JP2884755B2 - Projection display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device using a transmission scattering type display element.

[Prior Art] Conventionally, a projection type display device generally uses a CRT, but has a drawback that the device becomes larger. For this reason, a small projection display device has been desired.

On the other hand, liquid crystal display elements are flat panel display elements, and are used as various display devices by taking advantage of their features such as small size, light weight, and low power consumption.

In recent years, the use of this liquid crystal display element in a projection type display device has been put to practical use, as a large and heavy projection type display device can be reduced in size.

The first practical use was a device using a normal TN type liquid crystal display device, and an active matrix liquid crystal display device used as a liquid crystal TV was used. However, this TN type liquid crystal display element has a problem that since two polarizing plates are used, light loss is large and a bright projected image cannot be obtained.

For this reason, a flat display element having a high transmittance at the time of transmission has been desired, and it has been proposed to use a transmission / scattering display element which takes a transmission state and a scattering state depending on a voltage application state.

Because this transmission scattering type display element does not use a polarizing plate,
At the time of transmission, light is transmitted with little loss of light, so that a bright projected image can be obtained.

For this reason, various projection display devices using transmission-scattering display elements have been proposed. But they are traditional TN
Since the optical system of the projection type display device using the liquid crystal display device is employed as it is, the advantage of brightness using the transmission scattering display device cannot be fully utilized.

[Problems to be Solved by the Invention] FIGS. 6 (A), (B) and (C) are side views of a projection light source system proposed in the drawings.
The projection optical system and the like arranged on the light emission side of the transmission / scattering display element are not shown.

FIG. 6A shows a light source 71A and an elliptical mirror or a parabolic mirror 72A.
An example is shown in which a light source system for projection is used, and light is incident on the transmission-scattering display element 75A without using a condensing lens. In this example, there is a problem that a large elliptical mirror or a parabolic mirror is required. Further, a part of the light from the light source is directly incident on the transmission-scattering display element, and the light is shifted from the light incident by reflection,
The scattered light mixes with the original transmitted light, and TN
There is a large problem that the contrast ratio is reduced which is not caused when the liquid crystal display element is used.

FIG. 6 (3) shows a projection light source system using a light source 71B, a spherical mirror 72B, and a condensing lens 74B. Light is incident on a transmission / scattering display element 75B using the lens 74B. Here is an example. In this example, the spherical mirror may be small, but there is a problem that the light of the light source is not sufficiently used.

FIG. 6 (C) shows a projection light source system using a light source 71C, an elliptical mirror 72C, and a condensing lens 74C so that light is incident on a transmission / scattering display element 75C using the lens 74C. Here are some examples. In this example, the elliptical mirror is small and the light of the light source is often used. However, as in the example of (A), a part of the light from the light source is obliquely directly incident on the transmission-scattering display element, and the scattered light mixes with the originally transmitted light, thereby lowering the contrast ratio. There is a big problem that causes.

Further, the light source has a finite length even though it is a point light source. Elliptical mirrors such as (A) and (C) have the same luminous flux if they are ideal point light sources. However, since they have a finite length, the divergence of light increases, and the luminous flux is uniform. It becomes difficult.

However, in a projection type display device using a TN type liquid crystal display element, if a strong light is applied to brighten a projected image,
Since the polarizing plate of the liquid crystal display element absorbs light and generates heat, there is a problem that the polarizing plate is deteriorated and cannot be used. Therefore, it was not possible to simply use a strong projection light source system.

On the other hand, these transmission / scattering display elements operate depending on whether light is transmitted or scattered, and therefore, there is little problem that light becomes heat. Of course, light is slightly absorbed due to the absorption of light by the substrate and electrodes, but it is less than the absorption by the polarizing plate, and its heat resistance is high. It can withstand, and a bright display is possible.

However, the transmission-scattering display element tends to have a lower contrast ratio on the screen than the TN liquid crystal display element.

This is because light is not emitted to the side opposite to the light source in the TN type liquid crystal display element in the off part, whereas light is emitted in the off part in the transmission scattering type display element. Then, the emitted scattered light is removed by means for removing scattered light arranged between the transmission scattering type display element and the screen.
If the scattered light cannot be sufficiently removed, the scattered light appears to be superimposed on the original transmitted light on the screen, so that the contrast ratio decreases.

Therefore, if the luminous fluxes incident on the transmission / scattering display element are not uniform, even if a means for removing scattered light with high accuracy is provided on the emission side, only the display becomes dark, and the contrast ratio is hardly improved.

