Optical film, and optical barrier film, color conversion film, and backlight unit using optical film

Abstract

One aspect of the present disclosure provides an optical film comprising a first film substrate and a coating layer formed on the first film substrate. The coating layer of the optical film comprises a binder resin and fine particles having an average particle size of 0.5 μm or more and 10.0 μm or less, and a standard deviation of the particle size of less than half of the average particle size.

Description

Technology Field

[0001] The present disclosure relates to an optical film, and, an optical barrier film, a color conversion film, and a backlight unit using the same. Background Technology

[0002] Various optical films are used in electronic devices such as liquid crystal displays. The invention described in Patent Document 1 relates to a light-diffusing sheet used in lighting fixtures, electrical signboards, back-projection screens, liquid crystal displays, etc. The light-diffusing sheet described in Patent Document 1 comprises a light-diffusing layer containing spherical particles made of polymethyl methacrylate. Prior art literature

[0003] Japanese Patent Publication No. 3790571 The problem to be solved

[0004] However, in the invention described in Patent Document 1, if there is a large variation in the particle size of the spherical particles contained in the light-diffusing layer, or if the spherical particles aggregate to form secondary particles, or if the dispersibility in the light-diffusing layer is insufficient, a variation in the haze value (cloudiness), which is an indicator of light diffusivity, is likely to occur, and there is room for improvement in this regard.

[0005] The present disclosure aims to provide an optical film having a sufficiently small in-plane deviation of haze value, and an optical barrier film, a color conversion film, and a backlight unit using the same. means of solving the problem

[0006] One aspect of the present disclosure provides an optical film. The optical film comprises a first film substrate and a coating layer formed on the first film substrate, wherein the coating layer contains a binder resin and fine particles having an average particle size of 0.5 μm or more and 10.0 μm or less, and a standard deviation of the particle size of less than half of the average particle size. According to the optical film, since the variation in particle size of the fine particles in the coating layer is sufficiently small, more specifically, since the average particle size is within a predetermined range (0.5 μm or more and 10.0 μm or less) and the standard deviation of the particle size of less than half of the average particle size, an optical film having a coating layer having a sufficiently small variation in the haze value is provided. More specifically, the following problems can be solved.

[0007] In the manufacturing process of the above optical film, a coating layer can be formed on a first film substrate, for example, by wet coating. Wet coating is a method of forming a coating layer by applying a coating solution containing a binder resin and fine particles dispersed therein onto a first film substrate. If the deviation (standard deviation) of the particle size of the fine particles contained in the coating solution is large, the particle size distribution of the fine particles observed in the formed coating layer inevitably becomes large. On the other hand, even if the design value of the particle size of the fine particles has a sufficiently small deviation, if the dispersibility of the fine particles in the binder resin is insufficient due to aggregation of the fine particles, the particle size distribution of the fine particles observed in the formed coating layer becomes larger than the design value of the particle size of the fine particles. According to the inventors' investigation, there is a problem that if the deviation of the particle size of the fine particles contained in the coating layer is large, the light diffusivity (haze value) expressed by the coating layer is not stable (the deviation within the plane of the optical film becomes large).

[0008] In addition to the above problems, in the manufacturing process of a color-converting film using an optical film, the thickness of the optical film (and the thickness of the optical barrier film containing it) affects the coating thickness of the color-converting material, and thus significantly affects the performance of the color-converting film. More specifically, if there is a large variation in the particle size of the fine particles contained in the optical film, for example, large particles protrude from the surface of the binder resin, and since this part can become the maximum thickness of the optical film, it causes variation in the performance of the color-converting film. According to the optical film related to the present disclosure, these problems can be sufficiently solved.

[0009] In order to suppress the detachment (falling off of powder) of fine particles from the coating layer, it is preferable that the arithmetic mean roughness Ra of the coating layer (14) be 0.4 μm or less.

[0010] In order to prevent the coating layer from being damaged by other members (e.g., prism sheets) or the coating layer from being damaged by other members (e.g., light guide plates), it is preferable that the hardness of the coating layer be in the range of H to 2H in pencil hardness. Since the variation in the particle size of fine particles in the coating layer is sufficiently small, the variation in pencil hardness in the coating layer can also be sufficiently small.

[0011] It is preferable that the hardness of the above fine particles be 100 or less on the Rockwell R hardness scale. By keeping the hardness of the fine particles within the above range, damage to the coating layer and other components can be suppressed. The surface resistivity of the coating layer is 1.0 × 10⁻⁶ 13 It is preferable that the value be Ω / □ or less. By having the surface resistivity of the coating layer within the above range, the coating layer can preferably be provided with antistatic performance.

[0012] The present disclosure provides an optical barrier film related to a first embodiment. The optical barrier film comprises a barrier layer and the optical film, wherein the barrier layer is formed on the surface of the optical film facing the first film substrate. The present disclosure provides an optical barrier film related to a second embodiment. The optical barrier film comprises a barrier composite layer including a second film substrate and a barrier layer, and the optical film, wherein the barrier composite layer is formed on the surface of the optical film facing the first film substrate. Since the optical barrier films of these embodiments comprise the optical film, it is possible to resolve the problem described above, and at the same time, prevent damage to the coating layer and other members while suppressing blocking with other members in contact with the optical barrier film.

[0013] The above barrier layer is SiO x It is preferable to include an inorganic deposition thin film layer made of silicon oxide represented by (1.0 ≤ x ≤ 2.0). As the barrier layer includes the inorganic deposition thin film layer, the barrier performance of the optical barrier film tends to be improved.

[0014] One aspect of the present disclosure provides a color conversion film. The color conversion film comprises a color conversion layer and two protective films disposed to sandwich the color conversion layer, wherein at least one of the two protective films is an optical barrier film, and the optical barrier film is disposed such that the coating layer faces the opposite side to the color conversion layer. Since the color conversion film comprises the optical barrier film, it is possible to resolve the problem described above, and, for example, even if it overlaps with a light guide plate constituting a backlight unit, damage to the light guide plate can be suppressed. Furthermore, since damage to the barrier layer itself is also suppressed, the intrusion of air and water vapor into the color conversion layer is appropriately reduced, and the color conversion performance of the color conversion film can be maintained over a long period of time.

