JP4860448B2 - Insulated metal foil for electronic device fabrication - Google Patents

Description

  The present invention relates to an insulating coated metal foil for producing an electronic device used as a substrate or the like on which an electronic device such as a thin film transistor (TFT) is formed, and in particular, to display an image such as an organic EL display and an electronic paper. The present invention relates to an insulating coated metal foil for producing an electronic device suitable for a substrate of an apparatus.

  TFTs using semiconductor thin films such as polysilicon films and amorphous silicon films are widely applied to electronic devices, and are particularly developed as drive elements for image display devices. Compared with conventional cathode ray tubes (CRTs), active matrix liquid crystal display devices using TFTs as drive elements have features such as thinness, light weight, low power consumption, and high image quality. Screening is also easy. Also, TFTs are used as driving elements in next-generation image display devices such as moving image displays using organic EL elements as display media and electronic paper. A TFT having a polysilicon film or an amorphous silicon film is usually formed on a glass substrate because a high temperature process of 350 to 500 ° C. is required in an annealing process or the like.

  In recent years, in organic EL displays and electronic paper, there is a movement to use a resin film (Patent Document 1) or a metal foil (Patent Document 2) instead of a glass substrate from the viewpoint of light weight, thinness, and resistance to breakage. is there. Since the resin film and the metal foil are flexible, there is a possibility that a flexible TFT substrate can be manufactured. By using such a flexible TFT substrate, it is possible to pioneer new applications such as a curved display device that cannot be realized with a glass substrate, and electronic paper that can be rolled.

  However, in the case of a resin film, a TFT having a polysilicon film or an amorphous silicon film that requires a high-temperature process cannot be manufactured from the viewpoint of heat resistance.

  In contrast, when a metal foil is used, a TFT having a polysilicon film or an amorphous silicon film can be manufactured from the viewpoint of heat resistance. However, since the metal foil itself is conductive, a circuit cannot be formed directly on the metal foil, and it is necessary to provide insulation on the surface by covering with an insulating film. Such insulating film materials can be broadly classified into organic materials, organic-inorganic composite materials (organic-inorganic hybrid materials), and inorganic materials.

  However, since the organic material film has a low Young's modulus, it can follow the deformation of the substrate, but cannot be used from the viewpoint of heat resistance, like the resin film.

  In addition, the inorganic material film has no problem in terms of heat resistance, but has a problem in terms of flexibility. That is, since the Young's modulus is high, it cannot follow the deformation such as the curvature of the substrate, and cracks or peeling easily occurs.

  In contrast, an organic-inorganic composite material having characteristics of an organic material and an inorganic material has heat resistance higher than that of an organic material and has a relatively low Young's modulus, so that it can flexibly follow the deformation of a substrate ( Low Young's modulus). Therefore, a material having such characteristics of an organic material and an inorganic material is considered promising. Organic-inorganic composite materials are called by various names such as organic-inorganic (inorganic-organic) hybrid, organic modified silicate, Ormosil, Ormocer, Ceramer, Polyceram, etc. A material composed of a substance in which an organic substance and an inorganic substance are bonded by a strong chemical bond such as a covalent bond (Non-Patent Documents 1 and 2). As such an organic-inorganic composite material, those having a structure in which an organic component is introduced into an inorganic siloxane skeleton are mainly used.

JP 2006-5329 A JP 2002-49056 A Sakuna Sakuo, “Science of Sol-Gel Method” Agne Jofusha (1990) p. 115-153 Sakuo Sakuo, “Application of Sol-Gel Method”, Agne Jofusha (1997) p. 57-115

  The present inventors have a structure in which a metal foil is covered with an insulating film made of a material (organic polymer modified with an organic group) in which the above-described organic-inorganic composite material, particularly an inorganic polymer containing siloxane is modified with an organic group. It has been found that even when the metal foil substrate is bent, the material of the insulating coating has a lower Young's modulus than that of inorganic silica, so that it can follow the deformation of the metal foil without peeling off the insulating coating.

  However, if only an inorganic polymer film modified with an organic group is formed on the metal foil, if an electronic device such as a TFT is formed thereon, peeling or cracking of the film constituting the electronic device may occur. It turned out to be.

  The present invention provides an insulating coated metal foil for an electronic device substrate that has high heat resistance and flexibility (flexibility), and can prevent peeling and cracking of a film constituting an electronic device such as a TFT. The purpose is to do.

  In order to solve the above problems, the present inventors have used TFT or the like when using a metal foil coated with an insulating film made of an inorganic polymer modified with an organic group (an inorganic polymer film modified with an organic group). The present inventors have intensively studied the peeling and cracking of the film constituting the electronic device that occurs in the process of forming the electronic device, and found the following causes.

Here, as an example, a description will be given of cracks and peeling occurring when a TFT as shown in FIG. 1 is formed. First, as shown in FIG. 1, a metal foil (here, SUS304 foil) 11 covered with an inorganic polymer film 12 modified with an organic group is prepared, and an Al—Mo alloy film 13 is formed thereon as a gate electrode. And patterning was performed by etching. Thereafter, a Si ₃ N ₄ layer 14 having a film thickness of about 0.5 μm was formed as a device insulating layer by a chemical vapor deposition (CVD) method. However, when this laminate was taken out of the chamber and observed, many cracks were generated in the Si ₃ N ₄ layer 14.

