JP2009231214A - Front plate for plasma display panel, and plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a front plate for plasma display panel (PDP) in which a suitably design is optically made, and the PDP assembling the front plate for a PDP. <P>SOLUTION: The front plate 11 for a PDP includes a transparent substrate 30, a plurality of display electrodes 41, 42 formed on the substrate, a transparent dielectric layer 34 formed on the substrate 30 so as to cover the display electrodes 41, 42, and a transparent protection layer 35 formed on the dielectric layer 34. The dielectric layer 34 is formed to be a laminated structure including a first layer and a second layer respectively having different refractive indexes. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a front plate for a plasma display panel and a plasma display panel.

  A plasma display panel (hereinafter referred to as “PDP”) has been commercialized as a display panel of a thin television using plasma emission of gas discharge. There are direct current (DC) and alternating current (AC) types of PDPs due to the difference in discharge formation technique, but the AC type PDP is superior to the DC type PDP in terms of luminance, luminous efficiency, and life. Therefore, at present, AC type PDP is widely used as a display panel of a large screen thin television.

  In the front plate of the AC type PDP, a plurality of pairs of display electrodes, each consisting of a scan electrode and a sustain electrode, which are parallel to each other, are formed on the back surface of the front glass substrate. A dielectric layer and a protective layer are formed on the back surface of the front glass substrate so as to cover the pair of display electrodes. Then, by applying an appropriate alternating voltage between the pair of display electrodes, a sustain discharge (surface discharge) is formed between both electrodes substantially parallel to the front plate. Thereby, appropriate luminance of the PDP is ensured.

By the way, in the PDP described above, various efforts have been conventionally made to improve the brightness of the PDP (see, for example, Patent Document 1). According to the PDP described in Patent Document 1, a dielectric layer having reflectivity is formed on the back plate facing the front plate of the above-described PDP. As a result, light directed toward the back plate of the PDP can be reflected by the dielectric layer in the direction of the front plate of the PDP, so that unnecessary emission of light is reduced and the brightness of the PDP can be improved.
JP 2001-15035 A

  By the way, as far as the inventors of the present invention know, there is a serious oversight in the conventional efforts in terms of improving the brightness of the PDP. The critical oversight is the optimal optical design of the dielectric layer formed on the front glass substrate of the PDP.

The conventional dielectric layer is a transparent film made of, for example, lead-based or lead-free low-melting glass or silicon oxide (SiO ₂ layer), and the thickness is adjusted to a range of several μm to several tens μm. It is provided on the back surface (discharge cell side) of the front glass substrate 30. Thereby, a current limiting function peculiar to AC type PDP is exhibited, and a long life is realized compared with DC type PDP.

FIG. 6 is a cross-sectional view showing a configuration example of a conventional front plate for PDP. FIG. 7 is a diagram showing a calculation result of the reflectance of the conventional front plate, where the horizontal axis represents the wavelength of light (nm) and the vertical axis represents the light reflectance (%). This numerical calculation is performed using a commercially available optical simulator (“Optcalc” manufactured by Techwave). In this numerical calculation, the refractive index of the front glass substrate 60 is set to 1.54 when the center wavelength (λ ₀ ) is 550 nm, and the reflection by the back surface opposite to the incident light of the front glass substrate 60 is performed. Is ignored.

The front glass substrate 60 of the front plate 61 has a 20000 nm silicon oxide layer (SiO ₂ layer) as the dielectric layer 64 and a 200 nm magnesium oxide layer (MgO layer) as the protective layer 65 in this order. Is formed. The material, refractive index (n), film thickness (d), and “nd × 4 / λ” of each layer of the conventional front plate 61 are collectively shown in Table 1 below.

  In the design of the optical film, the optical thin film (nd), which is the product of the deposition thickness (physical film thickness (d)) of the substance and the refractive index (n) of the substance, is set to 1 / (wavelength). The value “nd × 4 / λ” divided by 4 is often used because it represents a phase shift.

