JP5584160B2 - Method for manufacturing plasma display panel - Google Patents

Description

The present invention relates to a plasma display panel and a method for manufacturing the same, and more particularly to a method for manufacturing a plasma display panel having excellent discharge characteristics.

  A typical AC surface discharge type plasma display panel as a plasma display panel (PDP) has a basic configuration in which a large number of discharge cells are formed between a front plate and a back plate arranged to face each other.

  The front plate has a display electrode made of a glass front substrate and a pair of scan electrodes and sustain electrodes formed on the inner surface thereof, and a dielectric layer and a protective layer covering them. Here, the protective layer is provided such that electrons are emitted to generate a stable discharge, and ions generated by the discharge do not sputter the dielectric layer. The back plate includes a glass back substrate, data electrodes formed on the inner surface thereof, a dielectric layer covering the data electrode, barrier ribs, and a phosphor layer. Then, the front plate and the back plate are arranged opposite to each other so that the display electrode and the data electrode are three-dimensionally crossed, and the discharge gas is sealed in the internal discharge space. Here, a discharge cell is formed in a portion where the display electrode and the data electrode face each other, and discharge for image display is generated.

  In the plasma display panel, a gas discharge is generated in each discharge cell configured as described above, and red, green, and blue phosphors are excited and emitted to perform color display.

  As a protective layer used in plasma display panels, the electron emission characteristics and sputter resistance are improved because of the arrangement purpose of emitting electrons and generating a stable discharge and preventing the ions generated by the discharge from spattering the dielectric layer. Excellent magnesium oxide (MgO) has been mainly used. In response to recent demands for power saving of plasma display panels, for example, a predetermined concentration of cerium (Ce) is added to MgO in order to realize stable driving at lower power with a protective layer using MgO. Thus, it has been proposed to improve the secondary electron emission characteristics and the charge retention characteristics by forming an energy level due to Ce in the forbidden band in the protective layer (see Patent Document 1).

JP 2009-301841 A

  Although the conventional plasma display panel described above has a certain effect of reducing the discharge start voltage in the protective layer mainly composed of MgO, it is different from other flat panel image display devices such as the recent ecology boom and liquid crystal display. It could not be said that it was able to respond sufficiently to the demand for energy saving of plasma display panels, which has been strengthened from the comparison.

  The present invention has been made in view of such a current situation, and an object of the present invention is to provide a plasma display panel and a method for manufacturing the same, which can perform good image display at a low voltage.

According to the present invention, a pair of substrates on which electrodes for generating a discharge are formed on the respective inner surfaces are opposed to each other through a space, and the dielectric covers the electrodes formed on one of the pair of substrates. A plasma display panel manufacturing method comprising a layer and a protective layer covering the dielectric layer, wherein one of calcium oxide, strontium oxide, and barium oxide is formed on the dielectric layer of the one substrate, or these The protective layer forming step of forming the protective layer formed from a mixture of the above is performed by a vacuum deposition method in an oxygen atmosphere with an oxygen partial pressure of 0.05 Pa or more and an environmental temperature of a substrate temperature of 300 to 380 degrees. And the protective layer has an optical refractive index of 1.57 or less with respect to light having a wavelength of 406 nm.

  In the plasma display panel of the present invention, the protective layer covering the dielectric layer formed on the inner surface of the substrate is formed of any one of calcium oxide, strontium oxide, barium oxide, or a mixture thereof, and the protective layer The optical refractive index for light having a wavelength of 406 nm is 1.57 or less. For this reason, it is possible to provide a plasma display panel that can easily emit an impurity gas adsorbed inside the protective layer in the exhaust process and can perform good image display at a low voltage.

Further, in the method of manufacturing a plasma display panel according to the present invention, the step of forming a protective layer formed of any one of calcium oxide, strontium oxide, barium oxide, or a mixture thereof includes an oxygen partial pressure of 0.05 Pa or more. It is performed by a vacuum deposition method in an atmosphere and at an environmental temperature of 300 to 380 degrees . For this reason, the surface of the formed protective layer can be sufficiently roughened, and a plasma display panel that can perform good image display at a low voltage can be manufactured.

