JP5097049B2 - Method for producing antistatic multilayer sheet - Google Patents

Description

  The present invention relates to a method for producing an antistatic multilayer sheet having sustained antistatic properties. Furthermore, with regard to multilayer sheets having antistatic properties and light diffusibility, various parts such as lighting fixtures, lighting covers, electronics products, home appliances, office automation equipment, signs, displays, front plates of various devices, etc. The present invention relates to a method for producing a multilayer sheet that is suitable as a material for preventing light diffusion plates.

  Conventionally, highly transparent resins such as acrylic resins have excellent transparency, weather resistance, and rigidity. For example, various parts such as electronics products, home appliances, OA equipment, signs, decoration materials, It has been widely used as a material for the front plates of displays and various devices, and light diffusion sheets containing a light diffusing agent have been widely used for display diffusion plates, lighting signs, and lighting covers. In addition, it has been used as a light diffusing plate for a backlight unit of a liquid crystal panel of a personal computer.

  Various resin sheets mainly composed of acrylic resin with light transmission and diffusibility as light diffusion sheets for various parts such as lighting fixtures, lighting covers, electronics products, home appliances, office automation equipment, signboards, displays, and various devices. Are known. For example, Patent Document 1, Patent Document 2, Patent Document 3 and the like disclose the use of specific resin particles as a diffusing agent, and Patent Document 3 discloses a resin composition containing a specific ultraviolet light inhibitor. It is disclosed.

  Synthetic resin products, on the other hand, are generally easily charged by friction, etc., so that dust and dirt adhere to them and damage their appearance, or electronic parts have troubles caused by static electricity, while maintaining transparency. Development of a highly transparent resin sheet with improved antistatic properties has been demanded. In addition, the light diffusion sheet obtained by adding a light diffusing agent to the resin sheet is used for a long period of time. If dust is adsorbed by charging, the transmittance of the projection light is reduced. In addition, when processing and slitting, there is a problem that the face sticks to the sheet and causes a trouble. Therefore, development of a light diffusing sheet having a continuous antistatic property while maintaining high transparency and light diffusing property has been desired.

  In general, as a method for imparting antistatic properties to a synthetic resin sheet, a method in which a surfactant is kneaded into a base resin or a surfactant is applied to the surface of a product sheet is known. However, in the antistatic method using a surfactant as an antistatic agent, the antistatic agent is easily removed by washing with water or friction, and it has been impossible to provide a continuous antistatic performance.

  On the other hand, as a method for imparting sustained antistatic performance to a synthetic resin sheet, a polymer type antistatic agent is added to the base resin and the antistatic agent is contained in the product sheet, thereby providing continuous antistatic properties. It is known that performance can be obtained. As such a polymer type antistatic agent, for example, a polyethylene glycol-methacrylate copolymer, a polyether ester amide, a polyether amide imide, and a polyethylene oxide-epichlorohydrin copolymer have been put into practical use. By using such a polymer type antistatic agent, it is possible to prevent the disappearance of the antistatic effect seen in the case of a surfactant.

  Patent Document 4 discloses a light diffusing plate having an antistatic property obtained by adding a polymer type antistatic agent to a styrene resin as a light diffusing plate used in a backlight unit of a direct irradiation type. In Patent Document 5, a layer of a resin composition containing a light diffusing agent in a copolymer resin of a styrene monomer unit and a (meth) acrylic acid ester unit is combined with a styrene monomer unit and (meta A light diffusing plate in which a polymer type antistatic agent is added to a laminated sheet composed of a copolymer layer having a specific ratio of acrylate units has been proposed.

When a resin sheet is continuously produced by the extrusion sheet molding method using a light diffusing plate to which these polymer type antistatic agents are added, the polishing roll surface is contaminated by the polymer type antistatic agent, and as a result, the surface of the sheet is uneven. Thus, it was difficult to continuously obtain a good product having a smooth surface.

  In Patent Document 6, as a sheet using a polymer-type antistatic agent, a resin layer containing a polymer-type antistatic agent is laminated on at least one surface of the acrylic resin layer of the substrate, and an acrylic resin and A laminated sheet in which resin layers made of vinylidene fluoride are laminated is disclosed. However, in Patent Document 6, contamination of the polishing roll surface that occurs when a sheet product is continuously produced by an extrusion sheet molding method using a polymer type antistatic agent, and the resulting surface condition of the product sheet is deteriorated. This issue is not considered at all.

  The above “extrusion sheet forming method” is a method in which a molten resin is extruded into a sheet form from a slit of a flat die (T die) provided at the tip of an extruder, and a take-up roll (such as a polishing roll) provided on the downstream side of the die Is a method of taking a sheet and forming it into a sheet. Usually, a metal roll having a smooth surface coated with hard chrome plating and mirror-finished is used as the polishing roll.

  As a method for solving the problem that the surface of the roll is contaminated by the polymer-type antistatic agent and the surface condition of the product sheet is deteriorated due to the contamination, Patent Document 7 discloses that the roll temperature is 50 to 80 ° C. It is disclosed that by controlling to a low temperature, the migration of the polymer antistatic agent can be prevented and the roll contamination can be solved. However, at such a low roll temperature, when a thick sheet is produced, the resulting sheet is easily warped and a smooth surface is difficult to obtain. In order to produce a sheet that has a smooth surface and does not warp, the roll temperature must be increased. However, if the roll temperature is raised, roll contamination is likely to occur, and it is necessary to remove the contamination of the roll surface and to replace the roll. Unfortunately, there is a problem that the cost increases as a result.

  Patent Document 8 proposes a polymer antistatic agent having low roll contamination, and discloses that a product having a good surface condition can be obtained by using the polymer antistatic agent. . However, in Patent Document 8, the roll contamination is evaluated for a film obtained by pulling a thin film having a thickness of 200 μm with a roll adjusted to 20 ° C., and a sheet thicker than the film by extrusion sheet molding. No mention is made of the presence or absence of contamination of the polishing roll in the production of. When a sheet is produced at a relatively high roll temperature by extrusion sheet molding using the above-mentioned polymer type antistatic agent, prevention of contamination of the roll is not fully satisfactory, and it has not been fully solved yet. is there.

  Further, Patent Document 9 discloses a multilayer film that uses a polymer-type antistatic agent, has no change in surface characteristics, has little elution of ionic impurities, and suppresses contamination of an object to be packaged. Is a multilayer film for packaging by casting or inflation, and there is no disclosure about contamination of the polishing roll and deterioration of the surface state of the product sheet when producing a multilayer sheet by extrusion sheet molding.

Therefore, in reality, production of a transparent sheet having a good surface state, particularly a thick sheet, using a polymer-type antistatic agent by an extrusion sheet forming method has not been realized.
In addition, even in the light diffusion sheet, a sheet having a good surface state and a large thickness has not been obtained.

Japanese Patent Laid-Open No. 3-231954 JP-A-9-255839 JP 2003-26888 A JP 2006-133567 A JP 2006-154445 A Japanese Patent Laid-Open No. 7-1682 Japanese Patent Laid-Open No. 8-80599 JP 2006-206894 A JP 2006-15741 A

  The present invention is a multilayer sheet having antistatic performance and excellent surface smoothness and good appearance by extrusion sheet molding, and also has antistatic performance and surface smoothness and good appearance, and light diffusion. It is providing the multilayer sheet which has property.

The reason why a sheet having a surface layer containing a polymeric antistatic agent causes roll contamination during extrusion sheet molding is presumed to be due to the properties specific to the polymeric antistatic agent. That is, the polymer antistatic agent is a copolymer having a hydrophilic polymer unit and a lipophilic polymer unit, and imparts an ion conductive function by introducing an alkali metal salt into the copolymer. In order to impart antistatic performance when mixed with a thermoplastic resin, it is necessary to increase the compatibility with the thermoplastic resin. When such properties are provided, the polymer antistatic agent must be highly polar. Furthermore, since high molecular weight antistatic agents include low molecular weight organic substances that are added to enhance the antistatic effect, they are hard chrome plated at a temperature of 60 to 180 ° C. used in ordinary extrusion sheet molding. There was a fundamental problem that it easily adheres to the surface of the polishing roll.
In view of this, the present inventors have formed a transparent resin layer to which no polymer antistatic agent is added on the outside of a resin composition layer in which a polymer antistatic agent is added to a transparent resin in order to prevent roll contamination. Thus, a method of co-extrusion was tried. As a result, it was confirmed that roll contamination was prevented for a long time.
However, as described above, in the case of multilayering by the coextrusion method, another problem has occurred in that a scale pattern is generated at the interface of each layer of the resulting multilayer sheet.

The present invention has been made in view of the above circumstances, and it is possible to prevent the occurrence of contamination on the surface of the polishing roll in extrusion sheet molding and to stably produce a thick multilayer sheet product without impairing the appearance of the sheet. It is an object of the present invention to provide a multi-layer sheet having a stable manufacturing method and a continuous antistatic performance and a light diffusing sheet having the same function and effect.
In the present invention, the “polymeric antistatic agent” is sometimes simply referred to as “antistatic agent”, and the “layer containing the polymeric antistatic agent” is simply referred to as “antistatic layer”.

The present invention
(1) Formation of core layer (A) forming melt using transparent resin (a) as base resin, and formation of antistatic layer (B) containing polymer antistatic agent using transparent resin (b) as base resin Electrification in which a melt for coating and a melt for forming a coating layer (C) containing a transparent resin (c) as a base resin and substantially free of a polymeric antistatic agent are laminated and combined in a die A method for producing a preventive multilayer sheet, wherein the coating layer is at least one outermost surface of the multilayer sheet, the antistatic layer is in contact with the inner surface of the coating layer, and at least the outer surface side of the core layer; The melts are laminated and merged in the die so as to form a laminated merged product, and the shear amount of the laminated merged product in the parallel land portion of the lip portion of the die represented by the following formula (1) is expressed. 0.1 to 170 antistatic multilayer sheet characterized by Method of manufacturing a door.
(Equation 2)

(2) In the antistatic layer, the ratio of the melt viscosity of the polymer antistatic agent to the melt viscosity of the transparent resin (b) is 1:35 to 1: 1.5. 1) The manufacturing method of the antistatic multilayer sheet | seat of description.

