JP4606191B2 - Manufacturing method of laminate - Google Patents

Description

  The present invention relates to a method for manufacturing a metal laminated board that is suitably used for an electric wiring circuit board such as a flexible printed circuit board.

Conventionally, vacuum deposition methods, sputtering methods, CVD methods, plating methods, metal paste methods, and the like are known as methods for forming a metal thin film on a substrate. The vacuum deposition method, the sputtering method, and the CVD method all require an expensive vacuum apparatus, and all have a problem that the film forming speed is low.
According to the plating method, it is possible to form a metal thin film on a conductive substrate relatively easily. However, when forming on an insulating substrate, it is necessary to form a conductive layer first. Therefore, there is a problem that the process becomes complicated. In addition, since the plating method uses a reaction in a solution, a large amount of waste liquid is produced as a by-product, and there is a problem that this waste liquid treatment requires a lot of labor and cost, and the adhesion of the resulting metal thin film to the substrate Is not enough.

The metal paste method is a method in which a metal thin film is obtained by applying a solution in which a metal filler is dispersed onto an insulating substrate, and performing heat treatment. According to this method, there is an advantage that a special apparatus such as a vacuum apparatus is not required and the process is simple. However, in order to melt the metal filler, a high temperature of 1000 ° C. or higher is usually required. Accordingly, the base material is limited to those having heat resistance such as a ceramic base material, and there is a problem that the base material is damaged by heat or the base material is easily damaged by residual stress generated by heating. Furthermore, the adhesion of the resulting metal thin film to the substrate is not sufficient.
On the other hand, a technique for reducing the firing temperature of the metal paste by reducing the particle size of the metal filler is known. For example, Patent Document 1 uses a dispersion in which metal fine particles having a particle size of 100 nm or less are dispersed. A method of forming a metal thin film directly on an insulating substrate is disclosed. However, the adhesion of the metal thin film prepared by this method to the insulating substrate is not sufficient. Furthermore, the method for producing metal particles of 100 nm or less used here is a method for rapidly cooling metal vapor volatilized in a low-pressure atmosphere, so that mass production is difficult and therefore the cost of the metal filler is increased. Have a problem.

  A method of forming a metal thin film directly on an insulating substrate using a metal oxide paste in which a metal oxide filler is dispersed is also known. Patent Document 2 discloses a method of heating a metal oxide paste containing a crystalline polymer and dispersing a metal oxide having a particle size of 300 nm or less to decompose the crystalline polymer to obtain a metal thin film. Yes. However, in this method, it is necessary to disperse a metal oxide of 300 nm or less in the crystalline polymer in advance, and in addition to requiring a great effort, in order to decompose the crystalline polymer, 400 ° C. to A high temperature of 900 ° C. is required. Therefore, the base material which can be used requires the heat resistance more than the temperature, and there exists a problem that the kind has a restriction | limiting. Also, the adhesion of the resulting metal thin film to the substrate is not sufficient.

As a method of manufacturing a metal thin film that solves these problems, the present applicant has already applied a dispersion in which an inexpensive metal oxide filler is dispersed on a substrate, and then applied the metal thin film by heat treatment at a relatively low temperature. The method of obtaining is disclosed (Patent Document 3). With this technology, it is possible to easily form a thin metal film such as thin copper, etc. on the substrate, and it can also be used as a flexible circuit board material by forming a copper film on a polyimide resin film, etc. Is possible.
Japanese Patent No. 2561537 Japanese Patent Laid-Open No. 5-98195 International Patent Publication No. 03-051562 pamphlet

  The subject of this invention is providing the manufacturing method of a laminated body which has the electroconductivity comparable as the conventional metal thin film, and has still higher adhesiveness with a board | substrate. Another object of the present invention is to provide a method for producing a laminate by forming a metal thin film on a substrate without requiring a high temperature.