It is a principal part disassembled perspective view which shows schematic structure of the plasma display panel concerning embodiment of this invention. It is a block block diagram which shows the state which drives the plasma display panel concerning embodiment of this invention. It is a scanning electron micrograph which shows the state of the protective layer of the plasma display panel concerning embodiment of this invention. FIG. 3A shows a state where the surface is viewed in plan, and FIG. 3B shows a cross-sectional configuration. It is a scanning electron micrograph which shows the state of the protective layer of the plasma display panel of a comparative example. 4A shows a state in which the surface is viewed in plan, and FIG. 4B shows a cross-sectional configuration. It is a figure which shows the relationship between the refractive index of the protective layer of a plasma display panel, and discharge characteristics by the difference in protective layer manufacturing conditions.

  In the plasma display panel according to the present invention, a pair of substrates on which electrodes for generating discharge are formed on the inner surfaces of the plasma display panel are arranged to face each other through a space, and the electrodes formed on one of the pair of substrates A dielectric layer covering the dielectric layer and a protective layer covering the dielectric layer, wherein the protective layer is formed of any one of calcium oxide, strontium oxide, barium oxide, or a mixture thereof, and The optical refractive index for light having a wavelength of 406 nm is 1.57 or less.

  In the plasma display panel of the present invention, the protective layer has an optical refractive index of 1.57 or less with respect to light having a wavelength of 406 nm. For this reason, the surface of the protective layer is in a moderately rough state, and in the exhaust process of exhausting the inside of the plasma display panel, gas impurities can be easily exhausted and oxidation with excellent electron emission characteristics Even when any one of calcium, strontium oxide, barium oxide, or a mixture thereof is used as the protective layer, it is possible to avoid a decrease in electron emission characteristics due to the adsorbed gas.

Further, in the method for manufacturing a plasma display panel according to the present invention, a pair of substrates on which electrodes for generating discharge are formed on the respective inner surfaces are disposed to face each other through a space, and one of the pair of substrates is disposed on the substrate. A plasma display panel manufacturing method comprising a dielectric layer covering the formed electrode and a protective layer covering the dielectric layer, wherein calcium oxide and strontium oxide are formed on the dielectric layer of the one substrate. The protective layer forming step of forming the protective layer formed from any one of barium oxide or a mixture thereof is performed in an oxygen atmosphere having an oxygen partial pressure of 0.05 Pa or more and a substrate temperature of 300 ° C. to 380 ° C. It is carried out by a vacuum deposition method at an ambient temperature of

  By doing in this way, the manufacturing method which can manufacture easily the plasma display panel provided with the protective layer which is excellent in an electron emission characteristic and the surface is moderately rough can be provided.

  The protective layer is preferably deposited by any one of a vacuum deposition method, a sputtering method, and an ion plating method.

  Furthermore, it is preferable that the optical refractive index of the protective layer with respect to light having a wavelength of 406 nm is 1.57 or less. By doing so, it is possible to manufacture a plasma display panel having a protective layer that is easy to release gas impurities and can be driven at a low voltage.

  Hereinafter, a plasma display panel and a method for manufacturing the plasma display panel of the present invention will be described with reference to the drawings.

  FIG. 1 is an exploded perspective view of a main part showing a schematic configuration of a plasma display panel described as an embodiment of the present invention.

  The plasma display panel 10 of the present embodiment is configured by disposing a front plate 20 and a back plate 30 so as to face each other through a space, and sealing a peripheral portion using a sealing member (not shown). A number of discharge cells are formed between 20 and the back plate 30.

  The front plate 20 includes a glass front substrate 21 which is one of the substrates, a display electrode 24 formed of scan electrodes 22 and sustain electrodes 23 formed on the inner surface of the front substrate 21, and a dielectric covering the display electrode 24. It has a layer 26 and a protective layer 27 covering the dielectric layer.

  The display electrodes 24 include a pair of scanning electrodes 22 and sustain electrodes 23 formed on the inner surface of the front substrate 21, and a plurality of display electrodes 24 are formed on the front substrate 21 in parallel with each other. 1 shows an example in which the display electrode 24 is repeatedly formed in the order of the scan electrode 22, the sustain electrode 23, the scan electrode 22, and the sustain electrode 23, the display electrode 24 includes the scan electrode 22, The sustain electrodes 23, the sustain electrodes 23, and the scan electrodes 22 may be formed so that the order of the scan electrodes 22 and the sustain electrodes 23 is alternately different.

