Optical laminate and method for manufacturing an optical laminate

Abstract

To provide an optical laminate capable of achieving thinning and capable of maintaining excellent optical performance and a method of manufacturing the optical laminate.SOLUTION: An optical laminate according to an embodiment of the present invention includes: a transparent layer having a thickness of 20 μm or less; a porous layer directly provided in a predetermined pattern on one surface in a thickness direction of the transparent layer and having a refractive index of 1.25 or less; an adhesive layer arranged opposite to the porous layer across the transparent layer and in direct contact with the transparent layer; and a sticky layer opposite to the adhesive layer across the transparent layer and covers the porous layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical laminate and a method for manufacturing the optical laminate.

Background Art

[0002] It is known to attach an optical laminate including a low refractive index layer having a refractive index smaller than that of a light guide plate for propagating light to the light guide plate to arbitrarily control the propagation of light in the light guide plate. Patterning such a low refractive index layer to impart a light extraction function to the optical laminate has been studied. For example, an optical laminate including a substrate and a variable refractive index extraction layer provided on the substrate, the variable refractive index extraction layer including a first region where a first substance having a relatively small refractive index is selectively printed and a second region where a second substance having a relatively large refractive index is overcoated on the first substance has been proposed (see, for example, Patent Document 1). In the optical laminate described in Patent Document 1, an adhesive layer is formed on the surface of the substrate opposite to the variable refractive index extraction layer, and the optical laminate is attached to the light guide plate by the adhesive layer. In recent years, the applications of optical products including light guide plates have diversified, and miniaturization of optical products, and thus thinning of the optical laminate attached to the light guide plate, are desired. However, the optical laminate described in Patent Document 1 includes a substrate on which the first substance is selectively printed, and it is difficult to reduce the thickness of the optical laminate. Thinning of the substrate or peeling and removing the substrate from the variable refractive index extraction layer have also been studied, but thinning of the substrate is difficult from the viewpoint of manufacturing stability of the optical laminate, and the variable refractive index extraction layer may be damaged when the substrate is peeled off. Further, when the substrate is peeled off and an adhesive layer is directly provided on the variable refractive index extraction layer, there is a problem that the optical performance of the variable refractive index extraction layer cannot be sufficiently maintained.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The present invention was made to solve the above-mentioned conventional problems, and its main objective is to provide an optical laminate and a method for manufacturing an optical laminate that can be made thinner while maintaining excellent optical performance. [Means for solving the problem]

[0005] An optical laminate according to an embodiment of the present invention comprises: a transparent layer having a thickness of 20 μm or less; a porous layer directly provided in a predetermined pattern on one side in the thickness direction of the transparent layer and having a refractive index of 1.25 or less; an adhesive layer positioned on the opposite side of the porous layer from the transparent layer and in contact with the transparent layer; and an adhesive layer positioned on the opposite side of the adhesive layer from the transparent layer and covering the porous layer. In one embodiment, the transparent layer has a barrier function that prevents the components constituting the adhesive layer from penetrating into the porous layer. In one embodiment, the porosity of the transparent layer is smaller than that of the porous layer. In one embodiment, the adhesive layer has a storage modulus of 1.0 × 10⁻⁶ at 23°C. 5 It is composed of an adhesive with a pressure of (Pa) or higher. A method for manufacturing an optical laminate according to another aspect of the present invention includes the steps of: forming a transparent layer having a thickness of 20 μm or less on a substrate; forming a pattern of porous layers having a refractive index of 1.25 or less on the surface of the transparent layer opposite to the substrate; forming an adhesive layer on the porous layer so as to cover it from the side opposite to the transparent layer; peeling the substrate from the transparent layer; and forming an adhesive layer on the surface of the transparent layer opposite to the porous layer. In one embodiment, the peeling force when peeling the substrate from the transparent layer is 1 N / 25 mm or less. [Effects of the Invention]

[0006] According to embodiments of the present invention, it is possible to realize an optical laminate that can be made thinner while maintaining excellent optical performance. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view of an optical product comprising the optical laminate shown in Figure 1. [Figure 3] Figures 3(a) to 3(e) are schematic cross-sectional views illustrating a method for manufacturing an optical laminate according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. First, the overall structure of the optical laminate will be described, and then the components of the optical laminate will be described in detail.

[0009] A. Overall configuration of the optical laminate Figure 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention; Figure 2 is a schematic cross-sectional view of an optical product comprising the optical laminate of Figure 1. The illustrated optical laminate 100 comprises: a transparent layer 1 with a thickness of 20 μm or less; a porous layer 2 directly provided in a predetermined pattern on one side in the thickness direction of the transparent layer 1 and having a refractive index of 1.25 or less; an adhesive layer 4 positioned on the opposite side of the porous layer 2 from the transparent layer 1 and in contact with the transparent layer 1; and an adhesive layer 3 positioned on the opposite side of the adhesive layer 4 from the transparent layer 1 and covering the porous layer 2. In this configuration, the transparent layer is positioned between the porous layer and the adhesive layer, and since the thickness of the transparent layer is 20 μm or less, the optical laminate can be made thinner, and the refractive index of the porous layer can be maintained below the above upper limit. Therefore, the excellent optical performance of the optical laminate can be sufficiently maintained. The thickness of the transparent layer 1 is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 4 μm or less, and is typically 0.1 μm or more. The porous layer 2 typically has voids inside. The refractive index of the porous layer 2 is preferably less than 1.20, more preferably 1.19 or less, and even more preferably 1.18 or less, and typically 1.10 or more. Unless otherwise specified, the refractive index refers to the refractive index measured at a wavelength of 550 nm.

