JP2018025740A - Light reflection film and backlight unit for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light reflection film having a high reflectance and high durability against irradiation of light in a dry high-temperature environment.SOLUTION: The light reflection film includes a substrate 11, a silver layer 12, a low refractive index layer group comprising one or more low refractive index layers L, and a high refractive index layer group comprising one or more high refractive index layers H, in this order, in which at least one of the low refractive index layer group and the high refractive index layer group includes an organic layer and an inorganic layer; a low refractive index layer Ladjacent to the silver layer is an organic layer; and at least one low refractive index layer L other than the low refractive index layer Land/or at least one high refractive index layer H is an inorganic layer. The low refractive index layer group satisfies λ/8<Σ(nxd)<λ/8, while the high refractive index layer group satisfies λ/4<Σ(nxd)<λ/4, where nand drepresent the refractive index and the film thickness of the low refractive index layer L, respectively; nand drepresent the refractive index and the film thickness of the high refractive index layer H, respectively; and λand λrepresent the minimum and the maximum in the wavelength region of incident light, respectively.SELECTED DRAWING: Figure 1

Description

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

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

  As such a reflective member, a reflective film including a silver layer is known. On the other hand, the silver layer has a problem that its durability is lower than that of aluminum. In order to overcome this problem, it has been studied to further laminate a layer made of a resin or an inorganic substance on the silver layer (for example, Patent Documents 1 and 2).

  Patent Document 1 describes a reflective sheet in which a low refractive index layer and a high refractive index layer are laminated on a metal layer mainly composed of silver or aluminum. Furthermore, a reflection sheet is also described in which a plurality of low refractive index layers and a plurality of high refractive index layers are alternately laminated one by one. Thereby, it is said that the reflectance of a reflective sheet can be increased and luminance unevenness can be reduced.

  Patent Document 2 describes a reflective sheet in which a base film, a metal deposition layer such as silver, a resin layer, and a metal compound layer are laminated in this order. Thereby, peeling with the base film of a reflective sheet and a metal vapor deposition layer is prevented, and it is supposed that a reflectance can be raised.

JP 2004-145239 A JP 2007-133003 A

  In recent years, a display device using an LED as a light source has been developed. However, since an LED is a directional light source, it is known to partially irradiate strong light. According to the research of the present inventor, it has been found that discoloration occurs in the portion where the strong light is continuously irradiated in the LED illumination reflecting member. In order to examine such discoloration, durability against light irradiation under a dry high temperature was tested. As disclosed in Patent Documents 1 and 2, a single layer of low refractive index was formed on the silver layer. It has been found that in a reflective film in which a layer and one high refractive index layer are laminated in this order, a black color change occurs in the light irradiated portion by continuous light irradiation for a long time. Such discoloration is considered to lead not only to poor appearance but also to a decrease in reflectance. It has also been found that there is a problem in strength such as delamination.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a light reflecting film having high reflectivity and high durability against light irradiation under dry high temperature.

（式（１）において、
ｎ_Ｌｋは、低屈折率層Ｌ_ｋの波長５５０ｎｍにおける屈折率であり、
ｄ_Ｌｋは、低屈折率層Ｌ_ｋの膜厚（ｎｍ）であり、
ｎは、低屈折率層群に含まれる低屈折率層Ｌの数であり、
λ_１は、入射光の波長領域の最小値であり、
λ_２は、入射光の波長領域の最大値である。）

（式（２）において、
ｎ_Ｈｋは、高屈折率層Ｈ_ｋの波長５５０ｎｍにおける屈折率であり、
ｄ_Ｈｋは、高屈折率層Ｈ_ｋの膜厚（ｎｍ）であり、
ｎは、高屈折率層群に含まれる高屈折率層Ｈの数であり、
λ_１は、入射光の波長領域の最小値であり、
λ_２は、入射光の波長領域の最大値である。）
［２］ １層以上の前記低屈折率層Ｌの波長５５０ｎｍにおける屈折率ｎ_Ｌは、それぞれ１．７未満である、［１］に記載の光反射フィルム。
［３］ 前記低屈折率層群が複数の前記低屈折率層Ｌからなる場合、
波長５５０ｎｍにおける屈折率が最も高い低屈折率層Ｌ_ｈｉｇｈと、波長５５０ｎｍにおける屈折率が最も低い低屈折率層Ｌ_ｌｏｗとの間の屈折率差Δｎ_Ｌは０．３以下である、［１］または［２］に記載の光反射フィルム。
［４］ １層以上の前記高屈折率層Ｈの波長５５０ｎｍにおける屈折率ｎ_Ｈは、それぞれ１．７以上である、［１］〜［３］のいずれかに記載の光反射フィルム。
［５］ 前記高屈折率層群が複数の前記高屈折率層Ｈからなる場合、
波長５５０ｎｍにおける屈折率が最も高い高屈折率層Ｈ_ｈｉｇｈと、波長５５０ｎｍにおける屈折率が最も低い高屈折率層Ｈ_ｌｏｗとの間の屈折率差Δｎ_Ｈは０．６以下である、［１］〜［４］のいずれかに記載の光反射フィルム。
［６］ 低屈折率層群に含まれる低屈折率層Ｌの数が１以上３以下であり、且つ高屈折率層群に含まれる高屈折率層Ｈの数が１以上３以下である、［１］〜［５］のいずれかに記載の光反射フィルム。
［７］ 前記低屈折率層群と前記高屈折率層群を合わせた群が複数の前記無機層を含む場合、
複数の無機層は、互いに隣接していない、［１］〜［６］のいずれかに記載の光反射フィルム。
［８］ 前記低屈折率層Ｌ_１は、アクリル系樹脂、アクリル系樹脂と複素環式化合物の混合物またはアクリル系樹脂の複素環式化合物による架橋物を含む、［１］〜［７］のいずれかに記載の光反射フィルム。
［９］ 前記低屈折率層群が、前記低屈折率層Ｌ_１以外の前記有機層からなる低屈折率層Ｌ_ｎをさらに含む場合、
前記有機層である前記低屈折率層Ｌ_ｎは、アクリル系樹脂、アクリル系樹脂と複素環式化合物の混合物またはアクリル系樹脂の複素環式化合物による架橋物を含む、［１］〜［８］のいずれかに記載の光反射フィルム。
［１０］ 前記低屈折率層群が、前記低屈折率層Ｌ_１以外の前記無機層からなる低屈折率層Ｌｎをさらに含む場合、
前記無機層である低屈折率層Ｌ_ｎは、ＳｉＯ_２からなる、［１］〜［９］のいずれかに記載の光反射フィルム。
［１１］ 前記高屈折率層群が、前記有機層からなる高屈折率層Ｈを含む場合、
前記有機層である高屈折率層Ｈは、樹脂と、金属酸化物粒子とを含む、［１］〜［１０］のいずれかに記載の光反射フィルム。
［１２］ 前記高屈折率層群が、前記無機層からなる高屈折率層Ｈを含む場合、
前記無機層である前記高屈折率層Ｈは、Ｎｂ_２Ｏ_５またはＺｎＳからなる、［１］〜［１１］のいずれかに記載の光反射フィルム。
［１３］ 前記銀層上に、前記有機層である低屈折率層Ｌ_１と、前記無機層である高屈折率層Ｈ_１と、前記有機層である高屈折率層Ｈ_２とがこの順に配置されている、［１］〜［１２］のいずれかに記載の光反射フィルム。
［１４］ 前記銀層上に、前記有機層である低屈折率層Ｌ_１と、前記有機層である高屈折率層Ｈ_１と、前記無機層である高屈折率層Ｈ_２とがこの順に配置されている、［１］〜［１２］のいずれかに記載の光反射フィルム。
［１５］ 前記銀層上に、前記有機層である低屈折率層Ｌ_１と、前記無機層である低屈折率層Ｌ_２と、前記有機層である高屈折率層Ｈ_１とがこの順に配置されている、［１］〜［１２］のいずれかに記載の光反射フィルム。
［１６］ 前記銀層上に、前記有機層である低屈折率層Ｌ_１と、前記無機層である低屈折率層Ｌ_２と、前記有機層である低屈折率層Ｌ_３と、前記無機層である高屈折率層Ｈ_１とがこの順に配置されている、［１］〜［１２］のいずれかに記載の光反射フィルム。
［１７］ 前記銀層上に、前記有機層である低屈折率層Ｌ_１と、前記無機層である低屈折率層Ｌ_２と、前記無機層である高屈折率層Ｈ_１とがこの順に配置されている、［１］〜［６］および［８］〜［１２］のいずれかに記載の光反射フィルム。
［１８］ 前記基材層と前記銀層との間に配置されたアンカー層をさらに含む、［１］〜［１７］のいずれかに記載の光反射フィルム。
［１９］ 光源と、［１］〜［１８］のいずれかに記載の光反射フィルムとを含む、液晶表示装置用バックライトユニット。 The above object of the present invention is achieved by the following configurations.
[1] a substrate;
A silver layer disposed on the substrate;
A low refractive index layer group composed of one or more low refractive index layers L disposed on the silver layer;
A light reflecting film including, in this order, a high refractive index layer group composed of one or more high refractive index layers H disposed on the low refractive index layer group,
At least one of the low refractive index layer group and the high refractive index layer group includes an organic layer mainly composed of a resin, and an inorganic layer mainly composed of an inorganic compound,
Low refractive index layer L ₁ adjacent to the silver layer is the organic layer,
At least one other than the low refractive index layer L ₁ of the one or more layers of the low refractive index layer L is at least one of the inorganic layer, and / or one or more layers of the high refractive index layer H is, The inorganic layer,
The low refractive index layer group satisfies the following formula (1),
The high refractive index layer group satisfies the following formula (2) and is a light reflecting film.

