JP4797921B2 - Light emitting device - Google Patents

Description

  The present invention relates to a light emitting device used for an exposure head of a printing apparatus.

  Conventionally, various attempts have been made to use an organic EL element as a light source such as an exposure head of a printing apparatus.

  For example, in Patent Document 1, in a configuration in which a microlens is arranged corresponding to each element of an array of organic EL elements, a light collecting position of light generated in each organic EL element is placed from an adjacent organic EL element. By arranging a partition wall with an optical hole that blocks light from entering on the light emitting side of the organic EL element, crosstalk in the exposure head is reduced, and light from each organic EL element is received with sufficient resolution. The light can be condensed.

Further, in Patent Document 2, a microlens array plate is arranged in alignment with the light emitting side of an organic EL element, and a groove surrounding each organic EL element is provided on the incident side surface of the microlens array plate. By disposing an absorption layer or a reflection layer, crosstalk in the exposure head is reduced, and light from each organic EL element can be condensed with sufficient resolution.
JP 2003-291404 A JP 2003-291406 A

  Here, in both Patent Document 1 and Patent Document 2 described above, an optical aperture, a microlens, a reflective layer, an absorption layer, and the like must be formed for each organic EL element. Since these structures need to be miniaturized as the resolution of the printing apparatus increases, the processing cost increases accordingly, and in some cases, the processing itself becomes difficult.

  Also, in Patent Document 1 and Patent Document 2, the diameter of the microlens is optically the same as that of the organic EL element. Since the lens has a single lens structure, the condensing position is very close to the organic EL element, and in order to condense on the image carrier, the exposure head and the image carrier must be brought as close as possible. Inevitably, when the image forming point is separated, the image is enlarged, the resolution is lowered, and the light quantity is also lowered. Even when exposure is performed using narrow directivity rather than image formation, the exposure head must be as close as possible to the image carrier.

  Furthermore, in the case of a structure using a microlens, the light irradiation surface of the exposure head has a convex shape, and thus cannot be easily removed when toner or the like adheres to the light irradiation surface of the exposure head.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a light emitting device that has high definition, high luminance, narrow directivity, and can be manufactured by a relatively simple manufacturing process.

In order to achieve the above object, the invention according to claim 1 has a plurality of light emitting portions, each of the light emitting portions having a light emitting layer and an electric field applied to the light emitting layer sandwiching the light emitting layer. provided for emitting the light emitting layer, a first electrode and a second electrode facing, is formed on the first one surface on the substrate has a light emitted from the light-emitting layer, the light emitting surface emitted from the first electrode forming a light-emitting unit array are linearly arranged each light emitting portion is spaced apart from each other on one surface of the first substrate, the light emitting surface side of the light emitting portion array A core layer provided so as to cover the whole, wherein the core layer is formed by laminating two diffraction grating forming layers having different refractive indexes , and each of the plurality of light emitting portions of the core layer . in a region corresponding to the light emitting surface, sequence the light emitted from said first electrode of said plurality of light emitting portions Is propagated in the direction perpendicular against the direction a plurality of optical waveguide gratings provided in the direction of emission to the outside is formed, a region corresponding to between the respective light emitting portions in the arrangement direction of the plurality of light emitting portions of the core layer In addition, a plurality of optical isolation gratings whose light propagation directions are orthogonal to the light propagation direction in the optical waveguide diffraction grating are formed, and the lattice spacing of each of the optical isolation diffraction gratings is determined by the first electrode. Each of the optical waveguide diffraction grating and each of the optical isolated diffraction gratings is formed of the same material in the core layer. It is a light-emitting device characterized by having.

  According to a second aspect of the present invention, in the light emitting device according to the first aspect, the optical waveguide diffraction grating is a distributed feedback diffraction grating having a spatial period of Bragg conditions.

  According to a third aspect of the present invention, in the light emitting device according to the first aspect, the optical waveguide diffraction grating is a diffraction grating having a λ / 4 phase shift structure.

