insulating material

Abstract

The present invention relates to an insulating material (100) comprising a first insulating layer (1) formed from a first resin composition containing inorganic filler, and a second insulating layer (2) provided on at least one surface of the first insulating layer (1) and formed from a second resin composition not containing inorganic filler.

Description

Technical Field

[0001] This invention relates to insulating materials. Background Technology

[0002] With the miniaturization and weight reduction of electronic devices, flexible printed wiring substrates are widely used. These flexible printed wiring substrates are formed, for example, by laminating a capping layer in a manner that covers copper wiring patterned on a polyimide substrate.

[0003] For example, Patent Document 1 describes a cover layer comprising a cover film having insulating, flexible, and light-reflective properties, and an adhesive layer laminated on one side of the cover film. In this cover layer, the cover film includes a substrate layer and a reflective layer laminated on the other side of the substrate layer. Furthermore, the reflective layer contains a white pigment.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-48736 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] On the other hand, low thermal expansion rates are also becoming required for coatings. Therefore, it is worth considering incorporating a large amount of inorganic fillers into the varnish used to form the coating. However, when a varnish containing a large amount of inorganic fillers is applied and allowed to cure, there is a problem of reduced voltage resistance.

[0009] The purpose of this invention is to provide an insulating material with low thermal expansion coefficient and excellent voltage resistance.

[0010] Problem Solving Methods

[0011] According to the present invention, the insulating material shown below can be provided.

[0012] [1] An insulating material comprising:

[0013] The first insulating layer formed by the first resin composition, and

[0014] The second insulating layer is disposed on at least one surface of the first insulating layer and is formed of the second resin composition.

[0015] The first resin composition described above contains inorganic fillers.

[0016] The above-mentioned second resin composition does not contain inorganic fillers.

[0017] [2] According to the insulating material described in [1], the thickness of the second insulating layer is 0.5 μm or more and 10 μm or less.

[0018] [3] According to the insulating material of [1] or [2], wherein the first resin composition contains 20% by mass and 70% by mass of inorganic filler relative to all solid components of the first resin composition.

[0019] [4] The insulating material according to any one of [1] to [3], wherein the inorganic filler is silicon dioxide.

[0020] [5] The insulating material according to any one of [1] to [4], wherein the first resin composition contains polyimide.

[0021] [6] The insulating material according to any one of [1] to [5], wherein the second insulating layer is disposed on both surfaces of the first insulating layer.

[0022] According to one aspect of the present invention, an insulating material with low thermal expansion coefficient and excellent voltage resistance can be provided. Attached Figure Description

[0023] Figure 1 This is a cross-sectional view showing the insulating material according to the first embodiment of the present invention.

[0024] Figure 2 This is a cross-sectional view showing the insulating material according to the second embodiment of the present invention.

[0025] Symbol Explanation

[0026] 1··· First Insulation Layer

[0027] 2. Second Insulation Layer

[0028] 3···Substrate

[0029] 100, 100A... Insulation materials Detailed Implementation

[0030] [First Implementation Method]

[0031] The present invention will now be described with reference to the accompanying drawings, using examples of embodiments. The present invention is not limited to the embodiments described herein. It should be noted that some parts in the accompanying drawings are enlarged or reduced for ease of explanation.

[0032] (Insulating material)

[0033] like Figure 1 As shown, the insulating material 100 of this embodiment includes: a first insulating layer 1 formed of a first resin composition, and a second insulating layer 2 formed of a second resin composition and disposed on at least one surface of the first insulating layer 1. Furthermore, the insulating material 100 is disposed on a substrate 3.

[0034] Furthermore, the first resin composition needs to contain inorganic fillers, while the second resin composition needs to be free of inorganic fillers.

[0035] The inventors speculate that the insulating material 100 of this embodiment has a low thermal expansion coefficient and excellent voltage resistance for the following reasons.

[0036] That is, in order to reduce the thermal expansion coefficient of the insulating material 100, a large amount of inorganic filler is required. However, when a varnish containing a large amount of inorganic filler is applied and cured, the inorganic filler is exposed on the film surface. The inventors speculate that this will lead to a decrease in voltage withstand capability. In contrast, in the insulating material 100 of this embodiment, a second insulating layer 2 without inorganic filler is provided on the upper surface of the first insulating layer 1 containing inorganic filler. Therefore, the exposure of inorganic filler on the surface of the insulating material 100 can be suppressed, and the surface can be smoothed. As a result, the voltage withstand capability of the insulating material 100 can be improved. As described above, the inventors speculate that the insulating material 100 of this embodiment has a low thermal expansion coefficient and excellent voltage withstand capability.

