KR20160081831A

KR20160081831A - Transparent Plastic Sheet

Info

Publication number: KR20160081831A
Application number: KR1020150189026A
Authority: KR
Inventors: 심상화; 김용수; 두준길
Original assignee: 코오롱인더스트리 주식회사
Priority date: 2014-12-30
Filing date: 2015-12-29
Publication date: 2016-07-08

Abstract

The present invention relates to a transparent plastic sheet, of which transmittance of the whole sheet is 89-94% as measured based on ASTM D1003. More particularly, the transparent plastic sheet comprises: a first layer including a polycarbonate (PC) layer; a second layer stacked on an upper surface of the first layer, and composed of a methylmethacrylate-styrene (MS) layer; and a third layer stacked on an upper part of the second layer, and composed of a polymethyl methacrylate (PMMA) layer. According to the present invention, the transparent plastic sheet has minimized alteration under the conditions of high temperature, thereby being useful for various display products as a window cover replacing glasses.

Description

Transparent Plastic Sheet {Transparent Plastic Sheet}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent plastic sheet, and more particularly, to a multilayered plastic sheet applied to a cover sheet for front protection of a display.

BACKGROUND OF THE INVENTION Glass has been used as a display material for most electrode substrates for liquid crystal display panels, plasma display panels, electroluminescence fluorescent display tubes or light emitting diodes. However, glass is prone to breakage and has a large specific gravity. Therefore, it is limited to pursue thinness and lightness, and is not suitable for implementation of a flexible display. In recent years, transparent plastic materials that can replace glass have attracted 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 a variety of display devices such as LCDs, PDPs, mobile phones, and projection TVs have been greatly developed, it has been desired to replace protective cover sheets, i.e. window sheets, located at the outermost portions of these display devices with plastic materials Attempts are being made rapidly. Polycarbonate (PC) resin is the most widely used plastic material for replacing glass. The PC is excellent in transparency, impact resistance, heat resistance, freedom of processing, and light weight, And liquid crystal display covers, as well as automobile applications such as windowpanes, sunroofs, instrument covers, and construction materials such as mining roofs and windowpanes.

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 the excellent cured coating is coated (see Japanese Patent 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) is also known.

In recent years, the use conditions of resin molded articles including liquid crystal display covers have become stricter in recent years as a result of miniaturization, lightweighting, high performance, and low cost in various apparatuses. In order to cope with low price and small- There is a strong demand for a high resin material. In this trend, PCs that are most widely used as glass substitute plastics are limited in surface characteristics such as low surface hardness and low reflectivity, so that there are many restrictions to expand to the supply stage. As a result, the development of materials capable of further improving the transparency, surface hardness, durability and heat resistance of plastic materials has been made in various aspects.

According to research and development trends so far, the plastic sheet showing the most stable physical properties is known as a sheet having a laminated structure of PC and PMMA. However, the laminated sheet of PC and PMMA has achieved some degree of transparency, surface hardness, durability and heat resistance, but the high strain, low light resistance and surface characteristics in high temperature and high humidity environment still remain as a problem .

Accordingly, it is an object of the present invention to provide a transparent plastic sheet having a multilayered structure in which strain is minimized in a high temperature and high humidity environment.

A preferred embodiment according to the present invention comprises a first layer comprising a polycarbonate (PC) layer; A second layer of a methyl methacrylate-styrene (MS) layer deposited on the top surface of the first layer; And a third layer of a polymethyl methacrylate (PMMA) layer laminated on the upper surface of the second layer, wherein the transmittance of the entire sheet is 89 to 94% as measured by ASTM D1003.

The first layer according to this embodiment is a single layer structure consisting of a polycarbonate layer; Or a multilayer structure in which a methyl methacrylate-styrene (MS) layer of 5 to 20% of the total sheet thickness is present between two layers of polycarbonate layers.

