JP2000075800A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of reducing the power consumed and achieving screen brightness suited for ambient illumination in a working environment having a wide illumination range from low to high illumination. SOLUTION: A light irradiation means 10 emitting illuminating light toward a liquid-crystal display element 1 and reflecting external light impinging thereon from in front of the display element 1 is placed behind the display element 1 and the display element 1 and the light irradiation means 10 together constitute a reflection display system by which the external light impinging thereon from in front of the display element 1 is reflected by the light irradiation means 10 and emitted in front of the display element 1 and a screen brightness compensating display system emitting the illuminating light from the light irradiation system 10 and compensating, using the illuminating light, the brightness of a screen as determined by the reflection display system. The reflectivity of the external light when the transmission of the display element 1 of the reflection display system 10 is controlled to be a maximum is set at about 16% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power-saving display device.

[0002]

2. Description of the Related Art A display device provided with a non-light-emitting display device such as a liquid crystal display device for controlling transmission of light incident from the outside to display an image is composed of a transmission display device and a reflection display device. There is.

In the transmissive display device, a backlight is arranged behind the display element, and display is performed using illumination light from the backlight. Illumination light from the backlight is transmitted to the display element. And the light is emitted to the front of the display element for display.

Further, the reflection type display device displays an image by using external light which is light of an environment in which the display device is used, and external light incident from the front of the display element is provided behind the display element. The light is reflected by the disposed reflector toward the display element, and the light is emitted to the front of the display element for display.

[0005] Comparing the transmissive display device with the reflective display device, the transmissive display device always turns on the backlight to perform display, and thus consumes power for lighting the backlight.

The preferred screen brightness of the display device varies depending on the illuminance of the environment in which the display device is used. For example, in a dark environment such as outdoors at night, display is performed even if the screen brightness is relatively low. Although observation can be performed with sufficient brightness, for example, in an environment of high illuminance such as direct sunlight, the display cannot be observed with sufficient brightness unless the screen luminance is considerably increased.

[0007] Therefore, in the transmissive display device, it is necessary to increase the light emission luminance of the backlight as the environmental illuminance increases, so that a large amount of power is consumed for lighting the backlight.

On the other hand, in the reflection type display device, reflected light having an intensity corresponding to the intensity of external light incident from the front of the display element can be obtained. And a backlight is not required, so that power consumption is small.

However, in the reflection type display device, the intensity of the reflected light emitted in front of the display element, that is, the brightness of the screen is reduced.
Since the brightness largely depends on the intensity of external light incident from the front of the display element, a screen brightness that can visually recognize a display cannot be obtained in a dark environment such as outdoors at night.

This problem is particularly remarkable in a display device using a display element having a color filter and displaying a color image by coloring transmitted light with the color filter. In this case, the light is incident on the display element. Since the light is absorbed by the color filter in the wavelength component in the absorption wavelength band and becomes colored light colored to the color of the color filter, the colored light colored by the color filter is compared with the intensity of the incident light. Is extremely weak.

[0011] In the reflective display device, the external light incident from the front surface of the display element is reflected by a reflector disposed behind the display element and emitted from the front of the display element in a color. Since the light passes through the filter twice, the light intensity is greatly attenuated by the color filter, and the intensity of the emitted colored light is extremely weak.

For this reason, conventionally, there has been proposed a reflection type display device having an auxiliary light source so that a display can be observed with sufficient brightness even in a dark environment such as outdoors at night.

[0013] The reflection type display device provided with the auxiliary light source,
Conventionally, a transflective plate is arranged behind a non-emissive display element, and an auxiliary light source is arranged behind the transflective plate.

This reflection type display device performs reflection type display by reflecting external light incident from the front of the display element by the semi-transmissive reflection plate and emitting the light to the front of the display element, and performs the auxiliary light illumination. The illumination light is emitted from the light source, and of the illumination light, the light transmitted through the semi-transmissive reflection plate is made incident on the display element from the back surface thereof, thereby compensating the screen luminance by the reflective display. According to the reflective display device, the display can be observed with sufficient brightness even in a dark environment such as outdoors at night.

Further, in this reflection type display device, the lack of the screen brightness due to the reflected light of the external light is compensated for by the illumination light from the auxiliary light source. The luminance of the illumination light emitted from the auxiliary light source in an environment in which reflected light having an intensity corresponding to the intensity is obtained is the emission luminance of the backlight in a normal transmissive display device that performs display using only illumination light from a backlight. And thus consumes less power than the conventional transmissive display device.

[0016]

However, in a conventional reflection type display device provided with an auxiliary light source, the semi-transmissive reflector reflects incident light with a reflectance according to its reflection / transmission characteristics. The reflectivity of light is considerably lower than that of a normal reflective display device having a high-reflectance reflector, and therefore, in the case of the normal reflective display device, in an illuminance environment where a sufficient screen luminance can be obtained. However, sufficient screen luminance cannot be obtained unless the auxiliary light source is turned on and the illumination light is used.

For this reason, the conventional reflection type display device provided with an auxiliary light source must turn on the auxiliary light source in a use environment in a wide illuminance range from low illuminance to high illuminance.
Since the brightness of the illumination light emitted from the auxiliary light source must be increased to some extent, it is not as large as that of a normal transmissive display device that displays only by using the illumination light from the backlight. Consume.

The present invention provides a display device which requires less power consumption and can obtain a screen luminance suitable for the illuminance in a wide usage range from low illuminance to high illuminance. It is intended for that purpose.

[0019]

A display device according to the present invention comprises:
A non-light-emitting display element that controls transmission of light incident from the outside and displays the light, and is arranged behind the display element, emits illumination light toward the display element, and enters from the front of the display element. A light irradiating unit that reflects external light toward the display element, and the display element and the light irradiating unit reflect the external light incident from the front of the display element by the light irradiating unit. A reflection display system that emits light in front of a display element, and a screen luminance compensation display system that emits the illumination light from the light irradiation unit and compensates the luminance of the display element screen by the reflection display system using the illumination light. And the reflectance of the external light when the transmittance of the display element of the reflective display system is controlled to a maximum is about 1
It is characterized by being set to 6% or more.

In this display device, the illuminance of the use environment is
When the illuminance is such that a sufficient screen luminance can be obtained in a reflective display using external light, a reflective display in which external light incident from the front of the display element is reflected by the light irradiation means and emitted to the front of the display element. Performing reflective display by the system, when the illuminance of the use environment is the illuminance at which sufficient screen luminance cannot be obtained only by the reflective display by the reflective display system, by emitting illumination light from the light irradiation means, The display for compensating the screen luminance is performed by the illumination light.

That is, when the illuminance of the use environment is an illuminance at which a sufficient screen luminance can be obtained by the reflection type display using external light, the illuminating light is not emitted from the light irradiating means. Performing a reflective display by the reflective display system, and when the illuminance of the use environment is an illuminance in which screen luminance is insufficient with only the reflective display by the reflective display system,
The illumination light is emitted from the light irradiating means to compensate for the lack of the screen luminance due to the reflective display, and when the illuminance of the use environment is almost 0 lux, that is, when almost no external light is obtained, The display is performed only by the illumination light emitted from the light irradiation means.

Therefore, according to this display device, even under an illuminance environment in which sufficient screen luminance cannot be obtained by the display using only the reflection display system, illumination light is emitted from the light irradiating means by the insufficient screen luminance. By doing so, it is possible to obtain a screen luminance suitable for the environmental illuminance in a usage environment in a wide illuminance range from low illuminance to high illuminance.

In the display device, when the illuminance of the use environment is an illuminance at which a sufficient screen luminance can be obtained by the reflective display using external light, the illumination light is not emitted from the light irradiating means. In addition, since the reflective display is performed by the reflective display system, the power consumption of the light irradiation means at that time is zero.

Further, in this display device, the reflectance of external light when the transmittance of the display element of the reflective display system is controlled to the maximum is set to about 16% or more.
External light can be used efficiently.

For this reason, if the environmental illuminance is not less than a certain level, the illumination light is not emitted from the light irradiating means.
Since it is possible to obtain a suitable screen luminance with respect to the environmental illuminance only by the reflected light of the external light, the illumination light is emitted from the light irradiating means only in a usage environment in a limited illuminance range where the illuminance is less than a certain level In addition, even if the lack of screen luminance due to reflected light of external light is compensated for by illumination light from the light irradiating means, the luminance of illumination light emitted from the light irradiating means may be relatively low, The power consumption of the light irradiation means is small.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the display device of the present invention directs illumination light toward the display element behind a non-light-emitting display element that controls transmission of light incident from the outside. A light irradiating unit that emits and reflects external light incident from the front of the display element toward the display element is disposed, and the display element and the light irradiating unit cause the external light to enter from the front of the display element. A reflective display system for reflecting light by the light irradiating means and emitting the light forward of the display element; and irradiating the illumination light from the light irradiating means and compensating for the brightness of the screen by the reflective display system with the illuminating light. By configuring a screen brightness compensation display system and setting the reflectance of external light to about 16% or more when the transmittance of the display element of the reflection display system is controlled to a maximum, power consumption is reduced. Sorry Also, in the environment of use in a wide illumination range of high illuminance from low illuminance, in which to be able to obtain suitable screen luminance for the environmental illumination.

In the display device of the present invention, when the display element has a color filter, for example, the reflectance (the transmittance of the display element) when the aperture ratio of the display element of the reflective display system is 100%. Is set to 70%, and the aperture ratio of the display element is about 60%.
% Or more and by providing a color filter having a transmittance of 36%, the reflectance of external light in the reflective display system when the transmittance of the display element is controlled to a maximum is about 16%.
Or more.

Further, the reflectivity of the external light of the reflective display system is more preferably set to 20% or more. By setting the reflectivity of the external light in this way, the utilization efficiency of the external light is improved. Higher, the luminance of the illuminating light emitted from the light irradiating means is further reduced, and the range of the environmental illuminance for emitting the illuminating light from the light irradiating means is further narrowed to further reduce the power consumption of the light irradiating means. Can be reduced.

Furthermore, in the display device of the present invention,
The light irradiating means includes an illumination luminance control means for controlling the luminance of the illumination light according to the environmental illuminance, so that the screen luminance is a predetermined luminance range according to the environmental illuminance,
It is preferable to set a luminance control condition of the illumination light by the illumination luminance control unit, and by configuring the light irradiation unit as described above, a screen more suitable for the environmental illuminance in accordance with the environmental illuminance. Brightness can be obtained.

In this case, the illumination luminance control means is constituted by an illuminance detector for measuring environmental illuminance, and means for controlling the luminance of illumination light emitted from the light irradiating means based on the measured environmental illuminance. It is preferable that the brightness of the illumination light be controlled in accordance with the illuminance of the actual use environment, and a screen brightness suitable for the illuminance of the environment can be obtained.

Furthermore, the light irradiating means includes means for irradiating the display element with illumination light, and reflecting means for reflecting external light incident from the front of the display element and irradiating the reflected light to the display element. The light irradiating means is preferably a light source, an emission surface for guiding illumination light from the light source and emitting the light toward the display element, and And a light guide having a reflection surface different from the emission surface for reflecting external light incident from the front toward the display element.

