KR20180048958A - Optical film and manufacturing method of optical film - Google Patents

Abstract

An optical film capable of suppressing light escape from the end face (EF) in a flexible device, and a device using the optical film.
The optical film of the present invention is a transparent optical film containing a polyimide-based polymer, and the end portion (EP) of the optical film is colored. The end portion EP may have a color of 2YR to 3Y in the Munsell color system or may be achromatic. It is preferable that the coloring of the end portion has a color of 2YR to 3Y on the white background in the Munsell colorimetric system, or is achromatic.

Description

Optical film and manufacturing method of optical film

The present invention relates to an optical film and a method for producing the optical film.

In a device having a display such as a smart phone or a tablet PC, it is required to make a narrow bezel of the display, and design of the optical path around the end of the film becomes important. It is possible to absorb unnecessary light by using reflected light by using a white member at the end or by using a black member. For example, in the case of surface illumination used for a display device, There has been proposed an increase in luminance and a reduction in luminance unevenness by designing (see Patent Document 1).

In a flexible device, a transparent resin film has been studied as a front plate. For example, the use of a film containing a polyimide-based polymer as a front plate has been studied (see Patent Document 2).

Japanese Patent Application Laid-Open No. 09-5740 Japanese Unexamined Patent Application Publication No. 2016-93992

It is necessary to design the flexible device so as not to cause uneven brightness of the display end, deterioration of efficiency due to light escaping from the vicinity of the end portion, unnecessary light leaking to the outside, and deterioration of designability.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical film capable of suppressing light escape from a cross section in a flexible device and a flexible device using the optical film.

An optical film related to the present invention is a transparent optical film comprising a polyimide-based polymer, wherein the end portion of the optical film is colored.

According to the present invention, due to coloring of the end portion, light escaping from the inside to the outside through the end face is suppressed. Therefore, light that escapes from the end portion to the outside can be suppressed regardless of the member of the frame body.

Here, the coloration of the end portion may have a color of 2YR to 3Y on the white background in the Munsell color system, or may be achromatic.

The coloration of the end portion may have a color of 3YR to 10YR on the white background in the Munsell colorimetric system.

Also, the thickness may be 20 to 100 mu m.

The present invention also relates to a method of producing an optical film for coloring an end portion by laser irradiation. In this manufacturing method, the optical film may be a transparent optical film containing a polyimide-based polymer.

The front plate for a flexible device according to the present invention has any of the above optical films.

The flexible device according to the present invention has a flexible functional layer and any of the above optical films.

According to the present invention, there is provided an optical film capable of suppressing light escape from an end face in a flexible device, and a flexible device using the optical film.

1 is a perspective view showing an example of an optical film according to an embodiment of the present invention.
2 is a perspective view showing an example of a flexible display according to an embodiment of the present invention.

The optical film 10 according to the present embodiment is a transparent optical film containing a polyimide-based polymer, and the end portion EP of the optical film 10 is colored as shown in Fig.

The end portion (EP) is a portion along the cross section (EF) of the optical film (10). The width W of the end portion EP can be 10 to 500 占 퐉 as viewed from the direction perpendicular to the surface of the optical film 10. [ The entirety of the annular end portion EP along all the cross sections EF may be colored, but only a part of the annular end portion EP (for example, a portion along one end face EF) may be colored .

The coloring is expressed in the Munsell color system. This means that even when the film is placed on the background color of white (N9 in the Munsell color system), even if the film is placed on the background color of pale green color (10 GY8 / 6 in the Munsell color system) It means that the same color is determined. The fact that the color is substantially the same means that the color difference is 5 or less (for example, when the background color is white, the background color is 2YR to 10YR or 1Y to 2Y ), It means that the difference between the saturation and the brightness is all 2 or less.

More preferably, it is most preferable that the difference in hue is within 3, the difference between saturation and lightness is within 1 each, and that all of them are the same value.

On the other hand, the end portion (EP) of the conventional transparent polyimide-based film which is not colored has a transmittance higher than a certain level, and thus is determined to be a different color depending on the background color. Specifically, the Munsell evaluation value in the case of a white background and the Munsell evaluation value in a case of a pale green background have the following characteristics: (a) the color is different by 6 or more, (b) the chroma is different by 3 or more, and (c) When at least one of them is satisfied, no coloring occurs.