Further, when the Al—Mo alloy film 13 is etched off, as shown in FIG. 2, the Si ₃ N ₄ layer 14 swells and peels off at the interface with the inorganic polymer film 12 modified with an organic group. occured. When the peeling shape and structure were observed in detail, it was not possible to follow the shrinkage of the metal foil 11 that occurred during the cooling from the formation temperature (about 180 ° C.) of the Si ₃ N ₄ layer 14 to the room temperature after the formation. It was clarified that cracks occurred and the Si ₃ N ₄ layer 14 was peeled off. That is, the thermal expansion coefficient of SUS304 constituting the metal foil 11 is 17.3 × 10 ⁻⁶ / K, whereas the thermal expansion coefficient of Si ₃ N ₄ constituting the device insulating layer is 2.5 × 10 ⁻ to be ⁶ / K, upon cooling after the formation of the Si ₃ N ₄ layer 14, Si ₃ N metal foil 11 is significantly shrunk compared to the _four layers 14, the large shrinkage difference Si ₃ N ₄ layer 14 It peeled off so that it swelled up.

The inorganic polymer film 12 modified with an organic group exists as an intermediate layer between the metal foil 11 and the Si ₃ N ₄ layer 14. Although details will be described later, the inorganic polymer film 12 modified with an organic group has a low Young's modulus and a very high adhesion to SUS304. For this reason, the inorganic polymer film 12 modified with an organic group shrinks without causing peeling as the metal foil 11 made of SUS304 shrinks, and as a result, directly imparts a shrinkage stress to the Si ₃ N ₄ layer 14. become. On the other hand, since Si ₃ N ₄ has a high Young's modulus and a low coefficient of thermal expansion, the Si ₃ N ₄ layer 14 cannot shrink as much as the inorganic polymer film 12 and the metal foil 11 modified with an organic group, Swelling occurs on the inorganic polymer film 12 modified with the group, and peeling occurs. Incidentally, a substrate (5 × 10 ⁻⁶ / K) made of glass or the like having a small coefficient of thermal expansion can provide a sound coating without cracks and peeling even when the Si ₃ N ₄ layer 14 is formed.

  As described above, in the conventional technology, even if an inorganic polymer film modified with an organic group having a low Young's modulus capable of following deformation, thermal expansion and contraction of a substrate made of a metal foil is used as an insulating film, A ceramic film (non-oxide ceramics such as silicon nitride or oxide ceramics such as silica or alumina) having a low coefficient of thermal expansion and a high Young's modulus is used as a material for electronic devices on a foil substrate by CVD. When formed, the stress applied to the ceramic film due to the shrinkage of the metal foil substrate can hardly be absorbed by the intermediate layer, the ceramic film swells, and peeling occurs at the interface with the intermediate layer.

  As a result of further research based on this finding, the present inventors have found that the stress applied to the high Young's modulus film constituting the electronic device such as a TFT due to the thermal contraction of the metal foil is moderately roughened on the surface of the metal foil. Thus, the present inventors have found that swelling and peeling can be prevented by dispersing and mitigating in an intermediate layer of an inorganic polymer film modified with an organic group.

  That is, the present invention has the following gist.

(1) A metal foil having a surface roughness Ra of 30 nm to 500 nm and an inorganic polymer modified with a phenyl group, and having a Young's modulus of 10 ² MPa to 10 ⁴ MPa , covering the surface of the metal foil And an insulating coating metal foil for producing an electronic device.

( 2 ) The insulating coated metal foil for producing an electronic device according to (1 ), wherein the insulating film has a thickness of 0.8 μm or more and 40 μm or less.

( 3 ) The insulating coated metal foil for producing an electronic device according to (1) or (2) , wherein the metal foil is a stainless steel foil.

( 4 ) The electronic device according to ( 3 ), wherein the glossiness Gs (45 °) of the stainless steel foil is 300 or more and less than 500, and the surface roughness Ra of the stainless steel foil is 100 nm or less. Insulation coated metal foil for production.

  According to the present invention, even if an element (particularly a non-oxide ceramic film and an oxide ceramic film) constituting an electronic device is formed on the insulating coated metal foil of the present invention, The peeling and cracking of these components can be suppressed. Therefore, the insulating coated metal foil for producing an electronic device of the present invention is particularly effective as a substrate for forming a TFT having a polysilicon film and / or an amorphous silicon film that requires a high temperature process. Furthermore, the present invention can be applied to flexible displays using organic EL or E-INK, and displays having characteristics such as thinness, light weight, and resistance to cracking.

  Hereinafter, the configuration of the insulating coated metal foil for manufacturing an electronic device according to the present invention will be described. As described above, this insulating coated metal foil for producing an electronic device includes at least an insulating film made of an inorganic polymer modified with a metal foil and an organic group.

