Optical film, polarizing plate, front plate, image display device, and method for manufacturing optical film

Abstract

This invention provides an optical film that can efficiently block harmful blue light in the wavelength range without blocking light in the necessary wavelength range. [Solution] The optical film comprises a cycloolefin resin having structural units derived from norbornene monomers and a dye compound represented by the following formula (1). The transmittance T(460) of the optical film at a wavelength of 460 nm is 70% or more, and the difference △T(T(460)-T(450)) between the transmittance T(460) at a wavelength of 460 nm and the transmittance T(450) at a wavelength of 450 nm is 20% or more. TIFF2026095325000017.tif55137

Description

[Technical Field]

[0001] The present invention relates to an optical film, a polarizing plate, a front plate, an image display device, and a method for manufacturing an optical film. [Background technology]

[0002] In recent years, blue light emitted from display devices and other equipment has been said to place a significant burden on the eyes and body. Blue light refers to blue light with a wavelength of 380-495 nm and possesses high energy within the visible light spectrum. It has been pointed out that prolonged exposure to light containing such blue light can cause eye strain, decreased vision, dry eyes, and sleep disorders. Therefore, blocking blue light emitted from display devices and other equipment is desirable.

[0003] One proposed method for cutting blue light is to laminate a blue light-cutting film onto the display surface. For example, Patent Document 1 proposes an optical film comprising a triacetylcellulose substrate (light-transmitting substrate) and a light-transmitting functional layer comprising a cured product of a composition containing an acrylic polymer to which a sesamol-type benzotriazole monomer (spectral transmittance adjusting agent) is bonded, an acrylic monomer, and a polymerization initiator. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-159190 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the film described in Patent Document 1 had a high transmittance of 87.3% or more at a wavelength of 440 nm, and was not able to adequately block light in the harmful wavelength range.

[0006] Furthermore, our studies have shown that attempting to increase the blocking of harmful wavelengths of light sometimes resulted in blocking of necessary wavelengths as well. Image display devices using such films may experience screen dimming or power loss.

[0007] The present invention has been made in view of the above circumstances, and aims to provide an optical film that can transmit light in the necessary wavelength range while efficiently blocking blue light in the harmful wavelength range, a method for manufacturing the same, a polarizing plate, a front plate, and an image display device. [Means for solving the problem]

[0008] The present invention relates to the following optical film, polarizing plate, front plate, image display device, and method for manufacturing the optical film.

[0009] [1] An optical film comprising a cycloolefin resin having structural units derived from norbornene monomers and a dye compound represented by the following formula (1), wherein the transmittance T(460) of the optical film at a wavelength of 460 nm is 70% or more, and the difference △T(T(460)-T(450)) between the transmittance T(460) at a wavelength of 460 nm and the transmittance T(450) at a wavelength of 450 nm is 20% or more. [ka] (In equation (1), R1 is an alkyl group, m is a non-negative integer, L1 and L2 are linking groups, R2 and R3 are alkyl or aryl groups, respectively. R4 and R5 are, respectively, a cyano group, an alkoxycarbonyl group, or an aryloxycarbonyl group. If both R4 and R5 are alkoxycarbonyl or aryloxycarbonyl groups, they may bond to each other to form a ring. [2] The norbornene-based monomer is the optical film according to [1], which has an ester-containing group. [3] The content of the dye compound is 0.1% by mass or more and 10% by mass or less based on the total mass of the optical film, the optical film according to [1] or [2]. [4] The optical film according to any one of [1] to [3], having a thickness of 20 μm or less. [5] The optical film according to any one of [1] to [4], which is a foldable optical film. [6] A polarizing plate including a polarizer and the optical film according to any one of [1] to [5] disposed on at least one surface side of the polarizer. [7] A front panel including a base film and the optical film according to any one of [1] to [5] disposed on at least one surface side of the base film. [8] An image display device including a display panel and the optical film according to any one of [1] to [5] disposed on the viewing side of the display panel. [9] The image display device according to [8], wherein the display panel is an organic EL display panel.

[10] A method for manufacturing the optical film according to any one of [1] to [5], including a step of preparing a solution containing the cycloolefin-based resin, the dye compound, and a solvent, and a step of applying the solution onto a support and then drying it to obtain a coating film. [Effect of the Invention]

[0010] According to the present invention, it is possible to provide an optical film capable of blocking harmful blue light in a harmful wavelength range with high efficiency without blocking light in a necessary wavelength range, a method for manufacturing the same, a polarizing plate, a front panel, and an image display device. [Brief Description of the Drawings]

[0011] [Figure 1] FIG. 1 is a graph showing an example of the spectral transmittance of the optical film according to an embodiment of the present invention. [Figure 2]FIG. 2 is a schematic cross-sectional view showing an image display device according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic cross-sectional view showing an image display device according to another embodiment of the present invention. MODE FOR CARRYING OUT THE INVENTION

[0012] As a result of intensive studies, the present inventors have found that a film containing a dye compound having a specific structure, specifically, a dye compound represented by the formula (1), can favorably block light in a harmful short wavelength region (wavelength of 450 nm or less). Further, it has been found that the spectral transmittance of the film containing the above dye compound also depends on the type of resin to be combined. As a result of further studies, the present inventors have found that when combined with a resin having a relatively low polarity, particularly a cycloolefin resin, light in a necessary wavelength region can be favorably transmitted while blocking light in a harmful short wavelength region with high efficiency.

[0013] The reason for this is not clear, but it is considered as follows. In order to favorably transmit light in a necessary wavelength region while blocking light in a harmful short wavelength region with high efficiency, it is desirable to sharply change the transmittance of the optical film in a wavelength region near the middle thereof. For this purpose, it is desirable that the absorption spectrum of the dye compound to be used is as sharp as possible. Since the dye compound represented by the formula (1) has an ester bond, the interaction between the dye compounds is large, and a sharp absorption spectrum is shown. On the other hand, in the combination of the above dye compound and resin, since a resin having a large polarity has a large interaction with the dye compound, the absorption characteristics of the dye compound may be blunted (the absorption spectrum is broadened). In contrast, since the cycloolefin resin has a relatively small polarity, the interaction with the dye compound is small. Therefore, the original properties of the dye compound are hardly impaired, and the desired properties can be exhibited.

[0014] Furthermore, we found that such an optical film, when its transmittance T(460) at a wavelength of 460 nm is 70% or more, and the difference between the transmittance T(460) at 460 nm and the transmittance T(450) at 450 nm, ΔT(T(460)-T(450)), is 20% or more, can effectively transmit light in the wavelength range necessary for image viewing while efficiently blocking harmful short-wavelength light (see, for example, Figure 1).

