JP2000334871A - Laminate substrate, prepreg, and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a laminate base material having excellent properties as a laminate base material and capable of being subjected to heat and pressure treatment at a sufficiently high temperature. A base material for a laminated board having a multilayer structure having at least three layers, wherein both outer and inner layers have the following constitution. (1) A nonwoven fabric containing a synthetic organic fiber whose inner layer has a softening temperature of 320 ° C. or less and a moisture absorption of 1.5% or less. (2) Both outer layers contain 70% or more of synthetic organic fibers having no melting point and a decomposition temperature of 400 ° C. or more, and a softening temperature of 3 or more.
A nonwoven fabric containing less than 20 ° C. of synthetic organic fibers than the inner layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a laminate used for a printed wiring board.

[0002]

2. Description of the Related Art In recent years, electronic devices have become smaller and more sophisticated, and accordingly high-density wiring of printed wiring boards has progressed. The mounting method has become mainstream. In this method, the connection reliability between a component such as a chip mounted on a surface and a printed wiring board becomes a serious problem. That is, it is necessary to make the thermal expansion coefficients of the two as close as possible. The thermal expansion coefficient of recent thin surface mount type chips is 5 × 10 ^-6 / ° C
On the other hand, the substrate in which the glass nonwoven fabric is impregnated with epoxy has a thermal expansion coefficient that is about three times that of the substrate.

In addition, since the delay time due to signal propagation in a printed wiring board becomes very important, a base material for a laminate having a low dielectric constant is required. Generally, the dielectric constant of conventional FR-4 is 4.
The relatively high permittivity, which is about 7 to 5.1, slows down the propagation speed of the electric pulse of the adjacent signal circuit, and causes an excessive signal delay time. FR-4 is a copper-clad laminate for printed wiring boards made by impregnating a glass cloth substrate with an epoxy resin and laminating it (JIS standard NEMA number).

[0004] In view of the above demands, as a laminate as a basic material of a printed wiring board, a laminate in which a nonwoven fabric made of synthetic organic fiber is impregnated with an epoxy resin or the like has been studied. For example, a laminate using a nonwoven fabric made of a para-aramid fiber having a negative coefficient of thermal expansion and a low dielectric constant has been studied.

Other polyarylate fibers, fluorine fibers,
There are many fibers such as PPS fibers which are considered to be excellent for use in laminates from the viewpoint of moisture absorption, dielectric constant, and the like. For example, JP-A-10-37054 is composed of wholly aromatic polyamide, polyparaphenylene benzobisoxazole (PBO), wholly aromatic polyester, polyphenylene oxide (PPO), polyphenylene sulfide (PPS), fluororesin, etc. A substrate for a laminate is disclosed.

As described above, by blending various kinds of organic fibers, laminates having excellent performances, such as thermal expansion coefficient, moisture absorption coefficient, and dielectric constant, which are not provided by conventional substrates are being manufactured. . On the other hand, low moisture absorption and low dielectric constant are useful properties of the base material for a laminate, but most of the fibers having such properties are softened by heat at present. When a large amount of such fibers are blended, the following problems occur.

In general, the base material for a laminated board mainly composed of synthetic organic fibers needs to be adjusted in density in order to obtain an appropriate varnish resin impregnation amount, and is subjected to heat and pressure treatment using a hot roll or the like. In addition, these substrates are likely to be warped by heat such as solder reflow, and in order to reduce the warp, it is desirable to treat at least a temperature higher than the solder reflow equivalent temperature from the viewpoint of warping. However, when the content of the fiber softened by heat is large, the fiber is fused to a heat and pressure treatment tool such as a heat calender, causing the tool to be contaminated, resulting in a significant decrease in production efficiency or in some cases impossible to manufacture. It became. Alternatively, a treatment at a low temperature was inevitable in order to avoid heat and pressure treatment tool stains, and only a laminate base material having an excessively low density was obtained, or only a laminate having a large warp was obtained.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a laminate base material and a prepreg from which a laminate having low moisture absorption can be obtained. Another object of the present invention is to provide a laminate base material that can be heated and pressed at a sufficiently high temperature without causing contamination of tools such as a heat roll, and a method for producing the same. It is another object of the present invention to provide a laminate substrate having excellent properties such as low dielectric constant and warpage.

