TW202122462A - Polyimide-based film and display device including the same - Google Patents

Abstract

Provided are a polyimide-based film and a display device including the same. More particularly, a polyimide-based film having an excellent press characteristic and a display device including the same are provided. As an exemplary embodiment, a polyimide-based film is provided, wherein when a load is applied to a surface of the film with an Erichsen pen, a maximum load satisfies the following Relation 1: [Relation 1] 0.07 ≤ Fe/Te ≤ 0.11 wherein Fe is a maximum load (N) at which when a load is applied to the surface of the polyimide-based film with the Erichsen pen, the surface is not scratched, and Te is a thickness ([mu]m) of the polyimide-based film.

Description

Polyimide film and display device including the polyimide film

The present invention relates to a polyimide-based film and a display device including the polyimide-based film. More specifically, the present invention relates to a polyimide-based film having excellent pressing characteristics and a display device including the polyimide-based film.

In order to protect the display panel from scratches or external impact, the display panel of the display device is provided with a transparent cover window including a polyimide film, so that the user can see the display part in front of the display panel.

This kind of cover window plays a role in protecting the display panel. The cover window is a structure formed on the outermost part of the display device. Therefore, it is necessary to resist external shocks to protect the display panel inside the display device.

Especially with the application of display devices to various mobile devices, in recent years, the structure of the touch panel integrated with the display screen has been widely promoted to replace traditional electronic devices that use input devices such as switches or keyboards alone, and is compatible with traditional mobile devices. Compared with devices, the surface of the cover window frequently comes into contact with fingers and the like, so a stronger cover window is required.

Conventionally, tempered glass for displays has been used as a cover window. The tempered glass for displays is characterized by being thinner than ordinary glass, but having high strength and excellent scratch resistance. However, toughened glass has the disadvantage of being heavy and not suitable for lightweight portable devices such as mobile devices, and it has poor resistance to external impact and cannot be bent above a certain level, so it is difficult to be used as a flexible display material.

As described above, display devices are gradually being reduced in weight, thinner, and flexible. Therefore, a large number of researches are being conducted on cover windows made of polymer films with high hardness, high rigidity, and flexibility, instead of tempered glass.

Although the above-mentioned cover window satisfies the flexibility and flexibility, but the rigidity is reduced, there are problems of generation of scratches and poor appearance due to pressing.

That is, although various polymer cover window materials have been developed to replace expensive tempered glass, it is currently necessary to develop a cover window that satisfies both bending characteristics and impact resistance.

[Related technical literature]

[Patent Literature]

(Patent Document 1) Korean Published Patent No. 10-2015-0104282

Technical problem to be solved

An object of the present invention is to provide a polyimide-based film, which has excellent scratch resistance and high strength, thereby preventing appearance defects caused by pressing.

In particular, one object of the present invention is to provide a polyimide-based film and a display device including the polyimide-based film. When an external force is applied with a touch pen or hand, the polyimide-based film has excellent properties. The surface resilience.

In addition, an object of the present invention is to provide a polyimide-based film which does not cause white turbidity even if a hard coat layer is formed on the film.

Technical solutions

In order to achieve the above object, when a load is applied to the surface of the polyimide-based film of the present invention with an Erichsen pen, the maximum load satisfies the following relational expression 1.

[Relationship 1]

In relation 1, F _e is the maximum load (N) that does not cause scratches when a load is applied to the surface of the polyimide film with a Yilixin pen, and T _e is the thickness of the polyimide film (μm) .

In an embodiment of the present invention, in relation 1, F _e may be 2.0 to 6.5 N, and T _e may be 20 to 100 μm.

In an embodiment of the present invention, F _e may be 4.0 to 6.0 N.

The polyimide-based film of one embodiment of the present invention may have a yellow index measured in accordance with the ASTM E313 standard of 3.0 or less.

The polyimide-based film of one embodiment of the present invention is manufactured by the following method: prepolymerizing a diamine containing an aromatic group and an aromatic diacid chloride (diacid chloride) to prepare an amine-terminated polyimide intercalation The polyamide is then added with an aromatic dianhydride containing a fluorine-based aromatic dianhydride to prepare a polyamide imide, which is then made into a film.

In an embodiment of the present invention, with respect to 1 mol of the diamine containing an aromatic group, 0.6 to 0.9 mol of aromatic dichloride and 0.05 to 0.3 mol, specifically 0.1 to 0.3 can be used. The aromatic dianhydride containing the fluorine-based aromatic dianhydride of mol is polymerized.

In an embodiment of the present invention, in the dimethicone chloride, more than 80 mole% of the total dimethicone chloride can be used for terephthalic acid chloride.

In one embodiment of the present invention, in the aromatic dianhydride containing the fluorine-based aromatic dianhydride, the content of the fluorine-based aromatic dianhydride may be 30 to 100 mol% of the total aromatic dianhydride.

Another object of the present invention is to provide a display device including a display panel and the above-mentioned polyimide-based film formed on the display panel.

Beneficial effect

The polyimide-based film of the present invention has excellent scratch resistance and strength, and therefore has the advantage of being able to prevent poor appearance caused by pressing caused by external force.

In particular, the polyimide-based film can be used for cover window films and display devices, so that it can be applied to various display fields that require pressing characteristics such as smart devices.

The polyimide-based film of the present invention has excellent optical properties, and even if a hard coat is formed on the upper part thereof, it does not produce white turbidity, and has excellent surface restoring force when external force such as pressing is applied. Therefore, the polyimide film has excellent optical properties. The imine-based film is particularly suitable for use in cover window film materials and display devices containing the cover window film materials.

