JPH0534817A - Projection type color image display device - Google Patents

Abstract

PURPOSE:To realize the projection type color image display device which has a bright screen and generates no color slurring. CONSTITUTION:The projection type color image display device is equipped with a light source 3, a transmission type liquid crystal display panel 1 formed by charging liquid crystal between a couple of transparent substrates 1a and 1b and arraying display picture elements in a matrix shape, microlenses 2 provided corresponding to the individual picture elements of the liquid display crystal panel 1, color filters 3R, 3G, and 3B of the primary colors R, G, and B which are arranged corresponding to the individual picture elements of the liquid crystal display panel and have specific transmission spectra, and a projection lens 7 which projects an image, displayed on the liquid crystal display panel 1, on a screen 8. Then the relation between the numerical aperture (Na) (a) of the projection lens 7 and the numerical aperture (Na) (b) of the microlenses 2 is set to 0.8*b<=a<=1.2*b to cut light of a component which has inferior parallelism and is made incident on the projection lens 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a transmissive display panel having a plurality of display picture elements arranged in a matrix, and as a light condensing means for brightening the display.
A microlens array that collects illumination light for the display panel in a pixel region, a color filter that is arranged so as to correspond to each pixel of the display panel, and has a predetermined transmission spectrum, and the display panel Relates to a projection type color image display device having a projection lens for enlarging and projecting a color image displayed on a screen onto a screen, and particularly a projection type color image display expected to be applied to a large screen projection type TV system or information display system. Regarding the device.

[0002]

2. Description of the Related Art In a conventional general transmission type display panel, the transmittance of a display panel which does not emit light itself is changed by a drive signal, and the intensity of illumination light from a light source for illuminating the display panel is modulated. Image and characters are displayed on the screen. As such a display panel, a liquid crystal display panel, an electrochromic display, a PL
There are displays using translucent ceramics such as ZT, and liquid crystal display panels are widely used for pocket TVs, word processors and the like.

In such a liquid crystal display panel, a minimum display unit called a picture element is regularly arranged, and an independent drive voltage is applied to each picture element to determine the optical characteristics of liquid crystal as a display medium. The image is changed and the image is displayed. Here, as a method of applying an independent drive voltage to each picture element, a simple matrix drive method and MIM (Me
There is an active matrix drive system in which a nonlinear 2-terminal switching element such as a tal Insulator Metal) diode or a 3-terminal switching element such as a TFT (thin film transistor) is provided in each pixel.

Further, as modes for observing the transmissive display panel, there are a mode for directly looking at the display panel and a projection mode for enlarging and projecting an image or a character on a screen by a projection lens.

Then, in the projection type display panel whose observation mode is the projection mode, R (red), G (green) and B (blue) are provided.
There are a so-called one-panel system using one color liquid crystal display panel in which mosaic color filters of three primary colors are arranged, and a so-called three-panel system using three liquid crystal display panels for monochrome display. The former is a method in which a color image displayed on a liquid crystal display panel is projected by a projection lens, and compared to the latter, there are advantages that the liquid crystal display panel can be made smaller and lighter and the manufacturing cost can be significantly reduced.

In the former method, a color filter is arranged in a liquid crystal layer, and the color filter is disclosed in, for example, Japanese Patent Application Laid-Open No. 49-74438 (Japanese Patent Publication No. 54-18886). There is known a so-called color filter external mounting method, in which is disposed on the outer surface side of one glass substrate of the liquid crystal display panel.

[0007]

However, in the above-mentioned active matrix driving method, in order to supply an independent driving voltage to each picture element, a switching element such as a thin film transistor or MIM is provided in each picture element, and the switching is performed. Bus lines (gate bus lines and source bus lines) that supply drive signals to the elements must be wired between the picture elements. Therefore, the ratio (aperture ratio) of the picture element area in the screen of the liquid crystal display panel becomes small, and there are the following drawbacks.

Of the illumination light emitted from the light source to the liquid crystal display panel, the light incident on the area other than the picture element area is not modulated by the display signal. Therefore, in a liquid crystal display panel whose display operation mode is a normally black mode (an operation mode in which light is not transmitted when an electric field is not applied to the liquid crystal layer), it contributes to a display incident on a region other than the pixel region. Light that does not pass through the liquid crystal display panel.

