CN109119550B

CN109119550B - Ink-jet printing method, pixel structure, OLED substrate and display device

Info

Publication number: CN109119550B
Application number: CN201811056395.1A
Authority: CN
Inventors: 廖金龙
Original assignee: BOE Technology Group Co Ltd; Hefei Xinsheng Optoelectronics Technology Co Ltd
Current assignee: BOE Technology Group Co Ltd; Hefei Xinsheng Optoelectronics Technology Co Ltd
Priority date: 2018-09-11
Filing date: 2018-09-11
Publication date: 2021-02-26
Anticipated expiration: 2038-09-11
Also published as: CN109119550A

Abstract

The invention provides an inkjet printing method, a pixel structure, an OLED substrate, and a display device, belonging to the technical field of display, which can at least partially solve the problem of uneven distribution of printing droplets in the existing inkjet printing method. An inkjet printing method of the present invention includes: forming a groove for accommodating droplets in a confinement structure, and the confinement structure is lyophobic to the droplets; dropping droplets into the groove, wherein at least two The droplets of the droplets are arranged along the first direction, the two opposite edges of the groove in the first direction are the first edges, the droplet closest to one first edge in the first direction is the first droplet, and the first droplet is the first droplet. The drop falls at least partially on its corresponding first edge.

Description

Ink-jet printing method, pixel structure, OLED substrate and display device

Technical Field

The invention belongs to the technical field of display, and particularly relates to an ink-jet printing method, a pixel structure, an OLED substrate and a display device.

Background

An organic light emitting diode display (OLED display) is an important display device because it has the advantages of self-luminescence, fast response, wide viewing angle, high brightness, bright color, lightness and thinness, etc. In the prior art, an inkjet printing technology can be generally used to prepare organic functional layers (such as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer) of an organic light emitting diode in an organic light emitting diode display device, which can improve the utilization rate of an organic light emitting diode material and reduce the production cost of the organic light emitting diode display device, and therefore, research on the inkjet printing technology is receiving more and more attention from researchers.

The prior art of forming organic functional layers in organic light emitting diodes using ink jet printing techniques requires the formation of a pixel definition layer (having a plurality of recesses 10 therein corresponding to pixel areas) on a substrate in advance and the precise ejection of print drops 20 into the designated pixel areas. In general, in order to prevent the droplet 20 from falling outside the designated pixel region, the drop position of the droplet 20 is spaced a certain distance from the edge of the pixel region (as shown in fig. 1, for example, the distance d between the center position of the droplet 20 closest to the left edge of the pixel region and the edge of the corresponding pixel region is 2r, where the print droplet 20 is approximately spherical and r is the radius). However, since the wetting property of the liquid droplet 20 and the layer structure material located therebelow is generally poor, the liquid droplet 20 may not be spread smoothly and may not be spread over the whole designated pixel region, so that the uniformity of the formed organic functional layer is poor, and further, the luminance of the pixel region of the organic light emitting diode display device is uneven when the organic light emitting diode display device emits light, and the organic light emitting diode display device does not emit light, even has a short circuit phenomenon, and the display effect of the organic light emitting diode display device is seriously affected.

Disclosure of Invention

The invention at least partially solves the problem of uneven droplet distribution in the existing ink-jet printing method and provides an ink-jet printing method for enabling uniform droplet distribution.

The technical scheme adopted for solving the technical problem of the invention is an ink-jet printing method, which comprises the following steps:

forming a recess for receiving a liquid droplet in a defining structure, the defining structure having lyophobicity to the liquid droplet;

and dripping liquid drops into the grooves, wherein at least two liquid drops are arranged along a first direction, two opposite edges of the grooves in the first direction are first edges, the liquid drop closest to one first edge in the first direction is a first liquid drop, and at least part of the first liquid drop falls on the corresponding first edge.

It is further preferred that the droplets are spherical; the center of the first liquid drop falls on the corresponding first edge or in the groove, and the distance between the position and the corresponding first edge is smaller than that

Wherein V represents the volume of the first droplet.

