JP2003107470A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element with excellent visibility in either of in a transmission mode and a reflection mode. SOLUTION: An EL emission layer 5 is placed between a rear substrate and a liquid crystal layer of the liquid crystal display element where the liquid crystal layer is located between a front substrate and the rear substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device capable of displaying in both reflective and transmissive modes.

[0002]

2. Description of the Related Art Generally, a liquid crystal display element that constitutes a liquid crystal display is a non-emission type, and thus requires external irradiation light. As external irradiation light used in the liquid crystal display, external light such as sunlight or a backlight provided in the liquid crystal display is often used.

In the case of a liquid crystal display for a vehicle, a liquid crystal display for a mobile phone, etc., it is characterized in that there is a large variation in the use environment in relation to the externally radiated light from darkness at night to direct sunlight. The design of a liquid crystal display capable of coping with the fluctuation of the external irradiation light is required.

As a liquid crystal display which is effective for use in the case where there is a large fluctuation in the externally radiated light, a transmissive display system (hereinafter, referred to as a transmissive display system) which utilizes illumination from the back surface of the liquid crystal display element in a dark environment Mode), and when the environment is bright, it reflects the external light and adopts a reflective display system (hereinafter, reflective mode), which is a semi-transmissive function that has both transmissive and reflective functions. Those using a reflective liquid crystal display element have been developed.

In such a semi-transmissive reflection type liquid crystal display element, a semi-transmissive reflection film is arranged on the outside of the substrate located rearward of the liquid crystal layer, and a backlight unit is further arranged on the outside thereof.

Here, the structure of a conventional general liquid crystal display device will be briefly described.

The liquid crystal display element has a transparent substrate (hereinafter referred to as a front substrate) located in front of the viewer and a transparent substrate (hereinafter referred to as rear substrate) located in the rear opposite to the viewer. The front substrate and the rear substrate are arranged substantially parallel to each other with a space therebetween, and the outer peripheries thereof are sealed with a sealing material.

A transparent common electrode is disposed on the lower surface of the front substrate so as to be in close contact therewith, and liquid crystal molecules are aligned below the transparent common electrode in accordance with a voltage applied between the electrodes. The alignment film for controlling the film is disposed so as to be in close contact with the film. Further, a polarizing film is arranged on the upper surface of the front substrate.

On the other hand, a transparent segment electrode is arranged on the upper surface of the rear substrate, a color filter film is arranged above this transparent segment electrode, and an alignment film is adhered above this color filter film. It is arranged to do. Further, a polarizing film and a semi-transmissive reflective film are provided outside the rear substrate.

On the lower surface of the rear substrate, a light source,
A backlight unit having a light guide plate for emitting the light of the light source toward the liquid crystal display element is provided.

A liquid crystal is enclosed in a sealed space surrounded by the front substrate, the rear substrate and a sealing material, and further, in order to keep the distance between the front substrate and the rear substrate constant accurately, A plurality of spherical or columnar spacers are interposed between both alignment films.

However, in the liquid crystal display device having such a structure, when light is incident from the oblique direction of the panel in the reflection mode, the pixels through which the incident light and the outgoing light pass differ depending on the thickness of the rear substrate. Parallax occurs, and as a result,
There are problems that the displayed images are duplicated, the contrast ratio is lowered, and in the case of color display, the color purity of the display colors is lowered due to color mixing.

In order to solve the problem caused by such parallax, in recent years, a structure in which a semi-transmissive reflective film is arranged inside the rear substrate as viewed from the liquid crystal layer has been adopted (hereinafter, the inside of the rear substrate will be described). The internal reflection film is the reflection film that is placed on).

[0014]

However, it is self-evident that the internal reflection film reduces the light utilization efficiency when a transmissive mode is adopted and a display is performed using a backlight.

Therefore, if the transmissivity of the transflective plate is increased in order to improve the appearance of the screen in the transmissive mode, the reflectivity decreases and the screen of the reflective mode becomes unattractive. On the contrary, the reflection of the transflective film is reduced. There is a trade-off problem that if the ratio is increased to improve the appearance of the reflection mode screen, the transmittance is decreased and the appearance of the transmission mode screen is deteriorated.

The present invention has been made to solve the above problems.
It has been obtained as a result of earnest efforts, and its purpose is to realize a reflection mode with high reflectance and a transmission mode with high transmittance in one liquid crystal display element.

[0017]

In order to achieve the above-mentioned object, a liquid crystal display element according to claim 1 of the present invention is a liquid crystal display element in which a liquid crystal layer is sandwiched between a front substrate and a rear substrate. An EL light emitting layer is provided between the liquid crystal layer and the rear substrate.

According to the liquid crystal display element of the present invention, a voltage can be applied to the EL light emitting layer to cause it to emit light, which can be used as a light source. In that case, the light emission efficiency is good, and battery consumption is reduced, which is economical. It becomes a liquid crystal display element.

