KR101929588B1 - Plastic Films for Transparent Flexible Substrates - Google Patents

Abstract

In order to further improve the thermal stability of a plastic film made of a phenoxy resin, a bisphenol-A type epoxy resin is blended with a phenoxy resin, and an imidazole type curing agent, which is a basic curing agent, and an isocyanate type curing agent are mixed, The present invention relates to a plastic film for a transparent flexible substrate having transparency and excellent heat resistance and flexibility. To this end, the plastic film for a transparent flexible substrate according to the present invention is characterized by comprising a bisphenol-A type epoxy resin, a phenoxy resin, and a curing agent, wherein the plastic film is formed in a thickness of 10 to 500 μm do.

Description

TECHNICAL FIELD [0001] The present invention relates to a plastic film for transparent flexible substrates,

In order to further improve the thermal stability of a plastic film made of a phenoxy resin, a bisphenol-A type epoxy resin is blended with a phenoxy resin, and an imidazole type curing agent, which is a basic curing agent, and an isocyanate type curing agent are mixed, To a plastic film for a transparent flexible substrate having transparency and excellent heat resistance and flexibility without being restricted by the curing property.

The development trend of information display is aimed at mobility and convenience in accordance with the mobility of information display terminal such as mobile phone and PDA at the center of high performance and high function that realizes objects in a realistic manner, There is a growing demand for transparent flexible displays (FDs) that are lightweight and easily foldable.

The above-mentioned transparent flexible display is a display manufactured using a thin and flexible substrate which can be bent or bent, and is distinguished as a rugged display, a bendable display, and a rollable display depending on the purpose and function thereof can do. In addition, it is also possible to use a conventional thin film transistor (TFT) substrate, a color filter substrate, a touch screen panel substrate, and a solar cell substrate for a liquid crystal display device (LCD) It is a display that is being developed to replace the heavy and fragile plate glass used in the flat panel display (FPD) with a thin and flexible substrate to secure various applications from space and form restrictions. Accordingly, ultimately, research and development are being continuously carried out aiming at the commercialization of a paper-like display.

As a key technology for realizing such transparent flexible display, transparent flexible substrate material technology, oil / inorganic material technology for low temperature process, flexible electronics and sealing technology are required in combination. Among them, Transparent flexible substrate materials have been recognized as the most critical component to determine performance, reliability and price.

Therefore, explaining the core characteristics required for a transparent flexible substrate material, thinner, lighter, cost and fairness can be suggested. As a substrate material for realizing this, metal foil, very thin glass, and a plastic substrate using a polymer have been studied. However, in order to realize industrial commercialization, Plastic substrates have attracted the greatest attention in terms of ensuring mass productivity through a roll-to-roll process.

Here, the advantages and disadvantages of each substrate material will be briefly described as follows. First, although the metal foil has heat resistance and flexibility, it is naturally limited in the field where a separate insulating coating layer is required and transparency is required. Next, thin glass has the advantages of good surface flatness and low permeability of moisture and oxygen, but it has a drawback that it is hard to apply to continuous process unlike other substrate materials. On the other hand, plastic substrates have been attracting attention as the most promising substrate materials in that the disadvantages of the above two substrate materials are overcome, and furthermore, they are not only lighter but also easily processed and have almost no restrictions on their form.

Examples of the polymer used for the plastic substrate include polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyarylate (PAR), polycarbonate (PC) and polyimide have.

However, these conventional plastic substrates commonly have a large coefficient of thermal expansion (CTE). That is, a polymer typically begins to undergo a physical change by the action of a local molecular chain near the glass transition temperature (Tg) of the polymer, and accordingly, in a high temperature process above the glass transition temperature, The thermal expansion coefficient of the glass is generally about several ppm / ° C, and the coefficient of thermal expansion of the polymer is relatively large at several tens ppm / ° C. Such a disadvantage may deteriorate the dimensional stability of a device such as a TFT or the like on a plastic substrate and cause cracking and peeling of the inorganic vapor deposition layer.

Recently, for the purpose of supplementing the disadvantages of these plastic substrate materials, there has been studied a thermosetting epoxy resin or a composite resin reinforced with a glass filler in a transparent resin such as acrylic. Such resin compositions are disclosed, for example, in Japanese Patent Application Laid-Open Nos. 6-337408, 200159015, 54-24993, 6-94523, and 5-140376 . However, when a thermosetting epoxy resin is used in a substrate using these conventional composite resins, the impact resistance is lowered due to the strong brittleness of the epoxy resin, so that it is difficult to produce a flexible film. When a glass filler is used for a transparent polymer resin, The birefringence phenomenon can be a problem. There is a disadvantage in that the thermal expansion coefficient is still large and the heat resistance is insufficient so that it is difficult to maintain high dimensional stability.

Apart from the above-mentioned conventional plastic substrate material and the composite resin, a resin composition which solves the refractive index problem in the case of using a siloxane non-water-soluble reaction to form a glass filler composite has recently been disclosed. For example, Korean Patent Publication No. 10-2010-0083697 discloses a composition having a high transparency and a low thermal expansion coefficient by using a transparent siloxane resin in which a glass filler is produced by a non-water-soluble reaction.

However, it still has weak mechanical strength such as rigidity, low durability, and is particularly susceptible to cracking and peeling in the manufacturing process due to its low adhesion to the inorganic vapor deposition layer. Further, due to the batch production process in which the glass filler is impregnated and subjected to an additional yield reaction, there is a limit to the production of a film by a continuous process for a reduction in price in addition to a sheet, and in particular, There is a difficulty in manufacturing the substrate material.

