JPH1115079A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a projection optical system constituting a display device by which a background existing behind a screen can be viewed through the screen. SOLUTION: A liquid crystal display element 103 is illuminated by a plate-like organic electric field light emitting element 104 arranged at the back of the element 103. A picture displayed on the element 103 is projected to a dichroic screen 101 by a projection lens 105. The screen 101 is provided with a dichroic filter layer 108 on a transparent base plate 107. The layer 108 reflects only the light of a wavelength band corresponding to the wavelength of the light radiated from the element 104 and transmits the light of other wavelength bands.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for projecting an image displayed on a display element onto a screen having dichroism in reflectance and displaying the same, and more particularly to a structure of a light source.

[0002]

2. Description of the Related Art Heretofore, in a projection type liquid crystal display device in which an image displayed on a liquid crystal display element is enlarged and projected, a reflective screen is used as a screen.

Further, as a display device using a screen having a light transmitting property, there has been a so-called head-up display for displaying an enlarged virtual image of a display element using a dichroic mirror or a holographic mirror.

In a head-up display, a cathode ray tube (CR) is used as an image generating device to obtain a bright display image.
T) was used. In addition, a head-up display using a liquid crystal display element as an image generation device has been configured to illuminate the liquid crystal display element using a discharge lamp as a light source.

A dichroic mirror or a holographic mirror is configured to reflect only light in a wavelength band corresponding to the wavelength of light emitted from an image generating device, and transmit light outside the wavelength band. Thus, the background behind the mirror can be seen through these mirrors.

[0006]

However, the above-mentioned conventional projection type liquid crystal display device has a problem that the background behind the screen cannot be seen through the screen because the screen is of a reflection type. .

Further, the above-mentioned conventional head-up display has a problem that the display device cannot be miniaturized because a CRT or a discharge lamp is used as an image generating device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a display device which can be viewed in the background of a screen while being small.

[0009]

According to a first aspect of the present invention, there is provided a display device, comprising: a liquid crystal display element; an organic electroluminescent element for illuminating the liquid crystal display element; and a projection lens for projecting light modulated by the liquid crystal display element. And a display device including a screen disposed between the projection lens and the observer, wherein the screen reflects light in a wavelength band corresponding to the emission wavelength of the organic electroluminescent element, and the other wavelengths It is characterized by having a structure for transmitting light in a band.

[0010] According to the above configuration, in a display device capable of seeing the background behind the screen through the screen, there is an effect that the projection optical system constituting the display device can be reduced in size.

According to a second aspect of the present invention, there is provided a display device including first, second, and third liquid crystal display elements corresponding to three primary colors, and first, second, and third organic light sources respectively illuminating the liquid crystal display elements. An electroluminescent element, a color synthesizing optical system that synthesizes light modulated by each of the liquid crystal display elements, a projection lens that projects an image synthesized by the color synthesizing optical system, and a projection lens and an observer. A display device including a screen disposed therebetween, wherein the screen reflects light in a wavelength band corresponding to an emission wavelength of the first organic electroluminescent element,
A first structure that transmits light in other wavelength bands, a second structure that reflects light in a wavelength band corresponding to the emission wavelength of the second organic electroluminescent element and transmits light in other wavelength bands, And a third structure for reflecting light in a wavelength band corresponding to the emission wavelength of the third organic electroluminescent element and transmitting light in other wavelength bands.

According to the above arrangement, in a display device capable of projecting a full-color image on the screen and allowing the background of the screen to be viewed through the screen, the size of the projection optical system constituting the display device can be reduced. Having.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1, 2 and 3
A first embodiment of the display device of the present invention will be described with reference to FIG. FIG. 1 is a sectional view showing a main optical system in a first embodiment of the display device of the present invention. FIG. 2 is a reflectance spectrum of a dichroic filter layer constituting a dichroic screen used in the first embodiment of the display device of the present invention. FIG. 3 is a first view of the display device of the present invention.
FIG. 3 is a cross-sectional view illustrating a structure of an organic electroluminescent device used in the embodiment.

A transmissive liquid crystal display element 103, an organic electroluminescent element 104 disposed on the back of the liquid crystal display element 103,
The projection lens 105 is incorporated in the housing 106 to configure the projection optical system 100. A display device is composed of the projection optical system 100 and the dichroic screen 101.

