JP2019149428A - Support substrate for forming flexible substrate, regeneration process thereof, and manufacturing method of flexible substrate - Google Patents

Abstract

To provide a support substrate and a flexible substrate, in which a resin film can be easily peeled, and which can be regenerated.SOLUTION: A support substrate (1) comprises an amorphous silicon thin film (15) onto a front surface of a hard substrate (10). A resin film (20) is formed onto the amorphous silicon thin film of the support substrate, and the resin film is peeled off from the support substrate in a boundary surface of the amorphous silicon thin film, and a flexible substrate (2) can be obtained. The flexible substrate may provide an electronic element (30) on the resin film (20). It is preferred that a surface of the amorphous silicon thin film before the formation of the resin film is in a non-oxidation state, and an ionization potential of the surface is 4.4 eV or less. For example, the characteristics of the amorphous silicon thin film can be controlled by performing a hydrogen plasma treatment to the surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a support substrate used for forming a flexible substrate and a method for regenerating the same. Furthermore, this invention relates to the manufacturing method of a flexible substrate.

  Electronic devices such as displays and solar cells are required to be thin, light, and flexible, and use of a flexible substrate made of a resin film or the like instead of a hard substrate such as a glass substrate has been studied.

  In the manufacturing process of an electronic device, a semiconductor or the like such as a thin film transistor or an electronic element such as an electrode is formed on a substrate. The process of forming electronic elements on a flexible substrate is roughly divided into a batch type and a roll-to-roll type. Since existing equipment using a hard substrate such as a glass substrate can be diverted and the process stability is excellent, a batch type is mainly used as a manufacturing process of electronic devices on a flexible substrate.

  In the batch process, a resin solution is applied and dried on a hard support substrate to form a film substrate which is an embodiment of a flexible substrate, and after an electronic element is formed thereon, the interface between the hard support substrate and the film substrate is formed. By performing peeling, a flexible element substrate in which an electronic element is provided on a film substrate is obtained. As the resin material for the film substrate, polyimide is generally used because it has heat resistance in the element formation process and is excellent in dimensional stability.

  Polyimide has high adhesion to a glass substrate and is often difficult to peel. In patent document 1, after forming a polyimide film on a glass substrate and producing an element on it, adhesiveness is reduced using laser irradiation or an etchant, and the polyimide film is peeled from the glass substrate. In Patent Document 2, an amorphous silicon thin film is formed on a glass substrate, a polyimide film is formed on the amorphous silicon thin film, amorphous silicon is crystallized by laser irradiation, and hydrogen generated at that time is generated. A method of peeling a polyimide film from a glass substrate with a gas is described.

WO2009 / 104371 pamphlet WO2005 / 050754 pamphlet

  The method of peeling a film from a glass substrate by laser irradiation has a problem that it takes a long time to cope with an increase in equipment size and laser processing. In addition, laser-induced damage may occur, or a semiconductor element or the like provided on the film may be damaged along with the deformation of the film at the time of peeling.

  By using a support substrate provided with a release layer for reducing the adhesion of the resin film on the glass substrate, it is possible to suppress problems caused by deformation of the film at the time of peeling. However, because the properties of the release layer change due to heating during film formation, if the support substrate is reused, it may be difficult to remove the resin film from the support substrate. There is a problem with sex.

  In view of the above, an object of the present invention is to provide a flexible substrate-forming support substrate in which a resin film can be easily peeled and reused. Furthermore, the present invention relates to a method for forming a flexible substrate using a support substrate and a method for regenerating the support substrate.

  As a result of investigations by the present inventors, in a support substrate in which an amorphous silicon thin film is provided on the surface of a hard substrate, when the amorphous silicon thin film has predetermined surface characteristics, the resin film has an appropriate adhesion. In addition, the present inventors have found that the resin film can be easily peeled from the support substrate. Furthermore, the present inventors have found that the support substrate can be recycled and reused by subjecting the support substrate after the resin film is peeled off to a surface treatment.

  The support substrate used in the present invention includes an amorphous silicon thin film on the surface of a hard substrate made of glass or the like. After a resin film is formed on the amorphous silicon thin film of the support substrate, the resin film is peeled off from the support substrate at the interface with the amorphous silicon thin film, whereby a flexible substrate made of the resin film is obtained. The adhesion force between the resin film and the support substrate is preferably 0.03 to 0.25 N / 10 mm. A polyimide film is mentioned as an example of the resin film formed on a support substrate.

  After forming the resin film on the support substrate and before peeling the resin film from the support substrate, by forming the electronic element on the resin film, a flexible substrate (element substrate) including the electronic element on the resin film is obtained. .

