INSULATING FILM OR DIELECTRIC FILM

Abstract

An object of the present disclosure is to provide an insulating film or dielectric film comprising a fluoropolymer and having electrical insulation and hardness. The present disclosure relates to an insulating film or dielectric film comprising a fluoropolymer, wherein the fluoropolymer comprises, as a main component, a monomer unit represented by formula (1):

##STR00001##

wherein
R.sup.1 to R.sup.4 are each independently a fluorine atom, a fluoroalkyl group, or a fluoroalkoxy group.

Claims

1. An insulating film or dielectric film comprising a fluoropolymer, wherein the fluoropolymer comprises, as a main component, a monomer unit represented by formula (1): ##STR00012## wherein R.sup.1 to R.sup.4 are each independently a fluorine atom, a fluoroalkyl group, or a fluoroalkoxy group.

2. The insulating film or dielectric film according to claim 1, wherein the fluoropolymer further comprises a fluoroolefin unit.

3. The insulating film or dielectric film according to claim 2, wherein the fluoroolefin unit is at least one member selected from the group consisting of a fluorine-containing perhaloolefin unit, a vinylidene fluoride unit, a trifluoroethylene unit, a pentafluoropropylene unit, and a 1,1,1,2-tetrafluoro-2-propylene unit.

4. The insulating film or dielectric film according to claim 3, wherein the fluorine-containing perhaloolefin unit is at least one member selected from the group consisting of a chlorotrifluoroethylene unit, a tetrafluoroethylene unit, a hexafluoropropylene unit, a perfluoro(methyl vinyl ether) unit, a perfluoro(ethyl vinyl ether) unit, a perfluoro(propyl vinyl ether) unit, a perfluoro(butyl vinyl ether) unit, and a perfluoro(2,2-dimethyl-1,3-dioxol) unit.

5. The insulating film or dielectric film according to claim 2, wherein the fluoroolefin unit is at least one member selected from the group consisting of a chlorotrifluoroethylene unit, a tetrafluoroethylene unit, a hexafluoropropylene unit, a perfluoro(methyl vinyl ether) unit, and a perfluoro(propyl vinyl ether) unit.

6. The insulating film or dielectric film according to claim 1, wherein the film has an average film thickness of 10 nm or more.

7. The insulating film or dielectric film according to claim 1, wherein the film has a relative permittivity at 6 GHz of 1.5 or more and 2.5 or less; a dielectric dissipation factor at 6 GHz of 0.0002 or less; an indentation elastic modulus of 2.5 GPa or more and 10 GPa or less; an indentation hardness of 250 N/mm.sup.2 or more and 1000 N/mm.sup.2 or less; and a glass transition temperature of 110° C. or higher.

8. The insulating film or dielectric film according to claim 7, wherein the film has a dielectric dissipation factor at 6 GHz of 0.00005 or more and 0.0002 or less.

9. The insulating film or dielectric film according to claim 1, wherein the film has a volume resistivity of 1.0×10.sup.15Ω.Math.cm or more.

10. The insulating film or dielectric film according to claim 1, wherein the film has a total light transmittance of 90% or more.

11. The insulating film or dielectric film according to claim 1, wherein the film is for an electrical article or for a signal wire covering material.

12. The insulating film or dielectric film according to claim 11, wherein the film is for an electrical article, and the electrical article is a semiconductor.

13. The insulating film or dielectric film according to claim 11, wherein the film is for an electrical article, and the electrical article is a printed circuit board.

14. An electrical article comprising the insulating film or dielectric film of claim 1.

15. A coating agent for forming the insulating film or dielectric film of claim 1, the coating agent comprising a fluoropolymer and an aprotic solvent, wherein the fluoropolymer comprises, as a main component, a monomer unit represented by formula (1): ##STR00013## wherein R.sup.1 to R.sup.4 are each independently a fluorine atom, a fluoroalkyl group, or a fluoroalkoxy group.

16. The coating agent according to claim 15, wherein the content of the fluoropolymer is 20 mass % or more and 65 mass % or less based on the total mass of the coating agent.