On the other hand, in a liquid crystal display panel whose display mode is a normally white mode (an operation mode in which light is transmitted when an electric field is not applied to the liquid crystal layer), light incident on a region other than the pixel region is When is transmitted through the liquid crystal display panel, the black level of the display screen rises and the contrast decreases.

Therefore, in order to prevent the above problems, a structure is provided in which a light-shielding mask is provided in a region other than the picture element region to absorb or reflect light that does not contribute to display to improve display quality. .

However, in order to surely absorb or reflect light which does not contribute to display by such a light-shielding mask, it is necessary to provide the light-shielding mask up to a portion corresponding to the peripheral portion of the picture element (picture element electrode). Therefore, when the light shielding mask is provided, the aperture ratio is further reduced.

Therefore, in both the normally black mode and the normally white mode,
There is a drawback that the screen becomes dark due to the reduction of the aperture ratio. Such a defect occurs in any liquid crystal display panel regardless of whether it is a direct-view type or a projection type.

In order to solve the above-mentioned drawbacks, JP-A-60-165
Japanese Patent Laid-Open No. 621-165624 discloses a method in which a microlens array (microlens array) is provided on the light source side of a liquid crystal display panel, and illumination light is focused on each pixel region to improve the utilization rate of illumination light. It is disclosed. However, since the parallelism of the illumination light incident on the liquid crystal display panel is limited, the light passing through the microlens is not focused only on the corresponding picture element, but a part thereof is incident on the adjacent picture element.

Therefore, for example, JP-A-49-74438 and JP-A-
When a microlens is applied to a projection type color image display device of a color filter external type as disclosed in Japanese Patent Laid-Open No. 3-51882, this causes color misregistration.

The present invention solves the above-mentioned drawbacks of the prior art, and an object thereof is to provide a projection type color image display device having a bright display screen and no color shift.

[0016]

A projection type color image display device of the present invention is a transmissive device in which a display medium is enclosed between a light source and a pair of transparent substrates, and display picture elements are arranged in a matrix. Type display panel, a microlens provided corresponding to each picture element of the display panel, and a color arranged so as to correspond to each picture element of the display panel and having a predetermined transmission spectrum In a projection type color image display device provided with a filter and a projection lens for projecting an image displayed on the display panel onto a screen, the numerical aperture a of the projection lens and the numerical aperture b of the macro lens are approximately They are matched, which achieves the above objectives.

Preferably, the numerical aperture a of the projection lens is
And the numerical aperture b of the macro lens is 0.8 * b ≦
Set a ≦ 1.2 * b.

[0018]

According to the above construction, the light of the substantially parallel components incident on the microlens array (microlens) is first converged by the convex lens portion of the microlens provided on the light source side of the transparent substrate, and the image of the display panel is displayed. After entering the elementary region and being modulated according to the image signal, it spreads within a cone of an angle determined by the numerical aperture (Na) of the microlens.

Further, when light having a component with poor parallelism is incident on the microlens, a component of light which is incident not on the corresponding picture element but on the adjacent picture element is generated, and a color filter is formed outside the display panel. If so, this causes color misregistration. However, after passing through the display panel, this light spreads outside the light (parallel component light) that has passed through the picture elements corresponding to the respective microlenses in the vicinity of the pupil of the projection lens.

Here, the numerical aperture (Na) a of the projection lens
And the numerical aperture (Na) b of the microlens is 0.8 *
When the relationship of b ≦ a ≦ 1.2 * b is set, the aperture of the projection lens is selected so that the former light passes and the latter light is cut for the reason described later. Therefore, by setting such a relationship, it is possible to prevent color misregistration while maintaining the effect of the microlens.

[0021]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows the construction of the projection type color image device of the present invention. The illumination light emitted from the light source 4 is converted into a parallel light flux by the condenser lens 6 and applied to the liquid crystal display panel 1. The light transmitted through the liquid crystal display panel 1 is magnified by the projection lens 7 and projected on the screen 8. As a result, the image or character on the liquid crystal display panel 1 is displayed on the screen 8.

