JPH10325953A - Reflection type-cum-transmission type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make possible always displaying without being affected with environment by operating as a reflection type in bright environment, saving power consumption and operating as a transmission type assembled with a back side light source in dark environment. SOLUTION: In a reflection type-cum-transmission type display device, a guest host liquid crystal 3 is held in a gap between a pair of transparent substrates 1, 2 as electrooptical substance, and the device modulates incident light according to a voltage applied between electrodes 6, 11 to perform a display. A light reflection layer 9 is arranged on the back transparent substrate 2 side, and the majority of the light made incident from the front is reflected by it to be transmitted partially. The backside light source 30 is arranged backward from the transparent substrate 2, and the light is made incident toward front according to need. In the bright environment, the majority of external light made incident from the outside from the front toward the back is reflected by the light reflection layer 9, and a display is performed, and in the dark environment, a part of light source light made incident from the back side light source 30 from the back toward the front is transmitted to the front without shielding by the light reflection layer 9, and the display is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type for displaying an image by using a backlight (back light source) when outside light is poor, such as at night, while using the light when the outside light is bright, such as at daytime. The present invention relates to a transmissive display device.

[0002]

2. Description of the Related Art There are various modes in a display device using a liquid crystal as an electro-optical material. At present, a T-mode using a twisted or super-twisted nematic liquid crystal is used.
The N mode or the STN mode is mainly used. However, these modes require a pair of polarizing plates in terms of operation principle, and because of their light absorption, a low transmittance and a bright display screen cannot be obtained. In addition to these modes, a guest-host mode using a dichroic dye has also been developed. The guest-host mode liquid crystal display device performs display using the anisotropy of the absorption coefficient of the dichroic dye added to the liquid crystal. When a dichroic dye having a rod-like structure is used, the dye molecules have a property of being arranged in parallel to the liquid crystal molecules. Therefore, when an electric field is applied to change the molecular alignment of the liquid crystal, the alignment direction of the dye also changes. Since this dye is colored or not depending on the direction, it is possible to switch between coloration and colorlessness of the liquid crystal display device by applying a voltage.

FIG. 26 shows a transmission type Heilmeier (HE).
(A) shows the structure of a (ILMEIER) type guest-host liquid crystal display device, (A) shows a state where no voltage is applied, and (B)
Indicates a voltage applied state. This liquid crystal display device
Type dye and dielectric anisotropy are using positive nematic liquid crystal (N _p LCD). The p-type dichroic dye has an absorption axis substantially parallel to the molecular axis, and a polarized light component Lx parallel to the molecular axis.
Is strongly absorbed, and the polarization component Ly perpendicular to it is hardly absorbed. In the state where no voltage is applied as shown in (A), the polarization component Lx contained in the incident light from the light source is strongly absorbed by the p-type dye, and the liquid crystal display is colored. In contrast,
In the voltage application state shown in (B), N _p has a positive dielectric anisotropy.
The liquid crystal rises in response to the electric field, and the p-type dye is aligned in the vertical direction accordingly. Therefore, the liquid crystal display device is almost colorless only by absorbing the polarization component Lx slightly. The other polarization component Ly contained in the incident light is hardly absorbed by the dichroic dye in both the voltage applied state and the voltage non-applied state. Therefore, in the transmission type guest-host liquid crystal display device, one polarizing plate is interposed in advance, and the other polarization component Ly is removed to improve the contrast.

In the transmission type guest-host liquid crystal display device described above, in order to obtain a sufficient contrast, one polarizing plate is disposed on the incident side of the liquid crystal display device, and the polarization direction of the incident light is aligned with the orientation direction of the liquid crystal. Are matched. However, in this case, in principle, 50% of the incident light is
(Actually, about 40%) is lost, and the display becomes dark as in the TN mode. As a method for solving this problem, simply removing the polarizing plate is not appropriate because the on / off ratio of absorbance is remarkably reduced, and various measures have been proposed. For example, as shown in FIG. 27, a reflection type guest-host liquid crystal display device has been proposed in which a polarizing plate is removed from the incident side and a quarter-wave plate and a reflecting plate are attached to the output side. In this method, two polarization components Lx and Ly orthogonal to each other are rotated by 90 ° in the forward and backward directions by a quarter-wave plate, and the polarization planes are exchanged. Therefore, in the off state (absorption state) shown in (A), the polarization components Lx and Ly are absorbed in either the incident optical path or the reflected optical path. Also (B)
In the ON state (transmission state) shown in FIG.
x and Ly are hardly absorbed. Thereby, the utilization efficiency of the incident light can be remarkably improved, and the display device becomes bright.

[0005]

As described above, the conventional guest-host liquid crystal display devices include the transmission type shown in FIG. 26 and the reflection type shown in FIG. In the transmission type, a rear light source (backlight) for illumination is arranged on the rear surface opposite to the front surface of the display device where the observer is located, to illuminate the screen brightly. On the other hand, the reflection type projects a screen using external light such as sunlight. The former uses a backlight, so that a bright display is possible and is particularly suitable for color display, but the backlight consumes a large amount of power. For example, when used outdoors, the power consumption is large, so it is not suitable as a display for a portable device. In contrast, in a bright environment with abundant external light, the contrast is reduced. On the other hand, the latter uses external light and does not require a backlight, thereby reducing power consumption. Also, unlike the transmission type, the reflection type has a high contrast in a bright environment. However, the reflection type has a low absolute image luminance and is difficult to display high-quality color. Further, in an environment where external light is scarce such as at night, the visibility of display is significantly reduced.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, an object of the present invention is to provide a reflection-type and transmission-type display device capable of obtaining a good display state regardless of daytime or nighttime. And The following measures were taken to achieve this purpose. That is, the reflective / transmissive display device according to the present invention has, as a basic configuration, a first transparent substrate provided with an electrode at the front and an electrode located at a rear from the first transparent substrate via a predetermined gap. A second transparent substrate, an electro-optical material that modulates incident light held in the gap in accordance with a voltage applied to the electrode and performs display, and a large amount of incident light arranged on the second transparent substrate side. A light reflecting layer that reflects a part and allows a part to pass therethrough, and a back light source that is arranged behind the second transparent substrate and that enters light forward as necessary.
In such a configuration, usually, most of the light incident from the outside from the front to the rear is reflected forward by the light reflection layer to perform display, and if necessary, the light is incident from the rear light source from the rear to the front. The display is performed by transmitting a part of the light to be transmitted forward without being blocked by the light reflection layer. Preferably, each electrode provided on the first and second transparent substrates faces each other to define a matrix-shaped pixel, and the light reflection layer is formed from a set of reflection elements subdivided corresponding to each pixel. Each reflective element has a metal film that reflects most of the light incident from the front and a small opening in which a part of the metal film is removed to transmit a part of the light that is incident from the rear, In addition, a microlens located behind the light reflecting layer and condensing light emitted from the rear light source toward the opening of each pixel is provided. Also preferably, the electro-optical material is a guest host liquid crystal in which a dichroic dye serving as a guest is added to a nematic liquid crystal serving as a host, and the second transparent substrate is provided between the light reflection layer and the guest host liquid crystal. And a quarter-wave layer for efficiently modulating light incident from the outside, wherein the back light source enables modulation of light incident from the back light source between the back light source and the second transparent substrate. A polarizing plate and a quarter-wave plate are provided.

A reflective / transmissive display device according to the present invention includes a light reflecting layer that reflects most of incident light and transmits part of the light. During normal use, such as in the daytime, display is performed by reflecting most of external light such as sunlight, which is incident from the outside from the front toward the rear, forward on the light reflection layer. At this time, there is no need to turn on the back light source, so that power consumption can be saved. On the other hand, when external light is poor, such as at night, display is performed by transmitting a part of the light incident from the rear light source from the rear toward the front without being blocked by the light reflection layer. That is, the present reflective and transmissive display device allows the display to be visually recognized even when external light is poor.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic partial sectional view showing a first embodiment of a reflective / transmissive display device according to the present invention. As shown in the figure, this display device is configured using a pair of upper and lower substrates 1 and 2 joined to each other with a predetermined gap therebetween. The upper substrate 1 is located on the incident side and is made of a transparent base material such as glass. On the other hand, the lower substrate 2 is located on the reflection side,
This also uses a transparent substrate such as glass. In the gap between the pair of substrates 1 and 2, a guest-host liquid crystal 3 is held as an electro-optical material. The guest-host liquid crystal 3 mainly includes nematic liquid crystal molecules 4 having negative dielectric anisotropy.
And the dichroic dye 5 is contained in a predetermined ratio. On the inner surface of the upper substrate 1, a counter electrode 6 and an alignment layer 7 are formed. The counter electrode 6 is made of a transparent conductive film such as ITO. The alignment layer 7 is made of, for example, a polyimide film, and vertically aligns the guest-host liquid crystal 3. The present invention is not limited to this, and the guest-host liquid crystal may be horizontally aligned as shown in FIG. 26 and FIG. In the present embodiment, the guest host liquid crystal 3 is vertically aligned when no voltage is applied, and shifts to horizontal alignment when a voltage is applied.