[0010] In one embodiment, a portion of one side of the transparent layer 1 in the thickness direction may be exposed from the porous layer 2. The exposed portion is in contact with the adhesive layer 3. Therefore, the adhesive layer 3 is in contact with both the porous layer 2 and the transparent layer 1. This suppresses the peeling of the transparent layer 1 from the porous layer 2 during handling of the laminate before processing. The refractive index of the adhesive layer 3 is typically greater than that of the porous layer 2. The refractive index of the adhesive layer 3 is greater than 1.25, preferably 1.4 or higher, and typically 1.7 or lower.

[0011] In one embodiment, the transparent layer 1 is a barrier layer 1a that has a barrier function to suppress the penetration of components constituting the adhesive layer 4 into the porous layer 2. Therefore, the increase in the refractive index of the porous layer can be stably suppressed. The adhesive layer 4 may be a tack layer or an adhesive layer.

[0012] In one embodiment, the porosity of the transparent layer 1 is smaller than that of the porous layer 2. With this configuration, the barrier performance of the transparent layer 1 can be sufficiently ensured, and the intrusion of the adhesive or bonding agent constituting the adhesive layer into the voids of the porous layer can be stably suppressed. The porosity of the transparent layer 1 is, for example, 15 vol% or less, preferably 10 vol% or less, with a lower limit of, for example, 1 vol% or more. The porosity of the porous layer 2 is, for example, greater than 10 vol%, preferably 20 vol% or more, more preferably 30 vol% or more, even more preferably 35 vol% or more, for example, 60 vol% or less, preferably 55 vol% or less, even more preferably 50 vol% or less, and even more preferably 45 vol% or less. If the porosity is within this range, the refractive index of the porous layer can be set to an appropriate range, and a predetermined mechanical strength can be ensured. The porosity is a value calculated from the refractive index value measured with an ellipsometer using the Lorentz-Lorenz formula.

[0013] In one embodiment, the adhesive layer 3 has a storage modulus of 1.0 × 10⁻⁶ at 23°C. 5 The adhesive is composed of an adhesive with a pressure of (Pa) or higher. The storage modulus of the adhesive constituting the adhesive layer 3 at 23°C is preferably 1.1 × 10⁻⁶. 5 (Pa) or more, more preferably 1.2 × 10 5 It is (Pa) or higher. If the storage modulus of the adhesive is above the lower limit above, it is possible to suppress the adhesive constituting the adhesive layer from penetrating into the voids of the porous layer. Therefore, the increase in the refractive index of the porous layer can be suppressed more stably. The storage modulus is determined by reading the value at 23°C when measured at a frequency of 1 Hz in the range of -50°C to 150°C with a heating rate of 5°C / min, in accordance with the method described in JIS K 7244-1 "Plastics - Test methods for dynamic mechanical properties". The upper limit of the storage modulus of the adhesive constituting the adhesive layer 3 at 23°C is typically 100 × 10⁻¹⁰ 5 It is less than or equal to (Pa).

[0014] Hereinafter, the transparent layer, porous layer, adhesive layer, and adhesive layer will be specifically described.

[0015] B. Transparent layer The transparent layer 1 is capable of transmitting light. The total light transmittance of the transparent layer 1 is, for example, 70% - 100%, preferably 80% - 99%. If the total light transmittance of the transparent layer is within the above range, excellent transparency can be realized for the entire optical laminate. As a result, the adverse effects in the applications of the optical laminate can be suppressed.

[0016] The transparent layer 1 can adopt any appropriate configuration as long as it can transmit light. Examples of the transparent layer 1 include a resin film and an inorganic thin film. Examples of the material of the resin film include polyvinyl alcohol (PVA); (meth)acrylic resins such as polymethyl methacrylate (PMMA); polyvinyl acetal resin; thermoplastic resin materials having polar groups such as polycarbonate resin, polyarylate resin, and polyurethane-based resin; heat- or UV-curable resin materials such as acrylic hard coat resin materials, epoxy hard coat resin materials, and silicone hard coat resin materials. Note that (meth)acrylic refers to acrylic and / or methacrylic. The materials of the resin film can be used alone or in combination. Also, the resin film may be composed of only the resin composition, or other substances may be added for changing the physical properties of the resin film. Specifically, the addition of a boric acid compound or a silane-based compound for introducing a cross-linked structure into PVA can be mentioned.

[0017] Examples of the material of the inorganic thin film include SiO2, ZTO, ITO, IZO, TiO2, Si, ZnO, AZO, Al2O3, MgO, MgF2, and SiN. The materials of the inorganic thin film can be used alone or in combination.

[0018] C. Porous layer The porous layer 2 is provided directly on one side of the transparent layer 1 in the thickness direction and has a predetermined pattern shape. Typically, the porous layer 2 has a plurality of openings 21 that define the pattern. In one embodiment, the porous layer 2 has a gradient pattern in which the ratio of openings per unit area increases toward one predetermined direction perpendicular to the thickness direction of the transparent layer 1. The openings 21 can adopt any appropriate shape and size. When the porous layer 2 has a gradient pattern, the openings 21 of the same size may be distributed so as to become sparser toward one predetermined direction, or the size of the openings 21 may be changed so as to become larger toward one predetermined direction.

