Patent Description:
For an organic light-emitting device, light is emitted by an organic thin film formed of an organic light-emitting material. In conventional structures of a pixel unit, the luminance of the organic light-emitting device depends on the thickness of the organic thin film, and the entire organic light-emitting device has a uniform luminance when the organic thin film has a uniform thickness. In practice, however, the thickness of the organic thin film of the organic light-emitting device is not uniform due to the imperfection of the manufacture process.

For example, a solution process is employed to form the organic thin film in the procedure of manufacturing the organic light-emitting device, which is applicable for a polymeric organic light-emitting material and a soluble-micromolecule organic light-emitting material and is characterized by the low cost for manufacture apparatus, thereby having a distinct advantage in massive production for large sizes. In the case of manufacturing a full-color organic light-emitting device, an inkjet printing technology, among the technologies of solution process, is generally used. In the inkjet printing technology, the solution is jetted into a pixel region accurately by a piezoelectric nozzle and then the solvent of the solution is removed by evaporation, such that the organic thin film is formed within the pixel region. However, due to the difference of the evaporation rate of the solvent at an edge area and at a central area of the pixel region, it is difficult to form an organic thin film having a uniform thickness within the pixel region.

<FIG> shows a structure of a pixel unit in the prior art, the pixel unit including a substrate <NUM>, a pixel defining layer <NUM>, a pair of pixel electrodes <NUM> and <NUM>, and an organic-light-emitting-display-device functional layer (i.e., an organic thin film) <NUM>. A pixel region is defined by the pixel defining layer <NUM>, the pixel electrode <NUM> is positioned within the pixel region, and the organic-light-emitting-display-device functional layer <NUM> is positioned on the pixel electrode <NUM>. After preparing the organic-light-emitting-display-device functional layer <NUM> by the inkjet printing technology and the like, since the solvent at the edge area of the organic-light-emitting-display-device functional layer <NUM> has a higher vapor pressure than that of the solvent at the central area of the organic-light-emitting-display-device functional layer <NUM>, the evaporation rate of the solvent at the edge area is faster than that of the solvent at the central area, such that the concentration of the solution at the edge area of the organic-light-emitting-display-device functional layer <NUM> is higher than that of the solution at the central area thereof, and the solution at the central area flows towards the edge area, which causes the thickness of the edge area of the organic-light-emitting-display-device functional layer <NUM> to be always greater than that of the central area. When a voltage is applied to the organic-light-emitting-display-device functional layer <NUM> by the pixel electrodes <NUM> and <NUM>, both the edge area and the central area of the functional layer <NUM> emit light, and the luminance of the central area of the pixel region is higher than that of the edge area of the pixel region due to the nonuniformity of the thickness of the functional layer <NUM>, which causes the nonuniformity of the luminance of the organic light-emitting device.

In the prior art, the nonuniformity of the thickness of the organic thin film is decreased by using inkjet printing solutions which have different boiling points, adjusting the structure of the pixel defining layer, or performing surface treatment on the pixel defining layer. For example, in the European patent document <CIT>, the nonuniformity of the thickness of the organic thin film is decreased by the structure design of the pixel defining layer; and in the US patent publication document <CIT>, the shape and thickness of the organic thin film formed by the inkjet printing technology are controlled by using different high-boiling-point solutions. However, the nonuniformity of thickness of the organic thin film cannot be eliminated completely by the above technical solutions, and when using conventional structures of a pixel unit, the luminance of the central area of the pixel region in the light emitting device is higher than that of the edge area thereof due to the nonuniformity of thickness of the organic thin film. Document <CIT> shows an organic light-emitting device.

In order to solve the above problems existing in the prior art, the present invention provides a pixel unit and a method of manufacturing the same, a light emitting device, and a display device.

According to a first aspect of the present invention, there is provided a pixel unit according to claim <NUM>.

According to a second aspect of the present invention, there is provided a light emitting device according to claim <NUM>.

According to a third aspect of the present invention, there is provided a display device according to claim <NUM>.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a pixel unit according to claim <NUM>.

In order to make an object, a technical solution as well as advantages of the present invention more apparent, the present invention will be further described in detail below in conjunction with the specific embodiments and referring to the drawings.