[0009]

Means for Solving the Problems The present inventors have devised a laminate base material having a multilayer structure of three or more layers. This base material can be provided with layers having different physical properties in both the outer layer and the inner layer, and is characterized in that a base material for a laminate having the characteristics of each layer can be obtained. In other words, the inner layer has excellent properties as a base material for a laminate, but contains a large amount of fibers that are easily softened by heat. It is possible to be the subject. Therefore, it is possible to obtain a laminate base material which has excellent characteristics and does not cause tool contamination even when subjected to high-temperature heating and pressurizing treatment. The configuration of the present invention is as follows.

[0010] The first invention of the present invention relates to a laminate base material having a multilayer structure having at least three layers, wherein both outer and inner layers have the following constitution. (1) A nonwoven fabric containing a synthetic organic fiber whose inner layer has a softening temperature of 320 ° C. or less and a moisture absorption of 1.5% or less. (2) Both outer layers contain 70% or more of synthetic organic fibers having no melting point and a decomposition temperature of 400 ° C. or more, and a softening temperature of 3 or more.
A nonwoven fabric containing less than 20 ° C. of synthetic organic fibers than the inner layer. According to a second aspect of the present invention, in the first aspect, the softening temperature of the inner layer is 320 ° C. or less and the moisture absorption is 1.
The synthetic organic fiber of 5% or less relates to a substrate for a laminate, which is at least one kind of fiber selected from polyarylate fiber, polyphenylene sulfide fiber, and fluororesin fiber.

The third invention of the present invention is directed to the first or the second invention.
In the invention, the synthetic organic fiber having a softening temperature of the inner layer of 320 ° C. or less and a moisture absorption of 1.5% or less is contained in the inner layer by 3%.
The present invention relates to a laminate base material containing 0% or more. According to a fourth aspect of the present invention, in any one of the first to third aspects, the outer layer does not have a melting point and the decomposition temperature is 400 ° C.
The synthetic organic fiber described above is at least one fiber selected from p-phenylene terephthalamide fiber, p-phenylene phenyl ether terephthalamide fiber, and poly-P-phenylene benzobisoxazole (PBO) fiber. , A laminate substrate.

A fifth invention of the present invention is a method for producing a substrate for a laminated board having a multilayer structure having at least three layers, wherein nonwoven fabrics having the following constitutions are separately formed by wet papermaking and laminated. The present invention relates to a method for producing a laminate base material which is bonded while applying heat and pressure by a hot roll having a surface temperature of 280 ° C. to 450 ° C. (1) The nonwoven fabric for the inner layer contains a synthetic organic fiber having a softening temperature of 320 ° C. or less and a moisture absorption of 1.5% or less. (2) The nonwoven fabric for both outer layers has no melting point and a decomposition temperature of 40
A nonwoven fabric containing 70% or more of synthetic organic fibers of 0 ° C. or more and having a softening temperature of 320 ° C. or less and a moisture absorption of 1.5% or less in the content of synthetic organic fibers less than that of the inner layer. A sixth invention of the present invention relates to a prepreg using the base material for a laminate described in any one of the first to fourth inventions.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a laminate refers to a prepreg formed by heating and pressing a plurality of prepregs, or a prepreg covered with a metal foil. It also includes a so-called multilayer board having an inner layer and a surface layer printed wiring. In the present invention, the prepreg refers to a single sheet obtained by impregnating a thermosetting resin into a base material such as a nonwoven fabric and drying the sheet, which will be used for the laminate in the future. In the present invention, the laminate base material is the base material of the prepreg, and refers to a nonwoven fabric or the like before the prepreg is impregnated with the resin.

The substrate for a laminate of the present invention is a substrate for a laminate having a multilayer structure having at least three layers. Since the laminate base material of the present invention has at least three layers, it is possible to arrange layers having different physical properties in both the outer layer and the inner layer, and to obtain a laminate base material having the characteristics of each layer. be able to. The properties of the outer and inner layers can be arbitrarily selected according to the use of the electronic device in which the outer and inner layers are used.

In the present invention, when the nonwoven fabric for the inner layer described in claim 1 is represented by layer (A) and the nonwoven fabric for the outer layer is represented by layer (B), the outermost layer of the laminate substrate of the present invention has a layer ( B) is sufficient, and it does not prevent that there are more layers (B). Similarly, the layer (A) may be at least one layer other than the two outer layers, and does not prevent a plurality of layers (A) from being present. For example, a configuration such as B / A / A / B or B / B / A / B can be adopted. It is not necessary that the two outer layers have exactly the same structure, and it is sufficient that the outer layers have the same configuration as that of the first embodiment. Similarly, when there are a plurality of layers (A), it is not necessary that all the layers (A) have exactly the same configuration, and the layers (A) may be in the range described in claim 1.

