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

Abstract

The present application relates to optical film, polarizing plate, front panel, image display device and the manufacturing method of optical film. The optical film contains cycloolefin resin with structural unit from norbornene monomer, and the pigment compound represented by the following formula (1). The transmittance T (460) of the optical film at wavelength 460 nm is 70% or more, and the difference ΔT (T (460)-T (450)) between the transmittance T (460) of the optical film at wavelength 460 nm and the transmittance T (450) at wavelength 450 nm is 20% or more.[Chem. 1]

Description

Technical Field

[0001] This invention relates to optical films, polarizers, front panels, image display devices, and methods for manufacturing optical films. Background Technology

[0002] In recent years, it has been recognized that blue light emitted from display devices and other electronic devices places a significant burden on the eyes and body. Blue light refers to blue light with a wavelength of 380–495 nm, which possesses high energy even within the visible light spectrum. It has been pointed out that prolonged exposure to such blue light can cause eye fatigue, decreased vision, dry eyes, and sleep disorders. Therefore, there is a desire to block blue light emitted from display devices and other electronic devices.

[0003] As a method for blocking blue light, a method of attaching a blue light blocking film to the surface of a display has been proposed. For example, in Patent Document 1, an optical film comprising a triacetyl cellulose substrate (light-transmitting substrate) and a light-transmitting functional layer comprising a cured composition of an acrylic polymer containing a sesamol-type benzotriazole monomer (spectral transmittance modifier), an acrylic monomer, and a polymerization initiator is proposed.

[0004] Existing technical documents

[0005] Patent documents

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2023-159190 Summary of the Invention

[0007] The problem to be solved by the present invention

[0008] However, the membrane in Patent Document 1 has a transmittance of over 87.3% at a wavelength of 440nm, which is insufficient to block light in the harmful wavelength region.

[0009] Furthermore, according to the inventors' research, if the blocking performance of harmful wavelength regions is to be improved, sometimes even light in the necessary wavelength regions is blocked. In image display devices using such films, the image may become darker, or power consumption may be reduced.

[0010] The present invention was made in view of the above circumstances, and its object is to provide an optical film capable of transmitting light in the necessary wavelength range and efficiently blocking blue light in the harmful wavelength range, as well as a method for manufacturing the same, a polarizer, a front panel, and an image display device.

[0011] Methods for solving problems

[0012] This invention relates to optical films, polarizers, front panels, image display devices, and methods for manufacturing optical films.

[0013] [1] An optical film comprising: a cycloolefin resin having structural units derived from norbornene monomers, and a pigment 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 ΔT(T(460)-T(450)) between the transmittance T(460) of the optical film at a wavelength of 460 nm and the transmittance T(450) at a wavelength of 450 nm is 20% or more.

[0014] [Chemistry 1]

[0015]

[0016] (In formula (1),

[0017] R １ It is an alkyl group.

[0018] m is an integer greater than or equal to 0.

[0019] L １ and L ２ These are connecting groups,

[0020] R ２ and R ３ They are alkyl or aryl, respectively.

[0021] R ４ and R ５ They are cyano, alkoxycarbonyl, or aryloxycarbonyl, respectively, in R ４ and R ５ When these two groups are alkoxycarbonyl or aryloxycarbonyl groups, they can bond with each other to form a ring.

[0022] [2] According to the optical film described in [1], wherein the above-mentioned norbornene monomer has an ester group.

[0023] [3] According to the optical film described in [1] or [2], wherein the content of the above-mentioned pigment compound is 0.1% by mass or more and 10% by mass or less relative to the total mass of the optical film.

[0024] [4] The optical film according to any one of [1] to [3], wherein the thickness is 20 μm or less.

[0025] [5] The optical film according to any one of [1] to [4] is a foldable optical film.

[0026] [6] A polarizer comprising a polarizer and an optical film disposed on at least one side of the polarizer as described in any one of [1] to [5].

[0027] [7] A front panel comprising: a substrate film and an optical film disposed on at least one side of the substrate film as described in any one of [1] to [5].

[0028] [8] An image display device comprising: a display panel and an optical film disposed on the viewable side of the display panel as described in any one of [1] to [5].

[0029] [9] According to the image display device described in [8], the display panel is an organic EL display panel.

[0030]

[10] A method for manufacturing an optical film, which is a method for manufacturing an optical film as described in any one of [1] to [5], comprising: a step of preparing a solution containing the above-mentioned cycloolefin resin, the above-mentioned pigment compound and solvent; and a step of coating the above-mentioned solution onto a support and drying it to obtain a coated film.

[0031] The effects of the invention

[0032] According to the present invention, it is possible to provide: an optical film that can efficiently block blue light in a harmful wavelength region without blocking light in the necessary wavelength region, a method for manufacturing the same, a polarizer, a front panel, and an image display device. Attached Figure Description

[0033] Figure 1 A graph illustrating an example of the spectral transmittance of an optical film according to one embodiment of the present invention.

[0034] Figure 2 A schematic cross-sectional view illustrating an image display device according to one embodiment of the present invention.

[0035] Figure 3 A schematic cross-sectional view illustrating an image display device according to another embodiment of the present invention.

[0036] Explanation of reference numerals in the attached figures

[0037] 100 Image display devices

[0038] 110 Organic EL display panel (image display panel)

[0039] 120 touch sensor

[0040] 130 polarizer

[0041] 131 Polarizer

[0042] 132 Phase Retardation Film

[0043] 133 Protective Film

[0044] 134 Adhesive layer

[0045] 140 Front Panel

[0046] 141 Substrate

[0047] 142 First protective film

[0048] 143 Second protective film

[0049] 144 Adhesive layer

[0050] 150 Color Filter Components Detailed Implementation

[0051] The inventors conducted in-depth research and found that films containing pigment compounds with specific structures, specifically pigment compounds represented by formula (1), can effectively block harmful short-wavelength light (wavelength below 450 nm).

[0052] Furthermore, it was determined that the spectral transmittance of the membrane containing the aforementioned pigment compounds also depends on the type of resin used. The inventors further investigated and found that, when combined with a resin of low polarity, particularly a cycloolefin resin, it is possible to transmit light well in the necessary wavelength range and efficiently block harmful short-wavelength light.

[0053] The reasons are unclear, but the following is believed.

[0054] To ensure good transmission of light in the necessary wavelength range and efficient blocking of harmful short-wavelength light, it is desirable to drastically change the transmittance of the optical film in the wavelength range near the middle. Therefore, the absorption spectrum of the pigment compound used should preferably be as sharp as possible.

[0055] Since the dye compounds represented by formula (1) have ester bonds, the pigment compounds interact strongly with each other, resulting in sharp absorption spectra.

