WO2006027954A1

WO2006027954A1 - Paste, resistor paste, methods for producing those, and variable resistor

Info

Publication number: WO2006027954A1
Application number: PCT/JP2005/015345
Authority: WO
Inventors: Yoshifumi Ogiso
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2004-09-07
Filing date: 2005-08-24
Publication date: 2006-03-16
Also published as: JP4506756B2; CN101053045B; CN101053045A; JPWO2006027954A1

Abstract

Disclosed is a variable resistor comprising a resistor substrate (10), a slider (35) having a contact piece which slides on a collector (12b) and a resistor (15) formed on the major surface of the resistor substrate (10), and a rotating shaft which rotates while holding the slider (35). The resistor (15) is made from a starting material containing a conductive filler, a novolac type phenol resin to which no curing agent is added, and a resol type phenol resin. The content of the resol type phenol resin is the same as or higher than that of the novolac type phenol resin.

Description

Specification

PASTE, RESISTOR PASTE, METHOD FOR PRODUCING THEM, AND VARIABLE RESISTOR

Technical field

The present invention relates to a paste, a resistance paste, a manufacturing method thereof, and a variable resistor including a resistor made of a cured product of the resistance paste.

Background art

Conventionally, a resol-type or novolac-type phenol resin is used as a filler binder, and the paste or a cured product thereof is, for example, ink, adhesive, friction material, sealing material, antistatic It is used as a material, voltage ratio linear element, fuel cell separator, and the like. Depending on the application, the filler used at that time is conductive such as carbon or metal, non-conductive such as silica or alumina, and organic such as vinyl chloride. There are also whisker-like shapes other than particles.

[0003] In the field of variable resistors, carbon-based carbon paste for forming a thick film resistor has been used as a resistor having a thick film formed on a substrate. This type of resistance paste is a conductive filler such as carbon black or graphite added with resole phenolic resin (see Patent Document 1) or a novolak type phenolic resin (see Patent Document 2). ) Is known.

[0004] Phenolic resin is a thermosetting resin obtained by condensing phenols and aldehydes (mainly formaldehyde) with an acid or alkali, and is important as an electrical insulating material. A yellow transparent soluble fusible resin obtained by using an acid as a condensing agent is called a novolac type, and is molded by adding a hardener. Yellowish brown oily resin obtained with alkali as a condensing agent is called resole and hardens gradually with heat.

[0005] By the way, in a paste containing a resol-type phenol resin, when the temperature during kneading for improving dispersibility becomes sufficiently higher than room temperature, the polymerization reaction proceeds and the kneaded product becomes a gel. It has a certain problem. Resistors made by applying gelled paste on the substrate have poor adhesion strength and toughness with the substrate and low bulk density. Wears a long time and cannot withstand long-term use. In addition, since resole phenol resin is synthesized by adding a large amount of formaldehyde, there is a large amount of residual formaldehyde, and it is necessary to take measures against scattering during the production of resistors.

[0006] On the other hand, novolac phenol resin is added together with a curing agent (usually hexamethylenetetramine is used) and a solvent, and the gelling does not occur. However, ammonia is generated due to decomposition of the curing agent, so that if the environmental impact becomes a problem, the substrate material that can be removed by force is limited to materials having ammonia resistance. Further, since the curing reaction proceeds relatively rapidly, the storage stability as a paste is not preferable, although it depends on the amount of the curing agent added.

Patent Document 1: Japanese Patent Laid-Open No. 60-23460

Patent Document 2: Japanese Patent Application Laid-Open No. 11 251113

Disclosure of the invention

Problems to be solved by the invention

[0007] Therefore, an object of the present invention is to provide a paste with good storage stability that can prevent gelling at the time of production, generates less ammonia and generates less ammonia, and a method for producing the same. .

[0008] Another object of the present invention is to prevent paste gelling at the time of manufacture and to have good adhesion to a substrate with a small amount of residual formaldehyde scattered, and to reduce the strength of the substrate material due to the curing agent. Therefore, the present invention provides a resistance paste having good storage stability and a method for producing the same.

[0009] Still another object of the present invention is to provide a variable resistor that can withstand long-term use by using the resistor paste.

Means for solving the problem

[0010] In order to achieve the above object, the paste according to the first invention comprises a filler, a novolac-based phenolic resin to which no curing agent is added, and a resol-based phenolic resin. The phenolic resin is characterized by having a content that is higher than that of the novolac-based phenolic resin.

[0011] A resistance paste according to a second aspect of the present invention is a conductive filler and a novolac type to which no curing agent is added. A phenolic resin and a resol-based phenolic resin are contained, and the resol-based phenolic resin has a content higher than that of the novolac-based phenolic resin.

