JP2000098361A - Reflective liquid crystal display - Google Patents

Abstract

[57] [Abstract] [Problem] Achromatic white display with uniform wavelength dispersion of display light is possible, and by increasing the scattering effect, as much incident light as possible is collected at the observer's position. Provided is a reflective liquid crystal display device that enables bright color display. An observer-side substrate having a transparent electrode disposed on a transparent substrate, a light-reflecting film, a light-scattering film, and a transparent substrate corresponding to the transparent electrode are laminated on the substrate. In a reflective liquid crystal display device having at least a liquid crystal sandwiched between the two substrates, a microlens in which a plurality of the light scattering films are provided in each pixel portion and a non-pixel portion region, and a refractive index different from the microlens And a flattening layer made of a transparent resin that covers the microlens having
A reflection type liquid crystal display device, wherein the extinction coefficient of the micro lens at a light wavelength of 430 nm is 1.5 × 10 ⁻³ or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device having a light scattering film formed thereon to increase the viewing angle and improve the display quality.
The present invention relates to a liquid crystal display device for DA, personal portable information equipment, and the like.

[0002]

2. Description of the Related Art A liquid crystal display device generally comprises a pair of opposing electrode substrates on which a polarizing film and a transparent electrode are provided, respectively, and a liquid crystal material sealed between these electrode substrates. I have. Further, in a color liquid crystal display device for displaying a color image, a color filter layer for coloring polarized light is provided on one of the pair of electrode substrates.

When displaying a screen, a voltage is applied between the transparent electrodes facing each other to change the orientation of the liquid crystal material sealed between the electrode substrates, thereby controlling the plane of polarization of light transmitted through the liquid crystal material. At the same time, transmission and non-transmission are controlled by a polarizing film. In the following description, a pixel portion refers to a portion that applies a voltage to the sandwiched liquid crystal and changes the alignment state of the liquid crystal (usually, a portion where opposed electrodes overlap in plan view). The area between each pixel section is shown.

[0004] Here, the liquid crystal display device is an electrode substrate on the rear side of the liquid crystal display device (refers to an electrode substrate located on the opposite side to the viewer among a pair of opposing electrode substrates, and is hereinafter referred to as a rear side substrate). ), A built-in light source (backlight) is disposed on the back surface or side surface, and a light beam emitted from the built-in light source is incident on the back substrate to obtain a display screen. A transmissive liquid crystal display device with a built-in light is widely used. However, this transmission type liquid crystal display device consumes a large amount of power for a built-in light source, and has a power consumption that is not much different from other display devices other than the liquid crystal display device (for example, a CRT, a plasma display device, etc.). For this reason, it can be said that the transmission type liquid crystal display device loses the essential characteristics of the liquid crystal display device which should be portable with low power consumption. Also,
In the transmission type liquid crystal display device, the built-in light source is consumed over time, and when the built-in light source is consumed, the display quality is significantly impaired. Moreover, in many cases, it is difficult or impossible to replace the exhausted built-in light source.

Therefore, in recent years, as a liquid crystal display device,
Attention has been focused on a reflective liquid crystal display device without a built-in light source. That is, the reflection type liquid crystal display device is configured such that the electrode substrate located on the observer side (refers to the electrode substrate located on the observer side of the pair of opposing electrode substrates, hereinafter referred to as the observer-side substrate) from the indoor side. Light and external light are made to enter the display device, the incident light is reflected by a light reflecting plate made of a metal plate or the like provided on the rear substrate, and a screen display is performed using the reflected light. The reflection type liquid crystal display device can be said to be an ideal display device with low power consumption because it does not use a built-in light source, and can be said to be lightweight and convenient for portable use.

Conventionally, the following structures and the like have been known as the structure of a reflection type liquid crystal display device. That is, FIG.
As shown in (1), a TFT (thin film transistor) array is formed on the rear substrate 60, and an insulating film is formed on the TFT array. Next, a metal reflection film 69 made of aluminum (Al) or the like is laminated on a predetermined portion on the insulating film. Note that the surface of the insulating film is provided with irregularities so that when the metal reflective film 69 is stacked, the surface of the metal reflective film 69 becomes irregular and has a light scattering property. That is, by imparting light scattering to the metal reflective film 69 and scattering the reflected light, the incident light having a certain incident angle can be made the reflected light for screen display, so that the viewing angle of the display device is increased. is there. Also, the metal reflection film 69 and T
The FT array is electrically connected to the liquid crystal 65 through via holes in order to apply a voltage to the liquid crystal 65. As shown in FIG. 5, a transparent electrode 64 is formed on the observer-side substrate 61, and a voltage is applied between the metal reflective film 69 and the transparent electrode 64 when driving the liquid crystal 65 sandwiched between the substrates.