[0015] One embodiment of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. Furthermore, in this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit.

[0016] 1. Optical film As described above, the optical film of this embodiment contains a cycloolefin resin and a specific dye compound. The transmittance T(460) of the optical film at a wavelength of 460 nm is 70% or more, and the difference △T(T(460)-T(450)) between the transmittance T(460) at a wavelength of 450 nm and the transmittance T(450) at a wavelength of 450 nm is 20% or more.

[0017] If the transmittance T(460) of the optical film at a wavelength of 460 nm is 70% or higher, light in the wavelength range necessary for viewing the image can be transmitted well, thus suppressing the darkening of the display screen. From a similar viewpoint, it is more preferable that the transmittance T(460) of the optical film at a wavelength of 460 nm be 80% or higher, and even more preferable that be 85% or higher. The upper limit of the transmittance T(460) of the optical film at a wavelength of 460 nm is not particularly limited and may be 100% or 99.5% or lower.

[0018] Furthermore, the difference ΔT(T(460)-T(450)) between the transmittance T(460) at a wavelength of 460 nm and the transmittance T(450) at a wavelength of 450 nm of the optical film is 20% or more. When the above difference ΔT(T(460)-T(450)) is 20% or more, light in the required wavelength range can be transmitted well while harmful short-wavelength light can be sufficiently cut off. From a similar viewpoint, it is more preferable that the above transmittance difference ΔT be 25% or more, and even more preferable that it be 30% or more. There is no particular upper limit to the above transmittance difference ΔT, but it may be, for example, 60% or less. That is, the above transmittance difference ΔT can be, for example, 20% or more and 60% or less.

[0019] The transmittance of an optical film at each wavelength can be measured by the following method. Cut the optical film into 30mm x 30mm pieces to use as samples. Measure the transmittance of these samples at wavelengths of 200-800nm ​​using a spectrophotometer (e.g., Hitachi High-Tech U-3900H). The measurement conditions are as follows: (Measurement conditions) • Slit width: 2nm • Sampling interval: 1nm interval • Light source: WI lamp (visible range), D2 lamp (ultraviolet range) • Detector: Photomal The transmittance at wavelengths of 430 nm, 450 nm, and 460 nm will be the arithmetic mean of the values ​​obtained from three measurements.

[0020] The transmittance T(460) of an optical film at a wavelength of 460 nm, and the difference between the transmittance at 460 nm and 450 nm, ΔT(T(460)-T(450)), can be adjusted by the type and combination of resin and dye compound, as well as the content of the dye compound. For example, combining a cycloolefin resin with a specific dye compound tends to increase ΔT(T(460)-T(450)) while maintaining a high T(460) of the optical film. Also, increasing the content of the dye compound tends to increase ΔT(T(460)-T(450)).

[0021] The following provides a detailed explanation of each component contained in the optical film.

[0022] 1-1. Cycloolefin resins Cycloolefin resins are polymers that contain structural units derived from norbornene monomers.

[0023] Norbornene monomers are represented by the following formula (2). [ka]

[0024] R in equation (2) 1 ~R 4 These are preferably a hydrogen atom, a hydrocarbon group, or an ester-containing group, respectively.

[0025] Examples of hydrocarbon groups include alkyl groups and aryl groups. Alkyl groups are alkyl groups having 1 to 10 carbon atoms, preferably 1 to 4, more preferably 1 or 2 carbon atoms. Aryl groups are aryl groups having 6 to 14 carbon atoms, preferably 6 to 10 carbon atoms. These hydrocarbon groups may have further substituents. Examples of substituents include polar groups such as carboxyl groups, hydroxyl groups, amino groups, amide groups, and cyano groups. Among these, alkyl groups are preferred as hydrocarbon groups.

[0026] Examples of ester-containing groups include alkoxycarbonyl groups, aryloxycarbonyl groups, and groups in which these groups are bonded via a linking group (such as a methylene group). Among these, the ester-containing group is preferably an alkoxycarbonyl group, and more preferably an alkoxycarbonyl group in which the alkoxy portion has 1 to 10 carbon atoms, preferably 1 to 4, and more preferably 1 or 2 carbon atoms.

[0027] Among them, R 1 ~R 4At least one of them is preferably an ester-containing group. A cycloolefin resin having a structural unit derived from a norbornene monomer having an ester-containing group is suitable for film formation by a solution casting method because it is easily soluble in a solvent. As described above, from the viewpoint of further increasing the blue light cut-off rate, it is preferable that the polarity of the resin is small. On the other hand, if the polarity of the resin is too small, the solubility in the solvent may decrease, and film formation by coating may be difficult. In contrast, by using a cycloolefin resin having an ester-containing group, it is possible to enhance the blue light performance while ensuring the solubility in the solvent.

[0028] For example, R 1 is an ester-containing group, and R 2 , R 3 and R 4 may each be a hydrogen atom or a hydrocarbon group; R 1 and R 3 are each an ester-containing group, and R 2 and R 4 may each be a hydrogen atom or a hydrocarbon group.

[0029] p and m in formula (2) are each an integer from 0 to 3. Among them, m + p is preferably from 0 to 4, more preferably from 0 to 2, and even more preferably m = 1 and p = 0. A cycloolefin resin containing a structural unit derived from a norbornene monomer with m = 1 and p = 0 can provide an optical film with a high glass transition temperature and good mechanical strength.

[0030] Examples of the norbornene monomer represented by formula (2) include the following.

Chemical formula

[0031] The content of structural units derived from norbornene monomers is preferably 20 to 100% by mass, and more preferably 30 to 100% by mass, relative to the total structural units constituting the cycloolefin resin. Of the content of structural units derived from norbornene monomers, the proportion of structural units derived from norbornene monomers having ester-containing groups is, for example, 70% by mass or more, and preferably 100% by mass.

[0032] The cycloolefin resin may further contain structural units derived from other monomers copolymerizable with norbornene monomers. Examples of other copolymerizable monomers include cycloolefin monomers that do not have a norbornene skeleton, such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene. In particular, the number of carbon atoms in the cycloolefin monomer is preferably 4 to 20, and more preferably 5 to 12.

[0033] Commercially available cycloolefin resins may be used. Examples of commercially available products include ARTON® G, ARTON F, ARTON R, and ARTON RX manufactured by JSR Corporation.

[0034] The weight-average molecular weight Mw of the cycloolefin resin is not particularly limited, but is preferably between 20,000 and 300,000, more preferably between 30,000 and 250,000, and even more preferably between 40,000 and 200,000. When the weight-average molecular weight Mw of the cycloolefin resin is within the above range, the mechanical strength (especially toughness) of the optical film can be further increased while maintaining moldability.

