WO2010131784A1

WO2010131784A1 - Reflection type display and manufacturing method thereof

Info

Publication number: WO2010131784A1
Application number: PCT/KR2009/002476
Authority: WO
Inventors: Jhiyeon Jeanne Oh; Hyunwoo Michael Oh
Original assignee: Jhiyeon Jeanne Oh; Hyunwoo Michael Oh
Priority date: 2009-05-11
Filing date: 2009-05-11
Publication date: 2010-11-18
Also published as: KR101324658B1; KR20120017024A

Abstract

A reflection type display for controlling the interference of light in a piezoelectric manner and a manufacturing method thereof are provided. The reflection type display includes a lower substrate, a first electrode formed on the lower substrate, a piezoelectric film layer formed on the first electrode, and a second electrode formed on the piezoelectric film layer, wherein the piezoelectric film layer changes its thickness depending on the voltage applied to the first and second electrodes. Accordingly, the reflection type display may change reflectivity sufficiently even with a small thickness change, thereby ensuring high brightness just with a small intensity of radiation.

Description

REFLECTION TYPE DISPLAY AND MANUFACTURING METHOD THEREOF

This disclosure relates to a reflection type display that controls the interference of light in a piezoelectric manner, and a manufacturing method thereof.

Generally, flat plate displays are classified into (liquid crystal displays (LCDs), plasma display panels (PDPs), organic light emitting diodes (OLEDs) and so on.

PDPs or OLEDs realize color images by emitting light by themselves. And, LCDs may adopt a transmission type that transmits light from a backlight unit (BLU) composed of a light-emitting diode (LED) or a cold cathode fluorescent lamp (CCFL) or a reflection type that reflects an external light.

Among the above flat plate displays, LCDs are the most widely used for small displays such as cellular phones as well as large TVs. For using the LCD for portable displays such as cellular phones and lap-top computers, the operation time of the portable device should be extended. For this, power consumption of the display needs to be minimized.

However, the transmission type display consumes a lot of power since it uses a backlight, although it gives bright images in a dark environment.

Meanwhile, the reflection type display that realizes various colors based on interference by ambient light may reduce power consumption since it does not use a backlight.

An example of the reflection type display is a display using static electricity.

If one pixel of the display using static electricity is closely adhered to another electrode, the degree of adhesion is different at an edge of the pixel and at a center of the pixel.

As a result, the edge of each pixel may exhibit apparently different color from that of the center, which is called edge blurring.

This problem becomes more serious as the size of pixel is decreased. Thus, it makes it difficult to realize a high-density display.

In addition, if two electrodes not covered by protection films made of insulating materials are contacted by means of static electricity, serious electricity leakage may occur. It may cause increased power consumption of a display driving circuit.

This disclosure is designed to solve the above problems, and an object of the disclosure is to provide a reflection type display capable of reducing edge blurring and electricity leakage by controlling light interference in a piezoelectric manner, and a manufacturing method thereof.

In one aspect, there is provided a reflection type display, which includes a lower substrate; a first electrode formed on the lower substrate; a piezoelectric film layer formed on the first electrode; and a second electrode formed on the piezoelectric film layer, wherein the piezoelectric film layer changes a thickness depending on the voltage applied to the first and second electrodes.

The first electrode may be made of a reflective electrode that reflects the light incident from the outside, and the second electrode may be made of a transparent electrode that transmits the light incident from the outside and the light reflected on the first electrode.

The thickness of the piezoelectric film layer may be controlled such that destructive interference occurs between the light reflected on the second electrode and the light reflected on the first electrode if a bias voltage is not applied to the first and the second electrodes, and constructive interference occurs between the light reflected on the second electrode and the light reflected on the first electrode due to the change of thickness of the piezoelectric film layer caused by the piezoelectric effect if a bias voltage is applied to the first and the second electrodes.

