JP5235557B2 - Transparent multilayer sheet for display faceplate - Google Patents

Description

  The present invention relates to a transparent resin laminate, and specifically to a transparent multilayer sheet for a display face plate.

  A transparent thermoplastic resin sheet is used as a material for the transparent sheet for the display faceplate, and conventionally, for example, polymethyl methacrylate (PMMA) resin, polycarbonate (PC) resin, and the like have been used. Moreover, in order to prevent the surface from being damaged, it has been generally performed to form a hard layer (hard coat layer) by coating or the like.

  These various display devices, that is, display devices for mobile devices such as mobile phones and mobile information terminals, and in-vehicle display devices such as car navigation devices, are becoming more and more popular. Characteristics are increasing.

  In the case of acrylic resin such as polymethylmethacrylate resin, which is the material of the face plate that has been used in the past, its elastic modulus is high, so a practically sufficient hardness can be obtained by forming a hard cross-linked film on its surface However, since its thermal deformation temperature is about 100 ° C. or less, there is a growing concern that it will be slightly deformed during continuous use in a high temperature environment, causing problems such as cracks in the hard crosslinked film.

  On the other hand, when polycarbonate resin is used as the material for the faceplate, the deflection temperature under load is as high as about 130 ° C, so there is almost no deformation during continuous use in a normal use environment, thus cracking the hard crosslinked film. However, there is a problem that the hardness required for practical use is insufficient even when a hard cross-linked film is formed on the surface of the polycarbonate resin because of its low elastic modulus.

  Therefore, in order to solve such a problem, a resin laminate obtained by sequentially laminating an acrylic resin layer and a hard coat layer on at least one surface of a polycarbonate resin base material has good adhesion between the resin layers. Have excellent weather resistance, wear resistance, impact resistance, heat resistance and water resistance (for example, Patent Documents 1 to 12).

However, when the thickness of the hard coat layer of the resin laminate becomes as thin as about 1 to 10 μm, the occurrence of interference fringes may be noticeably observed. When this resin laminate is used for a display face plate such as a liquid crystal display device or a touch panel, the visibility of the display is greatly reduced due to the generation of the interference fringes, thereby impairing the commercial value. Therefore, there was room for further improvement for this resin laminate.
JP-A-8-309790 Japanese Patent Laid-Open No. 9-24553 JP-A-11-58654 JP 2003-11293 A JP 2003-165184 A JP 2003-201400 A JP 2004-1393 A JP 2004-250580 A JP 2004-250581 A JP 2004-250582 A Japanese Patent Application Laid-Open No. 2004-250583 JP 2006-103169 A

  An object of the present invention is to provide a transparent multilayer sheet for a display face plate that has good adhesion between resin layers, excellent transparency and hardness, and suppressed generation of interference fringes.

  As a result of intensive studies to solve the above-described problems of the prior art, the present inventor formed an acrylic resin layer on a polycarbonate resin (hereinafter also referred to as “PC resin”) layer, By forming a hard coat layer with a refractive index close to that of the acrylic resin layer on the surface, it is possible to achieve both the heat-resistant deformation characteristics of the polycarbonate resin and the surface hardness characteristics of the acrylic resin, and almost no interference fringes are generated. It has been found that a transparent multilayer sheet can be produced. The inventor has completed the present invention by further study.

  That is, this invention provides the following transparent multilayer sheet for display faceplates, and its manufacturing method.

  Item 1. A transparent multilayer sheet for a display face plate having an acrylic resin layer on at least one side of a polycarbonate resin base sheet, and further having a hard coat layer on the surface of at least one side of the acrylic resin layer, wherein the acrylic resin layer is methyl methacrylate And a styrene copolymer, the acrylic resin layer has a thickness of 40 μm or more, the hard coat layer has a thickness of 1 to 10 μm, and the generation of interference fringes is suppressed. Transparent multilayer sheet for face plates.

  Item 2. Item 2. The transparent multilayer sheet for display faceplate according to Item 1, wherein the total thickness is 250 to 1500 µm.

  Item 3. Item 2. The transparent multilayer sheet for display faceplate according to Item 1, wherein the thickness of the polycarbonate resin substrate sheet is 60% or more of the total thickness.

