JP2018036604A - Light reflection film and backlight unit for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light reflection film suppressing discoloration when irradiated with light from an LED for a long time and suppressing decrease in the reflectance.SOLUTION: The light reflection film includes a base material layer A (11), an organic coating layer B (13), a silver layer C (15), and an organic coating layer D (17), in this order, in which a percentage of (111) plane of the silver layer C represented by formula (1) of (percentage (%) of (111) plane)=I(111)/[I(111)+I(200)+I(220)+I(311)]×100 is 80% or more. In the formula (1), I(111), I(200), I(220) and I(311) represent integrated intensities of peaks corresponding to (111) plane, (200) plane, (220) plane and (311) plane of silver, respectively, measured by X-ray diffractometry.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a light reflecting film and a backlight unit for a liquid crystal display device.

  Conventionally, a reflective member has been used in applications such as a light reflecting film of a backlight unit for a liquid crystal display device, a reflecting mirror of a projection television or an optical system device, and a reflective member for LED illumination.

  As such a reflective member, a reflective film including a silver layer is known (for example, Patent Documents 1 and 2). Patent Document 1 discloses a reflecting member including a substrate, a silver thin film having a (111) plane as a main plane orientation, and a silicon nitride film in this order. It has been shown that a silver thin film having a (111) plane as a main plane orientation is formed by sputtering. Patent Document 2 discloses a base film, a silver layer, a low refractive index layer composed of an acrylic melamine resin, and a high refractive index layer containing titanium oxide particles and a cured product of a heat ray curable resin. Laminated films including in order are disclosed.

JP 2007-58194 A JP 2008-39960 A

  By the way, the reflective member of Patent Document 1 has insufficient interlayer adhesion between a silver layer (which is an inorganic thin film) and a silicon nitride film (which is an inorganic thin film). For this reason, there is a possibility that the wet heat durability is lowered.

On the other hand, the reflective member of Patent Document 2 is considered to have good interlayer adhesion between the silver layer (which is an inorganic thin film) and the low refractive index layer (which is a resin layer) and has good wet heat durability. However, the following new problems were discovered.
That is, in recent years, development of liquid crystal display devices using LEDs as light sources has been promoted. Since the LED is a directional light source, it is known to radiate strong light partially. However, it has been found that when a conventional reflecting member as disclosed in Patent Document 2 is irradiated with light from an LED for a long time, a black color change may occur from a portion where intense light is continuously irradiated. In order to examine this discoloration, for the reflective member of Patent Document 2, when a forced deterioration test was performed by irradiating light from an LED for a long time at a high temperature, black discoloration may occur in the light irradiated portion. It was found. Such discoloration not only causes poor appearance but also causes a decrease in reflectance.

  This invention is made | formed in view of the said situation, In the light reflection film which has the organic coating layer adjacent to a silver layer, discoloration when the light from LED is irradiated for a long time is suppressed, and a reflectance falls. An object of the present invention is to provide a light reflecting film in which is suppressed.

The above object of the present invention is achieved by the following configurations.
[1] A base layer A, an organic coating layer B, a silver layer C provided adjacent to the organic coating layer B, and an organic coating layer D provided adjacent to the silver layer C. It is a light reflection film included in order, Comprising: The light reflection film whose ratio of the (111) surface represented by following formula (1) of the said silver layer C is 80% or more.
(111) surface ratio (%) = I (111) / [I (111) + I (200) + I (220) + I (311)] × 100 (1)
(In Formula (1),
I (111): integrated intensity of peak corresponding to silver (111) plane measured by X-ray diffraction method I (200): peak intensity corresponding to silver (200) plane measured by X-ray diffraction method Integral intensity I (220): integrated intensity of peak corresponding to silver (220) plane measured by X-ray diffraction method I (311): corresponding to silver (311) plane measured by X-ray diffraction method Indicates the integrated intensity of the peak)
[2] The light reflecting film according to [1], wherein a ratio of the (111) plane is less than 95%.
[3] The light reflecting film according to [1] or [2], wherein the silver layer C is a vapor deposition film.
[4] The light reflecting film according to any one of [1] to [3], wherein the organic coating layer B and the organic coating layer D include an acrylic resin or a cured product thereof as a main component.
[5] The light reflecting film according to [4], wherein the organic coating layer B and the organic coating layer D further contain a thiol compound.
[6] The light reflecting film according to [5], wherein the thiol compound is a nitrogen-containing heterocyclic compound having a thiol group.
[7] The organic coating layer D further includes a protective layer E having a lower water vapor transmission rate at 40 ° C. and 90% RH than the organic coating layer D on the surface opposite to the silver layer C. [6] The light reflection film according to any one of [6].
[8] The light reflecting film according to [7], wherein the refractive index of the protective layer E at a wavelength of 550 nm is higher than the refractive index of the organic coating layer B at a wavelength of 550 nm.
[9] The light reflecting film according to [7] or [8], wherein the protective layer E is a layer including high refractive index particles and a cured product of a curable resin.
[10] The light reflecting film according to [9], wherein the high refractive index particles are zirconium oxide particles.
[11] A backlight unit for a liquid crystal display device, comprising a light source and the light reflecting film according to any one of [1] to [10].

  The present invention provides a light reflecting film having an organic coating layer adjacent to a silver layer, in which discoloration when light from an LED is irradiated for a long time is suppressed and a decrease in reflectance is suppressed. be able to.

FIG. 1A is an example of the SEM observation result of the surface of the silver deposition film, and FIG. 1B is an example of the SEM observation result of the surface of the silver sputtering film. FIG. 2 is a schematic view showing an example of the light reflecting film of the present invention. FIG. 3 is a cross-sectional view showing an example of the liquid crystal display device of the present invention. FIG. 4 is a diagram illustrating an example of an X-ray diffraction spectrum under film forming conditions 1 to 4.

  The reason why the reflecting member of Patent Document 2 causes a black change in the light irradiation portion when light from the LED is irradiated for a long time is not clear, but is estimated as follows.

  That is, the reflecting member of Patent Document 2 has a “resin layer containing titanium oxide particles” as a high refractive index layer. Since the titanium oxide particles have a photocatalytic action, when light from the LED is irradiated for a long time, the photocatalytic action of the titanium oxide particles facilitates the photodecomposition of the resin constituting the high refractive index layer. It tends to disappear with it. As a result, the low refractive index layer (resin layer) under the high refractive index layer is also easily irradiated with light from the LED, and the photocatalytic action of titanium oxide contained in the high refractive index layer causes the low refractive index layer. The resin constituting the resin is also easily photodegraded and easily disappears over time. As described above, when a part of the low refractive index layer (resin layer) provided adjacent to the silver layer disappears, the silver layer is exposed, so that the silver atoms constituting the silver layer easily move and diffuse (migration). Therefore, it is considered that aggregates are formed or mixed with other layers and appear to change to black.

  On the other hand, in this invention, the light which has the base material layer A, the organic coating layer B, the silver layer C adjacent to this organic coating layer B, and the organic coating layer D adjacent to this silver layer C in this order. In the reflective film, the ratio of the (111) plane of the silver layer C is adjusted to 80% or more. By adjusting the ratio of the (111) plane of the silver layer to 80% or more, the crystal structure of the silver atoms can be made highly regular, so that the silver atoms can be made difficult to move and diffuse. Thereby, even if a part of the organic coating layer D provided adjacent to the light incident side of the silver layer C disappears due to long-time light irradiation from the LED, migration of silver atoms constituting the silver layer C is performed. Since it can suppress highly, discoloration of black can be less than before.

  Furthermore, the protective layer E is provided, and the refractive index of the light with a wavelength of 550 nm of the protective layer E is made higher than the refractive index of the light with a wavelength of 550 nm of the organic coating layer D, that is, the organic coating layer D has a low refractive index. By causing the layer and the protective layer E to function as a high refractive index layer, the reflectance of light in the low wavelength region can be further increased, and the chromaticity of the reflected light can be further improved.

