JP6234391B2 - Manufacturing method of display device and resin solution for display device - Google Patents

Description

  The present invention relates to a method for manufacturing a display device, and more specifically, a display device or a display device member such as a liquid crystal display device, an organic EL display, organic EL illumination, electronic paper, a touch panel, and a color filter is formed on a flexible substrate. The present invention relates to a method for manufacturing a display device.

  Display devices such as liquid crystal display devices and organic EL display devices are used for various display applications such as large displays such as televisions and small displays such as mobile phones, personal computers, and smartphones. As a typical display device, there is an organic EL display device. For example, in this organic EL display device, a thin film transistor (hereinafter referred to as TFT) is formed on a glass substrate which is a supporting base, and an electrode, a light emitting layer, and an electrode Are sequentially formed and finally hermetically sealed with a glass substrate or a multilayer thin film.

  Here, by replacing the glass substrate with a resin base material from the conventional glass substrate, it is possible to realize thinness, light weight, and flexibility, and further expand the application of the display device. However, since resins are generally inferior in dimensional stability, transparency, heat resistance, moisture resistance, gas barrier properties and the like as compared with glass, they are currently in the research stage and various studies have been made.

  For example, Patent Document 1 relates to a polyimide useful as a plastic substrate for a flexible display and an invention relating to a precursor thereof, and uses tetracarboxylic acids containing an alicyclic structure such as cyclohexylphenyltetracarboxylic acid. It has been reported that polyimides reacted with various diamines are excellent in transparency. In addition to this, attempts have been made to reduce the weight by using a flexible resin for the support substrate. For example, in the following Non-Patent Documents 1 and 2, an organic material in which highly transparent polyimide is applied to the support substrate. An EL display device has been proposed.

  Thus, although it is known that resin films such as polyimide are useful for flexible substrates for flexible displays, the manufacturing process of display devices has already been performed using glass, and most of its production facilities are Designed on the premise of using glass. Therefore, it is desirable to be able to produce display devices while effectively utilizing existing production equipment.

  As one specific example of the study, glass is used as a support, a predetermined display device manufacturing process is completed in a state where a resin substrate is laminated on the glass, and then the glass is removed, so that the flexible substrate is removed. There are known methods for manufacturing a display device having a display unit (see Patent Documents 2 to 8 and Non-Patent Documents 3 to 4). In these cases, in a predetermined process of the display device manufacturing process, the glass and the resin substrate are not adhered to each other well, and the display unit (display unit) formed on the surface resin substrate is in good contact. It is necessary to separate the resin substrate and the glass without damaging them.

  That is, in Non-Patent Document 3, after a predetermined display portion is formed on a resin base material applied and fixed on glass, a laser is emitted from the glass side by a method called an EPLaR (Electronics on Plastic by Laser Release) process. Irradiate to separate the resin substrate with the display from the glass. In this method, since the laser is irradiated after forming the display portion on the resin base material, there is a possibility that the laser that has passed through the resin base material may damage functional layers such as TFTs and color filters. In particular, when a highly transparent resin is applied to the resin base material, the laser easily passes through the resin layer, and the risk of damage to the functional layer is further increased. If the intensity of the laser is lowered in order to avoid damage to the functional layer, there is a problem that productivity is lowered.

  On the other hand, the method described in Non-Patent Document 4 is a method in which the defects of the EPLaR method are improved, and after forming a release layer on a glass substrate, a polyimide resin is applied on the release layer to display an organic EL display. In this method, the polyimide film layer is peeled from the release layer after the manufacturing process of the device is completed. That is, in this method, after the release layer 2 is formed on the glass 1, the polyimide layer 3 is formed slightly larger than the release layer 2, and then a predetermined TFT and organic EL process process is performed. After forming the EL panel portion (display portion) 4, the polyimide layer 3 and the TFT / organic EL panel portion (display portion) 4 are peeled off by cutting to the peeling layer 2 along the cutting line 5 inside the peeling layer 2. It peels off from the layer 2. However, Non-Patent Document 4 has no specific description such as what to use for the release layer. For this reason, it is unclear how much force is actually required for separation from the release layer and what state the surface properties of the separated polyimide layer 3 will be. In addition, since it is necessary to make the area of the release layer smaller than the area of the polyimide layer, there is a limit to the area where the organic EL display device can be formed, and there is a problem in productivity. Increasing the area of the release layer to prevent a decrease in productivity reduces the area of the polyimide layer that adheres to the glass at the outer periphery of the release layer, and is prone to exfoliation due to stress during the process There is.

  In the method described in Patent Document 2, after forming a release layer made of parylene or a cyclic olefin copolymer on glass, a polyimide layer is formed to be slightly larger than the release layer in the same manner as in Non-Patent Document 4, This is a method in which an electronic device is fabricated thereon and then a polyimide layer is peeled off. In order to form TFTs required for display applications, an annealing process that generally reaches about 400 ° C. is necessary. However, in this method, the heat resistance of the release layer is inferior to that of polyimide. There exists a subject that the maximum temperature at the time of preparation is restrict | limited to the heat resistance of a peeling layer. Further, since the adhesion between the glass and the release layer and between the release layer and the polyimide layer is weak, it cannot withstand the stress during the process and may cause peeling. Furthermore, the thermal expansion coefficient of the release layer is larger than that of polyimide, and the difference in thermal expansion coefficient due to the difference in resin type can be a factor of warpage.

  The method described in Patent Document 3 is a method for manufacturing a photovoltaic device in which a photoelectric conversion element is formed on a resin layer after forming a resin layer on the support, and the support is positioned at a position surrounding the photoelectric conversion device portion. And a portion having a high adhesion between the resin layers. Polyimide is exemplified as the resin layer, but there is no disclosure about a technique for making the polyimide peelable from the support. Unlike a photovoltaic device, an organic EL display device requires a very high gas barrier property. Therefore, it is essential to form a dense barrier layer on the resin layer. However, the peel strength between the support and the resin layer is essential. If it is high, cracks may occur in the barrier layer at the time of peeling, and the gas barrier property may be lowered. Furthermore, display devices are required to be thinner and lighter, and the need for thin resin layers is much stronger than that of photovoltaic devices. When the thickness of the resin layer is 30 μm or less, if the peeling is performed without appropriately controlling the peeling strength between the support and the resin layer, the resin layer is stretched, and the gas barrier layer, circuit, TFT, color filter, ITO The functional layer of the display device is damaged. Further, in order to reuse the support, the part surrounding the photovoltaic device part also needs to be peeled off from the support, but the method of Patent Document 3 has a stronger adhesion than the photovoltaic device part. Since the part is essential, peeling of this part may be difficult.

  Patent Document 4 and Patent Document 5 disclose a device manufacturing method for controlling the peel strength between a support and a polyimide film substrate by changing the ratio of a diamine having a specific chemical structure and an acid anhydride. In addition, there is no description of a method that satisfies both the reliable prevention of peeling of the support and the polyimide film substrate in a predetermined process and the good peelability after the predetermined process. Furthermore, since the obtained polyimide is colored yellowish brown and inferior in transparency, the range of application to a display device is limited. Further, Patent Document 5 discloses that when the peel strength is less than 160 N / m, it cannot be used as a practical device because it cannot withstand the wet cleaning process in the process.

  The method of patent document 6 is a manufacturing method of the laminated body of the support body and resin layer which are inorganic materials, and after performing the coupling agent process of the surface of a support body, patterning process of this coupling agent by UV irradiation etc. Is a method for manufacturing a laminate having a good adhesion portion and an easy peel portion having different peel strengths. In this method, since a coupling agent treatment and patterning are required, there are problems of an increase in cost due to an increase in the number of steps and a decrease in yield. Also, it is difficult to control the peel strength of each part to a predetermined value with good reproducibility. Furthermore, in practice, the support is often reused and reused. For reuse, it is preferable that the good adhesion portion can be easily peeled off, but there is no consideration for the peelability of the good adhesion portion. According to an example, most of the peel strengths of the well-bonded portions are 500 N / m or more, and peeling is not easy.

  In the method of Patent Document 7, the film material layer provided on the support is heated to form a film layer, and then the peripheral portion is heated at a temperature higher than the film formation temperature before forming the display layer, thereby preventing peeling with high adhesive force. A method of manufacturing a display device is disclosed in which a part is provided, and further, after the display layer is formed, the peeling prevention part is heated to peel the film material from the support substrate. In this method, partial heating of the film material is required twice before and after the formation of the display layer, resulting in an increase in cost due to an increase in the number of steps and a need for a dedicated peeling apparatus such as a laser. Further, there is no description about means for controlling the peel strength of the display layer forming portion.

