JPH07318918A - Dispersion type display device and prism film - Google Patents

Abstract

PURPOSE:To obtain a dispersion type display device high in contrast which uses a scattering mode by disposing a transparent prism film layer and a low refractive index layer between an electro-optical material layer and a light- absorbing layer. CONSTITUTION:A prism film 3 is disposed between an electro-optical material layer 1 and a light-absorbing layer 2. An air layer being a low refractive index layer 4 is disposed between the prism film 3 and the light-absorbing layer 2. The electro-optical material layer 1 consists of a pair of substrates 1 having transparent electrodes formed on the surfaces and a liquid crystal material disposed between the substrates 11. Each transparent electrode 12 is connected to a power supply 16 with a switch 15 so that voltage can properly be applied. The prism film 3 consists of a polycarbonate film. Also pyramids with 90 deg. apex are formed with 30mum pitch on the surface of the electro-optical material layer 1 side, and the surface of the low refractive index layer 4 side is made to be a smooth surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prism film for converting an optical path and a dispersion type display device using the prism film.

[0002]

2. Description of the Related Art The basic structure of a dispersion type display device utilizing a scattering mode comprises an electro-optical material layer whose light scattering state and light transmitting state are controlled by the presence or absence of voltage application, and a light absorbing layer.

This display principle will be described with reference to the drawings. Figure 7
A cross-sectional view of a dispersion type display device using a scattering mode which has been conventionally used is shown in FIG. In FIG. 7, 1 is an electro-optical material layer, 2
7A shows a light absorption layer, FIG. 7A shows a light transmission state with a voltage applied, and FIG. 7B shows a light scattering state without a voltage applied. In the state where the voltage is applied, as shown in FIG. 7A, ambient light coming from above is transmitted through the electro-optical material layer 1 as it is and is absorbed by the light absorption layer 2 arranged on the back surface. It is displayed in black. On the other hand, in the state where no voltage is applied, as shown in FIG. 7B, most of the ambient light coming from above is scattered by the electro-optical material layer 1 to give a milky white display. . The black display and the milky white display are appropriately combined to provide an arbitrary display. As described above, a large number of dispersion type display devices using the scattering mode have been proposed in the past because of their simple structure.

[0004]

However, in the conventional dispersion type display device utilizing the scattering mode, as shown in FIG.
As indicated by the broken line in FIG. 5, a part of the light passes through the electro-optical material layer 1 and reaches the light absorption layer 2 as stray light even when no voltage is applied. Therefore, the stray light does not contribute to the milky white display, the contrast, which is the brightness ratio between the scattered state and the transmissive state, is as low as about 5, and it is not possible to obtain a high-quality display quality with clear contrast. Further, no member having an optical function for improving this state has been proposed.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a dispersion type display device using a scattering mode and having a high contrast, and an optimum prism film for achieving this object. To aim.

[0006]

According to a first aspect of the present invention, there is provided an electro-optical material layer in which visible light is electrically controlled in a scattering state and a transmitting state, and a light absorbing layer in which visible light is absorbed. Are opposed to each other, and between the electro-optical material layer and the light absorption layer, a transparent prism film having a large number of convex portions or concave portions formed on the surface facing the electro-optical material layer is arranged. A low-refractive index layer having a refractive index lower than that of the prism film is disposed between the prism film and the light absorbing layer. The invention according to claim 2 is characterized in that the convex portion or the concave portion is a ridge-shaped convex portion or concave portion having a triangular cross section and substantially parallel to each other.
The distributed display device described in 1. The invention according to claim 3 is the dispersion type display device according to claim 1, wherein the convex portion or the concave portion is a polygonal pyramid. Claim 4
The invention according to claim 3 is the distributed display device according to claim 3, wherein the polygonal pyramid is a triangular pyramid, a quadrangular pyramid, or a hexagonal pyramid. The invention according to claim 5 is characterized in that the convex portion or the concave portion has an apex angle in the range of 30 ° to 150 °, and the dispersion type display device according to any one of claims 1 to 4. Is. The apex angle of each polygonal pyramid is the α position in FIG. The invention according to claim 6 is
The formation pitch of the protrusions or recesses is 10 μm to 300
The dispersion type display device according to any one of claims 1 to 5, wherein the dispersion type display device has a range of μm. The invention according to claim 7 is the dispersion type display device according to any one of claims 1 to 6, wherein a liquid crystal material is used for the electro-optical material layer. The invention according to claim 8 is the dispersion type display device according to any one of claims 1 to 7, wherein the low refractive index layer is air.