  In the present invention, the metal foil is a thin metal plate having a thickness of 1 mm or less, preferably 30 μm or more and 600 μm or less. When the thickness is less than 30 μm, the metal foil is likely to bend and / or wrinkle, and handling may be difficult. Further, as the metal foil becomes thicker, the advantages of the glass substrate such as lightness, thinning and flexibility are reduced. Accordingly, a particularly preferable range of the thickness of the metal foil is 60 μm or more and 300 μm or less.

  The metal foil in this invention does not ask | require the kind of metal if the shape of foil is obtained. For example, steel, copper, nickel, titanium, aluminum, cobalt, zinc, etc. are mentioned. When an electronic device such as a TFT is formed, various etching solutions are used for the purpose of patterning a gate electrode. Therefore, when using as a substrate on which such an electronic device is formed, the etching solution is used. Metals that are not corroded and have high corrosion resistance, such as stainless steel and titanium, are preferred.

In the present invention, the inorganic polymer modified with an organic group constituting the insulating film is an organic-inorganic composite material (organic-inorganic hybrid material) having a structure in which an inorganic polymer having a metalloxane skeleton such as siloxane is modified with an organic group. ). For example, 1 to 3 oxygen atoms located at the apex of the SiO ₄ tetrahedron, which is the structural unit of the siloxane inorganic polymer, are substituted with organic groups. It is preferable that the main component of the inorganic component (metalloxane skeleton) of the inorganic polymer modified with an organic group is siloxane, but among the inorganic components, metalloxanes such as Ti, Y, Al, Nb, Ta, and Zr are used as subcomponents. May be included. In addition, the main skeleton of an inorganic polymer modified with an organic group is composed of a siloxane bond (Si—O), which is an inorganic component, and thus has better heat resistance than an organic material. Further, since the inorganic metalloxane skeleton of the inorganic polymer is modified with an organic group, it is flexible and excellent in crack resistance as compared with a complete inorganic material. That is, the Young's modulus of an inorganic polymer modified with an organic group is lower than the Young's modulus (about 10 ⁵ MPa) of inorganic silica, which is an inorganic polymer having a siloxane skeleton that does not contain an organic group. For this reason, compared with inorganic materials, such as inorganic silica, it is easy to form a thick film and can form an insulating film without a defect easily. Moreover, since the inorganic polymer modified with an organic group forms a Si-OM bond with the natural oxidation layer of the metal (M) at the interface with the surface of the metal foil, the adhesion with the surface of the metal foil is very high. high.

  As described above, when the surface of the metal foil is moderately rough, that is, when the surface roughness Ra is in the range of 30 nm to 500 nm, the inorganic polymer modified with the above organic group on the surface of the metal foil. When the film is formed as an insulating film, peeling and cracking of the ceramic film constituting the electronic device formed on the inorganic polymer film modified with the organic group can be further suppressed.

  When the surface roughness Ra is 30 nm or less, a smooth surface close to a mirror surface is obtained. When an inorganic polymer film modified with an organic group is formed as an insulating film on a metal foil having such a smooth surface, the electronic device Cracks and delamination occur during formation. As shown in FIG. 3, when the smoothness of the surface of the metal foil 31 is too high, the inorganic polymer film 32 modified with an organic group is formed after the ceramic film 33 is formed as an insulating film constituting the electronic device. When cooling from the film temperature to room temperature, it tends to remarkably shrink in the direction indicated by the arrow 34 in response to the shrinkage of the metal foil 31. For this reason, high stress is generally generated in the inorganic polymer film 32 modified with an organic group (graph in FIG. 3), and the inorganic polymer film modified with an organic group having a low Young's modulus so as to reduce the stress as much as possible. The polymer film 32 shrinks from the interface with the metal foil 31 to approximately the same extent. However, since the ceramic film 33 having a high Young's modulus cannot be relieved due to large shrinkage, microscopic distortion occurs at the interface with the inorganic polymer film 32 modified with an organic group, and blistering and peeling occur. .

  On the other hand, when the surface of the metal foil is rough, the above-described blistering and peeling are prevented. That is, as shown in FIG. 4, although the metal foil 41 contracts upon cooling after the ceramic film 43 is formed as the insulating film constituting the electronic device, the metal foil 41 and the organic group formed thereon are used. The stress generated at the interface with the modified inorganic polymer film 42 is dispersed by unevenness present on the surface of the metal foil 41 (dispersion in the stress direction 44 exemplified by the arrow in FIG. 4). As a result, the stress in the inorganic polymer film 42 modified with an organic group decreases as the distance from the metal foil 41 increases, as shown in the graph of FIG. For this reason, almost no deformation occurs on the surface of the inorganic polymer film 42 modified with an organic group, and the stress acting on the ceramic film 43 in contact with the inorganic polymer film 42 modified with the organic group becomes slight. . Therefore, peeling and cracking can be prevented.

