【発明の詳細な説明】[Detailed description of the invention]
〔産業上の利用分野〕
本発明はコンピユータなどの電子機器、テレ
ビ・ラジオなどの家庭電気製品あるいは各種の計
測機器などに利用されるプリント配線基板、電源
などのスイツチボツクス内の基板および配電盤な
どの基板（これらの基板は一般にベーク板と呼ば
れる）に利用される積層板を製造するための積層
板原紙に関するものである。
〔従来の技術〕
従来から積層板と呼ばれるものには、ガラス布
にエポキシ樹脂などの合成樹脂を含浸し圧締硬化
したもの、コツトンリンター紙にエポキシ樹脂や
フエノール樹脂などの合成樹脂を含浸し圧締硬化
したもの、および紙（通常晒しクラフト紙）にフ
エノール樹脂などの合成樹脂を含浸し圧締硬化し
たものなどがある。この中で紙にフエノール樹脂
を含浸圧締硬化したものは比較的安価で良好な性
能を有するため、家庭電気製品を中心に多く利用
されている。
この紙・フエノール積層板はプリント配線基板
として使われる場合は、その表面に貼り合わされ
た銅箔をエツチングして電気回路を構成し、これ
に各種の電気部品、例えばIC、コンデンサー、
抵抗器などをマウントした後ハンダ付けして完成
した配線基板となる。ここに述べた一連の加工工
程はほぼ完全に自動化されており、そのため工程
中に加えられる熱などによつて積層板にわずかな
反りやねじれが発生しても工程上のトラブルとな
る。また基板完成後においても経時変化などによ
り反りやねじれが発生すると基板上の隣接する電
気部品の接触などの事故を引き起こす恐れがあ
る。この様な理由で積層板に生るわずかな反りや
ねじれも極度に嫌われる。
またベーク板として使用される場合にも、上述
のプリント配線基板の場合ほど深刻な問題ではな
いものの、積層板の反りやねじれは作業性、寸法
精度などの点から極力少ないものが要求される。
ところが現状の紙・フエノール積層板は特に加
熱工程などでは、ある程度の反りやねじれは避け
られないとまで言われるほど制御の困難な現象で
あり、原紙の特性面からも、また含浸する樹脂の
面からも反り・ねじれ改善のための種々の研究が
行われてはいるものの未だ満足される反り・ねじ
れ特性を有する紙・フエノール積層板は得られて
いない。
〔本発明が解決しようとする問題点〕
本発明の発明者は積層板の反り・ねじりを抑制
する方法について種々検討した結果、積層板の反
り・ねじれと積層板を構成する原紙の水分による
伸縮率とが密接な関係にあることを見出し、原紙
の水分による伸縮率を小さくすることにより積層
板の反り・ねじれを大きく改善することが出来る
ことを確認した。原紙の水分による伸縮率を小さ
くする具体的方法としては、原紙を構成するパル
プ繊維の繊維長を数平均として0.4〜0.6mmとし、
且つ0.28mm以下のいわゆる微細繊維の数の上で30
〜65％にすることが最も有効であり、それを具現
化することによつて反り・ねじれの極めて小さい
積層板を製造し得る積層板原紙及びその製造法を
提供するものである。
〔発明の構成〕
本発明は、原紙を構成するパルプの数平均繊維
長が0.4〜0.6mmの範囲で、且つ、0.28mm以下の長
さのパルプの数が30〜65％の範囲であることを特
徴とする積層板原紙である。
以下、本発明を詳しく説明する。
積層板原紙製造用パルプ
積層板原紙製造用パルプとしては従来からＬ材
（広葉樹材）チツプをクラフト法蒸解し通常の晒
し工程を通したLBKP（広葉樹晒しクラフトパル
プ）が用いられている。このLBKPは積層板への
加工時の樹脂含浸性や加工後の反り・ねじれなど
への影響を考慮して、普通未叩解のまま抄紙され
る。しかしながらこの様にして製造された積層板
原紙においても、積層板加工後の反り・ねじれが
大きく、また原料チツプ、蒸解・晒し条件、抄造
条件などの微妙な変動により反り・ねじれの大き
さが一定しないのが重大な欠陥となつていた。
これに対し、、本発明は反り・ねじれの原因お
よびその変動の原因が原料パルプの繊維長分布並
びにその変動に依存することを突き止めた。そし
て種々検討の結果、数平均繊維長が0.4〜0.6mm
で、且つ、0.28mm以下の微細繊維量が数の上で30
〜65％の範囲にすることで極めて反り・ねじれの
小さい積層板を製造し得る積層板原紙を作ること
が可能であることを見いだした。
これに対し従来法による広葉樹さらしクラフト
パルプの数平均繊維長は0.3から0.4mm未満の範囲
で、0.28mm以下の長さのパルプの数は70〜80％の
範囲にある。
しかしながら、本発明で数平均繊維長が0.6mm
を越え、且つ0.28mm以下の長さのパルプの数が30
％未満とすると、積層板原紙としては好ましい性
質が得られるものの、除去される微細繊維量が多
くなり、歩留りの減少も20〜30％にも達し、コス
トの増加を招くので好ましくない。
繊維長分布の測定法
従来パルプの繊維長分布は重量分布として測定
されるのが普通であるが、重量分布の場合、全体
の繊維長分布への微細繊維の影響が非常に小さい
ため、本発明の様に微細繊維量を管理する目的に
は全く用をなさない。本発明に際して発明者は反
り・ねじれに重要な影響を及ぼす微細繊維量を敏
感に測定可能とするために、数繊維長分布を採用
した。
数繊維長分布を測定する方法に特に制限は無い
が、例えばパルプ繊維をスライドグラス上に分散
固定し、顕微鏡観察によりその数分布を求める方
法、あるいはパルプ希薄溶液を毛細管に導き、光
学系を介してその数分布を自動計測する装置
（Fiber Size Analyzer FS−100、Kajaani社、
公開特許公報昭58−52505）などを用いることが
出来る。顕微鏡観察による数繊維長分布の測定は