The invention according to claim 9 is the prism film, wherein a large number of convex portions or concave portions are formed on one surface of the transparent film. The invention according to claim 10 is the prism film according to claim 9, wherein the convex portion or the concave portion is a ridge-shaped convex portion or concave portion having a triangular sectional shape and being substantially parallel. The invention according to claim 11 is the prism film according to claim 9, wherein the convex portion or the concave portion is a polygonal pyramid. The invention according to claim 12 is the prism film according to claim 11, wherein the polygonal pyramid is a triangular pyramid, a quadrangular pyramid, or a hexagonal pyramid. The invention according to claim 13 is the prism film according to any one of claims 9 to 12, wherein the convex portion or the concave portion has an apex angle in a range of 30 ° to 150 °. . The invention according to claim 14 is the prism film according to any one of claims 9 to 13, characterized in that the formation pitch of the projections or recesses is in the range of 10 µm to 300 µm.

[0008]

The above technical means operates as follows. In the dispersion type display device according to claim 1, as shown in FIG. 1, when the electro-optical material layer 1 is in a transmissive state, as shown in FIG. Further, the light absorption layer 2 is directly viewed through the low refractive index layer 4, and black display as in the conventional case can be obtained. On the other hand, when the electro-optical material layer 1 is in a scattered state, as shown in FIG. 1B, among the ambient light, stray light that reaches the light absorption layer 2 in the conventional case and does not contribute to the scattering is generated. The prism film 3 and the low refractive index layer 4 are returned to the electro-optical material layer 1 and scattered. Therefore, an observer from the direction of arrow A can see a brighter milky white display with an increased scattering intensity as compared with the conventional case. This is because the low refractive index layer 4 having a low refractive index is disposed on the light absorption layer side of the prism film 3, so that the stray light incident on the low refractive index layer 4 at a low angle is totally reflected and the electro-optical material layer. This is because it is set back to 1. Note that when the electro-optical material layer 1 is in the transmissive state, light from the side may come out to the display surface side where the observer is, but since it comes out from the display surface at a low angle, it is observed from almost the front. Since it does not reach the eyes of the observer, the black display is not affected at all.

According to the dispersion type display device of the second aspect, in the dispersion type display device of the first aspect, the ambient light from a certain side can be effectively utilized. Therefore, the present invention works effectively in a distributed display device that observes while illuminating from a fixed direction such as a ceiling. According to the dispersion type display device of the third aspect, in the dispersion type display device of the first aspect, in particular, ambient light from each side direction can be effectively utilized.
Therefore, a brighter milky white display can be obtained even in a bright environment. According to a fourth aspect of the present invention, in the dispersion type display device according to the third aspect, a convex portion or a concave portion of a polygonal pyramid whose bottom surface is a regular triangle, a regular square or a regular hexagon is formed on the entire surface of the prism film. Can be formed, and ambient light can be more fully utilized. 2A, 2B and 2C are schematic plan views of the prism film of the present invention, in which the base of the polygonal pyramid is shown by a solid line and the ridge is shown by a broken line. According to the dispersion type display device described in claim 5, in the dispersion type display device according to any one of claims 1 to 4, in particular, ambient light can be effectively utilized for milky white display. According to a sixth aspect of the present invention, in the dispersion type display device according to any one of the first to fifth aspects, in particular, when the electro-optical material layer is in a scattering state, a conventional absorption film is used. Ambient light that reaches can be reliably and effectively returned to the electro-optical material layer, and the convex portions or concave portions of the prism film are not visually recognized. The dispersion-type display device according to claim 7 is the dispersion-type display device according to any one of claims 1 to 6, wherein a liquid crystal material is used particularly in the electro-optical material layer. It is possible to obtain a dispersion type display device utilizing the scattering mode, and it is possible to switch between the transmission state and the scattering state with low voltage and power saving. Also, since the liquid crystal material is flexible,
It is also possible to fill the space between resin films provided with a transparent electrode on the surface and use it after various deformations. An eighth aspect of the present invention is the dispersion type display device according to the first to seventh aspects, wherein the low refractive index layer is formed of air. Therefore, the effects of the first to seventh aspects can be obtained without using a special member as the low refractive index layer.

When the prism film according to any one of claims 9 to 14 is applied to the dispersion type display device, the dispersion type display device according to each of claims 1 to 6 can be realized.

