Plate-shaped molded products

Abstract

To provide a plate-like molded article which has good appearance and high transmittance, and has a plurality of fine convex shapes on at least one main surface.SOLUTION: A plate-like molded article has a plurality of fine convex shapes having a height a of 50-600 μm on at least one main surface, wherein in 12 mass% molded article-containing chloroform solution that contains a methacrylic resin composition having a glass transition temperature (Tg) of 115-150°C, has fluorine attached thereon, and is obtained by dissolving the plate-like molded article in chloroform, a difference in spectral transmittances at a wavelength of 600 nm measured before and after filtration treatment satisfies the following expression. (Spectral transmittance B)-(spectral transmittance A)≤3.5[%]. In the expression, spectral transmittance A represents spectral transmittance [%] before filtration treatment, and spectral transmittance B represents spectral transmittance [%] after filtration treatment.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a plate-like molded product having fine convex shapes on at least one main surface. [Background technology]

[0002] Injection-molded products with fine convex shapes are widely used as optical components such as Fresnel lenses and light guide plates, and are often required to have good appearance and excellent optical properties such as transmittance, haze, yellowness index (YI), etc. Furthermore, in the production of injection-molded products with fine convex shapes, it is required that the concave portions of the mold are sufficiently filled with resin.

[0003] Because the quality of mold releasability has a significant impact on the appearance and optical properties of a molded product, a method is used in which, for example, the mold surface on which the microstructure is formed is treated with an external mold release agent before the resin is injected to improve the mold releasability of the resin and prevent mold release problems (Patent Documents 1 and 2). In particular, spray-type external mold release agents are widely used in the molding of synthetic resins because they can improve the mold releasability of the resin simply by spraying them onto the mold. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-280200 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-111927 Summary of the Invention [Problem to be solved by the invention]

[0005] When using a spray-type external release agent, it is necessary to sufficiently volatilize the solvent components that adjust the release agent to form a release coating on the mold. However, when a spray-type external release agent is sprayed onto a mold having fine convex shapes on its surface, the efficiency of solvent evaporation decreases when the release agent-adjusting solvent penetrates into the fine convex shapes, preventing the formation of a sufficient release coating and leaving the solvent components in a state where they remain. The inventors' investigations have revealed that this phenomenon is particularly pronounced when the height of the convex shapes of the molded product is high (i.e., the depth of the concave parts of the mold that form the convex shapes of the molded product is deep). If the resin is injected without sufficient formation of a release coating, the release agent components are swept away in the direction of resin flow and remain in specific parts of the mold. As a result, the resin cannot be sufficiently filled into the concave parts of the mold that form the fine convex shapes of the molded product, causing defects (such as chipping of the convex shapes). When the molded product is used for optical purposes, there is a problem of reduced optical properties such as transmittance.

[0006] The present invention has been made in consideration of the above problems, and aims to provide a plate-shaped molded product that has a good appearance and high transmittance and has a plurality of fine convex shapes on at least one of its main surfaces. [Means for solving the problem]

[0007] The present inventors have discovered that the above-mentioned problems can be solved by controlling the difference in spectral transmittance at 600 nm before and after filtration of a 12% by mass chloroform solution of a plate-shaped molded article within a predetermined range, the difference being in a predetermined range, in a plate-shaped molded article having a plurality of fine convex shapes on at least one main surface thereof, the plate-shaped molded article containing a methacrylic resin composition having a glass transition temperature (Tg) within a specific range, and the surface layer containing fluorine, thereby completing the present invention.

[0008] That is, the present invention is as follows. [1] It is a plate-shaped molded product, At least one of the main surfaces has a plurality of fine convex shapes with a height a of 50 to 600 μm, It contains a methacrylic resin composition having a glass transition temperature (Tg) of 115 to 150°C, and has fluorine attached to the surface. A plate-like molded product, characterized in that the difference in spectral transmittance at a wavelength of 600 nm measured before and after filtration of a chloroform solution containing 12% by mass of the molded product obtained by dissolving the plate-like molded product in chloroform satisfies the following formula: (Spectral transmittance B)-(Spectral transmittance A)≦3.5[%] (In the formula, spectral transmittance A represents the spectral transmittance [%] before filtration treatment, and spectral transmittance B represents the spectral transmittance [%] after filtration treatment.) [2] The plate-like molded product according to [1], wherein on the main surface having the fine convex shapes, a ratio b / a of a pitch b of the fine convex shapes to a height a of the fine convex shapes is 0.1 to 1.0. [3] The plate-shaped molded product according to [1] or [2], wherein the in-plane retardation of the main surface having the fine convex shapes is 100 nm or less. [4] It is an injection molded product, The plate-shaped molded product according to any one of [1] to [3], 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. [Effects of the Invention]

[0009] According to the present invention, it is possible to obtain a plate-shaped molded product having a good appearance and high transmittance, and having a plurality of fine convex shapes on at least one of its main surfaces. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams showing a plate-shaped molded product of an example, in which (A) shows a plan view with the main surface having a convex shape facing upward, 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 molded product of this embodiment. [Figure 3]Figure 3 shows a modified example of a plate-shaped molded product of an embodiment different from that shown in Figure 1. (A) shows a plan view with the main surface having a convex shape facing upward, and (B) shows a perspective view of the convex shape observed obliquely from above. [Figure 4] FIG. 4 is a partial cross-sectional view showing an example of a convex shape (quadratic pyramid frustum) of the plate-shaped molded product of this embodiment, which is different from that shown in FIG. 2, as a modified example. [Figure 5A] FIG. 5(A) is a layout diagram of the equipment used to evaluate the characteristics of the plate-shaped molded products obtained in the examples and comparative examples when used as light direction converting elements. [Figure 5B] FIG. 5B is a plan view of the USAF Target 7 used in FIG. 5A, as viewed from the X-axis direction. [Figure 6] FIG. 6 is a diagram showing the optical path when the plate-shaped molded products obtained in the examples and comparative examples are used as light direction conversion elements. [Figure 7] FIG. 7 shows survey scan spectra obtained by XPS measurement of the plate-shaped molded products obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

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

[0012] (Plate-shaped molded product) The plate-shaped molded product of this embodiment (hereinafter also simply referred to as "molded product") is characterized in that the spectral transmittance at a wavelength of 600 nm of a chloroform solution containing 12 mass% of the molded product obtained by dissolving the plate-shaped molded product in chloroform satisfies the following formula: Spectral transmittance B - Spectral transmittance A≦3.5[%] (In the formula, spectral transmittance A represents the spectral transmittance [%] before filtration treatment, and spectral transmittance B represents the spectral transmittance [%] after filtration treatment.) The difference in spectral transmittance at 600 nm before and after the filtration treatment (spectral transmittance B - spectral transmittance A) is 3.5% or less, preferably 2% or less, more preferably 1% or less, and even more preferably 0.5% or less. When the difference in spectral transmittance is 3.5% or less, the molded article can be suitably used as an optical component, and the smaller the difference in spectral transmittance, the better. As a method for controlling the difference in spectral transmittance, as will be described later, there can be mentioned a method in which the maximum temperature during heating is set within a specific range in the step of heating and then cooling the mold during injection molding of the molded article, a method in which a release agent having a solvent component with a boiling point within a specific range is used as the release agent used during injection molding of the molded article, etc. If the components of the release agent are transferred to the surface of the molded article during injection molding of the molded article, causing haze on the surface, the transmittance will decrease and the difference in spectral transmittance will tend to increase. The spectral transmittance can be measured by the method described in the examples below.

