JP2002196114A - Forward scattering sheet, laminated sheet including the same, and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forward scattering sheet capable of giving brightness and contrast higher than before to a reflective or transflective liquid crystal display device, and a laminated film using the same. And a liquid crystal display device. SOLUTION: There is provided a forward scattering sheet having a non-uniform structure of a refractive index therein, the sheet having a total light transmittance of 90% or more and less than 100% and a transparency of 15% or more and 60% or less. Is done. A laminated sheet in which the forward scattering sheet 11 is laminated with another resin sheet 21 and the like, and a liquid crystal display device in which the laminated sheet is combined with a liquid crystal cell 41 are also provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forward scattering sheet, a laminated sheet using the same, and a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, with the spread of portable telephones and portable terminals, there has been an increasing demand for reflective or transflective liquid crystal display devices which consume less power. Further, in response to an increase in the amount of information, a demand for colorization is increasing. Conventionally, a black-and-white reflective or transflective liquid crystal display device has a polarizing film disposed on the front and back surfaces of a liquid crystal cell, and a reflective film or a transflective film disposed on the back surface of the rear polarizing film. Thus, white display at the time of use of reflection was enabled. However, in a color reflective or transflective liquid crystal display device, a reflective film is disposed outside the liquid crystal cell for the purpose of improving white display luminance and preventing a decrease in the saturation of a display color due to parallax. Instead, a method of providing a reflection layer in a liquid crystal cell is mainly used. In order to enable white display, external light must be scattered by the reflective layer. Therefore, there have been proposed a method of providing fine irregularities on the reflection layer provided in the liquid crystal cell, and a method of providing the reflection layer itself as a mirror reflection layer and providing a forward scattering layer on the front surface thereof. Such forward scattering layers include, for example,
Japanese Patent Application Laid-Open No. 9-113893 proposes a device using a light control plate, but has not achieved sufficient performance due to a problem of viewing angle dependence.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reflective or semi-transmissive and semi-reflective liquid crystal display device in which a mirror-reflective layer is formed in a liquid crystal cell. It is another object of the present invention to provide a forward scattering sheet which can be used to provide a laminated film and a liquid crystal display device using the same.

[0004]

That is, according to a first aspect of the present invention, there is provided a sheet having a non-uniform refractive index structure therein, wherein the total light transmittance is 90% or more and less than 100%. Further, a forward scattering sheet having a transparency of 15% or more and 60% or less is provided.

[0005] Here, the non-uniform refractive index structure may be a structure in which the refractive index changes intermittently or may change continuously. The structure can be formed, for example, by dispersing fine particles in a resin body. An acrylic pressure-sensitive adhesive may be used for the resin body. The fine particles are not particularly limited as long as they satisfy the range of the total light transmittance and the transparency, but a suitable example is a silicone resin. The non-uniform refractive index structure can also be separately formed by phase separation of the components constituting the sheet. The phase difference value of the forward scattering sheet is 3
It is preferably 0 nm or less.

Further, according to a second aspect of the present invention, there is provided a laminated sheet in which the above-mentioned forward scattering sheet is sandwiched between two resin sheets. Are provided.

Here, the stretched resin sheet may be a polarizing film or a retardation film, and the retardation film may be a 波長 wavelength film or a 波長 wavelength film. Of course, both a polarizing film and a retardation film can be laminated on the forward scattering sheet. In particular, for use in a liquid crystal display device, a polarizing film, at least one retardation film, and the A laminated sheet obtained by laminating the sheet and the sheet can be obtained.

Further, there is provided a laminated sheet in which the above-mentioned forward scattering sheet is laminated with a reflective film or a transflective film. In this case, a polarizing film may be further laminated to form a laminated sheet formed by laminating at least three layers of the polarizing film, the above-mentioned forward scattering sheet, and a reflective film or a transflective film.

Further, according to a third aspect of the present invention, a laminated sheet comprising a polarizing film, at least one retardation film, and the above-mentioned forward scattering sheet is laminated.
Provided is a liquid crystal display device laminated on a front surface of a liquid crystal cell. In this case, a polarizing film can be laminated also on the back surface of the liquid crystal cell, a retardation film can be laminated as necessary, and a backlighting device can be arranged on the back surface.

[0010] As another form, on the front surface of the liquid crystal cell,
A polarizing film is laminated, a retardation film is also laminated as necessary, and on the back surface of the liquid crystal cell, which is one of the embodiments specified from the second viewpoint described above, the forward scattering sheet is a reflective film. Alternatively, there is also provided a liquid crystal display device in which a laminated sheet laminated with a transflective film and, if necessary, laminated with a polarizing film is laminated. In this case, a retardation film can be laminated on the back surface of the liquid crystal cell together with the above-mentioned laminated sheet, and if necessary, a backlight device can be arranged on the back surface.

[0011]

DETAILED DESCRIPTION OF THE INVENTION In order to clarify the present invention, a detailed description will be given below. The forward scattering sheet according to the present invention has a non-uniform structure of the refractive index inside, and the total light transmittance is 90%.
Not less than 100% and the transparency is not less than 15% and 6
It is less than 0%. The total light transmittance here is specified by ASTM D1003 established by the American Society for Testing and Materials. In the present invention, the total light transmittance of the sheet is set to be 90% or more and less than 100%.

