JPS58176855A - Flat plate type picture display device - Google Patents

Abstract

PURPOSE:To prevent the color discrepancy, etc. and improve the picture quality by varying the distance between a pair of conductors constituting horizontal deflection electrodes in response to the curvature of a display surface respectively so as to unify the deflection distance of an electron beam. CONSTITUTION:A screen plate 59 is formed in a curve slightly protruding outward so as to withstand the atmospheric pressure, and the distance between horizontal deflection electrodes 71, 72...711 is varied in response to the curve of the screen plate 59. That is, even though the distance L from the center of the horizontal deflection electrodes 71...711 to the screen plate varies for each horizontal deflection plate due to the curve of the screen 59, the same deflection distance can invariably be maintained over the whole surface of the screen plate 59 by varying the distances d1...d5 between the horizontal deflection electrodes 71...711 in response to the L, and a picture with a good quality can be available.

Description

[Detailed description of the invention] The present invention relates to a flat panel image display device.

First, a basic configuration example of the image display element used here will be explained with reference to FIG.

This display element includes, in order from the back to the front, a back electrode 1, a line cathode 2 as a beam source, vertical focusing electrodes 3, 3', a vertical deflection electrode 4, a beam flow control electrode 5, a horizontal focusing electrode 6, a horizontal A deflection electrode 7, a beam acceleration electrode 8, and a screen plate 9 are arranged, and these are housed inside a flat glass bulb (not shown) which is made into a vacuum.

A line cathode 2 serving as a beam source is stretched horizontally so as to generate an electron beam distributed linearly in the horizontal direction, and a plurality of line cathodes 2 (here, (Only four wires, 2i to 22 are shown) are provided. In this embodiment, it is assumed that 16 pieces are provided. It will be from 2 to 2 evenings. These line cathodes 2 are, for example, 1
An oxide cathode material is coated on the surface of a tungsten wire having a diameter of 0 to 2 μΦ. Then, as will be described later, the electron beams are controlled to be emitted sequentially from the upper line cathode 2a for a fixed period of time. (The back electrode 1 suppresses generation of electron beams from line cathodes 2 other than the line cathode 2 that is controlled to emit electron beams for a certain period of time, and
It functions to push out the generated electron beam only in the forward direction. ) This back electrode 1 is BJ after glass pulp,
It may be formed by a coating film of an electrically conductive material attached to the inner surface. Further, instead of the back electrode 1 and the linear cathode 2, a planar electron beam emitting cathode may be used.

The vertical focusing electrode 3 is a conductive plate 11 having a horizontally long line 10 facing each of the line cathodes 2 to 2, and extracts the electron beam emitted from the line cathode 2 through its slit 1o, and Focus vertically.

(The slit 10 may be provided with crosspieces at appropriate intervals in the middle, or it may be a row of through holes arranged in large numbers at small intervals (nearly touching) in the horizontal direction. (It may also be configured as a slit.)
The vertical focusing electrode 3'' is also similar.

A plurality of vertical deflection electrodes 4 are arranged horizontally in the middle of each of the slits 10, and are each composed of conductors 13 and 13' provided on the upper and lower surfaces of the insulating substrate 12. has been done. Then, a vertical deflection voltage is applied between the opposing conductors 13 and 13' to deflect the electron beam in the vertical direction. In this example,
One wire formed by a pair of conductors 13 and 13'] Cathode 2
The electron beam from the center is deflected vertically to a position corresponding to 16 lines.

The 16 vertical deflection electrodes 4 constitute 15 pairs of conductors corresponding to each of the 16 line cathodes 2, and the electron beams are deflected to draw 240 horizontal lines on the screen 9. do.

Next, the control electrodes 5 are constituted by conductive plates 15 each having a slit 14 (elongated in the vertical direction), and a plurality of control electrodes 5 are arranged in parallel in the horizontal direction at predetermined intervals. In this embodiment, 320 conductive plates 15a to 15n for control electrodes are provided (only 1° is shown in the figure). (Each of the control electrodes 5 extracts the electron beam horizontally by dividing it into one picture element at a time, and controls the amount of the electron beam passing therethrough in accordance with a video signal for displaying each picture element.

) Therefore, if 320 control electrodes are provided, 320 pixels can be displayed per horizontal line.