The methyl methacrylate-styrene layer constituting the second layer may be prepared by copolymerizing methyl methacrylate and styrene at a ratio of 3: 1 to 1: 3 to obtain a copolymer having a weight average molecular weight of 50,000 to 200,000 and a glass transition temperature of 95 Lt; RTI ID = 0.0 > 125 C < / RTI > Also, the water absorption rate may be 0.25 to 0.35% based on a temperature condition of 35 캜 and a relative humidity condition of 97%, and the dimensional strain rate may be 0.20 to 0.35% based on a temperature condition of 60 캜 and a relative humidity condition of 90%.

The second layer and the third layer according to the embodiment may have a total thickness of 13 to 30% of the total sheet thickness and a thickness ratio of the second layer and the third layer of 10 to 20: 3 to 10.

In the case where the first layer is a multilayer structure in which a methyl methacrylate-styrene (MS) layer having a thickness of 5 to 20% of the total thickness of the sheet exists between two polycarbonate layers, The formed polycarbonate layer may have a thickness of 1 to 20% of the entire sheet.

Further, the transparent plastic sheet according to the embodiment may have a yellowness index (YI) of 0.20 to 0.50 as measured by ASTM E313, a haze of 0.05 to 0.20% as measured by ASTM D1003, a flexural modulus of 1.6 to 2.5 GPa, a unit area of 65 X 135 mm, and a unit thickness of 1.0 mm, a temperature of 85 캜 and a relative humidity of 85% for 72 hours, and a deflection change of 0.01 to 0.5 mm.

In the case of the transparent plastic sheet of the present invention, the deformation can be minimized under high-temperature and high-humidity conditions, and it is possible to substitute glass for various display products and to spread it as a cover sheet for front protection.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a transparent plastic sheet in which the first layer is a single layer of polycarbonate (PC) layer; Fig.
2 is a cross-sectional view of a transparent plastic sheet having a multilayer structure in which the first layer further comprises a methyl methacrylate-styrene (MS) layer between the polycarbonate (PC) layers.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising: a first layer comprising a polycarbonate (PC) layer; A second layer of a methyl methacrylate-styrene (MS) layer deposited on the top surface of the first layer; And a third layer laminated on the upper surface of the second layer and made of a polymethyl methacrylate (PMMA) layer. Here, 'transparent' in the present invention means that the light transmittance is 89% or more of the ASTM D1003 measurement standard. According to a preferred embodiment of the present invention, the plastic sheet may be a transparent plastic sheet having a transmittance of 89 to 94%.

In the plastic sheet of the multilayer structure of the present invention, the PC layer contained in the first layer is formed of polycarbonate resin. The polycarbonate resin may be formed of, for example, an aromatic dihydroxy compound alone or an aromatic dihydroxy compound in a small amount Or may be a linear or branched polycarbonate resin prepared by an ester exchange reaction between an aromatic dihydroxy compound and a diester of carbonic acid.

The molecular weight of the polycarbonate resin is not particularly limited as long as it is capable of producing a sheet by ordinary extrusion molding, but it is preferably 10,000 to 200,000, more preferably 40,000 to 80,000 as measured by GPC (Gel Permeation Chromatography) Is more preferable. The polycarbonate resin may have a glass transition temperature of 140 to 150 ° C and a refractive index of 1.55 to 1.60. Examples of possible additives include antioxidants, coloring inhibitors, ultraviolet absorbers, light diffusing agents, flame retardants, mold release agents, lubricants, antistatic agents, and salt pigments, and the like. But is not limited thereto.

Meanwhile, in the multilayer plastic sheet of the present invention, the PMMA layer constituting the third layer may be a general PMMA resin having a glass transition temperature of 100 to 110 DEG C or a modified PMMA resin having a glass transition temperature of 120 to 135 DEG C When the modified PMMA is used, it is possible to further improve the warping property of the plastic sheet. The modified PMMA may be obtained by polymerizing 15 to 70% of styrene, 25 to 80% of methyl methacrylate and 5 to 50% of maleic anhydride as a styrene methyl methacrylate maleic anhydride copolymer, and the water absorption rate is 97% And the dimensional strain may be 0.2 to 0.25% at a temperature of 65 캜 and a relative humidity condition of 90%.