For this reason, it has been desired to improve the light source utilization efficiency, reduce the size, and improve the contrast ratio while taking advantage of the bright display of the projection type display device using the transmission scattering type display element.

Means for Solving the Problems The present invention has been made to solve the above-described problems, and has a projection light source system, a transmission-scattering display element to which light from the projection light source system is incident, and In a projection type display device having a projection optical system for projecting light emitted from a transmission scattering type display element onto a screen, an elliptical mirror, a light source, a conical prism whose bottom section is larger than the top section, and a condensing prism A light source is disposed at a first focal position of the elliptical mirror, the bottom surface is disposed near a second focal position of the elliptical mirror, and light from the light source is Provided is a projection display device, wherein only light condensed at a second focal position and passing through the prism is condensed by a condensing lens and made incident on a transmission-scattering display element.

In the projection type display device of the present invention, since the transmission / scattering type display element and the projection light source system are used in combination, the brightness of the display with respect to the light incident on the transmission / scattering type display element is bright.

Furthermore, the most significant feature is that a projection light source system using an elliptical mirror, a light source, a conical prism, and a condenser lens is used. The scattered light can be removed with high efficiency by means for removing scattered light provided on the side, the utilization efficiency of the light source can be increased, the light source can be reduced in size, and a projected image with a high contrast ratio can be obtained.

In particular, as a transmission-scattering display element, a nematic liquid crystal having a positive dielectric anisotropy is dispersed and held in a resin matrix between substrates with electrodes, and the refractive index of the resin matrix is the ordinary refractive index n of the liquid crystal used. It is preferable to use a transmission-scattering type liquid crystal display element in which a liquid crystal resin composite made to substantially match the above is sandwiched.

Such a liquid crystal resin composite has good transmission-scattering characteristics and is in the form of a film, so that problems such as short-circuit between substrates due to pressurization of the substrates and destruction of the active element due to movement of the spacer hardly occur.

Since the transmission-scattering type display element sandwiching the liquid crystal resin composite has poor multiplex drive characteristics, an active element is usually provided for each pixel electrode except for displaying a simple pattern.

In addition, this liquid crystal resin composite has the same specific resistance as that of the conventional TN mode, and does not require a large storage capacitor for each pixel electrode as in the DS mode. In addition, the power consumption of the liquid crystal display element can be kept low. Therefore, the production can be facilitated because the production can be performed only by removing the alignment film forming step from the conventional TN mode liquid crystal display element production process.

These active elements include transistors, diodes,
There is a non-linear resistance element and so on.
The above active elements may be arranged.

The projection display apparatus of the present invention has a light source system for projection, a transmission / scattering display element, and a projection optical system.

The projection light source system according to the present invention includes an elliptical mirror, a light source, a body-shaped prism, and a condenser lens. The fiber-shaped prism may be a conical prism whose bottom cross section is larger than its top cross section, and the specific shape will be described later in detail. A light source is disposed at a first focal position of the elliptical mirror, light from the light source is collected at a second focal position, and is incident from the bottom surface of a conical prism disposed at the second focal position, The light emitted from the upper surface is condensed by a condensing lens and is arranged so as to be incident on a transmission-scattering display element.

It is most efficient to dispose the body-shaped prism at the second focal position, but in some cases, it may be displaced back and forth in the optical axis direction.

In the present invention, a substantial part of the light source is covered by the elliptical mirror, so that much of the light from the light source is available by reflection. Further, most of the reflected light returns to the light source as in the case of a spherical mirror, and the loss due to the fact that the light source itself does not allow the returned light to pass through is small, and the light use efficiency is improved. In addition, since a condensing lens is used, a small elliptical mirror is sufficient, and there is no need to use an expensive large elliptical mirror.
The projection light source system can be downsized.

Further, a conical prism is arranged at the second focal position of the elliptical mirror. At this time, it is preferable to prevent light that has reached other than the bottom surface of the conical prism from reaching the condenser lens. Specifically, a diaphragm having the same opening as the bottom surface may be arranged at the position of the bottom surface of the conical prism.

Accordingly, the light component having a shifted light flux more easily generated than the finite length light source and the spherical mirror formed by the elliptical mirror and the second component without reflection are obtained.
The light component that goes directly to the condenser lens without passing through the focal point can be removed, the light flux can be aligned, unnecessary light emitted from the transmission scattering type display element and reaching the screen is reduced, and the contrast ratio is improved. be able to.

This effect is particularly great when a means for removing scattered light, specifically, a second aperture is provided between the transmission scattering type display element and the screen.

