JP2012169159A - Method for measuring drive lifetime of organic el device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stably measuring the drive lifetimes of a plurality of organic EL devices.SOLUTION: In a method for measuring the drive lifetime of an organic EL (electroluminescent) device, the drive lifetime of an organic EL device is measured in a state where wind with a constant temperature is blown toward one or a plurality of organic EL devices while a direction of the wind is changed.

Description

  The present invention relates to a method for stably measuring the driving lifetime of a plurality of organic electroluminescent devices.

  The driving life of an organic electroluminescence device (hereinafter also referred to as an organic EL device) is one of the important performances of an organic EL device, but it cannot be measured stably due to the influence of ambient temperature, especially the heat generation of the device. There was a problem. That is, there is a problem that even if the light emission characteristics of a plurality of organic EL elements are measured for a long time at an arbitrary time interval in a constant temperature and humidity environment, the device surface temperature is different, so that a stable driving life cannot be measured. It was.

  As an example of an electronic device, an LED driving life test method is described (Non-Patent Document 1). According to this, as a driving life test of an LED, a technique is described in which cooling air is injected into an integrating sphere that lights the LED to keep the ambient temperature constant.

  However, in the case of an organic electroluminescence device that is a surface light emitting element, even if the ambient temperature is kept constant similarly to this, the device surface temperature varies depending on the position, and the driving life of a plurality of organic EL devices is reduced. It turned out to be difficult to evaluate stably.

The National Institute of Standards and Technology (NIST) Annual Council of Optical Radiation Measurements (CORM) meeting May 9-11, 2010

  An object of the present invention is to provide a method for stably measuring the driving lifetime of a plurality of organic EL devices.

  The above object of the present invention is achieved by the following means.

  1. An organic electroluminescence device driving lifetime measuring method, wherein the driving lifetime of an organic electroluminescence device is measured while applying a constant temperature wind to one or a plurality of organic electroluminescence devices while changing the wind direction.

2. The constant temperature wind,
(1) Move or swing the blower,
(2) moving or rotating the organic electroluminescence device;
Or
(3) Individually adjust the air volume of multiple fans.
2. The driving lifetime measurement method for an organic electroluminescent device according to 1 above, wherein the wind direction is changed by at least one method selected from the group consisting of:

  3. 3. The organic electroluminescent device according to 2 above, wherein the plurality of blowers are individually turned on and off from at least two directions to alternately change the direction of the wind and apply wind to the organic electroluminescent device. Driving life measurement method.

  4). 4. The driving lifetime measurement method for an organic electroluminescence device according to any one of 1 to 3, wherein the constant temperature wind is a constant wind speed on a surface of the organic electroluminescence device.

  According to the present invention, it is possible to stably measure the drive life of a plurality of organic EL devices.

A tray T for driving life measurement is shown. An example of the cross-sectional schematic of a lifetime measuring apparatus is shown. A flow of air in the life measuring apparatus is schematically shown. The numbering of the device in an Example is shown.

  The present invention relates to a method for measuring the lifetime of an organic electroluminescence device.

  Lifetime measurement of organic electroluminescence devices (hereinafter also referred to as organic EL devices) is a device that tests the lifespan of elements by measuring the light emission characteristics of organic EL elements under a constant temperature environment for a long time at arbitrary time intervals. Yes, it is possible to set a driving condition / temperature condition and to inspect a plurality of devices at the same time. It is possible to measure not only a luminance change but also a spatial luminance unevenness change and a dark spot change.

  In the method of measuring the lifetime, the present invention is a lifetime measurement for obtaining a constant and stable result by eliminating the variation in the measured values of the organic EL devices to be measured by making the environment for measuring the lifetime constant. It sometimes relates to a method for maintaining a constant environment.

  When measuring the lifetime of an organic EL device, the organic EL device must be surface emitting under a constant temperature environment, that is, by simply setting the temperature condition of the measurement environment and taking in air at a constant temperature. Therefore, it became clear that the device surface temperature varies depending on the position in the apparatus and the installation location, and stable life measurement cannot be performed due to the effect.

