KR20050084172A - Glass for flat panel display substrate and flat panel display substrate - Google Patents

Abstract

A glass for flat panel display substrate and flat panel display substrate that when applying an Ag paste onto a substrate glass and firing the same so as to form electrodes, effectively inhibit yellowing caused by diffusion of metal Ag colloids into the substrate glass. This glass for flat panel display substrate contains less than 6% by weight of Na2O, exhibiting a strain point of 560 to below 580°C, an average thermal expansion coefficient of 80 to 95 x 10-7/°C over a temperature range of 50 to 350°C and a density of 2.7 x 103 Kg/m3 or less, and has an optical basicity of 0.60 or less.

Description

GLASS FOR FLAT PANEL DISPLAY SUBSTRATE AND FLAT PANEL DISPLAY SUBSTRATE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to glass for flat panel displays (hereinafter referred to as "FPD (flat panel display)" substrates and FPD substrates, and in particular, to plasma display panels (hereinafter referred to as "plasma display panels") and electric fields. The present invention relates to a glass for an FPD substrate and an FPD substrate for use as a front panel and a rear panel of an FPD using a discharge panel (hereinafter, referred to as a "field emission display" (FED)).

Recently, the development of FPDs such as PDPs, FEDs, liquid crystal displays, and the like as large flat-panel televisions is rapidly progressing. Among the above, PDPs and FEDs are display devices using discharges generated when an electric field is applied between internal electrodes.

The PDP generates ultraviolet rays from the rare gas by a discharge phenomenon in a low pressure rare gas trapped inside the panel, and excites a predetermined phosphor to generate visible light, thereby generating images such as letters and graphics. It is driven by the display. On the other hand, the FED is a display device in which the inside of the panel is kept in a high vacuum state and is driven in a manner that generates visible light by exciting the phosphor using an electron beam generated by applying an electric field in the high vacuum.

The manufacturing method of PDP is demonstrated as an example below.

In order to manufacture the PDP, first, an address electrode made of silver (Ag) is formed on the back substrate glass using a screen printing method or the like, and a visible light reflecting layer made of dielectric glass and a glass partition wall are defined on the formed address electrode. Form to pitch. Thereafter, a phosphor layer having respective colors is applied to each space existing between these partition walls to form a phosphor layer, and the phosphor layer is fired at a temperature of about 500 ° C. to form the phosphor paste having the respective colors. Removes the resin component and the like.

After firing the phosphor layer, a low-melting glass frit is applied around the rear substrate glass to seal the rear substrate glass and the front substrate glass, and free at a temperature of about 300 ° C. By pre-baking, the resin component in the glass frit is removed.

Thereafter, the front substrate glass and the rear substrate glass on which the display electrode, the dielectric glass layer, and the protective layer were formed were arranged with the partition walls interposed therebetween, and the display electrode and the address electrode were arranged to face each other at about 600 ° C. After firing at a temperature of, the surroundings are sealed using the low melting glass frit. Then, the PDP is manufactured by evacuating the atmosphere present in the panel gap under reduced pressure while heating it to a temperature of about 300 ° C., and then filling the discharge gas.

As said glass for PDP substrates, glass with high strain point and large thermal expansion coefficient is widely used. The glass for PDP substrates is generally produced by a float process which is excellent in the flatness of the main surface and the homogeneity of the glass composition in the produced glass. Since float glass is exposed to a hydrogen atmosphere during the production process, a reducing layer having a thickness of several μm is formed on the glass surface, and tin ions derived from molten tin (hereinafter referred to as “Sn ²⁺ ”) are present in the reducing layer. It is known.

By the way, when the Ag paste is applied to the main surface of the glass for PDP substrate formed by the float method with the transparent electrode interposed therebetween, and the heat treatment step is repeated several times, silver ions (hereinafter, "Ag ⁺ ”) Diffuses into the transparent electrode and reaches the glass surface, whereby an ion exchange reaction between alkali ions (particularly sodium ions (hereinafter, referred to as“ Na ⁺ ”)) in the glass and Ag ⁺ occurs. As a result, when Ag ⁺ penetrates into the glass, the penetrated Ag ⁺ is reduced by Sn ²⁺ present in the reducing layer of the glass, thereby producing a colloid of metal Ag. As a result, there was a problem that the glass for the substrate was colored yellow (hereinafter referred to as "yellowing") by the colloid of the metal Ag produced as described above.

