JP4928766B2 - Oxide glass and display panel using the same - Google Patents

Description

  The present invention relates to an oxide glass and a display panel using the same.

  A substrate having an electrode or a wiring on its surface in a display device or integrated circuit such as a plasma display panel (hereinafter referred to as PDP), a field emission display (FED), a liquid crystal display (LCD), a ceramic laminated device, a hybrid integrated circuit, etc. Is used. An electrode or the like on the substrate surface is protected by being covered with an insulating glass material. A PDP will be specifically described as an example.

  A general PDP has a structure in which a pair of regularly arranged electrodes are provided on two opposing glass substrates, and a discharge gas containing an inert gas such as Ne or Xe is enclosed between the electrodes. . By applying a voltage between both electrodes and generating a discharge in a minute cell around the electrode, each cell can emit light and display can be performed. For example, a glass substrate serving as a front plate of an AC type PDP has a structure in which a transparent electrode is formed on a main surface on the back side and a metal electrode is formed on the transparent electrode. Further, a dielectric layer is formed so as to cover the composite electrode composed of the transparent electrode and the metal electrode, and a protective layer is formed on the dielectric layer.

  Usually, one material selected from the low resistivity metal group consisting of Ag, Cu and Al is used as the material of the metal electrode. There are a thin film method and a thick film method as a method of forming the metal electrode. In the thin film method, Cu or Al is used, and in order to improve adhesion and oxidation resistance with the underlying transparent electrode, an electrode with a laminated structure of different metal materials such as Cr / Cu / Cr or Cr / Al / Cr is used. Is generally configured.

  On the other hand, in the thick film method, a metal electrode is formed using a thick film conductor paste containing Ag or Cu, particularly Ag having excellent oxidation resistance. After the thick film conductor paste is patterned into an electrode shape by a printing method, the desired metal electrode can be formed by firing the thick film conductor paste together with the glass substrate. According to such a method, a vacuum apparatus is not required, and pattern processing can be performed with a minimum of one process. Therefore, there is a feature that the cost is low, and it is widely studied.

  The dielectric layer covering the metal electrode is usually formed of glass with a low softening temperature. Specifically, a dielectric layer is formed by applying a paste containing glass powder onto an electrode by a printing method or a die coating method, and then firing the applied glass paste together with the glass substrate.

Accordingly, the dielectric layer glass formed on the glass substrate is required to have the following characteristics.
(1) It must be insulative.
(2) The thermal expansion coefficient is close to the thermal expansion coefficient of the glass substrate (preferably somewhat smaller than the glass substrate) in order to prevent warping of the glass substrate and peeling and cracking of the dielectric layer.
(3) When the glass substrate is a PDP front plate, it is an amorphous glass having a high visible light transmittance in order to efficiently use light generated from the phosphor as display light.
(4) The softening temperature is low in accordance with the heat resistance of the glass substrate.

PbO—SiO ₂ glass mainly containing PbO is generally used as the glass that satisfies the above demands. In recent years, glass containing no Pb has also been studied in consideration of environmental problems. As such a glass, for example, there is a Bi ₂ O ₃ —B ₂ O ₃ —ZnO—SiO ₂ type glass mainly composed of zinc borate and realizing a low softening temperature by adding Bi instead of Pb ( Patent Document 1).

  On the other hand, in order to reduce the power consumption of the PDP, the dielectric layer glass is required to have a low dielectric constant. The Bi-based glass described above has a high relative dielectric constant of 9 to 13 like the Pb-based glass. On the other hand, glass having a relative dielectric constant of 8 or less is desired as a glass having a clear difference.

Therefore, in order to achieve both a low dielectric constant and a low softening temperature, a zinc borate glass having a relative dielectric constant of about 7 has been proposed by adding an alkali metal instead of Pb (Patent Document 2). . In addition, a glass containing Bi and an alkali metal at the same time has been proposed, although the relative dielectric constant is not low (Patent Document 3).
JP 2001-139345 A JP-A-9-278482 JP 2003-128430 A

  By the way, in the manufacturing process of the PDP, near 500 ° C. heat is applied to the dielectric layer covering the electrodes in the annealing process of the protective layer (MgO protective layer) and the sealing process of joining the front plate and the back plate. If the softening temperature of the dielectric layer glass is around 600 ° C., it seems that there is no problem even if a temperature of about 500 ° C. is applied, but this is not the case. This is because if the heating temperature in the annealing process or the sealing process significantly exceeds the glass transition temperature of the dielectric layer glass, the thermal expansion coefficient of the dielectric layer increases rapidly.

  The rapid increase in the coefficient of thermal expansion causes the dielectric layer to peel off from the substrate and generate cracks. As a result, the insulation between the electrodes may be reduced, and as a result, the reliability of the product may be reduced. Such a problem becomes particularly noticeable in a large-area PDP, but there is a risk that it also occurs in display devices and circuit boards other than the PDP. According to the study by the inventors, in order to reheat at about 500 ° C., the glass transition temperature of the dielectric layer glass needs to be at least 465 ° C., and more desirably 480 ° C. or more.

However, the conventional alkali zinc borate glass has a low glass softening temperature, an appropriate thermal expansion coefficient (in a temperature range lower than the glass transition temperature), and a low dielectric constant. It was not realized. Moreover, in order to achieve a low dielectric constant in an alkaline glass, it is necessary to increase the content of B ₂ O ₃ , but if B is contained excessively, there is a problem that the glass transition temperature is lowered.

Furthermore, the alkaline glass having a high B content also has a problem that its components are likely to sublime when subjected to heat treatment. The sublimation phenomenon presumed to be the evaporation of B ₂ O ₃ occurs remarkably mainly from the glass transition temperature to the softening temperature. In the PDP, the evaporation component may adhere to other portions of the substrate to lower the insulating property, or may penetrate into the MgO protective film formed on the dielectric layer to deteriorate the characteristics of the protective film. .

