JP2011018554A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device improving color purity with a simple structure.SOLUTION: The display device includes: a plurality of pixels having light emitting elements and arrayed on a substrate; and a single band-pass filter provided on the light emitting surface side of the light emitting elements to extend over the plurality of pixels and transmitting a part of light emitted from the light emitting elements of each pixel to emit outward. Each light emitting element in each pixel has any luminescent color among a plurality of luminescent colors for performing color display. A transmittance of the band-pass filter to a wavelength of light of the band-pass filter has a maximal value in each specific wavelength region containing a peak wavelength of an emission spectrum with respect to each of the plurality of luminescent colors in an emission spectrum distribution of the light emitting elements in the plurality of pixels, and has minimal values in the remaining wavelength regions excluding the specific wavelength regions from the wavelength region.

Description

  The present invention relates to a display device using a light emitting element.

  The organic EL element emits light by current driving. As a driving method of this organic EL element, there are an active driving system using a switching element for selecting an organic EL element constituting a pixel and a passive driving system not using a switching element. In a full-color organic EL display, in order to display different colors of RGB at the pixel level, it is known that an organic layer forms one pixel by three colors of organic EL elements that emit light of any of RGB colors. Yes.

  Also, in a display device that performs color display using an organic EL element that emits light in any one of RGB colors, a color filter is stacked on the light emitting surface side of the organic EL element, and the color purity is adjusted by the color filter. Has been proposed (see, for example, Patent Document 1).

JP-A-64-67895

  However, in order to form a different color filter for each of the three colors of organic EL elements that emit light in any one of RGB colors, the color filter must be formed in three steps, which is troublesome. There is also a problem that the viewing angle is narrowed by providing the color filter.

  An object of the present invention is to provide a display device that can improve color purity with a simple structure.

  In order to solve the above problems, according to the first aspect of the present invention, a plurality of pixels having a light emitting element and arranged on a substrate, and the plurality of pixels on the light emitting surface side of the light emitting element. A single band-pass filter that transmits part of the light emitted from the light emitting element of each pixel and emits the light to the outside, and the light emitting element in each pixel is a color filter. The light emission color of any one of a plurality of emission colors for display, and the transmittance of the bandpass filter with respect to the wavelength of the light of the plurality of emission colors in the emission spectrum distribution of the light emitting element of the plurality of pixels. Provided is a display device having a maximum value in a specific wavelength region including a peak wavelength of an emission spectrum for each, and a minimum value in a remaining wavelength region excluding the specific wavelength region from the wavelength region Is done.

Preferably, a half value width in an intensity of a spectrum distribution with respect to at least one specific emission color in the plurality of emission colors in the outgoing light transmitted through the bandpass filter and emitted to the outside corresponds to the specific emission color. The half width in the spectral distribution of the light emitted from the light emitting element is narrower.
Preferably, the half width of the band pass filter has a value of 15 nm to 50 nm.
Preferably, the transmittance of the bandpass filter is such that the area of the three primary color chromaticity points in the CIE color system by light emitted to the outside through the bandpass filter is an NTSC three primary color chromaticity point. It has a value which becomes 100% or more with respect to the area.
Preferably, a retardation plate and a polarizing plate for preventing reflection of external light are provided between the light emitting surface side of the light emitting element and the band pass filter.
Preferably, when the average transmittance of the bandpass filter is T1 [%], the orthogonal polarization transmittance T2 [%] of the polarizing plate is set to a value satisfying the formula (1).
50 × T2 × (T1) ² ≦ 3 [%] (1)

  ADVANTAGE OF THE INVENTION According to this invention, the display apparatus which can improve color purity with a simple structure can be provided.

1 is a schematic diagram showing a display device 1A according to a first embodiment of the present invention. It is a graph which shows an example of luminance distribution with respect to the wavelength of the light radiate | emitted from the light emission surface of organic EL element 10R, 10G, 10B. 4 is a graph showing ideal wavelength characteristics of transmittance of the bandpass filter 20. 4 is a graph showing the luminance distribution with respect to the wavelength of light emitted from the organic EL elements 10R, 10G, and 10B, transmitted through the bandpass filter 20 having the wavelength characteristics shown in FIG. 3 is a graph showing an example of wavelength characteristics of transmittance of an actual bandpass filter 20. 6 is a graph showing the luminance distribution with respect to the wavelength of light emitted from the organic EL elements 10R, 10G, and 10B, transmitted through the bandpass filter 20 having the wavelength characteristics shown in FIG. It is a schematic diagram which shows the display apparatus 1B which concerns on the modification of this invention.

