JP2001031774A - Transmission-type light-scattering sheet and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light-scattering sheet which imparts diffusibility and directivity to reflection light by forming the sheet of a sea polymer and an island polymer having a refractive index different from that of the sea polymer by a specified value, and by bringing the particle size of the island polymer, the wt. ratio of sea polymer to island polymer, and the sheet thickness each into a specified range. SOLUTION: The sheet is formed of a sea polymer and an island polymer having a refractive index different from that of the sea polymer by 0.01-0.08. The average particle size of the island polymer is 0.5-10 μm; the wt. ratio of sea polymer/island polymer is (70/30)-(40/60); and the sheet thickness is 5-200 μm. A thermoplastic polymer is suitable as the sea polymer, and a resin having a refractive index different from that of the sea polymer is suitably selected and used as the island polymer. The average particle density of the island polymer is adjusted to about 1-100 (1010/cm3). The use of such a sheet enable scattered light to be directed usually in a range of diffusion angle of 5-50 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission type light scattering sheet (film) useful for displaying a high-luminance screen in a reflection type liquid crystal display device, a method of manufacturing the same, and a reflection type liquid crystal using the sheet. It relates to a display device.

[0002]

2. Description of the Related Art Liquid crystal display devices (LCDs) are widely used for display units of electric products such as personal computers (personal computers), word processors (word processors), liquid crystal televisions, clocks, and calculators. Since the liquid crystal itself does not emit light, a backlight for illuminating the liquid crystal portion from the back surface is used except for low-brightness applications such as watches and calculators.

[0003] In recent years, infrastructure for information communication such as the Internet has been improved, and networking of information has been advanced by fusing computers and communication devices. With networking, access to information is no longer restricted by time and place. In order to use such networks efficiently, PDA (Personal Digital Assista)
portable information terminals such as nce) are being vigorously developed.
Further, instead of a notebook personal computer (PC), a thinner and lighter mobile personal computer (PC) has been developed. Since these portable communication devices are required to be portable, it is necessary to achieve both long battery driving time and thin and small communication devices. Therefore, displays used in these portable communication devices are required to be thin and lightweight, and to have low power consumption. In particular, in order to achieve low power consumption, a method of brightening a display unit using natural light has been considered instead of a conventional method using a backlight. The most promising display is a reflective liquid crystal display. In particular, in order to cope with the diversification of information accompanying the future progress of multimedia, colorization and high definition are important, and an inexpensive reflective liquid crystal display device is required.

Various devices are known as a reflection type liquid crystal display device constituting a reflection type liquid crystal display device. However, for colorization and high definition, a type using a polarizing plate (single polarizing plate type) is used. ) Is advantageous. For example, if the liquid crystal layer is HAN
(Hybrid Aligned Nematic) The aligned R-OCB mode has excellent characteristics in terms of low voltage, wide viewing angle, high-speed response, intermediate tone display, high contrast, and the like.

When such a reflection type liquid crystal display element is used, in order to impart brightness to a screen, light (natural light or external light) incident on the liquid crystal layer is efficiently taken in (to prevent total reflection), and a reflection plate is provided. (E.g., electrodes), scatter reflected light to such an extent that visibility is not impaired, and it is necessary to make full use of natural light or external light. Further, the combination of the light scattering sheet and the polarizing plate can improve the reflection efficiency.

For example, in JP-A-63-228887, a photofabrication symposium (sponsored by the Printing Society of Japan), etc., the basic technology of a reflection type liquid crystal display device and the use of a metal thin film having an uneven surface as a lower electrode. A liquid crystal display device that prevents total reflection and widens the viewing angle of the display unit is introduced. In addition, in a reflection type liquid crystal display device, in addition to the method using such a diffuse reflection plate, a method using a transmission type light scattering sheet (Japanese Patent Publication No. 61-1986).
No. 8430).

However, when colorizing a display device, a color filter is used in addition to a polarizing plate. Therefore, the color display device has a large ratio of loss of reflected light, and the above-mentioned diffuse reflection plate system has a sufficient ratio for a display screen. High brightness cannot be provided. In particular, in colorization, it is important to provide high luminance by directional diffusion for directing diffused light in a certain direction. In order to enhance the directivity by the diffuse reflection plate method, it is necessary to precisely control the shape and distribution of the concave and convex portions of the reflection plate, which increases the cost.

Further, a transmission type scattering sheet using a transmission type light scattering sheet instead of a diffusion reflection plate in order to impart high luminance by scattering reflected light is also known (Japanese Patent Publication No. 61-8 / 1986).
No. 430). However, in order to impart directivity to the transmission type light scattering sheet, it is necessary to polymerize the sheet resin using a hologram (1998 Abstract of the Liquid Crystal Society of Japan). , Resulting in high costs.

