JPH08304807A - Plasma address display panel - Google Patents

Abstract

(57) [Abstract] [Purpose] To alleviate the variation in thickness of the dielectric sheet incorporated in the plasma addressed display panel within the range permitted by human visual characteristics. The plasma addressed display panel includes a display cell 101 having a column-shaped signal electrode 5 to form a screen, a plasma cell 102 having a row-shaped discharge channel, and a dielectric sheet 107 interposed between the cells. It has a laminated structure in which the layers are stacked on each other. A desired image can be displayed on the screen by sequentially driving the discharge channels while applying an image signal to the signal electrode 105 in synchronization with this. As the dielectric sheet 107, a sheet whose thickness distribution within the screen does not visually notice the display unevenness of the image is used. For example, as the dielectric sheet 107, a sheet whose thickness distribution changes gently from the center of the screen to the periphery of the screen is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma addressed display panel having a laminated structure in which a display cell and a plasma cell are superposed with an intermediate dielectric sheet. More specifically, the present invention relates to a technique for preventing deterioration of display quality due to uneven thickness distribution of a dielectric sheet.

[0002]

2. Description of the Related Art A plasma addressed display panel is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-217396. This panel has a laminated structure in which a display cell and a plasma cell are stacked with a dielectric sheet made of thin plate glass or the like interposed therebetween.
The plasma cell is formed by using the lower glass substrate and is airtightly bonded to the dielectric sheet via a predetermined space. An ionizable gas is enclosed in the hermetically sealed space. A plurality of pairs of discharge electrodes that are parallel to each other are provided on the inner surface of the lower glass substrate. The pair of discharge electrodes function as an anode and a cathode for generating a plasma discharge by ionizing the hermetically sealed gas and forming a discharge channel. On the other hand, the display cell has a liquid crystal layer sandwiched by a dielectric sheet and an upper glass substrate. Striped signal electrodes are formed on the inner surface of the upper glass substrate. This signal electrode is orthogonal to the above-mentioned discharge channel. The signal electrode serves as a column driving unit and the discharge channel serves as a row scanning unit, and pixels in a matrix are defined at the intersections of the two. A desired image is displayed on the screen including the pixels.

[0003]

A thin glass sheet is usually used as the dielectric sheet from the viewpoint of panel manufacturing. The thin glass plate has a thickness of about several tens of μm, and its size also increases as the screen becomes larger. Therefore, it is not easy to manufacture thin glass, and it is very difficult to guarantee a uniform thickness over the entire surface of the glass. Therefore, the manufacturing yield decreases as the size increases. as a result,
The manufacturing cost of the dielectric sheet increases. If the thickness of the dielectric sheet varies, naturally the capacitance locally varies. In the plasma addressed display panel, an effective driving voltage is applied to the liquid crystal according to the capacitance division ratio of the liquid crystal layer and the dielectric sheet. Therefore, if the thickness of the dielectric sheet varies, a uniform drive voltage cannot be applied to the liquid crystal layer of the entire screen. In particular, the voltage-transmittance (V
-T) When the driving is performed within the steep range, a minute voltage fluctuation greatly affects the transmittance. Therefore, even if there is a slight variation in the thickness of the dielectric sheet, the transmittance of the panel fluctuates by several percent to several tens of percent. For example,
Even if a certain level of drive voltage is applied to the entire screen of the plasma addressed display panel to perform gray display, in the normally white mode, the thick part of the dielectric sheet becomes bright and the thin part is displayed dark. There is a problem in that it is not possible to display a uniform gray over the entire area, and display unevenness in the image appears.

[0004]

As described above, there is a problem in that the display unevenness of an image occurs when the thickness of the dielectric sheet varies. In order to completely remove the display unevenness, the thickness distribution of the dielectric sheet is set to, for example, 50 μm ±
It is necessary to suppress the thickness to 0.1 μm. However, such accuracy is unrealistic in view of the thin glass manufacturing technology.
Therefore, it is an object of the present invention to improve the display unevenness of an image by actually allowing an allowable width to some extent in the thickness distribution of the dielectric sheet. The following measures have been taken in order to achieve this object. That is, the plasma addressed display panel according to the present invention is basically a display cell having column-shaped signal electrodes to form a screen, a plasma cell having row-shaped discharge channels, and a dielectric material interposed between the cells. It has a laminated structure in which a sheet and a sheet are stacked on each other. While the discharge channels are sequentially driven to discharge, a desired image is displayed on the screen by applying an image signal to the signal electrodes in synchronization with this. As a characteristic item, the dielectric sheet whose thickness distribution in the screen does not visually notice the display unevenness of the image is used. Specifically, the dielectric sheet has a thickness distribution that changes gently from the center of the screen toward the periphery of the screen. Further, when the dielectric sheet has a periodically wavy thickness distribution, the waviness in the screen is one cycle or less. Further, as the dielectric sheet, one whose thickness distribution can suppress the fluctuation of the brightness of the screen within 20% is used.

