JPH11311973A - Display device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a display device which requires less power consumption and can obtain a screen luminance suitable for the environmental illuminance in a usage environment in a wide illuminance range from low illuminance to high illuminance. provide. An illumination light is emitted to the liquid crystal display element behind a liquid crystal display element and the liquid crystal display element is illuminated.
A light illuminating means 10 for reflecting external light incident from the front of the display device toward the liquid crystal display element 1 and an illumination luminance controlling means for controlling the luminance of the illuminating light according to the illuminance of the environment in which the display device is used 26, the liquid crystal display element 1
The reflectance of the external light of the light irradiating means 10 and the luminance control condition of the illumination light by the illumination luminance control means 26 are set so that the luminance of the screen is within a predetermined luminance range according to the environmental illuminance. It was set.

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 For example, a display device having a non-light-emitting display element, such as a liquid crystal display element, which uses light incident from the outside and controls transmission of the light to perform display, utilizes transmitted light. There are a transmissive display device and a reflective display device using reflected light.

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.

[0004] The reflection type display device uses external light which is light of a use environment of the display device to perform display, and external light incident from the front of the display element is arranged behind the display element. Reflected by the reflector toward the display element,
The light is emitted to the front of the display element for display.

[0005] The transmissive display device consumes a large amount of power to turn on a backlight. On the other hand, a reflective display device can obtain reflected light having an intensity corresponding to the intensity of external light incident from the front of the display element. Therefore, in an environment where external light exists, observe the display with sufficient brightness. Power consumption is low because a backlight is not required.

[0006]

The preferred screen luminance of the display device (the luminance at which the display can be observed with sufficient brightness under the use environment of the display device) depends on the illuminance of the environment in which the display device is used. Even with the same screen luminance, the screen may be too dazzling or too dark depending on the environmental illuminance.

[0007] Looking at the screen luminance of a reflection type display device, in the reflection type display device, the intensity of reflected light emitted in front of the display element largely depends on the intensity of external light incident from the front of the display element. Therefore, for example, in an environment of high illuminance exceeding 100,000 lux such as under direct sunlight in summer, the screen becomes too dazzling to make the display difficult to see, and in a dark environment such as outdoors at night, the display is visible. It cannot be used in a dark environment because it does not provide a sufficient screen brightness.

On the other hand, conventionally, a reflective display device provided with an auxiliary light source has been proposed so that observation can be performed even in a dark environment such as outdoors at night. This reflective display device has a transflective plate disposed behind a display element and an auxiliary light source disposed behind the transflective plate, and the transflective plate has a reflectance of the display device. In order to ensure a sufficiently high ratio (the ratio of the intensity of the external light incident from the front of the display element to the intensity of the output light reflected by the reflector and emitted to the front of the display element), a high reflectance / low transmittance is required. The characteristics are used.

However, in the reflection type display device provided with this auxiliary light source, the transmittance of the semi-transmissive reflection plate is extremely small, and the emission luminance of the auxiliary light source is extremely increased in order to reduce power consumption. Therefore, when the auxiliary light source is turned on, the luminance of the illumination light transmitted through the semi-transmissive reflector and incident on the display element is weak.

[0010] Therefore, the reflection type display device provided with the auxiliary light source has a low screen brightness when the auxiliary light source is turned on in a dark environment, and has a high illuminance environment such as direct sunlight in summer. Then, the screen is too dazzling and the display is difficult to see.

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

[0012]

A display device according to the present invention comprises:
A non-light-emitting display element that uses light incident from outside and controls transmission of the light for display, and is disposed behind the display element, and emits illumination light toward the display element, and displays the display. Light irradiation means for reflecting external light incident from the front of the element toward the display element, and illumination luminance control means for controlling the luminance of the illumination light according to the illuminance of the environment in which the display device is used, and As the luminance of the screen of the display element is in a predetermined luminance range according to the environmental illuminance,
It is characterized in that the reflectance of the external light of the light irradiating means and the luminance control condition of the illumination light by the illumination luminance control means are set.

This display device displays an image by using reflected light of external light by the light irradiating means and illumination light emitted by the light irradiating means. When the illumination light is emitted from the light irradiating means in an environment in which reflected light having an intensity corresponding to the intensity of the light is obtained, light having a luminance in which the reflected light of the external light and the illumination light are superimposed on the display element has a back surface. Incident from

Therefore, this display device can obtain a suitable screen luminance even in a dark environment, and has a reflectivity of the display device (reflected by the light irradiating means with respect to the intensity of external light incident from the front of the display element). The ratio of the intensity of the emitted light to the front of the display element) can be lower than that of a normal reflective display device using only reflected light of external light.
Even under a high illuminance environment such as direct sunlight in summer, a suitable screen luminance without excessive glare can be obtained.

Further, since the reflectance of the external light of the light irradiating means is constant, the luminance of the reflected light of the external light is a luminance corresponding to the environmental illuminance. An illumination brightness control unit for controlling the brightness of the illumination light, a reflectance of the external light of the light irradiation unit, and the illumination brightness control unit so that the screen brightness falls within a predetermined brightness range according to environmental illuminance. And the brightness control condition of the illumination light according to the above, the screen brightness suitable for the environmental illuminance can be obtained according to the environmental illuminance.

Moreover, the luminance of the illumination light may be any value as long as the screen luminance by both the reflected light of the external light and the illumination light is a luminance suitable for the environmental illuminance. Since the brightness of the illumination light emitted from the irradiation means may be controlled, the power consumption of the light irradiation means may be small.

Therefore, this display device requires less power consumption, and can obtain a screen luminance suitable for the environmental illuminance in a usage environment in a wide illuminance range from low illuminance to high illuminance.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the display device of the present invention emits illumination light toward the display element behind the display element and displays external light incident from the front of the display element on the display element. A light irradiating unit that reflects light toward the element is provided, and an illumination luminance control unit that controls the luminance of the illumination light in accordance with the illuminance of the environment in which the display device is used. The power consumption is set by setting the reflectance of the external light of the light irradiating unit and the luminance control condition of the illumination light by the illumination luminance control unit so that the luminance range becomes a predetermined luminance range according to the illuminance. 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 environment illuminance.

In the display device according to the present invention, the light irradiating means may have a screen luminance of 20 to 200 nits at an environmental illuminance of 50 lux and a screen luminance of 30 to 300 nits at an environmental illuminance of 1000 lux. , 300
It is desirable to control the luminance of the illumination light according to the environmental illuminance so that the luminance is represented by a quadratic function that satisfies the range of the screen luminance of 400 to 4000 nits at the environmental illuminance of 00 lux.

In other words, the light irradiating means, when the screen luminance with respect to the environmental illuminance is I (lux) for the environmental illuminance and L (nit) for the screen luminance, is -2 × 10 ^-8 × I ² +0.015 × I + 20 <L <-3 × 10 ⁻⁷ × I ²
It is desirable to control the luminance of the illumination light in accordance with the ambient illuminance so as to satisfy + 0.113 × I + 150. By controlling the luminance of the illumination light under such conditions, a wide range from low illuminance to high illuminance is obtained. In a usage environment in the illuminance range, it is possible to obtain a screen luminance suitable for the environment illuminance.

Further, the light irradiating means has a screen luminance of 20 to 60 nits at an environmental illuminance of 50 lux and a screen luminance of 60 to 2 at an environmental illuminance of 1000 lux.
The luminance of the illumination light is controlled in accordance with the environmental illuminance so that the luminance is represented by a quadratic function that satisfies the screen luminance range of 1000 to 3000 nits at a screen luminance of 00 nits and an environmental illuminance of 30,000 lux, respectively. Is more desirable.

In other words, the light irradiating means is such that when the screen luminance with respect to the environmental illuminance is I (lux) for the environmental illuminance and L (nit) for the screen luminance, -9 × 10 ^-8 × I ² +0.0453 × I + 20 <L <-2 × 10 ⁻⁷ × I ²
It is more desirable to control the luminance of the illumination light according to the environmental illuminance so as to satisfy + 0.0871 × I + 50. By controlling the luminance of the illumination light under such conditions, it is possible to control the luminance from low illuminance to high illuminance. In a use environment in a wide illuminance range, it is possible to obtain a more suitable screen luminance for the environment illuminance.

It is preferable that the illumination luminance control means controls the luminance of the illumination light from the light irradiating means at least in an environmental illuminance higher than the indoor illuminance. In an environment with a high illuminance, it is possible to obtain a screen luminance more suitable for the environment illuminance.

Further, it is more preferable that the illumination brightness control means controls the brightness of the illumination light from the light irradiating means in a range where the environmental illuminance is less than 50 lux to almost more than 30,000 lux. By
In an environment with a wide illuminance range from 50 lux or less to almost 30,000 lux, a more suitable screen luminance can be obtained for the environment illuminance.

The illumination brightness control means may control the light emission means so that the brightness of the illumination light continuously decreases as the environmental illuminance decreases in an illuminance range where the environmental illuminance is lower than the indoor illuminance. It is desirable to perform control. By doing so, in an environment of an illuminance range lower than the room illuminance, that is, in an environment in which the display can be visually recognized even if the screen brightness is low, a low level more suitable for the environment illuminance is obtained. It is possible to obtain the screen brightness of the brightness and to further reduce the power consumption of the light irradiation means.

In the illumination luminance control means, when the ambient illuminance is lower than a predetermined illuminance higher than the indoor illuminance in an illuminance range in which the ambient illuminance is higher than the indoor illuminance, the illumination illuminance increases. Brightness increases continuously,
When the environmental illuminance exceeds the predetermined illuminance, it is desirable to control the light irradiating means so that the luminance of the illuminating light continuously decreases as the environmental illuminance further increases.