As a result of diligent investigations to solve the above problems, the present inventors have completed the present invention.
That is, the present invention is as follows.
1. After applying a solution of a non-thermoplastic polyimide resin precursor on an insulating substrate, a part of the precursor is converted into a non-thermoplastic polyimide resin by performing a heat treatment for solvent removal and dehydration condensation reaction, A step (1) of forming a layer composed of a non-thermoplastic polyimide resin and a non-thermoplastic polyimide resin precursor on an insulating substrate, and heating the primary particle diameter on the layer to be 200 nm or less; By applying a dispersion containing metal thin film precursor fine particles that are fused to each other by heat treatment, the remaining precursor is converted into a non-thermoplastic polyimide resin, and from the non-thermoplastic polyimide resin. A step (2) of forming a metal thin film layer on the layer, comprising :
The metal thin film precursor fine particles are cuprous oxide fine particles, the dispersion is a polyhydric alcohol, a linear aliphatic polyether compound in which one terminal is an alkyl group and the other terminal is a hydroxyl group. Including
A method for producing a laminate, wherein the heat treatment is performed in an inert atmosphere .
2. Claim 1, characterized in that in the heat treatment of the step (2), above the glass transition temperature of the non-thermoplastic polyimide resin. The manufacturing method of the laminated body of description.
3. Item 1. The length of the terminal alkyl group of the linear aliphatic polyether compound is 1 to 4 carbon atoms. Or 2. The manufacturing method of the laminated body as described in 1 ..
4). The polyhydric alcohol is 5 to 70% by weight with respect to the total amount of the dispersion, the linear aliphatic polyether compound is 0.1 to 70% by weight with respect to the total amount of the dispersion, and the metal thin film precursor Item 1. The weight ratio of the linear aliphatic polyether compound to the body fine particles is 0.01 to 10. ~ 3. The manufacturing method of the laminated body in any one of.

  The laminate obtained by the method of the present invention has conductivity as high as that of a conventional metal thin film, and the adhesion between the metal thin film and the substrate is further enhanced. In addition, according to the present invention, it is possible to provide a method of manufacturing a laminate by forming a metal thin film on a substrate without requiring a high temperature. When the present invention is used, the thickness of the metal can be arbitrarily controlled, and a thin metal film can be easily formed. Therefore, it can be suitably used as a flexible circuit board material or the like. Furthermore, the above-mentioned problems in the prior art when forming a metal thin film on a substrate are solved.

The present invention is described in detail below.
A laminate in which a metal thin film having a structure in which metal fine particles having a particle diameter of 200 nm or less are fused to each other is laminated on an insulating substrate having a non-thermoplastic polyimide resin layer on the surface by the laminate production method of the present invention. can get.
The insulating substrate used in the laminated body of the present invention may be any insulating substrate as long as it is normally used in an electric wiring circuit board, and preferably has a surface resistance value of 10 ¹³ Ωcm or more. is there.
As the insulating substrate, either an organic material or an inorganic material may be used, but a heat-resistant substrate is preferable because a heat treatment is performed when forming the metal thin film. For example, inorganic materials such as ceramics and glass, and heat resistant resins such as polyimide films are preferably used.

In the present invention, a polyimide film particularly preferably used as an insulating substrate is a film obtained by condensing pyromellitic acid or a pyromellitic acid derivative and an aromatic diamine, for example, Kapton (registered trademark, Toray DuPont Co., Ltd.). Made by condensing biphenyltetracarboxylic acid or biphenyltetracarboxylic acid derivative with an aromatic diamine, such as Upilex (registered trademark, Ube Industries Ltd.) Etc.). Although the film thickness of a polyimide film is not limited, Usually, about 25-100 micrometers can be suitably selected and used according to a use.
In the present invention, such a substrate may be used as it is, but in order to improve the adhesion to the non-thermoplastic polyimide resin formed on the substrate, degreasing treatment, chemical treatment with acid or alkali, heat treatment, plasma Surface treatment such as treatment, corona discharge treatment, and sandblast treatment may be performed.

In the present invention, after applying a solution of a non-thermoplastic polyimide resin precursor on an insulating substrate, heat treatment for solvent removal and dehydration condensation reaction is performed, and a part of the precursor is non-thermoplastic polyimide resin. And a step (1) of forming a layer composed of a non-thermoplastic polyimide resin and a non-thermoplastic polyimide resin precursor on an insulating substrate, and a primary particle diameter of 200 nm or less on the layer. Then, a dispersion containing metal thin film precursor fine particles that are fused to each other by heating is applied, and the remaining precursor is converted into a non-thermoplastic polyimide resin by heating, and the non-thermal A step (2) of forming a metal thin film layer on the layer made of the plastic polyimide resin; By the combination of step (1) and step (2), the adhesion between the insulating substrate and the metal thin film is remarkably improved.
In the laminate obtained by the above method, a non-thermoplastic polyimide resin layer formed from a non-thermoplastic polyimide resin precursor is provided on the insulating substrate, and metal fine particles having a particle diameter of 200 nm or less are further formed thereon. Is a structure in which metal thin films having a structure in which are fused to each other are laminated.