In addition, in order to display images in color, each picture element is R, G.
, H, and each control electrode 6
The R, G, and H video signals are sequentially applied to the . Further, 320 sets of video signals of 1 line/min are simultaneously applied to the 320 control electrodes 5, so that one line of video is displayed at one time.

The horizontal focusing electrode 6 is composed of a conductive plate 17 having a plurality of 320 long slits 16 in the vertical direction facing the slits 14 of the control electrode 6, and focuses the electron beam for each pixel divided in the horizontal direction. Each is focused horizontally into a narrow electron beam.

The horizontal deflection electrode 7 is made up of a plurality of conductive plates 18 arranged vertically in the middle of each of the slits 16, and a horizontal deflection voltage is applied between each conductive plate 18 for each pixel. The electron beams are each deflected in the horizontal direction, and the R, G, and H phosphors are sequentially irradiated on the screen 9 to cause them to emit light. The width is one picture element.

The acceleration electrode 8 is composed of a plurality of conductive plates 19 provided horizontally at the same position as the vertical deflection electrode 4.
The electron beam is accelerated to collide with the screen 9 with sufficient energy.

The screen 9 is constructed by applying a phosphor 20 that emits light when irradiated with an electron beam to the back surface of a glass plate 21, and adding a metal bank layer (not shown).

The phosphor 20 is one of the three color phosphors of R2G and B for each one of the control electrodes 6 (IJ) 14, that is, for each one horizontally divided electron beam. They are provided in pairs and are applied vertically in stripes. In FIG. 1, the broken lines drawn on the screen 9 indicate divisions in the vertical direction that are displayed corresponding to each of the plurality of line cathodes 2, and the two-dot chain lines correspond to each of the plurality of control electrodes 5. Indicates the horizontal division displayed. As shown in the enlarged view in Figure 2, one section partitioned by these two has R, G, and B phosphors 2o for one pixel in the horizontal direction, and 16 lines in the vertical direction. It has a width of For example, the size of one section is 1 in the horizontal direction.
B, vertical direction is 16 panes.

Note that in FIG. 1, the length in the horizontal direction is greatly enlarged relative to the length in the vertical direction for clarity.

In addition, in this embodiment, only one pair of R, G, and B phosphors 2o is provided for one picture element for one control electrode 5, that is, one electron beam, but for two or more picture elements, Of course, two or more pairs of pixels may be provided; in that case, R, G, and B video signals for two or more picture elements are sequentially applied to the control electrode 6, and the horizontal deflection is synchronously applied to the control electrode 6. It will be done.

Next, the basic configuration of a drive circuit for displaying television images on this display element will be explained with reference to FIG. First, a driving portion for irradiating the screen 9 with an electron beam to emit raster light will be described.

The power supply circuit 22 is a circuit for applying a predetermined bias voltage (operating voltage) to each electrode of the display element. A DC voltage of (6) is applied to the focusing electrode 6, (28) to the accelerating electrode 8, and (3)9 to the screen 9.

Next, a composite video signal of a television signal is applied to the input terminal 23, and a synchronization separation circuit 24 separates and extracts a vertical synchronization signal V and a horizontal synchronization signal H.

The vertical drive pulse generation circuit 25 is composed of a counter that is reset by a vertical pulse and counts horizontal pulses, and has an effective vertical scanning period (in this case, a period of 24 OH) excluding the vertical retrace period of the vertical period. Then, 16 drive pulses each having a length of 16H periods and 47 pulses are generated sequentially. These 41 drive pulses...
The voltage is applied to the line cathode drive circuit 26, where it is inverted so that the line cathode drive valve switch "2" is brought to a low potential only during each pulse period and to a high potential of about 20 volts for the rest of the pulse period. It is converted into 口'... ゆ', and each line cathode 2i.

20,... will be added to the 2nd evening. Each line cathode 2
......At 2pm, a current is passed between the high potentials of the drive pulses I1 and Tough, and the drive pulse I' is heated.
The heated state is maintained so that electrons can be emitted even during the low potential period between ~ and evening. As a result, 15 line cathodes 2-2
From the evening, electrons are emitted only during the 16H period in which low-potential driving pulses I1 to E1 are applied to each of them. (During the period when a high potential is applied, the potential at the line cathode 2 is lower than the potential at the position of the line cathode 2 determined by the bias voltage applied to the back electrode 1 and the vertical focusing electrode 3. Since the high potential applied to the wire becomes positive, no electrons are emitted from the line cathodes 2-2.Thus,
In the line cathode 2, electrons are sequentially emitted from the upper line cathode 2 to the lower line cathode 2 for 16H periods during the effective vertical scanning period.