In addition, Ag ⁺ diffuses not only in the electrode forming portion but also in the peripheral portion thereof, as described above, is reduced by Sn ²⁺ , and a colloid of metal Ag is produced to yellow the glass for the substrate in many cases. There was a problem that the display performance of the substrate was impaired.

Accordingly, in the case of using the alkali-containing glass as the glass for the PDP substrate, various methods for suppressing the yellowing of the glass for the substrate have been proposed.

For example, Japanese Patent Application Laid-Open No. 10-255669 discloses a glass for an FPD substrate in which a reducing heterogeneous layer formed on the main surface is removed by polishing a main surface of the glass for a substrate produced by the float method. Is described.

As mentioned above, since the glass for a board | substrate formed by the float method is exposed to hydrogen atmosphere during shaping | molding process, the surface which contacted the tin bath (bottom surface), and the surface which contacted the atmosphere side ( It is known in the art that a reduction layer having a thickness of several micrometers is formed on the main surface of the glass for a substrate on both surfaces, and a Sn ²⁺ diffusion layer is formed on the reduction layer. It is also well known that the Sn ²⁺ diffusion layer has reducibility, and that the Sn ²⁺ diffusion layer reduces the iron component in the glass, causing the bottom surface to be colored blue. Therefore, polishing and removing the Sn ²⁺ diffusion layer present on the main surface of the substrate glass is a technique that can be easily performed by those skilled in the art. However, polishing of the entire glass for the substrate is expensive and therefore not suitable for practical use.

As another method, Japanese Patent Application Laid-Open No. 10-334813 discloses a plasma display device characterized in that the amount of Fe ₂ O ₃ contained in the glass for the front substrate is less than 2000 ppm, and the metal electrode is formed of Ag.

However, since the plate glass molded by the float method is usually about 1500 ppm of Fe ₂ O ₃ content of the impurity level mixed from the glass raw material, when the glass is used as the glass for the PDP substrate, due to the colloid of the metal Ag Since yellowing cannot be suppressed, the above-mentioned method is also not a realistic solution.

Further, Japanese Patent Laid-Open No. 2001-213634 discloses that the total content of Li ₂ O, Na ₂ O, and K ₂ O is 7.5-20 mol%, the Al ₂ O ₃ content is 1.5 mol% or more, and the BaO content is 0. As a plate glass shape | molded silicate glass of -3.5 mol% according to the float method in plate shape, it is described about the float glass for display substrates containing 1 or more types chosen from the group which consists of F, Cl, Br, and I.

In general, the plate glass formed by the float method is about 0.01% by weight of chlorine at the impurity level incorporated from the glass raw material, but strong bases such as F ^- and Cl ^- have a weak preferential bonding force with Ag ⁺ which is a weak acid, and thus have almost no color suppression effect. Can not get In addition, Br ^-, because when using a weak base such as there can be expected the coloring suppressing effect because it combines the Ag ⁺ and preferentially, without an appropriate material present in the use as an industrial, cost also large, ^- or I There is a difficulty in using it realistically.

Further, Japanese Laid-Open Patent Publication No. 2000-226233 discloses a float glass having a total content of Na ₂ O, K ₂ O, and Li ₂ O of 5% by weight or more and a specific gravity at 20 ° C of 2.7 or less. Before, from the transmittance | permeability (Tref) in wavelength 410nm of the said float glass, and the glass after silver-processing, from the transmittance | permeability (T) in the wavelength 410nm of the said float glass, Formula A = -log10 (T / Tref) The absorbance A calculated according to the present invention is described for a float glass for flat panel display substrates of 0.08 or less. The silver treatment is obtained by applying an Ag paste containing silver particles, an organic solvent, and a resin to the surface of the float glass surface that is not in contact with molten tin in a float bath (upper surface). Next, by firing at a temperature of 580 ° C. for 1 hour in an atmosphere, a film having a thickness of 10 μm or more and a silver content of 95 wt% or more was formed on the surface of the float glass, and then the film was removed with nitric acid from the surface of the float glass. It refers to a process including the step of doing.

