Light source device, illumination device liquid crystal device and electronic apparatus

A light source device 41A, 41B or 41C comprising a lens 44A, 44B or 44C which receives light from a light emitting device 43 such as LED. The lens 44A is a lens having the property that the directivity of exiting light in the Y direction is higher than the directivity in the X direction perpendicular to the Y direction. Namely, the light emitted from the light emitting device 43 is condensed in a narrow angular range in the Y direction, and is scattered in a wide angular range in the X direction. When the light source device 41A is used as a light source of an illumination device of a liquid crystal device, the height direction of a light guide in which the dimension is small coincides with the Y direction, and the width direction of the light guide in which the dimension is large coincides with the X direction.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a light source device using a light emitting device such as LED (Light Emitting Diode) or the like, an illumination device using the light source device, a liquid crystal device using the illumination device, and an electronic apparatus using the liquid crystal device.

2. Description of the Related Art

Recently, liquid crystal devices have widely been used for electronic apparatuses such as a computer and a cell phone. The liquid crystal device generally comprises a liquid crystal sandwiched between a pair of substrates each comprising an electrode so that the orientation of the liquid crystal is controlled by applying a voltage between both electrodes to modulate light transmitted through the liquid crystal, to display an image.

On the basis of the system for supplying light to the liquid crystal, various known liquid crystal devices are distinguished into a reflective liquid crystal device having a structure in which external light is reflected by a reflector plate provided on the outer surface or the inner surface of one of both substrates, a transmissive liquid crystal device having a structure in which light is supplied to the liquid crystal in a planar manner by using an illumination device provided outside one of the substrates, and a transflective liquid crystal device which functions as a reflective type when external light is incident, and functions as a transmissive type when external light is insufficient.

As the illumination device used for the transmissive liquid crystal device, the transflective liquid crystal device, and the like, a conventional known illumination device has a structure comprising a light source device which emits light, and a light guide which broadens the light exiting from the light source device in a planar manner and causes the light to exit. As the light source device, a conventional known device has a structure in which light from a light emitting device such as LED or the like is emitted to the outside through a lens, as disclosed in, for example, Japanese Unexamined Patent Application Publication No. 62-105486. According to this publication, it is known that an aspherical lens is used as the lens.

However, the aspherical lens used in the light source device disclosed in Japanese Unexamined Patent Application Publication No. 62-105486 is nondirectional, i.e., it has no directivity in condensation of the light emitted from the light emitting device. In other words, it has the property that light can be condensed in any directions all round.

Although the non-directivity for condensation of light is a preferable property according to circumstances, it is an undesirable property according to circumstances. For example, like in the case in which light is desired to be supplied as much as possible to the light guide used in a liquid crystal device, when light is desired to be condensed in the height direction of the light guide, but not condensed in the width direction perpendicular to the height direction, the light source device having no directivity for condensation of light is unsatisfactory for effectively utilizing light.

The present invention has been achieved in consideration of the above problem, and a first object of the present invention is to provide a light source device capable of efficiently applying light to an object according to the shape of the object to which light is supplied.

A second object of the present invention is to enable incidence of light with high efficiency to a light guide in an illumination device comprising the light guide.

A third object of the present invention is to enable a bright display easy to see without changing the light emitting ability, i.e., power consumption, of a light source in a liquid crystal device in which light is supplied to a liquid crystal panel to perform a display.

A fourth object of the present invention is to provide an electronic apparatus capable of performing a bright display easy to see with low power consumption.

SUMMARY OF THE INVENTION

In order to achieve the first object, a light source device according to a first aspect of the present invention comprises a light emitting device, and a lens which receives the light emitted from the light emitting device, wherein the lens is a lens, for example, an aspherical lens, having the property that directivity of exiting light in one direction is higher than directivity in exiting light in the direction perpendicular to the one direction.

The light source device having this construction has, for example, such a structure as shown in FIG.7(a), in which such measurement as shown in FIG.12(b) performed for the light source device21shown in FIG.7(a) exhibits such a directional property of exiting light as shown in FIG.12(a). In FIG.7(a), reference numeral43denotes the light emitting device, and reference numeral44denotes the lens.

In the measurement shown in FIG.12(b), the receiving angle θ of a light receiving device73with respect to the light emitting device43is successively changed from 0° to 90°, and luminous intensity is measured by the light receiving device73at each angle. In FIG.12(a), the relative luminous intensity is shown on the ordinate, and the angle of light emission is shown on the abscissa. In FIG.12(a), a curve X shows the directional property of exiting light in the transverse direction X of the light source device21shown in FIG.7(a), and a curve Y shows the directional property of exiting light in the longitudinal direction Y perpendicular to the transverse direction X.

For example, as shown in FIG.12(a), exiting light of the light source device of the present invention has no directivity in one direction X, and strong directivity in the direction Y perpendicular to the direction X. Namely, light is scattered at any angle all around in the X direction, but strong light is emitted in a narrow limited range in the Y direction. Therefore, the X direction and Y direction can be set appropriately according to the shape of an object to which light is supplied, to suppress ineffective travel of light to a portion other than the object, thereby permitting efficient incidence of light on the object.

In order to achieve the first object, a light source device according to a second aspect of the present invention comprises a light emitting device, and a lens which receives the light emitted from the light emitting device, wherein the lens has a planar light incidence plane and a non-planar light exiting plane having a shape in which the height from the light incidence plane changes in one direction, while the height is constant in the direction perpendicular to the one direction.