FIG. 6 shows another structure of a conventional reflection-type liquid crystal display device. That is,
A metal reflection film 79 is uniformly provided on the back surface side of the rear substrate 70 on which the transparent electrode 76 is formed, opposite to the surface on which the transparent electrode 76 is formed. In addition, in order to scatter incident light, irregularities are generally formed on the surface of the metal reflection film 79. When driving the sandwiched liquid crystal 75, the transparent electrode 74 formed on the observer-side substrate 71 and the transparent electrode 76 formed on the back-side substrate 70
And a voltage is applied.

In the reflection type liquid crystal display device represented by the above-described structural example, when performing color display on a display screen, the reflectance of light in the visible wavelength range (400 nm to 700 nm) is uniform at each wavelength. Is required. That is, if the reflectance at each wavelength is uniform, the reflected light becomes white and an achromatic white display becomes possible, so that a desired color display can be performed. However, an organic resin material such as a photosensitive resin conventionally used in a reflection type liquid crystal display device turns yellow by a heat treatment applied when manufacturing the liquid crystal display device, so that it absorbs light on a short wavelength side. become. For this reason, the conventional reflective liquid crystal display device using an organic resin material has a problem that reflected light has a yellow tint and a desired color display cannot be performed.

In addition, since the reflection type liquid crystal display device uses external light incident on the device as display light, it is required to have a high reflectance in a visible light range in order to obtain a bright display screen. In order to obtain a viewing angle, a scattering effect on the observer position is required.

In the conventional rear substrate shown in FIGS. 5 and 6, a reflection film made of aluminum (Al), an aluminum alloy, or the like is used as a light reflection film. But,
The reflectivity of a reflective film made of aluminum (Al) is as low as about 80% when formed by a sputtering method, and about 85% even when formed by a vapor deposition method. However, there is a problem that the reflectivity is lowered to a degree lower than the reflectivity required for practical use. Further, the light scattering effect is not satisfactory in the conventional reflection type liquid crystal display device.

Further, in the rear substrate having the structure shown in FIG. 5, light scattering is generated by unevenness formed on the surface of the insulating layer.
The viewing angle was secured. However, with such a structure,
There has been a problem that a complicated manufacturing process is required to form irregularities on the surface of the insulating layer and to form via holes for conducting between the wiring formed in the lower layer and the reflective film.
Further, the unevenness of the surface of the reflection film as a driving electrode for liquid crystal becomes large, and a problem that the usable liquid crystal driving method is limited is caused.

On the other hand, in the rear electrode substrate having the structure shown in FIG. 6, since the metal reflection film 79 (scattering film) is on the back surface of the rear substrate 70, there is also a problem that an optical path difference occurs due to the thickness of the substrate 70. . That is, after the light that has entered from the observer side substrate 71 and passed through the pixel portion is reflected by the metal reflective film 79, an optical path difference occurs due to the thickness of the substrate 70, so that the light enters the pixel portion adjacent to the pixel portion that has entered and passed therethrough. The reflected light will be incident. For this reason, display defects such as color mixing occur on the display screen, and light incident on the rear substrate 70 is
It can be said that there is also a problem that the image is reflected by the surface of the transparent electrode 76 formed on the substrate and the surface of the metal reflection film 79 on the back surface, thereby generating a double image.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an achromatic white display with uniform wavelength dispersion of display light. Another object of the present invention is to provide a reflection type liquid crystal display device capable of condensing as much incident light as possible at an observer's position and enabling a bright color display by enhancing a scattering effect.

[0014]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and have reached the present invention. That is, in claim 1 of the present invention, an observer side substrate in which a transparent electrode for driving liquid crystal is disposed on a transparent substrate;
A reflection type liquid crystal display device having at least a rear substrate on which a light reflection film, a light scattering film, and a transparent electrode for driving a liquid crystal corresponding to the transparent electrode are laminated, and a liquid crystal sandwiched between the two substrates. In the above, the light scattering film, a plurality of microlenses arranged in each pixel portion and the non-pixel portion region, and having a refractive index different from the microlens, a flattening layer made of a transparent resin covering the microlens, Wherein the extinction coefficient (k) of the microlens at a light wavelength of 430 nm is 1.5 × 10 ⁻³ or less.

The light-scattering film according to the present invention, which is composed of a plurality of microlenses and a flattening layer covering the microlenses, is formed on the light-reflecting film disposed on the rear substrate or on the observer substrate. It is formed in.