[0019] The total light transmittance of the porous layer 2 is, for example, 85% to 99%, preferably 87% to 98%, and more preferably 89% to 97%. The haze of the porous layer 2 is, for example, less than 5%, preferably less than 3%. On the other hand, the haze is, for example, 0.1% or more, preferably 0.2% or more. By providing such a porous layer at a predetermined position, excellent transparency can be achieved for the entire optical laminate. The haze can be measured, for example, by the following method. The void layer (porous layer) is cut to a size of 50 mm x 50 mm and set in a haze meter (Murakami Color Technology Research Institute: HM-150) to measure the haze. The haze value is calculated using the following formula. Haze (%) = [Diffuse transmittance (%) / Total light transmittance (%)] × 100 (%)

[0020] The thickness of the porous layer 2 is, for example, 30 nm to 5 μm, preferably 200 nm to 4 μm, more preferably 400 nm to 3 μm, and even more preferably 600 nm to 2 μm. When the thickness of the porous layer is within this range, the porous layer can effectively exhibit total internal reflection function for light in the visible to infrared region.

[0021] The porous layer 2 can be any suitable configuration, as long as it has the desired properties described above. The porous layer can preferably be formed by coating or printing. As materials constituting the porous layer, for example, materials described in International Publication No. 2004 / 113966, Japanese Patent Publication No. 2013-254183, and Japanese Patent Publication No. 2012-189802 can be used. Representative examples include silicon compounds. Examples of silicon compounds include silica compounds; hydrolyzable silanes, and their partial hydrolysates and dehydration condensates; silicon compounds containing silanol groups; and activated silica obtained by contacting silicates with acids or ion exchange resins. Organic polymers; polymerizable monomers (e.g., (meth)acrylic monomers and styrene monomers); and curable resins (e.g., (meth)acrylic resins, fluorine-containing resins, and urethane resins) can also be used. These materials may be used individually or in combination. The porous layer can be formed by coating or printing a solution or dispersion of such materials.

[0022] In a porous layer, the size of the voids (pores) refers to the diameter of the major axis of the void (pore) compared to the diameter of the major axis. The size of the voids (pores) is, for example, 2 nm to 500 nm. The size of the voids (pores) is, for example, 2 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. On the other hand, the size of the voids (pores) is, for example, 500 nm or less, preferably 200 nm or less, and even more preferably 100 nm or less. The range of the void (pore) size is, for example, 2 nm to 500 nm, preferably 5 nm to 500 nm, more preferably 10 nm to 200 nm, and even more preferably 20 nm to 100 nm. The size of the voids (pores) can be adjusted to a desired size depending on the purpose and application. The size of the voids (pores) can be quantified by the BET test method.

[0023] The size of the voids (pores) can be quantified using the BET test method. Specifically, 0.1 g of the sample (formed void layer) is placed in the capillary of a specific surface area measuring device (Micromeritic: ASAP2020), and then dried under reduced pressure at room temperature for 24 hours to remove gas from within the void structure. Then, nitrogen gas is adsorbed onto the sample to create an adsorption isotherm, and the pore distribution is determined. This allows for the evaluation of the void size.

[0024] Examples of porous layers having voids inside include porous layers and / or porous layers having at least a portion of an air layer. The porous layer typically includes aerogel and / or particles (e.g., hollow fine particles and / or porous particles). The porous layer may preferably be a nanoporous layer (specifically, a porous layer in which the diameter of 90% or more of the fine pores is in the range of 10⁻¹ nm to 10³ nm).

[0025] Any suitable particles can be used as the above-mentioned particles. Typically, the particles consist of silica-based compounds. Examples of particle shapes include spherical, plate-shaped, needle-shaped, string-shaped, and grape cluster-shaped. Examples of string-shaped particles include particles in which multiple spherical, plate-shaped, or needle-shaped particles are linked together in a chain-like manner, short fibrous particles (for example, short fibrous particles described in Japanese Patent Publication No. 2001-188104), and combinations thereof. String-shaped particles may be linear or branched. Examples of grape cluster-shaped particles include those formed by the aggregation of multiple spherical, plate-shaped, and needle-shaped particles to form a grape cluster. The shape of the particles can be confirmed, for example, by observation with a transmission electron microscope.

[0026] The following describes an example of the specific structure of a porous layer. The porous layer in this embodiment consists of one or more types of constituent units that form a fine void structure, and these constituent units are chemically bonded to each other via catalytic action. Examples of the shapes of the constituent units include particulate, fibrous, rod-shaped, and plate-shaped. The constituent units may have only one shape, or they may have a combination of two or more shapes. In the following, we will mainly describe the case in which the porous layer is a void layer of a porous material in which the fine pore particles are chemically bonded to each other.

[0027] Such void layers can be formed in the void layer formation process by, for example, chemically bonding microporous particles (porous particles) together. In embodiments of the present invention, the shape of the "particles" (e.g., the above-mentioned microporous particles) is not particularly limited and may be spherical or of other shapes. In embodiments of the present invention, the above-mentioned microporous particles may be, for example, sol-gel bead-like particles, nanoparticles (hollow nanosilica / nanoballoon particles), nanofibers, etc. Microporous particles typically include inorganic substances. Specific examples of inorganic substances include silicon (Si), magnesium (Mg), aluminum (Al), titanium (Ti), zinc (Zn), and zirconium (Zr). These may be used individually or in combination of two or more. In one embodiment, the above-mentioned microporous particles are, for example, microporous particles (porous particles) of a silicon compound, and the above-mentioned porous body is, for example, a silicone porous body. The above-mentioned microporous particles of a silicon compound include, for example, a pulverized gel-like silicon compound. Furthermore, another form of a porous layer having at least a porous layer and / or an air layer is a void layer made of fibrous material such as nanofibers, in which the fibrous material is intertwined to form voids and create a layer. The method for manufacturing such a void layer is not particularly limited and is similar to that of a void layer of a porous material in which the fine porous particles are chemically bonded together. Further other forms include void layers using hollow nanoparticles or nanoclay, and void layers formed using hollow nanoballoons or magnesium fluoride. The void layer may be made of a single constituent material or of multiple constituent materials. The void layer may consist of a single of the above forms or may include multiple of the above forms.