[0056] On the other hand, in the aforementioned combinations of pigment compounds and resins, the highly polar resins interact more strongly with the pigment compounds, sometimes thus passivating the absorption characteristics of the pigment compounds (broadening the absorption spectrum). In contrast, cycloolefin resins, due to their lower polarity, interact less with the pigment compounds. Therefore, the inherent properties of the pigment compounds are less likely to be impaired, allowing them to exhibit the desired properties.

[0057] Furthermore, it was found that for such an optical film, if the transmittance T(460) at a wavelength of 460 nm is 70% or more, and 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 is 20% or more, then it can transmit light in the wavelength region required for image visibility well, and efficiently block light in the harmful short wavelength region (e.g., see reference). Figure 1 ).

[0058] The following is a detailed description of one embodiment of the present invention. However, the present invention is not limited to the following embodiment. Furthermore, in this specification, the numerical range indicated by "~" refers to the range including the values ​​described before and after "~" as the lower limit and upper limit.

[0059] 1. Optical film

[0060] Regarding the optical film of this embodiment, as described above, it contains a cyclic olefin resin and a specific pigment compound. Furthermore, the transmittance T(460) of the optical film at a wavelength of 460 nm is 70% or more, and 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 is 20% or more.

[0061] If the transmittance T(460) of the optical film at a wavelength of 460 nm is 70% or more, then since light in the wavelength range required for image recognition can be transmitted well, the darkening of the displayed image can be suppressed. From the same point of view, the transmittance T(460) of the optical film at a wavelength of 460 nm is more preferably 80% or more, and even more preferably 85% or more. The upper limit of the transmittance T(460) of the optical film at a wavelength of 460 nm is not particularly limited, and can be 100% or less, or 99.5% or less.

[0062] 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 is 20% or more. If the aforementioned difference ΔT(T(460)-T(450)) is 20% or more, light in the necessary wavelength region can be transmitted well, while light in the harmful short wavelength region can be sufficiently blocked. From the same point of view, the aforementioned transmittance difference ΔT is more preferably 25% or more, and even more preferably 30% or more. The upper limit of the aforementioned transmittance difference ΔT is not particularly limited, for example, it can be 60% or less. That is, the aforementioned transmittance difference ΔT can be set to 20% or more and 60% or less, for example.

[0063] The transmittance of optical films at various wavelengths can be determined using the following methods.

[0064] The optical film was cut into 30mm × 30mm pieces as samples. For these samples, the transmittance at wavelengths of 200–800 nm was measured using a spectrophotometer (e.g., Hitachi Hightech U-3900H). The measurement conditions were as follows.

[0065] (Measurement conditions)

[0066] • Slit width: 2nm

[0067] • Sampling interval: 1nm interval

[0068] • Light source: WI lamp (visible area), D2 lamp (ultraviolet area)

[0069] • Detector: Photomultiplier tube

[0070] To clarify, the transmittance at wavelengths of 430nm, 450nm, and 460nm is the arithmetic mean of the values ​​obtained from three measurements.

[0071] Regarding the transmittance T(460) at a wavelength of 460 nm and the difference ΔT(T(460)-T(450)) between the transmittance at 460 nm and the transmittance at 450 nm, the transmittance of the optical film can be adjusted by the type and combination of resin and pigment compounds, and the content of pigment compounds. For example, if a cycloolefin resin and a specific pigment compound are combined, the T(460) of the optical film will be maintained at a high level, and ΔT(T(460)-T(450)) will easily increase. In addition, if the content of pigment compounds is increased, ΔT(T(460)-T(450)) will easily increase.

[0072] The following is a detailed explanation of the components contained in the optical film.

[0073] 1-1. Cycloolefin resins

[0074] Cycloolefin resins are polymers containing structural units derived from norbornene monomers.

[0075] Norbornene monomers are represented by the following formula (2).

[0076] [Chemistry 2]

[0077]

[0078] R in equation (2) １ ~R ４ The preferred components are hydrogen atoms, hydrocarbon groups, or ester groups.

[0079] Examples of hydrocarbon groups include alkyl and aryl groups. Alkyl groups are alkyl groups having 1 to 10 carbon atoms, preferably 1 to 4, more preferably 1 or 2. Aryl groups are aryl groups having 6 to 14 carbon atoms, preferably 6 to 10. These hydrocarbon groups may also have substituents. Examples of substituents include polar groups such as carboxyl, hydroxyl, amino, amide, and cyano groups. Alkyl groups are preferred among these substituents.

[0080] Examples of ester-containing groups include alkoxycarbonyl, aryloxycarbonyl, and groups to which these groups are bonded via a linking group (methylene, etc.). Among these, the ester-containing group is preferably alkoxycarbonyl, more preferably alkoxycarbonyl with 1 to 10 carbon atoms in the alkoxy moiety, more preferably 1 to 4, and even more preferably 1 or 2.

[0081] Among them, R is preferred. １ ~R ４ At least one of them contains an ester group. Cycloolefin resins having structural units derived from norbornene monomers containing ester groups are readily soluble in solvents, making them more suitable for film formation using solution casting. As mentioned above, from the viewpoint of further improving blue light cutoff, low resin polarity is preferred. On the other hand, if the resin polarity is too low, its solubility in solvents decreases, sometimes making film formation by coating difficult. In contrast, by using cycloolefin resins containing ester groups, solvent solubility can be ensured, and blue light performance can be improved.

[0082] For example, it could be R １ It contains ester group, R ２ R ３ and R ４ These are either hydrogen atoms or hydrocarbon groups; they can be R. １ and R ３ They are respectively ester-containing, R ２ and R ４ They are either hydrogen atoms or hydrocarbon groups, respectively.

[0083] In formula (2), p and m are integers from 0 to 3. Among them, m+p is preferably 0 to 4, more preferably 0 to 2, and even more preferably m=1 and p=0. For cycloolefin resins containing structural units from norbornene monomers with m=1 and p=0, the glass transition temperature is high, and optical films with good mechanical strength can be formed.

[0084] In the example of norbornene monomers represented by formula (2), the following are included.

[0085] [Chemistry 3]

[0086]

[0087]

[0088]

[0089] Regarding the content of structural units derived from norbornene monomers, it is preferably 20 to 100% by mass, more preferably 30 to 100% by mass, relative to all 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 groups is, for example, 70% by mass or more, preferably 100% by mass.

[0090] The cyclic olefin resin may further contain structural units from other monomers that can copolymerize with norbornene monomers. Examples of other copolymerizable monomers include cyclic olefin monomers that do not have a norbornene skeleton, such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene. Preferably, the cyclic olefin monomer has 4 to 20 carbon atoms, more preferably 5 to 12.

[0091] Commercially available products can be used as cyclic olefin resins. Examples of commercially available products include Arton (ARTON: a registered trademark) G, Arton F, Arton R, and Arton RX manufactured by JSR Corporation.