  Item 4. Item 2. The transparent multilayer sheet for display faceplate according to Item 1, wherein the polycarbonate resin base sheet has acrylic resin layers on both sides.

  Item 5. Item 2. The transparent multilayer sheet for display faceplate according to Item 1, wherein the acrylic resin layer is a methyl methacrylate resin.

  Item 6. Item 2. The transparent multilayer sheet for display faceplate according to Item 1, wherein the hard coat layer is an organic hard coat layer or an organic inorganic hard coat layer.

Item 7. Item 2. The display face plate according to Item 1, wherein the refractive index (R ₂ ) of the hard coat layer is in the range of 0.98 ≦ R ₂ / R ₁ ≦ 1.02 with respect to the refractive index (R ₁ ) of the acrylic resin layer. Transparent multilayer sheet.

Item 8. Item 2. The display face plate according to Item 1, wherein the refractive index (R ₂ ) of the hard coat layer is in the range of 0.99 ≦ R ₂ / R ₁ ≦ 1.01 with respect to the refractive index (R ₁ ) of the acrylic resin layer. Transparent multilayer sheet.

  Item 9. A polycarbonate resin and an acrylic resin, which is a copolymer of methyl methacrylate and styrene, are laminated to form a two-layer sheet by extrusion, and the thickness after drying / curing is 1 to 3 on the surface of the acrylic resin layer. A method for producing a transparent multilayer sheet for a display face plate, wherein a hard coat layer having a thickness of 10 μm is formed, and generation of interference fringes is suppressed.

  Hereinafter, the present invention will be described in detail.

  The transparent multilayer sheet for display faceplate of the present invention has an acrylic resin layer on at least one surface of a polycarbonate resin base sheet, and further has a hard coat layer on at least one surface of the acrylic resin layer. The acrylic resin layer is a copolymer of methyl methacrylate and styrene, the acrylic resin layer has a thickness of 40 μm or more, the hard coat layer has a thickness of 1 to 10 μm, The occurrence is suppressed.

Polycarbonate resin (PC resin) base sheet Polycarbonate resin is suitably used as the base of the transparent multilayer sheet for display faceplates of the present invention in terms of heat resistance, transparency, processing characteristics, market availability, etc. It is done.

  The polycarbonate resin base sheet plays a role of supporting the display face plate transparent multilayer sheet so as not to be deformed when used at a high temperature, particularly in a temperature range exceeding 80 ° C. Therefore, the thickness of the polycarbonate resin base sheet is desirably 60% or more, and further 75% to 95% of the total thickness of the transparent multilayer sheet for display face plate.

  The polycarbonate resin base sheet is highly transparent and preferably has a total light transmittance (JIS K7105) of 85% or more, more preferably 87% to 89%, as measured in the form of a sheet having a thickness of 2 mm.

  Moreover, the deflection temperature under load measured based on JIS K7191 (Method A; load 1.82 Mpa) is 125 ° C. or higher, and further 130 ° C. or higher. In general, it is known that a thermoplastic resin product having a deflection temperature under load by this measuring method of 125 ° C. or higher is not deformed by heat even when used in an automobile. In the present invention, the heat distortion temperature is important in order to support the heat-induced deformation of the transparent multilayer sheet for the display faceplate, but practically, a polycarbonate resin having a deflection temperature under load of 125 ° C. or more should be used. Is preferred.

  As the polycarbonate resin, a polymer derived from a divalent phenolic compound typified by bisphenol A is used. The method for producing the polycarbonate resin is not particularly limited, and any one produced by any of the phosgene method, the transesterification method, and the solid phase polymerization method can be used. There is no particular limitation on the molecular weight.

  Moreover, you may contain various additives, such as a general heat stabilizer used for polycarbonate resin, a ultraviolet absorber, a light-resistant stabilizer, a coloring agent, a mold release agent, a lubricant, and an antistatic agent.

Acrylic resin layer The acrylic resin layer in the present invention supports the hard coat layer formed on the surface of the transparent multilayer sheet for display face plate and exhibits sufficient hardness, so that the surface of the transparent multilayer sheet of the present invention is exposed. The purpose is to prevent damage. Since the thickness of the acrylic resin layer necessary for exerting the hardness of the hard coat layer is too thin, sufficient surface hardness cannot be obtained. Therefore, the thickness is from 40 μm or more, preferably from about 50 to 100 μm. It can be selected as appropriate. Here, the thickness of an acrylic resin layer means the thickness of one side, when an acrylic resin layer exists in both surfaces of a base material sheet.

