Display panel and display panel manufacturing method

A display panel enabling constraint of void formation between substrates and minimizing the effect of any voids formed, has for at least one pixel, a distance between the element surface and the element opposing surface corresponding to each light-emitting element of the pixel that is smaller than a distance between the inter-pixel surface and the inter-pixel opposing surface in an inter-pixel area between neighboring pixels, and smaller than a distance between the inter-element surface and the inter-element opposing surface corresponding to the light-emitting elements, and on the element substrate, the distance between neighboring pixels is greater than a distance between neighboring light-emitting elements, and a distance between the inter-pixel surface and the inter-pixel opposing surface is greater than a maximum distance between the inter-element surface and the inter-element opposing surface.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation application of PCT Application No. PCT/JP2011/003768 filed Jun. 30, 2011, designating the United States of America, the disclosure of which, including the specification, drawings and claims, is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure pertains to a display panel in which a sealing resin layer is interposed between an element substrate and an opposing substrate.

DESCRIPTION OF THE RELATED ART

Conventional technology allows for a sealing resin layer provided in order to prevent deterioration of a light-emitting element, such as an organic electroluminescence element, caused by the infiltration of water or oxygen from the outside atmosphere. That is, the sealing resin layer is formed between an element substrate, on which the light-emitting element is formed, and an opposing substrate (e.g., a CF substrate) opposite the element substrate.

The following describes a forming method for the sealing resin layer.

FIG. 24is a schematic diagram illustrating resin flow during sealing resin layer formation.FIG. 25is a magnified view of portion A ofFIG. 24.FIG. 26is a cross-section taken along line B1-B2ofFIG. 24.FIG. 27is a schematic view illustrating the spread of the resin material.

The sealing resin layer is formed, for example, by dropping resin material903, used for sealing, onto the opposing substrate901. The dropping of the resin material903is performed by dripping a drop of the resin material903at a plurality of positions on the opposing substrate901, in volumes sufficient for a single drop to cover multiple (e.g., on the order of 100) light-emitting elements.

Next, curing is initiated for the resin material903so dropped onto the opposing substrate901. The curing of the resin material903is initiated, for example, by UV irradiation. The curing duration is controllable by the adjustment of curing delay agents, polymerization initiators, and reactants.

Subsequently, before the dropped resin material903hardens, the element substrate is arranged opposite the opposing substrate, and the two substrates are joined. Here, as shown inFIGS. 24-26, the dropped resin material24spreads in concentric circles, expanding from the center of each drip position.

As a result, as shown inFIG. 27, resin material903a, spread in concentric circles from the center of a given drip position, mutually overlaps resin material903band903c, similarly spread in concentric circles from the respective centers of neighbouring drip positions. Thus, the sealing resin layer forms over a wide area between the opposing substrate901and the element substrate.

CITATION LIST

SUMMARY

However, the above-described technology is problematic in that voids905remain in the sealing resin layer, wherever unfilled by the resin material. When such a void905occurs on or above one of the light-emitting elements, the light-emitting element remains uncovered by the sealing resin layer. This is problematic in that the light-emitting element is not protected against the deterioration caused by infiltration of water or oxygen from the outside atmosphere.

One non-limiting and exemplary Embodiment provides a display panel in which void formation is constrained, and in which the effect of void formation on the light-emitting elements is minimized, as well as a manufacturing method for such a display panel.

In one general aspect, the techniques disclosed here feature a display panel, comprising: an element substrate having a plurality of pixels, each pixel having at least one light-emitting element; an opposing substrate arranged so as to oppose the element substrate; and a sealing resin layer interposed between and adjoining the element substrate and the opposing substrate, respective surfaces of the element substrate and the opposing substrate facing each other, and the sealing layer sealing the light-emitting elements, wherein an element surface is defined as a top surface of the element substrate on one of the light-emitting elements, an element opposed surface is defined as a surface of the opposing substrate opposite the element surface, an inter-pixel surface is defined as a top surface of the element substrate between neighbouring pixels, an inter-pixel opposing surface is defined as a top surface of the opposing substrate opposite the inter-pixel surface, an inter-element surface is defined as a surface of the element substrate between neighbouring light-emitting elements within one of the pixels, an inter-element opposing surface is defined as a surface of the opposing substrate opposite the inter-element surface, for at least one given pixel, a distance between the element surface and the element opposing surface corresponding to each of the light-emitting elements of the given pixel is smaller than: a distance between the inter-pixel surface and the inter-pixel opposing surface in an inter-pixel area between the given pixel and at least one neighbouring pixel; and a distance between the inter-element surface and the inter-element opposing surface corresponding to the light-emitting elements of the given pixel, and on the element substrate, the distance between the given pixel and the neighbouring pixel is greater than a distance between one of the light-emitting elements of the given pixel and a neighbouring light-emitting element of the given pixel, and a distance between the inter-pixel surface and the inter-pixel opposing surface in an expansion is greater than a maximum distance between the inter-element surface and the inter-element opposing surface, the expansion being located between the given pixel and the neighbouring pixel.

In another general aspect, the techniques here disclosed feature a display panel manufacturing method, comprising: an element substrate formation step of forming an element substrate having a plurality of pixels, each pixel having at least one light-emitting element; an opposing substrate formation step of forming an opposing substrate arranged so as to oppose the element substrate; and a sealing resin layer formation step of forming a sealing resin layer, respective surfaces of the element substrate formed in the element substrate formation step and the opposing substrate formed in the opposing substrate formation step facing each other, the sealing resin layer being interposed between and adjoining the element substrate and the opposing substrate, and the resin layer sealing the light-emitting elements, wherein for the element substrate formation step and the opposing substrate formation step, an element surface is defined as a region of the surface of the element substrate on one of the light-emitting elements, an element opposing surface is defined as a surface of the opposing substrate opposite the element surface, an inter-pixel surface is defined as a surface of the element substrate between neighbouring pixels, an inter-pixel opposing surface is defined as a region of the surface of the opposing substrate opposite the inter-pixel surface, an inter-element surface is defined as a surface of the element substrate between neighbouring light-emitting elements within one of the pixels, an inter-element opposing surface is defined as a surface of the opposing substrate opposite the inter-element surface, and the element substrate and the opposing substrate are formed such that: on the element substrate, for at least one given pixel, a distance between the element surface and the element opposing surface corresponding to each of the light-emitting elements of the given pixel is smaller than: a distance between the inter-element surface and the inter-element opposing surface in an inter-pixel area between the given pixel and at least one neighbouring pixel; and a distance between the inter-element surface and the inter-element opposing surface corresponding to the light-emitting elements of the given pixel, and on the element substrate, the distance between the given pixel and the neighbouring pixel is greater than a distance between one of the light-emitting elements of the given pixel and a neighbouring light-emitting element of the given pixel, and a distance in an expansion between the inter-pixel surface and the inter-pixel opposing surface is greater than a maximum distance between the inter-element surface and the inter-element opposing surface, the expansion being located between the given pixel and the neighbouring pixel.

According to the above structure, the distance between the element substrate and the opposing substrate is wider at portions where none of the light-emitting elements are formed than at portions where the light-emitting elements are formed. Thus, the distance between the element substrate and the opposing substrate is narrower at portions where the light-emitting elements are formed, such that the fluidity of the resin material is increased at such portions and thereby constraining void formation in the portions where the light-emitting elements are formed.

DETAILED DESCRIPTION

Overview of Embodiments

In one non-limiting aspect, a display panel of the present disclosure comprises: an element substrate having a plurality of pixels, each pixel having at least one light-emitting element; an opposing substrate arranged so as to oppose the element substrate; and a sealing resin layer interposed between and adjoining the element substrate and the opposing substrate, respective surfaces of the element substrate and the opposing substrate facing each other, and sealing the light-emitting elements, wherein an element surface is defined as a top surface of the element substrate on one of the light-emitting elements, an element opposing surface is defined a surface of the opposing substrate opposite the element surface, an inter-pixel surface is defined as a top surface of the element substrate between neighbouring pixels, an inter-pixel opposing surface is defined as a surface of the opposing substrate opposite the inter-pixel surface, an inter-element surface is defined as a top surface of the element substrate between neighbouring light-emitting elements within one of the pixels, an inter-element opposing surface is defined as a surface of the opposing substrate opposite the inter-element surface, for at least one given pixel, a distance between the element surface and the element opposing surface corresponding to each of the light-emitting elements of the given pixel is smaller than: a distance between the inter-pixel surface and the inter-pixel opposing surface in an inter-pixel area between the given pixel and at least one neighbouring pixel; and a distance between the inter-element surface and the inter-element opposing surface corresponding to the light-emitting elements of the given pixel, and on the element substrate, the distance between the given pixel and the neighbouring pixel is greater than a distance between one of the light-emitting elements of the given pixel and a neighbouring light-emitting element of the given pixel, and a distance between the inter-pixel surface and the inter-pixel opposing surface in an expansion is greater than a maximum distance between the inter-element surface and the inter-element opposing surface, the expansion being located between the given pixel and the neighbouring pixel.