  Thus, the conventionally proposed electrode coating glass (dielectric layer glass) has not been sufficiently studied for the glass transition temperature, and is not necessarily suitable for the production of PDPs and the like. Therefore, it is expected to develop a glass having a high glass transition temperature as well as a low softening temperature, a low dielectric constant, and an appropriate thermal expansion coefficient.

  In view of the above circumstances, the present invention is suitably used for oxide glass having a low softening temperature and dielectric constant, a good thermal expansion coefficient matching with the substrate, and a sufficiently high glass transition temperature, particularly a display panel. An object is to provide an oxide glass that can be formed. Another object of the present invention is to provide a display panel using the oxide glass.

The present invention is represented by the ratio of other elements excluding oxygen among the contained elements,
B is 55 atomic% or more and 85 atomic% or less,
Si is 0 atomic% or more and 15 atomic% or less,
Zn is 0 atomic% or more and 15 atomic% or less,
K is 0 atomic% or more and 10 atomic% or less,
Na is 0 atomic% or more and 10 atomic% or less,
Bi is 1 atomic% or more and 10 atomic% or less,
The total of Si and Zn is 5 atomic% or more and 30 atomic% or less,
The total of K and Na is 1 atomic% or more and 10 atomic% or less,
The total of K, Na and Bi is 8 atomic% or more and 15 atomic% or less,
An oxide glass is provided.

  The present invention also provides a display panel using the oxide glass as an electrode coating glass.

The present invention also provides:
A substrate,
An electrode mainly composed of Ag formed on the substrate;
A first dielectric layer that directly covers the electrode and is substantially free of alkali metal;
A second dielectric layer disposed on the first dielectric layer such that the first dielectric layer is located between the electrode and the electrode,
A display panel is provided in which a second dielectric layer is made of the above oxide glass.

The present invention also provides:
A substrate,
An electrode mainly composed of Ag formed on the substrate;
A first dielectric layer directly covering the electrode;
A second dielectric layer disposed on the first dielectric layer such that the first dielectric layer is located between the electrode and the electrode,
The first dielectric layer is made of the above oxide glass,
Provided is a display panel, wherein the second dielectric layer is made of glass having a lower dielectric constant than the oxide glass.

  As a result of detailed studies, the present inventors have used Bi and K or Na in combination, and (i) the softening temperature can be lowered in a small amount as compared with the case where they are contained alone, (Ii) The present invention has been completed by finding that the glass transition temperature can be sufficiently increased and the amount of component evaporation during heat treatment can be reduced even in a composition having a high B content of 55 atomic% or more. Since the amount of B can be increased while keeping the amount of Bi (content) small, it is possible to reduce the dielectric constant. Thus, the oxide glass having the composition of the present invention can balance a low softening temperature, an appropriate thermal expansion coefficient matching with the substrate, a low dielectric constant, and a high glass transition temperature. By forming a dielectric layer that covers an electrode or the like with such an oxide glass, a highly reliable product such as a display panel can be manufactured.

The oxide glass of the present invention will be described in detail.
The oxide glass of the present invention has B ₂ O ₃ , K ₂ O or Na ₂ O, and Bi ₂ O ₃ as essential components, and by adding SiO ₂ , ZnO, and other components to this, its characteristics are obtained. Is adjusted. In the present specification, the ratio of each element is displayed assuming that the total of the ratios (content ratios) of elements other than oxygen among the elements contained in the oxide glass is 100 atomic%.

B ₂ O ₃ is a main component of the oxide glass of the present invention. If the ratio of B is too small, the dielectric constant increases, and if it is too large, the glass transition temperature decreases. Therefore, the ratio of B is preferably 55 atom% or more and 85 atom% or less.

SiO ₂ has the effect of stabilizing the glass. However, if the Si ratio is too large, the glass transition temperature becomes too low, or the softening temperature becomes too high. Accordingly, the Si ratio is preferably 0 atomic% or more and 15 atomic% or less.

Similar to SiO ₂ , ZnO also has the effect of stabilizing the glass. However, when the ratio of Zn is too large, the dielectric constant becomes too high. Therefore, the Zn ratio is preferably 0 atomic% or more and 15 atomic% or less.

  In order to prevent the glass transition temperature from becoming too low, the sum of the Si ratio and the Zn ratio is preferably 5 atomic% to 30 atomic%.

K ₂ O or Na ₂ O is an essential component of the oxide glass of the present invention, and has an effect of lowering the softening temperature. When the sum of the ratio of K and the ratio of Na is too small, it becomes difficult to obtain a glass having a uniform structure, whereas when it is too large, yellowing tends to occur. Therefore, the sum of the ratio of K and the ratio of Na is preferably 1 atom% or more and 10 atom% or less.

  Yellowing refers to the following phenomenon. Since the glass containing an alkali metal such as the oxide glass of the present invention contains an alkali metal as a component, when used as a dielectric material for protecting an electrode containing Ag or Cu, depending on the firing conditions, the Ag Or Cu is oxidized and ionized, and these ions may diffuse in the glass. Ag and Cu ions are reduced again and deposited as colloidal metal, causing a so-called yellowing in which the dielectric layer and the glass substrate appear to be colored yellow. When yellowing occurs, the display performance deteriorates particularly when used as a dielectric layer for a front panel of a PDP. According to the oxide glass of the present invention, since the amount of the alkali metal is small, the yellowing phenomenon due to the reaction with the electrode material hardly occurs.

Bi ₂ O ₃ is an essential component of the oxide glass of the present invention, and has the effect of lowering the softening temperature and stabilizing the glass. If the ratio of Bi is too small, the amount of evaporation of B during heat treatment increases, and it becomes necessary to use a large amount of alkali metal to lower the softening temperature, and yellowing is likely to occur. On the other hand, if the ratio of Bi is too large, the dielectric constant becomes too high and the coloring of the glass becomes strong. Therefore, the ratio of Bi is preferably 1 atomic% or more and 10 atomic% or less.

  Furthermore, it is preferable that the total of the ratio of K, the ratio of Na, and the ratio of Bi is 8 atomic% or more and 15 atomic% or less. This is because if the sum of the ratio of K, the ratio of Na, and the ratio of Bi is too small, the softening temperature becomes too high, and if it is too large, the glass transition temperature becomes too low.

