Translucent resin sheet, method for manufacturing a translucent resin sheet, projection type display and mobile body

Abstract

To provide a translucent resin sheet which satisfies all of high transparency, scratch resistance and flame retardancy, and is usable in a dust-proof cover for an HUD, a production method of a translucent resin sheet, a projection type display and a movable body.SOLUTION: A translucent resin sheet includes a base material layer 10 which is a co-extrusion molding of polycarbonate and thermoplastic polymethyl methacrylate, and includes a polycarbonate layer and a polymethyl methacrylate layer, and a polycarbonate-based polyurethane resin layer 20 stacked on the polymethyl methacrylate layer 40, where the polycarbonate-based polyurethane resin layer is a cured product which contains ultraviolet curable polycarbonate-based polyurethane and thermosetting polycarbonate-based polyurethane in a mass ratio of 7:3 to 8:2, and further contains carbodiimide, light transmittance in a visible region is 90% or more, pencil hardness on the surface on the polycarbonate-based polyurethane resin layer is 2H or harder, and the translucent resin sheet exhibits self-extinguishing property in a combustibility test.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a translucent resin sheet, a method for manufacturing a translucent resin sheet, a projection display, and a mobile device, and more particularly to a translucent resin sheet that can be used as a dust cover for a head-up display (HUD) that is mounted on an electric vehicle. [Background technology]

[0002] HUDs are well-known as projection displays used on mobile devices such as automobiles. Furthermore, HUDs, which are beginning to be installed in recent automobiles, require a dust cover to prevent dust and debris from entering the projection opening that projects images from the device body onto a glass or other projection surface.

[0003] For example, Patent Document 1 proposes a transparent resin sheet as a conventional dust cover for a HUD, comprising a transparent resin layer mainly composed of a resin material and a hard coat layer laminated on this transparent resin layer. For example, the resin material is a polycarbonate-based resin, and a UV-curable resin mainly composed of an acrylic compound is preferred as the UV-curable resin constituting the hard coat layer. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-34790 [Overview of the project] [Problems that the invention aims to solve]

[0005] Dust covers for HUDs are positioned between the image display and projection units, and therefore require high transparency to avoid obstructing image projection. Furthermore, to prevent scratches from dust and debris, dust covers must have scratch resistance of at least 2H pencil hardness. In addition, with the rapid spread of electric vehicles in recent years, dust covers for HUDs installed in electric vehicles are required to have flame retardancy that passes the flammability test specified in FMVSS No. 302.

[0006] However, conventional dust covers for HUDs did not satisfy any of these requirements: high transparency, scratch resistance, or flame retardancy.

[0007] In view of the above problems, the present invention aims to provide a translucent resin sheet that can be used in a dust cover for a HUD that satisfies all of the following: high transparency, scratch resistance, and flame retardancy; a method for manufacturing the translucent resin sheet; a projection type display; and a mobile body. [Means for solving the problem]

[0008] To solve the above problems, the light-transmitting resin sheet of the present invention is a co-extruded molded product of polycarbonate and thermoplastic polymethyl methacrylate, comprising a base layer having a polycarbonate layer and a polymethyl methacrylate layer, and a polycarbonate-based polyurethane resin layer laminated on the polymethyl methacrylate layer of the base layer, wherein the thickness of the polycarbonate layer is 320 μm to 400 μm, the thickness of the polymethyl methacrylate layer is 18 μm to 45 μm, and the polycarbonate-based polyurethane The resin layer has a thickness of 3 μm to 10 μm, the polycarbonate-based polyurethane resin layer is a cured product containing UV-curable polycarbonate-based polyurethane, thermosetting polycarbonate-based polyurethane, and carbodiimide, the mass ratio of UV-curable polycarbonate-based polyurethane to thermosetting polycarbonate-based polyurethane is 7:3 to 8:2, the light transmittance in the visible region is 90% or more, the pencil hardness of the surface on the polycarbonate-based polyurethane resin layer side is 2H or more, and it is a translucent resin sheet that exhibits self-extinguishing properties in the flammability test specified in FMVSS No. 302.

[0009] In the translucent resin sheet of the present invention, the mass ratio of the total resin content of the ultraviolet-curable polycarbonate-based polyurethane and the thermosetting polycarbonate-based polyurethane to the carbodiimide may be 9:0.4 to 0.8.

[0010] Furthermore, in order to solve the above problems, the present invention provides a method for manufacturing a translucent resin sheet, comprising a step of forming a polycarbonate polyurethane resin layer by applying a paint to the base layer to form the polycarbonate polyurethane resin layer, wherein the paint is a mixture containing an ultraviolet-curable polycarbonate polyurethane dispersion, a thermosetting polycarbonate polyurethane dispersion, carbodiimide, a photopolymerization initiator, and a solvent, and the mass ratio of the resin content of the ultraviolet-curable polycarbonate polyurethane dispersion to the resin content of the thermosetting polycarbonate polyurethane dispersion is 7:3 to 8:2.

[0011] In the method for producing a translucent resin sheet of the present invention, the mass ratio of the total resin content of the ultraviolet-curable polycarbonate-based polyurethane dispersion and the thermosetting polycarbonate-based polyurethane dispersion to the carbodiimide may be 9:0.4 to 0.8.

[0012] The method for producing the translucent resin sheet of the present invention may include a base layer forming step in which the polycarbonate and the thermoplastic polymethyl methacrylate are co-extruded to form the base layer.

[0013] Furthermore, in order to solve the above problems, the projection display of the present invention is equipped with the translucent resin sheet of the present invention as a translucent dustproof cover.

