EP1258902A2 - Plasma display panel with improved white colour-point - Google Patents

Abstract

The invention relates to a plasma screen with an improved white color point. The front panel (1) of the plasma screen has a blue layer on the side facing the plasma discharge. This can be the dielectric layer (4), the protective layer (5) or an additional layer (14). <IMAGE>

Description

The invention relates to a plasma screen equipped with a front panel, the one Glass plate on which a dielectric layer and a protective layer are applied, has, equipped with a support plate with a phosphor layer, with a Rib structure that defines the space between the front plate and carrier plate in plasma cells are filled with a gas, split, with one or more electrode arrays on the Front plate and the carrier plate for generating silent electrical discharges in the plasma cells.

Plasma screens allow color images with high resolution, large screen diagonal and are of compact design. A plasma screen has a hermetic closed glass cell, which is filled with a gas, arranged with a grid Electrodes on. Applying an electrical voltage causes a gas discharge that produces light in the ultraviolet range. This can be done with phosphors Converted light into visible light and through the front panel of the glass cell to Viewers are emitted.

To display colored images on a plasma screen, use the additive color mixing. Leave a large part of the colors found in nature additive mixture of the three primary colors red, green and blue Represent intensity.

The representation of the different colors is determined by so-called standard color curves. A widely used standard is the CIE color triangle. The area of the representable Colors in a screen are given by the color points of the three phosphors defined by the respective emission spectrum.

Due to the characteristic color sensation of the human eye, the blue one Light emission at least contributes to the luminance (brightness) of a screen. In plasma screens in addition, the blue-emitting phosphors are not as efficient like the green and red emitting phosphors. A plasma screen with a blue-emitting Fluorescent material is known, for example, from DE 199 37 420. These two Effects cause the color temperature for white light for television applications with the same excitation of the red, green and blue emitting phosphors lower than is desired.

Therefore, it is an object of the invention to overcome the disadvantages of the prior art bypass and a plasma screen with an improved color temperature for white To provide light.

This task is solved by a plasma screen equipped with a front plate, which is a glass plate on which a dielectric layer and a protective layer are applied are equipped with a carrier plate with a phosphor layer, with a Rib structure that defines the space between the front plate and carrier plate in plasma cells are filled with a gas, split, with one or more electrode arrays on the Front plate and the carrier plate for generating silent electrical discharges in the plasma cells, with the front panel on the side facing the plasma cells has a blue layer.

The blue layer creates a blue color on the front panel and thus the White color point of the plasma screen shifted to lower x, y values. Also the Color temperature of the plasma screen is due to this coloring of the front panel elevated.

In an advantageous embodiment, the blue layer is the protective layer. this has the advantage that there is no additional protective layer, for example made of MgO, on the front panel must be applied.

In this advantageous embodiment, it can be preferred that the blue layer structured, located parallel to the electrodes on the front panel. With the help of this Measure, the addressing behavior of the plasma screen can be improved.

In a further advantageous embodiment, the blue layer is the dielectric Layer. By introducing blue colorant particles into the dielectric layer easily made a blue layer.

It may be advantageous for the blue layer to be an additional layer on the glass plate and is applied to the electrodes of the front panel.

It is particularly preferred that the blue layer contains fax particles selected from the group CoAl ₂ O ₄ and the blue Ultramarine.

These inorganic pigments are temperature stable and withstand rigorous conditions in the manufacture and operation of a plasma display. In particular, blue layers which contain CoAl ₂ O ₄ are resistant to the ion current generated during the plasma discharge. CoAl ₂ O ₄ also has a high secondary electron coefficient under ion bombardment.

Fig 1

den Aufbau und das Funktionsprinzip einer einzelnen Plasmazelle in einem AC-Plasmabildschirm,

Fig 2

den Aufbau und das Funktionsprinzip einer einzelnen Plasmazelle in einem AC-Plasmabildschirm mit einer blauen Schicht auf der Glasplatte und auf den Elektroden,

Fig.3

den Aufbau und das Funktionsprinzip einer einzelnen Plasmazelle in einem AC-Plasmabildschirm mit einer strukturierten blauen Schicht.

The invention will be explained in more detail below with the aid of three figures and six exemplary embodiments. It shows

Fig. 1

the structure and principle of operation of a single plasma cell in an AC plasma screen,

Fig. 2

the structure and principle of operation of a single plasma cell in an AC plasma screen with a blue layer on the glass plate and on the electrodes,

Figure 3

the structure and principle of operation of a single plasma cell in an AC plasma screen with a structured blue layer.