The light source 4 is a white light source, and a halogen lamp, a metal halide lamp, a xenon lamp or the like is used. At a position opposite to the condenser lens 6 of the light source 4, a reflecting mirror 5 for reflecting the light emitted from the light source 4 to the opposite side toward the liquid crystal display panel 1 is arranged.

The liquid crystal display panel 1 is a pair of glass substrates 1
Liquid crystal as a display medium is enclosed between a and 1a, the diagonal line of the display screen is 75 mm, and the pixel pitch is 190 μ in the vertical direction.
m, horizontal 161 μm. In addition, the pixel area is 88 μm long,
The width is 104 μm. Furthermore, the aperture ratio is 30%, the refractive index n of the substrate is n = 1.53, and the thickness of the substrate is 1.1 mm.

In the liquid crystal display panel 1 of the present embodiment, the operation mode of the liquid crystal is twisted nematic, but other modes can be used. In many liquid crystal operation modes, it is necessary to use a polarizing plate together. The polarizing plate can be directly attached to the liquid crystal display panel 1, but when a high-luminance light source such as a metal halide lamp is used, the temperature rise due to light absorption of the polarizing plate affects the operating characteristics of the liquid crystal. It is better not to directly bond the liquid crystal display panel 1. Further, the position where the polarizing plate is installed may be anywhere as long as there is no one that changes the polarization characteristic with the liquid crystal display panel 1. For example, the microlens 2 described below may be inserted between the liquid crystal display panel 1 and the polarizing plate.

A microlens 2 having a convex lens effect is provided on the light source 4 side of the liquid crystal display panel 1. The pitch of the microlens 2 corresponds to the pixel pitch of the liquid crystal display panel 1, its aperture is 160 μm, and its focal length is equal to the thickness of the glass substrate 1a of the liquid crystal display panel 1 (1.1 in air). /1.53 ∇ 0.72 mm.). Therefore, the numerical aperture (Na) of the microlens 2 is 80/72.
0 = 1/9. The microlenses 2 are associated with the positions of the picture elements on the liquid crystal display panel 1 and are bonded together with a transparent adhesive.

On the surface of the microlens 2 on the liquid crystal display panel 1 side, color filters 3R, 3G and 3B of three primary colors of R, G and B are formed corresponding to the picture elements. A pigment color filter, an interference color filter, or the like is used as these color filters 3R, 3G, and 3B.

The illumination light, which has been converted into a parallel light flux by the condenser lens 6 as described above, is converged by the microlens 2 as shown in FIG. 1, and the color filters 3R, 3G, 3B formed on the surface of the microlens 2 are converged. Also, the light is transmitted through the pixel region 1b of the liquid crystal display panel 1, is subjected to intensity modulation according to the image signal voltage applied to the liquid crystal layer, and is projected on the screen 8 by the projection lens 7. In addition, 1c has shown the light shielding area.

Of the light incident on the liquid crystal panel 1, the light with good parallelism passes through each microlens 2 and then passes through the center of each microlens 2 toward the center of the optical axis of the projection lens 7. It spreads in a conical shape within the angle of tan θ = ± 1/9 toward the projection lens 7. Here, when the distance between the liquid crystal display panel 1 and the projection lens 7 is L, the distance L is represented by the following formula by the focal length f _c of the projection lens 7 and the projection magnification m.

[0030] _{L = f c * (1 +} 1 / m) ... Therefore, the above equation, the focal length f _c of the projection lens 7 and 150 mm, when the projection magnification m and 5 to 30, L =
It becomes 155-180 mm. When L = 180 mm, the light transmitted through the liquid crystal display panel 1 has the above tan θ = ± 1.
Due to the relationship of / 9, the projection lens 7 spreads within a circle having a radius of 20 mm at the position.

On the other hand, of the light with poor parallelism, the light components indicated by the dotted lines in FIG. 2 are incident on the adjacent picture elements, not on the corresponding picture elements, so that the radius is near the pupil of the projection lens 7. Spread outside the 20 mm circle.

