JP2010072205A - Display panel apparatus - Google Patents

Abstract

Disturbance of display due to temperature rise is reduced.
In a display panel device having a plasma display panel having a screen on which a plurality of scan electrodes are arranged, and a chassis to which the plasma display panel is attached, the thermal conductivity is different between the plasma display panel and the chassis. A plurality of heat conductive sheets are arranged side by side along the arrangement direction of the scan electrodes. The thermal conductivity of the heat conductive sheet disposed on the side where the scan pulse is applied is later than the heat conductivity of the heat conductive sheet disposed on the side where the scan pulse is applied earlier.
[Selection] Figure 1

Description

  The present invention relates to a display panel device including a plasma display panel.

  The plasma display panel is composed of two glass substrates each having a thickness of about 2 to 3 mm, and is used by being attached to a chassis having a support surface larger in size than the screen. The chassis is made of a light metal having good thermal conductivity, such as aluminum or aluminum alloy, and functions as a heat sink that supports the plasma display panel and prevents the plasma display panel from overheating.

  Regarding the heat dissipation of the plasma display panel, there is a technique in which a uniform heat conductive sheet is interposed between the plasma display panel and the chassis over the entire screen (Patent Document 1). The thermal conductivity in the thickness direction and the surface direction of the glass substrate is increased by the interposition of the heat conductive sheet. The heat conductive sheet plays a role of making the temperature in the screen uniform.

When displaying on an AC plasma display panel, as is widely known, resetting to initialize the wall charges of all cells in the screen, and address discharge between the scan electrode and the data electrode of the selected cell determined by the display data. The addressing for raising and controlling the wall charge amount and the sustain for causing display discharge using the wall charge are repeated. In recent years, in resetting, charge adjustment is performed so that an appropriate amount of wall charge remains for each cell so as to compensate for variations in the address discharge start voltage between cells.
Japanese Patent No. 3503349

  Although heat is radiated by the heat conductive sheet and the chassis, it often occurs that the temperature of the glass substrate of the plasma display panel rises to 60 to 70 ° C. or higher due to heat generated by discharge. Naturally, when the temperature of the usage environment is high, or when a display state with a heavy load continues for a long time, the plasma display panel tends to be hot. When the temperature of the plasma display panel rises, flickering of light emission that impairs display quality is likely to occur in a region downstream of scanning in the screen.

  FIG. 16 shows the relationship between the temperature rise and the amount of change in the address discharge start voltage when the temperature is substantially uniform within the screen. As shown in FIG. 16, the degree of increase in the address discharge start voltage due to the temperature rise varies depending on the position of the scan electrodes in the arrangement direction on the screen. Compared with the cell to which the scanning pulse is applied in the first half of the scanning period, the address discharge start voltage increases significantly in the cell to which the scanning pulse is applied in the middle, and the address discharge in the cell to which the scanning pulse is applied in the second half. The degree of increase in the starting voltage is even greater. For example, in a cell to which a scanning pulse is applied in the previous period, even if the temperature rises from 30 ° C. to 80 ° C., the address discharge start voltage increases only by about 5 volts. In contrast, in a cell to which a scanning pulse is applied in the latter period, the address discharge start voltage increases by 6 volts when the temperature rises from 30 ° C. to 70 ° C., and increases by 13 volts or more when the temperature rises to 80 ° C. If the address discharge start voltage increases, the discharge probability decreases and a discharge error is likely to occur.

  In general, the higher the temperature, the easier the discharge. However, the results of FIG. 16 indicate that the address discharge is less likely to occur as the temperature increases. Considering that the change in the address discharge start voltage depends on the scanning timing, the wall charge remaining at the end of reset is weak in the semi-selected state where the pulse is not applied to the scan electrode but the pulse is applied to the address electrode. It can be inferred that the decrease due to a slow discharge is the cause of the rise in the address discharge start voltage.

  The present invention has been made in view of such circumstances, and an object of the present invention is to reduce display disturbance associated with a temperature rise.

  By positively generating a temperature gradient in the screen, erroneous discharge in a half-selected state preceding address discharge that causes an address discharge error that disturbs the display is suppressed. Thereby, the display quality of the entire screen is made uniform.