Above all, the multi-layered plastic sheet of the present invention comprises an MS layer as a second layer between the PC layer and the PMMA layer, wherein the MS layer is comprised of methyl methacrylate and styrene in a ratio of 1: 3 to 3: More preferably in a ratio of 1: 1, of a methyl methacrylate-styrene resin. The methyl methacrylate-styrene resin preferably has a weight average molecular weight measured by GPC (Gel Permeation Chromatography) of 50,000 to 200,000 and a glass transition temperature of 95 to 125 ° C.

The methyl methacrylate-styrene resin is composed of a copolymer of methyl methacrylate and styrene and may have properties similar to those of PS and close to that of PMMA depending on the copolymerization ratio. Accordingly, in order to improve the dimensional stability against heat and moisture in the final product, the content of styrene can be increased, and if the optical property is to be further enhanced, the content of methyl methacrylate can be increased to control the physical properties. Particularly, PS is not compatible with PC or PMMA, but when it is co-extruded, interfacial separation may occur. However, since MS is excellent in compatibility with PC and PMMA, it is advantageous to form a laminated structure. Can be easily expressed.

In the present invention, the methacrylate-styrene layer formed from the methyl methacrylate-styrene resin has a water absorption rate of 0.25 to 0.35% based on a condition of 35 ° C and 97% relative humidity, a dimensional strain of 60 ° C % Relative humidity condition based on the relative humidity of 0.20 to 0.35%.

In general, the PC has advantages of less transparency and dimensional change, but it is not suitable as a cover sheet for front cover of the display due to its low surface hardness. As a result, a method of laminating PMMA on the surface of a PC to compensate the surface hardness has been applied. However, PMMA has a water absorption rate of about 0.4% at 35 ° C and a relative humidity of 97%, and is relatively weak to moisture. At a temperature of 60 ° C and a relative humidity of 90%, the dimensional strain is 0.38% The dimensional stability under the conditions is very unstable, and warpage often occurs frequently.

On the other hand, in the present invention, by laminating the MS layer having excellent dimensional stability between the PC layer and the PMMA layer as described above, deformation under high temperature and high humidity conditions can be minimized. Particularly, according to a preferred embodiment of the present invention, the transparent plastic sheet has a unit area of 65 X 135 mm and a unit thickness of 1.0 mm, and even after being left for 72 hours at a temperature of 85 캜 and a relative humidity of 85% It can exhibit very small warpage changes. This is because the ordinary sheet having the PC / PMMA structure under the same conditions has a remarkably low strain rate as compared with the fact that a warping change of 1 mm or more is generated. Accordingly, the transparent plastic sheet of the present invention can secure excellent reliability as a window sheet.

The transparent plastic sheet of the present invention may have a yellowness index (YI) of 0.20 to 0.50 as measured by ASTM E313, a haze of 0.05 to 0.20% as measured on ASTM D1003, a flexural modulus of 1.6 to 2.5 GPa as measured by ASTM D790 have. In addition, according to the ASTM E313 standard, when UV was irradiated at 15W and 12CM for 96 hours and left for 30 minutes to measure the yellowness (QUV test), the yellowness of 0.5 to 2.0 was exhibited, and even after exposure to ultraviolet rays, .

According to this characteristic, the transparent plastic sheet of the present invention can satisfy particularly excellent optical characteristics as a window sheet which can be directly exposed to ultraviolet rays, and compared with a case where a flexural modulus is 1 to 1.6 GPa in a sheet made of a PC alone material Therefore, the flexural modulus can be realized at the same level as that of the PC / PMMA structure, so that the disadvantages of the existing window sheet can be complemented and the advantages can be maintained or improved.

