Laminate using polyimide films, method for producing the same, and use of the same

Abstract

To provide: a laminate having a large amount of mechanical deformation for thermal input in a domestic temperature zone of 100°C or lower and in a low temperature zone; a method for producing the same; and use of the same.SOLUTION: Provided is a laminate comprising: a first polyimide film; and a second polyimide film that is surface-joined to the first polyimide film, wherein the first polyimide film is configured so that its coefficient of thermal expansion is larger than that of the second polyimide film. In addition, it is configured so that, among the surfaces the two polyimide films have, at least one of the surfaces opposite to the joining surfaces has a texture formed, the texture having an uneven shape of a prescribed pattern.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a laminate using a polyimide film, a manufacturing method thereof, and uses thereof, and the use thereof mainly relates to an actuator. [Background technology]

[0002] 2. Description of the Related Art Conventionally, mechanical elements such as heat engines, shape memory alloys, and bimetals are known as elemental technologies for converting thermal energy into mechanical kinetic energy without using electrical energy.

[0003] Heat engines are a typical method of converting thermal energy into power, and there are two types: (1) internal combustion engines, which extract motion from the high-temperature, high-pressure combustion gases generated when fuel is burned, and (2) external combustion engines, such as steam turbines, which use the heat of combustion to create high-temperature, high-pressure steam and use that steam to rotate a turbine. Because motion is extracted by dissipating the thermal energy of a high-temperature heat source to a low-temperature heat source, the high-temperature heat source must constantly consume fuel and the low-temperature heat source must constantly be cooled, but as long as the thermal cycle continues, it is possible to continuously extract large motion, making it the most widely used mechanical element.

[0004] However, internal combustion engines have the problem of needing a high-temperature heat source because they extract work by heating and expanding the working fluid with high-temperature gases produced by the combustion of fuel. In addition, there is the problem that the equipment becomes large and heavy because of the need to utilize adiabatic change and to have a structure that can withstand high temperatures and pressures. The same is true for turbines, which convert the kinetic energy of working fluids such as combustion gas and high-temperature steam into rotational motion, so the temperature range in which the equipment is used is high, and there is the problem that the equipment becomes large and heavy.

[0005] Shape memory alloys are alloys that can recover to their original shape when a certain temperature is reached. Although shape memory alloys alone can only restore their shape, by combining them with a spring mechanism that applies a bias force, they can be used as a driving source that responds to temperature changes by deforming to their memorized shape when heated and to a state in which the bias force is applied when cooled. Since thermal energy can be directly converted to mechanical kinetic energy, complex heat conversion mechanisms and reduction mechanisms can be omitted. In addition, they are easy to heat electrically, and have the advantage of being quiet and oil-free because they utilize material deformation.

[0006] However, there are problems with the manufacturing of shape memory alloys, such as the need for multiple materials including rare metals, complex material compositions, and complex manufacturing processes. In addition, shape memory alloys alone can only perform a single action of returning to their original shape due to temperature changes, and in order to obtain repeated motion, they must be combined with a spring mechanism or the like. In addition, at temperatures below 100°C, the amount of deformation per unit length is small, and only a few millimeters of deformation can be obtained by adopting a displacement magnification structure. Shape memory alloys lose their shape memory effect when heated above their shape memory temperature, so there is also the problem that they must be handled with care when used, such as requiring a protection circuit in the control circuit.

[0007] A bimetal is a metal plate formed by bonding two metal plates with different thermal expansion coefficients together into a single plate. When the temperature rises, the metal with the larger thermal expansion coefficient expands more in-plane (horizontally to the surface of the metal plate) compared to the metal with the smaller thermal expansion coefficient, causing the metal plate to bend (warp) in the thickness direction. For this reason, bimetals can be made into a flat, spiral, helix, or other shape to convert bending deformation into motion in a single direction. As it utilizes the thermal expansion of metals, it can be used in a wide range of temperatures, from low to high. Mechanical elements that utilize the displacement of bimetals are used in temperature controller switches (thermostats), thermometers, thermal relays, etc.

[0008] However, bimetals have problems in that the amount of deformation per unit length with respect to temperature changes is small, and the motion that can be produced from a single bimetal metal plate is limited to bending motion in which the long side of the metal plate curves, or a single-direction motion that is a conversion of that motion. In addition, since the operating temperature and amount of deformation of a bimetal are controlled only by the materials and shapes that are combined, there is a problem that the materials must be changed each time according to the specifications of the usage environment, amount of mechanical deformation, etc. Another problem is that rare metals are required to manufacture the alloys used in bimetals.

[0009] Regarding actuators with a multilayer film, Patent Document 1 discloses an actuator that generates force or displacement by an electric signal. Specifically, in an actuator that includes a multilayer film in which a stretchable layer and a base layer are bonded, and an input electrode that applies a voltage to the stretchable layer, the stretchable layer includes conductive particles and a binder material as components, the base layer is made of a material with a linear thermal expansion coefficient smaller than that of the stretchable layer, and the stress distribution generated in the multilayer film is generated by the film thickness distribution of the multilayer film, and the shape of the film thickness distribution of the multilayer film is striped, so that the multilayer film is bent (curved) into a cylindrical shape with an axis parallel to the direction of the stripes as the central axis.

