KR100884183B1 - Multi-layered Plastic Substrate having Excellent Surface Hardness and Gas Barrier Properties, and Fabrication Method Thereof - Google Patents

Abstract

The present invention relates to a multi-layered plastic substrate having excellent surface hardness and gas barrier properties, and a method of manufacturing the same. In particular, the present invention relates to a multilayer plastic substrate having a symmetrical structure in which an organic or organic-inorganic hybrid layer and a polysilazane layer are stacked on both sides of a bonded plastic film in any order, and a method of manufacturing the same.

Since the plastic substrate of the present invention has a low coefficient of linear expansion, excellent dimensional stability and excellent gas barrier properties at the same time, it is possible to replace a glass substrate having a fragile and heavy disadvantage, and in addition to a substrate of a display device, a packaging material and a variety of packaging materials requiring excellent gas barrier properties are required. It can be used as the material of the container.

Multi-layered, symmetrical, polysilazane layer

Description

Multi-layered Plastic Substrate having Excellent Surface Hardness and Gas Barrier Properties, and Fabrication Method Thereof}

1A is a cross-sectional view of a multilayer plastic substrate according to the present invention;

FIG. 1B is a cross-sectional view of a multilayer plastic substrate further comprising a gas barrier layer between the organic or organic-inorganic hybrid layer and the polysilazane layer of FIG. 1A;

Figure 2 is a schematic diagram showing a manufacturing process of a multilayer plasma substrate according to an embodiment of the present invention; And

3 to 8 are cross-sectional structural views of the plastic substrate according to Comparative Examples 1 to 6.

* Description of the symbols for the main parts of the drawings *

110: plastic film

115: organic or organic-inorganic hybrid layer

120: gas barrier layer

125: polysilazane layer

130: adhesive layer

140: first organic crosslinked coating layer

142: second organic crosslinked coating layer

The present invention relates to a multilayer plastic substrate having excellent surface hardness and gas barrier properties and a method of manufacturing the same. More particularly, the present invention relates to a small linear expansion coefficient, excellent dimensional stability, and excellent gas barrier properties and excellent surface hardness to prevent surface scratches. The present invention relates to a plastic substrate having a satisfactory multilayer structure and a method of manufacturing the same.

The glass substrate used in the display device has various advantages such as small coefficient of linear expansion, excellent gas barrier property, high light transmittance, surface flatness, excellent heat resistance and chemical resistance, but has a weak point due to its weakness of impact and high density. .

Recently, as interest in liquid crystals, organic light emitting diode display devices, and electronic papers is rapidly increasing, studies are being actively conducted to replace the substrates of these display devices from glass to plastics. In other words, replacing the glass substrate with a plastic substrate may reduce the overall weight of the display device and provide design flexibility, and it may be more impact-resistant and economical than the glass substrate when manufactured in a continuous process.

Meanwhile, in order to be used as a plastic substrate of a display device, a process temperature of a transistor element, a high glass transition temperature capable of withstanding the deposition temperature of a transparent electrode, oxygen and water vapor blocking characteristics to prevent aging of liquid crystals and organic light emitting materials, and a process temperature Small linear expansion coefficient and dimensional stability to prevent warping of substrates due to changes, high mechanical strength compatible with process equipment used in conventional glass substrates, chemical resistance to withstand etching process, high light transmittance and low birefringence, Properties such as scratch resistance of the surface are required.

However, since there is no high functional polymer base film (including a polymer film and a polymer-inorganic composite film) satisfying all of these conditions, efforts have been made to satisfy the above properties by applying a functional coating of several layers to the polymer base film. Examples of the typical coating layer include an organic planarization layer that reduces defects on the surface of the polymer and gives flatness, a gas barrier layer made of an inorganic material for blocking gases such as oxygen and water vapor, a silicon-based inorganic hard coating layer for imparting scratch resistance to the surface, and the like. have.

Many conventional multilayer plastic substrates have a process of coating an inorganic gas barrier layer on a polymer substrate and a hard coating layer on the gas barrier layer. A problem in manufacturing the multilayer structure is that the polymer substrate and the gas barrier layer Deformation of the polymer substrate and cracking and peeling of the inorganic thin film may occur due to a large difference in coefficient of linear expansion. Therefore, it can be said that the adhesion between the coating layer and the design of an appropriate multilayer structure that can minimize the stress at the interface of each layer is very important.

Vitex Systems Co., Ltd. forms a monomer thin film on a polymer substrate film, polymerizes the polymerized reaction by irradiation with ultraviolet (UV) light, and polymerizes (solidified organic layer), and forms an inorganic thin film thereon by a sputtering method thereon. The process was repeated to prepare several layers of organic-inorganic layers, and a flexible substrate having excellent gas barrier properties. However, although a product having excellent gas barrier properties can be obtained by the above method, a solution for surface hardness preventing surface scratches of a substrate in a display manufacturing process involving various deposition processes has not been suggested.

In addition, US Pat. No. 6,465,953 proposes a method for dispersing getter particles that can react with incoming oxygen and water vapor in a plastic substrate in order to use the plastic substrate in an organic light emitting device sensitive to oxygen and water vapor. The size of the getter particles should be sufficiently smaller than the size of the characteristic wavelength to be emitted and evenly distributed so that the emitted light can pass through the substrate without being scattered. In addition, the method was intended to minimize the amount of oxygen and water vapor introduced by coating a gas barrier film made of an inorganic material on the plastic substrate. However, the method is difficult to produce a substrate by uniformly dispersing nanoparticles of 100 to 200 nm in size, and the thickness of the plastic substrate must be thick to contain a large amount of getter particles that can react with oxygen and water vapor. Since the barrier film is directly coated, there is a high possibility that cracks or peeling will occur on the gas barrier film due to temperature changes.

U.S. Patent No. 6,322,860 discloses a crosslinkable composition comprising a silica particle or the like on one or both sides of a polyglutamide sheet within 1 mm thickness prepared by reaction extrusion (polyfunctional acrylate monomer or oligomer, Alkoxysilane and mixtures thereof) and then photocuring or thermosetting to prepare a crosslinked coating film, coating a gas barrier film thereon, and then optionally coating the crosslinking coating film on the barrier film to provide a plastic substrate for a display device. It was prepared. However, the method is only small enough that the oxygen transmission rate and the water vapor transmission rate can be used in a liquid crystal display in some special cases, and still do not improve the surface hardness required for use as a glass replacement substrate.

