JP3472926B2 - Liquid crystal device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technical field of liquid crystal devices, and more particularly, to an anti-transmissive reflective liquid crystal device capable of switching between a reflective display and a transmissive display. . 2. Description of the Related Art Conventionally, a liquid crystal device is provided with a reflection type liquid crystal device which performs display by reflecting external light through a liquid crystal by a reflection means provided inside the device, and is provided inside the device. There are a transmissive liquid crystal device that performs display by emitting light from a light source through a liquid crystal, and a transflective liquid crystal device that can switch between such a reflective display and a transmissive display. [0003] Of these, the reflection type liquid crystal device does not use a light source and therefore consumes very little power. For this reason, it is frequently used for an auxiliary display unit of a portable device or device. A transflective liquid crystal device performs transmissive display using a light source in a dark place, but uses external light in a bright place like a normal reflective liquid crystal device. small. For this reason, it is frequently used for an auxiliary display unit of a portable device or device. [0004] Such a transflective liquid crystal device is, for example, disclosed in Japanese Utility Model Laid-Open Publication No. 57-049271, in which a polarizing plate is provided on the outer surface of the liquid crystal panel opposite to the observation side.
The transflective plate and the backlight are arranged sequentially. Furthermore, in comparison with these, the transflective plate, the polarizing plate, and the backlight are sequentially arranged on the outer surface of the liquid crystal panel opposite to the observation side, and there is no polarizing plate between the liquid crystal cell and the transflective plate. Japanese Patent Application Laid-Open No. 8-29241 discloses a transflective liquid crystal device in which the brightness of a reflective display is improved.
No. 3 publication. Further, with the recent development of portable equipment and OA equipment, colorization of liquid crystal display has been required, and even in equipment using a reflection type or transflective type liquid crystal device, color display is required. In many cases. Here, when the above-described reflective or transflective liquid crystal device is used for color display, R (red), G (line), and B ( A color filter having a number of colored regions (blue) is provided. In this case, in order to prevent color mixture between the colored regions in the color filter and to prevent a decrease in contrast ratio due to light leakage (white void) in the gap between the colored regions, a gap between the colored regions is provided. A light shielding film generally called a black mask or a black matrix is provided. However, in the above-mentioned reflection type liquid crystal device, the display is made visible using external light, so that the display is difficult to read or cannot be read in a dark place. There is a basic problem. For this reason, it is important to increase the reflectance of external light incident on the liquid crystal device and to increase the ratio of a portion of the incident external light that is reflected and emitted from the liquid crystal device as display light that contributes to display contrast. However, in the above-mentioned reflection type liquid crystal device, the reflectivity and the ratio of a portion emitted as display light are not sufficiently high. In particular, in the case of a reflection type liquid crystal device employing a configuration in which a transparent substrate is interposed between a liquid crystal layer and a reflection plate, problems such as double reflection and blurring of display are caused. There is. In this case, if a color filter is further combined, there is a problem that sufficient color development cannot be obtained due to parallax. Alternatively, in this case, if a configuration is employed in which no black mask is provided to prevent light absorption by the black mask and increase the brightness of the displayed image, light passing through the gap between the colored regions is reflected by the reflector, The portion of the external light that does not contribute to the display contrast, that is, the portion emitted from the liquid crystal device regardless of the display image relatively increases, and the contrast ratio decreases. On the other hand, Japanese Patent Application Laid-Open No. 9-258219 proposes a reflection type color liquid crystal device in which a reflection plate is arranged so as to be in contact with a liquid crystal layer. However, in this case, if a configuration in which a black mask is not provided between the colored regions of the color filter in order to brighten the display as described above is employed, the external light that has entered through the gap between the colored regions without the black mask is also used. Is reflected by the reflection plate and is emitted to the outside of the liquid crystal device while being mixed with a part of the display light, thereby causing color mixing, blurring or blurring of the color, and lowering the contrast ratio. As described above, the conventional reflection type liquid crystal device has a problem that it is difficult to display a bright and high-contrast image. On the other hand, in the transflective liquid crystal device described in the above-mentioned Japanese Patent Application Laid-Open No. 8-292413, etc., since a transmissive substrate is interposed between the liquid crystal layer and the transflective plate, double reflection is also caused. In addition, there is a problem that image blurring or display bleeding occurs, and furthermore, if a color filter is combined, sufficient color development cannot be obtained due to parallax. On the other hand, Japanese Patent Laid-Open No. Hei 7-318929 proposes a transflective liquid crystal device in which a pixel electrode serving as a transflective film is provided on the inner surface of a liquid crystal cell. In addition, ITO (In
