WO2007119851A1

WO2007119851A1 - Process for producing thermoplastic resin sheet with controlled warpage

Info

Publication number: WO2007119851A1
Application number: PCT/JP2007/058286
Authority: WO
Inventors: Takehisa Kishimoto; Akira Ueda
Original assignee: Nippon Shokubai Co., Ltd.
Priority date: 2006-04-19
Filing date: 2007-04-16
Publication date: 2007-10-25
Also published as: JP4843358B2; JP2007283700A; TW200744820A; KR20080099345A; KR101016997B1; US20070267773A1

Abstract

A process for producing a thermoplastic resin sheet with controlled warpage, characterized in that in the extrusion forming of a thermoplastic resin sheet, mechanically controlled warpage is applied to the sheet at the position where the temperature of extruded sheet is close to the glass transition temperature (Tg) of the thermoplastic resin constituting the sheet. In this process, preferably, mechanically controlled warpage is applied to the sheet by causing the sheet to pass through a gap of a vertical pair of warp controlling rolls at the above position and selecting the morphology of the warp controlling rolls and/or arranging the warpcontrolling rolls above or below the height for realizing a flat sheet. By this process, the thermoplastic resin sheet with controlled warpage can be efficiently produced in an easy manner.

Description

Specification

Method for producing thermoplastic resin sheet having controlled warpage

Technical field

[0001] The present invention relates to a method for producing a thermoplastic resin sheet having controlled warpage.

Background art

[0002] A thermoplastic resin sheet is produced by, for example, an extrusion molding method. In this case, the thermoplastic resin sheet is obtained by heating and melting the resin composition, extruding it from a die, rolling with a cooling roll, passing through a guide roll, and solidifying by cooling while taking it with a take-up roll. When a thermoplastic resin sheet is produced by an extrusion molding method, in general, various ideas have been made with the intention of obtaining a flat sheet while suppressing warpage.

[0003] For example, in JP-A-6-344417, the temperature of a cooling roll is adjusted, and the extruded sheet is heated to increase the temperature, and then slowly and slowly cooled. A method for relieving stress is disclosed, and Japanese Patent Application Laid-Open No. 7-276471 discloses a method for relieving internal stress by imparting stagnation to the sheet between the final cooling roll and the first guide roll. In JP-A-2001-139705 and JP-A-2005-81757, the internal stress is controlled by adjusting the speed ratio of the second and third cooling rolls and setting the roll temperature relatively low. A method for suppressing the occurrence is disclosed, and Japanese Patent Application Laid-Open No. 2004-126185 discloses an improved method using the methods disclosed in Japanese Patent Application Laid-Open Nos. 7-276471 and 2001-139705. .

[0004] As described above, in the prior art, the main focus has been on obtaining a flat sheet by suppressing the warpage by suppressing the generation of internal stress or relaxing the internal stress.

[0005] However, depending on the application of the thermoplastic resin sheet, it may be necessary to intentionally warp. For example, even if a light diffusion plate used in backlight units such as liquid crystal display devices and medical monitors is flat at the time of manufacture, after absorbing moisture in the air, the side facing the light is dried and contracted by the heat of the light. As a result, a convex warpage toward the display surface is generated, which adversely affects display performance when the backlight unit is used. [0006] In addition, when building on R-shaped parts in building materials, building materials that have been intentionally warped have better conformity to the base than flat building materials that do not warp. Such stress is also reduced. In the case of producing a thermoplastic resin sheet as a building material having warpage, a method in which a flat sheet is once extruded and then warped by hot forming has been adopted.

[0007] However, this method has a problem that an extra hot forming step is required in addition to the extrusion forming step, which increases the manufacturing cost of building materials.

[0008] In view of this, Japanese Patent Application Laid-Open No. 2002-120249 uses a thermoplastic resin sheet production line to heat a sheet when the temperature of the sheet coming out of the cooling roll is within a predetermined range. Alternatively, a method of adjusting the amount of warpage of the sheet by cooling and controlling the temperature difference between the upper and lower surfaces of the sheet has been proposed.

However, with this method, it is difficult to accurately control the temperature difference between the upper and lower surfaces of the sheet, and it seems difficult to produce a thermoplastic resin sheet having a controlled warpage.

Disclosure of the invention

The problem to be solved by the present invention is to provide a method for efficiently and simply producing a thermoplastic resin sheet having controlled warpage.

[0011] As a result of various studies, the present inventors have conducted extrusion molding of a thermoplastic resin sheet so that the temperature of the extruded sheet is around the glass transition temperature (Tg) of the thermoplastic resin constituting the sheet. It has been found that at some position the sheet can be mechanically (and possibly even thermally) controlled warped, completing the present invention.

That is, according to the present invention, in extruding a thermoplastic resin sheet, the extruded sheet is placed at a position where the temperature of the extruded sheet is near the glass transition temperature (Tg) of the thermoplastic resin constituting the sheet. Provided is a method for producing a thermoplastic resin sheet having controlled warpage (hereinafter, also referred to as “the production method of the present invention”) characterized by providing mechanically controlled warpage.