  However, when the surface roughness Ra exceeds 500 nm, the thickness of the inorganic polymer film modified with an organic group differs greatly between the concave portion and the convex portion on the surface of the metal foil. Since the modified inorganic polymer film becomes thin, sufficient insulation cannot be obtained. Moreover, since unevenness appears on the outermost surface of the inorganic polymer film modified with an organic group reflecting the uneven shape on the surface of the metal foil, it is difficult to form a good electronic device. That is, a metal foil substrate having a flat surface on which an electronic device such as a TFT can be manufactured is not obtained.

  Considering these, the surface roughness Ra is set to 30 nm to 500 nm, and more preferably 35 nm to 150 nm.

  When the metal foil is a stainless steel foil, the surface roughness Ra is not less than 30 nm and not more than 500 nm, and the glossiness when a 45 ° specular gloss Gs (45 °) is measured according to the specular gloss measurement method according to JIS Z8741. It is more preferable that Gs is 300 or more and less than 500. About the unevenness | corrugation shape of the surface of the metal foil measured with the contact-type roughness meter, since it is below a measurement limit about the fine unevenness of several hundred nm or less, the surface roughness of the metal foil which has a cross section shown in FIG. The surface roughness Ra of the metal foil having the cross section shown is approximately the same. On the other hand, the glossiness Gs reflects light reflection, scattering, diffraction, and the like caused by fine unevenness of 350 nm to 850 nm on the surface that cannot be measured with a contact-type roughness meter. Therefore, it can be considered that the low glossiness Gs indicates small irregularities in the range (350 nm to 850 nm), and the high glossiness Gs indicates large irregularities in the range. That is, even when almost the same surface roughness Ra is obtained, the higher the glossiness Gs and the smaller the unevenness of 350 nm to 850 nm, the better the crack resistance of the ceramic film constituting the electronic device. It can also be understood that peeling resistance is obtained. When the glossiness Gs is less than 300, the unevenness at the level of 350 nm to 850 nm is small (smooth), and the effect of further improving crack resistance and peeling resistance with respect to the ceramic film or the like due to the unevenness at the glossiness level is small. On the other hand, when the glossiness Gs exceeds 500, it becomes close to the unevenness size that can be measured with a contact roughness meter, and therefore there is little effect of further improving crack resistance and peeling resistance related to ceramic films and the like due to unevenness of the glossiness level. .

  Moreover, in the inorganic polymer film modified with an organic group, the organic group bonded to Si incorporates a structure in which a part of the Si-O-Si bond is cut by directly chemically bonding to Si, Any organic group may be used as long as it has an effect of loosening the rigid structure of inorganic silica. Examples of the organic group include a methyl group, an ethyl group, a propyl group, a glycidoxypropyl group, an amino group, a phenyl group, a vinyl group, a mercaptopropyl group, and a trifluoropropyl group. When high heat resistance is required, it is particularly desirable to use a methyl group, a phenyl group, or a mixture thereof. Since both the methyl group and the phenyl group are organic groups having a stable bond with Si and a high thermal decomposition temperature and excellent thermal stability, they are difficult to be thermally decomposed during the process of manufacturing an electronic device.

The Young's modulus of the inorganic polymer film modified with an organic group is lower than the Young's modulus of the metal foil and the material constituting the electronic device, and is 10 ² MPa or more and 10 ⁴ MPa or less. Is desirable. Within the above range, an electronic device can be manufactured with high yield. When the Young's modulus is smaller than 10 ² MPa, the inorganic polymer film modified with an organic group is soft, so that lithography becomes difficult and it becomes difficult to obtain an electronic device with good characteristics, and the yield may be reduced. On the other hand, when the Young's modulus is higher than 10 ⁴ MPa, when the metal foil is deformed such as curved, the inorganic polymer film modified with an organic group is too hard, and cracks are likely to be generated in the film. May be reduced. Furthermore, the stress dispersion effect due to the unevenness on the surface of the metal foil is reduced, and the possibility that the film swells and peels when the ceramic film of the electronic device is formed increases.

  In order to achieve the low Young's modulus in the inorganic polymer film modified with an organic group, the content of the organic group bonded to Si is 0.5 or more in terms of the molar ratio of the organic group to Si. .2 or less is desirable. When the molar ratio of the organic group to Si is less than 0.5, the Young's modulus of the inorganic polymer film modified with the organic group becomes high, it becomes difficult to follow the deformation of the metal foil, and it occurs due to the shrinkage due to cooling of the metal foil. There is a possibility that the effect of dispersing and relaxing the stress is reduced. Therefore, the effect of improving the crack resistance of the ceramic film or the like constituting the electronic device formed thereon may be reduced. On the other hand, when this ratio exceeds 2.2, the inorganic polymer film modified with an organic group is too soft and easily wrinkles. More preferably, the range of the organic group with respect to Si is 1.9 or more and 2.1 or less.