The nonwoven fabric constituting both outer layers according to the present invention comprises synthetic organic fibers having no melting point and a decomposition temperature of 400 ° C. or higher.
% Of a synthetic organic fiber having a softening temperature of 320 ° C. or less, which is lower than that of the inner layer. The softening temperature in the present invention is as follows. That is, the fiber
When the material is heated under tensile stress using TMA or the like, the material softens and flows when the melting point approaches, and the material rapidly expands and breaks. The temperature at which the flow starts is called the softening temperature, DS
The temperature is lower than the melting point measured by C etc. ("Basics of thermal analysis", Kyoritsu Shuppan, 3rd edition, published in 1996). This temperature is DM
It can also be determined by tan δ determined in the dynamic shearing property measurement by A. As a form of the synthetic organic fiber used for the nonwoven fabric for the outer layer, a fiber diameter of 5 to 15 μm and a fiber length of 1 to 6 mm are preferable. The smaller the fiber diameter of the synthetic organic fiber is, the more entangled portions of the nonwoven fabric are increased, and this is effective from the viewpoint of the strength of the mixed nonwoven fabric. I do. In addition, the longer the fiber length, the greater the number of entangled portions of the fibers, which is effective from the viewpoint of the strength of the mixed nonwoven fabric.However, the shorter the fiber length, the better the dispersibility of the slurry at the time of papermaking. select. A binder is added to the non-woven fabric for the outer layer as necessary.
As the binder, a water-soluble or emulsion resin or a fibrous material having thermal adhesiveness can be added. The fibrous material here may be chopped strand-like or fibril-like fiber. The binder is preferably a water-soluble or emulsion epoxy resin, acrylic resin, phenol resin, or a fibrous material of meta-aramid or polyarylate from the viewpoint of heat resistance, but is not limited thereto. The nonwoven fabric for the outer layer does not have a melting point from the viewpoint of reducing heat and pressure treatment tool stains, and preferably contains 70% or more of synthetic organic fibers having a decomposition temperature of 400 ° C or more, and is composed of only these fibers and a thermosetting binder. It is more preferable to use a nonwoven fabric to be used. Examples of the synthetic organic fiber having a melting point of 400 ° C. or more and having no melting point used for the outer layer include p-phenylene terephthalamide fiber, p-phenylene phenyl ether terephthalamide fiber, and poly-P-phenylene benzobisoxazole (PBO) fiber Is preferred.

The outer layers only need to contain 70% or more of synthetic organic fibers having a decomposition temperature of 400 ° C. or more, and other fibers can be used in combination as long as the object of the present invention can be achieved. For example, even a fiber having a softening temperature of 320 ° C. or less can be blended in the outer layer, and a fiber having excellent properties such as moisture absorption and dielectric constant can be blended to improve the properties. However, fibers having a softening temperature of 320 ° C or lower should be blended in a larger amount in the inner layer from the viewpoint of heat and pressure treatment tool contamination, and the blending amount of the fiber having a softening temperature of the outer layer of 320 ° C or lower should be smaller than that in the inner layer. This is preferable from the viewpoint of reducing the contamination of the heating and pressurizing tool and improving the characteristics. The fibers having a softening temperature of 320 ° C. or lower used for both the outer layer and the inner layer may be the same type of fiber or different fibers. For example, fibers having a softening temperature of 320 ° C. or lower and different moisture absorption rates may be used for the outer layer and the inner layer.

The inner layer of the present invention comprises a nonwoven fabric containing a synthetic organic fiber having a softening temperature of 320 ° C. or less and a moisture absorption of 1.5% or less. The inner layer preferably contains fibers having a moisture absorption of 1.5% or less from the viewpoint of reducing the moisture absorption of the laminate substrate. At present, most of such fibers have a melting point and a softening temperature of 320 ° C. or less, and it is a feature of the present invention that a large amount of such easily softening fibers can be blended in the inner layer. Currently, most fibers with low moisture absorption have a melting point and a softening temperature of 320 ° C or less. , A sufficient amount could not be blended. According to the present invention, by blending such fibers in a large amount in the inner layer, a laminate base material having a low moisture absorption rate can be obtained without causing heat and pressure treatment stains. Further, for example, fibers having useful properties such as a low relative dielectric constant such as a low dielectric constant, but which could not be blended in a large amount for the above-mentioned reason due to a property of softening having a melting point, a large amount of the whole substrate. It is possible to mix
A substrate for a laminated board having excellent properties without heat and pressure treatment tool stains can be obtained. In order to take advantage of these features, it is preferable that the content of the fibers having a softening temperature of 320 ° C. or lower is lower in both outer layers than in the inner layer. In the present invention, the moisture absorption is 24 ° C at 20 ° C and 65%.
Refers to the rate of moisture absorption when the humidity is adjusted over time, and the relative dielectric constant is 1 MHz.
Means the relative permittivity of The form of the synthetic organic fiber used for the nonwoven fabric for the inner layer is the same as that of the fiber used for the outer layer, and a binder can be added as necessary similarly to the outer layer. Preferred materials for the binder are the same as for the outer layer.

