JP2000111870A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device having a sufficiently wide viewing angle, requiring low power consumption, and also being able to obtain screen display brightness suited to the ambient illuminance in an ambience with a wide range of illuminance spreading over low and high illuminance. SOLUTION: This liquid crystal display device is provided with a light illuminating means 20 which emits illuminating light and reflects external incident light from the front side of a liquid crystal display element 1 arranged on the rear side of the liquid crystal display element 1 and an illumination brightness controlling means 36 which controls brightness of the illuminating light according to illuminance of an external ambience. A reflectance of external light of the light illuminating means 20 and a controlling condition of the brightness of the illuminating light with the illumination brightness controlling means 36 are set so as to make screen display brightness of the liquid crystal display element 1 fall within a range of brightness predetermined according to illuminance of an external ambience and also retardation of the liquid crystal display element 1 is set to fall within 400-600 nm range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A liquid crystal display device having a non-light-emitting type liquid crystal display element, such as a liquid crystal display element, which utilizes light incident from the outside and controls the transmission of the light to display the transmitted light is known. There are a transmissive liquid crystal display device using the same and a reflective liquid crystal display device using the reflected light.

In the transmissive liquid crystal display device, a backlight is arranged behind the liquid crystal display element, and an image is displayed using illumination light from the backlight. The light is emitted toward the display element, and the light is emitted to the front of the liquid crystal display element for display.

[0004] The reflection type liquid crystal display device uses external light which is light of an external environment (use environment of the liquid crystal display device) to perform display. The light is reflected toward the liquid crystal display element by a reflector disposed behind the liquid crystal display element, and the light is emitted to the front of the liquid crystal display element for display.

[0005] The transmissive liquid crystal display device consumes a large amount of electric power to turn on a backlight.

On the other hand, in a reflection type liquid crystal display device, reflected light having an intensity corresponding to the intensity of external light incident from the front of the liquid crystal display element can be obtained. Power consumption is low because a backlight is not required.

[0007]

The preferred screen brightness of the liquid crystal display device depends on the illuminance of the external environment (the use environment of the liquid crystal display device). Even with the same screen brightness, the screen may be too dazzling depending on the environmental illuminance. Or too dark.

[0008] Looking at the screen luminance of a reflection type liquid crystal display device, the reflection type liquid crystal display device is characterized in that the intensity of reflected light emitted in front of the liquid crystal display element is equal to the intensity of external light incident from the front of the liquid crystal display element. For example, in an environment of high illuminance exceeding 100,000 lux such as in 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 screen cannot be used in a dark environment because the screen brightness is low enough to make the display visible.

On the other hand, conventionally, a reflection type liquid crystal display device provided with an auxiliary light source has been proposed so that observation is possible even in a dark environment such as outdoors at night.

In this reflection type liquid crystal display device, a transflective plate is disposed behind a liquid crystal display element, and an auxiliary light source is disposed behind the transflective plate. In order to ensure a sufficiently high reflectance of the liquid crystal display device (ratio of intensity of external light incident from the front of the liquid crystal display element to intensity of outgoing light reflected by the reflector and emitted to the front of the liquid crystal display element). In addition, those having characteristics of high reflectance / low transmittance are used.

However, in the reflection type liquid crystal display device provided with the auxiliary light source, the transmittance of the transflective plate is extremely small.
In addition, since the emission luminance of the auxiliary light source cannot be extremely increased in order to reduce power consumption, when the auxiliary light source is turned on, the illumination light transmitted through the semi-transmissive reflection plate and incident on the liquid crystal display element. Brightness is weak.

Therefore, the reflective liquid crystal 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 such as in direct sunlight in summer. Below, the screen is too dazzling and the display is difficult to see.

Further, in the reflection type liquid crystal display device, a display image and a shadow thereof are observed twice, depending on an observation direction of the display, and the display becomes difficult to see, so that the viewing angle is narrow.

According to the present invention, it is possible to obtain a screen brightness suitable for the environment illuminance in an environment having a wide range of illuminance from low illuminance to high illuminance while consuming less power and to reflect external light. It is an object of the present invention to provide a liquid crystal display device having a sufficiently wide viewing angle, in which a display image and its shadow are not double-observed depending on an observation direction of display in light display.

[0015]

A liquid crystal display device according to the present invention is provided with a liquid crystal display element, and is disposed behind the liquid crystal display element, and emits illumination light toward the liquid crystal display element. Light illuminating means for reflecting external light incident from the front of the liquid crystal display element toward the liquid crystal display element, and illumination brightness control means for controlling the brightness of the illuminating light according to the illuminance of the external environment. The reflectance of the external light and the luminance control condition of the illumination light by the illumination luminance control means are set such that the luminance of the screen of the liquid crystal display element falls within a predetermined luminance range according to the illuminance of the external environment. And the liquid crystal display element is 400 to 600 n
It has a retardation in the range of m.

This liquid crystal display device uses an external light reflected by the light irradiating means and an illumination light emitted from the light irradiating means to display an image.
That is, when the illumination light is emitted from the light irradiating means in an environment where reflected light having an intensity corresponding to the intensity of the external light is obtained, light having a luminance in which the reflected light of the external light and the illumination light are superimposed on the liquid crystal display. Light enters the element from the back.

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

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 ambient illuminance. An illumination brightness control unit that controls the brightness of the illumination light, and a reflectance of the external light of the light irradiation unit and the illumination brightness control so that a screen brightness falls within a predetermined brightness range according to environmental illuminance. Since the brightness control condition of the illumination light by the means is set, it is possible to obtain a screen brightness suitable for the environmental illuminance according to the environmental illuminance.

Further, 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.

Further, in this liquid crystal display device, since the retardation of the liquid crystal display element is in the range of 400 to 600 nm, the transmittance of the liquid crystal display element in the display by the reflected light of the external light depends on the viewing direction of the display. The contrast between the dark area shadow, which appears at the boundary between the low-controlled dark area and the bright area, the transmittance of which is controlled to be high, and the bright area is reduced, so that the display image and the shadow are displayed twice. Thus, the viewing angle can be sufficiently widened.

Therefore, the liquid crystal display device requires less power consumption, and can obtain a screen luminance suitable for the environmental illuminance in an environment of a wide illuminance range from low illuminance to high illuminance. Viewing angle can be widened sufficiently

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the liquid crystal display device of the present invention emits illumination light behind the liquid crystal display element toward the liquid crystal display element and externally enters illumination light from the front of the liquid crystal display element. Light illuminating means for reflecting light toward the liquid crystal display element is provided, and illumination luminance control means for controlling the luminance of the illuminating light according to the illuminance of an external environment is provided. The power consumption is set by setting the rate and the luminance control condition of the illumination light by the illumination luminance control means so that the screen luminance of the liquid crystal display element falls within a predetermined luminance range according to the illuminance of the external environment. In a wide illuminance range from low illuminance to high illuminance, so that it is possible to obtain a suitable screen luminance for the illuminance of the environment. In the range of 400 to 600 nm, the display image and the shadow thereof are not double-viewed depending on the viewing direction of the display in the display by the reflected light of the external light, and the viewing angle is sufficiently widened. It was done.

In the liquid crystal display device of the present invention, the liquid crystal display element may be, for example, a liquid crystal cell in which a liquid crystal layer in which liquid crystal molecules are twisted is provided between a pair of substrates having electrodes on the inner surface, and the liquid crystal cell may be sandwiched therebetween. In the case of using a pair of polarizing plates arranged, the retardation of the liquid crystal cell may be set in the range of 400 to 600 nm.

Further, the liquid crystal display element includes the liquid crystal cell, the pair of polarizing plates, and a retardation plate disposed between the liquid crystal cell and one of the pair of polarizing plates. In this case, the total retardation of the liquid crystal cell and the retardation plate may be 400 to 60.
What is necessary is just to set it in the range of 0 nm.

Further, in the liquid crystal display device of the present invention,
The light irradiation means has a screen luminance with respect to the environmental illuminance of 50.
20-200 knit screen brightness with lux ambient illuminance, 1
In accordance with the environmental illuminance, the luminance is expressed by a quadratic function that satisfies the range of the screen luminance of 30 to 300 nits at the environmental illuminance of 000 lux and the screen luminance of 400 to 4000 nits at the environmental illuminance of 30,000 lux. It is desirable to control the luminance of the illumination light, and by controlling the luminance of the illumination light under such conditions, in an environment with a wide illuminance range from low illuminance to high illuminance, a screen luminance suitable for the environmental illuminance Can be obtained.

It is desirable that 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. In an environment with a high illuminance, it is possible to obtain a screen luminance more suitable for the environment illuminance.

[0027] The illumination brightness control means may control the light irradiation 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 brightness control means, when the environmental illuminance is equal to or less than a predetermined illuminance higher than the indoor illuminance in an illuminance range where the environmental 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 an illuminance range in which the ambient 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, the illumination brightness control means is arranged so that, in an 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 manner, in an environment having 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 having a low brightness 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.

[0032] The illumination brightness control means may include an illuminance detector for measuring environmental illuminance, and means for controlling the brightness of 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 according to the actual environmental illuminance, and obtain a screen luminance suitable for the environmental illuminance.

Further, the light irradiating means irradiates illumination light to the liquid crystal display element, and reflects external light incident from the front of the liquid crystal display element to irradiate the reflected light to the liquid crystal display element. Any configuration may be used as long as it comprises a reflection unit, but a preferred light irradiation unit is a light source, and an emission surface that guides illumination light from the light source and emits the light toward the liquid crystal display element. A light guide having a reflection surface different from the emission surface for reflecting external light incident from the front of the liquid crystal display element toward the liquid crystal 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 the external light on the reflection surface can be set so that the reflectance of the liquid crystal display device becomes a desired value.

The light irradiating means in which the emission surface of the illumination light and the reflection surface of the external light are different from each other includes an incident end surface in which at least one end surface of the light guide receives 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 one of the plurality of step surfaces and the back surface of the light guide to form a reflection surface of the external light, and the plurality of step surfaces are incident from the incident end surface. An illumination light emitting surface, and on the front side of the light guide, transmitting external light incident from the front of the liquid crystal display element and reflected light of the external light reflected by the reflecting surface, Illumination light emitted from the plurality of step surfaces of the light guide is referred to as the liquid crystal table. Having a structure in which an optical member for emitting towards the elements 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 liquid crystal display element, so that the illumination light from the light source can be made incident on almost the entire liquid crystal display element.

According to this light irradiation means, external light incident from the front of the liquid crystal display element passes through the optical member and is formed on a plurality of steps of the light guide or on the back of the light guide. The reflected light is reflected by the reflection surface, and the reflected light is transmitted through the optical member again and emitted toward the liquid crystal display element, so that most of the external light incident from the front of the liquid crystal display element is reflected without waste, The light can be incident on almost the entire liquid crystal 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 liquid crystal display element and a back surface facing the front surface of the light guide. A projection-shaped incident portion having an incident surface for taking in light emitted from the plurality of step surfaces of the light guide, and a refraction surface for refracting the light taken in from the incident surface toward the front surface is formed. Are preferred.

With the above-mentioned structure of the optical member, most of the light emitted from the plurality of step surfaces of the light guide is taken into the optical member without waste, and is directed from the front surface to the liquid crystal display element. And can be emitted.

Further, by configuring the optical member as described above, light emitted from the plurality of step surfaces of the light guide and incident on the plurality of incident portions of the optical member from the incident surface can be reflected by the optical member. The light is refracted by the refraction surface and is condensed in a predetermined direction. From the front surface of the optical member, illumination light having a high luminance distribution in a predetermined direction (for example, the front direction) can be emitted, and the light guide 21 can be emitted. The external light reflected on the reflection surfaces on the plurality of step surfaces can also be emitted from the front surface of the optical member as light having a luminance distribution with a high luminance in a predetermined direction (for example, the front direction).

