KR20170003183A - Transparent Plastic Sheet And Liquid Crystal Display Device Including The Same As A Front Sheet - Google Patents

Abstract

The present invention relates to a transparent plastic sheet and a liquid crystal display device comprising the same. The transparent plastic sheet comprises: a first layer including a polycarbonate (PC); a second layer laminated on an upper portion of the first layer and including a heat resistant polymethylmethacrylate (PMMA) having a glass transition temperature of 120 to 135 C; and a coating layer laminated on an upper portion of the second layer and formed with a cured product of a siloxane resin composition.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a transparent plastic sheet and a liquid crystal display (LCD)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent plastic sheet, and more particularly, to a transparent plastic sheet having a high hardness and having a laminated structure and applicable to a cover sheet for front protection of a display.

BACKGROUND ART [0002] Conventionally, a glass material has been widely used as a display material for an electrode substrate for a liquid crystal display panel, a plasma display panel, an electroluminescence fluorescent display tube, or a light emitting diode. However, glass is prone to breakage and has a large specific gravity, which makes it difficult to pursue thinness and lightness, and in particular, it is not suitable for a flexible display. Therefore, transparent plastic materials that can replace glass materials are attracting attention. It is expected that plastic materials will be very competitive if they are replaced with those where conventional glass materials were used because they are light and difficult to break and can reduce manufacturing cost.

In particular, as various display devices such as LCDs, PDPs, mobile phones, and projection televisions are greatly developed, in order to replace the front cover sheet, that is, the window sheet, located in the front portion of these display devices with plastic materials And polycarbonate (PC) resins are most widely used as plastic materials to replace glass. PC is excellent in transparency, impact resistance, heat resistance, freedom of processing, and light weight, and can be used for automobile applications such as window cover, liquid crystal display cover for electric and electronic devices, window glass, sunroof, instrument cover, It is also applied to construction materials such as window glass.

Conventional techniques related to a window sheet using a plastic material include a transparent resin plate (see Japanese Patent Laid-Open No. 2000-321993) provided with a UV coat film on the surface of a transparent resin plate and a retardation film on the back surface as a liquid crystal display cover, And a method for producing a polycarbonate resin laminate in which this excellent cured film is coated (see Japanese Patent Application Laid-Open No. 2004-130540). Further, a high hardness material containing a silsesquioxane resin having photo-curability is applied to the surface of the transparent plastic film and is photo-cured to obtain a material having excellent transparency, high surface hardness, weather resistance, chemical resistance, durability or heat resistance 2008-037101).

However, according to recent trends, various display devices and devices are becoming more and more sophisticated and slimmer at the same time and lightweight, so that the price is relatively higher in accordance with high performance, but device breakdown such as dropping easily with light weight is frequently occurring. As a result, consumers are demanding more impact resistant products. In this trend, PCs, which are most widely used as substitutes for glass, have limited surface properties such as low surface hardness and low reflectivity, The situation became constrained.

Therefore, researches to improve the transparency, surface hardness, durability and heat resistance of plastic materials have been carried out in various angles. According to the research and development trends so far, plastic sheets showing the most stable physical properties are laminated with PC and PMMA As a sheet having a structure. However, the laminated structure sheet of PC and PMMA has transparency, surface hardness, durability and heat resistance to some extent, but the PMMA layer forming the surface layer frequently has cracks at the edge portion thereof, Especially, it was not suitable to be applied to a device or an apparatus which extended the area of the display up to the edge portion.

In order to further improve the surface hardness, a hard coating treatment may be applied to the surface of the PMMA. However, most of them are hybrid type of acrylic or organic. In order to have a sufficient effect, a thick layer has to be formed. There is still a limit to the extent to which it is possible to solve this problem.

Accordingly, it is an object of the present invention to provide a transparent plastic sheet having a surface hardness close to that of glass, excellent interlaminar adhesion, impact resistance and abrasion resistance, and free from surface cracks during curved surface processing.

A first preferred embodiment according to the present invention comprises a first layer comprising a polycarbonate (PC); A second layer comprising a heat resistant polymethylmethacrylate (PMMA) layered on top of the first layer and having a glass transition temperature of from 120 to 135 占 폚; And a transparent plastic sheet laminated on the second layer and including a coating layer of a cured product of the siloxane resin composition.