In the present invention, the transparent plastic sheet having the multilayer structure can be produced by coextrusion. The temperature of the extruder for co-extrusion is usually from 220 to 290 DEG C, preferably from 230 to 280 DEG C, and it may be preferable to provide a polymer filter on the upstream side from the die of the extruder in order to remove foreign substances in the resin . As a method of laminating the injected resin, 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- May be used. However, the present invention is not limited to the conventional co-extrusion method.

In co-extrusion, the thickness of each layer can be controlled by the ratio of the amount of each layer discharged from the extruder. According to a preferred embodiment of the present invention, the total thickness of the second and third layers is from 13 to 30 %, And more preferably, the ratio of the respective thicknesses is in the range of 10 to 20: 3 to 10. If the sum of the thicknesses of the second layer and the third layer is less than 13% of the total thickness of the sheet, the mechanical properties including the flexural modulus may not be ensured. If the thickness exceeds 30%, the optical characteristics or impact strength may be lowered . In addition, it may be appropriate to adjust the ratio of the second layer and the third layer within the above-mentioned ratio in consideration of the surface hardness and the strain of the entire sheet.

Further, when the thickness ratio of the second layer and the third layer is out of the range of 10 to 20: 3 to 10, and the thickness of the second layer is formed thicker, the proportion of the MS having high yellowness becomes higher, If the thickness of the third layer is made thicker, the ratio of MS is low, so that the effect of lowering the water absorption rate is not as large as expected. Accordingly, the sheet size It is difficult to suppress the stability.

Further, the transparent plastic sheet of the present invention may be manufactured in various structures through the layer structure of the first layer. As shown in FIG. 1, the first layer may be formed as a single layer structure consisting of only a polycarbonate layer, Layer structure in which an MS layer having a thickness ratio of 5 to 20% of the total thickness of the sheet is further laminated between two polycarbonate layers as shown in Fig. When the first layer has a multi-layer structure, it is preferable that the MS layer included in the first layer is also formed of the same MS resin as the second layer, from the viewpoint of securing a balance of total sheet strain, The thickness ratio of the MS layer also preferably satisfies the above range in terms of optimizing reliability.

In order to minimize deformation such as warping and warping of the transparent plastic sheet in the present invention, it is more preferable that the first layer has a multilayer structure including an MS layer between two PC layers rather than a single layer structure. However, in the first layer of the multilayer structure, the PC layer formed on the bottom layer is preferably formed to have a thickness of 1 to 20% of the total sheet thickness in order to secure the impact strength of the entire sheet to the minimum. If the PC of the first layer forming the bottom layer is thicker than the above ratio, the MS layer of the first layer formed on the first layer becomes closer to the second layer, The warpage characteristics may deteriorate. Considering this, if the thickness of the bottom layer is made thicker while the position of the MS layer in the first layer is not close to the second layer and the MS layer is naturally thinned, the effect due to the MS layer reinforcement becomes insignificant, .

In addition, when the MS layer is further reinforced to form the first layer having a multilayer structure of four or more layers, it is difficult to manufacture and the ratio of PC may be relatively low. Therefore, in the present invention, Layer structure in which the MS single layer of the PC single layer or the two PC layers is reinforced in consideration of the impact strength and optical characteristics of the entire sheet.

On the other hand, the transparent plastic sheet of the present invention can further laminate a hard coat layer hardened by a thermosetting or active energy ray in order to improve scratch resistance on the upper surface of the third layer. In the case of a resin used for forming a hard coat layer, it is possible to use a hard coat agent in consideration of suitability with a coating line. If necessary, it may be an organic solvent, an ultraviolet absorber, Surfactants such as various stabilizers such as light stabilizers and antioxidants, leveling agents, antifoaming agents, thickening agents, antistatic agents, antifogging agents and the like can be suitably added.