On the other hand, a light-scattering sheet having a sea-island structure is known as a low-cost light-scattering sheet. JP 7
Japanese Patent Application Laid-Open No.-261171 discloses two or more resins having a difference in refractive index of 0.05 or more, for example, a low-refractive-index resin (such as a fluororesin or a silicon-based resin) and a high-refractive-index resin (an epoxy resin, (Acrylic resin, polyester resin, etc.) in combination to form a light scattering layer. In the examples of this document, the ratio between the low refractive index resin and the high refractive index resin is about the former / the latter = about 10/90 (weight ratio), and the thickness of the light scattering layer is about 4 μm. Also,
Japanese Patent Application Laid-Open No. 7-98452 discloses that transparent resin (acrylic resin, polyester resin, or the like) has fine particles (fluorine compound, fluorine-containing polymer) having a smaller refractive index than the transparent resin and having a particle size of 0.05 to 1 μm. Etc.) are disclosed. In the examples of this document, the amount of the fine particles in the light scattering layer is about 18 to 22% by weight,
It is described that the thickness of the light scattering layer is about 1 μm. However, in these methods, even if light can be scattered, directivity cannot be given to the scattered light.

Japanese Patent Application Laid-Open No. 7-27904 discloses that
Plastic beads (polypropylene, polyvinylidene chloride, etc.) with an average particle size of 5 to 50 μm and transparent resin (acrylic resin, styrene resin, etc.) on one side of a transparent resin sheet
There is disclosed a light diffusing sheet in which a mixed layer of the following is laminated.
The ratio of plastic beads to transparent resin is 30
It is described that the thickness of the mixed layer is about 1 to 2 times the average particle diameter of the plastic beads. Also, Japanese Patent Application Laid-Open No. Hei 9-113902
The publication discloses that 10 to 150 parts by weight of a bead-shaped light diffusing agent (acrylic, organic silicone, polystyrene, etc.) is 100 parts by weight of a light transmitting resin (polyester resin, acrylic resin, polystyrene resin, cellulose resin, etc.). A light-diffusing film in which a convex surface is formed by coating the surface of a light-transmitting substrate with one dispersed in a part is disclosed. According to the drawings of this document, the convex surface is formed by making the thickness of the light transmitting resin layer smaller than the particle diameter of the light diffusing agent. However, in these methods, basically,
Light is scattered using a sheet in which beads are adhered to the sheet surface by a transparent resin. For this reason, the distribution of the diffused light is close to a Gaussian distribution, and directivity cannot be imparted to the diffused light, and the brightness of the display screen is insufficient.

[0011]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a light scattering sheet (or film) capable of imparting diffused light and directivity to reflected light, a method of manufacturing the same, and a reflection type LCD using the sheet. Is to provide.

Another object of the present invention is to provide a light-scattering sheet (or film) which can be displayed with high luminance by a high directivity of scattered light even in a color display device, a method of manufacturing the same, and a reflection type using the sheet. An LCD is provided.

[0013]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have a specific refractive index difference from the sea polymer and a specific particle size in the sea polymer. When using a sheet containing a specific amount of polymer having,
The ability to form island polymer particles in the sheet at high density and to provide directivity to diffused light, especially when the average particle density of the island polymer is adjusted to a specific range, it is possible to provide high directivity to diffused light, and furthermore, the sheet thickness Has been found to be able to adjust the directivity to a preferable diffusion angle without impairing the transparency of the sheet, thereby completing the present invention.

That is, the light scattering sheet of the present invention comprises a sea polymer, and the sea polymer has a refractive index of 0.01 to 0.0.
It has a sea-island structure composed of eight different island polymers, the average particle size of the island polymer is 0.5 to 10 μm, and the ratio of the sea polymer and the island polymer is the former / the latter = 70/30 to
40/60 (weight ratio) and sheet thickness of 5 to 200
μm. Transmission type light scattering sheet. The average particle density of the island polymer is, for example, about 1 to 100 (10 ¹⁰ particles / cm ³ ). The sheet may be capable of directing diffused light at a diffusion angle of 5 to 50 °. Sea and island polymers are
It can be selected from styrene resins, (meth) acrylic resins, vinyl ester resins, vinyl ether resins, polycarbonate resins, polyester resins, polyamide resins, thermoplastic polyurethane resins, cellulose derivatives, and the like.

The present invention also includes a method for manufacturing the sheet and a reflection type liquid crystal display device provided with the sheet.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Polymer] In the present invention, a sea polymer and an island polymer having a different refractive index from the sea polymer are used. Such a sea polymer and an island polymer can be appropriately selected and used from various polymers.

