Plate-shaped injection-molded article and method for producing plate-shaped injection-molded article

Abstract

To provide a plate-like injection-molded article in which yellowing and poor appearance of the molded article are reduced even when the plate-like injection-molded article has a fine convex part on at least one main surface and the main surface has a large projected area.SOLUTION: A plate-shaped injection molded article having a plurality of fine convex portions having a height a of 50 to 700 μm at least on a first main surface, wherein a projected area of the first main surface is 225cm2 or more, wherein the plate-shaped injection molded article comprises a methacrylic resin component, and an amount of methyl methacrylate (MMA) contained in the plate-shaped injection molded article is 1600 to 6000 mass ppm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a plate-shaped injection-molded product and a method for producing the plate-shaped injection-molded product. [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). Furthermore, Patent Document 6 discloses a plate-shaped molded product having a plurality of fine convex portions with a height a of 50 to 600 μm on at least one main surface, the plate-shaped molded product being characterized by being produced by injection molding a methacrylic resin composition having a tensile fracture strain of 1.5% or more and a glass transition temperature (Tg) of 115 to 150°C, with the aim of providing a molded product with controlled appearance defects. [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 [Patent Document 6] Japanese Patent Application Publication No. 2023-013969 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above Patent Document 6, the main surface having the minute convex portions is 90 mm long and 90 mm wide (81 cm 2 ) molded products (small molded products). The inventors' investigations have revealed that when molding a molded product with a large main surface size (projected area) having fine convex portions, poor filling of the fine convex portions occurs near the end of the resin flow, and therefore the processing temperature and mold temperature during molding must be set higher than when molding a small molded product, thereby increasing the resin's fluidity. Furthermore, since a larger main surface size (projected area) requires a larger amount of resin to be injected, a molding machine with a larger cylinder diameter must be used. Molding using a molding machine with a large cylinder diameter at a high processing temperature can cause the resin to decompose due to heat, resulting in molding defects such as yellowing and silver discoloration of the molded product. Furthermore, because the mold temperature during molding is set higher than when molding a small molded product with a small main surface projected area having fine convex portions, it takes longer to heat up the mold, resulting in a longer molding cycle and making the product more susceptible to thermal decomposition due to resin retention in the cylinder, which can result in molded products with poor appearance.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a plate-shaped injection-molded product that has fine convex portions on at least one main surface and reduces yellowing and poor appearance of the molded product, even in the case of a plate-shaped injection-molded product having a large projected area of ​​the main surface. Another object of the present invention is to provide a method for producing a plate-shaped injection-molded product that can reduce yellowing and poor appearance of the molded product, even if the plate-shaped injection-molded product has fine convex portions on at least one main surface and the projected area of ​​the main surface is large. [Means for solving the problem]

[0006] The present inventors have found that even in the case of a plate-shaped injection-molded article containing a methacrylic resin composition having fine convex portions on at least a first main surface and having a large projected area of ​​the main surface, the above-mentioned problems can be solved by setting the amount of methyl methacrylate (MMA) contained in the plate-shaped injection-molded article within a predetermined range, and have thus completed the present invention.

[0007] That is, the present invention is as follows. [1] At least a first main surface has a plurality of minute convex portions having a height a of 50 to 700 μm, and the projected area of ​​the first main surface is 225 cm 2 The above plate-shaped injection molded product, The plate-shaped injection-molded product contains a methacrylic resin composition, The plate-shaped injection-molded product contains methyl methacrylate (MMA) in an amount of 1600 to 6000 ppm by mass. [2] The plate-shaped injection-molded article according to [1], which contains a methacrylic resin composition having a glass transition temperature of 115 to 160°C. [3] The plate-shaped injection-molded product according to [1] or [2], wherein the methacrylic resin composition contains a methacrylic resin having a structural unit with a ring structure. [4] The plate-shaped injection-molded article according to any one of [1] to [3], wherein the structural unit having a ring structure includes at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, an aromatic vinyl structural unit, an alicyclic vinyl structural unit, and a lactone ring structural unit. [5] The plate-shaped injection-molded article according to any one of [1] to [4], wherein the structural unit having a ring structure includes a structural unit derived from an N-substituted maleimide monomer. [6] The plate-shaped injection-molded product according to any one of [1] to [5], wherein, on the first main surface having the fine convex portions, the ratio b / a of the pitch b of the fine convex portions to the height a of the fine convex portions is 0.1 to 2.0. [7] The plate-like injection-molded article according to any one of [1] to [6], wherein the first main surface having the fine convex portions has an in-plane retardation of 100 nm or less. [8] The plate-shaped injection-molded product according to any one of [1] to [7], wherein a chloroform solution containing 12% by mass of the molded product obtained by dissolving the plate-shaped injection-molded product in chloroform has a yellowness index (YI) of 10 or less. [9] The plate-shaped injection-molded product according to any one of [1] to [8], which has no adhesive interface and is composed of a single resin.

[10] A semiconductor device having a second main surface opposite to the first main surface, The plate-shaped injection-molded product according to any one of [1] to [9], wherein the second main surface is a flat surface.

[11] The plate-shaped injection-molded product according to any one of [1] to

[10] , which is a member for an aerial display.

[12] The method for producing a plate-shaped injection-molded product according to any one of [1] to

[11] , wherein the surface temperature of a mold is heated to a temperature equal to or higher than the glass transition temperature (Tg) of the methacrylic resin composition, and then the methacrylic resin composition is injected and filled into the mold to obtain a plate-shaped injection-molded product. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a plate-shaped injection-molded product in which yellowing and poor appearance of the molded product are reduced, even if the plate-shaped injection-molded product has fine convex portions on at least one main surface and the projected area of ​​the main surface is large. According to the present invention, it is possible to provide a method for producing a plate-shaped injection-molded product that can reduce yellowing and poor appearance of the molded product, even if the plate-shaped injection-molded product has fine convex portions on at least one main surface and the projected area of ​​the main surface is large. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams showing an example of a plate-shaped injection-molded product of this embodiment, in which (A) shows a plan view (top view) when observed from above with the first main surface having fine convex portions as the upper surface, and (B) shows a side view. [Figure 2] FIG. 2 is a partial cross-sectional view showing an example of a convex shape (triangular pyramid shape) of the plate-shaped injection-molded product of this embodiment. [Figure 3]Figure 3 is a diagram showing an example of a plate-shaped injection-molded product of this embodiment different from that shown in Figure 1. (A) shows a plan view (top view) when observed from above with the first main surface having the fine convex portions as the upper surface, (B) shows a side view, and (C) shows a perspective view of the fine convex portions when observed obliquely from above. [Figure 4] FIG. 4 is a partial cross-sectional view showing an example of a convex shape (quadratic pyramid truncated shape) of the plate-shaped injection-molded product of this embodiment, which is different from that shown in FIG. [Figure 5] FIG. 1 is a diagram showing the optical path when the plate-shaped injection-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 injection-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 the USAF Target used in FIG. 6 as viewed from the X-axis direction. DETAILED DESCRIPTION OF THE INVENTION

[0010] Below, we will explain in detail the form for implementing the present invention (hereinafter referred to as the "present embodiment"). However, the present invention is not limited to the following description and can be implemented in various modifications within the scope of its gist.

[0011] (definition) In this specification, "large projected area of ​​the main surface" means that the projected area of ​​the main surface is 225 cm 2 This means that the above is the case. In this specification, the term "having a small projected area of ​​the main surface" means that the projected area of ​​the main surface is 225 cm 2 It means that it is less than.

[0012] (Plate-shaped injection molded product) The plate-shaped injection-molded product of this embodiment has a plurality of minute convex portions having a height a of 50 to 700 μm on at least the first main surface, and the projected area of ​​the first main surface is 225 cm 2 The above plate-shaped injection molded product, The plate-shaped injection-molded product contains a methacrylic resin composition, The amount of methyl methacrylate (MMA) contained in the plate-shaped injection molded article is 1600 to 6000 ppm by mass. The plate-shaped injection molded product has a first main surface with a projected area of ​​225 cm 2 Although the plate-shaped injection-molded product has a large projected area of ​​the main surface, yellowing and poor appearance of the molded product are reduced.

[0013] The plate-shaped injection-molded product of this embodiment has a second main surface opposite to the first main surface. The second main surface may be flat or may have a plurality of fine convex portions, but is preferably flat. Note that when the second main surface has a plurality of fine convex portions, the description of the fine convex portions on the first main surface described below can be used for the description of the fine convex portions on the second main surface.

[0014] The shape and other features of the plate-shaped injection molded product of this embodiment will be described in detail below.

