JP2011247918A - Low refractive index film and antireflection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low refractive index film and an antireflection film having sufficient mechanical strength, capable of supplying a composition having a low refractive index and forming the low refractive index film under normal temperature and normal pressure condition.SOLUTION: The low refractive index composition solving the problem can be provided by forming fine pores in the film or fine irregularities on the surface of the film constituted by using a borazine-based polymer or a boraizne-silicon based polymer as a main component. Moreover, the low refractive index film can be formed under the normal temperature and the normal pressure condition, and the antireflection film can be provided which has the sufficient mechanical strength by being formed on a transparent substrate.

Description

  The present invention relates to a low refractive index composition composed of a borazine polymer or a borazine silicon polymer. Further, the present invention relates to a low refractive index film and an antireflection film.

  The low refractive index composition is an important component of various optical devices. In particular, the low refractive index film is an antireflection film, a reflection film, a transflective film, a visible light reflection infrared transmission film, an infrared reflection visible light transmission film, a blue reflection film, a green reflection or red reflection film, a bright line cut filter, a color tone. An optical functional film included in the correction film is formed on the optical member.

  Not only optical members with a flat surface shape, but also optical function members such as brightness enhancement lens films and diffusion films for liquid crystal backlights, Fresnel lenses, lenticular lenses, and microlenses used for video projection television screens are all made of resin. The desired geometrical optical performance is obtained because the material has a microstructure. An optical functional film including a low refractive index film is also required on the surface of these fine structures.

  When a low refractive index film is used as an antireflection film, the low refractive index film having a single layer structure becomes an antireflection film as it is. The antireflection film having a single layer structure exhibits antireflection performance in a wider wavelength range, and the cost is reduced by reducing the number of layers. As the refractive index of the antireflection film having a single layer structure, a low refractive index in the range of 1.2 to 1.4 is desired when the substrate is a transparent material such as a resin material.

  Examples of the method for forming the low refractive index film include vapor phase methods such as vapor deposition and sputtering, and coating methods such as dipping and spin coating.

  Typical low refractive index thin films obtained by the vapor phase method are MgF 2 having a refractive index of 1.38 and LiF having 1.39, and the performance of these thin films as a single-layer antireflection film is low. On the other hand, typical materials for the low refractive index film obtained by the coating method include fluorine-based polymer materials having a refractive index of 1.35 to 1.4, and fluorine having a refractive index of 1.37 to 1.46. Although there is a porous material in which fine particles made of a monomer polymer are fused (see, for example, Patent Document 1), a fluorine-based polymer material having a refractive index of 1.3 or less has not been obtained.

  Furthermore, in recent years, application of borazine-silicon polymers has been studied, and a refractive index of 1.46 is obtained by copolymerizing a silicon compound having a hydrosilyl group with triethynyl-N, N ′, N ″ -trimethylborazine. It is disclosed that a low refractive index film can be formed (see Patent Document 2), and since Patent Document 3 shows a low refractive index of 1.45 to 1.47, borazine-based heat-resistant resin is low. Although there is a description that it can be applied to applications as a refractive index resin thin film, the refractive index of the obtained film is insufficient for use as an antireflection film.

Japanese Patent No. 3718031 JP 2002-359240 A JP 2005-104993 A

  An object of the present invention is to provide a low refractive index film and an antireflection film having sufficient mechanical strength while supplying a composition having a low refractive index.

  As a result of studies to solve the above problems, the following invention has been completed.

[1] A film composed mainly of a borazine-based polymer or a borazine-silicon-based polymer, characterized in that fine pores are formed in the film or fine irregularities are formed on the surface of the film. Low refractive index film.

[2] Antireflection film comprising the low refractive index film according to [1] as a constituent layer

Since the low refractive index composition of the present invention is based on a borazine polymer or a borazine silicon polymer, sufficient mechanical strength can be ensured, and since the constituent composition is hydrophobic, moisture absorption is suppressed, Even if fine pores are introduced inside, characteristic changes due to water absorption are unlikely to occur.
Therefore, a low refractive index film having sufficient mechanical strength and excellent stability over time can be formed. Further, by using the obtained low refractive index film alone or in a laminated state, it is possible to form an antireflection film having excellent mechanical characteristics and little change with time due to the influence of moisture in the atmosphere.