[0013] The plate-shaped molded product of this embodiment has a plurality of fine convex shapes (hereinafter referred to as "fine convex shapes" or simply "convex shapes") on at least one main surface, and the height a of the convex shapes is 50 to 600 μm. Furthermore, the ratio b / a of the pitch b of the convex shapes to the height a of the convex shapes is preferably 0.1 to 1.0. The shape of the plate-shaped molded product of this embodiment will be described in detail below.

[0014] The minute convex shapes formed on at least one of the main surfaces are not particularly limited, and include polygonal pyramids such as triangular pyramids, square pyramids, and pentagonal pyramids; curved cones such as cones, elliptical cones, semi-circular cones, semi-elliptical cones, and oval cones (cones having a cross section in a shape where both ends of a pair of parallel lines are 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-circular truncated cones, semi-elliptical truncated cones, and oval truncated cones (cones having a cross section in a shape where both ends of a pair of parallel lines are connected by a semicircle); Examples of such shapes include curved frustums such as triangular prisms, quadrangular prisms (cubes, rectangular parallelepipeds, etc.), polygonal prisms such as pentagonal prisms, curved prisms such as cylinders, elliptical cylinders, semicircular cylinders, semi-elliptical cylinders, and oblong cones (cylinders having a cross section formed by connecting the ends of a pair of parallel straight lines with a semicircle), and dome shapes (structures having a hemisphere, quarter sphere, aspherical surface, etc., in which the cross-sectional area when cut axially gradually decreases as one moves axially upward). In the case of polygonal pyramids, polygonal prisms, etc., the corners may be rounded. Furthermore, the side surfaces of the convex shapes may be flat or curved. These convex shapes may be of only one type or a combination of multiple types, but it is preferable that they are of only one type. Fig. 2 is a partial cross-sectional view showing an example of a plate-shaped molded product of this embodiment in which the fine protrusions are triangular pyramids, and Fig. 4 is a partial cross-sectional view showing an example of a plate-shaped molded product of this embodiment in which the fine protrusions are quadrangular pyramids. The convex shapes may be arranged in a linear, curved, dotted, or other pattern. The convex shapes may be arranged over the entire surface of one of the main surfaces, or only in a partial area of one of the main surfaces, or over the entire surfaces of both of the main surfaces, or only in a partial area of each of the main surfaces, or over the entire surface of one of the main surfaces and only in a partial area of the other main surface. For example, Fig. 1(A) and Fig. 3(A) are plan views of an example of a plate-shaped molded product in which convex shapes are arranged in only a partial area of one of the main surfaces, as viewed from the main surface side.

[0015] In the main surface having the fine convex shapes, the ratio b / a of the pitch b to the height a of the fine convex shapes is preferably 0.1 to 1.0, more preferably 0.2 to 1.0, and even more preferably 0.3 to 1.0. When b / a is in the above range, the molded product tends to be able to be cleanly released from the mold while maintaining an extremely good mold transfer rate. b / a is the average value of the height and pitch measured for five or more convex shapes. Therefore, as long as b / a is within the above range, the height and pitch of each convex shape may be changed arbitrarily. The height a of the convex shape is 50 to 600 μm, preferably in the range of 100 to 600 μm, more preferably 200 to 500 μm, and even more preferably 350 to 500 μm. The higher the height a of the convex shape, the deeper the concave portions of the mold that form the convex shape. This makes it more difficult for the solvent components used to adjust the release agent to volatilize when the mold surface is subjected to a release treatment. However, if the height a of the convex shape is within the above range, a release coating can be efficiently formed. If the height a of the convex shape is higher than this range, it is not impossible to obtain a molded product with good appearance and optical properties, but poor release of the resin from the mold is likely to occur. Therefore, considering mass productivity, it is preferable that the height a be within the above range. The pitch b of the convex shapes is preferably 50 to 600 μm, more preferably 100 to 500 μm, even more preferably 150 to 350 μm, and even more preferably 180 to 300 μm. When the pitch b of the convex shapes is in the above range, problems in releasing the resin from the mold are less likely to occur, a release coating can be formed deep into the concave portions of the mold that form the convex shapes, and molded products with good appearance and optical properties tend to be obtained. In this specification, the height of a convex shape refers to the highest value among the heights in the thickness direction of a molded article measured based on a flat portion of one main surface parallel to the other main surface, and height a is the average value of the heights of five or more convex shapes. For example, as shown in Figure 2, if the convex shape is a cone, it refers to the height to the apex of the cone. When one main surface does not have a flat portion parallel to the other main surface, the height of the convex shape may be the highest value among the heights in the thickness direction of the convex shape relative to the average thickness of the molded article. In this specification, the pitch of the convex shapes means the distance between the centers of two adjacent convex shapes (see Figures 2 and 4), and the pitch b is the average value of the pitches measured for five or more convex shapes. The height a and pitch b of the convex shapes can be visually measured from an observation image obtained using an optical microscope, an electron microscope, a digital microscope, or the like, and specifically, can be measured by the method described in the examples below.

[0016] When the main surface having the convex shapes is observed from above, the size of the convex shapes in plan view is preferably 0.1 to 600 μm in diameter, more preferably 0.5 to 500 μm, and even more preferably 1 to 400 μm. If the planar shape of the convex shape is a line pattern, the term refers to the width in the direction perpendicular to the line direction, and if the planar shape is other than a circle, the term refers to the diameter of the circumscribed circle. The diameter of the planar shape of the convex shape can be measured visually from an observation image obtained using an optical microscope, electron microscope, digital microscope, or the like. The size (height and diameter in plan view) of the convex shapes may be the same for all the convex shapes or may be different for all the convex shapes.

[0017] The overall shape of the molded article of this embodiment is not particularly limited as long as it is plate-like or approximately plate-like with a plurality of fine protrusions on at least one main surface. Examples of shapes (planar shapes) when the main surface having the fine convex shapes is observed from above include polygons such as triangles, squares, rectangles, parallelograms, trapezoids, and pentagons, as well as circles, ellipses, semicircles, semi-ellipses, ovals (shapes formed by connecting both ends of a pair of parallel lines with a semicircle), and rings. In the case of polygons, the corners may be rounded. Furthermore, when the area of the portion having the fine convex shapes on the main surface having the fine convex shapes is taken as 100%, the area of the flat portion of the other 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 other 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.

[0018] In this embodiment, the thickness of the molded article, excluding the fine convex shapes, is preferably 1.5 mm or more and less than 6 mm, more preferably 2 mm or more and less than 5 mm, and even more preferably 2 mm or more and less than 4 mm. The thinner the thickness, the more difficult it is to control warpage. On the other hand, the thicker the thickness, the more advantageous it is for warpage control, but the longer it takes to cool during molding, the greater the temperature difference between the surface and the interior, causing the center to sink and impairing the flatness of the plane, which may adversely affect the optical properties of the molded article. The size of each main surface of the molded article is not particularly limited and may be set according to the purpose.