Herein, the core required properties of the polymer as a plastic substrate material can be summarized as described below.

1) Dimensional stability

2) Low coefficient of thermal expansion (CTE)

3) High barrier properties

4) Rigidity

5) High visible light transmittance

6) Durability

In addition, thinness, weight reduction, and ensuring continuous processes are required, and compatibility with various display substrates is required.

First, the dimensional stability of the substrate is a physical property required to minimize the deformation caused by the phenomenon of expansion and contraction when the polymer substrate is exposed to the maximum process temperature and time, and the heat resistance of each material is mainly used as an index thereof. Generally, heat resistance of 200 DEG C or more is required, and depending on the type of high-temperature process, heat resistance of 300 DEG C or more may be required.

Next, a value of 20 ppm / DEG C or less is generally preferred for the thermal expansion coefficient, but no polymer substrate satisfying this value is currently available. This is because an inorganic material (particularly, a driving part) is laminated on a plastic substrate. If a difference in thermal expansion coefficient between the substrate and a substrate is large in a high temperature process, cracks or peeling may occur in the deposited layer. Therefore, a material having a low coefficient of thermal expansion is suitable for a flexible display.

Next, in the case of barrier properties, the level required as a substrate material for replacing existing glass is considerably high. This can cause contaminants (oxygen, moisture, particles, etc.) flowing from the outside of the display to contaminate the liquid crystal or the driving device, or oxidize the anode metal layer in the case of the OLED, and may affect the lifetime of the display. Typically gatneunde a high value of water vapor permeability of the polymer is ^{1 ~ 100g / m 2 [day} ], the case of ^{LCD ~ 10 -2 g / m 2} [day], when the OLED is ^{10 -6 g / m 2 [day} ] Water permeability is required.

In the case of the next rigidity, it is important to determine the process suitability of the substrate, which is defined as a function of young's modulus ( E ), thickness ( t ), and poisson's ratio (v).

Rigidity = E x t3 / 12 (1-v) (1)

In the case of a plastic substrate, rigidity over a certain range is required. As can be seen from Equation (1), the rigidity is better as the strain of the substrate is lower and the elastic modulus is higher regardless of the thickness variation.

In the case of the next transmittance, high transparency should be maintained, without any change in scattering or reflectivity depending on the crystallinity or surface change of the polymer material due to important material characteristics that greatly affect the image characteristics and power consumption of the display. Most optical substrates currently used exhibit a high transmittance of 85% or more at 550 nm and the transmittance of the laminated film should not be significantly different.

Finally, in the case of durability, the lifetime of the flexible plastic substrate is very related. That is, a plastic substrate is a multilayer structure in which organic substances such as a base substrate, a barrier, and a transparent electrode are laminated, and internal stress is generated on the substrate side when bending or bending is given. adhesive failure occurs and cohesive failure in the deposited thin film layer is accompanied. Therefore, in order to realize a display such as a paper to which the flexible substrate ultimately aims, in particular, the durability must be ensured.

The advantages and disadvantages of the polymer used in the above-mentioned plastic substrate will be described below. First, PCs are known to have poor mechanical and optical properties, but are poorly resistant to chemicals. Therefore, there are many restrictions on solvents used (PR developer, PR remover, metal etchant, cleaning solvent). In order to solve such a problem, it is necessary to form a separate chemical resistance layer in order to secure chemical resistance on both sides of the substrate in the case of a PC substrate, and it is resistant to ultraviolet rays, (Out-gas), the thermal expansion coefficient is about 10 times larger than that of inorganic materials, and it has a disadvantage that it must be carried out at a low-temperature process (maximum operating temperature range, 150 to 180 ° C.) have.

Next, PET has a low hygroscopicity and low melting temperature, so it is easy to mold a polymer substrate at low process and manufacturing cost at a relatively low temperature. However, since it exhibits poor thermal stability due to low Tg and optical anisotropy, it can not be applied as a substrate for a display using a polarizing plate such as an LCD. Particularly, the PET molecular chain is recrystallized by heat treatment at 150 ° C or higher, The whitening phenomenon occurs, which causes the optical transmittance of the substrate to decrease.

Next, PEN is an optically anisotropic plastic exhibiting similar behavior to the above-mentioned PET, and has problems similar to those of PET in terms of thermal stability. However, in recent research and development results, PEN has been used as a substrate material And it is necessary to further research and development.

On the other hand, PES, commercialized for the first time by Sumitomo Bakelite of Japan, has heat resistance and is considered to be most actively applied to other plastic substrates. However, PES has weak chemical resistance, high thermal expansion coefficient and low maximum process temperature (180 ° C) Is a polymer having a high hygroscopicity, it is difficult to further dehydrate when it is in contact with water or left in the air for a long time. In addition, the price is more expensive than glass.

Next, PI is a polymer film widely applied to electric and electronic parts due to its excellent chemical resistance and heat resistance. It has a hygroscopic property (about 3 times) larger than that of the above-mentioned PES, Is required. The imide group in the molecular chain of PI is a group that imparts heat resistance and causes yellowing of the material. In particular, the light transmittance of PI is about 30 to 50% with respect to visible light of 550 nm. Such low optical properties are a big obstacle to the application of PI as a substrate material for displays. In recent years, a PI substrate with high Tg (> 300 ° C) was developed by Mitsubishi Gas Co., Ltd. under the trade name of Neopulim ^® L while optically transparent (visible light transmittance of 80% or more) have.