  According to a fourth aspect of the present invention, in the light emitting device according to the first aspect, the light isolation diffraction grating cancels light from the adjacent light emitting portions reflected from unit cells having different periodic perturbations. It is a diffraction grating having a spatial period overlapping in phase.

According to a fifth aspect of the present invention, in the light emitting device according to the first aspect , the one surface side is provided on the light emitting surface side of the light emitting section array so as to face the one surface side of the first substrate. And the core layer is provided between the one surface side of the second substrate and the light emitting surface side of the light emitting section array, and the two diffraction gratings in which the core layers are stacked. is a diffraction grating shape formed at an interface forming layer, wherein the diffraction grating pattern and the optical waveguide diffraction grating and the respective optical isolate diffraction grating, orthogonal to the propagation direction of light in said optical waveguide grating It is characterized by being formed alternately and continuously along the direction .

According to a sixth aspect of the present invention, in the light emitting device according to the fifth aspect, between the one surface of the second substrate and the core layer , at a position facing the light emitting surface of each light emitting unit. And a reflecting portion configured to reflect the light emitted from the light emitting surface and incident on the one surface side of the second substrate to the optical waveguide diffraction grating side.

According to the present invention, an optical waveguide diffraction grating is provided in a core layer that has a light-emitting part array having a plurality of light-emitting parts arranged linearly apart and covers the light-emitting surface side of each light-emitting part. formed by the light emitted from the light emitting unit is emitted is propagated in a direction orthogonal to the array direction of the light emitting portion, the light isolated diffraction grating between each optical waveguide grating in the core layer and each optical waveguide grating formed of the same material, so as the light does not propagate between the light emitting portion adjacent, has a high resolution, high luminance and narrow directivity, is possible to provide a light emitting device can be fabricated by relatively simple fabrication processes it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a cross-sectional view schematically showing a light emitting device 1000 according to the first embodiment of the present invention. 1A is a top cross-sectional view of the light-emitting device 1000, FIG. 1B is a cross-sectional view taken along line AA of FIG. 1A, and FIG. 1C is FIG. It is a BB sectional view taken on the line.

  As shown in FIG. 1C, the light emitting device 1000 is configured with a structure in which a waveguide forming layer 200 is stacked on an organic EL light emitter forming layer 100. In FIG. 1C, the arrow C direction indicates the light propagation direction. Further, a reflective plate 300 made of, for example, an aluminum thin film is formed on the surface of the light emitting device 1000 facing the light exit surface. A light shielding plate may be formed instead of the reflection plate 300.

  The organic EL light emitter forming layer 100 is formed by, for example, forming a waveguide after patterning a lower electrode (second electrode) 20 made of, for example, Al with a photoresist on a light emitter substrate (first substrate) 10 made of, for example, a glass substrate. An insulating layer 30 that also serves as a clad layer in the formation layer 200 is laminated, and then an opening is patterned in the insulating layer 30 with, for example, a photoresist. The organic light emitting layer 40 and, for example, ITO (indium tin oxide) are formed in the opening. The upper transparent electrode (first electrode) 50 is formed in order to form the light emitting portion 44.

  Here, as shown to Fig.1 (a), the light emission part 44 is formed in multiple linear arrangement | sequences, and has comprised the light emission part array. Each light emitting section 44 is formed in a long shape with respect to the light emitting direction indicated by the arrow C in order to individually control light emission. Further, wiring is drawn out from the lower electrode 20 and the upper transparent electrode 50 as shown in FIG. 1A and connected to a driving device of a light emitting device (not shown).

  In such a configuration, when an electric field is applied to the organic light emitting layer 40 through the lower electrode 20 and the upper transparent electrode 50, electrons and electrons are transferred between the electron transport layer and the hole transport layer constituting the organic light emitting layer 40. Hole movement occurs, and as a result, electrons and holes recombine in the light emitting layer to emit light.