[0014] Furthermore, in order to solve the above problems, the mobile body of the present invention is equipped with the projection-type display of the present invention. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a translucent resin sheet that can be used in a dust cover for a HUD that satisfies high transparency, scratch resistance, and flame retardancy, a method for manufacturing the translucent resin sheet, a projection type display, and a mobile body. [Brief explanation of the drawing]

[0016] [Figure 1] It is a schematic view of a side cross-section of the light-transmissive resin sheet 100 according to the present invention. [Figure 2] As an example of a projection display according to the present invention, it is a schematic side view showing a head-up display device. [Figure 3] As an example of a moving body equipped with a projection display according to the present invention, it is a schematic side view showing a head-up display device mounted on a vehicle.

Embodiments for Carrying out the Invention

[0017] Hereinafter, an embodiment of a light-transmissive resin sheet, a method for manufacturing the light-transmissive resin sheet, a projection display, and a moving body according to the present invention will be described with reference to the drawings.

[0018] [Light-transmissive resin sheet] The light-transmissive resin sheet 100 shown in FIG. 1 is a sheet that can be used as a dust-proof cover for a HUD, and includes a base material layer 10 and a polycarbonate-based polyurethane resin layer 20 described below.

[0019] 〈Base material layer 10〉 The base material layer 10 is a co-extruded molded body of polycarbonate and thermoplastic polymethyl methacrylate, and includes a polycarbonate layer 30 and a polymethyl methacrylate layer 40. The base material layer 10 is a molded body in a state where polycarbonate and thermoplastic polymethyl methacrylate are melted and directly adhered without using an adhesive or the like by co-extrusion molding using, for example, a T-die, so that delamination between layers does not occur. It is a layer formed into a film with the minimum necessary thickness without impairing the properties of the resin.

[0020] (Polycarbonate layer 30) The polycarbonate layer 30 is the thickest layer in the translucent resin sheet 100 and has the greatest influence on the translucency, impact resistance, mechanical strength, heat resistance, and other properties of the translucent resin sheet 100. Therefore, the polycarbonate layer 30, which has excellent transparency (translucency), impact resistance, mechanical strength such as rigidity, and heat resistance, is adopted.

[0021] As for the polycarbonate, one synthesized from bisphenol A and phosgene, or diphenyl carbonate, can be used, and one with a refractive index of 1.58 to 1.59 and a light transmittance of 90% or more in the visible region can be used.

[0022] (Polycarbonate layer thickness 30) The thickness of the polycarbonate layer 30 shall be between 320 μm and 400 μm. If the thickness of the polycarbonate layer 30 is less than 320 μm, it may not satisfy the requirements for rigidity and flame retardancy. Furthermore, when the translucent resin sheet 100 is used as a dust cover for the HUD, if the thickness of the polycarbonate layer 30 is greater than 400 μm, the projected image transmitted through the translucent resin sheet 100 may appear as a double image due to the refractive index of the polycarbonate. By having the thickness of the polycarbonate layer 30 within the range of 320 μm to 400 μm, the requirements for rigidity and flame retardancy are satisfied, and no double image occurs in the projected image.

[0023] (Polymethyl methacrylate layer 40) Although polycarbonate has excellent mechanical strength such as impact resistance and rigidity, it is soft and has a pencil hardness of about B. Therefore, a layer of polymethyl methacrylate, which is also soft and has excellent pencil hardness, is provided. By providing a hard polymethyl methacrylate layer 40, even if a polycarbonate-based polyurethane resin layer 20 is further provided on top of this layer, the pencil hardness of the surface on the polycarbonate-based polyurethane resin layer 20 side can be made 2H or higher.

[0024] Furthermore, polymethyl methacrylate has a total light transmittance of approximately 94%, which is comparable to or greater than that of glass, and it is resistant to breakage and impact. Therefore, it can form a useful layer for the translucent resin sheet 100 used as a dust cover for HUDs.

[0025] (Thickness of the polymethyl methacrylate layer: 40) The thickness of the polymethyl methacrylate layer 40 shall be between 18 μm and 45 μm. If the thickness of the polymethyl methacrylate layer 40 is less than 18 μm, it may not be possible to counteract the softness of the polycarbonate layer 30 and achieve a pencil hardness of 2H or higher. Conversely, if the thickness of the polymethyl methacrylate layer 40 is greater than 45 μm, while it may be possible to achieve a pencil hardness of 2H or higher, the flame retardancy may decrease, and the required performance may not be met. By having the thickness of the polymethyl methacrylate layer 40 within the range of 18 μm to 45 μm, it is possible to satisfy both a pencil hardness of 2H or higher and flame retardancy.

[0026] <Polycarbonate-based polyurethane resin layer 20> The polycarbonate-based polyurethane resin layer 20 is a layer laminated on the polymethyl methacrylate layer 40 of the base layer 10. While the polymethyl methacrylate layer 40 improves pencil hardness, it is highly flammable, thus reducing flame retardancy. Therefore, by sandwiching the polymethyl methacrylate layer 40 between a polycarbonate layer 30, which has excellent flame retardancy, and the polycarbonate-based polyurethane resin layer 20, the flame retardancy of the translucent resin sheet 100 itself is satisfied.

[0027] Polycarbonate-based polyurethane is a resin whose main structure is composed of carbonate groups. Polycarbonate provides flame retardancy, while polyurethane provides hardness. The polycarbonate-based polyurethane resin layer 20 formed from such a resin becomes a hard coat layer with excellent hardness and flame retardancy.

[0028] The polycarbonate-based polyurethane resin layer 20 is a cured product containing the following: UV-curable polycarbonate-based polyurethane, thermosetting polycarbonate-based polyurethane, and carbodiimide.

[0029] (UV-curable polycarbonate-based polyurethane) This polyurethane polymerizes and hardens from a liquid to a solid in a short time in response to the light energy of ultraviolet light. An example is a dried cured product obtained by the evaporation of the solvent in an ultraviolet-curable polycarbonate-based polyurethane dispersion and further polymerization and hardening by ultraviolet light.

