Flexible display device

A flexible display device (10) is disclosed. The flexible display device comprises a flexible substrate (12), a number of display pixels (14) arranged in a form of rows and columns on the surface of the substrate, a number of grooves (16) in the surface of the substrate each of which is formed in between adjacent two rows or columns of the display pixels (14), and connection lines (18) for electrically interconnecting the plurality of display pixels (14), thereby providing flexibility to the display device and, at the same time, minimizing the propagation of mechanical stress caused when the display device is bent or rolled. A method of manufacturing the display device is also disclosed.

FIELD OF THE INVENTION

The present invention relates generally to a display device. More particularly, the invention relates to a flexible display device, which can be rolled up in a preferential direction. The invention also relates to a method of manufacturing such flexible display devices.

BACKGROUND OF THE INVENTION

In general, a display panel device consists of a substrate layer, a number of display pixels disposed on the surface of the substrate, and pixel switching circuitry. The display pixels are arranged in a form of plural rows and columns.

Conventionally, flexible substrates such as a plastic substrate have been utilized to provide a mechanical flexibility to display devices. However, there has been a limitation to the degree of flexibility since the flexibility of the display panel relies on only that of the plastic substrate. In addition, the mechanical stress caused by bending or flexing is propagated throughout the whole displaying area, particularly the display pixels. Therefore, the display performance characteristics of the pixels are adversely affected so that it can not work properly as a display device, especially when excessively bent or severely flexed.

Accordingly, there is a need to solve the conventional problems noted above and to provide a novel flexible display device in which its flexibility can be maximized and the propagation of mechanical stress can be minimized, without damaging the display performance.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a flexible display device. The display device comprises (a) a flexible substrate; (b) a plurality of display pixels arranged in a form of rows and columns on the surface of the substrate; (c) a plurality of first grooves in the surface of the substrate, the first groove being formed in between adjacent two rows or columns of the display pixels, thereby providing flexibility to the display device and, at the same time, minimizing the propagation of mechanical stress caused when the display device is bent or rolled; and (d) a plurality of connection lines for electrically interconnecting the plurality of display pixels. The display device can further include a plurality of second grooves, each of which is formed in between adjacent two columns or rows of the display pixels thereby enhancing the flexibility of the display device, the first and second grooves being substantially perpendicular to each other.

According to another aspect of the present invention, there is provided a flexible display device. The display device comprises (a) a flexible substrate having a first and second surfaces; (b) a plurality of display pixels arranged in a form of rows and columns on the first surface of the substrate; (c) a plurality of first parallel grooves in the first surface of the substrate, the first groove being formed in between adjacent two rows or columns of the display pixels, thereby providing flexibility to the display device and, at the same time, minimizing the propagation of mechanical stress caused when the display device is bent or rolled; and (d) a plurality of connection lines for electrically interconnecting the plurality of display pixels. The connection lines comprise: (a) a plurality of row connection lines provided on the second surface of the substrate, each row connection line corresponding to each respective row of display pixels; (b) a plurality of column connection lines provided on the second surface of the substrate, each column connection line corresponding to each respective column of display pixels; and (c) a plurality of vertical connection lines each connecting each display pixel on the first surface with a corresponding row or column connection line on the second surface, wherein an insulation layer is provided between the row and column connection lines.

According to one aspect of the present invention, there is provided a method of manufacturing a flexible display device. The method comprises the steps of: (a) providing a flexible substrate having a first and second surface; (b) forming a plurality of first parallel grooves in the first surface of the substrate, each adjacent two parallel grooves defining a pixel area therebetween; (c) providing a plurality of display pixels on the pixel area such that the display pixels are arranged in a pattern of rows and columns; and (d) providing a plurality of connection lines to electrically interconnect the display pixels. The method can further include a step of forming a plurality of second parallel grooves in the first surface of the substrate such that the second groove is substantially perpendicular to the first groove. The step of providing a plurality of connection line comprises steps of: (a) providing a first connection line to connect the first surface with the second surface of the substrate; and (b) providing a second connection line on the second surface of the substrate such that the first connection line serves to electrically connect the display pixel on the first surface to the second connection line on the second surface. The step of providing a first connection line comprises steps of: (a) forming a through-hole passing through the first and second surfaces of the substrate; and (b) carrying out metallization in the through-hole.

A further understanding of other aspects, features, and advantages of the present invention will be realized by reference to the following description, appended drawings and accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

InFIGS. 1 and 2, there is schematically illustrated a flexible display device in accordance with the first embodiment of the present invention, which is generally denoted by a reference numeral10.FIG. 1is the cross-sectional view of the display device, andFIG. 2illustrates the top plan view thereof.

Referring toFIGS. 1 and 2, the flexible display device10comprises a flexible substrate12such as a plastic substrate, a plurality of display pixels14provided on the surface of the substrate12, a plurality of grooves16formed between the display pixels14, and a plurality of connection lines18for electrically interconnecting the display pixels14. In this embodiment, the display pixels14are arranged in a pattern of plural rows and columns as is shown inFIG. 2. The groove16can be formed in between any adjacent rows or columns of the display pixels, for example, in a regular pattern. In this embodiment, the grooves16are provided in between every adjacent two columns of display pixels and formed substantially parallel to the columns. The connection lines18include a plural of column connection lines18C and a plural of row connection lines18R, which serve to electronically interconnect the columns and rows of display pixels respectively, as is illustrated inFIGS. 2. An insulation layer (not shown inFIGS. 1 and 2) is provided between the row and column connection lines18R and18C, which are substantially perpendicular to each other.

