JP2001166292A - Projection display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection display device having such a structure that a phase plate is disposed between a polarizing plate and a reflection type liquid crystal display panel, in which changes in the phase plate with temperature are prevented, high efficiency and low cost are obtained with a compact structure and moreover, high contrast is obtained. SOLUTION: The projection display device consists of a display part having a reflection type liquid crystal display panel, a polarizing plate as a polarizer and analyzer and disposed in the front side of the reflection type liquid crystal panel, and at least one phase plate disposed between the polarizing plate and the reflection type liquid crystal display panel, and of an illumination optical system to illuminate the reflection type liquid crystal display panel, and of an projection optical system to project the light from the reflection type liquid crystal display panel. In this device, the polarizing plate and the phase plate are disposed at a specified distance so that the heat from the polarizing plate is not transferred to the phase plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called projection type display device such as a projector display device using a so-called reflection type display panel such as a reflection type liquid crystal display device.

[0002]

2. Description of the Related Art Various types of optical systems have been proposed for a so-called projection display device such as a projector display device using a so-called reflective display panel such as a reflective liquid crystal display device. For example, there is a configuration that includes an illumination optical system, a display panel as a spatial modulation element, and a projection optical system, and further includes a polarizing plate disposed immediately before the display panel. This is because incident light having a specific polarization axis that has passed through the polarizing plate is modulated or reflected without being modulated by each pixel of the display panel, returns to the polarizing plate again, and is blocked or changed. Is transmitted, thereby displaying a desired image.

In this case, for example, illumination light from a so-called illumination optical system is made to enter the display panel from a direction slightly oblique to the normal direction of the display panel, and what is specularly reflected here is used as projection light to the so-called projection optical system. A configuration such as guiding is adopted. Further, a configuration has been proposed in which a polarizing plate (polarizer) corresponding to light incident on a display panel and a polarizing plate (analyzer) corresponding to light emitted from the display panel are separated. In addition, as another configuration, P
There is a configuration in which a BS (polarization beam splitter) prism is arranged to perform so-called crossed Nicols modulation.

[0004]

However, in the above-mentioned configuration in which the polarizer and the analyzer are separated, it is necessary to take a very large space for separating the incident light and the reflected light, and the projection is required. The size of the optical system is increased, and the cost is increased. In addition, as another configuration described above, when a PBS prism is arranged immediately before a display panel to perform so-called crossed Nicols modulation, the PBS prism is generally expensive, and when a so-called three-panel projection display device is used, each of the display panels is required. Each time, a PBS prism is required, resulting in a very high cost.

Therefore, if the same polarizer is used for both the polarizer and the analyzer, the space efficiency is improved and the cost can be reduced. At this time, in general, when a reflective liquid crystal display element is used as a display panel, in order to achieve good image contrast, a state where no voltage is applied to each pixel of the liquid crystal is set to an OFF state of image display, that is, a so-called OFF state. It is desirable to use normally black. In order to realize this in this configuration, it is necessary to arrange a phase plate between the polarizing plate and the reflective liquid crystal display panel.

Specifically, a polarizing axis (transmission axis) of a polarizing plate is provided between a display panel and a polarizing plate disposed immediately before the display panel.
1/4 having a slow axis or fast axis of 45 degrees
The configuration is such that the wave plate is arranged as a phase plate. This is because, when the incident light having a specific polarization axis that has passed through the polarizing plate is not modulated by the display panel, the light reciprocates and passes through the quarter-wave plate to act as a half-wave plate. The axis is rotated by 90 degrees, returns to the polarizing plate again and is blocked here, and black display is performed.

When the incident light is modulated by the display panel,
Thereby, it receives a function as a half-wave plate equivalent to that when the light beam reciprocates through a quarter-wave plate having a slow axis or a fast axis having a relation of 45 degrees with the polarization axis, and furthermore, actually By reciprocating the 1/4 wavelength plate itself
Receives the function as a / 2 wavelength plate. As a result, the polarization axis is returned to the original direction (actually rotated by 180 degrees) after passing through the one-wavelength plate. The color of the display panel is displayed.

However, when the image display is OFF, that is, when black display is performed, all the light is absorbed by the polarizing plate, so that much heat is generated here. At this time, if the phase plate is adhered to the polarizing plate or has a configuration close to each other, heat is transmitted from the polarizing plate to the phase plate, and the temperature of the phase plate rises. Changes, and the phase characteristics change. Then, the image display is O
Even in the FF state, the polarization axis of light that has reciprocated through the phase plate is
Since the angle does not form exactly 90 degrees with respect to the polarization axis (transmission axis) of the polarizing plate and the light is not completely blocked, it is difficult to obtain good contrast.

