JP3713993B2 - Reflective liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention can be used for an image display device using a reflective liquid crystal panel, such as a reflective liquid crystal television and a reflective liquid crystal monitor, and by using a light diffusion sheet suitable for realizing a bright and high-contrast image display. The present invention relates to a reflective liquid crystal display device that does not increase the power consumption of the device body.
[0002]
[Prior art]
In a reflective liquid crystal display device, a light reflector is arranged on the back surface (opposite to the viewer) of the liquid crystal panel, and the ambient light incident on the device is reflected to give the viewer a display image composed of the liquid crystal panel. It is a device for visual recognition.
The apparatus does not require a special light source such as a backlight or an edge light for obtaining display light, and is configured to use ambient light (sunlight or illumination light), and thus is effective in saving power consumption. .
[0003]
In order to display a bright and high-contrast image, the light reflector preferably has a high reflectance and a certain degree of directivity. In addition, a reflector having a diffusive reflecting surface is suitable as a light reflector in order to widen the viewing area (a visible range and direction of display light) and suppress glare of the display screen.
Therefore, the conventional reflector has been formed from a metal surface processed into a mat shape.
[0004]
A conventional reflector obtained by processing a metal surface into a mat shape has a mat surface formed by sandblasting the metal surface or dissolving treatment using a solution (acidic or alkaline). Therefore, it is difficult to control the light diffusivity (rough surface state), and when used in a reflective liquid crystal display device, unnecessary diffused light that does not contribute to observation is generated, resulting in a decrease in brightness and contrast. is there.
[0005]
In recent years, a reflective liquid crystal display device of a type in which an electrode for driving liquid crystal also serves as a reflector (hereinafter referred to as a reflective electrode) has been developed.
In addition, by spreading the display light, the light can be diffused on the front surface (observer side) of the liquid crystal panel in order to expand the visible range and make the intensity distribution of the display light uniform on the screen. A method of arranging sheets is also adopted.
[0006]
When a normal light diffusing sheet is used, light diffusion occurs both when light is incident and when it is reflected, so that there is a problem that a double image is generated due to pixel shift and high-definition display cannot be sufficiently performed.
In addition, a method of processing the electrode (reflector) into a mat shape is also employed, but there is a problem in that unnecessary diffused light is generated as in the conventional metal reflector described above.
[0007]
Japanese Laid-Open Patent Publication No. 9-152602 is known as a proposal for widening the viewing zone by arranging a scattering plate made of a hologram on the front surface of a liquid crystal panel. It is intended to control the emission range, and does not impart diffusibility to the display light in the reflective liquid crystal display device.
[0008]
[Problems to be solved by the invention]
The present invention provides a reflective liquid crystal display device using a light diffusing sheet suitable for placement on the front surface of a liquid crystal panel of a reflective liquid crystal display device that does not require a special light source (using ambient light as display light). The task is to do.
[0009]
That is, the light diffusion sheet has anisotropy (incidence angle selectivity) that diffuses and transmits only incident light within a specific range of angles. For example, light diffusion does not occur when light is incident on the device, but only when it is emitted. By causing light diffusion to occur (or vice versa), unnecessary light diffusion is eliminated, and a double image due to pixel shift is prevented, and
It is an object of the present invention to provide a reflective liquid crystal display device that can display a bright, high-contrast and high-definition display at an observation position by limiting the range of light diffusion.
[0010]
[Means for Solving the Problems]
According to the first aspect of the present invention, a reflector is disposed on the back surface (opposite side of the observer) of the liquid crystal panel, and ambient light incident from the front surface (observer side) of the liquid crystal panel is reflected on the liquid crystal panel by the reflector. In a reflective liquid crystal display device that allows an observer to view display light that is reflected to the side and modulated by the liquid crystal panel, the incident light at a specific angle is transmitted to the front surface (observer side) of the liquid crystal panel from another angle. A reflection type liquid crystal display device comprising a light diffusing sheet having an incident angle selectivity for diffusing incident light, or an exit angle selectivity capable of controlling the exit direction and range.
[0011]
The invention according to claim 2 is a volume phase transmission type in which the light diffusing sheet transmits and diffracts only light incident at an angle within a specific range, and does not transmit and diffract light incident at an angle other than the angle. The reflection type liquid crystal display device according to claim 1, comprising a hologram.