The transparency is a physical quantity measured by a haze meter described in ASTM D1044.
It can be measured by "Haze Guard Plus" (trade name) manufactured by YK Gardner. As an index for quantifying the degree of sheet scattering, for example, JIS K 6714-1977 and
Although there is a haze ratio shown in ASTM D1003, according to the study of the present inventors, when a forward scattering sheet is used for a liquid crystal display device which is a main application of the present invention, there is no correlation between the performance and the haze ratio. It was found that there was a correlation with the transparency. In the present invention, the transparency of the sheet is 15% or more and 60% or less. The transparency of the sheet is preferably low, more preferably 15% or more and 40% or less. Further, when used in a field such as an information portable terminal that requires a sufficiently wide angle range (viewing angle) in which a screen can be viewed brightly, the transparency is 15% or more and 30% or less. More preferred.

The non-uniform refractive index structure may have a structure in which the refractive index changes intermittently or may change continuously. In order to create a structure in which the refractive index changes, a method of dispersing fine particles in a resin body, a method of casting a liquid obtained by mixing two or more resins in a solvent, and kneading two or more polymers are used. It can be carried out by a method, a method utilizing the phase separation behavior in the curing process of a thermosetting or photocurable resin, or the like.

Here, when the resin body and the fine particles each have a uniform refractive index, unless the refractive indices of the resin body and the fine particles match, the forward scattering sheet has a structure in which the refractive index changes intermittently. can get. On the other hand, for example, when the refractive index of the resin body is uniform, but the refractive index of the fine particles continuously changes from the outer periphery toward the center, if the refractive index of the outer periphery of the fine particles matches the refractive index of the resin body, As the forward scattering sheet, a structure in which the refractive index continuously changes is obtained. Similarly, in the mixing or kneading of two or more resins, a structure in which the refractive index changes intermittently can be obtained by using a completely incompatible system. For example, the compatibility is controlled by graft polymerization or the like. Thus, a structure in which the refractive index changes continuously can be obtained. Furthermore, also when utilizing the phase separation behavior of a thermosetting or photocurable resin, it is possible to obtain a structure in which the refractive index changes intermittently or continuously by utilizing copolymerization and reactivity.

The material of the resin used in the present invention is not particularly limited, and various known resins can be used in a colorless and transparent range. For example, polyolefin resins such as polyethylene and polypropylene, polystyrene resins, polyvinyl chloride resins, polyvinyl acetate resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, cyclic polyolefin resins such as norbornene polymers Synthetic polymers such as resins, polycarbonate resins, polysulfone resins, polyethersulfone resins, polyarylate resins, polyvinyl alcohol resins, polyurethane resins, polyacrylate resins, and polymethacrylate resins; Natural polymers such as cellulose-based resins such as cellulose acetate and cellulose triacetate can be used. The synthetic polymer may, of course, be a homopolymer of one monomer, or may be a copolymer obtained by copolymerizing two or more of the monomers constituting each of the above resins.

The resin may be a pressure-sensitive adhesive.
In this case, acrylic pressure-sensitive adhesive, vinyl chloride-based pressure-sensitive adhesive, synthetic rubber-based pressure-sensitive adhesive, natural rubber-based adhesive,
A silicone adhesive or the like can be used. Among these pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are one of the preferable resins in terms of handling properties and durability. Acrylic pressure-sensitive adhesives are a main monomer component with a low glass transition temperature that gives tackiness, a comonomer component with a high glass transition temperature that gives adhesion and cohesive strength, and a monomer component containing a functional group for crosslinking and improving adhesion. And a copolymer mainly composed of
As the main monomer component, for example, ethyl acrylate,
Butyl acrylate, amyl acrylate, acrylic acid 2-
Alkyl acrylates such as ethylhexyl, octyl acrylate, cyclohexyl acrylate, and benzyl acrylate; and butyl methacrylate, amyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate And methacrylic acid alkyl esters. Examples of the comonomer component include methyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acetate, styrene, acrylonitrile, and the like. Examples of the functional group-containing monomer component include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and N- Examples include hydroxyl group-containing monomers such as methylol acrylamide, acrylamide, methacrylamide, glycidyl methacrylate and the like.

The pressure-sensitive adhesive is preferably of a cross-linking type.
In this case, for example, a method of crosslinking by adding various crosslinking agents such as an epoxy compound, an isocyanate compound, a metal chelate compound, a metal alkoxide, a metal salt, an amine compound, a hydrazine compound, and an aldehyde compound, irradiation with radiation And the like can be applied, and these are appropriately selected depending on the type of the functional group. Further, the weight-average molecular weight of the main polymer constituting the pressure-sensitive adhesive is preferably about 600,000 to 2,000,000, and more preferably 800,000 to 1,800,000. When the weight average molecular weight is less than 600,000, the adhesion and durability of the pressure-sensitive adhesive to the adherend are reduced when the amount of the plasticizer described later is large. Further, when the weight average molecular weight exceeds 2,000,000, particularly when the amount of the plasticizer is small, the elasticity of the pressure-sensitive adhesive increases and the flexibility decreases, and when the adherend generates shrinkage stress, Cannot be absorbed or alleviated. However, after cross-linking, mixing and kneading in a solvent cannot be performed. Therefore, when these production methods are adopted, fine particles are mixed or two or more resins are kneaded before cross-linking, and a casting method is used. It is necessary to form a sheet by extrusion or extrusion, and then perform a crosslinking treatment.