Furthermore, by making the protective layer E as the high refractive index layer a resin layer containing zirconium oxide particles, the photodecomposition of the resin constituting the protective layer E can be suppressed. Thereby, the loss | disappearance of the protective layer E and the organic coating layer D when the light from LED is irradiated for a long time can be suppressed, and the black discoloration when the light from LED is irradiated for a long time can be suppressed further.
The present invention has been made based on these findings.

1. Light Reflecting Film The light reflecting film of the present invention preferably includes a base material layer A, an organic coating layer B, a silver layer C, and an organic coating layer D in this order, and further includes a protective layer E.

1-1. Base material layer A
The base material layer A has a function of supporting the silver layer. The base material layer A is preferably a resin film.

  Examples of the resin film include polyester films such as polyethylene terephthalate film and polyethylene naphthalate film, polypropylene film, acrylic film, polycarbonate film, polyimide film, polysulfone film, polyether ether ketone film, fluororesin film, cellulose ester film, Polycycloolefin-based films and the like are included. Among these, a polyethylene terephthalate film and a polypropylene film are preferable from the viewpoint of high heat resistance, strength, and transparency.

  The thickness of the base material layer A can be set to 10 to 300 μm, for example. When the thickness of the base material layer A is 10 μm or more, not only the base material layer A has sufficient strength but also the surface smoothness is not easily impaired. The thickness of the base material layer A is preferably 20 to 200 μm, and more preferably 20 to 100 μm.

  In order to form a layer uniformly on the base material layer A, it is preferable that the base material layer A contains as little impurities as possible. From such a viewpoint, the base material layer A is preferably a transparent base material layer. The average transmittance of the transparent substrate layer at a wavelength of 360 to 400 nm is preferably 80% or more, and more preferably 85% or more.

1-2. Organic coating layer B
The organic coating layer B is disposed between the base material layer A and the silver layer C, and can not only function as an anchor layer that enhances adhesion between the base material layer A and the silver layer C, but also has high surface smoothness. The silver layer C can be easily formed.

  The organic coating layer B contains a resin as a main component. “Containing a resin as a main component” means that the content of the resin is 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more with respect to the total mass of the organic coating layer B.

  Examples of the resin contained in the organic coating layer B include polyester resins, acrylic resins or cured products thereof, heterocyclic compounds (for example, melamine resins) or cured products thereof, cured products of epoxy resins, and polyamide resins. , Vinyl chloride resin, vinyl chloride vinyl acetate copolymer and the like. These may be one type or a combination of two or more.

  Among these, the organic coating layer B preferably contains an acrylic resin or a cured product thereof from the viewpoint of good durability against light; from the viewpoint of adhesion with the silver layer C, the acrylic resin and the heterocyclic type are preferable. It is more preferable to include a mixture of compounds (for example, melamine resin) or a cured product of acrylic resin.

  The acrylic resin may be a homopolymer of (meth) acrylic acid ester or a copolymer of (meth) acrylic acid ester and another copolymerizable monomer. The (meth) acrylic acid ester may preferably be methyl methacrylate.

  Examples of copolymer monomers copolymerized with methyl methacrylate include (meth) acrylic acid alkyl esters other than methyl methacrylate; α, β-unsaturated acids such as acrylic acid and methacrylic acid; maleic acid, fumaric acid Unsaturated divalent carboxylic acids such as itaconic acid; 2-hydroxymethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, Hydroxyl group-containing (meth) acrylic acid esters such as diethylene glycol mono (meth) acrylate and dipropylene glycol mono (meth) acrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; alkoxy groups such as n-butoxymethylacrylamide (Meth) acrylic net It is included. These may be used alone or in combination of two or more. The proportion of the structural unit derived from the copolymer monomer in the copolymer of methyl methacrylate and another copolymer monomer is preferably 50% by mass or less, and more preferably 30% by mass or less.

  Examples of the acrylic resin include polymethyl methacrylate and a copolymer of methyl methacrylate / styrene / acrylamide / 2-hydroxyethyl acrylate.

  The weight average molecular weight of acrylic resin should just be a grade which can be apply | coated, for example, may be 1000 to 500,000. The weight average molecular weight of the resin can be measured in terms of polystyrene by gel permeation chromatography.

  The cured product of the acrylic resin may be a cured product (crosslinked product) obtained by directly reacting the functional groups of the “acrylic resin having a functional group”; and “the acrylic resin having a functional group”. However, from the viewpoint of excellent adhesion to the silver layer C, a curing agent for an acrylic resin (preferably Is preferably a cured product of a heterocyclic compound, more preferably a melamine resin.

  Examples of the functional group in the “acrylic resin having a functional group” include a carboxyl group, a hydroxy group, an amino group, an epoxy group, and a methylol group. Examples of “acrylic resin having a functional group” include a copolymer of the above-mentioned (meth) acrylic acid ester and a hydroxyl group-containing (meth) acrylic acid ester, or (meth) acrylic acid ester and (meth) acrylic acid. And the like. Examples of the curing agent include heterocyclic compounds such as melamine resins and isocyanates.

  The organic coating layer B preferably further contains a thiol compound. This is because the thiol group of the thiol compound easily interacts with the silver atoms constituting the silver layer C, and further suppresses migration of silver atoms.

  Examples of thiol compounds include thiol group-containing carboxylic acids such as mercaptoacetic acid, mercaptopropionic acid, mercaptobutanoic acid; thiophenol, 2-mercaptobenzyl alcohol, 2-phenoxythiophenol, 3-mercaptophenanthrene, 2-mercapto Aromatic hydrocarbon thiol compounds such as -4 (3H) -quinazoline and β-mercaptonaphthalene; ethanethiol, propanethiol, 1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 2, Alkane (poly) thiol compounds such as 3-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol; 3-mercapto-1,2,4-triazole, 1-methyl-3-mercapto-1, 2,4-triazole, 1-methyl-5-methyl Thiols such as capto-1H-tetrazole (MMT), 1- (2-dimethylaminoethyl) -5-mercapto-1H-tetrazole (DMT), 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole Group-containing aromatic heterocycle; thionalide; thiol group-containing alkoxysilane compound such as 3-mercaptopropyltrimethoxysilane; thiol group-containing carboxylic acid (mercaptoacetic acid, mercaptopropionic acid, etc.) and alcohol (methanol, ethanol, butanediol, hexane) Thiol group-containing carboxylic acid derivatives (methyl mercaptoacetate, methyl mercaptopropionate) obtained by ester reaction with diol, trimethylolpropane, and (poly) alcohols such as pentaerythritol Octyl mercaptopropionate, methoxybutyl mercaptopropionate, glycol dimercaptoacetate, butanediol bisthioglycolate (BDTG), trimethylolpropane tristhioglycolate (TMTG), trimethylolpropane tristhiopropionate (TMTP) and penta Erythritol tetrakisthiopropionate (PETG) and the like.

  The thiol compound is preferably a thiol group-containing nitrogen-containing aromatic heterocyclic ring, particularly from the viewpoint of easily interacting with silver atoms constituting the (111) plane, and the thiol group-containing nitrogen-containing aromatic heterocyclic 5-membered ring (thiol) Group-containing azole compound), more preferably a thiol group-containing tetrazole.

  The thiol compound may be a monofunctional thiol compound having one thiol group in the molecule, or may be a polyfunctional thiol compound having two or more thiol groups in the molecule.

The thiol group equivalent (g / eq) of the thiol compound is preferably 300 or less, and more preferably 200 or less. When the thiol group equivalent is below a certain level, the molecule contains many thiol groups, so that it easily interacts with the silver atoms constituting the silver layer C. Thereby, it is easy not only to form the silver layer C uniformly, but also to suppress migration of silver atoms. The thiol group equivalent is defined by the following formula.
Thiol group equivalent (g / eq) = weight average molecular weight of thiol compound / number of thiol groups per molecule

  The weight average molecular weight of the thiol compound is not particularly limited as long as it can be well dispersed in the resin, and is preferably 100 to 1000, for example, and more preferably 150 to 500.

