KR102367682B1 - Display device and method for manufacturing the same, and polyimide film for display device - Google Patents

Abstract

(Project) To provide a polyimide film having a low coefficient of thermal expansion, heat resistance, transparency, and strength of form, and suitable for use as a supporting substrate for forming an organic EL device, a display device using the same, and a method for manufacturing the same.
(Solution) A polyimide precursor or a polyimide solution is cast on an inorganic substrate and heat-treated to form a polyimide film, a display element is further mounted on the polyimide film, and the polyimide is removed from the inorganic substrate A display device obtained by peeling a film together with a display element, wherein the polyimide film has a glass transition temperature of 300° C. or higher, a 5% thermal decomposition temperature of 530° C. or higher, and a total light transmittance of 80% at a film thickness of 30 μm or less. As described above, a display device, a method for manufacturing the same, and a polyimide film for a display device, wherein the coefficient of thermal expansion is 40 ppm/K or less, and the tear propagation resistance is 1.3 mN/㎛ or more.

Description

Display device, manufacturing method thereof, and polyimide film for display device

The present invention relates to a polyimide film used as a supporting substrate for forming a display device, a display device using the same, and a method for manufacturing the same.

Organic EL devices used for various display applications, including large displays such as TVs and small displays such as mobile phones, PCs, and smartphones, generally form a thin film transistor (hereinafter, TFT) on a glass substrate as a supporting substrate, An electrode, a light emitting layer, and an electrode are further formed one by one thereon, and these are hermetically sealed with a glass substrate, a multilayer thin film, etc., and produced. The structure of the organic EL device includes a bottom emission structure for extracting light from the glass substrate side as a supporting substrate, and a top emission structure for extracting light from the side opposite to the glass substrate as a supporting substrate, They are used separately according to their intended use. Moreover, since a structure through which external light passes as it is can also be taken structurally, a transparent structure in which electronic elements, such as a TFT, can be seen from the outside has also been proposed. All of these can be realized by selecting a transparent electrode or substrate material.

Furthermore, by replacing the supporting base material of such an organic EL device with a resin from a conventional glass substrate, it can be made ultra-thin, lightweight, and flexible, and the use of the organic EL device can be further expanded. However, since resin is generally inferior to glass in dimensional stability, transparency, heat resistance, moisture resistance, the intensity|strength of a film, etc., various examinations have been made.

For example, Patent Document 1 relates to an invention related to a polyimide useful as a plastic substrate for a flexible display and a precursor thereof. A laminate comprising a film and an inorganic substrate is disclosed, and reports of high light transmittance and low outgassing. However, since the coefficient of thermal expansion (CTE) of the polyimide obtained here exceeds 40 ppm/K, the difference from the coefficient of thermal expansion of the glass substrate is large, causing warpage in the organic EL substrate, and peeling or cracking after device formation. It becomes difficult to obtain the organic EL device excellent in shape stability.

In addition, Patent Document 2 relates to an invention related to a polyimide precursor resin composition for forming a flexible device substrate such as a display device and a light receiving device manufactured by peeling from a carrier substrate, and has a glass transition temperature of 300° C. or higher and a glass transition temperature of 20 ppm/K or less. It is described showing the coefficient of thermal expansion. However, there is a problem in that the heat treatment time is long, 1 hour or more, and thus the productivity is low.

In addition, Patent Document 3 has a glass film with a thickness of 20-200 μm and a polyimide resin layer, and the polyimide resin layer has a coefficient of thermal expansion of 10 ppm/K or less, and a light transmittance of 80% or more at a wavelength of 500 nm. It is disclosed to provide a castle laminate. This transparent flexible laminate is excellent also in heat resistance and gas barrier property, and can be used suitably for the flexible substrate in a display apparatus, and the transparent substrate in a solar cell. However, the manufacturing process of forming a resin substrate on a support substrate such as an organic EL flexible display display device and an organic EL lighting display device, mounting a display element on the resin substrate, and then peeling the resin substrate together with the display element Since the strength of a resin substrate is required especially for what has, in order to apply to these uses, it is thought that further improvement is needed.

In addition to the above, attempts have been made to reduce the weight by using a flexible resin for the supporting substrate. For example, Patent Document 4 proposes an organic EL device in which a polyimide having high transparency and excellent low coefficient of thermal expansion is applied to the supporting substrate. However, the polyimide films described in these films still have a large coefficient of thermal expansion and a large amount of outgas, so that there is concern about device contamination and the like in the process.

However, the organic EL device has poor resistance to moisture, and the characteristics of the EL element serving as the light emitting layer are deteriorated by moisture. Therefore, when using a resin as a support base material, in order to prevent the penetration|invasion of water|moisture content or oxygen into organic electroluminescent apparatus, resin with a low moisture absorption rate is preferable. In general, inorganic materials typified by silicon oxide and silicon nitride are used as organic EL substrates, and their coefficient of thermal expansion (CTE) is usually 0 to 10 ppm/K. On the other hand, in general, transparent polyimide has a CTE of about 60 ppm/K, so when the transparent polyimide is only applied to the supporting substrate of an organic EL device, warpage or cracks occur due to thermal stress, or problems such as peeling may occur.