The pressure-sensitive adhesive preferably contains a plasticizer. As the plasticizer, for example, esters such as phthalic acid ester, trimellitic acid ester, pyromellitic acid ester, adipic acid ester, sebacic acid ester, phosphoric acid triester and glycol ester, process oil, liquid polyether, Examples thereof include liquid polyterpene and other liquid resins, and one of these can be used alone or a mixture of two or more can be used. Further, for pressure-sensitive adhesives, for example, if necessary,
Various additives such as an ultraviolet absorber, a light stabilizer, and an antioxidant can also be added.

Further, the resin may be a photo-setting or thermosetting resin. Known resins can be used as the photocurable or thermosetting resin. For example, a compound having a reactive double bond such as an acrylate group, a methacrylate group, or an aryl group, a compound having a ring-opening condensable reactive group such as an epoxy group, or a reaction system such as a mixture of a polyol compound and a polyisocyanate compound. Compound systems. When curing with light or heat, additives such as a photopolymerization initiator, a catalyst, a heat stabilizer, an ultraviolet stabilizer, and a leveling agent can be added to the resin. Curing by light or heat can be performed by a known method. Also in this case, after curing, mixing and kneading in a solvent cannot be performed. Therefore, when these production methods are employed, mixing of fine particles and kneading of two or more resins are performed before curing. It is necessary to form a sheet by a casting method or an extrusion method and then perform a curing treatment.

In consideration of the application of the forward scattering sheet of the present invention to a liquid crystal display device, which is a main application, it is preferable that reflection occurring at the interface between the forward scattering resin body and other members is small. For this purpose, the refractive index n (R) of the resin is 1.40 ≦
Preferably, n (R) ≦ 1.60.

The material of the fine particles used in the present invention is not particularly limited, and known organic fine particles and inorganic fine particles can be used. Examples of the organic fine particles include particles of a polyolefin resin such as polystyrene, polyethylene and polypropylene, and particles of a (meth) acrylic polymer such as a polymethacrylate resin and a polyacrylate resin. It may be. Further, a copolymer obtained by copolymerizing two or more monomers selected from ethylene, propylene, styrene, methyl methacrylate, benzoguanamine, formaldehyde, melamine, butadiene and the like can also be used. Examples of the inorganic fine particles include particles such as silica, silicone, titanium oxide, and aluminum oxide.

The surface of the fine particles may be subjected to a coupling treatment in order to improve the adhesion between the resin and the fine particles. The shape of the particles is not particularly limited, but a spherical shape is one of preferred shapes. The average particle size is not particularly limited, but is preferably in the range of 1 μm to 10 μm in consideration of the influence on polarized light and the display quality when used in a liquid crystal display device.

In using a forward scattering sheet for a liquid crystal display device, if the forward scattering sheet is too thin, it becomes difficult to handle it. If it is too thick, the thickness of the liquid crystal display device itself increases. The thickness is preferably about 100 μm. More preferably, 10-100μ
m.

When the forward scattering sheet is used in a liquid crystal display device, it is preferable that the in-plane retardation value of the forward scattering sheet is small. Specifically, the in-plane retardation value is preferably 30 nm or less, more preferably 10 nm or less, and most preferably 0 nm.

The forward scattering sheet is easy to handle.
As shown schematically in FIG. 1, two resin sheets 2
It can be stored or used as a laminated sheet in which the forward scattering sheet 11 is sandwiched between 4, 24. When used in a liquid crystal display device, it can be used as a laminated sheet in which a stretched resin sheet 24 and a forward scattering sheet 11 are laminated, as schematically shown in FIG. The material of the resin sheet 24 used here is not particularly limited, and a known resin sheet can be used. For example, polyolefin resins such as polyethylene and polypropylene, polyvinyl chloride resins, polyvinyl acetate resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, cyclic polyolefin resins such as norbornene polymers, polycarbonate resins Resin, polysulfone resin, polyethersulfone resin, polyarylate resin, polyvinyl alcohol resin, polyurethane resin, polyacrylate resin,
Synthetic polymers such as polymethacrylate resins and natural polymers such as cellulose resins such as cellulose diacetate and cellulose triacetate can be used. Further, the resin sheet 24 may be a pressure-sensitive adhesive. In this case, acrylic pressure-sensitive adhesive, vinyl chloride pressure-sensitive adhesive,
A synthetic rubber-based pressure-sensitive adhesive, a natural rubber-based adhesive, a silicone-based adhesive, and the like can be used.

The stretched resin sheet may be a polarizing film or a retardation film. Known polarizing films can be used, and those obtained by dyeing a polyvinyl alcohol resin with iodine or a dichroic dye are often used.
Since polyvinyl alcohol resin has poor water resistance, it is preferable that the polyvinyl alcohol resin is covered with a protective film, and a cellulose triacetate resin is usually used for the protective film. The retardation film may be a known one, and a polycarbonate resin, a polysulfone resin, a polyethersulfone resin, a polyarylate resin, a norbornene resin, or the like is mainly used. A known method can be used for stretching, and longitudinal stretching such as between-rolls stretching and transverse stretching such as tenter stretching are often used. The stretching direction may be uniaxial stretching. However, in order to adjust the viewing angle when used in a liquid crystal display device, thickness orientation may be performed as necessary. The retardation value of the retardation film is appropriately determined in accordance with desired characteristics. However, when used in a reflective or transflective liquid crystal display device, a retardation value of 10
Those having a range of 0 to 1,000 nm are usually used. Use of a quarter-wave film or a half-wave film is one of preferred embodiments.