In this manner, in the illuminance range where the environmental illuminance is higher than the indoor illuminance, the luminance of the illumination light is continuously increased as the environmental illuminance increases, which is suitable for the environmental illuminance. When the screen luminance is obtained and the environmental illuminance exceeds a predetermined illuminance higher than the indoor illuminance, and a suitable screen luminance for the environmental illuminance is obtained only with the reflected light of the external light, the environmental illuminance is further increased. Accordingly, it is possible to continuously reduce the luminance of the illumination light to obtain a screen luminance suitable for environmental illuminance, and to reduce power consumption.

Further, in the illumination brightness control means, in the illuminance range where the environmental illuminance is lower than the indoor illuminance, the light illuminating means is configured to continuously reduce the brightness of the illumination light as the environmental illuminance decreases. In the illuminance range where the environmental illuminance is higher than the indoor illuminance, when the environmental illuminance is equal to or less than a predetermined illuminance higher than the indoor illuminance, the luminance of the illumination light increases continuously as the environmental illuminance increases. More preferably, when the environmental illuminance exceeds the predetermined illuminance, the light irradiating means is controlled so that the luminance of the illumination light is continuously reduced as the environmental illuminance further increases.

In this manner, in an environment having an illuminance range lower than the indoor illuminance, that is, in an environment in which the display can be sufficiently viewed even when the screen brightness is low, a screen having a low brightness more suitable for the environment illuminance is provided. While obtaining the luminance, the power consumption of the light irradiation means can be further reduced, and in the illuminance range where the environmental illuminance is higher than the indoor illuminance, the luminance of the illumination light is continuously increased as the environmental illuminance increases. To obtain a suitable screen luminance for the environmental illuminance, the environmental illuminance exceeds a predetermined illuminance higher than the indoor illuminance, and a suitable screen luminance for the environmental illuminance can be obtained only by the reflected light of the external light. When, the luminance of the illumination light is continuously reduced as the environmental illuminance further increases, so that a suitable screen luminance with respect to the environmental illuminance can be obtained and the power consumption can be reduced.

The illumination brightness control means may include 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. By doing so, it is possible to control the luminance of the illuminating light in accordance with the illuminance of the actual use environment, and obtain a screen luminance suitable for the illuminance of the environment.

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 external light on the reflection surface Can be independently selected, and 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, and the emission luminance of the light source is correspondingly increased. By lowering the power consumption, the power consumption can be further reduced, and the reflectance of external light on the reflection surface can be set so that the reflectance of the display device becomes a desired value.

[0033] As such light irradiating means in which the emission surface of the illumination light and the reflection surface of the external light are different surfaces, at least one end surface of the light guide has an entrance end surface for receiving illumination light from the light source. The light guide has a front surface, a plurality of step surfaces gradually decreasing from the incident end surface side to the other end side, and a step-shaped surface including a plurality of step surfaces connecting these step surfaces. A reflection film is provided on the plurality of step surfaces to form a reflection surface of the external light, and the plurality of step surfaces are an emission surface of illumination light incident from the incident end surface, Transmitting, on the front side of the light guide, external light incident from the front of the display element and reflected light of the external light reflected by the reflection surface on each step surface of the light guide, Light emitted from each step surface toward the display element Having a structure in which members are arranged is desirable.

According to this light irradiating means, the illuminating 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, the plurality of step surfaces of the step-shaped surface of the light guide are reflection surfaces of external light, respectively, and external light incident from the front of the display element is prevented from being reflected. The light transmitted through the optical member is reflected by the reflection surface on each step surface of the light guide, and the reflected light is transmitted through the optical member again 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 first optical interface for taking in light emitted from each step surface of the light guide, and a second optical interface for reflecting or refracting light taken in from the first optical interface in a front direction.
It is preferable that a projection-shaped incident portion having the above optical interface is formed.

With the above-mentioned structure 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.

Moreover, 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 first optical interface can be used. The light is reflected or refracted by the second optical interface and condensed in a predetermined direction, and illumination light having a high luminance distribution in a predetermined direction (for example, a front direction) can be emitted from the front surface of the optical member. The external light reflected on the reflection surface on each step surface of the light guide 11 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 the optical member, the plurality of incident portions are provided at intervals, and a back region between the adjacent incident portions is provided with external light and the light guide which are incident from the front of the display element. More desirably, the third optical interface is configured to transmit the external light reflected by the reflecting surface on each step surface.

According to the optical member having such a configuration, external light that is incident from the front of the display element and incident on the optical member from the front surface is transmitted to the incident portion and the third portion therebetween.
Out of the optical interface to the back surface of the optical member, and reflects the external light reflected by the reflecting surface on each step surface of the light guide from the incident portion and the third optical interface to the optical member. The light can be captured and emitted from the front surface of the optical member toward the display element, and the reflected light can be
Light having a higher luminance distribution in a predetermined direction (for example, the front direction) can be obtained.

Preferably, the back surface of the light guide is a light diffusion surface for averaging the luminance distribution of the illumination light incident from the incident end face in the width direction of the light guide. By using a light guide having such a configuration, the luminance distribution of illumination light that is taken in from the incident end face of the light guide and emitted from the plurality of step surfaces is made substantially uniform in the light guide width direction. Can be.

Further, in this display device, it is preferable to provide a light diffusing film between the light irradiating means and the display element, whereby reflection of illumination light and external light from the light irradiating means is preferable. The light can be diffused by the light diffusion film and incident on the display element from the back as light having a substantially uniform luminance distribution.

Therefore, the light source 1 of the light irradiation means 20
6. Use both the reflected light of the external light reflected by the light irradiating means 10 and the illuminating light emitted by the light irradiating means 10 in the illuminance range in which the light 6 is turned on, and in an illuminance environment where external light can be obtained Also in the display, when the ambient illuminance is almost 0 lux, that is, in the display using only the illumination light emitted by the light irradiation unit 10 in an environment where external light is hardly obtained, the light source 16 is not turned on. Even in a display using only reflected external light in an environment with high illuminance, the screen brightness is made uniform over the entire screen, and the emission angle range of light emitted in front of the liquid crystal display element 1 is widened to provide a wide visual field. You can get the corner.

Also, in this display device, a reflection axis and a transmission axis are provided between the light irradiation means and the display element in directions substantially orthogonal to each other, and incident light of a polarization component along the reflection axis is transmitted. It is preferable to provide an optical sheet having a property of reflecting and transmitting incident light of a polarization component along the transmission axis.

As described above, if the optical sheet is provided between the light irradiating means and the display element, of the illuminating light from the light irradiating means, the light of the polarization component along the transmission axis of the optical sheet is provided. However, while passing through the optical sheet and entering the display element, of the illumination light from the light irradiating means, the light of the polarization component along the reflection axis of the optical sheet, the reflection on the optical sheet and the The direction of polarization is changed by repetition of reflection at the light irradiating means, and the light becomes polarized component light along the transmission axis of the optical sheet, passes through the optical sheet, and enters the display element. Most of the illuminating light can be made incident on the display element without waste. Therefore, the efficiency of using the illuminating light from the light irradiating means is increased, and the light emission luminance of the light source is reduced accordingly, further reducing the power consumption. Do Door can be.

In the case where the optical sheet is provided, for example, when the display element is a liquid crystal display element having a polarizing plate on the front and back sides, the transmission axis of the optical sheet is set on the rear side of the liquid crystal display element. It is desirable to dispose the optical sheet substantially in parallel with the transmission axis of the polarizing plate, and by arranging the optical sheet in this manner, light enters from the front of the liquid crystal display element, is reflected by the light irradiating means, and is incident on the liquid crystal display element. Most of the light incident from the rear surface can be transmitted without being reflected by the optical sheet.

[0047]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side view of a display device. The display device of this embodiment uses a liquid crystal display element as a non-light-emitting display element that uses externally incident light and controls transmission of the light to perform display. Things.

As shown in FIG. 1, this display device is disposed behind a liquid crystal display element 1 and the liquid crystal display element 1.
A light irradiating means for emitting illumination light toward the rear surface of the liquid crystal display element and reflecting external light incident from the front of the liquid crystal display element toward the rear surface of the liquid crystal display element; And an illumination brightness control means 26 for controlling the brightness of the illumination light according to the illuminance of the environment in which the device is used.

Although the internal structure of the liquid crystal display element 1 is not shown, a pair of front and rear transparent substrates 2 and 3 are joined via a frame-shaped sealing material 4, and the sealing material between the two substrates 2 and 3 is provided. Liquid crystal is sealed in a region surrounded by 4, and transparent electrodes for applying an electric field to the liquid crystal layer are provided on the inner surfaces of the substrates 2 and 3, respectively.

The liquid crystal display element 1 used in this embodiment
Is an active matrix liquid crystal display element for displaying a color image. On one substrate, for example, on the inner surface of the rear substrate 3, a plurality of pixel electrodes arranged in a matrix and a plurality of pixels respectively connected to these pixel electrodes are provided. A switching element composed of a TFT (thin film transistor), a gate line for supplying a gate signal to the TFT in each row, and a data line for supplying a data signal to the TFT in each column are provided. A plurality of color filters (for example, red, green, and blue) alternately arranged in correspondence with the pixel electrodes, and a counter electrode facing all of the pixel electrodes.

The liquid crystal display element 1 is of a TN (twisted nematic) type having polarizing plates 5 and 6 on the front and back sides, and the liquid crystal molecules sealed between the substrates 2 and 3 The orientation direction in the vicinity of each substrate is regulated by an orientation film provided on the inner surface of each of the substrates 2 and 3, and a predetermined twist angle (for example, approximately 9
0 °). In addition, the polarizing plate 5,
Reference numeral 6 designates a transmission axis oriented in a predetermined direction, and is attached to the outer surfaces of the substrates 2 and 3, respectively.

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 the liquid crystal display element 1 is provided on the front face 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. 2 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 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 extends in the width direction of the light guide 11 (the length of the incident end surface 11a). (Horizontal direction).

