JP2001235737A - Liquid crystal display device and electronic instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bright and clear liquid crystal display device with a wide viewing angle and a sufficient scattering effect obtainable even when particulate density contained in a resin is lowered, to provide a liquid crystal display device with high contrast by minimizing projecting and recessing parts on a surface of an optical scattering layer and furthermore to prevent reliability of the liquid crystal display device from lowering due to a large number of the particulates contained in the optical scattering layer. SOLUTION: By selecting the radii of the particulates contained in the resin in such a way that the scattering efficiency in 450-650 nm wavelength region is >=2, the optical scattering layer capable of attaining brightness and high contrast is manufactured with the lower diffusion density. Also the optical scattering layer is optionally made to be a color filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device for forming an image by applying a voltage to a liquid crystal material held between substrates, and an electronic device using the liquid crystal display device. Relates to an optical scattering layer of a liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device performs display by controlling the polarization direction of incident light. Such a liquid crystal display device includes a reflective liquid crystal display device using light incident from the front of the device, a transmissive liquid crystal display device using light incident from the back or side of the device, and a reflective liquid crystal display. A transflective liquid crystal display device having both functions of a device and a transmissive liquid crystal display device can be roughly classified into three types.

[0003] These liquid crystal display devices generally have a layer that scatters light emitted to widen the display recognition angle of the observer, that is, the viewing angle.

[0004] As a method for forming such an optical scattering layer, a resin and fine particles having a different refractive index are kneaded and dispersed in the resin, and are applied to the entire surface of the substrate by a spin coater method, a roll coat method or the like. After curing, the necessary parts were formed by patterning.

[0005]

However, since the refractive index and the radius of the fine particles kneaded in the resin were inappropriate, efficient scattering could not be obtained. For this reason, the density of the fine particles was increased in order to obtain a sufficient scattering intensity, so that the adhesion of the optical scattering layer to the substrate was poor, and the reliability of the liquid crystal display device could not be obtained.

Further, since the density of the fine particles is increased, irregularities are formed on the surface of the optical scattering layer, and there is a disadvantage that the orientation of the liquid crystal is disturbed.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal display device and an electronic device having a bright and easy-to-see display screen by increasing the scattering efficiency of an optical scattering layer. It is in.

[0008]

In order to achieve the above object, in a liquid crystal display device according to the present invention, a liquid crystal is held between a pair of substrates, and at least one of opposing surfaces of each substrate has an electrode. Is formed, and an optical scattering layer made of a resin is formed on a surface of at least one of the substrates facing each other, wherein the scattering layer has a refractive index that is different from that of the resin in the resin. Different fine particles, wherein the fine particles have a radius at which a scattering efficiency represented by (scattering cross-sectional area) / (geometric cross-sectional area) is 2 or more in a wavelength region of 450 nm to 650 nm. I have. According to the liquid crystal display device of the present invention, since the scattering efficiency of the optical scattering layer is increased, a brighter and easier-to-view display screen can be obtained.

Here, in the present invention, it is desirable that the optical scattering layer forms a color filter. According to this configuration, a bright and easy-to-see display screen can be obtained even when a color filter is provided.

In the present invention, it is preferable that a metal thin film is formed on a substrate, and the optical scattering layer is formed on the surface of the metal thin film.

Further, in order to achieve the above object, an electronic apparatus according to the present invention is provided with the above liquid crystal display device. According to the present invention, a bright and high-contrast display screen can be obtained by optimizing the refractive index and the radius of the fine particles contained in the resin when forming the optical scattering layer.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) First, the configuration of a first embodiment of the liquid crystal display device according to the present invention will be described. In the first embodiment, the present invention is applied to a transmission type liquid crystal device of a passive matrix driving system. Here, FIG. 1 is a plan view showing a configuration of the transmission type liquid crystal device, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. still,
In FIGS. 1 and 2, for convenience of explanation, six stripe-shaped electrodes are shown in each of the vertical and horizontal directions. However, actually, a large number of electrodes are present, and each layer and each member in FIGS. In order to make the size recognizable in the drawings, the scale is different for each layer and each member.

First, in these figures, a liquid crystal cell 51 is shown.
The front surface (that is, the upper surface in FIG. 2) and the back surface (that is, the lower surface in FIG. 2) respectively have a polarizer 2 containing a dichroic dye.
3, 22 are arranged. Although there is a gap between the elements constituting the transmissive liquid crystal display device, this is for convenience of illustration, and actually, the elements are almost in close contact with each other. ing.