It is further preferred that at least three of said droplets are arranged along said first direction, and in the first direction, said droplets other than two of said first droplets are uniformly distributed between two of said first droplets.

Further preferably, the opening of the recess has a rectangular shape, the first direction is a longitudinal direction thereof, and one droplet of the liquid droplets is distributed in a second direction perpendicular to the first direction.

It is further preferred that the forming of the recess in the defining structure for receiving the droplet comprises: forming a pixel defining layer on a substrate; forming a via in the pixel defining layer.

Further preferably, the droplet is formed of a soluble light-emitting material.

Further preferably, the pixel defining layer contains a fluorine element so that the pixel defining layer has liquid repellency to the liquid droplets.

The technical scheme adopted for solving the technical problem of the invention is a pixel structure, and the pixel structure is manufactured by the method.

The technical scheme adopted for solving the technical problem of the invention is an OLED substrate which comprises the pixel structure.

The technical scheme adopted for solving the technical problem of the invention is a display device which comprises the OLED substrate.

Drawings

FIG. 1 is a schematic view of a conventional inkjet printing method after dropping droplets;

FIG. 2 is a schematic diagram of a method of ink-jet printing according to an embodiment of the present invention after dropping droplets;

FIG. 3 is a schematic diagram of a method of ink-jet printing according to an embodiment of the present invention after dropping droplets;

wherein the reference numerals are: 10 grooves; 11 a first edge; 20 droplets; 21 a first droplet; d the distance between the center of the first droplet and its corresponding first edge.

Detailed Description

In order to make the technical solutions of the present invention better understood, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown in the figures.

In the following description, numerous specific details of the invention, such as structure, materials, dimensions, processing techniques and techniques of components, are set forth in order to provide a more thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.

Example 1:

as shown in fig. 2 and 3, the present embodiment provides a method of inkjet printing, including:

s10, forming a recess 10 for accommodating the liquid droplet 20 in the defining structure, the defining structure having lyophobicity to the liquid droplet 20.

Wherein the defining structure may comprise a plurality of grooves 10 distributed in an array, and adjacent grooves 10 are spaced apart. The composition of the drops 20 dropped in different grooves 10 may be different or the same. For the same recess 10, different droplets 20 may be dropped therein several times to form a plurality of different layers of structures therein.

Wherein the liquid repellency of the defined structure to the liquid droplet 20 means that the surface of the defined structure is resistant (i.e., repellent) to the material of the liquid droplet 20 such that when the liquid droplet 20 lands on the surface of the defined structure, its contact angle is greater than 45 degrees.

Preferably, forming the recess 10 for receiving the droplet 20 in the defined configuration comprises:

s11, forming a pixel defining layer on the substrate.

S12, forming a via hole in the pixel defining layer.

Wherein, that is to say, the above defining structure may be a pixel defining layer, and the above groove 10 is formed by the upper surface of the substrate (or other layer structure on the substrate) and the via holes in the pixel defining layer, wherein, if the groove 10 is plural and distributed in an array, the via holes in the pixel defining layer are also plural and distributed in an array.

Steps S11 and S12 may be a method for forming a pixel structure in an Organic Light Emitting Diode (OLED) substrate. The pixel defining layer is generally used to define the pixel area of adjacent sub-pixel structures in the pixel structure, that is, each recess 10 is used to form one sub-pixel structure. Since the pixel structure generally includes sub-pixel structures for emitting light of different colors (e.g., a red light emitting sub-pixel structure, a blue light emitting sub-pixel structure, and a green light emitting sub-pixel structure), the liquid droplets 20 in the plurality of grooves 10 may be liquid droplets 20 of different compositions, and the three sub-pixel structures of red, blue, and green are correspondingly formed, respectively.

Preferably, the droplet 20 is a droplet 20 formed of a soluble light emitting material.

That is, the liquid droplet 20 is formed by dissolving the luminescent material (e.g., dissolving in a solution), so that the organic functional layer with a corresponding color can be formed after the liquid droplet 20 is solidified.