  Here, as each material of the organic EL light-emitting body forming layer 100, various materials used in conventional organic EL light-emitting elements can be used. However, the lower electrode 20 is a metal material (for example, Al or Ag) having a high light reflectance in order to return the light emitted from the organic light emitting layer 40 to the light emitter substrate 10 side to the waveguide forming layer 200 side. It is desirable to form with.

  The waveguide forming layer 200 is formed of a waveguide substrate (second substrate) 55 that also serves as a cladding layer together with the insulating layer 30 and a core layer 60.

  The core layer 60 through which light generated in the light emitting unit 44 is propagated includes a first layer 60a and a second layer 60b having different refractive indexes, and a boundary between the first layer 60a and the second layer 60b. A diffraction grating 66 is formed in the region.

  Here, the diffraction grating 66 formed between the first layer 60a and the second layer 60b of the core layer 60 includes two types of optical waveguide diffraction gratings 67 and 68 shown in FIGS. It is comprised by arrange | positioning as shown to b) and FIG.1 (c).

  That is, an optical waveguide diffraction grating 67 having a diffraction grating with a Bragg condition in which light is fed back in phase with respect to the propagation direction of the light generated in the long light emitting section 44 is emitted immediately above the light emitting section 44. It is arranged at a position to be paired with the portion 44. In another type of diffraction grating, an optically isolated diffraction grating 68 having a diffraction grating with a condition that light is fed back with a phase shift of 180 degrees is disposed immediately above the space between adjacent light emitting portions 44. The optical isolation diffraction grating 68 is formed in a direction orthogonal to the optical waveguide diffraction grating 67.

Here, the optical waveguide diffraction grating 67 is, for example, a distributed feedback diffraction grating in which the grating interval is set with a spatial period that satisfies the black condition. That is, the optical waveguide diffraction grating 67 has a wavelength of light incident from the light emitting unit 44 via the first layer 60a as λ and a grating interval of the diffraction grating as Λ.
Λ = m (λ / 2) m = 1, 2, 3,... (Formula 1)
The Bragg condition indicated by is established. FIG. 2 is a diagram showing a distributed feedback optical waveguide diffraction grating 67. For example, assuming that the wavelength when the light emitted from the light emitting unit 44 travels in the air is λ0 = 750 nm, and the average refractive index of the material constituting the diffraction grating is n1 = 1.5, the wavelength of the light incident on the diffraction grating λg (= λ) is
λg = λ = λ0 / n1 = 500 nm (Formula 2)
It becomes. Therefore, the lattice spacing Λ shown in FIG. 2 can be selected from the dimensions obtained by multiplying (Equation 1) by a natural number of 250 nm, that is, Λ = 250, 500, 750, 1000, 1250, 1500. However, the smaller the grating interval is, the more times the light incident on the diffraction grating matches and the number of times of feedback increases. Therefore, it is desirable that the grating interval Λ be the minimum that can be manufactured with high accuracy.

  By forming the distributed feedback type diffraction grating under the Bragg condition as shown in FIG. 2, the light generated in the light emitting section 44 and reflected from each unit cell of the diffraction grating resonates in the waveguide forming layer 200, and as a result As the light is amplified. Therefore, it is possible to obtain light having excellent wavelength selectivity and directivity and a narrow emission spectrum width.

  Here, the optical waveguide diffraction grating 67 preferably has a λ / 4 phase shift structure as shown in FIG. The λ / 4 phase shift structure is composed of a combination of a grating having a spatial period satisfying the relationship of (Expression 1) and a grating having a half spatial period (= Λ / 2). For example, assuming that the wavelength λg (= λ) of light incident on the diffraction grating is 500 nm, the grating spacings Λ and Λ / 2 shown in FIG. 3 are 250 and 125, 500 and 250, 750 and 375, and 1000, respectively. , 500, 1250 and 625, 1500, 750... Also in this case, it is desirable that the lattice spacings Λ and Λ / 2 be the minimum spacing that can be manufactured with high accuracy.