[0037] (First insulating layer)

[0038] The first insulating layer 1 is a layer formed from a first resin composition. Furthermore, the first resin composition needs to contain an inorganic filler. This inorganic filler reduces the coefficient of thermal expansion of the insulating material 100.

[0039] Examples of inorganic fillers include silica, alumina, aluminum hydroxide, and magnesium hydroxide. Among these, silica is preferred from the perspective of balancing various physical properties. These can be used individually or in combination.

[0040] Relative to 100% by mass of the solid content of the first resin composition, the amount of inorganic filler is preferably 20% by mass or more and 70% by mass or less, more preferably 25% by mass or more and 65% by mass or less, and particularly preferably 30% by mass or more and 55% by mass or less. When the amount of inorganic filler is at or above the aforementioned lower limit, the thermal expansion coefficient of the insulating material can be further reduced. On the other hand, when the amount of inorganic filler is at or below the aforementioned upper limit, the inorganic filler can be sufficiently dispersed in the first resin composition.

[0041] The first resin composition contains a resin. Examples of resins include polyimide, polyetherimide, polyamide, polyamide-imide, polymethylpentene, polyester, polyetheretherketone, liquid crystal polymer, polyphenylene ether, polyphenylene sulfide, polyolefin, syndiotactic polystyrene, epoxy resin, maleimide resin, phenolic resin, and melamine resin. Among these, polyimide is preferred from the viewpoint of low thermal expansion coefficient and excellent voltage resistance. Furthermore, the polyimide is preferably a polyimide obtained by curing polyamic acid, which is a precursor of the polyimide.

[0042] In addition to inorganic fillers and resin, the first resin composition may also contain additives and solvents.

[0043] Examples of additives include curing accelerators and flame retardants.

[0044] Examples of solvents include N-methyl-2-pyrrolidone (N-methylpyrrolidone), diethylene glycol monomethyl ether acetate, cyclohexanone, and methyl ethyl ketone. These can be used individually or in combination.

[0045] From the viewpoint of voltage withstand capability, the thickness of the first insulating layer 1 is preferably 10 μm or more and 100 μm or less, more preferably 15 μm or more and 50 μm or less, and particularly preferably 20 μm or more and 30 μm or less.

[0046] (Second insulating layer)

[0047] The second insulating layer 2 is a layer formed from the second resin composition. Furthermore, the second resin composition needs to be free of inorganic fillers. Additionally, the second insulating layer 2 is disposed on at least one surface of the first insulating layer 1, such as... Figure 1 As shown, it is preferably disposed on the upper surface of the first insulating layer 1. In this way, the inorganic filler exposed on the upper surface of the first insulating layer 1 can be covered by the second insulating layer 2.

[0048] The second resin composition contains a resin. Examples of resins include the same resin used in the first resin composition. It should be noted that, from the viewpoint of interlayer adhesion, it is preferable that the resins used in the first and second resin compositions are of the same type.

[0049] In addition to resin, the second resin composition may also contain additives and solvents used in the first resin composition.

[0050] The thickness of the second insulating layer 2 is preferably 0.5 μm or more and 10 μm or less, more preferably 1 μm or more and 10 μm or less, even more preferably 1 μm or more and 5 μm or less, and particularly preferably 2 μm or more and 4 μm or less. When the thickness of the second insulating layer 2 is at or above the aforementioned lower limit, the exposure of inorganic fillers on the membrane surface can be suppressed more reliably. On the other hand, when the thickness of the second insulating layer 2 is at or below the aforementioned upper limit, a low coefficient of thermal expansion can be maintained.

[0051] From the viewpoint of balancing thermal expansion coefficient and voltage resistance, the ratio of the thickness of the second insulating layer 2 to the thickness of the first insulating layer 1 (thickness of the second insulating layer 2 / thickness of the first insulating layer 1) is preferably 1 / 20 or more and 1 / 2 or less, more preferably 1 / 15 or more and 1 / 4 or less, and particularly preferably 1 / 10 or more and 1 / 6 or less.

[0052] (Substrate)

[0053] As substrate 3, suitable and well-known substrates can be cited. Specifically, flexible wiring substrates, rigid wiring substrates, and semiconductor substrates can be cited.