On the lower substrate 2, at least a switching element comprising a thin film transistor 8, a light reflecting layer 9, a quarter wavelength layer 10, and a pixel electrode 11 are formed. The quarter wavelength layer 10 is formed above the thin film transistor 8 and the light reflection layer 9, and has a contact hole 12 communicating with the thin film transistor 8. Pixel electrode 1
1 is patterned on the quarter-wave layer 10. Therefore, it is possible to apply a sufficient electric field to the guest-host liquid crystal 3 between the pixel electrode 11 and the counter electrode 6. This pixel electrode 11 is electrically connected to the thin film transistor 8 via a contact hole 12 opened in the quarter wavelength layer 10. The light reflecting layer 9 has a structure capable of reflecting most of the incident light and transmitting part of the light.
Specifically, the light reflection layer 9 is composed of a fine projection 9a formed along a plane and a metal film 9b formed thereon.
An opening 9c in which a part of the metal film 9b is removed by etching.
Is provided, and most of the light incident from the front is scattered and reflected, while a part of the light incident from the rear is
Transmitted through. The opening 9c is formed in a part of the projection 9a.

[0010] A back light source 30 is arranged further rearward of the substrate 2 located at the rear, and enters light forward if necessary. In the present embodiment, the back light source 30 and the substrate 2
, A polarizing plate 31 and a quarter-wave plate 32 are interposed. In such a configuration, usually, most of light (external light) incident from the outside from the front to the rear is reflected forward by the light reflection layer 9 to perform display, and if necessary, the back light source is directed from the back to the front. A part of the light (light source light) incident from 30 is transmitted forward through the opening 9c without being blocked by the light reflection layer 9, and display is performed.

Hereinafter, a specific description will be given for each element. In the present embodiment, the quarter-wave layer 10 is composed of a uniaxially oriented polymer liquid crystal film. A base alignment layer 13 is used to uniaxially align the polymer liquid crystal film.
A flattening layer 14 is interposed to fill the unevenness of the thin film transistor 8 and the light reflection layer 9, and the above-described base alignment layer 13 is formed on the flattening layer 14. The quarter-wave layer 10 is also formed on the surface of the flattening layer 14. In this case, the pixel electrode 11 is connected to the thin film transistor 8 via the contact hole 12 provided through the quarter-wave layer 10 and the flattening layer 14. The light reflection layer 9 is subdivided corresponding to each pixel electrode 11. Each of the subdivided portions is connected to the same potential as the corresponding pixel electrode 11. With such a configuration, the light reflection layer 9
An unnecessary electric field is not applied to the quarter wavelength layer 10 or the flattening layer 14 interposed between the pixel electrode 11 and the quarter wavelength layer 10. The light reflecting layer 9 is provided with a scattering reflecting surface made of a metal film 9b as shown in the figure, and improves the image quality by preventing the specular reflection of incident light. As described above, the light reflection layer 9 is provided with the opening 9c for transmitting the illumination light incident from behind to the front. An alignment layer 15 is formed so as to cover the surface of the pixel electrode 11, and controls the alignment in contact with the guest-host liquid crystal 3. In the present embodiment, the alignment layer 15 and the facing alignment layer 7 vertically align the guest-host liquid crystal 3 together. The thin film transistor 8 has a bottom gate structure, and has a stacked structure in which a gate electrode 16, a gate insulating film 17, and a semiconductor thin film 18 are sequentially stacked from the bottom. The semiconductor thin film 18 is made of, for example, polycrystalline silicon, and a channel region aligned with the gate electrode 16 is protected from above by a stopper 19.

The bottom gate type thin film transistor 8 having such a configuration is covered with an interlayer insulating film 20.
A pair of contact holes are opened in the interlayer insulating film 20, and a source electrode 21 and a drain electrode 22 are electrically connected to the thin film transistor 8 through these. These electrodes 21 and 22 are, for example, patterned aluminum. The drain electrode 22 has the same potential as the light reflection layer 9. The pixel electrode 11 is electrically connected to the drain electrode 22 through the contact hole 12 described above. On the other hand, a signal voltage is supplied to the source electrode 21.

Here, a method for forming the light reflecting layer 9 will be described. The light reflection layer 9 includes a resin film on which the convex portions 9a are formed,
And a metal film 9b such as aluminum formed on the surface. The resin film is a photosensitive resin film having irregularities patterned by photolithography. The photosensitive resin film 9 a is made of, for example, a photoresist, and is applied to the entire surface of the interlayer insulating film 20. This is exposed through a predetermined mask, and is patterned into a cylindrical shape. Then, if the reflow is performed by heating, the projections 9a can be formed stably.
A metal film 9b of aluminum or the like having a desired film thickness and good light reflectance is formed on the surface of the projection 9a thus formed.
To form If the height of the projection 9a is set to, for example, several μm, good light scattering characteristics can be obtained, and the light reflection layer 9 exhibits white. After that, the metal film 9b is etched to
a is partially removed to provide an opening 9c.

Further, a method of forming the quarter wavelength layer 10 will be described. First, a flattening layer 14 is formed on the light reflection layer 9 to fill in irregularities. It is preferable to use a transparent organic material such as an acrylic resin for the planarizing layer 14. Thereafter, the process proceeds to the process of forming the quarter wavelength layer 10. First, the planarization layer 1
After a base alignment layer 13 is formed on 4, a polymer liquid crystal is applied thereon and is uniaxially aligned to form a quarter-wave layer 10. At this time, the formation of the underlying alignment layer 13 and the rubbing treatment can be stably performed by interposing the planarizing layer 14. For this reason, the quarter wavelength layer 10 can be formed accurately.

The underlying alignment layer 13 is made of, for example, a polyimide film, and is subjected to rubbing along a predetermined alignment direction. The quarter-wave layer 10 is actually formed on the base alignment layer 13. Specifically, a polymer liquid crystal is applied on the base alignment layer 13 with a predetermined thickness. This polymer liquid crystal is a material capable of phase transition between a high temperature side nematic liquid crystal phase and a low temperature side glass solid phase at a predetermined dislocation point. After dissolving this polymer liquid crystal in an organic solvent, it is applied to the surface of the base alignment layer 13 by spin coating. At this time, conditions such as the concentration of the solution and the number of spin rotations are appropriately set so that the thickness of the formed thin film is λ / 4 in the visible light region.
Is generated. Here, λ is the wavelength of the incident light. Thereafter, a temperature treatment is performed, and the substrate 2 is once heated to a temperature equal to or higher than the dislocation point, and then cooled to room temperature equal to or lower than the dislocation point. Form. In the film formation stage, the liquid crystal molecules contained in the polymer liquid crystal are in a random alignment state, but after cooling, the liquid crystal molecules are aligned along the alignment direction, and a desired uniaxial optical anisotropy can be obtained.

The operation of the first embodiment shown in FIG. 1 at the time of reflective display will be described with reference to FIG. When performing reflective display, the back light source is turned off. External incident light passes through the opposite substrate and the guest host liquid crystal, and is diffusely reflected by the light reflection layer 9. Switching between monochrome display is controlled by turning on / off the voltage applied to the pixel electrode 11. The monochrome display will be described with reference to FIG. In a voltage applied state, the nematic liquid crystal molecules 4 are horizontally oriented, and the dichroic dye 5 is similarly oriented. When light incident from the upper substrate 1 side travels to the guest-host liquid crystal 3, a component of the incident light having a vibration plane parallel to the major axis direction of the molecules of the dichroic dye 5 is changed by the dichroic dye 5. Absorbed. A component having a vibration plane perpendicular to the major axis direction of the molecules of the dichroic dye 5 passes through the guest-host liquid crystal 3 and is formed on the surface of the lower substrate 2 by a quarter-wavelength layer 10. Is converted into circularly polarized light by the light reflection layer 9.
Reflected by At this time, the polarization of the reflected light is reversed, passes through the quarter wavelength layer 9 again, and becomes a component having a vibration plane parallel to the major axis direction of the molecules of the dichroic dye 5. Since this component is absorbed by the dichroic dye 5, an almost complete black display is obtained. On the other hand, when no voltage is applied, the nematic liquid crystal molecules 4 are vertically oriented as shown, and the dichroic dye 5 is similarly oriented. Light incident from the upper substrate 1 side passes through the guest-host liquid crystal 3 without being absorbed by the dichroic dye 5, and is further not polarized by the quarter-wavelength layer 9 but is reflected by the light reflecting layer 9.
Reflected by The reflected light passes through the quarter-wave layer 10 again and exits without being absorbed by the guest-host liquid crystal 3. Therefore, white display is obtained.