[0028] In this embodiment, the porous structure of the porous body may be, for example, a continuous cell structure in which the pore structure is continuous. A continuous cell structure means, for example, in the above-mentioned porous silicone body, that the pore structure is connected in three dimensions, and can also be described as a state in which the internal voids of the pore structure are continuous. By having a continuous cell structure in the porous body, it is possible to increase the porosity. However, when using closed-cell particles (particles that each have a pore structure) such as hollow silica, a continuous cell structure cannot be formed. On the other hand, when using silica sol particles (pulverized gel-like silicon compounds that form a sol), for example, because the particles have a three-dimensional dendritic structure, it is possible to easily form a continuous cell structure by the sedimentation and accumulation of the dendritic particles in the coating film (a coating film of a sol containing the pulverized gel-like silicon compounds). The porous layer more preferably has a monolithic structure in which the continuous cell structure includes a plurality of pore distributions. A monolithic structure means, for example, a hierarchical structure that includes a structure in which nano-sized fine voids exist and a continuous cell structure in which these nano-voids are aggregated. When forming a monolithic structure, for example, it is possible to achieve both film strength and high porosity by providing fine voids while simultaneously providing high porosity with coarse, interconnected voids. Such a monolithic structure can preferably be formed by controlling the pore distribution of the resulting void structure in the gel (gel-like silicon compound) prior to grinding it into silica sol particles. Alternatively, for example, when grinding a gel-like silicon compound, a monolithic structure can be formed by controlling the particle size distribution of the resulting silica sol particles to a desired size.

[0029] The porous layer contains, for example, pulverized gel-like compounds as described above, and these pulverized particles are chemically bonded to each other. The form of chemical bonding between the pulverized particles in the porous layer is not particularly limited and includes, for example, cross-linking, covalent bonding, and hydrogen bonding.

[0030] The volume-average particle diameter of the pulverized material in the porous layer is, for example, 0.05 μm or more, preferably 0.10 μm or more, and more preferably 0.11 μm or more. On the other hand, the volume-average particle diameter is, for example, 1.00 μm or less, preferably 0.90 μm or less, and more preferably 0.50 μm or less. The range of the volume-average particle diameter is, for example, 0.05 μm to 1.00 μm, preferably 0.10 μm to 0.90 μm, and more preferably 0.11 μm to 0.55 μm. The particle size distribution can be measured, for example, by particle size distribution evaluation devices such as dynamic light scattering and laser diffraction, and by electron microscopes such as scanning electron microscopes (SEM) and transmission electron microscopes (TEM). Note that the volume-average particle diameter is an indicator of the variation in particle size of the pulverized material.

[0031] The type of gel-like compound is not particularly limited. Examples of gel-like compounds include gel-like silicon compounds.

[0032] Furthermore, in the porous layer (void layer), it is preferable that the silicon atoms contained are bonded together by siloxane bonds. Specifically, the proportion of unbonded silicon atoms (i.e., residual silanols) among the total silicon atoms contained in the void layer is, for example, less than 50%, preferably 30% or less, and more preferably 15% or less.

[0033] D. Adhesive layer The adhesive layer 4, as will be described in detail later, is provided to attach the optical laminate 100 to an optical component (typically the light guide plate 10). The adhesive layer 4 is provided on the side of the transparent layer 1 opposite to the porous layer 2. Since the adhesive layer 4 is not in contact with the porous layer 2, its configuration is not particularly limited, and any suitable configuration can be adopted. As described above, the adhesive layer 4 may be an adhesive layer or an adhesive layer. If the adhesive layer 4 is an adhesive layer, the adhesive layer 3 is distinguished as the first adhesive layer 3, and the adhesive layer 4 is distinguished as the second adhesive layer 4a. Examples of adhesives constituting the second adhesive layer 4a include (meth)acrylic adhesives. The thickness of the second adhesive layer 4a is, for example, 5 μm or more and 200 μm or less, preferably 100 μm or less. Examples of adhesives that make up the adhesive layer include thermosetting adhesives and ultraviolet curing adhesives. The thickness of the adhesive layer is, for example, 0.1 μm to 200 μm.

[0034] E. Adhesive layer (first adhesive layer) The adhesive layer 3, as will be described in more detail later, is provided for attaching the optical laminate 100 to the optical members. In other words, the optical laminate 100 has a double-sided adhesive structure that can connect two optical members. In one embodiment, the adhesive layer 3 covers the porous layer 2 so as to embed it and is in contact with the transparent layer 1 through the openings 21 in the porous layer 2.