  A display panel device that achieves the above object includes a plasma display panel having a screen on which a plurality of scan electrodes are arranged, a chassis to which the plasma display panel is attached, and heat that is interposed between the plasma display panel and the chassis. A display panel device comprising a conductive member, wherein a scanning circuit that sequentially applies a scan pulse to the plurality of scan electrodes in an order according to an array position, the plasma display panel as the heat conductive member, and the And a plurality of thermal conductive sheets having different thermal conductivities arranged side by side along the arrangement direction of the scan electrodes. In this display panel device, the thermal conductivity of the thermal conductive sheet disposed on the side where the application time of the scan pulse is late among the plurality of thermal conductive sheets is the heat conduction disposed on the early side. Greater than the thermal conductivity of the sheet.

  The heat generated by the plasma display panel is transferred to the chassis through the heat conductive sheet. At this time, a temperature gradient corresponding to the thermal conductivity of the heat conductive sheet is generated on the screen. Since the heat conduction sheet with a higher thermal conductivity corresponds to the region on the side where the scan pulse is applied later, the heat conduction sheet with the lower thermal conductivity corresponds to the region on the side where the scan pulse is applied earlier. The temperature of the region on the side where the scan pulse is applied later is lower than the temperature of the region on the earlier side.

  On a screen having such a temperature gradient, erroneous discharge is unlikely to occur in a half-selected state in which a voltage close to that applied to the cell is applied even though the scan pulse is not applied. In the region where the scan pulse is applied early, the time during which the half-selection state can be achieved is short, so that erroneous discharge is unlikely to occur. Further, in a region where the application time of the scan pulse is late, the time during which the half-selection state can be achieved is relatively long, but since the temperature is relatively low, erroneous discharge hardly occurs.

  According to the present invention, display disturbance due to temperature rise is reduced, and the display quality of the entire screen is made uniform.

  As shown in FIG. 1, a display panel device 1 according to an embodiment of the present invention includes an AC plasma display panel 2, a filter 3 attached to the front surface of the plasma display panel 2, a chassis 4 that supports the plasma display panel 2, Three heat conductive sheets 6, 7, and 8 that thermally couple the plasma display panel 2 and the chassis 4 and a drive circuit 9 that drives the plasma display panel 2 are provided, and are incorporated in, for example, a plasma television. FIG. 1 is an exploded perspective view. Actually, the elements are in contact with each other in the illustrated order.

  The plasma display panel 2 has a screen 50 capable of color display. On the screen 50, first and second display electrodes (not shown) extending in the horizontal direction and address electrodes (not shown) extending in the vertical direction are arranged. In addressing, the second display electrode is used as a scan electrode, and the address electrode is used as a data electrode. For example, when the screen size is 55 inches diagonal (1.23 m × 0.69 m), the plasma display panel 2 has a horizontal dimension of about 1.34 m and a vertical dimension of about 0.76 m.

  The filter 3 is a translucent laminated sheet including an antireflection layer, a dye filter layer, and an electromagnetic wave shielding layer. The filter 3 covers the entire screen 50 and has a function of protecting the plasma display panel 2 together with an optical function for improving display color and visibility.

  The chassis 4 is a bottomless box-shaped metal structure composed of a rectangular main surface portion larger than the screen 50 and a side surface portion connected to the periphery thereof. For example, an aluminum alloy plate having a thickness of about 1 to 5 mm It is produced by pressing. The front surface of the main surface portion is flat, and this front surface is a panel support surface. The plasma display panel 2 is fixed to the panel support surface by double-sided pressure-sensitive adhesive sheets 5 disposed on both sides of the heat conductive sheets 6 to 8 in the horizontal direction. And the circuit board group which comprises the drive circuit 9 is attached to the back surface of the main surface part in the chassis 4 with the block for reinforcement. A printed wiring board (not shown) is used for connection between the electrodes of the plasma display panel 2 and the drive circuit 9.