In addition, the formation of the TFT required for display applications generally requires an annealing process reaching about 400°C. When using a glass substrate as a support base material, it was not a problem in particular, but when resin is used as a support base material, it is required to be equipped with the heat resistance with respect to the heat processing temperature of TFT and dimensional stability. In this regard, the organic EL device for lighting may not require a TFT, but it is possible to reduce the power consumption of the organic EL device by lowering the resistance of the transparent electrode by increasing the film formation temperature of the transparent electrode adjacent to the supporting substrate. Therefore, it is the same that heat resistance is required of the supporting substrate even in the case of lighting applications. In addition, as such a transparent electrode, a metal oxide such as ITO is generally used, and since these CTEs are 0 to 10 ppm/K, a resin having the same CTE is required in order to avoid problems of cracks and peeling. .

In addition, in order to perform color display in an organic EL display device, a material capable of emitting three primary colors of red (R) green (G) blue (B) is deposited for each color using a shadow mask, respectively, but in this method, The production of the shadow mask is very difficult, and there is a problem that it is expensive. In addition, it is difficult to make the shadow mask high-definition or enlarge it in terms of production. In response to these problems, an organic EL display device that displays color by combining a color filter with organic EL emitting white light has been proposed. However, in order to form a color filter, heat treatment of a resist reaching 230° C. or higher is generally required, and in particular, resist It is said that heat treatment of 300°C or higher is preferable in order to reduce the outgas from the gas. When such a high-temperature heat treatment is performed, if the thermal expansion coefficient and humidity expansion coefficient of the TFT substrate and the color filter substrate do not match, a difference in the dimensional change of each substrate occurs due to changes in temperature and humidity, resulting in warpage of the display device or between substrates. The problem that it becomes a cause of the peeling in from arises. For this reason, when using resin as a support base material of a color filter, it is required to be equipped with the heat resistance in the heat processing temperature of a resist, and dimensional stability equivalent to a TFT substrate. These problems can be solved by making the support base material of TFT and the support base material of a color filter into the same material.

Moreover, since a polyimide film is generally colored yellowish-brown, when minute foreign material mixes in a polyimide film, there exists a problem that it is difficult to detect with the naked eye or an external appearance inspection apparatus. In particular, it is extremely difficult to find foreign substances such as rust of a metal having a color close to that of polyimide. When a foreign material exists in a polyimide film, the defect of the gas barrier layer formed on the surface, a short-circuit between electrodes, etc. will generate|occur|produce, and it will become a cause of defect. In this respect, since the use of a polyimide film having transparency facilitates the discovery of foreign substances and can contribute to preventing a decrease in yield, a display device such as electronic paper that does not require transparency in the supporting substrate as a function of the display device It is useful to use a polyimide film with transparency as a support base material also in this. In this regard, the transmittance of glass in the visible region is generally about 90%, and when resin is used as the supporting substrate, it is necessary to be as close to this as possible. Since the wavelength of light emitted from the light emitting layer of the organic EL is mainly 440 nm to 780 nm, it is required that the average transmittance in this wavelength range be at least 80% or more as the supporting substrate used for the organic EL device. Moreover, it is preferable to be equipped with moisture resistance also about resin itself which forms a support base material.

In addition, when the film is peeled from the inorganic substrate, mechanical properties such as mechanical strength and elongation of a film of a certain level or higher are required, and in particular, when the tear propagation resistance is small, there is a problem that the film is broken when peeling. Therefore, high tear propagation resistance is calculated|required by the film used as a support base material.

In this regard, various methods for peeling the film from the inorganic substrate have been proposed (Patent Documents 5 and 6), but the process is complicated and expensive in many cases, and the point of suppressing the breakage of the film has been noticed. there is not Further, in Patent Document 7, a display device having a gas barrier layer on a supporting substrate made of a polyimide film, wherein the polyimide film has a transmittance of 80% or more in a wavelength range of 440 nm to 780 nm, and a coefficient of thermal expansion of 15 ppm/K Below, a display device characterized in that the difference in coefficient of thermal expansion with the gas barrier layer is 10 ppm/K or less is disclosed. It can be made thin, lightweight, and flexible, there is no problem of cracks or peeling due to thermal stress, has excellent dimensional stability, and prevents defects in the manufacturing process, so that it can exhibit long life and good device characteristics. However, in the manufacturing process of the display device, for example, when the polyimide film is peeled from the inorganic substrate, attention is not paid to the point of suppressing the breakage of the polyimide film, and in terms of improving the yield of the manufacturing process, Further improvement is expected.

In consideration of the above points, when replacing the supporting substrate for a display device from a glass substrate to a resin substrate, it is necessary to simultaneously satisfy at least low CTE, heat resistance, transparency, and high tear propagation resistance, but a resin substrate that can satisfy all of these does not exist

Japanese Patent Laid-Open No. 2012-40836 Japanese Patent Laid-Open No. 2010-202729 Japanese Patent Laid-Open No. 2013-163304 WO2013/146460 pamphlet Japanese Patent Laid-Open No. 2011-65173 Japanese Patent Application Publication No. 2011-142168 WO2013/191180 pamphlet

However, the present inventors have conducted intensive research to solve the above problems. As a result, surprisingly, by using a polyimide film made of polyimide containing a predetermined repeating structural unit and specifying the ratio of these structural units, The present invention was completed by discovering that a polyimide film capable of simultaneously satisfying CTE, heat resistance, transparency, and high tear propagation resistance and a display device having the same were obtained.

