JP2001296410A - Reflecting sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper white type reflecting sheet which is brighter than a conventional one and has high durability when used in a reflective liquid crystal display. SOLUTION: A base layer, a silver-base metallic layer and a silicon oxide layer are successively disposed on a rugged layer formed on a polymer film by coating the film with fine particles and a binder in such a way that the weight of the film is adjusted to a specified weight range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reflection sheet used for a reflection type liquid crystal display device. For more information,
The present invention relates to a reflection sheet used for a reflection type liquid crystal display device such as a mobile phone, a PHS, an electronic organizer, a portable information terminal, an electronic calculator, and various operation panels.

[0002]

2. Description of the Related Art Liquid crystal display devices are small and space-saving, operate at a low voltage, consume little power and can save energy, and are used to display small and medium-sized devices as compared with conventional CRT displays. Widely used in the center. Above all, reflective liquid crystal has lower power consumption than transmissive liquid crystal display devices that always use a backlight, so it is used for mobile phones, PHS, electronic organizers, personal digital assistants, electronic calculators, and various operation panels. ing. At present, a reflection type liquid crystal display device for black and white display, which is mainly used, is composed of a polarizing plate, a liquid crystal display panel, a polarizing plate, and a reflecting sheet from the human side. In a reflective type color liquid crystal display device which is expected to increase in the future, a color filter may be used in addition to the above members. In addition, in the reflection type color liquid crystal display device, a device without a polarizing plate on the reflector side or a device without any polarizing plate has been devised.

[0003] An ideal liquid crystal display is a display which is bright and has a similar display quality from any point of view, and is said to be a printed matter such as a book which we usually use. I have. Therefore, it is considered that a reflection sheet (paper white type) that uniformly diffuses light in all directions like paper is also preferable for the reflection sheet used in the reflection type liquid crystal display device. However, in a liquid crystal display device,
Generally, because of the configuration described above, the incident light passes through the polarizing plate → the liquid crystal display panel → the polarizing plate, and after reaching the reflecting sheet, the light reflected by the reflecting sheet is again polarized light → the liquid crystal display panel → the polarizing plate. , And reaches the outside, the amount of reflected light with respect to the incident light becomes 3 in consideration of light loss.
There was a problem that it fell to less than one-half and became dark. Further, in the color reflection type liquid crystal display device, since a color filter is also used, the reflected light may be further reduced. Therefore, if a reflection sheet that uniformly diffuses light is used in a liquid crystal display device, it becomes darker and cannot be used.

At present, a bright display is realized by concentrating light in a certain range by using a reflection sheet having a metallic reflection and a large specular reflection component. However, such a reflection sheet having a large specular reflection component is very bright when the incident angle of light and the viewing angle (reception angle) match, but becomes dark at a stretch when the viewing angle (reception angle) deviates. That is, there is a disadvantage that the viewing angle is narrow. To widen the viewing angle, it is necessary to increase the diffusion component. However, increasing the diffusion component increases the intensity of the concentrated light, resulting in a problem that the entire image becomes dark. In order to widen the viewing angle, it is necessary to control the reflection characteristics (concentration and dispersion of light) of the reflector, and many studies have been made so far. As a method of controlling the reflection characteristics of the reflector, a method of making a substrate (polymer film) forming a reflection surface (metal thin film layer) uneven is generally used.

[0005] As roughening method, (1) forming an uneven structure embossed on the polymer film surface, a method of smoothing by treating the surface with a solvent, SiO ₂ in (2) a polymer film surface And (3) a chemical method such as an etching method. However,
In the methods (1) and (2), since the uneven shape is formed on the film surface by a mechanical and physical method, the width of the selection of the material of the film must be narrow and the thickness must be increased to some extent. There are drawbacks. In the method ( ₂ ), since the shape of the hard sand (SiO ₂ ) is not uniform, the resulting uneven shape is also severe and unevenly rough. Even if it dissolves, there is a drawback that the roughness cannot be made sufficiently uniform and the resulting uneven structure becomes very uneven. Furthermore, even in the chemical method as in (3), there is a drawback that the selection of the material of the film is severe, and the washing and drying after the treatment are difficult.

At present, these methods have drawbacks in the method of forming the concavo-convex layer itself, and even in the formed concavo-convex layer, the light (luminance) is equal because light is still concentrated in a narrow viewing angle range. The ideal reflection characteristics have not been obtained. Therefore, in order to obtain an ideal reflection characteristic with higher diffusion, it is necessary to use a more controlled uneven surface than before.

[0007] On the other hand, the reflectivity greatly depends on the metal used for the reflective layer. For example, comparing silver and aluminum as examples of commonly used metal layers, when silver is used, the reflectance is 90%.
As described above, the value is 85% or more when aluminum is used, and higher reflectance can be obtained by using silver.
However, with the spread of liquid crystal display devices in recent years, their uses have been diversified, demands under severer use conditions have increased, and long-term durability has been required. Regarding general mounting reliability, 60 ° C. × 90
% RH × 500 hr is required. However, when only silver is used for the reflective layer, a large number of aggregation points are generated on the surface under the above-mentioned medium durability conditions, and the appearance is deteriorated, and the reflectance is reduced. Has the drawback of causing a decrease in

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a paper white type which is brighter than the conventional one when used in a reflection type liquid crystal display device, and has high durability. It is an object to provide a reflection sheet having

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on the structure of the concave-convex structure and the reflection layer. As a result, surprisingly, the weight of the polymer film was reduced. A three-layer structure of an underlayer, a metal layer mainly composed of silver, and a silicon oxide layer is formed in order on an uneven layer formed by applying fine particles and a binder so as to have a specific weight range. As a result, they have found that the above problems can be solved, and have completed the present invention.