In this light irradiating means, since the emission surface of the illumination light and the reflection surface of the external light are different surfaces, the emission rate of the illumination light from the emission surface and the reflectance of the reflection surface are respectively set to You can choose your own.

Therefore, the efficiency of using the illumination light from the light source is increased by increasing the emission rate of the illumination light from the emission surface,
The light emission luminance of the light source is reduced by that much, and the power consumption is further reduced, and the reflectance of the reflective surface is controlled when the transmittance of the display element of the reflective display system is controlled to the maximum. About 16% or more (more preferably, 20% or more)
Can be chosen to be

As the light irradiating means in which the emission surface of the illumination light and the reflection surface of the external light are different from each other, the light guide has at least one end face provided with illumination light from the light source. With the incident end face to be taken in, the front face is formed as a step-shaped surface consisting of a plurality of step faces gradually decreasing from the incident end face side to the other end side and a plurality of step faces connecting these step faces. A reflection film provided on one of the plurality of step surfaces and the light guide back surface to form a reflection surface of the external light, and an emission surface of illumination light incident from the incident end face by the plurality of step surfaces. Is formed on the front surface side of the light guide, the external light entering from the front of the display element and the light reflected by the reflection surface are transmitted, and emitted from each step surface of the light guide. Optical unit that emits illumination light toward the display element That was placed is desirable.

According to this light irradiating means, the illumination light taken into the light guide from the incident end face is emitted from the plurality of step surfaces of the step-shaped surface of the light guide, and the light is transmitted to the optical member. Thus, the light is emitted toward the display element and the illumination light from the light source can be made incident on almost the entire display element.

According to this light irradiation means, one of the plurality of step surfaces of the stepped surface of the light guide and the back surface of the light guide is a reflection surface for external light, and External light incident from the front of the element is transmitted through the optical member and reflected by the reflection surface, and the reflected light is transmitted again through the optical member and emitted toward the display element. Most of the external light incident from the display element can be reflected without waste, and can be incident on almost the entire display element.

In this light irradiation means, the optical member is formed of a transparent plate having a front surface for emitting light toward the display element and a back surface facing the front surface of the light guide. A projection-shaped incident portion having an incident surface that captures light emitted from each step surface of the light guide and a refraction surface that refracts light captured from the incident surface toward the front is formed. preferable.

[0038] With this configuration of the optical member, most of the light emitted from each step surface of the light guide is taken into the optical member without waste and emitted from the front surface toward the display element. Can be.

Further, by configuring the optical member as described above, light emitted from each step surface of the light guide and incident on each incident portion of the optical member from the incident surface is
The light is refracted by the refraction surface and is condensed in a predetermined direction. From the front surface of the optical member, it is possible to emit illumination light having a high luminance distribution in a predetermined direction (for example, a front direction), and the light guide. The external light reflected by the reflection surface can also be emitted from the front surface of the optical member as light having a high luminance distribution in a predetermined direction (for example, the front direction).

Further, in this display device, it is preferable to provide a light diffusing means on at least one of between the light irradiation means and the display element and on the front side of the display element. Accordingly, the illumination light from the light irradiation means and the reflected light of the external light can be diffused by the light diffusion means and emitted forward as light having a substantially uniform luminance distribution.

Therefore, even when the illumination light from the light irradiating means is superimposed on the reflected light of the external light to supplement the screen brightness, the illumination light emitted by the light irradiating means in an environment where almost no external light can be obtained. Even when performing display only by itself, and also when performing display by only reflected light of external light without emitting illumination light from the light irradiating means, the screen brightness is made uniform over the entire screen, and in front of the display element. By widening the emission angle range of the emitted light, a wide viewing angle can be obtained.

[0042]

FIG. 1 is a side view of a display device showing an embodiment of the present invention. The display device includes a non-light-emitting type display element 1 for controlling transmission of light incident from the outside and displaying the same. Light irradiation that is disposed behind the display element 1 and emits illumination light toward the back of the display element 1 and reflects external light incident from the front of the display element 1 toward the back of the display element 1. Means 10.

Non-light-emitting display element 1 used in this embodiment
Is a liquid crystal display element for displaying a multicolor image such as a full-color image.

FIG. 2 is an enlarged sectional view of a part of the liquid crystal display element 1. The liquid crystal display element 1 has a front side and a back side joined to each other via a frame-shaped sealing material 3 (see FIG. 1). On the inner surfaces of the pair of transparent substrates 2a and 2b, respectively.
Transparent electrodes 4 and 5 that form a plurality of pixel regions by regions facing each other are provided, and a plurality of colors respectively corresponding to the plurality of pixel regions, for example, on the inner surface of one of the substrates, for example, the front substrate 2a. Three color filters 6R, 6G, and 6B of red, green, and blue are provided, and a liquid crystal layer 8 is provided in a region surrounded by the sealing material 3 between the pair of substrates 2a and 2b. .

The liquid crystal display element 1 is of an active matrix type using a TFT (thin film transistor) as an active element. The electrodes 5 provided on the inner surface of the rear substrate 2b have a plurality of electrodes arranged in a matrix. It is a pixel electrode.

Each of the pixel electrodes 5 is connected to a plurality of TFTs (not shown) provided on the inner surface of the rear substrate 2b so as to correspond to the respective pixel electrodes 5, respectively.
The plurality of TFTs are connected to a gate line and a data line (not shown) wired on the inner surface of the rear substrate 2b.

The electrode 4 provided on the inner surface of the front substrate 2a is a single-film counter electrode facing all of the plurality of pixel electrodes 5, and the counter electrode 4 is formed of the color filter 6R. , 6G, 6B.

Further, the liquid crystal display element 1 is of a TN (twisted nematic) type having polarizing plates 9a and 9b on the front and back sides thereof.
The liquid crystal molecules of the liquid crystal layer 8 provided between the substrates 2a and 2b are aligned with the alignment films 7a and 7 provided on the inner surfaces of the substrates 2a and 2b, respectively.
b restricts the orientation direction in the vicinity of each of the substrates 2a and 2b, is twisted at a predetermined twist angle (for example, approximately 90 °) between the substrates 2a and 2b, and the polarizing plates 9a and 9b are respectively Are attached to the outer surfaces of the pair of substrates 2a and 2b, respectively, with their transmission axes oriented in a predetermined direction.

Next, the light irradiating means 10 will be described. The light irradiating means 10 has one end face as a light incident end face 11a, and has the liquid crystal display element 1 provided on the front surface opposite to the rear face of the liquid crystal display element 1. And a light guide 11 formed with a reflection surface 14 for external light incident from the front of the lens and an emission surface (each step surface 12b of a step-shaped surface 12 described later in this embodiment) of illumination light incident from the incident end surface 11a. A light source 16 disposed opposite to the incident end face 11a of the light guide 11;
And a specular reflection plate 19 arranged opposite to the back surface of the light guide 11 and an optical member 20 arranged on the front side of the light guide 11.

FIG. 3 is an enlarged side view of a part of the light guide 11 and the optical member 20 constituting the light irradiation means 10, and FIG.
FIG. 2 is an enlarged perspective view of a part of the light guide 11.

The light guide 11 is a transparent plate made of an acrylic resin or the like, and one end surface thereof is an incident end surface 11a for taking in the light from the light source 16, and the front surface is from the incident end surface 11a side. It was formed so as to gradually decrease toward the other end side (narrow the gap with the back of the light guide).
A plurality of step surfaces 12a parallel to each other;
And a plurality of stepped surfaces 12b connecting the steps, the stepped surface 12 having a minute pitch.

The plurality of step surfaces 12b are surfaces substantially parallel to the incident end surface 11a, and the step surface 12a between these step surfaces 12b is in the width direction of the light guide 11 (the length of the incident end surface 11a). (Horizontal direction).

As shown in FIG. 4, the entire surface of the stepped surface 12a is covered with SiO.
_{2 A} base reflection film 1a formed by depositing a base film 13a made of (silicon oxide) and depositing a high reflectance metal film 13b made of aluminum or the like on the entire surface of the base film 13a.
3 is provided, and the surface of the reflection film 13 (the metal film 1) is provided.
3b) is a reflection surface 14 for external light incident from the front of the liquid crystal display element 1.

The underlayer 13a made of SiO _{2 is used.}
Is provided to increase the adhesion between the light guide 11 made of acrylic resin or the like and the metal film 13b made of aluminum or the like.

Each step surface 12 of the step-shaped surface 12
b is a light transmitting surface on which no reflection film is formed, and these step surfaces 12b are emission surfaces of illumination light incident from the incident end surface 11a.

Further, as shown in FIG. 4, the rear surface of the light guide 11 has a light diffusing surface 15 for averaging the luminance distribution of the illumination light incident from the incident end face 11a in the light guide width direction. It has become.

The light diffusing surface 15 includes a plurality of vertically elongated prism portions 15 a having a length extending over the entire length of the light guide 11.
1. The reflector 19 has a shape formed in parallel with each other at a fine pitch so as to be continuous in the width direction. The reflector 19 is arranged such that its reflection surface is close to or in contact with the tops of the plurality of prism portions 15a. I have.

The light source 16 includes, for example, a straight tubular fluorescent lamp 17 having a length extending over the entire length of the incident end face 11a of the light guide 11, and a reflector 18 for reflecting the radiated light from the fluorescent lamp 17. This light source 1
Numeral 6 is arranged on the side of the light guide 11 so as to face the incident end face 11a.

On the other hand, the optical member 20 emits the light incident from the front surface thereof to the rear surface and is reflected by the reflection surface 14 (the surface of the reflection film 13) on each step surface 12a of the light guide 11. The light incident from the rear surface of the optical member 20 is emitted to the front surface, and each step surface (emission surface) 1 of the light guide 11 is output.
It has a characteristic that the illumination light emitted from 2b is taken in from the back and emitted forward.

The optical member 20 is a transparent plate made of an acrylic resin or the like having substantially the same width as the light guide 11. A plurality of incident portions 21 for taking in light emitted from each step surface 12b of the shape surface 12 are provided integrally.

Each of the plurality of incident portions 21 is formed in the shape of a horizontally long protrusion that extends over the entire width of the optical member 20.
1 is made substantially parallel to the length direction of each stepped surface 12 b of the light guide 11, and the top surface of each of the incident portions 21 is brought close to or in contact with each stepped surface 12 a of the light guide 11. It is arranged.

Each of the plurality of incident portions 21 has a triangular cross-sectional shape, and one of the two side surfaces of each of the incident portions 21 that faces the step surface 12b of the light guide 11 has one side surface. , An incident surface 21a for taking in the light emitted from the stepped surface 12b, and the other side surface is the incident surface 21a.
Is a refraction surface 21b that refracts light taken in from the front side of the optical member 20.

The incident surface 21a has an inclination substantially parallel to or close to the step surface 12b of the light guide 11, and has an angle with respect to the step surface 12a of the light guide 11 (an angle in a direction facing the step surface 12b). ) Is a plane not exceeding 90 °.