  The content of the thiol compound is preferably 0.1 to 50% by mass with respect to the total mass of the organic coating layer B. When the content of the thiol compound is 0.1% by mass or more, the silver atoms constituting the silver layer C can be sufficiently interacted with each other, so that migration of silver atoms can be sufficiently suppressed. There is no possibility of bleeding out when the content of the thiol compound is 50% by mass or less. The content of the thiol compound is more preferably 1 to 20% by mass with respect to the total mass of the organic coating layer B.

  Since the organic coating layer B has little influence on the optical performance, the organic coating layer B only needs to have a sufficient thickness to suppress migration of silver atoms. The thickness of the organic coating layer B may be larger than the thickness of the organic coating layer D. Specifically, the thickness of the organic coating layer B can be set to, for example, 10 nm to 1000 nm. When the thickness of the organic coating layer B is 10 nm or more, the adhesion between the base material layer A and the silver layer C can be sufficiently enhanced. When the thickness of the organic coating layer B is 1000 nm or less, the organic coating layer B is unlikely to crack. The thickness of the organic coating layer B is preferably 10 nm to 500 nm, and more preferably 50 nm to 200 nm, from the viewpoint of easily suppressing migration of silver atoms.

1-3. Silver layer C
The silver layer C is provided adjacent to the organic coating layer B, and can function as a reflective layer that reflects incident light.

  The silver layer C contains Ag or an alloy thereof as a main component. The phrase “containing Ag or an alloy thereof as a main component” means that the content of Ag or an alloy thereof is 90 atomic% or more with respect to the total of the total atomic weights constituting the silver layer C. Therefore, the content of Ag or an alloy thereof is preferably 95 atomic percent or more, more preferably 99.9 atomic percent or more, based on the total total atomic weight of the silver layer C.

  The silver layer C may further contain other metals other than Ag or its alloy. Examples of other metals include at least one selected from the group consisting of Al, Cu, Pd, Cr, Cu, Ni, Ti, Mg, Rh, Pt and Au, and alloys thereof, preferably Al and alloys thereof Or Au and its alloys.

As described above, in order to suppress the black discoloration of the light reflecting film when the light from the LED is irradiated for a long time, the ratio of the (111) plane represented by the formula (1) of the silver layer C is 80% or more is preferable.
(111) surface ratio (%) = I (111) / [I (111) + I (200) + I (220) + I (311)] × 100 (1)
(In Formula (1),
I (111): integrated intensity of peak corresponding to silver (111) plane measured by X-ray diffraction method I (200): peak intensity corresponding to silver (200) plane measured by X-ray diffraction method Integral intensity I (220): integrated intensity of peak corresponding to silver (220) plane measured by X-ray diffraction method I (311): corresponding to silver (311) plane measured by X-ray diffraction method Indicates the integrated intensity of the peak)

  When the silver layer C is measured by X-ray diffraction, peaks derived from the (111) plane, (200) plane, (220) plane and (311) plane of silver are usually observed. The ratio of the peak intensity derived from these surfaces varies depending on the state of the crystal structure of the silver layer C. The silver layer C having a high (111) plane ratio has a structure in which silver atoms are regularly arranged (has a highly ordered crystal structure). That is, when the ratio of the (111) plane is 80% or more, silver atoms are arranged in a regular manner, so that silver atoms are less likely to be diffused / moved (migration). As a result, even if the light reflecting film is irradiated with light for a long time and a part of the organic coating layer D provided on the light incident side of the silver layer C is lost or damaged, the silver layer C Since the migration of the silver atoms constituting it can be suppressed, discoloration can be suppressed. The ratio of the (111) plane measured by the X-ray diffraction method of the silver layer C is more preferably 85% or more, and may be 100%. However, if the (111) plane ratio is too high, the surface energy of the silver layer C becomes small, and there is a possibility that the interlayer adhesion with the adjacent protective layer E is impaired. Therefore, from the viewpoint of making the interlayer adhesion difficult to be damaged, the ratio of the (111) plane of the silver layer C is preferably less than 95%.

The ratio of the (111) plane of the silver layer C can be measured by the following method.
1) The light reflecting film is immersed in a solvent that dissolves the organic coating layer D, and then dried to remove the organic coating layer D.
2) For the silver layer C of the light reflecting film obtained in 1) above, using an X-ray diffraction (XRD) analyzer (“RINT-TTRII” manufactured by Rigaku Corporation), the tube Cu, tube voltage 30 kV, tube current X-ray diffraction measurement is performed using a monochromator and a glass sample holder under the conditions of 30 mA and a sampling width of 0.020 °. Then, an X-ray diffraction spectrum (horizontal axis: 2θ, vertical axis: peak intensity) is obtained (see FIG. 4 described later). From the obtained X-ray diffraction spectrum, integrated intensities of peaks corresponding to the (111) plane, (200) plane, (220) plane, and (311) plane of the silver layer are obtained. The peak integrated intensity refers to the area of a region formed between a peak baseline (a baseline common to the above four peaks) and the peak.
3) The integrated intensity of the peak corresponding to each surface obtained in the above 2) is applied to the above equation (1) to obtain the ratio of the (111) surface.

  The ratio of the (111) plane of the silver layer C can be adjusted by the film formation conditions (specifically the film formation rate) when the silver layer C is formed in a vacuum. In order to increase the ratio of the (111) plane of the silver layer C, for example, it is preferable to decrease the deposition rate of the silver layer C. This is because by reducing the film formation rate, silver atoms can be easily deposited in a close-packed structure, and the ratio of the (111) plane of the resulting silver layer C can be easily increased.

In the case of the vacuum evaporation method, the film forming speed is adjusted by, for example, the heating temperature (deposition temperature) of the crucible charged with the raw material, the supply flow rate of the gas supplied into the chamber, the composition of the gas, or the degree of vacuum in the chamber. can do. From the viewpoint of easily reducing the deposition rate without reducing the production efficiency, the deposition temperature is set to a high temperature (for example, 900 ° C. or more), and the pressure in the chamber is within a predetermined range (preferably in the vicinity of 4 × 10 ⁻² Pascal). It is preferable to perform film formation while introducing a gas (preferably argon gas, xenon gas, or a mixed gas thereof) so that the gas is maintained at a low temperature.

  As described later, the vacuum film forming method includes a sputtering method and a vapor deposition method, but the vacuum vapor deposition method is preferable from the viewpoint of high production efficiency and the ratio of the (111) plane not excessively increasing. That is, the silver layer C is preferably a vapor deposition film.

  Whether or not the silver layer C is a vapor-deposited film depends on whether the surface of the silver layer C is SEM-observed using JSM-6060LA made by JEOL under the conditions of an applied voltage of 30 kV and a magnification of 15000 times. This can be confirmed by seeing the grain boundaries. FIG. 1A is an example of an SEM observation result of the surface of a 100 nm-thick silver deposited film, and FIG. 1B is an example of an SEM observation result of the surface of a 100 nm-thick silver sputtered film. In the deposited film, the silver grain boundaries are visible (see FIG. 1A), whereas in the sputtered film, the silver grain boundaries are not visible (see FIG. 1B).

  The thickness of the silver layer C is preferably 100 nm to 200 nm from the viewpoint of reflectance. When the thickness of the silver layer is 100 nm or more, a decrease in reflectance due to an increase in the ratio of transmitted light can be suppressed. The increase in manufacturing cost can be suppressed as the thickness of the silver layer C is 200 nm or less. The thickness of the silver layer C is more preferably 80 to 150 nm, and further preferably 90 to 150 nm.

1-4. Organic coating layer D
The organic coating layer D is provided adjacent to the silver layer C and has a function of suppressing migration of silver atoms constituting the silver layer C by sandwiching the silver layer C together with the organic coating layer B. The organic coating layer D further has a function of adjusting the chromaticity of the reflected light by increasing the reflectance of light in the low wavelength region (wavelength near 550 nm) of the silver layer C by combining with the protective layer E described later. It is preferable. That is, it is preferable that the organic coating layer D functions as a “low refractive index layer” and the protective layer E functions as a “high refractive index layer”.

  The organic coating layer D contains a resin as a main component. “Containing a resin as a main component” means that the resin content is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more based on the total mass of the organic coating layer D. As the resin contained in the organic coating layer D, the same resin as that contained in the organic coating layer B can be used.

