JPH1016112A - Reflecting member for liquid crystal displaying element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the displaying part of a reflecting type LCD easy to see by a method wherein a colorless semitransparent film equipped with high transmittance and reflectivity in combination is obtained by forming a filmy high reflectivity layer on at least one side of a transparent polymer film. SOLUTION: By forming a filmy transparent high reflectivity layer 20 on at least one side of a transparent polymer film 30, a reflecting member for semitransparent type liquid crystal displaying element is produced. As the stock of a polymer film 30 to use, there is no special limitation as for material as long as transparent material is concerned and polyethylene terephthalate and polyether sulfoneare preferably used. As for the thickness of this film 30, there is no critical limitation and the preferable thickness is 25-150μm. Further, the transparent high reflectivity layer 20 is produced from the oxide of indium and tin, zinc oxide, indium oxide, titanium oxide, aluminum nitride and silicon nitride. The reflecting member obtained as mentioned above has characteristics such as the reflectivity of 15% or more and the transmittance of 70% of more by the wavelength of 550nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transflective film having both high transmissivity and high reflectivity, and relates mainly to a reflective member which can be suitably used as a reflective type reflective member for a liquid crystal display.

[0002]

2. Description of the Related Art Liquid crystal display devices (LCDs) have been widely applied to one another by taking advantage of their features of thinness, light weight, and low power consumption. Currently, about 70% of LCDs are for notebook computers and word processors, but it is expected that demand for car navigation and PDAs (personal information terminals) will increase in the future. LCDs for notebook PCs and word processors are mainly backlit LCDs. However, small-sized portable information devices that are expected to spread in the future use reflection light liquid crystal display devices that use external light and consume less power. Is expected. In a reflection type liquid crystal display, when displaying characters or the like in a dark color (for example, black or dark blue), the display surface needs to be white like paper. Making the display surface of the LCD white like paper is called paper whitening of the LCD. Examples of the reflection sheet generally used at present include a resin sheet containing a white pigment, an aluminum reflection sheet, a silver reflection sheet, and the like. As the aluminum reflection sheet, a reflection sheet made of aluminum foil or PET
/ Reflective sheet made of aluminum thin film layer. The silver reflection sheet is made of a PET / silver thin film layer similarly to aluminum, but is a reflection sheet having a higher reflectance since silver having higher reflectance than aluminum is used.

However, a reflection type LCD in a scattering mode
For example, when the display portion is transparent and the non-display portion is relatively light, a colored reflection sheet is required. If a conventional reflection sheet is used for these reflection-type LCDs, the display portion becomes white or metal color, and is reflected, making it very difficult to see. However, if a dark sheet is used to make the display part darker, the non-display part becomes darker, far from paper white, and the contrast between the display part and the non-display part is lost, making it hard to see.

[0004]

In order to obtain an easy-to-view display screen, it is inserted between a reflective LCD in a scattering mode and a dark sheet. The display portion transmits the color of the dark sheet and the non-display portion is outside. There is a demand for a film that reflects light and has a proper reflectance and transmittance, and that has low absorption, so that contrast with the display portion can be obtained.

[0005]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by forming a transparent and high-refractive-index layer on a transparent film, A colorless transflective film having both high transmittance and high reflectance could be obtained.

That is, the present invention relates to (1) a reflective member for a transflective liquid crystal display device, wherein a transparent high refractive index layer (B) is formed on at least one surface of a transparent polymer film (A); Further, (2) a reflective member for a transflective liquid crystal display element formed by forming a transparent high refractive index layer (B) on both surfaces of a transparent polymer film (A), and (3) a transparent high refractive index (1) or (2), wherein the refractive index layer (B) is made of an oxide of indium and tin, zinc oxide, indium oxide, titanium oxide, aluminum nitride, or silicon nitride. And (4) a wavelength of 550 nm
The reflective member for a transflective liquid crystal display device according to any one of (1) to (3), wherein the reflectance is 15% or more and the transmittance is 70% or more.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 3, the present invention is a reflective member for a transflective liquid crystal display device in which a transparent high refractive index layer 20 is formed on at least one surface of a transparent polymer film 30. . Further, as shown in FIG. 4, a transparent high refractive index layer 20 may be formed on both surfaces of the transparent polymer film 30. The reflection member of the present invention can be used by inserting it between the scattering mode reflection type liquid crystal cell 10 and a dark sheet 40 such as black as shown in FIG.