In the light source device having this construction, for example, as shown in FIG.7(a), a light incidence plane44dof a lens44A is formed in a planar shape, and a light exiting plane44eis formed in a non-planar shape. The light exiting plane44eis formed in a shape in which the height from the light incidence plane44dis constant at any point in one direction X, and the height from the light incident plane44echanges with the points in the perpendicular direction Y. In the case shown in FIG.7(a), the light exiting plane44eis formed in a shape having a circular-arc section.

For example, when the lens is formed in the shape shown by reference numeral44A in FIG.7(a), light emitted from the light emitting device43can be scattered all around without directivity in the X direction, while the light can be emitted in the Y direction with directivity according to the change in the shape of the light exiting plane44e. Therefore, the X direction and Y direction can be set appropriately according to the shape of an object to which light is supplied, to suppress ineffective travel of light to a portion other than the object, thereby permitting efficient incidence of light on the object.

In each of the light source devices according to the first and second aspects, the lens can be formed in, for example, the semicircular pillar shape shown by reference numeral44A in FIG.7(a), the prismatic shape shown by reference numeral44B in FIG.7(b), or the partial circular pillar shape having a Fresnel lens surface as shown by reference numeral44C in FIG.7(c).

In order to achieve the second object, an illumination device according to a first aspect of the present invention comprises a light source device which emits light, and a light guide which receives light from the light source device by a light receiving plane and causes light to exit from a light exiting plane, wherein the light source device comprises a light emitting device and a lens which receives the light emitted from the light emitting device, wherein the lens is a lens having the property that directivity of exiting light in one direction is higher than directivity of exiting light in the direction perpendicular to the one direction, the one direction in which the exiting light has higher directivity being set to the height direction of the light guide, and the perpendicular direction in which the exiting light has lower directivity being set to the width direction of the light guide.

In this illumination device, the directivity of the light exiting from the light source device is set to be high in the height direction in which the dimension of the light receiving plane of the light guide is small, and thus the light from the light source device can be incident on the light guide as much as possible, thereby improving the efficiency of incidence of light on the light guide. Also, the directivity of the exiting light is set to be low in the width direction in which the dimension of the light receiving plane of the light guide is large, and thus uniformity of luminous intensity can be achieved.

In order to achieve the second object, an illumination device according to a second aspect of the present invention comprises a light source device which emits light, and a light guide which receives light from the light source device by a light receiving plane and causes light to exit from a light exiting plane, wherein the light source device comprises a light emitting device, and a lens which receives the light emitted from the light emitting device, wherein the lens has a planar light incidence plane and a non-planar light exiting plane having a shape in which the height from the light incidence plane changes in one direction, while the height is constant in the direction perpendicular to the one direction, the one direction being set to the height direction of the light guide, and the perpendicular direction being set to the width direction of the light guide.

In the illumination device, the shape of the light exiting plane of the lens changes in the height direction in which the dimension of the light receiving plane of the light guide is small, and the shape of the light exiting plane of the lens is kept constant in the width direction in which the dimension of the light receiving plane of the light guide is large. Therefore, a large quantity of light can be condensed and incident on the light guide in the height direction of the light receiving plane of the light guide to improve the efficiency of incidence of light on the light guide. Also, light can be scattered in the width direction of the light receiving plane of the light guide to achieve uniformity of luminous intensity.

In each of the illumination devices according to the first and second aspects, the lens can be formed in, for example, the semicircular pillar shape shown by reference numeral44A in FIG.7(a), the prismatic shape shown by reference numeral44B in FIG.7(b), or the partial circular pillar shape having a Fresnel lens surface as shown by reference numeral44C in FIG.7(c).

Furthermore, in each of the illumination devices according to the first and second aspects, the lens can be provided on the light source device side, and the lens can also be provided on the light receiving plane of the light guide. When it is desired to improve the efficiency of incidence of the light exiting from the light source device on the light guide, lenses are preferably provided on both the light source device side and the light guide side.

In order to achieve the third object, a liquid crystal device according to a first aspect of the present invention comprises a liquid crystal panel comprising a liquid crystal held between a pair of substrates, and an illumination device for supplying light to the liquid crystal panel, wherein the illumination device comprises a light source device which emits light, and a light guide which receives light from the light source device by a light receiving plane and causes light to exit from a light exiting plane, and the light source device comprises a light emitting device and a lens which receives the light emitted from the light emitting device, wherein the lens is a lens having the property that directivity of exiting light in one direction is higher than directivity of exiting light in the direction perpendicular to the one direction, the one direction in which the exiting light has higher directivity being set to the height direction of the light guide, and the perpendicular direction in which the exiting light has lower directivity being set to the width direction of the light guide.

In this illumination device used in the liquid crystal device, the directivity of the light exiting from the light source device is set to be high in the height direction in which the dimension of the light receiving plane of the light guide is small, and thus the light from the light source device can be incident on the light guide as much as possible, thereby improving the efficiency of incidence of light on the light guide. Also, the directivity of the exiting light is set to be low in the width direction in which the dimension of the light receiving plane of the light guide is large, and thus uniformity of luminous intensity can be achieved. As a result, in the liquid crystal device, a bright display easy to see can be performed without a change in the light emitting ability, i.e., a change in power consumption, of the light source.

In order to achieve the third object, a liquid crystal device according to a second aspect of the present invention comprises a liquid crystal panel comprising a liquid crystal held between a pair of substrates, and an illumination device for supplying light to the liquid crystal panel, wherein the illumination device comprises a light source device which emits light, and a light guide which receives light from the light source device by a light receiving plane and causes light to exit from a light exiting plane, and the light source device comprises a light emitting device, and a lens which receives the light emitted from the light emitting device, wherein the lens has a planar light incidence plane and a non-planar light exiting plane having a shape in which the height from the light incidence plane changes in one direction, while the height is constant in the direction perpendicular to the one direction, the one direction being set to the height direction of the light guide, and the perpendicular direction being set to the width direction of the light guide.

