JP2026083473A - Insulating resin - Google Patents

Abstract

[Problem] To provide an insulating resin that exhibits a uniform dielectric breakdown field improvement effect throughout the entire film and suppresses film degradation due to heating.
[Solution] The insulating resin comprises (A) a thermoplastic resin which is at least one selected from polycarbonate resin, polyester resin, and polyarylate resin, and (B) a metal diketone complex which is crosslinked by ether bonds and contains one or more β-diketones as ligands.
[Selection Diagram] Figure 1

Description

This disclosure relates to insulating resins. More specifically, it relates to insulating resins containing metal diketone complexes crosslinked by ether bonds.

Film capacitors are incorporated into various electronic devices, using resin films as insulating and dielectric materials. In recent years, the miniaturization and increased functionality of electronic devices have led to higher operating temperatures for electronic components. These electronic components require heat resistance to maintain stable electrical characteristics over long periods even in high-temperature environments. Methods for miniaturizing film capacitors include thinning the dielectric film and reducing the number of layers and turns. However, thinning the dielectric film requires improving its voltage withstand capability. As a method for improving voltage withstand capability, for example, Patent Document 1 proposes using an insulating resin containing a metal diketone complex as an additive in the thermoplastic resin to increase the voltage withstand capability of the dielectric film.

International Publication No. 2021/131654

In the prior art described in Patent Document 1, while insulating resins containing conventional metal diketone complexes as additives improve the dielectric breakdown field, there is a problem in that this effect is not uniformly exerted throughout the entire film. Furthermore, there is a problem in that heating decomposes the molecular chains of the polymer, which is the main component of the dielectric film, leading to deterioration of the dielectric film.

Therefore, there is a need for an insulating resin that uniformly improves the dielectric breakdown field throughout the entire film and suppresses the degradation of the dielectric film even when heated.

The thermoplastic resin of this disclosure comprises (A) a thermoplastic resin and (B) a metal diketone complex crosslinked by an ether bond.

According to this disclosure, it is possible to provide an insulating resin that exhibits a uniform dielectric breakdown field improvement effect throughout the entire film and suppresses film degradation even when heated.

This is a conceptual diagram showing the position of the central metal of a metal diketone complex in a thermoplastic resin film when a conventional metal diketone complex is replaced with a metal diketone complex crosslinked by an ether bond. This is a chemical formula showing the process by which polyarylate resin is decomposed by metal diketone complexes. This graph shows the change in weight-average molecular weight of a dielectric film with respect to heating time. This is a graph showing the measurement results of film BDE using the flat-plate electrode method.

The insulating resin of this embodiment comprises (A) a thermoplastic resin and (B) a metal diketone complex crosslinked by ether bonds.

(A) Thermoplastic resin The thermoplastic resin used in the present invention preferably includes at least one selected from polycarbonate resin, polyester resin, and polyarylate resin, which is one of aromatic polyester resins. Alternatively, copolymers or mixed resins containing any of these multiple types of resins may be used. These resins have excellent heat resistance, and by using these resins, an insulating resin with excellent heat resistance can be obtained.

For each of the resins mentioned above, examples include polymers having repeating units represented by general formula (1) for polycarbonate resin, and general formulas (2) or (3) for polyester resin and polyarylate resin.

In general formula (1), X represents at least one selected from aliphatic divalent groups, cyclic aliphatic divalent groups, and divalent groups represented by general formula (4). In general formula (2) or (3), X represents at least one selected from divalent groups represented by general formula (4). In general formula (3), Y represents a substituted or unsubstituted arylene group.

In general formula (4), R1 and R2 each independently represent a substituted or unsubstituted alkyl group, aryl group, or halogen atom. A represents a single bond, a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms.

Specific examples of X in the above general formulas (1), (2), and (3) include, for example, the divalent group represented by general formulas (5a) to (5n).