As shown in FIG. 3, SiO 2 is formed on each step 12a of the step-shaped surface 12 as a whole.
_{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. 3, 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 is provided on the back surface of the light guide 11. It has become.

The light diffusing surface 15 includes a plurality of vertically elongated prism portions 15a having a length extending over the entire length of the light guide 11,
1 and are formed in parallel with each other at a fine pitch in the width direction, and the reflection plate 19 is arranged such that its reflection surface is close to or in contact with the top surfaces of the plurality of prism portions 15a. ing.

The light source 16 comprises, 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 to the rear surface and is reflected by the reflection surface 14 (the surface of the reflection film 13) on each of the step surfaces 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, the front surface of which is a flat surface, and the rear surface of 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 extending 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.

The plurality of incident portions 21 have a triangular cross-sectional shape, and one of the two side surfaces of each of the incident portions 21 is opposed to one of the side surfaces facing the step surface 12b of the light guide 11. The interface with the outside air (air) serves as a first optical interface 21a for taking in the light emitted from the stepped surface 12b, and the interface between the other side and the outside air optically converts the light taken in from the first optical interface 21a. The second optical interface 21b reflects or refracts toward the front surface of the member 20.

The first optical interface 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 (facing the step surface 12b). Direction angle) does not exceed 90 °.

The second optical interface 21b has an inclined surface having an angle formed by a perpendicular to the front surface of the optical member 20 and a larger angle than the angle formed by the first optical interface 21a and the perpendicular. It has become.

The more desirable shape of the incident portion 21 is such that the first optical interface 21a is inclined by 5 to 15 ° with respect to the perpendicular to the step surface 12b of the light guide 11, and The optical interface 21b has a shape inclined by 20 to 50 ° in a direction opposite to the perpendicular.

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 and outside air (air) are provided. Is a third optical interface 22 facing the reflection surface 14 on each step surface 12a of the light guide 11.

The third optical interface 22 is connected to the light guide 1
The light incident on the liquid crystal display element 1 from the front and reflected by the reflecting surface 14 on each step 12a of the light guide 11 is a surface having an inclination substantially parallel to or close to the step 12a. This is an optical interface for transmission.

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 2, 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 2, 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 or an integer fraction of the pixel pitch, and the pitch of the step surface 12 b of the light guide 11 is smaller than the pitch of the incident portion 21 of the optical member 20. Is also a slightly larger pitch.

In the display device of this embodiment, the light guide 16 and the light source 16 arranged opposite to 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 mainly takes in external light in a direction inclined to 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 arranged such that the light irradiating means 10 is arranged on the upper edge side of the screen which is the main direction of capturing external light, that is, the upper edge side of the liquid crystal display element 1. (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. 4 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 a polarization component 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. 4, the optical sheet 24 has a polarization component (hereinafter referred to as an S-polarization component) light 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. 4 shows an example in which light is incident on the optical sheet 24 from the rear side, but the optical sheet 24 exhibits 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 / convex surfaces having a shape in which horizontally long prism-like portions having a minute width are continuously arranged in parallel in the width direction are formed on one surface. 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 so that its transmission axis 24p is substantially parallel to the transmission axis of the polarizing plate 6 on the back side of the liquid crystal display element 1. As shown in FIG.
Is attached to the front surface of the optical member 20 of the light irradiating 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 thereof (the back surface of the rear polarizing plate 6) is transparentized by a transparent adhesive or a double-sided adhesive sheet 25. It is attached to the front surface of the film 23.

Next, a description will be given of the 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 luminance control means 26 includes an illuminance detector 27 for measuring environmental illuminance, and illumination emitted by the light irradiating means 10 based on the environmental illuminance measured by the illuminance detector 27. Means for controlling the brightness of the light, wherein the means for controlling the brightness of the illumination light comprises a light source brightness adjustment circuit 28.
And a light source lighting circuit 29.

The illuminance detector 27 has a 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 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 to the screen of the liquid crystal display element 1. 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.

In this display device, basically, reflected light of external light which is incident from the front of the liquid crystal display element 1 and is reflected by the light irradiating means 10 and illumination light emitted by the light irradiating means 10 The light source 16 of the light irradiation means 10 is turned on when the illuminance of the environment in which the display device is used is within a predetermined illuminance range. In addition,
The range of the ambient illuminance for lighting the light source 16 is, for example, 0
Lux to over 30000 lux.

That is, the display device is provided with the light source 16
In an illuminance range where the light is lit, and under an illuminance environment where external light can be obtained, both the reflected light of the external light reflected by the light irradiating means 10 and the illumination light emitted by the light irradiating means 10 are used. When the ambient illuminance is almost 0 lux, that is, in an environment where external light is hardly obtained, the display is performed only by the illumination light emitted from the light irradiation means 10 and the light source 16 is not turned on. In an illuminance environment, display is performed using only reflected external light.

First, the emission path of the illumination light from the light irradiating means 10 will be described. The light guide 11 of the light irradiating means 10 takes in the illumination light from the light source 16 from the incident end face 11a and outputs the light. Is emitted from the plurality of step surfaces (outgoing surfaces) 12b of the step-shaped surface 12, and light incident on the plurality of step surfaces 12a of the step-shaped surface 12 from the front is reflected on the reflecting surfaces ( (The surface of the reflection film 13), and is reflected forward.
Illumination light taken from a is emitted from the plurality of step surfaces 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.

The light other than the light directly traveling to the step surface 12b, that is, the 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 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 15 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 on the first optical interface 21a on one side thereof.

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. 2, among the light emitted from b, there is light emitted toward the next step surface 12 a, but the light is
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 portion 21 from the first optical interface 21a of these incident portions 21, and the second optical interface on the opposite side thereof. The light is totally reflected at 21 b and changes its direction to the front surface of the optical member 20, passes through the optical member 20, and exits 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 first optical interface 21a, and is reflected or refracted by the second optical interface 21b to be directed in a predetermined direction. The light is a focused light having a high luminance distribution in a predetermined direction.

In this case, in this embodiment, the incident portion 2
The angle of inclination of the first second optical interface 21b is
Is set so that the direction of the light reflected by the optical member 20 is in the front direction (direction near the normal to the front surface of the optical member). 20 is a light having a directivity distribution with high luminance in the front direction.

The direction of emission of the illumination light emitted to the front surface of the optical member 20 is a direction corresponding to the angle of inclination of the second optical interface 21b of the incident portion 21, and is the direction of the second optical interface 21b. The angle of inclination is 20 to the normal to the front of the optical member.
When the angle is in the range of 50 °, the distance becomes closer to the front direction.

The light emitted in front of the optical member 20, ie, the light emitted from 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 thereof, and is 1 is incident from the back. In FIG. 2, the state of diffusion 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 polarized light 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.

The path of the light reflected by the optical sheet 24 is transmitted through the optical member 20 of the light irradiating means 10 and the reflection surface 14 on each step surface 12a of the light guide 11 is not shown. 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. Therefore, most of the illumination light from the light irradiation means 10 can be made incident on the liquid crystal display element 1 without waste.

[0104] Of the light reflected from the optical sheet 24 and incident on the optical member 20 from the front surface, a second optical interface 21b having a large inclination angle of each incident portion 21 on the rear surface of the optical member 20; Light traveling toward the third optical interface 22 between the adjacent incident portions 21 is reflected by these optical interfaces 21b and 2b.
2 and exits to the back. Further, the light traveling toward the first optical interface 21a having a small inclination angle of the incident portion 21 is totally reflected by the first optical interface 21a and changes its direction, and the direction is changed to the second optical interface 21b or the third optical interface 21b. The light exits from the interface 22 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 first optical interface 21a of each of the incident portions 21 of the optical member 20 is large, the reflection surface 1 on each step surface 12a of the light guide 11 is large.
Most of the light reflected by 4 is taken in from the second optical interface 21 b and the third optical interface 22 of each incident portion 21 of the optical member 20.

Then, of the light taken in from the second optical interface 21b and the light taken in from the third optical interface 22 goes directly to the front surface of the optical member 20,
Of the light transmitted through the optical member 20 in that direction and emitted from the front surface thereof and taken in from the second optical interface 21b, light traveling toward the first optical interface 21a on the opposite side is the optical interface 21a The direction is changed by being totally reflected by the second
The light exits from the front surface of the optical member 20 by changing its direction from the optical interface 21b and the third optical interface 22 to a direction close to the direction of light traveling directly toward 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 irradiation 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 polarizing plate 6 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 passes through the rear polarizing plate 6 and Incident on.

The illumination light (linearly polarized light) that has passed through the rear-side polarizing plate 6 and entered the liquid crystal display device 1 is transmitted through the liquid crystal layer, and the two substrates 2 and 3 of the liquid crystal display device 1 are being processed.
Of the liquid crystal molecules which changes according to the voltage applied between the electrodes formed on the inner surface of the front substrate 2 to be rotated by the birefringence effect according to the orientation state thereof, and by the color filters of a plurality of colors provided on the inner surface of the front substrate 2. The light of the wavelength component in the absorption wavelength band is absorbed to become colored light colored to the color of the color filter, and of the light, the light of the polarization component along the transmission axis of the front-side polarizing plate 5 is converted to the front-side polarized light. Through the plate 5,
The light is emitted to the front of the liquid crystal display element 1 as image light.

Next, the path of external light entering from the front of the liquid crystal display element 1 will be described.
As described above, in an environment where external light can be obtained, the screen direction is selected and used so as to mainly take in external light from a direction inclined to the upper edge side of the screen with respect to the normal of the screen. Mainly enter from the upper edge side of the screen (the upper edge side of the liquid crystal display element 1) at various incident angles.

External light incident from the front of the liquid crystal display element 1 is first absorbed by the front-side polarizing plate 5 as light having a polarization component along its absorption axis, and is transmitted along the transmission axis of the front-side polarizing plate 5. The light enters the liquid crystal display element 1 as linearly polarized light.

