Display device, bonding jig, bonding device, and stretching jig used for manufacturing the display device, and method for manufacturing display device

Provided is a display device 100 that includes a display panel having flexibility (an organic EL panel 1 as an example), and an optical member 2 having flexibility, arranged so as to be stacked on the display panel, wherein the display panel and the optical member 2 are stacked and bonded in a bent state, and thereafter stretched into a flat shape.

TECHNICAL FIELD

The present invention relates to a display device having flexibility, and a bonding jig, a bonding device, and a stretching jig used for manufacturing the display device, as well as a method for manufacturing a display device.

BACKGROUND ART

As a technique used for an organic EL display device in which organic electroluminescence (EL) elements are used, a technique of covering the organic EL elements with a sealing film in order to prevent organic EL elements from deteriorating due to moisture and the like that enters from the outside is known. In a case where such an organic EL display device is bent, there is a possibility that cracks are generated in the sealing film due to film stress, and moisture and the like intrudes therethrough, whereby the organic EL elements deteriorate.

Patent Document 1 discloses a configuration of a display device wherein, on organic EL elements formed on a first substrate, an inorganic insulating film (sealing film) is formed, and a second substrate is formed on the inorganic insulating film. In the display device, in order to prevent cracks from being generated in the sealing film due to bending stress, the materials and thicknesses of the first substrate and the second substrate are set so that the neutral axis, which is the intermediate axis of the display device in the thickness direction, is positioned in the vicinity of the interface between the inorganic insulating film and the second substrate when bending stress is applied.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

In the case of the method disclosed in Patent Document 1, however, since the thicknesses and materials of the first substrate and the second substrate are set so that the neutral axis coincides with the inorganic insulating film (sealing film) when bending stress is applied, the overall thickness of the display device increases, which degrades the flexibility of the display device.

It is an object of the present invention to provide a display device configured so that the display panel is hardly damaged when the display device is bent, without decrease of the flexibility of the display device.

Means to Solve the Problem

A display device in one embodiment of the present invention includes a display panel having flexibility, and an optical member arranged so as to be stacked on the display panel, wherein the display panel and the optical member are stacked and bonded in a bent state, and thereafter stretched into a flat shape.

Effect of the Invention

According to the present disclosure, the display panel and the optical member are stacked and bonded in a bent state, and thereafter stretched into a flat shape. Therefore, even when the display device is bent, accumulated stress of each layer does not occur to the bent part, and the display panel is hardly damaged.

MODE FOR CARRYING OUT THE INVENTION

A display device in one embodiment of the present invention includes: a display panel having flexibility; and an optical member arranged so as to be stacked on the display panel, wherein the display panel and the optical member are stacked and bonded in a bent state, and thereafter stretched into a flat shape (the first configuration).

According to the first configuration, the display panel and the optical member are stacked and bonded in a bent state, and thereafter stretched into a flat shape. Even when, therefore, the display device is bent, accumulated stress of each layer does not occur in the bent portion, and the display panel is hardly damaged.

In the first configuration, the display panel includes a moisture-proof layer that has a moisture-proof function and a sealing film, and the moisture-proof layer and the sealing film are formed on an outer side with respect to a midpoint, in the thickness direction, between a neutral axis of the display device and an outer surface of the display device (the second configuration).

In the case of the second configuration, even in a configuration in which the moisture-proof layer and the sealing film of the display panel are formed on an outer side with respect to a midpoint, in the thickness direction, between a neutral axis of the display device and an outer surface thereof, accumulated stress of each layer does not occur in the bent portion even when the display device is bent. Therefore, damage can be prevented from occurring to the moisture-proof layer and the sealing film.

A bonding jig used for manufacturing the display device according to the first or second configuration has: a first flat surface; a second flat surface opposed to the first flat surface; and a curved surface extended between the first flat surface and the second flat surface, wherein the first flat surface, the curved surface, and the second flat surface are used when the display panel and the optical member are bonded along these surfaces (the third configuration).

With the third configuration, the display panel and the optical member can be easily stacked and bonded in a bent state.

A bonding device used for manufacturing the display device according to the first or second configuration includes: an outer roller that is rotationally movable; and an inner roller that is rotationally movable, wherein the outer roller and the inner roller rotationally move in a state in which the display panel and the optical member are interposed therebetween, so that the display panel and the optical member are bent in a desired shape (the fourth configuration).