In the production method of the present invention, preferably, the sheet passes between a pair of upper and lower warp control rolls at the position, and the shape of the warp control roll is selected. And / or by placing the warpage control roll above or below the height at which a flat sheet is obtained, the sheet is given a mechanically controlled warpage. The temperature of the sheet at the position of the warpage control roll is preferably in the range of (Tg ± 20 ° C.). Further, by adjusting the temperature of the warpage control roll up and down to cause a difference in the cooling speed of the upper and lower surfaces of the sheet, and / or at or near the position of the warpage control roll, The sheet may be further thermally controlled by adjusting the temperature difference to cause a difference in the cooling rate between the upper and lower surfaces of the sheet.

[0014] In the production method of the present invention, the thermoplastic resin constituting the sheet is preferably a group consisting of a polycarbonate resin, a (meth) acrylic resin, a styrene resin, an acrylic-styrene resin, and a norbornene resin. In order to develop light diffusibility, fine particles may be contained.

[0015] The present invention also provides a thermoplastic resin sheet having controlled warpage, which is obtained by the production method.

[0016] According to the present invention, a thermoplastic resin sheet having controlled warpage can be obtained efficiently and simply. When the obtained thermoplastic resin sheet is used, for example, as a light diffusing plate in a backlight unit of a liquid crystal display device, a slight warp is given to the light side in advance, and the heat of the light is used during use. If it is designed to be almost flat, it will not cause a warp toward the display surface and will not push the liquid crystal display panel, so it will not adversely affect the display performance of the liquid crystal display device. Similarly, in the case of backlights for medical monitors and the like, if a slight warp is applied to the light side in advance and it is designed so that it is almost flat with the heat of the light during use, the medical monitor Display performance is not adversely affected.

Brief Description of Drawings

[0017] Fig. 1 is a schematic diagram showing the configuration of a typical sheet extruder used in the production method of the present invention.

[Fig. 2] When a thermoplastic resin sheet is produced using the sheet extruder shown in Fig. 1, a pair of upper and lower warp control rolls are moved upward to give an upward convex warp. It is a schematic diagram.

[Fig. 3] When manufacturing a thermoplastic resin sheet using the sheet extruder shown in Fig. 1, a pair of upper and lower warpage control rolls are moved downward to give a downward convex warpage. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, the present invention will be described in detail, but the scope of the present invention is not limited to these descriptions, and other than the following examples, the present invention is implemented with appropriate modifications within a range not impairing the gist of the present invention. can do.

In the production method of the present invention, in extruding a thermoplastic resin sheet, the extruded sheet is mechanically applied to the sheet at a position where the temperature of the extruded sheet is near the glass transition temperature (Tg) of the thermoplastic resin constituting the sheet. It is characterized by providing a controlled warp. Here, “warp” means a deviation from the case where the thermoplastic resin sheet is flat. Specifically, in the state in which the thermoplastic resin sheet is suspended, the flow direction of extrusion molding (hereinafter referred to as “longitudinal”). Direction)) and the distance from the center of the sheet to the yarn when the yarn is stretched at the center of the opposite sides of the width direction of extrusion (hereinafter referred to as the “lateral direction”). Means. When the sheet is warped to the front side (that is, when the warp is convex upward), the sheet is warped to the back side (that is, when the warp is convex downward) — Indicate.

[0020] In the production method of the present invention, the magnitude of the warpage may be appropriately set according to the application. Although not particularly limited, specifically, _ 100 mm or more, _ 5 mm or less or It is within the range of + 5mm or more and + 100mm or less. The warp of the thermoplastic resin sheet is applied along the vertical direction and the Z or horizontal direction. Here, warping is applied along the vertical direction, which means that when the sheet is viewed from the lateral direction, the sheet appears to be convex upward or downward, and warping is applied along the horizontal direction. When the sheet is viewed in the longitudinal force, it means that the sheet appears to be convex upward or downward, and warping is applied in the vertical and horizontal directions. It means that the curve is convex upward or downward from the peripheral part to the central part. In addition, when the thermoplastic resin sheet has warpage in the vertical and horizontal directions, the warpage is large depending on the application. It is preferable that the length is about the same in the vertical direction and the horizontal direction.

In the production method of the present invention, preferably, the sheet passes between a pair of upper and lower warpage control rolls at the position, and / or by selecting the shape of the warpage control roll, and / or By placing the warpage control roll above or below the height at which a flat sheet is obtained, a mechanically controlled warpage is imparted to the sheet. The temperature of the sheet at the position of the warpage control roll is preferably in the range of (Tg ± 20 ° C.). If the sheet temperature is less than (Tg_20 ° C), it may be difficult to warp the sheet because the sheet temperature is too low. Conversely, if the sheet temperature exceeds (Tg + 20 ° C), the sheet temperature is too high, so the amount of warpage applied to the sheet changes and the desired warpage cannot be applied to the sheet. Sometimes.