U.S. Patent No. 6,503,634 discloses an organic-inorganic hybrid ORMOCER and a silicon oxide layer coated on one polymer substrate or on the middle layer of two polymer substrates to coat 1/30 or less of the polymer substrate prior to the oxygen permeability coating and the water vapor transmission rate. A multilayer film of 1/40 or less of the previous polymer substrate was presented. The above method offers a possibility that the oxygen and water vapor transmission rate can be significantly reduced compared to the polymer substrate before coating, so that it can be used as a packaging material, but there is no mention of improvement of surface hardness due to surface scratches that may occur during the display manufacturing process. .

Accordingly, an object of the present invention is to replace glass substrates having excellent surface hardness, low linear expansion coefficient, excellent dimensional stability, and excellent gas barrier properties simultaneously, which are fragile and heavy disadvantages, and also for packaging materials and various applications. There is provided a plastic substrate having a multilayer structure and a method of manufacturing the same that can be used as a container material.

In order to achieve the above object, the present invention provides a multilayer plastic substrate having an organic or organic-inorganic hybrid layer, and a polysilazane layer on both sides of the bonded plastic film in any order to form a symmetrical structure.

In addition, the present invention,

a) coating an organic or organic-inorganic hybrid layer-forming coating composition on one side of the plastic film and curing to form an organic or organic-inorganic hybrid layer,

b) coating a polysilazane solution on the organic or organic-inorganic hybrid layer and curing at a low temperature to form a polysilazane layer to prepare a multilayer film,

c) repeating the steps a) to b) to prepare one more multilayer film of the same structure as b),

d) bonding the surfaces of the plastic film, in which the layers of the multilayer films of b) and c), are not formed, to each other to form a symmetrical structure;

It provides a method of manufacturing a plastic substrate of a multi-layer structure comprising a.

Hereinafter, the present invention will be described in detail.

The present invention provides a plastic substrate and a method for manufacturing the same, which can replace a glass substrate having a fragile and heavy disadvantage mainly used in a display device by securing a low linear expansion coefficient, excellent dimensional stability and gas barrier property at the same time.

The multi-layered plastic substrate of the present invention is characterized by a symmetrical laminated structure, and at least one of the above layers may be included because at least one of the layers may not function properly. In addition, the plastic substrate structure of the present invention is made of a symmetrical structure so that the plastic substrate does not bend in one direction according to the temperature change.

The method of manufacturing a plastic substrate having a symmetrical structure can increase productivity by using a simple process of laminating plastic films with each other, and can produce a plastic substrate excellent in gas barrier properties, small linear expansion coefficient, and dimensional stability even with low-cost equipment. have.

The multilayer plastic substrate of the present invention will be described in more detail with reference to the drawings.

FIG. 1A illustrates a cross-sectional structure of a multilayer plastic substrate of the present invention, and FIG. 1B illustrates a cross-sectional structure of a multilayer plastic substrate further comprising a gas barrier layer between the organic or organic-inorganic hybrid layer and the polysilazane layer of FIG. 1A. 2 illustrates a process for manufacturing the multilayer plastic substrate of FIG. 1B.

The multilayer plastic substrate of the present invention has a multilayer structure through a combination of two layers of plastic film, polysilazane layer, and organic or organic-inorganic hybrid layer, respectively. Optionally, it has a multilayer structure through combination with a gas barrier layer.

More specifically, as shown in Figure 1a, the plastic substrate 100 of the present invention is organic or organic-on both sides of the plastic film (110a, 110b) in the form of two or more bonded to each other, respectively- The inorganic hybrid layers 115a and 115b and the polysilazane layers 125a and 125b are sequentially stacked. Here, the organic or organic-inorganic hybrid layer serves as a buffer layer between the plastic film and the polysilazane layer, and serves to minimize the difference in the coefficient of linear expansion between layers and to improve the adhesion between the layers. In addition, the polysilazane layer not only serves as a protective layer for preventing cracking of the organic or organic-inorganic hybrid layer, but also has excellent gas barrier properties.

As another specific embodiment of the present invention, the plastic substrate 100 of the present invention further including a gas barrier layer is centered on the plastic films 110a and 110b in which two or more layers are bonded as shown in FIG. 1B. The organic or organic-inorganic hybrid layers 115a and 115b, the gas barrier layers 120a and 120b, and the polysilazane layers 125a and 125b are sequentially stacked on both sides thereof. In FIGS. 1A and 1B, reference numerals 100a and 100b denote plastic substrates having a symmetrical structure with respect to the adhesive layer 130 after laminating the plastic film surfaces of the multilayer films 100a and 100b.

In the multilayered plastic substrate structure 100b of FIG. 1B according to the present invention, an organic or organic-inorganic hybrid layer may be positioned as a buffer layer between the plastic film and the gas barrier layer, thereby minimizing the difference between the coefficients of linear expansion between layers and improving the adhesion between layers. The surface hardness of the substrate may be improved by placing a polysilazane layer as a hard coat layer on the gas barrier layer.

The organic or organic-inorganic hybrid layer serves to alleviate the difference in the large linear expansion coefficient between the plastic film and the gas barrier layer, and to improve the adhesion between the plastic film and the gas barrier layer by appropriately adjusting the composition of the organic and inorganic materials. In addition, the organic or organic-inorganic hybrid layer may planarize the surface of the plastic film to minimize defects formed during the deposition of the gas barrier layer.

The gas barrier layer is a high density inorganic layer having a small coefficient of linear expansion, and can block gases such as oxygen and water vapor.

In addition, the polysilazane layer not only serves as a protective layer to prevent cracking of the gas barrier layer, but also fills defects in the gas barrier layer to further improve gas barrier properties. In addition, by preventing scratches of the plastic substrate that may occur in the display manufacturing process serves to reduce the defects in the display manufacturing process.

In this case, the organic or organic-inorganic hybrid layer is formed from the partial hydrolyzate of the composition containing the organosilane and the metal alkoxide has the above-described effect.

The plastic film used in the present invention may be selected from the group consisting of a single polymer, at least one polymer blend, and a polymer composite material containing an organic or inorganic additive. As a preferred example, when the plastic substrate of the present invention is used as a substrate of a liquid crystal display device, a polymer having high heat resistance that can withstand such high temperatures because the manufacturing process for forming the thin film transistor and the transparent electrode is performed at a high temperature of 200 ° C. or higher. Is required. Examples of the polymer having such properties include polynorbornene, aromatic florene polyester, polyethersulfone, bisphenol-A polysulfone, polyimide and the like. In addition, as the recent research on lowering the temperature of high temperature substrate process is progressing, polymers such as polyethylene terephthalate, polyethylene naphthalene, polyarylate, polycarbonate, and cyclic olefin copolymer which can be used up to a temperature of around 150 ° C can be used. have.

