JPH0339725A - Display element unit and display method - Google Patents

Abstract

PURPOSE:To make bright display with excellent sharpness by forming the display element unit having an optical path control part in contact with a transparent substrate and a voltage impressing part and forming the optical path control part of a material the refractive index of which changes according to the potential impressed from the voltage impressing part. CONSTITUTION:Polyviny chloride having 1.55 refractive index is used as the transparent substrate 1 and the optical path control part 2 for which (4- cyanophenyl)-4'-n heptyl cyclohexane incorporated with the fine powder of titanium oxide is used is formed on this substrate 1. Transparent segment electrodes are formed atop the control part 2 and a common electrode is formed on the rear surface of the substrate 1 as the segment electrode constitution for displaying numbers as the voltage impressing part 3. Light 4 propagating in the transparent substrate is made incident at 75 deg. incident angle or the boundary of the substrate 1 and the control part 2 from the side face of the substrate 1. This light 4 is totally reflected by the boundary surface and is not made incident at all on the control part 2 and is, therefore, entirely prevented from leaking to the outside world. The bright display having the extremely good sharpness is executed in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to improving the clarity and brightness of liquid crystal displays.
The present invention relates to a display element unit that has an improved viewing angle and can also be used as a large-sized display.

[Conventional technology]

High-performance display elements or electronic display devices as materials include liquid crystal displays (LCDs),
Light emitting diode (LED), electroluminescent display (EL), plasma display (F
DP), fluorescent display tube (VFD) and cathode ray tube (CRT)
)and so on. The characteristics and practical applications of such display elements are described in numerous documents and books. For example, “Industrial Materials, Vol. 31, No. 1O (1983), P17
It is also described in ~P80J (published by Nikkan Kogyo Shimbun).

Among such display devices, LCDs have attracted attention in recent years as they have characteristics such as thinness, light weight, low voltage drive, and low power consumption, and technological innovation has been progressing. In particular, there has been a remarkable development in new applications such as for office equipment such as televisions, personal computers, and word processors, especially in recent years.
As dot matrix LCDs have increased display capacity,
STN type LCDs are currently becoming mainstream because they can provide several times higher contrast and viewing angle than conventional TN type LCDs.

Such liquid crystals themselves are described in detail in "Liquid Crystals" (Baifukan) co-edited by Okano and Kobayashi, and LCDs using them are described in "Liquid Crystal Electronics" by Matsumoto (Ohmsha) and "Electronic Materials," Volume 27, No. 2
No. (198B) J (Industrial Research Association), “Nikkei Electronics, N01245.249.258.351J
(Nikkei McGraw-Hill) etc. also have detailed descriptions.

However, in such liquid crystal displays, many problems still remain regarding display clarity, brightness, and viewing angle.

For example, when a selection voltage is applied, the external appearance is blue instead of black, and when no voltage is applied, the external appearance is not white, but a green to yellowish hue, with very poor contrast. Therefore, an attempt to improve the poor contrast by providing a second liquid crystal cell has been proposed in Japanese Patent Application Laid-Open No. 197928/1983.

Furthermore, since liquid crystals do not emit light by themselves, the display surface of the liquid crystal display panel becomes difficult to see at night or in dark places, so a back lighting structure or light condensing device is required. Publication No. 63-194231, Japanese Unexamined Patent Publication No. 63-1942
3-136021, etc. However, in such LCDs, orthogonal polarizing elements must be used, and the performance depends largely on the light transmission/blocking performance of the polarizing elements, and a fundamental solution has not yet been reached.

Furthermore, in liquid crystal displays, the number of scanning electrodes that can be time-divisionally driven is limited due to the steepness limit of the electro-optic response characteristics of the liquid crystal material and the voltage averaging method used to prevent strokes. was difficult. Active matrix driving has been proposed as a driving method for liquid crystal elements used in video displays and large-capacity displays comparable to CRTs, but it is impossible to create defect-free elements with such a method; Another problem was that it was very expensive.

On the other hand, examples of light-emitting displays include EL devices, but even in such devices, the area around the device that does not emit EL light is reflected and enters the eye. There is a problem that the contrast decreases, and various improvements such as semi-transparent filters have been proposed for the purpose of improving the contrast (Japanese Patent Laid-Open No. 63-48589, etc.), but they have not yet reached a satisfactory level. .

[Problem to be solved by the invention]

An object of the present invention is to provide a display element that has a bright and clear display performance, is thin and lightweight, and can be used as a large-capacity display or a large-sized display.

[Means to solve the problem]

As a result of intensive studies to achieve the object of the present invention, the present inventors installed TN (twisted nematic) array cells between orthogonal polarizers, as seen in conventional liquid crystal display elements (LCDs). However, instead of using the optical rotation caused by the electric field of the liquid crystal to control the blocking and transmission of light, a change in the refractive index due to the potential of the light path control section is used to control the propagation within the substrate through the light path control section. It has been discovered that the propagating light can be controlled to be radiated or blocked from the outside world by completely reflecting the light or partially transmitting the light, and that the method for display elements can be used as a new light path control method. The display element unit has been reached. That is, the present invention has the following configuration.