The refracting surface 21b is provided on the optical member 20.
Is an inclined surface having an inclination angle larger than the angle between the incident surface 21a and the normal line.

It is to be noted that a more desirable shape of the incident portion 21 is such that the incident surface 21a is formed so that the light guide 1
5 to 15 degrees in the direction facing the step surface 12b,
The refractive surface is 20 to 50 ° in a direction opposite to the normal line
It is an inclined shape.

The plurality of incident portions 21 are provided at a constant pitch with an interval therebetween, and a rear area between the incident portions 21 of the optical member 20 is provided with the light guide. The entrance / exit surface 22 faces the reflection surface 14 on each step surface 12a of the body 11.

The entrance / exit surface 22 is a surface having an inclination substantially parallel to or close to the step surface 12 a of the light guide 11, and enters from the front of the liquid crystal display element 1 and enters the light guide 1.
1 is a surface that transmits light reflected by the reflection surface 14 on each step surface 12a.

Further, the plurality of incident portions 21 are provided at a pitch different from the pitch of each step surface 12 b of the light guide 11. In this embodiment, as shown in FIGS. 1 and 3, each of the incident portions 21 of the optical member 20 is smaller than the pitch of each of the step surfaces 12 b of the light guide 11, and Are provided at a pitch larger than ピ ッ チ of the pitch of the optical member. Therefore, each step surface 12 b of the light guide 11
Are always opposed to at least one incident portion 21 of the optical disk.

In FIGS. 1 and 3, the stepped surface 12 of the light guide 11 and the respective incident portions 21 of the optical member 20 are greatly enlarged for convenience. The pitch is substantially the same as the pixel pitch of the liquid crystal display element 1 (the pitch of the pixel region) or is a fraction of the pixel pitch. The pitch of the step surface 12 b of the light guide 11 is the same as that of the optical member 20. The pitch is slightly larger than the pitch of the incident part 21.

Further, in the display device of this embodiment, the light guide 16 and the light source 16 arranged opposite the incident end face 11a thereof, and the optical member 20 arranged on the front side of the light guide 11 are provided. The light irradiating means 10 is disposed behind the liquid crystal display element 1 with its light source 16 disposed side facing the main direction of taking in external light.

That is, this display device emits external light mainly from a direction inclined toward the upper edge of the screen with respect to the normal of the screen in an environment where external light can be obtained, similarly to a normal reflection type display device. The light irradiating means 10 is used to select the orientation of the screen so as to capture the light. It is arranged toward the edge side (left side in FIG. 1).

Further, in the display device of this embodiment, FIG.
As shown in the figure, the light irradiation means 10 and the liquid crystal display element 1
A light diffusion film 23 and an optical sheet 24 having the following characteristics are stacked and disposed between them.

FIG. 5 is a perspective view of the optical sheet 24. The optical sheet 24 has a reflection axis 24s and a transmission axis 24p in directions substantially orthogonal to each other, and the polarization component is incident along the reflection axis 24s. It has a characteristic of reflecting light and transmitting incident light of a polarization component along the transmission axis 24p.

That is, as shown in FIG. 5, the optical sheet 24 has a polarization component (hereinafter referred to as an S-polarization component) s along its reflection axis 24s and a polarization component along the transmission axis 24p. When light including both light (hereinafter, referred to as P-polarized light component) p is incident, the light s of the S-polarized light component along the reflection axis 24 s of the incident light becomes the optical sheet 2.
The light p of the P-polarized light component reflected at 4 and transmitted along the transmission axis 24p passes through the optical sheet 24.

FIG. 5 shows an example in which light is incident on the optical sheet 24 from the rear side. However, the optical sheet 24 shows the same characteristics with respect to the incident light from the front side. . The optical sheet 24 is a non-colored sheet whose reflection and transmission characteristics have no wavelength dependence.

The structure of the optical sheet 24 is not shown, but, for example, a pair of concave and convex surfaces having a shape in which a horizontally long prism-like portion having a minute width is continuously arranged in parallel in the width direction on one surface is formed. The transparent film, the top of the uneven surface of one film and the valley of the uneven surface of the other film are overlapped facing each other, between the uneven surface of both films, a plurality of transparent refractive index different A laminated film in which films are alternately laminated is sandwiched.
U.S. Pat. Nos. 5,422,756 and 5,559,63
No. 4.

In this embodiment, the optical sheet 24 is disposed with its transmission axis 24p substantially parallel to the transmission axis of the polarizing plate 9b on the back side of the liquid crystal display element 1. As shown in FIG.
3 is attached to the front surface of the optical member 20 of the light irradiation means 10.

The light diffusion film 23 is made of, for example, a transparent adhesive in which light scattering fine particles are dispersed.
The optical sheet 24 is adhered to the front surface of the optical member 20 by the adhesive property of the light diffusion film 23.

The liquid crystal display element 1 is disposed so as to overlap the front surface of the optical sheet 24, and the back surface (the back surface of the rear polarizing plate 9 b) is light-diffused by a transparent adhesive or a double-sided adhesive sheet 25. It is attached to the front surface of the film 23.

In this display device, the liquid crystal display element 1 and the light irradiating means 10 allow external light incident from the front of the liquid crystal display element 1 to reach each stage of the light guide 11 of the light irradiating means 10. A reflective display system for reflecting the light by the reflective surface 14 on the surface 12a and emitting the light to the front of the liquid crystal display element 1; and an illumination light emitted from the light irradiating means 10 and the liquid crystal display by the reflective display system using the illumination light. A screen brightness compensation display system for compensating the brightness of the screen of the element 1, and the reflectance of external light when the transmittance of the liquid crystal display element 1 of the reflection display system is controlled to a maximum (the liquid crystal display element The ratio of the intensity of the external light incident from the front of the liquid crystal display device 1 to the intensity of the external light incident from the front of the liquid crystal display element 1 is set to about 16% or more.

Regarding the reflectance of external light of the reflective display system, the actual reflectance is R (%), the aperture ratio of the liquid crystal display element 1 is 100%, and there is no color filter (the color filters 6R and 6G). , 6B is 100%), R ′ (%) is the reflectance of external light in the reflective display system (hereinafter, referred to as basic reflectance), and
Assuming that the transmittances of R, 6G, and 6B are T _CF (%) and the actual aperture ratio of the liquid crystal display element 1 is S (%), it is expressed by the following equation (1).

R = R ′ × S × T _CF (1) The basic reflectance R ′ of the reflective display system is determined by the reflectance of the reflection surface 14 of the light guide 11 and the liquid crystal display element 1.
(The transmittance when the aperture ratio is 100% and the color filter is not used), the reflection surface 14 of the light guide 11 is formed by depositing a high-reflectivity metal film 13b made of aluminum or the like. Since the liquid crystal display element 1 is of a TN type, the base when the transmittance of the liquid crystal display element 1 of the reflective display system is controlled to the maximum is set. The reflectivity R 'is about 70
% Can be relatively high.

The color filters 6R, 6G, 6
The transmittance T _{CF of} B is such that light incident on the liquid crystal display element 1 from the front thereof passes through the color filters 6R, 6G, 6B, is reflected by the reflection surface 14 of the light guide 11, and is again reflected by the color filters 6R, 6G. , 6B, and the transmittance T _CF of the color filters 6R, 6G, 6B is about 36%. E Then, the reflective display system 70% basal reflectance R 'when the controlled maximum transmittance of the liquid crystal display device 1 of, and set the color filter 6R, 6G, the transmittance T _CF of the 6B 36% At this time, the aperture ratio S of the liquid crystal display element 1 at which the actual external light reflectance R of the reflective display system becomes 16% is S = 63% from the above equation (1).

Accordingly, the basic reflectance R 'when the transmittance of the liquid crystal display element 1 of the reflective display system is controlled to the maximum.
Is 70%, and the color filters 6R, 6G, 6B
(The transmittance of the color filter of light incident on the liquid crystal display element 1 from the front thereof and the reflection surface 14 of the light guide 11)
(The total transmittance of the light reflected by the liquid crystal with the transmittance of the color filter) T _CF is 36%, the aperture ratio of the liquid crystal display element 1 may be set to about 60% or more. Thus, the reflectance R of external light when the transmittance of the liquid crystal display element 1 of the reflective display system is controlled to the maximum.
Can be about 16% or more.

Further, the light irradiation means 10 includes an illumination brightness control means 26 for controlling the brightness of the illumination light from the light irradiation means 10 according to the illuminance of the environment in which the display device is used.

As shown in FIG. 1, the illumination brightness control means 26 includes an illuminance detector 27 for measuring environmental illuminance, and the light illuminating means 10 based on the environmental illuminance measured by the illuminance detector 27. The means for controlling the luminance of the emitted illumination light comprises a light source luminance adjustment circuit 28 and a light source lighting circuit 29.

The illuminance detector 27 sets the light receiving surface substantially parallel to the front surface of the liquid crystal display element 1 so as to measure the same environmental illuminance as the illuminance of the external light entering the liquid crystal display element 1 from the front. It is arranged near the leverage liquid crystal display element 1.

The light source luminance adjusting circuit 28 changes the luminance value of the illuminating light emitted from the light irradiating means 10 based on the environmental illuminance measured by the illuminance detector 27, Brightness is adjusted so as to be a predetermined brightness range according to the environmental illuminance,
The light source lighting circuit 29 includes the fluorescent lamp 17 of the light source 16.
Is driven to emit illumination light having a luminance corresponding to the luminance value from the light source luminance adjusting circuit 28.

This display device has the illuminance of its use environment,
When the illuminance is such that a sufficient screen luminance can be obtained by the reflective display using external light, external light incident from the front of the liquid crystal display element 1 is reflected by the light irradiating means 10 (a plurality of steps of the light guide 11). A reflection type display is performed by a reflection display system that emits light in front of the liquid crystal display element 1 after being reflected by the reflection surface 14 on the surface 12, and the illuminance of the use environment is sufficient only by the reflection type display by the reflection display system. When the illuminance is such that the screen luminance cannot be obtained, the light source 16 is turned on, the illumination light is emitted from the light irradiating means 10, and a display for compensating the screen luminance is performed by the illumination light.

That is, when the illuminance of the use environment is such that a sufficient screen luminance can be obtained by the reflection type display using external light, the light irradiating means 10 does not emit the illuminating light. In the case where the reflective display is performed by the reflective display system and the illuminance of the use environment is such that the screen luminance is insufficient with only the reflective display by the reflective display system, the illumination light is emitted from the light irradiating unit 10. The light irradiation means 10 emits light to compensate for the lack of screen brightness due to the reflective display, and when the illuminance of the use environment is almost 0 lux, that is, when almost no external light is obtained, the light irradiation means 10 emits light. The display is performed only by the illumination light.

