JP4984037B2 - Dry short fiber web and nonwoven fabric containing quartz glass fiber - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a quartz glass fiber-containing dry short fiber web and a quartz glass fiber-containing non-woven fabric, and particularly contains a quartz glass fiber used for a printed circuit board having a low dielectric constant and a low dielectric loss mainly required for a high frequency circuit of 1 GHz or higher. It relates to a nonwoven fabric.

The dry nonwoven fabric is a general term for nonwoven fabrics generally produced by a card method, an airlaid method, a needle punch method, a spunbond method, and a melt blow method.
Therefore, after opening the fibers into a web using a card machine, the fibers are entangled by the hydroentanglement method (dry spunlace nonwoven fabric) or bonded using a binder (chemical bond nonwoven fabric), or the fibers are thermally fused (thermal). Nonwoven fabrics made by the Bonded Nonwoven method are classified as dry nonwoven fabrics.
dT (decitex) is a unit representing the thickness of the fiber, and is a unit representing the gram weight per 10,000 m of fiber. The larger the dT, the thicker the fiber. Quartz glass fiber uses the notation in the usual mm or μm units because of its special characteristics.

Conventionally, a composite material of glass cloth and resin has been used for a printed wiring board, and E glass is generally used as the glass cloth.
The demand for high-speed semiconductor elements and high-speed and large-capacity transmission for communication equipment and broadcasting equipment has been rapidly increasing, and the improvement of the high-frequency characteristics of printed wiring boards has been demanded, so the frequency especially exceeds 1 GHz. In printed wiring boards for high-frequency circuits, lower-loss D glass or NE glass cloth has been used. (For example, refer to Patent Document 1 and Patent Document 2).
Furthermore, a printed wiring board using a quartz glass cloth having a particularly low dielectric constant and dielectric loss among glasses has also been developed (see, for example, Patent Document 3 and Patent Document 4).
Although this quartz glass cloth has very good electrical characteristics, it is very expensive, so in addition to the problem that its use is limited to some high-frequency circuits, because the quartz glass fiber is very hard, There is a drawback that the drillability of the drill is deteriorated.
Therefore, an attempt has been made to use a quartz glass nonwoven fabric having a lower price and better workability as a cloth for a printed wiring board (see Patent Document 5).

By the way, in general, in a high-frequency circuit of 1 GHz or more, it is preferable to control the variation of the characteristic impedance of the substrate to be ± 5% or less, and this value is adjusted by, for example, the thickness or width of the conductor. Because of such a demand, the impedance variation of the quartz glass nonwoven fabric itself constituting the printed wiring board should be suppressed as much as possible. As a result of the inventors' research, in order to control the variation in the characteristic impedance of the substrate to ± 5% or less in a high-frequency circuit of 1 GHz or higher, it is preferable to make the impedance variation of the quartz glass nonwoven fabric itself within ± 10%. found.
However, quartz glass nonwoven fabric is not woven compared to cloth, so it is structurally non-uniform, and unevenness in basis weight (or density) and thickness is likely to occur. This unevenness causes the resin to flow when it is combined with the resin. Are not uniform, flat bubbles are generated in the substrate, and thickness variations and electrical characteristics, especially impedance variations at high frequencies of 1 GHz or higher, become large even after the printed wiring board is formed. is there.
In particular, in the production of a quartz glass nonwoven fabric by the melt-blowing method described in the above-mentioned Patent Document 5, the diameter and length of each fiber varies because the glass solution is blown away, and the inside of each fiber However, it is difficult to create a nonwoven fabric with uniform electrical properties because it is difficult to maintain a uniform basis weight and thickness because the shape of the tip is narrow and thick at the center. understood.

Therefore, as with other nonwoven fabrics, an attempt was made to open the nonwoven fabric using a card machine in order to make the basis weight and thickness constant. However, when opening using a card machine, it is easy to make “dama”, the fibers often get tangled and cut, and it is difficult to form a good web with good yield. This is considered to be because the quartz glass fiber produced by the melt blow method is blown off by the high-pressure gas in the melted state, so that each fiber is bent or twisted.
In addition, various studies have been conducted to reduce the thickness of the printed circuit board and improve the durability of the printed circuit board. The factors described above are largely related to the basis weight of the nonwoven fabric. It has been found that it is necessary to specify the range of values.
Japanese Patent Laid-Open No. 03-37136 Japanese Patent Laid-Open No. 10-167759 JP 2004-099376 A JP 2004-099377 A JP 2004-353132 A

  The present invention relates to a quartz glass fiber-containing dry short fiber web suitable for producing a quartz glass nonwoven fabric suitable for a printed wiring board for high-frequency circuits, and a quartz glass fiber having high strength and suitable for a printed wiring board for high-frequency circuits. It aims at providing a containing nonwoven fabric.