Accordingly, it is an object of the present invention to provide a polyimide film having low CTE, heat resistance, low hygroscopicity, strength and transparency suitable as a supporting substrate for forming display devices such as organic EL displays, organic EL lighting, electronic paper, and touch panels. is in doing

Another object of the present invention is to provide a display device using the polyimide film as a supporting substrate. In the display device of the present invention, since the resin substrate is hardly damaged during the manufacturing process, it is not easily damaged in the device forming step and thereafter in the step of peeling it from the inorganic substrate, and thus the productivity is high.

That is, the present invention forms a polyimide film by casting a polyimide precursor or a polyimide solution on an inorganic substrate and performing heat treatment, further mounting a display element on the polyimide film, and removing the polyimide from the inorganic substrate A display device obtained by peeling a mid film together with a display element, wherein the polyimide film has a glass transition temperature of 300° C. or higher, a 5% thermal decomposition temperature of 530° C. or higher, and a total light transmittance of 80 at a film thickness of 30 μm or less. % or more, a coefficient of thermal expansion of 40 ppm/K or less, and a tear propagation resistance of 1.3 mN/㎛ or more.

In addition, in the display device, it is preferable that the polyimide component constituting the polyimide film includes structural units represented by the following formulas (1) and (2).

In formulas (1) and (2), X is a single bond or a substituent including -C- or -O-. However, m/(m+n)=0.11-0.40.

Further, in the display device, it is preferable that X is a single bond or a divalent substituent represented by the following formula (3), (4) or (5).

In addition, the display device preferably has a moisture absorption of 0.8 wt% or less of the polyimide film.

In addition, the display device is preferably a touch panel.

In addition, the present invention forms a polyimide film by casting a polyimide precursor or a polyimide solution on an inorganic substrate and performing heat treatment, further mounting a display element on the polyimide film, and removing the polyimide from the inorganic substrate A method for manufacturing a display device obtained by peeling a mid film together with a display element, wherein the polyimide film has a glass transition temperature of 300° C. or more, a 5% thermal decomposition temperature of 530° C. or more, and a total light beam at a film thickness of 30 μm or less. It relates to a method of manufacturing a display device, characterized in that the transmittance is 80% or more, the thermal expansion coefficient is 40ppm/K or less, and the tear propagation resistance is 1.3mN/㎛ or more.

In addition, the present invention forms a polyimide film by casting a polyimide precursor or a polyimide solution on an inorganic substrate and performing heat treatment, further mounting a display element on the polyimide film, and removing the polyimide from the inorganic substrate A polyimide film for display devices obtained by peeling a mid film together with a display element, wherein the polyimide film has a glass transition temperature of 300° C. or more, a 5% thermal decomposition temperature of 530° C. or more, and 30 μm or less in film thickness. It relates to a polyimide film for a display device, which has a light transmittance of 80% or more, a coefficient of thermal expansion of 40 ppm/K or less, and a tear propagation resistance of 1.3 mN/㎛ or more.

The polyimide film of the present invention has low thermal expansibility, high transmittance in the visible region, excellent transparency, excellent dimensional stability, high heat resistance, low moisture absorption, high strength, and high productivity. Therefore, it can be suitably used as a support base material for display apparatuses, such as an organic electroluminescent display, organic electroluminescent lighting, electronic paper, and a touch panel.

In addition, the display device of the present invention has high productivity because the resin substrate is hardly damaged during the manufacturing process.

Hereinafter, the present invention will be further described.

The display device of the present invention forms a polyimide film by casting a polyimide precursor or a polyimide solution on an inorganic substrate and performing heat treatment, further mounting a display element on the polyimide film, and A display device obtained by peeling a polyimide film together with a display element, wherein the polyimide film has a glass transition temperature of 300° C. or higher, a 5% thermal decomposition temperature of 530° C. or higher, and a total light transmittance at a film thickness of 30 μm or less. 80% or more, a thermal expansion coefficient is 40 ppm/K or less, and a tear propagation resistance is 2.0 mN/micrometer or more.

The polyimide film can be produced by polymerizing the raw material diamine and an acid anhydride in the presence of a solvent to obtain a polyimide precursor solution, then casting it on an inorganic substrate and imidizing it by heat treatment. Alternatively, it can be prepared by casting a solution of polyimide on an inorganic substrate and imidizing it by heat treatment.

The molecular weight of the polyimide film is mainly controllable by changing the molar ratio of the raw material diamine and the acid anhydride, but usually the molar ratio is 1:1. It can be adjusted to 0.985-1.025 as needed. As a range of molecular weight Mw (weight average molecular weight), 80,000 or more are preferable. Moreover, it is more preferable to adjust in the range of 80,000-400,000. More preferably, it is more than 100,000 and 400,000 or less, More preferably, it adjusts in the range of 120,000-400,000 or less. Here, the molecular weight Mw is a molecular weight in terms of polystyrene measured and calculated by GPC (gel permeation chromatography).

The polyimide precursor solution is prepared by first dissolving diamine in an organic solvent, and then adding an acid dianhydride to the solution to prepare polyamic acid as a polyimide precursor. Examples of the organic solvent include dimethylacetamide, dimethylformamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene, butyrolactone, and triethylene glycol dimethyl ether. It can also be used in combination.

