JP2024052308A - Optical Sheet - Google Patents

Abstract

[Problem] To provide a functional optical sheet that is excellent in both processability and wear resistance. [Solution] The optical sheet 15 of the present invention comprises a functional substrate 11 and a coating layer 12, the coating layer 12 being composed of a semi-cured product of a resin composition containing a soft component having a radical polymerizable group and a hard component having a cationic polymerizable group, the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, cooled, and then irradiated with ultraviolet light from the coating layer 12 side for 1000 hours, the change in YI of the optical sheet 15 is less than 1.0, the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, molded into a shape with a radius of curvature of 120 mmR, and then cooled to 25°C, no cracks are observed in the coating layer 12, and the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, cooled, and then subjected to a wiper laboratory test, the haze value of the optical sheet 15 is less than 5.0. [Selected Figure] Figure 3

Description

The present invention relates to an optical sheet.

In recent years, as lenses for eyewear such as spectacles and sunglasses, optical sheets with a half-mirror layer that selectively reflects light in a specific wavelength range (visible light), or optical sheets with a polarizer that provides polarizing properties, have been proposed on their surfaces, for example, to improve the design or to provide polarizing properties.

That is, a lens has been proposed in which a functional optical sheet is attached to the surface of the lens in order to provide functionality to the lens.

A lens having such an optical sheet on its surface is manufactured, for example, by preparing an optical sheet having the above-mentioned configuration as a flat plate in a planar view, and punching the optical sheet into a predetermined shape such as a circular shape in a planar view with protective films attached to both sides of the optical sheet. The optical sheet is then subjected to a thermal bending process under heating to form a curved optical sheet having a curved convex surface and a curved concave surface that are curved by thermal bending. After peeling the protective film from the curved optical sheet, the curved optical sheet is adsorbed to a mold having a curved concave surface so that the concave surface of the mold and the convex surface of the curved optical sheet come into contact with each other, and then the curved optical sheet is adsorbed to the mold, and a resin layer (molded layer) mainly made of a resin material is formed on the concave surface of the curved optical sheet by insert injection molding (see, for example, Patent Document 1).

In addition to being used on the surface of a lens, optical sheets with such functionality have also been proposed for use as a cover member that is provided to cover the window of a housing in a head-up display device that is mounted on an automobile.

When an optical sheet is placed as a cover member against a window portion of such a storage body so as to cover the window portion, the optical sheet is a curved optical sheet that has been thermally bent into a curved shape, similar to the case where the optical sheet is provided on the surface of a lens.

As described above, such optical sheets are curved optical sheets that are thermally bent into a curved shape, and therefore the optical sheets are required to have excellent processability (formability). Furthermore, the optical sheets are placed on the front side of lenses and head-up display devices, in positions where they may come into contact with people or objects, and therefore are required to have excellent abrasion resistance.

Therefore, there was a demand for the development of an optical sheet that combines excellent processability and abrasion resistance.

This demand is not limited to cases where the optical sheet is applied to a lens or a head-up display device, but also arises when the optical sheet is applied to a windshield or the like of a vehicle such as a motorcycle.

JP 2009-294445 A

The object of the present invention is to provide a functional optical sheet that combines excellent processability and abrasion resistance.

Such an object can be achieved by the present invention described in (1) to (10) below.
(1) An optical sheet comprising a functional substrate and a coating layer provided as an outermost layer on at least one surface of the functional substrate,
the coating layer is composed of a semi-cured product of a resin composition including a soft component having a radical polymerizable group and a hard component having a cationic polymerizable group;
The optical sheet is characterized by satisfying the following requirements A to C.
Requirement A: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, cooled, and then irradiated with ultraviolet light from the coating layer side for 1000 hours using a xenon weather meter in accordance with JIS K 7350-4, Table 3-A method, cycle No. 1. After that, the change in YI of the optical sheet as defined by JIS K 7373 is less than 1.0.
Requirement B: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, molded into a curved shape with a radius of curvature of 120 mmR, and then cooled to 25°C; no cracks are observed in the coating layer.
Requirement C: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, cooled, and then subjected to a wiper laboratory test in accordance with ECE43. After that, the haze value of the optical sheet is less than 5.0.

(2) The optical sheet according to (1) above, wherein the radical polymerizable group is at least one of a (meth)acryloyl group and a vinyl group.

(3) The optical sheet according to (1) or (2) above, in which the soft component has a main chain having a urethane bond and one or two of the radical polymerizable groups linked as side chains.

(4) An optical sheet according to any one of (1) to (3) above, in which the cationic polymerizable group is at least one of a cyclic ether group and a vinyl ether group.

(5) The optical sheet according to any one of (1) to (4) above, wherein the hard component is a main chain made of a repeating body of structural units having siloxane bonds, to which a plurality of the cationic polymerizable groups are linked as side chains.

(6) The optical sheet according to any one of (1) to (5) above, wherein the resin composition further contains a monomer component having both the radical polymerizable group and the cationic polymerizable group.

(7) The optical sheet according to any one of (1) to (6) above, wherein the functional substrate includes a first substrate and a second substrate, and at least one of a polarizing layer and a half mirror layer disposed between the first substrate and the second substrate.

(8) The optical sheet according to any one of (1) to (7) above, which is used as a cover member provided to cover a window portion of a container.

(9) An optical sheet according to any one of (1) to (7) above, the optical sheet being provided so as to cover the front side of a lens.

(10) The optical sheet according to any one of (1) to (7) above, which is used as a windshield plate provided in a vehicle.

According to the present invention, in an optical sheet comprising a functional substrate and a coating layer provided as an outermost layer on at least one side of the functional substrate, the coating layer is composed of a semi-cured resin composition containing a soft component having a radically polymerizable group and a hard component having a cationic polymerizable group, and further, the optical sheet satisfies the following requirement B. Therefore, when the optical sheet is made into a curved optical sheet by thermal bending into a curved shape, it can be said that the occurrence of cracks in the coating layer of the curved optical sheet is appropriately suppressed or prevented. Therefore, when the optical sheet is made of a semi-cured resin composition, it exhibits excellent processability.

Furthermore, this optical sheet satisfies the following requirements A and C. Therefore, after the optical sheet is curved by thermal bending to form a curved optical sheet, the semi-cured material is cured to form a coating layer with the cured product of the resin composition, and the curved optical sheet can be said to have the following functions. That is, when this curved optical sheet is used, for example, to cover the front side of a lens, or as a cover member to cover a window portion of a head-up display housing, or even as a windshield plate of a vehicle, the curved optical sheet can be said to have excellent abrasion resistance while exhibiting the function of an optical sheet for a long period of time. Therefore, when the optical sheet is composed of the cured product of the resin composition, it exhibits excellent abrasion resistance.

Requirement A: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, cooled, and then irradiated with ultraviolet light from the coating layer side for 1000 hours using a xenon weather meter in accordance with JIS K 7350-4, Table 3-A method, cycle No. 1. After that, the change in YI of the optical sheet as specified by JIS K 7373 must be less than 1.0.

Requirement B: After the optical sheet is heated in a hot air oven at 170°C for 10 minutes and molded into a curved shape with a radius of curvature of 120 mmR, it is cooled to 25°C and no cracks are observed in the coating layer.

Requirement C: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, cooled, and then subjected to a wiper laboratory test in accordance with ECE43. After that, the haze value of the optical sheet is less than 5.0.

1 is a perspective view showing an embodiment of sunglasses equipped with lenses having a curved optical sheet in which the optical sheet of the present invention is curved. 1A to 1C are schematic diagrams for explaining a method for producing a lens having a curved optical sheet obtained by curvedly forming the optical sheet of the present invention. 1 is a vertical cross-sectional view showing a first embodiment of an optical sheet of the present invention. FIG. 4 is a vertical cross-sectional view showing a second embodiment of the optical sheet of the present invention. FIG. 1 is a side view showing an embodiment in which a curved optical sheet obtained by curvedly forming the optical sheet of the present invention is applied to a cover member constituting a head-up display of an automobile. FIG. 6 is an enlarged cross-sectional view of an area [A] surrounded by a dashed line in FIG. 5 . 1A and 1B are diagrams showing an embodiment in which a curved optical sheet according to the present invention is applied to a windshield plate.

The optical sheet of the present invention will now be described in detail with reference to the preferred embodiment shown in the accompanying drawings.

The optical sheet of the present invention comprises a functional substrate and a coating layer provided as an outermost layer on at least one side of the functional substrate, the coating layer being composed of a semi-cured resin composition containing a soft component having a radical polymerizable group and a hard component having a cationic polymerizable group, and the optical sheet satisfies the following requirements A to C.

Requirement A: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, cooled, and then irradiated with ultraviolet light from the coating layer side for 1000 hours using a xenon weather meter in accordance with JIS K 7350-4, Table 3-A method, cycle No. 1. After that, the change in YI of the optical sheet as specified by JIS K 7373 must be less than 1.0.

Requirement B: After the optical sheet is heated in a hot air oven at 170°C for 10 minutes and molded into a curved shape with a radius of curvature of 120 mmR, it is cooled to 25°C and no cracks are observed in the coating layer.

Requirement C: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, cooled, and then subjected to a wiper laboratory test in accordance with ECE43. After that, the haze value of the optical sheet is less than 5.0.

In this way, in the present invention, the optical sheet satisfies requirement B as described above. Therefore, when this optical sheet is made into a curved optical sheet by thermal bending, it can be said that the occurrence of cracks in the coating layer of this curved optical sheet is appropriately suppressed or prevented. Therefore, when the resin composition is composed of a semi-cured product, this optical sheet exhibits excellent processability.

Furthermore, the optical sheet of the present invention satisfies requirements A and C. Therefore, after the optical sheet is curved by thermal bending to form a curved optical sheet, the semi-cured product is cured to form a coating layer with the cured product of the resin composition, and the curved optical sheet can be said to have the following functions. That is, when this curved optical sheet is used, for example, to cover the front side of a lens, or as a cover member to cover a window portion of a head-up display housing, or even as a windshield plate of a vehicle, the curved optical sheet can be said to have excellent abrasion resistance while exhibiting the function of an optical sheet for a long period of time. Therefore, when the optical sheet is composed of the cured product of the resin composition, it exhibits excellent abrasion resistance.

The optical sheet of the present invention is subjected to a thermal bending process under heating to obtain a curved shape. After the resin composition constituting the coating layer is cured, the curved optical sheet can be used, for example, as a cover member provided to cover the front side of a lens, a cover member provided to cover a window portion of a housing for a head-up display, or even as a windshield plate provided in a vehicle.

Therefore, before describing the optical sheet of the present invention, we will first describe sunglasses in which the optical sheet of the present invention is a curved optical sheet having a curved shape and is used to cover the front side of the lenses.

<Sunglasses>
Fig. 1 is a perspective view showing an embodiment of sunglasses having lenses with a curved optical sheet obtained by curvedly forming the optical sheet of the present invention. In Fig. 1, when the sunglasses are worn on the head of a user, the surface of the lens facing the user's eyes is referred to as the back surface, and the opposite surface is referred to as the front surface.

As shown in FIG. 1, the sunglasses 100 include a frame 20 and a lens 30 (eyeglass lens).

In this specification, the term "lens (spectacle lens)" includes both lenses that have a light-gathering function and lenses that do not have a light-gathering function.

The frame 20 is worn on the user's head and positions the lenses 30 near the front of the user's eyes.

The frame 20 has a rim portion 21, a bridge portion 22, a temple portion 23, and a nose pad portion 24.

The rim portion 21 is ring-shaped, with one for each right eye and one for each left eye, and a lens 30 is attached to the inside. This allows the user to view external information through the lens 30.

The bridge portion 22 is rod-shaped and is positioned in front of the upper part of the user's nose when the headset is worn on the user's head, connecting the pair of rim portions 21.

The temples 23 are vine-shaped and are connected to the edge of each rim 21 on the opposite side to where the bridges 22 are connected. The temples 23 are placed over the user's ears when the glasses are worn on the user's head.

When the sunglasses 100 are worn on the head of the user, the nose pads 24 are provided on the edges of the rims 21 that correspond to the user's nose, come into contact with the user's nose, and are shaped to correspond to the contacting portion of the user's nose. This allows the sunglasses 100 to be stably maintained when worn.

The materials that make up the frame 20 are not particularly limited, and may be, for example, various metal materials or various resin materials. The shape of the frame 20 is not limited to the one shown in the figure, as long as it can be worn on the user's head.

The lens 30 is attached to each rim portion 21. The lens 30 is a light-transmitting member having an overall shape of a plate curved outward, and has a resin layer 35 (molded layer) and a curved optical sheet 10.

The resin layer 35 is optically transparent and is located on the back side of the lens. When the lens 30 is given a light-collecting function, this resin layer 35 has the light-collecting function.

The material for the resin layer 35 is not particularly limited as long as it is a resin material that is optically transparent, but examples include various thermoplastic resins, thermosetting resins, photocurable resins, and other curable resins, and one or more of these can be used in combination.

