JP2006269515A - Backlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a backlight device for improving the radiation characteristic of heat generated by an organic EL element at low cost, and improving a lifetime without decreasing luminance in the backlight device using the organic EL element. <P>SOLUTION: The backlight device has a luminous section 3 formed flatly by using the organic EL element, and irradiates an image display surface 1 with irradiation light. The luminous section 3 holds an effective luminous area of 90% or higher of the image display surface, and is divided into a first luminous region 3a and a second luminous region 3b in a face direction with a size for covering a plurality of pixels. The divided first and second luminous regions 3a, 3b are subjected to luminous drive simultaneously by a constant current source. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a backlight device using an organic EL element as a backlight.

  In recent years, organic EL elements have attracted attention as self-luminous elements. An organic EL element has a configuration in which a thin light emitting layer made of an organic compound is sandwiched between electrode pairs, and emits light when a current is supplied between the electrodes. A backlight device using an organic EL element that is a thin film as a backlight can be reduced in thickness, so that it is often used in a liquid crystal display device and the like, and has the effect of reducing the size and weight of the entire liquid crystal display device. .

  When the organic EL element is used as a backlight, if the entire surface is lit continuously for a long time, a constant current is continuously supplied to the organic EL element for a long time, so that the organic EL element generates heat, and the organic EL element There is a problem that deterioration such as alteration occurs in the organic compound that constitutes, and the luminance is lowered or the life is shortened.

  In order to solve such a problem, an organic EL device is provided on a metal substrate through a metal thin film having high thermal conductivity in order to efficiently dissipate heat generated by light emission of the organic EL element. An electroluminescence device is disclosed (see Patent Document 1).

In addition, the Peltier element formed on at least a part of the semiconductor substrate and the organic EL element arranged directly or indirectly on the semiconductor substrate, and the thermal resistance of the organic EL element to the heat absorption side of the Peltier element is dissipated. An organic EL device arranged so that the thermal resistance on the side is small is disclosed (see Patent Document 2).
JP-A-8-124679 JP 2004-296100 A

  However, devices using conventional organic EL elements such as Patent Documents 1 and 2 require a member for radiating heat (for example, a Peltier element) in addition to the configuration necessary for spontaneous light emission. However, there is a problem that the manufacturing cost is increased and the thinning effect, which is also a feature of the backlight device using the organic EL element, is reduced.

  An object of the present invention is to provide a backlight device using an organic EL element, which can improve the heat dissipation characteristics of heat generated by the organic EL element at low cost and can improve the lifetime without reducing the luminance. Is to realize.

  The invention according to claim 1 is a backlight device which has a light emitting means formed in a planar shape using an organic EL element and irradiates an image display surface with illumination light. The light emitting means has an effective light emitting area. The image display surface is maintained at 90% or more and is divided into a plurality of light emitting regions in a surface direction so as to cover a plurality of pixels, and the plurality of divided light emitting regions are driven to emit light simultaneously by a light emission driving unit. It is characterized by being a backlight device.

  According to a second aspect of the present invention, in the backlight device according to the first aspect, the sum of the peripheral lengths of the plurality of divided light emitting regions is 1.3 times or more the peripheral length of the image display surface. It is characterized by that.

  According to a third aspect of the present invention, in the backlight device according to the first aspect, the sum of the perimeters of the plurality of divided light emitting regions is 1.9 times or more the perimeter of the image display surface. It is characterized by that.

  According to a fourth aspect of the present invention, in the backlight device according to any one of the first to third aspects, the light emitting means includes an anode layer and a cathode layer disposed opposite to each other, and the anode layer. And an organic layer interposed between the cathode layers and divided by separating the anode layers and / or cathode layers at intervals in a plane direction. It is a feature.

  According to a fifth aspect of the present invention, in the backlight device according to any one of the first to third aspects, the light emitting means includes an anode layer and a cathode layer that are arranged to face each other, the anode layer, And an organic layer interposed between the cathode layers, and the anode layer, the cathode layer, and the organic layer are separated by being separated at an interval in the plane direction. It is characterized by.

  According to a sixth aspect of the present invention, in the backlight device according to any one of the first to fifth aspects, the light emission driving means is provided independently for each of the plurality of divided light emission regions. It is characterized by that.

