JP6804042B2 - Bismuth glass, composite powder material and composite powder material paste - Google Patents

Description

The present invention relates to bismuth-based glass, composite powder material and composite powder material paste, and specifically to bismuth-based glass, composite powder material and composite powder material paste used for coating electrodes and resistors of thermal printheads.

In a thermal printer, for example, by heating the thermal paper while feeding it in one direction, the thermal dye in the thermal layer provided on the thermal paper is developed to form an image.

The printing section of the thermal printer is provided with a thermal print head for heating the thermal paper and a pressurizing roller for pushing the thermal paper toward the thermal print head and feeding it in one direction. The thermal print head has a laminated basic structure in which a heat storage layer, a line-shaped resistor layer, an electrode layer, a coating layer (protective layer), and the like are formed on a ceramic substrate such as alumina.

The coating layer of the thermal printhead is formed for the purpose of protecting the electrodes and resistors from contact with thermal paper. Then, as an electrode, for example, an Au lead electrode, an Ag external electrode, or the like is formed, and as a resistor, for example, a RuO ₂ resistor or the like is formed.

Special Fair 04-002533 Japanese Unexamined Patent Publication No. 2008-30307

The coating layer is generally formed by firing a powder material (glass powder). The firing temperature is limited to 900 ° C. or lower in order to prevent the characteristics of the electrodes and the like from deteriorating. Therefore, the powder material is required to be calcinable at a temperature of 900 ° C. or lower.

Further, the powder material is also required to have low reactivity with the Au lead electrode and the Ag external electrode so that the electrode does not break after firing.

Further, the coating layer of the thermal print head repeatedly contacts the thermal paper. Therefore, the powder material is also required to easily form a coating layer having high wear resistance and surface smoothness.

Conventionally, PbO-SiO ₂ glass has been used as a powder material satisfying these required characteristics (see Patent Document 1).

In recent years, from the viewpoint of environmental protection, reduction of environmentally hazardous substances, for example, reduction of PbO has been promoted, and various lead-free glasses have been proposed in place of PbO-B ₂ O _3- SiO ₂ glass. There is. For example, Patent Document 2 describes bismuth-based glass.

However, the bismuth-based glass described in Patent Document 2 has a problem that it has high reactivity with an Au lead electrode and an Ag external electrode, and the electrode is easily broken after firing.

Therefore, the present invention has been made in view of the above circumstances, and its technical problem is that it can be fired at a temperature of 900 ° C. or lower even if it does not contain PbO, and its reactivity with an electrode such as an Au lead electrode. The idea is to create a bismuth-based glass that has a low temperature and can contribute to the improvement of abrasion resistance and surface smoothness of the coating layer.

The present inventor has conducted various experiments, with the adoption of _{SiO 2 -B 2 O 3 -CaO-} Bi 2 O 3 based glass as bismuth-based glass-based, _SiO in the glass composition _2, B 2 _{O 3} , CaO, and Bi ₂ O ₃ are strictly regulated to solve the above technical problems, and the present invention proposes them. That is, the bismuth-based glass of the present invention has a glass composition of SiO ₂ 55 to 75%, B ₂ O ₃ 1 to 8%, CaO 5 to 17%, Bi ₂ O ₃ 10 to 23%, and ZrO in terms of glass composition. _It contains _{20 to} 6% and Al ₂ O _{30 to} 8%, and the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) is larger than 3.3 and less than 4.3. It is characterized by that. Here, "(SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ )" is the value obtained by dividing the total amount of SiO ₂ and CaO by the total amount of B ₂ O ₃ and Bi ₂ O _3. is there.

Bismuth-based glass generally has high reactivity with Au lead electrodes. On the other hand, the bismuth-based glass of the present invention has a SiO ₂ content of 55 mol% or more, a B ₂ O ₃ content of 8 mol% or less, a Ca O content of 5 mol% or more, and a Bi ₂ O ₃ content. Since the amount is 23 mol% or less and the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) is regulated to more than 3.3, the reactivity with the Au lead electrode is suppressed.