Said subject is achieved by the quartz glass fiber containing dry short fiber web and quartz glass fiber containing nonwoven fabric by this invention of the structure of following (1) to (11).
(1) A quartz glass fiber-containing dry short fiber web for producing a quartz glass fiber-containing non-woven fabric used for a printed wiring board that forms a high-frequency circuit having a frequency of 1 GHz or more, by cutting the quartz glass long fiber. It is composed of the obtained quartz glass fiber having a diameter of 1 μm or more and 20 μm or less, and a heat-fusible fiber, and has a basis weight of 5 g / m ² or more and 70 g / m ² or less. The relative dielectric constant ε ′ with respect to the high frequency is 2.5 or less, the dielectric loss tan δ is 3 × 10 ⁻³ or less, the fiber diameter is 0.5 dT or more and 10 dT or less, and the mixture ratio in the whole fiber is 5 mass% or more. The dry short fiber web containing quartz glass fibers is characterized by being 90% by mass or less.
(2) The quartz glass fiber-containing dry short fiber web according to (1), wherein the heat-fusible fiber is a polyolefin-based synthetic fiber.
(3) The diameter of the quartz glass fiber is 1 μm or more and 20 μm or less, the variation of the fiber diameter is within ± 10%, the length is 10 mm or more and 500 mm or less, and the length is aligned to a predetermined length. The quartz glass fiber-containing dry short fiber web according to the above (1) or (2), characterized by being opened by
(4) The quartz glass fiber-containing dry short fiber web described in any one of (1) to (3) above is obtained by entanglement by the hydroentanglement method, and the basis weight is 5 g / m ² or more and 70 g / m ^2. hereinafter der is, a quartz glass fiber-containing nonwoven fabric used for the printed wiring board with a frequency forming a high-frequency circuit of the above 1 GHz.
(5) By heating the quartz glass fiber-containing dry short fiber web described in any one of (1) to (3) above, the quartz glass fiber is obtained by heat-sealing with a heat-fusible fiber. A quartz glass fiber-containing nonwoven fabric having a basis weight of 5 g / m ² or more and 70 g / m ² or less.
(6) The quartz glass fiber-containing dry short fiber web described in any one of the above (1) to (3) is entangled by a hydroentanglement method, and further heated, whereby the quartz glass fiber is made of a heat-fusible fiber. A quartz glass fiber-containing nonwoven fabric obtained by heat sealing and having a basis weight of 5 g / m ² or more and 70 g / m ² or less.
(7) The quartz glass fiber-containing nonwoven fabric according to any one of (4) to (6), which has a thickness of 30 μm or more and 200 μm or less.
(8) The quartz glass fiber-containing nonwoven fabric according to any one of (4) to (7), wherein the variation in basis weight is within ± 20%.
(9) The quartz glass fiber-containing nonwoven fabric according to any one of (4) to (8), wherein the thickness variation is within ± 20%.
(10) The silica glass fiber-containing material according to any one of (4) to (9), wherein the relative dielectric constant ε ′ for a high frequency of 10 GHz is 3.8 or less and the dielectric loss tan δ is 3.5 × 10 ^−3. Non-woven fabric.
(11) The quartz glass fiber-containing nonwoven fabric according to any one of the above (4) to (10), wherein the tensile strength in the longitudinal direction is 10 N or more according to JIS L-1913 “General Short Fiber Nonwoven Fabric Test Method”.

The quartz glass fiber-containing dry short fiber web according to the embodiment of the present invention is a web produced by mixing a quartz glass fiber and a heat-fusible fiber by a card method, an airlaid method, or other dry methods. The quartz glass fiber has a diameter of 1 μm or more and 20 μm or less (preferably 2 μm or more and 10 μm or less), and the variation of the fiber diameter is within ± 10% of the diameter. , 500 mm or less (preferably 50 mm or more and 150 mm or less), and in the case of the airlaid system, the length is 1 mm or more and 30 mm or less (preferably 3 mm or more and 10 mm or less), and they are arranged to a predetermined length.
When the diameter of the quartz glass fiber is less than the above range, it is difficult to suppress variation in the fiber diameter, and at the same time, the yield in producing the fiber is lowered. When the above range is exceeded, it is difficult to reduce the thickness of the resulting quartz glass nonwoven fabric to, for example, 100 μm or less. When the variation in diameter exceeds ± 10%, when the web is formed by opening with a card machine, the yield decreases, and at the same time, the variation in the basis weight, thickness, and electrical characteristics of the obtained nonwoven fabric tends to increase. When the fiber length is less than the above range, the strength of the obtained nonwoven fabric tends to be lowered, and the yield in forming the nonwoven fabric tends to be poor. Further, if the above range is exceeded, it becomes difficult to form a web by a card machine, the texture of the nonwoven fabric obtained even when the web is formed, and the variation in basis weight, thickness, and electrical characteristics Easy to grow. Here, the texture represents homogeneity when the nonwoven fabric is visually observed.

The quartz glass fiber as described above is obtained by cutting a large number of quartz glass fibers having a constant diameter into a predetermined length after aligning the directions. The quartz glass fiber-containing dry short fiber web of the present invention is characterized in that the raw material is a group of quartz glass fibers made of quartz glass fibers having a certain length. The long silica glass fiber is manufactured by a rod drawing method in which a plurality of quartz glass rods are slowly passed through an electric furnace maintained at a high temperature inside a furnace whose upper and lower ends are opened, and the lower end of the rod is drawn at high speed. It is preferable that Since the rod stretching method itself is known, further detailed description is omitted.
By passing through the long fiber, the fiber diameter of the quartz glass fiber can be arbitrarily set within the above range, and the variation in the diameter can be suppressed within the above range. In addition, the long silica glass fibers drawn by the method described above are straight and free of twists, etc., so that the obtained quartz glass fibers have particularly good card characteristics and form a web with high yield and low density unevenness. it can.
Furthermore, when drawing the quartz glass long fiber, it becomes possible to apply a sizing material at the intermediate point between the lower end of the furnace and the winder, and it becomes possible to apply a sizing material that was very difficult by the melt blow method. As a result, the strength of the fiber is increased, and it is also possible to easily open the fiber using a card machine, which is a subsequent process.

