TWI787182B - Flexible display with repeated bending - Google Patents

Abstract

A hard coat film 1 comprising a base film 2, an optical adjustment layer 3 laminated on at least one main surface side of the base film 2, and an opposite side to the base film 2 laminated on the optical adjustment layer 3. The hard coating 4 on the main surface side, the base film 2 is a polyimide film, and the refractive index of the optical adjustment layer 3 is the value between the refractive index of the polyimide film and the refractive index of the hard coating 4. The thickness of the adjustment layer 3 is not less than 30 nm and not more than 700 nm. This kind of hard-coated film 1 has the bending resistance to withstand repeated bending, and at the same time, it is not easy to produce interference fringes.

Description

Flexible display with repeated bending

The present invention relates to a hard-coated film with a substrate film and a hard-coat layer, in particular to a hard-coated film suitable for use in flexible displays.

Various displays including liquid crystal displays (LCDs), organic EL displays (OELDs), and touch panels are widely used in various electronic devices. On the surface of these various displays, in order to prevent damage, a hard coat film in which a hard coat layer is provided on a base film is often provided.

In recent years, as the above-mentioned displays, displays capable of bending, that is, so-called flexible displays have been developed. Flexible displays are expected to be widely used, for example, they are used for placement displays that are bent and placed on columnar pillars, or for mobile displays that can be transported by bending or rounding. As a hard coat film for flexible displays, patent documents 1 and 2 series propose and disclose a hard coat film.

Here, the flexible display is not only formed into a curved surface once, but also repeatedly bent (bent) as described in Patent Document 3.

prior art literature patent documents

[Patent Document 1] Japanese Patent No. 5468167

[Patent Document 2] Japanese Unexamined Patent Publication No. 2015-69197

[Patent Document 3] Japanese Unexamined Patent Publication No. 2016-2764

However, when the conventional hard coat film is used for the above-mentioned flexible display, there is a problem that bending marks or whitening occur in the part repeatedly bent, resulting in poor appearance and low visibility as the display.

On the other hand, in hard-coated films, interference fringes may occur due to various factors. When interference fringes are generated on the hard coat film, there is still a problem of poor appearance and low visibility as a display.

The present invention is made in view of such actual situation, and its object is to provide a hard coating film which has the bending resistance to withstand repeated bending and is less likely to generate interference fringes.

In order to achieve the above object, the present invention firstly provides a hard coat film comprising a base film, an optical adjustment layer laminated on at least one main surface side of the base film, and an optical adjustment layer laminated on the optical adjustment layer. A hard-coated film with a hard coat layer on the main surface side opposite to the base film side is characterized in that the base film is a polyimide film, and the refractive index of the optical adjustment layer is the same as that of the polyimide film. The value between the refractive index and the refractive index of the hard coat layer, the thickness of the optical adjustment layer is not less than 30nm and not more than 700nm (Invention 1).

The hard coat film of the above invention (Invention 1) has excellent bending resistance because the base film is a polyimide film. Also, the hard coat film is The refractive index and thickness of the optical adjustment layer are in the above range, and interference fringes are not easily generated

In the above invention (Invention 1), it is preferable that the refractive index of the optical adjustment layer is not less than 1.45 and not more than 1.75 (Invention 2).

In the above inventions (Inventions 1 and 2), it is preferable that the refractive index of the hard coat layer is not less than 1.40 and not more than 1.70 (Invention 3).

In the above inventions (Inventions 1 to 3), it is preferable that the absolute value of the difference between the refractive index of the polyimide film and the refractive index of the hard coat layer and the refractive index of the optical adjustment layer be 0.025 or less in absolute value. (Invention 4).

In the above inventions (Inventions 1 to 4), it is preferable that the polyimide film has a thickness of not less than 5 μm and not more than 300 μm (Invention 5).

In the above inventions (Inventions 1 to 5), it is preferable that the thickness of the hard coat layer is not less than 0.5 μm and not more than 10 μm (Invention 6).

In the above inventions (Inventions 1 to 6), it is preferable that the optical adjustment layer contains metal oxide fine particles (Invention 7).

In the above inventions (Inventions 1 to 7), it is preferable that the optical adjustment layer is formed of a material obtained by curing a composition containing an active energy ray curable component (Invention 8)

The hard coat film in the above inventions (Inventions 1~8) is used as a flexible member constituting a flexible display (Invention 9)

In the above inventions (Inventions 1 to 9), preferably, an adhesive layer is laminated on at least one main surface side of the base film (Invention 10).

The hard-coated film of the present invention has the bending resistance to withstand repeated bending, and is not easy to produce interference fringes.

1, 1A, 1B‧‧‧hard coating film

2‧‧‧Substrate film

3‧‧‧Optical adjustment layer

4‧‧‧Hard Coating

5‧‧‧Adhesive layer

[FIG. 1] A cross-sectional view of a hard coat film according to an embodiment of the present invention.

[FIG. 2] A sectional view of a hard coat film according to another embodiment of the present invention.

[FIG. 3] A cross-sectional view of a hard coat film according to another embodiment of the present invention.

form for carrying out the invention

Embodiments of the present invention will be described below.

Fig. 1 is a cross-sectional view of a hard coat film according to an embodiment of the present invention. The hard coat film 1 of the present embodiment is provided with a base film 2, an optical adjustment layer 3 laminated on one main surface side (upper side in FIG. 1 ) of the base film, and an optical adjustment layer laminated between the optical adjustment layer 3 and The base film 2 side is constituted by the hard coat layer 4 on the opposite main surface side (upper side in FIG. 1 ).

In the hard coat film 1 described above, the base film 2 is a polyimide film. Since the base film 2 is a polyimide film, when the hard coat film 1 is applied to a flexible display and is repeatedly bent, it is possible to suppress bending marks or whitening of the base film 2 and to have excellent bending resistance. Therefore, when the flexible display using the hard coat film 1 of this embodiment repeatedly bends a predetermined portion, it is possible to suppress deterioration in appearance or deterioration in visibility at the bent portion.

In addition, the refractive index of the optical adjustment layer 3 is a value between the refractive index of the polyimide film and the refractive index of the hard coat layer 4, and the thickness of the optical adjustment layer 3 is not less than 30 nm and not more than 700 nm. That is, in the hard coat film 1 of this embodiment, there is an optical adjustment layer 3 and the refractive index of the optical adjustment layer 3 is a value between the refractive index of the polyimide film and the refractive index of the hard coat layer 4. . Thus, the substrate The difference between the refractive index of the thin film 2 and the optical adjustment layer 3 and the difference between the refractive index of the optical adjustment layer 3 and the hard coat layer 4 are each reduced. Thereby, reflection of light at each interface can be suppressed, and interference with light reflected at the surface of the hard coat layer 4 is less likely to occur. Moreover, the refractive index of the base film 2 and the refractive index of the optical adjustment layer 3 are refracted by the value between the refractive index of the polyimide film and the refractive index of the hard coat layer 4 by the refractive index of the optical adjustment layer 3. The index difference and the difference between the refractive index of the optical adjustment layer 3 and the refractive index of the hard coat layer 4 are small, and the thickness of the optical adjustment layer 3 is thin as described above. Thereby, the light waves reflected at the interface between the base film 2 and the optical adjustment layer 3 and the light waves reflected at the interface between the optical adjustment layer 3 and the hard coat layer 4 tend to be in a relationship of canceling each other out. These actions can suppress the occurrence of interference fringes in the hard coat film 1 . In addition, the measurement wavelength of the refractive index in this specification is set to 589 nm, and the measurement temperature is set to 25°C. The detailed measurement method of the refractive index is disclosed in the test example described later.