Examples of resin materials include polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers, polyvinyl chloride, polystyrene, polyamide, polyimide, polycarbonate, poly-(4-methylpentene-1), ionomers, acrylic resins, polymethyl methacrylate, acrylonitrile-butadiene-styrene copolymers (ABS resins), acrylonitrile-styrene copolymers (AS resins), butadiene-styrene copolymers, polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyethers, polyether ketones (PEK), and polyether ether ketones. Examples of the resin include polyether ether ketone (PEEK), polyetherimide, polyacetal (POM), polyphenylene oxide, polysulfone, polyethersulfone, polyphenylene sulfide, polyarylate, aromatic polyester (liquid crystal polymer), polytetrafluoroethylene, polyvinylidene fluoride, other fluorine-based resins, epoxy resins, phenolic resins, urea resins, melamine resins, silicone resins, polyurethanes, etc., or copolymers, blends, polymer alloys, etc., mainly made of these resins. Among these, it is preferable that the resin material is the same as or the same as the resin material that mainly constitutes the second substrate 112 of the curved optical sheet 10 described later. This can improve the adhesion between the resin layer 35 and the curved optical sheet 10. In addition, since the refractive index difference between the resin layer 35 and the curved optical sheet 10 (second substrate 112) can be set low, it is possible to appropriately suppress or prevent light from being diffused between the resin layer 35 and the curved optical sheet 10, and therefore light can be transmitted between the resin layer 35 and the curved optical sheet 10 with excellent light transmittance. In addition, the refractive index difference between the resin layer 35 and the curved optical sheet 10 (second substrate 112) is preferably 0.1 or less, and more preferably 0.05 or less. This allows the effect obtained by setting the refractive index difference low to be more pronounced.

The thickness of the resin layer 35 is not particularly limited, and is preferably, for example, 0.5 mm or more and 5.0 mm or less, and more preferably 1.0 mm or more and 3.0 mm or less. This allows the lens 30 to have both relatively high strength and light weight.

The curved optical sheet 10 is a curved resin substrate that is bonded to the outer surface of the resin layer 35, i.e., the curved convex surface of the resin layer 35, with a curved shape having a curved convex surface and a curved concave surface corresponding to the shape, with the curved concave surface of the curved optical sheet 10 being the curved convex surface side of the resin layer 35. By providing the lens 30 with this curved optical sheet 10, the sunglasses 100 is given functionality such as half-mirror properties and polarization properties. As a result, the sunglasses 100 exhibits the function of sunglasses having the above functionality. This curved optical sheet 10 is composed of the optical sheet 15 of the present invention that has a curved shape, but a detailed explanation of this will be given later.

As mentioned above, the lens 30 of the sunglasses 100 may or may not have a light-gathering function.

As described above, the sunglasses 100 may have a frame 20, or may be frameless from the standpoint of fashionability, lightweight, etc.

Furthermore, in this embodiment, glasses equipped with the lenses 30 are applied to sunglasses 100, but this is not limited thereto, and the glasses may be, for example, prescription glasses, fashion glasses, goggles that protect the eyes from wind, rain, dust, chemicals, etc.

In the sunglasses 100 (eyeglasses) configured as described above, the lenses 30 of the sunglasses 100 are configured to have a curved optical sheet 10 in which the optical sheet of the present invention has a curved shape, and are manufactured, for example, through a manufacturing method for the lenses 30 as shown below.

<Lens manufacturing method>
2 is a schematic diagram for explaining a method for manufacturing a lens having a curved optical sheet obtained by curvedly forming the optical sheet of the present invention. For convenience of explanation, the upper side of FIG. 2 is referred to as "upper" and the lower side is referred to as "lower".

The steps of the manufacturing method for the lens 30 having the curved optical sheet 10 in which the optical sheet 15 of the present invention has a curved shape are described below in detail.

[1] First, an optical sheet 15 (optical sheet of the present invention) having a flat overall shape is prepared, and then protective films 50 (masking tape) are attached to both sides of this optical sheet 15 to obtain a multilayer laminate 150 in which protective films 50 are attached to both sides of the optical sheet 15 (see FIG. 2(a)).

[2] Next, as shown in FIG. 2(b), the prepared multilayer laminate 150, i.e., the optical sheet 15 with the protective film 50 attached to both sides thereof, is punched out in its thickness direction to give the multilayer laminate 150 a circular shape in plan view.

[3] Next, as shown in FIG. 2(c), the circular multilayer laminate 150 is subjected to a thermal bending process under heating to form the multilayer laminate 150 into a curved multilayer laminate 200 having a curved shape in which the first substrate 111 side (one side) is a curved convex surface and the second substrate 112 side (the other side) is a curved convex surface. This allows the flat optical sheet 15 to be formed into a curved optical sheet 10 with protective films 50 attached to both sides.

This heat bending is usually carried out by press forming or vacuum forming.
In this embodiment, the heating temperature (molding temperature) of the multilayer laminate 150 (optical sheet 15) at this time is set to preferably 150° C. or more and 320° C. or less, more preferably 170° C. or more and 300° C. or less, taking into consideration the melting or softening temperature of the functional substrate 11, since the optical sheet 15 comprises a functional substrate 11 and coating layers 12, 13 provided as outermost layers on both sides of the functional substrate 11. By setting the heating temperature within this range, it is possible to prevent the optical sheet 15 from being altered or deteriorated, bring the optical sheet 15 into a softened or molten state, and reliably heat-bend the optical sheet 15 to form the curved optical sheet 10 having a curved shape.

In addition, in the present invention, during this thermal bending process, the optical sheet 15 satisfies the following requirement B. Therefore, when this optical sheet 15 is made into a curved optical sheet 10 by thermal bending in this step [3], it can be said that the occurrence of cracks in the coating layers 12 and 13 of the curved optical sheet 10 is appropriately suppressed or prevented, but a detailed explanation of this will be given later.

Requirement B: After the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes and molded into a curved shape with a radius of curvature of 120 mmR, it is cooled to 25°C and no cracks are observed in the coating layers 12 and 13.

In the present invention, prior to this step [3], the coating layers 12 and 13 of the optical sheet 15 are composed of a semi-cured resin composition, and the resin composition is cured by heating during the thermal bending process in this step [3]. However, if the curing of the resin composition due to this heating has not progressed sufficiently, the curved optical sheet 10 may be subjected to a heat treatment after the thermal bending process. This ensures that the resin composition constituting the coating layers 12 and 13 in the curved optical sheet 10 is composed of a cured product.

[4] Next, the protective film 50 is peeled off from the curved optical sheet 10 that has been thermally bent. Thereafter, as shown in FIG. 2(d), a mold 40 having a curved concave surface with a curved shape is placed in contact with the curved convex surface of the curved optical sheet 10, and in this state, a resin layer 35 composed mainly of a resin material is injection molded on the curved concave surface of the curved optical sheet 10, for example, by using an insert injection molding method. That is, the constituent material of the resin layer 35 in a molten state is cooled and solidified in a state of contact with the curved concave surface of the curved optical sheet 10, and the resin layer 35 is molded in a state of direct contact with the curved concave surface of the curved optical sheet 10 without an adhesive layer or the like. In this way, a lens 30 including the curved optical sheet 10 that has been thermally bent and the resin layer 35 is manufactured.

When injection molding the resin layer 35, the heating temperature (molding temperature) of the constituent material of the resin layer 35 to bring it into a molten state is set appropriately depending on the type of constituent material of the resin layer 35, but if the constituent material of the resin layer 35 is the same type or the same as the constituent material of the first substrate 111 of the curved optical sheet 10 described below, it is preferably set to 180°C or higher and 320°C or lower, more preferably 230°C or higher and 300°C or lower. By setting the heating temperature within this range, the constituent material of the resin layer 35 in a molten state can be reliably supplied to the curved concave surface of the curved optical sheet 10.

Among the insert injection molding methods, the injection compression molding method is preferably used. In the injection compression molding method, the resin material for forming the resin layer 35 is injected into the mold 40 at low pressure, and then the mold 40 is closed at high pressure to apply a compressive force to the resin material. This is because the resin layer 35 as a molded body, and in turn the lens 30, is less likely to suffer from molding distortion or optical anisotropy due to the local orientation of the resin molecules during molding. In addition, by controlling the mold compression force that is uniformly applied to the resin material, the resin material can be cooled at a constant specific volume, and therefore a resin layer 35 with high dimensional accuracy can be obtained.

The curved optical sheet 10 included in the lens 30 manufactured by the lens manufacturing method described above uses an optical sheet 15 with a curved shape. This optical sheet 15 is composed of the optical sheet of the present invention. Therefore, the optical sheet 15 satisfies the following requirements A and C, based on the fact that the resin composition constituting the coating layers 12 and 13 included in the optical sheet 15 is composed of a cured product by the thermal bending in the above-mentioned step [3]. Therefore, in the lens 30, the coating layers 12 and 13 are located on the front side when the lens 30 is attached to the sunglasses 100, and at this time, the curved optical sheet 10 can be said to have excellent abrasion resistance while performing the function of the optical sheet 15 for a long period of time, but a detailed explanation of this will be given later.

Requirement A: The optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, cooled, and then irradiated with ultraviolet light for 1000 hours from the coating layer 12 side using a xenon weather meter in accordance with JIS K 7350-4, Table 3-A method, cycle No. 1. After that, the change in YI of the optical sheet 15 as specified by JIS K 7373 must be less than 1.0.

Requirement C: After the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, cooled, and then subjected to a wiper laboratory test in accordance with ECE43, the haze value of the optical sheet 15 must be less than 5.0.

In the manufacturing method of the lens 30 described above, the optical sheet of the present invention is applied to the optical sheet 15 used to obtain the curved optical sheet 10. Below, each embodiment of this optical sheet 15, that is, the optical sheet 15 (optical sheet of the present invention) that satisfies requirements A to C, will be described in detail.

First Embodiment
FIG. 3 is a vertical cross-sectional view showing a first embodiment of the optical sheet of the present invention.

For ease of explanation, the upper side of FIG. 3 will be referred to as "top" and the lower side as "bottom." Additionally, the x direction in FIG. 3 will be referred to as the "left-right direction" or "flow direction (MD)," the y direction will be referred to as the "front-back direction" or "vertical direction (TD)," and the z direction will be referred to as the "up-down direction." Additionally, the thickness direction of the optical sheet is exaggerated in FIG. 3, so the actual dimensions are significantly different.

As shown in FIG. 3, the optical sheet 15 (optical substrate) comprises a functional substrate 11 having functionality, and coating layers 12 and 13 provided as outermost layers on both sides of the functional substrate 11.

In this embodiment, the functional substrate 11 includes a first substrate 111 having optical transparency, a second substrate 112 having optical transparency provided on one side of the first substrate 111, and a polarizing film 113 provided between the first substrate 111 and the second substrate 112.

By setting the positional relationship of the layers in the optical sheet 15 as described above, the polarizing film 113 is located between the first substrate 111 and the second substrate 112 with the coating layer 12 and the coating layer 13 as the outermost layers, and is not exposed on the surface of the optical sheet 15. That is, the polarizing film 113 does not constitute the outermost layer exposed on the upper or lower surface of the optical sheet 15. Therefore, it is possible to reliably prevent the polarizing film 113 from being hit by sand, dust, rain, etc., or being worn by other members, etc., as in the case where the outermost layer is constituted. Therefore, it is possible to reliably prevent the polarizing film 113 from being damaged by this collision or wear. Therefore, the optical sheet 15 can be one in which the design and optical properties are maintained for a long period of time. In addition, since the optical sheet 15 has the coating layers 12 and 13 configured as described below as the outermost layers, it is possible to more reliably prevent the polarizing film 113 from being damaged due to collision or wear.

In addition, in the optical sheet 15, in this embodiment, the functional substrate 11 is provided with a polarizing film 113 that has the function of extracting linearly polarized light having a polarization plane in a predetermined direction from the incident light (unpolarized natural light). Therefore, the light passing through the optical sheet 15 can be polarized. That is, in this embodiment, the functional substrate 11 exhibits polarization as an optical characteristic.

The functional substrate 11 and coating layers 12 and 13 that make up this optical sheet 15 are described below.

First, the functional substrate 11 includes a first substrate 111, a second substrate 112, and a polarizing film 113.

The first substrate 111 supports the polarizing film 113 (laminate), and by disposing the polarizing film 113 between the first substrate 111 and the second substrate 112, it functions as a protective layer that protects the polarizing film 113.

This first substrate 111 is not particularly limited as long as it is made primarily of a transparent resin material, but it is preferable that it contains a transparent resin (base resin) with thermoplastic properties as its main material.

In this specification, the term "main material" refers to a material that is contained in an amount of 50% by weight or more of the constituent materials that make up the layer (substrate) that contains this material.