  As the acrylic resin in the present invention, a styrene-methyl methacrylate copolymer (MS) is preferable because of its transparency, elastic modulus, and refractive index.

  The acrylic resin layer plays a role of reducing the thickness of the entire transparent multilayer sheet for display faceplates as much as possible and imparting difficulty to the sheet to bending. By forming the acrylic resin layer on at least one side of the polycarbonate resin base sheet, the bending elastic modulus of the transparent multilayer sheet for display face plate can be increased. In the case where it is used for an application that requires higher bending elastic modulus of the transparent multilayer sheet for display face plate, it is effective to appropriately increase the thickness of the acrylic resin layer.

  In the present invention, it is necessary that an acrylic resin layer is laminated on at least one side of a polycarbonate resin base sheet, but it is possible to laminate an acrylic resin layer on both sides of a base sheet for a display face plate to be obtained. The transparent multi-layer sheet is suitable because it can give difficulty to large bending. In general, in the laminated sheets of different resins, if the thermal expansion coefficient of each resin and the expansion / contraction ratio due to moisture absorption are different, a difference in dimensions occurs in each layer of the laminated sheet due to changes in environmental temperature and humidity. Warpage occurs in the laminated sheet. By laminating an acrylic resin layer on both surfaces of the polycarbonate resin base sheet, the above problem can be solved preferably.

  The acrylic resin layer has high transparency, and the total light transmittance measured in the form of a sheet having a thickness of 2 mm is preferably 85% or more, and more preferably 87% to 93%.

  Moreover, the bending elastic modulus measured based on JIK K7171 is 2800 MPa or more. In general, it is known that a higher surface hardness can be obtained by forming a hard coat layer on an acrylic resin layer having a high flexural modulus. In order for the hard coat layer to exhibit sufficient scratch resistance, the flexural modulus needs to be 2800 MPa or more.

  In the acrylic resin layer, the higher the ratio of the methyl methacrylate monomer in the styrene-methyl methacrylate copolymer, the lower the refractive index of the resin layer (for example, about 1.49 to 1.51). On the other hand, when an abrasion-resistant organic hard coat layer is used as the hard coat layer, the refractive index tends to increase (for example, about 1.52 to 1.53). When the thickness of the hard coat layer is reduced (for example, about 1 to 10 μm), interference fringes (that is, rainbow patterns) are likely to appear on the surface due to the difference in refractive index between the acrylic resin layer and the hard coat layer. The merchandise value may be impaired.

In order to avoid the generation of the interference pattern refraction index of the hard coat layer _{(R 2)} and relationship _{0.98 ≦ R 2 / R 1 ≦} 1.02 during refractive indexes of the acrylic resin layer _{(R 1)} It is important to adjust the composition of each layer to satisfy. Furthermore, by adjusting to the range of 0.99 ≦ R ₂ / R ₁ ≦ 1.01, generation of interference fringes, that is, rainbow patterns can be almost avoided, and a display plate protective sheet excellent in visibility can be obtained. it can.

The composition of the preferred styrene-methyl methacrylate copolymer is 45 to 95% by weight (especially 60 to 90% by weight) of methyl methacrylate and 5 to 55% by weight of styrene (depending on the composition of the corresponding hard coat layer). In particular, a copolymer consisting of 10 to 40% by weight) may be mentioned. As long as the desired effect of the present invention is not impaired, the copolymer can be used in combination with another monomer capable of copolymerization, if necessary. When the methyl methacrylate resin having such a composition is used, the refractive index (R ₁ ) of the acrylic resin layer is about 1.495 to 1.545, preferably about 1.500 to 1.530.

  Further, from the viewpoints of molding processability and transparent appearance characteristics of the polycarbonate resin and the acrylic resin, the MFR of the polycarbonate resin at 300 ° C./1.2 kg is about 7 to 22 g / 10 min, further about 9 to 16 g / 10 min. In addition, the MFR at 230 ° C./3.8 kg of the acrylic resin is preferably about 1 to 5 g / 10 min, more preferably about 1 to 3 g / 10 min.

