JP2015197973A - Method of manufacturing flexible electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a flexible electronic device so that the thickness and weight of the electronic device can reduced while the electronic device is made flexible, afterimage or burn-in of a display surface can be prevented by uniformly diffusing and discharging a heat distribution occurring under aging of an organic light emission element, and a support body and a flexible board can be easily exfoliated from each other after the flexible electronic device is prepares without any damage.SOLUTION: A method of manufacturing a flexible electronic device comprises a step of manufacturing a laminate comprising a thermal conductive substrate and a support body by coating the support body with a thermal conductive resin material formed of resin and filler, a step of forming a device layer on the thermal conductive substrate, and a step of exfoliating the support body and the thermal conduction substrate from each other.

Description

  The present invention relates to a method for manufacturing a flexible electronic device, and includes a substrate having excellent thermal conductivity, such as a display device such as a liquid crystal display, an organic EL display, and electronic paper, and a light receiving device such as a light receiving element of a thin film solar cell. The present invention relates to a method suitable for manufacturing various flexible electronic devices.

  Currently, glass substrates are mainly used in the field of electronic devices such as flat panel displays and electronic paper, but glass substrates are heavy and fragile, and there is a problem that the strength decreases when the weight is reduced and the thickness is reduced. Studies are being actively conducted to realize flexible electronic devices that are replaced with resin materials. Application of a resin substrate having a toughness higher than that of a glass substrate to a flexible display panel that can be bent or rolled is under consideration. However, since many of these technologies require new production technologies and equipment, they have not been mass-produced.

  In recent years, as a method for manufacturing a flat panel display, a method of using a material in which a resin layer is provided on a thin glass substrate has been proposed as a material that is light and difficult to break. That is, a laminate in which a resin layer is formed on a glass substrate is prepared, and a thin film transistor (hereinafter referred to as TFT), a transparent electrode, or the like is formed on the resin surface, and can be used as a display member. In addition, as a method for producing a member for a flexible electronic device, a thin film transistor, a transparent electrode, or the like is formed on the resin surface of the laminate, and then a glass substrate is heated by a laser or a peeling layer is provided to peel off (hereinafter referred to as a method) , Described as lift-off method). (Patent Documents 1 to 3 etc.).

  A lift-off method has been proposed as a method for manufacturing a member for a flexible electronic device, and the resin layer can be peeled from the glass substrate by irradiating the glass substrate with ultraviolet laser light (Patent Document 1). The ultraviolet laser light irradiates a wavelength exceeding 200 nm. However, there is a potential problem with using the heating effect when lifting off the resin layer from the glass substrate. In order to cause lift-off, sufficient energy is required. In this case, it is necessary to prevent damage to the resin substrate or a member formed thereon caused by thermal expansion.

  As a method for manufacturing a member for a flexible electronic device, for example, Patent Document 2 discloses that a release layer having a different degree of adhesion is provided between a glass substrate and a resin layer, and thus studies on lift-off from the glass substrate are also in progress. However, parylene and cyclic olefin copolymers have a problem that their heat-resistant temperature is low and they cannot be used in the TFT annealing process.

  Also in Patent Document 3, a method of peeling by providing a peeling layer between a glass substrate and a resin substrate has been studied. However, since the peeling layer is provided by vapor deposition or coating, the process becomes complicated and essential production is performed. It does not improve sex.

  On the other hand, the flexible electronic device member is required to have high heat dissipation, and how to release heat generated from the organic light emitting element from the apparatus is an important issue.

  An organic light emitting device emits light when a voltage is applied between the electrodes and a current corresponding to the display pattern flows through the light emitting device. At present, a part of the light is converted into thermal energy during light emission, and the organic light emitting device has Joule heat. May generate heat. It is said that the heat generation of the organic light emitting element may cause a decrease in light emission characteristics such as luminance and deterioration of the organic light emitting element itself. In addition, the higher the temperature of the organic light emitting element, the more likely it is to cause deterioration of the characteristics of the organic light emitting element.

  Examples of problems caused by excessive heat generation of the element include an afterimage and a burn-in phenomenon. As described above, since the current corresponding to the display pattern flows through the light emitting element, a portion where a large amount of current flows and a portion where the current hardly flows are generated depending on the display pattern, and the heat generation amount varies depending on the display pattern. For this reason, if the fixed pattern is continuously displayed for a long time, the amount of heat generated by the organic light emitting element is locally different, and an afterimage or image sticking occurs on the display screen. The fixed pattern gradually disappears in the afterimage, but the fixed pattern does not disappear permanently in burn-in. For this reason, an afterimage or burn-in of a fixed pattern results in a decrease in image quality. Therefore, in order to prevent local differences in the amount of heat generated, it is necessary to quickly diffuse the heat to the outside and make the amount of heat generated by the entire organic light emitting element uniform, and the heat generated by the organic light emitting element is dissipated outside the element. Various measures have been studied.

  Another problem caused by excessive heat generation of the element is, for example, luminance variation. For example, when the entire screen is displayed in white over a long period of time, a portion that is difficult to dissipate heat is generated due to differences in the structure of the organic light emitting element and the housing structure that stores the organic light emitting element. As a result, a difference in light emission characteristics is caused by a local temperature difference, and the brightness of the display screen may vary. In order to make the luminance of the display screen uniform, it is necessary to diffuse the heat generated locally and release it to the outside.

  Various approaches have been taken to solve the problems caused by excessive heat generation of these elements.