[0030] (Thermosetting polycarbonate-based polyurethane) This is a polyurethane that polymerizes and hardens upon heating. For example, it is a dried and cured product obtained by the evaporation of the solvent in a thermosetting polycarbonate-based polyurethane dispersion and further polymerization and hardening upon heating.

[0031] UV-curable polycarbonate polyurethane and thermosetting polycarbonate polyurethane utilize compatible resins. The compatibility of both resins results in a visible light transmittance of 90% or more for the translucent resin sheet 100, and prevents image blurring or indistinctness even when an image is transmitted through the translucent resin sheet 100.

[0032] (Mass ratio of UV-curable polycarbonate polyurethane to thermosetting polycarbonate polyurethane) While UV-curable polycarbonate polyurethane can form a hard film with a pencil hardness of 4H on its own, it may repel the polymethyl methacrylate layer 40 when attempting to form a film on it, preventing the formation of a continuous film. Similarly, while thermosetting polycarbonate polyurethane can form a continuous film on the polymethyl methacrylate layer 40 on its own, it is softer than UV-curable polycarbonate polyurethane, and therefore does not achieve a pencil hardness of 2H or higher.

[0033] Therefore, the mass ratio of UV-curable polycarbonate polyurethane to thermosetting polycarbonate polyurethane is set to 7:3 to 8:2. By setting the mass ratio within this range, wettability is improved, and a continuous film of polycarbonate polyurethane resin layer 20 can be formed on the polymethyl methacrylate layer 40, covering the entire surface 41 of the polymethyl methacrylate layer 40, while the pencil hardness of the surface 21 of the polycarbonate polyurethane resin layer 20 can be set to 2H or higher.

[0034] (Carbodiimide) If unreacted functional groups of UV-curable polycarbonate polyurethane remain inside the polycarbonate polyurethane resin layer 20, they are oxidized and carboxylic acids are generated. The generated carboxylic acids decompose the urethane components, reducing the weather resistance of the polycarbonate polyurethane resin layer 20.

[0035] Therefore, by including carbodiimide in the polycarbonate-based polyurethane resin layer 20, and encapsulating any unreacted functional groups that are oxidized with carbodiimide, the weather resistance of the polycarbonate-based polyurethane resin layer 20 can be satisfied.

[0036] Furthermore, by including carbodiimide, the chemical resistance of the polycarbonate-based polyurethane resin layer 20 can be improved.

[0037] As the carbodiimide, one that is compatible with UV-curable polycarbonate-based polyurethane and thermosetting polycarbonate-based polyurethane is used. By using a carbodiimide compatible with both resins, the light transmittance of the translucent resin sheet 100 in the visible region becomes 90% or more, and even when a displayed image is transmitted through the translucent resin sheet 100, no problems such as image blurring or blurring occur. As such a compatible carbodiimide, for example, a polycarbodiimide having a carbodiimide group in its molecule can be used.

[0038] When a mixture of UV-curable polycarbonate polyurethane, thermosetting polycarbonate polyurethane, and carbodiimide dries and hardens to form a polycarbonate polyurethane resin layer 20, the translucent resin sheet 100 exhibits excellent transparency, pencil hardness, and flame retardancy.

[0039] (Mass ratio of polyurethane to carbodiimide) The mass ratio of the total resin content of UV-curable polycarbonate polyurethane and thermosetting polycarbonate polyurethane to carbodiimide is preferably 9:0.4 to 0.8. If the amount of carbodiimide is too low, the effect of improving chemical resistance such as alkali resistance may not be achieved. Conversely, if the amount of carbodiimide is too high, it may inhibit the properties of the polyurethane and reduce chemical resistance such as alkali resistance.

[0040] (Thickness of the polycarbonate-based polyurethane resin layer 20) The thickness of the polycarbonate polyurethane resin layer 20 shall be between 3 μm and 10 μm. If the thickness of the polycarbonate polyurethane resin layer 20 is less than 3 μm, it may not satisfy the flame retardancy required for the translucent resin sheet 100. Furthermore, if the thickness of the polycarbonate polyurethane resin layer 20 is greater than 10 μm, curing defects may occur in UV curing or heat curing of the polyurethane resin, and the flame retardancy, weather resistance, chemical resistance, and other properties of the polycarbonate polyurethane resin layer 20 may not be able to be exhibited. By having the thickness of the polycarbonate polyurethane resin layer 20 within the range of 3 μm to 10 μm, the required performance such as flame retardancy, weather resistance, and chemical resistance can be fully exhibited.

[0041] <Light transmittance in the visible region> When the translucent resin sheet 100 is used as a dust cover for a HUD, the displayed image will pass through the translucent resin sheet 100. Therefore, to prevent the displayed image from becoming blurred due to the transmission of light through the translucent resin sheet 100, the translucent resin sheet 100 should have a light transmittance of 90% or more in the visible region (wavelength 380-780nm). While the upper limit of this light transmittance is 100%, in practice, a transmittance of around 90% to 95% is acceptable.

[0042] <Pencil hardness> The pencil hardness of the surface 21 on the polycarbonate-based polyurethane resin layer 20 side of the translucent resin sheet 100 is 2H or higher. Although the upper limit of pencil hardness is 9H, a hardness of around 2H to 3H can satisfy the required scratch resistance performance.

[0043] <Flame retardant> The flame retardancy of the translucent resin sheet 100 is determined by its self-extinguishing properties in the flammability test specified in FMVSS (Federal Motor Vehicle Safety Standard) No. 302. By exhibiting self-extinguishing properties, it can be suitably used in applications requiring high flame retardancy, such as automotive components and building materials.