It discloses a configuration in which pixel electrodes made of a dium tin oxide (xin) film are stacked via an insulating film. However, in this liquid crystal device, first, with respect to the pixel electrode also serving as the semi-transmissive reflective film or the semi-transmissive reflective film on which the pixel electrode is superimposed, a fine defect such as a hole defect or a dent defect or a fine opening is formed. Need to be provided, the structure of the device becomes complicated, and a special process is additionally required in the manufacture thereof, which makes it difficult to manufacture a reliable pixel electrode or a transflective film. In particular, when a pixel electrode serving also as a transflective film is employed, a liquid crystal portion through which light source light passing through an opening passes during transmissive display is obliquely distorted by a pixel electrode portion in a non-opening portion. Since the liquid crystal must be driven by an electric field, the display quality is degraded due to the disorder of the liquid crystal alignment as compared with the case where the liquid crystal is driven by a vertical electric field. Further, in a case where a pixel electrode is superposed on a semi-transmissive reflective film made of a metal film via an insulating film, each pixel electrode, the insulating film and the semi-transmissive film are located between adjacent pixel electrodes. Capacitance coupling occurs via the capacitance formed by the reflective film and the transflective film. For this reason, signals such as image signals supplied to a plurality of pixel electrodes cross each other or cross-talk with each other, causing a so-called waveform rounding, which eventually leads to deterioration in quality of a displayed image. Moreover, when the pixel electrode is used as a data line or a segment electrode to which an image signal having a complicated waveform and a high driving frequency is supplied as compared with a scanning signal or the like, such a deterioration in quality becomes more serious. As described above, the conventional transflective liquid crystal device has a problem that it is difficult to display a bright and high-contrast image. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. In a transflective liquid crystal device, a bright and high-contrast image can be displayed without causing double reflection or display bleeding due to parallax. It is an object to provide a possible liquid crystal device and an electronic device using the liquid crystal device. According to the present invention, the above object is achieved by providing a pair of first and second substrates , a liquid crystal layer sandwiched between the first and second substrates , On the liquid crystal layer side of the substrate
A plurality of transparent electrodes formed on a surface, and the plurality of transparent electrodes
A reflective film formed between the second substrate and the second
A liquid crystal comprising: a backlight disposed behind the substrate;
An apparatus, wherein the reflective film formed on the second substrate is
Transmits light from the backlight to the liquid crystal layer side
A gap is provided, and the reflective film and the plurality
Color filter with multiple colored areas between
This is achieved by a liquid crystal device characterized in that a filter is formed . According to the liquid crystal device of the present invention, of the external light incident from the first substrate side, the portion transmitted through the transparent electrode is reflected toward the liquid crystal layer by the reflection film formed in the region facing the transparent electrode. Then, a reflective display is performed. At this time, since the reflective film is disposed on the liquid crystal layer side of the second substrate, there is almost no gap between the reflective film and the liquid crystal layer, and therefore, the double reflection of the display due to the parallax and the bleeding of the display are caused. Does not occur. On the other hand, a portion of the external light that is incident from the first substrate side and that passes through the gap between the transparent electrodes, when reflected toward the liquid crystal layer, causes a so-called light loss (white loss) and lowers the contrast ratio. However, in the liquid crystal device of the present invention, the portion of the external light incident from the side of the first substrate that passes through the gap between the transparent electrodes corresponds to the area where the reflective film facing the gap is not provided. Since the light is transmitted, the light is not reflected by the reflective film toward the liquid crystal layer in this region. Therefore, it is possible to reduce the deterioration of the image quality caused by the light passing through the gap between the transparent electrodes being reflected by the reflection film and being mixed with the display light emitted to the outside. In one aspect of the liquid crystal device of the present invention, the reflection film includes a plurality of reflection films which are separated from each other in correspondence with the plurality of transparent electrodes. According to this aspect, the plurality of reflective films that are spaced apart from each other corresponding to the plurality of transparent electrodes can reflect the external light transmitted through the transparent electrodes, and the external light that passes through the gap between the transparent electrodes. Can be passed through the gap between the reflection films as they are to prevent reflection. In another aspect of the liquid crystal device of the present invention, the liquid crystal device further includes a color filter formed on at least one of the first and second substrates and having a colored region facing the plurality of transparent electrodes. The color filter does not have a light-shielding region in a region facing at least a part of a gap between the plurality of transparent electrodes. According to this aspect, light transmitted through the transparent electrode via the colored region of the color filter is reflected by the reflective film, and color reflective display is performed. At this time, the color