JP2000200049A - Reflection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove illumination unevenness which occurs when spot light sources are used for the front light of a reflection type display device. SOLUTION: The display device has a panel 0 of a reflection type, a light transmission plate 20 disposed thereon, the spot light sources 30 disposed at its one end and a reflection member 40 disposed at its other end. The spot light sources 30 consist of the plural spot light sources arrayed discretely along the one end of the light transmission plate 20. The light transmission plate 20 make plural beams of the illumination light emitted from the plural spot light sources 30 uniform and guide these beams from the one end to the other end. The reflection member 40 reflects the beams of the illumination light made uniform and turns back the beams from the other end toward the one end of the light transmission plate 20. The light transmission plate 20 guides the turned back illumination light, makes the light incident on the panel 0 and emits the illumination light reflected from the panel 0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a reflection type display device which performs display using external light such as natural light. More specifically, the present invention relates to an illumination structure of a reflective display device which is used as an auxiliary when external light is scarce.

[0002]

2. Description of the Related Art Flat panel display devices represented by a liquid crystal display are roughly classified into a transmission type and a reflection type. In a transmissive display device, a panel holding a liquid crystal or the like as an electro-optical material is created between a pair of transparent substrates, and a light source for illumination (backlight) is arranged on the back side, and an image is formed from the front of the panel. Observe. In the case of a transmissive type, a backlight is indispensable and, for example, a fluorescent tube is used. For this reason, the backlight consumes most of the power when viewed as a whole display, and is not suitable for a display of a portable device. On the other hand, in a reflective display device,
While a reflector is disposed on the back of the panel, external light such as natural light is incident on the panel from the front, and the reflected light is used to observe an image from the front. Unlike the transmissive type, which does not use a light source for backlighting, the reflective type requires relatively low power consumption and is suitable for a display of a portable device.

[0003]

However, the reflection type display device cannot observe an image in an environment where external light is poor such as at night. In order to solve this drawback, a reflection type display device provided with a front light that is turned on when necessary, such as at night, has been proposed, and this is shown in FIG. The light guide plate 20 is attached to the surface of the reflective panel 0.
A light source 30 is disposed at an end of the light guide plate 20, and the light source 30 is partially covered with a reflecting mirror 31. As the light source 30, a fluorescent tube (linear light source) having a long shape can be used. On the surface of the light guide plate 20, for example, a slope 21 having an inclination angle of 45 ° and a substantially flat trapezoid 22 are formed.
Illumination light emitted from the light source 30 is totally reflected by the slope 21 formed on the surface of the light guide plate 20 and guided to the panel 0 located below the light guide plate 20. Therefore, even under a dark environment, the image of the panel 0 can be displayed by the illumination of the light source 30.

FIG. 8 is an explanatory diagram of functions of a front light incorporated in the reflection type display device shown in FIG. As shown in the figure, the front light includes a light guide plate 20 and a light source 30 disposed at an end thereof and generating illumination light as needed. The light guide plate 20 normally transmits external light, enters the panel 0, and emits external light reflected from the panel 0, and guides illumination light as needed to enter the panel 0 and transmits the external light.
The illumination light reflected from the light source is emitted. Specifically, the light guide plate 2
Reference numeral 0 denotes a light source 30 having a trapezoidal portion 22 divided into strips and an inclined slope portion 21 located between the trapezoidal portions 22.
The illumination light emitted from each of the inclined surfaces 21 is reflected by each slope portion 21 to be incident on the panel 0, and the illumination light reflected from the panel 0 is emitted from each trapezoidal portion 22 toward the observer.

FIG. 9 is a schematic plan view showing an improved example of the reflective display device with the front light shown in FIG.
In this example, instead of a linear light source such as a fluorescent tube, the end of the light guide plate 20 in which the slope portion and the trapezoidal portion are formed in a stripe shape,
A plurality of light sources 30 including light emitting diodes (LEDs) are arranged. The LEDs are generally regarded as point light sources, and a plurality of LEDs are arranged along the end of the light guide plate 20 to replace the fluorescent tubes. However, although a point light source such as an LED has an advantage that it is easier to handle and has a more compact mounting than a linear light source such as a fluorescent tube, as shown in FIG. There is a problem that occurs.