Since the thickness of the optical adjustment layer 3 is less than 30 nm or greater than 700 nm, the effect of suppressing the occurrence of the interference fringes cannot be obtained, so the thickness of the optical adjustment layer 3 is set within the above range. From the viewpoint of suppressing the occurrence of interference fringes, the thickness of the optical adjustment layer 3 is preferably at least 50 nm, particularly preferably at least 80 nm. In addition, the thickness of the optical adjustment layer 3 is preferably not more than 600 nm, particularly preferably not more than 500 nm.

Again, similarly, from the viewpoint of suppressing interference fringes, the difference between the refractive index of the polyimide film and the median value of the hard coat layer 4 and the refractive index of the optical adjustment layer 3 has an absolute value of It is preferably 0.025 or less, particularly preferably 0.01 or less, and more preferably 0. Thereby, the difference between the refractive index of the base film 2 and the refractive index of the optical adjustment layer 3, and the difference between the refractive index of the optical adjustment layer 3 and the hard coat layer The difference in refractive index becomes smaller and the reflected light decreases. At the same time, the phase of the light reflected at the interface between the base film 2 and the optical adjustment layer 3 and the phase of the light reflected at the interface between the optical adjustment layer 3 and the hard coat layer 4 are shifted, and the light waves are mutually cancelled. Pin relationship, therefore, can effectively suppress the occurrence of interference fringes.

(1) Components of hard coat film

(1-1) Substrate film

The base film 2 of the hard coat film 1 of this embodiment is a polyimide film, and in the case of a display, a polyimide film that is transparent and less yellowish is preferred. Thereby, a display (particularly a flexible display) that displays a transparent image with high color reproducibility can be obtained.

Specifically, as the polyimide film used in this embodiment, from the viewpoint of transparency, the transmittance at a wavelength of 550 nm is preferably 75% or more, preferably 80% or more, and 85% or more. More than % is especially good. The method for measuring the transmittance in this specification is disclosed in the examples described later.

In addition, as the polyimide film used in this embodiment, the absolute value of b* in the L*a*b* colorimetric system using the transmission measurement method is 10 or less from the viewpoint of reducing yellowing. Preferably, less than 5 is more preferred, and less than 3 is particularly preferred. The measurement method of b* in this specification is as disclosed in the examples described later.

The so-called polyimide film in this specification refers to polyimide containing preferably more than 50% by mass, more preferably more than 80% by mass, more preferably more than 90% by mass of polyimide, that is, the main chain has amide Thin films of imine bonded polymers. Also, since poly(meth)acrylimide does not have an imide bond in the main chain, it is not a polyimide, and when such a poly(meth)acrylimide film is bent repeatedly, Whitening will occur.

The polyimide film is usually able to polymerize tetracarboxylic anhydride (preferably aromatic tetracarboxylic dianhydride) and diamine (preferably aromatic diamine) in solution to generate polyamic acid, and then The polyamic acid is formed into a film, and then obtained by dehydrating and ring-closing the polyamic acid site, but it is not limited thereto.

The polyimide in the polyimide film can also be modified. For example, the aromatic ring normally contained in polyimide may be modified by aliphatic hydrocarbon, and thereby the base film 2 has excellent adhesion to the hard coat layer 4 .

The lower limit of the refractive index of the polyimide film is usually not less than 1.50, preferably not less than 1.55, more preferably not less than 1.60. In addition, the upper limit of the refractive index of the polyimide film is usually 1.85 or less, preferably 1.80 or less, more preferably 1.75 or less.

In the above-mentioned polyimide film, in order to improve the adhesion with the layer (hard coat layer 4, or adhesive layer described later, etc.) provided on the surface, it can be treated by primer, oxidation, etc. as necessary. Surface treatment is performed on one or both sides by method, embossing method, etc. As an oxidation method, for example, corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone. Ultraviolet treatment etc., as a roughening method, a blasting method, a solvent treatment method, etc. are mentioned, for example.

The lower limit of the thickness of the polyimide film is preferably at least 5 μm , particularly preferably at least 7.5 μm , and more preferably at least 10 μm . When the thickness of the polyimide film is more than the above, the hard coat film 1 can exhibit a predetermined mechanical strength, and even when it is bent repeatedly, it is less likely to be broken. On the other hand, the upper limit of the thickness of the polyimide film is preferably not more than 300 μm , particularly preferably not more than 90 μm , and more preferably not more than 50 μm . Since the polyimide film is easy to be colored, when the thickness of the polyimide film is the above-mentioned or less, transparency can be ensured and the above-mentioned b* value can be kept low, and it can be suitably used for optical use. In addition, when the thickness of the polyimide film is below the above, the hard coat film 1 can exhibit predetermined flexibility and be easily bent.

(1-2) Optical adjustment layer

The optical adjustment layer 3 of the hard coat film 1 of this embodiment is laminated on one main surface side (upper side in FIG. 1 ) of the base film 2, and plays a role of suppressing interference fringes as described above.

The material of the optical adjustment layer 3 is not particularly special as long as the refractive index of the optical adjustment layer 3 shows a value between the refractive index of the base film 2 (polyimide film) and the refractive index of the hard coat layer 4. limited. Such an optical adjustment layer 3 is preferably formed of a composition containing a thermoplastic resin, or a material obtained by curing a composition containing an active energy ray-curable component. Either composition preferably contains The metal oxide particles are used to adjust the refractive index.

Here, the hard coat layer 4 is formed on the optical adjustment layer 3, but when the solvent contained in the coating liquid for the hard coat layer 4 is a good solvent for the thermoplastic resin, the difference between the optical adjustment layer 3 and the hard coat layer 4 The interface becomes unclear, and there are cases in which the occurrence of interference fringes cannot be suppressed. From this point of view, the optical adjustment layer 3 is preferably formed of a material formed by curing a composition containing an active energy ray-curable component, and in particular, is formed by making a composition containing an active energy ray-curable component and a metal oxide Preferably, the composition of the particles is formed from a hardened material.

(1-2-1) Thermoplastic resin

Thermoplastic resin, adhesiveness to substrate film 2 (polyimide film) And since it is excellent in adhesion (welding property) with the hard-coat layer 4, since it also achieves the same role as an easy-adhesion layer, it is preferable from this point of view.

The thermoplastic resin is preferably one that can achieve the aforementioned refractive index due to its relationship with metal oxide fine particles or the like. Specific examples of thermoplastic resins include polyester resins, polyurethane resins, acrylic resins, polyolefin resins, polyvinyl chloride, polystyrene, polyvinyl alcohol, polyvinylidene chloride, and the like. Among these, at least one selected from the group consisting of polyester resin, polyurethane resin, and acrylic resin is preferred from the viewpoint of adhesion to the polyimide film and weldability to the hard coat layer 4, At least one selected from polyester resins and polyurethane resins is preferred, and polyester resins are more preferred.