  The heat conductive sheets 6, 7, and 8 are arranged side by side along the arrangement direction of the scan electrodes between the plasma display panel 2 and the chassis 4, and are in close contact with both the plasma display panel 2 and the chassis 4. In this example, the three heat conductive sheets 6, 7, and 8 constitute a heat conductive member over the entire screen 50. The front and back surfaces of the heat conductive sheets 6, 7, 8 have adhesiveness, and the heat conductive sheets 6, 7, 8 contribute to fixing the chassis 4 and the plasma display panel 2. However, the adhesive strength of the heat conductive sheets 6, 7, 8 is smaller than the adhesive strength of the double-sided adhesive sheet 5.

  The thermal conductivity is uniform in each of the thermal conductive sheets 6, 7, and 8, but the thermal conductivity is different between the thermal conductive sheets 6, 7, and 8. As an example, the thermal conductivities of the heat conductive sheets 6, 7, and 8 are 0.5 W / mK, 1.0 W / mK, and 1.5 W / mK in this order. The arrangement order of the heat conductive sheets 6, 7, 8 is the order of the thermal conductivity. The upstream side in the scanning direction indicated by the arrows in FIG. 2 in the order of the heat conductive sheet 6 having the lowest thermal conductivity, the heat conductive sheet 7 having the second lowest thermal conductivity, and the heat conductive sheet 8 having the highest thermal conductivity. The heat conductive sheets 6, 7, and 8 are arranged from the downstream side to the downstream side. The upstream side is the side where scan pulses are applied earlier in the sequential application of scan pulses for addressing the scan electrodes (display electrodes Y) in the screen 50, and the downstream side is the application of scan pulses. It is the late side.

  Since the thermal conductivity is different between the thermal conductive sheets 6, 7, and 8, the thermal conductivity in the panel thickness direction between the plasma display panel 2 and the chassis 4 is from the upper end to the lower end of the screen 50 as shown in FIG. 3. In correspondence with the arrangement of the heat conductive sheets 6, 7, 8, the size increases stepwise. Thereby, a temperature gradient depending on the thermal conductivity is generated in the screen 50 in a state where the plasma display panel 2 is generating heat. The temperature of the region on the side where the scan pulse is applied later is lower than the temperature of the region on the earlier side. On a screen having such a temperature gradient, erroneous discharge is unlikely to occur in the half-selected state as will be described later.

  As the heat conductive sheets 6, 7, and 8, a sheet made of an acrylic, silicone, or urethane resin that does not exceed 1 mm in thickness is suitable. In order to make the color of the non-light emitting screen 50 uniform, it is desirable that the heat conductive sheets 6, 7, and 8 have the same color. In addition, it can replace with the heat conductive sheets 6, 7, and 8 and can use the double-sided adhesive tape which mixed heat conductive materials, such as carbon and a metal, into the contact bonding layer.

  The number of the heat conductive sheets 6, 7, 8, that is, the number of regions having different thermal conductivities on the screen 50 is not limited to three. In the modification shown in FIGS. 4 and 5, two heat conductive sheets 6 b and 8 d are arranged on the screen 50. The thermal conductivity in the panel thickness direction between the plasma display panel 2 and the chassis 4 is small in the region upstream of scanning in the screen 50 as shown in FIG. 5 and large in the region downstream. In this modification, the heat conductive sheet 6b can be omitted. That is, the heat conductive sheet 8d is unevenly distributed on the downstream side where the application time of the scan pulse is late, and a gap with low heat conductivity is formed between the plasma display panel 2 and the chassis 4 on the upstream side where the application time of the scan pulse is early. The temperature gradient that contributes to the suppression of erroneous discharge can be generated.

  In the modification shown in FIGS. 6 and 7, one heat conductive sheet 6 c is disposed on the screen 50. The thermal conductive sheet 6c has a thermal conductivity distribution in which the thermal conductivity increases continuously from the upstream side to the downstream side of the screen 50. The thermal conductivity in the panel thickness direction between the plasma display panel 2 and the chassis 4 continuously changes corresponding to the thermal conductivity distribution of the thermal conductive sheet 6c as shown in FIG.

  As described above, the configuration in which the thermal conductivity increases stepwise or continuously from one end to the other end of the screen 50 in the vertical direction is that scan pulses are sequentially applied to all the scan electrodes in the screen 50 one by one. Suitable for single-scan type drive to be applied. A known electric circuit and driving waveform can be applied to the driving. FIG. 8 shows an outline of an electric circuit configuration of the display panel device 1, and FIG. 9 shows an example of a drive waveform.