  The method of Patent Document 8 is a method in which after a release layer is formed on a support, a flexible substrate is formed on the release layer, and peeling is performed between the release layer and the flexible substrate. As the release layer, molybdenum, nickel, and silicon nitride are disclosed. In this method, steps such as sputtering and photolithography etching are required to form a patterned release layer, and there is a problem of an increase in cost due to an increase in the number of steps. In addition, during the manufacturing process, there is a risk of foreign matter contamination and process contamination due to the fallen material of the release layer. In the case where the release layer falls off by brush washing before the process is introduced into the support and before reuse, the problem of defective peeling of the flexible substrate also occurs.

In any of these methods, glass is used as a supporting substrate, and a display portion is formed on a flexible substrate fixed to the glass, thereby ensuring the handleability and dimensional stability of the flexible substrate. There is an advantage that glass can be used as it is in the current production line for producing display devices such as display devices and organic EL display devices.
However, in the above method, the support and the flexible substrate are laminated without peeling, and can be separated very easily after forming the predetermined display portion, and the damage to the flexible substrate and the display portion is small. From the standpoint that the flexible substrate remaining on the removed support substrate can be removed by simple means, further improvement is necessary.

JP 2008-231327 A JP 2010-67957 A JP-A-4-212475 JP 2012-140560 JP 2012-140561 A JP 2013-10340 JP 2013-73001 A JP 2013-168445 A

S. An et. al., "2.8-inch WQVGA Flexible AMOLED Using High Performance Low Temperature Polysilicon TFT on Plastic Substrates", SID2010 DIGEST, p706 (2010) Oishi et. al., "Transparent PI for flexible display", IDW'11 FLX2 / FMC4-1 E.I. Haskal et. Al. "Flexible OLED Displays Made with the EPLaR Process", Proc. Eurodisplay '07, pp. 36-39 (2007) Cheng-Chung Lee et. Al. "A Novel Approach to Make Flexible Active Matrix Displays", SID10 Digest, pp.810-813 (2010)

  Therefore, an object of the present invention is to easily obtain a display device by easily separating a flexible substrate from a support after forming a predetermined functional layer on a flexible substrate integrated with a support in advance. It is to provide a method that can do this.

  As a result of intensive studies to solve the above problems, the present inventors have made the peel strength between the flexible substrate and the support in the functional layer formation region where the functional layer is formed be 200 N / m or less and 0.1 N / m or more. At the same time, a peeling prevention portion for preventing the flexible substrate from being peeled from the support is formed at a position surrounding the functional layer formation region, and the flexible substrate and the peeling prevention portion in the functional layer formation region are separated. By removing the support from the flexible substrate with the functional layer, the functional layer can be accurately manufactured while ensuring the handleability and dimensional stability of the flexible substrate, and the flexible substrate can be easily removed from the support. The inventors have found that a display device can be obtained by separation, and completed the present invention.

That is, the present invention includes a flexible substrate forming step of forming a flexible substrate on a support by applying a resin solution to the support, a functional layer forming step of forming a functional layer on the flexible substrate, and a functional layer. And a support removing step of removing the support from the formed flexible substrate , and manufacturing the display device, wherein the flexible substrate is formed of two or more resin layers, and the functional layer is with the peel strength between the flexible substrate and the support in the functional layer forming region formed is 200 N / m or less 0.1 N / m or more, in a position to surround the functional layer forming region forms the flexible substrate peeling the any one or more of the resin layer is adhered to the support the outer periphery of the functional layer forming region overhangs sum, to prevent the flexible substrate is peeled off from the support Forming a prevention portion, and by leaving thinner than the thickness of the flexible substrate of the functional layer forming region the thickness of the separation preventing sections, to part of the support which corresponds to the functional layer forming region or the separation preventing sections In the support removing step, without performing local chemical surface treatment or local heating to the part of the support corresponding to the peel prevention part, the flexible substrate and the peel prevention part in the functional layer forming region And a support is removed from the flexible substrate provided with the functional layer.

The present invention also includes a flexible substrate forming step of forming a flexible substrate on the support by applying a resin solution to the support, a functional layer forming step of forming a functional layer on the flexible substrate, and a functional layer. And a support removing step for removing the support from the formed flexible substrate, and a method for manufacturing a display device, comprising: a flexible substrate and a support in a functional layer forming region where the functional layer is formed; Peel strength is 200 N / m or less and 0.1 N / m or more, and at a position surrounding the functional layer formation region, a part of the constituent material of the functional layer protrudes to the outer peripheral side of the functional layer formation region and becomes a support. By bonding and forming a peeling prevention portion that prevents the flexible substrate from being peeled off from the support, a local area on the portion of the support corresponding to the functional layer forming region or the peeling prevention portion is formed. In the support removing step, the flexible substrate in the functional layer forming region and the separation preventing portion are separated without performing chemical surface treatment or local heating on the portion of the supporting body corresponding to the separation preventing portion. Then, the support is removed from the flexible substrate having the functional layer.

The display device manufacturing method of the present invention is preferably characterized in that, in the support removing step, the support is removed from the flexible substrate having the functional layer after the peeling preventing portion is removed from the support. To do.

In the display device manufacturing method of the present invention, preferably, the peel strength between the flexible substrate and the support in the peel preventing portion is 500 N / m or less .

In the display device manufacturing method of the present invention, it is preferable that a part of the constituent material of the functional layer forming the peeling preventing portion is an inorganic layer formed of an inorganic base material .

In the display device manufacturing method of the present invention, preferably , prior to the functional layer forming step, UV laser light is irradiated only to a position corresponding to the functional layer forming region of the flexible substrate formed in the flexible substrate forming step. By doing so, the peeling strength between the flexible substrate and the support in the position surrounding the functional layer formation region is increased to form the peeling prevention portion compared to the peeling strength between the flexible substrate and the support in the functional layer formation region. It is characterized by.

In the display device manufacturing method of the present invention, preferably, the thickness of the flexible substrate is 0.
. It is 1 μm or more and 30 μm or less .

In the display device manufacturing method of the present invention, preferably, the flexible substrate is made of polyimide .

In the method for producing a display device of the present invention, preferably, in the flexible substrate forming step, a polyimide or polyimide precursor resin solution is applied to a support and then heat-treated in an oxidizing atmosphere to obtain a flexible substrate. It is characterized by.

Moreover, the manufacturing method of the display apparatus of this invention, Preferably, in the said flexible substrate formation process, after apply | coating the resin solution of a polyimide or a polyimide precursor to a support body, it heat-processes at 280 degreeC or more, and obtains a flexible substrate. It is characterized by.

The display device manufacturing method of the present invention is preferably characterized in that, in the flexible substrate forming step, a flexible substrate is obtained by continuous heat treatment after a polyimide or polyimide precursor resin solution is applied to a support. .

The display device manufacturing method of the present invention is preferably characterized in that the display device is a touch panel .

  In the manufacturing method of the display device of the present invention, in the manufacturing process, the support and the flexible substrate are laminated without occurrence of peeling without performing a local chemical surface treatment or heating on the support, and a predetermined functional layer. Since the display device can be separated very easily after forming the film, and the flexible substrate and the functional layer are not damaged, the mass productivity is excellent. In addition, since the frame-like flexible substrate remaining on the support after the display device is removed (that is, the portion corresponding to the peeling prevention portion) can be removed by simple means, the support can be easily reused. As a result, replacement of the glass substrate with the flexible substrate can be further promoted in the manufacture of the display device.

FIG. 1 is a schematic explanatory diagram illustrating a method for manufacturing a display device according to Reference Example 1. FIG. 2 is a schematic explanatory view illustrating the method for manufacturing the display device according to the second embodiment. FIG. 3 is a schematic explanatory view illustrating the method for manufacturing the display device according to the third embodiment. FIG. 4 is a schematic explanatory view illustrating the method for manufacturing the display device according to the fourth embodiment. FIG. 5 is a schematic explanatory view showing a method for manufacturing a display device according to Reference Example 5. FIG. 6 is a schematic explanatory view illustrating the method for manufacturing the display device according to the sixth embodiment. FIG. 7 is a schematic explanatory view illustrating the method for manufacturing the display device according to the seventh embodiment. FIG. 8 is a schematic explanatory view showing a method for manufacturing a display device according to Comparative Example 4. FIG. 9 is a schematic explanatory view showing a peeling apparatus having a base for fixing a functional layer forming region and used in a method for manufacturing a display device.