The material of the polymer film used in the present invention is not particularly limited as long as it is transparent. Examples thereof include polyethylene terephthalate, polyester, polyether, polyarylate, acrylic resin, methacrylic resin, polyolefin, and the like. Polyvinyl chloride,
Examples thereof include homopolymers and copolymers such as polyethersulfone, and more preferably, polyethylene terephthalate and polyethersulfone are used.

The material of the film can be easily confirmed by measuring the infrared absorption spectrum (IR).
There is no critical limit on the thickness of the film;
１５０150 μm is preferably used.

It is easily understood by those skilled in the art to apply a chemical cleaning treatment, a surface roughening treatment, a glow discharge treatment, a corona discharge treatment, etc. to the surface of such a transparent polymer film in advance in order to improve the adhesion and the like. Will.

The transparent high-refractive index layer is made of an oxide of indium and tin (ITO: Indium Tin Oxide) or zinc oxide (Zn).
A transparent and high-refractive-index material such as O), indium oxide, titanium oxide, aluminum nitride, or silicon nitride is used. The high refractive index preferably means that the refractive index is 1.6 or more. For example, the refractive index of the oxide thin film layer composed of indium and tin is usually about 2.0.

The transparent high refractive index layer is preferably formed by using a vacuum such as a vacuum evaporation method or a sputtering method. In the vacuum deposition method, metal is placed in a crucible,
Melting is performed by resistance heating or electron beam heating, and the vapor pressure is increased to form a thin film on a desired substrate. Examples of the sputtering method include a high-frequency sputtering method, a direct-current sputtering method, a high-frequency magnetron sputtering method, a direct-current magnetron sputtering method, and an electron cyclotron resonance sputtering method. The transparent high refractive index layer may be formed on one side of the transparent polymer film as shown in FIG.
The film may be formed on both sides as described above.

The thickness of the transparent high-refractive-index layer depends on the balance between the required reflectance and transmittance, the transparent polymer film to be used,
Since it differs depending on the material used for the transparent high refractive index layer, it is not particularly defined.

The refractive index n and the film thickness d when the reflectance at the wavelength λ is maximum have a relationship of λ / 4 = n · d. In the present invention, the product of the refractive index n and the thickness d of the transparent high refractive index layer is preferably 50 to 200, more preferably 7 to 200.
5 to 150, more preferably 100 to 125. For example, the refractive index of the transparent high refractive index layer is n =
At 2.2, the thickness d of the transparent high refractive index layer that maximizes the reflectance at a wavelength of 550 nm is 62.5 nm.

In the present invention, the transmittance and the reflectance at a wavelength of 550 nm are preferably 70% or more and 15% or more, more preferably 70% or more and 17% or more. % Or more, more preferably 70% or more in transmittance and 20% or more in reflectance.

In order to obtain a transflective film having desired reflectance and transmittance, a vector method using a refractive index and an extinction coefficient of a transparent polymer film and a transparent high refractive index layer material, a method using an admittance diagram, and the like are used. The optical design used is determined to determine the material of the transparent high refractive layer, the number of layers, the film thickness, and the like. For example, if it is desired to obtain a reflectance as high as possible, it can be understood from optical calculations that ITO is preferably formed to a thickness of about 60 nm on one surface of a polyethylene terephthalate film.

On the other hand, even if the thickness of the transparent high refractive index layer is too large, the reflectance does not increase, and the adhesion of the transparent high refractive index layer to the polymer film decreases, and further from the viewpoint of effective use of resources. Not preferred.

The film thickness of the transparent high refractive index layer can be measured by a stylus roughness meter, a repetitive reflection interferometer, a microbalance, a quartz oscillator method or the like. Since measurement is possible, it is suitable for obtaining a desired film thickness. There is also a method in which the conditions for film formation are determined in advance, a film is formed on a sample substrate, the relationship between the film formation time and the film thickness is examined, and the film is controlled by the film formation time.

Regarding the type of metal oxide used for the transparent high refractive index layer, X-ray diffraction (XRD), electron diffraction,
It can be determined by Auger electron spectroscopy (AES). The layer structure can be measured by observing a cross section with a transmission electron microscope.