[0015] The plate-shaped injection-molded article of this embodiment is composed of fine convex portions and a plate-shaped portion, but it is preferable that there is no adhesive interface between the fine convex portions and the plate-shaped portion and that the article is composed of a single resin. If a molded article without an adhesive interface is produced by injection molding the fine convex portions and the plate-shaped portion with a single resin composition, it is possible to obtain a plate-shaped injection-molded article without deterioration in appearance due to peeling at the adhesive interface, etc.

[0016] In this embodiment, the shape of the minute convex-shaped portion formed on at least the first main surface (hereinafter, sometimes referred to as "minute convex shape" or "convex shape") is not particularly limited, and examples thereof include polygonal pyramids such as triangular pyramids, square pyramids, and pentagonal pyramids, curved cones such as cones, elliptical cones, semi-cones, 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, semi-conical truncated cones, semi-elliptical truncated cones, and oval truncated cones ( Examples of suitable shapes include curved frustums such as a truncated cone (a truncated cone having a cross section shaped like a pair of parallel straight lines connected by a semicircle), triangular prisms, quadrangular prisms (cubes, rectangular parallelepipeds, etc.), polygonal prisms such as pentagonal prisms, circular cylinders, elliptical cylinders, semicircular cylinders, semi-elliptical cylinders, and oblong cones (a cylinder 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. The side surfaces of the convex portions may be flat or curved. The shape of these fine convex portions may be of only one type or a combination of multiple types, but it is preferable that the shape is of only one type.

[0017] Fig. 2 is a partial cross-sectional view showing an example of a plate-shaped injection-molded product of this embodiment, in which the fine convex portions 14 on the first main surface 11 having the fine convex portions are triangular pyramid-shaped. Fig. 4 is a partial cross-sectional view showing an example of a plate-shaped injection-molded product of this embodiment, in which the fine convex portions 24 are truncated quadrangular pyramid-shaped. In each figure, a and b represent the height a and pitch b of the fine convex portions, respectively. The fine convex portions may be arranged in a linear, curved, dot-like pattern, or the like. The fine convex portions 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 injection-molded product in which the fine convex portions are arranged only in a partial area of ​​the first main surface, as viewed from the first main surface side.

[0018] In this embodiment, on the main surface having the fine convex portions, the ratio b / a of the pitch b of the fine convex portions to the height a is preferably 0.1 to 2.0, more preferably 0.2 to 2.0, and even more preferably 0.3 to 2.0. 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. Furthermore, b / a may be 1.5 or less, 1.2 or less, 1.0 or less, 0.9 or less, or 0.8 or less. b / a is the average value of the height a and pitch b measured for five or more minute convex portions. Therefore, as long as b / a is within the above range, the height and pitch of each minute convex portion may be changed arbitrarily.

[0019] The height a of the minute convex portions is 50 to 700 μm, preferably in the range of 50 to 650 μm, more preferably 200 to 600 μm, and even more preferably 300 to 550 μm. When the height a of the minute convex portions is in the above range, warpage of the molded article tends to be effectively reduced by the present invention. The pitch b of the fine convex portions is preferably in the range of 100 to 500 μm, more preferably 150 to 450 μm, and even more preferably 180 to 400 μm. When the pitch b of the fine convex portions is in the above range, warpage of the molded product tends to be effectively reduced. In this specification, the height a of the fine convex portions 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 the height a is the average value of the heights of five or more fine convex portions. For example, as shown in FIG. 2, if the fine convex portions are conical, the height a refers to the height to the apex of the cone. When the first main surface does not have a flat portion parallel to the second main surface, the height a of the fine convex portions may be the highest value among the heights in the thickness direction of the fine convex portions relative to the average thickness of the molded article. In addition, in this specification, the pitch b of the fine convex portions means the distance between the centers of two adjacent convex portions when the fine convex portions 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 fine convex portions. The height a and pitch b of the minute convex portions can be measured visually 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.

[0020] When observed from above with the first main surface as the upper surface, the size of the planar shape of the minute convex portions is preferably 0.1 to 600 μm in diameter, more preferably 0.5 to 500 μm, and even more preferably 1 to 400 μm. In addition, when the planar shape of the minute convex portion is a line pattern, the length refers to the width in the direction perpendicular to the line direction, and in other cases when the planar shape is a shape other than a circle, the length refers to the diameter of the circumscribed circle. The diameter of the planar shape of the minute convex portion can be measured visually from an observation image obtained using an optical microscope, electron microscope, digital microscope, etc. The size (height and diameter in plan view) of the minute convex portions may be the same for all the minute convex portions or may be different for all the minute convex portions.

[0021] The overall shape of the molded article of this embodiment is not particularly limited as long as it has a plurality of fine convex portions on at least one main surface (first main surface). The other main surface (second main surface) is preferably flat, plate-shaped, or approximately plate-shaped. Examples of shapes (shapes in plan view) when observed from above with the first main surface having the minute convex portions as the upper surface 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 fine convex shapes is taken as 100%, the area of ​​the flat portion of the second main surface on the back side is preferably 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.

[0022] In this embodiment, the projected area of ​​the first main surface of the molded article is 225 cm 2 Above 225-2500 cm 2 may be 225 to 1000 cm 2 When the projected area of ​​the first main surface is within the above range, a molded article with a good appearance can be obtained without mold release defects. In addition, the projected area of ​​the first main surface may be 250 cm or less. 2 More than 300cm 2 More than 350cm 2 More than 400cm 2 It may be more than that. In this specification, the projected area of ​​the first main surface refers to the area of ​​the shape (plan view shape) when the molded article is placed with the first main surface facing up and the first main surface is observed from above. For example, the molded article in Figure 1(A) has an area of ​​552 cm 2 (=230mm x 240mm), and the molded product in Figure 3(A) is 702cm 2 (=260mm×270mm).

[0023] In this embodiment, the thickness of the molded article, excluding the fine convex portions, 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, and the thicker the thickness, although advantageous for warpage control, it takes longer to cool during molding, which creates a 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. Therefore, a thickness within the above range is preferable. The size of each main surface of the molded article is not particularly limited and may be set according to the purpose.

[0024] The plate-shaped injection-molded article of this embodiment preferably has a packing degree of 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 fine convex portions. The filling degree is a value calculated from the height a of the fine convex portions and the depth of the concave portions in the first mold for forming the fine convex portions 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 a of the minute convex part of the molded product) / (depth of the concave part of the mold)

[0025] When the plate-shaped injection-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 fine convex portions are formed is calculated when the surface on which the fine convex portions are formed is viewed in plan view with the surface on which the fine convex portions are formed being the upper surface (for example, in Figure 1, the shaping surface region is 210 mm square, so the square root is 210 mm), and if the amount of warpage 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, 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.

[0026] In the plate-shaped injection-molded product of this embodiment, the in-plane retardation of the main surface having the fine convex portions is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 20 nm or less. When the in-plane retardation is 100 nm or less, the optical properties are less likely to be adversely affected. The in-plane retardation can be measured by the method described in the examples below.

[0027] In this embodiment, the amount of methyl methacrylate (MMA) contained in the plate-shaped injection-molded product is 1600 to 6000 ppm by mass, preferably 1800 to 5000 ppm by mass, and more preferably 2000 to 4000 ppm by mass. When the amount of methyl methacrylate (MMA) contained in the molded product is 6000 ppm by mass or less, the molded product tends to have low yellowness and good appearance. On the other hand, when the amount of methyl methacrylate (MMA) contained in the molded product is 1600 ppm by mass or more, the molded product tends to have a good filling degree of fine convex portions and low yellowness. The amount of methyl methacrylate (MMA) can be measured by the method described in the Examples below.

[0028] The plate-shaped injection-molded article of this embodiment preferably has a yellowness index (YI) of 10.0 or less when a 12 mass % chloroform solution containing the molded article is obtained by dissolving the plate-shaped injection-molded article in chloroform. The yellowness index (YI) is preferably 3.0 to 10.0, more preferably 3.0 to 9.0, and even more preferably 3.0 to 8.0. A yellowness index (YI) within the above range tends to provide a molded article with low yellowness and good appearance. The yellowness index (YI) can be measured by the method described in the Examples below.

[0029] The plate-shaped injection-molded product of the present embodiment is preferably obtained by heating the surface temperature of a mold to a temperature equal to or higher than the glass transition temperature (Tg) of the methacrylic resin composition, and then injecting and filling the methacrylic resin composition into the mold.

[0030] (Methacrylic resin composition) The methacrylic resin composition contained in the plate-shaped injection-molded product of this embodiment contains a methacrylic resin, and may optionally contain additives in addition to the methacrylic resin. It may also contain other thermoplastic resins, rubbery polymers, etc., other than the methacrylic resin.