[0035] Any suitable adhesive can be used as the adhesive constituting the adhesive layer 3, as long as it has the characteristics described above. Typical adhesives include acrylic adhesives (acrylic adhesive compositions). Typical acrylic adhesive compositions contain (meth)acrylic polymers as the main component (base polymer). (Meth)acrylic polymers may be contained in the adhesive composition in a proportion of, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more, of the solid content of the adhesive composition. (Meth)acrylic polymers contain alkyl (meth)acrylate as the main component as monomer units. (Meth)acrylate refers to acrylate and / or methacrylate. Examples of alkyl groups in alkyl (meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms in the alkyl group is preferably 3 to 9. Examples of monomers constituting (meth)acrylic polymers include alkyl (meth)acrylates, as well as comonomers such as carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic (meth)acrylates. The comonomers are preferably hydroxyl group-containing monomers and / or heterocyclic (meth)acrylates, and more preferably N-acryloylmorpholine. The acrylic adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. Examples of silane coupling agents include epoxy group-containing silane coupling agents. Examples of crosslinking agents include isocyanate-based crosslinking agents and peroxide-based crosslinking agents. Details of such adhesive layers or acrylic adhesive compositions are described, for example, in Japanese Patent No. 4140736, and the contents of said patent publication are incorporated herein by reference.

[0036] The thickness of the adhesive layer 3 is, for example, 3 μm to 30 μm, preferably 5 μm to 10 μm. Within this range of adhesive layer thickness, it is possible to achieve a thinner optical laminate while maintaining sufficient adhesion.

[0037] F. Method for manufacturing optical laminates Next, a method for manufacturing an optical laminate according to one embodiment will be described. Figures 3(a) to 3(e) are schematic cross-sectional views illustrating a method for manufacturing an optical laminate according to one embodiment of the present invention. A method for manufacturing an optical laminate according to one embodiment includes the steps of: forming a transparent layer 1 having a thickness of 20 μm or less on a substrate 5; forming a pattern of porous layers 2 having a refractive index of 1.25 or less on the surface of the transparent layer 1 opposite to the substrate 5; forming an adhesive layer 3 on the porous layer 2 so as to cover the porous layer 2 from the side opposite to the transparent layer 1; peeling the substrate 5 from the transparent layer 1; and forming an adhesive layer 4 on the surface of the transparent layer 1 opposite to the porous layer 2.

[0038] In this method, as shown in Figure 3(a), first, the transparent layer 1 is formed on the substrate 5 by any suitable method. The substrate 5 is not particularly limited in its composition as long as it can support the transparent layer 1 and the porous layer 2 so that the pattern formation of the porous layer 2 can be stably carried out. Any suitable resin film can be used as the substrate 5. Specific examples of materials that are the main components of the resin film include cellulosic resins such as triacetylcellulose (TAC); polyester resins such as polyethylene terephthalate (PET); polyvinyl alcohol resins; polycarbonate resins; polyamide resins; polyimide resins; polyethersulfone resins; polysulfone resins; polystyrene resins; polynorbornene resins; polyolefin resins; (meth)acrylic resins; and acetate resins. Thermosetting resins or UV-curing resins such as (meth)acrylic resins, urethane resins, (meth)acrylic urethane resins, epoxy resins, and silicone resins can also be used. An inorganic thin film, such as a copper oxide film, may be provided on the surface of the substrate 5. The thickness of the base material 5 is, for example, greater than 5 μm, preferably 10 μm or more, and for example 100 μm or less.

[0039] When the transparent layer 1 is composed of a resin film, a solution containing the dissolved resin film material is applied to the substrate 5, and then the coating is dried to form the transparent layer 1 (resin film). Alternatively, a separately prepared transparent layer (resin film) can be attached to the substrate. When the transparent layer 1 is composed of an inorganic thin film, the inorganic thin film material is deposited on the substrate 5 by a film deposition method such as sputtering to form the transparent layer 1 (inorganic thin film).

[0040] Next, as shown in Figure 3(b), the porous layer 2 is patterned on the surface of the transparent layer 1 opposite to the substrate 5 using any appropriate method. In other words, the porous layer 2 is patterned on the transparent layer 1 while the transparent layer 1 is supported by the substrate 5. Therefore, the patterning of the porous layer 2 can be carried out stably.

[0041] In one embodiment, the process typically includes a precursor formation step of forming a void structure, which is a precursor of a porous layer (void layer), on a transparent layer, and a crosslinking reaction step of causing a crosslinking reaction within the precursor after the precursor formation step. The process further includes a containing liquid preparation step of preparing a containing liquid containing microporous particles (hereinafter sometimes referred to as "microporous particle containing liquid" or simply "containing liquid"), and a drying step of drying the containing liquid, wherein in the precursor formation step, the microporous particles in the dried body are chemically bonded together to form the precursor. The containing liquid is not particularly limited and is, for example, a suspension containing microporous particles. In the following, the case in which the microporous particles are pulverized gel-like compounds and the void layer is a porous body (preferably a silicone porous body) containing pulverized gel-like compounds will be mainly described. However, the porous layer can be formed similarly even when the microporous particles are not pulverized gel-like compounds.

[0042] According to the method described above, for example, a porous layer (void layer) with a very low refractive index is formed. The reason for this is presumed to be as follows. However, this presumption does not limit the method of forming the porous layer.