Examples of the resin constituting the sea polymer and the island polymer include styrene resins, (meth) acrylic resins, vinyl ester resins, vinyl ether resins, halogen-containing resins, olefin-containing resins, polycarbonate resins, and polyester resins. Resin, polyamide resin, thermoplastic polyurethane resin, polysulfone resin,
Polyphenylene ether resins, cellulose derivatives (cellulose esters, cellulose carbamates, cellulose ethers, etc.), silicone resins (polydimethylsiloxane, polymethylphenylsiloxane, etc.),
Rubbers or elastomers (diene rubbers such as polybutadiene and polyisoprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylic rubber, urethane rubber, silicone rubber, etc.) are exemplified. Preferred resins include styrene resins, (meth)
Acrylic resins, vinyl ester resins, vinyl ether resins, polycarbonate resins, polyester resins, polyamide resins, thermoplastic polyurethane resins, and cellulose derivatives are included. The sea polymer and the island polymer are usually composed of different resins, and are incompatible with each other.

The styrene resin includes a styrene monomer homopolymer or copolymer (polystyrene, styrene-α-methylstyrene copolymer, styrene-vinyltoluene copolymer, etc.), a styrene monomer and another copolymer. Copolymers with polymerizable monomers ((meth) acrylic monomers, maleic anhydride, maleimide monomers, dienes, etc.) are included.
Examples of the styrene-based copolymer include a styrene-acrylonitrile copolymer (AS resin), a copolymer of styrene and a (meth) acrylic monomer [styrene-methyl methacrylate copolymer, styrene-methacrylic acid Methyl- (meth) acrylic acid ester copolymer, styrene-methyl methacrylate- (meth) acrylic acid copolymer], and styrene-maleic anhydride copolymer. Preferred styrene resins include polystyrene, a copolymer of styrene and a (meth) acrylic monomer [a copolymer containing styrene and methyl methacrylate as a main component such as a styrene-methyl methacrylate copolymer], AS resin, styrene-butadiene copolymer and the like are included.

As the (meth) acrylic resin, a homopolymer or a copolymer of the above (meth) acrylic monomer or a copolymer of a (meth) acrylic monomer and a copolymerizable monomer is used. it can. (Meth) acrylic monomers include, for example,
Methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate C _1-10 alkyl (meth) acrylate; (meth)
Aryl (meth) acrylates such as phenyl acrylate; polyhydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; glycidyl (meth) acrylate; N, N-dialkylaminoalkyl (meth) ) Acrylate; (meth) acrylonitrile and the like. Examples of the copolymerizable monomer include the above-mentioned styrene monomer, vinyl ester monomer, maleic anhydride, maleic acid, fumaric acid, and the like. These monomers can be used alone or in combination of two or more.

Examples of the (meth) acrylic resin include poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, and methyl methacrylate-acrylate- ( (Meth) acrylic acid copolymer, methyl methacrylate-
(Meth) acrylic acid ester copolymers, (meth) acrylic acid ester-styrene copolymers (MS resin and the like) and the like can be mentioned. Preferred (meth) acrylic resins include poly (meth) acrylates such as poly (methyl) acrylate.
C _1-5 alkyl acrylate.

As the vinyl ester resin, a homopolymer or a copolymer of vinyl ester monomer (polyvinyl acetate,
Copolymers of vinyl ester monomers and copolymerizable monomers (vinyl acetate-vinyl chloride copolymers, vinyl acetate- (meth) acrylate copolymers, etc.) or And derivatives thereof. Derivatives of vinyl ester resins include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinyl acetal resin, and the like.

Examples of vinyl ether resins include vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether and vinyl t-butyl ether.
_1-10 alkyl ether homo- or copolymer, vinyl C
_A copolymer of a _1-10 alkyl ether and a copolymerizable monomer (eg, a vinyl alkyl ether-maleic anhydride copolymer) may be mentioned.

Examples of the halogen-containing resin include polyvinyl chloride, polyvinylidene fluoride, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride- (meth) acrylate copolymer, and a vinylidene chloride- (meth) acrylate copolymer. Coalescence and the like.

The olefin-containing resin includes, for example, olefin homopolymers such as polyethylene and polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene- (meth) acrylic acid copolymer, ethylene And copolymers such as-(meth) acrylate copolymers.

Examples of the polycarbonate resin include aromatic polycarbonates based on bisphenols (such as bisphenol A) and aliphatic polycarbonates such as diethylene glycol bisallyl carbonate.

Examples of the polyester resin include aromatic polyesters using an aromatic dicarboxylic acid such as terephthalic acid (such as poly C _2-4 alkylene terephthalate such as polyethylene terephthalate and polybutylene terephthalate and poly C _2-4 alkylene naphthalate). Fats using homopolyesters, copolyesters containing C _2-4 alkylene terephthalate and / or C _2-4 alkylene naphthalate units as a main component (for example, 50% by weight or more), and aliphatic dicarboxylic acids such as adipic acid Group polyesters and the like. The polyester-based resin also includes a homo- or copolymer of a lactone such as ε-caprolactone.