First, the reflection path of the external light by the reflective display system of the display device will be described. As described above, this display device, when in an environment where external light can be obtained, has a screen normal to the screen normal. It is used by selecting the orientation of the screen to take in external light mainly from the direction inclined to the upper edge side of the
External light is mainly at the upper edge of the screen (the upper edge of the liquid crystal display element 1).
At various angles of incidence.

External light incident from the front of the liquid crystal display element 1 is first absorbed by the front-side polarizing plate 9a as a component having a polarization component along its absorption axis, and is transmitted along the transmission axis of the front-side polarizing plate 9a. The light enters the liquid crystal display element 1 as linearly polarized light.

External light (linearly polarized light) transmitted through the front-side polarizing plate 9a and incident on the liquid crystal display element 1 is applied to the color filters 6R, 6G, 6 provided on the inner surface of the front-side substrate 2a.
B absorbs the light of the wavelength component in the absorption wavelength band to become colored light colored to the color of the color filter, and then, in the process of transmitting through the liquid crystal layer 8, according to the orientation state of the liquid crystal molecules which changes with the applied voltage. The optical element is rotated by the birefringence effect, and of the light, the light of the polarization component along the transmission axis of the rear-side polarizing plate 9b is transmitted through the rear-side polarizing plate 9b to become image light to be image light. Out to the back of

The light emitted to the back of the liquid crystal display element 1 passes through the optical sheet 24 and the light diffusing film 23 in order and enters the optical member 20 of the light irradiation means 10 from the front. The transmission axis 24p of the optical sheet 24 and the transmission axis of the rear polarizing plate 9b of the liquid crystal display element 1 are substantially parallel to each other. Most of the light emitted through the optical sheet 24 passes through the optical sheet 24 and enters the optical member 20.

In this display device, the light irradiating means 10 is disposed with the light source 16 disposed side facing the upper edge of the screen, which is the main direction of capturing external light of the display device. External light incident on the member 20 is mainly the light source 16.
Incident from the side where.

External light incident on the optical member 20 from the front thereof passes through the optical member 20 and exits from the rear surface thereof, and is reflected by the reflecting surfaces 14 on the plurality of step surfaces 12a of the light guide 11. .

That is, the external light entering the optical member 20 from the front thereof enters the optical member 20 at various incident angles as shown by broken lines in FIG. The light traveling toward the entrance / exit surface 22 between the adjacent entrances 21 and the refraction surface 21b with a large inclination angle of each entrance 21 on the back surface of The light passes through the interface between the light guide 11 and the outside air and the interface between the input / output surface 22 and the outside air, exits to the back surface, and is reflected by the reflection surface 14 on the step surface 12 a of the light guide 11.

Further, of the incident light, the incident portion 21
The light traveling toward the incident surface 21a having a small inclination angle is totally reflected at the interface between the incident surface 21a and the outside air, and its direction is changed, and the light is directed from the refraction surface 21b or the entrance / exit surface 22 to the back surface. The light is emitted and the step surface 12 of the light guide 11 is emitted.
The light is reflected by the reflection surface 14 on the line a.

The light guide 11 has a front surface formed on a stepped surface 12, a reflective film 13 is provided on the plurality of step surfaces 12 a over the entire surface, and the surface is formed on the reflective surface 14.
Therefore, the light guide 11 has the same reflection characteristic as that of a normal reflector having a flat reflection surface on the front surface. Therefore, most of the light emitted to the rear surface of the optical member 20 is wasted. It can be reflected without.

The light reflected on the reflecting surface 14 on each step 12a of the light guide 11 is reflected by the optical member 20.
The light is taken in from the rear surface, passes through the light guide 20, and exits from the front surface.

At this time, since the angle between the step surface 12a of the light guide 11 and the incident surface 21a of each of the light incident portions 21 of the optical member 20 is large, the reflecting surface 14 on the step surface 12a of the light guide 11 is large. Most of the reflected light reflected by the refracting surface 21b and the input / output surface 22 of each of the incident portions 21 of the optical member 20
Taken from.

Then, of the light taken in from the refracting surface 21b and the light taken in from the entrance / exit surface 22 and directing toward the front surface of the optical member 20, the light passes through the optical member 20 in the same direction. Of the light emitted from the front surface and taken in from the refraction surface 21b,
The light traveling toward 1a is totally reflected at the interface between the incident surface 21a and the outside air and changes its direction, and is directed in a direction close to the direction of the light traveling directly from the refraction surface 21b and the entrance / exit surface 22 toward the front surface of the optical member 20. And the light is emitted from the front surface of the optical member 20.

Therefore, as the reflected light of the external light emitted to the front surface of the light irradiating means 10 (the front surface of the optical member 20), the external light incident from the front of the liquid crystal display element 1 at various incident angles is collected. The reflected light of the external light is light of a luminance distribution in which the luminance of light emitted in the front direction is high.

That is, the reflected light of the external light emitted to the front surface of the optical member 20 is converted into the light having a high luminance in the front direction, which is incident and condensed from the incident portion 21, and is reflected by the incident portion 21. The light having a higher luminance in the front direction is a light having a higher luminance distribution in which the light incident from the entrance / exit surface 22 between the light beams and transmitted in the front direction is superimposed.

The reflected light emitted from the front surface of the light irradiating means 10 is transmitted through the light diffusion film 23 and diffused, passes through the optical sheet 24 on the front surface, and enters the liquid crystal display element 1 from the rear surface. . In FIG. 3, the state of diffusion of the reflected light transmitted through the light diffusion film 23 is omitted for simplification of the drawing.

At this time, the transmission axis 24p of the optical sheet 24 and the transmission axis of the rear polarizing plate 9b of the liquid crystal display element 1 are substantially parallel to each other.
Most of the reflected light transmitted through the rear-side polarizing plate 9b passes through the rear-side polarizing plate 9b and enters the liquid crystal display element 1 from the rear side.

The reflected light incident on the liquid crystal display element 1 from the back thereof passes through the liquid crystal layer 8 and the color filters 6R, 6G, 6B in that order, and further passes through the front polarizing plate 9a, and then the liquid crystal. Light is emitted from the front surface of the display element 1.

Next, an emission path of the illumination light from the light irradiating means 10 by a screen luminance compensation display system for compensating the screen luminance by emitting the illumination light from the light irradiating means 10 will be described. The light guide 11 takes in the illumination light from the light source 16 from the incident end face 11a,
The light is transmitted to a plurality of step surfaces (outgoing surfaces) of the step-shaped surface 12.
12b, the light incident on the plurality of step surfaces 12a of the stepped surface 12 from the front is reflected forward by the reflection surface (the surface of the reflection film 13) on these step surfaces 12a. The illumination light taken in from the incident end face 11a is emitted from the plurality of step faces 12b along a path shown by a solid line in FIG.

That is, the illuminating light taken into the light guide 11 from its incident end face 11a travels in the light guide 11 in the length direction thereof, and includes a plurality of steps of the step-shaped surface 12. Light directed directly to one of the surfaces 12b is emitted from the step surface 12b.

Light other than the light directly traveling to the step surface 12b, that is, a plurality of step surfaces 12
The light traveling toward the light guide 11 and the light traveling toward the back of the light guide 11 are reflected on the back surface of the reflection film 13 on each of the stepped surfaces 12a, and are reflected between the back of the light guide 11 and the outside air (air). The light is guided inside the light guide 11 in the length direction by total reflection at the interface, and changes its direction. The light is incident on any of the plurality of step surfaces 12b and is emitted from the step surface 12b.

The light traveling inside the light guide 11 toward the rear surface includes an incident angle smaller than the total reflection critical angle (closer to the vertical) with respect to the interface between the rear surface of the light guide 11 and the outside air. Some of the light is incident, and the light passes through the interface and leaks to the back of the light guide 11.
The light is reflected by the reflector 19 disposed behind the light guide 11 and enters the light guide 11 from the back thereof, and is reflected on the back of the reflective film 13 on each of the stepped surfaces 12a and the back of the light guide 11 and the outside air. The direction is changed by total reflection at the interface with the light guide 11 and the light is emitted from any one of the plurality of step surfaces 12b. Out of the step surface 12b.

As described above, the back surface of the light guide 11 has a light diffusion surface 15a having a vertically elongated prism-shaped surface 15a continuous with the width direction of the light guide 11 and formed parallel to each other at a fine pitch. When light guided inside the light guide 11 is totally reflected at the interface between the back surface and the outside air, or light leaking to the back surface of the light guide 11 is reflected by the reflection plate 19.
The light is diffused when reentering the light guide 11 from its rear surface, and becomes light with a substantially uniform luminance distribution in the width direction of the light guide 11, and is emitted from the plurality of step surfaces 12b.

Then, each step surface 12b of the light guide 11
Illumination light emitted from the plurality of incident portions 2 formed on the rear surface of the optical member 20 disposed on the front side of the light guide 11
1 is incident from one side of the incident surface 21a.

At this time, each step surface 12 of the light guide 11
b, each of them always faces at least one incident portion 21 of the optical member 20, so that most of the light emitted from each stepped surface 12 b of the light guide 11 can be used without waste. The light enters one of the incident portions 21.

The light guide 11 has a plurality of step surfaces 12.
As shown in FIG. 3, some of the light beams emitted from the light source b may be emitted toward the next step surface 12a.
The light is reflected by the reflection surface 14 on the next step surface 12a and is incident on the incident portion 21 of the optical member 20.

Then, each step surface 12b of the light guide 11
The light emitted from the optical member 20 and incident on the respective incident portions 21 of the optical member 20 is taken into the incident portions 21 from the incident surfaces 21a of the incident portions 21, and the refraction surface 21b on the opposite side is exposed to outside air (light guide). The light is totally reflected at the interface between the body 11 and the air layer between the optical member 20), refracted toward the front surface of the optical member 20, transmitted through the optical member 20, and emitted from the front surface.

The illumination light emitted to the front surface of the optical member 20 enters each of the incident portions 21 from the incident surface 21a.
The light is refracted by the refraction surface 21b and condensed in a predetermined direction, and has a high luminance distribution in a predetermined direction.

In this case, in this embodiment, the incident portion 2
1 is set such that the direction of the light refracted by the refraction surface 21b is in the front direction (direction near the normal to the front surface of the optical member). The illumination light emitted to the front surface of the member 20 is a light having a directivity distribution with high luminance in the front direction of the light guide 20.

The direction of emission of the illuminating light emitted to the front surface of the optical member 20 is a direction corresponding to the inclination angle of the refraction surface 21b of the incident part 21, and the inclination angle of the refraction surface 21b is adjusted to the front surface of the optical member. Is closer to the front when the angle is within a range of 20 to 50 ° with respect to the normal line.

The light emitted in front of the optical member 20, that is, the light emitted from the light irradiating means 10, is transmitted through the light diffusion film 23 and diffused, and is transmitted through the optical sheet 24 on the front surface thereof. 1 is incident from the back. In FIG. 3, the diffusion state of the illumination light transmitted through the light diffusion film 23 is omitted for simplification of the drawing.

