JP7016258B2 - Method of manufacturing polyimide film and glass-polyimide laminate - Google Patents

Description

The present invention relates to a method for producing a polyimide film or a polyimide film with a functional layer, and a glass-polyimide laminate.

In recent years, a light and flexible resin substrate has come to be used as an electronic device substrate. Such flexible substrates are beginning to be preferably used as substrates for flexible devices such as organic electroluminescence element substrates, circuit boards, display substrates, and touch panels.

In the manufacture of flexible devices, a process of forming a resin layer to be a resin substrate on a glass substrate, further forming a functional layer such as a transparent electrode, a thin film transistor, and a color filter on the resin substrate, and peeling the glass substrate to obtain a flexible device. Is generally included. In this step, one of the methods for peeling the glass substrate is a method of irradiating the interface between the glass substrate and the resin layer with a laser to peel the glass substrate, that is, a so-called laser lift-off (LLO) process. Since the LLO process does not apply mechanical stress during peeling, it has the advantage that the resin substrate and functional layer are not easily damaged. Therefore, a plurality of studies on applying the LLO process to the manufacturing process of the flexible device are disclosed.

For example, in Patent Document 1, a resin film and a display element are formed in this order on a first glass substrate, a resin film and a color filter are formed in this order on a second glass substrate, and two glass substrates are attached. A method of manufacturing a display device for peeling the glass substrate from the resin film by irradiating each glass substrate with a laser after the combination has been proposed.

Further, in Patent Document 2, in a method of manufacturing an electronic device such as a light emitting device using an EL material, a glass substrate and a resin substrate are bonded together with an adhesive layer, and a base insulating film, a semiconductor layer, and the like are formed on the resin substrate. Functional layers such as a gate insulating film and a conductive layer are formed, and these functional layers are further covered with an insulating film bonded to a resin substrate, and laser light is irradiated from the glass substrate side to all or part of the adhesive layer. Disclosed is a method of obtaining a light emitting device by vaporizing the glass substrate and peeling the glass substrate.

However, the surface shape and contaminated state of the resin substrate obtained by the LLO process may be affected by the surface shape and surface properties of the glass substrate and the adhesive layer in contact with the resin substrate, and in particular, the organic EL display device having a bottom emission structure. It is considered that there is room for improvement of the LLO process in order to apply it to flexible devices that require high optical characteristics for resin substrates such as touch panels and touch panels.

Japanese Unexamined Patent Publication No. 2014-74757 Japanese Unexamined Patent Publication No. 2016-131162

In view of the above problems, an object of the present invention is a polyimide film having excellent optical properties and a small amount of impurities without being affected by the surface shape and surface properties of the material in contact with the resin layer to be the resin substrate, and a polyimide film with a functional layer. Is to provide a method of manufacturing.

That is, in the present invention, a polyimide precursor solution is applied on a glass substrate and heat-treated to form a polyimide layer having an average film thickness of 5 to 50 μm, and then a laser is irradiated from the glass substrate side to irradiate the glass substrate. In the method for producing a polyimide film by peeling off the polyimide film, the difference (α-β) between the average film thickness α of the polyimide layer and the average film thickness β of the polyimide film is set to 10 nm to 500 nm. It is a manufacturing method of.

Further, in the present invention, a polyimide precursor solution is applied on a glass substrate and heat-treated to form a polyimide layer having an average film thickness of 5 to 50 μm, and then a functional layer is formed on the polyimide layer. In a method of irradiating a laser from the glass substrate side to peel off the glass substrate to produce a polyimide film with a functional layer, the average film thickness α of the polyimide layer and the average film thickness β of the polyimide film in the polyimide film with a functional layer It is a method for producing a polyimide film with a functional layer, characterized in that the difference (α-β) from the above is 10 nm to 500 nm.

Further, the present invention is a glass-polyimide laminate characterized in that a polyimide layer having an average film thickness of 10 nm to 500 nm is laminated on a glass substrate.

According to the production method of the present invention, a polyimide film having a small surface roughness, a low impurity concentration, and excellent transparency can be obtained regardless of the glass substrate or the adhesive layer used. Therefore, this polyimide film or the polyimide film with a functional layer can be suitably used as a substrate for a flexible device such as a liquid crystal display device, an organic EL display device, and a touch panel, which require particularly high optical characteristics.
Further, in the glass-polyimide laminate of the present invention obtained by the above manufacturing method, since an ultrathin film of polyimide is formed on the glass substrate, the characteristics of the glass substrate are not impaired, and the polyimide laminate is different depending on the type of polyimide to be laminated. The surface condition and adhesive properties can be controlled. Therefore, this glass-polyimide laminate can be suitably used for various applications such as a support for manufacturing flexible devices.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following description.

