Sony Patent | Display device, method for manufacturing display device, and electronic apparatus

Patent: Display device, method for manufacturing display device, and electronic apparatus

Drawings: Click to check drawins

Publication Number: 20210111228

Publication Date: 20210415

Applicant: Sony

Abstract

In a display device, a reflection film and a semi-transmissive reflection film are disposed at a distance from each other, the distance differing depending on an emission color of a pixel, an organic layer and a cathode electrode being transparent are stacked between the reflection film and the semi-transmissive reflection film, the organic layer including a light emission layer, the semi-transmissive reflection film is formed on the cathode electrode, and the cathode electrode is formed to have a film thickness that differs depending on the emission color.

Claims

  1. A display device, wherein a reflection film and a semi-transmissive reflection film are disposed at a distance from each other, the distance differing depending on an emission color of a pixel, an organic layer and a cathode electrode being transparent are stacked between the reflection film and the semi-transmissive reflection film, the organic layer including a light emission layer, the semi-transmissive reflection film is formed on the cathode electrode, and the cathode electrode is formed to have a film thickness that differs depending on the emission color.

  2. The display device according to claim 1, wherein the reflection film has a function of an anode electrode.

  3. The display device according to claim 1, wherein the cathode electrode includes indium zinc oxide (IZO).

  4. The display device according to claim 1, wherein the cathode electrode is formed as an electrode common to individual pixels, and a recess is disposed in a portion of the cathode electrode, the portion corresponding to the reflection film.

  5. The display device according to claim 4, wherein a depth of the recess differs depending on the emission color.

  6. The display device according to claim 1, wherein an optical distance between the reflection film and the semi-transmissive reflection film is set to be an optical distance in accordance with a display color of the pixel, because of the cathode electrode being formed to have a film thickness that differs depending on the emission color.

  7. The display device according to claim 6, wherein the optical distance L satisfies a condition: 2L/.lamda.+.PHI./2.pi.=m (m is an integer) where symbol .PHI. represents a phase shift of reflected light generated in the semi-transmissive reflection film and the reflection film, symbol L represents the optical distance between the reflection film and the semi-transmissive reflection film, and symbol .lamda. represents a peak wavelength of a spectrum of light taken from the pixel.

  8. The display device according to claim 1, wherein the semi-transmissive reflection film includes silver or an alloy including silver.

  9. The display device according to claim 1, wherein the light emission layer is formed in common throughout individual pixels.

  10. The display device according to claim 9, wherein the light emission layer emits white light.

  11. The display device according to claim 1, wherein the light emission layer is formed for each pixel.

  12. The display device according to claim 11, wherein the light emission layer emits light of a color in accordance with the emission color of the pixel.

  13. A method for manufacturing a display device, wherein a reflection film and a semi-transmissive reflection film are disposed at a distance from each other, the distance differing depending on an emission color of a pixel, an organic layer and a cathode electrode being transparent are stacked between the reflection film and the semi-transmissive reflection film, the organic layer including a light emission layer, the semi-transmissive reflection film is formed on the cathode electrode, and the cathode electrode is formed to have a film thickness that differs depending on the emission color, the method comprising steps of: forming the cathode electrode on an entire surface including the organic layer; and making the cathode electrode in such a way as to have a film thickness that differs depending on the emission color.

  14. The method for manufacturing the display device according to claim 13, the method further comprising: making the cathode electrode in such a way as to have a film thickness that differs depending on the emission color by forming a recess in a portion of the cathode electrode, the portion corresponding to the reflection film.

  15. An electronic apparatus comprising a display device, wherein a reflection film and a semi-transmissive reflection film are disposed at a distance from each other, the distance differing depending on an emission color of a pixel, an organic layer and a cathode electrode being transparent are stacked between the reflection film and the semi-transmissive reflection film, the organic layer including a light emission layer, the semi-transmissive reflection film is formed on the cathode electrode, and the cathode electrode is formed to have a film thickness that differs depending on the emission color.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a display device, a method for manufacturing a display device, and an electronic apparatus.

BACKGROUND ART

[0002] In recent years, an organic electroluminescence (EL) display device employing EL based on an organic material has been attracting attention as an alternative display device to liquid crystal display devices. In addition, organic EL display devices are being applied not only to direct-view displays such as monitors but also to micro-displays in which a pixel pitch as fine as several microns is required.