[0011]

EXAMPLES The present invention will be described in detail below with reference to examples, but it goes without saying that the present invention is not limited to these examples. (Embodiment 1) An embodiment of the present invention will be described with reference to FIG. In the dispersion type display device of the first embodiment, the prism film 3 is arranged between the electro-optical material layer 1 and the light absorption layer 2, and between the prism film 3 and the light absorption layer 2,
An air layer is sandwiched as the low refractive index layer 4. The electro-optic material layer 1 has ITO (indium tin oxide) on the surface.
Between the pair of base materials 11 on which the transparent electrodes 12 made of
A cholesteric liquid crystal material containing about 3% of a chiral agent is sandwiched, the plate thickness is 1.1 mm, and the substrate 11
Was set to 12 μm. A power supply 16 is connected to each transparent electrode 12 via a switch 15 so that an appropriate voltage can be applied. In the dispersion type display device of this embodiment, a liquid crystal material is used as the electro-optical material layer 1,
An alignment film for controlling the alignment direction of the liquid crystal material is not required on the surface of the base material. The prism film 3 has a thickness of 100 μm
In the above polycarbonate film, quadrangular pyramids having an apex angle of 90 ° are formed at a pitch of 30 μm on the surface on the electro-optical material layer 1 side, and the low refractive index layer 4 side has a smooth surface. The light absorption layer 2 is a black vinyl chloride plate having a thickness of 1 mm. The low refractive index layer 4 is a layer of air having a thickness of about 0.5 mm. Between the prism film 3 and the light absorption layer 2,
An appropriate spacer is arranged so that the light absorption layer 2 does not directly contact the prism film 3.

In this embodiment, when the switch 15 is closed and a voltage is applied to the liquid crystal material as shown in FIG. 1A, the liquid crystal material is regularly arranged in one direction according to the applied voltage, and as a whole. The layer becomes an optically homogeneous layer, and the incident light is transmitted and goes straight, resulting in a black display. On the other hand, when the switch 15 is opened as shown in FIG. 1B, the liquid crystal material is in an irregular state, and the incident light is scattered in the liquid crystal material to display a milky white display. At this time, a part of the scattered light passes through the electro-optical material layer 1, but is totally reflected at the interface between the prism film 3 and the low refractive index layer 4 and again enters the electro-optical material layer 1 to be scattered again, and Since it comes out as scattered light to the side, it contributes to milk whitening.

This distributed display device is arranged horizontally, illuminated uniformly from the surroundings, and when no voltage is applied (milky white display).
The contrast, which is the ratio of the brightness when a voltage of volt was applied (black display) was measured, and is shown by the solid line in FIG. Figure 4
The vertical axis represents the contrast, and the horizontal axis represents the tilt angle (viewing angle) in the left direction (-direction) and the right direction (+ direction) from the normal line set on the display surface of the dispersion type display device. The higher the value, the larger the difference between the lightness and darkness of the display surface, indicating that the display is sharp and of high quality. In FIG. 4, for comparison, a broken line shows a similar relationship in a dispersion type display device having a conventional structure in which the prism film 3 and the low refractive index layer 4 are not used, and the other structures are exactly the same. .

From FIG. 4, the contrast in the normal direction is 1: 5 in the conventional structure, whereas it is 1: in this embodiment.
A high contrast of about 7 was obtained. The material of the prism film 3 applicable to the present embodiment is not limited to polycarbonate, and may be, for example, polyethylene terephthalate (PET) or polymethylmethacrylate (PMM).
Similar effects were obtained with A) and the like. Furthermore, the film thickness of the prism film 3 need not be limited to 100 μm, but if the film thickness is less than 50 μm, the strength and rigidity of the film itself will be insufficient, and the production yield will be significantly reduced, and the handling will be very difficult. Become complicated. On the other hand, the film thickness is 500μ
If it exceeds m, the light absorption of the film itself cannot be ignored. Although a glass base material is used in this embodiment, the base material to which the present invention is applicable is not limited to this, and a PE base material is used.
Of course, a transparent resin base material made of T or the like can also be applied, but since it is not necessary to strictly control the base material spacing as in a TN mode or STN mode liquid crystal display device, a flexible resin base material is used. Even if the prism film, the low refractive index layer and the light absorbing layer are deformed into a curved surface, sufficient contrast can be obtained. In addition, although a phase transition type electro-optical material layer was used in this example, a polymer dispersion type in which a liquid crystal material is dispersed in a resin, a microcapsule type in which a liquid crystal material is enclosed in a microcapsule, and a liquid crystal material Even if the electro-optical material layer is a type in which a transparent member is filled in, the same operational effect is exhibited.

