WO2019240003A1

WO2019240003A1 - Optical property control film and display device using same

Info

Publication number: WO2019240003A1
Application number: PCT/JP2019/022496
Authority: WO
Inventors: 治加増田
Original assignee: コニカミノルタ株式会社
Priority date: 2018-06-14
Filing date: 2019-06-06
Publication date: 2019-12-19
Also published as: JPWO2019240003A1

Abstract

The present invention addresses the problem of providing an optical property control film which is used in a peep-preventing film for a smartphone or tablet and which has an excellent visibility from the front and suppresses the occurrence of malfunctions in a touch panel caused by moisture condensation, etc. in a cold region. This optical property control film is characterized in that: a reflection layer unit is formed on a resin substrate by laminating a plurality of high-refractive-index layers and low-refractive-index layers which contain hydrophilic polymers and fine particles; the visible light transmittance (Tvis(a)) as seen in a normal direction of the optical property control film surface is 83% or higher; and the ratio of the visible light transmission (Tvis(a)) as seen in a normal direction of the optical property control film surface and the visible light transmission (Tvis(b)) as seen in a direction inclined by 60° with respect to the normal direction of the optical property control film surface satisfies relational expression (1). Relational expression (1) 1.4≤(Tvis(a))/(Tvis(b))

Description

Optical property control film and display device using the same

The present invention relates to an optical property control film and a display device using the same. More specifically, it is an optical property control film that is applied to peep prevention films for smartphones and tablets. It has excellent visibility from the front and prevents touch panel malfunction due to moisture condensation in cold regions. The present invention relates to an optical property control film.

As a peep prevention film for smartphones and tablets, as a technology using a dielectric multilayer film, a peep prevention film comprising a dielectric multilayer film using polyester and nylon and an adhesive containing a light-shielding pigment is known. (For example, refer to Patent Document 1).

When used as a peep prevention film for smartphones and tablets, the dielectric multilayer film described in Patent Document 1 has a small difference in refractive index, so it is necessary to increase the number of layers in order to make the color development when viewed obliquely. Yes, a thick film was necessary. Moreover, since the light-shielding pigment is contained, there is a problem that the screen becomes darker when viewed from the front.

Further, according to the study of the present inventor, it was found that in a display device equipped with a peep prevention film using the dielectric multilayer film, the touch panel malfunctions in a cold place. Examining this cause, the screens of smartphones and tablets in recent years have become increasingly high-definition, and the number of scenes that can be operated close to the face has increased, so the breath on the screen has dropped in cold places. The dew point is reached on the surface of the screen, and fine condensation of water occurs. Capacitive touch panels often used in smartphones and tablets cannot distinguish whether it is due to changes in capacitance due to finely condensed water or changes in capacitance due to touch. It was found that the operation occurred.

JP 2006-168335 A

The present invention has been made in view of the above problems and situations, and the solution is an optical property control film applied to a peep prevention film for smartphones and tablets, and has excellent visibility from the front, Another object of the present invention is to provide an optical property control film in which the malfunction of the touch panel due to moisture condensation or the like is suppressed in cold regions.

In order to solve the above problems, the present inventor, in the process of examining the cause of the above problems, on the resin substrate, a plurality of high refractive index layers and low refractive index layers containing a hydrophilic polymer and fine particles. It is a film having a configured reflection layer unit, and has a visible light transmittance (Tvis (a)) of a specific value or more when viewed from the normal direction of the film surface, and the normal of the film surface The ratio of the visible light transmittance (Tvis (a)) when viewed from the direction and the visible light transmittance (Tvis (b)) when viewed from a position of 60 ° with respect to the normal direction of the film is specified. By satisfying this relational expression, when applied to a peep prevention film for smartphones and tablets, it is highly visible from the front and prevents touch panel malfunction due to moisture condensation in cold regions. Controlling an optical property films were found to be obtained.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. An optical property control film having a reflective layer unit composed of a plurality of high refractive index layers and low refractive index layers containing a hydrophilic polymer and fine particles on a resin substrate,
Visible light transmittance (Tvis (a)) when viewed from the normal direction of the optical property control film surface is 83% or more, and
Visible light transmittance (Tvis (a)) when viewed from the normal direction of the optical property control film surface and visible light when viewed from a direction inclined by 60 ° with respect to the normal direction of the optical property control film A ratio of transmittance (Tvis (b)) satisfies the following relational expression (1): an optical property control film.
Relational expression (1) 1.4 ≦ Tvis (a) / Tvis (b)

2. 2. The optical property control film according to item 1, wherein the hydrophilic polymer is polyvinyl alcohol, and the fine particles are metal oxide fine particles.

3. Item 1 or Item 2 is characterized in that the thickness of the high refractive index layer of the reflective layer unit is in the range of 95 to 120 nm, and the thickness of the low refractive index layer is in the range of 110 to 135 nm. Item 3. The optical property control film according to Item 2.

4. The optical characteristic control according to any one of Items 1 to 3, further comprising a reflective layer unit in which the total number of the high refractive index layer and the low refractive index layer is 20 or more. the film.

5. The refractive index of the high refractive index layer at a light wavelength of 589.3 nm is in the range of 1.63 to 1.83, and the refractive index of the low refractive index layer is in the range of 1.40 to 1.60. The optical property control film according to any one of items 1 to 4, which is characterized in that it exists.

6. A display device comprising the optical property control film according to any one of items 1 to 5.

By the above means of the present invention, an optical property control film applied to a peep prevention film of a smartphone or a tablet, which has excellent visibility from the front, and the occurrence of malfunction of the touch panel due to condensation of moisture in a cold region. Can be provided.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

Since the optical property control film of the present invention uses fine particles to adjust the refractive index, the refractive index difference between the high refractive index layer and the low refractive index layer becomes large. It becomes more prominent. As a result, the layer thickness is not increased, and a light-shielding pigment is not required, so that it looks brighter when observed from the front.

In addition, by adjusting the wavelength of optical interference with a multilayer film in which a high refractive index layer and a low refractive index layer are laminated, when viewed from the front, the minimum value of the spectral transmittance is in the infrared region, and when viewed from an oblique direction. By designing the minimum value of the spectral transmittance to be in the visible light range, it is presumed that a peep prevention effect is exhibited.

In addition, because it uses a hydrophilic polymer, it prevents water from condensing on the film by absorbing the adhering water and not forming water droplets, and does not cause a change in capacitance due to water droplet formation. It is assumed that malfunction of the touch panel can be prevented.

The schematic diagram which shows an example of a structure of the optical characteristic control film of this invention

The optical property control film of the present invention is an optical property control film having a reflective layer unit composed of a plurality of high refractive index layers and low refractive index layers containing a hydrophilic polymer and fine particles on a resin substrate. The visible light transmittance (Tvis (a)) when viewed from the normal direction of the optical property control film surface is 83% or more, and when viewed from the normal direction of the optical property control film surface The ratio between the visible light transmittance (Tvis (a)) and the visible light transmittance (Tvis (b)) when viewed from a direction inclined by 60 ° with respect to the normal direction of the optical property control film is the relationship described above. The expression (1) is satisfied. This feature is a technical feature common to or corresponding to the embodiments described below.

As an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, the hydrophilic polymer is polyvinyl alcohol, and the fine particles are metal oxide fine particles, from the viewpoint of adjusting water absorption and refractive index. Therefore, it is preferable.

The thickness of the high refractive index layer of the reflective layer unit is in the range of 95 to 120 nm, and the thickness of the low refractive index layer is in the range of 110 to 135 nm. It is preferable from the viewpoint.

Further, the reflective layer unit has a total number of the high refractive index layer and the low refractive index layer of 20 or more, and the refractive index of the high refractive index layer at a light wavelength of 589.3 nm is 1.63 to 1 .83 and the refractive index of the low refractive index layer is in the range of 1.40 to 1.60, both the visibility from the front and the effect as a peep prevention film are compatible. From the viewpoint, it is preferable.

The display device of the present invention is characterized by comprising the optical property control film, and can be suitably used as a peep prevention film for smartphones and tablets.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

<< Outline of Optical Property Control Film of the Present Invention >>
The optical property control film of the present invention is an optical property control film having a reflective layer unit composed of a plurality of high refractive index layers and low refractive index layers containing a hydrophilic polymer and fine particles on a resin substrate. The visible light transmittance (Tvis (a)) when viewed from the normal direction of the optical property control film surface is 83% or more, and when viewed from the normal direction of the optical property control film surface The ratio of visible light transmittance (Tvis (a)) to visible light transmittance (Tvis (b)) when viewed from a direction inclined by 60 ° with respect to the normal direction of the optical property control film The expression (1) is satisfied.