[0010] Polyimides are organic polymers obtained by polycondensation of acid dianhydrides and diamines. One of the long-known polyimides is the aromatic polyimide "KAPTON (registered trademark)" developed by DuPont. Aromatic polyimides including KAPTON have high heat resistance and insulating properties, and are particularly attractive as materials for items used in extreme environments where humans find it difficult to approach, such as space environments, high temperature environments, extremely low temperature environments, and acidic and alkaline solutions.

[0011] However, aromatic polyimides generally melt at a very high temperature, and therefore often have a melting point close to the thermal decomposition temperature, or the melting point is difficult to identify (in this specification, "polyimides having a melting point close to the thermal decomposition temperature, or the melting point is difficult to identify" are referred to as "refractory polyimides"). Therefore, even if such polyimides are heated in an attempt to melt them, holes are formed or the polyimides are carbonized, and it was thought that welding was impossible. In this regard, Patent Document 2 discloses a method of directly bonding (joining) difficult-to-melt polyimide films, which were previously thought to be impossible to weld, by contacting a hot plate with the overlapping portion of two polyimide films. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Patent No. 4732876 [Patent Document 2] International Publication No. 2023 / 095869 Summary of the Invention [Problem to be solved by the invention]

[0013] The contents of the present disclosure have been made in consideration of the above-mentioned circumstances regarding the basic technologies for converting thermal energy into mechanical kinetic energy, and its purpose is to provide a laminate that has a large amount of mechanical deformation even when subjected to heat input in the living temperature range and low temperature range below 100°C, a manufacturing method thereof, and uses thereof. [Means for solving the problem]

[0014] In order to solve the above problems, the laminate of the present disclosure comprises a first polyimide film and a second polyimide film surface-bonded to the first polyimide film, the first polyimide film having a thermal expansion coefficient greater than that of the second polyimide film, and at least one of the surfaces of both polyimide films opposite to the bonding surfaces of both polyimide films is characterized in that a texture having a predetermined pattern of concave and convex shape is formed.

[0015] In order to solve the above problems, the actuator of the present disclosure includes the laminate, and is characterized in that a conductive member is disposed on at least one of the surfaces of the first and second polyimide films that is opposite to the bonding surfaces of the two polyimide films.

[0016] In order to solve the above problems, the generator disclosed herein is characterized in that the laminate generates electricity by being driven to bend, stretch or vibrate in response to temperature changes.

[0017] In order to solve the above problem, the camera module driving device disclosed herein includes the actuator.

[0018] In order to solve the above problems, the method for producing a laminate disclosed herein comprises the steps of: arranging the first and second polyimide films in this order from the opposing member side between a heated mold having a predetermined pattern of concave-convex shape on its surface and an opposing member having an elastic surface that faces the mold; and sandwiching and pressing both polyimide films between the mold and the opposing member to bond the two polyimide films together; and forming a texture having the predetermined pattern of concave-convex shape on the surface of the first polyimide film that contacts the opposing member. Effect of the Invention

[0019] The laminate, its manufacturing method and uses of the present disclosure exhibit excellent effects, such as a large amount of mechanical deformation even when subjected to heat input in the living temperature range and low temperature range of 100° C. or less. [Brief description of the drawings]

[0020] [Figure 1] 3A to 3C are front views each showing a schematic diagram of a manufacturing process of the laminate according to the embodiment; [Diagram 2] FIG. 2 is a front view showing a schematic view of a laminate according to the present embodiment. [Diagram 3] 13 is a copy of a photograph showing that the amount of displacement of a laminate before and after heating differs greatly depending on whether or not the texture is present. [Figure 4] This is a photograph showing that changing the shape of the texture changes the shape of the laminate. [Figure 5A] 3 is a front view showing the order of lamination of a polyimide film and a conductive member in the manufacturing method of a laminate according to the embodiment. FIG. [Figure 5B] FIG. 5B is a front view showing a case where the lamination order of polyimide films is changed from that of FIG. 5A. [Figure 5C] FIG. 5B is a front view showing a case where the layering order of the conductive members is changed from that of FIG. 5A. [Figure 6] 1 is a copy of a photograph of an actuator using a laminate of the present disclosure, which is driven by applying electricity to a conductive member to heat it. [Figure 7] FIG. 1 is a perspective view showing an example of a method for manufacturing an actuator using a laminate according to the present disclosure, which is driven by applying electrical current to a conductive member to heat it. [Figure 8] 7 is a copy of a photograph showing the temperature of the actuator shown in FIG. 6 when it is driven, measured by thermography. [Figure 9] 1 is a photographic copy of an inchworm-type microrobot using a laminate of the present disclosure. [Figure 10] This is a copy of a photograph taken of the operation of the inchworm-type microrobot in Figure 9. [Figure 11] 1 is a copy of a photograph showing a laminate of the present disclosure placed over a cup of hot water at 86° C. vibrating due to thermal fluctuations. [Figure 12A]FIG. 2 is a front view showing a schematic diagram of a step of producing a laminate according to the present disclosure by molding a resin precursor. [Figure 12B] FIG. 12B is a front view showing a schematic diagram of a process subsequent to that shown in FIG. 12A. [Figure 12C] FIG. 12C is a front view showing a schematic diagram of a process subsequent to that shown in FIG. 12B. [Figure 13] FIG. 1 is a schematic diagram for explaining power generation using vibrations caused by thermal fluctuations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present disclosure relates to a laminate using a polyimide film, a manufacturing method thereof, and uses thereof, and the use thereof mainly relates to an actuator. These will be described below.