  Especially, it is preferable that the organic coating layer D contains an acrylic resin or its hardened | cured material similarly to the organic coating layer B, and from an adhesive viewpoint with the silver layer C, acrylic resin and a heterocyclic compound (for example, It is more preferable to include a cured product of a mixture of melamine resin) or a heterocyclic compound of acrylic resin (for example, melamine resin). As the acrylic resin or its cured product contained in the organic coating layer D, the same acrylic resin or its cured product contained in the organic coating layer B can be used.

  As with the organic coating layer B, the organic coating layer D preferably further contains a thiol compound. The thiol compound is preferably a thiol group-containing nitrogen-containing aromatic heterocycle from the viewpoint of easily suppressing migration of silver atoms constituting the (111) plane of the silver layer C. As the thiol compound and thiol group-containing nitrogen-containing aromatic heterocycle contained in the organic coating layer D, the same thiol compound and thiol group-containing nitrogen-containing aromatic heterocycle as those contained in the organic coating layer B may be used. it can.

  The thiol compound or thiol group-containing nitrogen-containing aromatic heterocycle contained in the organic coating layer D may be the same as or different from the thiol compound or thiol group-containing nitrogen-containing aromatic heterocycle contained in the organic coating layer B. It may be. Since the organic coating layer D affects optical characteristics, the thiol compound and the thiol group-containing nitrogen-containing aromatic heterocycle included in the organic coating layer D may be a compound having a low light absorptance at a wavelength of 550 nm. preferable. This is because when the light absorptivity of the thiol compound or the thiol group-containing nitrogen-containing aromatic heterocycle has a low light absorptivity of 550 nm, a decrease in reflectance can be suppressed.

  The content of the thiol compound contained in the organic coating layer D is preferably 0.1 to 30% by mass with respect to the total mass of the organic coating layer D. When the content of the thiol compound is 0.1% by mass or more, the silver atoms constituting the silver layer C can be sufficiently interacted with each other, so that migration of silver atoms can be sufficiently suppressed. When the content of the thiol compound is 30% by mass or less, the reflection performance is hardly impaired. The content of the thiol compound is more preferably 1 to 10% by mass with respect to the total mass of the organic coating layer D.

  The organic coating layer D may further contain other components as necessary. Examples of other components include low refractive index particles. The low refractive index particles are preferably inorganic particles having a refractive index of light having a wavelength of 550 nm of 1.5 or less, and examples thereof include silica particles. By further including such low refractive index particles, the refractive index difference between the organic coating layer D and the protective layer E can be easily adjusted.

  The content of the low refractive index particles may be 1 to 40% by mass with respect to the total mass of the organic coating layer D, for example.

The refractive index n _L of light with a wavelength of 550 nm of the organic coating layer D is not particularly limited, but by combining with the protective layer E described later, the reflectance of light in the low wavelength region of the silver layer C (wavelength near 550 nm) is increased. In order to adjust the chromaticity of the reflected light, the refractive index of the light having a wavelength of 550 nm of the protective layer E is preferably lower. That is, the refractive index n _L of light having a wavelength of 550 nm of the organic coating layer D is set in consideration of the refractive index difference from the protective layer E, and is preferably 1.4 to 1.6, for example, 1.3 More preferably, it is -1.5. The refractive index of light having a wavelength of 550 nm of the organic coating layer D may be lower than the refractive index of light having a wavelength of 550 nm of the base material layer A.

The refractive index n _L of the organic coating layer D is adjusted by the type and combination of materials constituting the organic coating layer D and the density of the organic coating layer D. When the organic coating layer D includes, for example, a cured product of an acrylic resin melamine resin, the refractive index can be adjusted by the ratio of the acrylic resin to the melamine resin.

The refractive index n _L of the organic coating layer D can be measured by the following method. That is, an organic coating layer D having a thickness of 100 nm is applied and formed on a polyethylene terephthalate substrate to obtain a measurement sample. The refractive index of light having a wavelength of 550 nm of the obtained measurement sample is measured using a spectroscopic ellipsometer UVISEL manufactured by Horiba.

  The thickness of the organic coating layer D depends on the wavelength range of light to be increased in reflection, but is preferably 40 nm or more and 80 nm or less, and preferably 40 nm or more and 70 nm or less in terms of enhancing the effect of increasing the reflection of light in the vicinity of a wavelength of 550 nm. More preferred. The thickness of the organic coating layer D can be measured using a spectroscopic ellipsometer UVISEL manufactured by Horiba.

1-5. Protective layer E
The protective layer E can function as a barrier layer that suppresses the permeation of moisture into the silver layer C. That is, the protective layer E preferably has a water vapor transmission rate lower than that of the organic coating layer D.

The water vapor permeability at 40 ° C. and 90% RH of the protective layer E is preferably 20 / m ² · day or less, and more preferably 10 g / m ² · day or less. This is because moisture permeation into the silver layer C can be sufficiently reduced.

The water vapor transmission rate of the protective layer E can be measured by the following method.
1) The water vapor transmission rate of the light reflection film is measured under an environment of a temperature of 40 ° C. and a humidity of 90% RH by using PERMATRAN-W 3/32 manufactured by MOCON.
2) Next, after the light reflecting film is immersed in a solvent that dissolves the protective layer E to remove the protective layer E, the water vapor permeability of the resulting film is measured by the same method as described above.
3) The water vapor transmission rate of the protective layer E is obtained by subtracting the water vapor transmission rate of the above 1) from the water vapor transmission rate of 2).

  Furthermore, the protective layer E further has a function of adjusting the chromaticity of the reflected light by increasing the reflectance of light in the low wavelength region (wavelength near 550 nm) of the silver layer C by combining with the organic coating layer D in particular. It is preferable. That is, it is preferable that the protective layer E has a higher refractive index of light having a wavelength of 550 nm than the organic coating layer D.

  The protective layer E may be a resin layer containing high refractive index particles and a resin.

  The high refractive index particles constituting the protective layer E are preferably particles having a refractive index of light having a wavelength of 550 nm of 2.0 or more, and examples thereof include titanium oxide, zirconium oxide, zinc oxide, niobium oxide, Metal oxide particles such as indium tin oxide (ITO) and copper oxide; metal sulfide particles such as zinc sulfide and manganese sulfide; metal particles such as zinc, chromium and tungsten are included. Among these, particles of zirconium oxide, niobium oxide, or zinc sulfide are more preferable, and particles of zirconium oxide are more preferable from the viewpoint that the photocatalytic action is small and discoloration is easily suppressed when light is irradiated for a long time.

  The average particle diameter of the high refractive index particles can be, for example, 5 to 30 nm.

  The average particle diameter of the high refractive index particles can be measured by the following procedure. First, the light reflecting film is dissolved in an organic solvent that dissolves the resin component, and the high refractive index particles are separated and recovered from the protective layer E. The average particle diameter of the separated high-refractive index particles is measured by SEM. SEM observation is carried out with s-4800 manufactured by Hitachi High-Technology Co., Ltd. at a magnification of 500,000; an average value of 20 particle sizes is obtained from the obtained image data, and is taken as the average particle size.

  The content of the high refractive index particles is preferably set so that the refractive index of the protective layer E falls within a predetermined range, for example, 1 to 40% by volume, preferably 10 to 10% by volume with respect to the total volume of the protective layer E. It may be 30% by volume.

  The resin constituting the protective layer E has good dispersibility of the high refractive index particles and achieves a refractive index suitable for the protective layer E when mixed with the high refractive index particles to form the protective layer E. Any resin may be used. Examples of such resins include: polyester resins such as polyethylene terephthalate (PET), polyethylene terephthalate copolymer (coPET), terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer (PETG); acrylic resins; melamine Heterocyclic compounds such as resins; polyvinyl alcohol resins, gelatin, celluloses, thickening polysaccharides and the like. As the acrylic resin, the same acrylic resin used in the organic coating layer B or the organic coating layer D can be used. Among these resins, a curable resin (for example, an acrylic resin having a functional group used in the organic coating layer B or the organic coating layer D) may be a cured product. That is, the resin layer may contain a cured product of a curable resin.