[0022] Further, by adjusting the temperature of the warp control roll up and down to cause a difference in the cooling rate of the upper and lower surfaces of the sheet, and / or at or near the position of the warp control roll on the sheet A more thermally controlled warpage may be applied to the sheet by adjusting the temperature difference on the lower surface to cause a difference in the cooling rate between the upper and lower surfaces of the sheet.

[0023] In the manufacturing method of the present invention, if a pair of upper and lower warpage control rolls used for extrusion molding are arranged above or below the height at which a flat sheet is obtained, warpage is given along the longitudinal direction of the sheet. be able to. In addition, if a roll having a shape such as crowning, reverse crowning or bow is used as one set of upper and lower warpage control rolls, warpage can be given along the lateral direction of the sheet. Furthermore, by changing the temperature of one set of upper and lower warp control rolls up and down, warping can be applied even if the temperature difference between the upper and lower surfaces of the sheet is adjusted to cause a difference in the cooling rate of the upper and lower surfaces of the sheet. . In contrast to the warpage control by the warpage control roll, the temperature difference between the upper and lower surfaces of the sheet is adjusted by heating and / or cooling the sheet at a position downstream of the warpage control roll in the flow direction of extrusion. Thus, a difference may be caused in the cooling rate of the upper and lower surfaces of the sheet. The position where the temperature difference between the upper and lower surfaces of the sheet is adjusted by heating and / or cooling the sheet is preferably as close to the warp control roll as possible.

[0024] As described above, in addition to the control of the warp by the warp control roll, the combined use of adjusting the temperature difference between the upper and lower surfaces of the sheet can give a larger warp. Giving greater warpage For example, a roll having an inverted crown shape is used as the upper warp control roll, a roll having a crown shape is used as the lower warp control roll, and / or a flat sheet is used as the warpage control roll. The temperature of the upper warpage control roll is set lower than the temperature of the lower warpage control roll, and the surface of the sheet that has passed through the warpage control roll is cooled and / or Or a force for heating the back surface of the sheet; or, as an upper warp control roll, a crown-shaped roll is used, as a lower warp control roll, an inverted crown-shaped roll is used, and / or Alternatively, the warp control roll is placed below the height at which a flat sheet can be obtained, and the temperature of the upper warp control roll is set lower than the temperature of the lower warp control roll. Ku is set, and then heating the surface of the sheet which has passed through the warp control roll, and / or may be cooled back surface of the sheet.

[0025] The production method of the present invention is a method of giving warpage controlled according to the height, shape, and temperature of the warpage control roll to the extruded sheet when extruding the thermoplastic resin sheet. Compared to the method described in Japanese Patent Application Laid-Open No. 2002-120249, that is, the method of adjusting the amount of warpage of the sheet by controlling the temperature difference between the upper and lower surfaces of the sheet by heating or cooling the sheet. Therefore, a thermoplastic resin sheet that is easy and reliable and has a controlled warp can be produced efficiently and simply.

[0026] Examples of the material of the thermoplastic resin sheet include polycarbonate resins; (meth) acrylic resins such as polymethylmethacrylate; styrene resins such as polystyrene; attalinole styrene resins; norbornene resins. Of these thermoplastic resins, polycarbonate resins are particularly suitable.

[0027] The thermoplastic resin sheet may be formed of a single material or two or more materials, and may be formed of a plurality of layers even if it is configured of a single layer force. It may be composed of force.

[0028] The thermoplastic resin constituting the sheet may contain, for example, additives such as a stabilizer, an antioxidant, an antistatic agent, a plasticizer, a dispersant, an optical brightener, and a diffusing agent. . The blending amount of these additives is not particularly limited as long as it is appropriately adjusted according to the kind thereof.

[0029] Alternatively, on at least one surface of the thermoplastic resin sheet, an antioxidant, an antistatic agent, purple You may provide the thin layer containing additives, such as an external line | wire prevention agent, a fluorescent whitening agent, and a spreading | diffusion agent. These additives may be contained entirely in a single thin layer, or may be contained separately or in combination in a plurality of thin layers.

[0030] Examples of the material constituting the thin layer include (meth) acrylic resins, polyester resins, epoxy resins, silicone resins, and the like. These resins may be used alone or in combination of two or more. Of these resins, (meth) acrylic resins are preferred. In this case, instead of or together with the addition of an antistatic agent or an ultraviolet absorber, an antistatic (meth) acrylic resin or an ultraviolet absorbing (meth) acrylic resin is used. Anyway.

[0031] The thickness of the thin layer (when there are a plurality of thin layers, the thickness of each thin layer) is preferably 100 zm or less, more preferably 50 μm or less. If the thickness of the thin layer exceeds 100 μm, unintentional warping due to differences in thermal shrinkage and water absorption will occur if a material different from the thermoplastic resin sheet is used. The thickness of the thin layer is determined by slicing any 10 points on the thermoplastic resin sheet on which the thin layer is formed to a thickness of 15 / im with a microtome, and observing the cross section with a microscope to obtain the thickness of the thin layer. And measure the average value of the 10 points.