The lower limit of the number average molecular weight of the thermoplastic resin is preferably 1,000 or more, particularly preferably 5,000 or more, and further preferably 10,000 or more. Also, the upper limit of the number average molecular weight of the thermoplastic resin is preferably 100,000 or less, particularly preferably 75,000 or less, and further preferably 50,000 or less. When the number average molecular weight of the thermoplastic resin is in this range, the degree of dissolution of the thermoplastic resin by the organic solvent is improved, thereby further improving the fusion property between the thermoplastic resin and the hard coat layer 4, and the optical adjustment layer 3 and the hard coat layer. The adhesiveness of the layer 4 becomes more excellent. In addition, the number average molecular weight in this specification is the value of standard polystyrene conversion measured using the gel permeation chromatography (GPC) method.

(1-2-2) Active Energy Ray Curing Ingredients

The active energy ray curable component is preferably one that is cured by irradiation with active energy ray and that can achieve the above-mentioned difference in refractive index due to its relationship with metal oxide fine particles and the like.

Examples of specific active energy ray-curing components include polyfunctional Functional (meth)acrylate monomers, (meth)acrylate prepolymers, active energy ray-curable polymers, etc., especially polyfunctional (meth)acrylate monomers and/or The (meth)acrylate-based prepolymer is preferable, and the polyfunctional (meth)acrylate-based monomer is more preferable. A polyfunctional (meth)acrylate type monomer and a (meth)acrylate type prepolymer may be used individually, respectively, and may use both together. In addition, in this specification, (meth)acrylate means both acrylate and methacrylate. The same applies to other similar expressions.

Examples of polyfunctional (meth)acrylate monomers include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl Glycol di(meth)acrylate, Polyethylene glycol di(meth)acrylate, Neopentyl glycol di(meth)acrylate, Dicyclopentyl di(meth)acrylate, Caprolactone modified dicyclopentenyl di(meth)acrylate, Ethylene oxide modified phosphate di(meth)acrylate, Allylated di(meth)acrylate cyclohexyl, Trimeric isocyanate di (meth)acrylate, trimethylolpropane tri(meth)acrylate, diperythritol tri(meth)acrylate, propionic acid-modified dipenteoerythritol tri(meth)acrylate, Neopentylthritol tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, isocyanuric acid ginseng (acryloxyethyl) ester, propionic acid modified Di-Neopentylthritol Penta(Meth)acrylate, Di-Neopentylthritol Hexa(Meth)acrylate, Ethylene Oxide-modified Di-Neopentyl-Ritol Hexa(meth)acrylate, Caprolactone-modified Polyfunctional (meth)acrylates such as diperythritol hexa(meth)acrylate. These may be used individually by 1 type, and may use it in combination of 2 or more types.

Among the above, polyfunctional (meth)acrylic acid having three or more (meth)acryloyl groups in one molecule is used from the viewpoint of film curability. The ester-based monomer is preferable, and a polyfunctional (meth)acrylate-based monomer having four or more (meth)acryl groups in one molecule is particularly preferable. By using such a polyfunctional (meth)acrylate monomer, the obtained optical adjustment layer 3 is sufficiently cured, so that the hard coat layer 4 will not be corroded by a diluent solvent or the like when the hard coat layer 4 is subsequently formed. Therefore, it is possible to prevent the gradient of the refractive index at the interface between the optical adjustment layer 3 and the hard coat layer 4 from becoming gentle. As a result, it is possible to more effectively prevent interference fringes from being generated on the surface of the hard coat layer 4 due to the interference of light caused by the optical adjustment layer 3 . Also, the upper limit of the number of functional groups of the polyfunctional (meth)acrylate monomer is not particularly limited, and from the viewpoint of adhesion to the polyimide film, 20 or less polyimides are contained in one molecule. (Meth)acryloyl is preferred.

In addition, from the viewpoint of easy adjustment of the refractive index of the optical adjustment layer 3 and no coloring, it is particularly preferable to use an aliphatic polyfunctional (meth)acrylate monomer.

On the other hand, examples of (meth)acrylate-based prepolymers include prepolymers such as polyester acrylate, epoxy acrylate, urethane acrylate, and polyol acrylate. .

As a polyester acrylate prepolymer, for example, the hydroxyl groups of polyester oligomers having hydroxyl groups at both ends obtained by condensation of polycarboxylic acids and polyhydric alcohols can be esterified with (meth)acrylic acid. , or by adding alkylene oxide (alkylene oxide) to the terminal hydroxyl group of the oligomer obtained by adding polycarboxylic acid, and obtaining it by esterifying it with (meth)acrylic acid.

Epoxy acrylate-based prepolymers can be esterified, for example, by reacting (meth)acrylic acid with the oxirane rings of bisphenol-type epoxy resins or novolak-type epoxy resins with low molecular weights. to get.

The urethane acrylate prepolymer is, for example, a polyurethane oligomer obtained by reacting polyether polyol or polyester polyol with polyisocyanate, by using (meth)acrylic acid to perform esterification to get.

The polyol acrylate prepolymer can be obtained, for example, by esterifying the hydroxyl group of polyether polyol using (meth)acrylic acid.

The above prepolymers may be used alone or in combination of two or more.

(1-2-3) Photopolymerization initiator

When the optical adjustment layer 3 is formed of a material obtained by curing a composition containing an active energy ray-curable component, when ultraviolet rays are used as the active energy ray, the composition preferably contains a photopolymerization initiator. By containing the photopolymerization initiator in this way, the active energy ray-curable component can be polymerized efficiently, and the polymerization hardening time and the irradiation amount of ultraviolet rays can be reduced.

、2-乙基9-氧硫

、2-氯9-氧硫

、2,4-二甲基9-氧硫

、2,4-二乙基9-氧硫

、苄基二甲縮酮、苯乙酮二甲縮酮、對二甲胺基苯甲酸酯、寡聚[2-羥基-2- 甲基-1[4-(1-甲基乙烯基)苯基]丙酮]、2,4,6-三甲基苯甲醯基-二苯基-氧化膦等。該等可單獨使用，亦可組合2種以上而使用。 Examples of such photopolymerization initiators include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, Acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy- 2-Methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholine-propane- 1-keto, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylamine Diphenyl ketone, dichlorodiphenyl ketone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methyl 9-oxygen sulfur

, 2-Ethyl 9-oxosulfur

, 2-chloro 9-oxysulfur

, 2,4-Dimethyl 9-oxosulfur

, 2,4-Diethyl 9-oxosulfur

, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl) phenyl] acetone], 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, etc. These may be used individually or in combination of 2 or more types.

The lower limit of the content of the photopolymerization initiator in the composition is preferably 0.01 part by mass or more, particularly preferably 0.1 part by mass or more, and furthermore, 1 part by mass relative to 100 parts by mass of the active energy ray-curing component. More than one serving is better. Moreover, the upper limit is preferably at most 20 parts by mass, particularly preferably at most 10 parts by mass, and further preferably at most 5 parts by mass.

(1-2-4) Metal oxide fine particles

The composition constituting the optical adjustment layer 3 preferably contains metal oxide fine particles. Accordingly, the refractive index of the optical adjustment layer 3 can be easily set to a value between the refractive index of the polyimide film and the refractive index of the hard coat layer 4 .

Examples of metal oxide fine particles include titanium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, hafnium oxide, cerium oxide, tin oxide, niobium oxide, tin-doped indium oxide (ITO), antimony-doped oxide Fine particles such as tin (ATO), especially transition metal oxide fine particles such as titanium oxide, zirconium oxide, tantalum oxide, zinc oxide, hafnium oxide, cerium oxide, and niobium oxide, are preferable. These metal oxide fine particles may be used alone or in combination of two or more.

