WO2025142103A1 - ディスプレイ用樹脂製導光体、画像表示装置、及びディスプレイ用樹脂製導光体の製造方法 - Google Patents

ディスプレイ用樹脂製導光体、画像表示装置、及びディスプレイ用樹脂製導光体の製造方法 Download PDF

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WO2025142103A1
WO2025142103A1 PCT/JP2024/038583 JP2024038583W WO2025142103A1 WO 2025142103 A1 WO2025142103 A1 WO 2025142103A1 JP 2024038583 W JP2024038583 W JP 2024038583W WO 2025142103 A1 WO2025142103 A1 WO 2025142103A1
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Prior art keywords
light guide
resin
resin composition
structural unit
methacrylic
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English (en)
French (fr)
Japanese (ja)
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勇太 山畑
裕 多田
法子 美河
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Asahi Kasei Corp
Asahi Chemical Industry Co Ltd
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Asahi Kasei Corp
Asahi Chemical Industry Co Ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/02—Viewing or reading apparatus
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/32—Holograms used as optical elements

Definitions

  • the present invention relates to a resin light guide for displays, an image display device, and a method for manufacturing a resin light guide for displays.
  • AR Augmented Reality
  • Patent Documents 1 and 2 disclose light guides made by injection molding.
  • resin light guides manufactured by injection molding tend to have higher birefringence than glass light guides. It is known that some hologram elements, liquid crystal diffraction elements, and surface relief type diffractive optical elements used together with light guides have polarization dependency, in which the diffraction efficiency changes depending on the polarization state of the incident light. Therefore, when a light guide with large birefringence is used in an image display device, the image observed by the viewer has uneven brightness and rainbow-like color unevenness, deteriorating the image quality.
  • the thickness of the light guide tends to be thin in order to reduce the weight, but the inventors have found that it is difficult to obtain a light guide having good appearance and optical performance (low birefringence, flatness, surface accuracy, etc.) when a thin light guide is manufactured by injection molding.
  • a thin light guide is manufactured by injection molding.
  • the thickness of the light guide is thin, cracks are likely to occur when the light guide is released from the mold, and the appearance of the light guide is deteriorated.
  • the thickness of the light guide is thin, warping and thickness unevenness tend to occur, and the surface flatness tends to deteriorate.
  • the image quality is deteriorated.
  • the present invention has been made in consideration of the above problems, and has an object to provide a resinous 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 including such a resin light guiding element for displays. It is yet another object of the present invention to provide a method for producing a resin light guide for displays, which is capable of producing a resin light guide for displays such as head mounted displays, having good appearance and image quality.
  • Tg glass transition temperature
  • An image display device comprising the resin light guide for a display according to any one of [1] to [12].
  • a method for producing a resin light guide for a display by injection compression molding of a thermoplastic resin composition comprising the steps of: The method includes a resin filling step and a compression step. a temperature from the nozzle tip to the center of an 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 a mold temperature is set in a range of (Tg-80)° C. to (Tg-35)° C.
  • Tg glass transition temperature
  • a method for manufacturing a resin light guide for a display characterized in that each of the conditions, i.e., injection speed and filling time in a resin filling step, compression distance, compression time and compression pressure in the compression step, as well as a 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).
  • the absolute value of the in-plane retardation of the resin light guiding body for displays is 10 nm or less.
  • the PV value of the effective area surface along which image light is guided is 100 ⁇ m or less.
  • a resin light guide for displays having good appearance and image quality.
  • an image display device including such a resin light guide for a display.
  • a method for producing a resin light guide for displays which can produce a resin light guide for displays having good appearance and image quality.
  • R 1 represents either 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 represent either 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.
  • R2 or R3 may contain a halogen atom as a substituent.
  • examples of the arylalkyl group having 7 to 14 carbon atoms include, but are not limited to, a benzyl group, a phenylethyl group, a phenylpropyl group, a naphthylmethyl group, a naphthylethyl group, and a naphthylpropyl group.
  • halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.
  • Examples of monomers (N-arylmaleimides, N-aromatic substituted maleimides, etc.) that form 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, and the like.
  • Examples of monomers that form 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.