In the illumination device used in this liquid crystal device, the shape of the light exiting plane of the lens changes in the height direction in which the dimension of the light receiving plane of the light guide is small, and the shape of the light exiting plane of the lens is kept constant in the width direction in which the dimension of the light receiving plane of the light guide is large. Therefore, a large quantity of light can be condensed and incident on the light guide in the height direction of the light receiving plane of the light guide to improve the efficiency of incidence of light on the light guide. Also, light can be scattered in the width direction of the light receiving plane of the light guide to achieve uniformity of luminous intensity. As a result, in the liquid crystal device, a bright display easy to see can be performed without a change in the light emitting ability, i.e., a change in power consumption, of the light source.

In each of the liquid crystal devices according to the first and second aspects, the lens can be formed in, for example, the semicircular pillar shape shown by reference numeral44A in FIG.7(a), the prismatic shape shown by reference numeral44B in FIG.7(b), or the partial circular pillar shape having a Fresnel lens surface as shown by reference numeral44C in FIG.7(c).

Furthermore, in the illumination device as a component of each of the liquid crystal devices according to the first and second aspects, the lens can be provided on the light source device side, and the lens can also be provided on the light receiving plane of the light guide. When it is desired to improve the efficiency of incidence of the light exiting from the light source device on the light guide, lenses are preferably provided on both the light source device side and the light guide side. As a result, a bright display easy to see can be performed on the display plane of the liquid crystal device.

In order to achieve the fourth object, an electronic apparatus according to the present invention comprises a liquid crystal device for displaying an image such as a character, and a control circuit for controlling the operation of the liquid crystal device, wherein the liquid crystal device comprises the liquid crystal device according to first or second aspect of the present invention. The liquid crystal device used in the electronic apparatus is capable of performing a bright display easy to see on the display plane of the liquid crystal device without increasing the light emitting ability of the light source, and thus the electronic apparatus using the liquid crystal device can perform a bright display easy to see with low power consumption.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG.7(a) shows a light source device according to an embodiment of the present invention. The light source device41A shown in the drawing comprises a light emitting device43provided on the surface of a base42, and a lens44A provided on the light emitting plane of the light emitting device43. The lens44A is formed in a semicircular pillar shape, i.e., a so-called semicylindrical shape. The base42and the lens44may be formed separately and then boded together, or may be formed integrally.

The light emitting device43comprises, for example, a LED (Light Emitting Diode). When it is desired to obtain white light from the light source device41A, for example, a blue LED is used as the light emitting device43, and a resin containing a YAG fluorescent material is provided on the light receiving plane of the blue LED. As a result, a part of the blue light emitted from the blue LED is applied to the YAG fluorescent material to be converted to yellow light (i.e., mixture of green light and red light) when passing through the resin, and the yellow light is mixed with the blue light emitted to the outside without being applied to the YAG fluorescent material to obtain white light.

The lens44A has a planar incidence plane44dand a non-planar exiting plane44ehaving a shape in which the height from the light incidence plane44dchanges in one direction Y, for example, changes along an arch shape in this embodiment. The height from the incidence plane44dis constant at any point in the X direction perpendicular to the Y direction.

Since the light exiting plane of the lens44A is formed in a semicylindrical shape as described above, exiting light has no directivity in the X direction, and high directivity in the Y direction. Namely, the lens44A causes scattered light to exit in a wide angular range in the X direction, and causes condensed light with high intensity to exit in a limited narrow angular range in the Y direction. Such directivity characteristics of exiting light can be indicated by a graph of FIG.12(a).

FIG.7(b) shows a light source device according to another embodiment of the present invention. The light source device41B shown in the drawing is different from the light source device41A shown in FIG.7(a) in that a pillar member having a prismatic shape, i.e., a triangular sectional shape, is used as a lens44B. The same members as those shown in FIG.7(a) are denoted by the same reference numerals, and a description thereof is omitted. In this embodiment, the base42and the lens44B may be formed separately and then bonded together, or may be formed integrally.

The lens44B has a planer incidence plane44dand a non-planer exiting plane44ehaving a shape in which the height from the light incidence plane44dchanges in one direction Y, for example, changes along a triangular sectional shape in this embodiment. The height from the incidence plane44dis constant at any point in the X direction perpendicular to the Y direction.

Since the light exiting plane of the lens44B is formed in a prismatic shape as described above, exiting light has no directivity in the X direction, and high directivity in the Y direction. Namely, the lens44B causes scattered light to exit in a wide angular range in the X direction, and causes condensed light with high intensity to exit in a limited narrow angular range in a Y direction. Such directivity characteristics of exiting light can be indicated by a graph of FIG.12(a).

FIG.7(c) shows a light source device according to another embodiment of the present invention. The light source device41C shown in the drawing is different from the light source device41A shown in FIG.7(a) in that a pillar member having a partial circular pillar shape having a Fresnel lens surface, is used as a lens44C. The same member as those shown in FIG.7(a) are denoted by the same reference numerals, and a description thereof is omitted. In this embodiment, the base42and the lens44C may be formed separately and then bonded together, or may be formed integrally.

The lens44C has a planar light incidence plane44d, and a non-planar light exiting plane44ehaving a shape in which the height from the light incidence plane44dchanges in one direction Y; in this embodiment, the height changes along a Fresnel lens shape. The height from the light incidence plane44dis constant at any point in the X direction perpendicular to the Y direction.