In another non-limiting aspect of the display panel of the present disclosure, an element substrate reference surface is defined as a surface of the element substrate located on the inter-pixel area and nearest the opposing substrate, the element substrate has primary recesses (or primary concavities) each located on one of the light-emitting elements and recessed with respect to the element substrate reference surface, a bottom of each primary concavity being the element surface and the element substrate reference surface being the inter-pixel surface, an opposing substrate reference surface is defined as a surface of the opposing substrate opposite the element substrate reference surface, and the opposing substrate has primary protrusions each located opposite one of the primary concavities and protruding from the opposing substrate reference surface, a top face of each primary protrusion being the element opposing surface and the opposing substrate reference surface being the inter-pixel opposing surface.

Accordingly, a distance between the element surface and the element opposing surface, where the light-emitting elements are formed, is narrower than a distance between the inter-pixel surface and the inter-pixel opposing surface in an inter-pixel area between the given pixel and at least one neighbouring pixel, in inter-pixel areas where no light-emitting elements are formed. Thus, the fluidity of the resin material is increased where the light-emitting elements are formed, thereby constraining void formation in the vicinity of the light-emitting elements.

Conversely, the distance between the inter-pixel surface and the inter-pixel opposing surface in an inter-pixel area where no light-emitting elements are formed between the given pixel and at least one neighbouring pixel is greater than the distance between the element surface and the element opposing surface where the light-emitting elements are formed. Thus, the resin material flows less easily through the inter-pixel areas, which easily induce the voids therein.

However, void formation in the inter-pixel areas has little effect on the light-emitting elements, as no light-emitting elements are located in the inter-pixel areas.

Furthermore, void formation is constrained in the areas where the light-emitting elements are formed, such that upon light emission, the voids are less likely to cause a decrease in luminance. Additionally, this enables the suppression of flicker due to external light reflection when no light is being emitted.

In a further aspect of the display panel of the present disclosure, on the element substrate, the expansion making the distance, in the expansion, between the inter-pixel surface and the inter-element opposing surface greater than the distance, in areas other than the expansion, between the inter-pixel surface and the inter-pixel opposing surface is located between the given pixel and the neighbouring pixel.

Accordingly, the expansion easily induces the voids therein. Thus, in the event of void formation, it is more likely that the void formation occurs in the inter-pixel area where no light-emitting elements are located. Thus, a high-quality display panel is made available.

In yet a further aspect of the display panel of the present disclosure, the light-emitting elements are formed between partition walls. Accordingly, irregularities are more easily formed in the surface of the element substrate that faces the opposing substrate. By satisfying the above-discussed distance relationships, void formation over the light-emitting elements can be suppressed.

In another aspect of the display panel of the present disclosure, the partition walls are of uniform height. Accordingly, the irregularities in the surface of the element substrate that faces the opposing substrate can more easily be reduced. This simplifies control of the distance between the element substrate and the opposing substrate, so as to produce a high-quality display panel.

In an alternate aspect of the display panel of the present disclosure, an auxiliary electrode is provided between the pixels. Accordingly, in the event of void formation, the voids are collected in regions near the auxiliary electrodes, which do not affect light emission. As such, void formation between the element surface of the element substrate and the element opposing surface of the opposing substrate can be suppressed. As a result, the infiltration of water and oxygen from the outside atmosphere to the light-emitting elements and the like is preventable.

In another alternate aspect of the display panel of the present disclosure, the light-emitting elements of the pixels each emit a different color of light. Further, the colours of light emitted by the light-emitting elements of the pixels are at least three in number. Accordingly a color display panel is made available.

In yet another alternate aspect of the display panel of the present disclosure, each one of the light-emitting elements is an electroluminescence light-emitting element. Accordingly, a thin, high-efficiency display panel is made available.

In yet a further alternate aspect of the display panel of the present disclosure, the opposing substrate includes a plurality of color filters arrayed in correspondence with the different colours of light emitted by the light-emitting elements, and the primary protrusions of the opposing substrate are the color filters. Accordingly, although irregularities are more easily formed in the surface of the opposing substrate that faces the element substrate, void formation over the light-emitting elements can be suppressed by satisfying the above-discussed distance relationship.

In still a further aspect of the display panel of the present disclosure, the opposing substrate includes a black matrix partitioning the color filters in correspondence with the colours of light, and the opposing substrate reference surface is a surface of the black matrix facing the element substrate. Accordingly, the reference surface is more likely made more uniform (i.e., the reference surface is less subject to fluctuations). This simplifies control of the distance between the element substrate and the opposing substrate, so as to produce a high-quality display panel.

In still another aspect of the display panel of the present disclosure, the expansion is located at an approximate midpoint of the inter-pixel area. Accordingly, there is an increase in probability that void formation will occur at the position farthest from the light-emitting elements, i.e., in the inter-pixel area between neighbouring pixels where no light-emitting elements are formed. As such, a high-quality display panel is made available.

In still another alternate aspect of the display panel of the present disclosure, the primary protrusions equivalent to the color filters each protrude with respect the opposing substrate reference surface to a different degree, such that the distance between the element surface and the element opposing surface is minimized at a middle light-emitting element for each of the pixels. Further, for at least one given pixel, the distance between the element surface and the element opposing surface corresponding to each of the light-emitting elements of the given pixel is greater than a distance between neighbouring light-emitting elements of the given pixel. Accordingly, the inter-pixel area easily induces the voids therein, such that a high-quality display panel is made available.

A display panel manufacturing method of the present disclosure comprises: an element substrate formation step of forming an element substrate having a plurality of pixels, each pixel having at least one light-emitting element; an opposing substrate formation step of forming an opposing substrate arranged so as to oppose the element substrate; and a sealing resin layer formation step of forming a sealing resin layer, respective surfaces of the element substrate formed in the element substrate formation step and the opposing substrate formed in the opposing substrate formation step facing each other, the sealing resin layer being interposed between and adjoining the element substrate and the opposing substrate, and sealing the light-emitting elements, wherein for the element substrate formation step and the opposing substrate formation step an element surface is defined as a top surface of the element substrate on one of the light-emitting elements, an element opposing surface is defined as a surface of the opposing substrate opposite the element surface, an inter-pixel surface is defined as a top surface of the element substrate between neighbouring pixels, an inter-pixel opposing surface is defined as a surface of the opposing substrate opposite the inter-pixel surface, an inter-element surface is defined as a top surface of the element substrate between neighbouring light-emitting elements within one of the pixels, an inter-element opposing surface is defined as a surface of the opposing substrate opposite the inter-element surface, and the element substrate and the opposing substrate are formed such that: on the element substrate, for at least one given pixel, a distance between the element surface and the element opposing surface corresponding to each of the light-emitting elements of the given pixel is smaller than: a distance between the inter-element surface and the inter-element opposing surface in an inter-pixel area between the given pixel and at least one neighbouring pixel; and a distance between the inter-element surface and the inter-element opposing surface corresponding to the light-emitting elements of the given pixel, and on the element substrate, the distance between the given pixel and the neighbouring pixel is greater than a distance between one of the light-emitting elements of the given pixel and a neighbouring light-emitting element of the given pixel, and a distance in an expansion between the inter-pixel surface and the inter-pixel opposing surface is greater than a maximum distance between the inter-element surface and the inter-element opposing surface, the expansion being located between the given pixel and the neighbouring pixel.

Further, an element substrate reference surface is defined as a surface of the element substrate located on the inter-pixel area and nearest the opposing substrate, the element substrate has primary recesses each located on one of the light-emitting elements and recessed with respect to the element substrate reference surface, a bottom of each primary concavity being the element surface and the element substrate reference surface being the inter-pixel surface, an opposing substrate reference surface is defined as a surface of the opposing substrate opposite the element substrate reference surface, and the opposing substrate has primary protrusions each located opposite one of the primary concavities and protruding from the opposing substrate reference surface, a top face of each primary protrusion being the element opposing surface and the opposing substrate reference surface being the inter-pixel opposing surface.

