CN113844149A

CN113844149A - Method for producing laminate

Info

Publication number: CN113844149A
Application number: CN202011410648.8A
Authority: CN
Inventors: 福岛和宏
Original assignee: Premetku Co ltd
Current assignee: Premetku Co ltd
Priority date: 2020-06-27
Filing date: 2020-12-04
Publication date: 2021-12-28
Anticipated expiration: 2040-12-04
Also published as: KR20220000973A; KR102493270B1; CN113844149B; TWI823035B; TW202200389A

Abstract

The present invention discloses a method for manufacturing a laminate, which includes: a step of subjecting the surface of the liquid crystal polymer film (10) to plasma treatment to impart a functional group, which is a hydrophilic group, to the surface of the liquid crystal polymer film; a step of forming a laminate (12) by hot-pressing the liquid crystal polymer film and the copper foil at a first temperature at which the functional group movement is activated, with the surface of the liquid crystal polymer film which has been subjected to the plasma treatment being opposed to the copper foil (11); a step of heat-treating the laminate at a second temperature at which the molecular orientation of the liquid crystal polymer film becomes random; and a step of quenching the laminate to a temperature at which the liquid crystal polymer film does not promote the reorientation. The laminate is formed by laminating a liquid crystal polymer film and a copper foil and has sufficient peel strength.

Description

Method for producing laminate

Technical Field

The present invention relates to a method for producing a laminate comprising a liquid crystal polymer film and a copper foil laminated together.

Background

Most of the flexible wiring substrates are constituted of a laminate in which an insulating polymer film and a copper foil are laminated. The circuit pattern is formed by etching the copper foil of the laminate.

In recent years, devices have been increasingly higher in frequency in order to increase the communication rate. As the insulating polymer film, a liquid crystal polymer film having a small dielectric loss and a small dielectric loss tangent has been used.

As a method for producing a laminate comprising a liquid crystal polymer film and a copper foil laminated, for example, patent document 1 discloses the following method: the liquid crystal polymer film and the copper foil are stacked and hot-pressed at a temperature not lower than the melting point of the liquid crystal polymer film to form a laminate.

Patent document 2 discloses a method for improving dimensional stability, which comprises: the liquid crystal polymer film and the copper foil are hot-pressed at a temperature of 260 ℃ to form a laminate, and the laminate is heat-treated at a temperature of not less than the melting point of the liquid crystal polymer film.

Patent document 1: japanese laid-open patent publication No. 2010-221694

Patent document 2: japanese laid-open patent publication No. 2000-343610

Disclosure of Invention

Technical problems to be solved by the invention

However, the laminate formed by the methods disclosed in patent documents 1 and 2 has the following problems: the peel strength when the copper foil is peeled from the liquid crystal polymer film cannot be sufficiently obtained, and the variation in peel strength is large.

The inventor of the application finds that: the problem of failing to obtain sufficient peel strength is a problem inherent to liquid crystal polymer films.

That is, a liquid crystal polymer film produced by a melt method, a solution method, or the like has small intermolecular cohesive energy in the thickness direction because molecules are oriented in a direction parallel to a plane (plane direction). Therefore, when the copper foil is peeled from the liquid crystal polymer film, the copper foil is peeled from the liquid crystal polymer film not from the interface between the copper foil and the liquid crystal polymer film but because the liquid crystal polymer film is damaged in the thickness direction.

That is, the peel strength of the polymer film other than the liquid crystal polymer film is generally determined by the adhesion at the interface between the copper foil and the liquid crystal polymer film; the peel strength of the liquid crystal polymer film is determined by weak intermolecular cohesive energy in the thickness direction of the liquid crystal polymer film.

The present invention has been made to solve the above problems, and has as its main object: provided is a method for producing a laminate which is obtained by laminating a liquid crystal polymer film and a copper foil and has sufficient peel strength with little variation.