  Table 1 Configuration of the front plate for conventional PDP

  According to FIG. 7, the reflectance of the conventional front plate 61 reaches 12% near the wavelength of 450 nm, and it was confirmed that the light reflection loss of the front plate 61 is extremely large.

  That is, in the conventional front plate 61, as the material for the dielectric layer 64, only silicon oxide having a good light transmittance and a low refractive index is selected. In this case, it cannot be said that the above-described dielectric layer 64 is optically optimally designed.

  Further, as an adverse effect of selecting silicon oxide having a low refractive index, the dielectric constant of the dielectric layer 64 is lowered. For this reason, the defect that the thickness of the dielectric material layer 64 becomes thick so that a wall charge can be appropriately hold | maintained in a discharge cell is also included.

  The present invention has been made in view of such circumstances, and includes a PDP front plate having a dielectric layer that is optically designed appropriately, and a PDP incorporating the PDP front plate. The purpose is to provide.

In order to solve the above problems, the present invention provides a transparent substrate, a plurality of display electrodes formed on the substrate, a transparent dielectric layer formed on the substrate so as to cover the display electrodes, and the dielectric A transparent protective layer formed on the body layer,
Provided is a front plate for a plasma display panel, wherein the dielectric layer has a laminated structure in which the dielectric layer includes a first layer and a second layer having different refractive indexes.

  In the stacked structure, the first layer and the second layer having a refractive index higher than that of the first layer may be alternately stacked.

  As described above, since the dielectric layers are laminated with layers having different refractive indexes, the reflection of incident light (visible light) can be prevented using the light interference effect, and the light reflection loss can be appropriately and sufficiently reduced. .

  The first layer may be a layer made of magnesium fluoride.

  This is preferable because the refractive index of the first layer can be appropriately and sufficiently reduced.

  The second layer may be a layer made of tantalum oxide.

  Thereby, the relative dielectric constant of the second layer can be appropriately and sufficiently increased, and as a result, the thickness of the dielectric layer can be reduced, which is preferable.

  The display electrode may include a transparent electrode in contact with the dielectric layer, and a refractive index of the transparent electrode may be different from a refractive index of the first layer.

  As a result, an optical design that takes into account the refractive index of the transparent electrode can be performed, and as a result, the light reflection loss of the front plate for PDP is appropriately and sufficiently reduced.

  The display electrode may include a transparent electrode in contact with the dielectric layer, and a refractive index of the transparent electrode may be equal to a refractive index of the first layer.

  As a result, an optical design that takes into account the refractive index of the transparent electrode can be performed, and as a result, the light reflection loss of the front plate for PDP is appropriately and sufficiently reduced.

  As a specific configuration example, the thickness of the first layer may be equal to the thickness of the transparent electrode, or the first layer may be formed only on the substrate other than the region where the transparent electrode is formed. Good. In this case, if both materials are appropriately selected so that the refractive index of the transparent electrode and the refractive index of the first layer are equivalent, it is convenient because the transparent electrode can exhibit the same optical function as the first layer. .

  As another configuration example, the first layer may be formed on the substrate so as to cover the display electrode, and the electrode formation surface of the substrate and the surface of the first layer are formed over the entire surface of the substrate. The distance between them may be constant. In this case, if both materials are appropriately selected so that the refractive index of the transparent electrode and the refractive index of the first layer are equal, the transparent electrode can apparently function optically as a part of the first layer. convenient.

  The protective layer may be a layer made of magnesium oxide.

  In addition, the present invention provides a plasma display panel for a plasma display panel in which a plurality of data electrodes are formed so as to face the front plate for the plasma display panel and the front plate for the plasma display panel and intersect the display electrodes. And a back panel of the plasma display panel.

  The above-described dielectric layer can appropriately function as an antireflection film that improves light transmittance. For this reason, the visible light transmittance of the front plate is increased, and as a result, the brightness of the plasma display panel can be improved.