As the polyamide resin, nylon 4
6, nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, and other aliphatic polyamides, dicarboxylic acids (eg, terephthalic acid, isophthalic acid, adipic acid, etc.) and diamines (eg, hexamethylene diamine, meta (Xylylenediamine). The polyamide-based resin may be a homo- or copolymer of a lactam such as ε-caprolactam, and may be a copolyamide as well as a homopolyamide.

Examples of the cellulose esters among the cellulose derivatives include, for example, aliphatic organic acid esters (eg, cellulose acetate such as cellulose diacetate and cellulose triacetate; cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate). Organic acid esters such as C _1-6 ), aromatic organic acid esters (C _7-12 aromatic carboxylic acid esters such as cellulose phthalate and cellulose benzoate), and inorganic acid esters (for example,
Cellulose phosphate, cellulose sulfate, etc.)
It may be a mixed acid ester such as acetic acid / cellulose nitrate ester. Cellulose derivatives include cellulose carbamates (eg, cellulose phenyl carbamate, etc.), cellulose ethers (eg, cyanoethyl cellulose; hydroxy-C _2-4 alkyl cellulose such as hydroxyethyl cellulose and hydroxypropyl cellulose); C ₁ such as methyl cellulose and ethyl cellulose. _-6 alkylcellulose; carboxymethylcellulose or a salt thereof, benzylcellulose, acetylalkylcellulose, etc.).

(Sea Polymer) In the present invention, among the above resins, a thermoplastic polymer having moldability, film forming property and transparency can be suitably used as the sea polymer. Moldability,
Examples of the resin having film forming properties and transparency include a styrene resin, a (meth) acrylic resin, a polycarbonate resin, a polyester resin, a polyamide resin, a thermoplastic polyurethane resin, and a cellulose derivative.

The light transmittance of the sea polymer is, for example, 85
% (About 85 to 95%), preferably 87% or more (about 87 to 95%), and more preferably 90% or more (about 90 to 95%).

From the viewpoint of the strength and rigidity of the sheet, the glass transition temperature of the sea polymer can be selected, for example, from about 50 to 300 ° C., preferably from about 80 to 250 ° C.

(Island polymer) In the present invention, the average particle size of the island polymer is about 0.5 to 6 μm, preferably 0.5 to 6 μm.
It is about 5 μm, more preferably about 0.5 to 4 μm (particularly about 1 to 4 μm). When the average particle size is less than 0.5 μm, the ratio of the backscattered light becomes too large, and natural light is reflected on the sheet surface, so that the display screen of the LCD has a white tint (white blur). Conversely, the average particle size of the island polymer is 1
If it exceeds 0 μm, the directivity of the scattered light will decrease.

In the present invention, the island polymer has a refractive index (n _D ) of about 0.01 to 0.08, preferably about 0.01 to 0.06, more preferably about 0.01 to 0.08. Use island polymers that differ by about 0.04. If the refractive index difference is less than 0.01, the light scattering property is insufficient. On the other hand, if the refractive index is larger than 0.08, the ratio of the backscattered light becomes too large, and the display screen of the LCD becomes white. The refractive index of the island polymer is often smaller than the refractive index of the sea polymer.

The resin constituting such an island polymer is as follows:
From the resins that can constitute the sea polymer and the island polymer, resins having different refractive indices and types from the sea polymer can be appropriately selected and used. The resin constituting the preferred island polymer can be selected from the same resins as the preferred sea polymer. Further, a preferable island polymer may be a vinyl ester resin, a vinyl ether resin, or the like.

Examples of the combination of the sea polymer and the island polymer include the following specific examples.

(1) Sea polymer: cellulose derivative [particularly cellulose acetate
Tate (n_D= 1.48)] Island polymer: (meth) acrylic resin [for example, polymer
Methyl acrylate (n _D= 1.49)
A) Acrylic esters, etc.], styrene resins [Examples
For example, polystyrene; acrylonitrile-styrene copolymer
(2) Sea polymer: styrene-based resin [especially, polystyrene (n
_D= 1.595)] Island polymer: polycarbonate resin [for example, bisulfate
Enol A type polycarbonate (n_D= 1.585)
Which aromatic polycarbonate etc.], different from sea polymer
Styrene resin [for example, the sea polymer is polystyrene
In the case of styrene, styrene-acrylonitrile copolymer (n_D
= 1.57) and the like, and cellulose derivatives [eg, ethyl
(3) Sea polymer: polyester resin [especially polyethylene]
Terephthalate (n_D= 1.65)] Island polymer: Styrene resin [for example, polystyrene
(N_D= 1.595); acrylonitrile-styrene
Polymer (AS resin) (n_DStyrene such as 1.58)
(4) Sea polymer: (meth) acrylic resin [especially,
(T) Methyl acrylate (n_D= 1.49)] Island polymer: polyamide-based resin [eg amorphous Niro
66 (n_D= 1.53), crystalline nylon 66 (n_D=
1.475) etc. [Transmissive light scattering sheet] The transmission light scattering sheet of the present invention
Is an island polymer with a specific refractive index and particle size
Limmer is contained at a specific concentration. And the sheet
In addition, island polymer particles are dispersed at a constant density. this
By using such a sheet, high directivity can be given to scattered light.
Wear. In general, the light diffusion intensity of a sheet is
Degree, ie, the product of the particle density and the sheet thickness.
Scattered light theory).
In addition, the refractive index, particle size and concentration of the island polymer (for example,
Ratio of polymer to island polymer)
It appears that the particle density of the mer has a major effect.

