JP2003172959A - Image display method and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate an unevenness of luminance, and to manufacture a large screen for a picture display device with an upconversion system. <P>SOLUTION: Two or more exciting light rays are introduced from a direction which is almost orthogonal to a panel surface to a display panel containing a luminescent material which emits light by two-photon excitation, and the luminescent material emits light. As for exciting light, for example, two or more infrared-laser lights are radiated. The luminescent material which emits light by two-photon excitation is, for example, a rare earth ion. In order to introduce exciting light from the direction which is almost orthogonal to the panel surface, opposing to the display panel, a light transmission plate or a thin prism is installed. A light guide means which guides exciting light, such as a Fresnel lens, an optical waveguide, or an optical fiber is formed on an end surface of the light transmission plate or the thin prism. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display method and an image display device for displaying by utilizing a so-called up-conversion phenomenon.

[0002]

2. Description of the Related Art In recent years, in the field of image display devices (displays), there has been a demand for larger size (larger screen size) and thinner size, and commercialization of large size displays and thin flat displays has been promoted.

Various types of conventional large-sized displays and thin flat-screen displays are known, and they are roughly classified into the following four types. First of all, it is a type of display in which a phosphor is excited by ultraviolet rays or an electron beam to emit light. This type of display includes FED (Field Emission Displa)
y), CRT, plasma display (PDP), inorganic EL display and the like. Secondly, it is a type of display that changes the optical characteristics of pixels by an electric field to display. Examples of this type of display include a liquid crystal display (LCD), a plasma addressed liquid crystal display (PALC), and an electric floating display. Thirdly, it is a type of display that emits light by recombination of electrons and holes in the thin film. Examples of this type of display include organic EL displays and LED displays. Fourthly, there is a projector type display in which a halogen lamp, a laser beam and the like are combined with an element capable of changing optical characteristics for each pixel. LCD projectors and GLV (Grating Li
ght Valve), DMD (Digital Micromirror Device)
Etc. are typical examples. Each of these has a mechanism for displaying an image by causing an optical or luminescent color change of a pixel by an electrical stimulus.

However, in the image display device using these electrical stimuli, it is essential to form a wiring matrix for driving pixels and a switching element such as a thin film transistor (TFT) for operating the electrical stimulus inside the image display panel. is there. In addition, for example, in PDPs and FEDs, it is necessary to provide a minute space inside the display device, and the forming method and holding method thereof are complicated. Further, in an organic EL display which is a completely solid-state element, a special gas barrier film is indispensable for preventing the deterioration of the organic material due to oxygen, moisture in the air, etc., which hinders its practical use.

[0005]

In such a situation,
A type of display that changes the optical characteristics of each pixel or emits light when stimulated by light is also being studied. An example of such an optical display is the thin flat display disclosed in US Pat. No. 5,764,403.

This optical thin flat display has two
Of two laser beams, a mirror for reflecting the laser beams, and a transparent medium doped with rare earth ions and having a low phonon production rate. The two laser beams are introduced from the end face of the medium and intersect in the medium. Is. At the intersection of the two laser beams, the doped rare earth ion is excited by two-photon absorption and emits fluorescence due to a so-called up-conversion phenomenon. In an optical display based on such a principle, the emission intersection can be selected at any position in the medium by changing the direction of introduction of the laser beam into the medium by a mirror or the like, and the emission brightness can be changed to that of the laser beam. It can be adjusted by changing the intensity. Therefore, a display using up-conversion by two-photon absorption is one means that can realize an image display device without forming a complicated wiring matrix for driving pixels or a switching element such as a TFT in the display screen. .

However, in an up-conversion type image display device by two-photon absorption in which a laser beam is introduced from the end face of the medium, the emission brightness directly depends on the intensity of the laser beam introduced into the medium, so that it is extremely small. There is a big problem that practical brightness cannot be ensured unless it is an image display device. This is because when the optical path length of the laser light in the medium becomes longer as the screen becomes larger, the intensity of the laser light is significantly reduced due to absorption and scattering of the laser light by the medium.