That is, the present invention relates to a polymer film (A), a concavo-convex layer (B) mainly composed of a particle layer, an underlayer (C), a metal layer mainly composed of silver (D), and a silicon oxide layer (E). And (E) a reflectance sheet having a reflectance of 85 to 99% at a wavelength of 550 nm measured from the layer side, and the uneven layer (B). Are formed of a binder and a fine particle having an average particle diameter of 1 μm or more and 15 μm or less, and are blended so that the fine particle has a ratio of 5 to 52% by volume with respect to the volume of the uneven layer, and The reflective sheet according to the above, wherein the dry weight (g / cm ² ) of the uneven layer satisfies the condition of the following formula (1). Formula (1): 0.75 × 2r × 10 ² / [p / a + (10
0-p) / b] ≦ dry weight (g / cm ² ) ≦ 2.5 × 2
r × 10 ² / [p / a + (100−p) / b] [However, p = 100 / [1+ (100 / v−1) × b /
a], and r is the average value of the radii of the fine particles used (c
m), p is the ratio of fine particles in the uneven layer (% by weight), v is the ratio of fine particles in the uneven layer (volume%), a is the density of the used fine particles (g / cm ³ ), b is It represents the density (g / cm ³ ) of the binder used. The present invention also provides the reflective sheet according to the above, wherein the fine particles are acrylic particles, the reflective sheet according to the above, wherein the binder is an acrylic resin, The formation layer (C) is a metal layer having a thickness of 5 to 50 nm made of gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, indium, manganese, titanium, or palladium, or aluminum oxide of 0%. ~ 5 wt% doped zinc oxide, or
Indium and tin oxide (ITO)
The reflective sheet according to any one of the above-described items, which is a transparent oxide layer having a thickness of 20 nm, wherein the metal layer (D) mainly composed of silver has a thickness of 70 to 40.
The reflective sheet according to any one of the above, wherein the thickness is 0 nm, and the thickness of the silicon oxide layer (E) is 1 to 50 nm. It is about.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The reflective sheet of the present invention is characterized in that fine particles (hereinafter, also referred to as filler) mainly composed of a specific average particle size are blended in a binder at a specific ratio on a polymer film (A), and a specific dry weight is obtained. After forming a layer (B) having a concavo-convex structure by applying so as to have a weight of
This is a reflection sheet in which a base layer (C) mainly composed of an oxide or a single metal layer, a metal layer (D) mainly composed of silver, and a silicon oxide layer (E) are sequentially formed.

In the reflection sheet of the present invention, the polymer film used as the base material includes, for example, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polycarbonates such as bisphenol A-based polycarbonate, polyethylene,
Polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate, vinyl resins such as polyvinylidene chloride, polyimides, polyamides, polyethersulfone, polysulfone resins, polyarylate resins, and various plastics such as fluororesins. Examples of the film include, but are not limited to, films having a high glass transition point and a smooth surface to some extent. Among them, polyethylene terephthalate is preferred. The thickness of the polymer film used is not particularly limited, but is usually about 10 to 400 μm, preferably 10 to 400 μm.
It is about 200 μm, more preferably about 25-100 μm.

In the present invention, the concavo-convex layer (B) formed on the polymer film is formed mainly of fine particles serving as a filler and a binder. As fine particles serving as a filler, for example, acrylic, polystyrene,
Including polymer (organic) particles such as vinylbenzene, polymethyl methacrylate, styrene methacrylate, styrene acrylate, styrene butadiene, silica, alumina, titania, zirconia, lead oxide (lead white), zinc oxide (zinc white), and carbonic acid Inorganic fine particles such as calcium, barium carbonate, barium sulfate, potassium titanate, and sodium silicate, and conductive transparent fine particles such as tin oxide, indium oxide, cadmium oxide, and antimony oxide can be used. It is not limited. Among them, an acrylic resin is preferable.

The method for preparing the fine particles composed of a polymer includes an emulsion polymerization method, a suspension polymerization method and a dispersion polymerization method. Among them, the emulsion polymerization method is the most common, but in recent years, dispersion polymerization has been actively performed. In any polymerization method, the produced polymer is hardly soluble in the dispersion medium, and is formed into particles by the surface tension between the dispersion medium and the polymer. Polymer particles are
It is stabilized by a protective colloid bonded or adsorbed to the particle surface, and further stabilized by intra-particle crosslinking. Among these methods, in particular, when a dispersion polymerization method is used, there is a feature that particles in a wide range from submicron to several tens of microns can be obtained.

The average particle size of the fine particles serving as a filler for obtaining the desired roughness on the surface of the polymer film is 1 to 15
μm, preferably 2 to 10 μm, and more preferably 3 to 8 μm. If the average particle diameter is less than 1 μm, it becomes difficult to form the surface of the concavo-convex structure by burying the particles,
On the other hand, if it exceeds 15 μm, the undulation of the uneven structure becomes large, and the reflection sheet becomes coarse. It is preferable that the particle size distribution of the fine particles is small. The ratio of the standard deviation of the particle size to the average particle size is preferably 50% or less, more preferably 30% or less, and even more preferably 20% or less.
If the particle size distribution greatly exceeds the above ratio, it is difficult to obtain a controlled uneven structure.

In the present invention, as a binder used, for example, an acrylic resin such as polymethyl methacrylate, a polyacrylonitrile resin, a polymethacrylonitrile resin, a silicon resin such as a polymer obtained from ethylsilicate, a fluorine resin Resin, polyester resin, polystyrene resin, acetate resin, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, polyurethane resin, urea resin, melamine resin, epoxy resin, These include mixtures, but are not necessarily limited to these. These are selected in consideration of the adhesion to the polymer film and the particles, and among them, acrylic resins are preferable.