The borazine polymer or borazine silicon polymer is used in a state where the borazine polymer or borazine silicon polymer is dissolved in an organic solvent.
The solvent is not particularly limited as long as the borazine polymer or the borazine silicon polymer is dissolved, but the following nonaqueous organic solvents are preferably used.

  That is, the solvent includes aromatic solvents such as benzene, toluene, ethylbenzene, and xylene, hydrocarbon solvents such as hexane, pentane, octane, and cyclohexane, ketones such as acetone and methyl ethyl ketone, and esters such as ethyl acetate and propyl acetate. Solvents, cyclic ether solvents such as tetrahydrofuran and dioxane, alcohol solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and t-butanol, ethylene glycol monomethyl ether, ethylene glycol mono Ethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol monoacetate, ethylene glycol diacetate, ethylene glycol monomethyl ether Le acetate, propylene glycol -α- monomethyl ether, propylene glycol -α- monoethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, glycol derivatives such as propylene glycol -α- acetate is used.

  The low refractive index film is formed by a method such as dip film formation, spin film formation, spray film formation, or bar coat film formation using a coating solution in which a borazine polymer or a borazine silicon polymer is dissolved in the solvent.

  By changing the composition, concentration and drying conditions of the coating solution, it is possible to introduce pores into the film and to form a film with a lower refractive index. In order to introduce pores, it is effective to combine a plurality of solvents having different volatilization temperatures.

  In order to reduce the refractive index, the pore diameter introduced is preferably 50 nm or less. If it exceeds 50 nm, the transparency decreases due to scattering, which is not preferable. More preferably, it is 20 nm or less.

  The amount of fine pores introduced is preferably 50% or less. If it exceeds 50%, the strength of the film cannot be maintained, which is not preferable. More preferably, it is 5 to 40%.

  Introduction of pores into the membrane is performed by multistage drying / heating treatment using one or more secondary additive solvents having different boiling points. By evaporating and removing the low boiling point solvent in the drying step after film formation, the high boiling point solvent remains in the film, and a fine structure is formed by phase separation from the film forming component. Further, the secondary additive solvent having the pore structure formed is removed by heat treatment, and a low refractive index film having pores introduced therein is formed.

Since the boiling point of the secondary additive solvent is determined by the type of the dispersion solvent, a solvent having a boiling point difference of 30 ° C. or more is used. Preferably it is 50 degreeC or more, More preferably, it is 80 degreeC or more. An organic substance having a boiling point of 150 ° C. or higher is used because the dispersion solvent needs to remain sufficiently in the film after being removed by drying. Preferably, it is 180 ° C. or higher, more preferably 200 ° C. or higher.
Since the solvent to be used needs to form a phase separation structure at a level of several tens of nm, compatibility with the dispersion solvent and the film forming component is important. Since the specific type depends on the type of the dispersion solvent, it is not particularly limited unless phase separation is performed.

  As the type of secondary additive solvent, hydrocarbons having 9 or more carbon atoms, such as n-nonane (151 ° C.), alcohols having 6 or more carbon atoms, such as 1-hexanol (156 ° C.), ketones having 7 or more carbon atoms, such as Amyl methyl ketone (151 ° C.), ketones having 7 or more carbon atoms, such as cyclohexanone (157 ° C.), aldehydes having 7 or more carbon atoms, such as heptanal (155 ° C.), hydrogenated naphthalene and its derivatives, such as tetralin (207 ° C.) , Dihydronaphthalene (1.2 or 1.4, 207-212 ° C.), tetralone (257 ° C.), indane (180 ° C.) or indane (179 ° C.), monocyclic monoterpenoids and derivatives thereof such as limonene (176 ° C.), terpinene (Α, β, 178, 183 ° C.), α-ferrandolene (175 ° C.), terpineol (α, β, γ, δ type, for example α type is 214 to 227 ° C.), fatty acid ester, for example diphthalate Chill (298 ° C), diethylene glycol derivatives such as diethylene glycol monoethyl ether (196 ° C), ethylene glycol monobutyl ether (230 ° C), diethylene glycol diethyl ether (188 ° C), diethylene glycol dibutyl ether (255 ° C), diethylene glycol monoacetate (182 ° C), diethylene glycol monoethyl ether acetate (219 ° C) or the like.

