Manufacturing method of plate-shaped molded product

Abstract

To provide a method for manufacturing a plate-shaped molding which is reduced in poor appearance and warpage and has a fine protruding part on at least one main surface.SOLUTION: There is provided a method for manufacturing a plate-shaped molding, wherein a plate-shaped molding contains a methacrylic resin composition having a glass transition temperature (Tg) of 115-150°C and tensile fracture strain of 1.5% or more, one main surface (first main surface) of the plate-shaped molding has a plurality of fine protruding shapes, the other main surface (second main surface) is a flat surface, a height a of the protruding shape is 0.5-600 μm, and a ratio b / a of a pitch b of the protruding shape to the height a of the protruding shape is 0.1-1.0. The method includes injection molding using a first mold on the side where the first main surface is formed, and a second mold on the side where the second main surface is formed, wherein when a highest temperature of the first mold is represented by Tmax1 and a lowest temperature of the first mold is represented by Tmin1, (1) a temperature of the second mold is set at (Tmax1-65) °C to (Tmax1-50) °C, or (2) when a highest temperature Tmax2 of the second mold is set at (Tmax1-30) °C to (Tmax1-5) °C, and a lowest temperature Tmin2 of the second mold is set at (Tmin1+10) °C to (Tmin1+30) °C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a plate-shaped molded product having fine convex shapes on one main surface. [Background technology]

[0002] Conventionally, injection molding methods for producing injection-molded products with fine irregularities involve heating the entire surface of the mold cavity in contact with the molded product to a preset temperature above the softening temperature of the resin, maintaining this preset temperature throughout the injection process, and then completing the heating and cooling the mold when the process switches to the cooling process. In such injection molding methods, heating the mold cavity surface to a preset temperature above the softening temperature of the resin before the injection process reduces residual stress, making it possible to resolve molding defects such as deformation, cracks, and worsening birefringence (see, for example, Patent Documents 1 to 5). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-80940 [Patent Document 2] Japanese Patent Application Publication No. 10-80938 [Patent Document 3] Japanese Patent Application Publication No. 11-58476 [Patent Document 4] Japanese Patent Application Publication No. 63-95919 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-264703 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a mold having a mechanism for heating and cooling only the micro-shape forming surface of the mold is used, a temperature difference occurs between the forming surface side and the opposing flat side, which often causes warping of the molded product during the cooling process. In particular, when the molded product is used for optical purposes, there is a problem in that the shape and warping of the molded product adversely affect the optical properties.

[0005] Patent Document 5, cited above, reports a method for controlling warpage of a molded product by controlling the temperature of each heating control zone, maintaining a temperature that eliminates weld lines, a defect in the molded product's appearance, while simultaneously promoting or suppressing shrinkage depending on the resin's shrinkage state. When using a mold in which the cavity surface is heated to above its deflection temperature under load using a heat transfer heater wire near the cavity surface and then cooled with water, this method simultaneously controls warpage of the molded product. However, when the height of the uneven portion increases, the resin sticks to the mold, making demolding difficult. This makes it difficult to obtain a molded product with a stable transfer rate of the uneven portion and a stable warpage state. Furthermore, when using low-strength resin materials, molding problems frequently occur, such as product cracking and residual resin remaining in the mold upon demolding.

[0006] The present invention has been made in consideration of the above problems, and aims to provide a method for producing a plate-shaped molded product having a fine convex shape on one main surface, which reduces appearance defects and warpage. [Means for solving the problem]

[0007] The inventors have investigated a manufacturing method using injection molding that does not result in poor appearance or warping, and have discovered that the above-mentioned problems can be solved by controlling the surface temperatures of the fine convex shape forming surface side and the opposing flat surface side of the mold during injection molding within an appropriate temperature range, thereby completing the present invention.

[0008] That is, the present invention is as follows. [1] A method for manufacturing a plate-shaped molded product, The plate-shaped molded product contains a methacrylic resin composition having a glass transition temperature Tg of 115 to 150°C and a tensile strain at break of 1.5% or more, One main surface (first main surface) of the plate-like molded product has a plurality of fine convex shapes, and the other main surface (second main surface) is flat, a height a of the convex shapes is 0.5 to 600 μm, and a ratio b / a of a pitch b of the convex shapes to the height a of the convex shapes is 0.1 to 1.0; A method for producing a plate-like molded product, comprising injection molding using a first mold on the side that forms the first main surface and a second mold on the side that forms the second main surface, characterized in that when the maximum temperature of the first mold is Tmax1, the temperature of the second mold is set to (Tmax1-65)°C to (Tmax1-50)°C. [2] A method for manufacturing a plate-shaped molded product, The plate-shaped molded product contains a methacrylic resin composition having a glass transition temperature Tg of 115 to 150°C and a tensile strain at break of 1.5% or more, One main surface (first main surface) of the plate-like molded product has a plurality of fine convex shapes, and the other main surface (second main surface) is flat, a height a of the convex shapes is 0.5 to 600 μm, and a ratio b / a of a pitch b of the convex shapes to the height a of the convex shapes is 0.1 to 1.0; A method for producing a plate-like molded product, comprising injection molding using a first mold on the side that forms the first main surface and a second mold on the side that forms the second main surface, characterized in that, when the maximum temperature of the first mold is Tmax1, the maximum temperature of the second mold, Tmax2, is set to (Tmax1-30)°C to (Tmax1-5)°C, and when the minimum temperature of the first mold is Tmin1, the minimum temperature of the second mold, Tmin2, is set to (Tmin1+10)°C to (Tmin1+30)°C. [3] The method for producing a plate-like molded product according to [1] or [2], wherein the first mold is heated and then cooled to set the maximum temperature Tmax1 of the first mold to (Tg + 15) ° C to (Tg + 40) ° C and the minimum temperature Tmin1 of the first mold to (Tg - 75) ° C to (Tg - 45) ° C. [4] The melt viscosity of the methacrylic resin composition is 270°C, 1000 sec -1The method for producing a plate-shaped molded product according to any one of [1] to [3], wherein the viscosity is 20 to 235 Pa·sec. [5] The method for producing a plate-like molded product according to any one of [1] to [4], wherein when the first mold is heated and then cooled, the rate of surface temperature increase of the first mold is 1 to 10°C / sec and the rate of temperature decrease is 0.5 to 10°C / sec. [Effects of the Invention]

[0009] According to the present invention, it is possible to produce a plate-shaped molded product having fine convex shapes on one main surface thereof, with reduced appearance defects and warpage. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams showing an example of a plate-shaped molded product of the present embodiment, in which (A) is a top view when the main surface having a convex shape is the upper surface, and (B) is a side view. [Figure 2] FIG. 2 is a partial cross-sectional view showing the convex shape (triangular pyramid shape) of the plate-shaped molded product shown in FIG. [Figure 3] 1A and 1B are diagrams showing another example of a plate-shaped molded product of this embodiment, in which (A) is a top view with the main surface having a convex shape facing up, (B) is a side view, and (C) is a perspective view of the convex-shaped portion. [Figure 4] FIG. 4 is a partial cross-sectional view showing the convex shape (quadratic pyramid trapezoid) of the plate-shaped molded product shown in FIG. [Figure 5] FIG. 1 is a diagram showing the optical path when the plate-shaped molded products obtained in the examples and comparative examples are used as light direction conversion elements. [Figure 6] FIG. 1 is a layout diagram of the equipment used to evaluate the characteristics of the plate-shaped molded products obtained in the examples and comparative examples when used as light direction conversion elements. [Figure 7] FIG. 7 is a plan view of USAF Target 7 used in FIG. 6 as viewed from the X-axis direction. DETAILED DESCRIPTION OF THE INVENTION

[0011] Below, we will explain in detail the form for implementing the present invention (hereinafter referred to as the ``present embodiment''), but the present invention is not limited to the following description and can be implemented in various modifications within the scope of the paper.

[0012] (Method of manufacturing plate-shaped molded products) The method for producing a plate-shaped molded product of this embodiment is a method for producing a plate-shaped molded product (hereinafter simply referred to as a "molded product") described below, and includes injection molding using a first mold on the side that forms the first main surface of the plate-shaped molded product (a main surface having a plurality of fine convex shapes) and a second mold on the side that forms the second main surface of the plate-shaped molded product (a main surface that is a flat surface), and is characterized in that when the maximum temperature of the first mold is Tmax1, the temperature of the second mold is set to (Tmax1-65)°C to (Tmax1-50)°C. The detailed conditions for injection molding in the method for producing a plate-shaped molded product of this embodiment will be described below.

[0013] In this embodiment, the temperature setting from the nozzle tip to the center of the injection molding machine cylinder is set to a temperature 120 to 180°C higher than the glass transition temperature (Tg) of the methacrylic resin composition used, thereby allowing the molten resin to flow sufficiently and enabling molding in a state where deterioration due to thermal decomposition of the resin is suppressed. Thermal decomposition of the resin not only adversely affects color tone, transmittance, and haze, but also generates gas during injection molding. This gas fills the mold, and the gas is forced into uneven areas during resin filling, preventing it from being discharged. This inhibits resin filling and reduces the mold transfer rate. A more preferred temperature is 130 to 170°C higher than the glass transition temperature (Tg) of the methacrylic resin composition used.

[0014] In a first aspect of this embodiment, when the maximum temperature of the first mold when the resin is injected into the mold is Tmax1, the temperature of the second mold is set to (Tmax1-65)°C to (Tmax1-50)°C. It is preferably (Tmax1-65)°C to (Tmax1-55)°C, and particularly preferably (Tmax1-65)°C to (Tmax1-60)°C. When the temperature of the second mold is (Tmax1-65)°C or higher, the amount of warpage of the molded article tends to be reduced. On the other hand, when the temperature is (Tmax1-50)°C or lower, deterioration of the flatness of the second main surface of the molded article due to effects such as thermal shrinkage of the resin and sticking to the mold is suppressed, making it possible to obtain a plate-shaped molded article with a good appearance.

[0015] In the first aspect of this embodiment, it is preferable to heat the first mold and then cool it. To improve the transferability (moldability) of fine convex shapes, the maximum temperature Tmax1 of the first mold during heating is preferably controlled within the temperature range of (Tg + 15)°C to (Tg + 40)°C, more preferably (Tg + 15)°C to (Tg + 35)°C, and even more preferably (Tg + 20)°C to (Tg + 35)°C. Setting the temperature above (Tg + 40)°C does not affect the transferability, but tends to have an adverse effect on the mold releasability. Furthermore, if the temperature is below (Tg + 15)°C, the transferability tends to decrease. The minimum temperature Tmin1 of the first mold during cooling is preferably controlled within a temperature range of (Tg-75)°C to (Tg-45)°C, more preferably (Tg-70)°C to (Tg-50)°C, and even more preferably (Tg-65)°C to (Tg-55)°C. If Tmin1 is lowered to a temperature below (Tg-75)°C, the cycle time will be longer. On the other hand, if it exceeds (Tg-45)°C, the amount of warpage of the molded product will tend to increase.