[0003] One method for achieving color display on an organic EL display device includes forming organic EL material layers, for each pixel, using a mask for light emission of a plurality of colors including, for example, red light emission, green light emission, and blue light emission. Furthermore, in addition to the aforementioned method, there is a method that includes forming an organic EL material layer for white light emission for all the pixels in common and disposing a color filter for each pixel. This method has an advantage that alignment is not required for forming the organic EL material layer. However, the method involving combination of an organic EL material layer for white light emission with a color filter suffers from reduced luminous efficacy because the white light is color-separated by the color filter. For this reason, there is known a technology for achieving improvement in luminous efficacy and color reproducibility by forming a resonator structure for enhancing the light having a particular wavelength by a resonance effect.

[0004] To enhance the light having a particular wavelength by the resonance effect, it is necessary to adjust the optical distance between the reflection film and the semi-transmissive reflection film in accordance with the wavelength. Patent Document 1 discloses a technology in which an optical path length adjustment layer is provided above a transparent electrode serving as an upper electrode, and a semi-transmissive reflection film is formed on the optical path length adjustment layer.

CITATION LIST

Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2009-272150

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0005] In general, a configuration in which an optical path length adjustment layer is provided above a transparent electrode serving as an upper electrode and a semi-transmissive reflection film is formed on the optical path length adjustment layer requires the optical path length adjustment layer to be formed into an extremely thin layer. Accordingly, it is difficult to control the film thickness with high precision, causing a problem of difficulty in manufacture.

[0006] Therefore, an object of the present disclosure is to provide a display device having a structure in which an optical distance in a resonator structure can be set with high precision without using an optical path length adjustment layer, an electronic apparatus equipped with the display device, and a method for manufacturing the display device.

Solutions to Problems

[0007] For achieving the above-described object, a display device according to the present disclosure is

[0008] a display device, in which

[0009] a reflection film and a semi-transmissive reflection film are disposed at a distance from each other, the distance differing depending on an emission color of a pixel,

[0010] an organic layer and a cathode electrode being transparent are stacked between the reflection film and the semi-transmissive reflection film, the organic layer including a light emission layer,

[0011] the semi-transmissive reflection film is formed on the cathode electrode, and

[0012] the cathode electrode is formed to have a film thickness that differs depending on the emission color.

[0013] For achieving the above-described object, a method for manufacturing a display device according to the present disclosure is

[0014] a method for manufacturing a display device, in which a reflection film and a semi-transmissive reflection film are disposed at a distance from each other, the distance differing depending on an emission color of a pixel, an organic layer and a cathode electrode being transparent are stacked between the reflection film and the semi-transmissive reflection film, the organic layer including a light emission layer, the semi-transmissive reflection film is formed on the cathode electrode, and the cathode electrode is formed to have a film thickness that differs depending on the emission color, the method including steps of:

[0015] forming the cathode electrode on an entire surface including the organic layer; and

[0016] making the cathode electrode in such a way as to have a film thickness that differs depending on the emission color.

[0017] For achieving the above-described object, an electronic apparatus according to the present disclosure is

[0018] an electronic apparatus including a display device, in which

[0019] a reflection film and a semi-transmissive reflection film are disposed at a distance from each other, the distance differing depending on an emission color of a pixel,

[0020] an organic layer and a cathode electrode being transparent are stacked between the reflection film and the semi-transmissive reflection film, the organic layer including a light emission layer,

[0021] the semi-transmissive reflection film is formed on the cathode electrode, and

[0022] the cathode electrode is formed to have a film thickness that differs depending on the emission color.

BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1 is a schematic plan view of a display device according to a first embodiment of the present disclosure.

[0024] FIG. 2 is a schematic partial cross-sectional view of the display device according to the first embodiment.

[0025] FIGS. 3A and 3B are schematic partial end views for explaining a method for manufacturing the display device according to the first embodiment.

[0026] FIG. 4 is a schematic partial end view for explaining the method for manufacturing the display device according to the first embodiment, as continued from FIG. 3B.

[0027] FIG. 5 is a schematic partial end view for explaining the method for manufacturing the display device according to the first embodiment, as continued from FIG. 4.

[0028] FIG. 6 is a schematic partial end view for explaining the method for manufacturing the display device according to the first embodiment, as continued from FIG. 5.

