KR102335085B1 - Polyimide flexible metal-clad laminate - Google Patents

Abstract

The present invention relates to a polyimide flexible metal foil laminate, and more particularly, to a polyimide flexible metal foil laminate in which electrical insulation properties are stably maintained while using a polyimide having low light transmittance.

Description

Polyimide flexible metal foil laminate {POLYIMIDE FLEXIBLE METAL-CLAD LAMINATE}

The present invention relates to a polyimide flexible metal foil laminate, and more particularly, to a polyimide flexible metal foil laminate in which electrical insulation properties are stably maintained while using a black polyimide having low light transmittance.

A flexible metal foil laminate used for manufacturing a flexible printed circuit board is a laminate of a conductive metal foil and an insulating resin, and has the advantage of being able to process fine circuits and bending in a narrow space.

Due to this, the flexible metal foil laminate is being used in notebook computers, portable information terminals, small video cameras, and storage disks, etc. according to the trend of miniaturization and weight reduction in electronic devices.

Polyimide, which is excellent in heat resistance and mechanical strength, is representative of the insulating resin used in the flexible metal foil laminate. The polyimide used in the flexible metal foil laminate itself has a yellow-brown color and has light transmittance. However, in recent years, the development of a flexible metal foil laminate using a black polyimide having low light transmittance is required for circuit location recognition through reflected light or for circuit design confidentiality.

It is effective to use a dye such as carbon black to lower the light transmittance of polyimide to such an extent that the circuit position cannot be recognized through transmitted light, but carbon black has conductivity. There is a problem in that the electrical insulating properties of the resin are impaired due to the decrease in resistance and volume resistance.

Therefore, in order to solve this problem, when the thermoplastic polyimide layer is formed between the polyimide layer containing carbon black and the metal foil, and then the metal foil is formed, a flexible metal foil laminate with low light transmittance while maintaining insulating properties can be implemented.

However, even in the case of a flexible metal foil laminate having such a structure, there was a difference in insulation properties depending on the type of metal foil used. The development of a mid-ductile metal foil laminate was required.

In relation to the present invention, Korean Patent Application Laid-Open No. 10-2012-0027178 (published on March 21, 2012) discloses a multilayer polyimide film including a pigment having a light-shielding property. nothing was mentioned about

It is an object of the present invention to provide a polyimide flexible metal clad laminate that simultaneously satisfies low light transmittance, stable insulation properties and low dimensional change rate by solving the above problems.

For the above purpose, the present invention is a metal foil; a first polyimide layer formed on the metal foil; a second polyimide layer formed on the first polyimide layer;

The second polyimide layer includes a pigment and provides a flexible metal foil laminate, characterized in that the L* value is 50 or less.

According to the flexible metal foil laminate of the present invention, there is an effect of stably maintaining electrical insulation properties while using a black polyimide having low light transmittance.

That is, in order to lower the light transmittance, a black pigment must be added. In particular, a pigment having excellent heat resistance and chemical resistance such as carbon black must be used. However, in the case of carbon black, since it has electrical conductivity, there is a problem in that electrical insulation properties are impaired when contained in an insulating resin.

The polyimide layer adjacent to the metal foil proposed in the present invention does not contain a black pigment, and a multi-layered polyimide laminate, for example, a polyimide having a multi-layer structure consisting of a thermoplastic polyimide layer/a polyimide layer containing carbon black In the case of using a laminate, the light transmittance is low due to carbon black, making it impossible to recognize the circuit position through transmitted light, so the security performance is excellent. and good adhesion to the metal foil.

In addition, when the metal foil proposed in the present invention is used, there is no need to increase the thickness of the thermoplastic polyimide layer in order to maintain insulating properties, so the dimensional change rate of the flexible metal foil laminate is stable.

Advantages and features of the present invention, and methods for achieving them, will become apparent with reference to the embodiments described below in detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only the present embodiment is intended to complete the disclosure of the present invention, and it is common knowledge in the art to which the present invention pertains. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims.

Hereinafter, the flexible metal foil laminate according to the present invention will be described in detail.

The flexible metal foil laminate of the present invention includes a metal foil; a first polyimide layer formed on the metal foil; a second polyimide layer formed on the first polyimide layer; Including, the second polyimide layer is characterized in that the L* value including the pigment is 50 or less.