filter does not have a light shielding region at least in a region where the reflection film is not provided facing the gap between the transparent electrodes. Therefore, although external light passes through the region between the colored regions that do not have the light-shielding region, since the reflective film is not formed in this region, the external light is reflected by the reflective film and the light is reflected between the adjacent colored regions. This prevents a situation in which the color image is mixed and the display is blurred or blurred. In another aspect of the first liquid crystal device of the present invention, an insulating film is interposed between the transparent electrode and the reflection film. In this embodiment, since the insulating film is interposed between the transparent electrode and the reflective film, even if the reflective film is made of a conductive material such as Al, a plurality of transparent electrodes may leak through the reflective film. The possibility of short-circuiting can be reduced, and the degree of freedom for the planar pattern of the reflection film can be increased. Embodiments of a liquid crystal device according to the present invention will be described based on embodiments with reference to the drawings. An embodiment of the liquid crystal device according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic longitudinal sectional view showing a structure of an embodiment of a liquid crystal device according to the present invention. Although this embodiment is basically related to a simple matrix type liquid crystal display device, it can be applied to an active matrix type device, another segment type device, and other liquid crystal devices with the same configuration. . In the transflective liquid crystal device of the embodiment, 2
A liquid crystal cell in which a liquid crystal layer 403 is sealed by a frame-shaped sealing material 404 is formed between the transparent substrates 401 and 402. The liquid crystal layer 403 is composed of a nematic liquid crystal having a negative dielectric anisotropy. A plurality of stripe-shaped transparent electrodes 409 are formed on the inner surface of the upper transparent substrate 401 by IT.
An alignment film 410 for vertical alignment of liquid crystal is formed on the surface of the transparent electrode 409 and is rubbed in a predetermined direction. By this rubbing treatment, the liquid crystal molecules have a pretilt angle of about 85 degrees in the rubbing direction.
In the case of a TFT element or an active matrix type device including a TFT element, the transparent electrode 409 is formed in a rectangular shape, and is connected to a wiring via the active element. On the other hand, irregularities having a height difference of about 8 μm are formed on the inner surface of the lower transparent substrate 402 by a photosensitive acrylic resin, and 1.0% by weight of Nd is formed on the surface.
Is sputtered to a thickness of 25 nm, and then is island-shaped (see FIG. 2A) or stripe-shaped (see FIG. 2).
(Refer to (b)) to form a reflective film 411. Here, FIGS. 2A and 2B referred to as examples of forming the reflection film 411 of the present invention will be briefly described.
FIG. 2A is a schematic front view of a lower transparent substrate when the present invention is applied to an active matrix type liquid crystal device using a TFD element, and the reflection film 503 is formed on an island-like Al reflection film 503. This shows that an island-shaped ITO transparent electrode 504 having an area slightly larger than the area is laminated. In addition,
501 is a scanning line, and 502 is a TFD element. FIG. 2B is a schematic front view of an example of a lower transparent substrate when the present invention is applied to a simple matrix type liquid crystal device, and shows a stripe pattern formed on the inner surface of the upper transparent substrate of the liquid crystal cell. A transparent electrode 603 in the form of a stripe is formed on the inner surface of the lower transparent substrate so as to cross the ITO transparent electrode 601 of FIG. In FIG. 1, a color filter 414 is formed on a reflective film 411 via a protective film 412.
The color filter 414 is provided with a transparent protective film 415 on the surface of the color filter 414 in which three colored layers of R, G, and B are arranged in a predetermined pattern. A plurality of stripe-shaped transparent electrodes 416 are formed by an ITO film or the like so as to intersect the transparent electrodes 409 for each color layer of the color filter 414 on the surface of the transparent electrode 409. An alignment film 417 is formed on the surface of the transparent electrode 416. Note that rubbing treatment is not performed on the alignment film 417. A polarizing plate 405 is disposed on the outer surface of the upper transparent substrate 401, and a retardation plate (１ ／ wavelength plate) 406 is disposed between the polarizing plate 405 and the transparent substrate 401. A retardation plate (1/4 wavelength plate) 408 is disposed behind the transparent substrate 402 below the liquid crystal cell, and a polarizing plate 407 is disposed behind the retardation plate (1/4 wavelength plate) 408. Are located. A backlight having a fluorescent tube 419 that emits white light and a light guide plate 418 having an incident surface along the fluorescent tube 419 is disposed behind the polarizing plate 407. The light guide plate 418 is a transparent body such as an acrylic resin plate having a scattering rough surface formed on the entire back surface or a scattering printing layer formed thereon. And emits substantially uniform light from the upper surface of the figure. As another backlight, an LED (light emitting diode), an EL (electroluminescence), or the like can be used. In this embodiment, in order to prevent light from leaking from the area between the dots during the transmissive display, the black matrix layer 413, which is a light shielding portion formed between the colored layers of the color filter 414, is provided. It is provided substantially corresponding to a plane. The black matrix layer 413 is formed by depositing a Cr layer or a photosensitive black resin layer. Here, as shown in FIG.