Another AryLite substrate is an optical substrate developed by Ferrania Image System, Italy. It has excellent heat resistance, optical and chemical properties compared to other plastic substrate materials, but also has a high thermal expansion coefficient and resistance to ultraviolet (UV) There is a limitation in the substrate process and the price is more expensive than the conventional glass.

Accordingly, the present inventors have studied various polymers that can be used as a plastic substrate material, and have come up with the inventions of a polymer capable of being used in addition to the polymer of the above-mentioned plastic substrate material and a composition therefor (Korean Patent Laid-Open Publication No. 10 -2012-0120643) . The inventors of the present invention have found that a thermosetting epoxy resin which is basically brittle and can not be obtained as a flexible film is sufficiently taken into consideration to fully satisfy the characteristics of a thermosetting epoxy resin, Of plastic film. Namely, the inventors came to develop a plastic film by paying attention to the thermoplastic and thermosetting properties of the phenoxy resin.

Japanese Patent Application Laid-Open No. 6-337408 Japanese Patent Application Laid-Open No. 2001-59015 Japanese Patent Office 54-24993 Japanese Patent Laid-Open No. 6-94523 Japanese Patent Laid-Open No. 5-140376 Korean Patent Publication No. 10-2010-0083697 Korean Patent Laid-Open No. 10-2012-0120643

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a plastic film made of a phenoxy resin, in which a bisphenol-A type epoxy resin is blended with a phenoxy resin, It is an object of the present invention to provide a plastic film for a transparent flexible substrate having an effect of being transparent and at the same time having excellent heat resistance and flexibility without being restricted in curability even when the thickness of the film is increased by using an imidazole type curing agent as a curing agent and an isocyanate type curing agent.

Another object of the present invention is to provide a thin film transistor (TFT) element substrate, a color filter substrate, a touch screen substrate, and the like for a liquid crystal display device (LCD) or an organic EL display device by using the plastic film as a polymer substrate material. Which can effectively replace glass substrates used in conventional flat panel displays (FPD) such as substrates for panels, touch screen panels, and solar cell substrates.

The above object is achieved by a plastic film for a transparent flexible substrate, characterized by comprising a bisphenol-A type epoxy resin, a phenoxy resin and a curing agent, wherein the plastic film is produced in the form of a thickness of 10 to 500 μm And a plastic film for a transparent flexible substrate.

The bisphenol-A epoxy resin has a weight average molecular weight of 200 to 10,000 and 5 to 30 parts by weight based on 100 parts by weight of the phenoxy resin.

Preferably, the phenoxy resin is selected from the group consisting of bisphenol A phenoxy, bisphenol F phenoxy, brominated phenoxy, phosphorus phenoxy, bisphenol A / bisphenol S phenoxy and caprolactone denatured phenoxy or siloxane denatured phenoxy And the like.

Here, the phenoxy resin has a weight average molecular weight of 1,000 to 100,000.

Here, the terminal of the phenoxy resin is characterized by containing at least one of an epoxy group, a hydroxyl group, an amine group, a fluorine group, a siloxane group and an amide group.

Preferably, the phenoxy resin comprises at least one of melamine, urea-formaldehyde, isocyanate functional prepolymer, phenol curing agent or amino-based curing agent as a crosslinking agent.

Here, the curing agent is a compound capable of reacting with an epoxy group and a compound capable of reacting with a hydroxyl group.

Here, the compound capable of reacting with the epoxy group is an amine type, acid anhydride type, phenol type or imidazole type, and the compound capable of reacting with the hydroxyl group is isocyanate type or urea type.

Preferably, the imidazole-based curing agent has the following structure, and is obtained by introducing a substituent substituting hydrogen at the 1-position and introducing a substituent into the carbon at 2-, 4- and 5-position of the imidazole ring Is a compound.

Here, the plastic film is prepared by solvent casting or melt extrusion, and the composition comprising the bisphenol-A type epoxy resin, the phenoxy resin and the curing agent alone or on a transparent polymer substrate is coated with a thin film or a thick film .

Here, the transparent polymer substrate may be any one of PET, PEN, PC, PES, and PI, and the coating thickness is 0.1 to 500 μm.

The plastic film for a transparent flexible substrate according to any one of claims 1 to 11 is used for a liquid crystal display element substrate, an organic EL display element substrate, a color filter substrate, a touch screen panel substrate, or a solar cell substrate And is used as a flexible plastic substrate replacing a glass substrate used for a TFT element substrate or an optical element substrate.

According to the present invention, in order to further improve the thermal stability of a plastic film made of a phenoxy resin, a bisphenol-A type epoxy resin is blended with a phenoxy resin, and an imidazole type curing agent which is a basic curing agent and an isocyanate type curing agent are mixed, The curing property is not restricted even if the thickness of the film is increased, and the film is transparent and at the same time has excellent heat resistance and flexibility.

Further, in the present invention, by using the plastic film as a polymer substrate material, a thin film transistor (TFT) element substrate, a color filter substrate, and a touch screen panel for a liquid crystal display (LCD) a flexible substrate can be advantageously replaced with a glass substrate used in a conventional flat panel display (FPD) such as a touch screen panel and a solar cell substrate.