  Further, in FIG. 1, the scan electrode 22 and the sustain electrode 23 are shown to be configured by a pair of electrode patterns, respectively, but the scan electrode 22 and the sustain electrode 23 are not limited to a pair formed, Further, the scan electrode 22 and the sustain electrode 23 can be configured as a combination of a transparent electrode using a transparent conductive film and a bus electrode made of a metal material, respectively.

  A dielectric layer 26 is formed so as to cover the display electrode 24 and the inner surface of the front substrate 21 where no electrode is formed, and a protective layer 27 is formed on the dielectric layer 26 so as to cover the dielectric layer 26. Is formed.

  The back plate 30 includes a glass back substrate 31 as the other substrate, a data electrode 32 formed on the inner surface of the back substrate 31, a dielectric layer 33 formed so as to cover the data electrode 32, It has a partition wall 34 formed on the dielectric layer 33 and a phosphor layer 35 formed on the surface of the partition wall.

  A plurality of data electrodes 32 on the back substrate 31 are formed in parallel to each other. On the dielectric layer 33 that covers the data electrode 32, a cross-shaped barrier rib 34 having a vertical barrier rib 34a and a horizontal barrier rib 34b is formed. Further, red (R), green (G), and blue (B) phosphor layers 35 are formed on the surface of the dielectric layer 33 and the side surfaces of the partition walls 34. In addition, it is not an essential requirement in the plasma display panel of the present embodiment that the barrier ribs 34 are configured in a grid pattern with the vertical barrier ribs 34a and the horizontal barrier ribs 34b, and the use of RGB three colors as the phosphors. Alternatively, a partition wall only in the horizontal direction can be used, and phosphors other than RGB three colors can be used.

  The front plate 20 and the back plate 30 are arranged to face each other so that the display electrode 24 and the data electrode 32 formed on the inner surfaces thereof are substantially orthogonally intersected with each other, and the display electrode 24 and the data electrode 32 face each other. Thus, discharge cells are formed at the intersecting portions. In the front substrate 21 and the rear substrate 31, the portion where the discharge cells are formed becomes an image display region for displaying an image, and the peripheral portions of the front substrate 21 and the rear substrate 31 surrounding the image display region from the outside are sealed with low melting glass. It is sealed with a receiving member. A discharge gas is sealed in a discharge space formed between the front plate 20 and the back plate 30.

  For the protective layer 27 of the plasma display panel according to the present embodiment, a vapor deposition film mainly composed of calcium oxide (CaO) is used, and a Ne—Xe mixed gas containing 20% Xe is used as a discharge gas. The size of one discharge cell corresponding to one pixel is 576 μm in length and 160 μm in width. The specifications of the other display electrodes 24, dielectric layer 26, phosphor layer 35, etc. are the same as those of a general plasma display panel, and detailed description thereof will be omitted.

  FIG. 2 is a block diagram showing a configuration example of a drive circuit for driving the plasma display panel of the present embodiment.

  As shown in FIG. 2, a scan driver 41 that applies a predetermined voltage is connected to the scan electrode 22 of the plasma display panel 10, and a sustain driver 42 is connected to the sustain electrode 23 of the plasma display panel 10. . Further, a data driver 43 for applying a voltage for determining a gradation in each pixel is connected to the data electrode 32 on the back plate, and a scan driver 41, a sustain driver 42, and a data driver 43 are connected to the panel drive circuit 44. Has been. Then, after applying a predetermined voltage between the scan electrode 22 and the data electrode 23 of the discharge cell to be turned on to perform address discharge, a pulse voltage is applied between the scan electrode 22 and the sustain electrode 23. Sustain discharge is performed. The ultraviolet rays generated by the discharge generated in the discharge cells in this way cause the phosphor layer 35 to emit light and display an image.

  In the plasma display panel 10 of the present embodiment, calcium carbonate (CaO) is used as the protective layer 27 as described above. CaO is superior in secondary electron emission characteristics of the member itself as compared with MgO that has been used as a typical protective layer material so far, so that the discharge start voltage of the plasma display panel can be lowered, and is lower. Image display with power consumption becomes possible. Further, the protective layer 27 of the plasma display panel 10 of the present embodiment has a refractive index of 1.560 at a wavelength of 406 nm.