With the fourth configuration, the display panel and the optical member can be easily stacked and bonded in a bent state.

A stretching jig used for manufacturing the display device according to the first or second configuration includes: a first surface part; a second surface part; and a connection part that connects the first surface part and the second surface part, wherein the first surface part and the second surface part are turnable via the connection part, and the display panel and the optical member stacked and bonded in a bent state are arranged between the first surface part and the second surface part arranged so as to be opposed to each other, and at least one of the first surface part and the second surface part is turned so that the first surface part and the second surface part become level with each other, in a state in which ends on one side of the display panel and the optical member are fixed to the first surface part, and ends on the other side of the display panel and the optical member are fixed to the second surface part, so that the display panel and the optical member are stretched into a flat shape, with tensile stress being applied to thereto (the fifth configuration).

With the fifth configuration, the display panel and the optical member stacked and bonded in a bent state can be stretched into a flat shape, without the occurrence of a recess in the bent portion.

A method for manufacturing a display device in one embodiment of the present invention includes the steps of: stacking and bonding a display panel having flexibility, and an optical member arranged so as to be stacked on the display panel, in a bent state; and stretching the display panel and the optical member, which are stacked and bonded in a bent state, into a flat shape (the sixth configuration).

According to the sixth configuration, the display panel and the optical member are stretched into a flat shape after being stacked and bonded in a bent state. Even in a case where the display device is bent, therefore, accumulated stress of each layer does not occur in the bent portion, and the display panel is hardly damaged.

Embodiment

The following describes embodiments of the present invention in detail, while referring to the drawings. Identical or equivalent parts in the drawings are denoted by the same reference numerals, and the descriptions of the same are not repeated. To make the description easy to understand, in the drawings referred to hereinafter, the configurations are simply illustrated or schematically illustrated, or the illustration of part of constituent members is omitted. Further, the dimension ratios of the constituent members illustrated in the drawings do not necessarily indicate the real dimension ratios.

FIG. 1illustrates a configuration of a display device in the present embodiment. The display device100in the present embodiment includes an organic EL panel1that is one kind of a display panel, and an optical member2arranged so as to be stacked on the organic EL panel1. The optical member2includes a polarizing plate3, a touch panel4, and a hard coat5. Each of the polarizing plate3, the touch panel4, and the hard coat5has flexibility. In the present description of the specification, a member that composes the display device100together with the display panel having a function of displaying images and video images, and that has a function of allowing light to pass therethrough, to be reflected thereon, and the like, is referred to as an optical member.

FIG. 2is a diagram for explaining a configuration of the organic EL panel1. The organic EL panel1has flexibility, and includes a TFT substrate10, a moisture-proof layer11, TFTs12, first electrodes13, an edge cover14, an organic EL layer15, a second electrode16, a sealing film17, and a counter substrate18.

The TFT substrate10, which is a flexible substrate, is in a sheet form and has flexibility, being formed with, for example, plastic or polyimide resin.

The moisture-proof layer11, having a moisture-proof function, is formed by repeatedly laminating a combination of, for example, SiNx with a thickness of 0.2 μm and SiOn with a thickness of 0.2 μm on the TFT substrate10.

The TFTs12function as switching elements that control light emission of the organic EL elements of respective colors of red (R), green (G), and blue (B).

A plurality of the first electrodes13are formed at predetermined intervals in matrix, and each of the first electrodes13forms each pixel region of the organic EL panel1.

The organic EL layer15is formed on the first electrode13, and the second electrode16is formed on the organic EL layer15.

The edge cover14is formed so as to cover ends of the first electrodes13. The edge cover14is an insulating layer for preventing the first electrode13and the second electrode16from being short-circuited in a case where the organic EL layer15is thinned or electric field concentration occurs at an end of the first electrode13. Openings in the edge cover14, that is, portions where the first electrodes13are exposed, are light emission areas of the respective pixels.