  The present invention can provide a front panel for a PDP having the above-described configuration and having a dielectric layer that is optically appropriately designed, and a PDP incorporating the front panel for the PDP. There is an effect.

  First, a schematic configuration of the plasma display panel of the present embodiment will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a main part of a plasma display panel used in an embodiment of the present invention. In FIG. 1, in order to facilitate understanding of the structure of the plasma display panel 100 (hereinafter referred to as “PDP 100”), a form in which the front plate 11 and the back plate 10 are separated in the thickness direction of the PDP 100 is depicted.

  As shown in FIG. 1, the PDP 100 mainly includes a rectangular back plate 10, a rectangular front plate 11, and striped partition walls 12 provided between the back plate 10 and the front plate 11. The back plate 10 has a transparent back glass substrate 20, and the front plate 11 has a transparent front glass substrate 30.

  In such a PDP 100, the electrode forming surface (back surface) of the back glass substrate 20 in the back plate 10 and the electrode forming surface (back surface) of the front glass substrate 30 in the front plate 11 are both electrodes (described later). Are opposed so as to be orthogonal. In a state where the back plate 10 and the front plate 11 are overlapped, the gap between the two is regulated by the height of the partition wall 12, and the discharge gas is sealed in this gap.

  A plurality of strip-shaped (stripe-shaped) data electrodes 21 made of an electrode material containing silver (Ag) or the like and extending in the first direction are provided on the back glass substrate 20 described above. The data electrode 21 functions as an address voltage application electrode that generates an address discharge for forming wall charges with the scan electrode 41 (described later).

In addition, a transparent dielectric layer 22 made of lead-based or non-lead-based low-melting glass or silicon oxide (SiO ₂ ) is adjusted to a thickness of several μm to several tens μm so as to cover the data electrode 21, and the back surface. It is provided on the back surface of the glass substrate 20. Thereby, a current limiting function peculiar to AC type PDP is exhibited, and a long life is realized compared with DC type PDP.

  An antireflection film (not shown) is attached to the surface of the front glass substrate 30 described above.

On the other hand, on the back surface of the front glass 30, a pair of high-resistance striped transparent electrodes 32 made of indium tin oxide (ITO), tin oxide (SnO ₂ ), or zinc oxide (ZnO) is adjusted to a thickness of about 100 nm. And extends in the second direction. Each transparent electrode 32 is formed wide on the back surface of the front glass substrate 30 while securing a certain gap G so that adjacent transparent electrodes 32 do not short-circuit each other. A pair of low-resistance strip-shaped bus electrodes (opaque electrodes) 33 made of silver (Ag) or aluminum (Al) -based electrode material for the purpose of lowering electrode resistance is provided on each surface of the pair of transparent electrodes 32. The thickness is adjusted to several μm and extends in the second direction. The width of each bus electrode 33 is set from the viewpoint that low resistance characteristics can be maintained and that light emission emitted from the discharge cell 23 to the outside is blocked and luminance reduction of the PDP 100 is not unnecessary. For this reason, the width of the bus electrode 33 is at least narrower than the width of the transparent electrode 32.

  The dielectric layer 34 is adjusted to a predetermined thickness so as to cover the transparent electrode 32 and the bus electrode 33 and is provided on the back surface of the front glass substrate 30. Thereby, a current limiting function peculiar to AC type PDP is exhibited, and a long life is realized compared with DC type PDP. The detailed configuration of the dielectric layer 34 will be described later.

  A transparent protective layer 35 using a metal oxide material such as MgO (magnesium oxide) is provided on the surface of the dielectric layer 34. This MgO material has a large secondary electron emission coefficient γ in order to enable the discharge start voltage to be lowered, has high sputter resistance so as to protect the dielectric layer 34 from discharge ion bombardment, and has transparency and insulation resistance. Are better. The protective layer 35 is adjusted to have a thickness of several hundred nm.