In the reflection type liquid crystal display device having the light scattering film according to the first aspect, the light incident on the device from the observer direction is made uniform by the light scatterers (microlenses) constituting the light scattering film. Scattered. Next, the scattered light is reflected by the light reflecting film and emitted from the observer-side substrate. For this reason, regardless of the incident angle of light incident on the device,
It is possible to observe a bright display screen with a wide viewing angle. Further, since the microlens condenses the light incident from the oblique direction to the central region (pixel region), it is possible to observe a bright display screen at the position of the observer.

Note that the refractive index of the microlens may be lower than the refractive index of the flattening layer covering the microlens, as long as the light scattering film only has a light scattering property. However, as described above, it is preferable that the refractive index of the microlens be higher than the refractive index of the flattening layer in order to converge the light incident from the oblique direction to the central region (pixel region).

Furthermore, by setting the extinction coefficient (k) of the microlens at a light wavelength of 430 nm to 1.5 × 10 ⁻³ or less, the absorption of light on the short wavelength side by the resin forming the microlens can be suppressed. And visible wavelength range (400n
(m-700 nm). This makes it possible to obtain reflected light without absorption of light on the short wavelength side.

Next, when the extinction coefficient (k) of the microlens at a light wavelength of 430 nm is 1.0 × 10 ⁻³ or less, the absorption of light on the short wavelength side by the resin constituting the microlens is further suppressed. Have been found by the present inventors and are proposed.

That is, the invention according to claim 2 provides an extinction coefficient (k) of a microlens at an optical wavelength of 430 nm.
2 is set to 1.0 × 10 ⁻³ or less.
The liquid crystal display device described in (1). With the reflective liquid crystal display device having such a configuration, uniform reflected light (achromatic white reflected light) can be obtained in the visible wavelength range (400 nm to 700 nm).

The above-mentioned microlenses are preferably those having a high light transmittance and a high refractive index. Examples of the material include polycarbonate resin, polystyrene resin, acrylic epoxy resin, fluorene-based acrylic resin, polyimide resin, and aliphatic polycondensation. (A bromide atom or a sulfur atom may be included in the chemical structure).

Next, the shape of the microlens is desirably a shape whose surface constitutes a part of a spherical surface (a so-called convex lens shape). In this case, the microlens has the function of a spherical lens, and the incident light incident on each pixel is refracted to the central area (pixel area) and then reflected by the reflective film. Can be. The bottom shape of the microlens in plan view may be a rectangle, a square, a hexagon, or the like in order to increase the filling rate of the microlens and increase the productivity and the production yield of the microlens. Further, in order to obtain a desired scattering effect, the surface shape of the microlens is not limited to a spherical surface, and a part thereof may be formed to be aspherical.

In order to make the light incident on the non-pixel portion refracted or scattered to be incident on the pixel portion, the micro-lens located in the non-pixel portion is formed instead of forming a micro lens alone in the non-pixel portion. It is preferable that the lens is formed so as to overlap with an adjacent pixel portion, that the width of the microlens is wider than the width of the non-pixel portion, and that the lens center of the microlens is located in the pixel portion. It can be said that.

Next, as a method of forming a microlens using the above-described organic resin, for example, a method of forming by printing can be used. In addition, the organic resin is composed of a photosensitive resin, and the photosensitive resin is applied to a portion where a microlens is to be formed (for example, on a light reflection film) to form a photosensitive resin film, and then the pattern exposure and development are performed. Then, a photosensitive resin film is selectively left at a portion where a microlens is to be formed. Next, a method of melting the remaining photosensitive resin film by heating and deforming the film into a microlens shape by the surface tension is also applicable. Further, the organic resin is applied to a portion where a microlens is to be formed (for example, on a light reflection film) to form an organic resin film, and then a photosensitive resin is applied to the organic resin film to form a photosensitive resin film. I do. Next, pattern exposure and development are performed to selectively leave a microlens-shaped photosensitive resin film on the portion where the microlens is to be formed. Thereafter, dry etching is performed. At this time, a method in which the etching amount of the lower organic resin film is controlled in accordance with the thickness of the remaining photosensitive resin film, and the organic resin film is formed into a microlens shape can be applied.

In forming the microlenses, it is preferable to form two or more microlenses on one pixel portion in order to obtain good light scattering properties, and the thickness of each microlens is 3 μm or less. It is desirable.
That is, when the thickness of the microlens exceeds 3 μm,
This is because the absorption of light in the short wavelength region (BLUE region) by the microlens material becomes large, and it becomes difficult to planarize by the planarization layer formed on the microlens. For this reason, the thickness of the microlens is preferably as thin as 2 to 3 μm or less, and more preferably, 1.5 μm or less.