Technical solutions for solving technical problems

The method for producing a laminate according to the present invention is a method for producing a laminate comprising a liquid crystal polymer film and a copper foil laminated together, the method comprising: a step of subjecting the surface of the liquid crystal polymer film to plasma treatment to impart a functional group, which is a hydrophilic group, to the surface of the liquid crystal polymer film; a step of forming a laminate by hot-pressing the liquid crystal polymer film and the copper foil at a first temperature at which the movement of the functional group is activated, with the surface of the liquid crystal polymer film which has been subjected to the plasma treatment being opposed to the copper foil; a step of heat-treating the laminate at a second temperature which is higher than the first temperature and at which the molecular orientation of the liquid crystal polymer film becomes random; and a step of quenching the laminate to a temperature at which the liquid crystal polymer film does not promote the reorientation.

Effects of the invention

According to the present invention, a method for producing a laminate which is obtained by laminating a liquid crystal polymer film and a copper foil and has a sufficient peel strength with less variation can be provided.

Drawings

Fig. 1(a) to (E) are diagrams schematically showing a method for producing a laminate in an embodiment of the present invention;

fig. 2 illustrates a method of forming a laminate in a roll-to-roll manner.

-description of symbols-

10-a liquid crystal polymer film; 10 a-the surface of a liquid crystalline polymer film; 11-copper foil; 12-a laminate; 12A-laminate roll; 23. 31-atmospheric pressure plasma device; 40-a preheating device; 41-hot pressing roller; 42-a heating device; 43-an insulating wall; 51-cooling means.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to the following embodiments, and can be modified as appropriate without departing from the scope of the present invention.

Fig. 1(a) to (E) schematically show a method for producing a laminate according to an embodiment of the present invention. The laminate in the present embodiment has a structure in which a liquid crystal polymer film and a copper foil are laminated. Here, the liquid crystal polymer film is formed of a thermotropic liquid crystal polymer which becomes liquid crystal in a molten state, and the liquid crystal polymer film is molecularly oriented in the front surface direction before lamination.

As shown in fig. 1(a), the surface 10a of the liquid crystal polymer film 10 is subjected to plasma treatment. Examples of gases used for plasma processing include: any one of argon, nitrogen, air, water vapor and carbon dioxide, or a mixture of two or more of the above gases. The plasma treatment can be, for example, atmospheric pressure plasma treatment.

A functional group which is a hydrophilic group is imparted to the surface of the liquid crystal polymer film 10 which has been subjected to plasma treatment. The functional group imparted to the surface of the liquid crystal polymer film 10 includes any of a hydroxyl group, a carbonyl group, and a carboxyl group.

If argon or nitrogen is used as a gas for plasma treatment, the plasma easily becomes stable. If water vapor and carbon dioxide are mixed into the gas for plasma treatment, hydroxyl groups, carbonyl groups, carboxyl groups, or functional groups are easily introduced into the surface of the liquid crystal polymer film 10.

The generation of the atmospheric pressure plasma can be performed by barrier discharge, arc discharge, microwave discharge, or the like, and the barrier discharge can be easily applied to a roll-to-roll process because the wide area is irradiated with the plasma.

As a plasma irradiation method for irradiating the liquid crystal polymer film 10 with plasma, a direct irradiation method in which the liquid crystal polymer film 10 is inserted into a barrier discharge electrode gap, a remote irradiation method in which plasma generated by barrier discharge, radicals, or the like is irradiated to the liquid crystal polymer film 10 by air flow, or the like can be employed.

The plasma irradiation power is preferably 1 W.min/cm per unit area of the liquid crystal polymer film 10²The above. When the plasma irradiation power is set to 10 W.min/cm²As described above, the molecular structure of the surface of the liquid crystal polymer film 10 is broken, and the peel strength is reduced. Therefore, the plasma irradiation power was 10 W.min/cm²The above is not preferred.

Next, as shown in fig. 1(B), the plasma-treated surface 10a of the liquid crystal polymer film 10 is made to face the copper foil 11. As shown in fig. 1(C), a liquid crystal polymer film 10 and a copper foil 11 are hot-pressed to form a laminate 12. Here, the temperature of the hot pressing (first temperature) is set to a temperature at which the movement of the functional groups imparted to the surface of the liquid crystal polymer film 10 is activated.