(B) Metal diketone complexes crosslinked by ether bonds In the present invention, metal diketone complexes crosslinked by ether bonds are oligomeric metal diketone complexes having a structure in which two or more metal diketone complexes are crosslinked by ether bonds. The metal diketone complex before crosslinking (hereinafter, when simply referred to as a metal diketone complex, it refers to the metal diketone complex before crosslinking) is a complex in which at least one or more ligands containing diketones are coordinated to the central metal. A diketone is a β-dicarbonyl compound having two carbonyl groups at the β position in the molecule, and coordination bonds with the central metal are formed by these two carbonyl groups in the metal diketone complex.

The chemical structure of a metal diketone complex crosslinked by an ether bond according to one embodiment of the present invention is shown below.

(Case 3)

X-[Zr(AcAc) ₂ -CH ₂ CH ₂ OCH ₂ CH ₂ O-] _n (Zr(AcAc) ₂ )-Y... (6)

Here, n is between 1 and _{5. The terminal is either H, -OCH₂CH₂OCH₂CH₂OH , or acetylacetone} .

In formula (6), as a specific example, tetravalent Zr is used as the central metal, with two acetylacetone molecules coordinated to each Zr molecule, and the remaining two linked by ether bonds, thus bridging the metal diketone complex via ether bonds.

For example, when n is 1, it is a dimer with two Zr atoms. When n is 2, it is a trimer with three Zr atoms. Also, although not shown in the chemical formula above, there are cases where both ends are acetylacetone.

When n is 1 or greater, an improvement in the dielectric breakdown field is obtained. When n is 5 or less, good dispersibility in thermoplastic resins is achieved.

Metal diketone complexes cross-linked by ether bonds are not particularly limited as long as the central metal of the metal diketone complex is cross-linked by an ether bond. For example, metal diketone complexes with a structure in which two central metals are linked by an -O-R-O- (where R is an alkylene group such as ethylene, propylene, or butylene, an alkylene group with an internal ether bond) are examples of such complexes.

The metal diketone complex crosslinked by ether bonds is linear, consisting of two or more metal diketone complexes bonded together, but it may also be branched. Mixtures of these are also acceptable. Preferably, from the viewpoint of solubility in thermoplastic resins and the effect of improving the dielectric breakdown field, it is linear and in the form of 2 to 5-mers.

In a metal diketone complex crosslinked by ether bonds, the central metal is at least one selected from Zr, Mo, V, Zn, Ti, and Al. The ether-linked metal diketone complex is dispersed in a thermoplastic resin, and the oxygen capture by the central metal improves the dielectric strength of the insulating resin. Besides the above, other metals such as Cu, Fe, Ni, Ca, Co, Mn, Mg, Ir, In, Cr, or La may also be present as the central metal.

In a metal diketone complex crosslinked by an ether bond, the diketone is not particularly limited as long as it coordinates to the central metal. The ligands of the ether-crosslinked metal diketone complex are the same as those of the original metal diketone complex, and may contain one or more β-diketones as ligands. The diketone is a β-dicarbonyl compound having two carbonyl groups at the β-position within the molecule, as described above. Examples include at least one selected from acetylacetonate (acetylacetone), dibenzoylmethane, acetate acetate, and diethyl malonate. In a metal diketone complex crosslinked by an ether bond, the number of ligands in the original metal diketone complex decreases by the amount used for bonding.

By incorporating a metal diketone complex crosslinked by ether bonds into the above-mentioned thermoplastic resin, the following two effects can be obtained.

(1) The dielectric breakdown field improvement effect can be uniformly exerted throughout the entire film, thereby improving the dielectric breakdown field of the thermoplastic resin film. Conventional metal diketone complex additives tended to aggregate in thermoplastic resins, resulting in uneven distribution of the metal diketone complex within the resin. Consequently, the dielectric breakdown field improvement effect could not be uniformly exerted throughout the thermoplastic resin film. As a result, the dielectric breakdown field of the dielectric film decreased. By using a metal diketone complex crosslinked by ether bonds instead of conventional metal diketone complexes, the metal diketone complex becomes oligomerized. This allows the central metal to be dispersed at a certain distance rather than in a disordered manner, reducing aggregation and sparse areas of the central metal. This reduces localized electric field concentration, and as a result, the overall dielectric breakdown field can be improved.