[0035] The weight-average molecular weight (Mw) of cycloolefin resins can be measured by gel permeation chromatography (GPC). Specifically, the measurement device used is a gel permeation chromatograph (HLC8220GPC manufactured by Tosoh Corporation), and the columns used are TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL manufactured by Tosoh Corporation, in series. Then, 20 ± 0.5 mg of the sample is dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution is injected into the above column (at 40°C), measured with a radioisotope detector at 40°C, and the weight-average molecular weight is determined by converting it to styrene equivalent.

[0036] The glass transition temperature (Tg) of cycloolefin resins is usually preferably 110°C or higher, more preferably 110 to 350°C, and even more preferably 120 to 250°C. The glass transition temperature can be measured using DSC (Differential Scanning Colorimetry) in accordance with JIS K 7121-2012.

[0037] The optical film may contain one type of cycloolefin resin, or it may contain two or more types of cycloolefin resins.

[0038] The content of cycloolefin resin in the optical film is not particularly limited, but is preferably 30% to 99.9% by mass, and more preferably 50% to 95.0% by mass, based on the total mass of the optical film.

[0039] 1-2. Specific dye compounds Dye compounds are compounds represented by the following formula (1). [ka]

[0040] In formula (1), R1 is an alkyl group, more preferably an alkyl group having 1 to 7 carbon atoms, and more preferably 1 to 4 carbon atoms. m is an integer of 0 or more, preferably 0 to 2, and more preferably 0 or 1.

[0041] In formula (1), L1 and L2 are linking groups. The linking group is a single bond or an alkylene group having 1 to 7 carbon atoms. Among these, a methylene group (-CH2-) is preferred. L1 and L2 may be the same or different.

[0042] In formula (1), R2 and R3 are each an alkyl group or an aryl group. Among these, alkyl groups are preferred, and more preferably alkyl groups having 1 to 7 carbon atoms, and more preferably 1 to 4 carbon atoms. R2 and R3 may be the same or different. The aryl group may be an aryl group having 6 to 12 carbon atoms. In formula (1), -CO2R2 and -CO2R3 are -C(=O)OR2 and -C(=O)OR3, respectively.

[0043] In formula (1), R4 and R5 are, respectively, a cyano group, an alkoxycarbonyl group (-C(=O)-OR), or an aryloxycarbonyl group (-C(=O)-OAr). The number of carbon atoms in the alkyl portion of the alkoxycarbonyl group is, for example, 1 to 10, preferably 1 to 4. The number of carbon atoms in the aryl portion of the aryloxycarbonyl group can be, for example, 6 to 12. Thus, R4 and R5 may be electron-withdrawing groups derived from, for example, the active methylene compound described later. When both R4 and R5 are alkoxycarbonyl groups or aryloxycarbonyl groups, they may be bonded to each other to form a ring (for example, a 6-membered ring containing an oxycarbonyl group).

[0044] Specific examples of compounds represented by formula (1) include the following: [ka]

[0045] The compound represented by formula (1) can be prepared, for example, by the following method. For example, it can be obtained by dehydration condensation (Kneefenagel condensation) of the following aldehyde compound and an active methylene compound (e.g., malononitrile or meldrumic acid) in a solvent such as toluene, in the presence of a catalyst such as morpholine. [ka]

[0046] The content of the dye compound in the optical film is not particularly limited as long as the above transmittance is satisfied, but it is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 5% by mass or less, relative to the total mass of the optical film. When the above content of the dye compound is 0.1% by mass or more, the transmittance of light with a wavelength of 450 nm or less can be made even lower, and the transmittance difference ΔT(T(460)-T(450)) can be made larger. Therefore, it is easier to transmit more light in the required wavelength range while blocking more light in the harmful wavelength range. When the above content of the dye compound is 10% by mass or less, the transmittance of light in the required wavelength range, for example, light with a wavelength of 460 nm or more, can be made even higher.

[0047] 1-3. Other ingredients The optical film may further contain other components not mentioned above, as long as they do not impair the effects of the present invention. Examples of other components include matting agents, ultraviolet absorbers, phase difference adjusting agents (phase difference increasing agents, phase difference decreasing agents), plasticizers, antioxidants, light stabilizers, antistatic agents, release agents, and thickeners. In particular, the optical film preferably contains a matting agent, from the viewpoint of providing irregularities on the surface of the optical film and providing appropriate slipperiness.

[0048] The matting agent is in the form of fine particles. These fine particles may be inorganic or resin particles. Examples of inorganic fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Examples of resin fine particles include silicone resin, fluororesin, and acrylic resin.

[0049] In particular, inorganic fine particles are preferred, and silicon dioxide fine particles are even more preferred from the viewpoint of not increasing the haze of the optical film and effectively lowering the coefficient of friction. Examples of silicon dioxide fine particles include Aerosil 200V, Aerosil R972V, and Aerosil R812 (all manufactured by Nippon Aerosil Co., Ltd.).

[0050] The average particle size of the primary particles of the fine particles is preferably 0.005 to 0.4 μm, and more preferably 0.01 to 0.3 μm. The average particle size of the primary particles of the fine particles can be measured using the ELSZ-2000 manufactured by Otsuka Electronics.

[0051] The content of fine particles in the optical film is preferably 0.01 to 3.0% by mass, and more preferably 0.01 to 2.0% by mass, relative to the total mass of the optical film.

[0052] 1-4. Physical properties of optical films (transmittance) As described above, the transmittance T(460) of the optical film at a wavelength of 460 nm is 70% or more, and the difference △T(T(460)-T(450)) between the transmittance T(460) at a wavelength of 450 nm and the transmittance T(450) at a wavelength of 450 nm is 20% or more.

[0053] The transmittance T(450) of the optical film at a wavelength of 450 nm is not particularly limited as long as the above characteristics are satisfied, but from the viewpoint of better blocking harmful short-wavelength light, it is preferably 60% or less, more preferably 50% or less, and even more preferably 35% or less. The lower limit of the transmittance T(450) of the optical film at a wavelength of 450 nm is not particularly limited, but may be 0%.

[0054] Furthermore, the transmittance T(430) of the optical film at a wavelength of 430 nm is not particularly limited as long as the above characteristics are satisfied, but it is preferably 5% or less, and more preferably 1% or less. The lower limit of the transmittance T(430) of the optical film at a wavelength of 430 nm is not particularly limited, but it may be 0%.

[0055] The transmittance of an optical film at each wavelength can be measured by the method described above.

[0056] (bending resistance) When an optical film is subjected to a bending test, the number of bending cycles before breakage is preferably 10,000 or more, and more preferably 100,000 or more. Such an optical film has excellent bending resistance and can therefore be suitably used, for example, in foldable devices.