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. PC / MS ( MMA: PS = 1: 1) / PMMA structure multilayer sheet

Polycarbonate (LG Chem) resin having a glass transition temperature of 147 캜, A PMMA resin (LG Chem) having a glass transition temperature of 110 캜, and an MS resin (MS500, manufactured by Shin-Etsu Chemical Co., Ltd.) in which methacrylate and styrene were copolymerized at a ratio of 1: Denka) were prepared. At this time, the MS resin exhibited a water absorption rate of 0.28% at 35 ° C / 97% and a dimensional change rate of 0.25% at 60 ° C / 90% as measured by Atomatic Film sizer (Dissem).

The prepared resin was charged into three extruders in the order of PC, MS, and PMMA, respectively, and the ratio of the discharge amounts in the respective extruders was set to be 16: 3: 1, and three types of resins were simultaneously melt-extruded. In addition, the temperature in the die pad was set to 270 占 폚, and the laminated and integrated resin in the die was passed through three polishing rolls of a horizontally arranged mirror-finished resin, and finally, the layer thicknesses of PC, MS and PMMA A transparent plastic sheet (total thickness of 1 mm) having 0.80 mm, 0.15 mm, and 0.05 mm, respectively, was produced.

Example 2. PC / MS ( MMA: PS = 3: 7) / PMMA structure multilayer sheet

Example 2 was prepared in the same manner as in Example 1, except that MS resin obtained by copolymerizing methacrylate and styrene with 3: 7 (MS 300, Denka) was used. The MS resin was an Atomatic Film The water absorption rate at 35 ° C / 97% as measured by sizer (Dissem) was 0.25%, and the dimensional change rate at 60 ° C / 90% was 0.23%.

Example 3. PC / MS ( MMA: PS = 3: 1) / PMMA structure multilayer sheet

Example 3 was prepared in the same manner as in Example 1 except that the MS resin obtained by copolymerizing methacrylate and styrene with 3: 1 (MS 750, Denka) was used. The MS resin was an Atomatic Film The water absorption rate at 35 ° C / 97% as measured by sizer (Dissem) was 0.30% and the dimensional change rate at 60 ° C / 90% was 0.28%.

Example 4. Multilayer sheet of (PC + MS + PC) / MS / PMMA structure

The same procedure as in Example 1 was carried out except that the three layers of the extruder forming the first layer were used and PC, MS (MS500, Denka) and PC were put in order to form the first layer with a three-layer structure Co-extrusion was carried out. The thickness of the PC layer formed on the bottom layer in the first layer was 0.1 mm, the thickness of the intermediate MS layer was 0.15 mm, and the thickness of the intermediate layer was 0.15 mm. The first layer was formed so that the thickness of the PC layer was 0.55 mm, and the MS layer and the PMMA layer formed on the first layer were made the transparent plastic sheet (total thickness 1 mm) in the same manner as in Example 1. [

Example 5. Multi-layer sheet of PC / MS / PMMA structure

PC, MS and PMMA in the order of the extruder, and the ratio of the amount of the extruder to the extruder was set to 7: 2: 1. Finally, the layer thicknesses of PC, MS and PMMA were 0.70 mm and 0.20 mm and 0.10 mm, a transparent plastic sheet (total thickness 1 mm) was prepared in the same manner as in Example 1 above.

Example 6. Multilayer sheet of (PC + MS + PC) / MS / PMMA structure

The ratio of the ejection amount of the sub-extruder forming the first layer was 1: 3: 12, the thickness of the PC layer formed on the bottom layer was 0.05 mm, the thickness of the intermediate MS layer was 0.15 mm, (Total thickness of 1 mm) was prepared in the same manner as in Example 5, except that the first layer was formed to have a thickness of 0.60 mm.