In the present invention,
The driving life of the organic electroluminescence device is measured while applying a constant temperature wind to the organic electroluminescence device while changing the direction of the wind.

The constant temperature wind is
(1) Move or swing the blower,
(2) moving or rotating the organic electroluminescence device;
Or
(3) Individually adjust the air volume of multiple fans.
The wind direction is changed by this method.

  In the lifetime measuring apparatus, air (air) having a constant temperature and a constant air volume is passed through the organic EL device (surface) while changing the direction (direction) of the wind by the above method. By hitting, the device surface temperature is kept constant, the difference (variation) in the device drive life measurement depending on the position in the apparatus and the installation location is eliminated, and the life of the organic EL device is stably measured.

  Hereinafter, preferred embodiments of the present invention will be described.

  FIG. 1 shows a drive life measurement tray T that can carry a plurality (four in the figure) of organic EL devices P whose drive life is to be measured. The measurement tray T incorporates terminals and the like necessary for supplying power to the device (not shown in the figure).

  The organic EL device applied to the present invention is generally a glass, ceramic, metal, thick resin plate, etc., but may be a flexible transparent resin film having a thickness of 1000 μm or less, In that case, it is preferable to fix the organic EL device so that the organic EL device does not vibrate or bend due to a change in wind direction at a constant temperature.

  As a fixing method, there is a method in which an organic EL device is placed on a tray or a holder and pressed by a frame member or a clip. Also, vibration and deflection can be prevented by fixing one side of the flexible organic EL device, leaving the other side free, and blowing wind on the front and back surfaces of the organic EL device.

  FIG. 1B shows a method of installing the organic EL device P on the tray T and pressing and fixing it with the frame material F. M indicates a fixing magnet.

  In this method, since the number of attachment jigs can be reduced, the temperature influence of the jigs can be reduced, which contributes to the stabilization of the surface temperature of the organic EL device.

  FIG. 2 is a cross-sectional view of a lifetime measuring apparatus 2 that accommodates the tray T and that can be simultaneously measured for the lifetimes of a plurality of organic EL devices P installed in an air conditioning room 1 set at an environmental temperature of 25 ° C., for example. It is an example of a schematic diagram. The life measuring apparatus 2 has a plurality of shelves s that can store a plurality of the trays T. Each shelf s is provided with terminals and wirings such as a power source necessary for supplying power to the tray T (that is, supplying power to the device P) when the tray T is stored (not shown in the drawing). . For example, the shelf s is a U-shaped guide provided on three sides of the wall, whereby the tray can be inserted into the shelf s along the guide. Between the shelves (that is, between the upper and lower guides), there is sufficient clearance so as not to obstruct the entry and exit of the wind (air) before and after the top and bottom.

  Further, the four surrounding surfaces of the life measuring device preferably have no walls, and for example, the floor, the top plate, and the four corners are preferably constituted by pillars. This structure is preferable because a blower can be disposed on all four surrounding surfaces.

  In the example shown in FIG. 2, a pair of fans f are installed as blowers on both sides of the opposing side surfaces. Further, for example, a φ1 mm stainless steel punch plate p is installed on the inner side (device P side) of the fan f in order to make the air flow uniform.

  By individually turning on and off a pair of fans (fans), the direction of the wind is alternately changed from at least two directions so that the temperature of the device is kept constant regardless of the position in the lifetime measuring apparatus. .

  By rotating the fan f in the reverse direction, the fan for blowing air is also used for removing air (for guiding air). A blower (fan) is defined as an on state when it is used for blowing. Further, the punch plate p is also a wind guide plate for uniforming the wind on the fan side for blowing, and the punch plate on the fan side for blowing (wind guide) is also a wind guide plate for uniformly guiding the wind.

  Here, the material of the punch plate is not limited. For example, the punch plate is a mesh plate in which holes having a diameter of about 1 mm are formed at intervals of about 2 to 3 mm in both vertical and horizontal directions.

  In FIG. 2, a fan f and a punch plate p are installed on both sides, and one fan is turned on for blowing air and the other fan is turned off to blow air uniformly in one direction for blowing air. In addition, the direction of the wind (air flow) is alternately reversed by switching on and off the fan for blowing and the fan for removing air at predetermined time intervals. Alternately, air is directed from both directions to the surface of the device so that the temperature of the device remains constant regardless of the device surface or position within the lifetime measuring device.