The heat-fusible synthetic fiber preferably has a relative dielectric constant ε ′ at 1 MHz of 2.5 or less and a dielectric loss (tan δ) of 3 × 10 ⁻³ or less. When the relative dielectric constant and dielectric loss of the heat-fusible synthetic fiber exceed the above values, a quartz glass fiber-containing nonwoven fabric is prepared using the dry short fiber web containing the quartz glass fiber, and the quartz glass fiber-containing nonwoven fabric is further contained. When a wiring board is produced using a non-woven fabric, it becomes difficult to achieve a relative dielectric constant of 3.8 or less and a dielectric loss of 3.5 × 10 ⁻³ or less, which are necessary for a high frequency circuit of 1 GHz or higher. The heat-fusible synthetic fiber used preferably has a fiber length substantially equal to that of the quartz glass fiber, and preferably has a fiber diameter in the range of 0.5 dT to 10 dT. When the fiber diameter is less than the above range, the strength of the heat-fusible fiber itself is lowered, and the yield of the dry short fiber web is likely to be lowered. The strength of the obtained nonwoven fabric tends to decrease. The fiber length is preferably close to the length of the quartz glass fiber. If the fiber length is too long or too short relative to the fiber length of the quartz glass fiber, it becomes difficult to mix with the quartz glass fiber when forming a dry short fiber web, and the resulting nonwoven fabric has sufficient strength. It becomes difficult to get.
Examples of the heat-fusible synthetic fibers that can be used include polyolefin-based synthetic fibers, Daiwabo Polypro PN, NBF (E), and the like. These polyolefin synthetic fibers have a relative dielectric constant ε ′ at 1 MHz of 2.3 and a dielectric loss tan δ of about 3.0 × 10 ⁻⁴ .
Using a mixed fiber group obtained by mixing quartz glass fibers and heat-fusible fibers having the above characteristics, a dry short fiber web containing quartz glass fibers by a card method, an airlaid method, or other similar methods. Get. As the card machine, it is possible to use a dry card machine used for manufacturing a conventional synthetic fiber nonwoven fabric by aligning the length and diameter of quartz glass fibers as described above. As in the case of manufacturing a conventional synthetic fiber nonwoven fabric, the basis weight, thickness, and texture of the card web can be changed as necessary by changing the setting of the dry card machine.

The quartz glass fiber-containing dry short fiber web has a basis weight of 5 g / m ² or more and 70 g / m ² or less. If the basis weight is less than 5 g / m ² , the fiber density is too low to make it very difficult to obtain a uniform dry short fiber web and thus a nonwoven fabric, and the thickness is also less than 30 μm, which is preferable as a quartz glass nonwoven fabric for printed wiring boards. End up. Furthermore, it becomes difficult to obtain a strength of 10 N or more, which is necessary as a quartz glass nonwoven fabric for printed wiring boards. On the other hand, if the basis weight is more than 70 g / m ² , the thickness tends to increase, exceeding 200 μm, which is a preferable thickness for the quartz glass fiber nonwoven fabric for printed wiring boards. In addition, the uniformity of the basis weight tends to deteriorate. In addition, the value of the thickness and intensity | strength considered preferable for the said printed wiring board is a value about the general nonwoven fabric and quartz glass fiber nonwoven fabric by the organic fiber which exists conventionally.
The basis weight is preferably 10 g / m ² or more and 40 g / m ² or less, more preferably 15 g / m ² or more and 30 g / m ² or less. The heat-fusible synthetic fiber preferably has a blending ratio of 5% by mass or more and 90% by mass in the whole fiber. When the blending ratio is less than the above range, sufficient strength cannot be obtained in the nonwoven fabric obtained because the quartz glass fibers cannot be completely bonded to each other. On the other hand, when the above range is exceeded, the electrical characteristics deteriorate. The strength does not increase due to the small number of quartz glass fibers. The blending ratio of the heat-fusible synthetic fiber is preferably 10% by mass to 60% by mass, and particularly preferably 15% by mass to 50% by mass. According to the experiments by the inventors, when the blending ratio is between 10% by mass and 60% by mass, the dielectric constant and the dielectric loss are lower than those within the range and the blending ratio exceeding the range. . Therefore, considering only the characteristics of dielectric constant and dielectric loss, the blending ratio is preferably 10% by mass to 60% by mass.

The method for producing the quartz glass fiber-containing dry short fiber web described above will be described below. In the following example, the card system will be described as a representative.
First, before opening with a carding machine, a mixture of quartz glass fibers and heat-fusible synthetic fibers (hereinafter sometimes referred to as raw cotton) having the above characteristics is unwound and uniformly mixed. This process improves card suitability by a later card machine. In addition, this mixture has the characteristic that card | curd suitability is better than the thing of quartz glass fiber single. Also in this process, if the fiber diameter of the quartz glass fiber is not constant, or if the quartz glass fiber is twisted or bent, the quartz glass fibers will be entangled with each other, and the uniform unraveling and heat fusion fiber will be uniform It becomes difficult to perform proper mixing. Furthermore, when the length of the quartz glass fiber is too long, it is not preferable because the fiber itself is torn or entangled in the beater roll described later.