[0032] The thin layer may contain, for example, additives such as a stabilizer, an antioxidant, a plasticizer, and a dispersant. The blending amount of these additives may be appropriately adjusted according to the type thereof, and is not particularly limited.

[0033] The thickness of the thermoplastic resin sheet (thickness including the thin layer when a thin layer is formed) is preferably 0.5 mm or more and 15 mm or less, more preferably 1 mm or more and 10 mm or less. If the thickness is less than 0.5 mm, the mechanical strength of the thermoplastic resin sheet may decrease. On the other hand, if the thickness exceeds 15 mm, it becomes difficult to extrude the thermoplastic resin sheet, and the quality of the sheet may deteriorate.

[0034] When the thermoplastic resin sheet is used as a light diffusing plate, for example, the above-described thermoplastic resin, transparent fine particles, and if necessary, a fluorescent whitening agent and an antioxidant, In this case, the thermoplastic resin sheet preferably has a haze of preferably 70% or more, more preferably 80% or more, still more preferably 90% or more, and / or. Total light transmittance is preferably 40% or more, more preferably 50% or more, and Preferably it is 60% or more. The haze and total light transmittance are values measured by a measuring method based on JIS K7105. Further, it is preferable that the fine particles contained in the thermoplastic resin sheet are substantially uniformly dispersed in order to uniformly and satisfactorily diffuse light having a light source power.

[0035] Examples of the material of the fine particles include (meth) acrylic resins, styrene resins, polyurethane resins, polyester resins, silicone resins, fluorine resins, and synthetic resins such as copolymers thereof; glass And clay compounds such as smectite and kaolinite; inorganic oxides such as silica and alumina; and the like. Of these materials, silicone resins and silica are particularly suitable.

[0036] The fine particles may be formed of a single material or may be formed of two or more types of materials, and may be formed of two or more types of different materials even if they are composed of the same type of fine particle force. It may be composed of the fine particles above.

[0037] Examples of the shape of the fine particles include a spherical shape, a flat shape, an ellipsoidal shape, a polygonal shape, and a plate shape. The fine particles having these shapes may be used alone or in combination of two or more. Among the fine particles having these shapes, spherical particles are preferred, but they have a light diffusibility stronger than spherical particles, and high luminance can be obtained with a small amount of addition, so that they are flat, elliptical, In some cases, irregularly shaped particles such as polygonal shapes and plate shapes are suitable.

[0038] The average particle size of the fine particles is preferably 0.1 / im or more and 30 / im or less, more preferably 0.

5 / im or higher and 25 / im or lower, more preferably 1 / im or higher and 20 / im or lower. If the average particle diameter is less than 0. μμ ΐη, the light incident on the thermoplastic resin sheet may not be sufficiently diffused. On the other hand, when the average particle size exceeds 30 / m, the amount of light passing through the thermoplastic resin sheet decreases, and the luminance may decrease. The average particle size of the fine particles is a value obtained by simply averaging the particle sizes of 100 arbitrary fine particles observed with a microscope. When the fine particles are irregularly shaped particles, the average of the maximum diameter and the minimum diameter is taken as the particle diameter.

[0039] The amount of the fine particles used is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 0.2 parts by mass or more and 10 parts by mass with respect to 100 parts by mass of the thermoplastic resin constituting the sheet. It is as follows. If the amount used is less than 0.1 parts by mass, the light incident on the thermoplastic resin sheet is filled. May not be spread over minutes. On the other hand, if the amount used exceeds 20 parts by mass, extrusion molding of the thermoplastic resin sheet may become difficult, or the amount of light passing through the thermoplastic resin sheet may be reduced, resulting in lower brightness.

[0040] A polycarbonate resin particularly suitable as a thermoplastic resin constituting the sheet can be obtained, for example, by reacting a divalent phenol and a carbonate precursor by an interfacial polycondensation method or a melting method.

[0041] Examples of the divalent phenol include 2,2_bis (4-hydroxyphenyl) propane [commonly known as bisphenol A], 1,1-bis (4-hydroxyphenol) ethane, 1, 1 —Bis (4-hydroxyphenyl) cyclohexane, 2,2_bis (3-methyl_4-hydroxyphenyl) propane, 2,2_bis (3,5-dimethyl_4-hydroxyphenyl) propane, bis ( 4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, and the like. These divalent phenols may be used alone or in combination of two or more. Of these divalent phenols, bisphenol A is particularly preferred.

[0042] Examples of the carbonate precursor include carbonyl halide, carbonate ester, and haloformate. Specifically, for example, phosgene, diphenyl carbonate, or dihaloformate of divalent phenol is used.

[0043] When a polycarbonate resin is produced by reacting the divalent phenol and the carbonate precursor as described above by an interfacial polycondensation method or a melting method, a catalyst, a terminal terminator, a divalent agent, and the like may be used as necessary. A phenol antioxidant or the like may be used.

[0044] Further, the polycarbonate resin is a branched polycarbonate resin obtained by copolymerizing a polyfunctional aromatic compound having three or more functional groups, but is copolymerized with an aromatic or aliphatic bifunctional carboxylic acid. It may be a polyester carbonate resin or a mixture of two or more of the obtained polycarbonate resins.