[0019] In the plate-shaped molded product of this embodiment, when a fine convex shape is formed on only one main surface and the other main surface is flat and has no concave or convex portions 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. A warpage of 0.4 mm or less can be said to be a molded product with good dimensional accuracy. Furthermore, the square root of the area of the region where the convex shapes are formed is calculated when the main surface on which the convex shapes are formed is viewed in plan view (for example, in Figure 1, the shaping surface region is 80 mm square, so the square root is 80 mm), and if the warpage amount relative to the obtained value is 0.50% or less, it can be determined that the dimensional accuracy of the molded product is within a preferable range, more preferably 0.44% or less, and even more preferably 0.38% or less. The amount of warpage is measured by placing the molded product on a metal surface plate with the main surface having a convex shape facing up, dividing the outer periphery of the molded product equally into four points, and measuring the gap between the molded product and the surface plate at the four points (see, for example, 3a to 3d in Figure 1), and the value is the value at the location where the gap is largest.Specifically, the amount of warpage can be measured by the method described in the examples below.

[0020] The packing degree of the plate-shaped molded article of this embodiment is preferably 0.92 or more, more preferably 0.95 or more, and even more preferably 0.99 or more. When the packing degree is 0.92 or more, it can be said that the molded article has well-formed convex shapes. The filling degree is a value calculated from the height a of the convex shape and the depth of the concave portion in the mold for forming the convex shape using 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 convex part of the molded product) / (depth of the concave part of the mold)

[0021] The plate-shaped molded product of this embodiment preferably has a birefringence value of 100 nm or less, more preferably less than 50 nm, and even more preferably less than 20 nm, as the in-plane retardation of the main surface having a fine convex shape. When the in-plane retardation is within the above range, the polarization of light transmitted through the molded product tends to be maintained constant, making it less likely to adversely affect optical properties. When polarized light passes through the molded product, the retardation changes in the presence of total reflection within the molded product. However, if the retardation is confirmed to be small by measuring the in-plane retardation of the molded product, the retardation imparted to the final transmitted light will be constant, and the product will function like a retarder. Because the polarization characteristics are uniform, the product is particularly effective when combined with optical devices such as projectors, head-up displays, and headsets that utilize various polarized light, as well as with video display devices such as in-vehicle displays that are expected to be viewed with polarized sunglasses. When combined with liquid crystal displays, optical elements using liquid crystals, and polarizing plates, it helps improve light utilization efficiency and reduce noise. It also works to the advantage of improving visibility when using a circular polarizing plate or polarizing plate to cut external light or when wearing polarized sunglasses. The in-plane retardation can be measured by the method described in the examples below.

[0022] The plate-shaped molded article of this embodiment contains a methacrylic resin composition having a glass transition temperature (Tg) of 115 to 150°C.

[0023] ((Methacrylic resin composition)) The methacrylic resin composition contained in the plate-shaped molded product of this embodiment is characterized by containing a methacrylic resin, and may optionally contain additives in addition to the methacrylic resin, and may also contain other thermoplastic resins, rubbery polymers, etc. other than the methacrylic resin.

[0024] -Methacrylic resin- The methacrylic resin contained in the methacrylic resin composition of this embodiment will be described below. The methacrylic resin is not particularly limited, and examples thereof include resins primarily composed of structural units derived from methyl methacrylate, such as homopolymers of methyl methacrylate and copolymers of methyl methacrylate with one or more copolymerizable monomers such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, butyl acrylate, acrylonitrile, acrylic acid, methacrylic acid, vinylpyridine, vinylmorpholine, vinylpyridone tetrahydrofurfuryl acrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylacrylamide, 2-hydroxyacrylate, 2-(hydroxymethyl)ethyl acrylate, ethylene glycol monoacrylate, glycerin monoacrylate, maleic anhydride, N-cyclohexylmaleimide, N-phenylmaleimide, styrene, and α-methylstyrene. Other examples include heat-resistant methacrylic resins having a structural unit derived from methyl methacrylate and a lactone ring or glutarimide in the main chain, and methyl methacrylate and low-moisture-absorbing methacrylic resins. These may be used alone or in a blend of two or more.

[0025] The methacrylic resin in this embodiment is preferably a methacrylic resin having a ring structure in the main chain from the viewpoint of transparency and heat resistance, and is particularly preferably a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer, since optical properties such as intrinsic birefringence and photoelastic coefficient can be easily controlled to a high degree without blending with other thermoplastic resins.

[0026] -Methacrylic resin manufacturing method- The method for producing the methacrylic resin of this embodiment will be described below. In the production method of this embodiment, a batch system, a semi-batch system, or a continuous system can be used as the polymerization system. Here, the batch system is a process in which the entire amount of raw materials is charged into a reactor, the reaction is initiated and allowed to proceed, and the product is recovered after completion. The semi-batch system is a process in which either the raw materials are charged or the product is recovered simultaneously while the reaction is in progress. Furthermore, the continuous system is a process in which both the raw materials are charged and the product is recovered simultaneously while the reaction is in progress. In this embodiment, the method for producing a methacrylic resin having a ring structure in the main chain is preferably a semi-batch system in which some of the raw materials are charged after the reaction has started, 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, there is an advantage that the difference in monomer composition between fractions with different molecular weights in the methacrylic resin can be reduced, but a large amount of unreacted monomer remains after polymerization, which 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] -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.

[0035] --Antioxidants-- The methacrylic resin composition according to this embodiment preferably contains an antioxidant that suppresses deterioration and coloration during molding or use. Examples of the antioxidant include, but are not limited to, hindered phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. In order to improve the transferability of the fine convex shaped portions of the mold while highly controlling the distortion and warpage of the surface of the molded product, it is essential that the methacrylic resin composition of this embodiment maintains the resin at a high temperature in the mold cavity and allows an appropriate cooling time. When subjected to a long-term thermal history, it is necessary to increase the amount of heat stabilizer added to achieve the desired thermal stability. However, from the viewpoint 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.

[0036] Examples of the hindered phenol antioxidant include, but are not limited to, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl ...octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propion pionate], hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylin)methyl]-1,3,5-triazine-2,4,6(1H,3H,5 H)-trione, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamine)phenol, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate, and the like. Particularly preferred are pentaerythritol terakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate.

[0037] Furthermore, as the hindered phenol-based antioxidant, a commercially available phenol-based antioxidant may be used. Examples of such commercially available phenol-based antioxidants include, but are not limited to, Irganox 1010 (Irganox 1010: pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], manufactured by BASF), Irganox 1076 (Irganox 1076: pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], manufactured by BASF), and the like. 1076: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, BASF), Irganox 1330 (Irganox 1330: 3,3',3'',5,5',5''-hexa-t-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, BASF), Irganox 3114 (Irganox 3114: 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, B ASF), Irganox 3125 (BASF), Adekastab AO-60 (pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (ADEKA), Adekastab AO-80 (3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane (ADEKA), Sumilizer BHT BHT, manufactured by Sumitomo Chemical), Cyanox 1790 (manufactured by Cytec), Sumilizer GA-80 (manufactured by Sumitomo Chemical), Sumilizer GS (Sumilizer GS: 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, manufactured by Sumitomo Chemical), Sumilizer GM (Sumilizer GM: 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate, manufactured by Sumitomo Chemical), and Vitamin E (manufactured by Eisai). Among these commercially available phenolic antioxidants, Irganox 1010, Adekastab AO-60, Adekastab AO-80, Irganox 1076, Sumilizer GS, etc. are preferred from the viewpoint of the effect of imparting thermal stability to the resin. These may be used alone or in combination of two or more.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] --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.