When the liquid crystal polymer film 10 and the copper foil 11 are hot-pressed at this temperature, a functional group (hydrophilic group) such as a hydroxyl group introduced into the surface of the liquid crystal polymer film 10 and the surface of the copper foil 11 undergo dehydration condensation. As a result, the adhesive force between the liquid crystal polymer film 10 and the copper foil 11 can be obtained. When the hydrophobic group of the silane coupling agent and the organic rust inhibitor are exposed on the outermost surface of the copper foil 11, it is preferable to remove the hydrophobic group of the silane coupling agent and the organic rust inhibitor by plasma treatment or the like on the outermost surface of the copper foil 11 or to add a hydrophilic group such as a hydroxyl group to the outermost surface of the copper foil 11.

For example, in the case where a hydroxyl group (C-OH) is introduced into a carbon atom of the surface of the liquid crystal polymer film 10, OH-Cu (copper) is dehydrogenatively condensed to form C-O-Cu. In the case of imparting a hydroxyl group to the surface of the copper foil 11, OH groups are hydrogen-bonded to each other, and then are finally subjected to dehydration condensation to form C — O — Cu. When a thin oxide film (CuO) is formed on the surface of the copper foil 11, OH and O are hydrogen-bonded, and then C-OH-O-Cu is dehydrogenated and condensed to finally form C-O-O-Cu.

The temperature of the hot pressing (first temperature) may be a temperature at which the movement of the functional group imparted to the surface of the liquid crystal polymer film 10 is activated. Specifically, the temperature of the hot pressing (first temperature) is preferably set to be not lower than the β relaxation temperature and not higher than the α relaxation temperature of the liquid crystal polymer film 10. In general, the values of the β relaxation temperature in the width direction and the length direction when the liquid crystal polymer film 10 is formed are different, and the values of the α relaxation temperature in the width direction and the length direction when the liquid crystal polymer film 10 is formed are also different. Here, the lower temperature among the above temperatures is taken as a representative value.

Here, the β relaxation temperature is defined as being determined by the rotational motion of small segments or side chains within chain molecules, and the α relaxation temperature is defined as being determined by the microscopic brownian motion of main chain segments. The liquid crystal polymer film 10 has a beta relaxation temperature of approximately 100 to 120 ℃ and an alpha relaxation temperature of approximately 230 to 250 ℃. The α relaxation temperature and the β relaxation temperature can be measured by a dynamic viscoelasticity measurement (DMA) device, respectively.

If the temperature of the hot press (first temperature) is lower than the β relaxation temperature, the adhesion between the liquid crystal polymer film 10 and the copper foil 11 cannot be sufficiently obtained. Therefore, the temperature of the hot pressing (first temperature) is lower than the β relaxation temperature, which is not preferable. If the temperature of the hot pressing (first temperature) is higher than the α relaxation temperature, the hardness (young's modulus) of the liquid crystal polymer film 10 is drastically decreased. Therefore, it is difficult to control the pressure at the time of hot pressing, the thickness of the liquid crystal polymer film 10 may be changed, or the liquid crystal polymer film 10 may be protruded from the copper foil 11. Therefore, the temperature of the hot pressing (first temperature) is preferably higher than the α relaxation temperature.

The pressure of the hot pressing is appropriately set in accordance with the temperature of the hot pressing, and is preferably in the range of 0.5MPa to 100MPa, and more preferably in the range of 5MPa to 50 MPa.

For example, an electrolytic copper foil, a rolled copper foil, or the like can be used as the copper foil 11. When the copper foil 11 having irregularities formed on the surface thereof is used, the adhesion between the liquid crystal polymer film 10 and the copper foil 11 can be further improved. When the copper foil 11 having a surface roughness (Rz) of 1.5 μm or less is used, the transmission loss can be suppressed even at a high frequency of about 10 GHz.

By forming a copper diffusion barrier layer (also serving as an adhesive layer) made of nickel, chromium, cobalt, manganese, titanium, or the like on the copper foil 11, the metal elements forming the copper diffusion barrier layer are coordinately bonded while maintaining the molecular structure of the liquid crystal polymer film 10. As a result, the adhesive force can be further improved. Further, by allowing the metal element to function as a copper diffusion barrier layer, the following phenomenon can be suppressed from occurring: the copper element serves as a catalyst (damage by copper) to decompose the liquid crystal polymer film 10 to deteriorate the liquid crystal polymer film 10, and the adhesion of the liquid crystal polymer film 10 to the copper foil 11 is reduced.