Further, in the optical member, the plurality of incident portions are provided at an interval, and a rear area between the adjacent incident portions is provided with an external light and a light guide incident from the front of the liquid crystal display element. It is more desirable to adopt a configuration in which the input / output surface transmits the reflected light of the external light reflected by the reflection surface of the body.

According to the optical member having such a configuration, external light that is incident from the front of the liquid crystal display element and incident on the optical member from the front surface is transmitted from the incident portion and the incident / exit surface therebetween to the optical member. And the reflected light of the external light reflected by the reflecting surfaces on the plurality of step surfaces of the light guide is taken into the optical member from the incident part and the entrance / exit surface, and the optical member The light can be emitted from the front toward the liquid crystal display element, and the reflected light is
Light having a higher luminance distribution in a predetermined direction (for example, the front direction) can be obtained.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a side view of a liquid crystal display device. The liquid crystal display device of this embodiment is provided with a liquid crystal display element 1 and disposed behind the liquid crystal display element 1, and illuminates light of the liquid crystal display element 1. A light irradiating unit 20 that emits light toward the rear surface and reflects external light incident from the front of the liquid crystal display device 1 toward the rear surface of the liquid crystal display device 1, and an external environment (environment using the liquid crystal display device) And an illumination brightness control means 36 for controlling the brightness of the illumination light emitted from the light irradiation means 20 in accordance with the illuminance of the light.

First, the liquid crystal display device 1 will be described. FIG. 2 is an enlarged sectional view of a part of the liquid crystal display device 1.

The liquid crystal display element 1 is of a TN (twisted nematic) type, and includes a liquid crystal cell 2 and a pair of polarizing plates 12 and 13 interposed between the liquid crystal cell 2.
It consists of

The liquid crystal cell 2 is formed on the inner surfaces of a pair of front and back transparent substrates 3 and 4 joined to each other via a frame-shaped sealing material 5 (see FIG. 1). Transparent electrodes 6 and 7 forming a plurality of pixel regions are provided, and a liquid crystal layer 11 is provided in a region surrounded by the sealing material 5 between the pair of substrates 3 and 4.

The liquid crystal cell 2 is of an active matrix type using a TFT (thin film transistor) as an active element. An electrode 7 provided on the inner surface of the rear substrate 4 has a plurality of pixels arranged in a matrix. The electrode, the electrode 6 provided on the inner surface of the front substrate 3, is a single-film counter electrode facing all of the plurality of pixel electrodes 7.

Each of the plurality of pixel electrodes 7 is connected to a plurality of TFTs (not shown) provided on the inner surface of the rear substrate 4 so as to correspond to the respective pixel electrodes 7.
The plurality of TFTs are connected to gate lines and data lines (not shown) wired on the inner surface of the rear substrate 4.

The liquid crystal cell 2 is for displaying a multi-color image such as a full-color image. One of the substrates, for example, the inner surface of the front substrate 3, corresponds to the plurality of pixel regions. A plurality of color filters, for example, three color filters 8R, 8G, and 8B of red, green, and blue are provided. The counter electrode 6 is provided with the color filter 8.
It is formed on R, 8G, 8B.

Further, alignment films 9 and 10 are formed on the inner surfaces of the pair of substrates 3 and 4, respectively, and the liquid crystal molecules of the liquid crystal layer 11 provided between the substrates 3 and 4 are aligned with the alignment film. The alignment directions near the substrates 3 and 4 are regulated by the substrates 9 and 10, and the substrates 3 and 4 are twist-oriented at a predetermined twist angle φ.

The pair of polarizing plates 12 and 13 disposed with the liquid crystal cell 2 interposed therebetween are attached to the outer surfaces of the pair of substrates 3 and 4 with their absorption axes directed in a predetermined direction.

FIG. 3 shows the orientation directions 3a and 4a of the liquid crystal molecules in the vicinity of the two substrates 3 and 4 of the liquid crystal cell 2 and the directions of the absorption axes 12a and 13a of the pair of polarizing plates 12 and 13. .

As shown in FIG. 3, in this embodiment, the liquid crystal molecule orientation direction 3a in the vicinity of the front substrate 3 of the liquid crystal cell 2 is positioned from the front with respect to the horizontal axis x of the screen of the liquid crystal display device 1. The liquid crystal molecule alignment direction 4a in the vicinity of the rear substrate 4 is substantially 45 ° counterclockwise when viewed from the front, and the liquid crystal molecule alignment direction 4a in the vicinity of the rear substrate 4 is substantially 45 ° counterclockwise when viewed from the front.

Therefore, the liquid crystal layer 11 of the liquid crystal cell 2
The initial alignment state of the liquid crystal molecules (the alignment state when an OFF voltage is applied between the electrodes 6 and 7) changes from the rear substrate 4 to the front substrate 3 with the twist direction indicated by the dashed arrow in the figure. In the opposite direction, the liquid crystal is twist-oriented with a twist angle φ of approximately 90 ° counterclockwise when viewed from the front side.

The polarizing plate 12 on the front side shifts its absorption axis 12a counterclockwise by approximately 135 ° with respect to the horizontal axis x when viewed from the front side (near the front side substrate 12 of the liquid crystal cell 2). In a direction substantially parallel to the liquid crystal molecule alignment direction 12a), the rear polarizing plate 13 shifts its absorption axis 13a counterclockwise by approximately 45 ° with respect to the horizontal axis x when viewed from the front side. (The rear substrate 13 of the liquid crystal cell 2)
(In the direction substantially parallel to the liquid crystal molecule alignment direction 13a in the vicinity of the liquid crystal molecules), the absorption axis 12a of the front-side polarizing plate 12 and the absorption axis 1
3a are substantially orthogonal to each other.

That is, in the liquid crystal display element 1 used in this embodiment, when an OFF voltage is applied to the electrodes 6 and 7 of the liquid crystal cell 2, that is, the liquid crystal molecules of the liquid crystal layer 11 are in the initial alignment state (the liquid crystal molecules are in the substrate state). The display when the liquid crystal molecules are in the twisted state which is the most inclined with respect to the 3rd and 4th planes) is a bright display, and the display becomes dark with the rising alignment of the liquid crystal molecules due to the application of the ON voltage between the electrodes 6 and 7. This is a so-called normally white mode.

The twist angle φ of the liquid crystal molecules of the liquid crystal cell 2 may be in the range of 90 ° ± 10 °, and the intersection angle between the absorption axes 12a, 13a of the pair of polarizing plates 12, 13 is also 90 °. The angle may be in the range of ± 10 °.

The liquid crystal display element 1 has an alignment direction 3a of liquid crystal molecules in the vicinity of both substrates 3 and 4 of the liquid crystal cell 2.
4a and the absorption axes 12a,
Since the direction of 13a is set as shown in FIG. 3, the viewing angle direction (direction in which the display can be observed with the best contrast) F is displayed on the screen (liquid crystal) as shown by arrows in FIGS. It is in a direction slightly inclined toward the lower edge of the screen along the vertical axis y (see FIG. 3) of the screen with respect to the normal h of the front surface of the display element 1).

In this liquid crystal display device, the retardation of the liquid crystal display element 1, ie, the liquid crystal cell 2
(The retardation when the liquid crystal molecules of the liquid crystal layer 11 are in the initial alignment state) is 400 to 600 n
m.

The retardation of the liquid crystal cell 2 is a product Δnd of the birefringence Δn of the liquid crystal of the liquid crystal layer 11 and the thickness d of the liquid crystal layer.
And the birefringence Δn of the liquid crystal changes depending on the alignment state of the liquid crystal molecules.

When the retardation of the liquid crystal cell 2 is considered, the retardation at which the liquid crystal cell 2 has a high transmittance, that is, the value of Δnd is determined by the twist angle φ of the liquid crystal molecules, and the value of Δnd is determined by the twist angle of the liquid crystal molecules. It was obtained by an experiment in which the twist angle φ was changed from 0 to 90 degrees, and it was found that the twist angle φ and the retardation (Δnd) can be expressed as a quadratic function of the twist angle φ as follows.

Δnd = 0.02593 × φ ² + k (φ: twist angle of liquid crystal molecules, k: constant determined by liquid crystal material) In this embodiment, the twist angle φ of the liquid crystal molecules of the liquid crystal cell 2 is approximately 90 ° ( since it is 90 ° ± 10 °), when the constant k was set to k = one hundred and ninety to three hundred and ninety , a ^{Δnd = 0.02593 × 90 2 + (} 190~390) = 400.033~600.033.

Therefore, in this embodiment, the retardation of the liquid crystal cell 2 is reduced to 400 to 600 n by using a liquid crystal material in which the constant k is 190 to 390.
m.

Next, the light irradiating means 20 will be described. The light irradiating means 20 has one end face as a light incident end face 21a, 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. A light guide 21 formed with a reflection surface 24 for external light incident from the front of the light source and an emission surface (a plurality of step surfaces 22b of a step-shaped surface 22 described later in this embodiment) of illumination light incident from the incident end surface 21a. And this light guide 2
1 light source 2 disposed so as to face the incident end face 21a
6, a specular reflection plate 29 arranged opposite to the back surface of the light guide 21, and an optical member 30 arranged on the front side of the light guide 21.

FIG. 4 is an enlarged side view of a part of the light guide 21 and the optical member 30 constituting the light irradiation means 20, and FIG.
FIG. 2 is an enlarged perspective view of a part of the light guide 21.

The light guide 21 is a transparent plate made of an acrylic resin or the like. One end surface of the light guide 21 is an incident end surface 21a for receiving the light from the light source 26, and the front surface is from the incident end surface 21a 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 22a parallel to each other;
And a plurality of stepped surfaces 22b connecting the steps, the stepped surface 22 having a minute pitch.

The plurality of step surfaces 22b are surfaces substantially parallel to the incident end surface 21a. The step surface 22a between these step surfaces 22b extends in the width direction of the light guide 21 (the length of the incident end surface 21a). (Horizontal direction).

As shown in FIG. 5, Si on the entire surface of the plurality of steps 22a of this step-shaped surface 22 is Si.
A base film 23a made of O ₂ (silicon oxide) is formed,
A mirror-reflective film 23 formed by evaporating a high-reflectance metal film 23b made of aluminum or the like is provided on the entire surface of the base film 23a, and the surface of the reflective film 23 (the surface of the metal film 23b) is It is a reflection surface 24 for external light incident from the front of the liquid crystal display element 1.

The underlayer 23a made of SiO _{2 is used.}
Is provided to increase the adhesion between the light guide 21 made of acrylic resin or the like and the metal film 23b made of aluminum or the like.

The plurality of step surfaces 22b of the step-shaped surface 22 are light transmitting surfaces on which no reflective film is formed.
These step surfaces 22b are emission surfaces of the illumination light incident from the incident end surface 21a.

Further, as shown in FIG. 5, the back surface of the light guide 21 has a light diffusing surface 25 for averaging the luminance distribution of the illumination light incident from the incident end face 21a in the light guide width direction. It has become.

The light diffusing surface 25 includes a plurality of vertically elongated prism portions 25 a having a length extending over the entire length of the light guide 21 and the light guide 2.
1. The reflector 29 has a shape formed in parallel with each other at a fine pitch so as to be continuous in the width direction, and the reflecting plate 29 is arranged with its reflecting surface close to or in contact with the tops of the plurality of prism portions 25a. I have.