17. The coating agent according to claim 15, wherein the aprotic solvent is at least one solvent selected from the group consisting of perfluoroaromatic compounds, perfluorotrialkylamines, perfluoroalkanes, hydrofluorocarbons, perfluorocyclic ethers, hydrofluoroethers, and olefin compounds containing at least one chlorine atom.

18. The coating agent according to claim 15, wherein the aprotic solvent is at least one hydrofluoroether.

Description

EXAMPLES

[0259] Embodiments of the present disclosure are described in more detail below with Examples; however, the present disclosure is not limited to these.

[0260] The symbols and abbreviations in the Examples are used with the following meanings.

Initiator solution (1): a methanol solution containing 50 mass % di-n-propyl peroxydicarbonate (10-hour half-life temperature: 40° C.)
Fluoropolymer (1-11): a polymer composed of unit (1-11) Mw: mass average molecular weight

GPC Analysis Method (Measurement of Mass Average Molecular Weight of Fluoropolymer)

Sample Preparation Method

[0261] A polymer was dissolved in perfluorobenzene to prepare a 2 mass % polymer solution, and the polymer solution was passed through a membrane filter (0.22 μm) to obtain a sample solution.

Measurement Method

[0262] Standard sample for measurement of molecular weight: polymethyl methacrylate
Detection method: RI (differential refractometer)

Confirmation of Polymer Solubility

[0263] Whether the polymer was dissolved in the liquid was determined as follows.

[0264] Each of the prepared liquids was visually observed, and when no undissolved polymer was observed and the entire liquid flowed uniformly at room temperature, it was determined that the polymer was dissolved.

Average Film Thickness

[0265] The average film thickness was defined as the average value of thickness measured 5 times with a micrometer. When measuring the thickness of a film itself was difficult, such as when a film formed on a base material of a substrate etc. could not be peeled off, the average film thickness was calculated by measuring the thickness of the base material before film formation and the thickness of the base material after film formation (the sum of the film thickness and the base material thickness) 5 times each with a micrometer, and subtracting the average value of the thickness before film formation from the average value of the thickness after film formation.

Relative Permittivity and Dielectric Dissipation Factor

[0266] The relative permittivity and dielectric dissipation factor at frequencies of 10, 20, 28, 60, and 80 GHz were determined by a split-cylinder resonator method. A resonator corresponding to each frequency produced by Kanto Electronic Application and Development Inc. was used as the split cylinder, and a Keysight N5290A was used as the network spectrum analyzer. For measurement at 10 GHz, a film with a thickness of 100 82 m, a width of 62 mm, and a length of 75 mm was used as the sample to be measured, and for measurement at 20, 28, 60, and 80 GHz, a film with a thickness of 100 μm, a width of 34 mm, and a length of 45 mm was used as the sample to be measured. The measurement temperature was 25° C.

[0267] The relative permittivity and dielectric dissipation factor at 6 GHz were measured using a cavity resonator produced by Kanto Electronic Application and Development Inc. The sample was formed into a cylinder shape (2 mm dia.×110 mm).

[0268] The real part of the complex relative permittivity was determined from the change in the resonance frequency indicated by the cavity resonator, and the imaginary part of the complex relative permittivity was determined from the change in the Q value. The relative permittivity and dielectric dissipation factor were then calculated according to the following formulas.

[00002]${\epsilon }_r^{*}={\epsilon }_r^{\prime }-j{\epsilon }_r^{″}{\epsilon }_r^{\prime }={\epsilon }_r{\epsilon }_r^{″}={\epsilon }_r\tan \delta \tan \delta =\frac{{\epsilon }_r^{″}}{{\epsilon }_r^{\prime }}$

In the formulas, ε.sub.r* represents a complex relative permittivity, ε.sub.r′ represents a relative permittivity, ε.sub.r″ represents a relative dielectric loss factor, and tan δ represents a dielectric dissipation factor.

[0269] The relative permittivity and dielectric dissipation factor at 1 kHz were determined as follows.