Hereinafter, the present invention will be described in more detail. However, the following specific embodiments or implementations are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and the present invention can be implemented through various implementations.

In addition, unless otherwise defined, all technical and scientific terms have the same meanings as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only used to effectively describe specific specific implementation aspects, and are not used to limit the present invention.

Unless otherwise specified to the contrary, in the entire specification describing the present invention, a certain part "includes" or "includes" a certain component means that it may also include other components, rather than exclude other components.

In addition, unless otherwise specified, the singular form used in the specification and the scope of the patent application may also include the plural form.

In display devices, in particular, cover window films applied to smart devices are pressed countless times by touch pens or nails. Therefore, when the anti-press performance is not good, the display surface will be worn or damaged, resulting in problems such as shortening the life of the display.

In addition, when a hard coat layer or the like is formed on the upper part, the film on the lower part may become cloudy due to the solvent. Therefore, the inventors of the present invention have found a polyimide-based film that allows the display to have excellent anti-pressing performance against external forces and excellent optical properties. Even if a hard coat layer is formed on the upper part, the polyimide-based film has excellent resistance to pressure. The phenomenon of white turbidity occurred, thus completing the present invention.

In order to achieve the above object, the present invention provides a polyimide-based film. When a load is applied to the surface of the polyimide-based film with a Yilixin pen, the maximum load satisfies the following relational formula 1.

[Relationship 1]

In relation 1, F _e is the maximum load (N) that does not cause scratches when a load is applied to the surface of the polyimide film with a Yilixin pen, and T _e is the thickness of the polyimide film (μm ).

Preferably, the relational expression 1 can satisfy 0.07 to 0.10.

When the relational expression 1 is satisfied as described above, it can have the performance of protecting internal components and modules that can replace the existing toughened glass. In addition, the polyimide-based film achieves remarkably excellent pressing characteristics, so when applied to a cover window film, there is no pressing phenomenon caused by a stylus or hand, and impact resistance can be further improved, and a hard coat is formed on the upper part. No white turbidity occurs after layering. On the other hand, when the relational expression 1 is less than 0.07, the pressing phenomenon caused by the stylus or hand may occur. When the relational expression 1 exceeds 0.11, in the case of being used as a flexible cover window film, a hard coat layer is formed on the upper part At times, white turbidity may occur.

By satisfying the relational formula 1 as described above, the polyimide-based film can achieve excellent pressing characteristics with the polyimide-based film of the present invention in the overall thickness without relying on the increase in thickness. In particular, when the relational expression 1 is satisfied, it has excellent pressing characteristics within the overall thickness range that can satisfy the weight reduction, thinning, and flexibility of the display device. Specifically, the display panel can be prevented from being deformed under pressure when pressurized, and it can be applied to display devices that require weight reduction, thinning, and flexibility.

The polyimide-based film of the present invention can achieve excellent anti-press performance and surface restoring force by satisfying the above-mentioned pressing characteristics, thereby preventing damage and loss of the protected display, and thus can bring about the effect of improving the lifespan.

Preferably, in the relational formula 1, F _e can be 3.0 to 6.5 N, and T _e can be 25 to 100 μm. More preferably, in relation 1, F _e may be 4.0 to 6.0 N, and T _e may be 40 to 90 μm.

When the maximum load and thickness of the measurement are satisfied as described above, when external force is continuously applied to the display, damage and wear of the display caused by a strong impact can be prevented, and therefore the life span of the display can be prevented from being drastically shortened. In addition, even if a hard coat layer is formed on the polyimide-based film, white turbidity does not occur, so it is particularly suitable for transparent displays.

When the load applied to the surface of the polyimide-based film of the present invention with the Yilixin pen has the aforementioned high value, the resistance to external force applied by a stylus or hand is excellent, and therefore it is provided as When covering the window film, the display can be more reliably protected from wear and tear. In addition, the external force has an excellent surface restoring force, and therefore is excellent in achieving the above-mentioned effects.

According to an embodiment of the present invention, the above-mentioned maximum load of the polyimide-based film measured with the yilixin pen varies according to the thickness, but has excellent pressing characteristics in the overall thickness. Therefore, when provided as a cover window film, the external force applied to the display can also provide excellent anti-press performance, and thus can prevent the loss and damage of the display.

According to an embodiment of the present invention, the yellow index of the polyimide film measured according to the ASTM E313 standard may be 3.0 or less, preferably 2.9 or less, specifically 1.0 to 3.0, preferably 1.0 to 2.9. By having a low yellow index as described above, not only pressing characteristics but also excellent optical characteristics can be achieved. The yellow index can be measured on the basis of a polyimide-based film having a thickness of 50 μm.

The polyimide-based film of one embodiment of the present invention is produced by the following method: prepolymerizing a diamine containing an aromatic group and an aromatic dichloride to obtain an amine-terminated polyamide-blocked polyamide An amine is then added to an aromatic dianhydride containing a fluorine-based aromatic dianhydride to prepare polyamide imide, which is then made into a film.

In the present invention, with respect to 1 mol of the aromatic group-containing diamine, 0.6 to 0.9 mol of aromatic dichloride and 0.05 to 0.3 mol of the aromatic containing fluorine-based aromatic dianhydride can be used. Group dianhydrides are polymerized.

In the present invention, in the dimethicone chloride, 80 to 100 mole% of the total dimethicone chloride can be used for terephthalic acid chloride.

In the present invention, in the aromatic dianhydride containing the fluorine-based aromatic dianhydride, the content of the fluorine-based aromatic dianhydride may be 30 to 100 mol% of the total aromatic dianhydride.