FIG. 1 is a schematic view of an example showing a basic configuration of a projection display device of the present invention. In the example of FIG. 1, the light source 1 is disposed at the first focal point of the elliptical mirror 2, and the light emitted from the light source 1 is reflected by the elliptical mirror 2, and the bottom of the aperture 3 is provided at the opening. The light enters from the bottom surface of the conical prism 4, passes through the prism, aligns the luminous flux, exits from the top surface, is condensed by the condensing lens 5, is converted into parallel light, and is transmitted and scattered. , The light is condensed by a condensing lens 7, the scattered light is removed by a second aperture 8 as a means for removing the scattered light, and projected onto a right screen (not shown) by a projection lens 9. Projected. The light source 1, the elliptical mirror 2, the stop 3, the prism 4, and the condensing lens 5 constitute a projection light source system, and the condensing lens 7, the second stop 8, and the projection lens 9. It constitutes a projection optical system.

FIG. 2 is a side view for explaining the shape of the conical prism.

FIG. 2 (A) shows a conical prism 11 having the simplest shape.
This is an example using A, and has a truncated cone or truncated pyramid shape. In this case, the bottom surface 22A matches the bottom cross section 14A at the bottom surface, and the top surface 13A matches the top cross section 15A at the top surface. The bottom and top surfaces of the prism are orthogonal to the optical axis and intersect with the side surfaces of the prism at an angle ψ.

FIG. 2B is an example in which the bottom surface 12B of the prism 11B is formed in a cone shape, and the conical surface forms an angle φ with the bottom surface cross section 14B. The upper surface is also provided so that the upper surface 13B is a curved surface and functions as a lens, and is formed in a convex shape from the upper surface cross section 15B to the emission side.

FIG. 2 (C) shows the bottom surface 12C of the prism 11C as a cone,
This is an example in which the upper surface 13C is a microlens array formed on the upper surface cross section 15C, and (D) shows the bottom surface 12D of the prism 11D.
Is an example in which the upper surface 13D is a rod lens array formed on the upper surface cross section 15D.

In (B) to (D), the bottom surfaces 12B to 12D have a convex cone shape, but may have a concave cone shape. Further, the side surface of the conical prism may be a curved surface other than a straight line in a cross section in the side view.

FIG. 3 is an enlarged sectional view of a projection light source system used in the present invention, in which a light source 21 is disposed at a first focal point of an elliptical mirror 22, and an aperture of a diaphragm 23 and a prism are disposed at a second focal point. twenty four
Place the bottom of. Only the light emitted from the light source 21 or reflected by the elliptical mirror 22 and reaching the opening of the diaphragm 23 enters the bottom surface of the prism 24, propagates through the prism, and exits from the top surface of the prism. Have been to be.

If the shape of such a conical prism is such that incident light is substantially totally reflected on the inner surface of the prism, the loss of light quantity in the prism is substantially eliminated. That is, only needs to be as prism is totally reflected internally against the maximum incident angle theta ₂ of the incident light of the light reaching it is reflected by the elliptical mirror. For this purpose, as shown in FIGS. 2 (B) to 2 (D), the bottom surface on the incident side of the prism is made convex on the incident side from the cross section of the bottom surface, or conversely, concave on the incident side. It is preferable to make the shape.

Specifically, the shape may be conical or pyramid so that the sides intersect the bottom cross section at an angle φ, and the angle φ has an optimal value according to the positions of the light source, the elliptical mirror, and the prism bottom. , -20 ° to 20 °. In general,
In order to use light efficiently, it is preferable that the second focal position is located slightly outside the bottom surface of the prism when it is convex, and the second focal point is located when it is concave. It is preferable that the focal position is located slightly inside the bottom surface of the prism.

By making the prism of bottom section> top section, the effect of apparently reducing the diameter of the diaphragm can be obtained.

For this reason, the effect of reducing the diameter of the stop apparently, that is, hardly causing a light amount loss, that is, a high emission light source close to an ideal point light source can be obtained.

Further, the upper surface of the prism is formed into a spherical or aspherical lens shape, the surface is roughened by etching, polishing, etc. to form a light diffusing surface, an antireflection film is formed, a micro lens array, a rod lens array, etc. are formed. As a result, it is possible to reduce the amount of emitted light and the non-uniformity due to reflection. Note that it is preferable to form an anti-reflection film on the incident side of the prism in order to prevent incident loss.