  As a method of improving heat dissipation, from the substrate to the outside by providing a highly thermally conductive substrate using glass, metal, ceramics material, heat dissipation by fan or water cooling, increase of surface area by unevenness, layer by coating or sheet, etc. A method has been proposed in which the heat radiation of the organic light emitting device is greatly improved and the temperature rise of the organic light emitting device is suppressed. (Patent Document 4)

  In general, since the thermal conductivity of glass is as low as 1 W / m · K, the generated heat is difficult to conduct from the inside to the outside of the glass. In addition, since heat is difficult to diffuse uniformly in glass, heat distribution is uneven in the glass substrate, resulting in differences in characteristics such as luminance variations and changes in lifetime over time in organic light-emitting elements and devices that mount them. May end up.

  Although examination using a metal substrate for a support is also performed in Patent Document 5, a Cu substrate having a thickness of 2 mm is used in the example, and it is difficult to make it flexible and thin. Further, in Patent Document 5, heat dissipation using an increase in surface area due to unevenness is also studied, but the structure of heat dissipation becomes complicated and the production efficiency decreases.

  A study using a ceramic substrate as an organic light-emitting element substrate was also made (Patent Document 6), but there was a drawback that it could not be applied to a flexible device. Although examination of the flexible electronic device board | substrate containing a filler is also performed (patent document 7), examination as an organic light emitting element board | substrate has not been performed until now. The thermal expansion coefficient involved in dimensional stability and delamination during production has not been studied, and the anisotropy of the thermal conductivity in the plane and longitudinal directions is not described.

  Studies on the production of a substrate using a composite composed of a resin and a filler for a flexible electronic device substrate are also underway, but these have the effect of increasing the mechanical strength and lowering the thermal expansion coefficient. For example, in Patent Document 3 and Patent Document 8, a glass filler having low thermal conductivity is used, and in Patent Document 9, colloidal silica is used. However, colloidal silica also contains filler because it has low thermal conductivity. However, there is a problem that heat cannot be radiated from the flexible electronic device substrate.

Japanese Patent No. 5033880 JP 2010-67957 A JP 2012-60103 A Japanese Patent No. 2945195 WO2009 / 066561 JP 63-34884 A JP 2008-7590 A WO2011 / 033751 WO2013 / 161970

  When existing materials (metals and ceramics) with conventional thermal conductivity are used for the support, the flexible electronic device substrate cannot be peeled off from the support or the shape can be maintained even if it can be peeled off. However, there was a problem that the performance deteriorated due to distortion with other members at the time of peeling, and thus a flexible electronic device substrate having thermal conductivity could not be made by the lift-off method.

  The lift-off of flexible electronic device substrates made of glass filler or colloidal silica and resin has been studied, but this is intended to increase the thermal expansibility and mechanical strength, which is the biggest problem of organic light-emitting devices. It was difficult to solve the problem.

  Accordingly, an object of the present invention is to provide a method for producing a flexible electronic device that can produce a flexible electronic device without breakage, and that can be easily separated between a support and a thermally conductive substrate after production.

  In addition, the object of the present invention is to make the display surface thin, lightweight and flexible. For example, by uniformly diffusing the heat distribution generated over time of the organic light emitting device and releasing it to the outside, An object of the present invention is to provide a method for manufacturing a flexible electronic device that can prevent afterimages and image sticking and can exhibit good performance with a long lifetime.

  As a result of repeated studies to solve the above problems, the present inventor has maintained a good shape in a method for manufacturing a flexible electronic device without causing separation of the device from adjacent members, damage to the members themselves, or distortion. In this state, the inventors have found a technique that can easily separate the support and the thermally conductive substrate, and have completed the present invention.

  That is, in the present invention, a process for producing a laminate comprising a heat conductive substrate and a support by applying a heat conductive resin material comprising a resin and a filler to a support, and forming a device layer on the heat conductive substrate. It is the manufacturing method of the flexible electronic device which has a process and the process of peeling a support body and a heat conductive substrate.

  In the method for manufacturing a flexible electronic device, the thermal conductivity λxy in the planar direction of the planar direction of the thermally conductive substrate is 0.7 W / mK or more, and the thermal conductivity λz in the thickness direction is 0.3 W / mK or more. Is preferred.

Moreover, in the said manufacturing method of a flexible electronic device, it is preferable that a heat conductive substrate contains the polyimide resin shown by the said Formula (1).

  Moreover, in the said manufacturing method of a flexible electronic device, the thermal expansion coefficient difference of a support body and a heat conductive board | substrate is 15 ppm / K or less, and the thermal expansion coefficient difference of a heat conductive board | substrate and a device layer is 15 ppm / K or less. Is preferred.

  Moreover, in the manufacturing method of the flexible electronic device, the heat conductive substrate has a multilayer structure composed of two or more layers of polyimide resin, and at least one layer is a heat conductive layer containing a heat conductive filler, The contacting layer is preferably a smooth layer having a smooth surface.

  The thermally conductive substrate in the present invention is excellent in heat dissipation, low thermal expansion, high heat resistance, and high toughness, and is suitable as a substrate for display devices or light receiving devices. In particular, it can be used for substrates of organic light emitting devices including organic EL lighting and organic EL televisions. In addition, instead of using a film with a fixed thickness that has already been formed as a film, a resin solution suitable for device manufacturing is used, so that it is applied to a support such as a glass substrate by spin coating or screen printing. Can be applied. At this time, since the thickness of the resin layer can be adjusted to an optimum thickness by changing the coating film thickness, the flexible electronic device can be thinned.

  In addition, a desired thin film can be formed by thinly applying a resin on a support such as a glass substrate, and a circuit, a display layer, or the like can be formed thereon. Because it is a thin film with excellent toughness and a low coefficient of thermal expansion, it does not cause peeling, defects or warpage from the thermally conductive substrate or support in the process of forming a circuit, etc. There is no defect in the heat conductive substrate itself or the circuit formed on it, and it can be removed cleanly. Therefore, a method for manufacturing a flexible electronic device that is a display device or a light receiving device using the same can be complicated because a circuit can be directly formed on a thermally conductive substrate formed on a support and then peeled off. A simple manufacturing process can be omitted. And even if the flexible electronic device obtained is thin, it will have high toughness and excellent heat resistance.

