JP2004287392A - Optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a surface protective film having excellent hard coatability and high transparency and having an interference fringe preventive effect in the entire visible ray region at low cost and a method for manufacturing an optical film with a high-performance antireflection function. <P>SOLUTION: The optical film obtained by laminating a hard coating layer on the surface of a transparent base material is characterized in that the reflection spectra in the visible ray region of 360 to 800 nm in wavelength do not have a maximal value. Also, the optical film is characterized in that the amplitude (maximal value-minimal value) of the reflection spectra indicating the relationship between the reflectivity and wavelength in the visible ray region of 360 to 800 nm in wavelength is ≤0.5 in the entire region of the visible rays. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a plastic film used for protecting a surface of a display such as a word processor, a computer, and a television, for example, a CRT display, a liquid crystal display, a projection display, a plasma display, and an EL display. The present invention relates to an optical film having an effect of preventing stripes and a method for producing the same.

  Conventionally, optical films used for various displays attach importance to high transparency and scratch resistance, chemical resistance and weather resistance, and often provide a hard coat layer using an active energy ray-curable resin on a substrate surface. Was. However, the refractive index (wavelength 550 nm) of the hard coat layer obtained by this active energy ray curing is as low as 1.49 in the case of, for example, an acrylic resin, and the refractive index (wavelength 550 nm) of the base material used, for example, polyethylene. In many cases, the refractive index of terephthalate is far from 1.65, causing interference between light reflected on the surface of the hard coat layer and light reflected on the interface between the hard coat layer and the base material, and a maximum value and a minimum value in a reflection spectrum. , A plurality of iridescent non-uniformities (interference fringes) occur. The interference fringes lower the visibility of the display and impair the aesthetic appearance of the display. Therefore, it is important to suppress this interference fringe, and the conventional interference fringe reduction technology employs unevenness in the base material itself and the intermediate layer between the base material and the hard coat layer to form an interface between the hard coat layer and the base material. (See, for example, Patent Document 1).

However, if the unevenness is large to scatter light, interference fringes are reduced, but the problem of a decrease in visible light transmittance occurs.If the unevenness is too small, the light scattering effect is reduced and the interference fringe reduction effect is reduced. There is a problem. Further, a technique of providing an intermediate layer between a base material and a hard coat layer has also been proposed (for example, see Patent Document 2). In this technique, an intermediate layer having a different refractive index is provided between the substrate and the hard coat layer. However, since the refractive index changes stepwise, the problem that the interference fringes do not disappear even if they are reduced. Has occurred. Further, these techniques have a problem that the number of steps increases, which leads to an increase in cost. Further, a technique for preventing interference fringes by reducing the refractive index difference between the base material and the hard coat layer has been proposed (for example, see Patent Document 3). However, considering the refractive index chromatic dispersion of the substrate, even if the refractive index difference at a certain wavelength is small, the refractive index in the entire visible light region does not match, so even if the interference fringe decreases, it does not disappear. The problem has arisen.
JP 08-197670 A JP 2000-111706 A JP-A-07-151902

  The present invention provides a method for producing a surface protective film having excellent hard coat properties and high transparency, and having an effect of preventing interference fringes in the entire visible light region at low cost in order to solve the above problems. It is the purpose. Still another object is to provide a method for producing a high-performance optical film with an antireflection function.

  The invention according to claim 1 is characterized in that, in an optical film formed by laminating a hard coat layer on a surface of a transparent substrate, a reflection spectrum in a visible light region having a wavelength of 360 nm to 800 nm does not have a maximum value. It is an optical film.

  The invention according to claim 2 is an optical film formed by laminating a hard coat layer on the surface of the transparent substrate, wherein the wavelength of the reflection spectrum in the visible light region of 360 nm to 800 nm indicates the relationship between the reflectance and the wavelength. An optical film having an amplitude (difference between a maximum value and a minimum value) of 0.5 or less in the entire visible light region.

  The invention according to claim 3 is an optical film, wherein a difference in refractive index between the transparent base material and the hard coat layer is within a range of 4% or less.

  The invention according to claim 4 is an optical film, wherein the transparent substrate is a substrate that is not easily eroded by a general-purpose solvent, and a dry film thickness of a hard coat layer is in a range of 5 to 15 μm. .