This fiber mixing is preferably performed by an opener 10 as shown in FIG.
The opener 10 includes a beater roll 12 for unwinding and uniformly mixing the raw cotton, and a first feed roll 16 for feeding the raw cotton m sent from the conveyor 14 into the beater roll 12 by a predetermined amount. The beater roll 12 is a roll in which countless needles of about 5 inch nails protrude from the surface, and the rotation speed thereof is about 800 to 1,000 rpm. On the downstream side of the beater roll 12, a blower 18 is provided for sending raw cotton pieces unraveled by the beater roll 12 and uniformly mixed with fibers to a subsequent opening process.
The amount of raw cotton fed into the beater roll 12 is adjusted by the rotational speed of the first feed roll 16, and the speed is about 0 to 5 m / min. The introduced raw cotton is broken into small pieces of raw cotton by the beater roll 12 rotating at high speed, and sent to the fiber opening process by the blower 18.
The fiber opening process is performed by a card machine 20 with a hopper feeder 22 for filling raw cotton as shown in FIG. The raw cotton unwound by the opener 10 is blown by the blower 18 and filled in the hopper feeder 22.
The card machine 20 includes a cylinder roll 24a for opening the raw cotton and a worker roll 24b, and a second feed roll for supplying the raw cotton to the cylinder roll 24a on the upstream side of the cylinder roll 24a. 26 is arranged.
The hopper feeder 22 is provided with an atmospheric pressure detector (not shown), and the atmospheric pressure in the hopper feeder 22 is constantly measured. The operation of the first feed roll 16 of the opener 10 is controlled by the atmospheric pressure detector, and the amount of raw cotton filled in the hopper feeder 22 is adjusted by the change in the atmospheric pressure in the hopper feeder 22. The That is, the atmospheric pressure in the hopper feeder is set to 2,000 to 2,500 mmAq, and the first feed roll 16 is activated when the atmospheric pressure in the hopper feeder becomes 2,000 mmAq or less by sending raw cotton to the card machine. The raw cotton is then filled. When the atmospheric pressure in the hopper feeder becomes 2500 mmAq or more, the first feed roll 16 stops and the feed of raw cotton is stopped. As a result, the amount of the raw cotton card machine 20 that is fed up to the second feed roll 26 is made constant in the flow direction. Thereby, the dispersion | variation in the fabric weight of the vertical direction (direction along the flow direction of the card machine 20) of the card web w obtained is suppressed as much as possible.
Further, as shown in FIG. 3, a nozzle 30 is provided at the inlet of the hopper feeder 22 that swings in the left-right direction (lateral direction of the card machine / direction perpendicular to the flow direction of the card machine). As a result, the amount of raw cotton pieces supplied to the hopper feeder 22 is made constant, and the raw cotton is uniformly filled in the horizontal direction in the hopper feeder 22. Thereby, the dispersion | variation in the fabric weight of the vertical direction (direction along the flow direction of the card machine 20) of the card web obtained is suppressed as much as possible. As described above, the obtained card web has a uniform basis weight in both the vertical and horizontal directions.

The amount of raw cotton input in the card machine is adjusted by the rotational speed of the second feed roll 26. The speed is fixed in the range of 2 to 5 m / min, and is adjusted according to the basis weight of the card web (nonwoven fabric) to be created.
A doffer roll 32, a condensation roll 34, and a conveyor 36 are disposed on the downstream side of the cylinder roll 24a. The doffer roll 32 receives the web on the cylinder roll 24a, which rotates at a high speed, at a low speed, thereby increasing the basis weight of the web. The condensation roll 34 rotates at a lower speed than the doffer roll 32, receives the web on the doffer roll 32, adjusts the shape of the web, and matches the web feed to the transfer speed of the conveyor 36. Further, the doffer roll 32 and the condensation roll 34 also perform an operation of changing the fiber arrangement from parallel to semi-random by repeating the delivery of the web. The produced card web is wound up by a winding drum (not shown).
Since the method for producing the card web may be the same as the conventional method, further detailed description is omitted.

The quartz glass fiber-containing nonwoven fabric according to the embodiment of the present invention is produced using the dry short fiber web, and the basis weight is preferably 5 to 70 g / m ² , similar to the card web. Variation is within ± 20%, preferably within ± 10%, the thickness is preferably 30 μm to 200 μm, and the variation in thickness is preferably within ± 20%, particularly preferably within ± 10%. The basis weight is more preferably ^{10g / m 2 ~40g / m 2} , especially 15g / ^{m 2} ~30g / ^m 2 preferred. Further, the thickness is preferably 50 μm to 150 μm, particularly preferably 50 μm to 100 μm.

Further, the relative dielectric constant at a high frequency of 10 GHz is 3.8 or less, the variation is within ± 10%, the dielectric loss (tan δ) is 3.5 × 10 ⁻³ or less, and the variation is ± 10%. Is preferably within.
As described above, if the basis weight is less than the above range, it is extremely difficult to obtain a uniform nonwoven fabric because the fiber density is too small, and the thickness is also thinner than 30 μm, which is preferable as a quartz glass nonwoven fabric for printed wiring boards. End up. Furthermore, it becomes difficult to obtain a strength of 10 N or more, which is necessary as a quartz glass nonwoven fabric for printed wiring boards. On the other hand, if the basis weight exceeds the above range, the thickness tends to increase, and exceeds 200 μm, which is a preferable thickness for a quartz glass fiber nonwoven fabric for printed wiring boards. In addition, the uniformity of the basis weight tends to deteriorate.
If the variation in basis weight and thickness of the nonwoven fabric exceeds the above values, it tends to be difficult to set the variation in relative permittivity and dielectric loss below the above values.

The nonwoven fabric preferably has a longitudinal tensile strength of 10 N or more. Here, the vertical direction is a direction in the card machine when the card web is used. In the case of the nonwoven fabric using the dry short fiber web produced by the airlaid system, the tensile strength in the longitudinal and transverse directions is almost the same. If the tensile strength is less than the above value, the nonwoven fabric may be stretched or broken when the nonwoven fabric is impregnated with the resin in the process of producing a prepreg for producing a printed wiring board.
The nonwoven fabric is suitably used for a printed wiring board that forms a high-frequency circuit having a frequency of 1 GHz or more.
This nonwoven fabric can be obtained by entanglement of the above-mentioned dry short fiber web by the hydroentanglement method (water punch method), or heat-fuse quartz glass fibers with heat-fusible fibers (thermal bond) Method). In addition, the present nonwoven fabric is obtained by entanglement of the above-mentioned dry short fiber web by a hydroentanglement method and further heating, thereby thermally fusing quartz glass fibers with heat-fusible fibers.
The hydroentanglement method is a method in which fibers constituting a dry short fiber web are entangled with a water stream using an apparatus called a water jet machine. It is possible to suppress the degree of entanglement between the fibers by adjusting the pressure of the water flow. In recent years, since the processing speed is very fast, it has been widely used in the production of nonwoven fabrics using general organic fibers, but this is the first time that it is applied to quartz glass fibers.
The thermal bond method is a method of forming a non-woven fabric by thermally fusing the dry short fiber web (including those treated by the hydroentanglement method). As a method for heat-sealing synthetic fibers having heat-fusibility, there are a dryer, a method using a heater, and a method using a hot press roll used in a conventional nonwoven fabric manufacturing apparatus. In the heat fusion method using a hot press roll, it is possible to produce a quartz glass nonwoven fabric having a more uniform thickness and a thinner thickness by adjusting the gap between the press rolls. The heating temperature in the thermal bonding method is appropriately set according to the melting characteristics of the synthetic fiber having heat fusion properties to be blended. For example, when using a polyolefin-based heat-fusible fiber, the temperature is set to about 130 to 140 ° C.