The light exiting plane of the lens44C is formed in the Fresnel lens shape, as described above, and thus exiting light has no directivity in the X direction, and high directivity in the Y direction. Namely, the lens44C causes scattered light to exit in a wide angular range in the X direction, and causes condensed light with high intensity to exit in a limited narrow angular range in the Y direction. The directivity characteristics of exiting light can be indicated by, for example, a graph of FIG.12(a).

On the basis of the driving system, liquid crystal devices are distinguished into an active matrix system liquid crystal device on a system in which pixel electrodes are driven by a switching element (i.e., a nonlinear element), and a passive matrix system liquid crystal device having a simple matrix arrangement without using switching elements. In comparison between both systems, the active matrix system is thought to be advantageous from the viewpoint of good contrast, responsiveness, etc., and ease of achievement of a high-definition display.

Systems known as the active matrix system liquid crystal device include a system using a three-terminal element such as a thin film transistor (TFT) or the like as a switching element, and a system using a two-terminal element such as a thin film diode (TFD). Of these systems, the liquid crystal device using TFD or the like has the advantages that no defective short-circuit occurs between wirings because there is no intersection of the wirings, and the deposition step and photolithography step can be shortened.

A description will now be made of the case in which the present invention is applied to an active matrix system liquid crystal device using TFD as a switching element for a pixel electrode in accordance with an embodiment of the present invention. A liquid crystal device according to an embodiment of the present invention is a transflective liquid crystal device which functions as a reflective type when external light is present, and functions as a transmissive type when external light is insufficient.

FIG. 1shows a liquid crystal device1according to this embodiment. The liquid crystal device1comprises a liquid crystal panel2to which a FPC (Flexible Printed Circuit)3aand FPC3bare connected, and a light guide4mounted to the non-display side (the lower side shown inFIG. 1) of the liquid crystal panel2. A control substrate5is provided on the side of the light guide4opposite to the liquid crystal panel2side thereof. The control substrate5is used as a component of the liquid crystal device, or a component of an electronic apparatus to which the liquid crystal device is mounted. In this embodiment, the FPCs3aand3bare used for electrically connecting the liquid crystal panel2and the control substrate5.

The liquid crystal panel2comprises a pair of substrates7aand7bwhich are bonded together with a ring sealing material6. Liquid crystal driving ICs8aare mounted on the surface of the portion of the first substrate7a, which projects from the second substrate7b, by using AFC (Anisotropic Conductive Film). Liquid crystal driving ICs8bare mounted on the surface of the portion of the second substrate7b, which projects from the first substrate7a, by using AFC (Anisotropic Conductive Film)9.

The liquid crystal device of this embodiment is an active matrix system liquid crystal device using TFDs as switching elements, in which one of the first and second substrates7aand7bis an element substrate, and the other is a counter substrate. In this embodiment, the first substrate7ais considered as the element substrate, and the second substrate7bis considered as the counter substrate.

As shown inFIG. 2, pixel electrodes66are formed on the inner surface of the first substrate7aserving as the element substrate, and a polarizer plate12ais attached to the outer surface. In addition, data lines52are formed on the inner surface of the second substrate7aserving as the counter substrate, and a polarizer plate12bis attached to the outer surface thereof. A liquid crystal L is sealed in the gap surrounded by the first substrate7a, the second substrate7band the sealing material6, i.e., in the cell gap.

Although not shown inFIG. 2, various optical components other than the above are provided on the first substrate7aand the second substrate7baccording to demand. For example, an alignment film is provided on the inner surface of each of the substrates, for aligning the orientation of the liquid crystal L. The alignment film is formed by coating a polyimide solution and then burning the coating. It is said that the polymer main chains of polyimide are oriented in a predetermined direction by rubbing so that the liquid crystal molecules of the liquid crystal L sealed in the cell gap are oriented in the orientation direction of the alignment film.

In a color display, color filters of the primary colors including R (red), G (green) and B (blue) are formed in a predetermined arrangement on the portions of the counter substrate, which are opposed to the pixel electrodes formed on the element substrate, and a black matrix of Bk (black) is formed in the regions not opposed to the pixel electrodes. Furthermore, a smoothing layer is coated for smoothing and protecting the surfaces of the color filters and the black matrix. A counter electrode provided on the counter substrate is formed on the smoothing layer.

FIG. 3schematically shows the electrical configuration of the liquid crystal panel2. As shown inFIG. 3, in the liquid crystal panel2, a plurality of scanning lines51are formed in the line direction (X direction), and a plurality of data lines52are formed in the column direction (Y direction), pixels53being formed at the intersections of the scanning lines51and the data lines52. Each of the pixels53is formed by series connection of a liquid crystal layer54and a TFD (Thin Film Diode)56.

The scanning lines51are driven by a scanning line driving circuit57, and the data lines52are driven by a data line driving circuit58. In this embodiment, the scanning line driving circuit57is included in the liquid crystal driving ICs8a, and the data line driving circuit58is included in the liquid crystal deriving ICs8b.

InFIG. 3, the scanning lines51and the TFDs56are formed on the inner side of the element substrate7ashown inFIG. 2, and the pixel electrodes66formed on the inner surface of the element substrate7aare connected to the scanning lines51. On the other hand, inFIG. 3, the data lines52are formed as stripe electrodes on the inner surface of the counter substrate7bshown in FIG.2. The element substrate7aand the counter substrate7bare bonded together so that the pixel electrodes on one line and one data line52have an opposite positional relation. Therefore, the liquid crystal layer54comprises the data lines52and the pixel electrodes66, and the liquid crystal L held therebetween.