(In Formula (1),
n _Lk is the refractive index of the low refractive index layer L _{k at} a wavelength of 550 nm,
d _Lk is the film thickness (nm) of the low refractive index layer L _k ,
n is the number of low refractive index layers L included in the low refractive index layer group,
λ ₁ is the minimum value of the wavelength region of incident light,
λ ₂ is the maximum value in the wavelength region of incident light. )

(In Formula (2),
n _Hk is the refractive index of the high refractive index layer H _{k at} a wavelength of 550 nm,
d _Hk is the film thickness (nm) of the high refractive index layer H _k ,
n is the number of high refractive index layers H included in the high refractive index layer group,
λ ₁ is the minimum value of the wavelength region of incident light,
λ ₂ is the maximum value in the wavelength region of incident light. )
[2] The light reflecting film according to [1], wherein the refractive index n _{L at} a wavelength of 550 nm of the one or more low refractive index layers _L is less than 1.7.
[3] When the low refractive index layer group is composed of a plurality of the low refractive index layers L,
The refractive index difference Δn _L between the low refractive index layer L _high having the highest refractive index at a wavelength of 550 nm and the low refractive index layer L _low having the lowest refractive index at a wavelength of 550 nm is 0.3 or less, [1] Or the light reflection film as described in [2].
[4] the refractive index _{n H} at a wavelength 550nm of one or more layers of the high refractive index layer H is respectively 1.7 or more, [1] the light reflecting film according to any one of - [3].
[5] When the high refractive index layer group includes a plurality of the high refractive index layers H,
The refractive index difference Δn _H between the high refractive index layer H _high having the highest refractive index at a wavelength of 550 nm and the high refractive index layer H _low having the lowest refractive index at a wavelength of 550 nm is 0.6 or less, [1] -The light reflection film in any one of [4].
[6] The number of low refractive index layers L included in the low refractive index layer group is 1 or more and 3 or less, and the number of high refractive index layers H included in the high refractive index layer group is 1 or more and 3 or less. The light reflecting film according to any one of [1] to [5].
[7] When the group including the low refractive index layer group and the high refractive index layer group includes a plurality of the inorganic layers,
The light reflecting film according to any one of [1] to [6], wherein the plurality of inorganic layers are not adjacent to each other.
[8] The low refractive index layer L ₁ is an acrylic resin comprises a crosslinked product with a mixture or heterocyclic compounds acrylic resin acrylic resin and a heterocyclic compound, any of [1] to [7] A light reflecting film according to claim 1.
[9] When the low refractive index layer group, further comprising a low refractive index layer L _n consisting of the low refractive index layer L ₁ other than the organic layer,
Wherein the organic layer low refractive index layer L _n comprises an acrylic resin, a crosslinked product with a mixture or heterocyclic compounds acrylic resin acrylic resin and a heterocyclic compound, [1] to [8] The light reflecting film according to any one of the above.
[10] The case low refractive index layer group, further comprising a low refractive index layer Ln comprising the low refractive index layer L ₁ other than the inorganic layer,
Low refractive index layer _{L n} which is the inorganic layer is composed of SiO _2, the light reflective film according to any one of [1] to [9].
[11] When the high refractive index layer group includes a high refractive index layer H composed of the organic layer,
The high refractive index layer H that is the organic layer is the light reflecting film according to any one of [1] to [10], including a resin and metal oxide particles.
[12] When the high refractive index layer group includes a high refractive index layer H composed of the inorganic layer,
The high refractive index layer H the inorganic layer consists of _Nb 2 _{O 5} or ZnS, light reflecting film according to any one of [1] to [11].
[13] on the silver layer, the low refractive index layer L ₁ is the organic layer, the high refractive index layer H ₁ is the inorganic layer, the organic layer and the high refractive index layer H ₂ is in this order The light reflecting film according to any one of [1] to [12], which is disposed.
[14] on the silver layer, the low refractive index layer L ₁ is the organic layer, the high refractive index layer H ₁ is the organic layer, the inorganic layer and the high refractive index layer H ₂ is in this order The light reflecting film according to any one of [1] to [12], which is disposed.
[15] on the silver layer, the low refractive index layer L ₁ is the organic layer, the low refractive index layer L ₂ is the inorganic layer, the organic layer and the high refractive index layer H ₁ is in this order The light reflecting film according to any one of [1] to [12], which is disposed.
[16] on the silver layer, the organic layer and the low refractive index layer L _1, and the low refractive index layer L ₂ is an inorganic layer, and the organic layer low refractive index layer L _3, wherein the inorganic light reflecting film according to any one of the high refractive index layer H ₁ with a layer are disposed in this order, [1] to [12].
[17] on the silver layer, the organic layer and the low refractive index layer L _1, the low refractive index layer L ₂ is the inorganic layer, the inorganic layer and the high refractive index layer H ₁ is in this order The light reflecting film according to any one of [1] to [6] and [8] to [12], which is disposed.
[18] The light reflecting film according to any one of [1] to [17], further including an anchor layer disposed between the base material layer and the silver layer.
[19] 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 [18].

  The present invention can provide a light reflecting film having high reflectivity and high durability against light irradiation at a dry high temperature.

It is a schematic diagram which shows an example of the light reflection film of this invention. It is sectional drawing which shows an example of the liquid crystal display device of this invention.

1. Light Reflective Film The light reflective film of the present invention has a substrate, a silver layer, a low refractive index layer group composed of one or more low refractive index layers L, and a high refractive index composed of one or more high refractive index layers H. The rate group is included in this order.

However, at least one of the low refractive index layer group and the high refractive index layer group includes an organic layer mainly composed of a resin and an inorganic layer mainly composed of an inorganic compound.
Further, the low refractive index layer L ₁ adjacent to the silver layer is an organic layer mainly composed of a resin; and at least one of the one or more low refractive index layers L other than the low refractive index layer L ₁ is: At least one of the above-described inorganic layers and / or one or more high refractive index layers H is the above-mentioned inorganic layer.

  The light reflecting film of the present invention is a light reflecting film having high durability against light irradiation under a dry high temperature, and such high durability is achieved by the above-described layer configuration. The mechanism for obtaining high durability is not clear, but is estimated as follows.