Production of long silica glass fibers 200 synthetic quartz glass rods having a diameter of 5 mm were set on the top of a vertical tubular electric furnace having holes in the top and bottom. After confirming that the furnace temperature is heated to 2000 ° C. or higher, slowly lower (feed) these rods through the furnace, and continuously draw out the molten end from the lower part of the vertical tubular electric furnace, 200 were simultaneously wound on the bobbin. Various lengths of silica glass long fibers were prepared by adjusting the feeding speed of the synthetic silica glass rod and the winding speed of the long silica glass fibers. Table 1 shows the average value, the maximum value, the minimum value, the feeding speed and the winding speed of the fiber diameters prepared in this example. The length of the formed long fiber was 10,000 m.
In addition, when winding up, it applied to the 1 mass% acetic acid aqueous solution of 3-methacryloxypropyl trimethoxysilane (trade name Shin-Etsu Chemical Co., Ltd. KBM-503) as a sizing agent through a roller.

上記結果から、上記各径の繊維についての繊維径のばらつきに付いて計算した。本明細書においては、この繊維径のばらつきは、正負、二つの数字が存在するが、正側のばらつきは最大値から平均値を引いた値を平均値で除した値、負側のばらつきは最小値と平均値の差を平均値で除した値を％で表したものを指す。以下、目付、厚さ、比誘電率、誘電損失、物理強度のばらつき等についても同様の定義とする。
即ち、繊維径の最大値をｄ_ｍａｘ、最小値をｄ_ｍｉｎ、平均値をｄ_ａｖｅとした場合、繊維径のばらつきは、以下の式で表される。

ばらつき（正）＝（ｄ_ｍａｘ−ｄ_ａｖe）／ｄ_ａｖｅ × １００
ばらつき（負）＝（ｄ_ｍｉｎ−ｄ_ａｖe）／ｄ_ａｖｅ × １００

従って、平均径３．０μｍの場合の繊維径のばらつきは±３．３％、平均径６．０μｍの場合の繊維径のばらつきは±１．７％、そして平均径９．０μｍの場合の繊維径のばらつきは±１．１％である。従って、全ての径の繊維が、本発明の範囲であるばらつき±１０％を満たしている。
なお、繊維径１μｍ未満の石英ガラス長繊維も作成したが、径の均一性を維持することが難しくなる上、繊維が極端に切れ易かった。繊維径が１μｍより細い超極細繊維は歩留まりが悪く製造に適さない。
一方、繊維径が２０μｍを超える太径繊維は、製造的にも容易でまた繊維径の均質性も良好であるが、不織布とした際の厚さが厚くなり、また目付も大きくなり易く、目付及び厚さをそれぞれ７０ｇ／ｍ^２以下、２００μｍ以下にするためには好ましくない。

From the above results, calculation was performed for variations in fiber diameters for the above-mentioned diameter fibers. In the present specification, there are two numbers of variations in the fiber diameter, positive and negative, but the variation on the positive side is the value obtained by subtracting the average value from the maximum value by the average value, and the variation on the negative side is The value obtained by dividing the difference between the minimum value and the average value by the average value is expressed in%. Hereinafter, the same definition is applied to the basis weight, thickness, relative dielectric constant, dielectric loss, physical strength variation, and the like.
That is, when the maximum value of the fiber diameter is d _max , the minimum value is d _min , and the average value is d _ave , the variation of the fiber diameter is expressed by the following formula.

Variation (positive) = (d _max −d _ave ) / d _ave × 100
Variation (negative) = (d _min −d _ave ) / d _ave × 100

Therefore, the fiber diameter variation when the average diameter is 3.0 μm is ± 3.3%, the fiber diameter variation when the average diameter is 6.0 μm is ± 1.7%, and the fiber when the average diameter is 9.0 μm. The variation in diameter is ± 1.1%. Therefore, the fibers of all diameters satisfy the variation ± 10% which is the range of the present invention.
Although long quartz glass fibers having a fiber diameter of less than 1 μm were prepared, it was difficult to maintain the uniformity of the diameter, and the fibers were extremely easy to cut. Ultrafine fibers with a fiber diameter of less than 1 μm are not suitable for production due to poor yield.
On the other hand, a thick fiber having a fiber diameter of more than 20 μm is easy to manufacture and has good fiber diameter homogeneity. However, when it is made into a non-woven fabric, the thickness becomes thick and the basis weight tends to be large. And thicknesses of 70 g / m ² or less and 200 μm or less, respectively.

[Adjustment of quartz glass fiber]
The obtained bundle of synthetic quartz glass fibers was cut using a cutting machine with a ceramic blade attached to lengths of 30 mm, 100 mm, and 300 mm in the same direction. Created.