Hereinafter, one mode of a method for manufacturing a display device of the present invention will be described in detail.
First, a support is prepared. This support body plays the role of the base at the time of forming a display part as a functional layer in the manufacture process of an organic electroluminescence display, for example. Also, in the touch panel manufacturing process, it plays the role of a pedestal when forming an electrode layer such as film formation or circuit processing of a transparent conductive film. The support is not particularly limited as long as it has chemical strength and mechanical strength that can withstand the heat history, atmosphere, etc. in the manufacturing process of the functional layer such as a display unit forming various display devices. Examples thereof include glass, ceramic, silicon, metal foil, a rigid resin plate, and a composite material of glass and resin, but a glass plate or a silicon wafer is preferably used. The support may be subjected to a known cleaning method or surface treatment, but does not require patterning for locally performing cleaning or chemical surface treatment on the support. When glass is used as the support, for example, those generally used in the manufacture of organic EL display devices and touch panels can be used. However, in the display device manufactured by the present invention, the support base material in the display device is a flexible substrate made of a resin layer. In other words, the support serves as a pedestal when a functional layer such as a display unit is formed on the flexible substrate, and ensures the handling and dimensional stability of the flexible substrate in the process of manufacturing the functional layer. Even if it does, it will eventually be removed and will not constitute a display device.

The display device manufacturing method of the present invention includes a flexible substrate forming step of applying a resin solution on the support and forming a flexible substrate on the support, and a functional layer such as a display unit on the flexible substrate. And a functional layer forming step for forming the functional layer, and a support removing step for removing the support from the flexible substrate on which the functional layer is formed.
First, the flexible substrate forming process will be described.

In the flexible substrate forming step, it is preferable to perform heat treatment after applying the resin solution on the support. The heat treatment removes the solvent from the resin solution applied on the support and cures the resin to form a flexible substrate excellent in heat resistance, solvent resistance, etc., and the support for the flexible substrate There is an effect of imparting releasability from. This condition is defined as a heating time in a high temperature heating temperature range (hereinafter referred to as “high temperature holding time”) from a temperature 20 ° C. lower than the maximum heating temperature (maximum temperature reached) at the time of temperature increase in the heat treatment to the maximum temperature reached. It is preferable to make it within 15 minutes. If this high temperature holding time exceeds 15 minutes, the flexible substrate tends to become brittle. Moreover, when transparency is calculated | required by a flexible substrate, when high temperature holding time exceeds 15 minutes, it exists in the tendency for transparency of a flexible substrate to fall by coloring etc. In order to maintain the mechanical strength and transparency of the flexible substrate, the high temperature holding time is preferably short, but if it is too short, the effect of the heat treatment may not be sufficiently obtained. The optimum high temperature holding time varies depending on the heating method, the heat capacity of the support, the thickness of the flexible substrate, etc. For example, when the flexible substrate is polyimide, it is more preferably 0.5 minutes or more and 5 minutes or less.
In the present invention, in the flexible substrate forming step, local chemical surface treatment or heating is not performed on the portion of the support corresponding to the functional layer forming region or the peeling preventing portion. Here, the chemical surface treatment includes, for example, coating of low molecular compounds such as silane coupling agents, inorganic substances or high molecular compounds such as molybdenum, nickel, and silicon nitride, sputtering, vapor deposition, or laminating, roughening, etc. This is different from the physical surface treatment.

  The appropriate maximum heating temperature in the heat treatment in the flexible substrate forming step varies depending on the type of resin and solvent, the resin thickness, the material and thickness of the support, and the heating time, but when the flexible substrate is polyimide, it is 230 ° C or higher. It is preferable that When the maximum heating temperature is lower than 230 ° C., a solvent remains in the obtained flexible substrate, which may cause a problem in the manufacturing process. In order to facilitate the removal of the support in the subsequent support removal process, the maximum temperature is preferably higher than 280 ° C, more preferably higher than 330 ° C. The heat treatment may be a batch heat treatment in which the laminated body is installed in a heat treatment apparatus and the heat treatment is performed without moving. The heat treatment is performed by continuously transferring the laminate in a heat treatment apparatus set to a predetermined temperature. It may be a continuous heat treatment. Compared with the batch heat treatment, the continuous heat treatment is advantageous in improving productivity, making the heat treatment temperature uniform, and shortening the maximum heating temperature. In the case where the flexible substrate is polyimide, the upper limit of the heat treatment temperature varies depending on the chemical structure of the polyimide. However, if the heat treatment temperature is too high, the mechanical properties and optical properties of the polyimide deteriorate, and so on. is there.

  When the flexible substrate is polyimide, it is preferable to perform the heat treatment in an oxidizing atmosphere. By heat-treating in an oxidizing atmosphere, there is an effect that the flexible substrate can be easily peeled from the support. Here, the oxidizing atmosphere is a gas containing 5% or more of oxygen atoms, and specifically includes air, oxygen, oxygen-enriched air, a mixed gas of oxygen gas and inert gas, and the like. The heat treatment is preferable because the cost is low.

  In addition, the chemical structure of the resin constituting the flexible substrate is referred to as “peel strength between the flexible substrate and the support in the functional layer formation region” (hereinafter referred to as “peel strength of the functional layer formation region”), as described below. ) Is not limited as long as it is 200 N / m or less and 0.1 N / m or more, but polyimide is preferable from the viewpoint of heat resistance and dimensional stability.

ここで、Ａｒ₁は４価の有機基を表し、Ａｒ_２は２価の有機基を表す。
Ａｒ₁は、好ましくは、下記式（４）で表される４価の有機基のいずれかである。

また、Ａｒ₂は、好ましくは下記一般式（２）又は（３）で表される。ここで、Ｒ₁〜Ｒ₈は、それぞれ独立に水素原子、フッ素原子、炭素数１〜５までのアルキル基若しくはアルコキシ基、又はフッ素置換炭化水素基である。

フレキシブル基板と支持体の剥離性を良好とするためには、Ａｒ₁またはＡｒ_２においてフッ素原子またはフッ素置換炭化水素基を含む、いわゆる含フッ素ポリイミドを用いるのがより好ましい。例えば、一般式（２）にあってはＲ₁〜Ｒ₄のうち、また、一般式（３）にあってはＲ₁〜Ｒ₈のうち、それぞれ少なくとも一つはフッ素原子又はフッ素置換炭化水素基であるのが好ましい。 When the flexible substrate is polyimide, the structure of the polyimide includes a structural unit represented by the following general formula (1).

Here, Ar ₁ represents a tetravalent organic group, and Ar ₂ represents a divalent organic group.
Ar ₁ is preferably any one of tetravalent organic groups represented by the following formula (4).

Ar ₂ is preferably represented by the following general formula (2) or (3). Here, R _{1 to} R ₈ are each independently a hydrogen atom, a fluorine atom, an alkyl group or an alkoxy group having 1 to 5 carbon atoms, or a fluorine-substituted hydrocarbon group.

In order to improve the peelability between the flexible substrate and the support, it is more preferable to use a so-called fluorine-containing polyimide that contains a fluorine atom or a fluorine-substituted hydrocarbon group in Ar ₁ or Ar ₂ . For example, at least one of R _{1 to} R _{4 in} the general formula (2) and R _{1 to} R _{8 in} the general formula (3) is a fluorine atom or a fluorine-substituted hydrocarbon. A group is preferred.

Moreover, when the said flexible substrate is a polyimide, the said resin solution is a solution of a polyimide or a polyimide precursor. In the case of a polyimide precursor solution, the raw material diamine and acid anhydride are polymerized in the presence of a solvent to obtain a polyimide precursor solution, which is then applied onto a support and imidized by heat treatment. Can be manufactured. In the case of a polyimide solution, it can be produced by applying a polyimide solution on a support and drying it by heat treatment.
The molecular weight of the polyimide film can be mainly controlled by changing the molar ratio of the raw material diamine and acid anhydride, but the molar ratio is usually 1: 1. As needed, it can adjust to 0.985-1.015.

  The polyimide precursor solution can be prepared by first dissolving diamine in an organic solvent and then adding an acid dianhydride to the solution to produce a polyamic acid which is a polyimide precursor. Examples of the organic solvent include dimethylacetamide, dimethylformamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene and the like, and these can be used alone or in combination of two or more.

  When the obtained polyimide precursor solution is applied to a support, the viscosity of the solution is preferably in the range of 500 to 70000 cps by adjusting the concentration and molecular weight of the polyimide precursor. The application method is not particularly limited, and a known method such as a spin coater, a spray coater, a bar coater, or a method of extruding from a slit nozzle can be applied as long as a predetermined thickness accuracy can be obtained. In addition, the coating may be performed after appropriately performing a surface treatment on the surface of the substrate or the base material to be the coated surface of the resin solution.