  Below, the manufacturing method of the flexible electronic device of this invention is demonstrated in detail.

  The present invention includes a step of applying a thermally conductive resin material comprising a resin and a filler to a support to produce a laminate comprising the thermally conductive substrate and the support, a step of forming a device layer on the thermally conductive substrate, And it is a manufacturing method of the heat conductive flexible electronic device which has the process of peeling a support body and a heat conductive board | substrate.

  According to this method, for example, a mixed solution of a polyamic acid (formal name; polyamic acid, the same shall apply hereinafter), which is a polyimide resin precursor, and a filler is directly applied onto an appropriate support, dried and cured. (So-called casting method). Therefore, a device can be directly formed on a thermally conductive substrate made of a resin and a filler, and a step of attaching a heat dissipation layer such as a metal can be omitted. Moreover, after forming a device, a flexible electronic device can be obtained by peeling a heat conductive substrate from a support body. Furthermore, this method has an advantage that a production apparatus using an existing glass substrate can be used as it is, can be used effectively in the field of electronic devices such as flat panel displays and electronic paper, and is suitable for mass production. A known method can be used as a method of peeling from the support. For example, it may be peeled off by a person, or may be peeled off by using a mechanical device such as a drive roll or a robot. Furthermore, the method of providing a peeling layer between a support body and a heat conductive substrate, and the method of separating with a laser beam can be mentioned. The removal from the support can be performed by the above-mentioned known method, but it is preferably removed by a mechanical method. In the following, an example in which a polyimide resin layer is formed using polyamic acid, which is a polyimide resin precursor, as a thermally conductive resin material will be described, but the present invention is not limited to this.

  Moreover, it can also be used integrally, without removing from a support body. In this case, heat conductivity and heat dissipation can be improved by using a metal layer as a support in contact with the heat conductive substrate. The metal species is not particularly limited, but preferably aluminum, copper, or an alloy containing them as a main component.

  The polyamic acid solution can be applied by a known method, for example, by appropriately selecting from a bar code method, a gravure coating method, a roll coating method, a die coating method and the like.

  The support used in the present invention is not particularly limited as long as it has supportability and resistance to high-temperature processes, but a glass substrate is preferable in terms of handling properties and transparency.

  In the method for manufacturing a flexible electronic device of the present invention, the thermal conductivity of the thermally conductive substrate is such that the thermal conductivity λxy in the planar direction is 0.7 W / mK or more and the thermal conductivity λz in the thickness direction is 0.3 W / mK or more. Preferably, the thermal conductivity λxy in the planar direction is 1.0 W / mK or more, and the thermal conductivity λz in the thickness direction is more preferably 0.4 W / mK or more. If the thermal conductivity λxy in the planar direction is less than 0.7 W / mK, heat cannot be sufficiently diffused, and if the thermal conductivity λz in the thickness direction is less than 0.3 W / mK, heat generated in the device layer As a result, sufficient cooling efficiency cannot be obtained.

  The filler in the thermally conductive resin material is preferably a filler having thermal conductivity, and the content ratio of the thermally conductive filler in the thermally conductive resin material is preferably in the range of 30 to 80 wt%, A range of 70 wt% is preferred. If the filler content in the thermally conductive resin material is less than 30 wt%, the heat dissipation characteristics when an electronic member such as an organic light emitting element substrate is used will be insufficient. Moreover, when it exceeds 80 wt%, the reduction | decrease of flexibility (flexibility) which is the characteristics of this invention will become remarkable, and the intensity | strength of a polyimide resin layer may also fall, and adjacent members, such as an organic light emitting element and a barrier layer, are laminated | stacked. There is a risk of damage or curling.

  The thermally conductive substrate preferably has good peelability from the support, and the peel strength can be adjusted by the filler content. The peelability can be expressed by the strength of peel strength. As above-mentioned, the content rate of a heat conductive filler should be in the range of 30-80 wt%, and the range of 40-70 wt% is preferable. If the filler content in the thermally conductive resin material is less than 30 wt%, the peel strength is improved and peeling becomes difficult. If it is difficult to peel off, adjacent device members (device layers) such as organic light emitting elements and barrier layers may be damaged. On the other hand, if it exceeds 80 wt%, the peel strength is excessively lowered, and there is a risk of peeling during production, or wrinkles and misalignment.

  In the present invention, for example, an organic light emitting device can be cited as an electronic device. In order to prevent moisture and oxygen from entering the organic light emitting element layer, it is common to provide a gas barrier layer on at least one surface of the thermally conductive substrate. . Here, an inorganic oxide film such as silicon oxide, aluminum oxide, silicon carbide, silicon oxide carbide, silicon carbonitride, silicon nitride, or silicon nitride oxide is preferably exemplified as a gas barrier layer having a barrier property against oxygen, water vapor, or the like. Is done. Moreover, as a support body, metal materials, such as glass, a silicon material, copper, and aluminum, etc. are illustrated suitably. If the difference in thermal expansion coefficient between the support and the thermally conductive substrate and the difference in thermal expansion coefficient between the inorganic oxide gas barrier layer and the thermally conductive substrate are large, curling may occur during the subsequent TFT manufacturing process. May occur, dimensional stability may deteriorate, and cracks may occur.

  In general, warpage is a problem when a large-area film is manufactured. However, if the thermal conductive substrate of the present invention is used, the difference in thermal expansion coefficient with the gas barrier layer is small, thus eliminating such problems. Is done. In the method for manufacturing a flexible electronic device, the difference in thermal expansion coefficient between the support and the thermally conductive substrate is 15 ppm / K or less, and the difference in thermal expansion coefficient between the thermally conductive substrate and the device layer is 15 ppm / K or less. More preferably, the difference in thermal expansion coefficient between the support and the thermally conductive substrate is 10 ppm / K or less, and the difference in thermal expansion coefficient between the thermally conductive substrate and the device layer is 10 ppm / K or less.