That is, in the insulating resin of the flexible metal foil laminate of the present invention, the second polyimide layer contains the pigment and the L* value satisfies 50 or less, so that the light transmittance is low and the electrical insulation properties are stably maintained.

In the present invention, one or more pigments selected from carbon black, titanium black, and black iron oxide may be used as a pigment in order to satisfy the light transmission property of the second polyimide layer having an L* value of 50 or less.

Among these, it is most preferable to use carbon black. In the case of titanium black or black iron oxide, there is a problem in that the degree of dispersion in the polyimide film is lowered and the degree of blackness is low. In the case of general organic pigments, it is difficult to use because a problem of dissolving the pigment may occur due to discoloration in the process of chemical treatment or heat treatment in the process of forming a flexible printed circuit board by processing a flexible metal foil laminate, or by an organic solvent used during processing.

In this case, the content of the pigment is preferably 0.2 to 15 parts by weight based on 100 parts by weight of the polyamic acid formed by chemical/thermal imidization, that is, 100 parts by weight of the polyimide precursor.

If the content of the pigment is less than 0.2 parts by weight, the amount of dye is insufficient and the light transmittance is high, so there is a problem in that the circuit shape and position are recognized through transmitted light. There is a problem with degradation.

As described above, in the flexible metal foil laminate of the present invention, it is effective to use a dye such as carbon black to lower the light transmittance of polyimide to the extent that the circuit position cannot be recognized through transmitted light, but carbon black has electrical conductivity. For this reason, the surface resistance and volume resistance of the polyimide flexible metal foil laminate including carbon black may decrease, and thus electrical insulation properties may be impaired.

Therefore, in order to stably maintain the electrical insulation properties, specifically, the flexible metal foil laminate of the present invention has a thickness of t of the first polyimide layer formed on the metal foil, and is located on the surface of the metal foil in contact with the first polyimide layer. When the particle diameter is D, it is characterized in that the condition of Equation 1 below is satisfied.

[Equation 1]

t/6 > D

That is, by forming a thermoplastic polyimide layer between the polyimide layer and the metal foil, which contains a dye such as carbon black, the resistance is lowered, and a flexible metal foil laminate with low light transmittance while maintaining insulating properties was realized, but the present invention is a type of metal foil It was discovered that there is a difference in insulation properties depending on the use of polyimide, and developed a polyimide flexible metal foil laminate in which electrical insulation properties are stably maintained while using polyimide with low light transmittance.

This is determined by the diameter (D) of the roughened particles mentioned in the condition of Equation 1 and the thickness (t) of the first polyimide layer in contact with the metal foil, and the specific reasons are as follows.

In the case of using a metal foil having a large roughened particle diameter (D), the distance between the roughened particle (nodule) present on the surface of the metal foil and the second polyimide layer containing the black pigment is reduced, and there is a problem in that insulation is reduced. The thickness of the contacting first polyimide layer should be increased or the diameter (D) of roughened particles of the metal foil should be decreased.

However, in general, when the thickness of the first or third polyimide layer in contact with the metal foil is increased, the thermoplastic first polyimide layer/low-resistance second polyimide layer or the first thermoplastic polyimide layer/low-resistance second polyimide layer The thermal expansion coefficient of the multilayer polyimide film having the structure of the mid layer/thermoplastic third polyimide layer becomes larger than the thermal expansion coefficient of the metal foil, which may cause warpage or increase the rate of dimensional change.

Therefore, it can be solved by reducing the diameter (D) of the roughened particles of the metal foil. As a result of repeated research in the present invention, the diameter (D) of the roughened particles of the metal foil is correlated with the thickness of the first thermoplastic polyimide layer in contact with the metal foil. It is stated that it is determined in

That is, in the flexible metal foil laminate of the present invention, if the diameter (D) of the roughened particles of the metal foil is less than 1/6 of the thickness of the first polyimide layer in contact with the metal foil, a polyimide having low light transmittance is used while electrically insulating properties This has the effect of keeping it stable.

On the other hand, in order to stably maintain electrical insulation properties, in the flexible metal foil laminate of the present invention, the thickness of the first polyimide layer formed on the metal foil is t, and the surface roughness value of the metal foil in contact with the first polyimide layer is Rz. , the condition of Equation 2 below may be satisfied.

[Equation 2]

t/3 > Rz

That is, when the condition of Equation 2 is satisfied, the problem of reduced insulation due to the close distance between the roughening particles (nodules) present on the surface of the metal foil and the second polyimide layer containing the pigment can be solved.