[0044] Furthermore, considering the use of the translucent resin sheet 100 of the present invention as a dust cover for a HUD, it is preferable that the translucent resin sheet 100 further satisfies the following performance requirements.

[0045] (Hayes) When the translucent resin sheet 100 is used as a dust cover for a HUD, the displayed image will pass through the translucent resin sheet 100. Therefore, to prevent the displayed image from becoming blurred due to the transmission of light through the translucent resin sheet 100, it is preferable that the haze (turbidity) of the translucent resin sheet 100 be 1.0% or less. The lower limit of the haze is 0%, but in practice, a haze of around 0.1% to 0.5% is acceptable.

[0046] (Scratch resistance) Since the surface 21 of the translucent resin sheet 100 on the polycarbonate-based polyurethane resin layer 20 side is exposed as the surface of the dust cover for the HUD, it is preferable that this surface 21 be resistant to scratches. As a guideline for scratch resistance, it is preferable that the surface has a pencil hardness of 2H or higher as described above. Furthermore, as a guideline for scratch resistance performance, it is preferable that it meets the requirements of the European automotive standard TL226.

[0047] Specifically, the test involves wrapping gauze around a 15mm diameter terminal, pressing it against surface 21 with a load of 9N, and then moving the pressed gauze back and forth 100 times at a stroke of 10cm and 60 back-and-forth movements per minute. If there are no scratches on surface 21 after the test, the conditions of the European automotive standard TL226 are met.

[0048] (weather resistance) The translucent resin sheet 100 preferably has excellent weather resistance. Weather resistance can be evaluated, for example, by performing an accelerated weathering test using a xenon weatherometer with the surface 21 on the polycarbonate polyurethane resin layer 20 side as the exposed surface.

[0049] Specifically, a xenon weather meter SX75 (manufactured by Suga Test Instruments Co., Ltd.) was used, with the following test conditions: black panel temperature 63±2℃, humidity 50%RH, rainfall cycle (non-rainfall time / rainfall time) 102 min / 18 min, and irradiance 180 W / m². 2 Tank temperature 25-35℃, cumulative light intensity 500 MJ / m 2 The color difference of surface 21 before and after the test is measured using a colorimeter CM-3600A (manufactured by Konica Minolta), and a result of △E = 3.0 or less is considered a guideline for satisfying the weather resistance requirement.

[0050] (Chemical resistance) The translucent resin sheet 100 preferably has excellent weather resistance. Specifically, it is preferable that when a solvent such as alcohol or sunscreen is left on the surface 21 on the polycarbonate polyurethane resin layer 20 side, the part of the translucent resin sheet 100 to which the solvent is attached does not discolor, such as becoming cloudy.

[0051] [Method for manufacturing translucent resin sheets] Next, the method for manufacturing the translucent resin sheet of the present invention will be described. The method for manufacturing the translucent resin sheet includes the following polycarbonate-based polyurethane resin layer formation step, and may also include a base layer formation step.

[0052] <Polycarbonate-based polyurethane resin layer formation process> This process involves applying the following coating to the base layer 10 to form a polycarbonate-based polyurethane resin layer 20. Specifically, the coating is applied to the surface 41 of the polymethyl methacrylate layer 40 using a die coater or the like to form a coating film, and the coating film is heated and dried at 120°C to 140°C for about 2 minutes, and then irradiated at an illumination of 150 W / m². 2 Approximately, the cumulative light intensity is 600 mJ / cm². 2 By irradiating the coating film with ultraviolet light under certain conditions, a polycarbonate-based polyurethane resin layer 20 can be formed.

[0053] <paint> The paint is a mixture containing UV-curable polycarbonate polyurethane dispersion, thermosetting polycarbonate polyurethane dispersion, carbodiimide, a photopolymerization initiator, and a solvent, and is a mixture in which these raw materials are uniformly mixed.

[0054] (UV-curable polycarbonate-based polyurethane dispersion) A dispersion can be used that exhibits excellent adhesion to polymethyl methacrylate as well as excellent chemical resistance. Given that the translucent resin sheet 100 is used inside a vehicle and from the perspective of environmental considerations, for example, a water-based dispersion in which polycarbonate polyurethane is dispersed in water can be used.

[0055] (Thermosetting polycarbonate-based polyurethane dispersion) A dispersion with excellent wettability with polymethyl methacrylate can be used. Given that the translucent resin sheet 100 is used inside a vehicle and from the perspective of environmental considerations, for example, a water-based dispersion in which polycarbonate polyurethane is dispersed in water can be used.

[0056] (Carbodiimide) As the carbodiimide, one that is compatible with UV-curable polycarbonate-based polyurethane dispersion and thermosetting polycarbonate-based polyurethane dispersion is used. By using a carbodiimide compatible with both resins, the light transmittance of the translucent resin sheet 100 in the visible region becomes 90% or more, and even when a displayed image is transmitted through the translucent resin sheet 100, no problems such as image blurring or blurring occur. As such a compatible carbodiimide, for example, a water-soluble polycarbodiimide having a carbodiimide group in its molecule can be used.

[0057] (Photopolymerization initiator) This material allows for the polymerization and high-molecular-weight conversion of UV-curable polycarbonate-based polyurethanes through irradiation with ultraviolet light.

[0058] (solvent) Solvents can be added to adjust the resin solid content in the paint. When using a water-based dispersion in the paint, water can be used as the solvent. Furthermore, if the water contains an unnecessary photoinitiator, an alcohol such as isopropyl alcohol can be used in combination with water as a solvent to dissolve the photoinitiator.

[0059] (Other ingredients) The paint may contain components other than those listed above. For example, it may contain additives such as leveling agents and defoamers, as well as colorants and matting agents.