  • keeping the content of the structural unit derived from the N-substituted maleimide monomer to 40% by mass or less is effective in preventing a decrease in the physical properties of the methacrylic resin due to a decrease in the reactivity of the monomer 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, it is possible to reduce birefringence caused by orientation during molding or residual stress, and obtain a resin light guide for display having an average absolute value of in-plane retardation of 10 nm or less.
  • the optimal content of the structural units derived from the N-substituted maleimide monomer varies depending on the type of N-substituted maleimide, but for example, when methyl methacrylate is used as the methacrylic acid ester monomer and N-phenylmaleimide and N-cyclohexylmaleimide are used as the N-substituted maleimide monomers, it is preferable to adjust the content within the ranges of 79 to 83 mass% of the structural units derived from methyl methacrylate, 6 to 8 mass% of the structural units derived from N-phenylmaleimide, and 11 to 13 mass% of the structural units derived from N-cyclohexylmaleimide.
  • the methacrylic resin having a structural unit derived from an N-substituted maleimide monomer may contain a structural unit derived from another monomer copolymerizable with the methacrylic acid ester monomer and the N-substituted maleimide monomer, as long as the object of the present invention is not impaired.
  • the other copolymerizable monomer may include aromatic vinyls; unsaturated nitriles; acrylic esters having a cyclohexyl group, a benzyl group, or an alkyl group having 1 to 18 carbon atoms; glycidyl compounds; and unsaturated carboxylic acids.
  • Examples of the aromatic vinyl include styrene, ⁇ -methylstyrene, and divinylbenzene.
  • Examples of the unsaturated nitrile include acrylonitrile, methacrylonitrile, and ethacrylonitrile.
  • Examples of the acrylic ester include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, and butyl acrylate.
  • the glycidyl compound includes glycidyl (meth)acrylate and the like.
  • the unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and half-esters 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.
  • the content of the structural units derived from these other copolymerizable monomers is preferably 0 to 10 mass%, more preferably 0 to 9 mass%, and even more preferably 0 to 8 mass%, based on 100 mass% of the methacrylic resin. It is preferable that the content of the structural units derived from other monomers is within this range, since it is possible to improve the molding processability and mechanical properties of the resin without impairing the inherent effect of introducing a ring structure into the main chain.
  • the content of structural units derived from the N-substituted maleimide monomer and the content of structural units derived from other copolymerizable monomers can be determined by 1 H-NMR measurement and 13 C-NMR measurement.
  • 1 H-NMR measurement and 13 C-NMR measurement can be performed, for example, using CDCl 3 or DMSO-d 6 as a measurement solvent at a measurement temperature of 40° C.
  • methacrylic resins having glutarimide structural units in the main chain include methacrylic resins having glutarimide structural units described in JP-A-2006-249202, JP-A-2007-009182, JP-A-2007-009191, JP-A-2011-186482, and Republished Japanese Patent Publication No. 2012/114718, and the like.
  • the resins can be formed by the methods described in these publications.
  • the glutarimide structural unit constituting the methacrylic resin may be formed after polymerization of the resin. Specifically, the glutarimide structural unit may be represented by the following formula (3).
  • the content of the glutarimide structural unit is preferably in the range of 3 to 70% by mass, and more preferably in the range of 3 to 60% by mass, based on 100% by mass of the methacrylic resin. It is preferable that the content of the glutarimide structural unit is within the above range, since a resin having good moldability, heat resistance, and optical properties can be obtained. Furthermore, by appropriately adjusting the content of the glutarimide structural units within this range, it is possible to reduce birefringence caused by orientation and residual stress during molding, and obtain a resin light guide for displays having an absolute value of in-plane retardation of 10 nm or less.
  • the optimal content of the glutarimide structural units varies depending on the type of the substituents R 7 to R 9 in formula (3), but for example, when R 7 and R 8 are hydrogen atoms and R 9 is a methyl group, if the content of the glutarimide structural units is in the range of 3 to 10 mass%, it is possible to reduce birefringence caused by orientation and residual stress during molding, and obtain a resin light guide for displays having an absolute value of in-plane retardation of 10 nm or less.
  • the content of glutarimide structural units in the methacrylic resin can be determined by the method described in the aforementioned patent document.
  • 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 ⁇ -methylstyrene, with styrene being preferred.
  • the content of aromatic vinyl structural units in the methacrylic resin having glutarimide structural units is not particularly limited, but is preferably 0 to 20% by mass, with the methacrylic resin having glutarimide structural units being 100% by mass.
