The present invention relates to a back-lighting system for a transmissive electrooptic modulator using the light polarization effect.

The present invention relates to a back-lighting system for a transmissive electrooptic modulator using the light polarization effect.
Transmissive electrooptic modulators using the light polarization effect, such as, for example, liquid-crystal screens of the twisted nematic type, require for their operation a pair of polarizers which are positioned at the input and at the output of the modulator, respectively. When the transmissive electrooptic modulator is used in direct viewing mode, the polarizer 1 positioned at the input of the modulator is illuminated by unpolarized light 2, as shown diagrammatically in FIG. 1. Since the polarizer only transmits correctly polarized light rays, an absorption of approximately 60% of the total light flux is observed. Moreover, when transmissive electrooptic modulators using the light polarization effect are used in direct viewing mode, a large variation is observed in the contrast and brightness characteristics, depending on the viewing angle.
In order to remedy these drawbacks, it has been proposed to illuminate the electrooptic modulator by collimated light. A system of this type is illustrated diagrammatically in FIG. 2. In this figure, the reference 10 denotes the light source which may be produced by a cold-cathode fluorescent tube or a similar device. The reference 11 denotes a reflector sending the light rays back in the direction referenced x, the reference 12 denotes a light pipe or waveguide, the reference 13 denotes a microprismatic structure and the reference 14 denotes the viewing angle of the light rays at the output. Moreover, a collimation section 15 may be provided between the reflector and the input of the waveguide 12.
With this structure, as illustrated in FIG. 3, the light emitted by the tube 10 is sent back by the reflector 11 in the direction x into the waveguide 12. In this case, the light rays reflected by the reflector 11 pass through the collimation section, producing a first collimation in the xy plane, and are then sent into the waveguide 12. In the guide, the rays emanating from the collimation region 15 are reflected by total reflection off the upper face opposite the microprismatic structure 13, towards this structure, and are then reflected by specular reflection off the said microprismatic structure 13 so as to leave the waveguide approximately perpendicularly through the upper face towards the electrooptic modulator (not illustrated). The path of the light rays is illustrated by the arrows 1 and 1xe2x80x2. With this structure, the light flux is scattered mono-directionally at the output of the electrooptic modulator, thereby making it possible to improve the contrast characteristics.
The object of the present invention is specially, but not exclusively, to improve this type of structure so as to obtain a novel system having a high luminance gain.
The subject of the present invention is therefore a back-lighting system for a transmissive electrooptic modulator using the light polarization effect, comprising at least one means for generating light rays, at least one reflector for sending the light rays back in a first direction x and means for guiding the light rays towards the electrooptic modulator, characterized in that it includes a reflective linear polarizing film positioned in front of the said means for guiding the light rays.
Preferably, the orientation of the reflective linear polarizing film and the means for guiding the light rays are chosen so that the state of polarization of the light remains unchanged from the input to the output of the said means. This is because, from the laws of reflection, a polarization exists which is not disturbed too much by the multiple reflections inside the guiding means. Depending on the coordinate system chosen, if the output of the rays is along z, this preferred polarization is the polarization along y.
With this system, back-lighting is created such that the light rays have a linear polarization favourable to transmission through the polarizer. In addition, the rays emanating from the means for generating light rays or light source, as soon as they have this polarization, keep it throughout the propagation in the means for guiding the light rays towards the electrooptic modulator, the rays which do not have this state being recycled.
According to a preferred embodiment of the present invention, the reflective linear polarizing film, which constitutes a prepolarization and polarization return means, is a thin-layer film which transmits a linear polarization of given optic axis and which reflects all the others. Preferably, this film consists of the film sold by the company 3M under the trademark xe2x80x9cDBEFxe2x80x9d.
According to another characteristic of the present invention, the means for guiding the light rays consist of a waveguide positioned at the output of the reflector so as to transport the light rays in the x direction, one of the faces of the waveguide, parallel to the x direction, having a microprismatic structure which specularly reflects the light rays and extracts them from the waveguide in a second direction, referenced z, perpendicular to the first direction.
Thus, inside the waveguide, the light propagates by total reflection off the upper plane surface of the waveguide and is extracted from the waveguide by reflection off the microprismatic structures. Since the reflections occur mostly in the plane, the linear polarization least affected during the propagation is therefore that along the y axis, i.e. the p polarization for the microprisms.
According to another characteristic of the present invention, the system includes a prismatic film which is oriented so as to be perpendicular to the means for generating light rays and is positioned between these generating means and the reflective linear polarizing film. The function of this film is to increase the luminance at the centre. The film used in this case may be the film sold by 3M under the trademark xe2x80x9cBEFxe2x80x9d or similar films sold by Japanese companies.
Moreover, a half-wave retardation plate is positioned at the output of the means for guiding the light rays. This half-wave retardation plate makes it possible to preserve the linearity of the output polarization and ensures 45xc2x0 azimuthal rotation towards the optic axis of the input polarizer.