The transparent resin is not particularly limited, but examples thereof include transparent resins such as acrylic resins, polystyrene resins, polyethylene resins, polypropylene resins, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate resins, polyamide resins, cycloolefin resins, vinyl chloride resins, and polyacetal resins, and one or more of these resins may be used in combination. Among these, polycarbonate resins or polyamide resins are preferable. Polycarbonate resins are rich in mechanical strength such as transparency (translucency) and rigidity, and also have high heat resistance, so that the use of polycarbonate resin as the transparent resin can improve the transparency of the first substrate 111 and the impact resistance and heat resistance of the first substrate 111. In addition, polyamide resins can improve chemical resistance, stress resistance, and the like in addition to transparency and impact resistance.

A variety of resins can be used as the polycarbonate resin, but aromatic polycarbonate resin is preferable. Aromatic polycarbonate resin has aromatic rings in its main chain, which allows the first substrate 111 to have superior strength.

This aromatic polycarbonate resin is synthesized, for example, by an interfacial polycondensation reaction between bisphenol and phosgene, or an ester exchange reaction between bisphenol and diphenyl carbonate.

Examples of bisphenols include bisphenol A and bisphenol (modified bisphenol) which is the source of the repeating units of polycarbonate shown in the following formula (1A).

(In formula (1A), X is an alkyl group, an aromatic group, or a cyclic aliphatic group having 1 to 18 carbon atoms, Ra and Rb are each independently an alkyl group having 1 to 12 carbon atoms, m and n are each an integer of 0 to 4, and p is the number of repeating units.)

Specific examples of bisphenols that are the source of the repeating units of the polycarbonate represented by formula (1A) include 4,4'-(pentane-2,2-diyl)diphenol, 4,4'-(pentane-3,3-diyl)diphenol, 4,4'-(butane-2,2-diyl)diphenol, 1,1'-(cyclohexanediyl)diphenol, 2-cyclohexyl-1,4-bis(4-hydroxyphenyl)benzene, 2,3-biscyclohexyl-1,4-bis(4-hydroxyphenyl)benzene, 1,1'-bis(4-hydroxy-3-methylphenyl)cyclohexane, and 2,2'-bis(4-hydroxy-3-methylphenyl)propane, and these can be used alone or in combination of two or more.

In particular, it is preferable that the polycarbonate resin is mainly composed of a bisphenol-type polycarbonate resin having a skeleton derived from bisphenol. By using such a bisphenol-type polycarbonate resin, the first substrate 111 exhibits even greater strength.

The polyamide resin is not particularly limited, and various types can be used, such as alicyclic polyamide and semi-aromatic polyamide. Alicyclic polyamide is a material with excellent impact resistance. Therefore, the optical sheet 15 can be made to exhibit excellent impact resistance. Furthermore, semi-aromatic polyamide is a material with a high elastic modulus. Therefore, the optical sheet 15 can be made to have excellent resistance to stress such as bending.

In this specification, semi-aromatic polyamide refers to a polyamide in which one of the dicarboxylic acid and diamine monomers constituting the polyamide is an aromatic compound and the other is an aliphatic compound, and can be specifically represented by the following formula (1B).

(In the formula (1B), one of ^R1 and ^R2 is a divalent aromatic substituent and the other is a divalent aliphatic substituent, and n is an integer of 2 or more.)

The polyamide may be a copolymer (random copolymer, block copolymer, etc.) containing two or more types of monomers of at least one of dicarboxylic acid and diamine.

The aromatic substituents of R ¹ and R ² in the above formula (1B) are preferably those represented by the following formula (2B).

(In formula (2B), l and m each independently represent an integer of 0 to 2.)

This allows the polarizing film 113 to be better protected and also makes the optical sheet 15 easier to process.

The aliphatic substituents of R ¹ and R ² in the above formula (1B) preferably have 4 to 18 carbon atoms, more preferably are hydrocarbon groups having 4 to 18 carbon atoms, and even more preferably are saturated hydrocarbon groups having 4 to 18 carbon atoms.
This can improve the workability of the optical sheet 15 .

Furthermore, it is preferable that the semi-aromatic polyamide contains an aromatic dicarboxylic acid and an aliphatic diamine as constituent monomers. This can better protect the polarizing film 113 and improve the processability of the optical sheet 15.

Alicyclic polyamides have an alicyclic chemical structure in their molecules, and may have an alicyclic chemical structure in their main chain structure or in their side chain structure.

Examples of such alicyclic polyamides include compounds in which at least one of the dicarboxylic acid and diamine monomers constituting the polyamide has an alicyclic chemical structure, and specifically, for example, can be represented by the following formula (3B).

(In formula (3B), R ³ and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 4 or less carbon atoms, o represents an integer of 2 or more and 14 or less, p represents an integer of 0 or more and 6 or less, and n represents an integer of 2 or more.)

The glass transition temperature (Tg) of the resin material contained as the main material in the first substrate 111 is preferably 100°C or higher and 190°C or lower, and more preferably 105°C or higher and 155°C or lower. This makes it relatively easy to form the curved optical sheet 10 by thermal bending the optical sheet 15 in the step [3]. In addition, the optical sheet 15 can have excellent durability and reliability.

Furthermore, as long as the first substrate 111 is optically transparent, its color may be any color, such as colorless, red, blue, yellow, etc.

These colors can be selected by incorporating a dye or pigment into the first substrate 111. Examples of such dyes include acid dyes, direct dyes, reactive dyes, and basic dyes, and one or more of these can be used in combination.

Specific examples of dyes include, for example, C.I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. Acid Red 52, 80, 82, 249, 254, 289, C.I. Acid Blue 9, 45, 249, C.I. Acid Black 1, 2, 24, 94, C.I. Food Black 1, 2, C.I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, C.I. Direct Red 1, 4, 9, 80, 81, 225, 227, C.I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. Direct Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. Reactive Red 14, 32, 55, 79, 249, C.I. Reactive Black 3, 4, 35, etc.

In addition to the transparent resin, dye, or pigment described above, the first substrate 111 may further contain various additives such as antioxidants, fillers, plasticizers, light stabilizers, ultraviolet absorbers, heat absorbers, and flame retardants, as necessary.

In this case, the content of the resin material in the first substrate 111 is not particularly limited, but is preferably 75% by weight or more, and more preferably 85% by weight or more. By keeping the content of the resin material within the above range, the optical sheet 15 can exhibit excellent strength.

In addition, the refractive index of the first substrate 111 at a wavelength of 589 nm is preferably 1.3 or more and 1.8 or less, and more preferably 1.4 or more and 1.65 or less. By setting the refractive index of the first substrate 111 within the above numerical range, it is possible to accurately suppress or prevent the function of the polarizing film 113 from being impaired.

The average thickness of the first substrate 111 is preferably set to 0.1 mm or more and 1.5 mm or less, and more preferably 0.2 mm or more and 0.8 mm or less. By setting the average thickness of the first substrate 111 within this range, it is possible to reduce the thickness of the optical sheet 15 while accurately suppressing or preventing the occurrence of bending in the optical sheet 15.

The second substrate 112 supports the polarizing film 113 (laminate), and by disposing the polarizing film 113 between the second substrate 112 and the first substrate 111 described above, it also functions as a protective layer that protects the polarizing film 113.

This second substrate 112, like the first substrate 111, is not particularly limited as long as it is made primarily of a transparent resin material, but it is preferable that it contains a transparent resin (base resin) with thermoplastic properties as its main material.

This transparent resin can be the same as that mentioned above for the first substrate 111, but it is preferable that the main material is a polycarbonate-based resin or a polyamide-based resin.

The polycarbonate-based resin or polyamide-based resin is not particularly limited, but may be, for example, the same as those listed for the first substrate 111 described above.

The glass transition temperature (Tg) of the resin material contained as the main material in the second substrate 112 is preferably 100°C or higher and 190°C or lower, and more preferably 105°C or higher and 155°C or lower. This makes it relatively easy to form the curved optical sheet 10 by thermal bending the optical sheet 15 in the step [3]. In addition, the optical sheet 15 can have excellent durability and reliability.

The second substrate 112 may contain other components in addition to the resin material contained as the main material. Such components are not particularly limited, but may include, for example, a resin material other than the main material, a colorant such as a dye or pigment, a filler, an alignment aid, a stabilizer (such as a heat stabilizer, an ultraviolet absorber, and an antioxidant), a plasticizer, a flame retardant, an antistatic agent, and a viscosity adjuster.

In this case, the amount of the resin material contained in the second substrate 112 is not particularly limited, but is preferably 75% by weight or more, and more preferably 85% by weight or more, based on 100% by weight of the second substrate 112. By keeping the amount of the resin material contained within the above range, the optical sheet 15 can exhibit excellent strength.

In addition, the refractive index of the second substrate 112 at a wavelength of 589 nm is preferably 1.3 to 1.8, and more preferably 1.4 to 1.65. By setting the refractive index of the second substrate 112 within the above numerical range, it is possible to accurately suppress or prevent the function of the polarizing film 113 from being impaired.

The average thickness of the second substrate 112 is preferably set to 0.1 mm or more and 1.5 mm or less, and more preferably 0.2 mm or more and 0.8 mm or less. By setting the average thickness of the second substrate 112 within this range, it is possible to reduce the thickness of the optical sheet 15 while accurately suppressing or preventing the occurrence of bending in the optical sheet 15.

The polarizing film 113 constitutes a polarizer that has the function of extracting linearly polarized light with a polarization plane in a specific direction from the incident light (unpolarized natural light). This imparts polarization to the functional substrate 11, and the light passing through the optical sheet 15 becomes polarized.

The degree of polarization of the polarizing film 113 is not particularly limited, but is preferably, for example, 50% to 100%, and more preferably, 80% to 100%. The visible light transmittance of the polarizing film 113 is not particularly limited, but is preferably, for example, 10% to 80%, and more preferably, 20% to 50%.

The material for the polarizing film 113 is not particularly limited as long as it has the above-mentioned functions, but examples include polymer films made of polyvinyl alcohol (PVA), partially formalized polyvinyl alcohol, polyethylene vinyl alcohol, polyvinyl butyral, polycarbonate, ethylene-vinyl acetate copolymer partially saponified product, etc., which are dyed and uniaxially stretched with dichroic substances such as iodine or dichroic dyes, and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride.

Among these, the polarizing film 113 is preferably a polymer film whose main material is polyvinyl alcohol (PVA) that is dyed with iodine or a dichroic dye and then uniaxially stretched. Polyvinyl alcohol (PVA) is a material that has excellent transparency, heat resistance, affinity with the dyeing agent iodine or a dichroic dye, and orientation when stretched. Therefore, the polarizing film 113 whose main material is PVA has excellent heat resistance and polarizing ability.

Examples of the dichroic dyes include Chloratin Fast Red, Congo Red, Brilliant Blue 6B, Benzopurpurine, Chlorazol Black BH, Direct Blue 2B, Diamine Green, Chrysophenone, Sirius Yellow, Direct Fast Red, and Acid Black.

The refractive index of this polarizing film 113 at a wavelength of 589 nm is not particularly limited, but is preferably, for example, 1.45 or more and 1.55 or less, and more preferably 1.47 or more and 1.53 or less.

The thickness of the polarizing film 113 is not particularly limited, but is preferably, for example, 5 μm or more and 60 μm or less, and more preferably 10 μm or more and 40 μm or less.

The first adhesive layer 114 is provided between the first substrate 111 (one of the substrates) and the polarizing film 113, and has the function of bonding the first substrate 111 and the polarizing film 113 together. This allows excellent adhesion to be imparted between the first substrate 111 and the polarizing film 113 via the first adhesive layer 114.

The second adhesive layer 116 is provided between the second substrate 112 (the other substrate) and the polarizing film 113, and has the function of bonding the second substrate 112 and the polarizing film 113 together. This allows excellent adhesion between the second substrate 112 and the polarizing film 113 via the second adhesive layer 116.

The first adhesive layer 114 and the second adhesive layer 116 are each composed of an adhesive having optical transparency. The adhesive is not particularly limited, but examples thereof include silicone-based, silylated urethane resin-based, urethane resin-based, epoxy-based, polyolefin-based, chlorinated polyolefin-based, acrylic-based, cyanoacrylate-based, rubber-based, polyester-based, polyimide-based, and phenol-based adhesives.

Among these, it is preferable that the first adhesive layer 114 and the second adhesive layer 116 are made of a urethane resin-based adhesive. This can provide the heat resistance required for the thermal bending process when the optical sheet 15 is subjected to thermal bending process to form the curved optical sheet 10 having a curved shape. It is also preferable that they are made of a silicone-based adhesive. This can adequately suppress or prevent gas generation when the adhesive hardens. Therefore, it is possible to adequately suppress or prevent air bubbles from remaining in the adhesive layers 114 and 116.

The first adhesive layer 114 and the second adhesive layer 116 may be the same or of the same type, or may be different from the same or of the same type.