  • the content of the aromatic vinyl structural unit is within the above range, it is possible to achieve both heat resistance and excellent photoelasticity, which is preferable.
  • a resin 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 ranges of 65 to 90 mass % of structural units derived from methyl methacrylate, 5 to 15 mass % of structural units derived from styrene, and 5 to 20 mass % of glutarimide-based structural units, it is possible to reduce birefringence caused by orientation and residual stress during molding and to obtain a resin light guide for displays having an absolute value of in-plane retardation of 10 nm or less.
  • the aromatic vinyl structural unit is not particularly limited, but examples thereof include structural units derived from styrene and ⁇ -methylstyrene, with a structural unit derived from styrene being preferred.
  • the alicyclic vinyl structural unit can be formed by the methods described in, for example, JP-A-2006-291184, JP-A-2006-291184, JP-A-2014-77043, JP-A-2014-77044, etc.
  • --Lactone ring structural unit-- Methacrylic resins having a lactone ring structural unit can be formed by the methods described in, for example, JP-A-2001-151814, JP-A-2004-168882, JP-A-2005-146084, JP-A-2006-96960, JP-A-2006-171464, JP-A-2007-63541, JP-A-2007-297620, JP-A-2010-180305, etc.
  • the lactone ring structural unit constituting the methacrylic resin may be formed after polymerization of the resin.
  • the lactone ring structural unit is preferably a six-membered ring because this provides excellent stability of the ring structure.
  • a structure represented by the following formula (4) is particularly preferred.
  • R 10 , R 11 and R 12 are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms.
  • 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, a propyl group, etc.; unsaturated aliphatic hydrocarbon groups (e.g., alkenyl groups) having 2 to 20 carbon atoms, such as an ethenyl group, a propenyl group, etc.; aromatic hydrocarbon groups (e.g., aryl groups) having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, etc.; and groups in which one or more hydrogen atoms in these saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, and aromatic hydrocarbon groups have been substituted with at least one group selected from the group consisting of a hydroxy group
  • 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 "cyclization condensation reaction") between the hydroxy group and the ester group or the carboxyl group.
  • a methacrylic acid ester monomer such as methyl methacrylate
  • acrylic acid monomers having a hydroxy group used in the polymerization include 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, 2-(hydroxymethyl)alkyl 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), and 2-(hydroxyethyl)alkyl acrylates.
  • 2-(hydroxymethyl)acrylic acid 2-(hydroxyethyl)acrylic acid
  • 2-(hydroxymethyl)alkyl 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
  • 2-(hydroxyethyl)alkyl acrylates
  • the content of the antioxidant may be any amount that provides the effect of improving thermal stability. If the content is excessive, problems such as bleeding out during processing may occur, so the content is preferably 5 parts by mass or less per 100 parts by mass of the methacrylic resin, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, even more preferably 0.8 parts by mass or less, even more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass.
  • the content of the hindered amine light stabilizer may be any amount that provides an effect of improving light stability. If the content is excessive, problems such as bleeding out during processing may occur. 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.
  • the methacrylic resin composition contained in the light guide of the present embodiment may contain an ultraviolet absorbing agent.
  • the ultraviolet absorbent is not particularly limited, but is preferably an ultraviolet absorbent having a maximum absorption wavelength of 280 to 380 nm, and examples thereof include benzotriazole-based compounds, benzotriazine-based compounds, benzophenone-based compounds, oxybenzophenone-based compounds, benzoate-based compounds, phenol-based compounds, oxazole-based compounds, cyanoacrylate-based compounds, and benzoxazinone-based compounds. These ultraviolet absorbents may be used alone or in combination of two or more.
  • the content of the UV absorber is not particularly limited as long as it does not impair heat resistance, moist heat resistance, thermal stability, and moldability and exerts 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, per 100 parts by mass of methacrylic resin. Within this range, an excellent balance of UV absorption performance, moldability, etc. is achieved.
  • the methacrylic resin composition contained in the light guide of the present embodiment may contain a release agent, which may include, but is not limited to, fatty acid esters, fatty acid amides, fatty acid metal salts, hydrocarbon lubricants, alcohol lubricants, polyalkylene glycols, carboxylates, and hydrocarbon paraffin mineral oils. These release agents may be used alone or in combination of two or more.