  For example, if the fan on the blower side is turned on and the wind is sent, the fan on the exhaust side rotates freely even when the power is off, so that the wind direction is changed alternately by driving on and off alternately. I can do it.

  The fan f rotates freely with the power off, and the fan on the exhaust side does not necessarily need to be turned on and rotated (reversed) in the opposite direction to the case of blowing air, but the fan on the air vent side is also reversed. Driving is preferable because it creates a more stable wind flow and makes the environment uniform. Even when the power is turned on and reversely driven as an exhaust fan, it is not a blower, so it is defined as an off state.

  In this way, the wind direction is changed by changing the air volume to plus or minus by the on / off drive of the blower.

  The blower is not necessarily limited to one fan, and may have a plurality of fans.

  Under such environmental conditions, the organic EL device is subjected to test light emission and the driving life is measured. By creating an air flow on the surface of the organic EL device, the environmental conditions depending on the position in the device surface and in the lifetime measuring apparatus are made uniform, and the variation in the measured value of the driving lifetime of the device is reduced.

  FIG. 3 schematically shows the air flow in the lifetime measuring apparatus in more detail.

  In the example of the lifetime measuring apparatus in FIG. 2, a set of two fans is used, but the air flow is switched alternately as shown in FIG. The figure schematically shows the air flow (arrow) when the life measuring device is viewed from above the shelf or tray. What is necessary is just to set so that the state of A and B may alternate every fixed time. In this way, by changing the wind direction alternately from two directions (on / off drive of a fixed fan) and applying the wind, the wind at a constant temperature is applied while changing the wind direction in the life measuring device. Can be averaged to eliminate surface temperature differences due to the position of the trays or devices.

  The change direction of the wind direction is determined by the relationship with the life, but it is preferable to be within 1 hour at the longest. More preferably, the wind direction is changed within 20 minutes, and more preferably within 5 minutes.

  Moreover, it is preferable that the ventilation from a fan is a fixed wind speed (air volume). This facilitates setting of the scheme such as the direction of air blowing and the switching time for averaging the environmental conditions in the apparatus.

  The wind speed is preferably in the range of 0.1 m / s to 2.0 m / s, and it is preferable that the wind speed is further constant within this range. It should be noted that hunting within a set wind speed of ± 0.05 m / sec is allowed with a constant wind speed.

  When the wind speed and air volume are small, heat from the device surface is not sufficiently removed, and temperature distribution occurs on the windward and leeward sides. On the other hand, if the amount is too large, a part with a large air volume is likely to occur, which causes a temperature distribution.

  Moreover, it is preferable that the temperature of the wind is kept constant in the range of 20 ° C to 30 ° C, preferably 22 ° C to 27 ° C. Since the organic EL element lifetime is basically measured at 25 ° C., it can be set within this range. The constant temperature wind allows hunting within the set temperature ± 2 ° C.

  Also, in the above, an example in which a pair of two fans are arranged on both sides of the wall of the device and the direction of the wind is switched by turning on and off the fan has been shown. You may install a fan and a mesh board in all. In this case, since the fans are installed on all four sides when the life measuring device is viewed from the upper surface, the two fans are opposed to each other as a set, and the two sets are independently and alternately in the direction of the wind for a predetermined period. The temperature in the apparatus may be averaged by driving as described above so as to be reversed.

  FIG. 3 (2) shows a preferred example of a scheme in which when the blower (fan) is installed on all four surfaces around the life measuring device, the wind direction is changed alternately by driving the fan on and off. Here, three fans are driven as a blower fan and one is used as a wind blower fan, which is sequentially changed at predetermined intervals to drive the wind direction. For example, three fans for air blowing are sequentially shifted one by one at a predetermined time (→ A → B → C → D →). Here, the exhausted air from the air vent fan is three times the air flow so that the air volume from the air fan (on) is balanced with the air volume of the air vent (off) fan.