  As described above, the oxide glass of the present invention contains B, at least one of Si and Zn, at least one of K and Na, and Bi as essential elements.

  Hereinafter, optional components that can be added to the oxide glass of the present invention will be described. Examples of optional components that can be added include Mg, Ca, Sr, Ba, Mo, and W.

  Mg, Ca, Sr, and Ba are not essential components, but when these alkaline earth metals are added, the glass transition temperature can be increased without greatly changing the softening temperature. However, if the ratio of these alkaline earth metals is too large, both the dielectric constant and the softening temperature are too high. Therefore, it is preferable to contain at least one selected from Mg, Ca, Sr and Ba in the range of more than 0 atomic% and 5 atomic% or less. For the same amount, the effect of increasing the glass transition temperature is greatest for Ca and decreases in the order of Sr, Ba, and Mg. The dielectric constant is highest for Ba and decreases in the order of Sr, Ca, and Mg. Therefore, among these, Ca is most preferable.

  Moreover, although Mo and W are not essential components, the addition of these further reduces yellowing that may occur when the oxide glass of the present invention is used as a dielectric material for coating an electrode such as Ag. be able to. However, at least one selected from Mo and W should be contained in the range of more than 0 atomic% and less than 5 atomic%, preferably in the range of 3 atomic% or less so that coloring by adding these does not become too dark. .

The mechanism of reducing yellowing by adding Mo and W is not necessarily clear at this stage. However, perhaps these metals become MoO ₄ ²⁻ or WO ₄ ²⁻ in the glass and bind to Ag ⁺ and Cu ²⁺ that are generated by heating and diffuse in the glass to stabilize these metal ions, It is considered that these Ag ⁺ and Cu ²⁺ are reduced and prevented from precipitating as metal colloids, that is, they act as stabilizers for Ag ions and Cu ions.

  The glass of the present invention contains the above components, and typically consists essentially of only the above components (in other words, substantially does not contain the components other than those described above). These components may be contained. The total ratio of such other components is 5 atomic% or less, more preferably 3 atomic%, and even more preferably 1 atomic% or less.

  Specific examples of other components include Cu, Co, Ti, V, Sb or P.

  Among these, Cu, Co, or Ti has the effect of coloring the glass blue, and also has the effect of canceling the coloration due to the presence of Bi and the coloration due to yellowing. However, when used in a large amount, the transparency of the glass decreases.

  V, Sb or P decreases the glass transition temperature by about 10 to 20 ° C., but also decreases the softening temperature to the same extent. Therefore, when the glass transition temperature and the softening temperature of the basic composition are sufficiently high, they may be used to lower them. However, if it is used in a large amount, the glass is colored or the dielectric constant is increased.

  In addition to the above, Li, Al, Zr, La, Ce, Y, Mn, Nb, Ta, Te, Ag are used for adjusting the thermal expansion coefficient, stabilizing the glass and improving chemical durability. And at least one selected from Sn may be added in a small amount.

  Moreover, the oxide glass of the present invention can be a lead-free glass that does not substantially contain Pb.

  In the present specification, “substantially free” means that a very small amount of the component is industrially difficult to remove and does not affect the characteristics in the ratio of other elements excluding oxygen. is there. Specifically, the proportion of the component is less than 0.1 atomic%, desirably less than 0.05 atomic%, and more desirably less than 0.01 atomic%.

In the present specification, the ratio of elements is expressed as a ratio of only cations. However, since the present invention is an oxide glass, naturally, oxygen exists as anions in the glass. When the cations contained in the oxide glass of the present invention are expressed by unit oxides as usual, B ₂ O ₃ , Bi ₂ O ₃ , SiO ₂ , ZnO, K ₂ O, Na ₂ O, MgO, CaO, SrO, BaO, MoO ₃ , WO ₃ . However, this notation does not limit the valence of each cation in the glass. For example, Bi can exist in the glass even with a valence other than trivalent.

The oxide glass of the present invention has both an appropriate thermal expansion coefficient and a low softening temperature by adjusting the composition within the range described above. In general, glass substrates used for PDP include soda lime glass, which is a window glass that is manufactured by a float process and is generally easily available, and high strain point glass developed for PDP. They usually have a heat resistance up to 600 ° C. and a coefficient of thermal expansion of 75 × 10 ^{−7 to} 85 × 10 ⁻⁷ / ° C. For this reason, the thermal expansion coefficient of the oxide glass of the present invention is desirably 60 × 10 ^{−7 to} 85 × 10 ⁻⁷ / ° C., and more desirably 65 × 10 ^{−7 to} 85 × 10 ⁻⁷ / ° C. The softening temperature of the oxide glass of the present invention is such that the glass paste must be fired at 600 ° C. or lower, which is the strain point of the glass substrate. In addition, it is desirable that the temperature be at least 595 ° C. or less, more desirably 590 ° C. or less.

(About the display panel which can employ | adopt the oxide glass of this invention suitably)
Next, as a display using the oxide glass of the present invention, a plasma display panel (PDP) will be described as an example. FIG. 1 is a cross-sectional perspective view of the main part of the PDP. 2 is a cross-sectional view taken along the line II-II in FIG. The PDP 100 shown in this embodiment is an AC surface discharge type.

  The PDP 100 includes a front plate 1 and a back plate 8 that are bonded to each other. The front plate 1 includes a front glass substrate 2, display electrodes 5 formed on the inner side surface (surface on the discharge space 14 side), a dielectric layer 6 that covers the display electrodes 5, and a protective layer that covers the dielectric layer 6. 7 and the like. The display electrode 5 has a structure in which the thin bus electrode 4 is laminated on the transparent electrode 3. The transparent electrode 3 is mainly composed of ITO (Indium Tin Oxide) or tin oxide. The bus electrode 4 is mainly composed of one type selected from Ag, Cu and Al. Among these, Ag is recommended because it is excellent in oxidation resistance. The oxide glass of the present invention can be used for the dielectric layer 6 covering the display electrode 5.

