JPH04107528A - Display device - Google Patents

Abstract

PURPOSE:To make a wide-area display by using a cell which provides optical switch operation and arranging SELFOC lens array between the cell and a light source. CONSTITUTION:The SELFOC lens array 7 is arranged between the light source 6 and cell 1 and scattered light, radiant light, etc., emitted by the light source 6 is changed into a parallel light beam state by the SELFOC lens array 7 and made incident on an incidence-side substrate 2. Therefore, the parallel light beam can be made incident on the entire surface of the display cell (element) at a constant incidence angle. Consequently, this device is effective to a display device which creates two states wherein the incident light is reflected totally and transmitted by the display element which has large area exceeding a certain level like a display and uses them for display operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to display devices used in watches, personal computers, word processors, flat-screen televisions, and the like.

[Prior Art] Display devices used in watches, personal computers, word processors, flat-screen televisions, etc. usually perform display operations by changing the arrangement state of liquid crystals by applying an electric field and changing their optical properties. There is.

Typical operating methods for realizing such a display operation include a TN type in which a nematic liquid crystal is twisted by 90 degrees, a birefringence control type, and an STN type in which the twist angle is set to 90 degrees or more. However, all of these methods require the use of two polarizing plates placed on both sides of the cell. Due to the nature of this polarizing plate, which converts unpolarized light into linearly polarized light, it blocks at least 50% of the incident light, resulting in a decrease in brightness. Since light passes through, it is impossible to create a completely dark state, and the contrast is not satisfactory.

In addition, some operating methods that do not use a polarizing plate have been proposed, such as a guest-host type and a light scattering type, but for example, the guest-host type has a slow operating speed, and the light scattering type has a There is also considerable light transmission due to scattered light,
It has drawbacks such as the inability to create a dark state, so it is not widely used as a display element.

On the other hand, as typified by Japanese Patent Publication No. 59-808,
An optical switch has been proposed in which a transparent electrode and a material whose refractive index changes due to the action of an electric field are interposed between two transparent substrates, and the light path is switched by total reflection or partial transmission of light at the interface between the substrate and the material. has been done. This method is characterized by the ability to perform optical switching without using a polarizing plate, and the operating speed is not so slow. The problem was how to display the entire surface by making light incident on the entire surface of the interface at a constant angle of incidence.

[Problems to be Solved by the Invention] In view of the above-mentioned points, the present invention aims to eliminate all of the light at the interface between the substrate and the material in order to prevent contrast reduction caused by the polarizing plate, which has been a problem in conventional display elements. In applying the principle of an optical switch that reflects or partially transmits light to a display element such as a display, we aim to provide a display device that allows parallel light to be incident on the entire surface of a display cell (element) at a constant angle of incidence. be.

[Means for Solving the Problems] In order to achieve the above object, the present invention requires the following configuration.

That is, the display device of the present invention is a display device using a cell having an optical switching function in which an optical path is switched at the interface between a transparent substrate and a material portion whose refractive index changes by changing an electric field. This is a display device characterized by disposing a SELFOC lens array between it and a light source.

Further, in the display element according to the present invention described above, the display device preferably uses a SELFOC lens array having an aperture angle of 15 degrees or less.

[Effect] The present invention will be explained in detail below.

The display device of the present invention allows light to be incident on a display cell consisting of a transparent substrate and a material whose refractive index changes by changing the action of an electric field, and by changing the electric field, Two states are created at the interface with the side substrate, in which incident light is totally reflected or transmitted, and these states are applied to display operations. The present invention is particularly characterized in that a SELFOC lens array is installed between the cell and the light source in order to convert the incident light into substantially parallel light when performing such a display operation.

In other words, by installing a SELFOC lens array, the above two states, which could conventionally only be achieved in a spot or a small area, can be achieved. This made it possible. This method has the advantage that the entire device is compact, lightweight, and inexpensive, compared to, for example, a method of obtaining parallel rays by combining several lenses.

In the present invention, the SELFOC lens array is an array in which a large number of SELFOC lenses that have a refractive index distribution in the radial direction and self-converge light are arranged in a strip or flat plate shape, or several rows of such flat arrays are stacked. The SELFOC lens array used in copying machines can basically be used as is.

In order to cause total reflection and transmission of light in a certain area according to the display operation principle of the present invention described above, it is necessary that the light that reaches the liquid crystal molecules be incident in a substantially parallel state. For this purpose, the smaller the aperture angle of the SELFOC lenses used in the SELFOC lens array, the better. Therefore, the SELFOC lens array used in the present invention usually preferably has an aperture angle of 15 degrees or less, more preferably 10 degrees or less.