  Since the protective layer E is provided on the outermost surface of the light reflecting film, the resin constituting the protective layer E is preferably a cured product of a curable resin from the viewpoint of enhancing scratch resistance.

  The resin content can be 60 to 99% by volume, preferably 70 to 90% by volume, based on the total volume of the protective layer E.

The refractive index n _H of light having a wavelength of 550 nm of the protective layer E is set in consideration of the refractive index difference with the organic coating layer D, and is preferably 1.7 to 2.4, for example, 1.75 to 2 .3 is more preferable. The refractive index of the protective layer E is adjusted by the type and combination of materials constituting the protective layer E, the density of the protective layer E, and the like.

  The difference in the refractive index of light having a wavelength of 550 nm between the protective layer E and the organic coating layer D is preferably 0.35 or more and preferably 0.4 or more from the viewpoint of sufficiently adjusting the chromaticity. Is more preferable.

The refractive index n _H of the protective layer E can be measured in the same manner as described above except that a high refractive index layer E having a thickness of 100 nm is formed on a polyethylene terephthalate substrate to obtain a measurement sample.

The thickness _{d H} of the protective layer E, depending on the wavelength range of light to be enhanced reflection in terms of enhancing the increased reflection effect of light near a wavelength of 550nm is preferably 30nm or more 80nm or less, 40nm or more 70nm or less Is more preferable. The thickness of the protective layer E can be measured using a spectroscopic ellipsometer UVISEL manufactured by Horiba.

1-6. Laminated structure Each of the organic coating layer D and the protective layer E contained in the light reflecting film of the present invention may be one or plural. The plurality of organic coating layers D may be the same as or different from each other. The plurality of protective layers E may be the same as or different from each other. From the silver layer C side, the organic coating layer D and the protective layer E may be laminated in total in this order by 2 m layers (m is an integer of 1 or more, for example, 1 to 5, preferably 1 or 2).

Examples of the laminated structure of the light reflecting film of the present invention include the following aspects. In the following embodiments, A is a base material layer A, B is an organic coating layer, C is a silver layer, D is an organic coating layer, and E is a protective layer. In the following embodiments, the right side corresponds to the light incident side.
A / B / C / D
A / B / C / D / E
A / B / C / D / E / D / E

  FIG. 2 is a schematic view showing an example of the light reflecting film of the present invention. The light reflecting film 10 includes a base material layer A11, an organic coating layer B13, a silver layer C15, an organic coating layer D17, and a protective layer E19 in this order. The light incident surface of the light reflecting film 10 is the surface of the protective layer E19.

2. Method for Producing Light Reflecting Film The light reflecting film of the present invention may be produced by any method, for example, on the base material layer A, the organic coating layer B, the silver layer C, the organic coating layer D, and as necessary. The protective layer E can be manufactured by laminating in this order.

(Formation of silver layer C)
The silver layer C can be formed by a vacuum film forming method. Examples of the vacuum film forming method include a vacuum vapor deposition method (resistance heating type, electron beam heating type), an ion plating method, an ion beam assisted vacuum vapor deposition method, and a sputtering method. Among these, the vacuum evaporation method or the sputtering method is preferable, and the vacuum evaporation method is more preferable from the viewpoint that the film formation rate can be easily adjusted without reducing the production efficiency.

  As described above, in order to obtain the silver layer C having a high ratio of the (111) plane, it is preferable to reduce the film formation rate when forming the silver layer C. In the vacuum deposition method, the deposition rate can be adjusted by the deposition temperature (heating temperature of the crucible containing the raw material), the gas supply flow rate into the chamber, the composition of the gas, or the degree of vacuum in the chamber. If the deposition temperature is lowered, the deposition rate is reduced. However, this alone cannot cope with film formation on the base material layer A that is conveyed at high speed, and the production efficiency is low. In order to reduce the deposition rate without reducing the productivity, the vapor deposition temperature is set high, and the gas is supplied at a constant flow rate so that the pressure in the chamber is maintained within a predetermined range. preferable. In addition, it is preferable that the gas supplied into the chamber increases the proportion of gas components that tend to decrease the film formation rate.

That is, the vapor deposition temperature (heating temperature of the crucible containing the raw material) is preferably 900 ° C. or higher, and more preferably 1000 ° C. or higher. The gas supply flow rate into the chamber is preferably 200 cc / min or more and 300 cc / min with the pressure in the chamber maintained within a predetermined range (preferably in the vicinity of 4 × 10 ⁻² Pascal). More preferably. As for the composition of the gas supplied into the chamber, for example, in the case of a mixed gas of xenon gas and argon gas, it is preferable to increase the ratio of xenon gas.

  The gas supplied into the chamber is preferably a rare gas, and may be argon gas, xenon gas, or nitrogen gas.

(Formation of organic coating layer B and organic coating layer D)
The organic coating layer B and the organic coating layer D can be formed by applying a resin composition and then drying or curing. Curing when forming the organic coating layer B and the organic coating layer D may be thermal curing or photocuring, but is preferably thermal curing.

  The application of the resin composition can be performed by, for example, a gravure coating method, a spin coating method, a bar coating method, or the like.

  The thermosetting resin composition for forming the organic coating layer B and the organic coating layer D includes an acrylic resin having a functional group and a solvent, and further includes a curing agent (thermosetting agent) as necessary. May be included.

  Any solvent may be used as long as it can disperse the above-mentioned resin satisfactorily. For example, an aprotic solvent is preferable. Examples of aprotic solvents include hydrocarbon solvents such as pentane, hexane, cyclohexane and toluene; halogen hydrocarbon solvents such as methylene chloride and trichloroethane; esters such as ethyl acetate and butyl acetate; ketones such as acetone and methyl ethyl ketone And ethers such as dibutyl ether, dioxane, and tetrahydrofuran are included.

  Examples of the curing agent include melamine resin, polyisocyanate, epoxy compound and the like. Content of a hardening | curing agent can be about 0.1-15 mass% with respect to the above-mentioned curable resin.

(Formation of protective layer E)
The protective layer E may be formed by applying a resin composition containing high refractive index particles and a resin, followed by drying or curing. The curing for forming the protective layer E may be thermal curing or photocuring, but is preferably photocuring from the viewpoint of enhancing scratch resistance.

  The photocurable resin composition for forming the protective layer E contains a photocurable monomer or oligomer having an ethylenic double bond, and a photopolymerization initiator, and may further contain a solvent as necessary.

  Examples of photocurable monomers having an ethylenically unsaturated double bond include (meth) acrylic acid ester monomers or oligomers, specifically (meth) acrylic acid alkyl esters such as methyl (meth) acrylate. Is included.

  Examples of the photo radical polymerization initiator include benzoin, acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone, α-amyloxime ester, and thioxanthone photo radical polymerization initiators. The content of the radical photopolymerization initiator may be about 0.1 to 15% by mass, preferably 1 to 10% by mass with respect to the total mass of the photocurable resin composition. A radical photopolymerization initiator may be used together with a photosensitizer as necessary.

The light source used for light irradiation is not particularly limited, and a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, or the like can be used.
Although the light irradiation intensity depends on the composition of the resin composition, it is preferable that the irradiation intensity in the wavelength region effective for activating the radical photopolymerization initiator is 0.1 to 1000 mW / cm ² .
The light irradiation time may be sufficient as long as the resin composition is cured. For example, the integrated light amount expressed as the product of the irradiation intensity and the irradiation time may be set to 10 to 5000 mJ / cm ^2. .

3. Use of Light Reflecting Film The light reflecting film of the present invention can be used as a reflecting member for various uses, for example, a light reflecting film of a backlight unit for a liquid crystal display device, a reflecting mirror of a projection television, a lamp reflector and the like. Among them, the light reflecting film of the present invention can suppress discoloration when irradiated with light for a long time, so that the light reflecting film of a backlight unit for a liquid crystal display device, particularly a liquid crystal display using a light emitting diode element (LED) as a light source. It is preferably used as a light reflecting film of a backlight unit for an apparatus.