[0031] -Methacrylic resin- The properties of the methacrylic resin used in this embodiment will be described below.

[0032] 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 methacrylic resins include heat-resistant methacrylic resins having structural units derived from methyl methacrylate and lactone rings or glutarimide in the main chain, and methyl methacrylate and low-moisture-absorbing methacrylic resins, etc. These may be used alone or in a blend of two or more. The phrase "mainly composed of structural units derived from methyl methacrylate" means that structural units derived from methyl methacrylate account for 50% by mass or more of the structural units in the methacrylic resin.

[0033] In view of transparency and heat resistance, the methacrylic resin in this embodiment is preferably a methacrylic resin having a structural unit with a ring structure. The structural unit having a ring structure preferably contains at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, an aromatic vinyl structural unit, an alicyclic vinyl structural unit, and a lactone ring structural unit. Furthermore, it is particularly preferred that the structural unit having a ring structure contains a structural unit derived from an N-substituted maleimide monomer, since this makes it easy to highly control optical properties such as intrinsic birefringence and photoelastic coefficient without blending with other thermoplastic resins.

[0034] --Structural units derived from N-substituted maleimide monomers-- Next, the structural unit derived from the N-substituted maleimide monomer will be described. The structural unit derived from the N-substituted maleimide monomer may be at least one structural unit selected from the group consisting of structural units represented by the following general formula (1) and structural units represented by the following general formula (2), and is preferably formed from both structural units represented by the following general formula (1) and the following general formula (2).

[0035] [ka] In general formula (1), R 1 represents an arylalkyl group having 7 to 14 carbon atoms or an aryl group having 6 to 14 carbon atoms, and R 2 and R 3 each independently represents a hydrogen atom, an oxygen atom, a sulfur atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms. Also, R 2 or R 3 When is an aryl group, R 2 or R 3 may contain a halogen atom as a substituent. Also, R 1 may be substituted with a substituent such as a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a nitro group, or a benzyl group. [ka] In general formula (2), R 4 represents a hydrogen atom, a cycloalkyl group having 3 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms; R 5 and R 6 each independently represents a hydrogen atom, an oxygen atom, a sulfur atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

[0036] In the above general formula (1), the arylalkyl group having 7 to 14 carbon atoms is not limited, but examples thereof include a benzyl group, a phenylethyl group, a phenylpropyl group, a naphthylmethyl group, a naphthylethyl group, and a naphthylpropyl group.

[0037] In the above general formulas (1) and (2), the aryl group having 6 to 14 carbon atoms is not limited, but examples thereof include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a biphenyl group, an anthracenyl group, and a phenanthryl group.

[0038] In the above general formula (1) and general formula (2), the alkyl group having 1 to 12 carbon atoms may be linear or branched and is not particularly limited, but examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a 2-methylbutyl group, an n-pentyl group, a 2-pentyl group, a 3-pentyl group, a 2,2-dimethylpropyl group, an n-hexyl group, a heptyl group, an n-octyl group, a 1,1,3,3-tetramethylbutyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group.

[0039] In the above general formula (1), examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0040] In the above general formula (1), the alkoxy group having 1 to 6 carbon atoms is not limited, but examples thereof include a methoxy group, an ethoxy group, an n-butoxy group, and a methoxyethoxy group.

[0041] In the above general formula (2), examples of the cycloalkyl group having 3 to 12 carbon atoms include, but are not limited to, a cyclopropyl group, a cyclopropylmethyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclohexylmethyl group, a trimethylcyclohexyl group, a thujyl group, a norbornyl group, a bornyl group, a norcaryl group, a caryl group, a menthyl group, a norpinyl group, a pinyl group, a 1-adamantyl group, and a 2-adamantyl group.

[0042] Specific examples of the structural units represented by the above general formula (1) and the above general formula (2) are shown below. Examples of the monomers (N-arylmaleimides, N-aromatic substituted maleimides, etc.) that form the structural unit represented by general formula (1) include N-phenylmaleimide, N-benzylmaleimide, N-(2-chlorophenyl)maleimide, N-(4-chlorophenyl)maleimide, N-(4-bromophenyl)maleimide, N-(2-methylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, N-(2-ethylphenyl)maleimide, N-(2-methoxyphenyl)maleimide, N-(2-nitro ... N-(4-benzylphenyl)maleimide, N-(2,4,6-trimethylphenyl)maleimide, N-(4-benzylphenyl)maleimide, N-(2,4,6-tribromophenyl)maleimide, N-naphthylmaleimide, N-anthracenylmaleimide, 3-methyl-1-phenyl-1H-pyrrole-2,5-dione, 3,4-dimethyl-1-phenyl-1H-pyrrole-2,5-dione, 1,3-diphenyl-1H-pyrrole-2,5-dione, 1,3,4-triphenyl-1H-pyrrole-2,5-dione, and the like. Among these monomers, N-phenylmaleimide and N-benzylmaleimide are preferred because they have excellent heat resistance and optical properties such as birefringence. These monomers may be used alone or in combination of two or more.

[0043] Examples of the monomer that forms the structural unit represented by general formula (2) include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N -laurylmaleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, 1-cyclohexyl-3-methyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-dimethyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3-phenyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-diphenyl-1H-pyrrole-2,5-dione, and the like. Among these monomers, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, and N-cyclohexylmaleimide are preferred because they provide excellent weather resistance to the methacrylic resin, and N-cyclohexylmaleimide is particularly preferred because it has excellent low moisture absorption, which is a requirement for optical materials in recent years. These monomers may be used alone or in combination of two or more.

[0044] In the methacrylic resin in the methacrylic resin composition, it is particularly preferable to use a structural unit represented by general formula (1) in combination with a structural unit represented by general formula (2), in order to develop highly controlled birefringence characteristics. The molar ratio (X1 / X2) of the content (X1) of the structural unit represented by general formula (1) to the content (X2) of the structural unit represented by general formula (2) is preferably more than 0 and not more than 15, more preferably more than 0 and not more than 10. When the molar ratio (X1 / X2) is within this range, the plate-shaped injection-molded article of this embodiment maintains its transparency, does not yellow, and exhibits good heat resistance and good photoelastic properties without impairing environmental resistance.

[0045] The content of the structural units derived from the N-substituted maleimide monomer is preferably in the range of 5 to 40% by mass, and more preferably in the range of 5 to 35% by mass, based on 100% by mass of the methacrylic resin. When the content of the structural units derived from the N-substituted maleimide monomer is within this range, the methacrylic resin exhibits a more sufficient improvement in heat resistance, and also exhibits more favorable improvements in weather resistance, low water absorption, and optical properties. Note that keeping the content of the structural units derived from the N-substituted maleimide monomer to 40% by mass or less is effective in preventing a decrease in the physical properties of the methacrylic resin due to a decrease in the reactivity of the monomer components during the polymerization reaction and an increase in the amount of unreacted remaining monomer. Furthermore, by appropriately adjusting the content of structural units derived from N-substituted maleimide monomers within the above range, birefringence caused by orientation or residual stress during molding can be reduced, and a plate-shaped injection-molded product having a main surface with fine convex portions and an in-plane retardation of 100 nm or less can be obtained. The optimal content of structural units derived from N-substituted maleimide monomers varies depending on the type of N-substituted maleimide. For example, when methyl methacrylate is used as the methacrylic acid ester monomer and N-phenylmaleimide and N-cyclohexylmaleimide are used as the N-substituted maleimide monomers, it is preferable to adjust the content within the ranges of 79 to 83 mass% of structural units derived from methyl methacrylate, 6 to 8 mass% of structural units derived from N-phenylmaleimide, and 11 to 13 mass% of structural units derived from N-cyclohexylmaleimide.

[0046] The methacrylic resin having a structural unit derived from an N-substituted maleimide monomer may contain a structural unit derived from another monomer copolymerizable with the methacrylic acid ester monomer and the N-substituted maleimide monomer, as long as the object of the present invention is not impaired. For example, the other copolymerizable monomers include aromatic vinyls; unsaturated nitriles; acrylic esters having a cyclohexyl group, a benzyl group, or an alkyl group having 1 to 18 carbon atoms; glycidyl compounds; and unsaturated carboxylic acids. Examples of the aromatic vinyl include styrene, α-methylstyrene, and divinylbenzene. Examples of the unsaturated nitrile include acrylonitrile, methacrylonitrile, and ethacrylonitrile. Examples of the acrylic ester include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, and butyl acrylate. Examples of the glycidyl compound include glycidyl (meth)acrylate. Examples of the unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and half-esters or anhydrides of these acids. The structural unit derived from the other copolymerizable monomer may be of only one type, or may be of two or more types.