[0015] One aspect of the present disclosure provides a backlight unit. The backlight unit comprises a light source, a light guide plate, and a color conversion film disposed on the light guide plate, wherein the color conversion film is disposed such that the coating layer contacts the light guide plate. Since the backlight unit comprises the color conversion film, it is possible to resolve the problem described above and, at the same time, prevent damage to the light guide plate that the color conversion film contacts. Furthermore, since damage to the barrier layer itself is also prevented, the intrusion of air and water vapor into the color conversion layer is appropriately reduced, thereby allowing good white light to be obtained from the backlight unit over a long period of time. Effects of the invention

[0016] According to the present disclosure, an optical film having a sufficiently small in-plane deviation of haze value, and an optical barrier film, a color conversion film, and a backlight unit using the same are provided. Brief explanation of the drawing

[0017] FIG. 1 is a schematic cross-sectional view of an optical film related to one embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of an optical barrier film related to a first embodiment of the present disclosure. FIG. 3 is a schematic cross-sectional view of an optical barrier film related to a second embodiment of the present disclosure. FIG. 4 is a schematic cross-sectional view of an optical barrier film related to a third embodiment of the present disclosure. FIG. 5 is a schematic cross-sectional view of an optical barrier film related to a fourth embodiment of the present disclosure. FIG. 6 is a schematic cross-sectional view of a color conversion film related to one embodiment of the present disclosure. FIG. 7 is a schematic cross-sectional view of a backlight unit related to one embodiment of the present disclosure. FIG. 8(a) is an image showing the coating layer of the optical film related to Example 2 magnified with an optical microscope, and FIG. 8(b) is an image showing the particles surrounded by circles in FIG. 8(a) further magnified. FIG. 9 is an optical microscope image showing a point where fine particles are confirmed to have been eroded in the coating layer of the optical film related to Example 2. Specific details for implementing the invention

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, in the drawings, the same or equivalent elements are given the same reference numerals, and redundant descriptions are omitted.

[0019] [Optical Film]

[0020] FIG. 1 is a schematic cross-sectional view of an optical film related to one embodiment of the present disclosure. In FIG. 1, the optical film (10) comprises a first film substrate (12) and a coating layer (14) formed on the first film substrate (12).

[0021] (Coating layer)

[0022] The coating layer (14) is a layer that has the function of diffusing light and may also be referred to as a "matte layer," etc. The coating layer (14) contains fine particles (18), and at least some of the fine particles (18) protrude from the surface opposite to the first film substrate (12) of the coating layer (14). By having at least some of the fine particles (18) among the plurality of fine particles in the coating layer (14) protrude from the surface of the coating layer (14), the coating layer (14) may have an uneven shape on its surface. By having the coating layer (14) have an uneven shape on the surface opposite to the first film substrate (12), that is, by having an uneven surface (14A), blocking (adhesion) with said other member can be suppressed when another member is overlapped on the surface of the coating layer (14) of the optical film (10). In addition, the microparticle (18) is said to "protrude" on the surface of the coating layer (14), so that at least a portion of the surface of the microparticle (18) is located outside the reference plane, using the surface of the part of the coating layer (14) where the microparticle (18) is not present as a reference plane. The surface of the protruding microparticle (18) may be exposed or covered with a binder resin, etc., as described later.

[0023] The average particle size of the microparticles (18) is 0.5 μm or more and 10.0 μm or less, preferably 1.0 μm or more and 10.0 μm or less, and more preferably 2.0 μm or more and 8.0 μm or less. If the average particle size of the microparticles (18) is 0.5 μm or more, it becomes easier to suppress the occurrence of blocking between the coating layer (14) and other members in contact with it. On the other hand, if the average particle size of the microparticles (18) is 10.0 μm or less, it becomes easier to control the uneven shape of the surface of the coating layer (14) to be small due to the protruding microparticles (18), so it becomes easier to suppress damage to other members in contact with the uneven surface (14A) of the coating layer (14).

[0024] The standard deviation of the particle size of the fine particles (18) is less than 1 / 2 of the average particle size of the fine particles (18), preferably less than 1 / 3, and more preferably less than 1 / 4. If this value is less than 1 / 2, the in-plane deviation of the haze value (blur) in the coating layer (14) can be made sufficiently small. Also, since the standard deviation of the particle size of the fine particles (18) is less than 1 / 2 of the average particle size of the fine particles (18) means that there are sufficiently few particles with an excessively large particle size, in the manufacturing process of the optical film (10), problems such as powdering (fluffing) or appearance caused by large particles detaching after coating can be sufficiently suppressed. In addition to this, when forming a coating layer (14) by wet coating, the thickness of the coating layer (14) can be managed by adjusting the amount of application, so there is an advantage that it is easy to form a coating layer (14) of the desired thickness. Also, the lower limit of this value is about 1 / 5 in terms of the manufacturing technology of the fine particles (18).

[0025] As described above, the detachment of fine particles (powder shedding) from the coating layer (14) can be sufficiently suppressed if there are few particles with an excessively large particle size in the coating layer (14). Whether there are many large particles in the coating layer (14) (whether powder shedding is likely to occur) can be determined by measuring the arithmetic mean roughness Ra of the coating layer (14). In terms of sufficiently suppressing powder shedding, the arithmetic mean roughness Ra of the coating layer (14) is preferably 0.4 μm or less, and more preferably 0.3 μm or less.

[0026] It is preferable that the pencil hardness of the coating layer (14) be in the range of H to 2H. Since the variation in particle size of the fine particles (18) contained in the coating layer (14) is sufficiently small, the variation in pencil hardness in the coating layer (14) can also be sufficiently small. By having a pencil hardness of H or higher, the coating layer (14) can be prevented from being damaged by other components (e.g., prism sheets). On the other hand, by having a pencil hardness of 2H or lower, the coating layer (14) can be prevented from being damaged by other components (e.g., light guide plates). The pencil hardness referred to here is a value measured in accordance with JIS K 5600-5-4 : 1999 (ISO / DIS 15184 : 1996) “Scratch hardness (pencil method)”, and means a value measured by applying a load of 500 g to the tip of the pencil.