Figure 1 is a conceptual diagram showing the position of the central metal of a metal diketone complex in a thermoplastic resin film when a conventional metal diketone complex is replaced with a metal diketone complex crosslinked by an ether bond.

In Figure 1, the left-hand diagram shows the state when using a conventional metal diketone complex, while the right-hand diagram shows the state when using a metal diketone complex crosslinked by ether bonds. The black circles represent a single central metal. In the left-hand diagram, the central metals are scattered, resulting in dense and sparse regions of central metals within the thermoplastic resin, indicating poor dispersibility of the metal diketone complex. The right-hand diagram shows a dimer with two central metals, where the central metals are separated by a certain distance, demonstrating a more uniform arrangement of the ether-linked metal diketone complex within the thermoplastic resin. As a result, the conventional localized electric field concentration shown in the left-hand diagram can be prevented, improving the dielectric breakdown field.

(2) Even when the dielectric film is heated, the molecular chains of the polymer, which are the main component of the dielectric film, are less likely to decompose. Conventional additives had molecular structures that readily reacted with the functional groups of the polymer chains (e.g., polyarylate resin) that are the main component of the dielectric film. When the dielectric film was heated, the molecular chains of the polymer, which are the main component of the dielectric film, decomposed, and the dielectric film deteriorated. Since the metal diketone complex crosslinked by ether bonds is a liquid, it disperses easily in thermoplastic resins, eliminating the need to add acetylacetone as a dispersion aid. Therefore, the decomposition of polyarylate resin at high temperatures caused by acetylacetone can be reduced. In addition, because it is a metal diketone complex crosslinked by ether bonds, the steric hindrance of the molecular structure is significant, making it difficult for it to approach the polymer chains, and thus suppressing the progression of the polymer chain decomposition reaction. As a result of these factors, the dielectric film is thought to have become more resistant.

Figure 2 shows the chemical formulas illustrating the decomposition process of polyarylate resin by metal diketone complexes. The decomposition process of polyarylate resin is shown in formulas 8-10. The central metal of the metal diketone complex approaches the carbonyl group of the polyarylate resin (formula 8), Zr bonds to the carbonyl group, and acetylacetone is removed (formula 9). Furthermore, the polyarylate resin at this site decomposes into carboxylic acid and OH groups with water (formula 10). Because the metal diketone complex is crosslinked by ether bonds, steric hindrance makes it difficult for the central metal to approach the carbonyl group of the polyarylate resin, thus inhibiting the decomposition of the polyarylate resin.

Metal diketone complexes cross-linked by ether bonds can be produced by ligand exchange reactions via heating, ligand exchange reactions via ultraviolet irradiation, nucleophilic substitution reactions with weak bases, and ligand exchange reactions via microwaves and ultrasound. While the production method is not limited as long as the structure meets the above criteria, ligand exchange reactions via heating of the metal diketone complex are preferred due to their high ligand exchange efficiency.

The following describes a method for obtaining metal diketone complexes bridged by ether bonds through ligand exchange reactions caused by heating. This method involves exchanging the diketone present in the metal diketone complex with a polyol such as a diol.

The metal diketone complex used has the same central metal and ligand as described in the section on metal diketone complexes bridged by ether bonds. That is, the central metal is at least one selected from Zr, Mo, V, Zn, Ti, and Al. Other central metals may also be present, such as Cu, Fe, Ni, Ca, Co, Mn, Mg, Ir, In, Cr, or La.

The ligand is not particularly limited as long as it coordinates to the central metal mentioned above. The ligand may contain one or more β-diketones. The diketone is a β-dicarbonyl compound having two carbonyl groups at the β-position within the molecule, as described above. Examples include at least one selected from acetylacetonate (acetylacetone), dibenzoylmethane, ethyl acetoethyl, and diethyl malonate.