[0047] The content of structural units derived from these other copolymerizable monomers is preferably 0 to 10% by mass, more preferably 0 to 9% by mass, and even more preferably 0 to 8% by mass, based on 100% by mass of the methacrylic resin. If the content of the structural units derived from other copolymerizable monomers is within this range, the molding processability and mechanical properties of the resin can be improved without impairing the inherent effect of introducing a ring structure, which is preferable.

[0048] The content of the structural unit derived from the N-substituted maleimide monomer and the content of the structural unit derived from other copolymerizable monomers are as follows: 1 H-NMR measurement and 13 It can be determined by C-NMR measurement. 1 H-NMR measurement and 13 C-NMR measurement can be carried out, for example, using CDCl3 or DMSO-d6 as a measurement solvent at a measurement temperature of 40°C.

[0049] --Glutarimide structural unit-- Examples of methacrylic resins having glutarimide structural units include those described in JP 2006-249202 A, JP 2007-009182 A, JP 2007-009191 A, JP 2011-186482 A, and Republished Patent Publication No. 2012 / 114718, and can be formed by the methods described in these publications. The glutarimide structural units constituting the methacrylic resin may be formed after polymerization of the resin. Specifically, the glutarimide structural unit may be represented by the following general formula (3).

[0050] [ka] In the above general formula (3), preferably R 7 and R 8 are each independently a hydrogen atom or a methyl group, and R 9 is a hydrogen atom, a methyl group, a butyl group, or a cyclohexyl group, and more preferably, R 7 is a methyl group, and R 8 is a hydrogen atom, and R 9 is a methyl group. The glutarimide-based structural unit may include only one type, or may include multiple types.

[0051] In the methacrylic resin having glutarimide structural units, the content of the glutarimide structural units is preferably in the range of 3 to 70% by mass, and more preferably in the range of 3 to 60% by mass, with the methacrylic resin being 100% by mass. When the content of the glutarimide structural unit is within the above range, a resin having good moldability, heat resistance, and optical properties can be obtained, which is preferable. Furthermore, by appropriately adjusting the content of the glutarimide-based structural unit within this range, it is possible to reduce birefringence caused by orientation during molding or residual stress, and to obtain a plate-shaped injection-molded product having a first main surface with a fine convex portion and an in-plane retardation of 100 nm or less. 7 ~R 9 The optimum content of glutarimide structural units varies depending on the type of substituent of R. 7 and R 8 is a hydrogen atom, R 9 When is a methyl group, if the content of glutarimide structural units is in the range of 3 to 10 mass %, birefringence caused by orientation or residual stress during molding is reduced, and it is possible to obtain a plate-shaped injection-molded product having a main surface with a fine convex portion and an in-plane retardation of 100 nm or less. The content of glutarimide structural units in the methacrylic resin can be determined using the method described in the aforementioned patent document.

[0052] The methacrylic resin having glutarimide structural units may further contain aromatic vinyl monomer units, if necessary. The aromatic vinyl monomer is not particularly limited, but examples thereof include styrene and α-methylstyrene, with styrene being preferred.

[0053] The content of aromatic vinyl units in the methacrylic resin having glutarimide structural units is not particularly limited, but is preferably 0 to 20% by mass, with the methacrylic resin having glutarimide structural units being 100% by mass. When the content of the aromatic vinyl unit is within the above range, it is possible to achieve both heat resistance and excellent photoelasticity, which is preferable. For example, when a resin is obtained by glutarimidating a methyl methacrylate-styrene copolymer obtained by copolymerizing methyl methacrylate as the methacrylic acid ester monomer and styrene as the aromatic vinyl monomer, by adjusting the ratio of structural units derived from methyl methacrylate, structural units derived from styrene, and glutarimide-based structural units to within the ranges of 65 to 90 mass %, 5 to 15 mass % and 5 to 20 mass %, it is possible to reduce birefringence caused by orientation and residual stress during molding and to obtain a plate-shaped injection-molded product having a main surface with a fine convex shape portion and an in-plane retardation of 100 nm or less.

[0054] --Aromatic vinyl structural unit-- The aromatic vinyl structural unit is not particularly limited, but examples thereof include structural units derived from styrene and α-methylstyrene, with styrene-derived structural units being preferred.

[0055] --Alicyclic vinyl structural unit-- The alicyclic vinyl structural unit can be formed by the methods described in, for example, JP-A Nos. 2006-291184, 2006-291184, 2014-77043, and 2014-77044.

[0056] --Lactone ring structural unit-- Methacrylic resins having lactone ring structural units can be formed by the methods described in, for example, JP-A Nos. 2001-151814, 2004-168882, 2005-146084, 2006-96960, 2006-171464, 2007-63541, 2007-297620, and 2010-180305.

[0057] The lactone ring structural unit constituting the methacrylic resin may be formed after polymerization of the resin. The lactone ring structural unit in this embodiment is preferably a six-membered ring because it has excellent stability of the ring structure. As the 6-membered lactone ring structural unit, for example, a structure represented by the following general formula (4) is particularly preferred.

[0058] [ka]

[0059] In the above general formula (4), R 10 , R 11 and R 12 are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms. Examples of organic residues include saturated aliphatic hydrocarbon groups (e.g., alkyl groups) having 1 to 20 carbon atoms, such as a methyl group, an ethyl group, or a propyl group; unsaturated aliphatic hydrocarbon groups (e.g., alkenyl groups) having 2 to 20 carbon atoms, such as an ethenyl group or a propenyl group; aromatic hydrocarbon groups (e.g., aryl groups) having 6 to 20 carbon atoms, such as a phenyl group or a naphthyl group; and groups in which one or more hydrogen atoms in these saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, or aromatic hydrocarbon groups have been substituted with at least one group selected from the group consisting of a hydroxy group, a carboxyl group, an ether group, and an ester group.

[0060] The lactone ring structural unit can be formed, for example, by copolymerizing an acrylic acid monomer having a hydroxy group with a methacrylic acid ester monomer such as methyl methacrylate to introduce a hydroxy group and an ester group or a carboxyl group into the molecular chain, and then causing dealcoholization (esterification) or dehydration condensation (hereinafter also referred to as a "cyclization condensation reaction") between the hydroxy group and the ester group or the carboxyl group.

[0061] Examples of the acrylic acid monomer having a hydroxy group used in the polymerization include 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, alkyl 2-(hydroxymethyl)acrylates (e.g., methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, t-butyl 2-(hydroxymethyl)acrylate), alkyl 2-(hydroxyethyl)acrylates, and the like. Preferred are 2-(hydroxymethyl)acrylic acid and alkyl 2-(hydroxymethyl)acrylates, which are monomers having a hydroxyalkyl moiety, and particularly preferred are methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate.

[0062] The content of the lactone ring structural unit in the methacrylic resin having the lactone ring structural unit is preferably 5 to 40 mass %, more preferably 5 to 35 mass %, relative to 100 mass % of the methacrylic resin. When the content of the lactone ring structural unit is within this range, the effects of introducing a ring structure, such as improved solvent resistance and surface hardness, can be achieved while maintaining moldability. Furthermore, by appropriately adjusting the content of the lactone ring structural unit within this range, birefringence caused by orientation and residual stress during molding can be reduced, and a plate-shaped injection-molded product can be obtained in which the first main surface has a fine convex portion and an in-plane retardation of 100 nm or less. The content of lactone ring structures in the methacrylic resin can be determined by the method described in the aforementioned patent document (JP-A No. 2001-151814, etc.).

[0063] The methacrylic resin having a lactone ring structural unit may have a structural unit derived from another monomer copolymerizable with the above-mentioned methacrylic acid ester monomer and acrylic acid monomer having a hydroxy group. Examples of such copolymerizable other monomers include monomers having a polymerizable double bond, such as styrene, vinyltoluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, ethylene, propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinylpyrrolidone, and N-vinylcarbazole. The copolymer may contain only one type of these other monomers (structural units), or may contain two or more types.

[0064] The content of structural units derived from these other copolymerizable monomers is preferably 0 to 20% by mass relative to 100% by mass of the methacrylic resin, and from the viewpoint of weather resistance, it is more preferably less than 10% by mass, and even more preferably less than 7% by mass. The methacrylic resin in the present embodiment may have only one type of structural unit derived from the other copolymerizable monomer, or may have two or more types.

[0065] -Methacrylic resin manufacturing method- The method for producing the methacrylic resin of this embodiment will be described below.

[0066] In the production method of this embodiment, the polymerization method can be a batch method, a semi-batch method, or a continuous method. Here, the batch method 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 method 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 method 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 method 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] -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.

