JP5096045B2 - Foam and production method thereof - Google Patents

Description

The present invention relates to a foam and a method for producing the same. More specifically, the present invention relates to a foam for a substrate that is excellent in heat resistance and low dielectric constant, which is suitable as an electronic member such as flexible.

  Conventionally, plastic film has high insulation performance, so it must be applied to electronic and electrical equipment such as cable insulation, printed wiring board, slot insulation of rotating machines, and electronic parts such as film capacitors as parts and members that require high reliability. Has been. The history of development of such plastic insulating films has been advanced by the synthesis development of engineer plastics with excellent heat resistance. As electronic parts such as film capacitors, in addition to the development of heat-resistant plastic materials, development of materials having a high dielectric constant has been promoted in order to obtain higher capacitance.

  In recent years, plastic materials are required to have high performance in electronic devices that store a large amount of information corresponding to an advanced information society, and can process and transmit them at high speed. In particular, low electrical permittivity and low dielectric loss tangent are required as electrical characteristics corresponding to higher frequencies. Furthermore, in an apparatus having a rotating machine such as a motor, inverter control that can be precisely controlled for higher efficiency and higher functionality is performed. For this reason, an increase in leakage current of high-frequency components in the insulating component occurs, and therefore, a low dielectric constant that prevents this is required as an electrical characteristic.

  In the field of electronic materials, particularly for circuit boards, materials having high heat resistance such as solder heat resistance and low dielectric constant are desired. Among these, the dielectric characteristics are inherent basic physical properties determined from the molecular structure of the material, and therefore a corresponding material must be selected in order to obtain the required dielectric characteristics. For example, polyethylene terephthalate (PET), which is used as a material having solder heat resistance, has a dielectric constant of about 3.1, and a liquid crystal polymer has a dielectric constant of about 2.8. It was difficult to obtain rate characteristics.

  Thus, as one means for reducing the dielectric constant of the resin material, it is conceivable to use the resin material as a foam. As such a technique using a material having high heat resistance, for example, Patent Document 1 discloses a polyarene sulfide foam having a crystallinity of 20% or more and an expansion ratio of 2 or more. Patent Document 2 discloses a step of bringing carbon dioxide gas into contact with a resin molded body made of aromatic polyethersulfone under pressure and infiltrating the carbon dioxide gas, and after releasing the pressure, the resin molded body is not less than the start of foaming. There is disclosed a method for producing a polyethersulfone resin foam, comprising the steps of heating and foaming to less than Tg of the resin and cooling the resulting resin foam.

Japanese Patent No. 3459454 Japanese Patent No. 3449447

  However, any of the above-described manufacturing methods foams the resin composition alone, and if the resin composition having heat resistance is to be foamed, the foaming temperature becomes high or the foaming temperature range becomes narrow. There are restrictions on foaming conditions, and a production method capable of achieving both heat resistance and foaming characteristics has not been established yet.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to achieve a balance between heat resistance and foaming characteristics, and to provide a foam having excellent foaming characteristics and heat resistance and a method for producing the same. It is to provide.

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by impregnating a molded product blended with a specific material with a pressurized gas and foaming, and have completed the present invention. .
That is, the present invention is as follows.
[1] A component (a) in which at least one of a crystal melting temperature, a glass transition temperature, and a liquid crystal transition temperature is 260 ° C. or higher, and a component (b) that is an amorphous resin having a glass transition temperature of 230 ° C. or lower. It is a foam formed by foaming a molded body composed of a main component and having a mass ratio of (a) / (b) = 70/30 to 30/70 after impregnating with a pressurized gas. A foam for a substrate, wherein the dielectric constant is larger than 2.5 and 3.0 or less, and the average pore diameter is 3 μm or less.
[2] Foaming is performed at a temperature condition not lower than the glass transition temperature of the component (b) and not higher than the crystal melting temperature, glass transition temperature, and liquid crystal transition temperature of the component (a). The foam for a substrate according to [1].
[3] The component (a) is a crystalline resin, the crystal melting temperature is 260 ° C. or higher, and the glass transition temperature is lower than the glass transition temperature of the component (b). The foam for a substrate according to [1] or [2].
[4] The foam for a substrate according to any one of [1] to [3], wherein the component (a) comprises a polyaryl ketone resin, and the component (b) comprises a polyetherimide resin.