The coloring may be chromatic color (saturation exceeding 0) or achromatic color N (saturation may be 0).

The preferable color is 2YR to 3Y or achromatic (N) on the white background in the Munsell color system. A more preferable color is 3YR to 10YR. Such coloration of the end portion is preferable because it can be easily obtained by laser cutting.

It is possible to adjust the color, the saturation and the brightness appropriately within these ranges from the viewpoint that the color of the end portion EP is not conspicuous, so that the color resembles the member disposed in the periphery of the optical film 10.

The evaluation of the color of the end portion EP in the Munsell color system can be performed by comparing the color of the color sample of the Munsell color system with the color of the end portion EP. The color of the end portion EP of the optical film 10 is observed by observing the end portion EP from a direction perpendicular to the surface of the optical film 10. [ When observing the end portion (EP), it is observed with a microscope. The color, saturation, and brightness of the Munsell color system are determined by comparing the color of the film with the background color of the back (N9 in the Munsell colorimetric system). Next, the background color of the green color (10GY8 / 6 in the Munsell color system) The color, the saturation and the brightness in the Munsell colorimetric system are judged, and it is judged whether or not the edge EP is substantially the same color, that is, the difference in hue is within 5, and the difference in chroma and brightness is judged to be 2 or less It is determined that the film is colored.

The refractive index of the above optical film 10 is usually 1.45 to 1.7, preferably 1.5 to 1.66.

The thickness of the optical film 10 is appropriately adjusted according to the type of the flexible device and the like, but is usually 10 to 500 占 퐉, preferably 15 to 200 占 퐉, and more preferably 20 to 100 占 퐉.

In the optical film 10, the total light transmittance in accordance with JIS K 7105: 1981 is usually 85% or more, and preferably 90% or more.

The optical film 10 may have haze of not more than 1 and not more than 0.9 according to JIS K 7105: 1981.

The refractive index, total light transmittance and haze are values measured in the thickness direction of the optical film.

The size of the optical film 10 can be appropriately adjusted in accordance with the size of the flexible device used. In addition, the shape of the optical film 10 is not limited to a rectangle, but can be appropriately adjusted according to a flexible device such as an ellipse, a trapezoid, and a circle.

(Material of film)

(Transparent resin)

The optical film includes a transparent resin such as a polyimide-based polymer.

(Polyimide-based polymer)

In the present specification, the polyimide is a polymer containing a repeating structural unit containing an imide group, and the polyamide is a polymer containing a repeating structural unit containing an amide group. The polyimide-based polymer refers to a polymer containing repeating structural units including both polyimide and imide groups and amide groups.

The polyimide-based polymer according to the present embodiment can be produced as a main raw material of a tetracarboxylic acid compound and a diamine compound described later, and has a repeating structural unit represented by the formula (10). Here, G is a tetravalent organic group and A is a divalent organic group. G, and / or A may contain two or more kinds of structures represented by formula (10).

The polyimide-based polymer according to the present embodiment may include a structure represented by any one of the formulas (11) to (13) within a range that does not impair various physical properties of the resulting polyimide-based polymer film.

The polyimide-based polymer is preferable from the viewpoints of strength and transparency of the film if the repeating structural unit represented by the formula (10) is the main structural unit of the polyimide-based polymer. The repeating structural unit represented by the formula (10) is preferably not less than 40 mol%, more preferably not less than 50 mol%, still more preferably not less than 70 mol%, based on the total repeating structural units of the polyimide- , Particularly preferably 90 mol% or more, and even more preferably 98 mol% or more. The repeating structural unit represented by the formula (10) may be 100 mol%.

[Chemical Formula 1]

(2)

(3)

[Chemical Formula 4]

(21), (22), (23), and (23), G and G ¹ are each a tetravalent organic group and are preferably organic groups which may be substituted by a hydrocarbon group or a fluorine- Examples of the group represented by the formula (24), the formula (25), the formula (26), the formula (27), the formula (28) or the formula (29) and the quadrivalent cyclic hydrocarbon group having 6 or less carbon atoms are exemplified. Z represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH (CH ₃ ) -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ -, -Ar-, -SO ₂ -, -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar-C CH ₃ ) ₂ -Ar- or -Ar-SO ₂ -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms which may be substituted with a fluorine atom, and specific examples thereof include a phenylene group. It is preferable that G and G ¹ are any groups selected from the groups represented by formulas (20) to (27) since the degree of yellowness of the resulting film is easily suppressed.