The low refractive index layer laminated on the silver layer is a low refractive index layer made of an inorganic material such as SiO ₂ and has poor adhesion to the silver layer. It is thought that the nature is lowered. On the other hand, a low refractive index layer made of an organic material such as a resin has good adhesion to a silver layer, but tends to have low durability against light irradiation at a dry high temperature. Specifically, the resin constituting the low refractive index layer is decomposed and dissipated by light irradiation under dry high temperature, so that the film thickness of the low refractive index layer made of the resin material decreases with time. It was found that the low refractive index layer itself made of the resin material disappeared. Such disappearance of the organic layer is not a phenomenon limited to a low refractive index material, and it is considered that only a resin is decomposed even for a high refractive index material such as a metal oxide particle-containing resin. Such decomposition and dissipation of the organic layer is a phenomenon that is not seen in a durability test under high humidity and high temperature without light irradiation.

  Since the said organic layer is a refractive index layer provided in order to raise a reflectance, when an organic layer lose | disappears, the reflectance of a light reflection film will fall. Furthermore, gaps are generated on the silver layer due to the disappearance of the organic layer (low refractive index layer) adjacent to the silver layer, and as a result, the surface of the silver layer rises or particles and mixes with other layers. Thus, it is considered that the film turns black.

Prevent photolysis of the resin material, and a high reflection film extensive studies were carried out the results in order to obtain a reflectance in the present invention, a low refractive index layer L ₁ adjacent to the silver layer, the silver layer and high adhesion organic layer, and than the low refractive index layer L ₁ by disposing the at least one inorganic layer on the light incident side, to prevent degradation and dissipation of the low refractive index layer L ₁ is an organic layer .
Inorganic layer than the low refractive index layer L ₁ is disposed on the light incidence side, specifically, at least one other than the low refractive index layer L ₁ of the one or more layers of a low refractive index layer L or 1 layer, At least one of the high refractive index layers H described above. Inorganic layer disposed on the light incident side than those of the low refractive index layer L ₁ not only functions as a refractive index layers for controlling the refractive index, also functions as a barrier layer. Specifically, it is considered that the discoloration accompanying the deformation of the silver layer can be prevented by protecting the organic layer provided on the lower side from light and also blocking the diffusion of the decomposed resin to the outside.

Further, at least one of the low refractive index layer group and the high refractive index layer group includes an organic layer containing a resin as a main component and an inorganic layer containing an inorganic compound as a main component, thereby improving the adhesion between the layers. Can do. Furthermore, the low refractive index layer and / or the high refractive index layer is not a single thick layer, but a laminate of two or three thin layers, thereby reducing the rigidity of the light reflecting film and delamination. And the occurrence of problems such as distortion can be prevented. Furthermore, when the low refractive index layer and / or the high refractive index layer is formed as a single layer, the refractive index is substantially determined by the material used, but it can be obtained by forming a laminate composed of two to three layers. It becomes easy to adjust the refractive index flexibly.
Therefore, in the present invention, the low refractive index layer and / or the high refractive index layer provided on the silver layer is a laminate composed of the above specific layer structure, so that the dry high temperature can be achieved without sacrificing the high reflectance. It becomes possible to provide a light reflecting film having high durability against light irradiation below.

1-1. Base material layer The base material layer has a function of supporting the silver layer. The base material layer 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 can be set to, for example, 10 to 300 μm. When the thickness of the base material layer is 10 μm or more, the base material layer has sufficient strength and is easy to handle. The surface smoothness of a base material layer is hard to be impaired as the thickness of a base material layer is 300 micrometers or less. The thickness of the base material layer is preferably 20 to 200 μm, and more preferably 20 to 100 μm.

  In order to uniformly form the silver layer on the base material layer by vacuum vapor deposition or the like, it is preferable that the base material layer contains as little impurities as possible. From such a viewpoint, the base material layer 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. The average transmittance of the transparent substrate layer can be measured in the same manner as described above.

1-2. Silver layer The silver layer has a function of reflecting light. The silver layer is a layer containing Ag or an alloy thereof as a main component. “Containing Ag or an alloy thereof as a main component” means that the Ag content in the silver layer is 90 atomic% or more. Therefore, the content of Ag or an alloy thereof is preferably 90 atomic% or more, more preferably 99.9 atomic% or more with respect to the silver layer.

  A silver layer may further contain other metals other than Ag or its alloy. Examples of other metals include Au, Pd, Sn, Ga, In, Cu, Ti, Bi, and alloys thereof, and may preferably be an alloy of Au and Ag. As will be described later, the silver layer is preferably a thin film formed by a vacuum film forming method, and more preferably a deposited film.

  The thickness of the silver layer 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 a silver layer is 200 nm or less. The thickness of the silver layer is more preferably 80 to 150 nm, and further preferably 90 to 150 nm.

  The surface reflectance of the silver layer is preferably 80% or more, and more preferably 90% or more. The surface reflectance of the silver layer can be measured with a spectrophotometer U-4100 manufactured by Hitachi High-Technologies Corporation.

1-3. Low-refractive index layer group / high-refractive index layer group The low-refractive index layer group and the high-refractive index layer group can function as an increased reflection layer that increases the reflectance of the silver layer. The low refractive index layer group is composed of one or more low refractive index layers L, and the high refractive index layer group is composed of one or more high refractive index layers H. Of the one or more low refractive index layers L constituting the low refractive index layer group, the refractive index of the low refractive index layer L _high having the highest refractive index of light having a measurement wavelength of 550 nm is the same as that of the high refractive index layer group. Of the one or more high-refractive index layers H to be configured, the refractive index of light having a measurement wavelength of 550 nm is lower than the refractive index of the lowest high-refractive index layer H _low .

1-3-1. Low Refractive Index Layer Group The low refractive index layer group is composed of one or more low refractive index layers L. The number of the low refractive index layers L constituting the low refractive index layer group is not particularly limited, but is preferably 1 layer or more and 3 layers or less.

The refractive index n _L of light having a wavelength of 550 nm of the low refractive index layer L is set in consideration of the refractive index difference from the high refractive index layer H, but is preferably less than 1.7, More preferably, it is 1.5. The refractive index n _L of the low refractive index layer _L is mainly adjusted by the refractive index of the material contained in the low refractive index layer L and the density of the low refractive index layer L.

The refractive index n _L of the low refractive index layer L can be measured by the following method. That is, a low refractive index layer (single layer) having a thickness of 100 nm is applied and formed on a polyethylene terephthalate substrate to obtain a sample for refractive index measurement. The refractive index of light having a wavelength of 550 nm of the obtained sample is measured using a spectroscopic ellipsometer UVSEL manufactured by Horiba.

When the low refractive index layer group includes a plurality of (preferably two or three) low refractive index layers L, the refractive index of light having a wavelength of 550 nm and the refractive index of the low refractive index layer Lh having the highest refractive index The refractive index difference Δn _L between the lowest refractive index layer Ll and the refractive index of light having a wavelength of 550 nm is preferably 0.3 or less, and more preferably 0.2 or less. By setting the refractive index difference Δn _L in the low refractive index layer group to 0.3 or less, reflection loss at the interface having a refractive index difference can be suppressed.

Low refractive index layer thickness of L constituting the low refractive index layer group (the physical thickness) d _L preferably satisfies the following formula (1). By the film thickness d _L of the low refractive index layer L which constitutes the low refractive index layer group satisfies the following formula (1), a high reflectivity film is obtained.

(In Formula (1),
n _Lk is the refractive index of the low refractive index layer L _{k at} a wavelength of 550 nm,
d _Lk is the film thickness (nm) of the low refractive index layer L _k ,
n is the number of low refractive index layers L included in the low refractive index layer group,
λ ₁ is the minimum value of the wavelength region of incident light,
λ ₂ is the maximum value of the wavelength region of incident light)

The total value of the film thickness d _L of the low refractive index layer L which constitutes the low refractive index layer group, depending on the set wavelength may be in the range satisfying Formula (1) above. For example, the total value of the film thickness d _L of the low refractive index layer L is preferably 30 nm or more and 80 nm or less, and more preferably 40 nm or more and 70 nm or less.

Incident light is usually light in a certain wavelength region. The wavelength region of incident light is usually within the visible light region, but is not limited thereto. For example, in the case of a reflective film used by being incorporated in a backlight unit using an LED light source, λ ₁ can be set to 360 nm and λ ₂ can be set to 830 nm.

