Resin light guide for display, image display device, and method for manufacturing resin light guide for display

Abstract

The purpose of the present invention is to provide a resin light guide for a display, such as a head-mounted display, having good appearance and image quality. The foregoing is achieved by a resin light guide for a display, the light guide containing a methacrylic resin composition. The absolute value of the degree of orientation of a methacrylic acid ester monomer unit in the methacrylic resin composition is 0.10-0.25, and the PV value of an effective area surface for guiding image light is 100 μm or less.

Description

Resin light guide for display, image display device, and method for manufacturing resin light guide for display

[0001] The present invention relates to a resin light guide for a display, an image display device, and a method for manufacturing a resin light guide for a display.

[0002] In recent years, AR (augmented reality) displays have been commercialized, in which light emitted from an image display element is guided to the viewer's eyeball through a waveguide, and an image is displayed by the viewer through a diffractive optical element. Because AR (augmented reality) displays are image display devices worn on the head, they are required to be small, thin, lightweight, and comfortable to wear. To achieve this, attempts have been made to replace conventional glass light guides with resins, and Patent Documents 1 and 2 below disclose light guides manufactured by injection molding.

[0003] JP 2021-162621 A JP 2023-059010 A

[0004] Generally, resin light guides manufactured by injection molding tend to have higher birefringence than glass light guides. Hologram elements, liquid crystal diffraction elements, and surface-relief diffractive optical elements used with light guides are known to exhibit polarization dependence, in which the diffraction efficiency varies depending on the polarization state of incident light. Therefore, when a light guide with high birefringence is used in an image display device, the image viewed by the viewer exhibits uneven brightness and rainbow-like color variations, resulting in poor image quality. Meanwhile, while light guides tend to be made thinner to reduce weight, the inventors' research has revealed that thin light guides manufactured by injection molding are difficult to obtain with good appearance and optical performance (low birefringence, flatness, surface accuracy, etc.). For example, a thin light guide is prone to cracking during release from a mold, resulting in poor appearance. Furthermore, a thin light guide tends to warp and have uneven thickness, resulting in poor surface flatness. Furthermore, when an image is viewed using a light guide with poor surface flatness, the image quality deteriorates, which has been a problem.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a resin light guide for displays such as head-mounted displays, which has good appearance and image quality. Another object of the present invention is to provide an image display device equipped with such a resin light guide for displays. A still further object of the present invention is to provide a method for manufacturing a resin light guide for displays, which can produce a resin light guide for displays such as head-mounted displays, which has good appearance and image quality.

[0006] As a result of extensive research, the present inventors have completed the inventions described in the following items [1] to

[14] .

[0007] That is, the present invention is as follows: [1] A resin light guide for displays containing a methacrylic resin composition, wherein the absolute value of the degree of orientation of methacrylic acid ester monomer units in the methacrylic resin composition contained in the resin light guide for displays is 0.10 to 0.25, and the PV value of the effective area surface along which image light is guided is 100 μm or less. [2] The absolute value of the photoelastic coefficient of the methacrylic resin composition contained in the resin light guide for displays is 10×10 -１２ Pa -1[3] The resin light guide for displays according to [1], wherein the methacrylic resin composition has a weight-average molecular weight of 110,000 to 170,000. [4] The resin light guide for displays according to any one of [1] to [3], wherein the glass transition temperature (Tg) is 115°C to 150°C. [5] The resin light guide for displays according to any one of [1] to [4], wherein the absolute value of the in-plane retardation is 10 nm or less. [6] The resin light guide for displays according to any one of [1] to [5], wherein the methacrylic resin composition contains a methacrylic resin having a structural unit with a ring structure. [7] The resin light guide for displays according to any one of [1] to [6], wherein the structural unit having a ring structure comprises at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, an aromatic vinyl structural unit, an alicyclic vinyl structural unit, and a lactone ring structural unit. [8] The resin light guide for displays according to any one of [1] to [7], wherein the structural unit having a ring structure comprises a structural unit derived from an N-substituted maleimide monomer. [9] The resin light guide for displays according to any one of [1] to [8], which has a thickness of 0.8 mm or less.

[10] The resin light guide for displays according to any one of [1] to [9], which comprises a diffractive optical element at at least one of the light entrance and exit sections.

[11] The resin light guiding body for displays according to any one of [1] to

[10] , having fine convex shapes on a part or a plurality of parts of its surface, wherein the line width of the fine convex shapes is 0.10 to 2.00 μm.

[12] The resin light guiding body for displays according to

[11] , wherein the ratio of the line width to the height of the fine convex shapes (height) / (line width) is 0.10 to 1.50.

[13] An image display device comprising the resin light guiding body for displays according to any one of [1] to

[12] .

[14] A method for manufacturing a resin light guide for displays by injection compression molding of a thermoplastic resin composition, comprising a resin filling step and a compression step, wherein the temperature 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 thermoplastic resin composition, and the mold temperature is set in the range of (Tg-80)°C to (Tg-35)°C relative to the glass transition temperature (Tg) of the thermoplastic resin composition, and the injection speed and filling time in the resin filling step, the compression distance, compression time and compression pressure in the compression step, and the compression delay time and cooling time set between the resin filling step and the compression step are adjusted to satisfy the following (1) and (2): (1) the absolute value of the in-plane retardation of the resin light guide for displays is 10 nm or less, and (2) the PV value of the effective area surface through which image light is guided in the resin light guide for displays is 100 μm or less.

[0008] According to the present invention, it is possible to provide a resin light guide for displays having good appearance and image quality. According to the present invention, it is possible to provide an image display device including such a resin light guide for displays. According to the present invention, it is possible to provide a method for manufacturing a resin light guide for displays, which is capable of manufacturing a resin light guide for displays having good appearance and image quality.

[0009] Fig. 1 is a schematic diagram for evaluating the clarity of a displayed image of a resin light guide for displays in Examples. Fig. 2 is a schematic diagram for measuring the PV value of a light guide. Fig. 3 is a diagram of a fine convex portion measured with an atomic force microscope. Fig. 4 is a schematic diagram for evaluating the polarization retention of a resin light guide for displays in Examples.

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

[0011] (Resin light guide for displays) The resin light guide for displays of this embodiment (hereinafter also simply referred to as "resin light guide" or "light guide") is characterized by containing a methacrylic resin composition, the degree of orientation of methacrylic acid ester monomer units in the methacrylic resin composition being 0.10 to 0.25, and the PV value of the effective area surface through which image light is guided being 100 μm or less.

[0012] Here, examples of the display in the resin light guide for display of the present invention include display devices such as head-mounted displays, wearable displays, and in-vehicle displays.

[0013] The degree of orientation of the methacrylic acid ester monomer units in the methacrylic resin composition contained in the lightguide of this embodiment is 0.10 to 0.25, preferably 0.11 to 0.20, more preferably 0.12 to 0.15, and even more preferably 0.12 to 0.13. When the degree of orientation of the methacrylic acid ester monomer units is within the above range, orientation birefringence is suppressed, thereby suppressing birefringence in the lightguide and preventing a decrease in image quality. Furthermore, when the degree of orientation is within the above range, the lightguide has adequate strength, resulting in a lightguide with a good appearance without cracks when released from the mold during molding. Methods for controlling the degree of orientation include controlling the weight-average molecular weight of the resin contained in the lightguide, the mold temperature during injection molding, the injection speed, and other parameters, as described below. The degree of orientation can be measured using the method described in the Examples section below.

[0014] In the light guide of this embodiment, the PV value of the effective area surface through which the image light is guided is 100 μm or less, preferably 95 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less. The smaller the PV value, the higher the flatness of the light guide, and the better the appearance with reduced warping and thickness unevenness, tending to result in a light guide with excellent image quality. Therefore, a smaller PV value is preferable. As described above, a smaller PV value is preferable, but from the perspective of efficient light guide manufacturing, the PV value may be 3 μm or more. The effective area surface refers to each surface used to guide the image light, and the PV value of the effective area surface refers to the PV value of each surface used to guide the image light. The PV value can be controlled by controlling the mold temperature and molding conditions during resin molding, as described below. For example, if the mold temperature is too high, warping tends to occur, resulting in a deterioration in the PV value. The PV value can be measured using the method described in the examples below. If the light guide surface has a diffractive portion, the PV value can be obtained by measuring the surface excluding that portion. If the light guide surface does not have a diffractive portion, the PV value can be obtained by measuring the surface without the diffractive portion.

[0015] The resin light guide of this embodiment can have micro-convex shapes with diffractive properties on a portion of its surface or multiple locations. The micro-convex shapes can be molded integrally with the resin light guide. The light guide can have multiple micro-convex shapes, whether they are on a portion of its surface or multiple locations. Instead of molding the micro-convex shapes integrally with the resin light guide, a diffractive optical element may be bonded to the resin light guide via an adhesive or pressure-sensitive adhesive in a process after molding the resin light guide. When a diffractive optical element is bonded, it is preferable to provide a diffractive optical element on at least one of the light entrance and exit portions.

[0016] The planar shape of the pattern of fine convex shapes is not particularly limited, and examples thereof include polygonal pyramids such as triangular pyramids, square pyramids, and pentagonal pyramids; curved cones such as cones, elliptical cones, semicones, semi-elliptical cones, and oval cones (cones having a cross section shaped like a pair of parallel straight lines connected by a semicircle); polygonal truncated cones such as truncated triangular pyramids, truncated square pyramids, and truncated pentagonal pyramids; curved cones such as truncated cones, elliptical cones, semi-circular cones, semi-elliptical cones, and oval cones (cones having a cross section shaped like a pair of parallel straight lines connected by a semicircle); polygonal prisms such as triangular prisms, square prisms (cubes, rectangular parallelepipeds, etc.), and pentagonal prisms; curved prisms such as cylinders, elliptical cylinders, semi-circular cylinders, semi-elliptical cylinders, and oval cones (cylinders having a cross section shaped like a pair of parallel straight lines connected by a semicircle); and dome shapes. In the case of polygonal pyramids and polygonal prisms, the corners may be rounded. The side surface of the fine convex shape may be flat or curved. The shape of the fine convex shape portion may be one type or a combination of multiple types, but it is preferable to use one type only. The arrangement pattern of the above shapes is not particularly limited, and may be, for example, linear, curved, or dot-like.

[0017] The line width of the fine convex shapes is preferably in the range of 0.10 to 2.00 μm, more preferably in the range of 0.30 to 1.80 μm, and even more preferably in the range of 0.40 to 1.50 μm. When the line width of the fine convex shapes is in this range, the fine convex shapes tend to be formed well by injection molding. The ratio of the height to the line width of the fine convex shapes (height / line width) is preferably in the range of 0.10 to 1.50, more preferably in the range of 0.20 to 1.30, and even more preferably in the range of 0.25 to 1.20. When the line width to the height of the fine convex shapes is in the above range, the fine convex shapes tend to be free of defects and to produce molded products with good appearance. In this specification, the height of the fine convex shapes refers to the highest value of the height in the thickness direction of the molded product measured using the flat portion of the light guide as the reference, and the height is the average height of five or more fine convex shapes. When the light guide does not have a flat portion, the height of the fine convex shapes may be the highest value of the thickness direction height of the fine convex shapes relative to the average thickness of the molded article. Furthermore, in this specification, the line width of the fine convex shapes means the center-to-center distance between two adjacent fine convex shapes when the fine convex shapes are viewed in plan, and the line width is the average value of the pitches measured for five or more fine convex shapes. Specifically, the line width and height of the fine convex shapes can be measured by the methods described in the examples below.

[0018] The planar shape of the resin light guide of this embodiment is not particularly limited, and may be flat or, if necessary, curved. It may also be molded into a shape that can be attached to an image display device. For example, if the shape of the light guide is larger than the shape to be attached to the image display device, it is molded by cutting it into a shape that can be attached.

[0019] From the viewpoint of reducing the weight of the image display device, the thickness of the light guide is preferably 0.8 mm or less, more preferably 0.7 mm or less, and even more preferably 0.6 mm or less. The thickness can be measured using an instrument such as a micrometer. Furthermore, the thickness of the light guide may be 0.1 mm or more, taking into consideration ease of processing in the manufacturing process. If the thickness of the light guide is less than 0.1 mm, cracks tend to occur easily. The thickness of the light guide refers to the thickness in the direction perpendicular to the surface of the light guide.