The external light (linearly polarized light) transmitted through the front-side polarizing plate 5 and incident on the liquid crystal display element 1 is subjected to a plurality of color filters provided on the inner surface of the front substrate 2 so as to have the absorption wavelength band. The light of the wavelength component is absorbed to become colored light colored to the color of the color filter, and then, in the process of transmitting through the liquid crystal layer, the light is rotated by a birefringence action according to the orientation state of the liquid crystal molecules which changes according to the applied voltage. Of the light, the light of the polarization component along the transmission axis of the rear-side polarizing plate 6 transmits through the rear-side polarizing plate 6 and is emitted as image light to the rear surface of the liquid crystal display element 1.

The light emitted to the back of the liquid crystal display element 1 passes through the optical sheet 24 and the light diffusion film 23 in order and enters the optical member 20 of the light irradiation means 10 from the front. Since the transmission axis 24p of the optical sheet 24 and the transmission axis of the rear polarizing plate 6 of the liquid crystal display element 1 are substantially parallel to each other, the transmission axis 24p of the optical sheet 24 is transmitted through the rear polarizing plate 6 and the rear surface of the liquid crystal display element 1. 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, since the light irradiating means 10 is disposed with the light source 16 disposed on the upper edge side of the screen, which is the main direction in which external light of the display device is taken in, the optical irradiating means 10 is provided. 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, external light incident on the optical member 20 from the front thereof enters at various incident angles as shown by broken lines in FIG. The light traveling toward the third optical interface 22b between the incident surface 21 and the second optical interface 21b where the inclination angle of each incident portion 21 on the back surface is large and the optical interface 21b, 2
2 and exits to the back, and the step surface 12 of the light guide 11
The light is reflected by the reflection surface 14 on the line a.

Further, of the incident light, the incident portion 21
The light traveling toward the first optical interface 21a having a small inclination angle is
Although the path is not shown, it is totally reflected at the first optical interface 21a and changes its direction, and is emitted from the second optical interface 21b or the third optical interface 22 to the back surface, and the light guide 11 The light is reflected by the reflection surface 14 on the step surface 12a.

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 characteristics as a normal reflector having a flat front surface as a reflection 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, the first optical interface 21 between the stepped surface 12a of the light guide 11 and each of the incident portions 21 of the optical member 20 is used.
a is large, so that the step surface 12a of the light guide 11 is
Most of the light reflected by the upper reflecting surface 14 is taken in from the second optical interface 21 b and the third optical interface 22 of each of the incident portions 21 of the optical member 20.

Then, of the light taken in from the second optical interface 21b and the light taken in from the third optical interface 22 are directed toward the front surface of the optical member 20 directly.
Of the light transmitted through the optical member 20 in that direction and emitted from the front surface thereof and taken in from the second optical interface 21b, light traveling toward the first optical interface 21a on the opposite side is the optical interface 21a The direction is changed by being totally reflected by the second
The light exits from the front surface of the optical member 20 while changing its direction from the optical interface 21b and the third optical interface 22 to a direction close to the direction of light traveling directly toward 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. This is high-luminance light, and therefore, the reflected light of the external light is also light having 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 light incident from the optical interface 22 and transmitted in the front direction is superimposed.

The reflected light emitted from the front surface of the light irradiation 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. 2, the state of diffusion of the reflected light transmitted through the light diffusion film 23 is omitted to simplify the drawing.

Also at this time, since the transmission axis 24p of the optical sheet 24 and the transmission axis of the rear polarizing plate 6 of the liquid crystal display element 1 are substantially parallel to each other, almost all reflected light transmitted through the optical sheet 24 is transmitted. Are transmitted through the rear-side polarizing plate 6 and enter 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 and the color filter in order, further passes through the front polarizing plate, and emerges from the front of the liquid crystal display element 1. I do.

Next, the brightness of the screen of the liquid crystal display element 1 in this display device will be described. As described above, this display device basically includes reflected light of external light that enters from the front of the liquid crystal display element 1 and is reflected by the light irradiating means 10 and illumination emitted by the light irradiating means 10. The display is performed by simultaneously using both light and light, and the range of the environmental illuminance for lighting the light source 16 of the light irradiation means 10 is as follows.
For example, when the illuminance is in a range from 0 lux to more than 30,000 lux and the ambient illuminance is almost 0 lux, that is, when external light is hardly obtained, the light irradiating means 1 is used.
The display is performed only by the illumination light emitted by the light source 0, and the display is performed only by the reflected light of the external light in a high environmental illuminance where the light source 16 is not turned on.

On the other hand, the suitable screen luminance of the display device (the luminance at which the display can be observed with sufficient brightness under the use environment of the display device) depends on the illuminance of the environment in which the display device is used. Depending on the illuminance, the screen may be too dazzling or too dark.

Therefore, in this display device, the light irradiating means 10 is mainly used so as to obtain a suitable screen luminance that is not excessively dazzling even in an environment of high illuminance exceeding 100,000 lux, for example, under direct sunlight in summer. Of the display device (in front of the liquid crystal display element 1) determined by the external light reflectance (the reflectance of the reflection surface 14 on each stepped surface 12a of the light guide 11) and the light transmittance of the liquid crystal display element 1. (The ratio of the intensity of the external light incident on the liquid crystal display element 1 to the intensity of the external light incident on the liquid crystal display element 1 with respect to the intensity of the external light incident on the liquid crystal display element 1). Reflected light of external light which is set lower than that of the device and which is incident from the front of the liquid crystal display element 1 and reflected by the light irradiation means 10;
The screen luminance due to both the illumination light emitted from the light irradiating means 10 (however, when the environmental illuminance is almost 0 lux, the screen luminance due to only the illumination light emitted from the light irradiating means 10) depends on the environmental illuminance. The luminance of the illumination light emitted from the light irradiating means 10 is controlled by the illumination luminance control means 26 in accordance with the environmental illuminance so that a suitable screen luminance is obtained.

The screen luminance of this display device is obtained by setting the environmental illuminance to I
(Lux, hereinafter referred to as lx), the luminance of the illumination light emitted from the light irradiation means 10 is B (nit, hereinafter referred to as nit), the light transmittance of the liquid crystal display element 1 is T (%), Is defined as R (%), and the screen luminance is L (nit, hereinafter referred to as nit), and is obtained by the relational expression of L = I × R / 400 + B × T / 100.

Further, a suitable screen luminance according to the environmental illuminance is, for example, 2 liters at an environmental illuminance of 50 lx such as a street lamp at night.
0 to 200 nits, 30 to 300 liters at 1000 lx ambient illuminance, such as indoor when lighting indoors during the day and night
nit, 400-4000 nits at 30,000 lx of ambient illuminance such as shade of trees in fine weather, more preferably 50 lx
20 to 60 nits of ambient illuminance, 60 to 200 nits of 1000 lx ambient illuminance, 1000 at 30,000 lx ambient illuminance
~ 3000 nits.

Therefore, in this embodiment, the luminance of the illumination light from the light irradiating means 10 is controlled by the illumination luminance control means 26 so that the screen luminance with respect to the environmental illuminance is 20 to 200 nit at an environmental illuminance of 50 lx and 1000 lux. 30-30
0-nit, 400-4000ni at 30000lx ambient illumination
Control is performed according to the ambient illuminance so that the luminance is represented by a quadratic function that satisfies the range of t.

The luminance control condition of the illumination light is that the value of the screen luminance L (nit) obtained by the above-mentioned relational expression (L = I × R / 400 + B × T / 100) is obtained by setting the environmental illuminance to I (lx). And the following equation (1): -2 × 10 ⁻⁸ × I ² + 0.015 × I + 20 <L <−3 × 10 ⁻⁷ × I ²
+ 0.113 × I + 150.

As described above, a more preferable screen luminance according to the environmental illuminance is 20 to 60 at an environmental illuminance of 50 lx.
nit, 60-200 nit, 30 at 1000lx ambient illumination
It is 1000-3000 nits in the environment illumination of 000 lx,
The luminance control condition of the illumination light is determined by the relational expression (L = I × R).
/ 400 + B × T / 100), the value of the screen luminance L (nit) is given by
(2) Formula -9 × 10 ⁻⁸ × I ² + 0.0453 × I + 20 <L <−2 × 10 ⁻⁷ × I ²
+ 0.0871 × I + 50 is satisfied.

That is, in this embodiment, the luminance of the illumination light from the light irradiating means 10 is more desirably controlled by the illumination luminance control means 26 so that the screen luminance with respect to the environmental illuminance satisfies the above equation (1). Is controlled according to the ambient illuminance so as to satisfy the above equation (2).

FIG. 5 shows the relationship between the environmental illuminance (lx) and the screen luminance (nit) suitable for the environmental illuminance. In the figure, a1 and a2 are obtained by the above equation (1). The maximum value and the minimum value of the screen luminance range are shown.

That is, a1 is the screen luminance when L = −3 × 10 ⁻⁷ × I ² + 0.113 × I + 150, and a2 is L = −2 × 10 ⁻⁸ × I ² + 0.015 × I + 20 Is the screen brightness at the time of setting, and the preferable screen brightness is a1
This is the luminance in the range A between and a2.

Also, in FIG. 5, b1 and b2 are
It shows the maximum value and the minimum value of the screen luminance range obtained by equation (2). That is, b1 is the screen brightness when L = −2 × 10 ⁻⁷ × I ² + 0.0871 × I + 50, and b2 is the screen brightness when L = −9 × 10 ⁻⁸ × I ² + 0.0453 × I + 20 Therefore, a more preferable screen luminance is a luminance in a range B between b1 and b2.

A comparison between the preferred screen brightness range A and the more preferred screen brightness range B and the screen brightness of a normal reflective display device shown by a two-dot chain line in FIG. Of the screen changes linearly according to the environmental illuminance.