Relational expression (1) 1.4 ≦ Tvis (a) / Tvis (b)
Here, the “visible light transmittance” is a value obtained by a visible light transmittance test defined in JIS S 3107: 2013. In the present invention, the visible light transmittance (Tvis (a)) measured from the normal (90 °) direction with respect to the film specimen and the visible light transmittance (Tvis (a)) measured from a direction inclined by 60 ° from the normal direction ( The value of Tvis (b)) is used.

<Outline of visible light transmittance test>
The test piece is produced by uniformly attaching a film having the same dimensions to a 3 mm-thick plate glass so that air bubbles do not enter. In addition, the magnitude | size shall be a dimension suitable for a measuring instrument. The test piece is pretreated for 24 hours or longer.

Visible light transmittance (Tvis) is measured with a spectrophotometer such as the UV-Vis near-infrared spectrophotometer V-670 manufactured by JASCO Corporation, and the transmission spectrum of light wavelengths 380 to 780 nm is measured at different angles. The weighted average is obtained by multiplying the weight coefficient for each light wavelength.

Specifically, the visible light transmittance (Tvis) is determined by the test method defined in ISO 9050 using the above spectrophotometer, and the spectral transmittance of each wavelength 380 to 780 nm defined in Table 8 described in JIS S 3107: 2013. [T (λ)] is measured and multiplied by the weight distribution coefficient [D _λ V (λ) Δλ] obtained from the spectral distribution of the CIE daylight D ₆₅ , the wavelength distribution of the CIE light adaptation standard relative luminous sensitivity, and the wavelength interval. Obtained by weighted average. Said heavy valence coefficient _{[D λ V (λ) Δλ} ] is, JIS S 3107: using the values specified in Table 8 of 2013.

An example of the configuration of the optical property control film of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of the configuration of the optical property control film of the present invention.

The optical property control film 1 of the present invention preferably has a configuration in which a low refractive index layer 3a and a high refractive index layer 3b are laminated as a reflective layer unit 3 on a transparent resin substrate 2 as a substrate. An adhesive layer, an antistatic layer, and a backcoat layer may be provided on the back surface of the transparent resin substrate 2, and an undercoat layer may be provided between the transparent resin film 2 and the reflective layer unit 3. Further, a hard coat layer 4 containing fine particles may be laminated on the reflective layer unit 3 if necessary for preventing scratches or slipping.

≪Configuration of optical property control film≫
1. Transparent resin substrate The substrate used in the optical property control film of the present invention is preferably a transparent resin substrate, and is not particularly limited.

There is no restriction | limiting in particular as resin which can be used as a transparent resin base material, For example, polyester-type resins, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and modified polyester, polyethylene (PE), polypropylene (PP), polystyrene ( PS), polyolefin resins such as cyclic olefin resins, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polyether ether ketone (PEEK), polysulfone (PSF), polyether sulfone (PES), polycarbonate (PC ), Polyamide, polyimide resin, acrylic resin, triacetyl cellulose (TAC) and the like.

These resins may be used alone or in combination.

The thickness and type of the resin base material are not particularly limited as long as they are selected within a range that satisfies the visible light transmittance characteristics of the optical property control film of the present invention.

The thickness of the resin base material is preferably about 5 to 200 μm, more preferably 15 to 150 μm. Two or more resin substrates may be stacked, and in this case, the type of the resin substrate may be the same or different.

Further, the resin base material preferably has a transmittance in the visible light region represented by JIS R 3106: 1998 of 85% or more, and particularly preferably 90% or more. It is preferable that the resin base material has the above transmittance or more from the viewpoint of easily adjusting the visible light transmittance according to the present invention in the film normal direction to 83% or more.

The resin substrate may be an unstretched film or a stretched film. A stretched film is preferable from the viewpoint of strength improvement and thermal expansion suppression.

The resin base material can be manufactured by a conventionally known general method. For example, an unstretched substrate that is substantially amorphous and not oriented can be produced by melting a resin as a material with an extruder, extruding it with an annular die or a T-die, and quenching. In addition, the unstretched base material is subjected to a known method such as uniaxial stretching, tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, tubular simultaneous biaxial stretching, and the like (vertical axis) direction of the base material, Or the extending | stretching base material can be manufactured by extending | stretching in the orthogonal | vertical (horizontal axis) direction with the flow direction of a base material. The draw ratio in this case can be appropriately selected according to the resin as the raw material of the resin base material, but is preferably 2 to 10 times in the vertical axis direction and the horizontal axis direction.

In addition, the resin base material may be subjected to relaxation treatment or offline heat treatment from the viewpoint of dimensional stability. The relaxation treatment is preferably carried out in the process from the heat setting in the stretching film-forming process of the resin base material to the winding in the transverse stretching tenter or after exiting the tenter.

The relaxation treatment is preferably performed at a treatment temperature in the range of 80 to 200 ° C., and more preferably at a treatment temperature in the range of 100 to 180 ° C.

Further, it is preferable that the relaxation rate is in the range of 0.1 to 10% in both the longitudinal direction and the width direction, and more preferably, the relaxation rate is in the range of 2 to 6%.

The relaxation-treated resin base material is improved in heat resistance by being subjected to off-line heat treatment, and further has good dimensional stability.

It is preferable to apply the coating liquid for forming the undercoat layer inline on one side or both sides of the resin base material during the film forming process. In the present invention, undercoating during the film forming process is referred to as in-line undercoating. Resins used for the coating solution for forming the undercoat layer useful in the present invention include polyester resins, acrylic-modified polyester resins, polyurethane resins, acrylic resins, vinyl resins, vinylidene chloride resins, polyethyleneimine vinylidene resins, polyethyleneimine resins, polyvinyl Examples include alcohol resin, modified polyvinyl alcohol resin, gelatin, and the like, and any of them can be preferably used. A conventionally well-known additive can also be added to these undercoat layers. The undercoat layer can be coated by a known method such as roll coating, gravure coating, knife coating, dip coating, or spray coating. The coating amount of the undercoat layer is preferably about 0.01 to 2 g / m ² (dry state).

2. Reflective Layer Unit The reflective layer unit according to the present invention is a laminate in which two or more layers containing a hydrophilic polymer and fine particles and having different refractive indexes are laminated. The fine particles are preferably metal oxide particles.

The reflective layer unit is preferably a laminate in which high refractive index layers and low refractive index layers are alternately laminated. Here, the terms “high refractive index layer” and “low refractive index layer” mean that when a difference in refractive index between two adjacent layers is compared, a layer with a high refractive index is a high refractive index layer and a refractive index is low. It means that the layer is a low refractive index layer. Therefore, the terms “high refractive index layer” and “low refractive index layer” mean that each refractive index layer constituting the light reflecting film has the same refractive index when attention is paid to two adjacent refractive index layers. It includes any form other than the form it has.

In the reflective layer unit, the low refractive index layer is mainly composed of a hydrophilic polymer and first metal oxide particles, and the high refractive index layer is mainly composed of a hydrophilic polymer and second metal oxide particles. It is preferable that it is comprised from these. The hydrophilic polymer used in each layer may be the same or different.

[1] Hydrophilic polymer In the present invention, the hydrophilic polymer refers to a polymer that dissolves 0.001 g or more in 100 g of water at 25 ° C.

Examples of hydrophilic polymers include polyvinyl alcohol, polyethyleneimine, gelatin, starch, guar gum, alginate, methylcellulose, ethylcellulose, hydroxyalkylcellulose, carboxyalkylcellulose, polyacrylamide, polyethyleneimine, polyethyleneglycol, polyalkyleneoxide, and polyvinylpyrrolidone (PVP). ), Polyvinyl methyl ether, carboxyvinyl polymer, polyacrylic acid, sodium polyacrylate, naphthalenesulfonic acid condensate, proteins such as albumin and casein, or sugar derivatives such as sodium alginate, dextrin, dextran, dextran sulfate, etc. Among them, polyvinyl alcohol is preferable.