(3) The melt viscosity of the transparent resin (b) is 600 to 2500 Pa · s, and the melt viscosity of the transparent resin (c) is less than or equal to the melt viscosity of the transparent resin (b). A method for producing an antistatic multilayer sheet according to 1) or (2).

(4) In the antistatic layer, the addition amount of the polymer antistatic agent is 5% by weight to 40% by weight with respect to the total amount of the transparent resin (b) and the polymer antistatic agent. The method for producing an antistatic multilayer sheet according to any one of (1) to (3), wherein the antistatic layer has a thickness of 20 to 300 μm.

(5) The method for producing an antistatic multilayer sheet according to any one of (1) to (4), wherein the coating layer in the antistatic multilayer sheet has a thickness of 2 to 50 μm.

(6) The method for producing an antistatic multilayer sheet according to any one of (1) to (5), wherein the total thickness of the antistatic multilayer sheet is 0.5 to 15 mm.

(7) The antistatic multilayer sheet is a multilayer sheet having a yellow index value of 2.6 or less and an initial charged voltage of 2.5 kV or less in the measurement of the charged voltage half-life of the antistatic multilayer sheet. The method for producing an antistatic multilayer sheet according to any one of (1) to (6), which is characterized in that

(8) Any of the above (1) to (7), wherein the antistatic multilayer sheet is a multilayer sheet containing a light diffusing agent in at least one of the core layer or the antistatic layer. A method for producing an antistatic multilayer sheet as described in 1 above.

(9) In the coating layer, the additive amount of the weather stabilizer is 0.05 to 0.8 parts by weight with respect to 100 parts of the base resin of the coating layer. The method for producing an antistatic multilayer sheet according to any one of 8).

(10) The method for producing an antistatic multilayer sheet according to any one of (1) to (9), wherein the base resin of each layer constituting the antistatic multilayer sheet is an acrylic resin .
Is the gist.

The multilayer sheet obtained by the present invention comprises a melt for forming a core layer (A) having a transparent resin (a) as a base resin, and a polymer type antistatic agent having the transparent resin (b) as a base resin. The melt for forming the prevention layer (B) and the melt for forming the coating layer (C) containing the transparent resin (c) as a base resin and substantially free of a polymer type antistatic agent are laminated in a die. The respective melts are formed such that the coating layer is at least one outermost surface of the multilayer sheet, and the antistatic layer is in contact with the inner surface of the coating layer and at least the outer surface side of the core layer. Manufactured by stacking together in a die.
In the above-mentioned coextrusion, when the material to be extruded passes through the parallel land portion of the die lip, it is distorted at the interface between the layer containing the antistatic agent and the layer containing no antistatic agent, especially the antistatic layer and the coating layer by shearing ( A scale) that can be visually confirmed over the entire surface of the multilayer sheet occurs. The above-mentioned scale pattern deteriorates the sheet appearance and decreases the commercial value.

  The above-mentioned scale pattern controls the shear that the laminated product of each layer melt formed in a multi-layered sheet passes through the parallel land portion of the lip of the T die, and the shear amount of the parallel land portion is specified. The present inventors have found that the generation of a scale pattern can be prevented by adjusting to the range and extruding. Here, in this invention, a parallel land part means the substantially parallel final part of die | dye.

The amount of shear can be controlled by the die lip gap, the parallel land length of the lip, and the amount of extrusion, and the amount of shear determined by the formula (1) is greatly reduced compared to the usual case of manufacturing this type of sheet. The present inventors have found that a multi-layered sheet having a good reduction in the scale pattern or good appearance without the scale pattern can be obtained by coextrusion.

Further, the multilayer sheet manufacturing method of the present invention makes it possible to manufacture an antistatic multilayer sheet in which various additives are introduced into the core layer.
Further, since a light diffusing agent can be contained in at least one layer constituting the multilayer sheet, it is possible to prevent dust and dust from being attached due to charging, and to prevent occurrence of trouble due to static electricity. It is possible to provide a light diffusing multilayer sheet that has a continuous antistatic property and a light diffusive surface with a smooth surface and good appearance.

In the present invention, in particular, since the light diffusing agent is contained in the core layer and / or the antistatic layer, the antistatic performance is sustained, and the surface having transparency and light diffusibility is smooth. A light diffusing multilayer sheet having a good appearance can be provided.
Therefore, the multilayer sheet of the present invention is used as a cover material for lighting equipment that requires light diffusibility, as a front plate of a display unit in various devices such as electronics products, home appliances, OA devices, and instruments, and as light diffusibility. In addition, it is useful for other applications where transparency and antistatic properties are required.

The antistatic multilayer sheet (hereinafter sometimes simply referred to as “multilayer sheet”) obtained by the present invention will be specifically described.
The multilayer sheet obtained by the present invention comprises a melt for forming a core layer (A), a melt for forming an antistatic layer (B) containing a polymer type antistatic agent, and a melt for forming a coating layer (C). So that the coating layer is at least one outermost surface of the multilayer sheet, and the antistatic layer is in contact with the inner surface of the coating layer and is at least one side of the core layer. The melts are laminated.
When a light diffusing agent is added, the light diffusing agent is added to at least one of the core layer (A) and the antistatic layer (B) constituting the multilayer sheet.

An embodiment of a sheet that can be produced by the method for producing a multilayer sheet according to the present invention will be described with reference to the drawings (schematic diagrams), with an example in which a light diffusing agent is specifically added.
In FIG. 1, an antistatic layer (B1) containing a light diffusing agent is located on both sides of the core layer (A), and the antistatic agent and the light diffusing agent are contained on the outer surface of the antistatic layer (B1). It is a multilayer sheet which consists of a structure in which the coating layer (C) which does not exist.

  FIG. 2 shows that an antistatic agent layer (B) containing a light diffusing agent in the core layer (A) and not containing a light diffusing agent is located on both sides of the core layer (A). B) is a multilayer sheet having a structure in which a coating layer (C) containing no antistatic agent and no light diffusing agent is present on the outer surface, and FIG. 2 (1) contains the light diffusing agent in the entire core layer (A1). ) A mode is shown. FIG. 2 (2) shows an embodiment in which a layer (A2) containing a light diffusing agent is provided unevenly on the core layer (A).

  FIG. 3 shows a multilayer sheet comprising a core layer (A) and an antistatic layer (B) containing a light diffusing agent and a coating layer (C) containing no light diffusing agent on the outer surface of the antistatic layer. Yes, FIG. 3 (1) shows a mode in which the entire core layer contains a light diffusing agent (A1), and antistatic layers (B1) containing the light diffusing agent are provided on both sides of the core layer (A1). FIG. 3 (2) shows an embodiment in which a layer (A2) containing a light diffusing agent is provided unevenly on the core layer (A).

  In addition to the above-described embodiment, a small amount of a light diffusing agent can be further contained in the coating layer in FIGS. 1 to 3 show an embodiment in which the antistatic layer (B) and the coating layer (C) are arranged on both surfaces of the core layer (A). In FIGS. 1 to 3, the antistatic layer (B) is shown. And the coating layer (C) can also be arranged on one side of the core layer depending on the application and field of use.

  In the multilayer sheet obtained by the present invention, the light diffusing agent is contained in the core layer and / or the antistatic layer as described above. When the light diffusing agent is contained in the core layer, the light diffusing agent may be contained in the entire core layer as shown in FIG. 2 (1). As shown in FIG. A diffusing agent may be provided unevenly. Moreover, as shown in FIG. 3, it can also be contained in an antistatic layer and a core layer. Also in this case, as shown in FIG. 3B, the light diffusing agent can be unevenly distributed in the core layer. Further, as shown in FIG. 1, a light diffusing agent can be contained only in the antistatic layer.

  As shown in FIGS. 2 (2) and 3 (2), when the light diffusing agent is unevenly distributed in the core layer, the layer (A2) containing the light diffusing agent is a single layer or a plurality of two or more layers. The number of layers of the light diffusing agent and the position of the layer containing the light diffusing agent may be selected depending on the application, and may be provided in the core layer while being biased toward the light source side.

  The method for producing a light-diffusing multilayer sheet having antistatic properties of the present invention comprises a melt for forming a core layer (A) having a transparent resin (a) as a base resin, and the transparent resin (b) as a base resin. Melt for forming antistatic layer (B) containing polymer type antistatic agent and melting for forming coating layer (C) substantially free of polymer type antistatic agent using transparent resin (c) as base resin The coating layer is at least one outermost surface of the multilayer sheet, and the antistatic layer is in contact with the inner surface of the coating layer and is at least one side of the core layer. In this way, all standard melts are laminated and co-extruded and co-extruded using a T-die attached to the extruder under the extrusion conditions where the shear amount of the parallel land portion of the lip portion of the T-die is 0.1 to 170. Polishing roll (hereinafter referred to as polishing roll) It is produced by take-Ru multilayer sheet molding through simply referred to as "roll").

  The multilayer sheet obtained by the present invention having the structure shown in FIG. 1 includes a base resin melt of the transparent resin (a) that forms the core layer (A) and a transparent resin that forms the antistatic layer (B) ( The melt obtained by blending the base resin of b) with the polymer antistatic agent and the light diffusing agent, and the melt of the base resin of the transparent resin (c) forming the coating layer (C), Using a T-die attached to the extruder, the antistatic layer is positioned on both sides of the sheet, and the coating layer (C) is positioned on the multilayer sheet surface in contact with the antistatic layer (B). A multilayer sheet coextruded under the following extrusion conditions is obtained.