  The thickness of the inorganic polymer film modified with an organic group is preferably 0.8 μm or more in order to ensure insulation. However, if it is too thick, cracks are likely to occur when an inorganic polymer film modified with an organic group is formed. More preferably, it is 1.0-4.0 micrometers. Furthermore, it is desirable that the surface of the inorganic polymer film modified with an organic group is small in both surface roughness Ra and Rz and high in smoothness so that patterning or the like can be performed with high precision when an electronic device is manufactured. As a measure of smoothness, it is desirable that the surface roughness Rz is 500 nm or less and the surface roughness Ra is 50 nm or less. When the surface roughness exceeds these values, the surface unevenness level becomes close to the thickness of the ceramic film or the like constituting the electronic device, and it becomes difficult to form the ceramic film or the like.

  The inorganic polymer film modified with an organic group can be formed through a process of applying a coating solution, drying and heat treatment using, for example, a sol-gel method. A sol can be prepared by hydrolysis in an organic solvent using a siloxane polymer and one or more metal alkoxides selected from Si, Y, Al, Ti, Zr, Nb, Ta and W as starting materials. As the metal alkoxide, an alkoxide of a trivalent to hexavalent metal element which can inorganically crosslink a siloxane polymer is used. Examples of the siloxane polymer include polydimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, and polydimethyldiphenylsiloxane. In addition to silanol groups, both ends of the polysiloxane may be carbinol-modified, amino-modified, alkoxy-modified or the like. The mass average molecular weight of the polysiloxane is preferably 500 or more and 15000 or less, and particularly preferably 2500 or more and 10,000 or less. When the mass average molecular weight is less than 500, it becomes a low-viscosity coating solution, so that it is difficult to obtain a sufficient film thickness. When the mass average molecular weight exceeds 15000, it takes time to cure the film, and the resulting inorganic polymer film modified with an organic group is also soft and easily damaged.

  When forming an inorganic polymer film modified with an organic group, the molar ratio of one or more metal alkoxides selected from Si, Y, Al, Ti, Zr, Nb, Ta and W to Si in the siloxane polymer is 1 / It is particularly desirable to carry out hydrolysis after dispersing in an organic solvent so that it is 40 or more and 1/4 or less. When the molar ratio of the metal alkoxide to Si in the siloxane polymer is less than 1/40, the three-dimensional network structure is difficult to develop, and the inorganic polymer film modified with an organic group may be insufficiently cured. On the other hand, when this molar ratio exceeds 1/4, the inorganic polymer film modified with an organic group becomes too hard, and cracks are likely to occur. Moreover, it may be an inorganic polymer film modified with an organic group having a high Young's modulus and a low stress dispersion relaxation effect.

  As the Si alkoxide, organoalkoxysilane can be used in addition to tetraethoxysilane and tetramethoxysilane. Examples of the organoalkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, dimethoxydimethylsilane, Diethoxydimethylsilane, phenyltrimethoxysilane, phenyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, aminopropyltrimethoxysilane And aminopropyltriethoxysilane. Since the metal alkoxides of Y, Al, Ti, Zr, Nb, Ta, and W are all more reactive than alkoxysilane, some alkoxy groups are β-diketone, β-ketoester, alkanolamine, and alkylalkanol. An alkoxide derivative substituted with an amine, an organic acid or the like may be used.

  Without using a siloxane polymer, the sol can be prepared by hydrolyzing the above-mentioned Si alkoxide or organoalkoxysilane in an organic solvent. At this time, it is desirable to use an acid, an alkali, or one or more metal alkoxides selected from Y, Al, Ti, Zr, Nb and Ta as a catalyst during hydrolysis. In this case, the metal alkoxide used as a catalyst for the hydrolysis / condensation reaction of Si alkoxide or organoalkoxysilane is a coordination unsaturated metal alkoxide, that is, a trivalent to pentavalent metal element having a coordination number of 8. An alkoxide of (coordination number> valence) is mentioned.

  As the organic solvent, for example, various alcohols such as methanol, ethanol, propanol and butanol, acetone, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone and the like can be used. The hydrolysis is preferably performed by adding 0.5 to 2 times as much water as the number of moles of all alkoxy groups in the starting material. If it is less than 0.5 times, the progress of hydrolysis is slow, and it takes time to gel. On the other hand, when it exceeds 2 times, the condensation ratio of metal alkoxides increases, and the contribution of effectively crosslinking the siloxane polymer decreases.

  Coating on the metal foil can be performed by a bar coating method, a roll coating method, a spray coating method, a dip coating method, a spin coating method, a slit coating method, a curtain coating method, or the like.

  As described above, in forming an inorganic polymer film modified with an organic group, when the raw material is formed by a wet process and cured by heat treatment, a large number of silanols are present in the film in the wet state immediately after the film formation. Although the (SiOH) group exists, the dehydration condensation reaction proceeds by heat treatment and a siloxane bond is formed. At this time, since a natural oxidation layer of metal (M) and a Si-OM bond are formed at the interface with the metal foil surface, the adhesion between the metal foil surface and the inorganic polymer film modified with an organic group is Become very expensive.

  In addition, in order to improve the adhesiveness with the inorganic polymer film modified with the organic group, the metal foil can be pretreated before application as necessary. Typical pretreatments include pickling, alkali degreasing, chemical conversion treatment such as chromate, grinding, polishing, blasting, and the like, and these can be performed alone or in combination as necessary.