A metal diketone complex may consist entirely of the same diketone, or it may contain multiple types of diketones. For example, when the central metal is Zr, four diketones coordinate to form a metal diketone complex. Its chemical structure is shown in formula 11.

In formula 11, all four ligands of Zr are acetylacetonates, and the metal diketone complex is Zr acetylacetonate. When multiple types of diketones are coordinated, some of the acetylacetonates may be substituted with other diketones. For example, one of the four acetylacetonates may be substituted with dibenzoylmethane.

The polyol is not limited as long as it can form an ether bond through ligand exchange with a metal diketone complex, but examples include diols and triols. Preferably, it is a diol having 2 to 6 carbon atoms. Specifically, examples include alkylene glycols such as ethylene glycol, propylene glycol, and n-butylene glycol, and alkylene glycols having an ether bond internally, such as diethylene glycol and triethylene glycol.

The metal diketone complex, crosslinked by ether bonds, is preferably reacted using the above-mentioned starting materials under the following conditions.
1. Mix 1 mole of a metal alkoxide complex, such as zirconium tetraalkoxide, with 1.5 moles of a diketone, such as acetylacetone.
2. Heat the mixture and stir at 80-95°C for 24-48 hours to carry out a ligand exchange reaction in which the alkoxide is replaced with a diketone. To further accelerate the ligand exchange reaction, degas the mixture at the same temperature under reduced pressure of -0.06 to -0.02 MPa until no more bubbles (alcohol) are produced. This yields the metal diketone complex described above.
3. Once no more bubbles appear, add 1.5 moles of a diol such as diethylene glycol and stir. Increase the temperature to 100-120°C and continue stirring at the same temperature for 24-48 hours to carry out a ligand exchange reaction in which diketones are exchanged for diols. To further promote the ligand exchange reaction (crosslinking reaction), degas the mixture under reduced pressure of -0.06 to -0.02 MPa at the same temperature until no more bubbles (diketones) appear.
4. The temperature is further increased to 170-220°C (referred to as the crosslinking completion temperature), and the mixture is allowed to stand for 30 minutes to 1 hour to complete the crosslinking reaction, yielding a metal diketone complex crosslinked by ether bonds.

The central metal of the metal diketone complex crosslinked by the ether bond obtained by the above method bonds to both the diketone and the ether bond. The number of diketone and ether bonds, i.e., the state of crosslinking, varies depending on the valence of the central metal, but can be controlled to some extent by the type and amount of polyol added to the metal diketone complex and the reaction temperature. If one ligand is exchanged, mainly dimers are formed; with two ligands, mainly linear trimers are formed; with three to four ligands, branched crosslinking occurs.

Furthermore, the degree of crosslinking and the resulting crosslinked state vary depending on the temperature during the crosslinking completion reaction described in point 4 above. This, in turn, affects the dispersibility in the thermoplastic resin. The preferred crosslinking completion temperature is 170–190°C. At this temperature, a balance is achieved between the degree of crosslinking and dispersibility in the thermoplastic resin, resulting in the most improved dielectric breakdown field.

The insulating resin of this embodiment is obtained by blending (A) a thermoplastic resin with (B) a metal diketone complex crosslinked by ether bonds.
In insulating resins, the content of metal diketone complexes crosslinked by ether bonds is 0.1 to 10% by mass relative to the thermoplastic resin (A). When the content of metal diketone complexes crosslinked by ether bonds is 0.1% by mass or more and 10% by mass or less, the dielectric breakdown field is improved.

The insulating resin of this embodiment may contain various additional components depending on the intended use and the type of electronic component used. For example, when the insulating resin is used as a dielectric film for film capacitors, it may further contain at least one of (C) diketones, alcohols, or carboxylic acids as an additive. Additive (C) can improve the oxidation suppression effect of the thermoplastic resin.