The data lines52are made of, for example, a transparent conductive material such as ITO (Indium Tin Oxide). The pixel electrodes66are made of a reflecting material such as Al (aluminum). InFIG. 3, the TFDs56are connected to the scanning lines51, and the liquid crystal layer54is connected to the data lines52. However, conversely, the TFDs56may be connected to the data lines52, and the liquid crystal layer54may be connected to the scanning lines51.

Next,FIG. 4shows the construction of one pixel of the element substrate7a. Particularly, FIG.4(a) shows the planar structure of one pixel, and FIG.4(b) shows the sectional structure taken along line A—A in FIG.4(a). In these drawings, the TFT56comprises two TFD portions including a first TFD56aand a second TFD56bwhich are formed on an insulating film61deposited on the surface of the element substrate7a. The insulating film61is formed to a thickness of about 50 to 200 mm by using tantalum oxide (Ta2O5).

The TFDs56aand56bcomprise a first metal film62, an oxide film63formed on the surface of the first metal film62to function as an insulator, and second metal films64aand64b, respectively, which are formed on the surface of the oxide film63to be spaced therebetween. The oxide film63comprises tantalum oxide (Ta2O5) formed by, for example, anodic oxidation of the surface of the first metal film62. In anodic oxidation of the first metal film62, the surfaces of the basic portions of the scanning lines51are also oxidized at the same time to form an oxide film composed of tantalum oxide.

As the thickness of the oxide film63, a preferred value is selected according to applications, for example, about 10 to 35 nm. The thickness is a half of the thickness of the case in which one TFD is used for one pixel. Although the chemical solution used for anodic oxidation is not limited, for example, a 0.01 to 0.15 by weight citric acid aqueous solution can be used.

The second metal films64aand64bare formed by depositing a reflecting material such as Al (aluminum) by using a deposition technique such as sputtering, and then patterning the film by photolithography and etching processes to form the films having a final thickness of about 50 to 300 nm. The second metal film64ais used as one scanning line51, and the other second metal film64bis connected to one pixel electrode66.

The first TFD56ahas a laminated structure of the second metal film64a/the oxide film63/the first metal film62, i.e., the sandwiched structure of metal/insulator/metal, in the order from the scanning line51side, and thus the current-voltage characteristic is nonlinear in both the positive and negative directions. On the other hand, the second TFD56bcomprises the first metal film62/the oxide film63/the second metal film64bin the order from the scanning line51side, and thus has the current-voltage characteristic opposite to the first TFD56a. Therefore, the TFD has a system in which two elements are oppositely connected in series, and the non-linearity of the current-voltage characteristic is symmetrized in both the positive and negative directions, as compared with the case in which one element is used.

The first metal film62is made of, for example, a tantalum single material or a tantalum alloy. As the thickness of the first metal film62, a preferred value is selected according to the application of the TFD56, and ordinarily about 100 to 500 nm. In use of a tantalum alloy for the first metal film62, an element of the V to VIII groups in the periodic table, such as tungsten, chromium, molybdenum, rhenium, yttrium, or lanthanum dysprosium is added to the main component tantalum. In this case, tungsten is preferred as an additive element, and the content is preferably, for example, 0.1 to 6% by weight.

A base17awhich constitutes the element substrate7ais made of, for example, quartz, glass, or plastic, together with a base17b(refer toFIG. 2) which constitutes the counter substrate7b. In a simple reflective type, the base17aof the element substrate is not necessarily required, but like in this embodiment, when the liquid crystal device is used as both the reflective type and the transmissive type, it is essential that the element substrate base17ais transparent.

The reasons for providing the insulating film61on the surface of the element substrate7aare the following. First, the first metal film62is prevented from being separated from an underlying layer in heat treatment after deposition of the second metal films64aand64b. Secondary, diffusion of impurities into the first metal film62is prevented. Therefore, if these points do not matter, the insulating film61can be omitted.

The TFD56is an example of a two-terminal nonlinear element, and an element using a diode element structure, such as MSI (Metal Semi-Insulator), or these elements oppositely connected in series or in parallel can also be used. Furthermore, when the current-voltage characteristics need not be strictly symmetrized in both the positive and negative directions, TFD comprising only one element may be used.

InFIG. 4, the pixel electrode66formed to extend from the second metal film64bcomprises a metal film of Al (aluminum) or the like having high reflectance. Also, as shown in FIG.4(a), slit apertures67obliquely formed are provided in the pixel electrode66. When the liquid crystal device of this embodiment functions as the transmissive type, light passing through the apertures67enter the liquid crystal layer54(refer to FIG.3). The pixel electrode66preferably has micro protrusions so that reflected light is scattered.

In the liquid crystal panel2(refer to FIG.1), the element substrate7aand the counter substrate7bare bonded together with a space kept constant therebetween, and the liquid crystal L (refer toFIG. 2) is sealed in the space. In consideration of the visual characteristics of the liquid crystal panel, the direction of rubbing for imparting orientation to the liquid crystal L is set to the direction shown by allow RAinFIG. 4for the element substrate7a, and set to the direction shown by arrow RBfor the counter substrate7b. Namely, the rubbing direction which determines the orientation direction of the liquid crystal molecules with no voltage applied is the upward direction RBinclined to the left at 45° for the counter substrate7bon the front side as the bonded substrates are viewed from the counter substrate7bside, and the rubbing direction is the downward direction RAinclined to the left at 45° for the element substrate7aon the back side. Therefore, the slit direction of the apertures67formed in the element substrate7acoincides with the rubbing direction RA.