In this example, one transmission / scattering display element has been described. However, in a case other than monochrome display, a plurality of transmission / scattering display elements are generally used for each color. For example, in the case of full-color display such as color TV display, three transmission / scattering display elements for three colors of RGB may be used. Of course, even if three color filters are incorporated into one transmission-scattering display element for display, the image becomes brighter than when the same TN-type liquid crystal display element is used. It becomes much darker. For this reason, usually, the light is separated into three colors of RGB by a dichroic mirror, a dichroic prism, etc., and the transmission and scattering is controlled by a transmission / scattering type display element without a color filter, and the transmitted light is combined and projected. You.

FIG. 4 shows the example, and is a schematic view of an example using a dichroic mirror. In FIG. 4, 31 is a light source, 32 is an elliptical mirror, 33 is a diaphragm, 34 is a prism, 35 is a condensing lens, 41 and 43 are dichroic mirrors for spectrum, and 42 are mirrors. Construct the system. 37A, 37
B and 37C are lenses corresponding to each color, 36A, 36B and 36C are transmission / scattering display elements corresponding to each color, 44 and 46 are dichroic mirrors for synthesis, 45 is a mirror, and these 44 to 46 are not shown ( A projection optical system is configured by a second stop as means for reducing diffused light and a projection lens (shown on the right side of the figure).
Thus, the image is projected on the screen on the right side of the figure.

FIG. 5 shows an example of a projection type display device using a reflection type transmission scattering type display element. In FIG. 5, reference numeral 51 denotes a light source, 52 denotes an elliptical mirror, 60 denotes a mirror, 53 denotes an aperture, 54 denotes a prism, 55 denotes a condensing lens, and 61 denotes a spectral and combining dichroic prism. Construct a light source system. 56A, 56B, 56
C is a reflection-type transmission / scattering display element corresponding to each color, 58 is a second diaphragm as a means for reducing diffused light, 59 is a projection lens, which is projected by these and a dichroic prism 61 for spectral / combination. An optical system is configured to project light on the screen on the left side of the figure.

As a light source used in these projection light source systems, a light source having a short emission length such as a halogen lamp, a metal halide lamp, or a xenon lamp can be used.

The elliptical mirror may be any as long as the light source can be arranged at the first focal position and the bottom surface of a prism described later can be arranged at the second focal position. In addition, it is only necessary that the size be such that light from the light source can be used efficiently. Usually, it is a cold mirror, so a small size is a great advantage.

The prism disposed at the second focal position is for using only the light with the uniform light flux of the light collected at the second focal position. In particular, it is preferable to dispose a diaphragm to block light except for the bottom surface of the prism. Specifically, an aperture having a hole as shown in the above example, a small mirror, or the like can be used. When a small mirror is used, the light source and the transmission-scattering display element do not have to be arranged on a straight line.

In the case of an aperture, the hole becomes the opening,
Only the light transmitted through the hole is collected by the condensing lens, and in the case of a small mirror, the reflection surface becomes the opening, and only the light reflected by the reflection surface enters the prism,
The light is focused by the focusing lens.

The diameter D ₁ of the bottom cross section of the prism (same as the diameter of the opening if a diaphragm is provided) and the diameter D ₂ of the top cross section of the prism are determined in consideration of the size of the light source, desired brightness, contrast ratio, and the like. You only have to decide.

Normally, when parallel light is used as in the example of FIG. ₁ , the ratio D ₂ / f ₁ of the diameter D _{2 of the} cross section of the upper surface of the prism to the focal length f ₁ of the condensing lens is 0.02 to 0.02. Preferably, it is set to 0.18.

This projection light source system may be used in combination with other mirrors, optical fibers, fiber arrays, lenses, cooling systems, infrared cut filters, ultraviolet cut filters, and the like as long as the effects of the present invention are not impaired. .

As the projection optical system, a conventionally known projection optical system such as a lens can be used. The projection optical system only needs to have a configuration in which only linearly transmitted light of the light emitted from the transmission / scattering display element is projected onto the screen, and the scattered light is removed.

In the simplest configuration, there is only a configuration in which a projection lens is provided immediately after the transmission / scattering type display element. If necessary, a condensing lens, a reflecting mirror, and the like may be used in combination.

However, if the projection distance is not increased, scattered light cannot be sufficiently removed unless the projection distance is increased, which is not practical. Therefore, it is preferable to provide a means for removing scattered light. Specifically, the transmitted light may be once collected after passing through the transmission / scattering display element, and a second aperture may be provided at the focal position. As the second stop, an aperture having a hole similar to the stop of the projection light source system, a small mirror, or the like can be used.