[0005]

According to the human visual characteristics, when the peripheral portion of the screen of the panel shows a pattern that is about 20 to 20% darker than the central portion of the screen, it is difficult to easily distinguish the difference. vice versa,
When a pattern in which the center of the screen is darker than the surroundings is displayed, the difference can be immediately identified. When a pattern in which bright and dark parts are periodically arranged is displayed on the screen, even if the difference in brightness is about 5%,
It can be immediately identified by the description "striped pattern" or "wave pattern". Therefore, the present invention skillfully utilizes human visual characteristics to allow uneven thickness distribution in the screen of the dielectric sheet at a realistic level. That is, when the thickness distribution in the screen of the dielectric sheet is in line with the above-mentioned visually inconspicuous light-dark distribution, this is not rejected as a defective product, but is adopted as a good product, and thus the dielectric sheet This contributes to yield improvement.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic perspective view showing the structure of a plasma addressed display panel according to the present invention. As shown in the figure, this plasma addressed display panel has a display cell 1
01 and the plasma cell 102 are laminated on each other with a dielectric sheet 107 made of thin glass plate or the like interposed therebetween. The plasma cell 102 has a lower glass substrate 104.
And is airtightly bonded to the dielectric sheet 107 through a predetermined space. An ionizable gas is enclosed in the hermetically sealed space. On the inner surface of the lower glass substrate 104, a plurality of pairs of discharge electrodes 108 and 109 which are parallel to each other are provided along the row direction. The pair of discharge electrodes 108 and 109 is an anode A for ionizing the gas which is hermetically sealed and generating plasma discharge.
And function as cathodes K to form row-shaped discharge channels. On the other hand, the display cell 101 has a liquid crystal layer 1 sandwiched between a dielectric sheet 107 and an upper glass substrate 103.
It is equipped with 06. The present invention is not limited to this, and other electro-optical substances may be used instead of the liquid crystal layer. Column-shaped signal electrodes 105 are formed on the inner surface of the upper glass substrate 103. This signal electrode 105 is orthogonal to the above-mentioned discharge channel. The signal electrode 105 serves as a column driving unit and the discharge channel serves as a row scanning unit, and pixels in a matrix are defined at the intersections of the two. A screen is composed of this set of pixels. While the discharge channels described above are sequentially driven to discharge, the signal electrodes 105 are synchronized with this.
A desired image can be displayed on the screen by applying an image signal to.

A feature of the present invention is that the dielectric sheet 1 is used.
As for 07, the one whose thickness distribution on the screen does not visually notice the display unevenness of the image is used. Specifically, as the dielectric sheet 107, a sheet whose thickness distribution changes gently from the center of the screen to the periphery of the screen is used. When the dielectric sheet 107 has a periodically wavy thickness distribution, a waviness within one cycle is used in the screen. Further, as the dielectric sheet 107, one whose thickness distribution can suppress the fluctuation of the brightness of the screen within 20% is used. As described above, according to the present invention, even when the dielectric sheet has a local variation in thickness, when the thickness distribution is along a certain pattern, it is allowed to be incorporated as a component of the plasma addressed display panel. ing.
As a result, a dielectric sheet such as a thin glass sheet can be mass-produced with an allowable width of, for example, about 50 μm ± 3 μm without requiring the conventional strict precision of about 50 μm ± 0.1 μm.

FIG. 2 briefly shows the operating principle of the plasma addressed display panel shown in FIG. For ease of understanding, one pixel located at the intersection of one discharge channel and one signal electrode is cut out and schematically shown. As shown, the display cell has a liquid crystal layer 106 held by an upper glass substrate 103 and a dielectric sheet 107. A signal electrode 105 is formed on the inner surface of the upper glass substrate 103 in contact with the liquid crystal layer 106. A predetermined image signal is supplied from the signal source 202 to the signal electrode 105. On the other hand, the plasma cell is configured by using the lower glass substrate 104, on which a pair of discharge electrodes are patterned. One discharge electrode is the anode (A) electrode 108, and the other discharge electrode is the cathode (K) electrode 109, forming a discharge channel between them. A switch 201 is connected to the discharge channel and drives the discharge channel in a line-sequential manner. That is, according to the selection pulse, the switch 20
1 is opened and closed, and the anode electrode 108 and the cathode electrode 109
A discharge is generated in the meantime. An image signal is supplied between the anode electrode 108 and the signal electrode 105 via the signal source 202 by utilizing the electric charge appearing directly under the dielectric sheet 107 during or immediately after the discharge, and a predetermined signal is supplied to the liquid crystal layer 106. It is a mechanism to write voltage. When the thickness distribution of the dielectric sheet 107 has unevenness in the panel screen, the capacitance of the sheet locally changes. Due to the presence of the dielectric sheet 107, the signal voltage actually applied to the liquid crystal layer 106 varies according to the thickness distribution of the dielectric sheet even if the image signal is uniformly controlled over the panel screen.