  In the multilayer sheet obtained by the present invention having the configuration shown in FIG. 2, the core layer (A) is formed when the multilayer sheet having the configuration shown in FIG. A melt in which a light diffusing agent is blended with the base resin of the transparent resin (a) and a melt in which a polymer antistatic agent is blended with the base resin of the transparent resin (b) forming the antistatic layer (B) And a melt of the base resin of the transparent resin (c) that forms the coating layer (C), the antistatic layer (B) is located on both sides of the core layer (A), and the surface of the multilayer sheet Then, a multilayer sheet is obtained by co-extrusion under predetermined extrusion conditions using a T-die laminated and attached to the extruder so that the coating layer (C) is in contact with the antistatic layer (B).

  When the light diffusing agent is unevenly distributed in the multilayer sheet having the structure shown in FIG. 2 (2), that is, the base resin of the transparent resin (a) forming the core layer (A), and the transparent resin A polymer type antistatic agent is blended with a base material resin of (a) a melt (light diffusion layer (A2)) containing a light diffusing agent and a transparent resin (b) forming the antistatic layer (B). The melt (light diffusion) containing the light diffusing agent at a desired position in the core layer and the melt of the base resin of the transparent resin (c) forming the coating layer (C) Layer (A2)), the antistatic layer (B) is located on both sides of the core layer (A), and the coating layer is in contact with the antistatic layer (B) on the surface of the multilayer sheet. Lamination is performed so that (C) is positioned, and a multi-layer sheet is obtained by co-extrusion under predetermined extrusion conditions using a T-die attached to the extruder. .

  In the multilayer sheet having the structure shown in FIG. 3, when a light diffusing agent is blended in the multilayer sheet shown in FIG. 3 (1), that is, the core layer and the antistatic layer, the transparent resin (a And a melt obtained by blending an antistatic agent and a light diffusing agent with a base resin of the transparent resin (b) forming the antistatic layer (B), and a coating. The base resin melt of the transparent resin (c) forming the layer (C) is charged on the surface of the multilayer sheet with the antistatic layer (B) positioned on both sides of the core layer (A). Lamination is performed so that the coating layer (C) is positioned in contact with the prevention layer (B), and co-extrusion is performed under a predetermined extrusion condition using a T die attached to the extruder to obtain a multilayer sheet.

  In addition, when the light diffusing agent is unevenly distributed in the multilayer sheet having the structure shown in FIG. 3 (2), that is, when the light diffusing agent is blended in the antistatic layer, a transparent resin that forms the core layer (A) ( a) base resin, transparent resin (a) containing a light diffusing agent (light diffusion layer (A2)), and transparent resin (b) base material forming antistatic layer (B) A melt obtained by blending a polymer-type antistatic agent and a light diffusing agent with a resin, and a base resin of the transparent resin (c) that forms the coating layer (C) are placed at a desired position in the core layer. A melt containing a diffusing agent (light diffusing layer (A2)) is disposed, and a melt containing the light diffusing agent at a desired position in the core layer on both sides of the core layer (A). The antistatic material in which the object (light diffusing layer (A2)) is disposed and the light diffusing agent is blended on both sides of the core layer (A) Is laminated on the surface of the multilayer sheet so that the coating layer (C) is located in contact with the antistatic layer (B), and the T die attached to the extruder is used under predetermined extrusion conditions. Co-extrusion to obtain a multilayer sheet.

Moreover, in the multilayer sheet obtained by this invention, a coating layer can also be provided only in one side if desired (FIGS. 4-6). In addition, the antistatic agent and the light diffusing agent are basically not blended in the coating layer of the multilayer sheet obtained by the present invention, but the coating layer contains the light diffusing agent within a range that does not impair the surface smoothness and gloss. May be.
Further, although not shown, a new layer can be laminated between the core layer and the antistatic layer or on the outermost surface side of the coating layer.

  The multilayer sheet obtained by the present invention has a structure in which a coating layer not containing an antistatic agent is formed in contact with the antistatic layer so as to cover an antistatic layer containing a polymer type antistatic agent. Because it can prevent adhesion of the polymer antistatic agent to the roll and prevent contamination of the roll surface even at a relatively high roll temperature, it has no warpage, good appearance, and excellent antistatic properties. A multilayer sheet having light diffusibility can be produced efficiently and stably over a long period of time.

  In order to produce the multilayer sheet of the present invention, it is important to perform coextrusion by adjusting the shear amount of the inside of the die during extrusion, particularly the parallel land portion of the lip, to a specific range obtained from the following formula (1). is there.

FIG. 8 shows a schematic diagram of a longitudinal section of an example of the T die 10 in extrusion sheet molding. In FIG. 8, 11 is a lip portion, h is a lip gap, and t is a parallel land length. The said parallel land part means the last parallel part of the die | dye which the molten resin provided in order to control sheet | seat thickness contacts. Alternatively, it may be substantially tapered. The shear amount of the parallel land portion is a dimensionless numerical value obtained by the following formula (1). It is considered that the molten resin flows in a laminar flow state in the parallel land portion. The following equation (1) is a product of the shear rate for the molten resin in the parallel land portion and the time for the molten resin to pass through the parallel land portion (parallel land portion passing time). The parallel land portion passage time is a value obtained by dividing the volume (cm ³ ) of the space of the parallel land portion by the extrusion rate (cm ³ / s) per second of the molten resin. The volume of the space in the parallel land portion is the product of the parallel land length t, the lip gap h, and the lip width w. The amount of extrusion (cm ³ / s) needs to be determined by dividing the weight of the extruded material extruded per second by the density of the molten resin. The density is calculated assuming 1 g / cm ³ . Generally, the density of the transparent resin at room temperature is around 1.1 g / cm ³ , and the density in the molten state is smaller than the density at room temperature. For convenience, there is no problem even if the density of the molten resin is regarded as 1 g / cm ³ .

(Equation 3)

In this invention, the suitable range of the shear amount of the parallel land part obtained by said Formula (1) is 0.1-170. If the amount of shear is too large, a scale pattern is generated at the interface of each layer of the multilayer sheet (Comparative Example 2). From this viewpoint, the shear amount is preferably 100 or less, and more preferably 50 or less. On the other hand, if the shearing amount is too small, the extrusion stability is hindered. From this viewpoint, it is more preferably 0.2 or more, and further preferably 0.3 or more.
In Example 1, it can be calculated by the following method. The discharge weight per hour is 60 kg. In this case, the discharge weight per second is calculated as 16.7 g / second (60000 g ÷ 3600 seconds). When the density of the resin at the time of melting is 1.0 g / cm ³ at room temperature and the extrusion rate (Q) per second is calculated for Example 1 as described above, 16.7 cm ³ / sec (27. 8 g / second ÷ 1.0 g / cm ³ ).
In the case of Example 1, the shear amount is the shear amount of the parallel land portion of FIG. The volume of the resin flow path in the parallel land portion is calculated as 30 cm ³ from the length of 15 mm, the lip width (w) of 500 mm, and the lip gap (h) of 4 mm. The residence time of the molten resin passing through the parallel land portion is calculated as 1.8 seconds by dividing the volume of the parallel land portion by the extrusion amount (30 cm ³ ÷ 16.7 cm ³ / second).
The shear rate for determining the amount of shear is determined by 6Q / Wh ² and is 12.5 (s ⁻¹ ). In summary, since the shear amount is the product of the shear rate and the residence time of the parallel land portion, it is calculated as 22.5 (12.45 seconds− ¹ × 1.81 seconds).
In Example 1, the calculation was performed assuming that the parallel land portion has a parallel slit shape. However, in this specification, the parallel land portion refers to a substantially parallel final portion of the die. For example, the parallel land portion may be substantially tapered as long as it is within the range of the shear amount. In this case, the shear rate at the cross-section of the midpoint of the land portion can be adopted and similarly calculated.

The amount of shear can be controlled by the die lip gap, the parallel land length of the lip, and the amount of extrusion. The amount of shear determined by equation (1) is greatly reduced compared to the usual case of manufacturing this type of sheet. By co-extrusion, it is possible to obtain a multi-layer sheet in which the scale pattern is significantly reduced or the appearance without the scale pattern is good.
The above formula (1) is expressed by the product of the shear rate for the molten resin in the parallel land portion and the time for the molten resin to pass through the parallel land portion (parallel land portion passage time). Therefore, the shear rate is 3 to 30 s ⁻¹ . Preferably it is 5-25s < ^-1 >, and it is still more preferable that it is 10-20s < ^-1 >.

Generally, since it is difficult to measure the thickness of each layer of a multilayer sheet by coextrusion using a transparent resin as a base resin, the extrusion amount of the resin that forms each layer for a certain period of time, and the area of each formed layer From this, the basis weight, which is the weight per 1 m ^{2 of the} layer, is calculated, and this is the density of the transparent resin that is the base resin forming each layer at 23 ° C. (according to method A of JIS K7112 (1999)). The thickness calculated by dividing is adopted. For example, when the basis weight of the coating layer is 50 g / m ² and the density of the transparent resin at 23 ° C. is 1.19 g / cm ³ , the basis weight of 50 g / m ² is divided by the density of 1.19. The value 42 (μm) obtained in this manner is the thickness of the coating layer. The other layers can be calculated in the same way. In addition, each layer has a form in which an antistatic agent, a light diffusing agent, and other raw materials are mixed in a transparent resin alone, a mixture of transparent resins, a transparent resin alone or a mixture of transparent resins. As the resin density used for conversion into the density, the density at 23 ° C. of the transparent resin, which is the main component occupying 50% by weight or more in each layer, is adopted for convenience. In addition, when using 2 or more types of transparent resin in mixture, the average value of the density in 23 degreeC of each transparent resin is employ | adopted.