[Chemical Formula 5]

G ² is a trivalent organic group, preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group, and is an organic group represented by Formula (20), Formula (21), Formula (22) Any one of the groups bonded to each other represented by the formulas (24), (25), (26), (27), (28) or (29) Of the chain hydrocarbon group are exemplified.

G ³ is a divalent organic group, preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group, and is an organic group represented by Formula (20), Formula (21), Formula (22) Of the groups bonded to each other represented by formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) The following chain hydrocarbon groups are exemplified.

A, A ¹ , A ² , and A ³ are both organic divalent organic groups, preferably organic groups which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group and are represented by formulas (30), 32, 33, 34, 35, 36, 37, or 38; A group substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a chain hydrocarbon group having 6 or less carbon atoms.

Z ¹ , Z ² and Z ³ each independently represent a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH (CH ₃ ) -, _{, -C (CH 3) 2 -} , -C (CF 3) 2 - or denotes a -CO- -, -SO _2. One example is where Z ¹ and Z ³ are -O- and Z ² is -CH ₂ -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ - or -SO ₂ -. Z ¹ and Z ² and Z ² and Z ³ are each preferably a meta position or a para position with respect to each ring.

[Chemical Formula 6]

The polyamide according to the present embodiment is a polymer mainly comprising a repeating structural unit represented by the formula (13). Preferred examples and specific examples are the same as G ³ and A ³ in the polyimide-based polymer. G ³ and / or A ³ may contain two or more kinds of structures represented by formula (13).

The polyimide-based polymer is obtained, for example, by polycondensation of a diamine with a tetracarboxylic acid compound (tetracarboxylic acid dianhydride or the like). For example, JP-A-2006-199945 or JP- Can be synthesized according to the method described in JP-A-2008-163107. Commercially available products of polyimide include Neoprim from Mitsubishi Gas Chemical Co., Ltd.

Examples of the tetracarboxylic acid compound used for the synthesis of polyimide include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compound may be used alone or in combination of two or more. The tetracarboxylic acid compound may be a tetracarboxylic acid compound derivative such as an acid chloride compound in addition to dianhydrides.

Specific examples of the aromatic tetracarboxylic acid dianhydride include 4,4'-oxydiphthalic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzo 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, Bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, Bis (2,3-dicarboxyphenyl) propane dianhydride, 4,4 '- (hexafluoroisopropylidene) diphthalic dianhydride, 1,2-bis Ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1- (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 '- (p-phenylene) Oxy) diphthalic dianhydride, 4,4 '- (m-phenylenedioxy) diphthalic dianhydride and 2,3,6,7-naphthalenetetracarboxylic dianhydride, preferably 4,4' 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, Biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 2'- Bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) Propane dianhydride, 4,4'- (hexafluoroisopropylidene) diphthalic dianhydride, 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1- Bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1- (Dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 '- (p-phenylenedioxy) diphthalic dianhydride and 4,4' Oxy) diphthalic dianhydride. These may be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic acid dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic acid dianhydride is tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclo Butane tetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride and the like, cycloalkanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5 , 6-tetracarboxylic dianhydride, dicyclohexyl 3,3'-4,4'-tetracarboxylic dianhydride, and positional isomers thereof. These may be used alone or in combination of two or more. Specific examples of the non-cyclic aliphatic tetracarboxylic acid dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride, etc., Two or more species may be used in combination.

Among the tetracarboxylic dianhydrides, from the viewpoint of high transparency and low coloring property, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo [2.2.2] oct- 5,6-tetracarboxylic dianhydride and 4,4 '- (hexafluoroisopropylidene) diphthalic dianhydride are preferable.