[0057] Cut an optical film to a size of 150mm x 30mm to use as a sample. Place this sample in a durability testing machine (for example, a DLDM111LH manufactured by Yuasa Systems Equipment) and repeatedly perform a bending operation with a radius of curvature (R) of 3mm. Then, count the number of bends until a fracture occurs on the surface of the sample.

[0058] Bending resistance can be adjusted by factors such as the molecular weight of the cycloolefin resin and the thickness of the optical film. For example, the larger the molecular weight of the cycloolefin resin and the thinner the optical film, the easier it is to improve bending resistance.

[0059] (Glass transition temperature) The glass transition temperature (Tg) of the optical film is preferably, for example, 110 to 250°C. A Tg of 110°C or higher can further enhance the heat resistance of the optical film. The glass transition temperature of the optical film can be measured using the same method as described above.

[0060] (Hayes) The haze of the optical film is not particularly limited, but is preferably 2.0 or less, and more preferably 1.0 or less. The haze of the optical film can be measured using a haze meter (NDH 2000: manufactured by Nippon Denshoku Industries Co., Ltd.) after 24 hours of humidity control in an environment of 25°C and 60% RH.

[0061] (Phase difference Ro) The phase difference Ro of an optical film is not particularly limited, but for example, the in-plane phase difference Ro measured at a measurement wavelength of 550 nm and under conditions of 23°C and 55% RH is preferably 0 nm to 150 nm, and more preferably 1 nm to 110 nm. Such an optical film is suitable, for example, as a protective film for polarizing plates or front plates.

[0062] Ro is defined by the following formula: Equation (3): Ro = (nx - ny) × d (In formula (3), nx represents the refractive index in the in-plane slow axis direction of the film (the direction in which the refractive index is maximum). ny represents the refractive index in the direction perpendicular to the in-plane slow axis of the film. 'd' represents the film thickness (nm).

[0063] The in-plane slow axis of an optical film can be confirmed using an automated birefringence meter (e.g., Axo Scan Mueller Matrix Polarimeter, manufactured by Axonometrics). The in-plane slow axis of an optical film may be approximately parallel to the width direction of the optical film.

[0064] Ro can be measured by the following method. 1) The optical film is conditioned for 24 hours in an environment of 23°C and 55% RH. The average refractive index of this film is measured using an Abbe refractometer, and its thickness d is measured using a commercially available micrometer. 2) The retardation Ro of the film after humidity control is measured at a measurement wavelength of 550 nm using an automated birefringence meter (e.g., Axo Scan Mueller Matrix Polarimeter: manufactured by Axonometrics) in an environment of 23°C and 55% RH.

[0065] The phase difference Ro of an optical film can be adjusted, for example, by the stretching conditions. The phase difference Ro tends to increase as the stretching ratio increases.

[0066] (Thickness) The thickness of the optical film is not particularly limited, but is preferably 80 μm or less, more preferably 60 μm or less, and even more preferably 20 μm or less from the viewpoint of further improving bending resistance. The lower limit of the thickness of the optical film is not particularly limited, but is preferably 5 μm or more, and more preferably 10 μm or more.

[0067] 2. Method for manufacturing optical films The optical film described above can be manufactured by any method. Among these methods, manufacturing by solution film formation is preferable because it is less susceptible to thermal degradation of the dye compound and has fewer restrictions on the materials used.

[0068] In other words, an optical film can be obtained by 1) preparing a solution containing the above-mentioned cycloolefin resin, the above-mentioned dye compound, and a solvent (solution preparation step), and 2) applying the obtained solution onto a support, then drying and peeling it off to obtain a coated film (coating step).

[0069] 2-1. Solution preparation process A solution is prepared by dissolving or dispersing a cycloolefin resin and a dye compound in a solvent.

[0070] The solvent used in the solution must contain at least one solvent capable of dissolving cycloolefin resins (a good solvent). Examples of good solvents include chlorinated organic solvents such as methylene chloride; and non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, tetrahydrofuran, cyclopentyl methyl ether, and toluene. Among these, toluene is preferred from the viewpoint of stably and well dispersing the dye compound.

[0071] The solvent used in the solution may further contain a poor solvent. Examples of poor solvents include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. When the proportion of alcohol in the solution increases, the film-like material is more likely to gel, and peeling from the metal support is easier. Examples of linear or branched aliphatic alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and methyl ethyl ketone. Of these, methyl ethyl ketone is preferred due to its solution stability, relatively low boiling point, and good drying properties.

[0072] 2-2.Coating process The obtained coating solution is applied onto the support. There are no restrictions on the coating method, but gravure printing, die printing, etc., can be used.

[0073] The support material should preferably be PET, PEN, PC, PI, or other materials that are resistant to the solvent of the coating solution and do not deform or melt when the coating film dries. The surface of the support material may also be treated with an easy-adhesion process or a release process. The thickness of the support material is not particularly limited, but can be between 25 μm and 188 μm.

[0074] The solvent is evaporated from the coated film on the support until it can be peeled off the support. The method of evaporating the solvent is not particularly limited, but may include methods such as blowing air onto the coated film. The drying temperature should be a temperature at which the solvent can be removed and the dye compound does not undergo thermal degradation, for example, 80°C to 150°C. The drying temperature may be the temperature of the air.

[0075] Subsequently, the solvent is evaporated and the resulting coating film is peeled off the support.

[0076] The amount of residual solvent in the coating film on the support after peeling depends on drying conditions and the length of the support, but can be, for example, between 0.1% by mass and 10% by mass. When the amount of residual solvent is within this range, the coating film is not too soft, so flatness is less likely to be impaired during peeling. The amount of residual solvent is defined by the following formula.

[0077] Residual solvent amount (mass %) = (mass of coating film before heat treatment - mass of coating film after heat treatment) / (mass of coating film after heat treatment) × 100 The heat treatment used to measure the amount of residual solvent is a heat treatment at 150°C for 1 hour.

[0078] 2-3. Other processes In this embodiment, other steps may be performed in addition to these steps. For example, a step of stretching the coated film (stretching step) or a step of drying the coated film (drying step) may be performed. Alternatively, a step of laminating a peelable protective film to the surface of the coated film peeled off from the support may be performed.

[0079] For example, the drying process can be carried out while the coated film is transported by multiple conveyor rolls (for example, multiple conveyor rolls arranged in a staggered pattern when viewed from the side). The drying method is not particularly limited, and hot air, infrared rays, heated rolls, or microwaves can be used. Hot air drying is preferred because it is simple.

[0080] The drying temperature can be any temperature at which the solvent can be removed without causing thermal degradation of the dye compound, and can be the same as the drying temperature described above.