  In the multilayer sheet obtained by the present invention, when the light diffusing agent is blended in the core layer, the blending amount of the light diffusing agent is the kind of the light diffusing agent used, for example, the inorganic light diffusing agent or the organic light. Depending on the diffusing agent, etc., when it is contained in the entire core layer, when the light diffusing agent is unevenly distributed in the core layer (including the case where a plurality of layers containing the light diffusing agent are present), the core 0.1 to 10 parts by weight, preferably 0.3 to 5 parts by weight can be added to 100 parts by weight of the base resin of the layer. In the case where the light diffusing agent is unevenly distributed in the core layer, when the light diffusing agent layer is a single layer, a slightly larger blending amount is adopted than the amount blended in the entire core layer within the above blending range, In the case of multiple layers, the desired light diffusibility can be obtained with a blending amount approximately the same as the blending amount in the entire core layer.

  In addition, when blending the light diffusing agent in the antistatic layer, as in the case of blending in the core layer, although slightly different depending on the type of the light diffusing agent used, with respect to 100 parts by weight of the base resin of the antistatic layer, 0.1-10 weight part, Preferably 0.3-5 weight part is mix | blended.

  In any of the above cases, it is desirable that the light diffusing agent is blended in an amount of 0.5 to 5.0% by weight based on the entire multilayer sheet. If the blending amount of the light diffusing agent is too large, the light transmittance, moldability, fluidity and the like are unfavorably affected. On the other hand, if the blending amount is small, the desired effect cannot be obtained. Further, some light diffusing agents are light transmissive, while others are light transmissive or inferior. In actual use, the light diffusing agent is selected and used in consideration of the type of light diffusing agent and the degree of light transmission.

  In the multilayer sheet obtained by the present invention, as the base resin used for the core layer, a transparent resin (a) having a total light transmittance of 70% or more is used. Moreover, the thickness of the core layer is approximately the thickness of the laminated sheet itself, and the thickness of the core layer including the layer containing the light diffusing agent is 0.5 to 15 mm.

  Further, in the multilayer sheet obtained by the present invention, the base resin used for the antistatic layer containing the polymer type antistatic agent is also transparent with a total light transmittance of 70% or more, as in the case of the core layer. Resin (b) is used. The polymer antistatic agent is added in a range of 5 to 40% by weight with respect to the total amount of the base resin and the polymer antistatic agent. If the addition amount is less than 5% by weight, the required antistatic effect cannot be obtained, the saturation voltage exceeds 2.5 kV, and the antistatic performance is not exhibited. Therefore, in order to fully develop the antistatic performance, the blending amount of the antistatic agent is preferably 8% by weight or more, more preferably 12% by weight or more. On the other hand, when the blending amount of the antistatic agent exceeds 40% by weight, there is no particular problem from the viewpoint of the antistatic effect, but there is a problem in yellowing and weather resistance due to blending of the antistatic agent. Is not preferred, preferably 35% by weight or less, more preferably 30% by weight or less.

  In the multilayer sheet obtained by the present invention, the blending amount of the antistatic agent is blended within the above range. However, since the antistatic layer is disposed in contact with the coating layer, the antistatic effect can be achieved with a small amount of antistatic agent. Can be demonstrated. The blending amount of the antistatic agent is 5% by weight or less with respect to the entire multilayer sheet. From the viewpoint of balance between antistatic performance and required optical properties such as light transmittance and light diffusivity and weather resistance. It is preferably 4% by weight or less, and most preferably 3% by weight or less.

  In the case where the multilayer sheet obtained by the present invention is a light diffusive sheet, in order to develop antistatic performance while maintaining light transmission and light diffusibility, the layer configuration constituting each multilayer sheet, the thickness of each layer, and antistatic It is important to balance the blending amount of the agent and the light diffusing agent. However, in the multilayer sheet obtained by the present invention, the thickness of each layer in the above-described each layer configuration, the blending amount of the antistatic agent and the light diffusing agent are If it is the range specified by invention, an effect can fully be expressed.

The base resin used for the antistatic agent and the antistatic layer preferably has the same refractive index, but the difference in refractive index between the two may be within 0.05. When the refractive index difference exceeds 0.05, haze generated when resins having different refractive indexes are blended increases. A large haze is not preferable because the light transmittance is lowered. Therefore, the difference in refractive index is more preferably within 0.04, and even more preferably within 0.03.
In particular, if an acrylic resin is selected, the refractive index of the polymer antistatic agent is close.
Further, the acrylic resin is preferably polymethyl methacrylate, methyl methacrylate / ethyl methacrylate copolymer, or methyl methacrylate / ethyl acrylate copolymer.

  The antistatic layer has a thickness of 20 μm to 300 μm. When the thickness is small, the antistatic performance cannot be exhibited. Therefore, the thickness of the antistatic layer is more preferably 40 μm or more, and further preferably 60 μm or more. On the other hand, when the thickness is thick, there is no particular problem from the viewpoint of antistatic performance, but the polymer type antistatic agent may be slightly colored in yellow, and its blending amount is as large as 5 to 40% by weight. If the antistatic layer is thick, the multilayer sheet obtained is also likely to be colored and the yellow index value may be increased. Further, many polymer type antistatic agents have an ether bond in the molecule, and there is a concern in terms of weather resistance. From this point of view, if the thickness is 300 μm or less, there is no practical problem even if there is a secular change, but it is more preferably 250 μm or less, and still more preferably 180 μm or less. When providing an antistatic layer on both surfaces of a core layer, each thickness is 20-300 micrometers. Further, the thickness of the antistatic layer may be the same thickness on both sides, may be different, and can be changed according to the application. It is desirable that the thickness of both surfaces is the same from the viewpoint of the balance of antistatic performance of the product.

In the multilayer sheet obtained by the present invention, a transparent resin (c) having a total light transmittance of 70% or more is also used as the base resin used for the coating layer disposed on the outermost surface.
The coating layer, which is a resin layer located on the outermost surface of the multilayer sheet in contact with the antistatic layer (B), is a thin film having a thickness of 2 to 50 μm. The thinner the coating layer, the more effectively the antistatic performance can be expressed. However, when the coating layer is too thin, it becomes difficult to control the thickness of the entire sheet, causing the problem of contamination of the roll surface, the surface is smooth, and the appearance is good. It is difficult to obtain a sheet. In addition, stable antistatic performance may not be exhibited. From this viewpoint, it is necessary to be in contact with the antistatic layer (B), and the thickness is preferably 3 μm or more, more preferably 4 μm or more. On the other hand, if the coating layer is too thick, the antistatic effect is hindered. The thickness of the coating layer is preferably 25 μm or less, more preferably 15 μm or less.
Further, from the viewpoint of preventing roll contamination, it is necessary that the coating layer is substantially free of an antistatic agent. Here, the phrase “substantially free of antistatic agent” means that the content is zero or contained to the extent that it does not have antistatic properties. Specifically, it is 0-4 weight part with respect to 100 parts of coating layers, Preferably it is 0-2 weight part.

  In order to impart weather resistance to the coating layer, it is preferable to add a weather stabilizer or an ultraviolet absorber. Content, such as a weather stabilizer and an ultraviolet absorber, is 0.05 to 0.8 part by weight with respect to the entire sheet. A large amount is not preferable because it causes yellowing and increases the yellow index value of the multilayer sheet. Therefore, the content is preferably 0.07 to 0.6 parts by weight, more preferably 0.1 to 0.4 parts by weight.

When the antistatic multilayer sheet obtained by the present invention is a light diffusion sheet, the total light transmittance is preferably 50% or more. In the case of the light diffusing sheet, the total light transmittance is preferably 55% or more in order to prevent energy loss of the light source.
On the other hand, the maximum value of the total light transmittance is 94%, which is approximately equal to the light transmittance of the transparent resin of the base resin, but is preferably 93% or less in terms of balance with haze.
The haze needs to consider the balance with light transmittance, and is preferably 40% or more, more preferably 50% or more, and particularly preferably 60% or more from the viewpoint of light diffusibility. On the other hand, the maximum value is 93%, but if it is too high, it results in energy loss of the light source, preferably 90% or less, particularly preferably 85% or less.

In the multilayer sheet obtained by the present invention, it is preferable that the yellow index value is low, but the light diffusing multilayer sheet according to the present invention is somewhat colored due to the presence of an antistatic layer containing an antistatic agent. . The yellow index value correlates with the blending amount and type of antistatic agent, the ratio of the antistatic layer of the entire multilayer sheet, etc., and can be suppressed by controlling these, but in the case of a light diffusing laminated sheet The acceptable yellow index value (YI value) is 2.6 or less, preferably 2.3 or less, and more preferably 2.0 or less.
The yellow index value is generally 1.0 or more depending on the type and amount of the light diffusing agent to be blended. The yellow index value can be lowered somewhat by adding a dye called a bluing agent. However, when added in a large amount, the total light transmittance is reduced.

In the multilayer sheet obtained by the present invention, the surface resistivity preferably has 10 ¹² Ω or more. Usually, the surface resistivity of an antistatic sheet having no coating layer is 10 ¹² Ω or less, but this is not the case in the multilayer sheet of the present invention because it has a coating layer.
The surface resistivity of the multilayer sheet obtained by the present invention is 5 × 10 ¹² Ω or more, preferably 10 ¹³ Ω or more. That is, the thickness of the coating layer is sufficiently ensured, thereby ensuring the smoothness of the surface, and the coating layer can contain a weather resistance stabilizer and an ultraviolet absorber.

In the multilayer sheet obtained by the present invention, the initial charged voltage is preferably 2.5 kV or less. It is. When it is higher than 2.5 kV, the application range is limited to a specific one. Therefore, the initial charging voltage is preferably 2.3 kV or less, and most preferably 2.0 kV or less.
The initial charged voltage is more preferably close to 0 (zero), but is approximately 0.3 kV or more because of the performance of the antistatic agent and the presence of a coating layer that prevents roll contamination.
As described above, the higher the amount of the polymeric antistatic agent added to the antistatic layer and the higher the basis weight of the antistatic layer, the higher the antistatic effect, but on the other hand, light diffusibility and transparency Since the optical characteristics such as haze and yellow index value increase and the weather resistance also decreases, the initial charged voltage of the laminated sheet of the present invention required from the balance with the optical characteristics is preferably 0.4 kV or more, and further 0 More preferably, 5 kV or more.