  According to the first aspect of the present invention, since the light emitting means is divided into a plurality of light emitting areas so as to cover a plurality of pixels, heat generated from the divided light emitting areas that are simultaneously emitted can be divided. Since heat can be dissipated from the periphery of the light emitting region, the heat dissipation characteristic can be improved while ensuring a desired luminance characteristic, and the lifetime of the backlight device can be improved.

  According to the second aspect of the present invention, it is possible to obtain the same effect as that of the first aspect, and to dissipate the heat generated by the light emitting means from the divided portion as compared with the case where the light emitting means is not divided. Therefore, the luminance half-life can be extended and the lifetime can be improved while reducing the manufacturing load of the backlight device.

  According to the third aspect of the invention, the same effect as in the first aspect can be obtained, and the heat generated by the light emitting means can be dissipated from the divided portion as compared with the case where the light emitting means is not divided. Therefore, since the luminance half-life can be extended while maintaining a high luminance maintenance rate, the lifetime of the backlight device can be improved.

  According to the invention described in claim 4, the same effect as in any one of claims 1 to 3 can be obtained, and the light emitting means is spaced in the plane direction of the anode layer and / or the cathode layer. By being separated by placing and separating, the manufacturing process of the light emitting means can be simplified.

  According to the fifth aspect of the invention, the same effect as in any one of the first to third aspects can be obtained, and the light emitting means is integrally formed with the cathode, the anode, and the organic layer spaced in the plane direction. It is possible to simplify the manufacturing process of the light emitting means.

  According to the invention described in claim 6, it is possible to obtain the same effect as that of any one of claims 1 to 5, and by providing the light emission driving means for each divided light emitting region, Compared with the case where the light emission driving unit is driven, it is possible to prevent luminance unevenness between the issue areas caused by a difference in wiring resistance for supplying a current to each light emission area.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In this embodiment mode, a case where a backlight device using an organic electroluminescence (EL) element (hereinafter referred to as an organic EL element) of the present invention is applied as a backlight of a liquid crystal display device will be described.

First, the configuration will be described.
FIG. 1 is a plan view showing an example of a correspondence relationship between the liquid crystal display screen 1 of the liquid crystal display device according to the present embodiment and the backlight device of the present invention, and FIG. 2 is an AA view in FIG. The schematic diagram which expanded the partial cross section of the backlight apparatus in alignment with a line is shown.

  As shown to Fig.1 (a), the backlight apparatus is arrange | positioned so that the light emission part 3 formed using the organic EL element may oppose the liquid crystal display screen 1 as an image display surface, and a light emission part 3 is a size that covers the plurality of pixels 2 and is equally divided into a first light emitting region 3a and a second light emitting region 3b as a plurality of light emitting regions in the surface direction, and the first light emitting region 3a and the second light emitting region 3b are divided into two. 90% or more of the area of the liquid crystal display screen 1 is maintained as the sum of the effective light emitting areas with the light emitting region 3b (effective light emitting area of the light emitting unit 3). If the effective light emitting area of the light emitting unit 3 is 90% or more of the area of the liquid crystal display screen 1, the luminance is reduced as compared with the case where the effective light emitting area of the light emitting unit 3 is 100% of the area of the liquid crystal display screen 1. Is not recognized by human eyes, on the other hand, when the effective light emitting area of the light emitting unit 3 is smaller than 90% of the area of the liquid crystal display screen 1, to increase the light emission intensity to compensate for the decrease in luminance. The current supply value must be increased, leading to a reduction in the lifetime of the organic EL element.

  The light emitting unit 3 of the backlight device shown in FIG. 1A shows an example in which the light emitting region of the light emitting unit 3 is equally divided into two by dividing the width W direction of the liquid crystal display screen 1 into two. However, the depth D direction of the liquid crystal display screen 1 may be divided into two. Further, the place where the first light emitting area 3a and the second light emitting area 3b are divided is on a black matrix that divides each pixel 2, and the dividing interval between the first light emitting area 3a and the second light emitting area 3b is as follows. The distance is preferably shorter than the pitch between pixels.

FIG. 1B is a plan view showing another example of the correspondence between the liquid crystal display screen and the organic EL element backlight.
The light emitting unit 4 of the backlight device shown in FIG. 1B divides the width W direction of the liquid crystal display screen 1 into two equal parts and evenly divides the depth D direction into two parts, so that the light emitting region of the light emitting part 4 is obtained. However, the depth D direction of the liquid crystal display screen 1 may be equally divided into four, or the width W direction may be equally divided into four.