  The amorphous silicon thin film before the resin film is formed preferably has a non-oxidized surface. The amorphous silicon thin film before forming the resin film preferably has a surface ionization potential of 4.4 eV or less. Before forming the resin film, the surface of the amorphous silicon thin film may be subjected to hydrogen plasma treatment. By the hydrogen plasma treatment, the surface of the amorphous silicon thin film is etched or reduced to be in a non-oxidized state. Further, the ionization potential on the surface of the amorphous silicon thin film can be reduced to 4.4 eV or less by hydrogen plasma treatment.

  The support substrate can be regenerated by performing a hydrogen plasma treatment on the amorphous silicon thin film of the support substrate after the resin film is peeled off. Specifically, the surface of the amorphous silicon thin film can be etched and / or reduced to a non-oxidized state by hydrogen plasma treatment. Further, the ionization potential on the surface of the amorphous silicon thin film can be increased by hydrogen plasma treatment.

  In the support substrate after being regenerated by the hydrogen plasma treatment, the amorphous silicon thin film preferably has a non-oxidized surface. Further, the amorphous silicon thin film of the regenerative support substrate preferably has a surface ionization potential of 4.4 eV or less.

  A flexible substrate is formed using the regenerated support substrate by forming a resin film on the amorphous silicon thin film of the regenerated support substrate and peeling the resin film from the support substrate at the interface with the amorphous silicon thin film. it can. A flexible element substrate can be formed using a reproduction | regeneration support substrate by forming an electronic element on a resin film before peeling a resin film from a reproduction | regeneration support substrate.

  In the present invention, since the amorphous silicon thin film of the support substrate has predetermined characteristics, the resin film formed on the support substrate can be easily peeled off. In addition, by applying hydrogen plasma treatment to the support substrate after the resin film is peeled off, the surface state of the amorphous silicon thin film can be returned to the same state as before the resin film is formed, so the support substrate can be reused. It becomes.

It is a process conceptual diagram which shows the manufacturing process of the flexible element board | substrate by a batch process. It is an infrared spectroscopy spectrum of the amorphous silicon thin film of the support substrate surface of an Example and a comparative example.

  FIG. 1 is a process conceptual diagram showing a manufacturing process of a flexible element substrate by a batch process. First, a hard substrate 10 is prepared (FIG. 1A), and an amorphous silicon thin film 15 is formed on the hard substrate 10 as a release layer (FIG. 1B). A resin film 20 is formed on the support substrate 1 on which the amorphous silicon thin film 15 is provided on the hard substrate 10 (FIG. 1C), and an electronic element 30 is formed on the resin film 20. (FIG. 1D). By peeling at the interface between the resin film 20 and the amorphous silicon thin film 15 and separating the laminate, the flexible element substrate 2 including the electronic element 30 on the flexible substrate made of the resin film 20 is obtained (FIG. 1E). .

  The support substrate 1 after peeling the flexible element substrate 2 is reused (FIG. 1B), the formation of the resin film 20 on the amorphous silicon thin film 15 (FIG. 1C), and the formation of the electronic element 30 on the resin film 20 (FIG. 1D) and separation of the support substrate 1 and the flexible element substrate 2 (FIG. 1E) are repeated.

  As the hard substrate 10, glass, a silicon wafer, a metal plate, or the like is used. A glass substrate is preferable as the hard substrate 10 because of its excellent applicability to existing batch processes. From the viewpoint of preventing deterioration of characteristics due to diffusion of alkali metal into the amorphous silicon thin film 15 formed on the hard substrate 10 and the resin film formed thereon, it is possible to use alkali-free glass as the hard substrate 10. preferable. The thickness of the hard substrate 10 is generally about 0.5 to 5 mm.

  An amorphous silicon thin film 15 is formed on the hard substrate 10. The amorphous silicon thin film 15 has an action of controlling the adhesion between the support substrate 1 and the resin film 20. Amorphous silicon has better adhesion to a glass substrate than metals such as molybdenum and tungsten. Therefore, when the resin film 20 after the electronic element 30 is formed is peeled from the support substrate 1, Peeling is unlikely to occur at the interface. In addition, amorphous silicon is less likely to migrate due to heat or the like during the formation of an electronic element, as compared to a metal material.

  As will be described in detail later, by forming the resin film 20 on the amorphous silicon thin film 15 having predetermined characteristics, the resin film 20 is formed on the support substrate 1 when the electronic element 30 is formed on the resin film 20. The state of being in close contact with the surface can be maintained, and the resin film 20 can be easily peeled from the support substrate 1 after the electronic element 30 is formed.

