimum.

[Brief description of drawings]

FIG. 1 is a PDP configuration diagram of the present invention.

FIG. 2 is a block diagram of a PDP drive circuit according to the present invention.

FIG. 3 is a structural diagram of a heat conductive sheet of the present invention.

FIG. 4 is a block diagram of a PDP drive circuit corresponding to a change with time.

FIG. 5 is a block diagram of a conventional PDP drive circuit.

[Explanation of symbols]

 1 Plasma Display Panel Front Plate 2 Plasma Display Panel Back Plate 3 Thermal Conductive Sheet 4 Thermal Conductive Sheet 5 Discharge Cell Part 11, 21 Temperature Detection Means 12, 22 First Signal Processing Circuit 13, 23 Storage Means 14, 24 Second Signal processing circuit 15,25 Signal converting means 16,26 Driving circuit control means 17,18,27,28 Driving circuit 29 Recognition circuit 31 Thermal insulation part 32 Thermal conduction part

Claims (5)

[Claims] 1. A plasma display, comprising: a transparent heat conducting means on a front surface of a panel displaying an image; and a heat conducting means on a rear surface of the panel. 2. The plasma display according to claim 1, wherein the transparent heat conducting means has a characteristic of transmitting a light ray having a desired wavelength with a desired transmittance. 3. A first signal processing circuit, comprising transparent heat conducting means and temperature detecting means in the heat conducting means, and inputting an output signal of the temperature detecting means, and temperatures of the transparent heat conducting means and the heat conducting means. 2. The plasma display according to claim 1, further comprising: a storage unit that stores data relating to the brightness of the panel and a second signal processing circuit that controls the brightness with a signal from the storage unit. 4. The plasma display according to claim 1, wherein the heat conducting means comprises a heat conducting portion and a heat disconnecting portion. 5. A signal processing circuit for suppressing and outputting the brightness of an input image signal, a second signal converting means for converting a signal from the signal processing circuit into data for image display, and the signal converting means. A drive circuit control means for inputting a signal from the drive circuit to output a signal for driving the panel to the drive circuit, and a signal recognition circuit for comparing the brightness of the signal from the drive circuit control means with the input image signal, A heat conduction means having a temperature detection means for detecting the temperature of the panel displaying an image, a first signal processing circuit for inputting an output signal of the temperature detection means, and data for the temperature and the brightness of the panel are stored. A plasma display device, wherein the second signal processing circuit controls the brightness with a signal from the storage device.