The operation of the first embodiment shown in FIG. 1 during the transmissive display will be described with reference to FIG. At the time of transmissive display, the back light source is turned on. The light source light emitted from the rear light source passes through the substrate 2, is reflected on the back surface of the metal film 9b forming the light reflection layer 9, and is emitted from the opening 4c.
Is diffusely reflected by the surface of the liquid crystal and enters the guest-host liquid crystal.
Switching between black and white display is controlled by turning on and off the voltage applied to the pixel electrode 11 as in the reflective display. In this regard, a description will be given again with reference to FIG. The light from the rear light source 30 is linearly polarized by the polarizing plate 31 and enters the guest-host liquid crystal 3 with the polarization axis rotated by 90 ° by the quarter-wave plate 32 and the quarter-wave layer 10. Therefore,
Black and white display can be performed according to the same principle as that of the transmission type guest host liquid crystal display device shown in FIG. That is, in the state where no voltage is applied, the dichroic dye 5 included in the guest-host liquid crystal 3 is vertically aligned following the liquid crystal molecules 4. In this orientation state, the light source light emitted from the back light source 30 is not absorbed by the guest-host liquid crystal 3 but is transmitted as it is, resulting in white display. On the other hand, the dichroic dye 5 shifts to the horizontal alignment together with the liquid crystal molecules 4 when the voltage is applied. By appropriately controlling the pretilt angle of the liquid crystal molecules 4, the orientation direction of the liquid crystal molecules 4 and the dichroic dye 5 can be set, for example, parallel to the paper surface. The light source light emitted from the rear light source 30 is converted into linearly polarized light by the polarizing plate 31. This linear polarization axis is perpendicular to the paper. When the linearly polarized light passes through the quarter-wave plate 32 and the quarter-wave layer 10, the polarization axis is rotated by 90 °. Therefore, at the time of incidence on the guest-host liquid crystal 3, the polarization axis becomes parallel to the paper surface. For this reason, it is absorbed by the guest host liquid crystal 3 and black display can be performed. The quarter-wave plate 32 and the quarter-wave layer 10 overlap each other to function as a half-wave plate, and rotate the polarization axis of linearly polarized light by 90 °. If the quarter-wave plate 32 is not provided, the linearly polarized light passing through the polarizing plate 31 is converted into circularly polarized light by the quarter-wave layer 10, so that the guest-host liquid crystal 3 may receive sufficient absorption. Can not. To cope with this, an external quarter-wave plate 32 is introduced to eliminate the influence of the built-in quarter-wave layer 10. That is, the external quarter-wave plate 32 is mounted to enable light modulation by the guest-host liquid crystal 3 when performing transmissive display.

As described above, the present reflective / transmissive display device comprises the first transparent substrate 1 provided with the electrode 6 located in front thereof,
From this, the second transparent substrate 2 provided with the electrode 11 located rearward through a predetermined gap and the light held in this gap and incident light are modulated according to the voltage applied to the electrodes 6 and 11 to perform display. A guest-host liquid crystal 3 as an electro-optical material,
A light reflecting layer 9 disposed on the side of the second transparent substrate 2 for reflecting most of incident light and transmitting a part thereof, and disposed rearward of the second transparent substrate 2 and facing forward as necessary. And a back light source 30 for receiving light. Usually, most of the light (external light) incident from the outside from the front toward the rear is reflected forward by the light reflection layer 9 to perform display, and if necessary, enters from the rear light source 30 from the rear toward the front. The display is performed by transmitting a part of the light forward without being blocked by the light reflection layer 9. The electro-optical material is a guest host liquid crystal 3 in which a dichroic dye 5 serving as a guest is added to a nematic liquid crystal including liquid crystal molecules 4 serving as a host. The second transparent substrate 2 includes a light reflecting layer 9 and a guest host liquid crystal 3. And a quarter-wave layer 10 that efficiently modulates light incident from the outside.
The back light source 30 includes a polarizing plate 31 and a quarter-wave plate 32 that enable modulation of light incident from the back light source 30 between the back light source 30 and the second transparent substrate 2. The light reflection layer 9 includes a fine projection 9a formed along a plane and a metal film 9b formed thereon, and has an opening 9c in which a part of the metal film 9b is removed by etching. Most of the light incident from the front is scattered and reflected, while part of the light incident from the rear is transmitted through the opening 9c. The opening 9c is formed in a part of the projection 9a. With this configuration, the reflective and transmissive display device can provide high-quality display even in a dark environment or a bright environment. That is, outdoor /
An innovative display device that can be used both indoors can be realized.

FIG. 4 is a partial sectional view showing a reflective and transmissive display device according to a second embodiment of the present invention, and shows only one pixel on the substrate 2 side. The present embodiment includes a projection 9a made of a photoresist, a metal film 9b, a planarizing layer 14, a quarter-wave layer 10, a pixel electrode 11, and the like. The signal voltage supplied through the thin film transistor 8 having the double gate structure is applied to a part of the metal film 9b and the intermediate electrode 12a.
Is applied to the pixel electrode 11. As in the first embodiment, an opening 9c is formed in the light reflection layer 9, and transmission display in combination with a back light source is possible. Thus, the device functions as a reflective display device that does not use a back light source in a place where the surrounding environment is bright, and functions as a transmissive display device that uses a back light source in a dark place. In this example, the auxiliary capacitance Cs for assisting the thin film transistor 8 is formed at the same time. Further, a laminated structure in which the gate insulating films 17a and 17b are stacked is adopted, and the interlayer insulating films 20a and 20b are also two layers.

FIG. 5 is a plan view showing an example of the pattern design for one pixel shown in FIG. An opening 9c is formed in a part of the light reflection layer 9.
Is provided, there is a concern that the display characteristics of the reflective display device may be deteriorated. However, if the openings 9c are provided only in the flat portions of the light reflecting layer 9 as shown in FIG. No degradation occurs. Therefore, it is possible to suppress a decrease in display characteristics as a reflection type. As shown in FIG. 5, the light reflection layer 9 is subdivided for each pixel. Specifically, the light reflection layer 9 for one pixel is formed in a region defined by the gate wiring X and the signal wiring Y. The pixel electrode 11 is also formed for each pixel so as to match the light reflection layer 9. The pixel electrode 11 is connected to the drain electrode 22 of the thin film transistor 8 via a contact hole, and the signal wiring Y
Is also connected to the source electrode 21 via the contact hole, and the gate wiring X is connected to the gate electrode 16.
The light reflection layer 9 includes a myriad of discretely arranged projections 9a, which are covered with a metal film 9b. An opening 9c is partially formed in the flat portion left between the convex portions 9a.

The operation of the second embodiment shown in FIGS. 4 and 5 will be described in detail with reference to FIG. In the present embodiment, the transparent substrate 2 on the side of the rear light source 30, the transparent substrate 1 facing the transparent substrate 2,
It has a color filter 40 formed on the inner surface thereof, a counter electrode 6, a guest-host liquid crystal 3 held on both substrates 1 and 2, and the like. The guest-host liquid crystal 3 contains liquid crystal molecules 4 and dichroic dyes 5 which are horizontally aligned without applying a voltage. First, the operation principle of the reflection mode will be described. When the potential of the gate electrode 16 is at a low level, no voltage is applied to the drain electrode 22 and the pixel electrode 11, so that the horizontally aligned guest-host liquid crystal 3 does not change. Light incident from the counter substrate 1 side is converted into linearly polarized light by the guest-host liquid crystal 3, and further becomes circularly polarized light by passing through the quarter-wave layer 10. Further, the light is reflected by the light reflection layer 9,
The light passing through the return quarter-wave layer 10 becomes linearly polarized light.
This linearly polarized light is absorbed by the guest-host liquid crystal 3 because the polarization axis is rotated by 90 °. Therefore, black display is performed. When the potential of the gate electrode 16 is at a high level, a signal voltage is applied to the pixel electrode 11 via the drain electrode 22, causing a potential difference between the pixel electrode 11 and the counter electrode 6. Arrange vertically in parallel. In this case, the light incident from the front substrate 1 is not converted into linearly polarized light by the guest-host liquid crystal 3, so that all the light is reflected by the light reflection layer 9 and returns to the substrate 1. Therefore, white display is performed. The above description is for the case of horizontal alignment using liquid crystal molecules 4 having a positive dielectric anisotropy, but the initial alignment may be vertical using liquid crystal having a negative dielectric anisotropy. When the liquid crystal molecules 4 are horizontally aligned, the optically anisotropic axis of the quarter wavelength layer 10 is set to form an angle of 45 ° with the alignment direction. When the liquid crystal molecules 4 are vertically aligned, the optically anisotropic axis of the quarter-wave layer 10 is set to have an angle of 45 ° with respect to the cosine direction having a pretilt angle. .

Next, the principle of operation in the transmission mode will be described. This embodiment includes a back light source 30, a linear polarizing plate 31, and a quarter-wave plate 32. The absorption axis of the polarizing plate 31 is set in the same direction as the orientation direction of the guest-host liquid crystal 3,
The optical anisotropic axis of the external quarter-wave plate 32 is set in the same direction as the optical anisotropic axis of the built-in quarter-wave layer 10. The light emitted from the rear light source 30 becomes linearly polarized light by the polarizing plate 31 and further becomes circularly polarized light by the quarter-wave plate 32 and enters the rear substrate 2. The incident light passes through the quarter wavelength layer 10 through the opening 9c provided in the light reflection layer 9. As a result, the light is converted into linearly polarized light, but the polarization axis is rotated by 90 ° with respect to the polarization axis immediately after passing through the polarizing plate 31. When the guest-host liquid crystal 3 is horizontally aligned, the linearly polarized light that has passed through the quarter-wave layer 10 is absorbed by the guest-host liquid crystal 3 and black display is performed. When the guest-host liquid crystal 3 shifts to the vertical alignment in response to the voltage application, the linearly polarized light that has passed through the quarter-wave layer 10 is transmitted and white display is performed.

As described above, in this embodiment, a backlight can be used together by providing an opening in a part of the light reflection layer, and the backlight can be used as a transmissive type even in a dark environment where it cannot be used as a reflective type. It will be able to function. In particular, by providing the opening 9c in a part of the plane left between the convex portions of the light reflecting layer 9, it is possible to use a backlight together without impairing the light scattering effect of the light reflecting layer. A conventional light-reflection type liquid crystal display device is a display that can be visually recognized only by external light without using a backlight, and thus has low power consumption and is suitable as a display for a portable terminal. However, in a situation where there is no or little external light, visibility deteriorates, so that use of the terminal is limited to the surrounding environment. As an auxiliary light source, a unit that emits light from near the upper portion of the display device may be attached, but this is not suitable for portable use because the terminal itself becomes too large. On the other hand, in the present embodiment, a reflective and transmissive display device with an extremely compact configuration can be realized.