According to an embodiment of the present invention, the diamine containing an aromatic group (hereinafter referred to as "aromatic diamine") may be selected from 2,2'-bis(trifluoromethyl)-benzidine, for example (TFMB), bis(3-aminophenyl) ash (3DDS), bis(4-aminophenyl) ash (4DDS), o-phenylenediamine (o-PDA), p-phenylenediamine (p-PDA), M-phenylenediamine (m-PDA), diaminodiphenyl ether (ODA), diaminodiphenylmethane (MDA), bisaminophenylhexafluoropropane (HFDA), 1,3-bis(4-aminophenoxy) One or more of benzene (TPE-R), etc., but it is not limited to this. In addition, when 2,2'-bis(trifluoromethyl)-benzidine (TFMB) is used in the present invention, the desired effect of the present invention can be better obtained, so it is better.

According to an embodiment of the present invention, the fluorine-based aromatic dianhydride may be, for example, an aromatic dianhydride substituted with a fluorine group without limitation, such as 4,4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA) , But not limited to this. In addition, the aromatic dianhydride that can be mixed with the fluorine-based aromatic dianhydride may be selected from, for example, 1,2,4,5-pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), and two Benzophenone tetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic dianhydride (ODPA), sulfonic acid diphthalic anhydride (SO2DPA), (isopropylidene diphenoxy) Bis(phthalic anhydride) (6HDBA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride ( TDA), bis (3,4-dicarboxyphenyl) dimethyl silane dianhydride (SiDA) and bis (dicarboxy phenoxy) diphenyl sulfide dianhydride (BDSDA), etc., but not Limited to this.

In the present invention, in the aromatic dianhydride containing the fluorine-based aromatic dianhydride, when the content of the fluorine-based aromatic dianhydride is 30 to 100 mol% of the total aromatic dianhydride, the present invention can be well realized The purpose is therefore better.

In the present invention, the aromatic dichloride contains terephthalic acid chloride (TPC). Examples of the dimethicone chloride that can be mixed with the terephthalic acid chloride are not limited as long as it is an aromatic dimethicone chloride. It may contain, for example, selected from isophthalic acid chloride (IPC), 4,4'-dichlorodiphenyl ether (DEDC), 1,1'-biphenyl-4,4'-dimethyl chloride (BPDC) , 1,4-naphthalenedimethic acid chloride (1,4-NaDC), 2,6-naphthalenedimethic acid chloride (2,6-NaDC) and 1,5-naphthalenedimethic acid chloride (1,5-NaDC) ), etc., or a mixture of two or more of them, preferably one or more selected from the group consisting of terephthalic acid chloride, meta-phthalic acid chloride, and the like.

In the present invention, in the dimethicone chloride, 80 to 100 mol% of the total dimethicone chloride can be used for terephthaloyl chloride. When the content is as described above, the pressing characteristics can be improved, and by satisfying the above content At the same time, it satisfies the oligomer polymerization and heat treatment conditions, which can achieve more excellent pressing characteristics.

In addition, it is surprising that the polyimide film of the present invention can significantly reduce the yellow index, and at the same time can have excellent anti-press performance and external force recovery.

The polyimide-based film of the present invention is produced by the following method: prepolymerizing an aromatic diamine and an aromatic dichloride to obtain an amine-terminated polyimide block polyamide, and then adding a fluorine-based aromatic The aromatic dianhydride of the dianhydride is used to prepare polyamide acid, and the polyamide acid is imidized to form a polyamide imide film.

The polyamide resin composition is a solution of the above-mentioned monomers, and may contain a polymerization solvent to perform solution polymerization. The type of the polymerization solvent is not particularly limited. For example, the polymerization solvent may be a polar solvent, and specifically may include N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP). , Dimethylformamide (DMF), dimethyl sulfide (DMSO), acetone, ethyl acetate and m-cresol, etc., one or more polymerization solvents.

According to an embodiment of the present invention, the polyamide resin composition can be amideified to obtain a polyamide resin.

The imidization may be performed, for example, by thermal imidization, chemical imidization, or may be simultaneously performed by thermal imidization and chemical imidization. In addition, the imidization may be performed before coating the polyamide resin composition on the substrate, or may be performed after coating the polyamide resin composition on the substrate, but is not limited thereto.

As a specific example, the chemical imidization may include one or more selected from the group consisting of an imidization catalyst and a dehydrating agent in the polyamide acid resin composition. Here, the dehydrating agent can be selected from acetic anhydride (Acetic anhydride), phthalic anhydride (Phthalic anhydride) and maleic anhydride (Maleic anhydride), for example, one or more selected from the group, the imidization catalyst can be used, for example, selected from One or more of Pyridine, Isoquinoline, β-quinoline, etc., but not limited thereto.

More preferably, the chemical imidization may include an imidization catalyst and a dehydrating agent in the polyamide resin composition, and may be performed at a temperature of 30 to 70° C. for more than 20 minutes, specifically, it may be performed for 30 minutes. the above. In addition, by performing chemical imidization as described above, it is possible to ensure excellent anti-press performance and surface restoring force, and no white turbidity occurs after the hard coat layer is formed on the polyimide-based film. In addition, by satisfying the relational formula 1, the display can be more reliably protected from wear and damage.