The ratio between the sea polymer and the island polymer is about the former / the latter = about 70/30 to 40/60 (weight ratio), preferably about 70/30 to 45/55 (weight ratio), and more preferably about 70/30 to 45/55 (weight ratio). It is about 30 to 50/50 (weight ratio), and may be about 60/40 to 40/60 (weight ratio). If the proportion of the island polymer is too small, even if the island polymer particles are dispersed at a high density, light cannot be diffused effectively because the amount of the island polymer in the sheet is insufficient. On the other hand, if the proportion of the island polymer is too large, the uniform dispersibility of the island polymer is reduced, so that the directivity is significantly reduced. Further, the island polymer concentration in the sheet may be, for example, about 30 to 60% by weight, preferably about 40 to 60% by weight.

The average particle density of the island polymer is from 1 to 100.
(10 ¹⁰ / cm ^3), preferably about 4 to 80 (10 ¹⁰ / c
m ³ ). When the average particle density is too small, directivity cannot be given to the scattered light. On the other hand, if the average particle density is too large, the ratio of backscattered light becomes too large, and natural light is reflected on the sheet surface.

The average particle density can be calculated, for example, by measuring the average particle diameter and using the following formula (I).

Average particle density (particles / cm ³ ) = 1 cm ³ × Vs / [(4/3) π (Ds × 10 ⁻⁴ / 2) ³ ] (I) (where Vs is the ratio of island polymer in the sheet) (Volume basis), π is pi, Ds is particle size of island polymer (μm)
In the above formula, the ratio Vs of the island polymer is, for example, such that the sheet is composed of the island polymer and the sea polymer, and if necessary, other components (for example, additives such as a compatibilizer described below). In this case, it is represented by the following formula (II).

Vs = [Ws / ρs] / [Ws / ρs + Wu / ρu + Wo / ρo] (II) (where Ws, Wu and Wo are island polymers, respectively)
The ratio (weight percentage) of the sea polymer and other components in the sheet is shown. ρs, ρu and ρo indicate the density of the island polymer, sea polymer, and other components, respectively. The transmission type light scattering sheet of the present invention is adjusted to a specific sheet thickness. By adjusting the sheet thickness,
The directivity of diffused light can be adjusted while maintaining the light transmittance of the sheet. The thickness of the sheet is, for example, about 5 to 200 μm, preferably about 10 to 150 μm, and more preferably about 30 to 120 μm. The sheet thickness is
It may be, for example, about 5-200 times (based on length), preferably about 10-150 times, the average particle size of the island polymer.

When such a sheet is used, the diffused light is
Usually, the diffusion angle is about 5 to 50 °, preferably 10 to 40.
It can be oriented in the range of about {, more preferably about 10 to 30}. If the angle at which the diffused light is directed is less than 5 °,
Directivity is insufficient, and a bright screen cannot be displayed over a wide viewing angle. On the other hand, when the angle at which the diffused light is directed exceeds 60 °, the ratio of the backscattered light becomes too large, and L
The display screen of the CD becomes white.

Whether the diffused light is directed or not is determined by plotting the intensity of the light diffused by the sheet (diffusion intensity) with respect to the diffusion angle when the plotted curve is within a specific diffusion angle range. It can be determined based on whether or not it has a shoulder or a maximum value.

The total light transmittance of the transmission type light scattering sheet is, for example, 85% or more (about 85 to 95%), preferably 9%.
0% or more (about 90 to 95%).

The transmission type light scattering sheet may contain a compatibilizer in order to improve the dispersibility of the island polymer. The ratio of the compatibilizer is, for example, about 1 to 20 parts by weight, preferably about 2 to 10 parts by weight, based on 100 parts by weight of the total amount of the sea polymer and the island polymer.

The compatibilizing agent can be used according to the combination of the sea polymer and the island polymer. For example, it is selected from oxazoline compounds and modified resins (for example, carboxyl groups, acid anhydride groups, epoxy groups, oxazoline groups, etc.). A modified resin modified with at least one modifying group), a block or graft copolymer (acrylonitrile-butadiene-styrene copolymer (ABS resin), a hydrogenated styrene-butadiene (SB) block copolymer,
Hydrogenated styrene-butadiene-styrene block copolymer, hydrogenated (styrene-ethylene / butylene-styrene) block copolymer, styrene-butadiene (SB)
Examples include block copolymers and epoxidized ABS resins (Epofriend manufactured by Daicel Chemical Industries, Ltd.). The compatibilizer is usually a block or graft copolymer having the same or similar components as the constituent resin of the polymer blend system, a block or graft copolymer containing a component having an affinity for the constituent resin of the polymer blend system, or the like. used.