FIG. 1 does not show an electronic circuit such as a circuit for displaying an image on the liquid crystal display element 103 or a circuit for turning on the organic electroluminescent element 104 for easy viewing. Although the projection lens 105 is depicted as a single lens, it is actually composed of a plurality of lenses. Further, a cooling mechanism for cooling the organic electroluminescent element 104 is not shown.

The dichroic screen 101 has a configuration in which a dichroic filter layer 108 made of a dielectric multilayer film is formed on one surface of a transparent substrate 107 made of glass. As the dichroic filter layer exhibiting dichroism in reflectance, a laminated structure including thin films such as a dielectric thin film, a semiconductor thin film, and a metal thin film can be used. Further, a transparent resin film can be used as the transparent substrate 107.

The dichroic filter layer 108 reflects light of a wavelength in the green region, and its reflectance spectrum is shown in FIG. Of the light almost perpendicularly incident on the dichroic filter layer 108, 5
Light having a wavelength of 10 to 570 nm is reflected at a reflectance of 50% or more. Light of other wavelengths passes through the dichroic filter layer 108 and passes through the dichroic screen 101.

FIG. 3 shows a cross-sectional structure of the organic electroluminescent device 104.
Shown in In FIG. 3, the thickness of the thin film is exaggerated for easy understanding.

An anode 30 is provided on one surface of a glass substrate 300.
1, an ITO (indium tin oxide) thin film, and a hole transport layer 302, a TPD (triphenyldiamine derivative)
It has a structure in which a thin film, an Alq ₃ (tris (8-quinolinonato) aluminum) thin film serving as the light emitting layer 303, and a MgAg thin film serving as the cathode 304 are sequentially stacked.

From the organic electroluminescent device having such a structure, emitted light 305 having an emission spectrum having a peak wavelength of 530 nm and a full width at half maximum of about 100 nm is emitted.

The wavelength band of light emitted from the organic electroluminescent element 104 is wider than the reflection wavelength band of the dichroic filter layer 108 shown in FIG. Light having a wavelength that is reflected and not included in the reflection wavelength band is transmitted through the dichroic filter layer 108.

The thickness of the glass substrate 300 is about 1 mm. Assuming that the size of each of the thin film layers formed on the glass substrate is 29 mm × 22 mm, this region becomes a light emitting region, and light is emitted from the entire surface of this region.

Assuming that the size of the display area of the liquid crystal display element 103 is 27 mm × 22 mm, this display area is smaller than the light emitting area of the organic electroluminescent element 104 and can be illuminated by the organic electroluminescent element 104.

According to the structure of the display device described above, the liquid crystal display element 103 is illuminated from the back by the organic electroluminescent element 104 emitting green light, and the image displayed on the liquid crystal display element 103 is projected by the projection lens 105. The image is projected on the dichroic screen 101.

The dichroic screen is arranged so that the normal line of the dichroic screen 101 substantially coincides with the optical axis of the projection lens 105. When the observer 102 views the dichroic screen 101 from a position close to the optical axis of the projection lens 105, The person 102 can see a green image on the dichroic screen.

On the other hand, since light having a wavelength other than 510 to 570 nm is transmitted through the dichroic screen 101, the observer 102 removes the color corresponding to the wavelength of 510 to 570 nm from the background 109 behind the dichroic screen 101. You can see the background.

The organic electroluminescent device 104 has a flat plate structure in which a thin film is laminated on a glass substrate, and is a small light source that can emit light with a luminance of tens of thousands of cd / m ² by a DC voltage of about 10V. Therefore, the size of the projection optical system constituting the display device can be reduced.

The organic electroluminescent device 104 emits light in a region where a thin film structure as shown in FIG. 3 is formed, so that the liquid crystal display device 103 can be used without using other optical devices.
Can be uniformly illuminated.

(Second Embodiment) A display device according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a sectional view showing a main optical system in a second embodiment of the display device of the present invention. FIG. 5 is a reflectance spectrum of a dichroic filter layer constituting a dichroic screen used in the second embodiment of the display device of the present invention.

In the present embodiment, three liquid crystal display elements for displaying images of three primary colors, that is, red, green, and blue, and an organic electric field that emits red, green, and blue light that illuminates the respective liquid crystal display elements from behind. A light emitting element is provided, and images displayed on the three liquid crystal display elements are combined and projected on a dichroic screen.