As described above, the multilayer sheet obtained by the present invention is produced by a method of forming an extruded sheet different from film molding, that is, a multilayer sheet extruded into a sheet form from a T-die attached to the tip of the extruder (polishing roll). ) To form a multilayer sheet having a uniform sheet thickness. The resulting product multilayer sheet can be in the form of a sheet or plate having a thickness of about 0.5 to 15 mm.
In a multilayer sheet having a thickness of 15 mm or more, when a roll (polishing roll) is passed, a sheet having a certain plate shape cannot be obtained. From this viewpoint, the thickness is preferably 0.5 mm to 10 mm. Such a multilayer sheet is formed into a light diffusing product having antistatic properties formed into various shapes such as a lighting cover, a display diffusion plate, and a lighting signboard.
The multilayer sheet obtained by the present invention depends on the rigidity of the raw material base resin, but a relatively thin laminated sheet having a thickness of 1 mm or less is generally wound into a roll shape to obtain a product, which is stored and transported. The The thick plate-like multilayer sheet is cut to a required length, stored and transported.

The transparent resins (transparent resin (a), transparent resin (b) and transparent resin (c)) used as the base resin for each layer in the multilayer sheet obtained by the present invention are all known by JIS K7361 (1997). The “transparent plastic” produced is preferably used.
Specific examples of the transparent resin include acrylic resins, styrene resins, polycarbonate resins, thermoplastic polyester resins, and cyclic olefin resins. The acrylic resin is a homopolymer of acrylic acid alkyl ester or / and methacrylic acid alkyl ester (hereinafter collectively referred to as (meth) acrylic acid ester) or a copolymer of (meth) acrylic acid esters, A (meth) acrylic acid ester-based copolymer having a unit based on a (meth) acrylic acid ester of 50 mol% or more and a unit based on another comonomer of 50 mol% or less, and a mixture of two or more thereof. Examples of the (meth) acrylic acid ester homopolymer or copolymer include polymethyl methacrylate, polyethyl methacrylate, polypropyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, and methacrylic acid. Examples include methyl acrylate-ethyl methacrylate copolymer, methyl methacrylate-butyl methacrylate copolymer, and methyl methacrylate-ethyl acrylate copolymer. Among these, polymethyl methacrylate, polymethyl acrylate, methyl methacrylate-ethyl methacrylate copolymer and methyl methacrylate-ethyl acrylate copolymer are preferable, and polymethyl methacrylate is more preferable.

  Examples of the (meth) acrylic acid ester-based copolymer include methyl methacrylate-styrene-butylene copolymer, (meth) methyl acrylate-styrene copolymer, (meth) ethyl acrylate-styrene copolymer, Examples include methyl methacrylate-acrylonitrile-butadiene-styrene copolymer. Of these, methyl methacrylate-styrene-butylene copolymer and methyl methacrylate-styrene copolymer are preferred.

  The styrenic resin is a homopolymer of styrene, a styrene copolymer in which the unit based on styrene exceeds 50 mol%, and the unit based on another comonomer is less than 50 mol%, and a mixture of two or more thereof. Examples of the styrenic resin include polystyrene, AS resin, ABS resin, methyl methacrylate-styrene copolymer, styrene-diene block copolymer and the like in which the unit based on styrene exceeds 50 mol%.

  Examples of the polycarbonate resin include bisphenol A (4,4′-dihydroxydiphenyl-2,2-propane) polycarbonate, bisphenol F (4,4′-dihydroxydiphenyl-2,2-methane) polycarbonate, and bisphenol S (4,4). 4'-dihydroxydiphenylsulfone) polycarbonate, 2,2-bis (4-dihydroxyhexyl) propane) polycarbonate and the like are exemplified. Of these, optical grade polycarbonate resins are particularly preferred.

In addition, thermoplastic polyester resins, aromatic ring-containing polyester resins (for example, polyethylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate and polyethylene naphthalate) and aliphatic polyesters (for example, polybutylene adipate, polyethylene adipate and poly (polyethylene adipate)) -Ε-caprolactone), a cyclic olefin polymer is a homopolymer of cyclic olefin, a copolymer of cyclic olefins, or a copolymer of cyclic olefin and ethylene or α-olefin, or a mixture of two or more thereof. Etc. can be used. Examples of the cyclic olefin-based polymer include “Apel” and “Topas” from Mitsui Chemicals, Inc., and “Zeonex” and “Zeonor” from Zeon Corporation.
These resins can be used in a small amount as long as optical properties such as transparency of the multilayer sheet are not impaired.

  The said transparent resin used for each layer which comprises the multilayer sheet obtained by this invention can be used 1 type or in mixture of 2 or more types. In addition, when 1 type of transparent resin is used, the resin used for each layer may be the same or different. When using a mixture of two or more of the transparent resins, or when mixing and using other thermoplastic resins within the range that does not impair the purpose of the present invention, It is preferable that the refractive index is approximate or equal. If the difference in refractive index between the transparent resins or the difference in refractive index between the transparent resin and the other thermoplastic resin is large, the mixed resin becomes cloudy depending on the mixing ratio, and therefore it is desirable that the difference in refractive index is small. Specifically, the refractive index difference is preferably within 0.05, more preferably within 0.04, even more preferably within 0.03, and the refractive index difference is optimally 0 (zero).

As the polymer type antistatic agent used in the present invention, a polyolefin block and a hydrophilic polymer block having a volume resistivity of 1 × 10 ⁵ to 1 × 10 ¹¹ Ω · cm are an ester bond and an amide bond. A block polymer (a), a polyether ester amide, a polyether amide, and a polyether amide imide having a structure in which they are repeatedly and alternately bonded through at least one bond selected from the group consisting of an ether bond and an imide bond At least one polyether-containing hydrophilic polymer (b) selected from: amide group-containing hydrophobic polymer comprising polyamide and / or polyamideimide, polyether-containing hydrophilic polymer comprising polyether diol and / or polyether diamine And aromatic ring-containing polyester A block polymer (c) composed of

  The block polymer (a) is disclosed in JP-A No. 2004-190028, the polyether-containing hydrophilic polymer (b) is disclosed in JP-A No. 2006-206894, and the block polymer (c) is disclosed in JP-A No. 2006. -233204, each of which is described in detail.

  Examples of the light diffusing agent used in the present invention include conventionally used inorganic light diffusing agents and organic light diffusing agents. Specific examples of the inorganic light diffusing agent include barium sulfate, calcium carbonate, Examples thereof include particles of titanium oxide, aluminum hydroxide, magnesium oxide, zinc oxide, silica, glass, mica, and the like. These may be subjected to surface treatment with a fatty acid, a silicone coupling agent, a titanate coupling agent, or the like. Specific examples of the organic light diffusing agent include styrene resin particles, acrylic resin particles, and silicon resin particles, and these resins are desirably crosslinked resin particles. The cross-linked styrene resin particles are resins composed of at least 50% by mass of a styrene monomer, and the cross-linked acrylic resin particles are at least 50% by mass of methyl methacrylate, butyl methacrylate, fluorine-modified methyl methacrylate or the like. Is a resin composed of acrylic monomers. The styrene-acrylic resin particles are a crosslinked resin composed of at least a styrene monomer and an acrylic acid monomer. The crosslinked silicone resin particles are generally called silicone rubber or silicone resin, and those that are solid at room temperature are preferably used.

  The difference in refractive index between the light diffusing agent and the base resin is preferably 0.02 or more and 0.2 or less in view of satisfying both requirements of light diffusibility and brightness (luminance). The average particle diameter of the light diffusing agent is 1 μm to 20 μm, preferably 2 to 15 μm. If the average particle size is less than 1 μm, the color may change and the color may turn yellow. On the other hand, if it exceeds 20 μm, the light diffusibility may not be sufficiently imparted by addition to the light diffusing agent. Among the light diffusing agents, in the present invention, crosslinked silicone resin particles and crosslinked acrylic resin particles having particularly excellent weather resistance are suitable. The shape is spherical, elliptical, hemispherical, or the like.

  The amount of the light diffusing agent used depends on the particle size of the added light diffusing agent, the type of the light diffusing agent, and the refractive index, but is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin component. Is 0.3 to 5 parts by weight. When the amount is 0.1 parts by weight, the light diffusing effect is not sufficiently obtained. On the other hand, when the amount exceeds 10 parts by weight, the light diffusing effect is increased, but the brightness (luminance) is lowered, which is not preferable. In addition, the quantity of a light-diffusion agent is a compounding ratio with respect to the basic weight of the whole lamination sheet.

When the multilayer sheet of the present invention is used for a diffusion plate of a backlight unit, an ultraviolet absorber or a hindered amine light stabilizer is used for the coating layer in order to reduce color change due to resin deterioration caused by long-time lighting of the cold cathode tube. It is desirable to add.
The ultraviolet absorber is selected from benzophenone series, benzotriazole series, and malonic ester series. As for the addition amount of a ultraviolet absorber and a hindered amine light stabilizer, 0.05-0.8 weight part is preferable with respect to 100 weight part of coating layers. When the addition amount is small, it is difficult to impart sufficient light resistance to the light diffusion sheet. On the other hand, when the addition amount is large, coloring of the light diffusable sheet and a decrease in brightness (luminance) are likely to occur, which further leads to an increase in cost. Preferably it is 0.1-0.6 weight part. Here, the addition amount is an amount with respect to the basis weight of the coating layer. In addition, an ultraviolet absorber and a weather resistance stabilizer can be added to the antistatic layer and the core layer. In this case, it is necessary to adjust the addition amount of the light diffusing agent to be within the range of the addition amount as a whole of the laminated sheet. An increase in the amount of the entire multilayer sheet is not preferable because it causes coloring.

