JP5662361B2 - Resistor paste for ceramic substrate heater and ceramic substrate heater - Google Patents

Description

  The present invention relates to a ceramic substrate heater resistor paste and a ceramic substrate heater using the same, and more particularly to a resistor paste suitable for manufacturing a heater circuit by forming a resistor on a substrate, and the resistor. The present invention relates to a ceramic substrate heater including a resistor obtained by using a body paste.

  A heater of a thermal print head or a toner fixing heater of a printer is manufactured by forming a heater circuit on a ceramic substrate. In such a ceramic substrate heater, a resistor paste is used to form a resistor constituting the circuit. In particular, in the case of a toner fixing heater, for example, a resistor is designed so that a resistance value is in the region of several hundred mΩ / □ / 10 μm. As a composition of the resistor paste, silver powder and palladium powder are conductive powder (conductor powder). ). In general, the resistance value of the resistor paste can be adjusted by blending glass powder, metal oxide powder, or the like that is an insulator.

  In a general toner fixing heater or the like, examples of components formed on the heater include a resistor, an electrode, and an overcoat glass. These parts are formed by independently printing and baking the paste forming the parts. For example, the resistor is formed by printing and baking the resistor paste, and then other components are formed by printing and baking another paste.

  Therefore, when the ceramic substrate heater is manufactured, the resistor formed earlier is refired along with the formation of components to be formed later. Here, it is known that the resistance value of the resistor changes every time it is fired. Therefore, when designing the composition of the resistor paste, it is necessary to know in advance the rate of change of the resistance value associated with re-baking. There is.

  By the way, regarding the resistor paste used for forming the resistor for the ceramic substrate heater, for example, techniques disclosed in Patent Documents 1 to 3 are disclosed.

  First, Patent Document 1 includes one or more metal powders selected from the group consisting of platinum, palladium, silver, and gold, and a glass frit having a crystallization temperature of 700 ° C. or higher. The area resistivity after firing is 0.05Ω / A resistor for an aluminum nitride heater having a □ of 10Ω / □ or less and a paste composition used therefor are disclosed. In this technique, the bonding strength of the obtained resistor to the aluminum nitride substrate is increased by optimizing the crystallization temperature of the glass frit.

  Patent Document 2 discloses a heater resistor paste in which 1 to 50 parts by weight of aluminum powder is blended with 100 parts by weight of silver powder. That is, in this technique, silver powder is used as the conductive powder, and the resistance value of the resistor is adjusted by the blending amount of alumina.

  Patent Document 3 discloses that a green sheet using glass powder and an internal circuit containing conductive powder are simultaneously fired to produce a low-temperature fired substrate, and the conductive powder and glass powder are used as a vehicle. A built-in resistor paste dispersed therein is disclosed, and the relationship between the softening temperature of the glass powder used in the built-in resistor paste and the softening temperature of the glass powder used in the green sheet is defined. According to the example of Patent Document 3, by defining the paste composition in addition to the softening temperature of the glass powder, it is possible to reduce the resistance value change even if refiring is repeated in the manufacturing process of the low-temperature fired substrate. It is said that there is. In the examples, ruthenium oxide powder is used as the conductive powder, and the resistance value of the resistor is adjusted by the blending amount of the glass powder and alumina.

Japanese Patent No. 3033852 JP 09-139278 A Japanese Patent Laid-Open No. 09-153681

  However, as described above, even if the composition of the resistor paste is designed after grasping in advance the change rate of the resistance value associated with refiring, the change rate of the resistance value actually varies. Therefore, even if the resistor paste has a composition designed to reflect the rate of change, the resistance value of the obtained resistor may be out of the preferred range, and as a result, the yield may decrease. . In addition, since the resistance value is also affected by the temperature distribution in the furnace during firing, a resistor is formed when the composition of the resistor paste deviates from the preferred range (or when the dispersibility of the powder is poor). Therefore, there is a possibility that the variation of the resistance value becomes larger depending on the initial firing temperature.

  As described above, if the rate of change in resistance value varies with re-firing, or if the resistance value fluctuates due to the influence of the firing temperature during the formation of the resistor, a resistor having a desired resistance value cannot be obtained. In addition, problems such as a decrease in yield, an increase in manufacturing cost, and a decrease in design freedom occur. In particular, if the resistance value of the resistor does not fall within a desired range before refiring, various problems such as low yield cannot be effectively suppressed or avoided.

  Further, in Patent Documents 1 to 3 described above, there may be a case where the variation of the resistance value due to the influence of the firing temperature or the variation in the change rate of the resistance value accompanying the refiring cannot be sufficiently suppressed.

  For example, Patent Document 1 does not particularly examine the variation in the resistance value or the variation in the change rate. Moreover, in patent document 2, since use of noble metal powders other than silver as electroconductive powder is not disclosed, the application range is limited. Similarly, Patent Document 3 does not disclose the use of noble metal powder as the conductive powder, and therefore its application range is limited.

  Furthermore, these patent documents do not fully disclose the preferred particle sizes of the respective powder components. For example, in Patent Document 2, the upper limit of the particle size of silver powder and aluminum powder is defined, but the particle size of glass powder (glass frit) or the like is not particularly disclosed. Patent Documents 1 and 3 only give examples of average particle diameters for some of the powder components in the examples, and do not specifically disclose the preferred range of particle diameters.

  Improving the dispersibility of the powder component is one of the important considerations in order to reduce the variation in the resistance value or the variation in the resistance value change rate due to re-firing and to obtain a resistor having the desired resistance value. Become. And, according to the study by the present inventors, it has been clarified that limiting the particle size to a suitable range greatly contributes to the improvement of the dispersibility of the powder component. It is not disclosed in Patent Documents 1 to 3.