[0060] (Mass ratio of UV-curable polycarbonate polyurethane resin content to thermosetting polycarbonate polyurethane resin content) While UV-curable polycarbonate polyurethane can form a hard film with a pencil hardness of 4H on its own, it may repel the polymethyl methacrylate layer 40 when attempting to form a film on it, preventing the formation of a continuous film. Similarly, while thermosetting polycarbonate polyurethane can form a continuous film on the polymethyl methacrylate layer 40 on its own, it is softer than UV-curable polycarbonate polyurethane, and therefore does not achieve a pencil hardness of 2H or higher.

[0061] Therefore, the mass ratio of the resin content of the UV-curable polycarbonate-based polyurethane dispersion to the resin content of the thermosetting polycarbonate-based polyurethane dispersion in the paint is set to 7:3 to 8:2. By setting the mass ratio within this range, the wettability of the paint is improved, a continuous film of polycarbonate-based polyurethane resin layer 20 covering the entire surface 41 of the polymethyl methacrylate layer 40 can be formed on the polymethyl methacrylate layer 40, and the pencil hardness of the surface 21 of the polycarbonate-based polyurethane resin layer 20 can be set to 2H or higher.

[0062] (Mass ratio of polyurethane to carbodiimide) The mass ratio of the total resin content of the UV-curable polycarbonate polyurethane dispersion and the thermosetting polycarbonate polyurethane dispersion to the carbodiimide is preferably 9:0.4 to 0.8. If the amount of carbodiimide is too low, the effect of improving the chemical resistance, such as alkali resistance, of the polycarbonate polyurethane resin layer 20 may not be achieved. Conversely, if the amount of carbodiimide is too high, it may inhibit the properties of the polyurethane and reduce the chemical resistance, such as alkali resistance, of the polycarbonate polyurethane resin layer 20.

[0063] <Base material layer formation process> This process involves co-extruding polycarbonate and thermoplastic polymethyl methacrylate to form a base layer 10. For example, molten polycarbonate and thermoplastic polymethyl methacrylate are supplied to a two-layer feed block type T-die, the two-layer sheet is extruded by a die adjusted to an appropriate lip clearance, rolled with three polishing rolls, cooled to room temperature, and the two-layer sheet is formed and then wound into a roll to produce a base layer 10 comprising a polycarbonate layer 30 and a polymethyl methacrylate layer 40. In addition, a multi-manifold type T-die can be used instead of a feed block type T-die.

[0064] Co-extrusion molding using a T-die allows for direct melt-bonding of polycarbonate and thermoplastic polymethyl methacrylate without the use of adhesives, and enables the creation of a film with the minimum necessary thickness without compromising the properties of the resin.

[0065] The base layer formation process is not a mandatory step; the base layer 10 may be obtained by purchase or other means, and the translucent resin sheet 100 may be manufactured by performing the polycarbonate-based polyurethane resin layer formation process on the base layer 10.

[0066] [Projection type display] Next, the projection display of the present invention will be described. The projection display of the present invention is equipped with the translucent resin sheet of the present invention as a translucent dustproof cover. Figure 2 shows a schematic side view of a head-up display device 200 as an example of the projection display of the present invention.

[0067] The head-up display device 200 comprises a display unit 210, a folding mirror 220, a concave mirror (reflective member) 230, a translucent dustproof cover 240, and a control board 250. Furthermore, the head-up display device 200 includes a housing 260, which houses the display unit 210, the folding mirror 220, the concave mirror 230, and the control board 250.

[0068] The display unit 210 emits, for example, information to be provided to the driver of the vehicle 300 as display light A. The display light A from the display unit 210 is emitted toward the folding mirror 220 shown in Figure 2, and is reflected toward the concave mirror 230 by the folding mirror 220. The concave mirror 230 reflects the display light A and projects the display image onto the windshield 310 (Figure 1) of the vehicle 300 via a translucent dustproof cover 240 provided in the opening of the housing 260. The display image projected onto the windshield 310 is perceived by the driver B as a virtual image C.

[0069] As the translucent dust cover 240, a translucent resin sheet 100 processed into a predetermined shape is used so that it can be incorporated as the translucent dust cover 240 of the head-up display device 200. The surface 21 of the polycarbonate-based polyurethane resin layer 20, which has excellent scratch resistance, weather resistance, and chemical resistance, is exposed to the outside, while the surface 31 of the polycarbonate layer 30 is located inside the head-up display device 200.

[0070] The displayed image does not necessarily have to be projected onto the windshield 310. For example, the head-up display device 200 may be equipped with a clear panel for projection that is visible to driver B, and the displayed image may be projected onto that clear panel.

[0071] [Mobile] Next, the mobile body of the present invention will be described. The mobile body of the present invention is equipped with the projection-type display of the present invention. Figure 3 shows a schematic side view of a head-up display device 200 mounted on a vehicle 300, as an example of a mobile body equipped with the projection-type display of the present invention.

[0072] As shown in Figure 3, the head-up display device 200 is housed and positioned in an opening 330 formed on the upper surface of the instrument panel 320 of the vehicle 300. However, the head-up display device 200 is not limited to this configuration; in cases where there is no opening 330, the head-up display device 200 may be mounted on the upper surface of the instrument panel 320. [Examples]

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0074] [Manufacturing of translucent resin sheets] <Base material layer formation process> Molten polycarbonate and thermoplastic polymethyl methacrylate were supplied to a two-layer feed block type T-die, and the two-layer sheet was extruded by the die adjusted to the appropriate lip clearance. The sheet was then rolled with three polishing rolls, cooled to room temperature, and the two-layer sheet was formed and wound into a roll to produce a base layer 10 with a total thickness of 375 μm, comprising a polycarbonate layer 30 with a thickness of 355 μm and a polymethyl methacrylate layer 40 with a thickness of 20 μm.