The present invention has been proposed in view of such a conventional situation, and it is easy to make a large screen and an image display method and image of an up-conversion system capable of ensuring high brightness over the entire screen. An object is to provide a display device. Another object of the present invention is to provide an up-conversion image display method and an image display device that are compatible with high definition.

[0009]

In order to achieve the above-mentioned object, the image display method of the present invention provides a display panel containing a light-emitting material which emits light by two-photon excitation, and applies two or more excitation lights to the panel surface. It is characterized in that the light emitting material is introduced in a substantially orthogonal direction to cause the light emitting material to emit light. The image display device of the present invention includes a display panel including a light emitting material that emits light by two-photon excitation, and two or more excitation lights are introduced from a direction substantially orthogonal to the panel surface of the display panel. It is a feature.

By introducing excitation light into the medium (display panel) from a direction (perpendicular direction) orthogonal to the panel surface,
The optical path length in the medium is at most the thickness of the medium, and the reduction in the intensity of the excitation light due to absorption and scattering by the medium does not pose a problem. Therefore, sufficient excitation light intensity is secured at each emission intersection, and high-luminance display is realized. Further, the above advantages are realized regardless of the screen size, and even if the screen is enlarged, the brightness is not lowered due to the decrease in the intensity of the excitation light. further,
If multiple sets of laser light are used as excitation light and the display panel is virtually divided to perform display, it is possible to deal with higher definition and there is no need to provide complicated matrix wiring or switching elements. A display panel with a simple structure enables large-screen, high-definition display.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An image display method and an image display apparatus to which the present invention is applied will be described in detail below with reference to the drawings.

The configuration of an up-conversion image display device to which the present invention is applied is, for example, as shown in FIG. That is, this image display device has the transparent substrate 1
A light emitting layer 2 is provided on the top, and is used as a display panel. Light guide plates 3 and 4 are attached to the front and rear surfaces of the light emitting layer 2, respectively, and infrared rays from laser light sources 5 and 6 are passed through these light guide plates 3 and 4. It has a structure in which the laser light is applied to the light emitting layer 2 in a vertical direction.

The light emitting layer 2 constituting the display panel contains a light emitting material which emits light by two-photon excitation, and emits light in a region where two infrared laser beams from the laser light sources 5 and 6 are simultaneously irradiated. To do. As the light emitting material, any material can be used as long as it emits light by two-photon excitation, and a typical example thereof is a rare earth ion. As rare earth ions, Pr, Ho, Er, Tm
Preferred are ions of rare earth elements belonging to the lanthanoid series. For example, Pr doped in ZrF ₄ system glass
By exciting ³⁺ with two wavelengths of 1010 nm and 870 nm, 490 nm (blue), 520 nm (green), 61
It has been reported to emit light at each wavelength of 0 nm (orange) and 640 nm (red).

Therefore, the light emitting layer 2 is, for example, rare.
Earth ion thin film or transparent medium doped with rare earth ions
A film or the like can be used. In the latter case, it should be a transparent medium.
Selection of host glass that improves up conversion efficiency
It will be important to improve, but for example fluoride, especially heavy metal
A halide-based glass or the like having a fluoride composition is suitable. Inside
However, the ZBLAN (ZrF
_Four-BaF_Two-LaF _Three-AlF_Three-NaF) and other materials
Is preferred. Other fluoride glass compositions include I
nF_Three-PbF_Two-BaF_Two-LaF_Three, ThF_Four-I
nF_Three-ZnF _Two-BaF_Two-YF_Three, ZrF_Four-Ba
F_Two-LaF_Three, HfF_Four-BaF_Two-NaF-AlF
_Three-LaF_Three, HfF_Four-AlF_Three-YF_Three-MgF_Two
-CaF _Two-SrF_Two-BaF_Two-NaF, ZrF_Four−
AlF_Three-YF_Three-MgF_Two-CaF_Two-SrF_Two-B
aF_Two-NaF, ZrF_Four-AlF_Three-YF_Three-MgF
_Two-CaF_Two-BaF_Two-PbF_Two, AlF_Three-YF_Three
-MgF_Two-CaF_Two-BaF_Two-PbF_Two, AlF_Three
-YF_Three-MgF_Two-CaF_Two-SrF_Two-BaF _Two,
AlF_Three-CaF_Two-BaF_TwoEtc. can also be used.