[0092] The weight-average molecular weight (Mw) of the cyclic olefin resin is not particularly limited, but is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and even more preferably 40,000 to 200,000. If the weight-average molecular weight (Mw) of the cyclic olefin resin is within the above range, the formability can be maintained and the mechanical strength (especially the toughness) of the optical film can be further improved.

[0093] The weight-average molecular weight (Mw) of cyclic olefin resins can be determined by gel permeation chromatography (GPC).

[0094] Specifically, as the measuring device, a gel permeation chromatography (HLC8220GPC manufactured by Tosoo Corporation) was used, and as the column, a TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL manufactured by Tosoo Corporation was used in series.

[0095] Then, 20 ± 0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution was injected into the column (temperature 40 °C) and measured with a detector RI at 40 °C. The weight-average molecular weight was calculated by converting to styrene.

[0096] The glass transition temperature (Tg) of cycloolefin resins is generally preferably above 110°C, more preferably 110–350°C, and even more preferably 120–250°C. The glass transition temperature can be determined using DSC (Differential Scanning Colorimetry) according to the method in accordance with JIS K 7121-2012.

[0097] Optical films may contain one type of cyclic olefin resin or two or more types of cyclic olefin resin.

[0098] The content of cyclic olefin resin in the optical film is not particularly limited, but is preferably 30% by mass or more and 99.9% by mass or less relative to the total mass of the optical film, and more preferably 50% by mass or more and 95.0% by mass or less.

[0099] 1-2. Specific pigment compounds

[0100] The pigment compound is a compound represented by the following formula (1).

[0101] [Chemistry 4]

[0102]

[0103] In equation (1), R １ It is an alkyl group. Preferably, it is an alkyl group with 1 to 7 carbon atoms, more preferably 1 to 4. m is an integer of 0 or more, preferably 0 or more and 2 or less, more preferably 0 or 1.

[0104] In equation (1), L １ and L ２ These are connecting groups. The connecting groups are single bonds or alkylene groups having 1 to 7 carbon atoms. Preferably, they are methylene (-CH4). ２ -). L １ and L ２ They can be the same or different.

[0105] In formula (1), R2 and R3 are alkyl or aryl groups, respectively. Alkyl groups are preferred, and alkyl groups having 1 to 7 carbon atoms are more preferably 1 to 4 carbon atoms. R2 and R3 can be the same or different. The aryl group can be an aryl group having 6 to 12 carbon atoms. For reference, -CO2R2 and -CO2R3 in formula (1) are -C(=O)OR2 and -C(=O)OR3, respectively.

[0106] In equation (1), R ４ and R ５ These are, respectively, cyano, alkoxycarbonyl (-C(=O)-OR), or aryloxycarbonyl (-C(=O)-OAr). The alkyl moiety of the alkoxycarbonyl group has, for example, 1 to 10 carbon atoms, preferably 1 to 4. The aryl moiety of the aryloxycarbonyl group can, for example, have 6 to 12 carbon atoms. Thus, R... ４ and R ５ This can be, for example, an electron-withdrawing group from an active methylene compound described later. In R ４ and R ５When both are alkoxycarbonyl or aryloxycarbonyl, they can bond together to form a ring (e.g., a 6-membered ring containing an oxycarbonyl group).

[0107] As specific examples of compounds represented by formula (1), the following compounds can be listed.

[0108] [Chemistry 5]

[0109]

[0110]

[0111] The compound represented by formula (1) can be prepared, for example, by the following method. For example, it can be obtained by carrying out a dehydration condensation reaction (Knoevenagel condensation) of the following aldehyde compound and an active methylene compound (e.g., malononitrile, Michaelis-McCl3, etc.) in a solvent such as toluene in the presence of a catalyst such as morpholine.

[0112]

[0113] Regarding the content of the pigment compound in the optical film, there is no particular limitation as long as the transmittance described above is met. It is preferably 0.1% by mass or more and 10% by mass or less relative to the total mass of the optical film, more preferably 0.5% by mass or more and 5% by mass or less. If the content of the pigment compound is 0.1% by mass or more, it is particularly possible to further reduce the transmittance of light with wavelengths below 450 nm, and to further increase the transmittance difference ΔT(T(460)-T(450)). Therefore, it is easier to allow light in the necessary wavelength range to pass through, and easier to block light in the harmful wavelength range. If the content of the pigment compound is 10% by mass or less, it is possible to further increase the transmittance of light in the necessary wavelength region, such as light with wavelengths above 460 nm.

[0114] 1-3. Other ingredients

[0115] The optical film may further contain other components besides those described above, without impairing the effects of the present invention. Examples of other components include matting agents, ultraviolet absorbers, phase difference modifiers (phase difference increasers, phase difference decreasers), plasticizers, antioxidants, light stabilizers, antistatic agents, release agents, and thickeners. From the viewpoint of imparting unevenness and appropriate slipability to the surface of the optical film, the optical film preferably contains a matting agent.

[0116] The matting agent is a particulate. These particulates can be inorganic or resin-based. Examples of inorganic particulates include silica, titanium dioxide, alumina, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Examples of resin-based particulates include silicone resins, fluoropolymers, and acrylic resins.

[0117] Among these, inorganic microparticles are preferred, and silica microparticles are more preferred from the viewpoint of minimizing the haze of the optical film and effectively reducing the coefficient of friction. Examples of silica microparticles include Aerogel 200V, Aerogel R972V, and Aerogel R812 (all manufactured by Aerogel Co., Ltd., Japan).

[0118] The average particle size of the primary particles is preferably 0.005 to 0.4 μm, more preferably 0.01 to 0.3 μm. The average particle size of the primary particles can be measured using an Otsuka Electronics ELSZ-2000.

[0119] Regarding the content of microparticles in the optical film, for example, it is preferably 0.01 to 3.0% by mass relative to the total mass of the optical film, and more preferably 0.01 to 2.0% by mass.

[0120] 1-4. Physical properties of optical films

[0121] (Transmission rate)

[0122] As mentioned above, the transmittance T(460) of the optical film at a wavelength of 460nm is more than 70%, and the difference between the transmittance T(460) at a wavelength of 460nm and the transmittance T(450) at a wavelength of 450nm is more than 20%.

[0123] Regarding the transmittance T(450) of the optical film at a wavelength of 450 nm, there is no particular limitation as long as the above characteristics are met. However, from the viewpoint of further 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 and can be 0%.

[0124] Furthermore, regarding the transmittance T(430) of the optical film at a wavelength of 430 nm, there is no particular limitation as long as the above characteristics are met, but it is preferably 5% or less, 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, and can be 0%.

[0125] The transmittance of the optical film at various wavelengths can be determined using the methods described above.

[0126] (Bending resistance)

[0127] When conducting a bending test on the optical film, the number of bends until breakage is preferably 10,000 or more, more preferably 100,000 or more. Such an optical film exhibits excellent bending resistance and is therefore suitable for applications such as foldable devices.