  FIG. 3 is a scanning electron microscope (SEM) photograph of the protective layer of the plasma display according to the present embodiment. FIG. 3A shows a state in which the surface is viewed in plan, and FIG. 3B shows a cross-sectional configuration.

  FIG. 4 is a scanning electron micrograph of a protective layer of a plasma display panel as a comparative example. FIG. 4A is a plan view of the surface of FIG. ) Shows the structure of the cross section. The protective layer of the comparative example shown in FIG. 4 is made of the same CaO as the protective layer of this embodiment, but differs in that the refractive index at a wavelength of 406 nm is 1.575.

  As can be seen by comparing FIG. 3 and FIG. 4, the protective layer of CaO is formed such that columnar crystal grains are closely arranged. Then, the surface of the protective layer of the plasma display panel of this embodiment is formed with a square crystal having one side exceeding 100 nm as shown in FIG. 3A, as shown in FIG. Even in the cross-sectional configuration shown, each crystal grain grows larger and the protective layer is thick. On the other hand, as is clear from FIG. 4A, the plasma display protective layer of the comparative example shown in FIG. 4 is a small square whose surface crystal is several tens of nanometers or less in length, and FIG. In the cross-sectional structure shown, each crystal is small and the entire film thickness is thin.

  As described above, in the protective layer of the plasma display panel of this embodiment, crystals are greatly grown and a certain amount of voids exist in the film. In contrast, in the protective layer of the plasma display panel of the comparative example, since each crystal grain is small, a gap exists in the film, but its size is small. It can be understood that it appears as a rate.

  Next, the optical refractive index and discharge characteristics due to differences in the manufacturing conditions of the CaO protective layer will be described.

  FIG. 5 shows measurement results obtained by measuring the refractive index of the protective layer having a wavelength of 406 nm and the discharge voltage when operated as a completed panel when the deposition conditions of the CaO protective layer are changed.

  The measured plasma display panel is the same as the known plasma display panel manufacturing method, except for the material of the protective layer and the manufacturing conditions thereof.

  Specifically, as a front plate manufacturing process, a display electrode 24 composed of a scanning electrode 22 and a sustain electrode 23 is formed on a glass front substrate 21 by vapor deposition of a metal thin film or a transparent conductive film, and a dielectric is formed thereon. The body layer 26 is formed by vapor deposition or the like. On the dielectric layer 26 formed in this manner, while protecting the oxygen partial pressure and the substrate temperature, a protective layer 27 was formed by depositing CaO as a protective layer material by vacuum deposition.

  Further, as the back plate manufacturing process, the data electrode 32 is formed on the glass back substrate 31 by vapor deposition of a metal thin film, and the dielectric layer 33 that functions as a visible reflection layer is formed so as to cover the data electrode 32. . Further, vertical and horizontal grid-shaped partition walls 34 having a predetermined height are formed on the dielectric layer 33 at a predetermined pitch, and inside the space surrounded by the surfaces of the partition walls 34 and the surface of the dielectric layer 33, R, G, and B phosphor layers 35 are formed, respectively. Further, a low-melting glass paste as a sealing member is applied to a peripheral region on the back substrate 31 where the partition walls are not formed, and calcining is performed to remove a resin component or the like in the low-melting glass paste.

  Next, as a superimposition process, the front panel 20 on which the protective layer 27 is formed and the rear panel 30 after the rear panel process are separated from each other by the partition wall 34 between the display electrode on the front panel 20 and the data electrode 32 on the rear panel 30. The pixels are overlapped and held so as to cross each other at a predetermined interval and at a predetermined interval between the substrates.

  Thereafter, a sealing process is performed in which the periphery of the front plate 20 and the back plate 30 is sealed by heating to a temperature at which the low-melting glass, which is a sealing member applied around the back plate 30, melts. While heating the panel to the following temperature, the inside of the panel was evacuated, and after the completion of evacuation, an Ne—Xe mixed gas containing 20% Xe was introduced.