[0016] In a second aspect of this embodiment, when the maximum temperature of the first mold when the resin is injected into the mold is Tmax1, the maximum temperature of the second mold, Tmax2, is set to (Tmax1-30)°C to (Tmax1-5)°C. It is preferably (Tmax1-30)°C to (Tmax1-10)°C, and particularly preferably (Tmax1-30)°C to (Tmax1-20)°C. When the maximum temperature of the second mold, Tmax2, is (Tmax1-30)°C or higher, the amount of warpage of the molded article tends to be reduced. On the other hand, when it is (Tmax1-5)°C or lower, deterioration of the flatness of the second main surface of the molded article due to effects such as thermal shrinkage of the resin and sticking to the mold is suppressed, making it possible to obtain a plate-shaped molded article with a good appearance. Furthermore, when the minimum temperature of the first mold is Tmin1, the minimum temperature of the second mold, Tmin2, is set to (Tmin1 + 10)°C to (Tmin1 + 30)°C. It is preferably (Tmin1 + 10)°C to (Tmin1 + 20)°C, and more preferably (Tmin1 + 10)°C to (Tmin1 + 15)°C. If the minimum temperature of the second mold, Tmin2, is lowered to a temperature below (Tmin1 + 10), the amount of warpage of the molded article tends to increase. On the other hand, if it exceeds (Tmin1 + 30)°C, the molded article tends to stick, resulting in poor mold releasability.

[0017] By controlling the temperature by heating and cooling the second mold, it is possible to obtain a molded product with reduced warpage.

[0018] In the second aspect of this embodiment, it is preferable to heat the first mold and then cool it. To improve the transferability (moldability) of fine convex shapes, the maximum temperature Tmax1 of the first mold during heating is preferably controlled within the temperature range of (Tg + 15)°C to (Tg + 40)°C, more preferably (Tg + 15)°C to (Tg + 35)°C, and even more preferably (Tg + 20)°C to (Tg + 35)°C. Setting the temperature above (Tg + 40)°C does not affect the transferability, but tends to have an adverse effect on the mold releasability. Furthermore, if the temperature is below (Tg + 15)°C, the transferability tends to decrease. The minimum temperature Tmin1 of the first mold during cooling is preferably controlled within a temperature range of (Tg-75)°C to (Tg-45)°C, more preferably (Tg-70)°C to (Tg-50)°C, and even more preferably (Tg-65)°C to (Tg-55)°C. If Tmin1 is lowered to a temperature below (Tg-75)°C, the cycle time will be longer. On the other hand, if it exceeds (Tg-45)°C, the amount of warpage of the molded product will tend to increase.

[0019] In this embodiment, the method for heating the mold is not particularly limited, and any method may be used. Examples include a method in which a water or oil flow path is provided in the mold and the mold temperature is adjusted to a temperature equal to or higher than the Tg of the methacrylic resin composition using a medium such as water or oil, a method in which a heater is embedded in the mold and the mold is heated, a method in which an electrically conductive layer that can be electrically conducted is provided on the surface of the mold and electricity is passed through to generate heat, a method in which the mold is heated from the outside or inside using an induction heating device, and a method in which the mold is heated from the outside by radiation of far infrared rays using a halogen lamp or a ceramic heater. In this embodiment, the method for cooling the mold is not particularly limited, and any method may be used, such as a method in which water or oil flow paths are provided in the mold and the mold is cooled by a medium such as water or oil.

[0020] In this embodiment, the rate of temperature increase of the surface temperature of the first mold during heating is preferably 1 to 10°C / sec, more preferably 1.5 to 10°C / sec, and even more preferably 2 to 10°C / sec. A faster temperature increase rate is more effective in shortening the cycle time, but it is acceptable to deviate from this range as long as there are no constraints on the cycle time and deterioration of the resin due to heat retention in the cylinder is not a problem. Furthermore, the rate of temperature decrease of the surface temperature of the first mold during cooling is preferably 0.5 to 10°C / sec, more preferably 1 to 10°C / sec, and even more preferably 2 to 10°C / sec. A faster temperature decrease rate is more effective in shortening the cycle time, but maintaining the mold temperature at a high temperature is more effective in improving transferability, as described below. However, a temperature decrease rate outside this range is undesirable because it tends to increase the cycle time and worsen warpage of the molded product. In this embodiment, the temperature control can be adjusted by raising or lowering the temperature at a constant rate, slowing the rate of temperature increase or decrease, or holding the temperature at a predetermined temperature for a certain period of time, depending on the condition of the molded product. To improve the transfer of the convex shape, it is preferable to maintain the temperature at a temperature at which the resin flows (preferably above the glass transition temperature) for a long time. Furthermore, if the temperature is maintained for a short period of time, birefringence will develop due to the formation of a skin layer. Therefore, in order to prevent this, it is preferable to slow down the rate of temperature decrease.

[0021] In this embodiment, the rate of temperature increase of the surface temperature of the second mold during heating is preferably 1 to 10°C / sec, more preferably 1.5 to 10°C / sec, and even more preferably 2 to 10°C / sec. A faster temperature increase rate is more effective in shortening the cycle time, but it is acceptable to deviate from this range as long as there are no constraints on the cycle time and deterioration of the resin due to heat retention in the cylinder is not a problem. Furthermore, the rate of temperature decrease of the surface temperature of the second mold during cooling is preferably 0.5 to 10°C / sec, more preferably 1 to 10°C / sec, and even more preferably 2 to 10°C / sec. A faster temperature decrease rate is more effective in shortening the cycle time, but a temperature decrease rate outside this range is undesirable because it tends to increase the cycle time and worsen warpage of the molded product. In this embodiment, the temperature control can be appropriately set while observing the state of the molded product, such as raising and lowering the temperature at a constant rate, slowing down the rate of temperature increase and decrease, or holding at a predetermined temperature for a certain period of time. If the holding time is too short, birefringence will occur due to the formation of a skin layer, so from the perspective of suppressing this, it is preferable to slow down the rate of temperature decrease.

[0022] The surface of the mold may be subjected to a release treatment as appropriate. A release coating or a release agent applied to the mold surface is preferably used as the release treatment. Baked fluorine-based resins, silicone-based resins, etc. can be used as the release coating. Furthermore, for the release agent applied to the mold, for example, a fluorine-based, silicone-based, or wax-based release agent can be used. In particular, for a spray-type external release agent that is sprayed onto the mold, for example, a fluorine-based release agent that has excellent release properties and forms a monomolecular film that does not affect the transfer of the fine shape of the mold can be used. It is preferable to use a non-curing release agent because of its low residual property on the mold.

[0023] (Plate-shaped molded product) The plate-shaped molded product of this embodiment is manufactured by the method for manufacturing a plate-shaped molded product of this embodiment, and is characterized in that it contains a methacrylic resin composition having a glass transition temperature Tg of 115 to 150°C and a tensile strain at break of 1.5% or more, one main surface (first main surface) having a plurality of fine convex shapes, the other main surface (second main surface) being flat, the height a of the convex shapes on the first main surface being 0.5 to 600 μm, and the ratio b / a of the pitch b of the convex shapes to the height a of the convex shapes being 0.1 to 1.0. The shape of the plate-shaped molded product of this embodiment will be described in detail below.

[0024] In this embodiment, the fine convex shapes formed on the first main surface are not particularly limited, and may be polygonal pyramids such as triangular pyramids, square pyramids, and pentagonal pyramids; curved cones such as cones, elliptical cones, semicones, semi-elliptical cones, and oval cones (cones having a cross section shaped like a pair of parallel straight lines connected by a semicircle); polygonal truncated cones such as triangular truncated cones, square truncated cones, and pentagonal truncated cones; truncated cones, elliptical truncated cones, semiconical truncated cones, semi-elliptical truncated cones, and oval truncated cones (cones having a cross section shaped like a pair of parallel straight lines connected by a semicircle). Examples of such shapes include curved frustums such as triangular prisms, quadrangular prisms (cubes, rectangular parallelepipeds, etc.), polygonal prisms such as pentagonal prisms, curved prisms such as cylinders, elliptical prisms, semicircular prisms, semi-elliptical prisms, and oblong cones (cylinders having a cross section shaped like a pair of parallel straight lines connected by a semicircle), and dome shapes (structures having a hemisphere, quarter sphere, aspherical surface, etc., in which the cross-sectional area when cut axially gradually decreases as one moves axially upward). In the case of polygonal pyramids, polygonal prisms, etc., the corners may be rounded. Furthermore, the side surfaces of the convex shapes may be flat or curved. These convex shapes may be of only one type or a combination of multiple types, but it is preferable that they are of only one type. Fig. 2 is a partial cross-sectional view showing an example of a plate-shaped molded product of this embodiment in which the fine protrusions are triangular pyramids, and Fig. 4 is a partial cross-sectional view showing an example of a plate-shaped molded product of this embodiment in which the fine protrusions are quadrangular pyramids. The convex shapes may be arranged in a linear, curved, dotted, or other pattern. The convex shapes may be arranged over the entire surface of the first main surface, or may be arranged only in a partial area of ​​the first main surface. For example, Fig. 1(A) and Fig. 3(A) are plan views (top views) of an example of a plate-shaped molded product in which convex shapes are arranged only in a partial area of ​​the first main surface, as viewed from the first main surface side.

[0025] In this embodiment, the ratio b / a of the pitch b to the height a of the fine convex shapes is 0.1 to 1.0, preferably 0.2 to 1.0, and more preferably 0.3 to 1.0. When b / a is in the above range, the molded product tends to be able to be cleanly released from the mold while maintaining an extremely good mold transfer rate. b / a is the average value of the height and pitch measured for five or more convex shapes. Therefore, as long as b / a is within the above range, the height and pitch of each convex shape may be changed arbitrarily. The height a of the convex shapes is 0.5 to 600 μm, preferably in the range of 50 to 600 μm, more preferably 200 to 600 μm, and even more preferably 300 to 600 μm. When the height a of the convex shapes is in the above range, warpage of the molded article tends to be effectively reduced by the present invention. The pitch b of the convex shapes is preferably in the range of 100 to 500 μm, more preferably 150 to 350 μm, and even more preferably 180 to 300 μm. When the pitch b of the convex shapes is in the above range, warpage of the molded product tends to be effectively reduced. In this specification, the height of a convex shape refers to the highest value among the heights in the thickness direction of the molded article measured based on a flat portion of the first main surface parallel to the second main surface, and height a is the average value of the heights of five or more convex shapes. For example, as shown in Figure 2, if the convex shape is a cone, it refers to the height to the apex of the cone. If the first main surface does not have a flat portion parallel to the second main surface, the height of the convex shape may be the highest value among the heights in the thickness direction of the convex shape relative to the average thickness of the molded article. In addition, in this specification, the pitch of the convex shapes means the distance between the centers of two adjacent convex shapes when the convex shapes are viewed in a plane (see Figures 2 and 4), and the pitch b is the average value of the pitches measured for five or more convex shapes. The height a and pitch b of the convex shapes can be visually measured from an observation image obtained using an optical microscope, an electron microscope, a digital microscope, or the like, and specifically, can be measured by the method described in the examples below.