Here, the non-thermoplastic polyimide-based resin is a polymer having an imide ring and has a large elastic modulus at the glass transition temperature even if it has no glass transition temperature or has a glass transition temperature. It refers to a resin that is not lowered and does not plasticize (does not melt and flow). This non-thermoplastic polyimide-based resin preferably has an insulating property that is usually used as an insulating film for electric wiring, and preferably has an insulating property with a volume resistivity of 10 ¹³ Ωcm or more.
In view of the heat resistance of the resin and the industrial availability, a polyimide obtained by polycondensation of tetracarboxylic dianhydride and diamine or diisocyanate is particularly preferable among non-thermoplastic polyimide resins. Resin. Examples of such resins include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone as a tetracarboxylic acid component. Examples of the tetracarboxylic dianhydride and the diamine component include polyimide resin resins obtained by polycondensation using 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, and the like.

The non-thermoplastic polyimide resin precursor is a compound in a state where conversion to a non-thermoplastic polyimide resin by a condensation reaction is not completed, and examples thereof include polyamic acid and diisocyanate adducts. The non-thermoplastic polyimide resin precursor may be used alone or in combination of two or more.
A part of the non-thermoplastic polyimide resin precursor is converted into a non-thermoplastic polyimide resin by heat treatment in the step (1). Although the conversion rate in the step (1) is not limited, it is preferably adjusted to be 70% or more and less than 100%. By adjusting the conversion rate in this way by the conversion in the step (1), the adhesion with the metal thin film to be formed next is further improved.
The unconverted non-thermoplastic polyimide resin precursor is converted into a non-thermoplastic polyimide resin in the step (2). If the unconverted precursor remains in the manufactured laminate, the insulation reliability is likely to decrease due to water absorption or the like, and therefore it is preferable to convert the non-thermoplastic polyimide resin precursor to 100%.
The conversion of the non-thermoplastic polyimide resin precursor to the non-thermoplastic polyimide resin in the step (1) and the step (2) is to adjust the conversion rate by adjusting the heating temperature and heating time in the heat treatment. I get out. The conditions may be appropriately determined according to the type of the non-thermoplastic polyimide resin precursor to be used. Usually, step (1) is heating in a temperature range of 150 ° C. to 250 ° C., and step (2) is 300 to 300 ° C. Conversion is performed by heating in a temperature range of 400 ° C.

For example, when a polyimide film is formed using polyamic acid as a non-thermoplastic polyimide-based resin precursor, after preheating at about 120 ° C., a conversion reaction is performed at about 200 ° C., whereby an imidization conversion rate ( A polyimide film having a R1) of about 90% is obtained. When a dispersion containing metal thin film precursor fine particles is applied onto this polyimide film and then heat-treated at 350 ° C., a metal thin film is formed from the metal thin film precursor fine particles and at the same time, an imidization conversion rate in the polyimide film (R2) reaches 100%, and the laminate is completed.
The above conversion rate is an index representing the ratio of condensation among the condensable functional groups that form imide bonds in the non-thermoplastic polyimide resin layer. A case where all the condensable functional groups are condensed and converted into an imide bond is defined as a conversion rate of 100%. Usually, this conversion rate can be estimated by measuring the amount of imide bonds after the conversion treatment by infrared absorption measurement. Specifically, the relative intensity of the infrared absorption peak of the imide group near 1780 cm ⁻¹ can be estimated by comparing with a sample having a conversion rate of 100%.

Various additives such as a smoothing agent, a leveling material, and a defoaming agent are added to the solution of the non-thermoplastic polyimide resin precursor as necessary to impart smoothness to the surface of the non-thermoplastic polyimide resin layer. be able to. In order to adjust the evaporation rate of the solvent, an aromatic hydrocarbon solvent can be used as long as it dissolves uniformly. Furthermore, you may add various additives and catalysts, such as well-known hardening | curing agents, such as an amine type hardening | curing agent, adhesiveness imparting agents, such as a silane coupling agent and an epoxy compound, and flexibility imparting agents, such as rubber | gum.
The method of applying the precursor solution on the insulating substrate is not limited, and for example, dip coating, bar coating, spin coating, roll coating, spray coating, or the like is used.
The concentration of the solution is usually 5 to 30% by weight, preferably 10 to 20% by weight, although it depends on the degree of polymerization of the non-thermoplastic polyimide resin precursor. When the polymer concentration is lower than 5% by weight, a sufficient film thickness may not be obtained by one coating. When the polymer concentration is higher than 30% by weight, the viscosity of the solution may increase and the coating may be difficult. .
The thickness of the non-thermoplastic polyimide resin precursor layer in the laminate of the present invention is preferably in the range of 0.1 to 5 μm after the conversion reaction by heating, that is, as the non-thermoplastic polyimide resin layer, ˜2 μm is more preferable. When it is applied so that the film thickness is thinner than 0.1 μm, a uniform non-thermoplastic polyimide resin layer is difficult to be formed, and the effect of improving the adhesive strength between the insulating substrate and the metal thin film layer may not be sufficiently exhibited. Even if the film thickness exceeds 5 μm, the effect of the present invention is not disturbed, but the film thickness of the laminated substrate becomes thicker than necessary and is often not economical.