The grooves16define a pixel area13in-between where the display pixels14are placed. Accordingly, by virtue of the grooves16, the pixel area13is mechanically isolated, and the whole display device10is provided with a greater flexibility, especially to the extent that it can be rolled up or folded. The mechanical isolation of the pixel area13serves to minimize the stress propagation from the substrate12to the pixel area13, i.e., the display pixels14when rolled or bent. That is, the minimal influence on display performance characteristics can be achieved. Therefore, the display device10of the invention can be stored in a compact rolled state, for example, in a cylindrical casing, and can be flattened out when in use. Furthermore, the flexible display device10can operate even when it remains bent or wrapped around a cylindrical surface.

In the embodiment ofFIGS. 1 and 2, although the display device10is provided with a plural of columnar grooves16only, it can further include a plural of row grooves16R as illustrated inFIG. 7. Each row groove16R is provided in between each adjacent two rows of display pixels, thereby improving the flexibility of the display device. The column and row grooves16C,16R are substantially perpendicular to each other.

As illustrated inFIG. 1, the grooves16can take either a rectangular or rounded cross-section.

Each display pixel14includes an electro-luminescent display layer such as a polymer or organic emitting diode (OLED) and pixel electronics such as thin-film-transistor based switching circuitry. The pixel electronics can be integrated in a stacked pixel configuration on the pixel area13.

FIGS. 3 to 6schematically depict a flexible display device10in accordance with the second embodiment of the present invention.FIG. 3is the cross-sectional view of the display device, andFIG. 4illustrates the top plan view thereof.FIGS. 5 and 6are cross-sectional views taken along the lines A—A and B—B respectively inFIG. 4.

Similar to the previous embodiment ofFIGS. 1 and 2, the flexible display device10ofFIGS. 3 to 6comprises a flexible substrate12such as a plastic substrate, a plurality of display pixels14provided on the surface of the substrate12, a plurality of grooves16formed between the display pixels14, and a plurality of connection lines17and18for electrically interconnecting the display pixels14. Likewise, the configuration of the elements is essentially identical in both embodiments, except for that of the connection lines.

Referring toFIGS. 3 to 6, the structure of the connection line of this embodiment will be described hereafter in greater detail.

In this embodiment, the connection line for electrically interconnecting the display pixels comprise a plural of row connection lines18R, a plural of column connection lines18C, and a plural of vertical connection lines17. According to this embodiment, the row and column connection lines18R and18C are provided on the opposite side to the surface of the substrate12where the display pixels14are disposed. An insulation layer19ais provided between the row and column connection lines18R,18C, as clearly illustrated inFIGS. 5 and 6. The vertical connection line17serves to connect each display pixel14, for example a pixel contact15(on which the display pixel is integrated) with each corresponding row or column connection lines. More specifically, the vertical connection line17includes a column vertical connection line17C and a row vertical connection line17R. In this embodiment, each display pixel14is provided with a row vertical connection line17R and a column vertical connection line17C, which electronically connect the display pixel14to a corresponding row and column connection lines18R,18C respectively, as clearly depicted inFIGS. 5 and 6. Further detail of the connection lines17,18will be described hereinafter, in conjunction with manufacturing processes of the flexible display of the invention.

InFIG. 7, there is schematically shown a top plan view of a flexible display device in accordance with the third embodiment of the invention. As noted above and illustrated inFIG. 7, the display device of the invention can be further provided with a plurality of row grooves16R together with a plurality of column grooves16C, thereby improving the flexibility of the display device. Likewise, each row groove is formed in between each adjacent two rows of display pixels14.

According to another embodiment of the invention, there is provided a method of manufacturing the flexible display devices described above. The method, in general, includes a step of forming a number of parallel grooves in the surface of a flexible substrate, such that a columnar pixel area is defined between each adjacent two grooves as illustrated inFIGS. 2 and 4. The parallel grooves can consist of a plurality of parallel row grooves and a plurality of parallel column grooves. In this case, each adjacent two row grooves define an isolated pixel area in combination with each adjacent two column grooves, as shown inFIG. 7. According to the method, then, a number of display pixels are provided on the pixel area defined between the grooves such that the display pixels are arranged in a form of parallel rows and columns, and the row and column of pixels are parallel with the row and column grooves respectively. The method of the invention also includes a step of forming a connection line to electronically interconnect the display pixels, depending on the design of the display device. Details of the above steps will be described hereinafter, in conjunction withFIGS. 8ato9r.

It is noted that the order of the steps of the method, which is described above and will be further described hereafter, can be switched with each other, depending on the design of the display, or under certain manufacturing conditions and circumstances.