[0026] The size of the convex shape in plan view when observing the first main surface from above is preferably 0.1 to 600 μm in diameter, more preferably 0.5 to 500 μm, and even more preferably 1 to 400 μm. If the planar shape of the convex shape is a line pattern, the term refers to the width in the direction perpendicular to the line direction, and if the planar shape is other than a circle, the term refers to the diameter of the circumscribed circle. The diameter of the planar shape of the convex shape can be measured visually from an observation image obtained using an optical microscope, electron microscope, digital microscope, or the like. The size (height and diameter in plan view) of the convex shapes may be the same for all the convex shapes or may be different for all the convex shapes.

[0027] The overall shape of the molded article of this embodiment is not particularly limited as long as it is plate-like or approximately plate-like with a plurality of fine protrusions on one main surface and the other main surface being flat. Examples of shapes (shapes in plan view) when the first main surface having the minute convex shapes is observed from above include polygons such as triangles, squares, rectangles, parallelograms, trapezoids, and pentagons, as well as circles, ellipses, semicircles, semi-ellipses, ovals (shapes formed by connecting both ends of a pair of parallel lines with a semicircle), and rings. In the case of polygons, the corners may be rounded. Furthermore, when the area of ​​the portion of the first main surface having the fine convex shapes is taken as 100%, the area of ​​the flat portion of the second main surface on the back side may be 80% or more, and in consideration of mounting the molded article on various products, part of the second main surface may have an uneven portion for connection to the product. The shape of the uneven portion for connection is not particularly limited, and for example, an uneven portion for connection 2 to 10 mm in size and 2 to 10 mm in height can be provided near the outer periphery of the molded article for fixing to the product. Furthermore, from the viewpoint of demolding during molding, a frame for ejection by an ejector pin may be provided on the outer periphery of the molded product.

[0028] In this embodiment, the thickness of the molded article, excluding the fine convex shapes, is preferably 1.5 mm or more and less than 6 mm, more preferably 2 mm or more and less than 5 mm, and even more preferably 2 mm or more and less than 4 mm. The thinner the thickness, the more difficult it is to control warpage. On the other hand, the thicker the thickness, the more advantageous it is for warpage control, but the longer it takes to cool during molding, the greater the temperature difference between the surface and the interior, causing the center to sink and impairing the flatness of the plane, which may adversely affect the optical properties of the molded article. The size of each main surface of the molded article is not particularly limited and may be set according to the purpose.

[0029] The packing degree of the plate-shaped molded article of this embodiment is preferably 0.92 or more, more preferably 0.95 or more, and even more preferably 0.99 or more. When the packing degree is 0.92 or more, it can be said that the molded article has well-formed convex shapes. The filling degree is a value calculated from the height a of the convex shape and the depth of the concave shape in the first mold for forming the convex shape by the following formula, and is the average value at four locations. Specifically, it can be measured by the method described in the Examples below. (Filling degree) = (height of the convex shape of the molded product a) / (depth of the concave shape of the mold)

[0030] When the plate-shaped molded product of this embodiment has a shape in which no irregularities are formed on the second main surface as shown in Fig. 1, the amount of warpage is preferably 0.4 mm or less, more preferably 0.35 mm or less, and even more preferably 0.3 mm or less. When the amount of warpage is 0.4 mm or less, the molded product can be said to have good dimensional accuracy. Furthermore, the square root of the area of ​​the region where the convex shape is formed is calculated when the surface on which the convex shape is formed is viewed in plan view (for example, in Figure 1, the shaping surface area is 80 mm square, so the square root is 80 mm), and if the warpage amount relative to the obtained value is 0.50% or less, it can be determined that the dimensional accuracy of the molded product is within a preferable range. It is more preferably 0.44% or less, and even more preferably 0.38% or less. The amount of warpage is the value at the location with the largest gap when the molded product is placed on a metal surface plate with the first main surface facing up, the outer periphery of the molded product is equally divided into four points, and the gap between the molded product and the surface plate is measured at these four points (see, for example, 15a to 15d in Figure 1), and specifically, it can be measured by the method described in the examples below.

[0031] The plate-shaped molded product of this embodiment preferably has a birefringence value of less than 100 nm, more preferably less than 50 nm, and even more preferably less than 20 nm, as an in-plane retardation. When the in-plane retardation is within the above range, the polarization of light transmitted through the molded product tends to be maintained constant, making it less likely to adversely affect optical properties. When polarized light passes through the molded product, the retardation changes in the presence of total reflection within the molded product. However, if the retardation is confirmed to be small by measuring the in-plane retardation of the molded product, the retardation imparted to the final transmitted light will be constant, and the product will function like a retarder. Because the polarization characteristics are uniform, it is particularly effective when combined with optical devices such as projectors, head-up displays, and headsets that utilize various polarized light, components for aerial displays, and video display devices such as in-vehicle displays that are expected to be viewed with polarized sunglasses. When combined with liquid crystal displays, optical elements using liquid crystals, and polarizing plates, it helps improve light utilization efficiency and reduce noise. It also works to the advantage of improving visibility when using a circular polarizing plate or polarizing plate to cut external light or when wearing polarized sunglasses. The in-plane retardation can be measured by the method described in the examples below.

[0032] (Methacrylic resin composition) The methacrylic resin composition used in the method for producing a plate-shaped molded product of this embodiment is characterized by containing a methacrylic resin, and may optionally contain additives in addition to the methacrylic resin, and may also contain other thermoplastic resins, rubbery polymers, etc. other than the methacrylic resin.

[0033] -Methacrylic resin- The properties of the methacrylic resin used in this embodiment will be described below.

[0034] The methacrylic resin used in the present embodiment is not particularly limited, and examples thereof include resins primarily composed of structural units derived from methyl methacrylate, such as homopolymers of methyl methacrylate, and copolymers of methyl methacrylate with one or more copolymerizable monomers such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, butyl acrylate, acrylonitrile, acrylic acid, methacrylic acid, vinylpyridine, vinylmorpholine, vinylpyridone tetrahydrofurfuryl acrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylacrylamide, 2-hydroxyacrylate, 2-(hydroxymethyl)ethyl acrylate, ethylene glycol monoacrylate, glycerin monoacrylate, maleic anhydride, N-cyclohexylmaleimide, N-phenylmaleimide, styrene, and α-methylstyrene. Other examples include heat-resistant methacrylic resins having a structural unit derived from methyl methacrylate and a lactone ring or glutarimide in the main chain, and methyl methacrylate and low-moisture-absorbing methacrylic resins. These may be used alone or in a blend of two or more.

[0035] The methacrylic resin in this embodiment is particularly preferably a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer, since optical properties such as intrinsic birefringence and photoelastic coefficient can be easily controlled to a high degree without blending with other thermoplastic resins.

[0036] -Methacrylic resin manufacturing method- The method for producing the methacrylic resin of this embodiment will be described below.

[0037] In the production method of this embodiment, a batch system, a semi-batch system, or a continuous system can be used as the polymerization system. Here, the batch system is a process in which the entire amount of raw materials is charged into a reactor, the reaction is initiated and allowed to proceed, and the product is recovered after completion. The semi-batch system is a process in which either the raw materials are charged or the product is recovered simultaneously while the reaction is in progress. Furthermore, the continuous system is a process in which both the raw materials are charged and the product is recovered simultaneously while the reaction is in progress. As the method for producing a methacrylic resin in this embodiment, a semi-batch system in which some of the raw materials are charged after the reaction has started is preferred from the viewpoint of precisely controlling the copolymer composition. The continuous system is not preferred as a production method in this embodiment for the following reasons. When the polymerization reaction is carried out in a single complete mixing reactor, the continuous system has the advantage of being able to reduce the difference in monomer composition between fractions with different molecular weights in the methacrylic resin. However, since a large amount of unreacted monomer remains after polymerization, this tends to have an adverse effect on color tone. On the other hand, when a plug flow reactor is used, the amount of unreacted monomer can be reduced, but the difference in monomer composition between fractions with different molecular weights in the methacrylic resin tends to be large. When multiple complete mixing reactors or a complete mixing reactor and a plug flow reactor are combined in series, the amount of unreacted monomer can also be reduced, but the difference in monomer composition between the fractions tends to be large.

[0038] The polymerization solvent is not particularly limited, and examples thereof include aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and isopropylbenzene; esters such as methyl isobutyrate; ketones such as methyl isobutyl ketone, butyl cellosolve, methyl ethyl ketone, and cyclohexanone; and polar solvents such as dimethylformamide and 2-methylpyrrolidone. Furthermore, alcohols such as methanol, ethanol, and isopropanol may be used in combination as a polymerization solvent to the extent that they do not inhibit the dissolution of the polymerization product during polymerization. The amount of solvent used during polymerization is not particularly limited as long as it allows the polymerization to proceed, does not cause precipitation of the copolymer or the monomers used during production, and can be easily removed. For example, when the total amount of the monomers to be blended is 100 parts by mass, the amount of solvent is preferably 10 to 200 parts by mass, more preferably 25 to 200 parts by mass, even more preferably 50 to 200 parts by mass, and still more preferably 50 to 150 parts by mass.

[0039] As the polymerization initiator, any initiator generally used in radical polymerization can be used, and examples thereof include organic peroxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyisononanoate, and 1,1-di(t-butylperoxy)cyclohexane; and azo compounds such as 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl-2,2'-azobisisobutyrate. These may be used alone or in combination of two or more. These polymerization initiators may be added at any stage as long as the polymerization reaction is in progress. The amount of the polymerization initiator added may be 0.01 to 1 part by mass, and preferably 0.05 to 0.5 part by mass, when the total amount of the monomers used in the polymerization is 100 parts by mass.