The method for producing a polyimide film of the present invention is a step of applying a polyimide precursor solution on a glass substrate and performing heat treatment to form a polyimide layer having an average film thickness of 5 to 50 μm, and irradiating a laser from the glass substrate side. Then, the glass substrate is peeled off to obtain a polyimide film. Then, in the step of obtaining the polyimide film, the difference (α-β) between the average film thickness α of the polyimide layer and the average film thickness β of the polyimide film is controlled in the range of 10 nm to 500 nm.
The method for producing a polyimide film with a functional layer of the present invention is the same as the method for producing a polyimide film described above, except that the functional layer is formed on the polyimide layer before irradiating the laser from the glass substrate side. The average film thickness β of the polyimide film in the polyimide film with a functional layer is the thickness obtained by subtracting the thickness of the functional layer from the thickness of the polyimide film with a functional layer after peeling.

Hereinafter, the glass substrate, the polyimide layer, the functional layer and the like will be described.
As the glass substrate, for example, those commonly used in the manufacture of flexible devices can be used. The glass substrate splits the pedestal when forming the polyimide film, and although it may ensure the handleability and dimensional stability of the polyimide film, it is finally removed and the polyimide film is removed. Does not constitute. In addition, in order to prevent the polyimide layer from peeling off during the treatment step, the glass substrate may be subjected to, for example, a functional group having an affinity for polyimide or a surface treatment for increasing the surface roughness. You may also wash the glass before use. Examples of the cleaning method include UV irradiation, removal of organic stains by spraying water or an organic solvent, and removal of adhering dust by high-pressure air.

This glass substrate is not particularly limited as long as it has chemical strength and mechanical strength that can withstand the thermal history and atmosphere in the manufacturing process for forming the polyimide layer and the functional layer, and is soda lime glass. , Non-alkali glass, phosphoric acid glass, quartz and the like. Further, if the glass substrate expands during the heat treatment for curing the polyimide precursor solution, a uniform resin layer may not be obtained. Therefore, the coefficient of thermal expansion of the glass substrate is 10 ppm / ° C. or less, preferably 5 ppm / ° C. The temperature is preferably below ° C. From this point of view, non-alkali glass is more preferably used as the glass substrate. The surface of the glass substrate is chemically surface-treated by introducing a functional group having an affinity for polyimide such as -OH, -NH, and -Si into the surface of the glass for the purpose of improving the adhesiveness. Alternatively, physical surface treatment may be applied so as to form an uneven surface on the glass surface by etching with a chemical solution.

The glass substrate needs to transmit laser light. Therefore, a laser beam having a high wavelength transmittance is suitable. Specifically, it is preferable that the transmittance of the wavelength of the laser light used is 30% or more. For example, a glass substrate having a light transmittance of 30% or more at a wavelength of 308 nm output by an excimer laser is suitable. However, the type of laser that can be used in the present invention is not limited to the excimer laser, and other lasers may be used. In this case, it is preferable that the laser has a light transmittance corresponding to the wavelength.

There is no particular limitation on the thickness of the glass. Commonly used thicknesses are 0.5 mm and 0.7 mm. The thinner the thickness, the higher the transparency of the laser beam, and the higher the intensity of the laser beam arriving at the interface of the glass / polyimide layer. On the other hand, 100 μm and 200 μm glass is soft and fragile. The preferred thickness is 0.5 to 1.0 mm.

As for the polyimide layer, if it has the releasability from the glass substrate in the LLO process and the chemical strength and mechanical strength that can withstand the thermal history and atmosphere when forming the functional layer on the polyimide layer. There are no particular restrictions. Here, excellent peelability from the glass substrate means that the difference (α-β) between the average film thickness α of the polyimide layer and the average film thickness β of the polyimide film is 10 nm to 500 nm.
The polyimide layer means a polyimide layer having an average thickness of 5 to 50 μm formed on a glass substrate, and the polyimide film means a polyimide film obtained by peeling off the glass substrate. The portion corresponding to the difference in film thickness is the polyimide layer remaining laminated on the glass substrate and the polyimide vaporized by the LLO process, and as a result, the peeled glass substrate becomes a glass-polyimide laminate having an ultrathin polyimide layer. ..