Among the above, a higher refractive index can be imparted to the optical adjustment layer 3, and at the same time, it is not easy to increase the haze of the optical adjustment layer 3. The oxide particles of group 4 elements, specifically, zirconia particles and oxide particles Titanium fine particles are particularly preferred. The crystal structure of the titanium oxide microparticles is not particularly limited, but the rutile type is preferable. With the rutile type, it is possible to suppress temporal deterioration of the optical adjustment layer 3 due to photocatalytic activity.

Zirconia fine particles and titanium oxide fine particles may be surface-treated. For example, it can be covered with oxides such as aluminum and silicon, and can also be modified by organic compounds. Examples of organic compounds include polyhydric alcohols, alkanolamines, stearic acid, silane coupling agents, and titanate coupling agents. By such a surface treatment, the dispersibility and the like can be improved, and the above-mentioned effects can be made more excellent.

The shape of the metal oxide fine particles may be spherical or non-spherical.

The lower limit of the average particle diameter of the metal oxide fine particles is preferably at least 1 nm, particularly preferably at least 3 nm, and further preferably at least 5 nm. When the average particle diameter of the metal oxide fine particles is 1 nm or more, the dispersibility is improved. Also, the upper limit of the average particle diameter of the metal oxide fine particles is preferably at most 500 nm, particularly preferably at most 200 nm, and further preferably at most 50 nm. When the average particle diameter of the metal oxide fine particles is 500 nm or less, light scattering is less likely to occur in the obtained optical adjustment layer 3 , and the transparency of the optical adjustment layer 3 becomes high. In addition, the average particle diameter of the metal oxide fine particles is a primary particle diameter measured by a Zeta-potential (Zeta-potential) measurement method.

In the optical adjustment layer 3 of the present embodiment, the content of the metal oxide fine particles in the optical adjustment layer 3 is preferably at least 15% by mass, particularly preferably at least 20% by mass, and further preferably at least 25% by mass. better. When the content of the metal oxide fine particles is 15% by mass or more, the refractive index of the optical adjustment layer 3 can be easily set to a value between the refractive index of the polyimide film and the refractive index of the hard coat layer 4 . On the other hand, the upper limit of the content of the metal oxide fine particles in the optical adjustment layer 3 is preferably 80% by mass or less, more preferably 70% by mass or less, further preferably 60% by mass or less. By the content of metal oxide fine particles is 80% by mass or less, similar to the above, the refractive index of the optical adjustment layer 3 can be easily set to a value between the refractive index of the polyimide film and the refractive index of the hard coat layer 4, and at the same time, it is easy to form a hard coat layer. Layers of composition.

Here, the content of the metal oxide fine particles can be obtained from the compounding ratio, and when the compounding ratio is unclear, it can be obtained as follows. That is, a part of the optical adjustment layer 3 of the hard coat film 1 is separated from the base film 2 by fragments or the like, and the separated fragments of the optical adjustment layer 3 are burned with organic components in accordance with JIS 7250-1. Next, the mass % of the metal oxide fine particles can be calculated from the obtained ash content.

In addition, the refractive index of the optical adjustment layer 3 can also be adjusted only by the refractive index of the active energy ray curable component, and in this case, it is not necessary to add metal oxide fine particles. Examples of active energy ray-curable components having a relatively high refractive index include novolac-type epoxy resins and the like. However, since fine adjustment of the refractive index can be easily performed by adding metal oxide fine particles, it is also preferable to use metal oxide fine particles from this point of view.

In order to improve the dispersibility of the metal oxide fine particles in the composition, a dispersant may also be used. As the dispersant, an acrylic resin is preferable from the viewpoint of compatibility with a thermoplastic resin or an active energy ray-curable component.

(1-2-5) Other ingredients

The composition constituting the optical adjustment layer 3 of this embodiment may contain various additives in addition to the aforementioned components. Examples of various additives include ultraviolet absorbers, antioxidants, light stabilizers, antistatic agents, silane coupling agents, anti-aging agents, thermal polymerization inhibitors, colorants, surfactants, preservation Stabilizers, plasticizers, lubricants, defoamers, organic fillers, wettability improvers, coating improvers, etc.

(1-2-6) Physical properties

The lower limit of the refractive index of the optical adjustment layer 3 is preferably at least 1.45, particularly preferably at least 1.47, and more preferably at least 1.50. Also, the upper limit of the refractive index of the optical adjustment layer 3 is preferably 1.75 or less, particularly preferably 1.72 or less, and further preferably 1.70 or less. When the refractive index of the optical adjustment layer 3 is within the above-mentioned range, it becomes easy to have a value between the refractive index of the polyimide film and the refractive index of the hard coat layer 4 .

(1-3) Hard coating

The hard-coat layer 4 of the hard-coat film 1 of this embodiment imparts high surface hardness to the hard-coat film 1 and has excellent scratch resistance. The hard coat layer 4 is not particularly limited as long as the refractive index of the optical adjustment layer 3 and the refractive index of the base film 2 (polyimide film) satisfy the aforementioned relationship and have a predetermined hardness. Such a hard coat layer 4 is preferably formed of a material obtained by curing a composition containing an active energy ray curable component.

As the active energy ray curable component, the same one as the above-mentioned active energy ray curable component used in the optical adjustment layer 3 can be used. In particular, from the viewpoint of scratch resistance, it is preferable to use a trifunctional or higher polyfunctional (meth)acrylate monomer, and it is preferable to use a tetrafunctional or higher polyfunctional (meth)acrylate monomer. better. For example, diperythritol hexa(meth)acrylate etc. are suitably mentioned.

In addition, when considering the viewpoint of making the obtained hard coat film 1 have more excellent bending resistance, an alkylene oxide containing 2 to 4 carbon atoms in the molecule is used together. A polyfunctional (meth)acrylate monomer (hereinafter referred to as "polyfunctional acrylate containing an alkylene oxide chain") is preferable.

When using a polyfunctional acrylate containing an alkylene oxide chain, from the viewpoint of exhibiting the effect of improving bending resistance, the content of the polyfunctional acrylate containing an alkylene oxide chain is 10% relative to the entire active energy ray-curable component. It is preferably at least 20% by mass, more preferably at least 20% by mass, and particularly preferably at least 40% by mass. On the other hand, from the viewpoint of ensuring scratch resistance, the content is preferably at most 90% by mass, more preferably at most 80% by mass, and particularly preferably at most 70% by mass.

In addition, the polyfunctional acrylate containing an alkylene oxide chain, from the viewpoint of improving the bending resistance, preferably contains more than 1 mole of alkylene oxide units in the molecule, and preferably contains 5 moles of alkylene oxide units. The above is preferred, and it is particularly preferred to contain more than 9 moles. On the other hand, when considering the compatibility with other active energy ray-curing components used in combination, the multifunctional acrylate containing alkylene oxide chains preferably contains 30 moles or less of alkylene oxide units in the molecule. It is preferable to contain 20 moles or less, and it is especially preferable to contain 15 moles or less. As such an alkylene oxide chain-containing polyfunctional acrylate, ethylene oxide-modified dipenteoerythritol hexa(meth)acrylate etc. are suitably mentioned, for example.

When ultraviolet rays are used as active energy rays to be irradiated in order to cure the active energy ray-curable component, it is preferable that the above-mentioned composition contains a photopolymerization initiator. As the photopolymerization initiator, the same thing as the aforementioned photopolymerization initiator used in the optical adjustment layer 3 can be used.