Further, the transmission type light scattering sheet may contain other additives such as a stabilizer (an antioxidant, an ultraviolet absorber, a heat stabilizer, etc.), a plasticizer, a colorant (a dye or a pigment), a flame retardant. , An antistatic agent, a surfactant and the like.

Various coating agents, for example, antistatic agents, antifogging agents (sucrose fatty acid esters, glycol fatty acid esters, polyglycol fatty acid esters, etc.), release agents and the like are coated on the surface of the transmission type light scattering sheet. You may.

The transmission type light scattering sheet according to the present invention may be used as a substrate film (eg, a cellulose triacetate film).
May be laminated on at least one surface.

Such a transmission type light scattering sheet can be produced by molding a resin mixture containing the sea polymer and the island polymer by a conventional method, for example, a casting method, a melt extrusion method or the like.

As the casting method, for example, a solution of a sea polymer (cellulose derivative (eg, cellulose triacetate)) and island polymer particles (beads) insoluble in this solution ((meth) acrylic resin (polymethacrylic acid) Methyl))),
A method of casting a mixture (liquid-liquid phase separated state) of a solution of a sea polymer and a solution of an island polymer incompatible with the solution may be used.

The solution of the sea polymer or the solution of the island polymer may be, for example, a solution of the sea polymer or the island polymer in an organic solvent (ketones, esters, halogenated hydrocarbons,
Alcohols, or mixtures thereof).

In the melt extrusion method, a sea polymer (polyester resin (amorphous polyethylene terephthalate, etc.)) and an island polymer incompatible with the sea polymer (styrene resin (polystyrene, etc.)) are melt-kneaded. (T-die method, etc.). [Reflection type LCD] The transmission type light scattering sheet of the present invention can be applied to a reflection type LCD provided with a reflection means and a polarization means.
For example, the present invention can be applied to a reflective LCD of a two-polarizer type using two polarizers having different polarizabilities, a reflective LCD of a one-polarizer type using one polarizer, and the like. The reflection type LCD of the single polarizing plate type is, for example, one polarizing plate,
Reflective LC combining various modes (mode using twisted nematic liquid crystal, R-OCB (Optically Compensated Bend) mode, parallel alignment mode, etc.)
D may be used.

FIG. 1 is a schematic sectional view for explaining a reflection type LCD. The reflective LCD shown in FIG. 1 has a liquid crystal cell 6 having a liquid crystal 4 (liquid crystal layer or the like) sealed between a pair of transparent substrates 3 (glass plates or the like). One of the transparent substrates reflects incident light. (For example, a reflection layer such as a specular reflection plate) is laminated. Further, on the other transparent substrate of the liquid crystal cell 6, the transmission type light scattering sheet 2 of the present invention is laminated via a coloring means 8 (color filter or the like) for color display. On the other surface of the transmission type light scattering sheet 2, a polarizing means 1 (a polarizing layer such as a polarizing plate) for polarizing reflected light is laminated. When the reflective LCD is used for monochrome display, the colorizing means 8 is not always necessary.

In such a reflection type LCD, the light (incident light) incident from the front surface 7 on the observer side is reflected by the reflection means 5 and diffused again by the transmission type light scattering sheet 2. The reflection type L using the transmission type light scattering sheet of the present invention.
When a CD is configured, the scattered light can be directed in a certain direction while imparting diffusivity to the reflected light, so that the screen display can be brightened. Further, since sufficient brightness can be ensured even in color display, a clear color image can be displayed on the color reflection type liquid crystal display device.

When the transmission type light scattering sheet of the present invention is used,
Since high directivity can be given to the scattered light, high brightness display can be performed over a wide viewing angle. Therefore, it can be suitably used for a reflective LCD, particularly for a color liquid crystal display of a portable information device.

[0057]

According to the present invention, since a sheet having a specific thickness is formed by blending a sea polymer and an island polymer in a specific ratio, high diffusivity and directivity can be imparted to the reflected light. For this reason, when this sheet is used for a color display device, it is possible to display with high luminance by high directivity of scattered light.

[0058]

The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 As a sea polymer, cellulose triacetate (TAC,
60 parts by weight of Daicel Chemical Industries Ltd. (LT-105) were dissolved in 900 parts by weight of a mixed solvent of methylene chloride / methanol = 9/1 (weight ratio). To this solution was added 40 parts by weight of crosslinked polymethyl methacrylate fine particles (PMMA, manufactured by Sekisui Chemical Co., Ltd., MBX-2AB) as an island polymer,
The mixture was kneaded, cast, and dried at 100 ° C. for 10 minutes to obtain a sheet having a sheet thickness of 50 μm. Observation of the obtained sheet with an optical microscope revealed that the average particle size of the island polymer was 2.5 μm.