  In this way, the scanning electrode 41 of the band-like display electrode pair 50 in which the pair of transparent electrodes 32 and the pair of bus electrodes 33 are stacked is formed between the data electrode 21 and the above-described data electrode 21 for wall charge formation. It functions as an electrode for applying an address voltage for generating an address discharge. The scan electrode 41 also functions as a display electrode for applying a sustain voltage for generating a sustain discharge (surface discharge for ensuring PDP luminance) between the display electrode pair 50 and the sustain electrode 42. In other words, the sustain electrode 42 of the display electrode pair 50 functions as a display electrode for applying a sustain voltage that generates a sustain discharge with the scan electrode 41.

  Further, as shown in FIG. 1, a phosphor material paste corresponding to any one of red (R), green (G), and blue (B) is applied to an appropriate position of the back plate 10 by a screen printing method. Has been. As a result, the phosphors 24R, 24G, and 24B are not directly exposed to the sustain discharge (discharge plasma), for example, the surface of the dielectric layer 22 corresponding to the bottom surface of the discharge space of the discharge cell 23 and both side surfaces of the barrier rib 12. In addition, patterning is formed.

  Next, a configuration example of the dielectric layer 34 formed on the front glass substrate 30, which is a characteristic part of the present embodiment, will be described with reference to the drawings.

  FIG. 2 is a cross-sectional view showing an example of the configuration of the front plate for PDP according to the present embodiment. FIG. 2 shows a cross section of the gap G in FIG. 1 as viewed from the first direction.

  As shown in FIG. 2, the dielectric layer 34 formed on the front glass substrate 30 is made of a plurality of materials (two types here) having different refractive indexes and functions as an AR coat film (antireflection film). have. This laminated structure has a low refractive index layer 34a that is a layer in contact with the front glass substrate 30, and a high refractive index layer 34b having a higher refractive index than the low refractive index layer 34a. The low refractive index layers 34 a and the high refractive index layers 34 b are alternately stacked on the front glass substrate 30.

  Here, each of the low refractive index layer 34a and the high refractive index layer 34b is four layers, and the total number of layers in the laminated structure is eight. Further, a protective layer 35 (MgO layer) is provided on the surface of the finally laminated high refractive index layer 34b.

When magnesium fluoride (MgF ₂ ) having a refractive index of about 1.38 and a relative dielectric constant of about 5.0 is used as the material of the low refractive index layer 34a, the refractive index of the low refractive index layer 34a is appropriately set. Moreover, it can be sufficiently reduced, which is preferable. However, instead of magnesium fluoride, silicon oxide (SiO ₂ ) having a refractive index of 1.47 and a relative dielectric constant of about 3.9 may be used.

When tantalum pentoxide (Ta ₂ O ₅ ) having a refractive index of about 2.22 and a relative dielectric constant of about 25.0 is used as the material of the high refractive index layer 34b, the relative dielectric constant of the high refractive index layer 34b. The rate can be increased appropriately and sufficiently, and as a result, the thickness of the dielectric layer 34 can be reduced. However, instead of this tantalum pentoxide, titanium dioxide (TiO ₂ ) having a refractive index of 2.4 and a relative dielectric constant of about 8.0 may be used.

  Here, the dielectric layer 34 may be formed in multiple layers using a vacuum process (dry process) such as vacuum deposition or sputtering, or may be formed using a coating process (wet process) such as a screen printing method. Alternatively, a film may be formed.

Here, the AR coating film is realized by the combination of the low refractive index layer 34a and the high refractive index layer 34b described above, but instead, a medium refractive index layer made of a medium refractive index material is used. May be. Examples of materials for such a medium refractive index layer include magnesium oxide (MgO; refractive index: about 1.7, relative dielectric constant: about 10.0) and aluminum oxide (Al ₂ O ₃ ; refractive index: about 1.7). , Relative dielectric constant: about 10.0).