[0045] The molecular weight of the polycarbonate-based resin is preferably from 15,000 to 40,000, more preferably from 18,000 to 35,000, expressed as a viscosity average molecular weight. The viscosity average molecular weight is a value obtained by inserting the specific viscosity (ηsp) obtained from a solution obtained by dissolving 0.7 g of a polycarbonate-based resin at 20 ° C. in 10 mL of methylene chloride.

r] [? 7] + 0. 45 X [7]] ² c [77] = 1 · 23 Χ 10 " ⁴ Μ ° · ⁸³

(However, c = 0.7, [77] is intrinsic viscosity, M is viscosity average molecular weight)

[0046] For the polycarbonate resin, if necessary, for example, heat stabilizers such as phosphorous acid, phosphoric acid, phosphorous acid ester, phosphoric acid ester, phosphonic acid ester; triazole-based, acetophenone-based, salicylic acid UV absorbers such as esters; anionic, cationic, amphoteric and nonionic surfactants and antistatic agents such as conductive resins; bluing agents such as anthraquinone dyes; tetrabromobisphenol Additives such as Nole A, low molecular weight polycarbonate of tetrabromobisphenol A, flame retardants such as deca-buffed di-diethylene ether, flame retardants such as antimony trioxide, etc. May be combined.

[0047] As described above, the production method of the present invention was controlled in accordance with the height, shape, and temperature of the warpage control roll on the extruded sheet when the thermoplastic resin sheet was extruded. It is a way to give warpage.

[0048] The extrusion molding conditions in the production method of the present invention, such as the amount discharged from the die, the temperature and interval of the cooling roll, the take-up speed of the take-up roll, etc. are substantially the same as in the case of producing a flat thermoplastic resin sheet. However, it is not particularly limited if similar conditions are set. However, by adjusting the discharge rate from the die and / or using heating means such as various heaters, the temperature of the sheet at the position of the warpage control roll is such that the glass transition temperature (Tg of the thermoplastic resin constituting the sheet) ), Preferably within the range of (Tg ± 20 ° C). In general, the position at which the temperature of the extruded sheet is near the glass transition temperature (Tg) of the thermoplastic resin constituting the sheet increases the discharge amount from the die in the flow direction of the extrusion. In contrast, if the discharge amount from the die is reduced, it moves to the upstream side in the flow direction of extrusion molding.

[0049] Fig. 1 schematically shows the configuration of a typical sheet extruder used in the production method of the present invention.

This sheet extruder 10 is an ordinary sheet extruder comprising an extrusion device (not shown), a die 11, a first cooling roll 12, a second cooling roll 13, a third cooling roll 14, a guide roll 15, and a take-up roll 16. In addition, a pair of upper and lower warpage control rolls 17 are arranged between the third cooling roll 14 and the guide roll 15. The warpage control roll 17 is Or you can move down and adjust its height.

In manufacturing a thermoplastic resin sheet using the sheet extruder shown in FIG. 1, in addition to the movement of the warpage control tool 17, in order to adjust the temperature difference between the upper and lower surfaces of the sheet, for example, warpage Between the control roll 17 and the guide roll 15, preferably warped in the flow direction of extrusion, immediately downstream of the control roll 17, heating means for heating the sheet, cooling means for cooling the sheet, necessary Depending on the situation, it may be necessary to arrange heat insulation means to keep the sheet warm. In order to set the upper surface of the sheet to the high temperature side and the lower surface of the sheet to the low temperature side, a heating means and a heat retaining means are arranged on the upper side of the sheet and / or a cooling means on the lower side of the sheet, respectively. Or, to make the upper surface side of the sheet a low temperature side and the lower surface of the sheet a high temperature side, a cooling means is arranged on the upper side of the sheet, and a heating means is necessary on the lower side of Z or the sheet. Depending on the condition, a heat retaining means is arranged. Examples of the heating means include an electric heater, an infrared heater, and a hot air blower. Examples of the cooling means include a blower and a cold air blower. Examples of the heat keeping means include a heat insulation cover. Any force is not particularly limited.

[0051] The process of producing the thermoplastic resin sheet of the present invention using the sheet extruder 10 shown in Fig. 1 will be described below. First, the thermoplastic resin constituting the sheet and, if necessary, various additives are supplied to an extrusion device (not shown), kneaded sufficiently, and then formed into a molten sheet form from the die 11. Extrude. The extruded sheet is introduced between the first cooling roll 12 and the second cooling roll 13 to advance on the peripheral surface of the second cooling roll 13, and then the second cooling roll 13 and the third cooling roll Introduced between the roll 14 and advanced on the circumferential surface of the third cooling roll 14, separated from the third cooling roll 14 at the position of the peeling line 18, and between the upper and lower one set of warpage control rolls 17. After passing, it passes through the guide roll 15 and is taken up by the take-up roll 16.