  The low refractive index layer L may be an inorganic layer (preferably a vapor deposition film) containing an inorganic material as a main component or an organic layer containing a resin as a main component. Hereinafter, the “main component” refers to a component having a content of 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more based on the entire layer.

(Inorganic layer)
When the low refractive index layer L is an inorganic layer, examples of the inorganic material constituting the inorganic layer include Si oxide (for example, SiO ₂ ), Si nitride (for example, Si ₃ N ₄ ), and Si acid. Includes nitrides (SiOxNy), metal fluorides (eg, magnesium fluoride, lithium fluoride, cryolite, sodium fluoride, calcium fluoride, lanthanum fluoride, neodymium fluoride, cesium fluoride, lead fluoride), etc. . Examples of Si oxynitrides include polysilazane. Polysilazane is a polymer having a silicon-nitrogen bond and can be represented by the following general formula (I).

R ₁ , R ₂ and R _{3 in} formula (I) are each independently a hydrogen atom, a substituted or unsubstituted alkyl group (preferably a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms). Group), an aryl group (preferably an aryl group having 6 to 30 carbon atoms), a vinyl group, or a trialkoxysilyl (preferably a silyl substituted with an alkoxy group having 1 to 8 carbon atoms) alkyl group. R ₁ , R ₂ and R ₃ may be the same or different.

  N in the general formula (I) is an integer of 1 or more. The number average molecular weight of the compound having the structure represented by the general formula (I) is preferably 150 to 150,000.

Examples of the compound having a structure represented by the general formula (I) include perhydropolysilazane (PHPS) in which all of R ₁ , R ₂ and R ₃ are hydrogen atoms.

The inorganic material constituting the low refractive index layer L is preferably SiO ₂ . The inorganic layer made of SiO ₂ is suitable from the viewpoints of a low refractive index, transparency and barrier properties.

  When the low refractive index layer L is an inorganic layer, the content of the inorganic material is preferably 90 atomic percent or more, more preferably 95 atomic percent or more with respect to the total atomic weight of the low refractive index layer L. .

(Organic layer)
When the low refractive index layer L is an organic layer, the resin constituting the organic layer may be a resin having a refractive index suitable for the low refractive index layer L. Examples thereof include polyethylene terephthalate (PET), Polyester resins such as polyethylene terephthalate copolymer (coPET) and terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer (PETG); poly (methyl methacrylate) (PMMA), poly (methyl methacrylate) copolymer (coPMMA), etc. Acrylic resins; heterocyclic compounds such as melamine resins; polyvinyl alcohol resins, gelatin, celluloses, thickening polysaccharides and water-soluble resins such as polymers having reactive functional groups. These resins may be only one kind, or two or more kinds may be combined. Of these resins, a curable resin having a functional group that reacts with a curing agent (for example, an acrylic resin having a hydroxyl group) may be a cured product. Examples of such a cured product include a crosslinked product obtained by crosslinking an acrylic resin having a functional group with a heterocyclic compound (curing agent).

  Among these, from the viewpoint of durability against light irradiation at a dry high temperature, an acrylic resin, a mixture of an acrylic resin and a heterocyclic compound, or a crosslinked product of an acrylic resin with a heterocyclic compound is preferable.

  The weight average molecular weight of resin should just be the extent 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.

1-3-2. High Refractive Index Layer Group The high refractive index layer group is composed of one or more high refractive index layers H. The number of high refractive index layers H constituting the high refractive index layer group is not particularly limited, but is preferably 1 layer or more and 3 layers or less.

The refractive index n _H of light having a wavelength of 550 nm of the high refractive index layer H can be set in consideration of the refractive index difference from the low refractive index layer L, and is preferably 1.7 or more, for example, 2.0 More preferably, it is 2.4 or less. The refractive index of the high refractive index layer H is mainly adjusted by the refractive index of the material contained in the high refractive index layer H and the density of the high refractive index layer H.

The refractive index n _H of the high refractive index layer H is the same as described above except that a high refractive index layer (single layer) having a thickness of 100 nm is vacuum deposited or formed on a polyethylene terephthalate substrate to obtain a sample for refractive index measurement. Can be measured.

When the high refractive index layer group includes a plurality of (preferably two or three) high refractive index layers H, the wavelengths of the high refractive index layer Hh having the highest refractive index and the high refractive index layer Hl having the lowest refractive index. The refractive index difference Δn _H of light at 550 nm is preferably 0.6 or less, and more preferably 0.5 or less. By setting the refractive index difference Δn _H in the high refractive index layer group to 0.6 or less, reflection loss at the interface having a refractive index difference can be suppressed.

Thickness d _H of the high refractive index layer H constituting the high refractive index layer group preferably satisfies the following formula (2). Thickness d _H of the high refractive index layer H constituting the high refractive index layer group by satisfying the relation of the following formula (2), a high reflectivity film is obtained.

(In Formula (2),
n _Hk is the refractive index of the high refractive index layer H _{k at} a wavelength of 550 nm,
d _Hk is the film thickness (nm) of the high refractive index layer H _k ,
n is the number of high refractive index layers H included in the high refractive index layer group,
λ ₁ is the minimum value of the wavelength region of incident light,
λ ₂ is the maximum value in the wavelength region of incident light. )

The total value of the film thickness d _H of the high refractive index layer H constituting the high refractive index layer group, depending on the set wavelength may be in the range satisfying Formula (2) above. For example, the total value of the film thickness _{d H} of the high refractive index layer H constituting the high refractive index layer group is preferably 30nm or more 80nm or less, and more preferably 40nm or more 70nm or less.

  The high refractive index layer H may be an inorganic layer (preferably a vapor deposition film) mainly composed of an inorganic material, or an organic layer made of a resin alone or a resin containing a resin and an inorganic material (particles). There may be.

(Inorganic layer)
When the high refractive index layer H is an inorganic layer, examples of the inorganic material constituting the inorganic layer include a metal oxide or a metal sulfide. Examples of the metal constituting the metal oxide or metal sulfide include Zn, Ti, Zr, Nb, Ta and In. Examples of metal oxides include TiO ₂ , ITO (indium tin oxide), ZnO, Nb ₂ O ₅ , ZrO ₂ , CeO ₂ , SnO ₂ , WO ₃ , TNO, Ta ₂ O ₅ , Ti ₃ O ₅ , Ti ₄ O ₇ , Ti ₂ O _3, TiO and the like are included. Examples of the metal sulfide include ZnS, MnS, and the like.

The inorganic material constituting the high refractive index layer H is preferably Nb ₂ O ₅ or ZnS from the viewpoint of high refractive index, transparency, and barrier properties.

  The content of the metal oxide or metal sulfide is preferably 90 atomic percent or more, more preferably 95 atomic percent or more, based on all atoms of the high refractive index layer H.

(Organic layer)
When the high refractive index layer H is an organic layer, the organic material constituting the organic layer may be a resin having a high refractive index or a resin similar to the resin used for the low refractive index layer L that is an organic layer. it can. Among these, a curable resin is preferable. Examples of the curable resin include a functional group-containing acrylic resin.

  Examples of the metal oxide fine particles constituting the organic layer are preferably fine particles having a refractive index of light having a wavelength of 550 nm of 2.0 or more. Examples of such fine particles include metal compound fine particles such as titanium oxide, zinc sulfide, zirconium oxide or copper oxide, and metal fine particles such as zinc, chromium and tungsten.

  The average particle diameter of the metal oxide fine particles can be, for example, 5 to 30 nm.

  The content of the metal oxide fine particles is preferably 40 to 90% by mass, and more preferably 50 to 80% by mass with respect to the total mass of the high refractive index layer H.

1-3-3. Layer Configuration of Low Refractive Index Layer Group and High Refractive Index Layer Group In the light reflecting film of the present invention, the low refractive index layer group is composed of one or more low refractive index layers L, and the high refractive index layer group is one layer. It consists of the above high refractive index layer H.