Either of the first electrode13and the second electrode16is an anode, and the other of the same is a cathode. In a case where the first electrode13is an anode and the second electrode16is a cathode, the first electrodes13are a layer for injecting (supplying) holes to the organic EL layer15, and the second electrode16is a layer for injecting electrons to the organic EL layer15. In this case, the organic EL layer15includes a hole injection layer, a hole transport layer, a light emission layer, an electron transport layer, and an electron injection layer in this order from the first electrode13side.

The hole injection layer is a layer having a function of enhancing the efficiency of hole injection with respect to the organic EL layer15.

The hole transport layer is a layer having a function of enhancing the efficiency of hole transport with respect to the light emission layer.

The light emission layer is a layer having a function of recombining the holes injected from the first electrode13side and the electrons injected from the second electrode16side thereby emitting light, and emits any of red color light, green color light, and blue color light. The light emission layer may have a configuration of emitting white light by combining red color light, green color light, and blue color light.

The electron transport layer is a layer having a function of enhancing the efficiency of electron transport from the second electrode16to the light emission layer.

The electron injection layer is a layer having a function of enhancing the efficiency of electron injection from the second electrode16to the organic EL layer15.

The above-described layers that compose the organic EL layer15may be configured so that a single layer has two or more functions (for example, the hole injection layer may double as the hole transport layer). Further, the organic EL layer15may include another layer such as a carrier blocking layer, as required. For example, by adding a hole blocking layer as a carrier blocking layer between the light emission layer and the electron transport layer, holes can be prevented from passing therethrough to the electron transport layer, whereby the light emission efficiency can be enhanced.

In the foregoing description, the first electrode13is an anode and the second electrode16is a cathode, but the configuration may be such that the first electrode13is a cathode and the second electrode16is an anode. In this case, the order in which the layers composing the organic EL layer15are laminated is reversed.

The entirety of the organic EL layer15and the second electrode16is covered with the sealing film17. The sealing film17, having the moisture-proof function, is provided so as to prevent moisture or oxygen from intruding from the outside. With film exfoliation due to film stress and the like taken into consideration, organic substances and inorganic substances are laminated, whereby excellent moistureproofness is achieved, while film stability is ensured. The sealing film17is formed by repeatedly laminating a combination of, for example, SiNx with a thickness of 0.5 μm and SiCN with a thickness of 0.5 μm.

The counter substrate18, which is a flexible substrate, is in a sheet form and has flexibility, being formed with, for example, plastic or polyimide resin.

The polarizing plate3has a function of absorbing light having a particular polarization direction, and allowing light having a polarization direction rotated by a predetermined angle (for example, 90 degrees) with respect to the foregoing polarization direction to pass therethrough. In particular, in a case where the polarizing plate3is used together with the organic EL panel1, the polarizing plate3is combined with a retarder (¼λ plate) so as to be used as a circularly polarizing plate. This makes it possible to reduce reflection light caused by metal lines and the like, thereby improving visibility in a bright place such as the outdoors.

The polarizing plate3has, for example, a three-layer structure composed of a top surface film, a polarization layer, and a retarder (¼λplate). To form the top surface film, for example, triacetyl cellulose (TAC) is used. To form the polarization layer, for example, polyvinyl alcohol (PVA) is used. To form the retarder, for example, a norbornene-based resin or the like is used.

PVA is dyed with iodine, and thereafter is uniaxially stretched. PVA absorbs polarized light that is parallel with the stretching direction, and allows polarized light that is perpendicular to the stretching direction to pass therethrough. The retarder has a function of giving a phase difference to light having passed through the polarizing plate, and converts light having passed through the polarizing plate into circularly polarized light, by the phase difference design (¼λ condition). When the circularly polarized light is reflected at metals and the like (for example, the lines in the organic EL panel1), the rotation direction of the polarized light is reversed (reverse circularly polarized light), and in a case where the polarized light reaches the polarizing plate after the polarized light is reflected and again passes through the retarder, the light is allowed to have polarization twisted by 90 degrees with respect to the state upon the incidence. Since light having polarization twisted by 90 degrees is absorbed by the polarizing plate, unnecessary reflection of external light can be effectively reduced, and visibility in a bright place such as the outdoors can be drastically improved.