The second layer according to the first embodiment may include a heat resistant polymethyl methacrylate having a glass transition temperature of 120 to 135 DEG C based on the total weight of the resin in an amount of 50 wt% or more.

The siloxane resin composition according to the first embodiment may include a siloxane resin having an alicyclic epoxy group in the molecular structure and having a weight average molecular weight of 1000 to 15000 and a polydispersion index (PDI) of 5.0 to 1.2, The transparent plastic sheet may further include the coating layer in a lower portion of the first layer.

The siloxane resin may be an alkoxysilane containing an alicyclic epoxy group and an alkoxy group represented by the following formula (1) alone; Or an alkoxysilane containing an alicyclic epoxy group and an alkoxy group represented by the following formula (1) and an alkoxysilane compound represented by the following formula (2) may be chemically bonded.

???????? R ¹ _n -Si- (OR ² ) _4-n ?????

???????? R ³ _m -Si- (OR ⁴ ) _4-m ?????

Wherein R ¹ is a linear or branched C1 to C6 alkyl group containing an alicyclic epoxy group, the alicyclic epoxy group has a structure having an epoxy group as a C3 to C6 cycloalkyl group, and R ₂ is a linear or branched C1 to C7 R ³ is an alkyl group having from 1 to 20 carbon atoms, such as a C 1 to C 20 alkyl group, a C 3 to C 8 cycloalkyl group, a C 2 to C 20 alkenyl group, a C 2 to C 20 alkynyl group, a C 6 to C 20 aryl group, an acrylic group, a methacrylic group, R ⁴ is a linear or branched C 1 to C 7 alkyl group, and n is an integer of 1 to 3, preferably 1 to 3 carbon atoms, And m is an integer of 0 to 3.

In this case, the alkoxysilane represented by Formula 1 may be selected from the group consisting of 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and 2- 4-epoxycyclohexyl) ethyltripropoxysilane, and the siloxane resin may have an epoxy equivalent of 0.35 to 0.6 mol / 100 g.

The siloxane resin composition according to the first embodiment may further include one or more additives selected from the group consisting of reactive monomers, crosslinking agents, organic solvents, photoinitiators, thermal initiators, antioxidants, leveling agents and coating aids.

The thickness ratio of the first layer to the second layer according to the first embodiment is 95 to 80: 5 to 20, the thickness of the coating layer is 10 to 100 탆, and the thickness of the whole sheet may be 0.5 to 1.0 mm .

When the transparent plastic sheet according to the first embodiment is bent at room temperature, the degree of bending of the coating layer without generating cracks may be 200 mm or less based on the radius of curvature.

The transparent plastic sheet according to the first embodiment has a surface hardness of 4H to 9H measured in terms of pencil hardness on the surface of the coating layer laminated on the upper side of the second layer according to ASTM D3363, The impact strength measured with the laminated coating layer as the uppermost portion may be 20 to 50 J / cm ² , and the standard of leaving at 120 ° C for 120 hours at a temperature of 60 ° C and a relative humidity of 90% Lt; / RTI >

The transparent plastic sheet may have a total transmittance of 89 to 94% as measured by ASTM D1003. The transparent plastic sheet of the first embodiment may be a front cover sheet, A liquid crystal display device is a second preferred embodiment of the present invention.

The transparent plastic sheet of the present invention exhibits a surface hardness of 4H or more, so that the surface hardness can be much better than that of a conventional cover sheet for general protection, that is, a window cover sheet. Even if a coating layer is formed to a thickness of up to 100 μm, And the impact strength can be excellent.

In addition, cracks (cracks) on the surface or edges due to the coating layer do not occur during processing, and various designs can be easily processed, so that the present invention can be applied without restrictions to the shape of the display.