<FIG> illustrates a cross-sectional structure of a pixel unit according to an embodiment of the present invention, and <FIG> illustrates a plan structure of a pixel defining layer and a first electrode in the pixel unit according to an embodiment of the present invention. As illustrated in <FIG>, the pixel unit includes a pixel defining layer <NUM>, a first electrode <NUM>, an organic-light-emitting-display-device functional layer <NUM> and a second electrode <NUM>. The pixel defining layer <NUM> includes first and second pixel defining portions <NUM> and <NUM> having ring-shaped structures, respectively, wherein a region defined by an inner side surface of the first pixel defining portion <NUM> is a pixel region <NUM> (shown in <FIG>), an outer side surface of the second pixel defining portion <NUM> is in contact with the inner side surface of the first pixel defining portion <NUM>, and the first pixel defining portion <NUM> has a thickness greater than that of the second pixel defining portion <NUM>. The first electrode <NUM> is positioned within a central area of the pixel region <NUM>, such that the second pixel defining portion <NUM> is disposed around the first electrode <NUM>. The organic-light-emitting-display-device functional layer <NUM> is positioned on the first electrode <NUM> and the second pixel defining portion <NUM>. The second electrode <NUM> is positioned on the organic-light-emitting-display-device functional layer <NUM>.

It can be seen from <FIG> that, in the pixel unit according to an embodiment of the present invention, an area of an upper surface of the first electrode <NUM> is smaller than that of a bottom plane of the organic-light-emitting-display-device functional layer <NUM>, in other words, the first electrode <NUM> is only positioned under a central area of the organic-light-emitting-display-device functional layer <NUM>. In this case, even if the thickness of the edge area of the organic-light-emitting-display-device functional layer <NUM> is greater than that of the central area thereof, since the first electrode is not provided under the edge area, light is not emitted from the thick edge area of the organic-light-emitting-display-device functional layer <NUM> when a voltage is applied to the organic-light-emitting-display-device functional layer <NUM> by the electrodes <NUM> and <NUM>, thereby avoiding the nonuniformity of luminance of an organic light-emitting display device.

The pixel defining layer <NUM> is made of an inorganic material such as SiO<NUM>, SiNx or the like. In some embodiments, the pixel defining layer <NUM> is made of an organic material such as a photoresist. The first pixel defining portion <NUM> and the second pixel defining portion <NUM> are formed integrally.

The pixel defining layer <NUM> is formed on a substrate <NUM>. The substrate is a glass substrate or an array substrate provided with an array circuit. The pixel defining layer <NUM> includes the first pixel defining portion <NUM> and the second pixel defining portion <NUM>, the first and second pixel defining portions have ring-shaped structures, respectively, the inner side surface of the first pixel defining portion <NUM> is in contact with the outer side surface of the second pixel defining portion <NUM>, and the thickness of the first pixel defining portion <NUM> is greater than that of the second pixel defining portion <NUM>. That is, the second pixel defining portion <NUM> is formed at the edge area of the pixel region <NUM>, which is defined by the inner side surface of the first pixel defining portion <NUM>, and the first electrode <NUM> is formed at the central area of the pixel region <NUM>, such that the second pixel defining portion <NUM> is disposed around the first electrode <NUM>. It can be seen that the area of the pixel region <NUM>, which is defined by the inner side surface of the first pixel defining portion <NUM>, is larger than that of a region in which the first electrode <NUM> is formed. In <FIG>, the second pixel defining portion <NUM> is in contact with the first electrode <NUM>, but the embodiments of the present invention are not limited thereto. In some embodiments, the second pixel defining portion <NUM> is spaced apart from the first electrode <NUM>.

<FIG> illustrates that the first pixel defining portion <NUM> has a thickness gradually changed, that is, the first pixel defining portion <NUM> has an inclined inner side surface which is connected to the upper surfaces of the first and second pixel defining portions <NUM> and <NUM>, but the embodiments of the present invention are not limited thereto. In some embodiments, the first pixel defining portion <NUM> has a constant thickness, that is, the first pixel defining portion <NUM> has a vertical inner side surface.

<FIG> illustrates that the organic-light-emitting-display-device functional layer <NUM> fits and is in contact with an inner side surface of the first pixel defining portion <NUM>, but the embodiments of the present invention are not limited thereto. In some embodiments, other layer(s) are interposed between the organic-light-emitting-display-device functional layer <NUM> and the first pixel defining portion <NUM>.

The thickness of the second pixel defining portion <NUM> is equal to or greater than that of the first electrode <NUM>, and it is preferable that the second pixel defining portion <NUM> and the first electrode <NUM> have the same thickness. The thickness of the first electrode <NUM> ranges from <NUM> to <NUM>.

