JP4360926B2 - Plasma display panel - Google Patents

Description

  The present invention relates to a plasma display panel (hereinafter referred to as “PDP”) used as a light-emitting element in a color image display device for a large-size screen with high accuracy and low cost.

  Conventionally, CRTs that have been frequently used as image display devices have the disadvantages that they are large in volume and weight and require a high voltage. Therefore, with the recent penetration of multimedia, the information interface is a large screen such as PDP, light emitting diode (LED), liquid crystal display element (LCD), etc. Planar image display devices having features such as not selecting a place have been developed, and the range of use of these devices is expanding (see, for example, Patent Document 1).

  FIGS. 1A and 1B show an example of a general AC type PDP. This AC type PDP substantially includes a front substrate 1, a display electrode 2, a dielectric layer 3, a protective layer 4, a phosphor layer 6, an address electrode 7, a rear substrate 8, a partition wall 9, And the dielectric layer 10. In such an AC type PDP, the display electrode 2 is generally formed on a glass front substrate 1 and covered with a dielectric layer 3 and a protective layer 4. The address electrode 7 and the phosphor layer 6 are provided on a glass back substrate 8.

A discharge space 5 in which a discharge gas is enclosed is formed between the front substrate 1 (protective layer 4) and the back substrate 8 (phosphor layer 6). In the discharge space 5, vacuum ultraviolet rays (mainly at a wavelength of 147 nm) are generated along with the discharge, and the phosphor layer 6 is excited to emit light, thereby displaying.
JP 2002-367518 A (paragraph [0015], FIG. 1)

  However, in such a conventional PDP, the secondary electron emission efficiency of the protective layer is reduced due to impurities adsorbed on the protective layer and the phosphor layer, and impurities adsorbed in the manufacturing process and brought into the panel. There is a problem that variations and lighting timing shifts occur and image uniformity is impaired.

  The present invention has been made to solve the above-described conventional problems. The secondary electron emission efficiency of the protective layer is maintained and uniformed at a high level so that luminance variations and lighting timing shifts do not occur, and an image is generated. It is a problem to be solved to provide a plasma display panel (PDP) with good uniformity.

  The present inventors have intensively studied to achieve the above object, and by adding titanium oxide to the protective layer, pollutants such as organic substances are decomposed by the catalytic properties of titanium oxide, and the pollutants become phosphors. It was found that the adsorption is suppressed and the variation in luminance is reduced. Based on the results of this study, the present inventors provide a PDP excellent in image uniformity with little luminance variation and lighting timing shift.

  The PDP according to the present invention includes a front substrate on which display electrodes are wired and a back substrate on which address electrodes are wired. A phosphor layer is provided on at least one of the opposing surfaces of the front substrate and the rear substrate. In addition, a dielectric layer and a protective layer for protecting the dielectric layer are provided on at least one of the opposing surfaces of the front substrate and the rear substrate. The PDP displays an image by discharging in a minute discharge space formed between the front substrate and the rear substrate. Here, the protective layer mainly contains magnesium oxide and contains 0.2 to 10 wt% of titanium oxide. Titanium oxide is mainly composed of anatase crystals, and the content ratio of rutile crystals and brookite crystals is 20 wt% or less.

  Titanium oxide is physically and chemically stable, has a good hiding power and colorability for hiding the underlying color, and has an ultraviolet shielding effect. For this reason, it is a cheap and safe material widely used as a pigment such as paint or plastic, an ultraviolet shielding material for cosmetics, or a dielectric raw material for electronic parts, and also recognized as a food additive. Titanium oxide has a band gap of 3.0 eV and is excited by light having a wavelength of 410 nm or less. Excited titanium oxide acts as a catalyst for contaminants.

  Titanium oxide has three crystal forms, anatase (Anatase), rutile (Rutile), and brookite (Brookite), and the anatase crystal has a catalytic effect in an ultraviolet light environment. Next, rutile crystals have a large catalytic effect in an ultraviolet light environment. Therefore, the titanium oxide used for the protective layer is preferably titanium oxide mainly composed of anatase crystals, and the content of rutile crystals and brookite crystals is preferably 20 wt% or less.

  When the protective layer mainly composed of magnesium oxide contains titanium oxide having a catalytic effect, the content of titanium oxide is preferably 0.2 wt% or more. Further, the content of titanium oxide is preferably 10 wt% or less so as not to impair the electron emission characteristics of magnesium oxide and the insulating property for accumulating wall charges.

  Thus, according to the present invention, by maintaining and uniformizing the secondary electron emission efficiency at a high level, it is possible to provide a PDP in which luminance variation and lighting timing shift do not occur and image uniformity is good. it can.

  Hereinafter, a PDP and a method for manufacturing the same according to an embodiment of the present invention will be described in detail with reference to FIGS.