FIG. 1 is a sectional view showing a cross-section of a transparent plastic sheet of the present invention in which a coating layer is laminated on top of a second layer.
FIG. 2 is a cross-sectional view showing a structure of a transparent plastic sheet of the present invention in which the coating layer is laminated on the lower part of the first layer and the upper part of the second layer.
FIG. 3 is a schematic representation of a ball drop test method for determining surface breakage when a 130 gram metal ball is dropped at a height of 20 cm.
Fig. 4 is a photograph showing that there is no surface cracking of the transparent plastic sheet of the present invention in the ball drop test conducted by the method of Fig. 3;
Fig. 5 is a photograph showing that cracking (cracking) of the coating layer does not occur when the sheet is bent at room temperature with the coating layer of the transparent plastic sheet of the present invention directed outward.

According to one aspect of the present invention, there is provided a liquid crystal display comprising: a first layer comprising polycarbonate (PC); A second layer comprising a heat resistant polymethylmethacrylate (PMMA) layered on top of the first layer and having a glass transition temperature of from 120 to 135 占 폚; And a transparent plastic sheet laminated on the second layer and including a coating layer of a cured product of the siloxane resin composition.

In this case, the plastic sheet may be 'transparent' having a light transmittance of 89% or more as measured by ASTM D1003. In the plastic sheet, the thickness ratio of the first layer to the second layer is 95 to 80: 5 to 20, It is more preferable that the transmittance is 89 to 94%.

In the present invention, the first layer serves to secure the impact strength of the sheet, and the first layer means a resin containing polycarbonate, and more preferably a polycarbonate resin. At this time, the polycarbonate resin may be obtained by, for example, an aromatic dihydroxy compound alone or an aromatic dihydroxy compound and a small amount of a polyhydroxy compound and phosgene, or an aromatic dihydroxy compound and di Or may be a linear or branched polycarbonate resin produced by an ester exchange reaction with an ester.

The molecular weight of the polycarbonate resin is not particularly limited as long as the sheet can be produced by ordinary extrusion molding, but it is preferably 10,000 to 200,000, more preferably 40,000 to 80,000. The polycarbonate resin may have a glass transition temperature of 140 to 150 ° C and a refractive index of 1.55 to 1.60. The polycarbonate resin may contain various commonly used additives. Examples of possible additives include antioxidants, antistatic agents, ultraviolet absorbers, light diffusing agents, flame retardants, release agents, lubricants, antistatic agents and the like, but are not limited thereto .

Meanwhile, in the present invention, the second layer plays a role of securing the surface hardness, and it means a resin containing PMMA, more preferably PMMA resin. Particularly, in the present invention, it is preferable that the second layer contains heat resistant PMMA having a glass transition temperature of 120 to 135 DEG C at a content ratio of 50 wt% or more based on the total weight of the resin. The heat-resistant PMMA having a glass transition temperature of 120 to 135 ° C according to the present invention is more specifically a styrene methyl methacrylate maleic anhydride copolymer containing 15 to 70% of styrene, 25 to 80% of methyl methacrylate and 5 to 50% of maleic anhydride, , And can be distinguished from a conventional PMMA resin (hereinafter referred to as general PMMA) having a glass transition temperature of 100 to 110 占 폚.

The heat resistant PMMA having the glass transition temperature of 120 to 135 캜 has a water absorption rate of 0.15 to 0.2% based on a temperature of 35 캜 and a relative humidity of 97%, a dimensional strain of 0.2% at a temperature of 65 캜 and a relative humidity of 90% To 0.25%. Accordingly, when heat-resistant PMMA having a glass transition temperature of 120 to 135 占 폚 is used, the deformation of the sheet can be minimized as compared with the case of using general PMMA, which is highly affected by moisture, and consequently the reliability of the final sheet can be remarkably increased. More specifically, the transparent plastic sheet of the present invention may be one which does not cause warpage or has a warpage change of 0.3 mm or less on a standard of leaving for 120 hours at a temperature of 60 캜 and a relative humidity of 90%.

The heat resistant PMMA having a glass transition temperature of 120 to 135 占 폚 exhibits excellent adhesion with an epoxy based hard coating solution and has a surface energy as high as 29 nN / m. As a result, the adhesion with the coating layer formed on the upper portion of the second layer can be improved, and surface cracking and edge cracking can be remarkably reduced. However, in order to secure the reliability and adhesion as described above, it is preferable that the second layer contains modified PMMA having a glass transition temperature based on the total weight of the resin of 120 to 135 占 폚 at a content of 50 wt% or more.