The display element unit of the present invention includes at least a transparent substrate, a light path control section that is in contact with the transparent substrate, and a voltage application section, and the light path control section is configured to respond to a potential applied from the voltage application section. A display element unit characterized by being formed from a material whose refractive index changes.

Alternatively, a light path control section whose refractive index changes depending on the electric potential and a voltage application section are provided on at least one side of the transparent substrate, and the refractive index of the light path control section is changed by changing the voltage applied to the voltage application section. By changing the angle of incidence θ0 with respect to the interface between the transparent substrate and the light path control section, sin Refractive index in state, nb
represents the refractive index of the transparent substrate), by controlling the transmission and reflection of the light propagating within the transparent substrate into the light path control unit, thereby controlling the emission and blocking of the propagating light to the outside world. It is a characteristic display element unit.

Further, in the display element unit of the present invention,
Preferably, the refractive index of the light path control section is from no to n. (Here, when changing to n ml <n at), n @
1 < n 4 < na t (where nb represents the refractive index when a voltage is applied to the light path control section).

Further, the display method according to the present invention includes a transparent substrate through which light can propagate, a light path control section in contact with the transparent substrate, and a voltage application section, and the display method according to the potential applied from the voltage application section. This is a display method characterized by controlling emission and blocking of light propagating within the transparent substrate to the outside world by changing the refractive index of the transparent control section.

[Effect]

The display element unit of the present invention mainly comprises a transparent substrate,
It is formed from a light path control section and a voltage application section. The material constituting the transparent substrate portion may be either an inorganic substance or an organic substance, but examples of inorganic substances include some glasses such as ordinary glass, lead glass, hard glass, and quartz glass, and transparent crystallized glass. It will be done. Further, as the organic substance, any highly transparent polymeric substance can be preferably used. For example, polymethyl methacrylate,
Polycarbonate, diethylene glycol bisacrylic carbonate, polyacrylic ester, polymethacrylic ester, polyvinyl chloride, polymethyl acrylate, polyacrylonitrile, polystyrene, polycyclohexyl methacrylate, poly 4-methylpentene-1,
Examples include acrylonitrile-styrene copolymers and random copolymers of methyl methacrylate and styrene. In particular, polymethyl methacrylate, polycarbonate, acrylonitrile-styrene copolymer, and polystyrene are more preferable because they have good light transmittance.

Now, as the light path control section for controlling the light path by changing the refractive index, which is a component of the present invention, any material can be used as long as the refractive index changes with electric potential. In the present invention, a change in refractive index refers to a change in the refractive index in the bulk state by changing the potential, and in the case of a substance with birefringence, in the direction of incident light. It also includes those in which the refractive index of ordinary light or extraordinary light changes by changing the electric potential.

Here, when the voltage is applied to the light path control section (na1), it is necessary that the refractive index (nb) is smaller than the refractive index (nb) of the transparent substrate. Furthermore, the range of change in refractive index is 0.
It is preferable that the change is 0.05 or more, and more preferably 0.1 or more. In addition, the refractive index when a voltage is applied is n. It is preferable to obtain the relationship na1<na1+<nbz.

In addition, in the case of a material having birefringence, it is preferable that either normal light or extraordinary light be in such a relationship with respect to the incident optical axis.

Examples of materials whose refractive index changes depending on such potential include transparent electro-optic ceramics in which a part of pb in a P b (Z r % T t ) Os solid solution is replaced with La, and organic materials such as 4 , 4゛-dimethoxyazoxybenzene, p-azoxyanisole (FAA)
, N-(4-methoxybenzylidene)-4°-n-butylaniline (MBBA), Schiff salt compounds such as p-ethoxybenzylidene-po-butylaniline, benzoic acid ester compounds, 4-cyano-4'-n - Cyanobiphenyl compounds with an alkyl or alkoxy terminal group represented by pentylbiphenyl (CB-5>), cyanobiphenyl compounds, cyanophenylcyclohexane compounds, cyanobiphenylcyclohexane compounds, cyanophenylpyrifruitdine compounds , cyanophenyl dioxane compounds, cyclohexylethane compounds, cholesterol derivatives having a cholesteryl group such as cholesterol acetate, cholesterol palmitate, cholesterol benzoate, N-(4-cyanobenzylidene)-41-n-octyloxyaniline (CBOOA)
), and liquid crystal compounds such as terephthal-bis-4-n-butylaniline (TBBA).

The principle of the display element of the present invention is to utilize the refractive index difference between the transparent substrate section and the light path control section to radiate the light propagating within the transparent substrate to the outside world through the light path control section (ON shape 7L).
i), or by completely blocking radiation to the outside world by causing total reflection at the interface between the transparent substrate section and the light path control section (OF condition a).