  Further, the thickness of the flexible substrate is not limited, but the lower limit of the thickness is preferably 0.1 μm, and more preferably 0.3 μm. If the thickness is less than 0.3 μm, there is a possibility that pinholes will be generated in the flexible substrate due to foreign matters mixed during the manufacturing process, and if it is less than 0.1 μm, pinholes may be generated due to abnormal protrusions on the support surface. There is. The upper limit of the thickness is preferably 30 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. In order to sufficiently reduce the thickness of the display device, the thickness of the flexible substrate is preferably 30 μm or less, and in order to obtain good flexibility, the thickness is preferably 10 μm or less. Furthermore, by setting the thickness to 5 μm or less, it is possible to obtain a high transmittance in a wide wavelength region, which is necessary for display device applications.

  Here, the peel strength between the flexible substrate and the support in the functional layer formation region needs to be 200 N / m or less and 0.1 N / m or more.

  When the peel strength of the functional layer formation region is higher than 200 N / m, the barrier layer formed on the flexible substrate and further the functional layer such as TFT, color filter, circuit, ITO, etc. are damaged when peeled from the support. It becomes easy. When the barrier layer is damaged, even if there is no problem in the characteristics as an initial display device, the characteristics after long-term use deteriorate. If the support and flexible substrate are not bonded, the flexible substrate may float from the support due to differences in thermal expansion between the support and flexible substrate due to stress or temperature changes during the functional layer formation process. The functional layer forming region needs to be bonded to the support at a peel strength of 0.1 N / m or more. For this reason, in the present invention, the peel strength of the functional layer forming region is preferably low, and the peel strength of the functional layer forming region is 200 N / m or less and 0.1 N / m or more, preferably 50 N / m or less. 1 N / m or more, more preferably 10 N / m or less and 0.1 N / m or more.

  The transmittance of the flexible substrate in the wavelength region from 440 nm to 780 nm is preferably 80% or more. When the display device is an organic display EL device, the wavelength of light emitted from the light emitting layer of the organic EL is mainly 440 nm to 780 nm. Therefore, an average transmission in this wavelength region is used as a substrate used in the organic EL display device. The rate is preferably at least 80% or more. More preferably, the average transmittance at 440 nm to 780 nm is 85% or more.

The flexible substrate may be formed of a single resin layer or a plurality of resin layers. For example, a layer that is in contact with a support is a first resin layer, and a resin layer that is in contact with a surface opposite to the surface that is in contact with the support of the first resin layer is a second resin layer. The first resin layer and the second resin layer may have the same chemical structure or different chemical structures. When the flexible substrate is composed of a plurality of resin layers, it is preferable that at least a layer in contact with the support (first resin layer in the above example) has the above-described polyimide structure. More preferably, all of the plurality of resin layers have the polyimide structure described above. In the case where the flexible substrate is composed of a plurality of resin layers may be provided an inorganic layer such as SiO ₂ between these resin layers.

  When the flexible substrate is formed of a plurality of resin layers, at least a part of any of the resin layers may be formed so as to protrude from the peripheral portion of the other resin layer. As a result, a portion thinner than the functional layer forming region is provided in the peripheral portion of the flexible substrate, so that stress concentrated on the end surface of the flexible substrate can be dispersed during the manufacturing process, and the support and the flexible substrate are in the manufacturing process. Can be prevented from peeling off.

That is, for example, on the first resin layer obtained by applying a resin solution on a support and heat-treating, the resin solution is applied and heat-treated, and the film thickness is larger than that of the first resin layer. A second resin layer that is slightly smaller than the resin layer is laminated, and the protruding portion of the first resin layer that protrudes from the second resin layer forms a peeling prevention portion.
And if a peeling prevention part is cut-separated after forming a functional layer on the 2nd resin layer, the remaining 1st and 2nd resin layers will comprise a flexible substrate. Here, the protruding distance (width) of the first resin layer is preferably equal to or greater than the combined thickness of the first resin layer and the second resin layer, and the combined thickness of the first resin layer and the second resin layer. More preferably, it is 10 times or more. In this way, the peel strength between the flexible substrate in the functional layer formation region where the functional layer is formed and the support is 200 N / m or less and 0.1 N / m or more, and surrounds the functional layer formation region ( A laminated structure suitable for manufacturing a display device having a functional layer on a flexible substrate by forming a separation preventing portion that is less likely to be separated from the flexible substrate in the functional layer forming region at a position surrounding the flexible substrate; can do. The film thickness of the second resin layer may be the same as or smaller than the film thickness of the first resin layer. Moreover, it is preferable that the sum total of the layer thickness of the 1st resin layer and the 2nd resin layer laminated | stacked on the 1st resin layer is larger than the layer thickness of the 1st resin layer on a peeling prevention part. More preferably, the average value of the film thickness is 1 μm or more. Here, the average value of the film thickness is an average value of film thicknesses at arbitrary 10 points measured with a dial gauge or a micrometer.

Next, the functional layer forming process will be described.
The functional layer varies depending on the display device to be manufactured. For example, in the case of an organic EL device, a barrier layer, TFT, ITO, an organic EL light emitting layer, a color filter layer, and the like can be given. Moreover, in the case of a touch panel, electrode layers, such as a transparent conductive film and a metal mesh, are mentioned. A known method can be applied as a method of forming these functional layers.

  Further, a peeling prevention portion for preventing the flexible substrate from being peeled from the support is formed at a position surrounding the functional layer, and in the next support removing step, the flexible layer in the functional layer forming region is formed from the peeling prevention portion. After separating the substrate, the support is removed from the flexible substrate having the functional layer.

  Here, the shape and properties of the peeling preventing portion are not specified if it is difficult to peel from other portions (that is, the flexible substrate in the functional layer forming region) in the support removing step. For example, the peel strength between the flexible substrate corresponding to the peel prevention portion and the support (hereinafter referred to as “peel strength of the peel prevention portion”) is the same as the peel strength between the flexible substrate and the support in the functional layer formation region. It may be higher or lower than the peel strength of the functional layer forming region. For example, when the support is reused, it is necessary to completely remove the frame-like flexible substrate remaining on the support after the flexible substrate having the functional layer is removed. For this reason, it is preferable that the peeling strength of the said peeling prevention part is 500 N / m or less, and it is further more preferable that it is 200 N / m or less. If the peel strength of the peel preventing portion is higher than 500 N / m, it may be difficult to remove the peel preventing portion using, for example, a scraper or a clip. When it is 200 N / m or less, it is easy to remove the peeling preventing portion by vacuum suction or an adhesive. In addition, the preferable minimum of the peeling strength of this peeling prevention part is 0.1 N / m similarly to the minimum of the peeling strength of the flexible substrate of a functional layer formation area.

  Although the formation method of a peeling prevention part will not be limited if the function of the said peeling prevention part is satisfy | filled, For example, the formation method shown below is preferable.

  First, one of the preferable examples of the method for forming the peeling preventing portion is to make the flexible substrate a plurality of resin layers. That is, the surface of the first resin layer formed on the support is covered with the second resin layer so that the flexible substrate has at least the first resin layer and the second resin layer, and the outer periphery of the second resin layer The outer peripheral portion of the second resin layer serves as a locking member so as to form a peel preventing portion so that the first resin layer is prevented from peeling from the support. . Thereby, after forming the functional layer on the second resin layer and cutting and separating the flexible substrate in the functional layer forming region from the separation preventing portion, the first and second resin layers excluding the separation preventing portion are flexible substrates. It becomes. In this way, the peel strength between the flexible substrate and the support in the functional layer formation region in which the functional layer is formed is 200 N / m or less and 0.1 N / m or more, and at a position surrounding the functional layer formation region. By forming a peeling prevention portion that is less likely to peel from the flexible substrate in the functional layer formation region, a laminated structure suitable for manufacturing a display device including the functional layer on the flexible substrate can be obtained. . The film thickness of the second resin layer may be the same as or smaller than the film thickness of the first resin layer. In this case, the total thickness of the first resin layer and the second resin layer laminated on the first resin layer is preferably larger than the thickness of the first resin layer on the peeling preventing portion. More preferably, the average value of the film thickness is 1 μm or more.

  Another preferred example of the method for forming the peeling preventing portion is to make a part of the surface of the support in contact with the flexible substrate roughened. That is, the support has a partially roughened surface at a position in contact with the flexible substrate on the outer peripheral side of the functional layer forming region, and it is difficult to peel the peripheral portion of the flexible substrate laminated corresponding to the partially roughened surface. To do. Here, roughening also includes forming a recess on the surface of the support. The roughening method may be a known method, but is preferably sand blasting or etching. When roughening by sand blasting, the roughness Ra of the peel preventing portion is preferably 0.01 μm or more, more preferably 0.1 μm or more, and preferably 10 μm or less, more preferably 3 μm or less.