In the reflection type display device, the range of the environmental illuminance at which a suitable screen luminance (screen luminance in the range of A) according to the environmental illuminance can be obtained is from about 300 to about 5000 lx. The range of the environmental illuminance at which the brightness (the screen brightness in the range of B) is obtained is about 500 to about 2000 lx. At the environmental illuminance exceeding this range, the screen becomes too bright, for example, in direct sunlight in summer. 100000lx
In an environment of high illuminance exceeding, the screen becomes too dazzling and the display becomes difficult to see. In addition, the screen becomes dark when the environment illuminance is lower than the above range, and in a dark environment such as outdoors at night, for example, the screen brightness is low enough to make the display visible.

In contrast to such a reflection type display device, the display device of this embodiment uses the reflected light of the external light by the light irradiation means 10 and the illumination light emitted by the light irradiation means 10 to display. When illumination light is emitted from the light irradiating means 10 in an environment where external light is present, that is, an environment where reflected light having an intensity corresponding to the intensity of the external light is obtained, the reflected light of the external light and the Light having a luminance superimposed on the illumination light is incident on the liquid crystal display element 1 from the back.

Therefore, this display device can obtain a suitable screen luminance even in a dark environment, and the display device has a reflectance higher than that of a normal reflection type display device using only reflected light of external light. Since it may be low, a suitable screen luminance without excessive glare can be obtained even in a high illuminance environment such as direct sunlight in summer.

Further, even when the ambient illuminance is almost 0 lx, that is, when almost no external light is obtained, the display device can display a suitable screen luminance by using the illumination light emitted from the light irradiating means 10. Can be performed.

The reflectance of the light irradiating means 10 for external light (the reflectance of the reflecting surface 14 on each step 12a of the light guide 11)
Is constant, the luminance of the reflected light of the external light is the luminance corresponding to the environmental illuminance, but the display device includes an illumination luminance control unit 26 that controls the luminance of the illumination light according to the environmental illuminance, The external light reflectivity of the light irradiating means 10 is set so that the screen luminance becomes a predetermined luminance range (the luminance range of A, more preferably the luminance range of B shown in FIG. 5) in accordance with the environmental illuminance. Since the brightness control condition of the illumination light by the illumination brightness control means 26 is set, a suitable screen brightness can be obtained for the environmental illuminance in accordance with the environmental illuminance.

In addition, the luminance of the illumination light may be a value at which the screen luminance by both the reflected light of the external light and the illumination light is a luminance suitable for the environmental illuminance. Since the brightness of the illumination light emitted from the irradiation means may be controlled, the power consumption of the light irradiation means may be small.

Therefore, this display device requires less power consumption and can 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 this display device, the light irradiating means 1
0 indicates that the screen luminance with respect to the environmental illuminance is, as described above,
20-200 nit screen brightness at 50lx ambient illuminance, 10
30-300 nit screen brightness, 30 lux at 00lx ambient illuminance
It is desirable to control the luminance of the illumination light in accordance with the environmental illuminance so that the luminance represented by a quadratic function satisfying the range of the screen luminance of 400 to 4000 nit at the environmental illuminance of 000 lx.

In other words, when the screen luminance with respect to the environmental illuminance is I (lx) and the screen luminance is L (nit), the light irradiating means 10 calculates the above equation (1) −2 × 10 ^−8. × I ² +0.015 × I + 20 <L <-3 × 10 ⁻⁷ × I ²
It is desirable to control the luminance of the illumination light in accordance with the ambient illuminance so as to satisfy + 0.113 × I + 150. By controlling the luminance of the illumination light under such conditions, a wide range from low illuminance to high illuminance is obtained. In a usage environment in the illuminance range, it is possible to obtain a screen luminance suitable for the environment illuminance.

Further, the light illuminating means 10 has a screen luminance with respect to the environmental illuminance of 20 to 60 ni at an environmental illuminance of 50 lx.
t screen brightness, 1000lx ambient illuminance 60-200ni
screen brightness of t, 1000-3x at ambient illuminance of 30000lx
It is more desirable to control the luminance of the illumination light in accordance with the ambient illuminance so that the luminance is represented by a quadratic function that satisfies the range of the screen luminance of 000 nit.

In other words, when the screen luminance with respect to the environmental illuminance is I (lx) and the screen luminance is L (nit), the light irradiating means 10 calculates the above equation (2) -9 × 10 ^-8. × I ² + 0.0453 × I + 20 <L <−2 × 10 ⁻⁷ × I ²
It is more desirable to control the luminance of the illumination light according to the environmental illuminance so as to satisfy + 0.0871 × I + 50. By controlling the luminance of the illumination light under such conditions, it is possible to control the luminance from low illuminance to high illuminance. In a use environment in a wide illuminance range, it is possible to obtain a more suitable screen luminance for the environment illuminance.

In order to obtain a suitable screen brightness (screen brightness in the range of A or B shown in FIG. 5) which satisfies the above equation (1) or (2) according to the environmental illuminance, As an example, FIG. 6 shows a calculational relationship between the environmental illuminance (lx) at which a suitable screen illuminance is obtained with respect to the environmental illuminance and the screen luminance (nit) using only the illumination light from the light irradiation unit 10. Is shown.

The relationship between the environmental illuminance and the screen luminance by only the illumination light shown in FIG. 6 is based on the range of the environmental illuminance using the illumination light for obtaining a suitable screen luminance satisfying the above equation (1). 0 to about 120,000 lx, the range of environmental illuminance using illumination light for obtaining a more suitable screen luminance satisfying the above equation (2) is set to 0 to about 63000 lx, and the reflectance of the display device from the light irradiation means 10 Of high ambient illuminance (approximately 12
When the screen brightness at 000 lx or an illuminance exceeding about 6300 lx) is a suitable screen brightness (for example, 1
Approximately 2200 to 12000ni at 10000lx ambient illumination
t) or a more suitable screen luminance satisfying the above equation (2) (for example, about 5300 to about 9 at an environmental illuminance of 110,000 lx).
500 nit).

In FIG. 6, a1 'and a2' are
This is the screen luminance by only the illumination light for obtaining the maximum value (the luminance of a1 in FIG. 5) and the minimum value (the luminance of a2 in FIG. 5) of the screen luminance range obtained by the equation (1).

That is, a1 'is illumination for setting the screen luminance L (nit) to L = -3 × 10 ⁻⁷ × I ² + 0.113 × I + 150 with respect to the environmental illuminance I (lx). Screen brightness by light only, a
2 'is the screen luminance L (nit) with respect to the environmental illuminance I (lx).
Is the screen brightness only by the illumination light so that L = −2 × 10 ⁻⁸ × I ² + 0.015 × I + 20.

Therefore, the screen luminance by only the illumination light for obtaining a suitable screen luminance satisfying the above equation (1) is a
This is the luminance in the range between 1 'and a2'. In calculation, as shown in FIG. 6, when the ambient illuminance exceeds about 300 lx, the screen brightness of a2 'becomes 0 nit or less. However, when the light irradiating means 10 emits the illuminating light, (1)
The range of the screen brightness by only the illumination light for obtaining a suitable screen brightness that satisfies the expression is a range below the brightness of a1 'and higher than 0 nit at an ambient illuminance exceeding about 300 lx.

In FIG. 6, b1 'and b2' are
This is the screen brightness using only the illumination light for obtaining the maximum value (b1 brightness in FIG. 5) and the minimum value (b2 brightness in FIG. 5) of the screen brightness range obtained by the above equation (2).

That is, b1 'is illumination for setting the screen luminance L (nit) to L = -2 × 10 ^-7 × I ² + 0.0871 × I + 50 with respect to the environmental illuminance I (lx). Screen brightness by light only, b
2 'is the screen luminance L (nit) with respect to the environmental illuminance I (lx).
Is the screen brightness only by the illumination light so that L = −9 × 10 ⁻⁸ × I ² + 0.0453 × I + 20.

Therefore, the screen luminance by only the illumination light for obtaining a more preferable screen luminance satisfying the above equation (2) is a luminance in a range between b1 'and b2'. In addition,
According to the calculation, as shown in FIG. 6, when the ambient illuminance exceeds about 800 lx, the screen luminance of the b2 ′ becomes 0 nit or less. As described above, when the light irradiating unit 10 emits the illumination light, Since the screen luminance only by the illumination light does not become 0 nit or less, the range of the screen luminance only by the illumination light to obtain a suitable screen luminance satisfying the above equation (2) is about 800 lx.
When the ambient illuminance exceeds 0 nits,
Higher range.

Therefore, the illumination brightness control means 26
Controls the luminance of the illumination light from the light irradiating means 10 at least in an environment illuminance higher than the indoor illuminance (around 1000 lx) so that the screen luminance only by the illumination light is in the range shown in FIG. In this way, it is preferable to provide a screen brightness (range A, more preferably range B shown in FIG. 5) more suitable for the environmental illuminance at least in an environment with an illuminance higher than the indoor illuminance. Screen brightness) can be obtained.

In this case, when the ambient illuminance is lower than the indoor illuminance,
The luminance of the illumination light may be kept constant. Even in this case, if the luminance of the illumination light is set so that the screen luminance by the illumination light alone is within the range shown in FIG. In this environment, it is possible to obtain a screen luminance suitable for the environmental illuminance.

Further, the illumination luminance control means 26 adjusts the luminance of the illumination light from the light irradiating means 10 when the environmental illuminance is in a range from 50 lx or less to almost exceeding 30000 lx.
It is more desirable to control the screen brightness only by the illumination light to be in the range of the range shown in FIG. 6. By doing so, under a wide illuminance range of 50 lx or less to almost 30000 lx, the environment is controlled. It is possible to obtain a more suitable screen luminance with respect to the illuminance.