Back-lighting system for a transmissive electrooptic modulator using the light polarization effect

Abstract: The system comprises a means for generating light rays, a reflector for sending the rays back in a direction x and means for guiding the light rays towards the electrooptic modulator, with a reflective linear polarizing film positioned in front of the said means for guiding the light rays.

Abstract: The invention applies to projection.


A light guide plate is described that includes a plurality of reflection areas and a plurality of scattering areas arranged to provide light to a display panel to display images with parallax. A display apparatus is described that can include a light guide plate comprising a plurality of scattering areas and a plurality of reflection areas arranged to form a parallax barrier, and a display panel that displays an image based on light received from the light guide plate. A display apparatus is described that can include a light guide plate comprising a plurality of scattering areas and a plurality of reflection areas arranged in an alternating pattern, and a display panel that displays an image based on light received from the light guide plate. An apparatus is described that includes a backlight positioned on a first side of the light guide plate.

1. Field of the Invention
The present invention relates to a light source device with a light guide plate arranged as a parallax barrier to enable stereoscopic vision, and a stereoscopic display apparatus using the light source device.
2. Description of Related Art
In the past, a parallax-barrier stereoscopic display apparatus has been known as one of stereoscopic display methods enabling stereoscopic vision with a naked eye without need of special eyeglasses. FIG. 14 shows a typical configuration example of a parallax-barrier stereoscopic display apparatus. In the stereoscopic display apparatus, a parallax barrier 101 is disposed facing a front face of a two-dimensional display panel 102. In a typical structure of the parallax barrier 101, shading portions 111 shading display image light from the two-dimensional display panel 102 and stripe openings (slit portions) 112 transmitting the display image light are alternately provided in a horizontal direction.
The two-dimensional display panel 102 displays images based on three-dimensional image data. For example, a plurality of parallax images different in parallax information from one another is prepared as three-dimensional image data, and, for example, a plurality of stripe-shaped, divided images extending in a vertical direction is cut out from each parallax image. The divided images are alternately arranged in a horizontal direction for the parallax images, and therefore a composite image, including a plurality of stripe-shaped parallax images in a screen, is formed, and displayed on the two-dimensional display panel 102. In the case of the parallax barrier type, the composite image displayed on the two-dimensional display panel 102 is viewed though the parallax barrier 101. Width of each divided image to be displayed or slit width of the parallax barrier 101 are appropriately set, and therefore when a viewer watches a stereoscopic display apparatus from a predetermined position or in a predetermined direction, light of different parallax images may be separately injected into left and right eyes 10L and 10R of the viewer through the slit portions 112. In this way, when a viewer watches a stereoscopic display apparatus from a predetermined position or in a predetermined direction, the viewer senses a stereoscopic image. To achieve stereoscopic vision, different parallax images need to be shown to the left eye 10L and the right eye 10R. Therefore, at least two parallax images, an image for right eye and an image for left eye, are desired. When at least three parallax images are used, multi view may be achieved. An increased number of parallax images enable stereoscopic vision in correspondence to change in position of a viewing point of a viewer. In other words, motion parallax is achieved.
The parallax barrier 101 is disposed in the front of the two-dimensional display panel 102 in the configuration example of FIG. 14. However, for example, when a transmissive liquid-crystal display panel is used, the parallax barrier 101 may be disposed in the back of the two-dimensional display panel 102 (see FIG. 10 of Japanese Patent Publication No. 3565391 and FIG. 3 of Japanese Unexamined Patent Application Publication No. 2007-187823). In this case, the parallax barrier 101 is disposed between the transmissive liquid-crystal display panel and a backlight, and therefore stereoscopic display may be achieved in accordance with the same principle as in the configuration example of FIG. 14.