(Backlight unit for liquid crystal display)
The backlight unit for liquid crystal display devices includes a light source and the light reflecting film of the present invention. The light reflecting film of the present invention is disposed such that the outermost layer (organic coating layer D or protective layer E) faces the back surface (the surface not facing the liquid crystal display panel) of the light source or the light guide plate.

  Examples of the light source include a cold cathode tube (CCFL), a hot cathode tube (HCFL), an external electrode fluorescent tube (EEFL), a flat fluorescent tube (FFL), a light emitting diode element (LED), and an organic electroluminescence element (OLED). Etc. are included. Especially, a cold cathode tube (CCFL) and a light emitting diode element (LED) are preferable, and a light emitting diode element (LED) is more preferable.

  The backlight unit for a liquid crystal display device may further include another optical film. Examples of other optical films include light diffusion films and prism films. Examples of the light diffusion film include a diffusion film coated with a filler or a bead-containing binder.

  The backlight unit for a liquid crystal display device may be a direct type backlight unit or a side edge type backlight unit. A side-edge type backlight unit is preferable because it is suitable for a medium / small-sized liquid crystal display device.

  The side-edge type backlight unit includes a light source, a light guide plate disposed adjacent to the light source, and a light reflection film disposed on the back side of the light guide plate, and further includes other optical films as necessary. But you can. An example of the side edge type backlight unit includes a backlight unit 40 shown in FIG. 3 to be described later.

(Liquid crystal display device)
The liquid crystal display device of the present invention includes a liquid crystal display panel and a backlight unit. FIG. 3 is a cross-sectional view showing an example of the liquid crystal display device of the present invention. The figure shows an example in which a side edge type backlight unit is used. As shown in FIG. 3, the liquid crystal display device 20 includes a liquid crystal display panel 30 and a side edge type backlight unit 40.

  The liquid crystal display panel 30 includes a liquid crystal cell 31 and a pair of polarizing plates 33 and 35 sandwiching the liquid crystal cell 31. The display method of the liquid crystal cell 31 is not particularly limited, and may be various display modes such as VA (MVA, PVA) and IPS. Each of the polarizing plates 33 and 35 includes a polarizer and a protective film disposed on at least one surface thereof.

  The side-edge type backlight unit 40 includes a rod-shaped light source 41, a light guide plate 43 disposed so that the side end portion is adjacent to the light source 41, and the light reflecting film 10 disposed on the back side of the light guide plate 43. And a plurality of optical films 45 disposed on the surface side of the light guide plate 43.

  The light source 41 is covered with a lamp reflector 42. The plurality of optical films 45 are not limited to the embodiment of FIG. 3, and the optical film 45 may not be provided, and the combination and number of optical films may be changed.

  In the side edge type backlight unit 40, the light emitted from the light source 41 propagates through the light guide plate 43. A part of the light emitted from the light guide plate 43 is reflected by the light reflecting film 10 and emitted to the surface side of the light guide plate 43 (the liquid crystal display panel 30 side). The light emitted to the surface side of the light guide plate 43 is diffused by the light diffusion film 47, refracted by the prism film 49, and incident on the entire surface of the liquid crystal display panel 30.

  For example, the light reflecting film 10 can suppress discoloration when the light from the LED is irradiated for a long time. Therefore, even when the liquid crystal display device 20 using a light emitting diode element (LED) as a light source is used for a long time, good light use efficiency can be maintained.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

1. Preparation of material of light reflecting film (1) Solution for organic coating layer B (anchor layer) / solution for organic coating layer D (low refractive index layer) As a solution for organic coating layer B or organic coating layer D, the following solution 1- 1-1-6 were prepared.

(Preparation of Solution 1-1)
Acrylic resin (Dianar BR-608 manufactured by Mitsubishi Rayon Co., Ltd.) and melamine resin (MX-730 manufactured by Sanwa Chemical Co., Ltd.) are mixed at a mass ratio of 1: 1, and these resins are mixed. Solution 1-1 was obtained such that the total of the components was 1% by mass with respect to methyl ethyl ketone.

(Preparation of solution 1-2)
Solution 1-2 was obtained in the same manner as Solution 1-1, except that melamine resin (MX-730 manufactured by Sanwa Chemical Co., Ltd.) was not added.

(Preparation of Solution 1-3)
As a thiol compound, trimethylolpropane tristhiopropionate (TMTP) was added except that acrylic resin (Dynar BR-608 manufactured by Mitsubishi Rayon Co., Ltd.): TMTP = 95: 5 was used. Gave Solution 1-3 in the same manner as Solution 1-2.

(Preparation of solution 1-4)
As a thiol compound, 1-methyl-5-mercapto-1H-tetrazole (MMT) is used so that the mass ratio of acrylic resin (Dynar BR-608 manufactured by Mitsubishi Rayon Co., Ltd.): MMT = 95: 5. A solution 1-4 was obtained in the same manner as the solution 1-2 except that it was added.

(Preparation of Solution 1-5)
As a thiol compound, 1- (2-dimethylaminoethyl) -5-mercapto-1H-tetrazole (DMT) is an acrylic resin (Dynar BR-608 manufactured by Mitsubishi Rayon Co., Ltd.): DMT = 95: 5. Solution 1-5 was obtained in the same manner as Solution 1-2, except that it was added so as to have a mass ratio.

(Preparation of Solution 1-6)
Solution 1-6 was obtained in the same manner as Solution 1-1, except that silica particles (average particle size 5 nm) were added so as to be 10% by mass with respect to the total solid content.

  Table 1 shows the compositions of the solutions 1-1 to 1-6.

(2) Solution for protective layer E (high refractive index layer) As solutions for protective layer E, the following solutions 2-1 to 2-2 were prepared.
Solution 2-1
Zirconium oxide particle-containing resin solution (manufactured by Toyochem Co., Ltd., dispersion TYZ76 containing UV curable acrylic resin and zirconium oxide particles having an average particle diameter of 6 nm)
Solution 2-2:
Titanium oxide particles (TiO ₂ particles) -containing resin solution (manufactured by Toyochem Co., Ltd., dispersion TYT90 containing UV curable acrylic resin and titanium oxide particles having an average particle diameter of 6 nm)

(3) Physical properties of each layer (3-1) Measurement of refractive index of organic coating layer D and protective layer E One of solutions 1-1 to 1-6 is applied on a polyethylene terephthalate film (PET film) having a thickness of 100 μm. After that, the sample for measurement having an organic coating layer D (low refractive index layer) having a thickness of 50 nm was obtained by drying and thermosetting under the same conditions as in Example 1 described later.
Similarly, after coating the solution 2-1 or 2-2 on a PET film having a thickness of 100 μm, drying and photocuring were performed under the same conditions as in Example 2 described later, and a protective layer E having a thickness of 50 nm (high refractive index) A sample for measurement having a rate layer) was obtained. After applying the solution 2-3 on a PET film having a thickness of 100 μm, it was dried under the same conditions as in Example 10 described later. A measurement sample having a protective layer E (high refractive index layer) having a thickness of 50 nm was obtained.
The refractive indexes of light having a wavelength of 550 nm of these samples were measured using a Horiba spectroscopic ellipsometer UVISEL. These results are shown in Table 3 below.

(3-2) X-ray diffraction measurement of silver layer C (3-2-1) Silver layer C formed under film formation conditions 1 to 4 On a PET film having a thickness of 100 μm, the same as in Example 1 described later After forming the organic coating layer B under the conditions, a silver layer C was further formed under the following film formation conditions to obtain a measurement sample having a laminated structure of PET film / organic coating layer B / silver layer C.
Film formation condition 1 (invention): vacuum deposition method, deposition temperature (heating temperature of crucible): 900 ° C., pressure in chamber: 4 × 10 ⁻² Pascal, gas supply flow rate into chamber: 380 cc / min, Gas composition: Argon gas / xenon gas = 3/7 (volume ratio)
Film formation condition 2 (invention): Same as film formation condition 1 except that the gas composition was changed to argon gas / xenon gas = 7/3 (volume ratio) Film formation condition 3 (invention): sputtering method, chamber Inside pressure: 4 × 10 ⁻² Pascal, Gas supply flow rate: 500 cc / min, Gas composition: Argon gas Film formation condition 4 (for comparison): Same as film formation condition 1 except that no gas was supplied

  Next, with respect to the silver layer C of the obtained sample, using an X-ray diffraction (XRD) analyzer (“RINT-TTRII” manufactured by Rigaku Corporation), the tube Cu, tube voltage 30 kV, tube current 30 mA, sampling width 0. Under the condition of 020 °, X-ray diffraction measurement was performed using a monochromator and a glass sample holder to obtain an X-ray diffraction spectrum.