If the manufacturing method of the multilayer sheet of this invention is shown concretely, as illustrated previously, the multilayer sheet obtained by this invention will use the equipment shown, for example in FIG. Can be manufactured. When a five-layer multilayer sheet comprising coating layer / antistatic layer / core layer / antistatic layer / coating layer obtained by the present invention is produced, it is coextruded by connecting at least three extruders.
In the five-layer multilayer sheet, when a light diffusing agent is added to the entire core layer, a resin composition in which the light diffusing agent is added to the base resin forming the core layer, and a group forming the antistatic layer A resin composition in which an antistatic agent is added to the material resin, and a resin that forms a coating layer are melt-kneaded in each extruder, the molten resin composition is laminated in a die, and extruded into a sheet through a T-die, The extruded sheet is passed through at least two rolls (polishing rolls), and the thickness of the sheet is made uniform to obtain a laminated sheet as a take-up product.

In the multilayer sheet obtained by the present invention, when the light diffusing agent is unevenly distributed in the core layer, for example, the light diffusion in the core layer is performed so that the light diffusion layer (A2) is unevenly distributed in the core layer. When the layer (A2) is a single layer, an extruder is further added and coextruded so as to form a resin composition containing a light diffusing agent. In this case, the resin for forming the core layer, the resin composition containing the light diffusing agent, the resin composition to which the antistatic agent is added, and the resin for forming the coating layer are melt-kneaded in each extruder, and the molten resin The composition is laminated in a die, extruded into a sheet shape through a T-die, and the extruded sheet is passed through at least two rolls (polishing rolls) to make the sheet thickness uniform, and taken as a multilayer sheet. Is done.
Further, when blending the light diffusing agent into the antistatic layer, the antistatic layer forming base resin is blended with the antistatic agent and the light diffusing agent and extruded as in the case of the five-layer laminated sheet. The desired multilayer sheet is produced.
When a light diffusing agent is blended in the core layer and the antistatic layer, the core layer forming resin composition blended with the light diffusing agent, the antistatic layer forming resin composition blended with the light diffusing agent, and the coating layer forming The target multilayer sheet is produced by extruding the resin in the same manner as in the case of the five-layer laminated sheet.

  In the method for producing a multilayer sheet of the present invention, a resin or a resin composition for forming each layer is supplied to each extruder, melted and kneaded in the extruder, and a molten resin or a molten resin composition is formed so as to form each layer in a die. Are joined together and laminated, and a multilayer sheet coextruded from a T-die is passed through the roll to obtain a target multilayer sheet. The resin temperature of each layer immediately before the molten resin or molten resin composition is merged in the die is slightly different depending on the type of base resin used, but is usually 180 to 280 ° C. Said resin temperature is measured in the breaker plate part arrange | positioned at the exit of the extruder or the exit of the gear pump installed in the tip (downstream side). If it is not affected by the temperature of the other layers due to the merge, it is coextruded at substantially the same temperature. In general, since polymer antistatic agents have low thermal stability, it is desirable that the resin temperature of the layer to which the polymer antistatic agent is added is set to be slightly lower, and usually 180 to 265 ° C. is adopted. Preferably, 195 to 265 ° C, more preferably 210 to 250 ° C is employed.

In melt-kneading the antistatic agent and the base resin, it is preferable that the antistatic agent is dispersed and formed in a network in the base resin layer in order to develop antistatic performance. In order to disperse the antistatic agent in the above-described state, the antistatic agent preferably has a lower melt viscosity than the base resin at the same temperature. The resin temperature of the layer containing the antistatic agent may vary somewhat depending on the type of resin, but is approximately around 230 ° C., so that the melt viscosity (unit: Pa) measured at a temperature of 230 ° C. and a shear rate of 100 s ^−1. S, this melt viscosity is hereinafter simply referred to as melt viscosity), the ratio of the melt viscosity of the antistatic agent to the melt viscosity of the base resin is preferably 1:35 to 1: 1.5, and 1:25 to 1 : 2 is more preferable. However, for the polycarbonate resin, the value measured at 260 ° C. is adopted.
Each melt viscosity of the base resin (transparent resin) mixed with the antistatic agent is generally about 300 to 3000 Pa · s. However, in order to improve kneadability and film-forming property. 600 to 2500 Pa · s, more preferably 900 to 2200 Pa · s is preferable.

  In the present invention, the transparent resin (c), which is the base resin of the coating layer constituting the multilayer sheet, is in contact with the inner wall surface of the die in the die at the time of extrusion. Deviation tends to occur with the antistatic layer (B) in contact with the coating layer, which causes deterioration of surface properties. Therefore, the melt viscosity of the transparent resin (c) is preferably not more than the melt viscosity of the transparent resin (b) of the antistatic layer. Specifically, 300 to 2500 Pa · s is preferred, 500 to 2300 Pa · s is more preferred, and 700 to 2000 Pa · s is even more preferred.

  In addition, since some base resin used has a hygroscopic property, a vent type extruder is preferable. In addition, a lamination method using a feed block method or a multi-layer method using a hold die method is adopted as the lamination structure. In order to form a thin coating layer on the outermost surface, a method using a multi-manifold die is more preferable.

  As a sheet take-up machine, a normal polishing roll with hard chrome plating is used. As the polishing roll, a triple polishing roll is generally used, but a four-roll polishing roll may be used as necessary. An example of the arrangement of the polishing roll is shown in FIG.

  The temperature of the polishing roll is arbitrarily selected, but may vary depending on the glass transition temperature of the base resin used and the target product thickness. However, the gloss of the sheet surface is appropriately adjusted so that warpage of the plate product does not occur. The following temperature conditions are adopted. The roll temperature is generally 30 to 180 ° C, preferably 40 to 160 ° C, and most preferably 50 to 140 ° C. Usually, in the case of a product having a thin sheet thickness, the low temperature side is adopted, and in the case of a product having a large sheet thickness, the high temperature side is adopted. The roll temperature is generally set to a higher temperature as the downstream side roll is turned on. The most downstream roll temperature is preferably 85 ° C. or higher, more preferably 90 to 170 ° C., more preferably 90 to 145 ° C., and even more preferably 90 to 140 ° C. from the viewpoint of preventing warpage of the laminated sheet.

The evaluation method of the multilayer sheet of the present invention and the measurement method of resin physical properties are described below.
[Total light transmittance and haze]
Multiple sheets are cut out from the multilayer sheet into a size of 50 mm × 50 mm (thickness is the thickness of the multilayer sheet), and these are used as test pieces, using a turbidimeter (NDH2000, Nippon Denshoku Industries Co., Ltd.), JIS K7136 (2000) Each test piece is measured according to, and each measured value is averaged to obtain the total light transmittance.
In addition, the plurality of test pieces, the first base point is a place that enters the inner side 50 mm from one end of the width direction of the multilayer sheet to the other end side, from the first base point, Test each base point including the first base point with a new location every 100 mm toward the other end side as the base point (however, the last base point is 50 mm or more from the other end side). Each of the test pieces was cut out so as to be the center of the piece and so that one side of the test piece coincided with the extrusion direction of the multilayer sheet.
For the transparent resin, a flat molded plate (size of 50 mm × 50 mm) having a smooth surface with a thickness of 2 mm was used as a test piece, and in the same manner as described above, a turbidity meter (NDH2000 from Nippon Denka Kogyo Co., Ltd.) was used. The total light transmittance and haze are measured according to JIS K7136 (2000).

[Yellow Index (YI value)] (Yellowness)
A plurality of sheets of 50 mm × 50 mm in size (thickness is the thickness of the multilayer sheet) are cut out from the multilayer sheet, and these are used as test pieces in accordance with ASTM D1925 by a transmission method using a spectroscopic color difference meter (SE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.). Each test piece was measured by the method according to the above, and each measured value was averaged to obtain a YI value. As the light source in this measurement, a C light source having a viewing angle of 2 degrees in the CIE light source is selected.
The plurality of test pieces were cut out from different positions of the multilayer sheet in the same manner as the total light transmittance and haze measurement test pieces.

[Initial voltage]
A plurality of sheets of 40 mm × 40 mm in size (thickness is the thickness of the laminated sheet) are cut out from the multilayer sheet, and these are used as test pieces for 24 hours in a 23 ° C., 50% RH environment. TIPE S-5109 manufactured by Co., Ltd. was used to apply a voltage to each test piece in accordance with JIS L1094 (1988) A method in an environment of 23 ° C. and 50% RH. As a measured value, each measured value is averaged to obtain an initial charging voltage. The plurality of test pieces were cut out from different positions of the multilayer sheet in the same manner as the total light transmittance and haze measurement test pieces. Each test piece was cut out, washed in an ultrasonic cleaner for 10 minutes while immersed in 60 ° C. ion-exchanged water, and further rinsed with ion-exchanged water. The condition is adjusted after drying in an oven for 1 hour. When the test piece is immersed in warm water, the end of the test piece is pressed from above with a metal jig from which oil has been removed in advance so as not to float from the warm water.

[Surface resistivity]
A plurality of sheets of 100 × 100 mm in size (thickness is the thickness of the multilayer sheet) are cut out from the multilayer sheet, and these are used as test pieces, and the test pieces are washed, rinsed and dried in the same manner as in the measurement of the initial charging voltage. After conditioning for 24 hours in a 23 ° C., 50% RH environment, using a super insulation resistance / microammeter (TR-8601, Takeda Riken Kogyo Co., Ltd.), in a 23 ° C., 50% RH environment. The surface resistance was measured for each test piece in accordance with JIS K6911 (1995), and the surface resistance value (the reading value of the device) obtained by averaging the measured values was multiplied by a coefficient of 18.8 to obtain the surface resistance. Rate. The measurement is performed in an insulation resistance measurement sample box (TR42 manufactured by Takeda Riken Kogyo Co., Ltd.), and the electrode used for the measurement has a surface electrode whose inner circle has an outer diameter of 50 mm and the surface annular electrode has an inner diameter of 70 mm. use. Further, the plurality of test pieces are cut out from different positions of the multilayer sheet in the same manner as the total light transmittance and haze measurement test pieces.