Further, in bismuth-based glass, when the content of SiO ₂ is high and the content of CaO is high, anorthite (CaAl ₂ Si ₂ O ₈ ) crystals are precipitated during firing to ensure desired surface smoothness. It may be difficult to do. Therefore, in the bismuth-based glass of the present invention, the precipitation of anorthite crystals is suppressed by restricting the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) to 4.1 or less.

Secondly, the bismuth-based glass of the present invention has a glass composition of SiO ₂ 60 to 70%, B ₂ O ₃ 1 to 7%, Ca O 6 to 15%, and Bi ₂ O ₃ 10 to 20% in mol%. , ZrO ₂ 0.1-5%, Al ₂ O ₃ 0.1-7%, molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) is larger than 3.3, and It is less than 4.3 and is preferably used for coating a thermal printhead.

Thirdly, the bismuth-based glass of the present invention has a glass composition of SiO ₂ 60 to 70%, B ₂ O ₃ 2 to 6%, Ca O 6 to 15%, and Bi ₂ O ₃ 10 to 20% in mol%. , ZrO ₂ 0.5-4%, Al ₂ O ₃ 2-7%, and the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) is 3.4-4.1. , Preferably used for coating thermal printheads.

Fourth, it is preferable that the bismuth-based glass of the present invention substantially does not contain PbO in the glass composition. Here, "substantially free of PbO" means that PbO is allowed to be mixed at the impurity level, but positive introduction is avoided. Specifically, the content of PbO in the glass composition. Refers to the case where is less than 1000 ppm (less than 0.1 mol%).

Fifth, the composite powder material of the present invention is a composite powder material containing the above-mentioned glass powder made of bismuth-based glass and alumina powder, and the content of the glass powder is 60 to 90% by volume, that of the alumina powder. The content is preferably 10 to 30% by volume.

Sixth, the composite powder material of the present invention preferably has a softening point of 600 to 800 ° C. Here, the "softening point" refers to the temperature of the fourth inflection point measured by a macro differential thermal analyzer (DTA).

Seventh, the composite powder material paste of the present invention is a powder material paste containing a composite powder material and a vehicle, and the composite powder material is preferably the above-mentioned composite powder material.

The bismuth-based glass of the present invention has a glass composition of SiO ₂ 55 to 75%, B ₂ O ₃ 1 to 8%, CaO 5 to 17%, Bi ₂ O ₃ 10 to 23%, ZrO _{20 in} mol%. It contains ~ 6% and Al ₂ O _{30 to} 8%, and the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) is larger than 3.3 and less than 4.3. The reason for restricting the content range of each component as described above will be described below. In the description of the content range of each component, the% indication means mol%.

SiO ₂ is a component that forms a glass skeleton and is a component that suppresses reactivity with an Au lead electrode. The content of SiO ₂ is 55 to 75%, preferably 60 to 70%, and more preferably 62 to 68%. When the content of SiO ₂ is low, the reactivity with the Au lead electrode is high, and the electrode is easily broken. On the other hand, when the content of SiO ₂ increases, the softening point rises unreasonably, making it difficult to bake at a temperature of 900 ° C. or lower.

B ₂ O ₃ is a component that forms a glass skeleton and widens the vitrification range, but if the content thereof is large, the reactivity with the Au lead electrode becomes high, and the electrode may be broken. Therefore, the content of B ₂ O ₃ is 1 to 8%, preferably 1 to 7%, more preferably 1 to 6%, and further preferably 2 to 5%.

CaO is a component that stabilizes the glass and a component that suppresses the reactivity with the Au lead electrode. The CaO content is 5 to 17%, preferably 6 to 15%, more preferably 8 to 13%. When the CaO content is high, anorthite crystals are likely to be precipitated, and the surface smoothness of the coating layer is likely to be lowered.

Bi ₂ O ₃ is a component that lowers the softening point, but if the content is large, the reactivity with the Au lead electrode becomes high, and the electrode may be broken. The content of Bi ₂ O ₃ is 10 to 23%, preferably 10 to 20%, and more preferably 12 to 18%.

ZrO ₂ is a component that enhances wear resistance. The content of ZrO ₂ is 0 to 6%, preferably 0.1 to 5%, more preferably 0.5 to 4%, still more preferably 1 to 4%. When the content of ZrO ₂ is low, the wear resistance of the coating layer tends to be lowered. On the other hand, when the content of ZrO ₂ increases, the softening point rises unreasonably, making it difficult to bake at a temperature of 900 ° C. or lower.