[0012] In the resistance paste according to the second invention, carbon black and graphite can be used as the conductive filler. In addition, the component ratio of each of the above components may include 35 to 62 wt% of conductive filler, 6 to 38 wt% of novolac phenolic resin, and 12 to 47 wt% of resole phenolic resin! / I like it!

[0013] A method for producing a paste according to a third invention includes a step of kneading a filler and a novolac-type phenol resin not added with a curing agent at a temperature equal to or higher than a soft melting point or a melting point of the resin, A step of cooling the kneaded product to around room temperature, and then adding and mixing a resol-based phenolic resin and a solvent in an amount equal to or greater than that of the novolac-based phenolic resin added at the time of kneading.

[0014] The method for producing a resistance paste according to the fourth invention comprises a step of kneading a conductive filler and a nopolac-based phenolic resin to which no curing agent is added at a temperature equal to or higher than the soft melting point or melting point of the resinous resin. And, after the kneaded product has been cooled to around room temperature, a step of adding and mixing the resol phenolic resin and the solvent in an amount equal to or greater than the novolac phenolic resin added during the kneading. And It is preferable to use carbon black and graphite as the conductive filler!

[0015] A variable resistor according to a fifth aspect of the present invention includes a resistor disposed on a main surface of a substrate and a slider that slides on the resistor, and the resistor includes the resistor. It is characterized by the cured product strength of the paste.

The invention's effect

[0016] According to the paste and the resistance paste according to the first and second inventions, the filler is obtained by adding a novolac-type phenolic resin and a resol-type phenolic resin that are not added with a curing agent to the filler. Thus, gelation during kneading can be prevented, and the amount of residual formaldehyde scattered is reduced because the amount of resole phenolic resin added is small. In addition, since no curing agent is added, the storage stability without generation of ammonia is improved.

[0017] In particular, according to the resistance paste according to the second aspect of the present invention, gelling at the time of kneading is prevented, so that the resistance of the resistor to the substrate is good, and it can be used for a long time. , The power is also ammo Since there is no generation of air, there is no restriction on the substrate material and ammonia resistance.

[0018] Further, according to the production methods according to the third and fourth inventions, the addition amount of the resol-type phenol resin is not less than the addition amount of the novolac-type phenol resin, and the novolac-type resin contains no filler and no curing agent. After kneading with phenolic resin, the resol-based phenolic resin and solvent are added and mixed to obtain a paste and resistance paste free from residual formaldehyde scattering and ammonia generation.

[0019] In particular, according to the manufacturing method of the fourth invention, it is possible to obtain a resistance paste that can be used as a resistor having good characteristics with small resistance change and sliding resistance noise.

[0020] That is, the present invention provides a paste and resistance that eliminates the problems caused by the single addition by using a novolac-type phenol resin and a resole-type phenol resin that were conventionally used alone. A paste can be obtained.

Brief Description of Drawings

FIG. 1 shows a variable resistor according to an embodiment of the present invention, in which (A) is a plan view and (B) is a side view.

FIG. 2 is a cross-sectional view showing the variable resistor.

FIG. 3 is a plan view showing a resistor substrate of the variable resistor.

FIG. 4 is a plan view showing a molding state of the substrate.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of a paste, a resistance paste, a manufacturing method thereof, and a variable resistor according to the present invention will be described with reference to the accompanying drawings.

First, an embodiment of a variable resistor according to the present invention will be described with reference to FIGS.

This variable resistor includes a resistor substrate 10 made of a resin molded product, a force bar 20 that also has a resin molded product force, and a rotary shaft 30 made of a resin molded product having a slider 35. It is configured. The substrate 10 has a central hole 11 and terminals 12 and 13 are embedded. The end 12a of the terminal 12 protrudes from the side force of the substrate 10, and the central portion is exposed to the surface of the substrate 10 as an annular current collector 12b. The terminal 13 has an end portion 13a (see FIG. 4) protruding from the side surface of the substrate 10 and the other end portion 13b exposed on the surface of the substrate 10. As shown in FIG. 4, the terminals 12 and 13 are formed by punching a long hoop material 40 into a predetermined shape, and are inserted into a molding die (not shown) to form the substrate 10. After this resin molding, a resistor 15 (see FIG. 3) is formed in a substantially annular shape on the surface of the substrate 10, and both end portions 15 a that oppose each other of the resistor 15 are the other end portions of the terminals 13. Connected with 13b. The resistor 15 is formed by forming a thick film of the resistor paste according to the present invention, and the components of the resistor paste and the manufacturing method thereof will be described later.