At this time, the position of the warp control roll 17 is such that the temperature of the extruded sheet is near the glass transition temperature (Tg) of the thermoplastic resin constituting the sheet, preferably within the range of (Tg ± 20.C). By selecting the shape of the warpage control roll 17 at this position and / or by placing the warpage control roll 17 above or below the height at which a flat sheet can be obtained. The mechanically controlled warpage is given to the thermoplastic resin sheet 20.

In order to give a warp controlled according to the shape of the warp control roll 17, the warp control roll 17 For example, if a roll having a shape such as crowning, reverse crowning, or arcuate shape is used, upward or downward warping is given along the lateral direction. In this case, the amount of warpage can be controlled in accordance with the amount of bow of the warpage control roll 17.

[0054] Further, in order to give a warp controlled according to the height of the warp control roll 17, for example, as shown in FIG. On the contrary, as shown in FIG. 3, if the warp control roll 17 is arranged on the lower side, the warp is given downward along the vertical direction. In this case, the amount of warpage can be controlled according to the height of the warpage control roll 17 (movement distance from the height at which a flat sheet is obtained). Specifically, for example, if the warpage control roll 17 is arranged within the range of about 100 mm or less on the upper or lower side with respect to the height at which a flat sheet can be obtained, the range is about 10 Omm or less, respectively. Warping is given upward or downward inside.

[0055] Further, by controlling the temperature of the warp control roll 17 up and down to make a difference in the cooling rate of the upper and lower surfaces of the sheet, it is possible to give a thermally controlled warp. In this case, the magnitude of the warp can be controlled according to the temperature difference between the upper warp control roll 17 and the lower warp control roll 17.

[0056] The glass transition temperature (Tg) of the thermoplastic resin constituting the sheet may be measured in advance by DSC (differential scanning calorimetry). Further, since the surface temperature and the back surface temperature of the sheet at the position of the warpage control roll are substantially the same, the temperature of the extruded sheet means the surface temperature of the sheet and can be measured with a radiation thermometer.

[0057] The thermoplastic resin sheet thus obtained has a warpage controlled according to the height, shape, and temperature of a pair of upper and lower warpage control tools used for extrusion formation. According to the production method of the present invention, a thermoplastic resin sheet having a controlled warpage can be produced efficiently and simply without providing a hot molding step separately from the extrusion molding step. It is beneficial to.

[0058] << Thermoplastic resin sheet >>

The thermoplastic resin sheet of the present invention is a thermoplastic resin sheet produced by the method as described above. For example, in a backlight unit such as a liquid crystal display device or a medical monitor. It can be used as a light diffusing plate and building materials, but it can stabilize the display performance of liquid crystal display devices over a long period of time, so in particular, liquid crystal televisions exceeding 15 inches and desktop personal computers. It is suitably used as a light diffusing plate of a backlight unit in a large liquid crystal display device used in such a liquid crystal display. Example

[0059] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and is appropriately within a range that can meet the gist of the preceding and following descriptions. It is also possible to carry out with modifications, and they are all included in the technical scope of the present invention.

[0060] First, a method for measuring the glass transition temperature (Tg) of the thermoplastic resin constituting the sheet, the temperature of the sheet, and the amount of warpage will be described.

[0061] <Glass transition temperature (Tg)>

The glass transition temperature (Tg) of the thermoplastic resin was measured according to JIS K 7121 using a differential scanning calorimeter (trade name: Thermo PI us DSC8230, manufactured by Rigaku Corporation). Specifically, the sample is set on a differential scanning calorimeter, held at 180 ° C for 10 minutes, then rapidly cooled to 80 ° C, and when stabilized, at a speed of 20 ° CZ up to 180 ° C. The temperature was raised, and the obtained DSC curve force glass transition temperature (Tg) was determined.

[0062] <Sheet temperature>

The temperature of the extruded sheet was measured using a radiation thermometer (trade name: IR_TAF, manufactured by Chinoichi Co., Ltd.). Since the surface temperature and the back surface temperature of the sheet at the position of the warpage control roll are substantially the same, the surface temperature of the sheet was taken as the sheet temperature.

[0063] <Size of warpage>

The size of warpage is vertical 1, OOOmm X horizontal 1, OOOmm thermoplastic resin sheet, a hole is made at a position where one side of the horizontal direction is divided into three equal parts near the end, and the sheet is suspended through the string. In this state, a thread was stretched at the center of the opposite sides of the sheet in the longitudinal and lateral directions, and the distance from the center of the sheet to the thread was measured with a steel ruler. In addition, the case where the warp is convex upward is indicated by +, and the case where the warp is downward convex is indicated by 1.

[0064] << Reference Example >> Sheet extruder equipped with a T die with a width of 1,200mm, first, second and third cooling rolls with a diameter of 300mm, a warp control roll with a diameter of 200mm, a guide roll, and a take-up roll (the configuration is shown in Fig. 1) A polycarbonate resin sheet was produced in the following manner using a sheet extruder.