In the present invention, the first layer comprising polycarbonate and the second layer deposited thereon may be produced by co-extrusion. The extruder for co-extrusion consists of a main extruder for extruding the first layer and a sub-extruder for extruding the second layer. However, since the thermal properties of PC and PMMA are different, the temperature condition of the main extruder is 270 to 290 ° C And the temperature condition of the sub-extruder is preferably controlled to 230 to 250 ° C. The extruder may preferably be provided with a polymer filter to remove foreign substances in the resin, but is not limited thereto.

Examples of the method of extruding the injected resin include a multi-manifold method in which different resins are molded into a sheet form inside the die, a feed block method in which the resin is introduced into a sheet forming die such as a T- Known methods can be used. At this time, the temperature of the die is 250 to 320 占 폚, preferably 270 to 300 占 폚, and the temperature of the forming roll is usually 100 to 140 占 폚, preferably 110 to 130 占 폚, .

In this case, the thickness of each layer can be controlled by controlling the speeds of the main extruder and the sub-extruder. According to a preferred embodiment of the present invention, the thickness ratio of the first layer including PC to the second layer including PMMA is 95 - 80: 5 ~ 20. If the thickness of the second layer is less than 5%, the effect of improving the surface hardness is insignificant. If the thickness exceeds 20%, the plastic sheet may be deformed in size.

According to a preferred embodiment of the present invention, the siloxane resin composition may include a siloxane resin containing an alicyclic epoxy group in its molecular structure and having a weight average molecular weight of 1000 to 15000 and a polydispersion index (PDI) of 5.0 to 1.2 have. Here, the weight average molecular weight may be a value measured by a conventional method using GPC (Gel Permeation Chromatography), and PDI is a value obtained by dividing the measured weight average molecular weight by a number average molecular weight (which can also be measured by GPC) Can be calculated separately.

In the present invention, the coating layer by the cured product of the siloxane resin composition may be further included in the lower part of the first layer as well as the upper part of the second layer. When the coating layer is formed on both the upper and lower portions of the entire sheet, it may be easier to minimize the warping generated in the aging process after the formation of the coating layer.

However, it is preferable that the thickness of the coating layer is controlled to 10 to 100 mu m so that the surface hardness can be improved without increasing the thickness of the entire sheet. Thus, the thickness of the entire sheet can be maintained at 0.5 to 1.0 mm . In the present invention, the coating layer may be formed by a slot die coating method to form a uniform thickness, but the present invention is not limited thereto.

In the present invention, the coating layer is laminated to further improve the surface hardness of the sheet, and the role of the coating layer may be important. In general, the plastic sheet made of PC is very weak in hardness and the plastic sheet made of PMMA is very weak in impact resistance. Therefore, a sheet is formed by laminating a PMMA layer on a PC layer, and the surface hardness of the plastic sheet is set to 2H . In order to further improve the surface hardness, a hard coating layer is applied. In general, the acrylic type coating composition used as the hard coating composition has a high degree of crosslinking for securing hardness, so that it is possible to secure hardness, but the coating film is hardened, In addition, a large amount of cracks may occur during bending workability.

However, in the case of the present invention, since the siloxane chain has a strong inorganic property and at the same time has an alicyclic structure at the terminal, excellent hardness can be secured and flexibility can be ensured. That is, even if the coating layer is formed to a thickness of 10 to 100 탆, the coating layer exhibits a soft characteristic, so that the impact strength measured with ASTM D256 as the uppermost coating layer on the second layer is 20 J / cm ² The surface hardness (pencil hardness) measured on the surface of the coating layer according to ASTM D3363 can be secured to 4H to 9H while exhibiting excellent impact resistance.