  The present invention has been made to solve such problems, and when forming a resistor constituting a heater circuit of a ceramic substrate heater, even if the firing temperature is different, at least fluctuation of the resistance value can be suppressed. Preferably, it is an object of the present invention to provide a resistor paste that can reduce variation in the rate of change in resistance value even when the resistor is refired.

In order to solve the above problems, the resistor paste for ceramic substrate heaters according to the present invention includes (A) (A-1) silver powder and (A-2) palladium powder as conductive powder, and (B) glass. A resistor paste containing a frit and (C) an inorganic metal oxide powder and used for a ceramic substrate heater, wherein the softening point of the (B) glass frit is 750 ° C. or higher, and The particle size is in the range of 1 to 3 μm, and the (C) inorganic metal oxide powder is a powder of at least one inorganic metal oxide selected from the group consisting of alumina, zirconia, titania, and yttria. The particle size is in the range of 0.1 to 1 μm, and firing is performed at a plurality of temperature levels within the temperature range of 800 to 900 ° C., and the resistance value of the resistor after firing is measured at each temperature level. In case The following formula (1)
VR = (Rmax−Rmin) / Rave × 100 (1)
(However, Rmax is the maximum value of the 10 μm equivalent resistance value among the plurality of resistance values, Rmin is the minimum value of the 10 μm equivalent resistance value, and Rave is the average value of the 10 μm equivalent value.)
The resistance value fluctuation rate VR of the resistor after firing is defined as follows.

  According to the above configuration, in the resistor paste containing silver powder and palladium powder as the conductive component, the particle size of the glass frit that is the insulating component, the kind and particle size of the inorganic metal oxide are defined, and further, these blends The amount is prescribed. Thereby, since the resistance value variation rate VR defined by the equation (1) can be suppressed within 10%, it is possible to effectively suppress an increase in the resistance value variation of the resistor obtained after firing. .

In the resistor paste having the above structure, the primary particle diameter of the (A-1) silver powder is in the range of 0.1 to 3 μm, and the primary particle diameter of the (A-2) palladium powder is 0.1 to 0. Further, the content of the (B) glass frit is 70% by weight or less based on the total amount of the (B) glass frit and the (C) inorganic metal oxide powder. Yes, when the resistance value of the resistor at the time of firing is 1000 mΩ / □ / 10 μm or less and the resistor is refired three times within the temperature range of 800 to 900 ° C. Formula (2)
CR = ( Rn + 1−Rn ) / Rn × 100 (2)
(However, Rn + 1 indicates a 10 μm equivalent resistance value after firing n + 1 times, Rn indicates a 10 μm equivalent resistance value after firing n times, and n is an integer of 1 to 3.)
10% or less may be sufficient as the sum total of the absolute value of resistance value change rate CR of the said resistor defined by (3).

  According to the above configuration, by defining the primary particle diameter of silver powder and palladium powder as the conductive component, the total of the three absolute values of the resistance value change rate CR defined by the formula (2) can be 10% or less. It becomes possible. Therefore, not only can the fluctuation of the resistance value of the resistor increase effectively, but also the variation in the change rate of the resistance value during refiring can be effectively suppressed.

  Further, the present invention includes a ceramic substrate heater provided with a resistor obtained by firing the resistor paste.

  As described above, in the present invention, in the resistor paste used to form the resistor constituting the heater circuit of the ceramic substrate heater, even if the firing temperature is different, at least fluctuation of the resistance value can be suppressed, preferably Even if the resistor is refired, it is possible to reduce the variation in the change rate of the resistance value.

It is a top view which shows the printing pattern of the resistor produced in the Example of this invention. (A) is a figure which shows the particle state by the electron microscope of the resistor produced in Example 1, (b) is a figure which shows the particle state by the electron microscope of the resistor produced in Example 4. (C) is a figure which shows the particle state by the electron microscope of the resistor produced in the comparative example 1. FIG.

  The resistor paste according to the present invention comprises (A) (A-1) silver powder and (A-2) palladium powder, (B) glass frit, (C) inorganic metal oxide powder as conductive powder, And a resistor paste used for a ceramic substrate heater. Among these powder components (A) to (C), the glass frit (B) has a softening point of 750 ° C. or higher and a particle size in the range of 1 to 3 μm. The metal oxide powder is a powder of at least one inorganic metal oxide selected from the group consisting of alumina, zirconia, titania, and yttria, and has a particle size in the range of 0.1 to 1 μm. And (B) content of glass frit is 70 weight% or less by weight ratio with respect to content of said (C) inorganic metal oxide powder, and the resistance value fluctuation rate VR after baking mentioned later is 10%. It is as follows.

  Furthermore, in the resistor paste of the said structure, the primary particle diameter of (A-1) silver powder is 0.1-3 micrometers, and the primary particle diameter of the said (A-2) palladium powder is 0.1-0.5 micrometer. It is preferable that In addition to the fact that these (A) conductive powders have such a primary particle size, the total absolute value of the resistance value change rate CR when the re-baking is performed three times as described later is 10 % Is more preferable.

  Hereinafter, a preferred embodiment of the resistor paste according to the present invention having the above-described configuration will be specifically described.

[(A) Conductive powder]
As described above, the resistor paste according to the present invention contains two kinds of noble metal powders (A-1) silver powder and (A-2) palladium powder as (A) conductive powder. These noble metal powders become a conductive component in a resistor obtained by firing the resistor paste according to the present invention.