[First Embodiment]
FIG. 1 is a schematic diagram showing one pixel of the display device 1A according to the first embodiment of the present invention. The display device 1A includes a large number of pixels arranged in a matrix. As shown in FIG. 1, each pixel is provided with organic EL elements (light emitting elements) 10R, 10G, and 10B having three colors of RGB for performing color display, and on the light emitting surface side of the organic EL elements 10R, 10G, and 10B. And a single band-pass filter 20 provided across the organic EL elements 10R, 10G, and 10B. The band pass filter 20 transmits part of the light emitted from the light emitting surface side of the organic EL elements 10R, 10G, and 10B and emits the light to the outside (upward in the drawing).

Although not shown, the organic EL elements 10R, 10G, and 10B have an organic EL layer interposed between a pair of electrodes, and light is emitted from the organic EL layer by applying a voltage between the electrodes. One electrode is a transparent electrode and transmits light emitted from the organic EL layer. The transparent electrode side is the light emitting surface of the organic EL elements 10R, 10G, and 10B. The organic EL elements 10R, 10G, and 10B are sandwiched between the two substrates 11 and 12. Here, the substrates 11 and 12 are, for example, glass or a transparent film, and insulate the electrodes. The organic EL element includes a bottom emission type and a top emission type, and the present invention is applicable to both. When the organic EL element is a bottom emission type, the organic EL element is formed on the substrate 12, a transparent electrode is formed on the substrate 12, and the light emitted from the organic EL layer is emitted to the substrate 12 side. The substrate 11 becomes a sealing substrate. When the organic EL element is a top emission type, the organic EL element is formed on the substrate 11, the substrate 12 becomes a sealing substrate, a transparent electrode is formed on the substrate 12 side, and is emitted from the organic EL layer. The emitted light is emitted to the substrate 12 side.
FIG. 2 is a graph showing an example of a luminance distribution (spectral distribution) with respect to the wavelength of light emitted from the light emitting surfaces of the organic EL elements 10R, 10G, and 10B. The luminance is shown as a relative value with the peak wavelength being 1. As shown in FIG. 2, the blue organic EL element 10B and the green organic EL element 10G are distributed to the long wavelength side.

  A band pass filter 20 is provided outside the substrate 12 on the light emitting surface side of the organic EL elements 10R, 10G, and 10B.

  FIG. 3 shows an ideal wavelength characteristic of the transmittance of the band-pass filter 20. This bandpass filter has a transmittance peak (maximum value) at about 440 nm (blue light), about 530 nm (green light), and about 640 nm (red light), and a wavelength range in which the transmittance is ½ of the peak. (Half width) is 50 nm.

FIG. 4 is a graph showing the luminance distribution (spectral distribution) with respect to the wavelength of light emitted from the organic EL elements 10R, 10G, and 10B, transmitted through the bandpass filter 20 having the wavelength characteristics shown in FIG. It is. The luminance is shown by the same relative value as in FIG. In this case, as shown in FIG. 4, due to the wavelength characteristics of the transmittance of the bandpass filter 20, in each of the blue light, the green light, and the red light in the spectrum distribution of the light emitted through the bandpass filter 20, The wavelength range (half-value width) that is half the peak brightness is narrower than the half-value width in the spectral distribution of the light emitted from the light emitting surfaces of the organic EL elements 10R, 10G, and 10B shown in FIG. ing. As a result, as will be described later, the ratio of the area of the three primary color chromaticity points in the CIE color system to the area of the three primary color chromaticity points in the NTSC system (NTSC ratio) is larger than the value when the bandpass filter 20 is not provided. As a result, the color purity is improved.
Here, the relationship between the half-value width of the bandpass filter 20 and the luminance of the display device 1A will be described. In the display device 1A shown in FIG. 1, when the luminance when the bandpass filter 20 is not provided is 304 cd / m ² , the bandpass filter 20 shown in FIG. As a result of calculating the luminance at the time of simulation by simulation, it was found that the luminance was 148 cd / m ² . Since the wavelength distribution for each luminescent color becomes narrower as the value of the half-value width becomes smaller, the color purity improves. However, it is expected that the luminance decreases because the amount of transmitted light decreases as the half-value width decreases. Therefore, as a result of calculating the luminance when the half-value width of the bandpass filter 20 is 15 nm, it was found that the luminance was 60 cd / m ² . This luminance value is a value that can be used as a display device. Therefore, it was found that the band-pass filter 20 having a half width of 50 nm to 30 nm can be used.

FIG. 5 shows an example of the wavelength characteristic of the transmittance of the actual bandpass filter 20. This band pass filter has transmission wavelength peaks at about 430 nm (blue light), about 520 nm (green light), and about 630 nm (red light). Such a bandpass filter 20 can be formed using a dye that absorbs light of a wavelength other than the transmission region, such as an azo dye. Moreover, it can also form by adjusting the absorption wavelength using the pigment (or dye) used for liquid crystals, and disperse | distributing it to a base material. Furthermore, the bandpass filter 20 can also be formed using thin film interference. In this case, for example, as described in JP-A-2003-337337, a plurality of TiO ₂ / SiO ₂ thin films can be laminated, or a fluorine-based acrylate resin and an inorganic high refractive index can be formed. The fine particle-containing acrylate resin can be formed by laminating a plurality of layers by a multilayer thin film coating process.