[0065] A T-die lip with a screw diameter of 120mm is attached to the sheet extruder as described above, and a polycarbonate resin (trade name: 302-6, manufactured by Sumitomo Dow Co., Ltd .; glass transition temperature (Tg) is used as the thermoplastic resin. : 153 ° C), continuously extruded at a temperature of about 280 ° C and a width of 1,100mm, rolled with the first cooling roll and the second cooling roll (double-sided touch method), and cooled while being cooled to polycarbonate For example, as shown in Fig. 1, one set of upper and lower warpage control rolls 17 (upper and lower roll temperature: 95 ° C) is applied so that the sheet is flat from the peeling line 18 to the guide roller 15. It was placed and taken up by the take-up roll 16, and a flat polycarbonate resin sheet 20 was obtained. The sheet temperature at the position of the warpage control roll was (Tg + 5 ° C.). Both ends in the width direction of the obtained sheet were side-trimmed by 50 mm to obtain a width of 1,000 mm and cross-cut to a length of 1,000 mm to obtain a polycarbonate resin sheet having a thickness of 2 mm. Table 1 shows the results of measuring the warpage of the obtained sheet.

[0066] <Example 1>

For example, as shown in Fig. 2, one set of upper and lower warpage control rolls 17 (upper and lower roll temperature: 95 ° C) was placed from the peeling line 18 to the guide roll 15 so that the sheet is convex upward. More specifically, a polycarbonate resin sheet was obtained in the same manner as in the reference example, except that the height of the warpage control roll was moved 2 cm upward with respect to the height at which a flat sheet was obtained. . Table 1 shows the results of measuring the warpage of the obtained sheet.

[0067] <Example 2>

For example, as shown in FIG. 2, a warp control roll 17 (upper and lower roll temperature: 95 ° C.) is arranged from the peeling line 18 to the guide roll 15 so that the sheet is convex upward, and the upper side A reverse crown-shaped roll was used as the warp control roll, and a crown-shaped roll was used as the lower warp control roll, more specifically, one set of upper and lower warp control rolls each having a crowning amount of 2 cm. The polycarbonate tree is the same as the reference example, except that the height is moved 2 cm upward from the height at which a flat sheet is obtained. A fat sheet was obtained. The sheet temperature at the position of the warpage control roll was (Tg-10 ° C). Table 1 shows the results of measuring the warpage of the obtained sheet.

[Example 3]

For example, as shown in Fig. 3, one set of upper and lower warpage control rolls 17 (upper and lower roll temperature: 95 ° C) was arranged from the peeling line 18 to the guide roll 15 so that the sheet is convex downward. More specifically, a polycarbonate resin sheet was obtained in the same manner as in the reference example, except that the height of the warp control roll was moved 4 cm downward from the height at which a flat sheet was obtained. It was. The sheet temperature at the position of the warpage control roll was (Tg-5 ° C.). Table 1 shows the results of measuring the warpage of the obtained sheet.

[0069] Example 4 »

For example, as shown in Fig. 3, one set of upper and lower warpage control rolls 17 is arranged from the peeling line 18 to the guide roll 15 so that the sheet is convex downward, and the upper and lower warpage control rolls are Adjusting the temperature difference, more specifically, the height of the warpage control roll (upper roll temperature: 100 ° C, lower roll temperature: 80 ° C) is based on the height at which a flat sheet can be obtained. A polycarbonate resin sheet was obtained in the same manner as in the Reference Example, except that it was moved 4 cm to the side. The sheet temperature at the position of the warpage control roll was (Tg + 10 ° C.). Table 1 shows the results of measuring the warpage of the obtained sheet.

[0070] Example 5

Polystyrene resin (trade name: HH203, manufactured by PS Japan Co., Ltd.); glass transition temperature (Tg): 108 ° C) as the thermoplastic resin, molding temperature of about 220 ° C, temperature of warpage control roll 17 A polystyrene resin sheet was obtained in the same manner as in Example 1, except that the temperature was set to 60 ° C. Table 1 shows the results of measuring the warpage of the obtained sheet.

[Example 6]

Methacrylic resin (trade name: Sumipex EX, manufactured by Sumitomo Chemical Co., Ltd .; glass transition temperature (Tg): 97 ° C) is used as the thermoplastic resin, the molding temperature is about 250 ° C, and the temperature of warpage control roll 17 A methacrylic resin sheet was obtained in the same manner as in Example 1 except that the temperature was set to 80 ° C. Table 1 shows the results of measuring the warpage of the obtained sheet.

[Example 7] Polycarbonate resin (trade name: Iupilon E2000FN, manufactured by Mitsubishi Engineering Plastics Co., Ltd .; glass transition temperature (Tg): 154 ° C) is used as the thermoplastic resin, and 100% by mass of this polycarbonate resin is used as fine particles. Silica spherical fine particles (trade name: Seahoster KE_P150, manufactured by Nippon Shokubai Co., Ltd .; average particle size: 1. 33-1. 83 zm) ¾r0.5 Similar to Example 1 except that 5 mass% was mixed, A polycarbonate resin sheet was obtained. Table 1 shows the results of measuring the warpage of the obtained sheet.