[0012]
The invention according to claim 3 is the reflection type liquid crystal display device according to claim 1 , wherein the light diffusion sheet is made of a surface relief hologram.
[0014]
The invention according to claim 4 is the reflective liquid crystal display device according to any one of claims 1 to 3, wherein the reflector has a function of regularly reflecting incident light.
[0015]
The invention according to claim 5 is the reflection type liquid crystal display device according to any one of claims 1 to 3, wherein the reflector has a function of diffusing incident light.
[0016]
A sixth aspect of the present invention is the reflective liquid crystal display device according to any one of the first to fifth aspects, wherein the reflector also serves as an electrode for driving the liquid crystal.
[0017]
<Action>
When the light diffusing sheet is a hologram, it is possible to provide a light diffusing function having incident angle selectivity according to the photographing conditions, and the range (direction) in which the diffracted light is diffused and emitted is vertical. It is also possible to arbitrarily control the horizontal direction. In other words, it is also possible to provide emission angle selectivity. Including the angle selectivity, the term “anisotropic” is used in the following description.
[0018]
When the hologram is a volume phase transmission hologram, the wavelength width of the diffracted light is relatively wide, so that diffracted light close to white can be emitted. Display light with little color change accompanying movement can be made visible. (Claim 2)
In addition, for example, anisotropy (angle selectivity) in which incident light to a display device at an angle other than a specific range is transmitted and display light emitted at an angle within a specific range is diffracted and diffused by a hologram. This avoids the problem of double images due to pixel shifts that depend on twice diffraction at the time of entry and exit.
[0019]
When the hologram is a surface relief hologram, the light diffusing sheet can be mass-produced at low cost by emboss replication to a thermoplastic resin with a stamper raised from the master hologram. (Claim 3)
[0020]
The reflection type liquid crystal display device according to the present invention has the above light diffusion sheet disposed on the front surface of the liquid crystal panel,
Light that is transmitted through the light diffusing sheet from the front surface of the liquid crystal panel is transmitted without passing through the transparent sheet without being diffused, reaches the reflector, is reflected by the reflector, passes through the light diffusing sheet, and is liquid crystal. The light emitted from the front surface of the panel is diffused as if passing through a light-transmitting light diffusing sheet (or, conversely, diffused and transmitted when incident, and simply transmitted when emitted). The light is emitted as light that diffuses while condensing (in the range where the observer observes the display screen).
Therefore, there is no unnecessary diffusion of display light, the display becomes bright, and light diffusion occurs only when light is emitted (or only when it is incident), so that the display image observed from the front surface of the liquid crystal panel In addition, there is no phenomenon such as pixel shift, double pixel or pixel blur, and high-definition display is possible.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a reflective liquid crystal display device according to the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, a reflective liquid crystal display device 1 of the present invention includes a liquid crystal panel 2, a regular reflective or diffusive reflector 3 disposed on the back surface thereof, and a front surface of the liquid crystal panel 2. The light diffusion sheet 4 is used.
[0022]
In the figure, in order to schematically represent optical characteristics (optical path of incoming / outgoing light), the light diffusion sheet 4, the liquid crystal panel 2, and the reflector 3 are shown separated from each other, but in actuality, they are bonded. The layers (not shown) are bonded and stacked. In addition, incident light, reflected light, display light, and the like are all shown as light rays so that all claims can be explained conceptually.
[0023]
In the reflective liquid crystal display device 1, the reflector 3 may be included in the liquid crystal panel 2 as an electrode for driving liquid crystal instead of being separated from the liquid crystal panel 2.
[0024]
The liquid crystal panel 2 has a known structure that modulates incident light according to the presence or absence of an applied voltage and displays white / black (transmission / non-transmission).
[0025]
As shown in the figure, when incident light 5 that is ambient light enters the light diffusion sheet 4 from the front side of the display device 1, the incident light 5 is transmitted as it is, and the transmitted light is reflected by the reflector 3 on the back side of the liquid crystal panel 2. At the time of emission, light diffusion is caused by the light diffusion sheet 4 and emitted to the front, and the display light reaches the observation area of the observer 7 so as to be condensed.