  Table 1 shows typical inorganic films forming the support and the gas barrier layer and their thermal expansion coefficients. Here, since the coefficient of thermal expansion varies depending on the manufacturing method even if the composition is the same, the values shown in Table 1 are approximate. Further, the gas barrier layer may be formed from one kind of the inorganic film as described above, or may be formed so as to include two or more kinds.

  In the present invention, the types of fillers contained in the thermally conductive resin material are specifically aluminum, copper, nickel, silica, diamond, alumina, magnesia, beryllia, boron nitride, aluminum nitride, silicon nitride, silicon carbide. The heat conductive filler which consists of etc. is mentioned. Among these, at least one filler selected from silica, alumina, aluminum nitride, boron nitride, silicon nitride, and magnesia is preferable. The filler shape is not particularly limited, and may be a plate shape, a needle shape, or a rod shape. It is also preferable to use a spherical filler and a plate-like filler in combination when the content of these heat conductive fillers is increased and the balance with characteristics such as heat conductivity is taken into consideration. When the smooth layer described later is 10 μm or less, or when the smooth layer is not used, it is preferable to use a plate-like filler in order to make the smoothness of the surface of the thermally conductive substrate on which the device layer is formed good. Note that, depending on the type of filler, although it contains a trace amount of metal impurities, if this metal impurity is mixed in the manufacturing process of the organic light-emitting element device, there is a concern that a malfunction may occur. Is preferably used.

  From the viewpoint of uniformly dispersing the filler in the thickness direction of the thermally conductive substrate, the particle size of the thermally conductive filler is preferably in the range of 0.01 to 25 μm and preferably in the range of 1 to 8 μm. It is more preferable. If the average particle diameter of the filler is less than 0.01 μm, the heat conduction inside each filler is reduced, and as a result, the thermal conductivity of the thermally conductive substrate is not improved, and the particles are likely to aggregate. And it may be difficult to uniformly disperse. On the other hand, if it exceeds 25 μm, the possible filling rate to the heat conductive layer is lowered, and the heat conductive substrate tends to become brittle due to the filler interface. The average particle size referred to here is the cumulative curve of the volume fraction of the particle size when the total particle size is 100% in the particle size distribution measured by the laser diffraction / scattering method (measuring device: Microtrack MT3300EX). The particle size when 50% accumulation is achieved.

  The most suitable spherical filler used in the present invention is a filler having an average particle size in the range of 0.5 to 3.0 μm, and it is preferable to use aluminum oxide or aluminum nitride. Moreover, the optimal thing of the plate-shaped filler used for this invention is the range whose average particle diameter is 0.1-15 micrometers, Most preferably, it is the range which is 0.5-8 micrometers. Boron nitride is preferably used as the plate-like filler. If this average particle size is less than 0.1 μm, the thermal conductivity is lowered and the plate-like effect is reduced. On the other hand, if it exceeds 15 μm, it is difficult to orient at the time of film formation. Moreover, the average particle diameter of a heat conductive filler is related also to the thickness of a polyimide resin layer. The average particle diameter of the heat conductive filler is 70% or less, preferably 50% or less of the thickness of the polyimide resin layer.

  In the present invention, the thermally conductive substrate may have a multilayer structure made of two or more layers of polyimide resin. In that case, at least one layer is a heat conductive layer containing a heat conductive filler, and the layer in contact with the device layer is preferably a smooth layer having a smooth surface. That is, when another smooth layer is provided on the surface of the heat conductive layer containing the resin and the heat conductive filler, the surface roughness (Ra) of the smooth layer is preferably 100 nm or less. If the roughness is further increased, the unevenness may affect the light emitting element, which may lead to deterioration in image quality. The smooth layer may be formed of resin alone or may include a heat conductive filler. When the smooth layer contains a thermally conductive filler, it is preferable to use a nanofiller so that the surface to be formed is smooth. The surface roughness (Ra) of the surface of the heat conducting layer or smooth layer that is in contact with the atmosphere is observed four times with a 10 μm square field observation in tapping mode using an atomic force microscope (AFM). The arithmetic average roughness (JIS B0601-1991) from which the average value was obtained is represented.

  The average particle diameter of the nanofiller used for the smooth layer is preferably in the range of 200 nm or less, and more preferably in the range of 100 nm or less. If the average particle size of the nanofiller exceeds 200 nm, the surface becomes rough, and smoothness may be reduced. If the roughness is further increased, the unevenness may affect the light emitting element, which may lead to deterioration in image quality. However, the lower limit of the average particle diameter of the nanofiller is substantially 10 nm. The nanofiller is not particularly limited, and specific examples include aluminum, copper, nickel, silica, diamond, alumina, magnesia, beryllia, boron nitride, aluminum nitride, silicon nitride, and silicon carbide. Among these, at least one nanofiller selected from silica, alumina, aluminum nitride, boron nitride, silicon nitride, and magnesia is preferable. The filler shape is not particularly limited, and may be a plate shape, a needle shape, or a rod shape. It is preferable to use a surface-treated nanofiller. As for the average particle size of the nanofiller, in the particle size distribution measured by the laser diffraction / scattering method (measuring device: Microtrac MT3300EX) as in the case of the average particle size in the thermally conductive filler, the total particle volume is 100%. It means the particle diameter when it becomes 50% cumulative in the cumulative curve of the volume fraction of particle diameter.