In the present invention, the concavo-convex layer is formed by applying fine particles as a filler and a binder on a polymer film. At the time of coating, as a solvent for dispersing fine particles as a filler in a binder, toluene, methyl ethyl ketone, ethyl acetate, isopropyl alcohol, and the like are preferably used. These are solvents generally used at the time of the coating operation, and any other solvent that does not affect the base polymer film or the filler fine particles can be used without any problem. Further, additives such as a wetting agent, a thickener, a dispersant, and an antifoaming agent may be added to the coating solution as needed.

The mixing ratio of the fine particles serving as the filler is determined by the solid content (filler + binder) in the coating solution.
It is represented by the volume% of the filler therein, and is usually preferably 5% by volume or more and 52% by volume or less based on 100% by volume of the solid content,
More preferably, it is 10% by volume or more and 45% by volume or less, and still more preferably 20% by volume or more and 40% by volume or less. When the used amount of the filler is 5% by volume or less, sufficient light diffusibility cannot be obtained, and when it exceeds 52% by volume, sufficient reflected light cannot be obtained due to birefringence.

In the production of the reflection sheet of the present invention, when applying a solution in which fine particles made of a polymer are dispersed in a binder using a solvent, 4 hours after mixing the dispersion solution, preferably 12 hours It is preferable to apply the coating after leaving for an hour, more preferably 24 hours. Since the fine particles made of a polymer are affected by the solvent and swell with the lapse of time for several hours, if the coating is performed immediately after preparing the dispersion solution, the particle size of the fine particles changes with the lapse of time. Since the structure becomes uneven and the viscosity of the dispersion solution changes with time, it may be difficult to adjust the coating conditions.

The reflection sheet of the present invention is characterized in that the reflection sheet has a concavo-convex layer obtained by applying a specific weight of the composition mainly composed of the binder and the fine particles on a polymer film. The weight of the uneven layer formed on the polymer film is such that the dry weight (g / cm ² ) satisfies the condition of the following formula (1). Formula (1): 0.75 × 2r × 10 ² / (p / a + (10
0-p) / b) ≦ dry weight (g / cm ² ) ≦ 2.5 × 2
r × 10 ² / (p / a + (100−p) / b) Preferably, the condition of the following formula (2) is satisfied. Formula (2): 0.75 × 2r × 10 ² / (p / a + (10
0-p) / b) ≦ dry weight (g / cm ² ) ≦ 2.0 × 2
r × 10 ² / (p / a + (100−p) / b) More preferably, the condition of the following formula (3) is satisfied. Formula (3): 0.75 × 2r × 10 ² / (p / a + (10
0-p) / b) ≦ dry weight (g / cm ² ) ≦ 1.5 × 2
r × 10 ² / (p / a + (100−p) / b) If the weight of the uneven layer is smaller than the value on the left side of the formula (1), the number of particles for forming the uneven layer is too small, and The desired uneven structure cannot be obtained on the film. On the other hand, if the weight of the uneven layer is larger than the value on the right side of the expression (1), the number of particles becomes too large, and it becomes difficult to form a controlled uneven structure.

In the present invention, the weight refers to after drying (dry)
Indicates weight. Weight (application amount) before drying (wet)
Is useful in selecting the number of gravure plates or Meyer bars used for coating, but is often difficult to measure. Therefore, in practice, the film thickness after drying and the coating weight after drying are often measured and evaluated. However, since the particle layer is an uneven layer, the coating amount and the film thickness do not always match. Therefore, it is considered preferable to carry out the evaluation based on the weight after drying (dry). As a method for measuring the dry weight, for example, it can be easily weighed by carefully wiping with a solvent that dissolves the fine particles and the binder on the surface of the uneven layer, drying the peeled uneven layer and the solvent, and evaporating the solvent. .

In the present invention, as a method of forming a concavo-convex layer by fine particles on a base polymer film, various solution coating methods are considered, and the coating amount (g / cm ² ) at that time is determined by the wet weight. Is controlled by When the weight% of solids in the coating liquid is indicated by N, the wet weight (g / cm ² ) = the dry weight (g / c) is substantially between the wet weight and the dry weight.
m ² ) / N × 100. Therefore, equation (1) can be expressed as equation (4). Formula (4): 0.75 × 2r / N × 10 ⁴ / (p / a +
(100-p) / b) ≦ application amount ≦ 2.5 × 2r / N × 1
0 ⁴ / (p / a + (100−p) / b) However, as described above, the wet weight is determined by the coating method,
In many cases, consistency with the final dry weight cannot be obtained depending on the drying conditions. Therefore, the value is only a reference value during coating, and the evaluation is performed based on the dry weight.

Hereinafter, a method for forming the uneven layer according to the present invention will be described. First, the roll coater will be described. The roll coater is composed of three, a metering roll, an applicator roll, and a backup roll, and is divided into a forward rotation roll coater and a reverse roll coater according to the position where the metalling roll is arranged. The role of the metering roll is to maintain a precise and constant amount of coating agent on the applicator roll, and the amount of coating agent present on the applicator roll depends on the nip between the applicator roll and the metering roll. The width and the relative surface speed are adjusted. In actual operation, the applicator roll and the metering roll each control the speed independently. This is especially important when dealing with a wide range of coatings, and for most coatings, by properly adjusting the relative velocity relationship at the metalling nip,
A coating film having an extremely smooth appearance can be obtained. In the case of a forward rotation roll coater, if the peripheral speed of the metering roll and the applicator roll is made equal, when the coating liquid splits at the exit of the nip between the rolls, the liquid is pulled up and down, causing a split pattern. Rotate the tallon faster. In general, the spacing between the metering roll and the applicator roll is slightly spaced to take part of the metering. If this gap is too far, there is a disadvantage that a ring-shaped pattern is generated.