  First, the specific configuration of (A-1) silver powder in (A) conductive powder is not particularly limited, and the production method thereof is not particularly limited, but the primary particle size is within a range of 0.1 to 3 μm. Preferably there is. (A-1) If the primary particle diameter of the silver powder is within this range, at least the dispersibility in the resistor paste can be improved, and the rate of change in resistivity after firing can be favorably controlled. It becomes. Here, (A-1) The primary particle diameter of the conductive powder is an average particle diameter of 10 or more particles observed by SEM (electron microscope).

  On the other hand, (A-1) If the primary particles of the silver powder are less than 0.1 μm, the amount of oil absorption as powder increases and the paste viscosity may increase, so a large amount of solvent is used to reduce the paste viscosity. May need to be added. When a large amount of a solvent is added, physical properties at the time of printing the resistor paste are affected, and there is a possibility that a sufficient film thickness as a resistor cannot be secured.

  On the other hand, if the primary particle size of (A-1) silver powder exceeds 3 μm, the sinterability may generally decrease. In this case, if the sinterability is lowered, a resistor that is not sufficiently sintered may be formed. When such a resistor is refired, the resistance value of the sufficiently sintered resistor is reduced. The change of will become large. Note that “sintering” in this case generally forms an object (sintered body) having a dense structure by forming a solid powder such as a metal powder into a predetermined shape and heating it at a temperature lower than the melting point. To do. On the other hand, “baking” in the present embodiment broadly refers to a process of baking a resistor paste or paste for forming other components with high heat.

  Next, the specific configuration of (A-2) palladium powder in (A) conductive powder is not particularly limited, and the production method thereof is not particularly limited, but the primary particle size is 0.1 to 0.5 μm. It is preferable to be within the range. (A-2) If the primary particle diameter of the palladium powder is within this range, at least the dispersibility in the resistor paste can be improved, and the rate of change in resistivity after firing can be well controlled. It becomes possible.

  (A-2) If the primary particle size of the palladium powder is less than 0.1 μm, the primary particle size is relatively smaller than the other powder components, so that the dispersion state in the resistor paste may be lowered. There is. On the other hand, if the primary particle size of (A-2) palladium powder exceeds 0.5 μm, (A-1) it becomes difficult to adhere to the surface of the silver powder, and therefore the predetermined effect as “palladium” may not be sufficiently exhibited. There is.

[(B) Glass frit]
The (B) glass frit (glass powder) contained in the resistor paste according to the present invention is one of the insulating components of the resistor obtained by firing. (B) The specific configuration of the glass frit is not particularly limited, and the specific components, the production method thereof, and the like are not particularly limited, but at least the softening point is 750 ° C. or higher, and the particle size is 1 to It is within the range of 3 μm.

  (B) If the softening point of a glass frit is 750 degreeC or more, the degree of softening with respect to the calcination temperature of 800-900 degreeC can be made favorable. If the particle size of the glass frit (B) is 1 μm or more and 3 μm or less, at least dispersibility in the resistor paste can be improved, and the rate of change in resistivity after firing can be well controlled. It becomes possible. The softening point of the glass frit is defined as the temperature at the bottom of the secondary hot part of the DTA curve.

  On the other hand, when the softening point of (B) the glass frit is less than 750 ° C., the degree of softening tends to be too large with respect to the firing temperature of 800 to 900 ° C. For example, when the resistor paste is fired by setting the firing temperature to 800 ° C. and 900 ° C., respectively, the rate of change in resistance value increases.

  In addition, if the particle size of (B) glass frit is less than 1 μm or more than 3 μm, it becomes smaller or larger than the particle size of other powder components, so that the dispersibility in the resistor paste decreases. There is a fear. As a result, the variation in the change rate of the resistance value is increased. In addition, the measuring method of the particle size of a glass frit is an average particle diameter of 10 or more particles observed by SEM (electron microscope).

  In the present embodiment, (A-1) silver powder, (A-2) palladium powder, and the like are often those in which individual particles are aggregated. Therefore, the particle size of the aggregated particles is referred to as “primary particle size”. ing. On the other hand, since glass frit and the like do not aggregate, the particle size of each particle is simply referred to as “particle size”.

[(C) Inorganic metal oxide powder]
The (C) inorganic metal oxide powder contained in the resistor paste according to the present invention is one of the insulating components of the resistor obtained by firing together with (B) the glass frit (glass powder). The (C) inorganic metal oxide powder used in the present invention is a powder of at least one inorganic metal oxide selected from the group consisting of alumina, zirconia, titania, and yttria. Therefore, as the inorganic metal oxide powder (C), any one of alumina powder, zirconia powder, titania powder, and yttria powder may be used, or two or more powders may be used in appropriate combination. Alternatively, all four types of powders may be used in combination.

  The particle size of the four types of (C) inorganic metal oxide powders may be in the range of 0.1 to 1 μm. (C) If the particle size of the inorganic metal oxide powder is less than 0.1 μm or more than 1 μm, it becomes smaller or larger than the particle size of the other powder components, so dispersibility in the resistor paste May decrease. As a result, the variation in the change rate of the resistance value is increased.

  In addition, it does not specifically limit about the manufacturing method of (C) inorganic metal oxide powder. In the examples described later, (C) alumina powder is used as an example of the inorganic metal oxide powder. However, in the resistor paste according to the present invention, alumina powder, zirconia powder, titania powder, and yttria powder are: Is substantially equivalent in its intended function. That is, in the present invention, (C) the inorganic metal oxide powder is blended mainly for the purpose of adjusting the resistance value after firing of the resistor paste. For this purpose, the alumina powder used in the examples is used. Can be replaced with zirconia powder, titania powder, or yttria powder.

