JP2005231989A - Lead-free glass composition for plasma display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead-free glass composition containing no element which is undesirable in environmental view and having excellent properties useful as a glass composition for a plasma display. <P>SOLUTION: The lead-free glass composition for the plasma display contains substantially no alkaline earth metal and fluoride and comprises substantially 10-35 mol% SiO<SB>2</SB>, 20-35 mol% B<SB>2</SB>O<SB>3</SB>, 15-40 mol% ZnO, 3-10 mol% Al<SB>2</SB>O<SB>3</SB>and 10-20 mol% in tatal of Na<SB>2</SB>O and Li<SB>2</SB>O. The molar ratio Na<SB>2</SB>O/Li<SB>2</SB>O is in a range of 0.5-2.5, particularly 1-2. The coefficient of thermal expansion of the glass composition is approximate to a glass substrate. The properties such as water resistance, gas adsorbing property and a softening point is suitable to the glass composition for the plasma display (for example, a dielectric layer, a diaphragm, a glass component in an electrode material). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lead-free glass composition used for a plasma display panel. Specifically, the present invention relates to a lead-free glass composition used as a material for forming dielectric layers, partition walls, and the like formed on the front panel and the back panel of a plasma display panel.

  The plasma display panel can obtain a clear image even on a large screen and can be reduced in thickness as compared with a conventional cathode ray tube. For this reason, in recent years, it has become widespread in televisions and computer screens. In the plasma display panel, a large number of cells, that is, discharge spaces, are separated by barrier ribs between the front glass substrate and the rear glass substrate on which electrodes and a dielectric layer are formed, and phosphors are formed on the surface. It has been applied. Each cell is filled with a discharge gas, and when a voltage is applied to the electrodes, a discharge occurs and ultraviolet rays are generated. As a result, the phosphor is colored to display an image. Yes.

Conventionally, lead glass having a low melting point has been used as the dielectric layer and the partition wall, but the use of glass containing lead has been refrained due to increasing environmental problems. Therefore, in order to be comparable to leaded glass, performance required as a dielectric layer and partition walls, that is, water resistance, softening point equivalent to the firing temperature (for example, 560 ° C. or less), thermal expansion coefficient approximate to a glass substrate ( For example, various lead-free glass compositions that can satisfy about 70 × 10 ⁻⁷ / K) have been developed (see, for example, Patent Documents 1 to 4). Specifically, Patent Document 2 discloses ZnO, B ₂ O ₃ , SiO ₂ , R ₂ O (where R ₂ O is K ₂ O, Na ₂ O, and Li ₂ O), RO (here, RO Discloses a lead-free low-melting glass composition containing CaO, BaO, and MgO), TiO ₂ , and NaF in a predetermined composition ratio. According to this lead-free low-melting-point glass composition, it is said that the performance suitable for the dielectric layer and the partition can be satisfied by being constituted with this composition.

JP 2000-16834 A JP 2000-226231 A JP 2001-163635 A JP-A-9-295830

However, the lead-free low-melting glass composition contains sodium fluoride, but it is more preferable that the lead-free low-melting glass composition does not contain an environmentally undesirable element such as fluoride due to an increase in environmental problems.
Therefore, there is a need for a lead-free glass composition that does not contain environmentally undesirable elements such as lead and fluoride, and that is useful as a glass composition for plasma displays, such as water resistance, softening point, gas adsorption, and thermal expansion coefficient. Has been.

  Accordingly, the present invention has been developed to solve such conventional problems, and provides a lead-free glass composition that does not contain environmentally undesirable elements and that is excellent in performance useful as a glass composition for a plasma display. With the goal.

The lead-free glass composition for plasma display according to the present invention is substantially free of alkaline earth metal in the lead-free glass composition used for the plasma display panel. Further, the composition is essentially _SiO 2: 10 to 35 _{mol%, B} 2 O 3: _20~35 mol%, ZnO: 15 to 40 _{mol%, Al} 2 O 3: _3~10 mol%, and Na total ₂ O and Li ₂ O: is composed at a ratio of 10 to 20 mol%. In particular, the molar ratio of Na ₂ O / Li ₂ O is included in the range of 0.5 to 2.5.