信頼性は高いが測定に非常に多くの手間と時間を
要するため、本発明においては市販の繊維長分布
測定器（FS−100、Kajaani社）を用いた。この
繊維長分布測定器は短時間に多量の繊維長を自動
測定出来るが、微細繊維に対する測定感度が毛細
管中を通過するパルプ希薄溶液の速度に依存する
という欠点を持つている。そこで本発明者等は顕
微鏡観察とほぼ同一の結果を与える上記FS−100
の測定条件を見出し、その測定条件において、パ
ルプの数平均繊維長が0.4〜0.6mmで、且つ0.28mm
以下の微細繊維量が数の上で30〜65％にすること
になり、極めて反り・ねじれの小さい積層板を製
造し得る積層板原紙を作ることが可能であること
を確認した。なお顕微鏡観察とほぼ同一の測定結
果を与えるFS−100の測定条件は以下の通りであ
る。
測定レンジ：１（測定範囲0.00mm〜2.40mm）
測定温度：25℃
吸引圧力：−５cmHg
本発明を具現化する方法
積層板原紙を構成するパルプの数平均繊維長を
0.4mm以上、且つ長さ0.28mm以下の微細繊維を数
の上で65％以下にする方法に特に制限はないが、
例えばその例として１法は、抄紙の前段階におい
てパルプ懸濁液中から微細繊維を選択的に取り除
く方法であり、例えば洗浄工程においてワイヤー
メツシユを粗くしたり、水量を増加して洗浄白水
の回収率を下げたり、あるいはスクリーンなどを
用いて微細繊維を取り除くことで目的を達成する
ことが出来る。
第２の方法は、抄紙工程において比較的微細繊
維の濃度の高い一部ワイヤ白水を取り除く方法で
あり、少なくともワイヤ白水の５％以上を白水循
環系から取り除くことにより目的を達成できる。
〔実施例〕
実施例 １
広葉樹材チツプを原料として、晒しクラフトパ
ルプ（LBKP）を製造し、このパルプをJIS規格
ふるい分け試験機に通し、150メツシユパス成分
の一部を取り除いて、いわゆる微細繊維除去パル
プを作成した。この微細繊維除去パルプを用い
て、テストマシンにより、坪量130ｇ／m2、厚さ
260μの積層板原紙を抄造した。この積層板原紙
にフエノール樹脂（PR9480、住友ベークライト
社製）を重量比で紙：樹脂＝１：１となる様に含
浸・乾燥して、プリプレグと呼ばれる含浸紙を作
成した。このプリプレグを８枚積層して加熱・圧
締し、積層板を製造した。加熱・圧締条件は、
150℃、90Kg／cm2、120分間であつた。
この様にして成型した積層板を200mm×200mmの
大きさに切断し、150℃の乾燥器で10分間加熱後、
冷水中に１分間放置した後の反り・ねじれを測定
した。反りの大きさは、積層板の四隅が持ち上が
る様に平面上に置いた時の、四隅の持ち上がり量
の最大値、ねじれは積層板の上記の逆向きに置
き、三隅を平面に付けた時の他の一隅の持ち上が
り量の最大値と定義した。その結果および原紙の
パルプの繊維長分布は他の実施例および比較例と
共に表１に示した。
表１からわかる様に、微細繊維除去パルプを原
料とした積層板原紙のパルプの数平均繊維長は
0.48mm、長さ0.28mm以下の微細繊維量は数の上で
57％であり、この原紙から製造した積層板は、な
んら繊維長分布に対して対策を施さない比較例に
比べ、反り・ねじり共に極めて低い水準であつ
た。
実施例 ２
実施例１と同様にしてテストマシンにより、坪
量130ｇ／m2、厚さ260μの積層板原紙を抄造し
た。但し、ここでは微細繊維の除去処理は全く行
わず、それに代わつて、抄紙温度を27℃に保持し
た。この積層板原紙から実施例１と同様にして積
層板を製造し、反り・ねじれを測定した。その結
果は表１に示した。
抄紙温度を27℃に保持した積層板原紙のパルプ
の数平均繊維長は0.40mm、長さ0.28mm以下の微細
繊維量は数の上で64％であり、、この原紙から製
造した積層板は比較例に比べ反り・ねじれ共に極
めて低い水準であつた。
実施例 ３
実施例１と同様にしてテストマシンにより、坪
量130ｇ／m2、厚さ260μの積層板原紙を抄造し
た。但し、ここでは微細繊維の除去処理は全く行
わず、それに代わつて、ワイヤ白水を約10％だけ
白水循環系に戻さず、ほぼ同量の水道水を補つて
水バランスを取つた。この積層板原紙から実施例
１と同様にして積層板を製造し、反り・ねじれを
測定した。その結果を表１に示した。
ワイヤ白水を約10％廃棄した積層板原紙のパル
プの数平均繊維長は0.44mm、長さ0.28mm以下の微
細繊維量は数の上で61％であり、この原紙から製
造した積層板は比較例に比べ反り・ねじれ共に極
めて低い水準であつた。
比較例
実施例１と同様にして、広葉樹材チツプを原料
とした晒しクラフトパルプ（LBKP）を製造し、
テストマシンにより、坪量130ｇ／m2、厚さ260μ
の積層板原紙を抄造した。この時の抄造は、微細
繊維除去処理なし、抄紙温度18℃、白水循環系ほ
ぼ完全クローズド化という条件下で行つた。この
積層板原紙から実施例１と同様にして積層板を製
造し、反り・ねじれを測定した。その結果は表１
に示した。
この原紙の再離解パルプの数平均繊維長は0.36
mm、長さ0.28mm以下の微細繊維量は数の上で71％
であり、本発明の実施例１〜３に比較して反り・
ねじれ共に非常に大きく、実用に供することの出
来るものではなかつた。