[0042] 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.

[0043] The content of the ultraviolet absorber is not particularly limited as long as it does not impair heat resistance, moist heat resistance, thermal stability, and moldability and exhibits the effects of the present invention, but is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, more preferably 0.25 to 3 parts by mass, and even more preferably 0.3 to 3 parts by mass, relative to 100 parts by mass of the methacrylic resin. Within this range, an excellent balance of ultraviolet absorption performance, moldability, etc. is achieved.

[0044] --Mold release agent-- The methacrylic resin composition of the present embodiment may contain a release agent, including, but not limited to, fatty acid esters, fatty acid amides, fatty acid metal salts, hydrocarbon-based lubricants, alcohol-based lubricants, polyalkylene glycols, carboxylic acid esters, and hydrocarbon paraffin-based mineral oils. These release agents may be used alone or in combination of two or more.

[0045] 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.

[0046] The content of the release agent may be an amount sufficient to obtain the effect as a release agent, and since an excessive content may cause problems such as bleed-out during processing or poor extrusion due to screw slippage, the content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, still more preferably 0.8 parts by mass or less, still more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass, per 100 parts by mass of the methacrylic resin. Addition in the above ranges inhibits the decrease in transparency due to the addition of the release agent and also tends to inhibit poor release during injection molding.

[0047] --Other thermoplastic resins-- The methacrylic resin composition of the present embodiment may contain a thermoplastic resin other than the methacrylic resin for the purposes of adjusting birefringence or improving flexibility without impairing the object of the present invention. Other thermoplastic resins include, for example, polyacrylates such as polybutyl acrylate; styrene-based polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene block copolymer; and acrylic rubber particles having a three- to four-layer structure described in, for example, JP-A-59-202213, JP-A-63-27516, JP-A-51-129449, and JP-A-52-56150; rubbery polymers disclosed in JP-B-60-17406 and JP-A-8-245854; and methacrylic rubber-containing graft copolymer particles obtained by multistage polymerization, described in WO 2014-002491. Among these, from the viewpoint of obtaining good optical properties and mechanical properties, rubber-containing graft copolymer particles having a graft portion on their surface layer made of a composition compatible with styrene-acrylonitrile copolymers and methacrylic resins containing structural units (X) having a ring structure in the main chain are preferred. The average particle size of the acrylic rubber particles, methacrylic rubber-containing graft copolymer particles, and rubbery polymer described above is preferably 0.03 to 1 μm, more preferably 0.05 to 0.5 μm, from the viewpoint of improving the impact strength and optical properties of the molded article obtained from the composition of this embodiment.

[0048] 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.

[0049] The methacrylic resin composition of this embodiment has a glass transition temperature (Tg) of 115 to 150°C, as measured by the midpoint method in accordance with JIS-K7121. When the Tg of the methacrylic resin composition is 115°C or higher, it is higher than the boiling point of the solvent component used to prepare the general mold release agent used during molding. Therefore, the mold temperature can be set to a temperature above the boiling point to volatilize the solvent. Furthermore, if the molded article does not have heat resistance of 115°C or higher, warpage and convex deformation may occur in reliability tests such as high-temperature aging tests, adversely affecting optical properties. On the other hand, a glass transition temperature (Tg) of more than 150°C is undesirable because there are few types of equipment capable of raising the maximum mold temperature (Tmax) to an appropriate temperature, and the mold temperature increase and decrease require time, resulting in a long cycle time. The glass transition temperature (Tg) is preferably 120 to 145°C, particularly preferably 125 to 140°C. The glass transition temperature of the methacrylic resin composition can be measured by the method described in the examples below.

[0050] The methacrylic resin composition used in this embodiment preferably has a low viscosity corresponding to the time of injection and high fluidity in order to improve the transferability of the fine convex shapes. -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. If the melt viscosity is less than 20 Pa·sec, it becomes difficult to control the flow of the resin during injection, and air entrapment tends to deteriorate the transferability of fine convex shapes. If the melt viscosity is greater than 235 Pa·sec, the fluidity of the resin decreases, which tends to deteriorate the transferability of the convex shapes of the molded product. 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.

[0051] 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 1.5% or more, preferably 2.0% or more, and more preferably 2.5% 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.

[0052] ((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.

[0053] The plate-shaped molded article of this embodiment has fluorine attached to its surface, which is derived from a fluorine-based mold release agent described later. When fluorine is attached to the surface, the transmittance (spectral transmittance A) of the molded article before filtration tends to decrease. The presence or absence of fluorine on the surface of the plate-shaped molded product can be measured specifically by the method described in the examples below.

[0054] The method for producing the plate-shaped molded product of this embodiment will be described below. (Method of manufacturing plate-shaped molded products) In this embodiment, the temperature setting from the nozzle tip to the center of the injection molding machine cylinder is set to a temperature 120 to 180°C higher than the glass transition temperature (Tg) of the methacrylic resin composition used, allowing the molten resin to flow sufficiently and enabling molding while suppressing deterioration due to thermal decomposition of the resin. Thermal decomposition of the resin not only adversely affects color tone, transmittance, and haze, but also generates gas during injection molding. This gas fills the mold, and the gas is forced into uneven areas during resin filling, preventing it from being discharged. This inhibits resin filling and reduces the mold transfer rate. More preferably, the temperature is 130 to 170°C higher than the glass transition temperature (Tg) of the methacrylic resin composition used.

[0055] In this embodiment, after the mold surface is subjected to a release treatment with a mold release agent, the temperatures of the mold forming one main surface and the mold forming the other main surface can be set as desired to volatilize the solvent component that adjusts the mold release agent. In order to improve the transferability of the molded product, it is preferable to heat the mold temperature to and maintain it at or above the Tg of the methacrylic resin composition before injecting the methacrylic resin composition into the mold. For example, when molding a molded article having fine convex shapes on only one main surface and a flat main surface, the mold forming the fine convex shape is designated as the first mold, and the mold forming the flat main surface is designated as the second mold. When the maximum temperature of the first mold when the methacrylic resin composition is injected into the mold is designated as Tmax, the temperature of the second mold is preferably set to (Tmax-65)°C to (Tmax-50)°C. It is more preferably set to (Tmax-65)°C to (Tmax-40)°C, and particularly preferably set to (Tmax-60)°C to (Tmax-35)°C. When the temperature of the second mold is (Tmax-65)°C or higher, the amount of warpage of the molded article tends to be reduced. On the other hand, when the temperature is (Tmax-50)°C or lower, deterioration of the flatness of the second main surface of the molded article due to effects such as thermal shrinkage of the resin and sticking to the mold is suppressed, and a plate-like molded article with good appearance can be obtained.