[0040] As the chain transfer agent, any chain transfer agent used in general radical polymerization can be used, and examples thereof include mercaptan compounds such as n-butyl mercaptan, n-octyl mercaptan, n-decyl mercaptan, n-dodecyl mercaptan, and 2-ethylhexyl thioglycolate; halogen compounds such as carbon tetrachloride, methylene chloride, and bromoform; and unsaturated hydrocarbon compounds such as α-methylstyrene dimer, α-terpinene, dipentene, and terpinolene. These may be used alone or in combination of two or more. These chain transfer agents may be added at any stage as long as the polymerization reaction is in progress, and there are no particular limitations on the addition stage. The amount of the chain transfer agent added may be 0.01 to 1 part by mass, and preferably 0.05 to 0.5 part by mass, when the total amount of the monomers used in the polymerization is 100 parts by mass.

[0041] The method for recovering a polymer from a polymerization solution obtained by solution polymerization is not particularly limited, and examples thereof include a method in which the polymerization solution is added to an excess amount of a poor solvent, such as a hydrocarbon solvent or an alcohol solvent, in which the polymerization product obtained by polymerization is not soluble, followed by treatment with a homogenizer (emulsification dispersion), and unreacted monomers are separated from the polymerization solution by pretreatment such as liquid-liquid extraction or solid-liquid extraction; or a method in which the polymerization solvent and unreacted monomers are separated via a step called a devolatilization step, and the polymerization product is recovered. Here, the devolatilization step refers to a step of removing volatile components such as the polymerization solvent, residual monomers, and reaction by-products under heated and reduced pressure conditions.

[0042] Examples of equipment used in the devolatilization step include a devolatilizer consisting of a tubular heat exchanger and a devolatilization tank; thin-film evaporators such as Wiblen and Exeba manufactured by Kobelco Environmental Solutions Co., Ltd., and Contra and tilted blade Contra manufactured by Hitachi, Ltd.; and a vented extruder having a residence time and surface area sufficient to exhibit devolatilization performance. A devolatilization step using a devolatilization apparatus that combines two or more of these devices can also be used.

[0043] From the viewpoint of improving the color tone, it is preferable to use a devolatilizer that is mainly composed of a heat exchanger and a reduced pressure vessel and does not have a rotating part in its structure. Specifically, a devolatilization apparatus can be used which comprises a devolatilization tank having a structure in which a heat exchanger is disposed at the top of the tank and a pressure reduction unit is attached to a pressure reduction container having a size sufficient for devolatilization, and a discharge device such as a gear pump for discharging the polymer after devolatilization. In the volatilizing apparatus, the polymerization solution is preheated by being fed to a heated heat exchanger, such as a multi-tube heat exchanger, a plate-fin heat exchanger, or a flat-plate heat exchanger having a flat-plate flow path and a heater, which is disposed above the reduced-pressure vessel, and then fed to a volatilizing tank which is heated and under reduced pressure, to separate and remove the polymerization solvent, unreacted raw material mixture, polymerization by-products, and the copolymer. Use of a volatilizing apparatus having no rotating part as described above is preferred because it allows the production of a methacrylic resin having a good color tone.

[0044] The treatment temperature in the devolatilizer is preferably 150 to 350° C., more preferably 170 to 300° C., and even more preferably 200 to 280° C. By setting the temperature at or above the lower limit temperature, the remaining volatile content can be suppressed, and by setting the temperature at or below the upper limit temperature, coloration and decomposition of the resulting acrylic resin can be suppressed.

[0045] -Additives- The methacrylic resin composition according to this embodiment may contain various additives within the range that does not significantly impair the effects of the present invention. The additives are not particularly limited, and examples thereof include antioxidants, light stabilizers such as hindered amine light stabilizers, ultraviolet absorbers, release agents, thermoplastic resins other than methacrylic resins, softeners / plasticizers such as paraffinic process oil, naphthenic process oil, aromatic process oil, paraffin, organic polysiloxane, and mineral oil, flame retardants, antistatic agents, inorganic fillers such as organic fibers and pigments such as iron oxide, reinforcing agents such as glass fibers, carbon fibers, and metal whiskers, colorants, organic phosphorus compounds such as phosphites, phosphonites, and phosphate esters, and mixtures thereof.

[0046] --Antioxidants-- The methacrylic resin composition according to this embodiment preferably contains an antioxidant that suppresses deterioration and coloration during molding or use. Examples of the antioxidant include, but are not limited to, hindered phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. In order to improve the transferability of the fine convex shaped portions of the first mold while highly controlling the distortion and warpage of the surface of the molded product, it is essential that the methacrylic resin composition of this embodiment maintains the resin at a high temperature in the mold cavity and allows an appropriate cooling time. When subjected to a long-term thermal history, the amount of heat stabilizer added must be increased to achieve the desired thermal stability. However, from the viewpoints of suppressing bleed-out of the heat stabilizer and preventing it from sticking to the mold, it is preferable to use multiple types of heat stabilizers in combination. For example, it is preferable to use a hindered phenol-based antioxidant in combination with at least one selected from a phosphorus-based antioxidant and a sulfur-based antioxidant. These antioxidants may be used alone or in combination of two or more.

[0047] Examples of the hindered phenol antioxidant include, but are not limited to, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl ...octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propion pionate], hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylin)methyl]-1,3,5-triazine-2,4,6(1H,3H,5 H)-trione, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamine)phenol, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate, and the like. Particularly preferred are pentaerythritol terakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate.

[0048] Furthermore, as the hindered phenol-based antioxidant, a commercially available phenol-based antioxidant may be used. Examples of such commercially available phenol-based antioxidants include, but are not limited to, Irganox 1010 (Irganox 1010: pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], manufactured by BASF), Irganox 1076 (Irganox 1076: pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], manufactured by BASF), and the like. 1076: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, BASF), Irganox 1330 (Irganox 1330: 3,3',3'',5,5',5''-hexa-t-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, BASF), Irganox 3114 (Irganox 3114: 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, B ASF), Irganox 3125 (BASF), Adekastab AO-60 (pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (ADEKA), Adekastab AO-80 (3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane (ADEKA), Sumilizer BHT BHT, manufactured by Sumitomo Chemical), Cyanox 1790 (manufactured by Cytec), Sumilizer GA-80 (manufactured by Sumitomo Chemical), Sumilizer GS (Sumilizer GS: 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, manufactured by Sumitomo Chemical), Sumilizer GM (Sumilizer GM: 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate, manufactured by Sumitomo Chemical), and Vitamin E (manufactured by Eisai). Among these commercially available phenolic antioxidants, Irganox 1010, Adekastab AO-60, Adekastab AO-80, Irganox 1076, Sumilizer GS, etc. are preferred from the viewpoint of the effect of imparting thermal stability to the resin. These may be used alone or in combination of two or more.

[0049] Furthermore, examples of the phosphorus-based antioxidant include, but are not limited to, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, tetrakis(2,4-di-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methyl phenyl)pentaerythritol diphosphite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, tetrakis(2,4-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonite, di-t-butyl-m-cresylphosphonite, 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol, and the like. Furthermore, commercially available phosphorus-based antioxidants may be used as the phosphorus-based antioxidant. Examples of such commercially available phosphorus-based antioxidants include, but are not limited to, Irgafos 168 (Irgafos 168: tris(2,4-di-t-butylphenyl)phosphite, manufactured by BASF), Irgafos 12 (Irgafos 12: tris[2-[[2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphen-6-yl]oxy]ethyl]amine, manufactured by BASF), Irgafos 38 (Irgafos 38: bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, manufactured by BASF), Adeka STAB 329K (ADK STAB-229K, manufactured by ADEKA), Adeka STAB PEP-36 (ADK STAB PEP-36 (ADEKA), ADK STAB PEP-36A (ADEKA), ADK STAB PEP-8 (ADEKA), ADK STAB HP-10 (ADEKA), ADK STAB HP-10 (ADEKA), ADK STAB 2112 (ADEKA), ADK STAB 1178 (ADEKA STAB 1178), ADK STAB 1500 (ADEKA), Sandstab P-EPQ (Clariant), Weston 618 (GE), Weston 619G (GE), Ultranox 626 (GE), Sumilizer GP GP: 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol, manufactured by Sumitomo Chemical Co., Ltd.), HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, manufactured by Sanko Co., Ltd.), and the like. Among these commercially available phosphorus-based antioxidants, from the viewpoint of the effect of imparting thermal stability to the resin and the effect of using them in combination with various other antioxidants, Irgafos 168, ADK STAB PEP-36, ADK STAB PEP-36A, ADK STAB HP-10, and ADK STAB 1178 are preferred, with ADK STAB PEP-36A and ADK STAB PEP-36 being particularly preferred. These phosphorus-based antioxidants may be used alone or in combination of two or more.

[0050] Furthermore, examples of the sulfur-based antioxidant include, but are not limited to, 2,4-bis(dodecylthiomethyl)-6-methylphenol (Irganox 1726, manufactured by BASF), 2,4-bis(octylthiomethyl)-6-methylphenol (Irganox 1520L, manufactured by BASF), 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1 ,3-diylbis[3-dodecylthio]propionate] (ADEKA STAB AO-412S, manufactured by ADEKA Corporation), 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1,3-diylbis[3-dodecylthio]propionate] (ChemiNox PLS, manufactured by Chemipro Chemical Co., Ltd.), and di(tridecyl) 3,3'-thiodipropionate (AO-503, manufactured by ADEKA Corporation). Among these commercially available sulfur antioxidants, Adekastab AO-412S and Cheminox PLS are preferred from the viewpoints of their effect of imparting thermal stability to the resin, their effect in combination with various antioxidants, and ease of handling. These sulfur-based antioxidants may be used alone or in combination of two or more.

[0051] The content of the antioxidant may be any amount that is effective in improving thermal stability. If the content is excessive, problems such as bleeding out during processing may occur. Therefore, the content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, still more preferably 0.8 parts by mass or less, still more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass, relative to 100 parts by mass of the methacrylic resin.

[0052] --UV absorber-- The methacrylic resin composition of the present embodiment may contain an ultraviolet absorber. The ultraviolet absorber is not particularly limited, but is preferably an ultraviolet absorber having a maximum absorption wavelength of 280 to 380 nm, and examples thereof include benzotriazole-based compounds, benzotriazine-based compounds, benzophenone-based compounds, oxybenzophenone-based compounds, benzoate-based compounds, phenol-based compounds, oxazole-based compounds, cyanoacrylate-based compounds, and benzoxazinone-based compounds. These ultraviolet absorbents may be used alone or in combination of two or more.

[0053] As the ultraviolet absorber, benzotriazole-based compounds and benzotriazine-based compounds having a molecular weight of 400 or more are preferred, particularly from the viewpoints of compatibility with the resin and volatility upon heating, and benzotriazine-based compounds are particularly preferred from the viewpoint of suppressing decomposition of the ultraviolet absorber itself due to heating during extrusion processing.