[0027] The thickness of the coating layer (14) is preferably 0.5 μm to 30 μm. In this specification, the thickness of the coating layer (14) is the average thickness including the uneven shape. The thickness of the coating layer (14) is measured by the mass method according to JIS K 5600. If the coating layer (14) has a thickness in this range, fine particles (18) are more likely to protrude from the surface of the coating layer (14), and an uneven surface (14A) is more likely to be formed on the coating layer (14).

[0028] The content of fine particles (18) in the coating layer (14) is preferably 2 to 80 mass% based on the total amount of the coating layer (14), and more preferably 5 to 50 mass%. If the content of fine particles (18) is 2 mass% or more, the fine particles (18) are more likely to protrude from the surface of the coating layer (14), making it easier to suppress the occurrence of blocking between the coating layer (14) and other members in contact with it. On the other hand, if the content of fine particles (18) is 80 mass% or less, it is easier to suppress damage to other members in contact with the uneven surface (14A) of the coating layer (14).

[0029] Among the fine particles (18) contained in the coating layer (14), the ratio of fine particles (18) protruding on the surface of the coating layer (14) is preferably 10 to 100%, and more preferably 50 to 100%. If the ratio of protruding fine particles (18) is 10% or more, it becomes easier to suppress the occurrence of blocking.

[0030] The hardness of the fine particles (18) is preferably 100 or less on the Rockwell R hardness scale and 90 or less. If the hardness of the fine particles (18) on the Rockwell R hardness scale is 100 or less, it becomes easier to prevent other members in contact with the uneven surface (14A) of the coating layer (14) from being damaged by the protruding fine particles (18). Also, from the same perspective, the hardness of the fine particles (18) is preferably 50 or less on the Rockwell M hardness scale.

[0031] The microparticles (18) are not particularly limited as long as their Rockwell hardness is within the above range, and may be inorganic microparticles or organic microparticles. In order to achieve Rockwell hardness within the above range, it is preferable that the microparticles (18) be organic microparticles. Examples of organic microparticles include polyolefin resins such as polypropylene; polyamide resins such as nylon; acrylic urethane resins; styrene resins; urethane resins; benzoguanamine resins; silicone resins; acrylic resins, etc. It is more preferable that the microparticles (18) be at least one type of organic microparticle selected from the group consisting of polyolefin resins, polyamide resins, urethane resins, and silicone resins, and it is even more preferable that they be polypropylene resin particles or urethane resin particles. Furthermore, if the microparticles (18) are organic microparticles, the microparticles (18) are prone to becoming spherical particles, and shape control for smooth uneven shapes becomes easier. The microparticles (18) may be used as a single type or in combination of multiple types. Additionally, the coating layer (14) may contain, in addition to the microparticles (18), particles whose Rockwell hardness is not within the above range, to the extent that it does not impede the effects of the present disclosure.

[0032] The coating layer (14) may contain a conductive material. If the coating layer (14) contains a conductive material, the surface resistivity of the coating layer (14) tends to decrease. The surface resistivity of the coating layer (14) is 1.0 × 10⁻⁶. 13 It is preferable that the surface resistivity of the coating layer (14) be Ω / □ or less. 13If Ω / □ or less, the coating layer (14) is preferably provided with antistatic performance, so the attachment or incorporation of dust or the like to the coating layer (14) tends to decrease. Because of this, in the manufacturing process of the backlight unit, damage to the coating layer (14) or other components caused by dust tends to decrease. Examples of conductive materials include quaternary ammonium salt compounds, conductive polymers, metal oxides, etc. The conductive material may be used as a single type or in combination with multiple types.

[0033] A quaternary ammonium salt compound is a compound having a quaternary ammonium salt as a functional group within its molecule, for example, a (meth)acrylate compound having a quaternary ammonium salt as a functional group within its molecule. A (meth)acrylate compound having a quaternary ammonium salt as a functional group within its molecule may be, for example, a (meth)acrylic acid ester of a polyhydric alcohol having a quaternary ammonium salt as a functional group within its molecule (i.e., a quaternary ammonium salt (meth)acrylate ester compound), or a reaction product such as a diisocyanate, a polyhydric alcohol, and a hydroxyalkyl ester of (meth)acrylic acid (i.e., a quaternary ammonium salt urethane (meth)acrylate compound). In addition, polyether resins, polyester resins, epoxy resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol-polyene resins, etc., having acrylate-based functional groups may be used as quaternary ammonium salt compounds. The quaternary ammonium salt comprises a quaternary ammonium cation and an anion. As the anion of the quaternary ammonium salt, for example, Cl - , Br - , I - , F - , HSO4 - , SO4 2- , NO3 - , PO4 3- , HPO4 2- , H2PO4 - , SO3 - , OH -You can lift the back.

[0034] The conductive polymer may consist of one or more mixtures selected from polyacetylene, polyaniline, polythiophene, polypyrrole, polyphenylene sulfide, poly(1,6-heptadiene), polybiphenylene (polyparaphenylene), polyparaphenylene sulfide, polyphenylacetylene, poly(2,5-thienylene), and derivatives thereof.

[0035] Examples of metal oxides include zirconium oxide, antimony-containing tin oxide (ATO), phosphorus-containing tin oxide (PTO), tin-containing indium oxide, aluminum oxide, cerium oxide, zinc oxide, aluminum-containing zinc oxide, tin oxide, lithium salts, antimony-containing zinc oxide, indium-containing zinc oxide, etc.

[0036] The particle size of the conductive material is, for example, 500 nm or less, and preferably 100 nm or less. If the particle size of the conductive material is 500 nm or less, even if particles with Rockwell hardness not within the above range are used as the conductive material, there is a tendency to lower the surface resistivity of the coating layer (14) without hindering the effect of damage suppression. The content of the conductive material in the coating layer (14) is appropriately set for each type of conductive material so that the surface resistivity of the coating layer (14) is within the desired range. In addition, from the perspective of adhesion between the coating layer (14) and the first film substrate (12), the content of the conductive material in the coating layer (14) may be 30 mass% or less.