[0022] <Manufacturing method> Fig. 1 is a front view showing a manufacturing process of the laminate according to the present embodiment, and Fig. 2 is a front view showing the laminate according to the present embodiment. The following description will be given with reference to these drawings. As described below, the laminate according to the present embodiment can be manufactured by laminating two polyimide films, so that a thin, lightweight, and inexpensive actuator can be realized.

[0023] In the method for manufacturing a laminate according to the present embodiment, first, as shown in FIG. 1, a conductive member 3, a first polyimide film 1, and a second polyimide film 2 are placed in this order as workpieces on an opposing member 5. From this state, a mold 4 is pressed against the upper surface of the second polyimide film 2 to apply pressure to the first polyimide film 1 and the second polyimide film 2, so that the conductive member 3, the first polyimide film 1, and the second polyimide film 2 are surface-bonded to each other, and a texture 1a having a predetermined pattern of unevenness is formed on the lower surface (the surface in contact with the opposing member 5) of the first polyimide film 1. In addition, in the laminate manufactured through the process shown in FIG. 1, a laminate in which the conductive member 3 is surface-bonded to the textured surface side of the first polyimide film 1 is obtained, but in the laminate of the present disclosure, the conductive member 3 is an optional component member. Therefore, FIG. 2 illustrates a laminate A1 in which the first polyimide film 1 and the second polyimide film 2 are surface-bonded.

[0024] The mold 4 is a mold having a predetermined pattern of unevenness 4a on its surface (the surface that contacts the workpiece), and is heated to a high temperature. The heating temperature of the workpiece by the mold 4 varies depending on the type of polyimide film used, but when a difficult-to-melt polyimide film is used as the first polyimide film 1, it is preferably 500°C to 600°C, and more preferably 520°C to 570°C. The time for which the mold 4 is in contact with the workpiece is preferably 0.3 seconds to 12 seconds, and more preferably 0.5 seconds to 5 seconds. The pressing pressure of the mold 4 against the workpiece is preferably about 100 kPa, and more specifically, the pressing pressure is preferably 50 kPa to 200 kPa, and more preferably 75 kPa to 150 kPa. The material of the mold 4 includes a metal mold, and a mold made of iron, copper, or silver is preferable.

[0025] The facing member 5 has a structure in which a cushioning material 52 and a protective film 51 for protecting the workpiece are arranged in this order on a base 53. The structure of the facing member 5 is not limited to this, and it is sufficient that the surface in contact with the first polyimide film 1 is configured to have elasticity. Because of this structure, by applying pressure with a mold 4 (pressing with the mold 4) as shown in FIG. 1, it is possible to form a texture 1a on the surface of the first polyimide film 1 that is in contact with the surface of the facing member 5 having elasticity.

[0026] The shape of the texture 1a can be controlled by the shape (unevenness 4a) of the surface of the mold 4. In Fig. 1, a plurality of parallel ridges (protrusions) are provided on the surface of the mold 4, and therefore a plurality of parallel grooves (recesses) are formed on the surface of the first polyimide film 1 as shown in Fig. 2. In other words, a striped texture is imparted.

[0027] The shape of the unevenness 4a (such as the size of the parallel ridges) can be appropriately changed according to the thickness of the polyimide film used as the workpiece in order to realize a laminate having a large mechanical deformation amount. For example, the distance between adjacent ridges can be 0.5 mm to 4 mm, the width of the ridges can be 0.5 mm to 1.5 mm, and the height of the ridges can be 0.5 mm to 1.0 mm. Grooves of a size corresponding to the ridges are formed as texture on the surface of the first polyimide film 1. The ridges in the mold 4 in FIG. 1 have a rectangular cross section, but the shape of the ridges is not limited to this, and may be a triangular cross section as shown in FIG. 7.

[0028] As shown in FIG. 1, after pressing with a mold 4, the protective film 51 is removed, and the welding margin generated in the laminate in which both polyimide films are bonded together is removed. If necessary, stress remaining in the laminate due to pressing is removed by a heat treatment or the like, thereby producing the laminate according to this embodiment.