[Adjustment of heat-fusible synthetic fiber]
In this example, a fiber bundle of NBF (E) manufactured by Daiwabo, which is a heat-fusible fiber having a core-sheath structure, and a heat-bonding structure having a single composition structure. Polypropylene PN manufactured by Daiwabo, an adhesive fiber, was used. The former Daiwabo NBF (E) has a relative dielectric constant ε 'of 2.3 MHz and a dielectric loss tan δ of 3.0 × 10 ⁻⁴ for a high frequency of 1 MHz, and the latter Daiwabo polypro PN has a high frequency of 1 MHz. The relative dielectric constant ε ′ is 2.4, and the dielectric loss tan δ is 3.0 × 10 ⁻⁴ .
In the case of Daiwabo NBF (E), fiber lengths of 38 mm to 64 mm are commercially available, and those closest to the length of the quartz glass fiber used therein were used.
In addition, since fiber diameters of 2.2 to 4.4 dT are commercially available, the one closest to the length of the quartz glass fiber used was used.

Example 1
[Create card web]
Of the group of quartz glass fibers having a fiber diameter of 6 μm, the mixing ratio of the fiber having a length of 100 mm and the Daiwabo core-sheath synthetic fiber NBF (E) having a fiber diameter of 2.2 dT and a length of 64 mm was changed to three types. As shown in the figure, the fiber is mixed using an opener and a hopper feeder, and further, the basis weight is changed to 10 g / m ² , 30 g / m ² , 60 g / m ² and a card machine (manufactured by Daiwa Kiko Co., Ltd.) Roller card 30-300DR) was opened to create three types of card webs.
The mixing ratio was 90% by mass for quartz glass fiber, 10% by mass for synthetic fiber, 70% by mass for quartz glass fiber, 30% by mass for synthetic fiber, 40% by mass for quartz glass fiber, and 60% by mass for synthetic fiber.

The fiber diameter, fiber length, basis weight, and synthetic fiber mixing ratio corresponding to each example are as follows.
Examples 1-1 to 1-3: Fiber diameter 6 μm, fiber length 100 mm, quartz glass fiber vs. synthetic fiber 9: 1, basis weight 10 g / m ² , 30 g / m ² , 60 g / m ² ,
Examples 1-4 to 1-6: Fiber diameter 6 μm, fiber length 100 mm, quartz glass fiber vs. synthetic fiber 7: 3, basis weight 10 g / m ² , 30 g / m ² , 60 g / m ² ,
Examples 1-7 to 1-9: Fiber diameter 6 μm, fiber length 100 mm, quartz glass fiber vs. synthetic fiber 4: 6, basis weight 10 g / m ² , 30 g / m ² , 60 g / m ²
The basis weight was set by measuring the weight of the fiber bundle to be put in advance and measuring the area of the card web obtained by opening it with a card machine. If the opening conditions of the card machine are constant, the area of the card web obtained is almost constant regardless of the amount of input, so after obtaining the relationship between the opening conditions and the area of the card web, The basis weight was set by feeding a fiber bundle of the corresponding weight.
Opening conditions are: raw material input speed 8 g / min (raw material input conveyor speed 3 m / min), cylinder roll speed 600 m / min, high speed worker roll speed 600 m / min, low speed worker roll speed 8 m / min, take-up drum speed 3 m / min. Although it was done in minutes, these condition settings were made by adjusting the speed of the drive unit so as to obtain a good texture while looking at the texture of the obtained card web, and the diameter, length, Fine adjustment is required according to temperature and humidity. Actually, the basic conditions were set as described above, and each speed was finely adjusted while visually observing the texture of the card web that was formed. In this way, a card web containing quartz glass fibers was produced.

[Creation of thermal bond nonwoven fabric by hot press]
The obtained card web was hot-pressed using a flat hot press. The hot press conditions are a pressure load of 2 kgf / cm ² and a temperature of 130 ° C. for 2 minutes. After hot pressing, it was allowed to stand at room temperature in a clean atmosphere and allowed to cool to produce a thermal bond nonwoven fabric containing quartz glass fibers.

[Evaluation]
Cut the obtained non-woven fabric into 40 cm × 25 cm, cut out 5 small samples of 5 cm × 5 cm from the four corners and the center of the cut sheet, and measure the weight of each sample to determine the basis weight and thickness. Was measured. In addition, an average value, a maximum value, and a minimum value were obtained from these numerical values, respectively, and variations in basis weight and thickness were obtained.
Table 2 shows the basis weight and thickness of the nonwoven fabric in the examples, and variations thereof, together with other examples. The basis weight was obtained by measuring the weight of each sheet. The thickness was measured at 53.9 kPa (550 gf / cm ² ) according to JIS P8118 “Paper and paperboard—Test method for thickness and density”.
The electrical characteristics of the nonwoven fabrics in the examples using the 5 small samples used for the measurement of the basis weight and the thickness were measured at a specific dielectric constant and dielectric loss (tan δ) at a frequency of 12 GHz according to JIS R1641. Measured every time. In addition, an average value, a maximum value, and a minimum value were obtained from these numerical values, and variations in relative permittivity and dielectric loss were obtained. The evaluation results are shown in Table 3 (dielectric constant) and Table 4 (dielectric loss) together with other examples.
Moreover, from the obtained thermal bond nonwoven fabric, 5 samples of width 5cm and length 20cm were cut out from arbitrary places, and the tensile strength was measured for every sheet. Moreover, the average value, the maximum value, and the minimum value were obtained from these five numerical values, and the variation in tensile strength was obtained. The tensile strength was evaluated in accordance with JIS L1913 “General Short Fiber Nonwoven Fabric Testing Method” at a test piece width of 5 cm, a grip interval of 20 cm, and a tensile speed of 100 mm / min.
Table 5 shows the physical strength (tensile strength) and variations of the nonwoven fabric in each example.