[Industrial Field of Application] The present invention is applicable to printed wiring boards used in electronic equipment such as computers, home appliances such as televisions and radios, and various measuring instruments, boards in switch boxes such as power supplies, and switchboards. The present invention relates to laminate base paper for producing laminates used for substrates (these substrates are generally called bakeboards). [Conventional technology] Conventionally, laminates are made by impregnating glass cloth with synthetic resin such as epoxy resin and hardening it by pressing, or by impregnating cotton linter paper with synthetic resin such as epoxy resin or phenolic resin. There are those that have been pressed and hardened, and those that have been pressed and hardened by impregnating paper (usually bleached kraft paper) with a synthetic resin such as phenolic resin. Among these, paper made by impregnating and pressing hardening a phenolic resin is relatively inexpensive and has good performance, so it is widely used mainly in household electrical appliances. When this paper/phenol laminate is used as a printed wiring board, the copper foil bonded to the surface is etched to form an electrical circuit, and various electrical parts such as ICs, capacitors, etc.
After mounting resistors and other components, soldering is performed to create a completed wiring board. The series of processing steps described here are almost completely automated, so even slight warping or twisting of the laminate due to heat applied during the process can cause problems in the process. Further, even after the board is completed, if warping or twisting occurs due to changes over time, there is a risk of accidents such as contact between adjacent electrical components on the board. For this reason, slight warping or twisting in laminates is extremely disliked. Furthermore, when used as a bake board, although the problem is not as serious as that in the case of the above-mentioned printed wiring board, warping and twisting of the laminated board must be kept to a minimum from the viewpoint of workability and dimensional accuracy. However, current paper/phenol laminates suffer from a certain degree of warping and twisting, which is a phenomenon that is so difficult to control that it is said to be unavoidable, especially during the heating process. Although various studies have been conducted to improve warpage and twisting, a paper/phenol laminate with satisfactory warpage and twisting properties has not yet been obtained. [Problems to be Solved by the Present Invention] As a result of various studies on methods for suppressing warpage