[0075] --Antioxidants-- The methacrylic resin composition contained in the plate-shaped injection-molded product of this embodiment preferably contains an antioxidant that suppresses deterioration and discoloration 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. The methacrylic resin composition contained in the plate-shaped injection-molded product of this embodiment is preferably maintained at a high temperature in the mold cavity and allowed to cool for an appropriate period of time in order to improve the transferability of the fine convex shaped portions of the first mold while highly controlling distortion and warpage of the molded product surface. 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.

[0076] 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, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene bis[ 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,5H)-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, etc. 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.

[0077] 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: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, manufactured by 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, BASF), Irganox 3125 (Irganox 3125, BASF), ADK STAB AO-60 (pentaerythritol tetrakis[3-(3, 5-di-t-butyl-4-hydroxyphenyl)propionate, manufactured by ADEKA Corporation), 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, manufactured by ADEKA Corporation), Sumilizer BHT (Sumilizer 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, and the like are preferred from the viewpoint of the effect of imparting thermal stability to the methacrylic resin composition. These may be used alone or in combination of two or more.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] --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.

[0082] 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.

[0083] 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. When the content of the ultraviolet absorber is within this range, an excellent balance of ultraviolet absorption performance, moldability, etc. is achieved.

[0084] --Mold release agent-- The methacrylic resin composition contained in the plate-shaped injection-molded product of this embodiment may contain a mold release agent, which may include, but is 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.

[0085] 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.

[0086] 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, relative to 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.

[0087] --Other thermoplastic resins-- The methacrylic resin composition contained in the plate-shaped injection-molded product of this embodiment may contain a thermoplastic resin other than the methacrylic resin for the purpose 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 plate-shaped injection-molded product of this embodiment.

[0088] 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.

[0089] From the viewpoint of heat resistance, the methacrylic resin composition contained in the plate-shaped injection-molded article of this embodiment preferably has a glass transition temperature (Tg) of 115 to 160°C. When the glass transition temperature (Tg) is 115°C or higher, the occurrence of warpage and convex deformation is reduced in reliability tests such as high-temperature aging tests, and optical properties tend not to be adversely affected. On the other hand, when the glass transition temperature (Tg) is 160°C or lower, melt processing at extremely high temperatures can be avoided, thermal decomposition of the resin, etc. is suppressed, and a plate-shaped injection-molded article with good appearance tends to be obtained. From the viewpoint of further achieving the above-mentioned effects, the glass transition temperature (Tg) is preferably 115 to 145°C, more preferably 120 to 145°C, and particularly preferably 120 to 140°C. 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.

[0090] The methacrylic resin composition used in this embodiment preferably has a low viscosity at the time of injection and a moderately high fluidity in order to improve the transferability of the fine convex portions. -1In 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. When the melt viscosity is 20 Pa·sec or higher, it becomes easier to control the flow of the resin during injection, and it tends to be easier to mold the desired shape. On the other hand, when the melt viscosity is 235 Pa·sec or lower, the resin has good fluidity and good processability, and molding defects such as poor filling tend to be less likely to occur. 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.

[0091] The methacrylic resin composition used in this embodiment preferably has a large tensile elongation at break to prevent cracking during mold release and resin residue in the mold. The tensile elongation at break is preferably 1.2% or more, more preferably 1.5% or more, and even more preferably 2.0% or more. The tensile elongation at break is a value measured in accordance with ISO 527, and specifically, can be measured by the method described in the examples below.

[0092] The methacrylic resin composition used in this embodiment preferably has a terminal double bond ratio of 2.0 to 5.0%, more preferably 2.2 to 4.0%, and even more preferably 2.5 to 3.8%, in order to suppress thermal decomposition during molding processing. When molding a molded article with a large projected area, molding is often performed by increasing the processing temperature to improve the fluidity of the resin. When the processing temperature is high, the resin tends to decompose due to heat, which tends to cause molding defects such as yellowing and silver discoloration of the molded article. However, when the terminal double bond ratio of the methacrylic resin composition is within the above range, the yellowness is small, and molded articles with good appearance tend to be obtained without molding defects. The terminal double bond ratio of a methacrylic resin composition can be controlled by adjusting the amount of a chain transfer agent during polymerization or by hydrogenating the double bond moiety, but hydrogenating the double bond moiety by a hydrogenation reaction hydrogenates not only the double bonds at the polymer terminals but also the double bond moieties within the polymer. As a result, the heat resistance of the resin decreases and it becomes more susceptible to thermal decomposition during processing, so it is preferable to control the terminal double bond ratio by adjusting the amount of a chain transfer agent. The terminal double bond ratio can be measured by the method described in the Examples below.

[0093] The methacrylic resin composition contained in the light guide of this embodiment preferably has a weight-average molecular weight (Mw) of 90,000 to 170,000, more preferably 95,000 to 160,000, and even more preferably 100,000 to 150,000, as measured by gel permeation chromatography (GPC) in terms of polymethyl methacrylate. When Mw is 90,000 or more, there is a tendency for a plate-shaped injection-molded product to be obtained that has a good appearance without the occurrence of defects or cracks in the fine convex portions during molding. On the other hand, when Mw is 170,000 or less, there is a tendency for a plate-shaped injection-molded product to be obtained that has an excellent balance between mechanical strength and fluidity and has a good appearance during molding processing. The weight average molecular weight of the methacrylic resin composition can be measured by the method described in the examples below.

[0094] [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.

[0095] (Method for manufacturing plate-shaped injection molded products) The method for producing a plate-shaped injection-molded product of this embodiment is characterized in that the surface temperature of a mold is heated to a temperature equal to or higher than the glass transition temperature (Tg) of a methacrylic resin composition, and then the methacrylic resin composition is injected into the mold to obtain a plate-shaped injection-molded product. The plate-shaped injection-molded product produced in this manner does not have an adhesive interface and is composed of a single resin composition. More specifically, the method for producing a plate-shaped injection-molded product of this embodiment includes injection molding using a first mold on the side that forms the first main surface (the main surface having a plurality of fine convex portions) of the plate-shaped injection-molded product and a second mold on the side that forms the second main surface (the main surface that is flat) of the plate-shaped injection-molded product, and it is preferable that the maximum temperature Tmax of the first mold be (Tg + 40)°C to (Tg + 70)°C (Tg is the glass transition temperature of the methacrylic resin composition) and the temperature of the second mold be (Tmax - 90)°C to (Tmax - 65)°C. The detailed conditions for injection molding in the method for producing a plate-shaped injection-molded product of this embodiment will be described below.

[0096] In this embodiment, the temperature setting from the nozzle tip to the center of the injection molding machine cylinder is set to (Tg + 120)°C to (Tg + 200)°C relative to the glass transition temperature (Tg) of the methacrylic resin composition used. This allows the molten resin to flow sufficiently and enables molding while suppressing deterioration due to thermal decomposition of the resin. The temperature is preferably (Tg + 130)°C to (Tg + 180)°C, more preferably (Tg + 140)°C to (Tg + 170)°C, and even more preferably (Tg + 150)°C to (Tg + 160)°C. Keeping the molding temperature within the above ranges can suppress thermal decomposition of the resin while improving its durability, which tends to facilitate the production of plate-shaped injection-molded products with good color tone and fine feature transfer rate.

[0097] In this embodiment, the maximum temperature Tmax of the first mold when the resin is injected into the mold is preferably controlled to a temperature range of (Tg + 40) ° C. to (Tg + 70) ° C. in order to improve the transferability (moldability) of the fine convex portions. The maximum temperature Tmax of the first mold is more preferably (Tg + 45) ° C. to (Tg + 65) ° C., and even more preferably (Tg + 50) ° C. to (Tg + 60) ° C. When Tmax is (Tg + 70) ° C. or less, transferability and mold releasability tend to be good. On the other hand, when Tmax is (Tg + 40) ° C. or more, transferability tends to be good. When molding a large molded product having fine convex portions on its main surface, it is preferable to set the maximum temperature Tmax of the first mold high to improve the transferability of the fine convex portions. However, setting Tmax too high increases the temperature rise time and the molding cycle. As a result, thermal decomposition of the resin is likely to proceed, so it is preferable to set Tmax within the above range.

[0098] In this embodiment, when the maximum temperature of the first mold when the resin is injected into the mold is Tmax, the temperature of the second mold is preferably set to (Tmax-90)°C to (Tmax-65)°C. The temperature of the second mold is more preferably (Tmax-85)°C to (Tmax-70)°C, and particularly preferably (Tmax-80)°C to (Tmax-75)°C. When the temperature of the second mold is (Tmax-90)°C or higher, the amount of warpage of the molded article tends to be small. On the other hand, when the temperature is (Tmax-65)°C or lower, the amount of warpage of the molded article tends to be small, and 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, so that a plate-shaped injection-molded article with good appearance can be obtained.