Accordingly, a distance between the element surface and the element opposing surface, where the light-emitting elements are formed, is narrower than a distance between the inter-pixel surface and the inter-pixel opposing surface in an inter-pixel area between the given pixel and at least one neighbouring pixel, in inter-pixel areas where no light-emitting elements are formed. Thus, the fluidity of the resin material is increased where the light-emitting elements are formed, thereby enabling the suppression of void formation in the vicinity of the light-emitting elements. Conversely, the distance between the inter-pixel surface and the inter-pixel opposing surface in an inter-pixel area between the given pixel and at least one neighbouring pixel is greater than the distance between the element surface and the element opposing surface in the inter-pixel areas, where no light-emitting elements are formed. Thus, the resin material flows less easily through the inter-pixel areas, which easily induce the voids therein. However, void formation in the inter-pixel areas has no effect on the light-emitting elements, as no light-emitting elements are located in the inter-pixel areas.

In an alternative aspect of the display panel manufacturing method of the present disclosure, an auxiliary electrode is provided between the pixels. Accordingly, any voids formed are collected in regions near the auxiliary electrodes without affecting light emission. As such, void formation between the element surface of the element substrate and the element opposing surface of the opposing substrate is constrainable. As a result, the infiltration of water and oxygen from the outside atmosphere to the light-emitting elements and the like is preventable.

In another alternate aspect of the display panel manufacturing method of the present disclosure, the light-emitting elements of the pixels each emit a different color of light. Accordingly, a color display panel is made available.

In still a further aspect of the display panel manufacturing method of the present disclosure, the opposing substrate includes a plurality of color filters arrayed in correspondence with the different colours of light emitted by the light-emitting elements, and a black matrix partitioning the color filters in correspondence with the colours of light, the primary protrusions of the opposing substrate are the color filters, and the opposing substrate reference surface is a surface of the black matrix facing the element substrate. Accordingly, the reference surface is more easily made uniform (i.e., the reference surface is free of fluctuations). This simplifies control of the distance between the element substrate and the opposing substrate, so as to produce a high-quality display panel.

In still another aspect of the display panel manufacturing method of the present disclosure, the expansion is located at an approximate midpoint of the inter-pixel area. Accordingly, there is an increase in probability that void formation will occur at the position farthest from the light-emitting elements, i.e., in the inter-pixel area between neighbouring pixels where no light-emitting elements are formed. As such, a high-quality display panel is made available.

In still another alternate aspect of the display panel manufacturing method of the present disclosure, the primary protrusions equivalent to the color filters each protrude with respect the opposing substrate reference surface to a different degree, such that the distance between the element surface and the element opposing surface is minimized at a middle light-emitting element for each of the pixels. Further, for at least one given pixel, the distance between the element surface and the element opposing surface corresponding to each of the light-emitting elements of the given pixel is greater than a distance between neighbouring light-emitting elements of the given pixel. Accordingly, the inter-pixel area is made to more easily induce the voids therein, such that a high-quality display panel is made available.

Exemplary Embodiment

The display panel pertaining to the exemplary Embodiment is described below, with reference to the accompanying drawings. No particular limitation is intended regarding the materials and quantities thereof used in the present disclosure as described in the exemplary Embodiment. The exemplary Embodiment may be optionally modified, as appropriate, and combined with other Embodiments, provided that the technical scope of the disclosure is not exceeded in doing so, and that no contradictions result.

1. Overall Configuration

The overall configuration of a display device1pertaining to the exemplary Embodiment is described below, with reference to the accompanying drawings.

FIG. 1is a block diagram schematically representing the overall configuration of the display device1.

As shown, the display device1includes a display panel10and a drive control unit20connected thereto.

The display panel10is, for example, a top emission organic electroluminescent display panel making use of the organic material electroluminescence effect. The drive control unit20includes four drive circuits21-24and a control circuit25controlling the drive circuits21-24.

No limitation is intended regarding the display panel being an organic electroluminescent panel using organic materials. The display panel may optionally be an inorganic electroluminescent panel using inorganic materials. Further, no limitation is intended regarding the display panel being a top emission device. The display panel may optionally be a bottom emission device.

No limitation is intended regarding the arrangement of the drive control unit20, nor regarding the quantity of drive circuits. For example, the control circuit and drive circuits may optionally be integrated as a single circuit.

2. Configuration of Display Panel10

The configuration of the display panel10is described below.

FIG. 2is a cross-sectional diagram schematically illustrating the key components of the display panel10pertaining to the Embodiment.

As shown, the display panel10has an electroluminescent substrate11(hereinafter, EL substrate, corresponding to the element substrate of the disclosure), a color filter substrate12(hereinafter, CF substrate, corresponding to the opposing substrate of the disclosure), and a sealing resin layer13that is interposed between the EL substrate11and the CF substrate12. The sealing resin layer13is provided in order to join the EL substrate11and the CF substrate12, as well as to prevent the intrusion of water, gases, and other outside elements into the EL substrate11(i.e., to the light-emitting elements).

Let the light output surface of the display panel10be the top or upper surface thereof, so as to correspond to the arrow indicating the Z axis inFIG. 2.

The EL substrate11includes a plurality of pixels, each including at least one light-emitting element for display purposes. The EL substrate11is made up of a substrate body, an inter-layer insulating membrane, anodes, banks, light-emitting layers, and so on.

FIG. 3is a plane-view diagram of the EL substrate11.FIG. 4is a cross-sectional diagram taken along line A1-A2ofFIG. 3.FIG. 5is a cross-sectional diagram taken along line B1-B2ofFIG. 3.

The top or upper surface of the EL substrate11is the surface thereof joined to the CF substrate12, corresponding to the Z-axis direction indicated byFIG. 2.

The EL substrate11has a plurality of pixels30arranged in the X-Y plane along the substrate body surface. Each one of the pixels30is made up of three sub-pixels (in three colors (R, G, and B))31(R),31(G), and31(B).

Each one of the sub-pixels31corresponds to one of the light-emitting elements of the disclosure. Each of the pixels is made up of three of the sub-pixels. Reference sign31hereinafter denotes the sub-pixels in generality, without regard for the color emitted thereby.

Each of the sub-pixels31is elongated in the Y direction. The three sub-pixels31(R),31(G), and31(B) are aligned in the X direction such that each of the pixels30forms an approximate square when viewed in the plane.

The following explanations primarily referenceFIGS. 4 and 5.

A thin-film transistor (hereinafter, TFT) substrate111serves as the substrate body. An inter-layer insulating membrane112is, for example, formed on the top surface of the TFT substrate111. The inter-layer insulating membrane112is provided so as to compensate for surface gradations in the TFT substrate111. The TFT substrate111with the inter-layer insulating membrane formed thereon may optionally serve as the substrate body.

An anode113ais disposed at the top surface of the inter-layer insulating membrane112for each of the sub-pixels31. Each anode113ais shaped so as to be elongated in the Y direction, like the sub-pixels31as seen in the plane view.

As shown inFIGS. 2 and 4, auxiliary electrodes113bare formed at the top surface of the inter-layer insulating membrane112between the pixels30.

A bank114(corresponding to the partition walls of the disclosure) is formed between any two neighbouring anodes113aand between any given anode113aand neighbouring auxiliary electrode113b. Each bank114extends from an area on the inter-layer insulating membrane112where no anode113aor auxiliary electrode113bis formed so as to pass between the anodes113aand the auxiliary electrodes113bwhile partly overlapping the top circumferential edges thereof. Each bank is, for example, shaped as an upwardly-protruding trapezoid when viewed in cross-section.

A light-emitting layer emitting light of a predetermined color, e.g., an organic light-emitting layer115, is layered over each anode113awithin a region defined by the banks114(i.e., surrounded by the banks114).

A blue organic light-emitting layer115(B), a green organic light-emitting layer115(G), and a red organic light-emitting layer115(R) are represented in the drawings. Reference sign115hereinafter denotes the organic light-emitting layers in generality, without regard for the color emitted thereby.

A cathode116and a sealing layer117are respectively formed on the organic light-emitting layer115so as to traverse the areas defined by the banks114and be continuous with the neighbouring organic light-emitting layers115and auxiliary electrodes113b. That is, the cathode116is formed at the top surface of the organic light-emitting layer115, at the top face of each auxiliary electrode113bin areas thereof not covered by the banks114, and at the top face and side faces of the banks114. The sealing layer117is formed at the top face of the cathode116.