  The thickness of the amorphous silicon thin film 15 is preferably 10 to 200 nm, more preferably 30 to 150 nm, and still more preferably 50 to 120 nm. If the film thickness of the amorphous silicon thin film 15 is in the above range, the stress balance at the interface is excellent, and the adhesion between the hard substrate 10 and the amorphous silicon thin film 15 is high, and therefore the resin film 20 is peeled from the support substrate 1. It is difficult for the amorphous silicon thin film 15 to peel off.

The amorphous silicon thin film 15 is preferably a hydrogenated amorphous silicon thin film formed by plasma enhanced chemical vapor deposition (CVD). As conditions for forming an amorphous silicon thin film by plasma CVD, for example, a substrate temperature of 100 to 300 ° C., a pressure of 20 to 300 Pa, and a high frequency power density of 0.05 to 0.5 W / cm ² are preferable. The source gas is preferably a silicon-containing gas such as SiH ₄ or Si ₂ H ₆ or a mixed gas of silicon-containing gas and hydrogen.

  When hydrogen is used as the source gas in addition to the silicon-containing gas, if the amount of hydrogen supplied increases, the silicon tends to be crystalline and the resin film 20 tends to be difficult to peel off. Therefore, the supply amount of hydrogen at the time of forming the amorphous silicon thin film 15 is preferably 5 times or less, more preferably 3 times or less, and further preferably 1 time or less of the silicon-containing gas.

  In film formation of hydrogenated amorphous silicon as a semiconductor material, silicon dangling bonds are terminated by supplying hydrogen, and the film quality tends to be improved. On the other hand, the amorphous silicon thin film 15 provided for the purpose of controlling adhesion to the resin film substrate is not required to have characteristics as a semiconductor. Therefore, in the formation of the amorphous silicon thin film 15, it is preferable to reduce the supply amount of hydrogen and suppress the film quality from becoming crystalline. Further, even when hydrogen is not supplied at the time of forming the amorphous silicon thin film, the dangling bond of silicon on the surface portion of the amorphous silicon thin film 15 is terminated by performing hydrogen plasma treatment as will be described later. Therefore, film quality deterioration due to surface oxidation or the like can be prevented.

In the formation of the amorphous silicon thin film 15, conductivity may be imparted to the amorphous silicon thin film 15 by adding a doping gas such as PH ₃ or B ₂ H ₆ to the source gas. By imparting conductivity to the amorphous silicon thin film 15, characteristics such as ionization potential can be controlled. By imparting p-type characteristics using B ₂ H ₆ or the like, the ionization potential of the amorphous silicon thin film 15 tends to increase, and by imparting n-type characteristics using PH ₃ or the like, There is a tendency that the ionization potential of the amorphous silicon thin film 15 decreases.

As will be described later in detail, the amorphous silicon thin film 15 may be subjected to surface treatment with hydrogen plasma or the like for the purpose of controlling the adhesion between the amorphous silicon thin film 15 and the resin film 20. During the hydrogen plasma treatment, a doping gas such as PH ₃ or B ₂ H ₆ may be added to make the surface of the amorphous silicon thin film have n-type or p-type conductivity.

  As the resin film 20, a resin material having flexibility and heat resistance in the process of forming the electronic element 30 is used. As the resin material, polyimide, polyamideimide, polyparaphenylenebenzobisoxazole and the like are preferably used. Among these, polyimide is preferable because of excellent heat resistance and a small coefficient of thermal expansion. From the viewpoint of achieving both mechanical strength, handling properties and flexibility, the thickness of the resin film 20 is preferably 3 to 200 μm, more preferably 5 to 100 μm, further preferably 7 to 50 μm, and particularly preferably 10 to 30 μm.

  The resin film 20 is formed by applying a resin solution on the support substrate 1 and drying the solvent. The resin solution may contain a silane coupling agent, a titanium coupling agent, or the like for the purpose of adjusting the adhesion between the resin film 20 and the support substrate 1. The resin solution may contain a filler and the like. In the case of forming a polyimide film, a soluble polyimide resin may be applied on the support substrate 1, or imidization may be performed after applying a polyamic acid solution as a polyimide precursor on the support substrate 1. The polyamic acid solution may contain a dehydrating agent, an imidization catalyst, or the like for the purpose of promoting the imidization reaction.