The first electrode <NUM> and the second electrode <NUM> constitute a pair of pixel electrodes. The first electrode <NUM> is an anode or a cathode. In the case that the first electrode <NUM> is an anode, the material thereof includes a transparent conductive material or a translucent conductive material, such as ITO, Ag, NiO, Al or graphene. In the case that the first electrode <NUM> is a cathode, preferably, the material thereof includes a metal or a combination of metals having a low work function, such as one of Al, Mg, Ca, Ba, Na, Li, K and Ag, or any combination of Al, Mg, Ca, Ba, Na, Li, K and Ag.

When viewed in a plan view, a shape of the first electrode <NUM> includes a parallelogram shape, such as a rectangle shape, a square shape or a diamond shape, or an ellipse shape. Depending on the requirements in practice applications, in some embodiments, the first electrode <NUM> includes any other shape, for example, a quadrangle having any specific shape.

The organic-light-emitting-display-device functional layer <NUM> includes one or more layers of a hole injection layer, a hole transmission layer, a light emitting layer, a hole barrier layer, an electron barrier layer, an electron transmission layer and an electron injection layer.

The second electrode <NUM> has a polarity opposite to that of the first electrode <NUM>, that is, the first electrode <NUM> is one of the anode and the cathode, and the second electrode <NUM> is the other thereof. In the case that the second electrode <NUM> is a cathode, the material thereof includes a metal or a combination of metals having a low work function, such as one of Al, Mg, Ca, Ba, Na, Li, K and Ag, or any combination of Al, Mg, Ca, Ba, Na, Li, K and Ag. In the case that the second electrode <NUM> is an anode, the material thereof includes a transparent conductive material or a translucent conductive material, such as ITO, Ag, NiO, Al or graphene.

In the pixel unit according to the embodiments of the present invention, the organic-light-emitting-display-device functional layer <NUM> is positioned on the first electrode <NUM> and the second pixel defining portion <NUM>, and the area of the bottom plane of the organic-light-emitting-display-device functional layer <NUM> is larger than that of the upper surface of the first electrode <NUM>. Therefore, in the case that the thickness of the edge area of the organic-light-emitting-display-device functional layer <NUM> is greater than that of the central area of the organic-light-emitting-display-device functional layer <NUM>, since the first electrode <NUM> is not disposed under the edge area, light is not emitted from the edge area of the organic-light-emitting-display-device functional layer <NUM> when a voltage is applied to the organic-light-emitting-display-device functional layer <NUM> by the electrodes <NUM> and <NUM>, thereby avoiding the nonuniformity of luminance of an organic light-emitting display device.

The pixel unit is an organic light-emitting diode (OLED) unit.

The embodiments of the present invention further include a display panel comprising the above pixel unit. The display panel is an OLED display panel.

<FIG> illustrates a flowchart of a method of manufacturing a pixel unit, according to an embodiment of the present invention. <FIG> are cross-sectional views illustrating the method of manufacturing a pixel unit, according to an embodiment of the present invention.

As illustrated in <FIG>, the method of manufacturing a pixel unit according to an embodiment of the present invention includes a step <NUM>, a step <NUM>, a step <NUM> and a step <NUM>.

In the step <NUM>, as illustrated in <FIG>, a first electrode <NUM> is formed.

In the step <NUM>, as illustrated in <FIG>, a pixel defining layer <NUM> is formed. Then, the pixel defining layer <NUM> is patterned to form a first pixel defining portion <NUM> and a second pixel defining portion <NUM>, wherein a pixel region is defined by an inner side surface of the first pixel defining portion <NUM>, an outer side surface of the second pixel defining portion <NUM> is in contact with the inner side surface of the first pixel defining portion <NUM>, and the second pixel defining portion <NUM> is disposed around the first electrode <NUM>, as illustrated in <FIG>. The second pixel defining portion <NUM> has a thickness equal to or slightly greater than that of the first electrode <NUM>. The second pixel defining portion <NUM> is in contact with the first electrode <NUM>.

The step <NUM> specifically comprises the following steps: forming, on a substrate <NUM> provided with the first electrode <NUM>, the pixel defining layer; performing a photolithography process on the pixel defining layer, such that an area of an exposure region is larger than that of the upper surface of the first electrode <NUM>; and removing the material of the pixel defining layer positioned on the upper surface of the first electrode <NUM> and thinning a side portion of the pixel defining layer, which is close to an edge of the first electrode <NUM>, so as to form the first pixel defining portion <NUM> and the second pixel defining portion <NUM>.