[0270] Aluminum was deposited on both sides of each film in vacuo to make a sample. The static capacitance and dielectric dissipation factor of this sample were measured at a frequency of 1 kHz at 25° C. with an LCR meter. The dielectric permittivity was calculated from each static capacitance obtained.

Volume Resistivity

[0271] Each sample was sandwiched between a lower electrode and an upper electrode provided in a thermostatic chamber. An electric field of 50 V/μm was applied to each film with a digital super insulation/microcurrent meter (DSM-8104; produced by Hioki Electric Co., Ltd.), the leakage current was measured, and the volume resistivity at 25° C. was calculated. Specifically, the volume resistivity is a value determined by the method described in a specific example of the present disclosure.

Indentation Hardness and Indentation Elastic Modulus

[0272] The indentation hardness (H.sub.IT; indentation hardness) of each sample was measured using an ENT-2100 ultra-fine hardness tester produced by Nanotec Corporation. The indentation elastic modulus was also measured at the same time. The test was performed by adjusting the indentation depth to be 1/10 or less of the thickness.

Measurement Method for Total Light Transmittance and Haze

[0273] The total light transmittance and haze were measured using an NDH 70005PII haze meter (produced by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136 (haze value) and JIS K7361-1 (total light transmittance). A film with an average film thickness of 100 μm was used as the sample to be measured. The sample was produced by coating a glass plate with a coating agent such that the thickness after drying was 100 μm, performing drying at 80° C. for 4 hours, and peeling off the resulting dried film with an average film thickness of 100 μm from the glass plate.

Transmittance at Each Wavelength

[0274] The transmittance of each sample (film with an average film thickness of 100 μm) at a specific wavelength was measured using a Hitachi U-4100 spectrophotometer. An integrating sphere detector was used as the detector.

Water Absorption (24° C.)

[0275] The weight of a sample that had been thoroughly dried beforehand was measured and set as W0. The sample was then completely immersed in 24° C. water whose mass was 100 times the mass of W0 or more. The weight of the sample after 24 hours was measured and set as W24. The water absorption was determined from the following formula.

Water absorption rate (%)=100×(W24−W0)/W0

Water Absorption (60° C.)

[0276] The weight of a sample that had been thoroughly dried beforehand was measured and set as W0, and then completely immersed in 60° C. water whose mass was 100 times the mass of W0 or more. The weight of the sample after 24 hours was measured and set as W24. The water absorption was determined from the following formula.

Water absorption rate (%)=100×(W24−W0)/W0

Tensile Elastic Modulus

[0277] A sample (length: 30 mm, width: 5 mm, thickness: 0.1 mm) was measured with a DVA220 dynamic viscoelasticity measuring device produced by IT Measurement Control Co., Ltd. under the conditions of a tensile mode, a grip width of 20 mm, a measurement temperature of 25° C. to 150° C., a temperature-increasing rate of 2° C./min, and a frequency of 1 Hz. The elastic modulus value at 25° C. was defined as a tensile elastic modulus.

Tensile Strength

[0278] The tensile strength of a film was measured using an autograph AGS-100NX produced by Shimadzu Corporation. The sample was cut to a dumbbell shape 5B as stated in JIS K7162. The measurement was performed under the conditions of a chuck-to-chuck distance of 12 mm, a crosshead speed of 1 ram/min, and room temperature.

Thermal Decomposition Temperature

[0279] The temperatures at which the mass loss percentage of a sample became 0.1% and 5% were measured at a temperature-increasing rate of 10° C./minute in an air atmosphere using a thermogravimetric-differential thermal analyzer (Hitachi High-Tech Science Corporation; STA7200).

Glass Transition Temperature (Tg)

[0280] The temperature was increased (first run), decreased, and then increased (second run) at 10° C./minute in the temperature range of 30° C. or higher and 200° C. or lower using a DSC (differential scanning calorimeter; Hitachi High-Tech Science Corporation, DSC7000). The midpoint of the endothermic curve in the second run was determined to be the glass transition temperature (° C.).