  The acrylic resin layer has a pearl shape having a core-shell structure (multilayer polymer particles) in which a core layer made of a rubber-like polymer (crosslinked elastic polymer) is covered with a shell layer of a glass-like polymer (thermoplastic polymer). It is also possible to disperse the fine particles. Furthermore, the acrylic resin layer may contain various additives such as a general heat stabilizer, ultraviolet absorber, light resistance stabilizer, colorant, mold release agent, lubricant, and antistatic agent.

Hard coat layer Generally, an organic hard coat layer, an organic inorganic hard coat layer or the like can be used as the hard coat layer in the present invention.

  Examples of the organic hard coat layer include a type in which a melamine type, alkyd type, urethane type and acrylic resin paint is heat-cured, a type in which a polyfunctional acrylic resin paint is UV-cured, and the like.

  Examples of the organic / inorganic hard coat layer include those in which a photopolymerization reactive functional group is introduced on the surface of silica ultrafine particles and uniformly dispersed in the organic component of the ultraviolet curable hard coat material. Ultraviolet curable hard coat components and photosensitive groups of inorganic ultrafine particles undergo a polymerization reaction, resulting in the formation of a network-like crosslinked coating film in which ultrafine silica particles mediated by chemical bonds are uniformly dispersed in an organic matrix, etc. Is mentioned.

The refractive index (R ₂ ) of the hard coat layer is about 1.49 to 1.53 according to JIS K7105. The pencil hardness (JIS K5600) is about 2H to 5H. The total light transmittance (JIS K7105) is 80% to 93%.

  As a hard coat layer in the present invention, a transparent multilayer sheet for a display face plate can be stably produced with high productivity by using a scratch-resistant organic hard coat film of a type that is cured by irradiation with ultraviolet rays. Can do.

  Since the transparent multilayer sheet for display face plate of the present invention is used in an environment from low temperature to high temperature, it is necessary to determine the thickness of the hard coat layer in consideration of expansion and contraction of the sheet due to temperature change. In order to follow the expansion and contraction of the sheet due to temperature change, it is desirable that the thickness of the hard coat layer is thin, but the hardness of the sheet surface tends to decrease. On the other hand, if the thickness of the hard coat layer is large, curing shrinkage due to UV curing increases and cracks may occur. Therefore, it is preferable that the thickness of the hard coat layer in the transparent multilayer sheet for display face plate is about 1 to 10 μm, particularly about 3 to 8 μm, thereby satisfying both hardness and durability. Here, when there are two hard coat layers, the thickness of the hard coat layer means the thickness of one layer.

Transparent multilayer sheet for display face plate The transparent multilayer sheet for display face plate of the present invention can be produced, for example, as follows.

  First, as a method of laminating an acrylic resin on at least one surface of a polycarbonate resin base sheet, a method of continuously laminating a sheet of an acrylic resin sheet wound around a sheet of a polycarbonate resin base sheet, melting Various methods such as a method of pasting a wound sheet on a sheet that is continuously extruded by an extrusion method, a method of processing a sheet while continuously bonding a polycarbonate resin and an acrylic resin by a melt extrusion method Can be adopted. Among them, the adhesion of the bonding surface can be improved, and as a method for preventing foreign matter from being sandwiched in the bonding surface at the time of bonding, it is processed into a sheet while continuously bonding different kinds of resin materials by a melt extrusion method. The method is preferred.

  In the method of continuously joining different types of resin materials while melting, a method of bonding after discharging from a die for film extrusion, and a film-shaped die after being integrated inside the die for film extrusion There is a method of forming a laminated film by extrusion. Any method can be applied to produce the transparent multilayer sheet for display face plate of the present invention. In the present invention, a method of forming a laminated film by extruding from a film-shaped die after being integrated inside a film extrusion die, that is, a method using a multilayer die is a method suitable for increasing the adhesion. It is.

  As the die used in the method using the multilayer die, those generally used when producing a multilayer film or a multilayer sheet can be used. Feed block type dies or multi-manifold type dies may be used, but in order to minimize variations in the thickness of each layer, it is better to use multi-manifold type dies. Bring.