In the case of an aperture, the hole becomes the opening,
Linearly transmitted light (light that passes through the part where the pixel part is in the transmission state)
In the case of a small mirror, only the linearly transmitted light is reflected by the reflective surface and can pass through. In the case of a small mirror, only the linearly transmitted light is reflected by the reflective surface. Since the light scattered in the state portion hardly reaches the focal position, it is almost removed, and only the linearly transmitted light necessary for the original image is projected.

Diameter D ₂ of the opening of the second diaphragm, a desired brightness, may be determined in consideration of the contrast ratio and the like. It is also preferable to be able to change the size of the opening so that it can be adjusted.

When a plurality of transmission / scattering display elements are provided for each color, they may be configured to be combined with a dichroic prism or a dichroic mirror and projected as in the above-described example, or may be individually projected. The image may be synthesized on the screen, but it is more advantageous to project the image after the image is synthesized, since the optical axis becomes one.

The means for removing the scattered light may also be arranged between the transmission scattering type display element and the screen, and may be arranged in the optical path after synthesis as in the above-described example, It may be arranged immediately after the scattering type display element together with the condenser lens, and after scattered light is removed, synthesized and projected.

The transmission / scattering display element of the present invention can be used as long as it is a flat display element that can take on a transmission state and a scattering state depending on the voltage application state.

Specifically, a DSM (Dynamic Scattering Mode) liquid crystal display device, a liquid crystal resin in which liquid crystal is dispersed and held in a resin matrix, and the transmission and scattering is controlled by the mismatch between the refractive index of the liquid crystal and the refractive index of the resin matrix. There are a liquid crystal display element using a composite, an element in which fine needle-like particles are dispersed in a solution, and transmission scattering is controlled by a voltage application state.

Above all, liquid crystal display elements using liquid crystal resin composites have good transmission-scattering properties, can be manufactured by a manufacturing process similar to conventional TN-type liquid crystal display elements, and can be driven using the same driving IC. It's easy to do.

The liquid crystal resin composite of the liquid crystal display element using the liquid crystal resin composite is composed of a resin matrix in which a large number of fine holes are formed and a liquid crystal filled in the holes, and the liquid crystal is refracted by a voltage application state. Light is transmitted when the refractive index matches the refractive index of the resin matrix, and is scattered when the refractive indexes do not match.

More preferably, using dielectric anisotropy of the nematic liquid crystals having positive, by the refractive index of the resin matrix is such that substantially coincides with the ordinary refractive index n _o of the liquid crystal used, high permeability when a voltage is applied And the portion between pixels without electrodes is in a scattered state (it becomes black when projected on a screen), so that the contrast ratio of the projected image is increased without providing a light-shielding film between pixels. It is preferred.

The liquid crystal resin composite composed of the resin matrix in which a large number of fine holes are formed and the liquid crystal filled in the holes has a structure in which the liquid crystal is sealed in a liquid bubble such as a microcapsule. The individual microcapsules do not have to be completely independent, and liquid bubbles of individual liquid crystals may be communicated via the slits like a porous body.

This liquid crystal resin composite is prepared by mixing a liquid crystal and a material constituting a resin matrix into a solution or a latex, and then subjecting the mixture to photo-curing, heat curing, curing by removing a solvent, reaction curing, etc. May be separated so that the liquid crystal is dispersed in the resin matrix.

In particular, it is preferable to use a photo-curing or heat-curing resin as the resin to be used, so that the resin can be cured in a closed system. Among them, a photo-curing resin is not affected by heat and is cured in a short time. Is more preferable.

More specifically, use of a photocurable vinyl resin is preferable, and a photocurable acrylic resin is exemplified. In particular, a resin containing an acrylic oligomer which is polymerized and cured by light irradiation is preferable.

As a specific manufacturing method, cells are formed using a sealing material in the same manner as a conventional ordinary TN type liquid crystal display element, a mixture of uncured liquid crystal and resin matrix is injected from the injection port, and the injection port is sealed. After stopping, it can be cured by irradiating light or heating.

Alternatively, an uncured mixture of the liquid crystal and the resin matrix may be supplied onto the substrate with electrodes, and then another substrate with electrodes may be overlaid and cured by light irradiation or the like.

Further, to this uncured mixture, ceramic particles for controlling the substrate gap, plastic particles, spacers such as glass fibers, pigments, dyes, viscosity modifiers, and other additives that do not adversely affect the performance of the present invention may be added. Good.

In the case of such an element, during the curing step, only a specific portion is cured while a sufficiently high voltage is applied, so that the portion can always be in a light transmitting state. In some cases, such a normally transparent portion may be formed.