  When the smooth layer contains a nanofiller, it is preferably smaller than the content of the heat conductive filler in the heat conductive layer. Moreover, it is preferable that the content rate is the range of 1-50 wt%, and the range of 10-40 wt% is more preferable. When the content ratio of the nano filler in the smooth layer exceeds 50 wt%, not only the adhesion to adjacent members is deteriorated, but also the strength of the smooth layer is lowered.

  As described above, in the case of a multilayer structure, all layers constituting the thermally conductive substrate may contain a filler, and if at least one layer contains a filler, a layer containing no filler is used. May be included. In that case, the thickest layer is preferably a layer containing a filler. That is, in the above example, the thickness of the heat conductive layer may be 1 μm to 100 μm, and preferably 5 μm to 50 μm. If it is smaller than this range, the unevenness due to the filler becomes large, and if it is larger than this range, the heat conduction efficiency may decrease. Further, the thickness of the smooth layer is preferably 0.1 μm to 30 μm, and preferably 2 μm to 5 μm. If it is smaller than this range, a sufficient smoothing effect cannot be obtained, and if it is larger than this range, the thermal conductivity is inhibited, which is not preferable.

  As an example of manufacturing a flexible electronic device, when forming a TFT as an example, the annealing process of the TFT generally requires a heat treatment temperature of about 300 to 400 ° C. Therefore, when a resin is used as the support substrate, the heat treatment of the TFT is performed. It is necessary to have heat resistance and dimensional stability at temperature. On the other hand, a TFT may not be required unlike an organic EL device for illumination, but the resistance value of the transparent electrode is lowered by increasing the film formation temperature of the transparent electrode adjacent to the support substrate, and the organic EL device Since power consumption can be reduced, it is the same that heat resistance is required for the supporting base material in the case of lighting applications. Therefore, the resin used in the present invention preferably has a glass transition temperature of 280 ° C. or higher, more preferably 350 ° C. or higher.

  As another example, when the formation of a transparent electrode is taken as an example, a metal oxide such as ITO is generally used as the transparent electrode, and since these have a coefficient of thermal expansion of 0 to 10 ppm / K, cracks and peeling In order to avoid this problem, a resin having the same thermal expansion coefficient is required. The resin preferably has a thermal expansion coefficient of 60 ppm / K or less, more preferably 15 ppm / K or less.

Although there is no limitation in resin used for a heat conductive board | substrate, a polyimide resin is preferable from a viewpoint of making a thermal expansion coefficient small. The polyimide resin preferably has a linear structure, and since the thermal conductivity in the plane direction is higher than the thermal conductivity in the vertical direction, the linear structure is preferable. More preferred is a polyimide resin structure represented by the following general formula (1). It is preferable to contain 10 to 95 mol%, preferably 50 to 95 mol% of the structural unit represented by the general formula (1). That is, by blending a certain amount or more of the structural unit represented by the following general formula (1), it is possible to reduce the linear expansion coefficient, increase the thermal conductivity in the surface direction, and expect a heat diffusion effect.

In General Formula (1), Ar ₁ is a tetravalent organic group having one or more aromatic rings, R is a lower alkyl group having 1 to 6 carbon atoms, a lower alkoxy group having 1 to 6 carbon atoms, a phenyl group, Phenoxy group or halogen. Since Ar ₁ can be regarded as a residue of an aromatic tetracarboxylic acid that is a polyimide raw material, Ar ₁ is understood by showing a specific example of an aromatic tetracarboxylic acid. R can be regarded as a part of the residue of aromatic diamine which is a polyimide raw material.

  Specific examples of aromatic tetracarboxylic acids include pyromellitic dianhydride (PMDA), 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 2,2', 3,3'-benzophenone Tetracarboxylic dianhydride, 2,3,3 ', 4'-benzophenonetetracarboxylic dianhydride, naphthalene-2,3,6,7-tetracarboxylic dianhydride (NTCDA), naphthalene-1,2 , 5,6-tetracarboxylic dianhydride, naphthalene-1,2,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1, 2,6,7-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5, 8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid Anhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7- Tetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 2,3, 3 ', 4'-biphenyltetracarboxylic dianhydride, 3,3``, 4,4' '-p-terphenyltetracarboxylic dianhydride, 2,2``, 3,3' '-p -Terphenyltetracarboxylic dianhydride, 2,3,3``, 4 ''-p-terphenyltetracarboxylic dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -propane Anhydride, 2,2-bis (3,4-dicarboxyphenyl) -propane dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenyl) methane Anhydride, bis (3.4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) Hong dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-di Carboxyphenyl) ethane dianhydride, perylene-2,3,8,9-tetracarboxylic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, perylene-4,5,10, 11-tetracarboxylic dianhydride, perylene-5,6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic dianhydride, phenanthrene-1, 2,6 , 7-tetracarboxylic dianhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3 , 5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4 ' -Oxydiphthalic dianhydride It is.

As the structural unit other than the structural unit represented by the general formula (1), the aromatic tetracarboxylic acid residue which is a polyimide raw material and the aromatic diamine residue will be described separately. Examples of the residue include the same aromatic tetracarboxylic acid residues as those described above for Ar ₁ .

  Examples of the aromatic diamine residue include the following aromatic diamine residues. For example, 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2 , 6-Xylidine, 4,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3'- Diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-bis [4- (4-amino Phenoxy) phenyl] propane 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3 , 3-Diaminodiphenyl ether, 1 , 3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, benzidine, 3,3'-diaminobiphenyl, 3, 3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4'-diamino-p-terphenyl, 3,3'-diamino-p-terphenyl, bis (p-amino (Cyclohexyl) methane, bis (p-β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) benzene, p -Bis (1,1-dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (β-amino-t-butyl) toluene, 2,4- Diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diamino Lysine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,7-diaminodibenzofuran, 1 , 5-diaminofluorene, dibenzo-p-dioxin-2,7-diamine, 4,4′-diaminobenzyl and the like.