(Embodiment 2) Another embodiment of the present invention will be described as a second embodiment. This example is different from Example 1 only in the prism film used. The prism film used in this example is a polycarbonate film having a thickness of 100 μm, in which ridge-shaped protrusions having a vertical angle of 90 ° and a substantially triangular cross section are formed on the surface at a pitch of 30 μm. This prism film was arranged between the electro-optical material layer and the low refractive index layer so that the ridges would run laterally.

The dispersive display device of this example was arranged vertically and illuminated uniformly from the ceiling direction, and the contrast in the normal direction was measured.

As a result, the contrast is 1: 5 in the conventional dispersion type display device as described above, while the contrast is 1: 7 in the dispersion type display device of this embodiment.
was gotten.

(Embodiment 3) Another embodiment of the present invention will be described as a third embodiment. This example is different from Example 1 only in the prism film used. The prism film used in this example is a 100 μm thick polycarbonate film having triangular pyramids or hexagonal pyramids with an apex angle of 90 ° formed at a pitch of 30 μm.

The dispersive display device of this example was placed horizontally, illuminated uniformly from the surroundings, and the contrast in the normal direction was measured.

As a result, the contrast was 1: 5 in the dispersion type display device having the conventional structure, whereas in the dispersion type display device having the prism film of the present embodiment, the convex portion was a triangular pyramid or a hexagonal pyramid. A contrast of 1: 7 was obtained.

(Fourth Embodiment) Another embodiment of the present invention will be described as a fourth embodiment. This example differs from Example 1 only in the apex angle of the convex portion of the prism film. In this example, a prismatic film having apex angles of 30 °, 60 °, 120 ° and 150 ° was used to form a dispersion type display device, which was placed horizontally and uniformly illuminated from the surroundings to obtain contrast in the normal direction. Was measured. Vertical angles of 20 ° and 1 for comparison
A dispersion type display device was constructed using a prism film having an angle of 60 °, and the contrast was measured in the same manner. The measurement result is shown in FIG.

As a result, it was confirmed that high contrast is obtained when the apex angle is in the range of 30 ° to 150 °, but the contrast is lowered when the apex angle is out of this range.

(Fifth Embodiment) Another embodiment of the present invention will be described as a fifth embodiment. This example differs from Example 1 only in the formation pitch of the convex portions of the prism film. In this embodiment, the formation pitch of the convex portions is 10 μm, 100 μm, 20
A dispersion type display device was constructed using prism films of 0 μm and 300 μm, arranged horizontally, and uniformly illuminated from the surroundings, and the contrast in the normal direction was measured. For comparison, the formation pitch of the convex portions is 5 μm and 400 μm,
A dispersion type display device was constructed using a prism film having a thickness of 500 μm, and the contrast was measured in the same manner. The measurement result is shown in FIG.

As a result, it was confirmed that high contrast can be obtained when the pitch of formation of the convex portions is 10 μm or more. On the other hand, the protrusions become large and the formation pitch is 300μ.
When it exceeds m, the convex portion is visually recognized and the display quality is impaired.

The examples of the dispersion type display device having the voltage-driven electro-optical material layer have been described above. However, the electro-optical material layer effective in the present invention is not limited to this, and for example, the scattering state may occur depending on the frequency used. It goes without saying that even an electro-optical material layer that can be switched to a transparent state is effective.

[0026]

In the dispersion type display device utilizing the scattering mode of the present invention, almost all the light effectively contributes to the scattering in the scattering state, so that the contrast between the scattering state and the transmitting state is about 1: 7. High quality display quality with high brightness and clear darkness can be obtained. Further, the prism film of the present invention can be dramatically improved in contrast by being applied to a dispersion type display device utilizing a scattering mode.

When the projections or depressions of the prism film are triangular and substantially parallel ridge-like projections or depressions in cross section, it is particularly effective in a distributed display device such as a ceiling for observing while illuminating from a certain direction. It is possible to improve the contrast.

