JP2003279714A - Reflector, side light type back light device using the same, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflector for preventing brightness irregularity due to distorsion in the case that the reflector is excellent in durability at high brightness and further the distortion occurs on the reflector, and to provide a side light type back light device incorporating the reflector, and a liquid crystal display. <P>SOLUTION: In the reflector comprising at least a substrate and a reflective layer, a rate of a diffusion reflectance (diffusion ratio) to an entire reflectance is 1-50%, a thermal contraction rate of the substrate at 80°C is 0.5% or less, and a tension elastic modulus is 2000 MPa or greater. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflector having high reflectance and high luminance and little unevenness in luminance, and a sidelight type backlight device and a liquid crystal display device applied to a liquid crystal display device using the same. .

[0002]

2. Description of the Related Art Liquid crystal displays have been used in conventional CRTs (Ca
thode Ray Tube) Compared with displays, it is thinner and saves space, operates at low voltage, consumes less power, and saves energy.
Widely used for displays of small and medium-sized equipment.

A liquid crystal display that is widely used at present is a transmissive liquid crystal display that uses a backlight as a light source. The visibility of the display on the liquid crystal display depends not only on the performance of the liquid crystal itself but also on the performance of the backlight. In recent years, the backlight system requires lighter and thinner LCDs, the brightness is uniform, and heat from the light source is difficult to transfer to the LCD panel. Instead of a direct type in which a reflection plate is placed on, a side light type backlight is often used in which a light guide plate is used and a surface light source is obtained by multiple reflection of light from a light source arranged at one end thereof.

A diffuse reflection member made of a white PET (polyethylene terephthalate) film or the like is often provided under the light guide plate. By diffusing light with this diffuse reflection member, uniform brightness can be obtained. I can. However, this irregular reflection member has almost no regular reflection component, and thus there is a problem that sufficient brightness cannot be obtained although it is uniform as a whole. When a sheet obtained by vapor-depositing aluminum on a PET film having transparency or translucency is used, the brightness is improved as compared with white PET, but since there is no diffuse reflection component, slight distortion of the sheet causes a large unevenness in brightness. It will affect and you will not be able to get a beautiful image. In order to solve this problem, a sheet in which a metal is vapor-deposited on a film having a roughened surface has been developed. When aluminum is used as the metal used, the durability is excellent but the brightness is not so high. Further, when silver having the highest reflectance in the visible light region is used, sufficient brightness can be obtained, but since silver has poor durability, there is a problem that the deterioration is rapid and the brightness decreases with time. . Further, the backlight using these reflection sheets has a problem that the brightness unevenness increases with time.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a reflector having high brightness and excellent durability and capable of preventing uneven brightness due to the distortion when the reflector is distorted, and the reflector incorporated therein. It is an object of the present invention to provide a sidelight type backlight device and a liquid crystal display device.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have conducted a reflector having a substrate having a low heat shrinkage and a reflective layer and having an appropriate diffuse reflectance. By installing it on the lower surface of the light guide plate with a specific gap between the light plate and the reflective layer on the reflector, it is possible to eliminate or significantly reduce the uneven brightness, and to achieve high brightness and durability at the same time. I found it.

In the present invention, the ratio of the diffuse reflectance (diffusivity) to the total reflectance of at least the substrate and the reflective layer is 1%.
A reflector having a heat shrinkage of not more than 0.5% at 80 ° C. and a tensile elastic modulus of not less than 2000 MPa at 80 ° C. of the substrate.

According to the present invention, when it is provided for a backlight of a liquid crystal display device or the like by having an appropriate diffusion rate,
It is possible to eliminate or significantly reduce the brightness unevenness, and simultaneously achieve high brightness and durability. Further, the present invention is characterized in that the substrate is a polymer film.

According to the present invention, a reflector having a high degree of freedom in shape and good productivity can be realized. Further, the present invention is characterized in that the total reflectance at a wavelength of 550 nm is 90% or more and the diffuse reflectance is 10% or less.

According to the present invention, it is possible to realize a reflectance suitable for human's light receiving sensitivity. Further, in the present invention, the maximum width is 0.1 μm to 50 μm and the height is 0.1 μm to 45 μm on the reflective layer side.
The number of protrusions is 2 to 100 per 1 mm ² .

According to the present invention, an optimum diffusion rate can be realized. In the present invention, the maximum width of the protrusion is 10 μm to 5 μm.
It is preferable that the thickness is 0 μm and the height is 5 μm to 45 μm.