  Examples of the resin solution coating method include a gravure coating method, a spin coating method, a bar coating method, a knife coating method, a roll coating method, a die coating method, a silk screen method, and a dip coating method. The drying method and drying temperature of the solvent are not particularly limited. When using a polyamic acid solution, in order to advance imidation, you may heat further after drying of a solvent. When imidization is performed by heating on the support substrate 1, it is preferable to use alkali-free glass as the hard substrate 10 in order to prevent imidization inhibition by an alkali metal.

  An electronic element 30 is formed on the resin film 20. As electronic elements, driving elements such as thin film transistors (TFTs); display elements such as liquid crystal, organic EL, and electronic paper; light emitting elements; photoelectric conversion elements such as solar cells and CMOS; light transmission state depending on current, voltage, temperature, etc. A light control element for controlling light; an electrode or an electric circuit made of a metal, a metal oxide, a conductive organic material, or the like; a thin film storage element, or the like. A plurality of elements may be formed on the resin film 20 to produce a display device, a light receiving device, or the like. A sealing resin layer or the like may be formed on the electronic element 30.

  After forming the electronic element 30, the flexible element substrate 2 is obtained by peeling the resin film 20 from the support substrate 1. Examples of the peeling method include a method of winding a flexible element substrate with a driving roll, peeling with an adhesive sheet or a suction pad, blowing air from an end face, peeling with a human hand, and the like. At the time of peeling, the resin film 20 in a region where the electronic element 30 is not formed may be cut to provide a trigger for peeling.

  In the formation process of the electronic element 30, in order to maintain the state in which the resin film 20 is in close contact with the support substrate 1 and to facilitate the peeling of the resin film 20 from the support substrate 1 after the element formation, the support substrate 1 and the resin film 20 are preferably 0.03 to 0.25 N / 10 mm, more preferably 0.04 to 0.20 N / 10 mm, and 0.05 to 0.15 N / 10 mm. More preferably. The adhesion force is a peel strength according to a peel test at a pulling speed of 100 mm / min and a peeling angle of 180 °.

  By controlling the surface state of the amorphous silicon thin film 15 before the resin film 20 is formed, the resin film 20 can be easily peeled from the support substrate 1. Specifically, if the resin film 20 is formed on the amorphous silicon thin film 15 whose surface is not oxidized, the resin film 20 can be easily peeled from the support substrate 1. Moreover, if the resin film 20 is formed on the amorphous silicon thin film 15 having a surface ionization potential of 4.4 eV or more, the resin film 20 can be easily peeled from the support substrate 1.

Whether or not the surface of the amorphous silicon thin film is oxidized is determined based on the presence or absence of an absorption peak of 1000 to 1100 cm ⁻¹ derived from Si—O stretching vibration in an infrared absorption spectrum by total reflection measurement (ATR). it can. In the spectrum normalized transmittance as a wave number 840 cm ^-1, when the normalized transmittance does not have an absorption peak of less than 0.8 at a wave number region of 1000~1100cm ^-1, amorphous silicon It can be determined that the surface of the thin film is not oxidized. In the measurement of the infrared absorption spectrum by ATR, the measurement conditions may be adjusted so that the penetration depth of infrared light having a wave number of 1000 to 1100 cm ⁻¹ is about 15 nm. The ionization potential of the amorphous silicon thin film surface is measured by ultraviolet photoelectron spectroscopy (UPS).

  The oxidation state and ionization potential can be adjusted by surface treatment of the amorphous silicon thin film. As the surface treatment, an etching treatment or a reduction treatment is preferable. Among these, hydrogen plasma treatment is preferable. While the surface of the amorphous silicon thin film 15 is etched by hydrogen plasma treatment, the dangling bonds of the amorphous silicon can be terminated with hydrogen to increase the ionization potential.

As conditions for the hydrogen plasma treatment, for example, a substrate temperature of 100 to 180 ° C. and a pressure of 20 to 1200 Pa are preferable. RF power density is preferably ^{0.003~0.5W / cm 2, 0.01~0.3W / cm} 2 is more preferable. If the power density is excessively small, the effect of hydrogen plasma etching may be insufficient. On the other hand, if the power density is excessively high, the ionization potential may not be sufficiently increased due to the effects of plasma damage and crystallization. As the input gas in the hydrogen plasma treatment, only hydrogen is preferable. When the influence of etching of the amorphous silicon thin film by hydrogen plasma is large, the number of repeated uses of the support substrate 1 is limited due to the decrease in the thickness of the amorphous silicon thin film. Therefore, 5% by volume or less of source gas (for example, SiH ₄ , CH ₄ or the like) may be added to hydrogen to suppress a decrease in film thickness due to hydrogen plasma.