  The back plate 8 includes a back glass substrate 9, an address electrode 10 formed on one surface thereof, a dielectric layer 11 covering the address electrode 10, a partition wall 12 provided on the top surface of the dielectric layer 11, and partition walls 12 and 12. And a phosphor layer 13 formed between them. The phosphor layer 13 includes a red phosphor layer 13 (R), a green phosphor layer 13 (G), and a blue phosphor layer 13 (B) arranged in order. The dielectric layer 11 of the back plate 8 can also be formed of the oxide glass of the present invention.

As the phosphor constituting the phosphor layer 13, for example, BaMgAl ₁₀ O ₁₇ : Eu is used as a blue phosphor, Zn ₂ SiO ₄ : Mn is used as a green phosphor, and Y ₂ O ₃ : Eu is used as a red phosphor. it can.

  The front plate 1 and the back plate 8 are joined to each other using a sealing member (not shown) in such a manner that the longitudinal direction of the display electrodes 5 and the longitudinal direction of the address electrodes 10 are orthogonal to each other.

  A discharge gas composed of at least one kind of rare gas component selected from He, Xe and Ne is sealed in the discharge space 14 at a pressure of about 66.5 kPa to 79.8 kPa (500 Torr to 600 Torr).

  The display electrode 5 and the address electrode 10 are each connected to an external drive circuit (not shown), and a discharge is generated in the discharge space 14 by a voltage applied from the drive circuit. The phosphor contained in the phosphor layer 13 is excited by ultraviolet rays having a short wavelength (wavelength of 147 nm) generated along with the discharge, so that visible light is emitted.

  The dielectric layer 6 can be formed as follows. First, a glass paste is obtained by adding appropriate amounts of a binder and a solvent to the raw material powder prepared so as to obtain the oxide glass of the present invention. This glass paste is applied to a uniform thickness from above the display electrode 5 formed on the front glass substrate 2. The coated glass paste is baked (simultaneously baked) together with the front glass substrate 2 and the display electrode 5. In this way, the dielectric layer 6 can be formed. Note that the baking may not be simultaneous baking, but may be individual baking in which a glass paste is applied and fired after the display electrode 5 is fired.

  The glass paste may contain an additive in addition to the raw material powder, the solvent, and the resin (binder). For example, additives suitable for various purposes such as surfactants, development accelerators, adhesion assistants, antihalation agents, storage stabilizers, antifoaming agents, antioxidants, UV absorbers or pigment dyes should be used. Can do.

  The kind of resin (binder) contained in the glass paste is not particularly limited as long as the reactivity with the raw material powder is low. From the viewpoints of chemical stability, cost and safety, for example, cellulose derivatives such as nitrocellulose, methylcellulose, ethylcellulose and carboxymethylcellulose, polyvinyl alcohol, polyvinyl butyral, polyethylene fglycol, carbonate resins, urethane resins, acrylic resins In addition, at least one selected from melamine resins can be used.

  The kind of the solvent contained in the glass paste is not particularly limited as long as the reactivity with the raw material powder is low. From the viewpoints of chemical stability, cost and safety, and compatibility with the binder, for example, butyl acetate, ethyl 3-ethoxypropionate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Ethylene glycol monoalkyl ethers such as propyl ether and ethylene glycol monobutyl ether; ethylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, Diethylene glycol dials such as diethylene glycol dibutyl ether Propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether; propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dipropyl ether, propylene glycol Propylene glycol dialkyl ethers such as dibutyl ether; propylene glycol alkyl ether acetates such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate Lactic acid esters such as methyl lactate, ethyl lactate, butyl lactate, methyl formate, ethyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, isobutyl acetate, amyl acetate, isoamyl acetate, acetic acid Hexyl, 2-ethylhexyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butanoate (methyl butyrate), ethyl butanoate (ethyl butyrate), propyl butanoate (propyl butyrate), isopropyl butanoate (isopropyl butyrate) Esters of aliphatic carboxylic acids such as carbonates; carbonates such as ethylene carbonate and propylene carbonate; alcohols such as terpineol and benzyl alcohol; aromatic hydrocarbons such as toluene and xylene; methyl ethyl ketone, 2-heptanone, 3-he Ketones such as butanone, 4-heptanone, cyclohexanone; ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutyrate, 3- Methyl methoxypropionate, ethyl 3-methoxypropionate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, butyl carbitol acetate, 3-methyl-3-methoxybutyl propionate, 3-methyl-3 Esters such as methoxybutyl butyrate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate methyl acetoacetate, ethyl acetoacetate, methyl pyruvate, ethyl pyruvate, ethyl benzoate, benzyl acetate N-methyl pyro Don, NN- dimethylformamide, N- methylformamide, N, can be used organic solvents such as N- dimethylacetamide.

  Examples of the method for applying the glass paste include a screen method, a bar coater method, a roll coater method, a die coater method, and a doctor blade method. The coated glass paste is fired in a firing furnace adjusted to an atmospheric temperature higher than the softening temperature of the glass to be obtained (dielectric layer 6) and lower than the strain point of the front glass substrate 2. When the softening temperature of the dielectric layer 6 to be formed of the oxide glass of the present invention and the strain point of the front glass substrate 2 are very close to each other, firing becomes difficult. Therefore, it is desirable that the difference between the strain point of the front glass substrate 2 and the softening temperature of the dielectric layer 6 is, for example, 5 ° C. or more (more preferably 10 ° C. or more). Alternatively, a self-supporting green sheet may be produced using the glass paste, and the green sheet may be attached to the front glass substrate 2 and fired.

  The thickness of the dielectric layer 6 is preferably about 10 μm to 50 μm in order to achieve both insulation and light transmission.

  Next, a PDP in which the dielectric layer provided on the front glass substrate has a two-layer structure will be described. In the PDP 101 shown in FIG. 3, the dielectric layers 15 and 16 on the front glass substrate 2 have a two-layer structure of a first dielectric layer 15 and a second dielectric layer 16. Other points are the same as those of the PDP shown in FIGS.