  The optical film according to claim 5, wherein the transparent substrate is a substrate that is easily eroded by a general-purpose solvent, and the hard coat layer is laminated using a solvent that dissolves or swells the substrate. It is.

  The invention according to claim 6 is the optical film according to any one of claims 1 to 5, wherein the hard coat layer contains fine particles.

  The invention according to claim 7 is the optical film according to any one of claims 1 to 5, wherein the hard coat layer contains an ultraviolet ray and an electron beam curable resin.

  The invention according to claim 8 is the optical film according to any one of claims 1 to 7, wherein an antireflection layer is provided on the hard coat layer.

  The present invention can provide a method for producing an optical film having excellent hard coat properties and high transparency, and having an effect of preventing interference fringes in the entire visible light region at low cost. Further, it is possible to provide a method for producing a high-performance optical film with an antireflection function.

  Hereinafter, embodiments of the present invention will be described in detail.

  Since the refractive index difference between the substrate and the hard coat layer in the optical film of the present invention is as small as 4% or less, the reflection spectrum showing the relationship between the reflectance and the wavelength in the visible light region (wavelength 360 to 800 nm). The amplitude (maximum value-minimum value) at is small. In addition, when a base material that is not easily eroded by a general-purpose solvent is used, if the film thickness is 5 to 15 μm, the peak of the maximum value and the valley of the minimum value increase in the visible light region. Averaged to be macroscopically achromatic, and secondly, because the reflectance is averaged because it exceeds the sensitivity of the eyes and measuring instruments, there is no interference fringes and excellent visibility A film is obtained.

  When the difference in the refractive index between the base material and the hard coat layer outside the above-mentioned range is 4% or more, the amplitude in the reflection spectrum is large, so that the color contrast is strong, it is difficult to perform color mixing averaging, and by setting the film thickness to 15 μm or more. Although the reflectance is averaged, cracks tend to occur in the minimum bending test, and the transmittance is reduced.

  When using a substrate that is easily eroded by a general-purpose solvent, a hard coat layer is formed using a resin containing a solvent that dissolves or swells the substrate. Since the components with the coating layer are mixed and the refractive index near the interface can be continuously changed, a film having no reflected light at the interface, no interference fringes, and excellent visibility can be obtained.

  If the difference between the refractive index of the hard coat layer and the substrate outside the above range is 4% or more, the substrate must be more dissolved or swelled, so that the productivity is deteriorated and the performance as the hard coat is reduced. The problem of not being satisfied arises.

  As the substrate used in the present invention, a known substrate can be used. For example, a substrate made of a film or sheet made of various organic polymers having translucency can be used. When used for an optical member such as a display, it is necessary to consider optical properties such as transparency and refractive index of light, and various physical properties such as impact resistance, heat resistance, and durability.

  Such materials include polyolefins (polyethylene, polypropylene, polycycloolefin, etc.), polyesters (polyethylene terephthalate, polybutylene terephthalate, polyethylene nartalate, etc.), cellulosics (triacetyl cellulose, diacetyl cellulose, cellophane, etc.), and polyamides Organic polymers (eg, nylon-6, nylon-66, etc.), acrylics (eg, polymethyl methacrylate), polystyrene, polyvinyl chloride, polyimide, polyvinyl alcohol, ethylene vinyl alcohol, and polycarbonate are used.

  In the present invention, examples of the substrate which is hardly eroded by the general-purpose solvent include polyethylene terephthalate film (stretched crystallized film) and polycycloolefin film. , Triacetylcellulose film, polyethylene terephthalate film (unstretched non-crystallized film), polycarbonate film and the like.

  Further, known additives such as an antistatic agent, an ultraviolet absorber, an infrared absorber, a plasticizer, a lubricant, a coloring agent, an antioxidant, and a flame retardant are added to these organic polymers to add a function. Can also be used. Further, the base material may be a single substance of the above-mentioned substances or a laminate of a plurality of substances or a mixture thereof. The thickness of the substrate can be appropriately selected depending on the use of the surface protective film, and is preferably 25 to 300 μm. However, it is not limited to this. In addition, surface treatment can be performed for the purpose of improving adhesion to a hard coat layer formed on a substrate. As the surface treatment method, for example, surface roughening treatment by a sand blast method or a solvent treatment method, or surface oxidation treatment such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, and the like. No.