  Next, the operation of the PDP 100 will be described.

  First, the discharge space of the discharge cell 23 is filled with a mixed rare gas composed of Xe (xenon) and Ne (neon) or a mixed rare gas composed of Xe and He (helium) while maintaining a gas pressure of about several tens of kPa. The Then, by applying a voltage pulse of a sustain discharge as an appropriate AC voltage between the scan electrode 41 and the sustain electrode 42, a pulse discharge (sustain discharge) is generated in the discharge cell 23 in which an appropriate amount of wall charges is formed. appear. Then, based on the generation of the discharge gas plasma by the sustain discharge, a resonance line (ultraviolet ray) of 147 nm is emitted from the excited xenon atom existing in the discharge space of the discharge cell 23, and a molecular beam (ultraviolet ray) mainly composed of 173 nm is emitted from the excited xenon molecule. Radiated.

  Next, these ultraviolet rays strike each phosphor 24R, 24G, 24B of the discharge cell 23 and are converted into visible light corresponding to the color of each phosphor 24R, 24G, 24B, and this visible light is converted into each phosphor 24R, The light is emitted to the outside through the front plate 11 from 24G and 24B. As a result, the discharge cell 23 functions as a light emission minimum region of any one of R, G, and B. In addition, the discharge cell 23 in which an appropriate amount of wall charges is not formed does not generate a sustain discharge, and such a discharge cell 23 displays black.

  As described above, the front plate 11 for the PDP of the present embodiment is formed on the front glass substrate 30, and a plurality of display electrode pairs 50 each consisting of a scanning electrode 41 and a sustaining electrode 42 that make a pair, A transparent dielectric layer 34 formed on the front glass substrate 30 so as to cover the pair 50 of display electrodes, and a transparent protective layer 35 formed on the dielectric layer 34, the dielectric layer 34 having A laminated structure in which a low refractive index layer 34a made of a low refractive index material (for example, magnesium fluoride) and a high refractive index layer 34b made of a high refractive index material (for example, tantalum pentoxide) are alternately stacked. Yes.

  Thus, the dielectric layer 34 employs a configuration in which a plurality of two types of thin films having different refractive indexes are alternately stacked on the front glass substrate 30, so that compared to the conventional dielectric layer 64, By utilizing the light interference effect, reflection of incident light (visible light) can be prevented, and light reflection loss can be appropriately and sufficiently reduced. That is, the dielectric layer 34 can appropriately function as an antireflection film that improves the light transmittance. For this reason, the visible light transmittance of the front plate 11 for PDP is increased, and as a result, the luminance of the PDP can be improved.

  Further, since the relative dielectric constant of the high refractive index layer 34b in the dielectric layer 34 is high, there is an advantage that wall charges can be appropriately held in the discharge cell 23 even if the thickness of the dielectric layer 34 is reduced.

In addition, although the example using the front glass substrate 30 was described here, the thickness of the low-refractive index layer 34a and the high-refractive index layer 34b is not limited to such a substrate other than glass (for example, a resin substrate). By adjusting, the light transmittance of the front plate can be improved appropriately. Further, the number of layers of the low refractive index layer 34a and the high refractive index layer 34b can be changed according to the withstand voltage and the relative dielectric constant required for the low refractive index layer 34a and the high refractive index layer 34b. FIG. 2 illustrates an example in which the number of layers of the low refractive index layer 34a and the number of layers of the high refractive index layer 34b are the same, but the present invention is not necessarily limited thereto. For example, in FIG. 2, the number of layers of the low-refractive index layer 34a is increased by one from the number of layers of the high-refractive index layer 34b, and the uppermost layer (the last layer stacked) of the dielectric layer 34 is low-refracted. It is good also as the rate layer 34a (refer the below-mentioned Example).
(Modification)
In the present embodiment, the optical design of the front plate 11 has been described from the viewpoint of reducing the light reflection loss of the dielectric layer 34 that covers the scan electrode 41 and the sustain electrode 42, but the portion of the transparent electrode 32 that contacts the dielectric layer 34. Application to an antireflection film is also possible. That is, the material of the transparent electrode 32 constituting the scan electrode 41 and the sustain electrode 42 (display electrode) includes, for example, indium tin oxide (ITO), and taking into consideration such an indium tin oxide layer, Optical design of the front plate 11 may be performed. In this case, the refractive index of the transparent electrode 32 may be different from the refractive index of the low refractive index layer 34a, but indium tin oxide belongs to a high refractive index category (the refractive index of indium tin oxide is 2.0). About 2.1), the layer in contact with the front glass substrate 30 has a high refractive index equivalent to that of indium tin oxide such as Ta ₂ O ₅ (refractive index: 2.22) or TiO ₂ (refractive index: 2.4). You may comprise with the material which has.