The softening temperature used for the inner layer of the present invention is 320 ° C.
In the following, as a synthetic organic fiber having a moisture absorption of 1.5% or less,
From the viewpoint of hygroscopicity, polyarylate fibers, polyphenylene sulfide fibers, and fluororesin fibers are preferred. Further, since the fluororesin fiber has a low specific permittivity as well as a moisture absorption rate, it is preferable from the viewpoint of the permittivity. The content of the low moisture-absorbing fiber is particularly preferably 30% or more in the inner layer in order to reduce the moisture absorption of the entire base material for a laminate.

In the present invention, the method for producing the base material for a laminated board is not particularly limited, but one of the preferred methods is to separately fabricate the nonwoven fabric by a wet papermaking method, heat-dry it, and then heat and dry it. Superposition, surface temperature 280 ℃ ~ 450
This is a method in which heat and pressure are applied by a pair of hot rolls at a temperature of ℃ ° C. to soften a binder component contained in the sheet and then to bond the sheet. The surface temperature of the heat roll is preferably higher, and is preferably at least 280 ° C. or more, in order to prevent warpage from occurring in a solder reflow step or the like. If the surface temperature of the heat roll is too high, tool stains are liable to occur, and fibers and binders are deteriorated to lower the strength.
50 ° C. or lower is preferred. In particular, when processing at a high temperature is necessary, the material does not have a melting point used for both outer layers and has a decomposition temperature of 400.
It is preferable to further increase the content of the synthetic organic fiber at a temperature of not less than ° C. The heating and pressurizing treatment by the hot roll calender is not limited to one time, but may be performed twice or several times.

The density of the laminate base material in the present invention is not particularly limited, and can be appropriately selected depending on the type and use of the resin impregnated during the production of the prepreg.
It is suitably a 0.5~0.8g / m ^3.

A prepreg can be obtained by impregnating the thermosetting resin varnish into the substrate for a laminate of the present invention and drying by heating.
The resin to be impregnated is generally an epoxy resin, but is not particularly limited, and a resin usually used for a laminated board such as a phenol resin and a polyimide resin is appropriately selected and used.

A laminate using the prepreg of the present invention is manufactured as follows. Placing copper foil on both sides of the prepreg obtained according to the present invention, curing the semi-cured resin contained in the prepreg by heat and pressure molding and attaching the copper foil, creating a circuit pattern by a normal method, A circuit is formed by etching. It is also possible to obtain a so-called multilayer board in which a plurality of prepregs are stacked and pressed. The pressing method is not particularly limited, and can be appropriately determined depending on the characteristics of the resin to be impregnated.

[0024]

The present invention will be described in more detail with reference to the following examples. The present invention is not limited to the following embodiments.

Hereinafter, raw materials used in Examples and Comparative Examples will be described.・ Para-type aramid fiber (Technola, moisture absorption: 2.0%, no melting point, decomposition temperature: 500 ° C or more, fiber diameter: 12 μm, fiber length: 3 mm, manufactured by Teijin) ・ Para-type aramid fiber (Kevlar 49, poly (P- (Phenylene terephthalamide), moisture absorption: 2.0%, no melting point, decomposition temperature: 630 to 650 ° C, manufactured by DuPont) ・ Poly-P-phenylene benzobisoxazole fiber (Zylon, no melting point, decomposition temperature: 560 ° C, manufactured by Toyobo) ) ・ Polyarylate fiber (Vectran HS, Vectran NT,
Moisture absorption rate: 0.07%, melting point: 308 ° C, softening temperature 257 ° C, fiber diameter 16μm, fiber length 6mm, all made by Kuraray Co., Ltd. ・ Polyphenylene sulfide fiber (moisture absorption rate: 0.05%,
Melting point: 280 ° C, prepared by melt spinning, fiber diameter 12μm, fiber length 5mm)-Fluororesin fiber (moisture absorption: 1% or less, melting point: 327 ° C, PT
Fiber diameter 12μ made by extruding FE resin with an injection molding machine
m, fiber with a fiber length of 3 mm)-Thermosetting resin binder (applied by spraying an aqueous epoxy resin (glass transition point 110 ° C) on a wet sheet, heating and drying)

<Examples 1 to 12><Manufacture of base material (manufacture of wet-type nonwoven fabric)> Table 1 shows two nonwoven fabrics arranged in the outer layer and one nonwoven fabric arranged in the inner layer. Sheets were prepared by wet papermaking with the indicated rice tsubo and composition, and dried to produce a sheet.