  When synthesizing the polyimide resin constituting the heat conductive layer, each of diamine and acid anhydride may be used alone or in combination of two or more, but at least one of diamine and acid anhydride may be used. Use two or more. Preference is given to using diamines which give structural units of the general formula (1) such as 2,2′-dimethyl-4,4′-diaminobiphenyl as diamines and in addition to those represented by the general formula (1). It is better to use other diamines that give structural units that are not.

  In the present invention, since the heat conductive layer contains a heat conductive filler, it is necessary to maintain the mechanical strength while maintaining the excellent heat resistance and dimensional stability of the polyimide resin. From such a viewpoint, as the other diamine, an aromatic diamine having a structure having less rigidity than the diamine that gives the structural unit represented by the general formula (1) is suitable. Advantageously, the diamine component contains 2,2'-dimethyl-4,4'-diaminobiphenyl as the main component, which includes 1,3-bis (3-aminophenoxy) benzene and 1,3-bis (4-amino). At least one diamine selected from phenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 3,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether as another diamine, It is preferable to use pyromellitic dianhydride as the main component for the anhydride. The proportion of other diamine used is preferably in the range of 5 to 50 mol%.

  Since the polyimide having the structural unit represented by the general formula (1) has a relatively hard property with an elastic modulus of about 5 GPa to 10 GPa, a polyimide layer (smooth layer) having a lower elastic modulus is used as a device. It may be arranged so as to be in contact with the layer so as to play a role of stress relaxation.

  The polyimide resin that forms the smooth layer preferably has a glass transition temperature (Tg) lower than that of the polyimide resin that forms the heat conduction layer, but is a thermoplastic polyimide resin layer having a Tg of 200 ° C. or higher. Is preferred. More preferably, it is a thermoplastic resin having a Tg in the range of 200 to 350 ° C., and a layer having a Tg lower by 20 ° C. or more than the polyimide resin constituting the heat conductive layer. On the other hand, since the heat conductive layer becomes a base layer having a thickness of 50% or more of the heat conductive substrate, Tg is preferably high, preferably 310 ° C. or higher, and in the range of 350 to 450 ° C. More preferred. As long as the said polyimide resin which comprises a smooth layer satisfies the said physical property, a well-known polyimide resin can be used and it can obtain from an above-described acid dianhydride component and a diamine component.

  Here, as the acid dianhydride component used for producing the smooth layer, pyromellitic dianhydride (PMDA), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3', 4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalate Aromatic dianhydrides such as acid dianhydride (ODPA) are exemplified. Examples of the diamine component include 2,2-bis (4-aminophenoxyphenyl) propane (BAPP), bis [4- (4-aminophenoxy) phenyl] sulfone (BAPS), 3,4′-diaminodiphenyl ether (3 , 4'-DAPE), 4,4'-diaminodiphenyl ether (4,4'-DAPE), 1,4-bis (4-aminophenoxy) benzene (TPE-Q), 4,4'-bis (4- Aminophenoxy) biphenyl (BAPB), 1,3-bis (3-aminophenoxy) benzene (APB), 1,3-bis (4-aminophenoxy) benzene (TPE-R), 1,3-bis (4- Aromatic diamines such as aminophenoxy) -2,2-dimethylpropane (DANPG) are preferred.

  Since the smooth layer is mainly provided to give the substrate smoothness, it is preferable that the thickness is thin, and it depends on the size of the heat conductive substrate and the amount of heat generated by the light emitting element. As a guideline, it is preferably 30 μm or less, more preferably 5 μm or less. If the thickness becomes thicker than this, the thermal conductivity may decrease.

  At least in the case of forming the heat conductive layer, the polyamic acid solution containing the heat conductive filler is added, for example, by adding a certain amount of the heat conductive filler to the polyamic acid solution containing a solvent obtained by polymerization in advance. The method of preparing by dispersing by, etc., and the method of adding a diamine and an acid anhydride and polymerizing, dispersing a heat conductive filler in a solvent, are mentioned. Either method may be used, but when using a polyamic acid with a high viscosity, it is preferable to mix a heat conductive filler in a solvent in advance before polymerization. When using a polyamic acid with a low viscosity, after the polymerization, It is preferable to mix a heat conductive filler in the acid solution.

  The polyamic acid can be produced by a known method in which an aromatic diamine component and an aromatic tetracarboxylic dianhydride component are used in substantially equimolar amounts and polymerized in a solvent. That is, it can be obtained by dissolving the diamine in a solvent such as N, N-dimethylacetamide under a nitrogen stream, adding aromatic tetracarboxylic dianhydride, and reacting at room temperature for about 3 hours. The preferred degree of polymerization of the polyamic acid suitable for forming the heat conductive layer and the smooth layer is, when expressed in the viscosity range, the solution viscosity is in the range of 5 to 2,000 P from the viewpoint of ease of handling and flattening ability. The range of 10-300P is more preferable. The solution viscosity can be measured with a cone plate viscometer with a thermostatic water bath. Examples of the solvent include N, N-dimethylacetamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene and the like, and these can be used alone or in combination of two or more.