  Although the optimum addition amount of the secondary additive solvent is determined depending on the type of the solvent in the mixed solution, the weight ratio is preferably 0.1 to 10 times the solid content. If it is less than 0.1, it volatilizes together with the dispersion solvent during initial drying, and sufficient pores cannot be introduced. Even if it is added more than 10 times, the effect does not change, so 10 times is sufficient. Preferably, it is 0.2 to 5 times, more preferably 0.2 to 2 times.

  On the other hand, a low refractive index film can be obtained by introducing fine irregularities on the film surface by imprinting. After film formation and drying, the target shape is transferred by pressure bonding of a mold, and further heat-cured to obtain a low refractive index film in which a fine uneven structure is introduced on the film surface.

  Imprinting is performed on either a low refractive index film having a borazine-based polymer or a borazine silicon-based polymer main composition or a low refractive index film in which fine pores are formed in the low refractive index film. be able to.

  The shape of the unevenness formed is not particularly limited as long as it does not cause scattering. It is formed by a shape such as a cylindrical shape, a conical shape, a polygonal middle shape, a polygonal pyramid shape, or a combination thereof. In order to suppress the scattering of visible light, the length of the columnar and conical shapes at the longest position needs to be 80 nm or less. More preferably, it is 60 nm or less. The number of columnar and conical holes is determined by the required amount of membrane porosity.

  The columnar and conical shapes are formed by transfer from the template after the formation of the low refractive film after drying or primary heating or after removal of the secondary additive solvent, and the film is subjected to final curing treatment to form the low refractive index film of the present invention. .

  The antireflection film of the present invention is formed by laminating a low refractive index film according to the present invention with a single layer or another high refractive index composition film.

  High refractive index composition films include perovskites such as titanium oxide, zirconium oxide, niobium oxide, tantalum oxide, zinc oxide, tin oxide, cerium oxide, aluminum oxide, barium titanate, strontium titanate, potassium niobate, and potassium tantalate. Compounds and their solid solutions, ilmenite compounds such as lithium niobate and lithium tantalate and their solid solutions, or composite films containing these compounds are used.

  An organic composite film containing the above oxide particles is used as the high refractive index film. As the organic matrix, (meth) acrylic resin, epoxy resin, polyester resin, styrene resin, urethane resin, imide resin, amide resin, cellulose resin, or a copolymer resin thereof is used. It is formed by mixing with oxide particles as a monomer, forming a film by heat / photocuring, or mixing with a polymer, and drying after film formation.

Usually, the antireflection film of the present invention is formed on a transparent substrate.
The transparent substrate on which the antireflection film is formed is not particularly limited as long as it is determined by its use and has transparency that can be used as an optical material, but is typically represented by glass, polycarbonate, acrylic resin, and PET. Polyester resins, alicyclic hydrocarbon resins and the like are used.

  Next, the borazine polymer or borazine silicon polymer used in the present invention will be described.

  The borazine polymer is a polymer of a substituted borazine represented by the chemical formula (1) (wherein R represents an alkyl group having 1 to 3 carbon atoms, and R ′ represents an alkyl group having a polymerizable terminal).

  The borazine silicon-based polymer has the chemical formula (2) (wherein R1 and R2 represent the same or different monovalent groups selected from alkyl groups, aryl groups, aralkyl groups or hydrogen atoms, and R3 represents a substituted group). An aromatic divalent group which may have a group, an oxygen atom, or an oxypoly (dimethylsiloxy) group) or a chemical formula (3) (wherein R4 is an alkyl group, an aryl group or an aralkyl group) Wherein n represents an integer of 3 or more), and is a copolymer of a substituted borazine represented by the above chemical formula (1) and a silicon compound having at least two hydrosilyl groups.