[0099] In this embodiment, the first mold is preferably cooled after heating. The minimum temperature Tmin of the first mold upon 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. When Tmin is (Tg-75)°C or higher, it is possible to prevent the molding cycle from becoming extremely long and suppress thermal degradation of the resin in the cylinder. On the other hand, when Tmin is (Tg-45)°C or lower, the amount of warpage of the molded product tends to be small.

[0100] In the present 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 heated by passing electricity through it, 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 a water or oil flow path is provided in the mold and the mold is cooled by a medium such as water or oil.

[0101] 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 as described below, maintaining the mold temperature at a high temperature is more effective in improving transferability. 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 appropriately set while observing the state of the molded product, such as by raising or lowering the temperature at a constant rate, slowing the rate of temperature increase or decrease, or holding at a predetermined temperature for a certain period of time. In order to improve the transfer of the fine convex shapes, 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, since a short holding time will cause birefringence due to the formation of a skin layer, it is preferable to slow the rate of temperature decrease in order to suppress this.

[0102] It is preferable to apply a release treatment to the surface of the mold. Organic or inorganic release coatings may be used as the release treatment for the mold surface. For example, organic coatings such as fluorine-based, silicone-based, and wax-based coatings, and inorganic coatings such as DLC-based, Cr-based, and Ti-based coatings can be used. Organic and inorganic release coatings can also be used in combination. The release coating can be formed on the mold by a known wet or dry method. However, when the fine convex portions of the mold are deep or have a complex shape, film formation by PVD (Physical Vapor Deposition), such as vacuum deposition, sputtering, and ion plating, tends to be unable to form a coating deep into the fine convex portions. Because this method allows for the application of a release coating deep into the fine convex portions and improves the releasability of molded products, it is preferable to use a release agent in which a release component is dissolved or dispersed in a solvent, then applied or sprayed onto the mold, and then dried or cured to form a release film.

[0103] Applications of the plate-shaped injection-molded product of this embodiment include, but are not limited to, various optical components such as Fresnel lenses, lenticular lenses, light guide plates, components for aerial displays, diffractive optical elements, anti-reflection sheets, anti-glare sheets, and cell culture sheets. Among these, components for aerial displays are preferred. [Example]

[0104] The present invention will be explained below by way of specific examples and comparative examples, but is not limited to these.

[0105] [Raw materials] The raw materials used in the examples and comparative examples described later are shown below.

[0106] [[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

[0107] [[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.

[0108] [[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.

[0109] [[Chain transfer agent]] n-Octyl mercaptan: Chevron Phillips Chemical Company n-Dodecyl mercaptan: Fujifilm Wako Pure Chemical Industries, Ltd.

[0110] [[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. Adeka 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.

[0111] (Evaluation of properties of methacrylic resin compositions) The methods for measuring the properties of the methacrylic resin composition will be described below.

[0112] (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.

[0113] (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.

[0114] (3) Measurement of tensile elongation at break 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 break elongation (%).

[0115] (4) Measurement of terminal double bond ratio In order to measure the terminal double bond ratio of the methacrylic resin composition, dissolution and reprecipitation were carried out as a pretreatment to remove low molecular weight materials. 500 mg of the pellet was weighed and dissolved in 5 ml of chloroform, and then 30 ml of methanol was added to precipitate the polymer. The precipitated polymer was collected and dried in a vacuum dryer at 40 °C for 5 hours. The polymer was then dissolved in CDCl3 at 100 mg / ml to prepare a sample for NMR measurement. 1 H-NMR was measured, and the terminal double bond ratio was calculated according to the following formula using the integrated intensity of the peaks of the terminal double bonds (resonance frequencies of 5.5 ppm and 6.1 ppm), the integrated intensity of the peak of the methoxy group in the main chain in the MMA unit (resonance frequency of 3.6 ppm), and the number average molecular weight (Mn) of the methacrylic resin composition measured using the method described below.

number

[0116] (5) Measurement of weight average molecular weight and number average molecular weight of methacrylic resin composition The weight average molecular weight (Mw) and number average molecular weight (Mn) of the methacrylic resin composition were measured using the following apparatus and conditions. Measurement equipment: Tosoh Corporation gel permeation chromatography (HLC-8320GPC) Measurement conditions: Columns: One TSKguardcolumn SuperH-H, two TSKgel SuperHM-M, and one TSKgel SuperH2500 were connected in series. Column temperature: 40°C, developing solvent: tetrahydrofuran, flow rate: 0.6 mL / min, 2,6-di-t-butyl-4-methylphenol (BHT) was added as an internal standard at 0.1 g / L. Detector: RI (differential refractive index) detector Detection sensitivity: 3.0 mV / min Sample: 0.02 g of resin light guide in 20 mL of tetrahydrofuran Injection volume: 10μL Standard samples for calibration curve: The following ten types of polymethyl methacrylate (PMMA Calibration Kit MM-10, manufactured by Polymer Laboratories) with known monodisperse weight peak molecular weights and different molecular weights were used. Weight peak molecular weight (Mp) Standard sample 1 1,916,000 Standard sample 2 625,500 Standard sample 3 298,900 Standard sample 4 138,600 Standard sample 5 60,150 Standard sample 6 27,600 Standard sample 7 10,290 Standard sample 8 5,000 Standard sample 9 2,810 Standard sample 10,850 Under the above conditions, the RI detection intensity was measured against the elution time of the resin light guide. The weight average molecular weight (Mw) of the resin light guide was determined based on each calibration curve obtained by measuring the standard samples for the calibration curve.

[0117] (Evaluation method for molded products) The evaluation methods for plate-shaped injection molded products are described below.

[0118] (1) Measurement of the height a and pitch b of minute convex shapes on plate-shaped injection molded products The cross section of the plate-shaped injection-molded product was cut in the direction perpendicular to the main surface (thickness direction) and observed using a digital microscope (Keyence Corporation, VHX-1000). The height a and pitch b of the fine convex portions formed on the first main surface of the molded product were measured from the obtained observation image, and the average values ​​of five fine convex portions were recorded as height a and pitch b, respectively, in Table 2. In addition, the ratio b / a (protrusion pitch b / height a) of the pitch b of the fine protrusions to the height a of the fine protrusions was calculated from the measured height a and pitch b of the fine protrusions.

[0119] (2) Measurement of the filling level of minute convex parts of molded products The cross section of the plate-shaped injection-molded product was cut in the direction perpendicular to the main surface (thickness direction) and observed using a digital microscope (Keyence Corporation, VHX-1000). The height a of the minute convex portions formed on the first main surface of the molded product was determined, and the filling degree, defined as the ratio of the height a to the depth of the concave portions in the first mold used to form the convex portions, was calculated using the following formula. The average value of four locations is shown in Table 2 as the filling degree value. In practice, a packing degree of 0.92 or more can be judged to be preferable as a molded article having transferred fine convex portions. (Filling degree) = (height a of the minute convex part of the molded product) / (depth of the concave part of the mold)

[0120] (3) Measurement of warpage of molded products The plate-shaped injection-molded product was placed on a metal surface plate with the first main surface with the fine convex portions 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 injection-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.

[0121] (4) Evaluation of the appearance of the molded product The plate-shaped injection molded product was visually inspected for uneven gloss on the first main surface due to insufficient filling of the resin on the fine convex shaped surface of the first mold, and poor appearance due to waviness on the second main surface. Poorly filled areas of the resin can be seen as chipped areas. The waviness of the second main surface can be assessed by checking whether a straight line is distorted when a fluorescent lamp housed in a rectangular case with a long side is shone from above and reflected from the surface. The yellowness index (YI) of the molded product measured using the method described below was determined to be less than 7.0 as a state in which yellowing was suppressed, between 7.0 and 10.0 as a state in which slight yellowing occurred, and over 10.0 as a state in which severe yellowing occurred. The case where neither uneven gloss on the first main surface nor waviness on the second main surface was observed and yellowing was suppressed was rated as "A." The case where either uneven gloss on the first main surface, waviness on the second main surface, or yellowing was observed was rated as "B." The case where two or more of uneven gloss on the first main surface, waviness on the second main surface, and yellowing were observed was rated as "C."

[0122] (5) Measurement of in-plane retardation of molded products The plate-shaped injection-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 added to the Petri dish so that the product was filled up to the tops of the fine convex portions of the molded product. 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 fine convex portions were formed (see Figures 1(A) and 3(A)) was calculated and used as the measured value of retardation (nm). The birefringence value is preferably in a range where the in-plane retardation is 100 nm or less, which is less likely to adversely affect the optical properties.