Example 2 50 parts by weight of sea polymer (TAC) and island polymer (PM)
MA) was the same as Example 1 except that 50 parts by weight of MA) was used. Observation of the obtained sheet with an optical microscope revealed that the average particle size of the island polymer was 2.5 μm.

Comparative Example 1 80 parts by weight of sea polymer (TAC) and island polymer (PM)
MA) in the same manner as in Example 1 except that 20 parts by weight of MA) was used and the sheet thickness was 100 μm. Observation of the obtained sheet with an optical microscope revealed that the average particle size of the island polymer was 2.5 μm.

Comparative Example 2 75 parts by weight of sea polymer (TAC) and island polymer (PM)
MA) in the same manner as in Example 1 except that 25 parts by weight of MA) was used and the sheet thickness was 105 μm. Observation of the obtained sheet with an optical microscope revealed that the average particle size of the island polymer was 2.5 μm.

Comparative Example 3 50 parts by weight of sea polymer (TAC) and 50 parts by weight of a benzoguanamine / formaldehyde condensate (cured fine resin of benzoguanamine resin, MS, manufactured by Nippon Shokubai Co., Ltd.) were used as the island polymer. Except for the above, it was the same as Comparative Example 1. Observation of the obtained sheet with an optical microscope revealed that the average particle size of the island polymer was 2 μm.

Comparative Example 4 The procedure of Comparative Example 3 was repeated except that the thickness of the sheet was changed to 8 μm. Observation of the obtained sheet with an optical microscope revealed that the average particle size of the islands was 2 μm.

Table 1 shows the average particle density and light particle collision frequency (= average particle density × sheet thickness) of the sheets obtained in Examples 1 and 2 and Comparative Examples 1 to 4.

[0066]

[Table 1]

(Directivity 1) The reflection type LCD model device shown in FIG. 2 was constructed using the obtained light diffusion sheet. Laser light (NIHON KAGAKU)
ENG NEO-20MS), and the intensity (diffusion intensity) of the reflected light corresponding to the diffusion angle θ1 was measured. FIG. 4 shows the measurement results. As is evident from FIG. 4, the diffused light of the sheet of the example is directed around the diffusion angle of 11 to 14 ° as compared with the sheet of the comparative example.

In the particle scattering theory, if the frequency (= average particle density × sheet thickness) of the light before it enters the particle dispersion sheet and collides with the particle is the same,
The light diffusion intensity is the same. However, the sheet of Example 1 and the sheet of Comparative Example 1 are different from the sheet of Comparative Example 1 irrespective of substantially the same collision frequency factor (= average particle density × sheet thickness). It has strong diffusion intensity around 11 °. Similarly, the sheet of Example 2 and the sheet of Comparative Example 2 have the same collision frequency (= average particle density × sheet thickness), but the sheet of Example 2 is different from the sheet of Comparative Example 2. , Around 12 °. (Directivity 2) A reflective LCD model device similar to that shown in FIG. 2 was constructed, spotlight white light was emitted from an oblique direction, and the intensity of light reflected vertically was measured (FIG. 3). The intensity of the reflected light in the vertical direction corresponding to the incident angle (diffusion angle θ2) was evaluated according to the following criteria.

：: Brighter than the sheet of Comparative Example 1 Δ: Brightness similar to that of the sheet of Comparative Example 1 ×: Darker than the sheet of Comparative Example 1 The results are shown in Table 2.

[0070]

[Table 2]

As is clear from Table 2, in the transmission type light diffusion sheet of the example, the diffused light is directed near the diffusion angle (incident angle) of 15 ° as compared with the sheet of the comparative example. Therefore, high-luminance display can be performed over a wide diffusion angle.

Example 3 63 parts by weight of a polyethylene terephthalate copolymer (PET-G manufactured by Toyobo Co., Ltd.) as a sea polymer,
30 parts by weight of polystyrene (GPPS # 30, manufactured by Daicel Chemical Industries, Ltd.) as an island polymer and a compatibilizer (Epofriend AT20, manufactured by Daicel Chemical Industries, Ltd.)
2) Kneading machine with 7 parts by weight (TOYOSEIKI LABO PLASTOMIL
In L), the mixture was kneaded at 220 ° C. and extruded to obtain pellets. The pellets were hot pressed at 240 ° C.
A μm sheet was obtained. When the sheet was observed with a microscope, the average diameter of the fine particles was 1 μm.

Comparative Example 5 The sheet thickness was determined using 78.2 parts by weight of the sea polymer (PET-G), 13 parts by weight of the island polymer (GPPS # 30), and 8.8 parts by weight of the compatibilizer (Epofriend AT202). Was obtained in the same manner as in Example 3 except that the thickness was changed to 200 μm. When the sheet was observed with a microscope, the average diameter of the fine particles was 1 μm.