  The borazine-based polymer or borazine-silicon-based polymer is represented by the chemical structure represented by the chemical formulas (4) to (6) (wherein, as the compound of the chemical formula (1), R: methyl, R ′ : Shows examples of compounds in the case of ethynyl).

Moreover, in the formula of chemical formula (5), x and y are 0 or a positive integer, and neither is 0.
In the chemical formula (6), x and y are 0 or a positive integer, both are not 0, and p and q are 0 or a positive integer.

  The synthesis of the borazine polymer or the borazine silicon polymer can be obtained by polymerizing the monomer represented by the chemical formula (1) or the chemical formula (1) and the chemical formula (2) or (3) in the presence of a catalyst such as platinum.

(Synthesis of borazine resin 1)
0.03 mol of ethylenediamine was dissolved in 30 mL of dry toluene, and 0.03 mol of N, N ', N ”-trimethylborazine was added dropwise. The obtained homogeneous solution was placed in a reaction vessel at 110 ° C. under a small amount of nitrogen gas. The mixture was heated and stirred for a day to obtain a borazine polymer.

(Synthesis of borazine resin 2)
B, B ', B "-triethynyl-N, N', N" -trimethylborazine 1 mol and p-bis (dimethylsilyl) benzene 1 mol are dissolved in ethylbenzene, and platinum 1,3-divinyl ( Hydrosilylation polymerization was performed by reacting 1,1,3,3 tetramethyl-1,3-disiloxane (Pt2 (dvs) 3) as a catalyst at 50 ° C. for 2 hours.

(Synthesis of borazine resin 3)
1 mol of B, B ', B "-triethynyl-N, N', N" -trimethylborazine and 1 mol of 1,3,5,7-tetramethylcyclotetrasiloxane are dissolved in ethylbenzene, and Pt2 ( The reaction was carried out at 50 ° C. for 2 hours using dvs) 3 as a catalyst to carry out hydrosilylation polymerization.

(Synthesis of borazine resin 4)
B, B ', B "-tris (1'-propynyl) -N, N', N" -trimethylborazine 3.6 g (15 mmol) and 1,3,5,7-tetramethylcyclotetrasiloxane 3.6 g (15 mmol) Was dissolved in 150 ml of mesitylene, 30 μl of a Pt2 (dvs) 3 xylene solution (containing 2% platinum) was added, and the mixture was stirred at 40 ° C. for 1 day under nitrogen. Thereto was added 30 μl of a Pt2 (dvs) 3 xylene solution (containing 2% platinum), and the mixture was stirred at 40 ° C. for 1 day under nitrogen. Subsequently, 1,3,5,7-tetramethylcyclotetrasiloxane (0.36 g, 1.5 mmol) was added, and the mixture was stirred at 40 ° C. for 1 day under nitrogen.

(Synthesis of borazine resin 5)
B, B ′, B ″ -tris (1′-propynyl) -N, N ′, N ″ -trimethylborazine 5.0 mmol, 1,3,5,7-tetramethylcyclotetrasiloxane 5.0 mmol are dissolved in ethylbenzene, 10 μl of Pt2 (dvs) 3 in xylene (containing 2% platinum) was added, and the mixture was stirred at 40 ° C. for 1 day under nitrogen, and then at room temperature for 3 days.

(Synthesis of borazine resin 6)
B, B ′, B ″ -tris (1′-propynyl) -N, N ′, N ″ -trimethylborazine 1.0 mmol and p-bis (dimethylsilyl) benzene 1.0 mmol were dissolved in ethylbenzene, and Pt2 (dvs) 3 Of xylene was added and stirred at 40 ° C. under nitrogen for 3 days.

(Synthesis of borazine resin 7)
B, B ', B "-triethynyl-N, N', N" -trimethylborazine 1.0mmol, 1,1,3,3-tetraphenyl-1,3-disiloxane 1.0mmol dissolved in ethylbenzene, platinum divinyl A xylene solution of tetramethyldisiloxane was added, and the mixture was stirred at 40 ° C. for 3 days under nitrogen.