However, the above-mentioned Japanese Unexamined Patent Application Publication No. 2000-226233 discloses that "the lower the amount of tin penetration into the glass, the smaller the color development level is, so that the glass with the lowest tin content is preferred as much as possible, '' and the metal. It is only a description of how to evaluate the yellowing caused by colloid of Ag, and there is no suggestion on the fundamental solution.

An object of the present invention is to provide a glass for an FPD substrate and an FPD substrate capable of suppressing yellowing due to a colloid of metal Ag, in order to solve the problems of the prior art described above.

In order to achieve the above object, the present invention, in the first aspect, contains less than 6% by weight of Na ₂ O, the strain point is in the range of less than 560 ~ 580 ℃, average thermal expansion coefficient in the temperature range of 50 ~ 350 ℃ The glass for an FPD board | substrate which is 80-95x10 <^-7> / degreeC, density is 2.7x10 <^3> kg / m <^3> or less, and optical basicity is 0.60 or less is provided.

In the first aspect of the present invention, the glass preferably has a K ₂ O / Na ₂ O value of 2 or more as a ratio by weight.

In a first aspect of the invention, the glass comprises 0.2% to 2.5% by weight of zirconium oxide (in terms of ZrO ₂ ), and total iron oxide (T-Fe ₂ O _{3) in the} range of 0.01% to 0.5% by weight. ) (In terms of Fe ₂ O ₃ ).

In the first aspect of the present invention, the glass for FPD is, as a base glass composition, 55 to 70 wt% SiO ₂ , 0.2 to 5 wt% Al ₂ O ₃ , 0 to 15 wt% MgO, 2 to 15 Wt% CaO, 0-15 wt% SrO, 10-30 wt% (MgO + CaO + SrO + BaO), 0-5 wt% Li ₂ O, 0-6 wt% Na ₂ O, 0 15 wt% K ₂ O, 5-25 wt% (Na ₂ O + K ₂ O), 0.2-2.5 wt% zirconium oxide (in terms of ZrO ₂ ), 0.1 wt% to less than 0.5 wt% It is preferable to contain all the iron oxides (T-Fe ₂ O ₃ ) (in terms of Fe ₂ O ₃ ), and 0 to 5% by weight of B ₂ O ₃ .

In the first aspect of the present invention, it is preferable that the glass is substantially free of BaO.

Moreover, this invention provides the FPD board | substrate provided with the glass for FPD board | substrate which concerns on 1st aspect of this invention as 2nd aspect.

(The best mode for carrying out the invention)

Hereinafter, embodiments of the present invention will be described in detail.

Na ₂ O contained in the glass for FPD substrate according to one embodiment of the present invention has the effect of improving the solubility of the glass and lowering the dissolution load, thereby improving productivity. In addition, the Na ₂ O increases the coefficient of thermal expansion of the glass, thereby lowering chemical durability and electrical insulation. In addition, when considering the yellowing by the colloid of the metal Ag, it is estimated that Na ₂ O has a great influence on the above-described yellowing phenomenon.

Considering the case where Ag ions penetrate into the glass, it is first assumed that Ag deprives electrons to become Ag ⁺ ions and penetrates into the glass in the form of ion exchange with alkali ions in the glass. In particular, Na ⁺ in the glass has a fast diffusion rate and is considered to play a dominant role in ion exchange with Ag ⁺ ions. Therefore, in order to inhibit Ag ⁺ from invading the glass, Na ₂ O should be included in the glass in an amount of less than 6 wt%.

Ag ⁺ which penetrates into the glass does not contribute to color development by itself. The electron is donated in the glass to form a metal Ag (Ag ⁰ ), and then aggregated to form a colloid of Ag. It is considered yellowing.

The donation of electrons to the Ag ⁺ in the glass is Sn ²⁺ or iron ions (Fe ²⁺ ), but the present inventors can lower the electron donation of the glass itself, thereby obtaining a color suppression effect of the Ag ⁺ . I found it.