A dichroic prism 405, a three dichroic prism disposed opposite to three surfaces of the dichroic prism
Sheets of transmissive liquid crystal display elements 403R, 403G, 403
B, the organic electroluminescent elements 404R, 404G, 404B and the projection lens 406 disposed on the back of each liquid crystal display element are incorporated in the housing 407, and the projection optical system 4
00. A display device is configured by the projection optical system 400 and the dichroic screen 401.

In FIG. 4, the electronic circuit is omitted, as in FIG. 1, for the sake of clarity. Although the projection lens is depicted as a single lens, it is actually composed of a plurality of lenses. Also, a cooling mechanism for cooling the organic electroluminescent element is omitted.

The dichroic screen 401 has a configuration in which a dichroic filter 408 made of a dielectric multilayer film is formed on one surface of a transparent substrate 409 made of glass. The dichroic filter 408 has three dichroic filter layers 408R, 408G, and 408.
B are laminated. Each of the dichroic filter layers 408R, 408G, and 408B is composed of a dielectric multilayer film, and has a different laminated structure.

The dichroic filter layer 408R is formed by laminating a dielectric multilayer film so as to selectively reflect a wavelength in the red region, and its reflectance spectrum is shown by a curve referred to by R in FIG. Of the light that has entered the dichroic filter layer 408R almost perpendicularly, light having a wavelength of 590 to 650 nm around 620 nm is reflected at a reflectance of 50% or more.

The dichroic filter layer 408G is formed by laminating a dielectric multilayer film so as to selectively reflect a wavelength in the green region, and its reflectance spectrum is shown by a curve referred to by G in FIG. Of the light that has entered the dichroic filter layer 408G almost perpendicularly, light having a wavelength of 510 to 570 nm centered at 540 nm is reflected at a reflectance of 50% or more.

The dichroic filter layer 408B is formed by laminating a dielectric multilayer film so as to selectively reflect a wavelength in the blue region, and its reflectance spectrum is shown by a curve referred to by B in FIG. Of the light almost perpendicularly incident on the dichroic filter layer 408B, light having a wavelength of 450 to 510 nm centered at 480 nm is reflected at a reflectance of 50% or more.

The above three dichroic filter layers 40
Light outside the wavelength band reflected by 8R, 408G, and 408B passes through dichroic filter 408 and passes through dichroic screen 401.

Three organic electroluminescent elements 404R, 404
G and 404B are made of organic materials whose light emitting layers emit light in the red, green, and blue wavelength regions, respectively.

Organic electroluminescent device 404G emitting green light
Can be the structure described in the first embodiment.

A thin film containing an Eu (europium) complex can be used as a light emitting layer constituting the organic electroluminescent element 404R that emits light at a wavelength in the red region. The structure of such an organic electroluminescent device is described in Japanese Journal of Applie
d Physics Vol. 34 (1995) Pt. 1, No. 4A pp. 1883-1887. With such a structure, the peak wavelength of the emitted light can be about 614 nm.

As the organic light emitting layer that emits light at a wavelength in the red region, a material obtained by adding a dye emitting red light to Alq ₃ can be used in addition to the Eu complex. Since the Eu complex has a narrow emission spectrum, its emission wavelength is a dichroic filter layer 408 that selectively reflects light of a wavelength in the red region.
Almost included in the reflection wavelength band of R.

A distyrylbiphenyl derivative thin film can be used as a light emitting layer constituting the organic electroluminescent element 404B that emits light in a wavelength in the blue region. The structure of such an organic electroluminescent device is described in Applied Physics Vol. 62, No. 10, No. 1
015 to 1018 (1993).
With such a structure, the peak wavelength of the emitted light can be set to about 480 nm.

Three organic electroluminescent elements 404R, 404
G and 404B emit red, green and blue light, respectively, from the liquid crystal display elements 403R, 403G and 403, respectively.
The light is modulated by B and combined by the dichroic prism 405.

The image synthesized by the dichroic prism is projected on a dichroic screen 401 by a projection lens 406.

The dichroic screen 401 is arranged so that the normal line of the dichroic screen substantially coincides with the optical axis of the projection lens 406. When the observer 102 views the dichroic screen 401 from a position close to the optical axis of the projection lens 406, The person 102 can see a full-color image on the dichroic screen.