The lead-free glass composition for a plasma display having such a structure does not contain an alkaline earth metal. By not containing an alkaline earth metal, gas adsorption can be reduced, and release of gas due to heating during discharge can be suppressed. Further, by including Na ₂ O and Li ₂ O, it is possible to lower the softening point. Further improve the water resistance by including _Al 2 _{O 3} with these Na ₂ O and Li ₂ O. In particular, by setting the Na ₂ O / Li ₂ O molar ratio within a predetermined range, the coefficient of thermal expansion can be made a range that approximates that of a glass substrate, and cracks and breakage during firing can be prevented.

Preferably, the lead-free glass composition for a plasma display is substantially free of fluoride. According to the composition having the above-described structure, performance suitable as a glass composition for a plasma display can be obtained without containing fluoride. Specifically, by including Na ₂ O and Li ₂ O at a predetermined content, the softening point can be lowered without containing fluoride. For this reason, environmentally preferable among lead-free glasses. And, by being composed of the above-mentioned composition in a predetermined ratio, all performances such as water resistance, gas adsorbability, softening point, and thermal expansion coefficient can be plasma without containing undesirable lead and fluoride components in the environment. It can be optimized as a glass composition for a display.

In particular, the molar ratio of Na ₂ O and Li ₂ O contained is preferably in the range of 1 to 2. When these alkali metals are contained in this molar ratio, the thermal expansion coefficient can be made particularly equal to that of the glass substrate, and the effect of preventing cracks and breakage during firing is extremely excellent.

  The lead-free glass composition for a plasma display of the present invention can be suitably used for forming a plasma display. In particular, it can be used as a material for forming a dielectric layer or a partition wall. Moreover, it is useful also as any glass component used for formation of a plasma display, for example, a glass component in paste for electrode (for example, Ag electrode) formation.

Hereinafter, preferred embodiments of the present invention will be described. In addition, matters other than the matters specifically mentioned in the present specification (for example, glass composition, particularly Na ₂ O / Li ₂ O ratio, etc.) and matters necessary for carrying out the present invention are the prior art in the field. It can be grasped as a design matter of those skilled in the art based on the above. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

Next, each component contained in the lead-free glass composition for plasma display of this invention is explained in full detail.
The lead-free glass composition for plasma display of the present invention is substantially free of alkaline earth metal. In the lead-free glass composition for a plasma display, water resistance can be improved depending on the composition by adding an alkaline earth metal. However, on the other hand, there was a tendency for gas adsorption to increase. When the gas adsorption property is high, the adsorbed gas is released when the temperature is applied to the substrate during discharge in the plasma display panel. By this gas, impurities in the discharge gas (for example, xenon gas) increase, and the luminance decreases. In the present composition, the water resistance can be improved without containing an alkaline earth metal. Here, “substantially free” means that it does not actively contain an alkaline earth metal component, and can be contained as an impurity component or the like in other components (for example, 0.01 mol%). The following does not exclude the inclusion of an alkaline earth metal component in an amount that does not substantially make sense as described below.

The SiO ₂ component is contained in an amount of 10 to 35 mol%, preferably 10 to 30 mol%, more preferably 10 to 20 mol%, and particularly 13 to 18 mol%. If the content is less than this range, the water resistance tends to decrease. On the other hand, if the content is larger than this range, the compactness tends to decrease and the mechanical strength and the like tend to decrease.

B ₂ O ₃ is 20 to 35 mol%, in particular 25 to 35 mol%. When the content is less than this range, the softening point is not sufficiently lowered. On the other hand, if the content is higher than this range, the water resistance tends to decrease. From the viewpoint of emphasizing good water resistance, the B ₂ O ₃ component is preferably 20 to 30 mol%, particularly preferably 25 to 30 mol%.

  ZnO is contained at 15 to 40 mol%, particularly 30 to 40 mol%. If the content is less than this range, the water resistance tends to decrease. On the other hand, if the content is higher than this range, the glass forming ability tends to be reduced, and crystallization is likely to occur.

Al ₂ O ₃ is contained at 3 to 10 mol%, particularly 3 to 8 mol%. If the content is less than this range, the water resistance tends to decrease. On the other hand, when there is more content than this range, it is inferior to the effect which reduces a softening point.

Then, Na ₂ O and Li ₂ O is, the total 10 to 20 mol%, is contained preferably 10 to 16 mol%, in particular 13 to 16 mol%. If the content is less than this range, the effect of lowering the softening point tends to be inferior. On the other hand, when the content is higher than this range, the gas adsorption property tends to increase. As the alkali metal, it is necessary to use both Na ₂ O and Li ₂ O. Li ₂ O is excellent in the effect of lowering the softening point, but the gas adsorbability tends to increase with Li ₂ O alone. On the other hand, Na ₂ O alone is inferior in the effect of lowering the softening point. By using these Na ₂ O and Li ₂ O in combination, the effect of lowering the softening point is obtained and the gas adsorbability is not increased.