  Thus, the luminance of the entire display screen can be made uniform by equally dividing the light emitting section into a plurality of parts.

  As shown in FIG. 2, the backlight device includes an anode 220 or first and second anodes 220 a and 220 b, an organic layer 230 or first and second organic layers 230 a and 230 b, and a cathode 240 on the surface of one side of the transmission substrate 210. Alternatively, the organic EL element as a light emitting means (light emitting part) formed by sequentially laminating the first and second cathodes 240a and 240b, and the anode 220 or the first and second anodes 220a and 220b and the cathode 240 or the first and second cathodes. The first and second constant current sources 250a and 250b function as light emission driving means for supplying a constant current to 240a and 240b.

  The light emission mechanism of the organic EL element is as follows. When a forward current is supplied from the constant current source via the anode and the cathode, electrons and holes injected in the organic layer are combined, and organic molecules are excited by the combination. When the excited organic molecule returns to the ground state, the difference energy is emitted as light. The light emitted from the organic layer is emitted through the anode and the transmission substrate.

  Further, the energy that is not converted as light when the excited organic molecules return to the ground state is converted into Joule heat. When this Joule heat is generated, the organic EL element generates heat.

  That is, when a current is supplied to a portion where the anode and the cathode overlap, light is emitted from the organic layer to become a light emitting region, and also a heat generating region that generates heat with light emission. On the other hand, the portion of the organic layer that does not overlap with the cathode becomes a non-light emitting region where no light is emitted from the organic layer and does not generate heat.

  Therefore, by dividing the light emitting region by separating the light emitting region in the plane direction to form a non-heat generating region, heat accompanying light emission generated from the light emitting region can be dissipated through the non light emitting region, The temperature of the whole organic EL element (light emitting part) can be lowered.

  The light emitting region and the non-light emitting region can be formed by a combination of divided patterns of the anode, the organic layer, and the cathode.

  In FIG. 2A, an anode 220 laminated as a plate-shaped solid electrode having a planar shape substantially the same as the entire size of the liquid crystal display screen 1 on the surface of one side of the transparent substrate 210, and on the anode 220 The stacked organic layer 230, the first cathode 240 a and the first cathode 240 a stacked on the organic layer 230 by performing mask processing so as to be separated by being evenly separated in the plane direction of the liquid crystal display screen 1. A back formed by two cathodes 240b, a first constant current source 250a for supplying constant current to the anode 220 and the first cathode 240a, and a second constant current source 250b for supplying constant current to the anode 220 and the second cathode 240b. The schematic diagram of a light apparatus is shown.

  As shown in FIG. 2A, when current is supplied from the first constant current source 250a to the anode 220 and the first cathode 240a, light is emitted from the organic layer 230 where the anode 220 and the first cathode 240a overlap. When the current is supplied from the second constant current source 250b to the anode 220 and the second cathode 240b, the portion from which the light is emitted becomes the first light emitting region 3a as a divided light emitting region. The portion where light is emitted from the organic layer 230 in the overlapping portion of the organic layer 230 becomes the second light emitting region 3b as a divided light emitting region.

  In FIG. 2B, on the surface of one side of the transparent substrate 210, an anode 220 laminated as a plate-shaped solid electrode having a planar shape substantially the same as the overall size of the liquid crystal display screen 1, and on the anode 220 The first organic layer 230a, the second organic layer 230b, and the first and second organic layers 230a, which are stacked by performing a mask process so that the liquid crystal display screen 1 is divided by being evenly separated in the surface direction of the liquid crystal display screen 1. 230b, the first cathode 240a, the second cathode 240b, the anode 220 and the first cathode 240a that supply a constant current to the first cathode 240a, and the anode 220 and the second cathode 240b. The schematic diagram of the backlight apparatus formed from the 2nd constant current source 250b which supplies 2 is shown.

  As shown in FIG. 2B, when current is supplied from the first constant current source 250a to the anode 220 and the first cathode 240a, light is emitted from the first organic layer 230a where the anode 220 and the first cathode 240a overlap. When the current is supplied from the second constant current source 250b to the anode 220 and the second cathode 240b, the portion from which the light is emitted becomes the first light emitting region 3a as a divided light emitting region. A portion where light is emitted from the second organic layer 230b that overlaps with each other becomes a second light emitting region 3b as a divided light emitting region.