[0029] Since the laminate manufactured through the manufacturing process shown in FIG. 1 includes the conductive member 3, the first and second polyimide films 1, 2 can be heated by passing a current through the conductive member 3. In this embodiment, an aluminum thin film electrode is used as the conductive member 3, but the conductive member 3 is not particularly limited as long as it generates heat when a current is passed through it, and one example is a metal thin film electrode. In addition, in the manufacturing method illustrated in FIG. 7, a second polyimide film 20 on which aluminum is vapor-deposited is used as the second polyimide film. In this way, the conductive member 3 may be vapor-deposited on the polyimide film in advance before the manufacturing process shown in FIG. 1 is performed.

[0030] In this embodiment, polyimide films having different thermal expansion coefficients are used for both polyimide films. In terms of the magnitude relationship of the thermal expansion coefficients, a polyimide film having a larger thermal expansion coefficient than that of the second polyimide film 2 is used for the first polyimide film 1. This allows the laminate according to this embodiment to be curved, stretched, or vibrated by temperature changes.

[0031] However, simply surface-bonding polyimide films with different thermal expansion coefficients cannot produce a laminate that has a large amount of mechanical deformation in response to heat input. The present inventors have discovered that a laminate that has a large amount of mechanical deformation in response to heat input can be realized by surface-bonding first and second polyimide films 1 and 2 and providing a texture to the surface of the first polyimide film 1, as shown in Figures 1 and 2.

[0032] This point is clearly shown in Figure 3, which is a copy of a photograph showing that the amount of displacement of the laminate before and after heating differs greatly depending on whether or not there is a texture on the surface of the first polyimide film 1. Details of the example of this photograph will be explained in the "Example" section below, but the photograph of Figure 3 shows that the formation of a texture on the surface of the first polyimide film 1 makes it possible to realize a laminate that exhibits a large amount of mechanical deformation in response to heat input.

[0033] Figure 4 is a copy of a photograph showing that the shape of the laminate changes by changing the shape of the texture. For example, when a plurality of parallel grooves are formed as a texture on the surface of the first polyimide film 1, forming the grooves in a direction perpendicular to the long side of the first polyimide film 1 (width direction) can result in a laminate deformed into a "curl (curved)" shape as shown in Figure 4(b), and tilting the direction in which the grooves are formed can result in a laminate deformed into a "twisted" or "torsional" shape as shown in Figures 4(a) and (c). All of these laminates undergo a motion (drive) in which the curved parts expand when heated, and therefore have a large amount of mechanical deformation in response to heat input.

[0034] 5A to 5C are diagrams for explaining that the lamination order of the workpieces in the laminate manufacturing method according to the present embodiment affects the magnitude of the mechanical deformation of the laminate. FIG. 5A is a front view showing the lamination order of the polyimide film and the conductive member in the laminate manufacturing method according to the present embodiment. FIG. 5B is a front view showing a case where the lamination order of the polyimide film is changed from that of FIG. 5A. FIG. 5C is a front view showing a case where the lamination order of the conductive member is changed from that of FIG. 5A. The present inventors have found that the mechanical deformation amount is extremely large in the laminate manufactured in the lamination order shown in FIG. 5A among the lamination orders shown in FIG. 5A to C. In contrast, when a conductive member is present between both polyimide films as in FIG. 5C, the mechanical deformation amount is extremely small, and it has been confirmed that the mechanical deformation amount is also small when the lamination order of both polyimide films is different as in FIG. 5B. Therefore, in the manufacturing method according to the present embodiment, the lamination order of the workpieces shown in FIG. 1 and FIG. 5A is used.

[0035] <Polyimide film> Next, the polyimide film used as the material of the laminate according to this embodiment will be described. Polyimide is an organic polymer obtained by polycondensation of acid dianhydride and diamine. Aromatic polyimide has high heat resistance and insulating properties, and has attractive properties as a material for items used in extreme environments where it is difficult for humans to approach, such as space environments, high temperature environments, extremely low temperature environments, and acidic and alkaline solutions.

[0036] Aromatic polyimides generally melt at a very high temperature, and therefore often have a melting point close to the thermal decomposition temperature, or the melting point is difficult to identify (as described above, hereinafter, "polyimides having a melting point close to the thermal decomposition temperature, or the melting point is difficult to identify" will be referred to as "refractory polyimides"). Physical properties of a refractory polyimide film include a melting point and thermal decomposition temperature both being 400°C or higher, and the melting point and the thermal decomposition temperature being close to or the same as each other.

[0037] In the laminate of the present disclosure, the first polyimide film has a larger thermal expansion coefficient than the second polyimide film, so that the laminate can be deformed in response to heat input. In the method for producing the laminate according to the present embodiment shown in FIG. 1, a difficult-to-melt polyimide film (a polyimide film that has not been chemically modified, such as by introducing a thermoplastic segment) is used as the first polyimide film, and a thermosetting polyimide film is used as the second polyimide film. By using such a combination, the above relationship in thermal expansion coefficient can be satisfied.

[0038] The refractory polyimide film used as the first polyimide film preferably has a glass transition temperature of 200° C. or more and 450° C. or less, more preferably 220° C. or more and 450° C. or less, and particularly preferably 250° C. or more and 420° C. or less. The glass transition temperature of the refractory polyimide film is measured by differential scanning calorimetry (DSC).