05 and the transmission axes Pl and P2 of the polarizing plate 407 are set in the same direction, and the slow axes of the phase difference plates (1/4 wavelength plates) 406 and 408 are set with respect to the transmission axes P1 and P2 of these polarizing plates. The directions of Cl and C2 are set to directions rotated clockwise by θ = 45 degrees. Further, the direction R1 of the rubbing process of the alignment film 410 on the inner surface of the transparent substrate 401 is also performed in a direction coinciding with the directions of the slow axes C1 and C2 of the phase difference plates (1/4 wavelength plates) 406 and 408. ing. The rubbing direction R1 defines the direction in which the long axis of the liquid crystal molecules falls when an electric field is applied to the liquid crystal layer 403. For the liquid crystal layer 403, a negative nematic liquid crystal is used. FIG. 3B shows the driving voltage characteristics of the reflectance in the reflective display according to the present embodiment and the driving voltage characteristics of the transmittance in the transmissive display. The display state when no electric field is applied is dark (black). When this liquid crystal cell is used, it is not necessary to form the black matrix layer 413. Next, the operation of the reflection type display and the transmission type display in the present embodiment configured as described above will be described with reference to FIG. First, in the case of a reflective display, external light incident on the liquid crystal device from above in FIG.
05 and the liquid crystal layer 403
Pass through the color filter 414 and pass through the reflective film 411
And is emitted again from the polarizing plate 405.
At this time, the bright state, the dark state, and the intermediate brightness are controlled by the voltage applied to the liquid crystal layer 403. In the case of a transmissive display, light from a backlight is converted into a predetermined polarized light by a polarizing plate 407 and a phase difference plate 408, and is introduced into the liquid crystal layer 403 from each gap of the reflection film 411. After passing through 403, the light passes through the phase difference plate 406. At this time, the liquid crystal layer 40
Depending on the voltage applied to 3, the state of transmission (bright state) from the polarizing plate 405, the state of absorption (dark state), and the intermediate brightness can be controlled. Referring to FIGS. 2A and 2B which are referred to in the above description of the reflection film 411 of the present invention, at the time of the transmissive display, the reflection film 503 or the reflection film 503 out of the light incident on the liquid crystal cell from the backlight. Only the light source light from the backlight that passes through the gap between the reflective films 602 and enters the transparent electrode 504 or the transparent electrode 603 is introduced into the liquid crystal layer. According to the configuration of the present embodiment as described above,
A color liquid crystal device capable of switching and displaying between a reflective display and a transmissive display without double reflection or display bleeding is realized. The reflective film 411 of this embodiment uses a metal layer mainly composed of Al, and its surface is covered with a protective film 412, on which a color filter 414, a protective film 415, and a transparent electrode 416 are formed. I have. Therefore, the Al metal layer is directly
Since there is no contact with the TO developer or the color filter developer, the A1 metal layer is not dissolved by the developer. Further, the Al metal layer which is easily damaged can be easily handled. For example, 2 containing 1.0% by weight of Nd
Al having a thickness of 5 nm has a reflectance of 80% and a transmittance of 10%, and functions sufficiently as the reflective film 411. Further, since the reflection film 411 provided with irregularities can reflect the reflected light at a wide angle, a liquid crystal device having a wide viewing angle is realized. In the present embodiment, instead of forming a protective film on the reflective film, the reflective film is formed by utilizing anodizing or thermal oxidation, or in addition to an oxide film obtained by anodizing, and spin coating the organic material. May be applied and laminated to form an insulating film on the reflective film. The coloring layer of the color filter 414 used in the embodiment described above will be described with reference to FIG. FIG. 4 is a characteristic diagram showing the transmittance of each colored layer of the color filter 414. In this embodiment, in the case of performing the reflection type display, the incident light once passes through one of the coloring layers of the color filter 414, then passes through the liquid crystal layer and is reflected by the reflection film, and the coloring layer is formed again. Released after transmission. Therefore, unlike a normal transmission type liquid crystal device, the light passes through the color filter 414 twice, so that the display becomes dark and the contrast is