FIG. 3 shows changes in the microlens effect when the diameter of the projection lens 7 is changed. However, the vertical axis represents the microlens effect (times), and the horizontal axis represents the aperture (mm) of the projection lens 7. Further, FIG. 4 shows a change in chromaticity when the aperture of the projection lens 7 is changed, together with a chromaticity diagram introduced by the International Commission on Illumination (CIE). However, R, G, and B are NTSC (National
Television System Committee
The reference chromaticity of e) is shown. Further, the illustrated example shows changes in chromaticity when the apertures of the projection lens 7 are set to 60 mm, 54 mm, and 48 mm.

First, according to FIG. 3, in order to maintain the microlens effect to more than double, the aperture a of the projection lens 7 is set to 32.
It is necessary to set it to mm or more. Further, in order to improve the color reproduction range from FIG. 4, the aperture a of the projection lens 7 is set to 48
It is necessary to set it to mm or less. Further, at this time, the color filters 3R, 3G, 3B need to have a predetermined transmission spectrum in the chromaticity diagram shown in FIG.

From the above reason, it is understood that the aperture a of the projection lens should be set to about 32 mm ≦ a ≦ 48 mm in order to improve the color reproduction range while maintaining the effect of the microlens 2.

In order to prevent the occurrence of color misregistration,
It suffices that the projection lens 7 can transmit light having a parallel component of the aperture a and cut non-parallel light. Therefore,
For that purpose, the diameter a of the projection lens a = 32 to 48 mm,
The numerical aperture of the microlens 2 is 1/9, the interval L = 180 mm
Under the above condition, it suffices that the end portion of the non-parallel light component on the projection lens 7 side indicated by the broken line in FIG. 5 passes through a position deviating from the aperture of the projection lens 7. For that purpose, the center of the parallel component and the center of the non-parallel component may be shifted by 40 mm near the pupil of the projection lens. This shift amount of 40 mm is
It is a value defined by the numerical aperture (Na) of the microlens 2.

Therefore, the aperture a of the projection lens 7 satisfying the above conditions, that is, the numerical aperture (Na) a and the microlens 2 are used.
Considering the relationship with the numerical aperture (Na) b of
= 0.8 and 48 ÷ 40 = 1.2, it can be seen that both need only satisfy the relationship shown in the following equation.

0.8 * b.ltoreq.a.ltoreq.1.2 * b ... When the numerical aperture (Na) a of the projection lens is larger than this range, color misregistration occurs, and when it is smaller, the effect of the microlens decreases, The screen becomes dark. For the above reasons, in order to make the screen bright and to prevent color misregistration,
It suffices that the numerical aperture (Na) a of the projection lens 7 and the numerical aperture (Na) b of the microlens 2 are substantially the same, and preferably the relationship of the above expression is satisfied.

In this embodiment, the case of Koehler illumination is shown, but other illumination methods such as critical illumination and telecentric illumination can be applied.

Further, in this embodiment, the color filter 3 is used.
Although R, 3G, and 3B are arranged on the light source side of the liquid crystal display panel 1, they may be arranged on the screen 8 side as shown in FIG.

The formation of the microlens array in each of the above embodiments can be carried out by the following method.

(1) A method of machining plastic or glass by machining or molding.

In addition to the direct processing of the mold, a mold formed by the methods (2) to (5) and (7) described below is used as a prototype and transferred by a method such as electrocasting. Good.

(2) A method of forming a convex lens by utilizing the phenomenon that when a certain kind of photosensitive resin is exposed in a pattern, unreacted monomer moves from the non-exposed area to the exposed area and the exposed area rises. .

This method is described in the Journal of Applied Physics, Opinion on Micro Optics Research Group, vol. 5 No. Two
p118 (1987), ibid. 6 NO. 2 p
87 (1988).

(3) The thermoplastic resin is patterned into a plane shape of the lens by a known photography technique or the like,
After that, it is heated to a temperature above the softening point to have fluidity,
A method of obtaining a convex lens by causing edge sag.

In this case, if the thermoplastic resin is photosensitive, it can be patterned by exposing itself.