  However, at least one of the low refractive index layer group and the high refractive index layer group includes an organic layer mainly composed of a resin and an inorganic layer mainly composed of an inorganic compound. For example, when the low refractive index layer group is composed of three low refractive index layers L, two low refractive index layers L are organic layers, and one low refractive index layer L is an inorganic layer. Good. When the high refractive index layer group is composed of three high refractive index layers H, the two high refractive index layers H may be organic layers and the one high refractive index layer H may be an inorganic layer.

In the present invention, the low refractive index layer L ₁ adjacent to the silver layer is an “organic layer”, and at least one “inorganic layer” is disposed closer to the light incident side than the low refractive index layer L ₁ . "Inorganic layer" disposed on the light incident side than the low refractive index layer L ₁ may be a low refractive index layer L _n other than the low refractive index layer L _1, a high refractive index layer H Also good. Between the inorganic layer and the low refractive index layer L _1, without impairing the effect of the present invention, it may further contain other layers.

  However, when the group including the low refractive index layer group and the high refractive index layer group includes a plurality of inorganic layers, the plurality of inorganic layers may be adjacent to each other, or an organic layer between the inorganic layer and the inorganic layer. May be arranged.

The following are mentioned as an example of the preferable layer structure of the light reflection film of this invention.
Silver layer / low refractive index layer L ₁ that is an organic layer / high refractive index layer H ₁ that is an inorganic layer / high refractive index layer H ₂ that is an organic layer (for example, the light reflecting film of Example 1).
Silver layer / low refractive index layer L ₁ that is an organic layer / high refractive index layer H ₁ that is an organic layer / high refractive index layer H ₂ that is an inorganic layer (for example, the light reflecting film of Example 3).
Silver layer / low refractive index layer L ₁ that is an organic layer / low refractive index layer L ₂ that is an inorganic layer / high refractive index layer H ₁ that is an organic layer (for example, the light reflecting film of Example 6).
Silver layer / low refractive index layer L ₁ which is an organic layer / low refractive index layer L ₂ which is an inorganic layer / low refractive index layer L ₃ which is an organic layer / high refractive index layer H ₁ which is an inorganic layer (for example, implementation) The light reflecting film of Example 9).
Silver layer / low refractive index layer L ₁ that is an organic layer / low refractive index layer L ₂ that is an inorganic layer / high refractive index layer H ₁ that is an inorganic layer (for example, the light reflecting film of Example 19).

  FIG. 1 is a schematic view showing an example of the light reflecting film of the present invention. The light reflecting film shown in the figure has three low-refractive index layers L and one high-refractive index layer H in the same manner as the film produced in Example 9.

  As shown in FIG. 1, the light reflecting film 10 includes a base layer 11, a silver layer 12, low refractive index layers 13, 15 and 17, and a high refractive index layer 19 in this order. In the film produced in Example 9, the low refractive index layers 13 and 17 are organic layers, and the low refractive index layer 15 and the high refractive index layer 19 are inorganic layers.

In the light reflecting film having the layer structure as described above, the low refractive index layer 15 and the high refractive index layer 19 which are inorganic layers arranged on the light incident side with respect to the low refractive index layer 13 adjust the reflectance of the film. In addition to this, it is considered to function as a barrier layer for preventing the decomposition and diffusion of the organic layers (low refractive index layers 13 and 17) located on the substrate side relative to the inorganic layer. It is considered that the inorganic layer not only prevents the entry of light and oxygen from the outside, but also has a function of preventing the decomposed organic layer from diffusing to the outside.
Furthermore, by including at least one of the low refractive index layer group and the high refractive index layer group, an organic layer containing a resin as a main component and an inorganic layer containing an inorganic compound as a main component, the adhesion between layers is increased. Furthermore, the rigidity of the light reflecting film can be relaxed, and problems such as delamination and distortion can be prevented.
Therefore, it is possible to provide a light reflecting film having high durability against light irradiation under a dry high temperature without sacrificing high reflectance.

1-4. Other Layers The light reflecting film of the present invention may further include other layers as long as the effects of the present invention are not impaired. Examples of other layers include an anchor layer disposed between the base material layer and the silver layer.

  An anchor layer is arrange | positioned, for example between a base material layer and a silver layer, can improve the adhesiveness of a base material layer and a silver layer, and can provide the surface smoothness of the grade which does not impair the reflective performance of a silver layer.

  The anchor layer contains a resin as a main component. Examples of such resins include polyester resins, acrylic resins, resins made of acrylic resins and heterocyclic compounds, epoxy resins, polyamide resins, vinyl chloride resins, and vinyl chloride vinyl acetate copolymer systems. Resin etc. are included. Among these, acrylic resins and resins made of acrylic resins and heterocyclic compounds are preferable from the viewpoint of good durability. The anchor layer may be a thermosetting composition containing a curing agent such as isocyanate.

  The thickness of the anchor layer can be set to 0.01 to 3 μm, for example. When the thickness of the anchor layer is 0.01 μm or more, the adhesion between the base material layer and the silver layer can be sufficiently enhanced. When the thickness of the anchor layer is 3 μm or less, the film thickness uniformity of the anchor layer is hardly impaired. The anchor layer preferably has a thickness of 0.1 to 1 μm.

2. Method for Producing Light Reflecting Film The light reflecting film of the present invention may be produced by any method, for example, a silver layer, low refractive index layers L _{1 to} L ₃ , and high refractive index layers H _{1 to} H ₃ are sequentially laminated. May be manufactured. Specifically, a silver layer, low refractive index layers L _{1 to} L _n , and high refractive index layers H _{1 to} H _n are sequentially laminated on _one surface of the base material layer to obtain a laminate. n is an integer greater than or equal to 1, Preferably it is an integer of 1-3.

  The silver layer can be formed by a wet method or a dry method. The wet method is a plating method in which a film is formed by depositing a metal from a solution, and specific examples thereof include a silver mirror reaction method. The dry method is a vacuum film forming method, and specific examples thereof include a resistance heating vacuum deposition method, an electron beam heating vacuum deposition method, an ion plating method, an ion beam assisted vacuum deposition method, and a sputtering method. Of these, the dry method is preferable from the viewpoint of production efficiency, and the vacuum evaporation method is more preferable from the viewpoint that film formation by a roll-to-roll method, which is a continuous film formation method, is possible.

  In order to improve the adhesion between the base material layer and the silver layer, the surface of the base material layer may be subjected to a surface treatment such as a corona treatment or an ion coating treatment before the silver layer is formed. An anchor layer may be further formed on the surface of the base material layer.

  The low refractive index layer L and the high refractive index layer H can be formed by a dry method or a wet method. The organic layer mainly containing a resin is preferably formed by a wet method, and the inorganic layer mainly containing an inorganic material is preferably formed by a dry method.

  In the dry method, an inorganic layer is formed by forming the above-described inorganic material by a vacuum film-forming method similar to that described above. The vacuum film forming method is preferably a vacuum vapor deposition method from the viewpoint that continuous film forming is possible.

  In the wet method, for example, the resin composition constituting the organic layer described above is applied and then cured to form an organic layer made of a cured product of the resin composition. In addition, an inorganic layer can be formed by applying a sol in which inorganic particles are dispersed in a solvent and containing no binder component, and then drying.

  The resin composition includes the above-described curable resin and a curing agent, and may further include a solvent as necessary. Examples of the curing agent include polyisocyanate and epoxy compound. Content of a hardening | curing agent can be about 0.1-15 mass% with respect to the above-mentioned curable resin. 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.

  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. Curing is photocuring or thermal curing, and thermal curing is preferable in that sufficient curing is possible.

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. Especially, the light reflection film of this invention is preferably used as a light reflection film of the backlight unit for liquid crystal display devices from the point which has a favorable reflectance and durability.

(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 arranged so that the outermost high refractive index layer H faces the light source or the back surface of the light guide plate (the surface not facing the liquid crystal display panel).

  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. Among these, a cold cathode tube (CCFL) and a light emitting diode element (LED) are 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 aspect of the side edge type backlight unit includes a backlight unit 50 shown in FIG. 2 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. 2 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. 2, the liquid crystal display device 30 includes a liquid crystal display panel 40 and a side edge type backlight unit 50.