The transflective film thus obtained can be suitably used for a reflective LCD. That is, as shown in FIG. 5, a backlight is provided on the back surface of the LCD in addition to being provided between the reflective LCD and a dark sheet such as black to clarify the contrast between the display portion and the non-display portion. In the case where the backlight is turned off, it can be inserted between the LCD and the backlight.

In addition to using the translucent film as it is,
It can be easily analogized that an adhesive is applied, and the film is bonded to another film or a plate-like molded product. For example, if it is used by being attached to a dark sheet, it is excellent in workability and can be suitably used. Even if release paper is attached to the adhesive-applied surface without immediately bonding, workability is improved.

[0022]

The present invention will be described below with reference to examples. Example 1 An 80 nm thick ITO film was formed as a transparent high refractive index layer on one side of a polyethylene terephthalate film (O-100 manufactured by Teijin Limited, film thickness: 100 μm) as a transparent polymer film. The film is formed by a sputtering method. The target is an oxide having a weight ratio of indium oxide to tin oxide of 50:50, and oxygen is added to the target.
Sputtering was performed with an argon gas containing 0%. The layer configuration is as shown in FIG. (Example 2) On the back surface of the semi-transmissive film produced in Example 1, ITO was further deposited to a thickness of 80 nm in the same manner.
This layer configuration is as shown in FIG.

The samples of Examples 1 and 2 were measured for reflectance and transmittance at a wavelength of 800 to 300 nm. The reflectivity was measured using a Hitachi automatic recording spectrophotometer (U-34).
At 00), a 150φ integrating sphere was set, and a black plate having a small reflectance was set on the back surface of the sample, and the reflectance from the transparent high refractive index layer side, that is, the specular reflectance + diffuse reflectance was measured.
The reflectance of the back black plate was measured by the same apparatus, and the reflectance of the sample was determined by calculation. The results are shown in FIG.
The transmittance was measured as a parallel light transmittance. The results are shown in FIG. It can be seen that each has a reflectance of 15% or more and a transmittance of 70% or more at a wavelength of 550 nm. The values of the transparent polymer film used for both the reflectance and the transmittance are presented for comparison.

Next, as shown in FIG. 5, for example, the samples of Examples 1 and 2 were sandwiched between a reflective liquid crystal cell in a scattering mode and a black sheet, and the visibility of the display portion was checked. As a comparative example, a case where only the black sheet was provided on the back surface of the reflection type liquid crystal cell in the scattering mode was performed. The results are shown in (Table 1).

[0025]

[Table 1]

[0026]

By forming a transparent layer (B) having a high refractive index on the transparent polymer film (A), a transparent semi-transparent film having both high transmittance and high reflectance was obtained. . Thus, a reflecting member that can be used as a reflector of a liquid crystal display device can be provided.

[Brief description of the drawings]

FIG. 1 is a graph showing the reflectance of a reflective member and a transparent polymer film used in Examples 1 and 2.

FIG. 2 is a graph showing the parallel light transmittance of the reflecting member and the transparent polymer film used in Examples 1 and 2.

FIG. 3 is a schematic view showing an example of a reflecting member according to the present invention.

FIG. 4 is a schematic view showing another example of the reflection member according to the present invention.

FIG. 5 is a schematic view showing an example of a practical structure of a reflecting member according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 scattering mode reflection type liquid crystal cell 20 transparent high refractive index layer 30 transparent polymer film 40 dark color sheet such as black

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G02F 1/1335 520 G02F 1/1335 520 (72) Inventor Shin Fukuda 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Address Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. A reflecting member for a transflective liquid crystal display device comprising a transparent high-refractive index layer (B) formed on at least one surface of a transparent polymer film (A). 2. A reflective member for a transflective liquid crystal display device comprising a transparent high-refractive index layer (B) formed on both sides of a transparent polymer film (A). 3. The transflective liquid crystal display according to claim 1, wherein the transparent high refractive index layer (B) is made of an oxide of indium and tin, zinc oxide, indium oxide, titanium oxide, aluminum nitride, or silicon nitride. Reflecting member for element. 4. The reflectance at a wavelength of 550 nm is 15%.
The reflective member for a transflective liquid crystal display element according to any one of claims 1 to 3, having a transmittance of 70% or more.