  • the fatty acid ester that can be used as the release agent is not particularly limited, and any of the conventionally known fatty acid esters can be used.
  • fatty acid esters that can be used include ester compounds of fatty acids having 12 to 32 carbon atoms, such as lauric acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, arachic acid, and behenic acid, with monohydric aliphatic alcohols, such as palmityl alcohol, stearyl alcohol, and behenyl alcohol, and polyhydric aliphatic alcohols, such as glycerin, pentaerythritol, dipentaerythritol, and sorbitan; and complex ester compounds of fatty acids, polybasic organic acids, and monohydric aliphatic alcohols or polyhydric aliphatic alcohols.
  • fatty acid esters examples 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 citric acid fatty acid ester, pentaerythritol adipic acid stearate, partially saponified montanic acid ester, pentaerythritol tetrastearate, dipentaerythritol hexastearate, sorbitan tristearate, and the like.
  • 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, Leo D'or series, Exepar series, and Coconard series manufactured by Kao Corporation. 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 Leo D'or MS-50.
  • the amount of release agent contained may be an amount that is effective as a release agent, and if the amount is excessive, problems such as bleed-out during processing or poor extrusion due to screw slippage may occur, so the amount is preferably 5 parts by mass or less per 100 parts by mass of methacrylic resin, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, even more preferably 0.8 parts by mass or less, even more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass. Adding an amount within the above range not only prevents the decrease in transparency caused by the addition of the release agent, but also tends to prevent poor release during injection molding.
  • rubber-containing graft copolymer particles having, on their surface layer, a graft portion 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 above-mentioned acrylic rubber particles, methacrylic rubber-containing graft copolymer particles, and rubber polymer is preferably 0.03 to 1 ⁇ m, and more preferably 0.05 to 0.5 ⁇ m, from the viewpoint of improving the impact strength and optical properties of the light guide of this embodiment.
  • the content of the other thermoplastic resin is preferably 0 to 50 parts by mass, and more preferably 0 to 25 parts by mass, per 100 parts by mass of the methacrylic resin.
  • the method for producing a resin light guide for a display includes the steps of: A method for producing a resin light guide for a display by injection compression molding of a thermoplastic resin composition, comprising the steps of: The method includes a resin filling step and a compression step. a temperature from the nozzle tip to the center of an 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 a mold temperature is set in a range of (Tg-80)° C. to (Tg-35)° C.
  • Tg glass transition temperature
  • the resin light guide for display of this embodiment can be manufactured by injection compression molding of the above-mentioned thermoplastic resin composition 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, making it possible to mold in a state where deterioration due to thermal decomposition of the resin is suppressed.
  • Thermal decomposition of the resin not only has a negative effect on the color tone, transmittance, and haze, but also generates gas during injection molding, so that the generated gas fills the mold, and the gas pushed in during resin filling is not discharged, inhibiting the filling of the resin and thereby worsening the mold transfer rate.
  • the temperature from the nozzle tip to the center of the injection molding machine cylinder is more preferably a temperature 130 to 170°C higher than the glass transition temperature (Tg) of the thermoplastic resin composition used.
  • the mold temperature when injection-compression molding 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.
  • the fluidity of the resin in the mold decreases, so the light guide tends to have uneven thickness and poor surface accuracy.
  • the mold temperature is higher than (Tg-35)°C, the light guide will warp and poor surface accuracy, so it is preferable that the mold temperature is within the above range.
  • thermoplastic resin composition used in the manufacturing method for a resin light guide for displays is the same as the thermoplastic resin composition described above in the section on resin light guides for displays, and the explanation in the section on resin light guides for displays is incorporated herein.
  • the manufacturing method of the resin light guide for a display of this embodiment includes a resin filling step and a compression step, and adjusts each of the conditions, i.e., 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, so as to satisfy the following (1) and (2).
  • the absolute value of the in-plane retardation of the resin light guiding body for displays is 10 nm or less.
  • the PV value of the effective area surface along which image light is guided is 100 ⁇ m or less.
  • an annealing process 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, based on the glass transition temperature (Tg) of the resin composition, and more preferably in the range of (Tg-30)°C to (Tg-10)°C. If the annealing temperature is within the above range, the residual stress can be removed without the light guide deforming in shape.
  • the injection pressure when injection compression molding the light guide of this embodiment may be set appropriately to achieve the desired injection speed.