In forming the polyimide layer, a polyimide precursor solution in which the polyimide precursor is dissolved or dispersed in a solvent is applied on a glass substrate and then heat-treated. A polyamic acid obtained from an acid dianhydride and / or a tricarboxylic acid anhydride (hereinafter, also referred to as an acid anhydride) can be used. The diamine and the acid anhydride may each be composed of a single species or a plurality of species.

Generally, polyimide is obtained by polymerizing acid anhydride as a raw material monomer and diamine, and can be represented by the following general formula (1). The polyimide precursor can be represented by the general formula (2), and the polyimide can be obtained by heat-treating the polyimide precursor. Therefore, since the polyimide precursor can be understood from the explanation of polyimide, it is represented by the explanation of polyimide.

式中、Ａｒ_１は酸無水物残基である４価の有機基を表し、Ａｒ_２はジアミン残基である２価の有機基であり、耐熱性の観点から、Ａｒ_１、Ａｒ_２の少なくとも一方は、芳香族残基を有することが望ましい。

In the formula, Ar ₁ represents a tetravalent organic group which is an acid anhydride residue, and Ar ₂ is a divalent organic group which is a diamine residue. From the viewpoint of heat resistance, at least Ar ₁ and Ar ₂ are used. One is preferably having an aromatic residue.

The polyimide used in the present invention is not particularly limited, but a preferable example thereof is fluorine-containing polyimide. Here, the fluorine-containing polyimide refers to a polyimide structure having a fluorine atom, and has fluorine in at least one of an acid anhydride and a diamine, which are raw materials for polyimide. As such a fluorine-containing polyimide, for example, in the above general formula (1), Ar ₁ is a tetravalent organic group, and Ar ₂ is a divalent group represented by the following general formula (3) or (4). Those represented by organic groups are exemplified.

In the above general formula (3) or general formula (4), R ₁ to R ₈ are substituents, and are independent of each other by a hydrogen atom, a fluorine atom, an alkyl group or an alkoxy group having 1 to 5 carbon atoms, or a fluorine-substituted hydrocarbon. It is a hydrogen group, and in the general formula (3), at least one of R ₁ to R ₄ is a fluorine atom or a fluorine-substituted hydrocarbon group, and in the general formula (4), R 1 to R ₁ to _At least one of R8 is a fluorine atom or a fluorine-substituted hydrocarbon group. Suitable specific examples of these R ₁ to R ₈ include -H, -CH ₃ , -OCH ₃ , -F, -CF ₃ , and the like, but at least one in the formula (3) or the formula (4). The substituent is preferably either -F or -CF ₃ .

As a specific example of Ar ₁ in the general formula (1) in the case of a fluorine-containing polyimide, for example, the following tetravalent acid is given from the balance of peelability, heat resistance and transparency from the glass substrate in the LLO process. Anhydrous residues are mentioned.

In addition to the above, the following residues resulting from acid anhydride can be mentioned.

The polyimide layer having the above-mentioned acid anhydride residue has both transparency and heat resistance. For example, it is suitable as a flexible substrate that requires transparency and heat resistance, including display devices such as liquid crystal displays and organic EL display devices.
Considering that the peelability, heat resistance and transparency from the glass substrate in the LLO process are improved, preferable examples of the diamine residue which becomes Ar ₂ in the general formula (1) are shown below.

ここで、ｎは２～１６の整数である。 In addition to the above, there are residues resulting from diamines such as:

Here, n is an integer of 2 to 16.

In addition to these preferable diamine residues and acid anhydride residues, the fluorine-containing polyimide exhibits desired properties of known diamine-derived diamine residues and acid anhydride-derived acid anhydride residues. It may be obtained by appropriately combining one kind or two or more kinds so as to obtain.

Further, in such a fluorine-containing polyimide, when any of the following structural units represented by the general formulas (5), (6), (7), or (8) is contained in a proportion of 50 mol% or more. Is more preferable because it has excellent transparency, low thermal expansion, excellent dimensional stability, and excellent peelability from the glass substrate in the LLO process. More preferably, it is 70% or more. That is, in the case of a polyimide having a structural unit represented by the following general formula (5), (6), (7), or (8), the light transmittance in the wavelength region of 440 nm to 780 nm is 70% or more. Since it preferably shows 80% or more, it is more advantageous for forming a polyimide layer in a laminated member that requires transparency such as a display device. Further, the glass transition temperature can be 250 ° C. or higher, preferably 300 ° C. or higher, and the coefficient of thermal expansion can be 80 ppm / K or lower, preferably 50 ppm / K or lower. Therefore, by using such a polyimide, it is possible to prevent warping and wrinkling because the thermal expansion coefficients of both are close to each other even if the temperature is changed during the process.