[0123] (6) Projected area of ​​the first principal surface The plate-shaped injection-molded product was placed with the first main surface facing up, and the area of ​​the planar shape of the first main surface was determined by observing the first main surface from above, and the projected area (cm) of the first main surface was calculated. 2 ) was decided.

[0124] (7) Measurement of the amount of methyl methacrylate (MMA) contained in plate-shaped injection molded products The amount of methyl methacrylate (MMA) contained in the plate-shaped injection molded product was measured as follows. [Sample preparation] A measurement sample was cut from the opposite side of the gate of a plate-shaped injection-molded product, and 0.36 g of it was precisely weighed. 2.5000 g of internal standard solution (0.9100 g of decane dissolved in 70.0000 g of chloroform) was added and thoroughly stirred to dissolve. After dissolution, 20.0000 g of isopropyl alcohol was added, stirred, and then allowed to stand to reprecipitate the copolymer, and the supernatant solution was collected. [Measurement conditions] Equipment: GC-2025 (Shimadzu Corporation) -column- Column name: Zebron ZB-1 (Phenomenex) P / N:7HM-G001-11 Length: 30.0 mm Inner diameter: 0.32mm ID Film thickness: 0.25 μm -Column oven conditions- Initial temperature: 45°C (hold for 5 minutes) Heating rate: 20.00°C / min Final temperature: 300.0℃ (hold for 12.25 minutes) -Sample vaporization conditions- Vaporization chamber temperature: 210.0℃ Carrier gas: Helium Pressure: 70.1kPa Total flow rate: 93.2mL / min Column flow rate: 2.20 mL / min Linear speed: 71.0cm / sec Purge dose: 3.0mL / min Split ratio: 40 -Detector conditions- Detector temperature: 300.0℃ Sampling rate: 40msec Make-up gas: N2 Make-up flow rate: 30.0 mL / min H2 flow rate: 40.0mL / min Air flow rate: 400.0mL / min -Autosampler conditions- Injection amount: 1.0μm

[0125] (8) Yellowness Index (YI) measurement of plate-shaped injection molded products The plate-shaped injection-molded product was crushed and dissolved in chloroform for high-performance liquid chromatography (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare a 12% by mass chloroform solution. The solution was placed in a quartz cell with a 10 cm optical path length to prepare a measurement sample. Then, using a UV-2600 ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation), a quartz cell with a 10 cm optical path length containing chloroform for high-performance liquid chromatography (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed as a reference cell, and the 12% by mass chloroform solution was placed as a measurement cell, and the yellowness index (YI) was measured. [Measurement conditions] Measurement value: Transmitted light Measurement range: 0.0 to 100.0 Wavelength range: 780~360nm Scan speed: Fast Slit width: 2.0 Sampling pitch: 2.0 Lighting: C light source Viewing angle: 10°

[0126] The methacrylic resin compositions used in the examples and comparative examples were synthesized as follows. (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. Furthermore, 6 hours after the start of polymerization, the addition rate of the polymerization initiator solution was reduced to 0.25 kg / hour. The temperature was lowered and the addition was stopped 7 hours after the start of polymerization. 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.

[0127] (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.

[0128] (Synthesis Example 3 [Methacrylic Resin Composition C]) A 30 L reaction vessel equipped with a stirrer equipped with paddle blades, 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 by mass 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.

[0129] (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 placed at the end of the reaction zone (before the vent port) to fill the zone with resin. Post-reaction by-products and excess monomethylamine were removed by reducing the pressure at the vent port to 50 Torr. The resin emerging as strands from the die at the extruder outlet was cooled in a water bath and pelletized in a pelletizer to obtain an imide resin. Next, a co-rotating twin-screw extruder with a screw diameter of 40 mm was used. The extruder cylinder temperature was set to 255°C and the screw rotation 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 after the reaction. The resin emerged as strands from the die at the extruder outlet and was cooled in a water bath and then pelletized in a pelletizer to obtain methacrylic resin composition D having a glutarimide structure.

[0130] (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.

[0131] (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.

[0132] (Synthesis Example 7 [Methacrylic Resin Composition G]) 146.0 kg of MMA, 14.6 kg of PMI, 22.0 kg of CMI, 0.174 kg of n-octyl mercaptan as a chain transfer agent, and 147.0 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, 271.2 kg of MMA, 27.1 kg of PMI, 40.9 kg of CMI, and 273.0 kg of mXy were weighed and added to Tank 1 with stirring to obtain a mixed monomer solution for addition. Additionally, 58.0 kg of MMA was weighed into Tank 2. 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 polymerization was initiated by adding a polymerization initiator solution prepared by dissolving 0.348 kg of 1,1-di(t-butylperoxy)cyclohexane in 4.652 kg of mXy at a rate of 2 kg / hour while stirring at 50 rpm. During the polymerization, the solution temperature in the reactor was controlled at 124±2° C. by adjusting the temperature with the jacket. 30 minutes after the start of the polymerization, the addition rate of the initiator solution was reduced to 1 kg / hour, and additional mixed monomer solution was added from Tank 1 at a rate of 306.1 kg / hour for 2 hours. Then, 2 hours and 45 minutes after the start of polymerization, MMA was added in its entirety from Tank 2 at a rate of 116 kg / hour over 30 minutes. The addition rate of the initiator solution was further reduced to 0.5 kg / hour 3.5 hours after the start of polymerization, 0.25 kg / hour 4.5 hours later, and 0.125 kg / hour 6 hours later, and the addition was stopped 7 hours after the start of polymerization. After 10 hours had passed since the start of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in the main chain was obtained. This polymer solution was fed to a concentration device consisting of a tubular heat exchanger and a vaporization tank that had been preheated to 170°C, and the concentration of the polymer contained in the solution was increased to 70% by mass. The resulting polymerized solution was heated in a 0.2 m 2 The mixture was fed to a thin film evaporator and subjected to devolatilization. The temperature inside the apparatus was 280°C, the feed rate was 30 L / hr, the rotation speed was 400 rpm, and the vacuum was 30 Torr. After devolatilization, the polymer was pressurized with a gear pump, extruded through a strand die, cooled with water, and pelletized to obtain methacrylic resin G having N-substituted maleimide structural units.

[0133] (Synthesis Example 8 [Methacrylic Resin Composition H]) 285.18 kg of MMA, 34.4 g of PMI, 65.5 kg of CMI, 1.100 kg of n-octyl mercaptan as a chain transfer agent, and 165.0 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, 91.7 kg of mXy was weighed and added to Tank 1 to prepare the additional solvent. Furthermore, 165.0 kg of MMA and 110.0 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, polymerization was initiated by adding a polymerization initiator solution (0.693 kg of 1,1-di(t-butylperoxy)cyclohexane in 1.67 kg of mXy) ​​at a rate of 0.900 kg / h. mXy was added from Tank 1 at a rate of 45.8 kg / h for two hours after the start of polymerization. The solution temperature in the reactor was controlled at 125±2°C during polymerization using the jacket temperature control. Thirty minutes after the start of polymerization, the addition rate of the polymerization initiator solution was reduced to 0.225 kg / h. Two hours after the start of polymerization, the addition rate of the polymerization initiator solution was changed to 0.675 kg / h, and additional MMA solution was added from Tank 2 at a rate of 275.0 kg / h for two hours. Four hours after the start of polymerization, the addition rate of the polymerization initiator solution was increased to 0.45 kg / h. Six hours after the start of polymerization, the addition rate of the polymerization initiator solution was reduced to 0.225 kg / hour, and seven 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 this solution, 0.55 kg of Irganox 1010 and 0.83 kg of Irgafos 168 were added as antioxidants, and 1.10 kg of Rikemal H-100 was added 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 H having N-substituted maleimide structural units.

[0134] (Examples 1 to 3) - Molding of plate-shaped injection molded products with fine convex shapes on one main surface The methacrylic resin composition A obtained in Synthesis Example 1 was injection molded using an injection molding machine (FANUC, α-S250iA). The mold consisted of a first mold (forming a main surface with triangular pyramidal micro-protrusions, each with a height a of 400 μm and a pitch b of 300 μm) and a second mold (forming a flat main surface). A nested mold with heater wires embedded inside the mold near the surface forming each main surface was used and attached to the injection molding machine. After a fluorine-based release coating was applied to the surface of the first mold, the first mold was heated to a maximum temperature Tmax listed in Table 1 at a heating rate of approximately 3°C / s using a heater. The mold was then closed and injection molding was performed. The resin was filled into the mold at a cylinder temperature of 290°C, and the first mold was cooled to a minimum temperature Tmin listed in Table 1 at a cooling rate of approximately 1.2°C / s. After reaching Tmin, the mold was cooled for 90 seconds. The runner and gate were removed to obtain a plate-shaped injection-molded product (240 mm long, 230 mm wide, 2.5 mm thick, see Figure 1) with a fine convex portion on one main surface. The holding pressure was set high at 100 MPa in the first stage to ensure good transfer immediately after injection, 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 2. As is clear from Table 2, the molded articles of Examples 1 to 3 exhibited a filling degree of 0.98 to 0.99, and very excellent results were obtained. In addition, the warpage and appearance were also good.