  In this way, by making the optical waveguide diffraction grating 67 have a λ / 4 phase shift structure, it is possible to match the phase of the emitted light and emit more single mode light. Note that a gain-coupled structure diffraction grating may be used instead of the λ / 4 phase shift structure diffraction grating.

  The optical isolation diffraction grating 68 is a diffraction grating in which the grating interval is set with a spatial period that does not satisfy the Bragg condition. That is, in order not to satisfy the condition of (Equation 1), the grating interval Λ is set to be a non-natural number multiple of the wavelength λ of the incident light. By forming such a diffraction grating, light from the adjacent light emitting portions 44 reflected from each unit cell of the grating is canceled, so that light can be emitted from each light emitting portion with reduced crosstalk.

  Here, the diffraction grating structure of the waveguide forming layer 200 has a thin layer resin for forming the first layer 60a of the core layer, such as polymethyl methacrylate [PMMA], polycarbonate [PC], polyimide [PI], etc. The above-mentioned diffraction grating shape is transferred and formed, for example, by a thermal nanoimprint method on a base material obtained by thinly coating a resin material having a good light transmission property and an excellent optical property on a waveguide substrate 55 made of a glass material, for example. Can be created. The creation method of the diffraction grating structure is not limited to the thermal nanoimprint method, and may be created by, for example, an injection molding method.

  The waveguide forming layer 200 is manufactured by applying and planarizing the second layer 60b having a refractive index different from that of the first layer 60a on the diffraction grating 66 formed in the first layer 60a. be able to. The first layer 60a and the second layer 60b may have different refractive indexes. For example, polymethyl methacrylate is used for the first layer 60a and polycarbonate is used for the second layer 60b, or vice versa. Alternatively, polycarbonate can be used for the first layer 60a, and polymethyl methacrylate can be used for the second layer 60b.

  Thus, since the waveguide forming layer 200 has a shape formed with respect to the thin resin layer coated on the waveguide substrate 55, it is possible to suppress distortion and dimensional variation due to thermal contraction of the resin portion. .

  Here, the luminescent accuracy substrate 10 of the organic EL luminescent material forming layer 100 also has the same level of dimensional accuracy and thermal expansion by selecting the same material (glass material in the example) as the waveguide substrate 55. This facilitates bonding and can improve the yield particularly when an array with a fine pitch is formed.

  In addition, the life of the organic light emitting layer 40 of the organic EL light emitter forming layer 100 is remarkably reduced due to moisture absorption such as moisture. On the other hand, in the present embodiment, it is possible to arrange the light emitting unit 44 at a sufficiently inner position where a gas barrier can be provided with respect to the substrate end surface. By stacking the formation layer 200, the organic EL can be sealed, and the light from the light emitting portion 44 can be guided to the light emitting surface of the light emitting device by the optical waveguide diffraction grating 67.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 4 is a cross-sectional view schematically showing the light emitting device 1000 according to this embodiment. 4A is a top cross-sectional view of the light-emitting device 1000, FIG. 4B is a cross-sectional view taken along line AA of FIG. 4A, and FIG. 4C is FIG. 4A. It is a BB sectional view taken on the line.

  As in the first embodiment, the light emitting device 1000 according to the present embodiment has a structure in which a waveguide forming layer 200 is stacked on an organic EL light emitter forming layer 100. The difference between the second embodiment and the first embodiment is that a reflection mirror 80 as a reflection portion is formed between the waveguide substrate (second substrate) 55 and the core layer 60. Since other structures are the same as those of the first embodiment, description thereof is omitted.

  The reflection mirror 80 is formed by depositing a high reflectance material such as Al or Ag on the waveguide substrate 55 by vapor deposition, for example. The reflection mirror 80 is more preferably a multi-reflection mirror for forming several layers of dielectrics. By providing such a reflection mirror 80, even when light emitted from the light emitting unit 44 enters the waveguide substrate 55, the incident light is reflected by the reflection mirror 80 toward the optical waveguide diffraction grating 67. Therefore, the light confinement rate can be improved as compared with the first embodiment.