In addition to the anhydride of the tetracarboxylic acid used in the polyimide synthesis, the polyimide-based polymer according to the present embodiment may contain tetracarboxylic acid, Tricarboxylic acid, dicarboxylic acid and anhydrides and derivatives thereof may be further reacted.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids and their acid chloride compounds and acid anhydrides, and two or more of them may be used in combination. Specific examples include anhydrides of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; Compounds in which phthalic anhydride and benzoic acid are linked by a single bond, -CH ₂ -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ -, -SO ₂ - or phenylene group.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids and their flexible acid chloride compounds and acid anhydrides, and two or more of them may be used in combination. Specific examples include terephthalic acid; Isophthalic acid; Naphthalene dicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; A dicarboxylic acid compound of a cyclic hydrocarbon having 8 or less carbon atoms and two benzoic acids are bonded to a single bond, -CH ₂ -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ -, -SO ₂ - And the like.

The diamine used for the synthesis of the polyimide may be an aliphatic diamine, an aromatic diamine or a mixture thereof. In the present embodiment, the term "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and a part of the structure may contain an aliphatic group or other substituent. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring and a fluorene ring, but are not limited thereto. Of these, benzene rings are preferable. The term " aliphatic diamine " means a diamine in which an amino group is bonded directly to an aliphatic group, and an aromatic ring or other substituent may be contained in a part of the structure.

Examples of the aliphatic diamines include alicyclic diamines such as hexamethylene diamine and the like; alicyclic diamines such as 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornanediamine, -Diaminodicyclohexylmethane, and the like, and they may be used alone or in combination of two or more.

Examples of the aromatic diamine include aromatic diamines such as p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, Aromatic diamines having one aromatic ring such as 6-diaminonaphthalene, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-dia (4-aminophenoxy) benzene, 4,4'-diaminodiphenylsulfone, bis [4- (4-aminophenoxy) Bis (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2- (4-aminophenoxy) phenyl] propane, 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, 4 , 4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 9,9-bis (4-aminophenyl) fluorene, (4-amino-3-methylphenyl) fluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9,9- Aromatic diamines having two or more aromatic rings, which may be used alone or in combination of two or more.

Among the above diamines, from the viewpoints of high transparency and low coloring property, it is preferable to use at least one selected from the group consisting of aromatic diamines having a biphenyl structure. (4-aminophenoxy) biphenyl and 4,4'-diaminodiphenyl ether, which is composed of 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, , More preferably at least one selected from the group consisting of 2,2'-bis (trifluoromethyl) benzidine, and still more preferably 2,2'-bis (trifluoromethyl) benzidine.

Polyimide-based polymers and polyamides, which are polymers containing at least one repeating structural unit represented by any one of formulas (10) to (13), are obtained by reacting a diamine with a tetracarboxylic acid compound (acid chloride compound, tetracarboxylic acid 2 (A derivative of a tetracarboxylic acid compound such as an anhydride), a tricarboxylic acid compound (an acid chloride compound, a tricarboxylic acid compound such as a tricarboxylic acid anhydride) and a dicarboxylic acid compound ) And at least one kind of compound contained in the group consisting of the compound represented by the general formula (1). As the starting material, there may be used a dicarboxylic acid compound (including a derivative such as an acid chloride compound) in addition to these. The repeating structural unit represented by the formula (11) is usually derived from diamines and tetracarboxylic acid compounds. The repeating structural unit represented by the formula (12) is usually derived from a diamine and a tricarboxylic acid compound. The repeating structural unit represented by the formula (13) is usually derived from a diamine and a dicarboxylic acid compound. Specific examples of the diamine and tetracarboxylic acid compound are as described above.

The weight average molecular weight of the polyimide-based polymer and the polyamide according to the present embodiment in terms of standard polystyrene standards is generally 10,000 to 500,000, preferably 50,000 to 500,000, and more preferably 100,000 to 400,000. The larger the weight average molecular weight of the polyimide-based polymer and the polyamide tends to exhibit the higher flex resistance when formed into a film, but when the weight average molecular weight of the polyimide-based polymer and the polyamide is too large, the viscosity of the varnish becomes higher, Is lowered.

When the polyimide-based polymer and the polyamide contain a fluorine-substituted group, the modulus of elasticity of the film is improved and the YI value tends to be reduced. If the elastic modulus of the film is high, the occurrence of scratches and wrinkles tends to be suppressed. From the viewpoint of transparency of the film, it is preferable that the polyimide-based polymer and the polyamide have fluorine-substituted groups. Specific examples of fluorine-substituted groups include a fluoro group and a trifluoromethyl group.