[0054] (Methods for manufacturing insulating materials)

[0055] The method for manufacturing the insulating material 100 in this embodiment is not particularly limited. The insulating material 100 can be manufactured, for example, by a method comprising the following steps: a first film-forming step, wherein a first resin composition is coated onto a substrate 3 to form a coated film; a first drying step, wherein the coated film formed in the first film-forming step is dried to form a precursor film of the first insulating layer 1; a second film-forming step, wherein a second resin composition is coated onto the precursor film of the first insulating layer 1 obtained in the first drying step to form a coated film; a second drying step, wherein the coated film formed in the second film-forming step is dried to form a precursor film of the second insulating layer 2; and a curing step, wherein the precursor films of the first insulating layer 1 and the second insulating layer 2 are cured to form the first insulating layer 1 and the second insulating layer 2.

[0056] In the first film-forming process, the first resin composition is coated onto the substrate 3 to form a film.

[0057] Examples of coating apparatuses for the first resin composition include bar coaters, curtain coaters, spray coaters, roller coaters, and screen printing machines.

[0058] The coating thickness of the first resin composition is preferably adjusted in such a way that the thickness of the first insulating layer 1 falls within the range described above.

[0059] In the first drying step, the coating film formed in the first film forming step is dried (hereinafter also referred to as pre-baking) to form the precursor film of the first insulating layer 1.

[0060] The drying conditions can be appropriately set depending on the type of resin. For example, when the resin is polyamic acid, which is a precursor to polyimide, the following conditions can be given.

[0061] The drying temperature is preferably 60°C or higher and 150°C or lower, more preferably 70°C or higher and 140°C or lower, and particularly preferably 80°C or higher and 130°C or lower. When the temperature is within the above range, the solvent in the first resin composition can be dried.

[0062] The drying time is preferably 10 seconds or more and 45 minutes or less, more preferably 1 minute or more and 40 minutes or less, and particularly preferably 5 minutes or more and 35 minutes or less. When the time is within the above range, the solvent in the first resin composition can be dried.

[0063] In the second film-forming process, the second resin composition is coated onto the precursor film of the first insulating layer 1 obtained in the first drying process to form a coated film.

[0064] The same apparatus as the one used for coating the first resin composition can be used as the coating apparatus for the second resin composition.

[0065] The coating thickness of the second resin composition is preferably adjusted in such a way that the thickness of the second insulating layer 2 falls within the range described above.

[0066] In the second drying process, the coating film formed in the second film forming process is dried to form the precursor film of the second insulating layer 2.

[0067] The drying conditions are the same as those in the first curing process.

[0068] In the curing process, the precursor films of the first insulating layer 1 and the second insulating layer 2 are cured to form the first insulating layer 1 and the second insulating layer 2.

[0069] The curing conditions can be appropriately set depending on the type of resin. For example, when the resin is polyamic acid, which is a precursor to polyimide, the following conditions can be given.

[0070] The curing temperature is preferably 140°C or higher and 250°C or lower, more preferably 150°C or higher and 240°C or lower, and particularly preferably 160°C or higher and 230°C or lower. When the temperature is within the above range, the first resin composition and the second resin composition can be properly cured.

[0071] The curing time is preferably 10 minutes or more and 300 minutes or less, more preferably 15 minutes or more and 200 minutes or less, and particularly preferably 20 minutes or more and 100 minutes or less. When the time is within the above range, the first resin composition and the second resin composition can be properly cured.

[0072] It should be noted that curing can be carried out in one stage or in two or more stages.

[0073] As described above, the insulating material 100 of this embodiment can be manufactured.

[0074] (Effects of the first embodiment)

[0075] According to this embodiment, the following effects can be achieved.

[0076] (1) The inorganic filler exposed on the upper surface of the first insulating layer 1 can be covered by the second insulating layer 2. Moreover, an insulating material 100 with low thermal expansion coefficient and excellent voltage resistance can be obtained.

[0077] [Second Implementation]

[0078] Next, a second embodiment of the present invention will be described based on the accompanying drawings. It should be noted that descriptions of configurations identical to those in the first embodiment will be omitted.

[0079] like Figure 2 As shown, the insulating material 100A of this embodiment includes: a first insulating layer 1 formed of a first resin composition, and a second insulating layer 2 formed of a second resin composition and disposed on both surfaces of the first insulating layer 1. Furthermore, the insulating material 100A is disposed on a substrate 3.

[0080] Furthermore, the first resin composition needs to contain inorganic fillers, while the second resin composition needs to be free of inorganic fillers.

[0081] The first insulating layer 1, the second insulating layer 2, and the substrate 3 are as described above.