[0128] The optical film was cut into 150mm × 30mm pieces as samples. The samples were placed in a durability testing machine (e.g., Yuasashistem Machine Manufacturing DLDM111LH) and repeatedly bent at a radius of curvature (R) of 3mm. The number of bends until the sample broke at its surface was counted.

[0129] Bending resistance can be adjusted according to the molecular weight of the cyclic olefin resin and the thickness of the optical film. For example, the higher the molecular weight of the cyclic olefin resin and the thinner the optical film, the easier it is to improve bending resistance.

[0130] (Glass transition temperature)

[0131] The glass transition temperature (Tg) of the optical film is preferably, for example, 110–250 °C. If the Tg of the optical film is 110 °C or higher, the heat resistance of the optical film can be further improved. The glass transition temperature of the optical film can be determined by the same method described above.

[0132] (Haze)

[0133] 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 (NDH2000: manufactured by Nippon Denshoku Kogyo Co., Ltd.) after conditioning at 25°C and 60%RH for 24 hours.

[0134] (Phase difference Ro)

[0135] The phase difference Ro of the optical film is not particularly limited. For example, the in-plane phase difference Ro measured under conditions of 550 nm wavelength, 23 °C, and 55% RH is preferably 0 nm or more and 150 nm or less, more preferably 1 nm or more and 110 nm or less. Such an optical film is suitable, for example, as a polarizer or a protective film for a front panel.

[0136] Ro is defined by the following formula.

[0137] Formula (3): Ro = (nx-ny)×d

[0138] (In formula (3),

[0139] nx represents the refractive index of the film along the in-plane hysteresis axis (the direction in which the refractive index becomes maximum).

[0140] ny represents the refractive index in the direction orthogonal to the in-plane hysteresis axis of the film.

[0141] d represents the film thickness (nm).

[0142] The in-plane hysteresis axis of an optical film can be confirmed using an automated birefringence meter (e.g., AxoScan Mueller MatrixPolarimeter). The in-plane hysteresis axis of the optical film can be approximately parallel to the width direction of the optical film.

[0143] Ro can be determined using the following methods.

[0144] 1) Condition the optical film at 23°C and 55%RH for 24 hours. Measure the average refractive index of the film using an Abbe refractometer and the thickness d using a commercially available micrometer.

[0145] 2) Using an automated birefringence meter (e.g., AxoScan Mueller Matrix Polarimeter, manufactured by AxoScan), the retardation Ro at a measurement wavelength of 550 nm was measured in an environment of 23°C and 55%RH.

[0146] Regarding the phase difference Ro of the optical film, it can be adjusted, for example, according to the stretching conditions. The greater the stretching ratio, the easier it is for the phase difference Ro to increase.

[0147] (thickness)

[0148] The thickness of the optical film is not particularly limited, but is preferably 80 μm or less, more preferably 60 μm or less, and from the viewpoint of further improving bending resistance, is even more preferably 20 μm or less. The lower limit of the thickness of the optical film is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more.

[0149] 2. Manufacturing method of optical film

[0150] The aforementioned optical film can be manufactured using any method. However, considering the reduced risk of thermal degradation of the pigment compound and fewer restrictions on the materials used, solution-based film fabrication is preferred.

[0151] That is, the optical film can be obtained by: 1) preparing a solution containing the above-mentioned cyclic olefin resin, the above-mentioned pigment compound and solvent (solution preparation process); 2) coating the obtained solution onto a support, drying and peeling it off to obtain a coated film (coating process).

[0152] 2-1. Solution preparation process

[0153] A solution is prepared by dissolving or dispersing cyclic olefin resins and pigment compounds in a solvent.

[0154] The solvent used in the solution must contain at least a solvent capable of dissolving cyclic olefin resins (a good solvent). Examples of good solvents include chlorinated organic solvents such as dichloromethane; 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 stabilizing and dispersing the pigment compound well.

[0155] The solvent used in the solution may further contain undesirable solvents. Examples of undesirable solvents include straight-chain or branched aliphatic alcohols with 1 to 4 carbon atoms. If the proportion of alcohols in the solution increases, the film is prone to gelation and peeling off from the metal support. Examples of straight-chain or branched aliphatic alcohols with 1 to 4 carbon atoms include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, and methyl ethyl ketone. Among these, methyl ethyl ketone is preferred from the viewpoints of solution stability, relatively low boiling point, and good drying properties.

[0156] 2-2. Coating process

[0157] The obtained coating liquid is applied to the support. There are no restrictions on the coating method; gravure printing or a die can be used.

[0158] As a support, a support that is resistant to solvents in coating solutions such as PET, PEN, PC, and PI, does not deform or melt during the drying and coating process, and is suitable for use as a support. Additionally, the surface of the support can be treated with easy-to-adhere or demolding processes. The film thickness of the support is not particularly limited and can be set to 25 μm or more and 188 μm or less.

[0159] The solvent is evaporated until the coating film on the support can be peeled off. There are no particular limitations on the method of solvent evaporation; it can be methods such as blowing air onto the coating film. As for the drying temperature, any temperature that can remove the solvent without causing thermal degradation of the dye compound is acceptable; for example, it can be set to 80°C or higher and 150°C or lower. The drying temperature can be set to the temperature of the airflow.

[0160] Then, the coating film obtained by evaporating the solvent is peeled off from the support.

[0161] The amount of residual solvent on the coating film on the support during peeling depends on the drying conditions, the length of the support, etc., and can be, for example, 0.1% by mass or more and 10% by mass or less. If the amount of residual solvent is within the above range, the coating film is not too soft, and therefore its planarity is less likely to be damaged during peeling. The amount of residual solvent is defined by the following formula.

[0162] Residual solvent content (mass%) = (Mass of coated film before heat treatment - Mass of coated film after heat treatment) / (Mass of coated film after heat treatment) × 100

[0163] The heat treatment for determining the residual solvent amount was a heat treatment at 150°C for 1 hour.

[0164] 2-3. Other processes

[0165] In this embodiment, in addition to these steps, other steps may be performed. For example, a step of stretching the coated film (stretching step) and a step of drying the coated film (drying step) may also be performed. In addition, a step of attaching a peelable protective film to the surface of the coated film peeled from the support may also be performed.

[0166] For example, the drying process can be carried out while the coated film is being conveyed using multiple conveyor rollers (e.g., multiple conveyor rollers arranged in an alternating pattern when viewed from the side). The drying method is not particularly limited and can use hot air, infrared radiation, heated rollers, or microwaves. For simplicity, hot air drying is preferred.

[0167] As for the drying temperature, any temperature that can remove the solvent without causing thermal degradation of the pigment compounds is acceptable, and it can be set to the same drying temperature as mentioned above.