The emitted electrons are pushed forward by the back electrode 1, pass through the opposing slits 10 of the vertical focusing electrode 3, and are vertically focused to form a flat electron beam.

Next, the vertical deflection drive circuit 2A is composed of a counter that is reset by each of the vertical drive pulses I to I and counts horizontal synchronization words, and a conversion circuit that converts the count output into D/A. A pair of vertical deflection signals V, V" are generated that change in 16 steps by 1H during the 18H period of each vertical drive pulse I to I. The vertical deflection signals V and ■1 both have a center voltage of ■4. So, ■
vl increases sequentially and vl decreases sequentially, so that they change in opposite directions. These vertical deflection signals V and V' are applied to electrodes 13 and 1 of the vertical deflection electrode 4, respectively.
3', so that each line cathode 2-2
The electron beam generated from the evening is vertically deflected in 16 steps, and as mentioned earlier, on the screen 9, one electron beam can scan 16 lines of raster one by one from the top.
It is deflected to draw line by line.

As a result of the above, electron beams are emitted sequentially from the upper part of the 15 line cathodes 2A to 2E for a period of 16H, and each electron beam is sequentially emitted for one line from the top to the bottom within 15 sections in the vertical direction. By being deflected one by one, the electron beam is vertically deflected one line at a time on the screen 9 from the first line at the top end to the 240th line at the bottom end.
A total of 240 lines of raster are drawn.

The electron beam thus vertically deflected is horizontally divided into 320 sections by the control electrode 6 and the horizontal focusing electrode 6 and extracted. Figure 1 shows one of these categories. The amount of passage of this electron beam is controlled for each section by a control electrode 5, and is focused horizontally by a horizontal focusing electrode 6 into a single thin electron beam.
The light is deflected horizontally in three stages by the horizontal deflection means described below, and is sequentially irradiated onto each of the R, G, and H phosphors 2° on the screen 9.

That is, the horizontal drive pulse generation circuit 2B is composed of three cascaded monostable multivibrators, etc.
Triggered by a horizontal synchronization signal, three horizontal drive pulses r, q, and b of equal pulse width are generated within one horizontal period. Here, as an example, each pulse width is about 17μ8eC, and the effective horizontal scanning period is 50μ8eC.
Three pulses r, g, and b are generated during μsec. Their horizontal drive pulses r, q
, b are applied to the horizontal deflection drive circuit 29. This horizontal deflection and drive circuit 29 is switched by the horizontal drive pulses r, q, and b to generate a pair of water moth deflection signals RI and h" that change in three stages.Horizontal deflection signal RI.

Both hl have a center voltage of 7, and change in opposite directions such that h increases sequentially and hl decreases sequentially. These horizontal deflection signals h' are applied to electrodes 18 and 18'' of the horizontal deflection electrode A, respectively.As a result, each horizontally segmented electron beam is applied to the R, G.

The light is horizontally deflected so that the phosphor B is sequentially irradiated for 17 μSec. However, in the display element of FIG. 1, in the horizontal deflection electrode 7, one conductor 18 or 18'' is used for deflecting the electron beams of two adjacent sections. Since the electron beams are deflected in opposite directions, the electron beams in 320 sections are divided into odd-numbered sections R-+G.
-+ H If the waves are deflected in the order of B - + G - + R, then those in even-numbered sections are deflected in the opposite direction every 1 minute in each section. Ru.

Thus, in each line raster, the horizontal 3
The electron beams are R and G for each of the 20 sections.

Each phosphor 20K of B is sequentially irradiated.

Therefore, for each horizontal section of each line, the R and G electron beams are
, B, a color television image can be displayed on the screen 9.

Next, the modulation control portion of the electron beam will be explained.