The present invention has been made in view of the above problems, and in a configuration in which a phase plate is disposed between a polarizing plate and a reflection type liquid crystal display panel, a temperature change of the phase plate is prevented, and the efficiency is reduced by a compact configuration. It is an object of the present invention to provide a projection type display device which is good, low cost, and can obtain high contrast.

[0010]

In order to achieve the above object, according to the present invention, there is provided a reflective liquid crystal display panel, and a polarizing plate disposed in front of the reflective liquid crystal display panel and serving as a polarizer and an analyzer. Display unit having a plate, at least one phase plate disposed between the polarizing plate and the reflective liquid crystal display panel, an illumination optical system for illuminating the reflective liquid crystal display panel, and the reflective liquid crystal A projection optical system for projecting light from a display panel, wherein the polarizing plate and the phase plate are separated by a predetermined distance so that heat from the polarizing plate is not transmitted to the phase plate. It is characterized by opening.

Further, the present invention is characterized in that the following conditional expression is satisfied. 0.3 <d <20, where d is a distance (mm) between the polarizing plate and the phase plate.

Further, a fluid is caused to flow between the polarizing plate and the phase plate. Also, the direction of flowing the fluid is
The reflection type liquid crystal display panel is characterized by being substantially parallel to a side to which a connection substrate is connected.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view schematically showing a main configuration of an optical system of a projection display apparatus according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a light source, 2 denotes a light source, and 2 denotes a light source.
This is an umbrella-shaped reflector that reflects light from the umbrella. Also,
Behind the reflector 2, a condenser lens 3, a first lens array 4, and a second lens array 5 are arranged a little apart in the order in which light travels. The first lens array 4 has cells combined in a lattice shape, and the second lens array 5 has cells combined in a different lattice shape from the first lens array 4. .

The condenser lens 3 condenses the light from the light source 1 and the reflector 2 to the second lens array 5 via the first lens array 4. Further, the images of the cells of the first lens array 4 are overlapped as illumination light by the second lens array 5 and a superimposed lens (not shown). The above configuration is called an illumination optical system. Further, behind the second lens array 5, a condenser lens 6 whose light axis is decentered upward, condenses illumination light as incident light on the display panel and guides reflected light from the display panel as projection light to a projection optical system. Is arranged. The condenser lens 6
A display panel 9 using a polarizing plate 7, a phase plate 8, and a reflective liquid crystal display element is disposed behind the display panel.

Light from the light source 1 and the reflector 2 passes through the optical members 6 to 8 via the illumination optical system, and is incident on the display panel 9 along the optical axis L from slightly obliquely above. The display panel 9 is disposed slightly inclined rightward from the vertical direction in the figure. The incident light that has entered the display panel 9 is reflected horizontally forward (to the left in the figure) as reflected light, passes through the above optical members again along the optical axis Z in the direction opposite to the direction of 8 to 6, and is projected by the projection optical system. The light is guided to the system 10, whereby the image is projected as projection light.

By illuminating the display panel 9 obliquely, incident light and reflected light can be separated. Further, the display panel 9 is arranged to be inclined with respect to each optical axis, and the condenser lens 6 is also inclined with respect to each optical axis and is largely decentered. For this purpose, the projection optical system 10 has a configuration in which the lens groups 10a, 10b, 10c, and 10d are decentered from each other.

Further, in the present embodiment, for example, the cooling fan 11 forcibly flows air from above into the space between the polarizing plate 7 and the phase plate 8, thereby promoting heat radiation from the polarizing plate 7. The heat is released to the outside without being transmitted to the phase plate 8. Details will be described later.

FIG. 2 is a partially enlarged view showing a display section from the condenser lens 6 to the display panel 9. As shown in FIG. 1, a polarizing plate 7, a phase plate 8, and a display panel 9 using a reflective liquid crystal display element are arranged behind the condenser lens 6. Of these, the phase plate 8 is 1/4
The display panel 9 is a wave plate, and has a characteristic that it functions as a half-wave plate in a reciprocating manner when a voltage is applied and does not function as a wave plate when no voltage is applied.

The configuration of image display by a display panel using such a reflective liquid crystal display device (hereinafter referred to as a reflective liquid crystal display panel) will be described again. In general, when a reflective liquid crystal display panel is used, as described above, it is known that higher contrast is obtained by performing black display when no voltage is applied. In particular, when liquid crystal that is vertically aligned when no voltage is applied is used, the contrast is increased. However, as in the present embodiment, when a single polarizing plate that also serves as a polarizer and an analyzer is disposed immediately before a reflection-type liquid crystal display panel, white display is obtained when no voltage is applied as it is. This results in a display method called normally white.

Therefore, in the present embodiment, a quarter-wave plate whose polarization direction is rotated by 90 degrees due to reciprocal passage is disposed between the polarizer and the reflective liquid crystal display panel as a phase plate. With this, a black state is displayed when no voltage is applied,
A so-called normally black state can be realized, and high contrast can be achieved.