In another aspect, there is also provided a reflection type display, which includes a lower substrate; a reflection film formed on the lower substrate to reflect the light incident from the outside; a piezoelectric film layer formed on the reflection film; and first and second electrodes formed on the piezoelectric film layer to be spaced apart from each other in parallel, wherein the piezoelectric film layer changes a thickness depending on the voltage applied to the first and second electrodes.

The first and second electrodes may be made of electrodes that transmit the light incident from the outside and the light reflected on the reflection film.

The thickness of the piezoelectric film layer may be controlled such that destructive interference occurs between the light reflected on the reflection film and the light reflected on the first and second electrodes if a bias voltage is not applied to the first and the second electrodes; and constructive interference occurs between the light reflected on the reflection film and the light reflected on the first and second electrodes due to the change of thickness of the piezoelectric film layer caused by the piezoelectric effect if a bias voltage is applied to the first and the second electrodes.

In still another aspect, there is also provided a method for manufacturing a reflection type display, which includes preparing a lower substrate; forming a first electrode on the lower substrate, the first electrode being made of a reflective electrode that reflects the light incident from the outside; forming a piezoelectric film layer on the first electrode, the piezoelectric film changing a thickness depending on voltage; and forming a second electrode on the piezoelectric film layer, the second electrode being made of a transparent electrode that transmits the light incident from the outside and the light reflected on the first electrode.

In further another aspect, there is also provided a method for manufacturing a reflection type display, which includes preparing a lower substrate; forming a reflection film on the lower substrate, the reflection film reflecting the light incident from the outside; forming a piezoelectric film layer on the reflection film, the piezoelectric film changing a thickness depending on voltage; and forming first and second electrodes on the piezoelectric film layer to be spaced apart from each other in parallel, the first and second electrodes which could be made of electrodes that transmit the light incident from the outside and the light reflected on the reflection film.

According to the reflection type display and a manufacturing method thereof disclosed herein, the interference of light is controlled in a piezoelectric manner, so occurrence of edge blurring caused by bending or moving may be decreased as compared with the displays using static electricity. Also, since the interference of light is controlled in a piezoelectric manner, current leakage may be reduced as compared with the displays using static electricity.

In addition, since the piezoelectric material provided between two electrodes exhibits great variation of reflectivity depending on thickness, the reflectivity may be sufficiently changed even with a small displacement. Thus, high brightness may be ensured with a small intensity of radiation.

The above and other aspects, features and advantages of the disclosed exemplary embodiments will be more apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

Figs. 1 and 2 are sectional views schematically showing a reflection type display according to one embodiment;

Figs. 3 and 4 are sectional views schematically showing a reflection type display according to another embodiment;

Fig. 5 is a flowchart illustrating a method for manufacturing a reflection type display according to one embodiment;

Fig. 6 is a flowchart illustrating a method for manufacturing a reflection type display according to another embodiment; and

Fig. 7 is a graph showing a reflectivity of the reflection type display against RGB wavelengths depending on the thickness of a piezoelectric film changed by applied voltage.

Exemplary embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth therein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art. In the description, details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the presented embodiments.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, the use of the terms a, an, etc. does not denote a limitation of quantity, but rather denotes the presence of at least one of the referenced item. The use of the terms "first", "second" and the like does not imply any particular order, but they are included to identify individual elements. Moreover, the use of the terms first, second, etc. does not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. It will be further understood that the terms "comprises" and/or "comprising", or "includes" and/or "including" when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In the drawings, like reference numerals in the drawings denote like elements. The shape, size and regions, and the like, of the drawing may be exaggerated for clarity.

Hereinafter, a reflection type display and a manufacturing method thereof according to an embodiment are explained in detail with reference to the accompanying drawings.

Figs. 1 and 2 are sectional views schematically showing a reflection type display according to one embodiment.

In Figs. 1 and 2, a lower substrate 10 is made of glass or formed as a flexible substrate.

A first electrode 20 is formed on the lower substrate 10, and it may be configured as a reflective electrode that reflects light incident from the outside.

The first electrode 20 is formed on the lower substrate 10 by vacuum deposition or printing.