  As shown in FIG. 8, on the screen 50 of the plasma display panel 2, the first display electrodes X and the second display electrodes Y that are alternately arranged extend in the horizontal direction, and the address electrodes A extend in the vertical direction. The display electrode X and the display electrode Y define a display line in the screen 50, and constitute an electrode pair for generating a display discharge in a surface discharge type in each display line. A cell is defined at each intersection between the display electrode pair and the address electrode A. The display electrode X and the display electrode Y are made of a patterned transparent conductive film and a metal band superimposed thereon, and are covered with a dielectric layer (not shown) for AC driving. As described above, the display electrode Y is used as a scan electrode.

  The drive circuit 9 includes an X driver 91 connected to the display electrode X, a Y driver 92 connected to the display electrode Y, an A driver 93 connected to the address electrode A, a controller 95 for controlling the operation of the driver, and driving. A power supply circuit 96 that supplies necessary power to the driver is provided.

  The X driver 91 includes a sustain circuit 911 that applies a sustain pulse and a reset circuit 922 that applies a pulse for resetting. The Y driver 92 includes a scanning circuit 921 that applies a scan pulse, a sustain circuit 922, and a reset circuit 923.

  A color video signal S1 having a predetermined frame rate is input to the drive circuit 9 from an external image output device. The color video signal S1 is converted into subframe data for gradation display by a known subframe method in a data processing block of the controller 95. The subframe data indicates whether or not the cells need to be lit in each of the plurality of subframes displayed in place of the frames, strictly speaking, whether or not the address discharge is necessary.

  The waveform illustrated in FIG. 9 corresponds to one subframe. A reset period, an address period, and a sustain period are assigned to each of the plurality of subframes. Regardless of the luminance weight given to the subframe, the length of the reset period and the address period is common between the subframes, but the length of the sustain period depends on the luminance weight.

  In the reset period, a reset operation (wall charge initialization) for reducing the wall voltage of each cell in the screen 50 is performed. In the illustration of FIG. 9, so-called blunt wave reset is performed during the reset period. In the blunt wave reset, a weak discharge is continuously generated between the electrodes of the display electrode pair that defines each display line by the application of a blunt wave pulse typified by a ramp waveform pulse, and thereby in the dielectric covering the display electrode pair. This is an operation for adjusting the wall charge amount. According to the blunt wave reset, unlike the forced wall charge erasing, an appropriate amount of wall charge that supports the address discharge can be left.

  Write addressing is performed in the address period. All the display electrodes Y (scan electrodes) are biased to the negative half-selection potential Vay, and in this state, the display electrodes Y are sequentially negative one by one from the first to the last nth in the array. A scan pulse Py is applied. That is, display lines are sequentially selected (scanned). In synchronization with the selection of the display line, a positive address pulse Pa is applied to the address electrode A as the data electrode corresponding to the cell to be lit in the selected display line. In the cell to be turned on to which the scan pulse Py and the address pulse Pa are simultaneously applied, an address discharge is generated between the display electrode Y biased to the negative selection potential Vy and the address electrode A biased to the positive selection potential Va. Occurs, and an address discharge occurs between the display electrode X and the display electrode Y, which are appropriately biased, as a trigger. Wall charges necessary for display discharge are formed in the cells by these address discharges. The wall charges that are adjusted by the reset and remain when the scan pulse Py is applied contribute to causing address discharge by applying a lower voltage than when there is no scan pulse Py.

  In the sustain period, the sustain pulse Ps is alternately applied to the display electrode Y and the display electrode X. The amplitude of the sustain pulse is a sustain voltage Vs slightly lower than the surface discharge start voltage. If the address discharge is correctly generated in the address period, a surface discharge as a display discharge is generated in the cell to be lit every time the sustain pulse is applied. The discharge gas that has obtained the discharge energy emits ultraviolet light, and the ultraviolet light excites the phosphor to emit light. However, a cell to be lit in which an address discharge error has occurred in the address period does not emit light. When an address discharge error occurs in a cell that should be lit in any of a plurality of subframes, a situation occurs where light is emitted in one subframe and not emitted in another subframe. In this case, display flicker is observed.