When a stainless steel foil is used as the metal foil, a ferritic stainless steel foil, a martensitic stainless steel foil, an austenitic stainless steel foil, and the like can be given. Thermal expansion coefficient is ^{17 × 10 -6 / K, 10} × 10 -6 / degree K ferritic and martensitic stainless austenitic stainless steel. Therefore, ferrite and martensitic stainless steels with smaller thermal expansion coefficients are more susceptible to distortions of inorganic polymer films modified with organic groups due to differences in thermal expansion coefficients and distortions of the films constituting the electronic devices formed thereon. Is preferable. The surface of the stainless steel foil may be subjected to a surface treatment such as bright annealing.

For example, when an insulating coating metal foil for producing an electronic device according to the present invention is used as a substrate and a TFT is produced thereon, this can be used as a substrate for driving an organic EL display element. Further, electronic paper can be manufactured in combination with E-INK using microcapsules. Further, using the insulating coated metal foil for manufacturing an electronic device of the present invention as a substrate, for example, an Al electrode, an n-type silicon layer, an i layer serving as an active layer, a p-type silicon layer, and an ITO film are sequentially laminated. A solar battery cell made of thin film microcrystalline silicon can also be manufactured by forming a mold electrode. In particular, when a coated stainless steel foil is used as an insulating coated metal foil for producing an electronic device, a solar cell having the same characteristics as when a conventional glass substrate with SnO ₂ texture is used is formed on the coated stainless steel foil. It becomes possible. Since the coated stainless steel foil is lighter and harder to break than a glass substrate and can be easily increased in area, it is suitable as a solar cell substrate for building materials such as a roof. It can also be applied as a flexible solar cell.

  Next, the contents and results of tests actually conducted by the inventors of the present application will be described.

  First, a coating solution A ′ for producing an inorganic polymer film A modified with an organic group was prepared by adding 0.2 mol of terminal silanol polydimethyldiphenylsiloxane having a mass average molecular weight of 1700, 1 mol of zirconium butoxide, 2 mol of ethyl acetoacetate, It was prepared by mixing 10 mol of 1-butanol and 20 mol of methyl isobutyl ketone and hydrolyzing with 2 mol of water.

  A coating solution B ′ for producing an inorganic polymer film B modified with an organic group was prepared by using 1 mol of methyltriethoxysilane, 0.01 mol of titanium isopropoxide, 0.02 mol of ethyl acetoacetate, 2-ethoxyethanol 5 Mole and 1 mol of methyl ethyl ketone were mixed and prepared by hydrolysis with 2 mol of water.

  A coating liquid C ′ for producing an inorganic polymer film C modified with an organic group was prepared by adding 0.3 mol of terminal silanol polydimethylsiloxane having a mass average molecular weight of 6000, 1 mol of titanium isopropoxide, 2 mol of ethyl acetoacetate, -Prepared by mixing 10 mol of butanol and 20 mol of methyl isobutyl ketone and hydrolyzing with 1 mol of water.

  A coating solution for producing an inorganic polymer film not modified with an organic group is composed of 1 mol of tetraethoxysilane, 0.003 mol of titanium isopropoxide, 0.006 mol of ethyl acetoacetate, 5 mol of 2-ethoxyethanol, methyl ethyl ketone. It was prepared by mixing 1 mol and hydrolyzing with 2 mol of 2N aqueous hydrochloric acid (2 mol of water).

  Table 1 shows conditions and evaluation results of Examples and Comparative Examples.

  The surface finish MW of the metal foil is a milk white finishing material manufactured by Nippon Steel Materials Co., Ltd. Bright B, Bright D and BA are surface finishes by annealing. BK is a finish by buffing.

The insulation achievement rate was evaluated by using a 1 cm square Pt film formed by sputtering as the upper electrode, using a metal foil as the lower electrode, and applying a voltage of 100 V between the upper electrode and the lower electrode. The resistance value was determined. And 16 places were measured about the inorganic polymer film modified with each organic group, and the thing whose insulation resistance value is 1.0x10 < ⁸ > ohm-cm < ² > or more was determined to be a pass. The insulation achievement rate represents the number of passing out of 16 places.

Evaluation of crack resistance and peel resistance of ceramic films is based on the fabrication of electronic devices in which each of these ceramic films is formed in the atmosphere from the chamber after depositing 1 μm each of Si ₃ N ₄ films or SiO ₂ films by CVD. The insulation coated metal foil was taken out and visually checked for cracks / peeling. The result is shown in the “immediately after film formation” column. Further, after taking out to the atmosphere, additional heat treatments of 300 ° C. × 1 h and 450 ° C. × 1 h were performed in vacuum in order to investigate how much high-temperature process can be endured during the TFT process. These results are shown in the columns of “300 ° C.” and “450 ° C.”. 300 ° C. is a typical annealing temperature of an electronic device (for example, TFT) having an amorphous Si film, and 450 ° C. is a typical deposition temperature of a low-temperature polysilicon film. As a result of visual inspection, “◯” if there is no defect, “△” if the peeling / cracking is only on the peripheral part of the insulating coated metal foil for producing an electronic device, and the peeling / cracking is an insulating coated metal foil for producing an electronic device. Items extending to the center of are indicated by “x”.