剥離性、耐熱性、製膜性などを調整するために、上記一般式（５）～（８）の構造単位を複数有しても良い。

In order to adjust the peelability, heat resistance, film forming property and the like, a plurality of structural units of the above general formulas (5) to (8) may be provided.

Further, it may have a structural unit derived from the diamines of the following general formulas (9) and (10). It is more preferable to add 10 mol% or less of the diamine of the formula (9) or 20 wt% or less of the diamine of the formula (10).

The fluorine-containing polyimide as described above has excellent peelability from the glass substrate in the LLO process. Therefore, by using these fluorine-containing polyimides as the polyimide layer, it is possible to obtain a smooth polyimide film having excellent optical properties or a polyimide film with a functional layer without being affected by the surface roughness and surface properties.

When the laser beam is irradiated from the glass substrate side of the laminate in which the polyimide layer is formed on the glass substrate, the polyimide layer absorbs the laser beam and peels off from the glass substrate. When the functional layer is provided on the polyimide layer, when the light such as a laser reaches the functional layer, the functional layer may not operate, which may have an adverse effect. Therefore, the light blocking effect of the laser beam is also required. It is also necessary to absorb the laser beam and generate heat to partially vaporize it. Therefore, the transmittance of a wavelength close to that of laser light is 20% or less, preferably 10% or less, and more preferably 1% or less. Specifically, the polyimide layer formed on the glass substrate has a light transmittance of 20% or less, preferably 10% or less, and more preferably 1% or less at a wavelength of 355 nm. If the light transmittance at 308 nm is less than or equal to this range, it can be peeled off by a laser having a wavelength of 308 nm. If the light transmittance at 355 nm is less than or equal to this range, it can be peeled off by a YAG laser having a wavelength of 355 nm.

It is preferable to control the fluorine atom concentration in the polyimide layer in order to adjust the transmittance in the visible light region to be high and the transmittance in the short wavelength region to be low. It is preferable that the molecular structure of the polyimide constituting the polyimide layer contains 5 wt% to 40 wt% of fluorine, and more preferably 15 wt% to 30 wt%. The fluorine concentration is the weight concentration of the fluorine atom contained in the repeating unit represented by the general formula (1) constituting the polyimide.

Further, in order to increase the transmittance in the visible light region and absorb light in the short wavelength region, it is necessary to control the aromatic ring concentration in the molecular structure of the polyimide. The molecular structure of the polyimide preferably contains 5 wt% to 63 wt% of aromatic rings, and more preferably 35 wt% to 50 wt%. The aromatic ring concentration is the weight concentration of an aromatic ring such as a benzene ring contained in the repeating unit represented by the general formula (1) constituting the polyimide.

The polyimide precursor solution is preferably obtained by reacting a raw material diamine and an acid anhydride in substantially equimolar amounts in an organic solvent. Also, the acid anhydride and diamine may be slightly offset between 0.980 and 1.03 in order to adjust the molecular weight. Specifically, after dissolving diamine in an organic polar solvent such as N, N-dimethylacetamide, N-methyl-2-pyrrolidone under a nitrogen stream, tetracarboxylic acid dianhydride and / or tricarboxylic acid anhydride is added. In addition, it can be obtained by reacting at room temperature for about 20 hours. In order to increase the solubility in the solvent, when the monomer is added to the solvent, it may be heated for 10 min to 2 hr at a temperature of 30 to 50 ° C. From the viewpoint of uniform film thickness during coating and mechanical strength of the obtained polyimide film, the weight average molecular weight of the obtained polyamic acid is preferably 10,000 to 300,000. The preferable molecular weight range of the obtained polyimide layer is also the same molecular weight range as this polyamic acid.

The method of applying the polyimide precursor solution on the glass substrate is not particularly limited, and any known method, for example, a spin coater, a spray coater, a bar coater, a roll coater, or a knife coater, can be obtained as long as a predetermined thickness accuracy can be obtained. , Slit die coater, inkjet printing, screen printing, and extruding method from a slit-shaped nozzle can be applied. Further, the surface of the glass substrate to be the coated surface of the polyimide precursor solution may be appropriately surface-treated and then coated.