When casting|flow_spreading the solution of the obtained polyimide precursor to an inorganic substrate, it is preferable to make the viscosity of the said solution into the range of 500-70000 cps by adjustment of the density|concentration and molecular weight of a polyimide precursor. More preferably, it is 2000-20000cps.

Moreover, you may cast|flow_spread, after surface-treating suitably with respect to the surface of the base|substrate or base material used as the application surface of a resin solution. In the above, it is suitable for drying conditions to be performed at 150°C or lower for 2 to 10 minutes, and heat treatment for imidization at a temperature of about 130 to 360°C for about 2 to 60 minutes. Although a well-known method can be used for the casting method, Preferably they are the spin coating method and the coater method.

In addition to thermal imidization by heat dehydration, the process of imidation by subsequent heat treatment can also be performed using chemical imidation by adding and reacting a dehydrating agent and a catalyst to a polyimide precursor. In the case of thermal imidization, it is preferable that a heating temperature is 90-360 degreeC. On the other hand, in the case of chemical imidation, it is preferable that a heating temperature is 50-250 degreeC. In addition, when a polyimide solution is cast on an inorganic substrate and a polyimide film is formed by heat treatment, the temperature may be sufficient to volatilize the solvent in the solution, and it is preferably 100 to 250°C.

As the inorganic substrate, any known substrate can be used without limitation, but glass, SUS, and aluminum are preferable, and glass is more preferable from the reasons of smoothness, high heat resistance, and a small rate of dimensional change.

By the above heat treatment, a polyimide film having a total light transmittance (in the present invention, meaning transmittance in a wavelength range of 380 nm to 780 nm) of 80% or more at a film thickness of 30 µm or less on the inorganic substrate is obtained, Setting the heating time (hereinafter referred to as high temperature holding time) in the high temperature heating temperature range from a temperature 20 ° C lower than the highest heating temperature (maximum achieved temperature) at the time of temperature increase in the heat treatment to the highest achieved temperature is 60 minutes or less desirable. When this high temperature holding time exceeds 60 minutes, the production efficiency of a process may worsen, and transparency of a polyimide film may fall by coloring etc. In order to maintain transparency, the high temperature holding time is preferably short, but if the time is too short, there is a possibility that the heat treatment effect may not be sufficiently obtained. The optimal high temperature holding time varies depending on the heating method, the heat capacity of the substrate, the thickness of the polyimide film, and the like, but is preferably set to 0.5 minutes or more and 120 minutes or less. More preferably, they are 0.5 minutes or more and 60 minutes or less.

In addition, the polyimide film obtained by the heat treatment has a total light transmittance of 80% or more at a film thickness of 30 µm or less, a glass transition temperature of 300°C or more, a 5% thermal decomposition temperature of 530°C or more, and a coefficient of thermal expansion. 40 ppm/K or less and a tear propagation resistance of 1.3 mN/micrometer or more.

When the total light transmittance is less than 80%, when an organic EL element is used as a display element, light emitted from the light emitting layer of the organic EL (wavelength is mainly 380 nm to 780 nm) does not sufficiently penetrate the polyimide film. For this reason, for example, in the case of a back light emitting structure, light emission from the light emitting layer cannot be sufficiently extracted. More preferably, the total light transmittance is 85% or more. Moreover, when the transparent conductive film for touch panels is used as a display element, from the reason that sufficient visibility is ensured, the total light transmittance is 85 % or more.

In addition, the film thickness of the said polyimide film is although it will not restrict|limit as long as the total light transmittance in a film thickness of 30 micrometers or less is 80% or more, Preferably it is 5-30 micrometers, More preferably, it is 10-20 micrometers.

In addition, the glass transition temperature of the polyimide film is 300 ℃ or more. Preferably it is 330 degreeC or more, More preferably, it is 350 degreeC or more. When the glass transition temperature is less than 300° C., there is a fear that the polyimide film may be deformed by heat during mounting of the display device.

In addition, the 5% thermal decomposition temperature (Td5%) of the polyimide film is 530° C. or higher. If the temperature is less than 530°C, the polyimide film may be partially decomposed by heat during mounting of a display element such as a TFT or a transparent conductive film. More preferably, the weight reduction rate in 530 degreeC is 3 % or less.

Moreover, as mentioned above, although the thermal expansion coefficient of a polyimide film is 40 ppm/K or less, Preferably it is between -10 ppm/K and 40 ppm/K. If it is less than -10 ppm/K or exceeds 40 ppm/K, problems such as warping, cracking, or peeling may occur in the display device due to thermal stress at the time of mounting the display element. More preferably, they are 0 ppm/K - 30 ppm/K.

Moreover, the tear propagation resistance of the said polyimide film is 1.3 mN/micrometer or more. If it is less than 1.3 mN/micrometer, there exists a possibility that a polyimide film may fracture|rupture in the process of mounting a display element on a polyimide film, peeling a polyimide film from an inorganic substrate, etc., for example. A more preferable range is 1.5 mN/µm or more. A more preferable range is 2.0 mN/μm or more.

In addition, in the organic EL device and the touch panel device, in order to prevent adsorption of moisture into the device, the low hygroscopicity of the supporting substrate is preferable. Therefore, it is preferable that the said polyimide film has a moisture absorption of 0.8 wt% or less. More preferably, it is 0.6 wt% or less. In addition, when the moisture absorption rate is 0.8 wt% or less, the reliability as a display device is improved because expansion and foaming do not occur when the TFT is mounted or when the transparent conductive film is laminated.