The first electrode 20 may be made of metal film with high reflectivity so as to reflect the light incident from the outside. The metal film may include Al or its alloys.

A piezoelectric film layer 30 is formed on the first electrode 20. Also, the piezoelectric film layer 30 changes its thickness due to the piezoelectric effect caused by the voltage applied to the first electrode 20 and a second electrode 40.

The piezoelectric film layer 30 may be made of materials with excellent piezoelectric characteristics by means of sputtering, laser abrasion, chemical vapor deposition (CVD), sol-gel method, and so on.

As shown in Fig. 1, the thickness of the piezoelectric film layer 30 is controlled such that destructive interference occurs between the light reflected on the second electrode 40 and the light reflected on the first electrode 20 if a bias voltage is not applied to the first electrode 20 and the second electrode 40. Also, as shown in Fig. 2, the thickness of the piezoelectric film layer 30 is controlled such that constructive interference occurs between the light reflected on the second electrode 40 and the light reflected on the first electrode 20 due to the change of thickness of the piezoelectric film layer 30 caused by the piezoelectric effect if a bias voltage is applied to the first electrode 20 and the second electrode 40.

The thickness of the piezoelectric film layer 30 may be controlled through calculation of Fabry-Perot interference depending on thickness and refractive index of each film layer.

The second electrode 40 is formed on the piezoelectric film layer 30. Also, the second electrode 40 may be formed as a transparent electrode that transmits the light incident from the outside and the light reflected on the first electrode 20.

Figs. 3 and 4 are sectional views schematically showing a reflection type display according to another embodiment.

In Figs. 3 and 4, a lower substrate 50 is made of glass or formed as a flexible substrate.

A reflection film 60 is formed on the lower substrate 50 and reflects the light incident from the outside.

The reflection film 60 may be made of metal film with high reflectivity so as to reflect the light incident from the outside. The metal film may include Al or its alloys.

A piezoelectric film layer 70 is formed on the reflection film 60 and changes its thickness depending on the voltage applied to a first electrode 80 and a second electrode 90.

The piezoelectric film layer 70 may be made of materials with excellent piezoelectric characteristics by means of sputtering, laser abrasion, CVD, sol-gel method, and so on.

As shown in Fig. 3, the thickness of the piezoelectric film layer 70 is controlled such that destructive interference occurs between the light reflected on the reflection film 60 and the light reflected on the first and

second electrodes

80, 90 if a bias voltage is not applied to the first electrode 80 and the second electrode 90. Also, as shown in Fig. 4, the thickness of the piezoelectric film layer 70 is controlled such that constructive interference occurs between the light reflected on the reflection film 60 and the light reflected on the first and

second electrodes

80, 90 due to the change of thickness of the piezoelectric film layer 70 caused by the piezoelectric effect if a bias voltage is applied to the first electrode 80 and the second electrode 90.

The first electrode 80 and the second electrode 90 are formed on the piezoelectric film layer 70 to be spaced apart from each other in parallel. Also, the first electrode 80 and the second electrode 90 may be able to be made of transparent electrodes that transmit the light incident from the outside and the light reflected on the reflection film 60 or narrow opaque electrodes.

Fig. 5 is a flowchart illustrating a method for manufacturing a reflection type display according to one embodiment.

First, the lower substrate 10 is prepared (S10). The first electrode 20 made of a reflective electrode reflecting the light incident from the outside is formed on the prepared lower substrate 10 (S12).

The lower substrate 10 prepared in the step S10 is made of glass or formed as a flexible substrate. In the step S12, the first electrode 20 may be formed on the lower substrate 10 by means of vacuum deposition or printing. Also, the first electrode 20 formed on the lower substrate 10 in the step S12 may be configured as a reflective electrode that reflects the light incident from the outside. Thus, the first electrode 20 may be made of metal film with good reflectivity so as to reflect the light incident from the outside. The metal film may be Al or its alloys.