The light source 26 comprises, for example, a straight tubular fluorescent lamp 27 having a length extending over the entire length of the incident end face 21 a of the light guide 21, and a reflector 28 for reflecting light emitted from the fluorescent lamp 27. This light source 2
Numeral 6 is arranged on the side of the light guide 21 so as to face the incident end face 21a.

On the other hand, the optical member 30 emits light incident from the front surface to the rear surface, and reflects light on the plurality of step surfaces 22a of the light guide 21 (surface of the reflection film 23).
The light reflected by the optical member 30 and incident from the back surface of the optical member 30 is emitted to the front surface, and the illumination light emitted from the plurality of step surfaces (emission surfaces) 22b of the light guide 21 is taken in from the back surface and emitted forward. Has characteristics.

The optical member 30 is a transparent plate made of an acrylic resin or the like having substantially the same width as the light guide 21, and has a flat front surface and a stepped surface of the light guide 21 on the rear surface. A plurality of incident portions 31 for taking in light emitted from the plurality of step surfaces 22b of the shape surface 22 are provided integrally.

Each of the plurality of incident portions 31 is formed in the shape of a horizontally long protrusion that extends over the entire width of the optical member 30. The optical member 30 is arranged in the longitudinal direction of the plurality of incident portions 31 on the back surface thereof. Are substantially parallel to the length direction of the plurality of step surfaces 22 b of the light guide 21, and the apex portions of the plurality of incident portions 31 are arranged so as to approach or contact the plurality of step surfaces 22 a of the light guide 21. ing.

The plurality of incident portions 31 have a triangular cross-sectional shape, and one of two side surfaces of the plurality of incident portions 31 that faces the step surface 22b of the light guide 21. Is an incident surface 31a for taking in the light emitted from the step surface 22b of the light guide 21, and the other side surface is a refraction surface 31b for refracting the light taken from the incident surface 31a toward the front surface of the optical member 30. It has become.

The incident surface 31a has an inclination substantially parallel to or close to the step surface 22b of the light guide 21 and has an angle with respect to the step surface 22a of the light guide 21 (the angle in the direction facing the step surface 22b). ) Is a plane not exceeding 90 °.

The refracting surface 31b is provided on the optical member 30.
Is an inclined surface having an inclination angle larger than the angle between the incident surface 31a and the normal.

The more desirable shape of the incident portion 31 is such that the incident surface 31a is inclined by 5 to 15 ° with respect to the normal to the step surface 22b of the light guide 21, and the refracting surface 31b is The shape is inclined by 20 to 50 ° in the opposite direction to the normal line.

Further, the plurality of incident portions 31 are provided at a constant pitch with an interval therebetween, and the rear surface area between the adjacent incident portions 31 of the optical member 30 is provided with the guide portion. Reflecting surface 24 on a plurality of step surfaces 22a of optical body 21
Is formed as an entrance / exit surface 32 facing the front end.

The entrance / exit surface 32 is a surface having an inclination substantially parallel to or close to the step surface 22 a of the light guide 21, and enters from the front of the liquid crystal display element 1 and enters the light guide 2.
The light reflected by the reflection surface 24 on one of the plurality of step surfaces 22a is transmitted.

Further, as shown in FIGS. 1 and 2, the plurality of incident portions 31 of the optical member 30 are
The plurality of step surfaces 22b of the light guide 21 are always provided at at least one incident portion 31 of the optical member 30. Are facing each other.

In FIGS. 1 and 2, the stepped surface 22 of the light guide 21 and the plurality of incident portions 31 of the optical member 30 are greatly enlarged for convenience.
The pitch of the light incident portion 31 is substantially the same as the pixel pitch of the liquid crystal display element 1 or an integer fraction of the pixel pitch, and according to the pitch of the step surface 22b of the light guide 21, the optical member The pitch of the 30 incident portions 31 is set slightly larger than the pitch of the step surface 22 b of the light guide 21.

Then, in the liquid crystal display device of this embodiment,
The light irradiating means 20 including the light guide 21 and the light source 26 arranged to face the incident end face 21a thereof and the optical member 30 arranged on the front side of the light guide 21 is provided by the optical member 30. The length direction of the plurality of incident portions 31 and the length direction of the plurality of stepped surfaces 22b of the light guide 21 are substantially parallel to the horizontal axis x (see FIG. 3) of the screen of the liquid crystal display element 1, and the light source The liquid crystal display element 1 is arranged behind the liquid crystal display element 1 with the arrangement side of the liquid crystal display element 1 facing the main direction of capturing external light and the side opposite to the arrangement side of the light source 26 facing the viewing angle direction F of the liquid crystal display element 1. I have.

That is, the display of the liquid crystal display device is generally
The liquid crystal display device is observed from the direction of the viewing angle possessed by the liquid crystal display device, and the reflection type liquid crystal display device has a screen orientation such that external light is mainly taken in from a direction opposite to the viewing angle direction with respect to a normal line of the screen. Used to choose.

In this embodiment, the viewing angle direction F of the liquid crystal display element 1 is slightly different from the normal h of the screen of the liquid crystal display element 1 in the lower edge direction of the screen as shown in FIGS. Because of the inclined direction, the main direction of taking in external light is the direction inclined toward the upper edge of the screen with respect to the normal h of the screen.

For this reason, in this embodiment, the light irradiating means 20 is arranged such that the light source 26 is disposed on the upper edge side of the screen, which is the main direction of capturing external light, that is, on the upper edge side of the liquid crystal display element 1 (left side in FIG. 1). ), The side opposite to the side on which the light source 26 is disposed is oriented in the viewing angle direction F of the liquid crystal display element 1.

Further, in the liquid crystal display device of this embodiment,
As shown in FIG. 1, a light diffusing film 33 and an optical sheet 34 having the following characteristics are stacked between the light irradiation means 20 and the liquid crystal display element 1. .

FIG. 6 is a perspective view of the optical sheet 34. The optical sheet 34 has a reflection axis 34s and a transmission axis 34p in directions substantially orthogonal to each other, and the polarization component is incident along the reflection axis 34s. It has a characteristic of reflecting light and transmitting incident light of a polarization component along the transmission axis 34p.

That is, as shown in FIG. 6, the optical sheet 34 has a polarization component (hereinafter referred to as an S-polarization component) light s along its reflection axis 34s and a polarization component along the transmission axis 34p. When light including both light p (hereinafter, referred to as P-polarized light component) is incident, the light s of the S-polarized light component along the reflection axis 34 s of the incident light becomes the optical sheet 3.
The light p of the P-polarized light component, which is reflected at 4 and is along the transmission axis 34p, passes through the optical sheet 34.

FIG. 6 shows an example in which light is incident on the optical sheet 34 from the rear side, but the optical sheet 34 exhibits the same characteristics with respect to the incident light from the front side. . The optical sheet 34 is a non-colored sheet whose reflection and transmission characteristics have no wavelength dependence.

Although the structure of the optical sheet 34 is not illustrated, for example, a pair of concave and convex surfaces having a shape in which a horizontally long prism-like portion having a minute width is continuously formed in the width direction on one surface thereof is formed. The transparent film, the top of the uneven surface of one film and the valley of the uneven surface of the other film are overlapped facing each other, between the uneven surface of both films, a plurality of transparent refractive index different A laminated film in which films are alternately laminated is sandwiched.
U.S. Pat. Nos. 5,422,756 and 5,559,63
No. 4.

In this embodiment, the transmission axis 34p of the optical sheet 34 is set to the transmission axis of the rear polarizer 13 of the liquid crystal display element 1 (in a direction substantially orthogonal to the absorption axis 13a shown in FIG. 3). The optical sheet 34 is attached to the front surface of the optical member 30 of the light irradiation means 20 via the light diffusion film 33 as shown in FIG.

The light diffusion film 33 is made of, for example, a transparent adhesive in which light scattering fine particles are dispersed.
The optical sheet 34 is adhered to the front surface of the optical member 30 by the adhesive property of the light diffusion film 33.

The liquid crystal display element 1 is disposed so as to overlap with the front surface of the optical sheet 34, and the back surface (the back surface of the rear polarizing plate 13) is light-diffused by a transparent adhesive or a double-sided adhesive sheet 35. It is attached to the front surface of the film 33.

Next, a description will be given of the illumination brightness control means 36 for controlling the brightness of the illumination light from the light irradiation means 20 according to the illuminance of the external environment.

As shown in FIG. 1, the illumination luminance control means 36 includes an illuminance detector 37 for measuring the environmental illuminance, and the light illuminating means 20 based on the environmental illuminance measured by the illuminance detector 37. The means for controlling the luminance of the emitted illumination light comprises a light source luminance adjustment circuit 38 and a light source lighting circuit 39.

The illuminance detector 37 has its 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 38 changes the luminance value of the illumination light emitted from the light irradiating means 20 based on the environmental illuminance measured by the illuminance detector 37, Brightness is adjusted so as to be a predetermined brightness range according to the environmental illuminance,
The light source lighting circuit 39 includes the fluorescent lamp 27 of the light source 26.
Is driven to emit illumination light having a luminance corresponding to the luminance value from the light source luminance adjusting circuit 38.

In this liquid crystal display device, basically, reflected light of external light which enters from the front of the liquid crystal display element 1 and is reflected by the light irradiating means 20, and illumination light which is emitted by the light irradiating means 20 The light source 26 of the light irradiation unit 20 is turned on when the illuminance of the environment in which the liquid crystal display device is used is within a predetermined illuminance range.

The range of the ambient illuminance for lighting the light source 26 is, for example, a range from 0 lux to more than approximately 30,000 lux.

That is, in this liquid crystal display device, in an illuminance range in which the light source 26 is turned on, and in an illuminance environment where external light can be obtained, the reflected light of the external light reflected by the light irradiating means 20 and The display is performed using both the illumination light emitted from the light irradiating means 20 and when the ambient illuminance is almost 0 lux, that is, in an environment where external light is hardly obtained, the illumination emitted by the light irradiating means 20 is used. In a high illuminance environment in which only light is displayed and the light source 26 is not turned on, display is performed using only reflected light of external light.

First, the emission path of the illumination light from the light irradiating means 20 will be described. The light guide 21 of the light irradiating means 20 takes in the illumination light from the light source 26 from the incident end face 21a and outputs the light. Are emitted from the plurality of step surfaces (outgoing surfaces) 22b of the step-shaped surface 22 and light incident on the plurality of step surfaces 22a of the step-shaped surface 22 from the front is reflected on the reflecting surfaces ( (The surface of the reflective film 23), and is reflected forward.
The illumination light taken from a is emitted from the plurality of step surfaces 22b along a path shown by a solid line in FIG.

That is, the illuminating light introduced into the light guide 21 from its incident end face 21a travels in the light guide 21 in the length direction thereof, and includes a plurality of steps of the step-shaped surface 22. Light directly traveling to one of the surfaces 22b is emitted from the step surface 22b.

Light other than the light directly traveling to the step surface 22b, that is, a plurality of step surfaces 22 of the step-shaped surface 22
The light traveling toward the light guide 21a and the light traveling toward the back of the light guide 21 are reflected on the back surface of the reflection film 23 on the step surface 22a, and between the back of the light guide 21 and the outside air (air). While being guided in the length direction of the light guide 21 by total reflection at the interface, the light guide body 21 changes its direction, enters one of the plurality of step surfaces 22b, and exits from the step surface 22b.