Light source device and stereoscopic display apparatus


An electrophotographic photoreceptor including: an electrically conductive substrate; a charge generating layer disposed on the electrically conductive substrate and includes a charge generating material dispersed or dissolved in a binder resin and an asymmetric naphthalenetetracarboxylic acid diimide derivative having a nitro group dispersed or dissolved in the binder resin. The photoreceptor also has a charge transporting layer that is disposed on the charge generating layer and includes a charge transporting material that is dispersed or dissolved in the binder resin. An electrophotographic image forming apparatus including the electrophotographic photoreceptor. The two-layered type electrophotographic photoreceptor has good interlayer adhesive force and good electrical properties such as good photosensitivity and low residual potential after exposure.

1. Field of the Invention
The present invention relates to an electrophotographic photoreceptor and an electrophotographic image forming apparatus. More particularly, the invention relates to a two-layered type electrophotographic photoreceptor including a naphthalenetetracarboxylic acid diimide derivative having a nitro group as an electron transporting material in a charge generating layer including a charge generating material. The photoreceptor has improved electrostatic properties such as photosensitivity and residual potential. The present invention also relates to an electrophotographic image forming apparatus including the electrophotographic photoreceptor.
2. Description of the Related Art
Electrophotography is widely used in laser printers, photocopiers, facsimile machines, LED printers, CRT printers, and laser electrophotographs, and the like. An electrophotographic photoreceptor includes a photosensitive layer formed on an electrically conductive substrate and can be in the form of a plate, a disk, a sheet, a belt, or a drum, etc. In an electrophotographic photoreceptor, a surface of the photosensitive layer is uniformly and electrostatically charged, and then the charged surface is exposed to a pattern of light, thus forming an image. The light exposure selectively dissipates the charge in the exposed regions where the light strikes the surface, thereby forming a pattern of charged and uncharged regions. This pattern is referred to as a latent image. Then a wet or dry toner is supplied in the vicinity of the latent image, and toner droplets or particles are deposited in either the charged or uncharged region to form a toner image on the surface of the photosensitive layer. The resulting toner image can be transferred and fixed to a suitable final or intermediate receiving surface, such as paper, or the photosensitive layer can function as the final receptor for receiving the image.
Electrophotographic photoreceptors can be classified into two types. The first is a type having a structure including a charge generating layer (CGL) comprising a charge generating material (CGM), a binder resin, and a charge transporting layer (CTL) comprising a binder resin and a charge transporting material (primarily, a hole transporting material (HTM)). In general, the two-layered type electrophotographic photoreceptors are used in the fabrication of negative (−) type electrophotographic photoreceptors. The other type is a single-layered type photoreceptor in which a binder resin, a charge generating material, a hole transporting material (HTM), and an electron transporting material (ETM) are contained in a single layer. In general, the single-layered type photoreceptors are used in the fabrication of positive (+) type electrophotographic photoreceptors.
The charge generating material is provided for the purpose of generating charge carriers (that is, holes and/or electrons) upon exposure. The purpose of the charge transporting material is to receive at least one type of the charge carriers and transport them through the charge transporting layer in order to facilitate the discharge of the surface charges on the photoreceptor.