  The foam for a substrate of the present invention foams a molded body made of a blend of a component (a) having heat resistance and a component (b) that imparts foaming characteristics using a pressurized gas. For this reason, the foam which can make heat resistance and foaming characteristics which are contradictory characteristics compatible can be obtained.

The present invention will be described in detail below.
It should be noted that the upper limit and lower limit of the numerical range in the present invention are the same as those in the present invention as long as they have the same effects as those in the numerical range, even if they are slightly outside the numerical range characterized by the present invention. It is included in the equivalent range. In addition, the main component in the present invention is a component that is contained in the largest amount, and is usually a component that is 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more. .

  In the present invention, unless otherwise specified, the state before foaming is referred to as a molded body, and the state after foaming is referred to as a foam to distinguish them.

The foam for a substrate of the present invention is a component (a) in which at least one of crystal melting temperature, glass transition temperature, and liquid crystal transition temperature is 260 ° C. or higher, and an amorphous resin having a glass transition temperature of 230 ° C. or lower. (B) a step of obtaining a molded product comprising a component as a main component and a mass ratio of (a) / (b) = 70/30 to 30/70; and a pressurized gas in the molded product. It is obtained by the impregnation step and the step of foaming after containing the pressurized gas.
In addition, the foam for a substrate of the present invention includes a heat-resistant film or sheet made of the foam for a substrate, and further includes a laminate having a conductive foil provided on at least one surface of the film or sheet. It is a waste.

  The foam for a substrate in the present invention contains a component (a) in which at least one of a crystal melting temperature, a glass transition temperature, and a liquid crystal transition temperature is 260 ° C. or higher. The component (a) uses a crystalline thermoplastic resin having a crystal melting temperature of 260 ° C. or higher, an amorphous thermoplastic resin having a glass transition temperature of 260 ° C. or higher, and a liquid crystal polymer having a liquid crystal transition temperature of 260 ° C. or higher. be able to.

  Examples of the crystalline thermoplastic resin having a crystal melting temperature (hereinafter sometimes referred to as “Tm”) of 260 ° C. include polyether ether ketone (PEEK: Tg = 145 ° C., Tm = 335 ° C.), poly Polyaryl ketones (PAr) such as ether ketone (PEK: Tg = 165 ° C., Tm = 355 ° C.), polyphenylene sulfide (PPS: Tg = 100 ° C., Tm = 265 ° C.), polyethylene terephthalate (PET: Tg = 80 ° C., Tm = 265 ° C.) or the like can be used.

  As an amorphous thermoplastic resin having a glass transition temperature (hereinafter sometimes referred to as “Tg”) of 260 ° C. or higher, polyamideimide (PAI: Tg = 280 ° C.) can be used. As the liquid crystal polymer having a transition temperature (hereinafter sometimes referred to as “Tl”) of 260 ° C. or higher, wholly aromatic polyester (PE: Tl = 330 ° C.) or the like can be used.

  Next, the foam for a substrate in the present invention contains the component (b) which is an amorphous resin having a glass transition temperature of 230 ° C. or lower. The component (b) in the present invention is not specified below. For example, polysulfone (PSF: Tg = 190 ° C.), polyacrylate (PAr: Tg = 175 ° C.), polyether sulfone (PES: Tg = 230) ° C), polyetherimide (PEI: Tg = 216 ° C), polycarbonate (PC: Tg = 150 ° C), modified polyphenylene ether (modified PPE: Tg = 145 ° C), polyphenylsulfone (PPSU: Tg = 220 ° C) Etc. can be used.