The heat treatment is carried out at 500 ° C. or lower, preferably 450 ° C. or lower to imidize the polyimide precursor and convert it into polyimide. The heat treatment time is usually selected from 1 minute to 20 hours, preferably 2 minutes to 10 hours, and the heat treatment may be performed by raising the temperature step by step. Further, the heat treatment for imidization may be performed in the atmosphere or in nitrogen. If necessary, the heat treatment may be performed two or more times.

The functional layer constitutes a liquid crystal display device, an organic EL display device, a display device such as an electronic paper or a touch panel, a lighting device, a detection device, a layer constituting the component thereof, or various functional material layers. Specifically, it means one or a combination of one or more of an electrode layer, a light emitting layer, a gas barrier layer, an adhesive layer, an adhesive layer, a thin film transistor, a wiring layer, a transparent conductive layer and the like.
The polyimide film with a functional layer has various functions such as being used in an organic EL lighting device, a conductive film on which ITO and the like are laminated, a gas barrier film that prevents the penetration of moisture and oxygen, and components of a flexible circuit board. It is used as a flexible substrate, which is a functional material that it has.

Examples of the laser include various gas lasers and solid-state lasers (semiconductor lasers), and an excima laser, an Nd-YAG laser, an Ar laser, a CO ₂ laser, a He-Ne laser and the like can be used. These lasers are UV region laser (410 nm or less), green, visible light region vs. laser (500 to 700 nm), near infrared region large laser (700 to 2000 nm), and infrared region vs. laser (400 to 2000 nm), depending on the wavelength. It can be roughly divided into 2000 nm and above).

In the present invention, it is preferable to use a laser beam having a wavelength region of 410 nm or less as a UV laser, and specifically, to irradiate a laser beam having any wavelength in a wavelength region of 300 nm to 410 nm from the glass substrate side. Preferred laser light includes a third harmonic (355 nm) of an Nd-YAG laser having a wavelength of 360 nm or less, and more preferably an Xe-Cl excimer laser (308 nm) having a wavelength of 310 nm or less.

The laser irradiation preferably irradiates the entire back surface of the glass substrate on the side opposite to the surface on which the resin layer is formed. As a method of irradiating the entire surface, the laser nozzle may be fixed and the stage may be irradiated while moving in the XY direction, or the laser nozzle may be irradiated while moving in the XY direction. The nozzle shape of the laser can be arbitrarily selected, and examples thereof include a point laser and a line laser. In the present invention, irradiation with a line laser having an irradiation width as wide as possible is preferable.

Preferably, the laser irradiation is pulsed while moving the nozzle. The laser intensity is distributed within the irradiation range, and generally the intensity of the central portion is high and the intensity of the peripheral portion is low. Therefore, when irradiating a laser, it is preferable to irradiate the laser with a laser intensity as uniform as possible, or to irradiate the laser while overlapping a part of the laser irradiation area. It is preferable that the overlap is small because the irradiation speed is high.

Further, when irradiating while overlapping a part of the laser irradiation area, strong energy is applied to the overlapping portion, so that the resin layer may be deteriorated. Therefore, it is preferable to irradiate the laser light a plurality of times so that the overlapping width of the laser light overlaps with a length of 50% or less of the beam size width, preferably 30% or less.

The laser irradiation energy strongly depends on the difference (α-β) between the average film thickness α of the polyimide layer and the average film thickness β of the polyimide film. If the irradiation energy is too large, the value of α-β becomes small, and when the polyimide layer is peeled from the glass substrate by the LLO process, the peeled polyimide film surface is affected by the surface shape of the glass substrate, or the surface of the glass substrate is affected. Contaminants and ionic impurities may adhere to or mix with the polyimide layer. In addition, the strong energy may change the quality of the polyimide layer. On the other hand, if the irradiation energy is too small, the value of α-β becomes large. That is, in order to obtain a polyimide film having a desired thickness, a large amount of the required polyimide precursor is required, which increases the manufacturing cost. In addition, the polyimide layer may not peel off from the glass substrate. In order to achieve these balances, it is important that the value of α-β is 10 to 500 nm, preferably 10 to 300 nm, and more preferably 10 to 200 nm. In order to obtain a value in this range, it is effective to control the irradiation energy density, and this density (mJ / cm ² ) is preferably 10 to 500, more preferably 50 to 500, and further. It is preferably 80 to 500.

In order to facilitate the peeling of the glass substrate by the LLO process, a mold release agent or a sacrificial layer may be applied to the glass substrate before the polyimide precursor solution is applied to the glass substrate. Examples of the release agent include vegetable oil-based, alkyd-based, silicone-based, fluorine-based, aromatic polymer-based, alkoxysilane-based, and the like, and the sacrificial layer includes a metal film, an oxide film, and an amorphous silicon film. And so on.