[0026]
2 and 3 are configuration diagrams showing an example of an optical system for producing the light diffusion sheet 4 shown in FIG. 1 by hologram recording.
[0027]
A laser beam emitted from one laser light source 10 as shown in FIG. 2 has an optical axis shifted from the optical axis of incident light to the light diffusing sheet. Is divided into two by a beam splitter 11, one of which is an object light that is a diffused light 13 that illuminates a diffuser plate 12 such as a ground glass, and the other is a reference light 14 that is a spherical wave or a plane wave, and interference fringes of the two light waves. Is first recorded on the photosensitive material 15 for hologram, and can be produced by developing and bleaching.
[0028]
Also, the master hologram produced as shown in FIG. 2 as shown in FIG. 3 is the same as the optical axis of the incident light on the light diffusion sheet and the optical axis of the outgoing light (diffused light) from the light diffusion sheet. 22 is reproduced to form an image of the diffusion plate on the hologram photosensitive material 25, and the hologram photosensitive material 25 is illuminated with the reference light 23 in which the optical axis of the reproduction light 23 and the optical axis of the reference light 23 coincide with each other. Then, it can be produced by performing holographic photographing recording again and developing and bleaching it.
[0029]
The light diffusing sheet 4 can be produced by the above-described hologram recording method using the optical system of FIGS. 2 and 3 and is used by being disposed on the front surface of the liquid crystal display panel 2.
[0030]
2 and 3, the distance between the diffusing plate 12 and the hologram photosensitive material 15 and the size of the diffusing plate 12 when the light diffusing sheet 4 is produced are the light diffusing characteristics of the light diffusing sheet 4. In consideration of the viewing area of the reflection type liquid crystal display device 1 of the present invention that can be observed most favorably, 0 to ±± with respect to the normal direction from the center of the liquid crystal panel at a distance of about 0 to 1 m. Appropriate selection is made within a range of about 75 degrees.
[0031]
In FIGS. 2 and 3, the exposure light beam is obliquely incident on the photosensitive material. However, since the incident angle affects the selectivity of the angle that causes the function of light diffusion / direct transmission, reflection is performed. Depending on the use of the liquid crystal display device 1, it is appropriately selected between 0 and 80 degrees.
[0032]
Moreover, since the size and diffusibility of the diffusion plate 21 affect the light diffusibility of the light diffusion sheet 4, the size is in the range of 1 to 500 mm in length on one side, and the diffusibility is 10 to 10,000 in terms of the number of frosted glass. The appropriate number between numbers is selected as appropriate.
[0033]
As the liquid crystal display panel 2 of the reflective liquid crystal display device of the present invention, either a color display panel or a monochrome display panel on which color filters are mounted corresponding to R, G, B pixels may be used.
Further, the liquid crystal driving method is not particularly limited, such as a TN method, an STN method, a guest host method, and a polymer dispersion type.
[0034]
Further, as the reflecting plate 3 disposed on the back surface of the liquid crystal display panel 2, either a regular reflecting plate or a light diffusing reflecting plate may be used.
Alternatively, the electrode that drives the liquid crystal contained in the liquid crystal panel 2 may be a reflective electrode.
[0035]
The argon ion laser used to manufacture the light diffusion sheet 4 uses a laser beam with a wavelength of 514.5 nm (green), a laser beam with a wavelength of 488 nm (blue green), or a laser beam with a wavelength of 457.9 nm (blue). Can do.
In addition to the argon ion laser, any laser light source having good coherency can be used. For example, a helium neon laser or a krypton ion laser can be used.
[0036]
Further, as the diffusing plate 12 for the subject, for example, frosted glass can be used, and as the hologram photosensitive materials 15 and 25, for example, silver and silver hologram photosensitive materials for holograms manufactured by Agfa Gebalt can be used.
[0037]
In one embodiment of the present invention, ground glass No. 1000 was recorded on a silver salt light-sensitive material for 8E56 hologram manufactured by Agfa Gebalt by using 514.5 nm oscillation light of an argon laser by a hologram recording method, and then developed for CWC2 A developer, which was developed, bleached, washed with water and dried using a PBQ2 bleaching solution for bleaching, was applied to a reflective liquid crystal display device using TN type liquid crystal with the configuration shown in FIG.