[0168] 3. Image display device

[0169] The aforementioned optical film can be applied to an image display device. That is, the image display device includes a display panel and the aforementioned optical film disposed on its visible side.

[0170] The display panel has display elements. Examples of display elements include organic light-emitting diode (OLED) elements, liquid crystal display (LCD) elements, and inorganic light-emitting diode (OLED) elements, with organic light-emitting diode (OLED) elements being preferred. That is, as an image display device, examples include organic electroluminescent (OLED) display devices, liquid crystal display devices, and inorganic electroluminescent (OLED) display devices, with organic EL display devices being preferred.

[0171] [First Implementation Method]

[0172] Figure 2 A schematic cross-sectional view is provided to illustrate the image display device 100 according to the first embodiment of the present invention. For example... Figure 2 As shown, the image display device 100 has, in sequence, an organic EL display panel 110 (display panel), a touch sensor 120, a polarizer 130, and a front panel 140 facing the viewable side.

[0173] (1) Organic EL display panel 110

[0174] 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, a light-emitting layer, a transparent electrode, and a sealing layer are sequentially stacked on a substrate such as glass or polyimide.

[0175] (2) Touch sensor 120

[0176] In this embodiment, the touch sensor 120 is disposed between the organic EL display panel 110 and the polarizer 130. A known touch sensor can be used as the touch sensor 120. As for the touch sensor 120, it is only necessary to detect the location touched by the front panel 140 (described later); for example, a capacitively coupled touch sensor can be used. Furthermore, the touch sensor 120 can be of the On-Cell type (see [reference]). Figure 2 (It can also be of type In-Cell).

[0177] For example, a capacitively coupled touch sensor includes a substrate layer, a light-transmitting electrode layer for position detection disposed on the substrate layer, and a touch position detection circuit. Thus, for example, if the surface of the front panel 140 (described later) is touched, the light-transmitting electrode is grounded at the point of touch via the electrostatic capacitance of the human body. The touch position detection circuit detects the grounding of the light-transmitting electrode and detects the position of the touch.

[0178] (3) Polarizing filter 130

[0179] The polarizer 130 includes a polarizer 131, a phase difference film 132, a protective film 133, and two adhesive layers 134.

[0180] (3.1) Polarizer 131

[0181] Polarizer 131 is a component that allows light to pass through a polarization plane in a specific direction only. Polarizer 131 is, for example, a polyvinyl alcohol stretched film doped with iodine or dichroic pigments.

[0182] The thickness of the polarizer 131 is not particularly limited, for example, it is 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.

[0183] (3.2) Phase retardation film 132

[0184] A phase retardation film 132 is disposed on one side of the polarizer 131 (in this embodiment, between the polarizer 131 and the organic EL display panel 110). In this embodiment, the phase retardation film 132 is preferably a λ / 4 phase retardation film. Thus, the polarizer 130 can function as a circular polarizer and has anti-reflective properties.

[0185] The material of the phase retardation film 132 is not particularly limited, and a light-transmitting thermoplastic resin can be used. Examples of thermoplastic resins include cellulose ester resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polycarbonate resins; polyimide resins; cyclic olefin resins; and (meth)acrylic resins. Among these, cyclic olefin resins, polyester resins, and polycarbonate resins are preferred, and cyclic olefin resins are more preferred. Furthermore, the term "(meth)acrylic" refers to acrylic resins, methacrylic resins, or both.

[0186] When the phase lag film 132 is a λ / 4 phase lag film, the angle between the in-plane hysteresis axis of the phase lag film 132 and the absorption axis of the polarizer 131 is preferably 30° or more and 60° or less, and more preferably 45°.

[0187] The thickness of the phase retardation film 132 is not particularly limited, for example, it is 5 μm or more and 50 μm or less, preferably 10 μm or more and 45 μm or less.

[0188] (3.3) Protective film 133

[0189] A protective film 133 is disposed on the other side of the polarizer 121 (in this embodiment, between the polarizer 131 and the front panel 140). In this embodiment, the protective film 133 is the optical film described above.

[0190] (3.4) Adhesive layer 134

[0191] Two adhesive layers 134 are respectively disposed between the polarizer 131 and the phase difference film 132, and between the polarizer 131 and the protective film 133. The adhesive layer 134 can be a layer obtained from an aqueous adhesive, or a layer of cured material containing an active energy line curing adhesive.

[0192] As a water-based adhesive, examples include aqueous solutions containing polyvinyl alcohol resins (such as fully saponified polyvinyl alcohol aqueous solutions).

[0193] Examples of active energy line curing adhesives include adhesives that are cured by irradiation with active energy lines such as ultraviolet light, such as curable compositions containing active energy line polymerizable compounds and photopolymerization initiators.

[0194] The thickness of the adhesive layer 134 is not particularly limited, for example, it is 0.01 μm or more and 10 μm or less, preferably 0.01 μm or more and 5 μm or less.

[0195] (4) Front panel 140

[0196] The front panel 140 is a cover member disposed on the most visible side of the image display device 100, also known as a cover window or window film. As for the front panel 140, any light-transmitting component is acceptable, such as a glass plate, a glass film, a resin film, or a combination thereof.

[0197] Thin glass plates can be used as glass plates or glass films. The same materials as those exemplified as the materials used for the phase retardation film 132 can be used as resin films. Among these, considering excellent transparency and heat resistance, polyimide films, polyester films (e.g., polyethylene terephthalate films, polyethylene naphthalate films, etc.), cyclic olefin resin films, (meth)acrylic acid resin films, and cellulose ester films (e.g., triacetyl cellulose films, etc.) are preferred. The resin film preferably does not substantially have a phase retardation and is preferably an unstretched film.

[0198] The front panel 140 can have a single-layer structure or a multi-layer structure. In this embodiment, the front panel 140 has a multi-layer structure, including: a substrate 141, a first protective film 142, a second protective film 143, and two adhesive layers 144.

[0199] (4.1) Substrate 141

[0200] As the substrate 141, examples include the aforementioned glass plate or glass film, resin film, etc. Among them, glass film or polyimide film is preferred in terms of excellent flexibility and transparency.

[0201] The thickness of the substrate 141 is not particularly limited, for example, it is 10 μm or more and 100 μm or less, preferably 20 μm or more and 80 μm or less.

[0202] (4.2) First protective film 142

[0203] The first protective film 142 is disposed on the side of the substrate 141 opposite to the visible side of the polarizer 130. As the first protective film 143, the above-mentioned resin film can be cited as an example. Preferably, polyester resin film (e.g., polyethylene terephthalate film, etc.), (meth)acrylic resin film, polycarbonate resin film, etc. can be cited as examples. More preferably, it is a polyester resin film.

[0204] The thickness of the first protective film 142 is not particularly limited, for example, it is 3 μm or more and 40 μm or less, preferably 5 μm or more and 30 μm or less.