In this case, the light emitted from the light irradiating means 10 is light containing light of polarization components in various directions, and the optical sheet 24 is, as shown in FIG.
It has a characteristic of reflecting the incident light s of the S-polarized component along the transmission axis 24p and transmitting the incident light p of the P-polarized component along the transmission axis 24p. Of the light that is diffused by the diffusion film 23 and enters the optical sheet 24, light of a polarization component along the transmission axis 24p of the optical sheet 24 passes through the optical sheet 24 and enters the liquid crystal display element 1. The light of the polarization component along the reflection axis 24s of the optical sheet 24 is reflected by the optical sheet 24.

Although the path of the light reflected by the optical sheet 24 is not shown, the light passes through the optical member 20 of the light irradiating means 10 and passes through the reflecting surface 14 on each step surface 12a of the light guide 11. The light is reflected by the optical member 20 and changes its polarization direction to some extent, passes through the optical member 20 again, enters the optical sheet 24, and of the light, the transmission axis 24p of the optical sheet 24
Is transmitted through the optical sheet 24 and is incident on the liquid crystal display element 1, and the light having a polarization component along the reflection axis 24 s of the optical sheet 24 is reflected by the optical sheet 24 again.

The following is the repetition, and
Of the illumination light from the light irradiating means 10, the light of the polarization component along the reflection axis 24 s of the optical sheet 24 is reflected by the optical sheet 24 and reflected by the light irradiating means 10 (the light guide 11). Reflection on the reflection surface 14 on each step surface 12a)
The polarization direction is changed by repetition of the above, and eventually, the light becomes a polarized component along the transmission axis 24p of the optical sheet 24, passes through the optical sheet 24, and enters the display element. For this reason, most of the illumination light from the light irradiation means 10 can be made incident on the liquid crystal display element 1 without waste.

In the light reflected from the optical sheet 24 and incident on the optical member 20 from the front surface, the refracting surface 21b of the rear surface of the optical member 20 where the incident angle 21 is large and the adjacent incident surface 21b Light traveling toward the entrance / exit surface 22 between the portions 21 passes through the interface between the refraction surface 21 and the outside air and the interface between the entrance / exit surface 22 and the outside air and exits to the back.
Further, the light traveling toward the incident surface 21a having a small inclination angle of the incident portion 21 is totally reflected at the interface between the incident surface 21a and the outside air and changes its direction.
The light exits from 2 to the back.

The light emitted to the back surface of the optical member 20 and reflected by the reflection surface 14 on each step surface 12a of the light guide 11 enters the optical member 20 from the back surface. Since the angle between the step surface 12a of the light guide 11 and the incident surface 21a of each of the light incident portions 21 of the optical member 20 is large, the light reflected by the reflection surface 14 on each step 12a of the light guide 11 Are mostly taken in from the refraction surface 21b and the entrance / exit surface 22 of each entrance 21 of the optical member 20.

Then, of the light taken in from the refraction surface 21b and the light taken in from the entrance / exit surface 22,
The light that directly goes to the front surface of the optical member 20 passes through the optical member 20 in the same direction and exits from the front surface, and of the light taken in from the refraction surface 21b, the opposite incident surface 2
The light traveling toward 1a is totally reflected at the interface between the incident surface 21a and the outside air and changes its direction. Is emitted from the front surface of the optical member 20.

Therefore, the light reflected by the optical sheet 24, reflected by the reflection surface 14 on each step surface 12a of the light guide 11, and emitted to the front of the optical member 20 is also emitted to the front. Is light with a high luminance distribution.

The illumination light emitted from the front surface of the light irradiating means 10 (the front surface of the optical member 20), sequentially transmitted through the light diffusion film 23 and the optical sheet 24, and incident on the liquid crystal display element 1 from the rear surface is The light is linearly polarized light along the transmission axis 24p of the optical sheet 24, and the light is incident on the liquid crystal display element 1 from the back side.
And the transmission axis of the rear polarizer 9b of the liquid crystal display element 1 is substantially parallel to each other, so that most of the illumination light transmitted through the optical sheet 24 transmits through the rear polarizer 9b and Incident on.

The illumination light (linearly polarized light) that has passed through the rear-side polarizing plate 9b and entered the liquid crystal display element 1 passes through the liquid crystal layer 8 in the process of passing through the two substrates 2 of the liquid crystal display element 1.
a and 2b are rotated on the basis of the birefringence effect according to the orientation state of the liquid crystal molecules which change according to the voltage applied between the electrodes 4 and 5 formed on the inner surface of the front substrate 2a, and are provided on the inner surface of the front substrate 2a. The color filters 6R, 6G, and 6B absorb the light of the wavelength components in the absorption wavelength band and become colored light colored by the color filters 6R, 6G, and 6B, of which light is transmitted through the front-side polarizing plate 9a. Light having a polarization component along the axis passes through the front-side polarizing plate 9a, and is emitted as image light to the front surface of the liquid crystal display element 1.

As described above, the screen brightness compensation display system is used when the illuminance of the environment in which the display device is used is such that sufficient screen brightness cannot be obtained only by the reflection type display using the reflection display system. The light irradiating means 1 in an environment where external light is present, but in an environment of illuminance where screen brightness is insufficient with only the reflective display by the reflective display system.
When the illumination light is emitted from 0, the reflected light of the external light which enters from the front of the liquid crystal display element 1 and is reflected by the light irradiating means 10 is emitted from the light irradiating means 10 to the liquid crystal display element 1. Light having a luminance on which the illumination light incident from the rear side is superimposed is emitted to the front of the liquid crystal display element 1.

When the illuminance of the use environment is almost 0 lux, that is, when the external light is hardly obtained, the light reflected by the reflective display system is hardly obtained. When the illuminating light is emitted from the light emitting device 10, the illuminating light emitted from the light irradiating means 10 and incident on the liquid crystal display element 1 from the back side is emitted forward of the liquid crystal display element 1.

Therefore, according to this display device, even under an illuminance environment where a sufficient screen luminance cannot be obtained by the display using only the reflection display system, the deficiency of the screen luminance is reduced by the illumination light from the light irradiation means 10. By emitting light, it is possible to obtain a screen luminance suitable for the environmental illuminance in a usage environment in a wide illuminance range from low illuminance to high illuminance.

When the illuminance of the use environment is such that a sufficient screen luminance can be obtained by the reflective display using external light, the light irradiating means 10 emits the illuminating light. However, since the reflective display is performed by the reflective display system, the light irradiating means 1 at that time is used.
The power consumption of 0 is 0.

Further, in this display device, as described above, the reflectance of the external light when the transmittance of the liquid crystal display element 1 of the reflective display system is controlled to the maximum is set to about 16% or more. Therefore, external light can be used efficiently.

For this reason, if the ambient illuminance is a certain level or more, it is possible to obtain a screen brightness suitable for the ambient illuminance only by the reflected light of the external light without emitting the illumination light from the light irradiation means 10. Therefore, it is sufficient that the illumination light is emitted from the light irradiating means 10 only in a usage environment in a limited illuminance range where the illuminance is less than a certain level. Even in the case where the illumination light from the means 10 is used to compensate, the luminance of the illumination light emitted from the light irradiation means 10 may be relatively low, so that the power consumption of the light irradiation means 10 may be small.

The screen brightness of the display device when the illumination light is emitted from the light irradiating means 10 of the display device is as follows.
), The brightness of the illuminating light emitted by the light irradiating means 10 is B (nit, hereinafter referred to as nit), and the color filter 6
The transmittance in one direction of the liquid crystal display element 1 including R, 6G, and 6B is T (%), and the reflectance of the reflective display system is R (%).
(%), And the screen brightness is L (nit, hereinafter referred to as nit), and is obtained by the following equation (2).

L = I × R / 400 + B × T / 100 It is obtained by the following relational expression.

Therefore, when performing the reflection type display only by the reflection display system, that is, when the illumination light is not emitted from the light irradiation means 10 (when the luminance B of the illumination light from the light irradiation means 10 is B = 0 nit) Is L = I × R / 400.

In this embodiment, the reflectance R of external light when the transmittance of the liquid crystal display element 1 of the reflective display system is controlled to the maximum is set to about 16% or more. The screen luminance L when performing the reflective display only by the display system is, for example, 1200 lx (L = 30000 × 16/400 = 12 when the environmental illuminance I is 30000 lx).
00), when the environmental illuminance I is 10,000 lx,
0 lx (L = 10000 × 16/400 = 400) or more.

On the other hand, a suitable screen luminance according to the environmental illuminance is generally about 500 nit or more at an environmental illuminance of 10000 lx, and about 1200 nit or more at an environmental illuminance of 30000 lx.

This means that the display device is 3000
At an ambient illuminance of less than lx, a suitable screen luminance (for example, 10
Although it is not possible to obtain about 500 nits or more with an environmental illuminance of 000 lx, at an environmental illuminance of 30000 lx or more, a suitable screen luminance (30 liters) is obtained only by the reflective display using the reflective display system.
2,000 lx of ambient illuminance can be obtained.

Therefore, when the illuminance of the use environment is 30,000 lx or more, the display device can
It is possible to perform display at a screen luminance suitable for environmental illuminance without emitting illumination light from the.

FIG. 6 is a graph showing fine weather and cloudy weather in three cities of Sapporo, Hokkaido, Fukuoka, Fukuoka, and Naha, Okinawa.
Outdoor daytime (9: 00-17: 00) including all weather days such as rainy weather
The hourly average illuminance at each hour is shown. The annual average illuminance is based on the 1996 meteorological data.

As shown in FIG. 6, the average annual illuminance of the outdoors including all weather days is about 9 to 15:10 in Sapporo.
In Fukuoka City, more than 30,000 lx
In the time zone from about 9:20 to about 16:20, it is more than 30,000 lx. In Naha city, it is more than 30,000 lx in the time zone from about 9:10 to about 16:40.

Therefore, when the display device is used outdoors, it is generally from about 9:00 to about 15:10 in Sapporo, from about 9:20 to about 16:20 in Fukuoka, Naha, throughout the year. Thus, display can be performed at a screen luminance suitable for environmental illuminance without emitting illumination light from the light irradiating means 10 over a time period from about 9:10 to about 16:40.

FIGS. 7 to 10 show outdoor daylight hours (9:00 o'clock) in three cities of Sapporo, Fukuoka and Naha in January, April, July and October. 17:00 to 17:00) indicates the monthly average illuminance at each time. The monthly average illuminance in each figure is based on the 1996 meteorological data.

As shown in FIG. 7, the average monthly illuminance outdoors on a sunny day in January is more than 30,000 lx in the time zone from about 9:00 to about 15:20 in Sapporo, and about 9:00 in Fukuoka. 3 in the time zone from 30 minutes to about 16:20
More than 0000lx, in Naha city from about 9:20 to about 17
It is more than 30,000 lx in the time zone up to the hour.

As shown in FIGS. 8 and 9, the average monthly illuminance outdoors on sunny days in April and July is 3 in the time period from 9 o'clock to 17 o'clock in any of the three cities.
0000lx or more.