The light traveling inside the light guide 21 toward the rear surface includes an incident angle smaller than the critical angle for total reflection (closer to vertical) with respect to the interface between the rear surface of the light guide 21 and the outside air. Some light is incident, and the light passes through the interface and leaks to the back surface of the light guide 21.
Is reflected by the reflector 29 disposed behind the light guide 21 and enters the light guide 21 from the back thereof, and the plurality of stepped surfaces 22
The direction of the light guide is changed by reflection on the back surface of the reflective film 23 on the substrate a and total reflection at the interface between the back surface of the light guide 21 and the outside air, and the light is emitted from any of the plurality of stepped surfaces 22b. Most of the illumination light that has been captured by the light-receiving surface 21 from the incident end surface 21a is emitted from the plurality of step surfaces 22b without waste.

As described above, the back surface of the light guide 21 has a light diffusion surface 25 having a vertically elongated prism-shaped surface 25a continuous with the width direction of the light guide 21 and formed parallel to each other at a fine pitch. When light guided inside the light guide 21 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 21 is reflected by the reflection plate 29.
The light is diffused when re-entering the light guide 21 from the rear surface thereof, and is emitted as light having a substantially uniform luminance distribution in the width direction of the light guide 21 from the plurality of step surfaces 22b.

The light guide 21 has a plurality of step surfaces 2.
The illumination light emitted from 2b enters a plurality of incident portions 31 formed on the back surface of the optical member 30 disposed on the front side of the light guide 21 from an incident surface 31a on one side thereof.

At this time, since the plurality of step surfaces 22 b of the light guide 21 always face at least one incident portion 31 of the optical member 30, the plurality of step surfaces 22 b of the light guide 21 Most of the light emitted from the step surface 22b is incident on any one of the incident portions 31 of the optical member 30 without waste.

The light guide 21 has a plurality of step surfaces 22.
Among the light emitted from b, as shown in FIG. 4, there is light emitted toward the next step surface 22a.
The light is reflected by the reflection surface 24 on the next step surface 22a and is incident on the incident portion 31 of the optical member 30.

The plurality of step surfaces 2 of the light guide 21
2b, a plurality of incident portions 31 of the optical member 30
Is incident on the incident portion 31 from the incident surface 31a of the incident portion 31, and the refraction surface 31b on the opposite side and the outside air (the air layer between the light guide 21 and the optical member 30). The light is totally reflected at the interface with the optical member 30 and changes its direction toward the front surface of the optical member 30, passes through the optical member 30, and exits from the front surface.

The illumination light emitted to the front surface of the optical member 30 is applied to the plurality of incident portions 31 on one side of the incident surface 31a.
, Is refracted by the refracting surface 31b on the opposite side and condensed in a predetermined direction, and has a luminance distribution with high luminance in a predetermined direction.

In this case, in this embodiment, the incident portion 3
The angle of inclination of the first refraction surface 31b is set so that the direction of the light refracted by the refraction surface 31b is the front direction (direction near the normal to the front surface of the optical member). The illumination light emitted to the front of the light guide 30
Is a light having a high directivity distribution in the front direction.

The direction in which the illumination light exits from the front surface of the optical member 30 is in accordance with the angle of inclination of the refraction surface 31b of the incident portion 31, and the angle of inclination of the refraction surface 31b is equal to the front surface of the optical member. Is closer to the front when the angle is within a range of 20 to 50 ° with respect to the normal line.

The light emitted in front of the optical member 30, that is, the light emitted from the light irradiating means 20, is transmitted and diffused through the light diffusion film 33, and is transmitted through the optical sheet 34 on the front surface of the light diffusion film 33. 1 is incident from the back. In FIG. 4, the state of diffusion of the illumination light transmitted through the light diffusion film 33 is omitted for simplification of the drawing.

In this case, the light emitted from the light irradiating means 20 is light containing polarized light components of various directions, and the optical sheet 34 is, as shown in FIG.
It has a characteristic of reflecting the incident light s of the S-polarized component along the transmission axis 34p and transmitting the incident light p of the P-polarized component along the transmission axis 34p. Of the light that is diffused by the diffusion film 33 and enters the optical sheet 34, light of a polarization component along the transmission axis 34p of the optical sheet 34 passes through the optical sheet 34 and enters the liquid crystal display element 1. The light of the polarization component along the reflection axis 34s of the optical sheet 34 is reflected by the optical sheet 34.

The path of the light reflected by the optical sheet 34 is transmitted through the optical member 30 of the light irradiating means 20, though the path of the light is not shown.
The light is reflected by the upper reflecting surface 24, changes the polarization direction to some extent, passes through the optical member 30 again, enters the optical sheet 34, and of the light, the transmission axis 3 of the optical sheet 34
4p is transmitted through the optical sheet 34 and is incident on the liquid crystal display element 1. The light of the polarized component along the reflection axis 34s of the optical sheet 34 is reflected by the optical sheet 34.
Is reflected again.

The following is the repetition, and
Of the illuminating light from the light irradiating means 20, light having a polarization component along the reflection axis 34s of the optical sheet 34 is reflected by the optical sheet 34 and reflected by the light irradiating means 20 (light guide 21). (Reflection on the reflection surface 24 on the plurality of step surfaces 22a), the polarization direction is changed, and eventually, the light becomes a polarized component light along the transmission axis 34p of the optical sheet 34 and transmits through the optical sheet 34. Incident on the liquid crystal display element. For this reason, most of the illumination light from the light irradiation means 20 can be incident on the liquid crystal display element 1 without waste.

In the light reflected from the optical sheet 34 and incident on the optical member 30 from the front surface, the refraction surface 31b having a large inclination angle of the plurality of incident portions 31 on the rear surface of the optical member 30 is adjacent to the refraction surface 31b. Incoming / outgoing surface 32 between incident parts 31
Is transmitted through the interface between these surfaces 31b and 32 and the outside air (the air layer between the light guide 21 and the optical member 30) and exits to the back. Further, the light traveling toward the incident surface 31a having a small inclination angle of the incident portion 31 is totally reflected at the interface between the incident surface 31a and the outside air and changes its direction.
b or the light exits from the entrance / exit surface 32 to the back.

The light emitted to the back surface of the optical member 30 and reflected by the reflection surfaces 24 on the plurality of step surfaces 22a of the light guide 21 enters the optical member 30 from the back surface. The step surface 22a of the light guide 21 and the optical member 30
Since the angle between the plurality of incident portions 31 and the incident surface 31a is large (close to a right angle), the plurality of step surfaces 2 of the light guide 21 are formed.
Most of the light reflected by the reflection surface 24 on the light receiving surface 2a is taken in from the refraction surfaces 31b of the plurality of incident portions 31 of the optical member 30 and the input / output surface 32.

Then, of the light taken in from the refraction surface 31b of the entrance section 31, the light heading directly to the front surface of the optical member 30 and the light taken in from the entrance / exit surface 32 remain in the same direction as the optical member. 30 out of the front surface, which is emitted from the front surface and is taken in from the refraction surface 31b of the incident portion 31, the light traveling toward the opposite incident surface 31a is totally reflected at the interface between the incident surface 31a and the outside air. The optical member 3 directly from the refraction surface 31b and the entrance / exit surface 32.
Change the direction to the direction close to the direction of the light going to the front of 0,
The light exits from the front surface of the optical member 30.

Therefore, the light is reflected by the optical sheet 34 and is reflected on the plurality of step surfaces 22 a of the light guide 21.
The light that is reflected at and exits the front surface of the optical member 30 also
The light emitted in the front direction has high luminance distribution.

The illumination light emitted from the front surface of the light irradiation means 20 (the front surface of the optical member 30), sequentially transmitted through the light diffusion film 33 and the optical sheet 34, and incident on the liquid crystal display element 1 from the rear surface is The light is linearly polarized light along the transmission axis 34p of the optical sheet 34, and the light is incident on the liquid crystal display element 1 from the back thereof.
Is almost parallel to the transmission axis of the rear polarizing plate 13 of the liquid crystal display element 1, so that most of the illuminating light transmitted through the optical sheet 34 and incident on the liquid crystal display element 1 can be efficiently used. The light passes through the plate 13 and enters the liquid crystal cell 2.

The illumination light (linearly polarized light) transmitted through the rear-side polarizing plate 13 and incident on the liquid crystal cell 2 is applied to the liquid crystal layer 1.
In the process of transmitting light through the first substrate 3, the light is rotated by a birefringence effect according to the alignment state of the liquid crystal molecules that changes according to the voltage applied between the electrodes 6 and 7, and a plurality of light beams are provided on the inner surface of the front substrate 3. The light of the wavelength component in the absorption wavelength band is absorbed by the color filters 8R, 8G, and 8B to become colored light colored by the color filters 8R, 8G, and 8B, and the light emitted to the front surface of the liquid crystal cell 2. Of the above, the light of the polarization component along the absorption axis 12a of the front-side polarizing plate 12 is absorbed by the front-side polarizing plate 12, and the light of the polarization component along the transmission axis passes through the front-side polarizing plate 12. The light is emitted from the front surface of the liquid crystal display element 1 as color 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, this liquid crystal display device is, as described above, under the environment where external light can be obtained, relative to the normal of the screen. It is used by selecting the screen orientation so that it mainly takes in external light from the direction inclined to the upper edge of the screen,
External light is mainly at the upper edge of the screen (the upper edge of the liquid crystal display element 1).
At various angles of incidence.

External light incident from the front of the liquid crystal display element 1 is absorbed by the front-side polarizing plate 12 as light having a polarization component along its absorption axis 12a, and travels along the transmission axis of the front-side polarizing plate 12. The light enters the liquid crystal cell 2 as linearly polarized light.

The external light (linearly polarized light) incident on the liquid crystal cell 2 is applied to the color filters 8R, 8G, 8B.
Absorbs the light of the wavelength component in the absorption wavelength band to become colored light, and in the process of passing through the liquid crystal layer 11, in accordance with the orientation state of the liquid crystal molecules which is changed by the voltage applied between the electrodes 6 and 7. The optical element is rotated by the birefringence effect, and of the light, the light of the polarization component along the absorption axis 13a of the rear polarizing plate 13 is absorbed by the rear polarizing plate 13 and the polarization component along the transmission axis is absorbed. The light passes through the rear-side polarizing plate 13 and is emitted as color image light to the rear surface of the liquid crystal display device 1.

The light emitted to the back of the liquid crystal display element 1 passes through the optical sheet 34 and the light diffusing film 33 in order and enters the optical member 30 of the light irradiation means 20 from the front. Since the transmission axis 34p of the optical sheet 34 is substantially parallel to the transmission axis of the rear polarizing plate 13 of the liquid crystal display element 1, the transmission axis 34p transmits through the rear polarizing plate 13 and
Most of the light emitted to the back of the optical member 30 passes through the optical sheet 34 and enters the optical member 30.

In this liquid crystal display device, as described above, the light irradiating means 20 is disposed with the light source 26 disposed on the upper edge side of the screen, which is the main direction of capturing external light of the liquid crystal display device. Therefore, external light incident on the optical member 30 mainly enters from the side where the light source 26 is disposed.

External light incident on the optical member 30 from the front thereof passes through the optical member 30 and exits from the rear surface thereof, and is reflected by the reflection surfaces 24 on the plurality of step surfaces 22a of the light guide 21. .

That is, the external light incident on the optical member 30 from the front thereof enters the optical member 30 at various incident angles as shown by broken lines in FIG. A refracting surface 31b having a large inclination angle of the plurality of incident portions 31 on the back surface, and an incident / exit surface 32 between adjacent incident portions 31
Is transmitted through the interface between these surfaces 31b and 32 and the outside air (the air layer between the light guide 21 and the optical member 30), and exits to the back surface. The light is reflected by the upper reflecting surface 24.