1 shows a plasma cell of an AC plasma screen with a coplanar Arrangement of the electrodes on a front plate 1 and a carrier plate 2. The front panel 1 contains a glass plate 3 on which a dielectric layer 4 and a protective layer thereon 5 are applied. Parallel, strip-shaped discharge electrodes are on the glass plate 3 6.7 applied, which are covered by the dielectric layer 4. The discharge electrodes For example, 6.7 are made of metal or ITO. The carrier plate 2 is off Glass and on the carrier plate 2 are parallel, strip-shaped, perpendicular to the discharge electrodes 6.7 extending address electrodes 10 made of Ag, for example. These are from a phosphor layer 9, which emits light in one of the three primary colors, emitted green or blue, covered. For this purpose, the phosphor layer 9 is in several color segments divided. Usually the red, green or blue emitting color segments are the phosphor layer 9 applied in the form of vertical strip triplets. The individual plasma cells are preferably formed by a rib structure 12 with separating ribs dielectric material separated.

In the plasma cell, as well as between the discharge electrodes 6,7, each of which one acts alternately as a cathode or anode, there is a gas, preferably a Noble gas mixture, for example from He, Ne or Kr with Xe as UV light generating Component. After ignition of the surface discharge, creating charges on one discharge path lying in the plasma region 8 between the discharge electrodes 6, 7 can flow, a plasma forms in the plasma area 8, depending on the composition radiation 11 in the UV range, in particular in the VUV range, is produced. This radiation 11 stimulates the fluorescent layer 9 to glow visible light 13 emitted in one of the three primary colors, which through the front panel 1 steps outwards and thus represents a luminous pixel on the screen.

The front panel 1 of the plasma screen has a blue one on the side of the plasma cells Layer on. This can be either the dielectric layer 4, the protective layer 5 or one additional layer 14. The additional layer 14 is preferably on the Glass plate 3 and on the discharge electrodes 6.7. But it can also be between dielectric layer 4 and the protective layer 5 or between the glass plate and the Discharge electrodes 6.7 are located.

The blue layer preferably contains colorant particles which are selected from the group CoAl ₂ O ₄ and the blue Ultramarine.

If the blue layer is to be the protective layer 5, a layer of CoAl ₂ O ₄ with a layer thickness of 300 to 1500 nm is applied to the dielectric layer 4, which preferably contains PbO-containing glass. This can be done by vacuum evaporation of CoO and Al ₂ O ₃ or by wet chemical application of a CoAl ₂ O ₄ -containing suspension. The particle diameter of the CoAl ₂ O ₄ particles of such suspensions is preferably less than 200 nm. Alternatively, the blue layer can be produced from CoAl ₂ O ₄ by means of screen printing or other printing processes.

In this embodiment it can also be advantageous that the CoAl ₂ O ₄ -containing protective layer 5 is not applied over the entire surface of the dielectric layer 4, but structured. For example, as shown in FIG. 2, the CoAl ₂ O ₄ -containing protective layer 5 can be applied in a strip shape, parallel to the discharge electrodes 6, 7, on the dielectric layer 4. In this embodiment, the area between two pairs of discharge electrodes 6, 7 in which no plasma discharge takes place is not covered with the protective layer 5 containing CoAl ₂ O ₄ .

If the blue layer is to be the dielectric layer 4, blue colorant particles are added to the starting material which is used to produce the dielectric layer 4. The starting material can be a glass material or a ceramic material. The dielectric layer 4 can be one or more oxides selected from the group Li ₂ O, Na ₂ O, K ₂ O, SiO ₂ , B ₂ O ₃ , BaO, Al ₂ O ₃ , ZnO, MgO, CaO and PbO mixed with CoAl ₂ O ₄ or Ultramarinen included. The particle size of the colorant particles is preferably between 20 and 5000 nm.

In order to produce a dielectric layer 4, which contains CoAl ₂ O ₄ or Ultramarine, a screen printing paste is first produced from equal parts by weight of the screen printing paste base and the glass material or the ceramic material. The screen printing paste base is preferably p- ment-1-en-8-ol with 5% by weight of ethyl cellulose. Furthermore, a colorant particle paste is produced from the screen printing paste base and 70 parts by weight of colorant particles. The screen printing paste is then mixed in a ratio of 10: 1 with the colorant particle paste. The paste obtained is applied by screen printing to the front plate 1, which has a glass plate 3 and discharge electrodes 6, 7. The dielectric layer 4 is dried and then the entire front plate 1 is exposed to a temperature of 485 ° C. The layer thickness of the finished dielectric layer 4 is preferably between 20 and 40 μm.