Since rubbing is generally performed by rubbing with a buff cloth wound on a roller in a predetermined direction, undesirable situations such as the occurrence of static electricity and the occurrence of dust particles easily occur in the manufacturing process. In this embodiment, the moving direction of the buff cloth in rubbing is caused to coincide with the slit direction of the apertures67to decrease the influence of steps formed by the pixel electrodes66, thereby suppressing the occurrence of static electricity and various dust particles.

Although, in the above description, the composition of the second metal films64aand64bis the same as the pixel electrodes66, the second metal films64aand64bmay be formed by patterning a non-reflecting metal such as chromium, titanium, or molybdenum, and then the pixel electrodes66may be formed by patterning a reflecting metal such as Al.

As shown inFIG. 5, the direction of an electric field produced by one pixel electrode66and the corresponding data line52is perpendicular to both substrates in the regions other than the apertures67, and thus the strength of the field is also uniform. However, the electrode is absent from the apertures67, and thus an electric field occurs due to only a leakage from the aperture ends of the pixel electrodes66. Therefore, the strength of the electric field near each of the apertures67gradually decreases as the distance from the aperture ends increases, and is thus not uniform. Conversely, this means that the strength of the electric field is substantially constant at points at equal distances from the side end of each of the apertures67formed in the pixel electrodes66, i.e., at the points shown by broken lines in FIG.6(a).

On the other hand, since the rubbing direction of the element substrate7ahaving the pixel electrodes66formed thereon coincides with the slit direction of the apertures67formed in the pixel electrodes66, and thus the liquid crystal molecules M on the element substrate7aside are oriented in parallel with the side ends of the apertures67with no voltage applied. Therefore, when a potential difference occurs between the pixel electrodes66and the data lines52, and particularly when the potential difference is small, the strength of the electric field at one end of each liquid crystal molecule M is equal to that at the other end thereof, and thus the liquid crystal molecules M located in the apertures67are tilted in the same manner as the liquid crystal molecules located in the regions where the electrodes are present, i.e., the regions which contribute to a display when the device functions as the reflective type. As a result, the rotatory direction of the light passing through the apertures67is substantially the same as that of the light reflected by the pixel electrodes66, decreasing a difference in display quality between the transmissive type and the reflective type.

Although, as described above, the slit direction of the apertures67preferably coincides with the rubbing direction, the difference in display quality can be possibly decreased to a level with no practical problem even when the angle between the both directions is in the range of ±15°.

When the rubbing direction does not coincide with the slit direction of the apertures67, as shown in FIG.6(b), the liquid crystal molecules M located in the apertures67are oriented in the direction crossing the side ends of the apertures67with no voltage applied. Therefore, even when a potential difference occurs between the pixel electrodes66and the data lines52, and particularly, when the potential difference is small, the strength of an electric field at one end of each liquid crystal molecule M is different from that at the other end thereof, and thus the liquid crystal molecules M located in the aperture67are tilted in a different manner from the liquid crystal molecules located in the regions which contribute to a display when the device functions as the reflective type. As a result, the rotatory direction of the light passing through the apertures67is different from the light reflected by the pixel electrodes66, thereby causing a difference in display quality between the transmissive type and the reflective type.

Next, the width and area of the apertures67formed in the pixel electrodes66will be described. When the liquid crystal sealed between a pair of the substrates is a TN (Twisted Nematic) type, the distance between the substrate is generally several μm. In this case, for example, in a normally white display, even at a point at a distance of about 1.5 μm from the end of each of the intersections of the electrodes of both substrates, a black display is obtained by the influence of a leakage electric field from one end of the periphery of each electrode by applying a voltage. On the basis of this, when the width of the slit apertures67is about twice as large as 1.5 μm, i.e., 3 μm, or less, the liquid crystal molecules in the apertures67are tilted by a leakage electric field from the both ends of each aperture67in the same manner as the liquid crystal molecules in the regions where the electrode are present. Conversely, when the width W of the slit apertures67is 3 μm or more, a dead space is formed in each of the pixel electrodes66, in which the liquid crystal molecules M do not tilt according to the electric field in both the reflective type and the transmissive type. Therefore, the width W of the apertures67is possibly preferably be 3 μm or less.

When the width W of the apertures67is 3 μm or less, it is supposed that a sufficient quality of light cannot be obtained for causing the device to function as the transmittive type unless a plurality of apertures67are provided according to the size of the pixel electrodes66. In contrast, when many apertures67are provided to increase the total area of the apertures67, the quantity of transmitted light in the transmmisive type is increased, but a display screen in use as the reflective type is darkened due to a decrease in quality of reflected light corresponding to an increase in quality of transmitted light. It was found by experiment that when the area of the apertures67is set to 10 to 25% of the area of the pixel electrodes66, the transmissive display is well balanced with the reflective display. The area of the pixel electrodes66strictly means the area of the intersections of the pixel electrodes and the data lines, i.e., the effective display region not shielded by the black matrix or the like.

Returning toFIG. 1, a plurality of terminal13aare formed on the projecting portion of the first substrate7aserving as the element substrate. These terminals are formed at the same time the pixel electrodes66are formed on the region of the surface of the first substrate7a, which is opposed to the second substrate7bserving as the counter substrate. Also, a plurality of terminal13bare formed on the projecting portion of the second substrate7b. These terminals are formed at the same time the data lines52are formed on the region of the surface of the second substrate7b, which is opposed to the first substrate7a.