The sealing layer117serves to prevent the exposure of the organic light-emitting layers115and so on to water and air. The top surface of the sealing layer117is uneven due to irregularities caused by the banks114. The term “irregularities” is hereinafter used to denote a combination of concavities and protrusions.

On the surface of the EL substrate11, configured as described above, opposite the CF substrate12(i.e., the top surface of the sealing layer117), any portion arranged above the area between neighbouring pixels30, or in other words, a portion of the surface above the banks114formed between neighbouring pixels30, is termed an inter-pixel surface, or reference surface.

Also, on the top face of the EL substrate11, configured as described above, any portion arranged above the sub-pixels making up each of the pixels30, or in other words, a (portion of the) surface arranged above the organic light-emitting layers115, is termed a primary concavity118with respect to the reference surface of the EL substrate11. The bottom of the primary concavity118is termed a sub-pixel surface (or element surface).

Further, on the top face of the EL substrate11, configured as described above, any portion arranged above a midpoint between adjacent pixels30is termed a secondary concavity119in the reference surface of the EL substrate11. The portion in which the secondary concavity119is formed corresponds to the expansion (or an expansion portion) of the present disclosure.

FIG. 6is a plane-view diagram of the CF substrate12.FIG. 7is a cross-sectional diagram taken along line C1-C2ofFIG. 6.FIG. 8is a cross-sectional diagram taken along line D1-D2ofFIG. 6.

The CF substrate12includes a substrate body121, color filters122, and so on.

As shown inFIG. 6, each of the color filters122is elongated in the Y direction when viewed in the plane, similar to the sub-pixels31illustrated byFIG. 3.

The following explanations primarily referenceFIGS. 7 and 8.

The substrate body121is the frontal substrate of the display panel10, and is made of a translucent material. Color filters122(B),122(G), and122(R) are formed on the top surface of the substrate body121, respectively corresponding to the organic light-emitting layers115(B),115(G), and115(R) of the EL substrate11, i.e., to the sub-pixels31(B),31(G), and31(R). Reference sign122hereinafter denotes the color filters in generality, without regard for emitted color.

A black matrix (hereinafter abbreviated BM)123is arranged at the top surface of the substrate body121between the color filters122, that is, between the sub-pixels31. As shown inFIGS. 7 and 8, each of the color filters122is shaped so as to partly overlap the top circumferential edge of the neighbouring BM123to each side.

The BM123is a black layer provided to improve display contrast by preventing external light from reflecting on or entering the display surface of the display panel10. As shown inFIG. 2, the BM123is shaped to correspond to (i.e., to oppose) the banks114of the EL substrate11. Specifically, portions thereof between pixels (i.e., any portion facing one of the auxiliary electrodes113b) are shaped to correspond to two of the banks114a, having a greater width (shown as the lateral dimension in the drawings) than the BM123(a) portions between the color filters122.

In order to distinguish BM portions arranged between the sub-pixels31from BM portions arranged between the pixels30, the former portions are termed inter-subpixel BM and take the reference sign123awhile the BM portions arranged between neighbouring pixels30are termed inter-pixel BM and take the reference sign123b. Also, reference sign123hereinafter denotes the BM in generality, without regard for position.

As shown inFIG. 6, the BM123is shaped so as to be between the sub-pixels31of the EL substrate11and exclude the areas where the color filters122are formed. That is, as shown inFIGS. 6 through 8, the BM123is shaped as a grid partitioning the color filters122.

On the surface of the CF substrate12, configured as described above, opposite the EL substrate11, any portions facing the sub-pixel surface of the EL substrate11, or in other words, a top face of the color filter122corresponding to a primary protrusion of the disclosure, is termed a sub-pixel opposing surface (or element opposing surface).

Also, on the top face of the CF substrate12, configured as described above, any portion arranged to face inter-pixel surfaces of the EL substrate11, or in other words, a portion where the inter-pixel BM123bis formed, is termed an inter-pixel opposing surface or reference surface.

(3) Positional Relationship of EL Substrate and CF Substrate

FIG. 9illustrates the positional relationship of the EL substrate11and the CF substrate12.

As described above, with respect to the inter-pixel surface (reference surface), the surface of the EL substrate has primary concavities118each formed in a portion corresponding to an area between the banks114.

The primary concavities118are made to correspond to the organic light-emitting layers115(B),115(G), and115(R). A specific primary concavity is indicated using the reference sign118(B),118(G), or118(R), while the primary concavities in generality take the reference sign118.

As described above, with respect to the inter-pixel opposing surface (reference surface), the surface of the CF substrate12has protruding portions where the color filters122are formed.

In the CF substrate12, the respective distance between the sub-pixel opposing surface, which is the top face of each color filter122(B),122(G), and122(R), and the sub-pixel surface, which is the respective bottom of each primary concavity118(B),118(G), and118(R) in the EL substrate11, is termed D1(B), D1(G) and D1(R). Likewise, the distance between the reference surface of the CF substrate12(i.e., the top surface of the BM123) and the reference surface of the EL substrate11(i.e., the inter-pixel surface) is termed D2, while the distance between the reference surface of the CF substrate12and one of the secondary concavities119between the pixels in the EL substrate11is termed D3. These distances are expressed as the minimum distances between the two substrates.

Thus, the following relations hold between the EL substrate11and the CF substrate12.
GivenD2>D1,D2>D1(B),
givenD2>D1,D2>D1(G), and
givenD2>D1,D2>D1(R).

Further, the following relation beneficially holds, in addition to the above.
D3>D2.

When the EL substrate11and the CF substrate12are viewed in the plane, any area of the EL substrate11corresponding to one of the pixels30is termed a pixel area, and any area of the EL substrate11corresponding to an area between adjacent pixels30is termed an inter-pixel area.

As shown inFIG. 7, the color filter surface (element surface, i.e., the top face of each primary protrusion) at D1(B), D1(G), and D1(R), described above, is at the center of each color filter122, as viewed in the plane. In this example, this is the thinnest portion of the thin film.

By satisfying the above-stated relations, void formation can be suppressed in the sealing resin layer13, and it becomes more likely that the voids are located in the inter-pixel area over the inter-pixel BM123b, in the event of void formation.

This is because, within the pixel area, distance D1is the narrowest distance between the EL substrate11and the CF substrate12, and the resin material of the sealing resin layer13is pressed therein. As a result, any voids are also pressed along with the resin material, such that the voids are unlikely to remain in any of the pixel areas. The pressing action of the resin material in narrow-distance areas is theorized to be driven by a mechanism similar to the capillary action effect, as described later.

Also, as shown inFIG. 9, with respect to the CF substrate12, the distance between the pixels is termed B1while the distance between the color filters122is termed B2.

As such, the following relation holds, regarding the distance between protrusions (i.e., the color filters) on the CF substrate12.
B1>B2
Furthermore,
B2<D1

Satisfying the above-stated relations allows the constraint of void formation in the pixel areas, and also improves the likelihood that any voids formed are located in the inter-pixel areas over the inter-pixel BM123b. This occurs due to the reasons described above. In contrast to conventional technology, voids do not form over the sub-pixels, as any voids formed do so in the inter-pixel areas over the inter-pixel BM123band have little effect on the sub-pixels.

Furthermore, the position at which the distance between the EL substrate11and the CF substrate12is greatest (i.e., the position of distance D3) is the approximate midpoint between pixels (while designed to be at the midpoint, manufacturing variations may lead to deviations). Accordingly, any voids formed in the sealing resin layer13are more likely to be in the inter-pixel area. This occurs due to the reasons described above.

3. Manufacturing Method

The display panel10is manufactured in a process that involves a preparation step for the EL substrate11, a preparation step for the CF substrate12, and a joining step of joining the EL substrate11and the CF substrate12so prepared.

(1) EL Substrate Preparation Step

The manufacturing process for the EL substrate11is described below.

FIGS. 10A through 10Dand HA through11D illustrate the manufacturing process for the EL substrate11.

First, the inter-layer insulating membrane112is formed over the TFT substrate111(FIG. 10A). Subsequently, a metallic thin-film151is formed on the top surface of the inter-layer insulating membrane112for use as the anodes113aand the auxiliary electrodes113b(FIG. 10B). Patterning is applied to the metallic thin-film151to obtain the anodes113aand the auxiliary electrodes113b(FIG. 10C). For example, the metallic thin-film151is formed using a sputtering method, and patterning is applied thereto using a photolithography method.