In this case, the surface roughness value corresponds to the 10-point average roughness, that is, the Rz value, and is a result of measurement by a prescribed general method.

In other words, in the flexible metal foil laminate of the present invention, when the surface roughness value of the metal foil is less than 1/3 of the thickness of the first thermoplastic polyimide layer in contact with the metal foil, a polyimide having low light transmittance is used while the electrical insulation properties are stable. has the effect of maintaining

In the present invention, Equations 1 and 2 may be independent of each other or may be mutually exclusive. That is, each condition may be independently satisfied or may be satisfied at the same time. When it is satisfied at the same time, the effect of stably maintaining the electrical insulation properties may be more excellent.

The metal foil used in the present invention is not limited, but an electrodeposited copper foil, a rolled copper foil, a stainless foil, an aluminum foil, a nickel foil, or two or more alloy foils may be used.

In the single-sided flexible metal foil laminate of the present invention, the polyamic acid solution capable of forming the first polyimide layer is coated/dried on the metal foil, and then the polyamic acid solution capable of forming the second polyimide layer is coated thereon. / After drying, it can be prepared by a manufacturing method through various thermal or chemical imidization reactions.

Alternatively, after preparing a polyimide film having a first polyimide layer/second polyimide layer structure, lamination, vacuum deposition, sputtering, ion plating, and plating are used on the first polyimide layer using any one method selected from the group consisting of: It can be manufactured by laminating a metal foil on the

In the present invention, the first polyimide layer formed on the metal foil may include a thermoplastic polyimide, and the glass transition temperature may be 200 ~ 300 ℃.

According to an embodiment of the present invention, the first polyimide layer may be prepared by imidizing a polyamic acid solution as a precursor layer. The polyamic acid solution may be a polyamic acid solution commonly used in the art within the technical scope of the present invention.

Specifically, the first polyimide layer of the present invention is a layer adjacent to the metal foil, and the polyamic acid that can be used as a component of this layer has thermoplastic properties, and the glass transition temperature (Tg) after complete imidization is 300° C. or less, More preferably, the temperature is 200 to 300° C., and a thermoplastic polyimide resin or polyamic acid resin having thermoplastic properties may be used, and the type is not particularly limited.

In the present invention, the coefficient of linear thermal expansion of the second polyimide layer formed on the first polyimide layer is preferably 1 to 20 ppm/K.

That is, the second polyimide layer having a coefficient of linear thermal expansion of 1 to 20 ppm/K can match the coefficient of linear thermal expansion of the entire polyimide film similar to that of metal foil, thereby minimizing the occurrence of warpage (curl) and dimensional change. there is

In the present invention, the second polyimide layer may be a single layer including a black pigment, but may have a multilayer structure.

That is, in order to realize high insulating properties of the flexible metal foil laminate of the present invention and obtain a desired level of light transmittance, the second polyimide layer may have different or the same black pigment content for each layer. It is most preferable to form a multi-layer structure comprising the first layer, the second layer having a high pigment content, and the third layer having a low pigment content. The method for manufacturing the multi-layer structure can be prepared by repeating the process of coating/drying a polyamic acid solution having the same or different black pigment content.

Meanwhile, the flexible metal foil laminate of the present invention may further include a third polyimide layer formed on the second polyimide layer and a second metal foil formed on the third polyimide layer.

That is, the present invention includes a double-sided flexible metal foil laminate in which the metal foil is formed on both sides of the polyimide layer, and after coating/drying the polyamic acid solution capable of forming the first polyimide layer on the metal foil by a specific manufacturing method, the After coating/drying the polyamic acid solution capable of forming the second polyimide layer, coating/drying the polyamic acid solution capable of forming the third polyimide layer, various imidization reactions are performed to form a multi-layered form on the metal foil. A method of manufacturing a polyimide laminate and forming a second metal foil may be used.

Alternatively, after preparing a film composed of a second polyimide layer containing a black pigment, coating/drying a polyamic acid solution on the second polyimide layer using a casting method and then imidizing the first or third polyimide Forming a layer or using a method of bonding a first or third polyimide thin film already prepared on a second polyimide layer made of a film with a second polyimide layer through a lamination process, or using the first, second, After preparing a multi-layered polyimide laminate by a method of manufacturing a polyamic acid solution forming the third polyimide layer using a co-extrusion or multi-coating method, the first and third polyimide layers are applied to the first and third polyimide layers. It may be manufactured by forming a second metal foil.