That is, the incident angle θ of the light propagating within the transparent substrate, which is incident from the transparent substrate section to the light path control section, is expressed by the following formula % formula %) However, nal < nb, (here, nb is the When the light is incident at an angle that satisfies the refractive index, n□ is the refractive index when the light path control section is in a state where there is no potential charge, and no is the refractive index when the light path control section is in a state where a potential is applied. , is totally reflected at the interface between the transparent substrate part and the light path control part,
No light propagating within the transparent substrate is incident on the light path control section. Therefore, the light propagating within the transparent substrate does not leak to the outside world at all.

On the other hand, by applying an applied voltage and changing the potential, if nb<not, the light propagating within the transparent substrate can enter the light path control section. Here, the light path control section is made to contain substances such as fine particles that can scatter the incident light, or the surface shape of the light path control section is made into a circular or spherical shape, etc. so that the light propagates into the light path control section. By using means that can radiate the light to the outside world, the light that has entered the light path control section is radiated to the outside world through the light path control section. By using the principle of the present invention, it becomes possible to use the display element as a display element with better brightness and clarity than before.

In addition, in the present invention, the voltage application section may be provided on both sides of the transparent substrate and the light path control section in such a manner that it is sandwiched therebetween, or may be provided on both sides of the light path control section on the transparent substrate. It doesn't matter. Such application can be handled by appropriately selecting the refractive index of the light path control section so as to be able to change the refractive index greatly.

Furthermore, by using the display principle of the present invention, the display capacity of conventional multi-drive dot matrix liquid crystal devices can be increased, which may require strict control of the liquid crystal cell thickness in order to obtain steepness. It has also been found that the display capacity can be easily increased.

Examples will be shown next, but the validity and scope of rights of the present invention are not limited or restricted thereby.

〔Example〕

Example 1 As shown in FIG. 1, the transparent substrate 1 has a refractive index of 1.
．． 55 polyvinyl chloride was used.

Fine powder of titanium oxide was contained on the transparent substrate (4-
cyanofpentyl) -4° -n hebdyrsik.

A light path control unit 2 was created using lohexane.

Next, as the voltage application section 3, a segment transparent electrode was formed on the upper surface of the light path control section, and a common electrode was formed on the back surface of the transparent substrate as a segment electrode configuration for displaying numbers.

Thereafter, the light 4 propagated within the transparent substrate was made to enter the interface between the transparent substrate and the light path control section from the side surface of the transparent substrate at an angle of 756, which is the angle of incidence e'.

The thus obtained device was placed in a somewhat dimly lit place, and the degree of display was evaluated. When no voltage was applied, no numbers appeared at all, but when voltage was applied, the numbers appeared bright and clear.

In addition, even in total darkness, the device was able to display very bright images, and the clarity was also very good.

〔Effect of the invention〕

The display element unit of the present invention utilizes a change in refractive index and uses the principle of total reflection or partial transmission of light, so the transmission and blocking of light can be completely controlled, resulting in brightness and excellent clarity. It is something that can be displayed. Furthermore, it is possible to display clearly even in a dark place.

Furthermore, it is also possible to easily increase the display capacity.
In addition to thin display panels, large panel displays and large wall hangings can be preferably used as displays.

[Brief explanation of drawings]

FIG. 1 is a sectional view illustrating, as a model, an example of the structure of each display element according to the present invention. In the figure, 1 is a transparent substrate, 2 is a light path control section, 3 is a voltage application section, and 4 is light propagating within the transparent substrate. Note that O7 in the figure represents the angle of incidence.

Claims (4)

[Claims] (1) It has at least a transparent substrate, a light path control section in contact with the transparent substrate, and a voltage application section, and the light path control section has a refractive index that changes depending on the potential applied from the voltage application section. A display element unit characterized by being formed from a substance. (2) A light path control section whose refractive index changes with electric potential and a voltage application section are provided on at least one side of the transparent substrate, and the refractive index of the light path control section is adjusted by changing the voltage applied to the voltage application section. is changed, and the incident angle Θ° with respect to the interface between the transparent substrate and the light path control section is sin^-(n_a_1/n_b)<Θ<90 (where n_a_1 is the state in which no voltage is applied to the light path control section). By controlling the transmission and reflection of the light propagating within the transparent substrate, which has a refractive index of 100 mm and n_b is the refractive index of the transparent substrate, into the light path control unit, the propagating light is emitted and blocked from the outside world. A display element unit characterized by controlling. (3) The refractive index of the light path control section is from n_a_1 to n_a_2
(Here, when it changes to n_a_1<n_a_2),
The display element unit according to claim 2, characterized in that n_a_1<n_b<n_a_2 (where n_a_2 represents a refractive index when a voltage is applied to the light path control section). (4) A transparent substrate through which light can propagate, a light path control section in contact with the transparent substrate, and a voltage application section are provided, and the refractive index of the transparent control section is adjusted according to the potential applied from the voltage application section. A display method characterized by controlling emission or blocking of light propagating within the transparent substrate to the outside world by changing the transparent substrate.