[0029] FIG. 7 is a schematic partial end view for explaining the method for manufacturing the display device according to the first embodiment, as continued from FIG. 6.

[0030] FIG. 8 is a schematic partial end view for explaining the method for manufacturing the display device according to the first embodiment, as continued from FIG. 7.

[0031] FIG. 9 is a schematic partial end view for explaining the method for manufacturing the display device according to the first embodiment, as continued from FIG. 8.

[0032] FIG. 10 is a schematic partial cross-sectional view of a display device according to a second embodiment.

[0033] FIG. 11 is a schematic partial end view for explaining a method for manufacturing the display device according to the second embodiment, as continued from FIG. 10.

[0034] FIG. 12 is a schematic partial end view for explaining the method for manufacturing the display device according to the second embodiment, as continued from FIG. 11.

[0035] FIG. 13 is a schematic partial cross-sectional view of a display device according to a third embodiment.

[0036] FIG. 14 is a schematic partial cross-sectional view of a display device according to a fourth embodiment.

[0037] FIG. 15 is a schematic partial cross-sectional view of the display device according to the fourth embodiment.

[0038] FIG. 16 is a schematic partial end view for explaining a method for manufacturing the display device according to the second embodiment, as continued from FIG. 15.

[0039] FIG. 17 is an external view of a lens-interchangeable single-lens reflex type digital still camera; FIG. 17A shows a front view thereof and FIG. 17B shows a rear view thereof.

[0040] FIG. 18 is an external view of a head-mounted display.

[0041] FIG. 19 is an external view of a see-through head-mounted display.

MODE FOR CARRYING OUT THE INVENTION

[0042] With reference to the drawings, the present disclosure will now be described on the basis of embodiments. The present disclosure is not limited to the embodiments, and various numerical values and materials in the embodiments are examples. In the following description, the same elements or elements having the same functions will be denoted by the same reference symbols, and redundant descriptions will be omitted. Note that descriptions will be provided in the order mentioned below.

[0043] 1. General description of a display device, a method for manufacturing a display device, and an electronic apparatus of the present disclosure

[0044] 2. First Embodiment

[0045] 3. Second Embodiment

[0046] 4. Third Embodiment

[0047] 5. Fourth Embodiment

[0048] 6. Description of electronic apparatus and others

[General Description of a Display Device, a Method for Manufacturing a Display Device, and an Electronic Apparatus of the Present Disclosure]

[0049] A display device according to the present disclosure, a display device used for an electronic apparatus according to the present disclosure, and a display device obtained by a method for manufacturing the display device according to the present disclosure (hereinafter may be simply referred to as a “display device of the present disclosure”) may have a configuration in which a reflection film has a function of an anode electrode.

[0050] The reflection film can be formed by using light reflecting material such as aluminum (Al), an aluminum alloy, platinum (Pt), gold (Au), chromium (Cr), tungsten (W), and the like. The thickness of the reflection film is preferably set to a range of, for example, 100 to 300 nanometers.

[0051] Note that in a case where the reflection film and the anode electrode are separately formed, the anode electrode can be formed by using a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). In this case, the anode electrode is only needed to be disposed between the reflection film and the organic layer.

[0052] In the display device of the present disclosure including various preferred configurations described above, the cathode electrode can be formed by using a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or the like. Preferably, the cathode electrode is formed by using indium zinc oxide (IZO), among others. The cathode electrode can be formed by a film forming method such as a sputtering method, for example.

[0053] The film forming temperature for indium zinc oxide (IZO) is lower than the film forming temperature for indium tin oxide (ITO). Since a film of the cathode electrode is formed on the organic layer, in consideration of the influence on the organic layer, it is preferable to select indium zinc oxide (IZO), which allows the cathode electrode to be film-formed at a lower temperature.

[0054] In the display device of the present disclosure including various preferred configurations described above, the cathode electrode is formed into an electrode common to the individual pixels, and a recess may be disposed in a portion of the cathode electrode corresponding to the reflection film. In this case, the depth of the recess may differ depending on the emission color. Furthermore, a method for manufacturing the display device according to the present disclosure may include making the cathode electrode in such a way as to have a film thickness that differs depending on the emission color by forming a recess in a portion of the cathode electrode corresponding to the reflection film. In this case, it is preferable to make the cathode electrode using a dry etching technology.