In the present invention, the third polyimide layer is formed on the second polyimide layer. Specifically, the polyamic acid that can be used as a component of the third polyimide layer has thermoplastic properties, and the glass transition temperature ( Tg) is 300° C. or less, more preferably 200 to 300° C., and a thermoplastic polyimide resin or polyamic acid resin having thermoplastic properties can be used, and the type is not particularly limited.

In this case, since the third polyimide layer is in contact with the second metal foil, the properties of the first polyimide layer can be applied as it is.

In the present invention, the first metal foil is adjacent to the first polyimide layer, the second metal foil is adjacent to the third polyimide layer, and the first or second metal foil is lamination, vacuum deposition, sputtering, or ion plating. , may be formed on the first or third polyimide layer by any one or a plurality of methods selected from among plating methods.

In the present invention, the first, second, and third polyimide layers are inorganic materials such as silica, talc, alumina, etc., epoxy, acrylic, silane, etc. for the purpose of increasing adhesion with various materials such as coverlays, prepregs, and bonding sheets Various organic additives such as compounds may be included.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and cannot be construed as limiting the present invention in any sense.

Content not described here will be omitted because it can be technically inferred sufficiently by a person skilled in the art.

Before referring to Examples, the synthesis of polyamic acid used to form a film of a multilayer polyimide will be described. Polyamic acid is converted to polyimide by imidization reaction, and polyamic acid is prepared through the synthesis of compounds to be described below. The abbreviations used in the following synthesis examples are as follows.

DMAc: N-N-dimethylacetamide (N,N-dimethylacetamide)

BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (3,3',4,4'-biphenyltetracarboxylic acid dianhydride)

PDA: para-phenylenediamine (p-phenylenediamine)

ODA: 4,4'-diaminodiphenyl ether (4,4'-diaminodiphenylether)

TPE-R: 1,3-Bis (4-aminophenoxy) benzene (1,3-Bis (4-aminophenoxy) benzene)

On the other hand, the physical properties mentioned in this example were by the following measurement method.

One. Transmittance and color measurement

After etching the metal foil of the multi-layer flexible metal foil laminate, the transmissivity was measured through the JIS K7361 method using the COH-400 equipment of Nippon Denshoku after cutting in the forward direction with a width and length of 5 cm, respectively, and the haze value was measured according to the JIS K7136 method. did The color was measured using the JIS Z8722 method.

2. Multilayer polyimide film and metal foil adhesion between

To measure the peel strength of the multi-layer polyimide film and the metal foil, pattern the metal foil of the multi-layer flexible metal foil laminate to a width of 1 mm, and then measure the peel strength of 180° using a universal testing machine (UTM). measured.

3. metal foil surface roughness and harmonic particle size measurement

The surface roughness of the metal foil was measured according to JIS 1994. The average size of roughened particles on the surface of the metal foil in contact with the polyimide layer was measured using a scanning electron microscope. The surface roughness Rz and Ra values were measured using a contact-type surface roughness measuring instrument (SJ-401) from Mitutoyo, using a stylus with a radius of curvature of 2㎛. The cutoff length was 0.8mm, the measurement length was 4mm, and the scan speed was 0.1mm/s. was measured with

4. Coefficient of thermal expansion ( CTE , Coefficient of Thermal Expansion )

The coefficient of thermal expansion is increased to 400°C at a rate of 10° per minute using TMA (Thermomechanical Analyzer), and among the measured thermal expansion values, 100° to 200° It was obtained by averaging the values between them.

5. Surface and volume resistance

The surface and volume resistance of the prepared polyimide film were measured according to IPC-TM 650 2.5.17.1.

6. Dimensional change rate after etching and dimensional change rate after heating

IPC-TM-650, 'Method B' of 2.2.4 was followed. Drill a hole for position recognition at the four vertices of a square specimen with MD (Mechanical Direction) and TD (Transverse Direction) of 275 × 255 mm, respectively, and store the distance between each hole at 23℃ and 50%RH for 24 hours. After three repeated measurements, they were averaged. After that, the metal foil was etched, and the distance between the holes was measured again after storage for 24 hours at 23°C and 50%RH. The rate of change in the MD and TD directions of the measured values was calculated to obtain the rate of dimensional change after etching. After that, the film with the metal foil etched is stored in an oven at 150°C for 30 minutes, stored at 23°C, 50%RH for 24 hours, and then the distance between the holes is measured again to calculate the rate of change in the MD and TD directions after heating. The dimensional change rate was calculated.