  • the compression pressure be 100 to 5,000 kN.
  • the light guide of this embodiment has a fine convex shape on a portion or multiple locations on its surface, in order to improve the transferability of the fine convex shape, it 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 it is heated, and then the mold is cooled.
  • the method of heating the mold when heat and cool molding is used is not particularly limited, and any method may be used.
  • a method of arranging a flow path for water or oil in the mold and adjusting the mold temperature to a temperature equal to or higher than the Tg of the methacrylic resin composition by a medium such as water or oil a method of embedding a heater in the mold and heating the mold, a method of providing an electrically conductive layer that can be electrically conducted on the surface of the mold and heating by generating heat by passing electricity through it, a method of heating from the outside or inside of the mold by an induction heating device, and a method of heating from the outside of the mold by radiation of far infrared rays from a halogen lamp or a ceramic heater.
  • the method for cooling the mold is not particularly limited, and any method may be used, for example, a method in which water or oil passages are provided in the mold and the mold is cooled by a medium such as water or oil.
  • the compression distance in the compression step is 100-300% of the thickness of the light guide, more preferably 120-250%, and even more preferably 150-200%. If the compression distance is less than 100%, it becomes difficult to fill with resin, and the light guide tends to be insufficiently filled. On the other hand, if the compression distance is greater than 300%, the light guide tends to have uneven thickness and a large PV value, so it is preferable to set the compression distance to 100-300% of the thickness of the light guide.
  • 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 direction and the injection direction during injection, making the flow unstable and making it difficult to control the thickness of the light guide. As a result, the thickness of the light guide becomes uneven and the PV value tends to increase.
  • the compression delay time is greater than 150% of the injection time, it takes time from injection to compression, the resin solidifies and the fluidity becomes insufficient, and the thickness of the light guide becomes uneven and the PV value tends to increase, so it is preferable to set the compression delay time in the above range.
  • the surface of the light guide of this embodiment can be further subjected to surface functionalization treatments such as hard coat treatment, anti-reflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, gas barrier treatment, etc.
  • surface functionalization treatments such as hard coat 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 ⁇ m.
  • the hard coat layer applied to the surface of the light guide is formed by applying a coating liquid obtained by dissolving or dispersing an acrylate such as a silicone-based curable resin, an organic polymer composite inorganic fine particle-containing curable resin, urethane acrylate, epoxy acrylate, or polyfunctional acrylate in an organic solvent, and a photopolymerization initiator, to a film or sheet obtained from the resin composition of this embodiment by a conventionally known coating method, drying, and photocuring.
  • an acrylate such as a silicone-based curable resin, an organic polymer composite inorganic fine particle-containing curable resin, urethane acrylate, epoxy acrylate, or polyfunctional acrylate in an organic solvent, and a photopolymerization initiator
  • a method can also be used in which an easy-adhesion layer, a primer layer, an anchor layer, or the like containing inorganic fine particles in its composition is previously provided, and then the hard coat layer is formed.
  • the anti-glare layer applied to the surface of the light guide is formed by making fine particles of silica, melamine resin, acrylic resin, or the like into an ink, applying it to another functional layer by a conventionally known coating method, and curing it with heat or light.
  • anti-reflection layers applied to the surface of the light guide include thin films of inorganic materials such as metal oxides, fluorides, silicides, borides, nitrides, and sulfides, and single or multiple layers of resins with different refractive indices such as acrylic resins and fluororesins. Also usable are thin layers containing composite particles of inorganic and organic compounds.
  • the image display device of this embodiment preferably includes the resin light guide for display of this embodiment.
  • the image display device includes the light guide of this embodiment, and therefore has good image quality.
  • the image display device of this embodiment can be manufactured by a conventionally known method, for example, by the method described in WO2017/047528.
  • the glass transition temperature of the methacrylic resin composition was measured in accordance with JIS-K7121.
  • a differential scanning calorimeter (DSC8000, manufactured by PerkinElmer Japan Co., Ltd.) was used under the condition 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 above heating conditions (second heating).
  • the intersection (midpoint glass transition temperature) of the stepwise change partial curve during the second heating and a straight line equidistant in the vertical direction from each baseline extension line was measured as the glass transition temperature (Tg) (°C).