  Therefore, as shown in FIGS. 2A and 2B, the portion where the anode 220 and the first cathode 240a or the second cathode 240b do not overlap becomes the non-light emitting region 5, which is the first than when the division is not performed. The heat radiation effect due to the light emission generated from the two light emitting regions 3a and 3b is improved.

  In FIG. 2 (c), the first anode 220a laminated on the surface of one side of the transparent substrate 210 by performing mask processing so as to be divided by being separated evenly in the plane direction of the liquid crystal display screen 1. A second anode 220b, an organic layer 230 laminated on the first and second anodes 220a and 220b to approximately the same dimensions as the entire liquid crystal display screen 1, and a cathode 240 laminated on the organic layer 230. A schematic of a backlight device formed by a first constant current source 250a that supplies a constant current to the first anode 220a and the cathode 240, and a second constant current source 250b that supplies a constant current to the second anode 220b and the cathode 240. The figure is shown.

  As shown in FIG. 2C, when current is supplied from the first constant current source 250a to the first anode 220a and the cathode 240, light is emitted from the organic layer 230 where the first anode 220a and the cathode 240 overlap. When the current is supplied from the second constant current source 250b to the second anode 220b and the cathode 240, the portion from which the light is emitted becomes the first light emitting region 3a as a divided light emitting region. The portion where light is emitted from the organic layer 230 in the overlapping portion of the organic layer 230 becomes the second light emitting region 3b as a divided light emitting region.

  Therefore, as shown in FIG. 2C, the portion where the first anode 220a or the second anode 220b and the cathode 240 do not overlap becomes the non-light emitting region 5, and the first and second light emitting regions than when the division is not performed. The heat radiation effect due to the light emission generated from 3a and 3b is improved.

  In FIG. 2D, the first anode 220a is laminated on the surface of one side of the transparent substrate 210 by performing mask processing so as to be divided by being separated evenly in the plane direction of the liquid crystal display screen 1. , The second anode 220b, the organic layer 230 laminated on the first and second anodes 220a, 220b in substantially the same dimensions as the whole liquid crystal display screen 1, and the surface of the liquid crystal display screen 1 on the organic layer 230 The first cathode 220a, the second cathode 220b, and the first anode 220a, which are stacked by performing a mask process so as to be divided in the same manner as the first and second anodes 220a and 220b by separating them evenly in the direction. And a first constant current source 250a for supplying a constant current to the first cathode 240a, a second constant current source 250b for supplying a constant current to the second anode 240b, and a second anode 220b. Show.

  As shown in FIG. 2 (d), when current is supplied from the first constant current source 250a to the first anode 220a and the first cathode 240a, the organic portion of the portion where the first anode 220a and the first cathode 240a overlap each other. When a portion from which light is emitted from the layer 230 becomes the first light emitting region 3a as a divided light emitting region, and current is supplied to the second anode 220b and the second cathode 240b from the second constant current source 250b, A portion where light is emitted from the organic layer 230 where the two anodes 220b and the second cathode 240b overlap is a second light emitting region 3b as a divided light emitting region.

  In FIG. 2 (e), the first anode 220a is laminated on the surface of one side of the transparent substrate 210 by performing mask processing so as to be divided by being separated evenly in the plane direction of the liquid crystal display screen 1. The second anode 220b, the first organic layer 230a, the second organic layer 230b, and the first and second organic layers 230a, 230b respectively stacked on the first and second anodes 220a, 220b. The first cathode 220a, the second cathode 220b, the first constant current source 250a for supplying a constant current to the first anode 220a and the first cathode 240a, and the first current for supplying a constant current to the second anode 220b and the second cathode 240b. The schematic diagram of the backlight apparatus formed from 2 constant current sources 250b is shown.

  As shown in FIG. 2E, when a current is supplied from the first constant current source 250a to the first anode 220a and the first cathode 240a, the first organic layer in which the first anode 220a and the first cathode 240a overlap each other. When a portion from which light is emitted from the layer 230a becomes the first light emitting region 3a as a divided light emitting region, and current is supplied from the second constant current source 250b to the second anode 220b and the second cathode 240b, A portion from which light is emitted from the second organic layer 230b where the two anodes 220b and the second cathode 240b overlap becomes a second light emitting region 3b as a divided light emitting region.