In addition, a phenomenon that the coating layer is broken or separated from the first layer or the second layer does not occur at the time of processing, and it is possible to provide a plastic sheet excellent in workability as well as physical properties. In particular, since the modified PMMA having a glass transition temperature of 120 to 135 ° C is included in the second layer, the present invention can further improve the bonding force with the coating layer and thus has excellent processability. Therefore, It can be bent without causing cracks of the coating layer, and the degree of bending of the transparent plastic sheet of the present invention without cracks can be 200 mm or less based on the radius of curvature. In particular, such properties can be excellent regardless of the direction of the coating layer or the direction opposite to the direction of the coating layer.

Hereinafter, the coating layer of the present invention will be described in more detail as follows.

In the present invention, the coating layer is formed of a cured product of a siloxane resin composition containing a siloxane resin, wherein the siloxane resin has an alicyclic epoxy group and has a weight average molecular weight of 1000 to 15000 and a polydispersion index (PDI) of 5.0 to 1.2 An alkoxysilane containing an alicyclic epoxy group and an alkoxy group represented by the following general formula (1); Or an alkoxysilane containing an alicyclic epoxy group and an alkoxy group represented by the following formula (1) and an alkoxysilane compound represented by the following formula (2) may be chemically bonded.

???????? R ¹ _n -Si- (OR ² ) _4-n ?????

???????? R ³ _m -Si- (OR ⁴ ) _4-m ?????

Wherein R ¹ is a linear or branched C1 to C6 alkyl group containing an alicyclic epoxy group and the cycloaliphatic epoxy group has a structure having an epoxy group as a C3 to C6 cycloalkyl group and R ₂ is linear or branched And R ³ is a C1 to C20 alkyl group, a C3 to C8 cycloalkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 to C20 aryl group, an acrylic group, a methacrylic group, a halogen group R ⁴ is a linear or branched C 1 to C 7 alkyl group, n is an integer of 1 to 3, n is an integer of 1 to 5, n is an integer of 1 to 5, Is an integer of 1 to 3, and m is an integer of 0 to 3.

In the present invention, the term 'chemical bond' refers to a bond formed by hydrolysis and condensation reaction of alkoxysilane in the presence of water and a catalyst. The alkoxy group of the starting alkoxysilane is hydrolyzed by water to form a hydroxyl group And a siloxane bond is formed through a condensation reaction with another hydroxyl group or alkoxy group of the silane to form a chemical bond.

In the present invention, the weight average molecular weight and PDI of the siloxane resin are controlled through controlling the reaction rate, and when the weight average molecular weight is 1000 to 15000 and the polydispersion index (PDI) is not 5.0 to 1.2, The film may not be formed, or it may be difficult to secure optical properties and hardness. In addition, the epoxy equivalent of the siloxane resin is preferably 0.35 to 0.6 mol / 100 g, and it is preferable to have a relatively high epoxy equivalent so as to increase the degree of crosslinking so that the cured film is densely formed.

According to a preferred embodiment of the present invention, the alkoxysilane represented by Formula 1 is selected from the group consisting of 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane And 2- (3,4-epoxycyclohexyl) ethyltripropoxysilane.

In addition, the alkoxysilane represented by the above-mentioned general formula (2) is preferably a tetramethoxysilane, a tetraethoxysilane, a methyltrimethoxysilane, a methyltriethoxysilane, a methyltripropoxysilane, a dimethyldimethoxysilane, Diphenylmethoxysilane, diphenyldiethoxysilane, triphenylmethoxysilane, triphenylethoxysilane, ethyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, diphenyldiethoxysilane, diphenyldiethoxysilane, triphenylmethoxysilane, Vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, N- (3-acryloxy-2-hydroxypropyl) -3-aminopropyltrimethoxysilane, N- Acryloxy-2-hydroxypropyl) -3-aminopropyltriethoxysilane, N- (3-acryloxy-2- hydroxypropyl) -3-aminopropyltripropoxysilane, 3-acryloxypropylmethyl Bis (trimethoxy) silane, 3-acryloxypropyltrimethoxy (Meth) acryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (Meth) acryloxypropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- Propyltrimethoxysilane, 3-aminopropyltriethoxysilane, chloropropyltrimethoxysilane, chloropropyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, and the like. However, the But may not be limited.