In a roll coater, a reverse roll coater performs coating while the applicator roll rotates in the reverse direction. In a reverse roll coater, the coating thickness is determined by the size of the gap between the rolls in contact with each other, the peripheral speed ratio of each roll,
It is determined by the viscosity of the coating solution, the solid content concentration, and the like. The advantages of this coater are (1) coating is possible over a wide viscosity range, (2) coating thickness can be adjusted during running,
(3) The thickness of the coating film can be greatly changed. (4) The coating film surface is formed along the surface of the support, and the coating film thickness is uniform microscopically. A small loss of solvent due to sharing.

However, on the other hand, (1) if the speed of the metering roll is too high, a rough wavy pattern is formed on the coating agent weighed on the applicator roll, and this pattern becomes the same pattern when moved to the film surface. Will appear as
(2) If the speed of the metering roll is lower than the ideal speed,
Concentric bulges occur in the coating agent measured on the applicator roll, (3) a strong stirring effect in the coating agent tank is likely to generate bubbles, and (4) homing action by the application roll becomes strong. It is necessary to make the coating agent reservoir deep to prevent overflow, (5) it is difficult to attach the edge doctor, and it is necessary to make a step on the backup roll, and (6) the problem of scattering of the coating agent due to the pumping action. There are also drawbacks such as a limitation on the coating speed.

The gravure coater method is composed of a gravure roll, a backup roll, and an adjustment roll. The gravure roll immersed in a liquid tank has an uneven engraving on its surface and adheres to the convex portion. The coating liquid is scraped off with a doctor blade, the coating liquid is measured in the recesses and transferred to the support.The coating amount is adjusted by adjusting the shape, depth, mesh, and solid concentration of the coating liquid. It is performed by such as. Factors affecting the transfer of the coating agent from the gravure cell to the substrate are viscosity and surface tension. The cell shape is a pyramid type, a lattice type, or a diagonal line type, and the coating amount increases in the order of pyramid type <lattice type <diagonal line type.
The advantage of this method is that the coating thickness is uniform even when it is wide, and a thin film coating can be performed without any operation technique. On the other hand, (1) the transfer rate of the coating agent is extremely small in a shallow cell and is about 50% at the maximum. (2) In a cell deeper than the transfer mechanism of the coating agent, the meniscus of the coating agent is concave at the center of the cell. ,
Because the coating is applied along the cell walls,
There are also disadvantages such as that the coated film after being applied to the object to be coated has a center that comes off and appears as a donut-shaped ring.

In the rod coater method, the coating liquid is transferred to the support with a forward rotating applicator roll, and then the outer diameter is 6 to 10 mm.
It is a system in which a piano wire or stainless steel wire with a thickness of about 0.1 to 0.8 mm is densely wound around a rod of about mm, and the excess coating liquid is scraped off and weighed.In this method, It is important to keep the tension of the support on the rod constant to obtain a stable coating amount. Therefore, if there is a difference in tension in the width direction of the support, there is a difference between the left and right coating amounts. If the distance between the pressing rollers before and after the rod is as short as possible in order to prevent wrinkles and sagging of the support at this portion, there is a drawback that a streak occurs in the running direction.

The blade coater method is a method in which a coating agent is measured and flattened by a blade, as in the case of buttering bread. Factors affecting the coating amount include:
The information includes the thickness of the blade, the pressure of the blade, the angle to the cutting line of the blade, the length of the crimped portion of the blade, the oblique angle of the blade, the viscoelasticity of the coating agent, and the coating speed. Also, in a knife coater in which a knife is installed vertically on the upper part of the backup roll and the coating thickness is measured by the gap between the support conveyed by the roll and the knife edge, the determinants of the coating amount are: Examples include the gap between the knife edges, the coating speed, the viscosity of the coating agent, the pressure on the support of the coating liquid reservoir, and the shape of the knife edge.

The die coating (extrusion) method is a method in which a solution stored in a hopper or the like is extruded from a die by a pump pressure and applied to a film surface. In the die coating method, all of the supplied coating liquid is usually coated on the film without recirculation. Therefore, the application amount is determined by the pump delivery amount and the line speed. In addition, when a coating liquid having a very low viscosity is used, a sufficient die internal pressure cannot be obtained in the width direction, and the coating amount may be non-uniform. This is addressed by making the internal pressure of the die uniform by making it narrower. The tip of the die is used as a measuring blade to increase the uniformity of the coating amount in the width direction. For example, the die coating method in which the tip is rounded in a lip shape is also called a lip coating method.However, in order to obtain a good coating surface as well as a uniform coating amount, it is necessary to devise the tip of the die in this way. Elaborate ones are preferably used. The advantages of the die coating (extrusion) method include high-speed coating, high productivity, uniform coating thickness, and the ability to apply a wide range of coatings. Loss when changing the width may be slightly increased. In addition to the above, various coating methods are conceivable, but as a coating method that satisfies the requirements of the present invention, in consideration of the occurrence of bumps due to gelation during coating, the die coating method is used, and the use of the lip coating method is particularly preferable. preferable.

In the reflection sheet of the present invention, the reflection layer comprises three layers formed on the uneven layer. The first layer from the uneven layer side is a base layer (C), the second layer is a metal layer (D) mainly composed of silver, and the third layer is a silicon oxide layer (E). The underlayer (C) as the first layer includes gold, copper, nickel, iron,
Metal such as cobalt, tungsten, molybdenum, tantalum, chromium, indium, manganese, titanium, palladium, etc., or transparent such as zinc oxide or indium and tin oxide (ITO) doped with 0 to 5% by weight of aluminum oxide Oxides are preferably used. It is desirable that the second metal layer (D) mainly composed of silver is basically composed of silver alone, but gold, copper, nickel, iron, cobalt, tungsten which does not adversely affect its performance. , Molybdenum, tantalum, chromium, indium, manganese, titanium, palladium and other metal impurities. For the silicon oxide layer (E) which is the third layer, it is usually preferable to use silicon dioxide which is a general silicon oxide. However, the number of oxygen does not necessarily need to be two. There is no problem even if it is 8.