Further, of the incident light, the incident portion 31
The light traveling toward the entrance surface 31a having a small inclination angle is totally reflected at the interface between the entrance surface 31a and the outside air, and its direction is changed, and the light exits from the refraction surface 31b or the input / output 32 to the rear surface. Then, the step surface 22a of the light guide 21
The light is reflected by the upper reflecting surface 24.

The light guide 21 has a front surface formed on a stepped surface 22, a reflective film 23 is provided on the plurality of step surfaces 22 a over the entire surface, and the surface is formed as a reflective surface 24.
Therefore, the light guide 21 has the same reflection characteristics as a normal reflection plate having a flat reflection surface on the front surface. Therefore, most of the light emitted to the rear surface of the optical member 30 is wasted. It can be reflected without.

The light guide 21 has a plurality of step surfaces 22.
The light reflected by the reflection surface 24 on the optical member 30a is taken into the optical member 30 from the rear surface thereof, passes through the light guide 30 and exits from the front surface.

At this time, since the angle between the step surface 22a of the light guide 21 and the incident surfaces 31a of the plurality of incident portions 31 of the optical member 30 is large (close to a right angle), the step surface of the light guide 21 is formed. Most of the light reflected by the reflection surface 24 on the reflection surface 22 a is the refraction surface 3 of the plurality of incident portions 31 of the optical member 30.
1b and the incident / exit surface 32.

[0138] Of the light taken in from the refraction surface 31b of the entrance section 31, the light heading directly to the front surface of the optical member 30 and the light taken in from the entrance / exit surface 32 are the optical members in the same direction. 30 out of the front surface, which is emitted from the front surface and is taken in from the refraction surface 31b of the incident portion 31, the light traveling toward the opposite incident surface 31a is totally reflected at the interface between the incident surface 31a and the outside air. The optical member 3 directly from the refraction surface 31b and the entrance / exit surface 32.
The light is emitted from the front surface of the optical member 30 while changing its direction to a direction close to the direction of the light heading toward the front surface of the optical member 30.

Therefore, as the reflected light of the external light emitted to the front surface of the light irradiating means 20 (the front surface of the optical member 30), 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 30 is converted into light having a high luminance in the front direction, which is incident and condensed from the incident portion 31, and is reflected by the incident portion 31. The light having a higher luminance in the front direction is light having a higher luminance in the front direction in which light incident from the entrance / exit surface 32 and transmitted in the front direction is superimposed.

The reflected light emitted from the front surface of the light irradiation means 20 is transmitted through the light diffusion film 33 and diffused, passes through the optical sheet 34 on the front surface, and enters the liquid crystal display element 1 from the back surface. . In FIG. 4, the state of diffusion of the reflected light transmitted through the light diffusion film 33 is omitted for simplification of the drawing.

Also at this time, since the transmission axis 34p of the optical sheet 34 and the transmission axis of the rear polarizing plate 13 of the liquid crystal display element 1 are substantially parallel, most of the reflected light transmitted through the optical sheet 34 is transmitted. The back side polarizing plate 1 without waste
3 and enter the liquid crystal cell 2.

The reflected light incident on the liquid crystal cell 2 from the back thereof passes through the liquid crystal layer 11 and the color filters 8R, 8G, 8B in that order, and further passes through the front polarizing plate 12 to display the liquid crystal. Light is emitted forward from the front surface of the element 1.

Next, the brightness of the screen of the liquid crystal display element 1 in this liquid crystal display device will be described.

As described above, the liquid crystal display device basically includes external light reflected from the light irradiating means 20 which is incident from the front of the liquid crystal display element 1 and reflected by the light irradiating means 20. Are simultaneously used to display the illumination light. The range of the ambient illuminance for turning on the light source 26 of the light irradiating means 20 is, for example, a range from 0 lux to more than approximately 30,000 lux. When the illuminance is almost 0 lux, that is, when almost no external light is obtained, the display is performed only by the illuminating light emitted from the light irradiating means 20, and in a high environmental illuminance where the light source 26 is not turned on, The display is performed only by the reflected light.

On the other hand, a preferable screen luminance of the liquid crystal display device is as follows.
Depending on the illuminance of the external environment (the environment in which the liquid crystal display device is used), the screen may be too dazzling or too dark depending on the environmental illuminance even with the same screen luminance.

Therefore, in this liquid crystal display device, the light irradiating means is mainly used so as to obtain a suitable screen luminance which is not excessively dazzling even in an environment of high illuminance exceeding 100,000 lux, for example, under direct sunlight in summer. 20 (reflectance of the reflection surface 24 on the plurality of step surfaces 22a of the light guide 21) and the light transmittance of the liquid crystal display device 1 determined by the transmittance of the liquid crystal display device 1. The ratio of the intensity of the external light incident from the front of the liquid crystal display element 1 to the intensity of the external light incident from the front of the liquid crystal display element 1 to the intensity of the external light incident from the front of the liquid crystal display element 1) It is set lower than that of the reflection type liquid crystal display device, and the reflected light of the external light which is incident from the front of the liquid crystal display element 1 and is reflected by the light irradiation means 20, and the illumination light emitted by the light irradiation means 20 Painting by both The light irradiating means 20 is controlled so that the luminance (when the ambient illuminance is almost 0 lux, the screen luminance only by the illumination light emitted from the light irradiating means 20) becomes a suitable screen luminance according to the environmental illuminance. Is controlled by the illumination brightness control means 36 according to the environmental illuminance.

The screen luminance of this liquid crystal display device is such that the environmental illuminance is I (lux, hereinafter referred to as lx), the luminance of the illuminating light emitted from the light irradiation means 20 is B (nit, hereinafter referred to as nit), When the light transmittance of the display element 1 is T (%), the reflectance of the liquid crystal device is R (%), and the screen luminance is L (nit, hereinafter referred to as nit), 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 under 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 20 is controlled by the illumination luminance control means 36 so that the screen luminance with respect to the environmental illuminance is 20 to 300 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 such that the value of the screen luminance L (nit) obtained by the above-mentioned relational expression (L = I × R / 400 + B × T / 200) 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 A more suitable screen luminance according to the environmental illuminance is 2 to 60 nits and 1000 nits at an environmental illuminance of 50 lx as described above.
The illuminance control condition of the illumination light is 60 to 200 nit at an ambient illuminance of lx and 1000 to 3000 nit at an ambient illuminance of 30,000 lx. The relational expression (L = I × R / 400 + B ×
T / 100), the value of the screen luminance L (nit) is given by the following equation (2) with respect to the environmental illuminance I (lx): -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 irradiation means 20 is more preferably controlled by the illumination luminance control means 36 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. 7 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. 7, 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 luminance when L = −2 × 10 ⁻⁷ × I ² + 0.0871 × I + 50, and b2 is L = −9 × 10 ⁻⁸ × I ² + 0.0453 × I + 20 , And therefore, a more preferable screen luminance is a luminance in a range B between b1 and b2.

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

In this reflection type liquid crystal 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 is obtained is more preferably in the range of about 300 to about 5000 lx. The range of the environmental illuminance at which the screen luminance (the screen luminance in the range of B) is obtained is about 500 to about 2000 lx. At the environmental illuminance beyond that, the screen becomes too bright, for example, in direct sunlight in summer. 100000
In an environment of high illuminance exceeding lx, 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 liquid crystal display device, the liquid crystal display device of this embodiment uses the reflected light of the external light by the light irradiation means 20 and the illumination light emitted by the light irradiation means 20. When illumination light is emitted from the light irradiating means 20 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 is displayed. The light having a luminance in which the light and the illumination light are superimposed is incident on the liquid crystal display element 1 from the back.

Therefore, this liquid crystal display device can provide a suitable screen luminance even in a dark environment, and the reflectivity of the liquid crystal display device is a normal reflection type liquid crystal display device using only the reflected light of external light. Therefore, even in an environment of high illuminance such as direct sunlight in summer, a suitable screen luminance without excessive glare can be obtained.

Further, even when the ambient illuminance is almost 0 lx, that is, when almost no external light can be obtained, the liquid crystal display device uses the illumination light emitted from the light irradiating means 20 to obtain a suitable screen luminance. Display can be performed.

Since the reflectance of the external light of the light irradiating means 20 (the reflectance of the reflecting surface 24 on the plurality of step surfaces 22a of the light guide 21) is constant, the brightness of the reflected light of the external light is low. This liquid crystal display device includes an illumination luminance control unit 36 that controls the luminance of the illumination light according to the environmental illuminance, and the screen luminance is a luminance that is predetermined according to the environmental illuminance. The light irradiating means 20 so as to be in a range (the luminance range of A shown in FIG. 7, more preferably the luminance range of B).
Since the reflectance of external light and the luminance control condition of the illumination light by the illumination luminance control means 36 are set, it is possible to obtain a screen luminance suitable for the environmental illuminance according to the environmental illuminance. it can.

Further, 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, the liquid crystal display device requires less power consumption, and can obtain a screen luminance suitable for the environmental illuminance in an environment of a wide illuminance range from low illuminance to high illuminance.

In this liquid crystal display device, the light irradiating means 20 has a screen luminance of 20 to 200 nit at an environmental illuminance of 50 lx as described above.
Screen brightness of 30-300 nits at 1000lx 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 that satisfies the range of the screen luminance of 400 to 4000 nit at the environmental illuminance of 30,000 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 20 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 an environment in the illuminance range, it is possible to obtain a screen luminance suitable for the environment illuminance.

Further, the light irradiating means 20 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), the screen luminance with respect to the environmental illuminance is L (nit), and the screen luminance is L (nit), the above-mentioned 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 an environment with 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. 7) which satisfies the above equation (1) or (2) according to the environmental illuminance, As an example, FIG. 8 shows a calculation relationship between the environmental illuminance (lx) that provides a suitable screen illuminance with respect to the environmental illuminance and the screen luminance (nit) only by the illumination light from the light irradiating means 20. Is shown.

The relationship between the environmental illuminance and the screen luminance due to only the illumination light shown in FIG. 8 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 0 to about 63000 lx, and the reflectance of the liquid crystal display device is set to High ambient illuminance (approximately 1
A screen luminance at 2000 lx or an illuminance exceeding about 6300 lx) is a suitable screen luminance satisfying the above equation (1) (for example, about 2200 to about 12000 at an environmental illuminance of 110000 lx).
nit) or a more suitable screen luminance that satisfies the above equation (2) (for example, about 5300 to about 9 at an environmental illuminance of 110,000 lx).
500 nit).

In FIG. 8, 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. 7) and the minimum value (the luminance of a2 in FIG. 7) of the screen luminance range obtained by Expression (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. 8, when the ambient illuminance exceeds about 300 lx, the screen luminance of the a2 'becomes 0 nit or less. However, when the light irradiating means 20 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. 8, b1 'and b2' are
This is the screen brightness using only illumination light for obtaining the maximum value (b1 brightness in FIG. 7) and the minimum value (b2 brightness in FIG. 7) 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 illuminating light for obtaining a more preferable screen luminance satisfying the expression (2) is a luminance in a range between b1 'and b2'. In addition,
According to the calculation, as shown in FIG. 8, 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 means 20 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 36
Controls the luminance of the illuminating light from the light irradiating means 20 at least in an environmental illuminance higher than the indoor illuminance (around 1000 lx) so that the screen luminance by the illuminating light alone is within the range shown in FIG. In this way, at least in an environment where the illuminance is higher than the indoor illuminance, the screen brightness (the range of A shown in FIG. 7, more preferably the range of B shown in FIG. 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 36 adjusts the luminance of the illumination light from the light irradiation means 20 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 36, in the illumination range where the environmental illuminance is lower than the indoor illuminance, the light illuminating means 36 continuously reduces the brightness of the illumination light as the environmental illuminance decreases. 20 is desirably controlled, and 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 sufficiently viewed even when the screen luminance is low, the environment illuminance is more suitable. It is possible to obtain an extremely low screen luminance and further reduce the power consumption of the light irradiation means 20.