[0037] In FIG. 1, the coating layer (14) additionally contains a binder resin (16). The binder resin (16) is a resin with excellent optical transparency and may be a molded body of a thermoplastic resin, or a cured body of a thermosetting resin or a radiation-curable resin. Examples of resins constituting the binder resin include polyester resin, acrylic resin, acrylurethane resin, polyester acrylate resin, polyurethane acrylate resin, epoxy acrylate resin, urethane resin, epoxy resin, polycarbonate resin, cellulose resin, acetal resin, polyethylene resin, polystyrene resin, polyamide resin, polyimide resin, melamine resin, phenol resin, silicone resin, etc.

[0038] When the binder resin (16) is a cured product of a thermosetting resin, the cured product of the thermosetting resin may be a reaction product of the thermosetting resin and the curing agent. It is preferable that the binder resin (16) be a cured product of a thermosetting resin having hydroxyl groups and an isocyanate curing agent. In this case, the isocyanate groups of the isocyanate curing agent and the hydroxyl groups of the thermosetting resin react to cure the thermosetting resin and the isocyanate curing agent.

[0039] In terms of being able to crosslink polyol resins, it is preferable that the isocyanate curing agent be an isocyanate curing agent having two or more isocyanate groups, and more preferable that it be a diisocyanate curing agent having two isocyanate groups. Examples of diisocyanate curing agents include aliphatic diisocyanates such as hexamethylene diisocyanate and xylylene diisocyanate, aromatic diisocyanates such as toluene diisocyanate and diphenylmethane diisocyanate, and derivatives thereof.

[0040] A coating layer (14) is formed, for example, by applying a coating layer composition onto a first film substrate (12) and, if necessary, drying and curing the coating film or molding it. The coating layer composition is composed of, for example, the fine particles (18) described above, a conductive material, and a thermoplastic resin, a thermosetting resin, or a radiation-curable resin. The coating layer composition may additionally contain a solvent, a photopolymerization initiator, a leveling agent, or a lubricant. For applying the coating layer composition, for example, a roll coater, a reverse roll coater, a gravure coater, a micro-gravure coater, a knife coater, a bar coater, a wire bar coater, a die coater, a dip coater, etc., are used.

[0041] When the coating layer composition contains a solvent, the coating film is dried by heating or blowing air. When heating, the drying temperature is, for example, about 60 to 100°C, and the drying time is, for example, about 10 seconds to 10 minutes. Most of the solvent is removed from the coating film by the above drying.

[0042] When the coating layer composition contains a thermosetting resin, the coating film is heated after drying. The heating temperature is, for example, about 50 to 100°C, and the heating time is, for example, about 12 hours to 3 days. The coating film is cured by the above heating.

[0043] When the coating layer composition contains a radiation-curable resin, radiation is irradiated onto the coating film after drying. The radiation may be, for example, ultraviolet rays or electron beams. Ultraviolet rays are generated from light sources such as, for example, high-pressure mercury lamps, low-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, carbon arcs, and xenon arcs. In addition, electron beams are generated from various electron beam accelerators such as, for example, Cockcroft-Walton type, Van de Graaff type, resonant transformer type, insulated core transformer type, linear type, dynamiteron type, and high-frequency type. The coating film is cured by the radiation irradiation.

[0044] (Installation on the first film)

[0045] The first film substrate (12) may be, for example, an organic polymer film. The first film substrate (12) is preferably transparent, and specifically, the total light transmittance of the first film substrate (12) is preferably 80% or more. The first film substrate (12) may be, for example, a polyolefin-based film substrate such as polyethylene or polypropylene, a polyester-based film substrate such as polyethylene terephthalate or polyethylene naphthalate, a cellulose-based film substrate such as triacetylcellulose, diacetylcellulose, or cellophane, a polyamide-based film substrate such as 6-nylon or 6,6-nylon, an acrylic-based film substrate such as polymethyl methacrylate, a polystyrene-based film substrate, a polyvinyl chloride-based film substrate, a polyimide-based film substrate, a polyvinyl alcohol-based film substrate, a polycarbonate-based film substrate, and an ethylene vinyl alcohol-based film substrate.

[0046] The thickness of the first film substrate (12) is preferably, for example, 5 μm or more and 300 μm or less. If the thickness of the first film substrate (12) is 5 μm or more, the strength of the first film substrate (12) is improved, and, for example, in a backlight unit manufacturing process, the handling of the first film substrate (12) tends to become easier. On the other hand, if the thickness of the first film substrate (12) is 300 μm or less, the handling of the first film substrate (12) tends to become easier during a roll-to-roll film formation process.

[0047] [Optical Barrier Film]

[0048] (First embodiment)

[0049] FIG. 2 is a schematic cross-sectional view of an optical barrier film related to a first embodiment of the present disclosure. In FIG. 2, the optical barrier film (20A) comprises a barrier layer (24) and an optical film (10). The barrier layer (24) is formed on the surface of the optical film (10) on the side of the first film substrate (12). That is, the optical barrier film (20A) may be said to comprise a first film substrate (12), a coating layer (14) formed on one surface of the first film substrate (12), and a barrier layer (24) formed on the other surface of the first film substrate (12). As described above, since the coating layer (14) has a sufficiently small in-plane deviation of the haze value, the in-plane deviation of the haze value of the optical barrier film (20A) can also be made sufficiently small.

[0050] The optical film (10) has an uneven shape on the surface of the coating layer (14), that is, it has an uneven surface (14A). By doing so, when another member is overlapped on the surface of the optical film (10) (coating layer (14)) of the optical barrier film (20A), blocking with said other member can be suppressed. Also, even when the optical barrier film (20A) is overlapped with another member, damage to the other member in contact with the coating layer (14) and the uneven surface (14A) of the coating layer (14) by protruding fine particles (18) can be suppressed. Additionally, the barrier layer (24) may be formed on the surface of the first film substrate (12) of the optical film (10) with an adhesive layer interposed therebetween.