As the method for forming the light emitting layer 2, for example, a glass substrate or a plastic substrate or each film substrate having a small infrared absorption is placed in a vacuum, and a film is formed by an RF sputtering method using, for example, Pr-doped ZBLAN as a target. I do. As a film forming method, in addition to the sputtering method, a CVD method, an evaporation method by resistance heating, an evaporation method using an electron beam, and a method of dissolving ultrafine particles of a rare earth element in an organic solvent and directly coating the same on a substrate, etc. Can also be adopted. In the above film formation, it is preferable to set the substrate temperature to 200 ° C. or higher and 800 ° C. or lower. By performing the above film formation in such a temperature range,
The efficiency of two-photon excitation can be increased. In the case of a plastic substrate, the substrate temperature is 120 ° C or higher and 250 ° C.
Set as follows.

On the other hand, the light guide plates 3 and 4 are for guiding the infrared laser light emitted from the laser light sources 5 and 6 to the light emitting layer 2 of the display panel, and each has a predetermined angle with respect to the display panel. It has reflecting surfaces 3a and 4a inclined at. Specifically, the reflection surface 3a of the light guide plate 3 is inclined in the vertical direction (y direction), and the reflection surface 4a of the light guide plate 4 is inclined in the horizontal direction (x direction). The infrared laser light emitted from the laser light sources 5 and 6 is reflected by the reflecting surfaces 3a and 4a as shown in FIG. 2 or 3, and is almost perpendicular to the light emitting layer 2 (of the light emitting layer 2). Irradiation is performed from a direction substantially orthogonal to the main surface). As the light guide plates 3 and 4, a thin prism or the like can be used in addition to the normal light guide plate. In addition, as these light guide plates and thin prisms,
For example, a light guide plate and a thin prism similar to those used for reflective liquid crystal or the like can be used.

When a normal light guide plate is used as the light guide plates 3 and 4, as shown in FIG. 4, it is necessary to make the infrared laser light incident perpendicularly to the end faces, which causes the reflection faces 3a and 4 to be incident.
The infrared laser light reflected by a is emitted perpendicularly to the light emitting layer 2. Therefore, when a normal light guide plate is used, the laser light sources 5 and 6 are moved in the arrow z direction in the drawing to select the irradiation position in the vertical direction (y direction) in the light emitting layer 2. When using a thin prism,
As shown in FIG. 5, the incident angle of the infrared laser light reflected by the reflecting surfaces 3a and 4a with respect to the prism layers 3b and 4b is arbitrary, and the infrared laser light with respect to the light emitting layer 2 is caused by the prism layers 3b and 4b. Are regulated so that they are vertically irradiated. Therefore, when the thin prism is used, the irradiation position of the light emitting layer 2 in the vertical direction (y direction) can be selected by changing the incident angle of the infrared laser light with respect to the end face.

In the image display device having the above-mentioned structure, the two infrared laser beams are irradiated so as to collide with each other in the light emitting layer 2 to selectively emit light at an arbitrary position of the light emitting layer 2. . For example, these two infrared laser beams are C
Scanning is performed in the same manner as the electron gun in RT, and one or both of them are turned on / off to control light emission at each point and display an image.

Here, it is ideal that the two infrared laser beams irradiate so as to collide with each other without any positional deviation, but for that purpose, a very highly accurate beam position control mechanism is required. . Therefore, for example, as shown in FIG. 6, if the beam shape of the two infrared laser beams is elliptical (or oval) and one beam A and the other beam B are irradiated so as to be orthogonal to each other, The positional deviation can be absorbed to some extent, and the beam position control mechanism can be simplified. If the elliptical beam A and the beam B are set to intersect with each other, the beams A and B are
Even if there is some misalignment, they will overlap.
Similarly, as shown in FIG. 7, it is possible to absorb the positional deviation to some extent by changing the size (diameter) of the two beams A and B. Also in this case, as shown by the broken line in the figure, even if the beams A and B are slightly displaced, they will overlap.