Al ₂ O ₃ is a component that enhances wear resistance. The content of Al ₂ O ₃ is 0 to 8%, preferably 0.1 to 7%, more preferably 2 to 7%, still more preferably 3 to 6%. When the content of Al ₂ O ₃ decreases, the wear resistance of the coating layer tends to decrease. On the other hand, when the content of Al ₂ O ₃ is large, anorthite crystals are likely to be precipitated, and the surface smoothness of the coating layer is likely to be lowered.

The molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) is greater than 3.3 and less than 4.3, preferably 3.4 to 4.1, more preferably 3.5 to. It is 3.9. When the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) becomes small, the reactivity with the Au lead electrode becomes high, and the electrode is easily broken. On the other hand, when the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) is large, anorthite crystals are likely to be precipitated, and the surface smoothness of the coating layer is likely to be lowered.

In addition to the above components, for example, the following components may be introduced.

MgO, SrO, BaO and ZnO are components that lower the softening point and stabilize the glass. The MgO, SrO, BaO and ZnO contents are preferably 0 to 5% in total or alone, particularly 0 to 1%. When the contents of MgO, SrO, BaO and ZnO are high, feldspar-based crystals are likely to be precipitated during firing, and the surface smoothness of the coating layer is likely to be lowered.

In addition to the above components, various components may be introduced as long as the characteristics of the thermal printhead are not significantly impaired. For example, in order to lower the softening point, Cs ₂ O, Rb ₂ O and the like may be introduced in a combined amount or alone up to 5%, particularly 1%. In addition, in order to stabilize the glass, Y ₂ O ₃ , La ₂ O ₃ , Ta ₂ O ₅ , SnO ₂ , TiO ₂ , Nb ₂ O ₅ , P ₂ O ₅ , CuO, CeO ₂ , V ₂ O _5, etc. May be introduced in a combined amount or alone up to 10%, especially up to 1%.

PbO is a component that lowers the softening point, but since it is an environmentally hazardous substance, it is preferable to substantially avoid its introduction.

The composite powder material of the present invention is a composite powder material containing the above-mentioned glass powder made of bismuth-based glass and alumina powder, and has a glass powder content of 60 to 90% by volume and an alumina powder content of 10. It is preferably ~ 30% by volume.

Glass powder is a material that melts during firing to form a coating layer. The glass powder can be produced, for example, by forming molten glass into a film and then crushing and classifying the obtained glass film.

The content of the glass powder is preferably 60 to 90% by volume, preferably 70 to 88% by volume, and more preferably 76 to 85% by volume. When the content of the glass powder is low, it becomes difficult to form a dense coating layer, and it becomes difficult to secure the desired surface smoothness. On the other hand, when the content of the glass powder is high, the content of the alumina powder is relatively low, so that the wear resistance and thermal conductivity of the coating layer are likely to decrease.

The average particle size D ₅₀ of the glass powder is preferably 2.0 μm or less, and the maximum particle size D _max is preferably 10 μm or less. If the particle size of the glass powder is too large, the surface smoothness of the coating layer tends to decrease, and large bubbles tend to remain in the coating layer. Here, the "average particle size D ₅₀ " refers to a value measured by a laser diffractometer, and the integrated amount is cumulative from the smallest particle in the volume-based cumulative particle size distribution curve measured by the laser diffractometer. The particle size is 50%. Further, "maximum particle size D _max " refers to a value measured by a laser diffractometer, and in a volume-based cumulative particle size distribution curve measured by a laser diffractometer, the integrated amount is accumulated from the smallest particle. Represents a particle size of 99%.

Alumina powder is a material that enhances the wear resistance of the coating layer and also enhances the thermal conductivity of the coating layer. The content of the alumina powder is preferably 10 to 30% by volume, more preferably 15 to 23% by volume. When the content of the alumina powder is large, anorthite crystals are likely to be precipitated, and the surface smoothness of the coating layer is likely to be lowered. Further, when the content of the alumina powder is large, the ratio of the glass powder is relatively small, so that it becomes difficult to form a dense coating layer and it becomes difficult to secure the desired surface smoothness.