The content of fluorine atoms in the polyimide-based polymer and the polyamide is preferably 1% by mass or more and 40% by mass or less, more preferably 5% by mass or less, and still more preferably 5% by mass or less, based on the mass of the polyimide- Or more and 40 mass% or less.

In the optical film related to the present embodiment, the content of the polyimide-based polymer is 40% by mass or more, preferably 50% by mass or more, and more preferably 60% by mass or more.

(Inorganic particles)

The optical film according to this embodiment may further contain an inorganic material such as inorganic particles in addition to the above-mentioned polyimide-based polymer and / or polyamide.

The inorganic material is preferably a silicon compound such as silica particles or quaternary alkoxysilane such as tetraethylorthosilicate (TEOS), and from the viewpoint of the varnish stability, silica particles are preferable.

The average primary particle size of the silica particles is preferably 10 to 100 nm, more preferably 20 to 80 nm. When the average primary particle diameter of the silica particles is 100 nm or less, the transparency tends to be improved. When the average primary particle diameter of the silica particles is 10 nm or more, the cohesive force of the silica particles is weakened, and therefore, the silica particles tend to be easy to handle.

The silica fine particles according to the present embodiment may be silica sol in which silica particles are dispersed in an organic solvent or the like, and silica fine particle powders produced by a vapor phase method may be used, but silica sol is preferable because handling is easy.

The (average) primary particle size of the silica particles in the optical film can be obtained by observation with a transmission electron microscope (TEM). The particle size distribution of the silica particles before forming the optical film can be obtained by a commercially available laser diffraction particle size distribution meter.

In the optical film according to the present embodiment, the inorganic material is 0 mass% or more and 90 mass% or less. Preferably 10 mass% or more and 60 mass% or less, and more preferably 20 mass% or more and 50 mass% or less. When the compounding ratio of the polyimide-based polymer and the polyamide to the inorganic material (silicon material) is within the above range, the transparency and the mechanical strength of the optical film tends to be compatible with each other.

(Ultraviolet absorber)

The optical film may contain one or more ultraviolet absorbers. The ultraviolet absorber is suitably selected because it is usually used as an ultraviolet absorber in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400 nm or less. Examples of the ultraviolet absorber include at least one compound selected from the group consisting of benzophenone compounds, salicylate compounds, benzotriazole compounds, and triazine compounds.

In the present specification, the term "system compound" refers to a derivative of a compound to which the "system compound" is attached. For example, the "benzophenone compound" refers to a compound having a substituent bonded to benzophenone and benzophenone as a matrix skeleton.

(Other additives)

The optical film may further contain other additives insofar as the transparency and flexibility are not impaired. Other components include, for example, antioxidants, releasing agents, stabilizers, coloring agents such as bluing agents, flame retardants, lubricants, thickeners and leveling agents.

The components other than the resin component and the inorganic material are preferably 0% or more and 20% or less by mass with respect to the mass of the optical film. More preferably more than 0% but not more than 10% by mass.

(Manufacturing method)

Next, an example of a manufacturing method of the optical film of the present embodiment will be described.

The varnish used for preparing the optical film according to the present embodiment can be obtained, for example, by reacting a polyimide-based polymer and / or polyamide obtained by reacting the tetracarboxylic acid compound, the diamine and the above- The solvent, the ultraviolet absorber to be used as required, and the other additives may be mixed and stirred. Instead of the reaction liquid such as the polyimide-based polymer, a solution of the purchased polyimide-based polymer or the like or a solution of the purchased solid polyimide-based polymer may be used.

Subsequently, the above liquid is applied onto a resin substrate, a stainless steel belt, or a glass substrate by a known roll-to-roll or batch method to form a coated film, and the coated film is dried and peeled off from the substrate, To obtain a film containing the polymer. After the peeling, the film may be further dried.

The coating film is dried by evaporating the solvent at a temperature of 50 to 350 캜. The drying may be carried out under the atmosphere, in an inert atmosphere, or under reduced pressure.

Examples of the resin substrate include PET, PEN, polyimide, and polyamideimide.