Next, as the material of the flattening layer formed on the microlens according to the present invention, a material having a lower refractive index is more preferable. For example, an organic silicate having a refractive index of 1.46 to 1.48, or a refractive index is preferably used. A fluorine-based resin having a ratio of 1.34 to 1.45 can be used. The invention according to claims 3 and 4 has been made based on this. That is, in claim 3, the reflective liquid crystal display device according to claim 1 or claim 2 is premised, and the resin constituting the planarizing layer is an organic silicate. Things. A fourth aspect of the present invention is based on the reflection type liquid crystal display device according to the first or second aspect, wherein the resin forming the flattening layer is a fluorine-based resin. It was done.

The organic silicate according to the third aspect is, for example, "FP" manufactured by Tokyo Ohka Kogyo Co., Ltd.
CF series "(refractive index: 1.46 to 1.48) and the like can be used. Examples of the fluorine-based resin according to claim 4 include a tetrafluoroethylene-hexafluoropropylene copolymer (refractive index: 1.34) and a fluorine-based acrylic resin (refractive index: 1.34 to 1.40). Applicable.

Further, the flattening layer is intended to form a flat surface by filling a step between the microlenses.
Thereby, when providing a transparent electrode or an alignment film on the flattening layer, the transparent electrode or the alignment film can be formed flat, and display unevenness or response unevenness caused when the transparent electrode or the alignment film is formed with irregularities. Etc. can be prevented. In the case where the flatness is not sufficient just by forming a flattening layer on the microlens due to the properties of the liquid crystal used, another transparent resin layer is interposed between the flattening layer and the microlens. The flatness of the flattening layer may be improved by forming the flattening layer after the formation. By improving the flatness of the flattening layer, the light-scattering film according to the present invention can be used for a liquid crystal display device (for example, STN liquid crystal, OCB, HAN, ECB or BTN) which requires a high level of flatness on the transparent electrode forming surface. Liquid crystal display devices using liquid crystal, ferroelectric liquid crystal, antiferroelectric liquid crystal, etc.) can also be used.

Next, in the present invention, the light reflecting film constituting the reflection type liquid crystal display device is formed of a light reflecting metal thin film. Conventionally, there is a technique of forming a light reflection film with a multilayer film of an inorganic oxide or the like. However, it is difficult to say that the technique is a simple technique, and a film forming process is complicated. In that respect, Al (aluminum) and Ag
If the light reflection film is formed of a metal thin film having a high light reflectance such as (silver), the process can be simplified. That is, the invention according to claim 5 is the reflection type liquid crystal display device according to claim 1, 2, 3 or 4, wherein the light reflection film is a light reflection metal thin film.

As described above, the material of the light reflecting film may be aluminum, silver, or the like. At a light wavelength in the visible region, silver has a reflectance of about 10% higher than that of aluminum. It can be said that use is preferable. However, silver is apt to cause migration, and in the presence of moisture, alkali metal, etc., the durability is significantly reduced. In order to stabilize silver and improve reliability, it is desirable to add a small amount of metal such as gold (Au) or copper (Cu) to silver to form a silver alloy. That is, in claim 6, the light-reflective film includes a metal thin film made of silver or a silver alloy as a part of the structure, and the reflective liquid crystal according to claim 1, 2, 3, 4, or 5 According to a seventh aspect of the present invention, in the display device, the light reflecting film is formed of a metal oxide multilayer film having a light reflecting function.
A reflective liquid crystal display device as described in 5 or 6.

Since the metal thin film used as the light reflection film has conductivity, it can be used also as an electrode for driving a liquid crystal. In this case, the metal thin film serving as the light reflection film is formed in a predetermined pattern shape so as to also serve as an electrode for driving the liquid crystal. Further, it is preferable to pattern the metal thin film serving as the light reflecting film and remove the metal thin film portion corresponding to the non-pixel portion, since normally white display improves the contrast of the screen display. That is, in the present invention, the metal thin film is formed in a lump to the size of the display screen or divided into a plurality of pixel regions. , 6 or 7.

As the substrate serving as the observer-side substrate and the back-side substrate, a plastic film, a plastic board, or the like can be used in addition to a transparent glass substrate. Also,
The liquid crystal display device can perform color display by providing a color filter layer that colors light transmitted through each pixel portion to a corresponding color. At this time, the formation position of the color filter layer may be any one of the observer side substrate and the back side substrate, and may be appropriately configured according to the configuration of the liquid crystal display device. The invention according to claim 9 is based on such a technical reason, and presupposes the reflection type liquid crystal display device according to claims 1 to 8, and transmits transmitted light transmitted through each pixel unit to a corresponding color. A reflection type liquid crystal display device characterized in that a plurality of color filters for coloring the liquid crystal are arranged on one of the observer side substrate and the back side substrate.