and twisting of laminates, the inventors of the present invention found that warping and twisting of laminates and expansion and contraction due to moisture in the base paper constituting the laminates. They found that there is a close relationship between the expansion and contraction ratio of the base paper due to moisture, and confirmed that the warping and twisting of the laminate can be greatly improved by reducing the expansion and contraction ratio of the base paper due to moisture. A specific method for reducing the expansion and contraction rate of base paper due to moisture is to set the fiber length of the pulp fibers constituting the base paper to 0.4 to 0.6 mm as a number average;
And the number of so-called fine fibers of 0.28 mm or less is 30
-65% is the most effective, and by implementing this, we provide a laminate board base paper and a method for manufacturing the same that can produce laminates with extremely small warpage and twist. [Structure of the Invention] The present invention provides that the number average fiber length of the pulp constituting the base paper is in the range of 0.4 to 0.6 mm, and the number of pulps with a length of 0.28 mm or less is in the range of 30 to 65%. This is a laminated board base paper characterized by: The present invention will be explained in detail below. Pulp for producing base paper for laminated boards As pulp for producing base papers for laminate boards, LBKP (bleached hardwood kraft pulp), which is produced by cooking L wood (hardwood wood) chips using the kraft method and passing them through a normal bleaching process, has been used. This LBKP is usually made into paper without being beaten, taking into consideration the resin impregnation properties during processing into laminates and the effects on warping and twisting after processing. However, even in the laminated board base paper manufactured in this way, the warpage and twisting after processing the laminate is large, and the magnitude of warping and twisting remains constant due to subtle fluctuations in raw material chips, cooking/bleaching conditions, papermaking conditions, etc. Not doing so had become a serious flaw. On the other hand, the present invention has found that the causes of warping and twisting and the causes of their fluctuations depend on the fiber length distribution of the raw material pulp and its fluctuations. As a result of various studies, the number average fiber length was 0.4 to 0.6 mm.