Of course, the organic functional layer in the sub-pixel structure may be a multi-layer structure (e.g., including a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer), so that different layers may be formed by different soluble light emitting materials in different dropping processes, i.e., the above soluble light emitting materials are not limited to the materials for forming the light emitting layer.

Preferably, the opening of the recess 10 has a rectangular shape, the first direction is a longitudinal direction thereof, and one droplet 20 is distributed in the second direction perpendicular to the first direction.

In which the length direction (horizontal direction in the figure) of the rectangular parallelepiped groove 10 is a first direction, the width direction (vertical direction in the figure) is a second direction, and the width direction is just capable of accommodating the droplets 20 arranged in a line, when the inkjet printing method is used for manufacturing a pixel structure, the shape of such a groove 10 conforms to the shape of the formed sub-pixel structure.

Preferably, the pixel defining layer contains fluorine element to make the pixel defining layer liquid-repellent to the liquid droplets 20.

Here, the liquid droplet 20 refers to a liquid droplet 20 forming a sub-pixel structure. The liquid droplets 20 can be made liquid-repellent with respect to the liquid droplets 20 by adding fluorine element to the pixel defining layer.

And S20, dropping the droplets 20 into the groove 10, wherein at least two droplets 20 are arranged along the first direction, two opposite edges of the groove 10 in the first direction are first edges 11, the droplet 20 closest to one first edge 11 in the first direction is a first droplet 21, and the first droplet 21 at least partially falls on the corresponding first edge 11.

In other words, the grooves 10 are distributed with two opposite first edges 11 (edges on the left and right sides of the grooves 10 in the figure) in the first direction (the transverse direction in the figure), and since there are at least two droplets 20 in the first direction, there are two first droplets 21 (two droplets 20 on the leftmost side and the rightmost side in the figure) adjacent to the two first edges 11. At least a portion of each first droplet 21 lands on its corresponding first edge 11, i.e., each first droplet 21 cannot land completely in the groove 10 without contacting the first edge 11 upon dropping into the groove 10.

Since the defining structure is lyophobic to the liquid drop 20, the part of the first liquid drop 21 which does not fall into the groove 10 can finally fall into the groove 10 completely through the repulsive force generated by the defining structure, and the liquid drop 20 at this time can contact with the side wall of the groove 10, so that the liquid drop is spread over the groove 10, and thus, the uneven distribution of the dropped liquid drop 20 in the groove 10 caused by the fact that the position of the dropped liquid drop 20 is too close to the center of the groove 10 or the wetting property of the liquid drop 20 and the bottom surface of the groove 10 is poor can be avoided.

Preferably, the droplets 20 are spherical; the center of the first droplet 21 falls on its corresponding first edge 11 or in the recess 10, and the distance between the position and its corresponding first edge 11 is smaller than

Where V represents the volume of the first droplet 21.

Wherein, that is to say when the droplet 20 is spherical, the distance between the position at which the centre of sphere of the first droplet 21 falls and its corresponding first edge 11 is smaller than the radius of that droplet 20 (i.e. the leftmost and rightmost droplet 20 is necessarily located between the positions shown in fig. 2 and 3), and the position at which the centre of sphere of the first droplet 21 falls is close to the centre of the recess 10. The falling position of the center of the sphere of the first droplet 21 corresponds to the position of the center of the drop opening for dropping the first droplet 21, and since the volume and the drop position of each droplet 20 are controllable, the relationship therebetween can be determined in the above manner.

The falling position of the sphere center of the first droplet 21 satisfies the above condition, which not only ensures that the first droplet 21 completely enters the groove 10 under the action of the repulsive force, so that the droplets 20 are fully and uniformly distributed in the groove 10, but also prevents the first droplet 21 from partially remaining outside the groove 10. When the method of ink-jet printing is used for manufacturing the pixel structure, the formed sub-pixel structure can uniformly cover the grooves 10 due to the liquid drops 20, and the sub-pixel structure can uniformly emit light, so that the performance of the sub-pixel structure is improved.