Hereinafter, the present invention will be described in detail with reference to examples of the present invention. It will be apparent to those skilled in the art that these embodiments are provided by way of illustration only for the purpose of more particularly illustrating the present invention and that the scope of the present invention is not limited by these embodiments .

The present invention relates to a plastic film for a transparent flexible substrate, wherein the plastic film is composed of a bisphenol-A type epoxy resin and a phenoxy resin and is characterized by containing an imidazole-based curing agent and an isocyanate-based curing agent as a curing agent, To 500 [mu] m.

The bisphenol-A type epoxy resin and the phenoxy resin of the plastic film are basically thermoplastic polymers and have a low melting point, so that they can be used not only as a solvent casting method using a solvent but also as a direct melt extrusion ) Can be manufactured in a blend state with each other. By doing so, it can be freely obtained as a polymer substrate having various thicknesses in sheet or film form. Further, the bisphenol-A type epoxy resin and the phenoxy resin of the above plastic film have a structure capable of cross-linking due to the hydroxyl group located in the molecular chain, so that after the formation of the sheet or film, curing) can be performed. By doing so, a polymer substrate having more excellent thermal properties can be obtained.

Further, the bisphenol-A type epoxy resin and the phenoxy resin of the plastic film can be used as a plastic substrate material of a transparent flexible substrate which is excellent in transparency and is required to have transparency. Particularly, since there is no resistance against ultraviolet rays, It is possible to obtain a transparent flexible plastic substrate having no limitation in the substrate process. For example, it does not affect the curing process of the ultraviolet curable resin used for encapsulating the substrate as in the case of the OLED substrate.

Further, the bisphenol-A type epoxy resin and the phenoxy resin of the plastic film can be used as a composite of various compositions in order to more satisfactorily fulfill the functions required for the transparent flexible plastic substrate, and to obtain the phenoxy resin composition alone Or by applying it on another polymer base material.

Here, the bisphenol-A type epoxy resin of the plastic film is used as a main raw material for making a phenoxy resin as a transparent epoxy resin, so that it has the same molecular structure as the phenoxy resin in the basic structure, And having an epoxy functional group at both terminals, which is excellent in curing performance for forming a crosslinked structure compared to a phenoxy resin. When the bisphenol-A type epoxy resin is blended with a phenoxy resin, The heat resistance of the plastic substrate material can be increased.

On the other hand, an imidazole-based curing agent which is a basic compound as a curing agent for the plastic film has good curing properties at high temperatures and is excellent in heat resistance and can cure the bisphenol-A type epoxy resin alone. In addition, it functions as a curing accelerator capable of bonding an epoxy functional group of a bisphenol-A type epoxy resin with a hydroxyl group in the phenoxy resin, thereby forming a cured structure having a superior heat resistance. Therefore, if the imidazole-based curing agent is mixed with the isocyanate-based curing agent, the epoxy resin can be cured alone, the phenoxy resin can be cured alone, and the epoxy resin and the phenoxy resin can be cured. .

In the present invention, a polymer substrate material is prepared by using a bisphenol-A type epoxy resin and a phenoxy resin as described above and an imidazole-based curing agent and an isocyanate-based curing agent as a curing agent to form a polymer substrate material for a liquid crystal display device A glass substrate used in a conventional flat panel display (FPD) such as a thin film transistor (TFT) element substrate, a color filter substrate, a touch screen panel substrate, and a solar cell substrate. Which makes it possible to manufacture an excellent transparent flexible substrate which can be usefully replaced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is characterized in that the bisphenol-A type epoxy resin is contained in an amount of 5 to 30 parts by weight based on 100 parts by weight of the phenoxy resin in order to further improve the heat resistance of the transparent flexible substrate material. When the blending ratio of the bisphenol-A type epoxy resin exceeds 30 parts by weight, the brittleness of the finally obtained film is increased and the flexibility is lost. If the blending ratio is less than 5 parts by weight, the curing performance is not improved. Accordingly, the amount is preferably 5 to 30 parts by weight, more preferably 10 to 25 parts by weight, and most preferably 15 to 20 parts by weight.

The bisphenol A epoxy resin is most commonly used among epoxy resins and preferably has a weight average molecular weight of 200 to 10,000. Bisphenol A (BPA) and epichlorohydrin (ECH) are reacted in the presence of Alkali . The present invention includes those having the following structures.

In this case, n in the above structure is 0.12 to 12.0.

The bisphenol-A type epoxy resin has the following advantages. First, the curing shrinkage is less than that of other thermosetting resins due to the presence of epoxy functional groups at both ends. Second, it is repeated in C-C and C-O bonds in the basic structure and excellent in toughness and high temperature characteristics. Third, the existence of ether bond is excellent in chemical resistance and water resistance. Fourth, the ether bond is rotatable and has plasticity. Finally, the adhesiveness is high due to the regularity of the hydroxyl groups and the hydrocarbons.

Furthermore, since the bisphenol-A type epoxy resin has an epoxy group at the molecular end, it can basically form an intermolecular crosslinking structure by an epoxy curing reaction. Due to the hydroxyl group located in the molecular chain, (inter-molecular cross-linking) can be formed more densely. Therefore, additional curing can be performed before and after the formation of the sheet or film, and a plastic substrate having more excellent thermal properties can be obtained.