In addition, in the polyimide film satisfying the above performance, it is preferable that the polyimide component constituting the polyimide film consists of structural units represented by the formulas (1) and (2).

In the formula (2), X is a single bond or a substituent containing -C- or -O-. However, m/(m+n)=0.11-0.40. More preferably, it is 0.12-0.40, More preferably, it is 0.15-0.40.

Here, the substituent including -C- includes, for example, -CO-, -C(CF ₃ ) ₂ -, and -C(CH ₃ ) ₂ -. More preferably, it is a substituent represented by said Formula (3) or (5).

In addition, the substituent containing -O- is, for example, -O-Ph-O-, -O-Ph-Ph-O-, -O-, -O-Ph-C(CF ₃ ) ₂ -Ph- O- can be mentioned. Here, Ph is a phenylene group. More preferably, it is a substituent represented by said Formula (3) or (4).

Here, the structural unit of Formula (1) mainly improves properties such as low thermal expansion and high heat resistance, and the structural unit of Formula (2) is also effective in improving high transparency and tear propagation resistance. Therefore, when m/(m+n) is less than 0.11, the coefficient of thermal expansion is large, the glass transition temperature is low, and there is a tendency that the TFT mounting process cannot be tolerated. More preferably, it is 0.20 or more. On the other hand, when it exceeds 0.40, tear propagation becomes low, and the polyimide film tends to break easily in, for example, a step of mounting a display element on a polyimide film and peeling the polyimide film from an inorganic substrate. . Moreover, there exists a tendency for transparency to fall.

In order to obtain high molecular weight resin, in this invention, it is preferable to adjust the molar ratio of an acid anhydride and diamine in the range of 0.985-1.025, More preferably, it is the range of 1.000-1.020. More preferably, it is 1.002 to 1.015. At a molar ratio other than that, molecular weight becomes low and tear propagation resistance becomes small.

In addition, the said polyimide film may add inorganic fine particles, such as silica, alumina, boron nitride, aluminum nitride, for the objective, such as an improvement of slidability and thermal conductivity, for example.

In addition, you may make it consist of polyimide of multiple layers of the said polyimide film. In the case of a single layer, it is preferable to have a thickness of 3 μm to 50 μm. On the other hand, in the case of multiple layers, a main polyimide layer may just be a polyimide film which has the said thickness. Here, the main polyimide layer refers to a polyimide layer having the largest ratio among polyimides of a plurality of layers, and preferably the thickness is 3 µm to 50 µm, more preferably 4 µm to 30 µm μm.

After the heat treatment is completed, a display device is mounted on the polyimide film. Here, although the type of the display element is not particularly limited, components of the display device such as a liquid crystal display device, an organic EL display device, a display device including electronic paper, and a color filter are also included. In addition, organic EL lighting devices, touch panel devices, conductive films stacked with ITO, etc., gas barrier films that prevent penetration of moisture or oxygen, components of flexible circuit boards, etc. are used incidentally to the display devices. Various functional devices are also included. That is, the display element referred to in the present invention refers to not only constituent parts such as a liquid crystal display device, an organic EL display device, and a color filter, but also an electrode layer or a light emitting layer of an organic EL lighting device, a touch panel device, and an organic EL display device, a gas barrier film, One type or a combination of two or more types such as an adhesive film, a thin film transistor (TFT), a wiring layer of a liquid crystal display device, or a transparent conductive layer is also included.

In addition, the method of forming a display element includes a display element (for example, in the case of an organic EL display device, a barrier layer, TFT, ITO, an organic EL light emitting layer, a color filter layer, and in the case of a touch panel, a transparent conductive film, Forming conditions are set appropriately depending on the electrode layer such as a metal mesh), but in general, after forming a film on a polyimide film, a metal or the like is patterned into a predetermined shape or heat-treated as necessary. It can be obtained using a well-known method. That is, the means for forming these display elements is not particularly limited, and, for example, sputtering, vapor deposition, CVD, printing, exposure, immersion, etc. are appropriately selected. If necessary, these processes are performed in a vacuum chamber or the like. You can do it. In addition, the inorganic substrate and the polyimide film may be separated immediately after formation of the display element through various process treatments, and may be integrated with the inorganic substrate for a certain period of time, for example, immediately before use as a display device. So you may want to remove it.

After the display element is mounted, the polyimide film is peeled from the inorganic substrate together with the display element. When a polyimide film is peeled from an inorganic substrate and a polyimide film is extended|stretched, retardation will become large. For this reason, the method of peeling so that the stress applied to a polyimide film at the time of peeling may become small is preferable.

In order to prevent elongation of the polyimide film, another layer is formed on the inorganic substrate, polyimide is formed thereon, and the display element is mounted thereon, and then the polyimide film is peeled off together with the other layer and the display element. , a method of dispersing the stress required for peeling to the other layers is preferred. It is particularly effective when the polyimide film is thin. In this case, it is regarded as the polyimide film of the present invention including the above other layers. As an example of the method of forming another layer, adhesion, application|coating, vapor deposition of a resin film or metal foil by an adhesive is mentioned.