Furthermore, the refractive index at a wavelength of 589 nm of the first adhesive layer 114 and the second adhesive layer 116 is preferably independently 1.3 or more and 1.7 or less, and more preferably 1.4 or more and 1.65 or less.

The thickness of the first adhesive layer 114 and the second adhesive layer 116 is preferably, for example, 2 μm or more and 100 μm or less, and more preferably 5 μm or more and 35 μm or less. Such a first adhesive layer 114 and second adhesive layer 116 can reliably bond the first adhesive layer 114 and the second adhesive layer 116 to the polarizing film 113, respectively.

The first coating layer 12 (first covering layer) is provided to cover the first substrate 111 (one side of the functional substrate 11), constitutes the outermost layer of the optical sheet 15, and functions as a protective layer that protects the polarizing film 113 located as an intermediate layer of the functional substrate 11.

The second coating layer 13 (second covering layer) is provided to cover the second substrate 112 (the other surface of the functional substrate 11), constitutes the outermost layer of the optical sheet 15, and functions as a protective layer that protects the polarizing film 113 located as an intermediate layer of the functional substrate 11.

By configuring the optical sheet 15 to include the first coating layer 12 and the second coating layer 13 that cover the first substrate 111 and the second substrate 112, respectively, it is possible to more reliably prevent the first substrate 111 and the second substrate 112, and in turn the polarizing film 113, from being damaged.

These coat layers 12 and 13 (coating layers) are so-called hard coat layers formed using a resin composition that exhibits curability. In the present invention, the resin composition used contains a soft component having a radical polymerizable group and a hard component having a cationic polymerizable group as the curable resin.

Here, the reaction rate of a soft component having a radical polymerizable group (hereinafter sometimes simply referred to as a "radical polymerization component" or "soft component") and a hard component having a cationic polymerizable group (hereinafter sometimes simply referred to as a "cationic polymerization component" or "hard component") is faster for the radical polymerization component than for the cationic polymerization component, based on the properties of these polymerizable groups. In the present invention, both the soft component and the hard component are curable resins that exhibit curability, and when a cured product consisting of only the soft component and a cured product consisting of only the hard component are formed and compared, the one that forms a soft cured product is called the soft component, and the one that forms a hard cured product is called the hard component.

Therefore, in a resin composition containing both a radical polymerization initiator and a cationic polymerization initiator, when the curing of the radical polymerization component and the cationic polymerization component is started almost simultaneously and then a semi-cured product of the resin composition is obtained, the degree of curing (reaction rate) of the radical polymerization component in the semi-cured product of the resin composition is higher than the degree of curing of the cationic polymerization component. In this case, in the present invention, the radical polymerization component constitutes the soft component and the cationic polymerization component constitutes the hard component. That is, the degree of curing (reaction rate) of the soft component and the hard component in the semi-cured product is higher than that of the hard component. Therefore, the semi-cured product of the resin composition can be made soft relatively easily. Therefore, the coating layers 12 and 13 can be made to satisfy the following requirement B relatively easily. Therefore, when the optical sheet 15 having these coating layers 12 and 13 is made into a curved optical sheet 10 by thermal bending in the above-mentioned step [3], the occurrence of cracks in the coating layers 12 and 13 of the curved optical sheet 10 can be appropriately suppressed or prevented.

The scratch hardness of the coating layers 12 and 13 of the optical sheet 15 before the thermal bending process, measured by the pencil method described in JIS K 5400, is preferably 3B or more and B or less. The semi-cured resin composition can be said to be soft.

Requirement B: After the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes and molded into a curved shape with a radius of curvature of 120 mmR, it is cooled to 25°C and no cracks are observed in the coating layers 12 and 13.

In the semi-cured resin composition of optical sheet 15 (the optical sheet of the present invention), as described above, the degree of cure (reaction rate) of the soft component (radical polymerization component) is higher than that of the hard component (cationic polymerization component). Therefore, by appropriately setting the degree of cure (reaction rate) of the cationic polymerization component that remains predominantly in the resin composition, the requirement B can be satisfied relatively easily.

Next, for the optical sheet 15 having the coating layers 12 and 13 composed of the semi-cured product of the resin composition that satisfies the requirement B, the curing of the semi-cured product of the resin composition is promoted by heating the optical sheet 15 by thermal bending in the step [3]. That is, the cationic polymerization component that remains predominantly in the semi-cured product of the resin composition is cured. As a result, in the curved optical sheet 10 in which the optical sheet 15 is curved, the coating layers 12 and 13 can be composed of the cured product of the resin composition. In curing the cationic polymerization component, since the cationic polymerization component is composed of a hard component as described above, the cured product of the resin composition, i.e., the coating layers 12 and 13 of the curved optical sheet 10 can be made to have excellent hardness, and as a result, the coating layers 12 and 13 can be made to satisfy the following requirements A and C. Therefore, in the lens 30 equipped with the curved optical sheet 10, the coating layers 12 and 13 are located on the front side when the lens 30 is attached to the sunglasses 100, and at this time, the curved optical sheet 10 exhibits excellent abrasion resistance while functioning as an optical sheet 15 for a long period of time.

The scratch hardness of the coating layers 12 and 13 of the curved optical sheet 10 that has been subjected to thermal bending processing, measured by the pencil method described in JIS K 5400, is preferably HB or more and 4H or less. The semi-cured product of the resin composition can be said to be soft.

Requirement A: The optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, cooled, and then irradiated with ultraviolet light for 1000 hours from the coating layer 12 side using a xenon weather meter in accordance with JIS K 7350-4, Table 3-A method, cycle No. 1. After that, the change in YI of the optical sheet 15 as specified by JIS K 7373 must be less than 1.0.

Requirement C: After the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, cooled, and then subjected to a wiper laboratory test in accordance with ECE43, the haze value of the optical sheet 15 must be less than 5.0.

Hereinafter, we will explain a resin composition that contains a soft component having a radical polymerizable group and a hard component having a cationic polymerizable group, and that satisfies the above requirements A to C.

(Soft component having a radically polymerizable group)
The soft component having a radically polymerizable group already forms a network of the radically polymerizable component in the semi-cured product, because the radically polymerizable component is more reactive than the cationic polymerization component. Furthermore, since the radically polymerizable component constitutes the soft component, this semi-cured product is considered to be soft, and the coating layers 12 and 13 are included in the resin composition as those that satisfy the above-mentioned requirement B.

As described above, in the semi-cured resin composition, the soft component (radical polymerization component) has a higher degree of cure (reaction rate) than the hard component (cationic polymerization component). Therefore, the radical polymerization component forms a network by the radical polymerization component more predominantly than the cationic polymerization component, resulting in a degree of polymerization where the curing (reaction) is progressing. That is, in the step [1], the optical sheet 15 is provided with coating layers 12 and 13 made of a semi-cured resin composition containing a radical polymerization component that cures more predominantly than the cationic polymerization component.

The soft component having this radical polymerizable group is not particularly limited as long as it can make the semi-cured product soft and can satisfy the above-mentioned requirement B for the coating layers 12 and 13. For example, it can be one in which a radical polymerizable group is linked as a side chain to a main chain that exhibits flexibility.

In addition, examples of main chains that exhibit flexibility include straight chains with urethane bonds, straight chains with ester bonds, and straight chains with epoxy bonds, among which straight chains with urethane bonds are preferred. This ensures that the semi-cured product of the resin composition is flexible.

Examples of side chains, i.e., radically polymerizable groups, include (meth)acryloyl groups and vinyl groups, among which the (meth)acryloyl group is preferred. The (meth)acryloyl group is preferably selected as the radically polymerizable group from the viewpoints of excellent radical polymerizability and ease of availability of compounds having a (meth)acryloyl group as a side chain.

In view of the above, it is preferable that the soft component having a radical polymerizable group is one in which a (meth)acryloyl group is linked as a side chain to a straight chain having a urethane bond (-OCONH-), i.e., a urethane (meth)acrylate. This ensures that the semi-cured product is soft, and that the coating layers 12, 13 satisfy the above-mentioned requirement B. The urethane (meth)acrylate may be either a monomer or an oligomer.

This urethane (meth)acrylate can be obtained, for example, as a reaction product between an isocyanate compound obtained by reacting a polyol with a diisocyanate, and a (meth)acrylate monomer having a hydroxyl group.

Examples of polyols include polyether polyols, polyester polyols, and polycarbonate diols.

Polyester polyols can be obtained, for example, by polycondensation of a diol with a dicarboxylic acid or dicarboxylic acid chloride, or by esterifying a diol or dicarboxylic acid and then carrying out an ester exchange reaction. Examples of dicarboxylic acids include adipic acid, succinic acid, glutaric acid, pimelic acid, sebacic acid, azelaic acid, maleic acid, terephthalic acid, isophthalic acid, and phthalic acid, and examples of diols include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, tripropylene glycol, and tetrapropylene glycol.

Furthermore, examples of polycarbonate diols include reaction products of diols and carbonate esters. Examples of diols that can be used include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 2-ethyl-1,3-hexanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanediol, polyoxyethylene glycol, etc., and these can be used alone or in combination of two or more.

Examples of (meth)acrylate monomers having a hydroxyl group include trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, and polyethylene glycol monoacrylate.

Furthermore, it is preferable that the urethane (meth)acrylate in which a (meth)acryloyl group is linked as a side chain to a straight chain having a urethane bond (-OCONH-) has a (meth)acryloyl group as a side chain, i.e., one or two radical polymerizable groups linked. This makes it possible to make the network in the semi-cured material denser and more reliably softer, so that the coating layers 12 and 13 can more reliably satisfy the requirement B.

The content of the radical polymerization component in the resin composition is not particularly limited, but is preferably 7.0 parts by weight or more and 55.0 parts by weight or less, and more preferably 10.0 parts by weight or more and 35.0 parts by weight or less, per 100.0 parts by weight of the resin composition. If the content of the radical polymerization component in the resin composition is less than the lower limit, depending on the type of radical polymerization component, the semi-cured product of the resin composition may not be sufficiently soft, and the requirement B may not be satisfied. If the content of the radical polymerization component in the resin composition exceeds the upper limit, the content of the cationic polymerization component in the resin composition may be relatively reduced, and the cured product of the resin composition may not be sufficiently hard, and the requirements A and C may not be satisfied.

(Hard Component Having a Cationic Polymerizable Group)
The cationic polymerization component has a slower reactivity than the radical polymerization component, and therefore the formation of a network by the cationic polymerization component in the semi-cured product is not completed in the optical sheet 15 prepared in the step [1]. The formation of the network by the cationic polymerization component is completed by heating the optical sheet 15 by thermal bending in the step [3], and the resin composition becomes a cured product in the curved optical sheet 10 that has been thermally bent. At this time, since the cationic polymerization component constitutes the hard component, the cured product is considered to be hard, and the coating layers 12 and 13 in the curved optical sheet 10 obtained by thermal bending in the step [3] are considered to satisfy the requirements A and B, and the hard component having a cationic polymerization group is included in the resin composition.

In the semi-cured resin composition, a portion of the cationic polymerization component remains without forming a network of the cationic polymerization component, resulting in an incomplete polymerization degree of curing (reaction). That is, in the step [1], the optical sheet 15 is prepared having coating layers 12 and 13 made of a semi-cured resin composition containing a predominantly uncured cationic polymerization component.

The hard component having this cationic polymerizable group is not particularly limited as long as it can harden the cured product and can form the coating layers 12 and 13, satisfying the above-mentioned requirements A and C. For example, it can be one in which a cationic polymerizable group is linked as a side chain to a main chain that exhibits hardness.

In order to make the cured product particularly hard, the main chain that exhibits hardness is preferably a compound consisting of repeating units having siloxane bonds with high bonding strength, that is, a polymer (prepolymer) having repeating units of siloxane bonds (-Si-O-Si-).

Examples of the side chain, i.e., the cationic polymerizable group, include cyclic ether groups such as epoxy groups and oxetanyl groups, and vinyl ether groups, among which cyclic ether groups are preferred. Cyclic ether groups are preferably selected as cationic polymerizable groups from the viewpoints of, for example, the excellent cationic polymerizability and the ease of obtaining compounds having cyclic ether groups as side chains.

For these reasons, the hard component having a cationic polymerizable group is preferably a siloxane compound in the form of a polymer (prepolymer) having repeating siloxane bonds (-Si-O-Si-) to which a cyclic ether group is linked as a side chain, i.e., a silicon-modified cyclic ether compound. This ensures that the cured product is hard, and that the coating layers 12, 13 reliably satisfy the above requirements A and C.

This silicon-modified cyclic ether compound can be obtained, for example, by introducing a cyclic ether group as a side chain into a main chain consisting of a polymer (prepolymer) having repeating siloxane bonds (-Si-O-Si-).

Specific examples of repeating units having siloxane bonds include those having repeating units having siloxane bonds of at least one of the following formulas (3) and (4).

(In formula (3), _X1 represents a hydrocarbon group or a hydroxyl group.)