Example 7. Multilayer sheet of (PC + MS + PC) / MS / PMMA structure

The ratio of the ejection amount of the sub-extruder forming the first layer was set to be 4: 3: 9. The thickness of the PC layer formed on the bottom layer was 0.20 mm, the thickness of the intermediate MS layer was 0.15 mm, (Total thickness 1 mm) was prepared in the same manner as in Example 5 except that the first layer was formed so as to have a thickness of 0.45 mm.

Comparative Example 1. Single layer sheet of PC structure

A single-layer sheet was prepared by extruding the same PC resin as that used in Example 1, but using a number of PCs to 1 mm.

Comparative Example 2. Multi-layer sheet of PC / PMMA structure

The PC resin and the PMMA resin were co-extruded in the ratio of 4: 1 thickness under the same conditions as in Example 1, except for the omission of the MS for pneumatic pressure, to obtain a multilayered structure having a PC layer thickness of 0.80 mm and a PMMA layer thickness of 0.2 mm Sheet.

Comparative Example 3. Multi-layer sheet of PC / MS structure

Pneumatic release The PC resin and the MS resin were co-extruded in the ratio of 4: 1 thickness under the same conditions as in Example 1 except for the omission of the PMMA, and a multilayer having a PC layer thickness of 0.80 mm and a MS layer thickness of 0.2 mm Sheet.

Comparative Example 4. Multi-layer sheet of PC / MS / PMMA structure

PC, MS, and PMMA in the order of 6: 3: 1, and finally the layer thicknesses of PC, MS, and PMMA were set to 0.60 mm and 0.30 mm and 0.10 mm, a transparent plastic sheet (total thickness 1 mm) was prepared in the same manner as in Example 1 above.

Comparative Example 5. Multi-layer sheet of PC / MS / PMMA structure

PC, MS, and PMMA in the order of 14: 1: 5, and finally the layer thicknesses of PC, MS, and PMMA were set to 0.7 mm and 0.05 mm, and 0.25 mm, a transparent plastic sheet (total thickness of 1 mm) was prepared in the same manner as in Example 1 above.

Comparative Example 6. Multilayer sheet of (PC + MS + PC) / MS / PMMA structure

The ratio of the ejection amount of the sub-extruder forming the first layer was set to be 6: 3: 7, the thickness of the PC layer formed on the bottom layer was 0.30 mm, the thickness of the intermediate MS layer was 0.15 mm, (Total thickness of 1 mm) was prepared in the same manner as in Example 5, except that the first layer was formed to have a thickness of 0.35 mm.

Comparative Example 7. Multilayer sheet of MS / PC / PMMA structure

A transparent plastic sheet (total thickness 1 mm) was prepared in the same manner as in Example 1, except that the order of MS and PC was changed to coextrusion.

The sheet structures of Examples 1 to 7 and Comparative Examples 1 to 7 were summarized in the following Table 1, and the properties of each sheet were evaluated as follows. The results are shown in Table 2 below.

Measurement example

(1) Measurement of haze and transmittance: Measured haze and transmittance were measured according to ASTM D1003 standard.

(2) Yellowness (YI) measurement: Measured yellowness was measured according to ASTM E313 standard.

(3) QUV test: To determine if exposure to UV light can minimize yellowing UV was irradiated at 15W and 12CM for 96 hours and left for 30 minutes to measure the yellowness according to ASTM E313 standard.

(4) Flexural modulus measurement: A three-point bending test was conducted in accordance with ASTM D790 standard to confirm how much it is not bent and endured when a load is applied.

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

(6) Measurement of curl characteristics: Sixteen 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 a temperature of 85 DEG C and a humidity of 85% for 72 hours to allow the sample to stand at room temperature for 30 minutes, and the degree of warpage after the reliability evaluation was measured. 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.

(7) Impact resistance Test: 130 g of Ball Drop Test, Steel Ball, and 30 cm Ball were dropped to check sheet breakage.