[0020] The thickness unevenness of the light guide is preferably 0.05 mm or less, more preferably 0.04 mm or less, and even more preferably 0.03 mm or less. The thickness unevenness can be measured using an instrument such as a micrometer. The thickness unevenness of the light guide refers to the variation in thickness in a direction perpendicular to the surface of the light guide. The thickness unevenness of the light guide can be measured specifically by the method described in the examples below. Furthermore, if the surface of the light guide has a portion with a diffractive function, the thickness unevenness can be measured by measuring the surface area excluding that portion.

[0021] The absolute value of the in-plane retardation of the light guide is preferably 10 nm or less, more preferably 5 nm or less, and even more preferably 3 nm or less. When the absolute value of the in-plane retardation is 10 nm or less, the polarization of light transmitted through the light guide tends to be kept constant before and after incidence, and the optical properties are less likely to be adversely affected. The in-plane retardation can be measured by the method described in the Examples below.

[0022] The polarization retention of the light guide, Tp / (Tc+Tp), is preferably 95% or more, more preferably 98% or more, and even more preferably 99% or more. A polarization retention within the above range indicates that the polarization of light transmitted through the light guide is maintained constant before and after incidence, and optical properties are less likely to be adversely affected. The material constituting the light guide is preferably a methacrylic resin from the viewpoint of suppressing in-plane retardation. The polarization retention can be measured by the method described in the examples below. Furthermore, the Tp refers to the amount of light measured when two polarizing plates are arranged in parallel, and the Tc refers to the amount of light measured when two polarizing plates are arranged in a crossed configuration.

[0023] (Thermoplastic Resin) The light guide of the present embodiment contains a thermoplastic resin. As the thermoplastic resin, known thermoplastic transparent resins such as cyclic polyolefin resins, polycarbonate resins, polyester resins, and methacrylic resins can be used without any particular restrictions. From the viewpoints of transparency and low birefringence, it is preferable to use a methacrylic resin as the thermoplastic resin.

[0024] (Methacrylic Resin Composition) The methacrylic resin composition contained in the light guide of the present embodiment contains a methacrylic resin. The methacrylic resin composition 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.

[0025] The methacrylic resin composition contained in the light guide of this embodiment preferably has a glass transition temperature (Tg) of 115 to 150°C, measured by the midpoint method in accordance with JIS-K7121. When the glass transition temperature (Tg) of the methacrylic resin composition is 115°C or higher, shape deformation such as warping does not occur in reliability tests such as high-temperature aging tests, and optical properties are not adversely affected. On the other hand, when the glass transition temperature (Tg) is 150°C or lower, melt processing at extremely high temperatures is avoided, thermal decomposition of the resin, etc. is suppressed, and a good product can be obtained. From the viewpoint of further achieving the above-mentioned effects, 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 specifically measured by the method described in the Examples below.

[0026] The methacrylic resin composition contained in the lightguide of this embodiment preferably has a weight-average molecular weight (Mw) of 110,000 to 170,000, more preferably 120,000 to 160,000, and even more preferably 130,000 to 150,000, as measured by gel permeation chromatography (GPC) in terms of polymethyl methacrylate. If the Mw is less than 110,000, the degree of orientation of the methacrylic acid ester monomer units in the methacrylic resin composition tends to be small, resulting in small birefringence, but cracks tend to occur during molding, making it difficult to obtain a lightguide with a good appearance. On the other hand, if the Mw is higher than 170,000, the degree of orientation tends to be high, resulting in high birefringence, which in turn tends to reduce the fluidity of the resin, increase thickness unevenness of the lightguide, and increase the PV value. Therefore, the Mw is preferably within the above range, as it allows for easy control of the degree of orientation of the lightguide, provides an excellent balance between mechanical strength and fluidity, and provides a lightguide with good appearance during molding and good optical properties. The weight average molecular weight of the methacrylic resin composition can be measured by the method described in the examples below.

[0027] The photoelastic coefficient (C R ) absolute value |C R | is 10 x 10 -12 Pa-1 It is preferably equal to or less than 5.0 × 10 -12 Pa -1 is preferably 3.0×10 or less. -12 Pa -1 is preferably 1.0×10 or less. -12 Pa -1 The photoelastic coefficient (C R ) absolute value |C R | is 10 x 10 -12 Pa -1 If the photoelastic coefficient (C) is less than or equal to the above, the stress generated when fixing the light guide and the photoelastic birefringence generated due to the dimensional change caused by temperature are sufficiently small, and a light guide capable of providing a clear image can be obtained. R The measurement of the optical transmittance (O) is carried out by forming a pressed film using a vacuum compression molding machine. When a hard coat or an anti-reflection coat is applied to the surface of the resin light guide, the measurement is carried out after removing the coat. Specifically, the optical transmittance (O) can be determined by the method described in the examples below.

[0028] The total light transmittance of the methacrylic resin composition contained in the light guide of this embodiment is preferably 85% to 100%, more preferably 87.5% to 99%, and even more preferably 90% to 99%. A methacrylic resin composition having a total light transmittance within the above range can be suitably used as a light guide. The total light transmittance is measured in accordance with JIS K 7210A, and specifically, can be measured by the method described in the Examples below.

[0029] The methacrylic resin composition contained in the light guide of this embodiment preferably has a low viscosity and high fluidity equivalent to the injection molding process in order to produce a thin light guide. Therefore, the melt flow rate (MFR) at a temperature of 230°C and a load of 37 N is preferably 1.0 g / 10 min to 8.0 g / 10 min, more preferably 3.0 g / 10 min to 7.0 g / 10 min, and even more preferably 5.0 g / 10 min to 6.0 g / 10 min. If the MFR value is greater than 8.0 g / 10 min, it becomes difficult to control the flow of the resin during injection molding, which tends to result in burrs on the light guide and a poor appearance. On the other hand, if the MFR value is less than 1.0 g / 10 min, the resin fluidity decreases, making it difficult to obtain a light guide with the desired shape. The melt flow rate is a value measured in accordance with JIS K7210 Method A, and can be measured specifically by the method described in the Examples section below.

[0030] -Methacrylic Resin- The methacrylic resin contained in the methacrylic resin composition will be described below. The methacrylic resin is not particularly limited, but examples include resins primarily composed of structural units derived from methyl methacrylate, such as a homopolymer of methyl methacrylate or a copolymer 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, ethyl 2-(hydroxymethyl)acrylate, ethylene glycol monoacrylate, glycerin monoacrylate, maleic anhydride, N-cyclohexylmaleimide, N-phenylmaleimide, styrene, or α-methylstyrene. Other examples include heat-resistant methacrylic resins having structural units derived from methyl methacrylate and lactone rings or glutarimide in the main chain, and low-moisture-absorbing methacrylic resins containing methyl methacrylate. These may be used alone or in a blend of two or more. The phrase "mainly composed of structural units derived from methyl methacrylate" means that 50% by mass or more of the structural units in the methacrylic resin are derived from methyl methacrylate.

[0031] From the viewpoints of transparency and heat resistance, the methacrylic resin in this embodiment is preferably a methacrylic resin having a structural unit with a ring structure. The structural unit with a ring structure preferably includes at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, an aromatic vinyl structural unit, an alicyclic vinyl structural unit, and a lactone ring structural unit. Furthermore, from the viewpoint of easily controlling optical properties such as intrinsic birefringence and photoelastic coefficient to a high degree without blending with other thermoplastic resins, it is particularly preferable that the structural unit with a ring structure includes a structural unit derived from an N-substituted maleimide monomer.

[0032] --Structural Unit Derived from N-Substituted Maleimide Monomer-- Next, the structural unit derived from the N-substituted maleimide monomer will be described. The structural unit derived from the N-substituted maleimide monomer may be at least one structural unit selected from the group consisting of structural units represented by the following formula (1) and structural units represented by the following formula (2), and is preferably formed from both structural units represented by the following formula (1) and the following formula (2).

[0033] In formula (1), R １ represents an arylalkyl group having 7 to 14 carbon atoms or an aryl group having 6 to 14 carbon atoms; R ２ and R ３ each independently represents a hydrogen atom, an oxygen atom, a sulfur atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms. ２ or R ３ When is an aryl group, R ２ or R ３ may contain a halogen atom as a substituent. １ may be substituted with a substituent such as a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a nitro group, or a benzyl group. In formula (2), R ４ represents a hydrogen atom, a cycloalkyl group having 3 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms; R ５ and R ６ each independently represents a hydrogen atom, an oxygen atom, a sulfur atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

[0034] In the above formula (1), the arylalkyl group having 7 to 14 carbon atoms is not limited, but examples thereof include a benzyl group, a phenylethyl group, a phenylpropyl group, a naphthylmethyl group, a naphthylethyl group, and a naphthylpropyl group.

[0035] In the above formulas (1) and (2), the aryl group having 6 to 14 carbon atoms is not limited, but examples thereof include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a biphenyl group, an anthracenyl group, and a phenanthryl group.

[0036] In the above formulas (1) and (2), the alkyl group having 1 to 12 carbon atoms may be linear or branched, and is not particularly limited. Examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a 2-methylbutyl group, an n-pentyl group, a 2-pentyl group, a 3-pentyl group, a 2,2-dimethylpropyl group, an n-hexyl group, a heptyl group, an n-octyl group, a 1,1,3,3-tetramethylbutyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group.

[0037] In the above formula (1), examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0038] In the above formula (1), the alkoxy group having 1 to 6 carbon atoms is not limited, but examples thereof include a methoxy group, an ethoxy group, an n-butoxy group, and a methoxyethoxy group.

[0039] In the above formula (1), examples of the cycloalkyl group having 3 to 12 carbon atoms include, but are not limited to, a cyclopropyl group, a cyclopropylmethyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclohexylmethyl group, a trimethylcyclohexyl group, a thujyl group, a norbornyl group, a bornyl group, a norcaryl group, a caryl group, a menthyl group, a norpinyl group, a pinyl group, a 1-adamantyl group, and a 2-adamantyl group.

[0040] Specific examples are shown below. Examples of the monomer (N-arylmaleimides, N-aromatic substituted maleimides, etc.) that forms the structural unit represented by formula (1) include N-phenylmaleimide, N-benzylmaleimide, N-(2-chlorophenyl)maleimide, N-(4-chlorophenyl)maleimide, N-(4-bromophenyl)maleimide, N-(2-methylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, N-(2-ethylphenyl)maleimide, N-(2-methoxyphenyl)maleimide, N-(2-nitrophenyl)maleimide, N-(2-nitrophenyl)maleimide, N-(2-nitrophenyl)maleimide, N-(2-nitrophenyl)maleimide, N-(2-nitrophenyl)maleimide, N-(2-nitrophenyl)maleimide, N-(2-nitrophenyl)maleimide, N-(4 ... Examples of suitable monomers include N-(2,4,6-trimethylphenyl)maleimide, N-(4-benzylphenyl)maleimide, N-(2,4,6-tribromophenyl)maleimide, N-naphthylmaleimide, N-anthracenylmaleimide, 3-methyl-1-phenyl-1H-pyrrole-2,5-dione, 3,4-dimethyl-1-phenyl-1H-pyrrole-2,5-dione, 1,3-diphenyl-1H-pyrrole-2,5-dione, and 1,3,4-triphenyl-1H-pyrrole-2,5-dione. Among these monomers, N-phenylmaleimide and N-benzylmaleimide are preferred because of their excellent heat resistance and optical properties such as birefringence. These monomers may be used alone or in combination of two or more.

[0041] Examples of the monomer that forms the structural unit represented by formula (2) include N-methylmaleimide, N-ethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide, N-isobutylmaleimide, N-s-butylmaleimide, N-t-butylmaleimide, N-n-pentylmaleimide, N-n-hexylmaleimide, N-n-heptylmaleimide, and N-n-octylmaleimide. Examples of suitable monomers include N-laurylmaleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, 1-cyclohexyl-3-methyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-dimethyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3-phenyl-1H-pyrrole-2,5-dione, and 1-cyclohexyl-3,4-diphenyl-1H-pyrrole-2,5-dione. Among these monomers, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, and N-cyclohexylmaleimide are preferred because they provide excellent weather resistance to the methacrylic resin, and N-cyclohexylmaleimide is particularly preferred because it has the low moisture absorption property that has been required for optical materials in recent years. These monomers can be used alone or in combination of two or more.