  In the present invention, at least one of crystal melting temperature, glass transition temperature, and liquid crystal transition temperature is 260 ° C. or higher, and component (b) is an amorphous resin having a glass transition temperature of 230 ° C. or lower. It is important to have as a main component. In the present invention, the component (a) serves as a support for stabilizing the heat resistance and the structure of the foam, and the component (b) is used to adjust the foaming start temperature and foam when impregnating the pressurized gas and foaming. It mainly plays the role of forming the starting point and the foamed region. From this, heat resistance can be imparted to the foam by setting at least one of the component (a) of crystal melting temperature, glass transition temperature, and liquid crystal transition temperature to 260 ° C. or higher. In addition, by making the component (b) an amorphous resin having a glass transition temperature of 230 ° C. or lower, the glass transition temperature of the component (b), the crystal melting temperature, the glass transition temperature, the liquid crystal transition of the component (a) Foaming can be performed in a temperature range below the highest temperature.

  Next, it is important that the mass ratio of the component (a) and the component (b) is in the range of (a) / (b) = 70/30 to 30/70. If the component (a) is within such a mass ratio, a heat-resistant foam can be obtained. When importance is attached to heat resistance, the component (a) is preferably 50 to 70% by mass and particularly preferably 60 to 70% by mass in the total of both components. If the component (b) is within the range of the mass ratio, a foam having foaming characteristics and low dielectric constant can be obtained. When emphasizing the expansion ratio, the component (b) is preferably 50 to 70% by mass, particularly preferably 60 to 70% by mass in the total of both components.

  Next, it is important that the foam for a substrate of the present invention has a dielectric constant of more than 2.5 and 3.0 or less. As an electrical property corresponding to the high frequency required for plastic materials, there is a low dielectric constant. When a plastic film is used for an insulating part of an AC device, the electrical loss leaking at the insulating part is proportional to the product of frequency, dielectric constant, and dielectric loss tangent. Therefore, power loss increases as the frequency increases. In order to prevent this, it is necessary to reduce the relative dielectric constant or the dielectric loss tangent.

  The value of the dielectric constant effective for reducing the loss due to the high frequency is effectively 3.0 or less, preferably 2.9 or less, particularly preferably 2.8 or less. Further, the dielectric constant of the foam for a substrate of the present invention is preferably larger than 2.5. If the dielectric constant of the foam for a substrate is larger than 2.5, it is preferable because the specific strength of the obtained foam for a substrate becomes good.

  In addition, it is important that the average pore diameter of the foam for a substrate of the present invention is 3 μm or less. If the average cell diameter of the foam is 3 μm or less, when the through-hole is formed in the obtained foam for the substrate to form a via hole, and then the conductive paste is charged in the via hole, the conductive paste is a bubble in the foam. An internal short circuit that contacts the conductive paste that has flowed into another via hole through does not occur. In this respect, the average bubble diameter is preferably 3 μm to 5 nm, more preferably 2 μm to 10 nm, and still more preferably 1 μm to 20 nm.

Next, the component (a) in the present invention preferably has a crystal melting temperature of 260 ° C. or higher, and the glass transition temperature is lower than the glass transition temperature of the amorphous resin as the component (b). In the present invention, the component (a) serves as a support for stabilizing the heat resistance and the structure of the foam, and the component (b) is used to adjust the foaming start temperature and foam when impregnated with a pressurized gas. It mainly plays the role of forming the starting point and the foamed region. Therefore, if the crystalline melting temperature of the component (a) is 260 ° C. or higher and the glass transition temperature is lower than the glass transition temperature of the amorphous resin as the component (b),
It is possible to foam within the range of the glass transition temperature of the component (a) to the crystal melting temperature of the component (a), and after foaming, the foam having heat resistance is obtained by crystallizing the component (a). It is preferable because it becomes possible.

  In the present invention, the (a) component is preferably a polyaryl ketone resin, and the (b) component is a polyetherimide resin.