[Other ingredients]
The resistor paste according to the present invention is other than the above-described (A) conductive powder ((A-1) silver powder and (A-2) palladium powder), (B) glass frit, and (C) inorganic metal oxide powder. In addition, various components known in the field of resistor paste can be blended. Specific examples include resins, solvents, dispersants, and other additives, but are not particularly limited. Of these, the resin and the solvent constitute the organic vehicle of the resistor paste.

  Specific examples of the resin include ethyl cellulose and the like. Specific examples of the solvent include terpineol and the like, but are not particularly limited. Moreover, a dispersing agent should just be what can improve the dispersibility of the powder component of (A)-(C) in this invention, For example, fatty acids, such as a stearic acid and an oleic acid, are mentioned.

  Furthermore, in the resistor paste according to the present invention, powder components other than the powder components (A) to (C) can be added within a range that does not affect the change in resistance value of the resistor after firing.

[Resistor paste and ceramic substrate heater]
The resistor paste according to the present invention is prepared (manufactured) by using the powder components (A) to (C) as essential components and further mixing and mixing the above-described resin, solvent, dispersant and the like as appropriate. The Although the specific manufacturing method of a resistor paste is not specifically limited, Typically, the method of kneading | mixing with a 3 roll mill after stirring and premixing each said component on well-known conditions can be used suitably.

  Here, among the powder components (A) to (C), the blending ratio of (B) glass frit and (C) inorganic metal oxide powder, which are insulating components, is set within a preferred range in the present invention. . Specifically, the content of (B) glass frit is blended so as to be 70% by weight or less with respect to the total amount of (B) glass frit and (C) inorganic metal oxide powder. That is, when (B) the blending amount of the glass frit is WB (weight basis) and (C) the blending amount (weight basis) of the inorganic metal oxide powder is WC, WB / (WB + WC) ≦ 0.7 I just need it. Further, the lower limit of the blending ratio of (B) glass frit is not particularly limited, but it is preferably over 40% by weight.

  In order to protect the resistor obtained by firing the resistor paste, an overcoat glass is formed on the surface thereof. This glass for overcoat is formed by printing and baking the paste for glass in a form laminated on the resistor after baking. Here, when the glass paste is fired to form the overcoat glass, the resistor is also refired. At this time, as will be described later, the glass frit (B) in the resistor has a temperature in the vicinity of the softening point, so that it can flow in the resistor. Thereby, since the conductive network due to sintering of the (A) conductive powder (particularly (A-1) silver powder) in the resistor body is easily broken, the resistance value is greatly changed.

  (B) When the content WB of the glass frit exceeds 70% by weight of WB + WC, the phenomenon of breaking the conductive network tends to become remarkable. Therefore, in the resistor paste according to the present invention, the blending ratio of (B) glass frit is preferably 70% by weight or less with respect to (C) the inorganic metal oxide powder. Further, when the content WB of (B) glass frit is 40% by weight or less of WB + WC, there are cases where (C) the inorganic metal oxide powder is too much and the conductive network is not formed well.

  Moreover, in this invention, the weight ratio (composition ratio) of (A-1) silver powder and (A-2) palladium powder among (A) electroconductive powder is (A-1) compounding quantity of silver powder ( It is preferable that WA1 / WA2 = 9/1 to 43/57 when the weight basis is WA1 and (A-2) the blending amount of palladium powder (weight basis) is WA2. Palladium is added to lower the TCR (temperature change rate of resistance value), and the performance of the heater is greatly affected by the TCR value. When WA1 / WA2 = 43/57, the TCR becomes almost zero. Therefore, in the present invention, a necessary and sufficient range of the silver / palladium compounding ratio for use as a heater, that is, WA1 / WA2 = 9/1 to A range of 43/57 is preferred. Moreover, if a compounding ratio exists in this range, (A-2) palladium powder will adhere to the surface of (A-1) silver powder, and will exhibit the effect | action which inhibits sintering of (A-1) silver powder effectively. be able to.

  Furthermore, in the present invention, the blending ratio of (A) conductive powder, (B) glass frit, and (C) inorganic metal oxide powder is not particularly limited, but (A) blending amount of conductive powder (weight basis) ) Is WA, it may be within the range of WA: WB: WC = 98: 0.8: 1.2 to 40:28:12. In other words, the blending of the powder components (A) to (C) is sufficient if (A) the conductive powder is in the range of 40 to 98 parts by weight, and (B) the glass frit is 0.8 to 28 parts by weight. (C) The inorganic metal oxide powder may be in the range of 1.2 to 12 parts by weight.

  In the present invention, the resistance value of the resistor paste is determined by (A) the amount of conductive powder (WA) and the insulating powder, that is, (B) glass frit + (C) the amount of inorganic metal oxide powder (WB + WC). Is determined. For example, in many of the examples described later, the resistance value is 200 mΩ by setting WA = 46.5 parts by weight and WB + WC = 32.5 parts by weight (WB / (WB + WC) = 69%). By setting WA = 41 parts by weight and WB + WC = 38.5 parts by weight, the resistance value becomes 1000 mΩ, but when WB + WC further increases, the resistance value tends to increase rapidly, and the resistance value is controlled. It becomes difficult. Therefore, the upper limit of WB + WC is preferably 38.5 parts by weight.

  In addition, the blending amount of the other components other than (A) to (C) is not particularly limited, but the blending ratio of the resin and the solvent (that is, the organic vehicle) is in the range of 20 to 25% by weight with respect to the total powder components. If it is in.