Further, the combination of these Na ₂ O and Li ₂ O and _Al 2 _{O 3,} without free alkaline earth metal, it is possible to achieve high water resistance.

A preferable Na ₂ O / Li ₂ O molar ratio is in the range of 0.5 to 2.5, and further in the range of 1 to 2. In particular, the molar ratio is preferably about 1. The thermal expansion coefficient is substantially the same as that of the glass substrate when the Na ₂ O / Li ₂ O molar ratio is in the range of 1 to 2 (particularly a molar ratio of approximately 1). The thermal expansion coefficient gradually decreases as the Na ₂ O / Li ₂ O molar ratio becomes smaller than the range of 1 to 2 (that is, the ratio of Li ₂ O to Na ₂ O increases) It gradually increases as it becomes larger than the molar ratio (ie, the ratio of Li ₂ O to Na ₂ O decreases). Therefore, when it deviates from the molar ratio in the range of 0.5 to 2.5, the difference in thermal expansion coefficient from the glass substrate increases, and the effect of preventing cracks and breakage during firing tends to be inferior.

Particularly preferred compositions are substantially free of alkaline earth metals, the composition is substantially _SiO 2: 13 to 18 _{mol%, B} 2 O 3: _25~35 mol%, ZnO: 30 to 40 mol% , _Al 2 _O 3: 3~8 mole%, and the total of Na ₂ O and Li ₂ O: 13 to 16 are composed at a ratio of mol%. In particular, the Na ₂ O / Li ₂ O molar ratio is within the range of 1-2.

  By being comprised from the above composition, the lead-free glass composition for plasma displays of this invention can obtain performance suitable as a panel for plasma displays, even if it does not contain a fluoride substantially. In addition, “substantially does not contain” has the same meaning as the alkaline earth metal.

Furthermore, the lead-free glass composition for a plasma display of the present invention is one or two kinds of other conventionally known components applicable to the glass composition for other purposes, as desired, within a range not impairing the effects of the present invention. It can be contained above. Examples of such other components include SnO, SnO ₂ , CuO, Cu ₂ O, TiO ₂ , ZrO ₂ , and CeO ₂ . Moreover, the content is not specifically limited, For example, about 0-10 mol% is suitable in a glass composition.

The lead-free glass composition for plasma display of the present invention has the above-described configuration, and in particular, from 60 × 10 ⁻⁷ / K whose thermal expansion coefficient approximates to about 70 × 10 ⁻⁷ / K of a general glass substrate. And can be smaller than 75 × 10 ⁻⁷ / K. In particular, it can be set to around 70 × 10 ⁻⁷ / K, for example, from 65 × 10 ⁻⁷ / K to 73 × 10 ⁻⁷ / K. Further, the softening point can be lowered to 560 ° C. or lower, preferably 550 ° C. or lower, particularly 540 ° C. or lower. In a more preferred embodiment, there is one that can realize a softening point as low as 530 ° C. or less. Moreover, water resistance can be improved. Specifically, reducing the weight loss after immersion in warm water at 80 ° C. for about 15 hours (that is, the weight loss after immersion relative to the weight before immersion in warm water) to 5% or less, particularly 2% or less. Can do. Furthermore, the gas adsorbability can be made extremely low. Specifically, after the glass powder is left in the room temperature atmosphere for 100 hours and then heated to 600 ° C., the weight reduction rate (that is, the weight reduction rate when heated to 600 ° C. relative to the weight at room temperature) is 5 % Or less, particularly 2% or less.