In the PDP according to this embodiment, the ultraviolet rays generated in the discharge space 5 due to the discharge between the display electrode 2 and the address electrode 7 excite the phosphor layer 6 (phosphor) formed on the inner surface of the panel, Visible light having an emission spectrum specific to the phosphor material is emitted by the principle of photoluminescence. In each display cell, the discharge space 5 is separated by the barrier rib 9. The partition walls 9 are made of alumina-containing glass, and protrude from the surface of the visible light reflection layer with a height and a pitch of about 0.15 mm with the adjacent partition walls. The size of the PDP having such a configuration is set to a display for a high-definition television of 106.68 cm (42 inches). The number of pixels is 1920 × 1125, the cell pitch is 0.15 mm × 0.48 mm, and the unit cell area is 0.072 mm ² .

  The PDP according to this embodiment is manufactured by the following manufacturing method. In addition, red, green, and blue light emitting phosphors are formed in the display cells, respectively. Full color display is performed by changing the emission intensity of the red, green, and blue light emitting phosphors of the respective display cells. In general, an AC drive type PDP has a memory function that takes on and off states by controlling charged particles accumulated on a protective layer or a dielectric layer.

  In this embodiment, the front substrate 1 and the rear substrate 8 are made of soda-lime glass having a diagonal of 106.68 cm (42 inches). As a substrate for PDP, a plate glass having a large size exceeding a diagonal of 101.6 cm (40 inches) is required. There are several methods for manufacturing such a glass plate, but it is preferable to manufacture by a float method that is excellent in terms of flatness and parallelism. In the manufacturing process of the PDP, a heat treatment process must be repeated. Therefore, it is desirable that the substrate for PDP is a material having a high thermal deformation temperature, and it may be higher than the firing temperature of the dielectric layer 3. Furthermore, any material in consideration of electrical insulation may be used, and a transparent glass substrate such as soda lime glass, low soda glass, lead alkali silicate glass, or borosilicate glass may be used.

  In the display electrode of the AC type PDP, a structure in which electrodes are arranged in a wide range is necessary in order to realize surface discharge. In addition, a transparent electrode material is desirable for allowing the emitted phosphor visible light to pass through the front substrate 1. Therefore, the display electrode 2 has a high visible light transmittance, a low resistance value so that high-speed signal transmission is possible, a good patterning property, and a good matching such as durability with peripheral materials, A material having a uniform film quality over a large area may be used.

The display electrode 2 was formed by magnetron sputtering under the condition of 0.266 Pa (2 × 10 ⁻³ Torr) in an argon atmosphere at a target ratio of 9 (In ₂ O ₃ ): 1 (SnO ₂ ). Indium tin oxide thin film having a transmittance of 90% and a resistance of 2 × 10 ⁻⁴ Ωcm. Magnetron sputtering may mix a small amount of oxygen. Further, SnO ₂ , ZnO, CdSnO or the like may be used as the material of the other display electrode 2, but is not limited thereto. As a manufacturing method of the display electrode 2, a printing method, a coating method, a CVD method such as thermal CVD, or a PVD method such as a vacuum evaporation method may be used. After film formation, patterning may be performed by a photoetching method. In order to reduce the resistance value of the display electrode, an auxiliary electrode made of Ag, Al, MgAg, Cr / Cu / Cr, or the like may be formed on the transparent electrode.

  The characteristics of the dielectric layer 3 in the AC drive PDP are required to have good withstand voltage, transmittance, capacitance, surface roughness, and matching with the protective layer. The dielectric layer 3 is mainly composed of low melting point glass of lead oxide-boron oxide-silicon oxide, lead oxide-boron oxide-silicon oxide-zinc oxide, and lead oxide-boron oxide-silicon oxide-aluminum oxide. The glass paste is formed by a known coating method such as screen printing, die coating, or roll coating, and then dried and fired. In this embodiment, a dielectric paste made of 75 wt% lead oxide, 15 wt% boron oxide, and 10 wt% silicon oxide was used to form a film by a screen printing method, followed by baking at 580 ° C. The film thickness was 20 μm.

  The protective layer 4 is for protecting the dielectric layer 3 from ion bombardment caused by plasma, and magnesium oxide is widely used because the discharge start voltage can be lowered by high secondary electron emission efficiency. As the film formation method, an electron beam evaporation method, a CVD method, a sputtering method, or the like is used. Alternatively, the paste may be formed into a film by a screen printing method and then fired. In order to reduce pinholes, a film may be formed by an atomic layer epitaxy method (ALE method). In order to remove the adsorbate, the magnesium oxide may be heated before and / or after the film formation. In this embodiment, first, a paste was prepared by adding 10 wt% magnesium diethoxide or octylic acid (2-ethylhexanoic acid) magnesium solution to magnesium oxide powder. A mixture obtained by mixing arbitrary titanium oxide and the like was formed into a film by a screen printing method and then baked at 500 to 600 ° C. The film thickness was 0.5 μm.