  The thermally conductive substrate in the present invention is preferably used as a substrate for an organic light emitting device, that is, a flat panel display, a backlight for a liquid crystal display or a light source for illumination, and more preferably configured as a top emission method for an organic light emitting device. It is preferable to use it as a substrate. In the top emission method, there is no member that contributes to heat dissipation on the light emitting element side, and heat is easily stored. Therefore, it is preferable to use a substrate having high thermal conductivity. The thermally conductive substrate is a member constituting the organic light emitting device, and a thin film transistor, an electrode layer, an organic EL light emitting layer, electronic ink, a color filter, or two or more are formed on the thermally conductive substrate. It is preferable. Moreover, the organic light emitting element in the present invention means an element made of an organic substance that emits light by itself, and examples thereof include an organic electroluminescence element. The structure of the organic electroluminescence element is composed of layers having necessary functions such as a light emitting layer, an electrode, and an electron injection layer, and has a structure in which a light emitting layer containing a light emitting compound is sandwiched between a cathode and an anode. An element that emits light by using the emission of light (fluorescence / phosphorescence) when excitons are generated by injecting electrons and holes into the recombination to generate excitons. is there.

  EXAMPLES Hereinafter, although the content of this invention is demonstrated concretely based on an Example, this invention is not limited to the range of these Examples.

The abbreviations used in the examples represent the following compounds.
m-TB: 2,2′-dimethyl-4,4′-diaminobiphenyl 4,4′-DAPE: 4,4′-diaminodiphenyl ether TPE-R: 1,3-bis (4-aminophenoxy) benzene BAPP: 2,2-bis (4-aminophenoxyphenyl) propane PMDA: pyromellitic dianhydride BPDA: 3,3′4,4′-biphenyltetracarboxylic acid ODPA: 4,4′-oxydiphthalic acid dianhydride DMAc: N, N-dimethylacetamide

  Moreover, the following evaluation method was followed about each characteristic evaluated in the Example.

[Measurement of viscosity]
The viscosity of the polyamic acid solution was measured at 25 ° C. with a cone plate viscometer (manufactured by Tokimec Co., Ltd.) equipped with a constant temperature water bath.

[Thickness direction thermal conductivity (λzTC)]
A polyimide resin film is cut into a size of 30 mm × 30 mm, and the thermal diffusivity in the thickness direction by the periodic heating method (FTC-1 apparatus manufactured by ULVAC-RIKO), the specific heat by DSC, and the density by the underwater substitution method are measured, Based on this, the thermal conductivity (W / m · K) was calculated.

[Surface direction thermal conductivity (λxyTC)]
A polyimide resin film was cut into a size of 30 mm × 30 mm, and the thermal diffusivity in the surface direction by the optical alternating current method (Laser PIT device manufactured by ULVAC-RIKO), the specific heat by DSC, and the density by the underwater substitution method were measured, respectively. And thermal conductivity (W / m · K) was calculated.

[Coefficient of thermal expansion (CTE)]
A tensile test was performed on a polyimide resin film having a size of 3 mm × 15 mm in a temperature range of 30 ° C. to 260 ° C. at a constant heating rate (20 ° C./min) while applying a load of 5 g with a thermomechanical analysis (TMA) apparatus. The thermal expansion coefficient (ppm / K) was measured from the amount of elongation of the polyimide film with respect to temperature.

[Glass transition temperature (Tg)]
When a polyimide resin film (10 mm × 22.6 mm) is heated at a rate of 5 ° C./min from 20 ° C. to 500 ° C. with a dynamic thermal instrument analyzer (official name; dynamic viscoelasticity measuring device (DMA)) The dynamic viscoelasticity was measured to determine the glass transition temperature (tan δ maximum value: ° C.).

[180 degree peel strength]
The copper foil layer of the laminate was pattern-etched into a long rectangle having a width of 1.0 mm and a length of 180 mm, and a test piece was cut out to a width of 20 mm and a length of 200 mm so that the pattern was in the center, and IPC-TM-650. A 180 ° peel test was conducted according to 2.4.19.

Synthesis Examples 1 to 4
In order to synthesize the polyamic acid solution A, a solvent was stirred while stirring m-TB (32 g, 0.90 mol) and TPE-R (4.8 g, 0.10 mol) in a 1000 ml separable flask under a nitrogen stream. Dissolved in 425 g of DMAc. Then BPDA (9.7 g, 0.197 mol) and PMDA (28.5 g, 0.788 mol) were added. Thereafter, the solution was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a dark brown viscous polyamic acid solution A. Hereinafter, based on the composition shown in Table 2, the polyamic acid solutions B to D were synthesized by the same method as described above. The polyamic acid solutions A to D were composed of polyamic acid and a solvent DMAc, and the viscosity, thermal expansion coefficient, and glass transition temperature of the polyamic acid solution were measured.

Synthesis Examples 5-18
Next, 43.5 parts by weight of a polyamic acid solution A having a solid content concentration of 15 wt%, 3.25 parts by weight of aluminum oxide [spherical, average particle size 3 μm], and boron nitride [plate-like, average particle size 4. 5 μm] and 3.25 parts by weight were mixed with a centrifugal stirrer until uniform to obtain a mixed solution of polyamic acid and filler (sample E) containing a thermally conductive filler.

  Hereinafter, based on the compositions shown in Tables 3 and 4, the remaining samples F to R were synthesized by the same method as described above. At this time, the solid content concentration in the polyamic acid solution B was 15 wt%, and the solid content concentration in the polyamic acid solutions C and D was 12 wt%. In the case of using the polyamic acid solutions A and B (samples E5 to 15), 20% (8.72 parts by weight) of DMAc is added to the polyamide resin solution for viscosity adjustment, and a centrifugal stirrer is used until it becomes uniform again. Mixed. The numerical values of diamine, tetracarboxylic dianhydride, polyamic acid solution and filler in Tables 2 to 4 represent parts by weight of each component.

Samples E to R are mixed solutions in which the polyamic acid solutions A to D in Table 2 and the thermally conductive filler are mixed based on the recipe of Table 3. As the thermally conductive filler, Al ₂ O ₃ is a spherical filler having an average particle diameter of 3 μm and 0.6 μm, BN is a plate-like filler having an average particle diameter of 4.5 μm and 2.3 μm, and AlN is an average particle diameter of 1.1 μm. A spherical filler was used. The average particle size here is a cumulative curve of the volume fraction of the particle size when the total particle volume is 100% in the particle size distribution measured by the laser diffraction / scattering method (measuring device: Microtrack MT3300EX). The particle diameter when 50% accumulation is obtained.