In addition, as the plastic film, a nanomaterial is dispersed in a polymer, and a polymer composite material containing an organic or inorganic additive may be used.

The polymer composite material may include a polymer-clay nanocomposite in which clay nanomaterials are dispersed in a polymer matrix. The polymer-clay nanocomposite has a smaller amount of clay than a conventional composite such as glass fiber due to the small particle size (<1 μm) and the large aspect ratio of the clay. And physical properties such as dimensional stability can be improved. That is, in order to improve the above properties, it is important to peel off the clay layer having a layered structure and disperse it well in the polymer matrix, and to satisfy this, the polymer-clay nanocomposite is satisfied.

Polymers that can be used in the polymer-clay nanocomposite include polystyrene, polymethacrylate, polyethylene terephthalate, polyethylene naphthalene, polyarylate, polycarbonate, cyclic olefin copolymer, polynorbornene, aromatic florene polyester, Polyether sulfone, polyimide, epoxy resin, polyfunctional acrylate, and the like, and as the clay, laponite, montmorillonite, megadite and the like can be used.

In the multilayer plastic substrate of the present invention, the plastic film is preferably in the form of a film or sheet having a thickness of 10 microns (µm) to 2,000 µm. The plastic film may be manufactured by a solution casting method or a film extrusion process, and may be briefly annealed for several seconds to several minutes near the glass transition temperature in order to minimize deformation due to temperature after the production. After annealing, primer coating may be applied to the surface of the plastic film in order to improve the coating property and adhesion, or surface treatment may be performed by plasma treatment using corona, oxygen or carbon dioxide, ultraviolet-ozone treatment, ion beam treatment with a reaction gas, or the like. have.

The method for producing a multilayer plastic substrate of the present invention comprises coating and curing an organic or organic-inorganic hybrid layer-forming coating composition on one side of a plastic film to form an organic or organic-inorganic hybrid layer as a buffer layer; Coating and curing a coating solution containing polysilazane thereon to form a polysilazane layer to produce a multilayer film; Through the same process as described above to produce one more multilayer film. Thereafter, the plastic film surfaces on which the layers of each multilayer film are not formed are bonded to each other to form a symmetrical structure, thereby manufacturing a plastic substrate having a multilayer structure. Optionally, the method may further include forming a gas barrier layer by depositing and coating an inorganic material on the organic or organic-inorganic hybrid layer to manufacture a plastic substrate having a multilayer structure.

The organic or organic-inorganic hybrid layer may be obtained by partially hydrolyzing the composition for forming an organic or organic-inorganic hybrid layer to form a sol solution, and then coating and curing it on a plastic film. The coating method may be a method such as spin coating, roll coating, bar coating, dip coating, gravure coating, spray coating. The sol state curing method may be used, such as thermal curing, UV curing, infrared curing, high frequency heat treatment. The thickness of the organic or organic-inorganic hybrid layer after curing is 0.1 µm to 50 µm, preferably 0.1 µm to 20 µm, more preferably 0.1 µm to 10 µm. When the thickness is thinner than 0.1 μm, it is susceptible to obstacles due to pinhole defects, and later, a leakage current occurs, and when the thickness exceeds 50 μm, distortion of the film during curing may occur. There is a problem of surface irregularities formation.

 The organic or organic-inorganic hybrid layer may be a monomer of an organic compound having two or more polymerizable unsaturated groups in a molecule, or an oligomer having a weight average molecular weight of 100 or more and 1,000 or less having two or more polymerizable unsaturated groups in a molecule; And a coating composition containing a weight average molecular weight of 1,000 or more and 500,000 or less of an organic compound having one or more polymerizable unsaturated groups in the molecule and then curing the coating composition.

In addition, the composition for forming the organic or organic-inorganic hybrid layer may include an organosilane, and / or metal alkoxide.

The organosilane may be used by selecting one or more from the group consisting of compounds represented by the following formulas (1) to (3), wherein at least one organosilane compound should be crosslinkable.

(R ¹ ) _m -Si-X _(4-m)

(R ¹ ) _m -O-Si-X _(4-m)

(R ¹ ) _m -N (R ² ) -Si-X _(4-m)

In Chemical Formulas 1 to 3,

X may be the same or different from each other, hydrogen, halogen, alkoxy, acyloxy, alkylcarbonyl, alkoxycarbonyl, or -N (R ² ) ₂ having 1 to 12 carbon atoms,

R ¹ may be the same or different from each other, alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl, alkynylaryl, halogen, amide having 1 to 12 carbon atoms , Aldehyde, keto, alkylcarbonyl, carboxy, mercapto, cyano, hydroxy, alkoxy having 1 to 12 carbon atoms, alkoxycarbonyl having 1 to 12 carbon atoms, sulfonic acid, phosphoric acid, acryloxy, methacryloxy, epoxy, Or vinyl group,

R ² is hydrogen or alkyl having 1 to 12 carbon atoms,

m is an integer of 1-3.

Examples of the organosilane include methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxy Silane, phenyldimethoxysilane, phenyldiethoxysilane, methyldimethoxysilane, methyldiethoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, triphenylmethoxysilane, Triphenylethoxysilane, phenyldimethylmethoxysilane, phenyldimethylethoxysilane, diphenylmethylmethoxysilane, diphenylmethylethoxysilane, dimethylethoxysilane, dimethylethoxysilane, diphenylmethoxysilane, diphenyl Ethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-aminophenylsilane, allyltrimethoxysilane, n- (2-aminoethyl) -3-aminopropyltri Methoxysilane, 3-amine Propyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyldiisopropylethoxysilane, (3-glycidoxypropyl) methyldiethoxysilane, 3-glycidoxypropyltrimethoxy Silane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyl Trimethoxysilane, n-phenylaminopropyltrimethoxysilane, vinylmethyl diethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and a mixture thereof can be selected and used.

The metal alkoxide may be used by selecting one or more from the group consisting of compounds represented by the following formula (4).