  Thereafter, a plasma display panel is completed by performing an aging process in which a strong discharge is generated by applying an alternating voltage higher than that during normal operation to the display electrodes 24 formed in the panel so that stable discharge can be performed. . In measuring the data in FIG. 5, the aging process was performed for about 10 hours with a sustain discharge having a frequency of 150 kHz using the drive circuit shown in FIG.

  In FIG. 5, the panel 1 has a CaO vapor deposition condition of an oxygen partial pressure of 0.058 Pa, a front plate 20 temperature of 380 degrees, and a CaO vapor deposition rate of 4 angstroms / second. The panel 1 is the panel of the Example which showed the scanning electron micrograph of the protective layer in FIG.

  Panel 2 has an oxygen partial pressure of 0.058 Pa, a substrate temperature of 300 degrees, and a deposition rate of 4 angstroms / second. Panel 3 has an oxygen partial pressure of 0.058 Pa, a substrate temperature of 300 degrees, and a deposition rate of 2 Angstrom / second.

  In FIG. 5, what is described as panel 4 is a comparative panel whose scanning electron micrograph is shown in FIG. 4. The oxygen partial pressure is 0.03 Pa, the substrate temperature is 300 degrees, and the deposition rate is 4. The CaO protective layer is vacuum-deposited under the condition of angstrom / second.

  In addition, when the protective layer was vacuum-deposited, the oxygen partial pressure was adjusted under the above conditions. However, the oxygen partial pressure was temporarily reduced to 0.1 Pa due to the influence of the gas released from the vapor deposition source and the chamber during the vapor deposition. There was also a rise to the extent.

  As shown in FIG. 5, the protective layer of panel 1 had an optical refractive index of 1.560 with respect to light having a wavelength of 406 nm, and the discharge voltage between the display electrodes was 145V. Also, in both panel 2 and panel 3 in which the oxygen partial pressure is 0.058 Pa, the optical refractive index for light with a wavelength of 406 nm is 1.552 or 1.553, and the discharge voltage between the display electrodes is 2 was 158V and panel 3 was 155V, and almost the same characteristics were obtained.

  On the other hand, as a comparative example, in the protective layer of panel 4 in which CaO is deposited at a low oxygen partial pressure of 0.03 Pa, the optical refractive index for light with a wavelength of 406 nm is as high as 1.575, and the discharge voltage between display electrodes is also high. It was as high as 209V.

  In the above examination, the optical refractive index is measured by using a prism coupler (manufactured by Metricon), which is an analyzer for measuring the refractive index and film thickness of a film, and allowing a laser beam having a wavelength of 405 nm to enter the film and optical waveguide. The incident angle at which the propagation mode was reached was measured, and the refractive index of the film was determined from the incident angle.

  As apparent from FIG. 5, the protective layer has an optical refractive index of 1.57 or less for light having a wavelength of 406 nm, and in the vapor deposition process of the protective layer, the oxygen partial pressure is 0.05 Pa or more and the substrate temperature is 300. It can be seen that a plasma display panel having a low discharge voltage and capable of being driven with low power consumption is obtained when the angle is ˜380 °.

  The reason can be considered as follows.

  When depositing a CaO film, the deposition source CaO, which is the material of the film, is decomposed into Ca clusters and O clusters, vaporized, and then recombined. Therefore, the deposited film is generally a film with many oxygen vacancies. For this reason, an oxygen gas is introduced into a chamber for vapor deposition at the time of vapor deposition, and the film formation is performed by increasing the oxygen partial pressure, whereby a CaO film having good crystallinity and large crystal grains can be obtained.

  Further, the vaporized CaO particles are deposited in a more stable state when adhering to the evaporation target substrate. For this reason, by heating the substrate to an appropriate temperature during vapor deposition, energy is given to the adhered CaO particles, and the CaO particles can grow as stable larger crystal grains. Furthermore, the size of the crystal grains also depends on the growth rate of the crystal grains, and larger crystal grains can be formed when the deposition rate is reduced and the growth rate is decreased.

  As shown in FIGS. 3 and 4, a film having large crystal grains has a large surface area due to a large number of crystal grain boundaries, that is, gaps between crystal grains, and is a film that easily absorbs gas. Thus, a film having a large porosity has a small optical refractive index.