Next, the polyamic acid synthesis example is demonstrated below.

[Synthesis Example 1]

In 30,780 g of DMAc solution, 2,226 g of TPE-R diamine was completely dissolved by stirring under a nitrogen atmosphere, and 2,240 g of BPDA as dianhydride was added in several divided portions. After that, stirring was continued for about 24 hours to prepare a polyimide precursor (polyamic acid) solution. After casting the polyimide precursor solution prepared in this way into a film having a thickness of 20 μm, the temperature was raised to 350° C. for 60 minutes and maintained for 30 minutes to cure. The measured coefficient of thermal expansion and glass transition temperature were 51.1ppm/K and 232℃, respectively.

[Synthesis Example 2]

In a 32,416 g DMAc solution, 1,638 g of PDA and 758 g of ODA diamine were completely dissolved by stirring under a nitrogen atmosphere, and then 5,700 g of BPDA as dianhydride was added in several portions. After that, stirring was continued for about 24 hours to prepare a polyimide precursor (polyamic acid) solution. The thus-prepared polyimide precursor solution was cast on a 12 μm-thick copper foil (Rz=1.6 μm) into a 20 μm-thick film, then heated to 350° C. for 60 minutes and maintained for 30 minutes to cure. The measured coefficient of thermal expansion and glass transition temperature were 13.3 ppm/K and 321 °C, respectively. Table 1 shows the color and transmittance results of the polyimide film measured after the copper foil was removed after complete curing.

[Synthesis Example 3]

1.5 wt% of the total weight of dianhydride and diamine using carbon black is dispersed in 10,000 g of DMAc solution. In a solution in which carbon black was dispersed, 1,638 g of PDA and 758 g of ODA in a DMAc solution of 22,416 g were completely dissolved by stirring under a nitrogen atmosphere, and then 5,700 g of BPDA as dianhydride was added in several portions. After that, stirring was continued for about 24 hours to prepare a polyimide precursor (polyamic acid) solution containing carbon black. The thus-prepared polyimide precursor solution was cast on a 12 μm-thick copper foil (Rz=1.6 μm) into a 20 μm-thick film, then heated to 350° C. for 60 minutes and maintained for 30 minutes to cure. Table 1 shows the color and transmittance results of the polyimide film measured after the copper foil was removed after complete curing.

[Synthesis Examples 4 to 6]

A polyimide precursor (polyamic acid) solution and polyimide film containing carbon black were prepared in the same manner as in Synthesis Example 3 except that the carbon black content was changed to 3 wt%, 4 wt%, and 5 wt%, respectively.

Color of polyimide/carbon black mixed film according to carbon black content Carbon black content (wt%) L* a* b* T Haze Synthesis Example 2 0 92.65 -8.88 44.65 82.16 23.65 Synthesis Example 3 1.5 40.03 0.32 33.05 11.27 28.47 Synthesis Example 4 3 12.02 3.22 16.85 1.41 30.55 Synthesis Example 5 4 1.72 1.43 2.75 0.19 23.28 Synthesis Example 6 5 1.06 0.97 1.78 0.12 26.66

Using the synthesized polyamic acid, that is, the polyimide precursor solution, flexible metal foil laminates of Examples and Comparative Examples were prepared as follows.

The metal foil used in Examples and Comparative Examples was copper foil, and the surface roughness value and roughening particle size of each metal foil were as follows.

Surface roughness of copper foil
(Rz, um) Surface roughness of copper foil
(Ra, um) Harmonic particle size (um) Copper Foil A 1.6 0.3 0.65 copper foil B 1.2 0.19 0.06 copper foil C 0.5 0.07 0.1

The surface roughness Rz is a value calculated by measuring the degree of small irregularities on the surface of the metal foil adjacent to the multilayer polyimide using the 10-point averaging method. 5 in order from the mountain and 5 in order from the deepest valley, the average of the distance values from the average line of each of the 5 points is obtained, and the difference is expressed in microns (㎛).