In addition, as the hydrophilic polymer, JP 2012-27288 A, JP 2012-139938 A, JP 2012-185342 A, JP 2012-215733 A, JP 2012-220708 A, JP JP2012-242644, JP2012-252137, JP2013-4916, JP2013-97248, JP2013-148849, JP2014-89347, JP2014 Examples described in JP2013450A, JP2014215513A, and the like.

The hydrophilic polymer can be used alone or in combination.

The polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate preferably has an average degree of polymerization of 1000 or more, and particularly preferably has an average degree of polymerization in the range of 1500 to 5000.

The degree of saponification is preferably in the range of 70 to 100 mol%, particularly preferably in the range of 80 to 99.9 mol%.

As the polyvinyl alcohol, a synthetic product or a commercially available product may be used. Examples of commercially available products used as polyvinyl alcohol include PVA-102, PVA-103, PVA-105, PVA-110, PVA-117, PVA-120, PVA-124, PVA-203, PVA-205, PVA- 210, PVA-217, PVA-220, PVA-224, PVA-235 (above, manufactured by Kuraray Co., Ltd.), JC-25, JC-33, JF-03, JF-04, JF-05, JP-03, JP-04, JP-05, JP-45 (the above-mentioned, manufactured by Nippon Vinegar Poval Co., Ltd.) and the like.

Each layer constituting the reflective layer unit may contain modified polyvinyl alcohol partially modified in addition to normal polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, as long as the effects of the present invention are not impaired. . When such a modified polyvinyl alcohol is included, the adhesion, water resistance, and flexibility of the film may be improved.

Examples of the modified polyvinyl alcohol include cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, nonion-modified polyvinyl alcohol, and vinyl alcohol-based polymers. Also, vinyl acetate resins (for example, “Exeval” manufactured by Kuraray Co., Ltd.), polyvinyl acetal resins obtained by reacting polyvinyl alcohol with aldehydes (for example, “ESREC” manufactured by Sekisui Chemical Co., Ltd.), silanols having silanol groups Modified polyvinyl alcohol (for example, “R-1130” manufactured by Kuraray Co., Ltd.), modified polyvinyl alcohol resin having an acetoacetyl group in the molecule (for example, “Gosefimer (registered trademark) Z / WR series ") and the like are also included in the polyvinyl alcohol resin.

Anion-modified polyvinyl alcohol is described in, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-206088, JP-A-61-237681 and JP-A-63-307979. Examples thereof include a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265.

Nonionic modified polyvinyl alcohol includes, for example, a polyvinyl alcohol derivative in which a polyalkylene oxide group is added to a part of vinyl alcohol as described in JP-A-7-9758, and JP-A-8-25795. A block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol as described, a silanol-modified polyvinyl alcohol having a silanol group, or a reaction having a reactive group such as an acetoacetyl group, a carbonyl group, or a carboxy group And a functional group-modified polyvinyl alcohol.

The cation-modified polyvinyl alcohol has, for example, primary to tertiary amino groups and quaternary ammonium groups as described in JP-A-61-10483 in the main chain or side chain of the polyvinyl alcohol. It is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

Examples of the vinyl alcohol polymer include EXEVAL (trade name: manufactured by Kuraray Co., Ltd.) and Nichigo G polymer (trade name: manufactured by Nippon Synthetic Chemical Industry Co., Ltd.).

Each layer constituting the reflective layer unit may contain, in addition to the above-described hydrophilic polymer, other known binder resins as long as the object and effects of the present invention are not impaired.

[2] Metal oxide particles In the present invention, the low refractive index layer and the high refractive index layer preferably contain metal oxide particles.

[2.1] Metal oxide particles in the low refractive index layer: first metal oxide particles Examples of the metal oxide particles used in the low refractive index layer include synthetic amorphous silica, colloidal silica, and zinc oxide. , Alumina, colloidal alumina and the like. Of these, colloidal silica sol, particularly acidic colloidal silica sol is more preferably used, and colloidal silica dispersed in an organic solvent is particularly preferably used.

In order to further reduce the refractive index, hollow fine particles having voids inside the particles may be used as the metal oxide particles of the low refractive index layer, and hollow fine particles of silicon oxide (silicon dioxide) are particularly preferable. . Also, known metal oxide particles (inorganic oxide particles) other than silicon oxide can be used.

In order to adjust the refractive index, the metal oxide particles may be used alone or in combination of two or more.

The silicon dioxide particles contained in the low refractive index layer preferably have an average particle diameter (number average: diameter) in the range of 3 to 100 nm. The average particle size of primary particles of silicon dioxide dispersed in the state of primary particles (particle size in the dispersion state before coating) is more preferably in the range of 3 to 50 nm. It is more preferably within the range, particularly preferably within the range of 3 to 20 nm, and most preferably within the range of 4 to 10 nm. Moreover, as an average particle diameter of secondary particle | grains, it is preferable from a viewpoint with few hazes and excellent visible light transmittance | permeability that it is 30 nm or less.

Further, the particle diameter of the silicon dioxide particles contained in the low refractive index layer can be determined by the volume average particle diameter in addition to the primary average particle diameter.

The colloidal silica used in the present invention is obtained by heating and aging a silica sol obtained by metathesis with an acid of sodium silicate or the like and passing through an ion exchange resin layer. For example, JP-A-57-14091 JP, 60-219083, JP 60-218904, JP 61-20792, JP 61-188183, JP 63-17807, JP 4-207 No. 93284, JP-A-5-278324, JP-A-6-92011, JP-A-6-183134, JP-A-6-297830, JP-A-7-81214, JP-A-7-101142 Described in Japanese Patent Laid-Open No. 7-179029, Japanese Patent Laid-Open No. 7-137431, International Publication No. 94/26530, etc. A.

Such colloidal silica may be a synthetic product or a commercially available product. Examples of commercially available products include Snowtex series (Snowtex OS, OXS, S, 20, 30, 40, O, N, C, etc.) sold by Nissan Chemical Industries, Ltd.

The surface of the colloidal silica may be cation-modified, or may be treated with Al, Ca, Mg, Ba or the like.

Moreover, as described above, hollow particles can be used as the silicon dioxide particles of the low refractive index layer. When hollow fine particles are used, the average particle pore size is preferably in the range of 3 to 70 nm, more preferably in the range of 5 to 50 nm, and still more preferably in the range of 5 to 45 nm. The average particle pore size of the hollow fine particles is an average value of the inner diameters of the hollow fine particles. If the average particle pore diameter of the hollow fine particles is within the above range, the refractive index of the low refractive index layer is sufficiently lowered.

The average particle diameter is 50 or more at random, which can be observed as an ellipse in a circular, elliptical or substantially circular shape by electron microscope observation. Is obtained. The average particle hole diameter means the minimum distance among the distances between the outer edges of the hole diameter that can be observed as a circle, an ellipse, or a substantially circle or ellipse, between two parallel lines.

The content of silicon dioxide particles in the low refractive index layer is preferably in the range of 20 to 90% by mass, and in the range of 30 to 85% by mass, based on the total solid content of the low refractive index layer. Is more preferable, and still more preferably in the range of 40 to 80% by mass. When it is 20% by mass or more, a desired refractive index is obtained, and when it is 90% by mass or less, the coatability is good, which is preferable.

[2.2] Metal oxide particles in the high refractive index layer: second metal oxide particles The high refractive index layer preferably contains the second metal oxide particles. The second metal oxide particles applied to the high refractive index layer are preferably metal oxide particles different from the first metal oxide particles applied to the low refractive index layer described above.

Examples of the metal oxide particles used in the high refractive index layer include titanium oxide particles, zirconium oxide particles, zinc oxide particles, alumina particles, colloidal alumina, niobium oxide particles, europium oxide particles, and zircon particles. The metal oxide particles may be used alone or in combination of two or more. Among the metal oxide particles, it is preferable to contain zirconium oxide particles. The high refractive index layer containing zirconium oxide particles is transparent and can exhibit a higher refractive index. Further, since the photocatalytic activity is low, the light resistance and weather resistance of the high refractive index layer and the adjacent low refractive index layer are increased. In the present invention, zirconium oxide means zirconium dioxide (ZrO ₂ ).

The zirconium oxide particles may be cubic or tetragonal, or a mixture thereof.

The size of the zirconium oxide particles contained in the high refractive index layer is not particularly limited, but can be determined by the volume average particle size or the primary average particle size. The volume average particle diameter of the zirconium oxide particles used in the high refractive index layer is preferably 100 nm or less, more preferably in the range of 1 to 100 nm, and still more preferably in the range of 2 to 50 nm. .