When the forward scattering sheet of the present invention is used in particular as a forward scattering plate of a reflective or transflective liquid crystal display device, a polarizing film, at least one retardation film, and a forward scattering sheet. Are preferably used in layers. For example, in the case of a TFT (thin film transistor) driven reflection type liquid crystal display device, as shown in FIG. 3, FIG. 4, and FIG. Are stacked in this order, and further, as schematically shown in FIG. 6, the optical axis 82 of the 波長 wavelength film and the optical axis 83 of the 波長 wavelength film
Intersect at an angle of approximately 60 °, and the absorption axis 81 of the polarizing film and the optical axis 82 of the half-wave film are approximately 15 °.
So-called broadband circularly polarizing film that intersects at an angle of
It is preferable to use a sheet laminated with the forward scattering sheet 11.

In FIG. 3, the polarizing films 21 and 1 /
The two-wavelength film 22 and the quarter-wave film 23 are laminated via the pressure-sensitive adhesive 31, respectively, and have a structure in which the quarter-wave film 23 is further laminated on the forward scattering film 11 on the side of the quarter-wave film 23. I have. FIG. 4 is substantially the same as FIG. 3, but has a structure in which layers of the pressure-sensitive adhesive 31 are provided on both surfaces of the forward scattering film 11, and one of the layers is adhered to the 波長 wavelength film 23. FIG. 5 shows that a layer of a pressure-sensitive adhesive 31 is provided on both sides of the forward scattering film 11, and a 波長 wavelength film 22 is provided on one of the layers, and a polarizing film 21 is further provided thereon via the pressure-sensitive adhesive 31. Are laminated on each other, a 波長 wavelength film 23 is laminated on the other layer, and a layer of a pressure-sensitive adhesive 31 is provided on the opposite side of the 波長 wavelength film 23.

When the forward scattering sheet of the present invention is used, in particular, as a transflective plate of a reflective or transflective liquid crystal display device, the forward scattering sheet and a reflective film or transflective panel are used. It can be used as a laminated sheet in which a functional film is laminated. It is also preferable to use a laminated sheet formed by laminating a polarizing film, a forward scattering sheet, and a reflective film or a transflective film. As used herein, the term "reflective film" means a film that reflects incident light. The transflective film refers to a film that transmits a part of incident light and reflects the remaining part. The remaining portion that is not transmitted and reflected by all the incident light rays is absorbed by the transflective layer and cannot be used effectively. Therefore, the absorption is preferably as small as possible.

FIG. 7 shows an example of a laminated sheet in which a polarizing film, a front diffusion sheet, and a reflective film or a transflective film are laminated. In FIG.
A substrate 26 provided with a metal thin film 25 constitutes a reflective film or a transflective film, on which a pressure-sensitive adhesive 31, a polarizing film 21, and a front diffusion sheet 11 are arranged in this order. Are laminated. As the reflective film or the transflective film, a film formed by laminating two or more kinds of polymer thin films in addition to a substrate 26 provided with a metal thin film 25 as shown in FIG. Can also be used. Each of these layers alone,
Alternatively, two or more layers can be used. When two or more layers are stacked, the same layer may be used or different layers may be used.

The material of the substrate used for the reflective film or the transflective film is not particularly limited. For example, polyolefin resins such as polyethylene and polypropylene, polyvinyl chloride resins, polyvinyl acetate resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, cyclic polyolefin resins such as norbornene polymers, polycarbonate resins Synthetic polymers such as resins, polysulfone resins, polyethersulfone resins, polyarylate resins, polyvinyl alcohol resins, polyurethane resins, polyacrylate resins, polymethacrylate resins,
Furthermore, natural polymers such as cellulose resins such as cellulose diacetate and cellulose triacetate can be used. Further, a thin metal film such as aluminum, silver, and stainless steel can be directly used as a reflective film or a transflective film.

The metal used as the metal thin film in the reflective film or the transflective film is not particularly limited, but aluminum and silver are preferably used.
The thickness of the metal thin film is adjusted according to desired transmission performance and reflection performance. In other words, for the semi-transmissive semi-reflective layer, if it is important to increase the transmittance, and if the purpose is to reduce the reflectance, the metal thin film is thinned to maintain the transmittance high, and to reflect light. The rate can be lowered. Conversely, if the emphasis is placed on increasing the reflectance and the aim is to lower the transmittance, the transmittance can be reduced and the reflectance can be increased by increasing the thickness of the metal thin film. Therefore, the thickness of the metal thin film is usually 1 nm or more and 100
μm or less, and more preferably a thickness of 10 nm or more and 1 μm or less. As a method for attaching a metal thin film to the transparent polymer film, a vapor deposition method or a sputtering method is suitably used, but a film obtained by thinly rolling a metal may be bonded with an adhesive including a pressure-sensitive type. When attaching the metal thin film to the resin body, a known undercoat layer may be provided for improving the adhesion, or a known overcoat layer may be provided for protecting the metal thin film.