  Accordingly, as shown in FIGS. 2D and 2E, a portion where the first anode 220a or the second anode 220b and the first cathode 240a or the second cathode 240b do not overlap becomes the non-light emitting region 5, and the division is performed. The heat radiation effect due to the light emission generated from the first and second light emitting regions 3a and 3b is improved as compared with the case where it is not performed.

Moreover, as shown in FIG. 2, although the case where the independent constant current source was provided for every divided light emitting area was described, a constant current source common to the divided light emitting areas may be provided. However, if a constant current source is provided independently for each divided light emitting region as shown in FIG. 2, a current is supplied independently for each divided light emitting region, and a current is supplied from a common constant current source. As compared with the case where the light is emitted, luminance unevenness caused by a difference in wiring resistance for supplying current to each light emitting region can be prevented, and uniform luminance can be ensured for the entire backlight. In addition, although the constant current source is provided for every light emission area | region, lighting control is simultaneous lighting.
In addition,

  The configuration of the organic EL element is not limited to the mode shown in FIG. 2, and the anode and the cathode may be laminated in the order opposite to the order shown in FIG. A top emission structure in which light is emitted from a substantially transparent cathode obtained by laminating a cathode material having a high transmittance and an anode material having a high transmittance may be employed.

  As the transmissive substrate, the anode, the organic layer, and the cathode, known materials that have been conventionally used in the production of organic electroluminescent elements can be appropriately used.

The transmissive substrate may be a solid substrate or a flexible substrate.
As the base material of the solid substrate, glass, quartz or the like can be used.
As the base material of the flexible substrate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), Cellulose triacetate (TAC), cellulose acetate propionate (CAP) and the like can be used.

  The anode is a transparent electrode that transmits light generated in the organic layer, and an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function is preferably used. For example, indium tin oxide (ITO) , Indium zinc oxide (IZO), gold, tin oxide, zinc oxide, or the like, and a conductive material having a work function of 4 eV or more and a transmittance of 40% or more can be used. By depositing these electrode materials on a transmissive substrate by a method such as vacuum deposition or sputtering, the anode can be formed as a thin film.

  The organic layer may have a single-layer configuration consisting of only a light-emitting layer, or a multi-layer configuration including a three-layer configuration in which a light-emitting layer having a light-emitting material is sandwiched between a hole transport layer and an electron transport layer. Also good. The organic layer has a thickness of several nm to several μm.

  The light emitting layer includes an organic light emitting material composed of an organic compound or a complex. In order to emit light efficiently, it is effective to shorten the moving distance of carriers, and it is desirable to reduce the thickness of the light emitting layer. Organic light-emitting materials include fluorescent materials that emit the energy difference as fluorescence when returning from the single excited state to the ground state, and phosphorescent materials that emit the energy difference when returning from the triple excited state to the ground state as phosphorescence. However, it is particularly preferable to use a phosphorescent material from the viewpoint of luminous efficiency and lifetime.

  Note that organic molecules are generally vulnerable to moisture and oxygen, and have a high probability of being deteriorated by reacting with oxygen or moisture in the atmosphere, particularly when in an excited state. Therefore, in an organic EL element, it is common to cover and seal the organic layer with a metal tube or glass tube in an inert gas atmosphere such as nitrogen, and shield from the external atmosphere. For simplification of the drawings, drawings and explanation of sealing of the organic EL element are omitted.

  When the hole transport layer is provided, the hole transport layer is provided in contact with the anode. When the electron transport layer is provided, the electron transport layer is provided in contact with the cathode. In the case where the organic layer has a plurality of layers, a lithium fluoride layer, an inorganic metal salt layer, a layer containing them, or the like may be disposed at an arbitrary position.

  The cathode is a reflective electrode that reflects light generated in the organic layer, and it is preferable to use an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a low work function. For example, aluminum, sodium, lithium , Magnesium, silver, calcium, and the like, which can be made of a metal material having a work function of less than 5 eV and a reflectance of 60% or more. The cathode 240 can be formed as a thin film by forming these electrode materials by a method such as a vacuum evaporation method or a sputtering method.