The pixel defining layer <NUM> is made of an inorganic material such as SiO<NUM>, SiNx or the like. In some embodiments, the pixel defining layer <NUM> is made of an organic material such as a photoresist and the like.

In the case that the pixel defining layer <NUM> is made of an inorganic material, the step <NUM> further comprises: forming, on the substrate provided with the first electrode, a layer of inorganic material by using a technology such as chemical vapor deposition, the layer of inorganic material has a thickness ranging from <NUM> to <NUM>, which is greater than the thickness of the first electrode <NUM>. Next, a photoresist is spin coated on the layer of inorganic material and is exposed and developed, where the exposure area of the photoresist is larger than that of the upper surface of the first electrode <NUM>. Thereafter, the layer of inorganic material is dry etched to remove the inorganic material positioned on the upper surface of the first electrode <NUM>, and a side portion of the layer of inorganic material close to an edge of the first electrode <NUM> is thinned, such that the thickness of the inorganic material close to the edge of the first electrode <NUM> is equal to or slightly greater than that of the first electrode <NUM>, and then the remaining photoresist is removed, so as to form the first pixel defining portion <NUM> and the second pixel defining portion <NUM>.

In the case that the pixel defining layer <NUM> is made of an organic material, the step <NUM> further comprises: coating, on the substrate provided with the first electrode, an organic photoresist material by coating processes such as slit coating, spin coating and the like, to form an organic thin film having a thickness ranging from <NUM> to <NUM>, wherein the thickness of the organic photoresist material is greater than that of the first electrode <NUM>. Thereafter, the organic photoresist material is exposed and developed, and the exposure area of the photoresist is larger than that of the upper surface of the first electrode <NUM>. When performing the exposure, the photoresist positioned on the upper surface of the first electrode <NUM> is over exposed to be removed completely, while the exposure amount for exposing the photoresist close to the edge portion of the first electrode <NUM> is controlled such that the developed photoresist has a thickness equal to or slightly greater than that of the first electrode <NUM>, thereby eventually forming the first pixel defining portion <NUM> and the second pixel defining portion <NUM>.

In the step <NUM>, an organic-light-emitting-display-device functional layer <NUM> is formed on the first electrode <NUM> and the second pixel defining portion <NUM>, and the organic-light-emitting-display-device functional layer <NUM> fits and is in contact with the inner side surface of the first pixel defining portion <NUM>, as illustrated in <FIG>.

In the step <NUM>, the organic-light-emitting-display-device functional layer <NUM> is formed by a solution process and/or an evaporation process. As an example, the formation of the organic-light-emitting-display-device functional layer <NUM> specifically includes: forming a hole injection layer, a hole transmission layer, a light emitting layer and the like within the pixel region <NUM>, respectively, by using the inkjet printing technology, and forming an electron transmission layer, an electron injection layer and the like by using the evaporation process.

In the step <NUM>, a second electrode <NUM> is formed on the organic-light-emitting-display-device functional layer <NUM>, as illustrated in <FIG>.

Claim 1:
A pixel unit, comprising:
a pixel defining layer (<NUM>), the pixel defining layer(<NUM>) comprising first and second pixel defining portions having ring-shaped structures, respectively, wherein the first pixel defining portion (<NUM>) has an inner side surface defining a pixel region (<NUM>), the second pixel defining portion (<NUM>) has an outer side surface in contact with the inner side surface of the first pixel defining portion(<NUM>), and the first pixel defining portion (<NUM>) has a thickness greater than that of the second pixel defining portion (<NUM>);
a first electrode (<NUM>) positioned within a central area of the pixel region (<NUM>);
an organic-light-emitting-display-device functional layer (<NUM>), which is formed within the pixel region (<NUM>) and positioned on the second pixel defining portion (<NUM>) and on the first electrode (<NUM>); and
a second electrode (<NUM>) formed on the organic-light-emitting-display-device functional layer (<NUM>),
an area of a bottom plane of the organic-light-emitting-display-device functional layer (<NUM>) is larger than that of an upper surface of the first electrode (<NUM>), an inner side surface of the second pixel defining portion (<NUM>) is in contact with an entire outer side surface of the first electrode (<NUM>),
the pixel unit being characterized in that, an orthographic projection of the second pixel defining portion (<NUM>) on a substrate (<NUM>) does not overlap with an orthographic projection of the first electrode (<NUM>) on the substrate (<NUM>), and the second pixel defining portion (<NUM>) has a thickness equal to that of the first electrode (<NUM>).