  The optical film of the present invention has a hard coat layer on the plastic film, and it is necessary to adjust the refractive index of this hard coat layer. Colloidal metal oxide fine particles are homogeneously dispersed therein.

  As the ultraviolet ray and electron beam curable resin used for the hard coat layer, for the purpose of surface modification of the substrate, abrasion resistance of an optical film by a steel wool rubbing test, hardness by a pencil scratch test, adhesion by a cellophane peel test, Resins can be selected and used so as to satisfy the specifications required for various properties such as cracking property by the minimum bending test and to adjust the refractive index. This ultraviolet curable resin contains a photopolymerizable prepolymer, a photopolymerizable monomer, a photopolymerization initiator, and the like.

  The electron beam-curable resin contains a photopolymerizable prepolymer and a photopolymerizable monomer.

  Examples of the photopolymerizable prepolymer include polyester acrylate, epoxy acrylate, urethane acrylate, and polyol acrylate. One of these photopolymerizable prepolymers may be used, or two or more thereof may be used in combination.

  Examples of the photopolymerizable monomer include polymethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, Examples thereof include dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and neopentyl glycol di (meth) acrylate.

  The refractive index of these monomers is around 1.5, but the monomers having a high refractive index include those having a cyclic group and / or those containing halogen atoms other than fluorine atoms and atoms such as S, N and P. No. The cyclic group includes an aromatic group, a heterocyclic group and an aliphatic ring group. For example, bis (4-methacryloylthiophenoxy) sulfide, vinyl phenyl sulfide, bisphenoxyethanol full orange acrylate, tetrabromobisphenol A diepoxy acrylate and the like can be mentioned. In particular, in the present invention, it is preferable to use a urethane acrylate-based prepolymer and dipentaerythritol hexa (meth) acrylate, bisphenoxyethanol fluorene acrylate or the like as a monomer.

  Further, examples of the photopolymerization initiator include acetophenones, benzoins, benzophenones, phosphine oxides, ketals, anthraquinones, thioxanthones, and the like.

  Further, n-butylamine, triethylamine, poly-n-butylphosphine and the like can be mixed and used as a photosensitizer.

The metal oxide fine particles used for the hard coat layer in the optical film of the present invention are, for example, TiO ₂ (refractive index: 2.3 to 2.7), ZrO ₂ (refractive index: 2.0), La ₂ O. ₃ (refractive index: 2.0), Y ₂ O ₅ (refractive index: 1.9), SnO ₂ (refractive index: 1.9), Al ₂ O ₃ (refractive index: 1.6), SiO ₂ ( Metal oxide fine particles having a refractive index of 1.5), or composite metal oxide fine particles of two or more of these, or conductive metal oxides such as ATO (antimony-tin oxide) and ITO (indium-tin oxide) Ultrafine particles can be mentioned, and the refractive index of the base plastic film and the refractive index of the hard coat layer can be adjusted to be equal by adjusting the addition amount of these metal oxide ultrafine particles. The metal oxide fine particles preferably have a particle size of 1 to 100 nm from the viewpoint of transparency and dispersibility. However, it is not limited to this. If the particle size exceeds 100 nm, light is remarkably reflected by Rayleigh scattering, the film becomes white, and the transparency is reduced. If the particle size is less than 1 nm, problems such as non-uniformity of the film due to aggregation between particles occur.

  In the hard coat layer of the optical film of the present invention, the content of the metal oxide ultrafine particles is 0 to 600 parts by weight based on 100 parts by weight of the cured product of the ultraviolet ray and the electron beam curable resin from the viewpoint of adjusting the refractive index. Is preferably within the range. Further, it is preferable that the surface of the ultrafine particles is subjected to a surface treatment to increase the affinity with an organic substance as a binder. The surface treatment can be classified into a physical surface treatment such as a plasma discharge treatment or a corona discharge treatment, and a chemical surface treatment using a coupling agent. It is preferred to carry out only the chemical surface treatment or both the physical / chemical surface treatment. As the coupling agent, an organoalkoxy metal compound such as a silane coupling agent or a titanium coupling agent is preferable. For surface treatment with a coupling agent, inorganic acids (eg, sulfuric acid, hydrochloric acid, nitric acid, chromic acid, hypochlorous acid, carbonic acid, etc.) and organic acids (eg, acetic acid, polyacrylic acid, polyglutamic acid, etc.) are used as catalysts. Preferably, it is used.