Next, as shown in fig. 1(D), the laminate 12 is heat-treated at a temperature (second temperature) at which the molecular orientation of the liquid crystal polymer film 10 becomes random. Here, the second temperature is set to a temperature higher than the hot-pressing temperature (first temperature) and in the vicinity of the melting point of the liquid crystal polymer film 10. Specifically, the second temperature is preferably not less than 20 ℃ lower than the melting point of the liquid crystal polymer film 10 and not more than 20 ℃ higher than the melting point of the liquid crystal polymer film.

If the second temperature does not reach a temperature 20 ℃ lower than the melting point of the liquid crystal polymer film 10, the molecular orientation of the liquid crystal polymer film 10 becomes insufficiently random, and therefore the second temperature does not reach a temperature 20 ℃ lower than the melting point of the liquid crystal polymer film 10, which is not preferable. If the second temperature exceeds a temperature 20 ℃ higher than the melting point of the liquid crystal polymer film 10, the liquid crystal polymer film 10 and the copper foil 11 are oxidized and deteriorated, and therefore the second temperature exceeds a temperature 20 ℃ higher than the melting point of the liquid crystal polymer film 10, which is not preferable.

As a heating method of the laminated body 12, for example, a heater heating method, a lamp heating method, an infrared heating method, an induction heating method, or the like can be used. When heating is performed by a heater, as shown in fig. 1(D), the heating member 13 is preferably brought into contact with the copper foil 11.

When the laminate 12 is heat-treated, it is not necessary to apply pressure to the laminate 12, but if pressure of 5MPa or more is applied to the laminate 12, the molecular orientation of the liquid crystal polymer film 10 in the in-plane direction is enhanced. Therefore, it is not preferable to apply a pressure of 5MPa or more.

Next, after the heat treatment of the laminate 12, as shown in fig. 1(E), the laminate 12 is quenched to a temperature at which the liquid crystal polymer film 10 is not promoted to be re-oriented. Specifically, the laminate 12 is preferably quenched to 80 ℃ or lower. For example, as shown in fig. 1(E), when the laminate 12 is cooled, the cooling member 14 is preferably brought into contact with the copper foil 11.

According to the present embodiment, after the laminate 12 is formed by hot-pressing the liquid crystal polymer film 10 and the copper foil 11 that have been subjected to the plasma treatment, the laminate 12 is heat-treated, whereby the molecular orientation of the liquid crystal polymer film 10 can be randomized. This increases the intermolecular cohesive energy in the thickness direction of the liquid crystal polymer film. As a result, when the copper foil 11 is peeled from the liquid crystal polymer film 10, a large amount of intermolecular cohesive energy is consumed to break the liquid crystal polymer film 10 in the thickness direction. So that higher anti-stripping strength can be obtained.

That is, the peel strength between the liquid crystal polymer film 10 and the copper foil 11 is not determined by weak intermolecular cohesive energy in the thickness direction of the liquid crystal polymer film 10 oriented in the plane direction, but the adhesive force at the interface between the copper foil and the liquid crystal polymer film is exhibited to the maximum. Thus, the peeling strength can be sufficiently increased, and variation in the peeling strength can be suppressed.

Note that, if it takes time to cool the laminate 12 to room temperature after the heat treatment is performed on the laminate 12, the following may occur: the liquid crystal polymer film 10 becomes fragile because of its excessively high crystallinity, and the peel strength of the laminate 12 is lowered by promoting the reorientation of the liquid crystal polymer film 10. Therefore, in order to suppress the promotion of the re-orientation, it is preferable that the laminate 12 is quenched to a temperature at which the crystallization of the liquid crystal polymer film 10 is not promoted and the re-orientation of the liquid crystal polymer film 10 is not promoted after the heat treatment of the laminate 12. Specifically, it is 80 ℃ or lower.