In the above image display device, the brightness of the image can be adjusted by adjusting the excitation amount of the two-photon excitation. The excitation amount is determined by the irradiation amount of the infrared laser light, and therefore the brightness can be adjusted by adjusting the intensity of the infrared laser light, for example. Alternatively, the brightness can be adjusted by irradiating the infrared laser light in pulses and adjusting the pulse width.

As described above, when the two infrared laser beams are simultaneously irradiated, the light emitting layer 2 emits light by two-photon excitation. Hereinafter, the light emission by the two-photon excitation will be described in detail. Light emission by two-photon excitation is called an up-conversion phenomenon, and light of a shorter wavelength than incident light is obtained by utilizing the electronic excitation level of rare earth ions. Ordinary fluorescence emits light having a wavelength longer than that of excitation light.

For example, a zirconium fluoride glass (ZBLAN) lightly doped with Pr ³⁺ is added to a wavelength of 807 nm.
When the infrared laser light (λ ₁₂ ) is irradiated with another infrared laser light (λ ₂₃ ) having a wavelength of 1014 nm in this state, electrons in the ground state are excited twice as shown in FIG. It emits visible light (λ ₃₁ ). This phenomenon is considered to be two-step upconversion or two-frequency upconversion.
ersion), and the image display device of the present invention is a flat light emitting screen utilizing this phenomenon.

In the two-step up-conversion of zirconium fluoride glass (ZBLAN) lightly doped with Pr ³⁺ , as shown in FIG. 9, since the light emission by the electrons excited twice occurs at various energy levels, the emission spectrum is As shown in FIG. 10, the emission color is white emission. Therefore, color display is also possible by disposing a color filter on the front surface of the light emitting layer 2 which is a flat light emitting screen, for example.

By the way, in the above-mentioned up-conversion phenomenon, two or more photons must be involved in the excitation process in order to generate one photon of short wavelength. The two-photon excitation has some excitation mechanisms as shown in FIG. For example, FIG. 11A shows a two-step excitation process (Energy Transfer Upconversi) by energy transfer between ions of the same kind or different kinds in two intermediate excited states.
on: ETU) and energy donating ion (donor)
Energy is transferred by the dipole interaction between and the acceptor ion (acceptor). FIG. 11B is a process in which ions in the intermediate excited state further absorb the excitation light and are excited to a higher energy state, and the excited state absorption (Excited Stat
e Absorption: ESA). Figure 11
(C) is a process called two photon absorption (TPA) in which two photons are simultaneously excited and excited. In the above example, the light-emitting layer 2 is caused to emit light by two-photon excitation using two infrared laser lights, but by selecting an excitation mechanism, two-photon excitation is performed with only one excitation light (infrared laser light). It is also possible to realize light emission by.

In the image display device, the light guide plate 3,
Although No. 4 is attached to the display panel, it can be integrally formed by a thin film forming technique as shown in FIG. In this example, thin prisms 13 and 14 are laminated on the back surface of the transparent substrate 11 on which the light emitting layer 12 is formed and on the surface in contact with the light emitting layer 12, respectively. The thin prisms 13 and 14 can be formed by, for example, an RF sputtering film forming method. FIG. 13 shows a method for forming a thin prism by the RF sputtering film forming method. The target 17 is placed on the cathode 16 connected to the RF power source 15, and the target 17 is mounted on the cathode 16.
It is arranged so as to face the transparent substrate 11 on which is formed, and RF sputtering is performed. As a result, a thin film type thin prism is formed.

Next, a modified example of the image display device to which the present invention is applied will be described. First, FIG. 14 shows an example in which a Fresnel lens and a polygon mirror are combined with the image display device shown in FIG. 1 to facilitate scanning with infrared laser light. In the image display device of this example, the configuration of the display panel is similar to that of the example shown in FIG. 3 and 4 are pasted together. In this example, Fresnel lenses 21 and 22 are adhered to the end faces of the light guide plates 3 and 4 on the infrared laser light introduction side by an optical adhesive, respectively. Further, polygon mirrors 23, 24 or micromirrors manufactured by the micromachine technology (MEMS technology) are installed at the focal positions of these Fresnel lenses 21, 22. In the image display device having such a configuration, the infrared laser light from the laser light sources 5 and 6 scans the light emitting layer 2 of the display panel by rotating the polygon mirrors 23 and 24. In addition,
Also in this case, the laser light sources 5 and 6 are provided by the light guide plates 3 and 4.
The infrared laser light emitted from is emitted from the direction perpendicular to the light emitting layer 2.