  The cause of the address discharge error is the disappearance (including the decrease) of the wall charges that support the address discharge. In addition, an erroneous discharge at the time of half-selection can be considered as a cause of disappearance of wall charges. Half-selection means that the address pulse Pa is inevitably applied to the non-selected display line by the application of the address pulse Pa to the selected display line. Since the scan pulse Py is not applied to the non-selection display line, the voltage applied to the non-selection display line is lower than the voltage at the time of selection to which the scan pulse Py is applied, but is unintentionally weak in response to the application of the address pulse Pa. There is a risk of a serious discharge. In particular, when the display electrode Y is biased to the non-selection potential Vay for the convenience of the circuit configuration as in the example of FIG. 9, a weak discharge that is an erroneous discharge is likely to occur. In addition, erroneous discharge is likely to occur in an area downstream of scanning in the screen 50. This is because the frequency of half-selection before the address discharge should normally be selected in the downstream region is higher than that in the upstream region. For example, if the number of display lines is 1080, the last selected display line can be half-selected up to 1079 times before it is selected.

  However, as described above, in the display panel device 1, the heat conduction sheet is arranged so that the downstream area in the screen 50 has a relatively low temperature compared to the upstream area. The occurrence probability of erroneous discharge at the time of half-selection is reduced, and the occurrence probability of erroneous discharge is made uniform within the screen 50. Therefore, in the display panel device 1, an address discharge error is unlikely to occur, and a high-quality display can be provided.

  In the above embodiment, driving of the single scanning type is assumed. However, intentionally generating a temperature gradient on the screen 50 is effective in improving display quality even when the driving of the double scanning type is performed.

  In the example of FIG. 10, the screen 50 is divided into two partial screens 50A and 50B arranged vertically, and the partial screen 50A and the partial screen 50B are scanned from top to bottom simultaneously. In this case, a plurality of heat conductive sheets 6d and 8d having different thermal conductivities are arranged on the partial screens 50A and 50B as shown in FIG. The thermal conductivity of the heat conductive sheet 8d disposed on the downstream side of scanning is selected to be larger than the thermal conductivity of the heat conductive sheet 6d disposed on the upstream side. The thermal conductivity in the panel thickness direction between the plasma display panel 2 and the chassis 4 corresponds to the arrangement of the thermal conductive sheets 6d and 8d from top to bottom in each of the partial screens 50A and 50B as shown in FIG. Then it grows step by step.

  In the example of FIG. 13, the screen 50 is divided into two partial screens 50 </ b> A and 50 </ b> B that are arranged vertically as in FIG. 10. Scanning is performed on the partial screen 50A and the partial screen 50B simultaneously from the upper and lower ends of the screen 50 toward the center in the vertical direction. In this case, a plurality of thermal conductive sheets 6e and 8e having different thermal conductivities are arranged as shown in FIG. The thermal conductivity of the heat conductive sheet 8e disposed at the center of the screen 50 corresponding to the downstream side of scanning in both the partial screen 50A and the partial screen 50B is disposed at both ends of the screen 50 corresponding to the upstream side of scanning. The value is selected to be larger than the thermal conductivity of the heat conductive sheet 6e. The thermal conductivity in the panel thickness direction between the plasma display panel 2 and the chassis 4 is increased stepwise corresponding to the arrangement of the thermal conductive sheets 6e and 8e in each of the partial screens 50A and 50B as shown in FIG. Become.

  In the above embodiment, the thermal conductivity, material, thickness, and dimensions of the thermal conductive sheet can be appropriately changed according to the specifications of the plasma display panel 2, the heat dissipation characteristics of the chassis 4, and the like. The plasma display panel 2 may be fixed to the chassis 4 by using a frame-like double-sided pressure-sensitive adhesive sheet 5 surrounding the screen 50 instead of the double-sided pressure-sensitive adhesive sheet 5, or the double-sided pressure-sensitive adhesive sheet 5 is omitted and heat conduction with high adhesive force is achieved. The plasma display panel 2 may be fixed by a sheet.