As a method of forming the metal thin film layer, there are a wet method and a dry method. The wet method is a general term for the plating method, and is a method of depositing a metal from a solution to form a film. A specific example is a silver mirror reaction. On the other hand, the dry method is a general term for a vacuum film forming method, and specific examples thereof include a resistance heating type vacuum deposition method, an electron beam heating type vacuum deposition method, an ion plating method, and an ion beam assisted vacuum deposition method. And a sputtering method. In particular, in the present invention, a vacuum film forming method capable of a roll-to-roll method for continuously forming a film is preferably used.

In the vacuum deposition method, a raw material of a metal is melted by electron beam, resistance heating, induction heating, or the like, and the vapor pressure is increased, and preferably 13.3 mPa (0.1 mTorr).
It is evaporated on the substrate surface below. 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 a 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 can be used. In the sputtering method, a metal plate-shaped target may be used as a raw material, and helium,
Neon, argon, krypton, xenon and the like may be used, but preferably argon is used. The purity of the gas is preferably 99% or more, more preferably 99.5%.
That is all.

For forming the transparent oxide film, a vacuum film forming method is preferably used. A sputtering method is mainly used, and helium, neon, argon, krypton, xenon, or the like is used as a sputtering gas, and in some cases, an oxygen gas is used.

The thickness of the thin film formed on the base polymer film is determined in consideration of a light transmittance of less than 1% when the reflection sheet is used. In the case where a metal layer is used as the first underlayer, the thickness is 5 to 50 nm.
Is more preferable, and more preferably 5 to 30 nm. If the thickness of the layer is smaller than 5 nm, the desired barrier effect cannot be obtained, and the silver-based layer of the second layer causes aggregation. Further, even if the thickness is more than 50 nm, not only the effect is not changed but also it is not preferable from the viewpoint of effective use of resources. When a transparent oxide is used, the thickness of the layer is preferably 1 to 20 nm, more preferably 5 to 20 nm.
〜１０10 nm. If the thickness of the layer is less than 1 nm,
The desired barrier effect cannot be obtained, and aggregation occurs in the silver-based layer of the second layer.

The thickness of the second layer, which is mainly composed of silver, is
70 to 400 nm is preferable, and more preferably 100 to 400 nm.
It is 300 nm, more preferably 150 to 250 nm. If the thickness of the layer is smaller than 70 nm, a desired reflectance cannot be obtained because a sufficient metal layer cannot be formed. Even if the thickness is more than 400 nm, the effect is not changed, and it is not preferable from the viewpoint of effectively using resources.

The thickness of the silicon oxide layer as the third layer is from 1 to
It is preferably 10 nm, more preferably 1 to 7 nm, and still more preferably 1 to 5 nm. When the thickness of the layer is smaller than 1 nm, the desired barrier effect cannot be obtained, and the silver-based layer of the second layer causes aggregation. If the thickness is more than 10 nm, the effect is not changed, and it is not preferable from the viewpoint of effective use of resources.

As a method for measuring the film thickness of each layer, there are a method using a stylus roughness meter, a repetitive reflection interferometer, a microbalance, a crystal oscillator method, and the like. Since the thickness can be measured, it is suitable for obtaining a desired film thickness. There is also a method in which the conditions for film formation are determined in advance, a film is formed on a sample substrate, the relationship between the film formation time and the film thickness is examined, and the film thickness is controlled by the film formation time.

The reflecting sheet formed as described above is
When the reflectance is measured from the layer side, at a wavelength of 550 nm, it is usually 85 to 99%, preferably 90 to 99%.
It is. If the reflectance is lower than 85%, the display surface becomes dark when incorporated in a reflection type liquid crystal display device, which is not preferable.
Here, the upper limit of the reflectivity is set to 99%. However, the reflectivity is preferably as high as possible. The reflectivity is more than 99%, for example, by alternately laminating thin films having a high refractive index and a low refractive index to form an enhanced reflection film. Achieving the reflectance has a trade-off with cost, but it is very preferable in terms of performance.

Further, providing a protective sheet on the third layer for the purpose of preventing corrosion such as oxidation and sulfidation of the metal thin film layer and for improving the handleability can improve the reliability of the reflection sheet of the present invention. It is preferable from the viewpoint of improving. As the protective sheet, a transparent resin such as a polyester resin, an acrylic resin, and a urethane resin, and a transparent inorganic thin film such as silicon oxide, magnesium fluoride, and silicon nitride are used. The protective layer is laminated on the metal thin film layer with an adhesive. As the pressure-sensitive adhesive, any material having transparency, such as an acrylic resin, a urethane resin, or an epoxy resin, can be used without any problem.

[0041]

The present invention will be described below in detail with reference to examples.