As described above, according to the first to ninth aspects of the present invention, a plurality of light scattering films constituting a reflection type liquid crystal display device are provided in each pixel portion and non-pixel portion region. Microlenses and a flattening layer made of a material having a lower refractive index than the microlenses. For this reason, the light rays incident on the observer-side substrate from the observer direction are uniformly scattered by the light-scattering elements (microlenses) formed on the light-scattering film, and then the light-reflective film formed on the back-side substrate. And emitted from the observer side substrate. Thereby, the reflected light emitted from the observer-side substrate is focused on the observer position. That is, a bright screen can be observed in a wide field of view regardless of the angle of light incident on the observer-side substrate.

Further, by setting the extinction coefficient (k) of the microlens at a light wavelength of 430 nm to 1.5 × 10 ⁻³ or less, absorption of light in a short wavelength region by the resin constituting the microlens is suppressed. , Visible wavelength range (400-700n
m), the wavelength distribution of the reflected light is made uniform. Thus, the reflective liquid crystal display device of the present invention enables achromatic white display.

In the formation of the light-scattering film according to the present invention, a conventional microlens forming technique can be applied, so that the reflection-type liquid crystal display device of the present invention can be manufactured simply and reliably. it can.

Further, the light scattering film according to the present invention has a flatness by forming a flattening layer. Further, another transparent resin layer is provided between the microlens and the flattening layer. By intervening, it is possible to further improve the flatness of the flattening layer. Thereby, when providing a transparent electrode or an alignment film on the flattening layer, the transparent electrode or the alignment film can be formed flat, and display unevenness or response unevenness caused when the transparent electrode or the alignment film is formed with irregularities. Etc. can be prevented. In other words, the reflection type liquid crystal display device having the light scattering film according to the present invention is a reflection type liquid crystal display device (for example, STN liquid crystal,
OCB, HAN, ECB, BTN liquid crystal, ferroelectric liquid crystal,
It can also be said that the present invention can be applied to a liquid crystal display using an antiferroelectric liquid crystal.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below.

<Embodiment 1> FIG. 1 is a sectional view schematically showing a reflection type liquid crystal display device according to Embodiment 1. As shown in FIG. 1, in the reflection type liquid crystal display device according to the first embodiment, the observer side substrate and the back side substrate are arranged such that transparent electrodes (transparent electrodes 5 and 6) formed on each substrate face each other. The liquid crystal is sealed and sandwiched between both substrates.

The rear substrate using the glass substrate 1 having a thickness of 0.7 mm is a metal light reflection film 2 formed on the glass substrate 1 in a lump to the size of a display screen, and the light reflection film 2 2
A plurality of microlenses 3 (convex lenses) formed in position alignment above, a flattening layer 4 for covering the plurality of microlenses 3 and flattening the surface, and the microlenses 3 and the flattening layer 4 The transparent electrode 6 formed on the light scattering film 8 and the transparent electrode 5 formed on the observer side substrate and the transparent electrode 6 in a stripe shape corresponding to the transparent electrode 5 are formed.

The light reflecting film 2 according to the first embodiment was formed by the following procedure. That is, first, after cleaning the surface of the glass substrate 1 by glow discharge, a transparent oxide thin film (thickness 10 nm) and a silver-based thin film (thickness 150 nm) were sequentially formed on the glass substrate 1 by sputtering film formation. . Next, after applying and forming a photosensitive resist film on the glass substrate 1, after exposing a predetermined area (an area to be a display screen),
The photosensitive resist film was developed, and the photosensitive resist film was selectively left in a predetermined region (region serving as a display screen). Next, the metal thin film exposed from the photosensitive resist film was removed by etching with a mixed acid composed of sulfuric acid, nitric acid and acetic acid, and then the photosensitive resist film was stripped.

Next, the micro lens 3 was formed as follows. That is, first, an ultraviolet curable photosensitive acrylic resin having a refractive index of 1.58 and an extinction coefficient (k) of 1.4 × 10 ⁻³ is applied onto the substrate 1 on which the light reflection film 2 is formed. Then, a predetermined pattern exposure and development were performed on the photosensitive acrylic resin, and the photosensitive acrylic resin was selectively left in a predetermined region. Next, the remaining photosensitive acrylic resin is melted by heating, and is deformed into a microlens shape having a spherical surface by its surface tension. According to the above method, in the first embodiment, the size is 10 μm × 10 μm.
m, a thickness of 1.5 μm, and a plurality of microlenses 3 having a pattern gap of 4 μm.

Next, a fluorine compound-modified acrylic resin having a refractive index of 1.40 was applied on the microlenses 3 to form a flattening layer 4. At this time, in the first embodiment, the flattening layer 4 was applied so that the total thickness of the microlenses 3 and the flattening layer 4 was about 2.5 μm.