And the amount of fine fibers of 0.28 mm or less is 30 in number.
It has been found that by setting the amount in the range of ~65%, it is possible to make a laminate board base paper that can produce laminates with extremely small warpage and twist. On the other hand, the number average fiber length of conventionally bleached hardwood kraft pulp is in the range of 0.3 to less than 0.4 mm, and the number of pulps with a length of 0.28 mm or less is in the range of 70 to 80%. However, in the present invention, the number average fiber length is 0.6 mm.
and the number of pulps with a length of 0.28 mm or less is 30
If it is less than %, although desirable properties can be obtained as a base paper for laminated board, the amount of fine fibers removed increases, the yield decreases by as much as 20 to 30%, and this is not preferable because it causes an increase in cost. Method for Measuring Fiber Length Distribution Conventionally, the fiber length distribution of pulp is usually measured as a weight distribution, but in the case of weight distribution, the influence of fine fibers on the overall fiber length distribution is very small. It is completely useless for the purpose of controlling the amount of fine fibers. In the present invention, the inventor adopted a number fiber length distribution in order to be able to sensitively measure the amount of fine fibers that have an important effect on warping and twisting. There are no particular restrictions on the method for measuring the number fiber length distribution, but for example, pulp fibers may be dispersed and fixed on a slide glass and the number distribution may be determined by microscopic observation, or a dilute pulp solution may be introduced into a capillary tube and measured through an optical system. Fiber Size Analyzer FS−100, Kajaani Co., Ltd.
Publication of Japanese Patent Publication No. 58-52505) can be used. Measuring the number fiber length distribution by microscopic observation is highly reliable, but requires a lot of effort and time, so in the present invention, a commercially available fiber length distribution measuring device (FS-100, Kajaani) was used. . Although this fiber length distribution measuring device can automatically measure a large amount of fiber length in a short period of time, it has the drawback that the measurement sensitivity for fine fibers depends on the speed of the dilute pulp solution passing through the capillary tube. Therefore, the present inventors developed the above-mentioned FS-100, which gives almost the same results as microscopic observation.
Under the measurement conditions, the number average fiber length of the pulp is 0.4 to 0.6 mm, and 0.28 mm.
It was confirmed that it is possible to make a laminate board base paper that can produce laminates with extremely small warpage and twist by having the following fine fiber content in the numerical range of 30 to 65%. The measurement conditions of the FS-100, which give almost the same measurement results as those observed under a microscope, are as follows. Measuring range: 1 (measuring range 0.00mm to 2.40mm) Measuring temperature: 25℃ Suction pressure: -5cmHg Method for embodying the present invention The number average fiber length of the pulp constituting the laminate base paper
There is no particular restriction on the method of reducing the number of fine fibers of 0.4 mm or more and 0.28 mm or less in number to 65% or less, but
For example, one method is to selectively remove fine fibers from the pulp suspension in the pre-papermaking process. This goal can be achieved by lowering the recovery rate or removing fine fibers using a screen or the like. The second method is to remove part of the wire white water with a relatively high concentration of fine fibers during the papermaking process, and the objective can be achieved by removing at least 5% or more of the wire white water from the white water circulation system. [Example] Example 1 Bleached kraft pulp (LBKP) was produced using hardwood chips as a raw material, and this pulp was passed through a JIS standard sieving tester to remove a part of the 150 mesh pass component and produce so-called fine fiber-removed pulp. It was created. Using this pulp from which fine fibers have been removed, the test machine has a basis weight of 130 g/m 2 and a thickness of