  In the resistor paste according to the present invention, the variation rate of the resistance value under a specific condition is adjusted to 10% or less. Specifically, first, when the resistor paste according to the present invention is fired at a plurality of temperature levels within a temperature range of 800 to 900 ° C., and the resistance value of the resistor after firing at each temperature level is measured. The resistance value fluctuation rate VR defined by the following formula (1) is 10% or less. In equation (1), Rmax represents the maximum value of 10 μm equivalent resistance values among the plurality of measured resistance values, Rmin represents the minimum value of 10 μm equivalent resistance values, and Rave represents the average value of 10 μm equivalent resistance values. .

VR = (Rmax−Rmin) / Rave × 100 (1)
In addition, the firing temperature in the temperature range of 800 to 900 ° C. used in the formula (1) may be two or more temperature levels, and preferably three or more temperature levels. In the examples described later, three temperature levels of 820 ° C., 850 ° C., and 890 ° C. are employed. In calculating the resistance value fluctuation rate VR, two or more temperature levels suitable for evaluation can be selected as the temperature level of the plurality of firings according to the specific composition of the resistor, the firing conditions, and the like. It is not limited to only the three temperature levels in the example.

  Furthermore, the resistance value (10 μm conversion value) at the time of firing of the resistor formed of the resistor paste according to the present invention is 1000 mΩ / □ / 10 μm or less, and three times within a temperature range of 800 to 900 ° C. When refiring is performed (that is, when the resistor paste is fired to obtain a resistor, and then the resistor is refired three times), the following equation (2) is defined. The total absolute value of the resistance value change rate CR is particularly preferably 10% or less. In the formula (2), Rn + 1 represents a 10 μm equivalent resistance value after performing the (n + 1) th firing, Rn represents a 10 μm equivalent resistance value after performing the nth firing, and n is any of 1 to 3 Is an integer.

CR = (Rn + 1−Rn) / Rn × 100 (2)
In the present invention, the resistance value fluctuation rate VR defined by the formula (1) is at least 10% or less, and more preferably, the resistance value change rate at the time of the third refiring defined by the formula (2). If the total absolute value of CR is 10% or less, even if the initial firing temperature (the firing temperature for forming the resistor) changes, the variation in resistance value can be reduced. A resistor having a small variation in the change rate of the resistance value even when refiring is repeated can be manufactured on the ceramic substrate. As a result, it is possible to manufacture a heater circuit with a high yield.

  Note that the surface resistance value (sheet resistance) is measured by a digital multimeter, two-terminal method, and converted by the following formula (3) after forming a sample with a resistor paste and firing it. To measure.

(Sheet resistance) = (Measured resistance value) / (Aspect ratio) [Unit: mΩ / □] (3)
Moreover, it is set as a 10 micrometer resistance value by converting a surface resistance value by the following Formula (4). In this embodiment, since the film thickness of the resistor actually formed is approximately 10 μm, the film thickness measured for evaluation is compared with a value converted to 10 μm.

(Resistance value) = (sheet resistance) × (film thickness / 10) [unit: mΩ / □ / 10 μm] (4)
In the ceramic substrate heater, the following is assumed as a mechanism of the change in resistance value when the resistor is formed or when the resistor is refired.

  First, the silver / palladium resistor manufactured with the resistor paste according to the present invention contains (A-1) silver powder and (A-2) palladium powder as (A) conductive powder. The (insulating powder) contains (B) glass frit and (C) inorganic metal oxide powder, and adjusts the resistance value of the resistor by appropriately adjusting and mixing these powder components. Can do. In other words, by appropriately changing the blending ratio of the powder component and firing, the resulting resistor is electrically conductive by dispersion and mixing of silver, which is the main component of the conductive material, and glass and inorganic metal oxide, which are the insulating materials. A network is formed.

  Here, when firing of the resistor is repeated, among the substances constituting the resistor, the glass having a softening point lower than the firing temperature softens and flows, destroys the conductive network by the sintered silver, and the resistance value To change. It is presumed that such glass flow changes the resistance value of the resistor in the increasing direction.

  On the other hand, when silver sintering proceeds by refiring, it is estimated that the resistance value changes in a decreasing direction, but the other (A) conductive powder (A-2) palladium powder is (A- 1) Easy to make silver powder and alloy. Therefore, it is considered that (A-2) palladium powder adheres to the surface of (A-1) silver powder and acts in the direction of inhibiting sintering. Therefore, it is considered that the blending of (A-2) palladium powder works to suppress the decrease in resistance value even when silver sintering is repeated.

  Thus, when a resistor is formed with a resistor paste containing (A-1) silver powder, (A-2) palladium powder, (B) glass frit and (C) inorganic metal oxide powder, (B) Due to the balance between the flow of the glass frit and (A-2) inhibition of silver sintering (or sintering suppression) by (A-2) palladium powder, a change in resistance value during firing occurs. In addition, when the dispersibility of the powder component is poor, it is presumed that the degree of destruction of the conductive network due to the flow of glass increases, and the rate of change in resistance value after refiring tends to increase. Further, if the particle size of the powder component is not within the proper range, the dispersibility of the powder component is lowered, and as a result, the rate of change in resistance value after refiring tends to increase.

  In the present invention, if the particle size and the composition of at least (B) glass frit and (C) inorganic metal oxide powder, which are insulating powders, are defined, the resistance value fluctuation rate VR defined by the above formula (1) is obtained. If the primary particle diameter of (A-1) silver powder and (A-2) palladium powder is specified, re-firing is defined up to 3 times. Can be suppressed to 10% or less.