M- (R ³ ) _z

Where

M represents a metal selected from the group consisting of aluminum, zirconium, and titanium,

R ³ may be the same as or different from each other, and is a halogen, an alkyl, alkoxy, acyloxy, or hydroxy group having 1 to 12 carbon atoms,

Z is an integer of 3 or 4.

The organic or organic-inorganic hybrid layer may optionally further include suitable fillers, solvents and polymerization catalysts as additives.

The filler may be selected from one or more of metals, glass powder diamond powder, silicon oxide (SiO _x , where x is an integer of 2-4), clay and the like. Examples of the filler include metal, glass powder diamond powder, silicon oxide, clay (bentonite, smectite, kaolin and the like), calcium phosphate, magnesium phosphate, barium sulfate, aluminum fluoride, calcium silicate, magnesium silicate, barium silicate, barium carbonate , Barium hydroxide, aluminum silicate, and mixtures thereof.

The solvent may be a solvent used in a conventional partial hydrolysis reaction, preferably distilled water may be used. In addition, the catalyst is also not particularly limited, but preferably aluminum butoxide and zirconium propoxide may be used.

The amount of the filler, the solvent and the catalyst to be used is not particularly limited as added as needed.

The content of the organosilane in the composition for forming an organic or organic-inorganic hybrid layer is preferably 20 to 99.99% by weight, more preferably 50 to 99% by weight, still more preferably 70 to 99% by weight. In addition, the content of the metal alkoxide may be used in 0.01 to 80% by weight, more preferably less than 70% by weight, most preferably less than 20% by weight.

In the present invention, the surface flatness Ra (average of roughness) of the organic or organic-inorganic hybrid layer functioning as a buffer layer is very important. If the organic or organic-inorganic hybrid layer is not flat, defects occur when the barrier layer is deposited. This results in no barrier property. Therefore, the lower the flatness value, the higher the barrier property. In the present invention, the surface flatness of the organic or organic-inorganic hybrid layer is preferably about 1 nm or less, more preferably 1 nm or less, based on the stylus method. Specifically, the flatness may have a Ra value of 0.1 nm to 1.2 nm.

When the gas barrier layers 120a and 120b, which are preferably inorganic, are stacked on the organic or organic-inorganic hybrid layer thus prepared, the adhesion between the inorganic layer and the organic or organic-inorganic hybrid layer is excellent and the gas barrier characteristics are increased by the inorganic layer. Since the modulus of the inorganic layer itself is high and the coefficient of linear expansion is small, the mechanical properties of the entire substrate can be improved.

In the method of forming the gas barrier layer, since the oxygen permeability and the water vapor permeability of the plastic film itself generally have values of several tens to thousands of units, a thin or thin metal thin film having a high density of transparent inorganic material or nanometers is physically or chemically formed on the polymer film. The method of vapor deposition coating to block oxygen and water vapor may be used. In the case of the transparent inorganic oxide thin film, if there are defects such as pinholes or cracks, it is difficult to obtain a sufficient oxygen and water vapor blocking effect, and in the case of a thin metal thin film, it is difficult to obtain a uniform thin film having a few nanometers thickness without defects as well as visible light. The light transmittance of the region is difficult to exceed 80%. The thickness of the gas barrier layer formed through the method is 5 nm to 1,000 nm, preferably 10 nm to 500 nm, more preferably 20 nm to 300 nm.

The inorganic material may be at least one metal oxide selected from the group consisting of SiOx (wherein x is an integer of 1 to 4), SiOxNy (wherein x and y are each an integer of 1 to 3), Al ₂ O ₃ and ITO. Or metal nitride can be used. As the deposition coating method, a sputtering method, a chemical vapor deposition method, an ion plating method, a plasma chemical vapor deposition method, a sol-gel method, or the like can be used.

The polysilazane layer formed on the gas barrier layer minimizes the possibility of cracking in the barrier layer and is used on the surface to impart chemical resistance and scratch resistance. In addition, in the present invention, a hydration reaction occurs between the hydroxyl group of the inorganic layer and the hydroxyl group of the polysilazane layer at a defective portion such as pinholes or cracks that may exist in the inorganic layer to heal the defect of the gas barrier layer, which is an inorganic layer, to prevent the gas barrier. The sex can be further improved. The polysilazane layer stacked on the gas barrier layer (inorganic layer) is a perhydropolysilazane represented by the following formula (5); And at least one of an organopolysilazane represented by Formula 6 and an organopolysilazane represented by Formula 7. Perhydropolysilazane represented by the following formula (5); And an organopolysilazane represented by the following formula (6) or (7) by curing the composition blended in a weight ratio of 100/0 to 50/50.

In Formula 5, n is a positive integer;

In Formula 6, n is a positive integer, R ⁴ , R ⁵ , and R ⁶ are each hydrogen, alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 12 carbon atoms, alkylsilyl of 1 to 12 carbon atoms, 1 to Alkylamino of 12, cycloalkyl of 1 to 12 carbon atoms, alkenyl of 1 to 12 carbon atoms, and allyl of 1 to 12 carbon atoms;

In Formula 7, n and m are positive integers, R is alkyl having 1 to 12 carbon atoms.

The polysilazane layer-forming composition is crosslinked by reacting a solution of polysilazane dissolved in an organic solvent such as xylene solvent at a temperature of 300 ° C. or lower, preferably 50 ° C. to 150 ° C., at a relative humidity of 50% or more, and oxygen. It is composed of silicon oxide (silicone oxide), and the reaction produces ammonia and hydrogen. The reaction proceeds at room temperature, but the reaction rate may be improved at a catalyst or a high temperature.

The polysilazane layers 125a and 125b may be formed by spin coating, roll coating, bar coating, dip coating, gravure coating, spray coating, or the like in the same manner as the method of forming the organic or organic-inorganic hybrid layer. It can be prepared by coating on the barrier layer by the method, thermosetting, plasma curing, the thickness after curing is 0.1 ㎛ to 50 ㎛, preferably 0.1 ㎛ to 20 ㎛, more preferably 0.1 ㎛ to 10 ㎛.