When the convex portion or the concave portion of the prism film is a polygonal pyramid, it is possible to improve the contrast particularly effectively in a dispersion type display device which is observed in a bright surrounding. At this time, particularly when the polygonal pyramid is a triangular pyramid, a quadrangular pyramid or a hexagonal pyramid, the ambient light can be utilized more completely, and the contrast can be effectively improved. The apex angle of the convex portion or the concave portion is 30 ° to 150
In the range of °, a particularly high contrast can be obtained.
The formation pitch of the protrusions or recesses is 10 μm to 300 μm.
In the range of m, ambient light can be effectively utilized, so that it is possible to realize a dispersion type display device having high contrast and good display quality. When a liquid crystal material is used for the electro-optical material layer, it is possible to easily obtain a dispersion type display device having a high contrast and directly inheriting the characteristics of the liquid crystal display device. When air is used for the low refractive index layer, the above effect can be easily obtained without using a special member as the low refractive index layer.

With the prism film according to the ninth to fourteenth aspects, it is possible to easily realize a dispersion type display device having the above effects.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining one embodiment of a distributed display device of the present invention, (A) shows a transmission state to which a voltage is applied, and (B) shows a scattering state without a voltage applied. FIG.

FIG. 2 is a schematic plan view for explaining an example of the prism film of the present invention, where (A) has a triangular pyramid convex portion, (B) has a quadrangular pyramidal convex portion, and (C) has a hexagonal pyramidal convex portion. In the figure, the solid line indicates the base of the polygonal pyramid and the broken line indicates the ridgeline of the polygonal pyramid.

FIG. 3 is a perspective view for explaining the apex angle of the prism film of the present invention, (A) having a triangular pyramid convex portion, (B) having a quadrangular pyramidal convex portion, and (C) having a hexagonal pyramidal convex portion. It is a figure.

FIG. 4 is a diagram for explaining the relationship between the contrast and the viewing angle in the dispersed display device of the present invention and the conventional example.

FIG. 5 is a diagram illustrating the relationship between the contrast and the apex angle of the convex portion in the dispersion type display device of the present invention.

FIG. 6 is a diagram illustrating the relationship between the contrast and the interval between the convex portions according to the dispersion type display device of the present invention.

FIG. 7 is a schematic cross-sectional view for explaining a conventional distributed display device, in which (A) shows a transmissive state to which a voltage is applied,
(B) is a diagram showing a scattering state in which no voltage is applied.

[Explanation of symbols]

 1 Electro-Optical Material Layer 2 Light Absorption Layer 3 Prism Film 4 Low Refractive Index Layer 11 Base Material 12 Transparent Electrode 15 Switch 16 Power Supply

Claims (14)

[Claims] 1. An electro-optical material layer in which visible light is electrically controlled in a scattering state and a transmissive state is opposed to a light absorbing layer in which visible light is absorbed, and the electro-optical material layer and the A transparent prism film having a large number of convex portions or concave portions formed on the surface facing the electro-optical material layer is arranged between the light absorbing layer and the light absorbing layer, and between the prism film and the light absorbing layer. Is a low-refractive-index layer having a refractive index lower than that of the prism film. 2. The distributed display device according to claim 1, wherein the projections or recesses are ridge-shaped projections or recesses having a triangular cross section and substantially parallel to each other. 3. The distributed display device according to claim 1, wherein the convex portion or the concave portion is a polygonal pyramid. 4. The distributed display device according to claim 3, wherein the polygonal pyramid is a triangular pyramid, a quadrangular pyramid, or a hexagonal pyramid. 5. The apex angle of the convex portion or the concave portion is 30 ° to
The dispersion type display device according to any one of claims 1 to 4, which is in a range of 150 °. 6. The formation pitch of the protrusions or recesses is 1
The dispersion type display device according to any one of claims 1 to 5, wherein the dispersion type display device has a range of 0 µm to 300 µm. 7. A liquid crystal material is used for the electro-optical material layer, according to any one of claims 1 to 6.
The dispersed display device according to any one of 1. 8. The dispersion type display device according to claim 1, wherein the low refractive index layer is air. 9. A prism film having a large number of projections or depressions formed on one surface of a transparent film. 10. The prism film according to claim 9, wherein the protrusions or recesses are ridge-shaped protrusions or recesses having a triangular cross section and substantially parallel to each other. 11. The prism film according to claim 9, wherein the convex portion or the concave portion is a polygonal pyramid. 12. The prism film according to claim 11, wherein the polygonal pyramid is a triangular pyramid, a quadrangular pyramid or a hexagonal pyramid. 13. The prism film according to claim 9, wherein the convex portion or the concave portion has an apex angle in a range of 30 ° to 150 °. 14. The formation pitch of the protrusions or recesses is
The prism film according to any one of claims 9 to 13, wherein the prism film has a range of 10 µm to 300 µm.