(C) Diketone, alcohol, or carboxylic acid A dielectric film can be obtained, for example, by dissolving a thermoplastic resin and a metal diketone complex crosslinked by ether bonds in a solvent and forming a film of the resin solution. Here, the metal diketone complex crosslinked by ether bonds may have poor dispersibility because it is poorly soluble in the solvent in which the thermoplastic resin is soluble. By adding a diketone, alcohol, or carboxylic acid, it becomes possible to highly disperse the metal diketone complex crosslinked by ether bonds in the thermoplastic resin. When the metal diketone complex crosslinked by ether bonds is highly dispersed in the thermoplastic resin, the probability of oxygen capture by the central metal increases, improving the oxidation suppression effect of the thermoplastic resin and improving the dielectric breakdown field of the dielectric film. In the following, a dielectric film will be described as one example of an application of the insulating resin of this disclosure, but the applications are not limited to this.

(C-1) Diketone The diketone additive may be added separately from the diketone ligand of the metal diketone complex crosslinked by the ether bond described above. The diketone additive may exist as a single compound in the resin solution and in the dielectric film. Some of the diketone additive may form a complex as a ligand of some of the metal diketone complex crosslinked by the ether bond.

The diketone used as an additive can be the same as the diketone used as the ligand described above. For example, a β-diketone or a ketoacetic acid ester may be used. As a β-diketone, at least one of acetylacetonate (acetylacetone) or dibenzoylmethane can be used. As a ketoacetic acid ester, at least one of acetate acetate or diethyl malonate can be used. The diketone used as an additive may be the same compound as the diketone used as the ligand described above, or a different compound may be used. For example, even if acetylacetone is used as the diketone in the metal diketone complex crosslinked by ether bonds, the additive may be the same compound, acetylacetone, or a different compound, dibenzoylmethane. If a different compound is used, the diketone additive may be substituted for some of the ligands of the metal diketone complex crosslinked by ether bonds in the resin solution and dielectric film.

In the dielectric film of this embodiment, the diketone content is, for example, 0.05 to 10% by mass.

(C-2) Alcohol The alcohol is a monoalcohol. By using alcohol as an additive, it becomes possible to highly disperse the metal diketone complex crosslinked by ether bonds in thermoplastic resins. In the resin solution, the alcohol replaces some of the ligands of the metal diketone complex crosslinked by ether bonds. The alcohol-substituted metal diketone complex has higher solubility in the solvent than the unsubstituted complex.

As the additive alcohol, for example, at least one selected from methanol, ethanol, propanol, butanol, hexanol, 2-ethylhexanol, octanol, nonanol, and decanol can be used. In the dielectric film of this embodiment, the alcohol content is, for example, 0.05 to 10% by mass.

(C-3) Carboxylic acid As the carboxylic acid additive, for example, at least one selected from acetic acid, propionic acid, butyric acid, valeric acid, lauric acid, tridecyl acid, palmitic acid, stearic acid, oleic acid, maleic acid, fumaric acid, succinic acid, citric acid, fumaric acid, lactic acid, tartaric acid, benzoic acid, and phthalic acid can be used. In the dielectric film of this embodiment, the alcohol content is, for example, 0.05 to 10% by mass.

The dielectric film of this embodiment can be obtained, for example, as follows: A thermoplastic resin is dissolved in a solvent, and a metal diketone complex crosslinked by ether bonds is added to obtain a resin solution. Further additives may be added as needed. Using this resin solution, a dielectric film can be deposited on a substrate, for example, made of polyethylene terephthalate (PET). Known methods can be used for film deposition; for example, a molding method selected from the doctor blade method, die coater method, and knife coater method can be used.

The dielectric film of this embodiment has a thickness of, for example, 0.1 to 10 μm. Furthermore, the dielectric breakdown field strength of the dielectric film for film capacitors, when measured using the flat-plate electrode method specified in JIS-C2151 section 17.2.2 and the measurement method compliant with JIS C2110-2, is 405 to 430 V/μm, compared to a film without additives (365 V/μm) and a general polypropylene film for film capacitors (316 V/μm).