FIG. 7 is a schematic diagram showing a third embodiment of a reflective / transmissive display device according to the present invention. (A) schematically shows a method of forming a light reflection layer, and (B)
Indicates schematically the structure of the light reflection layer for one pixel.
As shown in (A), pixels PXL are formed on a substrate 2 in an integrated manner. As shown in (B), each pixel is provided with a scattering light reflecting layer 9. The light reflection layer 9 has a structure capable of transmitting light from behind in a part of the effective pixel area. On the substrate 2, a projection 9 a is formed with an interlayer insulating film 20 interposed therebetween. When aluminum is sputtered (or vapor-deposited) to form the metal film 9b on the projections 9a, the substrate 2 is inclined with respect to the sputtering direction S to create a shadow of unevenness, so that an aperture through which light is transmitted. 9c. When sputtering aluminum or the like of the target T on the substrate 2 on which the projections 9a are formed in advance by using photolithography and reflow in the effective pixel region, the substrate 2 is inclined with respect to the sputtering direction S to form a film. Do. As a result, there is a portion which is shaded from the sputtering direction due to the shape of the convex portion 9a, and an opening 9c through which light can be transmitted from the back side of the substrate 2 is formed here since aluminum is not attached.

As shown in FIG. 8, the control of the size of the shaded portion of the projection 9a is determined by the relationship between the inclination angle α of the projection 9a and the sputtering direction S. In order to form a shadow, the relationship between the sputtering angle θs based on the normal line of the substrate 2 and the inclination angle α of the hemispherical projection 9a is 90 ° −α <θs <90 °.
Must be satisfied. By appropriately controlling the sputtering angle θs within this range, the area ratio between the transmitting portion and the reflecting portion can be changed.

As described above, in this embodiment, the light reflection layer 9
Is composed of a fine projection 9a formed along a plane and a metal film 9b formed by vapor deposition or sputtering from an orientation inclined with respect to the normal to the surface. Most of the light incident from the front is scattered and reflected by the metal film 9b attached to the convex portion 9a, while part of the light incident from the rear is covered by the metal film 9b behind the convex portion 9a. Transmits from places that are not. The area of the transmissive portion can be easily controlled only by adjusting the inclination angle of the substrate 2. In the above-described first and second embodiments, as a method of forming an opening in the light reflecting layer, aluminum is sputtered and then selectively etched to remove the aluminum and form an opening through which light can pass. In this method, a certain degree of accuracy is required for mask alignment required for etching.
Also, if there is a design change of the area ratio of the transmission part and the reflection part,
The mask pattern must be changed each time.

FIG. 9 is a schematic partial sectional view showing a fourth embodiment of the reflection-type and transmission-type display device according to the present invention.
As shown in the figure, the light reflection layer 9 is composed of fine projections 9a formed along a plane and a semi-transparent mirror film 9z formed thereon, and reflects most of the light incident from the front in a scattering manner. On the other hand, a part of the light incident from behind is transmitted. Note that, unlike the first to third embodiments, this embodiment is not an active matrix type but a simple matrix type.
In this relation, the substrate 1 is formed with the column-shaped electrodes 6y, and the substrate 2 is formed with the row-shaped electrodes 11x. A pixel is defined at the intersection of both electrodes 6y and 11x. The light reflecting layer 9 is made of a metal thin film that plays the role of the semi-transparent mirror film 9z so that the present display device can be used in both the reflective mode and the transmissive mode. Regarding the optical characteristics of the semi-transparent mirror film 9z made of a metal thin film, it is necessary that the reflectance is relatively higher than the light transmittance so that the reflectance does not decrease significantly.
Further, it is necessary that the transmittance and the reflectance have little wavelength dependence. For example, rhodium (Rh) is a metal thin film that satisfies these conditions, and its reflectivity is about 80%. Titanium (Ti) can also be used, and its reflectance is about 60%.

The display principle in the reflection mode of this embodiment will be described with reference to FIG. The incident light passes through the guest host liquid crystal 3 and reaches the light scattering layer 9. Here, when a metal thin film having a relatively higher reflectance than the transmittance is used as the semi-transparent mirror film 9z, light loss due to transmission can be reduced, so that most of all incident light contributes to display. Is possible.

Referring to FIG. 10A, the display principle in the transmission mode of this embodiment will be described. The light source light emitted from the back light source 30 composed of a fluorescent tube or the like
And becomes linearly polarized light. The polarization direction is orthogonal to the orientation direction (rubbing direction) of the guest-host liquid crystal 3. Further, this polarized light passes through an external quarter-wave plate 32. The quarter-wave plate 32 is made of, for example, a material such as a polymer liquid crystal having optically uniaxial or biaxial properties, and its optic axis is oriented at about 45 ° with respect to the rubbing direction of the guest-host liquid crystal 3. It is inclined. When linearly polarized light passes through the quarter-wave plate 32, it becomes circularly polarized light. further,
When a part of this circularly polarized light passes through the semi-transparent mirror film 9z and enters the built-in quarter-wave layer 10, it is converted into linearly polarized light parallel to the rubbing direction of the guest-host liquid crystal 3. At this time, if no voltage is applied to the pixel, the linearly polarized light is absorbed by the guest-host liquid crystal 3 and black display is performed. When a voltage is applied, the dichroic dye 5 shifts to the vertical alignment together with the liquid crystal molecules 4, so that white display is performed without absorbing linearly polarized light. Although the translucent mirror film 9z used in the present display device has a small transmittance, a bright display can be obtained by using the strong back light source 30. According to the above principle, the present display device can perform display in both the reflection mode and the transmission mode. In addition,
In this embodiment, a base insulating film 20c is interposed between the substrate 2 and the light reflection layer 9. An underlayer 10a is also interposed between the quarter wavelength layer 10 and the electrode 11x.

An optical element capable of dividing incident light into transmitted light and reflected light is called a half mirror. In the present embodiment, a reflective / transmissive display device is realized by using a semi-transparent mirror film 9z as a half mirror. As described above, a semi-transparent mirror film 9z on which a metal is deposited is simple as a half mirror,
For example, it can be easily made of aluminum or silver.
However, since the metal film has an absorption component in addition to the reflection component and the transmission component, light loss occurs. Instead,
As shown in (B), a desired semi-transparent mirror (half mirror) can be obtained by coating a dielectric film 9z1 having an optical thickness of λ / 4 on the underlying transparent resin film 20. By using a dielectric film having a high refractive index instead of a metal film, it is possible to produce a half mirror having substantially no absorption loss. In (B), assuming that the refractive index of the dielectric film 9z1 is n1 and the refractive index of the underlying transparent resin film 20 is n0, the reflectance R of the half mirror is represented by the following equation.
Note that n1 is larger than n0.

(Equation 1) As is clear from the above formula, by appropriately setting the values of n1 and n0, it is possible to form a half mirror having a desired reflectance and having almost no absorption. However, the reflectance R shown in the above equation is a value with respect to vertically incident light. As the dielectric film 9z1, for example, ZnS, TiO ₂ , CeO ₂ or the like having a relatively high refractive index is used.

FIG. 3C shows a specific configuration of the light reflection layer 9 using the above-described dielectric film 9z1. Parts corresponding to the configuration of the light reflection layer 9 shown in FIG. 1A are given corresponding reference numerals to facilitate understanding. On the underlying insulating film 20c, fine projections 9a are formed. The projections 9a can be formed by patterning using a photosensitive resin and then applying a heat flow. By applying a transparent resin 9y having a refractive index n0 on the convex portion 9a, the shape of the convex portion 9a is optimized, and a desired light diffusion characteristic is obtained. A half mirror structure is obtained by forming a dielectric film 9z1 having a refractive index n1 on the transparent resin 9y. If the value of n1 is set to 1.4 to 1.5 and the value of n0 is set lower than this, the desired light reflectance R calculated from the above equation can be obtained. Normally, when used as a reflective display device, the intensity of external light is difficult to adjust, but when used as a transmissive display device, the transmitted light can be freely adjusted by a backlight. In view of this point, in the present embodiment, the half mirror is designed so that the reflectance is higher than the transmittance. Specifically, it is preferable to set the reflectance in the range of 50 to 90%. More preferably, when the reflectance is set in the range of 60 to 80%, the most balanced display image can be obtained.

(D) schematically shows another configuration of the half mirror. In this example, a half mirror having a composite structure is obtained by forming a metal film (Metal) 9z2 on the underlying resin film 20 and further forming a dielectric film 9z1 thereon.

When the guest-host liquid crystal display device is used as a transmission type, it is necessary to dispose a polarizing plate outside the substrate 1 or outside the substrate 2. In the embodiment shown in (A), a polarizing plate 31 is provided outside the substrate 2. In this structure, an additional quarter-wave plate 32 needs to be inserted outside the substrate 2 in order to negate the effect of the quarter-wave layer 10 formed inside the substrate 2. In this structure, since the polarizing plate 31 is provided behind the substrate 2, when used as a reflection type, the polarizing plate 31 has no influence, so that a bright display can be obtained by external light. On the other hand, a structure in which a polarizing plate is arranged outside the substrate 1 is also conceivable. In this case, since the reflection type functions as a normal guest-host liquid crystal display device, the built-in quarter-wave layer 10 is not required. In this structure, since the polarizing plate is located ahead of the substrate 1, (A)
However, the displayed image is darker than the structure shown in FIG.