Next, the method for producing the polyimide film with a functional layer of the present invention will be more specifically exemplified.
As an example, a TFT substrate provided with an inorganic film and a TFT as a functional layer on a polyimide film will be described.

The TFT substrate can be manufactured through at least the following steps.
(1) Step of applying the polyimide precursor solution on the glass substrate (2) Step of removing the solvent from the applied polyimide precursor solution (3) Step of imidizing the polyimide precursor to obtain a polyimide layer (4) Polyimide A step of forming an inorganic film (functional layer) on the layer (5) a step of further forming a TFT (functional layer), and (6) a step of peeling off a glass substrate.

As the inorganic film here, it is preferable to form a gas barrier layer on the polyimide layer in order to suppress the permeation of gas such as steam and oxygen. Preferred gas barrier layers include, for example, a metal oxide containing one or more metals selected from the group consisting of silicon, aluminum, magnesium, zinc, zirconium, titanium, ittrium, and tantalum, silicon, and aluminum. , Metal nitrides of boron or mixtures thereof. Above all, it is preferable to use silicon oxide, nitride, or oxynitride as a main component from the viewpoints of gas barrier property, transparency, surface smoothness, flexibility, film stress, cost and the like. These inorganic gas barrier layers can be produced by a vapor phase deposition method such as a sputtering method, a vacuum vapor deposition method, an ion plating method, a plasma CVD method, or the like, in which a material is deposited from the gas phase to form a film. Above all, the sputtering method is preferable from the viewpoint of obtaining excellent gas barrier properties. The film thickness of the inorganic gas barrier layer is preferably 10 to 300 nm, more preferably 30 to 200 nm.

Examples of the semiconductor layer for forming the TFT include an amorphous silicon semiconductor, a polycrystalline silicon semiconductor, an oxide semiconductor typified by IGZO, and an organic semiconductor typified by pentacene and polythiophene. For example, using the polyimide layer as a base material, a gas barrier film, a gate electrode, a gate insulating film, an IGZO semiconductor layer, an etching stopper film, and a source / drain electrode are sequentially formed by a known method to produce a bottom gate type TFT. Through the above steps, a TFT substrate using a polyimide layer can be manufactured. Such a TFT substrate can be used as a drive substrate for a liquid crystal device or an organic EL element.

Further, among the polyimide layers, those having high transmittance in the visible light region can be suitably used for the color filter base material. That is, it is possible to obtain a color filter having a black matrix and colored pixels on the polyimide film of the present invention.

Further, a transparent conductive layer can be formed on the surface of the polyimide film as a functional layer, and the polyimide film can be suitably used as a touch panel base material. As the transparent conductive layer, a known metal film, metal oxide film or the like can be applied, but it is preferable to apply the metal oxide film from the viewpoint of transparency, conductivity and mechanical properties. Examples of the metal oxide film include indium oxide, cadmium oxide and tin oxide to which tin, tellurium, cadmium, molybdenum, tungsten, fluorine, zinc, germanium and the like are added as impurities, and zinc oxide and titanium oxide to which aluminum is added as impurities. Such as a metal oxide film. Among them, a thin film of indium oxide containing 2 to 15% by mass of tin oxide or zinc oxide is preferably used because of its excellent transparency and conductivity.

Further, when the polyimide film is non-transparent, it is preferably used for an organic EL display device having a bottom emission structure, which does not require the transparency of the resin substrate.

The method for forming the transparent conductive layer may be any method as long as it can form a desired thin film, but for example, from a vapor phase such as a sputtering method, a vacuum vapor deposition method, an ion plating method, or a plasma CVD method. A vapor deposition method in which a material is deposited to form a film is suitable. Above all, from the viewpoint of obtaining particularly excellent conductivity and transparency, it is preferable to form a film by using a sputtering method. The film thickness of the transparent conductive layer is preferably 5 to 500 nm, more preferably 10 to 300 nm.

Further, the polyimide film and the polyimide film with a functional layer obtained by the manufacturing method of the present invention are based on display devices such as liquid crystal displays, organic EL displays and electronic papers, color filters, touch panels, solar cells, light receiving devices such as CMOS and the like. It can be used as a material. In particular, these display devices and light receiving devices are preferably used as bendable flexible devices.