  This is because the mixed composition of the polyaryl ketone resin as the component (a) and the polyetherimide resin as the component (b) has good compatibility, has a microphase separation structure, and the component (b) This is because a molded body having a fine and dense structure can be obtained. In addition, when an amorphous polyetherimide resin is blended with a polyaryl ketone resin having a crystal melting temperature of 260 ° C. or higher, the crystallization rate of the polyaryl ketone resin becomes slow as the blend ratio of the polyetherimide increases. For this reason, the crystallinity of the molded product before impregnation with the pressurized gas can be controlled relatively arbitrarily, and foaming is performed in a temperature range from the glass transition temperature of the component (a) to the crystal melting temperature of the component (a). Is possible. Moreover, it becomes possible to obtain the foam excellent in the porous structure and heat resistance of the foam obtained by crystallizing (a) component after making it foam.

  Next, the manufacturing method of the molded object of this invention is demonstrated. As a method for producing the molded product of the present invention, a known method such as an extrusion casting method using a T-die or a calender method can be adopted, and although not particularly limited, stable productivity of the molded product, etc. From this aspect, the extrusion casting method using a T die is preferable. The molding temperature in the extrusion casting method using a T die is appropriately adjusted in terms of the flow characteristics of the component (a) and the component (b), but is generally higher than the flow start temperature, preferably the flow start temperature + 20 ° C. to 430 ° C. A range of ° C is preferred.

  In addition, the thickness of the molded body in the present invention is preferably 10 μm or more. If the thickness of the molded body is 10 μm or more, the pressurized gas contained does not diffuse from the surface of the molded body during the step of heating the molded body containing the pressurized gas, and a good porous structure is obtained. It can be expressed and has good productivity. The thickness of the especially preferable molded object is 50 micrometers-1 mm, More preferably, it is 75-500 micrometers.

  As the next step, the compact is impregnated with a pressurized gas. The impregnation referred to in this step means, for example, the same state as when the pressurized gas is dissolved in the molded body. The impregnation conditions depend on the components constituting the molded body, but are not particularly limited as long as the pressurized gas can be impregnated. A specific method for impregnating the molded body with the pressurized gas may be in accordance with a known method. For example, the compact is placed in a pressure-resistant container such as an autoclave, and the compact and a gaseous or liquid gas are enclosed. Accordingly, a batch processing method for increasing the pressure in the pressure vessel, a method in which a resin molded body is introduced into a processing zone for pressurized gas and continuously processed, and the like can be adopted.

  The pressurized gas that can be used in the present invention is not limited to the following, but for example, carbon dioxide, nitrogen, helium, argon, nitrous oxide, ethylene, ethane, tetrafluoroethylene, perfluoroethane, tetra Fluoromethane, trifluoromethane, 1,1-difluoroethylene, trifluoroamide oxide, cis-difluorodiamine, trans-difluorodiamine, nitrogen difluoride, tritiated phosphorus, dinitrogen tetrafluoride, ozone, phosphine, nitrosyl Fluoride, nitrogen trifluoride, deuterium chloride, xenon, sulfur hexafluoride, fluoromethane, pentafluoroethane, 1,1-difluoroethene, diborane, water, tetrafluorohydrazine, silane, silicon tetrafluoride, tetrahydrogen Germanium fluoride, boron trifluoride, carbon fluoride fluoride , Chlorotrifluoromethane, bromotrifluoromethane and vinyl fluoride, and the like.

  Among these, preferred pressurized gases include carbon dioxide, nitrogen, nitrous oxide, ethylene, ethane, tetrafluoroethylene, perfluoroethane, tetrafluoromethane, trifluoromethane, and 1,1-difluoroethylene.

  Of these, carbon dioxide, nitrogen, helium, and argon, which are inert gases, are nonflammable and are preferable. Further, carbon dioxide and nitrogen are more preferable from the viewpoint of non-toxicity, low cost, and non-reactivity with most resin compositions, and carbon dioxide having a relatively high solubility in the resin composition is particularly preferable.