Examples of the curing agent for the curing reaction of the bisphenol-A type epoxy resin include an amine compound, an acid anhydride compound, a phenol compound, an imidazole compound, And compounds capable of reacting with hydroxyl groups can be used as long as they can cure a resin having a hydroxyl group as a functional group such as an isocyanate group or a urea group.

The present invention is characterized in that it comprises an imidazole curing agent which is a typical basic compound having a tertiary nitrogen especially for the curing reaction of a bisphenol-A type epoxy resin, 20 parts by weight, more preferably 3 to 15 parts by weight, and most preferably 5 to 10 parts by weight may be used.

The basic structure of the imidazole-based curing agent is as follows.

Herein, the imidazole compound as an epoxy resin curing agent or a curing accelerator is a pi hyper-heteroaromatic compound composed of two nitrogen atoms and three carbon atoms as in the above structure. In the imidazole ring, pyrrolyl nitrogen atom 3 Type nitrogen source is present in the ring and both of them have a mutual influence relationship. Both the pyrrolyl nitrogen and the pyridine-type nitrogen of the imidazole ring contribute to the reaction as the catalytic curing agent of the epoxy resin.

Further, in the imidazole compound, the basicity of the pyridine type tertiary nitrogen in the imidazole ring 3 position can be controlled to some extent by introducing a substituent at the 1-position and introducing a substituent at each position of the imidazole ring, By substituting hydrogen for positional nitrogen in accordance with various substitution reactions, it is possible to control the basicity of the imidazole ring as well as the pyridine-type 3-position nitrogen. Particularly, the carbon at the 2, 4 and 5 positions of the imidazole ring is suitable for the addition reaction, and the reactivity with the epoxy group can be controlled even when the substituent is introduced at the 4-position and the 5-position, and the imidazole compound Are conveniently classified into original imidazole, 1-position substituted imidazole, and imidazole-modified products. However, the present invention is not particularly limited in its use.

In addition, in the classification of the imidazole compound, the original imidazole is a compound obtained by dissolving 1,2-dicarbonyl compound, all compounds synthesized from aldehydes and ammonia, all compounds obtained via dehydrogenation of imidazoline compounds synthesized from dicyan and nitrile compounds Typically, 2-methylimidazole (2MZ), 2-ethyl-4 (5) methylimidazole (2E4MZ) and the like can be used in the present invention as catalyst type curing agents.

1-cyanoethyl-2-methylimidazole (2MZ-CN) or the like is an imidazole compound in which hydrogen at the 1-position of the original imidazole is substituted with acrylonitrile or benzylchloride And can be used for the present invention representatively. In addition, imidazole-modified products were obtained by modifying original imidazole and 1-position substituted imidazole with various compounds. In order to make the curing agent latent, 2,4-diamino-6- [2'-methylimidazole - (1 ')] - ethyl-1,3,5-triazone (2MZ-A) can be used in the present invention in the same manner as in the case of providing a one-component epoxy resin formulation. In addition, 2-Methylimidazole (2-methylimidazole), 2-Methyl-5-Nitroimidazole (2-methyl-5-nitroimidazole), 1-Methylimidazole (1-methylimidazole) 2-ethylimidazole, 2-phenylimidazole (2-PZ) (2-phenylimidazole), 2-ethylimidazole N-carbonyldiimidazole (NN-carbonylimidazole), 2-ethyl-4-carbaldehyde, 4-nitroimidazole Methylimidazole (2E4MZ) (2-ethyl-4-methylimidazole), 1,2-dimethylimidazole (1,2-dimethylimidazole), N-methylimidazole (N-methylimidazole) -Ethylimidazole), 2-propylimidazole (2-propylimidazole), 2-Isopropylimidazole (2-isopropylimidazole), 2-Bromo-4-Nitroimidazole ), 4-Iodoimidazole (4-iodoimidazole).

The imidazole-based curing agent has good curing properties at a high temperature and is excellent in heat resistance, and can not only cure the bisphenol-A type epoxy resin alone but also can cure the epoxy functional group of the bisphenol-A type epoxy resin and the hydroxyl group in the phenoxy resin And serves as a curing accelerator capable of bonding, thereby forming a cured structure having excellent heat resistance. Therefore, if the imidazole-based curing agent is mixed with the isocyanate-based curing agent, the epoxy resin can be cured alone, the phenoxy resin can be cured alone, and the epoxy resin and the phenoxy resin can be cured. .

The phenoxy resin used in the present invention is characterized in that the molecular chain has a linearly large molecular weight, unlike a solid epoxy resin in general, and is obtained through addition reaction from a solid epoxy resin such as bisphenol- do. Generally, a solid epoxy resin means a resin in which the number n of repeating molecular chains is usually in a solid state at room temperature or more, and solid epoxy resins having a number average molecular weight of about 900 (n = 1.97) to 10,000 (n = 34), and those with larger molecular weights are linear and classified as phenoxy resins. Generally, if the molecular weight is increased linearly, the thermoplastic property is obtained and the phenoxy resin is also basically thermoplastic. At the same time, the phenoxy resin contains a functional group capable of crosslinking reaction in the repeating unit of the molecular chain, and has a thermosetting property through thermal curing under the reaction catalyst.

The present invention includes a phenoxy resin having the following structure.

In this case, n in the structure is 35 to 400.