[0075] Here, lupilon S-2000UR (Mitsubishi Engineering Plastics Corporation) was used as the polycarbonate, and Sumipex MHF (manufactured by Sumitomo Chemical Co., Ltd.) was used as the thermoplastic polymethyl methacrylate.

[0076] <Polycarbonate-based polyurethane resin layer formation process> (Paint creation) Based on the formulations shown in Table 1, the raw materials were mixed to produce paints No. A to F for forming polycarbonate-based polyurethane resin layers.

[0077] In the coating, ETERNACOLL® UW9102 (30% by mass resin solids, manufactured by Ube Industries, Ltd.), a water-based resin, was used as the UV-curable polycarbonate polyurethane dispersion, and ETERNACOLL® UW5002E (30% by mass resin solids, manufactured by Ube Industries, Ltd.), a water-based resin, was used as the thermosetting polycarbonate polyurethane dispersion. Carbodiimide was Carbodilite V-02 (40% by mass carbodiimide content, manufactured by Nisshinbo Chemical Inc.), BYK-333 (polyether-modified polydimethylsiloxane) (manufactured by BYK-Chemie) as the leveling agent, and Doblecure550 (manufactured by DOUBLE BOND CHEMICAL) as the photopolymerization initiator. Isopropyl alcohol (IPA) and water were used as solvents.

[0078] [Table 1]

[0079] (Formation of polycarbonate-based polyurethane resin layer 20) The prepared paint was applied to the surface 41 of the polymethyl methacrylate layer 40 using a die coater, and after drying the painted film at 130°C for 2 minutes, an illuminance of 150 W / m² was applied. 2 , cumulative light intensity 600 mJ / cm 2 The coating was cured by ultraviolet irradiation under these conditions to obtain a translucent resin sheet 100.

[0080] Tables 2 and 3 show the dry film thickness of the polycarbonate-based polyurethane resin layer 20 after curing. For the paints in Examples 1 and 2, the dry film thickness of the polycarbonate-based polyurethane resin layer 20 after curing was changed, and the physical properties were evaluated.

[0081] <Evaluation of physical properties of translucent resin sheet 100> (Appearance of the polycarbonate-based polyurethane resin layer 20) The appearance of the polycarbonate-based polyurethane resin layer 20 was observed visually, and it was evaluated as follows: ○ if the polycarbonate-based polyurethane resin layer 20 formed a uniform continuous film on the surface 41 of the polymethyl methacrylate layer 40, and × if the coating repelled from the surface 41 and the surface 41 was exposed without forming a uniform continuous film.

[0082] (Measurement of light transmittance and haze in the visible region) Using a Haze Meter NDH 7000SP2 (NIPPON DENSHOKU) K7105, the light transmittance and haze of the translucent resin sheet 100 in the visible region (wavelength 380-780 nm) were measured on the surface 21 of the polycarbonate polyurethane resin layer 20.

[0083] (Pencil hardness) The surface 21 of the polycarbonate polyurethane resin layer 20 was used as the test surface, and the pencil hardness of the translucent resin sheet 100 was evaluated with a load of 750g based on JIS K 5600 scratch hardness (pencil method).

[0084] (Scratch resistance) The surface 21 of the polycarbonate polyurethane resin layer 20 was used as the test surface. Based on the conditions of the European automotive standard TL226, a gauze wrapped around a 15 mm diameter terminal was pressed against the surface 21 with a load of 9 N, and the pressed gauze was moved back and forth for XX minutes at a stroke of 10 cm and 60 reciprocations / minute. If no damage occurred on the surface 21 after the test, it was evaluated as ○, and if damage occurred, it was evaluated as ×.

[0085] (Flame retardant) The flame retardancy of translucent resin sheet 100 was evaluated using the flammability test specified in FMVSS (Federal Motor Vehicle Safety Standard) No. 302. The specific test details are as follows. Based on the test results, a ○ was used to indicate flame retardancy if the sheet passed the FMVSS No. 302 standard, and a × was used to indicate non-flammability if the sheet did not pass the FMVSS No. 302 standard.

[0086] A translucent resin sheet 100 was used as the test specimen (350 mm x 100 mm). In a test environment of 21°C x 50% RH, the test specimen was held horizontally, and a 38 mm flame was applied indirectly for 15 seconds. The determination was made based on the burning rate relative to the 254 mm distance between mark A and mark B. Judgment Criteria: Products that meet any of the following FMVSS No. 302 combustion test criteria are considered to have passed the FMVSS No. 302 standard. • The test specimen does not ignite, or it extinguishes before reaching the A mark. • Self-extinguishing devices with a burning distance of 51mm or less (and within 60 seconds). • Burning distance of 102 mm / min or less

[0087] (weather resistance) An accelerated weathering test was conducted using a xenon weatherometer on the surface 21 of the translucent resin sheet 100, specifically on the side with the polycarbonate polyurethane resin layer 20, which was the exposed surface. Specifically, a xenon weatherometer SX75 (manufactured by Suga Test Instruments Co., Ltd.) was used, with the following test conditions: black panel temperature 63±2℃, humidity 50%RH, rainfall cycle (non-rainfall time / rainfall time) 102 min / 18 min, and irradiance 180 W / m². 2 Tank temperature 25-35℃, cumulative light intensity 500 MJ / m 2 The color difference of surface 21 before and after the test was measured using a color difference meter CM-3600A (manufactured by Konica Minolta). A color difference of △E = 3.0 or less was judged as satisfying the weather resistance requirement (○), and a color difference exceeding △E = 3.0 was judged as not satisfying the weather resistance requirement (×).