lowered in the normal color filter. Therefore, in this embodiment, as shown in FIG. 4, the color filter 414 is light-colored so that the minimum transmittance 61 in the visible region of each of the R, G, and B colored layers is 25 to 50%. Has formed. Lightening of the colored layer is achieved by reducing the thickness of the colored layer or reducing the concentration of the pigment or dye mixed in the colored layer. Thus, it is possible to configure so as not to lower the brightness of the display when performing the reflective display. The lightening of the color filter 414 results in the lightening of the display because the light is transmitted through the color filter 414 only once in the case of the transmissive display. Is often blocked, which is rather convenient in securing the brightness of the display. The liquid crystal device of the present invention is not limited to the above-described embodiments, but can be appropriately modified without departing from the spirit or spirit of the invention which can be read from the claims and the entire specification. Liquid crystal devices with modifications are also included in the scope of the present invention. The liquid crystal device according to the present invention can be used as various display devices capable of displaying a bright and high-contrast image, and furthermore, a liquid crystal device constituting a display section of various electronic devices. Available as Further, the electronic apparatus according to the present invention is a liquid crystal television configured using such a liquid crystal device, a viewfinder-type or monitor direct-view type video tape recorder, a car navigation device, an electronic organizer, a calculator, a word processor, a workstation, It can be used as a mobile phone, videophone, POS terminal, touch panel, and the like. In particular, if the liquid crystal device according to the present invention is used as a display unit of a portable information device, a portable information device with a bright and vivid display can be obtained regardless of whether it is a reflection type, a transflective type, or a transmission type.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic longitudinal sectional view showing a schematic structure of an embodiment of a liquid crystal device according to the present invention. FIG. 2A is a plan view showing an example of a semi-transmissive reflective film composed of reflective films arranged at intervals in an embodiment of the liquid crystal device according to the present invention, and FIG. FIG. 10 is a plan view showing another example of a semi-transmissive reflective film composed of reflective films arranged at intervals in the embodiment of the liquid crystal device according to the present invention. FIG. 3A is an explanatory diagram showing a relationship between a rubbing direction of a polarizing plate, a retardation plate, and a liquid crystal cell in an example of a liquid crystal device according to the present invention. FIG. 2B is a characteristic diagram showing a driving voltage-reflectance / transmittance characteristic of the liquid crystal device having the relationship of FIG. FIG. 4 is a graph showing light transmittance of each color layer of a color filter in an example of a liquid crystal device according to the present invention. DESCRIPTION OF SYMBOLS 401, 402 Transparent substrate 403 Liquid crystal layer 404 Sealing material 406, 408 Phase difference plate (1/4 wavelength plate) 407 Polarizing plate 409, 416, 504, 601, 603 Transparent electrodes 410, 417 Alignment film 411, 503, 602 Reflective film 412, 415 Protective film 414 Color filter 418 Light guide plate 419 Fluorescent tube

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takumi Seki 3-5-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Corporation (56) References JP-A-6-313890 (JP, A) JP-A-7 JP-A-134300 (JP, A) JP-A-8-136939 (JP, A) JP-A-9-61854 (JP, A) JP-A-10-253951 (JP, A) JP-A-11-52366 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/1343 G02F 1/1335 G02F 1/13357 G02F 1/1362 G02F 1/1333 G02B 5/20

Claims (1)

(57) Claims 1. A pair of first and second substrates, a liquid crystal layer sandwiched between the first and second substrates, and a liquid crystal layer side of the second substrate. a plurality of transparent electrodes made form <br/> apart from each other on a plane, a reflective film formed between the second substrate and said plurality of transparent electrodes, the reflective film and the plurality of Formed between the transparent electrode
And opposed to each of the plurality of transparent electrodes.
A liquid crystal device comprising: a color filter having a colored region; and a backlight disposed behind the second substrate, wherein the reflective film has a gap for transmitting light from the backlight to the liquid crystal layer side. Is provided between the plurality of transparent electrodes.
The colored region of the color filter is
A liquid crystal device, wherein the liquid crystal device is disposed on an area where the gap between the projection film and the transparent electrode overlaps and on the reflection film.