FIG. 11 is a graph showing the reflectance characteristics of various metal thin films. The horizontal axis represents wavelength, and the vertical axis represents reflectance. For example, in the case of Rh, the reflectance in the visible light region is about 80%. In the case of Ti, the reflectance is about 60% in the visible light region. Any of them can be used as a semi-transparent mirror film. In that case, the film thickness is set to about 50 to 200 nm. It should be noted that Al can be used as a semi-transparent mirror film if the film thickness is 50 nm or less. As the semi-transparent mirror film, a dielectric film can be used instead of the metal thin film. As described above, in the present embodiment, the light reflection layer is composed of the fine projections formed along the plane and the semi-transparent mirror film formed thereon, and the most of the light incident from the front is scattered. It reflects and transmits a part of the light incident from behind. As the semi-transparent mirror film, a metal thin film made of rhodium, titanium, chromium, chromel or inconel can be used. Chromel is nickel 8
It is an alloy of 0% and chromium 20%. Inconel is an alloy of 80% nickel, 15% chromium and 5% iron. As described above, the rear substrate has a structure capable of passing a part of the light source light emitted from the rear light source, and has a structure in which the light incident from the front substrate hits and diffusely reflects the light. doing. That is, it has both transmission type and reflection type display capabilities. The conventional reflective liquid crystal display device can be used only in an environment where external light such as illumination or sunlight exists, and an observer cannot see the display in an environment where no external light exists. However, there is a demand that the reflective liquid crystal display device be used even in an environment where no external light exists. In the present embodiment, display in a reflective mode using external light is performed in an environment where external light exists, and display in a transmissive mode using a back light source (backlight) is performed in an environment where external light does not exist. Do.

FIG. 12 is a schematic partial sectional view showing a fifth embodiment of the reflection-type and transmission-type display device according to the present invention.
This represents four pixels. The liquid crystal 3z does not need to be limited to the guest-host liquid crystal described in the first to fourth embodiments. For example, an ECB mode liquid crystal using a single polarizing plate or a phase change liquid crystal can be used. The feature of this embodiment is that the metal film 9b formed on the light reflection layer 9 is
That is, they are not parallel to the substrate 2 but are inclined at a certain angle θ. First, when the rear light source 30 is off, incident light from the outside enters through the light diffusion layer 42. Here, the light diffusion layer 42 provided on the front substrate 1 is one that reduces backscattering and causes only forward scattering.
Light incident on the metal film 9b made of aluminum or the like is specularly reflected and returns to the light diffusion layer 42 again. It is scattered here and goes outside. Therefore, even if the metal film 9b is inclined, it functions as a normal reflective display device in a wide viewing angle range. Next, when the back light source 30 is on, light from the light source that enters perpendicularly to the substrate 2 from now on is reflected. However, since the metal film 9b is inclined, light rays that travel obliquely through the pixels enter the liquid crystal 3z. can do. Since the transmitted lights (a) and (b) further pass through the light diffusion layer 42, they are diffused over a wide range. As a result, it functions as a normal transmissive display device in a wide viewing angle direction. In order to form the inclined metal film 9b, etching using a laser beam or a stamper technique can be used. When a laser beam is used, the resin film can be processed into an inclined surface by laser etching while performing intensity modulation along a sawtooth waveform. As the laser light, for example, a line beam output from a YAG laser can be used. In the stamper method, a resin film having an inclined shape can be formed by using a stamper whose cross section is previously processed into a saw blade shape and transferring the stamper to the substrate 2. The metal film 9b may be formed thereon by vapor deposition or sputtering.

In the configuration shown in FIG. 12, when the phase-change guest-host type is used as the liquid crystal 3z, the configuration shown in FIG. However, when the liquid crystal panel (LCD) is a guest-host type having a built-in quarter-wave layer, the configuration on the back light source side needs to be as shown in FIG. Here, the externally attached quarter-wave plate 32 functions as a half-wave plate together with the built-in quarter-wave layer, and converts the linearly polarized light from the rear light source 30 passing through the polarizing plate 31 to a polarization direction of 90 °. Output with rotated linearly polarized light.

As described above, in the present embodiment, in the display device having the light reflection layer inside, the light reflection layer is not parallel to the substrate but is inclined at a certain angle.
It can be used as a transmission type without reducing the reflectance when used as a reflection type. Specifically, as shown in FIG. 12, each of the electrodes 6 provided on the first and second transparent substrates 1 and 2
Numeral 11 designates a matrix of pixels facing each other, and the light reflecting layer 9 is composed of a set of reflective elements subdivided corresponding to individual pixels. Each reflecting element is composed of a transparent inclined convex portion 9s having an inclined plane and a side end face, and a metal film 9b selectively formed on the inclined plane. Most of the light incident from the front is specularly reflected by the metal film 9b, while part of the light incident from the rear is transmitted from the side end surface. The inclined plane is inclined in the range of 1 ° to 45 ° with respect to the transparent substrate 2, and a part of the light source light incident from the rear passes through the rear end face reflected by the back surface of the metal film 9b belonging to one reflecting element. Then, the light is reflected by the surface of the metal film 9b belonging to another reflection element and directed forward. The first transparent substrate 1 has a black mask 4
In addition to the light diffusion layer 1, a light diffusion layer 42 is provided, and diffuses light reflected specularly by the light reflection layer 9 or light transmitted through the light reflection layer 9 toward the front. With such a configuration, the display device can be used in the transmission mode without sacrificing brightness when used in the reflection mode. As a method of achieving both the reflection type and the transmission type, for example, as in the above-described fourth embodiment,
It is conceivable that the light reflecting layer is not formed as a 100% completely reflecting film, but is formed as a semi-transparent mirror film (half mirror) that reflects some light and transmits some light. However, in this method, when viewed as a reflection type, the light reflection layer partially transmits light when viewed as a reflection type, so that the reflectance may decrease and a dark display may be obtained. In addition, when viewed as a transmissive type, light from the rear light source is partially reflected by the light reflection layer, so that the transmittance is reduced and a dark display may also be obtained. The present embodiment can eliminate such a trade-off relationship.

FIG. 14 is a schematic partial sectional view showing a sixth embodiment of the reflective and transmissive display device according to the present invention. As shown in the figure, the present display device utilizes a guest-host liquid crystal 3 and incorporates a quarter-wave layer 10. However, the present embodiment is not limited to this, and can be similarly applied to an ECB method using one polarizing plate. As shown, the light reflection layer 9 has a minute opening 9c. Back light source 30 located on the rear side of the display device
An array of microlenses 35 is arranged between the rear light source 30 and the substrate 2 so that light from the light source is efficiently condensed into the aperture 9c provided for each pixel.

The brightness of the rear light source 30 is, for example, 3000 ni.
In the case of t, when a polarizing plate is arranged on the incident side and light absorption by the color filter and light absorption by the guest-host liquid crystal 3 are taken into consideration, 3000 nit × 0.4 × 0.7 / 3 = 28
A luminance of 0 nit is obtained when the aperture ratio is 100%. On the other hand, in order not to lose the brightness when using it as a reflection type,
The aperture ratio of the opening 9c that does not contribute to the reflectance needs to be 10% or less. Therefore, if this is set to, for example, 5%, the brightness when used as a transmission type after all is 280 nit ×
0.05 = 14 nit, which is a bit too dark. In order to solve this, in the present embodiment, as shown in FIG.
5 array sheets are used. This array sheet is arranged so that the opening 9c comes to the focal position of each micro lens 35. The light source light from the back light source 30 is condensed by the microlens 35 and efficiently passes through the opening 9c. If the light-collecting effect of the microlens 35 is tripled, a brightness of about 40 nit can be obtained, and the brightness is sufficient in a dark environment. The light collection efficiency of the microlens 35 depends on the parallelism of the light source light emitted from the rear light source 30. Therefore, as a method of increasing the parallelism of the light from the light source, a prism sheet can be arranged on the rear light source 30. With the above configuration, a portable device display that can be used anywhere can be obtained by using a reflective type using external light when using it in a bright environment and a transmissive type using a back light source when using it in a dark environment. . From another point of view, this concept is basically a reflection type display, but it is also a transmissive type with a back light source (backlight) in a dark place. Therefore, in the case of the transmission type, brightness of several tens of nits is sufficient as described above. A microlens was used as a method for realizing this.

FIG. 15 is a schematic plan view showing an example of the arrangement of the openings 9c. In the pattern example of (A), one opening 9c is arranged for each pixel. In the pattern example of (B), two openings 9c are arranged in each pixel. (A) and (B)
In any of the pattern examples, the aperture 9c is made to correspond to the microlens 35 so as to have the same period as the pixel pitch or a period that is an integral multiple. As shown in (C), the opening 9c may not be circular but may be slit-shaped. In this case, the micro lens 35 may be a cylindrical lens having a curvature only in the x direction. That is, in the pattern examples (A) and (B), the individual microlenses are two-dimensionally arranged.
In the case of (C), a one-dimensional array may be used.

FIG. 16 is a schematic partial sectional view showing a modification of the sixth embodiment. In this modification, the micro lens 3
Reference numeral 5 denotes a structure built in the substrate 2. In particular,
A transparent resin having a refractive index of n2 is applied on the substrate 2 and processed into a shape of the microlens 35 by using a method of photolithography and reflow. This is covered with a transparent flattening film 35a having a different refractive index n1. The light reflection layer 9 described above is formed on the flattening film 35a. This light reflection layer 9 is composed of a projection 9a and a metal film 9b formed thereon. Part of the metal film 9b is missing, and an opening 9c through which light from the light source passes is provided here. In addition, in order for the microlens 35 to convert the parallel light source light into the focused transmitted light, the refractive index needs to satisfy the relationship of n2> n1.

