JP6952949B2 - Borosilicate glass, composite powder material and composite powder material paste - Google Patents

Description

The present invention relates to borosilicate glass, composite powder material and composite powder material paste, and specifically to borosilicate 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 unit 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 basic laminated 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 Gazette Japanese Unexamined Patent Publication No. 2008-150269

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 an Au lead electrode or an Ag external electrode. If the reactivity with the Au lead electrode or the Ag external electrode is high, the electrode may be disconnected 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 system glass.} There is. For example, Patent Document _{2, ZnO-B 2 O 3} -BaO based glass are described.

However, _ZnO-B 2 O 3 -BaO based glass described in Patent Document 2 has a problem of a high reactivity with Ag external electrodes or the like.

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 it has reactivity with an electrode such as an Ag external electrode. The idea is to create a glass that has a low temperature and can contribute to improving the abrasion resistance and surface smoothness of the coating layer.

As a result of conducting various experiments, the present inventor has found that the above technical problems can be solved by adopting a predetermined borosilicate glass as the glass-based glass, and proposes the present invention. That is, borosilicate glass of the present invention has a glass composition, in _{mol%, SiO 2 20~40%, B} 2 O 3 25~45%, CaO 3~15%, SrO + BaO + 5~30% ZnO, ZrO 2 0 It contains ~ 6%, Al ₂ O _{30 to} 8%, and CuO 0 to 1%, and is characterized in that the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) is larger than 0.50. Here, "SrO + BaO + ZnO" is the total amount of SrO, BaO and ZnO. Further, "(SiO ₂ + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO)" refers to a value obtained by dividing the total amount of _{SiO 2} and CaO by the total amount of B ₂ O _{3, SrO, BaO and ZnO.}

Borosilicate-based glass generally has high reactivity with an Ag external electrode. However, the borosilicate glass of the present invention _{is regulated to have a SiO 2} content of 20 mol% or more, a B ₂ O ₃ content of 45 mol% or less, and a Ca O content of 3 mol% or more. , Ag The reactivity with the external electrode is low.

Further, in the borosilicate glass, when _{the content of SiO 2} is large and the content of SrO, BaO and ZnO is large, feldspar-based crystals are precipitated at the time of firing, and it becomes difficult to secure the desired surface smoothness. In some cases. Therefore, the borosilicate glass of the present invention _{suppresses the precipitation of feldspar-based crystals by restricting the molar ratio (SiO 2} + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) to more than 0.50.

Secondly, the borosilicate glass of the present invention has a glass composition of SiO ₂ 25-40%, B ₂ O ₃ 25-40%, CaO 5-15%, SrO 0.1-10% in mol%. , BaO 0.1 to 10%, ZnO 5 to 15%, ZrO ₂ 0.1 to 4%, Al ₂ O ₃ 0.1 to 7%, CuO 0.005 to 0.09%, and a molar ratio. (SiO ₂ + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) is 0.55 or more, and it is preferable to use it for coating a thermal print head.

Third, the borosilicate glass of the present invention has a glass composition of SiO ₂ 25-40%, B ₂ O ₃ 25-40%, CaO 5-15%, SrO 1-10%, BaO in mol%. _{1~10%, 5~15% ZnO, ZrO} 2 0.5~4%, Al 2 O 3 1~7%, containing 0.01 to 0.09% CuO, the molar ratio _(SiO 2 + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) is 0.55 or more, and it is preferable to use it for coating a thermal print head.

Fourth, it is preferable that the borosilicate glass of the present invention _{does not substantially contain PbO and Bi 2} O _{3 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%). Further, "substantially free of Bi ₂ O _{3 " means that although Bi 2} O ₃ is allowed to be mixed at the impurity level, positive introduction is avoided. Specifically, in the glass composition. The content of Bi ₂ O ₃ 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 borosilicate glass and alumina powder, and has a glass powder content of 60 to 90% by volume and an alumina powder. The content of is preferably 10 to 30% by volume.

Sixth, the composite powder material of the present invention preferably has a softening point of 650 to 850 ° 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.

As described above, the borosilicate glass of the present invention has a glass composition of SiO ₂ 20 to 40%, B ₂ O _{3 25 to 45%, CaO 3 to} 15%, SrO + BaO + ZnO 5 to 30%, ZrO in terms of glass composition. _{It contains 20 to} 6%, Al ₂ O _{30 to} 8%, and CuO 0 to 1%, and is characterized in that the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) is larger than 0.50. .. 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 Ag external electrode. The content of SiO ₂ is 20 to 40%, preferably 25 to 40%, and more preferably 27 to 38%. When _{the content of SiO 2} is low, the reactivity with the Ag external electrode is high. 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 the higher the content, the higher the reactivity with the Ag external electrode. Therefore, _{the content of B 2} O ₃ is 25 to 45%, preferably 25 to 40%, and more preferably 27 to 38%.

CaO is a component that stabilizes glass and a component that suppresses reactivity with an Ag external electrode. The CaO content is 3 to 15%, preferably 5 to 15%, more preferably 6 to 14%. When the CaO content is high, feldspar-based crystals are likely to be precipitated, and the surface smoothness of the coating layer is likely to be lowered.

SrO, BaO and ZnO are components that stabilize the glass. The total amount of SrO, BaO and ZnO is 5 to 30%, preferably 10 to 25%. The content of SrO is preferably 0 to 12%, more preferably 0.1 to 11%, still more preferably 1 to 10%, and particularly preferably 3 to 9%. The content of BaO is preferably 0 to 12%, more preferably 0.1 to 10%, still more preferably 1 to 10%, and particularly preferably 3 to 8%. The ZnO content is preferably 0 to 15%, more preferably 1 to 15%, still more preferably 3 to 15%, still more preferably 5 to 14%, and particularly preferably 6 to 12%. When the contents of SrO, BaO and ZnO are increased, feldspar-based crystals are likely to be precipitated, and the surface smoothness of the coating layer is likely to be lowered.