Therefore, a preferred form of the present invention is substantially free of alkaline earth metal and fluoride, and the composition is substantially SiO ₂ : 10 to 35 mol%, B ₂ O ₃ : 20 to 35 mol%, ZnO: 15 to 40 _{mol%, Al} 2 O 3: _3~10 mol%, and the total of Na ₂ O and Li ₂ O: is composed at a ratio of 10 to 20 mol%, and _{Na 2} O / Li 2 The O molar ratio is included in the range of 0.5 to 2.5 (particularly approximately 1, for example, 0.9 to 1.1). Typically, the composition has a coefficient of thermal expansion of greater than 60 × 10 ⁻⁷ / K and less than 75 × 10 ⁻⁷ / K, and a softening point of 550 ° C. or lower.
Particularly preferred forms are substantially free of alkaline earth metals and fluorides, and the composition is substantially SiO ₂ : 10-20 mol%, B ₂ O ₃ : 20-35 mol%, ZnO: 15 40 _{mol%, Al} 2 O 3: _3~10 mol%, and the total of Na ₂ O and Li ₂ O: 10 to 20 is composed of a proportion of mol%, and _{Na 2} O / Li 2 O molar ratio of It is included in the range of 0.5 to 2.5 (particularly approximately 1, for example, 0.9 to 1.1). And it is a composition whose thermal expansion coefficient is larger than 60 * 10 < ^-7 > / K and smaller than 75 * 10 < ^-7 > / K, and a softening point is 540 degrees C or less.

Further preferred form, substantially free of alkaline earth metals and fluorides, the composition is substantially _SiO 2: 13 to 18 _{mol%, B} 2 O 3: _25~35 mol%, ZnO:. 30 to 40 _{mol%, Al} 2 O 3: _3~8 mole%, and the total of Na ₂ O and Li ₂ O: 13 to 16 is composed of a proportion of mol%, and _{Na 2} O / Li 2 O molar ratio It falls within the range of 1-2. Then, the thermal expansion coefficient in the range of ^{65 × 10 -7 / K~73 × 10} -7 / K, softening point, 540 ° C. or less, in particular 530 ° C. or less composition.

The lead-free glass composition for a plasma display of the present invention can be used in any shape when forming a plasma display, but is usually used in a powder state. The average particle diameter of the powder is not particularly limited, but for example, it is preferably 1 to 10 μm, preferably 1 to 7 μm, particularly about 1 to 5 μm. When it has an average particle diameter in this range, it is particularly excellent in denseness, and water resistance, mechanical strength and the like are improved. In the present specification, the “average particle diameter” refers to D ₅₀ (median diameter) in the particle size distribution of the powder. Such D ₅₀ is, for example, can be easily measured by a conventionally known laser diffraction method, the particle size distribution measurement apparatus based on light scattering method or the like.

  The lead-free glass composition for a plasma display in a powder state can be formed into a paste in the same manner as a conventional glass composition to form each component of the plasma display. That is, a dielectric layer is formed by applying, printing, or patterning and baking a paste in which a glass composition powder is mixed with a binder, an organic solvent, and, if necessary, other additive components such as an inorganic filler and an inorganic pigment. A partition wall, an electrode, or the like can be formed. The binder, organic solvent, and other components used in the paste according to the purpose (for example, Ag powder or other conductive metal powder for electrode formation) are not particularly limited. Can be appropriately selected from conventionally known ones.

<Test Example 1: Effect of not containing alkaline earth metal>
Each raw material powder was mixed so as to have the glass composition shown in Table 1 below, and melted at 1200 ° C. for 30 minutes in an oxygen-containing atmosphere. As the raw material _{powder, SiO 2, H 3 BO 3} ( boric acid), ZnO (zinc white), _Al 2 _{O 3} (alumina), CaCO ₃ (calcium carbonate), SrCO ₃ (strontium carbonate), _Li 2 CO ₃ (Lithium carbonate), Na ₂ CO ₃ (sodium carbonate), and K ₂ CO ₃ (potassium carbonate) were used. This was put in an agate vessel together with an agate cobblestone in a planetary mill, and wet pulverized at 200 rpm for about 15 to 20 hours to obtain glass composition powders (sample Nos. 1 to 4). The average particle diameter D ₅₀ is laser diffraction method (i.e. a laser beam is irradiated to the sample, the scattering pattern when scattered determining particle size distribution.) A particle size distribution measuring apparatus based on (manufactured by Horiba, Ltd. of the type " LA920 ").

<Test Example 2: Effect of Alkali Metal Na ₂ O / Li ₂ O Molar Ratio>
Glass composition powders (Sample Nos. 5 to 8) were obtained in the same manner as in Test Example 1 so as to obtain the glass composition shown in Table 2 below.

<Test Example 3: Other preferred examples>
Glass composition powders (Sample Nos. 9 to 12) were obtained in the same manner as in Test Example 1 so that the glass compositions shown in Table 3 below were obtained.