  The partition wall 9 molding composition may be any glass material as long as it becomes glassy after firing and can maintain airtightness. For example, a mixture of a low melting glass powder and an oxide ceramic powder can be used as an inorganic component, and a mixture of the inorganic component and an organic substance such as a binder, a solvent, and various additives can be appropriately selected depending on the molding conditions of the partition walls. Can be prepared and used.

  And what is necessary is for the coating layer of the composition for partition wall shaping | molding to finally have a plastic deformation property. For example, it is possible to form the coating layer with a partition wall molding composition having plastic deformability, or to form the coating layer of the partition wall molding composition and then impart plastic deformation properties to the coating layer. The interval between the partition walls may be changed in each of red, green, and blue in order to adjust the color. In this embodiment, in order to adjust the white balance, the red portion is 0.153 mm, the green portion is 0.133 mm, and the blue portion is 0.16 mm.

  In addition, as an organic substance suitable for the partition molding composition having plastic deformability, the binder includes, for example, an acrylic or butyral thermoplastic binder, an ultraviolet curable resin, a photocurable resin, or a thermosetting resin. A reaction curable resin such as can be used.

  On one main surface of the back substrate 8, a silver paste for the address electrode 7 was screen-printed in a stripe shape at a pitch of 0.15 mm, and then baked to form the address electrode 7. The dielectric layer 10 is substantially the same as the dielectric layer 4 except that the dielectric layer 10 is whitened to have the role of a reflective layer in order to improve luminance, so that the same kind of low-melting glass and the same kind of glass are used. A film forming method can be used. In this embodiment, some titanium oxide particles are mixed in a dielectric paste made of 75 wt% lead oxide, 15 wt% boron oxide, and 10 wt% silicon oxide, and this is added to the main surface of the back substrate 8 with the above address. A film was formed by screen printing so as to cover the electrode 7, and then baked at 580 ° C. The film thickness was 20 μm. Subsequently, a glass paste containing alumina was screen-printed in a stripe shape at a pitch of 0.15 mm, and this was laminated several times and then baked to form a partition wall 9 having a height of 0.15 mm. The address electrode 7 can be formed using a conductive metal such as Ag, Ni, Cu, or Al, or an alloy thereof, or a conductive paste in which a small amount of glass is mixed with the conductive metal or the alloy. An etching method may be used.

The phosphor is applied and baked in each discharge display cell through a mask pattern. Thereafter, the back plate and the front plate are sealed, and a discharge gas mainly containing Xe, He-Xe, Ne-Xe, or the like is hermetically sealed at 1330 to 79800 Pa (10 to 600 Torr) to complete the PDP. In this embodiment, the phosphor layer 6 uses YBO ₃ : Eu for red, BaAl ₁₂ O ₁₉ : Mn for green, and BaMgAl ₁₀ O ₁₇ : Eu for blue, and has a thickness of 5 to 50 μm. Since the phosphor adjusts the white balance, the thickness may be adjusted.

  After forming each member on the front substrate 1 and the back substrate 8, both the substrates 1 and 8 were put together so that both members were in a predetermined position, and a glass paste for sealing was applied to the periphery and sealed. Thereafter, the air in the discharge space was evacuated, and a xenon mixed gas of 8% neon was sealed at a pressure of 62500 Pa (about 470 Torr), and aging was performed to make the surface of the electrode uniform. As the gas to be sealed, a gas such as neon, xenon, argon, helium, or a mixed gas of these gases can be used. However, in order to use 147 nm, which is a resonance line of xenon, for ultraviolet rays for exciting the phosphor, it is preferable to use xenon or a xenon mixed gas.

  Using the PDP produced as described above, light is emitted at an alternating voltage, and the screen is divided into an upper stage, a middle stage, and a lower stage, and the luminance of the area portion of 3 × 4 cm in each of the right, center, and left parts is totaled. Measured and evaluated its variation. Although the applied voltage is about 200V, it is preferable that the applied voltage is 200V or less because an increase in voltage causes generation of unlit cells.

Variation in luminance, can recognize visually that more than 10% with respect to the luminance, for example, the luminance, if it is 300 cd / ^{m 2,} variations should not exceed ± 15cd / ^{m 2.}

In Example 1, 10 wt% of anatase crystal titanium oxide was mixed in the protective layer. The discharge start voltage was 170 V, the luminance was 250 ± 5 cd / m ² , and the variation was 10% or less with respect to the luminance.