[0081] 3. Image display device The above-mentioned optical film can be applied to an image display device. That is, the image display device includes a display panel and the optical film disposed on its viewing side.

[0082] The display panel has a display element. Examples of display elements include organic light-emitting diodes, liquid crystal display elements, and inorganic light-emitting diodes, with organic light-emitting diodes being preferred. That is, examples of image display devices include organic electroluminescent (organic EL) display devices, liquid crystal display devices, and inorganic electroluminescent (inorganic EL) display devices, with organic EL display devices being preferred.

[0083] [First Embodiment] Figure 2 is a schematic cross-sectional view showing an image display device 100 according to the first embodiment of the present invention. As shown in Figure 2, the image display device 100 has, in order facing the viewing side, an organic EL display panel 110 (display panel), a touch sensor 120, a polarizing plate 130, and a front panel 140.

[0084] (1) Organic EL display panel 110 As the organic EL display panel 110, a known organic EL display panel can be used. The organic EL display panel 110 may have a structure in which a metal electrode, an emissive layer, a transparent electrode, and a sealing layer are stacked in this order on a substrate such as glass or polyimide.

[0085] (2) Touch sensor 120 In this embodiment, the touch sensor 120 is positioned between the organic EL display panel 110 and the polarizing plate 130. Any known touch sensor can be used as the touch sensor 120. The touch sensor 120 only needs to be capable of detecting the position touched on the front panel 140 (described later), for example, a capacitively coupled touch sensor. Furthermore, the touch sensor 120 may be an on-cell type (see Figure 2) or an in-cell type.

[0086] A capacitively coupled touch sensor includes, for example, a substrate layer, a translucent electrode layer for position detection provided on the substrate layer, and a touch position detection circuit. When the surface of the front panel 140 (described later) is touched, the translucent electrode is grounded at the touched point via the capacitance of the human body. The touch position detection circuit detects the grounding of the translucent electrode and detects the touched position.

[0087] (3) Polarizing plate 130 The polarizing plate 130 includes a polarizer 131, a phase difference film 132, a protective film 133, and two adhesive layers 134.

[0088] (3.1) Polarizer 131 The polarizer 131 is an element that allows only light with a specific polarization plane to pass through. The polarizer 131 is, for example, a polyvinyl alcohol-based stretched film doped with iodine or a dichroic dye.

[0089] The thickness of the polarizer 131 is not particularly limited, but is, for example, 5 μm or more and 40 μm or less, preferably 5 μm or more and 30 μm or less, and more preferably 5 μm or more and 20 μm or less.

[0090] (3.2) Phase difference film 132 The phase difference film 132 is positioned on one side of the polarizer 131 (in this embodiment, between the polarizer 131 and the organic EL display panel 110). In this embodiment, it is preferable that the phase difference film 132 is a λ / 4 phase difference film. As a result, the polarizer 130 can function as a circular polarizer and have an anti-reflective function.

[0091] The material of the phase difference film 132 is not particularly limited, but a translucent thermoplastic resin can be used. Examples of thermoplastic resins include cellulose ester resins such as triacetylcellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polycarbonate resins; polyimide resins; cycloolefin resins; and (meth)acrylic resins. Among these, cycloolefin resins, polyester resins, and polycarbonate resins are preferred, and cycloolefin resins are more preferred. (Meth)acrylic refers to acrylic, methacrylic, or both.

[0092] When the phase difference film 132 is a λ / 4 phase difference film, the angle between the in-plane slow axis of the phase difference film 132 and the absorption axis of the polarizer 131 is preferably 30° or more and 60° or less, more preferably 45°.

[0093] The thickness of the phase difference film 132 is not particularly limited, but is, for example, 5 μm or more and 50 μm or less, preferably 10 μm or more and 45 μm or less.

[0094] (3.3) Protective film 133 The protective film 133 is positioned on the other side of the polarizer 121 (in this embodiment, between the polarizer 131 and the front plate 140). In this embodiment, the protective film 133 is the optical film described above.

[0095] (3.4) Adhesive layer 134 The two adhesive layers 134 are positioned between the polarizer 131 and the phase difference film 132, and between the polarizer 131 and the protective film 133, respectively. The adhesive layers 134 may be layers obtained from a water-based adhesive, or layers containing a cured product of an active energy ray-curable adhesive.

[0096] Examples of water-based adhesives include aqueous solutions containing polyvinyl alcohol-based resins (such as fully saponified polyvinyl alcohol aqueous solutions).

[0097] Examples of active energy ray curing adhesives include adhesives that harden when irradiated with active energy rays such as ultraviolet light, for example, curable compositions containing an active energy ray polymerizable compound and a photopolymerization initiator.

[0098] The thickness of the adhesive layer 134 is not particularly limited, but is, for example, 0.01 μm or more and 10 μm or less, preferably 0.01 μm or more and 5 μm or less.

[0099] (4) Front plate 140 The front panel 140 is a cover member positioned on the most visible side of the image display device 100, and is also referred to as a cover window or window film. The front panel 140 can be any material that can transmit light, and may be a glass plate, a glass film, a resin film, or a combination thereof.

[0100] Examples of glass plates or glass films include thin glass plates. Examples of resin film materials include those similar to those exemplified as materials for phase difference film 132. Among these, polyimide films, polyester films (e.g., polyethylene terephthalate film, polyethylene naphthalate, etc.), cycloolefin resin films, (meth)acrylic resin films, and cellulose ester films (e.g., triacetylcellulose film, etc.) are preferred because they have excellent transparency and heat resistance. It is preferable that the resin film has substantially no phase difference and is an unstretched film.

[0101] The front panel 140 may have a single-layer structure or a multi-layer structure. In this embodiment, the front panel 140 has a multi-layer structure and includes a base material 141, a first protective film 142, a second protective film 143, and two adhesive layers 144.

[0102] (4.1) Base material 141 Examples of the base material 141 include the glass plate or glass film, resin film, etc., as described above. Among these, glass film or polyimide film is preferred due to its excellent flexibility and transparency.

[0103] The thickness of the substrate 141 is not particularly limited, but is, for example, 10 μm or more and 100 μm or less, preferably 20 μm or more and 80 μm or less.

[0104] (4.2) First protective film 142 The first protective film 142 is positioned on the side of the substrate 141 opposite to the side where the polarizing plate 130 is visible. The first protective film 143 can be any of the resin films mentioned above, preferably a polyester resin film (e.g., polyethylene terephthalate film), a (meth)acrylic resin film, a polycarbonate resin film, etc., and more preferably a polyester resin film.

[0105] The thickness of the first protective film 142 is not particularly limited, but is, for example, 3 μm or more and 40 μm or less, preferably 5 μm or more and 30 μm or less.