[0042] In the methacrylic resin in the methacrylic resin composition, it is particularly preferable to use a structural unit represented by formula (1) in combination with a structural unit represented by formula (2), in order to develop highly controlled birefringence characteristics. The molar ratio (X1 / X2) of the content (X1) of the structural unit represented by formula (1) to the content (X2) of the structural unit represented by formula (2) is preferably more than 0 and not more than 15, more preferably more than 0 and not more than 10. When the molar ratio (X1 / X2) is within this range, the resin light guide of this embodiment maintains transparency, does not yellow, and develops good heat resistance and good photoelastic properties without impairing environmental resistance.

[0043] The content of the structural units derived from the N-substituted maleimide monomer is preferably in the range of 5 to 40% by mass, and more preferably in the range of 5 to 35% by mass, based on 100% by mass of the methacrylic resin. When the content of the structural units derived from the N-substituted maleimide monomer is within this range, the methacrylic resin exhibits a more sufficient improvement in heat resistance, and also exhibits more favorable improvements in weather resistance, low water absorption, and optical properties. Furthermore, keeping the content of the structural units derived from the N-substituted maleimide monomer at 40% by mass or less is effective in preventing a decrease in the physical properties of the methacrylic resin due to a decrease in the reactivity of the monomer component during the polymerization reaction and an increase in the amount of unreacted remaining monomer. Furthermore, by appropriately adjusting the content of the structural units derived from the N-substituted maleimide monomer within this range, birefringence caused by orientation and residual stress during molding can be reduced, and a resin light guide for displays can be obtained having an average absolute value of in-plane retardation of 10 nm or less. The optimal content of structural units derived from the N-substituted maleimide monomer varies depending on the type of N-substituted maleimide. For example, when methyl methacrylate is used as the methacrylic acid ester monomer and N-phenylmaleimide and N-cyclohexylmaleimide are used as the N-substituted maleimide monomers, it is preferable to adjust the content within the ranges of 79 to 83% by mass of structural units derived from methyl methacrylate, 6 to 8% by mass of structural units derived from N-phenylmaleimide, and 11 to 13% by mass of structural units derived from N-cyclohexylmaleimide.

[0044] The methacrylic resin having structural units derived from an N-substituted maleimide monomer may contain structural units derived from other monomers copolymerizable with the methacrylic acid ester monomer and the N-substituted maleimide monomer, provided that the objectives of the present invention are not impaired. For example, examples of the other copolymerizable monomers include aromatic vinyls; unsaturated nitriles; acrylic acid esters having a cyclohexyl group, a benzyl group, or an alkyl group having 1 to 18 carbon atoms; glycidyl compounds; unsaturated carboxylic acids; and the like. Examples of the aromatic vinyls include styrene, α-methylstyrene, and divinylbenzene. Examples of the unsaturated nitriles include acrylonitrile, methacrylonitrile, and ethacrylonitrile. Examples of the acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, and butyl acrylate. Examples of the glycidyl compounds include glycidyl (meth)acrylate. Examples of the unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and semi-esterified products or anhydrides thereof. The structural unit derived from the other copolymerizable monomer may be of only one type or may be of two or more types.

[0045] The content of the structural units derived from these other copolymerizable monomers is preferably 0 to 10% by mass, more preferably 0 to 9% by mass, and even more preferably 0 to 8% by mass, based on 100% by mass of the methacrylic resin. When the content of the structural units derived from the other monomers is within this range, it is preferable because it is possible to improve the moldability and mechanical properties of the resin without impairing the inherent effect of introducing a ring structure into the main chain.

[0046] The content of the structural unit derived from the N-substituted maleimide monomer and the content of the structural unit derived from other copolymerizable monomers are as follows: １ H-NMR measurement and １３ It can be determined by C-NMR measurement. １ H-NMR measurement and １３ C-NMR measurement is carried out using, for example, CDCl as a measurement solvent. ３ or DMSO-d ６The measurement can be carried out at a temperature of 40°C.

[0047] --Glutarimide-Based Structural Unit-- Examples of methacrylic resins having glutarimide-based structural units in the main chain include methacrylic resins having glutarimide-based structural units described in, for example, JP 2006-249202 A, JP 2007-009182 A, JP 2007-009191 A, JP 2011-186482 A, and Republished Japanese Patent Application Publication No. 2012 / 114718, and can be formed by the methods described in these publications. The glutarimide-based structural units constituting the methacrylic resin may be formed after resin polymerization. Specifically, the glutarimide-based structural unit may be represented by the following formula (3):

[0048] In the above formula (3), preferably R ７ and R ８ are each independently a hydrogen atom or a methyl group, and R ９ is any one of a hydrogen atom, a methyl group, a butyl group, and a cyclohexyl group, and more preferably, R ７ is a methyl group, and R ８ is a hydrogen atom, and R ９ is a methyl group. The glutarimide structural unit may contain only one type, or may contain multiple types.

[0049] In a methacrylic resin having a glutarimide structural unit, the content of the glutarimide structural unit is preferably in the range of 3 to 70% by mass, more preferably in the range of 3 to 60% by mass, based on 100% by mass of the methacrylic resin. A content of the glutarimide structural unit within the above range is preferred because it results in a resin with good moldability, heat resistance, and optical properties. Furthermore, by appropriately adjusting the content of the glutarimide structural unit within this range, it is possible to reduce birefringence caused by orientation and residual stress during molding, and to obtain a resin light guide for displays with an absolute value of in-plane retardation of 10 nm or less. R in formula (3) ７ ~R ９The optimum content of glutarimide structural units varies depending on the type of substituent of R ７ and R ８ is a hydrogen atom, R ９ When is a methyl group, if the content of glutarimide structural units is in the range of 3 to 10 mass %, birefringence caused by orientation or residual stress during molding can be reduced, and a resin light guide for displays having an absolute value of in-plane retardation of 10 nm or less can be obtained. The content of glutarimide structural units in the methacrylic resin can be determined using the method described in the aforementioned patent document.

[0050] The methacrylic resin having a glutarimide structural unit may further contain an aromatic vinyl structural unit, if necessary. The aromatic vinyl monomer is not particularly limited, but examples thereof include styrene and α-methylstyrene, with styrene being preferred.

[0051] The content of aromatic vinyl structural units in a methacrylic resin having glutarimide structural units is not particularly limited, but is preferably 0 to 20% by mass, based on 100% by mass of the methacrylic resin having glutarimide structural units. Having the aromatic vinyl structural unit content within this range is preferable because it enables both heat resistance and excellent photoelastic properties to be achieved. For example, when a resin is obtained by glutarimidating a methyl methacrylate-styrene copolymer obtained by copolymerizing methyl methacrylate as the methacrylic acid ester monomer and styrene as the aromatic vinyl monomer, by adjusting the content within the ranges of 65 to 90% by mass of methyl methacrylate-derived structural units, 5 to 15% by mass of styrene-derived structural units, and 5 to 20% by mass of glutarimide-based structural units, birefringence caused by orientation and residual stress during molding can be reduced, and a resin light guide for displays with an absolute value of in-plane retardation of 10 nm or less can be obtained.

[0052] --Aromatic Vinyl Structural Unit-- The aromatic vinyl structural unit is not particularly limited, but examples thereof include structural units derived from styrene and α-methylstyrene, with structural units derived from styrene being preferred.

[0053] --Alicyclic vinyl structural unit-- The alicyclic vinyl structural unit can be formed by the methods described in, for example, JP-A Nos. 2006-291184, 2006-291184, 2014-77043, and 2014-77044.

[0054] --Lactone ring structural unit-- Methacrylic resins having a lactone ring structural unit can be formed by methods described in, for example, JP-A Nos. 2001-151814, 2004-168882, 2005-146084, 2006-96960, 2006-171464, 2007-63541, 2007-297620, and 2010-180305.

[0055] The lactone ring structural unit constituting the methacrylic resin may be formed after resin polymerization. In this embodiment, the lactone ring structural unit is preferably a six-membered ring because of its excellent ring structure stability. As the six-membered lactone ring structural unit, for example, a structure represented by the following formula (4) is particularly preferred.

[0056] In the above formula (4), R １０ , R １１ and R １２ are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms. Examples of the organic residue include saturated aliphatic hydrocarbon groups (e.g., alkyl groups) having 1 to 20 carbon atoms such as a methyl group, an ethyl group, or a propyl group; unsaturated aliphatic hydrocarbon groups (e.g., alkenyl groups) having 2 to 20 carbon atoms such as an ethenyl group or a propenyl group; aromatic hydrocarbon groups (e.g., aryl groups) having 6 to 20 carbon atoms such as a phenyl group or a naphthyl group; and groups in which one or more hydrogen atoms in these saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, or aromatic hydrocarbon groups have been substituted with at least one group selected from the group consisting of a hydroxy group, a carboxyl group, an ether group, and an ester group.

[0057] The lactone ring structural unit can be formed, for example, by copolymerizing an acrylic acid monomer having a hydroxy group with a methacrylic acid ester monomer such as methyl methacrylate to introduce a hydroxy group and an ester group or a carboxyl group into the molecular chain, and then causing dealcoholization (esterification) or dehydration condensation (hereinafter also referred to as a "cyclization condensation reaction") between the hydroxy group and the ester group or the carboxyl group.

[0058] Examples of the acrylic acid monomer having a hydroxy group used in the polymerization include 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, alkyl 2-(hydroxymethyl)acrylates (e.g., methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, t-butyl 2-(hydroxymethyl)acrylate), alkyl 2-(hydroxyethyl)acrylates, and the like. Preferred are 2-(hydroxymethyl)acrylic acid and alkyl 2-(hydroxymethyl)acrylates, which are monomers having a hydroxyalkyl moiety, and particularly preferred are methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate.

[0059] The content of lactone ring structural units in methacrylic resins having lactone ring structural units is preferably 5 to 40% by mass, and more preferably 5 to 35% by mass, based on 100% by mass of the methacrylic resin. When the content of lactone ring structural units is within this range, the effects of introducing ring structures, such as improved solvent resistance and surface hardness, can be achieved while maintaining moldability. Furthermore, by appropriately adjusting the content of lactone ring structural units within this range, birefringence caused by orientation and residual stress during molding can be reduced, resulting in a resin light guide for displays with an absolute in-plane retardation of 10 nm or less. The content of lactone ring structures in methacrylic resins can be determined using the method described in the aforementioned patent document.

[0060] The methacrylic resin having a lactone ring structural unit may have a structural unit derived from another monomer copolymerizable with the above-mentioned methacrylic acid ester monomer and acrylic acid monomer having a hydroxy group. Examples of such other copolymerizable monomers include monomers having a polymerizable double bond, such as styrene, vinyltoluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, ethylene, propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinylpyrrolidone, and N-vinylcarbazole. These other monomers (structural units) may be present alone or in combination of two or more.

[0061] The content of the structural units derived from these other copolymerizable monomers is preferably 0 to 20% by mass relative to 100% by mass of the methacrylic resin, and from the viewpoint of weather resistance, is more preferably less than 10% by mass, and even more preferably less than 7% by mass. The methacrylic resin in this embodiment may have only one type of structural unit derived from the other copolymerizable monomer, or may have two or more types.

[0062] -Method for Producing Methacrylic Resin- The method for producing a methacrylic resin according to this embodiment will be described below. In the method for producing a methacrylic resin, a batch system, a semi-batch system, and 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 raw material charging or product recovery is carried out simultaneously while the reaction is in progress. Furthermore, the continuous system is a process in which both raw material charging and product recovery are carried out simultaneously while the reaction is in progress. As a method for producing a methacrylic resin, a semi-batch system in which some raw materials are charged after the start of the reaction is preferred from the viewpoint of precisely controlling the copolymer composition. Furthermore, although a continuous system can be used, it is preferable not to use it as a method for producing a methacrylic resin 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 the color tone tends to be adversely affected because a large amount of unreacted monomer remains after polymerization. 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.

[0063] The polymerization method for the methacrylic resin is not particularly limited, but examples thereof include emulsion polymerization, solution polymerization, radical polymerization, anionic polymerization, and cationic polymerization.

[0064] The polymerization solvent used in the method for producing a methacrylic resin 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, provided 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 monomers used during production, and is an amount that can be easily removed. For example, when the total amount of the monomers to be blended is 100 parts by mass, the amount 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 even more preferably 50 to 150 parts by mass.

[0065] 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, 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.