  First, the influence of the surface roughness of the metal foil will be described.

In Examples 1-4 and Comparative Examples 1-2, the coating liquid A ′ was used, and various metal foils were dip coated at a pulling rate of 10 mm / s to form a coating film of the coating liquid A ′. Next, after drying at 150 ° C. for 10 minutes, an inorganic polymer film modified with an organic group was baked by performing a heat treatment at 300 ° C. for 6 hours in the air. This inorganic polymer film modified with an organic group has a network structure in which polydimethyldiphenylsiloxane is crosslinked with an oxide of zirconium, and the siloxane skeleton is modified with a methyl group and a phenyl group. Using the same inorganic polymer film modified with an organic group formed on a slide glass, the Young's modulus of the film was measured by the nanoindentation method and found to be 10 ³ MPa. Moreover, the thickness of the inorganic polymer film modified with an organic group was 2 μm, and a healthy film could be formed regardless of the type of metal foil.

In each of Examples 1 to 4, the surface roughness Ra of the metal foil was 30 nm or more and 500 nm or less, and the insulation achievement rate was 15/16 or more. In Examples 1 to 3, the surface roughness Ra was relatively small, and the metal foil had no protrusions or the like that deteriorated the insulation, so that the insulation achievement rate was 16/16. Further, immediately after the formation of the Si ₃ N ₄ film or the SiO ₂ film and after the additional heat treatment at 300 ° C. × 1 h, the Si ₃ N ₄ film and the SiO ₂ film are defect-free films, and the process up to at least 300 ° C. Was shown to be tolerable. In the metal foil of MW finishing shown in Example 1, the glossiness Gs is 300 or more and less than 500. This means that light is easily diffusely reflected although the surface roughness Ra is small, that is, the wavelength level is fine. It shows that the surface has an uneven structure. For this reason, the stress is easily relaxed at the interface between the metal foil surface and the inorganic polymer film A modified with an organic group, and the residual stress of the inorganic polymer film A modified with an organic group was extremely low. Therefore, it was excellent in peeling resistance and crack resistance, and both the Si ₃ N ₄ film and the SiO ₂ film were sound even when an additional heat treatment up to 450 ° C. was performed.

On the other hand, in Comparative Example 1, since the mirror finish was performed by buffing, the surface roughness Ra was reduced, and the inorganic polymer film A modified with an organic group was subjected to a large compressive stress due to the difference in thermal expansion coefficient from the metal foil. There was a high residual stress on the surface of the inorganic polymer film modified with this organic group. Therefore, the Si ₃ N ₄ film and the SiO ₂ film formed thereon are likely to be cracked and peeled off, and as shown in Table 1, the result was that the TFT fabrication process temperature could not be endured. In Comparative Example 2, the surface roughness Ra is high and the Si ₃ N ₄ film and the SiO ₂ film are excellent in peel resistance and crack resistance, but the surface is too rough, so the inorganic polymer is modified with an organic group. As a result, it was not possible to ensure insulation with the film (0/16), and the result was that it was not suitable for a substrate for manufacturing an electronic device.

  Next, the influence of the inorganic polymer film modified with the organic group covering the metal foil will be described.

In Example 5, the coating liquid B ′ was used and dip coating was performed at a lifting speed of 10 mm / s to form a coating film of the coating liquid B ′. Next, after drying at 150 ° C. for 10 minutes, an inorganic polymer film modified with an organic group was baked by performing heat treatment at 450 ° C. for 10 minutes in nitrogen. In this inorganic polymer film modified with an organic group, all the organic groups modifying the siloxane skeleton are methyl groups, and there is one mole of methyl group for one mole of Si. Using the same inorganic polymer film modified with an organic group formed on a slide glass, the Young's modulus of the film was measured by the nanoindentation method. As a result, it was 2 × 10 ⁴ MPa. Moreover, the film thickness after heat processing was 1.2 micrometers, and the healthy film without a crack was obtained. Moreover, the insulation achievement rate was favorable. Furthermore, since the Young's modulus is higher than that of the inorganic polymer film A modified with an organic group, it is slightly inferior in crack resistance and peel resistance at high temperatures as compared with Example 1, but the process temperature up to 300 ° C. It was able to withstand enough.

  In Example 6, the coating liquid C ′ was used and dip coating was performed at a lifting speed of 20 mm / s to form a coating film of the coating liquid C ′. Next, after drying at 150 ° C. for 10 minutes, an inorganic polymer film modified with an organic group was baked by performing a heat treatment at 300 ° C. for 6 hours in the air. In this inorganic polymer film modified with an organic group, all the organic groups modifying the siloxane skeleton are methyl groups, and there are 2 moles of methyl groups per mole of Si. Using the same inorganic polymer film modified with an organic group formed on a slide glass, the Young's modulus of the film was measured by the nanoindentation method. As a result, it was 50 MPa. Since the Young's modulus was low, the inorganic polymer film modified with an organic group was soft and a 38 μm thick film, but a sound film without cracks or the like was obtained. Moreover, the insulation achievement rate was favorable. Since it is a thick film, the amount of deformation of the inorganic polymer film modified with an organic group is large, and it is slightly inferior in crack resistance and peel resistance at high temperatures as compared with Example 1, but the process temperature up to 300 ° C. Was well tolerated.

