【発明の詳細な説明】[Detailed description of the invention]
〔産業上の利用分野〕
この発明は、主として可変抵抗器および半固定
抵抗器に用いる抵抗層を有する積層板、さらに詳
しくは、抵抗層の抵抗値の変動が少なく、かつ、
ノイズ特性が良好な抵抗素材を得るための抵抗層
を有する積層板の製造方法に関するものである。
〔従来の技術〕
従来から可変抵抗器または半固定抵抗器などに
用いられている抵抗ワニスは液状の熱硬化性樹脂
に必要量のカーボン微粒子を溶剤と共に混合した
ものである。この抵抗ワニスを熱硬化性樹脂積層
板の表面にシルクスクリーン法等で塗布して焼き
付けているが、この方法では、
積層板と抵抗層との密着性が悪く、剥離する
危険がある。
抵抗層表面の平滑性が悪く、摺動時にノイズ
が発生する。
吸湿や加熱処理による抵抗値の変化が大き
い。
等の欠点があつた。そこで、これらの欠点を改善
するために、熱硬化性樹脂を含浸させて得たプリ
プレグに、熱硬化性樹脂にカーボン粒子を混合し
た抵抗ワニスを塗布乾燥して得た抵抗層付きプリ
プリグを、通常の積層基材と重ね合わせて加熱、
加圧して一体化する方法が考案されているが、こ
の方法では抵抗層表面の平滑性および抵抗層の密
着性は良好であつても、なお、つぎのような欠点
がある。すなわち、
Ｂステージ状態のプリプレグの上にカーボン
混合の抵抗ワニスを塗布してさらに乾燥するた
め、プリプレグの樹脂の硬化が促進され、通常
のプリプレグと加熱、加圧して一体化した場合
に、その層間で剥離しやすくなる。
抵抗層付きプリプレグと通常のプリプレグと
を重ねて加熱、加圧して積層すると、カーボン
の微粒子が通常のプリプレグ中に浸透するた
め、抵抗層の厚さが不均一になり、したがつ
て、抵抗層の抵抗値のバラツキが大きくなる。
等である。
〔発明が解決しようとする課題〕
以上述べたように、従来の技術においては、積
層板と抵抗層との密着性、抵抗層表面の平滑性、
温度および湿度による抵抗値の変化などの点で優
れ、しかも層間剥離がなく、抵抗層の厚みが均
一、ひいては抵抗層の抵抗値のバラツキが小さい
樹脂積層板は得られていないという問題点があ
り、これを解決することが課題であつた。
〔課題を解決するための手段〕
上記の課題を解決するために、この発明は抵抗
層を有する積層板を製造するにあたつて、Ｂステ
ージ状態にある熱硬化性樹脂積層板の少なくとも
片面に、離型性フイルム上に抵抗ワニスを塗布乾
燥してＢステージ状態にした抵抗層を、この離型
性フイルムを外側にして重ね合わせ、加熱、加圧
して一体化成形するという手段を採用したもので
ある。以下その詳細を述べる。
まず、この発明におけるＢステージ状態の熱硬
化性樹脂積層板は、通常の熱硬化性樹脂を含浸し
たプリプレグを必要枚数重ね合わせ、加熱、加圧
して積層する際に、加熱、加圧時間を短縮して樹
脂が完全には硬化していない状態（Ｂステージ状
態）にある積層板である。そして、離型性フイル
ム上に抵抗ワニスを塗布乾燥して抵抗層を形成す
る場合においても、抵抗ワニスが完全硬化するの
に要する乾燥時間を短縮してワニスが完全には硬
化していない状態に留めればＢステージの状態は
容易に得られる。
つぎに、この発明に使用する熱硬化性樹脂積層
板は、フエノール樹脂、エポキシ樹脂、ポリエス
テル樹脂、キシレン樹脂等の熱硬化性樹脂を単独
のままもしくは混合して、紙、布、ガラスクロ
ス、ガラス不織布等の基材に含浸させて得たプリ
プレグを加熱、加圧して得られ、この加熱時間
は、樹脂の種類により異なるが、フエノール樹脂
を例にとると、樹脂がゲル化（流動性が無くなる
状態）した時点からゲル化後20分間の範囲が適当
である。樹脂がゲル化するまでに取り出すと、プ
リプレグ間が層間剥離をする危険があり、また、
樹脂のゲル化後20分間以上の加熱を行なうと、樹
脂の硬化が進み過ぎて抵抗層と積層板との密着性
が悪くなる。
また、この発明に使用する離型性フイルム、た
とえば、ポリエステル、ポリプロピレン、ナイロ
ン、ポリアセテート等の耐熱性の良好な樹脂のフ
イルムである。そして離型フイルム上に形成する
抵抗ワニス層は、フイルムの全面に塗布して形成
するか、または抵抗回路をスクリーン印刷、グラ
ビア印刷等によつて部分的に形成しても良い。こ
こで、カーボン微粒子は、アセチレンブラツクを
主体として、必要に応じてフアーネスブラツクも
しくはチヤンネルブラツクの混合物が用いられ、
さらにグラフアイトの微粉または金属微粉等を混
合しても良い。いずれにしても、抵抗ワニスを塗
布した離型性フイルムを、完全硬化に至らない積
層板の少なくとも片面に、離型性フイルム面を外
側にして重ね合わせ、加熱、加圧して積層板を完
全に硬化させるとともに、抵抗層を強固に積層板
と接着一体化させることにより、この発明の抵抗
層を有する積層板が得られるのである。
〔作用〕
この発明の製造方法は、Ｂステージ状態の熱硬
化性樹脂積層板と離型性フイルム上に抵抗ワニス
を塗布乾燥してＢステージ状態にした抵抗層とを
重ねて、加熱、加圧する方法であるから、Ｂステ
ージ状態の熱硬化性樹脂積層板と抵抗層とはそれ
ぞれ反応硬化しながら接合面で接着してＣステー
ジ状態以上に硬化し、従来の印刷法における抵抗
層の剥離というような問題は起きなくなる。ま
た、この発明の方法においては抵抗ワニスを塗布
乾燥してＢステージ状態にした抵抗層を、Ｂステ
ージ状態の熱硬化性樹脂積層板に重ねて加熱、加
圧して一体化するので、熱硬化性樹脂積層板とし
てプリプレグシートを積み重ねた積層体を加熱、
加圧する時に、抵抗層のプリプレグシートも同時
に重ねて一体化する製法に比べて、カーボン微粒
子の積層板内部への侵入がきわめて少なくなり、
抵抗層の抵抗値の変動が少なくなる。
〔実施例〕
厚さ10ミルのリンター紙にフエノール樹脂を含
浸させて得たプリプレグを８枚重ね合わせ、さら
にその片面に離型性フイルムとして厚さ40μｍの
ポリプロピレンフイルムを重ねて、温度160℃、
圧力100Kg／cm2の条件で加熱、加圧した。約15分
後に樹脂がゲル化し、その後さらに15分間加熱、
加圧を継続した後冷却し、離型フイルムを剥離し
て厚さ1.5mmの完全硬化していない積層板を得た。
つぎに、前記フエノール樹脂100部（重量）に対
し、アセチレンブラツク40部とフアーネスブラツ
ク10部とを、溶剤としてのメチルエチルケトンと
ともに混合して抵抗ワニスを得た。このワニスを
厚さ40μｍのポリプロピレンフイルム上に、抵抗
層の厚さが20μｍになるように塗布、乾燥してＢ
ステージの状態にした抵抗層付き離型フイルムを
得た。前記の完全硬化していない積層板の離型フ
イルム剥離面に、この抵抗層付き離型フイルムの
フイルム面が外側になるように重ね合わせ、温度
160℃、圧力100Kg／cm2で30分間加熱、加圧して一
体化し、離型性フイルムを剥離して厚さ1.5mmの
片面抵抗層付き積層板を得た。この積層板の抵抗
層の抵抗値のバラツキと表面粗度を測定した。結
果を第１表に示した。
[Industrial Application Field] The present invention is directed to a laminate having a resistance layer used mainly for variable resistors and semi-fixed resistors, and more specifically, to a laminate having a resistance layer with little variation in resistance value, and
The present invention relates to a method of manufacturing a laminate having a resistive layer for obtaining a resistive material with good noise characteristics. [Prior Art] Resistance varnishes conventionally used for variable resistors or semi-fixed resistors are made by mixing a liquid thermosetting resin with a required amount of carbon fine particles and a solvent. This resistance varnish is applied to the surface of a thermosetting resin laminate using a silk screen method and then baked, but with this method, the adhesion between the laminate and the resistance layer is poor and there is a risk of peeling. The surface of the resistance layer has poor smoothness and generates noise when sliding. The resistance value changes significantly due to moisture absorption and heat treatment. There were other drawbacks. Therefore, in order to improve these drawbacks, a prepreg with a resistance layer obtained by applying and drying a resistance varnish containing a mixture of thermosetting resin and carbon particles to a prepreg obtained by impregnating a thermosetting resin is usually used. Laminated with the laminated base material and heated,