  Further, the hardness of the hard coat layer is preferably 3H or more as a pencil hardness under a load of 500 g, and the hard coat film can have necessary scratch resistance.

  In the adjustment of the hard coat agent for forming the hard coat layer, there is no particular limitation on the mixing order of each component, and the ultraviolet and electron beam curable resin, the metal oxide ultrafine particles, the photopolymerization initiator and the like are added in various solvents. And mix.

  The solvent can be appropriately selected after confirming whether or not the base material is eroded. Solvents include ketones such as methyl ethyl ketone, acetone and methyl isobutyl ketone, esters such as methyl acetate, ethyl acetate and butyl acetate, aromatic compounds such as toluene and xylene, ethers such as diethyl ether and tetrahydrofuran, methanol and ethanol. And alcohols such as isopropanol. In addition, known additives such as an antifoaming agent and a leveling agent can be added to the hard coat agent, if desired. The solid content concentration of the hard coat agent is not particularly limited, and is preferably in the range of 10 to 70% by weight, and particularly preferably in the range of 30 to 50% by weight from the viewpoints of coating properties, drying properties, economy and the like.

  The method of applying the hard coat agent to the substrate is not particularly limited, and a bar coat method, a knife coat method, a roll coat method, a blade coat method, a die coat method, or the like can be used.

  The thickness of this coating layer can be controlled by calculating the required coating amount of the hard coating agent from the solid content concentration of the hard coating agent and the density of the antiglare layer after curing.

  Further, the coating layer after drying may be cured by irradiating the coating layer with ultraviolet rays and electron beams in an atmosphere purged with nitrogen to form a hard coat layer with less oxygen damage and high surface hardness.

  There is no particular limitation on the ultraviolet irradiation device used for curing, and a known ultraviolet irradiation device using, for example, a high-pressure mercury lamp, a xenon lamp, a metal halide lamp, a fusion lamp, or the like can be used.

The amount of ultraviolet irradiation is usually about 100 to 800 mJ / cm ² . There is no particular limitation on the electron beam irradiation device, and the acceleration voltage is usually 50 to 300 kV.

  The optical film thus obtained is excellent in hard coat properties, transparency and interference fringe prevention properties, and has good visibility when used for various displays. Therefore, it can be used as a protective film for various displays.

  The antireflection layer provided on the hard coat layer has a configuration having a low refractive index layer and a high refractive index layer. In the present invention, a single layer of a low refractive index layer is preferred. For example, when the substrate of the present invention is a polyethylene terephthalate film, the refractive index of the entire substrate having a hard coat layer is high, the refractive index difference from the low refractive index layer is large, and the antireflection performance is improved. It is.

Here, the low-refractive-index layer is, for example, an ultraviolet ray and an electron beam curable type in which fine particles having a low refractive index, such as MgF ₂ (refractive index; 1.4) and SiO ₂ (refractive index; 1.5), are dispersed. Various sols made of resin or oligomers obtained by hydrolyzing a mixture of a silane coupling agent and a fluorine-based silane coupling agent with a catalyst are used. However, it is not limited to this.

  The low-refractive-index layer is formed by applying the above-described various coating methods so that the cured film thickness becomes 0.01 to 1 μm, performing a drying treatment, and then, if necessary, using ultraviolet rays and electrons. Perform line irradiation.

Other methods of forming the low refractive index layer may be any suitable means such as a vacuum evaporation method, a sputtering method, a reactive sputtering method, an ion plating method, and an electroplating method. It may be formed of a paint film, an ultra-thin film of about 0.1 μm of MgF ₂ or the like, a metal vapor-deposited film, or a vapor-deposited film of SiO _x or MgF ₂ .

The high refractive index layer in the antireflection layer of the present invention is made of fine particles having a high refractive index, such as TiO ₂ (refractive index; 2.3 to 2.7), Y ₂ O ₃ (refractive index; 1.9), It is made of an ultraviolet or electron beam curable resin in which La ₂ O ₃ (refractive index; 2.0), ZrO ₂ (refractive index; 2.1), Al ₂ O ₃ (refractive index; 1.6) or the like is dispersed. However, the present invention is not limited to this.

  As a method of forming the high refractive index layer, the composition is applied by the above-mentioned various application methods so that the cured film thickness becomes 0.01 to 1 μm, dried, and then irradiated with ultraviolet rays and electron beams as necessary. I do.