As shown in FIG. 10, the average monthly illuminance outdoors on a sunny day in October is about 15
30000lx or more in the time zone until 10:00, and in Fukuoka City, 30 hours in the time zone from before 9:00 to about 17:00.
In Naha city, it is more than 30,000 lx in the time zone from before 9 o'clock to after 17 o'clock.

Therefore, when the above-mentioned display device is used outdoors on a fine day, Naha city has a daytime (9
The light irradiating means 10 over the entire time zone
It is possible to perform display at a screen luminance suitable for environmental illuminance without emitting illumination light from the.

In the city of Fukuoka, the illumination light is not emitted from the light irradiating means 10 during the entire daytime (9:00 to 17:00) during most of the year from spring to autumn. It is possible to perform display at a screen luminance suitable for environmental illuminance, and even in winter, without emitting illumination light from the light irradiating means 10 over a time period from before 10:00 to just after 16:00, the environmental illuminance is reduced. On the other hand, display can be performed with a suitable screen luminance.

Further, in Sapporo city, during the period from spring to summer, during the daytime (9:00 to 17:00), the illuminating light is not emitted from the light irradiating means 10 and the environmental illuminance is reduced. The display can be performed with a suitable screen luminance, and even in the fall to winter, the illumination light is not emitted from the light irradiating means 10 over a time period from around 9 o'clock to after 15 o'clock. Display can be performed with a high screen brightness.

The display device performs the reflective display by the reflective display system without emitting the illumination light from the light irradiating means 10 in the use environment of the illuminance of 30000 lx or more. At this time, since reflected light having an intensity corresponding to the intensity of external light incident from the front of the liquid crystal display element 1 is obtained, the screen luminance increases as the environmental illuminance increases, which is suitable for the environmental illuminance. A high screen brightness can be obtained.

As described above, if the reflectance of the external light of the reflective display system is 16% or more, the light irradiating means 10 does not emit the illumination light in the use environment of the illuminance of 30000 lx or more. Although a suitable screen luminance can be obtained with respect to the environmental illuminance, if the reflectance of the external light of the reflective display system is too high, the screen becomes dazzling as the environmental illuminance increases.

For this reason, it is desirable that the reflectance of the external light of the reflective display system be kept at most 35% or less, preferably 25% or less, and the reflectance of the external light is 16 to 35% (preferably 16%). (25%), it is possible to obtain a suitable screen luminance that is not too dazzling even in a high illuminance environment exceeding 100,000 lux such as in direct sunlight in summer.

On the other hand, in the display device described above, in a use environment with an illuminance of less than 30,000 lx, the screen brightness is insufficient only by the reflective display by the reflective display system. Then, the lack of the screen brightness due to the reflected light of the external light is compensated for by the illumination light from the light irradiation means 10.

In this case, in this embodiment, the reflected light of the external light incident from the front of the liquid crystal display element 1 and reflected by the light irradiation means 10 and the illumination light emitted by the light irradiation means 10 are used. The light intensity is adjusted so that the screen luminance by both methods (however, when the environmental illuminance is almost 0 lux, the screen luminance only by the illumination light emitted from the light irradiating means 10) becomes a suitable screen luminance according to the environmental illuminance. The luminance of the illumination light emitted from the irradiation means 10 is controlled by the illumination luminance control means 26 according to the environmental illuminance.

That is, in this embodiment, the luminance of the illuminating light from the light irradiating means 10, that is, the luminous luminance of the fluorescent lamp 17 of the light source 16 is calculated by the illuminating luminance controlling means 26 by the above-mentioned equation (2) [L = I × R / 400 + B × T / 10
0] is controlled so as to be a suitable screen luminance corresponding to the environmental illuminance I.

Therefore, according to this display device, it is possible to obtain a screen luminance suitable for the environmental illuminance even in an illuminance environment where a sufficient screen luminance cannot be obtained by the display using only the reflection display system.

FIG. 11 shows the display device of the above embodiment in which the reflectance of the reflective display system for external light is set to 16%, and a white background behind the same liquid crystal display device as the liquid crystal display device 1 used in this display device. 7 shows the environmental illuminance-screen luminance characteristics of a reflective display device in which a reflective plate is disposed and a transmissive display device in which a backlight is disposed behind the display element.

Each of the reflective display device and the transmissive display device is designed based on the ambient illuminance of about 1000 lx, which is the illuminance in the room when the indoor lighting is turned on during the day or at night. And a suitable screen brightness at an environment illuminance of 1000 lx is about 80 nit or more (however, about 80 to 300 nit to prevent the screen from being too dazzling).
It is.

Therefore, in the above-mentioned reflection type display device, the reflectance of the external light is set to 90 at an ambient illuminance of 1000 lx.
The screen brightness is set so as to be 150 nits.
At an ambient illuminance of 0 lx or less, light of a constant luminance that can always obtain a screen luminance of 90 to 150 nits is emitted. In an environment exceeding 1000 lx, the luminance is controlled so as to increase as the environmental illuminance increases. ing.

As can be seen from the environmental illuminance-screen luminance characteristics of each display device shown in FIG.
At an ambient illuminance near 1000 lx, a suitable screen brightness (100
90-150 nits) can be obtained at an ambient illuminance near 0 lx. However, if the ambient illuminance is low, the screen luminance is too low, and the screen luminance is low enough to make the display visible, and if the environmental illuminance is high, As a result, the screen brightness increases and the screen becomes too dazzling.

In addition, the transmission type display device is 1000 lx
A suitable screen brightness (90-150 nits at an environment illuminance near 1000 lx) can be obtained at a nearby environment illuminance, but when the environment illuminance is low, the screen brightness becomes too high compared to the environment illuminance and the screen looks dazzling. In addition, there is a limit to the light emission luminance of the backlight (the light emission luminance of the backlight cannot be unnecessarily increased in consideration of power consumption). Becomes darker.

On the other hand, the screen luminance of the display device of the above embodiment is, for example, about 30 nits under a 50 lx ambient illuminance such as a street lamp at night, and 1000 lx as in an indoor room when daylight or nighttime indoor lighting is turned on. Approximately 120 nits in ambient illuminance and approximately 1200 in 3,000 lx ambient illuminance such as shade of a tree in fine weather
nit, about 4000 nits at 100,000 lx of ambient illuminance such as direct sunlight in summer, the screen brightness at any environmental illuminance is sufficient for that illuminance, and it is a suitable screen that is not too dazzling Brightness.

Therefore, according to the display device of the above embodiment, in a use environment in a wide illuminance range from low illuminance to high illuminance, it is possible to obtain a screen luminance suitable for the illuminance.

The external light reflectance of the reflective display system is as follows.
More preferably, it is set to 20% or more. By setting the reflectivity of the external light in this way, the use efficiency of the external light is increased, and the luminance of the illumination light emitted from the light irradiation unit 10 is further increased. Light emitting means 1
The power consumption of the light irradiation means 10 can be further reduced by further narrowing the range of the environmental illuminance for emitting the illumination light from 0.

That is, assuming that the reflectance of external light when the transmittance of the liquid crystal display element 1 of the reflective display system is controlled to the maximum is, for example, 20%, the above-mentioned equation L = I × R / 400
(L: screen luminance, I: environmental illuminance, R: reflectivity of reflective display system) The screen luminance L by only the reflective display system obtained by the equation is 500 when the environmental illuminance is 10000 lx.
lx (L = 10000 × 20/400 = 500).

Therefore, in a display device in which the reflectance of external light is set to 20% or more when the transmittance of the liquid crystal display element 1 of the reflective display system is controlled to the maximum, the illuminance of the use environment is 100%.
If it is not less than 00 lx, display can be performed at a screen luminance suitable for environmental illuminance without emitting illumination light from the light irradiation means 10.

As shown in FIG. 6, the annual average illuminance of each day in the outdoor daytime (9:00 to 17:00) including all weather days is 100 times in any of the cities of Sapporo, Fukuoka and Naha.
00lx or more, and when it comes to sunny days, the average monthly illuminance range of each hour during the daytime (9:00 to 17:00) on sunny days is, as shown in FIGS. About 1 of city
Except after 6:00, the cities of Sapporo, Fukuoka and Naha are almost 10,000 lx or more throughout the year.

Therefore, a display device in which the reflectance of external light is set to 20% or more when the transmittance of the liquid crystal display element 1 of the reflective display system is controlled to a maximum is available in any of Sapporo, Fukuoka and Naha cities. In most time periods during the day, display can be performed at a screen luminance suitable for environmental illuminance without emitting illumination light from the light irradiation means 10.

Further, the display device has an ambient illuminance of not less than a certain level (30000 lx or more when the reflectance of the external light of the reflective display system is 16%, and a reflectance of 20% or more of the external light of the reflective display system). If it is more than 10000 lx), it is possible to obtain a screen brightness suitable for environmental illuminance only by reflected light of external light without emitting illumination light from the light irradiating means 10, It is sufficient that the illumination light is emitted from the light irradiating means only in a usage environment in a limited illuminance range where the illuminance is a certain level or less. Even in the case of supplementing with illumination light, the brightness of the illumination light emitted from the light irradiating means may be relatively low, so that the light irradiating means requires less power.

In the above embodiment, the light irradiating means 10 is provided with the illumination luminance controlling means 26 for controlling the luminance of the illuminating light emitted from the light irradiating means 10 in accordance with the environmental illuminance. Since the luminance control condition of the illumination light by the illumination luminance control means 26 is set so that the luminance range becomes a predetermined luminance range according to the illuminance, it is more suitable for the environmental illuminance according to the environmental illuminance. A high screen brightness can be obtained.

In the above embodiment, the illumination luminance control means 26 emits light to the illuminance detector 27 for measuring the environmental illuminance, and the light irradiating means emits light based on the environmental illuminance measured by the illuminance detector 27. Since it is constituted by means for controlling the luminance of the illumination light (the light source luminance adjustment circuit 28 and the light source lighting circuit 29), the luminance of the illumination light is controlled in accordance with the illuminance of the actual use environment, and On the other hand, a suitable screen luminance can be obtained.

Further, in the above embodiment, the liquid crystal display element 1
A light irradiating means 10 disposed behind the light source 16 is provided with a light source 16, an emission surface for guiding illumination light from the light source 16 and emitting the light toward the liquid crystal display element 1 (each step surface of the step-shaped surface 12 of the light guide 11). 12b) and a reflecting surface (the step-shaped surface 12 of the light guide 11) different from the emission surface for reflecting external light incident from the front of the liquid crystal display element 1 toward the liquid crystal display element 1.
And the light guide 11 on which the reflection film 13 formed on each of the step surfaces 12b is formed, so that the emission rate of the illumination light from the output surface (the step surface 12b) is improved. , And the reflectance of external light on the reflection surface 14 can be independently selected.

Therefore, the efficiency of use of the illumination light from the light source 16 is increased by increasing the emission rate of the illumination light from the emission surface, and the reflectance of the reflection surface is changed by the reflection rate of the liquid crystal display element 1 of the reflection display system. When the transmittance is maximally controlled, the reflectance is about 16
% Or more (more preferably 20% or more).