[0054] The content of the ultraviolet absorber is not particularly limited as long as it does not impair heat resistance, moist heat resistance, thermal stability, and moldability and exhibits the effects of the present invention, but is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, more preferably 0.25 to 3 parts by mass, and even more preferably 0.3 to 3 parts by mass, relative to 100 parts by mass of the methacrylic resin. Within this range, an excellent balance of ultraviolet absorption performance, moldability, etc. is achieved.

[0055] --Mold release agent-- The methacrylic resin composition of the present embodiment may contain a release agent, including, but not limited to, fatty acid esters, fatty acid amides, fatty acid metal salts, hydrocarbon-based lubricants, alcohol-based lubricants, polyalkylene glycols, carboxylic acid esters, and hydrocarbon paraffin-based mineral oils. These release agents may be used alone or in combination of two or more.

[0056] The fatty acid ester that can be used as the release agent is not particularly limited, and any of the conventionally known fatty acid esters can be used. Examples of fatty acid esters that can be used include ester compounds of fatty acids having 12 to 32 carbon atoms, such as lauric acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, arachic acid, and behenic acid, with monohydric aliphatic alcohols, such as palmityl alcohol, stearyl alcohol, and behenyl alcohol, and polyhydric aliphatic alcohols, such as glycerin, pentaerythritol, dipentaerythritol, and sorbitan; and complex ester compounds of fatty acids, polybasic organic acids, and monohydric aliphatic alcohols or polyhydric aliphatic alcohols. Examples of such fatty acid ester lubricants include cetyl palmitate, butyl stearate, stearyl stearate, stearyl citrate, glycerin monocaprylate, glycerin monocaprate, glycerin monolaurate, glycerin monopalmitate, glycerin dipalmitate, glycerin monostearate, glycerin distearate, glycerin tristearate, glycerin monooleate, glycerin dioleate, glycerin trioleate, glycerin monolinoleate, and the like. glycerin monobehenate, glycerin mono-12-hydroxystearate, glycerin di-12-hydroxystearate, glycerin tri-12-hydroxystearate, glycerin diacetomonostearate, glycerin citrate fatty acid ester, pentaerythritol adipate stearate, partially saponified montanic acid ester, pentaerythritol tetrastearate, dipentaerythritol hexastearate, sorbitan tristearate, and the like. These fatty acid ester lubricants can be used alone or in combination of two or more. Examples of commercially available products include the Rikemal series, Poem series, Rikestar series, and Rikemaster series manufactured by Riken Vitamin Co., Ltd., and the Excel series, Leodor series, Excelpearl series, and Coconard series manufactured by Kao Corporation, and more specific examples include Rikemal S-100, Rikemal H-100, Poem V-100, Rikemal B-100, Rikemal HC-100, Rikemal S-200, Poem B-200, Rikestar EW-200, Rikestar EW-400, Excel S-95, and Leodor MS-50.

[0057] The content of the release agent may be an amount sufficient to obtain the effect as a release agent, and since an excessive content may cause problems such as bleed-out during processing or poor extrusion due to screw slippage, the content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, still more preferably 0.8 parts by mass or less, still more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass, per 100 parts by mass of the methacrylic resin. Addition in the above ranges inhibits the decrease in transparency due to the addition of the release agent and also tends to inhibit poor release during injection molding.

[0058] --Other thermoplastic resins-- The methacrylic resin composition of the present embodiment may contain a thermoplastic resin other than the methacrylic resin for the purposes of adjusting birefringence or improving flexibility without impairing the object of the present invention. Other thermoplastic resins include, for example, polyacrylates such as polybutyl acrylate; styrene-based polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene block copolymer; and acrylic rubber particles having a three- to four-layer structure described in, for example, JP-A-59-202213, JP-A-63-27516, JP-A-51-129449, and JP-A-52-56150; rubbery polymers disclosed in JP-B-60-17406 and JP-A-8-245854; and methacrylic rubber-containing graft copolymer particles obtained by multistage polymerization, described in WO 2014-002491. Among these, from the viewpoint of obtaining good optical properties and mechanical properties, rubber-containing graft copolymer particles having a graft portion on their surface layer made of a composition compatible with styrene-acrylonitrile copolymers and methacrylic resins containing structural units (X) having a ring structure in the main chain are preferred. The average particle size of the acrylic rubber particles, methacrylic rubber-containing graft copolymer particles, and rubbery polymer described above is preferably 0.03 to 1 μm, more preferably 0.05 to 0.5 μm, from the viewpoint of improving the impact strength and optical properties of the molded article obtained from the composition of this embodiment.

[0059] The content of the other thermoplastic resin is preferably 0 to 50 parts by mass, more preferably 0 to 25 parts by mass, based on 100 parts by mass of the methacrylic resin.

[0060] The methacrylic resin composition used in this embodiment has a glass transition temperature (Tg) of 115 to 150°C from the viewpoint of heat resistance. If the material does not have heat resistance of 115°C or higher, warping and convex deformation will occur in reliability tests such as high-temperature aging tests, adversely affecting optical properties. Furthermore, a heat resistance temperature higher than 150°C is undesirable because there are few types of equipment capable of raising the maximum temperature Tmax1 of the first mold to an appropriate temperature, and the mold temperature increase and decrease require time, resulting in a long cycle time. Furthermore, a temperature of 120 to 145°C is more preferable, and 125 to 140°C is particularly preferable. The glass transition temperature can be measured by the midpoint method in accordance with JIS-K7121, and specifically, can be measured by the method described in the examples below.

[0061] The methacrylic resin composition used in this embodiment preferably has a low viscosity corresponding to the time of injection and high fluidity in order to improve the transferability of the fine convex shapes. -1 In this case, the melt viscosity is preferably 20 to 235 Pa·sec, more preferably 20 to 230 Pa·sec, even more preferably 30 to 180 Pa·sec, and particularly preferably 50 to 150 Pa·sec. If the melt viscosity is less than 20 Pa·sec, it is difficult to control the flow of the resin during injection, and air entrapment tends to deteriorate the transferability of fine convex shapes. If the melt viscosity is greater than 235 Pa·sec, the fluidity of the resin decreases, which tends to deteriorate the transferability of convex shapes to molded products. The melt viscosity is a value measured in accordance with JIS-K7199, and specifically, can be measured by the method described in the examples below.

[0062] The methacrylic resin composition used in this embodiment preferably has a large tensile strain at break to prevent cracking during mold release and resin residue in the mold. The tensile strain at break is 1.5% or more, preferably 2.0% or more, and more preferably 2.5% or more. The tensile breaking strain is a value measured in accordance with ISO 527, and specifically, can be measured by the method described in the examples below.

[0063] (Method for producing methacrylic resin composition) Examples of the method for producing the methacrylic resin composition of the present embodiment include a method of kneading using a kneader such as an extruder, a heated roll, a kneader, a roller mixer, a Banbury mixer, etc. Among these, kneading using an extruder is preferred in terms of productivity. The kneading temperature may be determined according to the preferred processing temperatures of the polymers constituting the methacrylic resin and the other resins to be mixed, and is generally in the range of 140 to 300° C., preferably 180 to 280° C. It is also preferable to provide the extruder with a vent port for the purpose of reducing volatile content. [Example]

[0064] The present invention will be explained below by way of specific examples and comparative examples, but is not limited to these.

[0065] [Raw materials] The raw materials used in the examples and comparative examples described later are shown below.

[0066] [[Monomers that make up methacrylic resins]] Methyl methacrylate (MMA): manufactured by Asahi Kasei Corporation N-phenylmaleimide (PMI): Nippon Shokubai Co., Ltd. N-Cyclohexylmaleimide (CMI): Nippon Shokubai Co., Ltd. Styrene: Fujifilm Wako Pure Chemical Industries, Ltd. Methyl 2-(hydroxymethyl)acrylate (MHMA): Combi-Blocks

[0067] [[Organic solvents]] Meta-xylene (mXy): Mitsubishi Gas Chemical Company, Ltd. Methyl isobutyrate: manufactured by Kanto Chemical Co., Ltd. Toluene: Fujifilm Wako Pure Chemical Industries, Ltd.

[0068] [[Polymerization initiator]] 1,1-Di(t-butylperoxy)cyclohexane: NOF Corporation t-Amylperoxy-2-ethylhexanoate: "Luperox 575" manufactured by Arkema Yoshitomi Co., Ltd. t-Amyl peroxyisononanoate: Arkema Yoshitomi Co., Ltd.

[0069] [[Chain transfer agent]] n-Octyl mercaptan: Chevron Phillips Chemical Company n-Dodecyl mercaptan: Fujifilm Wako Pure Chemical Industries, Ltd.

[0070] [[Additives]] Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]: BASF "Irganox 1010" Tris(2,4-di-t-butylphenyl)phosphite: BASF "Irgafos168" Rikemal H-100: manufactured by Riken Vitamin Co., Ltd. ADK STAB 2112: ADEKA Corporation Stearyl phosphate / distearyl phosphate mixture: Sakai Chemical Industry Co., Ltd. ADK STAB PEP-36: ADEKA Corporation Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate: BASF "Irganox 1076" Monomethylamine: Mitsubishi Gas Chemical Company, Inc. Dimethyl carbonate: Fujifilm Wako Pure Chemical Industries, Ltd. Triethylamine: Fujifilm Wako Pure Chemical Industries, Ltd.

[0071] (Evaluation of properties of methacrylic resins and methacrylic resin compositions) The methods for measuring the properties of the methacrylic resin composition will be described below.

[0072] (1) Measurement of glass transition temperature The glass transition temperature of the methacrylic resin composition was measured in accordance with JIS-K7121. A differential scanning calorimeter (DSC8000, manufactured by Perkin-Lumer Japan Co., Ltd.) was used under conditions of a nitrogen gas flow rate of 25 mL / min. The sample was heated from room temperature (23°C) to 200°C at a rate of 10°C / min (first heating), held at 200°C for 5 minutes to completely melt the sample, then cooled from 200°C to 40°C at a rate of 10°C / min, held at 40°C for 5 minutes, and heated again under the same heating conditions (second heating). Of the DSC curves drawn during this period, the glass transition temperature (Tg) (°C) was measured at the intersection (midpoint glass transition temperature) of the step-like change portion of the second heating curve with a straight line equidistant in the vertical direction from each extended baseline line.

[0073] (2) Measurement of melt viscosity Under conditions conforming to JIS-K7199, a twin capillary rheometer (manufactured by ROSAND) was used at a temperature of 270°C and a shear rate of 1000 sec -1 The melt viscosity (Pa·sec) of the methacrylic resin composition was measured using a capillary die with a diameter of 1 mm.