The primary average particle diameter of the zirconium oxide particles used in the high refractive index layer is preferably 100 nm or less, more preferably in the range of 1 to 100 nm, and in the range of 2 to 50 nm. Is more preferable.

When the volume average particle size or primary average particle size is in the range of 1 to 100 nm, the haze is small and the visible light transmittance is excellent.

In the present invention, the volume average particle size refers to a method of observing the particle itself using a laser diffraction scattering method, a dynamic light scattering method, or an electron microscope, or a particle image appearing on the cross section or surface of the refractive index layer. By measuring with an electron microscope, the particle size of 1000 arbitrary particles is measured, and particles having particle sizes of d1, d2,..., Di,. .., Ni,..., Nk, a volume average particle diameter mv = {Σ (vi · di)} / {Σ (vi )} Can be obtained by calculating the average particle size weighted by the volume.

Further, the primary average particle diameter can be measured from an electron micrograph with a transmission electron microscope (TEM) or the like. You may measure by the particle size distribution meter etc. which utilize a dynamic light scattering method, a static light scattering method, etc.

When obtained from a transmission electron microscope, the primary average particle diameter of the particles is determined by observing the particles themselves or the particles appearing on the cross section or surface of the refractive index layer with an electron microscope, and measuring the particle diameter of 1000 arbitrary particles. And it is calculated | required as the simple average value (number average). Here, the particle size of each particle is represented by a diameter assuming a circle equal to the projected area.

Further, as the zirconium oxide particles, particles obtained by modifying the surface of an aqueous zirconium oxide sol so as to be dispersible in an organic solvent or the like may be used.

As a method for preparing zirconium oxide particles or a dispersion thereof, any conventionally known method can be used. For example, as described in JP-A-2014-80361, a method can be used in which a zirconium salt is reacted with an alkali in water to prepare a slurry of zirconium oxide particles, and an organic acid is added to perform hydrothermal treatment. .

Commercially available zirconium oxide particles may be used. For example, SZR-W, SZR-CW, SZR-M, SZR-K, etc. (above, manufactured by Sakai Chemical Industry Co., Ltd.) are preferably used. Can do.

Furthermore, the zirconium oxide particles used in the present invention are preferably monodispersed.

The content of zirconium oxide particles in the high refractive index layer is not particularly limited, but is preferably in the range of 15 to 95% by mass, and preferably 20 to 90% by mass with respect to the total solid content of the high refractive index layer. More preferably, it is within the range of 30 to 90% by mass. By setting it as the said range, it can be set as the favorable thing of a light reflection characteristic.

When combining zirconium oxide with other metal oxide fine particles, the total amount of metal oxide particles used in the high refractive index layer (total amount of zirconium oxide particles and high refractive index metal oxide fine particles other than zirconium oxide) On the other hand, the content of zirconium oxide particles is preferably in the range of 80 to 100% by mass, preferably in the range of 90 to 100% by mass, and more preferably 100% by mass.

[2.3] Other additives applicable to each refractive index layer Various additives applicable to the high refractive index layer and the low refractive index layer are listed below. For example, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, JP-A-62-261476, JP-A-57-74192, JP-A-57-87989 Of fading inhibitors, anions, cations or nonions described in JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, JP-A-3-13376, etc. Various surfactants, such as JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, etc. Lubricants such as fluorescent brighteners, sulfuric acid, phosphoric acid, acetic acid, citric acid, pH adjusters such as sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents, diethylene glycol, etc. , Antiseptics, antifungal agents, antistatic agents, matting agents, heat stabilizers, antioxidants, flame retardants, crystal nucleating agents, inorganic particles, organic particles, polyester resins, viscosity reducers, lubricants, infrared absorbers, dyes Or various known additives such as pigments.

[3] Method for Forming Reflective Layer Unit As a method for forming the reflective layer unit, as described above, a unit composed of a high refractive index layer and a low refractive index layer can be formed on a resin substrate. Any method can be used.

Specifically, it is preferable that a high refractive index layer and a low refractive index layer are alternately coated on a resin base material and dried to form a laminate. Specifically, the following forms are mentioned.

(I) A high refractive index layer forming coating solution is applied and dried on a resin substrate to form a high refractive index layer, and then a low refractive index layer forming coating solution is applied and dried to form a low refractive index layer. (Ii) A low refractive index layer is formed on a resin substrate by applying and drying a coating solution for forming a low refractive index layer. A method of forming a reflective layer unit by applying a coating solution for forming a refractive index layer and drying to form a high refractive index layer and sequentially repeating this process. (Iii) Coating for forming a high refractive index layer on a resin substrate A method of forming a reflective layer unit composed of a high refractive index layer and a low refractive index layer having a predetermined number of layers (iv) ) A plurality of layers of a coating solution for forming a high refractive index layer and a coating solution for forming a low refractive index layer are laminated in a wet state on a resin substrate. Among the methods of forming a reflective layer unit including a high refractive index layer and a low refractive index layer by simultaneously applying and drying a certain number of layers, the method (iv) above, which is a simpler manufacturing process, is preferred. That is, the method for forming the reflective layer unit preferably includes laminating a plurality of high refractive index layers and low refractive index layers by an aqueous simultaneous multilayer coating method.

Examples of the coating method include a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, a slide using a hopper described in U.S. Pat. Nos. 2,761,419 and 2,761791. A bead coating method or an extrusion coating method is preferably used.

The solvent for preparing the coating solution for forming the high refractive index layer and the coating solution for forming the low refractive index layer is not particularly limited, but water, an organic solvent, or a mixed solvent thereof is preferable. In the present invention, it is preferable to mainly use polyvinyl alcohol as the constituent binder resin of each refractive index layer, but application with an aqueous solvent is possible by using polyvinyl alcohol.

Furthermore, in the present invention, it is preferable to add two or more kinds of cationic polymers to the low refractive index layer coating solution in order to reduce haze and suppress cracks. Compared to the case where an organic solvent is used, the aqueous solvent does not require a large-scale production facility, so that it is preferable in terms of productivity and also in terms of environmental conservation.

The content of the two or more kinds of cationic polymers is, for example, in the range of 0.5 to 20% by mass with respect to the total mass of the metal oxide particles including the silicon oxide particles, and 2 to 20% by mass. %, Preferably 3 to 10% by weight, more preferably 1 to 10% by weight, and more preferably 2 to 5% by weight. It is particularly preferred.

Examples of the organic solvent include alcohols such as methanol and ethanol, esters such as ethyl acetate, butyl acetate and propylene glycol monomethyl ether acetate, ethers such as diethyl ether and propylene glycol monomethyl ether, amides such as dimethylformamide, Or ketones, such as acetone and methyl ethyl ketone, are mentioned.

These organic solvents may be used alone or in combination of two or more. From the viewpoint of environment and simplicity of operation, the solvent of the coating solution is preferably an aqueous solvent, more preferably water or a mixed solvent of water and methanol, ethanol, or ethyl acetate, and water is particularly preferable.

When using a mixed solvent of water and a small amount of an organic solvent, the content of water in the mixed solvent is preferably in the range of 80 to 99.9% by mass, based on 100% by mass of the entire mixed solvent, More preferably, it is within the range of 85 to 99.5% by mass. By making the content of water in the mixed solvent 80% by mass or more, volume fluctuation due to volatilization of the solvent can be reduced, handling is improved, and by making the content 99.9% by mass or less, Homogeneity increases and stable liquid properties can be obtained.

The concentration of the resin in the coating solution for forming a high refractive index layer (when using a plurality of types of resins, the total concentration) is preferably in the range of 0.5 to 10% by mass.

The total concentration of the metal oxide particles in the coating solution for forming a high refractive index layer is preferably in the range of 1 to 50% by mass.

The concentration of the resin in the coating solution for forming the low refractive index layer is preferably in the range of 0.5 to 10% by mass.

Further, the total concentration of the metal oxide particles in the coating solution for forming the low refractive index layer is preferably in the range of 1 to 50% by mass.

The method for preparing the coating solution for forming a high refractive index layer is not particularly limited, and for example, metal oxide particles, hydrophilic polymer, for example, polyvinyl alcohol, and other additives that are added as necessary, The method of stirring and mixing is mentioned. At this time, the order of addition of the respective components is not particularly limited, and the respective components may be sequentially added and mixed while stirring, or may be added and mixed at one time while stirring.