According to the present invention, the optimum spreading factor can be realized. Further, in the invention, the reflection layer is (a) an underlayer,
It is preferable that (b) a metal layer mainly composed of silver and (c) a protective layer are laminated at least in the order of (a), (b) and (c).

According to the present invention, a reflector having high reflectivity and excellent durability can be formed. Further, the present invention is
(A) The underlayer is composed of a single metal selected from gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, indium, manganese, titanium, or palladium and / or two or more of these metals. It is preferable that the alloy is a metal layer having a thickness of 5 nm to 50 nm and / or a transparent oxide, and a transparent oxide layer having a thickness of 1 nm to 20 nm.

According to the present invention, a sufficient barrier effect can be obtained, and no aggregation occurs during the formation of a metal layer composed mainly of silver.
Also, the adhesion between the substrate and the reflective layer is excellent. Further, in the present invention, (b) the metal layer mainly composed of silver is composed of silver alone or
As impurities, gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, indium,
A material containing at least one metal selected from manganese, titanium, and palladium, or an alloy mainly composed of silver and having a thickness of 70 nm or more and 400 n
It is preferably m or less.

According to the present invention, a desired reflectance can be realized. Further, in the present invention, (c) the protective layer is a simple substance of a metal selected from gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, indium, manganese, titanium, or palladium and / or these. An alloy consisting of two or more of the above and having a thickness of 5 nm or more 5
A metal layer and / or a transparent oxide having a thickness of 0 nm or less, and a transparent oxide layer having a thickness of 1 nm or more and 20 nm or less are preferable.

According to the present invention, a sufficient barrier effect can be obtained, and no aggregation occurs during the formation of the metal layer mainly containing silver. Further, the present invention is a sidelight type backlight device, wherein the reflector is arranged on a lower surface of a light guide plate that emits light incident from a light source installed on a side surface to an upper surface.

According to the present invention, when it is provided in a backlight of a liquid crystal display device or the like by having an appropriate diffusivity,
It is possible to eliminate or significantly reduce the brightness unevenness and simultaneously achieve high brightness and durability. Further, in the present invention, it is a preferable aspect to dispose the reflector so that the reflection layer is on the light guide plate side.

According to the present invention, it is possible to easily control the distance between the light guide plate and the reflective layer by the protrusion. Further, the present invention is a liquid crystal display device including the above sidelight type backlight device. According to the present invention, while eliminating or significantly reducing the uneven brightness,
It is possible to provide a liquid crystal display device that achieves high brightness and durability at the same time.

In the sidelight type backlight device incorporating the reflector using the reflector substrate of the present invention, even if the reflector is distorted, the unevenness in brightness due to the distortion does not occur. By providing the backlight device, a liquid crystal display with high visibility can be provided. In addition, since the reflector has higher brightness than the conventional reflector and is excellent in durability,
Since the uniform and high-luminance light can be obtained, the display capability of the liquid crystal can be improved, so that the industrial significance of the present invention is great.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. In this specification, the surface of the substrate on which the reflective layer is formed, which will be described later, may be referred to as A surface, and the opposite surface may be referred to as B surface. FIG. 1 is a cross-sectional view showing an example of a reflector 1 which is an embodiment of the present invention. The reflector of the present invention comprises a substrate 10 and a reflective layer 20, and has particles 3 on the A surface side.
0 is applied to form protrusions, and the easy sliding surface 40 is formed on the B surface side. FIG. 2 is a perspective view of the sidelight type backlight device 2 including the reflector 1. In the sidelight type backlight device 2, the reflector 1 is arranged on the back surface of the light guide plate 80 so that the reflection layer 20 is in contact therewith, and the light source 60 and the lamp reflector 70 are provided on the side surfaces. Light from the light source 60 is reflected by the reflector 1 and mounted on the back surface of the liquid crystal display panel to function as a surface light source device.

In the present invention, at least A of the reflector 1 is used.
Wavelength 550 of the reflectance measured from either the surface side or the B surface side
Ratio of diffuse reflectance and total reflectance in nm (diffuse reflectance /
Total reflectance: diffusivity) is 1 to 50%, preferably 1
-20%, particularly preferably 1-17%, more preferably 1-15%. Also, the total reflectance is usually 85% or more,
It is preferably 90% or more, particularly preferably 90 to 99%, and the diffuse reflectance is 50% or less, preferably 20% or less, more preferably 17% or less, particularly preferably 1 to 1
It is 0%. It should be noted that 550 nm is the wavelength at which the light reception sensitivity of the human eye is highest, and is suitable for evaluating the actual visibility.