As a solvent, for example, an organic solvent containing ethylene glycol monopropyl ether, methyl ethyl ketone, methyl isobutyl ketone, xylene, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, dimethylacetamide, cyclohexane, ethylcyclohexane, toluene, chloroform, tetrahydrofuran, or a mixture of two or more solvents selected from these may be used.

The concentration of the thermoplastic resin (resin concentration) in the resin solution is, for example, 1 to 25% by mass. The concentration of the metal diketone complex crosslinked by ether bonds in the resin solution is, for example, 0.015 to 3% by mass. The concentration of the diketone, monoalcohol, or carboxylic acid is, for example, 0.005 to 3% by mass.

The above describes dielectric films as an example of an insulating resin application, but insulating resins can be used in a variety of applications. For example, they can be used as wire and cable coating resins, electronic component encapsulation resins, insulating paints, and insulating adhesives. In the case of wire and cable coating resins, for example, the insulating resin disclosed herein can be molded into strips or sheets and wrapped around the cable surface. It can also be molded into tubes and used by inserting cables through them. In the case of encapsulation resins, for example, entire coils and transformers can be embedded in the insulating resin. Semiconductor elements and electronic components mounted on wiring boards can be coated with the insulating resin, or the insulating resin can be used to fill the gaps between connection terminals. In the case of insulating paints, for example, it can be used as a resin component in various paints such as solvent-based paints and powder coatings, together with colorants and other necessary components. In the case of insulating adhesives, for example, it can be used as a solvent-based adhesive by dissolving the insulating resin in a solvent.

(Examples)
The insulating resin of this disclosure will be described in detail below based on examples. A dielectric film using the insulating resin was used as an example.

(Manufacturing example 1)
23.02 g (0.06 mol) of zirconium tetra-n-butoxide and 9.01 g (0.09 mol) of acetylacetone were mixed and stirred. The mixture was heated to 80°C and stirred at the same temperature for 24 hours. The mixture was then degassed at the same temperature under reduced pressure of -0.06 to -0.02 MPa until no more n-butanol bubbles were produced. Once no more bubbles were produced, 9.55 g (0.09 mol) of diethylene glycol was added and the mixture was heated to 100°C while stirring. After stirring at the same temperature for 24 hours, the mixture was degassed at the same temperature under reduced pressure of -0.06 to -0.02 MPa until no more acetylacetone bubbles were produced. After no more bubbles were produced, the mixture was further heated to 200°C and allowed to stand for 30 minutes to complete the crosslinking reaction, yielding a metal diketone complex (KZ-1) crosslinked by ether bonds.

(Manufacturing example 2)
In the same manner as in Production Example 1, except that the final crosslinking reaction temperature was changed from 200°C to 180°C, a metal diketone complex (KZ-2) crosslinked by ether bonds was obtained.

(Example 1)
Polyarylate was used as the thermoplastic resin, and the metal diketone complex KZ-1, which was crosslinked by ether bonds as prepared in Production Example 1, was used as the metal diketone complex. Polyarylate was dissolved in toluene, and then KZ-1 was dissolved to obtain a resin solution with a thermoplastic resin concentration of 12% by mass. Resin solutions with KZ-1 concentrations of 0.3% by mass and 3.0% by mass were also obtained.

(Example 2)
Resin solutions with concentrations of 0.3% by mass and 3.0% by mass of KZ-2 were obtained in the same manner as in Example 1, except that the ether-linked metal diketone complex KZ-2, prepared in Preparation Example 2, was used instead of the ether-linked metal diketone complex KZ-1.

(Comparative Example 1)
Polyarylate was used as the thermoplastic resin, and a resin solution with a thermoplastic resin concentration of 12% by mass was obtained.

(Comparative Example 2)
In the same manner as in Example 1, a resin solution was obtained with a thermoplastic resin concentration of 12% by mass and a zirconium acetylacetone complex concentration of 3.0% by mass, except that a zirconium acetylacetone complex was used instead of the metal diketone complex KZ-1 crosslinked by ether bonds.