[0074] (3) Measurement of tensile breaking strain Pellets of the methacrylic resin composition were dried at 80 to 100°C for 24 hours and injection-molded using an injection molding machine (Toshiba Machine Co., Ltd., EX-100SX) in accordance with JIS-K6717 to prepare 4.0 mm thick ISO 3167 A-type dumbbell test specimens. Tensile tests were performed on these test specimens in accordance with ISO 527 using a low-load universal testing machine (Instron) at a measurement temperature of 23°C and a crosshead speed of 5 mm / min. Five measurements were performed, and the chuck elongation at tensile break was measured. The average value was calculated as the tensile fracture strain (%). The tensile fracture strain is synonymous with the tensile fracture elongation and tensile fracture strain.

[0075] (Evaluation method for molded products) The evaluation methods for the plate-shaped molded products are described below.

[0076] (1) Measurement of the height and pitch of the convex shapes of molded products The plate-shaped molded article was cut in the direction perpendicular to the main surface (thickness direction) and the cross section obtained was observed using a digital microscope (Keyence Corporation, VHX-1000). The height and pitch of the convex shapes formed on the first main surface of the molded article were measured from the obtained observation image, and the average values ​​of the five convex shapes were recorded as height a and pitch b, respectively, in Table 1.

[0077] (2) Measurement of the filling degree of the convex shape of the molded product The cross section obtained by cutting the plate-shaped molded article in the direction perpendicular to the main surface (thickness direction) was observed using a digital microscope (Keyence Corporation, VHX-1000). The height a of the convex shape formed on the first main surface of the molded article was determined, and the filling degree, defined as the ratio of the height a of the convex shape to the depth of the concave shape in the first mold used to form the convex shape, was calculated using the following formula. The average value of four locations is shown in Table 1 as the filling degree value. In practice, a filling degree of 0.92 or more can be judged to be preferable as a molded article having a transferred convex shape. (Filling degree) = (height of the convex shape of the molded product a) / (depth of the concave shape of the mold)

[0078] (3) Measurement of warpage of molded products The plate-shaped molded product was placed on a metal surface plate with the first main surface having a convex shape facing up, and the outer periphery of the molded product was equally divided into four points. The gaps between the molded product and the surface plate at these four points (points 15a, 15b, 15c, and 15d in Figure 1(A)) were measured with a thickness gauge, and the value at the point with the largest gap (amount of warpage) was taken as the amount of warpage (mm) of the molded product. In the case of a molded product having an uneven portion for connection to other parts on the back side (second main surface) of the first main surface of the molded product, the product is trimmed so that only the portion that does not include the uneven portion for connection remains, and the cross section is polished with sandpaper before measuring the amount of warpage. In practice, in the case of a plate-shaped molded product having the shape shown in Figs. 1 and 3, if the amount of warpage is 0.4 mm or less, it can be determined that this is within a preferable range for the dimensional accuracy of the molded product.

[0079] (4) Evaluation of the appearance of the molded product The plate-shaped molded product was visually inspected for uneven gloss on the first main surface due to insufficient filling of the resin on the fine convex shape forming surface of the first mold, and for poor appearance due to waviness on the second main surface. If there are any areas where the resin has not been filled properly, they will appear as chipped parts.The quality of the flatness of the second main surface can be determined by checking whether a straight line is distorted when checking the reflected image when a fluorescent lamp housed in a rectangular case with one long side is shone from above. When neither gloss unevenness on the first main surface nor waviness on the second main surface was observed, the sample was evaluated as "○ (good)", and when at least one of gloss unevenness on the first main surface and waviness on the second main surface was observed, the sample was evaluated as "× (bad)".

[0080] (5) Measurement of in-plane retardation of molded products The plate-shaped molded product was placed in a Petri dish on the measurement stage of a PA-300-L (Photonic Lattice, Inc.) with the first principal surface facing up. A low-viscosity liquid (Shimadzu Corporation contact liquid) with a refractive index close to that of the methacrylic resin used and non-corrosive to the methacrylic resin was then poured into the Petri dish so that the product was filled up to the top of the convex shape. The first principal surface of the molded product was immersed in the liquid, and the liquid surface was flat with no elevation differences. The in-plane retardation distribution was measured in this state at a wavelength of 520 nm. The average absolute value of the in-plane retardation (Re) in the area where the convex shape was formed (see Figures 1(A) and 3(A)) was calculated, and this was used as the measured value of retardation (nm). The birefringence value is preferably in a range where the optical properties are not adversely affected, and the in-plane retardation is less than 100 nm.

[0081] Synthesis Example 1 [Methacrylic Resin Composition A] 318.7 kg of methyl methacrylate (hereinafter referred to as MMA), 35.5 g of N-phenylmaleimide (hereinafter referred to as PMI), 63.7 kg of N-cyclohexylmaleimide (hereinafter referred to as CMI), 0.341 kg of n-octyl mercaptan as a chain transfer agent, and 225.1 kg of meta-xylene (hereinafter referred to as mXy) ​​were weighed and placed in a 1.25 m 3 The mixture was added to the reactor and stirred to obtain a mixed monomer solution. Next, 116.9 kg of mXy was weighed and added to Tank 1 to prepare the additional solvent. Furthermore, 104.5 kg of MMA and 85.5 kg of mXy were weighed into Tank 2 and stirred to obtain an MMA solution for further addition. The liquid in the reactor was bubbled with nitrogen at a rate of 30 L / min for 1 hour, and the liquid in Tank 1 and Tank 2 was bubbled with nitrogen at a rate of 10 L / min for 30 minutes each to remove dissolved oxygen. Steam was then blown into the jacket to raise the solution temperature in the reactor to 125°C. While stirring at 50 rpm, a polymerization initiator solution (0.457 kg of 1,1-di(t-butylperoxy)cyclohexane in 2.67 kg of mXy) ​​was added at a rate of 1 kg / h to initiate polymerization. During polymerization, the solution temperature in the reactor was controlled at 125±2°C using the temperature control in the jacket. Thirty minutes after the start of polymerization, the rate of addition of the polymerization initiator solution was reduced to 0.25 kg / h, and mXy was added from Tank 1 at a rate of 29.24 kg / h for 3.5 hours. Then, 4 hours after the initiation of polymerization, the rate of addition of the polymerization initiator solution was increased to 0.75 kg / hour, and additional MMA solution was added from Tank 2 at a rate of 95 kg / hour for 2 hours. Further, 6 hours after the start of polymerization, the addition rate of the polymerization initiator solution was reduced to 0.25 kg / hour, and 7 hours after the start of polymerization, the addition was stopped. Eight hours after the start of polymerization, a polymerization solution containing a methacrylic resin was obtained, to which 0.261 kg of Irganox 1010 and 0.784 kg of Irgafos 168 were added as antioxidants, and 0.784 kg of Rikemal H-100 as a mold release agent. Next, the obtained polymerization solution was fed to a concentrator consisting of a tubular heat exchanger and a vaporizer preheated to 250°C for devolatilization. The degree of vacuum in the vaporizer was set to 10 to 15 Torr. The resin flowing down the vaporizer was discharged with a screw pump, extruded through a strand die, cooled with water, and pelletized to obtain a methacrylic resin composition A having N-substituted maleimide structural units. The obtained pellets had a Tg of 133°C, a melt viscosity of 131 Pa·sec, and a tensile breaking strain of 1.7%.

[0082] Synthesis Example 2 [Methacrylic Resin Composition B] A monomer composition consisting of 60.000 mol% methyl methacrylate, 39.998 mol% styrene, and 0.002 mol% t-amylperoxy-2-ethylhexanoate as a polymerization initiator was continuously fed into a 10-L inert mixing vessel equipped with a helical ribbon impeller at a rate of 1 kg / h. Continuous polymerization was carried out at an average residence time of 2.5 hours and a polymerization temperature of 150°C. The liquid was continuously withdrawn from the bottom to maintain a constant liquid level in the vessel, and then fed into a concentrator consisting of a tubular heat exchanger and a vaporizer for devolatilization. The vacuum in the vaporizer was maintained at 10-15 Torr. The resin flowing down the vaporizer was discharged using a screw pump, extruded through a strand die, water-cooled, pelletized, and introduced into a solvent removal apparatus to obtain pelletized methyl methacrylate-styrene copolymer. This copolymer was dissolved in methyl isobutyrate to prepare a 10% by mass methyl isobutyrate solution. A 1000 mL autoclave was charged with 500 parts by mass of this 10% by mass methyl isobutyrate solution of this copolymer and 1 part by mass of 10% by mass Pd / C (manufactured by NE Chemcat Corporation) as a hydrogenation catalyst. The mixture was maintained at 200°C under a hydrogen pressure of 9 MPa for 15 hours to hydrogenate the aromatic double bonds of the styrene moieties of the copolymer. The hydrogenation catalyst was removed using a filter, and 0.05 parts by mass of Rikemal H-100 was added to the polymer solution and mixed. The mixture was then fed to a concentrator consisting of a tubular heat exchanger and a vaporizer for devolatilization. The vacuum in the vaporizer was set to 10 to 15 Torr. The resin flowing down the vaporizer was discharged using a gear pump, extruded through a strand die, cooled with water, and pelletized to obtain methacrylic resin composition B. The obtained pellets had a Tg of 118°C, a melt viscosity of 67 Pa·sec, and a tensile breaking strain of 2.2%.

[0083] Synthesis Example 3 [Methacrylic Resin Composition C] A 30 L reaction vessel equipped with a stirrer equipped with a paddle blade, a temperature sensor, a cooling tube, and a nitrogen inlet tube was charged with 5.0 kg of methyl methacrylate, 1.25 kg of methyl 2-(hydroxymethyl)acrylate, 0.025 parts by mass of n-dodecyl mercaptan and 0.025 parts of ADK STAB 2112 as chain transfer agents relative to 100 parts by mass of the total amount of all monomers, and 6.25 kg of toluene, and the mixture was heated to 105°C with stirring while nitrogen was passed through. While refluxing, 0.05 parts by mass of t-amyl peroxy isononanoate was added to the polymerization vessel relative to 100 parts by mass of the total amount of all monomers, and then 0.1 parts by mass of t-amyl peroxy isononanoate was added dropwise over 2 hours while polymerization was carried out under reflux at a polymerization temperature of 105 to 110°C, and the polymerization reaction was further carried out for 6 hours. To the obtained polymer solution, 6.3 g of a stearyl phosphate / distearyl phosphate mixture was added, and a cyclization condensation reaction was carried out for 5 hours at 90 to 110° C. Thereafter, 0.10 parts by mass of Rikemal H-100 was added per 100 parts by mass of the total amount of all monomers, and the mixture was stirred and mixed. The resulting polymer solution was subjected to a cyclocondensation reaction and devolatilization treatment using a φ42 mm devolatilizing extruder equipped with four front vents and one back vent at 120 rpm at a resin equivalent rate of 2.2 kg / hour to obtain pellets of methacrylic resin composition C. The resulting pellets had a Tg of 133°C, a melt viscosity of 165 Pa·sec, and a tensile breaking strain of 3.2%.