In the present invention, the siloxane resin composition may further include at least one additive selected from the group consisting of reactive monomers, crosslinking agents, organic solvents, photoinitiators, thermal initiators, antioxidants, leveling agents and coating aids, The reactive monomer may be a monomer having an alicyclic epoxy group or a monomer having an oxetane group, and the crosslinking agent may be an acid anhydride monomer capable of reacting with an alicyclic epoxy group of the siloxane resin to form a crosslink.

Thus, the transparent plastic sheet of the present invention can provide excellent impact resistance, surface hardness, and processability in spite of forming a coating layer of a thick film, and can be easily applied as a front cover sheet of a droplet display device.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for the purpose of illustrating the present invention more specifically, and the present invention is not limited thereto.

Example  1. Production of a sheet having a coating layer formed on its upper surface

A polycarbonate (LG Chem) resin having a glass transition temperature of 147 캜 and Heat resistant PMMA resin (15 to 70% of styrene, 25 to 80% of methyl methacrylate, and maleic (meth) acrylate having a glass transition temperature of 129 占 폚, a water absorption rate of 35 占 폚 / 97% and a dimensional change rate of 0.21% at 60 占 폚 / anhydride 5 to 50% copolymerization) were prepared. The prepared PC resin and heat-resistant PMMA resin were mixed with a main extruder having a barrel diameter of 150 mm, a screw L / D of 35 and a cylinder temperature of 270 캜, and a barrel having a diameter of 45 mm, a screw L / D of 35 and a cylinder temperature of 245 캜 Extruded into a set sub-extruder to simultaneously melt-extrude the two resins.

The temperature in the die pads was then set to 270 and 245 DEG C respectively and the laminated and integrated resin in the die was passed through three polishing rolls of mirror-finished horizontal arrangement. At this time, the temperature of the first roll was set to 100 ° C, the temperature of the second roll was set to 130 ° C and the temperature of the third roll was set to 120 ° C. The number of revolutions of the main extruder (support layer forming extruder) and the sub- A plastic sheet (thickness: 1 mm) was prepared so that the discharge amount ratio was set to be Main / Sub = 85/15, so that the PC layer was 0.85 mm and the PMMA layer was 0.15 mm thick.

On the other hand, 10 parts by weight of a monomer having an oxetane group and 1 part by weight of a photoinitiator were mixed with 100 parts by weight of a siloxane resin (weight average molecular weight: 1000 to 15000, PDI: 5.0 to 1.2) % To prepare a coating solution (siloxane resin composition). Thus, after the solvent for 5 to 15 minutes, the prepared coating solution 10 to the PMMA layer thickness 100㎛ upper portion of the plastic sheet and coating Slot Die, in the drying oven at 70 ~ 80 ℃ drying temperature, 600 ~ 4000mJ / cm ² intensity And then cured with a UV-B lamp under the conditions to finally produce a transparent plastic sheet.

Example  2. Sheet manufacture with coating layer on both sides

Example 2 was prepared in the same manner as in Example 1 except that a coating layer was formed on the lower part of the PC layer in the same manner.

Comparative Example  1. Production of sheet without coating layer

The plastic sheet before the formation of the coating layer in Example 1 was regarded as Comparative Example 1.

Comparative Example  2. General hard  The coating layer PMMA Sheet manufacture on layer

A transparent plastic sheet was prepared in the same manner as in Example 1 except that a general acrylic resin was used for forming a coating layer

Comparative Example  3. General PMMA ≪ RTI ID = 0.0 > sheet < / RTI >

The second layer was formed by using general PMMA (LGMMA, glass transition temperature of 110 占 폚, water absorption rate at 35 占 폚 / 97%, 0.41% at 60 占 폚 / 90%) instead of PMMA used in Example 1 A plastic sheet was produced in the same manner as in Example 1 above.

Comparative Example  4. Different molecular weight Siloxane  Sheet production with a coating layer formed of resin

A plastic sheet was prepared in the same manner as in Example 1 except that a coating layer was formed using a siloxane resin having a weight average molecular weight of 800 and a PDI of 2.1 in Example 1 at all times.