Moreover, as a method of facilitating peeling of a polyimide film from a base material and preventing extending|stretching, other well-known methods are also applicable. For example, in Japanese Patent Application Laid-Open No. 2007-512568, a yellow film such as polyimide is formed on glass, and then a thin film electronic device is formed on the color film, and then a UV laser is applied to the bottom of the yellow film through the glass. It is disclosed that it is possible to peel glass and a yellow film by irradiating light. According to this method, since the polyimide film is separated from the glass by UV laser light, no stress is generated at the time of peeling, and it is one of the preferable methods as the peeling process of this invention. However, it is also disclosed that, unlike the yellow film, since the transparent plastic does not absorb UV laser light, it is necessary to form an absorption/release layer such as amorphous silicone in advance under the film.

Moreover, in Unexamined-Japanese-Patent No. 2012-511173, in order to perform peeling of a glass and a polyimide film by irradiation of UV laser beam, using the laser within the spectral range of 300-410 nm is disclosed. In this regard, as a peeling method, a laser is irradiated from the glass side to separate a resin substrate having a display unit from the glass, a peeling layer is applied to a glass substrate to form, and then a polyimide resin is applied on the peeling layer, A method of peeling the polyimide film layer from the peeling layer after the manufacturing process of the organic EL display device is completed, and after performing a coupling agent treatment on the surface of the inorganic layer, patterning the coupling agent by UV irradiation, etc. The method of forming a laminated body which has a favorable adhesion part and an easy peeling part, and peeling from it, etc. are mentioned.

Since the wavelength of the light emitted from the light emitting layer of the organic EL device is mainly 440 nm to 780 nm, it is required as a supporting substrate used for the organic EL device that the average transmittance in this wavelength region is at least 80% or more. On the other hand, when the glass and polyimide film are peeled by irradiation with UV laser light as described above, if the transmittance at the wavelength of UV laser light is high, it is necessary to form an absorption/peelable layer under the film, whereby productivity this lowers In order to perform peeling without forming an absorption/release layer, the polyimide film itself needs to sufficiently absorb laser light, and the transmittance of the polyimide film at 400 nm is preferably 60% or less, more preferably less than 40%.

Moreover, in order to prevent the penetration|invasion of moisture and oxygen into the inside of organic electroluminescent device or the inside of a touchscreen device, you may provide a gas barrier layer in the said polyimide film. In this case, it is considered as the polyimide film of this invention including a gas barrier layer. You may form from a single polyimide film, and you may form with base materials, such as glass and metal foil, and a laminated body of a polyimide film. A known gas barrier layer can be used, but as a gas barrier layer having barrier properties against oxygen, water vapor, etc., silicon oxide, aluminum oxide, silicon carbide, silicon oxide, silicon carbide, silicon nitride, silicon nitride, silicon oxide, etc. Inorganic oxides are exemplified suitably, and may be composed of only one type of composition, or a film obtained by mixing two or more types of compositions may be selected.

Example

Hereinafter, the content of the present invention will be described in more detail based on Examples and the like, but the present invention is not limited to the scope of these Examples.

First, the abbreviation of a monomer and a solvent at the time of synthesizing a polyimide, the measuring method of various physical properties in an Example, and its conditions are shown below.

TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl

PMDA: pyromellitic dianhydride

DMAc: N,N-dimethylacetamide

6FDA: 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride

ODPA: 4,4'-oxydiphthalic dianhydride

BPADA: 2,2'-bis(4-(3,4-dicarboxyphenoxy)phenyl)propanoic acid dianhydride

BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

m-TB: 2,2'-dimethylbenzidine

TPE-R: 1,3-bis(4-aminophenoxy)benzene

Support Substrate: Glass Substrate (Corning Incorporated, 0.7mm thick)

Solvent: dimethylacetamide (DMAc)

[Coefficient of Thermal Expansion (CTE)]

A polyimide film with a size of 3 mm × 15 mm was manufactured by Seiko Instruments Inc. With the thermomechanical analysis (TMA) device TMA100 of the product, while applying a load of 5.0 g, the temperature is raised from 30°C to 280°C at a constant temperature increase rate (20°C/min), and the temperature is lowered from there to 30°C, and tensile strength in this temperature range The test was done, and the coefficient of thermal expansion (ppm/K) was measured from the elongation amount of the polyimide film with respect to the temperature change from 250 degreeC to 100 degreeC.

[Tear propagation resistance]

A test piece of polyimide film (63.5 mm x 50 mm) was prepared, and a cut of 12.7 mm in length was put on the test piece, and TOYO SEIKI KOGYO CO., LTD. The product was measured at room temperature using a light load tear tester. The measured tear propagation resistance value was expressed as a resistance value per unit thickness (mN/μm).

[Glass transition temperature Tg]

The dynamic viscoelasticity of a polyimide film (10 mm × 22.6 mm) was measured with a dynamic viscoelasticity measuring (DMA) device RSA3 manufactured by TA Instruments Japan at a rate of 5° C./min from 20° C. to 500° C., and the glass transition temperature Tg ( tanδ maximal value) was obtained.

[Light transmittance]

The average value of the light transmittance in 440 nm - 780 nm was calculated|required for the polyimide film (50 mm x 50 mm) with a U4000 type|mold spectrophotometer.

[Total light transmittance]

Polyimide film (5cm×5cm) was manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD. The total light transmittance was measured using the product HAZE METER NDH-5000.