As a specific example, the thermal imidization may be heat-treated at a temperature above 250°C. Specifically, the heat treatment may be performed at 250 to 350°C for 1 minute to 2 hours, and preferably, the heat treatment may be performed at 260 to 350°C for 30 minutes to 2 hours. When the heat treatment is performed as described above, a degree of imidization of 99% or more can be ensured, the problem of solvent residue can be minimized, and excellent pressing characteristics and strength can be provided. In addition, when thermal imidization and chemical imidization are performed at the same time, the above-mentioned physical properties can be further improved. In addition, in the thermal imidization, before the heat treatment is performed at a temperature of 250° C. or higher, the temperature rise may be performed at a temperature of 250° C. or lower in stages, but it is not limited thereto.

The production method of the present invention may carry out the following steps: the first step is to react the aromatic diamine and the aromatic dichloride to prepare the amide-based oligomer; and the second step is to further include the amide-based oligomer. Add dianhydride and react.

When a film is produced by the polymerization of the amine-terminated polyamide oligomer as described above, even if the polymerization concentration is increased, that is, the solid content is increased, it has the advantage of excellent uniformity of the polymerization reaction, and in addition to achieving excellent optical properties In addition, it is also possible to achieve high-pressing characteristics satisfying relational formula 1.

Specifically, according to an embodiment of the present invention, the formula weight of the amide-based oligomer in the first step may be 500 to 10,000 grams/mole (g/mol), and the molecular weight may preferably be 500 To 5000 g/mol. When having the molecular weight as described above, the relational formula 1 can be satisfied, and thus the external force has excellent surface restoring force, and excellent optical characteristics can be achieved. In addition, it is possible to prevent the phenomenon of cloudiness that occurs after the hard coat layer is formed on the manufactured polyimide-based film.

According to an embodiment of the present invention, the weight average molecular weight of the polyimide film used to make the polyimide film may be 300,000 to 400,000 g/mol, and the polydispersity index (PDI) related to the molecular weight distribution may be, for example 2.3 to 2.8, but not limited to this.

The polyimide film of the present invention is made of polyimide or polyimide having a uniform and narrow polydispersity index as described above, so that uniform physical properties are achieved in the entire polyimide film , And can show excellent pressing characteristics. Moreover, when the temperature and time conditions of the oligomerization method and the imidization described above are satisfied, the above-mentioned weight average molecular weight and polydispersity index can be realized, and the above-mentioned weight average molecular weight and polydispersity index can be realized by satisfying the relationship The excellent pressing characteristics of Formula 1 further ensure safety, and can prevent white turbidity after forming a hard coat layer on the upper part.

According to an embodiment of the present invention, relative to the total weight, the content of the residual solvent of the polyimide-based film may be 3% by weight or less. Specifically, relative to the total weight, the content of the residual solvent of the polyimide-based film may be 0.01 to 3% by weight, preferably 0.01 to 1% by weight. Here, the residual solvent content is measured as follows, that is, the weight change of the polyimide-based film measured by thermogravimetric analysis in the range of 150 to 370 ℃ is measured, and the weight W ₁₅₀ at 150 ℃ is subtracted at 370 ℃ The value of the lower weight W ₃₇₀ was judged to be the solvent remaining in the film. By having the above-mentioned content of the residual solvent, the pressing characteristics can be significantly improved, and swelling or shrinkage caused by the external environment does not occur, so the quality reliability can be further improved. In addition, after forming a hard coat layer on the polyimide-based film, white turbidity does not occur, so it can be used as a high-quality cover window film.

Another embodiment of the present invention provides a display device including a display panel and the above-mentioned polyimide-based film formed on the display panel.

According to an embodiment of the present invention, as far as the display device is concerned, as long as it is a field that requires excellent pressing characteristics, there is no particular limitation, and a display panel suitable for the display device can be selected and provided.

Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following embodiment is only a preferred embodiment of the present invention, and the present invention is not limited to the following embodiment.

The physical properties of the present invention are measured in the following manner.

(1) Yellow index

According to the ASTM E313 standard, the films produced in the Examples and Comparative Examples were measured with a Colorimeter (HunTerLab, ColorQuest XE) based on a film with a thickness of 50 μm.

(2) Weight average molecular weight (Mw) and polydispersity index (PDI)

The weight average molecular weight and polydispersity index of the produced film were measured in the following manner.

First, the film sample was dissolved in a DMAc eluent containing 0.05 M LiBr and used as a sample.

GPC (Waters GPC system), Waters 1515 isocratic HPLC Pump (Waters 1515 isocratic HPLC Pump), Waters 2414 refractive index detector (Waters 2414) are used in the measurement. Refractive Index detector), gel permeation chromatography column (GPC Column) is connected to Olexis column, Polypore column and mixed D column, the solvent uses DMAc solution, the standard substance uses polymethyl methacrylate (PMMA STD, Mw 2136000 g/mol ), and perform analysis at 35 ℃ with a flow rate of 1 mL/min.

(3) Pressing characteristics measured by Yilixin pen

The film sample stored in a constant temperature and humidity room with a temperature of 25 ℃ and a humidity of 50% for more than 24 hours is placed on the glass plate and fixed, and then the hardness test pen 318S (Hardness Test Pencil Model 318S) a pen with a test lead of 0.75 cm in diameter, change the load in 0.1 N steps each time, and scratch more than 3 cm in the vertical direction, and record the maximum value of the load that does not produce scratches. After a total of 5 times, the average value is taken, and the average value is rounded up and used as the measurement value.

(4) Measurement of residual solvent content

The content of the residual solvent is measured as follows, that is, using TGA (Discovery of TA Company), the value of the weight W ₁₅₀ at 150 ℃ minus the weight W ₃₇₀ at 370 ℃ is judged as the solvent remaining in the film. Here, the measurement conditions are as follows: the temperature is increased to 400°C at a heating rate of 30°C/min, and the weight change in the range of 150 to 370°C is measured.