After that, a piezoelectric film layer changing its thickness depending on voltage is formed on the first electrode 20 (S14).

In the step S14, the piezoelectric film layer 30 may be made of materials with excellent piezoelectric characteristics by means of sputtering, laser abrasion, CVD, sol-gel method, and so on.

The thickness of the piezoelectric film layer 30 formed on the first electrode 20 in the step S14 is controlled such that destructive interference occurs between the light reflected on the second electrode 40 and the light reflected on the first electrode 20 if a bias voltage is not applied to the first electrode 20 and the second electrode 40. Also, the thickness of the piezoelectric film layer 30 is controlled such that constructive interference occurs between the light reflected on the second electrode 40 and the light reflected on the first electrode 20 due to the change of thickness of the piezoelectric film layer 30 caused by the piezoelectric effect if a bias voltage is applied to the first electrode 20 and the second electrode 40.

After the piezoelectric film layer 30 is formed in the step S14, the second electrode 40 made of a transparent electrode transmitting the light incident from the outside and the light reflected on the first electrode 20 is formed on the piezoelectric film layer 30 (S16).

Fig. 6 is a flowchart illustrating a method for manufacturing a reflection type display according to another embodiment.

First, the lower substrate 50 is prepared (S20), and then the reflection film 60 reflecting the light incident from the outside is formed on the lower substrate 50 (S22).

The lower substrate 50 prepared in the step S20 is made of glass or formed as a flexible substrate, and, in the step S22, the reflection film 60 may be formed on the lower substrate 50 by means of vacuum deposition or printing. The reflection film 60 formed on the lower substrate 50 in the step S22 may be made of metal film with high reflectivity so as to reflect the light incident from the outside. The metal film may include Al or its alloys.

After that, the piezoelectric film layer 70 changing its thickness depending on voltage is formed on the reflection film 60 (S24).

In the step S24, the piezoelectric film layer 70 may be made of materials with excellent piezoelectric characteristics by means of sputtering, laser abrasion, CVD, sol-gel method, and so on.

The thickness of the piezoelectric film layer 70 formed on the reflection film 60 in the step S24 is controlled such that destructive interference occurs between the light reflected on the reflection film 60 and the light reflected on the first and

second electrodes

80, 90 if a bias voltage is not applied to the first electrode 80 and the second electrode 90. Also, the thickness of the piezoelectric film layer 70 is controlled such that constructive interference occurs between the light reflected on the reflection film 60 and the light reflected on the first and

second electrodes

After the piezoelectric film layer 70 is formed in the step S24, the first electrode 80 and the second electrode 90, made of electrodes that transmit the light incident from the outside and the light reflected on the reflection film 60, are formed on the piezoelectric film layer 70 to be spaced apart from each other in parallel (S26).

As described above, the reflection type display disclosed herein provides constructive interference and destructive interference depending on thickness and refractive index of the piezoelectric film layer.

The reflectivity of light depending on the intensity of electric field applied to the piezoelectric film layer of the reflection type display disclosed herein may be calculated as follows using the Fresnel equations.

For example, in case the substrate has a refractive index of N₁= n₁- ik₁, and the piezoelectric film layer has a refractive index of N₂= n₂- ik₂ and a thickness of d, the reflectivity for the light with wavelength is calculated according to the following Equation 1.

[Equation 1]

In Equation 1,

,

, and .

.

If the piezoelectric film layer is made of ZnO and the first electrode is made of Al, the reflectivity depending on the thickness of the piezoelectric film layer made of ZnO is calculated according to Equation 1, and the results shown in Fig. 7 may be obtained.

As seen from Fig. 7, if thickness is changed as much as about 25 to 30 mm in red, green and blue wavelengths, the reflectivity may be varied from 1% to 90%. In other words, an ON/OFF ratio becomes about 90, and the reflectivity may be sufficiently changed just with a small thickness change since the change of reflectivity depending on thickness is great. The reflectivity of about 90% gives a sufficient intensity of radiation, not expected in existing transmission type displays, so high brightness may be ensured with a small intensity of radiation (Actually, in case a transmission type display with color filters is employed, about 50% of light is absorbed, and thus, the intensity of radiation actually displayed is very low).