This method is described in JP-A-60-38989, JP-A-60-165623 and JP-A-61-67003.

(4) The photosensitive resin is subjected to proximity exposure (a method of exposing without exposing the photomask) to give a distribution of the amount of the photoreaction product according to the blur of the edge of the pattern, and to form a convex lens. How to get the shape.

This method is described in JP-A-61-153602.

(5) A method of irradiating the photosensitive resin with light having an intensity distribution to form a pattern of a refractive index distribution according to the intensity of the light so as to have a lens effect.

This method is described in JP-A-60-72927. A material whose refractive index changes by light irradiation is described in JP-A-60-166946.

(6) A method of obtaining a gradient index lens by selective ion diffusion.

This is a mask pattern in which a mother glass plate is immersed in a molten salt, and different kinds of ions such as alkali ions are exchanged between the glass plate and the molten salt through a mask provided on the glass plate. It is a method of obtaining a glass plate having a refractive index distribution corresponding to, Electronics Letters vol.
17 No. 13 p452 (1981).

When a microlens is formed by this method, the outer shape of the lens has no unevenness, so that it can be attached to a liquid crystal display panel using Canada balsam or a photocurable resin without an air layer. The reflection loss on the substrate surface can be reduced to a negligible level.

(7) A method of obtaining a convex lens by utilizing contraction due to crystallization caused by light irradiation on the photosensitive glass.

This method is based on Applied Optics Vol.24 No.1
6p2520 (1985), the principle of which is as follows. When light is radiated on glass to which photosensitivity is given by a silver salt, silver is released and a latent image of crystal nuclei is formed. When this is heated, the glass crystallizes around the crystal nuclei and the volume shrinks. When light is patterned and applied, the light-irradiated portion contracts, but the non-irradiated portion does not contract, so that the light-irradiated portion is relatively left behind and rises, and becomes a convex lens shape due to surface tension.

[0057]

In the projection type color image display device of the present invention described above, the numerical aperture (Na) a of the projection lens and the numerical aperture (Na) b of the microlens are substantially the same, preferably 0.8 * b≤.
Since it is set so as to satisfy the relationship of a ≦ 1.2 * b, it is possible to cut the component having poor parallelism with the projection lens without reducing the effect of the microlens provided on the light source side of the display panel. You can Therefore, it is possible to realize an image display device in which a bright screen is obtained and there is no color misregistration in the single-panel system in which a color filter is externally attached. Therefore, it can be expected to be applied to large-screen projection TV systems and information display systems.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a projection type color image display device of the present invention.

FIG. 2 is an enlarged view of the liquid crystal display panel of FIG.

FIG. 3 is a graph showing measurement results of changes in the microlens effect when the aperture of the projection lens is changed.

FIG. 4 is a graph showing the measurement results of chromaticity shift when the aperture of the projection lens is changed, together with a chromaticity diagram introduced by the International Commission on Illumination (CIE).

FIG. 5 is an explanatory view of the principle of the present invention.

FIG. 6 is a view showing another embodiment of the present invention.

[Explanation of symbols]

1 Liquid crystal display panel 1a, 1a glass substrate 1b Picture element area 1c shade area 2 micro lens 3R R color filter 3G G color filter 3B B color filter 4 light sources 5 reflector 6 condenser lens 7 Projection lens 8 screen

Claims (2)

[Claims] 1. A transmissive display panel in which a display medium is enclosed between a light source and a pair of transparent substrates, and display picture elements are arranged in a matrix, and an individual picture element of the display panel. A microlens provided correspondingly, a color filter arranged so as to correspond to each picture element of the display panel and having a predetermined transmission spectrum, and an image displayed on the display panel on a screen. In a projection type color image display device provided with a projection lens for projecting, a numerical aperture a of the projection lens and a numerical aperture b of the macro lens
A projection type color image display device in which and are substantially matched. 2. The relationship between the numerical aperture a of the projection lens and the numerical aperture b of the macro lens is 0.8 * b ≦ a ≦ 1.2 * b.
The projection type color image display device according to claim 1, wherein