[0051] The barrier layer (24) is a layer capable of blocking the intrusion of gas. The barrier layer (24) preferably includes an inorganic thin film layer. The inorganic thin film layer preferably contains an inorganic compound and contains a metal or a metal oxide. Examples of the metals include aluminum, copper, and silver. In addition, the metal oxide may be at least one metal oxide selected from the group consisting of, for example, yttrium tantalum oxide, aluminum oxide, silicon oxide, and magnesium oxide, and it is preferably silicon oxide because it is inexpensive and has excellent barrier performance in blocking the intrusion of water vapor, etc. Silicon oxide is SiO x It is represented as such, and it is preferable that x in the formula be 1.5 or more and 2.0 or less. If x is 1.5 or more, more preferably 1.7 or more, transparency tends to improve. Also, if x is 2.0 or less, barrier properties tend to be excellent. The inorganic thin film layer is formed, for example, by a deposition method or a sputtering method, and it is preferable that it be an inorganic deposition thin film layer formed by a deposition method. The thickness of the inorganic thin film layer is preferably 10 to 300 nm, and more preferably 20 to 100 nm. When the thickness of the inorganic thin film layer is 10 nm or more, it is easier to obtain a uniform film and gas barrier properties tend to be obtained. On the other hand, when the thickness of the inorganic thin film layer is 300 nm or less, flexibility can be maintained in the inorganic thin film layer, and it tends to be difficult for cracks, etc., to occur due to external forces such as bending or tension after film formation.

[0052] The barrier layer (24) may include a gas barrier coating layer. It is preferable that the gas barrier coating layer be formed from a composition containing at least one selected from the group consisting of a metal alkoxide represented by the following formula (1) and its hydrolysate.

[0053] M(OR 1 ) m (R2 ) n-m … (1)

[0054] In the above equation (1), R 1 and R 2 Each is independently a monovalent organic group having 1 to 8 carbon atoms, and is preferably an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer from 1 to n. Examples of metal alkoxides include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum [Al(O-iso-C3H7)3]. It is preferable that the metal alkoxide be tetraethoxysilane or triisopropoxyaluminum because it is relatively stable in an aqueous solvent after hydrolysis. Examples of the hydrolysis products of the metal alkoxides include silica (Si(OH)4), which is the hydrolysis product of tetraethoxysilane, and aluminum hydroxide (Al(OH)3), which is the hydrolysis product of tripropoxyaluminum. These can be used not only as a single type, but also in combination with multiple types.

[0055] The above composition may additionally contain a hydroxyl group-containing polymer compound. Examples of hydroxyl group-containing polymer compounds include water-soluble polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and starch. For barrier properties, the hydroxyl group-containing polymer compound is preferably polyvinyl alcohol. These may be used not only as a single type but also in combination of multiple types. The content of the hydroxyl group-containing polymer compound in the above composition is, for example, 10 to 90 mass%.

[0056] The thickness of the gas barrier coating layer is preferably 50 to 1000 nm, and preferably 100 to 500 nm. If the thickness of the gas barrier coating layer is 50 nm or more, it tends to provide more sufficient gas barrier properties, and if it is 1000 nm or less, it tends to maintain sufficient flexibility.

[0057] In the case where the barrier layer (24) includes both an inorganic thin film layer and a gas barrier coating layer, an inorganic thin film layer may be formed on the surface of the first film substrate (12), and a gas barrier coating layer may be formed on the surface of the inorganic thin film layer.

[0058] (Second embodiment)

[0059] FIG. 3 is a schematic cross-sectional view of an optical barrier film related to a second embodiment of the present disclosure. In FIG. 3, the optical barrier film (20B) comprises a barrier composite layer (22a) comprising a second film substrate (12a) and a barrier layer (24a), and an optical film (10). The barrier composite layer (22a) is formed on the optical film (10) with an adhesive layer (26a) interposed therebetween the first film substrate (12) and the barrier layer (24a).

[0060] By providing a barrier composite layer (22a) comprising a second film substrate (12a) to the optical barrier film (20B), an optical barrier film can be realized that has excellent water vapor barrier properties and oxygen barrier properties, and further reduces damage to the barrier layer, etc. The material of the second film substrate (12a) may be the same as that of the first film substrate (12). The thickness of the second film substrate (12a) is preferably, for example, 5 μm or more and 50 μm or less. If the thickness of the second film substrate (12a) is 5 μm or more, the strength of the second film substrate (12a) is improved, and, for example, in a backlight unit manufacturing process, the handling of the second film substrate (12a) tends to become easier. On the other hand, if the thickness of the second film substrate (12a) is 50 μm or less, the decrease in barrier properties due to the intrusion of water vapor or oxygen from the cross-section of the substrate can be suppressed.

[0061] The adhesive layer (26a) is formed with an adhesive or a pressure-sensitive adhesive. Examples of the adhesive include acrylic adhesives, epoxy adhesives, urethane adhesives, etc. It is preferable that the adhesive contains epoxy resin. By the adhesive containing epoxy resin, the adhesion between the optical film (10) and the barrier composite layer (22a) can be improved. In addition, examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesives, polyvinyl ether pressure-sensitive adhesives, urethane pressure-sensitive adhesives, silicone pressure-sensitive adhesives, starch paste adhesives, etc. The thickness of the adhesive layer (26a) is preferably 0.5 to 50 μm, more preferably 1 to 20 μm, and even more preferably 2 to 6 μm. Since the thickness of the adhesive layer (26a) is 0.5 μm or more, it is easier to obtain adhesion between the optical film (10) and the barrier composite layer (22a), and since the thickness is 50 μm or less, it is easier to obtain better gas barrier properties.

[0062] The optical barrier film (20B) related to the second embodiment can be obtained, for example, by forming a barrier layer (24a) on a second film substrate (12a) separately from the optical film (10) to produce a barrier composite layer (22a), then laminating the optical film (10) and the barrier composite layer (22a), and performing aging as needed. The method of manufacturing the optical barrier film (20B) related to the second embodiment is not limited to the above.