The current collector 12 b and the resistor 15 are provided concentrically on the surface of the substrate 10, and the current collector 12 b is located inside the resistor 15.

The rotating shaft 30 has a center hole 31, and a slider 35 is attached around the flange portion 32. The rotating shaft 30 is rotatably mounted in the center hole 11 of the substrate 10. The slider 35 also has a conductive metal material force, and the brush-like first contact piece 35a sliding on the resistor 15 in an elastically pressed state and the current collector 12b on an elastically pressed state are slid. And a moving brush-like second contact piece 35b.

As shown in FIG. 1 (A), the central hole 31 of the rotating shaft 30 has a shape in which a part of a circular hole is embedded! /. Not shown in the center hole 31! When the operating shaft is inserted and rotated in the left or right direction, the slider 35 rotates with the rotating shaft 30, and the resistance of the contact pieces 35a and 35b. The resistance value between the terminals 12 and 13 is adjusted by changing the contact position with respect to the body 15 and the current collector 12b.

Hereinafter, the resistance paste used for the resistor 15 will be described. This resistance paste contains a conductive filler (conductive particles), a novolak-type phenol resin without a curing agent, and a resol-type phenol resin, and the resol-type phenol resin is a novolak-type phenol resin. The content is more than fat. Carbon black and black ship are usually used as the conductive filler.

[0030] In this resistance paste, conductive particles and a novolac-type phenol resin without addition of a curing agent were kneaded at a temperature equal to or higher than the soft melting point or melting point of the resin, and the kneaded product was cooled to around room temperature. Thereafter, it is produced by adding and mixing a resol phenolic resin and a solvent in an amount equal to or more than the novolac phenolic resin.

[0031] In the resistance paste, first, a novola to which no curing agent is added to the conductive particles. Since the resin-based phenolic resin is added and kneaded, and then the resol-based phenolic resin is added, the gelling is prevented when the resol-based phenolic resin is added alone. The adhesion strength to 10 increases toughness, and the sliding wear resistance of the resistor 15 improves. In addition, since the amount of the resol-based phenol resin added is small, the amount of scattered formaldehyde is reduced. In recent years, resin containing a reduced amount of phenol monomer has been marketed as a novolak phenol resin, and if such a resin is used, the amount of phenol monomer scattered is reduced.

[0032] In addition, since novolac-based phenol resin is not added with a curing agent, ammonia substrate is used as a substrate 10 that does not generate ammonia due to decomposition of the curing agent (usually used is hexamethylenetetramine). Therefore, there are no material restrictions and the storage stability of the paste is good.

[0033] Here, specific examples of the manufacturing method performed by the present inventors and experimental results will be described. First, carbon black 45 wt%, graphite 17 wt%, novolac phenol resin 6 wt% were kneaded in a pressure-type unit set at 120 ° C, cooled to room temperature, and then resole phenolic resin. A paste having a roll of 32 wt% and a solvent having a boiling point of around 200 ° C was further added and mixed. This resistance paste corresponds to sample number 3 in Table 1 below.

[0034] This paste was printed on a variable resistor substrate in a horseshoe pattern and cured at 220 ° C to form a resistor. Then, a variable resistor was fabricated by assembling a slider having a contact brush with a Pd alloy plating so as to slide on the resistor. The change in resistance after 10 million rotation tests was 0.82%, and the sliding resistance noise was 0.44% with respect to the input voltage.

[0035] Further, the present inventor prepared a resistance paste at the component ratios of Sample Nos. 1, 2, and 4 to 16 shown in Table 1 below and the addition temperature of the resole phenol resin, and the same as described above. Variable resistors were assembled, and their resistance value change and sliding resistance noise were measured.

[0036] [Table 1] (table 1 )

[0037] As is clear from Table 1, the resistance pastes of Sample Nos. 1 to 9 showed good resistance value change and sliding resistance noise. Content power of resol phenolic resin When the content was less than the content of pollack phenolic resin (see Sample Nos. 10 to 13), changes in resistance value and deterioration of sliding resistance noise were observed.

[0038] Further, when the resol type phenolic resin is mixed before kneading the novolak type phenolic resin as in sample number 14, or during mixing of the novolak type phenolic resin as in the sample number 15 and at room temperature or higher. When resole-based phenolic resin is mixed, as shown in Sample No. 16, even after the completion of kneading of novolac-based phenolic resin, mixing of resole-based phenolic resin at a relatively high temperature causes a change in resistance value. The sliding resistance noise became large.

[0039] Next, the operational effects of the embodiment will be described in more detail.