In addition, the light irradiation means 1 used in the above embodiment
Numeral 0 denotes an incident end face 11a in which one end face of the light guide 11 takes in the illumination light from the light source 16;
A plurality of step surfaces 12a whose front surfaces are gradually lowered from the incident end surface 11a side to the other end side;
A stepped surface 12 is formed of a plurality of step surfaces 12b connecting the first and second reflective surfaces 2a.
3 is provided to form a reflection surface 14 for external light, and the plurality of step surfaces 12b serve as emission surfaces of illumination light incident from the incident end surface 11a, and on the front side of the light guide 11, The light guide 11 transmits the external light incident from the front of the liquid crystal display element 1 and the reflected light of the external light reflected by the reflection surface 14 on each step surface 12a of the light guide 11.
The optical member 20 for emitting the illumination light emitted from each stepped surface 12b toward the liquid crystal display element 1 is disposed.

According to the light irradiating means 20, the illumination light taken into the light guide 11 from the incident end face 11a is
A plurality of step surfaces 12b of the step-shaped surface 12 of the light guide 11
And the light is redirected by the optical member 20 and is emitted toward the liquid crystal display element 1, so that the illumination light from the light source 16 can be made incident on almost the entire liquid crystal display element 1. .

In addition, according to the light irradiating means 10, the plurality of step surfaces 12 a of the step-shaped surface 12 of the light guide 11 serve as external light reflecting surfaces 14, respectively. External light incident from the front passes through the optical member 20 and is reflected on the reflection surface 14 on each step surface 12 a of the light guide 11.
And the reflected light passes through the optical member 20 again and exits toward the liquid crystal display element 1. Therefore, most of the external light incident from the front of the liquid crystal display element 1 is reflected without waste, and The light can be incident on almost the entire display element 1.

The optical member 20 is formed of a transparent plate having a front surface for emitting light toward the liquid crystal display element 1 and a back surface opposite to the front surface of the light guide 11. An incident surface 21a for taking in light emitted from each step surface 12b of the light guide 11, and a refraction surface 21b for refracting light taken in from the incident surface 21a toward the front.
Therefore, most of the light emitted from each stepped surface 12b of the light guide 11 is taken into the optical member 20 without waste, and the liquid crystal is introduced from the front surface thereof. Light can be emitted toward the display element 1.

That is, in principle, the light irradiating means 10 can emit almost 100% of the light from the light source 16 and can reflect and emit almost 100% of the external light incident from the front.

Furthermore, if the optical member 20 is configured as described above, the light exits from each stepped surface 12b of the light guide 11 and enters the incident surface 2 at each incident portion 21 of the optical member 20.
The light incident from 1a is refracted by the refraction surface 21b and condensed in a predetermined direction, and illumination light having a high luminance distribution in a predetermined direction (for example, the front direction) is emitted from the front surface of the optical member 20. The external light reflected on the reflection surface 14 on each step surface 12a of the light guide 11 is also converted into light having a high luminance distribution in a predetermined direction (for example, the front direction). Can be emitted.

Further, in the above-described embodiment, the optical member 20 is provided with the plurality of incident portions 21 on the rear surface thereof at intervals, and the rear surface area between these incident portions 21 is formed by the light guide. 11 is configured as an input / output surface 22 corresponding to the reflection surface 14 on each step surface 12a of the liquid crystal display element 1
The external light incident from the front of the optical member 20 and incident on the optical member 20 from the front surface is emitted to the rear surface of the optical member 20 from the incident portion 21 and the entrance / exit surface 22 therebetween,
The reflected light of the external light reflected by the reflection surface 14 on each step surface 12a of the light guide 11 is taken into the optical member 20 from the incident part 21 and the incident / exit surface 22, and the front surface of the optical member 20 is Can be emitted toward the liquid crystal display element 1 and the reflected light can be converted into light having a higher luminance distribution in a predetermined direction (for example, the front direction).

In the above embodiment, the light irradiation means 1
0 on the back of the light guide 11 constituting the light guide 11
Since the light diffusing surface 15 for averaging the luminance distribution in the width direction of the light guide of the illumination light incident from the incident end face 11a of the light guide 11 is formed on the light guide 11,
The luminance distribution of the illumination light taken in from the light guide and emitted from each stepped surface 12b on the front surface of the light guide can be made substantially uniform in the width direction of the light guide 11.

Further, in the display device of the above embodiment, the light diffusing film 23 is provided between the light irradiation means 10 and the liquid crystal display element 1.
Is provided, the illuminating light from the light irradiating means 10 and the reflected light of the external light are diffused by the light diffusing film 23 to be incident on the liquid crystal display element 1 from the back as light having a substantially uniform luminance distribution. The brightness can be made uniform over the entire screen, and the emission angle range of the light emitted in front of the liquid crystal display element 1 can be widened to obtain a wide viewing angle.

In the above embodiment, the reflection axis 24s and the transmission axis 24p are provided between the light irradiation means 10 and the liquid crystal display element 1 in directions substantially orthogonal to each other, and extend along the reflection axis 24s. An optical sheet 24 having a property of reflecting incident light of the polarization component and transmitting incident light of the polarization component along the transmission axis 24p is provided.

For this reason, of the illumination light from the light irradiating means 10, light having a polarization component along the transmission axis 24 p of the optical sheet 24 passes through the optical sheet 24 and enters the liquid crystal display element 1. The light of the polarization component along the reflection axis 24s of the optical sheet 24 of the illumination light from the light irradiating unit 10 is polarized by the repetition of the reflection on the optical sheet 24 and the reflection on the light irradiating unit 10. Since the direction is changed, the light becomes a polarized light component along the transmission axis 24p of the optical sheet 24, passes through the optical sheet 24, and enters the liquid crystal display element 1, so that most of the illumination light from the light irradiation unit 10 Can be made incident on the display element without waste. Therefore, the use efficiency of the illumination light from the light irradiating means 10 is increased, and the light emission luminance of the light source 16 is reduced accordingly. It is possible to reduce the cost of power.

Further, in the above embodiment, the optical sheet 24 is disposed with its transmission axis 24p substantially parallel to the transmission axis of the rear polarizing plate 9b of the liquid crystal display element 1.
Most of the light that enters from the front of the liquid crystal display element 1 and is reflected by the light irradiating means 10 and enters the liquid crystal display element from the back can be transmitted without being reflected by the optical sheet 24. .

In the above embodiment, the light irradiation means 1
The light diffusion film 23 is provided on the front surface of the optical member 20 (the front surface of the optical member 20), and the optical sheet 24 is provided on the front surface of the light diffusion film 23. The light diffusion film 23 and the optical sheet 24 are stacked in reverse to the above embodiment. You may provide.

Further, in the above embodiment, the light irradiation means 10
Although the light diffusion film 23 is provided between the liquid crystal display element 1 and the liquid crystal display element 1, the light diffusion film 23 may be provided on the front side of the liquid crystal display element 1. Even if the light diffusion film 23 is provided, the illumination light from the light irradiating means 10 and the reflected light of the external light are diffused by the light diffusion film 23 and emitted to the front of the liquid crystal display element 1 as light having a substantially uniform luminance distribution. In addition to this, a wide viewing angle can be obtained by widening the emission angle range of the light emitted in front of the liquid crystal display element 1.

The light diffusion film 23 is not limited to a transparent adhesive applied film in which light scattering fine particles are dispersed, but may be a light diffusion plate or a surface perpendicular to the plate surface and along a specific direction. Shows a scattering property for light incident at an incident angle in an angle range inclined at a predetermined angle or more, and a selective scattering property showing almost no scattering property for light incident at an incident angle in an angle range smaller than the predetermined angle. May be used. However,
The light diffusion film 23 is not always necessary, and the optical sheet 24 may be omitted.

Further, the refracting surface 21b of the incident part 21 of the optical member 20 constituting the light emitting means 10 may be a linear surface having a constant inclination angle as shown in FIGS. If the refracting surface 21b is a curved converging / refracting surface, light that is taken in from the incident surface 21a of the incident portion 21 and refracted toward the front by the refracting surface 21b will be curved. The refracting surface 21b which is a light refracting surface
Since the light is condensed in a predetermined direction by the light condensing function, illumination light and reflected light having a luminance distribution with stronger directivity can be emitted.

In the above embodiment, the luminance distribution in the light guide width direction of the illumination light incident from the incident end face 11a of the light guide 11 on the back surface of the light guide 11 constituting the light irradiation means 10 is averaged. Although the light diffusion surface 15 for forming the light guide 11 is formed, the back surface of the light guide 11 may be a flat surface,
In addition, most of the illumination light incident from the incident end face 11a of the light guide 11 toward the back surface of the light guide 11,
When total reflection can be performed at the interface between the back surface of the light guide 11 and the outside air (air), the reflection plate 19 disposed behind the light guide 11 in the above embodiment may be omitted.

Further, in the above embodiment, the light guide 11
The reflection film 13 is provided on the plurality of step surfaces 12a of the step-shaped surface 12 to form a reflection surface 14 for external light. However, a reflection film is provided on the back surface of the light guide 11 to reflect the external light. May be formed, and external light incident from the front may be transmitted through the plurality of step surfaces 12 of the stepped surface 12 and reflected by the reflection surface on the back surface of the light guide plate.

Further, the light irradiating means 10 used in the above embodiment is used.
Is a light source 16 and an emission surface (stepped surface 12) for guiding illumination light from the light source 16 and emitting the light toward the liquid crystal display element 1.
A light guide 11 formed with each step surface 12b) and a reflection surface 14 different from the emission surface for reflecting external light incident from the front of the liquid crystal display element 1 toward the liquid crystal display element 1. The light irradiating means 1
Reference numeral 0 denotes a means for irradiating the liquid crystal display element 1 with illumination light, and a reflecting means for reflecting external light incident from the front of the liquid crystal display element 1 and irradiating the reflected light to the liquid crystal display element 1. Any configuration may be used.

The display device of the above embodiment uses the active matrix type TN type liquid crystal display element 1, but the liquid crystal display element 1 may be of a simple matrix type or a segment type. Also, TN
The liquid crystal display device 1 is not limited to a liquid crystal display device, but may be a STN (super twisted nematic) type, a dynamic scattering effect type, or a liquid crystal display device using a ferroelectric liquid crystal. Further, the liquid crystal display device 1 does not include a color filter. A monochrome display type may be used.

Further, the display device of the above embodiment uses the liquid crystal display device 1 as a display device. However, the present invention provides a display device for displaying another electro-optical display device, a translucent image printing film, or the like. The present invention can be widely applied to a display device using a non-light emitting display element as an element.

[0198]

According to the display device of the present invention, the illuminating light is emitted toward the display element behind the non-emissive display element and the external light incident from the front of the display element is directed toward the display element. A reflection display in which a light irradiating means for reflecting is arranged, and the display element and the light irradiating means reflect the external light incident from the front of the display element by the light irradiating means and emit the light to the front of the display element. And a screen brightness compensation display system that emits the illumination light from the light irradiation unit and compensates the brightness of the screen by the reflection display system by the illumination light, and the display element of the reflection display system. When the transmittance is maximally controlled, the reflectance of external light is about 1
Since it is set to 6% or more, power consumption is small, and in a usage environment in a wide illuminance range from low illuminance to high illuminance, it is possible to obtain a screen luminance suitable for the environmental illuminance.