Each of the FPC3aand FPC3bcomprises a flexible base layer made of polyimide or another material, and a metal film pattern formed on the base layer. A plurality of terminals22are provided at a side end of the FPC3b, and are conductively connected to the terminals13bof the second substrate7bwith a conductive adhesive element such as ACF or the like. A plurality of terminals23formed at another side end of the FPC3bare connected to terminals (not shown) provided at an appropriate position of the control substrate5.

On the other hand, in the FPC3a, a plurality of panel side terminals14are formed on the back (the lower side shown inFIG. 1) at the side end on the liquid crystal panel2side, and a plurality of control substrate side terminals16are formed on the surface (the upper side shown inFIG. 1) at the side end opposite to the liquid crystal panel2side. Also, a wiring pattern18is appropriately formed over a wide range of the surface of the FPC3aso that one end of the wiring pattern18is connected directly to the control substrate side terminals16, and the other end is connected to the panel side terminals14via through holes19.

The light source devices21which constitute an illumination device in cooperation with the light guide4are mounted at appropriate intervals on a line on the back of the FPC3a, i.e., the side opposite to the wiring pattern18side. Wiring for these light source devices21is connected to the control substrate side terminals16via, for example, through holes. The light emitting surface of each of the light source devices21, i.e., the side on which the lens44ashown in FIG.7(a) is formed, is arranged to face in the direction shown by arrow B inFIG. 1, i.e., the direction away from the FPC3a.

A diffusion plate27is mounted to the liquid crystal panel2side surface of the light guide4by adhesion or the like, and a reflection plate28is mounted to the surface of the light guide4, which is opposite to the liquid crystal panel2side, by adhesion or the like. The reflection plate28reflects the light received by the light receiving plane4aof the light guide4to the liquid crystal panel2. The diffusion plate28diffuses the light exiting from the light guide4to the liquid crystal panel2so that the strength is uniform in a plane.

As shown inFIG. 2, the light guide4is mounted to the non-display side of the liquid crystal panel2with a buffer32made of rubber, plastic, or the like and provided therebetween. The control substrate5is provided on the side of the light guide4, which is opposite to the side on which the reflection plate28is mounted. The control substrate5is mounted as a component of the liquid crystal device1to the non-display side surface of the light guide in some case, or mounted as a component of an electronic apparatus using the liquid crystal device1in some cases. Furthermore, terminals33are formed at a side end of the control substrate5, for connection with external circuits.

In assembling the components of the liquid crystal device1shown in an exploded state inFIG. 1, as shown inFIG. 2, the liquid crystal panel2side end of the FPC3ais bonded to the projecting portion of the first substrate7awith ACF34. This bonding causes conductive connection of the terminals13aof the first substrate7aand the terminals14of the FPC3athrough the conductive particles contained in the ACF34. Then, the FPC3ais bent along the light receiving plane4aof the light guide4, and the side end of the FPC3ain the bent state is overlapped with the side end of the control substrate5. The terminals16on the FPC3aare connected to the terminals33on the control substrate5by soldering or another conductive connection method.

In bending the FPC3afor conductive connection, as described above, the light emitting planes of the plurality of light source devices21mounted on the surface of the FPC3a, i.e., the planes on each of which the lens44ais provided, are arranged to face the light receiving surface4aof the light guide4. In this way, the light source devices21are arranged to face the light receiving surface4aof the light guide4to form the illumination device for supplying light to the liquid crystal panel2. Similarly, in the other FPC3bshown inFIG. 1, the side end where the terminals23are formed is conductively connected to the terminals formed at the appropriate portion of the control substrate5.

When the positions of the light source devices21relative to the light receiving plane4aare desired to be precisely determined, appropriate positioning means is preferably provided for positioning the light source devices21relative to the light guide4. As a conceivable example of such positioning means, as shown inFIG. 8, a plurality of positioning pins26are preferably provided at appropriate positions of the base42, and recesses are provided at the positions of the light receiving plane4aof the light guide4corresponding to the pins26so that the pins26can be tightly contained in the recesses. When the light source devices21are arranged opposite to the light receiving plane4aof the light guide4, the pins26are engaged in the recesses to position the light source devices21.

In this embodiment, the X direction in which the light exiting from the light source device41A shown in FIG.7(a) has no directivity coincides with the width direction X of the light guide4shown inFIG. 1, and the Y direction in which the light exiting from the light source device41A shown in FIG.7(a) has high directivity coincides with the height direction Y of the light guide4shown in FIG.1.

In the liquid crystal device1constructed as described above, when the LED43shown in FIG.2and serving as the light emitting device emits light, the light passes through the lens44A and is supplied to the inside of the light guide4through the light receiving plane4a. At this time, since the directivity of the light exiting from the light source device21is set to be high in the height direction (i.e., the Y direction) of the light guide4in which the dimension of the light receiving plane4ais small, the light from the light source device21can be condensed and incident on the light guide4as much as possible. Therefore, the efficiency of incidence of light on the light guide4can be improved. On the other hand, the directivity of the exiting light is set to be low in the width direction (i.e., the X direction) of the light guide4in which the dimension of the light receiving plane4ais large, so that the light is scattered, whereby uniformity of intensity of light can be achieved.

The light incident on the light guide4is reflected by the reflection plate28, travels to the liquid crystal panel2, and then supplied to the liquid crystal panel2after it is diffused by the diffusion plate27so that the intensity is uniform in a plane. The component of the supplied light, which is transmitted through the polarizer plate12aon the guide plate side is supplied to the liquid crystal layer, and modulated for each pixel by the liquid crystal with the orientation controlled for each pixel according to the change in the voltage applied between the pixel electrodes66and the data lines52. Furthermore, the modulated light is transmitted through the display side polarizer plate12bto display an image on the outside.