Next, the metal thin film precursor fine particles having a primary particle diameter of 200 nm or less and fused to each other by heat treatment on the non-thermoplastic polyimide resin precursor and the non-thermoplastic polyimide resin layer formed above. A thin metal film layer having a structure in which the remaining precursor is converted into a non-thermoplastic polyimide-based resin by applying a dispersion containing Nd and heat treatment, and metal fine particles having a particle diameter of 200 nm or less are fused together. To form.
Metal thin film precursor fine particles that are fused to each other by heat treatment means that a dispersion containing the precursor fine particles is applied in the form of a film, and the metal fine particles are joined to each other by heating to form an apparently continuous metal. Fine particles forming a thin film formed of layers. When the surface of the metal layer is observed with a microscope, a portion where the interface between the metals is observed and a portion observed as a continuous layer are mixed.

The metal thin film precursor fine particles have a primary particle size of 200 nm or less, preferably 100 nm or less, more preferably 30 nm or less. When the primary particle diameter of the metal thin film precursor fine particles exceeds 200 nm, it becomes difficult to obtain a dense metal thin film by heat treatment.
The metal thin film precursor fine particles used in the present invention are not limited as long as the metal thin film is formed by heat treatment, and preferably include metal fine particles, metal oxide fine particles, and metal hydroxide fine particles.
As the metal fine particles, copper fine particles formed by a method such as a wet method or a gas evaporation method are preferable.
Examples of the metal hydroxide fine particles include fine particles composed of compounds such as copper hydroxide, nickel hydroxide, and cobalt hydroxide, but copper hydroxide fine particles that give a copper thin film are particularly preferable.
The metal oxide fine particles are particularly preferable from the viewpoint of dispersibility in a dispersion medium and ease of forming a metal thin film by heat treatment. Examples of the metal oxide fine particles include copper oxide, silver oxide, palladium oxide, nickel oxide and the like. As the copper oxide capable of providing copper by heat treatment, any of cuprous oxide, cupric oxide, and other copper oxides having an oxidation number can be used. Cuprous oxide fine particles are particularly preferred because they can be easily reduced.
These metal oxide fine particles may be commercially available products or may be synthesized using a known synthesis method. For example, as a method for synthesizing cuprous oxide ultrafine particles having a particle diameter of less than 100 nm, a method in which an acetylacetonato copper complex is synthesized by heating at about 200 ° C. in a polyol solvent is known (Angevante Chemi International Edition, 40, 2 volumes, p.359, 2001).

As a method of applying a dispersion of metal thin film precursor fine particles on a substrate having a non-thermoplastic polyimide resin, for example, a dip coating method, a spray coating method, a spin coating method, a bar coating method, a roll coating method, an inkjet method, Examples thereof include a contact printing method and a screen printing method. What is necessary is just to select the optimal application | coating method suitably according to the viscosity of a dispersion.
By adjusting the film thickness of the dispersion to be applied, it is possible to adjust the film thickness of the finally obtained metal thin film. Usually, the thickness of the dispersion to be applied is 0.1 to 100 μm, and the thickness of the obtained metal thin film is 0.05 to 50 μm.

After the dispersion of the metal thin film precursor fine particles is applied on a substrate having a non-thermoplastic polyimide resin, heat treatment is performed.
The purpose of the heat treatment is to [1] convert an unconverted non-thermoplastic polyimide resin precursor into a non-thermoplastic polyimide resin, and [2] a structure in which metal fine particles having a particle diameter of 200 nm or less are fused together. Forming a metal thin film layer. [1] and [2] are usually performed simultaneously, but may be performed sequentially.
The heating temperature is preferably equal to or higher than the temperature at which the non-thermoplastic polyimide resin precursor is completely imidized, and is usually 300 ° C. or higher and 450 ° C. or lower, preferably 300 ° C. or higher and 400 ° C. or lower. When the non-thermoplastic polyimide resin has a glass transition temperature, higher adhesive strength can be obtained by performing a heat treatment at a temperature equal to or higher than the glass transition temperature.