  When manufacturing a laminated sheet by a method using a multilayer die, it became clear that the difference in fluidity between the polycarbonate resin and the acrylic resin affects the appearance and thickness accuracy of the product sheet. Therefore, as described above, the MFR of the polycarbonate resin at 300 ° C./1.2 kg is preferably about 9 to 16 g / 10 min, and the MFR of the acrylic resin at 230 ° C./3.8 kg is preferably about 1 to 3 g / 10 min. .

  Examples of the method for laminating the hard coat layer on the acrylic resin layer include the following. For example, there is a roll coating method in which coating is performed by supplying paint to two metal or rubber rolls and passing a plate through the gap between the rolls. This is suitable when painting a plate or film. There is a spin coating method in which a coating material is dropped on the center of the product to be painted and rotated to spread the coating material on the surface of the product. This is suitable for the case where a shape close to a circle is coated with a uniform film thickness. There is a spray coating method in which the paint is sprayed on the surface of the coated product. This is suitable for painting molded articles having a three-dimensional shape. There is a dip coating method in which an article to be coated is dipped in a paint liquid and gently pulled up. Thereby, the front and back, such as plate shape, a curved surface, and a three-dimensional shape, can be painted at a time. There is a flow coat method in which a paint is cast on a product to be painted. This can be coated on both sides, such as a plate or curved surface, or on one side.

The transparent multilayer sheet for display face plate obtained as described above has a high pencil hardness (JISK5600) of about 2H to 5H on the hard coat layer, and the sheet was visually confirmed with transmitted light and reflected light. However, interference fringes could not be confirmed. Further, even after 10 reciprocations at 250 gf / cm ² with steel wool # 0000 (manufactured by Nippon Steel Wool Co., Ltd.), no scratches are observed and the film has excellent scratch resistance.

  Specific examples of the layer structure of the transparent multilayer sheet for display faceplate of the present invention include a polycarbonate resin base sheet as a PC sheet, an acrylic resin layer as an MS layer, a hard coat layer as an HC layer, and a PC sheet / MS layer. / HC layer, MS layer / PC sheet / MS layer / HC layer, HC layer / MS layer / PC sheet / MS layer / HC layer, and the like. In addition, other layers can be added to these layer structures as long as the effects of the present invention are achieved.

  In particular, specific examples of the layer structure of a transparent multilayer sheet for display faceplates having an acrylic resin layer on both sides of a polycarbonate resin base sheet include MS layer / PC sheet / MS layer / HC layer, HC layer / MS layer / PC Examples include sheet / MS layer / HC layer.

  The transparent multilayer sheet for display face plate of the present invention is mainly intended to protect display devices of flat display devices such as liquid crystal (TN liquid crystal, STN liquid crystal, TFT liquid crystal, etc.) display devices and organic electroluminescence (organic EL) devices. Attached to its surface.

  The thickness of the transparent multilayer sheet for display face plate of the present invention can be appropriately selected as necessary, but the required thickness of the transparent multilayer sheet for display face plate is often determined by the size of the display. In recent years, there is a strong tendency to reduce the thickness of the display device itself, and a thin transparent multilayer sheet for a display face plate has been demanded.

  In order to protect the surface of a liquid crystal display device having a large size, for example, 30 inches or more, a sheet thickness of about 1000 to 2000 μm can sufficiently maintain the flatness of display, the face plate is difficult to bend, and the display element is protected. Can serve the purpose. In addition, for example, in order to protect the surface of a mobile phone display device of about 1.5 inches, if the sheet thickness is about 200 to 400 μm, the flatness of display can be sufficiently maintained, and the face plate is not easily bent, The display element can be protected. That is, the transparent multilayer sheet for a display face plate according to the present invention has a thickness range of about 200 to 2000 μm, preferably 250 to 1500 μm, and serves the purpose of protecting display elements of various display devices from large to small and yet thin. It can respond sufficiently to the demand for conversion.

  The transparent multilayer sheet for display face plate of the present invention has good adhesion between resin layers, is excellent in transparency, heat distortion resistance and hardness, and can suppress the occurrence of interference fringes. Therefore, it is suitably used as a transparent multilayer sheet for protecting the display device of the flat display device.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the examples.

[Test method]
Specifically, each test in the examples was performed as follows.