[0038]
Further, in the case of a volume phase hologram, it is produced using the above-mentioned silver salt photosensitive material, dichromated gelatin, a photopolymer or the like.
In the case of a surface relief hologram, use an embossed hologram produced by using a photoresist as the hologram photosensitive material 25 in FIG. 3 or replicated as an original plate (stamper) by an embossing method on a thermoplastic resin sheet. Can do.
[0039]
In the embodiment of FIG. 1, the anisotropy is such that the light is transmitted without being diffused when ambient light is incident on the display device, and the display light is diffused when emitted from the display device. On the contrary, the anisotropy may be such that light is diffused and transmitted when ambient light is incident on the display device, and display light is transmitted from the display device without being diffused when emitted.
[0040]
In fact, when the light diffusion sheet is applied to a reflective liquid crystal display device, the display pattern after modulation is diffused in order to clearly view the display pattern in which the reflected light from the reflector passes through the liquid crystal panel. Rather than being modulated (when ambient light is incident on the display device), it is preferable for high-definition display to be diffused.
[0041]
【The invention's effect】
As described above, by disposing a light diffusion sheet having anisotropy and a light diffusivity with a limited range on the front surface of the liquid crystal display panel as a light diffusion plate of the reflective liquid crystal display device, the following is achieved. Can be enumerated.
Anisotropy (incident angle selectivity) can eliminate unnecessary light diffusion and prevent double images due to pixel shift.
By limiting the light diffusion range by condensing (emitting angle selectivity), a large amount of display light can be emitted to the observation position, and bright, high-contrast and high-definition display is possible.
[0042]
[Brief description of the drawings]
FIG. 1 is an explanatory diagram conceptually showing a reflective liquid crystal display device of the present invention.
FIG. 2 is an explanatory view showing an example of an optical system (first step) for producing a light diffusion sheet by hologram recording.
FIG. 3 is an explanatory view showing an example of an optical system (second step) for producing a light diffusion sheet by hologram recording.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reflective type liquid crystal display device 2 ... Liquid crystal display panel 3 ... Reflector 4 ... Light diffusion sheet 5 ... Incident light (ambient light)
6 ... Outgoing light (display light)
7 ... observer 10 ... laser light source 11 ... beam splitter 12 ... diffuser plate 13 ... diffused light 14 ... reference light 15 ... photosensitive material for holograms 16a, 16b, 16c, 26a, 26b, 26c ... reflecting mirrors 17a, 17b, 27 a, 27b ... Spatial filters 1 8a, 18b, 2 8a, 28b ... Lens 20 ... Laser light source 21 ... Beam splitter 22 ... Master hologram 23 ... Diffraction light 24 ... Reference light 25 ... Photosensitive material for hologram

Claims (6)

A reflector is placed on the back side of the liquid crystal panel (opposite to the observer), and ambient light incident from the front side of the liquid crystal panel (observer side) is reflected by the reflector to the liquid crystal panel side and modulated by the liquid crystal panel. In a reflective liquid crystal display device that allows the viewer to visually observe the displayed light, the incident angle selectivity allows the incident light at a specific angle to be transmitted and diffused from other angles to the front surface (observer side) of the liquid crystal panel . A reflection-type liquid crystal display device comprising: a light diffusion sheet having an emission angle selectivity that can control the emission direction and range . The light diffusion sheet is composed of a volume phase transmission hologram having an incident angle selectivity so that only light incident at an angle within a specific range is transmitted and diffracted, and light incident at other angles is not transmitted and diffracted. The reflective liquid crystal display device according to claim 1. 2. The reflective liquid crystal display device according to claim 1, wherein the light diffusion sheet is made of a surface relief hologram. Reflector, a reflection type liquid crystal display device according to claim 1, characterized by having a function of specular reflected incident light 3. 4. The reflective liquid crystal display device according to claim 1, wherein the reflector has a function of diffusing incident light. 6. The reflective liquid crystal display device according to claim 1 , wherein the reflector also serves as an electrode for driving the liquid crystal.

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