In recent years, white LEDs have been developed, and a fluorescent tube can be used in some applications. In fact, as shown in FIG. 10, a backlight using a point light source 30 and a light guide plate 20 is supplied to the market in combination with a transmissive panel 0. In the case of a backlight, even if an LED that easily causes streaks or unevenness is used as the light source, the streaks or unevenness can be eliminated by applying some kind of diffusion system to the back surface of the light guide plate 20. In the example of FIG. 10, a diffusion layer 29 is disposed on the bottom surface of the light guide plate 20 to eliminate streaks and unevenness. In the case of the backlight, no matter what kind of diffusing means is applied, since it is located on the back side of the panel 0, the observer cannot see it and there is no adverse effect on the image quality. On the other hand, since the front light combined with the reflection type display device is arranged on the side of the observer who looks at the panel, if the light guide plate is directly provided with the diffusing means, the image quality will be deteriorated. Accordingly, the light guide plate of the front light itself could hardly be expected to have the function of eliminating uneven streaks. In fact, the end of the front light guide plate is LE
When D is directly attached, as shown in FIG. 9, streaks are generated along the light beam emitted from the point light source, and the image quality is significantly impaired. From the above, conventionally, only a fluorescent tube which is a line light source can be used as a front light. An object of the present invention is to solve the above-described problem of uneven streaks and to provide a front light using a point light source that satisfies light use efficiency, uniformity, and image quality.

[0007]

The following means have been taken in order to solve the above-mentioned problems of the prior art and achieve the object of the present invention. That is, the reflective display device according to the present invention basically includes:
It includes a panel, a light guide plate, and a light source. The panel is of a reflection type, and a transparent first substrate located on the side of incidence of external light,
A second substrate joined to the first substrate via a predetermined gap and positioned on the reflection side, an electro-optical material held in the gap, and the electric substrate formed on at least one of the first and second substrates; An electrode for applying a voltage to the optical material is provided. The light guide plate is disposed outside the first substrate of the panel and forms a front light. The light source is provided at one end of the light guide plate and generates illumination light as needed. As a characteristic feature, a reflection member is provided at the other end of the light guide plate (the side opposite to the one end where the light source is provided). The light source comprises a light emitting diode disposed at one end of the light guide plate. In such a configuration, the light guide plate functions as an integrator that equalizes the illumination light emitted from the light source and guides the light from one end to the other end. The reflection member reflects the uniformed illumination light and folds it from the other end to the one end of the light guide plate. The light guide plate guides the folded illumination light to form the first light guide panel.
The illumination light that is incident on the substrate and reflected from the second substrate of the panel is emitted. Thus, this light guide plate functions as a front light. When the light source is not turned on, the light guide plate transmits external light, enters the first substrate of the panel, and emits external light reflected from the second substrate.
That is, in an environment where the outside light is abundant, such as in the daytime, the light guide plate simply exists on the front surface of the panel as a transparent plate.

Preferably, the light guide plate has a trapezoidal portion divided into strips and an inclined slope positioned between the trapezoidal portions. The illumination light reflected by the portion and incident on the first substrate of the panel is emitted from each trapezoidal portion while the illumination light reflected by the second substrate of the panel is emitted. Preferably, the angle of inclination of the slope is shifted from 45 degrees, and unnecessary reflection of the illumination light from one end of the light guide plate toward the other end by the slope is removed from the normal direction of the panel. Alternatively, a polarizing plate may be disposed on one or both sides of the light guide plate at one end of the light guide plate to remove the S-polarized component from the illumination light and to suppress unnecessary reflection by the inclined surface portion. Alternatively, an optical unit for narrowing the incident angle of the illumination light entering the one end of the light guide plate from the light emitting diode is provided, and leakage of the illumination light guided from one end to the other end of the light guide plate can be prevented. Alternatively, a light absorption band may be arranged in a predetermined range on one or both sides of the light guide plate at one end side of the light guide plate, and components of the illumination light leaking from the light guide plate may be removed in advance.

In the above-mentioned reflection type display device, the light guide plate itself has both the function of the integrator for the point light source and the function of the front light. The present invention also includes a structure in which the functions of the integrator and the front light are divided into separate light guide plates. That is, the present reflective display device has a panel, transparent first and second light guide plates disposed on the outside of the panel, and illumination light provided as needed at one end of the first light guide plate. A light source to be generated; and a connecting member for optically connecting the other end of the first light guide plate and the other end of the second light guide plate. The light source comprises a light emitting diode disposed at one end of the first light guide plate. The first light guide plate equalizes the illumination light emitted from the light source and guides it from one end to the other end.
That is, the first light guide plate functions as an integrator. The connection member turns the uniformed illumination light back and introduces it from the other end of the first light guide plate to the other end of the second light guide plate. The second light guide plate normally transmits external light to enter the panel and emits external light reflected from the panel, and guides the folded illumination light as needed to enter the panel, and The illumination light reflected from the panel is emitted. That is, the second light guide plate functions as a front light.
This is a structure in which the integrator and the front light are connected to each other via a connection member. Preferably, the first light guide plate also serves as a touch sensor combined with the panel. Also preferably, an additional connecting member is provided for optically connecting one end of the first and second light guide plates to each other, and is returned from the other end of the second light guide plate toward one end. The rest of the illuminated light is again introduced into one end of the first light guide plate for reuse.