[0082] The insulating material 100A of this embodiment can be manufactured by the following method, which further includes, before the first film-forming step in the above-described method for manufacturing the insulating material 100: a pre-coating film forming step, in which a second resin composition is coated on a substrate 3 to form a coating film; and a pre-coating film drying step, in which the coating film formed in the pre-coating film forming step is dried to form a precursor film of the second insulating layer 2.

[0083] (Effects of the second embodiment)

[0084] According to this embodiment, it can achieve the same effect as the effect (1) in the first embodiment described above, as well as the effect (2) described below.

[0085] (2) Insulating material 100A with further improved voltage resistance and elongation can be obtained.

[0086] [Variations on the implementation method]

[0087] This invention is not limited to the embodiments described above. Modifications or improvements that achieve the purpose of this invention are also included in this invention.

[0088] For example, in the above-described embodiments, the insulating material 100 is made using both a first resin composition and a second resin composition as coating liquids, but this is not a limitation. For example, the insulating material 100 may also be made using a coating liquid in which inorganic fillers precipitate and separate into two layers as the resin composition.

[0089] Example

[0090] The present invention will now be described in further detail through examples and comparative examples, but the present invention is not limited to these examples in any way. It should be noted that the materials used in the examples and comparative examples are as follows.

[0091] (resin)

[0092] Polyamic acid solution: The polyamic acid solution obtained in Preparation Example 1 below

[0093] (Inorganic packing)

[0094] Inorganic filler: Silica, trade name "SC2500-SQ", manufactured by Admatechs.

[0095] (solvent)

[0096] Solvent A: N-methyl-2-pyrrolidone (N-methylpyrrolidone), manufactured by Sakamoto Pharmaceutical Co., Ltd.

[0097] Solvent B: Cyclohexanone, manufactured by Sanyo Chemical Co., Ltd.

[0098] [Preparation Example 1]

[0099] In a 1L four-necked separable flask equipped with a stirrer, reflux condenser, and thermometer, 0.5g of 4,4'-diaminodiphenyl ether, 4g of dimerized diamine ("PRIAMINE 1075" manufactured by Croda Japan), 6.2g of 2,2',3,3',5,5'-hexamethyl[1,1'-biphenyl]-4,4'-diyl=bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylic acid ester), and 32g of N-methyl-2-pyrrolidone were added. Nitrogen gas was purged into the reaction vessel at 0.1mL / sec while the mixture was heated and stirred at 50°C for approximately 3.5 hours. After confirming salt dissolution, the mixture was further stirred at room temperature for 24 hours to synthesize polyamic acid, a precursor to polyimide, yielding a polyamic acid solution (solid content: 20% by mass). This polyamic acid solution can be directly used as a varnish for coating copper foil.

[0100] [Example 1]

[0101] The polyamic acid solution (71% by mass), inorganic filler (14% by mass), solvent A (3% by mass), and solvent B (12% by mass) obtained in Preparation Example 1 were mixed and dispersed using a three-roll mixer to obtain the first resin composition.

[0102] In addition, the polyamic acid solution obtained in Preparation Example 1 was used directly as the second resin composition.

[0103] After the first resin composition was coated on the substrate (PET film, 40 μm thick), it was pre-baked at 120°C for 10 minutes to form a precursor film of the first insulating layer (thickness: 20 μm).

[0104] Then, after coating the precursor film of the first insulating layer with the second resin composition, pre-baking was performed under the same conditions as described above to form a precursor film of the second insulating layer (thickness: 3 μm). Next, a thermosetting treatment was performed at 150°C for 60 minutes, followed by a further thermosetting treatment at 180°C for 30 minutes, thereby causing the polyamic acid to undergo ring-closed polymerization to obtain polyimide, forming the first and second insulating layers, and producing an insulating material.

[0105] [Example 2]

[0106] The first resin composition and the second resin composition were obtained in the same manner as in Example 1.

[0107] After the second resin composition was coated on the substrate (PET film, 40 μm thick), it was pre-baked at 120°C for 10 minutes to form a precursor film of the second insulating layer (thickness: 3 μm).

[0108] Next, after the first resin composition was coated onto the precursor film of the second insulating layer, it was pre-baked under the same conditions as described above to form the precursor film of the first insulating layer (thickness: 20 μm).

[0109] Then, after coating the precursor film of the first insulating layer with the second resin composition, pre-baking was performed under the same conditions as described above to form a precursor film of the second insulating layer (thickness: 3 μm). Next, a thermosetting treatment was performed at 150°C for 60 minutes, followed by a further thermosetting treatment at 180°C for 30 minutes, thereby causing the polyamic acid to undergo ring-closed polymerization to obtain polyimide, forming the first and second insulating layers, and producing an insulating material.