In the illumination brightness control means 26, in the illumination range where the environmental illumination is lower than the room illumination, the light emitting means is controlled so that the brightness of the illumination light is continuously reduced as the environmental illumination is reduced. It is desirable to control 10 and, by doing so, in an environment of an illuminance range lower than the room illuminance, that is, in an environment where the display can be sufficiently viewed even when the screen brightness is low, the environment illuminance is more suitable. In addition to obtaining a very low screen luminance, the power consumption of the light irradiation means 10 can be further reduced.

In the illumination luminance control section 26, when the ambient illuminance is lower than a predetermined illuminance higher than the indoor illuminance in the illuminance range where the ambient illuminance is higher than the indoor illuminance, the illumination illuminance increases. When the luminance of light continuously increases, and when the environmental illuminance exceeds the predetermined illuminance, the light irradiating unit 10 is configured to continuously reduce the luminance of the illumination light as the environmental illuminance further increases. It is desirable to control.

The predetermined environmental illuminance higher than the indoor illuminance is:
For example, when a suitable screen luminance satisfying the above equation (1) is obtained, the luminance is about 60000 lx.
When it exceeds 0000 lx, it is desirable to control the luminance of the illumination light so that the screen luminance by only the illumination light is continuously reduced as the environmental illuminance further increases.

The predetermined environmental illuminance higher than the indoor illuminance for obtaining a suitable screen luminance satisfying the above equation (2) is about 3
0000 lx, in which case the ambient illuminance is about 3000
It is desirable to control the luminance of the illumination light so that when it exceeds 0lx, the screen luminance by only the illumination light is continuously reduced as the environmental illuminance further increases.

In this manner, in the illuminance range where the environmental illuminance is higher than the room illuminance, the luminance of the illumination light is continuously increased as the environmental illuminance is increased, and this is suitable for the environmental illuminance. When the screen luminance is obtained and the environmental illuminance exceeds a predetermined illuminance higher than the indoor illuminance, and a suitable screen luminance for the environmental illuminance is obtained only with the reflected light of the external light, the environmental illuminance is further increased. Accordingly, it is possible to continuously reduce the luminance of the illumination light to obtain a screen luminance suitable for environmental illuminance, and to reduce power consumption.

Furthermore, the illumination brightness control means 26
In the illuminance range where the environmental illuminance is lower than the indoor illuminance, the light irradiating means 10 is controlled so that the luminance of the illumination light is continuously reduced as the environmental illuminance is reduced as described above, In an illuminance range higher than the indoor illuminance, when the environmental illuminance is equal to or lower than a predetermined illuminance higher than the indoor illuminance as described above, the luminance of the illumination light increases continuously with the increase in the environmental illuminance, and When the illuminance exceeds the predetermined illuminance, it is more preferable to control the light irradiating means 10 so that the luminance of the illumination light is continuously reduced as the environmental illuminance further increases.

In this manner, in an environment in an illuminance range lower than the room illuminance, that is, in an environment in which the display can be sufficiently viewed even if the screen brightness is low, a screen with a lower brightness more suitable for the environment illuminance is provided. While obtaining the luminance, the power consumption of the light irradiation means can be further reduced, and in the illuminance range where the environmental illuminance is higher than the indoor illuminance, the luminance of the illumination light is continuously increased as the environmental illuminance increases. To obtain a suitable screen luminance for the environmental illuminance, the environmental illuminance exceeds a predetermined illuminance higher than the indoor illuminance, and a suitable screen luminance for the environmental illuminance can be obtained only by the reflected light of the external light. When, the luminance of the illumination light is continuously reduced as the environmental illuminance further increases, so that a suitable screen luminance with respect to the environmental illuminance can be obtained and the power consumption can be reduced.

That is, in this display device, the range of the environmental luminance at which the illumination light is emitted from the light irradiating means 10 is set to a range from 0 lx to almost more than 30000 lx, and the reflectance of the display device is adjusted from the light irradiating means 10. The screen brightness at a high environmental illuminance, in which the display of only the reflected light of the external light is stopped by stopping the emission of the illumination light, can be obtained as the screen brightness that satisfies the above formula (1), more preferably the above formula (2). With such setting, in the illuminance range where the environmental illuminance is lower than the indoor illuminance, the light irradiating means 10 is controlled such that the luminance of the illumination light is continuously reduced as the environmental illuminance is reduced,
In the illuminance range where the environmental illuminance is higher than the indoor illuminance, when the environmental illuminance is equal to or less than a predetermined illuminance higher than the indoor illuminance, the luminance of the illumination light increases continuously as the environmental illuminance increases, and the environmental illuminance is reduced. When the illuminance exceeds the predetermined illuminance, it is most preferable to control the light irradiating means 10 so that the luminance of the illumination light continuously decreases as the environmental illuminance further increases.

By doing so, it is possible to obtain a suitable screen luminance in an environment of a wide illuminance range from 0 lx to a high ambient illuminance in which display is performed only by reflected light of external light, and it is possible to suppress power consumption. .

In the above embodiment, the illumination luminance control means 26 emits light to the illuminance detector 27 for measuring 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 exit surface (step surface 12b)
The emission efficiency of the illumination light from the light source 16 is increased to increase the efficiency of using the illumination light from the light source 16, and the light emission luminance of the light source 16 is reduced accordingly, thereby further reducing the power consumption and the reflection surface 14. Can be set so that the reflectance of the display device has a desired value.

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 illuminating light taken into the light guide 11 from its 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. .

Further, 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 opposed to the front surface of the light guide 11. A first optical interface 21a for taking in light emitted from each stepped surface 12b of the light guide 11, and a second optical interface 21b for reflecting or refracting light taken in from the first optical interface 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 a liquid crystal display is formed from the front surface. Light can be emitted toward the 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.

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

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 region between these incident portions 21 is defined by the light guide. Since the third optical interface 22 is configured to correspond to the reflection surface 14 on each of the step surfaces 12a of FIG. 11, external light that enters from the front of the liquid crystal display element 1 and enters the optical member 20 from the front is The light exits from the incident portion 21 and the third optical interface 22 therebetween to the back surface of the optical member 20 and reflects the external light reflected by the reflection surface 14 on each step surface 12a of the light guide 11. Light can be taken into the optical member 20 from the incident part 21 and the third optical interface 22 and emitted from the front surface of the optical member 20 toward the liquid crystal display element 1, and the reflected light can be
Light having a higher luminance distribution in a predetermined direction (for example, the front direction) can be obtained.

The light irradiating means 10 is such that an optical member 20 having a plurality of incident portions 21 on the back is disposed on the front side of the light guide 11 having a stepped surface 12 on the front. The plurality of step surfaces 12b of the light guide 11 and the optical member 2
0 are provided at different pitches from each other, so that the relative pitch shift between the plurality of step surfaces 12 b of the light guide 11 and the plurality of incident portions 21 of the optical member 20 is aperiodic. Or make the cycle longer,
Good light without moire fringes can be emitted.

That is, when the pitch of the plurality of stepped surfaces 12b of the light guide 11 is equal to the pitch of the plurality of incident portions 21 of the optical member 20, the processing accuracy of both the light guide 11 and the optical member 20 is adjusted. If there is no error, no moire fringes will occur in the emitted light. However, in reality, some error cannot be avoided, and if there is an error in the processing accuracy of the light guide 11 and the optical member 20, the light guide Since the pitch of the step surface 12b of the body 11 and the pitch of the incident portion 21 of the optical member 20 are periodically shifted, Moire fringes are generated in the emitted light.

However, as in the above embodiment, the light guide 11
If the pitch of the step surface 12b is different from the pitch of the incident portion 21 of the optical member 20, the light guide 11 can be used regardless of whether there is an error in the processing accuracy of the light guide 11 and the optical member 20.
Since the relative pitch shift between the stepped surface 12b of the optical member 20 and the incident portion 21 of the optical member 20 is aperiodic, or even if it is periodic, the period thereof becomes large, so that moire fringes occur in the emitted light. There is no.

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 polarizing plate 6 on the back side 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.

The light-diffusing film 23 is not limited to a transparent adhesive-coated film in which light-scattering fine particles are dispersed, but may be a light-diffusing plate or a surface perpendicular to the plate surface and in 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 second optical interface 21b 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. 1 and 2. If the second optical interface 21b is a curved converging / refracting surface, the second optical interface 21b is taken in from the first optical interface 21a and reflected or refracted toward the front by the second optical interface 21b. Since the light is condensed in a predetermined direction by the condensing action of the second optical interface 21b, which is a curved converging / refracting surface, the illumination light and the reflected light having a luminance distribution with stronger directivity are emitted. can do.

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, the light guide 11 may have a plurality of end faces as entrance end faces for receiving illumination light from the light source 16, for example, two opposite end faces of the light guide 11 are respectively incident. When the light guide 11 is an end face, the front surface of the light guide 11 is a step-shaped surface that gradually decreases from both the incident end faces toward the middle part of the light guide 11, and is opposed to the both incident end faces. The light source 16 may be provided.

The light source 16 is not limited to the one using the fluorescent lamp 17, but may be an LED array in which a plurality of LEDs (light emitting diodes) are arranged, an EL (electroluminescence) panel, or the like.

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 is not limited to a liquid crystal display device, but may be an STN (parts nematic) type, an ECB (birefringence effect) type, a dynamic scattering effect type, or a ferroelectric liquid crystal.

Further, the display device of the above embodiment uses the liquid crystal display element 1 as a display element.
The present invention can be widely applied to other electro-optical display devices and display devices using a non-light emitting display device using a light-transmitting image printing film as a display device.

[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. While arranging the reflecting light irradiation means,
An illumination brightness control unit that controls the brightness of the illumination light according to the illuminance of the environment in which the display device is used, so that the brightness of the screen of the display element is a brightness range that is predetermined according to the environment illuminance. Since the reflectance of the external light of the light irradiation unit and the brightness control condition of the illumination light by the illumination brightness control unit are set, the power consumption is small,
In addition, 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 environment illuminance.