Next, the glass substrate 1 on which the light reflecting film 2 and the light scattering film 8 (the microlenses 3 and the flattening layer 4) are formed.
After uniformly depositing an ITO (mixed oxide composed of tin oxide and indium oxide) thin film on the ITO film, a known photolithography process using a positive resist is performed on the ITO thin film to obtain a substrate on the observer side. A transparent electrode 6 in the form of a stripe corresponding to the transparent electrode 5 formed as described above was formed as a rear substrate.

Next, a color filter 7 composed of a red (R) color filter 7R, a green (G) color filter 7G, and a blue (B) color filter 7B formed according to a predetermined pattern, and a transparent electrode The observer-side substrate on which No. 5 was formed and the back-side substrate were bonded together so as to sandwich a liquid crystal therebetween, thereby forming the reflection type liquid crystal display device of FIG. Prior to the formation of the transparent electrode 5, an undercoat layer 10 made of a transparent resin is formed on the color filter 7 to perform planarization.

FIG. 3 shows that a silver (Ag) alloy
μm × 10 μm, thickness 2.0 μm, pattern gap 4
FIG. 8 is a graph showing spectral reflectances obtained when a plurality of microlenses 3 having a thickness of μm are formed. Here, a line A in FIG. 3 is a spectral reflectance when a microlens having an extinction coefficient (k) of 1.5 × 10 ⁻³ at a light wavelength of 430 nm is formed, and a line B is a light wavelength. This is the spectral reflectance when a microlens having an extinction coefficient (k) at 430 nm of 1.0 × 10 ⁻³ is formed. The vertical axis represents a barium sulfate white plate as a reference, and silver (A).
g) The ratio (%) of brightness at each wavelength of a reflector having a microlens formed on an alloy film.

As shown in FIG. 3, when the light wavelength is 430 nm,
Extinction coefficient (k) is 1.5 × 10 ^-3Microre
About 80% of the barium sulfate white plate
It became a spectral reflectance of more than degree. In addition, light wavelength of 430 nm
Extinction coefficient (k) at 1.0 × 10^-3Microphone
When the lens is formed, the barium sulfate white plate
The spectral reflectance was about 85% or more. In addition, micro
The base for forming the lens was an aluminum (Al) evaporated film
In this case, the spectral reflectance is lower than that in FIG.
Only about 75% or less of the spectral reflectance of the white
won.

Next, FIG. 4 shows that on a silver (Ag) alloy film,
FIG. 9 is a graph showing spectral reflectances obtained when a plurality of microlenses 3 having six different thicknesses are formed. Each microlens was only changed in thickness, and the other shapes each had a size of 10 μm × 10 μm and a pattern gap of 4 μm.
m. Each micro lens has an optical wavelength of 4
The extinction coefficient (k) at 30 nm was the same as 1.5 × 10 ⁻³ . Here, the line C in FIG. 4 shows the spectral reflectance when the microlens is formed with a thickness of 3.0 μm, and similarly, the line D has a thickness of 2.5 μm, and the line E has a thickness of 2.0 μm. 0 μm
The line F has a thickness of 1.5 μm, and the line G has a thickness of 1.0 μm.
Further, a line H indicates a spectral reflectance when a microlens is formed to a thickness of 0.5 μm. The vertical axis represents a barium sulfate white plate as a reference, and silver (A).
g) The ratio (%) of brightness at each wavelength of a reflector having a microlens formed on an alloy film.

As shown in FIG. 4, in order to obtain a reflectance of about 80% or more of the barium sulfate white plate, it can be said that the thickness of the microlens is preferably 2 μm or less.

<Embodiment 2> FIG. 2 is a sectional view schematically showing a reflection type liquid crystal display device according to Embodiment 2. As shown in FIG. 2, in the reflection type liquid crystal display device according to the second embodiment, the observer side substrate and the back side substrate are arranged such that transparent electrodes (transparent electrodes 25 and 26) formed on each substrate face each other. The liquid crystal is sealed and sandwiched between both substrates.

The rear substrate used was a glass substrate 21 having a thickness of 0.7 mm. Here, on the glass substrate 21, a metal light reflection film 22 formed collectively to the size of the display screen
In addition, a color filter 27 is formed on the light reflection film 22. Next, an undercoat layer 30 is formed on the color filter 27 in order to flatten the unevenness generated on the surface of the color filter 27 and the light reflection film 22. A light scattering film 28 composed of a plurality of microlenses 23 provided for each pixel and a flattening layer 24 that covers the microlenses 23 and flattens the surface is formed.

Next, on the light scattering film 28, a striped transparent electrode 26 is formed so as to correspond to each pixel portion of the color filter 27.