The sheets obtained in Example 3 and Comparative Example 5 were evaluated in the same manner as in Examples 1 and 2 and Comparative Examples 1 to 4 (directivity 2). The results are shown in Tables 3 and 4.

[0075]

[Table 3]

[0076]

[Table 4]

As is clear from the table, in the transmission type light diffusion sheet of the example, the diffusion angle (= average particle density × sheet thickness) was almost the same as that of the sheet of the comparative example. The diffused light is directed at around (incident angle) 20 °.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining a transmissive LCD of the present invention.

FIG. 2 is a schematic diagram for explaining a method for evaluating the directivity of a transmission type light scattering sheet.

FIG. 3 is a schematic diagram for explaining another evaluation method of the directivity of the transmission type light scattering sheet.

FIG. 4 is a graph showing the directivity of a transmission type light scattering sheet in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Polarizing means 2 ... Transmissive light scattering sheet 3 ... Glass plate 4 ... Liquid crystal 5 ... Reflecting means 6 ... Liquid crystal cell

Continued on the front page F term (reference) 2H042 BA02 BA15 BA20 4F071 AA09 AA12 AA13 AA15 AA20 AA22 AA22X AA24 AA24X AA25 AA26 AA28 AA28X AA29 AA29X AA30 AA32X AA33 AA33A AA AA AA AA AA AA AA AA AA AA AH19 BA01 BA02 BB02 BB06 BC01 BC12 4J002 AB02W AB02X AB03W AB03X AC03W AC03X AC06W AC06X AC07W AC07X AC08W AC08X BB03W BB03X BB06W BB06X BB07W BB07X BB08W BB08X BB12W BB12X BC03W BC03X BC06W BC06X BC07W BC07X BC08W BC08X BC09W BC09X BD04W BD04X BD08W BD08X BD09W BD09X BD10W BD10X BD14W BD14X BE02W BE02X BE03W BE03X BE04W BE04X BE06W BE06X BF01W BF01X BF02W BF02X BG03W BG03X BG04W BG04X BG05W BG05X BG06W BG06X BG07W BG07X BG10W BG10X BH01X BH011 BH02W BH02X CD19W CD19X CF03W CF03X CF05W CF05X CF06W CF06X CF07W CF07X CF08W CF08X CF19W CF19X CG01W CG01X CH07 CH07W CK02W CK02X CL01W CL01X CL03W CL03X CL05W CL05X CN03W CN03X CP03W CP03X FD020 FD050 FD060 FD070 FD090 FD100 FD130 FD310

Claims (7)

[Claims] 1. A sheet having a sea-island structure comprising a sea polymer and an island polymer having a refractive index different from that of the sea polymer by 0.01 to 0.08, wherein the average particle size of the island polymer is 0.5. A transmission type light-scattering sheet wherein the ratio of the sea polymer to the island polymer is 70/30 to 40/60 (weight ratio) and the sheet thickness is 5 to 200 μm. 2. The transmissive light diffusion sheet according to claim 1, wherein the diffusion light can be directed at a diffusion angle of 5 to 50 °. 3. An island polymer having an average particle density of 1 to 100.
The transmission type light-scattering sheet according to claim 1, wherein the number is (10 ¹⁰ / cm ³ ). 4. A method according to claim 1, wherein the sea polymer and the island polymer are styrene resin, (meth) acrylic resin, vinyl ester resin, vinyl ether resin, polycarbonate resin,
The transmission type light scattering sheet according to claim 1, wherein the sheet is at least one selected from a polyester resin, a polyamide resin, a thermoplastic polyurethane resin, and a cellulose derivative. 5. A sheet having a sea-island structure comprising a sea polymer and an island polymer having a refractive index different from that of the sea polymer by 0.01 to 0.06, wherein the average particle diameter of the island polymer is 0.5. ４4 μm, the ratio of the sea polymer and the island polymer is the former / the latter = 70/30 to 50/50 (weight ratio), the average particle density of the island polymer is 4 to 80 (10 ¹⁰ / cm ³ ), and the sheet 2. The transmission type light scattering sheet according to claim 1, having a thickness of 20 to 150 [mu] m. 6. A sea polymer having a refractive index different from that of the sea polymer by 0.01 to 0.2 and an average particle size of 1 to 10 μm.
A method for producing a transmission-type light-scattering sheet, wherein a resin composition containing an island polymer in a ratio (sea polymer / island polymer) of 70/30 to 40/60 (weight ratio) is formed into a sheet with a thickness of 5 to 200 μm. 7. A reflection device in which a reflection means for reflecting incident light is provided on one surface of a liquid crystal cell in which liquid crystal is sealed, and a polarization means for polarizing reflected light is provided on the other surface. A reflection type liquid crystal display device, wherein the transmission type light scattering sheet according to claim 1 is disposed between a polarizing means and a liquid crystal cell.