[0063] (Third embodiment)

[0064] FIG. 4 is a schematic cross-sectional view of an optical barrier film related to a third embodiment of the present disclosure. In FIG. 4, the optical barrier film (20C) comprises a barrier composite layer (22a) comprising a second film substrate (12a) and a barrier layer (24a), and an optical film (10). The barrier composite layer (22a) is formed on the optical film (10) with an adhesive layer (26a) interposed therebetween the first film substrate (12) and the second film substrate (12a).

[0065] (Fourth embodiment)

[0066] FIG. 5 is a schematic cross-sectional view of an optical barrier film related to a fourth embodiment of the present disclosure. In FIG. 5, the optical barrier film (20D) comprises a barrier composite layer (22a) comprising a second film substrate (12a) and a barrier layer (24a), a barrier composite layer (22b) comprising a third film substrate (12b) and a barrier layer (24b), and an optical film (10). The barrier composite layer (22a) is formed on the optical film (10) with an adhesive layer (26a) interposed so that the first film substrate (12) and the second film substrate (12a) face each other, and the barrier composite layer (22b) is formed on the barrier composite layer (22a) with an adhesive layer (26b) interposed so that the barrier layer (24a) and the barrier layer (24b) face each other.

[0067] [Color conversion film]

[0068] FIG. 6 is a schematic cross-sectional view of a color conversion film related to one embodiment of the present disclosure. The color conversion film is a film capable of converting the wavelength of a portion of light from a light source of a backlight unit for a liquid crystal display. In FIG. 6, the color conversion film (30) comprises a color conversion layer (32) and an optical barrier film (20) positioned between the color conversion layer (32). The optical barrier film (20) may be any of the optical barrier films (20A, 20B, 20C, 20D) described above, and the configurations of the two optical barrier films (20) may be identical or different from each other. The optical barrier film (20) is positioned on the color conversion layer (32) such that a coating layer (14) faces the opposite side of the color conversion layer (32). Accordingly, the color conversion film (30) has an uneven surface (20F, 20G) derived from the uneven surface (14A) of the coating layer (14). As described above, since the variation in particle size of the fine particles contained in the coating layer (14) of the optical barrier film (20) is sufficiently small, the variation in performance of the color conversion film (30) can also be sufficiently small.

[0069] The color conversion film (30) has an uneven surface (20F, 20G) on its surface, so that when another member is overlapped on the uneven surface (20F, 20G) of the color conversion film (30), blocking with said other member can be suppressed. Also, even if the color conversion film (30) is overlapped with, for example, a light guide plate constituting a backlight unit, damage to the light guide plate by protruding fine particles (18) can be suppressed. In addition, damage to the barrier layer itself is also suppressed, so that the intrusion of air and water vapor into the color conversion layer (32) is appropriately reduced, and the color conversion performance of the color conversion film (30) is maintained for a long period of time.

[0070] The color conversion film related to the present disclosure is not limited to the above embodiments. In FIG. 6, a color conversion film (30) is illustrated in which the color conversion layer (32) is sandwiched between two optical barrier films (20) (protective films), but one of the two protective films sandwiching the color conversion layer (32) may be an optical barrier film (20) and the other may be a protective film of a different configuration.

[0071] The color conversion layer (32) contains a resin and a phosphor. The thickness of the color conversion layer (32) is tens to hundreds of μm. For example, a photocurable resin or a thermosetting resin may be used as the resin. It is preferable that the color conversion layer (32) contains two types of phosphors composed of light-emitting nanocrystals (quantum dots). Additionally, the color conversion layer (32) may be a structure in which two or more layers are stacked, one containing one type of phosphor and the other containing a different type of phosphor. For the two types of phosphors, the same excitation wavelength is selected. The excitation wavelength is selected based on the wavelength of light irradiated by the light source of the backlight unit. The fluorescent colors of the two types of phosphors are different from each other. When a blue light-emitting diode (blue LED) is used as the light source, each fluorescent color is red and green. The wavelength of each fluorescent and the wavelength of light irradiated by the light source are selected based on the spectral characteristics of the color filter. The peak wavelength of the fluorescence is, for example, 610 nm in red and 550 nm in green.

[0072] Next, the particle structure of the phosphor is described. As the phosphor, core-shell type luminescent nanocrystals with particularly good luminescence efficiency are preferably used. Core-shell type luminescent nanocrystals are manufactured, for example, from a material containing an inorganic material, preferably a material containing an inorganic conductor or semiconductor material.

[0073] Examples of semiconductor materials include group II-VI, group III-V, group IV-VI, and group IV semiconductors. Semiconductor materials are, more specifically, for example, Si, Ge, Sn, Se, Te, B, C (including diamond), P, BN, BP, BAs, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe, GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF, CuCl, CuBr, CuI, Si3N4, Ge3N4, Al2O3, (Al,Ga,In)2(S,Se,Te)3, and It includes any one of Al2CO, or any combination of two or more of these.

[0074] Nanocrystals may include, for example, p-type or n-type dopants. Additionally, nanocrystals may include, for example, II-VI or III-V semiconductors. II-VI semiconductor nanocrystals include, for example, any combination of Group II elements such as Zn, Cd, and Hg, and Group VI elements such as S, Se, Te, and Po. III-V semiconductor nanocrystals include, for example, any combination of Group III elements such as B, Al, Ga, In, and Tl, and Group V elements such as N, P, As, Sb, and Bi.

[0075] A core-shell type light-emitting nanocrystal is one in which a semiconductor crystal core serving as a light-emitting part is coated by a shell serving as a protective film. For example, cadmium selenide (CdSe) can be used for the core and zinc sulfide (ZnS) for the shell. The quantum yield is improved by coating the surface defects of the CdSe particles with ZnS, which has a large band gap. Additionally, the phosphor may be one in which the core is double-coated by a first shell and a second shell. In this case, CdSe can be used for the core, zinc selenide (ZnSe) for the first shell, and ZnS for the second shell.