[0056] In this embodiment, the mold forming the main surface having the fine convex shape is preferably heated and then cooled. The maximum temperature Tmax of the mold during heating is preferably controlled within the range of (Tg + 15)°C to (Tg + 40)°C, where Tg is the glass transition temperature of the methacrylic resin composition, to improve the volatility of the solvent components adjusting the mold release agent and enhance the transferability (moldability) of the fine convex shape. More preferably, it is controlled within the range of (Tg + 15)°C to (Tg + 35)°C, and even more preferably (Tg + 20)°C to (Tg + 35)°C. Setting the temperature above (Tg + 40)°C improves the volatility of the solvent components adjusting the mold release agent, but the resin becomes too fluid, which tends to result in molding defects due to the entrapment of air or gas. On the other hand, if the temperature is below (Tg + 15)°C, transferability decreases and the appearance of the molded product tends to deteriorate. Furthermore, the volatility of the solvent components used to prepare the release agent is reduced, inhibiting the formation of a release coating and increasing the transfer of the release components to the surface of the molded article. As a result, the transmittance of the molded article is reduced, and the difference in spectral transmittance at a wavelength of 600 nm measured before and after filtration, when the molded article is dissolved in chloroform, tends to exceed 3.5%. Therefore, it is preferable to control the maximum temperature Tmax of the mold that forms the main surface having the fine convex shapes within the temperature range of (Tg + 15)°C to (Tg + 40)°C. The minimum temperature Tmin of the mold that forms the main surface having the fine convex shapes 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, where Tg is the glass transition temperature of the methacrylic resin composition. If Tmin is lowered to a temperature below (Tg-75)°C, the cycle time will be longer. On the other hand, if Tmin exceeds (Tg-45)°C, the amount of warpage of the molded article will increase, tending to deteriorate the appearance of the molded article.

[0057] In this embodiment, the method for heating the mold is not particularly limited, and any method may be used. Examples include a method in which a water or oil flow path is provided in the mold and the mold temperature is adjusted to a temperature equal to or higher than the Tg of the methacrylic resin composition used 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 water or oil flow paths are provided in the mold and the mold is cooled by a medium such as water or oil.

[0058] In this embodiment, for a mold forming a main surface having a fine convex shape, the surface temperature increase rate 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 surface temperature decrease rate during cooling of the mold is preferably 0.5 to 10°C / sec, more preferably 1 to 10°C / sec, and even more preferably 2 to 10°C / sec. A faster temperature decrease rate is more effective in shortening the cycle time, but maintaining the mold temperature at a high temperature is more effective in improving transferability, as described below. However, a temperature decrease rate outside this range is undesirable because it tends to increase the cycle time and worsen warpage of the molded product. In this embodiment, the temperature control can be adjusted by raising or lowering the temperature at a constant rate, slowing the rate of temperature increase or decrease, or holding the temperature at a predetermined temperature for a certain period of time, depending on the condition of the molded product. To improve the transfer of the convex shape, it is preferable to maintain the temperature at a temperature at which the resin flows (preferably above the glass transition temperature) for a long time. Furthermore, if the temperature is maintained for a short period of time, birefringence will develop due to the formation of a skin layer. Therefore, in order to prevent this, it is preferable to slow down the rate of temperature decrease.

[0059] In this embodiment, a release coating or a release agent is preferably used as the release treatment for the mold surface. As the release coating, a baked fluorine-based resin or a silicone-based resin can be used. As the release agent for application, for example, a fluorine-based, silicone-based, or wax-based release agent can be used. In particular, as a spray-type external release agent that is sprayed onto the mold, for example, a fluorine-based release agent that has excellent release properties and forms a monomolecular film that does not affect the transfer of the fine shape of the mold can be used. It is preferable to use a non-curing release agent because it is less likely to remain on the mold. Furthermore, the highly volatile solvent component containing the active ingredient is primarily a solvent component that does not readily dissolve the methacrylic resin composition injected into the mold. Furthermore, by using a solvent component whose boiling point is lower than or close to the Tg of the methacrylic resin composition, the solvent is less likely to remain in the recessed portions of the mold that form the convex shapes, and a good release coating can be formed. It is preferable to use a solvent component with a low boiling point for the release agent. Specifically, the boiling point is preferably in the range of (Tg-50)°C to (Tg+5)°C, more preferably (Tg-40)°C to (Tg+5)°C, and even more preferably (Tg-30)°C to (Tg+5)°C, where Tg is the glass transition temperature of the methacrylic resin composition. By using a release agent in this range, a release film can be formed efficiently, and the transfer of the release component to the surface of the molded article is reduced, improving the transmittance of the molded article, and the difference in transmittance measured before and after filtration by dissolving the molded article in chloroform tends to be 3.5% or less. As a result, molded articles with good optical properties and appearance can be obtained. [Example]

[0060] The present invention will be explained below by way of specific examples and comparative examples, but is not limited to these.

[0061] [Raw materials] The raw materials used in the examples and comparative examples described later are shown below.

[0062] [[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

[0063] [[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.

[0064] [[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.

[0065] [[Chain transfer agent]] n-Octyl mercaptan: Chevron Phillips Chemical Company n-Dodecyl mercaptan: Fujifilm Wako Pure Chemical Industries, Ltd.

[0066] [[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. Monomethylamine: Mitsubishi Gas Chemical Company, Inc. Dimethyl carbonate: Fujifilm Wako Pure Chemical Industries, Ltd. Triethylamine: Fujifilm Wako Pure Chemical Industries, Ltd.

[0067] (Evaluation of properties of methacrylic resins and methacrylic resin compositions) The methods for measuring the properties of the methacrylic resin composition will be described below.

[0068] (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.

[0069] (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.

[0070] (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 (%).

[0071] (Methods for measuring and evaluating molded products) The measurement and evaluation methods for plate-shaped molded products are described below.

[0072] (1) Measurement of spectral transmittance of molded products The 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 an optical path length of 10 cm, and the spectral transmittance A (%) was measured using a UV-2600 ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation). Thereafter, the chloroform solution containing 12% by mass of the molded article was filtered using an MS syringe filter with a pore size of 1 micrometer (manufactured by Osaka Chemical Co., Ltd.) The spectral transmittance B (%) of the filtered solution was measured in the same manner as before filtration, and the spectral transmittance difference was calculated using the following formula. (spectral transmittance difference) = (spectral transmittance B) - (spectral transmittance A)

[0073] (2) Measurement of the height and pitch of the convex shapes of molded products The plate-shaped molded product was cut in the direction perpendicular to the main surface (thickness direction) and the cross section obtained was observed using a digital microscope (Keyence Corporation, VHX-1000). The height and pitch of the convex shapes formed on the main surface of the molded product were measured from the obtained observation image, and the average values of five convex shapes were recorded as height a and pitch b, respectively, in Table 1.