  The temperature at which the pressurized gas is impregnated is preferably equal to or lower than the glass transition temperature of the component (a) and the component (b). If it is below the glass transition temperature of (a) component and (b) component, when a molded object is impregnated with pressurized gas, it is preferable because a molded object does not deform | transform.

  The time for impregnating the pressurized gas varies depending on the composition of component (a) and component (b), and / or the mixing ratio, the thickness of the molded article, etc. More preferably, it is 30 minutes or more. If it is less than 5 minutes, there may be a case where the central part of the molded body cannot be sufficiently impregnated due to the diffusion of the pressurized gas to the molded body. The upper limit is influenced by the impregnation temperature of the pressurized gas and / or the contained pressure, but is 48 hours or less, preferably 24 hours or less, more preferably 12 hours or less from the viewpoint of production efficiency.

  In the next step, the molded body is released from the pressurized gas, and the molded body impregnated with the pressurized gas is foamed. In this step, foaming is performed by heating to a temperature condition that is equal to or higher than the glass transition temperature of component (b) and not higher than the crystal melting temperature, glass transition temperature, and crystal transition temperature of component (a). It is preferable to make it.

  In the present invention, the temperature at which the molded body is foamed is set to be equal to or higher than the glass transition temperature of component (b) and not higher than the highest temperature among the crystal melting temperature, glass transition temperature, and crystal transition temperature of component (a). The reason why is preferable is as follows.

  This is because if the foaming is performed in such a temperature range, the rigidity of the component (a) is high and the elasticity of the component (b) is sufficient for foaming, so that the component (b) is mainly foamed. By foaming at a temperature below the highest temperature among the crystal melting temperature, glass transition temperature, and crystal transition temperature of component (a), the rigidity of component (a) does not decrease, and only component (b) In addition, the component (a) does not foam, and the bubbles do not burst or become too large.

  When the component (a) in the present invention is a crystalline resin having a crystal melting temperature of 260 ° C. or higher and a glass transition temperature lower than the glass transition temperature of the amorphous resin as the component (b) Foaming can be achieved by setting the temperature at which the molded body is foamed to a temperature not lower than the glass transition temperature of component (a) and not higher than the crystal melting temperature of component (a).

  As a method of foaming, the molded body is released from the pressurized gas, and the molded body containing the pressurized gas is heated under non-pressurization to create a non-equilibrium state, and the impregnated gas is vaporized to foam. Method (heating method) is used.

  If such a heating method is used, it is taken out from the pressurized gas and foamed by reheating under non-pressurized, so that the foaming temperature can be easily controlled.

  As a heating means in the case of using the heating method, a known means may be used, and examples thereof include a hot air circulation heat treatment furnace, an oil bath, a molten salt bath and the like. A hot-air circulating heat treatment furnace is preferable from the viewpoint of handleability. What is necessary is just to set the time for which foaming is completed as the heating time.

  After the foaming, it is preferable to cool in order to control to a desired porous structure. The cooling temperature varies depending on the glass transition temperature of the component (a) and the component (b) and / or the mixing ratio of the component (a) and the component (b) and the thickness of the molded body. It is preferable to cool rapidly.

  When the component (a) is a crystalline resin, heat treatment may be performed after the cooling to crystallize the component (a). The heat treatment conditions for crystallizing the component (a) are not particularly limited as long as the temperature and time are sufficient to complete the crystallization of the component (a). Preferably, the treatment is performed in a temperature range where the crystallization speed of the component (a) is high.

  The molded body of the present invention may be a single layer, or may have a laminated structure for the purpose of imparting properties such as smoothness, heat resistance, solvent resistance, and pressure gas diffusibility to the surface of the molded body. good. In the case of a laminated structure, layers having different resin compositions and additives can be appropriately combined. Moreover, the lamination ratio of each layer can be suitably adjusted according to a use and the objective.

  Examples of the method for forming the laminate include a co-extrusion method, a method of forming a film of each layer, and then superposing and heat-sealing, a method of bonding with an adhesive, and the like.