[0084] Synthesis Example 4 [Methacrylic Resin Composition D] A methacrylic resin composition having a glutarimide structure was obtained by imidizing polymethyl methacrylate with monomethylamine using a co-rotating twin-screw extruder. A co-rotating twin-screw extruder with a screw diameter of 40 mm was used. The extruder cylinder temperature was set to 275°C and the screw rotation speed to 150 rpm. Polymethyl methacrylate with a weight average molecular weight of 10,8000, containing 0.1 parts by weight of Rikemal H-100 per 100 parts by weight of the total polymer, was fed from the hopper at a rate of 20 kg / h, and nitrogen was flowed into the extruder at a flow rate of 200 mL / min. After the resin was melted and filled using a kneading block, 1.8 parts by weight of monomethylamine per 100 parts by weight of raw resin was injected through a nozzle to carry out the imidization reaction. A reverse flight was installed at the end of the reaction zone (before the vent port) to fill the resin. Post-reaction by-products and excess monomethylamine were removed by reducing the pressure at the vent port to 50 Torr. The resin exiting the die at the extruder outlet as strands was cooled in a water bath and then pelletized in a pelletizer to obtain imide resin. Next, a 40mm co-rotating twin-screw extruder was used. The extruder cylinder temperature was set to 255°C and the screw speed to 150 rpm. The resulting imide resin was fed at 20 kg / hr. The resin was melted and filled using a kneading block. After that, a mixture of dimethyl carbonate and triethylamine was injected through the nozzle as an esterifying agent to reduce the carboxylic acid groups in the resin. The amount of dimethyl carbonate was 3.2 parts by mass and triethylamine was 0.8 parts by mass per 100 parts by mass of imide resin. The pressure at the vent port was reduced to 50 Torr to remove the by-products and excess dimethyl carbonate. The resin exited the die at the extruder outlet as strands, which were then cooled in a water bath and pelletized in a pelletizer to obtain methacrylic resin composition D having a glutarimide structure. The obtained pellets had a Tg of 122°C, a melt viscosity of 158 Pa·sec, and a tensile breaking strain of 7.9%.

[0085] Synthesis Example 5 [Methacrylic Resin Composition E] Polymerization was carried out in the same manner as in Synthesis Example 1, except that the amount of n-octyl mercaptan used as a chain transfer agent was changed to 0.708 kg, to obtain a methacrylic resin composition E. The obtained pellets had a Tg of 134°C, a melt viscosity of 102 Pa·sec, and a tensile breaking strain of 1.2%.

[0086] Synthesis Example 6 [Methacrylic Resin Composition F] 291.5 kg of MMA, 44.0 kg of PMI, 104.5 kg of CMI, 0.20 kg of n-octyl mercaptan as a chain transfer agent, and 247.0 kg of mXy were weighed and placed in a 1.25 m 3 The mixture was added to the reactor and stirred to obtain a mixed monomer solution. Next, 123.0 kg of mXy was weighed and added to Tank 1. Furthermore, 110.0 kg of MMA and 80.0 kg of mXy were weighed and stirred in tank 2 to prepare a monomer solution for addition. The liquid in the reactor was bubbled with nitrogen at a rate of 30 L / min for 1 hour, and the liquid in Tank 1 and Tank 2 was bubbled with nitrogen at a rate of 10 L / min for 30 minutes each to remove dissolved oxygen. Thereafter, steam was blown into the jacket to raise the solution temperature in the reactor to 124°C, and while stirring at 50 rpm, a polymerization initiator solution prepared by dissolving 0.35 kg of 1,1-di(t-butylperoxy)cyclohexane in 4.652 kg of mXy was added at a rate of 1 kg / hour to initiate polymerization, and mXy was added from Tank 1 at a rate of 30.75 kg / hour for 4 hours. During the polymerization, the solution temperature in the reactor was controlled at 124±2° C. by temperature regulation using a jacket. Then, between 4 hours and 6 hours later, a monomer solution containing MMA was added from Tank 2 at a rate of 95 kg / hour. Furthermore, the addition rate of the polymerization initiator solution was reduced to 0.25 kg / hour 0.5 hour after the start of polymerization, to 0.75 kg / hour after 4 hours, and to 0.5 kg / hour after 6 hours. Seven hours after the start of polymerization, the addition of the polymerization initiator solution was stopped, and polymerization was continued for another 3 hours, thereby obtaining a polymerization solution containing a methacrylic resin having a ring structural unit in its main chain. To this polymerization solution, 0.83 kg of Adekastab PEP-36, 0.28 kg of Irgafos168, 0.44 kg of Irganox1076, and 1.10 kg of Rikemal H-100 were added under stirring. Next, the resulting polymerization solution was fed to a concentration apparatus consisting of a tubular heat exchanger preheated to 260°C and a vaporization tank for devolatilization. The degree of vacuum in the vaporization tank was set to 10 to 15 Torr. The resin flowing down the vaporization tank was discharged with a screw pump, extruded through a strand die, cooled with water, and pelletized to obtain methacrylic resin F having N-substituted maleimide structural units. The obtained pellets had a Tg of 153°C, a melt viscosity of 245 Pa·sec, and a tensile breaking strain of 4.5%.

[0087] (Examples 1 to 3) - Forming of plate-shaped products with a convex shape on one main surface The methacrylic resin composition A obtained in Synthesis Example 1 was used in an injection molding machine (SE180EV-A, manufactured by Sumitomo Heavy Industries, Ltd.). The mold consisted of a mold (first mold) forming a main surface with triangular pyramidal convex shapes with a convex shape height a = 400 μm and a pitch b = 300 μm, and a mold (second mold) forming a flat main surface. A nested mold was used, with heater wires embedded inside the mold near the surfaces forming each main surface, and attached to the injection molding machine. The mold temperature of the first mold was heated to the maximum temperature Tmax1 listed in Table 1 using a heater at a heating rate of approximately 3°C / sec, and the mold was closed to perform injection molding. After filling the mold with resin, the mold temperature of the first mold was cooled at a rate of approximately 1.2°C / sec to the minimum temperature Tmin1 listed in Table 1. After reaching Tmin1, cooling was continued for 30 seconds to obtain a plate-shaped molded product (90 mm long, 90 mm wide, 2.5 mm thick, see Figure 1) with a convex shape on one main surface. The holding pressure was set high at 80 MPa in the first stage immediately after injection to ensure good transfer, and then lowered to 30 MPa in the second stage to alleviate stress distortion inside the molded product. The evaluation results are shown in Table 1. As is clear from Table 1, the filling degree was 0.97 to 0.98, and very excellent results were obtained in Examples 1 to 3. In addition, the warpage and appearance were also good.

[0088] Example 4 Except for using the methacrylic resin composition B obtained in Synthesis Example 2, molding was carried out under the same conditions as in Example 1. The evaluation results are shown in Table 1.

[0089] Example 5 Molding was carried out under the same conditions as in Example 1, except that the methacrylic resin composition C obtained in Synthesis Example 3 was used. The evaluation results are shown in Table 1.

[0090] Example 6 Except for using the methacrylic resin composition D obtained in Synthesis Example 4, molding was carried out under the same conditions as in Example 1. The evaluation results are shown in Table 1.

[0091] Example 7 The mold was for a plate-shaped molded product (length 90 mm, width 90 mm, thickness 2.4 mm, see Figure 3) with a rectangular truncated pyramidal convex shape (140 μm square, the angle between the base and the side 85 degrees) of convex shape height a = 400 μm and pitch b = 160 μm on one main surface, and the other main surface was flat, and molding was performed under the same conditions as in Example 1, except that a nested mold was used in which heater wires were embedded inside the mold near the surfaces forming each main surface. The evaluation results are shown in Table 1. As is clear from Table 1, Example 7 showed a filling degree of 0.97, and very excellent results were obtained. In addition, warpage and appearance were also good.

[0092] Example 8 The methacrylic resin composition A obtained in Synthesis Example 1 was injection molded using an injection molding machine (SE180EV-A, manufactured by Sumitomo Heavy Industries, Ltd.). The mold consisted of a first mold (forming a main surface with triangular pyramidal convex shapes with a convex shape height a = 400 μm and a pitch b = 300 μm) and a second mold (forming a flat main surface). A nested mold was used, with heater wires embedded inside the mold near the surface forming each main surface, and attached to the injection molding machine. The maximum temperature Tmax1 of the first mold was set to 165°C, and the maximum temperature Tmax2 of the second mold was set to 150°C. The molds were heated to their respective temperatures at a rate of approximately 3°C / sec using heaters. After the temperatures were raised, a fluorine-based mold release agent was sprayed onto the surface of the first mold for release treatment. The mold was then closed, and injection molding was performed. After filling the mold with the resin composition, the minimum temperature of the first mold, Tmin1, was set to 60°C, and the minimum temperature of the second mold, Tmin2, was set to 75°C. The mold was cooled at a rate of approximately 1.2°C / sec. After reaching the set temperature, the mold was cooled for 90 seconds, yielding a plate-shaped molded product (90 mm long, 90 mm wide, 2.5 mm thick, see Figure 1) with a convex shape on one main surface. The holding pressure was set high at 80 MPa in the first stage immediately after injection to ensure good transfer. The holding pressure was then lowered to 30 MPa in the second stage to alleviate stress distortion within the molded product. The evaluation results are shown in Table 1. As is clear from Table 1, in Example 8, a molded product with good appearance was obtained without any mold release defects.

[0093] Example 9 Molding was performed under the same conditions as in Example 8, except that methacrylic resin composition B obtained in Synthesis Example 2 was used and injection was performed by setting the maximum temperature Tmax1 of the first mold to 150°C, the minimum temperature Tmin1 to 65°C, and the maximum temperature Tmax2 of the second mold to 145°C, and the minimum temperature Tmin2 to 75°C. The evaluation results are shown in Table 1.

[0094] Example 10 Molding was performed under the same conditions as in Example 8, except that methacrylic resin composition C obtained in Synthesis Example 3 was used and injection was performed by setting the maximum temperature Tmax1 of the first mold to 155°C, the minimum temperature Tmin1 to 60°C, and the maximum temperature Tmax2 of the second mold to 145°C, and the minimum temperature Tmin2 to 80°C. The evaluation results are shown in Table 1.