InFIGS. 8ato8j, there is sequentially and schematically illustrated a method of manufacturing a flexible display device in accordance with the fourth embodiment of the invention. The method will be explained in greater detail hereafter.

FIGS. 8ato8dshow, in sequence, a process of forming a plurality of grooves in the surface of a flexible substrate12. For convenience of the illustration and description, there is shown only two parallel grooves16, between which a pixel area13is defined. The grooves16can be formed in the flexible plastic substrate12by using, for example, a metal (or other) masking technique and reactive ion etching (RIE) process in an atmosphere of CF4+O2mixture. That is, a thin-film metal12ais first deposited on the flexible substrate12and then patterned according to a desired outline and dimensions of the grooves as shown inFIG. 8b. Then, the metal-patterned substrate is transferred into a RIE chamber, where the area of the substrate surface which is free from the metal12ais etched and eventually results in the grooves16as depicted inFIG. 8c. After RIE-etching of the substrate, the metal mask12ais removed by using a wet etchant, or the like as shown inFIG. 8d. Alternatively, the grooves in the plastic substrate can be formed by means of a laser micromachining process or a projection laser micromachining process, which are well-known in the art.

Depending on the requirements of pixel size and the desired degree of bending (radius of curvature), the depth and width of the grooves can be controlled during the above processes such that the mechanical integrity of the substrate can be maintained while minimizing the influence on display performance characteristics.

FIGS. 8eto8jsequentially illustrate the step of providing a display pixel14and a connection line18between adjacent pixels. As well-known in the art, the display pixel14associates various pixel electronics, including conducting layers, several dielectric layers11a,11cand11d, and can electrode11b, a source and drain metal11f, an OLED (Organic Light Emitting Diode) cathode11e, an organic layer11g, or the like. Although an OLED device is illustrated as a display pixel, various other types of pixel devices can be integrated together with other necessary components. The above display pixel and related components, and the connection line18can be formed by means of various conventional semiconductor processes such as lithography or the like.

InFIGS. 9ato9r, there is sequentially and schematically illustrated a method of manufacturing a flexible display device in accordance with the fifth embodiment of the invention. The method will be explained in greater detail, referring to the flexible display device shown inFIGS. 3 to 6.

In this embodiment, the step of forming a connection line between the display pixels is different from that of the previous one. Other steps are essentially identical with those of the previous embodiment. That is, the step of forming the connection lines includes steps of providing a first connection line perforating a flexible substrate, and providing a second connection line on the opposite side to the surface of the substrate where the display pixels are placed, such that the first connection line serves to electrically connects the display pixel on the surface to the second connection line. In the figures, the first connection line is denoted by reference numerals17C or17R, and the second connection line by18C or18R. The first connection lines17C,17R correspond to the vertical connection lines17C,17R inFIGS. 3 to 6.

According to this embodiment of the invention, the step of providing a first connection line comprises steps of forming a through-hole passing through the substrate, and carrying out metallization in the through-hole.

FIGS. 9ato9fshow the forming procedures of a first connection line17C or17R. As illustrated inFIGS. 9ato9d, the step of making a through-hole11is similar to the groove forming process described above in conjunction withFIGS. 8ato8d. That is, a metal masking and patterning process and a reactive ion etching (RIE) process, a laser micromachining process, or a projection laser micromachining process can be utilized, which are well-known processes in the art. A metal layer12bsuch as an Al layer is provided on the opposite side to the substrate surface where the metal masking12ais deposited. The metal layer12bis used for providing the second connection lines18C and18R in subsequent steps of the method.

FIGS. 9eand9fschematically illustrate the step of metallizing the through-holes11to forming the first connection lines17C and17R. Various conventional processes can be used for metallization of the through-holes11, including an electro- or electroless deposition process.

InFIGS. 9gto9l, there is schematically depicted the step of providing the second connection lines18C and18R. Specifically, as shown inFIG. 9h, by patterning the metal layer12b, a second connection line18C is formed, which corresponds to the column connection line inFIGS. 4 to 6. Then, a first insulation layer19asuch as a dielectric layer is deposited over the second connection line18C. As illustrated inFIGS. 9jto9l, opening vias in the insulation layer19a, and deposition and patterning another metal layer are carried out to provide another second connection line18R, which corresponds to the row connection line inFIGS. 4 to 6. Then another insulation layer19bsuch as a dielectric encapsulation layer is provided above the second connection line18R, as shown inFIG. 9l.

Subsequently, as shown inFIG. 9m, the grooves16are formed by means of the same processes noted above, in conjunction with the previous embodiment ofFIGS. 8ato8j. The grooves16define a pixel area13.

Similar toFIGS. 8eto8j,FIGS. 9nto9rschematically and sequentially illustrate the step of providing a display pixel14. As well-known in the art, the display pixel14associates various pixel electronics, including conducting layers, several dielectric layers, a electrode, a source and drain metal, an OLED cathode, an organic layer, or the like. Although an OLED device is illustrated as a display pixel, various other types of pixel devices can be applied to the present invention. The above display pixel and related components can be formed by means of various conventional semiconductor processes such as lithography or the like.

While this invention has been described with reference to several specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications and variations may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.