Comparative Example  5. Different molecular weights Siloxane  Sheet manufacture with a coating layer formed on both sides with resin

A plastic sheet was prepared in the same manner as in Example 2 except that a coating layer was formed using a siloxane resin having a weight average molecular weight of 800 and a PDI of 2.1 in Example 2 at all times.

Then, the physical properties of the above Examples 1 to 2 and Comparative Examples 1 to 5 were evaluated as follows. The results are shown in Table 1 below.

Measurement example

1) Haze and transmittance measurement: Measured haze and transmittance were respectively measured according to ASTM D1003 standard.

2) Measurement of YI value: After the UV-B lamp was mounted on the QUV instrument, the sample was dropped by 60 cm from the lamp, and the YI value was measured based on the ASTM E-313 calculation method.

3) Measurement of curl characteristics: 16 samples each having a size of 65X135 (mm) were prepared, and the degree of curl of the edge before testing was measured using a steel jig or a Gab gauge. The sample was then subjected to a reliability test at 120 DEG C for 120 hours at a temperature of 60 DEG C and a humidity of 90%. Then, the sample was left at room temperature for 30 minutes and the degree of warpage was measured after reliability evaluation. At this time, the maximum value among the measured bending values before and after the test was selected, and the difference was reflected as the final bending characteristic.

4) Measurement of ball drop characteristics: According to ASTM D5628-10, 130g of ball is vertically dropped from 10cm to 100cm distance to check the point at which scratches occur, (See Figure 3. Typically, the set maker specifies a specification that will not break at a height of 20 cm or more).

5) Measurement of surface hardness (pencil hardness): The surface hardness was measured using a pencil (Mitsubishi 6B to 9H) manufactured by Mitsubishi in accordance with the ASTM D3363 standard under an electric load of 1 kg.

6) Flexural modulus measurement: A 3-point bending test was performed according to ASTM D790.

7) Notched Impact Strength Measurement: Notch was made in each sample and measured according to ASTM D256 at 23 ° C.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Haze (%) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Transmittance (%) 92 91 92 92 92 92 91 YI 0.56 0.74 0.25 0.42 .0.58 0.59 0.57 Bending characteristic
(ΔWarpage, mm) 0.45 0.31 0.78 0.67 0.56 0.61 0.63 Ball drop characteristic (20cm) scratch
none scratch
none fracture fracture fracture scratch
none scratch
none Surface hardness
(Pencil hardness) 9H 9H 1H 4H 9H 9H 9H Flexural modulus (GPa) 2.1 2.3 2.2 2.2 2.5 2.3 2.3 Impact strength
(J / cm ² ) 40 42 38 30 12 41 42

As shown in Table 1, Comparative Example 1 in which the hard coating treatment was not performed had a significantly low surface hardness and poor impact resistance. Even in the case where the coating layer is formed to have the same thickness, the coating layer is cracked in the ball drop test in the case of Comparative Example 2 in which the general hard coat layer is applied as compared to Examples 1 and 2. However, in Examples 1 and 2, (See Fig. 4).

On the other hand, in the case of the warpage characteristics, the two-side coating as in Example 2 was symmetrical to the one-side coating as in Example 1, and the warpage characteristics were somewhat good. Particularly, even in the same coating liquid, when the general PMMA was applied to the surface of the base material as in Comparative Example 3, the adhesion to the coating layer was remarkably lowered, and water was infiltrated into the peeled space. In addition, a phenomenon of cracking occurred in the ball drop test result due to peeling due to lack of adhesion with the coating layer. In addition, Comparative Examples 4 and 5 showed excellent surface hardness and impact resistance, but the compatibility of the coating layer and the PMMA layer was inferior and the flexural characteristics were not excellent.

As can be seen from the comparison of Examples 1 and 2 and Comparative Examples 3 to 5, the impact strength is not significantly affected by the coating layer even if the base layer is the same, even though the bending property is different. However, The impact strength was small even with the same coating composition. That is, it was judged from the above results that excellent bending properties and impact strength can be secured only when the conditions of the base layer and the coating layer satisfy the conditions of the present invention.