In addition, in the present invention, the flatness and surface hardness of the polysilazane layer are very important. Since devices such as ITO used in an LCD process or an OLED manufacturing process are deposited directly on the layer, these devices are a phenomenon in which current is concentrated when the flatness is high. I can't function properly. Current trends require better flatness in OLEDs, the next generation of displays rather than LCDs. Therefore, in the present invention, the surface flatness of the polysilazane layer is also preferably about 1 nm or less, more preferably 1 nm or less, based on the styling method, so as to satisfy such conditions. Specifically, the flatness may have a Ra value of 0.1 nm to 1.2 nm. Bonding method between the plastic film of the multi-layer film may be made by an acrylic adhesive or a thermal bonding method commonly used as an adhesive, but is not necessarily limited thereto. In this case, the content of the adhesive is not particularly limited, but the thickness of the formed adhesive layer is greater than 0 and less than 50 μm, preferably less than 0 and less than 10 μm, more preferably less than 0 and more than 5 μm. good.

As described above, the multi-layered plastic substrate of the present invention has a very small linear expansion coefficient of 6.5 (ppm / K), an oxygen transmission rate of less than 0.05 (cc / m 2 / day / atm), and a water vapor transmission rate of 0.005 (g / M 2 / day), excellent gas barrier properties and dimensional stability is also excellent. Therefore, the multi-layered plastic substrate of the present invention can replace the fragile and heavy glass substrate that has been mainly used in conventional display devices, etc., and can also be used as a material requiring excellent gas barrier property.

Hereinafter, the present invention will be described in more detail by the following examples. However, the following examples presented to aid the understanding of the present invention are merely to illustrate the best preferred embodiments of the present invention, and the scope of the present invention is not limited to the following examples, of course.

<Example 1>

A 100 μm thick PET (Polyethyleneterephthalate, SH38, SK) film prepared by coating a double-sided acrylic primer by a biaxial stretching extrusion process was heat treated in a convection oven at 150 ° C. for 1 minute to remove residual stress, and then used as a plastic film.

As an initiator for forming an organic or organic-inorganic hybrid layer, 32.5 parts by weight of tetraethoxysilane, 64 parts by weight of glycidyloxypropyltrimethoxysilane, 0.5 part by weight of aminopropyltrimethoxysilane, aluminum butoxide 2 Parts by weight, and 1 part by weight of zirconium propoxide were used, and 80 parts by weight of distilled water was added thereto to partially hydrolyze at 25 ° C. for 24 hours to prepare a sol composition. The composition was bar-coated on one side of PET and dried for 3 minutes at 50 ° C., followed by gel reaction for 1 hour in a convection oven at 125 ° C. The thickness of the organic or organic-inorganic hybrid layer measured by alpha stepper after the gel reaction was 3 μm. After coating the solution dissolved in xylene solvent with 20% by weight of perhydropolysilazane on the organic or organic-inorganic hybrid layer, the gel reaction was completed, and then exposed to amine and water vapor as a catalyst at room temperature for 1 minute, and then to 50 ° C. After curing for 10 minutes at 90% RH and finally exposed to oxygen plasma for several seconds to fully cure to form a polysilazane layer to prepare a multilayer film (100b of FIG. 1). At this time, the thickness of the polysilazane layer measured by alpha stepper after the gel reaction was 3 µm. In FIG. 1, reference numeral 130 is an adhesive layer, 110a and 110b are plastic films, 115a and 115b are organic or organic-inorganic hybrid layers, 120a and 120b are gas barrier layers, and 125a and 125b are polysilazane layers. to be.

The surface roughness of the polysilazane layer measured in the room temperature tapping mode of the AFM is 0.4 nm or less at a measurement area of 50 μm × 50 μm.

Thereafter, the multilayer film (100a of FIG. 1A) was once more prepared in the same manner as above.

Finally, after coating the adhesive composition, the main component of the acrylate oligomer having a multifunctional group, on the uncoated PET side of the multilayer film 100b prepared by the above process, the multilayer film 100b prepared in the same manner as described above. ) And the plastic surface were laminated on each other and irradiated with an ultraviolet irradiator (DYMAX 2000-EC) for 6 minutes to induce a curing reaction of the adhesive composition, thereby making a plastic substrate having a structure as shown in 100a of FIG. 1A.

For the plastic substrate of Example 1, optical transmittance, haze, oxygen transmittance, water vapor transmittance, linear expansion coefficient, and pencil hardness, which are the main required physical properties of the display device substrate, were measured, and the results are shown in Table 1. Each of the physical property measurement methods are as follows and the same applies to all Examples and Comparative Examples below.

1) Light transmittance: Based on ASTM D1003, each was measured in the visible light range of 380 to 780 nm using a Varian UV-spectrometry.

2) Haze: Hazemeter TC-H3DPK of Tokyo Denshoku was measured by the method of ASTM D1003.

3) Oxygen permeability: measured at 0% relative humidity at room temperature using the method of ASTM D 3985 using OX-TRAN 2/20 of MOCON.

4) Water vapor transmission rate: Using a PERMATRAN-W-3 / 33 was measured for 48 hours at room temperature with a relative humidity of 100% by the method of ASTM F 1249.

5) Linear expansion coefficient: measured by a thermomechanical analysis (TMA; Thermomechanical Analysis) based on ASTM D696 at a temperature of 10 ℃ / min under a stress of 5gf, pencil hardness was measured by the method of ASTM D3363 under a load of 200 g.

All properties described are averaged for at least five measurements so that they can be statistically representative.

For reference, the oxygen and water vapor transmission rates of the PET film itself used in Example 1 are 25 cc / m 2 / day / atm and 4.5 g / m 2 / day, respectively, and the coefficient of linear expansion is 22.4 ppm / K.

In Table 1 above,

a) Instrument measuring range: 0.05 cc / ㎡ / day / atm

b) Instrument measuring range: 0.005 g / ㎡ / day

The multi-layered plastic substrate prepared by Example 1 had no bending when placed on a flat bottom, and as shown in Table 1, the prepared plastic substrate satisfies the properties of excellent gas barrier properties, small linear expansion coefficient, and dimensional stability at the same time. It can be seen that, especially when the surface hardness measured by a pencil hardness tester showed a very excellent hardness of more than 8H.

<Example 2>

A 100 μm thick PET (Polyethyleneterephthalate, SH38, SK) film prepared by coating a double-sided acrylic primer by a biaxial stretching extrusion process was heat treated in a convection oven at 150 ° C. for 1 minute to remove residual stress, and then used as a plastic film.