(Rating 1)
The above resin solution was applied to a polyethylene terephthalate (PET) substrate using a coater, and the solvent was removed by drying at 125°C for 3 hours to produce a dielectric film with a thickness of 2.0 μm. These dielectric films were heated under reduced pressure at 160°C, and removed after 0 hours, 48 hours, and 140 hours. The weight-average molecular weight was measured to investigate the change in weight-average molecular weight with respect to heating time. The results are shown in Figure 3.

Figure 3 is a graph showing the change in weight-average molecular weight of a dielectric film with respect to heating time. The horizontal axis represents heating time (hrs), and the vertical axis represents the weight-average molecular weight. The weight-average molecular weight was measured by gel permeation chromatography.

The weight-average molecular weight of the unadded sample gradually decreased, but the sample with 0.3 wt% KZ-1 and KZ-2 added showed almost no change with heating time. Furthermore, the sample with 3.0 wt% zirconium acetylacetone added decreased from approximately 86,000 to approximately 65,000 immediately after heating, decreased to approximately 42,000 after 48 hours of heating, and to approximately 39,000 after 140 hours. In contrast, the sample with 3.0 wt% KZ-1 and KZ-2 added decreased from approximately 86,000 to approximately 60,000 immediately after heating, but only decreased to approximately 53,000 after 48 hours of heating and to approximately 49,000 after 140 hours. In other words, the solution with 3.0 wt% KZ-1 and KZ-2 added showed a significantly smaller decrease in weight-average molecular weight compared to the solution with 3.0 wt% zirconium acetylacetone added, confirming that KZ-1 and KZ-2 have an effect in suppressing the decomposition of thermoplastic resins.

(Example 3)
In the same manner as in Example 1, polyarylate was used as the thermoplastic resin, and metal diketone complexes KZ-1 and KZ-2, which were crosslinked by ether bonds as prepared in Production Examples 1 and 2, were used as the metal diketone complexes. The polyarylate was dissolved in toluene, and then KZ-1 and KZ-2 were dissolved to obtain a resin solution with a thermoplastic resin concentration of 12% by mass. Resin solutions with various concentrations of KZ-1 and KZ-2 were obtained.

(Rating 2)
The above-mentioned resin solutions were applied to a polyethylene terephthalate (PET) substrate using a coater, dried at 125°C for 3 hours to remove the solvent, and a dielectric film with a thickness of 2.0 μm was fabricated.
The BDE (dielectric breakdown field strength) of the dielectric film was measured.
The measurement method followed the planar electrode method specified in JIS-C2151 section 17.2.2 and JIS C2110-2, with 24 points measured for each film.
The test was conducted in a dry air environment with a dew point of approximately -30°C. The results are shown in Figure 4.

Figure 4 shows graphs of the BDE measurement results for films using the planar electrode method. The graph on the left is for films containing KZ-1, and the graph on the right is for films containing KZ-2. The horizontal axis shows the amount of KZ-1 and KZ-2 added to the polyarylate resin (wt%), and the vertical axis shows the BDE (V/μm).

In all cases, those with 10.0 wt% or less of the additive showed higher BDE values than those without the additive. This was the result of measurements at 24 points on the film, indicating that the dielectric breakdown field improvement effect was uniformly exerted throughout the entire film. Although not shown in this graph, the BDE value of the film with 3.0 wt% zirconium acetylacetone added was 392 V/μm. From the graph, KZ-2 (slightly less than 430 V/μm) and KZ-1 (405 V/μm) showed even higher BDE values. This indicates that metal diketone complexes cross-linked by ether bonds exhibit a higher dielectric breakdown field improvement effect than uncross-linked metal diketone complexes.

Furthermore, as mentioned above, KZ-2 (slightly less than 430 V/μm) shows a higher BDE value than KZ-1 (405 V/μm). However, since the crosslinking completion temperature for KZ-2 (180°C) is lower than that of KZ-1 (200°C), it is thought that if the temperature is too high, crosslinking will proceed too much, reducing dispersibility in the thermoplastic resin. This suggests that 180°C is a balanced crosslinking completion temperature.