1. Refractive index The refractive index was measured according to JIS K7142.

2. Pencil hardness The pencil hardness was measured according to JIS K5600.

3. Interference fringe evaluation The interference fringe evaluation was evaluated according to the following five levels depending on the degree of visible interference fringes. 5 (not noticeable), 4 (little noticeable), 3 (slightly noticeable), 2 (noticeable), 1 (well noticeable).

[Example 1]
Extruder (main single-screw extruder made by Tanabe Plastics, extruder screw diameter φ40mm L / D = 32, sub-single screw extruder made by Pla Giken, extruder screw diameter φ25mm L / D = 24) and feed block die , Polycarbonate resin (manufacturer: Sumitomo Dow Co., Ltd., varieties: Caliber 301-15) in the main extruder, and MS resin (manufacturer: Japan A & L Co., Ltd., varieties: Planetero KM-6A, methyl methacrylate): 60 wt%), the main extruder was tested at a cylinder temperature of 270 ° C. and a screw speed of 60 rpm, and the sub-extruder was tested at a cylinder temperature of 240 ° C. and a screw speed of 30 rpm. As described above, two 0.6 mm sheets each having a polycarbonate layer of about 540 μm and an acrylic resin layer of 60 μm were obtained.

  On this acrylic resin layer, UV curable hard coat paint (Nippon Synthetic Chemical Industry Co., Ltd. UV-1700B 9 g, Shin-Nakamura Chemical Co., Ltd. A-LEN-10 1 g) made of polyfunctional acrylic resin A hard coat layer of about 4 μm was formed by roll coating.

The refractive index (R ₁ ) of the MS resin was 1.530, the refractive index (R ₂ ) of the hard coat was 1.531, and the ratio (R ₂ / R ₁ ) was 1.001. The pencil hardness (JIS K5600) was 3H. Further, the hard coat product was transparent and free from rainbow patterns due to interference, and a plate having good adhesion was obtained.

[Example 2]
Implemented except that MS resin (manufacturer: Denki Kagaku Kogyo Co., Ltd., varieties: TX-80, methyl methacrylate: 80% by weight) was used instead of MS resin (manufacturer: Japan A & L Co., Ltd., variety planetary: KM-6A) Using the same apparatus as in Example 1, two 0.6 mm sheets each consisting of a polycarbonate layer of about 540 μm and an acrylic resin layer of 60 μm were obtained.

  On the acrylic resin layer, a hard coat layer of about 4 μm was formed by a roll coating method using an ultraviolet curable hard coat paint (Nippon Synthetic Chemical Industry Co., Ltd. UV-1700B) made of a polyfunctional acrylic resin.

The refractive index (R ₁ ) of the acrylic resin was 1.51, the refractive index (R ₂ ) of the hard coat was 1.524, and the ratio (R ₂ / R ₁ ) was 1.009. The pencil hardness (JISK5600) was 4H. In the hard coat product, a rainbow pattern due to interference was not noticeable visually, and a transparent plate having good adhesion was obtained.

[Example 3]
Implemented except using MS resin (Manufacturer: Nippon A & L Co., Ltd., Variety Planeteroy: KM-6A) instead of MS Resin (Manufacturer: Denki Kagaku Kogyo Co., Ltd., Variety: KX-285, Methyl methacrylate: 90% by weight) Using the same apparatus as in Example 1, two 0.6 mm sheets each consisting of a polycarbonate layer of about 540 μm and an acrylic resin layer of 60 μm were obtained.

  On the acrylic resin layer, a hard coat layer of about 4 μm was formed by a roll coating method using an ultraviolet curable hard coat paint (Nippon Synthetic Chemical Industry Co., Ltd. UV-1700B) made of a polyfunctional acrylic resin.

[Comparative Example 1]
In the same apparatus as in Example 1, a 0.6 mm sheet of two layers consisting of a polycarbonate layer of about 540 μm and an acrylic (PMMA) resin layer (manufacturer: Sumitomo Chemical Co., Ltd., varieties: Sumipex MH) 60 μm was obtained.

  On the acrylic resin layer, a hard coat layer of about 4 μm was formed by a roll coating method using an ultraviolet curable hard coat paint (Nippon Synthetic Chemical Industry Co., Ltd. UV-1700B) made of a polyfunctional acrylic resin.