Resins having excellent heat resistance are preferable. In particular, the PET substrate is preferable from the viewpoint of adhesion with the film and cost.

Subsequently, the end portion (EP) of the film is colored. The coloring can be performed, for example, by dyeing the end portion (EP) with a dye.

For example, when the dye solution is applied to the end portion (EP), the dyeing of the end portion is possible. The dye is not particularly limited. The coloring sun can be easily controlled by adjusting the combination of the dyes in the dye solution and the concentration.

The coloring of the end portion EP can also be performed by irradiating a laser beam. A suitable laser is a CO ₂ laser. Specifically, the colored original EP is formed along the cross section EF by cutting the original film with a CO ₂ laser to a desired size. The principle of coloring of the end portion (EP) by laser irradiation is unclear, but it is considered that the modification of the component in the film, for example, the polyimide compound contributes.

In the case of using a laser, since it is possible to cut the laser irradiated portion, the end portion can be colored simultaneously with the cutting process of the film, and the process can be simplified.

As a method of controlling the coloring by the laser, a method of changing the structure of the polyimide, a method of controlling the output of the laser, and the like can be given. For example, a polyimide having an aliphatic structure in a part of its main chain tends to have high coloring tendency. In the case of the all-aromatic polyimide, the lightness of the end portion tends to be lowered. If the laser output is lowered, the lightness of the color tends to be higher. Therefore, if the laser output is made higher, the lightness of the coloring can be lowered.

The term "all-aromatic polyimide" refers to a polyimide having an aromatic group in both of G and A in the structural formulas (10) to (13).

(Usage)

Such an optical film can be suitably used as a front plate of a flexible device. The flexible device according to the present embodiment has a flexible functional layer and the above optical film which overlaps the flexible functional layer and functions as a front plate. That is, the front plate of the flexible device is disposed on the visible side on the flexible functional layer. This front plate has a function of protecting the flexible functional layer.

Examples of the flexible device include an image display device (a flexible display, an electronic paper, etc.), a solar cell, and the like. For example, the display functional layer and the solar cell functional layer are flexible functional layers.

An example of the flexible display is shown in Fig. The front plate 110, the polarizing plate protecting film 120B, the polarizing plate 120A, the polarizing plate protecting film 120B, the touch sensor film 130, and the organic EL element 110B are sequentially stacked on the front side of the flexible display 100 Layer 140 / TFT substrate 150. In this case, The flexible functional layer 190 is a layer other than the front plate 110 in the flexible display 100. [ The polarizing plate protective film 120B / polarizer 120A / polarizing plate protective film 120B constitute the polarizing plate 120. A hard coating layer, an adhesive layer, an adhesive layer, a retardation layer, and the like may be included between the surface of each layer and each layer. As the front plate 110, the above optical film 10 can be used. Such a flexible display can be used as an image display unit of a tablet PC, a smart phone, a portable game machine, or the like.

According to the flexible device according to the present embodiment, the above optical film 10 is used as the front plate 110. The end portion EP of the optical film 10 is colored, and it is possible to suppress the escape of light from the end face EF to the outside.

It is possible to suppress the phenomenon that light passing through the center of the film in the thickness direction is scattered and escapes from the end face due to the coloring of the end portion EP. It is considered that the light directed toward the end face EF is attenuated by the reflection or absorption of the light in the colored portion and consequently the light escape from the end portion is suppressed.

It is also possible to form a laminate in which various functional layers such as an ultraviolet absorbing layer, a hard coat layer, an adhesive layer, a color adjusting layer, and a refractive index adjusting layer are added to the surface of the optical film.

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Example 1)

A commercially available polyimide-based polymer solution ("Neoprim C6A20", manufactured by Mitsubishi Gas Chemical Co., Ltd.) (varnish 1) was cast on a substrate and formed into a 50 μm thick polyimide-based polymer film disc ). The refractive index of the original disc was 1.56. Thereafter, a rectangular (100 mm x 100 mm) area was cut out from the original disc using a CO ₂ laser to obtain an optical film.

The CO ₂ laser irradiation was performed under the following conditions.