The substrate 10 has a heat shrinkage rate of 0.5% or less, preferably 0.4% or less at 80 ° C. for 2 minutes, and a tensile elastic modulus of 2000 MPa or more, preferably 2500.
MPa or more, more preferably 3000 MPa or more, and particularly preferably 3500 MPa or more. The heat shrinkage ratio is mainly measured according to JIS K 6714 standard, and the tensile elastic modulus is mainly measured according to ASTM D-882 standard. Specifically, a physically or chemically stable plate-like material such as a glass plate or a ceramic plate, a sheet-like inorganic material, an organic material such as a polymer sheet or a polymer film, and the like are appropriately used. Among these, a polymer film having a high degree of freedom in shape and to which a roll-to-roll process can be applied when forming the reflection layer 20 is desirable.

In the reflector 1 of the present invention, preferred polymer films to be used are, for example, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polycarbonates such as bisphenol A-based polycarbonate, cyclic olefin copolymers, Polyimides, polyamides such as nylon, polyether sulfone, polysulfone-based resins, polyarylate-based resins, fluororesins, polyether-terketones, films made of various plastics such as polyacetals such as Poval, but not necessarily these However, it is not limited to the above, and any material having a high crystallization temperature or glass transition point and a smooth surface can be used. Among them, polyesters such as polyethylene terephthalate, polycarbonates and polyamides are preferable.

The thickness of the polymer film used is usually 1 to 250 μm, preferably 5 to 200 μm,
Particularly preferably, it is 10 to 200 μm. The reflector 1 of the present invention preferably has a protrusion on the surface of the substrate 10 on which the later-described reflective layer 20 is provided. The above protrusions can be formed directly on the substrate 10, or a separately formed protrusion layer film or sheet can be attached to the substrate 10. It can also be formed on the reflective layer 20 described later.

The maximum width of the above-mentioned protrusion is 0.1 to 50 μm.
And preferably 1 to 50 μm, more preferably 10
˜50 μm, more preferably 15 to 45 μm, and particularly preferably 20 to 40 μm. The height of the protrusions is 0.1 to 45 μm, preferably 1 to 45 μm.
m, more preferably 5 to 45 μm, still more preferably 10
-40 μm, particularly preferably 15-35 μm. The shape of the protrusion is not particularly limited, and examples thereof include particle type, dome type, mountain type, pyramid type, columnar type, prismatic type, trapezoidal type, prism type, and amorphous type. Further, it may have a single-stage shape or a multi-stage shape, and these shapes may be mixed or combined in multiple stages. The number of protrusions is preferably 2 or more and 100 or less per 1 mm ² , and more preferably 5 or more and 90 or less.

The method for producing these projections is not particularly limited, but (1) a method of applying solid matter such as particles, (2) kneading the solid matter such as particles with a resin to form a film or sheet. Forming method, (3) a method of spraying a solid material such as particles onto a semi-molten film or sheet and then cooling and fixing, (4) a method of forming protrusions using a printing technique such as screen printing , (5) a method of transferring the uneven shape of the roll as a protrusion by using a cooling roll having an uneven shape when the thermoplastic resin is molded into a sheet or film, (6) forming using a micro mold A method (7) such as sandblasting, a method having a friction step, (8) a method of forming using photolithography, (9) a method of forming using an etching method, and the like can be applied. It is also possible to deform the protrusions obtained by the above method by heat treatment or the like.

Among the above methods for forming the projections, the method for forming the projections by coating the particles 30 is preferable because the surface condition is relatively easy to adjust. As the particles to be applied, for example, acrylic, polystyrene, vinylbenzene, styrene methacrylate, styrene acrylate,
Polymer (organic) particles such as styrene-butadiene,
Inorganic fine particles composed of silica, alumina, titania, zirconia, lead oxide (white lead), zinc oxide (zinc white), calcium carbonate, barium carbonate, barium sulfate, potassium titanate, sodium silicate, etc., tin oxide, indium oxide ,
Conductive transparent fine particles such as cadmium oxide and antimony oxide can also be used, but are not necessarily limited thereto. It is particularly preferable to use acrylic resin or silica.

The particles 30 applied in the present invention have an average particle diameter of 0.1 to 50 μm, preferably 1 to 50 μm.
m, more preferably 10 to 50 μm, still more preferably 1
It is preferred to use particles of 5-45 μm, particularly preferably 20-40 μm. The particle size distribution of the particles 30 is preferably small, and the ratio of the standard deviation of the particle size to the average particle size is preferably 50% or less. More preferably, it is 40% or less. However, two or more kinds of particles can be used if necessary. In this case, the proportion of the main component particles is 50% or more, preferably 70% or more, more preferably 75% or more, and particularly preferably 80% or more.