Next, a bank material layer153is formed from an insulating organic material serving as the material for the banks (FIG. 10D). Patterning is then applied to the bank material layer153to obtain the banks114(FIG. 11A). For example, the bank material layer is formed by coating or similar, and patterning is applied thereto by, for example, overlaying with a mask having apertures of predetermined dimensions, exposing the top of the mask to light, and then washing the remnants of the bank material layer153with developer solution (i.e., by a wet process).

Once the banks114are formed, the organic light-emitting layers115are formed in the regions partitioned by the banks114(FIG. 11B). For example, the organic light-emitting layers115are formed by using an inkjet method to drip an ink compound that includes an organic EL material, and then drying the ink.

Subsequently, the cathode116is formed so as to cover the top faces of the banks114and of the organic light-emitting layers115(FIG. 11C). Then, the sealing layer117is formed (FIG. 11D).

For example, the cathode116is formed using sputtering, and the sealing layer117is formed using sputtering, chemical vapor deposition (hereinafter, CVD), atomic layer deposition (hereinafter, ALD), or similar methods.

(2) Color Filter Preparation Step

The manufacturing process for the CF substrate12is described below.

FIGS. 12A through 12Cand13A through13C illustrate the manufacturing process for the CF substrate12.

First, BM material, having a UV-curable resin (e.g., a UV-curable acrylic resin) serving as the principal component with a black pigment added thereto, is dissolved in a solvent to prepare a BM paste161. The BM paste161is then used to coat one face of the substrate body121(FIG. 12A).

After coating, the BM paste161is dried until the solvent is vaporized and the paste can hold a shape, whereupon a pattern mask163having apertures163aof predetermined dimensions is overlaid so as to correspond to the positions of the banks114(FIG. 12B).

UV rays are then used to irradiate the top of the overlaid pattern mask163. As a result, the BM paste161is baked, the pattern mask163and any unsolidified BM paste161are removed, and then developing and curing are performed. Thus, as shown inFIG. 12C, the BM123aand123bis formed so as to correspond to the banks114.

Next, material for color filter122(R), having a UV-curable resin as the principal component, is dissolved in solvent to obtain filter paste (R), which is coated onto the surface (i.e. the top face) of the substrate body121where the BM123is formed. Upon removing a certain amount of the solvent, a predetermined pattern mask is installed and irradiated with UV rays.

Afterward, curing is performed, the pattern mask and any uncured filter paste (R) are removed, and development is performed. Thus, as shown inFIG. 13A, the color filter122(R) is formed. The color filter122(R) is formed along a piece of the BM123so as to partly overlap the edges of neighbouring pieces of the BM123.

The steps described above for forming the color filter122(R) are repeated with appropriately-coloured materials to form the color filters122(G) and122(B). Accordingly, color filters122(G) and122(B) are formed so as to match the position of the organic light-emitting layer115(FIGS. 13B and 13C).

Like the color filter122(R), the color filters122(G) and122(B) are each formed along a piece of the BM123so as to partly overlap the edges of neighbouring pieces of the BM123.

The CF substrate12is complete when the above steps are complete.

(3) Joining Step

The process of joining the EL substrate11and the CF substrate12includes a step of dripping resin material for the sealing resin layer onto the joining face (top face) of the EL substrate11at a plurality of locations, a step of causing the joining face (top face) of the CF substrate12to adhere to the EL substrate11having the resin material dripped thereon, and step of curing the resin during adhesion.

While the following describes dripping the resin material onto the EL substrate11, the resin material may optionally be dripped onto the CF substrate12.

FIGS. 14A through 14Cillustrate an example of the joining process.

First, a seal material (i.e., DAM) paste is applied to prevent leakage of the resin material for the sealing resin layer13that seals the prepared (i.e., manufactured) EL substrate11and the prepared (i.e., manufactured) CF substrate12. Furthermore, resin material (FILL)165for the sealing resin layer13is dripped at predetermined space intervals onto interior portions of the CF substrate12(i.e., onto portions where the organic light-emitting layer115is formed) excluding the circumferential area of the CF substrate12(Dripping step,FIG. 14A).

Once the dripping of the resin material165is complete, the EL substrate11and the CF substrate12are joined under a vacuum (FIG. 14B). At this point, the resin material165so dripped spreads throughout the space between the EL substrate11and the CF substrate12such that gaps between drops of the resin material165are eliminated (seeFIGS. 24 and 25).

The resin material165is then irradiated with UV rays, for example. Such irradiation may occur while dripping the resin material165, or may occur once all of the resin material165has been dripped. Upon irradiation by the UV rays, resin curing is delayed. While some curing may begin during UV irradiation, most curing progresses after the EL substrate11and the CF substrate12have been joined.

Then, the resin material165is cured once the dripped resin material165has sufficiently spread (curing step). Upon curing, the resin material165forms the sealing resin layer13(FIG. 14C).

The above-described steps complete the display panel10.

Given the above-described positional relationships between the EL substrate11and the CF substrate12, any voids formed in the sealing resin layer13are likely to occur over the inter-pixel BM123b.

The TFT substrate111is made up of a main substrate on which are formed a TFT, a wiring member, a passivation membrane covering the TFT, and so on (none diagrammed).

The main substrate is, for example, made of an insulating material such as a non-alkali glass, a soda glass, a non-fluorescent glass, a phosphoric glass, a boric gas, quartz, an acrylic resin, a styrene resin, a polycarbonate resin, an epoxy resin, a polyethylene resin, a polyester resin, a silicone resin, aluminium oxide, and so on. The main substrate may optionally be an organic resin film.

The inter-layer insulating membrane112is, for example, made of an insulating material such as polyimide resin or acrylic resin.

(1-2) Anodes and Auxiliary Electrodes

The anodes113aand the auxiliary electrodes113bare metallic wiring made of, for example, Al (aluminium) or an Al alloy.

The anodes113amay optionally be formed from Ag (silver), an alloy of Ag, Pd (palladium), and Cu (copper), an alloy of Ag, Rb (rubidium), and Au (gold), MoCr (an alloy of molybdenum (Mo) and chromium (Cr)), NiCr (an alloy of nickel (Ni) and Cr), or similar.

Given that a top emission panel is used as the display panel10of the exemplary Embodiment, the anodes113aare beneficially formed of a material having high reflectivity.

The banks114are formed from insulating material. Specifically, the banks are formed from a resin or a similar organic material. For example, the organic material may be an acrylic resin, a polyimide resin, a novolac-type phenol resin, and so on. The bank114are beneficially resistant to organic solvents.

Further, processes such as etching and baking are applied to the banks114. Consequently, a material with high resistance to deformity and transformation under these processes is desirable.

The organic light-emitting layer115is, for example, beneficially formed from a fluorescent material as recited in Japanese Patent Application No. H5-163488, such as an oxinoid compound, a perylene compound, a coumarin compound, an azacoumarin compound, an oxazole compound, an oxadiazole compound, a perinone compound, a pyrrolo-pyrrole compound, a naphthalene compound, an anthracene compound, a fluorene compound, a fluoranthene compound, a tetracene compound, a pyrene compound, a coronene compound, a quinolone and azaquinolone compound, a pyrazoline and pyrazolone derivative, a rhodamine compound, a chrysene compound, a phenanthrene compound, a cyclopentadiene compound, a stilbene compound, a diphenylquinone compound, a styryl compound, a butadiene compound, a dicyanomethylene pyran compound, a dicyanomethylene thiopyran compound, a fluorescein compound, a pyrylium compound, a thiapyrylium compound, a selenapyrylium compound, a telluropyrylium compound, an aromatic aldadiene compound, an oligophenylene compound, a thioxanthene compound, a cyanine compound, an acridine compound, an 8-hydroxyquinoline compound metal complex, a 2-bipyridine compound metal complex, a Schiff base and group 3 metal complex, an oxine metal complex, and a rare earth metal complex.

A transparent electrode is used as the cathode116. Specifically, the cathode is ITO (indium tin oxide), IZO (indium zinc oxide), or similar. As described above, the display panel10is a top-emission panel. As such, the cathode116is beneficially formed of a transparent material.

The substrate body121of the CF substrate12is, for example, made of a material identical to that used for the main substrate of the above-described TFT substrate111. Optionally, a material different from that used for the main substrate of the TFT substrate111may be used. However, given that the display panel10is a top emission panel, a material of advantageous transparency is beneficial.