[0040] The form of life deterioration in the resin composite resistor is plastic deformation of the resistor!ヽ is the sliding noise that accompanies the change in resistance value due to wear, the generation of cracks due to fatigue wear of resistors, and the change in contact resistance due to reattachment of wear powder. [0041] In order to prevent such life deterioration, it is most important to reduce the amount of wear and to reduce the size of the insulating wear powder even if it is worn. For that purpose, it is necessary to uniformly disperse the conductive particles (conductive filler), and this makes it possible to form a tough resistor. In order to obtain the optimum dispersibility, it is most effective to disperse the resin and the conductive filler using a kneading method such as a kinder that can apply a strong shearing force.

[0042] In the above-described embodiment, since the resol-type phenolic resin having a curing action is added after being sufficiently cooled, the kneaded product does not go into gelling, and the adhesion strength to the substrate is strong and the toughness is high. A resistor having a sufficient bulk density can be obtained.

[0043] If the amount of resol phenolic resin such as the resistance pastes of Sample Nos. 10 to 13 is less than the amount of carbolac phenolic resin, the curing reaction becomes insufficient and the amount of wear of the resistor increases. As a result, the resistance value changes greatly and thermal stability is lacking.

[0044] When the resol-based phenolic resin is added before kneading, during kneading or at the end of kneading (sample numbers 14 to 16), the polymerization reaction proceeds and the kneaded product is gelled. Resistors made of paste using gelled kneaded material have weak adhesion to the substrate as described above, and the toughness is weak, and the bulk density is also small, so the resistance value changes greatly as the contact slides. It is difficult to withstand long-term use with large sliding resistance noise.

[0045] It should be noted that the paste, the resistance paste, the manufacturing method thereof, and the variable resistor according to the present invention can be variously modified within the scope of the gist thereof, not limited to the above-described embodiments.

[0046] In particular, the variable resistor according to the present invention is not limited to the variable resistor having the structure described as an embodiment, but can be applied to variable resistors having other structures.

[0047] Further, as the filler, particle whisker having various material strengths can be used, and the obtained paste and molded product can be used for various applications. For example, it can be suitably used for inks, adhesives, friction materials, sealing materials, antistatic materials, voltage ratio linear elements, fuel cell separators, and the like.

[0048] In addition, in the production method, the amount of the novolac phenolic resin added first is slightly reduced, and after kneading and cooling, the novolac is added when the resol phenolic resin is added. You can also add phenolic resin.

[0049] In addition, a part of the filler (particles having a relatively large particle size such as easily dispersible graphite) may be added simultaneously with the resole phenolic resin. Further, in the above examples, the force at which the boiling point of the solvent is around 200 ° C. The present invention is not limited to this.

Industrial applicability

[0050] As described above, the present invention is useful for pastes and resistance pastes, and is particularly excellent in that gelling can be prevented during production and storage stability is good.

Claims

The scope of the claims

[1] A filler, a novolak-type phenolic resin without a curing agent, and a resol-type phenolic resin, wherein the resol-type phenolic resin has a content greater than that of the novolac-type phenolic resin. A paste characterized by being.

[2] It contains a conductive filler, a novolac phenolic resin to which no curing agent is added, and a resol type phenolic resin, and the resol type phenolic resin is more than the novolac type phenolic resin. A resistance paste characterized by having a content of

[3] The resistance paste according to claim 2, wherein the conductive filler is carbon black and graphite.

[4] 35 to 62 wt% of the conductive filler and 6 to 38 wt of the novolac phenol resin

The resistance paste according to claim 2 or 3, wherein the resol phenol resin is contained in an amount of 12 to 47 wt%.

[5] a step of kneading a filler and a novolac-type phenol resin not added with a curing agent at a temperature equal to or higher than the soft melting point or melting point of the resin;

And after the kneaded product has been cooled to around room temperature, a step of adding and mixing a resol phenolic resin and a solvent in an amount equal to or greater than the novolac phenolic resin added at the time of kneading. Manufacturing method of paste.

[6] a step of kneading a conductive filler and a novolac-type phenol resin not added with a curing agent at a temperature equal to or higher than the soft spot or melting point of the resin;

And after the kneaded product has been cooled to around room temperature, a step of adding and mixing a resol phenolic resin and a solvent in an amount equal to or greater than the novolac phenolic resin added at the time of kneading. Resistance paste manufacturing method.

7. The method for producing a resistance paste according to claim 6, wherein carbon black and graphite are used as the conductive filler.

[8] A resistor provided on the main surface of the substrate, and a slider that slides on the resistor, and the resistor according to claim 2 or 4 The resistance paste hard A variable resistor comprising a compound.