The method for preparing the coating solution for forming the low refractive index layer is not particularly limited, and for example, metal oxide particles, a hydrophilic polymer, for example, polyvinyl alcohol, and other additives that are added as necessary, The method of stirring and mixing is mentioned. At this time, the order of addition of the components is not particularly limited, and the components may be added and mixed sequentially with stirring, or may be added and mixed at one time with stirring.

In the present invention, when simultaneous multilayer coating is performed, it is preferable that the saponification degrees of polyvinyl alcohol used in the coating solution for forming a high refractive index layer and the coating solution for forming a low refractive index layer are different. By different saponification degrees, mixing of layers can be suppressed in each step of coating and drying.

The temperature of the coating solution for forming the high refractive index layer and the coating solution for forming the low refractive index layer in the simultaneous multilayer coating is preferably in the temperature range of 25 to 60 ° C. when using the slide hopper coating method, and is preferably 30 to 45. A temperature range of ° C is more preferred. When the curtain coating method is used, a temperature range of 25 to 60 ° C. is preferable, and a temperature range of 30 to 45 ° C. is more preferable.

The viscosity of the coating solution for forming a high refractive index layer and the coating solution for forming a low refractive index layer during simultaneous multilayer coating is not particularly limited. However, when the slide bead coating method is used, it is preferably in the range of 5 to 160 mPa · s, more preferably in the range of 60 to 140 mPa · s, in the preferred temperature range of the coating solution. When the curtain coating method is used, it is preferably within the range of 5 to 1200 mPa · s, and more preferably within the range of 25 to 500 mPa · s, in the preferable temperature range of the coating solution.

In such a viscosity range, simultaneous multi-layer coating can be performed efficiently.

The conditions for the coating and drying method are not particularly limited. For example, in the case of the sequential coating method, first, the coating solution for forming the high refractive index layer and the coating solution for forming the low refractive index layer heated to 30 to 60 ° C. Either one is applied onto a resin substrate and dried to form a layer, and then the other coating solution is applied onto this layer and dried to form a laminated film precursor (unit). When drying, it is preferable to dry the formed coating film at 30 ° C. or higher. For example, drying is preferably performed in the range of wet bulb temperature 5 to 50 ° C. and film surface temperature 5 to 100 ° C. (preferably 10 to 50 ° C.). For example, hot air of 40 to 60 ° C. is blown for 1 to 5 seconds. dry.

In addition, the conditions for the coating and drying method when performing simultaneous multilayer coating are as follows. The coating solution for forming the high refractive index layer and the coating solution for forming the low refractive index layer are heated to 30 to 60 ° C., and then applied onto the resin substrate. After simultaneous multi-layer coating of a coating solution for forming a high refractive index layer and a coating solution for forming a low refractive index layer, the temperature of the formed coating film is preferably cooled (set) preferably to 1 to 15 ° C., and then 10 ° C. It is preferable to dry by the above. More preferable drying conditions are a wet bulb temperature of 5 to 50 ° C. and a film surface temperature of 10 to 50 ° C. For example, it is dried by blowing warm air of 40 to 80 ° C. for 1 to 5 seconds. Moreover, as a cooling method immediately after application | coating, it is preferable to carry out by a horizontal set system from a viewpoint of the uniformity improvement of the formed coating film.

[4] Design of layer structure The total number of layers of the high-refractive index layer and the low-refractive index layer of the reflective layer unit according to the present invention is 50 layers from the viewpoint of improving visibility (Tvis (a)) from the front. Below, more preferably 45 layers or less. Further, from the viewpoint of peep prevention, the lower limit of the total number of high refractive index layers and low refractive index layers is preferably 15 layers or more, more preferably 20 layers or more.

In the reflective layer unit, it is preferable to design a large difference in refractive index between the high refractive index layer and the low refractive index layer from the viewpoint that the reflectance with respect to a desired light beam can be increased with a small number of layers. In the present invention, the difference in refractive index between at least two adjacent layers (high refractive index layer and low refractive index layer) is preferably 0.15 or more, more preferably 0.2 or more, and particularly preferably 0. .21 or more. The upper limit is not particularly limited, but is usually 0.5 or less.

This refractive index difference and the required number of layers can be calculated using commercially available optical design software. For example, in order to obtain a near-infrared reflectance of 90% or more, if the difference in refractive index is smaller than 0.1, it is necessary to laminate 200 layers or more, which not only lowers productivity but also causes scattering at the lamination interface. Larger, less transparent, and very difficult to manufacture without failure.

In the reflective layer unit, when the high refractive index layer and the low refractive index layer are alternately laminated, the refractive index difference between the high refractive index layer and the low refractive index layer is within the range of the preferred refractive index difference. It is preferable. However, for example, in the case where the lowermost layer is formed as an adhesion improving layer with the resin substrate, the lowermost layer may have a configuration outside the range of the preferable refractive index difference.

The optical property control film of the present invention has a visible light transmittance (Tvis (a)) of 83% or more when viewed from the normal direction of the optical property control film surface, and the optical property control film surface Visible light transmittance (Tvis (a)) when viewed from the normal direction and visible light transmittance (Tvis (b) when viewed from a direction inclined by 60 ° with respect to the normal direction of the optical property control film ) Ratio satisfies the following relational expression (1) to achieve both visibility when viewed from the front and prevention of peeping.

Relational expression (1) 1.4 ≦ Tvis (a) / Tvis (b)
Visible light transmittance (Tvis (a)) when viewed from the normal direction of the optical property control film surface is preferably 85% or more, more preferably 87% or more, and visibility when viewed from the front. Excellent.

Peep prevention is achieved by adjusting the wavelength of optical interference with a multilayer film in which a high-refractive index layer and a low-refractive index layer are stacked, so that when viewed from the front, the minimum value of the transmission spectrum is viewed in the infrared region and obliquely. By designing the minimum value of the transmission spectrum to be in the visible light range, the visibility when viewed from an oblique angle is lowered, and the effect of preventing peeping is exhibited.

In order to enhance the peep prevention property, in the relational expression (1), the preferred range of Tvis (a) / Tvis (b) is within the range of 1.4 to 2.0, more preferably 1.5 to 1. Is within the range of 7.

As a result of obtaining the multilayer structure necessary for developing such a function by optical simulation (FTG Software Associates Film DESIGN Version 2.23.3700), a high refraction of 1.7 or higher, preferably 1.73 or higher. It has been found that when the refractive index layer is used and the total number of layers of the high refractive index layer and the low refractive index layer is 20 or more, excellent characteristics can be obtained. For example, looking at the simulation results of a model in which 20 layers of high refractive index layers and low refractive index layers (refractive index = 1.45) are alternately stacked, the reflectance is 1.6 when the refractive index of the high refractive index layer is 1.6. Although it does not reach 30%, a reflectance of about 60% is obtained at 1.7.

The high refractive index layer preferably has a refractive index in the range of 1.63-1.83, more preferably in the range of 1.70-1.80 at a light wavelength of 589.3 nm.

The low refractive index layer preferably has a refractive index in the range of 1.10 to 1.60 at a light wavelength of 589.3 nm, more preferably in the range of 1.40 to 1.60.

The thickness per layer (excluding the lowermost layer and the outermost layer) of the refractive index layer (thickness after drying) is preferably in the range of 20 to 1000 nm, and preferably in the range of 50 to 500 nm. More preferably, it is particularly preferably in the range of 50 to 350 nm.

In particular, according to the optical simulation, considering the use of the optical property control film of the present invention as a peep prevention film, in order to satisfy the relational expression (1), the high refractive index layer of the reflective layer unit It is preferable to adjust the layer thickness within the range of 95 to 120 nm and the thickness of the low refractive index layer within the range of 110 to 135 nm.

3. Other Constituent Layers The optical property control film of the present invention is a conductive layer, antistatic layer for the purpose of adding further functions on the outermost surface facing the reflective layer unit of the resin base material or on the semi-wildflower unit. Layer, gas barrier layer, easy adhesion layer (adhesion layer), antifouling layer, deodorant layer, droplet layer, slippery layer, hard coat layer, wear-resistant layer, antireflection layer, electromagnetic wave shielding layer, ultraviolet absorption layer , Infrared absorbing layer, printed layer, fluorescent light emitting layer, hologram layer, release layer, adhesive layer, or infrared cut layer (metal layer, liquid crystal layer) other than the above high refractive index layer and low refractive index layer, colored layer (visible light) One or more functional layers such as an absorbing layer may be included.