  The resistor paste according to the present invention is suitably used for manufacturing a resistor constituting a heater circuit of a ceramic substrate heater such as a heater of a thermal print head or a toner fixing heater of a printer. Therefore, the present invention also includes a ceramic substrate heater including a resistor obtained by firing a resistor paste.

  The specific configuration of the ceramic substrate heater, the manufacturing method of the ceramic substrate heater, and the like are not particularly limited, and can be suitably used for various known ceramic substrate heaters and manufacturing methods thereof.

  In general, when a heater circuit is manufactured on a ceramic substrate, a resistor is formed by printing and baking a resistor paste in a predetermined pattern. The firing temperature at this time is in the range of 800 to 900 ° C. However, if the resistor paste according to the present invention is used, the resistance value of the resistor depends on the firing temperature even if it is fired again in this temperature range. In addition to being able to reduce the rate of change in resistance value after refiring, the heater circuit can be manufactured with a high yield and a high degree of design freedom.

  The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention. In the following Examples and Comparative Examples, the variation rate and the variation rate of the resistance value were evaluated as follows.

(Evaluation method)
[Evaluation of resistance value fluctuation rate VR]
Resistance values obtained from resistors obtained by firing the resistor pastes obtained in the following examples and comparative examples at firing temperatures of 820 ° C. × 7 minutes, 850 ° C. × 7 minutes, and 890 ° C. × 7 minutes, respectively. (The maximum value of 10 μm equivalent resistance value, the minimum value of 10 μm equivalent resistance value, and the average resistance value) are measured, and the resistance value fluctuation rate VR of the resistor formed using the resistor paste is calculated from the measurement data. Evaluation was performed by calculating from the formula (1).

[Evaluation of resistance value change rate CR during re-firing]
Each resistor formed using the resistor paste obtained in each of the following Examples and Comparative Examples was similarly refired three times under the condition of 850 ° C. × 7 minutes, and the resistance value was measured. And resistance value change rate CR at the time of rebaking was computed from said Formula (2).

As will be described later, since the firing for forming the resistor is also performed under the condition of 850 ° C. × 7 minutes, this is “first firing” (n = 1), and the resistance value is R1. . Further, since the first re-baking is “second baking” (n = 2), the resistance value is R2, and the second re-baking is “third baking” (n = 3). The resistance value is R3, and the third re-baking is “ fourth baking” (n = 4), so the resistance value is R4.

  As shown in the equation (2), the resistance value change rate CR is calculated from the difference from the n + 1th resistance value Rn + 1 with the nth resistance value Rn as a reference. Therefore, when the re-baking is performed three times after the first baking, a total of three resistance value change rates CR are obtained. Therefore, the resistance value change rate CR was evaluated by calculating a value when the absolute values of the three resistance value change rates CR were summed (referred to as a CR total value for convenience).

Example 1
Among the powder components, (B) glass powder B-1 having a softening point of 795 ° C. containing silicon oxide, boron oxide and barium oxide was selected as the glass frit, and (C) alumina powder was selected as the inorganic metal oxide powder.

  And (A-1) silver powder and (A-2) palladium powder (collectively (A) conductive powder), (B) glass frit (glass powder B-1) which have the primary particle size shown in Table 1, and (C) Alumina powder (collectively insulating powder) as an inorganic metal oxide powder was weighed in a container at a blending ratio shown in Table 2. In addition to these powder components, ethyl cellulose, terpineol, and stearic acid are mixed by stirring and premixing 2.6 parts by weight, 26 parts by weight, and 1.3 parts by weight when the total amount of the powder components is 100 parts by weight. Got. The obtained mixture was kneaded with a three-roll mill to obtain a resistor paste of Example 1.

  The paste viscosity by adding a solvent to the obtained resistor paste was adjusted to about 300 Pa · s, and the folded pattern 10 shown in FIG. 1 was printed on the ceramic substrate 20 by screen printing. The ceramic substrate 20 was a 2 inch × 1 inch alumina substrate.

  Thereafter, the ceramic substrate 20 is dried under a condition of 150 ° C. × 5 minutes by a hot air dryer, and then fired under a condition of 850 ° C. × 7 minutes and in-out 40 minutes by a belt-type firing furnace. A resistor (fired at 850 ° C.) was formed thereon. An electron micrograph of the obtained resistor is shown in FIG.

  The dried ceramic substrate 20 was fired in the same manner as described above under the condition of 820 ° C. × 7 minutes, and a resistor (820 ° C. fired) was formed on the ceramic substrate. Similarly, the dried ceramic substrate 20 was fired in the same manner as described above under the condition of 890 ° C. × 7 minutes, and a resistor (fired at 890 ° C.) was formed on the ceramic substrate 20. With respect to these three types of resistors, 10 μm equivalent resistance values were measured, and the resistance value variation rate VR was calculated from the obtained measurement data and evaluated.

  Further, a ceramic substrate provided with the resistor (fired at 850 ° C.) was used as a ceramic substrate heater model sample of Example 1, and this ceramic substrate heater model sample was subjected to 850 ° C. × 7 minutes firing temperature three times as described above. After refiring, the resistance value of 10 μm equivalent (unit: mΩ / □ / 10 μm) of the resistor was measured after each refiring, and the resistance value change rate CR was calculated as described above to evaluate the CR total value. The results are shown in Table 3.