[0074] (3) Measurement of the filling degree of the convex shape of the molded product The cross section of the plate-shaped 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 convex shapes formed on the main surface of the molded product was determined, and the filling degree, defined as the ratio of the height a of the convex shapes to the depth of the concave shapes in the mold used to form the convex shapes, was calculated using the following formula. The average value of four points is shown in Table 1 as the filling degree value. In practice, a filling degree of 0.92 or more can be judged to be preferable as a molded article having a transferred convex shape. (Filling degree) = (height a of the convex part of the molded product) / (depth of the concave part of the mold)

[0075] (4) Measurement of warpage of molded products The plate-shaped molded product was placed on a metal surface plate with the convex main surface facing up, and the outer periphery of the molded product was divided equally into four points. The gaps between the molded product and the surface plate at these four points (see 3a to 3d in Figure 1) 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 in which an uneven portion for connection to other parts is provided on the back surface (the other main surface) of the main surface having the above-mentioned convex shape of the molded product, the molded product is trimmed so that only the portion that does not include the uneven portion for connection remains, and the cross section is polished with sandpaper before measuring the amount of warpage. In practice, in the case of a plate-shaped molded product having the shape shown in Figs. 1 and 3, if the amount of warpage is 0.4 mm or less, it can be determined that this is within a preferable range for the dimensional accuracy of the molded product.

[0076] (5) Evaluation of the appearance of the molded product The plate-shaped molded product was visually inspected to find that the gloss unevenness of the main surface having a convex shape was caused by insufficient filling of the resin on the fine convex shape forming surface of the mold on the main surface side having a convex shape, and the appearance was poor due to waviness on the back side of the main surface having a convex shape (the other flat main surface). If there are any areas where the resin has not been filled properly, they will appear as chipped parts.The quality of the flat surface can be determined by checking whether the reflected image of the other main surface is distorted when, for example, a fluorescent lamp housed in a rectangular case with one long side is shone from above. When neither uneven gloss on the main surface having a convex shape nor waviness on the other main surface was observed, the sample was evaluated as "○ (good)", and when at least one of uneven gloss on the main surface having a convex shape and waviness on the other main surface was observed, the sample was evaluated as "× (bad)".

[0077] (6) Measurement of in-plane retardation of molded products The plate-shaped molded product was placed in a Petri dish on the measurement stage of a PA-300-L (Photonic Lattice, Inc.) with the convex main surface facing up. A low-viscosity liquid (Shimadzu Corporation contact liquid) with a refractive index close to that of the methacrylic resin used and non-corrosive to the methacrylic resin was then poured into the Petri dish so that the product was filled up to the top of the convex shape. The convex main surface of the molded product was immersed in the liquid, and the liquid surface was flat with no elevation differences. The in-plane retardation distribution was measured in this state at a wavelength of 520 nm. The average absolute value of the in-plane retardation (Re) in the area where the convex shape was formed (see Figures 1(A) and 3(A)) was calculated and used as the measured value of retardation (nm). The birefringence value is preferably in a range where the optical properties are not adversely affected, and the in-plane retardation is less than 100 nm.

[0078] (7) Qualitative analysis of fluorine adhering to the surface of molded products Small pieces of 5 mm square were cut from the center and edge of the molded product, and the elements detected on the molded product surface and the relative element concentrations were measured using XPS composition analysis using Versaprobell II (manufactured by ULVAC-PHI, Inc.) to confirm whether fluorine was present on the molded product surface. (XPS measurement conditions) Equipment used: Alpha Backfi Versaprobe II Excitation source: mono. A1Kα 20kV x 5mA 100 Analysis size: 100μm x 1.4mm Photoelectron acceptance angle: 65°

[0079] Synthesis Example 1 [Methacrylic Resin Composition A] 318.7 kg of methyl methacrylate (hereinafter referred to as MMA), 35.5 g of N-phenylmaleimide (hereinafter referred to as PMI), 63.7 kg of N-cyclohexylmaleimide (hereinafter referred to as CMI), 0.341 kg of n-octyl mercaptan as a chain transfer agent, and 225.1 kg of meta-xylene (hereinafter referred to as mXy) were weighed and placed in a 1.25 m 3 The mixture was added to the reactor and stirred to obtain a mixed monomer solution. Next, 116.9 kg of mXy was weighed and added to Tank 1 to prepare the additional solvent. Furthermore, 104.5 kg of MMA and 85.5 kg of mXy were weighed into Tank 2 and stirred to obtain an MMA solution for further addition. The liquid in the reactor was bubbled with nitrogen at a rate of 30 L / min for 1 hour, and the liquid in Tank 1 and Tank 2 was bubbled with nitrogen at a rate of 10 L / min for 30 minutes each to remove dissolved oxygen. Steam was then blown into the jacket to raise the solution temperature in the reactor to 125°C. While stirring at 50 rpm, a polymerization initiator solution (0.457 kg of 1,1-di(t-butylperoxy)cyclohexane in 2.67 kg of mXy) was added at a rate of 1 kg / h to initiate polymerization. During polymerization, the solution temperature in the reactor was controlled at 125±2°C using the temperature control in the jacket. Thirty minutes after the start of polymerization, the rate of addition of the polymerization initiator solution was reduced to 0.25 kg / h, and mXy was added from Tank 1 at a rate of 29.24 kg / h for 3.5 hours. Then, 4 hours after the initiation of polymerization, the rate of addition of the polymerization initiator solution was increased to 0.75 kg / hour, and additional MMA solution was added from Tank 2 at a rate of 95 kg / hour for 2 hours. Further, 6 hours after the start of polymerization, the addition rate of the polymerization initiator solution was reduced to 0.25 kg / hour, and 7 hours after the start of polymerization, the addition was stopped. Eight hours after the start of polymerization, a polymerization solution containing a methacrylic resin was obtained, to which 0.261 kg of Irganox 1010 and 0.784 kg of Irgafos 168 were added as antioxidants, and 0.784 kg of Rikemal H-100 as a mold release agent. Next, the obtained polymerization solution was fed to a concentrator consisting of a tubular heat exchanger and a vaporizer preheated to 250°C for devolatilization. The degree of vacuum in the vaporizer was set to 10 to 15 Torr. The resin flowing down the vaporizer was discharged with a screw pump, extruded through a strand die, cooled with water, and pelletized to obtain a methacrylic resin composition A having N-substituted maleimide structural units. The resulting pellets had a Tg of 133°C, a melt viscosity of 131 Pa·sec, and a tensile elongation at break of 1.7%.

[0080] 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 for 15 hours under a hydrogen pressure of 9 MPa, to hydrogenate the aromatic double bonds of the styrene moieties of the copolymer. The hydrogenation catalyst was removed using a filter, and 0.1 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 10-15 Torr. The resin flowing down the vaporizer was discharged using a gear pump, extruded through a strand die, cooled with water, and pelletized to obtain methacrylic resin composition B. The resulting pellets had a Tg of 118°C, a melt viscosity of 67 Pa·sec, and a tensile elongation at break of 2.2%.