[0076] The color conversion layer (32) may have a single-layer configuration in which all phosphors are dispersed in a single layer, or a multi-layer configuration in which each phosphor is dispersed separately in multiple layers and stacked thereon.

[0077] Next, a method for manufacturing the color conversion film (30) of the present embodiment will be described. The method for forming the color conversion layer (32) is not particularly limited, and for example, the method described in Japanese Patent Publication No. 2013-544018 may be used. A phosphor dispersion solution prepared by dispersing a phosphor in a binder resin is applied to the surface opposite to the coating layer (14) of the optical barrier film (20) (first protective film), and then another optical barrier film (20) (second protective film) is laminated to the applied surface such that the coating layer (14) faces opposite to the color conversion layer (32), and the color conversion layer (32) is cured to manufacture the color conversion film (30).

[0078] [Backlight Unit]

[0079] FIG. 7 is a schematic cross-sectional view of a backlight unit related to one embodiment of the present disclosure. In FIG. 7, the backlight unit (40) comprises a light source (42), a light guide plate (46), and a color conversion film (30) disposed on the light guide plate (46). The color conversion film (30) is disposed such that its uneven surface (20F) (i.e., the uneven surface (14A) of the coating layer (14)) contacts the light guide plate (46). In detail, the backlight unit (40) has the light guide plate (46) and the reflector (44) disposed in this order on the uneven surface (20F) of the color conversion film (30), and the light source (42) is disposed on the side of the light guide plate (46) (in the direction of the surface of the light guide plate (46). Since the backlight unit (40) is equipped with a color conversion film (30) that has a sufficiently small deviation in performance, the deviation in the performance (color, brightness, etc.) of the backlight unit (40) can also be sufficiently small. The backlight unit (40) can prevent damage to the light guide plate (46) that the color conversion film (30) contacts. In addition, since damage to the barrier layer itself is also prevented, the intrusion of air and water vapor into the color conversion layer is appropriately reduced, and good white light can be obtained from the backlight unit for a long period of time.

[0080] The light guide plate (46) and the reflector (44) efficiently reflect and guide light irradiated from the light source (42), and known materials are used. For example, acrylic, polycarbonate, and cycloolefin film are used as the light guide plate (46). The materials used for the light guide plate (46) often do not have high hardness and tend to be easily damaged by contact with other components. In particular, polycarbonate is generally used due to its high transparency and ease of processing, but it is easily damaged because of its low surface hardness. For example, a plurality of blue light-emitting diode elements are formed in the light source (42). These light-emitting diode elements may be violet light-emitting diodes or light-emitting diodes with even lower wavelengths. Light irradiated from the light source (42) is incident on the light guide plate (46) (D1 direction), and then incident on the color conversion layer (32) (D2 direction) accompanied by reflection and refraction. The light that passes through the color conversion layer (32) becomes white light by mixing the yellow light generated in the color conversion layer (32) with the light before passing through the color conversion layer (32).

[0081] Examples

[0082] The inventions related to the present disclosure will be described in detail below with reference to examples, but the scope of the inventions related to the present disclosure is not limited thereto.

[0083] (Ingredients used)

[0084] To prepare the coating layer composition (coating solution) of Examples 1 to 5 and Comparative Example 1, the following components were prepared.

[0085] · Subject 1: Mixture of urethane-based fine particles (average particle size 6.20 µm, standard deviation of particle size 2.25 µm) and clearing agent (manufactured by DIC Graphics Co., Ltd.)

[0086] · Topic 2: Mixture of urethane-based fine particles (average particle size 7.46 μm, standard deviation of particle size 13.39 μm) and clearing agent (manufactured by DIC Graphics Co., Ltd.)

[0087] · Clearant: Varnish for adjusting the fine particle concentration of Main Components 1 and 2 (Manufactured by DIC Graphics Co., Ltd.)

[0088] · Curing agent: Isocyanate curing agent (Manufactured by DIC Graphics Co., Ltd.)

[0089] · Antistatic agent: Resisat PU-101 (Product name, manufactured by Daiichi Industrial Pharmaceutical Co., Ltd.)

[0090] · Solvent: Toluene (Manufactured by Wako Pure Chemical Industry Co., Ltd., Shika Grade 1)

[0091] (Measurement of physical property values ​​of fine particles contained in Topics 1 and 2)

[0092] The "average particle size" and "standard deviation of particle size" of the fine particles contained in Topics 1 and 2 were measured as follows. Specifically, the subject was placed in a glass bottle and shaken 100 times, after which ethyl acetate was added. The average particle size and standard deviation of the fine particles contained in the resulting sample were measured using a laser diffraction and scattering particle size distribution measuring device (Nikkiso Co., Ltd., MicroTrack MT3300 (product name)). The results are shown in Table 1.

[0093]

[0094] (Manufacture of optical films)

[0095] A coating layer composition formed by mixing the compositions shown in Table 2 was applied onto a first film substrate, and a coating film was formed using a wire bar coater. Subsequently, the coating film was heated at 80°C for 30 seconds to dry the coating film. The dried coating film was then aged at 60°C for 2 days to produce the optical films of Examples 1 to 5 and Comparative Example 1, respectively. In Examples 1 to 5, when forming the coating film of the coating layer composition, the amount of application was varied by using wire bars with different wire counts, thereby forming coating layers of different thicknesses on the first film substrate, respectively.

[0096]

[0097] For the optical films related to the above examples and comparative examples, evaluations were performed on the following items. The results are shown in Table 3.

[0098] (Haze and total light transmittance)

[0099] The haze and total light transmittance of the optical films related to the examples and comparative examples were measured using a haze meter (turbidimeter) NDH-2000 (product name, manufactured by Nippon Denk Industry Co., Ltd.).