In the display device of the present invention, the light irradiating means may have a screen luminance of 20 to 200 nits at an environmental illuminance of 50 lux, and a screen luminance of 30 to 300 nits at an environmental illuminance of 1000 lux. , 300
It is desirable to control the luminance of the illumination light according to the environmental illuminance so that the luminance is represented by a quadratic function that satisfies the range of the screen luminance of 400 to 4000 nits at the environmental illuminance of 00 lux.

In other words, the light irradiating means is such that when the screen luminance with respect to the environmental illuminance is I (lux) for the environmental illuminance and L (nit) for the screen luminance, -2 × 10 ⁻⁸ × I ² +0.015 × I + 20 <L <-3 × 10 ⁻⁷ × I ²
It is desirable to control the luminance of the illumination light in accordance with the ambient illuminance so as to satisfy + 0.113 × I + 150. By controlling the luminance of the illumination light under such conditions, a wide range from low illuminance to high illuminance is obtained. In a usage environment in the illuminance range, it is possible to obtain a screen luminance suitable for the environment illuminance.

Further, the light irradiating means may have a screen luminance of 20 to 60 nits at an environmental illuminance of 50 lux and a screen luminance of 60 to 2 nits at an environmental illuminance of 1000 lux.
The luminance of the illumination light is controlled in accordance with the environmental illuminance so that the luminance is represented by a quadratic function that satisfies the screen luminance range of 1000 to 3000 nits at a screen luminance of 00 nits and an environmental illuminance of 30,000 lux, respectively. Is more desirable.

In other words, the light irradiating means is such that, when the screen luminance with respect to the environmental illuminance is I (lux) for the environmental illuminance and L (nit) for the screen luminance, -9 × 10 ^-8 × I ² +0.0453 × I + 20 <L <-2 × 10 ⁻⁷ × I ²
It is more desirable to control the luminance of the illumination light according to the environmental illuminance so as to satisfy + 0.0871 × I + 50. By controlling the luminance of the illumination light under such conditions, it is possible to control the luminance from low illuminance to high illuminance. In a use environment in a wide illuminance range, it is possible to obtain a more suitable screen luminance for the environment illuminance.

It is preferable that the illumination luminance control means controls the luminance of the illumination light from the light irradiating means at least in an environmental illuminance higher than the indoor illuminance. In an environment with a high illuminance, it is possible to obtain a screen luminance more suitable for the environment illuminance.

Further, it is more preferable that the illumination brightness control means controls the brightness of the illumination light from the light irradiation means in a range where the environmental illuminance is less than 50 lux to almost more than 30,000 lux. By
In an environment with a wide illuminance range from 50 lux or less to almost 30,000 lux, a more suitable screen luminance can be obtained for the environment illuminance.

Further, the illumination brightness control means controls the light emission means so that the brightness of the illumination light continuously decreases as the environmental illuminance decreases in the illuminance range where the environmental illuminance is lower than the indoor illuminance. It is desirable to perform control. By doing so, in an environment of an illuminance range lower than the room illuminance, that is, in an environment in which the display can be visually recognized even if the screen brightness is low, a low level more suitable for the environment illuminance is obtained. It is possible to obtain the screen brightness of the brightness and to further reduce the power consumption of the light irradiation means.

In the illumination brightness control means, when the ambient illuminance is lower than a predetermined illuminance higher than the indoor illuminance in the illuminance range where the ambient illuminance is higher than the indoor illuminance, the illumination light increases as the environmental illuminance increases. Brightness increases continuously,
When the environmental illuminance exceeds the predetermined illuminance, it is desirable to control the light irradiating means so that the luminance of the illuminating light continuously decreases as the environmental illuminance further increases.

In this manner, in the illuminance range where the environmental illuminance is higher than the indoor illuminance, the luminance of the illumination light is continuously increased as the environmental illuminance increases, which is suitable for the environmental illuminance. When the screen luminance is obtained and the environmental illuminance exceeds a predetermined illuminance higher than the indoor illuminance, and a suitable screen luminance for the environmental illuminance is obtained only with the reflected light of the external light, the environmental illuminance is further increased. Accordingly, it is possible to continuously reduce the luminance of the illumination light to obtain a screen luminance suitable for environmental illuminance, and to reduce power consumption.

Further, in the illumination brightness control means, in the illuminance range where the environmental illuminance is lower than the room illuminance, the light illuminating means is configured to continuously reduce the brightness of the illumination light as the environmental illuminance decreases. In the illuminance range where the environmental illuminance is higher than the indoor illuminance, when the environmental illuminance is equal to or less than a predetermined illuminance higher than the indoor illuminance, the luminance of the illumination light increases continuously as the environmental illuminance increases. More preferably, when the environmental illuminance exceeds the predetermined illuminance, the light irradiating means is controlled so that the luminance of the illumination light is continuously reduced as the environmental illuminance further increases.

In this way, in an environment where the illuminance is lower than the room illuminance, that is, in an environment where the display can be visually recognized even if the screen luminance is low, a screen with a lower luminance that is more suitable for the environment illuminance can be obtained. While obtaining the luminance, the power consumption of the light irradiation means can be further reduced, and in the illuminance range where the environmental illuminance is higher than the indoor illuminance, the luminance of the illumination light is continuously increased as the environmental illuminance increases. To obtain a suitable screen luminance for the environmental illuminance, the environmental illuminance exceeds a predetermined illuminance higher than the indoor illuminance, and a suitable screen luminance for the environmental illuminance can be obtained only by the reflected light of the external light. When, the luminance of the illumination light is continuously reduced as the environmental illuminance further increases, so that a suitable screen luminance with respect to the environmental illuminance can be obtained and the power consumption can be reduced.

[0210] Further, the illumination brightness control means is constituted by an illuminance detector for measuring the environmental illuminance, and means for controlling the brightness of the illumination light emitted from the light irradiating means based on the measured environmental illuminance. By doing so, it is possible to control the luminance of the illuminating light in accordance with the illuminance of the actual use environment, and obtain a screen luminance suitable for the illuminance of the environment.

[0211] Further, the light irradiating means includes means for irradiating illumination light to the display element, 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 may be any structure, provided that the light irradiating unit includes a light source, an emission surface that guides illumination light from the light source and emits the light toward the display element, and a light emitting unit. A light guide formed with a reflection surface different from the emission surface for reflecting external light incident from the front toward the display element,
It is possible to independently select the emission rate of the illumination light from the emission surface and the reflectance of the external light on the reflection surface, and thus increase the emission rate of the illumination light from the emission surface. The illumination efficiency of the illumination light from the light source is increased, and the light emission luminance of the light source is reduced accordingly, thereby further reducing the power consumption and increasing the reflectance of the external light on the reflection surface by the reflection of the display device. The rate can be set to a desired value.

[0212] As such light irradiating means in which the illumination light emitting surface and the external light reflecting surface are different surfaces, at least one end surface of the light guide has an incident end surface for receiving illumination light from the light source. The light guide has a front surface, a plurality of step surfaces gradually decreasing from the incident end surface side to the other end side, and a step-shaped surface including a plurality of step surfaces connecting these step surfaces. A reflection film is provided on the plurality of step surfaces to form a reflection surface of the external light, and the plurality of step surfaces are an emission surface of illumination light incident from the incident end surface, Transmitting, on the front side of the light guide, external light incident from the front of the display element and reflected light of the external light reflected by the reflection surface on each step surface of the light guide, Light emitted from each step surface toward the display element It is preferable that the member is disposed, and according to this light irradiation means, the illuminating light taken into the light guide from the incident end face is transmitted from a plurality of step surfaces of the step-shaped surface of the light guide. The light is emitted, the light is redirected by the optical member, and is emitted toward the display element, 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, the plurality of steps of the step-shaped surface of the light guide are reflection surfaces of external light, and the external light incident from the front of the display element is The light transmitted through the optical member is reflected by the reflection surface on each step surface of the light guide, and the reflected light is transmitted through the optical member again 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.

[0214] In this light irradiation means, 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. A first optical interface for taking in light emitted from each step surface of the light guide, and a second optical interface for reflecting or refracting light taken in from the first optical interface in a front direction.
It is preferable that a projection-shaped incident portion having an optical interface is formed, and by configuring the optical member as described above, most of the light emitted from each step surface of the light guide is efficiently used. The light can be taken into the optical member and emitted from the front surface toward the display element.

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 first optical interface can be used. The light is reflected or refracted by the second optical interface and condensed in a predetermined direction, and illumination light having a high luminance distribution in a predetermined direction (for example, a front direction) can be emitted from the front surface of the optical member. The external light reflected on the reflection surface on each step surface of the light guide 11 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).

[0216] Further, in the optical member, the plurality of incident portions are provided at intervals, and a rear area between the adjacent incident portions is provided with the external light and the light guide that enter from the front of the display element. It is more preferable that the third optical interface is configured to transmit the reflected light of the external light reflected by the reflecting surface on each step surface. According to the optical member having such a configuration, the display element External light incident from the front of the optical member and incident on the optical member from the front surface is emitted from the incident portion and the third optical interface therebetween to the rear surface of the optical member, and on each step surface of the light guide. The reflected light of the external light reflected by the reflection surface can be taken into the optical member from the incident portion and the third optical interface, and can be emitted from the front surface of the optical member toward the display element, and More reflected light (E.g., the front direction) can be brightness of the light of a high luminance distribution.

The light guide preferably has a rear surface serving as a light diffusion surface for averaging the luminance distribution of the illumination light incident from the incident end face in the width direction of the light guide. By using a light guide having such a configuration, the luminance distribution of illumination light that is taken in from the incident end face of the light guide and emitted from the plurality of step surfaces is made substantially uniform in the light guide width direction. Can be.