FIG. 3 shows a liquid crystal layer 106 and a dielectric sheet 107.
Represents an electrical equivalent circuit of. Dielectric sheet 10
If the capacitance, the permittivity, and the thickness of 7 are C _G , ε _G , and d _{G, respectively,} and the capacitance, the permittivity, and the thickness of the liquid crystal layer 106 are C _LC , ε _LC , and d _LC , respectively, the dielectric sheet. Capacitances per unit area S of the liquid crystal layer 107 and the liquid crystal layer 106 are represented by the following formulas 1 and 2, respectively.

[Equation 1]

[Equation 2] In addition, the voltage of the image signal supplied from the signal source 202 is set to Vi.
When n is set, the effective signal voltage V _LC applied to the liquid crystal layer 106 is expressed by the following mathematical formula 3.

(Equation 3) Therefore, even if the voltage Vin of the image signal is constant, when the thickness d _G of the dielectric sheet increases, the signal voltage V _LC applied to the liquid crystal becomes smaller than the original level. or,
Generally, the dielectric constant of liquid crystal changes depending on the alignment state according to the applied voltage. Therefore, when the change in the dielectric constant of the liquid crystal is large, the “dielectric constant in consideration of the applied voltage” must be introduced into the above formula for calculation. However, if the liquid crystal material in which the variation of the dielectric constant ε _LC is suppressed with respect to the applied voltage is used, it is not necessary to take the above consideration into consideration. As can be understood from the above description, if the dielectric sheet 107 has a thickness distribution in the panel screen, the sheet capacitance inevitably becomes uneven. Therefore, even if the applied voltage Vin supplied from the signal source 202 is set to a uniform value over the entire screen,
The voltage actually applied to the liquid crystal layer 106 fluctuates due to the influence of the thickness distribution of the dielectric sheet 107, and as a result, it may not be possible to obtain uniform brightness display over the entire screen.

FIG. 4 shows an example in the case where a voltage for displaying gray as an image signal is applied and uneven thickness distribution of the dielectric sheet occurs in the vertical direction with respect to the effective screen of the panel. The dielectric sheet is larger than the reference thickness near the center of the screen of the panel. As is clear from the above-mentioned formula 3, and as schematically shown in FIG. 4, the voltage applied to the thick portion of the dielectric sheet is smaller than the signal voltage amount that should be originally applied to the liquid crystal layer. Therefore, in the normally white mode, the gray level becomes brighter than the gray level originally desired to be displayed. On the contrary, in the thin portion, a voltage larger than the original signal voltage amount is applied to the liquid crystal layer, and it becomes darker than the set gray level. Therefore, even if an image signal having a required brightness is applied, it is inevitable that the transmittance unevenness corresponding to the thickness distribution unevenness of the sheet occurs in the panel.

On the other hand, according to human visual characteristics, when the peripheral portion of the screen of the panel is darker by 10 to 20% than the central portion of the screen, the difference cannot be clearly discriminated. On the contrary, when the center of the screen is darker than the surroundings, the difference can be immediately discriminated. Further, as shown in FIG. 5, when a bright portion and a dark portion are periodically present in the screen, even if the relative luminance difference is about 5%, the shape of "striped pattern" or "wave pattern" is used. It is possible to judge immediately. Therefore, in the present invention,
By utilizing this visual characteristic, a certain pattern allowed for the thickness distribution of the dielectric sheet is defined. First of all
In the normally white mode, a dielectric sheet is used in which the thickest region of the dielectric sheet is arranged in the center of the effective screen and the thinnest portion is arranged around the effective screen.
In the case of the normally black mode, on the contrary, a dielectric sheet in which the thinnest region is arranged in the center of the effective screen and the thickest region is arranged in the periphery of the effective screen is used. For example, FIG.
When a thin glass sheet is used as the dielectric sheet as shown in FIG. 3, a portion 3 having a thickness distribution suitable for a plasma addressed display panel is formed from a large thin glass sheet 301 as a raw material.
02 is cut out and used. In FIG. 6, a light-colored part indicates a thick part of the sheet, and a dark-colored part indicates a light part of the sheet. The dielectric sheet 302 thus cut out is thick in the center of the screen and thin in the periphery along the vertical direction. When displaying a pattern (image) of uniform brightness on the entire screen, the plasma address display panel created using this dielectric sheet adopts the normally white mode, where the central part of the screen is bright and the peripheral part is bright. Get dark. In this case, if the luminance of the dark portion is about 80 to 90% of the luminance of the bright portion, the difference cannot be easily recognized due to human visual characteristics.