(Synthesis of borazine resin 8)
B, B ', B "-triethynyl-N, N', N" -trimethylborazine 1.0 mmol, 1,3,3,5-tetramethyl-1,5-diphenyl-1,3,5-trisiloxane 1.0 mmol Was dissolved in ethylbenzene, a xylene solution of platinum divinyltetramethyldisiloxane was added, and the mixture was stirred at 40 ° C. for 3 days under nitrogen.
In all synthesis examples, it was confirmed by gas chromatography (GC) analysis that no residual monomer remained.

[Examples 1 to 14]
After adding a high-boiling solvent to a 10% solution of borazine resin in ethylbenzene, apply it to a glass substrate (Corning7059, nd = 1.52) and Si substrate by spin coating, dry at 100 ° C for 1 minute, and then at 180 ° C in the atmosphere. A high refractive index film having a high hardness was obtained by heating for 30 minutes at 300 ° C. for 10 minutes. The number of rotations was adjusted so that the film thickness was 0.1 μm.
The refractive index (nd) of the film formed on the Si substrate was measured by a spectral reflection method. Moreover, the pencil hardness of the film | membrane formed on the glass substrate was measured. Table 1 summarizes the film forming conditions, the refractive index, and the reflectance at the bottom position.

Example 15
A 10% ethylbenzene solution of borazine resin 3 is applied to a glass substrate (Corning 7059) and Si substrate by spin coating, dried at 100 ° C for 1 minute, and then a mold having a cylindrical shape with a pitch of 90 nm, a height of 80 nm, and a diameter of 60 nm A low refractive index film having a high hardness was obtained by curing at 300 ° C. for 30 minutes using imprinting. The number of rotations was adjusted so that the film thickness was 0.1 μm.
The refractive index (nd) of the film formed on the Si substrate was measured by a spectral reflection method. Moreover, the brush hardness of the film | membrane formed on the glass substrate was measured. The refractive index was 1.30, the reflectance at the bottom position was 0.3%, and the pencil hardness was 1H. No haze that is a problem in appearance was observed.

[Comparative Example 1]
A 10% solution of borazine resin 3 was applied to a glass substrate (Corning 7059) and Si substrate by spin coating, dried at 100 ° C. for 1 minute, and post-annealed at 300 ° C. in the air to obtain a borazine resin film. . The number of rotations was adjusted so that the film thickness was 0.1 μm.
In the embodiment of the present invention, as shown in Table 1, when a sufficiently low reflectance is achieved as compared with the glass substrate (refractive index 1.52, reflectance on one side 4.3%) and the antireflection effect is confirmed. Furthermore, it was possible to make the refractive index lower than that of the film of Comparative Example 1 (refractive index: 1.47) using only the borazine resin. Further, no haze was observed on the appearance and transparency was maintained, and in all Examples, a pencil hardness of 1H or more was shown. As a result, it was possible to form an antireflection film having a low reflectance shown in Table 1 as a single layer film.

Example 16
A two-layer reflective film (substrate: Corning 7059) using a titania-acrylic composite film having a refractive index of 1.65 and a thickness of 88 nm as a lower layer of the low refractive index film of the present invention (Example 4, film thickness 110 nm, nd = 1.33). With a refractive index of 1.52), an antireflection film having a reflectance of 0.1% or less could be formed at the bottom position.

The low refractive index composition of the present invention is superior in mechanical properties as compared to conventionally known low refractive index materials, and is excellent in stability over time due to the influence of moisture in the atmosphere. Spread. Whereas the range of use is limited to places where the low refractive index film with weak mechanical strength is not directly touched, the low refractive index composition of the present invention is applied to the outermost surface portion of the optical element as an antireflection film. Is also possible.

Claims (2)

A film composed mainly of a borazine-based polymer or a borazine-silicon-based polymer, characterized in that fine pores are formed in the film or fine irregularities are formed on the surface of the film. Refractive index film. An antireflection film comprising the low refractive index film according to claim 1 as a constituent layer