The average particle size distribution can be determined by measuring the solution in which a small amount of particles are dispersed by the dynamic light scattering method. In addition, SEM (Scanning E
lectron Microscope) It can also be obtained from the particle size of 100 particles randomly selected from the photograph. The particle size is S
It can be read by using an optical microscope in addition to the EM photograph. The particle size distribution can also be obtained by subjecting the obtained photograph or image to image processing.

The particles 30 are usually applied in a state of being dispersed in a resin used as a binder. Examples of the binder resin include acrylic resins such as polymethylmethacrylate, polyacrylonitrile resins, polymethacrylonitrile resins, silicon resins such as polymers obtained from ethyl silicate, fluorine resins, polyester resins, polystyrene resins, acetate resins. Resins, polyether sulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, polyurethane-based resins, urea resins, melamine resins, epoxy resins, and mixtures thereof, but these are not always required. It is not limited to. These are substrate 1
0 and the adhesion with the particles 30 are taken into consideration. Of these, polyester resins and acrylic resins are preferable.

A solvent is usually used to disperse the particles 30 in the binder resin. As the solvent, toluene, methyl ethyl ketone, ethyl acetate, isopropyl alcohol and the like are preferably used. These are solvents that are generally used in the coating operation, and other solvents that do not affect the substrate 10 and the particles 30 can be used without problems. Further, if necessary, a crosslinking agent such as isocyantanates and melamines, a wetting agent and a thickener, a dispersant,
You may add additives, such as a defoaming agent.

The mixing ratio of the particles 30 to the binder resin is preferably 0.1 wt% to 10 wt% of the particles 30 to the binder resin. The mixing ratio is
If it is less than 0.1 wt%, it is not preferable because the necessary diffusion characteristics of reflected light cannot be obtained. On the other hand, if it is more than 10 wt%, the light diffusivity becomes too strong, which is not preferable.

The coating liquid containing the particles 30 is deposited on the substrate 10 as w.
It is preferable to apply a coating amount of 10 g / m ² or more and 40 g / m ² in an et state. The blending ratio of the particles is reflected in the particle density on the surface of the reflector 1 and affects the diffusivity of the reflector 1. Further, the coating amount is reflected on the thickness of the binder layer on the substrate 10, and affects the height difference between the tops of the particles 30 and the reflective layer 20, that is, the distance when the light guide plate 50 and the reflector 1 are in contact with each other. . When the amount of the coating liquid is less than 10 g / m ^2, the amount of the particles 30 contained in the coating liquid becomes insufficient, and the necessary diffusion characteristics of reflected light may not be obtained, which is not preferable. Further, when the coating liquid amount is larger than 40 g / m ² , the particles 3
0 is buried in the binder resin, and the required protrusion height may not be obtained, which is not preferable. That is, by adjusting the particle blending amount and the coating amount of the coating liquid within the above range,
Two or more and 100 or less protrusions can be obtained per 1 mm ² on the substrate 10. Further, the height of the protrusions from the surface of the binder resin to the top of the particles can be easily measured with a tactile roughness meter or a surface shape measuring device.

As a method of applying the mixed solution containing the particles 30 and the binder resin to the substrate 10, it is possible to apply over a wide viscosity range, the thickness of the coating film can be adjusted during coating, and the coating film can be adjusted. There are roll coater method and reverse roll coater method, which have the feature that the thickness can be changed drastically. There is relatively no need for operating technology, the coating thickness is uniform even with a wide width, and thin film coating is possible. Examples include the characteristic clavia coater method, high-speed coating, high productivity, die coating (extrusion) method, which has characteristics such as uniform coating thickness and wide range of coating. Can realize the above-mentioned protrusion density and protrusion height.

As another preferable method of forming the protrusions, a method of adding particles to the polymer film which is the substrate 10 may be used. As the particles used in the method of adding particles, the same materials as the particles described in the above coating method can be used.

These particles may be kneaded with a resin in a molten state to form a film or sheet, or the above particles may be dispersed on a film or sheet in a semi-molten state, and pressed and cooled as necessary. The particles can be fixed by and the projection layer can be formed.

As a method of forming protrusions in printing, screen printing using an ultraviolet (UV) curable resin is preferably used. Specifically, it is a method of imprinting a UV curable resin through a mesh (screen) and then exposing it to cure the resin. This method has a feature that relatively high protrusions (height 10 to 30 μm) can be formed on objects of various shapes.

The reflector 1 of the present invention can be obtained, for example, by forming the reflective layer 20 on the protrusions produced by the above method. Further, after forming the reflective layer 20 on the substrate 10, it is possible to form protrusions, and it is also possible to further form protrusions on the reflective layer.