In the illuminance control means 36, 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 the light continuously increases, and when the environmental illuminance exceeds the predetermined illuminance, the light irradiating unit 20 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 way, in the illuminance range where the ambient illuminance is higher than the indoor illuminance, the luminance of the illumination light is continuously increased as the environmental illuminance increases, 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.

Further, the illumination brightness control means 36
In the illuminance range where the environmental illuminance is lower than the indoor illuminance, the light irradiating means 20 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 desirable to control the light irradiating means 20 so that the luminance of the illumination light continuously decreases 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 sufficiently viewed even if the screen illuminance is low, a screen with a low luminance suitable for the illuminance is more suitable. 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 liquid crystal display device,
The range of the environmental luminance at which the illumination light is emitted from the light irradiating means 20 is set to a range from 0 lx to more than about 30,000 lx, and the reflectance of the liquid crystal display device is changed by stopping the emission of the illumination light from the light irradiating means 20. The screen luminance at a high ambient illuminance for displaying only the reflected light is set so that the screen luminance that satisfies the expression (1), more preferably the expression (2), is obtained. In an illuminance range lower than the illuminance, the light irradiating unit 20 is controlled so that the luminance of the illumination light is continuously reduced as the environmental illuminance decreases.In an illuminance range in which 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 continuously increases with the environmental illuminance, and when the environmental illuminance exceeds the predetermined illuminance, the environmental illuminance is It is most preferable to control the light irradiating means 20 so that the luminance of the illuminating light continuously decreases as the luminance increases.

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

Further, in the above embodiment, the illumination luminance control means 36 emits light to the illuminance detector 37 for measuring environmental illuminance, and the light irradiating means emits light based on the environmental illuminance measured by the illuminance detector 37. Since it is constituted by means for controlling the luminance of the illumination light (the light source luminance adjustment circuit 38 and the light source lighting circuit 39), the luminance of the illumination light is controlled in accordance with the actual environmental illuminance, and Suitable screen brightness can be obtained.

Further, in the above embodiment, the liquid crystal display element 1
A light irradiating means 20 disposed behind the light source 26, and an emission surface (a plurality of steps of the step-shaped surface 22 of the light guide 21) for guiding the illumination light from the light source 26 and emitting the light toward the liquid crystal display element 1. Surface 22 b) and a reflection surface (a plurality of stair-shaped surfaces 22 of the light guide 21) 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 21 having the surface 24 of the reflective film 23 formed on the step surface 22b, so that the emission rate of the illumination light from the output surface (step surface 22b) and The reflectance of external light on the reflection surface 24 can be independently selected.

Therefore, the exit surface (step surface 22b)
The efficiency of use of the illumination light from the light source 26 is increased by increasing the emission rate of the illumination light from the light source 26, and the light emission luminance of the light source 26 is reduced accordingly, thereby further reducing the power consumption and the reflection surface 24. Can be set so that the reflectance of the liquid crystal display device has a desired value.

In addition, the light irradiation means 2 used in the above embodiment
Reference numeral 0 designates one end face of the light guide 21 as an incident end face 21a for receiving illumination light from the light source 26.
A plurality of step surfaces 22a whose front surface is gradually lowered from the incident end surface 21a side to the other end side;
2a, and a step-shaped surface 22 composed of a plurality of step surfaces 22b connecting the reflection film 2 on the plurality of step surfaces 22a.
3 is provided to form a reflection surface 24 for external light, and the plurality of step surfaces 22b serve as emission surfaces of illumination light incident from the incident end surface 21a, and on the front side of the light guide 21, The liquid crystal display device 1 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 surfaces 24 on the plurality of stepped surfaces 22a of the light guide 21, and transmits a plurality of the light guides 21. The optical member 30 that emits the illumination light emitted from the step surface 22b toward the liquid crystal display element 1 is disposed.

According to the light irradiation means 30, the illumination light introduced into the light guide 21 from the incident end face 21a is
A plurality of step surfaces 22b of the step-shaped surface 22 of the light guide 21
And the light is redirected by the optical member 30 and is emitted toward the liquid crystal display element 1, so that the illumination light from the light source 26 can be made to enter almost the entire liquid crystal display element 1. .

In addition, according to the light irradiating means 20, the plurality of step surfaces 22a of the step-shaped surface 22 of the light guide 21 serve as external light reflecting surfaces 24, respectively. External light incident from the front passes through the optical member 30 and is reflected by the reflecting surfaces 24 on the plurality of stepped surfaces 22a of the light guide 21, and the reflected light passes through the optical member 30 again and returns to the liquid crystal. Since the light is emitted toward the display element 1, most of the external light incident from the front of the liquid crystal display element 1 can be reflected without waste and can be incident on almost the entire liquid crystal display element 1.

The optical member 30 is composed of a transparent plate having a front surface for emitting light toward the liquid crystal display element 1 and a back surface opposite to the front surface of the light guide 21. An incident surface 31a for taking in light emitted from the plurality of step surfaces 22b of the light guide 21, and a refracting surface 3 for refracting light taken in from the incident surface 31a toward the front.
1b, so that most of the light emitted from the plurality of stepped surfaces 22b of the light guide 21 is taken into the optical member 30 without waste and the front surface thereof is formed. From the liquid crystal display element 1.

That is, in principle, the light irradiating means 20 can emit almost 100% of the light from the light source 26 and can reflect and emit almost 100% of the external light incident from the front.

Further, if the optical member 30 is configured as described above, the light exits from the plurality of step surfaces 22b of the light guide 21 and enters the plurality of incident portions 31 of the optical member 30 from the incident surface 31a. The incident light is refracted by the refraction surface 31b and condensed in a predetermined direction, and illumination light having a high luminance distribution in a predetermined direction (for example, the front direction) is emitted from the front surface of the optical member 30. The external light reflected by the reflection surfaces 24 on the plurality of step surfaces 22a of the light guide 21 is also converted from the front surface of the optical member 30 into light having a high luminance distribution in a predetermined direction (for example, the front direction). Can be emitted.

Further, in the above-described embodiment, the optical member 30 is provided with the plurality of incident portions 31 on the back surface thereof at intervals, and the rear surface region between these incident portions 31 is defined by the light guide. Since the input / output surface 32 corresponds to the reflection surface 24 on the plurality of step surfaces 22a of the liquid crystal display 21, external light incident from the front of the liquid crystal display element 1 and incident on the optical member 30 from the front is The light exits from the entrance portion 31 and the entrance / exit surface 32 between the entrance portion 31 and the rear surface of the optical member 30, and the reflection surface 24 on the plurality of step surfaces 22 a of the light guide 21.
The reflected light of the external light reflected by the
In addition, the light can be taken into the optical member 30 from the input / output surface 32 and emitted from the front surface of the optical member 30 toward the liquid crystal display element 1, and the reflected light can be reflected in a predetermined direction (for example, in the front direction). Light with a high luminance distribution can be obtained.

In the above embodiment, the light irradiation means 2
0 on the back surface of the light guide 21 constituting the light guide 21.
Since the light diffusing surface 25 for averaging the luminance distribution in the width direction of the light guide of the illumination light incident from the incident end face 21a of the light guide 21 is formed on the light guide 21.
The luminance distribution of the illumination light taken in from the light guide and emitted from the plurality of stepped surfaces 22 b on the front surface of the light guide can be made substantially uniform in the width direction of the light guide 21.

Further, in the liquid crystal display of the above embodiment,
Since the light diffusion film 33 is provided between the light irradiation means 20 and the liquid crystal display element 1, the illumination light from the light irradiation means 20 and the reflected light of the external light are diffused by the light diffusion film 33 to be substantially uniform. The liquid crystal display element 1 is made to enter the liquid crystal display element 1 from the back as light having a uniform luminance distribution, so that the screen luminance is made uniform over the entire screen, and the emission angle range of the light emitted in front of the liquid crystal display element 1 is widened to obtain a wide viewing angle. Can be obtained.

In the above embodiment, the reflection axis 34s and the transmission axis 34p are provided between the light irradiating means 20 and the liquid crystal display element 1 in directions substantially orthogonal to each other, and extend along the reflection axis 34s. An optical sheet 34 having a characteristic of reflecting the incident light of the polarization component and transmitting the incident light of the polarization component along the transmission axis 34p is provided.

For this reason, of the illumination light from the light irradiating means 20, light having a polarization component along the transmission axis 34p of the optical sheet 34 is transmitted through the optical sheet 34 and enters the liquid crystal display element 1, and Of the illumination light from the light irradiating means 20, light of a polarization component along the reflection axis 34s of the optical sheet 34 is polarized by repetition of reflection on the optical sheet 34 and reflection on the light irradiating means 20. Since the direction is changed, the light becomes a polarized component along the transmission axis 34p of the optical sheet 34, passes through the optical sheet 34, and enters the liquid crystal display device 1, so that most of the illumination light from the light irradiation unit 20 is emitted. Can be made incident on the liquid crystal display element without waste, and therefore, the efficiency of using the illumination light from the light irradiation means 20 is increased, and the emission luminance of the light source 26 is reduced accordingly. It is possible to reduce the power consumption.

Furthermore, in the above embodiment, the optical sheet 34 is disposed with its transmission axis 34p substantially parallel to the transmission axis of the rear polarizing plate 13 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 20 and enters the liquid crystal display element from the back can be transmitted without being reflected by the optical sheet 34. .

Further, in the liquid crystal display device, the retardation of the liquid crystal display element 1 (in this embodiment, the liquid crystal cell 2
, That is, Δnd) is 400 to 600 n
m, in the display by the reflected light of the external light, depending on the viewing direction of the display, a dark area in which the transmittance of the liquid crystal display element 1 is controlled to be low and a bright area in which the transmittance is controlled to be high. Lowering the contrast (hereinafter referred to as shadow contrast) between the shadow of the dark area and the bright area, which appears on the boundary,
Eliminate the double display of the display image and its shadow,
The viewing angle can be made sufficiently wide.

That is, external light is incident on the liquid crystal display device at an incident angle inclined at 30 ° to the upper edge of the screen with respect to the normal of the screen, and the reflected light (emitted light) is reflected on the screen with respect to the normal. The relationship between the retardation of the liquid crystal display element 1 and the shadow contrast when observed from a direction inclined by 20 ° toward the lower edge side (viewing angle direction side) is, according to an actually measured value, that when the retardation is 300 nm, the shadow contrast is 5.
9 When the retardation is 400 nm, the shadow contrast is 4.
9 When the retardation is 500 nm, the shadow contrast is 3.
8. Shadow contrast at a retardation of 600 nm
9

As can be seen from this relationship, when the retardation of the liquid crystal display element 1 is 300 nm, the shadow contrast is as large as 5.9, and when the retardation of the liquid crystal display element 1 is 400 nm or more, for example, the retardation is 400 nm. When the shadow contrast is 4.9,
When the retardation is 500 nm, the contrast is 3.8, and when the retardation is 600 nm, the shadow contrast is 2.9.

Further, in the liquid crystal display element 1, when the retardation is less than 400 nm, the brightness of white display is insufficient, and when the retardation exceeds 600 nm, gradation display is deteriorated.
A sufficiently wide viewing angle can be obtained within the range of -600 nm.