[0066] The chain transfer agent may be any of those commonly used in radical polymerization, including, for example, 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 are not particularly limited. The amount of chain transfer agent added may be 0.01 to 1 part by mass, and preferably 0.05 to 0.5 parts by mass, relative to 100 parts by mass of the total amount of monomers used in the polymerization.

[0067] When solution polymerization is used, the method for recovering the polymer from the polymerization liquid obtained by solution polymerization is not particularly limited, and examples thereof include a method in which the polymerization liquid is added to the presence of 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 liquid 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; etc. Here, the devolatilization step refers to a step in which volatile components such as the polymerization solvent, residual monomers, and reaction by-products are removed under heated and reduced pressure conditions.

[0068] Examples of the apparatus used in the devolatilization step include a devolatilizer consisting of a tubular heat exchanger and a devolatilizer 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 devolatilizer combining two or more of these devices can also be used.

[0069] From the viewpoint of improving color tone, it is preferable to use a devolatilizer mainly composed of a heat exchanger and a reduced-pressure vessel, and having no rotating part in its structure. Specifically, a devolatilizer can be used that includes a devolatilizer tank configured with a reduced-pressure vessel having a size large enough for devolatilization and a heat exchanger disposed above the vessel, and a decompression unit attached thereto, and a discharge device such as a gear pump for discharging the polymer after devolatilization. The devolatilizer preheats the polymerization solution by passing it through a heated heat exchanger disposed above the reduced-pressure vessel, 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, and then supplies it to a devolatilizer tank that is heated and under reduced pressure, thereby separating and removing the polymerization solvent, unreacted raw material mixture, polymerization by-products, and the copolymer. Using a devolatilizer without a rotating part as described above is preferable because it allows the production of a methacrylic resin having a good color tone.

[0070] 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 to be equal to or higher than the lower limit temperature, the remaining volatile content can be suppressed, and by setting the temperature to be equal to or lower than the upper limit temperature, the coloration and decomposition of the obtained methacrylic resin can be suppressed.

[0071] Additives The methacrylic resin composition contained in the light guide of the present embodiment may contain various additives within a 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.

[0072] --Antioxidant-- The methacrylic resin composition contained in the light guide of this embodiment preferably contains an antioxidant that suppresses deterioration and discoloration during molding or use. Examples of such antioxidants include, but are not limited to, hindered phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. To enhance the transferability of the fine convex shapes of the mold while highly controlling the distortion and warpage of the molded product's surface, it is essential to maintain the resin at a high temperature within the mold cavity and allow an appropriate cooling time. When subjected to long-term thermal history, the amount of heat stabilizer added must be increased to achieve the desired thermal stability. However, from the perspective of suppressing bleedout of the heat stabilizer and preventing adhesion to the mold, it is preferable to use multiple types of heat stabilizers in combination. For example, it is preferable to use at least one selected from a phosphorus-based antioxidant and a sulfur-based antioxidant in combination with a hindered phenol-based antioxidant. These antioxidants may be used alone or in combination of two or more.

[0073] Examples of hindered phenol-based antioxidants include, but are not limited to, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, , 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene bis[ 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylin)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2 ,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamine)phenol, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate, etc. In particular, 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 are preferred.

[0074] Furthermore, as the hindered phenol-based antioxidant, a commercially available phenol-based antioxidant may be used. Examples of such commercially available phenol-based antioxidants include, but are not limited to, Irganox 1010 (Irganox 1010: pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], manufactured by BASF), Irganox 1076 (Irganox 1076: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, manufactured by BASF Corporation), Irganox 1330 (Irganox 1330: 3,3',3'',5,5',5''-hexa-t-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, manufactured by BASF Corporation), 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, manufactured by BASF Corporation), 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 (Cyanox 1790, manufactured by Cytec), Sumilizer GA-80 (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), Vitamin E (manufactured by Eisai), and the like.Among these commercially available phenolic antioxidants, from the viewpoint of the effect of imparting thermal stability to the resin, preferred are Irganox 1010, Adekastab AO-60, Adekastab AO-80, Irganox 1076, Sumilizer GS, etc. These may be used alone or in combination of two or more.

[0075] 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-cresyl-phosphonite, 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), Adekastab 329K (ADK STAB-229K, manufactured by ADEKA), and Adekastab PEP-36 (ADK ADK STAB PEP-36 (manufactured by ADEKA), ADK STAB PEP-36A (manufactured by ADEKA), ADK STAB PEP-8 (manufactured by ADEKA), ADK STAB HP-10 (manufactured by ADEKA), ADK STAB 2112 (manufactured by ADEKA), ADK STAB 1178 (manufactured by ADEKA), ADK STAB 1500 (manufactured by ADEKA), Sandstab P-EPQ (manufactured by Clariant), Weston 618 (manufactured by ADEKA), 618, manufactured by GE), Weston 619G (manufactured by GE), Ultranox 626 (manufactured by GE), Sumilizer GP (4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepine)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol, manufactured by Sumitomo Chemical), and HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, manufactured by Sanko Co., Ltd.).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 antioxidants, Irgafos 168, Adekastab PEP-36, Adekastab PEP-36A, Adekastab HP-10, and Adekastab 1178 are preferred, and Adekastab PEP-36A and Adekastab PEP-36 are particularly preferred. These phosphorus-based antioxidants may be used alone or in combination of two or more types.

[0076] 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 Examples of commercially available sulfur antioxidants include 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1,3-diylbis[3-dodecylthio]propionate] (ADK 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, ADK STAB AO-412S and CHEMINOX PLS are preferred from the viewpoints of the effect of imparting thermal stability to the resin, the effect of using them in combination with various antioxidants, and ease of handling. These sulfur-based antioxidants may be used alone or in combination of two or more.

[0077] 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.

[0078] -Hindered amine light stabilizer- The resin composition contained in the resin light guide for displays of this embodiment can contain a hindered amine light stabilizer. The hindered amine light stabilizer is not particularly limited, but is preferably a compound containing three or more ring structures. Here, the ring structure is preferably at least one selected from the group consisting of an aromatic ring, an aliphatic ring, an aromatic heterocycle, and a non-aromatic heterocycle. When a single compound contains two or more ring structures, the ring structures may be the same or different.Examples of the hindered amine light stabilizer include, but are not limited to, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate, a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidylsebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, N , N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-N,N'-diformylhexamethylenediamine, polycondensation product of dibutylamine, 1,3,5-triazine, N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexamethylenediamine and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl -4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, 2,2,6,6-tetramethyl-4-piperidiol, and 2,2,6,6-tetramethyl-4-piperidyl methacrylate.Among these, hindered amine light stabilizers include bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, which contains three or more ring structures, polycondensation polymer of dibutylamine, 1,3,5-triazine, N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexamethylenediamine and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine 1,2,2,6,6-pentamethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol; and 2,2,6,6-tetramethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol are preferred. The content of the hindered amine light stabilizer may be any amount that provides the effect of improving light stability. If the content is excessive, problems such as bleeding out may occur during processing. Therefore, the content is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, still more preferably 0.8% by mass or less, still more preferably 0.01 to 0.8% by mass, and particularly preferably 0.01 to 0.5% by mass, relative to 100% by mass of the methacrylic resin.

[0079] --UV Absorber-- The methacrylic resin composition contained in the light guide of this embodiment may contain an UV absorber. The UV absorber is not particularly limited, but is preferably an UV absorber having a maximum absorption wavelength of 280 to 380 nm, such as 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 UV absorbers may be used alone or in combination of two or more.

[0080] As the ultraviolet absorber, from the viewpoints of compatibility with the resin and volatility upon heating, benzotriazole compounds and benzotriazine compounds having a molecular weight of 400 or more are preferred, and from the viewpoint of suppressing decomposition of the ultraviolet absorber itself due to heating during extrusion processing, benzotriazine compounds are particularly preferred.

[0081] 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.

[0082] --Release Agent-- The methacrylic resin composition contained in the light guide of this embodiment may contain a release agent. Examples of the release agent include, but are 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.

[0083] The fatty acid ester that can be used as the release agent is not particularly limited, and conventionally known fatty acids can be used. Examples of the fatty acid ester that can be used include ester compounds of a fatty acid having 12 to 32 carbon atoms, such as lauric acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, arachic acid, or behenic acid, with a monohydric aliphatic alcohol, such as palmityl alcohol, stearyl alcohol, or behenyl alcohol, or a polyhydric aliphatic alcohol, such as glycerin, pentaerythritol, dipentaerythritol, or sorbitan; and complex ester compounds of a fatty acid, a polybasic organic acid, and a monohydric aliphatic alcohol or a polyhydric aliphatic alcohol. Examples of such fatty acid esters 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, and glycerin monolinoleate. , 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, etc. These fatty acid esters may 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, Leodol series, Excelpar 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 Leodol MS-50.

[0084] The content of the release agent may be any amount that is effective as a release agent, and since an excessive content may cause problems such as bleed-out during processing or poor extrusion due to screw slippage, the content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, still more preferably 0.8 parts by mass or less, still more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass, relative to 100 parts by mass of the methacrylic resin. Addition of the release agent in an amount within the above range not only suppresses the decrease in transparency due to the addition of the release agent, but also tends to suppress poor release during injection molding.

[0085] --Other Thermoplastic Resins-- The methacrylic resin composition of this embodiment may contain other thermoplastic resins in addition to methacrylic resins 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, acrylonitrile-butadiene-styrene block copolymer; and further, for example, JP-A-59-202213, JP-A-63-27516, JP-A-51-129449, JP-A-52-56150, etc., described in acrylic rubber particles having a 3-4 layer structure; JP-B-60-17406, rubbery polymers disclosed in JP-A-8-245854; and methacrylic rubber-containing graft copolymer particles obtained by multistage polymerization, as described in WO 2014-002491; and the like. Among these, from the viewpoint of obtaining good optical properties and mechanical properties, rubber-containing graft copolymer particles having, on their surface layer, a graft moiety made of a composition compatible with a styrene-acrylonitrile copolymer or a methacrylic resin containing a structural unit 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 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 light guide of this embodiment.

[0086] 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.

[0087] (Method for manufacturing a resin light guide for displays) The method for manufacturing a resin light guide for displays of this embodiment is a method for manufacturing a resin light guide for displays by injection compression molding of a thermoplastic resin composition, and includes a resin filling step and a compression step, wherein the temperature from the tip to the center of the nozzle of the injection molding machine cylinder is set to a temperature that is 120 to 180°C higher than the glass transition temperature (Tg) of the thermoplastic resin composition, and the mold temperature is set in the range of (Tg-80)°C to (Tg-35)°C relative to the glass transition temperature (Tg) of the thermoplastic resin composition, and each of the conditions, namely the injection speed and filling time in the resin filling step, the compression distance, compression time and compression pressure in the compression step, and the compression delay time and cooling time set between the resin filling step and the compression step, are adjusted so as to satisfy the following (1) and (2): (1) the absolute value of the in-plane retardation of the resin light guide for displays is 10 nm or less. (2) In the resin light guide for a display, the PV value of the effective area surface along which image light is guided is 100 μm or less. According to the above manufacturing method, a resin light guide for a display having good appearance and image quality can be manufactured.

[0088] The resin light guide for displays of this embodiment can be manufactured by injection compression molding the above-described thermoplastic resin composition using an injection molding machine. In the manufacturing method for a resin light guide for displays of this embodiment, when manufacturing the light guide using an injection molding machine, 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 thermoplastic resin composition used. This allows the molten resin to flow sufficiently, enabling molding in a state where deterioration due to thermal decomposition of the resin is suppressed. Thermal decomposition of the resin not only adversely affects color tone, transmittance, and haze, but also generates gas during injection molding. This generated gas fills the mold, preventing the gas from being expelled during resin filling, thereby hindering resin filling and reducing mold transfer rate. The temperature from the nozzle tip to the center of the injection molding machine cylinder is more preferably 130 to 170°C higher than the glass transition temperature (Tg) of the thermoplastic resin composition used.