According to the present invention, an auxiliary front illumination system for a reflective display device is constructed by using a single point light source composed of light emitting diodes or a plurality of point light sources composed of light emitting diodes arranged in a line. An integrator is used to eliminate the uneven streaks inherent in the point light source. In other words, one or a plurality of point light sources arranged discretely are converted into one line light source by the integrator. Further, the linear light source is converted into a panel surface light source to be used as a front light. In the present invention, a compact and high-quality auxiliary lighting system is obtained by integrating a light guide plate functioning as an integrator and a light guide plate functioning as a surface light source of a front light. Alternatively, a light guide plate functioning as an integrator and a light guide plate functioning as a surface light source of a front light may be separately provided, and a structure in which both are stacked may be employed.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing a first embodiment of the reflective display device according to the present invention. As shown in the figure, the reflective display device has a panel 0 and a light guide plate 2.
0, a light source 30, and a reflecting member 40. The panel 0 is of a reflection type, and includes a transparent first substrate 1 located on the incident side of external light, a second substrate 2 joined to the first substrate 1 via a predetermined gap and located on the reflection side, And an electrode formed on at least one of the first substrate 1 and the second substrate 2 for applying a voltage to the electro-optical material. The light guide plate 20 is disposed on the front side of the panel 0 (outside the first substrate 1). The light source 30 is the reflecting mirror 3
1 and is disposed at one end (right side in the drawing) of the light guide plate 20 to generate illumination light as needed, such as at night. The reflection member 40 is disposed on the other end (left side in the drawing) of the light guide plate 20. In other words, the light source 30 and the reflection member 40 face each other via the light guide plate 20. Here, the light source 30 includes a plurality of point light sources discretely arranged along one end of the light guide plate 20. For example, a light emitting diode (LED) that emits white illumination light can be used as the point light source 30. The light guide plate 20 equalizes the plurality of illumination lights emitted from the plurality of point light sources 30 to one end (right side in the drawing).
To the other end (left side in the drawing). That is, the light guide plate 2
Numeral 0 functions as an integrator and converts the discretely arranged point light sources 30 into apparent overhead light sources. The converted line light source will be exactly at the position of the reflecting member 40. The reflection member 40 reflects the uniformed illumination light and folds the light guide plate 20 from the other end on the left side in the drawing to one end on the right side in the drawing. At this time, the light guide plate 20 guides the folded illumination light to enter the first substrate 1 of the panel 0 and emit the illumination light reflected from the second substrate 2. That is, the light guide plate 20 includes the reflecting member 4.
The line light source apparently arranged at the position of 0 is converted to the surface light source for the panel 0. When the light source 30 is not turned on, the light guide plate 20 transmits the external light and transmits the first substrate 1 of the panel 0.
And the external light reflected from the second substrate 2 of the panel 0 is emitted. At this time, the light guide plate 20 merely exists on the surface of the panel 0 as a transparent plate.

A detailed description will be given below of each component of the reflection type display device. First, the light guide plate 20 has a trapezoidal portion 22 divided into strips and an inclined slope portion 21 located between the trapezoidal portions 22, and the illumination light turned back by the reflection member 40 is applied to each slope portion. The illumination light totally reflected at 21 is incident on the first substrate 1 of the panel 0, and the illumination light reflected from the second substrate 2 is emitted from each trapezoidal portion 22. The inclination angle of the slope portion 21 is, for example, 45 °, and the illumination light returned from the reflection member 40 is almost totally reflected and directed to the panel 0. On the other hand, the trapezoidal portion 20 has an inclination angle of about 1 ° and is substantially planar. For this reason, the illumination light emitted from the point light source 30 can be substantially totally reflected, and functions sufficiently as an integrator. The light source 30 is a white LED as described above. When the light guide plate 20 is made of a PMMA resin having a refractive index of n = 1.49, the critical angle of total reflection on the upper and lower surfaces is 42.2 °. In this case, the illumination light diverging from the light source 30 is
Almost 100 if within the angle range of 47.8 °
The light is totally reflected by the upper and lower surfaces of the% light guide plate 20, is made uniform, and reaches the reflection member 4 side. To adjust this angle range,
The LED of the light source 30 may have a desired directivity, or a cylindrical lens or the like may be inserted between the light source 30 and one end of the light guide plate 20. The reflecting member 40 facing the light source 30 may be specularly reflective or diffusely reflective. In some cases, a concave mirror or a convex mirror may be used to completely collimate the illumination light.