<Manufacture of base material (lamination with hot roll)> The obtained nonwoven fabrics are superposed so that the inner layer is sandwiched between two outer nonwoven fabrics, and heated at the hot roll temperature shown in Table 1. A pressure treatment was performed to obtain a laminate substrate of 72 g / m ^{2 in} rice tsubo. All of the obtained base materials for laminates were heat-pressable without heat roll contamination, and had low moisture absorption.

<Comparative Examples 1 to 7> Same as in Example 1 except that the paper was made with the composition shown in Table 2 and heated and pressed with a hot roll at the temperature shown in Table 2, and the rice tsubo was 72 g / m ^2. Was obtained. Note that Comparative Examples 1, 3, and 7 are all substrates having a single-layer structure, and the heating and pressing conditions are the same as in Example 1. Comparative Example 1 is the same as Example 1 in the composition of the entire substrate (that is, all the raw materials of the outer and inner layers of Example 1 were uniformly mixed to produce a single-layer nonwoven fabric), and Comparative Example 3 was implemented. Example 1
Is the same as the composition of the outer layer. The compounding ratio of the entire base material is equivalent to that of Example 1, and of Comparative Example 1 having a single-layer structure and the outer layer,
70 non-melting fiber (para-aramid fiber)
%, The roll stain was large. Comparative Example 6 in which the heating and pressing treatment roll temperature was 450 ° C. or higher
In this case, paper breakage occurred at the roll portion, and production was impossible.

Using the laminate base materials obtained in Examples 1 to 12 and Comparative Examples 1 to 7, laminates were prepared by the following method, and the following evaluations were made. The results are shown in Tables 1 and 2. <Measurement of moisture absorption> Brominated bisphenol is used as a base material for laminates
A type epoxy resin varnish impregnated and dried, resin adhesion amount 50%
Was prepared, 5 ply of the prepreg was stacked, and a copper foil of 18 μm was placed on both sides of the prepreg, and a copper-clad laminate having a thickness of 0.5 mm was obtained by heat-press lamination molding. The obtained laminate was completely etched to remove the copper foil, allowed to stand at 60 ° C. and 95% for 6 days, allowed to absorb moisture, then subjected to absolute drying treatment at 105 ° C. for 24 hours, and the weight difference was calculated. . The difference in weight was divided by the weight of the laminate at the time of the absolute drying treatment to obtain a moisture absorption rate, which was evaluated according to the following five grades. A 1.0% or more and less than 1.5% B 1.5% or more and less than 2.0% C 2.0% or more and less than 2.5% D 2.5% or more and less than 3.0% E 3.0% or more <Measurement of warpage> A laminate manufactured in the same manner as the laminate used for the measurement of the moisture absorption was cut into 400 mm x 300 mm, and the whole was etched to remove the copper foil. After heating for a period of time, the lifting amounts at the four corners were measured and averaged to be the warpage amount. The warpage was measured for the following examples, and the values were as follows. Example 4: 1.2 mm Example 12: 1.0 mm Comparative Example 5: 6.0 mm <Dielectric constant of laminate> A laminate manufactured by the same method as the laminate used for the measurement of moisture absorption was subjected to full etching. The conductive foil was removed, and subjected to absolute drying at 105 ° C. for 24 hours. After that, the humidity was adjusted in an atmosphere of 20 ° C and 65%, and RF Impedance of Hewlett-Packard Company was used.
The relative permittivity at 1 MHz was measured using a / Material Analyzer 4291A. The dielectric constant of the laminate was measured for the following examples, and the values were as follows. Example 11: 2.7 Comparative Example 7: 3.9

[0030]

[Table 1]

[0031]

[Table 2]

In each of the examples, a laminate having a low moisture absorption was obtained, and the heat roll was less contaminated. On the other hand, in the comparative example, the moisture absorption rate is large except for the one in which the roll contamination occurs. In addition, from the comparison between Example 11 and Comparative Example 7, the base material using a large amount of fluorine fiber for the inner layer has good heat roll dirt and good laminate moisture absorption, and also has a particularly low dielectric constant. Is obtained. Also, from the comparison between Example 12 and Comparative Example 5, the temperature of the heating / pressurizing heat roll was 28%.
It can be seen that the laminate using the laminate substrate treated at a temperature lower than 0 ° C. has good heat roll contamination and laminate moisture absorption, but has a large warpage.