  Another preferred example of the method for forming the peeling preventing portion is to form a peeling preventing layer adhered to both the support and the flexible substrate. That is, the peeling prevention layer is interposed between the peripheral edge portion of the flexible substrate and the support on the outer peripheral side of the functional layer forming region. Here, examples of the peeling prevention layer include tape, double-sided tape, polyimide, epoxy resin, acrylic resin, and metal. From the viewpoint of heat resistance and handling properties, it is preferable to use polyimide. When using a tape or a double-sided tape, the tape film is preferably made of polyimide. The metal may be formed by applying silver paste, aluminum paste, copper paste or the like to the support surface and then heating and sintering. As long as the peeling prevention layer adheres to both the support and the flexible substrate, the peeling prevention layer may be formed before the formation of the flexible substrate, or the peeling prevention layer may be formed after the formation of the flexible substrate.

  In addition, another preferable example of the method for forming the peeling prevention portion is that, prior to the functional layer forming step, only the position corresponding to the functional layer forming region of the flexible substrate formed in the flexible substrate forming step is irradiated with UV laser light. The outer peripheral side of the functional layer forming region is not irradiated with UV laser light, and the flexible substrate at a position surrounding the functional layer forming region is compared with the peel strength between the flexible substrate in the functional layer forming region and the support. It is to form a peeling prevention portion having a high peeling strength with the support. A method for removing the support from the flexible substrate by irradiating the functional layer with UV laser light is known (Non-Patent Document 3, etc.). In this case, the UV laser light passes through the flexible substrate, and the functional layer is removed. May cause damage. In particular, when the transmittance of the flexible substrate in the wavelength region of the UV laser light is high, a problem of damaging the functional layer is likely to occur. Therefore, by irradiating the region where the functional layer is formed with UV laser light before forming the functional layer, the display device can be manufactured without damaging the functional layer.

  Another preferable example of the above-mentioned peeling preventing part is that the peeling preventing part is formed of a part of the functional layer constituting material constituting the functional layer, and a part of the surface of the flexible substrate formed on the support, The surface of the support that corresponds to the outer periphery of the substrate is covered with a film made of a functional layer constituent material, and the film made of the functional layer constituent material constitutes a locking member, and the flexible substrate peels from the support. To prevent. Preferably, the functional layer constituent material is continuously formed from the surface of the flexible substrate to the support, and the functional layer constituent material is bonded to the support, and a part of the functional layer is configured. The material is projected on the outer peripheral side of the functional layer forming region. That is, the functional layer constituting material constituting such a locking member is made of the same material as at least one material forming the functional layer, and the functional film formed on the functional layer forming region in the flexible substrate In the case of being connected, the functional film forms at least a part of the functional layer after the functional layer is formed and cut and separated from the peeling preventing portion.

  Here, the functional layer constituting material is a material constituting the final display device after the completion of the manufacturing process. For example, the inorganic layer includes silicon oxide, aluminum oxide, silicon carbide, silicon oxide carbide, nitrogen carbide silicon. And a barrier layer made of an inorganic oxide film such as silicon nitride or silicon nitride oxide, or a transparent conductive film such as ITO (tin-doped indium oxide), SnO, ZnO, or IZO. Further, a color filter material such as a color resist or a black resist may be used as the functional layer constituent material. For example, in the case of a touch panel, a transparent conductive film such as ITO, SnO, ZnO, or IZO or a metal mesh is used as the inorganic layer. “Consecutively formed” means that the functional layer constituent material is formed to be connected from the surface of the flexible substrate to the surface of the support via the end surface of the flexible substrate. It is not essential that the functional layer constituent material is continuously formed on the entire periphery of the flexible substrate. However, when an inorganic layer is used as the functional layer constituent material, moisture or a solvent is used in the flexible substrate during the manufacturing process. It is also a preferred form to continuously form the functional layer constituting material on the entire periphery of the flexible substrate because it has a function of preventing contact with the flexible substrate.

  Next, the support removing process will be described. In this step, the support is removed from the flexible substrate after separating the peeling prevention portion and the flexible substrate in the functional layer forming region. That is, after the functional layer is formed on the flexible substrate, the functional layer forming region of the flexible substrate provided with the functional layer is cut and separated from the separation preventing portion, and the support is removed from the flexible substrate, thereby A display device having a functional layer can be obtained.

  Separation of the flexible substrate in the functional layer formation region and the peeling prevention portion may be performed so that when the flexible substrate in the functional layer formation region is peeled from the support, the separation prevention portion is not subjected to stress. You may isolate | separate and you may isolate | separate the whole support body. The separation means is not particularly limited, and for example, a blade such as a knife or a roller blade may be used. Here, for example, after forming a barrier layer that constitutes a part of the functional layer, when separating the functional layer formation region and the peeling prevention portion using a blade, the barrier layer generated from the cut surface when the flexible substrate is cut In order to prevent cracks, at least one of the flexible substrate and the blade may be heated. The appropriate heating temperature varies depending on the cutting method, the type of the flexible substrate and the barrier layer, etc., but it is preferable to heat the glass substrate at a temperature higher than the glass transition temperature of the flexible substrate. Further, etching with an alkaline aqueous solution or plasma, or laser may be used as the separation means.

  The process for removing the support from the flexible substrate is not particularly limited, but for example, using a peeling apparatus having a base for fixing the functional layer forming region as shown in FIG. In addition to the flexible substrate in the layer formation region, the functional layer formation region may be separated from the substrate after the support is removed. At that time, in order to prevent the flexible substrate from being stretched or the functional layer from being damaged by the stress applied to remove the support, the entire surface of the functional layer forming region may be fixed to the substrate by a method such as suction or adhesion. Good. When the functional layer forming region is fixed to the substrate by suction, a substrate having pores connected from the inside of the substrate to the surface of the substrate is used, the inside of the substrate is decompressed, and the functional layer forming region is fixed to the surface of the substrate using vacuum. In this state, after the support is removed from the flexible substrate, the pressure inside the base is released to separate the functional layer forming region from the base. Here, the substrate may be a resin or a metal such as stainless steel. Further, stress may be applied to the end portion of the substrate-functional layer forming region laminated portion and separated from the end portion, or stress may be applied to the entire surface of the substrate-functional layer forming region laminated portion to separate the entire surface almost simultaneously. You may do it. The surface shape of the substrate may be a curved surface. In addition to the method using such a peeling apparatus, a known method can be adopted. For example, an organic solvent or an alkaline aqueous solution may be used, or peeling by UV laser light or heating may be applied.

  After separating the flexible substrate in the functional layer formation region and the peeling prevention portion, the separation prevention portion is first removed from the support, leaving only the flexible substrate in the functional layer formation region on the support, and then the functional layer formation region The support may be removed from the flexible substrate. When removing the support from the flexible substrate that constitutes the functional layer formation region, it is necessary to fix the functional layer formation region to the peeling device by methods such as adhesion and suction, and to apply stress necessary for peeling to the functional layer formation region However, according to the above method for removing the peeling preventing portion from the support first, it is not necessary to perform precise alignment in order to fix the functional layer forming region to the peeling device. Therefore, the stress can be efficiently transmitted to the functional layer formation region.

  Further, after separating the flexible substrate in the functional layer formation region and the peeling prevention portion, the separation prevention portion is first removed from the support, leaving only the flexible substrate in the functional layer formation region on the support, and then the functional layer. According to the method of removing the support from the flexible substrate in the formation region, when removing the support from the flexible substrate constituting the functional layer formation region, a scraper is inserted from the end surface of the flexible substrate between the flexible substrate and the support It becomes easy to do. By using a scraper, stress applied to the functional layer at the time of peeling can be reduced, and damage to the functional layer can be prevented.

  Hereinafter, the contents of the present invention will be described more specifically based on examples and the like, but the present invention is not limited to the scope of these examples. Various evaluations were performed as follows.

"Peel strength"
Using a strograph manufactured by Toyo Seiki Seisakusho Co., Ltd., a sample obtained by cutting polyimide into strips was evaluated by measuring the peel strength by a 180-degree peel test method.

"Thermal expansion coefficient"
Tensile test of polyimide film with a size of 3 mm x 15 mm in a temperature range from 30 ° C to 260 ° C at a constant heating rate (20 ° C / min) while applying a 5.0 g load with a thermomechanical analysis (TMA) device The coefficient of thermal expansion (× 10 ⁻⁶ / K) was measured from the amount of elongation of the polyimide film with respect to temperature.

"Transmissivity"
The average value of the light transmittance from 440 nm to 780 nm was determined for a polyimide film (50 mm × 50 mm) with a U4000 spectrophotometer.