In the method for manufacturing a polyimide film and a polyimide film with a functional layer of the present invention, in the manufacturing process, a glass-polyimide laminate in which a polyimide layer (residual polyimide layer) having an average film thickness of 10 nm to 500 nm is laminated on a glass substrate is formed. can get. The average film thickness of the residual polyimide layer constituting this glass-polyimide laminate substantially corresponds to the value of α-β.
In this glass-polyimide laminate, an ultrathin polyimide film is formed on a glass substrate. Therefore, the surface condition and the adhesive property can be controlled by the type of the polyimide to be laminated without impairing the property of the glass substrate. For example, when the residual polyimide layer is transparent, it is possible to impart functions such as water repellency, scratch prevention, scattering prevention, and heat insulation to the surface while maintaining the optical characteristics of the glass substrate. Therefore, it can be suitably used for various applications such as windows and supports for manufacturing flexible devices.

The residual polyimide layer may be removed from the glass-polyimide laminate and reused as a glass substrate. The support may be cleaned, heat treated and surface treated prior to reuse.

Hereinafter, the present invention will be described in more detail based on examples. The present invention is not limited to the contents of the following examples.

The abbreviations in the examples, the methods for measuring various physical properties, and the conditions thereof are shown below.
TFMB: 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl AI: 5-amino-2- (4-aminophenyl) benzoimidazole PDA: p-phenylenediamine 6FDA: 4,4'- (2,2'-Hexafluoroisopropylidene) Diphthalic acid dianhydride PMDA: Pyromellitic acid dianhydride CBDA: Cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride BPDA: 3,3', 4 , 4'-biphenyltetracarboxylic acid dianhydride NMP: N-methyl-2-pyrrolidone glass substrate A: AN-100 (non-alkali glass manufactured by Asahi Glass Co., Ltd., thickness 0.7 mm, light transmission rate at 308 nm wavelength is 36% )
Glass substrate B: Eagle XG (Non-alkali glass manufactured by Corning, thickness 0.7 mm, light transmittance at wavelength of 308 nm is 72%)

Light transmittance and YI;
The polyimide film (50 mm × 50 mm) obtained in the production example was used to determine the light transmittance (T ₄₃₀ ) at 430 nm using a SHIMADZU UV-3600 spectrophotometer.
Further, YI (yellowness) was calculated based on the calculation formula represented by the following formula (5).
YI = 100 × (1.2879X-1.592Z) / Y (5)
Here, X, Y, and Z are the tristimulation values of the test piece specified in JIS Z 8722.

Surface roughness;
In Examples 1 to 6 and Comparative Example 1, the surface roughness of the polyimide layer and the glass substrate after peeling was determined according to JIS B0601-1982 using a high-precision fine shape measuring machine SUFCORDER ET4000 (manufactured by Kosaka Laboratory). Was measured. The measurement length was 0.25 mm and the feed speed was 0.005 mm / sec. For the polyimide layer, the surface on the side that was in contact with the glass substrate (glass surface) and the surface on the side opposite to the glass surface (non-glass surface) were measured, and for the glass substrate, the surface was in contact with the polyimide layer. The surface, in other words, the surface on which the residual polyimide layer may exist was measured.

The conditions for the laser lift-off (LLO) process were as follows.
Using an industrial excimer laser (IPEX-840 manufactured by Light Machinery) for the laminate of the polyimide layer and the glass substrate, the wavelength is 308 nm, the frequency is 30 Hz, the pulse width is 50 ns, the beam size is 14 mm × 1.2 mm, and the moving speed is 6 mm / s. The laser beam was irradiated from the glass substrate side under the condition of overlap of 80%. Specifically, the overlapping width of the laser beam was set to 2 mm so that the energy distribution was uniform on the surface of the laminated body on the glass substrate side, and irradiation was performed over 5 round trips. The peeling range was determined with a cutter, and after making one round of the cut, the polyimide film spontaneously peeled from the glass.

The conditions for the mechanical lift-off (MLO) process were as follows.
Regarding the polyimide layer of the laminate of the polyimide layer and the glass substrate obtained in the comparative example, cut the periphery of the peeling target area with a cutter, pinch the end with tweezers, and from the glass substrate of the laminate. The polyimide layer was peeled off.

Production Example 1
Under a nitrogen stream, 8.521 g of TFMB was dissolved in NMP of solvent NMPg in a 300 ml separable flask. Next, 1.4614 g of 6FDA and 5.0176 g of PMDA were added to this solution, 15 g of NMP was added so that the solid content became 15 wt%, and the mixture was stirred at room temperature for 10 hours to carry out a polymerization reaction. After the reaction, a viscous colorless and transparent polyimide precursor solution A was obtained.