  A CaO film having large crystal grains has a structure in which voids in the film are easily exposed to space. Therefore, gas impurities such as carbon dioxide adsorbed after the film formation are easily desorbed from the CaO film by a vacuum heat treatment such as a subsequent exhaust process. In addition, when a discharge is generated in the completed panel, the CaO film on the display electrode is sputtered by the discharge, but gas impurities are easily released due to the wide gap between the crystal grains, and further released. Gas impurities are likely to be adsorbed by a protective layer that is not located on the display electrode that is not sputtered. For this reason, in the protective layer with a wide space between crystal grains, the CaO protective layer on the display electrode is more easily cleaned.

As described above, in the plasma display panel of this embodiment, the refractive index of the protective layer with respect to light having a wavelength of 406 nm is smaller than 1.57, that is, the protective layer surface is moderately rough. For this reason, although it has a high secondary electron emission characteristic, its activity is also high. It reacts with H ₂ O in the atmosphere to calcium hydroxide (Ca (OH) ₂ ), and reacts with CO _{2 in} the atmosphere to produce calcium carbonate. Even CaO, which is easily changed to (CaCO ₃ ), is sputtered by the subsequent discharge during the vacuum heating process or panel operation, so that the adsorbed H ₂ O and CO ₂ are easily released, and the original high discharge characteristics of CaO are obtained. A plasma display panel capable of utilizing the low voltage operation can be obtained.

  In addition, according to the method for manufacturing a plasma display panel of the present invention, since the CaO protective layer is deposited under the conditions of an oxygen partial pressure of 0.05 Pa or more and a substrate temperature of 300 to 380 degrees, the growth of CaO crystal grains And a protective layer having a large gap can be formed.

  In addition, since the oxygen partial pressure at the time of vapor deposition is set to 0.05 Pa or less and the substrate temperature is set to 300 ° C. to 380 ° C., it is possible to promote the growth of crystal grains of the CaO film. Can be formed. However, in order to obtain a better protective layer, the refractive index of the formed protective layer with respect to light having a wavelength of 406 nm is preferably 1.57 or less.

  In the description of the plasma display panel of the present invention, the case where CaO is used as the protective layer material has been exemplified. However, the protective layer material of the plasma display panel of the present embodiment is not limited to CaO, and as a protective layer member having a high electron emission characteristic and high so-called γ characteristics as compared with MgO that has been conventionally used in the same way as CaO, Strontium (SrO) and barium oxide (BaO) can be used. Furthermore, a mixture containing two or more substances of CaO, SrO, and BaO described above can be suitably used for the protective layer as a material having high secondary electron emission characteristics.

In any protective layer using any material, the optical refractive index with respect to light having a wavelength of 406 nm is 1.57 or less, so that H ₂ O and CO ₂ absorbed in the film can be easily released, and the low voltage A plasma display panel capable of operation can be obtained.

  Further, as a method for depositing a protective layer such as CaO, the above embodiment has exemplified the vacuum deposition method. However, as a method for depositing the protective layer in the plasma display panel manufacturing method of the present invention, various physical vapor deposition methods (PVD) such as sputtering method or ion plating method are similarly used in addition to the vacuum vapor deposition method. be able to.

  As described above, the plasma display panel and the plasma display panel manufacturing method of the present invention are useful in providing a plasma display device that is driven at a low voltage with reduced power consumption.

10 Plasma display panel 20 Front plate 21 Front substrate (one substrate)
24 display electrode (electrode)
26 Dielectric layer 27 Protective layer 30 Back plate 31 Back substrate 32 Data electrode

Claims (1)

A pair of substrates on which electrodes for generating discharge are formed on the respective inner surfaces are opposed to each other through a space, and a dielectric layer covering the electrodes formed on one of the pair of substrates and the dielectric A method of manufacturing a plasma display panel comprising a protective layer covering a body layer,
The protective layer forming step of forming the protective layer formed of any one of calcium oxide, strontium oxide, barium oxide, or a mixture thereof on the dielectric layer of the one substrate has an oxygen partial pressure of 0. Under an oxygen atmosphere of 05 Pa or more and under an environmental temperature of 300 to 380 degrees, the substrate temperature is performed by vacuum deposition.
The method for manufacturing a plasma display panel, wherein the protective layer has an optical refractive index of 1.57 or less with respect to light having a wavelength of 406 nm.