In the present embodiment, the laminate 12 is formed by hot-pressing the liquid crystal polymer film 10 and the copper foil 11 that have been subjected to the plasma treatment before randomizing the molecular orientation of the liquid crystal polymer film 10, and therefore, it is not necessary to apply excessive pressure to the laminate 12 in the subsequent heat treatment of the laminate 12. As a result, since excessive pressure is not applied to the liquid crystal polymer film 10, randomization of the molecular orientation of the liquid crystal polymer film 10 is not hindered.

In the present embodiment, since the laminate 12 is formed by hot-pressing the liquid crystal polymer film 10 and the copper foil 11 that have been subjected to the plasma treatment, the adhesion between the liquid crystal polymer film 10 and the copper foil 11 can be sufficiently ensured. Therefore, the peel strength between the liquid crystal polymer film 10 and the copper foil 11 can be sufficiently secured.

(method of producing a roll-to-roll laminate)

Fig. 2 shows a method for producing the laminate 12 by performing a step of subjecting the surface of the liquid crystal polymer film 10 to plasma treatment, a step of forming the laminate 12 by hot-pressing the liquid crystal polymer film 10 and the copper foil 11, a step of heat-treating the laminate 12, and a step of rapidly cooling the laminate 12 as a series of steps in a roll-to-roll manner.

As shown in fig. 2, the liquid crystal polymer film 10 in a roll form fed out from the transport drum 20 is subjected to plasma treatment by the atmospheric pressure plasma apparatus 23 while being supported by the metal belt transport apparatus 22 via the heating roller 21.

A plasma gas such as argon, nitrogen, air, or water vapor is supplied to the atmospheric pressure plasma device 23 through a flow meter (not shown), and the atmospheric pressure plasma device 23 is connected to a high frequency power supply (not shown) for generating plasma. If necessary, a plurality of atmospheric pressure plasma devices 23 are used to increase the processing speed.

On the other hand, the copper foil 11 in a roll form fed out from the transport drum 30 is transported and laminated with the liquid crystal polymer film 10 which has been subjected to the plasma treatment by the atmospheric pressure plasma device 23. The surface of the copper foil 11 may be subjected to plasma treatment by the atmospheric pressure plasma device 31 before lamination.

The liquid crystal polymer film 10 and the copper foil 11 in a laminated state are preheated by a preheating device 40 composed of a heating roll and a metal tape, and then laminated by a pair of heat and pressure rolls 41 to form a laminated body 12. The laminated body 12 obtained by the lamination is immediately thereafter subjected to a heat treatment by a heating device 42 composed of a heating roller and a metal belt. The preheating device 40, the pair of heat and pressure rolls 41, and the heating device 42 are covered with a heat insulating wall 43, and the inside is replaced with nitrogen gas or the like.

The heat-treated laminate 12 is cooled to 80 ℃ or lower by a cooling device 51 composed of a cooling roll and a metal belt after passing through a roll 50. After that, the cooled laminate 12 is wound around the transport drum 52 as a laminate roll 12A.

If the atmospheric

pressure plasma devices

23 and 31 are barrier discharge type atmospheric pressure plasma devices, it is easy to perform wide and uniform processing, and therefore, it is preferable to use the atmospheric

pressure plasma devices

23 and 31 as barrier discharge type atmospheric pressure plasma devices. If the remote atmospheric pressure plasma device is used as the atmospheric

pressure plasma device

23, 31, it is difficult to excessively destroy the molecules on the surface of the liquid crystal polymer film 10, and therefore, it is preferable to use the remote atmospheric pressure plasma device as the atmospheric

pressure plasma device

23, 31. From the viewpoint of plasma stability and cost reduction, it is preferable that the gas used for discharge contains nitrogen as a main component. Since hydroxyl groups, carbonyl groups, carboxyl groups, etc. are easily introduced into the surface of the liquid crystal polymer film 10 if air is added to nitrogen in an amount of several% to about 10%, it is preferable to add air in an amount of several% to about 10%.