The hard coat layer 4 of this embodiment may also contain a filler. Therefore, high surface hardness can be imparted by the hard-coat layer 4, and it can become what has more excellent scratch resistance.

As the filler, either an organic filler or an inorganic filler may be used. From the viewpoint of being able to impart high surface hardness to the hard coat layer 4, it is preferable to use an inorganic filler. An inorganic filler obtained by chemically modifying an organic compound is preferred, wherein the organic compound has a polymerizable functional group that can be polymerized by irradiation of active energy rays. Moreover, a filler system can be used individually by 1 type, in combination, or 2 or more types.

Examples of inorganic fillers include metal oxides made of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide. substances; fillers formed by metal fluorides such as magnesium fluoride and sodium fluoride. Among the above, silicon oxide and aluminum oxide are preferable, and silicon oxide is particularly preferable in terms of less influence on optical properties.

The surface of fillers, especially silicon oxide fillers, can also be chemically modified, especially chemically modified by organic compounds, wherein the organic compounds have polymerizable functional groups that can be polymerized by irradiation of active energy rays. The specific structure of the chemical modification is not limited, but one example includes a structure in which a polymerizable functional group is added through a silane coupling agent or the like. In such a structure, the filler and the active energy ray curable component are chemically bonded by irradiation of active energy rays, and peeling between them is less likely to occur, and the hardness of the hard coat layer 4 tends to be higher. A filler chemically modified by an organic compound having a polymerizable functional group in this way is called a reactive filler. For example, as long as the type of the filler is silicon oxide, it can be called a reactive silica filler.

The shape of the filler may be spherical or non-spherical. In the case of a non-spherical shape, it may be indeterminate, or may be a needle-like or scaly shape with a high aspect ratio. From the viewpoint of securing the transparency of the hard coat layer 4, the filler is preferably spherical.

The lower limit of the average particle size of the filler is preferably above 1 nm, particularly preferably above 3 nm, and more preferably above 5 nm. When the average particle diameter of the filler is 1 nm or more, the dispersibility is improved. Also, the upper limit of the average particle diameter of the filler is preferably at most 500 nm, particularly preferably at most 200 nm, and further preferably at most 50 nm. When the average particle diameter of the filler is 500 nm or less, it is difficult for light to scatter in the hard coat layer 4 obtained, and the transparency of the hard coat layer 4 becomes high. In addition, the average particle diameter of a filler is set as the primary particle diameter measured by the zeta potential measurement method.

When the hard coat layer 4 of this embodiment contains fillers, the lower limit of the content is preferably at least 10% by mass, particularly preferably at least 20% by mass, and more preferably at least 40% by mass. When the content of the filler is 10% by mass or more, the hardness of the hard coat layer 4 can be effectively increased. On the other hand, in the hard coat layer 4, the upper limit of the content of the filler is preferably not more than 90% by mass, particularly preferably not more than 80% by mass, and further preferably not more than 70% by mass. When content of a filler is 90 mass % or less, it becomes easy to form a layer.

The hard coat layer 4 of the present embodiment may contain various additives similar to those used in the optical adjustment layer 3 described above, in addition to the above-mentioned components.

The lower limit of the refractive index of the hard coat layer 4 is preferably at least 1.40, particularly preferably at least 1.43, and more preferably at least 1.45. In addition, the upper limit of the refractive index of the hard coat layer 4 is preferably not more than 1.70, more preferably not more than 1.65, more preferably not more than 1.60, most preferably not more than 1.54. With the refractive index of the hard coat layer 4 within the above range, the difference between the refractive index of the hard coat layer 4 and the refractive index of the optical adjustment layer 3 can be reduced, thereby reducing the difference between the refractive index of the optical adjustment layer 3 and the polyimide film. The difference in refractive index, and can effectively suppress interference fringes.

The lower limit of the thickness of the hard coat layer 4 is preferably at least 0.5 μm , more preferably at least 0.75 μm , and more preferably at least 1 μm . In addition, the upper limit of the thickness of the hard coat layer 4 is preferably not more than 10 μm , more preferably not more than 8 μm , and more preferably not more than 4 μm . When the thickness of the hard coat layer 4 is 0.5 μm or more, the scratch resistance of the hard coat layer 4 becomes more excellent. On the other hand, when the thickness of the hard coat layer 4 is 10 μm or less, the hard coat film 1 is easily bent and has more excellent bending resistance.

(2) Manufacturing method of hard coat film

The hard coat film 1 of this embodiment can be manufactured suitably using the following method. Also, in this method, as an example, the hard coat layer 4 is formed using a composition containing an active energy ray-curable component.

First, a coating solution of the composition for the optical adjustment layer 3 containing the composition constituting the optical adjustment layer 3 (the composition for the optical adjustment layer 3 ) and, if necessary, a solvent is prepared. Moreover, similarly, the coating liquid containing the composition for hard-coat layer 4 which comprises the composition for hard-coat layer 4 (composition for hard-coat layer 4), and a solvent as needed is prepared.

Examples of solvents include aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene dichloride, methanol, ethanol, propanol, and butanol. , alcohols such as propylene glycol monomethyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, 2-pentanone, isophorone, cyclohexanone and other ketones, ethyl acetate, butyl acetate, etc. Celuso-based solvents such as esters, ethyl celuso, etc. A solvent may be used only by 1 type, and may mix and use 2 or more types. The concentration of the coating solution. The viscosity is not particularly limited as long as it is within a range that can be applied, and can be appropriately selected according to the situation.

On one side of the base film 2, the above coating liquid of the composition for the optical adjustment layer 3 is applied and dried. When the optical adjustment layer 3 is formed of a composition containing a thermoplastic resin, the optical adjustment layer 3 is formed at this point. On the other hand, when the optical adjustment layer 3 is formed of a composition containing an active energy ray-curable component, it is applied and dried in the same manner as the composition containing a thermoplastic resin, and then irradiated with active energy rays. By irradiating active energy rays, the coating film of the composition for the optical adjustment layer 3 is cured, and the optical adjustment layer 3 is formed.

Next, the above-mentioned coating liquid of the composition for the hard coat layer 4 is applied on the optical adjustment layer 3, dried, and then irradiated with active energy rays. By irradiating active energy rays, the coating film of the composition for the hard coat layer 4 is cured, and the hard coat layer 4 is formed on the side opposite to the side in contact with the base film 2 of the optical adjustment layer 3 .

Coating of the coating liquid may be carried out by a common method, for example, bar coating, knife coating, wire wound rod, roll coating, blade coating, die coating, gravure coating, etc. It can be carried out according to the cloth method. Drying of the coating film can be performed, for example, by heating at 40 to 180° C. for about 30 seconds to 5 minutes.

As the active energy rays, ultraviolet rays, electron rays, and the like can be used. Ultraviolet irradiation can be carried out using high-pressure mercury lamps, Fusion H lamps, xenon lamps, etc. The irradiation amount of ultraviolet rays is preferably about 50~1000mW/cm ² illuminance and 50~1000mJ/cm ² light intensity. On the other hand, electron beam irradiation can be performed using an electron beam accelerator or the like, and the irradiation dose of electron beam is preferably about 10 to 1000 krad.