In the hydrogen plasma treatment, a doping gas such as PH ₃ or B ₂ H ₆ may be added in addition to hydrogen to impart n-type or p-type conductivity to the surface of the amorphous silicon thin film 15. Good. As described above, when the p-type characteristic is given, the ionization potential of the amorphous silicon thin film 15 tends to increase, and when the n-type characteristic is given, the ionization potential of the amorphous silicon thin film 15 tends to decrease. There is. In the hydrogen plasma treatment, when a doping gas is used, the doping gas is preferably added in an amount of 1 to 10000 ppm, more preferably 10 to 5000 ppm with respect to hydrogen.

  Even when the surface of the amorphous silicon thin film is oxidized, the oxide film can be reduced or etched away by hydrogen plasma treatment, so that an amorphous silicon thin film whose surface is not oxidized can be obtained. Also, the ionization potential tends to increase due to termination of silicon dangling bonds on the surface of the amorphous silicon thin film.

  When the surface of the amorphous silicon thin film 15 is not oxidized, since the electrostatic interaction in the vicinity of the film forming interface is small when the resin film is formed, the adhesion between the amorphous silicon thin film 15 and the resin film 20 is reduced. Is expected to decrease. The ionization potential measured by UPS is the minimum energy for extracting electrons from the surface of the thin film. When amorphous silicon is oxidized, the ionization potential tends to decrease. The ionization potential is empirically related to the likelihood of electrostatic interaction, and the higher the ionization potential, the more difficult it is to charge, and the generation of static electricity tends to be suppressed. Therefore, it is considered that the greater the ionization potential, the smaller the electrostatic interaction in the vicinity of the film forming interface during the formation of the resin film, and the lower the adhesion between the amorphous silicon thin film 15 and the resin film 20.

  The surface of the amorphous silicon thin film 15 after the resin film 20 is formed and peeled off is often oxidized, and the ionization potential tends to be lower than before the resin film 20 is formed. . This is considered to be the influence of the contact with the solvent at the time of resin film formation and the heating for drying. In particular, when a polyimide precursor solution is applied onto the amorphous silicon thin film 15 of the support substrate 1 and imidization is performed by heating, the ionization potential of the amorphous silicon thin film 15 tends to decrease significantly. This is probably because the surface of the amorphous silicon thin film 15 is easily oxidized because heating at a high temperature (for example, 300 ° C. or higher) is performed during imidization.

  In the process of forming the resin film 20, even if the surface of the amorphous silicon thin film 15 is oxidized and the ionization potential is lowered, the surface of the amorphous silicon thin film 15 before the resin film is formed is not oxidized and the ionization potential is 4. If it is 0.4 eV or more, the resin film 20 has an appropriate adhesion to the amorphous silicon thin film 15 and can be easily peeled off from the support substrate 1. However, if a resin film is formed again on an amorphous silicon thin film whose surface has been oxidized due to the formation of the resin film and the ionization potential has been lowered, the adhesive force tends to be excessively large and peeling tends to be difficult.

  Even when the surface of the amorphous silicon thin film 15 is oxidized due to the formation of the resin film 20 and the ionization potential is lowered, the above-mentioned hydrogen plasma treatment is performed to change the oxide film on the surface of the amorphous silicon thin film 15. Reduction or etching can be performed to increase the ionization potential. By performing this treatment, the resin film 20 formed on the amorphous silicon thin film 15 can be easily peeled off. That is, when the amorphous silicon thin film 15 of the support substrate 1 once used is subjected to hydrogen plasma treatment, the support substrate can be recycled.

  As described above, if the support substrate 1 provided with the amorphous silicon thin film 15 having predetermined characteristics on the hard substrate 10 is used, the process of reducing the adhesion force by a laser or the like is not performed, and the support substrate 1 The resin film 20 formed on the amorphous silicon thin film 15 and the flexible element substrate 2 on which the electronic element 30 is formed on the resin film 20 can be easily peeled from the support substrate 1. Therefore, the process can be simplified and damage to the support substrate and the electronic element due to a laser or the like can be prevented. Moreover, since the support substrate 1 can be recycled by performing the hydrogen plasma process on the amorphous silicon thin film 15 of the support substrate 1 after the resin film 20 is peeled off, it is possible to reduce manufacturing costs and waste.

  With reference to FIG. 1, although the method to manufacture the flexible element board | substrate 2 provided with the electronic element 30 on the resin film 20 was demonstrated, you may provide thin films, elements, etc. other than an electronic element on a resin film. Further, without forming an element or the like on the resin film, the resin film 20 may be peeled from the support substrate and used as it is as a flexible substrate.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to a following example.