For a non-thermoplastic polyimide resin having a glass transition temperature, it is preferable to perform a heat treatment at a temperature 20 to 100 ° C. higher than the glass transition temperature. For example, when the glass transition temperature is 285 ° C., after applying a dispersion containing metal thin film forming precursor fine particles on the polyimide resin film, the glass transition temperature is 310 ° C. to higher than the glass transition temperature of the non-thermoplastic polyimide resin. A heat treatment is performed at 360 ° C. to form a metal thin film from the metal thin film precursor fine particles, and at the same time, the non-thermoplastic polyimide resin layer and the metal thin film are interfaced at a temperature higher than the glass transition temperature of the non-thermoplastic polyimide resin. By adhering, extremely high adhesive force is expressed.
For the heat treatment, a heating means such as a radiation heating furnace such as far infrared rays, infrared rays, microwaves, and electron beams, an electric furnace, or an oven may be appropriately selected and used.

The formation of the metal thin film may be performed in the atmosphere as long as it is a metal that is not affected by oxidation, but heat treatment in an inert atmosphere is preferable when a metal species that is easily oxidized is included. In some cases, the heat treatment temperature can be reduced by firing in a reducing atmosphere. For example, the inert atmosphere refers to an atmosphere filled with an inert gas such as argon or nitrogen, and the reducing atmosphere refers to an atmosphere in which a reducing gas such as hydrogen or carbon monoxide exists. These gases may contain a trace amount of oxygen as long as they do not contribute to oxidation. The oxygen concentration at that time is preferably 2000 ppm or less, more preferably 500 ppm or less.
The reason why the adhesion between the insulating substrate layer and the metal layer is remarkably improved by the method of the present invention is not necessarily clear, but between the imide group in the insulating resin and the metal thin film precursor or the thin film formed product thereof. This may be because some chemical bond is formed.
The dispersion medium used for the metal thin film precursor fine particle dispersion of the present invention is not limited as long as the fine particles can be uniformly dispersed.
It is more preferable that the dispersion contains a polyhydric alcohol and / or a linear aliphatic polyether compound, because the film-forming property when the metal thin film precursor fine particles are obtained by heat treatment is improved.

  The polyhydric alcohol is a compound having a plurality of hydroxyl groups in the molecule. The polyhydric alcohol has a moderately high boiling point and thus hardly volatilizes, and it is preferable to use the polyhydric alcohol because it is excellent in the printability of the dispersion and the film formability when forming the metal thin film. Among the polyhydric alcohols, polyhydric alcohols having 10 or less carbon atoms are preferred, and among them, low viscosity, such as ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1 , 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, pentanediol, hexanediol, octanediol and the like are particularly preferable. These polyhydric alcohols may be used alone or in combination.

The reason why polyhydric alcohol improves the film-forming property when forming a metal thin film is not necessarily clear, but when the metal thin film precursor fine particles are metal oxide fine particles or metal hydroxide fine particles, the polyhydric alcohol is on the surface of the fine particles. It seems that it acts to protect the particle surface by interacting with the hydroxyl groups of the particles and to suppress aggregation between the particles. Polyhydric alcohol is also preferable because it has an effect of reducing metal oxide fine particles or metal hydroxide fine particles.
When the dispersion contains a linear aliphatic polyether compound, it is preferable because the resistance value of the metal thin film obtained by the heat treatment is reduced in addition to the effect of improving the film formability when forming the metal thin film. The reason why the linear aliphatic polyether compound improves the film formability and reduces the resistance value is that the linear aliphatic polyether compound is a metal thin film precursor during heat treatment as a readily decomposable and easily burnable binder. This is considered to prevent local granulation of fine particles.

The preferable average molecular weight of the linear aliphatic polyether compound is 150 to 600. When the molecular weight is in this range, the film formability during the formation of the metal thin film is extremely high, and on the other hand, the volume resistance value of the metal thin film obtained tends to decrease because it easily decomposes and burns out. When the molecular weight is less than 150, the film formability when firing to obtain a metal thin film tends to decrease, and when the molecular weight exceeds 600, the volume resistance value of the resulting metal thin film tends to increase.
The linear aliphatic polyether compound is preferably an alkylene group having 2 to 6 carbon atoms as a repeating unit. It may be a linear aliphatic polyether compound, a binary or higher polyether copolymer or a polyether block copolymer.