[0073] << Comparative example:! ~ 3 »

Except that the temperature of the sheet at the position of the warpage control roll was set to (Tg + 30 ° C.), polycarbonate resin sheets were obtained in the same manner as in Examples 1 to 3, respectively. Table 1 shows the results of measuring the warpage of the obtained sheet.

[0074] << Comparative Examples 4 to 6 »

Except that the temperature of the sheet at the position of the warp control roll was set to (Tg_30 ° C), polycarbonate resin sheets were obtained in the same manner as in Examples 1 to 3, respectively. Table 1 shows the results of measuring the warpage of the obtained sheet.

[0075] [Table 1]

1) Tg is the glass transition temperature (153 ° C) of polycarbonate resin.

2) The longitudinal direction is the flow direction of extrusion molding.

3) The horizontal direction is the width direction of extrusion.

[0076] As is clear from Table 1, the warpage control roll is flattened at a position where the temperature of the extruded sheet is in the range of (Tg—20 ° C) or more and (Tg + 20 ° C) or less. The thermoplastic resin sheets of Examples 1 to 7 arranged on the upper side or the lower side from the height at which the sheet is obtained have a flat warp control roll at a position where the temperature of the extruded sheet is (Tg + 5 ° C). Compared to the thermoplastic sheet of the reference example placed at such a height that a simple sheet can be obtained, the mechanically controlled warpage is clearly given. More specifically, the thermoplastic resin sheets of Examples 1, 3, 5, 6 and 7 using a warpage control roll having a flat shape are each given an upward or downward warpage along the longitudinal direction. The magnitude of the warpage is controlled according to the movement distance of the warpage control roll. Further, the thermoplastic resin sheet of Example 2 using a roll having a shape selected as a warp control roll is given the same degree of warpage along the vertical and horizontal directions, and the magnitude of the warpage is It is controlled according to the movement distance of the warpage control roll and the amount of crowning. Furthermore, the thermoplastic resin sheet of Example 4 in which the temperature of the warpage control roll was adjusted up and down to produce a difference in the cooling rate of the upper and lower surfaces of the sheet gave a greater warpage along the vertical and horizontal directions. It has been.

[0077] On the other hand, Comparative Examples 1 to 6 in which the warp control roll is arranged on the upper side or the lower side from the height at which a flat sheet is obtained at a position where the temperature of the extruded sheet is (Tg ± 30 ° C). Since the temperature of the extruded sheet is too low or too high, the thermoplastic resin sheet of this type has a flat sheet for the warpage control roll at a position where the temperature of the extruded sheet is (Tg + 5 ° C). Similar to the thermoplastic resin sheet of the reference example arranged at a height at which the dent is obtained, no mechanically controlled warpage is given.

[0078] From the above results, when extruding a thermoplastic resin sheet, it is preferable that the temperature of the extruded sheet is in the vicinity of the glass transition temperature (Tg) of the thermoplastic resin constituting the sheet, preferably ( The ability to give mechanically controlled warpage to the sheet at a position within the range of (Tg ± 20 ° C), preferably controlled warpage according to the height, shape and temperature of the warpage control roll. S

Industrial applicability

[0079] The present invention can provide a thermoplastic resin sheet having a controlled warpage efficiently and simply, and such a thermoplastic resin sheet can be used, for example, for a liquid crystal display device or a medical monitor. It makes a great contribution in a wide range of fields by using it as a light diffuser plate used in backlight units and other building materials.

Claims

The scope of the claims

[1] When extruding a thermoplastic resin sheet, the extruded sheet is mechanically controlled at a position where the temperature of the extruded sheet is close to the glass transition temperature (Tg) of the thermoplastic resin constituting the sheet. A method for producing a thermoplastic resin sheet having a controlled warpage, characterized by providing a warped surface.

[2] A flat sheet can be obtained by allowing the sheet to pass between a pair of upper and lower warp control rolls at the position and selecting the shape of the warp control roll and / or the warp control roll. 2. The manufacturing method according to claim 1, wherein a mechanically controlled warp is given to the sheet by arranging the sheet at an upper side or a lower side from a height.

[3] The manufacturing method according to claim 2, wherein the temperature of the sheet at the position of the warpage control roll is within a range of (Tg ± 20 ° C.).

[4] The manufacturing according to claim 2, wherein the sheet is further thermally controlled by adjusting the temperature of the warpage control roll up and down to cause a difference in the cooling rate of the upper and lower surfaces of the sheet. Method.

[5] The sheet is further thermally controlled by adjusting the temperature difference between the upper and lower surfaces of the sheet at or near the position of the warpage control roll to cause a difference in the cooling rate of the upper and lower surfaces of the sheet. The manufacturing method of Claim 2 which gives a curvature.

6. The production method according to claim 1, wherein the thermoplastic resin constituting the sheet contains fine particles.

7. The production according to claim 1, wherein the thermoplastic resin constituting the sheet is selected from the group consisting of a polycarbonate resin, a (meth) acrylic resin, a styrene resin, an acrylic monostyrene resin, and a norbornene resin. Method.

[8] A thermoplastic resin sheet having a controlled warpage, which is obtained by the production method according to any one of [1] to [7].