[3.1] Hard Coat Layer The optical property control film may have a hard coat layer containing a resin that is cured by heat, ultraviolet rays, or the like as a surface protective layer for enhancing the scratch resistance.

Examples of the curable resin used in the hard coat layer include a thermosetting resin and an ultraviolet curable resin, but an ultraviolet curable resin is preferable because it is easy to mold, and among them, those having a pencil hardness of at least 2H. More preferred. Such curable resins can be used singly or in combination of two or more.

Examples of the ultraviolet curable resin include (meth) acrylate, urethane acrylate, polyester acrylate, epoxy acrylate, epoxy resin, and oxetane resin, and these can also be used as a solvent-free resin composition.

When using the ultraviolet curable resin, it is preferable to add a photopolymerization initiator to accelerate curing.

As photopolymerization initiators, acetophenones, benzophenones, ketals, anthraquinones, thioxanthones, azo compounds, peroxides, 2,3-dialkyldione compounds, disulfide compounds, thiuram compounds, or fluoroamines A compound or the like is used. Specific examples of the photopolymerization initiator include 2,2′-diethoxyacetophenone, p-dimethylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 1-hydroxydimethylphenyl ketone, 2-methyl-4′-methylthio-2-mori. Acetophenones such as holinopropiophenone and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone 1, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldimethylletal, etc. Benzoins, benzophenone, 2,4'-dichlorobenzophenone, 4,4'-dichlorobenzophenone, benzophenones such as p-chlorobenzophenone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, an Rakinon acids, or the like thioxanthones.

These photopolymerization initiators may be used alone, or may be a combination of two or more or a eutectic mixture. In particular, acetophenones are preferably used from the viewpoints of stability of the curable composition and polymerization reactivity.

Commercially available products may be used as such photopolymerization initiators, and preferred examples include Irgacure (registered trademark) 819, 184, 907, 651 manufactured by BASF Japan.

In the hard coat layer, as additives, for example, stabilizers, surfactants, infrared absorbers, ultraviolet absorbers, flame retardants, antistatic agents, antioxidants, thermal stabilizers, lubricants, fillers, colorants, dyes Alternatively, an adhesion adjusting agent or the like can be contained.

The thickness of the hard coat layer is preferably in the range of 0.1 to 50 μm, preferably in the range of 1 to 20 μm, from the viewpoints of improving the hard coat properties and improving the transparency of the light reflecting film. Is more preferable.

The method for forming the hard coat layer is not particularly limited. For example, after preparing a coating liquid for forming a hard coat layer containing the above components, the coating liquid is applied with a wire bar or the like, and the coating liquid is cured with heat or ultraviolet rays. And a method of forming a hard coat layer.

[3.2] Other layers The optical property control film may have layers (other layers) other than the layers described above. For example, an intermediate layer can be provided as the other layer. Here, the intermediate layer means a layer between the resin substrate and the reflective layer unit (the undercoat layer) or a layer between the resin substrate and the hard coat layer. Examples of the constituent material of the intermediate layer include polyester resin, polyvinyl alcohol resin, polyvinyl acetate resin, polyvinyl acetal resin, acrylic resin, urethane resin, and the like. Any of them may be used as long as they are satisfied.

The glass transition temperature (Tg) of the intermediate layer is preferably in the range of 30 to 120 ° C because sufficient weather resistance can be obtained, and more preferably in the range of 30 to 90 ° C.

In the intermediate layer, as additives, for example, stabilizers, surfactants, infrared absorbers, ultraviolet absorbers, flame retardants, antistatic agents, antioxidants, thermal stabilizers, lubricants, fillers, colorants, pigments, An adhesion regulator or the like can also be contained.

4). The optical property control film of this invention is bonded on the touch panel of the said smart phone or tablet as a peep prevention film of a smart phone or a tablet.

In the case of pasting, it is preferable that an adhesive layer is formed on the surface of the resin substrate of the present invention opposite to the reflective layer unit, and the adhesive layer is pasted to the touch panel via the adhesive layer.

Adhesives used in the adhesive layer are urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, polyether methacrylate types, ester methacrylate types. Alternatively, an anaerobic adhesive such as oxidized polyether methacrylate can be used. The pressure-sensitive adhesive may be a one-component type or a two-component type in which two or more components are mixed before use. The concentration of the pressure-sensitive adhesive liquid may be appropriately determined depending on the layer thickness after bonding, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.

The thickness of the pressure-sensitive adhesive layer is usually preferably in the range of about 1 to 50 μm from the viewpoint of the pressure-sensitive adhesive effect, the drying speed and the like. Specific materials used for the adhesive layer include, for example, “SK Dyne Series” manufactured by Soken Chemical Co., Ltd. “Oribain BPW Series, BPS Series” manufactured by Toyo Ink Co., Ltd. “Arcon” “Superester” “High Pale” manufactured by Arakawa Chemical Co., Ltd. Etc. can be suitably used.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

≪Preparation of optical property control film≫
<Preparation of optical property control film 1>
(1) Preparation of Coating Solution 1 for Forming Low Refractive Index Layer Methyldiallylamine hydrochloride polymer (including tertiary amine salt) as a cationic polymer in a stirring vessel (PAS-M-1, weight average molecular weight 20000, 50% by mass) Aqueous solution, manufactured by Nitto Bo Medical Co., Ltd.) 4.0 g, diallyldimethylammonium chloride polymer (including quaternary ammonium group) (PAS-H-5L, weight average molecular weight 30000, 28% by weight aqueous solution, manufactured by Nitto Bo Medical Co., Ltd.) 5.0 g, 31 g of rinse water, and 31.9 g of boric acid (3 mass% aqueous solution) were mixed. To this was added 489.9 g of an aqueous solution of 10% by mass acidic colloidal silica (ST-OXS, concentration 10%, average primary particle size: 4 to 6 nm, manufactured by Nissan Chemical Industries, Ltd., indicated as SiO _{2 in} the table). It was. This was heated to 40 ° C. with stirring. Here, 386.3 g of an 8% by mass aqueous solution of polyvinyl alcohol as a hydrophilic polymer (JP-45, polymerization degree 4500, saponification degree 88 mol%, manufactured by Nippon Acetate / Poval Co., Ltd.), emulsion resin (Superflex 650, Daiichi Kogyo Seiyaku Co., Ltd.) 30.5 g and a 5% by weight surfactant solution (SOFTAZOLIN LMEB-R, Kawaken Fine Chemical Co., Ltd.) 6.3 g and pure water 15 g were added and mixed at 40 ° C. The mixture was stirred and mixed to obtain a coating solution 1 for forming a low refractive index layer.

The refractive index at a light wavelength of 589.3 nm of a single layer produced using the coating liquid 1 for forming a low refractive index layer was 1.50. In addition, the measuring method of a refractive index is as follows (Hereinafter, in the Example, the refractive index was measured similarly.).
(Measurement of single-film refractive index)
In order to measure the refractive index, a sample in which the coating liquid 1 for forming a low refractive index layer is applied as a single layer on a substrate is prepared, and after cutting this sample into 10 cm × 10 cm, the refractive index is obtained according to the following method. It was. Using Hitachi spectrophotometer U-4100 (solid sample measurement system), the surface opposite to the measurement surface (back surface) of each sample is roughened and then light absorption is performed with a black spray. Then, reflection of light on the back surface was prevented, and a reflectance of 589.3 nm was measured under the condition of 5 ° regular reflection, and the refractive index was obtained from the result.

(2) Preparation of Coating Solution 1 for Forming High Refractive Index Layer 30% by Mass of Zirconium Oxide Particle Dispersion (SZR-W, Zirconia Sol, Particle Size Distribution: D50 3-5 nm, Sakai Chemical Industry Co., Ltd., ZrO in Table It was added 175.4g of an aqueous solution of citric acid (1.9 wt%) with respect to ₂ and notation) 384.8G. To this was added 1.94 g of a 5% by mass aqueous solution of a surfactant (SOFTAZOLINE LMEB-R, manufactured by Kawaken Fine Chemical Co., Ltd.), and this was heated to 40 ° C. Next, 120.4 g of an 8% by mass aqueous solution of ethylene-modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., EXVAL RS2117, saponification degree: 97.5 to 99 mol%) was further added, and 9.9 g of pure water was further added. After stirring this for 10 minutes, 60.8% aqueous solution of polyvinyl alcohol as a hydrophilic polymer (JC-40, saponification degree: 99 mol% or more, manufactured by Nihon Acetate / Poval Co., Ltd.) 240.8 g and pure water 66.7 g Was added. Then, it stirred for 180 minutes at 40 degreeC, and obtained the coating liquid 1 for high refractive index layer formation. The refractive index of the single layer produced using the coating liquid 1 for forming a high refractive index layer was 1.73.