  • the total light transmittance was measured on a molded body having a thickness of 3 mm using a turbidity meter COH7700 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with the provisions of JIS K7361.
  • the molded body was produced by drying the pellets at 90° C. for 12 hours or more, and then using an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd., SE180EV-A) with a mold size of 100 mm ⁇ 100 mm ⁇ thickness of 3 mm.
  • 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.
  • the light guide was placed on the measurement table of PA-300-L (manufactured by Photonic Lattice, Inc.) and the in-plane retardation distribution was measured at a wavelength of 520 nm.
  • the average value of the absolute values of the in-plane retardation (Re) in the measurement area was calculated and used as the measured value of the retardation (nm).
  • the birefringence value is preferably in a range in which the optical characteristics are not adversely affected, that is, an in-plane retardation value of 10 nm or less.
  • a MD represents the absorbance in MD polarized light
  • a TD represents the absorbance in TD polarized light
  • ⁇ represents the angle between the direction of the transition dipole moment and the orientation axis.
  • the optical system is formed by combining an image projection unit, a bandpass filter (an optical filter that transmits only wavelengths of 615 to 645 nm), a light guide, a first reflection volume hologram (having selective diffraction characteristics for red wavelengths), and a second reflection volume hologram (having selective diffraction characteristics for red wavelengths).
  • a bandpass filter an optical filter that transmits only wavelengths of 615 to 645 nm
  • a light guide a first reflection volume hologram (having selective diffraction characteristics for red wavelengths)
  • a second reflection volume hologram having selective diffraction characteristics for red wavelengths.
  • the traveling direction of the image light is the X-axis, and the light guide is disposed so that the incident surface is the YZ plane.
  • a monochrome still image in red was projected from the image projection unit, and the clarity of the image observed at the position of the observer's pupil was evaluated according to the following evaluation criteria. [Evaluation Criteria] Image clarity A: No bleeding, blurring or distortion is observed in the image, and red is reproduced clearly. B: The image is somewhat unclear due to bleeding, blurring and distortion, and uneven brightness or reduced brightness is observed. C: The image is unclear due to bleeding, blurring and distortion, it is unclear what is being displayed, and uneven brightness or reduced brightness is observed.
  • the light source is formed by combining an image light projection unit, which is a red laser light source, a bandpass filter (an optical filter that transmits only wavelengths of 615 to 645 nm), a first linear polarizing plate, a second linear polarizing plate, a light guide, a first reflective volume hologram (having selective diffraction characteristics for red wavelengths), and a second reflective volume hologram (having selective diffraction characteristics for red wavelengths).
  • the light emitted from the image projection unit passes through the bandpass filter and the first linear polarizing plate, enters the light guide, is diffracted by the first reflective volume hologram to change direction, and is guided inside the light guide by total reflection.
  • the guided light reaches the second reflective volume hologram, is diffracted to change direction, and enters the second linear polarizing plate and a power meter.
  • the traveling direction of the image light is the X-axis
  • the light guide 2 is disposed so that the incident surface is the YZ plane.
  • a red monochromatic light was emitted from a red laser light source into the light guide, and the amount of light extracted by the reflection volume hologram was measured with a power meter. At this time, the optical path length was set to about 16 cm.
  • the amount of light measured when the second linear polarizer and the first linear polarizer are arranged parallel to each other is Tp (parallel)
  • the amount of light measured when the second linear polarizer and the first linear polarizer are arranged cross is Tc (cross)
  • the polarization retention degree was calculated from the formula Tp/(Tc+Tp).
  • the state in which the transmission axes of the second linear polarizer and the first linear polarizer are parallel is the parallel arrangement
  • the state in which the transmission axes of the second linear polarizer and the first linear polarizer are perpendicular to each other is the cross arrangement.
  • microshape measurement was performed using an AR-5T type Si single crystal probe (tip aspect ratio 5/high aspect ratio height 2 ⁇ m) to determine the line width and height of the microconvex shape.
  • the measurement pitch in the X direction was set to 1/1000 of the longest part of the length of the light guide in the X-axis direction
  • the measurement pitch in the Y direction was set to 1/10 of the longest part of the length of the light guide in the Y-axis direction.
  • the fabricated light guide was observed for the presence or absence of cracks.
  • the fabricated light guide was visually observed and evaluated for the presence or absence of cracks.