The preheating device 40 is composed of a plurality of heating rolls and a metal belt. If a stainless seamless belt is used as the metal belt, it is easy to obtain a state in which the contact state of the metal belt with the copper foil 11 is uniform, so that it is good to use a stainless seamless belt as the metal belt. Since it is easy to efficiently obtain a predetermined temperature if an induction heating roller is used as the heating roller, it is preferable to use the induction heating roller as the heating roller. The nip pressure of the heating roller may be a pressure sufficiently large enough to ensure heat conduction with the copper foil 11. If the preheating temperature of the copper foil 11 is controlled by the temperature set by the heating roll and the preheating temperature of the copper foil 11 is set in the range of 150 ℃ to the hot-pressing temperature, the moisture adsorbed on the liquid crystal polymer film 10 and the copper foil 11 can be removed and wrinkles and the like caused by thermal expansion at the time of hot-pressing can be easily suppressed. Therefore, the preheating temperature of the copper foil 11 is preferably controlled by the temperature set by the heating roller, and the preheating temperature of the copper foil 11 is preferably set within the range of 150 ℃ to the hot pressing temperature.

If a pressure control type roll is used for the pair of heat and pressure rolls 41, it is preferable to use the pressure control type roll for the pair of heat and pressure rolls 41 because the lamination conditions can be easily and stably reproduced even when the thicknesses of the liquid crystal polymer film 10 and the copper foil 11 are slightly changed. The upper and lower heating rollers of the heat and pressure roller 41 may have the same temperature, but if the temperature of the heating roller on the copper foil 11 side is increased, an excessive heat load is not applied to the liquid crystal polymer film 10 when the joining interface is heated, so that it is preferable to increase the temperature of the heating roller on the copper foil 11 side.

The heating device 42 is composed of a plurality of heating rollers and a metal belt. If a stainless seamless belt is used as the metal belt, it is easy to obtain a uniform state of contact between the metal belt and the copper foil 11, and therefore it is preferable to use a stainless seamless belt as the metal belt. If an induction heating roller is used as the heating roller, a temperature of 300 ℃ or higher can be easily and efficiently obtained, and therefore an induction heating roller is preferably used as the heating roller. The nip pressure of the heating roller may be a pressure sufficiently large to ensure heat conduction with the laminated body 12. In the heat treatment, the temperature of the surface of the liquid crystal polymer film 10 may be measured by a radiation thermometer or the like, and the measured value may be fed back to control the temperature of the heating roller.

The cooling device 51 is composed of a plurality of cooling rolls and a metal belt. If a stainless seamless belt is used as the metal belt, a uniform state of contact with the copper foil 11 is easily obtained, so that it is preferable to use a stainless seamless belt as the metal belt. The nip pressure of the heating roller may be a pressure sufficiently large enough to ensure heat conduction with the laminate. Since the change of the internal stress when the wound laminate roll 12A is cooled to room temperature can be reduced if the temperature of the cooled laminate 12 is 80 ℃ or lower, preferably 40 ℃ or lower, it is preferable to set the temperature of the cooled laminate 12 to 80 ℃ or lower, preferably 40 ℃ or lower.

(examples)

Next, the above embodiments will be described in more detail with reference to examples and comparative examples.

[ common conditions ]

The liquid crystal polymer films 10 used in the examples and comparative examples are specifically as follows: manufactured by kohly, inc, product number "Vecstar CTS 50N", thickness: 50 μm, width: 270mm, melting point: 325 ℃, α relaxation temperature: the width direction at the time of film formation is 236 ℃, and the length direction at the time of film formation is 237 ℃; β relaxation temperature: the width direction during film formation was 105 ℃ and the length direction during film formation was 110 ℃. The copper foil 11 used is specifically as follows: electrolytic copper foil manufactured by JX Metal products Ltd, product No. "JXEFL-V2", thickness 18 μm, width 270 mm.

The laminate 12 is formed by a roll-to-roll method shown in fig. 2. The processing speed at this time was 1m/min, the draw-out tension of the liquid crystal polymer film 10 was 100N/m, the draw-out tension of the copper foil 11 was 100N/m, and the winding tension of the laminate 12 was 150N/m.

The preheating device 40 of the liquid crystal polymer film 10 sets the temperature of the heating roller to 100 ℃.