Coefficient of Linear Expansion

[0281] A thermomechanical analyzer (TMA8310; produced by Rigaku Corporation) was set in a tensile mode with a chuck-to-chuck distance of 15 mm. A sample cut to a size of 5 mm in width and 20 mm in length was held with the chucks, and the temperature was increased from room temperature to 150° C. (1st up), decreased to room temperature, and then increased to 150° C. (2nd up) at 2° C./minute. The average coefficient of linear expansion at 25° C. or higher and 80° C. or lower in the 2nd up was determined and defined as the coefficient of linear expansion.

Preparation Example 1: Polymerization of Fluoropolymer Comprising Unit (1-11) as Main Component and Production of Polymer Solution (Polymerization Reaction Mixture)

[0282] The monomer (M1-11) (10 g), ethyl nonafluorobutyl ether (20 g) as a solvent, and the initiator solution (1) (0.041 g) were placed in a 50-mL glass container, and a polymerization reaction was then performed for 20 hours while the mixture was heated such that the internal temperature was 40° C., thereby producing a fluoropolymer (1-11) (9.0 g, Mw: 97533). The fluoropolymer in the polymerization reaction mixture was dissolved, and the concentration was 31 mass %.

[0283] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120° C. after the completion of the polymerization reaction.

Preparation Example 2: Polymerization of Fluoropolymer Comprising Unit (1-11) as Main Component and Production of Polymer Solution (Polymerization Reaction Mixture)

[0284] The monomer (M1-11) (10 g), perfluorotripropylamine (10 g) as a solvent, and the initiator solution (1) (0.052 g) were placed in a 20-mL glass container, and a polymerization reaction was then performed for 20 hours while the mixture was heated such that the internal temperature was 40° C., thereby producing a fluoropolymer (1-11) (9.5 g, Mw: 213475). The fluoropolymer in the reaction mixture was dissolved, and the concentration was 49 mass %.

[0285] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120° C. after the completion of the polymerization reaction.

Preparation Example 3

[0286] Ethyl nonafluorobutyl ether was further added to the polymerization reaction mixture obtained in Preparation Example 1 to obtain a solution of fluoropolymer at a concentration of 10 mass %.

Comparative Preparation Example 1: Production of Teflon (Registered Trademark) Solution

[0287] Teflon (registered trademark) AF1600 (2.0 g, Mw: 229738), which is a commercially available fluoropolymer, was added to methyl nonafluorobutyl ether (8.0 g), and the mixture was stirred at room temperature for 2 days to prepare a uniformly dissolved solution.

[0288] Teflon (registered trademark) AF1600 contains the monomer unit represented by the following formula (10) and the monomer unit represented by the following formula (20) in a ratio of 65:35 (molar ratio).

##STR00011##

Example 1

[0289] The polymerization reaction mixture obtained in Preparation Example 1 was directly used as a coating agent, and a silicon wafer was produced as follows.

[0290] The silicon wafer was spin-coated with the coating agent at a spin speed of 500 rpm for 2 seconds using a spin coater, and further spin-coated at 1000 rpm for 25 seconds. Subsequently, heating was performed at 80° C. for 2 hours, thereby obtaining a silicon wafer having a uniform, transparent fluoropolymer (1-11) film (average film thickness: 0.85 um) famed thereon.

Example 2

[0291] The polymerization reaction mixture obtained in Preparation Example 1 was directly used as a coating agent, and a film was produced as follows.

[0292] A glass substrate was coated with the coating agent such that the thickness after drying was 100 μm, and drying was performed at 80° C. for 4 hours to form a transparent film. The film was then peeled off from the glass plate, thereby obtaining a fluoropolymer (1-11) film with an average film thickness of 100 μm. The electrical properties of the obtained film were measured and the following results were obtained.

Relative permittivity (1 kHz): 2.2
Dielectric dissipation factor (1 kHz): 0.0001
Relative permittivity (6 GHz): 1.99
Dielectric dissipation factor (6 GHz): 0.00012
Volume resistivity: 4×10.sup.13Ω.Math.cm

[0293] The following items of the obtained film were also measured. The results are shown below.