[0106] (4.3) Second protective film 143 The second protective film 143 is positioned on the visible side of the substrate 141. The second protective film 143 can be the same as the first protective film 142. The second protective film 143 may further include a hard coat layer.

[0107] The hard coat layer includes, for example, a cured product of a curable composition. The curable composition is an active energy ray curable composition, preferably an ultraviolet light curable composition.

[0108] The UV-curable composition contains a UV-curable compound. The curable compound may be a monomer, oligomer, or prepolymer. Examples of curable compounds include those having multiple (meth)acryloyl groups. Examples of such curable compounds include tricyclodecanedimethanol diacrylate, pentaerythritol di(meth)acrylate, urethane (meth)acrylate, and their oligomers. The curable compound may further have hydroxyl groups in its molecule.

[0109] (4.4) Adhesive layer 144 The adhesive layer may contain a light-transmitting adhesive such as OCA (Optical Clear Adhesive). Examples of such adhesives include adhesive compositions containing base polymers such as (meth)acrylic, rubber, urethane, silicone, and polyvinyl ether. Among these, adhesive compositions containing (meth)acrylic resin as the base polymer are preferred because they offer excellent transparency, adhesive strength, and heat resistance.

[0110] The adhesive layer may include a crosslinked product of an adhesive composition containing the above-mentioned base polymer and a crosslinking agent. Examples of crosslinking agents include compounds that react with the functional groups of the base polymer. For example, if the base polymer has carboxyl groups, divalent or higher metal ions, polyamine compounds, polyisocyanate compounds, polyepoxy compounds, etc., can be used as crosslinking agents.

[0111] Furthermore, the adhesive layer may contain a cured product of an active energy ray-curable adhesive composition. The active energy ray-curable adhesive composition further contains an active energy ray polymerizable compound in addition to the base polymer and crosslinking agent described above, and may further contain a photopolymerization initiator, a photosensitizer, etc., as needed.

[0112] The thickness of the adhesive layer is not particularly limited, but is, for example, 1 μm to 200 μm, preferably 5 μm to 150 μm, and more preferably 10 μm to 100 μm.

[0113] (5) Others Furthermore, the adhesive layer described above may be placed between the organic EL display panel 110 and the touch sensor 120, between the touch sensor 120 and the polarizing plate 130, and between the polarizing plate 130 and the front panel 140. This may fix these components together.

[0114] (6) Effect The image display device 100 of the above embodiment includes the optical film as a protective film 133 for the polarizing plate 130. Therefore, it is possible to transmit light of the necessary wavelengths while efficiently blocking harmful short-wavelength blue light.

[0115] (7) Variant In the above embodiment, the optical film is used as the protective film 133 for the polarizing plate 130, but the embodiment is not limited to this. For example, the optical film may be used as the phase difference film 132 for the polarizing plate 130 or as the first protective film 142 and second protective film 143 for the front plate 140, or the optical film may be newly provided adjacent to any layer included in the polarizing plate 130. In that case, a known polarizing plate protective film (for example, a resin film made of the same material as exemplified as the material for the phase difference film 132) can be used as the protective film 133 for the polarizing plate 130.

[0116] Furthermore, in the above embodiment, the front panel 140, the circular polarizing plate 130, and the touch sensor 120 are arranged in that order from the viewing side, but the system is not limited to this, and they may be arranged in that order as well.

[0117] [Second Embodiment] The image forming apparatus of the second embodiment is the same as the image forming apparatus of the first embodiment, except that a color filter member 150 (COE) is used instead of the polarizing plate 130, and the optical film is used as the first protective film 142 of the front plate 140. Therefore, the same reference numerals are used for the same components or parts as in the first embodiment, and their detailed descriptions are omitted.

[0118] Figure 3 is a schematic cross-sectional view showing an image display device 100 according to a second embodiment of the present invention. As shown in Figure 3, the image display device 100 includes an organic EL display panel 110, a touch sensor 120, a color filter member 150, and a front panel 140.

[0119] (1) Color filter member 150 The color filter member 150 is a color filter with an anti-reflective function. The color filter member 150 may be a color filter itself, or it may be a color filter with other functions such as color compensation added. An example of a color filter with other functions such as color compensation is a COE (Color Filter On Encapsulation) which has a color filter layer placed on the thin film encapsulation (TFE) of the organic EL display panel 110 and is combined with a black PDL.

[0120] (2) Front plate 140 In this embodiment, the front panel 140 includes a base material 141, a first protective film 142, a second protective film 143, and two adhesive layers 144. In this embodiment, the first protective film 142 is the optical film described above.

[0121] (3) Others In the above embodiment, the optical film is used as the first protective film 142 of the front panel 140, but the invention is not limited to this, and the optical film may also be used as the second protective film 143.

[0122] The image display device can be used as a mobile device such as a smartphone or tablet, or as a personal computer. Because the image display device according to the present invention has excellent flexibility, it is suitable for flexible displays and the like. [Examples]

[0123] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0124] 1. Materials for optical films 1-1. Resin <Preparation of cycloolefin resin COP-1> 100 parts by mass of purified toluene and 100 parts by mass of norbornene carboxylate methyl ester (see formula below) were added to the reaction vessel. Next, 25 mmol (relative to monomer mass) of ethylhexanoate-Ni dissolved in toluene, 0.225 mol (relative to monomer mass) of tri(pentafluorophenyl)boron, and 0.25 mol (relative to monomer mass) of triethylaluminum dissolved in toluene were added to the reaction vessel and reacted at room temperature with stirring for 18 hours. After the reaction was complete, the reaction mixture was added to excess ethanol to precipitate the polymer. The precipitate was prepared. The precipitate was purified, and the resulting solid was dried under vacuum at 65°C for 24 hours to obtain cycloolefin resin COP-1 (weight-average molecular weight Mw: 140,000, Tg: 140°C). The weight-average molecular weight was measured using the method described above. [ka]

[0125] <Preparation of cycloolefin resin COP-2> Cycloolefin resin COP-2 was prepared in the same manner as COP-1, except that norbornene carboxylate methyl ester was replaced with the following compound. [ka]

[0126] <Preparation of cycloolefin resin COP-3> Cycloolefin resin COP-3 was prepared in the same manner as COP-1, except that norbornene carboxylate methyl ester was replaced with the following compound. [ka]

[0127] <(meth)acrylic resin> Asahi Kasei L13203

[0128] 1-2. Pigment compounds <Pigment compound 1> 1.17 g of compound (1-1) and 0.277 g of malononitrile were weighed into 100 ml of 3-column solution and dissolved in 18 ml of toluene. Next, 0.332 g of morpholine was added dropwise, and the mixture was heated under reflux for 4 hours. After the reaction was complete, the solvent was removed under reduced pressure, 5 ml of methanol was added, and the mixture was stirred in a suspended state. The precipitate was filtered and dried to obtain 0.91 g (71% yield) of dye compound 1 represented by the following formula. The structure of the compound was confirmed by NMR. [ka]