[0089] The mold temperature during injection compression molding of the light guide of this embodiment is set in the range of (Tg-80)°C to (Tg-35)°C, relative to the glass transition temperature (Tg) of the thermoplastic resin composition used. The mold temperature is more preferably (Tg-75)°C to (Tg-40)°C, and even more preferably (Tg-70)°C to (Tg-45)°C. Setting the mold temperature within this range controls the degree of orientation of the thermoplastic resin composition, reduces birefringence, and further suppresses warping, resulting in a light guide with excellent surface precision. If the mold temperature is lower than (Tg-80)°C, the degree of orientation tends to increase and birefringence tends to increase. Furthermore, the fluidity of the resin within the mold decreases, which tends to cause thickness unevenness in the light guide and deteriorate surface precision. On the other hand, if the mold temperature is higher than (Tg-35)°C, warping of the light guide occurs and surface precision deteriorates; therefore, the mold temperature is preferably within the above range.

[0090] The thermoplastic resin composition used in the method for producing a resin light guide for displays is the same as the thermoplastic resin composition described above in the section on resin light guide for displays, and the description in the section on resin light guide for displays is hereby incorporated by reference.

[0091] The manufacturing method of a resin light guide for displays of this embodiment includes a resin filling step and a compression step. The manufacturing method of a resin light guide for displays of this embodiment adjusts the following conditions (1) and (2): the injection speed and filling time in the resin filling step, the compression distance, compression time, and compression pressure in the compression step, and the compression delay time and cooling time set between the resin filling step and the compression step. (1) The absolute value of the in-plane retardation of the resin light guide for displays is 10 nm or less. (2) In the resin light guide for displays, the PV value of the effective area surface through which image light is guided is 100 μm or less. The resin filling step is a step of filling a mold with resin, and the compression step is a step of filling the mold with resin and then clamping and compressing the resin. The method of adjusting the conditions (1) and (2) to satisfy the above conditions will be described later.

[0092] The cooling time during injection compression molding can be set as appropriate, but it is better to make it as long as possible. By cooling slowly, the distortion caused by molding is alleviated by the annealing effect, which tends to reduce birefringence.

[0093] In the production of the light guide of this embodiment, an annealing step may be performed to relieve residual stress caused by injection compression molding and reduce birefringence of the light guide. The annealing temperature is preferably in the range of (Tg-50)°C to Tg, and more preferably in the range of (Tg-30)°C to (Tg-10)°C, based on the glass transition temperature (Tg) of the resin composition. If the annealing temperature is within the above range, the residual stress can be removed without deforming the light guide.

[0094] In the resin filling step, the injection speed when injection-compression molding the light guide of this embodiment can be appropriately selected depending on the thickness and dimensions of the resin light guide to be obtained, and can be appropriately selected from the range of 10 to 1,000 mm / sec, for example. There is a correlation between the injection speed and the degree of orientation; a faster injection speed tends to increase the degree of orientation, and a slower injection speed tends to decrease the degree of orientation. Furthermore, in the resin filling step, the filling time can be appropriately set.

[0095] The injection pressure when injection compression molding the light guide of this embodiment may be set appropriately so as to obtain a desired injection speed.

[0096] In the compression step, in order to satisfy (1) and (2), the compression pressure is preferably 100 to 5000 kN.

[0097] When the light guide of this embodiment has fine convex shapes on a part or multiple locations on the surface, in order to improve the transferability of the fine convex shapes, the light guide may be manufactured by heat-and-cool molding, in which the mold is heated to a temperature equal to or higher than the glass transition temperature of the resin used before filling the mold with resin, the resin is filled in the mold while the mold is heated, and then the mold is cooled.

[0098] In the production of the light guide of this embodiment, when heat-and-cool molding is used, the method for heating the mold is not particularly limited and may be any method. Examples include a method in which a water or oil flow path is arranged in the mold and the mold temperature is adjusted to a temperature equal to or higher than the Tg of the methacrylic resin composition using a medium such as water or oil; a method in which a heater is embedded in the mold and the mold is heated; a method in which an electrically conductive layer is provided on the surface of the mold and current is applied to generate heat; a method in which the mold is heated from the outside or inside using an induction heating device; and a method in which the mold is heated from the outside by radiation of far infrared rays using a halogen lamp or ceramic heater. Furthermore, the method for cooling the mold is not particularly limited and may be any method. Examples include a method in which a water or oil flow path is arranged in the mold and the mold is cooled using a medium such as water or oil.

[0099] When the light guide of this embodiment is produced by injection compression molding, the compression distance in the compression step is preferably set to 100 to 300% of the thickness of the light guide, more preferably 120 to 250%, and even more preferably 150 to 200%. If the compression distance is less than 100%, it becomes difficult to fill the resin, and the light guide tends to be insufficiently filled. On the other hand, if the compression distance is greater than 300%, thickness unevenness in the light guide tends to occur and the PV value tends to increase, so it is preferable to set the compression distance to 100 to 300% of the thickness of the light guide.

[0100] When fabricating the light guide of this embodiment by injection compression molding, it is preferable to set a compression delay time between the resin filling step and the compression step. The compression delay time is preferably set to 80 to 150% of the injection time, more preferably 90 to 120%, and even more preferably 100 to 110%. If the compression delay time is less than 80% of the injection time, pressure is applied to the resin from both the compression and injection directions during injection, causing unstable flow and making it difficult to control the thickness of the light guide. As a result, thickness unevenness in the light guide tends to occur, and the PV value tends to increase. On the other hand, if the compression delay time is greater than 150% of the injection time, it takes too long between injection and compression, causing the resin to solidify and lose fluidity, resulting in greater thickness unevenness in the light guide and a tendency for the PV value to increase. Therefore, it is preferable to set the compression delay time within the above range.

[0101] The surface of the light guide of this embodiment may be further subjected to surface functionalization treatments such as hard coating treatment, anti-reflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, gas barrier treatment, etc. The thickness of these functional layers is not particularly limited, but is usually in the range of 0.01 to 10 μm.

[0102] The hard coat layer applied to the surface of the light guide can be formed by applying a coating solution prepared by dissolving or dispersing a silicone-based curable resin, an organic polymer composite inorganic particle-containing curable resin, an acrylate such as urethane acrylate, epoxy acrylate, or polyfunctional acrylate, and a photopolymerization initiator in an organic solvent, to a film or sheet obtained from the resin composition of this embodiment using a conventional coating method, drying the coating, and then photocuring the coating. Furthermore, to improve adhesion, a method can also be used in which, before applying the hard coat layer, an easy-adhesion layer, a primer layer, an anchor layer, or the like containing inorganic particles is pre-formed, and then the hard coat layer is formed. The antiglare layer applied to the surface of the light guide can be formed by forming particles of silica, melamine resin, acrylic resin, or the like into an ink, applying the ink to another functional layer using a conventional coating method, and then curing the ink with heat or light. Examples of antireflection layers to be applied to the surface of the light guide include those made of thin films of inorganic materials such as metal oxides, fluorides, silicides, borides, nitrides, and sulfides, and those made by laminating single or multiple layers of resins with different refractive indices such as acrylic resins and fluororesins.In addition, those made by laminating thin layers containing composite fine particles of inorganic compounds and organic compounds can also be used.

[0103] (Image display device) The image display device of this embodiment preferably includes the resin light guide for displays of this embodiment. The image display device includes the light guide of this embodiment, and therefore has good image quality.

[0104] The image display device of this embodiment can be manufactured by a conventionally known method, for example, by the method described in WO2017 / 047528.

[0105] The present invention will be explained below by way of specific examples and comparative examples, but is not limited to these.

[0106] [Raw Materials] Raw materials used in the examples and comparative examples described later are shown below.

[0107] [Monomers constituting methacrylic resins] Methyl methacrylate (MMA): manufactured by Asahi Kasei Corporation N-phenylmaleimide (PMI): manufactured by Nippon Shokubai Co., Ltd. N-cyclohexylmaleimide (CMI): manufactured by Nippon Shokubai Co., Ltd. Styrene: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. 2-(hydroxymethyl)methyl acrylate (MHMA): manufactured by Combi-Blocks

[0108] [[Organic solvents]] Metaxylene (mXy): manufactured by Mitsubishi Gas Chemical Co., Ltd. Methyl isobutyrate: manufactured by Kanto Chemical Co., Ltd. Toluene: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0109] [Polymerization initiator] 1,1-di(t-butylperoxy)cyclohexane: manufactured by NOF Corporation t-Amylperoxy-2-ethylhexanoate: "Luperox 575" manufactured by Arkema Yoshitomi Co., Ltd. t-Amylperoxyisononanoate: manufactured by Arkema Yoshitomi Co., Ltd.

[0110] [Chain transfer agent] n-Octyl mercaptan: manufactured by Chevron Phillips Chemical Company n-Dodecyl mercaptan: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0111] [Additives] Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]: "Irganox 1010" manufactured by BASF Tris(2,4-di-t-butylphenyl)phosphite: "Irgafos 168" manufactured by BASF Rikemal H-100: manufactured by Riken Vitamin Co., Ltd. Stearyl phosphate / distearyl phosphate mixture: manufactured by Sakai Chemical Industry Co., Ltd. Monomethylamine: manufactured by Mitsubishi Gas Chemical Company, Inc.

[0112] (Evaluation of Properties of Methacrylic Resin Composition) Hereinafter, methods for measuring the properties of the methacrylic resin composition will be described.

[0113] (1) Measurement of Weight-Average Molecular Weight (Mw) The weight-average molecular weight (Mw) of the methacrylic resin composition was measured using the following apparatus and conditions. Measuring apparatus: Gel permeation chromatography (HLC-8320GPC) manufactured by Tosoh Corporation. Measurement conditions: Column: One TSKguard column Super H-H, two TSKgel Super HM-M, and one TSKgel Super H2500 were connected in series. Column temperature: 40°C. Developing solvent: tetrahydrofuran. Flow rate: 0.6 mL / min. 2,6-di-t-butyl-4-methylphenol (BHT) was added as an internal standard at 0.1 g / L. Detector: RI (differential refraction) detector Detection sensitivity: 3.0 mV / min Sample: 20 mL solution of 0.02 g of resin light guiding body in tetrahydrofuran Injection amount: 10 μL Standard sample for calibration curve: The following 10 types of polymethyl methacrylate (PMMA Calibration Kit M-M-10, manufactured by Polymer Laboratories) with known monodisperse weight peak molecular weights and different molecular weights were used. Weight peak molecular weight (Mp) Standard sample 1 1,916,000 Standard sample 2 625,500 Standard sample 3 298,900 Standard sample 4 138,600 Standard sample 5 60,150 Standard sample 6 27,600 Standard sample 7 10,290 Standard sample 8 5,000 Standard sample 9 2,810 Standard sample 10 850 Under the above conditions, the RI detection intensity was measured against the elution time of the resin light guide. Based on each calibration curve obtained by measuring the standard samples for the calibration curve, the weight average molecular weight (Mw) of the resin light guide was calculated.

[0114] (2) Measurement of photoelastic coefficient The methacrylic resin composition was pressed into a film using a vacuum compression molding machine to prepare a measurement sample. Specific sample preparation conditions included a vacuum compression molding machine (SFV-30 model manufactured by Shinto Metal Industries) preheating the resin composition at 260 ° C. under reduced pressure (approximately 10 kPa) for 10 minutes, compressing the resin composition at 260 ° C. and approximately 10 MPa for 5 minutes, releasing the reduced pressure and press pressure, and then transferring the resin composition to a cooling compression molding machine for cooling and solidification. The obtained pressed film was aged for 24 hours or more in a constant temperature and humidity chamber adjusted to 23 ° C. and 60% humidity, and then a measurement specimen (thickness approximately 150 μm, width 6 mm) was cut out. The photoelastic coefficient C was measured using a birefringence measurement device described in detail in Polymer Engineering and Science 1999, 39, 2349-2357. Ｒ (Pa －１ ) was measured. The film-like test piece was placed in a film tensioning device (manufactured by Imoto Manufacturing Co., Ltd.) similarly installed in a constant temperature and humidity chamber so that the distance between chucks was 50 mm. Next, a birefringence measuring device (manufactured by Otsuka Electronics, RETS-100) was placed so that the laser light path of the device was located at the center of the film, and the birefringence of the test piece was measured while applying a tensile stress at a strain rate of 50% / min (distance between chucks: 50 mm, chuck movement speed: 5 mm / min). The absolute value of birefringence (|Δn|) and the tensile stress (σ Ｒ ) relationship, the slope of the line is calculated by least squares approximation, and the photoelastic coefficient (C Ｒ ) (Pa －１ ) was calculated. For the calculation, the tensile stress was 2.5 MPa≦σ Ｒ Data between ≦10 MPa was used. Ｒ = |Δn| / σ Ｒ Here, the absolute value of birefringence (|Δn|) is the value shown below: |Δn|=|nx-ny| (nx: refractive index in the stretching direction, ny: refractive index in the in-plane direction perpendicular to the stretching direction).