Example 2
Example of Hydroentanglement Method + Thermal Bond A quartz glass dry spunlace nonwoven fabric was prepared from the card web containing nine types of quartz glass fibers prepared in Example 1 by the hydroentanglement method.
In the hydroentanglement method, a card web is supplied onto a conveyor belt made of a 50 mesh plastic net, and the conveyor belt is driven at a speed of about 7 m / min. Manufacture Co., Ltd. The water pressure was 160 kg / cm ^{2 at the} maximum, and the entanglement process by the high pressure liquid columnar flow was performed.
In the water jet processing apparatus, nozzle fine holes arranged in a horizontal row with a hole diameter of 0.08 to 0.1 mm and an interval of 0.6 to 1.0 mm are arranged horizontally 3 with respect to the traveling direction of the conveyor belt. It installed in the row | line | column, the distance of the nozzle pore of a water-jet processing apparatus and the surface of a card web was installed in 2 cm, and the water flow was injected with the water pressure of 1.0-5.0 Mpa from the three rows of water flow injectors.
The sheet entangled by the above method was dried at 120 ° C. for 1 minute using a through dryer type dryer to form a dry spunlace nonwoven fabric containing quartz glass fibers.

[Hot press]
The obtained spunlace nonwoven fabric containing quartz glass fibers was also hot-pressed under the same conditions as in Example 1 to obtain a thermal bond / spunlace nonwoven fabric.
[Evaluation]
In the same manner as in Example 1, the basis weight and thickness, variation thereof, relative dielectric constant and dielectric loss (tan δ), variation thereof, physical strength (tensile strength), and variation thereof were determined. The results are shown in Tables 2-5.

Example 3
Using a silica glass fiber having a fiber diameter of 3 μm and a length of 30 mm and a heat-fusible fiber Daiwabo Polypro PN having a fiber-based single composition structure having a fiber diameter of 2.2 dT and a length of 38 mm. A quartz glass fiber versus synthetic fiber was mixed at a weight of 7: 3 and a basis weight of 30 g / m ² in the same manner as in Example 1, and opened with a card machine to prepare a card web.
Opening conditions are raw material input speed 8g / min (raw material input conveyor speed 3m / min), cylinder roll speed 400m / min, high speed worker roll speed 400m / min, low speed worker roll speed 5.3m / min, winding drum speed Performed at 2.0 m / min.
The card web was hot-pressed in the same manner as in Example 1 to produce a thermal bond nonwoven fabric containing quartz glass fibers.
The same evaluation as in Examples 1 and 2 was performed for the nonwoven fabric of Example 3. The results are shown in Tables 2 to 5.

Example 4
Using a silica glass fiber having a fiber diameter of 9 μm and a length of 300 mm and a heat-fusible fiber Daiwabo polypro PN having a fiber diameter of 4.4 dT and a length of 68 mm, and a polyolefin-based single composition structure Quartz glass fibers versus synthetic fibers were mixed at a weight of 7: 3 and a basis weight of 30 g / m ² in the same manner as in Example 1 and opened with a card machine to prepare a card web.
Opening conditions are raw material input speed 8g / min (raw material input conveyor speed 3m / min), cylinder roll speed 700m / min, high speed worker roll speed 700m / min, low speed worker roll speed 8.2m / min, winding drum speed It was performed at 3.5 m / min.
The card web nonwoven fabric was hot-pressed in the same manner as in Example 1 to produce a thermal bond nonwoven fabric containing quartz glass fibers.
For the nonwoven fabric of Example 4, the same evaluation as in Examples 1 and 2 was performed. The results are shown in Tables 2 to 5.

Comparative Example 1
A quartz glass rod having a diameter of 0.3 mm is introduced into the flame of an oxyhydrogen burner by a raw material supply roller rotating at a linear velocity of 1.8 m / min, and is sucked and exhausted from above by an air suction. At this time, the gas pressure of the oxyhydrogen burner oxygen 8 kg / cm ^2, and hydrogen 2 kg / cm ^2. Quartz glass short fibers blown to a fiber diameter of about 6 μm were collected with a wire mesh, and the fiber length and fiber diameter variation were measured. As a result, the average length of the quartz glass fiber is 1.2 m, the minimum value is 0.5 m, the maximum value is 2.0 m, the average value of the fiber diameter is 6.0 μm, the minimum value is 3 μm, and the maximum value. Was 8.5 μm.
This short fiber was cut into a length of about 100 mm in the same manner as in the example, and Daiwabo core-sheath synthetic fiber NBF (E) having a fiber diameter of 2.2 dT and a length of 64 mm was mixed with quartz glass fiber 90 in a mixing ratio. After setting the mass% and NBF to 10 mass% to obtain a card web opened by a card machine, the basis weight was set to 30 g / m ² and a quartz glass nonwoven fabric was formed by a hydroentanglement method.
At this time, the card characteristics were not so good, and about 40% of the input weight could not be opened cleanly, which was fooled and excluded. Since the yield was poor, the characteristics were not measured.

Experimental example 1
A silica glass fiber having a fiber diameter of 6 μm and a length of 100 mm and a Daiwabo core-sheath synthetic fiber NBF (E) having a fiber diameter of 2.2 dT and a length of 64 mm are mixed at a mixing ratio of 70% by mass of silica glass fiber and 30% by mass of NBF. is set to be commingled basis weight by spreading the under the same conditions as in example 1 was set to 3 g / m ² and 100 g / m ² respectively, produced a card web.
The obtained card web nonwoven fabric containing quartz glass fibers was hot-pressed under the same conditions as in the examples to produce a thermal bond nonwoven fabric containing quartz glass fibers.
Evaluation similar to other examples is performed, and the results are shown in Tables 2 to 5.