The response time of a liquid crystal display device using such a liquid crystal resin composite is as follows: the rise of the voltage application is about 3 to 50 msec, and the fall of the voltage removal is about 10 to 80 msec, which is faster than the conventional TN type liquid crystal display element. The electro-optical characteristics of voltage-transmittance are also suitable for driving for gradation display.

Further, the volume fraction Φ of the operable liquid crystal in the liquid crystal resin composite is preferably Φ> 20% from the viewpoint of the scattering property in the absence of an electric field,
Φ> 35% is more preferable. On the other hand, if Φ is too large, the structural stability of the liquid crystal resin composite deteriorates.
70% is preferred.

Such a liquid crystal resin composite is used sandwiched between substrates with electrodes. Since a liquid crystal display element using this liquid crystal resin composite has poor multiplex drive characteristics, when a liquid crystal display element having a large number of pixels is used, an active element is arranged in each pixel. Of course, also in the case of other transmission scattering type display elements, active elements are arranged as needed.

As the active element, a TFT (thin film transistor) or the like is used.
When using terminal elements, the other electrode substrate may be provided with a solid electrode common to all pixels, but when using a two-terminal element such as a MIM element or PIN diode, the other electrode substrate is striped. Patterning is performed.

When a TFT is used as an active element, silicon is suitable as a semiconductor material. In particular, polycrystalline silicon is not as photosensitive as amorphous silicon,
Even if the light from the light source is not shielded by the light shielding film, no malfunction occurs, which is preferable. When amorphous silicon is used, a light-shielding film is also used.

The electrode is usually a transparent electrode, but when used as a reflective liquid crystal display element, it may be a reflective electrode of chromium, aluminum or the like.

As described above, the projection type display device normally uses a transmission / scattering type display element as a transmission type, and projects it on a separately provided screen. In this case, whether it is a front projection type (the observer is positioned on the projection type display device side and looks) or a rear projection type (the observer is positioned on the opposite side to the projection type display device and looks). Good.

In addition, a reflection type liquid crystal display device using a reflection electrode or a reflection layer provided on the back side of the device, and can be a reflection type projection display device that guides outgoing light to the incident side and projects it. In this case, it is preferable that the substrate surface be subjected to a non-reflection treatment in order to reduce reflection on the element surface.

This transmission / scattering display element can be used as a projection / display apparatus in combination with other optical elements, as a transmission / scattering display element with a solid electrode on the entire surface, or as a transmission / scattering display element with simple electrode patterning. Can be used as a lighting device.

For example, by making the device itself as shown in FIG. 1 such a configuration and embedding and arranging it in a wall, a ceiling, or the like,
Dimming can be performed at high speed without changing the color. Also,
The device itself of FIG. 4 or FIG.
By embedding and arranging in a wall, a ceiling, or the like, light can be adjusted at high speed without changing the color, or light can be adjusted while changing the color.

[Operation] According to the present invention, a projection light source system using an elliptical mirror, a light source, a conical prism, and a condenser lens is used.
Therefore, a large amount of light from the light source can be used by the small elliptical mirror, and the use efficiency of the light source can be increased and the light source can be downsized.

In addition, a prism is used, the effective light amount is increased by increasing the incident light range, and the diameter on the emission side is reduced to obtain light closer to a point light source, that is, light with a more uniform light flux. For this reason, the luminous flux is more uniform than when only a simple diaphragm having the same diameter as the prism bottom cross section is used without using a prism, and conversely, the light amount is larger than when only a simple diaphragm with the same diameter as the prism top surface is used. But many become bright.

Further, since the light beams incident on the transmission / scattering display element are uniform, scattered light can be removed with high efficiency from the linearly transmitted light passing through the transmission / scattering display element, and a projected image with a high contrast ratio can be obtained.

In the present invention, the prism has a truncated cone shape or a truncated pyramid shape, and a prism is used such that light incident on the prism is almost totally reflected on the side surface of the prism.

For example, the angle θ from the optical axis in the prism shown in FIG.
Light that is inclined and enters the prism bottom surface at an angle θ + φ (with respect to the direction perpendicular to the bottom surface) enters the prism at an angle θ ′ that satisfies an angle n · sin θ ′ = sin (θ + φ) determined by the refractive index n of the prism. I do. This light is applied to the side of the prism at an angle x
(X = φ + ψ−θ ′), and if x is greater than the critical angle for total reflection θ _c (= Sin ⁻¹ (1 / n)), the light is totally reflected on the side surface of the prism. Angle of incidence each time the reflections at the side surface in this way Yuki decreased by (180-2φ), and becomes equal to or less than the critical angle theta _c, so that the result is emitted from the side surface without being totally reflected.