On the other hand, light other than the wavelength reflected by the dichroic filter 408 is applied to the dichroic screen 40.
1 allows the observer 102 to see the background 410 behind the dichroic screen 401 from which the color corresponding to the wavelength reflected by the dichroic filter 408 has been removed.

As described in the first embodiment, since the organic electroluminescent elements 404R, 404G, and 404B have a flat plate shape and can uniformly illuminate the liquid crystal display element, the projection forming the display device is performed. It is possible to reduce the size of the optical system.

The embodiment of the display device of the present invention has been described above. Light is radiated from the entire region where the light emitting layer structure is formed in a flat plate shape, and high luminance light emission is performed at a low voltage of about 10 V. A book that uses a dichroic screen to illuminate a liquid crystal display element with an organic electroluminescent element that can selectively reflect light of the emission wavelength of the organic electroluminescent element and transmit light of other wavelengths. The technology of the invention includes a configuration in which the optical axis of the projection lens is arranged at an angle of 45 ° with respect to the normal of the dichroic screen, a configuration in which a hologram is used instead of the dielectric multilayer film,
Alternatively, the present invention can be applied to various display devices such as a configuration in which an enlarged virtual image of a liquid crystal display element is viewed through a dichroic screen by a combination of a dichroic screen and a projection lens.

[0050]

As described above, according to the display device of the present invention, a planar organic electroluminescent device is used as a light source for illuminating a liquid crystal display device, and light emitted from the organic electroluminescent device is used as a screen. Since a dichroic screen that selectively reflects only light in the wavelength band corresponding to the wavelength of light and transmits light in other wavelength bands is used, in a display device that can see the background behind the dichroic screen, the display device Has the effect that the projection optical system that constitutes can be downsized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main optical system in a first embodiment of a display device of the present invention.

FIG. 2 is a reflectance spectrum of a dichroic filter layer constituting a dichroic screen used in the first embodiment of the display device of the present invention.

FIG. 3 is a cross-sectional view illustrating a structure of an organic electroluminescent device used in the first embodiment of the display device of the present invention.

FIG. 4 is a sectional view showing a main optical system in a display device according to a second embodiment of the present invention.

FIG. 5 is a reflectance spectrum of a dichroic filter layer constituting a dichroic screen used in a second embodiment of the display device of the present invention.

[Explanation of symbols]

100, 400 Projection optical system 101, 401 Dichroic screen 102 Observer 103 Liquid crystal display element 104 Organic electroluminescent element 105, 406 Projection lens 106, 407 Housing 107, 409 Transparent substrate 108 Dichroic filter layer 109, 410 Background 300 Glass substrate 301 Anode 302 Hole transport layer 303 Light emitting layer 304 Cathode 403R, 403G, 403B Liquid crystal display element 404R, 404G, 404B Organic electroluminescent element 405 Dichroic prism 408 Dichroic filter 408R, 408G, 408B Dichroic filter layer

Claims (2)

[Claims] 1. A liquid crystal display element, an organic electroluminescent element for illuminating the liquid crystal display element, a projection lens for projecting light modulated by the liquid crystal display element, and an arrangement between the projection lens and an observer. A screen having a structure that reflects light in a wavelength band corresponding to the emission wavelength of the organic electroluminescent element and transmits light in other wavelength bands. A display device characterized by the above-mentioned. 2. First, second and third colors corresponding to three primary colors.
A liquid crystal display element, first, second, and third organic electroluminescent elements for illuminating each of the liquid crystal display elements, and a color combining optical system for combining light modulated by each of the liquid crystal display elements, In a display device comprising: a projection lens for projecting an image synthesized by the color synthesis optical system; and a screen disposed between the projection lens and an observer, the screen includes the first organic electroluminescence. A first structure that reflects light in a wavelength band corresponding to the emission wavelength of the element and transmits light in other wavelength bands, and reflects light in a wavelength band corresponding to the emission wavelength of the second organic electroluminescent element. A second structure that transmits light in other wavelength bands, and a third structure that reflects light in a wavelength band corresponding to the emission wavelength of the third organic electroluminescent element and transmits light in other wavelength bands. Having a structure The display device according to symptoms.