On the other hand, if the aperture angle is too small, there may be a problem that the brightness decreases, so it is preferable to use an aperture angle of 3 degrees or more, more preferably 5 degrees or more.

The SELFOC lens array of the present invention basically does not function to transfer figures or characters to a specified location, as is the case with copying machines, so the array length and depth of focus must be determined with particular precision. It is not necessary, and the width of the SELFOC lens array may be appropriately determined according to the width of the cell used. Also, the thickness of the input side substrate,
The number of stacked SELFOC lenses may be determined in accordance with the display area of the cell used, and the structure may be designed so that incident light from the side surface of the substrate reaches the entire display surface.

An example of one aspect of the display device of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic model diagram viewed from the side, and FIG. 2 is a schematic model diagram of the display device of the present invention shown in FIG. 1 viewed from the top.

Although the transparent electrodes and alignment films are omitted and not shown in these figures, the cell l has a transparent It has a structure in which a material part 4 whose refractive index changes due to the action of an electrode and an electric field is interposed, and a phosphor 5 for displaying is provided on the outer surface of the emission side substrate 3. A indicates the interface between the material portion 4 and the incident-side substrate 2 whose refractive index changes due to the action of an electric field, and B indicates the direction of incidence of light onto the incident-side substrate. Reference numeral 6 denotes a light source, and in the present invention, a SELFOC lens array 7 is arranged between the light source 6 and the cell 1. Scattered light and radial light emitted from the light source 6 is emitted from the SELFOC lens array 7. Due to the action of the lens array 7, the light is changed into a parallel light beam and enters the incident side substrate 2.

That is, according to the present invention, it is possible to cause parallel light rays to be incident on the entire surface of a display cell (element) at a constant angle of incidence. This is very effective for display devices used for display operations by creating two states, one in which the incident light is totally reflected and the other in which it is transmitted.

In the present invention, a material whose refractive index changes due to the action of an electric field refers to a material that is isotropic in itself and whose refractive index changes due to the electric field, or a material that has birefringence and cannot be used when an electric field is applied. , the arrangement state changes, and the apparent refractive index in the direction of light propagation changes. For example, a typical example of the former is a nonlinear material, and a representative example of the latter is a liquid crystal. Liquid crystals are preferable from the viewpoint of large change in refractive index, and liquid crystals normally used in displays such as TN type and STN type can be preferably used.

In the present invention, since the material constituting the substrate needs to transmit light, it is desirable that the material has excellent transparency. Specifically, various glasses such as quartz glass, Pyrex glass, and lead glass, and various plastics such as polymethyl methacrylate, polycarbonate, polystyrene, polyethylene terephthalate, polyvinyl chloride, and acrylonitrile-styrene copolymer can be used.

These materials can be processed by cutting,
It may also be produced by molding or the like. In addition, in the present invention, as described above, it is necessary to cause both total reflection and transmission phenomena at the interface between the substrate and the material whose refractive index in the direction of light propagation changes due to the action of the electric field described above. For this purpose, it is preferable that the refractive index of the substrate on the incident side be sandwiched between the upper and lower birefringence values of the material. Therefore, it is preferable to decide it appropriately in consideration of the material used. For example, the material has a birefringence value of 1.5 to 1.7.
When using a nematic liquid crystal in the vicinity, the refractive index of the substrate is preferably between 1.5 and 1.7;
．． More preferably, it is between 6 and 1.7. Refractive index 1.6-1.
Glass such as lead glass is preferred from the viewpoint of having a high refractive index of about 7 and ease of polishing to increase transparency, but plastic is preferred from the viewpoint of ease of molding and cost. Further, it is more preferable that the substrate itself has no birefringence.

On the other hand, the transparent substrate on the output side becomes a passage for light transmitted through the interface between the input side substrate and the material. Therefore, in order to increase the transmitted light index, the refractive index is preferably equal to or higher than the refractive index on the incident side.

The configuration of the display cell in the display device of the present invention can be the same as that of a conventional display cell, except that a polarizing plate is not used. That is, two transparent substrates (upper and lower) are sandwiched between them, transparent electrodes such as ITO are placed on opposing surfaces, and the above-mentioned materials are placed inside the electrodes. At this time, in order to control the alignment of the material, it is preferred to provide an alignment film between the transparent electrode and the material.

Various alignment films are used depending on the orientation determined by the type of material, and are usually made of organic materials such as polyimide or lecithin, or metals such as silicon oxide, gold, or platinum, which are applied to the substrate by coating or vapor deposition. Ru. It is also a preferable method to rub these alignment films with a raised fabric such as nylon or rayon to improve the alignment of the material.