[Pyrolysis temperature (Td5%)]

A polyimide film having a weight of 10 to 20 mg was prepared by Seiko Instruments Inc. under a nitrogen atmosphere. The change in weight when the temperature was raised from 30°C to 550°C at a constant rate was measured with a thermogravimetric analysis (TG) device TG/DTA6200 of the product, and the temperature when the weight loss rate was 5% was taken as the thermal decomposition temperature. In addition, when the weight loss rate did not reach 5% in the said temperature range, arbitrary temperature 530 degreeC or more and the weight loss rate in this temperature were described.

[Moisture absorption rate]

After drying a polyimide film (4 cm x 20 cm) at 120 degreeC for 2 hours, it left still for 24 hours in the thermo-hygrostat of 23 degreeC/50%RH, and calculated|required by the following formula from the weight change before and behind that.

Moisture absorption (%) = [(weight after moisture absorption - weight after drying) / weight after drying] × 100

[Peelability]

When a polyimide film could be peeled from a support body board|substrate without fracture|rupture and damage|damage, it was judged as (circle). In addition, in the process of peeling, when fracture|rupture and damage generate|occur|produced and it became impossible to peel, it was judged as x.

[Humidity Expansion Coefficient (CHE)]

Before application of the solution of polyamic acid, DMAc was added to adjust the viscosity to about 10000 cP. From there, using an applicator on copper foil having a thickness of 18 μm, it is applied so that the film thickness after drying is about 10 μm, dried at 50 to 130° C. for 2 to 60 minutes, and then from 130° C. to 360° C. over 30 minutes. It further heat-processed, the polyimide layer was formed on copper foil, and the laminated body was obtained. This laminate was cut out to a size of 25 cm x 25 cm, an etching resist layer was formed on the copper foil side, and this was formed in a pattern in which 16 dots having a diameter of 1 mm were arranged at 10 cm intervals on 4 sides of a 30 cm square. The exposed part of the etching resist opening part was etched, and the polyimide film for CHE measurement which has 16 copper foil residual points was obtained. After drying this film at 120 degreeC for 2 hours, it left still in the environment of 23 degreeC/30%RH, 23 degreeC/50%RH, and 23 degreeC/70%RH for 24 hours, respectively, and the dimensional change between copper foil points in each environment CHE (ppm/%RH) was obtained from In addition, the dimensional change was measured by a two-dimensional measuring machine.

[Bending]

The laminated body of copper foil and a polyimide film was cut out to the size of 10 cm x 10 cm, it put on a flat place, and the state of the curvature of a laminated body was judged. Those having a curvature of less than 1 mm were denoted as ○, those of 1 mm or more and less than 3 mm were denoted as △, and those of 5 mm or more were denoted as ×.

[weight average molecular weight Mw]

The weight average molecular weight Mw was measured and calculated with a GPC apparatus (TOSOH HLC-8220 GPC manufactured by Tosoh Corporation). As a column, Tskgel GMHHR-Mx2 by Tosoh Corporation was used. The standard sample is polystyrene, and the detector type is RI. As the solvent, a DMAc-based developing solvent was used.

[Synthesis Example 1]

(Polyamic Acid A)

TFMB 25.907 was dissolved in 200 g of DMAc as a solvent while stirring in a 500 ml separable flask under a nitrogen stream. Next, 14.0 g of PMDA and 5.019 g of ODPA were added to this solution. The molar ratio of the acid anhydride and diamine was 1.005. Then, 55 g of DMAc was added so that solid content might become 15 wt%. After that, the solution was stirred at room temperature for 5 hours to carry out polymerization reaction, and was maintained for a full day. A viscous, colorless polyamic acid solution was obtained, and it was confirmed that polyamic acid A having a high degree of polymerization was produced. Table 1 shows the weight composition of the monomers in the polyamic acid A.

[Synthesis Example 2-16]

(Polyamic acids B to P)

Polyamic acids B to P according to Synthesis Examples 2-16 were obtained in the same manner as in Synthesis Example 1 except that the compositions shown in Tables 1 to 3 were used. The Mw of polyamic acid E was 211,596. In addition, Mw of polyamic acid N was 195,170.

[Example 1]

DMAc was added to the polyamic acid A solution obtained above, and it diluted so that the viscosity might become 5000 cP. On a glass substrate with a thickness of 0.5 mm and 10 mm × 10 mm, using an applicator, the film thickness after heat treatment is applied so that the film thickness is about 25 μm, and the temperature is raised from 90° C. to 360° C. over 30 minutes to form polyimide on the glass substrate. A laminate A was obtained. Next, the polyimide film was peeled from the glass substrate, and the colorless polyimide film A was obtained. Table 4 shows the results of various evaluations of the obtained polyimide film A and the laminate A.

In addition, about evaluation of the humidity expansion coefficient (CHE) and warpage, it performed according to the procedure described in the above-mentioned [humidity expansion coefficient (CHE)] and [warpage], respectively. Table 3 shows the evaluation results.

[Example 2-7]

Laminates B to G and polyimide films B to G according to Examples 2-7 were produced in the same manner as in Example 1 except that polyamic acids B to G were used instead of polyamic acids A. The evaluation result is shown in Table 4 similarly.