[0115] (3) Measurement of Glass Transition Temperature The glass transition temperature of the methacrylic resin composition was measured in accordance with JIS-K 7121. Using a differential scanning calorimeter (DSC8000, manufactured by PerkinElmer Japan Co., Ltd.) 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). The DSC curve drawn during this period was measured. The intersection of the step-like change portion of the second heating and a straight line equidistant from each baseline extension in the vertical direction (midpoint glass transition temperature) was measured as the glass transition temperature (Tg) (°C).

[0116] (4) Measurement of Total Light Transmittance The total light transmittance was measured for a 3 mm thick molded body using a turbidity meter COH7700 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with the provisions of JIS K 7361. After drying the pellets at 90°C for 12 hours or more, molded bodies were produced using an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd., SE180EV-A) with a mold size of 100 mm x 100 mm x 3 mm thick.

[0117] (5) Measurement of Melt Flow Rate (MFR) The melt flow rate of the methacrylic resin composition was measured at a temperature of 230° C. and a load of 37 N using a melt indexer (manufactured by Toyo Seiki Seisakusho) under conditions in accordance with JIS K7210 Method A.

[0118] (Evaluation of Light Guide) The evaluation method of the light guide will be described below.

[0119] (1) Measurement of in-plane retardation of light guide The light guide was placed on the measurement table of a PA-300-L (manufactured by Photonic Lattice, Inc.), and the in-plane retardation distribution was measured at a wavelength of 520 nm. The average absolute value of the in-plane retardation (Re) in the measurement area was calculated, and this was used as the measured value of retardation (nm). The birefringence value is preferably 10 nm or less as the in-plane retardation, which is a range that is unlikely to adversely affect the optical properties.

[0120] (2) Evaluation of the Degree of Orientation The degree of orientation on the surface of the light guide was evaluated using a polarized ATR method under the following conditions: Measurement conditions: Apparatus: Fourier transform infrared spectrophotometer (JASCO FT / IR-4100) Spectral resolution: 4 cm －1 Measurement method: Polarized ATR method (using a polarized single-reflection ATR-PRO610P-S) Infrared polarization direction: Parallel polarization to the ATR crystal surface (measurement surface) ATR crystal: Diamond Number of measurements: 32 Parallel polarized light was incident on the sample surface using a polarized single-reflection ATR jig near the gate, center, and flow end of the light guide, and MD measurements were performed by aligning the polarization direction of the infrared light with the resin flow direction, and TD measurements were performed by rotating the sample 90°. To confirm data reproducibility, the ATR crystal and light guide were separated each time and measurements were taken four times at the same position. Note that the MD direction is the longitudinal direction (resin flow direction) when the light guide was molded, and the TD direction is the direction perpendicular to the MD direction. From the obtained MD / TD spectrum, the methylene CH asymmetric in-plane bending vibration (rolling vibration) of MMA, which is sensitive to orientation, was determined to be 750 cm -1 The peak intensity of 896 cm was calculated, and the peak intensity of 896 cm was calculated, which is insensitive to orientation, for correction of the contact pressure (vertical axis). －1 The ratio of the peak intensity (750 / 896 cm -1 ) and calculated the degree of orientation of MMA (orientation distribution function)<P from the following formula (i) described in APPLIED Optics, Vol. 54 Issue 4, pp. 779-788, 2015. ２ > was requested. (In formula (i), A ＭＤ represents the absorbance in MD polarized light, and A ＴＤ represents the absorbance in TD polarized light, and ψ represents the angle between the direction of the transition dipole moment and the orientation axis.) When calculating the degree of orientation, ψ was set to 17° based on the above literature. -1 and the peak intensity of 896 cm －1 The two-point baseline method was used to calculate the peak intensity, and the peak was calculated within the range described below. The average value of four measurements was used to evaluate the degree of orientation. -1 Intensity peak (left end) 781.029 cm －1 ~724.139cm －1 (Right end) 896cm -1Intensity peak (left end) 904.451 cm －1 ~879.381cm －1 (Right end) If the peak width is different from this range, the values ​​at both ends of the peak can be adjusted appropriately.

[0121] (3) Evaluation of Sharpness of Displayed Image The sharpness of the displayed image was evaluated as one indicator of image quality. Using the light guides obtained in the examples and comparative examples, reflection volume hologram diffraction gratings (first reflection volume hologram and second reflection volume hologram) were bonded to the opposing surfaces of the image light incident surface (incident surface) and the display light exit surface (exit surface) in the arrangement shown in Figure 1 to create an evaluation system as shown in Figure 1. Figure 1 is formed by combining an image projection unit, a bandpass filter (an optical filter that transmits only wavelengths between 615 and 645 nm), a light guide, a first reflection volume hologram (with diffraction properties selective for red wavelengths), and a second reflection volume hologram (with diffraction properties selective for red wavelengths). Light emitted from the image projection unit enters the light guide, is diffracted by the first reflection volume hologram, changes direction, and is guided through the light guide by total reflection. The guided light reaches the second reflection volume hologram, where it is diffracted, changing direction and entering the observer's pupil. In Figure 1, the X-axis is the direction of travel of the image light, and the light guide was installed so that the incident surface was the Y-Z plane. A monochrome red still image was projected from the image projection unit, and the clarity of the image when viewed at the position of the observer's pupil was evaluated using the following evaluation criteria. [Evaluation criteria] Image clarity A: No bleeding, blurring, or distortion was observed in the image, and the red color was clearly reproduced. B: The image was slightly unclear due to bleeding, blurring, and distortion, and uneven brightness and reduced brightness were observed. C: The image was unclear due to bleeding, blurring, and distortion, making it unclear what was being projected, and uneven brightness and reduced brightness were observed.

[0122] (4) Measurement of Polarization Retention Using the light guides obtained in the Examples and Comparative Examples, a reflection volume hologram diffraction grating was adhered to each of the opposing surfaces of the image light incident portion (incident surface) and the display light exit portion (exit surface) in the arrangement shown in Figure 4, to prepare an evaluation system as shown in Figure 4. Figure 4 is formed by combining an image light projection portion (a red laser light source), a bandpass filter (an optical filter that transmits only wavelengths between 615 and 645 nm), a first linear polarizer, a second linear polarizer, a light guide, a first reflection volume hologram (having diffraction properties selective for red wavelengths), and a second reflection volume hologram (having diffraction properties selective for red wavelengths). Light emitted from the image projection portion passes through the bandpass filter and the first linear polarizer, enters the light guide, is diffracted by the first reflection volume hologram, changes direction, and is guided through the light guide by total reflection. The guided light reaches the second reflection volume hologram, changes direction by being diffracted, and enters the second linear polarizer and power meter. In FIG. 4 , the X-axis represents the direction of travel of the image light, and the light guide 2 is installed so that the incident surface is the Y-Z plane. Monochromatic red light from a red laser light source is incident on the light guide, and the light extracted by the reflection volume hologram is measured using a power meter. The optical path length was set to approximately 16 cm. The light amount measured when the second linear polarizer is arranged parallel to the first linear polarizer is defined as Tp (parallel), and the light amount measured when the second linear polarizer and the first linear polarizer are arranged crosswise is defined as Tc (cross). The polarization retention was calculated using the formula Tp / (Tc+Tp). In FIG. 4 , the state in which the transmission axes of the second linear polarizer and the first linear polarizer are parallel is defined as a parallel arrangement, and the state in which the transmission axes of the second linear polarizer and the first linear polarizer are perpendicular is defined as a cross arrangement.

[0123] (5) Observation of Micro-Protrusions Micro-protrusion measurements were performed using an atomic force microscope Dimension Icon (manufactured by BRUKER) and an AR-5T type Si single crystal probe (tip aspect ratio 5 / high aspect ratio height 2 μm), and the line width and height of the micro-protrusions were determined.

[0124] (6) PV Value Measurement of Lightguide Using a non-contact three-dimensional measuring machine NH-3SP (manufactured by Mitaka Optical Instruments Co., Ltd.), measurements were performed in the X and Y directions along a distance of 1 / 4 of the length in the Y-axis direction (short side direction) from the outer periphery of the lightguide in the arrangement shown in Figure 2. PV value measurements were performed on all surfaces involved in the waveguiding of image light, and the value of the surface with the maximum PV value was taken as the PV value of the lightguide. The measurement pitch in the X direction was set to 1 / 1000 of the longest part of the length of the lightguide in the X-axis direction, and the measurement pitch in the Y direction was set to 1 / 10 of the longest part of the length of the lightguide in the Y-axis direction. If the lightguide surface contained a portion with diffractive properties, the surface excluding that portion was measured to determine the PV value. A smaller PV value indicates a higher flatness of the lightguide, a better appearance with reduced warping and thickness unevenness, and excellent image quality.

[0125] (7) Measurement of thickness unevenness of light guide The light guide was placed on a surface plate with the flat surface facing down, and the area where the PV value was measured was divided into six sections using a digital length measuring machine VL-50S (manufactured by Mitutoyo Corporation), and the thickness of each section was measured. The measured values ​​of the six sections were averaged, and the difference from the designed thickness was calculated. The absolute value of this average was used as the measurement value of thickness unevenness. Furthermore, if the light guide surface had a section with a diffractive function, the surface area excluding this section was divided into six sections, and the thickness of each section was measured to measure thickness unevenness.

[0126] (8) Presence or absence of cracks The presence or absence of cracks in the fabricated light guide was observed as an index showing the quality of the appearance. The fabricated light guide was visually observed and evaluated for the presence or absence of cracks.

[0127] (Preparation of Methacrylic Resin Compositions) 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 mixed in a 1.25 m ３The 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 additional addition. The contents of the reactor were subjected to nitrogen bubbling at a rate of 30 L / min for 1 hour, and Tank 1 and Tank 2 were each subjected to nitrogen bubbling at a rate of 10 L / min for 30 minutes to remove dissolved oxygen. Thereafter, steam was blown into the jacket to raise the solution temperature in the reactor to 125°C, and polymerization was initiated by adding a polymerization initiator solution prepared by dissolving 0.457 kg of 1,1-di(t-butylperoxy)cyclohexane in 2.67 kg of mXy at a rate of 1 kg / hr while stirring at 50 rpm. Note that during polymerization, the solution temperature in the reactor was controlled at 125±2°C by temperature control using the jacket. Thirty minutes after the start of polymerization, the addition rate of the polymerization initiator solution was reduced to 0.25 kg / hour, and mXy was added from Tank 1 at 29.24 kg / hour for 3.5 hours. Next, four hours after the start of polymerization, the addition rate of the polymerization initiator solution was increased to 0.75 kg / hour, and additional MMA solution was added from Tank 2 at 95 kg / hour for two hours. Furthermore, six hours after the start of polymerization, the addition rate of the polymerization initiator solution was reduced to 0.25 kg / hour, and addition was stopped seven hours after the start of polymerization. Eight hours after the start of polymerization, a polymerization solution containing a methacrylic resin was obtained. To this was added 0.261 kg of Irganox 1010 and 0.784 kg of Irgafos 168 as antioxidants, and 0.784 kg of Rikemal H-100 as a mold release agent. Next, the obtained polymerization solution was supplied to a concentrating apparatus consisting of a tubular heat exchanger preheated to 250°C and a vaporization tank, and devolatilization was carried out. The degree of vacuum in the vaporization tank was set to 10 to 15 Torr. The resin that flowed down the vaporization tank was discharged with a screw pump, extruded through a strand die, cooled with water, and pelletized to obtain a methacrylic resin composition A having N-substituted maleimide structural units. The obtained methacrylic resin composition A had a Tg of 133°C, a weight-average molecular weight of 130,000, and an MFR of 1.2 g / 10 min.The composition of the methacrylic resin composition A determined by NMR was as follows: MMA units: 81% by mass, PMI units: 7% by mass, and CMI units: 12% by mass.