Production Examples 2-3
Polyimide precursor solutions B and C were obtained in the same manner as in Production Example 1 except that the raw material monomers shown in Table 1 were used. In Table 1, the unit of the amount used is g. Further, Synthesis Examples 1, 2 and 3 correspond to the above-mentioned Production Examples 1, 2 and 3, respectively.

The heat treatment conditions after applying the polyimide precursor solution were as follows.
In the case of the polyimide precursor solution A, it is heated at 100 ° C. for 15 minutes, and then heated from room temperature to 360 ° C. at a constant temperature rise rate (3 ° C./min) in a nitrogen atmosphere, and then 130 ° C. on the way. The temperature was maintained at 160 ° C. and 200 ° C. for 30 min, respectively.
In the case of the polyimide precursor solution B, the conditions were the same as those of the polyimide precursor solution A, except that the temperature rising rate was 4 ° C./min and the maximum temperature reached was 300 ° C. In the case of the polyimide precursor solution C, the conditions were the same as those of the polyimide precursor solution A except that the temperature rising rate was 2 ° C./min and the maximum temperature reached was 400 ° C.

Production example 4
NMP was added to the polyimide precursor solution A, diluted to a viscosity of 3000 cP, and then coated on a 75 μm polyimide film (Upilex-S) substrate. Subsequently, heat treatment was performed under the above conditions to obtain a polyimide laminated film. Then, the base material was peeled off, and the polyimide precursor solution A was imidized to obtain a polyimide film as a simple substance. The above peeling was performed by peeling only the formed polyimide layer from the base material with tweezers after making one round of a cut with a cutter to determine the peeling range. The thickness of the polyimide film is shown in the section of thickness. The light transmittance was measured using the peeled film. The results are shown in Table 2.

Production Example 5
A polyimide film was obtained by the same method as in Production Example 4, except that the polyimide precursor solution B was used instead of the polyimide precursor solution A and the heat treatment was performed under the above conditions.

Production Example 6
A polyimide film was obtained by the same method as in Production Example 4, except that the polyimide precursor solution C was used instead of the polyimide precursor solution A and the heat treatment was performed under the above conditions.
Table 2 shows the results of measuring the light transmittance and the like of the polyimide films obtained in each production example.

Example 1
NMP was added to the polyimide precursor solution B, diluted to a viscosity of 3000 cP, and then coated on the glass substrate A. Subsequently, heat treatment was performed under the above conditions to form a polyimide layer having a thickness of 15 μm. Then, the glass substrate was peeled off by the above LLO process to obtain a polyimide film.

Examples 2 to 6, Comparative Examples 1 to 3
A polyimide film was obtained in the same manner as in Example 1 except that the conditions shown in Table 3 were used.
Tables 3 and 4 show the measurement results of the thickness of each polyimide layer, the thickness of the polyimide layer (residual polyimide layer) remaining on the glass substrate after peeling, the surface roughness, and the like. Since the thickness of the polyimide film is a value obtained by subtracting the thickness of the residual polyimide layer from the thickness of the polyimide layer, the thickness of the residual polyimide layer can be understood as (α-β). Further, the surface roughness (Ra) of the peeled glass substrate in Table 4 can be understood as the surface roughness of the residual polyimide layer.

※1；測定限界以下

* 1; Below the measurement limit

Claims (2)

A polyimide precursor solution (however, it does not contain an alkoxysilane compound) is applied on a glass substrate and heat-treated to form a polyimide layer having an average thickness of 5 to 50 μm, and then a laser is used from the glass substrate side. In the method of producing a polyimide film by irradiating the glass substrate with A method for producing a polyimide film, wherein the polyimide is a fluorine-containing polyimide (however, it is not a photosensitive polyimide) . A polyimide precursor solution is applied on a glass substrate and heat treatment is performed to form a polyimide layer having an average thickness of 5 to 50 μm, then a functional layer is formed on the polyimide layer, and then a laser is applied from the glass substrate side. In the method of irradiating and peeling off the glass substrate to produce a polyimide film with a functional layer, the difference between the average film thickness α of the polyimide layer and the average film thickness β of the polyimide film in the polyimide film with a functional layer (α-). A method for producing a polyimide film with a functional layer, wherein β) is set to 10 nm to 500 nm , and the polyimide is a fluorine-containing polyimide (however, it is not a photosensitive polyimide) .