[Examples 8-9, 11]

Laminate C- according to Example 8 in the same manner as in Example 1, except that polyamic acids C, E or N were respectively used instead of polyamic acid A, and the coating was applied so that the film thickness after heat treatment was about 10 μm. 2 and the polyimide film C-2, the laminated body E-2 and polyimide E-2 which concern on Example 9, and the laminated body N and polyimide film N which concern on Example 11 were produced. The evaluation results are similarly shown in Tables 4 and 6, respectively.

[Example 12]

Laminate O and polyimide film O according to Example 12 were prepared in the same manner as in Example 1, except that polyamic acid O was used instead of polyamic acid A, and the coating was applied so that the film thickness after heat treatment was about 8 μm. made The evaluation result is shown in Table 6 similarly.

[Example 10]

A laminate A was obtained in the same manner as in Example 1, and a color filter layer was further formed on the polyimide surface of the laminate A. Then, the said polyimide with a color filter layer was peeled from glass, and the color filter board|substrate which used the polyimide film A for the flexible board|substrate was obtained. In the manufacturing process of a color filter board|substrate, the curvature of the laminated body was less than 1 mm. Moreover, the polyimide was able to peel cleanly from glass. Moreover, in the obtained color filter board|substrate, the damage|damage of a flexible board|substrate was not seen.

[Comparative Example 1-6]

Laminates H to M and polyimide films H to M according to Comparative Examples 1-6 were produced in the same manner as in Example 1 except that polyamic acids H to M were used instead of polyamic acids A. Table 5 shows the evaluation results.

[Comparative Example 7-8]

The laminate P and the polyimide film according to Comparative Example 7 were used in the same manner as in Example 1 except that polyamic acid P or I was used instead of polyamic acid A, and the coating was applied so that the film thickness after heat treatment was about 10 μm. P and laminated body I-2 and polyimide film I-2 concerning Comparative Example 8 were produced. Table 6 shows the evaluation results.

As shown in Tables 4 and 6, the polyimide films according to Examples 1 to 9 and 11 to 12 satisfying the conditions of the present invention have excellent transparency while maintaining heat resistance, have small warpage, and have firm film, It was a thing which could peel cleanly from a support board|substrate. Therefore, such a polyimide film can be suitably used as a support base material which forms display apparatuses, such as an organic electroluminescent display, organic electroluminescent lighting, and electronic paper.

On the other hand, as shown in Table 4, those made of the polyimide films according to Comparative Examples 1 to 6 and 7 to 8, which do not satisfy the conditions of the present invention, have a large thermal expansion coefficient, so that the laminate with glass has large warpage, and the film It was brittle and could not be peeled cleanly from the glass substrate, and thus was not suitable as a polyimide film for forming a display device.

Claims (7)

A polyimide precursor or a polyimide solution is cast on an inorganic substrate and heat treatment is performed to form a polyimide film, a display element is further mounted on the polyimide film, and the polyimide film is formed from the inorganic substrate as a display element As a display device obtained by peeling with
The glass transition temperature of the polyimide film is 300°C or more, the 5% thermal decomposition temperature is 530°C or more, and the total light transmittance in a film thickness of 30 µm or less is 80% or more, the thermal expansion coefficient is 40ppm/K or less, tear propagation resistance is 1.3 mN/㎛ or more,
A display device, characterized in that the polyimide component constituting the polyimide film is composed of structural units represented by the following formulas (1) and (2).

[In formulas (1) and (2), X is a single bond or a substituent represented by the following formulas (3) or (4). However, m/(m+n) = 0.11 to 0.40]

delete delete The method of claim 1,
The display device, characterized in that the moisture absorption of the polyimide film is 0.6 wt% or less. The method of claim 1,
A display device, characterized in that it is a touch panel. A polyimide precursor or a polyimide solution is cast on an inorganic substrate and heat treatment is performed to form a polyimide film, a display element is further mounted on the polyimide film, and the polyimide film is formed from the inorganic substrate as a display element As a method of manufacturing a display device obtained by peeling with
The glass transition temperature of the polyimide film is 300°C or more, the 5% thermal decomposition temperature is 530°C or more, and the total light transmittance in a film thickness of 30 µm or less is 80% or more, the thermal expansion coefficient is 40ppm/K or less, tear propagation resistance is 1.3 mN/㎛ or more,
The method of manufacturing a display device, characterized in that the polyimide component constituting the polyimide film comprises structural units represented by the following formulas (1) and (2).

[In formulas (1) and (2), X is a single bond or a substituent represented by the following formulas (3) or (4). However, m/(m+n) = 0.11 to 0.40]

A polyimide precursor or a polyimide solution is cast on an inorganic substrate and heat treatment is performed to form a polyimide film, a display element is further mounted on the polyimide film, and the polyimide film is formed from the inorganic substrate as a display element As a polyimide film for display devices obtained by peeling with
The glass transition temperature of the polyimide film is 300°C or more, the 5% thermal decomposition temperature is 530°C or more, and the total light transmittance in a film thickness of 30 µm or less is 80% or more, the thermal expansion coefficient is 40ppm/K or less, tear propagation resistance is 1.3 mN/㎛ or more,
The polyimide component constituting the polyimide film is a polyimide film for a display device, characterized in that it consists of structural units represented by the following formulas (1) and (2).

[In formulas (1) and (2), X is a single bond or a substituent represented by the following formulas (3) or (4). However, m/(m+n) = 0.11 to 0.40]