  • the obtained polymerization solution was fed to a concentrating apparatus consisting of a tubular heat exchanger and a vaporizer tank preheated to 250°C to carry out devolatilization.
  • the degree of vacuum in the vaporizer tank was set to 10 to 15 Torr.
  • the resin flowing down the vaporizer tank was discharged by a screw pump, extruded through a strand die, cooled with water, and pelletized to obtain a methacrylic resin composition A having an N-substituted maleimide structural unit.
  • the resulting 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 mass %, PMI units: 7 mass %, and CMI units: 12 mass %.
  • the liquid was continuously withdrawn from the bottom so that the liquid level in the polymerization tank was constant, and was supplied to a concentrating device consisting of a tubular heat exchanger and a vaporization tank for devolatilization.
  • the vacuum degree of 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 from a strand die, pelletized after water cooling, and introduced into a desolvation device to obtain a pellet-shaped 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.
  • 500 parts by mass of this 10% by mass methyl isobutyrate solution of the copolymer and 1 part by mass of 10% by mass Pd/C (manufactured by NE Chemcat Corporation) as a hydrogenation catalyst were charged into a 1000 mL autoclave apparatus, and the mixture was maintained at 200°C and 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 by a filter, and 0.05 parts by mass of Rikemar H-100 was added to and mixed with the polymer solution, and the mixture was fed to a concentrator consisting of a tubular heat exchanger and a vaporization tank to perform devolatilization.
  • the vacuum degree of the vaporization tank was set to 10 to 15 Torr.
  • the resin that flowed down the vaporization tank was discharged by a gear pump, extruded from 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.
  • a stearyl phosphate/distearyl phosphate mixture was added, and a cyclization condensation reaction was carried out under reflux (about 90 to 110° C.) for 5 hours.
  • the obtained polymerization liquid was subjected to a cyclocondensation reaction and a devolatilization treatment using a ⁇ 42 mm twin-screw devolatilizing extruder equipped with four front vents and one back vent at 140 rpm and at a resin amount of 10 kg/hour, to obtain a methacrylic resin composition C.
  • the obtained 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 as follows: MMA unit: 82% by mass, lactone ring structure unit: 17% by mass, MHMA unit: 1% by mass.
  • the resulting polymer solution was subjected to a devolatilization treatment using a ⁇ 42 mm devolatilization extruder equipped with four front vents and one back vent at 140 rpm at a rate of 10 kg/hour in terms of resin amount, to obtain resin pellets.
  • 5 parts by mass of monomethylamine (40% by mass monomethylamine aqueous solution) was introduced from a side feeder into a vented twin-screw extruder at a barrel temperature of 250°C for 100 parts by mass of the obtained resin pellets, and an imidization reaction was carried out. Excess methylamine and moisture were appropriately removed from a vent port installed downstream of the extruder to obtain a methacrylic resin composition D.
  • the Tg of the obtained methacrylic resin composition D was 122°C, the weight average molecular weight was 130,000, and the MFR was 1.3 g/10 min.
  • the composition of the methacrylic resin composition D determined by NMR was 95% by mass of MMA units and 5% by mass of glutarimide structural units.
  • an initiator feed liquid was prepared by mixing 0.23 kg of 1,1-di(t-butylperoxy)cyclohexane and 1.82 kg of meta-xylene.
  • feeding (addition) of the initiator feed liquid was started according to the profiles (1) to (6).
  • a copolymerization reaction of ethylene and tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene was continuously carried out using a stirring polymerization vessel (inner diameter 500 mm, reaction volume 100 L).
  • ethylene was supplied into the polymerization vessel together with hydrogen gas.
  • the vanadium catalyst prepared by the above method was supplied into the polymerization vessel in such an amount that the vanadium catalyst concentration relative to the cyclohexane used as the polymerization solvent in the polymerization vessel was 0.6 mmol/L.
  • ethylaluminum sesquichloride an organoaluminum compound
  • the copolymerization reaction was continuously carried out at a polymerization temperature of 8° C. and a polymerization pressure of 1.8 kg/cm 2 G.
  • Water and a 25% by mass aqueous solution of sodium hydroxide as a pH regulator were added to the copolymer solution of ethylene and tetracyclo[4.4.0.1 2,5 . 1 7,10 ]-3-dodecene withdrawn from the polymerization vessel to terminate the polymerization reaction.