The liquid crystal display element according to claim 2 is
The liquid crystal display device according to claim 1, further comprising a reflective layer between the EL light emitting layer and the rear substrate.

According to the liquid crystal display element of the present invention, the loss of light can be almost prevented by reflecting the light emitted from the EL light emitting layer in the reflective mode on the reflective layer.

A liquid crystal display element according to a third aspect is the liquid crystal display element according to the first aspect, characterized in that a diffusion layer is provided between the reflective layer and the rear substrate.

According to the liquid crystal display element of the present invention, it is possible to surely diffuse light in the reflection mode, and to perform bright display.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystal display element of the present invention is a film that exhibits a phenomenon (electroluminescence (EL)) that emits light when a voltage is applied between the liquid crystal layer that constitutes the liquid crystal display element and the rear substrate. Layer (hereinafter, EL light emitting layer) is provided.

Since the EL light emitting layer generates little heat, it can be used by directly adhering to a liquid crystal display element whose characteristics change with temperature changes. Moreover, since the luminous efficiency is good, the battery has excellent performance that the battery consumption is small.

Therefore, in the present embodiment, this EL
The light emitting layer is composed of a semiconductor thin film composed of a light emitter (thin film type E
L) or the powder of the above-mentioned luminescent material is dispersed in a binder, and this is applied to form (dispersion type EL).
It is configured to emit light by applying a voltage of 100 V to several 100 V to the light emitting layer. Since the EL does not generate much heat, it can be used by directly adhering to a liquid crystal display element whose characteristics change due to temperature changes. Moreover, since the EL has good luminous efficiency, the battery consumption is small. Therefore, it can be said that it is particularly suitable as a thin backlight suitable for mobile devices.

The liquid crystal display device of this embodiment is shown in FIG.
And it demonstrates using FIG.

The liquid crystal display element of the present embodiment has the same structure as that of the conventional liquid crystal display element described above except for the structure described below, and further description is omitted.

FIG. 1 is a cross-sectional view showing a main structure of a rear substrate side in which a typical EL light emitting layer is arranged in a liquid crystal display device using a thin film type EL according to this embodiment.

As shown in this figure, the rear substrate 1 of the liquid crystal display device of this example is provided with a diffusion layer 2 having fine irregularities on the upper surface thereof. One electrode 3 for applying to the light emitting layer is provided.
An EL light emitting layer 5 is formed on the upper surface of the electrode 3 via an insulating layer 4, and an insulating layer 6 is formed on the upper surface.
Another electrode 7 for applying to the EL light emitting layer 5 via
Is provided.

Here, the EL light emitting layer 5 is composed of a semiconductor thin film having a thickness of 0.5 to 1 μm and made of zinc sulfide ZnS or the like which is a light emitting body.
It is configured to emit light by applying a voltage of 7 to 100V to several 100V.

In this case, the emission color of the EL emission layer 5 can be variously changed depending on the kind of the emission center element added to the EL emission layer 5. For example, when the light-emitting base is zinc sulfide ZnS and manganese is added, it turns yellow-orange, and terbium fluoride TbF ₃ ,
When samarium chloride SmCl ₃ , thulium TmCl ₃ and praseodymium fluoride PrF ₃ are added, green light, red light, blue light and white light are emitted, respectively. An organic EL material can be used for the EL light emitting layer 5, and in that case,
The evaluation is high in that it emits light at a voltage of several tens of V or less. Also, E
The other electrode 7 disposed above the L light emitting layer 5 is a transparent electrode 7, and examples of the transparent electrode 7 include Sn-doped indium oxide, Sn-tin oxide, and Al-doped zinc oxide. . Further, one electrode 3 is the metal electrode 3, and a metal material such as Al is used.

As the material of the insulating layers 4 and 6, those having a large breakdown voltage and a large dielectric constant are desirable. For example, yttria Y ₂ O ₃ and samarium oxide S which are oxides are preferable.
m ₂ O ₃ , alumina Al ₂ O ₃ , tantalum pentoxide Ta ₂ O ₅ ,
Hafnia HfO ₂ , silica SiO ₂ , silicon nitride Si ₃ N ₄ ,
Materials such as strontium titanate SrTiO ₃ , which is a perovskite type ferroelectric, barium titanate BaTiO ₃ , and lead titanate PbTiO ₃ can be used.

In the liquid crystal display element of the present invention,
It is possible to dispose the reflective layer 8 between the liquid crystal layer (not shown) and the EL light emitting layer 5, or between the EL light emitting layer 5 and the rear substrate 1. The reflective layer 8 is usually a reflective film 9 made of metal.
However, here, it includes one having both the reflection enhancing film 10 and an optical film such as an inclined reflector.