[0110] [Comparative Example 1]

[0111] The first resin composition was obtained in the same manner as in Example 1.

[0112] After the first resin composition was coated on the substrate (PET film, 40 μm thick), it was pre-baked at 120°C for 10 minutes, thermo-cured at 150°C for 60 minutes, and then further thermo-cured at 180°C for 30 minutes, thereby causing the polyamic acid to undergo closed-ring polymerization to obtain polyimide, forming the first insulating layer (thickness: 23 μm), and thus producing an insulating material.

[0113] [Comparative Example 2]

[0114] The polyamic acid solution obtained in Preparation Example 1 was used directly as the second resin composition.

[0115] After coating the second resin composition onto a substrate (PET film, 40 μm thick), the substrate was pre-baked at 120°C for 10 minutes, then thermo-cured at 150°C for 60 minutes, and then further thermo-cured at 180°C for 30 minutes, thereby causing the polyamic acid to undergo ring-closed polymerization to obtain polyimide, forming the second insulating layer (thickness: 23 μm), thus producing an insulating material.

[0116] [Evaluation of Insulation Materials]

[0117] The insulating materials were evaluated using the following methods (voltage resistance, thermal expansion coefficient, elongation). The results are shown in Table 1. Additionally, the formulation and layer composition of the resin compositions in the examples and comparative examples are shown in Table 1.

[0118] (1) Withstand voltage

[0119] The obtained insulating material was used as a sample. For a given area, a voltage was applied at a rate of 0.5 kV / sec relative to the thickness direction of the insulating material. The voltage at which conduction occurred was measured, and the insulation breakdown strength was calculated. The withstand voltage was then evaluated according to the following criteria.

[0120] AA: Insulation breakdown strength is above 450kV / mm.

[0121] A: The insulation breakdown strength is above 400kV / mm and less than 450kV / mm.

[0122] B: The insulation breakdown strength is above 350kV / mm and less than 400kV / mm.

[0123] C: Insulation breakdown strength is less than 350kV / mm.

[0124] (2) Thermal expansion coefficient

[0125] The obtained insulating material was cut into samples of a given size, and the coefficient of thermal expansion was determined according to IPC TM-650 2.4.24C. ​​The coefficient of thermal expansion was then evaluated according to the following criteria.

[0126] AA: Thermal expansion coefficient less than 80×10 -6 mm / ℃.

[0127] A: The thermal expansion coefficient is 80 × 10⁻⁶ -6 mm / ℃ or higher and less than 100×10 -6 mm / ℃.

[0128] C: Thermal expansion coefficient is 100×10 -6 mm / ℃ or higher.

[0129] (3) Elongation

[0130] The obtained insulating material was cut into samples of a given size, and the elongation was measured using an Autograph manufactured by SHIMAZU Corporation at a tensile speed of 5 mm / min. The elongation was then evaluated according to the following criteria.

[0131] AA: Elongation rate of 5% or more.

[0132] A: Elongation rate of 3% or more but less than 5%.

[0133] B: Elongation rate is 1% or more but less than 3%.

[0134] C: Elongation is less than 1%.

[0135]

[0136] As shown in Table 1, it is clear that the insulating materials of the present invention (Examples 1 and 2) all exhibit good results in terms of voltage resistance, thermal expansion coefficient, and elongation. Therefore, it is confirmed that the insulating materials of the present invention have a low thermal expansion coefficient and excellent voltage resistance.

Claims

1. An insulating material comprising: The first insulating layer formed by the first resin composition, and A second insulating layer is disposed on at least one surface of the first insulating layer and formed of a second resin composition. The first resin composition contains inorganic fillers. The second resin composition does not contain inorganic fillers.

2. The insulating material according to claim 1, wherein, The thickness of the second insulating layer is 0.5 μm or more and 10 μm or less.

3. The insulating material according to claim 1 or 2, wherein, The first resin composition contains 20% by mass and less than 70% by mass of inorganic filler relative to the total solids content of the first resin composition.

4. The insulating material according to claim 1 or 2, wherein, The inorganic filler is silicon dioxide.

5. The insulating material according to claim 1 or 2, wherein, The first resin composition contains polyimide.

6. The insulating material according to claim 1 or 2, wherein, The second insulating layer is disposed on both surfaces of the first insulating layer.

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