(1-8) Color Filters

The color filters122are each made of a known resin material through which visible light, at wavelengths respectively corresponding to red, green, and blue, is able to pass, such as a polyimide resin.

The BM123is, for example, made from a UV-curable resin material that includes a black pigment with superb light-absorbing and light-blocking characteristics. Acrylic resin or similar is optionally usable as the UV-curable resin material.

(1-10) Sealing Resin Layer

The sealing resin layer13is made of various transparent resin materials. Specifically, an epoxy resin or a silicone resin is selected so as to have a pre-curing viscosity adjusted in consideration of the resin material spread and adhesiveness. The viscosity is beneficially in a range of 50 mmPa·s to 1000 mmPa·s, in particular, in a range of 100 mmPa·s to 500 mmPa·s.

As described above, the surface of the EL substrate11features irregularities. The irregularities encompass protrusions with respect to the bottom of the concavities, concavities with respect to the top faces of the protrusions, and a combination of protrusions and recesses with respect to a position between the bottom of the concavities and the top faces of the protrusions.

Here, with respect to the surface above any position between pixels30, the concavities118and119are located between the banks114. The concavities118and119have a depth Del of 1.0 μm. Needless to say, with respect to the position on the EL substrate11nearest the TFT substrate111(i.e., the bottom surface between the banks114), any portions corresponding to the banks114are protrusions having a height of 1.0 μm.

In the exemplary Embodiment, the color filters122(R),122(G), and122(B) each have a membrane thickness t1of 2.5 μm, the membranes of each color having a uniform thickness.

Accordingly, with respect to the surface of the BM123(identical across the inter-subpixel BM123aand the inter-pixel BM123b), the irregularities in the CF substrate12are protrusions in the form of the color filters122having a height H1of 1.5 μm.

The distance between the EL substrate11and the CF substrate12in the exemplary Embodiment is described below.

Distance D1between the bottom of the primary concavities118between the banks114on the EL substrate11and the top faces of the color filters122of the CF substrate12is 10.00 μm. Here, the height of the color filters122and the depth of the concavities between the banks114are independent of color emitted, such that distance D1is invariant for all emitted colours.

Distance D2between the inter-pixel surface of the EL substrate11and the inter-pixel opposing surface of the CF substrate12is 10.50 μm. Further, distance D3between the bottom of the secondary concavity119at the approximate midpoint of the inter-pixel area and the surface of the inter-pixel BM123bof the CF substrate12is 11.50 μm.

In this example, distance D3is the greatest of the distances between the EL substrate11and the CF substrate12.

(3) Manufacturing Process

As described above, the resin material for the sealing resin layer13has a viscosity of 500 mmPa·s. The resin material is dripped using a syringe, for example. Each drop of resin material so dripped has sufficient volume to cover approximately 100 of the pixels30. The number of drops so dripped is dependent on the size of the display panel10.

The resin material is dripped in a zigzag pattern. That is, when dripping is performed in a matrix, for example, the drip positions on two neighbouring rows are offset by a half-pitch in the row direction.

UV rays irradiate the dripped or dripping resin material, for example. Here, a resin material is used in which curing is delayed upon UV irradiation. Therefore, resin material solidification progresses little before and after the joining of the EL substrate11and the CF substrate12, such that the resin material flows into the gaps between the EL substrate11and the CF substrate12.

Once the resin material has filled the gaps between the EL substrate11and the CF substrate12(alternatively, once an expected time for the resin material to fill the gap has elapsed), heat is applied to encourage solidification of the resin material. The display panel10is complete once the resin material has hardened.

As described under the Technical Field and Summary headings, the problem of void formation within the sealing resin layer was observed. Upon investigation of void formation positions and the like, it was discovered that void formation occurs in specific places.

First, in conformity with the resin material dripping pattern, void formation was found to occur regularly at positions most distant from the dripping points. Second, the voids were found to be concentrated in portions of specific colours.

Upon detailed investigation into several membrane thickness variations for each color, R, G, and B, of the color filters, it was found that the shape of the irregularities in the CF substrate had a major influence. That is, the ease of spreading (i.e., the fluidity) of the resin material when the EL substrate11and the CF substrate12are joined is influenced by the degree to which the color filters protrude (i.e., by the size of the gaps between the EL substrate11and the CF substrate12).

This influence is greater than that of wettability in the surfaces of the EL substrate11and the CF substrate12, and is not constrained by the presence of pigments or dyes in the color filters.

The following uses the results of an experiment in which the irregularities in the CF substrate12are varied to describe the separation of the EL substrate11and the CF substrate12, and the fluidity of the resin material used for the sealing resin layer13.

FIGS. 15A and 15Billustrate the overall experiment.FIG. 15Aillustrates the irregularities of the EL substrate and the CF substrate, whileFIG. 15Billustrates the distance between the EL substrate and the CF substrate.

As shown, the experiment was performed in three configurations. The irregularities in the EL substrate11were held constant, while three levels on the CF substrate12were investigated.

The EL substrate11used in the experiment was made concave to correspond with the color filters122on the CF substrate12, i.e., to assume the primary concavities118between the banks114. The concavity depth was of 1 μm.

Conversely, on the CF substrate12used in the experiment, the BM123had the height given as BM, the blue color filter122(B) had the height given as B, the green color filter122(G) had the height given as G, and the red color filter122(R) had the height given as R, all heights being measured with respect to the substrate body121and indicated inFIG. 15A. The heights in the experiment are shown in the table at the bottom ofFIG. 15B.

For reference purposes, the following describes the membrane thickness of conventional color filters122and BM (the conventional numbers being given as level 1 in the table at the bottom ofFIG. 15A).

The membrane thickness of the color filters122was determined according to the (type of) sub-pixel. For example, the membrane thickness of color filter122(B) was 1.62 μm, whereas the membrane thickness of color filters122(G) and122(R) was of 1.0 μm. The membrane thickness often varies by color.

For example, given a membrane thickness of 1.3 μm for the BM123, then with respect to the top surface of the BM123, color filter122(B) protruded by 0.32 μm whereas color filters122(G) and122(R) were recessed by 0.3 μm.

As given inFIG. 15B, distances D1and D2between the EL substrate11and the CF substrate12were found using the above-given levels 1 through 3 of the CF substrate.

Specifically, for level 1, distances D1(R) and D1(G) were 11.60 μm, distance D1(B) was 10.98 μm, and distance D2was 11.30 μm. Distances D1(R) and D1(G) in the pixel areas are each greater than distance D2in the non-pixel areas.

At level 2, distances D1(R), D1(G), and D1(B) were identical at 10.80 μm, and distance D2was 11.30 μm. As such, distance D2in non-pixel areas where sub-pixels are not formed (i.e., in the inter-pixel areas) was greater than distances D1(R), D1(G), and D1(B) in the pixel areas.

At level 3, distances D1(R), D1(G), and D1(B) were identical at 10.00 μm, and distance D2was 10.50 μm. As such, distance D2in non-pixel areas where sub-pixels are not formed (i.e., in the inter-pixel areas) was greater than distances D1(R), D1(G), and D1(B) in the pixel areas.

In the pixel areas, distance D1was 10.00 μm for level 3 and was 10.80 μm for level 2. That is, distance D1was smaller for level 3 than for level 2.

(2-1) Void Quantity

Using the three configurations (levels 1, 2, and 3) of the CF substrate12described above, an investigation was performed to examine the void quantity occurring in the sealing resin layer13when the resin material165is dripped in the manner used for actual manufacturing and the EL substrate11and the CF substrate12are subsequently joined. This investigation was performed on a display panel10having a screen size of 20 inches.

As shown inFIG. 16, the void quantity decreased across levels, such that a ranking in decreasing order of void quantity gives the order level 1, level 2, level 3. This observation is thought to be influenced by such factors as the size relationship between distance D1and distance D2at each level, as well as the magnitude of distance D1itself.

Comparing level 1 to level 2 revealed that, as stated above, fewer voids were present at level 2 than at level 1. That is, void formation is less likely to occur at level 2 than at level 1.

Comparing the configurations of level 1 and level 2 revealed that, at level 1, only distance D1(B) is smaller than distance D2, while at level 2, distances D1(R), D1(G), and D1(B) are all smaller than distance D2. Also, distance D1is smaller at level 2 than at level 1.