[Evaluation method]
(Adhesion)
The polyimide film formed on the substrate was cut with a width of 10 mm and a length of 120 mm, and the end of the cut was peeled from the substrate. Using a load cell having a capacity of 50 N, a peel test (peel length: 100 mm) was performed at a peeling angle of 180 ° and a tensile speed of 100 mm / min, and the area of 60 mm from which 20 mm from the start of the test and 20 mm before the end of the test was removed. The average value of the peel strength was taken as the adhesion between the polyimide film and the substrate.

(Ionization potential)
Using an ultraviolet photoelectron spectrometer (“AC-2” manufactured by Riken Keiki Co., Ltd.), measurement was performed in the irradiation light energy range of 3.0 to 6.0 eV, and the photoemission threshold (work function) was taken as the ionization potential. .

(Oxidation state)
A total reflection measurement attachment (“ATR-8000” manufactured by Shimadzu Corporation) is attached to a Fourier transform infrared spectrophotometer (“IRAffinity-1” manufactured by Shimadzu Corporation), and an amorphous silicon thin film in a wave number region of 600 to 3000 cm ^−1. The infrared absorption spectrum of was measured. The resulting spectrum, normalized transmittance of wave numbers 840 cm ^-1 as 1, transmittance normalized wave number region of 1000～1100Cm ^-1 confirms the presence of absorption peaks of less than 0.8. Those in which an absorption peak was not confirmed were regarded as having no oxygen, and those in which an absorption peak with a normalized transmittance of less than 0.8 was confirmed were regarded as having oxygen.

[Preparation of polyimide precursor solution]
In a reaction vessel equipped with a stirring blade, 567 parts by weight of N, N-dimethylacetamide dehydrated by molecular sieve was placed, and 27.1 parts by weight of paraphenylenediamine (PDA) was added and stirred for 15 minutes in a nitrogen atmosphere. . The solution was kept at 25 ° C., 36.7 parts by weight of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) was added and stirred for 10 minutes to completely dissolve, and then BPDA 36.2. Part by weight was added and stirred for 2 hours to obtain a polyamic acid (polyimide precursor) solution having a solid concentration of 15% by weight. The weight average molecular weight of the polyamic acid was 72,000.

[Example 1]
(Formation of amorphous silicon thin film)
An amorphous silicon thin film having a thickness of 100 nm was formed by plasma CVD on an alkali-free glass substrate (“OA-10G” manufactured by Nippon Electric Glass, thickness 0.7 mm). The film forming conditions were: substrate temperature: 150 ° C., input gas: SiH ₄ , pressure: 120 Pa, and power density 11 mW / cm ² . The ionization potential of this amorphous silicon thin film was 4.33 eV.

(Hydrogen plasma treatment)
A glass substrate on which an amorphous silicon thin film is formed is put into a CVD apparatus, and plasma discharge is performed for 60 seconds under the conditions of substrate temperature: 150 ° C., input gas: H ₂ , pressure: 50 Pa, power density: 70 mW / cm ^2. Then, a hydrogen plasma treatment was performed on the surface of the amorphous silicon thin film. The ionization potential of the amorphous silicon thin film after the hydrogen plasma treatment was 4.49 eV.

(Preparation of polyimide film)
On the amorphous silicon thin film after the hydrogen plasma treatment, the polyimide precursor solution was cast and applied by a bar coater so as to have a dry thickness of 20 μm, dried in a hot air oven at 125 ° C. for 1 hour, and then 150 ° C. For 30 minutes. Thereafter, the temperature was raised to 450 ° C. at 5 ° C./minute, and after reaching 450 ° C., the mixture was further heated for 10 minutes for thermal imidization.

(Removal of polyimide film)
By the above, the board | substrate with a polyimide film with which the amorphous silicon thin film was provided on the alkali free glass and the polyimide film with a thickness of 20 micrometers was laminated | stacked on it was obtained. The adhesion between the polyimide film and the substrate was 0.07 N / 10 mm. When the edge of the polyimide film was grasped by hand and peeled off from the substrate, it was easily peeled off at the interface between the amorphous silicon thin film and the polyimide film. The ionization potential of the amorphous silicon thin film after peeling the polyimide film was lowered to 4.29 eV.

[Example 2]
(Board recycling)
The substrate after peeling off the polyimide film of Example 1 was put into a CVD apparatus, and hydrogen plasma treatment was performed on the surface of the amorphous silicon thin film under the same conditions as described above. The ionization potential of the amorphous silicon thin film after the hydrogen plasma treatment was increased to 4.45 eV.