FIG. 2 schematically shows the function of the light guide plate 20 shown in FIG. 1 as an integrator.
The light guide plate 20 is made of a transparent resin having a high refractive index, for example, a thickness of 1 mm.
PMMA plate. A point light source 30 including four white LEDs is arranged at one end of the light guide plate 20 at an interval of 1: 2: 2: 1. The luminous flux emitted from each point light source 30 repeats multiple total reflection on the upper and lower surfaces of the light guide plate 20 functioning as an integrator to form a pseudo line light source. When the light reaches the reflecting member 40, it is almost completely uniform. Moreover, since total reflection is used, a light utilization efficiency of 100% can be theoretically achieved. The longer the size of the integrator, the greater the number of multiple reflections and the better the uniformity. However, if the LED has a wide directional characteristic, it is sufficient if the LED is short, and it may be almost the same as the panel size. 2A is a side view of the light guide plate 20, and FIG. 2B is a plan view of the light guide plate 20.

As described above, according to the present invention, the illumination light diverging from the point light source is made uniform by giving the integrator function to the light guide plate itself of the front light.
The front light of the present invention utilizes the light guide plate as a highly efficient integrator. That is, the LED on the opposite end
A light source is arranged, illumination light is made incident, and the illumination light is turned back at the other end having a reflection function when uniformization is performed, and is used as a front light. In particular, a white LED does not require an inverter, is light and small, has high brightness in cold weather, and has no risk of non-lighting as compared with a fluorescent tube. In addition, there are advantages such as low power consumption and no breakage. Therefore, it is very suitable as a light source for portable equipment as compared with a fluorescent tube.

In a small-sized liquid crystal panel, a single light emitting diode may provide a sufficient front illumination effect.
Even in such a case. By applying the present invention, sufficient uniformity of front illumination light and screen luminance can be obtained. By using the light guide plate for the integrator, front illumination with good uniformity can be obtained even with a small panel size and one light emitting diode. For reference, FIG. 3 shows a small-sized structure using a single light emitting diode as a light source in a conventional liquid crystal panel. As in the conventional example shown in FIG. 8, since the light guide plate is not used as an integrator, the illumination light emitted from the light emitting diode 30 does not sufficiently spread to the effective area of the panel, resulting in a shadow. Even in this case, according to the present invention,
Since the light guide plate is used as an integrator, the point light source 30 composed of a light emitting diode is arranged on the side opposite to that in FIG. 3, so that the illumination light can be made uniform and the shade shown in FIG. 3 does not occur. Therefore, the present invention is effective not only in the case of a plurality of light emitting diodes but also in the case of a single light emitting diode.

FIG. 4A schematically shows the cross-sectional structure of the reflective display device according to the first embodiment. As shown in the figure, a light source 30 composed of a light emitting diode is disposed at one end of the light guide plate, and a reflection member 40 is disposed at the other end. In the figure, a trapezoidal portion 22 formed on a light guide plate 20 is shown.
Depending on the design of the inclination angle θ2, the component of the illumination light exceeding the critical angle leaks from the light guide plate 20 without being totally reflected by the trapezoidal portion 22. The streak may be conspicuous due to the reflection when the unnecessary component re-enters the slope 21 with the inclination angle θ1.

As shown in FIG. 2B, in principle, light incident from the light source 30 at a certain incident angle α0 is the first reflection angle α.
1, the second reflection angle α2,..., The n-th reflection angle αn, and as the total reflection is repeated in the trapezoidal portion 22, the reflection angle becomes smaller due to the influence of the inclination angle θ2 of the trapezoidal portion 22. Go. In the range from the one end incidence side to the other end reflection side of the light guide plate 20, when the reflection angle αn becomes smaller than the critical angle and cannot be totally reflected at the n-th time, the illumination light leaks from the light guide plate 20. The position on the light guide plate 20 where the incident light from the light source 30 cannot satisfy the critical angle is determined by the incident angle α0. As the angle of incidence α0 is smaller, the light reaches a distant place without leaking by repeating total reflection. Now, in order to prevent the leakage of illumination light, a method of adjusting the inclination angle θ1 of the slope 21 to remove unnecessary reflected light from the normal direction of the panel (effective visual field) as shown in FIG. is there. In other words, the inclination angle θ1 of the slope 21 is shifted from 45 degrees, and unnecessary reflection of the illumination light from one end of the light guide plate 20 toward the other end by the slope 21 is removed from the normal direction of the panel. Reflections can be kept out of the observer's field of view.

As another means, as described above, the incidence angle α is increased by using a cylindrical lens or sharpening the directivity of the lens integrated with the light emitting diode.
There is a method of making 0 smaller and making it closer to parallel light. In order to adjust the incident angle range, the LED lens constituting the light source 30 has a desired directivity, or a cylindrical lens or the like is inserted between the light source 30 and one end of the light guide plate 20. By providing optical means for narrowing the incident angle of the illumination light entering the one end of the light guide plate from the light emitting diode, it is possible to prevent the leakage of the illumination light guided from one end to the other end of the light guide plate.