Therefore, in the present modification, as described below with reference to FIG. 8, the material of the transparent electrode 32 (so that the refractive index of the transparent electrode 32 is substantially equal to the refractive index of the layer in contact with the front glass substrate 30 ( Specifically, indium tin oxide) and the material of the layer in contact with the front glass substrate 30 (specifically, Ta ₂ O ₅ or TiO ₂ described above) are selected. As described above, even if the high-refractive index layer 34b is alternately laminated on the front glass substrate 30 as a layer having a high refractive index layer 34b as a layer in contact with the front glass substrate 30, a multilayer dielectric layer is formed. By adjusting the number of layers 34 and the thickness of each layer, the reflection of incident light (visible light) can be prevented using the light interference effect as compared with the conventional dielectric layer 64, and the light reflection loss can be appropriately and sufficiently reduced. .

  In this case, the uppermost layer (the last layer laminated) of the dielectric layer 34 may be the high refractive index layer 34b or the low refractive index layer 34a.

  FIG. 8 is a cross-sectional view showing a configuration example of a front plate according to a modification of the present invention. However, for convenience of explanation, only the first layer of the display electrode pair 50 and the high refractive index layer 34b formed on the front glass substrate 30 is shown in FIG. The illustration of the layers is omitted.

  FIG. 8A shows a cross section of the front plate 11A when the thickness of the transparent electrode 32 constituting the display electrode pair 50 is equal to the thickness of the high refractive index layer 34b. As shown in FIG. 8A, the high refractive index layer 34b is a front glass other than the region where the transparent electrode 32 is formed (here, the stripe region sandwiched between the pair of transparent electrodes 32). It is formed only on the substrate 30. In this case, as described above, when a material having the same refractive index is selected as the material of the transparent electrode 32 and the high refractive index layer 34b, the transparent electrode 32 is optically equivalent to the high refractive index layer 34b. It is convenient because it can function.

  FIG. 8B shows a cross section of the front plate 11B when the high refractive index layer 34b is formed on the front glass substrate 30 so as to cover the pair 50 of display electrodes. As shown in FIG. 8B, the distance “l” between the electrode forming surface (back surface) of the front glass substrate 30 and the surface of the high refractive index layer 34 b is constant over the entire surface of the front glass substrate 30. Yes. In this case, as described above, when materials having the same refractive index are selected as the material of the transparent electrode 32 and the high refractive index layer 34b, the transparent electrode 32 is apparently one of the high refractive index layers 34b. Since it can function optically as a part, it is convenient.

Hereinafter, the reflectance of the multilayer dielectric film (first embodiment and second embodiment) in which the low refractive index layer (MgF ₂ layer) and the high refractive index layer (Ta ₂ O ₅ layer) are alternately laminated is described. State the calculation results. The calculation result of the reflectance of the single-layer dielectric film (comparative example) of the low refractive index layer (MgF ₂ layer) is also described.