Also, when ultraviolet rays are used as the active energy rays, it is preferable to irradiate the coating film of the composition for the hard coat layer 4 with ultraviolet rays in a state shielded from oxygen. In this way, it will not be hindered by hardening caused by oxygen, and the surface hardness is effectively formed. High hard coating4.

To isolate the coating film of the composition of the hard coat layer 4 from oxygen, it is preferable to laminate a cover sheet on the coating film or keep it in an environment with a low oxygen concentration, such as a nitrogen atmosphere.

(3) Physical properties of hard coat film

(3-1) Maximum reflectance difference

As mentioned above, in the hard coat film 1 of this embodiment, the occurrence of interference fringes can be suppressed. This can be determined not only by visual evaluation but also by the measured value of the maximum reflectance difference. To measure the maximum reflectance difference, first set the normal direction of the film as 0°, irradiate light from the direction of incident angle 8°, collect the reflected light by an integrating sphere and detect it as reflected light. In addition, light irradiation is performed by changing the wavelength, and reflected light corresponding to each wavelength is detected.

The reflected light is a relative value (hereinafter referred to as "reflectance") with the reflected light by the barium sulfate crystal as 100, and is detected corresponding to each measurement wavelength. That is, it is possible to obtain a graph in which the horizontal axis represents the measurement wavelength and the vertical axis represents the reflectance. The graph usually has a fluctuating shape with a plurality of minima and maxima.

Here, among the differences between the adjacent maximum value and the minimum value in the graph of the reflectance measured at a wavelength of 500 to 600 nm, the largest difference was measured as the "maximum reflectance difference". The maximum reflectance difference is preferably 1.5 or less, particularly preferably 1.1 or less. When the reflectance is 1.5 or less, generation of interference fringes can be suppressed.

(3-2) Minimum mandrel diameter

As mentioned above, in the hard coat film 1 of this embodiment, it is excellent in bending resistance to withstand repeated bending, and it can be bent according to the minimum degree of bending. Shaft diameter is judged.

The hard coat film 1 of this embodiment is subjected to the bending resistance test according to the cylindrical mandrel method of JIS K5600-5-1, and the diameter of the mandrel that does not cause cracks and peeling of the hard coat layer 4 is the smallest. The mandrel diameter (minimum mandrel diameter) is preferably below 14mm, especially preferably below 6mm, and further preferably below 4mm.

(3-3) Image sharpness

In the hard coat film 1 of this embodiment, the prevention of interference fringes is solved by providing an optical adjustment layer 3 with a predetermined refractive index instead of adding microscopic particles. Therefore, the hard coat film 1 of the present embodiment can be a film having more excellent image clarity than the case where interference fringes are prevented by adding microscopic particles.

When a hard coat film having excellent image clarity is applied to a display, a display displaying an image having excellent contrast can be obtained. From this point of view, the image sharpness is preferably above 400%, preferably above 430%, and particularly preferably above 450%.

In addition, the image sharpness can be calculated as the total value of each image sharpness measured in 5 types of slits (slit width: 0.125mm, 0.25mm, 0.5mm, 1mm, and 2mm) according to JIS K7374 .

(3-4) Haze value

When applied to a display, from the viewpoint of displaying a clearer image, the haze value of the hard coat film 1 measured in accordance with JIS K7136 is preferably 1% or less, more preferably 0.8% or less, It is especially preferable to set it below 0.5%.

(3-5)60°gloss

When applied to a display, from the viewpoint of making it display a more vivid image, In the hard coat layer 4 of the hard coat film 1, the 60° gloss (Gloss value) according to JIS Z8741-1997 is preferably set to a value of 100% or more, preferably 120% or more , it is especially good to set the value above 140%.

(4) Other Embodiments-1

On the other main surface side of the base film 2 of the above-mentioned hard coat film 1 (the side opposite to the surface on which the above-mentioned optical adjustment layer 3 and hard coat layer 4 are laminated), as shown in FIG. 2 , The optical adjustment layer 3 and the hard coat layer 4 may be laminated in the same order as the hard coat film 1 (the symbol of the hard coat film shown in FIG. 2 is described as "1A"). In this way, by laminating the optical adjustment layer 3 and the hard coat layer 4 on the other main surface side of the base film 2, while suppressing the generation of interference fringes, the resistance of the other main surface side of the base film 2 can be reduced. Increased abrasion resistance. In addition, the hard coat layer 4 (and the optical adjustment layer 3 ) on the other main surface side of the base film 2 is cured and shrunk, and the hard coat layer 4 (and the optical adjustment layer 3 ) on the one main surface side of the base film 2 are Curing shrinkage of the optical adjustment layer 3) cancels out and suppresses curling of the hard coat film 1A.

The optical adjustment layer 3 and the hard coat layer 4 on the other main surface side of the base film 2 can be made of the same material or thickness as the optical adjustment layer 3 and the hard coat layer 4 on the one main surface side of the base film 2. Formed, can also be made of different materials or thickness. However, the refractive index of the optical adjustment layer 3 on the other main surface side of the base film 2 is preferably a value between the refractive index of the polyimide film and the refractive index of the hard coat layer 4, and the thickness of the optical adjustment layer 3 It is 30 nm or more and 700 nm or less.

The hard coat film 1A of this embodiment can basically be produced in the same manner as the hard coat film 1 described above. However, the curing of the hard coat layer 4 (and the optical adjustment layer 3 ) on one main surface side of the base film 2 is different from the hard coating layer 4 (and the optical adjustment layer 3 ) on the other main surface side of the base film 2 . ) can be hardened simultaneously or separately proceed elsewhere.

(5) Other Embodiments-2

On the other main surface side of the base film 2 of the hard-coated film 1 (the side opposite to the surface on which the optical adjustment layer 3 and the hard-coat layer 4 are laminated), as shown in FIG. The adhesive layer 5 is accumulated (the symbol of the hard coat film shown in FIG. 3 is described as "1B"). By laminating such an adhesive layer 5 , the hard coat film 1B can be easily attached to a desired adherend. Also, similarly, an adhesive layer may be laminated on the side opposite to the optical adjustment layer 3 side of the hard coat layer 4 on one main surface side and/or the other main surface side of the hard coat film 1A.

The adhesive constituting the adhesive layer 5 is not particularly limited, and known adhesives such as acrylic adhesives, rubber adhesives, and silicone adhesives can be used. The thickness of the adhesive layer 5 is not particularly limited, and is usually in the range of 5 to 100 μm , preferably in the range of 10 to 60 μm .

The hard coat film 1B of this embodiment can basically be produced in the same manner as the hard coat film 1 described above. The adhesive layer 5 may be formed by a commonly used method.

In addition, a release sheet may be laminated on the exposed surface of the adhesive layer 5 (the surface opposite to the base film 2 side).

(6) Other Embodiments-3

The hard coat film 1 of this embodiment may also be laminated with other layers, such as an adhesive layer, a barrier layer, a conductive layer, a low reflection layer, an easy-to-print layer, and an antifouling layer.

(7) Application of hard coating film

The hard coat films 1, 1A, and 1B of the above embodiments are, for example, suitable for use in flexible displays of various electronic devices, especially mobile electronic devices. Specifically, various flexible displays such as liquid crystal display (LCD), organic EL display (OELD), electronic paper module (film electronic paper), etc. are used as flexible members for the surface layer (protective film) or intermediate layer.

The embodiments described above are described in order to facilitate understanding of the present invention, and are not described in order to limit the present invention. Therefore, the meaning of each element disclosed in the above-mentioned embodiments includes all design changes and equivalents belonging to the technical scope of the present invention.