Accordingly, it can be concluded that void formation is less likely when all distances D1are as small as possible, specifically when all distances D1are smaller than distance D2.

Comparing level 2 to level 3 revealed that, as stated above, fewer voids were present at level 3 than at level 2. That is, void formation is less likely to occur at level 3 than at level 2.

Comparing the configurations of level 2 and level 3 revealed that on both levels, distances D1(R), D1(G), and D1(B) were all smaller than distance D2, and that all distances D1were smaller at level 3 than at level 2.

Accordingly, as described in the above comparison of level 1 and level 2, it can be concluded that void formation is less likely when all distances D1are smaller than distance D2, and all distances D1are small.

To summarise the above findings, void formation becomes less likely as distances D1are made smaller than distance D2, and as the gap (distance) between the EL substrate11and the CF substrate12is made smaller.

(2-2) Formation Position

FIGS. 17A and 17Billustrate the fluidity of the resin material in the above-discussed experiment.FIG. 17Ais given using level 3 of the CF substrate, whileFIG. 17Bis given using level 1 of the CF substrate.FIGS. 18A and 18Bare trace diagrams produced fromFIGS. 17A and 17B.FIG. 18Ais given using level 3 of the CF substrate, whileFIG. 18Bis given using level 1 of the CF substrate.

As shown inFIGS. 17A,17B,18A, and18B, and as confirmed at level 3, the resin material165(black side) was fluid enough to evenly spread over a plurality of pixel areas, and to flow evenly over a given pixel area. This is due to the sub-pixel positions, i.e., the distance between the EL substrate11and the CF substrate12at each color filter, being uniform and narrow.

As conversely confirmed, at level 1, although the resin material165(black side) flowed in a similar pattern over individual pixels (areas), at the pixel (area) level, the resin material165flowed (spread) between the blue color filter122(B) and the EL substrate11as well as between the BM123band the EL substrate11, flow was more difficult between the red color filter122(R) and the EL substrate11as well as between the green color filter122(G) and the EL substrate11.

At level 1, the difference between the fluidity of the resin material165at the blue color filter122(B) and the BM123band the fluidity of the resin material165at the red color filter122(R) and the green color filter122(G) lay in the distance between the EL substrate11and the CF substrate12. Specifically, the resin material fluidity was worse at the color filter122(R) and the color filter122(G), where the distance was large.

As confirmed by the above, the fluidity of the resin material165worsened as the distance between the EL substrate11and the CF substrate12increased, but improved at level 3. The conclusion that a configuration where void formation in the sealing resin layer13was less likely to occur was thus reached.

As shown, void formation occurred at level 3 in the inter-pixel area. That is, inFIGS. 19A and 20A, a void has formed so as to extend horizontally between pixels, and inFIGS. 19B and 20B, a void has formed along (two sides of) the perimeter of a pixel.

At level 3, the inter-pixel BM123bwas formed between pixels. The distance (D2) between the inter-pixel BM123band the EL substrate11was greater than the distance (D1) between the top surface of the color filters122and the primary concavity118on the substrate11. Thus, the resin material fluidity worsened in the corresponding inter-pixel area, leading to void formation.

That is, void formation is constrained by optimizing the distance between the EL substrate11and the CF substrate12. Further, adjusting the size of the distance between the EL substrate11and the CF substrate12(i.e., the separation) by parts enables the designation of specific void formation positions.

As confirmed by the above-described experiment, resin material fluidity worsens with increasing distance between the EL substrate and the CF substrate, and where variations in the distance between the EL substrate and the CF substrate are present, small (narrower) distances lead to more desirable resin material fluidity than large (wider) distances.

Accordingly, the following discussion concerning the distance between the EL substrate and the CF substrate is possible.

FIGS. 21A through 21Dillustrate the relationship of void formation to the distance between the EL substrate and the CF substrate.

In this example, the resin material flows easily in the region at D1, where the distance is smallest, and void formation is unlikely in this region (i.e., between pixel areas).

Specifically, the organic light-emitting layer is located in the region at D1. The exposure of the organic light-emitting layer of water, oxygen, and so on is thus preventable.

Also, D2is greater than D1, and D3is greater than D2. Therefore, resin material fluidity is worse in the region at D2than in the region at D1, and is still worse in the region at D3than in the region at D2.

Accordingly, void formation is less likely at D1and more likely at D3. The region at D3is positioned at the approximate midpoint of the inter-pixel area. Given the absence of organic light-emitting layers in this region, void formation in the region at D3has less effect on the organic light-emitting layers than void formation in the pixel areas where the organic light-emitting layers are present.

is plausibly the most beneficial.
D2<D1<D3  (b) Case B:

In this example, given that D1, in the pixel area, is greater than D2, in the inter-pixel area, the resin material flows less easily in the region at D1, and void formation is more likely therein.

appears to be non-beneficial.
D2<D3=D1  (c) Case C:

In this example, the resin material flows easily in the region at D2, where the distance is smallest, and void formation is unlikely therein.

However, D1, in the pixel areas having the organic light-emitting layers, is equal to D3, at the inter-pixel areas not having the organic light-emitting layers. Thus, void formation occurs with equal ease in the region at D1and in the region at D3. That is, void formation is equally likely in the region at D1and in the region at D3.

appears to be non-beneficial.
D2<D3<D1  (d) Case D:

In this example, the distance between the EL substrate11and the CF substrate12is greatest at D1, in the pixel area having the organic light-emitting layer. Void formation is thus most likely in this region.

appears to be non-beneficial.

The exemplary Embodiment focuses on the distance between the EL substrate and the CF substrate.

Here, as shown for example inFIG. 9, the distance between the surface of the CF substrate12(which is the top surface of the inter-subpixel BM123a) and the surface of the EL substrate11at a position above one of the banks114is equal to distance D2between the inter-pixel surface of the EL substrate11(the surface above the banks114a) and the inter-pixel opposing surface of the CF substrate12. Simply considering the distance between the EL substrate11and the CF substrate12, void formation is likely to occur in the portion corresponding to the top of the inter-subpixel BM123abetween the pixel areas.

However, the distance between the color filters122in the pixel areas is, for example, distance B2between color filter122(B) and color filter122(G) (seeFIG. 9), which is on the order of 3 μm to 8 μm. As such, when distance B2is, for example, 5 μm, and thus small in comparison to distance D1between the EL substrate11and the color filters122on the CF substrate12, then, considering the fact that the fluidity of the resin material increases with narrowing distance, there is no need to account for the distance between the CF substrate12and the EL substrate11between the color filters122.

For reference, when the ratio of the distance between the color filters122to distance D1between the CF substrate12and the EL substrate11is 1.0 or lower, the distance between the CF substrate12and the EL substrate11between the color filters122is plausibly ignorable, even if greater than distance D1.

On the other hand, when the distance between pixels (distance B1inFIG. 9) is small in comparison to distance D1and thus similar to the distance between neighbouring color filters122in the pixel areas, void formation becomes difficult to suppress in the pixel area despite distance D2being greater than distance D1. Accordingly, void formation in the pixel areas is constrainable by setting distance D1between the CF substrate12and the EL substrate11to be, for example, on the order of 5 μm or greater, which further improves the likelihood that any voids formed are located in the inter-pixel areas.

Reasoning Leading to Invention

The present inventors examined the causes of void formation in the sealing resin layer between the EL substrate and the CF substrate, and thus came to the following understanding.

Specifically, when the resin material used for sealing spreads in concentric circles, void formation does not occur in areas near the center of the concentric circles, but does occur in peripheral regions farther away from the center. Regions exist where the resin material spreading in concentric circles from the center of a given drip position (termed a first drip position) and the resin material spreading in concentric circles from the center of another drip position (termed a second drip position) neighbouring the first drip position do not overlap, as regional overlap is not perfect. Void formation then occurs in these non-overlapping regions.

Furthermore, during the analysis of void formation locations, the existence of environments more or less conducive to the spread of the resin material in concentric circles progressing with increasing distance from the center of the concentric circles (i.e., void formation does not occur in progress-conducive environments, but does occur in non-conducive environments) was determined.

When viewed in cross-section, the EL substrate has banks facing the CF substrate, and the sub-pixels are formed between the banks. Accordingly, the surface of the EL substrate has irregularities.

When viewed in cross-section, the CF substrate has BM on the surface thereof serving as the banks between the filters of each color, and these color filters are correspondingly formed between the BM. Accordingly, the surface of the CF substrate has irregularities.