Each numerical calculation described below is performed using a commercially available optical simulator (“Optcalc” manufactured by Techwave). In each numerical calculation, the refractive index of the front glass substrate is set to 1.54 at the center wavelength of 550 nm, and reflection by the back surface opposite to the incident light of the front glass substrate is ignored.
(First embodiment)
Table 2 below shows the material, refractive index (n), film thickness (d), and “nd × 4 / λ” of each layer of the multilayer dielectric film of the first example. That is, MgF ₂ layers and Ta ₂ O ₅ layers as dielectric layers are adjusted to the thicknesses shown in Table 2, and are alternately stacked in this order on the front glass substrate. Here, the MgF ₂ layer is 8 layers, the Ta ₂ O ₅ layer is 7 layers, and the total number of multilayer dielectric films is 15. In addition, an MgO layer of about 21 nm as a protective layer is provided on the surface of the last stacked MgF ₂ layer.

  Table 2 Configuration of front plate for PDP of first embodiment

  FIG. 3 is a graph showing the calculation result of the reflectance of the multilayer dielectric film of the front plate according to the first embodiment, where the horizontal axis represents the wavelength of light (nm) and the vertical axis represents the light reflectance (%). It is.

According to FIG. 3, the reflectance of the multilayer dielectric film of the front plate according to the first embodiment is 1% or less in almost the entire visible wavelength range (about 410 nm to 750 nm), and the light reflection of the front plate for PDP is reduced. It was found that the loss can be appropriately and sufficiently reduced.
(Second embodiment)
Table 3 below shows the material, refractive index (n), film thickness (d), and “nd × 4 / λ” of each layer of the multilayer dielectric film of the second example. That is, MgF ₂ layers and Ta ₂ O ₅ layers as dielectric layers are adjusted to the thicknesses shown in Table 3, and are alternately laminated on the front glass substrate in this order. Here, the MgF ₂ layer is 8 layers, the Ta ₂ O ₅ layer is 7 layers, and the total number of multilayer dielectric films is 15. In addition, an MgO ₂ layer having a thickness of about 155 nm is provided as a protective layer on the surface of the last stacked MgF ₂ layer.

  Table 3 Configuration of front plate for PDP of second embodiment

  FIG. 4 is a graph showing the calculation result of the reflectance of the multilayer dielectric film of the front plate according to the second embodiment, where the horizontal axis represents the wavelength of light (nm) and the vertical axis represents the light reflectance (%). It is.

  According to FIG. 4, the reflectance of the multilayer dielectric film of the front plate according to the second embodiment is 5% or less in almost the entire visible wavelength range (about 410 nm to 740 nm), and the light reflection loss of the front plate for PDP. It was found that can be adequately and sufficiently reduced.

Further, according to FIG. 4, even when the thickness (155 nm) of the MgO layer is the same level as the thickness (200 nm) of the MgO layer of the conventional front plate, the dielectric layer has a low refractive index made of magnesium fluoride. It was also found that the light reflection loss of the front plate can be reduced by using a laminated structure in which layers and high refractive index layers made of tantalum pentoxide are alternately laminated.
(Comparative example)
Table 4 below shows the material, refractive index (n), film thickness (d), and “nd × 4 / λ” of each layer of the single-layer dielectric film of the comparative example. That is, a 20000 nm MgF ₂ layer as a dielectric layer is formed on the front glass substrate, and a 200 nm MgO layer as a protective layer is formed on the surface of the MgF ₂ layer.

  Table 4 Film structure of front plate for PDP of comparative example

  FIG. 5 is a diagram showing numerical calculation results of the reflectance of the single-layer dielectric film of the front plate according to the comparative example, where the horizontal axis represents the wavelength of light (nm) and the vertical axis represents the light reflectance (%). It is.