The reflective layer 20 is formed in order from the substrate 10 side.
It is preferable that (a) a base layer, (b) a metal layer mainly containing silver, and (c) a protective layer be laminated.

Preferred examples of the underlayer (a) include metal layers and metal oxide layers different from silver.
Specifically, gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, indium,
Manganese, titanium, palladium, zirconium, bismuth, tin, zinc, antimony, cerium, neodymium,
Simple metals such as lanthanum, thorium, magnesium and gallium, or alloys of two or more kinds, indium,
Examples thereof include oxides of titanium, zirconium, bismuth, tin, zinc, antimony, tantalum, cerium, neodymium, lanthanum, thorium, magnesium, gallium, mixtures of these oxides, and metal compounds such as zinc sulfide.
Among these, gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, indium, manganese, titanium, palladium alone, or an alloy composed of two or more of these, zinc oxide, indium oxide, tin oxide, oxidation Silicon is preferable, and zinc oxide doped with 5% by weight or less of aluminum oxide, zinc oxide doped with 10% by weight or less of gallium, an oxide of indium and tin (ITO), or a transparent material such as silicon dioxide is preferable. An oxide having a light-transmitting property and a light-transmitting property can be given. Also, two or more of these may be combined or used in a multilayer structure.

(B) In the metal layer mainly composed of silver, a small amount of simple substance of silver, or gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, indium, manganese, titanium, palladium, etc. as impurities. An alloy containing silver or an alloy mainly composed of silver is preferably used. The content of these impurities varies depending on the type of metal, but is 0.002 to 8% by weight, preferably 0.004 to 5% by weight, particularly preferably 0.005 to 4% by weight.
% By weight.

(C) In the protective layer, in addition to the same metals and oxides as those used in (a) the underlayer, two or more kinds selected from these and alloys mainly containing silver may be used in combination or in a multilayer structure. I can.

Among these, metal oxides, preferably
Indium, titanium, zirconium, bismuth, tin,
Zinc, antimony, tantalum, cerium, neodymium,
Oxides of lanthanum, thorium, magnesium, gallium and the like, mixtures of these oxides, particularly preferably zinc oxide doped with aluminum oxide at 5 wt% or less, zinc oxide and indium doped with gallium at 10 wt% or less. A transparent oxide such as an oxide with tin (ITO) or silicon dioxide is used.

There are a wet method and a dry method as a method of forming the above-mentioned underlayer, the metal layer mainly containing silver and the metal thin film layer which is a protective layer. The wet method is a general term for a plating method and is a method for forming a film by precipitating a metal from a solution. Specific examples include silver mirror reaction. On the other hand, the dry method is a general term for vacuum film forming methods, and specific examples thereof include a resistance heating vacuum evaporation method, an electron beam heating vacuum evaporation method, an ion plating method, and an ion beam assisted vacuum evaporation method. , Sputtering method, etc. In particular, a vacuum film forming method capable of a roll-to-roll method of continuously forming a film is preferably used in the present invention.

In the vacuum deposition method, the metal raw material is melted by electron beam, resistance heating, induction heating or the like to increase the vapor pressure, and preferably 13.3 mPa (0.1 mTorr).
Below, the surface of the substrate is evaporated. At this time, a gas such as argon may be introduced at 13.3 mPa or more to cause high frequency or direct current glow discharge.

As the sputtering method, a DC magnetron sputtering method, an RF magnetron sputtering method, an ion beam sputtering method, an ECR sputtering method, a conventional RF sputtering method, a conventional DC sputtering method or the like is used. In the sputtering method, a metal plate-shaped target may be used as a raw material, and helium, neon, argon, krypton, xenon, or the like is used as a sputtering gas, but argon is preferably used. The gas purity is preferably 99% or higher, more preferably 99.5% or higher. A vacuum film forming method is preferably used for forming the transparent oxide film. A sputtering method is mainly used, and helium, neon, argon, krypton, xenon, or the like is used as a sputtering gas, and oxygen gas may be used depending on conditions.

The above-mentioned (a) underlayer, (b) silver-based layer, and (c) protective layer are laminated in the order of (a), (b), and (c), but are not limited to three layers. None (a) (b)
(C) (b) (c) (a) (b) (c) (b) (a)
The outermost layer as in (b) and (c) may be a multi-layer structure as long as it is a protective layer, but since the production efficiency tends to decrease as the number of layers increases, it is preferably 3 to 20 layers. Three
~ 15 layers.