The touch panel4has, for example, such a configuration that lines (transparent conductors such as metals or indium tin oxide (ITO)) are arranged in matrix on both surfaces of a polyethylene terephthalate (PET) film. By applying a high frequency signal to the above-described lines formed in matrix, and detecting changes in voltage waveforms caused by capacity coupling between the lines and a user's finger or a pen for a touch panel, a touched position on the surface of the display device100can be detected.

The hard coat5is a hard film for protecting the surface of the display device100, and the configuration thereof may be, for example, such that an acrylic resin film is formed on a PET film or a TAC film as a base film.

The display device100in the present embodiment is formed by stacking and bonding the organic EL panel1and the optical member2in a bent state, and stretching the same into a flat shape.

FIG. 3illustrates the organic EL panel1and the optical member2stacked and bonded in a bent state. In a case where the organic EL panel1and the optical member2are bonded in a flat state as is conventionally done, as the optical member2has a greater thickness, in a bent state, greater tensile stress accumulated from the optical member2is exerted on the organic EL panel1, which is formed on an outer side of the bent portion with respect to the neutral axis, which is an intermediate axis in the thickness direction of the display device100. In a case where the organic EL panel1and the optical member2are stacked and bonded in a bent state as is the case with the present embodiment, only compressive stress and tensile stress caused by the organic EL panel1and the optical member2themselves occur to the bent portion of the organic EL panel1and the optical member2. The moisture-proof layer11and the sealing film17of the organic EL panel1may be formed on an outer side with respect to the midpoint between the neutral axis of the display device100and the outer surface of the display device100.

The inventor of the present invention carried out an experiment for confirming effects in a case where the organic EL panel1and the optical member2are stacked and bonded in a bent state. In this experiment as a simple experiment, a polyethylene naphthalate (PEN) film was bonded with an adhesive to the top surface of the organic EL panel1, and a bending test was carried out ten thousand times at a bending radius R of 3 mm.

PEN films of five different thickness of 40 μm, 60 μm, 110 μm, 140 μm, and 160 μm were used. The thickness of adhesive used for bonding the organic EL panel1and the PEN film was 25 μm.

Regarding each of cases where any of the above-described PEN films of 5 different thicknesses and the organic EL panel1were bonded in a flat state (flat bonding) and cases where any of the PEN films and the organic EL panel1were bonded in a bent state (bent bonding), a bending test was carried out ten thousand times, and thereafter, it was confirmed whether or not the organic EL panel1was damaged.

FIG. 4is a diagram showing the results of the above-described simple experiments. InFIG. 4, “∘” indicates that no damage to the organic EL panel1was recognized after the bending test was carried out ten thousand times, “×” indicates that damage to the organic EL panel1was recognized after the bending test was carried out ten thousand times, and “××” indicates that damage to the organic EL panel1by carrying out the bending test once was recognized.

As shown inFIG. 4, in the case of flat bonding, in the case where the PEN film of 40 μm was bonded and the case where the PEN film of 60 μm was bonded, no damage to the organic EL panel1was recognized even if the bending test was carried out ten thousand times, but in the case where the PEN film of 110 μm was bonded, damage to the organic EL panel1was recognized after the bending test was carried out ten thousand times. Further, in the case where the PEN film of 140 μm was bonded and the case where the PEN film of 160 μm was bonded, damage to the organic EL panel1by carrying out the bending test once was recognized.

On the other hand, in the case of bent bonding where the PEN film and the organic EL panel1, both in a bent state, were bonded with each other, in any of the cases where the PEN films having 5 different thicknesses were used, no damage to the organic EL panel1was recognized after the bending test was carried out ten thousand times.

(Method for Bonding Organic EL Panel and Optical Member)

FIG. 5Ais a top view illustrating a bonding jig50for bonding the organic EL panel1and the optical member2, andFIG. 5Bis a side view of the bonding jig50. The bonding jig50is generally in a flat plate shape, and has a top surface that is a first flat surface, a lower surface that is a second flat surface opposed to the first flat surface, and a curved surface extended between the first flat surface and the second flat surface. The curved surface may be in a semicircular arc shape having a predetermined radius, or may be in a semi-elliptical shape.

FIG. 6is a diagram for explaining a method for bonding the organic EL panel1and the optical member2by using the bonding jig50. The organic EL panel1and the polarizing plate3are bonded with an adhesive, and so are the polarizing plate3and the touch panel4, as well as the touch panel4and the hard coat5.