Five devices with a width of 270mm were placed as the atmospheric pressure plasma device 23, and the power: 1.85 W.min/cm²Frequency: plasma irradiation was performed at 35kHz to 55 kHz. The gap between the atmospheric pressure plasma device 23 and the liquid crystal polymer film 10 was set to 2mm, the plasma gas was set to 95% nitrogen, the dry air was set to 5%, and the total flow rate was set to 100L/min/stage.

The pair of heat and pressure rollers 41 use a diameter: 6 inches, width: 500mm, pressing area: 5.4cm²The pressure of the heated roller (2) is set to 30 MPa. The inside environment of the heat insulating wall 43 is set to 2% or less of oxygen.

[ evaluation method ]

The peel strength between the liquid crystal polymer film 10 and the copper foil 11 was measured in accordance with IPC-TM-650.

[ example 1]

A20 m laminated body 12 was produced with the roll temperature (the temperature of the upper and lower heating rolls of the heat and pressure roll 41) set at 200 ℃ and the heat treatment temperature (the temperature of each heating roll of the heating device 42) set at 340 ℃. 340 ℃ is the melting point 325 ℃ plus 15 ℃ of the liquid crystal polymer film 10.

[ example 2]

A20 m laminated body 12 was produced with the roll temperature (the temperature of the upper and lower heating rolls of the heat and pressure roll 41) set at 200 ℃ and the heat treatment temperature (the temperature of each heating roll of the heating apparatus 42) set at 310 ℃. 310 ℃ is the temperature at which the melting point of the liquid crystalline polymer film 10 is 325 ℃ to 15 ℃.

Comparative example 1

A20 m laminated body 12 was produced with the roll temperature (the temperature of the upper and lower heating rolls of the heat and pressure roll 41) set at 200 ℃ and the heat treatment temperature (the temperature of each heating roll of the heating apparatus 42) set at 360 ℃. 360 ℃ is the melting point 325 ℃ plus 35 ℃ of the liquid crystal polymer film 10.

Comparative example 2

A20 m laminate 12 was produced while setting the roll pressure temperature (the temperature of the upper and lower heating rolls of the heat and pressure roll 41) to the non-heating temperature (25 ℃ C.) and the heat treatment temperature (the temperature of each heating roll of the heating apparatus 42) to 340 ℃.

Comparative example 3

A20 m laminated body 12 was produced with the roll temperature (the temperature of the upper and lower heating rolls of the heat and pressure roll 41) set to 80 ℃ and the heat treatment temperature (the temperature of each heating roll of the heating apparatus 42) set to 340 ℃. The temperature of 80 ℃ is the beta relaxation temperature of the liquid crystal polymer film 10 of 105 ℃ to 25 ℃.

Comparative example 4

A20 m laminated body 12 was produced with the roll temperature (the temperature of the upper and lower heating rolls of the heat and pressure roll 41) set to 260 ℃ and the heat treatment temperature (the temperature of each heating roll of the heating apparatus 42) set to 340 ℃. 260 ℃ is the temperature of 236 ℃ plus 24 ℃ alpha relaxation temperature of the liquid crystal polymer film 10.

Comparative example 5

The roll temperature (temperature of the upper and lower heating rolls of the heat and pressure roll 41) was set to 340 ℃ and the heat treatment temperature was set to non-heating (25 ℃) to prepare a laminate 12 of a laminate 20 m. 340 ℃ is the melting point 325 ℃ plus 15 ℃ of the liquid crystal polymer film 10.

Table 1 shows the results of the peel strengths of the laminates 12 formed in examples 1 to 2 and comparative examples 1 to 5.

(Table 1)

As shown in Table 1, the peel strength in examples 1 and 2 was 6.7N/cm or more, and the strength was not problematic in practical use. In addition, the appearance was normal.

The peel strength of comparative example 1 was 8.1N/cm, and there was no problem in strength, but the liquid crystal polymer film 10 turned brown. Consider that: this is because the liquid crystal polymer film 10 is deteriorated by oxidation when the heat treatment temperature is higher than the melting point.