[0081] Synthesis Example 3 [Methacrylic Resin Composition C] A 30 L reaction vessel equipped with a stirrer equipped with a paddle blade, a temperature sensor, a cooling pipe, a nitrogen inlet pipe, and a dropping pump was charged with 2.25 kg of methyl methacrylate, 0.32 kg of methyl 2-(hydroxymethyl)acrylate, 0.024 kg of styrene, 0.025 parts by mass of n-dodecyl mercaptan as a chain transfer agent relative to 100 parts by mass of the total amount of all monomers to be finally charged into the reaction vessel, 0.025 parts by mass of ADK STAB 2112, and 5.39 kg of toluene, and the mixture was heated to 105°C with stirring while nitrogen was passed through. As an initial initiator, a solution consisting of 0.20 kg of toluene and 0.014 kg of t-amyl peroxy isononanoate was added dropwise into the polymerization vessel over 10 minutes, while polymerization was carried out at 105 to 110 ° C. After another 10 minutes, a solution consisting of 0.26 kg of toluene and 0.017 kg of t-amyl peroxy isononanoate was added dropwise over 3 hours, and simultaneously with the addition of this initiator solution, a solution consisting of 2.75 kg of methyl methacrylate, 0.40 kg of methyl 2-(hydroxymethyl)acrylate, and 0.24 kg of styrene was added dropwise over 3 hours, while polymerization was carried out at a polymerization temperature of 105 to 110 ° C., and the mixture was then aged for another 2 hours. To the resulting polymer solution, 4.5 g of a stearyl phosphate / distearyl phosphate mixture and 72 g of a toluene mixture were added, and a cyclization condensation reaction was carried out for 1.5 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 finally charged into the reaction vessel, and the mixture was stirred and mixed. The resulting polymerization liquid was subjected to a cyclocondensation reaction and devolatilization treatment using a φ42 mm devolatilization extruder equipped with four front vents and one back vent, at a barrel temperature of 220°C, 120 rpm, and a resin amount of 5 kg / hour, to obtain pellets of methacrylic resin composition C. The resulting pellets had a Tg of 127°C, a melt viscosity of 72 Pa·sec, and a tensile elongation at break of 2.2%.

[0082] Synthesis Example 4 [Methacrylic Resin Composition D] A methacrylic resin composition having a glutarimide structure was obtained by imidizing polymethyl methacrylate with monomethylamine using a co-rotating twin-screw extruder. A co-rotating twin-screw extruder with a screw diameter of 40 mm was used. The extruder cylinder temperature was set to 275°C and the screw rotation speed to 150 rpm. Polymethyl methacrylate with a weight average molecular weight of 10,8000, containing 0.1 parts by weight of Rikemal H-100 per 100 parts by weight of the total polymer, was fed from the hopper at a rate of 20 kg / h, and nitrogen was flowed into the extruder at a flow rate of 200 mL / min. After the resin was melted and filled using a kneading block, 1.8 parts by weight of monomethylamine per 100 parts by weight of raw resin was injected through a nozzle to carry out the imidization reaction. A reverse flight was installed at the end of the reaction zone (before the vent port) to fill the resin. Post-reaction by-products and excess monomethylamine were removed by reducing the pressure at the vent port to 50 Torr. The resin exiting the die at the extruder outlet as strands was cooled in a water bath and then pelletized in a pelletizer to obtain imide resin. Next, a 40mm co-rotating twin-screw extruder was used. The extruder cylinder temperature was set to 255°C and the screw speed to 150 rpm. The resulting imide resin was fed at 20 kg / hr. The resin was melted and filled using a kneading block. After that, a mixture of dimethyl carbonate and triethylamine was injected through the nozzle as an esterifying agent to reduce the carboxylic acid groups in the resin. The amount of dimethyl carbonate was 3.2 parts by mass and triethylamine was 0.8 parts by mass per 100 parts by mass of imide resin. The pressure at the vent port was reduced to 50 Torr to remove the by-products and excess dimethyl carbonate. The resin exited the die at the extruder outlet as strands, which were then cooled in a water bath and pelletized in a pelletizer to obtain methacrylic resin composition D having a glutarimide structure. The resulting pellets had a Tg of 122°C, a melt viscosity of 158 Pa·sec, and a tensile elongation at break of 7.9%.

[0083] Example 1 - Forming of plate-shaped products with a convex shape on one main surface The methacrylic resin composition A obtained in Synthesis Example 1 was injection molded using an injection molding machine (SE180EV-A, manufactured by Sumitomo Heavy Industries, Ltd.). The mold consisted of a first mold (forming a main surface with triangular pyramidal convex shapes with a convex shape height a 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. The first mold temperature was raised to 165°C, and the second mold temperature was raised to 105°C using a heater at a heating rate of approximately 3°C / sec. After heating, the surface of the first mold was sprayed with a fluorine-based release agent prepared using isooctane (boiling point: 99°C), n-octane (boiling point: 126°C), and n-butyl acetate (boiling point: 126°C), followed by air blowing. The mold surface was treated for release over 300 seconds before the resin composition was injected into the mold. The mold was then closed and injection molding was performed. After filling the mold with the resin composition, the mold temperature of the first mold was cooled to 70°C at a rate of approximately 1.2°C / s. After reaching 70°C, cooling was continued for 90 seconds to obtain a plate-shaped molded product (90 mm long, 90 mm wide, 2.5 mm thick; see Figure 1). The holding pressure was set high at 80 MPa in the first stage immediately after injection to ensure good transfer. Subsequently, the holding pressure was lowered from the first stage to 30 MPa in the second stage to alleviate stress distortion within the molded product. The evaluation results are shown in Table 1. As is clear from Table 1, in Example 1, the Tg of the resin composition used was high, so the first mold temperature could be set at a high temperature. Therefore, by making the mold temperature sufficiently higher than the boiling point of the release agent adjusting solvent, the volatilization efficiency of the release agent adjusting solvent increased, making it possible to efficiently form a release coating. As a result, the transfer of the release agent components to the molded article surface was reduced, and a molded article with good appearance and high spectral transmittance was obtained. Furthermore, a fluorine peak was detected on the surface of the molded article from the results of XPS measurement. Figure 7 shows the survey scan spectrum obtained by XPS measurement.

[0084] Example 2 - Forming of plate-shaped products with a convex shape on one main surface Molding was carried out under the same conditions as in Example 1, except that the methacrylic resin composition B obtained in Synthesis Example 2 was used, the mold temperature of the first mold was set to 150°C, and a fluorine-based mold release agent prepared using isopropyl alcohol (boiling point: 83°C) was used. The evaluation results are shown in Table 1. In Example 2, the Tg of the resin composition used was lower than that of the resin composition of Example 1, so the temperature of the first mold could not be set to a high temperature as in Example 1. Therefore, if a release agent prepared using a solvent with a high boiling point was used in Example 2, the volatilization efficiency of the solvent would decrease, and the resin composition would be injected with the solvent remaining in the concave portions of the mold that formed the convex shapes. This would result in poor appearance due to dissolution of the molded product surface and deterioration of the transmittance of the molded product due to transfer of the release component. In practice, a release agent prepared using isopropyl alcohol, which has a low boiling point, was used, resulting in molded products with good appearance and spectral transmittance. Furthermore, fluorine peaks were detected on the surface of the molded product from the XPS analysis results.

[0085] Example 3 - Forming of plate-shaped products with a convex shape on one main surface Molding was carried out under the same conditions as in Example 1, except that the methacrylic resin composition C obtained in Synthesis Example 3 was used. The evaluation results are shown in Table 1. From the XPS measurement results, a fluorine peak was detected on the surface of the molded product.