[0039] The thermal decomposition temperature of the refractory polyimide film used as the first polyimide film is preferably 550° C. or higher, more preferably 580° C. or higher, and particularly preferably 600° C. or higher. More specifically, it is preferably 550° C. or higher and 900° C. or lower, more preferably 580° C. or higher and 850° C. or lower, and particularly preferably 600° C. or higher and 800° C. or lower. The thermal decomposition temperature of the refractory polyimide film is measured by a thermobalance (PGA).

[0040] The melting point of the refractory polyimide film used as the first polyimide film is preferably 480° C. or higher, more preferably 500° C. or higher, and particularly preferably 530° C. or higher. More specifically, it is preferably 480° C. or higher and 600° C. or lower, more preferably 500° C. or higher and 600° C. or lower, and particularly preferably 530° C. or higher and 595° C. or lower. The melting point of the refractory polyimide film is measured by differential thermal analysis (DTA).

[0041] Examples of the difficult-to-melt polyimide film (a polyimide film that has not been chemically modified by, for example, introducing a thermoplastic segment) used as the first polyimide film include a polyimide film containing a polyimide having a repeating unit represented by the following formula (1) and a polyimide film containing a polyimide having a repeating unit represented by the following formula (2).

[0042] [ka] (1)

[0043] [ka] (2)

[0044] An example of a polyimide film containing a polyimide having a repeating unit represented by the above formula (1) is "UPILEX (registered trademark)" manufactured by Ube Industries, Ltd.

[0045] Examples of polyimide films containing a polyimide having a repeating unit represented by the above formula (2) include "KAPTON (registered trademark)" manufactured by DuPont and "Apical (registered trademark)" manufactured by Kaneka Corporation.

[0046] The thermosetting polyimide film used as the second polyimide film is not particularly limited as long as it is a polyimide film having thermosetting properties, and examples thereof include "UPILEX (registered trademark)-S" and "UPILEX (registered trademark)-SGA" manufactured by UBE Corporation.

[0047] The thicknesses of the first and second polyimide films used in the manufacture of the laminate according to this embodiment are not particularly limited, and are preferably adjusted appropriately according to the displacement amount, generated force, response speed, weight, etc. required for the laminate. In this embodiment, in order to increase the displacement amount, the first polyimide film was made to have a thickness of 125 μm, and the second polyimide film was made to have a thickness of 25 μm.

[0048] <Actuator using the laminate of the present disclosure> The laminate of the present disclosure has a large mechanical deformation in response to heat input, and can therefore be used as an actuator. In addition, since it can collect thermal energy from the environment and convert it into motion, it can be used as a power generator or a temperature-sensing autonomous driving mechanism.

[0049] An example of the actuator is one in which a heating member is provided on the surface of the laminate A1 shown in Fig. 2, and the heating member can be a conductive member such as a metal thin film electrode. Examples of methods for manufacturing an actuator including a conductive member include the method shown in Fig. 1 in which a polyimide film and a conductive member are surface-bonded, and the method shown in Fig. 7 in which a polyimide film on which a metal such as aluminum is vapor-deposited is used. In the manufacturing method shown in Fig. 7, a first polyimide film 1 and a second polyimide film 20 on which aluminum is vapor-deposited are sandwiched between a heated mold 4 and an opposing member 5 and pressed to manufacture an actuator in which a thin film electrode is provided on the surface of a polyimide film laminate.

[0050] Furthermore, the laminate of the present disclosure can be used as an actuator by itself without providing a heating member such as a conductive member. Figure 11 is a copy of a photograph of the laminate of the present disclosure placed on a cup of hot water at 86°C vibrating due to thermal fluctuations. Details of the embodiment of this photograph will be described in the "Example" section below, but the laminate of the present disclosure undergoes significant mechanical deformation due to changes in the temperature environment and functions as an actuator.

[0051] The maximum output characteristic of the laminate of the present disclosure as an actuator can be controlled by the shape of the texture imparted to the polyimide film. In the case of a striped shape, which is the texture shape of the laminate according to the present embodiment shown in Figures 1 and 2, the deformation amount of the laminate of the present disclosure can be controlled by the width of the stripes (width of the grooves), the spacing between the stripes (distance between adjacent grooves), the number of stripes (number of grooves), the thickness of the polyimide film, the ratio of the thickness to the depth of the grooves, etc.

[0052] In addition, it is believed that the laminate of the present disclosure can produce various movements by changing the shape of the texture imparted to the polyimide film from the striped shape shown in Figures 1 and 2 to a different shape than the stripes. Therefore, this is a technical idea that leads to the realization of a sheet-like structure that generates movements with an ultra-high degree of freedom.

[0053] By changing the thickness of the polyimide film used as the material or by changing to a material with a higher elastic modulus, the mechanical rigidity of the laminate produced can be changed, making it possible to control the force generated when used as an actuator.