[0095] Example 11 Molding was carried out under the same conditions as in Example 10, except that the methacrylic resin composition D obtained in Synthesis Example 4 was used. The evaluation results are shown in Table 1.

[0096] Example 12 The mold was for a plate-shaped molded product (length 90 mm, width 90 mm, thickness 2.4 mm, see Figure 3) with a rectangular truncated pyramidal convex shape (140 μm square, the angle between the base and the side 85 degrees) of convex shape height a = 50 μm and pitch b = 50 μm on one main surface, and the other main surface was flat, and molding was performed under the same conditions as in Example 8, except that a nested mold was used in which heater wires were embedded inside the mold near the surfaces forming each main surface. The evaluation results are shown in Table 1. As is clear from Table 1, Example 12 showed a filling degree of 0.97, and very excellent results were obtained. In addition, warpage and appearance were also good.

[0097] Example 13 The mold had a rectangular pyramidal trapezoidal shape (140 μm square base, 85 degree angle between the base and the side) with a convex shape height a=400 μm and pitch b=160 μm on one main surface, and the other main surface was flat, for a plate-shaped molded product (length 90 mm, width 90 mm, thickness 2.4 mm, see FIG. 3), and molding was carried out under the same conditions as in Example 8, except that a nested mold was used in which heater wires were embedded inside the mold near the surfaces forming each main surface. The evaluation results are shown in Table 1.

[0098] (Comparative Example 1) Molding was carried out under the same conditions as in Example 1, except that heating with a heater was not performed and injection was carried out at a mold temperature equal to or lower than the glass transition temperature Tg of methacrylic resin composition A. The evaluation results are shown in Table 1. As a result of the evaluation, it could not be said that the convex shapes were transferred sufficiently.

[0099] (Comparative Example 2) Molding was carried out under the same conditions as in Example 1, except that injection was carried out at a temperature of the second mold of less than (Tmax1-65)° C. The evaluation results are shown in Table 1. As a result of the evaluation, the filling degree was found to be sufficient at 0.95, but the amount of warpage of the molded product was large at 0.80 mm, and the desired molded product could not be obtained.

[0100] (Comparative Example 3) Molding was carried out under the same conditions as in Example 1, except that injection was carried out at a temperature of the second mold exceeding (Tmax1-50)° C. The evaluation results are shown in Table 1. As a result of the evaluation, defects such as uneven gloss on the first main surface, waviness on the second main surface, and warpage of the molded product were confirmed.

[0101] Comparative Example 4 Molding was carried out under the same conditions as in Example 1, except that the methacrylic resin composition E (tensile strain at break: 1.2%) obtained in Synthesis Example 5 was used. When the molded article was ejected from the mold with an ejector pin and released, it stuck strongly and a popping sound was heard. Multiple chips were found at the top of the convex shape of the molded article, and when the first mold was observed, it was confirmed that there was residual resin in the shaped area (concave area) of the first mold. The evaluation results for the good areas of the obtained molded article are shown in Table 1. As a result of the evaluation, defects such as uneven gloss on the first main surface, waviness on the second main surface, and warpage of the molded product were confirmed.

[0102] (Comparative Example 5) Methacrylic resin composition F (glass transition temperature Tg 153°C, melt viscosity 245 Pa sec) obtained in Synthesis Example 6 was used, and molding was carried out under the same conditions as in Example 1, except that the first mold temperature was set to Tmax1 = 175°C, Tmin1 = 100°C, and the second mold temperature was set to 120°C. The evaluation results are shown in Table 1. As a result of the evaluation, it was confirmed that the filling degree of the first main surface was 0.76, which was insufficient.

[0103] (Comparative Example 6) Molding was carried out under the same conditions as in Example 8, except that injection was carried out at a maximum temperature Tmax2 of the second mold set to less than (Tmax1-30)° C. The evaluation results are shown in Table 1. As a result of the evaluation, the filling degree was found to be sufficient at 0.89, but the amount of warpage of the molded product was large at 0.80 mm, and the desired molded product could not be obtained.

[0104] (Comparative Example 7) Molding was carried out under the same conditions as in Example 8, except that injection was carried out at a maximum temperature Tmax2 of the second mold of more than (Tmax1-5)° C. The evaluation results are shown in Table 1. As a result of the evaluation, defects such as uneven gloss on the first main surface, waviness on the second main surface, and warpage of the molded product were confirmed.

[0105] (Comparative Example 8) Molding was carried out under the same conditions as in Example 8, except that injection was carried out at a minimum temperature Tmin2 of the second mold set to less than (Tmin1+10)° C. The evaluation results are shown in Table 1. As a result of the evaluation, defects such as uneven gloss on the first main surface, waviness on the second main surface, and warpage of the molded product were confirmed.

[0106] (Comparative Example 9) Molding was carried out under the same conditions as in Example 8, except that injection was carried out at a minimum temperature Tmin2 of the second mold of above (Tmin1 + 30)° C. The evaluation results are shown in Table 1. As a result of the evaluation, defects such as uneven gloss on the first main surface, waviness on the second main surface, and warpage of the molded product were confirmed.

[0107] [Table 1]

[0108] The plate-shaped molded products having fine convex shapes obtained in Example 1 and Comparative Example 1 were used as light direction conversion elements, and their properties were evaluated. 5, light incident at an incident angle of 45 degrees onto incident surface 81 (the main surface behind the main surface having the fine convex shapes) of plate-shaped molded product 8 having fine convex shapes is reflected by inclined surface 83 which forms an angle of 85 degrees with bottom surface 82, and then refracted from inclined surface 84 which forms an angle of 65 degrees with bottom surface 82, and emitted to the outside. At this time, the light is emitted from inclined surface 84 at a refraction angle of 64 degrees, so that the light is emitted at an angle of approximately 90 degrees with respect to incident surface 81. In other words, this is a light direction conversion element which bends light that is incident on the incident surface at an incident angle of 45 degrees to a direction perpendicular to the incident surface. The molded product 8 was positioned as shown in Figure 6, and the clarity of the reflected and transmitted images was evaluated as a light direction conversion element. An LED light source 5 (Thorlabs, M530L4) with a collimating lens emitting 530 nm light and a frosted diffuser plate 6 (Sigma Koki, #240) were positioned, and a USAF Target 7 (Edmund, USAF1951 target negative, target area approximately 12 mm) was irradiated from behind. The light of the target image formed by the light that passed through the transmission region 71 of the target (see Figure 7) was incident on the incident surface 81 of the molded article 8 at an incident angle of 45°, and the light that emerged from the convex-shaped surface (main surface having a fine convex shape) of the molded article 6 was photographed as a reflected image (an image formed by light that was reflected by the inclined surface 83 and then transmitted through the inclined surface 84) using a single-lens reflex camera 9 (E-PL5, manufactured by Olympus) positioned 350 mm away in the perpendicular direction from the incident surface 81. The reflected image observed when the molded product obtained in Example 1 was used was a clear image, but the reflected image observed when the molded product obtained in Comparative Example 1 was used showed distortions and chipping of the target image, and the image was less clear. [Industrial Applicability]

[0109] The plate-shaped molded product produced by the production method of the present invention has good appearance and dimensional accuracy, and can therefore be suitably used as various optical components such as Fresnel lenses, lenticular lenses, light guide plates, diffractive optical elements, anti-reflection sheets, anti-glare sheets, and cell culture sheets. [Explanation of symbols]

[0110] 1, 2: Plate-shaped molded products 11, 21: One of the main surfaces (first main surface) having a fine convex shape 12, 22: The other main surface (second main surface) on which the fine convex shape is not formed 13, 23: Areas where fine convex shapes are formed 14, 24: Convex shape 15a, 15b, 15c, 15d: Measurement points for the amount of warpage 5:LED light source 6: Frosted diffuser 7:USAF Target 71:Transparent area 72: Shading area 8: Plate-shaped molded product 81:Incidence plane 82: Bottom 83, 84: Slope 9: SLR camera

Claims

1. A method for producing a plate-shaped molded product, The plate-shaped molded product contains a methacrylic resin composition having a glass transition temperature Tg of 115 to 150°C and a tensile strain at break of 1.5% or more, One main surface (first main surface) of the plate-like molded product has a plurality of fine convex shapes, and the other main surface (second main surface) is a flat surface, the height a of the convex shapes is 0.5 to 600 μm, and the ratio b / a of the pitch b of the convex shapes to the height a of the convex shapes is 0.1 to 1.0; A method for manufacturing a plate-shaped molded product, comprising injection molding using a first mold on the side that forms the first main surface and a second mold on the side that forms the second main surface, characterized in that when the maximum temperature of the first mold is Tmax1, the temperature of the second mold is set to (Tmax1-65)°C to (Tmax1-50)°C.

2. A method for producing a plate-shaped molded product, The plate-shaped molded product contains a methacrylic resin composition having a glass transition temperature Tg of 115 to 150°C and a tensile strain at break of 1.5% or more, One main surface (first main surface) of the plate-like molded product has a plurality of fine convex shapes, and the other main surface (second main surface) is a flat surface, the height a of the convex shapes is 0.5 to 600 μm, and the ratio b / a of the pitch b of the convex shapes to the height a of the convex shapes is 0.1 to 1.0; A method for manufacturing a plate-shaped molded product, comprising injection molding using a first mold on the side that forms the first main surface and a second mold on the side that forms the second main surface, characterized in that when the maximum temperature of the first mold is Tmax1, the maximum temperature Tmax2 of the second mold is set to (Tmax1-30)°C to (Tmax1-5)°C, and when the minimum temperature of the first mold is Tmin1, the minimum temperature Tmin2 of the second mold is set to (Tmin1+10)°C to (Tmin1+30)°C.

3. The first mold is heated and then cooled, so that the maximum temperature Tmax1 of the first mold is (Tg + 15) ° C. to (Tg + 40) ° C., and the minimum temperature Tmin1 of the first mold is (Tg - 75) ° C. to (Tg - 45) ° C. The method for producing a plate-shaped molded product according to claim 1 or 2.

4. The melt viscosity of the methacrylic resin composition is 270°C, 1000 sec －１ The method for producing a plate-shaped molded product according to claim 1 or 2, wherein the viscosity is 20 to 235 Pa·sec.

5. When the first mold is heated and then cooled, the temperature rise rate of the surface temperature of the first mold is 1 to 10 ° C. / sec and the temperature drop rate is 0.5 to 10 ° C. / sec. The method for producing a plate-shaped molded product according to claim 1 or 2.

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