The phenoxy resin used in the present invention has the characteristics of a thermoplastic resin having a high molecular weight including a final curing structure of a thermosetting epoxy resin as a unit structure. Accordingly, it can be easily processed by a method such as melt extrusion by solid state resin melting or solvent casting by coating using a solvent. In the present invention, the structure of the phenoxy resin includes a bis-phenol structure containing a benzene nucleus in its molecular backbone, and has high heat resistance, durability, and high tensile strength due to the structure.

In the present invention, the structure of the phenoxy resin has a hydroxyl group and gives excellent adhesiveness. Therefore, a separate curing process is not required. When the molecular unit is repeated and the polyol property is obtained, So that it is possible to perform a very excellent function as a flexible substrate material claimed in the present invention. In addition, the structure of the phenoxy resin of the present invention includes an ether group, which can have a high chemical resistance and can impart a low melting point and a flexibility of a chain, thereby having good processing characteristics.

On the other hand, at the terminal of the phenoxy resin, a functional group may be present if necessary. For example, there are epoxy groups, hydroxyl groups, amine groups, and fluorine groups, which can be used to control the refractive index of phenoxy resins or to control the adhesion . The hydroxyl group in the phenoxy resin of the present invention can be substituted with a molecular chain having different characteristics as required. The hydroxyl group can be replaced with a siloxane group, an amide group, or other molecules capable of hydrogen bonding or dehydrogenation Replacement of the chains is possible. It is also possible to variously and easily modify the phenoxy resin for the purpose of obtaining heat resistance, refractive index, adhesiveness, tensile strength, moisture permeability and the like.

In the present invention, for the purpose of enhancing the chemical resistance of a solvent containing ketones, it is possible to use an acrylate-based low-molecular compound or acrylic polymer resin having an unsaturated group capable of being energy ray-curable. However, the acrylate compound or the acrylic polymer resin must be thermodynamically well mixed with the phenoxy resin so that the transmittance does not decrease, and the difference in refractive index value should not be large. The mixing amount may be 5 to 95 parts by weight based on 100 parts by weight of the phenoxy resin, preferably 10 to 70 parts by weight, more preferably 30 to 50 parts by weight.

Examples of the phenoxy resin include bisphenol A type phenoxy, bisphenol A type / bisphenol F type phenoxy, brominated phenoxy, phosphorous phenoxy, bisphenol A type / bisphenol S type phenoxy and caprolactone denatured phenoxy, siloxane Modified phenoxy and the like. Of these, bisphenol A-type phenoxy resins are more preferable because they are excellent in heat resistance, environmental friendliness, compatibility of curing agent, and curing speed. The weight average molecular weight of the phenoxy resin is preferably 1,000 to 100,000, more preferably 10,000 to 100,000, and most preferably 30,000 to 70,000. When the weight average molecular weight is less than 1,000, the curing reaction structure is preferentially formed and the brittleness is increased similarly to the epoxy resin. In such a case, it is difficult to obtain the film alone. When the weight average molecular weight is more than 100,000, the thermoplastic resin is in the form of a thermoplastic resin. However, since the cohesive force is high, the prolongation of the coating is not good when the film is obtained by the same method as the coating.

Examples of the organic solvent capable of dissolving the phenoxy resin include ketones, alcohols, glycol ethers, and esters. Some examples of the solvent include cyclohexanone, methyl ethyl ketone, benzyl alcohol, diethylene glycol alkyl ether, phenoxy propanol, propylene glycol methyl ether acetate, tetrahydrofuran, N-methylpyrrolidone, etc. Or a mixture of two or more of them may be used. When an organic solvent is used, 5 to 40 parts by weight, preferably 20 to 35 parts by weight, of a phenoxy resin is more preferably used per 100 parts by weight of the organic solvent.

On the other hand, the phenoxy resin can be used by adding a suitable crosslinking agent. Any crosslinking agent or curing agent can be used as long as it can cure a resin having a hydroxyl group as a functional group. Melamine, urea-formaldehyde, isocyanate functional prepolymer, phenol curing agent, amino-based curing agent and the like. The amount of the thermosetting agent is preferably 0.1 to 40 parts by weight, more preferably 5 to 20 parts by weight, per 100 parts by weight of the phenoxy resin.

In the present invention, an isocyanate-based curing agent can be used as the curing agent of the phenoxy resin, and the kind thereof is not particularly limited. Basically, the isocyanate-based curing agent reacts with the hydroxyl groups in the phenoxy resin to form a urethane bond, which is good for imparting ductility to the film, but it is difficult to increase the stability at high temperature and decomposition occurs at a temperature higher than 300 ° C. It is preferable to mix it with an imidazole-based curing agent to supplement it.

The bisphenol-A type epoxy resin and the phenoxy resin of the plastic film used in the present invention can be used in a blending form and can be directly extruded by melting the resin in a solid state due to the properties of the phenoxy resin, it can be easily processed by a solvent casting method such as extrusion or coating using a solvent. The above extrusion method can be adopted regardless of the type of the conventional film extrusion method. The coating method may be a solution method such as a knife coater, a gravure coater, And then drying it to form a film layer made of a solid phenoxy resin.

When the bisphenol-A type epoxy resin and the phenoxy resin of the above plastic film are obtained as a single film, the thickness of the film is preferably about 10 to 500 mu m, more preferably about 25 to 500 mu m, Is suitably from 30 to 100 mu m. When the thickness is less than 10 탆, the tensile properties of the film are deteriorated. When the thickness is more than 500 탆, the prognosis of the coating may be poor. When it is necessary to manufacture at 500 탆 or more, it is preferable to use a coating method using a slot die or a sheet by extrusion.