The average particle size D ₅₀ of the alumina powder is preferably 2.0 μm or less, and the maximum particle size D _max is preferably 10 μm or less. If the particle size of the alumina powder is too large, the surface smoothness of the coating layer tends to decrease.

In addition to the alumina powder, 0 to 10% by volume, particularly 0 to 8% by volume of other ceramic powder may be introduced. Various materials can be used as other ceramic powders. For example, zirconia, mullite, silica, cordierite, titanium, tin oxide, etc. can be used to adjust the coefficient of thermal expansion and abrasion resistance of the coating layer. Of these, one or more can be added.

In the composite powder material of the present invention, the softening point is preferably 600 to 800 ° C., more preferably 620 to 780 ° C., still more preferably 640 to 760 ° C. If the softening point is too high, it becomes difficult to form a dense coating layer at a firing temperature of 900 ° C. or lower, and it becomes difficult to secure desired surface smoothness. On the other hand, if the softening point is too low, the reactivity with the Au lead electrode becomes high, and the electrode is liable to break.

In the composite powder material of the present invention, the average coefficient of thermal expansion in the temperature range of 30 to 300 ° C. is preferably 53 × 10 ^-7 to 70 × 10 ^-7 / ° C., more preferably 55 × 10 ^{-7 to} 68 × 10. ^-7 / ° C. By doing so, it becomes easy to prevent the alumina substrate from warping after firing. Here, the "coefficient of thermal expansion" is a value measured by a thermomechanical analyzer (TMA).

The composite powder material paste of the present invention is a powder material paste containing a composite powder material and a vehicle, and the composite powder material is preferably the above-mentioned composite powder material. Here, the vehicle is a material for dispersing a composite powder material and forming a paste, and is usually composed of a thermoplastic resin, a plasticizer, a solvent, or the like.

The composite powder material paste can be prepared by preparing a composite powder material and a vehicle, mixing and kneading them at a predetermined ratio.

The thermoplastic resin is a component that enhances the film strength after drying and is a component that imparts flexibility. The content of the thermoplastic resin in the composite powder material paste is preferably 0.1 to 20% by mass. As the thermoplastic resin, polybutyl methacrylate, polyvinyl butyral, polymethyl methacrylate, polyethyl methacrylate, ethyl cellulose and the like are preferable, and one or more of these are preferably used.

The solvent is a component for dissolving the thermoplastic resin. The content of the solvent in the composite powder material paste is preferably 10 to 30% by mass. As the solvent, tarpineol, diethylene glycol monobutyl ether acetate, 2,2,4-trimethyl-1,3-pentadiol monoisobutyrate and the like are preferable, and one or more of these are preferably used.

The coating layer of the thermal printhead is first formed by applying a composite powder material paste on an alumina substrate on which an Au lead electrode, an Ag external electrode, a RuO ₂ resistor, etc. are formed to form a coating layer having a predetermined thickness. , Dry to obtain a dry film. Then, the dried film is fired at a temperature of 800 to 900 ° C. for 5 to 20 minutes to form a coating layer (fired film). If the firing temperature is too low or the firing time (holding time) is too short, the dried film is not sufficiently sintered, and the denseness and surface smoothness of the coating layer tend to decrease. On the other hand, if the firing temperature is too high or the firing time (holding time) is too long, the glass powder reacts with the RuO ₂ resistor, etc., and the characteristics of the resistor tend to deteriorate, or the wire of the Au lead electrode, etc. The width becomes smaller and the electrodes are more likely to break.

Hereinafter, the present invention will be described in detail based on Examples. The present invention is not limited to the following examples. The following examples are merely examples.

Table 1 shows Examples (Samples Nos. 1 to 4) and Comparative Examples (Samples Nos. 5 and 6) of the present invention.

Each sample was prepared as follows. First, the raw materials were mixed so as to have the glass composition shown in the table and mixed uniformly. Then, it was placed in a platinum crucible and melted at 1400 to 1500 ° C. for 2 hours, and then formed into a film.