  FIG. 4 is a diagram illustrating an example of an X-ray diffraction spectrum under film forming conditions 1 to 4. In FIG. 4, the horizontal axis represents 2θ (°), and the vertical axis represents peak intensity (−) (= photon number (counts)).

  As shown in FIG. 4, in the X-ray diffraction spectrum, peaks corresponding to the (111) plane, (200) plane, (220) plane, (311) plane, and (222) plane of silver are detected, respectively. I understand.

Furthermore, the integrated intensity of the peak corresponding to each surface was determined from the obtained line diffraction spectrum. The integrated intensity of each peak obtained was applied to the following formula (1) to determine the ratio of the (111) plane. Since the (222) plane is parallel to the (111) plane, it was not taken into account in calculating the ratio of the (111) plane.
(111) surface ratio (%) = I (111) / [I (111) + I (200) + I (220) + I (311)] × 100 (1)

Table 2 shows the calculation results of the integrated intensity of the peak and the ratio of the (111) plane.

  As shown in Table 2, the silver layer obtained under the film formation conditions 1 to 3 with a low film formation rate has a high ratio of the (111) plane, whereas it is obtained under the film formation condition 4 with a high film formation speed. It can be seen that the obtained silver layer has a low ratio of the (111) plane.

(3-2-2) Film-forming conditions About silver layer C formed into a film by Ag-1 to Ag-3 On the 100-micrometer-thick PET film, the organic coating layer B was formed on the conditions similar to Example 1 mentioned later. Thereafter, a silver layer C was further formed under the same conditions as in the corresponding examples or comparative examples, and a measurement sample having a laminated structure of PET film / organic coating layer B / silver layer C was obtained.
About the silver layer C of the obtained sample, the X-ray-diffraction measurement was performed on the conditions similar to above-mentioned (3-2-1), and the X-ray-diffraction spectrum was obtained. From the obtained X-ray diffraction spectrum, the integration of peaks corresponding to the (111) plane, (200) plane, (220) plane and (311) plane of silver was performed in the same manner as (3-2-1) described above. The strengths were determined, and the results were applied to the above formula (1) to calculate the ratio of the (111) plane. These results are shown in Table 3 below.

(3-3) Measurement of water vapor transmission rate of protective layer E A protective layer E was formed on a polyester film (T60, Toray, thickness 25 μm) under the same conditions as in the corresponding Example / Comparative Example. Got. On the other hand, the polyester film in which the protective layer E was not formed was used as a blank measurement sample.
The water vapor transmission rates of the obtained measurement sample and blank measurement sample were measured under an environment of a temperature of 40 ° C. and a humidity of 90% RH, respectively, using PERMATRAN-W 3/32 manufactured by MOCON. Then, the water vapor transmission rate of the protective layer E was determined by subtracting the water vapor transmission rate of the blank measurement sample from the water vapor transmission rate of the measurement sample. These results are shown in Table 3 below.
In addition, when the water vapor transmission rate under 40 degreeC90% RH of the organic coating layer B of Example 1 mentioned later was measured, the water vapor transmission rate under 40 degreeC90% RH of the protective layer E of Example 1 mentioned later Confirmed to be lower than.

2. Production and Evaluation of Light Reflecting Film <Example 1>
After applying the solution 1-1 on a polyethylene terephthalate film (HB3 manufactured by Teijin DuPont Co., Ltd.) as the base material layer A, it was dried and cured at 150 ° C. for 1 minute, and an organic coating layer B (100 nm thick) Anchor layer) was formed.
On this organic coating layer B, silver was deposited under the following conditions to form a silver layer C having a thickness of 100 nm. The film formation conditions for the silver layer C were vacuum deposition with an evaporation temperature (crucible heating temperature) of 900 ° C., an argon gas supply flow rate of 380 cc / min, and a pressure in the chamber of 4 × 10 ⁻² Pascal. (Deposition condition Ag-3).
Next, the solution 1-1 is applied on the silver layer C, dried and cured at 150 ° C. for 1 minute to form an organic coating layer D (low refractive index layer) having a thickness of 50 nm, and the light reflecting film 1 Got.

<Example 2>
The solution 2-1 was applied on the organic coating layer D and dried at 110 ° C. for 1 minute to form a coating film. Thereafter, the obtained coating film was irradiated with UV having an illuminance of 400 mW / cm ² and an integrated light amount of 1100 mJ / cm ² by a UV irradiation device Light Hammer 10 manufactured by Heraeus Co., Ltd., and photocured to form a protective layer having a thickness of 50 nm. A light reflecting film 2 was obtained in the same manner as in Example 1 except that E (high refractive index layer) was further formed.

<Examples 3 to 6>
Light reflecting films 3 to 6 were obtained in the same manner as in Example 2 except that the materials of the organic coating layer B (anchor layer) and the organic coating layer D (low refractive index layer) were changed to those shown in Table 3. .

<Example 7>
Except for changing the film formation method and film formation conditions of the silver layer C to the sputtering method and conditions (film formation conditions Ag-1) disclosed in Example 1 of JP-A-2007-58194, the same as in Example 2. Thus, a light reflecting film 7 was obtained.

<Example 8>
A light reflecting film 8 was obtained in the same manner as in Example 2 except that the material of the protective layer E was changed to that shown in Table 3.

<Comparative Example 1>
A light reflecting film 11 was obtained in the same manner as in Example 1 except that the organic coating layers B and D were not formed and the film formation conditions of the silver layer C were changed as follows. The film formation conditions for the silver layer C were vacuum deposition with an evaporation temperature (heating temperature of the crucible) of 900 ° C., an argon gas supply flow rate of 0 cc / min, and a pressure of 4 × 10 ⁻² Pascal in the chamber. (Deposition condition Ag-2).

<Comparative example 2>
A light reflecting film 12 was obtained in the same manner as in Example 1 except that the organic coating layers B and D were not formed.

<Comparative Example 3>
A light reflecting film 13 was obtained in the same manner as in Example 1 except that the film formation conditions of the silver layer C were changed as follows. Film formation conditions for the silver layer C were performed by a vacuum deposition method in which the deposition temperature was 900 ° C., the supply flow rate of argon gas into the chamber was 0 cc / min, and the pressure in the chamber was 4 × 10 ⁻² Pascal ( Film formation conditions Ag-2).

<Comparative Example 4>
A light reflecting film 14 was obtained in the same manner as in Example 1 except that the organic coating layer B was not formed.

<Comparative Example 5>
On the polyethylene terephthalate film (HB3 manufactured by Teijin DuPont Co., Ltd.) as the base material layer A, silver was used in the sputtering method and conditions disclosed in Example 1 of JP-A-2007-58194 (film formation conditions Ag-1). Was sputtered to form a 100 nm thick silver layer.
On this silver layer, silicon nitride was further sputtered by the sputtering method and conditions disclosed in Example 1 to form a silicon nitride film having a thickness of 8 nm, whereby a light reflecting film 15 was obtained.

  About the light reflection film obtained in Examples 1-8 and Comparative Examples 1-5, (1) UV-LED irradiation test (appearance change, amount of change in reflectance), (2) color of reflected light on display device Degree, (3) interlayer adhesion, and (4) productivity were evaluated by the following methods, respectively.