[0135] Example 4 Using the methacrylic resin composition B obtained in Synthesis Example 2, molding was performed under the same conditions as in Example 1, except that the cylinder temperature was 280°C, the maximum temperature Tmax of the first mold was 175°C, the minimum temperature Tmin was 60°C, the temperature of the second mold was 108°C, and the first-stage holding pressure was 95 MPa, as shown in Table 1. The evaluation results are shown in Table 2.

[0136] Example 5 Using the methacrylic resin composition C obtained in Synthesis Example 3, molding was carried out under the same conditions as in Example 1, except that the maximum temperature Tmax of the first mold was 190°C, the minimum temperature Tmin was 60°C, and the temperature of the second mold was 108°C, as shown in Table 1. The evaluation results are shown in Table 2.

[0137] Example 6 Molding was carried out under the same conditions as in Example 2, except that methacrylic resin composition D obtained in Synthesis Example 4 was used. The evaluation results are shown in Table 2.

[0138] Example 7 Using the methacrylic resin composition E obtained in Synthesis Example 5, molding was performed under the same conditions as in Example 2, except that a nested mold was used for a plate-shaped injection-molded product (270 mm long, 260 mm wide, 2.5 mm thick; see Figure 3) with fine convex portions in the shape of a trapezoidal pyramid (140 μm square base, with an 85-degree angle between the base and the side) on one main surface, with the convex portions having a height a of 400 μm and a pitch b of 160 μm, and the other main surface being flat, and with heater wires embedded inside the mold near the surfaces forming each main surface. The evaluation results are shown in Table 2. As is clear from Table 2, the molded product of Example 7 exhibited a filling rate of 0.99, and very excellent results were obtained. In addition, warpage and appearance were also good.

[0139] Example 8 Using the methacrylic resin composition A obtained in Synthesis Example 1, molding was performed under the same conditions as in Example 1, except that a nested mold was used for a plate-shaped injection-molded product (150 mm long, 150 mm wide, 2.5 mm thick) with triangular pyramidal fine convex portions on one main surface with a height a of 400 μm and a pitch b of 300 μm, and the other main surface was flat, and heater wires were embedded inside the mold near the surfaces forming each main surface. The evaluation results are shown in Table 2.

[0140] Example 9 Using the methacrylic resin composition A obtained in Synthesis Example 1, a mold was used to prepare a plate-shaped injection-molded product (240 mm long, 230 mm wide, 2.5 mm thick) with triangular pyramidal minute convex portions on one main surface with a height a of 550 μm and a pitch b of 300 μm, and the other main surface was flat, and molding was performed under the same conditions as in Example 1, except that a nested mold with heater wires embedded inside the mold near the surfaces forming each main surface was used and the molding temperature was set to 290°C. The evaluation results are shown in Table 2.

[0141] Example 10 Molding was carried out under the same conditions as in Example 9, except that the methacrylic resin composition E obtained in Synthesis Example 5 was used and the cylinder temperature was set to 290° C. The evaluation results are shown in Table 2.

[0142] (Comparative Example 1) Molding was performed under the same conditions as in Example 1, except that a mold (first mold) was used to form the main surface having triangular pyramidal fine convex portions with a height a of 800 μm and a pitch b of 300 μm, and a mold (second mold) was used to form the main surface which was flat. In Comparative Example 1, a demolding failure occurred in which part of the fine features remained inside the mold when the demolding height was high, so measurements were performed using a location where evaluation of the molded product was possible. The evaluation results are shown in Table 1.

[0143] (Comparative Example 2) Molding was carried out under the same conditions as in Example 1, except that the cylinder temperature was set to 330° C. The evaluation results are shown in Table 2. As a result of the evaluation, the molded product was found to have yellowed, and the desired molded product could not be obtained.

[0144] (Comparative Example 3) Molding was carried out under the same conditions as in Example 3, except that the methacrylic resin composition F obtained in Synthesis Example 6 was used. The evaluation results are shown in Table 2. As a result of the evaluation, it was confirmed that the degree of filling of the first main surface was 0.75, which was insufficient, and the obtained molded product was yellowed, so that the desired molded product could not be obtained.

[0145] Comparative Example 4 Molding was carried out under the same conditions as in Example 3, except that methacrylic resin composition G obtained in Synthesis Example 7 was used. The evaluation results are shown in Table 2.

[0146] (Comparative Example 5) Molding was carried out under the same conditions as in Example 3, except that the methacrylic resin composition H obtained in Synthesis Example 8 was used. Demolding failure occurred, with the finely shaped portion remaining in the mold upon demolding. Furthermore, the molded product cracked, making it impossible to obtain the desired molded product.

[0147] (Comparative Example 6) Using the methacrylic resin composition A obtained in Synthesis Example 1, molding was performed under the same conditions as in Example 1, except that the maximum temperature Tmax of the first mold was 165°C, the minimum temperature Tmin was 70°C, and the temperature of the second mold was 105°C, as shown in Table 1. There were areas in the molded product where the resin had not filled all the way to the ends of the fine shapes. The evaluation results are shown in Table 2.

[0148] [Table 1]

[0149] [Table 2]

[0150] The plate-shaped injection-molded articles having fine convex portions 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 portions) of plate-shaped injection-molded product 8 having fine convex portions 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 that 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 reflected image (an image formed by the light that was reflected by the inclined surface 83 and then transmitted through the inclined surface 84) of the light that emerged from the convex-shaped surface of the molded article 8 (the main surface having the fine convex portions) was photographed with 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]

[0151] The plate-shaped injection-molded product 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, components for aerial displays, diffractive optical elements, anti-reflection sheets, anti-glare sheets, and cell culture sheets. [Explanation of symbols]

[0152] 1, 2: Plate-shaped injection molded products 11, 21: First main surface having minute convex portions 12, 22: Second main surface on which no minute convex portions are formed 13, 23: Areas where fine convex portions are formed 14, 24: Fine convex part 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 injection molded product 81:Incidence plane 82: Bottom 83, 84: Slope 9: SLR camera

Claims

1. At least a first main surface has a plurality of minute convex portions each having a height a of 50 to 700 μm, and the projected area of ​​the first main surface is 225 cm ２ The above plate-shaped injection molded product, The plate-shaped injection-molded product contains a methacrylic resin composition, The plate-shaped injection-molded product, wherein the amount of methyl methacrylate (MMA) contained in the plate-shaped injection-molded product is 1600 to 6000 ppm by mass.

2. The plate-shaped injection-molded product according to claim 1, wherein the methacrylic resin composition has a glass transition temperature of 115 to 160°C.

3. 3. The plate-shaped injection-molded article according to claim 1, wherein the methacrylic resin composition contains a methacrylic resin having a structural unit with a ring structure.

4. 4. The plate-shaped injection-molded article according to claim 3, wherein the structural unit having a ring structure comprises at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, an aromatic vinyl structural unit, an alicyclic vinyl structural unit, and a lactone ring structural unit.

5. The plate-shaped injection-molded article according to claim 4, wherein the structural unit having a ring structure includes a structural unit derived from an N-substituted maleimide monomer.

6. 3. The plate-like injection-molded product according to claim 1, wherein, on the first main surface having the fine convex portions, a ratio b / a of a pitch b of the fine convex portions to a height a of the fine convex portions is 0.1 to 2.

0.

7. The plate-like injection-molded product according to claim 1 or 2, wherein the first main surface having the fine convex portions has an in-plane retardation of 100 nm or less.

8. 3. The plate-shaped injection-molded product according to claim 1, wherein a chloroform solution containing 12% by mass of the molded product obtained by dissolving the plate-shaped injection-molded product in chloroform has a yellowness index (YI) of 10 or less.

9. 3. The plate-shaped injection-molded product according to claim 1, which has no adhesive interface and is made of a single resin.

10. a second main surface opposite to the first main surface; The plate-shaped injection-molded product according to claim 1 or 2, wherein the second main surface is a flat surface.

11. 3. The plate-shaped injection-molded product according to claim 1, which is a member for an aerial display.

12. 3. The method for producing a plate-shaped injection-molded product according to claim 1 or 2, wherein the surface temperature of the mold is heated to a temperature equal to or higher than the glass transition temperature (Tg) of the methacrylic resin composition, and then the methacrylic resin composition is injected and filled into the mold to obtain a plate-shaped injection-molded product.

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