Alternatively, the blue layer can be an additional layer 14. In this embodiment can a layer of the colorant particles on the glass plate 3 or on the Glass plate 3 and the discharge electrodes 6,7 or between the dielectric layer 4 and Protective layer 5 applied. In Fig. 3 is a plasma screen with an additional Layer 14 shown, which on the glass plate 3 and on the discharge electrodes 6,7 is applied.

To produce a blue, additional layer 14, suspensions with colorant particles are first applied to the front plate 1 by means of a printing process, doctor blade process or spin coating process and then dried. The layer thickness of the blue, additional layer 14 is preferably between 0.1 and 2 μm. Alternatively, the blue, additional layer 14 can also be produced by means of known photolithographic processes or by means of vacuum evaporation of CoO and Al ₂ O ₃ .

A suspension which is applied to the front plate 1 by means of spin coating, preferably contains a low concentration of dissolved excipients, for example organic polymeric binders such as polyvinyl alcohol. The composition of the suspension of colorant particles is therefore advantageous to choose such that the dissolved proportions make up no more than 20 volume percent of the colorant particles. It is beneficial limit the volume ratio of colorant particles to binder to 10 to 1.

In the following, embodiments of the invention are explained, the exemplary implementation options represent.

Embodiment 1

To produce a front plate 1 with a blue layer, which is an additional layer 14, 3 discharge electrodes 6, 7 made of ITO were applied to a glass plate. A suspension of CoAl ₂ O ₄ and polyvinyl alcohol in a ratio of 10: 1 was applied to the glass plate 3 and the discharge electrodes 6, 7 by means of spin coating. After drying, a blue, additional layer 14 of CoAl ₂ O ₄ with a layer thickness of 0.7 μm was obtained. A dielectric layer 4 made of low-melting glass, which had a layer thickness of 30 μm, was applied to the blue, additional layer 14. A 700 nm thick protective layer 5 made of MgO was applied to the dielectric layer 4 by vacuum deposition. The front plate 1 was then used together with a carrier plate 2 and a xenon-containing gas mixture to build a plasma screen. The plasma screen had a color temperature of 8100 K. Furthermore, the luminance of the plasma screen was increased by 20 percent with the same contrast under ambient lighting.

Embodiment 2

To produce a front panel 1 with a blue, dielectric layer 4, a screen printing paste made of 100 g p- menth-1-en-8-ol, which contained 5% by weight of ethyl cellulose, and 100 g of a glass material (T _g ≈ 475 ° C), which contained Li ₂ O, Na ₂ O, K ₂ O, SiO ₂ , B ₂ O ₃ , BaO, Al ₂ O ₃ , ZnO, MgO and CaO, and then dispersed them through two passes through a three-roll mill.

In addition, 100 g of p- menth-1-en-8-ol, which contained 5% by weight of ethyl cellulose, and 70 g of CoAl ₂ O _{4 were} mixed. This colorant particle paste was dispersed on a three-roll mill by two passes.

The screen printing paste was in a dissolver with the paste with the colorant particle paste mixed in a ratio of 15: 1. After complete homogenization of the The resulting blue screen printing paste was mixed onto the front plate 1 of a plasma screen applied by screen printing. The layer obtained was dried and treated in an oven at 485 ° C. A transparent, blue dielectric was obtained Layer 4 35 µm thick. A 700 nm thick protective layer 5 of MgO layer applied to the dielectric layer 4. The front plate 1 was then together with a carrier plate 2 and one Xenon-containing gas mixture, used to build a plasma screen.

Embodiment 3

To produce a front panel 1 with a blue, dielectric layer 4, a screen printing paste made of 100 g p- menth-1-en-8-ol, which contained 5% by weight of ethyl cellulose, and 100 g of a glass material (T _g ≈ 475 ° C), which contained Li ₂ O, Na ₂ O, K ₂ O, SiO ₂ , B ₂ O ₃ , BaO, Al ₂ O ₃ , ZnO, MgO and CaO, and then dispersed them through two passes through a three-roll mill.

In addition, 100 g of p- menth-1-en-8-ol, which contained 5% by weight of ethyl cellulose, and 70 g of ultramarine (CI Pigment Blue 299) were mixed. This colorant particle paste was dispersed on a three-roll mill by two passes.

The screen printing paste was mixed in a dissolver with the colorant particle paste 10: 1 mixed. After the mixture had been completely homogenized, the blue screen printing paste obtained on the front plate 1 of a plasma screen Screen printing applied. The layer obtained was dried and placed in an oven 485 ° C treated. A transparent, blue dielectric layer 4 of 30 μm was obtained Thickness. A 700 nm thick protective layer 5 was removed by deposition in a vacuum MgO layer applied to the dielectric layer 4. Then the front panel 1 together with a carrier plate 2 and a xenon-containing gas mixture for Construction of a plasma screen used.