"Peelability of functional layer forming part"
From the laminate of polyimide and support, the polyimide in the functional layer forming region is manually peeled off. When the peel strength is strong and cannot be peeled by hand, x is given. When it was easy, it was evaluated as “good”, and when it was extremely easy to peel, it was evaluated as “good”.

"Barrier crack"
An 80 nm silicon nitride film was formed by CVD, and the occurrence of cracks was observed with Microskov KH-7700 manufactured by Yamato Kagaku. In a 10 mm square field of view, when the number of cracks was 20 or more, the evaluation result was x, when it was 10 or more and less than 20, the evaluation result was ◯, and when it was less than 10 or there was no crack, ◎.

"Water immersion"
After immersing the laminated body of a polyimide and a support in 20 degreeC water for 1 hour, it took out from water and confirmed the presence or absence of peeling of a polyimide and a support. When there was no peeling part, evaluation result was set as (circle), and when there existed whole surface peeling or peeling part, the evaluation result was set as x.

The raw materials, aromatic diamino compounds, aromatic tetracarboxylic acid anhydride compounds and solvents used in the synthesis of the polyamic acid (polyimide precursor) solution handled in the following synthesis examples, examples and comparative examples are shown below.
[Aromatic diamino compounds]
・ 1,4-Phenylenediamine (PPD)
・ 4,4'-diaminodiphenyl ether (DAPE)
・ 2,2'-dimethyl-4,4'-diaminobiphenyl (mTB)
1,3-bis (4-aminophenoxy) benzene (TPER)
2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP)
[Anhydrous compound of aromatic tetracarboxylic acid]
・ Pyromellitic anhydride (PMDA)
・ 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride (BPDA)
・ 4,4 '-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA)
〔solvent〕
・ N, N-dimethylacetamide (DMAc)

(Synthesis Example 1)
Under a nitrogen stream, 8.0 g of PPD was added to the solvent DMAcg while stirring in a 300 ml separable flask, and dissolved at 50 ° C. Then 22.0 g of BPDA was added. Thereafter, the solution was stirred at room temperature for 3 hours to carry out a polymerization reaction to obtain a viscous polyamic acid solution a. The brown acid a is obtained by heating the polyamic acid a.

(Synthesis Example 2)
Under a nitrogen stream, 18.9 g of TFMB was dissolved in the solvent DMAc with stirring in a 500 ml separable flask. Then 26.1 g of 6FDA was added. Thereafter, the solution was stirred at room temperature for 5 hours to carry out a polymerization reaction to obtain a viscous polyamic acid solution b. In addition, the transparent polyimide b is obtained by heating this polyamic acid b.

(Synthesis Example 3)
Under a nitrogen stream, 26.3 g of TFMB was dissolved in the solvent DMAc with stirring in a 500 ml separable flask. Next, 16.1 g of PMDA and 1.8 g of 6FDA were added. Thereafter, the solution was stirred at room temperature for 5 hours to carry out a polymerization reaction to obtain a viscous polyamic acid solution c. In addition, the transparent polyimide c is obtained by heating this polyamic acid c.

(Synthesis Example 4)
Under a nitrogen stream, 29.1 g of BAPP was dissolved in the solvent DMAc while stirring in a 500 ml separable flask. Then 3.23 g BPDA and 13.6 PMDA were added. Thereafter, the solution was stirred at room temperature for 3 hours to carry out a polymerization reaction to obtain a viscous polyamic acid solution d. The brown acid polyimide d is obtained by heating the polyamic acid d.

(Synthesis Example 5)
Under a nitrogen stream, 66.5 g of MABA and 34.5 g of DAPE were added and dissolved in the solvent DMAcg with stirring in a 2 L separable flask. Next, 92.6 g of PMDA was added. Thereafter, the solution was stirred for 1.5 hours at room temperature to carry out a polymerization reaction to obtain a viscous polyamic acid solution e. The brown acid polyimide e is obtained by heating the polyamic acid e.

(Synthesis Example 6)
Under a nitrogen stream, 20.3 g of mTB and 3.1 g of TPE-R were dissolved in the solvent DMAcg with stirring in a 500 ml separable flask. PMDA 18.4 and 6.2 g BPDA were then added. Thereafter, the solution was stirred at room temperature for 4 hours to carry out a polymerization reaction to obtain a viscous polyamic acid solution f. In addition, the brown acid polyimide f is obtained by heating this polyamic acid f.

[ Reference Example 1]
A ferrite stainless steel foil having a thickness of 30 μm was used as a support, and a 10 mm portion from the ends of the four sides was roughened by sandblasting. Subsequently, in order to form a flexible substrate, the polyamic acid solution a was applied using an applicator so that the thickness after heat treatment was 8 μm, leaving a portion of 5 mm inward from the four sides on the stainless steel foil. Next, after heating at 100 ° C. for 5 minutes using a hot air oven, the temperature was raised to 370 ° C. at 4 ° C./minute, then heated to 500 ° C. at 20 ° C./minute and held for 40 minutes. As shown, a laminate of stainless steel foil and polyimide a was obtained. Here, in the laminated portion of the stainless steel foil and the polyimide a, the roughened portion corresponds to the peeling prevention portion, and the non-roughened portion corresponds to the functional layer forming region. As a result of the water immersion test of this laminate, no peeling was observed. After cutting and removing 12 mm from the end of the four sides of the laminate, the remaining polyimide a (functional layer forming region) was very easily peelable from the support. The peel strength of the central portion (remaining polyimide a) of this laminate was 8 N / m, and the peel strength of the roughened portion (peel preventing portion) was 80 N / m. In addition, the evaluation results of the thermal expansion coefficient are shown in Table 1.

[Example 2]
Using a non-alkali glass having a thickness of 0.5 mm and 150 mm × 150 mm as a support, the polyamic acid solution b is 140 mm × 140 mm in size so that the film thickness after heat treatment is 3 μm by an applicator thereon. Then, it was heated and dried at 130 ° C. and 150 ° C. for 2 minutes using a hot air oven to remove the solvent in the resin solution. Next, the polyamic acid solution b is applied in a size of 130 mm × 130 mm so that the thickness after heat treatment is 22 μm, and heated at 130 ° C., 150 ° C., 200 ° C., 250 ° C. for a total of 30 minutes using a hot air oven. Then, it heated at 360 degreeC for 1 minute, and obtained the laminated body of the glass which is a support body and the polyimide b which is a flexible substrate as shown in FIG. The polyimide b formed on the support 1 has a 25 μm thick portion overlapped on two layers corresponding to a functional layer forming region (having a size of 130 mm × 130 mm), and a 3 μm thick protruding portion around it. Corresponds to an anti-peeling portion (having an overhang width of about 5 mm). As a result of the water immersion test of this laminate, no peeling was observed. After cutting the four sides of polyimide b at 8mm from the end, polyimide b can be peeled off from the support body very easily at the center (the inner part of the cut) and the peripheral part (the outer part of the cut). Met. In addition, the evaluation results of peel strength, thermal expansion coefficient, and transmittance are shown in Table 1.

[Example 3]
Using a non-alkali glass having a thickness of 0.5 mm and 150 mm × 150 mm as a support, the polyamic acid solution c is 130 mm × 130 mm in size so that the film thickness after heat treatment is 22 μm by an applicator thereon. Then, using a hot air oven, it was dried by heating at 120 ° C. for 5 minutes to remove the solvent in the resin solution. Next, the polyamic acid solution d is applied in a size of 140 mm × 140 mm so as to cover the polyamic acid c layer so that the thickness after the heat treatment is 3 μm, and using a hot air oven, 130 ° C., 150 ° C., 200 ° C. After heating at 250 ° C. for 30 minutes in total, it was heated at 360 ° C. for 1 minute to obtain a laminate of glass as a support, polyimide c, and polyimide d as shown in FIG. In this laminate, a flexible substrate is formed from polyimide c and polyimide d, and a portion having a thickness of 25 μm composed of a thickness of 22 μm of polyimide c and a thickness of 3 μm of polyimide d corresponds to a functional layer forming region (size of 130 mm × 130 mm). And a 3 μm thick protruding portion made of polyimide d around it corresponds to the peeling preventing portion (having a width protruding width of about 5 mm). As a result of the water immersion test of this laminate, no peeling was observed. After cutting the four sides of polyimide consisting of polyimide c and polyimide d at a position 8 mm from the end, the central part of polyimide (the inner part of the cut) can be peeled off very easily, and the peripheral part (the cut line) Peeling of the outer part) was also possible. In addition, the evaluation results of peel strength and thermal expansion coefficient are shown in Table 1.