In the case of considering a large-sized display device, it is necessary to increase the focal length in the structure in which the Fresnel lens is attached as in the example shown in FIG. 14, and the entire image display device becomes large. In such a case, as shown in FIG. 15, it is preferable to introduce the infrared laser light into the light guide plates 3 and 4 by an optical waveguide or an optical fiber instead of the Fresnel lens. In the example shown in FIG. 15, the light guide plate 3,
4 is slightly extended, and optical waveguides 25 and 26 are formed in that portion. The infrared laser light emitted from the laser light sources 5, 6 is reflected by the polygon mirrors 23, 24 and introduced into the light guide plates 3, 4 via the optical waveguides 25, 26.

Further, when the transparent substrate 11 has flexibility or when it is not desired to increase the widthwise dimension of the image display device, as shown in FIG. 16, the optical waveguide 26 formed on the light guide plate 4 is used. It is also possible to introduce infrared laser light from one side edge side of the image display device by arranging the laser light sources 5 and 6 to be drawn out to the lower end in the figure and arranging the laser light sources 5 and 6 below the image display device. . By doing this,
At the same time as the reduction in size is realized, the formed thin film, optical waveguide, optical fiber, etc. are not damaged (for example, diameter 5
It is also possible to wind up to about (cm), and an image display device that is easy to store and convenient to carry is realized.

Further, in order to realize an image display device capable of displaying a bright image, for example, as shown in FIG.
It is effective to subdivide the display panel into virtual regions and guide the infrared laser light to each display region by the above method to cause the light emitting layer to emit light. In the example shown in FIG. 17, one laser light source is arranged on each of the left and right (two laser light sources 6A and 6B in total), and two laser light sources are arranged on each of the upper and lower sides (four laser light sources 5A, 5B, 5C, total).
5D) is arranged. Further, polygon mirrors 24A, 24B and polygon mirrors 23A, 23B, 23C, 23D are arranged corresponding to these laser light sources.

By adopting the above configuration,
The display panel is virtually divided into four and driven,
A bright image can be displayed. Specifically, when the surface emission luminance when this display panel is subdivided into virtual regions is roughly calculated, the following results are obtained. As a prerequisite, 1
It is assumed that 200 mW of light is emitted by irradiating two kinds of excitation infrared laser light of 000 mW. The infrared laser light has a diameter of 200 μm. As a result, the emission luminance per unit area is 1.72 × 10 ⁸ cd / cm ² . In this case, the light emission brightness of each pixel is determined by the number of divisions of the panel. For example, in the case of 14 divisions, the results shown in Table 1 are obtained.

[0031]

[Table 1] The size of each pixel in the image display device can be controlled by the beam diameter of the infrared laser light, which determines the screen size of the image display device. For example, diameter 250
The resolution is SXGA (128
0 trio pixel x 1080), the effective display area 4
The image display device is about 8 inches.

[0032]

As is apparent from the above description, according to the present invention, it is easy to increase the screen size, and a low power consumption image display method and image display capable of ensuring high brightness over the entire screen. A device can be provided. Further, the image display method and the image display device of the present invention employ the up-conversion method. Therefore, the display panel has 2
A film containing a light emitting material that emits light by photon excitation may be used, and it is not necessary to form a complicated wiring matrix for driving a pixel, and it is not necessary to form a switching element such as a TFT for each pixel. For this reason, it is possible to realize a large screen while suppressing the manufacturing cost, and the significance thereof is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic perspective view schematically showing an example of an image display device to which the present invention is applied.

FIG. 2 is a schematic side view of the image display device shown in FIG.