(1) UV-LED irradiation test The obtained light reflection film was placed on a hot plate set at 160 ° C., and an LED having a center wavelength of 405 nm manufactured by Nichia Corporation was used at 176 mW / cm ² . Irradiation with light for 3 hours was performed.

(Appearance after irradiation test)
The appearance of the light reflecting film after the UV-LED irradiation test was visually observed and evaluated based on the following criteria.
5: There is no discoloration and cannot be distinguished from the light reflecting film before irradiation.
4: The color immediately below the LED light source is discolored but not black, and the surrounding area is not discolored.
3: Although the color immediately below and around the LED light source is discolored, neither is black.
2: The area immediately below the LED light source is black, and the surrounding area is discolored but not black.
1: Directly under and around the LED light source is black.
In the present invention, a film having an evaluation result of 3 or more in the above test is a film that can withstand practical use.

(Change in total light reflectance)
Before and after the start of the UV-LED irradiation test, the total light reflectance of the light reflecting film was measured using a spectrophotometer U-4100 manufactured by Hitachi High-Technologies Corporation under the conditions of a wavelength of 360 to 830 nm and an incident angle of 5 °. It was measured. The amount of change (%) in the total light reflectance after the test relative to the total light reflectance before the test was calculated based on the following formula.
Change amount of total light reflectivity (%) = [(total light reflectivity after test) − (total light reflectivity before test)] / (total light reflectivity before test) × 100

(2) Chromaticity The backlight unit was taken out from the liquid crystal display device (trade name: LC-37GX1W, manufactured by Sharp), and the light reflecting film of the backlight unit was replaced with the light reflecting film produced above. The light reflecting film was disposed so that the organic coating layer D or the protective layer E was a light incident surface.
A luminance meter (product name “CS-2000” manufactured by Konica Minolta Co., Ltd.) is located on the side opposite to the surface on which the light reflecting film of the obtained backlight unit is disposed and at a height of 200 mm from the light reflecting film. ) Was installed. Then, the chromaticity was measured at intervals of 0.6 mm from end to end while traversing the central portion of the surface light source device in the vertical direction of the light sources arranged in parallel. The measurement was performed at 25 ° C.
As the chromaticity reference, ESR65 (manufactured by 3M Company) was used, and differences Δx and Δy from the reference chromaticity when the reference chromaticity was set to 0 were calculated.

(3) Interlayer adhesion The above-prepared light reflecting film was stored at 60 ° C. and 90% RH for 500 hours. Then, the adhesiveness of the interface of silver layer C / organic coating layer D was evaluated by the cross-cut test based on JISK5600-5-6: 1999.
Specifically, the surface of the light reflecting film (the surface side on which the silver layer C was formed) was cut into 11 cuts vertically and horizontally at intervals of 1 mm to produce 100 1 mm square grids. Cellophane tape (registered trademark) was affixed thereon and quickly peeled off at an angle of 90 degrees. And the number of grids remaining without peeling was counted. The measurement was performed at 25 ° C.

(4) Productivity The time required from the start of film formation of the silver layer C to the end of film formation (however, excluding the preparation time until the start of film formation) was measured and evaluated according to the following criteria.
5: 1 to 3 hours 4: 3 to 6 hours 3: 6 to 9 hours 2: 9 to 12 hours 1:12 hours

  The structures of the light reflecting films of Examples 1 to 8 and Comparative Examples 1 to 5 are shown in Table 3, and the evaluation results are shown in Table 4.

  The light reflecting films of Examples 1 to 8 in which the ratio of the (111) plane of the silver layer C is 80% or more and the silver layer C is sandwiched between the organic coating layer B and the organic coating layer D are UV-LEDs. It can be seen that there is little change in appearance after the irradiation test, and the amount of change in reflectance is also small.

  In particular, when the ratio of the (111) plane of the silver layer C is less than 95%, a light reflecting film can be produced in a short time, so that productivity is high and interlayer adhesion is hardly impaired (Example 1). And 7).

  Furthermore, the organic coating layer D further contains a thiol compound; in particular, by including a nitrogen-containing heterocyclic compound having a thiol group, there is little change in appearance and reflectance after UV-LED irradiation test, and interlayer adhesion It turns out that property is also favorable (contrast with Example 3 and Examples 4-6).

  Furthermore, it can be seen that by further including the protective layer E, the amount of change in appearance and reflectance after the UV-LED irradiation test is small, and the chromaticity is also improved (contrast with Examples 1 and 2).

  Furthermore, when the protective layer E is a resin layer containing zirconium oxide particles, the appearance after the UV-LED irradiation test is less and the change in reflectance is less than that of a resin layer containing titanium oxide particles. It can be seen (contrast between Example 2 and Example 8).

On the other hand, the ratio of the (111) plane of the silver layer C is less than 80%, and the light reflection film of Comparative Example 1 having no organic coating layers B and D has a change in appearance after the UV-LED irradiation test. It can be seen that the amount of change in reflectance is large.
Moreover, even if it has both the organic coating layer B and the organic coating layer D, the ratio of the (111) plane of the silver layer C is less than 80%, and the (3) Even if the ratio of the 111) surface is 80% or more, the light reflecting films of Comparative Examples 2, 4 and 5 which do not have at least one of the organic coating layer B and the organic coating layer D are all after the UV-LED irradiation test. It can be seen that there are still many changes in the appearance and reflectance.

  According to the present invention, in a light reflecting film having an organic coating layer adjacent to a silver layer, a light reflecting film in which discoloration when light from an LED is irradiated for a long time is suppressed and a decrease in reflectance is suppressed. Can be provided.

10 Light Reflecting Film 11 Base Material Layer A
13 Organic coating layer B
15 Silver layer C
17 Organic coating layer D
19 Protective layer E
DESCRIPTION OF SYMBOLS 20 Liquid crystal display device 30 Liquid crystal display panel 31 Liquid crystal cell 33, 35 Polarizing plate 40 Side edge type backlight unit 41 Light source 42 Lamp reflector 43 Light guide plate 45 Optical film 47 Light diffusion film 49 Prism film

Claims (11)

Light including a base layer A, an organic coating layer B, a silver layer C provided adjacent to the organic coating layer B, and an organic coating layer D provided adjacent to the silver layer C in this order. A reflective film,
The light reflection film whose ratio of the (111) surface represented by following formula (1) of the said silver layer C is 80% or more.
(111) surface ratio (%) = I (111) / [I (111) + I (200) + I (220) + I (311)] × 100 (1)
(In Formula (1),
I (111): integrated intensity of peak corresponding to silver (111) plane measured by X-ray diffraction method I (200): peak intensity corresponding to silver (200) plane measured by X-ray diffraction method Integral intensity I (220): integrated intensity of peak corresponding to silver (220) plane measured by X-ray diffraction method I (311): corresponding to silver (311) plane measured by X-ray diffraction method Indicates the integrated intensity of the peak)   The light reflecting film according to claim 1, wherein a ratio of the (111) plane is less than 95%.   The said silver layer C is a light reflection film of Claim 1 or 2 which is a vapor deposition film.   The said organic coating layer B and the said organic coating layer D are light reflection films as described in any one of Claims 1-3 which contain acrylic resin or its hardened | cured material as a main component.   The light reflecting film according to claim 4, wherein the organic coating layer B and the organic coating layer D further contain a thiol compound.   The light reflection film according to claim 5, wherein the thiol compound is a nitrogen-containing heterocyclic compound having a thiol group.   The organic coating layer D further includes a protective layer E having a lower water vapor transmission rate at 40 ° C. and 90% RH than the organic coating layer D on the surface opposite to the silver layer C of the organic coating layer D. The light reflecting film according to claim 1.   The light reflection film according to claim 7, wherein a refractive index of the protective layer E at a wavelength of 550 nm is higher than a refractive index of the organic coating layer B at a wavelength of 550 nm.   The said protective layer E is a light reflection film of Claim 7 or 8 which is a layer containing high refractive index particle | grains and the hardened | cured material of curable resin.   The light reflecting film according to claim 9, wherein the high refractive index particles are zirconium oxide particles. The backlight unit for liquid crystal display devices containing a light source and the light reflection film as described in any one of Claims 1-10.