A 260μ laminated board base paper was made. This laminated board base paper was impregnated with phenol resin (PR9480, manufactured by Sumitomo Bakelite Co., Ltd.) at a weight ratio of paper:resin=1:1 and dried to produce impregnated paper called prepreg. Eight sheets of this prepreg were laminated and heated and pressed to produce a laminate. The heating and pressing conditions are as follows:
The temperature was 150°C, 90Kg/cm 2 , and 120 minutes. The laminated board formed in this way was cut into a size of 200 mm x 200 mm, heated in a dryer at 150°C for 10 minutes,
Warpage and twisting after being left in cold water for 1 minute were measured. The amount of warpage is the maximum amount of lift of the four corners when the four corners of the laminate are placed on a flat surface, and the amount of twist is when the laminate is placed in the opposite direction and the three corners are placed on a flat surface. It was defined as the maximum amount of lift at the other corner. The results and the fiber length distribution of the base paper pulp are shown in Table 1 together with other Examples and Comparative Examples. As can be seen from Table 1, the number average fiber length of the pulp of the laminated board base paper made from the fine fiber-removed pulp is
The amount of fine fibers less than 0.48mm and 0.28mm in length is
57%, and the laminate produced from this base paper had extremely low levels of both warping and twisting compared to a comparative example in which no measures were taken for fiber length distribution. Example 2 A laminated board base paper having a basis weight of 130 g/m 2 and a thickness of 260 μm was made using a test machine in the same manner as in Example 1. However, no fine fiber removal treatment was performed here, and instead, the papermaking temperature was maintained at 27°C. A laminate was produced from this laminate board base paper in the same manner as in Example 1, and warpage and twist were measured. The results are shown in Table 1. The number average fiber length of the pulp of the laminated board base paper kept at a papermaking temperature of 27℃ is 0.40 mm, and the amount of fine fibers with a length of 0.28 mm or less is 64%, and the laminated board manufactured from this base paper is Both warping and twisting were at extremely low levels compared to the comparative example. Example 3 A laminated base paper having a basis weight of 130 g/m 2 and a thickness of 260 μm was made using a test machine in the same manner as in Example 1. However, no fine fiber removal treatment was performed here, and instead, only about 10% of the wire white water was not returned to the white water circulation system, and approximately the same amount of tap water was supplemented to maintain the water balance. A laminate was produced from this laminate board base paper in the same manner as in Example 1, and warpage and twist were measured. The results are shown in Table 1. The number average fiber length of the pulp of the laminated board base paper in which approximately 10% of the wire white water was discarded is 0.44 mm, and the amount of fine fibers with a length of 0.28 mm or less is 61% in number, and the laminate manufactured from this base paper is compared to Both warping and twisting were at extremely low levels compared to the examples. Comparative Example Bleached kraft pulp (LBKP) made from hardwood chips was produced in the same manner as in Example 1,
According to the test machine, the basis weight is 130g/m 2 and the thickness is 260μ.
A laminated board base paper was made. The papermaking process was carried out under the following conditions: no fine fiber removal treatment, a papermaking temperature of 18°C, and a nearly completely closed white water circulation system. A laminate was produced from this laminate board base paper in the same manner as in Example 1, and warpage and twist were measured. The results are in Table 1
It was shown to. The number average fiber length of the redisintegrated pulp of this base paper is 0.36
mm, the amount of fine fibers with a length of 0.28 mm or less is 71% in number
, and compared to Examples 1 to 3 of the present invention, the warpage and
Both the twist and the twist were extremely large, making it impossible to put it to practical use.
【表】【table】
【表】
ここで実施した反り・ねじれ試験の測定値は、
実用に供される場合より苛酷な条件であり、この
測定値が反り５mm以上、ねじれ３mm以内であれば
実用上全く問題の無いレベルとなることを経験的
に確認している。[Table] The measured values of the warp/twist test conducted here are:
The conditions are more severe than those used in practical use, and it has been empirically confirmed that if the measured values are 5 mm or more in warpage and 3 mm or less in twist, there is no problem at all in practical use.