[0100] (Damage resistance)

[0101] The optical films obtained in the examples and comparative examples were cut to a size of 4 cm × 4 cm, and the coating layer of the cut optical film and the polycarbonate film were overlapped so that they came into contact with each other. They were then left at room temperature under a load of 25 kgf / ㎠ for 30 seconds. Afterward, the optical film and the polycarbonate film were observed visually and under a microscope, and their damage resistance was evaluated according to the following criteria. In addition, the polycarbonate film was prepared to mimic the light guide plate of a backlight unit. The thickness of the polycarbonate film was 188 μm.

[0102] A: No damage is found on the coating layer of the optical film and the polycarbonate film.

[0103] B: Damage is confirmed in at least one of the coating layer of the optical film and the polycarbonate film.

[0104] C: Significant damage is confirmed in at least one of the coating layer of the optical film and the polycarbonate film.

[0105] (Surface resistivity)

[0106] For the surface of the coating layer of the optical film obtained in the examples and comparative examples, a high-resistance resistivity meter (product name: Hiresta UP MCP-HT450, manufactured by Dia Instruments, Inc.) was used to measure the surface resistivity in accordance with JIS-K 6911 (conditions: applied voltage: 500 V, time: 10 sec, probe: URS, under 23 ℃ 55 % RH environment).

[0107]

[0108] As shown in Table 3, the haze value of the optical film of Example 2 (coating layer thickness 4.5 μm) was 44.0%, while the haze value of the optical film of Comparative Example 1 (coating layer thickness 6.0 μm) was 40.3%, and the values ​​of both were relatively close. Therefore, as described below, the in-plane deviation of the haze was evaluated by measuring the haze at multiple points on the optical films of Example 2 and Comparative Example 1, respectively, and the physical property values ​​(average particle size and standard deviation of particle size) of the fine particles contained in these coating layers were measured.

[0109] (Evaluation of Hayes' In-plane Deviation)

[0110] Samples were prepared by cutting the optical films of Example 2 and Comparative Example 1 into 100 mm by 100 mm sections, respectively. Haze was measured at a total of five points (measurement points 1 to 5) located near the center and the four corners of each sample. The average value of the haze and the standard deviation of the haze were calculated from these measurements. The results are shown in Table 4.

[0111]

[0112] (Measurement of physical properties of fine particles contained in the coating layer)

[0113] The "average particle diameter" and "standard deviation of particle diameter" of the microparticles contained in the coating layer of the optical film related to Example 2 and Comparative Example 1 were measured as follows. Specifically, the optical film related to Example 2 and Comparative Example 1 was magnified 1000 times using an optical microscope (see FIG. 8(a)), and the diameters of 50 randomly selected microparticles were measured. As shown in FIG. 8(b), the length in the horizontal direction (X) and the length in the vertical direction (Y) were measured, respectively, and the average value (= (X + Y) / 2) was taken as the diameter of the target particle. Table 5 shows the values ​​of the "average particle diameter" and "standard deviation of particle diameter" of the microparticles calculated from these measurements. In addition, FIG. 8(a) is an image showing the coating layer of the optical film related to Example 2 magnified with an optical microscope, and FIG. 8(b) is an image showing the particles surrounded by circles in FIG. 8(a) further magnified.

[0114]

[0115] (Measurement of the arithmetic mean roughness Ra of the coating layer)

[0116] The arithmetic mean roughness Ra of the coating layer of the optical film related to Example 2 and Comparative Example 1 was measured. A non-contact surface layer cross-sectional measurement system (BertScan, manufactured by Ryoka System Co., Ltd.) was used for the measurement. The results were as follows.

[0117] · Example 2: 0.27 μm

[0118] · Comparative Example 1: 0.42 μm

[0119] (Evaluation of the amount of fine particles detached from the coating layer)

[0120] After performing a rubbing treatment on the surface of the coating layer of the optical film related to Example 2, the surface was magnified using an optical microscope, and points within the image where fine particles were confirmed to have been removed by the treatment were counted; as a result, there were 8 such points. The horizontal length (X) and vertical length (Y) of each point were measured (see FIG. 9), and the average value (= (X + Y) / 2) was taken as the diameter of the removed portion, and the area of ​​each point was calculated. The results are shown in Table 6.

[0121] After performing the same treatment on the coating layer of the optical film related to Comparative Example 1, the surface was magnified using an optical microscope, and the points within the image where fine particles were confirmed to have been removed by the treatment were counted; as a result, there were 9 such points. For these points, the horizontal length (X) and the vertical length (Y) were measured respectively, and the average value (= (X+Y) / 2) was taken as the diameter of the removed portion, and the area of ​​each point was calculated. The results are shown in Table 7.

[0122]

[0123]

[0124] (Evaluation of pencil strength of the coating layer)

[0125] A coating layer composition formed by mixing the compositions shown in Table 8 was applied to a first film substrate with a width of 210 mm, and a film was formed over a length of 300 mm using a wire bar coater. Subsequently, the film was heated at 80°C for 30 seconds to dry the film. The dried film was then aged at 60°C for 2 days to produce the optical films of Example 6 and Comparative Example 2, respectively. In Example 6 and Comparative Example 2, the thickness of the coating layer formed on the first film substrate was 3 μm. Additionally, in Example 6, the same components as in Examples 1 to 5 were used, and in Comparative Example 2, the same components as in Comparative Example 1 were used.

[0126] The pencil hardness of 12 points on each of the coating layers related to Example 6 and Comparative Example 2 was measured in accordance with JIS K 5600-5-4: 1999 “Scratch Hardness (Pencil Method)”. The load applied to the tip of the pencil was 500 g. The results are shown in Table 9.

[0127]

[0128]

[0129] Industrial applicability

[0130] According to the present disclosure, an optical film having a sufficiently small in-plane deviation of haze value, and an optical barrier film, a color conversion film, and a backlight unit using the same are provided. Explanation of the symbols

[0131] 10: Optical film 12: First film substrate 14: Coating layer 14A: Uneven surface 16 : Binder resin 18 : Microparticles 20A, 20B, 20C, 20D, 20: Optical barrier film 22a, 22b: Barrier composite layer 24, 24a, 24b: Barrier layer 30: Color conversion film 32: Color conversion layer 40: Backlight unit

Claims

Claim 1 The invention described in the description of the present invention.

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