  In addition, when using an organic EL element as a light source of a backlight of a liquid crystal display device, it is desirable to whiten, but since there is no single luminescent material that shows white, it is whitened by a plurality of emission colors. . As a method of whitening with a plurality of light emission colors, a method of combining a plurality of light emission colors obtained from a plurality of light emission materials, a light emission by converting the wavelength of light using the light emission color of the light emission material and the light from the light emission material as excitation light. A method of combining with a fluorescent material or a method of dispersing a fluorescent material on a transparent substrate, absorbing light from an organic EL element as excitation light, and whitening by a plurality of light emission by wavelength conversion may be used.

  FIG. 3 shows an example of a graph of a remaining rate curve based on the sum of the perimeters of the plurality of divided light emitting regions (hereinafter referred to as the total perimeter of the light emitting regions) and the perimeter of the liquid crystal display screen. The luminance half-life of a conventional organic EL element that is not divided and an organic EL element in which a plurality of light emitting regions of the present invention are formed will be compared.

  The peripheral length of the light emitting area is the length of the end of the light emitting area surrounding the light emitting area as a boundary between the light emitting area and the non-light emitting area when viewed from the liquid crystal display screen side.

  Luminance half-life refers to the brightness of an organic EL element when a direct current determined to have a preset brightness (initial brightness) is supplied and the organic EL element is driven while keeping this direct current constant. This is the time required to decrease to 50% of the initial luminance.

  The remaining rate curves A1 to A4 shown in FIG. 3 indicate the relationship between the perimeter of the liquid crystal display screen and the total perimeter of the light emitting area when the ratio of the depth D to the width W of the liquid crystal display screen is 1: 1.85. The residual curve when the ratio is changed, and the residual curve B is obtained when the ratio of the depth D to the width W of the liquid crystal display screen is changed and the total perimeter of the light emitting region is shorter than that of the residual rate curve A2. It is a survival rate curve.

The residual rate curve shown in FIG. 3 is an example of the acceleration test result under the following conditions.
A constant current having a current density of 30 [mA / cm ² ] is used as a driving source.
• The initial luminance is 10,000 [cd / m ² ].
-The target luminance half-life is set to 100 [h].

  Note that a plurality of light emitting regions were formed so that the effective total light emitting area of the light emitting portion could hold 90% or more of the area of the liquid crystal display screen.

  Under the above conditions, first, in a Vista-sized liquid crystal display screen, when the total perimeter of the light emitting area is one time the perimeter of the liquid crystal display screen, that is, when the light emitting portion is not divided (residual rate curve A1), the light emitting portion is When the total perimeter of the light emitting region is 1.3 times the perimeter of the liquid crystal display screen (residual rate curve A2), the light emitting portion is divided into four and the total perimeter of the light emitting region of the liquid crystal display screen is divided. When the perimeter is 1.9 times (residual rate curve A3), the light emitting portion is divided into 10 and the total perimeter of the light emitting area is 10 times the perimeter of the liquid crystal display screen (residual rate curve A4). The characteristics of were determined.

  As a result, when the total perimeter of the light emitting region is one time the perimeter of the liquid crystal display screen (residual rate curve A1), the luminance half-life is reached at about 20 [h] When the total perimeter of the light emitting area is 1.3 times the perimeter of the liquid crystal display screen (residual rate curves A2, A3, A4), the target luminance half-life can be maintained and the life is improved by about 5 times. Can be made.

  Further, when the total perimeter of the light emitting area is 1.9 times or more of the perimeter of the liquid crystal display screen (residual rate curves A3 and A4), it is possible to secure a brightness maintenance ratio of 80% or more at the target brightness half-life. At the same time, it becomes saturated.

  Accordingly, while maintaining the high luminance maintenance ratio by forming the light-emitting area that is evenly divided so that the total peripheral length of the light-emitting area is 1.9 times or more of the peripheral length of the liquid crystal display screen. Luminance half-life can be extended.

  Next, in order to obtain the total perimeter of the light emitting region that can maintain the target luminance half-life even with the smallest number of divisions (two divisions), the ratio of the depth D to the width W of the liquid crystal display screen is changed, The case where the total perimeter of the light emitting region was 1.2 times the perimeter of the liquid crystal display screen (residual curve B) was determined.