In the present invention, a plastic film can be simply produced using bisphenol-A type epoxy resin and phenoxy resin as main components as described above. This can be easily mass-produced by a conventional widely used production process such as coating or extrusion. It is also possible to prepare the polymer composition by coating the polymer composition on a polymer substrate obtained by itself or by using a thin film or a thick film on a transparent polymer substrate It is also possible. Here, the other polymer substrate includes conventional polymer substrate materials such as PC, PES, PI, PET, and PEN mentioned above and is not particularly limited. It may be useful to coat bisphenol-A type epoxy resin and phenoxy resin with a thin film or a thick film to overcome the shortcomings of conventional polymer substrate materials. For example, it may be applied on a PC film having low chemical resistance, or may be applied on a film such as PES or PI which is vulnerable to moisture permeability, thereby significantly improving the functional properties of the substrate.

When the bisphenol-A type epoxy resin and the phenoxy resin composition are coated on different substrates, the thickness of the coating layer is preferably about 0.1 to 500 μm, more preferably 0.5 to 50 μm, most preferably 1 to 100 μm, 10 占 퐉 is suitable. When the thickness is less than 0.1 탆, the adhesion of the coating layer to the substrate is decreased. When the thickness is more than 500 탆, the prognosis of coating on the substrate may not be good.

The plastic film of the present invention can be used in a TFT (Thin Film Transistor) device, a display, or an optical device in which a glass substrate is used, and is not particularly limited thereto.

The plastic film of the present invention can be used as a substrate for a liquid crystal display (LCD), a substrate for a touch screen panel, a substrate for a color filter, a substrate for an organic EL display element, When used as a substrate, the composition is preferably in the form of a sheet, and its thickness may be 15 to 500 mu m, more preferably 30 to 80 mu m.

When the device is manufactured for the above purposes, the thermal expansion coefficient is preferably 50 ppm / ° C or less, more preferably 1 to 30 ppm / ° C, in the temperature range of 25 to 250 ° C. Regarding transparency, when used as a substrate for a display device, a transmittance of 85% or more is required at a wavelength of 550 nm, and it is most preferable that the transmittance is 90% or more. A transmittance of less than 80% at a wavelength of 550 nm may be insufficient due to poor visibility in display performance.

Hereinafter, the structure and effect of the present invention will be described in more detail with reference to examples and comparative examples. However, this embodiment is intended to explain the present invention more specifically, and the scope of the present invention is not limited to these embodiments.

[Example 1]

100 g of phenoxy resin (Yuko Chemical Co., Ltd., YP50) was dissolved in 300 g of methyl ethyl ketone, and 15 g of an isocyanate thermosetting agent (Dow Corning, CE138) was mixed and stirred for 1 hour. 10 g of a bisphenol-A epoxy resin (YD-128) was added to the stirred phenoxy resin composition and 0.5 g of an imidazole curing agent (Sigma-Aldrich, 2-phenyl imidazole) Respectively. The stirred film composition was coated on a release film (trade name: XD5BR, manufactured by Toray Industries, Inc.) with a doctor blade and dried in a dryer at 150 캜 for about 3 minutes. The film composition passed through the dryer was removed from the release film to finally obtain a film. Its thickness was confirmed to be about 30 mu m. The resulting film was pressed against the PTFE film in a 200 ° C dryer for additional curing and post-cured for 60 minutes.

[Example 2]

100 g of phenoxy resin (Yuko Chemical Co., Ltd., YP50) was dissolved in 300 g of methyl ethyl ketone, and 15 g of an isocyanate thermosetting agent (Dow Corning, CE138) was mixed and stirred for 1 hour. 20 g of a bisphenol-A epoxy resin (YD-128) was added to the stirred phenoxy resin composition, 1 g of an imidazole curing agent (Sigma-Aldrich, 2-phenyl imidazole) was added, and the mixture was stirred for 2 hours . The stirred film composition was coated on a release film (trade name: XD5BR, manufactured by Toray Industries, Inc.) with a doctor blade and dried in a dryer at 150 캜 for about 3 minutes. The film composition passed through the dryer was removed from the release film to finally obtain a film. Its thickness was confirmed to be about 30 mu m. The resulting film was pressed against the PTFE film in a 200 ° C dryer for additional curing and post-cured for 60 minutes.

[Example 3]

100 g of phenoxy resin (Yuko Chemical Co., Ltd., YP50) was dissolved in 300 g of methyl ethyl ketone, and 15 g of an isocyanate thermosetting agent (Dow Corning, CE138) was mixed and stirred for 1 hour. 20 g of a bisphenol-A epoxy resin (YD-128) was added to the stirred phenoxy resin composition, 1 g of an imidazole curing agent (Sigma-Aldrich, 2-phenyl imidazole) was added, and the mixture was stirred for 2 hours . The stirred film composition was coated on a release film (trade name: XD5BR, manufactured by Toray Industries, Inc.) with a doctor blade and dried in a dryer at 150 캜 for about 3 minutes. The film composition passed through the dryer was removed from the release film to finally obtain a film. Its thickness was confirmed to be about 60 탆. The resulting film was pressed against the PTFE film in a 200 ° C dryer for additional curing and post-cured for 60 minutes.