[Example 1]

Under a nitrogen atmosphere, add dichloromethane, pyridine, terephthalic acid chloride (TPC) and 2,2'-bis(trifluoromethyl)-benzidine (TFMB) to the reactor, and stir at 25°C for 2 hour. Here, the molar ratio of TPC:TFMB is set to 86:100, and the solid content is adjusted to 10% by weight.

After that, the reactant was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain an amide-based oligomer. The prepared amide The molecular weight (FW) of the oligomer is 1670 g/mol.

Under a nitrogen atmosphere, in the reactor, add the oligomer to N,N-dimethylacetamide (DMAc) and stir well, and then add 14 mol of 4, relative to 100 mol of TFMB, 4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA), fully stirred to dissolve, and reacted to obtain a polyamide resin composition. The solid content of each monomer was adjusted to 6.5% by weight. With respect to the number of moles of the total dianhydride, 2.5 moles of Pyridine and Acetic Anhydride were added to the polyamide resin composition, and the mixture was stirred at 60° C. for 1 hour. After that, the solution was precipitated in an excessive amount of methanol, and then filtered to obtain a solid material, and the solid material was vacuum dried at 50°C for 6 hours or more to obtain polyimide powder. Here, the weight average molecular weight of polyimide imine is 310,000 g/mol, and the polydispersity index (PDI) is 2.31. The polyimide powder was diluted in DMAc and dissolved to 20% by weight to prepare a composition for forming a polyimide-based film.

The obtained composition for forming a polyimide-based thin film was cast on a glass substrate by a bar coating method using an applicator (Applicator). Dry at 80 ℃ for 30 minutes and at 100 ℃ for 1 hour, after which, heat treatment in a vacuum oven at a heating rate of 20 ℃/min for 2 hours to 270 ℃, then cool at room temperature, and form on the glass substrate The film was separated from the substrate to obtain a polyamide imide film with a thickness of 50 μm. The residual solvent content of the polyimide film was 0.5% by weight.

[Example 2]

Under nitrogen atmosphere, add dichloromethane, pyridine, terephthalic acid chloride (TPC) and 2,2'-bis(trifluoromethyl)-benzidine (TFMB) to the reactor, and stir at 25 ℃ 2 hours. Here, the molar ratio of TPC:TFMB is set to 71:100, and the solid content is adjusted to 10% by weight.

After that, the reactant was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain an amide-based oligomer. The prepared amide The molecular weight (FW) of the oligomer is 1580 g/mol.

Under a nitrogen atmosphere, in a reactor, add the oligomer to N,N-dimethylacetamide (DMAc) and stir well, and then add 11 mol of 4, with respect to 100 mol of TFMB, 4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA) and 18 mols of biphenyltetracarboxylic dianhydride (BPDA), fully stirred to dissolve, and reacted to prepare a polyamide resin composition. The solid content of each monomer was adjusted to 6.5% by weight. With respect to the number of moles of the total dianhydride, 2.5 times moles of pyridine and acetic anhydride were added to the composition, and stirred at 60°C for 1 hour. After that, the solution was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain a polyimide powder. Here, the weight average molecular weight of polyimide imine is 315000 g/mol, and the polydispersity index (PDI) is 2.40. The polyimide powder was diluted in DMAc and dissolved to 20% by weight to prepare a composition for forming a polyimide-based film.

The obtained composition for forming a polyimide-based thin film was cast on a glass substrate by a bar coating method using a coater. After that, it was heat-treated in a vacuum oven for 1 hour to 270° C., and then cooled at normal temperature, and the film formed on the glass substrate was separated from the substrate to obtain a polyamide imide film with a thickness of 50 μm. The content of the residual solvent in the polyimide film was 0.4% by weight.

[Example 3]

It was manufactured by the same method as in Example 1, except that the polyimide film was made to be 80 μm. Here, the content of the residual solvent of the polyimide film is 0.45% by weight.

[Example 4]

It was manufactured by the same method as in Example 1, except that the polyimide film was made to be 30 μm. Here, the content of the residual solvent of the polyimide film is 0.5% by weight.

[Example 5]

Under a nitrogen atmosphere, add dichloromethane, pyridine, terephthalate chloride (TPC), 1,1'-biphenyl-4,4'-dimethyl chloride (BPDC) and 2,2' to the reactor -Bis(trifluoromethyl)-benzidine (TFMB), stirred at 25°C for 2 hours. Here, the molar ratio of TPC:BPDC:TFMB is set to 67:10:100, and the solid content is adjusted to 10% by weight.

After that, the reactant was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain an amide-based oligomer. The prepared amide The molecular weight (FW) of the oligomer is 1580 g/mol.

Under a nitrogen atmosphere, in the reactor, add the oligomer to N,N-dimethylacetamide (DMAc) and stir well, and then add 23 mol of 4, with respect to 100 mol of TFMB, 4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA), fully stirred to dissolve, and reacted to obtain a polyamide resin composition. The solid content of each monomer was adjusted to 6.5% by weight. With respect to the number of moles of the total dianhydride, 2.5 times moles of pyridine and acetic anhydride were added to the composition, and stirred at 60°C for 1 hour. After that, the solution was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain a polyimide powder. Here, the weight average molecular weight of polyimide imine is 303,000 g/mol, and the polydispersity index (PDI) is 2.35. The polyimide powder was diluted in DMAc and dissolved to 20% by weight to prepare a composition for forming a polyimide-based film.