(Preparation and peeling of polyimide film)
A polyimide precursor solution was applied on the amorphous silicon thin film after the hydrogen plasma treatment under the same conditions as in Example 1, and thermal imidization was performed to form a polyimide film. The adhesive force between the polyimide film and the substrate was 0.09 N / 10 mm, and could be easily peeled off at the interface between the amorphous silicon thin film and the polyimide film.

[Comparative Example 1]
In the same manner as in Example 1, formation of an amorphous silicon thin film on a crow substrate, hydrogen plasma treatment, production of a polyimide film, and peeling of the polyimide film were performed. Thereafter, the polyimide precursor solution was applied onto the amorphous silicon thin film and thermally imidized without performing hydrogen plasma treatment. The adhesion between the polyimide film and the substrate was 0.42 N / 10 mm. When the end of the polyimide film was grasped by hand and peeled off from the substrate, a strong force was required for peeling.

[Comparative Example 2]
The input gas at the time of forming the amorphous silicon thin film was changed to a mixed gas of SiH ₄ and H ₂ (SiH ₄ / H ₂ = 3/10), and the pressure was changed to 120 Pa. Otherwise, an amorphous silicon thin film was formed on the crow substrate under the same conditions as in Example 1. The ionization potential of this amorphous silicon thin film was 4.31 eV.

  Without performing the hydrogen plasma treatment, the polyimide precursor solution was applied onto the amorphous silicon thin film and thermal imidization was performed. The adhesion between the polyimide film and the substrate was 0.32 N / 10 mm.

[Comparative Example 3]
Without forming an amorphous silicon thin film, an imide precursor solution was applied on an alkali-free glass substrate, and thermal imidization was performed to form a polyimide film. The adhesion between the polyimide film and the glass substrate was 0.31 N / 10 mm.

[Examples 3 to 8]
The pressure and power density of the hydrogen plasma treatment were changed as shown in Table 1. In Example 7, PH ₃ gas having a concentration of 2000 ppm with respect to hydrogen was introduced as an additive gas. In Example 8, B ₂ H ₆ gas having a concentration of 2000 ppm with respect to hydrogen was introduced as an additive gas. Except for these changes, in the same manner as in Example 1, formation of an amorphous silicon thin film on a crow substrate, hydrogen plasma treatment, production of a polyimide film, and peeling of the polyimide film were performed. Table 1 shows the ionization potential of the amorphous silicon thin film after the hydrogen plasma treatment and before the polyimide film is formed, and the adhesion between the polyimide film and the substrate.

  When the edge of the polyimide film was grasped by hand and peeled off from the substrate, in Examples 2 to 5 and Example 8, as in Example 1, it was easy at the interface between the amorphous silicon thin film and the polyimide film. It was possible to peel off. In Example 6 and Example 7, a force was required for peeling compared to Example 1, but peeling was possible with a small force compared to Comparative Examples 1-3.

FIG. 2 shows an infrared spectrum (normalized at a wave number of 840 cm ⁻¹ ) of the amorphous silicon thin film before formation of the polyimide film of Example 2, Comparative Example 1 and Comparative Example 2. In addition, silane and hydrogen introduction ratio, hydrogen plasma treatment conditions, characteristics of amorphous silicon thin film (ionization potential, presence of oxygen determined by infrared spectroscopy, Table 1 shows the adhesive strength of the polyimide film.

  As shown in Table 1, when the surface of the amorphous silicon thin film before polyimide film formation was not oxidized, the adhesion of the polyimide film was 0.25 N / 10 mm or less, indicating good peelability. Further, a high correlation was observed between the ionization potential of the surface of the amorphous silicon thin film before the polyimide film was formed and the adhesion force of the polyimide film, and the adhesion force was decreased as the ionization potential was increased.

  In Example 1, the ionization potential of the amorphous silicon thin film before the hydrogen plasma treatment was 4.33 eV. However, the ionization potential increased by the hydrogen plasma treatment, and the polyimide film formed on the amorphous silicon thin film was removed. It could be easily peeled off. The surface of the amorphous silicon thin film after peeling the polyimide film was oxidized, and the ionization potential was lowered to 4.29 eV.

  In Comparative Example 1 in which a polyimide film was formed on this silicon thin film, adhesion was high and peeling was difficult. On the other hand, in Example 2 where the surface was subjected to hydrogen plasma treatment, the ionization potential increased and the film surface became non-oxidized, and the polyimide film could be easily peeled from the amorphous silicon thin film.