Preferably, at least three droplets are arranged in the first direction, and the droplets 20 other than the two first droplets 21 are uniformly distributed among the two first droplets 21 in the first direction.

Wherein, that is to say when there are three or more droplets 20 in the first direction, the rest of the droplets 20 are evenly distributed between two first droplets 21 except the first droplets 21 adjacent to the first edge 11, and the number of the rest of the droplets 20 can be determined by the volume of the groove 10, so that the droplets 20 dropped into the groove 10 can eventually fill the whole groove 10, and the droplets 20 overflow the groove 10.

The drop positions of the droplets 20 between the two first droplets 21 are uniformly distributed, which is favorable for the uniform distribution of the droplets 20 in the groove 10. When the method of ink-jet printing is used to make a pixel structure, the rest of the droplets 20 are uniformly distributed between the two first droplets 21, which can further make the brightness of the sub-pixel structure uniform, thereby further improving the performance of the sub-pixel structure.

S30, a desired layer structure is formed by the dropped droplets 20.

Specifically, that is, when the inkjet printing method is used to fabricate the pixel structure, the liquid layer formed by the droplets 20 in the grooves 10 is cured by a method such as heat drying, and the like, to obtain the desired organic functional layers (e.g., a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer) of the organic light emitting diode.

Example 2:

this embodiment provides a pixel structure, which is manufactured by the method of embodiment 1.

The light emitting layer of the pixel structure of the present embodiment is formed by the liquid droplets in embodiment 1, and the formed light emitting layer uniformly spreads over the entire pixel area (i.e., the groove in embodiment 1), so that the pixel structure of the present embodiment not only has uniform brightness and good performance, but also has low manufacturing cost.

Example 3:

the present embodiment provides an OLED substrate including the pixel structure of embodiment 2.

Due to the high-quality performance of the pixel structure of the OLED substrate, the OLED substrate is uniform in brightness, good in performance and low in manufacturing cost.

Example 4:

the present embodiment provides a display device including the OLED substrate of embodiment 3.

The display device of the embodiment has the advantages of uniform lightening, good performance and low manufacturing cost due to the excellent structure of the OLED substrate.

Specifically, the display device can be used in any products with display functions, such as electronic paper, mobile phones, tablet computers, televisions, notebook computers, digital photo frames, navigators and the like.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method of inkjet printing, comprising:

dropping droplets into the grooves, wherein at least two droplets of the droplets are arranged along a first direction, two opposite edges of the grooves in the first direction are first edges, the droplet closest to one of the first edges in the first direction is a first droplet, the first droplet is at least partially dropped on the corresponding first edge, and the droplets are spherical;

the center of the first liquid drop falls on the corresponding first edge or in the groove, and the distance between the position and the corresponding first edge is smaller than that

Wherein V represents the volume of the first droplet.

2. A method of inkjet printing according to claim 1 wherein there are at least three of said drops arranged along said first direction, and in the first direction, said drops other than two of said first drops are evenly distributed between two of said first drops.

3. Method of inkjet printing according to claim 1 wherein the opening of the recess is rectangular in shape, the first direction being the direction of one of its long sides, and one drop of the liquid droplet being distributed in a second direction perpendicular to the first direction.

4. The method of inkjet printing according to claim 1 wherein forming a recess in the defined structure for receiving a droplet comprises:

forming a pixel defining layer on a substrate;

forming a via in the pixel defining layer.

5. Method of inkjet printing according to claim 4, wherein the droplets are droplets of a soluble type luminescent material.

6. Method of inkjet printing according to claim 5 wherein the pixel defining layer contains fluorine elements to render the pixel defining layer liquid repellent to the droplets.

7. A pixel structure, characterized in that it is made by a method according to any one of claims 5-6.

8. An OLED substrate comprising the pixel structure of claim 7.

9. A display device comprising the OLED substrate of claim 8.