As another means, since the range of the incident angle α0 at which the above-mentioned streak is generated from the one end side entrance to the other end side of the light guide plate 20 is determined, the light component in this range is removed. Resolve. That is, as shown in (C), the light absorption band 3 is formed on one or both sides of the light guide plate 20 with a minimum necessary width.
3 is a method of absorbing unnecessary component light. At one end or both sides of the light guide plate 20, a light absorption band 33 is arranged in a predetermined range on one or both sides of the light guide plate 20, and components of the illumination light leaking from the light guide plate 20 are removed in advance. For example, a black tape is used for the light absorption band 33.

Alternatively, as shown in (D), instead of a light absorption band such as a black tape, a polarizing plate is stuck on one or both sides with a minimum necessary width to absorb only an S-polarized component which is an unnecessary component. There is a way to do that. FIG. 4D shows an optical path diagram in the light guide plate 20. As shown, a light source 30 composed of a light emitting diode disposed at one end of a light guide plate 20 is shown.
The illumination light emitted from the light guide plate 20 is totally reflected repeatedly on the upper and lower surfaces of the light guide plate 20, and reaches the reflection member 40 located on the other end side. In principle, the unnecessary components reflected to the observer side at the slope 21 are almost S-polarized components, and the P-polarized components pass through the slope 21 without being reflected and re-enter the light guide plate 20. Therefore, only the unnecessary S-polarized component needs to be absorbed at the time when the illumination light enters the light guide plate 20. For this purpose, a polarizing plate 35 is attached to the upper and lower surfaces of the light guide plate 20.

As shown in FIG. 4E, the absorption axis of the polarizing plate 35 is made parallel to the arrangement of the plurality of point light sources 30 arranged.
Thereby, much of the S-polarized light component can be absorbed.
In this case, the illumination light emitted from the light source 30 composed of a light emitting diode initially contains a P-polarized light component and an S-polarized light component.
It is led to. The P-polarized light component is substantially transmitted even after being incident on the inclined surface portion 21, and unnecessary reflected light reflected from the inclined surface portion 21 can be reduced to only the minutely remaining S-polarized light component. This method can reduce the optical loss to about half that of an absorption band using a black tape or the like. That is, about half of the P-polarized light component contributes to illumination as effective light, so that the illumination of the panel can be made brighter than the absorption band while the effect of eliminating streaks is equal to that of the absorption band. Incidentally, the polarizing plate 35 and the absorption band 33 may be provided in a band shape as shown in (E). However, as shown in FIG. The effect of extinguishing is obtained. In this way, light loss can be further reduced.

FIG. 5 is a schematic sectional view showing a second embodiment of the reflective display device according to the present invention. Unlike the first embodiment described above, in this embodiment, a light guide plate functioning as an integrator and a light guide plate functioning as a surface light source of a front light are separately provided. As shown in (A),
The present reflection type display device has a reflection type panel 0 and transparent first and second light guide plates 60 and 20 which are arranged to be superposed on the surface side thereof.
A light source 30 disposed at one end (right side in the drawing) of the first light guide plate 60 and generating illumination light as needed; the other end (left side in the drawing) of the first light guide plate 60; Connecting member 41 for optically connecting the other end (left side in the drawing) of the light guide plate 20
And As in the first embodiment described above, the light source 30 is covered with the reflecting mirror 31 and includes a plurality of point light sources discretely arranged along one end of the first light guide plate 60. For example, the point light source is a light emitting diode that emits white illumination light. The first light guide plate 60 functions as an integrator, equalizes a plurality of illumination lights emitted from the plurality of point light sources 30, and guides the light from one end on the right side in the drawing to the other end on the left side in the drawing. The first light guide plate 60 functions as an integrator, and a transparent plate having a high refractive index can be used. In this example, the first light guide plate 60 also serves as a touch sensor combined with the panel 0, and the surface thereof is made of ITO.
And a pattern of a transparent conductive film 61 made of the same. The connection member 41 is formed of a reflecting prism or the like, and turns the illumination light uniformed by the first light guide plate 60 to form the first light guide plate 6.
0 is introduced into the other end of the second light guide plate 20 from the other end.
The second light guide plate 20 functions as a surface light source of a front light, guides the illumination light turned back by the connection member 41, enters the panel 0, and emits the illumination light reflected from the panel 0. Specifically, the second light guide plate 20 has a trapezoidal portion 22 divided into strips and an inclined slope portion 21 located between the trapezoidal portions 22, and is folded back by the connecting member 41. The illuminating light is totally reflected by each slope 21 and is incident on the panel 0, and the illuminating light reflected from the panel 0 is emitted from each trapezoid 22 toward the observer.