For this reason, the inclination angle の of the prism side surface and the length of the prism (the distance between the bottom surface and the top surface) may be determined so that light is not emitted from the prism side surface. As a result, a projection light source system with a large amount of light and a uniform luminous flux can be obtained. Thereby, a bright projection display device having a high contrast ratio can be obtained.

Further, the second aperture is made variable. For example, when the surroundings are dark, the influence of light from the surroundings on the screen is small, and a dark point by the projection display device can be determined. However, the contrast ratio can be adjusted so as to be high, and a display image with a high contrast ratio and easy-to-see brightness can be obtained.

Conversely, when the surroundings are bright, the light from the surroundings is reflected on the screen, so that the dark spots of the projection display device do not appear dark but rather appear bright to some extent. By opening the aperture, increasing the amount of projection light and brightening the screen, it is easy to see and the contrast ratio looks high.

[Examples] Hereinafter, the present invention will be specifically described with reference to examples.

[Example 1] A glass substrate provided with an ITO pixel electrode provided with a polycrystalline silicon TFT in each pixel and a glass substrate provided with a solid ITO electrode on the entire surface were sprayed with spacers therein, and the periphery thereof was dispersed. An empty cell was manufactured by sealing with an epoxy-based sealing material except for the injection port.

To this, a photo-curable resin material containing an acrylic monomer and an acrylic oligomer, and a nematic liquid crystal having a positive dielectric anisotropy are mixed, and a melted mixture is injected. The liquid crystal resin composite was cured to produce a transmission scattering type liquid crystal display device.

The light source system for projection is a light source (light emitting arc length 3 mm, 250 mm
W metal halide lamp), elliptical mirror (first focus position F
₁ = 15 mm, second focal position F ₂ = 200 mm, total depth H = 100 m
m, aperture diameter D ₁ = 105 mm), prism (bottom tilt angle φ = 5)
°, side tilt angle [psi = 86 °, the bottom cross-sectional diameter 16 mm, (corresponding to the above D ₂₎ top sectional diameter 8 mm, the distance between the bottom section and the top section = 57.2 mm, a spherical top surface in which the surface and the diffusing surface Convex lens (focal length f ₁ = 80 m) that is disposed in front of a transmission-scattering type liquid crystal display element with a lens shape and a radius of curvature of 6 mm
m) and a stop (aperture) having an opening having the same diameter as the diameter at the bottom of the prism.

The distance between the prism upper surface and the converging convex lens is 120 mm, the distance between the converging convex lens and the second aperture is 240 mm, and the liquid crystal display element is disposed between the converging convex lens and the second aperture. The position was 200 mm from the second stop.

Using this projection display device, a display was projected on a reflective screen having a screen gain of 40 inches and a screen gain of 5. The maximum brightness on the screen in a dark room (ft-L)
And the contrast ratio are as shown in Table 1.

Further, Comparative Examples (Comparative Examples 1 and 2) of a projection light source system using only a diaphragm without using a prism and Comparative Example 3 using a conventional projection light source system using a spherical mirror and a lens are also shown.

As is apparent from this result, according to the present invention, a bright display can be achieved as in the case where the diameter of the aperture is increased.
A high contrast ratio can be obtained as when the aperture is stopped down.

Example 2 As shown in FIG. 4, light from a light source was separated into three colors of RGB using a dichroic mirror, and a liquid crystal display element similar to that of Example 1 was arranged for each color. A condensing lens was arranged in front of the lens, and the light was condensed and synthesized by a dichroic mirror, passed through a second stop disposed at the focal point, and projected onto a screen by a projection lens.

However, the prism has a focal length of 2 mm and an outer diameter of about 1
The same prism as in Example 1 was used except that a microlens array of mm was provided. The lens 35 is arranged so that the prism upper surface is located at the focal position, so that substantially parallel light enters the dichroic mirror 41. Second focusing lens
37 was disposed immediately before each liquid crystal display element 36.

In order to reduce the decrease in color purity due to PS polarization,
It was preferable to use a color filter in combination with each liquid crystal display element.

As a result, the brightness and the contrast ratio were the same as in Example 1, but the in-plane distribution of the light amount was more uniform.

Example 3 A projection display device was obtained in the same manner as in Example 2, except that the liquid crystal display element of Example 2 was replaced by a liquid crystal display element using solid electrodes on the entire surface. When this projection display device was fitted on a wall surface, it could be used as a color lighting device.