[0129] <Dye Compound 2> 1.17 g of compound (2-1) and 0.515 g of meldrum acid were weighed into 100 ml of 3-column solution and dissolved in 18 ml of toluene. Next, 0.332 g of morpholine was added dropwise, and the mixture was heated under reflux for 4 hours. After the reaction was complete, the solvent was removed under reduced pressure, 5 ml of methanol was added, and the mixture was stirred in a suspended state. The precipitate was filtered and dried to obtain 1.12 g (yield 68%) of dye compound 2 represented by the following formula. The structure of the compound was confirmed by NMR. [ka]

[0130] <Dye compound 3> The following compounds were prepared as comparative compounds. [ka]

[0131] 2. Fabrication and evaluation of optical films (1) 2-1. Preparation of optical film <Preparation of optical film 101> (Preparation of the solution containing fine particles) The following components were mixed in a dissolver for 50 minutes, and then dispersed in a Manton-Gorin. Further dispersion was performed using an attritor to achieve the desired particle size for the secondary particles. This was filtered using Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution. Fine particles (Aerosil R972: manufactured by Nippon Aerosil Co., Ltd., primary mean particle size: 16 nm, apparent specific gravity 50 g / L): 6 parts by mass Methyl ethyl ketone: 94 parts by mass

[0132] (Preparation of solution) The following components were placed in a sealed container while being thoroughly stirred, then heated to 80°C and held there for 1 hour. Next, the mixture was cooled to 30°C and filtered through a 5 μm pore size filter to obtain the solution. Cycloolefin resin COP-1: 26 parts by mass Toluene: 39 parts by mass Methyl ethyl ketone: 30 parts by mass Dye compound 1: 0.27 parts by mass Particulate additive liquid: 4.2 parts by mass

[0133] (Production of optical films) The prepared solution was extruded from a casting die and coated onto a PET support. The support was then dried with a 40°C dry air until a self-supporting coating film was obtained. Subsequently, the solvent was evaporated by drying in a 130°C oven for 30 minutes, and the coating film was peeled off the support to obtain an optical film 101 with a thickness of 20 μm.

[0134] <Preparation of optical film 102> Optical film 102 was obtained in the same manner as optical film 101, except that the amount of coating solution was changed to achieve the film thickness shown in Table 1.

[0135] <Preparation of optical films 103 and 104> Optical films 103 and 104 were obtained in the same manner as optical film 101, except that the dye compounds shown in Table 1 were used as the dye compounds.

[0136] <Preparation of optical films 105, 107, and 108> Optical films 105, 107, and 108 were obtained in the same manner as optical film 101, except that the resins shown in Table 1 were used.

[0137] <Preparation of optical film 106> Optical film 106 was obtained in the same manner as optical film 105, except that the amount of coating solution was changed to achieve the film thickness shown in Table 1.

[0138] <Preparation of optical film 109> Optical film 109 was obtained in the same manner as optical film 101, except that the content of the dye compound was changed as shown in Table 1.

[0139] <Preparation of optical film 110> Optical film 110 was obtained in the same manner as optical film 101, except that the dye compound was not added.

[0140] 2-2. Evaluation 2-2-1. Transmittance Cut the optical film into 30mm x 30mm pieces to use as samples. Measure the transmittance of these samples at wavelengths of 200-800nm ​​using a spectrophotometer (e.g., Hitachi High-Tech U-3900H). The measurement conditions are as follows: (Measurement conditions) • Slit width: 2nm • Sampling interval: 1nm interval • Light source: WI lamp (visible range), D2 lamp (ultraviolet range) • Detector: Photomal The transmittance at wavelengths of 450 nm and 460 nm was calculated using the arithmetic mean of values ​​obtained from three measurements.

[0141] 2-2-2. Bending resistance The obtained optical film was cut to a size of 150 mm x 30 mm to serve as a sample. This sample was placed in a durability tester DLDM111LH (manufactured by Yuasa System Equipment Co., Ltd.), and repeated bending operations were performed with a radius of curvature (R) of 3 mm. The number of bending cycles until fracture occurred was counted by visually observing the surface of the sample. The maximum number of tests was 1 million, and the number of times fracture occurred was confirmed by video and evaluated according to the following criteria. A higher number of bending cycles indicates better bending resistance. ◎: No cracks even after 200,000 uses ○: 100,000 to less than 200,000 times △: 10,000 to less than 100,000 times ×: Less than 10,000 times

[0142] 2-2-3. Evaluation Results and Discussion Table 1 shows the evaluation results for optical films 101-110.

[0143] [Table 1]

[0144] As shown in Table 1, optical film 104 using dye compound 3 (comparative compound) had a transmittance at a wavelength of 460 nm that was less than 70%, and the transmittance difference △T(T(460)-T(450)) was small, less than 20%. Furthermore, even when dye compound 1 was used, optical films 105 and 106 combined with acrylic resin had a transmittance at a wavelength of 460 nm that was less than 70%, or the transmittance difference △T(T(460)-T(450)) was less than 20%. Optical films 105-106 also had low bending resistance.

[0145] In contrast, optical films 101-103 and 107-109, which combine the dye compound represented by formula (1) with a cycloolefin resin, all exhibited a transmittance of 70% or more at a wavelength of 460 nm, and the difference between the transmittance at 460 nm and 450 nm, ΔT(T(460)-T(450)), was also 20% or more. This indicates that these optical films transmit light in the required wavelength range well while efficiently blocking harmful short-wavelength light. Furthermore, these optical films also exhibited high bending resistance.