  The liquid crystal display panel 40 includes a liquid crystal cell 41 and a pair of polarizing plates 43 and 45 sandwiching the liquid crystal cell 41. The display method of the liquid crystal cell 41 is not particularly limited, and may be various display modes such as VA (MVA, PVA) and IPS. Each of the polarizing plates 43 and 45 includes a polarizer and a protective film disposed on at least one surface thereof.

  The side-edge type backlight unit 50 includes a rod-shaped light source 51, a light guide plate 53 disposed so that the side end portion is adjacent to the light source 51, and the light reflecting film 10 disposed on the back side of the light guide plate 53. And a plurality of optical films 55 disposed on the surface side of the light guide plate 53.

  The light source 51 is covered with a lamp reflector 52. The plurality of optical films 55 are not limited to the mode of FIG. 2, and the optical film 55 may not be provided, and the combination and number of optical films may be changed.

  In the side-edge type backlight unit 50, light emitted from the light source 51 propagates inside the light guide plate 53. A part of the light emitted from the light guide plate 53 is reflected by the light reflecting film 10 and emitted to the front surface side (liquid crystal display panel 40 side) of the light guide plate 53. The light emitted to the surface side of the light guide plate 53 is diffused by the light diffusion film 57, refracted by the prism film 59, and incident on the entire surface of the liquid crystal display panel 40.

  Since the light reflection film 10 has high reflectance, the liquid crystal display device 30 including the light reflection film 10 can have high light utilization efficiency.

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

1. Preparation of Light Reflective Film Material Light including a low refractive index layer group and a high refractive index layer group using the materials shown in Table 1-1, Table 1-2, Table 2-1, and Table 2-2. A reflective film was prepared. The solution for the low refractive index layer and the solution for the high refractive index layer used for the organic layer are as follows.

(1) Low refractive index layer solution (Preparation of low refractive index layer solution 1)
As the resin 1, an acrylic resin (Dianar BR-608 manufactured by Mitsubishi Rayon Co., Ltd.) and a heterocyclic compound (melamine resin; MX-730 manufactured by Sanwa Chemical Co., Ltd.) have a refractive index of 1.575. And added to methyl ethyl ketone (MEK) at 3% by mass to obtain a solution 1 for a low refractive index layer.

(Preparation of low refractive index layer solution 2)
The low refractive index layer solution 2 is obtained in the same manner as the preparation of the low refractive index layer solution 1 except that the resin 1 is changed to the resin 2 (Dainal BR-608 manufactured by Mitsubishi Rayon Co., Ltd .; acrylic resin). It was.

(Preparation of solution 3 for low refractive index layer)
As the resin 3, a polysiloxane resin (Surcoat SCH72, manufactured by DOKEN Co., Ltd.) was diluted with 1-propanol so as to have a solid concentration of 0.2% by mass to obtain a solution 3 for a low refractive index layer.

(2) High refractive index layer solution High refractive index layer solution 4: UV curable coating material (manufactured by Nissan Chemical Industries, Ltd., Hypertech UR-101, Tables 2-1 and 2-2, resin 4 and Notation)
High refractive index layer solution 5: ZrO2 containing resin solution (manufactured by Toyochem Co., Ltd., dispersion TYZ76 containing UV curable acrylic resin and zirconium oxide, represented as resin 5 in Tables 2-1 and 2-2)

(3) Measurement of refractive index of low refractive index layer L and high refractive index layer H On a polyethylene terephthalate (PET) substrate having a thickness of 100 μm, a low refractive index layer L having a thickness of 50 nm is formed by vacuum deposition or coating, and is refracted. A sample 1 for rate measurement was obtained. Similarly, a high refractive index layer H having a thickness of 50 nm was vacuum deposited or formed on a PET substrate having a thickness of 100 μm to obtain a refractive index measurement sample 2. The refractive indexes of light having a wavelength of 550 nm of Samples 1 and 2 were measured using a Horiba spectroscopic ellipsometer UVSEL, respectively.

  In the following examples and comparative examples, the thicknesses of the low refractive index layers and the high refractive index layers are as shown in Table 1-1, Table 1-2, Table 2-1, and Table 2-2.

2. Production and Evaluation of Light Reflecting Film <Example 1>
On the 25 μm thick polyethylene terephthalate film (product name “Lumirror T-60” manufactured by Toray Industries, Inc.), the low refractive index layer solution 1 was applied by a gravure coating method and then dried to form an anchor layer having a thickness of 100 nm. Provided.
On this anchor layer, silver was laminated by a vacuum vapor deposition method to produce a silver layer having a thickness of 100 nm.
Next, a low refractive index layer solution 1 was applied on the silver layer by a gravure roll coating method, and dried and cured at 100 ° C. to form a low refractive index layer L ₁ as an organic layer.
Then, on the low refractive index layer L _1, the niobium oxide (Nb 2 _{O 5)} film was formed by a sputtering method to form a high refractive index layer H ₁ is an inorganic layer.
Next, after applying the high refractive index layer solution 4 (manufactured by Nissan Chemical Industries, Ltd., Hypertech UR-101) on the high refractive index layer H _1, it was dried at 130 ° C. for 1 minute, and then with a high pressure mercury lamp. The cured film was obtained by irradiating UV with an integrated light amount of 800 mJ / cm ² . The cured film was the high refractive index layer H ₂ is an organic layer.
Thereby, a light reflecting film having a laminated structure of a low refractive index layer L ₁ made of an organic layer / a high refractive index layer H ₁ that is an inorganic layer / a high refractive index layer H ₂ that is an organic layer was obtained.

<Examples 2 to 17, Examples 21 to 26, Comparative Examples 1 to 13>
The layer configuration of the low refractive index layer group is changed as shown in Table 1-1 and Table 1-2, and the layer configuration of the high refractive index layer group is shown in Table 2-1 and Table 2-2. A light reflecting film was obtained in the same manner as in Example 1 except for the change.
In Table 1-1 and Table 1-2, those corresponding to the low refractive index layer that is an organic layer are “resin 1”, “resin 2”, and “resin 3”, and the organic layer of Example 1 It was formed by the same method. In Table 1-1 and Table-2, those corresponding to the inorganic layer are “SiO ₂ ” and “Al ₂ O ₃ ”, which were formed by vacuum deposition, respectively.
In Tables 2-1 and 2-2, those corresponding to the organic layer are “resin 4” and “resin 5”, respectively, in the same manner as the high refractive index layer H ₂ that is the organic layer of Example 1. Formed. In Tables 2-1 and 2-2, those corresponding to the inorganic layer are “Nb ₂ O ₅ ” and “ZnS”, “Nb ₂ O ₅ ” is a sputtering method, and “ZnS” is a vacuum deposition method. Formed.

<Examples 18 and 19>
Silver was laminated on a polyethylene terephthalate film having a thickness of 25 μm (product name “Lumirror T-60” manufactured by Toray Industries, Inc.) to produce a silver layer having a thickness of 100 nm.
Next, on this silver layer, a low refractive index layer group having a layer configuration shown in Table 1-1 and a high refractive index layer group having a layer configuration shown in Table 2-1 were formed in the same manner as in Example 1. Thus, a light reflecting film was obtained.

<Example 20>
A solution was prepared by adding acrylic resin (Dianar BR-608 manufactured by Mitsubishi Rayon Co., Ltd.) to methyl ethyl ketone (MEK) so as to be 3% by mass. This solution was applied on a 25 μm thick polyethylene terephthalate film (product name “Lumirror T-60” manufactured by Toray Industries, Inc.) by a gravure coating method and then dried to provide an anchor layer having a thickness of 100 nm.
On this anchor layer, silver was laminated by a vacuum vapor deposition method to produce a silver layer having a thickness of 100 nm.
Next, on this silver layer, a low refractive index layer group having a layer configuration shown in Table 1-1 and a high refractive index layer group having a layer configuration shown in Table 2-1 were formed in the same manner as in Example 1. Thus, a light reflecting film was obtained.