Embodiment 4

To produce a front panel 1 with a blue protective layer 5, an aqueous suspension with a dispersant and 9.5% by weight of CoAl ₂ O _{4 was} produced. The viscosity of the suspension was adjusted to 100 mPa * s using polyvinyl alcohol. The suspension was applied to the dielectric layer 4 of a front plate 1, which had a glass plate 3, a dielectric layer 4 and discharge electrodes 6, 7. The dielectric layer 4 contained PbO-containing glass and the two discharge electrodes 6, 7 were made of ITO. After drying at 150 ° C., a 600 nm thick blue layer was obtained which also functioned as protective layer 5. The front plate 1 was then used together with a carrier plate 2 and a xenon-containing gas mixture to build a plasma screen. The white color point of the plasma screen was 7600 K.

Embodiment 5

To prepare a colorant particle paste, 100 g of p- menth-1-en-8-ol, which contained 5% by weight of ethyl cellulose, and 70 g of CoAl ₂ O _{4 were} mixed. This paste was dispersed on a three-roll mill by two passes.

The colorant particle paste was applied in strips to the dielectric layer 4 Front plate 1, which has a glass plate 3, discharge electrodes 6.7 and a dielectric Layer 4 had printed. The colorant particle paste was applied in such a way that a printed strip is structured in relation to a pair of discharge electrodes 6,7, between which a plasma discharge takes place. The distance between two printed strips was 30 µm and the layer thickness of one printed strip was 1.1 µm after drying. The dielectric layer 4 contained PbO-containing glass and the two discharge electrodes 6, 7 were made of ITO. Then the Front plate 1 together with a carrier plate 2 and a xenon-containing gas mixture, used to build a plasma screen. The white color point of the plasma screen was 7600 K.

Embodiment 6

A 700 nm thick layer of CoAl ₂ O _{4 was} applied to the dielectric layer 4 of a front plate 1, which had a glass plate 3, discharge electrodes 6, 7 and a dielectric layer 4, by means of electron beam evaporation of CoO and Al ₂ O ₃ in a high vacuum apparatus. The dielectric layer 4 contained PbO-containing glass and the two discharge electrodes 6, 7 were made of ITO. The front plate 1 was then used together with a carrier plate 2 and a xenon-containing gas mixture to build a plasma screen. The white color point of the plasma screen was 7600 K. Luminance contrast performance gain (LCP gain), color temperature, white color point and luminance of a plasma display depending on the thickness of a protective layer 5 made of CoAl ₂ O ₄ . thickness
[.Mu.m] LCP profit
[%] color temperature
[K] White color point
[X, y] luminance
[Cdm ^-2 ] 0 0 5966 0.3227, 0.3324 379.5 0173 2.6 6132 0.3193, 0.3327 341.7 0272 3.8 6389 0.3146, 0.3301 332.2 0487 6.8 7161 0.3024, 0.3227 305.4 0728 9.7 8109 0.2901, 0.3153 282.1 1570 15.3 > 11,000 0.2517, 0.2888 214.5

(Y, Gd) BO ₃ : Eu was used as the red-emitting phosphor, Zn ₂ SiO ₄ : Mn was used as the green-emitting phosphor and BaMgAl ₁₀ O ₁₇ : Eu was used as the blue-emitting phosphor. The gas mixture contained 5% by volume of Xe and 95% by volume of Ne.

Claims (6)

Plasma screen equipped with a front plate (1), which is a glass plate (3) on the a dielectric layer (4) and a protective layer (5) are applied, with a carrier plate (2) equipped with a phosphor layer (9) with a rib structure (12), the space between the front plate (1) and carrier plate (2) in plasma cells, which are filled with a gas, with one or more electrode arrays (6,7,10) on the front plate (1) and the support plate (2) to produce breastfeeding electrical discharges in the plasma cells, the front plate (1) on the Side facing plasma cells has a blue layer. Plasma display according to claim 1,
characterized in that the blue layer is the protective layer (5). Plasma display according to claim 2,
characterized in that the blue layer is structured, parallel to the electrodes (6, 7) on the front plate (1). Plasma display according to claim 1,
characterized in that the blue layer is the dielectric layer (4). Plasma display according to claim 1,
characterized in that the blue layer is applied to the glass plate (3) and to the electrodes (6, 7) of the front plate (1). Plasma display according to claim 1,
characterized in that the blue layer contains colorant particles selected from the group CoAl ₂ O ₄ and the blue Ultramarine.

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