[Thickness of multilayer sheet]
Measured with a digital micrometer manufactured by Mitutoyo Corporation in the width direction at intervals of 50 mm from the place where 30 mm entered from one end of the width direction of the multilayer sheet to the other end side in the width direction, Average thickness.
The first base point is a portion that enters 30 mm inside from one end in the width direction of the multilayer sheet that is randomly selected to the other end, and every 50 mm from the first base to the other end. Each new point is the base point (however, the last base point is 30 mm or more from the other end), and the thickness of the multilayer sheet is determined at each base point position including the first base point. Measure with a digital micrometer manufactured by Mitutoyo Co., Ltd., and average the measured values to obtain the thickness of the multilayer sheet.

[Resin melt viscosity]
The melt viscosity in the present invention is a value obtained by measuring with a capillograph model 1D manufactured by Toyo Seiki Seisakusho. Details of the measurement are as follows. Attach a capillary with a hole diameter of 1.0 mm and a length of 10 mm to the tip of a cylinder with an inner diameter of 9.55 mm (effective length of 250 mm), and raise the temperature of the cylinder and capillary to 230 ° C. (only polycarbonate resin is 260 ° C.). A measurement sample (resin pellet) is filled in the inside. After filling, the piston is loaded into the cylinder, and the measurement sample is melted by preheating for 4 minutes. During the preheating, the piston is temporarily pushed down to sufficiently remove bubbles from the molten measurement sample. Further, the filling amount of the measurement sample is set to a sufficient amount that can secure 15 cc or more of the measurement sample after removing the bubbles. After the preheating is completed, the measurement sample in the cylinder is extruded so that the shear rate of the capillary part becomes 100 s ⁻¹ with the piston, and the melt viscosity at that time is measured. The melt viscosity is measured after the extrusion load is stabilized.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples, and belongs to the scope of the present invention as long as it does not exceed the gist of the present invention.

The apparatuses used in the following examples and comparative examples are specifically as follows.
The extruder for forming the core layer uses a single screw extruder with an inner diameter of 65 mm, a single screw extruder with an inner diameter of 40 mm for forming the antistatic layer, and a single screw extruder with an inner diameter of 20 mm for the extruder for forming the clothing layer. Was used.
As the sheet molding and take-up machine, a triple polishing roll shown in FIG. 7 made of a metal roll having a mirror-like smooth surface coated with hard chrome plating with a roll diameter of 195 mm was used.
The maximum temperature of each resin or resin composition in each extruder was adjusted so as not to exceed the resin temperature plus 25 ° C. shown in Table 1.
In the kneading extruder having the inner diameter of 65 mm, the amount of extrusion with a gear pump attached to the outlet of the extruder was controlled. In addition, a multi-manifold T die with a lip width (W) of 500 mm capable of stacking three types and five layers is attached, and the total discharge amount for each layer is set to a discharge rate of 60 kg / hr. The conditions and layers shown in Tables 3 and 4 Coextruded with configuration.
The take-up speed was adjusted according to the desired product thickness. The thickness of each layer was adjusted by calculating the required basis weight (g / m ² ) from the specific gravity of each exemplified resin, and further changing the discharge amount of each layer forming extruder accordingly. The roll temperature was individually adjusted using three oil pumps. The positional relationship of the rolls was the arrangement shown in FIG. The roll temperature terms 1, 2 and 3 in Tables 3 and 4 refer to the polishing rolls 13, 14, and 15 shown in FIG. The roll temperature indicates the temperature of the temperature control oil of the roll temperature.
The resin temperatures in Tables 3 and 4 are the temperature at the center of the breaker plate installed at the gear pump outlet for the core layer, and the temperature at the center of the breaker plate attached to the extruder outlet for the antistatic layer and coating layer. Was measured and shown.

  Tables 1 and 2 show the transparent resins and antistatic agents used in Examples and Comparative Examples and their physical properties. Tables 3 and 4 show the constitution and production conditions of the multilayer sheet, and Table 5 shows the physical properties and evaluation results of the obtained laminated sheet.

Example 1
Acrylic resin (“VH5-000” manufactured by Mitsubishi Rayon Co., Ltd.) is used as the transparent resin for the core layer, antistatic layer, and coating layer, and the refractive index difference with respect to VH5-000 is 0. A polyether polymer type antistatic agent (VH230) manufactured by Sanyo Chemical Industries, Ltd., which is 01, was used.
In order to prevent coloring due to the antistatic agent, a dye called a bluing material was added to the antistatic layer by using a master batch so that the amount was 0.02% with respect to the antistatic layer.
In the core layer, cross-linked silicone resin particles having an average particle diameter of 3 μm (Toshiba Silicone Tospearl 130) and cross-linked silicone resin particles having an average particle diameter of 6 μm (Toshiba Silicone Tospearl 200) are used as a light diffusing material with respect to 100 parts of the core layer base material. 1.2 parts were added each (2.4 parts in total). And the weathering stabilizer was added so that the addition amount might be 0.3 weight part with respect to 100 parts of base resin of a coating layer and an antistatic layer, respectively. A master batch was used for the addition.
The weathering stabilizer is composed of a benzotriazole ultraviolet absorber (trade name “Tinuvin 234” manufactured by Ciba Specialty Chemicals) and a hindered amine light stabilizer (trade name “Cinuvin 770DF” manufactured by Ciba Specialty Chemicals). It is a 2: 1 mixture by weight.
A multilayer sheet was obtained by coextrusion as the conditions and layer constitution shown in Table 3. The T die lip used for extrusion had a clearance of 4 (h) mm, a land length (t) of 15 mm, and the shear amount was controlled to 23. And the lamination sheet which consists of 5 layer structure of thickness 2.0mm was obtained. As a result, even when continuously extruded for 12 hours, the roll surface was not contaminated at all by deposits, and a multilayer sheet could be obtained stably (Table 3). The measurement results are shown in Table 5. The obtained multilayer sheet was excellent in light diffusibility and antistatic property.

Example 2
A methyl methacrylate-styrene copolymer (“MS600” manufactured by Nippon Steel Chemical Co., Ltd.) is used as a transparent resin for the core layer, the antistatic layer M, and the coating layer. A polyether ester amide polymer antistatic agent (NC7530) manufactured by Sanyo Chemical Industries, Ltd. with a rate difference of 0 was used. A weathering stabilizer was added to the coating layer and antistatic layer, and a bluing material was added to the antistatic layer in the same manner as in Example 1. In the core layer, 1 part of crosslinked silicone particles (KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd.) having an average particle diameter of 2 μm was added as a light diffusing material to the core layer base resin. A multilayer sheet was obtained by coextrusion under the conditions and layer constitution shown in Table 3. The T die lip used for extrusion had a clearance of 4 mm, a land length of 3 mm, and the shear amount was controlled to 3. And the multilayer sheet which consists of a 5-layer structure of thickness 2.0mm was obtained. And the lamination sheet which consists of 5 layer structure of thickness 2.0mm was obtained. As a result, even if the extrusion was continued for 12 hours, the roll surface was not contaminated at all by deposits, and a multilayer sheet could be obtained stably. The measurement results are shown in Table 5. The obtained multilayer sheet was excellent in light diffusibility and antistatic property.

Example 3
Polymer type antistatic agent using polycarbonate resin (“H4000” manufactured by Mitsubishi Engineering Plastics) as the transparent resin for the core layer and acrylic resin (“VH5-000” manufactured by Mitsubishi Rayon Co., Ltd.) as the transparent resin for the antistatic layer and coating layer The polyether polymer type antistatic agent VH230 manufactured by Sanyo Kasei Kogyo Co., Ltd., having a refractive index difference of 0.01 from that of VH5-000, was used as a weathering stabilizer for the coating layer and antistatic layer. The material was added to the antistatic layer in the same manner as in Example 1. In the core layer, cross-linked silicone particles having an average particle size of 2 μm (Tospearl 120, manufactured by Toshiba Silicone Co., Ltd.) as a light diffusing material were 0.3% relative to the core layer substrate. A laminated sheet was obtained by adding a part, and a 5-layer structure having a thickness of 2.0 mm using the same lip part as in Example 1 by coextrusion as the conditions and layer constitution shown in Table 3. As a result, even after continuous extrusion for 12 hours, the roll surface was not contaminated with any deposits, and the multilayer sheet could be obtained stably. The obtained multilayer sheet was excellent in light diffusibility and antistatic property.

Example 4
A polystyrene resin (HH32 manufactured by PS Japan) is used as the core layer base material, and a methyl methacrylate-styrene copolymer (“MS600” manufactured by Nippon Steel Chemical Co., Ltd.) is used as the transparent resin for the antistatic layer and the coating layer. As a type antistatic agent, a polyether ester amide polymer type antistatic agent (NC7530) manufactured by Sanyo Kasei Kogyo Co., Ltd. having a refractive index difference of 0 from MS600 was used. A weathering stabilizer was added to the coating layer and antistatic layer, and a bluing material was added to the antistatic layer in the same manner as in Example 1. In the core layer, 3 parts of acrylic crosslinked particles (MBX-8 manufactured by Sekisui Plastics Co., Ltd.) having an average particle diameter of 8 μm were added as a light diffusing material to 100 parts of the core layer base resin. Co-extrusion was performed under the conditions and layer configurations shown in Table 3, and a multilayer sheet having a five-layer structure having a thickness of 2.0 mm was obtained using the one having the same T die lip portion as in Example 2. As a result, even if the extrusion was continued for 12 hours, the roll surface was not contaminated at all by deposits, and a multilayer sheet could be obtained stably. The measurement results are shown in Table 5. The obtained multilayer sheet was excellent in light diffusibility and antistatic property.