Table 1-1 and Table 1-2 show the materials used for forming each of the low refractive index layers L _{1 to} L ₃ , their refractive indexes and film thicknesses, and the following for the low refractive index layers L _{1 to} L ₃ . The value of formula (1), the average refractive index, and the refractive index difference are described.
Tables 2-1 and 2-2 show the materials used for forming the high refractive index layers H _{1 to} H ₃ , the refractive indexes and film thicknesses thereof, and the following for the high refractive index layers H _{1 to} H ₃ . The value of formula (2), average refractive index, and refractive index difference are described.
The refractive index difference in Table 1-1, Table 1-2, Table 2-1 and Table 2-2 is the highest refractive index layer in each of the low refractive index layer group and the high refractive index layer group. The difference in refractive index between the layer having the lowest refractive index.

Calculated value of formula (1) = (n _L1 × d _L1 ) + (n _L2 × d _L2 ) + (n _L3 × d _L3 )
Calculated value of formula (2) = (n _H1 × d _H1 ) + (n _H2 × d _H2 ) + (n _H3 × d _H3 )
(In the formulas (1) and (2),
n _{L1 to} n _L3 are refractive indexes at a wavelength of 550 nm of the low refractive index layers L _{1 to} L ₃ , respectively.
d _{L1 to} d _L3 are film thicknesses (nm) of the low refractive index layers L _{1 to} L ₃ , respectively.
n _{H1 to} n _H3 are refractive indexes at a wavelength of 550 nm of the high refractive index layers H _{1 to} H ₃ , respectively.
d _{H1 to} d _H3 are film thicknesses (nm) of the high refractive index layers H _{1 to} H ₃ , respectively.

In the present embodiment, since the wavelength range of the light from the LED light source is 360 to 830 nm, λ _{1 is set} to 360 nm and λ _{2 is set} to 830 nm. In this case, the values obtained by the above formulas (1) and (2) are as follows.
45 <calculated value of formula (1) <103.75
90 <calculated value of formula (2) <207.5

  The average reflectance and durability of the light reflecting film obtained in each example and comparative example were evaluated by the following methods, respectively.

(Average reflectance)
The average reflectance of the light reflection film was measured using a spectrophotometer U-4100 (solid sample measurement system) manufactured by Hitachi High-Technologies Corporation under the conditions of a wavelength of 360 to 830 nm and an incident angle of 5 °.
In the present invention, a film having an average reflectance measured by the above method of 97% or more is defined as a high reflectance film.

(durability)
The obtained reflective film was placed on a hot plate set at 160 ° C., and irradiated with light at 176 mW / cm ² for 3 h using an LED having a central wavelength of 405 nm manufactured by Nichia Corporation. Thereafter, the appearance of the film after light irradiation was visually observed and evaluated according to the following evaluation criteria.
5: No discoloration and indistinguishable from unirradiated film.
4: Although the color immediately below the LED light source is discolored, the surrounding area is not discolored.
3: The color immediately below and around the LED light source is discolored, but it is not black.
2: The area immediately below the LED light source is black, and its periphery 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.

  Furthermore, with respect to the light reflecting films obtained in Examples 5, 6, 9, 10, 14, 15, 17, 19 to 26 and Comparative Examples 8 to 10, initial relative luminance and wet heat resistance were evaluated by the following methods, respectively. .

(Initial relative luminance)
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 obtained above. The light reflecting film was disposed so that the high refractive index layer was the 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 tristimulus value Y (luminance) [cd / m ² ] was measured at intervals of 0.6 mm from end to end while traversing the center of the surface light source device in the vertical direction of the light sources arranged in parallel. .
Using ESR80 (manufactured by 3M Company) as a luminance reference, the relative luminance when the reference luminance was set to 100% was calculated for each reflective film and used as the initial relative luminance.
In the present invention, it is preferable that the initial relative luminance is 97% or more in the measurement method.

(Heat heat resistance)
The reflective film whose initial relative luminance was measured as described above was stored for 250 hours in an environment of 60 ° C. and relative humidity of 90%. Thereafter, the relative luminance was measured again by the above method, and the difference from the initial relative luminance (Δ relative luminance) was calculated. Based on the calculated Δ relative luminance, wet heat resistance was evaluated according to the following evaluation criteria.
5: −1.5% ≦ (Δ relative luminance) ≦ 0%
4: −3.5% ≦ (Δ relative luminance) <− 1.5%
3: −5.5% ≦ (Δ relative luminance) <− 3.5%
2: −7.0% ≦ (Δ relative luminance) <− 5.5%
1: (Δ relative luminance) <− 7.0%

  The evaluation results of each film are shown in Tables 3 and 4 together with the layer structure (material) of the film and the calculated values of Formula (1) and Formula (2).

As is apparent from Table 3 above, the low refractive index layer group composed of one or more and three or less low refractive index layers L and the low refractive index layer group disposed on the silver layer. A high refractive index layer group composed of one or more and three or less high refractive index layers H in this order, and at least one of the low refractive index layer group and the high refractive index layer group is an organic layer or an inorganic layer. includes both, the low refractive index layer L ₁ that is adjacent to the silver layer is an organic layer, than the low refractive index layer L _1, at least two layers is disposed on the upper side, the at least one layer wherein the inorganic layer, The low refractive index layer group satisfies the following formula (1), and the high refractive index layer group satisfies the following formula (2). Each of the light reflecting films of Examples 1 to 26 has a high average reflection of 97% or more. It was a light reflecting film having both the rate (%) and durability not exhibiting black discoloration.

  On the other hand, the light reflecting films of Comparative Examples 1 and 2 in which only one organic layer was provided as the low refractive index layer and the high refractive index layer were both low in durability and black discoloration was observed. Further, as the low-refractive index layer and the high-refractive index layer, the light reflecting film of Comparative Example 12 in which only one inorganic layer is provided, respectively, one organic layer as the high-refractive index layer, and one layer as the low-refractive index layer The light reflecting film of Comparative Example 13 provided with only the inorganic layer had high durability but low average reflectance.

Further, the light reflecting film of Comparative Example 5 in which the inorganic layer is provided on the silver layer has more black discoloration after the durability test than the light reflecting films of Example 14 and Example 15 including the same layer. The durability was very low.
Further, the low refractive index layer group does not satisfy the requirement of the formula (1) (the scope of the present invention: more than 45, deviates from less than 103.75), Comparative Examples 4, 6 and 8, and the high refractive index layer group has the formula (2 ) (The scope of the present invention: more than 90, deviating from less than 207.5) The light reflecting films of Comparative Examples 3, 7, 9 and 10 were all insufficient with a reflectance of less than 97%. It was.

  In the light reflecting film of Example 15 in which the inorganic layer and the organic layer were alternately laminated, and the light reflecting film of Example 14 in which the inorganic layer and the inorganic layer were adjacent to each other, the average reflectance and the durability test were performed. There was no significant difference in the results. Similarly, the light reflecting films of Examples 19 to 26 in which the inorganic layer that is the low refractive index layer and the inorganic layer that is the high refractive index layer are adjacent also showed good average reflectance and durability.

  Light of Examples 2 and 6 using Resin 1 (resin composed of an acrylic resin and a heterocyclic compound) as an organic layer included in the low refractive index layer group, and Example 5 using Resin 2 (acrylic resin) The reflective film had higher durability than Examples 16 and 17 using other resins (polysiloxane resin which is resin 3), and the color change was only directly under the LED.

In Example 7 using SiO ₂ as the inorganic layer included in the low refractive index layer group, both the average reflectance and durability were higher than Example 8 using Al ₂ O ₃ .
In addition, Example 2 provided with the anchor layer was higher in durability than Example 18 having the same layer configuration as Example 2 except that the anchor layer was not provided. Similar results were obtained for Examples 20 and 21 in which an anchor layer was provided, and Example 19 having the same layer structure as Examples 20 and 21 except that no anchor layer was provided.