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%, and particularly preferably 1 to 4%. When _{the content of ZrO 2} is small, the wear resistance 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 1 to 7%, still more preferably 2 to 6%. When _{the content of Al 2} O ₃ is small, the wear resistance tends to be lowered. On the other hand, when _{the content of Al 2} O ₃ is large, feldspar-based crystals are likely to be precipitated, and the surface smoothness of the coating layer is likely to be lowered.

CuO is a component that remarkably suppresses the reactivity with the Ag external electrode. The content of CuO is 0 to 1%, preferably 0.005 to 0.09%, and more preferably 0.01 to 0.08%. When the content of CuO is large, feldspar-based 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 + SrO + BaO + ZnO) is larger than 0.50, preferably 0.55 or more, and more preferably 0.60 or more. When the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) becomes small, feldspar-based crystals tend to precipitate and the surface smoothness of the coating layer tends to decrease.

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

In addition to the above components, various components may be introduced as long as the characteristics of the thermal print head 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 , CeO ₂ , V ₂ O _5, etc. are combined. It may be introduced in an amount or alone up to 10%, especially up to 1%.

Although PbO and Bi ₂ O ₃ are components that lower the softening point, they are also environmentally hazardous substances, so it is preferable to substantially avoid their introduction.

The composite powder material of the present invention is a composite powder material containing the above-mentioned glass powder made of borosilicate glass and alumina powder, and has a glass powder content of 60 to 90% by volume and an alumina powder content of 60 to 90% by volume. It is preferably 10 to 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 molding 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 large, the content of the alumina powder is relatively small, so that the abrasion resistance and the 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 in the volume-based cumulative particle size distribution curve measured by a laser diffractometer, the integrated amount is cumulative from the smallest particle. The particle size is 50%. The "maximum particle size D _max " refers to a value measured by a laser diffractometer, and the accumulated amount is accumulated from the smallest particle in the volume-based cumulative particle size distribution curve measured by the laser diffractometer. Represents a particle size of 99%.

Alumina powder is a material that enhances the abrasion 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, preferably 15 to 23% by volume. When the content of the alumina powder is large, feldspar-based 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 proportion 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, another ceramic powder may be introduced in an amount of 0 to 10% by volume, particularly 0 to 8% by volume. Various materials can be used as other ceramic powders, for example, zirconia, mullite, silica, cordierite, titania, tin oxide and the like in order 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 650 to 850 ° C, more preferably 670 to 830 ° C, and even more preferably 690 to 810 ° 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 Ag external electrode becomes high.

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, terpineol, 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 film 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 are likely to deteriorate, or with the Ag external electrode, etc. The reactivity becomes high, and there is a risk that the electrode may be broken.

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 (Sample Nos. 1 to 4) and Comparative Examples (Sample No. 5) 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 1350 to 1450 ° C. for 2 hours, and then formed into a film.

Subsequently, the above glass film was pulverized with a ball mill and then classified by airflow to obtain a glass powder having _{an average particle size of D 50 of} 2.0 μm or less and a maximum particle size of 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 (terpineol 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 (Ag external 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 Ag external electrode were evaluated.

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

The reactivity with the Ag external electrode was evaluated as "x" when yellowing was observed when observing the Ag external electrode after firing, and as "○" when no yellowing was observed. be. It should be noted that the yellowing of the Ag external electrode has a correlation with the reactivity with the Ag external electrode, and when the Ag external electrode yellows, it can be said that the reactivity with the Ag external electrode is high.

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 Ag external electrode were evaluated well. On the other hand, sample No. In No. 5, the softening point was low, but the molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) was small, so that the evaluation of surface smoothness was poor.

Claims (7)

As the glass composition, in mol%, SiO ₂ 25 to 40%, B ₂ O ₃ 27 to 45%, CaO 5 to 15%, SrO + BaO + ZnO 5 to 30%, ZrO _{20 to} 6%, Al ₂ O _{30 to} 8 %, CuO 0.005 to 0.09 %, and a borosilicate glass having a molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) larger than 0.50. As the glass composition, in mol%, SiO ₂ 25 to 40%, B ₂ O ₃ 27 to 40%, CaO 5 to 15%, SrO 0.1 to 10%, BaO 0.1 to 10%, ZnO 5 to 15 %, ZrO ₂ 0.1 to 4%, Al ₂ O ₃ 0.1 to 7%, CuO 0.005 to 0.09%, molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) The borosilicate-based glass according to claim 1, wherein the value is 0.55 or more and the glass is used for coating a thermal print head. As the glass composition, in mol%, SiO ₂ 25-40%, B ₂ O ₃ 27-40%, CaO 5-15%, SrO 1-10%, BaO 1-10%, ZnO 5-15%, ZrO ₂ It contains 0.5 to 4%, Al ₂ O ₃ 1 to 7%, and CuO 0.01 to 0.09%, and has a molar ratio (SiO ₂ + CaO) / (B ₂ O ₃ + SrO + BaO + ZnO) of 0.55 or more. The borosilicate-based glass according to claim 1, wherein the glass is used for coating a thermal print head. The borosilicate-based glass according to any one of claims 1 to ₃ , wherein PbO and Bi ₂ O 3 are substantially not contained in the glass composition. A composite powder material containing a glass powder made of borosilicate 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 high. Is a composite powder material, characterized in that the content is 10 to 30% by volume. The composite powder material according to claim 5, wherein the softening point is 650 to 850 ° 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.