In the illumination device used in the liquid crystal device1of this embodiment, the light exiting from the light source device has directivity in the height direction of the light guide in which the dimension is small, and the light exiting from the light source device has no directivity in the width direction of the light guide in which the dimension is large so that the light exiting from the light source device21can be efficiently received by the light guide4. As a result, light with high strength can be caused to exit from the light exiting plane of the light guide4, i.e., the plane on which the diffusion plate27is provided, with uniformity in a planar matter. Therefore, a bright, clear image can be displayed in the display region of the liquid crystal panel2.

In this embodiment, as shown inFIG. 1, the light source devices21are mounted to the same plane of the FPC3aas the terminals14provided on the liquid crystal panel2side, and the wiring pattern18of the FPC3ais provided on the side opposite to the light source device21side so that it is connected to the terminals14through the through holes19. However, the light source devices21may be mounted on the same plane as the wiring pattern18in place of the above construction.

Although, in this embodiment, as shown inFIG. 2, the light source devices21are supported by the FPC3acomprising a flexible substrate, the light source devices21can be supported by a non-flexible substrate such as an epoxy resin substrate in place of the flexible substrate. In this case, by positioning the non-flexible substrate relative to the light guide4, the light source devices21can be positioned relatively to the light receiving plane41of the light guide4.

Although, in this embodiment, the present invention is applied to an active matrix system transflective liquid crystal device using TFDs, the present invention can also be applied to other various system liquid crystal devices, for example, a reflective liquid crystal device, a transmissive liquid crystal device, an active matrix system liquid crystal device using switching elements other than TFD, a passive matrix system liquid crystal device without using switching elements, etc.

Although this embodiment uses the light source device41A shown in FIG.7(a) as each of the light source devices21, of course, the light source device41B shown in FIG.7(b) and the light source device41C shown inFIG. 7(c) can also be used. Of course, the positioning pins26shown inFIG. 8can be provided on each of the light source devices41B and41C so that each of the light source devices41B and41C can be positioned relative to the light guide4.

FIG. 9shows an embodiment in which the liquid crystal device of the present invention is used as a display device of one of various electronic apparatuses. The electronic apparatus shown inFIG. 9comprises a display information output source100, a display information processing circuit101, a power supply circuit102, a timing generator103, and a liquid crystal device104. The liquid crystal device104comprises a liquid crystal panel105and a driving circuit106. The liquid crystal device1shown inFIG. 1can be used as the liquid crystal device104, and the liquid crystal panel2shown inFIG. 1can be used as the liquid crystal panel105.

The display information output source100comprises memory such as ROM (Read Only Memory), or RAM (Random Access Memory), a storage unit such as any of various disks, a tuning circuit for tuning and outputting digital image signals, etc. and supplies display information such as an image signal in a predetermined format to the display information processing circuit101based on any of the various clock signals generated by the timing generator103.

The display information processing circuit101comprises various known circuits such as a serial-parallel conversion circuit, an amplification-inversion circuit, a rotation circuit, gamma correction circuit, a clamp circuit, etc. and executes processing of the input information to supply the image signal to the driving circuit106together with the clock signal CLK. The driving circuit106is a general term for the scanning line driving circuit57and the data line driving circuit58shown inFIG. 3, an inspection circuit, and the like. The power supply circuit102supplies predetermined electric power to each of the components.

FIG. 10shows a mobile personal computer as an electronic apparatus in accordance with an embodiment of the present invention. The personal computer110shown inFIG. 10comprises a body112comprising a keyboard111, and a liquid crystal display unit113. The liquid crystal display unit113comprises the liquid crystal device1shown in FIG.1.FIG. 11shows a cell phone as an electronic apparatus in accordance with another embodiment of the present invention. The cell phone120shown inFIG. 11comprises a plurality of operating buttons121and a liquid crystal device1.

The liquid crystal device1used in the embodiment shown in each ofFIGS. 10 and 11is a transflective liquid crystal device, as described above with reference to FIG.1. Therefore, even when the computer or cell phone is placed in a portion where external light is insufficient, a display can be seen without any trouble by lighting the illumination device, i.e., a back light, comprising the light source device and the light guide4.

As described above, a light source device of the present invention has the property that by virtue of a lens provided on a light emitting plane of a light emitting device, exiting light has high directivity in one direction, and low directivity in the direction perpendicular to the one direction. Namely, light with high strength is emitted in a limited narrow range in the one direction, and light is scattered all around at any wide angle in the direction perpendicular to the one direction. Therefore, the one direction and the perpendicular direction are appropriately set according to the shape of an object to which light is supplied, to suppress ineffective travel of light to a portion other than the object. As a result, light can be efficiently incident on the object.

In an illumination device of the present invention, the directivity of the light exiting from a light source device is set to be high in the height direction of a light guide in which the dimension of a light receiving plane is small, so that the light from the light source device can be incident on the light guide as much as possible, thereby improving the efficiency of incidence of light on the light guide. Also, the directivity of the light exiting from a light source device is set to be low in the width direction of the light guide in which the dimension of the light receiving plane is large, so that light is scattered, achieving uniformity in luminous intensity.

In the illumination device used in a liquid crystal device and electronic apparatus of the present invention, the efficiency of incidence of light on the light guide can be increased, thereby achieving a bright display easy to see in the display region of the liquid crystal device.