(In formula (4), _X2 represents a hydrocarbon group or a hydroxyl group, and _X3 represents a divalent group in which a hydrogen atom has been removed from a hydrocarbon group or a hydroxyl group.)

Specific examples of repeating units having siloxane bonds include those having polyorganosiloxane and those having silsesquioxane. The structure of the silsesquioxane may be any structure, such as a random structure, a cage structure, or a ladder structure.

Examples of the hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, and isopropyl groups; cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups; aryl groups such as phenyl, naphthyl, and 2-methylphenyl groups; aralkyl groups such as benzyl, diphenylmethyl, and naphthylmethyl groups; and biphenyl groups.

In addition, it is preferable that an unsaturated double bond is introduced into the end or side chain of the repeating unit in which a structural unit having a siloxane bond is repeated. As a result, when the resin composition contains a urethane (meth)acrylate as a radical polymerization component, it is possible to bond with the (meth)acryloyl group of this urethane (meth)acrylate to form a network of the silicon-modified cyclic ether compound and the urethane (meth)acrylate. Therefore, the cured product of the resin composition constituting the coating layers 12 and 13 can be made harder.

The silicon-modified cyclic ether compound having the above-mentioned structure is not particularly limited, but examples thereof include compounds represented by the following formulas (5) and (6).

(In formula (5), Me represents a methyl group, m and n each represent an integer of 1 or more, and R1 represents an organic group having a cationically polymerizable group.)

(In formula (6), Me represents a methyl group, m and n each represent an integer of 1 or more, and R1, R2, R3, R4, and R5 each independently represent an organic group having a cationically polymerizable group, a hydrocarbon group, an organic group, or a hydrogen atom, at least one of which represents an organic group having a cationically polymerizable group.)

The silicon-modified cyclic ether compound has a main chain made of a polymer (prepolymer) having repeating siloxane bonds (-Si-O-Si-) and has cyclic ether groups introduced as side chains. It is preferable that the number of cyclic ether groups, i.e., cationic polymerizable groups, as side chains is two or more. This makes it possible to make the network in the cured product denser and more reliably hard, so that the coating layers 12 and 13 in the curved optical sheet 10 obtained by heat bending in the step [3] can satisfy the requirements A and B.

The content of the cationic polymerization component in the resin composition is not particularly limited, but is preferably 35.0 parts by weight or more and 85.0 parts by weight or less, and more preferably 50.0 parts by weight or more and 70.0 parts by weight or less, per 100.0 parts by weight of the resin composition. If the content of the cationic polymerization component in the resin composition is less than the lower limit, depending on the type of cationic polymerization component, the cured product of the resin composition may not be sufficiently hard, and the requirements A and C may not be satisfied. If the content of the cationic polymerization component in the resin composition exceeds the upper limit, the content of the radical polymerization component in the resin composition is relatively reduced, and the semi-cured product of the resin composition may not be sufficiently soft, and the requirement B may not be satisfied.

(Monomer Component Having a Radically Polymerizable Group)
The resin composition preferably further contains a monomer component having a radical polymerizable group as an adhesive.

By including a monomer component having a radical polymerizable group in the resin composition, the monomer component having a radical polymerizable group is also incorporated into the network of the radical polymerization component. Furthermore, since the monomer component having a radical polymerizable group is composed of a monomer and has a small molecular weight, this monomer component is incorporated into the network of the radical polymerization component while being embedded in the recesses formed on the surfaces of the substrates 111 and 112. Therefore, an anchor effect is obtained between the network of the radical polymerization component and the recesses of the substrates 111 and 112, and the coating layers 12 and 13 can have excellent adhesion to the substrates 111 and 112.

Examples of monomer components having this radical polymerizable group include monomer components having a (meth)acryloyl group, a vinyl group, etc., but when the soft component having a radical polymerizable group is a urethane (meth)acrylate, it is preferable that it is a (meth)acrylate monomer. This ensures that the effect obtained by including a monomer component having a radical polymerizable group in the resin composition can be exerted.

The (meth)acrylate monomer is not particularly limited, but examples thereof include pentaerythritol tetraacrylate, ditrimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol triacrylate, ethoxylated pentaerythritol tetraacrylate, polyethylene glycol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated hydrogenated bisphenol A diacrylate, ethoxylated cyclohexane dimethanol diacrylate, tricyclodecane dimethanol diacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, isobornyl acrylate, and the like, and one or more of these can be used in combination. Among these, those that do not contain aromatic groups are preferable from the viewpoint of improving the weather resistance of the optical sheet 15.

The content of the monomer component having a radical polymerizable group in the resin composition is not particularly limited, but is preferably 1.0 parts by weight or more and 10.0 parts by weight or less, and more preferably 3.0 parts by weight or more and 7.0 parts by weight or less, per 100.0 parts by weight of the resin composition.

(Monomer component having both a radically polymerizable group and a cationically polymerizable group)
Moreover, the resin composition preferably further contains a monomer component having both a radical polymerizable group and a cationically polymerizable group as an adhesive.

By including a monomer component having both a radical polymerizable group and a cationic polymerizable group in the resin composition, the monomer component having both a radical polymerizable group and a cationic polymerizable group is also incorporated into the network of the radical polymerizable component and the network of the cationic polymerizable component, respectively. Furthermore, since the monomer component having both a radical polymerizable group and a cationic polymerizable group is composed of a monomer and has a small molecular weight, this monomer component is incorporated into the network of the radical polymerizable component and the network of the cationic polymerizable component in a state where it is inserted into the recesses formed on the surfaces of the substrates 111 and 112. Therefore, an anchor effect is obtained between the network of the radical polymerizable component and the network of the cationic polymerizable component and the recesses of the substrates 111 and 112, so that the coating layers 12 and 13 can have excellent adhesion to the substrates 111 and 112.

Examples of monomer components having both radical polymerizable groups and cationic polymerizable groups include monomer components having a radical polymerizable group such as a (meth)acryloyl group, a vinyl group, etc., and a cationic polymerizable group such as a cyclic ether group, a vinyl ether group, etc., but when the soft component having a radical polymerizable group is a urethane (meth)acrylate and the hard component having a cationic polymerizable group is a silicon-modified cyclic ether compound, it is preferable to use (3-ethyloxetan-3-yl)methyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, and 3,4-epoxycyclohexylmethyl (meth)acrylate. This ensures that the effect obtained by including a monomer component having both a radical polymerizable group and a cationic polymerizable group in the resin composition can be exerted.

The content of the monomer component having both a radically polymerizable group and a cationic polymerizable group in the resin composition is not particularly limited, but is preferably 0.1 parts by weight or more and 3.0 parts by weight or less, and more preferably 0.3 parts by weight or more and 1.0 parts by weight or less, per 100.0 parts by weight of the resin composition.

(Isocyanate Compounds)
In addition, when the hard component having a cationically polymerizable group is a silicon-modified cyclic ether compound, the resin composition preferably further contains a di- or higher functional isocyanate compound.

In this way, in the resin composition, the isocyanate compound functions as a cross-linking agent that bonds (cross-links) between the molecules of the silicon-modified cyclic ether compound. In other words, by including an isocyanate compound as a cross-linking agent, the hydroxyl group of the main chain of the silicon-modified cyclic ether compound reacts with the isocyanate group (functional group) of the isocyanate compound to form a cross-linked structure composed of urethane bonds, and as a result, a network can be formed between the silicon-modified cyclic ether compound and the isocyanate compound. Therefore, the cured product of the resin composition that constitutes the coating layers 12 and 13 can be made harder.

The isocyanate compound may be bifunctional or more, but is preferably trifunctional or tetrafunctional. This ensures that the compound can function as a crosslinking agent.

The amount of the isocyanate compound in the resin composition is not particularly limited, but is preferably 1.0 parts by weight or more and 10.0 parts by weight or less, and more preferably 3.0 parts by weight or more and 8.0 parts by weight or less, per 100.0 parts by weight of the resin composition.

(Radical Polymerization Initiator)
The resin composition also contains a radical polymerization initiator (radical generator) that generates radicals in order to start a polymerization reaction that forms a network using the radical polymerization components.

This ensures that the radicals generated by the radical polymerization initiator in the resin composition can reliably initiate a polymerization reaction that forms a network with the radical polymerization components. Therefore, in step [1], it is easy to prepare an optical sheet 15 that includes coating layers 12 and 13 made of a semi-cured resin composition that contains a radical polymerization component that is cured more preferentially than a cationic polymerization component.

The radical polymerization initiator is preferably a photoradical polymerization initiator that generates radicals by irradiating the resin composition with energy rays such as ultraviolet rays.

The photoradical polymerization initiator is not particularly limited, but examples thereof include acetophenone-based photoradical polymerization initiators, benzoin-based photoradical polymerization initiators, benzophenone-based photoradical polymerization initiators, thioxanthone-based photoradical polymerization initiators, ketone-based photoradical polymerization initiators, imidazole-based photoradical polymerization initiators, carbazole-based photoradical polymerization initiators, oxime ester-based photoradical polymerization initiators, titanocene-based photoradical polymerization initiators, acylphosphine oxide-based photoradical polymerization initiators, trichloromethyltriazine-based photoradical polymerization initiators, and the like. One or a combination of two or more of these can be used.

The content of the photoradical polymerization initiator in the resin composition is not particularly limited, but is preferably 0.5 parts by weight or more and 5.0 parts by weight or less, and more preferably 1.0 parts by weight or more and 4.0 parts by weight or less, per 100.0 parts by weight of the resin composition.

(Cationic Polymerization Initiator)
The resin composition also contains a cationic polymerization initiator (acid generator) that generates an acid in order to initiate a polymerization reaction that forms a network with the cationic polymerization components.

This allows the acid generated by the cationic polymerization initiator in the resin composition to reliably initiate a polymerization reaction that forms a network of cationic polymerization components. Therefore, in the step [1], it is easy to prepare an optical sheet 15 that includes coating layers 12 and 13 made of a semi-cured resin composition containing a part of the cationic polymerization component that has been cured. The generated acid remains in the semi-cured resin composition without disappearing. Therefore, by heating the optical sheet 15 by thermal bending in the step [3], it is possible to activate the polymerization reaction that forms a network of the cationic polymerization components based on this acid. This completes the formation of a network of the cationic polymerization components, and as a result, the resin composition can be reliably composed of a cured product.

The cationic polymerization initiator is preferably a photo-cationic polymerization initiator that generates an acid by irradiating the resin composition with energy rays such as ultraviolet rays.

The photocationic polymerization initiator is not particularly limited, but examples thereof include onium salt-based photocationic polymerization initiators such as sulfonium salt-based and iodonium salt-based initiators, and one or more of these can be used in combination.

The content of the photocationic polymerization initiator in the resin composition is not particularly limited, but is preferably 0.5 parts by weight or more and 5.0 parts by weight or less, and more preferably 1.0 parts by weight or more and 4.0 parts by weight or less, per 100.0 parts by weight of the resin composition.

(Ultraviolet absorber)
The resin composition preferably contains an ultraviolet absorbing agent.

By including an ultraviolet absorber in the resin composition, ultraviolet rays can be absorbed in the coating layers 12 and 13. This makes it possible to suppress the alteration and deterioration of other constituent materials contained in the resin composition. This improves the ultraviolet radiation resistance of the coating layers 12 and 13, and ensures that the requirement A is satisfied. In addition, the arrival of ultraviolet rays at the functional substrate 11 can be suppressed or prevented, so that alteration and deterioration of the functional substrate 11 can be suppressed.

The ultraviolet absorber is not particularly limited, but examples thereof include triazine-based, benzophenone-based, benzotriazole-based, and cyanoacrylate-based ones, and one or two of these can be used in combination. Among these, benzotriazole-based ultraviolet absorbers are particularly preferred, and among benzotriazole-based ultraviolet absorbers, hydroxyphenylbenzotriazole-based ultraviolet absorbers are more preferred. This allows the above-mentioned effect obtained by including an ultraviolet absorber in the coating layers 12 and 13 to be more pronounced. In addition, hydroxyphenylbenzotriazole-based ultraviolet absorbers can be obtained relatively easily and inexpensively as those having functional groups that are reactive with the radical polymerization component or cationic polymerization component described below.

Furthermore, it is preferable that the ultraviolet absorber has a functional group that is reactive with the radical polymerization component or cationic polymerization component. This allows the ultraviolet absorber to be incorporated into the network formed by the reaction of the radical polymerization component (e.g., urethane (meth)acrylate) or cationic polymerization component. Therefore, it is possible to appropriately suppress or prevent the ultraviolet absorber from leaking, i.e., bleeding out, from the coating layers 12, 13 composed of the cured product of the resin composition. Therefore, the requirement A can be more reliably satisfied over a long period of time.