[0088] (Chemical resistance) A translucent resin sheet 100 was immersed in 55°C hot water for 4 hours. Immediately after the immersion treatment, if the multilayer film, etc., removed from the hot water showed no abnormalities such as whitening, discoloration, or significant scarring, it was evaluated as having water resistance (○). If any of these abnormalities were observed, it was evaluated as not having water resistance (×).

[0089] The surface 21 of the translucent resin sheet 100 on the polycarbonate polyurethane resin layer 20 side was used as the test surface. An acid resistance test was performed by dropping 5 ml of 0.1 N H2SO4 aqueous solution onto the test surface and leaving it to stand at 20°C for 24 hours. An alkali resistance test was performed by dropping 5 ml of 0.1 N NaOH aqueous solution onto the test surface and leaving it to stand at 55°C for 4 hours. A chemical resistance test was performed by dropping 5 ml of white kerosene onto the test surface and leaving it to stand at 55°C for 4 hours. In addition, as a chemical resistance test, a test was performed by dropping 5 ml of 50% by mass ethanol onto the test surface and leaving it to stand at 55°C for 4 hours, and a test was performed by applying sunscreen cream (SPF45) to the test surface, leaving it to stand at 80°C for 24 hours, and then removing the cream. Immediately after the end of the test, if there were no abnormalities such as whitening, discoloration, or significant scarring on the translucent resin sheet 100 after the removal of each chemical, it was evaluated as ○, and if any of these abnormalities were observed it was evaluated as ×.

[0090] In Tables 2 and 3, a test result of ○ in any of the above tests was marked as ○, indicating that the chemical resistance requirement was met, while a test result of × in any of the above tests was marked as ×, indicating that the chemical resistance requirement was not met.

[0091] The results of the physical property evaluation are shown in Tables 2 and 3.

[0092] [Table 2]

[0093] [Table 3]

[0094] Table 2 shows the results of evaluating the physical properties of the translucent resin sheet 100 by varying the mass ratio of UV-curable polycarbonate polyurethane to thermosetting polycarbonate polyurethane from 5:5 to 10:0. From the results in Table 2, Examples 1 and 2, where the mass ratio of UV-curable polycarbonate polyurethane to thermosetting polycarbonate polyurethane was 7:3 to 8:2, showed excellent physical properties such as appearance, weather resistance, and chemical resistance of the resin layer 20, as well as higher transparency than the visible light transmittance and haze results, and good results in both scratch resistance and flame retardancy.

[0095] On the other hand, when the above mass ratio fell outside the range of 7:3 to 8:2, the results were inferior in pencil hardness, scratch resistance, and chemical resistance (Comparative Examples 1 and 2), and inferior in the appearance, flame retardancy, and weather resistance of the resin layer 20 (Comparative Examples 3 and 4).

[0096] Table 3 shows the results of evaluating the physical properties of the translucent resin sheet 100 by varying the dry film thickness of the resin layer 20, with the mass ratio of UV-curable polycarbonate polyurethane to thermosetting polycarbonate polyurethane set to 7:3 or 8:2. From the results in Table 3, Examples 1 to 6, in which the dry film thickness of the resin layer 20 was 3 μm to 10 μm, showed excellent physical properties such as appearance, weather resistance, and chemical resistance of the resin layer 20, as well as higher transparency than the visible light transmittance and haze results, and good results in both scratch resistance and flame retardancy.

[0097] On the other hand, when the dry film thickness of the resin layer 20 was 2 μm, the flame retardancy was inferior (Comparative Examples 5 and 7). Furthermore, when the dry film thickness of the resin layer 20 was 11 μm, the flame retardancy, weather resistance, and chemical resistance were inferior (Comparative Examples 6 and 8).

[0098] [Verification of the mass ratio of polycarbonate-based polyurethane and carbodiimide] The following shows the results of verifying that in the translucent resin sheet of the present invention, the mass ratio of the total resin content of the ultraviolet-curable polycarbonate-based polyurethane and the thermosetting polycarbonate-based polyurethane to carbodiimide is 9:0.4 to 0.8, resulting in excellent alkali resistance.

[0099] [Manufacture of Translucent Resin Sheet] The base material layer 10 used was the same as in the above example. That is, it is a base material layer 10 with a total thickness of 375 μm, comprising a polycarbonate layer 30 with a thickness of 355 μm and a polymethyl methacrylate layer 40 with a thickness of 20 μm.

[0100] 〈Process for Forming Polycarbonate-based Polyurethane Resin Layer〉 (Preparation of Paint) Based on the formulations shown in Table 4, the raw materials were mixed while varying the mixing amount of carbodiimide to prepare paints for forming the polycarbonate-based polyurethane resin layer of Paint Nos. C-1 to D-4. Each raw material was the same as in the above example. Also, Paint No. C-1 and Paint No. D-1 have the same formulations as Paint No. C and Paint No. D in the above example, respectively.

[0101]

Table 4

[0102] (Formation of Polycarbonate-based Polyurethane Resin Layer 20) The prepared paint was applied to the surface 41 of the polymethyl methacrylate layer 40 with a die coater. After drying the applied coating film at 130 °C for 2 minutes, it was irradiated with ultraviolet light under the conditions of an illuminance of 150 W / m 2 and an integrated light quantity of 600 mj / cm 2 to cure the coating film, obtaining the translucent resin sheet 100.

[0103] The dry film thickness of the cured polycarbonate-based polyurethane resin layer 20 is shown in Table 5.