The light emitted from the backlight 80 passes through the polarizer 22 to become linearly polarized light and enters the liquid crystal layer 50. The linearly polarized light incident on the liquid crystal layer 50 is divided into a transparent segment electrode 11 and a transparent common electrode 21.
The polarization axis is selected by the voltage applied by
The light enters the polarizer 23. Bright display and dark display can be selected according to the polarization axis direction selected at this time. At this time, the light incident on the polarizer 23 is scattered by the optical scattering layer 42. Thereby, light can be scattered at a wide angle.

Next, a more detailed structure and a manufacturing method of the liquid crystal cell 51 will be described.

First, the substrate on the lower side as viewed from the observer (ie,
A description will be given of a segment substrate which will be the lower side in FIG. 2).
After a conductive film made of ITO or the like having a thickness of 400 angstroms is formed, the conductive film is patterned by a photolithography method to form a segment electrode 11.

Next, the common substrate on which the optical scattering layer 42 is formed will be described.

The optical scattering layer 42 is formed by kneading fine particles 41 made of silicon resin having a refractive index of 1.48 at a weight ratio of 15% into a transparent fluoropolymer (refractive index: 1.35) 40, and then kneading them. After forming a film with a thickness of about 5 μm on the surface of the second substrate 20 by a spin coating method, patterning is performed by a photolithography method to form an optical scattering layer 42 in the pixel portion.

Further, a transparent conductor made of ITO or the like is formed to a thickness of 1400 angstroms by a vapor deposition method or a sputtering method, and is patterned by a photolithography method to form a common electrode 21.

At this time, the fine particles to be kneaded have a (scattering cross-sectional area) / wavelength range of 450 to 650 nm.
A particle radius at which the scattering efficiency represented by (geometric cross-sectional area) was 2 or more was selected. FIG. 3 shows 450 nm and 550 nm when (refractive index of fine particles) / (refractive index of resin) = 1.1.
The respective curves 204, 205, 206 of scattering efficiency versus particle radius at a wavelength of 650 nm are shown. In FIG. 3, the radius of the fine particles at which the scattering efficiency is 2 or more in the wavelength range from 450 nm to 650 nm is in the range of 1.2 μm to 2.3 μm. Therefore, in this embodiment, the average radius of the fine particles is 1.7 μm. And

In this embodiment, the fluoropolymer is used as the transparent resin. However, the resin has low birefringence,
Any material that can withstand heat treatment or chemical treatment in the liquid crystal display manufacturing process may be used. For example, acrylic resin (refractive index: 1.
47 to 1.59), epoxy resin (refractive index: 1.56 to
1.66), polyester resin (refractive index: 1.51 to 1.51)
1.57), silicone resin (refractive index: 1.35 to 1.4)
8), polyimide resin (refractive index: 1.57 to 1.69)
Etc. can be used.

Further, in this embodiment, fine particles made of silicon resin are used as fine particles, but fine particles made of inorganic materials can be used in addition to organic polymers.

Examples of the fine particles made of an organic polymer include polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer (ETF).
E) and fluorine-containing polymers such as polyfluorovinyl (PVF). The refractive indexes of these fluoropolymers are 1.35, 1.35, 1.40, and 1.35, respectively.

Further, a polymer obtained by adding a fluorine atom or a fluorinated alkyl group to another polymer may be used. Fine particles obtained by subjecting the surface of these organic polymers to an appropriate surface treatment may be used. Examples of surface treatment include, for example, Si
Examples of the treatment include a treatment of applying a surface such as O ₂ , ZrO ₂ , Al ₂ O ₃ , ZnO, a transparent resin, a coupling agent, and a surfactant.

In addition, examples of the fine particles made of an inorganic material include fine particles having a cubic structure, fine particles having a tetragonal structure, and amorphous fine particles. Specifically, for example, CaF ₂ , MgF ₂ , LaF ₃ , LiF ₂ , N
and fluorine compounds such as aF. The refractive index of these fluorine compounds is 1.43, 1.38, 1.59, respectively.
1.39, 1.34.

Finally, after an orientation film is applied to the opposing surfaces of the segment substrate and the common substrate manufactured by the above-described method and subjected to a rubbing treatment, the two segment electrodes 11 and the common electrode 21 are perpendicular to each other. Substrates 10, 20
Are bonded together via a sealing material 31, a liquid crystal material is sealed in a space between the two substrates, and then sealed with a sealing material 32 to obtain a liquid crystal display device 54.

In this embodiment, a transmissive liquid crystal display device driven by a passive matrix for monochrome display has been described as an example. However, a TFT (Thin Film Transistor) element, a TFD (Thin Film Diode) element, or the like is used. It can also be used for an active matrix drive type liquid crystal display device. Further, it may be a reflection type liquid crystal display device. Further, a color filter corresponding to each pixel may be provided between the second substrate 20 and the optical scattering layer 42 to form a liquid crystal display device capable of color display.