  Specifically, in addition to polyether homopolymers such as polyethylene glycol, polypropylene glycol, polybutylene glycol, ethylene glycol / propylene glycol, ethylene glycol / butylene glycol binary copolymer, ethylene glycol / propylene glycol / ethylene glycol, Examples include, but are not limited to, linear ternary copolymers such as propylene glycol / ethylene glycol / propylene glycol and ethylene glycol / butylene glycol / ethylene glycol. As block copolymers, binary block copolymers such as polyethylene glycol polypropylene glycol and polyethylene glycol polybutylene glycol, and linear chains such as polyethylene glycol polypropylene glycol polyethylene glycol, polypropylene glycol polyethylene glycol polypropylene glycol, polyethylene glycol polybutylene glycol polyethylene glycol, etc. And polyether block copolymers such as ternary block copolymers.

  The structure of the terminal of the linear aliphatic polyether compound is not limited as long as it does not adversely affect the dispersibility of the fine particles and the solubility in the dispersion medium, but if at least one terminal is an alkyl group, It is preferable because the decomposition and burn-out property of the polyether compound is improved and the volume resistance value of the obtained metal thin film is lowered. If the length of the alkyl group is too long, the dispersibility of the fine particles is hindered and the viscosity of the dispersion tends to increase. Therefore, the length of the alkyl group is preferably 1 to 4 carbon atoms. The reason why the decomposition / burning property at the time of firing is improved by having at least one terminal alkyl group is not clear, but hydrogen bonding between the fine particles and the polyether compound or between the polyether compound and the polyether compound, etc. It is surmised that the weakening of the interaction force based on this contributes.

A particularly preferable structure of the linear aliphatic polyether compound is a structure in which one terminal is an alkyl group and the other terminal is a hydroxyl group, and examples thereof include polyethylene glycol methyl ether and polypropylene glycol methyl ether. .
Although there is no restriction | limiting in the ratio of the metal thin film precursor microparticles | fine-particles in a dispersion, It is 5 to 90% by weight with respect to the total amount of a dispersion, More preferably, it is 20 to 80%. When the weight of the fine particles in the dispersion is in these ranges, it is preferable because the fine particles are dispersed, and a metal thin film having an appropriate thickness can be obtained by a single coating / heating treatment.
The ratio of the polyhydric alcohol in the dispersion is, by weight, preferably 5 to 70%, more preferably 10 to 50% with respect to the total amount of the dispersion.

The proportion of the linear aliphatic polyether compound in the dispersion is, by weight, preferably 0.1 to 70%, more preferably 1 to 50%, based on the total amount of the dispersion. When the addition amount of the polyether compound is less than 0.1%, the denseness of the resulting metal thin film may be lowered, or the adhesion with the substrate may be reduced. If the amount added exceeds 70%, the viscosity of the dispersion may increase.
The preferred weight ratio of the polyether compound to the metal thin film precursor fine particles varies depending on the kind of fine particles used and the kind of the polyether compound, but is usually in the range of 0.01 to 10. Within this range, the denseness of the resulting metal thin film is improved and the volume resistance value is further reduced.

In this invention, you may add additives, such as an antifoamer, a leveling agent, a viscosity modifier, a stabilizer, to the said dispersion as needed.
For the production of the dispersion, a general method for dispersing powder in a liquid can be used. For example, after mixing constituent raw materials such as metal thin film precursor fine particles, a dispersion medium, and a linear aliphatic polyether compound, dispersion may be performed by an ultrasonic method, a mixer method, a three-roll method, or a ball mill method. Of these dispersing means, a plurality of dispersing means can be combined for dispersion. These dispersion treatments may be performed at room temperature, or may be performed by heating in order to reduce the viscosity of the dispersion. When the constituents other than the metal thin film precursor fine particles are solid, it is preferable to perform the above operation by adding the fine particles while heating them to a liquid temperature. When the dispersion becomes a flowable solid, the dispersion is preferably performed while applying a shear stress, and a three-roll method, a mixer method, and the like are preferable.

  The laminate obtained by the present invention can be used for production of printed wiring boards or the like as it is or after being subjected to rust prevention treatment. It is also possible to use a metal film of the same kind on the metal thin film by a method such as electrolytic plating. Of course, it is also possible to use another type of metal film laminated on the laminated substrate by a technique such as electrolytic plating.