Film Preparation Examples and Reference Examples The polyamic acid resin solution C obtained in Synthesis Example 3 was applied to a glass substrate so that the thickness after curing was about 2 μm, and the solvent was removed by heating at 120 ° C. Next, the solution of the polyamic acid resin E obtained in Synthesis Example 5 was applied thereon so that the thickness after curing was about 21 μm, and dried by heating at 120 ° C. to remove the solvent. Furthermore, the polyamic acid resin solution C obtained in Synthesis Example 3 was applied thereon so that the thickness after curing was about 2 μm, and dried by heating at 120 ° C. to remove the solvent. Thereafter, the temperature-controlled heating is performed in a temperature range of 120 to 360 ° C. over 30 minutes, and a laminate for a thermally conductive substrate composed of three polyimide resin layers (C / E / C) is formed on the glass. Produced. In order to evaluate the characteristics of the polyimide resin layer, the polyimide resin layer was peeled from the glass substrate to produce a polyimide resin film (M1). The CTE and thermal conductivity of this polyimide resin film were evaluated. Thereafter, three-layer, two-layer, and single-layer polyimide resin films M2 to M14 and M16 to M21 were formed on a glass substrate in the same manner, and then CTE and thermal conductivity were evaluated. The results are shown in Table 5.

  Here, M1 to M6 in Table 5 are laminate films of a film made of polyimide resin and a thermally conductive filler and a film made of polyimide resin. M7 to M14 are single layer films made of a polyimide resin and a thermally conductive filler. M15 is a reference example for comparing physical properties, and is a heat conductive polyimide resin film (Kapton (registered trademark) MT: thickness 43 μm) manufactured by DuPont. M16 to M17 are laminates made of polyimide resin films having different compositions. M18 to M21 are single layer films made of polyimide resins having different compositions. Table 5 shows the layer structure and thickness structure of the film. About M1-M21, the thermal expansion coefficient, the heat conductivity of the vertical direction and the horizontal direction, and the surface roughness were measured. The thermal expansion coefficient of M3 could not be measured due to insufficient mechanical strength.

Examples 1-2
Applied a polyamic acid solution D and a resin composition (Q) comprising AlN (71 wt%) on a 20 μm copper foil and imidized to obtain a laminate film (M22) having a thickness of 5 μm. Table 6 shows the peel strength between the obtained laminate film and the copper foil. Using a known method for this laminate film, a SiN layer (150 μm) and a SiO layer (100 μm) as a gas barrier are sequentially formed, and then an amorphous silicon layer 50 μm to be a TFT is formed, and the laminate film in which the TFT is formed Then, the heat conductive substrate on which the TFT was formed was peeled from the copper foil to obtain a flexible electronic device. There was no significant change in peel strength even after TFT formation. Similarly, a laminated film (M23) obtained by applying a resin composition composed of a polyamic acid solution D and AlN (51 wt%) onto a copper foil to form an imidized film and forming a TFT, a similar flexible electronic device is obtained. Obtained

Comparative Examples 1 and 2
A laminate film (M24, M25) of a polyimide resin layer containing no thermal conductive filler and a copper foil (M24, M25). After measuring the 180 degree peel strength, a TFT was formed in the same manner as in Examples 1 and 2, but it was physically possible to peel from the copper foil, but cracking occurred in the TFT.

  About the said Example and comparative example, the film (M22 * 23) used for Example 1, 2 is the film (M24 * 25) used for Comparative Example 1,2 by the presence or absence of a heat conductive filler in a resin layer. It is an optimal material for display devices because of its different release characteristics from the support and the fact that the layer consisting of the resin and the thermally conductive filler is better than the resin alone layer. is there.

  In addition, not only the thermal conductivity increased due to the presence or absence of the thermally conductive filler in the resin layer, but also the amount and type of the thermally conductive filler were optimized to dramatically improve the lateral thermal conductivity. I was able to increase it. In other words, compared to the difference in thermal conductivity between the vertical direction and the horizontal direction in the comparative example, the difference in thermal conductivity in the same direction in the example is large, so the accumulated heat that caused image sticking and afterimages can be quickly removed. Can diffuse.

Claims (6)

  Applying a thermally conductive resin material comprising a resin and a filler to a support to produce a laminate comprising the thermally conductive substrate and the support, forming a device layer on the thermally conductive substrate, and the support A method for manufacturing a flexible electronic device, comprising a step of peeling a thermally conductive substrate.   The thermal conductivity λxy in the planar direction of the thermally conductive substrate is 0.7 W / mK or more, and the thermal conductivity λz in the thickness direction is 0.3 W / mK or more. A method of manufacturing a flexible electronic device. The method for manufacturing a flexible electronic device according to claim 1, wherein the thermally conductive substrate contains a polyimide resin represented by the following formula (1).

  The thermal expansion coefficient difference between the support and the thermally conductive substrate is 15 ppm / K or less, and the thermal expansion coefficient difference between the thermally conductive substrate and the device layer is 15 ppm / K or less. A method of manufacturing a flexible electronic device.   The heat conductive substrate has a multilayer structure composed of two or more layers of polyimide resin, and at least one layer is a heat conductive layer containing a heat conductive filler, and the layer on the side in contact with the device layer has a smooth surface. It is a layer, The manufacturing method of the flexible electronic device in any one of Claims 1-4 characterized by the above-mentioned.   The method for producing a thermally conductive flexible electronic device according to claim 1, wherein the flexible electronic device is a display device or a light emitting device.