  Based on the above results, by performing hydrogen plasma treatment before the formation of the resin film, the surface of the amorphous silicon thin film becomes non-oxidized and the ionization potential increases, and heating is performed at a high temperature during the formation of the resin film. It can be seen that the resin film can be easily peeled from the amorphous silicon thin film. In addition, it can be seen that even when the surface of the amorphous silicon thin film is oxidized and the ionization potential is lowered due to the formation of the resin film, the hydrogen plasma treatment can be used for recycling.

  From the comparison of Examples 1 to 8, it can be seen that the ionization potential can be adjusted to an arbitrary value by changing the plasma treatment conditions, and the adhesion between the amorphous silicon thin film and the resin film can be controlled.

  In Comparative Example 2 in which silane gas diluted with hydrogen was supplied during the formation of the amorphous silicon thin film, the dangling bond of silicon was considered to be terminated by hydrogen introduction, but the surface was oxidized and the ionization potential was also hydrogen. This was equivalent to Example 1 (before treatment) in which an amorphous silicon thin film was formed without introducing. This is because, when hydrogen is introduced during film formation, the film exhibits characteristics close to crystals rather than being completely amorphous, resulting in a decrease in ionization potential due to the influence of crystal grain boundaries and promotion of oxidation at grain boundaries. This is thought to have occurred.

  Both hydrogen introduction and hydrogen plasma treatment during film formation have the effect of terminating dangling bonds in silicon. From the above results, amorphous silicon having a high ionization potential with a non-oxidized surface is formed. Therefore, it can be seen that a method of performing hydrogen plasma treatment after film formation is suitable.

DESCRIPTION OF SYMBOLS 1 Support substrate 10 Hard substrate 15 Amorphous silicon thin film 2 Flexible element substrate 20 Resin film 30 Electronic element

Claims (12)

Preparing a support substrate provided with an amorphous silicon thin film on the surface of a hard substrate;
Forming a resin film on the amorphous silicon thin film of the support substrate; and peeling the resin film from the support substrate at an interface with the amorphous silicon thin film,
The method for manufacturing a flexible substrate, wherein the amorphous silicon thin film before forming the resin film has a non-oxidized surface. Preparing a support substrate provided with an amorphous silicon thin film on the surface of a hard substrate;
Forming a resin film on the amorphous silicon thin film of the support substrate; and peeling the resin film from the support substrate at an interface with the amorphous silicon thin film,
The method for producing a flexible substrate, wherein the amorphous silicon thin film before forming the resin film has a surface ionization potential of 4.4 eV or less. Preparing a support substrate provided with an amorphous silicon thin film on the surface of a hard substrate;
Forming a resin film on the amorphous silicon thin film of the support substrate; and peeling the resin film from the support substrate at an interface with the amorphous silicon thin film,
A method for producing a flexible substrate, wherein a surface of the amorphous silicon thin film is subjected to hydrogen plasma treatment before forming the resin film.   The electronic device according to any one of claims 1 to 3, wherein an electronic element is formed on the resin film after the resin film is formed on the support substrate and before the resin film is peeled from the support substrate. A manufacturing method of a flexible substrate.   The manufacturing method of the flexible substrate of any one of Claims 1-4 whose adhesive force of the said resin film and the said support substrate is 0.03-0.25N / 10mm.   The manufacturing method of the flexible substrate of any one of Claims 1-5 whose said resin film is a polyimide film. After peeling the resin film from the support substrate at the interface with the amorphous silicon thin film, a hydrogen plasma treatment is performed on the surface of the amorphous silicon thin film on the surface of the support substrate,
The resin film is peeled off from the support substrate at the interface with the amorphous silicon thin film after forming a resin film on the amorphous silicon thin film after the hydrogen plasma treatment. The manufacturing method of the flexible substrate of Claim 1.   The method for manufacturing a flexible substrate according to claim 7, wherein a surface of the amorphous silicon thin film after the hydrogen plasma treatment is in a non-oxidized state.   The method for producing a flexible substrate according to claim 7 or 8, wherein the amorphous silicon thin film after the hydrogen plasma treatment has a surface ionization potential of 4.4 eV or less. Equipped with an amorphous silicon thin film on the surface of a hard substrate,
A support substrate for forming a flexible substrate, wherein a surface of the amorphous silicon thin film is in a non-oxidized state. Equipped with an amorphous silicon thin film on the surface of a hard substrate,
A support substrate for forming a flexible substrate, wherein an ionization potential of a surface of the amorphous silicon thin film is 4.4 eV or more. A method for regenerating a support substrate for forming a flexible substrate, wherein a hydrogen plasma treatment is performed on a surface of the amorphous silicon thin film of a support substrate having an amorphous silicon thin film on a surface of a hard substrate.

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