First, the composite video signal applied to the television signal input terminal 23 is applied to the color demodulation circuit 30, where the R-Y
The G-Y color difference signals are demodulated, the G-Y color difference signals are subjected to Madnox synthesis, and further, they are combined with the luminance signal Y to obtain the R, G, and B primary color signals (hereinafter referred to as R, G, A B video signal) is output. These R, G, and B video signals are processed by 320 sample and hold circuit sets 31a to 3.
Added to 1n. Each sample and hold circuit group 31a~
31n each has three sample and hold circuits for R, G, and B. The sample and hold outputs of these sample and hold circuit sets 31a to 31n are applied to holding memory sets 32a to 32n, respectively.

On the other hand, the sampling reference long oscillator 33 is a PLL
(phase-locked loop) circuit, etc., and generates a reference clock of approximately 6.4 MHz in this embodiment. The reference clock is controlled to always have a constant phase with respect to the horizontal synchronizing signal H. This reference clock is applied to the sampling pulse generation circuit 34, where it is delayed by one clock period by a shift register, etc., and is delayed during an effective horizontal scanning period (approximately 5Qμ5ec) of the horizontal period (63,5μ5ec). 32
Zero sampling pulses a-n are generated in sequence, followed by one transfer pulse. These sampling pulses a - n correspond to each picture element when one line of the video to be displayed is divided into 320 picture elements in the horizontal direction, and their positions are always constant with respect to the horizontal synchronizing signal H. controlled by.

These 320 sampling pulses a-n correspond to the 320 sample-and-hold circuit sets 31a to 31, respectively.
As a result, one line is added to each sample 15, +- pull-hold circuit set 31a to 31n.
R, G of each picture element when divided into 0 picture elements,
Each H video signal is individually sampled and held. The sample held 320 pairs of R, G,
B video signal is 3 after sample hold for 1 line is completed.
The data is transferred all at once to 20 sets of memories 32a to 32c by a transfer pulse t, where it is held for the next one horizontal period.

One line of R, G stored in the memories 32a to 32n
, B video signals each have 320 switching circuits 3.
Added to 5a-35n. Switching circuit 35a~
35n are R and G respectively.

Each switching circuit 35a has individual input terminals of B and a common output terminal that sequentially switches and outputs them.
The output of ~35n is used as a control signal for modulating the electron beam by the 320 conductive plates 15a of the control electrode 5 of the display element.
-15H each separately. Each switching circuit 35a to 35n is a switching pulse generation circuit 36.
Switching is controlled simultaneously by switching pulses applied from the The switching pulse generation circuit 36 receives signals r and g from the horizontal drive pulse generation circuit 28 mentioned above.
, b, and the switching circuits 358 to 35n are controlled by dividing approximately 50μ east of the central portion of each horizontal period into three and switching circuits 358 to 35n for approximately 17μ each, and time-divisionally dividing and alternating the R, G, and H video signals. sequentially output to the control electrodes 15a to 15n.
Switching signals r, q, and b are generated so as to be supplied to the terminal. However, among the switching circuits 35a to 35n, odd-numbered switching circuits 35a, 35c...
・is switched in the order of R→G −+ B, and the even numbered switching circuits 35b, 35d...
35n is configured to be switched in the reverse order of B-+G-+H.

Here, what should be noted is that the switching circuits 35a to 35a
Switching the supply of R, G, and H video signals at 35n;
The horizontal deflection of the horizontal deflection drive circuit 29 for switching the irradiation of the electron beam onto the R, G, and B phosphors is synchronously controlled so that they completely match both in timing and order. As a result, when the electron beam is irradiating the R phosphor, the irradiation meter for the electron beam is set to R.
It is controlled by the video signal, and the G and H are also controlled in the same way, so that the light emission of the R, G, and B phosphors of each picture element is controlled by the R, G, and B video signals of that picture element. Each picture element is displayed by emitting light according to the input video signal. Such control is performed simultaneously on 320 picture elements for one line, and one line of video is displayed.
Furthermore, one image is displayed on the screen 9 by sequentially processing 240 lines starting from the upper line.

The above operations are performed on one input television signal.
This is repeated for each field, and as a result, a moving television image is displayed on the screen 9 in the same way as a normal television receiver.

The flat panel image display device described in detail above is different from a normal television receiver in which an electron gun is housed in a deep cathode ray tube, and can be made flat with an extremely small depth, as well as being lighter in weight. There are advantages.

However, there are some problems that are hindering efforts to make the device even flatter and lighter. In order to prevent the vacuum container (glass plate) 21 that houses the various electrodes shown in Fig. This is the point.