  As shown in FIG. 3, the first dielectric layer 15 directly covers the display electrode 5 (the transparent electrode 3 and the bus electrode 4). The second dielectric layer 16 is disposed on the first dielectric layer 15 such that the first dielectric layer 15 is located between the front glass substrate 2 and / or the display electrode 5. Therefore, the front glass substrate 2, the first dielectric layer 15, and the second dielectric layer 16 are arranged in this order in the thickness direction.

  When a dielectric layer having a two-layer structure is formed, the first dielectric layer 15 that is in direct contact with the display electrode 5 is formed of glass that does not substantially contain an alkali metal, and the second dielectric layer 16 is oxidized according to the present invention. It can be formed of physical glass. Since the first dielectric layer 15 that is in direct contact with the display electrode 5 does not contain an alkali metal, the problem of yellowing due to colloidal deposition of Ag or Cu and a decrease in breakdown voltage do not occur. Further, the first dielectric layer 15 prevents Ag or Cu ions from diffusing into the second dielectric layer 16. Therefore, even when the second dielectric layer 16 is formed of the oxide glass of the present invention containing a small amount of alkali metal, problems such as yellowing and reduced breakdown voltage do not occur in the second dielectric layer 16.

  Further, the conventional Pb-based glass and Bi-based glass have a large relative dielectric constant of 9 to 13, but according to the oxide glass of the present invention, the relative dielectric constant can be easily adjusted to around 7. If the second dielectric layer 16 is formed of the oxide glass of the present invention having a relative dielectric constant as small as about 7, even if a glass having a relatively high relative dielectric constant is used for the first dielectric layer 15 as a whole, A dielectric layer having a low dielectric constant can be formed, and power consumption can be reduced.

  Conversely, the first dielectric layer 15 can be formed of the oxide glass of the present invention. This is because according to the oxide glass of the present invention, since the content of alkali metal is small, the problem of yellowing does not become significant. In this case, the second dielectric layer 16 can be formed of glass having a lower dielectric constant than that of the first dielectric layer 15 (the oxide glass of the present invention). In such a case, the dielectric layer covering the display electrode 5 as a whole can be further reduced in dielectric constant, and thus can further reduce power consumption. Examples of the low dielectric constant glass used for the second dielectric layer 16 include glass that does not substantially contain Bi and contains more alkali metal, such as B-Si-Zn-KO-based glass. be able to.

  The dielectric layers 15 and 16 having a two-layer structure shown in FIG. 3 can be formed by coating and baking a glass paste for the second dielectric layer 16 after forming the first dielectric layer 15. . In order to employ such a procedure, the softening temperature of the first dielectric layer 15 needs to be higher than the softening temperature of the second dielectric layer 16.

  Further, in order to ensure insulation between the display electrode 5 (the transparent electrode 3 and the bus electrode 4) and the second dielectric layer 16 and prevention of an interface reaction, the thickness of the first dielectric layer 15 is set to 1 μm or more. preferable. Furthermore, in order to achieve both high insulating properties and high visible light transmittance, the total thickness of the first dielectric layer 15 and the second dielectric layer 16 is preferably 10 μm to 50 μm.

  In addition, as PDP which can employ | adopt the oxide glass of this invention suitably, although the surface discharge type thing as shown in FIGS. 1-3 is typical, it is not limited to this, Counter discharge type It can also be applied to. Further, the present invention is not limited to the AC type, and the oxide glass of the present invention can be applied to a DC type PDP having a dielectric layer.

[Example 1]
As a starting material for the oxide glass of the present invention, a metal oxide powder or carbonate powder of a reagent grade or better was prepared. These raw material powders were weighed and mixed so that the atomic ratio of each element was as shown in Table 1. Then, the mixed raw material powder was put into a platinum crucible and melted in an electric furnace at 1100 ° C. to 1200 ° C. for 1 hour. The obtained melt was quenched by pressing it with a brass plate to produce a glass cullet. The glass cullet was pulverized and the softening temperature Ts was measured using a macro-type differential thermal analyzer. Further, a weight decrease ΔW between 300 ° C. and 600 ° C. was measured by thermogravimetric analysis.

Next, the produced glass cullet was remelted to produce a 4 mm × 4 mm × 20 mm rod, and the glass transition temperature Tg and the thermal expansion coefficient α at 30 to 300 ° C. were measured using a thermomechanical analyzer. Further, the glass cullet was remelted to produce a glass plate of 20 mm × 20 mm × thickness 1 mm, and Au was vapor-deposited on the front and back of the glass plate to form electrodes. Then, an LCR meter was connected to the electrode, and the relative dielectric constant ε was measured at a frequency of 1 kHz and 25 ° C. The results are shown in Table 1. In the table, the unit of glass transition temperature Tg and softening temperature Ts is ° C., the unit of thermal expansion coefficient α is × 10 ⁻⁷ / ° C., and the unit of heating weight reduction ΔW is mass%.

  As shown in Table 1, sample Nos. 1 and 2 in which the K amount and Bi amount were fixed at 5 atomic%, the B amount was increased, and the Zn + Si amount was decreased. In 1 to 8 and 10, the relative dielectric constant ε decreased with an increase in the amount of B. However, at the same time, the glass transition temperature Tg is lowered, and B = 90 atomic%. 10 was less than 465 ° C. On the other hand, no. 1-4 were so large that the dielectric constant (epsilon) exceeded eight. No. In 1-4, 6 and 7, only the Zn amount is decreased and the Si amount is kept constant. No. in which the amount of Si and the amount of Zn are interchanged. 4 and no. As is clear from comparison with FIG. 5, when the amount of Si is large, the relative dielectric constant ε decreases, but the softening temperature Ts increases. No. in which the Zn content is 15 atomic% or less. In 6, 7, and 8, the relative dielectric constant ε was 8 or less, the softening temperature Ts was 580 ° C. or less, the glass transition temperature Tg exceeded 465 ° C., and the thermal expansion coefficient α was also appropriate. However, no. In No. 9, the glass transition temperature Tg was less than 465 ° C. No. B with 55 atomic% and 15 atomic% for both Si and Zn. For Nos. 11 and 12, good characteristics were obtained.