As described above, in the present embodiment, in the configuration in which the touch sensor is disposed on the front light guide plate 20, the first light guide plate 60 also serving as the touch sensor is used as an integrator. Also in this case, the illuminating light diverging from the LED point light source can be made uniform with high efficiency, and can be made incident on the second light guide plate 20 serving as the surface light source of the front light.
The reflecting surface of the reflecting prism constituting the connecting member 41 is 4
Although the angle is 5 °, it is generally necessary to optimize the angle depending on the directional characteristics of the LED light. The touch sensor has a structure in which a transparent electrode 61 is formed in a sheet shape on the surface of a transparent plate such as glass. When the LED light enters the transparent electrode 61, turbidity occurs. For this reason, the transparent electrode 61 is shortened by several mm from one end of the light guide plate 60 as indicated by Z, and
Light is blocked so as not to enter the transparent electrode 61.

FIG. 2B is a schematic sectional view showing a modification of the second embodiment shown in FIG. In this variation,
An additional connecting member 42 is used to optically connect one end (the right side in the drawing) of the first and second light guide plates 60 and 20 to each other. This additional connecting member 42 also comprises, for example, a reflecting prism. The thickness of the second light guide plate 20 is gradually reduced from the left end in the drawing to the right end in the drawing. With such a configuration, the rest of the illumination light returned from the other end (left side in the drawing) of the second light guide plate 20 toward the one end (right side in the drawing) is again applied to one end of the first light guide plate 60. It can be introduced and reused. This allows
The illumination brightness of the panel 0 can be improved, and the cost and power consumption can be reduced by reducing the number of LEDs used as point light sources. Although the inclination angle of the reflection prism used as the additional connection member 42 is set to 45 °, it is actually necessary to optimize it according to the directional characteristics of the LED light. In some cases, it needs to be devised. As described above, the second light guide plate 20
Is thinner from the other end to the one end, and by making the cross-sectional size of the entrance and exit of the reflection prism constituting the connection member 42 the same, it is possible to minimize light loss. .

Finally, FIG. 6 is a schematic partial sectional view showing a specific example of the configuration of a panel incorporated in the reflection type display device according to the present invention. In this example, TN-ECB (Twist
Nematic-Electrically Con
This is a liquid crystal panel in a controlled birefringence mode. As shown in the figure, a polarizing plate 70 and a quarter-wave plate 80 are arranged on the surface of the panel 0.
The panel 0 has a first substrate 1 made of transparent glass or the like located on the incident side of external light, and a second substrate 2 located on the reflection side joined to the first substrate 1 via a predetermined gap. A nematic liquid crystal layer 3a is held in a gap between the two substrates 1 and 2. The liquid crystal molecules 4 are twist-aligned by the upper and lower alignment films 6 and 7. On the inner surfaces of the substrates 1 and 2, electrodes 10 and
11 are formed, and the nematic liquid crystal layer 3 is provided for each pixel.
Apply a voltage to a. In this example, the electrodes 10 formed on the first substrate 1 are patterned in stripes, and the electrodes 11 formed on the second substrate 2 are also formed in stripes. The electrodes 10 and 11 are orthogonal to each other, and are of a so-called simple matrix type in which pixels are defined at intersections. The polarizing plate 70 and the quarter-wave plate 80 are provided on the first substrate 1 side of the panel 0. The reflection type liquid crystal display device having such a configuration is of the TN-ECB type and is in a normally white mode. That is, when no voltage is applied, the nematic liquid crystal layer 3a functions as a quarter-wave plate while maintaining the twist alignment, and cooperates with the polarizing plate 70 and the quarter-wave plate 80 to pass external light. To display white. When a voltage is applied, the nematic liquid crystal layer 3a shifts to vertical alignment and loses the function as a quarter-wave plate, and blocks external light in cooperation with the polarizing plate 70 and the quarter-wave plate 80. Perform black display.

Each component will be described in detail with reference to FIG. As described above, the polarizing plate 70 is disposed on the surface of the first substrate 1 of the panel 0. Polarizing plate 70 and first
A quarter-wave plate 80 is interposed between the substrate and the substrate 1. The quarter-wave plate 80 is made of, for example, a uniaxially stretched polymer film, and gives a phase difference of a quarter wavelength between ordinary light and extraordinary light. The optical axis (one-axis anisotropic axis) of the quarter-wave plate 80 is arranged so as to form an angle of 45 ° with the polarization axis (transmission axis) of the polarizing plate 70. External light becomes linearly polarized light when transmitted through the polarizing plate 70. When this linearly polarized light passes through the quarter-wave plate 80, it becomes circularly polarized light. Once again, it passes through a quarter-wave plate and becomes linearly polarized. In this case, the polarization direction is rotated by 90 ° from the original polarization direction. As described above, the quarter-wave plate can rotate the polarization direction by being combined with the polarizing plate, and this is used for display.