The amount of the charge generating material in the charge generating layer of the two-layered type electrophotographic photoreceptor needs to be large in order to obtain an electrophotographic photoreceptor with high photosensitivity. However, if the amount of the charge generating material is too large, the stability of the coating slurry for forming the charge generating layer may be degraded, thus degrading the coating quality of the charge generating layer. Also, the adhesive force of the charge generating layer and the charge generating layer and an electrically conductive substrate and the adhesive force of the charge transporting layer may be degraded. On the contrary, if the amount of the charge generating material is low, the stability of the coating slurry for forming the charge generating layer, the coating quality of the charge generating layer, the adhesive force of the charge generating layer and the electrically conductive substrate and the adhesive force of the charge generating layer and the charge transporting layer may be improved, but the electrostatic properties may be radically degraded such that the photosensitivity of the electrophotographic photoreceptor may decrease and the residual potential may increase.
Also, regardless of the amount of the charge generating material in the charge generating layer, electron transportation in the charge generating layer is not good, thereby adversely affecting the electrostatic properties of the electrophotographic photoreceptor such that the photosensitivity of the electrophotographic photoreceptor tends to be low and the residual potential thereof tends to be high. In particular, since the charges are mainly generated in the upper portion of the charge generating layer, degradation of the electrostatic properties due to poor electron transportation occurs more significantly when the thickness of the charge generating layer is increased for high photosensitivity.
U.S. Pat. Nos. 5,547,790, 5,571,648, and 5,677,094 respectively disclose an electrophotographic photoreceptor, for solving the above described problems,
U.S. Pat. No. 5,547,790 discloses an electrophotographic photoreceptor including at least a charge generating layer and a charge transporting layer that are sequentially stacked on an electrically conductive substrate. The charge generating layer includes a charge generating material selected from the group consisting of azo pigments, perynone pigments, and squaraines and a polymeric charge transporting material. The charge transporting layer includes a polymeric charge transporting material. The polymer charge transporting material in the charge generating layer is selected from a polysirylene, a polymer having a hydrazone structure on the main bone and/or side chain thereof, and a polymer having a tertiary amine structure on the main bone and/or side chain thereof. The polymer charge transporting material in the charge transporting layer is a polymer having a polysirylene, a polymer having a hydrazone on the main bone and/or side bone thereof, and a polymer having a tertiary amine structure on the main bone and/or side chain thereof.
U.S. Pat. No. 5,571,648 discloses an electrophotographic imaging member comprising a support substrate having a two electrically conductive ground plane layer comprising a layer comprising zirconium over a layer comprising titanium, a hole blocking layer, an adhesive layer comprising a copolyester film forming resin, an intermediate layer in contact with the adhesive layer, where the intermediate layer comprises a film forming carbazole polymer, a charge generating layer comprising perylene or phthalocyanine particles dispersed in a film forming a polymer binder blend of polycarbonate and carbazole polymer, and a hole transporting layer, wherein the hole transporting layer is substantially non-absorbing in the spectral region at which the charge generating layer generates and injects photogenerated holes but is capable of supporting the injection of photogenerated holes from the charge generating layer and transporting the holes through the charge transporting layer.
U.S. Pat. No. 5,677,094 discloses an electrophotographic photoconductor comprising an electroconductive support and a photoconductive layer formed on the electroconductive support and including a charge generating layer and a charge transporting layer, wherein the charge generating layer comprises a first polymeric charge transporting material having an ionization potential of 6.0 eV or less, and the charge transporting layer comprises a charge transporting small molecule and a binder.
The electrophotographic photoreceptors disclosed in the above U.S. Patents tried to improve electrostatic properties by further incorporating hole transporting material besides the charge generating material to the charge generating layer. However, an electrophotographic photoreceptor with improved electrostatic properties is still required.

This patent is subject to a terminal disclaimer.

Electrophotographic photoreceptor containing asymmetrical naphthalenetetracarboxylic acid diimide derivative as electron transporting material in a charge generating layer and electrophotographic image forming apparatus employing the photoreceptor