[Comparative Example 2]
In the same apparatus as in Example 2, a polycarbonate layer of about 580 μm and an acrylic (MS) resin layer (manufacturer: Japan A & L Co., Ltd., varieties: Planetloy KM-6A, methyl methacrylate: 60% by weight) of two layers of 0.6 mm sheets were obtained.

  On this acrylic resin layer, UV curable hard coat paint (Nippon Synthetic Chemical Industry Co., Ltd. UV-1700B 9 g, Shin-Nakamura Chemical Co., Ltd. A-LEN-10 1 g) made of polyfunctional acrylic resin A hard coat layer of 4 μm was formed by roll coating.

The refractive index (R ₁ ) of the MS resin was 1.530, the refractive index (R ₂ ) of the hard coat was 1.531, and the ratio (R ₂ / R ₁ ) was 1.001. Moreover, pencil hardness (JISK5600) was HB-F. The hard coat product had good adhesion, but although there was no rainbow pattern due to interference, it was insufficient in hardness and could not be used for the front plate of an optical liquid crystal display.

  Table 1 shows the results of Examples 1, 2, and 3 and Comparative Examples 1 and 2.

  From Table 1, the transparent multilayer sheets of Examples 1, 2, and 3 had high pencil hardness and no interference fringes. Therefore, it is suitable as a transparent multilayer sheet for display face plates. In contrast, although the pencil hardness was high in Comparative Example 1, interference fringes appeared remarkably, and in Comparative Example 2, the interference fringes were not noticeable, but the pencil hardness was low and both were practical as transparent multilayer sheets for display face plates. There wasn't.

It is sectional drawing of the transparent multilayer sheet for display faceplates of this invention.

Explanation of symbols

1 Hard Coat Layer 2 Acrylic Resin Layer 3 PC Base Sheet

Claims (8)

On one surface of a polycarbonate resin substrate sheet having an acrylic resin layer, it becomes more and a hard coat layer is laminated on the front surface of the acrylic resin layer on the other surface of the polycarbonate resin substrate sheet, acrylic A transparent multilayer sheet for display face plate , in which a resin layer, or an acrylic resin layer and a hard coat layer may be laminated in this order ,
The acrylic resin layer is a copolymer composed of methyl methacrylate and styrene,
The acrylic resin layer has a thickness of 40 μm or more,
The thickness of the hard coat layer is 1 to 10 μm,
The refractive index (R ₂ ) of the hard coat layer is in the range of 0.98 ≦ R ₂ / R ₁ ≦ 1.02 with respect to the refractive index (R ₁ ) of the acrylic resin layer .
A transparent multilayer sheet for a display face plate, wherein generation of interference fringes is suppressed. The transparent multilayer sheet for a display face plate according to claim 1, wherein the total thickness is 250 to 1500 μm. The transparent multilayer sheet for a display face plate according to claim 1, wherein the thickness of the polycarbonate resin base sheet is 60% or more of the total thickness. The transparent multilayer sheet for display faceplates of Claim 1 which has an acrylic resin layer on both surfaces of a polycarbonate resin base material sheet. The transparent multilayer sheet for a display faceplate according to claim 1, wherein the acrylic resin layer is a copolymer comprising 45 to 95% by weight of methyl methacrylate and 5 to 55% by weight of styrene. The transparent multilayer sheet for a display face plate according to claim 1, wherein the hard coat layer is an organic hard coat layer or an organic / inorganic hard coat layer. _2. The display faceplate according to claim 1, wherein the refractive index (R ₂ ) of the hard coat layer is in the range of 0.99 ≦ R ₂ / R ₁ ≦ 1.01 with respect to the refractive index (R ₁ ) of the acrylic resin layer. Transparent multilayer sheet. A polycarbonate resin and an acrylic resin, which is a copolymer of methyl methacrylate and styrene, are laminated to form a two-layer sheet by extrusion, and the thickness after drying / curing is 1 to 3 on the surface of the acrylic resin layer. The method for producing a transparent multilayer sheet for a display face plate according to claim 1 , wherein a hard coat layer having a thickness of 10 μm is formed, and generation of interference fringes is suppressed.

Images