In addition, the surface roughness Ra refers to the arithmetic mean roughness, calculates the sum of the total areas above and below the center line of the measurement section (measurement length), and divides the value by the length of the measurement section in microns (㎛) it will be indicated

[Example 1]

The first polyimide precursor solution prepared in [Synthesis Example 1] was applied on an electrolytic copper foil B (Rz=1.2 μm) having a thickness of 12 μm to a thickness of 4.0 μm after final curing, and then dried at 150° C. to obtain the first polyimide solution. A mid precursor layer was formed. The second polyimide precursor solution prepared in [Synthesis Example 6] was applied to one surface of the first polyimide precursor layer so that the thickness after final curing was 6.0 μm, and then dried at 150° C. to form a second polyimide precursor layer. did Thereafter, the first polyimide precursor solution prepared through [Synthesis Example 1] was applied to one surface of the second polyimide precursor layer so that the thickness after final curing was 3.0 μm, and then dried at 150° C. to form the first polyimide precursor layer. did The multilayer polyimide precursor layer on the thus-prepared copper foil was completely imidized using an infrared heating device under a nitrogen atmosphere. The multilayer polyimide layer on the copper foil thus prepared and the same copper foil as used above were adhered using a high-temperature laminator to prepare a double-sided multi-layer flexible metal foil laminate in which copper foils were laminated on both sides of the polyimide layer. Table 3 shows the physical properties and light transmittance of the double-sided multilayer flexible metal foil laminate prepared in this way.

[Example 2]

A double-sided multilayer flexible metal foil laminate was prepared in the same manner as in [Example 1] except that a rolled copper foil C having a thickness of 12 µm (Rz = 0.5 µm) was used. Table 3 shows the physical properties and light transmittance of the double-sided multilayer flexible metal foil laminate prepared in this way.

[Comparative Example 1]

The first polyimide precursor solution prepared in [Synthesis Example 1] was applied on an electrodeposited copper foil A (Rz=1.6 μm) having a thickness of 12 μm so that the thickness after final curing was 4.0 μm, and then dried at 150° C. to obtain the first polyimide solution. A precursor layer was formed. The second polyimide precursor solution prepared through [Synthesis Example 6] was applied to one surface of the first polyimide precursor layer so that the thickness after final curing was 6.0 μm, and then dried at 150° C. to form a second polyimide precursor layer. did Thereafter, the first polyimide precursor solution prepared through [Synthesis Example 1] was applied to one surface of the second polyimide precursor layer so that the thickness after final curing was 3.0 μm, and then dried at 150° C. to form the first polyimide precursor layer. did The multilayer polyimide precursor layer on the thus-prepared copper foil was completely imidized using an infrared heating device under a nitrogen atmosphere. The multilayer polyimide layer on the copper foil thus prepared and the same copper foil as used above were adhered using a high-temperature laminator to prepare a double-sided multi-layer flexible metal foil laminate in which copper foils were laminated on both sides of the polyimide layer. Table 3 shows the physical properties and light transmittance of the double-sided multilayer flexible metal foil laminate prepared in this way.

[Comparative Example 2]

The first polyimide precursor solution prepared in [Synthesis Example 1] was applied on an electrodeposited copper foil A (Rz = 1.6 μm) having a thickness of 12 μm so that the thickness after final curing became 5.5 μm, and then dried at 150° C. to obtain the first polyimide solution. A precursor layer was formed. On one surface of the first polyimide precursor layer, the second polyimide precursor solution prepared in [Synthesis Example 6] was applied to a thickness of 3.5 μm after final curing, and then dried at 150° C. to form a second polyimide precursor layer. did Thereafter, the first polyimide precursor solution prepared through [Synthesis Example 1] was applied to one surface of the second polyimide precursor layer so that the thickness after final curing was 4.1 μm, and then dried at 150° C. to form the first polyimide precursor layer. did The multilayer polyimide precursor layer on the thus-prepared copper foil was completely imidized using an infrared heating device under a nitrogen atmosphere. The multilayer polyimide layer on the copper foil thus prepared and the same copper foil as used above were adhered using a high-temperature laminator to prepare a double-sided multi-layer flexible metal foil laminate in which copper foils were laminated on both sides of the polyimide layer. Table 3 shows the physical properties and light transmittance of the double-sided multilayer flexible metal foil laminate prepared in this way.

[Comparative Example 3]

A double-sided multilayer flexible metal foil laminate was prepared in the same manner as in [Comparative Example 1] except that [Synthesis Example 4] was used for the second polyimide precursor solution. Table 3 shows the physical properties and light transmittance of the double-sided multilayer flexible metal foil laminate prepared in this way.