As is clear from the results in Table 4 above, the high refractive index layer is composed of two layers, an organic layer and an inorganic layer, as compared with the light reflecting films of Examples 5, 6 and 17 in which the high refractive index layer is only an organic layer. The light reflection films of Examples 14 and 15 had higher initial luminance. Furthermore, in Examples 9, 10, and 19 to 26, in which the high refractive index layer was composed of only one inorganic layer, the initial luminance exceeded 100%.
Moreover, the two layers of low refractive index layer of the organic layer and the inorganic layer in the light reflection film of Example 19-26 in which an inorganic layer made of a high refractive index layer, an organic layer having a low refractive index layer L ₁ thickness is not less 10nm or more and both of the light reflection film of example thickness of an inorganic layer low refractive index layer _{L 2} is 30nm or more 19-21 and 23 to 26, the initial brightness and wet heat resistance It was excellent.
Furthermore, Example 20 using a mixture of an acrylic resin and a heterocyclic compound for the anchor layer has the same layer structure as Example 21 except that only the acrylic resin is used for the anchor layer. It was higher than Example 19 having the same layer structure as Examples 20 and 21 except that no anchor layer was provided.

  On the other hand, the low refractive index layer group does not satisfy the requirement of the formula (1) (the scope of the present invention: more than 45, deviates from less than 103.75), and the high refractive index layer group satisfies the requirement of the formula (2). (The range of the present invention: more than 90, deviating from less than 207.5) The light reflecting films of Comparative Examples 9 and 10 both had low initial luminance.

The light reflecting film of the present invention comprises a silver layer, a low refractive index layer group composed of one or more low refractive index layers L, and a high refractive index layer group composed of one or more high refractive index layers H in this order. wherein in said at least one of the high refractive index layer group and the low-refractive index layer group comprises an organic layer and an inorganic layer, the low refractive index layer L ₁ adjacent to the silver layer is an organic layer, the low at least one other than the low refractive index layer L ₁ of the refractive index layers L, and / or at least one of the high refractive index layer H is a the inorganic layer, the following equation (1) and (2) It is a light reflecting film that fills. Such a light reflecting film can provide a film having high reflectivity and high durability against light irradiation at a dry high temperature.

10 the light reflecting film 11 substrate layer 12 a silver layer 13 low refractive index layer _{L 1} (organic layer)
15 Low refractive index layer L ₂ (inorganic layer)
17 Low refractive index layer L ₃ (organic layer)
19 High refractive index layer H ₁ (inorganic layer)
DESCRIPTION OF SYMBOLS 30 Liquid crystal display device 40 Liquid crystal display panel 41 Liquid crystal cell 43, 45 Polarizing plate 50 Side edge type backlight unit 51 Light source 52 Lamp reflector 53 Light guide plate 55 Optical film 57 Light diffusion film 59 Prism film

Claims (19)

A substrate;
A silver layer disposed on the substrate;
A low refractive index layer group composed of one or more low refractive index layers L disposed on the silver layer;
A light reflecting film including, in this order, a high refractive index layer group composed of one or more high refractive index layers H disposed on the low refractive index layer group,
At least one of the low refractive index layer group and the high refractive index layer group includes an organic layer mainly composed of a resin, and an inorganic layer mainly composed of an inorganic compound,
Low refractive index layer L ₁ adjacent to the silver layer is the organic layer,
At least one other than the low refractive index layer L ₁ of the one or more layers of the low refractive index layer L is at least one of the inorganic layer, and / or one or more layers of the high refractive index layer H is, The inorganic layer;
The low refractive index layer group satisfies the following formula (1),
The high refractive index layer group satisfies the following formula (2) and is a light reflecting film.

(In Formula (1),
n _Lk is the refractive index of the low refractive index layer L _{k at} a wavelength of 550 nm,
d _Lk is the film thickness (nm) of the low refractive index layer L _k ,
n is the number of low refractive index layers L included in the low refractive index layer group,
λ ₁ is the minimum value of the wavelength region of incident light,
λ ₂ is the maximum value in the wavelength region of incident light. )

(In Formula (2),
n _Hk is the refractive index of the high refractive index layer H _{k at} a wavelength of 550 nm,
d _Hk is the film thickness (nm) of the high refractive index layer H _k ,
n is the number of high refractive index layers H included in the high refractive index layer group,
λ ₁ is the minimum value of the wavelength region of incident light,
λ ₂ is the maximum value in the wavelength region of incident light. ) Refractive index n _L in the wavelength 550nm of one or more layers of the low refractive index layer L are each less than 1.7, the light reflection film of claim 1. When the low refractive index layer group is composed of a plurality of the low refractive index layers L,
The refractive index difference Δn _L between the low refractive index layer L _high having the highest refractive index at a wavelength of 550 nm and the low refractive index layer L _low having the lowest refractive index at a wavelength of 550 nm is 0.3 or less. Or the light reflection film of 2. Refractive index n _H at a wavelength 550nm of one or more layers of the high refractive index layer H is respectively 1.7 or more, the light reflecting film according to any one of claims 1-3. When the high refractive index layer group is composed of a plurality of the high refractive index layers H,
The refractive index difference Δn _H between the high refractive index layer H _high having the highest refractive index at a wavelength of 550 nm and the high refractive index layer H _low having the lowest refractive index at a wavelength of 550 nm is 0.6 or less. The light reflection film as described in any one of -4.   2. The number of low refractive index layers L included in the low refractive index layer group is 1 or more and 3 or less, and the number of high refractive index layers H included in the high refractive index layer group is 1 or more and 3 or less. The light reflection film as described in any one of -5. When the group including the low refractive index layer group and the high refractive index layer group includes a plurality of the inorganic layers,
The light reflecting film according to any one of claims 1 to 6, wherein the plurality of inorganic layers are not adjacent to each other. The low refractive index layer L ₁ is an acrylic resin, comprising a mixture or crosslinked product according to heterocyclic compounds acrylic resin acrylic resin and a heterocyclic compound, claimed in any one of claims 1 to 7 Light reflective film. If the low refractive index layer group, further comprising a low refractive index layer L _n consisting of the low refractive index layer L ₁ other than the organic layer,
Wherein the low refractive index layer L _n which is an organic layer, an acrylic resin, including cross-linked product with a mixture or heterocyclic compounds acrylic resin acrylic resin and a heterocyclic compound, any of the preceding claims The light reflecting film according to claim 1. Wherein when the low refractive index layer group, further comprising a low refractive index layer Ln comprising the low refractive index layer L ₁ other than the inorganic layer,
Low refractive index layer L _n which is the inorganic layer is composed of SiO _2, the light reflective film according to any one of claims 1-9. When the high refractive index layer group includes a high refractive index layer H made of the organic layer,
The high refractive index layer H which is the said organic layer is a light reflection film as described in any one of Claims 1-10 containing resin and a metal oxide particle. When the high refractive index layer group includes a high refractive index layer H made of the inorganic layer,
The high refractive index layer H the inorganic layer consists of _Nb 2 _{O 5} or ZnS, light reflecting film according to any one of claims 1 to 11. On the silver layer, a low refractive index layer L _{1 that} is the organic layer, a high refractive index layer H ₁ that is the inorganic layer, and a high refractive index layer H ₂ that is the organic layer are arranged in this order. The light reflecting film according to any one of claims 1 to 12. On the silver layer, the low refractive index layer L ₁ is the organic layer, wherein the high refractive index layer H ₁ is an organic layer, the inorganic layer and the high refractive index layer H ₂ is placed in this order The light reflecting film according to any one of claims 1 to 12. On the silver layer, a low refractive index layer L _{1 that} is the organic layer, a low refractive index layer L ₂ that is the inorganic layer, and a high refractive index layer H ₁ that is the organic layer are arranged in this order. The light reflecting film according to any one of claims 1 to 12. On the silver layer, the organic layer and the low refractive index layer L _1, the low refractive index layer L ₂ is the inorganic layer, the low refractive index layer L ₃ is the organic layer, is the inorganic layer and the high refractive index layer H ₁ are disposed in this order, the light reflecting film according to any one of claims 1 to 12. On the silver layer, a low refractive index layer L _{1 that} is the organic layer, a low refractive index layer L _{2 that} is the inorganic layer, and a high refractive index layer H ₁ that is the inorganic layer are arranged in this order. The light reflecting film according to any one of claims 1 to 6 and 8 to 12.   The light reflecting film according to claim 1, further comprising an anchor layer disposed between the base material layer and the silver layer.   The backlight unit for liquid crystal display devices containing a light source and the light reflection film as described in any one of Claims 1-18.

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