As an initiator for forming an organic or organic-inorganic hybrid layer, 32.5 parts by weight of tetraethoxysilane, 64 parts by weight of glycidyloxypropyltrimethoxysilane, 0.5 part by weight of aminopropyltrimethoxysilane, aluminum butoxide 2 Parts by weight, and 1 part by weight of zirconium propoxide were used, and 80 parts by weight of distilled water was added thereto to partially hydrolyze at 25 ° C. for 24 hours to prepare a sol composition. The composition was bar-coated on one side of PET and dried for 3 minutes at 50 ° C., followed by gel reaction for 1 hour in a convection oven at 125 ° C. The thickness of the organic or organic-inorganic hybrid layer measured by alpha stepper after the gel reaction was 3 μm. 50 sccm of Ar gas is injected onto the organic or organic-inorganic hybrid layer after gel reaction using Artec Systems' DC / RF magnetron sputter, and deposited for 10 minutes at 1000 Watt of RF (13.56MHz) power under a pressure of 5 mtorr. A silicon oxide (SiO _x , x = 1.8) thin film was deposited. The thickness of the silicon oxide film observed by SEM was 100 nm. Bar coating a solution dissolved in xylene solvent with 20% by weight of perhydropolysilazane on a silicon oxide thin film, exposed to amine and water vapor as a catalyst at room temperature for 1 minute, and then cured at 50 ° C. and 90% RH for 10 minutes. Then, finally exposed to oxygen plasma for several seconds to fully cure to form a polysilazane layer to prepare a multilayer film (100b of Figure 1). At this time, the thickness of the polysilazane layer measured by alpha stepper after the gel reaction was 3 µm. In FIG. 1, reference numeral 130 is an adhesive layer, 110a and 110b are plastic films, 115a and 115b are organic or organic-inorganic hybrid layers, 120a and 120b are gas barrier layers, and 125a and 125b are polysilazane layers. to be.

The surface roughness of the polysilazane layer measured in the room temperature tapping mode of the AFM is 0.4 nm or less at a measurement area of 50 μm × 50 μm.

Thereafter, the multilayer film (100a of FIG. 1) was once more prepared in the same manner as above.

Finally, after coating the adhesive composition, the main component of the acrylate oligomer having a multifunctional group, on the uncoated PET side of the multilayer film 100b prepared by the above process, the multilayer film 100b prepared in the same manner as described above. ) And the plastic surface were laminated on each other and irradiated with an ultraviolet irradiator (DYMAX 2000-EC) for 6 minutes to induce a curing reaction of the adhesive composition, thereby making a plastic substrate having a structure as shown in 100b of FIG. 1B.

The physical properties of the plastic substrate were measured in the same manner as in Example 1, and the results are shown in Table 2.

As shown in Table 2, the produced plastic substrate can be seen to satisfy the properties of excellent gas barrier properties, small linear expansion coefficient, and dimensional stability at the same time, in particular, the surface hardness showed a very excellent hardness of more than 8H when measured by a pencil hardness tester .

<Example 3>

After a corona surface treatment (Asung) on a 50 μm thick DuPont Kapton polyimide film, a bar-coated composition of the same composition as in Example 2 was coated with a bar, and the remaining solvent was kept at 50 ° C. for 3 minutes in a convection oven. Was dried and the gel reaction proceeded for 30 minutes in a convection oven at 200 ℃. The thickness of the organic or organic-inorganic hybrid layer measured by alpha stepper was 2 μm. Thereafter, a silicon oxide thin film having a thickness of about 100 nm was deposited on the coating layer under the same deposition conditions as in Example 2, followed by bar coating a solution dissolved in xylene solvent with 20 wt% of perhydropolysilazane on the silicon oxide thin film. After exposure to amine and water vapor acting as a catalyst for 1 minute at room temperature, then cured for 10 minutes at 75 ℃ and 90% RH and finally cured by exposure to oxygen plasma for a few seconds to prepare a polysilazane layer. The thickness of the polysilazane layer measured by alpha stepper was 2 micrometers. The multilayer film produced by the above process and one multilayer film also manufactured in the same manner were laminated together in the same manner as in Example 1 to form a plastic substrate having a structure as shown in 100b of FIG. 1B.

The physical properties of the plastic substrate were measured in the same manner as in Example 1, and the results are shown in Table 3.

<Example 4>

40 parts by weight of tetraethoxysilane, 56.5 parts by weight of glycidyloxypropyltrimethoxysilane as an initiator for forming an organic or organic-inorganic hybrid layer on the same plastic film (PET) as in Example 1, aminopropyltrimeth 0.5 parts by weight of oxysilane, 2 parts by weight of aluminum butoxide, and 1 part by weight of zirconium propoxide were used, and 60 parts by weight of distilled water was added thereto to partially hydrolyze at 25 ° C. for 24 hours to prepare a sol composition. . The composition was bar-coated on one side of PET, which is a plastic film, and the solvent was dried at 50 ° C. for 3 minutes, followed by gel reaction for 1 hour in a convection oven at 125 ° C. The thickness of the coating layer measured by alpha stepper was 2 μm. Thereafter, a silicon oxide thin film having a thickness of about 50 nm was deposited on the coating layer under the same deposition conditions as in Example 2, and then a bar solution was coated with a solution dissolved in xylene solvent at 20 wt% of perhydropolysilazane on the silicon oxide thin film. After exposure to amine and water vapor acting as a catalyst for 1 minute at room temperature, then cured for 10 minutes at 100 ℃ and 90% RH and finally cured by exposure to oxygen plasma for several seconds to prepare a polysilazane layer. The thickness of the polysilazane layer measured by alpha stepper was 2 micrometers. The multilayer film produced by the above process and one multilayer film also manufactured in the same manner were laminated together in the same manner as in Example 1 to form a plastic substrate having a structure as shown in 100b of FIG. 1B.

The physical properties of the plastic substrate were measured in the same manner as in Example 1, and the results are shown in Table 4.

Comparative Example 1

In Example 2, a multilayer film was prepared by coating an organic or organic-inorganic hybrid layer only on a gas barrier layer without coating an organic or organic-inorganic hybrid layer between PET, which is a plastic film, and a silicon oxide thin film, which is a gas barrier layer. Thereafter, the multilayer film and the plastic film surface manufactured in the same manner were laminated to each other to prepare the plastic substrate shown in FIG. 3.

The organic or organic-inorganic hybrid layer coated on the silicon oxide thin film as the gas barrier layer was prepared by coating in the same manner as in Example 2. Table 5 shows the measurement results of the physical properties of the thus prepared plastic substrate.