First of all, the hard coat5is caused to adhere to the bonding jig50, along the top surface, the curved surface, and the lower surface of the bonding jig50. More specifically, the hard coat5is placed on the top surface of the bonding jig50, and a roller60ais rolled over the hard coat5along the shape of the bonding jig50, whereby the hard coat5is caused to adhere to the bonding jig50.

Subsequently, the touch panel4is placed on the top surface of the hard coat5, and the roller60bis rolled over the touch panel4, along the shape of the bonding jig50, whereby the touch panel4is caused to adhere to the hard coat5.

Subsequently, the polarizing plate3is placed on the top surface of the touch panel4, and the roller60cis rolled over the polarizing plate3along the shape of the bonding jig50, whereby the polarizing plate3is caused to adhere to the touch panel4.

Finally, the organic EL panel1is placed on the top surface of the polarizing plate3, and the roller60dis rolled over the organic EL panel1along the shape of the bonding jig50, whereby the organic EL panel1is caused to adhere to the polarizing plate3.

InFIG. 6, four rollers60ato60dare illustrated, but one roller may be repeatedly used (in the example illustrated inFIG. 6, four times). Further, the bonding can be carried out by using something other than the rollers.

(Method for Stretching Display Device)

When the display device100produced by bonding the organic EL panel1and the optical member2in a bent state is simply unfolded into a flat shape, the most bent part is recessed, as illustrated inFIG. 7. In the present embodiment, therefore, by using a stretching jig80illustrated inFIG. 8, the display device100is stretched into a flat shape.

The stretching jig80includes a first surface part81, a second surface part82, a first connection part83, and a second connection part84. The first surface part81and the first connection part83are connected by a first movable part85, and the second surface part82and the second connection part84are connected by a second movable part86. The first surface part81and the first connection part83are turnable around the first movable part85as the center. Further, the second surface part82and the second connection part84are turnable around the second movable part86as the center.

The first connection part83and the second connection part84are connected at a fixing part87. The angle formed between the first connection part83and the second connection part84is therefore unchangeable.

In the above-described configuration, the first connection part83and the second connection part84constitutes a connection part that connects the first surface part81and the second surface part82. The first connection part83and the second connection part84may be integrally provided to form one connection part.

FIGS. 9A and 9Bare diagrams for explaining a method for stretching the display device100by using the stretching jig80.FIG. 9Ais a side view illustrating a state in which the display device100in a bent state is set on the stretching jig80, andFIG. 9Bis a side view illustrating a state in which the device100is stretched into a flat shape by the stretching jig80.

It is assumed that, as illustrated inFIG. 9A, the relationship of L2>L1is satisfied, where “L1” represents a distance from an end of the display device100in the bent state to the bent portion, and “L2” represents a distance from an end of the first surface part81(or the second surface part82) of the stretching jig80to the fixing part87.

The following describes a method for stretching the display device100. First of all, as illustrated inFIG. 9A, the display device100in the bent state is placed between the first surface part81and the second surface part82of the stretching jig80, which are arranged so as to be opposed to each other, and the end of the top surface of the display device100in the bent state is fixed to the end of the first surface part81of the stretching jig80, while the end of the lower surface of the display device100is fixed to the end of the second surface part82of the stretching jig80.

InFIG. 9A, the ends of the display device100in the bent state, and the ends of the surface parts81,82of the stretching jig80coincide with each other. In a case where they do not coincide, however, the configuration may be such that the end of the top surface of the display device100is fixed at the closest position in the first surface part81of the stretching jig80, and the end of the lower surface of the display device100is fixed at the closest position in the second surface part82of the stretching jig80.

Next, as illustrated inFIG. 9B, the first surface part81is turned so as to be opened, around the second movable part86as a fulcrum, so that the first surface part81and the second surface part82become level with each other. Here, the end portions of the display device100remain fixed at the end portion of the first surface part81and the end portion of the second surface part82. This causes tensile stress to occur in the horizontal direction of the display device100when the first surface part81is turned, and hence, no recess occurs at the bent position of the display device100, whereby the display device100can be stretched into a flat shape.