[0054] By changing the thermal expansion coefficient of at least one of the first and second polyimide films used as materials, it is possible to change the temperature sensitivity of the manufactured laminate. By using a material with anisotropic thermal expansion coefficient, it is thought that it is possible to realize a jump phenomenon in which a sudden and large deformation occurs when a specific temperature is reached, and this is expected to be applied to latch mechanisms, safety devices, etc.

[0055] The laminate of the present disclosure includes first and second polyimide films, but is not limited to a two-layer structure. A layer having a different thermal expansion coefficient may be laminated, and the layer may be a polyimide film or a material other than a polyimide film. By forming a structure of three or more layers having different thermal expansion coefficients, it is expected that the displacement will be increased and the generated force will be improved. In addition, for other purposes, further layers may be laminated. For example, by forming a laminate in which a film having piezoelectricity is laminated, a laminate capable of generating electricity from minute thermal changes such as thermal fluctuations can be realized.

[0056] <Applications of the actuator using the laminate of the present disclosure> -Use in camera module drive devices- A possible application of an actuator using the laminate of the present disclosure is to use it as a driving force in a camera module driving device used in a smartphone or the like.

[0057] In the past, the voice coil motor (VCM) type, which operates the lens by electromagnetic force using a magnet and a coil, was the mainstream for autofocus and image stabilization mechanisms in camera module driving devices used in smartphones and the like. However, since it requires a complex structure, it is said that there is a limit to the miniaturization of the device. Therefore, autofocus and image stabilization mechanisms using shape memory alloys (SMA) driven by electrical heating have been proposed (for example, JP 2022-163541 A).

[0058] Shape memory alloys have the property of transforming into a memorized shape when heated above a certain temperature, so they do not require a complex structure for the driving part, and because they are driven by passing electricity, they can simplify the internal structure of the camera unit, reduce the number of parts, and make the size smaller. However, shape memory alloys have the problem that when a voltage is applied due to momentary noise or the like and the temperature rises, the shape memory effect is lost, and it is said that the product has stability problems. Other issues with shape memory alloys include the use of rare metals and the complicated manufacturing process.

[0059] Therefore, it is believed that by using the laminate of the present disclosure as an actuator, it is possible to realize an autofocus and image stabilization mechanism that is thinner and more stable. Since the actuator made of the laminate of the present disclosure utilizes the difference in thermal expansion coefficient, it does not lose its shape memory effect at a specific temperature, unlike a shape memory alloy, and since it generates a linear deformation with respect to temperature, it is expected to improve the controllability of the deformation.

[0060] Since the laminate of the present disclosure is formed of a polyimide film, it has a high temperature resistance equal to or higher than the electronic components built into the camera module driving device. Therefore, it can fully withstand high temperatures in real life. In addition, it can be made lighter than a shape memory alloy made of metal. In addition, while a support member for supporting electronic components and lenses is sometimes made of a resin material such as polyimide, it is also possible to integrally (continuously) form such a support member and a portion that functions as an actuator from polyimide.

[0061] In addition, since polyimide is the same material as the flexible substrates used for wiring in cameras and smartphones, it can be directly introduced into the current manufacturing process. In contrast, in the case of the VCM type and SMA type, a manufacturing process needs to be prepared on a separate line and then the assembly process onto the flexible substrate needs to be performed. Therefore, by using the laminate of the present disclosure as an actuator for a camera module drive device, the manufacturing process can be simplified.

[0062] Therefore, by using the laminate of the present disclosure as an actuator in a camera module drive device, it is expected that the autofocus and image stabilization drive mechanism can be made more compact if the lens size is comparable, and that a larger lens can be installed if the actuator size is comparable.

[0063] In addition, in the zoom module, optical zoom has been realized by moving the lens with an ultrasonic motor or a stepping motor that is large relative to the size of the lens. This is because optical zoom requires a large deformation, which limits the use of small actuators such as voice coil motors. In contrast, the actuator using the laminate of the present disclosure is extremely thin and capable of large deformation. Therefore, even when an actuator using the laminate of the present disclosure is used in a zoom module, it is considered to have an advantage over conventional zoom modules.

[0064] -Use in generators- Since an actuator using the laminate of the present disclosure is capable of extracting mechanical motion even in the living temperature range and low temperature range of 100°C or less, by combining it with a vibration-type generator as shown in FIG. 13, a generator that utilizes waste heat from daily life can be realized.

[0065] The laminate of the present disclosure vibrates in quick response to small temperature changes such as thermal fluctuations, and therefore does not require the temperature difference (preparation of high and low temperature parts) that was necessary for thermal power generation using conventional thermoelectric conversion elements, and can generate thermal power in various temperature environments. For example, it is possible to generate power from slight differences in heat that were not previously expected to be utilized, such as waste heat from temperature control devices such as air conditioners and refrigerators, heat generated by batteries such as electric vehicles and smartphones, and fluctuations in the earth's surface temperature due to sunlight and light breezes. In addition, since thermal fluctuations exist in any climate zone, it can be used in sand dune areas, water areas with a lot of vegetation, mountainous areas, and other areas where it is impossible to install solar panels or wind turbines.