Example 1 An acrylic resin having an average particle size of 5 μm [manufactured by Negami Kogyo Co., Ltd., product name: Art Pearl], and an acrylic resin as a binder [manufactured by Mitsui Chemicals, Inc., product name: Armatex E269] ( A solution having a density of 1.2 g / cm ³ ) and a solvent having a solid content ratio of 35% and a particle ratio of 37.0% by volume in the solid content was prepared using a solvent composed of toluene and ethyl methyl ketone. The viscosity was 38 cps. The coating weight range was calculated by substituting these physical property values into the above formula (1). As a result, 4.5 (g / m ² ) ≦ dry weight (g / m ² ) ≦ 10.8 (g / m ² ) ² ), the pump pressure and line speed were adjusted so that the dry coating amount was 8.5 g / m ^2, and a 50 μm-thick polyethylene terephthalate (PET) film was applied by lip coating. Application was performed. At this time, no streaks due to bumps were observed, and a good coated surface was obtained. On the obtained sheet, as a base layer (C) (also referred to as a first layer), zinc oxide doped with 2% Al ₂ O ₃ (purity: 99.9%) was used as a target by DC magnetron sputtering, Using argon having a purity of 99.5% as a sputtering gas, zinc oxide was formed to a thickness of 5 nm. Subsequently, without removing the sheet from the sputtering apparatus, similarly, as a metal layer (D) (also referred to as a second layer), a target having a purity of 99.9% silver was obtained by DC magnetron sputtering.
Silver was formed to a thickness of 200 nm using argon having a purity of 99.5% as a sputtering gas. Subsequently, without removing the sheet from the sputtering apparatus, a silicon oxide layer (E) (also referred to as a third layer) was formed by RF magnetron sputtering using SiO ₂ having a purity of 99.9% as a target. SiO ₂ was formed to a thickness of 5 nm using 99.5% argon as a sputtering gas. After laminating a protective layer on the obtained sheet, a 150φ integrating sphere was placed on a Hitachi automatic recording spectrophotometer (model U-3400), and the total reflectance and diffuse reflectance at 550 nm were measured. 95.9%, diffuse reflectance 87.3
%. Put the reflective sheet after measurement in a thermo-hygrostat,
It was left for 500 hours under the condition of wet heat of 60 ° C. and 90% RH.
After a lapse of 500 hours, the sheet was taken out and the surface was observed. As a result, no metal aggregation was observed and the color remained white.
The total reflectance and the diffuse reflectance were measured again by the spectrophotometer. As a result, the reflectance was 95.5% and the diffuse reflectance was 87.4.
%, Almost the same as before the wet heat, and no deterioration of the optical characteristics was observed.

Example 2 A solution was prepared in the same manner as in Example 1 except that the ratio of the particles in the solid content was changed to 45.0% by volume. The viscosity was 50 cps. The coating weight range was calculated by substituting these physical property values into the above formula (1). As a result, 4.5 (g / m ² ) ≦ dry weight (g / m ² )
≦ 10.8 (g / m ² ), so the pump pressure and line speed were adjusted so that the dry coating amount was 9.0 g / m ^2, and a 50 μm-thick polyethylene terephthalate (PET) film was The coating was performed by a lip coating method. At this time, no streaks due to bumps were observed, and a good coated surface was obtained. The obtained sheet was sputtered in the same manner as in Example 1. After laminating a protective layer on this sheet, Hitachi Automated Recording Spectrophotometer (Model U-3400)
And a total reflectance and a diffuse reflectance at 550 nm were measured. The reflectance was 94.7.
% And a diffuse reflectance of 86.9%. The reflection sheet after the measurement was placed in a thermo-hygrostat, and left for 500 hours under the condition of 60 ° C. and 90% RH. After a lapse of 500 hours, the sheet was taken out and the surface was observed. As a result, no metal aggregation was observed and the color remained white. The total reflectance and the diffuse reflectance were measured again by the spectrophotometer, and as a result, the reflectance was 94.5.
%, And the diffuse reflectance was 87.0%, almost the same as before wet heat, and no deterioration in optical characteristics was observed.

Example 3 A reflection sheet was prepared in the same manner as in Example 1, except that the dry coating amount was 10.5 g / m ² . After laminating the protective layer on the obtained sheet,
A 150φ integrating sphere was installed on a Hitachi self-recording spectrophotometer (model U-3400), and total reflectance and diffuse reflectance at 550 nm were measured. The reflectance was 94.2% and the diffuse reflectance was 86.4%. Obtained. The reflection sheet after the measurement was placed in a thermo-hygrostat, and left for 500 hours under the condition of 60 ° C. and 90% RH. After a lapse of 500 hours, the sheet was taken out and the surface was observed. As a result, no metal aggregation was observed and the color remained white. The total reflectance and diffuse reflectance were measured again by a spectrophotometer. As a result, the reflectance was 94.0%, the diffuse reflectance was 86.7%, almost the same as before wet heat, and deterioration of optical characteristics was also observed. Did not.

Example 4 In Example 1, the thickness of zinc oxide doped with 2% Al ₂ O ₃ was 20 nm, the thickness of silver was 300 nm, and
A reflection sheet was prepared in the same manner as in Example 1 except that the thickness of O ₂ was changed to 10 nm. After laminating a protective layer on the obtained sheet, a Hitachi automatic recording spectrophotometer (model U-3)
An integrating sphere of 150φ was set in 400), and the total reflectance and diffuse reflectance at 550 nm were measured. As a result, a reflectance of 95.2% and a diffuse reflectance of 86.7% were obtained. The reflection sheet after the measurement was placed in a thermo-hygrostat, and left for 500 hours under the condition of 60 ° C. and 90% RH. After a lapse of 500 hours, the sheet was taken out and the surface was observed. As a result, no metal aggregation was observed and the color remained white. The total reflectance and the diffuse reflectance were measured again by the spectrophotometer, and as a result, the reflectance was 9
At 5.4%, the diffuse reflectance was 86.6%, almost the same as before wet heat, and no deterioration in optical characteristics was observed.