In addition, when the radical polymerization component is a urethane (meth)acrylate, an ultraviolet absorber having a (meth)acryloyl group as a functional group reactive with the radical polymerization component can form a network by radical polymerization between the (meth)acryloyl groups of both the urethane (meth)acrylate and the urethane (meth)acrylate, and is preferably used as an ultraviolet absorber having a functional group reactive with the radical polymerization component. In addition, an ultraviolet absorber having a (meth)acryloyl group as a functional group can be obtained, for example, as a reaction product of a hydroxyphenylbenzotriazole-based ultraviolet absorber having two or more hydroxyl groups and a (meth)acrylate monomer. In addition, in the hydroxyphenylbenzotriazole-based ultraviolet absorber, one hydroxyl group adjacent to the triazine skeleton exists to function as an ultraviolet absorber. Therefore, in order to impart reactivity with the (meth)acrylate monomer to the hydroxyphenylbenzotriazole-based ultraviolet absorber, it is required that the hydroxyphenylbenzotriazole-based ultraviolet absorber (benzotriazole-based ultraviolet absorber) has one or more hydroxyl groups different from this hydroxyl group.

Furthermore, when the hard component having a cationic polymerizable group is a silicon-modified cyclic ether compound and the resin composition contains an isocyanate compound, the UV absorber is preferably a benzotriazole-based UV absorber having two or more hydroxyl groups. This allows the benzotriazole-based UV absorber to be incorporated into the network formed by the reaction of the silicon-modified cyclic ether compound as the cationic polymerizable component with the isocyanate compound. Therefore, it is possible to accurately suppress or prevent the benzotriazole-based UV absorber from leaking, i.e., bleeding out, from the coating layers 12 and 13 composed of the cured product of the resin composition. Therefore, the requirement A can be more reliably satisfied over a long period of time.

The content of the ultraviolet absorber in the resin composition is not particularly limited, but is preferably 1.0 parts by weight or more and 10.0 parts by weight or less, and more preferably 3.0 parts by weight or more and 8.0 parts by weight or less, per 100.0 parts by weight of the resin composition. If the content of the ultraviolet absorber in the resin composition is less than the lower limit, depending on the type of ultraviolet absorber, the effect obtained by adding the ultraviolet absorber to the coating layers 12 and 13 may not be sufficiently obtained. Even if the content of the ultraviolet absorber in the resin composition exceeds the upper limit, no further improvement in ultraviolet irradiation resistance is observed, and the transparency of the coating layers 12 and 13 and the adhesion of the coating layers 12 and 13 to the substrates 111 and 112 may be impaired.

(Light stabilizer)
The resin composition preferably contains a light stabilizer.

By including a light stabilizer in the resin composition, it is possible to improve the stability of the coating layers 12 and 13 when exposed to sunlight. As a result, it is possible to improve the resistance to ultraviolet irradiation of the coating layers 12 and 13 and thus the curved optical sheet 10, i.e., it is possible to reliably satisfy the above-mentioned requirement A.

The light stabilizer is not particularly limited, but examples thereof include hindered amine-based and nickel-based stabilizers, and one or two of these may be used in combination. Among these, hindered amine-based stabilizers are particularly preferred. This allows the above-mentioned effects to be more pronounced. In addition, hindered amine-based light stabilizers are relatively easy and inexpensive to obtain, as they have functional groups that are reactive with the radical polymerization component or cationic polymerization component described below.

Furthermore, it is preferable that the light stabilizer has a functional group that is reactive with the radical polymerization component or cationic polymerization component. This allows the light stabilizer to be incorporated into the network formed by the reaction of the radical polymerization component (e.g., urethane (meth)acrylate) or cationic polymerization component. Therefore, it is possible to accurately suppress or prevent the light stabilizer from leaking, i.e., bleeding out, from the coating layers 12, 13 made of the resin composition. Therefore, the requirement A can be more reliably satisfied over a long period of time.

In addition, when the radical polymerization component is a urethane (meth)acrylate, a light stabilizer having a (meth)acryloyl group as a functional group reactive with the radical polymerization component is preferably used as a light stabilizer having a functional group reactive with the radical polymerization component, since the (meth)acryloyl groups of both the urethane (meth)acrylate and the light stabilizer can form a network by radical polymerization. In addition, a light stabilizer having a (meth)acryloyl group as a functional group can be obtained, for example, as a reaction product between a hindered amine stabilizer having a hydroxyl group and a (meth)acrylate monomer.

The content of the light stabilizer in the resin composition is not particularly limited, but is preferably 1.0 parts by weight or more and 10.0 parts by weight or less, and more preferably 3.0 parts by weight or more and 8.0 parts by weight or less, in 100.0 parts by weight of the resin composition. If the content of the light stabilizer in the resin composition is less than the lower limit, depending on the type of light stabilizer, the effect obtained by adding the light stabilizer to the coating layers 12 and 13 may not be sufficiently obtained. Even if the content of the light stabilizer in the resin composition exceeds the upper limit, no further improvement in UV radiation resistance is observed, and the transparency of the coating layers 12 and 13 and the adhesion of the coating layers 12 and 13 to the substrates 111 and 112 may be impaired.

The resin composition may further contain other additives in addition to the materials mentioned above.

Other additives include, for example, heat ray absorbers, plasticizers, colorants, sensitizers, surfactants, antioxidants, reduction inhibitors, antistatic agents, and surface conditioners (leveling agents).

The coating layers 12 and 13 are composed of the semi-cured resin composition in the optical sheet 15 prepared in the step [1]. The average thickness of each coating layer is not particularly limited, but is preferably 1.0 μm or more and 15.0 μm or less, and more preferably 6.0 μm or more and 9.0 μm or less. If the average thickness of each coating layer 12 and 13 is less than the lower limit, the abrasion resistance and ultraviolet radiation resistance of the optical sheet 15 may decrease. On the other hand, if the thickness of the coating layers 12 and 13 exceeds the upper limit, cracks may occur in the curved optical sheet 10 when the optical sheet 15 is made into a curved optical sheet 10 that is in a curved state.

The refractive index of the coating layers 12 and 13 at a wavelength of 589 nm is not particularly limited, but is preferably 1.40 or more and 1.60 or less, and more preferably 1.450 or more and 1.595 or less.

The coating layers 12 and 13 are composed of a semi-cured resin composition, and are formed, for example, by applying a varnish-like resin composition containing a solvent onto the substrates 111 and 112 to form a liquid coating, and then irradiating the liquid coating with ultraviolet light to semi-cure the liquid coating.

Here, the optical sheet 15 can satisfy the above requirements A to C by having the coating layers 12 and 13 made of a semi-cured material having the configuration described above, but it is preferable that the above requirements A to C further satisfy the following requirements:

That is, in the above requirement B, when the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, molded into a curved shape with a radius of curvature of 120 mmR, and then cooled to 25°C, no cracks should be observed in the coating layers 12 and 13. However, the radius of curvature when molding the optical sheet 15 into a curved shape is preferably 100 mmR, and more preferably 90 mmR. As a result, when the optical sheet 15 having these coating layers 12 and 13 is made into a curved optical sheet 10 by thermal bending in the above step [3], it can be said that the occurrence of cracks in the coating layers 12 and 13 of the curved optical sheet 10 is more appropriately suppressed or prevented.

In addition, in the above-mentioned requirement A, the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, cooled, and then irradiated with ultraviolet light for 1000 hours from the coating layer 12 side using a xenon weather meter in accordance with Table 3-A method-cycle No. 1 of JIS K 7350-4. After that, the optical sheet 15 may satisfy that the change in YI specified by JIS K 7373 is less than 1.0, but the change in YI is preferably 0.8 or less, and more preferably 0.5 or less. As a result, the optical sheet 15 having these coating layers 12 and 13 is made into a curved shape by thermal bending in the above-mentioned step [3] to become the curved optical sheet 10, and the resin composition constituting the coating layers 12 and 13 is cured. In the lens 30 having the curved optical sheet 10, discoloration of the curved optical sheet 10 is more accurately suppressed or prevented, and it can be said that the function as the curved optical sheet 10 (optical sheet 15) is more reliably maintained over a long period of time.

Furthermore, in the above requirement C, the optical sheet 15 is heated in a hot air oven at 170°C for 10 minutes, cooled, and then subjected to a wiper laboratory test according to ECE43. After that, it is sufficient that the haze value of the optical sheet 15 is less than 5.0, but the haze value is preferably 4.0 or less, and more preferably 3.0 or less. As a result, the optical sheet 15 having the coating layers 12 and 13 is made into a curved shape by thermal bending in the above step [3], and the resin composition constituting the coating layers 12 and 13 is cured, so that in the lens 30 having the curved optical sheet 10, the coating layers 12 and 13 are positioned as the outermost layers, and thus the curved optical sheet 10 can be said to exhibit excellent abrasion resistance.

In addition, in the optical sheet 15, if the optical sheet 15 satisfies the above requirements A to C, either one of the two coating layers 12, 13 provided on the upper and lower surfaces (particularly the coating layer 13 located on the back side) may be omitted.

The total thickness of the optical sheet 15 is not particularly limited, but is preferably about 0.2 mm to 3.0 mm, and more preferably about 0.4 mm to 1.6 mm. This provides the optical sheet 15 with excellent strength, while also providing the optical sheet 15 with excellent thermoformability when it is molded into the curved optical sheet 10 having a curved shape.

The optical sheet 15 may also have an adhesion layer as an intermediate layer at least between the first adhesive layer 114 and the polarizing film 113 and between the second adhesive layer 116 and the polarizing film 113. This can improve the adhesion between the adhesive layers 114, 116 and the polarizing film 113.

The adhesive layer is not particularly limited, but may be made of at least one of _SiO2 and _Al2O3 as a main material _, for example.

Second Embodiment
In addition, the optical sheet 15 may have a polarizing property by having the configuration described in the first embodiment, or may have a half-mirror property as described below.
FIG. 4 is a vertical cross-sectional view showing a second embodiment of the optical sheet of the present invention.

For ease of explanation, the upper side of FIG. 4 will be referred to as "top" and the lower side as "bottom." The x direction in FIG. 4 will be referred to as the "left-right direction," the y direction as the "front-back direction," and the z direction as the "up-down direction." Furthermore, the thickness direction of the optical sheet is exaggerated in FIG. 4, and therefore may differ significantly from the actual dimensions.

The second embodiment of the optical sheet of the present invention will be described below with reference to this figure, but the differences from the previous embodiment will be mainly described, and similar points will not be described.

The optical sheet 15 shown in FIG. 4 is similar to the optical sheet 15 shown in FIG. 3, except that the function imparted to the functional substrate 11 is different; specifically, instead of being imparted with polarization properties, the functional substrate 11 is imparted with half-mirror properties.

In other words, in the optical sheet 15 of the second embodiment, as shown in FIG. 4, the functional substrate 11 has a half-mirror layer 117 instead of the polarizing film 113 between the first substrate 111 and the second substrate 112. As a result, the optical sheet 15 (functional substrate 11) exhibits a function of selectively reflecting light in a specific wavelength range from the incident light and transmitting the remaining portion (half-mirror property) instead of the function of extracting linearly polarized light having a polarization plane in a specific direction from the incident light (polarization property).

The half mirror layer 117 selectively reflects light in a specific wavelength range from the incident light and transmits the rest, so that when a person is positioned on the back side of the curved optical sheet 10 in which the optical sheet 15 is curved, that is, when the person is wearing the sunglasses 100, the person (wearer) can see the front side of the curved optical sheet 10 through the curved optical sheet 10. In addition, the light in the specific wavelength range reflected on the front side of the curved optical sheet 10 is visible to a person positioned on the opposite side of the wearer through the curved optical sheet 10, so the curved optical sheet 10 can be made to have a design.

In this embodiment, as shown in FIG. 4, the half mirror layer 117 is composed of a laminate having a high refractive index layer 119 and a low refractive index layer 118 having a lower optical refractive index (hereinafter, sometimes simply referred to as "refractive index") than the high refractive index layer 119. In the illustrated configuration, the high refractive index layer 119 and the low refractive index layer 118 are laminated in this order from the front side (the second substrate 112 side).

The high refractive index layer 119 and the low refractive index layer 118 are deposition films formed by vacuum deposition such as resistance heating and electron beam heating (EB) methods, and the half mirror layer 117 is composed of a laminate of these layers.

Examples of materials constituting the high refractive index layer 119 and the low refractive index layer 118 include _SiO2 , SiO, TiO2, TiO, _Ti2O3 , _{Ti2O5 , Al2O3} , _TaO2 , _Ta2O5 , _NdO2 , _{NbO ,} Nb2O3 _{, NbO2 , Nb2O5} , CeO2, MgO, _Y2O3 , _{SnO2 , WO3 ,} HfO2 _{, ZrO2} , _{Sc2O3 , CrO, Cr2O3 , In2O3 , La2O3 , CaF2 , MgF2} , _{Na3AlF6 , AlF3} , _{and BaF3 .} Examples of the oxides or fluorides include _CeF3 , _LaF2 , LiF, _Na5Al3F14 , _NdF3 , and _{YF3 ,} and metal materials such as In, Cr, Ti, _Ni , Au, Cu, Sn, Zr, and Al.