[0066] -Use in microrobots and innocent-scale robots- The laminate of the present disclosure can be constructed only from polyimide film, so it is extremely thin and lightweight, and can generate large mechanical deformations, so by using it as an actuator, it can realize small, diverse, and high-density movements like those of insects, small animals, and small fish. Furthermore, it is believed that it can achieve a super aspect ratio (thickness is 1 / 1000 of the length and width of the surface) and extremely light weight that cannot be achieved by living organisms.

[0067] Therefore, by using the laminate of the present disclosure, it is possible to easily manufacture microrobots that can be directly inserted into the body to perform treatment, insect-scale robots that can be used to investigate ecosystems and search in the event of a disaster, etc. In addition, since it is possible to extract mechanical motion even in the living temperature range and low temperature range below 100°C, it is expected that non-contact and remote operation and energy supply will be possible by heating using electromagnetic induction or laser light.

[0068] -Use in temperature-sensing autonomous driving mechanisms- The laminate of the present disclosure generates a curved or vibrating motion when in a plate shape as shown in FIG. 2, but by changing the shape, various movements can be generated in response to heat input. For example, if it is formed into a coil shape, it can generate a linear motion, and if it is connected and arranged in a ring shape, it can generate a swinging (swaying) or eccentric rotation motion. It is considered that by combining these various movements, it is possible to realize a temperature-sensing autonomous driving mechanism that senses and uses changes in the environmental temperature and moves autonomously. For example, a temperature-sensing autonomous driving mechanism that uses the laminate of the present disclosure for the movable parts that open and close in ventilation for clothing, agricultural vinyl greenhouses, heat dissipation mechanisms for car bodies and batteries, etc., can be mentioned. In such a temperature-sensing autonomous driving mechanism, since it is driven by the deformation of the laminate of the present disclosure, electronic control is not required, and since the number of moving parts is small, it is possible to operate for a long time.

[0069] <Other embodiments> It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to provide a basis for a restrictive interpretation. Therefore, the technical scope of the present disclosure is not interpreted solely by the above-described embodiments, but is defined based on the claims. The technical scope of the present disclosure also includes all modifications within the scope and meaning equivalent to the claims.

[0070] For example, the laminate of the present disclosure is not limited to one produced by surface-bonding solid polyimide films together, but may also be produced by using a mold to cure a liquid (varnish-like) precursor resin, thereby forming a polyimide thin film having a texture formed on its surface.

[0071] 12A-C are front views showing a process for producing a laminate according to the present disclosure by molding a resin precursor, with FIG. 12B showing a process subsequent to that shown in FIG. 12A and FIG. 12C showing a process subsequent to that shown in FIG. 12B. As shown in FIG. 12A, a second polyimide film 2 is placed on a base 62, a liquid precursor resin 1' is applied thereon, and then a mold 61 for texture molding is used as shown in FIG. 12B, followed by a reaction process such as heat treatment, to obtain a laminate according to the present disclosure as shown in FIG. 12C. According to this manufacturing method, it is also possible to produce a laminate in which the first and second polyimide films 1 and 2 are both thermosetting polyimide films. EXAMPLES

[0072] The laminate and actuator of the present disclosure will be specifically described below based on examples.

[0073] <Example 1. Observation of the effect of expanding displacement by adding texture (Fig. 3)> The laminate shown in the lower part of Fig. 3 is one that has been given a texture with continuous unevenness in a single direction (a striped texture with multiple parallel grooves) during manufacturing, while the laminate shown in the upper part of Fig. 3 is one that has not been given a texture during manufacturing. Both laminates are similar except for the presence or absence of texture. Both laminates were manufactured by the method shown in Fig. 1, but no conductive member (thin film electrode for electrical heating) was laminated. The materials used and manufacturing conditions are as follows: The shape of the mold surface used to create the texture Distance between adjacent ridges (convex parts): 2.0 mm Ridge width: 1.0mm Number of ridges: 50 First polyimide film: Upilex (registered trademark)-RN (manufactured by UBE Corporation, thickness 25 μm) Second polyimide film: Upilex (registered trademark)-S (manufactured by UBE Corporation, thickness 25 μm) -Size of laminate (both films): long side 100mm, short side 10mm

[0074] The photographs in Figure 3 show the difference in the amount of deformation of laminates with and without texture when heated to 200° C. in a constant temperature oven. Note that in the photograph of the laminate with texture in Figure 3, the first polyimide film (the film with the larger thermal expansion coefficient) was placed on top, and the photograph of the laminate without texture was taken with the second polyimide film (the film with the smaller thermal expansion coefficient) placed on top.

[0075] When the bending deformation of both laminates was measured, the laminate without texture had a bending angle of 5 degrees, while the laminate with texture had a bending angle of 664 degrees. In other words, by imparting texture to the surface of the first polyimide film, it was possible to achieve a bending deformation amount that was approximately 133 times larger. In addition, the effect of reversing the direction of deformation with respect to temperature was observed.