In the display device of the present invention, when the display element has a color filter, for example, the reflection display when the aperture ratio of the display element is 100% and the transmittance of the color filter is 100%. The reflectance of the external light of the system (the reflectance when the transmittance of the display element is maximized) is 70%, and the transmittance of the color filter is 3%.
When it is 6%, the aperture ratio of the display element may be set to about 60% or more. By doing so, the transmittance of the reflective display system when the transmittance of the display element is maximized is controlled. External light reflectance can be about 16% or more.

Further, it is preferable that the reflectance of the external light of the reflective display system is set to 20% or more. By setting the reflectance of the external light in this way, the utilization efficiency of the external light is improved. Higher, the luminance of the illuminating light emitted from the light irradiating means is further reduced, and the range of the environmental illuminance for emitting the illuminating light from the light irradiating means is further narrowed to further reduce the power consumption of the light irradiating means. Can be reduced.

Further, in the display device of the present invention,
The light irradiating means includes an illumination luminance control means for controlling the luminance of the illumination light according to the environmental illuminance, so that the screen luminance is a predetermined luminance range according to the environmental illuminance,
It is preferable to set a luminance control condition of the illumination light by the illumination luminance control unit, and by configuring the light irradiation unit as described above, a screen more suitable for the environmental illuminance in accordance with the environmental illuminance. Brightness can be obtained.

In this case, the illumination brightness control means comprises an illuminance detector for measuring environmental illuminance, and means for controlling the brightness of the illumination light emitted from the light irradiating means based on the measured environmental illuminance. It is preferable that the brightness of the illumination light be controlled in accordance with the illuminance of the actual use environment, and a screen brightness suitable for the illuminance of the environment can be obtained.

Further, the light irradiating means includes a light source, an emission surface for guiding illumination light from the light source and emitting the light toward the display element, and directing external light incident from the front of the display element to the display element. And a light guide on which a reflection surface different from the emission surface for reflecting light is formed.The light irradiation means includes an emission surface for illumination light and a reflection surface for external light. Are different surfaces, it is possible to independently select the emission ratio of the illumination light from the emission surface and the reflectance of the reflection surface.

Therefore, the efficiency of use of the illumination light from the light source is increased by increasing the emission rate of the illumination light from the emission surface,
The light emission luminance of the light source is reduced by that much, and the power consumption is further reduced, and the reflectance of the reflective surface is controlled when the transmittance of the display element of the reflective display system is controlled to the maximum. About 16% or more (more preferably, 20% or more)
Can be chosen to be

[0205] As such a light irradiating means in which the exit surface of the illumination light and the reflection surface of the external light are different surfaces, the light guide is used, and at least one end surface thereof is provided with the illumination light from the light source. With the incident end face to be taken in, the front face is formed as a step-shaped surface consisting of a plurality of step faces gradually decreasing from the incident end face side to the other end side and a plurality of step faces connecting these step faces. A reflection film provided on one of the plurality of step surfaces and the light guide back surface to form a reflection surface of the external light, and an emission surface of illumination light incident from the incident end face by the plurality of step surfaces. Is formed on the front surface side of the light guide, the external light entering from the front of the display element and the light reflected by the reflection surface are transmitted, and emitted from each step surface of the light guide. Optical unit that emits illumination light toward the display element According to this light irradiation means, the illumination light taken into the light guide from the incident end face is emitted from a plurality of step surfaces of the step-shaped surface of the light guide, and the light Is emitted toward the display element after being changed in direction by the optical member, so that the illumination light from the light source can be made incident on almost the entire display element.

According to this light irradiation means, either one of the plurality of steps of the step-shaped surface of the light guide and the back surface of the light guide is a reflection surface for external light, and External light incident from the front of the element is transmitted through the optical member and reflected by the reflection surface, and the reflected light is transmitted again through the optical member and emitted toward the display element. Most of the external light incident from the display element can be reflected without waste, and can be incident on almost the entire display element.

In this light irradiation means, the optical member is formed of a transparent plate having a front surface for emitting light toward the display element and a back surface facing the front surface of the light guide. A projection-shaped incident portion having an incident surface that captures light emitted from each step surface of the light guide and a refraction surface that refracts light captured from the incident surface toward the front is formed. Preferably, with the optical member having such a configuration, most of light emitted from each step surface of the light guide is taken into the optical member without waste and emitted toward the display element from the front surface. it can.

Further, by configuring the optical member as described above, light emitted from each step surface of the light guide and incident on each incident portion of the optical member from the incident surface is
The light is refracted by the refraction surface and is condensed in a predetermined direction. From the front surface of the optical member, it is possible to emit illumination light having a high luminance distribution in a predetermined direction (for example, a front direction), and the light guide. The external light reflected by the reflection surface can also be emitted from the front surface of the optical member as light having a high luminance distribution in a predetermined direction (for example, the front direction).

Further, in this display device, it is preferable to provide a light diffusing means on at least one of between the light irradiation means and the display element and on the front side of the display element. Accordingly, the illumination light from the light irradiation means and the reflected light of the external light can be diffused by the light diffusion means and emitted forward as light having a substantially uniform luminance distribution.

Therefore, even when the illumination light from the light irradiating means is superimposed on the reflected light of the external light to supplement the screen luminance, the illumination light emitted from the light irradiating means in an environment where almost no external light can be obtained. Even when performing display only by itself, and also when performing display by only reflected light of external light without emitting illumination light from the light irradiating means, the screen brightness is made uniform over the entire screen, and in front of the display element. By widening the emission angle range of the emitted light, a wide viewing angle can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view of a display device showing one embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a part of a non-light-emitting display element (liquid crystal display element) used in the display device.

FIG. 3 is an enlarged side view of a part of a light guide and an optical member constituting a light irradiation unit of the display device.

FIG. 4 is an enlarged perspective view of a part of the light guide.

FIG. 5 is a perspective view of an optical sheet disposed between the light irradiation unit and a display element.

FIG. 6 is a view showing the annual average illuminance of each of the three outdoor cities of Sapporo, Fukuoka, and Naha during the daytime including all weather days such as fine weather, cloudy weather, and rainy weather.

FIG. 7 is a view showing monthly average illuminance at each time during the daytime outdoors on a sunny day in January in the three cities.

FIG. 8 is a diagram showing monthly average illuminances of the three cities during each daytime outdoors on a sunny day in April.

FIG. 9 is a diagram showing monthly average illuminance in each of the three cities during the daytime outdoors on a sunny day in July.

FIG. 10 is a diagram showing monthly average illuminances of the three cities at various times during the daytime outdoors on a sunny day in October.

FIG. 11 is a diagram showing environmental illuminance-screen luminance characteristics of a display device of an embodiment in which the reflectance of external light of a reflective display system is set to 16%, a reflective display device, and a transmissive display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 6R, 6G, 6B ... Color filter 10 ... Light irradiation means 11 ... Light guide 11a ... Incident end surface 12 ... Stepped surface 12a ... Step surface 12b ... Step surface (outgoing surface) 13 ... Reflection film 14 ... Reflecting surface 16 Light source 20 Optical member 21 Incident portion 21a Incident surface 21b Refracting surface 22 Input / output surface 23 Light diffusion film

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H079 AA02 AA13 BA01 CA22 DA08 GA05 KA05 KA16 KA18 2H091 FA02Y FA08X FA08Z FA23Z FA31Z FA32Z FD22 FD23 LA16 5G435 AA00 BB12 BB15 BB16 CC09 CC12 EE27 FF03 FF03 FF03 FF03 GG03 FF27

Claims (10)

[Claims] 1. A non-light-emitting display element for controlling transmission of light incident from the outside to display an image, and disposed behind the display element to emit illumination light toward the display element.
Light illuminating means for reflecting external light incident from the front of the display element toward the display element, and the external light incident from the front of the display element by the display element and the light irradiating means. A reflective display system for reflecting the light by the light irradiating means and emitting the light forward of the display element; and irradiating the illumination light from the light irradiating means and compensating the luminance of the screen of the display element by the reflective display system using the illuminating light. A screen brightness compensation display system that performs the control, and the reflectance of the external light in the reflection display system when the transmittance of the display element is controlled to a maximum is set to about 16% or more. Display device. 2. The reflection display system has a reflectance of 70% when the aperture ratio of the display element is 100%, the display element has an aperture ratio of about 60% or more, and has a transmittance. Is 36%
The display device according to claim 1, further comprising: a color filter. 3. The reflection display system according to claim 1, wherein said external light has a reflectivity of 20.
%. The display device according to claim 1, wherein 4. The light irradiating means includes illumination brightness control means for controlling the brightness of the illumination light in accordance with the illuminance of the environment in which the display device is used, and the screen brightness is predetermined in accordance with the environmental illuminance. 2. The display device according to claim 1, wherein a luminance control condition of the illumination light by the illumination luminance control unit is set so that the luminance range is adjusted. 5. The illumination luminance control means includes an illuminance detector for measuring the environmental illuminance, and means for controlling the luminance of illumination light emitted from the light irradiating means based on the measured environmental illuminance. The display device according to claim 4, wherein: 6. The light irradiating means includes means for irradiating the display element with illumination light, and reflecting means for reflecting external light incident from the front of the display element and irradiating the reflected light to the display element. The display device according to claim 1, comprising: 7. The light irradiating means includes: a light source; an emission surface for guiding illumination light from the light source and emitting the light toward the display element; and external light incident from the front of the display element toward the display element. 2. The display device according to claim 1, further comprising: a light guide having a reflection surface different from the emission surface for reflecting the light. 8. At least one end surface of the light guide is an incident end surface for receiving illumination light from the light source, and the front surface of the light guide is stepwise from the incident end surface side to the other end side. Are formed in a stair-shaped surface consisting of a plurality of step surfaces that are lowered to each other and a plurality of step surfaces connecting these step surfaces, and on one of the plurality of step surfaces and the back surface of the light guide. A reflection film is provided to form a reflection surface of the external light, and the plurality of step surfaces form an emission surface of illumination light incident from the incident end surface, and a front surface of the light guide, An optical member that transmits external light incident from the front of the display element and reflected light reflected by the reflection surface and emits illumination light emitted from each step surface of the light guide toward the display element is disposed. The display according to claim 7, characterized in that: Location. 9. The optical member comprises a transparent plate having a front surface for emitting light toward the display element and a back surface facing the front surface of the light guide, and the light guide includes a light guide. A projection-like incident portion having an incident surface for taking in light emitted from each step surface of the body and a refraction surface for refracting light taken from the incident surface toward the front is formed. Item 10. The display device according to item 8. 10. The display according to claim 1, wherein light diffusion means is provided between at least one of the light irradiation means and the display element and at least one of a front side of the display element. apparatus.