Therefore, in order to reduce the weight of the vacuum container 21,
If the shape of No. 1 is made into a curved surface with curvature, the vacuum pressure resistance can be sufficiently maintained, the glass plate thickness can be made thinner, and the weight can be reduced.

However, when this is done, the display surface, which was conventionally flat, now has a curved surface, and when the electrode configuration described above is used as it is in a glass container with a curved display surface, as shown in FIG.
As shown in a) to (C1), a problem occurred in which the image quality became non-uniform.

FIGS. 4(b) and 4(C) show that in the electrode configuration of FIG. 1, which has already been explained, a fourth
This figure shows the appearance of a display surface when the display glass 21 shown in FIG. 3A is made into a curved surface. Note that FIG. 4(b) is an enlarged view of the local area A at the left and right ends of the display glass 21, and FIG. 19/4(C) is an enlarged view of the central area B of the display glass 21.

As can be seen from FIG. 4(b), at the end A of the display surface, the red color (R) is sandwiched between the customer's display black 41.
The electron beam 42 hits the , green (G), and blue (B) phosphors accurately, but as can be seen from FIG. , the electron beam 43 that should strike the blue (B) phosphor is deviated from the phosphor.

If the electron beam deviates from a predetermined phosphor and hits the display surface in this way, image deterioration such as color shift occurs.

As described above, when the display surface is curved in order to reduce the weight of the vacuum container and increase its pressure resistance, there is a drawback that the image deteriorates.

This is because when the display surface is curved, the travel distance for the electron beam to pass through the deflection electrodes and reach the display surface is different for each part of the display surface, and unlike conventional methods, a constant deflection voltage is applied to every part of the horizontal deflection electrode. When applying , the deflection distance differs in each part of the linear electron beam, so the electron beams may not collide at the boundaries of the display area, or the electron beams may overlap and collide, resulting in image deterioration. It's for a reason.

The present invention solves the above problem by varying the distance between each pair of conductors constituting the horizontal deflection electrode in correspondence with the curvature of the display surface, thereby varying the electron beam deflection distance at each part of the display surface. It is something that I try to do.

The present invention will now be described in detail.

In the flat panel image display device of the present invention, the electron beam deflection is electrostatic deflection. In addition, in FIG. 6, only the portions corresponding to the horizontal deflection electrodes 7 (18, 18 degrees) and the screen plate 9 in FIG. 1 are extracted and drawn to simplify the explanation. Note that FIG. 6 is a diagram of the horizontal deflection electrode 7 viewed from the direction of FIG. 1.

Generally, the deflection distance in electrostatic deflection is approximately determined by the following equation as shown in FIG.

hdust Ltanθ=vdL/2avo...river...(1
), θ is the electron beam deflection angle, ■ is the voltage between the horizontal deflection electrodes 18.18", d is the width of the horizontal deflection electrodes, and a
is the spacing between the horizontal deflection electrodes 18, 18', v.

is the accelerating voltage applied between the horizontal deflection electrodes 18.18''.

As can be seen from the above formula (1), the horizontal deflection electrode 18.18'
It can be seen that as the distance between the center point of and the screen plate 9 increases, the deflection distance of the electron beam on the screen plate 9 increases accordingly. This is because the electron beams do not accurately strike each phosphor on the entire surface of the screen plate 9 due to variations in the deflection distance of the electron beams.

On the other hand, as can be seen from the above equation (1), when the distance a between the horizontal deflection electrodes 18 and 18° increases, the deflection distance on the screen plate 9 becomes smaller, and conversely, the distance between the horizontal deflection electrodes 18 and 18° becomes smaller.
As the distance a between the horizontal deflection electrodes 18 and 18' becomes smaller, the deflection distance on the screen plate 9 increases.As a result, the screen plate 9 becomes a curved surface and the distance between the horizontal deflection electrodes 18, 18' and the screen plate 9 increases. However, even if the size changes at each location on the screen plate 9, the horizontal deflection electrodes 18 and 1 will change accordingly.
If the distance a between 8" is changed in size, the screen plate 9
This means that the deflection distance of the electron beam can be kept constant over the entire surface.

Embodiments of the present invention will be described based on the drawings.