Next, due to the uneven thickness of the dielectric sheet,
The thickness distribution is specified so that bright and dark parts do not repeatedly exist in the screen. Specifically, as shown in FIG. 7, a dielectric sheet having a fluctuation period of 1 or less between the thick portion and the thin portion of the thin glass plate is used. However, also in this case, it is necessary to cut out the original thin glass material so that the thick portion of the thin glass is arranged in the center of the effective screen. According to the calculation, as shown in FIG. 8, when the position of the thick portion with respect to the center of the screen is about 10% or more of the effective screen size, the brightness unevenness can be visually identified.

Finally, some specific examples will be described with reference to FIG. In the specific example of (A), a dielectric sheet is used in which the screen center is thick in the vertical direction with respect to the effective screen, and the top and bottom are thin. When a plasma addressed display panel using this sheet is used to display an image of uniform brightness over the entire screen, the upper and lower peripheral parts of the screen are darker than the central part of the screen, but the brightness change is actually visual. Not noticeable. (B)
In the specific example shown in (1), a dielectric sheet is used which has a thick screen center in the horizontal direction with respect to the effective screen and a thin left and right periphery. When a plasma addressed display panel using this sheet displays an image of uniform brightness on the entire screen, the left and right peripheral parts of the screen are darker than the central part of the screen. However, the brightness change is visually inconspicuous. In the specific example shown in (C), a dielectric sheet having a thick central portion and a thin peripheral portion is used along the vertical and horizontal directions with respect to the effective screen. When an image with uniform brightness is displayed on the entire screen of a plasma addressed display panel using this sheet, the upper, lower, left, and right peripheral parts of the screen are darker than the central part of the screen, but the brightness change is not noticeable due to visual characteristics. .

[0014]

As described above, according to the present invention, by utilizing the human visual characteristics, the pattern of the thickness distribution of the dielectric sheet, which should be essentially infinite, is specified, whereby the plasma It is possible to allow the thickness distribution of the dielectric sheet to such an extent that the luminance difference within the screen of the address display panel can be suppressed within 10 to 20%. As a result, the allowable range of the thickness distribution of the dielectric sheet made of thin glass or the like is expanded, the yield of the dielectric sheet can be improved, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a basic configuration of a plasma addressed display panel according to the present invention.

FIG. 2 is a schematic diagram showing a driving principle of a plasma addressed display panel according to the present invention.

FIG. 3 is an equivalent circuit diagram of a liquid crystal layer and a dielectric sheet included in a plasma addressed display panel.

FIG. 4 is a schematic diagram showing an in-screen luminance distribution of a plasma addressed display panel.

FIG. 5 is a schematic diagram showing an example of brightness unevenness appearing on the screen of the plasma addressed display panel.

FIG. 6 is an explanatory view showing a method of cutting out a dielectric sheet from an original thin glass material according to the present invention.

FIG. 7 is a graph showing an example of a thickness distribution of a dielectric sheet.

FIG. 8 is a graph showing an example of a thickness distribution of the dielectric sheet.

FIG. 9 is a schematic plan view showing a specific example of the present invention.

[Explanation of symbols]

 101 Display Cell 102 Plasma Cell 103 Upper Glass Substrate 104 Lower Glass Substrate 105 Signal Electrode 106 Liquid Crystal Layer 107 Dielectric Sheet 108 Discharge Electrode (Anode Electrode) 109 Discharge Electrode (Cathode Electrode)

Claims (4)

[Claims] 1. A laminated structure in which a display cell having column-shaped signal electrodes to form a screen, a plasma cell having row-shaped discharge channels, and a dielectric sheet interposed between the cells are stacked. And, while the discharge channels are sequentially driven to discharge, a plasma address display panel capable of displaying a desired image on the screen by applying an image signal to the signal electrodes in synchronization with the discharge channel, wherein the dielectric sheet is A plasma addressed display panel characterized by using a film whose thickness distribution on the screen does not make the display unevenness of the image visually noticeable. 2. The plasma addressed display panel according to claim 1, wherein the dielectric sheet has a thickness distribution that changes gently from the center of the screen toward the periphery of the screen. 3. The plasma addressed display panel according to claim 1, wherein the dielectric sheet has a periodically wavy thickness distribution and has a waviness of one cycle or less in a screen. 4. The plasma address display panel according to claim 1, wherein the dielectric sheet has a thickness distribution that can suppress fluctuations in screen brightness within 20%.