[0076] <Example 2. Fabrication of an electric heating actuator by adding thin-film electrodes (Figs. 6 and 8)> By adding a thin-film electrode to the textured laminate of Example 1, a microactuator was fabricated that can be heated by applying a voltage to the thin-film electrode. It was confirmed that the microactuator was heated by applying a voltage to the thin-film electrode, and was driven to expand from the curved state shown in the photograph of FIG. 6, and was deformed to an expanded state. FIG. 8 is a copy of a photograph in which the temperature of this microactuator when it was driven was measured by thermography, and it can be seen that it was driven at 69.54°C. In other words, it was confirmed that the fabricated microactuator could be driven in a temperature range of 100°C or less.

[0077] <Example 3. Fabrication of an inchworm-type microrobot (FIGS. 9 and 10)> An inchworm-type microrobot was fabricated by adding thin-film electrodes to the textured laminate of Example 1. FIG. 9 is a copy of a photograph of the fabricated inchworm-type microrobot, and FIG. 10 is a copy of a photograph of the driving state of the inchworm-type microrobot. The fabricated inchworm-type microrobot has a total length of 30 mm excluding wiring, a total width of 20 mm, a thickness of 50 μm, and a mass of 0.05 g or less. The fabricated inchworm-type microrobot was driven as shown in FIG. 10 and was able to move at an average speed of 25 mm / min. This shows that the actuator using the laminate of the present disclosure is an actuator with sufficient performance for realizing a microrobot.

[0078] <Example 4. Observation of deformation caused by steam fluctuation (Fig. 11)> When the laminate with texture in Example 1 to which a thin film electrode was added was placed on a cup filled with hot water at 86°C, it was confirmed that the laminate vibrated due to minute thermal fluctuations. FIG. 11 is a copy of a photograph of this state. By placing hot water under the laminate, it moved in the opposite direction to the flow of steam (toward the surface of the hot water), and this direction coincided with the deformation direction when the temperature of the laminate rose, so it was confirmed that it was driven by heat. A temperature difference is required for a conventional vibrating body driven by heat to vibrate, whereas the laminate is thought to be driven by thermal fluctuations emitted from a single heat source. Therefore, it is expected that electric energy can be generated from thermal energy by using the vibration of the laminate disclosed herein to drive a conventional vibration-type generator. [Industrial Applicability]

[0079] As described above, the laminate of the present disclosure can be used as an actuator, and the actuator is expected to be used in camera module driving devices, power generators, temperature-sensitive autonomous driving mechanisms, and the like.

[0080] The present inventors have also proposed an academic field called Filmotics (Film + Robotics) as an extremely lightweight and extremely thin robotics in which the skeletal structure, actuators, and sensors are all constructed only from film. Filmotics is a robot system characterized by a mass-to-volume ratio that is far different from conventional robotics, and research is currently being conducted into this new field of microrobots that are expected to have activity performance and various characteristics that exceed those of insects. An actuator using the laminate of the present disclosure is suitable for application to such microrobots. [Explanation of symbols]

[0081] 1. First polyimide film 1' Liquid precursor resin 1a Texture (unevenness on the film surface) 2. Second polyimide film 20 A second polyimide film with aluminum vapor deposition 3 Conductive material (thin film electrodes for electrical heating) 4. Mold 4a Unevenness on the mold surface 5 Counterpart 51 Protective Film 52 Cushioning material 53 Pedestal 61 Texture molding mold 62 Pedestal A1 Laminate A2 laminate

Claims

1. A first polyimide film and a second polyimide film surface-bonded to the first polyimide film, the first polyimide film has a larger thermal expansion coefficient than the second polyimide film; A laminate comprising: at least one of the surfaces of the polyimide films opposite the bonding surfaces thereof, the surface having a predetermined pattern of projections and recesses formed thereon.

2. The laminate according to claim 1 , A laminate, wherein the texture is formed on the first polyimide film.

3. The laminate according to claim 1 or 2, The first polyimide film is a polyimide film containing a polyimide having a repeating unit represented by the following formula (1), or a polyimide film containing a polyimide having a repeating unit represented by the following formula (2), The laminate, wherein the second polyimide film is a thermosetting polyimide film. 【Chemistry 1】 ・・・（１） 【Chemistry 2】 ・・・（２）

4. An actuator comprising the laminate according to claim 1 or 2, An actuator, comprising: a conductive member disposed on at least one of the surfaces of the first and second polyimide films opposite to the bonding surfaces of the two polyimide films.

5. 3. A generator, comprising the laminate according to claim 1 or 2, which generates electricity by being driven to bend, stretch or vibrate in response to a temperature change.

6. A camera module driving device comprising the actuator according to claim 4.

7. A method for producing the laminate according to claim 2, comprising the steps of: a heated mold having a predetermined pattern of projections and recesses on its surface and an opposing member having an elastic surface, the first and second polyimide films being disposed in this order from the opposing member side between the heated mold and an opposing member facing the mold, and then the mold and the opposing member sandwich and press both polyimide films, A method for producing a laminate, comprising the steps of: surface-bonding the two polyimide films together; and forming a texture having a predetermined pattern of projections and recesses on the surface of the first polyimide film that comes into contact with the opposing member.

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