The obtained composition for forming a polyimide-based thin film was cast on a glass substrate by a bar coating method using a coater. After that, it was heat-treated in a vacuum oven for 1 hour to 270° C., and then cooled at normal temperature, and the film formed on the glass substrate was separated from the substrate to obtain a polyamide imide film with a thickness of 50 μm. The residual solvent content of the polyimide film was 0.5% by weight.

[Example 6]

Under a nitrogen atmosphere, the reactor was charged with dichloromethane, pyridine, terephthalic acid chloride (TPC), 4,4'-dichlorodiphenyl ether (DEDC) and 2,2'-bis(trifluoromethyl) Benzidine (TFMB), stirred at 25 ℃ for 2 hours. Here, the molar ratio of TPC:DEDC:TFMB is set to 68:11:100, and the solid content is adjusted to 10% by weight.

After that, the reactant was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain an amide-based oligomer. The prepared amide The molecular weight (FW) of the oligomer is 1520 g/mol.

Under a nitrogen atmosphere, in a reactor, add the oligomer to N,N-dimethylacetamide (DMAc) and stir well, and then add 21 mol of 4, with respect to 100 mol of TFMB, 4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA), fully stirred to dissolve, and reacted to obtain a polyamide resin composition. The solid content of each monomer was adjusted to 6.5% by weight. With respect to the number of moles of the total dianhydride, 2.5 times moles of pyridine and acetic anhydride were added to the composition, and stirred at 60°C for 1 hour. After that, the solution was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain a polyimide powder. Here, the weight average molecular weight of polyimide imine is 322,000 g/mol, and the polydispersity index (PDI) is 2.26. The polyimide powder was diluted in DMAc and dissolved to 20% by weight to prepare a composition for forming a polyimide-based film.

The obtained composition for forming a polyimide-based thin film was cast on a glass substrate by a bar coating method using a coater. After that, it was heat-treated in a vacuum oven for 1 hour to 270° C., and then cooled at normal temperature, and the film formed on the glass substrate was separated from the substrate to obtain a polyamide imide film with a thickness of 50 μm. The content of the residual solvent in the polyimide film was 0.3% by weight.

[Example 7]

Under a nitrogen atmosphere, add dichloromethane, pyridine, terephthalic acid chloride (TPC) and 2,2'-bis(trifluoromethyl)-benzidine (TFMB) to the reactor, and stir at 25°C for 2 hour. Here, the molar ratio of TPC:TFMB is set to 75:100, and the solid content is adjusted to 10% by weight.

After that, the reactant was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain an amide-based oligomer. The prepared amide The molecular weight (FW) of the oligomer is 1610 g/mol.

Under a nitrogen atmosphere, in the reactor, add the oligomer to N,N-dimethylacetamide (DMAc) and stir well, and then add 16 mol of 4, with respect to 100 mol of TFMB, 4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA) and 9 mols of biphenyltetracarboxylic dianhydride (BPDA), fully stirred to dissolve, and reacted to prepare a polyamide resin composition. The solid content of each monomer was adjusted to 6.5% by weight. With respect to the number of moles of the total dianhydride, 2.5 times moles of pyridine and acetic anhydride were added to the composition, and stirred at 60°C for 1 hour. After that, the solution was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain a polyimide powder. Here, the weight average molecular weight of polyimide imine is 311,000 g/mol, and the polydispersity index (PDI) is 2.33. The polyimide powder was diluted in DMAc and dissolved to 20% by weight to prepare a composition for forming a polyimide-based film.

The obtained composition for forming a polyimide-based thin film was cast on a glass substrate by a bar coating method using a coater. After that, it was heat-treated in a vacuum oven for 1 hour to 270° C., and then cooled at normal temperature, and the film formed on the glass substrate was separated from the substrate to obtain a polyamide imide film with a thickness of 50 μm. The residual solvent content of the polyimide film was 0.4% by weight.

[Example 8]

Under nitrogen atmosphere, add dichloromethane, pyridine, terephthalic acid chloride (TPC), isophthalic acid chloride (IPC) and 2,2'-bis(trifluoromethyl)-benzidine to the reactor (TFMB), stirring at 25°C for 2 hours. Here, the molar ratio of TPC:IPC:TFMB is set to 75:10:100, and the solid content is adjusted to 10% by weight.

After that, the reactant was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain an amide-based oligomer. The prepared amide The molecular weight (FW) of the oligomer is 1610 g/mol.

Under a nitrogen atmosphere, in a reactor, add the oligomer to N,N-dimethylacetamide (DMAc) and stir well, and then add 15 mol of 4, with respect to 100 mol of TFMB, 4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA), fully stirred to dissolve, and reacted to obtain a polyamide resin composition. The solid content of each monomer was adjusted to 6.5% by weight. With respect to the number of moles of the total dianhydride, 2.5 moles of pyridine and acetic anhydride were added to the polyamide resin composition, and the mixture was stirred at 60°C for 1 hour. After that, the solution was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain a polyimide powder. Here, the weight average molecular weight of polyimide imine is 340,000 g/mol, and the polydispersity index (PDI) is 2.42. The polyimide powder was diluted in DMAc and dissolved to 20% by weight to prepare a composition for forming a polyimide-based film.

The obtained composition for forming a polyimide-based thin film was cast on a glass substrate by a bar coating method using a coater. Dry at 80 ℃ for 30 minutes and at 100 ℃ for 1 hour, after which, heat treatment in a vacuum oven at a heating rate of 20 ℃/min for 2 hours to 270 ℃, then cool at room temperature, and form on the glass substrate The film was separated from the substrate to obtain a polyamide imide film with a thickness of 50 μm. The residual solvent content of the polyimide film was 0.5% by weight.