As shown in FIG. 17, when a guest-host LCD having a quarter-wave layer integrated in a panel is used for both transmission and reflection, a prism sheet 36 is provided between the back light source 30 and the LCD. Polarizing plate 31, quarter-wave plate 32,
A structure in which a microlens array sheet 35m is interposed is employed. Here, the external quarter-wave plate 32 is LC
It functions as a half-wave plate together with the quarter-wave layer built in D, and serves to maintain linearly polarized light.

As described above, in the present embodiment shown in FIG. 14, each of the electrodes 6 and 1 provided on the first and second transparent substrates 1 and 2 is used.
Numeral 1 designates a matrix of pixels facing each other, and the light reflecting layer 9 is composed of a set of reflecting elements subdivided corresponding to each pixel. Each reflection element has a metal film 9b for reflecting most of light incident from the front and a minute opening 9c in which a part of the metal film 9b is removed to transmit a part of light incident from the rear. . The micro lens 35 is located behind the light reflection layer 9 and condenses the light source light emitted from the back light source 30 toward the opening 9c of each pixel. Preferably, this opening 9
c is formed at an area ratio of 1 to 10% with respect to the pixel. The openings 9c are formed in a dot shape, and the micro lenses 35 are arranged in a matrix corresponding to the dot-shaped openings 9c formed for each pixel. In some cases, the openings 9c are formed in a linear shape, and the microlenses 35 may be arranged in stripes corresponding to the linear openings 9c along the pixel columns. This micro lens 3
5 may be formed integrally on the second transparent substrate 2 instead of externally attached. With such a configuration, in the reflective / transmissive display device, the reflectance when used as a reflective type is not significantly reduced. Further, it is possible to sufficiently secure the brightness when used as a transmission type. As a method for achieving both the reflection type and the transmission type, as shown in the fourth embodiment, instead of forming the light reflection layer as a 100% complete reflection film, a part of light is reflected and partially reflected. There is a means for making a form such as a half mirror that transmits the light. However, in this method, when viewed as a reflection type, the light reflection layer transmits a part of the light, so that the reflectance may decrease and a dark display may occur. In addition, when viewed as a transmissive type, the light from the backlight is partially reflected by the light reflecting layer, so that the transmittance is reduced and the display may be dark again. This embodiment can eliminate such a trade-off relationship of the fourth embodiment.

FIG. 18 is a schematic partial sectional view showing a seventh embodiment of the reflection-type and transmission-type display device according to the present invention. A conventional reflective liquid crystal display device functions as a display device in an environment where external light such as illumination exists, but does not function as a display device in an environment where no external light exists. In the present embodiment, in a state where external light exists, driving in a backlight-free reflection mode is realized, and in a state where no external light exists, driving in a transmission mode using a backlight is realized. Specifically, the boundary between the pixels PXL formed on the substrate 2 side is configured to transmit light from the back side of the display device. On the inner surface of the substrate 1 on the opposite side, a sub-scattering layer 51 having a structure for diffusing and reflecting light is formed in a portion where light transmitted from behind is applied. With such a structure, it is possible to obtain a reflective display device that can also support a transmissive display.

As shown in the figure, the light from the rear light source 30 is transmitted from the rear substrate 2 so that the light source can be used together with the reflection type. In this case, a boundary portion between pixels PXL which is not necessary in the reflection mode is formed so as to hardly lower the reflectance of the effective pixel when displaying in the reflection mode. (Window). A black mask 41 is provided on a portion of the opposite substrate 1 corresponding to the opening.
And a light scattering sub-light reflecting layer 51 is disposed. Further, in order to effectively use the light source light emitted from the rear light source 30, a microlens 35 is arranged in alignment between the pixels PXL. For example, the negative nematic liquid crystal 4 to which the dichroic dye 5 is added is vertically aligned, and the light scattering layer 9 of the pixel PXL is further aligned.
The quarter-wave layer 10 is disposed on the substrate. In this case,
A quarter-wave plate 32 further outside the micro lens 35
And a polarizing plate 31.

In the reflection mode, the black mask 4
Since 1 is arranged along the boundary of the pixel PXL, there is no extra reflection and an improvement in contrast can be expected. In the transmission mode, light from the rear light source 30 including a fluorescent tube and an EL element passes through the polarizing plate 31 and becomes linearly polarized light.
The polarization direction is parallel to the rubbing direction of the guest-host liquid crystal 3. This linearly polarized light is converted into a circularly polarized light by the quarter-wave plate 32. Further, a quarter-wavelength layer 10 is formed by tilting the optical axis in a direction of about 45 ° with respect to the rubbing direction using a material such as a polymer liquid crystal having optically uniaxial or biaxial properties. ing. The circularly polarized light described above is converted into linearly polarized light in a direction perpendicular to the rubbing direction by passing through the quarter wavelength layer 10. Therefore, this linearly polarized light is hardly absorbed by the dichroic dye 5,
It reaches the counter substrate 1 side. This light is scattered and retro-reflected by the sub-light reflection layer 51 and proceeds to the main light scattering layer 9 on the pixel PXL, where re-reflection occurs. At that time, the light reciprocates through the quarter-wave layer 10 so that the polarization axis of the linearly polarized light is 90.
And turns toward the opposite substrate 1 as linearly polarized light parallel to the rubbing direction of the guest-host liquid crystal 3. At this time, if no voltage is applied to the pixel PXL, the liquid crystal molecules 4 and the dichroic dye 5 are vertically aligned, so that linearly polarized light is not absorbed, and the color determined by the color filter 40 can be displayed. it can. Conversely, when a voltage is applied, the liquid crystal molecules 4 and the dichroic dye 5 are horizontally aligned along the rubbing direction as shown in the drawing, so that absorption by the dichroic dye occurs and black or gray display is possible. Become.

As described above, in the present embodiment, the electrodes provided on the first and second transparent substrates 1 and 2 face each other to define a matrix-shaped pixel PXL, and the light reflection layer 9 has It has a light-reflective main scattering surface subdivided corresponding to the pixel PXL and an opening arranged at the boundary between the adjacent pixels PXL. On the first transparent substrate 1, a light reflection layer 51 having a sub-scattering surface is formed along the boundary of the pixel PXL, and most of light incident from the front is a light reflection layer 9 having a main scattering surface. On the other hand, a part of the light incident from the rear is reflected back by the light reflecting layer 51 having the sub-scattering surface after passing through the opening, and further re-reflected forward by the light reflecting layer 9 having the main scattering surface. You. A light-shielding black mask 41 is provided on the first transparent substrate 1 ahead of the sub-scattering surface along the boundary of the pixel PXL.
Are formed. In this embodiment, a guest-host liquid crystal 3 in which a dichroic dye 5 serving as a guest is added to a nematic liquid crystal 4 serving as a host is used as an electro-optical material. In this case, at least a portion of the second transparent substrate 2 that is aligned with the pixel PXL is interposed between the light reflection layer 9 and the guest host liquid crystal 3 to improve the efficiency of modulation of light incident from the outside. One wavelength layer 10 is formed. In the present embodiment, the quarter-wave layer 10 extends to the opening located at the boundary of the pixel PXL. In this connection, between the rear light source 30 and the transparent substrate 2, a polarizing plate 31 and a quarter-wave plate 32 for modulating the light source light incident from behind are interposed. The sub-light scattering layer 51 formed on the black mask 41 has a structure similar to that of the main light scattering layer 9 formed on the pixel PXL. Metal film.

FIG. 19 is a schematic partial sectional view showing a modification of the seventh embodiment shown in FIG. In this modification, the same effect can be obtained by removing the external quarter-wave plate 32 and forming the eighth-wavelength layer 52 on the sub-light reflecting layer 51 of the counter substrate 1 instead. I have. The eighth-wavelength layer 52 is made of, for example, a material such as a polymer liquid crystal having optically uniaxial or biaxial properties, and the optical axis is inclined at about 45 ° with respect to the rubbing direction of the guest-host liquid crystal 3. It can be created with. In this modification, the built-in quarter-wave layer 10 extends to an opening located at the boundary of the pixel PXL, and a polarizing plate 31 is interposed between the back light source 30 and the second transparent substrate 2. Light reflecting layer 5 having a sub-scattering surface
An 八 wavelength layer 52 that allows modulation of light source light incident from behind through an aperture is disposed on 1.

FIG. 20 is a schematic partial sectional view showing another modification of the seventh embodiment shown in FIG. In this modification, the external quarter-wave plate and the polarizing plate are removed, and instead, the polarizer 53 is placed on the sub-light reflecting layer 51 of the counter substrate 1.
Is provided. The polarizer 53 can be formed of a material obtained by adding a black dichroic dye to a polymer liquid crystal having optical uniaxial or biaxial properties. When the absorption axis of the polarizer 53 is arranged to be perpendicular to the rubbing direction of the guest-host liquid crystal 3, the seventh
An effect similar to that of the embodiment can be obtained. In this modification, the built-in quarter-wave layer 10 is extended to the opening located at the boundary of the pixel PXL, and the light reflection layer 51 having a sub-scattering surface is provided.
Above is disposed a polarizer 53 that allows modulation of light incident from behind through an aperture.