[0128] 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 at 1 kg / h to a 10 L complete mixing vessel equipped with a helical ribbon blade, and 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 so that the liquid level in the polymerization vessel remained constant, and then fed to a concentration apparatus consisting of a tubular heat exchanger and a vaporization vessel for devolatilization. The vacuum in the vaporization vessel was set to 10 to 15 Torr. The resin flowing down the vaporization vessel was discharged with 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. The composition of the methyl methacrylate-styrene copolymer determined by NMR was 60% by mass of MMA units and 40% by mass of styrene units. 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 the 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, and the mixture was maintained at 200°C under a hydrogen pressure of 9 MPa for 15 hours to hydrogenate the aromatic double bonds of the styrene moiety of the copolymer. The hydrogenation catalyst was removed using a filter, and 0.05 parts by mass of Rikemal H-100 was added to and mixed with the polymer solution. The mixture was then supplied to a concentrator consisting of a tubular heat exchanger and a vaporization tank for devolatilization. The vacuum in the vaporization tank was set to 10 to 15 Torr. The resin that flowed down the vaporization tank was discharged with a gear pump, extruded through a strand die, cooled with water, and pelletized to obtain a methacrylic resin composition B with a hydrogenation reaction rate of 96%. The resulting methacrylic resin composition B had a Tg of 118°C, a weight average molecular weight of 170,000, and an MFR of 6.9 g / 10 min.

[0129] Synthesis Example 3 [Methacrylic Resin Composition C] A 200 L reactor equipped with a paddle-type stirrer, a temperature sensor, a cooling tube, and a nitrogen inlet tube was charged with 41.0 kg of methyl methacrylate (MMA), 10.0 kg of methyl 2-(hydroxymethyl)acrylate (manufactured by Combi Bloks), and 50.0 kg of toluene to prepare a raw material solution. The mixture was stirred while passing nitrogen through, and the liquid temperature was raised to 107°C. Separately, an initiator feed solution was prepared by mixing 0.05 kg of 1,1-di(t-butylperoxy)cyclohexane and 0.36 kg of toluene. When the raw material solution temperature reached 107°C, the feed of the initiator feed solution was initiated according to profiles (1) to (6). (1) 0.0 to 0.5 hours: Feed rate 0.20 kg / hr (2) 0.5 to 1.0 hours: Feed rate 0.10 kg / hr (3) 1.0 to 2.0 hours: Feed rate 0.08 kg / hr (4) 2.0 to 3.0 hours: Feed rate 0.07 kg / hr (5) 3.0 to 4.0 hours: Feed rate 0.028 kg / hr (6) 4.0 to 7.0 hours: Feed rate 0.026 kg / hr After the initiator was fed over a total of 7 hours, the reaction was continued for an additional 1 hour, and the polymerization reaction was completed over a total of 8 hours. During the polymerization reaction, the internal temperature was controlled at 107±2°C. 51 g of a stearyl phosphate / distearyl phosphate mixture was added to the resulting polymer solution, and the cyclization condensation reaction was carried out under reflux (approximately 90 to 110°C) for 5 hours. The resulting polymerization liquid was subjected to a cyclocondensation reaction and devolatilization treatment using a φ42 mm twin-screw devolatilizing extruder equipped with four front vents and one back vent, at 140 rpm and a resin equivalent of 10 kg / h, to obtain a methacrylic resin composition C. The resulting methacrylic resin composition C had a Tg of 129°C, a weight-average molecular weight of 130,000, and an MFR of 7.1 g / 10 min. The composition of the methacrylic resin composition C determined by NMR was: MMA units: 82 mass%, lactone ring structural units: 17 mass%, and MHMA units: 1 mass%.

[0130] Synthesis Example 4 [Methacrylic Resin Composition D] A 1.25 m methacrylic resin composition was prepared using a stirring device equipped with a paddle blade, a temperature sensor, a cooling tube, and a nitrogen inlet tube. ３A reactor was charged with 550 kg of methyl methacrylate (MMA), 450 kg of meta-xylene, and 0.18 g of n-octyl mercaptan and dissolved to prepare a raw material solution. The temperature was raised to 125°C while stirring and nitrogen was passed through the solution. Separately, an initiator feed solution was prepared by mixing 0.23 kg of 1,1-di(t-butylperoxy)cyclohexane and 1.82 kg of meta-xylene. When the raw material solution reached 127°C, feeding of the initiator feed solution was started according to profiles (1) to (6). (1) 0.0 to 0.5 hours: feed rate 1.00 kg / hr (2) 0.5 to 1.0 hours: feed rate 0.50 kg / hr (3) 1.0 to 2.0 hours: feed rate 0.42 kg / hr (4) 2.0 to 3.0 hours: feed rate 0.35 kg / hr (5) 3.0 to 4.0 hours: feed rate 0.20 kg / hr (6) 4.0 to 7.0 hours: feed rate 0.13 kg / hr After feeding the initiator over a total of 7 hours, the reaction was continued for another 1 hour, and the polymerization reaction was completed over a total of 8 hours. The obtained polymerization liquid was subjected to a devolatilization treatment using a φ42 mm devolatilization extruder equipped with four front vents and one back vent at 140 rpm and 10 kg / hr in terms of resin amount, to obtain resin pellets. Five parts by mass of monomethylamine (40% by mass monomethylamine aqueous solution) per 100 parts by mass of the resulting resin pellets was introduced into a vented twin-screw extruder via a side feeder at a barrel temperature of 250°C, and an imidization reaction was carried out. Excess methylamine and water were appropriately removed from a vent port installed downstream of the extruder, yielding methacrylic resin composition D. The resulting methacrylic resin composition D had a Tg of 122°C, a weight-average molecular weight of 130,000, and an MFR of 1.3 g / 10 min. Furthermore, the composition of methacrylic resin composition D determined by NMR was 95% by mass of MMA units and 5% by mass of glutarimide structural units.

[0131] Synthesis Example 5 [Methacrylic Resin Composition E] Polymerization was carried out in the same manner as in Synthesis Example 1, except that the amount of n-octyl mercaptan used as a chain transfer agent was changed to 0.708 kg, to obtain a methacrylic resin composition E. The resulting methacrylic resin composition E had a Tg of 134°C, a weight-average molecular weight of 90,000, and an MFR of 2.8 g / 10 min. The composition of the methacrylic resin composition E determined by NMR was: MMA units: 81% by mass, PMI units: 7% by mass, and CMI units: 12% by mass.

[0132] Synthesis Example 6 [Methacrylic Resin Composition F] A 1.25 m methacrylic resin composition was prepared using a stirring device equipped with a paddle blade, a temperature sensor, a cooling pipe, and a nitrogen inlet pipe. 3 A raw material solution was prepared by dissolving 445 kg of methyl methacrylate (MMA), 44 kg of N-phenylmaleimide (PMI), 61 kg of N-cyclohexylmaleimide (CMI), 450.0 kg of meta-xylene, and n-octyl mercaptan in an amount of 100 ppm by mass relative to 100 parts by mass of the total amount of all monomers in a reaction kettle. The temperature was raised to 125°C while stirring and nitrogen was passed through the solution. Separately, an initiator feed solution was prepared by mixing 0.23 kg of 1,1-di(t-butylperoxy)cyclohexane and 1.82 kg of meta-xylene. When the raw material solution reached 127°C, the feed (addition) of the initiator feed solution (polymerization initiator solution) was initiated according to the profiles (1) to (6). (1) 0.0 to 0.5 hours: feed rate 1.00 kg / hr (2) 0.5 to 1.0 hours: feed rate 0.50 kg / hr (3) 1.0 to 2.0 hours: feed rate 0.42 kg / hr (4) 2.0 to 3.0 hours: feed rate 0.35 kg / hr (5) 3.0 to 4.0 hours: feed rate 0.14 kg / hr (6) 4.0 to 7.0 hours: feed rate 0.13 kg / hr After the initiator was fed over a total of 7 hours, the reaction was continued for another hour, and the polymerization reaction was carried out for 8 hours from the start of initiator addition to obtain methacrylic resin composition F. The obtained methacrylic resin composition F had a Tg of 135°C, a weight average molecular weight of 180,000, and an MFR of 0.5 g / 10 min. The composition of methacrylic resin composition F determined by NMR was as follows: MMA units: 81% by mass, PMI units: 8% by mass, and CMI units: 11% by mass.

[0133] Synthesis Example 7 [Cyclic Olefin Resin Composition G] First, VO(OC ２ H ５ ) Cl ２ was diluted with cyclohexane to prepare a vanadium catalyst with a vanadium concentration of 6.7 mmol / L-cyclohexane. ２ H ５ ) １．５ Cl １．５ ) was diluted with cyclohexane to prepare an organoaluminum compound catalyst having an aluminum concentration of 107 mmol / L-hexane. Then, ethylene and tetracyclo[4.4.0.1 ２，５ .1 ７，１０ A copolymerization reaction with ethylene and 3-dodecene was carried out. Here, ethylene was supplied into the polymerization vessel together with hydrogen gas. When carrying out this copolymerization reaction, the vanadium catalyst prepared by the above method was supplied into the polymerization vessel in an amount such that the vanadium catalyst concentration relative to the cyclohexane used as the polymerization solvent in the polymerization vessel was 0.6 mmol / L. Furthermore, ethylaluminum sesquichloride, an organoaluminum compound, was supplied into the polymerization vessel in an amount such that Al / V = 18.0. The polymerization temperature was set to 8°C, and the polymerization pressure was set to 1.8 kg / cm. ２ The copolymerization reaction was carried out continuously as G. The ethylene and tetracyclo[4.4.0.1] ２，５ .1 ７，１０ To the copolymer solution of ethylene and tetracyclo[4.4.0.1]-3-dodecene, water and a 25% by mass aqueous solution of sodium hydroxide as a pH adjuster were added to terminate the polymerization reaction. Furthermore, catalyst residues present in the copolymer were removed (decalcified) from the copolymer solution. ２，５ .1 ７，１０ Irganox 1010 was added as a stabilizer to a cyclohexane solution (polymer concentration 7.7% by mass) of a copolymer of 1-3-dodecene and 2-octyldodecene in an amount of 0.4 parts by mass per 100 parts by mass of the copolymer. ３The mixture was mixed for 1 hour using a stirring tank with a heat source of 20 kg / cm ２ A cyclohexane solution of the copolymer, with the copolymer concentration in the cyclohexane solution being 5% by mass, was supplied at a rate of 150 kg / h to a double-pipe heater (outer pipe diameter 2B, inner pipe diameter 3 / 4B, length 21 m) using G steam, and heated to 180°C. ２ A double-tube flash dryer (outer tube diameter 2B, inner tube diameter 3 / 4B, length 27 m) using G steam and a flash hopper (volume 200 L) were used to remove most of the unreacted monomers together with cyclohexane, the polymerization solvent, from the cyclohexane solution of the copolymer that had been subjected to the heating step, thereby obtaining a flash-dried molten mixture of ethylene and tetracyclo[4.4.0.1]. ２，５ .1 ７，１０ A random copolymer (cyclic olefin resin) of cycloolefin copolymer (A-1) and cycloolefin copolymer (A-2) was obtained. A fatty acid ester, EXCEPARL PE-MS (Kao Corporation), was heated at 100°C for 4 hours and in a molten state, and then charged directly into a vented twin-screw kneading extruder in an amount of 2.1 parts by mass per 100 parts by mass of cycloolefin copolymer (A-1). The molten copolymer was kneaded with the cycloolefin resin charged through the resin charging section of the extruder and pelletized using an underwater pelletizer attached to the extruder outlet. The pellets were dried for 4 hours with hot air at a temperature of 100°C to obtain cycloolefin resin composition G. The Tg of the resulting cycloolefin resin composition G was 129°C. The oxygen weight percentage calculated from the monomer composition ratio was 0 wt%.