[Comparative Example 1]

Under nitrogen atmosphere, add dichloromethane and 2,2'-bis(trifluoromethyl)-benzidine (TFMB) to the reactor and stir well, then add 4,4'-(hexafluoroisopropylene) diphthalein After the acid anhydride (6FDA) is fully stirred to dissolve, terephthalic acid chloride (TPC) is added, and then stirred at 25°C for 6 hours to dissolve and react, thereby preparing a polyamide resin composition. Here, the amount of each monomer is shown in the composition ratio of Table 1 below, the molar ratio of TFMB:6FDA:TPC is set to 100:14:86, the solid content is adjusted to 6.5% by weight, and the temperature of the reactor is Keep it at 30°C. Next, 2.5 times moles of pyridine and acetic anhydride of the total dianhydride were added to the solution, and stirred at 60°C for 1 hour.

After that, the solution was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain a polyimide powder. Here, the weight average molecular weight of polyimide imine is 245000 g/mol, and the polydispersity index (PDI) is 3.2. The polyimide powder was diluted in DMAc and dissolved to 20% by weight to prepare a composition for forming a polyimide-based film.

The obtained composition for forming a polyimide-based thin film was cast on a glass substrate by a bar coating method using a coater. Dry at 80 ℃ for 30 minutes and at 100 ℃ for 1 hour, after which, heat treatment in a vacuum oven at a heating rate of 20 ℃/min for 2 hours to 270 ℃, then cool at room temperature, and form on the glass substrate The film was separated from the substrate to obtain a polyamide imide film with a thickness of 50 μm. The residual solvent content of the polyimide film was 0.5% by weight.

[Comparative Example 2]

It was manufactured by the same method as in Comparative Example 1, except that the polyimide film was made 30 μm. Here, the content of the residual solvent of the polyimide film is 0.5% by weight.

[Comparative Example 3]

It was produced by the same method as in Comparative Example 1, except that the polyimide film was made to be 80 μm. Here, the content of the residual solvent of the polyimide film is 0.6% by weight.

[Comparative Example 4]

The composition for forming the polyimide-based thin film obtained in Example 1 was cast on a glass substrate by using a coater and a bar coating method. Dry at 80 ℃ for 30 minutes and at 100 ℃ for 1 hour. After that, heat treatment in a vacuum oven at a temperature increase rate of 20 ℃/min for 30 minutes to 240 ℃, then cool at room temperature, and form on the glass substrate The film was separated from the substrate to obtain a polyamide imide film with a thickness of 50 μm. The content of the residual solvent in the polyimide film was 3.2% by weight.

[Comparative Example 5]

It was manufactured by the same method as Comparative Example 4 except that the polyimide film was made 30 μm. Here, the content of the residual solvent of the polyimide film is 3.1% by weight.

[Comparative Example 6]

It was produced by the same method as in Comparative Example 4 except that the polyimide film was made to be 80 μm. Here, the content of the residual solvent of the polyimide film is 3.2% by weight.

[Comparative Example 7]

Under nitrogen atmosphere, add dichloromethane, pyridine, terephthalic acid chloride (TPC), isophthalic acid chloride (IPC) and 2,2'-bis(trifluoromethyl)-benzidine to the reactor (TFMB), stirring at 25°C for 2 hours. Here, the molar ratio of TPC:IPC:TFMB is set to 20:50:100, and the solid content is adjusted to 10% by weight.

After that, the reactant was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for more than 6 hours to obtain an amide-based oligomer. The prepared amide The molecular weight (FW) of the oligomer is 1410 g/mol.

Under a nitrogen atmosphere, in a reactor, add the oligomer to N,N-dimethylacetamide (DMAc) and stir well, and then add 20 mol of 4, with respect to 100 mol of TFMB, 4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA), fully stirred to dissolve, and reacted to obtain a polyamide resin composition. The solid content of each monomer was adjusted to 6.5% by weight. With respect to the number of moles of the total dianhydride, 2.5 moles of pyridine and acetic anhydride were added to the polyamide resin composition, and the mixture was stirred at 60°C for 1 hour. After that, the solution was precipitated in an excess of methanol, and then filtered to obtain a solid. The solid was vacuum-dried at 50°C for 6 hours or more to obtain a polyimide powder. Here, the weight average molecular weight of polyimide imine is 300,000 g/mol, and the polydispersity index (PDI) is 2.52. The polyimide powder was diluted in DMAc and dissolved to 20% by weight to prepare a composition for forming a polyimide-based film.

The obtained composition for forming a polyimide-based thin film was cast on a glass substrate by a bar coating method using a coater. Dry at 80 ℃ for 30 minutes and at 100 ℃ for 1 hour. After that, heat treatment in a vacuum oven at a heating rate of 20 ℃/min for 2 hours to 270 ℃, and then cool at room temperature to form the glass substrate. The film was separated from the substrate to obtain a polyamide imide film with a thickness of 50 μm. The content of the residual solvent in the polyimide film was 0.6% by weight.

[Comparative Example 8]

Except that the same content of cyclobutanetetracarboxylic dianhydride (CBDA) is used instead of 4,4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA), a thickness of 50 μm is obtained by the same method as in Example 1. The polyimide film. The residual solvent content of the polyimide film was 0.5% by weight.

[Comparative Example 9]

It was obtained by the same method as in Example 1, except that 7 mol of 4,4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA) and 7 mol of cyclobutanetetracarboxylic dianhydride (CBDA) were used Polyimide film with a thickness of 50 μm. The residual solvent content of the polyimide film was 0.5% by weight.