Example 5 In Example 1, the thickness of zinc oxide doped with 2% Al ₂ O ₃ was 3 nm, the thickness of silver was 100 nm,
_A reflection sheet was produced in the same manner as in Example 1 except that the film thickness of ₂ was 3 nm. After laminating a protective layer on the obtained sheet, a Hitachi automatic recording spectrophotometer (model U-340) was used.
0), an integrating sphere of 150φ was installed, and the total reflectance and diffuse reflectance at 550 nm were measured.
4.9% and a diffuse reflectance of 85.8% were obtained. The reflection sheet after the measurement was placed in a thermo-hygrostat, and left for 500 hours under the condition of 60 ° C. and 90% RH. After a lapse of 500 hours, the sheet was taken out and the surface was observed. As a result, no metal aggregation was observed and the color remained white. The total reflectance and the diffuse reflectance were measured again by the spectrophotometer, and as a result, the reflectance was 9
5.2%, the diffuse reflectance was 84.6%, almost the same as before wet heat, and no deterioration in optical characteristics was observed.

Example 6 In Example 1, titanium (purity: 99.000) was used as the first layer.
(9%) was sputtered so as to have a film thickness of 10 nm, and a reflective sheet was produced in the same manner as in Example 1. After laminating a protective layer on the obtained sheet, a 150φ integrating sphere was placed on a Hitachi automatic recording spectrophotometer (model U-3400), and the total reflectance and diffuse reflectance at 550 nm were measured. 95.6%, diffuse reflectance 86.7%
I got Place the reflective sheet after measurement in a thermo-hygrostat,
It was left for 500 hours under the condition of 0 ° C. and 90% RH. 5
After a lapse of 00 hours, the sheet was taken out and the surface was observed. As a result, no metal aggregation was observed and the color remained white. The total reflectance and the diffuse reflectance were measured again by the spectrophotometer. As a result, the reflectance was 95.3% and the diffuse reflectance was 85.9%.
As before, almost no change in the optical characteristics was observed.

Example 7 In Example 1, chromium (purity 99.
(9%) was sputtered so as to have a film thickness of 10 nm, and a reflective sheet was produced in the same manner as in Example 1. After laminating a protective layer on the obtained sheet, a 150φ integrating sphere was placed on a Hitachi automatic recording spectrophotometer (model U-3400), and the total reflectance and diffuse reflectance at 550 nm were measured. 95.2%, diffuse reflectance 85.9%
I got Place the reflective sheet after measurement in a thermo-hygrostat,
The sample was left for 500 hours under the moist heat condition of 0 ° C. and 90% RH. 5
After a lapse of 00 hours, the sheet was taken out and the surface was observed. As a result, no metal aggregation was observed and the color remained white. The total reflectance and the diffuse reflectance were measured again by the spectrophotometer. As a result, the reflectance was 94.9% and the diffuse reflectance was 86.2%.
As before, almost no change in the optical characteristics was observed.

Comparative Example 1 In Example 1, Al (purity 99.9) was used as the second layer.
%) Was produced in the same manner as in Example 1 except that sputtering was performed. After laminating a protective layer on the obtained sheet, Hitachi Automated Spectrophotometer (Model U-3400)
And an integrating sphere having a diameter of 150 mm was installed, and total reflectance and diffuse reflectance at 550 nm were measured. After the measurement,
Put in a thermo-hygrostat at 60 ° C and 90% RH for 5 hours.
It was left for 00 hours. After a lapse of 500 hours, the sheet was taken out, and the surface was observed, and the reflectance and the diffuse reflectance were measured. The results are shown in (Table 1).

COMPARATIVE EXAMPLE 2 In Example 1, reflection was performed in the same manner as in Example 1 except that zinc oxide doped with 2% Al ₂ O ₃ (purity: 99.9%) was not sputtered as the first layer. A sheet was prepared. After laminating a protective layer on the obtained sheet, a 150φ integrating sphere was placed on a Hitachi automatic recording spectrophotometer (model U-3400), and the total reflectance and diffuse reflectance at 550 nm were measured. The sample after the measurement was placed in a thermo-hygrostat, and left for 500 hours under the condition of 60 ° C. and 90% RH. After a lapse of 500 hours, the sheet was taken out, and the surface was observed, and the reflectance and the diffuse reflectance were measured. The results are shown in (Table 1).

Comparative Example 3 A reflective sheet was produced in the same manner as in Example 1 except that SiO ₂ was not sputtered as the third layer. After laminating a protective layer on the obtained sheet, a 150φ integrating sphere was placed on a Hitachi automatic recording spectrophotometer (model U-3400), and the total reflectance and diffuse reflectance at 550 nm were measured. The sample after the measurement was placed in a thermo-hygrostat, and left for 500 hours under the condition of 60 ° C. and 90% RH. After a lapse of 500 hours, the sheet was taken out, and the surface was observed, and the reflectance and the diffuse reflectance were measured. The results are shown in (Table 1).

Comparative Example 4 In Example 1, the amount applied on the PET film was
A reflection sheet was produced in the same manner as in Example 1 except that the reflection sheet was 3 g / m ² . After laminating a protective layer on the obtained sheet, the sheet was passed through a Hitachi automatic recording spectrophotometer (model U-3400).
An integrating sphere of φ was installed, and total reflectance and diffuse reflectance at 550 nm were measured. The sample after the measurement was placed in a thermo-hygrostat, and left for 500 hours under the condition of 60 ° C. and 90% RH. After a lapse of 500 hours, the sheet was taken out, and the surface was observed, and the reflectance and the diffuse reflectance were measured. The results are shown in (Table 1).