In FIG. 1, the reflective layer 8 is arranged between the EL light emitting layer 5 and the rear substrate 1. That is, in the structure of the liquid crystal display element shown in FIG. 1, the metal electrode 3 which is the one electrode 3 is also used as the reflection film 9. Further, in the present embodiment, in order to further improve the reflection performance, the insulating layer 4 is also used as the increased reflection film 10.
The reflective layer 8 having a high reflectance is formed. The reflection enhancing film 10 is made of a combination of a low refractive index material and a high refractive index material such as SiO ₂ and Nb ₂ O ₅ .

By using the EL electrode 3 as the reflective film 9 in this manner, the reflective film can be simply provided without providing a separate reflective film, and the manufacturing cost can be reduced.

As described above, the reflective layer 8 can be disposed between the liquid crystal layer and the EL light emitting layer 5 or between the EL light emitting layer 5 and the rear substrate 1, but the liquid crystal layer And E
When it is arranged between the L light emitting layers 5, the transmittance decreases when the reflectance is increased. For the purpose of the present invention, there is no reflection between the EL light emitting layer 5 and the rear substrate 1. Layer 8
Is more preferable.

Further, although the flat metal reflection film reflects specularly,
As a liquid crystal display element, it is preferable that reflection has a diffusive property. Therefore, in the liquid crystal display element of the present invention, it is possible to dispose the diffusion layer 2 between the reflective layer 8 and the rear substrate 1. In FIG. 1, a diffusion layer 2 having surface irregularities is formed between the metal electrode 3 and the rear substrate 1 by a known photolithography method.

As described above, by providing the diffusion layer 2, it is possible to surely diffuse the light and perform bright display.

As another method for diffusing light,
Instead of the diffusion layer 2, it is also possible to use a resin layer in which the insulating layer 4 is mixed with inorganic particles such as titanium oxide having a diameter of about several μm.

FIG. 2 is a cross-sectional view showing the configuration of the main part on the rear substrate 1 side in which a typical EL light emitting layer 5 is arranged in the liquid crystal display element using the dispersion type EL according to the present embodiment.

In this embodiment, zinc sulfide (ZnS: Cu, Cl) doped with Cu and Cl having a particle size of 5 to 20 μm is used as the EL light emitting powder, and this is used as an organic dielectric. Disperse in the binder, 50-
It is made to have a thickness of about 100 μm and sandwiched between the transparent electrode 3 and the metal electrode 3 on the back side. As the binder of the organic dielectric, for example, an acrylic resin or a cyanocellulose resin can be used.

Further, the insulating layer 6 is provided above the EL light emitting layer 5, and the transparent electrode 7 is provided thereon.

The EL sandwiched between the electrodes 3 and 7
EL light emission is possible by applying an alternating current of about 200 V to the light emitting layer 5.

In the dispersion type EL as shown in FIG.
Since the light emitter itself is a light diffusing particle, the above-mentioned diffusion layer 2
In some cases, it can be combined.

Hereinafter, more specific examples of the liquid crystal display element of the present embodiment will be described, including manufacturing method steps.

Example 1 This example is an example of a liquid crystal display device having the thin film type EL light emitting layer 5 shown in FIG.

In this embodiment, low alkali glass AN100 (made by Asahi Glass Co., Ltd.) is used as the rear substrate 1,
Apply diffusible resin PC411B (made by JSR) to this,
Diffusion layer 2 consisting of fine unevenness after partial exposure and firing
Was produced.

Next, an Al layer was vapor-deposited on the upper surface of the diffusion layer 2 to form a metal electrode 3 which also serves as the reflection film 9.

Subsequently, an insulating layer 4 which also serves as a reflection increasing film 10 is formed on the upper surface of the metal electrode 3 by a combination of SiO ₂ —Nb ₂ O ₅ , and an EL light emitting layer 5 is formed on the upper surface of the insulating layer 4 using ZnS as a base material. Was deposited to form a film.

Further, SiO is formed on the upper surface of the EL light emitting layer 5.
_2- Nb ₂ O ₅ was deposited to form the insulating layer 6.

Furthermore, a transparent electrode 7 was formed by depositing Sn-doped indium oxide to enable application to the EL light emitting layer 5.

As a result of the manufacture in this way, as shown by an arrow in FIG. 1, no voltage is applied by 45 degree incidence and 45 degree emission (using a measuring instrument BM-7 manufactured by Minolta Co., standard white plate CS / A5). The reflectance at that time was 55%, which was a high value.

Next, a color filter (not shown) is manufactured on the upper surface of the transparent electrode 7 by a usual method, and a transparent electrode (not shown) made of ITO (Indium Tin Oxide) and an alignment film (not shown) are further formed on the upper surface of the color filter. (Not shown) was laminated.