Given that the sub-pixels are formed on the EL substrate between the banks, the sub-pixels are located in the concavities between the banks. Conversely, the color filters on the CF substrate are located opposite the sub-pixels on the EL substrate.

Upon critically examining and analyzing the relationship between the depth of the concavities where the sub-pixels are located between the banks on the EL substrate and the height of the color filters opposite the sub-pixels of the EL substrate on the CF substrate (including depressions and concavities with respect to the BM surface), the present inventors arrived at the following.

When the color filters on the CF substrate protrude toward the EL substrate relative to the BM surface, there is a tendency toward greater progress by the resin material between the concavities formed between the banks on the EL substrate and the color filters protruding from the substrate body.

In other words, when pressurized between the EL substrate and the CF substrate, the resin material used for sealing spreads into the gaps between the substrates, thereby determining the void locations. While spreading, the resin material is more easily drawn into narrow gaps between the substrates than into wide gaps between the substrates.

In addition, the progress of the resin material into the concavities between the banks on the EL substrate and the color filters protruding from the CF substrate is notably enhanced when the size of the protruding color filters (i.e., the degree of protrusion) is increased while the space between the concavities between the banks on the EL substrate and the color filters protruding from the CF substrate is narrowed and correspondingly made narrower than the space between the sides of the concavities between the banks (the EL substrate banks) and the space between the sides of the protruding color filters (the inter-subpixel BM on the CF substrate). In other words, void formation in the resin layer used for sealing is more easily made to occur in the inter-pixel areas between the EL substrate and the CF substrate, where no pixels are formed.

The reasons are not yet fully clear, but the mechanism is theorized to be similar to capillary action. The present disclosure has thus been reached in light the above-described new findings.

Assuming a mechanism similar to capillary action, the surface of the EL substrate or the surface of the CF substrate is activatable by irradiation under, for example, oxygen plasma or UV rays, prior to the joining of the substrates, in order to promote greater capillary action.

Although the exemplary Embodiment describes the surface irregularities of the EL substrate11as being caused by the banks114, the surface of the sealing layer (or encapsulation layer) (117) may optionally be made planar. The planarization of the sealing layer (117) is performable by a planarization process, or by thickening the resin layer (117).

Further, although the portions corresponding to the banks protrude with respect to the bottom of the surrounding concavities, this may be reversed. Optionally, the portions having the banks may, for example, be worked into concavities (such that the surrounding area forms a protrusion with respect to the bank portion).

However, this approach requires that, when the EL substrate opposes the CF substrate, the portion wider than the distance between the space between the banks of the EL substrate and the color filters on the CF substrate is arranged in an area other than the area sandwiched between the banks of the EL substrate and the color filters on the CF substrate.

In the exemplary Embodiment, each pixel is delimited by two banks. That is, two of the banks114are arranged between two neighbouring pixels, one of the banks114being located at the side of the organic light-emitting layer (115(B)) of a given pixel that faces the other pixel, and the other one of the banks114being located at the side of the organic light-emitting layer (115(R)) of the other pixel that faces the given pixel (i.e., the two banks114on either side of the auxiliary electrode113binFIG. 2).

However, a single bank may optionally be arranged between the pixels, as in the example described in Variation (1). In this example, the reference signs of the exemplary Embodiment are used for elements identical to those described therein.

FIG. 22is a cross-sectional diagram schematically illustrating the key components of a display panel200pertaining to Variation (1).

The display panel200has a sealing resin layer203joining an EL substrate201and a CF substrate12.

The EL substrate201includes a main substrate (TFT substrate)111, an inter-layer insulating membrane112, anodes113a, auxiliary electrodes113b, banks205, an organic light-emitting layer115, a cathode207, and a sealing layer209.

The banks205include two varieties, namely inter-subpixel banks205aarranged between the sub-pixels, and inter-pixel banks205barranged between the pixels. The inter-subpixel banks205aare configured identically to the inter-subpixel banks114adisposed between the sub-pixels in the exemplary Embodiment.

In Variation (1), a single bank (205b) is arranged between the pixels30. Thus, the Variation differs from the exemplary Embodiment in that the surface of the portion corresponding to the area between pixels on the CF substrate12is flat.

Let the distance between the inter-pixel opposing surface of the CF substrate12and the inter-pixel surface of the EL substrate201be D2, and let the distance between the sub-pixel surface of the EL substrate201and the sub-pixel opposing surface of the CF substrate12be D1. The distance between the EL substrate201and the CF substrate12then satisfies the relation:
D1<D2

Accordingly, void formation in the pixel areas having the organic light-emitting layers115(i.e., the sub-pixels) is constrainable.

In the exemplary Embodiment, the pixels are each made up of three sub-pixels each emitting a different color of light. However, the pixels may optionally be made up of a single sub-pixel.

(1) Color Filter Type

In the exemplary Embodiment, three types of color filters are discussed, namely red (R), green (G), and blue (B). However, no particular limitation is intended. For example, yellow (Y) may be optionally added for a total of four types, or the color filters may be optionally omitted for a monochrome result.

When the wavelengths of the light emitted by the organic light-emitting layer do not require color selection by color filter, then no color filter is required on the CF substrate opposite thereto. In such circumstances, the opposing substrate is configured to be transparent, and this transparent substrate is shaped to have a surface corresponding to the shape of the irregularities in the substrate having the sub-pixels. Thus, the transparent substrate is equivalent to the CF substrate of the exemplary Embodiment.

(2) Color Filter Locations

In the exemplary Embodiment, a uniform location pattern is used for the color filters in the pixel areas. However, the location pattern may optionally vary with each pixel area.

Furthermore, in the exemplary Embodiment, one of each of three types of color filter122are used for each individual pixel. However, a plurality of (e.g., two) predetermined color filters may optionally be used in a given color, for a total of four color filters making up the pixel (in such circumstances, the quantity of sub-pixels is four).

(3) Color Filter Thickness

In the exemplary Embodiment, the membrane thickness of the color filters122is uniform, irrespective of the color emitted thereby. However, the thickness of the color filters122may optionally vary. Nevertheless, distances D1(R), D1(G), and D1(B) between the respective top faces of the color filters122(i.e., the sub-pixel opposing surfaces) and the top surface of the sub-pixels on the EL substrate11or201are beneficially smaller than distance D2between the inter-pixel areas on the EL substrate11or201and the CF substrate12.

Portions of the EL substrate11or201opposite the color filters122(i.e., the sub-pixel surface) may, with respect to the inter-pixel surface of the EL substrate11or201, optionally be recessed, protrude, or be recessed and protrude to a degree varying according to the corresponding color filter, for example.

When distance D1between the CF substrate and the EL substrate varies at the color filters, D1at the central portion of the pixel areas is beneficially narrower than D1at edge portions of the pixel areas. This is because narrowing distance D1at the central portion of the pixel area increases the fluidity of the resin material therethrough and minimizes the occurrence of void formation therein. In other words, distance D1is made narrower at the center portion than at the edge portions to encourage void formation offset toward the edge portions.

That is, given similarly-sized voids forming in the pixel area, an occurrence of void formation so as to extend outside the pixel area and only partially into the pixel area is preferable to an occurrence of void formation occurring entirely within the pixel area in that the former is better able to minimize the effect on the organic light-emitting layer.

3. Display Device

FIG. 23is an overall schematic of the display device pertaining to the present disclosure. The display device1includes the above-described display panel10serving as the screen portion, as well as speakers, a power ON and OFF switch, and connection terminals for connecting to external speakers, a recorder for recording video, and so on.

4. Other

In the exemplary Embodiment, distance D3between the EL substrate and the CF substrate is greatest at the approximate midpoint of the inter-pixel area, regardless of the position of the pixels. That is, as shown inFIG. 2, the banks (114a) are formed separately on either side of the auxiliary electrode (113b), and distance D3is made greater by forming the secondary concavity119at the surface of the EL substrate12to correspond to the portion between the banks (114a).

However, during investigation, the present inventors determined that the regions most prone to void formation are the regions more distant from the position where the resin material is dripped. Thus, the secondary concavity119may optionally be formed so as to increase distance D3only in the regions particularly prone to void formation. Further, distance D2may optionally be greater than distance D1only in regions particular prone to void formation.

INDUSTRIAL APPLICABILITY

The present disclosure is widely applicable to constraining the formation of voids in any portion where a light-emitting element is formed between an element substrate and an opposing substrate.

REFERENCE SIGNS LIST