Example 4 Three reflective liquid crystal display elements were manufactured using one surface of the electrode of the liquid crystal display element of Example 1 as a reflective electrode. In this liquid crystal display element, an antireflection film was formed on the surface of the glass substrate on which the transparent electrode was formed.

Using this liquid crystal display element, using an elliptical mirror, a light source, a mirror, a prism, a diaphragm, and a condensing lens as shown in FIG. The prism 60 and a diaphragm 53 having an opening having the same shape as the bottom surface of the prism 54 are arranged at a second focal position where light reflected by the mirror is focused. Behind it a focusing lens
55, and then a dichroic prism 61 for RGB spectroscopy is provided to split the light into three colors. The light is made incident on three reflective liquid crystal display elements 56, reflected on the electrode surfaces, emitted again to the same dichroic prism 61, and made into three colors. Light was synthesized. The combined light is incident on the same condensing lens 55 from the opposite direction, is condensed, is separated from the condensing lens by the same distance as the stop, but has a different position in the horizontal direction. Aperture of 2 58
Through the projection lens 59 for projection on the left screen.

Also in this case, it was preferable to use a color filter in combination with each liquid crystal display element in order to reduce a decrease in color purity due to PS polarization.

Example 5 A projection display device was obtained in the same manner as in Example 4, except that the liquid crystal display element of Example 4 was replaced with a liquid crystal display element using solid electrodes. When this projection display device was fitted on a wall surface, it could be used as a color lighting device.

[Effects of the Invention] In the projection type display device of the present invention, since the light emitted from the light source is condensed using the elliptical mirror, the light condensing efficiency is high,
Bright display is possible.

In addition, a prism having a specific shape is provided at the second focal position to remove divergent light, so that the light source has an effective length and is reflected by an elliptical mirror and does not reach the second focal position; In addition, it is possible to remove light directed toward the transmission / scattering type display element without directly reflecting and passing through the second focal position, thereby improving the contrast ratio of the projected image.

In addition, since this prism has a bottom cross section> a top cross section, it emits outgoing light from a small area while taking in a large amount of incident light from a wide bottom surface. A projection display device having a contrast ratio can be obtained.

The present invention is also applicable to various applications within a range that does not impair the effects of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of a basic example of a projection display device of the present invention. 2 (A), (B), (C), and (D) are side views illustrating the shape of the prism used in the present invention. FIG. 3 is an enlarged sectional view of the projection light source system of the present invention. FIG. 4 and FIG. 5 are schematic views showing the configuration of an example of the color projection display device of the present invention. FIGS. 6A, 6B and 6C are schematic diagrams showing the configuration of an example of a conventional projection display device. Light source: 1, 21, 31, 51 Elliptical mirror: 2, 22, 32, 51 Aperture: 3, 23, 33 Prism: 4, 11A, 11B, 11C, 11D, 24,
34, 54 lenses: 5, 7, 9, 35, 37A, 37B, 37
C, 55 Transmission / scattering display device: 6, 36A, 36B, 36C, 56A, 56
B, 56C Dichroic mirror: 41, 43, 44, 46 Mirror: 42, 45, 60 Dichroic prism: 61

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03B 21/14 G03B 21/20 G02F 1/13

Claims (6)

(57) [Claims] 1. A projection type having a projection light source system, a transmission / scattering type display element on which light from the projection light source system enters, and a projection optical system for projecting light emitted from the transmission / scattering type display element onto a screen. In a display device, a projection light source system including a conical prism having a cross section of an elliptical mirror, a light source, and a bottom surface larger than a cross section of an upper surface and a condensing lens is used.
A light source is disposed at a focal position of the elliptical mirror, the bottom surface is disposed near a second focal position of the elliptical mirror, and light from the light source is collected at the second focal position of the elliptical mirror, and only light that has passed through the prism Wherein the light is condensed by a condensing lens and is incident on a transmission-scattering display element. 2. The projection display device according to claim 1, wherein said prism has a truncated cone shape or a truncated pyramid shape. 3. The projection type display device according to claim 1, wherein a reflection electrode is provided on the transmission scattering type display element, and a reflection type optical path is provided. 4. The projection type display device according to claim 1, wherein said bottom surface has a cone shape. 5. A projection type display device according to claim 1, wherein said upper surface is a curved surface. 6. A ratio D ₂ / f ₁ of a diameter D _{2 of a} cross section of an upper surface of the prism to a focal length f ₁ of the converging lens is 0.02 to 0.18. 6. The projection display device according to 3, 4, or 5.