The thickness of the thin film formed on the protrusions or the substrate is determined in consideration of the light transmittance of less than 1% when the reflector 1 is constructed. The thickness of each layer in the reflective layer of the present invention is preferably as follows. When the metal layer is used, the thickness of the underlayer (a) is preferably 5 nm or more and 50 nm or less, more preferably 5 nm or more and 30 nm or less. When the thickness of the layer is less than 5 nm, the desired barrier effect may not be obtained, and (b) the metal layer mainly composed of silver may cause aggregation. Also, 50
There is no change in the effect even if the thickness is thicker than nm. When a transparent oxide is used, the thickness of the transparent oxide layer is preferably 1 nm or more and 20 nm or less, more preferably 5 nm.
It is 10 nm or less. Thickness of transparent oxide layer is 1 nm
If it is thinner, the desired barrier effect cannot be obtained,
(B) Aggregation is generated in the metal layer mainly composed of silver. Further, even if the thickness is more than 10 nm, there is no change in the effect.

(B) The thickness of the metal layer mainly composed of silver is 7
It is preferably 0 nm or more and 400 nm or less, more preferably 100 nm or more and 300 nm or less, further preferably 13
It is 0 nm or more and 250 nm or less. When the thickness of the layer containing silver as a main component is smaller than 70 nm, the desired reflectance may not be obtained in some cases because a sufficient metal layer has not been formed. Further, even if the thickness is more than 400 nm, there is no change in the effect.

(C) The thickness of the protective layer is preferably 5 nm or more and 50 nm or less, and more preferably 5 nm or more and 30 nm or less when a metal layer is used. The thickness of the layer is 5 nm
If it is thinner, the desired barrier effect cannot be obtained,
(B) Aggregation may occur in the metal layer mainly composed of silver. Further, even if the thickness is more than 50 nm, there is no change in the effect. When a transparent oxide is used, the thickness of the layer is
It is preferably 1 nm or more and 20 nm or less, and more preferably 5 or more and 10 nm or less. When the thickness of the transparent oxide layer is less than 1 nm, the desired barrier effect cannot be obtained, and (b) the metal layer mainly containing silver is agglomerated.
Further, even if the thickness is more than 10 nm, there is no change in the effect.

As a method of measuring the film thickness of each layer, there are methods such as a stylus roughness meter, a repetitive reflection interferometer, a microbalance and a crystal oscillator method. Is suitable for obtaining a desired film thickness. Further, there is also a method in which the conditions for film formation are determined in advance, the film is formed on the sample substrate, the relationship between the film formation time and the film thickness is investigated, and then the film thickness is controlled by the film formation time.

Since the reflector of the present invention uses a substrate having a low heat shrinkage and a high tensile elasticity, it has little dimensional change due to heat or the like even when used in a sidelight type backlight device described later, and an uneven layer. It is considered that the increase in uneven brightness over time is suppressed because it is not affected by the distortion of the resin.

In the sidelight type backlight device 2 of the present invention, the reflector 1 manufactured as described above is arranged on the lower surface of the light guide plate 50, and the metal thin film layer side or the substrate 10 side is set as the upper surface. And As the backlight device, any device generally used as a side light type may be used.

The light guide plate 50 used is, for example, an acrylic resin such as polymethylmethacrylate, a polycarbonate resin such as polycarbonate or a polycarbonate / polystyrene composition, a transparent or translucent resin such as an epoxy resin, or glass. About 400nm-700
A material having transparency in the wavelength range of nm is preferably used, but the material is not necessarily limited to these as long as the material exhibits transparency depending on the wavelength range of the light source.
Further, the thickness of the light guide plate 50 can be appropriately determined depending on the size of the light guide plate to be used, the size of the light source, and the like.

Examples of the light source 60 to be used include an incandescent light bulb, a light emitting diode (LED), an electroluminescence (EL), a fluorescent lamp, a metal hydride lamp, and the like, and a fluorescent lamp is preferably used. Fluorescent lamps are roughly classified into a hot cathode type and a cold cathode type according to their electrode structure and lighting system, and the hot cathode type tends to be larger in both electrodes and inverters. The hot-cathode type has a small electrical decoration loss in the vicinity of the electrode that does not contribute to light emission and is highly efficient, and exhibits luminous efficiency several times superior to that of the cold-cathode type. Therefore, the cold cathode type is more preferably used in terms of low power consumption and durability.