On the other hand, the optical basicity of glass is known as one of the measures which show the electron donation of glass. By the way, there are various theories about the coefficients representing the acid and base of each element, and various values are suggested, but not all elements can be obtained. Thus, Duffy and Ingram's basicity moderating parameters, which are related to the electronegativity of polling and are believed to be estimated with relatively good precision even for elements whose coefficients are not clearly known. , γ) can be used to determine the optical basicity of each glass composition from the following formula (1):

[Equation (1)]

(In the formula (1),

 m: cationic species contained in the glass,

γ _m : basicity relaxation coefficient of the cation m).

In addition, the present inventors have found a correlation between the optical basicity of several kinds of glass composition components and yellowing due to colloid of metal Ag, and the optical basicity is not more than 0.60, especially in the range of 0.57 to 0.60. It was found that yellowing caused by colloid of Ag can be improved.

Below, the reason which limited the composition of the said glass to the range as mentioned above is demonstrated.

K ₂ O has the effect of improving the solubility of the glass, lowering the dissolution load, and improving productivity in the same manner as Na ₂ O described above. In addition, although the effect is smaller than that of Na ₂ O, the coefficient of thermal expansion is increased to reduce chemical durability and electrical insulation. However, in view of yellowing by the colloid of metal Ag, behavior of K ₂ O it is estimated significantly different than Na ₂ O.

That is, potassium ions (hereinafter referred to as "K ⁺ ") contribute to ion exchange with Ag ⁺ like Na ⁺ , but since K ⁺ diffusion rate is very slow compared to Na ⁺ , Ag ⁺ is the core of glass ( It prevents the formation of the diffusion layer to the deep side. Moreover, since K ⁺ once escaped to the outside of the glass interferes with ion exchange between Na ⁺ and Ag ⁺ , the rate at which Ag ⁺ penetrates into the glass can be lowered, and Ag ⁺ can be suppressed from diffusing. Therefore, it is preferable that a weight% ratio is greater than K ₂ O / Na ₂ O value of 2 is preferred, and the range of 6-14.

In addition, RO, an alkaline earth metal oxide, wherein R is one or more selected from the group consisting of Ca, Mg, Sr, and Ba, increases the strain point of the glass, thereby improving the durability of the glass and forming the glass. It is used to adjust the devitrification temperature and viscosity at the time. In addition, since the RO has a large effect of lowering the viscosity, it may be preferable to be included in an appropriate amount in the glass. However, in the content of RO contained in the glass, when the content of MgO exceeds 15% by weight, the devitrification temperature of the glass may increase. In addition, when the content of CaO is less than 2% by weight, or more than 15% by weight, or when the content of SrO is more than 15% by weight, the devitrification temperature of the glass may also increase.

Since Ba ions (Ba ²⁺ ) have a smaller basicity relaxation coefficient (γ) than other alkaline earth metal ions, they have an effect of increasing optical basicity. In addition, when BaO is added to the glass, the density of the glass increases. Therefore, in order to make the density of glass into 2.7 or less, it is preferable that the said glass does not contain BaO substantially.

Such BaO is industrially introduced as an impurity contained in other alkaline earth metal raw materials. In the present invention, "substantially free of BaO" means that the content of BaO contained in the glass is 0.2% by weight or less.

And ZrO ₂ acts to improve the durability of the glass by raising the strain point of the glass. The ZrO ₂ is preferably included in the glass in an amount of 0.2% by weight or more. By the way, since Zr ion (Zr4 ⁺ ) has a small basicity relaxation coefficient ((gamma)) compared with other network formation ion, it has an effect which makes optical basicity large. Further, according to Sikkim increase the devitrification temperature of the glass, due to high temperature of the molded glass, the ZrO ₂ is preferably contained in an amount of up to 2.5% by weight of the glass.

In addition, the Fe ₂ O to a total iron oxide (T-Fe ₂ O ₃₎ in terms of Ag ⁺ ₃ is a reducing action by, Fe ^2+, causing the yellowing of the substrate, which may contain more than 0.5% by weight in the amount of the glass This is undesirable because it can happen.