Further, in this display device, it is preferable to provide a light diffusing film between the light irradiating means and the display element, whereby reflection of illumination light and external light from the light irradiating means is preferable. The light is diffused by the light diffusion film and is incident on the display element from the back as light having a substantially uniform luminance distribution, so that the screen luminance is made uniform over the entire screen and the light emitted to the front of the liquid crystal display element 1 is emitted. By widening the angle range, a wide viewing angle can be obtained.

In this display device, a reflection axis and a transmission axis are provided between the light irradiating means and the display element in directions substantially orthogonal to each other, and incident light of a polarization component along the reflection axis is transmitted. It is preferable to provide an optical sheet having a property of reflecting and transmitting incident light of a polarization component along the transmission axis. In this way, if the optical sheet is provided between the light irradiation unit and a display element, Of the illumination light from the light irradiating means, the light of the polarization component along the transmission axis of the optical sheet is transmitted through the optical sheet and enters the display element, and the illumination light from the light irradiating means is The light of the polarization component along the reflection axis of the optical sheet changes the polarization direction by repeating the reflection on the optical sheet and the reflection on the light irradiation unit, and the polarization component along the transmission axis of the optical sheet. The light of Since the light passes through the optical sheet and is incident on the display element, most of the illumination light from the light irradiating means can be incident on the display element without waste, and therefore, the utilization efficiency of the illumination light from the light irradiating means is increased. However, the light emission luminance of the light source can be reduced accordingly, and the power consumption can be further reduced.

In the case where the optical sheet is provided, for example, when the display element is a liquid crystal display element having a polarizing plate on the front and back sides, the transmission axis of the optical sheet is set on the rear side of the liquid crystal display element. It is desirable to dispose the optical sheet substantially in parallel with the transmission axis of the polarizing plate, and by arranging the optical sheet in this manner, light enters from the front of the liquid crystal display element, is reflected by the light irradiating means, and is incident on the liquid crystal display element. Most of the light incident from the rear surface can be transmitted without being reflected by the optical sheet.

[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 side view of a part of a light guide and an optical member constituting a light irradiation unit of the display device.

FIG. 3 is an enlarged perspective view of a part of the light guide.

FIG. 4 is a perspective view of an optical sheet disposed between the light irradiation unit and a display element.

FIG. 5 is a diagram showing a relationship between environmental illuminance and screen luminance L suitable for the environmental illuminance.

FIG. 6 is a diagram illustrating a relationship between the environmental illuminance and a screen luminance using only illumination light, which provide a screen illuminance suitable for the environmental illuminance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 5, 6 ... Polarizing plate 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 ... Reflection surface DESCRIPTION OF SYMBOLS 15 ... Light diffusing surface 16 ... Light source 19 ... Reflective plate 20 ... Optical member 21 ... Incident part 21a ... First optical interface 21b ... Second optical interface 22 ... Third optical interface 23 ... Light diffusing film 24 ... Optical sheet 24s: Reflection axis 24p: Transmission axis

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI G09G 3/18 G09G 3/18 (72) Inventor Hisashi Aoki 5 Casio Computer Co., Ltd. Hachioji Laboratory, 2951 Ishikawacho, Hachioji-shi, Tokyo

Claims (20)

[Claims] 1. A non-light-emitting display element for displaying light by controlling the transmission of the light by using light incident from outside, and illuminating light emitted toward the display element, the light being emitted toward the display element. Light irradiating means for reflecting external light incident from the front of the display element toward the display element, and illumination brightness control means for controlling the luminance of the illumination light in accordance with the illuminance of the environment in which the display device is used The reflectance of the external light of the light irradiating means, and the illumination light by the illumination luminance control means, so that the luminance of the screen of the display element is within a predetermined luminance range according to the ambient illuminance. A display device, wherein the following brightness control conditions are set. 2. The light illuminating means, wherein the screen luminance with respect to the environmental illuminance is 20 to 200 nits at a luminance of 50 lux, 30 to 300 nits at a luminance of 1000 lux, and 30,000 lux. The luminance of the illuminating light is controlled according to the environmental illuminance so that the luminance is represented by a quadratic function that satisfies the range of 400 to 4000 nits of screen luminance at the environmental illuminance. The display device according to claim 1. 3. The light irradiation means, wherein the screen luminance with respect to the environmental illuminance is I (lux) for the environmental illuminance, and L (nit) for the screen luminance.
-2 × 10 ⁻⁸ × I ² + 0.015 × I + 20 <L <−3 × 10 ⁻⁷ × I ²
2. The display device according to claim 1, wherein the luminance of the illumination light is controlled according to the environmental illuminance so as to satisfy + 0.113 * I + 150. 4. The light illuminating means, wherein the screen luminance with respect to the environmental illuminance is 20 to 60 nits at a luminance of 50 lux, 60 to 200 nits at a luminance of 1000 lux, and 30,000 lux. The luminance of the illuminating light is controlled according to the environmental illuminance so that the luminance is represented by a quadratic function that satisfies the range of 1000 to 3000 nits of screen luminance at the environmental illuminance. The display device according to claim 1. 5. The light irradiation means, wherein the screen luminance with respect to the environmental illuminance is I (lux) for the environmental illuminance, and L (nit) for the screen luminance.
-9 × 10 ⁻⁸ × I ² + 0.0453 × I + 20 <L <−2 × 10 ⁻⁷ × I ²
2. The display device according to claim 1, wherein the luminance of the illumination light is controlled according to the ambient illuminance so as to satisfy + 0.0871 × I + 50. 6. The display device according to claim 1, wherein the illumination luminance control means controls the luminance of the illumination light from the light irradiating means at least at an environmental illuminance higher than the indoor illuminance. 7. The illumination brightness control means controls the brightness of the illumination light from the light irradiation means in a range where the environmental illuminance is less than 50 lux to more than approximately 30,000 lux. The display device according to the above. 8. The illumination luminance control means is arranged to reduce the luminance of the illumination light continuously as the environmental illuminance decreases in an illuminance range where the environmental illuminance is lower than the indoor illuminance. The display device according to claim 1, wherein the display device controls light irradiation means. 9. The illumination brightness control means increases the environmental illuminance when the environmental illuminance is equal to or less than a predetermined illuminance higher than the room illuminance in an illuminance range in which the environmental illuminance is higher than the room illuminance. With this, the luminance of the illumination light continuously increases, and when the environmental illuminance exceeds the predetermined illuminance, the luminance of the illumination light continuously decreases as the environmental illuminance further increases. The display device according to claim 1, wherein the light irradiation unit is controlled so that the light irradiation unit is controlled. 10. The illumination brightness control means includes: a light source that emits light in a manner that the brightness of the illumination light is continuously reduced as the environmental illuminance is reduced in an illuminance range in which the environmental illuminance is lower than room illuminance. Controlling the irradiating means, and in an illuminance range in which the environmental illuminance is higher than the room illuminance, when the environmental illuminance is equal to or less than a predetermined illuminance higher than the room illuminance, the environmental illuminance increases with the illumination. When the luminance of light continuously increases, and when the environmental illuminance exceeds the predetermined illuminance, the light irradiation is performed such that the luminance of the illumination light continuously decreases as the environmental illuminance further increases. The display device according to claim 1, wherein the display device is controlled. 11. The illumination brightness control means includes an illuminance detector for measuring the environmental illuminance, and means for controlling the brightness of illumination light emitted from the light irradiating means based on the measured environmental illuminance. The display device according to claim 1, wherein: 12. 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: 13. The light irradiating means includes: a light source; an emission surface that guides illumination light from the light source and emits the light toward the display element; and external light that enters 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. 14. The light guide according to claim 1, wherein at least one end face of the light guide is an incident end face for receiving illumination light from the light source, and the front face of the light guide is stepwise from the incident end face side to the other end side. It has a stepped surface composed of a plurality of step surfaces to be lowered and a plurality of step surfaces connecting these step surfaces, and a reflection film is provided on the plurality of step surfaces to form a reflection surface of the external light. And the plurality of step surfaces serve as emission surfaces of the illumination light incident from the incident end surface, and on the front side of the light guide, external light and light guide incident from the front of the display element. An optical member that transmits the reflected light of the external light reflected by the reflection surface on each step surface and emits illumination light emitted from each step surface of the light guide toward the display element is arranged. 2. The method according to claim 1, wherein
4. The display device according to 3. 15. The optical member is composed 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, and the light guide is provided on the back surface. A projection-shaped incident portion having a first optical interface for taking in light emitted from each step surface of the body and a second optical interface for reflecting or refracting light taken in from the first optical interface in the front direction is provided. 2. The semiconductor device according to claim 1, wherein:
5. The display device according to 4. 16. The optical member, wherein the incident portions of the optical member are provided with a space therebetween, and a rear area between the adjacent incident portions has an external light and a light guide which are incident from the front of the display element. 14. The display device according to claim 13, wherein the third optical interface is a third optical interface that transmits the reflected light of the external light reflected by the reflection surface on each of the step surfaces. 15. 17. A light diffusion surface for averaging a luminance distribution in a width direction of the light guide of illumination light incident from the incident end face, wherein a back surface of the light guide is provided. The display device according to any one of 13 to 16. 18. The display device according to claim 1, wherein a light diffusion film is provided between said light irradiation means and said display element. 19. A light transmission device, comprising: a reflection axis and a transmission axis in a direction substantially orthogonal to each other between said light irradiation means and said display element; 19. The display device according to claim 1, further comprising an optical sheet having a property of transmitting incident light of a polarization component along the axis. 20. The liquid crystal display device according to claim 10, wherein the display element includes a polarizing plate on a front surface and a rear surface. The transmission axis of the optical sheet is substantially equal to a transmission axis of the polarizing plate on the rear surface side of the liquid crystal display device. The display device according to claim 19, wherein the display device is arranged in parallel.