Comparative Example 5 In Example 1, the amount applied on the PET film was
A reflection sheet was produced in the same manner as in Example 1 except that the reflection sheet was 15 g / m ² . After laminating the protective layer on the resulting sheet, it was placed on a Hitachi autograph spectrophotometer (model U-3400) for 150
An integrating sphere of φ was installed, and total reflectance and diffuse reflectance at 550 nm were measured. The sample after the measurement was placed in a thermo-hygrostat, and left for 500 hours under the condition of 60 ° C. and 90% RH. After a lapse of 500 hours, the sheet was taken out, and the surface was observed, and the reflectance and the diffuse reflectance were measured. The results are shown in (Table 1).

Comparative Example 6 A reflection sheet was prepared in the same manner as in Example 1, except that a solution was prepared in which the proportion of particles in the solid content was 2% by volume during the preparation of the coating solution. After laminating a protective layer on the obtained sheet, an integrating sphere of 150φ was set on a Hitachi automatic recording spectrophotometer (model U-3400) and 550
The total reflectance and diffuse reflectance in nm were measured. Place the sample after measurement in a thermo-hygrostat, 60 ° C, 90% R
It was left for 500 hours under the wet heat condition of H. After a lapse of 500 hours, the sheet was taken out, and the surface was observed, and the reflectance and the diffuse reflectance were measured. The results are shown in (Table 1).

Comparative Example 7 The procedure of Example 1 was repeated, except that, at the time of preparing the coating solution, a solution in which the proportion of particles in the solid content was 70% by volume was prepared.
A reflection sheet was manufactured according to Example 1. After laminating a protective layer on the obtained sheet, an integrating sphere of 150φ was set on a Hitachi automatic recording spectrophotometer (model U-3400), and 5
The total reflectance and diffuse reflectance at 50 nm were measured.
The sample after measurement is placed in a thermo-hygrostat at 60 ° C. and 90 ° C.
% RH for 500 hours. After a lapse of 500 hours, the sheet was taken out, and the surface was observed, and the reflectance and the diffuse reflectance were measured. The results are shown in (Table 1).

Comparative Example 8 In Example 1, the first layer was made of titanium (purity 99.9%).
Was produced in the same manner as in Example 1 except that the film was sputtered to a film thickness of 3 nm. After laminating a protective layer on the obtained sheet, an integrating sphere of 150φ was set on a Hitachi automatic recording spectrophotometer (model U-3400), and 5
The total reflectance and diffuse reflectance at 50 nm were measured.
The sample after measurement is placed in a thermo-hygrostat at 60 ° C. and 90 ° C.
% RH for 500 hours. After a lapse of 500 hours, the sheet was taken out, and the surface was observed, and the reflectance and the diffuse reflectance were measured. The results are shown in (Table 1).

Comparative Example 9 In Example 1, the first layer was made of chromium (purity 99.9%).
Was produced in the same manner as in Example 1 except that the film was sputtered to a film thickness of 3 nm. After laminating a protective layer on the obtained sheet, an integrating sphere of 150φ was set on a Hitachi automatic recording spectrophotometer (model U-3400), and 5
The total reflectance and diffuse reflectance at 50 nm were measured.
The sample after measurement is placed in a thermo-hygrostat at 60 ° C. and 90 ° C.
% RH for 500 hours. After a lapse of 500 hours, the sheet was taken out, and the surface was observed, and the reflectance and the diffuse reflectance were measured. The results are shown in (Table 1).

[0058]

[Table 1]

[0059]

The reflective sheet of the present invention, when used in a reflective liquid crystal display device, has very excellent durability, does not show a decrease in reflectance even under moist heat conditions, and has a low surface color. Since there is no change, the display capability of the reflection type liquid crystal can be improved, and the present invention has great industrial significance.

Claims (7)

[Claims] 1. A polymer film (A), a concavo-convex layer (B) mainly composed of a particle layer, a base layer (C), a metal layer mainly composed of silver (D), and a silicon oxide layer (E) are made of ABCDE. A reflective sheet having a constitutional order, wherein the reflectivity of the reflective sheet at a wavelength of 550 nm measured from the (E) layer side is 85.
The reflective sheet is characterized by being about 99% or less. 2. An uneven layer (B) having an average particle size of 1 μm or more,
Fine particles having a size of 15 μm or less and a binder, and the fine particles have a volume of 5
2. The composition according to claim 1, wherein the composition is blended so as to have a proportion of about 52% by volume, and the dry weight (g / cm ² ) of the uneven layer satisfies the condition of the following formula (1). Reflective sheet. Formula (1): 0.75 × 2r × 10 ² / [p / a + (10
0-p) / b] ≦ dry weight (g / cm ² ) ≦ 2.5 × 2
r × 10 ² / [p / a + (100−p) / b] [However, p = 100 / [1+ (100 / v−1) × b /
a], and r is the average value of the radii of the fine particles used (c
m), p is the ratio of fine particles in the uneven layer (% by weight), v is the ratio of fine particles in the uneven layer (volume%), a is the density of the used fine particles (g / cm ³ ), b is It represents the density (g / cm ³ ) of the binder used. ] 3. The reflection sheet according to claim 2, wherein the fine particles are acrylic particles. 4. The reflection sheet according to claim 2, wherein the binder is an acrylic resin. 5. An underlayer (C) comprising gold, copper, nickel,
Iron, cobalt, tungsten, molybdenum, tantalum,
Chromium, indium, manganese, titanium, or palladium 5 to 50 nm thick metal layer, or
5. The transparent oxide layer of zinc oxide doped with 0 to 5% by weight of aluminum oxide or an oxide of indium and tin (ITO) with a thickness of 1 to 20 nm. The reflection sheet according to any one of the above. 6. The thickness of the metal layer (D) mainly composed of silver is:
The thickness is 70 to 400 nm.
The reflection sheet according to any one of the above. 7. The silicon oxide layer (E) has a thickness of 1 to 50.
The reflective sheet according to any one of claims 1 to 6, wherein