Example 5
A multilayer sheet was obtained under the same extrusion conditions as in Example 1, except that the coating layer thickness was 10 μm, the core layer thickness was adjusted to 1830 μm, and the addition amount of the antistatic agent was increased to 25%. Increasing the thickness of the coating layer tends to lower the antistatic performance, but with an increase in the amount of antistatic agent, the antistatic performance was almost the same as in Example 1. The YI value was on the rise but was in a sufficiently good range. The measurement results are shown in Tables 3-1 and 4.

Example 6
A multilayer sheet was obtained in the same manner as in Example 1 except that the belt-proof layer was 150 μm and the core layer was 1690 μm. Since the antistatic layer was thickened, the antistatic performance was improved. On the other hand, the YI value tended to increase, but was well within an acceptable range. The measurement results are shown in Table 5.

Example 7
The anti-static layer comprises the cross-linked silicone resin particles having an average particle diameter of 3 μm (Toshiba Silicone Tospearl 130) and the cross-linked silicone resin particles having an average particle diameter of 6 microns (Toshiba Silicone Tospearl 200) used in Example 1 as an antistatic layer. A laminated sheet was obtained in the same manner as in Example 6 except that 0.5 part each was added to 100 parts of the layer base material. Even when a light diffusing material was added to the antistatic layer, a light diffusing plate having antistatic performance could be obtained without any particular problem. The measurement results are shown in Table 5.

Example 8
Acrylic resin (“VH5-000” manufactured by Mitsubishi Rayon Co., Ltd.) is used as the transparent resin for the core layer, antistatic layer, and coating layer, and the refractive index difference with respect to VH5-000 is 0. A polyether polymer type antistatic agent (VH230) manufactured by Sanyo Chemical Industries, Ltd., which is 01, was used.
In order to prevent coloring due to the antistatic agent, a dye called a bluing material was added to the antistatic layer by using a master batch so as to be 0.02% by weight with respect to the antistatic layer.
And the weathering stabilizer was added so that the addition amount might be 0.3 weight part with respect to 100 parts of base resin of a coating layer and an antistatic layer, respectively. A master batch was used for the addition.
The weathering stabilizer is composed of a benzotriazole ultraviolet absorber (trade name “Tinuvin 234” manufactured by Ciba Specialty Chemicals) and a hindered amine light stabilizer (trade name “Cinuvin 770DF” manufactured by Ciba Specialty Chemicals). It is a 2: 1 mixture by weight.
Coextrusion was carried out under the conditions and layer constitution shown in Table 3 to obtain a multilayer sheet. The clearance and land length of the T die lip used for extrusion were the same as in Example 1, and a multilayer sheet having a thickness of 2.0 mm and having a five-layer structure was obtained. As a result, even when continuously extruded for 12 hours, the roll surface was not contaminated at all by deposits, and a multilayer sheet could be obtained stably (Table 3). The obtained multilayer sheet was excellent in transparency and antistatic properties.

Example 9
A multilayer sheet was obtained in the same manner as in Example 1 except that the coating layer was 1 μm, the thickness was adjusted, and the core layer thickness was set to 1848 μm. The measurement results are shown in Table 5.

Example 10
A laminated sheet was obtained in the same manner as in Example 1 except that the coating layer was 60 μm and the thickness was adjusted to 1730 μm. The measurement results are shown in Table 5.

Example 11
A multilayer sheet was obtained in the same manner as in Example 1 except that the antistatic layer was 400 μm, the thickness was adjusted, and the core layer thickness was set to 1190 μm. The measurement results are shown in Table 5.

Example 12
A multilayer sheet was obtained in the same manner as in Example 1 except that the antistatic layer was 10 μm, the thickness was adjusted, and the core layer thickness was set to 1970 μm. The measurement results are shown in Table 5.

Example 13
A multilayer sheet was obtained in the same manner as in Example 1 except that the blending amount of the antistatic agent in the antistatic layer was changed to 3%. The measurement results are shown in Table 5.

Example 14
A multilayer sheet was obtained in the same manner as in Example 1 except that the blending amount of the antistatic agent in the antistatic layer was 50%. The surface state was also a bumpy multilayer sheet due to a decrease in the viscosity of the antistatic layer. The measurement results are shown in Table 5.

Example 15
Under the manufacturing conditions shown in Table 3, co-extrusion was performed with a multi-manifold T-die as the layer configuration shown in Table 5, and a multilayer sheet having a five-layer structure with a thickness of 1.6 mm was obtained with a take-up speed of 1.14 m / min. . The parallel land portion (lip clearance 2.5 mm, parallel land length 55 mm) was changed, and the parallel land portion was formed with a shear amount of 132. Other conditions are the same as in the first embodiment. As a result, the resulting multi-layer sheet was slightly acceptable due to an increase in the amount of shear, but was within an acceptable range.

Comparative Example 1
A multilayer sheet was produced in the same manner as in Example 1 except that the coating layer was removed and the thickness was adjusted so that the core layer thickness was 1850 μm. However, the roll became dirty in a few minutes, and the sheet surface became uneven. Therefore, evaluation of light diffusibility and antistatic property was not performed.

Comparative Example 2
The clearance of the T die lip used for extrusion was 2 mm, the land length was 60 mm, and the shear amount was controlled to 180. Otherwise, a multilayer sheet of three types and five layers was obtained in the same manner as in Example 2.
Although the obtained multilayer sheet was not significantly inferior to Example 2 in light diffusibility and antistatic property, a non-uniform scale pattern was generated on the surface, and it could not be used as a light diffusive sheet.

The schematic diagram of the multilayer sheet which mix | blended the light-diffusion agent with the antistatic layer in an example of the embodiment of this invention. FIG. 2 (1) is an example of an embodiment of the present invention in which a light diffusing agent is blended in the core layer, FIG. 2 (1) is a multilayer sheet in which the light diffusing agent is blended in the entire core layer, and FIG. The schematic diagram of the multilayer sheet which made uneven distribution in the core layer. FIG. 3A is an example of an embodiment of the present invention, in which a light diffusing agent is blended in the core layer and the antistatic layer. FIG. 3A is a multilayer sheet in which a light diffusing agent is blended in the entire core layer and the antistatic layer. (2) is a schematic view of a multilayer sheet in which a light diffusing agent is unevenly distributed in the core layer. The schematic diagram which shows the example which provided the coating layer in the single side | surface by the deformation | transformation aspect of FIG. FIG. 5 (1) is a modification of FIG. 2, and FIG. 5 (2) is a schematic view showing an example in which a coating layer is provided on one side in FIG. 2 (2). FIG. 6 (1) is a modification of FIG. 3, and FIG. 6 (2) is a schematic diagram showing an example in which a coating layer is provided on one side in FIG. 3 (2). Explanatory drawing which shows an example of the equipment used for an extrusion sheet forming method. The schematic diagram of the longitudinal cross-section of an example of T-die in extrusion sheet | seat shaping | molding is shown.

Explanation of symbols

A Core layer A1 Core layer A2 containing a light diffusing agent Core layer B in which a light diffusing agent is unevenly distributed B Antistatic layer B1 Antistatic layer C containing a light diffusing agent C Coating layer 10 Die 11 Lip part 12 Extruders 13, 14, 15 Polishing roll 16 Multilayer sheet

Claims (10)

A melt for forming the core layer (A) using the transparent resin (a) as a base resin;
An antistatic layer (B) -forming melt containing a transparent resin (b) as a base resin and a polymeric antistatic agent, and a polymeric antistatic agent substantially comprising the transparent resin (c) as a base resin A method for producing an antistatic multilayer sheet in which a coating layer (C) forming melt not included is laminated and merged in a die and coextruded,
Each melt is placed in the die so that the coating layer is at least one outermost surface of the multilayer sheet, and the antistatic layer is in contact with the inner surface of the coating layer and at least the outer surface side of the core layer. By laminating and joining, there is no laminating merged product,
A method for producing an antistatic multilayer sheet, characterized in that a shear amount of the laminated combined product of the parallel land portions of the lip portion of the die represented by the following formula (1) is 0.1 to 170.
(Equation 1)

  The ratio of the melt viscosity of the polymer antistatic agent to the melt viscosity of the transparent resin (b) in the antistatic layer is 1:35 to 1: 1.5. A method for producing an antistatic multilayer sheet.   The melt viscosity of the transparent resin (b) is 600 to 2500 Pa · s, and the melt viscosity of the transparent resin (c) is equal to or lower than the melt viscosity of the transparent resin (b). The manufacturing method of the antistatic multilayer sheet of description.   In the antistatic layer, the addition amount of the polymer antistatic agent is 5% by weight to 40% by weight with respect to the total amount of the transparent resin (b) and the polymer antistatic agent, The method for producing an antistatic multilayer sheet according to any one of claims 1 to 3, wherein the antistatic layer has a thickness of 20 to 300 µm.   The method for producing an antistatic multilayer sheet according to any one of claims 1 to 4, wherein the coating layer in the antistatic multilayer sheet has a thickness of 2 to 50 µm.   The method for producing an antistatic multilayer sheet according to any one of claims 1 to 5, wherein the entire thickness of the antistatic multilayer sheet is 0.5 to 15 mm. The antistatic multilayer sheet has a yellow index value of 2.6 or less,
The antistatic multilayer sheet according to any one of claims 1 to 6, wherein the antistatic multilayer sheet is a multilayer sheet having an initial charged voltage of 2.5 kV or less in the measurement of the half-life of the charged voltage of the antistatic multilayer sheet. Method.   The antistatic property according to any one of claims 1 to 7, wherein the antistatic multilayer sheet is a multilayer sheet containing a light diffusing agent in at least one of the core layer or the antistatic layer. A method for producing a multilayer sheet.   In the said coating layer, the addition amount of a weathering stabilizer is 0.05-0.8 weight part with respect to 100 weight part of base resin of the said coating layer, The any one of Claims 1-8 characterized by the above-mentioned. A method for producing an antistatic multilayer sheet as described in 1 above.   The method for producing an antistatic multilayer sheet according to any one of claims 1 to 9, wherein the base resin of each layer constituting the antistatic multilayer sheet is an acrylic resin.

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