Experimental example 2
A silica glass fiber having a fiber diameter of 6 μm and a length of 100 mm and a Daiwabo core-sheath synthetic fiber NBF (E) having a fiber diameter of 2.2 dT and a length of 64 mm are mixed at a mixing ratio of 3% by mass of quartz glass fiber and 97% by mass of NBF. The card web was created by opening the fiber under the same conditions as in Example 1 with the basis weight set to 30 g / m ² .
The obtained card web nonwoven fabric containing quartz glass fibers was hot-pressed under the same conditions as in the examples to produce a thermal bond nonwoven fabric containing quartz glass fibers.
Evaluation similar to other examples is performed, and the results are shown in Tables 2 to 5.

Comparative Example 2
A quartz glass fiber having a fiber diameter of 6 μm and a length of 100 mm is set to a basis weight of 30 g / m ² , and is not mixed with a heat-sealing fiber. The fiber was opened by the machine.
Opening conditions are: raw material input speed 8 g / min (raw material input conveyor speed 3 m / min), cylinder roll speed 600 m / min, high speed worker roll speed 600 m / min, low speed worker roll speed 8 m / min, take-up drum speed 3 m / min. Went in minutes.
However, since it does not contain heat-fusible fibers, it was not a hot press and was a non-woven fabric.
Evaluation similar to other examples is performed, and the results are shown in Tables 2 to 5.

Table 2 continued

Table 2 continued

エアレイド方式により乾式短繊維ウェブを作製し実施例１と同様の実験をおこなったところ、引張強度については、実施例１のものより多少劣ったが、電気特性についてはほぼ同等のものが得られた。

When a dry short fiber web was produced by the airlaid system and the same experiment as in Example 1 was performed, the tensile strength was somewhat inferior to that of Example 1, but the electrical characteristics were almost the same. .

It is a schematic diagram of the opener used when manufacturing the quartz glass fiber containing dry short fiber web of this invention. It is a schematic diagram of the card machine used when manufacturing the quartz glass fiber containing dry short fiber web of this invention. It is the schematic diagram which looked at the hopper feeder used with the card machine of FIG. 2 from the front.

Explanation of symbols

m Raw cotton w Card web 10 Opener 12 Beater roll 14 Conveyor 16 First feed roll 18 Blower 20 Card machine 22 Hopper feeder 24a Cylinder roll 24b Worker roll 26 Second feed roll 30 Nozzle 32 Doffer roll 34 Condensation roll 36 Conveyor

Claims (11)

A quartz glass fiber-containing dry short fiber web for producing a quartz glass fiber-containing nonwoven fabric used for a printed wiring board for forming a high-frequency circuit having a frequency of 1 GHz or more, obtained by cutting quartz glass long fibers. It is composed of a quartz glass fiber having a diameter of 1 μm or more and 20 μm or less, and a heat-fusible fiber, and has a basis weight of 5 g / m ² or more and 70 g / m ² or less, and the heat-fusible fiber has a high frequency of 1 MHz. The relative dielectric constant ε ′ is 2.5 or less, the dielectric loss tan δ is 3 × 10 ⁻³ or less, the fiber diameter is 0.5 dT or more and 10 dT or less, and the mixture ratio in the whole fiber is 5 mass% or more and 90 mass. % Of the dry short fiber web containing quartz glass fibers.   The dry short fiber web containing quartz glass fibers according to claim 1, wherein the heat-fusible fibers are polyolefin synthetic fibers.   The diameter of the quartz glass fiber is 1 μm or more and 20 μm or less, and the variation in fiber diameter is within ± 10%. The length is 10 mm or more and 500 mm or less, and the length is set to a predetermined length. The dry short fiber web containing quartz glass fibers according to claim 1 or 2, wherein the dry short fiber webs contain quartz glass fibers. Obtained by the quartz glass fiber-containing dry staple fiber web as claimed in any one of claims 1 to 3 be entangled by hydroentangling, a basis weight of 5 g / m ² or more state, and are 70 g / m ² or less, the frequency A quartz glass fiber-containing non-woven fabric used for a printed wiring board that forms a high-frequency circuit of 1 GHz or higher . The quartz glass fiber-containing dry short fiber web according to any one of claims 1 to 3 is heated to heat-fuse the quartz glass fiber with a heat-fusible fiber, and the basis weight is 5 g / m. ^A quartz glass fiber-containing nonwoven fabric that is ² or more and 70 g / m ² or less. A quartz glass fiber-containing dry short fiber web according to any one of claims 1 to 3 is entangled by a hydroentanglement method, and further heated to heat-fuse the quartz glass fiber with a heat-fusible fiber. A quartz glass fiber-containing nonwoven fabric having a basis weight of 5 g / m ² or more and 70 g / m ² or less.   The quartz glass fiber-containing nonwoven fabric according to any one of claims 4 to 6, which has a thickness of 30 µm to 200 µm.   The quartz glass fiber-containing nonwoven fabric according to any one of claims 4 to 7, wherein the basis weight variation is within ± 20%.   The quartz glass fiber-containing nonwoven fabric according to any one of claims 4 to 8, wherein the variation in thickness is within ± 20%. The quartz glass fiber-containing nonwoven fabric according to any one of claims 4 to 9, wherein the relative dielectric constant ε 'for a high frequency of 10 GHz is 3.8 or less and the dielectric loss tan δ is 3.5 × 10 ^-3 .   The quartz glass fiber-containing nonwoven fabric according to any one of claims 4 to 10, wherein the tensile strength in the longitudinal direction is 10 N or more according to JIS L-1913 "General Short Fiber Nonwoven Fabric Test Method".

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