(Second Embodiment) A second embodiment of the present invention is as follows.
This is applied to an active matrix driven reflection type liquid crystal display device capable of color display using a TFD element.

First, the TFD element 30 will be described with reference to FIGS.
0 will be described.

The TFD element 300 is formed on an insulating film 312 formed on a first substrate 310 as a base, and the first metal film 30 is sequentially formed from the insulating film 312 side.
2, composed of an insulating layer 304 and a second metal film 306, and having a TFD structure (Thin Film Diode structure) or MI
It has an M structure (Metal Insulator Metal structure). The first metal film 302 of the TFD element 300 is connected to a scanning line 311 formed on the first substrate 310, and the second metal film 306 is connected to a transparent electrode 301 made of an ITO thin film. I have.

The insulating film 312 is made of, for example, tantalum oxide. Note that the insulating film 312 has a main purpose of preventing the first metal film 302 from peeling off from the base and preventing impurities from diffusing from the base into the first metal film 302 due to heat treatment performed after the deposition of the second metal film 306 or the like. Is formed. Therefore, when the first substrate 310 is formed of a substrate having excellent heat resistance and purity, such as a quartz substrate, the insulating film 441 is omitted when separation or diffusion of impurities does not pose a problem. can do. The first metal film 302 is made of a conductive metal thin film, for example, tantalum alone or a tantalum alloy. The insulating film 304
For example, it is formed of an oxide film formed by anodic oxidation on the surface of the first metal film 302 in a chemical conversion solution. The second metal film 306 is
It is made of a conductive metal thin film, for example, chromium alone or a chromium alloy.

Further, the transparent electrode 301 and the TFD element 30
A transparent insulating film 303 is provided on the side facing the liquid crystal such as the scanning line 311 (ie, the upper surface in FIG. 5).

Next, the reflection electrode 450 will be described with reference to FIGS.
A color filter 411 also serving as an optical scattering layer on the surface of
The common electrode substrate 400 on which 412 and 413 are formed will be described.

First, a 1500 angstrom aluminum thin film is formed on the second substrate 410 by a sputtering method, and a photosensitive organic film containing carbon black is applied to a thickness of 2 μm by a spin coating method, and then a photolithography method is performed. To form a pattern having a width of 20 μm to form a black stripe 420.

Further, a photosensitive acrylic resin containing a red, blue and green colorant, respectively (refractive index: 1.47)
After kneading fine particles composed of an epoxy resin (refractive index: 1.59) at a weight ratio of 15%, the mixture is applied by a spin coating method, and a color filter 411 serving also as an optical scattering layer is applied by a photolithography method. , 412,413
To form

Further, a transparent acrylic resin layer 440 is applied, flattened, and then a transparent conductive thin film made of ITO or the like is formed to a thickness of 1400 angstroms and patterned by photolithography to form a transparent electrode. Step 401 is formed.

At this time, the fine particles to be kneaded have a (scattering cross section) in a wavelength range from 450 nm to 650 nm.
A particle radius at which the scattering efficiency represented by // (geometric cross-sectional area) is 2 or more was selected. FIG. 8 shows 450 nm and 550 n when (refractive index of fine particles) / (refractive index of resin) = 1.08.
Curves 207, 208, and 209 of the scattering efficiency with respect to the particle radius at wavelengths of m and 650 nm are shown. In FIG. 8, the radius of the fine particles for which the scattering efficiency is 2 or more in the wavelength range from 450 nm to 650 nm is in the range of 1.5 μm to 2.9 μm. Therefore, in this embodiment, the average radius of the fine particles is 2.2 μm. And

Examples of the coloring agent contained in the photosensitive acrylic resin include oil dyes such as monoazo, disazo, metal complex, anthraquinone, phthalocyanine, and triallylmethane based dyes which have been conventionally used. Examples thereof include inorganic pigments such as carbon black, titanium oxide, zinc white, and zinc sulfide, and organic pigments such as monoazo, disazo, phthalocyanine, and quinacridone. For example, colorants for blue (B), green (G), and red (R) frequently used in liquid crystal display devices include (B) phthalocyanine blue, (G) phthalocyanine green, and (R) brilliant carmine, respectively. No.

Finally, the first substrate 310 and the second substrate 41
After applying an alignment film to the opposite surface of the substrate and performing a rubbing process, the two substrates are bonded together via a sealing material so that the scanning line 311 and the transparent electrode 401 are orthogonal to each other. After a liquid crystal substance is sealed in the space, it is sealed with a sealing material to obtain a liquid crystal display device.