FIG. 21 is a schematic partial sectional view showing another modification of the seventh embodiment shown in FIG. In the present modification, the quarter-wave layer 10 is removed from the opening located at the boundary of the pixel PXL, and the rear light source 30 and the second transparent substrate 2 modulate the light source light incident from behind. Is provided.

FIG. 22 is a schematic diagram showing a configuration example of the light reflection layer 51 formed on the opposite substrate. As shown in (A),
Black mask 41 formed in advance on counter substrate 1
The metal film 51a is formed to have a predetermined thickness along. The surface is covered with a photoresist PR. Subsequently, over-etching is performed as shown in (B), so that the end face of the metal film 51a has an inclined structure. Thereby, the light reflection layer 51 having a scattering property can be formed.

FIG. 23 is a schematic sectional view showing an eighth embodiment of the reflective / transmissive display device according to the present invention. As a characteristic feature, a third transparent substrate 68 is bonded to the front side of the counter substrate 1 with a predetermined gap therebetween. For example, a polymer-dispersed liquid crystal 60 is sealed between the first transparent substrate 1 and the third transparent substrate 68 to form a liquid crystal cell. The polymer dispersed liquid crystal 60 is held by transparent electrodes from above and below. By applying a voltage between the transparent electrodes, the polymer-dispersed liquid crystal 60 changes between a diffusion state and a transparent state. Note that an organic film can be used for the third transparent substrate 68 for weight reduction. A counter electrode 6 is formed on the inner surface of the first transparent substrate 1. On the other hand, a pixel electrode 11 is formed on the inner surface of the second transparent substrate 10. The guest host liquid crystal 3 is driven by a voltage applied to the pixel electrode 11 via the thin film transistor 8. The light reflection layer 9 located below the pixel electrode 11 has a mirror surface,
Some have been removed to form openings. The light source light emitted from the rear light source 30 is transmitted forward through this opening.

The reflection display mode of the eighth embodiment shown in FIG. 23 will be described in detail with reference to FIG. (A) shows a state where no voltage is applied, and (B) shows a state where a voltage is applied. In the reflection display, the back light source 30 and the polymer dispersion type liquid crystal cell 65 are both off. Therefore, the liquid crystal cell 65
Becomes diffused. The incident light is diffused when passing through the polymer-dispersed liquid crystal 60 in a diffused state, and enters the display panel. In the white display shown in (A), since the dichroic dye 5 is oriented perpendicular to the substrate, the incident light is specularly reflected by the light reflection layer 9 and goes out of the panel. In the black display shown in (B), since the dichroic dye 5 is oriented parallel to the substrate, it absorbs incident light.

FIG. 25 is a schematic diagram showing the transmissive display mode of the eighth embodiment shown in FIG. (A) shows a state where no voltage is applied, and (B) shows a state where a voltage is applied. In the transmissive display, both the back light source 30 and the polymer dispersion type liquid crystal cell 65 are on, and the liquid crystal cell 65 is in a transparent state. The light source light emitted from the rear light source 30 via the diffusion plate 39 is converted into linearly polarized light by the polarizing plate 31. Further, since the light passes through the external quarter-wave plate 32 and the built-in quarter-wave layer 10, the linearly polarized light is kept rotated by 90 °. When no voltage is applied, since the dichroic dye 5 is vertically aligned, the linearly polarized light goes out of the panel without being absorbed, and a white display is obtained. Since the dichroic dye 5 is oriented parallel to the substrate in the voltage application state shown in FIG. 3B, the light source light emitted from the back light source 30 is absorbed, and a black display is obtained.

As described above, in this embodiment, the light reflecting layer 9 has a mirror surface for reflecting most of external light incident from the front and an opening for transmitting a part of light source light incident from the rear. The rear light source 30 emits diffuse light toward the front via the diffusion plate 39. A liquid crystal cell 65 that changes between a diffusion state and a transparent state according to a voltage applied from the outside is disposed in front of the first transparent substrate 1. The liquid crystal cell 65 is normally placed in a diffused state, diffusely emits light that has been specularly reflected forward from the mirror surface of the light reflection layer 9, and is placed in a transparent state as needed and forwardly from the opening of the light reflection layer 9. The transmitted diffuse light is emitted as it is. The liquid crystal cell 65 is of a polymer dispersion type in which liquid crystal is dispersed in a polymer. With such a configuration, a liquid crystal display device having both transmission / reflection characteristics and capable of high-quality display can be realized. Conventional liquid crystal display devices are broadly classified into a transmission type using transmitted light from a backlight provided outside the panel and a reflection type using light from the outside. The former enables high-contrast color display, but a strong backlight is indispensable, so that when used outdoors, for example, it consumes large power and is not suitable for carrying. On the other hand, in a bright environment, the contrast is reduced. On the other hand, in the reflection type, a backlight is not required, so that the power consumption is small, and the contrast is high in a bright environment. However, the absolute contrast is low and high-quality display is impossible. The present embodiment is an improvement on the above-described drawbacks of the conventional reflection type and transmission type display devices.

[0056]

As described above, according to the present invention, the display device is provided with the first transparent substrate provided with the electrodes, which is located forward,
A second transparent substrate provided with an electrode positioned rearward through a predetermined gap, an electro-optical material that is held in the gap and modulates incident light according to a voltage applied to the electrode to perform display, A light reflecting layer disposed on the side of the transparent substrate and reflecting a large part of incident light and partially transmitting the light;
And a rear light source that is arranged rearward of the transparent substrate and that receives light forward when necessary. With such a configuration, a reflection-type and transmission-type display device can be realized. In a bright environment, most of the external light entering from the outside from the front to the rear is reflected forward by the light reflection layer to perform display, and in a dark environment, it enters from the back light source from the back to the front. It is possible to perform display by transmitting part of the light from the light source forward without being blocked by the light reflection layer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a reflective and transmissive display device according to the present invention.

FIG. 2 is an operation explanatory diagram of the first embodiment.

FIG. 3 is an operation explanatory diagram of the first embodiment.

FIG. 4 is a cross-sectional view showing a second embodiment of the reflective / transmissive display device according to the present invention.

FIG. 5 is a plan view of a reflective and transmissive display device according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating the entire configuration of the second embodiment.

FIG. 7 is a schematic view showing a third embodiment of a reflective and transmissive display device according to the present invention.

FIG. 8 is an explanatory diagram of a third embodiment.

FIG. 9 is a partial cross-sectional view showing a fourth embodiment of a reflective / transmissive display device according to the present invention.

FIG. 10 is a fourth view of the reflective / transmissive display device according to the present invention.
It is a partial sectional view of an embodiment.

FIG. 11 is a graph for explaining a fourth embodiment;

FIG. 12 is a fifth view of the reflective / transmissive display device according to the present invention;
It is sectional drawing which shows embodiment.

FIG. 13 is an explanatory diagram of the fifth embodiment.

FIG. 14 is a sixth view of the reflective / transmissive display device according to the present invention.
It is sectional drawing which shows embodiment.

FIG. 15 is a plan view for explaining a sixth embodiment;

FIG. 16 is a cross-sectional view showing a modification of the sixth embodiment.

FIG. 17 is a schematic diagram showing the overall configuration of the sixth embodiment.

FIG. 18 shows a seventh example of the reflective / transmissive display device according to the present invention.
It is sectional drawing which shows embodiment.

FIG. 19 is a cross-sectional view showing a modification of the seventh embodiment.

FIG. 20 is a schematic diagram showing another modification of the seventh embodiment.

FIG. 21 is a sectional view showing another modification of the seventh embodiment.

FIG. 22 is a schematic diagram for explaining a seventh embodiment; .

FIG. 23 is an eighth view of the reflective / transmissive display device according to the present invention;
It is sectional drawing which shows embodiment.

FIG. 24 is a schematic diagram for explaining the operation of the eighth embodiment;

FIG. 25 is a schematic diagram for explaining the operation of the eighth embodiment;

FIG. 26 is a schematic view showing an example of a conventional transmission type display device.

FIG. 27 is a schematic view showing an example of a conventional reflective display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Substrate, 3 ... Guest host liquid crystal, 4 ... Liquid crystal molecule, 5 ... Dichroic dye, 7 ...
Orientation layer, 8 thin film transistor, 9 light reflection layer, 9a projection, 9b metal film, 9c opening, 10 quarter-wave layer, 11 ..Pixel electrodes,
14 flattening layer, 15 alignment layer, 30 back light source, 31 polarizing plate, 32 quarter-wave plate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Nobuyuki Shigeno 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Masaki Munakata 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Takayuki Fujioka 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Yasutoshi Kawate 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Inside (72) Inventor Masataka Matsude Inside Sony Corporation 6-35 Kita Shinagawa, Shinagawa-ku, Tokyo

Claims (31)