And, SiO ₂ (silica) is a main component forming the skeleton of the glass. When the content of SiO ₂ is less than 55% by weight, durability of the glass may be lowered. On the other hand, when it exceeds 70% by weight, it may be difficult to dissolve the glass.

In addition, Al ₂ O ₃ is a component that improves the durability of the glass, but when the content thereof exceeds 5% by weight, dissolution of the glass becomes difficult. The Al ₂ O ₃ is preferably included in an amount of 0.2~2% by weight of the glass.

In addition, B ₂ O ₃ is a component used to improve the durability of the glass or as a dissolution aid. When the B ₂ O ₃ is contained in an amount of greater than 5% by weight in the glass, problems occur during molding due to volatilization or the like, so that the upper limit of the B ₂ O ₃ content is preferably 5%.

Since the glass having the composition range according to the present invention is preferably produced by the float method, in the production of the glass, sulfates of alkali metals or alkaline earth metals are usually used as clarifying agents. When using the sulphate, SO range of ₃ amount remaining in the glass is preferably 0.1~0.3 wt%.

Since the composition of the glass for a substrate of this invention has a mean coefficient of thermal expansion in the range of 80-95x10 <^-7> / degreeC in the temperature range of 50-350 degreeC, the crack or the crack of the glass for substrates resulting from thermal stress This can be suppressed from occurring. When the average coefficient of thermal expansion is less than 80 × 10 ⁻⁷ / ° C. or when the coefficient of thermal expansion exceeds 95 × 10 ⁻⁷ / ° C., it is difficult to match the peripheral material and the average coefficient of thermal expansion to each other.

The composition of the substrate glass according to the present invention can be produced by supplying a raw material combined to a desired composition into a melting furnace, vitrifying, and molding into a transparent plate glass having a predetermined thickness by a float method or the like.

EMBODIMENT OF THE INVENTION Below, the Example of this invention is given and this invention is demonstrated in detail.

(Example)

The glass sample of this Example was manufactured by supplying the glass raw material which has a composition shown in Table 1 to a standard glass melting kiln, melt | dissolving, and shape | molding to plate shape by the float method. The strain point, average thermal expansion coefficient, density, optical basicity, and absorbance change amount before and after silver treatment were measured for the glass sample, respectively. The strain point, average thermal expansion coefficient, and density of the glass sample were measured using a generally known method. In addition, the absorbance change amount of the said glass sample before and after silver treatment was measured in accordance with the method described in Unexamined-Japanese-Patent No. 2000-226233.

Table 1

As shown in Table 1, it was confirmed that the glass sample of this example had a strain point of 576 ° C., a coefficient of thermal expansion of 84 × 10 ⁻⁷ / ° C., and a density of 2.64 × 10 ³ kg / m ³ . Therefore, since the glass sample of this Example has a high strain point, when the said glass sample is used as a board | substrate for FPD, heat shrinkability is small, and it has the outstanding characteristic of a high thermal expansion coefficient and a low density. In addition, since the optical basicity is limited to 0.60 or less, the effect of suppressing yellowing by colloid of metal Ag is also excellent.

(Comparative Example 1 and Comparative Example 2)

Comparative Example 1 is a typical soda lime silica glass and has a composition range outside the composition range of the glass of the present invention. The glass of Comparative Example 1 had a coefficient of thermal expansion of 86 × 10 ⁻⁷ / ° C., but a coefficient of thermal expansion within the range of the present invention, but a strain point of 509 ° C., and a density of 2.49 × 10 ³ kg / m ³ , which is higher than the range of the present invention. It was quite low. In addition, Comparative Example 2 is glass having a glass composition of glass for typical PDP substrates currently commercially available. Since the glass of the comparative example 2 has an optical basicity larger than 0.60, it turns out that it is inferior to the inhibitory effect of yellowing by the colloid of metal Ag. In addition, the density of the glass of the comparative example 2 is 2.78, and is a large value out of the scope of the present invention.

In addition, about the distribution of silver after silver treatment, the Example and the comparative examples 1 and 2 were compared. As a result, compared with the comparative examples 1 and 2, the Example had a thin distribution layer thickness of silver which contributes to color development. From this point of view, it can be seen that in the glass for a substrate of the example, yellowing caused by colloidal diffusion of metal Ag into the glass was suppressed.