Subsequently, after pulverizing the above glass film with a ball mill, airflow classification was performed to obtain a glass powder having an average particle size D ₅₀ of 2.0 μm or less and a maximum particle size D _max of 10 μm or less. The two were weighed so that the obtained glass powder was 80% by volume and the alumina powder was 20% by volume, and then sufficiently mixed to obtain a composite powder material. The softening point and the coefficient of thermal expansion of the obtained composite powder material were evaluated. The average particle size D ₅₀ of the alumina powder was 2.0 μm or less, and the maximum particle size D _max was 10 μm or less.

The softening point is the temperature of the fourth inflection point measured by a macro differential thermal analyzer (DTA).

The coefficient of thermal expansion is determined by forming each composite powder material under pressure, firing it at (softening point +10) ° C., processing it to a diameter of 5 mm and a length of 20 mm, obtaining a measurement sample, and then using a thermomechanical analyzer (thermomechanical analyzer). It is an average value measured by TMA) in a temperature range of 30 to 300 ° C.

Next, the above composite powder and a vehicle (tarpineol containing 5% by mass of ethyl cellulose and 3% by mass of tributyl acetylcitrate) were mixed and kneaded with a three-roll mill to obtain a composite powder material paste. Further, a composite powder material paste is applied by a screen printing method on an alumina substrate with a heat storage layer having an electrode layer (Au lead electrode layer) and a resistor layer, and then the obtained coating film is dried and 800 in an electric furnace. It was fired at a temperature of ° C. for 20 minutes to obtain a fired film (coating layer) having a thickness of about 10 μm. The surface smoothness of the obtained alumina substrate with a laminated film and the reactivity with the Au lead electrode were evaluated.

The surface smoothness was evaluated by observing the surface of the fired film with a microscope and evaluating it as "x" when there was crystal precipitation and as "◯" when there was no crystal precipitation.

The reactivity with the Au lead electrode is "x" when the line width reduction rate is 40% or more when the line width of the Au lead electrode is measured before and after firing, and the line width reduction rate is less than 40%. The case is evaluated as "○". The smaller the reduction rate of the line width before and after firing, the lower the reactivity with the Au lead electrode.

As is clear from Table 1, the sample No. In Nos. 1 to 4, since the glass composition of the glass powder was regulated within a predetermined range, the softening point was low, and the surface smoothness and the reactivity with the Au lead electrode were evaluated well. On the other hand, sample No. No. 5 had a low softening point, but the evaluation of surface smoothness was poor because the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) was too large. In addition, sample No. In No. 6, the softening point was low, but the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) was too small, so that the evaluation of reactivity with the Au lead electrode was poor.

Claims (7)

As a glass composition, in _{mol%, SiO 2 60 ~75%,} B 2 O 3 1~8%, CaO 5~17%, Bi 2 O 3 10~23%, ZrO 2 0~6%, Al 2 O 3 A bismuth-based glass containing 0 to 8% and having a molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) of 3.4 to 4.1 . As the glass composition, in molar%, SiO ₂ 60 to 70%, B ₂ O ₃ 1 to 7%, CaO 6 to 15%, Bi ₂ O ₃ 10 to 20%, ZrO ₂ 0.1 to 5%, Al ₂ It contains O ₃ 0.1 to 7% and has a molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) of 3.4 to 4.1 , and can be used for coating thermal printheads. The bismuth-based glass according to claim 1, which is characterized. As the glass composition, in molar%, SiO ₂ 60 to 70%, B ₂ O ₃ 2 to 6%, CaO 6 to 15%, Bi ₂ O ₃ 10 to 20%, ZrO ₂ 0.5 to 4%, Al ₂ It contains O ₃ 2 to 7% and has a molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + Bi ₂ O ₃ ) of 3.4 to 4.1, and is characterized by being used for coating a thermal printhead. The bismuth-based glass according to claim 1. The bismuth-based glass according to any one of claims 1 to 3, wherein PbO is substantially not contained in the glass composition. A composite powder material containing a glass powder made of bismuth-based glass according to any one of claims 1 to 4 and an alumina powder, wherein the content of the glass powder is 60 to 90% by volume and the content of the alumina powder is A composite powder material characterized by being 10 to 30% by volume. The composite powder material according to claim 5, wherein the softening point is 600 to 800 ° C. A powder material paste containing a composite powder material and a vehicle, wherein the composite powder material is the composite powder material according to claim 5 or 6.