In the sidelight type backlight device 2 of the present invention, surprisingly, the unevenness of brightness is suppressed by disposing the reflector 1 at a specific interval between the light guide plate 50 and the reflective layer 20. Can be done. Specifically, this distance is the distance between the concave portion of the reflective layer 20 and the light guide plate 50 as viewed from the light guide plate 50. Normally, since the light guide plate 50 and the reflector 1 of the present invention are in direct contact with each other, this distance can be controlled by the height of the protrusion when the surface A is arranged on the light guide plate 50 side, and the surface B is on the light guide plate side. In the case of arranging in the above, it can be controlled by the thickness of the substrate 10 and the height of the protrusions. It is also possible to adjust the distance by inserting a spacer or the like between them. This interval is 5 μm or more, preferably 10 μm or more, more preferably 10 to 100 μm, particularly preferably 10 to 90 μm.
m, and more preferably 15 to 85 μm.

Of these arrangements, the method of arranging the A-plane on the accompanying plate 50 is more preferable. The reflector 1 and the reflector substrate 10 of the present invention may have a surface (B surface) on the substrate side that is subjected to an easy slip treatment. The slippery treatment improves workability in assembling the liquid crystal display device.

The method of slippery treatment is not particularly limited, but specifically, a method of applying a coating liquid containing fine particles and a method of forming irregularities closer to embossing. It is possible to use a sandblasting method in which particles of silica or the like are blown onto the surface of the substrate 10 together with high-pressure air, a chemical method such as etching, or the like. Among these, the method of applying the coating liquid is preferably used.

In the sidelight type backlight device of the present invention, by using the reflector 1 produced by the above-mentioned method, even if the reflecting surface is distorted, uneven brightness is unlikely to occur, and As a result, it is possible to significantly improve the brightness as compared with the conventional device.

[0060]

EXAMPLES The present invention will be specifically described below with reference to examples. First, the case where the surface A side of the reflector 1 is arranged on the light guide plate 50 and the distance between the light guide plate 50 and the reflection layer 20 is controlled by the height of the protrusion will be described.

Example 1 6 parts of acrylic particles having an average particle diameter of 30 μm as particles to form protrusions, 100 parts of polyester resin (Tg: 20 ° C., molecular weight: 50,000) as a binder resin, and aliphatic isocyanate as a curing agent. 20 parts, the blending amount of the particles with respect to the binder resin is 6.0 wt%, and the solution is prepared using a solvent composed of toluene and ethyl methyl ketone so that the solid content ratio is 24 wt%, and then the thickness is 188.
Coating was performed on a PET film (heat shrinkage rate ≦ 0.1%, tensile elastic modulus: 4500 MPa) of μm to obtain a protrusion on the A side. Next, acrylic particles having an average particle diameter of 1.5 μm and acrylic / melamine resin as a binder resin were used.
A solution was prepared by using a solvent consisting of toluene and ethyl methyl ketone so that the solid content ratio was 15% by weight, and then applied to the B side of the PET film to obtain an easy-sliding surface. Next, zinc oxide (purity: 9%) doped with 2% of Al ₂ O ₃ was applied to the A side by DC magnetron sputtering.
9.9%) as a target, and using argon having a purity of 99.5% as a sputtering gas, a base layer was formed to have a film thickness of zinc oxide of 5 nm. Subsequently, without taking out this film from the sputtering apparatus, similarly using the DC magnetron sputtering method, targeting silver having a purity of 99.9%, using argon having a purity of 99.5% as a sputtering gas, and making the silver film thickness 200 nm. Was molded so that Then, without removing this film from the sputtering device, DC
In the magnetron sputtering method, zinc oxide (purity 99.9%) doped with 2% Al ₂ O ₃ is used as a target, and argon 99.5% in purity is used as the sputtering gas so that the thickness of zinc oxide is 5 nm. A protective layer was formed on the substrate to obtain a desired reflector 1 as shown in FIG. This reflector 1 was installed on a Hitachi autograph spectrophotometer (type U-3400) with an integrating sphere of 150φ, and each reflectance at a wavelength of 550 nm was measured from the metal layer side. The total reflectance and the diffuse reflectance were 96, respectively. It was 0.4% and 5.0%, and the diffusion rate was 5.2%. Next, measure the height of the protrusion on the A side with the surface shape measuring device (D
When measured at 10 points with EKTAK3: manufactured by Veeco), the average value was 25.8 μm, and when the maximum width was measured at 10 points with an optical microscope, the average value was 31.2 μm. Further, the maximum width of 20 to 40 μm per 1 mm ² ,
There were 25 particles having a height of 15 to 35 μm. After the measurement, the reflector 1 is put in a constant temperature and humidity chamber, and the temperature is 60 ° C. and 90% RH.
It was left for 500 hours under the moist heat condition. After 500 hours,
When the reflector 1 was taken out and the surface was observed, metal aggregation was not observed. In addition, as a result of measuring the total reflectance and the diffuse reflectance with a spectrophotometer again, the reflectance was 96.0.
%, The diffuse reflectance was 5.4%, which was almost the same as before wet heat. Further, the reflector 1 was set on the lower surface of the light guide plate 50 so that the metal layer side faced up, and the sidelight type backlight device 2 as shown in FIG. 2 was obtained. In this state, the light source 60
Is turned on, and the brightness obtained in the front direction at the center of the surface is measured, and when the set reflector 1 is intentionally distorted or when the surface light source is left in a wet heat layer at 60 ° C. and 90% for 500 hours. Table 1 shows the results of observation of uneven brightness.