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention.

  Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some configuration requirements are deleted from all the configuration requirements shown in the embodiment, the above-described problem can be solved, and this configuration requirement is deleted when the above-described effects can be obtained. The configuration can also be extracted as an invention.

It is 3 sectional drawing which shows typically the light-emitting device which concerns on the 1st Embodiment of this invention. It is the figure which showed the distributed feedback type optical waveguide diffraction grating. It is the figure which showed the optical waveguide diffraction grating of (lambda) / 4 phase shift structure. It is 3 sectional drawing which shows typically the light-emitting device which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Luminescent substrate, 20 ... Lower electrode, 30 ... Insulating layer, 40 ... Organic light emitting layer, 44 ... Light emitting part, 50 ... Upper transparent electrode, 55 ... Waveguide substrate, 60 ... Core layer, 60a ... First layer 60b ... second layer, 66 ... diffraction grating, 67 ... optical waveguide diffraction grating, 68 ... optical isolation grating, 80 ... reflection mirror

Claims (6)

A plurality of light emitting portions, each light emitting portion including a light emitting layer, an opposing first electrode for sandwiching the light emitting layer and applying an electric field to the light emitting layer to cause the light emitting layer to emit light; is formed on the first one surface on the substrate having a second electrode, and light emitted from the light-emitting layer is emitted from the first electrode, the light emitting surface of the first electrode is the light emitting surface A light emitting section array in which each of the light emitting sections is linearly spaced apart from each other on one surface of the first substrate ;
A core layer provided to cover the entire light emitting surface side of the light emitting section array;
Comprising
The core layer is formed by laminating two diffraction grating forming layers having different refractive indexes,
In a region corresponding to the light emitting surface of each of the plurality of light emitting portions of the core layer, to the outside is propagated in the direction perpendicular against the light emitted from the first electrode in the array direction of the plurality of light emitting portions A plurality of optical waveguide diffraction gratings provided in the emission direction are formed , and the propagation direction of light is the optical waveguide diffraction in a region corresponding to the space between the light emitting units in the arrangement direction of the plurality of light emitting units of the core layer. A plurality of optically isolated diffraction gratings perpendicular to the light propagation direction in the grating are formed, and the interval between the optically isolated diffraction gratings is such that the light emitting units adjacent to the light emitted from the first electrode Set to a value that blocks propagation to
Each light guide diffraction grating and each light isolation diffraction grating are formed of the same material in the core layer .   The light-emitting device according to claim 1, wherein the optical waveguide diffraction grating is a distributed feedback diffraction grating having a spatial period of a Bragg condition.   The light-emitting device according to claim 1, wherein the optical waveguide diffraction grating is a diffraction grating having a λ / 4 phase shift structure.   2. The optically isolated diffraction grating according to claim 1, wherein the optically isolated diffraction grating is a diffraction grating having a spatial period overlapping with a phase in which light from the adjacent light emitting parts reflected from unit cells having different periodic perturbations cancel each other. The light emitting device according to 1. A first substrate having a second substrate provided on the light emitting surface side of the light emitting unit array facing the one surface side of the first substrate;
The core layer is provided between the one surface side of the second substrate and the light emitting surface side of the light emitting unit array,
Diffraction grating pattern is formed at the interface of the stacked the two diffraction grating layer of the core layer, and wherein each optical isolate diffraction grating and the respective optical waveguide grating by diffraction grating pattern, the optical waveguide The light emitting device according to claim 1, wherein the light emitting device is alternately and continuously formed along a direction orthogonal to a light propagation direction in the diffraction grating . Formed at a position facing the light emitting surface of each light emitting section between the one surface of the second substrate and the core layer , emitted from the light emitting surface, and on the one surface side of the second substrate The light-emitting device according to claim 5, further comprising a reflection unit configured to reflect light incident on the optical waveguide diffraction grating side.

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