The first layer Second layer Third Floor Example 1 PC 0.8mm MS (MS500) 0.15 mm PMMA 0.05mm Example 2 PC 0.8mm MS (MS300) 0.15 mm PMMA 0.05mm Example 3 PC 0.8mm MS (MS 750) 0.15 mm PMMA 0.05mm Example 4 PC ¹⁾ 0.1 mm / MS 0.15 mm / PC 0.55 mm MS 0.15 mm PMMA 0.05mm Example 5 PC 0.7mm MS 0.2 mm PMMA 0.10 mm Example 6 PC ¹⁾ 0.05 mm / MS 0.15 mm / PC 0.60 mm MS 0.15 mm PMMA 0.05mm Example 7 PC ¹⁾ 0.2 mm / MS 0.15 mm / PC 0.45 mm MS 0.15 mm PMMA 0.05mm Comparative Example 1 PC 1.0mm X X Comparative Example 2 PC 0.8mm X PMMA 0.2mm Comparative Example 3 PC 0.8mm MS 0.2 mm X Comparative Example 4 PC 0.6mm MS 0.3 mm PMMA 0.10 mm Comparative Example 5 PC 0.7mm MS 0.05 mm PMMA 0.25mm Comparative Example 6 PC ¹⁾ 0.3 mm / MS 0.15 mm / PC 0.35 mm MS 0.15 mm PMMA 0.05mm Comparative Example 7 MS 0.15 mm PC 0.8mm PMMA 0.05mm

1) PC ^{1) The} displayed PC is the PC layer on the bottom floor in the first floor

Haze (%) Transmittance (%) Yellowness QUV test curve
Modulus of elasticity (GPa) surface
Hardness Bending characteristic
(ΔWarpage, mm) Impact resistance Example 1 0.11 91.14 0.34 1.21 1.98 5H 0.36 OK Example 2 0.11 90.12 0.49 1.42 1.87 5H 0.31 OK Example 3 0.1 91.85 0.31 1.13 2.04 5H 0.39 OK Example 4 0.14 90.89 0.44 1.24 2.41 5H 0.22 OK Example 5 0.10 91.01 0.42 1.29 2.12 5H 0.45 OK Example 6 0.15 90.87 0.42 1.26 2.38 5H 0.21 OK Example 7 0.14 90.75 0.43 1.25 2.40 5H 0.34 OK Comparative Example 1 0.05 92.14 0.6 8.34 1.45 B 0.21 OK Comparative Example 2 0.07 90.34 0.3 1.14 2.05 5H 0.53 OK Comparative Example 3 0.07 89.9 0.55 2.24 1.79 2H 0.28 OK Comparative Example 4 0.11 91.01 0.45 1.25 2.21 5H 0.52 OK Comparative Example 5 0.10 91.80 0.33 1.19 2.24 6H 0.54 OK Comparative Example 6 0.15 90.81 0.43 1.26 2.39 5H 0.51 OK Comparative Example 7 0.12 91.12 0.35 1.23 2.41 5H 0.21 fracture

As can be seen from the analysis of Table 1, Comparative Example 1 consisting of a single layer of PC had excellent bending properties but the surface hardness and QUV test results were very poor. Also, in Comparative Example 2 of the PC / PMMA structure, the surface hardness was improved as compared with Comparative Example 1, but it was found that the bending property was greatly reduced. In Comparative Example 3 of the PC / MS structure, the surface hardness and QUV were not excellent.

On the other hand, even in the case of PC / MS / PMMA structure, as shown in Comparative Example 4, when the ratio of PC is decreased and the MS ratio is increased, the flexural modulus can be improved, but the water absorption rate is relatively higher than that of PC, And the flexural properties were lowered due to the increase of the ratio of MS. When the ratio of the thickness of the MS and PMMA constituting the second layer and the thickness of the third layer is larger than that of the PMMA as in Comparative Example 5, the transmittance, flexural modulus and surface The hardness value could be improved, but the improvement effect on the bending properties was not significant.