In the molded product of the present invention, other resins and various additives such as inorganic fillers, heat stabilizers, ultraviolet absorbers, light stabilizers, nucleating agents, coloring agents, lubricants, difficult to the extent that the properties are not impaired. A flame retardant etc. may be appropriately adapted. Moreover, you may contain another resin composition to such an extent that the property is not impaired.
In particular, when the present invention is applied to an electronic member such as a flexible printed wiring board, it is preferable to improve the dimensional stability by mixing an inorganic filler. In this case, the mixing amount of the inorganic filler is preferably 10 to 40 parts by mass with respect to 100 parts by mass in total of the components (a) and (b). If the inorganic filler is within such a range, it is preferable because the dimensional stability can be improved while maintaining the flexibility of the molded body.

  Moreover, there is no restriction | limiting in particular as an inorganic filler to be used, A well-known thing can be used. Examples include talc, mica, clay, glass, alumina, silica, aluminum nitride, and silicon nitride.

  The foam for a substrate of the present invention can be suitably used for an electronic member such as a flexible printed circuit board. Here, the conductive foil can be provided on at least one side, and in this case, a single layer (single side, double side) substrate or a multilayer substrate may be used.

  Moreover, when forming a conductive circuit in conductor foil, any well-known method can be employ | adopted and it does not specifically limit. For example, a known method such as a subtractive method (etching), an additive method (plating), a die stamp method (mold), or a conductor printing method (conductive paste) can be applied.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In addition, the various measured values and evaluation about a foam were performed as follows.

(1) Dielectric constant measurement The dielectric constant of the foam (molded body in Comparative Example 1) was measured at a frequency of 1 GHz using an impedance analyzer (manufactured by HEWLETT: HP4291B).

(2) Bubble diameter observation (average bubble diameter measurement)
Using a scanning electron microscope (manufactured by Hitachi, Ltd .: S-4500), the vicinity of the center of the cross section of the obtained foam was observed, and the obtained observation image was image processing software (manufactured by Nippon Visual Science Co., Ltd .: Image). -Pro Plus) was used to measure the diameter of 50 bubbles and determine the average value.

(3) Foaming ratio measurement Molding using a balance in which a specific gravity measurement kit (A & D: AD-1653) is installed on an electronic balance (A & D: GR-300). The density of the body and the density of the foam were measured, and the foaming ratio was calculated from the ratio of the density of the molded body and the density of the foam.

(Reference Example 1)
(A) Polyetheretherketone resin (manufactured by Victrex: PEEK) as component
40 parts by mass of 381G (Tg = 166 ° C., Tm = 334 ° C.), 60 parts by mass of amorphous polyetherimide resin (manufactured by General Electric Co., Ltd .: Ultem 1000 (Tg = 232 ° C.)) as component (b) The blended product was extruded at a preset temperature of 380 ° C. using an extruder equipped with a T die to obtain a molded product having a thickness of 250 μm. The obtained molded body was put into a pressure vessel adjusted to 60 ° C., pressurized to 20 MPa with carbon dioxide (carbon dioxide), and carbon dioxide (carbon dioxide) was contained in the pre-gas-containing sheet. The sheet was impregnated with carbon dioxide (carbon dioxide) for 9 hours. Thereafter, the leak valve of the pressure vessel is fully opened, the pressure in the vessel is released at a pressure reduction rate of 1 MPa / sec, the molded product is taken out from the vessel, and the molded product impregnated with gas is set to 180 ° C. It was put into a heat treatment furnace for 1 minute, and after the charging, the surface was cooled with compressed air to obtain a substrate foam.
The obtained results are shown in Table 1. A foam for a substrate having a dielectric constant of 2.6 and an average cell diameter of about 1.5 μm could be obtained. In addition, the foaming ratio of the obtained foam for substrates was about 1.6 times.