In a state in which the display device100is stretched into a flat shape, tensile stress occurs to the hard coat5, which is arranged on the inner side in a bent state, and compressive stress occurs to the organic EL panel1arranged on the outer side. Breakage of the moisture-proof layer11and the sealing film17in the organic EL panel1occurs due to tensile stress, and does not occur due to compressive stress. Even if, therefore, the organic EL panel1bonded in a bent state is stretched into a flat shape, the moisture-proof layer11and the sealing film17in the organic EL panel1do not break.

It should be noted that, from the state illustrated inFIG. 9A, the second surface part82may be turned so as to be opened, around the first movable part85as a fulcrum, so that the first surface part81and the second surface part82become level with each other.

In Embodiment 1, by using the bonding jig50illustrated inFIGS. 5A and 5B, the organic EL panel1and the optical member2are bonded. In Embodiment 2, as the bonding device, a pair of bonding rollers101composed of an outer roller101aand an inner roller101bare used to bond the organic EL panel1and the optical member2.

FIG. 10is a diagram for explaining a method for bonding the organic EL panel1and the optical member2by using the pair of bonding rollers101. InFIG. 10, (a) illustrates a state in which the touch panel4is bonded to the top surface of the hard coat5folded into two. InFIG. 10, (b) illustrates a state in which the touch panel4is bonded to the bent portion of the hard coat5, and (c) illustrates a state in which the touch panel4is bonded to the lower surface of the hard coat5in the bent state.

In order to bond the organic EL panel1and the optical member2, the hard coat5and the touch panel4are bonded first.

In order to bond the hard coat5and the touch panel4, first of all, the hard coat5is fixed in a bent state, being folded into two, and respective ends of the touch panel4and the hard coat5are stacked on each other so that the touch panel4is bonded onto the top surface of the hard coat5thus bent. Then, as illustrated in (a) ofFIG. 10, the pair of bonding rollers101composed of the outer roller101aand the inner roller101bare moved in a bonding direction, in a state in which the hard coat5and the touch panel4are interposed between the pair of bonding rollers101.

Here, the outer roller101aand the inner roller101bare controlled so as to move at the same speed. In a case where the diameter of the outer roller101aand the diameter of the inner roller101bare equal to each other, the rotation speeds of the outer roller101aand the inner roller101bmay be equal to each other, so that the outer roller101aand the inner roller101bmove at the same speed.

In a case where the touch panel4is bonded to the bent portion, that is, the curved surface portion, of the hard coat5(see (b) ofFIG. 10), the moving speed of the inner roller101bis made slower, with respect to the moving speed of the outer roller101a. This is because the distance through which the inner roller101bmoves on the inner side of the bent portion of the hard coat5is shorter than the distance through which the outer roller101amoves on the outer side of the bent portion of the hard coat5. In other words, when the bonding of the touch panel4is started on the lower surface of the hard coat5, the moving speeds of the outer roller101aand the inner roller101bare adjusted so that the positions of the outer roller101aand the inner roller101bcoincide with each other in the vertical direction. Further, the outer roller101aand the inner roller101bare rotationally moved so that the touch panel4and the hard coat5are bent in a desired shape.

Finally, as illustrated in (c) ofFIG. 10, the outer roller101aand the inner roller101bare moved at the same speed so that the touch panel4is bonded on the lower surface of the hard coat5.

Through the above-described steps, the touch panel4is bonded onto the hard coat5. After this, the polarizing plate3is bonded onto the outer side of the touch panel4through identical steps. Further, after the bonding of the polarizing plate3, the organic EL panel1is bonded on the outer side of the polarizing plate3.

It should be noted that the bending radius of the bent portion can be adjusted by adjusting the diameter of the inner roller101band the rotation speed (progression speed).

The present invention is not limited to the above-described embodiment. For example, in the description, the organic EL panel1is taken as one example of the display panel, but the display panel may be anything as long as it is a display panel having flexibility, and may be, for example, an electrophoretic display, or a liquid crystal display including a flexible substrate.

The polarizing plate3, the touch panel4, and the hard coat5are taken as exemplary optical members, but the optical members are not limited to these.

The display devices in the above-described embodiments are applicable to a variety of displays such as a television set, a smartphone, a tablet terminal, a game machine, and the like.

DESCRIPTION OF REFERENCE NUMERALS