Thereafter, a front substrate (not shown) facing the rear substrate 1 was produced, both substrates were superposed, and a desired liquid crystal display element was manufactured through a sealing process, a cutting process, a liquid crystal injection process, and the like.

The liquid crystal display element thus produced has no problem in display quality and reliability, and bright display is possible in both the transmissive mode and the reflective mode regardless of the presence or absence of external light.

Example 2 This example is an example of a liquid crystal display device having the dispersion type EL light emitting layer 5 shown in FIG.

In this embodiment, low alkali glass AN100 (made by Asahi Glass Co., Ltd.) is used as the rear substrate 1,
An Al layer was vapor-deposited on this upper surface, and a film was formed to form a metal electrode 3.

Next, a resin solution having ZnS particles as a base material dispersed in a resin was applied on the upper surface of the metal electrode 3 by a screen printing method and dried to form an EL light emitting layer 5.

Then, SiO is formed on the upper surface of the EL light emitting layer 5.
_An insulating layer 6 made of ₂ was formed, ITO was formed into a film, and a transparent electrode 3 was formed so that it could be applied to the EL light emitting layer 5.

As shown by the arrow in FIG. 2, the product manufactured in this way is at 45 ° incidence and 45 ° emission (measurement instrument BM-7 manufactured by Minolta Co., using standard white plate CS / A5) when no voltage is applied. The reflectance was 25%, indicating a relatively high numerical value.

Next, a color filter was manufactured on the upper surface of the transparent electrode 3 by a usual method, and further, ITO and an alignment film were laminated on the upper surface.

Thereafter, a front substrate side corresponding to the rear substrate 1 side was produced, both substrates were superposed, and a desired liquid crystal display element was manufactured through a sealing process, a cutting process, a liquid crystal injection process and the like.

The liquid crystal display element thus produced has no problem in display quality and reliability, and bright display is possible in both the transmissive mode and the reflective mode regardless of the presence or absence of external light.

Example 3 In the liquid crystal display element of Example 2, the low alkali glass substrate was replaced with polycarbonate, and a color filter was provided on the opposing front substrate side to apply a voltage to the EL light emitting layer 5. A liquid crystal display element was manufactured by adding acrylic resin having a thickness of 2 μm between the transparent electrode 7 and the ITO.

The liquid crystal display device thus produced has no problem in display quality and reliability, and bright display is possible in both the transmissive mode and the reflective mode regardless of the presence or absence of external light.

Example 4 Further, a liquid crystal display element was manufactured by changing the liquid crystal display element of Example 3 to a black and white display type by removing the color filter.

The liquid crystal display device thus produced has no problem in display quality and reliability even in black and white display, and bright display is possible in both transmission mode and reflection mode regardless of the presence or absence of external light.

The present invention is not limited to the above-mentioned embodiment, but various modifications can be made if necessary.

[0069]

As described above, according to the liquid crystal display element of the present invention, in the transmissive mode, there is almost no light loss because the reflective film is not interposed between the light source and the liquid crystal layer.
A bright display is obtained. As a result of the high energy utilization efficiency, the power consumption of the liquid crystal display element is low and the running cost is low, and in particular, it is possible to provide an optimal liquid crystal display element as a portable liquid crystal display element. Further, as compared with the separate type backlight, the overall manufacturing cost is reduced, and an excellent effect such as an integrated type thin and lightweight liquid crystal display element is exhibited.

[Brief description of drawings]

FIG. 1 shows a liquid crystal display element using a thin film EL,
Sectional drawing which shows the principal part structure at the rear substrate side

FIG. 2 shows a liquid crystal display device using a dispersion type EL.
Sectional drawing which shows the principal part structure at the rear substrate side

[Explanation of symbols]

1 Rear substrate 2 diffusion layer 3 electrodes (metal electrode) 4 insulating layers 5 EL light emitting layer 6 insulating layers 7 electrodes (transparent electrode) 8 reflective layer 9 Reflective film 10 Increased reflection film

Continued front page    F-term (reference) 2H091 FA14Z FA15Z FA31Z FA44Z                       FD06 FD23 LA13                 5C094 AA10 AA15 AA22 AA44 BA43                       DA11 EA04 EA05 EA06 EA07                       EB02 ED11 ED13 ED20                 5G435 AA00 AA03 AA17 AA18 BB12                       BB15 BB16 DD09 EE26 EE33                       FF03 FF06 GG25

Claims (3)

[Claims] 1. A liquid crystal display element in which a liquid crystal layer is located between a front substrate and a rear substrate, wherein the liquid crystal display element has an EL light emitting layer between the liquid crystal layer and the rear substrate. 2. The liquid crystal display device according to claim 1, further comprising a reflective layer between the EL light emitting layer and the rear substrate. 3. The liquid crystal display device according to claim 2, further comprising a diffusion layer between the reflective layer and the rear substrate.