When the high refractive index layer 119 is made of one of the above metal materials, it is preferably made of Cr or Zr. On the other hand, when the low refractive index layer 118 is made of one of the above metal materials, it is preferably made of In or Al. This allows the refractive index of the high refractive index layer 119 to be higher than the refractive index of the low refractive index layer 118. Therefore, the half mirror layer 117 reliably exhibits the half mirror function. Furthermore, the bendability of the half mirror layer 117 can be improved. Therefore, when the optical sheet 15 is made into a curved optical sheet 10 having a curved shape, the occurrence of cracks in the half mirror layer 117 can be accurately suppressed or prevented.

Moreover, when the high refractive index layer 119 _{is made of a metal oxide, the material is preferably Ta2O5, HfO2, ZrO2, Y2O3 , Sc2O3 , or CeO2 ,} and more preferably _{ZrO2 or CeO2} . On the other hand, when the low refractive index layer ₁₁₈ is made of a metal oxide, the material is preferably _SiO , _SiO2 , _MgF2 , _CaF2 , _Na3AlF6 , or _Na5Al3F14 . This allows the refractive index of the high refractive index layer 119 to be higher than that of the low refractive index layer 118. Therefore, the half mirror layer 117 exhibits _a half _mirror function.

By configuring the half mirror layer 117 in this way, a portion of the light incident from the lower side (front surface) of the optical sheet 15 (curved optical sheet 10) passes through the low refractive index layer 118 and is emitted from the upper side (back surface) of the optical sheet 15. Therefore, a person positioned above (back surface) the curved optical sheet 10 can view the lower side (front side) of the curved optical sheet 10 through the curved optical sheet 10. In addition, since the remaining portion of the incident light is reflected by the low refractive index layer 118, when the curved optical sheet 10 is viewed from the lower side (front surface), the low refractive index layer 118 also functions as a mirror layer.

In addition, the high refractive index layer 119 functions as a mirror layer that selectively reflects light in a specific wavelength region, and among the light incident from the lower side (front surface) of the curved optical sheet 10, the light in the specific wavelength region is selectively reflected at the interface between the low refractive index layer 118 and the high refractive index layer 119, and further at the interface between the second adhesive layer 116 and the high refractive index layer 119. Therefore, on the lower surface (front surface) of the curved optical sheet 10, i.e., the second substrate 112 side, the remaining part of the light reflected by the low refractive index layer 118 and the light in the specific wavelength region reflected by the high refractive index layer 119 are visible to a third party, and as a result, a color based on the light in the specific wavelength region selectively reflected by the high refractive index layer 119 is visible.

In addition to being configured as a laminate of high-refractive index layers 119 and low-refractive index layers 118 as described above, the half-mirror layer 117 can also be configured as a single layer made of a metal film mainly made of Au, Cu, In, etc. By configuring it as a single layer with such a configuration, the thickness of the half-mirror layer 117 can be made thinner. However, by configuring the half-mirror layer 117 as a laminate as described above, i.e., multiple layers (multilayer film), it is possible to reproduce a variety of reflected colors and achieve a design that is excellent.

By disposing the half mirror layer 117 having such a configuration between the first substrate 111 and the second substrate 112 as described above, it is possible to prevent a decrease in the reflectance of the half mirror layer 117 and a change in the color tone of the half mirror layer 117.

The average thickness (physical thickness) of the high refractive index layer 119 and the low refractive index layer 118 may be the same or different, but is preferably 1 nm or more and 200 nm or less, and more preferably 1.5 nm or more and 150 nm or less.

The thickness (optical thickness: for a wavelength of 500 nm) of the high refractive index layer 119 and the low refractive index layer 118 is preferably 0.002/4 λnm or more and 0.4/4 λnm or less, and more preferably 0.003/4 λnm or more and 0.3/4 λnm or less.

By making the high refractive index layer 119 and the low refractive index layer 118 have such thicknesses, it is possible to reliably impart the half mirror layer 117 with the functionality of a half mirror.

The total thickness of the half mirror layer 117 (the sum of the thicknesses of the high refractive index layer 119 and the low refractive index layer 118) is preferably 5 nm to 500 nm, more preferably 7.5 nm to 450 nm, and even more preferably 10 nm to 400 nm. This ensures that the half mirror layer 117 functions as a half mirror. In addition, when the optical sheet 15 (half mirror layer 117) is bent and deformed to thermally mold at least a portion of the optical sheet 15 into a curved optical sheet 10, the occurrence of cracks in the half mirror layer 117 can be accurately suppressed or prevented.

The refractive index difference (optical refractive index difference) between the high refractive index layer 119 and the low refractive index layer 118 is preferably 0.3 to 2, and more preferably 0.4 to 1.5. This allows the half mirror layer 117 to reliably function as a half mirror layer.

The optical sheet 15 of this second embodiment also provides the same effects as the first embodiment.

In the first embodiment, the functional substrate 11 includes a polarizing film 113, which imparts polarizing properties to the functional substrate 11 (optical sheet 15), and in the second embodiment, the functional substrate 11 includes a half-mirror layer 117, which imparts half-mirror properties to the functional substrate 11 (optical sheet 15). However, in the optical sheet 15, the functional substrate 11 is not limited to such a configuration. For example, the functional substrate 11 may include a polarizing film 113 and a half-mirror layer 117, and exhibit both polarizing properties and half-mirror properties. Furthermore, the functional substrate 11 may be one that does not include the polarizing film 113 and the half-mirror layer 117, and simply exhibits light transparency.

<Head-up display>
In addition, the above description has been given of the lens 30 provided in the sunglasses 100, in which the optical sheet 15 (the optical sheet of the present invention) has a curved shape and is provided with the curved optical sheet 10. However, below, a description will be given of the case in which the head-up display 350 is provided with the curved optical sheet 10 as a cover member arranged to cover the window portion 151 provided in the storage body 353.

Figure 5 is a side view showing an embodiment in which the optical sheet of the present invention is curved and applied to a cover member constituting a head-up display of an automobile, and Figure 6 is an enlarged cross-sectional view of the area [A] surrounded by the dashed line in Figure 5. Note that, for convenience of explanation, the upper side in Figures 5 and 6 will be referred to as "upper" or "upper side" and the lower side will be referred to as "lower" or "lower". Also, the left side in Figures 5 and 6 will be referred to as "front" or "forward" and the right side will be referred to as "rear" or "rear".

As shown in FIG. 5, the head-up display 350 is mounted on an automobile 300. The head-up display 350 is built into the upper part of the dashboard 301.

As shown in FIG. 6, the head-up display 350 includes a light source 351, a reflecting member 352, and a housing 353.

The light source 351 can independently emit laser light LS of each color, red (R), green (G), and blue (B). An image can be formed by scanning the light source 351 and controlling the emission timing of the laser light LS of each color. Examples of the light source 351 include a laser light source and an LCD light source.

The reflecting member 352 is composed of, for example, a prism, and can reflect the laser light LS from the light source 351. The laser light LS reflected by the reflecting member 352 is projected onto the rear surface 302a (inner surface) of the windshield 302, using the windshield 302 as a screen. This projected light is recognized by the driver H as the image (see Figures 5 and 6).

As shown in FIG. 6, the storage body 353 is box-shaped and can store the light source 351, the reflecting member 352, and other components that make up the head-up display 350 inside. The storage body 353 also has a window portion 151 that is an opening that opens toward the windshield 302. Through this window portion 151, the laser light LS is emitted to the outside of the storage body 353, i.e., toward the windshield 302.

In addition, a curved optical sheet 10 is installed as a cover member on the window portion 151 of the housing 353 so as to cover the window portion 151. This allows the laser light LS to be emitted toward the windshield 302, and prevents foreign matter such as dust and dirt from entering the housing 353 through the window portion 151. This prevents the lens of the light source 351 and the reflective member 352 from becoming cloudy or dirty due to the foreign matter.

The curved optical sheet 10 used as a cover member installed to cover this window portion 151 is an optical sheet 15 with a curved shape, and by configuring this optical sheet 15 with the optical sheet of the present invention, it is possible to obtain the same effect as that obtained when a curved optical sheet 15 (the optical sheet of the present invention) is applied to the curved optical sheet 10 provided to cover the front side of the lens 30 of the sunglasses 100.

<Windshield>
Furthermore, assuming that the optical sheet 15 (the optical sheet of the present invention) is provided with a curved optical sheet 10 having a curved shape, the following describes the case where the curved optical sheet 10 is used as a windshield (vehicle windshield) equipped on a motorcycle.

Figure 7 shows an embodiment in which the optical sheet of the present invention is curved and applied to a windshield ((a) plan view, (b) side view, (c) cross-sectional view along line B-B in Figure 7(a)). For ease of explanation, the front side of Figure 7(a) will be referred to as the "front", the back side of the page as the "rear", the left side as the "left", the right side as the "right", the top side as the "top", and the bottom side as the "bottom"; the front side of Figure 7(b) will be referred to as the "right", the back side of the page as the "left", the left side as the "front", the right side as the "rear", the top side as the "top", and the bottom side as the "bottom"; the front side of Figure 7(c) will be referred to as the "bottom", the back side of the page as the "top", the left side as the "left", the right side as the "right", the top side as the "front", and the bottom side as the "back".

As shown in FIG. 7, the windshield 400 has a main body (center) 451 formed long in the vertical direction, two side portions 452 protruding in the left and right directions below the main body 451, and a connecting portion 453 connecting the side portions 452 to the main body 451, and has an overall shape that is curved and symmetrical.

The main body 451 is located approximately in the center of the windshield 400, has a long shape in the vertical direction (a direction perpendicular to one direction), and is fixed at its bottom to the body of a motorcycle or the like, so that a person (pilot) can view things located in front of them through this main body 451.

In this main body 451, the front surface is formed as a curved convex surface, and the rear surface is formed as a curved concave surface, so that the main body 451 has a curved shape (curved surface shape) that protrudes and curves toward the front side. In addition, in the main body 451, this curved shape is formed along the left-right direction (one direction).

The two side sections 452 are formed below the main body section 451, one each protruding in the left and right directions, and are provided to prevent wind from being drawn in from the sides when riding a motorcycle or the like.

In this side portion 452, similar to the main body portion 451, the front surface is formed as a curved convex surface, and the rear surface is formed as a curved concave surface, so that the side portion 452 has a curved shape (curved surface shape) that protrudes and curves toward the front side. In addition, in the side portion 452, this curved shape is formed along the left-right direction.

The two connecting parts 453 are interposed between the main body part 451 and the two side parts 452, respectively, and connect them together.

In this connecting part 453, the front surface is formed as a curved concave surface, and the rear surface is formed as a curved convex surface, so that the connecting part 453 has a curved shape (curved surface shape) that protrudes and curves toward the rear side. In addition, in the connecting part 453, this curved shape is formed along the left-right direction.

In the windshield 400 having such a configuration and an overall shape that is a symmetrical curved shape, each part 451 to 453 that constitutes the windshield 400 is integrally formed, and this windshield 400 is made of a curved optical sheet 10 in which the optical sheet 15 is curved. By configuring this optical sheet 15 with the optical sheet of the present invention, it is possible to obtain the same effect as that obtained when the optical sheet 15 (the optical sheet of the present invention) in a curved shape is applied to the curved optical sheet 10 that is provided so as to cover the front side of the lens 30 of the sunglasses 100.

The optical sheet and optical components of the present invention have been described above with reference to the illustrated embodiments, but the present invention is not limited to this. For example, each part constituting the optical sheet can be replaced with any other part that can perform the same function. In addition, any other component may be added.

The present invention will be described in more detail below with reference to examples. Note that the present invention is not limited to these examples.

1. Preparation of Raw Materials First, the raw materials used in manufacturing the optical sheet 15 are shown below.

(Polycarbonate Resin 1)
As polycarbonate-based resin 1, bisphenol A polycarbonate (manufactured by Mitsubishi Engineering Plastics Corporation, "E2000FN") was prepared.

(Silicon-modified cyclic ether compound 1)
First, 60 g of "KBM-4803" manufactured by Shin-Etsu Chemical Co., Ltd. and 5.4 g of "KBM-303" manufactured by Shin-Etsu Chemical Co., Ltd. were dissolved in 15 mL of 1-methoxy-2-propanol (PGME) to obtain mixed solution A. Next, 0.01 g of magnesium chloride was dissolved in 12 mL of water and 4.8 mL of methanol to obtain mixed solution B. Then, mixed solution B was gradually added dropwise to mixed solution A over 5 minutes. Thereafter, the reaction was allowed to proceed by stirring for 6 hours under a condition of 80°C, and after completion of the reaction, the solvent was removed using a rotary evaporator to obtain silicon-modified cyclic ether compound 1, i.e., a hard component.