[Example 4]
Using a non-alkali glass with a thickness of 0.5 mm and 150 mm × 150 mm as a support, and using an applicator thereon, the polyamic acid solution e is 130 mm × 130 mm in size so that the film thickness after heat treatment is 25 μm. Then, it was applied and heated at 90 ° C. for 10 minutes using a hot air oven. Next, on the two parallel sides of the applied polyamic acid solution e, the polyamic acid solution d is applied so as to cover both the polyamic acid solution e and the glass in a width of 6 mm so that the thickness after heat treatment is 25 μm. Using an oven, heating was performed at 90 ° C. to 360 ° C. at 20 ° C./min to obtain a laminate of polyimide e forming a flexible substrate and glass as a support as shown in FIG. It was visually confirmed that the polyimide d was continuously formed from the surface of the polyimide e to the glass surface, and the polyimide d and the glass were in contact with each other by about 3 mm. Here, the portion where polyimide e is in contact with glass and not in contact with polyimide d corresponds to the functional layer forming region, and the portion where polyimide d is in contact with glass corresponds to the peeling preventing portion. As a result of the water immersion test of this laminate, no peeling was observed. After making a cut at a position 1 mm inside from the two sides of polyimide d in contact with polyimide d, the central portion (the inner portion of the cut) was easily peelable, and polyimide d was peelable from the glass. . In addition, the peel strength, thermal expansion coefficient, and barrier crack evaluation results are shown in Table 1.

[ Reference Example 5]
Using a non-alkali glass having a thickness of 0.5 mm and 150 mm × 150 mm as a support, and using an applicator thereon, the polyamic acid solution d is applied to the four sides of the glass so that the film thickness after heat treatment is 2 μm. The film was applied at a width of 10 mm, and heated at 130 ° C. for 20 seconds using a hot air oven. Next, the polyamic acid solution f is applied in a size of 140 mm × 140 mm and heated from 90 ° C. to 360 ° C. at 20 ° C./min using a hot air oven to form a flexible substrate as shown in FIG. A laminate of polyimide f to be made and glass as a support was obtained. At this time, the polyimide d was in contact with the polyimide f by about 5 mm. Here, the portion where the polyimide f is in contact with the glass corresponds to the functional layer forming region, and the polyimide d corresponds to the peeling preventing portion. As a result of the water immersion test of this laminate, no peeling was observed. After cutting the four sides of the polyimide f at 8 mm from the end, the central portion of the polyimide (corresponding to the inner portion of the cut and the functional layer forming portion) can be peeled off very easily, and the peripheral portion (above The peeling of the outer portion of the cut was also possible. In addition, the peel strength, thermal expansion coefficient, and barrier crack evaluation results are shown in Table 1.

[Example 6]
Using a non-alkali glass with a thickness of 0.5 mm and 150 mm × 150 mm as a support, the polyamic acid solution c is 140 mm × 140 mm in size so that the film thickness after heat treatment is 10 μm using an applicator. Then, using a hot air oven, it was heated and dried at 130 ° C. to remove the solvent in the resin solution. Next, after heating at 150 ° C., 200 ° C., and 250 ° C. for a total of 30 minutes, heating was performed at 360 ° C. for 1 minute to obtain a laminate of glass as a support and polyimide c as a flexible substrate. Next, as shown in FIG. 6, a silicon nitride film having a thickness of 80 nm was formed on the entire surface of the laminate on the polyimide c side by CVD. It was confirmed by SEM observation that the barrier layer made of a silicon nitride film was a functional layer and was continuously formed from the surface of polyimide c to the glass surface. Here, the portion where the silicon nitride film is formed on the polyimide c corresponds to the functional layer forming region, and the portion where the silicon nitride film is formed on the glass surface corresponds to the peeling preventing portion. As a result of the water immersion test of this laminate, no peeling was observed. After cutting the four sides of the polyimide c at a location 3 mm from the end, the central portion (the inner portion of the cut) and the peripheral portion (the outer portion of the cut) of the polyimide could be peeled off very easily. In addition, Table 1 shows the evaluation results of peel strength, thermal expansion coefficient, transmittance, and barrier crack.

[Example 7]
Using a non-alkali glass with a thickness of 0.5 mm and 150 mm × 150 mm as a support, the polyamic acid solution c is 140 mm × 140 mm in size so that the film thickness after heat treatment is 25 μm by an applicator thereon. Then, using a hot air oven, it was dried by heating at 130 ° C. for 5 minutes to remove the solvent in the resin solution. Next, after heating at 150 ° C., 200 ° C., and 250 ° C. for a total of 30 minutes, heating was performed at 360 ° C. for 1 minute to obtain a laminate of glass as a support and polyimide c as a flexible substrate. Next, after cutting the four sides of polyimide c to the glass surface using a razor blade at a position 5 mm from the end of the polyimide, all four sides of the polyimide were peeled from the glass. The peeling of the peripheral part was extremely easy. Next, as shown in FIG. 7, a glass paste is applied in a size of 140 × 140 mm so that the thickness after film formation is 5 μm so as to cover the polyimide c on the laminate, and 10 ° C. at 10 ° C. For 2 minutes at 150 ° C., 2 minutes at 380 ° C., and 10 minutes at 400 ° C. It was confirmed by SEM observation that the barrier layer formed from the glass paste was continuously formed from the surface of polyimide c to the glass surface. Here, the portion where the glass paste is formed on the polyimide c corresponds to the functional layer forming region, and the portion where the glass paste is formed on the glass surface corresponds to the peeling prevention portion. As a result of the water immersion test of this laminate, no peeling was observed. After cutting the four sides of the polyimide c at a location 3 mm from the end, the central portion (the inner portion of the cut) and the peripheral portion (the outer portion of the cut) of the polyimide could be peeled off very easily. In addition, Table 1 shows the evaluation results of peel strength, thermal expansion coefficient, transmittance, and barrier crack.

[Example 8]
The heat treatment after the polyamic acid solution b was applied in two layers on the glass, except that it was heated at 130 ° C, 150 ° C, 200 ° C, 250 ° C for a total of 30 minutes and then heated at 360 ° C for 6 minutes. In the same manner as in Example 2, a laminate of glass and polyimide b was obtained. As a result of the water immersion test of this laminate, no peeling was observed. After cutting the four sides of the polyimide b at 8 mm from the end, the polyimide b could be peeled off very easily both in the center (inner part of the cut) and in the peripheral part (outer part of the cut). . In addition, the evaluation results of peel strength, thermal expansion coefficient, and transmittance are shown in Table 1.

[Example 9]
As a heat treatment after applying the polyamic acid solution c on the glass, it is heated and dried at 130 ° C. for 5 minutes to remove the solvent in the resin solution, and then heated at 150 ° C., 200 ° C., 250 ° C. for a total of 30 minutes. A laminated body of glass and polyimide c was prepared in the same manner as in Example 6 except that it was heated at 320 ° C. for 1 minute, and a silicon nitride film was further formed in the same manner as in Example 6. It was confirmed by SEM observation that the barrier layer made of a silicon nitride film was continuously formed from the surface of polyimide c to the glass surface. As a result of the water immersion test of this laminate, no peeling was observed. After cutting the 4 sides of the polyimide at a location 3 mm from the end, the central portion (the inner portion of the cut) and the peripheral portion (the outer portion of the cut) of the polyimide were extremely easily peelable. In addition, the peel strength, thermal expansion coefficient, and barrier crack evaluation results are shown in Table 1.

[Example 10]
A laminated body of glass and polyimide c was prepared in the same manner as in Example 6 except that the polyamic acid solution c was applied so that the film thickness after the heat treatment was 4 μm. A membrane was formed. It was confirmed by SEM observation that the barrier layer made of a silicon nitride film was continuously formed from the surface of polyimide c to the glass surface. As a result of the water immersion test of this laminate, no peeling was observed. After cutting the 4 sides of the polyimide at a location 3 mm from the end, the central portion (the inner portion of the cut) and the peripheral portion (the outer portion of the cut) of the polyimide were extremely easily peelable. In addition, the evaluation results of peel strength and thermal expansion coefficient are shown in Table 1.

[Comparative Example 1]
A laminate of stainless steel foil and polyimide a was obtained in the same manner as in Example 1 except that roughening was not performed by sandblasting. As a result of the water immersion test of this laminate, polyimide a was peeled from the stainless steel foil. In addition, the evaluation results of peel strength and thermal expansion coefficient are shown in Table 1.

[Comparative Example 2]
A laminate of stainless steel foil and polyimide a was obtained in the same manner as in Example 1 except that the heat treatment was performed in an inert oven. The oxygen concentration in the oven was about 1%. As a result of the water immersion test of this laminate, no peeling was observed. After cutting and removing 12 mm from the end of the four sides of the laminate, the remaining polyimide a could not be peeled manually. The peel strength of the central portion (remaining polyimide a) of this laminate was 1800 N / m, and the peel strength of the peel preventing portion was too high to be measured. In addition, the evaluation results of the thermal expansion coefficient are shown in Table 1.