For example, other layers may be present between the layers of the hard coat films 1, 1A, and 1B as long as the effects of the above-mentioned embodiment are not hindered.

[Example]

Hereinafter, although an Example etc. demonstrate this invention more concretely, the scope of the present invention is not limited by these Examples etc.

[Manufacture Example 1] (Manufacture 1 of Base Film)

In N,N-dimethylacetamide solvent, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, biphenyltetracarboxylic dianhydride, and 2 , 2-bis(3,4-dicarboxyphenyl)hexafluoropropionic dianhydride was mixed and dissolved under cooling, followed by stirring at room temperature for 10 hours to obtain a polyamic acid solution.

Acetic anhydride and pyridine were added to the obtained polyamic acid solution, and after stirring well, it applied on the glass plate, and it heated up gradually from normal temperature to 180 degreeC. After reaching 180°C, the volatile matter is completely removed by heating for a certain period of time, followed by vacuuming. Finally, by cooling to room temperature under vacuum, a polyimide film A having a film thickness of 25 μm was obtained. When the polyimide film A was measured, b* was 0.61, the refractive index was 1.62, and the transmittance at a wavelength of 550 nm was 90%.

In addition, the film thickness of the polyimide film was measured using a constant pressure thickness measuring device (manufactured by Teclock Corporation, product name "PG-02") in accordance with JIS K7130.

Regarding b* above, based on JIS Z8722, a simultaneous measurement method spectroscopic colorimeter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "SQ-2000") was used as the measurement device, and a C light source with a 2° field of view (C/2) was used as the measurement device. As for the light source, b* of the L*a*b* colorimetric system was measured using a transmission measurement method.

The transmittance at the above wavelength of 550 nm was measured using an ultraviolet-visible-near-infrared spectral transmittance meter (manufactured by Shimadzu Corporation, product name "UV3600").

[Manufacture Example 2] (Manufacture 2 of Substrate Film)

In N,N-dimethylacetamide solvent, in addition to changing 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, biphenyltetracarboxylic dianhydride, and While adjusting the compounding ratio of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropionic dianhydride, the concentration of the obtained polyimide coating liquid was adjusted, and by performing the same procedure as in Production Example 1, According to the production method, polyimide film B (the measurement method is as above) with a thickness of 15 μm, a b* of 2.25, a refractive index of 1.70, and a transmittance of 87% at a wavelength of 550 nm was obtained.

[Example 1]

100 parts by mass of diperythritol hexaacrylate as an active energy ray-curing component (in terms of solid content; the same applies hereinafter), and surface-modified zirconia fine particles (manufactured by CIK Nanotec Co., Ltd., product name " ZRMIBK15WT%-F85", average particle size: 15nm) 85 parts by mass, and 5 parts by mass of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator, mixed with methyl isobutyl at a mass ratio of 1:1 The ketone and cyclohexanone were stirred and mixed in a mixed solvent to obtain a coating liquid of a composition for an optical adjustment layer.

In addition, diperythritol, which is an active energy ray-curing component, A mixture of 40 parts by mass of hexaacrylate, 60 parts by mass of reactive silica filler (average particle size: 15 nm) as a filler, and 10 parts by mass of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator, in In a mixed solvent in which methyl isobutyl ketone and cyclohexanone were mixed at a mass ratio of 1:1, stirring and mixing were performed to obtain a coating liquid of a composition for a hard coat layer.

Next, on one side of the polyimide film A as the base film, the above-mentioned coating liquid of the optical adjustment layer composition was coated using a wire bar, and heated and dried at 50° C. for 1 minute. Subsequently, the coating film of the composition for optical adjustment layer was cured by irradiating ultraviolet rays from the coating film side of the composition for optical adjustment layer under the following conditions to form an optical adjustment layer with a thickness of 327 nm.

Next, the coating liquid of the composition for a hard coat layer was coated on the formed optical adjustment layer using a wire bar, and heated and dried at 70° C. for 1 minute. Subsequently, under the following conditions, ultraviolet rays were irradiated from the coating film side of the composition for the hard coat layer to harden the coating film of the composition for the hard coat layer to form a hard coat layer with a thickness of 5 μm , to obtain Hard coat film.

<UV irradiation conditions>

． Ultraviolet radiation device: UV radiation device manufactured by GS Yuasa Corporation

． Light source: high pressure mercury lamp

． Lamp power: 1.4kW

． Illumination: 100mW/ ^cm2

． Light quantity: 240mJ/cm ²

． Conveyor belt speed: 1.2m/min

． Under nitrogen atmosphere, ultraviolet radiation (oxygen concentration below 1%)

[Examples 2~7, Comparative Examples 1~5]

Except that the types and compounding ratios of the components constituting the composition for the optical adjustment layer and the composition for the hard coat layer, the thicknesses of the optical adjustment layer and the hard coat layer, and the type and thickness of the base film were changed as shown in Table 1 , A hard coat film was produced in the same manner as in Example 1. However, during the formation of the optical adjustment layer in Examples 3 and 7, ultraviolet irradiation was not performed.

In addition, the details of the abbreviations and the like described in Table 1 are as follows.

A: diperythritol hexaacrylate

B: Polyester resin (thermoplastic resin) (manufactured by Toyobo Co., Ltd., product name "VYLON 200", number average molecular weight: 17000)

C: Surface-modified zirconia fine particles (manufactured by CIK Nanotec, product name "ZRMIBK15WT%-F85", average particle diameter: 15 nm)

D: 1-Hydroxycyclohexyl phenyl ketone

E: Mixture of 40 parts by mass of dipenteoerythritol hexaacrylate, 60 parts by mass of reactive silica filler (average particle diameter: 15 nm), and 10 parts by mass of 1-hydroxycyclohexyl phenyl ketone

F: Ethylene oxide modified diperythritol hexaacrylate (imported 12 moles of ethylene oxide)

PI-25: Polyimide film A

PI-15: Polyimide film B

PET: Polyethylene terephthalate film (manufactured by Mitsubishi Plastics Corporation, product name "Diafoil T-60", thickness: 50 μm )

[Test Example 1] (Measurement of Refractive Index)

(1) Refractive index of substrate film

Under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25° C., using an Abbe refractometer (manufactured by ATAGO Corporation, product name “Multi-Wavelength Abbe Refractometer DR-M2”), according to JIS K7142 (2008), measured in Examples and The refractive index of the base film used in the comparative example. The results are shown in Table 2.

(2) Refractive index of optical adjustment layer and hard coat layer

On the untreated side of a polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name "COSMOSHINE A4100", thickness: 50 μm ) that has been easily bonded on one side, it is formed in the same manner as in Examples and Comparative Examples. Optical adjustment layer or hard coat layer with a thickness of 200nm. Next, the easily-adhesive surface of the polyethylene terephthalate film was rubbed with sand paper, and filled with black using an oil-based pen (manufactured by ZEBRA, product name "Mckee black").

Then, under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25° C., the refraction of the above-mentioned hard coat layer was measured in accordance with JIS K7142 (2008) using a spectroscopic ellipsometer (manufactured by J.A. Woollam Co., Ltd., product name "M-2000"). Rate. The results are shown in Table 2.