In comparative example 2, the peel strength was 2.8 to 4.8N/cm, which was largely varied and was insufficient in practical use. Consider that: the reason why the peel strength is insufficient is that the rolling temperature is too low and adhesion between the liquid crystal polymer film 10 and the copper foil 11 is hardly obtained. Consider that: the reason for the large variation is that a region in which the liquid crystal polymer film 10 is aligned in the local plane direction remains.

In comparative example 3, the peel strength was 5.8N/cm, which is insufficient in practical use. Consider that: this is because the rolling temperature is low and the adhesion between the liquid crystal polymer film 10 and the copper foil 11 cannot be sufficiently obtained.

In comparative example 4, the peel strength was 5.5N/cm, which was insufficient in practical use. Consider that: this is because the rolling temperature is high, and the molecules of the liquid crystal polymer film 10 are strongly oriented in the plane direction, and cannot be sufficiently randomized by the heat treatment. The thickness of the liquid crystal polymer film 10 was reduced, and the end of the liquid crystal polymer film 10 was seen to protrude from the copper foil. Consider that: this is because the roll pressing is excessive with respect to the state in which the liquid crystal polymer film 10 is softened at the time of the roll pressing.

In comparative example 5, the peel strength was 3.4 to 5.2N/cm, which was largely varied and was insufficient in practical use. Consider that: this is because the liquid crystal polymer film 10 is damaged in the thickness direction because the molecular orientation of the liquid crystal polymer film 10 remains. The reason why the liquid crystal polymer film 10 is damaged in the thickness direction because the liquid crystal polymer film 10 and the copper foil 11 are thermally pressed at a temperature equal to or higher than the melting point of the liquid crystal polymer film to form the laminate 12 is that the molecular orientation of the liquid crystal polymer film 10 remains.

The present invention has been described above with reference to preferred embodiments, but the above description is not limitative, and it is needless to say that various modifications can be made to the present invention.

Claims

1. A method for producing a laminate comprising a liquid crystal polymer film and a copper foil, characterized in that:

the method for manufacturing the laminated body comprises the following steps: a step (A) of subjecting the surface of the liquid crystal polymer film to plasma treatment to impart a functional group which is a hydrophilic group to the surface of the liquid crystal polymer film;

a step (B) of forming the laminate by hot-pressing the liquid crystal polymer film and the copper foil at a first temperature at which the movement of the functional group is activated, while the surface of the liquid crystal polymer film which has been subjected to the plasma treatment is opposed to the copper foil;

a step (C) of heat-treating the laminate at a second temperature which is higher than the first temperature and at which the molecular orientation of the liquid crystal polymer film becomes random; and

and (D) quenching the laminate to a temperature at which the liquid crystal polymer film does not promote the reorientation.

2. The method of manufacturing a laminated body according to claim 1, characterized in that:

in the step (B), the first temperature is not lower than the β relaxation temperature and not higher than the α relaxation temperature.

3. The method of manufacturing a laminated body according to claim 1, characterized in that:

in the step (C), the second temperature is not less than 20 ℃ lower than the melting point of the liquid crystal polymer film and not more than 20 ℃ higher than the melting point of the liquid crystal polymer film.

4. The method of manufacturing a laminated body according to claim 1, characterized in that:

in the step (a), the gas used for the plasma treatment may be any one of argon, nitrogen, air, water vapor and carbon dioxide, or a mixture of two or more of argon, nitrogen, air, water vapor and carbon dioxide.

5. The method of manufacturing a laminated body according to claim 1, characterized in that:

in the step (a), the functional group imparted to the surface of the liquid crystal polymer film is any of a hydroxyl group, a carbonyl group, and a carboxyl group.

6. The method of manufacturing a laminated body according to claim 1, characterized in that:

in the step (D), the laminate is quenched to a temperature of 80 ℃ or lower.

7. The method of manufacturing a laminated body according to claim 1, characterized in that:

in the step (a), the plasma treatment is an atmospheric pressure plasma treatment.

8. The method of manufacturing a laminated body according to claim 7, characterized in that:

the step (a), the step (B), the step (C), and the step (D) are performed as a series of steps by a roll-to-roll method.