A method of pressurizing and integrating has been devised, but even though this method provides good surface smoothness of the resistive layer and good adhesion of the resistive layer, it still has the following drawbacks. In other words, a carbon-mixed resistance varnish is applied onto the B-stage prepreg and then dried, which accelerates the curing of the resin in the prepreg, and when it is integrated with regular prepreg by heating and pressurizing, the interlayer makes it easier to peel off. When a prepreg with a resistive layer and a regular prepreg are laminated by heating and pressurizing, the carbon particles penetrate into the regular prepreg, making the thickness of the resistive layer uneven. The variation in resistance value increases. etc. [Problem to be solved by the invention] As described above, in the conventional technology, the adhesion between the laminate and the resistance layer, the smoothness of the surface of the resistance layer,
There is a problem in that a resin laminate that is excellent in terms of changes in resistance due to temperature and humidity, has no delamination, has a uniform resistance layer thickness, and has small variations in resistance value of the resistance layer has not been obtained. The challenge was to solve this problem. [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a method for producing a laminate having a resistive layer on at least one side of a thermosetting resin laminate in a B-stage state. , which employs a method in which a resistive layer is formed by coating and drying a resistive varnish on a releasable film to bring it to a B-stage state, and the resistive layer is layered with the releasable film on the outside, and is integrally molded by heating and pressurizing. It is. The details will be described below. First, the thermosetting resin laminate in the B stage state of this invention shortens the heating and pressing time when stacking the required number of prepregs impregnated with a normal thermosetting resin and laminating them by heating and pressing. This is a laminate in which the resin is not completely cured (B stage state). Even when a resistive varnish is applied and dried on a release film to form a resistive layer, the drying time required for the resistive varnish to completely harden is shortened and the varnish is not completely hardened. If you keep it in place, you can easily achieve B stage status. Next, the thermosetting resin laminate used in this invention can be made by using thermosetting resins such as phenolic resin, epoxy resin, polyester resin, xylene resin alone or in combination with paper, cloth, glass cloth, glass, etc. It is obtained by heating and pressurizing a prepreg obtained by impregnating a base material such as a nonwoven fabric, and the heating time varies depending on the type of resin, but in the case of phenolic resin, for example, the resin gels (loss of fluidity). The appropriate range is from the time of gelation (condition) to 20 minutes after gelation. If you take it out before the resin gels, there is a risk of delamination between the prepregs, and
If heating is performed for 20 minutes or more after gelling the resin, the resin will harden too much and the adhesion between the resistance layer and the laminate will deteriorate. Further, the releasable film used in the present invention is, for example, a film made of a resin having good heat resistance such as polyester, polypropylene, nylon, or polyacetate. The resistive varnish layer formed on the release film may be formed by coating the entire surface of the film, or the resistive circuit may be formed partially by screen printing, gravure printing, or the like. Here, the carbon fine particles are mainly composed of acetylene black, and if necessary, a mixture of furnace black or channel black is used,