The panel 0 basically uses, as an electro-optical material, a nematic liquid crystal layer 3a composed of nematic liquid crystal molecules 4 having a horizontal orientation and a positive dielectric anisotropy. The nematic liquid crystal layer 3a functions as a quarter-wave plate by appropriately setting its thickness. In this example, the refractive index anisotropy Δn of the nematic liquid crystal layer 3a is about 0.7, and the thickness of the nematic liquid crystal layer 3a is about 3 μm. Therefore, the retardation Δn · of the nematic liquid crystal layer 3a
d is 0.2 to 0.25 μm. As shown
By twist-aligning the nematic liquid crystal molecules 4, the retardation value described above is substantially 0.15 μm.
(150 nm). This value is approximately 1/4 of the center wavelength of external light (about 600 nm), and the nematic liquid crystal layer 3a can optically function as a quarter-wave plate. By sandwiching the nematic liquid crystal layer 3a between the upper and lower alignment films 6, 7, a desired twist alignment can be obtained. The liquid crystal molecules 4 are aligned along the rubbing direction of the alignment film 6 on the first substrate 1 side, and the alignment film 7 is aligned on the second substrate 2 side.
The liquid crystal molecules 4 are aligned along the rubbing direction. By shifting the rubbing directions of the alignment films 6 and 7 by 60 ° to 70 °, a desired twist alignment can be obtained.

The light reflection layer 8 is formed below the electrode 11 on the second substrate 2 side. The light reflection layer 8 has irregularities on the surface and has light scattering properties. Accordingly, not only is the paper white appearance preferable as a display background, but also the incident light is reflected in a relatively wide angle range, so that the viewing angle is enlarged, the display is easy to see, and the brightness of the display is increased in a wide viewing angle range. A transparent flattening layer 12 for filling irregularities is interposed between the light reflecting layer 8 and the electrode 11. The light reflecting layer 8 is composed of a resin film 15 having unevenness and a metal film 16 such as aluminum formed on the surface thereof. The resin film 15 is a photosensitive resin film having irregularities patterned by photolithography. The photosensitive resin film 15 is made of, for example, a photoresist and is applied to the entire surface of the substrate. This is exposed through a predetermined mask, and is patterned into, for example, a cylindrical shape. Then, by heating and performing reflow, the uneven shape can be formed stably. A metal film 16 made of aluminum or the like having a desired film thickness and good light reflectivity is formed on the surface of the concavo-convex shape thus formed. Several μm depth of unevenness
, Good light scattering characteristics can be obtained and the light reflecting layer 8
Has a white color. A flattening layer 12 is formed on the surface of the light reflecting layer 8 to fill the irregularities. The flattening layer 12 is preferably made of a transparent organic material such as an acrylic resin. By interposing the planarizing layer 12, the electrode 11 and the alignment film 7 can be formed stably.

[0029]

As described above, according to the present invention,
A reflection type display device having a front light structure using, for example, an LED as a point light source is realized. LED light enters from one end of the light guide plate constituting the front light, and the light guide plate functions as an integrator, thereby eliminating streaks and unevenness inherent to the point light source. Further, the illumination light uniformized by the mirror disposed on the other end side of the light guide plate is returned and guided to the panel. With the above configuration, a point light source such as an LED can be efficiently converted to a surface light source without streaks, and can be put to practical use for front light applications. Point light sources such as LEDs are easier to handle than linear light sources such as fluorescent tubes. In addition, if the light guide plate is used as both the integrator and the surface light source for the front light, it is possible to realize a thin, lightweight, and low-cost reflective display device with auxiliary front illumination with a small number of components.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view and a plan view of a light guide plate incorporated in the reflective display device according to the first embodiment.

FIG. 3 is a plan view showing a reference example of the reflective display device.

FIGS. 4A and 4B are a cross-sectional view and a plan view illustrating an improved example of the reflective display device according to the first embodiment.

FIG. 5 is a cross-sectional view showing a second embodiment of the reflective display device according to the present invention and a modified example thereof.

FIG. 6 is a partial cross-sectional view showing a specific example of a panel incorporated in the reflective display device according to the present invention.

FIG. 7 is a perspective view showing a reference example of a reflective display device having a front light.

FIG. 8 is a schematic diagram for explaining the operation of the reference example shown in FIG. 7;

FIG. 9 is a plan view showing the appearance of a reflective display device using a point light source as a front light.