In the case of forming a semi-transmissive and semi-reflective layer by laminating a plurality of polymer thin films, the material of the polymer thin film is not particularly limited. Can be used as well. To provide reflective performance by laminating multiple polymer thin films, for example, JA RADFORD
Et al., “POLYMER ENGINEERING AND SCIENCE”, No. 13, (1973), p. 216, can be applied.

In producing the laminated sheet of the present invention, it is preferable to perform close lamination using a pressure-sensitive adhesive in order to reduce light loss due to reflection generated at the interface of each member.
Known pressure-sensitive adhesives can be used. For example, acrylate-based pressure-sensitive adhesives, methacrylate-based pressure-sensitive adhesives, vinyl chloride-based pressure-sensitive adhesives, synthetic rubber-based pressure-sensitive adhesives, and natural rubber-based adhesives And a silicone-based adhesive. Among these pressure-sensitive adhesives, acrylate-based pressure-sensitive adhesives are particularly preferable in terms of handling properties and durability.

One embodiment of a liquid crystal display device using the laminated sheet of the present invention is schematically shown in cross section in FIG. In this example, a liquid crystal display device 51 is configured by laminating a laminated sheet in which the polarizing film 21, the retardation films 22, 23, and the forward scattering sheet 11 are laminated on the front surface of the liquid crystal cell 41. The laminated sheet itself used here is the same as that shown in FIG. 3, and the polarizing film 21, the half-wave film 22, and the quarter-wave film 23 are respectively laminated via the pressure-sensitive adhesive 31. , １ ／ wavelength film 23, and further laminated on forward scattering film 11. Further, the liquid crystal cell 41 is obtained by injecting the liquid crystal 33 into the cell, and by changing the alignment state of the liquid crystal by applying a voltage, the polarized light passing through the cell is changed from linearly polarized light to circularly polarized light or circularly polarized light. The state is continuously changed from polarized light to linearly polarized light. As such a liquid crystal cell, known TN (twisted nematic) liquid crystal cell, STN (super twisted nematic) liquid crystal cell, OCB
(Optical compensation bend) A liquid crystal cell or the like can be used. In FIG. 8, a cell is constituted by two glass plates 32 and 32 facing each other and side walls (no number), a transparent electrode 34 is formed on the front glass plate, and a reflective electrode 35 is formed on the rear glass plate.
Are arranged, and a liquid crystal cell 41 is formed in a state where the liquid crystal 33 is injected into the cell.

Another embodiment of a liquid crystal display device using the laminated sheet of the present invention is schematically shown in FIG. In this example, the polarizing film 21 and the retardation films 22 and 23
And a laminated sheet on which the forward scattering sheet 11 is laminated,
The polarizing film 21 and the retardation film 23 are stacked on the rear surface of the liquid crystal cell 42, and the backlight device 60 is disposed on the rear surface of the liquid crystal cell 42.
The liquid crystal display device 52 is configured. In this type, the retardation film 23 on the back surface of the liquid crystal cell 42 is provided as needed.

The structure of the laminated sheet laminated on the front surface of the liquid crystal cell 42 in this example is the same as that in the example of FIG. As a liquid crystal cell in this case, a well-known TN liquid crystal cell, ST
An N liquid crystal cell, an OCB liquid crystal cell, or the like can be used. The liquid crystal cell 42 is composed of two opposing glass plates 32, 32 and side walls (not numbered), a transparent electrode 34 on the front glass plate, and a semi-transparent semi-reflective glass on the rear glass plate. The electrode 36 is arranged, and the liquid crystal 33 is injected into the cell. The transflective electrode 36 disposed on the back of the liquid crystal cell may be a transflective metal or a multi-layer thin film electrode, or may be formed by making a fine hole in a metal perfect reflection film to allow light rays to pass therethrough. An electrode processed so as to partially pass may be used.

The retardation film 23 is laminated on the back surface of the liquid crystal cell 42 via a pressure-sensitive adhesive 31, and the polarizing film 21 is laminated on the back surface via the pressure-sensitive adhesive 31. The rear lighting device 60 disposed further behind the rear polarizing film 21 of the liquid crystal cell 42 includes a lens sheet 61, a diffusion sheet 62, a light guide plate 63, a light source 64 for making light incident on the light guide plate, It comprises a reflection plate 65 for collecting light from the light source 64 to the light guide plate 63 and a reflection sheet 66 for collecting most of the light passing through the light guide plate 63 to the liquid crystal cell side.

Another embodiment of a liquid crystal display device using the laminated sheet of the present invention is schematically shown in FIG.
In this example, the polarizing film 21 is provided on the front surface of the liquid crystal cell 43.
On the other hand, on the back side of the liquid crystal cell 43, the polarizing film 21 and the forward scattering film 11 are laminated.
And a laminated sheet formed by laminating a reflective film or a semi-transmissive and semi-reflective film provided with a metal thin film 25 on a base material 26. Further, if necessary, a backlight device 60 is disposed on the back surface of the device, and the entire liquid crystal display device 53 is provided.
Is configured. In this type, the liquid crystal cell 43
The front surface retardation film 23 is provided as needed, and a retardation film may be laminated on the back surface of the liquid crystal cell 43 together with the polarizing film 21. In the liquid crystal cell 43 in this example, a cell is constituted by two glass plates 32 and 32 facing each other and side walls (not numbered). 37 is arranged, and the liquid crystal 33 is injected into the cell. The liquid crystal cell 43 changes the alignment state of the liquid crystal by applying a voltage, thereby rotating the polarized light passing through the cell, or converting the polarization state of the transmitted light by using the birefringence. The liquid crystal cell used in a normal transmission type liquid crystal display device can be used as it is. The configuration of the backlight device 60 is the same as that shown in FIG. 9, and the backlight device used in a normal transmissive or transflective liquid crystal display device can be used as it is.