The light source in the present invention is not particularly limited as long as light can be incident on the entire cross-section of the SELFOC lens array, and various types such as a point light source and a line light source can be used. The brighter the light source, the better, and in addition to general-purpose white light lamps, halogen lamps, metal halide lamps, etc. are used. A line light source is more preferable because the size of the entire display device can be made compact and the light can be incident on the SELFOC lens array without reducing the amount of light. Of course, it is equally acceptable to install a reflecting mirror behind the light source so as not to reduce the amount of light reaching the SELFOC lens array.

[Example code] Hereinafter, the present invention will be explained in detail using Examples.

Example Measures 5 cm long, 5 cm wide, and 10 mm thick, and has a refractive index of 1.
An incident-side substrate was prepared by processing a No. 62 transparent lead glass plate and cutting one end of the glass plate at an angle of 70 degrees as shown in FIG. 1 when viewed from the side. In addition, the output side substrate was made of lead glass, but it was 5 cm long, 5 cm wide, and 1.1 cm thick.
A transparent substrate with a refractive index of 1.70 at n+m was prepared.

Next, transparent electrodes of ITO were provided in stripes by vapor deposition on the 5 cm x 5 cm flat side of the input side substrate and on one side of the flat side of the output side substrate. In addition, a thin layer of fluorescent powder was attached to the other plane of the output side substrate in order to scatter the transmitted light to the outside.

Next, an alignment film was applied to the surface of the glass substrate provided with the transparent electrode, and the alignment film was rubbed with a nylon nap fabric. At this time, Semico Fine (IIT-21OA) manufactured by Toshi ■ was used as the alignment film processed on the transparent electrode substrate, and the rubbing conditions were as follows: the number of rotations of the roller was 70
rpm, roller diameter 50mmφ, stage speed 15mm
/se5 Rubbing was performed at a depth of 0°5 mm. Further, as for the rubbing direction, one sheet was rubbed in the same direction as the stripe direction of the transparent electrode, and one sheet was rubbed in the direction perpendicular to the stripe direction of the transparent electrode.

Next, using two glass substrates treated as described above, they were sealed so that the rubbing directions were antiparallel and the transparent electrode stripes were arranged orthogonally at the same time.
A liquid crystal cell was fabricated by injecting LI-2471 liquid crystal.

Next, as shown in FIG. 1, a self-cleaning lens array (SLA-9, TC) manufactured by Nippon Sheet Glass was used to allow light to enter the cell from the cut side surface of the input side substrate.
54 (numerical aperture 9 degrees, 2-row arrangement, lens width 15 cm)
were placed between the cell and the light source with a gap of 5 mm each, and the light was incident on the cell through the array. At this time, the light source used was a Pacha fluorescent lamp FL6AD70 manufactured by NEC Corporation, and the light from the light source entered the cross section of the SELFOC lens perpendicularly, and the light that passed through the SELFOC lens array was cut at 70 degrees. The light was also made to be incident almost perpendicularly to the side surface of the incident side substrate.

The cells were wired in a conventional manner to provide a multiplex drive system.

When the above cell was driven, at the point where the electric field was applied, the liquid crystal molecules were oriented perpendicular to the substrate, so the incident light passed through the liquid crystal layer and reached the output side substrate, where it was scattered by the upper phosphor and turned on. Ta. On the other hand, at points where no electric field was applied, the incident light was totally reflected in front of the liquid crystal layer, and no light was transmitted, resulting in an OFF state. This ON/OFF operation was possible over the entire surface of the substrate, and the contrast of the image was clearly superior to that of the conventional TN type using a polarizing plate.

[Advantageous Effects of the Invention] In a display device that uses total reflection and transmission of light without using a polarizing plate, it becomes possible to display a wide area, which was previously difficult.

[Brief explanation of drawings]

FIG. 1 is a schematic model diagram of one embodiment of the display device of the present invention, viewed from the side. FIG. 2 is a schematic model diagram of one embodiment of the display device of the present invention shown in FIG. 1, viewed from above. In these figures, transparent electrodes and alignment films are omitted. 1: Cell 2: Incoming side substrate 3: Outgoing side substrate 4: Material whose refractive index changes due to the action of an electric field 5: Phosphor 6: Light source 7: Selfoc lens array A: Material whose refractive index changes due to the action of an electric field and the incident Interface B with the side substrate: Direction of incidence of light on the incident side substrate

Claims (2)

[Claims] (1) In a display device using a cell that has an optical switching function in which the optical path is switched at the interface between a transparent substrate and a material whose refractive index changes by changing an electric field, there is a cell between the cell and the light source. A display device comprising a Fock lens array. (2) The display device according to claim (1), wherein the SELFOC lens array has an aperture angle of 15 degrees or less.