[0205] (4.3) Second protective film 143

[0206] A second protective film 143 is disposed on the visible side of the substrate 141. The same film as the first protective film 142 can be used as the second protective film 143. The second protective film 143 may further include a hard coating.

[0207] The hard coating comprises, for example, a cured product of a curable composition. Examples of curable compositions include active energy line curable compositions and, preferably, ultraviolet curable compositions.

[0208] The UV-curable composition comprises a UV-curable curable compound. The curable compound can be any of a monomer, oligomer, or prepolymer. Examples of such curable compounds include, for example, curable compounds having multiple (meth)acryloyl groups. Examples of such curable compounds include, for instance, tricyclodecanediethanol diacrylate, pentaerythritol di(meth)acrylate, urethane (meth)acrylate, and oligomers thereof. The curable compound may also further contain hydroxyl groups within the molecule.

[0209] (4.4) Adhesive layer 144

[0210] 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 resins as base polymers are preferred from the perspective of excellent transparency, adhesion, and heat resistance.

[0211] The adhesive layer may contain a crosslinked product comprising the aforementioned base polymer and crosslinking agent. Examples of crosslinking agents include compounds that react with functional groups present in the base polymer. For instance, when the base polymer has carboxyl groups, divalent or higher metal ions, polyamine compounds, polyisocyanate compounds, poly(poly)epoxide compounds, etc., can be used as crosslinking agents.

[0212] In addition, the adhesive layer may contain a cured product of an active energy line curing adhesive composition. Regarding active energy line curing adhesive compositions, in addition to the base polymer and crosslinking agent described above, they also contain active energy line polymerizable compounds, and may further contain photopolymerization initiators, photosensitizers, etc., as needed.

[0213] The thickness of the adhesive layer is not particularly limited, for example, it is 1 μm or more and 200 μm or less, preferably 5 μm or more and 150 μm or less, and more preferably 10 μm or more and 100 μm or less.

[0214] (5) Other

[0215] Alternatively, the aforementioned adhesive layer can be disposed in at least one of the following: between the organic EL display panel 110 and the touch sensor 120; between the touch sensor 120 and the polarizer 130; and between the polarizer 130 and the front panel 140. This allows these components to be fixed together.

[0216] (6) Function

[0217] The image display device 100 of the above embodiment includes the aforementioned optical film as a protective film 133 for the polarizer 130. Therefore, it is possible to allow light of the necessary wavelength to pass through while efficiently blocking harmful blue light in the short wavelength region.

[0218] (7) Variations

[0219] It should be noted that in the above embodiment, the protective film 133 of the polarizer 130 uses the aforementioned optical film, but is not limited thereto. For example, the phase retardation film 132 of the polarizer 130, the first protective film 142 and the second protective film 143 of the front panel 140 can use the aforementioned optical film, or the aforementioned optical film can be newly provided in a manner adjacent to any layer contained in the polarizer 130. In this case, the protective film 133 of the polarizer 130 can use a known polarizer protective film (e.g., a resin film of the same material as the material exemplified as the material of the phase retardation film 132).

[0220] In addition, in the above embodiment, the front panel 140, the circular polarizer 130, and the touch sensor 120 are arranged in this order from the visible side, but it is not limited to this, and the front panel 140, the touch sensor 120, and the polarizer 130 may also be arranged in this order.

[0221] [Second Implementation]

[0222] The image forming apparatus of the second embodiment is the same as that of the image forming apparatus of the first embodiment, except that a color filter member 150 (COE) is used instead of a polarizer 130, and the aforementioned optical film is used as the first protective film 142 of the front panel 140. Therefore, the same reference numerals are given to the same configurations or components as in the first embodiment, and detailed descriptions thereof are omitted.

[0223] Figure 3 A schematic cross-sectional view illustrating the image display device 100 according to the second embodiment of the present invention.

[0224] like Figure 3 As shown, the image display device 100 includes: an organic EL display panel 110, a touch sensor 120, a color filter component 150, and a front panel 140.

[0225] (1) Color filter component 150

[0226] The color filter component 150 is a color filter with anti-reflective function. The color filter component 150 can be the color filter itself, or it can be a color filter with additional functions such as color compensation. Examples of color filters with additional functions such as color compensation include: a color filter layer disposed on the thin film encapsulation (TFE) of the organic EL display panel 110, and a COE (Color Filter On Encapsulation) combined with a black PDL.

[0227] (2) Front panel 140

[0228] In this embodiment, the front panel 140 includes a substrate 141, a first protective film 142, a second protective film 143, and two adhesive layers 144. Moreover, in this embodiment, the first protective film 142 is the optical film described above.

[0229] (3) Other

[0230] It should be noted that in the above embodiment, the optical film is used as the first protective film 142 of the front panel 140, but it is not limited thereto, and the optical film can be used as the second protective film 143.

[0231] The image display device can be used as a mobile device such as a smartphone or tablet, or as a personal computer. Regarding the image display device of the present invention, its excellent flexibility makes it suitable for flexible displays and the like.

[0232] Example

[0233] The present invention will be specifically described below through embodiments, but the present invention is not limited to these embodiments.

[0234] 1. Materials of optical films

[0235] 1-1. Resin

[0236] <Preparation of cycloolefin resin COP-1>

[0237] 100 parts by mass of purified toluene and 100 parts by mass of methyl norbornene (see formula below) were added to a reaction vessel. Then, 25 mmol% (relative to monomer mass) of ethylhexanoic acid-Ni dissolved in toluene, 0.225 mol% (relative to monomer mass) of tris(pentafluorophenyl)boron, and 0.25 mol% (relative to monomer mass) of triethylaluminum dissolved in toluene were added to the reaction vessel, and the mixture was reacted at room temperature with stirring for 18 hours. After the reaction was completed, the reaction mixture was added to excess ethanol to form a polymer precipitate. The precipitate was purified, and the resulting solid was dried under vacuum at 65°C for 24 hours to obtain the cyclic olefin resin COP-1 (weight-average molecular weight Mw: 140,000, Tg: 140°C). Note that the weight-average molecular weight was determined using the method described above.

[0238] [Chemistry 7]

[0239]

[0240] <Preparation of cycloolefin resin COP-2>

[0241] Except for replacing methyl norborneol carboxylate with the following compound, the same procedure was followed as for COP-1 to prepare the cyclic olefin resin COP-2.

[0242] [Chemistry 8]

[0243]

[0244] <Preparation of cycloolefin resin COP-3>

[0245] Except for replacing methyl norborneol carboxylate with the following compound, the same procedure as for COP-1 was followed to prepare the cyclic olefin resin COP-3.