  When the above is comprehensively judged, the amount of B needs to be 55 atom% or more and 85 atom% or less, more desirably 60 atom% or more and 85 atom% or less, and further 70 atom% or more and 85 atom% or less. Is desirable.

  Further, the B content was fixed at 70 atomic%, the K content and the Bi content were fixed at 5 atomic%, and the Zn content and Si content were changed. 6 and no. 13-16, No. with Si amount of 20 atomic%. No. 13 had a softening temperature Ts as high as 600 ° C. Moreover, No. with Zn amount of 20 atomic%. In 16, the relative dielectric constant exceeded 8. Similarly, No. 1 in which the amount of Si + Zn exceeds 30 atomic%. 1-3, the relative dielectric constant exceeded 8.

  Further, the B amount was fixed at 75 atomic%, the K amount and the Bi amount were increased while being the same amount, and the Zn amount and the Si amount were decreased accordingly. 17 to 21, the K + Bi amount becomes zero. No. 17 could not obtain a uniform glass, and No. 17 with a small amount of K + Bi. No. 18 had a softening temperature Ts as high as 601 ° C. In addition, No. with a large amount of K + Bi. No. 21 had a glass transition temperature Tg as low as 459 ° C. On the other hand, K + Bi amount is 8 to 15 atomic%, No. In 19 and 20, good characteristics were obtained.

  In addition, the Si amount and the Zn amount were fixed at 5 atomic%, the Bi amount was set to zero, and the K amount was changed. In 22 to 24, the glass transition temperature Tg was low, and the weight loss ΔW during heating was large.

  Further, when the Si amount and the Zn amount were fixed to 5 atomic%, the K amount was zero, and the Bi amount was changed. In 27-29, uniform glass was not obtained.

  In addition, the B amount, the Si amount, and the Zn amount were fixed, and the ratio of K and Bi was changed. 7 and 24 to 27, No. 7 in which K and Bi coexist. In 7, 25, and 26, uniform glass was obtained, weight loss ΔW due to heating was reduced, and other properties were also good.

  Next, no. No. 7 in which all K was replaced with Na. 30 and No. replaced by half. In No. 31, no. Compared to 7, the thermal expansion coefficient α slightly decreased, the relative dielectric constant ε increased, and the softening temperature decreased. However, the change was not large and could be used as a substitute for K. However, if one of K and Na is selected, use of K is desirable because Na tends to have a smaller coefficient of thermal expansion α than K and tends to cause yellowing.

  Considering all the above samples, the softening temperature Ts and the dielectric constant ε are sufficiently low, and the thermal expansion coefficient α is most suitable when the B content is around 75 to 85 atomic%. Considering that the smaller amount of alkali is more advantageous for yellowing, Sample No. 7 and 8 are considered the best, but the glass transition temperature of these samples exceeded 465 ° C but did not reach 480 ° C.

In addition to those shown in Table 1, various combinations of compositions were examined. In any case, B = 55 to 85 atomic%, Si = 0 to 15 atomic%, Zn = 0 to 15 atomic%, By adjusting the composition in the range of Si + Zn = 5 to 30 atom%, K + Na = 1 to 10 atom%, Bi = 1 to 10 atom%, K + Na + Bi = 8 to 15 atom%, a relative dielectric constant ε of 8.0 or less It has excellent characteristics, including a glass transition temperature Tg of 465 ° C. or more, a softening temperature Ts of 595 ° C. or less, a thermal expansion coefficient α of 60 to 90 × 10 ⁻⁷ / ° C., and a weight loss ΔW of 0.1% by mass or less. Glass was obtained.

[Example 2]
A glass cullet and a glass rod in which the atomic ratio of each element is as shown in Table 2 by the same method as in Example 1 were prepared, and the glass transition temperature Tg, softening point Ts, The thermal expansion coefficient α and the relative dielectric constant ε were measured. The results are shown in Table 2.

  As is apparent from Table 2, by adding Mg, Ca, Sr, or Ba, the glass transition temperature Tg can be increased without significantly increasing the softening temperature Ts, and can be set to 480 ° C. or higher. . However, since the relative dielectric constant ε and the softening temperature Ts increase with the addition thereof, it is understood that the addition amount should be suppressed to 5 atomic% or less. Further, when compared with the kind of added alkaline earth metal, it can be seen that Ca is the least amount of addition necessary to make the glass transition temperature Tg 480 ° C. or higher. In addition, when Ca is added, the increase in relative dielectric constant ε is small. Therefore, it is desirable to use Ca when adding an alkaline earth metal.

  In addition, in the B: Si: Zn: Bi: K ratios other than those shown in Table 2, the same effect of adding an alkaline earth metal was examined, but the same effect was obtained in all cases. Moreover, when the simultaneous addition of a plurality of types of alkaline earth metals was examined, an average effect was shown. Even when a plurality of types of alkaline earth metals were added, good results were obtained when the total amount was 0.5 atomic% to 5 atomic%.

[Example 3]
In the same manner as in Example 1, the atomic ratio of each element is Si: Zn: Bi: K: Ca = 2: 5: 5.5: 5.5: 2, and B, Mo, and W are as shown in Table 3. A glass cullet and a glass rod having the ratio shown in FIG. 6 were prepared, and the glass transition temperature Tg, softening temperature Ts, thermal expansion coefficient α, and relative dielectric constant ε were measured in the same manner as in Example 1. For comparison, a glass cullet and a glass rod having B: Si: Zn: K: Ca = 80: 2: 5: 11: 2 were produced, and the same measurement was performed. After the measurement, the glass cullet was pulverized by a dry ball mill to obtain glass powder. In Table 3, the total of the components does not become 100% because the remainder is occupied by Si, Zn, Bi, K and Ca added at the above atomic ratio.

  Next, the glass powder was obtained by mixing and dispersing ethyl cellulose as a resin and α-terpineol as a solvent with the three rolls.