In the liquid crystal display of this embodiment, since the light diffusion film 33 is disposed between the liquid crystal display element 1 and the light irradiating means 20, the diffusion effect of the light diffusion film 33 and the liquid crystal A wider viewing angle can be obtained by the synergistic effect of both the wide viewing angle characteristic of the display element 1 and the wide viewing angle characteristic.

Therefore, the liquid crystal display device requires less power consumption, and can obtain a screen luminance suitable for the environment illuminance in an environment of a wide illuminance range from low illuminance to high illuminance. In this embodiment, the light diffusing film 3 is provided on the front surface of the light irradiation means 20 (the front surface of the optical member 30).
3, and an optical sheet 34 is provided on the front surface thereof.
The light diffusion film 33 and the optical sheet 34 may be provided by being stacked in a manner opposite to the above embodiment.

The light diffusion film 33 is not limited to a transparent adhesive coating film in which light scattering fine particles are dispersed, but may be applied to a light diffusion plate or a surface perpendicular to the plate surface and along a specific direction. Shows a scattering property for light incident at an incident angle in an angle range inclined at a predetermined angle or more, and a selective scattering property showing almost no scattering property for light incident at an incident angle in an angle range smaller than the predetermined angle. May be used. However,
The light diffusion film 33 is not always necessary, and the optical sheet 34 may be omitted.

Further, the refracting surfaces 31b of the plurality of incident portions 31 of the optical member 30 constituting the light emitting means 20 are:
Although it may be a linear surface having a constant inclination angle as shown in FIGS. 1 and 4, if the refraction surface 31b is a curved condensing refraction surface, the refraction surface 31b is taken in from the entrance surface 31a of the entrance section 31. The light refracted toward the front surface by the refraction surface 31b is converted to the refraction surface 31 which is a curved converging refraction surface.
Since the light is condensed in a predetermined direction by the light condensing action of b, illumination light and reflected light having a luminance distribution with stronger directivity can be emitted.

In the above embodiment, the luminance distribution in the light guide width direction of the illumination light incident from the incident end face 21a of the light guide 21 on the back surface of the light guide 21 constituting the light irradiation means 20 is averaged. Although the light diffusion surface 25 for forming the light guide is formed, the back surface of the light guide 21 may be a flat surface,
Also, of the illumination light incident from the incident end face 21a of the light guide 21, most of the light traveling toward the back of the light guide 21 is
When total reflection is possible at the interface between the back surface of the light guide 21 and the outside air (air), the reflection plate 29 disposed behind the light guide 21 in the above embodiment may be omitted.

Further, in the above embodiment, the light guide 21
The reflection film 23 is provided on the plurality of step surfaces 22a of the step-shaped surface 22 to form the reflection surface 24 for external light. However, the reflection film is provided on the back surface of the light guide 21 to reflect the external light. May be formed, and external light incident from the front may be transmitted through the plurality of step surfaces 22 of the step-shaped surface 22 and reflected by the reflection surface on the back surface of the light guide plate.

The light guide 21 may have a plurality of end faces as entrance end faces for receiving illumination light from the light source 26. For example, two opposite end faces of the light guide 21 may be incident. In the case where the light guides 21 are end faces, the front surface of the light guide 21 is formed as a step-shaped surface that gradually decreases from both the incident end faces toward the intermediate portion of the light guide 21, and is opposed to the both incident end faces. The light source 26 may be provided.

The light source 26 is not limited to the one using the fluorescent lamp 27, and may be, for example, 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 20 used in the above embodiment is used.
Is a light source 26 and an emission surface (stepped surface 22) for guiding illumination light from the light source 26 and emitting the light toward the liquid crystal display element 1.
Light guide 21 formed with a plurality of step surfaces 22b) and a reflection surface 24 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. Wherein the light irradiating means 20 irradiates the liquid crystal display element 1 with illumination light,
Any configuration may be used as long as it includes external light that reflects external light incident from the front of the liquid crystal display element 1 and irradiates the liquid crystal display element 1 with the reflected light.

Further, the liquid crystal display element 1 used in the above embodiment comprises a liquid crystal cell 2 and a pair of polarizing plates 12 and 13, and the liquid crystal display element compensates for the band of transmitted light. Provided with a phase difference plate for this purpose.

That is, in a liquid crystal display element including a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twisted and a pair of polarizing plates, linearly polarized light transmitted through one of the polarizing plates and incident on the liquid crystal cell changes the liquid crystal layer. In the process of transmission, the light of each wavelength becomes elliptically polarized light having a different polarization state due to the birefringence of the liquid crystal, and the light of the polarization component along the transmission axis of the other polarizing plate among the light of each wavelength. Is transmitted through the other polarizing plate, so that the light transmitted through the other polarizing plate is colored in a color corresponding to the difference in the intensity of each wavelength light constituting the light.

The liquid crystal display device provided with the phase difference plate cancels the band color of the transmitted light by the birefringence effect of the phase difference plate.

FIG. 9 is an enlarged sectional view of a part of a liquid crystal display device provided with a phase difference plate.
A liquid crystal cell 2; a pair of polarizing plates 12 and 13 disposed so as to sandwich the liquid crystal cell 2; one of the liquid crystal cell 2 and the pair of polarizing plates 12 and 13;
3 and a phase difference plate 14 disposed between them.
Since the liquid crystal cell 2 is the same as that in the above-described embodiment, the description of the configuration will be omitted by attaching the same reference numerals to the drawings.

FIG. 10 shows both substrates 3 and 4 of the liquid crystal cell 2.
, The directions of the absorption axes 12a, 13a of the pair of polarizing plates 12, 13 and the direction of the slow axis 14a of the retardation plate 14 (the orientation of the retardation plate 14). (A direction with a large refractive index in a plane).

As shown in FIG. 10, the liquid crystal molecule alignment direction 3a near the front substrate 3 of the liquid crystal cell 2 is counterclockwise as viewed from the front with respect to the horizontal axis x of the screen of the liquid crystal display device 1. The liquid crystal molecule orientation direction 4a in the direction shifted by approximately 135 ° and in the vicinity of the rear substrate 4 is shifted approximately 45 ° counterclockwise as viewed from the front side with respect to the horizontal axis x. The initial alignment state of the liquid crystal molecules of the second liquid crystal layer 11 (the alignment state when an OFF voltage is applied between the electrodes 6 and 7) is indicated by the twist direction from the rear substrate 4 as indicated by a broken arrow in the figure. Toward the front substrate 3,
This is a state where the liquid crystal is twist-oriented at a twist angle φ of approximately 90 ° counterclockwise as viewed from the front side.

The polarizing plate 12 on the front side shifts its absorption axis 12a counterclockwise by approximately 135 ° with respect to the horizontal axis x when viewed from the front side (in the vicinity of the front side substrate 12 of the liquid crystal cell 2). In a direction substantially parallel to the liquid crystal molecule alignment direction 12a), the rear polarizing plate 13 shifts its absorption axis 13a counterclockwise by approximately 45 ° with respect to the horizontal axis x when viewed from the front side. (The rear substrate 13 of the liquid crystal cell 2)
(In the direction substantially parallel to the liquid crystal molecule alignment direction 13a in the vicinity of the liquid crystal molecules), the absorption axis 12a of the front-side polarizing plate 12 and the absorption axis 1
3a are substantially orthogonal to each other.

The twist angle φ of the liquid crystal molecules in the liquid crystal cell 2 may be in the range of 90 ° ± 10 °, and the crossing angle between the absorption axes 12a, 13a of the pair of polarizing plates 12, 13 is also 90 °. The angle may be in the range of ± 10 °.

That is, the liquid crystal display element 1 'is of a normally white mode, and its viewing angle direction F is
As indicated by the arrow in FIG. 10, the direction is slightly inclined toward the lower edge of the screen along the vertical axis y of the screen with respect to the normal h of the screen.

The retardation plate 14 has its slow axis 1
4a is arranged substantially parallel to the horizontal axis x. Therefore, the slow axis 14a of the phase difference plate 14 is aligned with the liquid crystal molecule alignment direction 13a near the rear substrate 13 of the liquid crystal cell 2 and the rear side. Each of the absorption axes 13a of the polarizing plate 13 is obliquely shifted by approximately 45 °.

Since the liquid crystal display element 1 'includes the retardation plate 14, the retardation (Δ
nd) and the retardation (Re) of the retardation plate 14
And the retardation (Δnd + Re) can be expressed as a quadratic function of the twist angle φ of the liquid crystal molecule by the following equation.

Δnd + Re = 0.02593 × φ ² + k (φ: twist angle of liquid crystal molecules, k: constant determined by liquid crystal material) In this example, the constant k is 190 to 390.
By using a liquid crystal material which becomes
And the total retardation of the retardation plate 14 is 400
It is set in the range of -600 nm.

When the liquid crystal display element 1 'having the retardation plate 14 is used, the retardation (liquid crystal cell 2
And the total retardation of the retardation plate 14) is 400
In the range of from about 600 nm to about 600 nm, the display image and the shadow thereof are not double-viewed depending on the viewing direction of the display in the display by the reflected light of the external light, and the viewing angle can be sufficiently widened.

For example, when the retardation (Δnd) of the liquid crystal cell 2 is Δnd = 330 nm and the retardation (Re) of the retardation plate 14 is Re = 50 nm,
That is, the total retardation Δnd + Re is 3
The shadow contrast at 35 nm is 5.2.

The liquid crystal display elements 1 and 1 'shown in FIGS. 2 and 9 are of an active matrix type, but these liquid crystal display elements 1 and 1' may be of a simple matrix type. , Color filters 8R, 8
A black-and-white display element without G and 8B may be used.

Further, the liquid crystal display element 1, 1 'is of a normally white mode in which a pair of polarizing plates 12, 13 are arranged with their absorption axes 12a, 13a substantially orthogonal to each other. , 1 'may be a normally black mode in which a pair of polarizing plates 12, 13 are arranged with their absorption axes 12a, 13a substantially parallel to each other, and the twist angle φ of the liquid crystal molecules of the liquid crystal cell 2 is For example, as in an STN (super twisted nematic) type liquid crystal display device, the angle may be 180 to 270 °.

[0233]

According to the liquid crystal display device of the present invention, illumination light is emitted toward the liquid crystal display element behind the liquid crystal display element and external light incident from the front of the liquid crystal display element is applied to the liquid crystal display element. A light irradiating means for reflecting toward the light source is arranged, and an illumination luminance controlling means for controlling the luminance of the illuminating light according to the illuminance of the external environment is provided. The reflectance of external light of the light irradiating means so as to be a determined luminance range,
Since the brightness control condition of the illuminating light by the lighting brightness control means is set, power consumption can be reduced, and in an environment of a wide illuminance range from low illuminance to high illuminance,
A suitable screen luminance can be obtained for the ambient illuminance, and the retardation of the liquid crystal display element is 40
In the range of 0 to 600 nm, in a display using reflected external light, a dark region in which the transmittance of the liquid crystal display element is controlled to be low and a bright region in which the transmittance is controlled to be high, depending on the viewing direction of the display. , The contrast between the shadow of the dark area and the bright area, which appears at the boundary between the image and the bright area, is reduced, so that the display image and the shadow are not displayed twice, and the viewing angle can be sufficiently widened.

In the liquid crystal display device of the present invention, the liquid crystal display element is provided with a liquid crystal cell in which a liquid crystal layer in which liquid crystal molecules are twist-aligned is provided between a pair of substrates having electrodes on the inner surface, and the liquid crystal cell is interposed therebetween. When the liquid crystal cell is constituted by a pair of polarizing plates, the retardation of the liquid crystal cell is set to 400.
What is necessary is just to set to the range of -600 nm.