Example 2 A reflector was obtained in the same manner as in Example 1 except that acrylic particles having an average particle diameter of 35 μm were used as the particles to be the protrusions.
An evaluation was made. The results are shown in Table 1.

Example 3 PET film having a thickness of 188 μm (heat shrinkage ratio ≦ 0.1%,
On the surface A side above the tensile elastic modulus: 4500 MPa, DC
In the magnetron sputtering method, zinc oxide (purity 99.9%) doped with 2% Al ₂ O ₃ is used as a target, and argon 99.5% in purity is used as a sputtering gas to form the zinc oxide film having a thickness of 5 nm. Thus, the underlayer was formed. Subsequently, without removing this film from the sputtering apparatus, the purity was 99.
Using 9% silver as a target, argon having a purity of 99.5% was used as a sputtering gas, and silver was formed to have a film thickness of 150 nm. Subsequently, the film was removed by a DC magnetron sputtering method without removing it from the sputtering device.
% Al ₂ O ₃ -doped zinc oxide (purity 99.9
%) As a target, using argon having a purity of 99.5% as a sputtering gas, and forming a protective layer of zinc oxide so as to have a film thickness of 5 nm to form a reflective layer 20.

Subsequently, a coating liquid containing acrylic particles and a binder resin was applied to the sputtered surface in the same manner as in Example 1 to obtain protrusions. When the protrusions were observed with a microscope, 20 particles were confirmed per 1 mm ² .

Next, in the same manner as in Example 1, coating was performed on the B surface side of the PET film to obtain a desired reflector as shown in FIG. The results are shown in Table 1.

[Table 1] Comparative Example 1 Cellophane laminated with polyethylene instead of PET (heat shrinkage: 0.8%, tensile elastic modulus 800MP
a, thickness: 150 μm) A reflector was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a reflector 1 according to the present invention.

FIG. 2 is an example of a sidelight type backlight device 2 of the present invention.

FIG. 3 is a cross-sectional view showing an example of a reflector 1 according to the present invention. (Explanation of Codes) 10 Substrate 20 Reflective Layer 30 Particles 40 Easy Sliding Surface 50 Reflector 60 Light Source 70 Lamp Reflector 80 Light Guide Plate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hirotaka Yoshida             32 Mitsui Chemicals, 580 Nagaura, Sodegaura City, Chiba Prefecture             Within the corporation (72) Inventor Shin Fukuda             32 Mitsui Chemicals, 580 Nagaura, Sodegaura City, Chiba Prefecture             Within the corporation F-term (reference) 2H042 BA02 BA03 BA15 BA20 DA04                       DA11 DA15 DA18 DA21 DB08                       DC02 DC08 DD00 DE00                 2H091 FA14 FA23 FA41 FB02 LA18

Claims (6)

[Claims] 1. The ratio (diffusivity) of the diffused reflectivity to the total reflectivity of at least the substrate and the reflective layer is 1% to 5;
A 0% reflector having a thermal shrinkage of 0.5% or less at 80 ° C. and a tensile modulus of 2000.
A reflector having a pressure of at least MPa. 2. The reflector according to claim 1, wherein the substrate is a polymer film. 3. The total reflectance at a wavelength of 550 nm is 90.
% Or more and diffuse reflectance is 10% or less, The reflector of Claim 1 characterized by the above-mentioned. 4. A maximum width of 0.1 μm to 50 on the reflective layer side.
The reflector according to claim 1 or 3, wherein the number of the protrusions having a size of µm and the height of 0.1 µm to 45 µm is 2 or more and 100 or less per 1 mm ² . 5. A side characterized in that the reflector according to any one of claims 1 to 4 is disposed on a lower surface of a light guide plate that emits light incident from a light source installed on a side surface to an upper surface. Light type backlight device. 6. A liquid crystal display device comprising the sidelight type backlight device according to claim 5.