Next, on the main surface of a glass substrate made of flat soda-lime glass having a thickness of 2.8 mm (heat-resistant temperature: 600 ° C., thermal expansion coefficient: 82.7 × 10 ⁻⁷ / ° C. (30 ° C. to 300 ° C.)) The ITO material was applied in a predetermined pattern on the front glass substrate of the PDP and dried in a drying oven. Thereby, a glass substrate with an ITO film was obtained. An Ag paste, which is a mixture of Ag powder and an organic vehicle, was applied to the ITO film-coated glass substrate in a line by a screen printing method so as to overlap the ITO film. And the whole glass substrate was heated, Ag paste was baked and it was set as the glass substrate with an electrode.

  A glass paste prepared in advance was applied to the electrode-attached glass substrate by a blade coater method. Thereafter, the glass substrate with the electrode was held in a firing furnace at an atmospheric temperature of 90 ° C. for 30 minutes to dry the glass paste, and was baked at an ambient temperature of softening temperature + 10 ° C. for 10 minutes to form a dielectric layer. And the reflected color was measured using the color difference meter in the back surface side (side without an electrode) of the produced glass substrate with an electrode. Note that natural light was used for the measurement and the measurement was corrected with a reference white plate. The results are shown in Table 3.

The a ^* and b ^* shown in Table 3 are based on the L ^* a ^* b ^* color system. The a ^* value indicates that red increases as it increases in the positive direction, and green increases as it increases in the negative direction. The b ^* value indicates that yellow increases as it increases in the positive direction, and blue increases as it increases in the negative direction. In general, if the a ^* value is in the range of −5 to +5 and the b ^* value is in the range of −5 to +5, the panel is not colored so as to cause a problem. Also, even if the b ^* value exceeds +5, in order to cancel this color, it is possible to add normal blue Cu, Co, Ti, etc. to the glass by adding it, or by using a color filter. It is possible to return to color. However, when the b ^* value exceeds 10, it is necessary to use a darker colorant or filter, and as a result, the transmittance of the glass as a whole is lowered, which is not preferable. Therefore, there is no problem if b ^* is +5 or less, but it is desirable that b ^* be as low as possible even if it exceeds +5.

Based on the above findings, the results shown in Table 3 will be examined.
First, No. in which neither Mo nor W was added. Comparing 201 with a comparative example having the same amount of other components but containing a large amount of K and not containing Bi, the comparative example has a characteristic that the dielectric constant is slightly lower, but the value of b ^* is clear. No. 201 was small. That is, no. With the composition of 201, as described in Example 1, the glass transition temperature is high, the weight loss during heating is small, and yellowing hardly occurs as compared with the conventional material containing only alkali metal but not Bi. (Or its degree is low).

Next, No. with Mo or W added. In 202-218, b ^* value fell as the addition amount increased, and became 0.1 or less and 5.0 or less, and yellowing was suppressed. However, when the addition amount was further increased, the b ^* value also began to rise again, and when the addition amount reached 5 atomic%, the case of no addition was exceeded. This is presumably because the yellowing phenomenon itself due to the precipitation of Ag colloid is less likely to occur, but Mo or W itself colors the glass. Therefore, the addition amount of Mo and / or W is preferably 0.1 atomic% or more and less than 5 atomic%, preferably 0.1 atomic% or more and 3 atomic% or less.

Incidentally, in the composition range of the present invention, different or the main composition ratio of the mother glass, for which the material obtained by adding MoO ₃ or WO _3, was subjected to the same evaluation also b ^* values in any matrix composition Was relatively small, and the b ^* value could be easily reduced to 5 or less by addition of MoO ₃ or WO ₃ .

[Example 4]
Various raw material powders having the same atomic ratio of B: Si: Zn: Bi: K: Ca: Mo = 78.8: 3: 5: 5: 6: 2: 0.2 in the same manner as in Example 1. Were put in a platinum crucible and melted in an electric furnace at 1100 ° C. for 2 hours, and then a glass cullet was produced by a twin roller method. The glass cullet was pulverized by a dry ball mill to produce glass powder. The average particle size of the obtained glass powder was about 5 μm. This glass had a relative dielectric constant of 6.8, a glass transition temperature of 480 ° C., a softening temperature of 578 ° C., and a thermal expansion coefficient of 75 × 10 ⁻⁷ / ° C.

  Next, ethyl cellulose as a binder and α-terpineol as a solvent were added to the glass powder and mixed with three rolls to obtain a glass paste.

Next, the main surface of the front glass substrate made of flat soda lime glass (heat resistant temperature: 600 ° C., thermal expansion coefficient: 82.7 × 10 ⁻⁷ / ° C. (30 ° C. to 300 ° C.)) having a thickness of 2.8 mm The ITO material was applied in a predetermined pattern as shown in FIG. 2 and dried in a drying furnace. Thereby, a glass substrate with an ITO film was obtained. An Ag paste, which is a mixture of Ag powder and an organic vehicle, was applied to the ITO film-coated glass substrate in a line by a screen printing method so as to overlap the ITO film. And the whole glass substrate was heated, Ag paste was baked and it was set as the front glass substrate with an electrode.

  Next, a glass paste prepared in advance was applied to the front glass substrate on which the display electrodes were formed by a blade coater method. Thereafter, the front glass substrate is held in a firing furnace having an atmospheric temperature of 90 ° C. for 30 minutes to dry the glass paste, and further the atmospheric temperature is raised to 583 ° C. and baked for 10 minutes to thereby form a dielectric layer having a thickness of 20 μm. Formed.

  Further, magnesium oxide (MgO) was deposited on the dielectric layer by an electron beam deposition method, and then fired at 500 ° C. to form a MgO protective layer. In this way, the front plate 1 of the PDP 100 shown in FIG. 2 was obtained.