The reflection type display and the manufacturing method thereof disclosed herein are not limited to the above embodiments, but they may be changed or modified in various ways within the scope defined in the appended claims.

The reflection type display disclosed herein controls the interference of light in a piezoelectric manner, so the reflectivity is greatly changed depending on the thickness of a piezoelectric material formed between two electrodes. Thus, the reflectivity may be sufficiently changed even with a small displacement, so it is possible to provide a display that ensures high brightness with a small intensity of radiation.

While the exemplary embodiments have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made thereto without departing from the spirit and scope of this disclosure as defined by the appended claims.

In addition, many modifications can be made to adapt a particular situation or material to the teachings of this disclosure without departing from the essential scope thereof. Therefore, it is intended that this disclosure not be limited to the particular exemplary embodiments disclosed as the best mode contemplated for carrying out this disclosure, but that this disclosure will include all embodiments falling within the scope of the appended claims.

Claims

A reflection type display, comprising:

a lower substrate;

a first electrode formed on the lower substrate;

a piezoelectric film layer formed on the first electrode; and

a second electrode formed on the piezoelectric film layer,

wherein the piezoelectric film layer changes a thickness depending on the voltage applied to the first and second electrodes.
The reflection type display according to claim 1, wherein the first electrode is made of a reflective electrode that reflects the light incident from the outside, and the second electrode is made of a transparent electrode that transmits the light incident from the outside and the light reflected on the first electrode.
The reflection type display according to claim 1, wherein the thickness of the piezoelectric film layer is controlled such that:

destructive interference occurs between the light reflected on the second electrode and the light reflected on the first electrode if a bias voltage is not applied to the first and the second electrodes; and

constructive interference occurs between the light reflected on the second electrode and the light reflected on the first electrode due to the change of thickness of the piezoelectric film layer caused by the piezoelectric effect if a bias voltage is applied to the first and the second electrodes.
A reflection type display, comprising:

a lower substrate;

a reflection film formed on the lower substrate to reflect the light incident from the outside;

a piezoelectric film layer formed on the reflection film; and

first and second electrodes formed on the piezoelectric film layer to be spaced apart from each other in parallel,

wherein the piezoelectric film layer changes a thickness depending on the voltage applied to the first and second electrodes.
The reflection type display according to claim 4, wherein the first and second electrodes are made of electrodes that transmit the light incident from the outside and the light reflected on the reflection film.
The reflection type display according to claim 4, wherein the thickness of the piezoelectric film layer is controlled such that:

destructive interference occurs between the light reflected on the reflection film and the light reflected on the first and second electrodes if a bias voltage is not applied to the first and the second electrodes; and

constructive interference occurs between the light reflected on the reflection film and the light reflected on the first and second electrodes due to the change of thickness of the piezoelectric film layer caused by the piezoelectric effect if a bias voltage is applied to the first and the second electrodes.
A method for manufacturing a reflection type display, comprising:

preparing a lower substrate;

forming a first electrode on the lower substrate, the first electrode being made of a reflective electrode that reflects the light incident from the outside;

forming a piezoelectric film layer on the first electrode, the piezoelectric film changing a thickness depending on voltage; and

forming a second electrode on the piezoelectric film layer, the second electrode being made of a transparent electrode that transmits the light incident from the outside and the light reflected on the first electrode.
A method for manufacturing a reflection type display, comprising:

preparing a lower substrate;

forming a reflection film on the lower substrate, the reflection film reflecting the light incident from the outside;

forming a piezoelectric film layer on the reflection film, the piezoelectric film changing a thickness depending on voltage; and

forming first and second electrodes on the piezoelectric film layer to be spaced apart from each other in parallel, the first and second electrodes which could be made of electrodes that transmit the light incident from the outside and the light reflected on the reflection film.