FIG. 3 is a table showing the relationship between the voltage application state of the reflection type liquid crystal display panel in this embodiment and the polarization state after passing through each optical element. Here, the transition of each polarization state when a voltage is applied and when no voltage is applied is shown. In the same figure, the LCD indicates a reflection type liquid crystal display panel. First, the light emitted from the light source is in a state of random polarization, but is usually adjusted to a certain degree of uniform linear polarization by polarization conversion means (not shown). In the figure, this is indicated by a vertical arrow.

Next, the light incident on the polarizing plate in this state is
Only the polarized light component in the direction of the polarizing axis (transmission axis) of the polarizing plate is transmitted, and almost completely linearly polarized. Then, the light exiting the polarizing plate enters the phase plate. Here, if the slow axis or fast axis of the phase plate and the polarization axis (transmission axis) of the polarizing plate are arranged so as to form a predetermined angle (for example, 45 degrees), light transmitted through the phase plate becomes It becomes circularly polarized light.

At this time, it is desirable to provide a rotation adjusting mechanism on the holding member of the phase plate so that the axis of the phase plate can be accurately arranged at a desired angle. As a result, a slight phase difference caused by pretilt existing in the reflection type liquid crystal display panel can be canceled, and higher contrast can be achieved. The pretilt is a slight variation in the alignment when no voltage is applied, which is generally present in a reflection type liquid crystal display panel.

The circularly polarized light transmitted through the phase plate is incident on the reflection type liquid crystal display panel. The reflection type liquid crystal display panel functions as a phase plate when a voltage is applied, that is, functions as a half-wave plate in reciprocation of incidence and emission. Therefore, as shown in the upper part of FIG. When clockwise circularly polarized light enters, it is emitted as counterclockwise circularly polarized light. On the other hand, when no voltage is applied to the reflective liquid crystal display panel, it does not act as a phase plate, that is, does not change the polarization state, so that, for example, clockwise circularly polarized light from the phase plate is incident as shown in the lower part of FIG. Then, the light is emitted as clockwise circularly polarized light.

The light emitted from the reflection type liquid crystal display panel is
The light enters the phase plate again. At this time, the polarization state after passing through the phase plate differs depending on the voltage application state of the reflective liquid crystal display panel. That is, when a voltage is applied to the reflective liquid crystal display panel, the light is emitted as left-handed circularly polarized light as described above. Therefore, when this is transmitted through the phase plate, it is shifted with respect to the polarization axis (transmission axis) of the polarizing plate. The light becomes substantially parallel linearly polarized light. Therefore, the light finally passes through the polarizing plate, and as a result, the image display becomes O
The state becomes N.

On the other hand, when no voltage is applied to the reflection type liquid crystal display panel, the light is emitted as clockwise circularly polarized light as described above. When this is transmitted through the phase plate, the polarization axis (transmission axis) of the polarizing plate is transmitted. ) Is linearly polarized light that is almost perpendicular to the above.
In the figure, this is indicated by a horizontal arrow. Therefore, the light is finally blocked by the polarizing plate, and as a result, the image display is turned off.

Although not shown, by adjusting the voltage applied to the reflection type liquid crystal display panel, light emitted from the reflection type liquid crystal display panel, and furthermore, light transmitted through the phase plate can be converted into elliptically polarized light. Thus, the amount of light that finally passes through the polarizing plate can be controlled, and gradation can be expressed in image display.

As described above, in the configuration of the present embodiment, the ON state and the OFF state of the image display are determined by the respective phase differences of the phase plate and the reflection type liquid crystal display panel. It controls the final transmission and blocking of light in the plate. Therefore, if the phase difference of the phase plate changes for some reason, the brightness and contrast of the image will be reduced.

Here, when the image display in FIG. 3 is OFF, most of the light finally incident on the polarizing plate is absorbed here, so that the polarizing plate becomes a large heat source. In general, it is known that the phase plate changes its refractive index difference, that is, phase characteristics, depending on the temperature. When the temperature rises due to heat from the polarizing plate, the brightness and contrast of an image decrease as described above.

Therefore, in the present embodiment, as shown in FIG. 2, a direct heat conduction from the polarizing plate 7 to the phase plate 8 is cut off by separating the polarizing plate 7 and the phase plate 8 by a predetermined distance. And At this time, it is desirable to satisfy the following conditional expressions. 0.3 <d <20, where d is a distance (mm) between the polarizing plate and the phase plate.