Based on the above, it was confirmed that the insulating resin of this disclosure can uniformly exhibit a dielectric breakdown field improvement effect throughout the entire film, and that film degradation is suppressed even when heated.

This disclosure can be implemented in the following embodiments (1) to (11).

(1) An insulating resin comprising (A) a thermoplastic resin and (B) a metal diketone complex crosslinked by an ether bond.

(2) (B) The insulating resin according to embodiment (1) above, wherein the central metal of the metal diketone complex crosslinked by ether bonds is one of Zr, Mo, V, Zn, Ti, and Al.

(3) (B) The insulating resin according to embodiment (1) or (2) above, wherein the ligand of the metal diketone complex crosslinked by an ether bond contains one or more β-diketones.

(4) (B) The insulating resin according to embodiment (3) above, wherein the ligand of the metal diketone complex crosslinked by an ether bond comprises at least one selected from acetylacetonate, dibenzoylmethane, ethyl acetoethyl, and diethyl malonate.

(5) (C) An insulating resin according to any one of embodiments (1) to (4) above, further comprising at least one of a diketone, an alcohol, or a carboxylic acid.

(6) (C) The diketone is a β-diketone or a ketoacetic acid ester, as described in embodiment (5) above, for the insulating resin.

(7) The insulating resin according to embodiment (6), wherein the β-diketone comprises at least one of acetylacetonate or dibenzoylmethane, and the ketoacetic acid ester comprises at least one of ethyl acetoacetate or diethyl malonate.

(8) The insulating resin according to any one of the above embodiments (1) to (7), wherein the (C) alcohol is at least one selected from methanol, ethanol, propanol, butanol, hexanol, and 2-ethylhexanol, octanol, nonanol, and decanol.

(9) (A) The thermoplastic resin is an insulating resin according to any one of the above embodiments (1) to (8), wherein the glass transition temperature is 50°C or higher.

(10) (A) An insulating resin according to any one of the above embodiments (1) to (9), wherein the thermoplastic resin is at least one selected from polycarbonate resin, polyester resin, and polyarylate resin.

(11) (D) An insulating resin according to any one of the above embodiments (1) to (10), comprising toluene or tetrahydrofuran as a solvent.

Claims (11)

An insulating resin comprising (A) a thermoplastic resin and (B) a metal diketone complex crosslinked by ether bonds. (B) The insulating resin according to claim 1, wherein the central metal of the metal diketone complex crosslinked by ether bonds is one of Zr, Mo, V, Zn, Ti, and Al. (B) The insulating resin according to claim 1 or 2, wherein the ligand of the metal diketone complex crosslinked by ether bonds contains one or more β-diketones. (B) The insulating resin according to claim 3, wherein the ligand of the metal diketone complex crosslinked by an ether bond comprises at least one selected from acetylacetonate, dibenzoylmethane, ethyl acetoethyl, and diethyl malonate. (C) The insulating resin according to claim 1, further comprising at least one of a diketone, an alcohol, or a carboxylic acid. (C) The insulating resin according to claim 5, wherein the diketone is a β-diketone or a ketoacetic acid ester. The insulating resin according to claim 6, wherein the β-diketone comprises at least one of acetylacetonate or dibenzoylmethane, and the ketoacetic acid ester comprises at least one of ethyl acetoacetate or diethyl malonate. (C) The insulating resin according to claim 1, wherein the alcohol is at least one selected from methanol, ethanol, propanol, butanol, hexanol, and 2-ethylhexanol, octanol, nonanol, and decanol. (A) The insulating resin according to claim 1, wherein the thermoplastic resin has a glass transition temperature of 50°C or higher. (A) The insulating resin according to claim 1, wherein the thermoplastic resin is at least one selected from polycarbonate resin, polyester resin, and polyarylate resin. (D) The insulating resin according to claim 1, comprising toluene or tetrahydrofuran as a solvent.