[0043] Since the above-mentioned pulverized material is obtained by pulverizing a gel-like silicon compound, the three-dimensional structure of the gel-like silicon compound before pulverization is dispersed within the three-dimensional basic structure. Furthermore, in the above method, by coating or printing the crushed gel-like silicon compound onto a transparent layer, a precursor of a porous structure based on the three-dimensional basic structure is formed. In other words, according to the above method, a new porous structure (three-dimensional basic structure) is formed by coating with the pulverized material, which is different from the three-dimensional structure of the gel-like silicon compound. Therefore, the final void layer can achieve a low refractive index that functions to the same extent as, for example, an air layer. Furthermore, in the above method, the three-dimensional basic structure is fixed by chemically bonding the crushed materials together. Therefore, the final void layer can maintain sufficient strength and flexibility despite having a void structure. Details of the specific composition and formation method of the porous layer are described, for example, in International Publication No. 2019 / 151073. The description in that publication is incorporated herein by reference.

[0044] In one embodiment, the process is carried out by printing the above-described microporous particle-containing liquid into a predetermined pattern. Examples of printing methods include inkjet printing, gravure printing, and screen printing.

[0045] Next, as shown in Figure 3(c), an adhesive layer 3 covering the porous layer 2 is formed by any suitable method. In one embodiment, the adhesive constituting the adhesive layer 3 is applied to a resin film and dried to form the adhesive layer 3 on the resin film, and then the adhesive layer 3 is attached to the porous layer 2 and the transparent layer 1 so as to embed the porous layer 2.

[0046] Next, as shown in Figure 3(d), the substrate 5 is peeled off from the transparent layer 1. The peeling force when peeling the substrate 5 from the transparent layer 1 is preferably 1 N / 25 mm or less, more preferably 0.8 N / 25 mm or less. The peeling force is measured, for example, by the following method. A laminated film of base material 5 and transparent layer 1 is sampled in the form of a 50mm x 140mm strip, and the base material 5 side of the sample is fixed to a glass plate with double-sided tape. An acrylic adhesive layer (20μm thick) is bonded to a PET film (T100: manufactured by Mitsubishi Plastics Film Co., Ltd.), and a piece of adhesive tape cut to 25mm x 100mm is bonded to the transparent layer side of the laminated film, and the PET film is laminated. Next, the sample is chucked into an Autograph tensile tester (manufactured by Shimadzu Corporation: AG-Xplus) with a chuck distance of 100mm, and a tensile test is performed at a tensile speed of 0.3m / min. The average test force obtained from the 50mm peel test is defined as the adhesive peel strength, i.e., the adhesive force. The bonding force can also be measured using the same measurement method. In this invention, there is no clear distinction between "adhesion force" and "bonding force". In one embodiment, the adhesive layer 3 is in contact with the transparent layer 1 through the openings 21 of the porous layer 2, so that the peeling of the transparent layer 1 from the porous layer 2 when the substrate 5 is peeled off can be suppressed.

[0047] Next, as shown in Figure 3(e), an adhesive layer 4 is formed on the side of the transparent layer 1 opposite to the porous layer 2 by any suitable method. In one embodiment, the adhesive or bonding agent constituting the adhesive layer 4 is applied to a resin film and dried to form the adhesive layer 4 on the resin film, and then the adhesive layer 4 is attached to the transparent layer 1. Alternatively, the adhesive or bonding agent can be applied to the transparent layer and dried to form the adhesive layer.

[0048] As described above, an optical laminate having the components of an adhesive layer / porous layer / transparent layer / bonding layer is manufactured.

[0049] G. Usage of optical laminates An optical laminate according to an embodiment of the present invention is typically applicable to an optical product 200 comprising a light guide plate 10, and allows light propagating through the light guide plate 10 to be extracted to another optical component. In one embodiment, as shown in Figure 2, the optical laminate 100 is attached to the light guide plate 10 by an adhesive layer 4. Although not shown, other optical components are attached to the adhesive layer 3 of the optical laminate 100. The light guide plate 10 is capable of propagating light incident from a light source 11 (typically an LED) in a predetermined direction (left-right direction in Figure 2). Preferably, the porous layer 2 is arranged such that a portion with a relatively small aperture area is located on the light source 11 side of the light guide plate 10, and a portion with a relatively large aperture area is located on the opposite side from the light source 11. This allows the optical laminate 100 to uniformly extract light from the light guide plate 10 and propagate the extracted light to another optical component. Furthermore, as described above, since the optical laminate 100 is thin, color shift can be suppressed. [Examples]

[0050] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows. Unless otherwise specified, "%" and "parts" in the examples are based on mass.

[0051] (1) Refractive index Before bonding the adhesive layer onto the porous layer, a 25mm x 50mm piece was cut after the porous layer was formed and bonded to the surface of a glass plate (thickness: 3mm) via adhesive. The center of the back surface of the glass plate (approximately 20mm in diameter) was colored black with a marker to create a sample that did not reflect light from the back surface of the glass plate. The sample was placed in an ellipsometer (JAWoollam Japan: VASE) and the refractive index was measured under conditions of a wavelength of 550nm and an incident angle of 50-80 degrees. On the other hand, for refractive index measurements with an adhesive-coated configuration, after bonding the adhesive layer onto the formed porous layer, a laser (λ=407nm) was incident from the transparent layer side using a prism coupler (Metricon). The refractive index at 407nm was calculated from the measured total reflection angle, and the refractive index at 550nm was converted from the wavelength dispersion of the refractive index calculated separately using an ellipsometer (JAWoollam).

[0052] (2) Optical durability The optical laminates obtained in each example and comparative example were placed in an oven at 65°C and 95% RH (relative humidity) and subjected to a 1000-hour heating and humidification durability test. The degree of refractive index increase from the initial level after the heating and humidification durability test was measured, and laminates with an increase of 0.05 or less were marked with ○, while laminates with an increase exceeding 0.05 were marked with ×. The results are shown in Table 1.