<Performance evaluation test>
The following performance evaluation test was done about the glass composition powder obtained as mentioned above.
1. Softening point The softening point was measured using general DTA (differential thermal analysis). The value of the third peak of the DTA curve was taken as the softening point.
2. TG weight loss rate (adsorption gas property evaluation)
After 10 cc of the glass composition powder obtained above was dried at 200 ° C. for 3 hours and then allowed to stand in the atmosphere at room temperature for 100 hours, the glass composition powder was further heated to 600 ° C. The weight B was measured and evaluated by the weight decrease rate of the weight B after the temperature increase with respect to the weight A after being left in the atmosphere. That is,
TG weight loss rate (%) = {1- (weight B after temperature increase) / (weight A after standing in air)} × 100
3. Elution rate (water resistance evaluation)
The glass composition powder obtained as described above is made into a paste and printed and fired on a glass substrate. This was immersed in warm water at 80 ° C. for about 15 hours, the weight before and after immersion was measured, and the dissolution rate was evaluated based on the weight reduction rate. That is,
Dissolution rate (%) = {1- (weight after immersion C) / (weight D before immersion)} × 100
4). Coefficient of thermal expansion The glass composition powder obtained above is formed into a cylindrical shape having a diameter of 5 mm and a height of 20 mm, and is baked and hardened at a temperature near the softening point. Using this sample, the thermal expansion coefficient was measured by a TMA apparatus (manufactured by Rigaku Electric Co., Ltd.).

<Result>
These performance evaluation tests were performed on the glass composition powders obtained in the respective test examples. The results are shown in Tables 4 and 5. In addition, Sample No. For 1 to 4, a graph comparing the TG weight loss rate is shown in FIG. 1, and a graph comparing the elution rate is shown in FIG. Furthermore, sample No. The graph which compares a thermal expansion coefficient about 5-8 is shown in FIG.

The following can be understood from Table 4, FIG. 1 and FIG. That is, sample No. When comparing Nos. 1 to 4, Sample No. containing no alkaline earth metal was used. The glass composition of Example 4 (Example) has a softening point as low as 535 ° C., and the TG weight loss rate and elution rate are other sample Nos. 1 to 3 (both are comparative examples). Therefore, the softening point was low without containing an alkaline earth metal, and gas adsorption and water resistance could be improved.
Sample No. in Test Example 3 In the glass compositions of 9 to 12 (both examples), the TG weight loss rate and elution rate are the same as the sample numbers of Test Example 1. It was as low as 4. Sample No. 9 to 11, the softening point is as low as 540 ° C. or lower. In No. 9, a low softening point of 530 ° C. was realized.

Furthermore, the following can be seen from Table 5 and FIG. That is, the sample No. Comparing samples 5 to 8, sample no. 5 (comparative example) has a Na ₂ O / Li ₂ O molar ratio of 3 and a thermal expansion coefficient of 75 × 10 ⁻⁷ / K which is too high. In comparison with this, sample no. In 6 to 8 (both examples), since the Na ₂ O / Li ₂ O molar ratio is in the range of 0.5 to 2.5, the thermal expansion coefficient exceeds 60 × 10 ⁻⁷ / K and 75 ×. ^Less than 10 ⁻⁷ / K. In particular, sample No. 2 in which the molar ratio of Na ₂ O / Li ₂ O is in the range of 1 to 2 is used. In 6 and 7, the thermal expansion coefficient is in the range of ^{65 × 10 -7 / K~73 × 10} -7 / K, it is particularly suitable.

  The preferred embodiments of the present invention have been described in detail above, but these are only examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the above-described embodiments. In addition, the technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

It is a graph which compares the TG weight loss rate (gas adsorption test) in one test example. It is a graph which compares the elution rate (water resistance test) in one test example. It is a graph which compares the thermal expansion coefficient in another test example.

Claims (3)

In Pb-free glass composition for use in a plasma display panel, substantially free of alkaline earth metals, the composition is substantially _SiO 2: 10 to 35 _{mol%, B} 2 O 3: _20~35 mol%, ZnO: 15 to 40 _{mol%, Al} 2 O 3: _3~10 mol%, and the total of Na ₂ O and Li ₂ O: is composed at a ratio of 10 to 20 mol%, and _{Na 2} O / Li 2 A lead-free glass composition for a plasma display, wherein the O molar ratio is within the range of 0.5 to 2.5.   The lead-free glass composition for a plasma display according to claim 1, which is substantially free of fluoride. Na ₂ O / Li ₂ O molar ratio is within the scope of 1-2, according to claim 1 or 2 for a plasma display free glass composition.

Images