[0040]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. In Examples,% representing the content or the used amount is based on weight unless otherwise specified. The method used for evaluating the forward scattering sheet in the examples is as follows.

(A) Total light transmittance, transparency and haze ratio The forward scattering sheet itself or, if necessary, affixed to a glass plate via a pressure-sensitive adhesive, is measured from the forward scattering sheet side. It is placed in BYK Gardner's "Haze Guard Plus" so that it is incident, and the total light transmittance (AS
TM D1003), transparency (ASTM D1044) and haze ratio (ASTM
D1003) was measured.

(B) Reflection Luminance and Reflection Contrast The reflection white display luminance evaluation apparatus used here is schematically shown in FIG.
FIG. 12 schematically shows a reflection black display luminance evaluation apparatus.
Each is shown in a sectional view. Round loupe “ENV-B-2”
The one with the loupe removed from Otsuka Optical Co., Ltd. was used as an annular external light source device. An optical mirror 74 is placed just below the center of the annular fluorescent lamp 72 of the round loupe, and the forward scattering sheet 11 manufactured in each example is placed thereon.
Was attached to the glass plate 73 via a pressure-sensitive adhesive as necessary, and the glass plate 73 was arranged so as to face the optical mirror 74. A luminance meter 71 is arranged above the center of the annular fluorescent lamp 72 so that the luminance in the normal direction of the forward scattering sheet 11 can be measured. A state in which the polarizing film 21 is arranged on the forward scattering sheet 11 as shown in FIG.
The luminance was measured as a white display of a reflective liquid crystal display device in a simulated manner. On the other hand, as shown in FIG.
The state where the broadband circularly polarizing film 27 is arranged on
The luminance was measured as a simulated black display of a reflective liquid crystal display device. The contrast was indicated by the ratio of white luminance and black luminance measured at the same irradiation angle. The irradiation angle is the annular fluorescent lamp 72.
Is adjusted according to the distance between the optical mirror 74 and the optical mirror 7.
An illuminometer was placed at position 4 to measure the illuminance.

The polarizing film 21 is a commercially available polyvinyl alcohol / iodine polarizing film “Sumicaran”.
SR1862A "(manufactured by Sumitomo Chemical Co., Ltd.) The broadband circularly polarizing film 27 was a polarizing film" Sumikaran SR1862A "and a commercially available half-wave film" Sumikalite SEF460275 "(Sumitomo Chemical Industries, Ltd.). And a commercially available 1/4 wavelength film "Sumikalite SEF340138" (manufactured by Sumitomo Chemical Co., Ltd.) in this order at an axis angle shown in FIG.

The materials used for manufacturing the forward scattering sheet are as follows.

As a pressure-sensitive adhesive serving as a resin, a polarizing film with a single-sided adhesive layer sold by Sumitomo Chemical Co., Ltd. (for example, “K” at the end of “Sumikaran SR1862APK”)
Indicates the grade of the pressure-sensitive adhesive) or a retardation film with a single-sided adhesive layer (for example, "7" at the end of "Sumikalite SEF340138B7" indicates the grade of the pressure-sensitive adhesive) No. K (refractive index: 1.47), pressure-sensitive adhesive No. 7 (refractive index: 1.47) and pressure-sensitive adhesive No. T (refractive index: 1.47)
48) was used.

On the other hand, as the colorless transparent spherical fine particles, commercially available silicone resin fine particles “Tospearl # 145” are used.
(Refractive index: 1.44, average particle size: 4.5 μm, manufactured by Toshiba Silicone Co., Ltd.), and “Eposter S12”, a commercially available melamine / formaldehyde condensate fine particle (refractive index: 1.5)
7, an average particle size of 1-2 μm, manufactured by Nippon Shokubai Co., Ltd.).

Example 1 A raw material liquid of pressure-sensitive adhesive No. K was used as a resin, and "Tospearl # 145" was added thereto as fine particles at a solid content of 15%.
38 μm which was biaxially stretched after dispersion.
A 25 μm-thick forward scattering sheet was obtained by coating on a thick release-treated polyethylene terephthalate film, followed by air drying and heat curing. This forward scattering sheet was transferred onto glass, and the reflection luminance and reflection contrast at an irradiation angle of 15 ° were evaluated according to the above (B). At this time, the illuminance was 2,050 lux. Table 1 shows the physical property values and the results. The reflection white luminance is 600 cd / m ² or more, and a bright screen can be provided.

Example 2 A forward scattering sheet was prepared in the same manner as in Example 1 except that “Tospearl # 145” was added to the material solution of the pressure-sensitive adhesive No. K so that the solid content was 18%. Obtained. This forward scattering sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The reflection white luminance is 600 cd / m ² or more,
Can provide a bright screen.

Example 3 A forward scattering sheet was prepared in the same manner as in Example 1 except that “Tospearl # 145” was added to the raw material liquid of the pressure-sensitive adhesive No. K so that the solid content was 25%. Obtained. This forward scattering sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The reflection white luminance is 600 cd / m ² or more,
Can provide a bright screen.