The physical properties (yellowness index, pressing characteristics) of the polyimide films produced in Example 1 to Example 8 and Comparative Example 1 to Comparative Example 9 were measured and shown in Table 1 below. In addition, the following hard coating composition was coated on the polyimide film using #18 Mayer Bar, and then dried at 60 ℃ for 5 minutes, using a high-pressure metal lamp at 1 J/ cm ^{2 was} irradiated with ultraviolet rays (UV), and then cured at 120°C for 15 minutes to form a hard coat with a thickness of 10 μm. Then, it was visually confirmed whether white turbidity occurred and is shown in Table 1 below.

○: White turbidity occurs.

×: No white turbidity occurred.

[Preparation of composition for forming hard coat layer]

Mix 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (ECTMS, TCI company) and water in a ratio of 24.64 g: 2.70 g (0.1 mol: 0.15 mol) to prepare a reaction solution, and add it Into a 250 mL two-neck (2-neck) flask. Add 0.1 mL of tetramethylammonium hydroxide (Aldrich) catalyst and 100 mL of tetrahydrofuran (Aldrich) to the above mixture, and stir at 25°C for 36 hours. After that, the layers were separated, and the product layer was extracted with dichloromethane (Aldrich), the water in the extract was removed with magnesium sulfate (Aldrich), and the solvent was vacuum dried to obtain epoxy siloxane resin . As measured by Gel Permeation Chromatography (GPC), the weight average molecular weight of the epoxysiloxane-based resin is 2500 g/mol.

Prepare and mix 30 g of the epoxysiloxane resin prepared as described above, and 10 g of (3',4'-epoxycyclohexyl)methyl 3,4-epoxycyclohexanecarboxy as a crosslinking agent Acid ester and 5 g of bis[(3,4-epoxycyclohexyl)methyl]adipate, 0.5 g of (4-methylphenyl)[4-(2-methyl) as a photoinitiator Propyl) phenyl] iodonium hexafluorophosphate and 54.5 g of methyl ethyl ketone.

[Table 1] Yellow index Yilixin pen pressing characteristics After the hard coating is formed, is there any white turbidity? Example 1 2.0 4.5 X Example 2 2.1 4.5 X Example 3 2.0 6.0 X Example 4 2.0 2.5 X Example 5 1.9 4.5 X Example 6 1.8 4.3 X Example 7 1.9 4.6 X Example 8 2.0 4.4 X Comparative example 1 3.1 2.5 ○ Comparative example 2 3.3 1.5 ○ Comparative example 3 3.2 5.0 ○ Comparative example 4 3.5 3.0 ○ Comparative example 5 3.3 2.0 ○ Comparative example 6 3.2 4.5 ○ Comparative example 7 2.9 3.0 ○ Comparative example 8 4.0 1.8 ○ Comparative example 9 3.1 1.7 ○

As shown in Table 1, when a load is applied to the surface of the polyimide-based film of the present invention with a Yilixin pen, the maximum load satisfies the relational formula 1. Therefore, it has excellent scratch resistance and strength, and when external forces such as pressing are applied At this time, due to the excellent surface restoring force, poor appearance can be prevented. In addition, the polyimide-based film of the present invention has excellent pressing characteristics and does not cause white turbidity even if a hard coat layer is formed on the upper part, so it is also suitable for use in transparent displays. In addition, for the polyimide-based film, the content of p-xylylenedichloride meets 60 to 80 mol relative to 100 mol of diamine, and it is produced by two or more stages of oligomer polymerization. Moreover, when the heat treatment condition is performed at a temperature of 250° C. or higher for 30 minutes or longer, the pressing characteristics satisfying the relational expression 1 are realized, and therefore, the desired physical properties can be realized.

Therefore, the polyimide-based film of the present invention enables the display to have excellent anti-pressing performance against external forces and also has excellent optical properties, so it is possible to provide a display device that prevents appearance defects.

As described above, the present invention has been described through specific content and specific exemplary embodiments, but this is only provided to facilitate a more comprehensive understanding of the present invention, and the present invention is not limited to the above exemplary embodiments. Those skilled in the art to which the present invention pertains can make various modifications and variations through this record.

Therefore, the present invention should not be limited to the illustrated exemplary embodiments. The scope of the patent application of the present invention and all content equivalent to or with equivalent modifications to the scope of the patent application belong to the scope of the present invention.

no

no

Claims (7)

A polyimide-based film, wherein, when a load is applied to the surface of the polyimide-based film with a Yilixin pen, the maximum load satisfies the following relationship 1: [Relationship 1]

Wherein, F _e is the maximum load (N) that does not cause scratches when a load is applied to the surface of the polyimide-based film with a Yilixin pen, and T _e is the thickness (μm) of the polyimide-based film. The polyimide-based film according to claim 1, wherein, in relational formula 1, F _e is 2.0 to 6.5 N, and T _e is 20 to 100 μm. The polyimide-based film according to claim 2, wherein F _e is 4.0 to 6.0 N. The polyimide-based film according to claim 1, wherein the yellow index of the polyimide-based film measured in accordance with ASTM E313 is 3.0 or less. The polyimide-based film according to claim 1, wherein the content of p-xylylenedichloride is 60 to 80 mol relative to 100 mol of diamine. The polyimide-based film according to claim 1, wherein the content of biphenyltetracarboxylic dianhydride is 5 to 20 mols relative to 100 mols of diamine. A display device comprising a display panel and the polyimide-based film according to any one of claims 1 to 6 formed on the display panel.