FIG. 10 is a sectional view showing a conventional example of a transmission type display device provided with a backlight.

[Explanation of symbols]

0 ... Panel, 1 ... First substrate, 2 ... Second substrate, 20 ... Light guide plate, 21 ... Slope portion, 22 ...
Trapezoidal part, 30 ... light source, 31 ... reflecting mirror, 33 ...
Absorption band, 35: polarizing plate, 40: reflecting member, 4
DESCRIPTION OF SYMBOLS 1 ... Connection member, 42 ... Connection member, 60 ... Light guide plate, 61 ... Transparent electrode

Claims (10)

[Claims] 1. A transparent first substrate located on an incident side of external light, a second substrate joined to the first substrate via a predetermined gap and located on a reflection side, and electro-optic held in the gap. A panel provided with a substance and an electrode formed on at least one of the first substrate and the second substrate for applying a voltage to the electro-optical substance; a transparent light guide plate disposed outside the first substrate; A light source that is arranged at one end of the light guide plate and generates illumination light as needed,
A reflective member disposed at the other end of the light guide plate, wherein the light source comprises a light emitting diode disposed at one end of the light guide plate, and the light guide plate emits light from the light source. The reflecting member reflects the uniformed illumination light and returns from the other end of the light guide plate toward the one end to reflect the uniformed illumination light. The light plate normally transmits external light to enter the first substrate and emits external light reflected from the second substrate, and guides the folded illumination light as necessary to guide the first substrate. A reflection type display device, which emits illumination light incident on the substrate and reflected from the second substrate. 2. The light guide plate has a trapezoidal section divided into strips and an inclined slope positioned between the trapezoidal sections. 2. The reflection type display device according to claim 1, wherein the illumination light reflected from the second substrate is incident on the first substrate, and the illumination light reflected from the second substrate is emitted from each of the trapezoidal portions. 3. An undesired reflection of the illumination light from one end of the light guide plate toward the other end of the light guide plate from the normal direction of the panel by shifting an inclination angle of the slope from 45 degrees. The reflective display device according to claim 2. 4. The light guide plate according to claim 2, wherein a polarizing plate is disposed on one or both sides of the light guide plate on one end side of the light guide plate to remove an S-polarized component from the illumination light, thereby suppressing unnecessary reflection by a slope portion.
The reflective display device as described in the above. 5. An optical device for narrowing an incident angle of illumination light entering one end of a light guide plate from a light emitting diode, and preventing leakage of illumination light guided from one end to the other end of the light guide plate. 2. The reflection type display device according to claim 1, wherein: 6. The light guide plate according to claim 1, wherein one end or both sides of the light guide plate is provided with a light absorption band in a predetermined range on one or both sides of the light guide plate, and a component of illumination light leaking from the light guide plate is removed in advance. 2. The reflective display device according to 1. 7. A transparent first substrate located on an incident side of external light, a second substrate joined to the first substrate via a predetermined gap and located on a reflection side, and electro-optics held in the gap A material and a panel formed on at least one of the first substrate and the second substrate and having electrodes for applying a voltage to the electro-optical material; and a transparent first and a second layer disposed outside the first substrate. A second light guide plate, a light source arranged at one end of the first light guide plate to generate illumination light as necessary, and the other end of the first light guide plate and the other of the second light guide plate. A connection member for optically connecting an end portion, wherein the light source comprises a light emitting diode disposed at one end of the first light guide plate, and wherein the first light guide plate is The illumination light emitted from the light source is made uniform and guided from one end to the other end, and the connection member folds the uniformed illumination light. In turn, the light is introduced from the other end of the first light guide plate to the other end of the second light guide plate, and the second light guide plate normally transmits external light and enters the first substrate; While the external light reflected from the second substrate is emitted, the folded illumination light is guided as necessary to produce the first light.
A reflective display device, which emits illumination light incident on a substrate and reflected from the second substrate. 8. The second light guide plate has a trapezoidal section divided into strips and an inclined slope positioned between the trapezoidal sections, and the illumination light returned by the connecting member is provided. The reflection type display device according to claim 7, wherein the illumination light reflected from each slope portion is incident on the first substrate, and the illumination light reflected from the second substrate is emitted from each trapezoidal portion. 9. The light guide plate according to claim 7, wherein the first light guide plate also functions as a touch sensor combined with the panel.
The reflective display device as described in the above. 10. An additional connecting member for optically connecting one ends of the first and second light guide plates to each other,
8. The reflection type according to claim 7, wherein the rest of the illumination light returned from the other end of the second light guide plate toward the one end is again introduced into one end of the first light guide plate for reuse. Display device.