Indentation hardness: 420 N/mm.sup.2
Indentation elastic modulus: 3.3 GPa
Water absorption (24° C.): 0.00%
Water absorption (60° C.): 0.09%
Tensile modulus: 3.1 GPa
Tensile strength: 20.9 MPa
Thermal decomposition temperature (0.1%): 294.5° C.
Thermal decomposition temperature (5%): 439.4° C.
Glass transition temperature: 129° C.
Coefficient of linear expansion: 80 ppm
Total light transmittance: 96%

Haze: 0.34%

Transmittance (193 nm): 74.4%

Transmittance (550 nm): 94.6%.

Example 3

[0294] The polymerization reaction mixture obtained in Preparation Example 1 was directly used as a coating agent, and a film was produced as follows.

[0295] A glass substrate was coated with the coating agent such that the thickness after drying was 50 μm, and drying was performed at 80° C. for 4 hours to form a transparent film. The film was then peeled off from the glass plate, thereby obtaining a fluoropolymer (1-11) film with an average film thickness of 50 μm. The electrical properties, indentation hardness, and indentation elastic modulus of the obtained film were measured, and the following results were obtained.

Relative permittivity (1 kHz): 2.3
Dielectric dissipation factor (1 kHz): 0.0005
Relative permittivity (6 kHz): 1.99
Dielectric dissipation factor (6 GHz): 0.00011
Specific induced resonance (10 GHz): 2.02
Dielectric dissipation factor (10 GHz): 0.00015
Relative permittivity (20 GHz): 2.11
Dielectric dissipation factor (20 GHz): 0.00016
Relative permittivity (28 GHz): 2.09
Dielectric dissipation factor (28 GHz): 0.00019
Relative permittivity (60 GHz): 2.12
Dielectric dissipation factor (60 GHz) 0.00036
Relative permittivity (80 GHz): 2.10
Dielectric dissipation factor (80 GHz): 0.00031
Volume resistivity: 9×10.sup.13Ω/cm

Hardness: 415 N/mm.SUP.2

Elasticity: 3.5 GPa

[0296] Other items were also measured as in Example 1, and the results were similar to those of Example 1.

Example 4

[0297] The polymerization reaction mixture obtained in Preparation Example 3 was directly used as a coating agent, and a film was produced as follows.

[0298] A glass substrate was coated with the coating agent such that the thickness after drying was 25 pm, and drying was performed at 80° C. for 4 hours to form a transparent film. The film was then peeled off from the glass plate, thereby obtaining a fluoropolymer (1-11) film having an average film thickness of 25 μm. The electrical properties of the obtained film were measured. The results are shown below.

Relative permittivity (1 kHz): 2.3
Dielectric dissipation factor (1 kHz): 0.0003
Relative permittivity (6 GHz): 1.99
Dielectric dissipation factor (6 GHz): 0.00011
Volume resistivity 1×10.sup.16Ω.Math.cm

Comparative Example 1

[0299] A Teflon (registered trademark) AF1600 film having an average film thickness: 50 μm) was formed in the same manner as in Example 1, except that the fluoropolymer solution obtained in Comparative Preparation Example 1 was used as the coating agent. The electrical properties, indentation hardness, and indentation elastic modulus of the obtained film were measured. The results are as follows.

Relative permittivity (1 kHz): 1.93
Dielectric dissipation factor (1 kHz): 0.0002
Relative permittivity (6 GHz): 1.99
Dielectric dissipation factor (6 GHz): 0.00025
Indentation hardness: 145 N/mm.sup.2
Indentation elastic modulus: 2 GPa

Reference Example 1

[0300] The electrical properties, indentation hardness, and indentation elastic modulus of a Neoflon FEP NF-0100 film produced by Daikin Industries, Ltd. were measured. The results are as follows.

Relative permittivity (6 GHz): 1.99
Dielectric dissipation factor (6 GHz): 0.00031
Indentation hardness: 9.7 N/mm.sup.2
Indentation elastic modulus: 0.02 GPa