[0146] 4. Fabrication and evaluation of image display devices 4-1. Fabrication of image display devices 201-210 A TFT was placed on a glass substrate, and a reflective electrode made of chromium with a thickness of 80 nm was deposited on it by sputtering. An ITO anode was then deposited on the reflective electrode with a thickness of 40 nm by sputtering. A hole transport layer of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) was then deposited on the anode with a thickness of 80 nm by sputtering. Finally, using a shadow mask, each of the RGB light-emitting layers was formed with a thickness of 100 nm. For the red light-emitting layer, a 100 nm thick layer was formed by co-depositing (mass ratio 99:1) tris(8-hydroxyquinolinate)aluminum (Alq3) as the host and the luminescent compound [4-(dicyanomethylene)-2-methyl-6(p-dimethylaminostyryl)-4H-pyran] (DCM). For the green light-emitting layer, a 100 nm thick layer was formed by co-depositing (mass ratio 99:1) Alq3 as the host and the luminescent compound coumarin 6 (Coumarin6). For the blue light-emitting layer, a 100 nm thick layer was formed by co-depositing (mass ratio 90:10) BAlq as the host and the luminescent compound Perylene. Furthermore, a 4 nm thick layer of calcium was deposited by vacuum deposition as a first cathode (also called a buffer layer) with a low work function that allows electrons to be efficiently injected onto the light-emitting layer. A 2 nm thick layer of aluminum was then deposited on top of the first cathode as a second cathode (also simply called a cathode). The aluminum used as the second cathode serves to prevent the calcium, which is the first cathode, from undergoing chemical alteration when the transparent electrode formed on top of it is deposited by sputtering. In this way, an organic light-emitting layer was obtained. Next, a transparent conductive film with a thickness of 80 nm was deposited on the cathode by sputtering. ITO was used as the transparent conductive film. Furthermore, an insulating film was formed on the transparent conductive film by depositing a 200 nm silica film by CVD, and a sealing glass (1 mm thick) was bonded to it using an adhesive sheet C, thereby obtaining a display panel having an organic EL display element with the sealing glass as the surface layer. The average refractive index of the sealing glass was 1.51. An image display device was fabricated by laminating the optical films shown in Table 2 onto the above display panel. The adhesive sheet C was prepared by applying adhesive coating liquid C onto a silicone-treated polyethylene terephthalate film (release sheet), drying it at 130°C for 3 minutes to form an adhesive layer C with a thickness of 25 μm, and then adhering a silicone-treated polyethylene terephthalate film (release sheet) with a thickness of 38 μm onto the adhesive layer C. The adhesive coating liquid C was obtained by mixing 5 g of 2-ethylhexyl acrylate, 5 g of phenoxyethyl acrylate, 1 g of acrylic acid, and 0.2 g of AIBN with 0.15 g of isocyanate-based curing agent and 40.0 g of zirconium oxide transparent dispersion.

[0147] 4-2. Evaluation of Image Display Devices At room temperature (25°C), 2.5 mA / cm² 2 The displays were lit under constant current density conditions, and the luminescence of each display device was measured using a spectroradiometer CS-2000 (manufactured by Konica Minolta, Inc.). Subsequently, the blue light cut efficiency and luminous efficiency were evaluated using the following method.

[0148] <Blue light filtering efficiency> From the emission spectra obtained from the evaluation of the image evaluation device, the integrated intensity in the 400-450 nm range and the integrated intensity in the 400-550 nm range were determined, and the ratio of the former to the latter was calculated as the blue light ratio. Furthermore, the blue light ratio for each optical film was A X When the blue light ratio in optical film 110 is A0, (1-A X The blue light cut efficiency of each optical film was defined as (A0) × 100 (unit: %). The quality of the blue light cut efficiency was evaluated according to the following criteria. ◎: 70% or more ○: 50% or more but less than 70% ×: Less than 50%

[0149] <Luminous Efficiency> In the emission spectra obtained from the evaluation of the image evaluation device, the integrated intensity of 400-550 nm for each optical film is B X When the integrated intensity in the optical film 110 at 400-550 nm is B0, (B X The value of (B0) × 100 (unit: %) was defined as the luminous efficiency of each optical film. The quality of the luminous efficiency was evaluated according to the following criteria. ◎: 90% or more ○: 80% or more but less than 90% ×: Less than 80%

[0150] 4-3. Evaluation Results and Discussion Table 2 shows the evaluation results for image display devices 201 to 210. [Table 2]

[0151] As shown in Table 2, the image display devices 201-203 and 207-209, which use optical films 101-103 and 107-109 combining the dye compound represented by formula (1) with a cycloolefin resin, all achieve both high luminous efficiency and high blue light cut efficiency. This is thought to be due to the fact that they transmit light in the necessary wavelength range well while efficiently blocking harmful short-wavelength light. On the other hand, image display devices 204-206 and 210 using optical films 104-106 and 110, which have a transmittance lower than 70% or a transmittance difference △T(T(460)-T(450)) of less than 20%, were unable to achieve both luminous efficiency and blue light cut efficiency. [Industrial applicability]

[0152] The optical film of the present invention can efficiently block harmful blue light in the wavelength range without blocking light in the required wavelength range. Therefore, the optical film of the present invention is suitable, for example, as a blue light cut film. [Explanation of symbols]

[0153] 100 Image Display Devices 110 OLED display panels (image display panels) 120 touch sensors 130 Polarizing plate 131 Polarizer 132 Phase difference film 133 Protective film 134 Adhesive layer 140 Front plate 141 Base material 142 First protective film 143 Second protective film 144 Adhesive layer 150 Color filter components

Claims

1. It is an optical film, The material comprises a cycloolefin resin having structural units derived from norbornene monomers and a dye compound represented by the following formula (1), The transmittance T(460) of the optical film at a wavelength of 460 nm is 70% or more. The difference between the transmittance T(460) at a wavelength of 460 nm and the transmittance T(450) at a wavelength of 450 nm of the optical film, ΔT(T(460) - T(450)), is 20% or more. Optical film. 【Chemistry 1】 (In equation (1), R １ is an alkyl group, m is a non-negative integer, L １ and L ２ These are each linking groups, R ２ and R ３ These are, respectively, an alkyl group or an aryl group. R ４ and R ５ are each a cyano group, an alkoxycarbonyl group, or an aryloxycarbonyl group, and when both of R ４ and R ５ are an alkoxycarbonyl group or an aryloxycarbonyl group, they may be bonded to each other to form a ring.)

2. The norbornene monomer has an ester-containing group. The optical film according to claim 1.

3. The content of the dye compound is 0.1% by mass or more and 10% by mass or less, relative to the total mass of the optical film. The optical film according to claim 1.

4. The thickness is 20 μm or less. The optical film according to claim 1.

5. This is an optical film for foldable devices. The optical film according to claim 1.

6. Polarizer and, The optical film according to any one of claims 1 to 5, disposed on at least one side of the polarizer, Polarizing plate.

7. A base film and The optical film according to any one of claims 1 to 5, disposed on at least one side of the base film, Front plate.

8. Display panel and, The optical film according to any one of claims 1 to 5, disposed on the viewing side of the display panel, Image display device.

9. The aforementioned display panel is an organic EL display panel. The image display device according to claim 8.

10. A method for manufacturing an optical film according to any one of claims 1 to 5, A step of preparing a solution containing the cycloolefin resin, the dye compound, and a solvent, The process involves applying the aforementioned solution onto a support and then drying it to obtain a coated film, including, A method for manufacturing optical films.

Images