Example 1
A foam for a substrate was obtained in the same manner as in Reference Example 1 except that amorphous polyetherimide resin (manufactured by General Electric Co., Ltd .: Ultem CRS 5001 (Tg = 241 ° C.)) was used as the component (b). Next, the obtained foam for a substrate was put into a hot-air circulating heat treatment furnace set at 280 for 10 minutes, and after the charging, the surface was cooled with compressed air to obtain a foam for a substrate.
The obtained results are shown in Table 1. A foam for a substrate having a dielectric constant of 2.7 and an average cell diameter of about 1.3 μm could be obtained. In addition, the foaming ratio of the obtained foam for a substrate was about 1.4 times.

(Reference Example 2)
A molded body was produced in the same manner as in Example 1, and the obtained molded body was heat-treated at 240 ° C. for 1 hour, and then a foam for a substrate was obtained in the same manner as in Reference Example 1 .
The obtained results are shown in Table 1. A foam for a substrate having a dielectric constant of 2.9 and an average cell diameter of about 0.3 μm could be obtained. In addition, the foaming ratio of the obtained foam for a substrate was about 1.2 times.

(Reference Example 3)
(A) The component is a polyetheretherketone resin (manufactured by Victrex: PEEK
381G (Tg = 166 ° C., Tm = 334 ° C.) 70% by mass, component (b) is a polyphenylsulfone resin (PPSU: Solvay Advanced Polymer, Inc .: Radel R-5000 (Tg = 220 ° C.)) 30% by mass A foam for a substrate was obtained in the same manner as in Reference Example 1 except that.
The obtained results are shown in Table 1. A foam for a substrate having a dielectric constant of 2.7, an expansion ratio of 1.4, and an average cell diameter of 0.5 μm could be obtained. In addition, the foaming ratio of the obtained foam for a substrate was about 1.4 times.

(Comparative Example 1)
The molded body obtained in Reference Example 1 was used without foaming. The molded article had a dielectric constant of 3.3.

(Comparative Example 2)
In Reference Example 1 , a molded body was prepared in the same manner except that the component (b) was changed to 100% by mass, and the molded body impregnated with the gas was put into a hot-air circulating heat treatment furnace set at 350 ° C. for 1 minute. Except for the above, a foam for a substrate was obtained in the same manner as in Reference Example 1 .
The obtained foam for a substrate was severely deformed when put into a heat treatment furnace, and the dielectric constant could not be measured. In addition, the cell size of the obtained foam for a substrate could not be measured due to severe bubble breakage.

The foams for substrates of Reference Examples 1 to 3 and Example 1 have a dielectric constant in the range of 2.6 to 2.9, a bubble diameter of 3 μm or less, a good low dielectric constant characteristic, and a porous structure. It can be confirmed that On the other hand, when it is an unfoamed material (Comparative Example 1), it can be confirmed that the dielectric constant is 3.3 and the low dielectric constant characteristics are inferior. Moreover, when a molded object is only (b) component, even if it can be made to foam, it can confirm that a torn hole is severe and a foaming characteristic is bad.

Claims (3)

Crystalline melting temperature, glass transition temperature, at least one of the liquid crystal transition temperature but is 260 ° C. or more, consisting of polyaryl ketone resin and component (a), a glass transition temperature of amorphous resin 230 ° C. or less, poly A molded body composed mainly of (b) component made of etherimide resin and having a mass ratio of (a) / (b) = 70/30 to 30/70 is impregnated with pressurized gas. And then foaming to produce a foam having a dielectric constant of more than 2.5 and 3.0 or less, and an average pore diameter of 3 μm or less,
The foaming is carried out under a temperature condition that is not lower than the glass transition temperature of the component (b) and not higher than the crystal melting temperature, glass transition temperature, and liquid crystal transition temperature of the component (a). A method for producing foam.   The component (a) is a crystalline resin, has a crystal melting temperature of 260 ° C. or higher, and has a glass transition temperature lower than the glass transition temperature of the component (b). The manufacturing method of the foam as described in any one of. The foam obtained by the manufacturing method of the foam of Claim 1 or 2.