(3) Formation of reflection layer unit Using a slide hopper type coating apparatus capable of simultaneous coating of 32 layers, the prepared coating liquid 1 for forming a low refractive index layer and coating liquid 1 for forming a high refractive index layer at 45 ° C. On a long resin substrate (1000 m long, 50 μm thick polyethylene terephthalate (PET) film: Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) while being kept warm, 21 layers are simultaneously applied ( A total of 21 layers of low refractive index layers and high refractive index layers were alternately laminated). At this time, the lowermost layer (resin substrate side) and the uppermost layer are a low refractive index layer (thickness after drying: 108 nm), and the other layers are a low refractive index layer (thickness after drying: 117 nm) and a high refractive index. A reflective layer unit composed of a total of 21 layers was formed so that the layers (thickness after drying: 101 nm) were alternately laminated.

<Preparation of optical property control film 2>
(1) Preparation of coating solution 2 for forming a low refractive index layer Methyldiallylamine hydrochloride polymer (including tertiary amine salt) as a cationic polymer in a stirring vessel (PAS-M-1, weight average molecular weight 20000, 50% by mass) Aqueous solution, manufactured by Nitto Bo Medical Co., Ltd.) 4.0 g, diallyldimethylammonium chloride polymer (including quaternary ammonium group) (PAS-H-5L, weight average molecular weight 30000, 28% by weight aqueous solution, manufactured by Nitto Bo Medical Co., Ltd.) 5.0 g, 31 g of rinse water, and 31.9 g of boric acid (3 mass% aqueous solution) were mixed. 489.9 g of a 10% by mass magnesium fluoride aqueous solution (manufactured by Stella Chemifa Corporation, D50 30 nm, indicated as MgF _{2 in} the table) was added thereto. This was heated to 40 ° C. with stirring. Here, 18.9 g of sodium polyacrylate as a hydrophilic polymer, 30.5 g of emulsion resin (Superflex 650, Daiichi Kogyo Seiyaku Co., Ltd.), a solution of 5% by mass of a surfactant (SOFTAZOLINE LMEB-R, Kawasaki) Ken Fine Chemical Co., Ltd.) 6.3 g and 15 g of pure water were added and stirred and mixed at 40 ° C. to obtain a coating solution 2 for forming a low refractive index layer.
The refractive index of a single layer produced using the coating solution 2 for forming a low refractive index layer was 1.50.

(2) Preparation of coating solution 2 for forming a high refractive index layer 30% by mass of a zinc sulfide particle dispersion (prepared by the following method, zinc sulfide particles are indicated as ZnS in the table) 384.8 g of citric acid aqueous solution ( 1.9% by mass) was added. To this was added 1.94 g of a 5% by mass aqueous solution of a surfactant (SOFTAZOLINE LMEB-R, manufactured by Kawaken Fine Chemical Co., Ltd.), and this was heated to 40 ° C. Next, 14.3 g of sodium polyacrylate as a hydrophilic polymer and 66.7 g of pure water were added. Then, it stirred at 40 degreeC for 180 minutes, and obtained the coating liquid 2 for high refractive index layer formation.

(Preparation of zinc sulfide particles)
Preparation of Zinc Sulfide Nanoparticles 0.7 g of lithium sulfide was dissolved in 500 mL of water to prepare a lithium sulfide aqueous solution. Further, 2.7 g of zinc acetate and 5 g of hydroxyethyl cellulose (polymerization degree 600) were dissolved in 500 mL of water to prepare a zinc acetate aqueous solution. As a mixer, a microreactor (Interdigital single mixing device) having a channel width of 40 μm and a depth of 200 μm made by IMM (Institue for Microtechnique Milan) is used, the contact interface in the flow direction is 4 mm, and the contact time by the laminar flow is about 1 In milliseconds, zinc sulfide particles were prepared to obtain a dispersion having a solid content of 30% by mass. The obtained particles had an average particle size of 5 nm and a coefficient of variation of 18%.
The refractive index of the single layer produced using the coating liquid 2 for forming a high refractive index layer was 1.73.

(3) Formation of reflection layer unit Using a slide hopper type coating apparatus capable of simultaneous coating of 32 layers, the above-prepared coating solution 2 for forming a low refractive index layer and coating solution 2 for forming a high refractive index layer are heated to 45 ° C. Simultaneously layered 21 layers on a long resin base material (1000 m long, 40 μm thick triacetate (TAC) film: Konica Minolta, Konica Minolta TAC, KC4UA) heated to 45 ° C. while keeping warm. Application (a total of 21 layers of low refractive index layers and high refractive index layers alternately) was performed. At this time, the lowermost layer (resin substrate side) and the uppermost layer are low refractive index layers (thickness after drying: 108 nm), and other layers are low refractive index layers (thickness after drying: 113 nm) and high refractive index. A reflective layer unit composed of a total of 21 layers was formed so that the layers (thickness after drying: 98 nm) were alternately laminated.

<Preparation of optical property control film 3>
(1) Preparation of coating solution 3 for forming a low refractive index layer Methyldiallylamine hydrochloride polymer (including tertiary amine salt) as a cationic polymer in a stirring vessel (PAS-M-1, weight average molecular weight 20000, 50% by mass) Aqueous solution, manufactured by Nitto Bo Medical Co., Ltd.) 4.0 g, diallyldimethylammonium chloride polymer (including quaternary ammonium group) (PAS-H-5L, weight average molecular weight 30000, 28% by weight aqueous solution, manufactured by Nitto Bo Medical Co., Ltd.) 5.0 g, 31 g of rinse water, and 31.9 g of boric acid (3 mass% aqueous solution) were mixed. To this was added 489.9 g of an aqueous solution of 10% by mass acidic colloidal silica (ST-OXS, concentration 10%, average primary particle size: 4 to 6 nm, manufactured by Nissan Chemical Industries, Ltd., indicated as SiO _{2 in} the table). It was. This was heated to 40 ° C. with stirring. Here, 386.3 g of an 8% by weight aqueous solution of polyvinylpyrrolidone as a hydrophilic polymer (polyvinylpyrrolidone K-85W (manufactured by Nippon Shokubai) diluted with pure water), emulsion resin (Superflex 650, Daiichi Kogyo Seiyaku Co., Ltd.) Add 36.3 g and 5% by weight surfactant solution (Softazolin LMEB-R, Kawaken Fine Chemical Co., Ltd.) 6.3 g and pure water 15 g, stir and mix at 40 ° C., low refraction A coating liquid 3 for forming a rate layer was obtained.
The refractive index of a single layer produced using the coating solution 3 for forming a low refractive index layer was 1.50.

(2) Preparation of coating solution 3 for forming a high refractive index layer Citric acid with respect to 384.8 g of a dispersion of 20% by mass of silica-modified titanium oxide (prepared titanium oxide particles by the following method, expressed as TiO _{2 in} the table) 175.4g of aqueous solution (1.9 mass%) was added. To this was added 1.94 g of a 5% by mass aqueous solution of a surfactant (SOFTAZOLINE LMEB-R, manufactured by Kawaken Fine Chemical Co., Ltd.), and this was heated to 40 ° C. Subsequently, 14.3 g of polyvinylpyrrolidone as a hydrophilic polymer and 66.7 g of pure water were added. Then, it stirred for 180 minutes at 40 degreeC, and obtained the coating liquid 3 for high refractive index layer formation.

(Preparation of silica-modified titanium oxide particle dispersion)
A dispersion of silica-modified titanium oxide particles (rutile type) was prepared as follows.