Further, the liquid crystal display element comprises the liquid crystal cell, the pair of polarizing plates, and a retardation plate disposed between the liquid crystal cell and one of the pair of polarizing plates. In this case, the total retardation of the liquid crystal cell and the retardation plate may be 400 to 60.
What is necessary is just to set it in the range of 0 nm.

Also, in the liquid crystal display device of the present invention,
The light irradiation means has a screen luminance with respect to the environmental illuminance of 50.
20-200 knit screen brightness with lux ambient illuminance, 1
In accordance with the environmental illuminance, the luminance is expressed by a quadratic function that satisfies the range of the screen luminance of 30 to 300 nits at the environmental illuminance of 000 lux and the screen luminance of 400 to 4000 nits at the environmental illuminance of 30,000 lux. It is desirable to control the luminance of the illumination light, and by controlling the luminance of the illumination light under such conditions, in an environment with a wide illuminance range from low illuminance to high illuminance, a screen luminance suitable for the environmental illuminance Can be obtained.

Further, the light irradiation 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. More preferably, by controlling the brightness of the illumination light under such conditions, in an environment of a wide illuminance range from low illuminance to high illuminance,
It is possible to obtain a more suitable screen luminance for the environmental illuminance.

It is preferable that 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. In an environment with a high illuminance, it is possible to obtain a screen luminance more suitable for the environment illuminance.

[0239] The illumination luminance control means may control the light irradiating means so that the luminance of the illumination light decreases continuously 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 luminance control means, when the environmental illuminance is equal to or less than a predetermined illuminance higher than the indoor illuminance in an illuminance range where the ambient illuminance is higher than the indoor illuminance, the illuminating light 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 is increased, 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.

[0242] Further, in the illumination luminance 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 luminance 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 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 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.

[0244] The illumination brightness control means may include an illuminance detector for measuring environmental illuminance, and means for controlling the brightness of 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 according to the actual environmental illuminance, and obtain a screen luminance suitable for the environmental illuminance.

Further, the light irradiating means irradiates the liquid crystal display element with illumination light, and irradiates the liquid crystal display element with reflected light by reflecting external light incident from the front of the liquid crystal display element. Any configuration may be used as long as it comprises a reflection unit, but a preferred light irradiation unit is a light source, and an emission surface that guides illumination light from the light source and emits the light toward the liquid crystal display element. A light guide having a reflection surface different from the emission surface for reflecting external light incident from the front of the liquid crystal display element toward the liquid crystal 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 the external light on the reflection surface can be set so that the reflectance of the liquid crystal display device becomes a desired value.

The light irradiating means in which the emission surface of the illumination light and the reflection surface of the external light are different from each other is such that 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 one of the plurality of step surfaces and the back surface of the light guide to form a reflection surface of the external light, and the plurality of step surfaces are incident from the incident end surface. An illumination light emitting surface, and on the front side of the light guide, transmitting external light incident from the front of the liquid crystal display element and reflected light of the external light reflected by the reflecting surface, Illumination light emitted from the plurality of step surfaces of the light guide is referred to as the liquid crystal table. Having a structure in which an optical member for emitting towards the elements are arranged is desirable.

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

According to the light irradiation means, external light incident from the front of the liquid crystal display element passes through the optical member and is formed on a plurality of steps of the light guide or on the back of the light guide. The reflected light is reflected by the reflection surface, and the reflected light is transmitted through the optical member again and emitted toward the liquid crystal display element, so that most of the external light incident from the front of the liquid crystal display element is reflected without waste, The light can be incident on almost the entire liquid crystal display element.

In this light irradiation means, the optical member comprises a transparent plate having a front surface for emitting light toward the liquid crystal display element and a back surface facing the front surface of the light guide. A projection-shaped incident portion having an incident surface for taking in light emitted from the plurality of step surfaces of the light guide, and a refraction surface for refracting the light taken in from the incident surface toward the front surface is formed. Are preferred.

With the optical member having such a structure, most of the light emitted from the plurality of stepped surfaces of the light guide is taken into the optical member without waste, and directed toward the liquid crystal display element from the front surface. And can be emitted.

Further, by configuring the optical member as described above, light emitted from a plurality of step surfaces of the light guide and incident on a plurality of incident portions of the optical member from the incident surface can be transmitted to the optical member. The light is refracted by the refraction surface and is condensed in a predetermined direction. From the front surface of the optical member, illumination light having a high luminance distribution in a predetermined direction (for example, the front direction) can be emitted, and the light guide 21 can be emitted. The external light reflected on the reflection surfaces on the plurality of step surfaces can also be emitted from the front surface of the optical member as light having a luminance distribution with a high luminance in a predetermined direction (for example, the front direction).

Further, in the optical member, the plurality of incident portions are provided at an interval, and a rear region between the adjacent incident portions is provided with external light and light guide incident from the front of the liquid crystal display element. It is more desirable to adopt a configuration in which the input / output surface transmits the reflected light of the external light reflected by the reflection surface of the body.

According to the optical member having such a configuration, external light that enters from the front of the liquid crystal display element and enters the optical member from the front surface is transmitted from the incident portion and the incident / exit surface therebetween to the optical member. And the reflected light of the external light reflected by the reflecting surfaces on the plurality of step surfaces of the light guide is taken into the optical member from the incident part and the entrance / exit surface, and the optical member The light can be emitted from the front toward the liquid crystal display element, and the reflected light is
Light having a higher luminance distribution in a predetermined direction (for example, the front direction) can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an enlarged side view of a part of a liquid crystal display element used in the liquid crystal display device.

FIG. 3 is a diagram showing the orientation directions of liquid crystal molecules near both substrates of a liquid crystal cell constituting the liquid crystal display element and the directions of absorption axes of a pair of polarizing plates.

FIG. 4 is an enlarged side view of a part of a light guide and an optical member constituting light irradiation means of the liquid crystal display device.

FIG. 5 is an enlarged perspective view of a part of the light guide.

FIG. 6 is a perspective view of an optical sheet disposed between the light irradiation unit and a liquid crystal display element.

FIG. 7 is a diagram showing a relationship between environmental illuminance and screen luminance L suitable for the environmental illuminance.

FIG. 8 is a diagram showing a relationship between the environmental illuminance and a screen luminance using only illumination light, which provide a screen illuminance suitable for the environmental illuminance.

FIG. 9 is an enlarged side view of a part of another liquid crystal display element used in the liquid crystal display device.

FIG. 10 is a view showing the orientation directions of liquid crystal molecules in the vicinity of both substrates of the liquid crystal cell constituting the liquid crystal display element, the directions of the absorption axes of a pair of polarizing plates, and the directions of the slow axes of the phase difference plates.

[Explanation of symbols]

 1, 1 'liquid crystal display element 2 liquid crystal cell 12, 13 polarizing plate 14 retardation plate 20 light irradiating means 21 light guide 21a incident end face 22 stepped face 22a stepped face 22b stepped face (Emission surface) 23 ... Reflection film 24 ... Reflection surface 25 ... Light diffusion surface 26 ... Light source 29 ... Reflection plate 30 ... Optical member 31 ... Incident part 31a ... Incident surface 31b ... Refractive surface 32 ... Ingress / emission surface

Claims (14)

[Claims] A liquid crystal display element disposed outside the liquid crystal display element for emitting illumination light toward the liquid crystal display element and for transmitting external light incident from the front of the liquid crystal display element to the liquid crystal display element. Light illuminating means for reflecting toward the illuminator, and illumination brightness control means for controlling the brightness of the illumination light according to the illuminance of the external environment; reflectance of the external light of the light illuminating means; and the illumination brightness control means. And the luminance control condition of the illumination light are set so that the luminance of the screen of the liquid crystal display element falls within a predetermined luminance range according to the illuminance of the external environment, and the liquid crystal display element A liquid crystal display device having a retardation in the range of -600 nm. 2. A liquid crystal display device comprising: a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twist-aligned between a pair of substrates having electrodes on an inner surface thereof; and a pair of polarizing plates disposed so as to sandwich the liquid crystal cell. The liquid crystal display device according to claim 1, comprising: 3. A liquid crystal display device comprising: a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twist-aligned between a pair of substrates having electrodes on an inner surface thereof; and a pair of polarizing plates disposed so as to sandwich the liquid crystal cell. A retardation plate disposed between the liquid crystal cell and one of the pair of polarizing plates,
3. The liquid crystal display device according to claim 1, wherein the retardation of the liquid crystal cell and the total of the retardation plate is in a range of 400 to 600 nm. 4. The light irradiating 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 liquid crystal display device according to claim 1. 5. 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 liquid crystal display device according to claim 1. 6. The liquid crystal display according to claim 1, wherein the illumination brightness control means controls the brightness of the illumination light from the light irradiation means at least at an environmental illuminance higher than the indoor illuminance. apparatus. 7. The illumination brightness control means is configured to reduce the brightness of the illumination light continuously as the environmental illuminance decreases in an illuminance range where the environmental illuminance is lower than the indoor illuminance. 3. The liquid crystal display device according to claim 1, wherein the light irradiation unit is controlled. 8. The illumination luminance control means increases the ambient illuminance when the ambient illuminance is equal to or less than a predetermined illuminance higher than the indoor illuminance in an illuminance range in which the ambient illuminance is higher than the indoor 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. 3. The method according to claim 1, wherein the light irradiation unit is controlled so that
3. The liquid crystal display device according to 1. 9. The illumination brightness control means comprises: 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. The liquid crystal display device according to claim 1, wherein: 10. The light irradiating means irradiates illumination light to the liquid crystal display element, and reflects external light incident from the front of the liquid crystal display element to irradiate the reflected light to the liquid crystal display element. 3. The liquid crystal display device according to claim 1, comprising a reflection unit. 11. The liquid crystal display device according to claim 1, wherein the light irradiating means includes: a light source; an emission surface for guiding illumination light from the light source and emitting the light toward the liquid crystal display element; The liquid crystal display device according to claim 1, further comprising: a light guide having a reflection surface different from the emission surface for reflecting light toward an element. 12. At least one end surface of the light guide is an incident end surface for receiving illumination light from the light source, and the front surface of the light guide is stepwise from the incident end surface side to the other end side. A plurality of step surfaces to be lowered, and a step-shaped surface composed of a plurality of step surfaces connecting these step surfaces, and a reflection film is provided on any of the plurality of step surfaces and the back surface of the light guide. The liquid crystal display element is provided on the front surface side of the light guide, while the reflection surface of the external light is provided, and the plurality of step surfaces are an emission surface of the illumination light incident from the incident end surface. Optics that transmits external light incident from the front of the light guide and the external light reflected by the reflective surface, and emits illumination light emitted from the plurality of step surfaces of the light guide toward the liquid crystal display element. The member according to claim 11, wherein the member is disposed. The liquid crystal display device as described in the above. 13. The optical member comprises a transparent plate having a front surface for emitting light toward the liquid crystal display element and a back surface facing the front surface of the light guide. A projection-like incident portion having an incident surface for taking in light emitted from the plurality of step surfaces of the light body and a refraction surface for refracting the light taken in from the incident surface toward the front surface is formed. The liquid crystal display device according to claim 12, wherein 14. The light-entering portion of the optical member is provided with an interval, and a rear area between the adjacent light-entering portions has an external light and a light guide incident from the front of the liquid crystal display element. 14. The liquid crystal display device according to claim 13, wherein the liquid crystal display device is an input / output surface through which the reflected light of the external light reflected by the reflection surface of the body is transmitted.