[0086] Example 4 - Forming of plate-shaped products with a convex shape on one main surface Molding was carried out under the same conditions as in Example 1, except that the methacrylic resin composition D obtained in Synthesis Example 4 was used, the mold temperature of the first mold was set to 155°C, and a fluorine-based mold release agent prepared using isopropyl alcohol was used. The evaluation results are shown in Table 1. From the XPS measurement results, a fluorine peak was detected on the surface of the molded product.

[0087] Example 5 - Forming of plate-shaped products with a convex shape on one main surface The mold was for a plate-shaped molded product (length 90 mm, width 90 mm, thickness 2.4 mm, see Figure 3) with a rectangular truncated pyramidal convex shape (140 μm square, the angle between the base and the side 85 degrees) with a convex shape height a = 50 μm and pitch b = 50 μm on one main surface, and the other main surface was flat, and molding was performed under the same conditions as in Example 1, except that a nested mold was used in which heater wires were embedded inside the mold near the surfaces forming each main surface. The evaluation results are shown in Table 1. From the XPS measurement results, a fluorine peak was detected on the surface of the molded product. As is clear from Table 1, in Example 5, the spectral transmittance A before filtration was 97.7%, which was an extremely excellent result. The appearance was also good.

[0088] Example 6 - Forming of plate-shaped products with a convex shape on one main surface The mold was for a plate-shaped molded product (length 90 mm, width 90 mm, thickness 2.4 mm, see Figure 3) with a rectangular truncated pyramidal convex shape (140 μm square, the angle between the base and the side 85 degrees) of convex shape height a = 400 μm and pitch b = 160 μm on one main surface, and the other main surface was flat, and molding was performed under the same conditions as in Example 1, except that a nested mold was used in which heater wires were embedded inside the mold near the surfaces forming each main surface. The evaluation results are shown in Table 1. From the XPS measurement results, a fluorine peak was detected on the surface of the molded product. As is clear from Table 1, Example 5 exhibited a transmittance of 97.7%, which was an extremely excellent result. The appearance was also good.

[0089] (Comparative Example 1) Molding was carried out under the same conditions as in Example 1, except that the time from spraying the fluorine-based mold release agent until injecting the resin composition was changed to 90 seconds. The evaluation results are shown in Table 1. If the time between spraying the release agent and injecting the resin composition is too short, the release agent adjusting solvent will not have enough time to volatilize, which will result in dissolution of the surface of the molded article and transfer of the release component to the molded article. In fact, in Comparative Example 1, the evaluation results showed that the surface of the molded article was cloudy and had low transmittance, and it could not be said that the convex shape was sufficiently transferred. Furthermore, the XPS measurement results showed that a fluorine peak was detected on the surface of the molded product. Figure 7 shows the survey scan spectrum obtained by XPS measurement.

[0090] (Comparative Example 2) Molding was carried out under the same conditions as in Example 6, except that no heating was performed with a heater and the mold temperature of the first mold was set to 110° C. for injection. The evaluation results are shown in Table 1. As a result of the evaluation, the surface of the molded article was cloudy and had low transmittance, and it could not be said that the convex shapes had been transferred sufficiently. Furthermore, the XPS measurement results showed that a fluorine peak was detected on the surface of the molded product.

[0091] (Comparative Example 3) Molding was carried out under the same conditions as in Example 5, except that injection was carried out at a mold temperature of the first mold of 120° C. The evaluation results are shown in Table 1. From the XPS measurement results, a fluorine peak was detected on the surface of the molded product.

[0092] Comparative Example 4 Molding was carried out under the same conditions as in Example 1, except that methacrylic resin composition B obtained in Synthesis Example 2 was used and injection was performed at a mold temperature of 155° C. in the first mold. The evaluation results are shown in Table 1. The evaluation results showed that the spectral transmittance A before filtration was 96.0%, and the spectral transmittance B after filtration was 99.7%, for a transmittance difference of 3.7%. In addition, the surface of the molded article was cloudy, and the appearance could not be said to be good. Furthermore, the XPS measurement results showed that a fluorine peak was detected on the surface of the molded article. Compared with the surface composition analysis results of the molded article of the example, the relative intensity of fluorine was detected to be stronger.

[0093] [Table 1]

[0094] The plate-shaped molded products having fine convex shapes obtained in Example 1 and Comparative Example 1 were used as light direction conversion elements, and their properties were evaluated. As shown in Fig. 6, light incident at an incident angle of 45 degrees onto incident surface 81 (the main surface behind the main surface having the fine convex shapes) of plate-shaped molded product 8 having a fine convex shape 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 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 5(A) and used as a light direction conversion element to evaluate the clarity of the reflected and transmitted images. An LED light source 5 (Thorlabs, M530L4) with a collimating lens emitting 530 nm light and a frosted diffuser 6 (Sigma Koki, #240) were placed, 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 5(B)) was incident on the incident surface 81 of the molded article 8 at an incident angle of 45°, and the light that emerged from the convex-shaped surface ((the main surface having a fine convex shape) of the molded article 6) was photographed as a reflected image (an image formed by the light that was reflected by the inclined surface 83 and then transmitted through the inclined surface 84) using a single-lens reflex camera 9 (E-PL5, manufactured by Olympus) positioned 350 mm away in the perpendicular direction from the incident surface 81. The reflected image observed when the molded article obtained in Example 1 was used was a clear image, but the reflected image observed when the molded article obtained in Comparative Example 1 was used had a strong glare in the target image (there was a lot of light leakage in the area corresponding to the light-shielding region 72 (see Figure 5(B))) and was of low clarity. [Industrial Applicability]

[0095] The plate-shaped molded product provided by the present invention has good transmittance and appearance, and can therefore be suitably used as various optical components such as Fresnel lenses, lenticular lenses, light guide plates, anti-reflection sheets, anti-glare sheets, and cell culture sheets. [Explanation of symbols]

[0096] 1: Main surface with fine convex shape 2: Area where fine convex shapes are formed 3a, 3b, 3c, 3d: Warpage measurement points 4: Convex shape 5:LED light source 6: Frosted diffuser 7:USAF Target 71:Transparent area 72: Shading area 8: Plate-shaped molded product 81:Incidence plane 82: Bottom 83, 84: Slope 9: SLR camera

Claims

1. It is a plate-shaped molded product, At least one of the main surfaces has a plurality of minute convex shapes with a height a of 50 to 600 μm, The glass transition temperature (Tg) of the methacrylic resin composition is 115 to 150°C, and fluorine is attached to the surface. A plate-like molded product, characterized in that the difference in spectral transmittance at a wavelength of 600 nm measured before and after filtration of a chloroform solution containing 12% by mass of the molded product obtained by dissolving the plate-like molded product in chloroform satisfies the following formula: (Spectral transmittance B) - (Spectral transmittance A)≦3.5 [%] (In the formula, spectral transmittance A represents the spectral transmittance [%] before filtration treatment, and spectral transmittance B represents the spectral transmittance [%] after filtration treatment.)

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

0.

3. 3. The plate-like molded product according to claim 1, wherein the in-plane retardation of the main surface having the fine convex shapes is 100 nm or less.

4. It is an injection molded product, The plate-shaped molded product according to any one of claims 1 to 3, 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.

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