Claims (15)

A first layer comprising polycarbonate (PC);
A second layer comprising a heat resistant polymethylmethacrylate (PMMA) layered on top of the first layer and having a glass transition temperature of from 120 to 135 占 폚; And
A transparent plastic sheet laminated on the second layer and including a coating layer of a cured product of the siloxane resin composition.
The transparent plastic sheet according to claim 1, wherein the second layer contains heat resistant polymethylmethacrylate having a glass transition temperature of 120 to 135 占 폚 at a content of 50 wt% or more.
The transparent resin composition according to claim 1, wherein the siloxane resin composition comprises a siloxane resin having an alicyclic epoxy group in its molecular structure and having a weight average molecular weight of 1000 to 15000 and a polydispersion index (PDI) of 5.0 to 1.2. Sheet.
4. The positive resist composition according to claim 3, wherein the siloxane resin is an alkoxysilane containing an alicyclic epoxy group and an alkoxy group represented by Formula 1 below; Or an alkoxysilane comprising an alicyclic epoxy group and an alkoxy group represented by the following general formula (1) and an alkoxysilane compound represented by the following general formula (2).
≪ Formula 1 >
R ¹ _n -Si- (OR ² ) _4-n
(2)
_{^{R 3 m -Si- (OR 4)}} 4-m;
In the above formulas, R ¹ is a linear or branched C1 to C6 alkyl group containing an alicyclic epoxy group, the alicyclic epoxy group has a structure having an epoxy group as a C3 to C6 cycloalkyl group, and R ₂ is a linear or branched A C 1 to C 7 alkyl group and R ³ is a C 1 to C 20 alkyl group, a C 3 to C 8 cycloalkyl group, a C 2 to C 20 alkenyl group, a C 2 to C 20 alkynyl group, a C 6 to C 20 aryl group, an acryl group, a methacrylic group, R ⁴ is a linear or branched C 1 to C 7 alkyl group, n is an integer of 1 to ³ , and R ¹ is a linear or branched alkyl group having from 1 to 10 carbon atoms, R ² is a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, M is an integer of 0 to 3;
The method of claim 4, wherein the alkoxysilane represented by Formula 1 is 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and 2 - (3,4-epoxycyclohexyl) ethyltripropoxysilane. ≪ / RTI >
The resin composition for hard coating according to claim 3, wherein the siloxane resin has an epoxy equivalent of 0.35 to 0.6 mol / 100 g.
[6] The composition of claim 1, wherein the siloxane resin composition further comprises at least one additive selected from the group consisting of a reactive monoamine, a crosslinking agent, an organic solvent, a photoinitiator, a thermal initiator, an antioxidant, a leveling agent, Resin composition for hard coating.
The transparent plastic sheet according to claim 3, wherein the transparent plastic sheet further comprises the coating layer in a lower portion of the first layer.
The method according to claim 1, wherein the thickness ratio of the first layer to the second layer is 95 to 80: 5 to 20, the thickness of the coating layer is 10 to 100 탆, and the total thickness of the sheet is 0.5 to 1.0 mm Transparent plastic sheet.
The transparent plastic sheet according to claim 1, wherein the transparent plastic sheet has a degree of warpage of 200 mm or less based on a radius of curvature without causing cracks in the coating layer when the transparent plastic sheet is bent at room temperature.
The transparent plastic sheet according to claim 1, wherein the transparent plastic sheet has a surface hardness of 4H to 9H in terms of pencil hardness measured on the surface of the coating layer laminated on the second layer in accordance with ASTM D3363.
The transparent plastic sheet according to claim 1, wherein the transparent plastic sheet has an impact strength of 20 to 50 J / cm ² as measured with ASTM D256 as the uppermost coating layer on the second layer.
The transparent plastic sheet according to claim 1, wherein the transparent plastic sheet has no warpage or a warpage change of 0.3 mm or less on a standard of leaving for 120 hours at a temperature of 60 캜 and a relative humidity of 90%.
The transparent plastic sheet according to claim 1, wherein the transparent plastic sheet has a transmittance of 89 to 94% as measured according to ASTM D1003.
A liquid crystal display device comprising the transparent plastic sheet according to any one of claims 1 to 14 as a front cover sheet.

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