[Claims] 1. A first transparent substrate provided with an electrode at the front, a second transparent substrate provided with an electrode at a rear of the first transparent substrate via a predetermined gap, and light incident on the first transparent substrate. An electro-optical material that modulates the display according to the voltage applied to the electrode to perform display, a light reflection layer that is disposed on the second transparent substrate and reflects most of incident light and can partially transmit light, A reflective / transmissive display device having a rear light source disposed rearward of the second transparent substrate and incident light forward as necessary, wherein the light is normally incident from the outside from the front to the rear. Most of the light is reflected forward by the light reflection layer to perform display,
A reflective / transmissive display device wherein a part of the light incident from the rear light source from the rear to the front is transmitted forward as necessary without being blocked by the light reflection layer to perform display. 2. The electro-optical material is a guest-host liquid crystal obtained by adding a dichroic dye as a guest to a nematic liquid crystal as a host, and the second transparent substrate is formed of a light-reflecting layer and a guest-host liquid crystal. And a quarter-wavelength layer that efficiently modulates light incident from the outside between the light source and the rear light source, which enables modulation of light incident from the rear light source between the light source and the second transparent substrate. The reflective and transmissive display device according to claim 1, further comprising a polarizing plate and a quarter-wave plate. 3. The light reflection layer includes a fine projection formed along a plane and a metal film formed on the projection, and has an opening in which a part of the metal film is removed by etching. 2. The reflective and transmissive display device according to claim 1, wherein most of the light incident from the front is scatteredly reflected, and a part of the light incident from the rear is transmitted through the opening. 4. The reflective and transmissive display device according to claim 3, wherein said opening is formed in a part of said convex portion. 5. The reflective and transmissive display device according to claim 3, wherein said opening is formed in a part of a plane left between the convex portions. 6. The light reflection layer is composed of fine projections formed along a plane and a metal film formed by vapor deposition or sputtering from a direction inclined with respect to the normal to the plane, and is incident from the front. Most of the light that is reflected is scattered by the metal film deposited on the convex part, while part of the light incident from behind is transmitted from the part where the metal film is not deposited due to the shadow of the convex part. The reflective and transmissive display device according to claim 1. 7. The light reflection layer comprises a fine projection formed along a plane and a semi-transparent mirror film formed thereon, and reflects most of light incident from the front in a scattering manner. 2. The reflective and transmissive display device according to claim 1, wherein a part of light incident from behind is transmitted. 8. The reflective / transmissive display device according to claim 7, wherein said semi-transparent mirror film is a metal thin film made of rhodium, titanium, chromium, aluminum, silver, chromel or inconel. 9. The display device according to claim 7, wherein said semi-transparent mirror film is a dielectric film. 10. The reflective and transmissive display device according to claim 9, wherein said dielectric film is made of ZnS, TiO ₂ or CeO ₂ . 11. The reflective / transmissive display device according to claim 7, wherein said semi-transparent mirror film has a reflectance in a visible light range of 50 to 90%. 12. The reflective / transmissive display device according to claim 7, wherein said semi-transparent mirror film has a reflectance in a visible light range of 60 to 80%. 13. The electrodes provided on the first and second transparent substrates face each other to define a matrix-shaped pixel, and the light reflection layer is formed of a reflective element subdivided corresponding to each pixel. Each reflecting element is composed of a transparent oblique projection having an inclined plane and side end faces, and a metal film selectively formed on the inclined plane, and most of light incident from the front is formed by the metal film. 2. The reflective and transmissive display device according to claim 1, wherein a part of the light which is specularly reflected while being incident from behind is transmitted through a side end face. 14. The inclined plane is 1 ° with respect to a transparent substrate.
A part of the light incident from behind is reflected at the back surface of the metal film belonging to a certain reflection element, passes through the rear end face, and is further reflected at the surface of the metal film belonging to the next reflection element. 14. The reflective and transmissive display device according to claim 13, wherein the display device is directed forward. 15. A light diffusing layer is provided on the first transparent substrate, and diffuses light reflected specularly by the light reflecting layer or light transmitted through the light reflecting layer toward the front. The reflective and transmissive display device according to claim 13, wherein: 16. The electrodes provided on the first and second transparent substrates face each other to define a matrix-shaped pixel, and the light reflection layer is formed of a reflection element subdivided corresponding to each pixel. Each reflecting element has a metal film that reflects most of the light incident from the front and a small opening in which a part of the metal film has been removed to transmit a part of the light incident from the rear. 2. The reflection-type lens according to claim 1, further comprising a microlens located behind the light reflection layer and condensing light emitted from the rear light source toward an opening of each pixel. Transmission type display device. 17. The reflective and transmissive display device according to claim 16, wherein said opening is formed at an area ratio of 1 to 10% with respect to the pixel. 18. The device according to claim 16, wherein the openings are formed in a dot shape, and the microlenses are arranged in a matrix corresponding to the dot openings formed for each pixel. Reflective and transmissive display. 19. The device according to claim 1, wherein the openings are formed in a linear shape, and the microlenses are arranged in a stripe shape corresponding to the linear openings along a column of pixels.
6. The reflective and transmissive display device according to 6. 20. The micro lens according to claim 1, wherein the micro lens is formed integrally on the second transparent substrate.
6. The reflective and transmissive display device according to 6. 21. Each electrode provided on the first and second transparent substrates faces each other to define a matrix-shaped pixel, and the light reflection layer is formed of a light-reflecting subdivided corresponding to each pixel. And an opening arranged at the boundary between adjacent pixels, and a sub-scattering surface is formed on the first transparent substrate along the boundary between the pixels, so that most of the light incident from the front 2. The reflection according to claim 1, wherein a part of the light incident from behind is reflected by the main scattering surface, while part of the light incident from behind is reflected back by the sub-scattering surface after passing through the aperture and further reflected back by the main scattering surface. Type and transmission type display device. 22. The reflective and transmissive light-transmitting device according to claim 21, wherein a light-shielding black mask is formed on the first transparent substrate in front of the sub-scattering surface along a boundary between pixels. Type display device. 23. The electro-optical material is a guest-host liquid crystal in which a dichroic dye serving as a guest is added to a nematic liquid crystal serving as a host, and at least a portion of the second transparent substrate that matches a pixel is provided with the light. 22. The reflection type and transmission according to claim 21, wherein a quarter wavelength layer is formed between the reflection layer and the guest-host liquid crystal to efficiently modulate light incident from outside. Type display device. 24. The quarter-wave layer extends to an opening located at a boundary of a pixel, and modulates light incident from the rear between the back light source and the second transparent substrate. 24. The reflective and transmissive display device according to claim 23, wherein a polarizing plate and a quarter-wave plate enabling the interposition are interposed. 25. The quarter-wave layer extends to an opening located at a boundary of a pixel, and a polarizing plate is interposed between the back light source and the second transparent substrate. 24. The reflective / transmissive display device according to claim 23, wherein an eighth-wavelength layer is provided on the sub-scattering surface to enable modulation of light incident from behind through an aperture. . 26. The quarter-wave layer extends to an opening located at the boundary of a pixel, and allows modulation of light incident from behind through the opening on the sub-scattering surface. The reflective / transmissive display device according to claim 23, further comprising a polarizer. 27. The quarter-wave layer is removed from an aperture located at a pixel boundary, and allows modulation of light incident from behind between the rear light source and the second transparent substrate. 24. The reflective / transmissive display device according to claim 23, further comprising a polarizing plate. 28. The light reflecting layer has a mirror surface for reflecting most of light incident from the front and an opening for transmitting a part of light incident from the rear, and the rear light source diffuses forward. In front of the first transparent substrate, a liquid crystal cell which changes between a diffused state and a transparent state in accordance with a voltage applied from the outside is disposed, and the liquid crystal cell is normally in the diffused state. 2. The device according to claim 1, further comprising: diffusively emitting light specularly reflected forward from said mirror surface, and emitting diffuse light transmitted forward from said opening as required in a transparent state. Reflective and transmissive display device. 29. The reflective / transmissive display device according to claim 28, wherein said liquid crystal cell is of a polymer dispersion type in which liquid crystal is dispersed in a polymer. 30. A first transparent substrate, which is located forward and has electrodes, and a second transparent substrate, which is located rearward with electrodes therefrom via a predetermined gap, and light which is held in the gap and is incident. An electro-optical material that modulates the display according to the voltage applied to the electrode to perform display, a light reflection layer that is disposed on the second transparent substrate and reflects most of incident light and can partially transmit light, A rear light source disposed rearward of the second transparent substrate and receiving light toward the front as necessary, wherein most of the light incident from the outside from the front to the rear is usually forwarded by the light reflection layer. To reflect on the display
If necessary, a part of the light incident from the rear light source from the rear to the front is transmitted forward without being cut off by the light reflection layer, and the display is performed, and each of the first and second transparent substrates is provided. The electrodes define matrices of pixels facing each other, and the light reflecting layer is composed of a set of subdivided reflecting elements corresponding to individual pixels.
Each reflective element has a metal film that reflects most of the light incident from the front and a small opening in which a part of the metal film is removed to transmit a part of the light that enters from the rear. A reflective / transmissive display device, comprising: a microlens located behind the light reflecting layer and condensing light emitted from the back light source toward an opening of each pixel. 31. A first transparent substrate provided with an electrode located forward, a second transparent substrate provided with an electrode located backward from the first transparent substrate via a predetermined gap, and light incident and held in the gap. An electro-optical material that modulates the display according to the voltage applied to the electrode to perform display, a light reflection layer that is disposed on the second transparent substrate and reflects most of incident light and can partially transmit light, A rear light source disposed rearward of the second transparent substrate and incident light forward as necessary, and a large part of light incident from the outside usually forward to rearward is forwardly reflected by the light reflecting layer. To reflect on the display
If necessary, a part of the light incident from the rear light source from the rear to the front is transmitted forward without being blocked by the light reflection layer, and the display is performed. A guest-host liquid crystal to which a dichroic dye to be added is added, and the second transparent substrate is a quarter that efficiently modulates light incident from outside between the light reflection layer and the guest-host liquid crystal. A wavelength layer, wherein the rear light source includes a polarizer and a quarter-wave plate between the second transparent substrate and the second transparent substrate that enable modulation of light incident from the rear light source. Reflective and transmissive display device.