(Example 2)
As shown in Table 2, the blending ratio of (A-1) silver powder and (A-2) palladium powder was changed from 9/1 to 8/2, and the total amount of conductive powder was changed from 45 parts by weight to 43 parts by weight. In addition, the resistor paste of Example 2 was obtained in the same manner as in Example 1 except that the total amount of the insulating powder was changed from 32 parts by weight to 35 parts by weight. A ceramic substrate heater model sample was obtained. For the model sample, the resistance value fluctuation rate VR and the resistance value change rate CR were evaluated in the same manner as in Example 1. The results are shown in Table 3.

Example 3
As shown in Table 1, the resistor paste of Example 3 was the same as Example 1 except that (A-1) silver powder having a primary particle size of 2.8 μm was used instead of 0.6 μm. And a resistor was formed to obtain a ceramic substrate heater model sample of Example 3. For the model sample, the resistance value fluctuation rate VR and the resistance value change rate CR were evaluated in the same manner as in Example 1. The results are shown in Table 3.

Example 4
As shown in Table 2, the resistor paste of Example 4 was the same as Example 1 except that the blending amount of (B) glass frit was changed from 69% by weight to 50% by weight in the total amount of the insulating powder. And a resistor was formed to obtain a ceramic substrate heater model sample of Example 4. An electron micrograph of the obtained resistor is shown in FIG. Further, the resistance variation rate VR and the resistance value change rate CR were evaluated for the model sample in the same manner as in Example 1. The results are shown in Table 3.

(Example 5)
As shown in Table 1, (A-2) palladium powder having a primary particle size of 0.06 μm (outside the preferred range of 0.1 to 0.5 μm) was used instead of 0.3 μm. Except for the above, the resistor paste of Example 5 was obtained in the same manner as in Example 1, and the resistor was formed to obtain the ceramic substrate heater model sample of Example 5. For the model sample, the resistance value fluctuation rate VR and the resistance value change rate CR were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Example 6)
As shown in Table 2, the resistor paste of Example 6 was the same as Example 1 except that the blending amount of (B) glass frit was changed from 69 wt% to 80 wt% in the total amount of the insulating powder. And a resistor was formed to obtain a ceramic substrate heater model sample of Comparative Example 1. In addition, the electron micrograph of the obtained resistor is shown in FIG. Further, the resistance variation rate VR and the resistance value change rate CR were evaluated for the model sample in the same manner as in Example 1. The results are shown in Table 3.

(Example 7)
As shown in Table 2, the blending ratio of (A-1) silver powder and (A-2) palladium powder was changed from 9/1 to 72/28, and the total amount of conductive powder was changed from 45 parts by weight to 49 parts by weight. In addition, except that the total amount of the insulating powder was changed from 32 parts by weight to 27 parts by weight, the resistor paste of Example 7 was obtained in the same manner as in Example 1, and the resistor was formed. A ceramic substrate heater model sample was obtained. For the model sample, the resistance value fluctuation rate VR and the resistance value change rate CR were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Example 8)
As shown in Table 2, the blending ratio of (A-1) silver powder and (A-2) palladium powder was changed from 9/1 to 45/57, and the total amount of conductive powder was changed from 45 parts by weight to 41 parts by weight. In addition, except that the total amount of the insulating powder was changed from 32 parts by weight to 39 parts by weight, the resistor paste of Example 8 was obtained in the same manner as in Example 1, and the resistor was formed. A ceramic substrate heater model sample was obtained. For the model sample, the resistance value fluctuation rate VR and the resistance value change rate CR were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 1)
Among the powder components, glass powder B-2 having a softening point of 800 ° C. made of borosilicate glass was selected as the glass frit (B). As shown in Table 1, the primary particle size of the glass powder B-2 is 3.5 μm.

  And as shown in Table 1, while using (A-2) palladium powder with a primary particle size of 0.06 μm instead of 0.3 μm, (C) the inorganic metal oxide powder has a primary particle size of Except for using 1.4 μm alumina powder instead of 0.8 μm, a resistor paste of Comparative Example 1 was obtained and a resistor was formed in the same manner as in Example 1, and a ceramic substrate heater model of Comparative Example 1 was formed. A sample was obtained. For the model sample, the resistance value fluctuation rate VR and the resistance value change rate CR were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 2)
As shown in Table 1, except that (A-2) palladium powder having a primary particle diameter of 0.3 μm (the same primary particle diameter as (A-2) palladium powder of Example 1) was used, In the same manner as in Comparative Example 1, a resistor paste of Comparative Example 2 was obtained and a resistor was formed to obtain a ceramic substrate heater model sample of Comparative Example 2. For the model sample, the resistance value fluctuation rate VR and the resistance value change rate CR were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 3)
As shown in Table 2, comparison was made in the same manner as in Comparative Example 1 except that (B) the amount of borosilicate glass powder as the glass frit was changed from 69% by weight to 40% by weight in the total amount of the insulating powder. While obtaining the resistor paste of Example 3, the resistor was formed, and the ceramic substrate heater model sample of Comparative Example 3 was obtained. For the model sample, the resistance value fluctuation rate VR and the resistance value change rate CR were evaluated in the same manner as in Example 1. The results are shown in Table 3.

Each of the resistor pastes of Examples 1 to 8 uses (B) a glass frit having a softening point of 750 ° C. or higher and a particle size in the range of 1 to 3 μm. C) As the inorganic metal oxide powder, alumina powder having a particle size in the range of 0.1 to 1 μm is used. Therefore, as shown in Table 3, it can be seen that the resistance value variation rate VR when firing at 820 ° C., 850 ° C., and 890 ° C. is 10% or less.