  As a result, when the total perimeter of the light emitting region is 1.2 times the perimeter of the liquid crystal display screen (residual rate curve B), the luminance half-life is reached in about 80 [h], and the target It is not possible to ensure the luminance half life.

  In addition, when the total perimeter of the light emitting area is shorter than 1.3 times the perimeter of the liquid crystal display screen, the ratio of the depth D to the width W of the liquid crystal display screen is, for example, 4: 1, which is generally popular. In many cases, the ratio is not the ratio between the depth D and the width W of the display screen (for example, 4: 3 for TV and 16: 9 for wide TV).

  Therefore, by forming the light-emitting area evenly divided so that the total perimeter of the light-emitting area is 1.3 times or more of the perimeter of the liquid crystal display screen, the light-emitting portion is not divided. In addition, the heat generated by the light emitting part can be dissipated through the divided non-light emitting region, so that the luminance half-life can be extended and the lifetime can be improved while reducing the manufacturing load of the backlight device. be able to.

  As described above, since the light emitting unit is divided into a plurality of light emitting areas so as to cover a plurality of pixels, heat generated from each divided light emitting area that emits light simultaneously is radiated from the periphery of the divided light emitting areas. Therefore, the heat dissipation characteristic can be improved while ensuring the desired luminance characteristic constant, and the lifetime of the backlight device can be improved.

  In the case where an organic EL element is provided for each pixel, the stripe-shaped anode and cathode in the depth D direction and the width W direction are respectively intersected to be patterned as a point light source having a small area corresponding to each pixel in a lattice shape. Although it has been necessary, the manufacturing load can be reduced by patterning at least one of the anode and the cathode of the organic EL element so as to cover a plurality of pixels.

  In addition, since the light emitting region is formed so as to cover a plurality of pixels, the luminance variation for each pixel can be reduced, and uniform illuminance can be given to each pixel.

  In addition, this invention is not limited to the content of the said embodiment, In the range which does not deviate from the main point of this invention, it can change suitably.

It is a top view which shows the correspondence of the liquid crystal display screen 1 of the liquid crystal display device in this Embodiment, and the organic electroluminescent element backlight which has the light emission part divided | segmented. It is the schematic diagram which expanded the partial cross section of the backlight apparatus in alignment with the AA in FIG. It is a graph of the residual rate curve based on the total perimeter of a light emission area | region, and the perimeter of a liquid crystal display screen.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display screen 2 Pixel 3, 4 Light emission part 3a, 4a 1st light emission area | region 3b, 4b 2nd light emission area | region 4c 3rd light emission area | region 4d 4th light emission area | region 5 Non-light emission area | region 210 Transmission substrate 220 Anode 220a 1st anode 220b 1st 2 anode 230 organic layer 230a first organic layer 230b second organic layer 240 cathode 240a first cathode 240b second cathode 250 constant current source 250a first constant current source 250b second constant current source

Claims (6)

In a backlight device that has a light emitting means formed in a planar shape using an organic EL element and irradiates illumination light on an image display surface,
The light-emitting means is divided into a plurality of light-emitting regions in the surface direction with a size that covers an effective light-emitting area of 90% or more of the image display surface and covers a plurality of pixels,
The plurality of divided light emitting regions are driven to emit light simultaneously by a light emission driving unit;
A backlight device characterized by. The backlight device according to claim 1,
The sum of the perimeters of the plurality of divided light emitting regions is 1.3 times or more the perimeter of the image display surface;
A backlight device characterized by. The backlight device according to claim 1,
The sum of the perimeters of the plurality of divided light emitting regions is 1.9 times or more the perimeter of the image display surface;
A backlight device characterized by. The backlight device according to any one of claims 1 to 3,
The light emitting means is formed in a layer structure including an anode layer and a cathode layer arranged to face each other, and an organic layer interposed between the anode layer and the cathode layer, and the anode layer and / or Or divided by separating the cathode layer at an interval in the plane direction,
A backlight device characterized by. In the backlight device according to any one of claims 1 to 3,
The light emitting means is formed in a layered structure including an anode layer and a cathode layer disposed to face each other, and an organic layer interposed between the anode layer and the cathode layer. Divided by separating the layer and the organic layer together in the plane direction at intervals,
A backlight device characterized by. In the backlight device according to any one of claims 1 to 5,
The light emission driving means is provided independently for each of the plurality of divided light emitting regions;
A backlight device characterized by.

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