It is a disassembled perspective view which shows the structure of the display panel apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the order of scanning. It is a figure which shows the relationship between the position of the perpendicular direction in a screen, and the thermal conductivity of a panel thickness direction. It is a figure which shows the 1st modification of arrangement | positioning of a heat conductive sheet. FIG. 5 is a diagram showing a relationship between a vertical position in a screen corresponding to FIG. 4 and a thermal conductivity in a panel thickness direction. It is a figure which shows the 2nd modification of arrangement | positioning of a heat conductive sheet. It is a figure which shows the relationship between the position of the perpendicular direction in the screen corresponding to FIG. 6, and the thermal conductivity of a panel thickness direction. 1 is a diagram showing an outline of an electric circuit configuration of a display panel device 1. FIG. It is a figure which shows an example of a drive waveform. It is a figure which shows the other example of the order of scanning. It is a figure which shows an example of arrangement | positioning of the heat conductive sheet corresponding to FIG. It is a figure which shows the relationship between the position of the perpendicular direction in the screen corresponding to FIG. 11, and the thermal conductivity of a panel thickness direction. It is a figure which shows the other example of the order of scanning. It is a figure which shows an example of arrangement | positioning of the heat conductive sheet corresponding to FIG. It is a figure which shows the relationship between the position of the orthogonal | vertical direction in the screen corresponding to FIG. 14, and the thermal conductivity of a panel thickness direction. It is a figure which shows the relationship between the temperature rise in case temperature is substantially uniform within a screen, and the variation | change_quantity of an address discharge start voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display panel apparatus 2 Plasma display panel 50 Screen Y Display electrode (scan electrode)
4 Chassis 6, 7, 8 Thermal conductive sheet 6b, 6c, 6d, 6e Thermal conductive sheet 8b, 8d, 8e Thermal conductive sheet 921 Scanning circuit Py Scan pulse Vay Half-selection potential

Claims (6)

A display panel device comprising a plasma display panel having a screen on which a plurality of scan electrodes are arranged, a chassis to which the plasma display panel is attached, and a heat conductive member interposed between the plasma display panel and the chassis. And
A scanning circuit that sequentially applies scan pulses in an order according to the arrangement position with respect to the plurality of scan electrodes;
A plurality of heat conductive sheets having different thermal conductivities arranged in the arrangement direction of the scan electrodes between the plasma display panel and the chassis as the heat conductive member,
Among the plurality of thermal conductive sheets, the thermal conductivity of the thermal conductive sheet arranged on the side where the application time of the scan pulse is late is higher than the thermal conductivity of the thermal conductive sheet arranged on the early side of the period. A large display panel device. The scanning circuit biases the plurality of scan electrodes to a half-select potential having the same polarity as the scan pulse over a period from the start to the end of application of the scan pulse to the plurality of scan electrodes. The display panel device as described. The display panel device according to claim 2, wherein the scanning circuit sequentially applies the scan pulse to the plurality of scan electrodes one by one from one end to the other end of the array. The screen is divided into two partial screens in the arrangement direction of the scan electrodes,
The display panel device according to claim 2, wherein the scanning circuit sequentially applies the scan pulses one by one to a plurality of scan electrodes in each of the two partial screens. A display panel device comprising a plasma display panel having a screen on which a plurality of scan electrodes are arranged, a chassis to which the plasma display panel is attached, and a heat conductive member interposed between the plasma display panel and the chassis. And
A scanning circuit that sequentially applies scan pulses one by one from one end of the array to the other end of the plurality of scan electrodes;
Thermal conductivity of the scan electrodes arranged in the arrangement direction between the plasma display panel and the chassis is shorter than that of the screen so as to be unevenly distributed on the screen at a later time of application of the scan pulse. A display panel device comprising: a sheet; A display panel device comprising a plasma display panel having a screen on which a plurality of scan electrodes are arranged, a chassis to which the plasma display panel is attached, and a heat conductive member interposed between the plasma display panel and the chassis. And
A scanning circuit that sequentially applies scan pulses one by one from one end of the array to the other end of the plurality of scan electrodes;
The heat conduction member is disposed between the plasma display panel and the chassis as the heat conduction member, and the heat conductivity increases as the time of application of the scan pulse in the direction of arrangement of the scan electrodes goes from the early side to the late side. And a heat conductive sheet having a temperature distribution.

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