As described above, the glass for FPD substrates of the present invention contains less than 6% by weight of Na ₂ O, has a strain point of less than 560 to 580 ° C, and a coefficient of thermal expansion of 80 to 50 ° C in a temperature range of 50 to 350 ° C. 95 × 10 ⁻⁷ / ° C., density is 2.7 × 10 ³ kg / m ³ or less, and has an optical basicity of 0.60 or less, so that an Ag paste is applied onto the glass for a substrate and then fired to form an electrode It is possible to effectively suppress the yellowing of the colloid of metal Ag from diffusing into the glass for the substrate, and to obtain the glass for the FPD substrate having low thermal shrinkage and excellent chemical durability.

Further, according to the present invention, the glass for FPD substrate is a basic glass composition, 55 to 70% by weight SiO ₂ , 0.2 to 5% by weight Al ₂ O ₃ , 0 to 15% by weight MgO, 2 to 15 weight % CaO, 0-15 wt% SrO, 10-30 wt% (MgO + CaO + SrO + BaO), 0-5 wt% Li ₂ O, 0-6 wt% Na ₂ O, 0- 15 wt% K ₂ O, 5-25 wt% (Na ₂ O + K ₂ O), 0.2-2.5 wt% zirconium oxide (in terms of ZrO ₂ ), 0.1 wt% to less than 0.5 wt% Since it contains all iron oxide (T-Fe ₂ O ₃ ) (converted to Fe ₂ O ₃ ), and 0 to 5% by weight of B ₂ O ₃ , it is excellent in thermal shock resistance, crack resistance, and moldability, In addition, since the strain point is high and the heat shrinkability is small, it can be used as an FPD substrate.

Moreover, since the glass for FPD substrates which concerns on this invention does not contain BaO substantially as a base glass composition, the density of the said glass can be suppressed to 2.7 or less.

Moreover, since the FPD board | substrate which concerns on this invention is equipped with the glass for FPD board | substrate of this invention, it is suitable for being used as glass substrates for FPDs, such as PDP and FED, since it is small in heat shrinkability and excellent in chemical durability.

Claims (6)

It contains less than 6% by weight of Na ₂ O, has a strain point in the range of less than 560 to 580 ° C., an average coefficient of thermal expansion of 80 to 95 × 10 ⁻⁷ / ° C., and a density of 2.7 × in a temperature range of 50 to 350 ° C. 10 ³ kg / m ³ , the glass for a flat panel display substrate having an optical basicity of 0.60 or less. The method of claim 1, As% of the weight ratio, the glass for a flat panel display substrate, characterized in that at least the value of _{K 2 O / Na 2 O 2} . The method of claim 1, 0.2 to 2.5% by weight (also in terms of ZrO ₂₎ of zirconium oxide in% by weight, and 0.01 to 0.5 wt% total iron oxide (T-Fe ₂ O ₃₎ in the range of less than% by weight, include (also in terms of Fe ₂ O ₃₎ The glass for flat panel display substrates characterized by the above-mentioned. The method of claim 1, A base glass composition, SrO, 10 of 55-70% by weight of SiO _2, 0.2~5 wt% of Al ₂ O _3, 0~15 wt% of MgO, 2~15% of CaO, 0~15% by weight -30 wt% (MgO + CaO + SrO + BaO), 0-5 wt% Li ₂ O, 0-6 wt% Na ₂ O, 0-15 wt% K ₂ O, 5-25 wt% (Na ₂ O + K ₂ O), 0.2-2.5 wt% zirconium oxide (in terms of ZrO ₂ ), total iron oxide (T-Fe ₂ O ₃ ) (Fe _{2 in the} range of 0.1 wt% to less than 0.5 wt% O also converted to _3), and 0 to 5 glass for a flat panel display substrate comprising the% of B ₂ O ₃ by weight. The method of claim 1, A base glass composition, substantially free of BaO, characterized in that the glass for a flat panel display substrate. The flat panel display substrate provided with the glass for flat panel display substrates of Claim 1.