[0055] In the display device of the present disclosure including various preferred configurations described above, the cathode electrode may be formed to have a film thickness that differs depending on the emission color, whereby the optical distance between the reflection film and the semi-transmissive reflection film can be set in accordance with the display color of the pixel. In this case, the optical distance L may be needed to satisfy the following condition:

2L/.lamda.+.PHI./2.pi.=m (m is an integer)

[0056] where the symbol .PHI. represents the phase shift of reflected light generated in the semi-transmissive reflection film and the reflection film, the symbol L represents the optical distance between the reflection film and the semi-transmissive reflection film, and the symbol .lamda. represents the peak wavelength of a spectrum of light taken from a pixel.

[0057] In the display device of the present disclosure including various preferred configurations described above, the semi-transmissive reflection film can be formed by using a metal material having good light transmittance and light reflectivity, and examples thereof may include metals such as silver (Ag), gold (Au), copper (Cu), aluminum (Al), and magnesium (Mg), and alloys thereof. From the viewpoint of light transmittance and light reflectivity, the semi-transmissive reflection film preferably includes silver or an alloy including silver. The thickness of the semi-transmissive reflection film is preferably set to a range of, for example, 5 to 40 nanometers.

[0058] In the display device of the present disclosure including various preferred configurations described above, the light emission layer may be formed in common throughout the individual pixels. In this case, the light emission layer may be configured to emit white light.

[0059] In this configuration, the organic layer is disposed as a common continuous film on the entire surface including the reflection film. The organic layer emits light when a voltage is applied. The organic layer may have a structure in which, for example, a hole injection layer, a hole transport layer, a light emission layer, an electron transport layer, and an electron injection layer are stacked in the order mentioned from the reflection film side. A hole transport material, a hole transport material, an electron transport material, and an organic light emission material included in the organic layer are not particularly limited and a well-known material can be used.

[0060] The organic layer may have a so-called tandem structure in which a plurality of light emission layers is connected via a charge generation layer or an intermediate electrode. For example, a light emission layer that emits white light can be formed by stacking light emission layers that emit red light, green light, and blue light, or by stacking light emission layers that emit yellow light and blue light.

[0061] Alternatively, the light emission layer may be formed for each pixel. In this case, the light emission layer may be configured to emit light of a color corresponding to the emission color of the pixel. In this case, individual layers included in the organic layer except the light emission layer may still be disposed as a common continuous film over the entire surface including the reflection film.

[0062] In the case of a color display configuration, a single pixel may include a plurality of sub-pixels. Specifically, a single pixel may include three sub-pixels: a red display sub-pixel, a green display sub-pixel, and a blue display sub-pixel. Moreover, a single pixel may include a set of sub-pixels in which one or more types of sub-pixels are added to these three types of sub-pixels (for example, a set in which a sub-pixel that emits white light for higher brightness is added, a set in which a sub-pixel that emits complementary color light for expanding a color reproduction range is added, a set in which a sub-pixel that emits yellow light for expanding a color reproduction range is added, or a set in which sub-pixels that emit yellow light and cyan light for expanding a color reproduction range are added).

[0063] Examples of pixel values of the display device may include, without limitation, some resolutions for image display such as VGA (640, 480), S-VGA (800, 600), XGA (1024, 768), APRC (1152, 900), S-XGA (1280, 1024), U-XGA (1600, 1200), HD-TV (1920, 1080), Q-XGA (2048, 1536), as well as (1920, 1035), (720, 480), (1280, 960), and the like.

[0064] An insulation film and others used in the display device can be formed by using a material appropriately selected from known inorganic materials and organic materials, and can be formed by, for example, a well-known film forming method such as a physical vapor deposition method (PVD method) exemplified by a vacuum evaporation method and a sputtering method, various chemical vapor deposition methods (CVD methods), and the like. Furthermore, the patterning may be performed by a combination of well-known patterning methods such as an etching method and a lift-off method.

[0065] In the display device according to the present disclosure, the configuration of the drive circuit or the like that controls light emission from the light emission unit is not particularly limited. The light emission unit may be formed on a certain plane over the circuit board and, for example, disposed via the interlayer insulation layer above the drive circuit that drives the light emission unit. The configuration of the transistor included in the drive circuit is not particularly limited. The transistor may be a p-channel type field effect transistor or an n-channel type field effect transistor.