Furthermore, graphite fine powder, metal fine powder, etc. may be mixed. In any case, a release film coated with resistance varnish is placed on at least one side of the laminate that has not yet fully cured, with the release film side facing outward, and heated and pressurized to completely cure the laminate. By curing and firmly adhering and integrating the resistance layer with the laminate, the laminate having the resistance layer of the present invention can be obtained. [Function] The manufacturing method of the present invention is to stack a thermosetting resin laminate in a B-stage state and a resistance layer obtained by coating and drying a resistive varnish on a release film to bring it into a B-stage state, and then heat and pressurize. Since this is a method, the thermosetting resin laminate in the B-stage state and the resistance layer are bonded together at the bonding surfaces while reacting and curing, and are cured to a level higher than the C-stage state, which is similar to the peeling of the resistance layer in the conventional printing method. problems will no longer occur. In addition, in the method of this invention, the resistance layer, which has been brought into a B-stage state by applying and drying a resistance varnish, is stacked on a thermosetting resin laminate in a B-stage state and integrated by heating and pressurizing. Heating a laminate made of stacked prepreg sheets as a resin laminate,
Compared to the manufacturing method in which the prepreg sheets of the resistance layer are simultaneously stacked and integrated when pressurizing, the intrusion of carbon particles into the inside of the laminate is extremely reduced.
Fluctuations in the resistance value of the resistance layer are reduced. [Example] Eight sheets of prepreg obtained by impregnating 10 mil thick linter paper with phenol resin were stacked together, and a 40 μm thick polypropylene film was layered on one side as a release film, and heated at a temperature of 160°C.
Heating and pressure were applied at a pressure of 100 Kg/cm 2 . The resin gels after about 15 minutes, then heats for another 15 minutes,
After continuing to pressurize, the product was cooled and the release film was peeled off to obtain a 1.5 mm thick laminate that had not been completely cured.
Next, 40 parts of acetylene black and 10 parts of furnace black were mixed with 100 parts (by weight) of the phenolic resin together with methyl ethyl ketone as a solvent to obtain a resistance varnish. This varnish was applied onto a polypropylene film with a thickness of 40 μm so that the thickness of the resistance layer was 20 μm, and dried.
A release film with a resistance layer in a stage state was obtained. Lay the release film with a resistive layer on the release film release surface of the laminate that has not been completely cured, with the film surface facing outward, and heat
They were heated and pressed at 160° C. and a pressure of 100 Kg/cm 2 for 30 minutes to integrate, and the release film was peeled off to obtain a laminate with a single-sided resistive layer having a thickness of 1.5 mm. The resistance value variation and surface roughness of the resistance layer of this laminate were measured. The results are shown in Table 1.
〔効果〕〔effect〕
以上述べたように、この発明の製造方法によれ
ば、積層板と抵抗層との密着性、抵抗層表面の平
滑性、抵抗値のバラツキなどすべての点で優れた
抵抗層を有する積層板を得ることができた。
As described above, according to the manufacturing method of the present invention, a laminate having a resistance layer that is excellent in all respects such as the adhesion between the laminate and the resistance layer, the smoothness of the surface of the resistance layer, and the variation in resistance value can be produced. I was able to get it.