In Table 5, the plastic substrate prepared by Comparative Example 1 showed oxygen and water vapor transmission rates outside the range of instrument measurement, but including only one organic or organic-inorganic hybrid layer, the coefficient of linear expansion was linear expansion of the PET film itself. It is similar to the coefficient of 22.4. In addition, it can be seen that the pencil hardness indicating the surface hardness is significantly lower than the 8H of the example in HB.

Comparative Example 2

In Example 2, a multilayer film was prepared by coating an organic or organic-inorganic hybrid layer on the plastic film PET and depositing a silicon oxide thin film which is a gas barrier layer thereon, but did not coat the polysilazane layer. A plastic substrate having a structure as shown in FIG. 4 was prepared by laminating the multilayer film and the plastic film surface prepared in the same manner.

The organic or organic-inorganic hybrid layer coated on the plastic film was prepared by coating in the same manner as in Example 1. Table 6 shows the measurement results of the physical properties of the thus prepared plastic substrate.

In Table 6, the plastic substrate prepared by Comparative Example 2 showed oxygen and water vapor transmission rates outside the measurement range of the device, but this also included only one organic or organic-inorganic hybrid layer. It is similar to 22.4, its coefficient of linear expansion, and high, and its surface hardness is low below HB.

Comparative Example 3

In Example 2, a multilayer film was prepared by depositing a silicon oxide thin film, which is a gas barrier layer, on the plastic film PET, and neither the organic or organic-inorganic hybrid layer and the polysilazane layer were coated. The plastic substrate of FIG. 5 was prepared by laminating the plastic film sheet surfaces of the multilayer film manufactured in the same manner.

Table 7 shows the measurement results of the physical properties of the thus prepared plastic substrate.

In Table 7, the plastic substrate prepared by Comparative Example 3 had an oxygen transmission rate of 1.1 and a water vapor transmission rate of 2.0, which is significantly lower than that of the PET film but still shows a high value. In addition, it can be seen that the coefficient of linear expansion is high, similar to the coefficient of linear expansion of PET film itself 22.4. Therefore, it can be seen that it is not suitable for use as a substrate of the display device.

<Comparative Example 4>

In Example 2, a film obtained by depositing only a silicon oxide thin film as a gas barrier layer on the polymer film PET was prepared (FIG. 6), and the physical property measurement results for the plastic substrate are shown in Table 8. 6 is a substrate in which a gas barrier layer is deposited only on one side rather than on both sides.

In Table 8, the plastic substrate prepared by Comparative Example 4 had an oxygen transmission rate of 3.1 and a water vapor transmission rate of 3.0, which is lower than that of the PET film but still shows a high value. In addition, it can be seen that the coefficient of linear expansion is high, similar to the coefficient of linear expansion of PET film itself 22.4. Therefore, it can be seen that it is not suitable for use as a substrate of the display device.

Comparative Example 5

After coating the organic or organic-inorganic hybrid coating composition solution of Example 2 to a thickness of 2.5 ㎛ on one side of the PET film used in Example 2 and proceeding the crosslinking reaction as in Example 1, and in Example 2 and Under the same conditions, a silicon oxide thin film of about 100 nm was deposited to form a gas barrier layer. On the other hand, the coating and crosslinking reaction of the organic or organic-inorganic hybrid layer and the deposition of the silicon oxide thin film were repeated two more times in the same manner as described above, and then the organic or organic layer was formed to the outermost silicon oxide thin film at a thickness of about 3 μm. The inorganic hybrid layer was coated to remove residual solvent at 50 ° C. for 3 minutes and crosslinked at 125 ° C. for 1 hour to prepare a plastic substrate laminated only on one side rather than a symmetrical structure (FIG. 7). The lengths and widths of the substrates were all 12 cm, and when the uncoated side was placed on a flat floor, the center part was bent from the 3 cm floor. Table 9 shows the measurement results of the physical properties of the plastic substrate.

In Table 9, the oxygen and water vapor transmission rates were excellent, but the coefficient of linear expansion was not improved. Therefore, it can be seen that it is not suitable for use as a substrate of the display device.

Comparative Example 6

The PET film used in Example 2 was immersed in a solution in which 0.3 parts by weight of a photoinitiator was added to the polyfunctional methacrylate composition, and then pulled up at a speed of 10 cm per minute, deep coated, and UV cured to form organic crosslinked coating layers 140a and 140b on both sides. Formed. The thickness of the crosslinked coating layer after UV curing was 3 μm as a result of measurement with an alpha stepper. After depositing a 100 nm thick silicon oxide thin film on both sides of the organic cross-linked PET film in the same manner as in Example 2, the organic cross-linked coating layer (142a, 142b) is again 3 ㎛ on the silicon oxide thin film in the same manner as described above The plastic substrate of FIG. 8 was prepared by coating to a thickness of. Table 10 shows the measurement results of the physical properties of the substrates.

In Table 10, in the case of Comparative Example 6, the oxygen and water vapor transmission rates were considerably reduced compared to the PET film, but the linear expansion coefficient did not appear, and thus it was not suitable for use as a substrate of the display device.

As described above, the multilayer plastic substrate of the present invention simultaneously satisfies the characteristics of small linear expansion coefficient, excellent gas barrier property, dimensional stability, and excellent surface hardness, so that the glass substrate is a plastic substrate for an image display device including a liquid crystal display device. It can be used instead, and can also be very useful as a material for packaging materials and containers requiring gas barrier properties.

Claims (23)