[0053] [Manufacturing Example 1] Preparation of coating liquid for forming a porous layer (1) Gelation of silicon compounds Mixture A was prepared by dissolving 0.95 g of methyltrimethoxysilane (MTMS), a precursor of silicon compounds, in 2.2 g of dimethyl sulfoxide (DMSO). To this mixture A, 0.5 g of 0.01 mol / L aqueous oxalic acid solution was added, and the mixture was stirred at room temperature (23°C) for 30 minutes to hydrolyze the MTMS and produce mixture B containing tris(hydroxy)methylsilane. To 5.5 g of DMSO, 0.38 g of 28% by mass aqueous ammonia and 0.2 g of pure water were added. Then, the above mixture B was added, and the mixture was stirred at room temperature (23°C) for 15 minutes to gel tris(hydroxy)methylsilane, obtaining mixture C containing a gel-like silicon compound. (2) Aging process The mixed solution C containing the gel-like silicon compound prepared as described above was incubated at 40°C for 20 hours to perform the maturation process. (3) Grinding Next, the gel-like silicon compound, which had been aged as described above, was crushed into granules of several mm to several cm in size using a spatula. Then, 40 g of isobutyl alcohol (IBA) was added to mixture C, and after light stirring, it was left to stand at room temperature for 6 hours to decantate the solvent and catalyst in the gel. By performing the same decantation treatment three times, the solvent was replaced to obtain mixture D. Next, the gel-like silicon compound in mixture D was subjected to pulverization (high-pressure medialess pulverization). For the pulverization (high-pressure medialess pulverization), a homogenizer (manufactured by SMT Co., Ltd., product name "UH-50") was used, and 1.85 g of the gel-like compound and 1.15 g of IBA from mixture D were weighed into a 5 cc screw bottle, and pulverization was performed at 50 W, 20 kHz for 2 minutes. This grinding process pulverized the gel-like silicon compound in the above-mentioned mixture D, resulting in the mixture D becoming a sol E of the pulverized material. The volume-average particle size, which indicates the particle size variation of the pulverized material contained in sol E, was confirmed using a dynamic light scattering nanotrack particle size analyzer (Nikkiso Co., Ltd., UPA-EX150 model) and was found to be between 0.10 μm and 0.30 μm. Furthermore, to 0.75 g of sol E, 0.062 g of a 1.5 mass% MEK (methyl ethyl ketone) solution of a photobase generator (Wako Pure Chemical Industries, Ltd.: product name WPBG266) and 0.036 g of a 5% MEK solution of bis(trimethoxysilyl)hexane were added to obtain a coating solution for forming a porous layer.

[0054] [Manufacturing Example 2] Preparation of the First Adhesive Layer In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, 90.7 parts butyl acrylate, 6 parts N-acryloylmorpholine, 3 parts acrylic acid, 0.3 parts 2-hydroxybutyl acrylate, and 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator were charged together with 100 g of ethyl acetate. After introducing nitrogen gas and purging the mixture with nitrogen while gently stirring, the polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55°C to prepare an acrylic polymer solution. An acrylic adhesive solution was prepared by adding 0.2 parts isocyanate crosslinking agent (Coronate L, manufactured by Nippon Polyurethane Industries, Ltd., an adduct of trimethylolpropane tolylene diisocyanate), 0.3 parts benzoyl peroxide (Nippon Oil & Fats Co., Ltd., Niper BMT), and 0.2 parts γ-glycidoxypropyl methoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KBM-403) to 100 parts of the solids of the obtained acrylic polymer solution. Next, the above acrylic adhesive solution was applied to one side of a silicone-treated polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Films Co., Ltd., thickness: 38 μm) so that the thickness of the first adhesive layer after drying would be 10 μm. The film was then dried at 150°C for 3 minutes to form the first adhesive layer. The storage modulus of the obtained adhesive was 1.3 × 10⁻⁶. 5 It was (Pa).

[0055] [Manufacturing Example 3] Preparation of the second adhesive layer In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, 99 parts butyl acrylate, 1 part 4-hydroxybutyl acrylate, and 0.1 parts 2,2'-azobisisobutyronitrile as a polymerization initiator were charged together with 100 parts ethyl acetate. After introducing nitrogen gas and purging the mixture with nitrogen while gently stirring, the polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55°C to prepare an acrylic polymer solution. To 100 parts of the solid content of the obtained acrylic polymer solution, 0.1 parts isocyanate crosslinking agent (Takenate D110N, trimethylolpropane xylylene diisocyanate, manufactured by Mitsui Takeda Chemical Co., Ltd.), 0.1 parts benzoyl peroxide (Nippon Oil & Fats Co., Ltd., Niper BMT), and 0.2 parts γ-glycidoxypropyl methoxysilane (Shin-Etsu Chemical Co., Ltd.: KBM-403) were added to prepare an acrylic adhesive composition solution. Next, a solution of the above acrylic adhesive composition was applied to one side of a polyethylene terephthalate film (separator film: manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) treated with a silicone release agent, and dried at 150°C for 3 minutes to form a second adhesive layer with a thickness of 12 μm on the surface of the separator film. The storage modulus of the obtained adhesive was 8.2 × 10⁻⁶. 4 It was (Pa).