[Comparative Example 3]
In the same manner as in Example 3, after obtaining a laminate of glass and polyimide c and polyimide d, the polyimide c and d were peeled off without making a cut in the polyimide. As a result, peeling was possible. Wrinkles occurred in polyimides c and d during peeling. In addition, the evaluation results of peel strength and thermal expansion coefficient are shown in Table 1.

[Comparative Example 4]
In the same manner as in Example 7, after obtaining a laminate of polyimide c and glass with the four sides peeled off, an 80 nm silicon nitride film was formed on the entire surface of the laminate on the polyimide c side by CVD. As a result, as shown in FIG. 8, it was confirmed by SEM observation that a barrier layer made of a silicon nitride film was not continuously formed, and no silicon nitride film was formed on the side surface of polyimide c. . That is, there is no peeling prevention part. As a result of the water immersion test of this laminate, polyimide c was peeled from the glass. In addition, Table 1 shows the evaluation results of peel strength, thermal expansion coefficient, transmittance, and barrier crack.

[Comparative Example 5]
As a result of observing the silicon nitride film after peeling the polyimide from the glass in the same manner as in Example 6 except that no cuts were made on the four sides of the polyimide, the position corresponding to the central portion of the polyimide in Example 6 was observed. Although there were no cracks, many cracks were confirmed in the range of about 20 mm from the peripheral part. In addition, Table 1 shows the evaluation results of peel strength, thermal expansion coefficient, transmittance, and barrier crack.

[Comparative Example 6]
A laminated body of glass and polyimide d was prepared in the same manner as in Example 6 except that the polyamic acid solution d was applied instead of the polyamic acid solution c, and a silicon nitride film was formed in the same manner as in Example 6. did. It was confirmed by SEM observation that the barrier layer made of a silicon nitride film was continuously formed from the surface of polyimide d to the glass surface. As a result of the water immersion test of this laminate, no peeling was observed. Although the side of the polyimide was cut at 3 mm from the end, the center of the laminate (the inner part of the cut) and the peripheral part (the outer part of the cut) could be peeled manually. It was observed that the polyimide stretches and wrinkles are generated at the time of peeling. In addition, the peel strength, thermal expansion coefficient, and barrier crack evaluation results are shown in Table 1.

[Comparative Example 7]
The polyamic acid solution c is applied onto glass and dried by heating at 130 ° C. for 5 minutes, the solvent in the resin solution is removed, and then heated at 150 ° C., 200 ° C., 250 ° C. for a total of 30 minutes, and then 1 at 270 ° C. A laminated body of glass and polyimide c was prepared in the same manner as in Example 6 except that heating was performed for a minute, and a silicon nitride film was formed in the same manner as in Example 6. It was confirmed by SEM observation that the barrier layer made of a silicon nitride film was continuously formed from the surface of polyimide c to the glass surface. As a result of the water immersion test of this laminate, no peeling was observed. After cutting the four sides of the laminate at a location 3 mm from the end, the central portion (the inner portion of the cut) and the peripheral portion (the outer portion of the cut) of the laminate could not be peeled manually ( (Peel strength is over 200 N / m). In addition, the evaluation results of peel strength, thermal expansion coefficient, and transmittance are shown in Table 1.

[Comparative Example 8]
Using the polyamic acid solution a, it was separately coated on glass, and a polyimide a film was obtained under the same curing conditions as in Example 1. After applying adhesive to 5 mm from the end of the four sides of the obtained polyimide a film, the adhesive-coated surface is pressure-bonded to a 30 μm-thick ferrite-based stainless steel and laminated with stainless steel foil and polyimide a. Got the body. As a result of the water immersion test of this laminate, water entered the interface between stainless steel and polyimide, and the polyimide floated from the stainless steel. In addition, the evaluation results of peel strength and thermal expansion coefficient are shown in Table 1.

[Example 11]
In the same manner as in Example 6, a laminated body of glass and polyimide c was obtained, and a silicon nitride film having a thickness of 80 nm was formed by CVD on the entire surface of the laminated body on the polyimide c side. This silicon nitride film functioned as a gas barrier layer for preventing moisture permeation, and a color filter layer was formed on the upper surface. And, for the four sides of the polyimide c, after making a cut at a location 3 mm from the end, after peeling the central portion of the polyimide c corresponding to the portion where the color filter layer was formed (the inner portion of the cut), The gas barrier layer and the color filter layer could be peeled off very easily without generating cracks, and a color filter substrate using polyimide c as a flexible substrate could be obtained.

Claims (12)

From a flexible substrate forming step of forming a flexible substrate on a support by applying a resin solution to the support, a functional layer forming step of forming a functional layer on the flexible substrate, and a flexible substrate on which the functional layer is formed And a support removing step for removing the support, and a method of manufacturing a display device,
The flexible substrate is formed of two or more resin layers , and the peel strength between the flexible substrate and the support in the functional layer forming region where the functional layer is formed is 200 N / m or less and 0.1 N / m or more. , in a position to surround the functional layer forming region, the any one or more of the resin layer for forming the flexible substrate is bonded to the support projects on the outer peripheral side of the functional layer forming region thereof, the flexible substrate support Forming the peeling prevention part for preventing the peeling from the film and making the thickness of the peeling prevention part thinner than the thickness of the flexible substrate in the functional layer formation area, the functional layer formation area or the peeling prevention part The step of removing the support without performing local chemical surface treatment on the portion of the support corresponding to the above, or local heating of the portion of the support corresponding to the peeling preventing portion Oite, after separating the flexible substrate and the separation preventing sections of the functional layer forming region, the manufacturing method of a display device, and removing the support from a flexible substrate having a functional layer. From a flexible substrate forming step of forming a flexible substrate on a support by applying a resin solution to the support, a functional layer forming step of forming a functional layer on the flexible substrate, and a flexible substrate on which the functional layer is formed And a support removing step for removing the support, and a method of manufacturing a display device,
The peel strength between the flexible substrate and the support in the functional layer formation region where the functional layer is formed is 200 N / m or less and 0.1 N / m or more, and the position surrounding the functional layer formation region is A part of the constituent material projects to the outer peripheral side of the functional layer forming region and adheres to the support, thereby forming a peeling prevention portion that prevents the flexible substrate from being peeled from the support. The support without performing local chemical surface treatment on the part of the support corresponding to the formation region or the peeling prevention part or local heating on the part of the support corresponding to the peeling prevention part A method for manufacturing a display device, comprising: removing a support from a flexible substrate provided with a functional layer after separating the flexible substrate in the functional layer formation region and the peeling prevention portion in the removing step. In the support-removing step, after removing the separation preventing sections from the support, a method of manufacturing a display device according to claim 1 or 2, characterized in that to remove the support from a flexible substrate having a functional layer. Method of manufacturing a display device according to claim 1 or 2 peel strength between the flexible substrate and the support is less than 500 N / m in the separation preventing sections. The method for manufacturing a display device according to claim 2 , wherein a part of the constituent material of the functional layer forming the peeling preventing portion is an inorganic layer formed of an inorganic material. Prior to the functional layer forming step, by irradiating only the position corresponding to the functional layer forming region of the flexible substrate formed in the flexible substrate forming step with UV laser light, the flexible substrate and the support in the functional layer forming region, peel strength as compared with, the display device according to claim 1 or 2, characterized in that to form the separation preventing sections to increase the peel strength between the position of the flexible substrate surrounding the functional layer forming region and the support Production method. Method of manufacturing a display device according to claim 1 or 2 the thickness of the flexible substrate is 0.1μm or more 30μm or less. Method of manufacturing a display device according to claim 1 or 2, wherein the flexible substrate is made of polyimide. The method for manufacturing a display device according to claim 8 , wherein, in the flexible substrate forming step, a flexible substrate is obtained by applying a resin solution of polyimide or a polyimide precursor to a support and then heat-treating in an oxidizing atmosphere. The method for manufacturing a display device according to claim 8 , wherein, in the flexible substrate forming step, after applying a resin solution of polyimide or a polyimide precursor to a support, heat treatment is performed at 280 ° C. or higher to obtain a flexible substrate. The method for manufacturing a display device according to claim 8 , wherein in the flexible substrate forming step, a flexible substrate is obtained by continuous heat treatment after applying a resin solution of polyimide or a polyimide precursor to a support. Method of manufacturing a display device according to claim 1 or 2 display unit is a touch panel.

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