The organic or organic-inorganic hybrid layer and the polysilazane layer are laminated on both sides of the bonded plastic film in any order to form a symmetrical structure. Wherein the thickness of each of the organic or organic-inorganic hybrid layer and the polysilazane layer is 0.1 μm to 50 μm. The multilayer plastic substrate of claim 1, further comprising a gas barrier layer. The multilayer plastic substrate of claim 2, wherein an organic or organic-inorganic hybrid layer, a gas barrier layer, and a polysilazane layer are sequentially stacked on both sides of the bonded plastic film. The multilayer plastic substrate of claim 1, wherein the plastic film is selected from the group consisting of a single polymer, at least one polymer blend, and a polymer composite material containing an organic or inorganic additive. The method of claim 4, wherein the polymer for the single polymer or the polymer blend is polynorbornene, aromatic florene polyester, polyethersulfone, bisphenol A polysulfone, polyimide, polyethylene terephthalate, polyethylene naphthalene, polyarylate, poly And a carbonate, and a cyclic olefin copolymer. The multilayer plastic substrate of claim 4, wherein the polymer composite material containing the inorganic additive is a polymer-clay nanocomposite in which clay nanomaterials are dispersed in a polymer matrix. The method of claim 6, wherein the polymer used in the polymer composite material is polystyrene, polymethacrylate, polyethylene terephthalate, polyethylene naphthalene, polyarylate, polycarbonate, cyclic olefin copolymer, polynorbornene, aromatic florene poly At least one selected from esters, polyethersulfones, polyimides, epoxy resins, and polyfunctional acrylates, wherein the clay is selected from laponite, montmorillonite, and megadite. The organic or organic-inorganic hybrid layer according to any one of claims 1 to 7, wherein the organic or organic-inorganic hybrid layer has a monomer of an organic compound having two or more polymerizable unsaturated groups in a molecule or two or more polymerizable unsaturated groups in a molecule. An oligomer having a weight average molecular weight of 100 or more and 1,000 or less; And a coating composition containing a weight average molecular weight of 1,000 or more and 500,000 or less of an organic compound having one or more polymerizable unsaturated groups in a molecule thereof. The method of claim 8, wherein the organic or organic-inorganic hybrid layer is a metal, glass powder, diamond powder, silicon oxide, clay, calcium phosphate, magnesium phosphate, barium sulfate, aluminum fluoride, calcium silicate, magnesium silicate, barium silicate, At least one filler selected from the group consisting of barium carbonate, barium hydroxide, and aluminum silicate; And a solvent further comprising a composition. The method of claim 1, wherein the organic or organic-inorganic hybrid layer, (A) an organosilane partial hydrolyzate selected from the group consisting of compounds represented by the following formulas (1) to (3); Or (B) a multilayer plastic substrate formed by curing at least one metal alkoxide partial hydrolyzate selected from the group consisting of compounds represented by the following formula (4), [Formula 1] (R ¹ ) _m -Si-X _(4-m) [Formula 2] (R ¹ ) _m -O-Si-X _(4-m) [Formula 3] (R ¹ ) _m -N (R ² ) -Si-X _(4-m) [Formula 4] M- (R ³ ) _z In Chemical Formulas 1 to 3, X may be the same or different from each other, hydrogen, halogen, alkoxy, acyloxy, alkylcarbonyl, alkoxycarbonyl, or -N (R ² ) ₂ having 1 to 12 carbon atoms, R ¹ may be the same or different from each other, alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkynyl, alkynylaryl, halogen, amide having 1 to 12 carbon atoms , Aldehydes, ketones, alkylcarbonyl, carboxy, mercapto, cyano, hydroxy, alkoxycarbon having 1 to 12 carbon atoms, alkoxycarbonyl having 1 to 12 carbon atoms, sulfonic acid, phosphoric acid, acryloxy, methacrylicoxy, epoxy, Or vinyl group, R ² is hydrogen or alkyl having 1 to 12 carbon atoms, m is an integer of 1 to 3, In Chemical Formula 4, M represents a metal selected from the group consisting of aluminum, zirconium, and titanium, R ³ may be the same as or different from each other, and is a halogen, an alkyl, alkoxy, acyloxy, or hydroxy group having 1 to 12 carbon atoms, Z is an integer of 3 or 4. The method of claim 10, wherein the organic or organic-inorganic hybrid layer is a metal, glass powder, diamond powder, silicon oxide, clay, calcium phosphate, magnesium phosphate, barium sulfate, aluminum fluoride, calcium silicate, magnesium silicate, barium silicate, At least one filler selected from the group consisting of barium carbonate, barium hydroxide, and aluminum silicate; And a solvent further comprising a composition. The gas barrier of claim 8, wherein the gas barrier layer comprises SiO _x (where x is an integer of 1 to 4), SiO _x N _y (where x and y are integers of 1 to 3, respectively), Al ₂ O ₃ , and A multilayer plastic substrate formed from at least one inorganic material selected from the group consisting of ITO. The multilayer plastic substrate of claim 8, wherein the gas barrier layer has a thickness of 5 nm to 1,000 nm. The method according to any one of claims 1 to 7, and 10 to 11, wherein the polysilazane layer is a perhydropolysilazane represented by the following formula (5); And a multilayer plastic substrate formed by crosslinking at least one of an organopolysilazane represented by Chemical Formula 6 and an organopolysilazane represented by Chemical Formula 7, [Formula 5]

[Formula 6]

[Formula 7]

In Formula 5, n is a positive integer; In Formula 6, n is a positive integer, R ⁴ , R ⁵ , and R ⁶ is hydrogen, alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 12 carbon atoms, alkylsilyl of 1 to 12 carbon atoms, of 1 to 12 carbon atoms Alkylamino, cycloalkyl having 1 to 12 carbon atoms, alkenyl having 1 to 12 carbon atoms, and allyl having 1 to 12 carbon atoms; In Formula 7, n and m are positive integers, R is alkyl having 1 to 12 carbon atoms. The multilayer plastic substrate of claim 14, wherein the polysilazane layer is formed by crosslinking polysilazane at a temperature of 300 ° C. or less and a relative humidity of 50% or more, and performing oxygen plasma treatment. delete The multilayer plastic substrate according to claim 14, wherein the surface hardness of the plastic substrate is 8H or more as measured by a pencil hardness meter. a) coating an organic or organic-inorganic hybrid layer-forming composition on one side of the plastic film and curing to form an organic or organic-inorganic hybrid layer having a thickness of 0.1 μm to 50 μm, b) coating a polysilazane solution on the organic or organic-inorganic hybrid layer and curing at a low temperature to form a polysilazane layer having a thickness of 0.1 μm to 50 μm to prepare a multilayer film, c) repeating the steps a) to b) to prepare one more multilayer film of the same structure as b), d) bonding the surfaces of the plastic film, in which the layers of the multilayer films of b) and c), are not formed, to each other to form a symmetrical structure; Method for producing a multilayer plastic substrate comprising a. 19. The method of claim 18, further comprising forming a gas barrier layer over the organic or organic-inorganic hybrid layer formed in step a). 19. The method of claim 18, wherein the bonding in step d) is made by an acrylic adhesive or a thermal bonding method. An image display apparatus provided with the multilayer plastic substrate according to any one of claims 1 to 7 and 10 to 11. An image display device comprising the multilayer plastic substrate according to claim 8. An image display device provided with the multilayer plastic substrate according to claim 14.

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