FIG. 6 shows a flat panel image display device according to an embodiment of the present invention, in which a screen plate 59 is formed into a curved surface that protrudes slightly outward so as to withstand atmospheric pressure. Here, the screen plate 59 is part of a cylindrical body with a diagonal length of 16 inches and a curved surface with a radius of about 500 to 800 inches. By forming the screen plate 59 into such a shape, the withstand pressure of the vacuum container can be sufficiently increased even if the screen plate 59 is made thicker.

The feature of this device is that the screen plate 59 has a curved surface, and the horizontal deflection electrode "1 +72... River 711
The reason lies in the fact that the mutual support layers of the two have been changed.

That is, as shown in FIG.
, 7□ and 73 + 7s and 74y 74 and 76.7° and 76.76 and 7□ , 7□ and 7s + 7s and 79 +
The distance between 79 and 71°, and between 71° and 711 is dl
.

d2. d3. d4. d5. d5. d4. d3. d2. d
1, there is a magnitude relationship of dl<d2<d3<d4×d5.

In other words, even if the distance between the center point of the horizontal deflection electrodes 71 . If the spacing d1...d5 between the deflection electrodes 71 is changed,
This means that the same deflection distance can always be maintained over the entire surface of the screen plate 59.

In this device, the distance between each pair of conductors constituting the electron beam horizontal deflection electrode is made different depending on the curvature of the display surface, which has the effect of eliminating color shift and obtaining higher quality images. be.

The dimensions, materials, etc. of the horizontal deflection electrode shown in FIG. 6 will be specifically explained. The horizontal deflection electrodes 7.72...711 have 0.
42-6 alloy plate (42%Nt6%Cr, 5
2% Fe) is fabricated by forming a pair of two striped conductors and etching them so that they are arranged in each pinch. The size is about 340 ron x 260 morning.

The horizontal deflection at the center and both ends of the screen plate 69 in this case is illustrated by solid lines A and B with arrows in FIG. 7, respectively. When the distance between the horizontal deflection electrodes 76 and 76 at the center part B is about 0.3 - the distance between the pair of horizontal deflection electrodes 71 and 72 at one end part A is about 0.2 m+n, the same deflection When voltage is applied to the horizontal deflection electrodes 71...711 (50y to 1oOv (
p-p)), approximately the same deflection distance is obtained on the entire surface of the screen plate 59, and the screen voltage at this time is approximately 6V to 10V.
It is KV.

As described above, in the flat panel image display device of the present invention, the distance between each electron beam horizontal deflection electrode is made different depending on the curvature of the display surface, thereby making the deflection distance of the electron beam the same and preventing color shift. This has the effect of allowing you to obtain a better quality image than if you were to remove it.

As explained above, in response to the curved display surface of the flat panel image display device of the present invention, the structure of the electrodes related to the deflection of electron beams has been modified, and the image quality has been improved. It is extremely useful.

[Brief explanation of the drawing]

Figure 1 is a basic configuration diagram of the electrodes of a flat panel image display device.
Fig. 2 is an enlarged view of the main part of the screen plate of the same device, Fig. 3 is a basic configuration diagram of the drive circuit of the same device, Fig. 4(a),
(b) and (c) are diagrams showing non-uniform images seen in the conventional example, Figure 5 is a diagram for explaining the principle of electrostatic deflection in a flat panel image display device, and Figure 6 is a diagram showing the principle of electrostatic deflection in a flat panel image display device. FIG. 7 is a diagram showing the configuration of a flat panel image display device in an embodiment, and is a diagram for proving the configuration of the main part of the device. 1... Back electrode, 2... Line cathode, 3,
3゜... Vertical focusing electrode, 64... Vertical deflection electrode, 63.63''... Conductor, 5...
...Beam flow control electrode, 6...Horizontal focusing electrode, R1, 72...711...Horizontal deflection electrode,
8... Beam accelerating electrode, 59... Screen plate. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Figure 4 Figure 21 /bl (C) Li

I

Claims (1)

[Claims] A plurality of line cathodes, a plurality of electron beam control electrodes, an electron beam vertical deflection electrode, an electron beam horizontal deflection electrode,
It is formed on a curved surface that emits light due to the impact of an electron beam.
and a light emitting means, wherein the distance between each pair of conductors constituting the electron beam horizontal deflection electrode is different from each other corresponding to the curvature of the display surface. Display device.