Next, the present invention will be described specifically by way of examples.
The particle diameter of the metal thin film precursor fine particles, the volume resistivity of the metal thin film, the adhesiveness / adhesive strength, and the imidization conversion rate are measured according to the following methods.
(1) Particle diameter of metal thin film precursor fine particles One drop of a dissolved / diluted fine particle dispersion is deposited on a carbon-deposited copper mesh, and a sample dried under reduced pressure is prepared. Using a transmission electron microscope (JEM-4000FX) manufactured by Hitachi, Ltd., select three locations where the particle size is relatively uniform from the field of view. Shoot at a suitable magnification. From each photograph, select the three most likely particles, measure the diameter with a ruler, and multiply the magnification to calculate the primary particle size. Let the average value of these values be a particle diameter.
(2) Volume resistivity of metal thin film It measured using the low resistivity meter "Lorester (trademark)" GP (made by Mitsubishi Chemical Corporation).
(3) Tape peel test and adhesive strength measurement (90 degree peel test)
The tape peel test is based on whether or not the metal thin film adheres to the scotch tape and is peeled off from the substrate when the scotch tape (registered trademark, manufactured by Sumitomo 3M Limited) is applied to the obtained metal thin film. To do.
A sample for measuring the adhesive strength is prepared as follows. A metal film is thickened by electroplating on the obtained metal thin film to make the total thickness of the metal portion about 15 μm, and then a notch with a width of 10 mm and a length of 50 mm is made with a cutter knife. In the 90 degree peel test, one side of a 10 mm wide side is peeled off a little, and an aluminum tape is applied, this tape part is fixed to a peel tester, pulled up in the direction of 90 ° C., and the force required for peeling is measured. The adhesive strength (kgf / cm).
(4) Imidation conversion rate The relative intensity of the infrared absorption peak of the imide group near 1780 cm ^{−1 is} estimated by comparing it with a sample having a conversion rate of 100%. Specifically, heat treatment infrared absorption spectrum of the surface was measured after Get 1500 cm ^-1 vicinity of the peak intensity (B1) does not change by imidization reaction with imide group peak intensity at around 1780 cm ^-1 (A1) From these, the relative strength C1 = A1 / B1 of the imide group is derived. Next, as a comparative sample, a heat treatment was performed at 350 ° C. for 4 hours to prepare a sample subjected to 100% imidization conversion, and peak intensities (A0, B0) at 1780 cm ⁻¹ and 1500 cm ⁻¹ were measured. The intensity C0 = A0 / B0 is derived. When the relative strength C0 at this time is set to 100 and compared with C1, the imidization conversion rate by heat treatment is calculated as (100 × C1 / C0)%.

[Example 1]
(Preparation of metal thin film precursor fine particles and dispersion)
70 ml of purified water was added to 8 g of anhydrous copper acetate (manufactured by Wako Pure Chemical Industries, Ltd.). While stirring at 25 ° C., 2.6 ml of 64% by weight hydrazine hydrate was added and reacted so that the molar ratio of hydrazine to copper acetate was 1.2 to obtain cuprous oxide fine particles having a particle size of 20 nm. It was. 2.5 g of polyethylene glycol methyl ether (number average molecular weight 350, manufactured by Aldrich) and 8 g of diethylene glycol were added to 3 g of the obtained cuprous oxide, and ultrasonic dispersion was performed to obtain a cuprous oxide dispersion.

(Creation of surface-treated substrate)
20.2 g (0.10 mol) of bis (4-aminophenyl) ether was dissolved in 250 g of N-methylpyrrolidone (NMP). To this solution, 32.1 g (0.10 mol) of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride powder was added, and stirred at 5 ° C. for 8 hours to prepare an NMP solution of polyamic acid. Obtained. Furthermore, 7 g of NMP was added to 10 g of this polyamic solution to dilute to a concentration of 10 weight percent.
A polyimide film cut out to the same size on a 10cm square glass substrate (Kapton film manufactured by Toray DuPont Co., Ltd., film thickness 50 μm) is bonded to a double-sided tape and then set on a spin coater (1H-D7 type) manufactured by Mikasa Co., Ltd. did. The diluted polyamic acid was dropped, and after 500 rpm × 5 seconds press pin, spin coating was performed under the condition of 2000 rpm × 10 seconds. The spin-coated substrate was heated on a hot plate at 120 ° C. for 30 minutes and 200 ° C. for 30 minutes to obtain a polyimide substrate on which a polyimide film was formed. The imidation conversion rate R1 of this polyimide film was 90%.