[Comparative Example 4]

A double-sided multilayer flexible metal foil laminate was prepared in the same manner as in [Comparative Example 1] except that [Synthesis Example 2] was used for the second polyimide precursor solution. Table 3 shows the physical properties and light transmittance of the double-sided multilayer flexible metal foil laminate prepared in this way.

Evaluation results

Copper foil adhesion (kgf/cm) L* a* b* Surface resistance (Ω) Volume resistance (Ωcm) Dimensional change rate (%) After etching, MD/TD After heating, MD/TD Example 1 1.4 42.2 3.18 24.8 2.5E13 3.1E14 -0.01/-0.03 -0.04/-0.05 Example 2 1.3 46.4 3.2 25.1 3.3E14 5.7E14 -0.01/-0.02 -0.03/-0.04 Comparative Example 1 1.8 37.5 3.15 24.6 1.5E10 Over Current -0.01/-0.01 -0.03/-0.03 Comparative Example 2 1.7 52.4 3.4 29.4 2.9E13 4.5E14 -0.06/-0.05 -0.12/-0.13 Comparative Example 3 1.8 51.2 3.1 30.3 8.9E10 1.3E11 -0.03/-0.04 -0.06/-0.08 Comparative Example 4 1.8 76.99 0.70 38.79 8.4E14 6.9E14 0.01/-0.02 -0.03/-0.05

In the above, the embodiments of the present invention have been mainly described, but various changes or modifications can be made at the level of those skilled in the art to which the present invention pertains. Such changes and modifications can be said to belong to the present invention without departing from the scope of the technical spirit provided by the present invention. Accordingly, the scope of the present invention should be judged by the claims described below.

Claims (12)

A flexible metal foil laminate comprising:
metal foil;
a first polyimide layer formed on the metal foil; and
a second polyimide layer formed on the first polyimide layer;
includes,
The second polyimide layer is characterized in that the L* value including the pigment is 50 or less,
The flexible metal foil laminate has a surface resistance of 2.50E+13 Ω or more, and a volume resistance of 3.10E+14 Ωcm or more,
When the thickness of the first polyimide layer formed on the metal foil is t and the diameter of the roughened particles of the metal foil in contact with the first polyimide layer is D, the condition of the following formula 1 is satisfied,
The second polyimide layer formed on the first polyimide layer is characterized in that it has a multilayer structure,
The pigment is a flexible metal foil laminate, characterized in that at least one selected from carbon black, titanium black and black iron oxide:
[Equation 1]
t/6 > D.
delete The method of claim 1,
When the thickness of the first polyimide layer formed on the metal foil is t and the surface roughness value of the metal foil in contact with the first polyimide layer is Rz, the condition of Equation 2 below is satisfied. sifter.
[Equation 2]
t/3 > Rz
The method of claim 1,
The first polyimide layer formed on the metal foil is a thermoplastic polyimide, and the flexible metal foil laminate, characterized in that the glass transition temperature is 200 ~ 300 ℃.
The method of claim 1,
The flexible metal foil laminate, characterized in that the coefficient of linear thermal expansion of the second polyimide layer formed on the first polyimide layer is 1 to 20 ppm/K.
delete The method of claim 1,
The flexible metal foil laminate, characterized in that the second polyimide layer of the multi-layer structure has a different or the same pigment content for each layer.
delete The method of claim 1,
The content of the pigment is a flexible metal foil laminate, characterized in that 0.2 to 15 parts by weight relative to 100 parts by weight of the polyimide precursor.
The method of claim 1,
a third polyimide layer formed on the second polyimide layer; and
A flexible metal foil laminate, characterized in that it further comprises a second metal foil formed on the third polyimide layer.
The method of claim 1,
The flexible metal foil laminate is prepared by manufacturing a polyimide film having a first polyimide layer/second polyimide layer structure, and then using any one or a plurality of methods selected from lamination, vacuum deposition, sputtering, ion plating, and plating. A flexible metal foil laminate, characterized in that it is manufactured by laminating a metal foil on the first polyimide layer.
11. The method of claim 10,
The flexible metal foil laminate is prepared by manufacturing a polyimide film having a first polyimide layer/second polyimide layer/third polyimide layer structure, and then, lamination, vacuum deposition, sputtering, ion plating, and plating. or a flexible metal foil laminate, characterized in that it is manufactured by laminating a metal foil and a second metal foil on the first polyimide layer and the third polyimide layer, respectively, using a plurality of methods.