In this embodiment, the reflection type liquid crystal display device of the active matrix drive capable of color display using the TFD element has been described as an example. However, the active matrix drive system using the TFT element or the like is described. Alternatively, a liquid crystal display device driven by a passive matrix may be used. Further, a transmissive liquid crystal display device may be used.

(Third Embodiment) FIG. 9 shows an example of an electronic apparatus according to the present invention. This is an electronic book, which is a kind of portable information terminal. Reference numeral 600 denotes an electronic book main body,
Reference numeral 601 denotes a liquid crystal display unit using the liquid crystal display device of the present invention.

FIG. 10 shows a mobile phone as another example of the present invention. Reference numeral 605 denotes a mobile phone main body, and reference numeral 606 denotes a liquid crystal display unit using the liquid crystal display device of the present invention. Since these electronic devices are provided with the liquid crystal display device according to the present invention, they have a wide viewing angle, a bright display screen with high contrast, and a clear display screen.

[0043]

According to the present invention, a sufficient scattering effect can be obtained even if the density of the fine particles contained in the resin is low, so that a bright and clear liquid crystal display device having a wide viewing angle can be obtained. Further, since the unevenness on the surface of the optical scattering layer can be minimized, a liquid crystal display device with high contrast can be obtained. Further, it is possible to prevent a decrease in the reliability of the liquid crystal display device due to a large amount of fine particles contained in the optical scattering layer.

[Brief description of the drawings]

FIG. 1 is a schematic view of a liquid crystal display device according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line A-A 'of FIG.

FIG. 3 shows 450 nm, 550 nm, and 650 n when the ratio of the refractive index of the fine particles to the refractive index of the transparent resin is 1.1.
9 is a graph showing the relationship between particle radius and scattering efficiency at a wavelength of m.

FIG. 4 is a graph showing T of a liquid crystal display device according to another embodiment of the present invention.
It is a FD partial enlarged plan view.

FIG. 5 is a graph showing T of a liquid crystal display device according to another embodiment of the present invention.
It is a FD part enlarged sectional view.

FIG. 6 is a partially enlarged plan view of a colored optical scattering layer of a liquid crystal display device according to another embodiment of the present invention.

FIG. 7 is a partially enlarged sectional view of a colored optical scattering layer of a liquid crystal display device according to another embodiment of the present invention.

FIG. 8 shows 450 nm, 550 nm, and 650 when the ratio of the refractive index of the fine particles to the refractive index of the transparent resin is 1.08.
9 is a graph showing the relationship between particle radius and scattering efficiency at a wavelength of nm.

FIG. 9 is a perspective view illustrating an example of an electronic apparatus using the liquid crystal display device of the present invention.

FIG. 10 is a perspective view showing another example of an electronic apparatus using the liquid crystal display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10, 20 ... Substrate 11 ... Segment electrode 21 ... Common electrode 22 ... Polarizer 23 ... Polarizer 31 ... Sealing material 32 ... Sealing material 40 ... Transparent resin 41 ... Fine particles 42 ... Optical scattering layer 50 ... Liquid crystal layer 51 ... Liquid crystal cell 54 ... Transmission type liquid crystal display device 80 ... Backlight 300 ... TFD element 301 ... Transparent electrode 302 ... First metal thin film 303 ... Transparent insulating film 304 ... Insulating layer 306 ... Second metal film 310 ... First substrate 311 ... Scan line 312 ... insulating film 400 ... common electrode substrate 401 ... transparent electrode 410 ... second substrate 411, 412, 413 ... color filter 420 ... black stripe 440 ... acrylic resin layer 600 ... electronic book main body 601 ... liquid crystal display device 605 ... mobile phone main body 606: Liquid crystal display device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Keiji Takizawa 3-3-5 Yamato, Suwa-shi, Nagano F-term in Seiko Epson Corporation (reference) 2H091 FA02Y FA31Y FB02 FC02 GA03 GA07 GA13 LA17

Claims (4)

[Claims] An optical scattering layer made of resin is provided between a pair of substrates, wherein liquid crystal is held between at least one of the substrates, electrodes are formed on at least one of the opposing surfaces of the substrates, and at least one of the substrates has an opposing surface. Wherein the scattering layer contains fine particles having a different refractive index from the resin in the resin, and the fine particles have a (scattering cross section in a wavelength region of 450 nm to 650 nm). A liquid crystal display device having a radius such that the scattering efficiency represented by () / (geometric cross-sectional area) is 2 or more. 2. The liquid crystal display device according to claim 1, wherein the optical scattering layer forms a color filter. 3. A liquid crystal display device comprising: a metal thin film formed on a substrate; and the optical scattering layer according to claim 1 formed on a surface of the metal thin film. 4. An electronic apparatus comprising the liquid crystal display device according to claim 1.