Apparatus: ML-Z9510T manufactured by KEYENCE CORPORATION

Wavelength: 9.3 탆

Output: 80%

Processing speed: 150 mm / sec

The end portion (EP) of the film was colored. The color in the Munsell color system of the end (EP) of the film on the white background and the pale green background was 5YR, the brightness was 9, and the saturation was 2. [

(Preparation of varnish 2)

A solution prepared by dispersing silica particles having a solid content concentration of 30 mass% in? -Butyrolactone, a polyimide-based polymer solution "Neoprim C6A20" (? -Butyrolactone solvent, 22 mass%) manufactured by Mitsubishi Gas Chemical Co., , And water were mixed and stirred for 30 minutes to obtain a polymer solution (varnish 2). Here, the mass ratio of the silica and the polyimide-based polymer was 30:70, the amount of the alkoxysilane having the amino group was 1.67 parts based on the total 100 parts by mass of the silica and the polyimide-based polymer, and the total amount of the silica and the polyimide was 100 parts by mass To 10 parts by mass.

(Example 2)

(Same as polyimide B) was obtained from the varnish 2 in the same manner as in Example 1. The end portion (EP) of the film was colored. The color in the Munsell color system of the end (EP) of the film on the white background and the pale green background was 5YR, the brightness was 9, and the saturation was 2. [ The refractive index of the original disc was 1.57.

(Preparation of varnish 3)

(KPI-MX300F made by Kawamura Industries Co., Ltd.) was dissolved in? -Butyrolactone to obtain a polymer solution (varnish 3) having a polymer concentration of 18 mass%.

(Example 3)

The varnish 3 was used in the same manner as in Example 1, except that the thickness of the original disc (referred to as polyimide C) was 80 탆 and CO ₂ laser irradiation was performed under the following conditions. The refractive index of the original disc was 1.56.

Device: E400iCL manufactured by COHERENT

Optical system: digital scanner f? Lens 70 mm x 70 mm

Wavelength: 9.4 탆

Output: 17 W

Processing speed: 400 mm / sec

Frequency: 60 kHz

The end portion (EP) of the film was colored. The color of the end portion (EP) of the film on the white background and the pale green background in the Munsell color system was 7.5YR, the lightness was 2, and the saturation was 4.

(Comparative Example 1)

The same procedure as in Example 2 was performed except that a rectangular region was cut out from the film master with a blade (shear blade). The end portion (EP) of the film was not colored. The Munsell evaluation values on the white background and the pale green background are shown in Table 1.

(Comparative Example 2)

The same procedure as in Example 3 was performed except that a rectangular region was cut out from the film master with a blade (shear blade). The end portion (EP) of the film was not colored. The Munsell evaluation values on the white background and the pale green background are shown in Table 1.

(evaluation)

The exit of light from the end face (EF) was evaluated as follows. A film of 10 cm in length and width was sandwiched between two frames made of stainless steel and having a width of 10 cm, a width of 1 cm and a thickness of 1.5 mm, and the frame was fixed with a clip. Light was irradiated to the central portion of the frame of the frame in the dark room with the output of the apparatus being maximized by using LA-HDF15T (LED light source) manufactured by Hayashi Watch Industry Co., Ltd. with the lens removed. The frame was observed from the side, and light escape from the end face (EF) of the film sandwiched between the frames was observed. The results were evaluated as " x ", " o ", " o ", and " o ", respectively. The results are shown in Table 1. In the embodiment in which the end portion EP is colored, the outgoing light from the end face EF is suppressed as compared with the comparative example.

10: Optical film, 100: Flexible display.

Claims (8)

A transparent optical film comprising a polyimide-based polymer, wherein an end portion of the optical film is colored. The method according to claim 1,
Wherein the coloring of the end portion has a color of 2YR to 3Y on a white background in a Munsell colorimetric system or is achromatic. The method according to claim 1,
Wherein the coloring of the end portion has a color of 3YR to 10YR on a white background in a Munsell colorimetric system. 4. The method according to any one of claims 1 to 3,
And a thickness of 20 to 100 mu m. And the end portion is colored by laser irradiation. 6. The method of claim 5,
Wherein the optical film is a transparent optical film containing a polyimide-based polymer. A front panel for a flexible device comprising the optical film according to any one of claims 1 to 4. A flexible device having the flexible functional layer and the optical film according to any one of claims 1 to 4.

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