[0056] [Example 1] An aqueous solution of polyvinyl alcohol (PVA) was applied to a substrate (PET resin film), and the coating was dried. This formed a transparent PVA layer on the substrate. The thickness of the PVA layer was 3 μm. Next, the porous layer forming coating liquid from Production Example 1 was pattern-coated onto the side of the PVA layer opposite to the substrate using gravure printing, and the coating film was dried. This formed a patterned porous layer on the PVA layer. The pattern of the porous layer had a gradient distribution in which the aperture ratio per unit area increased towards one side in the width direction. The refractive index of the porous layer was 1.19. The thickness of the porous layer was 0.9 μm. Next, the first adhesive layer obtained in manufacturing example 2 was attached to the porous layer. Next, the PET substrate was peeled from the PVA layer at a peel angle of 180° and a peel speed of 300 mm / min. The peel force at this time was measured using an autograph tensile tester. The results are shown in Table 1. Next, the second adhesive layer obtained in Manufacturing Example 3 was attached to the side of the PVA layer opposite to the porous layer. As a result, an optical laminate having the configuration of a first adhesive layer / porous layer / transparent layer / second adhesive layer was obtained.

[0057] [Example 2] An optical laminate was obtained in the same manner as in Example 1, except that a polymethyl methacrylate (PMMA) aqueous solution was used instead of a PVA aqueous solution to form a PMMA layer as a transparent layer on the substrate.

[0058] [Example 3] An optical laminate was obtained in the same manner as in Example 1, except that an ethanol solution of polyvinyl acetal was used instead of an aqueous PVA solution to form a polyvinyl acetal layer as a transparent layer on the substrate.

[0059] [Example 4] An optical laminate was obtained in the same manner as in Example 1, except that a substrate was prepared in which a CuO sputtered film was laminated on a polyethylene terephthalate (PET) film, and an SiO2 layer as a transparent layer was formed on the CuO sputtered film by sputtering.

[0060] [Example 5] An optical laminate was obtained in the same manner as in Example 1, except that the porous layer-forming coating solution of Manufacturing Example 1 was pattern-coated using inkjet printing instead of gravure printing.

[0061] [Comparative Example 1] A 100 μm thick substrate (cycloolefin (COP) film; ZF16; manufactured by Nippon Zeon Co., Ltd.) was pattern-coated with the porous layer-forming coating liquid from Production Example 1 by gravure printing, and the coating film was then dried. This formed a patterned porous layer on the substrate. Next, the first adhesive layer obtained in Manufacturing Example 2 was attached to the porous layer. Then, the substrate was peeled off from the porous layer, and the second adhesive layer obtained in Manufacturing Example 3 was attached to the peeled surface. As a result, an optical laminate having the configuration of a first adhesive layer / porous layer / second adhesive layer was obtained.

[0062] [Comparative Example 2] A porous layer-forming coating solution from Manufacturing Example 1 was pattern-coated onto a 30 μm thick substrate (acrylic resin film) using gravure printing, and the coating film was then dried. This formed a patterned porous layer on the substrate. Next, the first adhesive layer obtained in Manufacturing Example 2 was attached to the porous layer. Then, the second adhesive layer obtained in Manufacturing Example 3 was attached to the side of the substrate opposite to the porous layer. As a result, an optical laminate having the configuration of a first adhesive layer / porous layer / substrate / second adhesive layer was obtained.

[0063] [Table 1]

[0064] As is clear from Table 1, according to the embodiments of the present invention, by providing a transparent layer with a thickness of 20 μm or less between the patterned porous layer and the adhesive layer, it is possible to reduce the thickness of the optical laminate and achieve excellent optical durability. [Industrial applicability]

[0065] The optical laminate according to the embodiment of the present invention can be used in various optical products, and is particularly suitable for use in optical products that include a light guide plate. [Explanation of Symbols]

[0066] 1 transparent layer 1a Barrier layer 2. Porous layer 21 Opening 3. Adhesive layer 4 Adhesive layer 100 Optical laminate 200 optical products

Claims

1. A transparent layer with a thickness of 5 μm or less; A porous layer having a refractive index of 1.25 or less is directly provided in a predetermined pattern on one side of the thickness direction of the transparent layer; An adhesive layer positioned on the opposite side of the transparent layer from the porous layer and in contact with the transparent layer; An adhesive layer positioned on the opposite side of the transparent layer from the adhesive layer and covering the porous layer; An optical laminate equipped with the following features.

2. The optical laminate according to claim 1, wherein the transparent layer has a barrier function that prevents components constituting the adhesive layer from penetrating into the porous layer.

3. The optical laminate according to claim 2, wherein the porosity of the transparent layer is smaller than that of the porous layer.

4. The adhesive layer has a storage modulus of 1.0 × 10 at 23°C. ５ An optical laminate according to any one of claims 1 to 3, comprising an adhesive having a strength of (Pa) or higher.

5. A step of forming a transparent layer with a thickness of 20 μm or less on a substrate; A step of forming a pattern of porous layers having a refractive index of 1.25 or less on the surface of the transparent layer opposite to the substrate; A step of forming an adhesive layer so as to cover the porous layer from the opposite side of the transparent layer to the porous layer; A step of peeling the substrate from the transparent layer; A method for manufacturing an optical laminate, comprising the steps of: forming an adhesive layer on the transparent layer opposite to the porous layer;

6. The method for manufacturing an optical laminate according to claim 5, wherein the peeling force when peeling the substrate from the transparent layer is 1 N / 25 mm or less.

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