The light reflecting film 22 according to the second embodiment was formed by the following procedure. That is, first, the glass substrate 21
After cleaning the surface by glow discharge, a transparent oxide thin film (10 nm thick) and a silver-based thin film (150 nm thick) were sequentially formed on the glass substrate 21 by sputtering film formation. Next, after applying and forming a photosensitive resist film on the glass substrate 21, a predetermined region (a region to be a display screen) is exposed, and then the photosensitive resist film is developed to a predetermined region (a region to be a display screen). , A photosensitive resist film was selectively left. Next, the metal thin film exposed from the photosensitive resist film was removed by etching with a mixed acid composed of sulfuric acid, nitric acid and acetic acid, and then the photosensitive resist film was stripped.

Next, a red photosensitive resin composed of a mixture of an acrylic transparent photosensitive resin and a red pigment was applied on the glass substrate 21 on which the light reflecting film 22 was formed, to form a red photosensitive resin film. Next, by performing predetermined pattern exposure and development, the above-mentioned red photosensitive resin film is selectively left at a portion where each red pixel is to be formed, and this is used as a red (R) color filter 27R. Subsequently, using a green photosensitive resin composed of a mixture of an acrylic transparent photosensitive resin and a green pigment, and a blue photosensitive resin composed of a mixture of an acrylic transparent photosensitive resin and a blue pigment, using the same method as described above. , A green (G) color filter 27G and a blue (B) color filter 27B.

Next, after forming the undercoat layer 30 with a transparent resin on the color filter 27, the refractive index is adjusted to 1.5.
8. An ultraviolet curable photosensitive acrylic resin having an extinction coefficient (k) of 1.4 × 10 ⁻³ was applied on the substrate 21. Next, a predetermined pattern exposure and development were performed on the photosensitive acrylic resin, and the photosensitive acrylic resin was selectively left in each pixel area. Next, the remaining photosensitive acrylic resin is melted by heating, and is deformed into a microlens shape having a spherical surface by its surface tension. According to the above method, in the second embodiment, the size is 20 μm × 20 μm.
A plurality of microlenses 23 having a thickness of 1.3 m and a pattern gap of 6 m were formed.

Next, a fluorine compound-modified acrylic resin having a refractive index of 1.40 was applied on the microlens 23 to form a flattened layer 24. At this time, in the second embodiment, the flattening layer 24 was applied so that the total thickness of the color filter 27, the microlenses 23, and the flattening layer 24 was about 5 μm.

Next, after forming the light scattering film 28 (microlens 23 and flattening layer 24), the substrate 2
After uniformly forming an ITO thin film on the substrate 1 by sputtering, a well-known photolithography process using a positive resist is performed.
By applying to the O thin film, a transparent electrode 26 in a stripe shape corresponding to the transparent electrode 25 formed on the observer side substrate is formed,
The back side substrate was used.

Next, the observer-side substrate on which the transparent electrode 25 was formed and the rear-side substrate were bonded so as to sandwich a liquid crystal therebetween, thereby forming a reflection type liquid crystal display device shown in FIG.

The embodiments of the present invention have been described above.
Embodiments of the reflective liquid crystal display device according to the present invention are not limited to the above description and drawings, and it goes without saying that various modifications may be made based on the gist of the present invention. For example, the extinction coefficient (k), size, thickness, refractive index, and the like of the microlens, including the curvature of the microlens to be formed, are appropriately determined according to the desired light-collecting properties and light-scattering properties. You can change the adjustment.

[0059]

As described above, according to the first to ninth aspects of the present invention, a plurality of light scattering films constituting a reflection type liquid crystal display device are arranged in each pixel portion and non-pixel portion region. It is formed of the provided fine microlenses and a flattening layer made of a material having a lower refractive index than the microlenses.
For this reason, the light rays incident on the observer-side substrate from the observer direction are uniformly scattered by the light-scattering elements (microlenses) formed on the light-scattering film, and then the light-reflective film formed on the back-side substrate. And emitted from the observer side substrate. Thereby, the reflected light emitted from the observer-side substrate is focused on the observer position. That is, a bright screen can be observed in a wide field of view regardless of the angle of light incident on the observer-side substrate. In addition, by appropriately changing the shape of the microlens and the refractive index difference between the microlens and the flattening layer, the scattered light distribution can be easily controlled, and an arbitrary viewing angle can be set.

Further, by setting the extinction coefficient (k) of the microlens at a light wavelength of 430 nm to 1.5 × 10 ⁻³ or less, absorption of light in a short wavelength region by the resin constituting the microlens is suppressed. , Visible wavelength range (400-700n
m), the wavelength distribution of the reflected light is made uniform. Thus, the reflective liquid crystal display device of the present invention enables achromatic white display.

In the formation of the light scattering film according to the present invention, the microlens forming technology conventionally used can be applied, so that the reflection type liquid crystal display device of the present invention can be manufactured simply and reliably. it can.