FIG. 3 is a schematic plan view of the image display device shown in FIG.

FIG. 4 is a schematic view showing an optical path in a light guide plate.

FIG. 5 is a schematic diagram showing an optical path in a thin prism.

FIG. 6 is a schematic diagram showing an example of a beam shape of infrared laser light.

FIG. 7 is a schematic diagram showing another example of the beam shape of infrared laser light.

FIG. 8 is a diagram illustrating an upconversion phenomenon.

FIG. 9 is a diagram showing an emission energy level in ZBLAN doped with Pr ³⁺ .

FIG. 10 is a characteristic diagram showing an emission spectrum of ZBLAN doped with Pr ³⁺ .

FIG. 11 is a diagram illustrating an excitation mechanism in two-photon excitation.

FIG. 12 is a schematic cross-sectional view showing an example of a display panel integrally formed with a thin prism by a thin film forming technique.

FIG. 13 is a schematic diagram illustrating an RF sputtering method.

FIG. 14 is a schematic perspective view schematically showing a modified example of the image display device to which the present invention is applied.

FIG. 15 is a schematic perspective view schematically showing another modified example of the image display device to which the present invention is applied.

FIG. 16 is a schematic perspective view schematically showing still another modified example of the image display device to which the present invention is applied.

FIG. 17 is a schematic perspective view schematically showing still another modified example of the image display device to which the present invention is applied.

[Explanation of symbols]

1, 11 transparent substrate, 2, 12 light emitting layer, 3, 4 light guide plate, 3a, 4a reflective surface, 5, 6 laser light source, 13,
14 Thin prism, 21, 22 Fresnel lens, 2
3,24 Polygon mirror 25,26 Optical waveguide

Claims (21)

[Claims] 1. An image display method comprising introducing excitation light into a display panel including a light emitting material that emits light by two-photon excitation in a direction substantially orthogonal to a panel surface to cause the light emitting material to emit light. 2. The image display method according to claim 1, wherein two or more laser lights are irradiated as the excitation light. 3. The image display method according to claim 1, wherein the light emitting material that emits light by two-photon excitation is a rare earth ion. 4. The image display method according to claim 2, wherein infrared laser light is used as the laser light. 5. The image display method according to claim 1, wherein the screen brightness is controlled by the amount of excitation in the two-photon excitation. 6. The image display method according to claim 5, wherein the excitation amount is controlled by the light intensity of the excitation light. 7. The image display method according to claim 5, wherein the excitation amount is controlled by the pulse width of the excitation light. 8. The image display method according to claim 2, wherein the display panel is divided and driven by a plurality of sets of laser beams. 9. An image display device comprising a display panel including a light emitting material which emits light by two-photon excitation, wherein excitation light is introduced from a direction substantially orthogonal to a panel surface of the display panel. 10. The image display device according to claim 9, wherein two or more laser lights are irradiated as the excitation light. 11. The image display device according to claim 9, wherein the light emitting material that emits light by two-photon excitation is a rare earth ion. 12. The image display device according to claim 11, wherein the display panel comprises a light-transmissive substrate on which a rare earth ion thin film is formed. 13. The display panel comprises a transparent medium doped with rare earth ions.
1. The image display device according to 1. 14. The image display device according to claim 10, wherein the laser light is infrared laser light. 15. A light guide plate or a thin prism is arranged so as to face the display panel.
The image display device described. 16. The image display device according to claim 15, further comprising a light guide means for guiding the excitation light to an end surface of the light guide plate or the thin prism. 17. The image display device according to claim 16, wherein the light guide means is at least one selected from a Fresnel lens, an optical waveguide, and an optical fiber. 18. The image display device according to claim 8, further comprising control means for controlling the amount of excitation in two-photon excitation and controlling the screen brightness. 19. The control means is a light intensity control means for controlling the light intensity of the excitation light.
8. The image display device according to item 8. 20. The image display device according to claim 18, wherein the control means is a pulse width control means for controlling the pulse width of the excitation light. 21. The image display device according to claim 10, further comprising a plurality of sets of laser light sources that drive the display panel in a divided manner.