[0134] Synthesis Example 8 [Cyclic Olefin Resin Composition H] A mixed monomer mixture was prepared by sealing 76 parts of styrene and 4 parts of isoprene in a nitrogen-purged stainless steel pressure vessel and stirring. Next, 320 parts of dehydrated cyclohexane, 4 parts of the mixed monomer mixture, and 0.1 parts of dibutyl ether were charged into a nitrogen-purged stainless steel autoclave equipped with an electromagnetic stirrer. While stirring at 50°C, 0.18 parts of a hexane solution of n-butyllithium (concentration 15%) was added to initiate polymerization. 0.5 hours after the start of the reaction (the polymerization conversion rate at this point was 96%), 76 parts of the mixed monomer mixture was continuously added to the polymerization reaction solution over 1 hour, and the polymerization reaction was continued. 0.5 hours after the completion of the addition (the polymerization conversion rate at this point was 95%), the polymerization reaction was terminated by adding 0.1 parts of isopropyl alcohol, yielding a styrene-isoprene copolymer. Next, 8 parts of a stabilized nickel hydrogenation catalyst (60% nickel supported on a silica-alumina carrier) was added to 400 parts of the polymerization reaction solution, and the mixture was placed in a stainless steel autoclave. The interior of the autoclave was purged with hydrogen gas, and hydrogen was supplied to maintain the pressure inside the autoclave at 4.5 MPa. A hydrogenation reaction was carried out for 6 hours at 160°C. Next, using a pressure filter equipped with a Radiolite #800 filter bed, the mixture was filtered at 0.25 MPa to obtain a colorless, transparent solution from which the catalyst had been removed. This hydrogenation reaction solution was poured into a mixed solution of 250 parts of acetone and 250 parts of isopropanol with stirring to precipitate a hydrogenated product, which was then recovered by filtration. The recovered hydrogenated product was further washed with 200 parts of acetone and then dried for 24 hours in a vacuum dryer at 100°C and reduced to 1 mmHg or less, to obtain a cyclic olefin resin composition H. The resulting cyclic olefin resin composition H had a Tg of 127°C.

[0135] Example 1 Using the methacrylic resin composition A obtained in Synthesis Example 1, a light guide was fabricated by injection compression molding using an injection molding machine (SE180EV-A, manufactured by Sumitomo Heavy Industries, Ltd.). The resin temperature was 270°C, the mold temperature was 70°C, the injection speed was 100 mm / s, the resin filling time was set to 0.168 seconds, the compression distance was 1.0 mm, and the resin was compressed with a force of 1000 kN 0.175 seconds after injection. The holding pressure was set to 20 MPa for the first stage and 15 MPa for the second stage to ensure a uniform thickness of the light guide. The holding pressure times were 2.0 seconds for the first stage and 1.0 second for the second stage, and the cooling time was 20 seconds, resulting in a light guide measuring 110 mm x 75 mm x 0.6 mm thick. Evaluation revealed that a light guide with small retardation and good appearance was obtained. When an image was observed using the obtained light guide in the arrangement shown in Figure 1, a clear displayed image was confirmed. The polarization retention was 99%. The evaluation results are shown in Table 1.

[0136] Example 2 A light guide was fabricated under the same conditions as in Example 1, except that the methacrylic resin composition A obtained in Synthesis Example 1 was used, the injection speed was set to 200 mm / s, the resin filling time was set to 0.087 seconds, the compression distance was set to 1.0 mm, and the resin was compressed with a force of 1000 kN 0.095 seconds after injection. When an image was observed in the arrangement shown in Figure 1, a clear displayed image was confirmed. The polarization retention was 99%. The evaluation results are shown in Table 1.

[0137] (Example 3) A light guide was produced under the same conditions as in Example 1, except that the methacrylic resin composition A obtained in Synthesis Example 1 was used and the mold temperature was set to 95°C. When the image was observed in the arrangement shown in Figure 1, a clear displayed image was confirmed. The polarization retention was 99%. The evaluation results are shown in Table 1.

[0138] Example 4 A light guide was produced under the same conditions as in Example 1, except that the light guide was produced using the methacrylic resin composition B obtained in Synthesis Example 2. The evaluation results are shown in Table 1.

[0139] Example 5 A light guide was produced under the same conditions as in Example 1, except that the light guide was produced using the methacrylic resin composition C obtained in Synthesis Example 3. The evaluation results are shown in Table 1.

[0140] Example 6 A light guide was produced under the same conditions as in Example 1, except that the light guide was produced using the methacrylic resin composition D obtained in Synthesis Example 4. The evaluation results are shown in Table 1.

[0141] Example 7: A light guide was fabricated using the methacrylic resin composition A obtained in Synthesis Example 1 and a mold having a fine convex shape in a portion thereof. The resin temperature was 270°C, the mold temperature was 90°C, the injection speed was 200 mm / s, the resin filling time was set to 0.092 seconds, the compression distance was 1.0 mm, and the resin was compressed with a force of 1000 kN 0.1 seconds after injection. The holding pressure was set to 20 MPa for the first stage and 15 MPa for the second stage to ensure a uniform thickness of the light guide. The holding pressure times were 2.0 seconds for the first stage and 1.0 second for the second stage, and the cooling time was 20 seconds. A 110 mm x 75 mm x 0.6 mm thick light guide having a fine convex shape in a portion thereof was fabricated. Aluminum was vapor-deposited on the fine convex portions of the obtained light guide, and the shape of the fine convex shapes was measured using an atomic force microscope. The resulting shape was as shown in FIG. 3, with a line width of 0.85 μm and a height of 0.21 μm. The clarity of the displayed image was evaluated by diffracting light using the fine convex shapes instead of the second reflection volume hologram shown in Figure 1, and the image was observed, confirming a clear displayed image. Furthermore, when the polarization retention was measured by diffracting light using the fine convex shapes instead of the second reflection volume hologram shown in Figure 4, the polarization retention was 99%. The evaluation results are shown in Table 1.

[0142] Example 8 A light guide was produced under the same conditions as in Example 1, except that cyclic olefin resin composition G was used. The evaluation results are shown in Table 1.

[0143] Example 9 A light guide was produced under the same conditions as in Example 1, except that cyclic olefin resin composition H was used. The evaluation results are shown in Table 1.

[0144] Comparative Example 1 A light guide was produced in the same manner as in Example 1, except that the methacrylic resin composition E obtained in Synthesis Example 5 was used. However, cracks occurred when the light guide was released from the mold, and the light guide could not be used. An evaluation was carried out using a portion that had no cracks. The evaluation results are shown in Table 1.

[0145] Comparative Example 2 A light guide was produced in the same manner as in Example 1, except that the methacrylic resin composition F obtained in Synthesis Example 6 was used. However, a short shot occurred, and the mold shape could not be completely transferred. Evaluation of the obtained light guide revealed a high degree of orientation and a large in-plane retardation. Furthermore, the thickness and unevenness increased, and the PV value deteriorated. The evaluation results are shown in Table 1.

[0146] Comparative Example 3 A light guide was produced in the same manner as in Example 1, except that the methacrylic resin composition A obtained in Synthesis Example 1 was used and the compression distance was set to 2.0 mm. The evaluation results are shown in Table 1. The PV value was large, and when the image was observed, distortion was confirmed in the clear displayed image.

[0147] Comparative Example 4 A light guide was produced in the same manner as in Example 1, except that the methacrylic resin composition A obtained in Synthesis Example 1 was used and the compression distance was set to 0.3 mm. The evaluation results are shown in Table 1. The PV value was large, and when the image was observed, distortion was confirmed in the clear displayed image.

[0148] Comparative Example 5 A light guide was produced in the same manner as in Example 1, except that the methacrylic resin composition A obtained in Synthesis Example 1 was used, the resin filling time was set to 0.168 seconds, and the conditions were set so that the resin was compressed with a force of 1000 kN 0.3 seconds after injection. The evaluation results are shown in Table 1. The PV value was large, and when the image was observed, distortion was confirmed in the clear displayed image.

[0149] Comparative Example 6 A light guide was produced in the same manner as in Example 1, except that the methacrylic resin composition A obtained in Synthesis Example 1 was used, the resin filling time was set to 0.168 seconds, and the conditions were set so that the resin was compressed with a force of 1000 kN 0.1 seconds after injection. The evaluation results are shown in Table 1. The PV value was large, and when the image was observed, distortion was confirmed in the clear displayed image.

[0150] Comparative Example 7 Using the methacrylic resin composition A obtained in Synthesis Example 1, a light guide measuring 110 mm x 75 mm x 0.6 mm thick was produced by injection molding at a resin temperature of 270°C, a mold temperature of 110°C, an injection speed of 100 mm / s, a first-stage dwell pressure of 10 MPa, a dwell time of 5 seconds, and a cooling time of 30 seconds. Cracks occurred when the light guide was released from the mold, and the light guide warped significantly. Evaluation was performed using a portion without cracks. The evaluation results are shown in Table 1. When the image was observed, distortion was confirmed in the clearly displayed image.

[0151] (Comparative Example 8) A light guide was produced in the same manner as in Comparative Example 7, except that the methacrylic resin composition A obtained in Synthesis Example 1 was used, the injection speed was 200 mm / s, and the mold temperature was 50° C. The evaluation results are shown in Table 1.

[0152] Comparative Example 9 A light guide was produced using Delpet 80NH (manufactured by Asahi Kasei Corporation) in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0153] (Comparative Example 10) A light guide was produced using the methacrylic resin composition B obtained in Synthesis Example 2 under the same conditions as in Example 2, except that the resin temperature was 250°C, the mold temperature was 50°C, and the compression distance was 0.5 mm. The evaluation results are shown in Table 1.

[0154]

[0155]

[0156] From Table 1, it can be seen that the light guide of the example has a small PV value and no cracks, and therefore has an excellent appearance, and also has good image clarity and therefore excellent image quality.

[0157] Furthermore, it can be seen from Table 2 that the production method using the thermoplastic resin composition of this embodiment makes it possible to produce a resin light guide for a display having good appearance and image quality.

[0158] According to the present invention, it is possible to provide a resin light guide for displays having good appearance and image quality, and the light guide can be suitably used as a light guide for display devices such as head-mounted displays and wearable displays.

Claims

1. A resin light guide for a display, comprising a methacrylic resin composition, wherein the absolute value of the degree of orientation of methacrylate monomer units in the methacrylic resin composition in the resin light guide for a display is 0.10 to 0.25, and the PV value of the effective area surface through which image light is guided is 100 μm or less.

2. The absolute value of the photoelastic coefficient of the methacrylic resin composition contained in the resin light guide for a display is 10 × 10 -１２ Pa -1 or less. The resin light guide for a display according to claim 1 3. The resin light guide for a display according to claim 1 or 2, wherein the weight average molecular weight of the methacrylic resin composition is 110,000 to 170,000.

4. The resin light guide for a display according to claim 1 or 2, wherein the glass transition temperature (Tg) of the methacrylic resin composition is 115°C to 150°C.

5. The resin light guide for a display according to claim 1 or 2, wherein the absolute value of the in-plane retardation is 10 nm or less.

6. The resin light guide for a display according to claim 1 or 2, wherein the methacrylic resin composition contains a methacrylic resin having a structural unit having a ring structure.

7. The resin light guide for a display according to claim 6, wherein the structural unit having a ring structure contains at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide-based structural unit, an aromatic vinyl structural unit, an alicyclic vinyl structural unit, and a lactone ring structural unit.

8. The resin light guide for a display according to claim 6, wherein the structural unit having a ring structure contains a structural unit derived from an N-substituted maleimide monomer.

9. The resin light guide for a display according to claim 1 or 2, wherein the thickness is 0.8 mm or less.

10. The resin light guide for a display according to claim 1 or 2, comprising a diffractive optical element at at least one of the light incident portion and the light exit portion.

11. The resin light guide for a display according to claim 1 or 2, having a fine convex shape on a part of the surface or at a plurality of locations, and the line width of the fine convex shape is 0.10 to 2.00 μm.

12. The resin light guide for a display according to claim 11, wherein the ratio (height) / (line width) of the line width to the height of the fine convex shape is 0.10 to 1.

50.

13. An image display device comprising the resin light guide for a display according to claim 1 or 2.

14. A method for manufacturing a resin light guide for a display by injection compression molding of a thermoplastic resin composition, comprising a resin filling step and a compression step, wherein the temperature from the tip of the nozzle to the center of the injection molding machine cylinder is set 120 to 180 °C higher than the glass transition temperature (Tg) of the thermoplastic resin composition, the mold temperature is set in the range of (Tg - 80) °C to (Tg - 35) °C with respect to the glass transition temperature (Tg) of the thermoplastic resin composition, and each condition of the injection speed and filling time in the resin filling step, the compression distance, compression time and compression pressure in the compression step, and the compression delay time and cooling time set between the resin filling step and the compression step is adjusted so as to satisfy the following (1) and (2). A method for manufacturing a resin light guide for a display, characterized in that: (1) The absolute value of the in-plane retardation of the resin light guide for a display is 10 nm or less. (2) In the resin light guide for a display, the PV value of the effective area surface through which image light is guided is 100 µm or less.