In Example 2, 0.2 wt% of anatase crystal titanium oxide was mixed in the protective layer. The discharge start voltage was 150 V, the luminance was 430 ± 20 cd / m ² , and the variation was 10% or less with respect to the luminance.

In Example 3, 10 wt% titanium oxide was mixed in the protective layer. As the titanium oxide, 80 wt% of titanium oxide of anatase crystal and 20 wt% of titanium oxide of rutile crystal were mixed. The discharge start voltage was 170 V, the luminance was 250 ± 8 cd / m ² , and the variation was 10% or less with respect to the luminance.

In Example 4, 10 wt% of titanium oxide was mixed in the protective layer. As the titanium oxide, 80 wt% of titanium oxide of anatase crystal and 20 wt% of titanium oxide of brookite crystal were mixed. The discharge start voltage was 170 V, the luminance was 250 ± 10 cd / m ² , and the variation was 10% or less with respect to the luminance.

(Comparative Example 1)
In Comparative Example 1, titanium oxide was not mixed in the protective layer. The discharge start voltage was 150 V, the luminance was 500 ± 35 cd / m ² , and the variation was 10% or more with respect to the luminance.

(Comparative Example 2)
In Comparative Example 2, 11 wt% of anatase crystal titanium oxide was mixed in the protective layer. The discharge start voltage was 170 V, the luminance was 230 ± 5 cd / m ² , and the variation was 10% or less with respect to the luminance.

(Comparative Example 3)
In Comparative Example 3, 0.1 wt% of anatase crystal titanium oxide was mixed in the protective layer. The discharge start voltage was 150 V, the luminance was 500 ± 30 cd / m ² , and the variation was 10% or more with respect to the luminance.

(Comparative Example 4)
In Comparative Example 4, 10 wt% titanium oxide was mixed in the protective layer. The titanium oxide was a mixture of 75 wt% of anatase crystal titanium oxide and 25 wt% of rutile crystal titanium oxide. The discharge start voltage was 180 V, the luminance was 240 ± 8 cd / m ² , and the variation was 10% or less with respect to the luminance.

(Comparative Example 5)
In Comparative Example 5, 10 wt% titanium oxide was mixed in the protective layer. As the titanium oxide, 75 wt% of titanium oxide of anatase crystal and 25 wt% of titanium oxide of brookite crystal were mixed. The discharge start voltage was 180 V, the luminance was 240 ± 22 cd / m ² , and the variation was 10% or less with respect to the luminance.

In Examples 1 to 4, all emitted light with an AC voltage of 200 V or less, a luminance of 250 cd / m ² or more was obtained, and the variation in luminance was 10% or less. In Comparative Example 4, no light was emitted at 200V. In Comparative Examples 1, 3, and 5, the variation in luminance was larger than 10%. In Comparative Example 2, the luminance decreased to less than 250 cd / m ² .

  When titanium oxide is mixed with magnesium oxide as the protective layer, luminance variation is reduced due to the catalytic effect. However, if it exceeds 10 wt%, the secondary electron emission efficiency of magnesium oxide and the insulating property for accumulating wall charges are reduced, so that the luminance is reduced to half or less. Titanium oxide has the effect of reducing the luminance variation due to the photocatalytic effect in the anatase crystal, but hardly has such an effect in the rutile crystal, and seems to have an adverse effect in the brookite crystal. Therefore, it is preferable that titanium oxide is mainly composed of anatase crystals and brookite crystals are not used as much as possible.

  As described above, the plasma display panel according to the present invention is useful as a large display panel which does not cause luminance variation and lighting timing shift and has good image uniformity, and is particularly a display screen for a large television or the like. Suitable for use as

(A) is sectional drawing of PDP concerning this invention cut | disconnected by the surface perpendicular | vertical to the extending direction of a display electrode, (b) is a cross section of PDP concerning this invention cut | disconnected by the surface perpendicular | vertical to the extending direction of an address electrode. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front substrate, 2 Display electrode, 3 Dielectric layer, 4 Protective layer, 5 Discharge space, 6 Phosphor layer, 7 Address electrode, 8 Back substrate, 9 Partition, 10 Dielectric layer

Claims (1)

A front substrate on which display electrodes are wired and a rear substrate on which address electrodes are wired;
A phosphor layer is provided on at least one of the opposing surfaces of the front substrate and the rear substrate,
A dielectric layer is provided on at least one of the opposing surfaces of the front substrate and the back substrate, and further, a protective layer for protecting the dielectric layer is provided,
In the plasma display panel that is designed to display an image by discharge in a minute discharge space formed between the front substrate and the rear substrate,
While the protective layer is mainly composed of magnesium oxide, it contains 0.2 to 10 wt% of titanium oxide,
The plasma display panel, wherein the titanium oxide is mainly composed of anatase crystals and the content ratio of rutile crystals and brookite crystals is 20 wt% or less.

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