The other method of forming the high refractive index layer may be any appropriate means such as a vacuum evaporation method, a sputtering method, a reactive sputtering method, an ion plating method, and an electroplating method. , A very thin film of TiO ₂ or the like having a thickness of about 0.1 μm, or a metal deposited film.

  Other layers may be further laminated on the optical film of the present invention. For example, an antistatic layer and an antifouling layer can be used.

  Hereinafter, the present invention will be described in detail based on specific experimental examples.

The performance of the optical film prepared in each experimental example was evaluated according to the following method.
<Spectral reflectance & fringe width>
The spectral reflectance at an incident angle of 5 ° was measured using an automatic spectrophotometer (U-4000, manufactured by Hitachi, Ltd.). From the spectrum data, the absolute value of the difference between the adjacent maximum value and minimum value of the reflectance was defined as the fringe width. At the time of the measurement, the surface opposite to the application surface was matted and a black paint was applied to perform anti-reflection treatment.
(Visual evaluation)
Light of the fluorescent lamp was incident on the surface of the hard coat at a distance of 20 cm from the 20 W fluorescent lamp, and visual evaluation of interference fringes was performed. At the time of evaluation, a matte black paint was applied to the surface opposite to the application surface, and antireflection treatment was performed.
(Scratch resistance)
Using # 0000 steel wool, the surface of 10 reciprocations was rubbed with a load of 250 g, and the presence or absence of scratches was visually evaluated.
(Total light transmittance and haze value)
The surface protective film was measured using an image clarity measuring device [NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd.].
(Pencil hardness)
Based on JIS K5400, it was evaluated at a load of 1 kg by a testing machine method.
<Experimental example 1>
Using a polyethylene terephthalate film (total light transmittance: 88.7%, haze value: 0.7%) that is hardly eroded by a general-purpose solvent having a thickness of 75 µm and a refractive index (550 nm) of 1.65 as a base material,
Pentaerythritol triacrylate 6 parts by weight
4 parts by weight of ultrafine zirconium oxide particles (particle size: 10 to 15 nm)
Irgacure 184 0.2 parts by weight
A coating solution obtained by stirring and mixing 10 parts by weight of methyl ethyl ketone is applied by a gravure coating method so as to have a WET film thickness of 6, 10, 20 μm (DRY film thickness after drying 3, 5, 10 μm), and dried. An optical film was produced by irradiating 1000 mJ of ultraviolet light to form a hard coat layer. The refractive index (550 nm) of the hard coat layer was 1.61. Table 1 shows the performance evaluation results of this optical film.
<Experimental example 2>
An optical film was produced in the same manner as in Example 1, except that 4 parts by weight of pentaerythritol triacrylate and 6 parts by weight of ultrafine zirconium oxide particles were used. The refractive index (550 nm) of the hard coat layer was 1.65. Table 1 shows the performance evaluation results of this optical film.
<Experimental example 3>
An optical film was produced in the same manner as in Example 1, except that 3 parts by weight of pentaerythritol triacrylate and 7 parts by weight of ultrafine zirconium oxide particles were used. The refractive index (550 nm) of the hard coat layer was 1.69. Table 1 shows the performance evaluation results of this optical film.
<Experimental example 4>
A triacetylcellulose film (total light transmittance: 94.1%, haze value: 0.1%) easily eroded by a general-purpose solvent having a thickness of 80 μm and a refractive index (550 nm) of 1.49 was used as a substrate. Using methyl ethyl ketone and methyl acetate to dissolve or swell the substrate,
Pentaerythritol triacrylate 5 parts by weight
Urethane acrylate 5 parts by weight
Irgacure 184 0.5 parts by weight
Methyl ethyl ketone 5 parts by weight
A coating solution obtained by stirring and mixing 5 parts by weight of methyl acetate is applied by a gravure coating method so as to have a WET film thickness of 10 μm (DRY film thickness after drying is 5 μm), and is dried. An optical film was produced by forming a coat layer. The refractive index (550 nm) of the hard coat layer was 1.51. Table 1 shows the performance evaluation results of this optical film.
<Experimental example 5>
Using a polyethylene terephthalate film having a thickness of 75 μm and a refractive index (550 nm) of 1.65 as a substrate,
Pentaerythritol triacrylate 5 parts by weight
Urethane acrylate prepolymer 5 parts by weight
Irgacure 184 0.5 parts by weight
A coating solution obtained by stirring and mixing 10 parts by weight of methyl ethyl ketone is applied by a gravure coating method to a WET film thickness of 6, 16, 24 μm (DRY film thickness after drying: 3, 8, 12 μm), dried, and dried with a high-pressure mercury lamp. An optical film was produced by irradiating 1000 mJ of ultraviolet light to form a hard coat layer. The refractive index (550 nm) of the hard coat layer was 1.50. Table 1 shows the performance evaluation results of this optical film.
<Experimental example 6>
Using a triacetyl cellulose film having a thickness of 80 μm and a refractive index (550 nm) of 1.49 as a base material, and using isopropyl alcohol which does not corrode the base material as a solvent,
7.5 parts by weight of pentaerythritol triacrylate
2.5 parts by weight zirconium oxide ultrafine particles
Irgacure 184 0.5 parts by weight
A coating solution obtained by stirring and mixing 10 parts by weight of isopropyl alcohol is applied by a gravure coating method to a WET film thickness of 6 μm (DRY film thickness after drying is 3 μm), dried, and irradiated with ultraviolet rays of 1000 mJ by a high pressure mercury lamp to harden. An optical film was produced by forming a coat layer. The refractive index (550 nm) of the hard coat layer was 1.55. Table 1 shows the performance evaluation results of this optical film.