[0033]

As described above, according to the present invention, it was possible to obtain a laminate substrate and a prepreg from which a laminate having low moisture absorption can be obtained. In addition, it was possible to obtain a base material for a laminate, which can be subjected to a heat and pressure treatment at a sufficiently high temperature, and a method for producing the same. As a result, the problem of dirt on the heat roll was solved. Further, according to the present invention, it was possible to obtain a laminate substrate having excellent properties such as low dielectric constant and warpage.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) D21H 13/26 D21H 13/26 (72) Inventor Takeichi Adachi 3465-1 Nakatsugawa, Nakatsugawa-shi, Gifu Prefecture Oji Paper Nakatsu Mill Co., Ltd. (72) Inventor Mamoru Murata 3465-1 Nakatsugawa, Nakatsugawa City, Gifu Prefecture Oji Paper Co., Ltd. Nakatsu Mill F-term (reference) 4F072 AA02 AB05 AB06 AB17 AB31 AB33 AG03 AH49 AJ02 AJ36 AJ37 AK05 AL09 AL13 4F100 AK01A AK01A AK01A AK47C AK47K AK54B AK54C AK54K AK57A BA03 BA08 BA10B BA10C DG01A DG01B DG01C DG15A DG15B DG15C EA061 EH411 EJ192 EJ422 EK04 GB43 JA04A JA04B JA04C JA20B JA20C JD04A JG05 JJ03 YY00A YY00B YY00C 4L035 EE01 EE05 FF01 FF05 MF02 MG02 MG04 MJ02 4L055 AF25 AF30 AF33 AF35 AJ01 BE02 BE14 EA04 EA06 EA20 FA18 FA19 GA33 GA39

Claims (6)

[Claims] 1. A base material for a laminate having a multilayer structure having at least three layers, wherein both outer and inner layers have the following constitution. (1) A nonwoven fabric containing a synthetic organic fiber whose inner layer has a softening temperature of 320 ° C. or less and a moisture absorption of 1.5% or less. (2) Both outer layers contain 70% or more of synthetic organic fibers having no melting point and a decomposition temperature of 400 ° C. or more, and a softening temperature of 3 or more.
A nonwoven fabric containing less than 20 ° C. of synthetic organic fibers than the inner layer. 2. The synthetic organic fiber having a softening temperature of 320 ° C. or lower and a moisture absorption of 1.5% or lower of the inner layer is at least one selected from polyarylate fiber, polyphenylene sulfide fiber and fluororesin fiber. Is a fiber of
The base material for a laminate according to claim 1. 3. The synthetic organic fiber having a softening temperature of 320 ° C. or less and a moisture absorption of 1.5% or less in the inner layer.
The base material for a laminate according to claim 1, which is contained in an amount of 0% or more. 4. Decomposition temperature is 400 ° C. without a melting point of both outer layers.
The synthetic organic fiber described above is at least one kind of fiber selected from p-phenylene terephthalamide fiber, p-phenylene phenyl ether terephthalamide fiber, and poly-P-phenylene benzobisoxazole (PBO) fiber. The base material for a laminate according to any one of claims 1 to 3. 5. A method for producing a laminate base material having a multilayer structure having at least three layers, wherein nonwoven fabrics having the following constitutions are separately formed by a wet papermaking method, and superposed.
A method for producing a base material for a laminate, wherein the laminate is bonded while being subjected to heat and pressure treatment by a hot roll at 280 ° C to 450 ° C. (1) The nonwoven fabric for the inner layer contains a synthetic organic fiber having a softening temperature of 320 ° C. or less and a moisture absorption of 1.5% or less. (2) The nonwoven fabric for both outer layers has no melting point and a decomposition temperature of 40
A nonwoven fabric containing 70% or more of synthetic organic fibers of 0 ° C. or more and having a softening temperature of 320 ° C. or less and a moisture absorption of 1.5% or less in the content of synthetic organic fibers less than that of the inner layer. 6. A prepreg using the base material for a laminate according to any one of claims 1 to 4.