Below the lower limit of the above conditional expression, the distance between the polarizing plate and the phase plate becomes too short, and the heat of the polarizing plate is transmitted to the phase plate, so that the phase characteristics of the phase plate change and the brightness of the image changes. And the contrast is lowered.
Conversely, if the temperature is higher than the upper limit value, it is advantageous in terms of blocking heat, but it is not preferable because the size of the entire apparatus is increased. Further, in order to obtain a more compact and high-performance projection display device, it is desirable to set the lower limit to 1 mm and the upper limit to 10 mm. On the other hand, if the polarizing plate and the phase plate are bonded or held by the same holding member, heat of the polarizing plate is transmitted to the phase plate directly or via the holding member, which is not preferable.

Further, in this embodiment, as shown by an arrow A in FIG. 2, a cooling fan 11 forcibly supplies a fluid (here, air) from above to a space between the polarizing plate 7 and the phase plate 8. Shedding. Thereby, heat radiation from the polarizing plate 7 is promoted, and the heat is radiated to the outside without being transmitted to the phase plate 8. As a result, the temperature rise of the phase plate can be reduced, which is preferable. In addition, it is preferable to make the structure such that the fluid flows on both surfaces of the polarizing plate 7 and both surfaces of the phase plate 8 because heat can be further promoted.

As shown by an arrow A in FIG. 4, the direction in which the fluid flows is the side 9 of the reflective liquid crystal display panel 9 to which the flexible substrate 12 as an example of the connection substrate is connected.
It is desirable that the direction be substantially parallel to a. By doing so, it is convenient to secure an arrangement space for the means for flowing the fluid (here, the cooling fan 11), and it is preferable because the space for the fluid to flow can be made wider. It is to be noted that the phase plate is mainly affected by the effect of the temperature change.However, since the polarization characteristics of the polarizing plate slightly change due to the temperature change, the polarizing plate itself is also cooled to prevent this. It is desirable to do.

Another example of the fluid is ethylene glycol. It is a colorless, transparent, non-human animal harmless liquid. More specifically, more efficient cooling can be performed by filling the phase plate and its surrounding space with this ethylene glycol and circulating it with a pump or the like, or stirring with a propeller or the like.

When the reflection type display panel is of a so-called multi-panel type, each display section corresponding to each reflection type liquid crystal display panel can have the same configuration as that described above.

[0036]

As described above, according to the present invention,
In a configuration in which a phase plate is arranged between a polarizing plate and a reflection type liquid crystal display panel, a temperature change of the phase plate is prevented, a compact configuration is efficient, and the cost is low, and a high contrast can be obtained. A projection display device can be provided.

More specifically, by providing a predetermined distance between the polarizing plate and the phase plate, heat from the polarizing plate is prevented from being transmitted to the phase plate, thereby preventing a change in phase characteristics of the phase plate.
High-efficiency, high-contrast image display can be performed.

Further, by flowing a fluid between the polarizing plate and the phase plate, the temperature rise of the phase plate can be further reduced. Further, by setting the direction of flowing the fluid to be substantially parallel to the side to which the connection substrate of the reflective liquid crystal display panel is connected, it is possible to secure a space for disposing the means for flowing the fluid, and to make the space in which the fluid flows wider. You can take it.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing a main configuration of an optical system of a projection display device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view showing a display unit from a condenser lens to a display panel.

FIG. 3 is a table showing a relationship between a voltage application state of a reflection type liquid crystal display panel and a polarization state after passing through each optical element.

FIG. 4 is a diagram schematically showing a direction in which a fluid flows.

[Explanation of symbols]

 Reference Signs List 1 light source 2 reflector 3 condenser lens 4 first lens array 5 second lens array 6 condenser lens 7 polarizing plate 8 phase plate 9 display panel 10 projection optical system 11 cooling fan

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H088 EA12 HA16 HA18 HA20 HA21 HA23 HA24 HA28 MA02 MA20 2H091 FA08X FA08Z FA10X FA11X FA14Z FA21X FA26X FA41Z LA04 LA17

Claims (4)

[Claims] 1. A reflective liquid crystal display panel, a polarizing plate disposed in front of the reflective liquid crystal display panel and serving also as a polarizer and an analyzer, and between the polarizer and the reflective liquid crystal display panel. A projection unit comprising: a display unit having at least one phase plate disposed therein; an illumination optical system for illuminating the reflective liquid crystal display panel; and a projection optical system for projecting light from the reflective liquid crystal display panel. In the display device, so that heat from the polarizing plate is not transmitted to the phase plate,
A projection-type display device, wherein the polarizing plate and the phase plate are separated by a predetermined distance. 2. The projection display device according to claim 1, wherein the following conditional expression is satisfied. 0.3 <d <20, where d is a distance (mm) between the polarizing plate and the phase plate. 3. The projection type display device according to claim 1, wherein a fluid is caused to flow between the polarizing plate and the phase plate. 4. The projection display device according to claim 3, wherein a direction in which the fluid flows is substantially parallel to a side of the reflection type liquid crystal display panel to which a connection substrate is connected.