表１，図２および図３から明らかなように、実験例１〜３と６の結果比較において、汎用溶剤により浸食されにくい基材を用いた場合には，屈折率および膜厚を制御することによりハードコート性能は十分な性能を保ちつつも、高透明で干渉縞のない光学フィルムを作製することができる。さらに、表１、図４および図５から明らかなように，実験例４と６の結果比較において、汎用溶剤により浸食されやすい基材を用いた場合には，屈折率の制御および溶剤選定によりハードコート性能は十分な性能を保ちつつも，高透明で干渉縞のない光学フィルムを作製することができる。
＜実験例７＞
実験例１と同様にしてハードコート層を積層した光学フィルムを作成した。次いで，テトラエトキシシランと、フッ化アルキルシランをモル比９５：５で混合し、この溶液の０．２２倍重量の溶媒（２−メトキシエタノール：イソプロピルアルコール＝１：１）により希釈した。この溶液に、前記シランに対し７．５倍モルの１規定塩酸（水重量換算による）を加えて１時間の攪拌により、加水分解してゾル溶液とた。そして，ここに上記の溶媒を加えて、固形分濃度４％としたものを反射防止層の塗工液とした。光学フィルム上に、前記反射防止層の塗工液を硬化膜厚が０．１μｍになるように塗工し、１２０℃で５分間加熱処理を行い、反射防止を単層で積層した光学フィルムを作成した。この光学フィルムを自動分光光度計（日立製作所製、Ｕ−４０００）を用い、入射角５°における分光反射率を測定した。なお、測定の際には塗布面と反対の面をにつや消し黒色塗料を塗布し、反射防止の処置を行った。ハードコート層膜厚１０μｍの分光反射率グラフを図６に示す。
＜実験例８＞
実験例７と同様にしてハードコート層を積層した光学フィルムを作成した。実施例５と同様にして反射防止を単層で積層した光学フィルムを作成した。この光学フィルムを自動分光光度計（日立製作所製、Ｕ−４０００）を用い、入射角５°における分光反射率を測定した。なお、測定の際には塗布面と反対の面をにつや消し黒色塗料を塗布し、反射防止の処置を行った。ハードコート層膜厚８μｍの分光反射率グラフを図７に示す。