  In any of the resistor pastes of Examples 1 to 4, (A-1) the primary particle diameter of the silver powder is in the range of 0.1 to 3 μm, and (A-2) the primary particle diameter of the palladium powder is The resistance value of the resistor at the time of firing (that is, before refiring) is in the range of 0.1 to 0.5 μm, and all of the three firing conditions are 1000 mΩ / □ / 10 μm or less. At this time, it can be seen that the sum of the absolute values of the resistance value change rate CR when the refiring is performed three times at 850 ° C., that is, the CR total value is 10% or less.

  However, in the resistor paste of Example 5, since the primary particle diameter of (A-2) palladium powder is smaller than the preferred range, the resistance value variation rate VR is 10% or less (3.8%). The total CR value is over 10%. Therefore, by adjusting the blending ratio of at least (B) glass frit and (C) inorganic metal oxide powder, it is possible to suppress variation in resistance value (Example 5), and (A) conductive powder. It can be seen that by adjusting the primary particle size, the rate of change in resistance during refiring can be reduced (Examples 1 to 4).

  In the resistor paste of Example 6, the content of (B) glass frit exceeds 70% by weight (80% by weight) with respect to the total amount of the insulating powder, so that the total CR value is Although it is 31.2%, the resistance value fluctuation rate VR is 10% or less. Therefore, at least (B) a glass frit having a softening point of 750 ° C. or higher and a particle size in the range of 1 to 3 μm is used. By using alumina powder having a diameter in the range of 0.1 to 1 μm, the resistance value fluctuation rate VR can be reduced to 10% or less, and when it is desired to reduce the CR total value to 10% or less, (B) It can be seen that the content of the glass frit is preferably 70% by weight or less with respect to the total amount of the insulating powder ((B) glass frit and (C) inorganic metal oxide powder).

  Moreover, in the resistor paste of Example 7, it mix | blends so that (A-2) palladium powder may be increased compared with Example 1 etc., In the resistor paste of Example 8, (A-2) palladium powder is mixed. (A-1) Although it mix | blends so that it may become more than silver powder, both CR total value and resistance value fluctuation | variation rate VR are 10% or less. As described above, when WA1 / WA2 = 43/57 (Example 8), the TCR becomes almost zero. Therefore, (A) palladium powder in the conductive powder (A-2) in Example 8 is used. It can be seen that even if the level is increased, fluctuations in the resistance value can be suppressed.

  On the other hand, in Comparative Examples 1 to 3, since the particle size of (B) glass frit and (C) inorganic metal oxide powder (alumina powder) is out of the scope of the present invention, the resistance value fluctuation rate VR is about 70% or more. As described above, it can be seen that the fluctuation rate of the resistance value accompanying firing is large. In Comparative Examples 2 and 4, since the primary particle size of (A-2) palladium powder is smaller than the preferred range, the CR total value is increased. Here, in Comparative Example 3, since the CR total value is larger than that in Comparative Example 1, it can be seen that the rate of change in resistance value increases even if the content of (B) glass frit is too small.

  It should be noted that the present invention is not limited to the description of the above-described embodiment, and various modifications can be made within the scope of the claims, and different embodiments, examples, or a plurality of modifications can be made. Embodiments obtained by appropriately combining the respective technical means disclosed are also included in the technical scope of the present invention.

  Since the present invention can be suitably used for manufacturing a resistor constituting a heater circuit of a ceramic substrate heater, for example, a heater (for toner fixing) used in a toner fixing device of an OA device such as a copying machine, a facsimile, or a printer. Heater) or a heater for a thermal print head and the like, and can be used suitably in the field of ceramic substrate heaters.

10 Spelling pattern (resistor paste)
20 Ceramic substrate (alumina substrate)

Claims (3)

(A) containing (A-1) silver powder and (A-2) palladium powder, (B) glass frit, and (C) inorganic metal oxide powder as conductive powder, and for ceramic substrate heaters A resistor paste used,
(B) the softening point of the glass frit is 750 ° C. or higher, and the particle size thereof is in the range of 1 to 3 μm;
The inorganic metal oxide powder (C) is a powder of at least one inorganic metal oxide selected from the group consisting of alumina, zirconia, titania, and yttria, and has a particle size of 0.1 to 1 μm. Is in range,
When firing at a plurality of temperature levels within a temperature range of 800 to 900 ° C. and measuring the resistance value of the resistor after firing at each temperature level, the following formula (1)
VR = (Rmax−Rmin) / Rave × 100 (1)
(However, Rmax is the maximum value of the 10 μm equivalent resistance value among the plurality of resistance values, Rmin is the minimum value of the 10 μm equivalent resistance value, and Rave is the average value of the 10 μm equivalent value.)
The resistance value variation rate VR of the resistor after firing defined by is characterized by 10% or less,
Resistor paste for ceramic substrate heater. The primary particle diameter of the (A-1) silver powder is in the range of 0.1 to 3 μm,
(A-2) The primary particle diameter of the palladium powder is in the range of 0.1 to 0.5 μm,
Furthermore, the content of the (B) glass frit is 70% by weight or less in a weight ratio with respect to the total amount of the (B) glass frit and the (C) inorganic metal oxide powder,
When the resistance value of the resistor at the time of firing is 1000 mΩ / □ / 10 μm or less and the resistor is refired three times within the temperature range of 800 to 900 ° C., the following formula ( 2)
CR = ( Rn + 1−Rn ) / Rn × 100 (2)
(However, Rn + 1 represents the resistance value after firing n + 1 times, Rn represents the resistance value after firing n times, and n is an integer of 1 to 3.)
The total absolute value of the resistance value change rate CR of the resistor is 10% or less, defined by
The resistor paste for a ceramic substrate heater according to claim 1.   A ceramic substrate heater comprising a resistor obtained by firing the resistor paste according to claim 1.