  FIG. 6 is a graph showing the distribution of luminance with respect to the wavelength of light emitted from the organic EL elements 10R, 10G, and 10B, transmitted through the bandpass filter 20 having the wavelength characteristics shown in FIG. The luminance is shown by the same relative value as in FIG. Also in this case, as shown in FIG. 6, due to the wavelength characteristics of the transmittance of the band-pass filter 20, the half-value widths of green light and red light in the spectral distribution of the light emitted to the outside through the band-pass filter 20 Is narrower than the half-value width in the spectrum distribution of the light emitted from the organic EL elements 10R and 10G shown in FIG. 2, and the half-value width in the blue light in the spectrum distribution of the light emitted to the outside is as shown in FIG. This is a value equivalent to the full width at half maximum in the spectral distribution of the light emitted from the organic EL element 10B. Thereby, as will be described later, the NTSC ratio is smaller than the value in FIG. 4 described above, but is larger than the value when the band-pass filter 20 is not provided. In this case, the color purity is improved.

  By using the bandpass filter 20 having such characteristics, the color purity can be improved without providing a different color filter for each color of RGB. In addition, since the single band-pass filter 20 is provided across all the sub-pixels, even when viewing the display from an oblique direction, the spectral distribution of the light emitted to the outside through the band-pass filter 20 is almost the same. The viewing angle characteristics can be improved as compared with the case where different color filters are provided for each color of RGB.

<Modification>
FIG. 7 is a schematic view showing a display device 1B according to a modification of the present invention. In the present modification, a polarizing plate 31 and a retardation plate 32 are provided between the organic EL elements 10R, 10G, and 10B and the bandpass filter 20. By providing the polarizing plate 31 and the phase difference plate 32, reflection of external light can be prevented.

In the case where the band pass filter 20 is provided and the external light reflectance may be equal to that of the conventional structure in which the band pass filter 20 is not provided, as described below, the polarizing plate 31 is used. Since the orthogonal transmittance of the orthogonally polarized light can be higher than a value generally used conventionally, a polarizing plate 31 having a lower cost than before can be used.
That is, assuming that the transmittance of the bandpass filter 20 is T2, and the orthogonal transmittance of the polarizing plate 31 at 30 ° incidence 30 ° emission is T1, the organic EL is incident at an angle of 30 ° from the bandpass filter 20 side. The external light reflectance Tout of the external light reflected by the electrodes of the elements 10R, 10G, and 10B and emitted to the outside at an angle of 30 ° is expressed by the following equation (10).
Tout = 50 [%] × T1 × (T2) ² (10)
Since the orthogonal transmittance T1 of the conventional generally used polarizing plate 31 is 0.05%, the external light reflectance Tout in the case of the conventional structure in which no bandpass filter is provided is expressed by the above formula ( Corresponding to T1 = 100% in 10), it is 2.5% (about 3%). On the other hand, in the structure provided with the bandpass filter 20 in this embodiment, if the average transmittance T1 of the bandpass filter 20 is 49%, the orthogonal transmittance T2 of the polarizing plate 31 is 0.05%. In some cases, the external light reflectance is about 0.6%, and when the orthogonal transmittance T2 of the polarizing plate 31 is 0.21%, the external light reflectance Tout is about 2.5%. It becomes a value equivalent to the external light reflectance Tout in the case of a structure in which is not provided. Therefore, even if a polarizing plate 31 having an orthogonal transmittance of 0.21% is used, the external light reflectance Tout can be set to a value equivalent to that of the conventional structure.

The following examples further illustrate the present invention. With respect to the organic EL element having the luminance characteristics shown in FIG. 2, the NTSC three primary color chromaticity points of the area of the three primary color chromaticity points in the CIE color system are changed by changing the presence or absence of a band pass filter, a phase difference plate and a polarizing plate. The ratio to the area (NTSC ratio), luminance (cd / m ² ), and external light reflectance Tout were calculated. The external light reflectance was calculated with an incident angle and a reflection angle of 30 °.