  On the other hand, a back plate was produced by the following known method. First, address electrodes mainly composed of Ag were formed in stripes on a back glass substrate made of soda lime glass by screen printing. Subsequently, a dielectric layer covering the address electrodes was formed by the same method as that for the front plate. Next, partition walls were formed on the dielectric layer so as to be positioned between adjacent address electrodes. The partition walls were formed by repeating a step of printing a Bi glass paste in a predetermined pattern by a screen printing method and a step of baking the printed pattern. Next, a phosphor layer of red (R), green (G), and blue (B) is applied to the surface of the dielectric layer exposed between adjacent barrier ribs, dried and fired, and then the phosphor layer Formed. In this way, the back plate 8 of the PDP 100 shown in FIG. 2 was obtained.

The front plate 1 and the back plate 8 produced as described above were bonded at 500 ° C. using Bi—Zn—B—Si—O based sealing glass. Then, after evacuating the inside of the discharge space to a high vacuum (about 1 × 10 ⁻⁴ Pa), Ne—Xe-based discharge gas was sealed so as to be a predetermined pressure (66.5 kPa to 79.8 kPa). Thus, PDP100 was produced.

  A controller was connected to the manufactured PDP to confirm operation. The manufactured PDP was confirmed to operate without any problem without causing defects in the dielectric layer.

[Example 5]
A B—Si—Zn—Bi—K—Ca—Mo—O-based glass paste was prepared for the first dielectric layer of the PDP front glass substrate by the same method and the same composition as in Example 4. On the other hand, a B—Si—Zn—K—Ca—O-based glass paste was prepared for the second dielectric layer in the same manner as in Example 4. The dielectric constant of the glass contained in the second dielectric layer glass paste was 6.2, the glass transition temperature was 480 ° C., the softening temperature was 575 ° C., and the thermal expansion coefficient was 78 × 10 ⁻⁷ / ° C.

  Using these glass pastes, the dielectric layer of the front glass substrate is formed on the first dielectric layer and the first dielectric layer directly covering the display electrodes in the same manner as in Example 3. A PDP panel having a two-layer structure with the second dielectric layer was produced. The first dielectric layer was fired at 583 ° C. to a thickness of about 20 μm, and the second dielectric layer was fired at 578 ° C. to a thickness of about 20 μm.

  A controller was connected to the manufactured PDP to confirm operation. The manufactured PDP was confirmed to operate without any problem without causing defects in the dielectric layer.

[Example 6]
B—Si—Zn—Bi—K—Ca—O-based glass having an atomic ratio of B: Si: Zn: Bi: K: Ca = 80: 3: 5: 5: 6: 2 in the same manner as in Example 4. A paste was prepared for the second dielectric layer. Separately, a Bi—Zn—B—Ca—Si—O-based glass paste containing Bi and having a relative dielectric constant of 11 was prepared for the first dielectric layer.

  Using these pastes, as in Example 5, the dielectric layer of the front plate is a first dielectric layer that directly covers the electrode, and the second dielectric layer formed on the first dielectric layer. A PDP panel having a two-layer structure was prepared. The first dielectric layer was fired at 590 ° C. to a thickness of about 20 μm, and the second dielectric layer was fired at 583 ° C. to a thickness of about 20 μm.

  A controller was connected to the manufactured PDP to confirm operation. The manufactured PDP was confirmed to operate without any problem without causing defects in the dielectric layer.

  The oxide glass of the present invention can be suitably used for forming a dielectric layer for covering an insulating coating glass for electrodes, particularly a display electrode and an address electrode of a plasma display panel.

The cross-sectional perspective view of the principal part of PDP. II-II sectional drawing of PDP of FIG. Sectional drawing of other embodiment of PDP.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front plate 2 Front glass substrate 3 Transparent electrode 4 Bus electrode 5 Display electrode 6 Dielectric layer 7 Dielectric protective layer 8 Back plate 9 Back glass substrate 10 Address electrode 11 Dielectric layer 12 Partition 15 15 1st dielectric layer 16 2nd Dielectric layer 100, 101 Plasma display panel (PDP)

Claims (3)

A substrate,
An electrode mainly composed of Ag formed on the substrate;
A first dielectric layer that directly covers the electrode and is substantially free of alkali metal;
A second dielectric layer disposed on the first dielectric layer such that the first dielectric layer is located between the electrode and the electrode,
The display panel , wherein the second dielectric layer is made of the following oxide glass .
Expressed by the ratio of other elements excluding oxygen among the contained elements,
B is 55 atomic% or more and 85 atomic% or less,
Si is 0 atomic% or more and 15 atomic% or less,
Zn is 0 atomic% or more and 15 atomic% or less,
K is 0 atomic% or more and 10 atomic% or less,
Na is 0 atomic% or more and 10 atomic% or less,
Bi is 1 atomic% or more and 10 atomic% or less,
The total of Si and Zn is 5 atomic% or more and 30 atomic% or less,
The total of K and Na is 1 atomic% or more and 10 atomic% or less,
The total of K, Na and Bi is 8 atomic% or more and 15 atomic% or less,
Is an oxide glass. A substrate,
An electrode mainly composed of Ag formed on the substrate;
A first dielectric layer directly covering the electrode;
A second dielectric layer disposed on the first dielectric layer such that the first dielectric layer is located between the electrode and the electrode,
The first dielectric layer is made of the following oxide glass,
The display panel, wherein the second dielectric layer is made of glass having a dielectric constant lower than that of the oxide glass.
Expressed by the ratio of other elements excluding oxygen among the contained elements,
B is 55 atomic% or more and 85 atomic% or less,
Si is 0 atomic% or more and 15 atomic% or less,
Zn is 0 atomic% or more and 15 atomic% or less,
K is 0 atomic% or more and 10 atomic% or less,
Na is 0 atomic% or more and 10 atomic% or less,
Bi is 1 atomic% or more and 10 atomic% or less,
The total of Si and Zn is 5 atomic% or more and 30 atomic% or less,
The total of K and Na is 1 atomic% or more and 10 atomic% or less,
The total of K, Na and Bi is 8 atomic% or more and 15 atomic% or less,
Is an oxide glass. The display panel according to claim 1 or 2, wherein the oxide glass contains at least one selected from Mg, Ca, Sr and Ba in a range of more than 0 atomic% and 5 atomic% or less.