[0066] Examples of a material included in the circuit board may include a semiconductor material, a glass material, or a plastic material. In a case where the drive circuit includes a transistor formed on a semiconductor substrate, for example, a well region is only needed to be disposed on the semiconductor substrate including silicon and the transistor is only needed to be formed in the well. On the other hand, in a case where the drive circuit includes a thin film transistor or the like, the drive circuit can be formed by forming a semiconductor thin film on a substrate that includes a glass material or a plastic material. Various types of wiring may have a well-known configuration and structure.

[0067] A condition shown in each of a variety of formulas herein is satisfied not only in a case where the formula is mathematically precisely satisfied but also in a case where the formula is substantially satisfied. For a formula to be satisfied, various variations occurring in the design or manufacture of the display element, the display panel, or the like are permitted to be present. Furthermore, the drawings referred to in the following description are schematic drawings. For example, FIG. 2 described later shows a cross-sectional structure of the display device, but does not indicate ratios of width, height, thickness, and the like.

First Embodiment

[0068] The first embodiment relates to a display device, a method for manufacturing a display device, and an electronic apparatus according to a first aspect of the present disclosure.

[0069] FIG. 1 is a schematic plan view of a display device according to a first embodiment of the present disclosure. The display device 1 includes a display region 11 in which pixels 10 each including a light emission unit ELP and a drive circuit that drives the light emission unit ELP are arranged in a two-dimensional matrix while being connected to a scanning line SCL extending along the row direction (X direction in FIG. 1) and to a data line DTL extending along the column direction (Y direction in FIG. 1), and also includes a power supply unit 100 that supplies voltages to a power supply line PS1, a scanning unit 101 that supplies scanning signals to the scanning line SCL, and a data driver 102 that supplies signal voltages to the data line DTL. Note that FIG. 1 shows a single pixel 10 for convenience of illustration, or more specifically, FIG. 1 shows a connection relationship in the (q, p)-th pixel 10 as described later.

[0070] The display device 1 further includes a common power supply line PS2 that is connected to all the pixels 10 in common. A predetermined drive voltage is supplied from the power supply unit 100 to the power supply line PS1, while a common voltage (a ground potential, for example) is supplied to the common power supply line PS2.

[0071] Although not illustrated in FIG. 1, the display region 11 includes a total of Q.times.P pixels (display elements) 10, namely Q pixels along the row direction and P pixels along the column direction, arranged in a two-dimensional matrix. In the display region, the number of rows of the pixels 10 is P and the number of pixels 10 constituting each row is Q.

[0072] Furthermore, the number of the scanning lines SCL and the number of power supply lines PS1 are each P. The pixels 10 in the p-th row (where p=1, 2, … , P) are connected to the p-th scanning line SCL.sub.p and the p-th power supply line PS1.sub.p to constitute a single display element row. Note that FIG. 1 shows the scanning line SCL.sub.p and the power supply line PS1.sub.p only.

[0073] Furthermore, the number of the data lines DTL is Q. The pixels 10 in the q-th column (where q=1, 2, … , Q) are connected to the q-th data line DTL.sub.q. Note that FIG. 1 shows the data line DTL.sub.q only.

[0074] The display device 1 is, for example, a color display device. A single pixel 10 constitutes a single sub-pixel. The display device 1 is line-sequentially scanned row by row in response to a scanning signal from the scanning unit 101. The pixel 10 located in the p-th row and the q-th column is hereinafter referred to as a (q, p)-th pixel 10 or the (q, p)-th pixel 10.

[0075] In the display device 1, Q pixels 10 arranged in the p-th row are simultaneously driven. In other words, in the Q pixels 10 arranged along the row direction, the timing of light emission/non-emission is controlled for each row to which the pixels belong. Assuming that the display frame rate of the display device 1 is denoted by FR (times/second), the scanning period (so-called horizontal scanning period) per row when the display device 1 is line-sequentially scanned row by row is less than (1/FR).times.(1/P) seconds.

[0076] The pixel 10 includes the light emission unit ELP and the drive circuit that drives the light emission unit ELP. The light emission unit ELP includes an organic electroluminescent light emission unit. The drive circuit includes a write transistor TR.sub.W, a drive transistor TR.sub.D, and a capacitance unit C.sub.1. When a current flows through the light emission unit ELP via the drive transistor TR.sub.D, the light emission unit ELP emits light. Each transistor includes a p-channel type field effect transistor.

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