(1) Example 1
A band pass filter having the characteristics shown in FIG. 5 was laminated on the organic EL element without using the retardation plate and the polarizing plate. The bandpass filter transmittance of external light was 49%.
(2) Example 2
While using a phase difference plate and a polarizing plate, a bandpass filter having the characteristics shown in FIG. 5 was laminated on the organic EL element. The orthogonal polarization transmittance of the polarizing plate was 0.05%. The bandpass filter transmittance of external light was 49%.
(3) Example 3
While using a phase difference plate and a polarizing plate, a bandpass filter having the characteristics shown in FIG. 5 was laminated on the organic EL element. The orthogonal polarization transmittance of the polarizing plate was 0.21%. The bandpass filter transmittance of external light was 49%.
(4) Example 4
The bandpass filter having the characteristics shown in FIG. 3 was laminated on the organic EL element without using the retardation plate and the polarizing plate. The bandpass filter transmittance of external light was 49%.
(5) Example 5
While using a retardation plate and a polarizing plate, a bandpass filter having the characteristics shown in FIG. 3 was laminated on the organic EL element. The orthogonal polarization transmittance of the polarizing plate was 0.05%. The bandpass filter transmittance of external light was 49%.

(6) Comparative Example 1
Only an organic EL element was used without using a bandpass filter, a retardation plate and a polarizing plate (external light bandpass filter transmittance 100%, orthogonal polarization transmittance 100%).
(7) Comparative Example 2
A retardation plate and a polarizing plate were laminated on the organic EL element without using a bandpass filter. The polarizing plate had an orthogonal polarization transmittance of 0.05% (external light bandpass filter transmittance of 100%).
Table 1 shows the results of calculating the NTSC ratio, luminance, and external light reflectance.

In Example 1, the NTSC ratio was 83%, the luminance was 148 cd / m ² , and the external light reflectance was 24.01%.
In Example 2, the NTSC ratio was 83%, the luminance was 67 cd / m ² , and the external light reflectance was 0.60%.
In Example 3, the NTSC ratio was 83%, the luminance was 67 cd / m ² , and the external light reflectance was 2.52%.
In Example 4, the NTSC ratio was 100%, the luminance was 148 cd / m ² , and the external light reflectance was 24.01%.
In Example 5, the NTSC ratio was 100%, the luminance was 67 cd / m ² , and the external light reflectance was 0.60%.

In Comparative Example 1, the NTSC ratio was 68%, the luminance was 304 cd / m ² , and the external light reflectance was 100%.
In Comparative Example 2, the NTSC ratio was 68%, the luminance was 137 cd / m ² , and the external light reflectance was 2.50%.

Thus, the NTSC ratio can be improved by providing the band pass filter. In addition, by setting the half-value width of the transmission wavelength to 50 nm or less, the NTSC ratio can be further improved and the color purity can be improved.
In addition, when the retardation plate and the polarizing plate are used, when the external light reflectance is set to a value equivalent to the value in the structure without the conventional bandpass filter, the average transmittance of the bandpass filter is T1 [ %], The value of the transmittance T2 [%] of the orthogonal polarization of the polarizing plate may be a value satisfying the following formula (11).
External light reflectance Tout = 50 × T2 × (T1) ² ≦ 3% (11)

In the above embodiment, the light emitting element is described as an organic EL element. However, the light emitting element is not limited to the organic EL element, and may be, for example, an inorganic EL element or a self light emitting element such as an LED.

1A, 1B Display devices 10R, 10G, 10B Organic EL element 20 Bandpass filter 31 Polarizing plate 32 Phase difference plate

Claims (6)

A plurality of pixels having a light emitting element and arranged on a substrate;
A single band-pass filter that is provided across the plurality of pixels on the light emitting surface side of the light emitting element, transmits a part of the light emitted from the light emitting element of each pixel, and emits to the outside;
With
The light emitting element in each pixel has a light emitting color of any of a plurality of light emitting colors for performing color display,
The transmittance of the bandpass filter with respect to the wavelength of the light has a maximum value in a specific wavelength region including a peak wavelength of an emission spectrum for each of the plurality of emission colors in an emission spectrum distribution of the light emitting element of the plurality of pixels. And having a minimum value in the remaining wavelength region excluding the specific wavelength region from the wavelength region.   The half-value width in the intensity of the spectrum distribution for at least one specific emission color in the plurality of emission colors in the outgoing light that passes through the bandpass filter and is emitted to the outside is the emission corresponding to the specific emission color. The display device according to claim 1, wherein the display device is narrower than a half-value width in a spectral distribution of light emitted from the element.   The display device according to claim 1, wherein the half width of the band pass filter has a value of 15 nm to 50 nm.   The transmittance of the bandpass filter is such that the area of the three primary color chromaticity points in the CIE color system by the light emitted to the outside through the bandpass filter is the area of the NTSC three primary color chromaticity points. The display device according to claim 1, wherein the display device has a value of 100% or more.   The phase difference plate and polarizing plate which prevent reflection of external light are provided between the light emission surface side of the said light emitting element, and the said band pass filter, The any one of Claims 1-4 characterized by the above-mentioned. The display device described in 1. The orthogonal polarization transmittance T2 [%] of the polarizing plate is set to a value satisfying the expression (1), where the average transmittance of the bandpass filter is T1 [%].
The display device described in 1.
50 × T2 × (T1) ² ≦ 3 [%] (1)

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