The titanium sulfate aqueous solution was thermally hydrolyzed by a known method to obtain titanium oxide hydrate. The obtained titanium oxide hydrate was suspended in water to obtain 10 L of an aqueous suspension of titanium oxide hydrate (TiO ₂ concentration: 100 g / L). To this, 30 L of an aqueous sodium hydroxide solution (concentration 10 mol / L) was added with stirring, the temperature was raised to 90 ° C., and the mixture was aged for 5 hours. The obtained solution was neutralized with hydrochloric acid, filtered and washed with water to obtain a base-treated titanium compound.

Next, the base-treated titanium compound was suspended in pure water and stirred so that the TiO ₂ concentration was 20 g / L. Under stirring TiO ₂ amount to the addition of 0.4 mole% of the amount of citric acid. The temperature was raised to 95 ° C., concentrated hydrochloric acid was added so that the hydrochloric acid concentration was 30 g / L, and the solution temperature was maintained, followed by stirring for 3 hours. Here, when the pH and zeta potential of the obtained mixed liquid were measured, the pH at 25 ° C. was 1.4, and the zeta potential was +40 mV. Further, when the particle size was measured by Zetasizer Nano (manufactured by Malvern), the volume average particle size was 35 nm and the monodispersity was 16%. Further, the titanium oxide sol solution was dried at 105 ° C. for 3 hours to obtain a particle powder, and X-ray diffraction measurement was performed using JDX-3530 type manufactured by JEOL Datum Co., Ltd. confirmed.

1 kg of pure water was added to 1 kg of a 20.0 mass% titanium oxide sol aqueous dispersion containing the rutile-type titanium oxide particles to prepare a 10.0 mass% titanium oxide sol aqueous dispersion.

2 kg of pure water was added to 0.5 kg of the 10.0 mass% titanium oxide sol aqueous dispersion, followed by heating to 90 ° C. Thereafter, 0.1 kg of an aqueous silicic acid solution having a SiO ₂ concentration of 2.0 mass% was gradually added. The resulting dispersion is subjected to heat treatment at 175 ° C. for 18 hours in an autoclave, desalted using ultrafiltration, and further concentrated to contain titanium oxide having a rutile structure coated with SiO ₂ . A dispersion (sol aqueous dispersion) of 20% by mass of silica-modified titanium oxide particles was obtained. At this time, the coating amount of silica was 4% by mass with respect to the titanium oxide particles. Further, when the particle size of silica-modified titanium oxide particles (rutile type) was measured using Zetasizer Nano (manufactured by Malvern), the volume average particle size was 35 nm and the monodispersity was 16%.
The refractive index of the single layer produced using the coating liquid 3 for forming a high refractive index layer was 1.73.

(3) Formation of reflection layer unit Using a slide hopper type coating apparatus capable of simultaneous coating of 32 layers, the above-prepared coating solution 3 for forming a low refractive index layer and coating solution 3 for forming a high refractive index layer are heated to 45 ° C. On a long resin substrate (1000 m long, 50 μm thick polyethylene terephthalate (PET) film: Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) while being kept warm, 21 layers are simultaneously applied ( A total of 21 layers of low refractive index layers and high refractive index layers were alternately laminated). At this time, the lowermost layer (resin substrate side) and the uppermost layer are low refractive index layers (thickness after drying: 108 nm), and other layers are low refractive index layers (thickness after drying: 121 nm) and high refractive index. A reflective layer unit composed of a total of 21 layers was formed such that the layers (thickness after drying: 105 nm) were alternately laminated.

<Preparation of optical property control film 4>
In the production of the optical property control film 1, the optical property control film 4 was similarly prepared except that the layer thickness of the low refractive index layer was changed to 109 nm and the layer thickness of the high refractive index layer was changed to 94 nm and TAC was used as the substrate. Got.

<Preparation of optical property control film 5>
In preparation of the optical property control film 2, the same except that TAC is used as the base material, polyvinylpyrrolidone is used as the hydrophilic polymer, the layer thickness of the low refractive index layer is changed to 125 nm, and the layer thickness of the high refractive index layer is changed to 109 nm. Thus, an optical property control film 5 was obtained.

<Preparation of optical property control film 6>
In the production of the optical property control film 1, sodium acrylate was used as the hydrophilic polymer, except that the layer thickness of the low refractive index layer was changed to 140 nm and the layer thickness of the high refractive index layer was changed to 121 nm. A control film 6 was obtained.

<Preparation of optical property control film 7>
In accordance with the description in paragraphs [0011] and [0013] of JP-A-2006-168335, on a polyethylene terephthalate (PET) film (Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) as a substrate, as a low refractive index layer The optical characteristic control film 7 was obtained by alternately laminating 60 layers of two different refractive indexes of nylon (refractive index 1.53) and polyester (refractive index 1.57) as a high refractive index layer.

<Evaluation>
The following evaluations were performed on the produced optical property control films 1 to 7.

Evaluation results are shown in Table I.

<Visible Light Transmittance>
The produced optical property control films 1 to 7 were subjected to a visible light transmittance (Tvis () measured from a normal (90 °) direction with respect to a film test piece by a visible light transmittance test defined in JIS S 3107: 2013. a)) and a visible light transmittance (Tvis (b)) measured from a direction inclined by 60 ° from the normal direction.

The visible light transmittance test was performed based on JIS S 3107: 2013.

The measurement of the spectral transmittance was carried out using an ultraviolet-visible near-infrared spectrophotometer V-670 manufactured by JASCO.

<Condensation evaluation>
The produced optical property control film was left in a constant temperature bath at 5 ° C. for 30 minutes, and then taken out into a room at a temperature of 20 ° C. and a humidity of 65% RH, and the condensation on the film surface was visually evaluated.

◎: Condensation on the film surface is not observed ○: Condensation on the film surface is slightly observed ×: Condensation on the film surface is clearly seen <Evaluation for peep prevention>
One application of the film of the present invention is a peep prevention film.

After forming an adhesive layer containing an epoxy adhesive on the base of the optical property control film that faces the reflective layer unit, paste it on the smartphone screen and view it from the front (normal direction of the film surface). And the visibility of characters when viewed from an oblique direction (a direction inclined by 60 ° from the normal direction of the film surface) was evaluated.

◎: When viewing from an angle of 60 °, the characters cannot be read at all, and the effect of preventing peeping is very high. ○: When viewed from an angle of 60 °, the characters are difficult to read, and an effect of preventing peeping is exhibited. ×: Characters can be read even when viewed from an angle of 60 °, and there is no peep prevention effect

From the results of Table I, the optical property control film of the present invention is excellent in visibility from the front (Tvis (a)) and peep prevention, and prevents condensation of moisture assuming a cold region, It is considered that the malfunction of the touch panel is suppressed.

The optical property control film of the present invention has excellent visibility from the front and anti-peeping properties, and prevents condensation due to moisture in cold regions. It is used as an optical film.

DESCRIPTION OF SYMBOLS 1 Optical characteristic control film 2 Transparent resin base material 3 Reflective layer unit 3a Low refractive index layer 3b High refractive index layer 4 Hard-coat layer

Claims

An optical property control film having a reflective layer unit composed of a plurality of high refractive index layers and low refractive index layers containing a hydrophilic polymer and fine particles on a resin substrate,
Visible light transmittance (Tvis (a)) when viewed from the normal direction of the optical property control film surface is 83% or more, and
Visible light transmittance (Tvis (a)) when viewed from the normal direction of the optical property control film surface and visible light when viewed from a direction inclined by 60 ° with respect to the normal direction of the optical property control film A ratio of transmittance (Tvis (b)) satisfies the following relational expression (1): an optical property control film.
Relational expression (1) 1.4 ≦ Tvis (a) / Tvis (b)
2. The optical property control film according to claim 1, wherein the hydrophilic polymer is polyvinyl alcohol, and the fine particles are metal oxide fine particles.
The thickness of the high refractive index layer of the reflective layer unit is in the range of 95 to 120 nm, and the thickness of the low refractive index layer is in the range of 110 to 135 nm. Item 3. The optical property control film according to Item 2.
4. The optical property control according to claim 1, further comprising a reflective layer unit in which a total number of the high refractive index layer and the low refractive index layer is 20 or more. 5. the film.
The refractive index of the high refractive index layer at a light wavelength of 589.3 nm is in the range of 1.63 to 1.83, and the refractive index of the low refractive index layer is in the range of 1.40 to 1.60. The optical property control film according to any one of claims 1 to 4, wherein the optical property control film is provided.
A display device comprising the optical property control film according to any one of claims 1 to 5.