According to FIG. 5, the reflectance of the single-layer dielectric film of the front plate according to the comparative example reaches 16% in the vicinity of the wavelength of 450 nm, which is the same level as the reflectance of the dielectric layer 64 of the conventional front plate 61. I found out. From this, it was confirmed that the single layer of MgF ₂ layer cannot exhibit the effect of reducing the light reflection loss of the front plate.

  According to the PDP front plate and the PDP of the present invention, the luminance of the PDP can be improved, and can be applied, for example, to a PDP as a display device for a thin television.

It is the perspective view which showed the principal part of the plasma display panel used for embodiment of this invention. It is sectional drawing which showed one structural example of the front plate for PDP of embodiment of this invention. It is the figure which showed the calculation result of the reflectance of the multilayer dielectric film of the front plate by a 1st Example by taking light wavelength (nm) on a horizontal axis and taking a light reflectance (%) on a vertical axis | shaft. It is the figure which showed the calculation result of the reflectance of the multilayer dielectric film of the front plate by a 2nd Example by setting light wavelength (nm) on a horizontal axis and taking a light reflectance (%) on a vertical axis | shaft. It is the figure which showed the numerical calculation result of the reflectance of the single layer dielectric film of the front plate by a comparative example by taking the wavelength (nm) of light on a horizontal axis, and taking light reflectance (%) on the vertical axis | shaft. It is sectional drawing which showed the example of 1 structure of the front plate for the conventional PDP. It is the figure which showed the calculation result of the reflectance of the conventional front board, taking the wavelength (nm) of light on a horizontal axis, and taking light reflectance (%) on the vertical axis | shaft. It is sectional drawing which showed one structural example of the front plate of the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Back plate 11, 11A, 11B Front plate 12 Partition 20 Back glass substrate 21 Data electrode 22 Dielectric layer 23 Discharge cell 24R, 24G, 24B Phosphor 30 Front glass substrate 32 Transparent electrode 33 Bus electrode 34 Dielectric layer 35 Protective layer 41 Scan electrode 42 Sustain electrode 50 Display electrode pair

Claims (10)

A transparent substrate,
A plurality of display electrodes formed on the substrate;
A transparent dielectric layer formed on the substrate so as to cover the display electrodes;
A transparent protective layer formed on the dielectric layer;
With
A front plate for a plasma display panel, wherein the dielectric layer has a laminated structure including a first layer and a second layer having different refractive indexes.   2. The front plate for a plasma display panel according to claim 1, wherein the laminated structure is formed by alternately laminating the first layer and the second layer having a refractive index higher than that of the first layer.   The front plate for a plasma display panel according to claim 2, wherein the first layer is a layer made of magnesium fluoride.   The front plate for a plasma display panel according to claim 2 or 3, wherein the second layer is a layer made of tantalum oxide.   The plasma display panel according to claim 1, wherein the display electrode includes a transparent electrode in contact with the dielectric layer, and a refractive index of the transparent electrode is different from a refractive index of the first layer. Front plate.   The front plate for a plasma display panel according to claim 1, wherein the display electrode includes a transparent electrode in contact with the dielectric layer, and a refractive index of the transparent electrode is equal to a refractive index of the first layer.   7. The plasma display panel for a plasma display panel according to claim 6, wherein the thickness of the first layer is equal to the thickness of the transparent electrode, and the first layer is formed only on the substrate other than the region where the transparent electrode is formed. Front plate.   The first layer is formed on the substrate so as to cover the display electrode, and the distance between the electrode forming surface of the substrate and the surface of the first layer is constant over the entire surface of the substrate. The front plate for a plasma display panel according to claim 6.   The front plate for a plasma display panel according to any one of claims 1 to 8, wherein the protective layer is a layer made of magnesium oxide. A front plate for a plasma display panel according to any one of claims 1 to 9,
A back plate for a plasma display panel, which is arranged opposite to the front plate for the plasma display panel and in which a plurality of data electrodes intersecting the display electrodes are formed,
A plasma display panel comprising:

Images