Further, the light scattering film according to the present invention has a flatness by forming a flattening layer. Further, another transparent resin layer is provided between the microlens and the flattening layer. By intervening, it is possible to further improve the flatness of the flattening layer. Thereby, when providing a transparent electrode or an alignment film on the flattening layer, the transparent electrode or the alignment film can be formed flat, and display unevenness or response unevenness caused when the transparent electrode or the alignment film is formed with irregularities. Etc. can be prevented. In other words, the reflection type liquid crystal display device having the light scattering film according to the present invention is a reflection type liquid crystal display device (for example, STN liquid crystal,
OCB, HAN, ECB, BTN liquid crystal, ferroelectric liquid crystal,
It can also be said that the present invention can be applied to a liquid crystal display device using an antiferroelectric liquid crystal.

Accordingly, the reflection type liquid crystal display device of the present invention
A wide viewing angle, bright, high-quality screen regardless of the position of the external light source, while maintaining the advantages inherent in a low-power, lightweight, portable, etc. reflective liquid crystal display device. Can be displayed.

[0064]

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a main part of one embodiment of a reflection type liquid crystal display device of the present invention.

FIG. 2 is an explanatory sectional view showing a main part of another embodiment of the reflection type liquid crystal display device of the present invention.

FIG. 3 is a graph showing an example of a change in brightness of reflected light when the extinction coefficient (k) of a microlens related to the reflection type liquid crystal display device of the present invention is changed.

FIG. 4 is a graph showing an example of a change in brightness of reflected light when the thickness of a microlens related to the reflection type liquid crystal display device of the present invention is changed.

FIG. 5 is an explanatory sectional view showing a main part of an example of a conventional reflection type liquid crystal display device.

FIG. 6 is an explanatory sectional view showing a main part of another example of a conventional reflection type liquid crystal display device.

[Explanation of symbols]

 1, 9, 21, 29 substrate 60, 61, 70, 71 substrate 2, 22 light reflection film 3, 23 micro lens 4, 24 flattening layer 5, 25 transparent electrode 6, 26 transparent electrode 7, 27 color filter 8, 28 Light scattering film 10, 30 Undercoat layer 64, 74, 76 Transparent electrode 65, 75 Liquid crystal 77 Flattening layer 68, 78 Color filter 69, 79 Reflective film

Continued on front page F-term (reference) 2H090 HA07 HB07X HC05 HD03 JB03 KA07 KA08 KA14 KA15 LA09 LA12 LA15 LA20 2H091 FA02Y FA16Z FA29Z FA31Z FB02 FB04 FB08 FC02 FC26 FD06 FD14 GA01 GA17 HA09 HA10 HA12 LA10 LA20

Claims (9)

[Claims] An observer side substrate having a transparent electrode for driving a liquid crystal disposed on a transparent substrate, a light reflecting film, a light scattering film, and a transparent electrode for driving a liquid crystal corresponding to the transparent electrode are disposed on the substrate. In a reflective liquid crystal display device having at least a laminated back side substrate and a liquid crystal sandwiched between the two substrates, a micro lens in which a plurality of the light scattering films are disposed in each pixel portion and a non-pixel portion region. A flattening layer having a refractive index different from that of the microlens and covering the microlens and made of a transparent resin, and having an extinction coefficient (k) of 1.5 × 10 at a light wavelength of 430 nm. ^-3
A reflective liquid crystal display device characterized by the following. 2. The reflection type liquid crystal display device according to claim 1, wherein the extinction coefficient (k) of the micro lens at a light wavelength of 430 nm is 1.0 × 10 ⁻³ or less. 3. The reflective liquid crystal display device according to claim 1, wherein the resin constituting the flattening layer is an organic silicate. 4. The reflection type liquid crystal display device according to claim 1, wherein the resin constituting the flattening layer is a fluorine-based resin. 5. The reflection type liquid crystal display device according to claim 1, wherein the light reflection film is a light reflection metal thin film. 6. The light reflecting film according to claim 1, wherein the light reflecting film includes a metal thin film made of silver or a silver alloy as a part of the structure.
6. The reflection type liquid crystal display device according to 2, 3, 4 or 5. 7. A light reflecting film comprising a metal oxide multilayer film having a light reflecting function.
7. The reflection type liquid crystal display device according to 3, 4, 5, or 6. 8. The light reflection film according to claim 1, wherein the light reflection film is formed collectively in a size of a display screen or divided into a plurality of pixel regions. 6 or 7
3. The reflection type liquid crystal display device according to item 1. 9. The apparatus according to claim 1, wherein the color filter is disposed on one of the observer side substrate and the back side substrate. Reflective liquid crystal display.