(Urethane (meth)acrylate 1)
As the soft component, that is, urethane (meth)acrylate 1, a bifunctional urethane acrylate (manufactured by Daicel Allnex Corporation, "EBECRYL270") was prepared.

(Urethane (meth)acrylate 2)
As the soft component, i.e., urethane (meth)acrylate 2, a bifunctional urethane acrylate (manufactured by Mitsubishi Chemical Corporation, "UV6640") was prepared.

(Urethane (meth)acrylate 3)
As the soft component, i.e., 3, a 10-functional urethane acrylate (manufactured by Mitsubishi Chemical Corporation, "UV1700B") was prepared.

(Adhesive Agent (Monomer Component Having a Radical Polymerizable Group) 1)
As the adhesive 1, that is, a monomer component having a radical polymerizable group, a bifunctional acrylate monomer (manufactured by Shin-Nakamura Chemical Co., Ltd., "A-BPE-4") was prepared.

(Adhesive Agent (Monomer Component Having a Radical Polymerizable Group and a Cationic Polymerizable Group) 2)
As the adhesive 2, that is, a monomer component having both a radical polymerizable group and a cationic polymerizable group, 3-hydroxybutyl acrylate and isobornyl acrylate (manufactured by Daicel Corporation, "CYM-M100") were prepared.

(Radical Polymerization Initiator 1)
As the radical polymerization initiator 1, a photoradical polymerization initiator (manufactured by IGM Resins BV, "Omnirad 754") was prepared.

(Cationic Polymerization Initiator 1)
As the cationic polymerization initiator 1, a photoacid generator (manufactured by San-Apro Co., Ltd., "CPI-101A") was prepared.

(Isocyanate Compound 1)
As isocyanate compound 1, a trifunctional polyisocyanate (manufactured by DIC Corporation, "Burnoc DN-992S") was prepared.

(Ultraviolet absorber 1)
A hydroxyphenyltriazine-based ultraviolet absorber ("Tinuvin 400" manufactured by BASF Japan) was prepared as the ultraviolet absorber 1. This ultraviolet absorber 1 (hydroxyphenyltriazine-based ultraviolet absorber) has two hydroxyl groups.

(Ultraviolet absorber 2)
As the ultraviolet absorber 2, a hydroxyphenyltriazine ultraviolet absorber (manufactured by BASF Japan, "Tinuvin 1577 ED") was prepared.

(Ultraviolet absorber 3)
A hydroxyphenyltriazine-based ultraviolet absorber ("Tinuvin 928" manufactured by BASF Japan) was prepared as the ultraviolet absorber 3. This ultraviolet absorber 3 (hydroxyphenyltriazine-based ultraviolet absorber) has one hydroxyl group.

(Light Stabilizer 1)
As light stabilizer 1, a hindered amine-based light stabilizer having a methacryloyl group (manufactured by Adeka Corporation, "LA-82") was prepared.

(Photosensitizer 1)
As photosensitizer 1, a photocationic sensitizer (manufactured by Air Water Performance Chemicals, Inc., "UVS-1331") was prepared.

2. Preparation of resin composition for forming coating layer 64.0 parts by weight of silicon modified cyclic ether compound 1, 15.0 parts by weight of urethane (meth) acrylate 1, 4.5 parts by weight of adhesion agent 1, 0.6 parts by weight of adhesion agent 2, 2.5 parts by weight of radical polymerization initiator 1, 2.6 parts by weight of cationic polymerization initiator 1, 5.0 parts by weight of isocyanate compound 1, 5.0 parts by weight of ultraviolet absorber 1, 0.3 parts by weight of light stabilizer 1, and 0.5 parts by weight of photosensitizer 1 are mixed, diluted with isobutyl acetate (AciBu) as a solvent, and then stirred to prepare a resin composition for forming a coating layer (see Table 1).

3. Formation of Optical Sheet (Example 1)
First, a resin composition consisting of 98.0 parts by weight of polycarbonate resin 1 and 2.0 parts by weight of ultraviolet absorber 2 was kneaded, and the kneaded product was extrusion-molded to obtain a transparent substrate having a thickness of 2.5 mm.

Next, the resin composition prepared in advance was applied to the front and back surfaces of the transparent substrate, respectively, and then heated and dried. After that, ultraviolet light was applied to form coating layers 12 composed of a semi-cured product of the resin composition having a thickness of 10.0 μm on the front and back surfaces of the transparent substrate, respectively, to obtain the optical sheet 15 of Example 1.

(Examples 2 to 5, Comparative Examples 1 to 3)
The optical sheets 15 of Examples 2 to 5 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1, except that the coating layer 12 was formed using a curable resin composition for forming the coating layer, which contained the constituent materials shown in Table 1 in the amounts shown in Table 1.

3. Evaluation The optical sheets 15 of the examples and comparative examples were evaluated by the following method.

<1> Confirmation of thermal bending property of optical sheet First, the optical sheets 15 of each Example and Comparative Example were heated in a hot air oven at 170° C. for 10 minutes, and then pressed against metal molds with a curvature radius of 100 mmR and 120 mmR to be thermally bent. Then, when cooled to 25° C., the presence or absence of cracks in the coating layer 12 was visually confirmed, and evaluated based on the following evaluation criteria.

[Evaluation criteria]
The occurrence of cracks in the coating layer 12
⊚: Not observed even when molded into a curved shape with a radius of curvature of 100 mmR.
○: It is acceptable for molding a curved shape with a radius of curvature of 100 mmR, but
This is not permitted for molding a curved shape with a radius of curvature of 120 mmR.
×: Even molding having a curved shape with a radius of curvature of 120 mmR was observed.

<2> Measurement of Color Change of Optical Sheet The optical sheets 15 of each of the examples and comparative examples were each heated in a hot air oven at 170°C for 10 minutes, cooled, and then irradiated with ultraviolet light for 1000 hours from the coating layer 12 side using a xenon weather meter in accordance with Table 3-A method-cycle No. 1 of JIS K 7350-4. After that, the change in YI of the optical sheet 15 as defined by JIS K 7373 was measured, and the optical sheet 15 was evaluated based on the obtained change (ΔYI) as follows.

[Evaluation criteria]
⊚: ΔYI is 0.5 or less and no change in appearance is observed.
Good: ΔYI is greater than 0.5 and less than 1.0;
Although some change in appearance was observed, this did not affect the use of the optical sheet 15.
×: ΔYI is 1.0 or more,
The change in appearance was clearly observed, making it difficult to use as the optical sheet 15.

<3> Abrasion Resistance Test of Optical Sheet The optical sheets 15 of the examples and comparative examples were each heated in a hot air oven at 170° C. for 10 minutes and then cooled. Thereafter, a wiper laboratory test in accordance with ECE43 was performed using a Gardner abrasion tester (manufactured by BYK Corporation). Then, the haze value of the optical sheets 15 was measured in accordance with JIS K 7136 using a haze meter (Nippon Denshoku Industries Co., Ltd., “COH7700”). Based on the obtained haze value, the optical sheets 15 were evaluated as follows.

[Evaluation criteria]
A: The haze value is 3.0 or less and no change in appearance is observed.
Good: the haze value is greater than 3.0 and less than 5.0;
Although some change in appearance was observed, this did not affect the use of the optical sheet 15.
×: The haze value is 5.0 or more.
The change in appearance was clearly observed, making it difficult to use as the optical sheet 15.

The laboratory wiper test in accordance with ECE43 using a Gardner abrasion tester (manufactured by BYK) was carried out under the following conditions: a 2.5% by weight aqueous dispersion of ISO Test Dust A4 was used as the suspension, a Bosch wiper blade (H-Stoff P6.3) was used, and the friction speed was 160±15 mm/s and the number of frictions was 20,000 cycles.

<4> Measurement of Pencil Hardness of Optical Sheet First, for each of the optical sheets 15 of the examples and comparative examples, the scratch hardness of the coating layer 12 was measured by the pencil method described in JIS K 5400.

Furthermore, after heating in a hot air oven at 170°C for 10 minutes, the sheet was pressed against a metal mold with a radius of curvature of 120 mmR and 100 mmR and subjected to a thermal bending process to form a curved shape, thereby obtaining a curved optical sheet 10. The scratch hardness of the coating layer 12 of each of the obtained curved optical sheets 10 was measured by the pencil method described in JIS K 5400.

<5> Cross-cut test for optical sheet For the optical sheet 15 of each of the examples and comparative examples, each was heated in a hot air oven at 170° C. for 10 minutes and then cooled. Thereafter, the presence or absence of adhesion of 100 pieces of the coating layer 12 cut into a lattice shape to the transparent substrate was observed by the cross-cut method specified in JIS K 5600-5-6.

For the optical sheets 15 of each of the Examples and Comparative Examples, ultraviolet rays were irradiated from the coating layer 12 side for 500 hours and 1000 hours using a xenon weather meter in accordance with Table 3-A method-Cycle No. 1 of JIS K 7350-4, and then the presence or absence of adhesion of 100 pieces of the coating layer 12 cut into a lattice shape to the transparent substrate was observed by the cross-cut method specified in JIS K 5600-5-6.
[Evaluation criteria]
⊚: After 1000 hours of irradiation, 100/100 particles were found to adhere.
○: After 500 hours of irradiation, 100/100 particles were found to adhere, but
After 1000 hours of exposure, no adhesion was observed, as shown by 0/100 particles.
×: No adhesion was observed, as shown by 0/100 particles, after 500 hours of irradiation.

The evaluation results for the optical sheets 15 of each of the examples and comparative examples obtained as described above are shown in Table 1 below.

As shown in Table 1, in the optical sheets in each example, the semi-cured resin composition constituting the coating layer contains both a soft component having a radical polymerizable group and a hard component having a cationic polymerizable group, and as a result, the results show that the above requirements A to C are satisfied.

In contrast, in the optical sheets in each comparative example, the semi-cured resin composition constituting the coating layer does not contain either a soft component having a radical polymerizable group or a hard component having a cationic polymerizable group, and as a result, it is clear that at least one of the requirements A to C is not satisfied.

10 Curved optical sheet 11 Functional substrate 12 First coating layer 13 Second coating layer 15 Optical sheet 20 Frame 21 Rim portion 22 Bridge portion 23 Temple portion 24 Nose pad portion 30 Lens 35 Resin layer 40 Mold 50 Protective film 100 Sunglasses 111 First substrate 112 Second substrate 113 Polarizing film 114 First adhesive layer 116 Second adhesive layer 117 Half mirror layer 118 Low refractive index layer 119 High refractive index layer 150 Multilayer laminate 151 Window portion 200 Curved multilayer laminate 300 Automobile 301 Dashboard 302 Windshield 302a Back surface 350 Head-up display 351 Light source 352 Reflecting member 353 Storage body 400 Windshield 451 Main body portion 452 Side portion 453 Connection portion H Driver LS Laser light

Claims (10)

An optical sheet comprising a functional substrate and a coating layer provided as an outermost layer on at least one surface side of the functional substrate,
the coating layer is composed of a semi-cured product of a resin composition including a soft component having a radical polymerizable group and a hard component having a cationic polymerizable group;
The optical sheet is characterized by satisfying the following requirements A to C.
Requirement A: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, cooled, and then irradiated with ultraviolet light from the coating layer side for 1000 hours using a xenon weather meter in accordance with JIS K 7350-4, Table 3-A method, cycle No. 1. After that, the change in YI of the optical sheet as defined by JIS K 7373 is less than 1.0.
Requirement B: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, molded into a curved shape with a radius of curvature of 120 mmR, and then cooled to 25°C; no cracks are observed in the coating layer.
Requirement C: The optical sheet is heated in a hot air oven at 170°C for 10 minutes, cooled, and then subjected to a wiper laboratory test in accordance with ECE43. After that, the haze value of the optical sheet is less than 5.0. The optical sheet according to claim 1, wherein the radical polymerizable group is at least one of a (meth)acryloyl group and a vinyl group. The optical sheet according to claim 2, wherein the soft component has a main chain having a urethane bond and one or two of the radical polymerizable groups linked as side chains. The optical sheet according to claim 1, wherein the cationic polymerizable group is at least one of a cyclic ether group and a vinyl ether group. The optical sheet according to claim 4, wherein the hard component is a main chain made of a repeating body of structural units having siloxane bonds, to which a plurality of the cationic polymerizable groups are linked as side chains. The optical sheet according to claim 1, wherein the resin composition further contains a monomer component having both the radical polymerizable group and the cationic polymerizable group. The optical sheet according to claim 1, wherein the functional substrate comprises a first substrate, a second substrate, and at least one of a polarizing layer and a half mirror layer disposed between the first substrate and the second substrate. The optical sheet according to claim 7, which is used as a cover member provided to cover a window portion of a container. The optical sheet according to claim 7, wherein the optical sheet is provided so as to cover the front side of the lens. The optical sheet according to claim 7, which is used as a windshield plate provided in a vehicle.

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