Comparative Example 1 Example 1 was repeated except that "Tospearl # 145" was added to the raw material liquid of the pressure-sensitive adhesive No. K so that the solid content was 5%.
In the same manner as in the above, a forward scattering sheet was obtained. This forward scattering sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The reflection white luminance is less than 600 cd / m ² , and the screen is dark.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the raw material liquid of the pressure-sensitive adhesive No. 7 was used as the resin, and "Eposter S12" was added as fine particles so as to have a solid content of 3%. To obtain a forward scattering sheet. This forward scattering sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The reflection white luminance is less than 600 cd / m ² , and the screen is dark.

[0052]

[Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Total light transmittance Transparency Haze ratio Reflected white luminance Contrast ━━━実 施 Example 1 93.4% 49.0% 77.1% 735 cd / m ² 63 Example 2 93.0% 45.5 % 80.3% 800 cd / m ² 66 Example 3 93.0% 34.2% 87.1% 831 cd / m ² 70 ────────────────────────── ────── Comparative Example 1 93.9% 81.6% 40.4% 365 cd / m ² 46 Comparative Example 2 91.0% 83.3% 83.7% 446 cd / m ² 23 ━━━━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━

Example 4 A raw material liquid of pressure-sensitive adhesive No. K was used as a resin, and "Tospearl # 145" was added as fine particles at a solid content of 27%.
Except that it was added so that
A forward scattering sheet was obtained. This forward scattering sheet was transferred onto glass, and the reflection luminance and reflection contrast at an irradiation angle of 15 ° were evaluated according to the above (B). At this time, the illuminance was 2,030 lux. Table 2 shows the physical property values and the results. In addition, we change irradiation angle to 30 degrees every 5 degrees,
The illuminance and reflected white luminance at each irradiation angle were evaluated, and the results were shown in Table 3.
It was shown to. From this result, the reflected white luminance in terms of 1,000 lux at each irradiation angle was calculated, and the results are shown in Table 4.

Example 5 A forward scattering sheet was prepared in the same manner as in Example 1 except that “Tospearl # 145” was added to the raw material liquid of the pressure-sensitive adhesive No. K so as to have a solid content of 36%. Obtained. This forward scattering sheet was evaluated in the same manner as in Example 4, and the results are shown in Tables 2 to 4. The irradiation angle dependence of the reflection white luminance is lessened than in the fourth embodiment.

Example 6 A raw material liquid of pressure-sensitive adhesive No. T was used as a resin, and "Tospearl # 145" was added thereto as fine particles at a solid content of 27%.
Except that it was added so that
A forward scattering sheet was obtained. About this forward scattering sheet,
The same evaluation as in Example 4 was performed, and the results are shown in Tables 2 to 4. The irradiation angle dependence of the reflected white luminance is further reduced than in the fifth embodiment.

Example 7 A forward scattering sheet was prepared in the same manner as in Example 1, except that “Tospearl # 145” was added to the raw material liquid of the pressure-sensitive adhesive No. K so as to have a solid content of 36%. Obtained. This forward scattering sheet was evaluated in the same manner as in Example 4, and the results are shown in Tables 2 to 4. The irradiation angle dependence of the reflected white luminance is further reduced than in the sixth embodiment.

[0057]

[Table 2] Measurement results of optical characteristics and reflection luminance and contrast ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Total light transmittance Transparency Haze ratio Reflected white luminance Contrast ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 4 92.9% 31.9% 87.7% 833 cd / M ² 69 Example 5 92.7% 25.9% 91.7% 825 cd / m ² 67 Example 6 92.9% 25.1% 91.7% 795 cd / m ² 65 Example 7 93.1% 17.5% 96.0% 750 cd / m ² 63 ━ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[0058]

[Table 3] Change in reflected white luminance due to change in irradiation angle 照射 Irradiation angle 15 ° 20 ° 25 ° 30 ° ━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Illuminance 2,030 lux 3,430 lux 4,690 lux 6,150 lux ─────────── ───────────────── Example 4 833 cd / m ² 762 cd / m ² 648 cd / m ² 459 cd / m ² Example 5 825 cd / m ² 827 cd / M ² 742 cd / m ² 561 cd / m ² Example 6 795 cd / m ² 805 cd / m ² 734 cd / m ² 572 cd / m ² Example 7 750 cd / m ² 845 cd / m ² 807 cd / m ² 674 cd / m ² ━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[0059]

[Table 4] Reflected white luminance in terms of 1,000 lux ━━━━━━━━━━━━━━━━━━━━ Irradiation angle 15 ° 20 ° 25 ° 30 ° ━━━━━━━━ ━━━━━━━━━━━━ Example 4 410 222 138 75 Example 5 406 241 158 91 Example 6 392 235 157 93 Example 7 369 246 172 110 ━━━━━━━━━━ ━━━━━━━━━━

[0060]

The forward scattering sheet of the present invention or a laminated sheet obtained by combining it with another sheet or film is
When used in a reflective or transflective liquid crystal display device, it provides a bright screen in a reflective use environment.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a laminated sheet of the present invention.

FIG. 2 is a schematic sectional view showing another example of the laminated sheet of the present invention.

FIG. 3 is a schematic sectional view showing another example of the laminated sheet of the present invention.