[0246] [Chemistry 9]

[0247]

[0248] <(meth)acrylic resins>

[0249] Asahi Kasei Corporation L13203

[0250] 1-2. Pigment compounds

[0251] <Pigment compound 1>

[0252] In a 100 mL three-necked flask, 1.17 g of compound (1-1) and 0.277 g of malononitrile were measured and dissolved in 18 mL of toluene. Then, 0.332 g of morpholine was added dropwise, and the mixture was heated to reflux for 4 hours. After the reaction was complete, the solvent was removed under reduced pressure, and 5 mL of methanol was added, stirring in suspension. The precipitate was filtered and dried to obtain 0.91 g (71% yield) of pigment compound 1 represented by the following formula. The structure of the compound was confirmed by NMR.

[0253] [Chemistry 10]

[0254]

[0255] <Pigment compound 2>

[0256] In a 100 mL three-necked flask, 1.17 g of compound (2-1) and 0.515 g of Michaelis-Menten acid were measured and dissolved in 18 mL of toluene. Then, 0.332 g of morpholine was added dropwise, and the mixture was heated to reflux for 4 hours. After the reaction was complete, the solvent was removed under reduced pressure, and 5 mL of methanol was added, stirring in suspension. The precipitate was filtered and dried to obtain 1.12 g (68% yield) of pigment compound 2 represented by the following formula. The structure of the compound was confirmed by NMR.

[0257] [Chemistry 11]

[0258]

[0259] <Pigment compound 3>

[0260] The following compounds are prepared as comparison compounds.

[0261] [Chemistry 12]

[0262]

[0263] 2. Fabrication and Evaluation of Optical Films (1)

[0264] 2-1. Fabrication of Optical Films

[0265] <Fabrication of Optical Film 101>

[0266] (Preparation of particulate additive solution)

[0267] The following components were mixed in a dissolver for 50 minutes and then dispersed using Manton-Gaulin. Further dispersion was achieved using a grinder to ensure the secondary particles reached the specified size. The mixture was then filtered using FinementNF (Finemete NF) manufactured by Nippon Seisen Co., Ltd., to prepare a microparticle additive solution.

[0268] Microparticles (Aerogel R972: manufactured by Aerogel Corporation of Japan, primary average particle size: 16nm, apparent specific gravity 50g / L): 6 parts by mass

[0269] Methyl ethyl ketone: 94 parts by weight

[0270] (Preparation of solution)

[0271] The following ingredients were added to a sealed container while being thoroughly stirred, and the temperature was raised to 80°C and maintained for 1 hour. Then, the mixture was cooled to 30°C and filtered through a 5μm pore size filter to obtain a solution.

[0272] Cycloolefin resin COP-1: 26 parts by weight

[0273] Toluene: 39 parts by weight

[0274] Methyl ethyl ketone: 30 parts by weight

[0275] Pigment compound 1: 0.27 parts by weight

[0276] Microparticle additive solution: 4.2 parts by weight

[0277] (Fabrication of optical films)

[0278] The prepared solution was discharged from the casting die and coated onto a PET support. Drying air at 40°C was blown onto the support to dry it until a self-supporting coated film was obtained. Then, it was dried in an oven at 130°C for 30 minutes to evaporate the solvent. The coated film was then peeled off from the support to obtain an optical film 101 with a thickness of 20 μm.

[0279] <Fabrication of Optical Film 102>

[0280] Except by changing the amount of coating liquid to form the film thickness shown in Table 1, optical film 102 is obtained in the same manner as optical film 101.

[0281] <Fabrication of Optical Films 103 and 104>

[0282] In addition to using the pigment compounds shown in Table 1 as pigment compounds, optical films 103 and 104 are obtained in the same manner as optical film 101.

[0283] <Preparation of optical films 105, 107 and 108>

[0284] In addition to using the resin shown in Table 1 as the resin, optical films 105, 107 and 108 are obtained in the same manner as optical film 101.

[0285] <Fabrication of Optical Film 106>

[0286] Except for changing the amount of coating liquid to form the film thickness shown in Table 1, optical film 106 is obtained in the same way as optical film 105.

[0287] <Preparation of Optical Film 109>

[0288] Except for changing the content of the pigment compound as shown in Table 1, optical film 109 is obtained in the same manner as optical film 101.

[0289] <Fabrication of Optical Film 110>

[0290] Optical film 110 is obtained in the same manner as optical film 101, except that no pigment compound is added.

[0291] SEQ danraku\# "0000"\* DBCHAR \* MERGEFORMAT \* MERGEFORMAT 00012-2. Evaluation

[0292] 2-2-1. Transmittance

[0293] The optical film was cut into 30mm × 30mm pieces as samples. For these samples, the transmittance at wavelengths of 200–800 nm was measured using a spectrophotometer (e.g., Hitachi Hightech U-3900H). The measurement conditions were as follows.

[0294] (Measurement conditions)

[0295] • Slit width: 2nm

[0296] • Sampling interval: 1nm interval

[0297] • Light source: WI lamp (visible area), D2 lamp (ultraviolet area)

[0298] • Detector: Photomultiplier tube

[0299] To clarify, the transmittance at wavelengths of 450nm and 460nm is the arithmetic mean of the values ​​obtained from three measurements.

[0300] 2-2-2. Bending resistance

[0301] The obtained optical film was cut into 150mm × 30mm pieces as samples. These samples were placed in a durability testing machine (DLDM111LH, manufactured by Yuasashim Machine) and repeatedly bent at a radius of curvature (R) of 3mm. The surface of the samples was then visually inspected, and the number of bends until breakage was recorded. The maximum number of tests was 1 million. The number of breaks observed in the animation was confirmed, and the samples were evaluated according to the following criteria: a higher number of bends indicates better bending resistance.

[0302] ◎: No cracks even after 200,000 cycles.

[0303] ○: More than 100,000 times but less than 200,000 times

[0304] △: More than 10,000 times but less than 100,000 times

[0305] ×: Less than 10,000 times

[0306] 2-2-3. Evaluation Results and Investigation

[0307] The evaluation results of optical films 101 to 110 are shown in Table 1.

[0308]

[0309] As shown in Table 1, for optical film 104 using pigment compound 3 (comparative compound), the transmittance at a wavelength of 460 nm is less than 70%, and the transmittance difference ΔT (T(460) - T(450)) is less than 20%. Furthermore, even when using pigment compound 1, in optical films 105 and 106 combined with acrylic resin, the transmittance at a wavelength of 460 nm is less than 70%, or the transmittance difference ΔT (T(460) - T(450)) is less than 20%. Additionally, optical films 105-106 also exhibit low flexural strength.

[0310] In contrast, for optical films 101–103 and 107–109, which combine pigment compounds represented by formula (1) and cyclic olefin resins, the transmittance at a wavelength of 460 nm is 70% or more, and the difference between the transmittance at 460 nm and the transmittance at 450 nm, ΔT(T(460)-T(450)), is also 20% or more. That is, it is known that these optical films transmit light well in the necessary wavelength range and block harmful short wavelength range light with high efficiency. In addition, these optical films also have high bending resistance.