(Formation of metal thin film)
The polyimide substrate was again set on a spin coater, and 2 mL of the above-mentioned cuprous oxide dispersion was dropped, and then spin-coated under the conditions of 500 rpm × 15 seconds for coating. Next, this coating film was baked on a hot plate under a condition of 350 ° C. × 1 h under nitrogen flow (at a temperature higher than Tg (278 ° C.) of the polyimide film after thermosetting). As a result, copper fine particles having a particle diameter of 20 nm or less were fused to each other, and a thin film having a large copper grain structure was obtained.
Further, when the imidization conversion rate R2 in the polyimide film was analyzed, it was 100%. The volume resistance value of the copper thin film was 3.9 × 10 ⁻⁶ Ωcm, and no peeling was observed in the tape peeling test. Further, the adhesive strength according to the 90-degree peel test was as extremely high as 0.7 kgf / cm.

[Example 2]
A polyimide film was formed on the polyimide film in the same manner as in Example 1 except that polyamic acid obtained from bis (4-aminophenyl) ether and pyromellitic anhydride was used as the polyimide film used as the insulating resin layer. . The imidation conversion rate R1 of this polyimide film was 90%.
After spin-coating the same cuprous oxide dispersion as in Example 1, it was lower than the Tg (417 ° C.) of the polyimide film after thermosetting while flowing nitrogen on a hot plate at 350 ° C. × 1 h. Calcined (at temperature). Similar to Example 1, a copper thin film having a fused structure was obtained. Further, when the imidization conversion rate R2 in the polyimide film was analyzed, it was 100%. The obtained copper thin film had a volume resistance value of 3.7 × 10 ⁻⁶ Ωcm, and no peeling was observed in the tape peeling test. Moreover, the adhesive strength by a 90 degree | times peeling test was 0.2 kgf / cm.

[Comparative Example 1]
A copper thin film was formed on a polyimide substrate on which no polyimide film was formed by the same method as in Example 1. However, the formed copper thin film was all peeled off by a tape peeling test.
[Comparative Example 2]
Except for using cuprous oxide having an average primary particle size of 1.2 μm obtained by pulverizing commercially available cuprous oxide (manufactured by Wako Pure Chemical Industries, Ltd.), it has a polyimide film in the same manner as in Example 1. Although a cuprous oxide dispersion was applied onto a polyimide substrate and heat treatment was performed, many cracks were generated on the copper surface, and only an incomplete copper thin film was obtained.

  The laminate obtained by the present invention has high conductivity equivalent to that of a conventional metal thin film, and has high adhesion between the metal thin film and the substrate. Further, since the thickness of the metal film can be arbitrarily controlled and a thin metal film can be easily formed, it can be used particularly suitably as a flexible circuit board material.

Claims (4)

After applying a solution of a non-thermoplastic polyimide resin precursor on an insulating substrate, a part of the precursor is converted into a non-thermoplastic polyimide resin by performing a heat treatment for solvent removal and dehydration condensation reaction, A step (1) of forming a layer composed of a non-thermoplastic polyimide resin and a non-thermoplastic polyimide resin precursor on an insulating substrate, and heating the primary particle diameter on the layer to be 200 nm or less; By applying a dispersion containing metal thin film precursor fine particles that are fused to each other by heat treatment, the remaining precursor is converted into a non-thermoplastic polyimide resin, and from the non-thermoplastic polyimide resin. A step (2) of forming a metal thin film layer on the layer, comprising :
The metal thin film precursor fine particles are cuprous oxide fine particles, the dispersion is a polyhydric alcohol, a linear aliphatic polyether compound in which one terminal is an alkyl group and the other terminal is a hydroxyl group. Including
A method for producing a laminate, wherein the heat treatment is performed in an inert atmosphere . The method for producing a laminate according to claim 1, wherein the heat treatment in the step (2) is performed at a temperature equal to or higher than the glass transition temperature of the non-thermoplastic polyimide resin. The length of the terminal alkyl group of the said linear aliphatic polyether compound is C1-C4, The manufacturing method of the laminated body of Claim 1 or 2 characterized by the above-mentioned. The polyhydric alcohol is 5 to 70% by weight with respect to the total amount of the dispersion, the linear aliphatic polyether compound is 0.1 to 70% by weight with respect to the total amount of the dispersion, and the metal thin film precursor The method for producing a laminate according to any one of claims 1 to 3, wherein the weight ratio of the linear aliphatic polyether compound to the body fine particles is 0.01 to 10.