(3) Calculation of refractive index difference

Calculate the median value (=(refractive index of the substrate film+refractive index of the hard coat layer)/2) of the above-mentioned measured refractive index of the base film and the hard coat layer, from the obtained median value The refractive index difference was calculated by subtracting the refractive index of the optical adjustment layer. The results are shown in Table 2.

(Test example 2) (Evaluation of interference fringes)

(1) Visual evaluation

The hard coat films produced in Examples and Comparative Examples were attached to a black acrylic plate (Mitsubishi manufactured by Rayon Corporation, product name "Acrylight L502"). At this time, it is attached in such a way that the base film of the hard coat film is in contact with the acrylic plate.

With regard to the obtained laminate, under a three-wavelength fluorescent lamp, interference fringes were visually confirmed from the hard-coat layer side, and evaluation was performed according to the following criteria. The results are shown in Table 2.

Good (◎): Almost no interference fringes can be seen

Generally good (○): Interference fringes are not easily seen

Slightly bad (△): Interference fringes can be seen

Bad (×): Interference fringes can be seen clearly

(2) Determination of maximum reflectance difference

With respect to the laminate obtained in (1), under the following conditions, the maximum reflectance difference between the wavelengths of 500 to 600 nm in the reflectance spectrum was measured using a spectrophotometer. The results are shown in Table 2.

<Measurement conditions>

． Spectrophotometer: manufactured by Shimadzu Corporation, product name "ultraviolet visible near infrared spectrophotometer UV-3600"

． Sample holder: manufactured by Shimadzu Corporation, product name "large sample chamber MPC-3100"

． Integrating sphere: Made by Shimadzu Corporation, product name "Integrating sphere attachment ISR-3100"

． Angle of incidence: 8°

[Test Example 3] (Evaluation of Scratch Resistance)

For the hard coat surface of the hard coat film manufactured in the examples and comparative examples, use #0000 steel wool to rub back and forth 10 times at a load of 125 g/cm ² , and set the range of length 100 mm and width 20 mm to be test range. Scratch resistance was evaluated by visually confirming the number of scratches in the test range under a 3-wavelength fluorescent lamp in accordance with the following criteria. The results are shown in Table 2.

◯: The number of scratches is less than 20.

×: The number of scars is 20 or more.

[Test example 4] (mandrel test)

About the hard coat film manufactured in the Example and the comparative example, the mandrel test based on JISK5600-5-1 was implemented using the cylindrical mandrel bending tester (made by CORTEC). This mandrel test was performed with the hard coat layer of the hard coat film on the outside. The diameter of the mandrel with the smallest diameter (minimum mandrel diameter) among the mandrels with no defects such as cracking and peeling of the hard coat layer and the optical adjustment layer was obtained. The results are shown in Table 2.

[Test Example 5] (bending resistance test)

For the hard-coated films produced in Examples and Comparative Examples, a durability tester (manufactured by YUASA SYSTEM Instruments Co., Ltd., product name "planar body no-load U-shaped stretch tester DLDMLH-FS") was used, and the hard-coated layer was turned to the outside. The test speed was 60 mm/s, and the number of tests (number of reciprocations) and the bending diameter were changed in various ways, and the bending was repeated. Next, it was checked whether there were any cracks in the hard coat layer and the optical adjustment layer. Peeling, whitening of hard coat film. Defects such as bending marks were evaluated for bending resistance according to the following criteria. The results are shown in Table 2.

⊚: The bending diameter is 5 mm or less, and no defect occurs even if the number of tests is 20,000 or more.

○: Bend diameter 10mm or less, and even if the number of tests is more than 20,000 times No defect occurs.

×: The standard level of ○ was not reached.

[Test Example 6] (Evaluation of Image Sharpness)

For the hard coat films manufactured in Examples and Comparative Examples, using an image clarity measuring device (manufactured by SUGA Testing Instrument Co., Ltd., product name "ICM-10P"), according to JIS K7374, the image clarity (%) was measured. The total value of the type of slit (slit width: 0.125mm, 0.25mm, 0.5mm, 1mm and 2mm). Based on the results, the image sharpness of less than 400% was rated as ×, 400% or more and less than 450% was rated as ◯, and 450% or more was rated as ⊚. The results are shown in Table 2.

[Test Example 7] (Evaluation of haze value)

The haze value (%) was measured based on JISK7136 about the hard-coat film manufactured in the Example and the comparative example using the haze meter (made by Nippon Denshoku Kogyo Co., Ltd., product name "NDH5000"). Based on this result, the haze value was rated as × greater than 1%, ○ as 1% or less and greater than 0.5%, and ◎ as 0.5% or less. The results are shown in Table 2.

[Test Example 8] (Evaluation of 60° Glossiness)

About the hard-coat film manufactured in the Example and the comparative example, 60 degree glossiness (gloss value) was measured based on JISZ8741-1997 using the gloss meter (made by Nippon Denshoku Kogyo Co., Ltd.). Based on the results, the 60° glossiness was rated as ×, 100% or more and less than 140% as ◯, and 140% or more as ⊚. The results are shown in Table 2.

It can be clearly seen from Table 2 that the hard-coated films obtained in Examples have excellent scratch resistance and optical properties, as well as excellent bending resistance, and are less prone to interference fringes.

Industrial availability

The hard-coated film of the present invention can be suitably used as a flexible member constituting a repeatedly bent flexible display, especially as a protective film on the surface layer.

1‧‧‧Hard Coating Film

2‧‧‧Substrate film

3‧‧‧Optical adjustment layer

4‧‧‧Hard Coating

Claims (9)

A flexible display repeatedly bent, wherein the flexible display has a hard-coated film, the hard-coated film has a base film, an optical adjustment layer laminated on at least one main surface side of the base film, and a The hard coat layer on the main surface side opposite to the base film side of the aforementioned optical adjustment layer is characterized in that: the aforementioned base film is a polyimide film, and the refractive index of the aforementioned optical adjustment layer is the same as that of the aforementioned polyimide The value between the refractive index of the thin film and the refractive index of the aforementioned hard coat layer, the thickness of the aforementioned optical adjustment layer is not less than 30nm and not more than 700nm, and the aforementioned flexible display is repeatedly bent 20,000 times by U-shaped expansion and contraction with a bending diameter of not more than 10mm above. The repeatedly bending flexible display described in claim 1, wherein the refractive index of the aforementioned optical adjustment layer is not less than 1.45 and not more than 1.75. In the repeatedly bending flexible display described in claim 1, the refractive index of the aforementioned hard coat layer is not less than 1.40 and not more than 1.70. The repeatedly bending flexible display as described in claim 1 of the patent application, wherein the difference between the refractive index of the aforementioned polyimide film and the refractive index of the aforementioned hard coat layer, and the refractive index of the aforementioned optical adjustment layer The absolute value is below 0.025. The repeatedly bending flexible display described in claim 1 of the patent application, wherein the thickness of the aforementioned polyimide film is not less than 5 μm and not more than 300 μm. The repeatedly bending flexible display as described in claim 1, wherein the thickness of the aforementioned hard coat layer is not less than 0.5 μm and not more than 10 μm. According to the repeated bending flexible display described in claim 1, the optical adjustment layer contains metal oxide particles. In the repetitively bending flexible display described in claim 1, the aforementioned optical adjustment layer is formed of a material obtained by hardening a composition containing an active energy ray hardening component. The repeatedly bending flexible display according to any one of claims 1 to 8 of the patent application, wherein an adhesive layer is laminated on at least one main surface side of the aforementioned base film.

Images