[0311] 4. Production and evaluation of image display devices

[0312] 4-1. Fabrication of image display devices 201-210

[0313] A TFT is disposed on a glass substrate, and a chromium-based reflective electrode with a thickness of 80 nm is formed on it by sputtering. An ITO film with a thickness of 40 nm is formed on the reflective electrode by sputtering to serve as the anode. An 80 nm thick poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) is formed on the anode by sputtering to serve as the hole transport layer. A shadow mask is used on the hole transport layer to form RGB light-emitting layers with a film thickness of 100 nm.

[0314] As the red luminescent layer, tris(8-hydroxyquinoline)aluminum (Alq) as the main body is co-deposited. ３ The luminescent compound [4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran] (DCM) (mass ratio 99:1) is formed to a thickness of 100 nm. As the green luminescent layer, Alq, as the main body, is co-deposited. ３ It is formed with the luminescent compound coumarin 6 (mass ratio: 99:1) to a thickness of 100 nm. As a blue luminescent layer, it is formed by co-evaporation of BAlq as the main body and the luminescent compound perylene (mass ratio: 90:10) to a thickness of 100 nm.

[0315] Furthermore, a first cathode (also called a buffer layer) with a low work function, capable of efficiently injecting electrons into the light-emitting layer, is formed with calcium by vacuum evaporation to a thickness of 4 nm. An aluminum film is then formed on the first cathode as a second cathode (also simply called a cathode) to a thickness of 2 nm. Here, the aluminum used as the second cathode, when used to form a transparent electrode film on it by sputtering, serves to prevent the calcium used as the first cathode from undergoing chemical degradation. As described above, an organic light-emitting layer is obtained.

[0316] Next, a transparent conductive film with a thickness of 80 nm is formed on the cathode by sputtering. ITO is used as the transparent conductive film here. Then, silicon dioxide is formed on the transparent conductive film by CVD to a thickness of 200 nm, thereby forming an insulating film. A sealing glass (1 mm thick) is then bonded onto this insulating film using an adhesive sheet C, resulting in 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 is 1.51. An image display device is fabricated by laminating the optical films shown in Table 2 onto the aforementioned display panel.

[0317] To clarify, adhesive sheet C is a product obtained by coating 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 bonding a silicone-treated polyethylene terephthalate film (release sheet) with a thickness of 38 μm onto this adhesive layer C. Adhesive coating liquid C is 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.

[0318] 4-2. Evaluation of Image Display Devices

[0319] The system was tested at room temperature (25°C) using 2.5 mA / cm². ２ Under constant current density conditions, the luminous intensity of each image display device was measured using a CS-2000 spectroradiometer (manufactured by Konica Minolta Corporation). Next, the blue light cutoff efficiency and luminous efficiency were evaluated using the following methods.

[0320] <Blue light cutoff efficiency>

[0321] Based on the emission spectrum obtained in the image evaluation device, the integrated intensity at 400–450 nm and the integrated intensity at 400–550 nm are calculated, and the ratio of the former to the latter is used as the blue light ratio. Furthermore, the blue light ratio in each optical film is set as A. Ｘ Set the blue light ratio in optical film 110 to A. ０ When, it is defined as (1-A) Ｘ / A ０ (%) × 100 (unit: %), blue light cutoff efficiency in each optical film. It should be noted that the quality of blue light cutoff efficiency is evaluated according to the following criteria.

[0322] ◎:More than 70%

[0323] ○: 50% or more but less than 70%

[0324] ×: Less than 50%

[0325] <Luminous Efficiency>

[0326] In the emission spectrum obtained from the evaluation by the image evaluation device, the integrated intensity of 400–550 nm in each optical film is set as B. Ｘ Let the integrated intensity of 400-550 nm in the optical film 110 be set as B. ０ At that time, (B) Ｘ / B ０ The value of 100 (unit: %) is defined as the luminous efficiency of each optical film. The quality of luminous efficiency is evaluated according to the following criteria.

[0327] ◎:More than 90%

[0328] ○: 80% or more but less than 90%

[0329] ×: Less than 80%

[0330] 4-3. Evaluation Results and Investigation

[0331] The evaluation results of image display devices 201 to 210 are shown in Table 2.

[0332]

[0333] As shown in Table 2, it is known that image display devices 201-203 and 207-209, which use optical films 101-103 and 107-109 composed of a combination of pigment compound represented by formula (1) and cyclic olefin resin, all possess both luminous efficiency and blue light cutoff efficiency. This is believed to be due to the good transmission of light in the necessary wavelength range and the efficient blocking of harmful short wavelength range light.

[0334] On the other hand, for image display devices 204-206 and 210 that use optical films 104-106 and 110 with transmittance of less than 70% or transmittance difference ΔT (T(460)-T(450)) of less than 20%, it is not possible to simultaneously achieve luminous efficiency and blue light cutoff efficiency.

[0335] This application claims priority based on Japanese Patent Application No. 2024-208378, filed November 29, 2024, and Japanese Patent Application No. 2025-165485, filed October 1, 2025. All contents set forth in the descriptions and drawings of these applications are incorporated herein by reference.

[0336] Industrial availability

[0337] The optical film of the present invention can efficiently block harmful blue light in the wavelength range without blocking light in the necessary wavelength range. Therefore, the optical film of the present invention is suitable as, for example, a blue light blocking film.

Claims

1. An optical film comprising: a cycloolefin resin having structural units derived from norbornene monomers, and a pigment compound represented by the following formula (1), The transmittance T(460) of the optical film at a wavelength of 460 nm is above 70%. The difference ΔT between the transmittance T(460) at a wavelength of 460 nm and the transmittance T(450) at a wavelength of 450 nm, i.e., T(460) - T(450), of the optical film is greater than 20%. In equation (1), R1 is an alkyl group. m is an integer greater than or equal to 0. L1 and L ２ These are connecting groups, R ２ and R ３ They are alkyl or aryl, respectively. R ４ and R ５ They are cyano, alkoxycarbonyl, or aryloxycarbonyl, respectively, in R ４ and R ５ When these two are alkoxycarbonyl or aryloxycarbonyl groups, they can bond with each other to form a ring.

2. The optical film according to claim 1, wherein, The norbornene monomer contains an ester group.

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

4. The optical film according to claim 1, wherein, The thickness is less than 20μm.

5. The optical film according to claim 1, wherein it is a foldable optical film.

6. A polarizer, comprising: polarizer, and The optical film of any one of claims 1 to 5 disposed on at least one side of the polarizer.

7. Front panel, including: Substrate film, and The optical film of any one of claims 1 to 5 disposed on at least one side of the substrate film.

8. An image display device, comprising: Display panel, and The optical film of any one of claims 1 to 5 disposed on the visible side of the display panel.

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

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

Images