Furthermore, from the results of Comparative Example 6, it was confirmed that the physical properties of the first layer were changed according to the position of the MS when the first layer had a multilayer structure. Compared with Examples 4, 6 and 7, When it becomes too thick, the expansion ratio balance of each layer is broken and warpage of 0.50 mm or more occurs. In the case of changing the stacking order of PC and MS, as in the case of Comparative Example 7, there was no significant difference in the optical characteristics and the flexural characteristics from the Examples, but the bottom surface cracking phenomenon can be confirmed after the ball drop test. This is considered to be the same as the reason why the PMMA / PC / PMMA structure can not use the cover sheet.

Compared with the results of these comparative examples, Examples 1 to 6 of the PC / MS / PMMA structure exhibited excellent optical properties as well as excellent surface hardness and flexural characteristics, and the flexural modulus was also equal to that of the PC / PMMA structure sheet Respectively. In particular, the flexural modulus of the PC / MS / PC multi-layered structures of Examples 4, 6, and 7 was more improved than that of the single layer of the first layer.

As a result, the transparent plastic sheet according to the present invention has a low degree of warpage even after being exposed to a high temperature and high humidity environment, thereby securing excellent reliability. In particular, since yellowing can be minimized even after exposure to ultraviolet rays, It was judged to be suitable as the material of the sheet.

Claims

A first layer comprising a polycarbonate (PC) layer;
A second layer of a methyl methacrylate-styrene (MS) layer deposited on the top surface of the first layer; And
A third layer of a polymethylmethacrylate (PMMA) layer stacked on an upper surface of the second layer,
And the transmittance of the entire sheet is 89 to 94% as measured by ASTM D1003.

The method according to claim 1,
The first layer is a single layer structure consisting of a polycarbonate layer; or
Layer structure in which a methyl methacrylate-styrene (MS) layer having a thickness of 5 to 20% of the total thickness of the sheet is present between the two layers of polycarbonate layers.

3. The method according to claim 1 or 2,
The methyl methacrylate-styrene layer constituting the second layer is obtained by copolymerizing methyl methacrylate and styrene at a ratio of 3: 1 to 1: 3, and has a weight average molecular weight of 50,000 to 200,000 and a glass transition temperature of 95 to 125 Lt; RTI ID = 0.0 > g / cm3. &Lt; / RTI >

3. The method according to claim 1 or 2,
The methyl methacrylate-styrene layer constituting the second layer has a water absorption rate of 0.25 to 0.35% at a temperature of 35 DEG C and a relative humidity of 97%, a dimensional strain of 60% and a relative humidity of 90% And the standard is 0.20 to 0.35%.

3. The method according to claim 1 or 2,
Wherein the total thickness of the second layer and the third layer is 13 to 30% of the total sheet thickness, and the thickness ratio of the second layer and the third layer is 10 to 20: 3 to 10, .

6. The method of claim 5, wherein the first layer of the plastic sheet is a multilayer structure having a methyl methacrylate-styrene (MS) layer between 5 and 20% of the total sheet thickness between two polycarbonate layers , And the polycarbonate layer forming the bottom layer in the first layer has a thickness of 1 to 20% of the entire sheet.

The transparent plastic sheet according to claim 1, wherein the transparent plastic sheet has a yellowness index (YI) of 0.20 to 0.50 as measured by ASTM E313 and a haze of 0.05 to 0.20% as measured by ASTM D1003.

The transparent plastic sheet according to claim 1, wherein the transparent plastic sheet has a flexural modulus of 1.6 to 2.5 GPa as measured by ASTM D790.

The transparent plastic sheet according to claim 1, wherein the transparent plastic sheet has a flexural change of 0.01 to 0.5 mm after being left for 72 hours at a temperature of 85 캜 and a relative humidity of 85% based on a unit area of 65 X 135 mm and a unit thickness of 1.0 mm Wherein the transparent plastic sheet is a transparent plastic sheet.