As is clear from Table 1, FIG. 2 and FIG. 3, in the comparison of the results of Experimental Examples 1 to 3 and 6, when the base material which is not easily eroded by the general-purpose solvent is used, the refractive index and the film thickness are controlled. Thereby, an optical film having high transparency and no interference fringes can be produced while maintaining sufficient hard coat performance. Furthermore, as is clear from Table 1, FIGS. 4 and 5, in the comparison of the results of Experimental Examples 4 and 6, when a base material which is easily eroded by a general-purpose solvent was used, the refractive index was controlled and the selection of the solvent was difficult. An optical film with high transparency and no interference fringes can be produced while maintaining sufficient coating performance.
<Experimental example 7>
An optical film having a hard coat layer laminated thereon was produced in the same manner as in Experimental Example 1. Then, tetraethoxysilane and fluorinated alkylsilane were mixed at a molar ratio of 95: 5, and the mixture was diluted with a solvent (2-methoxyethanol: isopropyl alcohol = 1: 1) 0.22 times the weight of this solution. To this solution was added 1N hydrochloric acid (in terms of water weight) 7.5 times the mol of the silane, and the mixture was hydrolyzed by stirring for 1 hour to form a sol solution. Then, a solution having a solid content of 4% by adding the above solvent was used as a coating liquid for the antireflection layer. On the optical film, a coating liquid of the antireflection layer is applied so that the cured film thickness becomes 0.1 μm, and a heat treatment is performed at 120 ° C. for 5 minutes to form an optical film having a single layer of antireflection. Created. Using this automatic film, the spectral reflectance at an incident angle of 5 ° was measured using an automatic spectrophotometer (U-4000, manufactured by Hitachi, Ltd.). At the time of the measurement, the surface opposite to the application surface was matted and a black paint was applied to perform anti-reflection treatment. FIG. 6 shows a spectral reflectance graph of the hard coat layer having a film thickness of 10 μm.
<Experimental example 8>
An optical film having a hard coat layer laminated thereon was produced in the same manner as in Experimental Example 7. In the same manner as in Example 5, an optical film laminated with a single layer of antireflection was prepared. Using this automatic film, the spectral reflectance at an incident angle of 5 ° was measured using an automatic spectrophotometer (U-4000, manufactured by Hitachi, Ltd.). At the time of the measurement, the surface opposite to the application surface was matted and a black paint was applied to perform anti-reflection treatment. FIG. 7 shows a spectral reflectance graph of the hard coat layer having a thickness of 8 μm.

  As is clear from the comparison between FIGS. 6 and 7, even when the antireflection layer is laminated, the product of the present invention does not cause light interference and is excellent in visibility. In addition, even when the same anti-reflection layer was formed, since no light interference occurred, the luminous average reflectance was low and the anti-reflection performance was improved.

FIG. 1 is a sectional view showing an optical film according to one embodiment of the present invention. 9 is a graph showing the spectral reflectance of the optical film prepared in Experimental Example 2 (film thickness 10 μm). 9 is a graph showing the spectral reflectance of an optical film prepared in Experimental Example 5 (film thickness: 8 μm). 9 is a graph showing the spectral reflectance of the optical film created in Experimental Example 4. 13 is a graph showing the spectral reflectance of the optical film created in Experimental Example 6. 13 is a graph showing the spectral reflectance of the optical film with an antireflection function created in Experimental Example 7. 19 is a graph showing the spectral reflectance of the optical film with an antireflection function created in Experimental Example 8.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Transparent base material 2 Resin 3 Hard coat layer 4 Metal oxide fine particles 5 Antireflection layer 6 Optical film

Claims (8)

  An optical film comprising a transparent substrate and a hard coat layer laminated on the surface thereof, wherein a reflection spectrum in a visible light region having a wavelength of 360 nm to 800 nm does not have a maximum value.   In an optical film obtained by laminating a hard coat layer on the surface of the transparent substrate, the amplitude of the reflection spectrum showing the relationship between the reflectance and the wavelength in the visible light region having a wavelength of 360 nm to 800 nm (the difference between the maximum value and the minimum value). ) Is 0.5 or less in the entire visible light region.   An optical film, wherein a difference in refractive index between the transparent substrate and the hard coat layer is within a range of 4% or less.   An optical film, wherein the transparent substrate is a substrate that is not easily eroded by a general-purpose solvent, and a dry film thickness of a hard coat layer is in a range of 5 to 15 μm.   An optical film, wherein the transparent substrate is a substrate that is easily eroded by a general-purpose solvent, and a hard coat layer is laminated using a solvent that dissolves or swells the substrate.   The optical film according to claim 1, wherein the hard coat layer contains fine particles.   The optical film according to any one of claims 1 to 5, wherein the hard coat layer contains an ultraviolet ray and an electron beam curable resin.   The optical film according to any one of claims 1 to 7, wherein an antireflection layer is provided on the hard coat layer.

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