[0104] 〈Alkali Resistance Evaluation of Translucent Resin Sheet 100〉 The test was performed using the same method and criteria as in the above examples. Specifically, the surface 21 of the translucent resin sheet 100 on the polycarbonate polyurethane resin layer 20 side was used as the test surface, and 5 ml of 0.1 N NaOH aqueous solution was dropped onto the test surface and left to stand at 55°C for 4 hours to perform the alkali resistance test. The translucent resin sheet 100, after the NaOH aqueous solution was removed immediately after the test, was evaluated as ○ if there were no abnormalities such as whitening, discoloration, or significant scarring, and as × if any of these abnormalities were observed.

[0105] The results of the physical property evaluation are shown in Table 5.

[0106] [Table 5]

[0107] The present invention aims to provide a translucent resin sheet, a method for manufacturing a translucent resin sheet, a projection display, and a mobile body that can be used in a dust cover for a HUD that satisfies high transparency, scratch resistance, and flame retardancy. While a translucent resin sheet with excellent alkali resistance is more preferable, the present invention does not aim to exclude translucent resin sheets with poor alkali resistance. Therefore, Table 5 includes examples that show poor alkali resistance.

[0108] Furthermore, although Table 5 does not show the results for the appearance, visible light transmittance, haze, pencil hardness, scratch resistance, flame retardancy, and weather resistance of the resin layer 20, these results for Examples 7 to 12 were similar to those for Examples 1 and 2, indicating good results.

[0109] As shown in Table 5, when the mass ratio of the total resin content of UV-curable polycarbonate polyurethane and thermosetting polycarbonate polyurethane to carbodiimide is 9:0.4 to 0.8, the material exhibits excellent alkali resistance even when the mass ratio of the resin content changes.

[0110] [Example 13] A polycarbonate-based polyurethane resin layer 20 with a dry film thickness of 8 μm was formed in the same manner as in Example 1, except that the thickness of the polymethyl methacrylate layer 40 of the base layer 10 was 40 μm and the total thickness of the base layer was 395 μm, thereby obtaining a translucent resin sheet 100.

[0111] The translucent resin sheet 100 obtained in Example 13 was then evaluated for its physical properties in the same manner as in Example 1, and its pencil hardness was found to be 3H. The appearance, visible light transmittance, haze, scratch resistance, flame retardancy, weather resistance, and chemical resistance of the resin layer 20 of the translucent resin sheet 100 in Example 13 were the same as those of the translucent resin sheet 100 in Example 1.

[0112] (summary) Based on the above, the present invention provides a translucent resin sheet that can be used in a dust cover for a HUD that satisfies high transparency, scratch resistance, and flame retardancy, a method for manufacturing the translucent resin sheet, a projection type display, and a mobile body, and is therefore industrially useful. [Explanation of Symbols]

[0113] 10: Base layer, 20: Polycarbonate-based polyurethane resin layer, 21: Surface, 30: Polycarbonate layer, 31: Surface, 40: Polymethyl methacrylate layer, 41: Surface, 100: Translucent resin sheet, 200: Head-up display device, 210: Display unit, 220: Folding mirror, 230: Concave mirror (reflective material), 240: Light-transmitting dustproof cover, 250: Control board, 260: Enclosure, 300: Car, 310: Windshield, 320: Instrument panel, 330: Aperture, A: Indicator light, B: Driver, C: Virtual image

Claims

1. A co-extruded molded article of polycarbonate and thermoplastic polymethyl methacrylate, comprising a base layer having a polycarbonate layer and a polymethyl methacrylate layer, The material comprises a polycarbonate-based polyurethane resin layer laminated on the polymethyl methacrylate layer of the base layer, The thickness of the polycarbonate layer is 320 μm to 400 μm. The thickness of the polymethyl methacrylate layer is 18 μm to 45 μm. The thickness of the polycarbonate-based polyurethane resin layer is 3 μm to 10 μm. The aforementioned polycarbonate-based polyurethane resin layer is a cured product containing UV-curable polycarbonate-based polyurethane, thermosetting polycarbonate-based polyurethane, and carbodiimide. The mass ratio of UV-curable polycarbonate polyurethane to thermosetting polycarbonate polyurethane is 7:3 to 8:

2. The light transmittance in the visible region is 90% or more. The pencil hardness of the surface on the polycarbonate-based polyurethane resin layer side is 2H or higher. A translucent resin sheet that exhibits self-extinguishing properties in the flammability test specified in FMVSS No.

302.

2. The translucent resin sheet according to claim 1, wherein the mass ratio of the total resin content of the ultraviolet-curable polycarbonate polyurethane and the thermosetting polycarbonate polyurethane to the carbodiimide is 9:0.4 to 0.

8.

3. A method for producing a translucent resin sheet according to claim 1, The process includes a step of forming a polycarbonate-based polyurethane resin layer by applying paint to the substrate layer to form the polycarbonate-based polyurethane resin layer, The aforementioned coating is a mixture containing an ultraviolet-curable polycarbonate-based polyurethane dispersion, a thermosetting polycarbonate-based polyurethane dispersion, carbodiimide, a photopolymerization initiator, and a solvent. The mass ratio of the resin content of the UV-curable polycarbonate-based polyurethane dispersion to the resin content of the thermosetting polycarbonate-based polyurethane dispersion is 7:3 to 8:

2. A method for manufacturing a translucent resin sheet.

4. A method for producing a translucent resin sheet according to claim 3, wherein the mass ratio of the total resin content of the ultraviolet-curable polycarbonate-based polyurethane dispersion and the thermosetting polycarbonate-based polyurethane dispersion to the carbodiimide is 9:0.4 to 0.

8.

5. A method for producing a translucent resin sheet according to claim 3, comprising a base layer forming step of co-extruding the polycarbonate and the thermoplastic polymethyl methacrylate to form the base layer.

6. A projection display comprising a translucent resin sheet as described in claim 1 as a translucent dustproof cover.

7. A mobile body comprising the projection-type display described in claim 6.

Images