[Comparative Example 1]

100 g of phenoxy resin (Yuko Chemical Co., Ltd., YP50) was dissolved in 300 g of methyl ethyl ketone, and 15 g of an isocyanate thermosetting agent (Dow Corning, CE138) was mixed and stirred for 1 hour. The agitated phenoxy resin composition was coated on a release film (trade name: XD5BR, manufactured by Toray Industries, Inc.) with a doctor blade and dried in a dryer at 150 캜 for about 3 minutes. The phenoxy resin composition having passed through the dryer was removed from the release film to finally obtain a film composed of the phenoxy resin composition alone. Its thickness was confirmed to be about 30 mu m. The resulting film was pressed against the PTFE film in a 200 ° C dryer for additional curing and post-cured for 60 minutes.

[Comparative Example 2]

100 g of phenoxy resin (Yuko Chemical Co., Ltd., YP50) was dissolved in 300 g of methyl ethyl ketone, and 15 g of an isocyanate thermosetting agent (Dow Corning, CE138) was mixed and stirred for 1 hour. The agitated phenoxy resin composition was coated on a release film (trade name: XD5BR, manufactured by Toray Industries, Inc.) with a doctor blade and dried in a dryer at 150 캜 for about 3 minutes. The phenoxy resin composition having passed through the dryer was removed from the release film to finally obtain a film composed of the phenoxy resin composition alone. Its thickness was confirmed to be about 60 탆. The resulting film was pressed against the PTFE film in a 200 ° C dryer for additional curing and post-cured for 60 minutes.

 [Experimental Example]

The physical properties of the samples obtained in Examples 1 to 3 and Comparative Examples 1 and 2 can be evaluated by the following conventional methods, and the evaluation results of the thermal stability that best match the object of the present invention are shown in Table 1 below.

1) Thermogravimetric analysis

The sample was heated to 600 占 폚 at a heating rate of 5 占 폚 / min under a nitrogen atmosphere using a thermogravimetric analyzer Q-600 manufactured by TA Instrument Co., Ltd. to measure the temperature at which the initial weight reduction was 5%.

2) Thermal expansion coefficient

The sample was heated to 300 DEG C at a heating rate of 5 DEG C / min under a nitrogen atmosphere using a thermomechanical analyzer Q-400 manufactured by TA Instrument Inc., and the temperature was measured in a temperature range of 30 to 80 DEG C. A load of 100 mN and a frequency of 20 Hz were used.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Total thickness (탆) 30 30 60 30 60 Tg (占 폚) 134 137 - 128 - Decomposition temperature (℃) 450 470 - 420 - Coefficient of thermal expansion (ppm / K) 45 40 42 53 65

As can be seen from the results of Table 1, the plastic film of the present invention shows better thermal stability than that of the comparative example, and it can be confirmed that the physical properties are stably maintained even when the thickness of the final film is increased by a factor of two . This indicates that the curing property of the film is improved. Thus, the present invention is a plastic substrate material for a transparent flexible substrate of a transparent flexible display which can replace a glass substrate. The plastic substrate material of the present invention is superior to the conventional plastic substrate material, It is possible to provide a plastic substrate material for an excellent transparent flexible substrate.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art.

Claims (12)

A plastic film for a transparent flexible substrate,
Bisphenol-A type epoxy resin;
Phenoxy resins; And
Characterized in that it comprises a curing agent,
Wherein the plastic film is made in the form of a thickness of 10 to 500 mu m and the curing agent is a mixture of an imidazole curing agent and an isocyanate curing agent. The method according to claim 1,
Wherein the bisphenol-A type epoxy resin has a weight average molecular weight of 200 to 10,000 and 5 to 30 parts by weight based on 100 parts by weight of the phenoxy resin. The method according to claim 1,
Wherein the phenoxy resin is at least one selected from the group consisting of bisphenol A phenoxy, bisphenol F phenoxy, brominated phenoxy, phosphorus phenoxy, bisphenol A / bisphenol S phenoxy and caprolactone denatured phenoxy or siloxane denatured phenoxy Wherein the plastic film is a transparent plastic film. The method of claim 3,
Wherein the phenoxy resin has a weight average molecular weight of 1,000 to 100,000. The method of claim 3,
Wherein the terminal of the phenoxy resin comprises at least one of an epoxy group, a hydroxyl group, an amine group, a fluorine group, a siloxane group and an amide group. The method of claim 3,
Wherein the phenoxy resin comprises at least one of melamine, urea-formaldehyde, isocyanate functional prepolymer, phenol curing agent or amino-based curing agent as a crosslinking agent. delete delete delete The method according to claim 1,
The plastic film is prepared by solvent casting or melt extrusion. The plastic film may be prepared by coating a composition comprising the bisphenol-A type epoxy resin, the phenoxy resin, and the curing agent alone or on a transparent polymer substrate with a thin film or a thick film Wherein the plastic film is a transparent plastic film. 11. The method of claim 10,
Wherein the transparent polymer substrate may be any one of PET, PEN, PC, PES, and PI, and the coating thickness is 0.1 to 500 μm. The plastic film for a transparent flexible substrate according to any one of claims 1 to 6, 10, and 11 is applied to a substrate for a liquid crystal display element, a substrate for an organic EL display element, a substrate for a color filter, Characterized in that the plastic film is used as a flexible plastic substrate for replacing a flat panel display of a substrate for a solar cell or a solar cell substrate and a glass substrate used for a TFT element substrate or an optical element substrate.