In Example 7, the coating liquid A ′ was used, and dip coating was performed at a lifting speed of 1 mm / s to form a coating film of the coating liquid A ′. Next, after drying at 150 ° C. for 10 minutes, an inorganic polymer film modified with an organic group was baked by performing a heat treatment at 300 ° C. for 6 hours in the air. The film thickness was 0.5 μm, and a healthy film without cracks or the like was obtained. The insulation achievement rate is 15/16, which is slightly inferior because the film thickness is thin. The Si ₃ N ₄ film and the SiO ₂ film had good crack resistance and peeling resistance.

  In Example 8, the coating liquid A ′ was used, and dip coating was performed at a lifting speed of 30 mm / s to form a coating film of the coating liquid A ′. Next, after drying at 150 ° C. for 10 minutes, an inorganic polymer film modified with an organic group was baked by performing a heat treatment at 300 ° C. for 6 hours in the air. The film thickness was 50 μm, and a healthy film without cracks or the like was obtained. Moreover, the insulation achievement rate was favorable. Since it is a thick film, the amount of deformation of the inorganic polymer film modified with an organic group increases, and is slightly inferior in crack resistance and peel resistance at high temperatures compared to Example 1, but the process temperature up to 300 ° C. It was able to withstand enough. In addition, a slightly inferior result was obtained as compared with Example 6, because the film having a lower Young's modulus is more easily deformed even when the film is thicker.

In Comparative Example 3, using a coating solution for forming an inorganic polymer film not modified with an organic group, dip coating was performed at a lifting speed of 3 mm / s to form a coating film of the coating solution. Next, after drying at 150 ° C. for 10 minutes, an inorganic polymer film not modified with an organic group was baked by performing a heat treatment at 450 ° C. for 10 minutes in nitrogen. In the inorganic polymer film not modified with the organic group, there is no organic group bonded to Si. The film thickness after the heat treatment was 0.3 μm, and a sound coating without cracks or the like was obtained. Using the same inorganic polymer film formed on a slide glass, the Young's modulus of the film was measured by the nanoindentation method. As a result, it was 5 × 10 ⁴ MPa. Since the film thickness was thin, the surface unevenness of the metal foil of MW finish could not be covered, and the insulation achievement rate was low. Therefore, it cannot be used as an insulating substrate. In addition, since the Young's modulus is high, the thermal expansion coefficient difference from the metal foil cannot be absorbed, and cracks occurred immediately after film formation when either the Si ₃ N ₄ film or the SiO ₂ film was formed. .

It is a model which shows the cross section which mounted TFT components using the metal foil which gave the insulating film as a board | substrate, and is a figure which shows the method of forming TFT. Is a SEM photograph showing blistering peeling the Si ₃ N ₄ layer. It is a cross-sectional schematic diagram which shows the swelling peeling of the ceramic film 33 at the time of using the smooth metal foil 31. FIG. It is a cross-sectional schematic diagram which shows the favorable adhesiveness of the ceramic film 43 at the time of using the moderately rough metal foil 41. FIG. It is a schematic diagram of the cross section which shows metal foil with small surface roughness Ra and high glossiness Gs. It is a schematic diagram of the cross section which shows metal foil with small surface roughness Ra and low glossiness Gs.

Explanation of symbols

11: Metal foil 12: Inorganic polymer film modified with an organic group (metal foil insulating film)
13: Al-Mo alloy film (gate electrode)
14: Si ₃ N ₄ film (device insulation layer)
31: Metal foil 32: Inorganic polymer film modified with organic group (metal foil insulating film)
33: Ceramic film (device insulation layer)
34: Arrow (arrow indicating the direction of contraction)
41: Metal foil 42: Inorganic polymer film modified with an organic group (metal foil insulating film)
43: Ceramic film (device insulation layer)
44: Stress direction (dispersion of stress direction exemplified by arrows)

Claims (4)

A metal foil having a surface roughness Ra of 30 nm to 500 nm,
An insulating film comprising an inorganic polymer modified with a phenyl group, having a Young's modulus of 10 ² MPa to 10 ⁴ MPa, and covering the surface of the metal foil;
An insulating coated metal foil for producing an electronic device, comprising: 2. The insulating coated metal foil for producing an electronic device according to claim 1, wherein the insulating film has a thickness of 0.8 μm or more and 40 μm or less. The said metal foil is stainless steel foil, The insulation coating metal foil for electronic device preparation of Claim 1 or 2 characterized by the above-mentioned. The glossiness Gs (45 °) of the stainless steel foil is 300 or more and less than 500, and
The surface roughness Ra of said stainless steel foil is 100 nm or less, The insulation coating metal foil for electronic device preparation of Claim 3 characterized by the above-mentioned.

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