FIG. 4 is a schematic sectional view showing still another example of the laminated sheet of the present invention.

FIG. 5 is a schematic sectional view showing still another example of the laminated sheet of the present invention.

FIG. 6 shows an absorption axis and 1 of a polarizing film used for a laminated sheet.
It is a schematic diagram which shows the axial angle which the optical axis of a 1/2 wavelength film and the optical axis of a 1/4 wavelength film make.

FIG. 7 is a schematic sectional view showing still another embodiment of the laminated sheet of the present invention.

FIG. 8 is a schematic sectional view illustrating an example of the liquid crystal display device of the present invention.

FIG. 9 is a schematic sectional view showing another example of the liquid crystal display device of the present invention.

FIG. 10 is a schematic sectional view showing another example of the liquid crystal display device of the present invention.

FIG. 11 is a schematic cross-sectional view showing a configuration of a reflection white luminance evaluation device used for measuring reflection luminance and reflection contrast in an example.

FIG. 12 is a schematic cross-sectional view showing a configuration of a reflection black luminance evaluation device used for measuring reflection luminance and reflection contrast in an example.

[Explanation of symbols]

 11: forward scattering sheet, 21: polarizing film, 22: 1/2 wavelength film, 23: 1/4 wavelength film, 24: resin sheet, 25: metal thin film, 26: base material, 27 ... Broad-band circularly polarizing film, 31... Pressure-sensitive adhesive, 32... Glass plate, 33... Liquid crystal, 34... Front transparent electrode, 35. 37: rear transparent electrode, 41, 42, 43: liquid crystal cell, 51: reflective liquid crystal display device, 52, 53: transflective liquid crystal display device, 60: rear lighting device, 61: Lens sheet 62 Diffusion sheet 63 Light guide plate 64 Light source 65 Reflector 66 Reflective sheet 71 Luminance meter 72 Fluorescent lamp 73 Glass plate , 74 ... Optical mirror, 81 ... Polarized The absorption axis of the film, 82 an optical axis of the ...... 1/2-wavelength film, the optical axis 83 ...... 1/4-wave film.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13357 G02F 1/13357 1/13363 1/13363 G09F 9/00 313 G09F 9/00 313 324 324 F Term (reference) 2H042 BA02 BA12 BA14 BA15 BA20 2H049 BA02 BA06 BA07 BB03 BB63 BC22 2H091 FA08X FA08Z FA11X FA11Z FA14Z FA23Z FA31X FA31Z FA41Z FB02 FB08 GA01 HA07 HA09 HA10 KA01 KA10 LA16 LA03 5G435 A03 FB03 KK07

Claims (20)

[Claims] 1. A sheet having a non-uniform refractive index structure inside, wherein the total light transmittance is 90% or more and less than 100%, and the transparency is 15% or more and 60% or less. Forward scattering sheet. 2. The forward scattering sheet according to claim 1, wherein the non-uniform refractive index structure is formed by dispersing fine particles in a resin body. 3. The forward scattering sheet according to claim 2, wherein the resin body is an acrylic pressure-sensitive adhesive. 4. The fine particle is a silicone resin.
Or the forward scattering sheet according to 3. 5. The sheet according to claim 1, wherein the non-uniform structure of the refractive index is generated by phase separation of components constituting the sheet.
3. The forward scattering sheet according to 1. 6. The forward scattering sheet according to claim 1, wherein the retardation value is 30 nm or less. 7. The method according to claim 1, wherein a space between the two resin sheets is provided.
A laminated sheet, wherein the forward scattering sheet according to any one of the above is sandwiched. 8. A laminated sheet comprising a stretched resin sheet and the forward scattering sheet according to claim 1 laminated on each other. 9. The laminated sheet according to claim 8, wherein the stretched resin sheet is a polarizing film or a retardation film. 10. The laminated sheet according to claim 9, wherein the stretched resin sheet is a retardation film selected from a 波長 wavelength film and a 波長 wavelength film. 11. The laminated sheet according to claim 8, wherein the stretched resin sheet comprises a polarizing film and at least one retardation film, which are laminated on a forward scattering sheet. 12. A laminated sheet comprising the forward scattering sheet according to claim 1 and a reflective film or a transflective film. 13. The laminated sheet according to claim 12, further comprising a polarizing film laminated thereon. 14. A liquid crystal display device comprising the laminated sheet according to claim 11 laminated on the front surface of a liquid crystal cell. 15. The liquid crystal display device according to claim 14, wherein a polarizing film is laminated on a back surface of the liquid crystal cell, and a back lighting device is disposed on the back surface. 16. The liquid crystal display device according to claim 15, wherein a retardation film is laminated on the back surface of the liquid crystal cell together with the polarizing film. 17. A liquid crystal display device comprising: a polarizing film laminated on a front surface of a liquid crystal cell; and a laminated sheet according to claim 12 laminated on a rear surface of the liquid crystal cell. 18. The liquid crystal display device according to claim 17, wherein a retardation film is laminated on the front surface of the liquid crystal cell together with the polarizing film. 19. A liquid crystal cell, wherein a retardation film is laminated together with the laminated sheet on the back surface of the liquid crystal cell.
3. The liquid crystal display device according to 1. 20. The liquid crystal display device according to claim 17, wherein a backlight unit is further disposed on a back surface of the liquid crystal cell having the laminated sheet laminated on the back surface.