  • the catalyst residue present in the copolymer was removed (demineralized) from the copolymer solution.
  • Irganox 1010 was added as a stabilizer to the cyclohexane solution (polymer concentration 7.7% by mass) of the copolymer of ethylene and tetracyclo[4.4.0.1 2,5 . 1 7,10 ]-3-dodecene that had been subjected to the above-mentioned demineralization treatment, so that the amount added to the copolymer was 0.4 parts by mass per 100 parts by mass of the copolymer.
  • the mixture was mixed for 1 hour using a stirring tank with an effective volume of 1.0 m 3 .
  • a cyclohexane solution of the copolymer in which the concentration of the copolymer in the cyclohexane solution was 5% by mass, was supplied at a rate of 150 kg/h to a double -tube heater (outer tube diameter 2B, inner tube diameter 3/4B, length 21 m) using steam at 20 kg/cm2G as a heat source, and heated to 180°C.
  • a fatty acid ester Exepar PE-MS (manufactured by Kao Corporation), was heated at 100°C for 4 hours and in a molten state, was directly charged into a vented twin-screw kneading extruder in an amount of 2.1 parts by mass per 100 parts by mass of the cyclic olefin copolymer (A-1), kneaded with the cyclic olefin resin charged through the resin charging section of the extruder, and pelletized with an underwater pelletizer attached to the outlet of the extruder.
  • the resulting pellets were dried with hot air at a temperature of 100°C for 4 hours to obtain a cyclic olefin resin composition G.
  • the resulting cyclic olefin resin composition G had a Tg of 129° C.
  • the weight percentage of oxygen calculated from the monomer composition ratio was 0 wt %.
  • Example 1 A light guide was produced by injection compression molding using the methacrylic resin composition A obtained in Synthesis Example 1 with an injection molding machine (SE180EV-A, manufactured by Sumitomo Heavy Industries, Ltd.).
  • the resin temperature was set to 270°C, the mold temperature to 70°C, the injection speed to 100 mm/s, the resin filling time to 0.168 seconds, the compression distance to 1.0 mm, and the resin was compressed with a force of 1000 kN 0.175 seconds after injection.
  • 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.
  • 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.
  • 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.
  • 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, when the light guide was released from the mold, cracks occurred, and the light guide could not be used. An evaluation was carried out using a part that did not have any cracks. The evaluation results are shown in Table 1.
  • 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. A short shot occurred, and the mold shape could not be completely transferred. When the obtained light guide was evaluated, the degree of orientation was high and the in-plane retardation was also large. In addition, the thickness and unevenness increased, and the PV value was deteriorated. The evaluation results are shown in Table 1.
  • 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.
  • 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.
  • Table 2 shows that the manufacturing method using the thermoplastic resin composition of this embodiment makes it possible to manufacture a resin light guide for displays with good appearance and image quality.
  • the present invention provides a resin light guide for displays that has 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.

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PCT/JP2024/038583 2023-12-27 2024-10-29 ディスプレイ用樹脂製導光体、画像表示装置、及びディスプレイ用樹脂製導光体の製造方法 Pending WO2025142103A1 (ja)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006249202A (ja) * 2005-03-09 2006-09-21 Kaneka Corp イミド樹脂およびこれを用いる光学用樹脂組成物、成形体
JP2009140916A (ja) * 2007-11-12 2009-06-25 Keio Gijuku 面発光装置及び偏光光源
JP2021504760A (ja) * 2017-12-15 2021-02-15 エルジー・ケム・リミテッド ウェアラブルデバイス
JP2023168362A (ja) * 2018-04-02 2023-11-24 マジック リープ， インコーポレイテッド 統合型光学要素を伴う導波管および同一物を作製する方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006249202A (ja) * 2005-03-09 2006-09-21 Kaneka Corp イミド樹脂およびこれを用いる光学用樹脂組成物、成形体
JP2009140916A (ja) * 2007-11-12 2009-06-25 Keio Gijuku 面発光装置及び偏光光源
JP2021504760A (ja) * 2017-12-15 2021-02-15 エルジー・ケム・リミテッド ウェアラブルデバイス
JP2023168362A (ja) * 2018-04-02 2023-11-24 マジック リープ， インコーポレイテッド 統合型光学要素を伴う導波管および同一物を作製する方法

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