  In this case as well, the direction of the wind is determined by sequentially turning on and off the fans arranged around the device as a blower. However, only the fan for blowing air may be driven, but the fan for blowing air is also driven in reverse. Is preferred. The air volume should be three times that of the fan for blowing air.

  In the above, the wind flow and the change in the wind direction for averaging the environmental conditions in the life measuring device have been explained with some examples. Any method can be used as long as it is applied to the device by changing the above, and is within the scope of the present invention without any limitation.

  For example, the wind direction (flow of air) itself may be fixed and may be continuous every time or, but in the example shown in FIG. 2, the tray (or device) itself is rotated. For example, the shelf may be installed on a rotary stage so that the entire shelf rotates at predetermined time intervals or at a constant speed. This also changes the direction of the wind that strikes the device, so the same effect can be obtained.

  Further, the direction of the wind may be changed by moving or swinging the blower. For example, the direction of the wind may be changed by moving the blower (fan) itself at regular intervals. This also makes it possible to average the environmental conditions so as to eliminate the difference in the device surface temperature depending on the device surface and the position of the device in the lifetime measuring apparatus.

  In the present invention, a specific temperature is applied to the organic EL device so that the surface temperature of the device (s) in the apparatus is uniform while changing the direction of the wind at a constant temperature and at a constant wind speed. The scheme (means) is not limited as long as it gives the same result even if it is other than those listed above. The point is to change the number or balance (ratio) of the blower fans and the blower fans, the air volume or the air flow ratio, and the direction of the wind so that the surrounding environment including the device surface temperature does not vary. Any method can be used as long as the variation in the measured value of the drive life of the device can be reduced by adjusting the above.

  As described above, according to the present invention, as an environment for measuring the driving life, not only the adjustment of the ambient temperature by air conditioning but also the air flow is created on the surface of the organic EL device by a predetermined method so as to keep the temperature of the device surface constant. By changing the direction of the wind, the organic EL device surface temperature is made uniform so as to eliminate the uneven surface temperature of the organic EL device due to variations in the surrounding environment. A stable measurement result can be obtained for the measurement. In particular, it is suitable for measuring the lifetime of organic EL devices used for applications such as backlights (for display elements) having a large light emitting surface size (for example, 5 cm × 5 cm or more) and illumination.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

  The organic EL device No. described in JP-A-2008-269962. In the same manner as in 201, an organic EL device having a light emitting surface size of 5 cm × 5 cm was produced.

  Four of the produced organic EL devices were mounted on a drive life measurement tray (described in FIG. 1). The tray incorporates terminals and the like necessary for supplying power to the device. In this way, two trays on which the organic EL devices were mounted were prepared.

  The drive life measuring tray is mounted on a life measuring device (FIG. 2) installed in an air-conditioned room set at an environmental temperature of 25 ° C. and a humidity of 50% RH. The life measuring device has a plurality of shelves for storing trays. When viewed from the top surface, this shelf has a “U” shape, and the left and right connecting portions are provided with terminals, wiring, and the like necessary for feeding power to the tray. In addition, there is a sufficient gap between the top and bottom of the shelf, and does not hinder the entry and exit of the wind.

  The life measuring device has no walls and is built only with pillars, and a fan for blowing air (FIG. 4) was installed on the side as needed. Further, a stainless steel punch plate having a hole diameter of Φ = 1 mm and a pitch of about 2 mm in both vertical and horizontal directions is installed on the inner side (device side) of the fan to make the air uniform.

Example 1 (Comparison: No wind)
As shown in FIG. 2, a lifetime measuring tray was mounted in the center two stages of the shelf in a lifetime measuring apparatus at an environmental temperature of 25 ° C. and a humidity of 50% RH, and was driven at a constant current with an initial luminance of 4000 cd / m ² . In particular, no ventilation is performed. The average luminance of the light emitting surface of each of the eight devices was measured at regular time intervals, and the time when the luminance remaining rate reached 50% was defined as the lifetime of the device. For measurement of luminance, a two-dimensional color luminance meter CA2000 (manufactured by Konica Minolta) was used. In addition, the temperature of the device surface was observed using a thermocouple. In addition, the device surface temperature measured continuously the site | part which hits the center of a device surface using a thermocouple. In the following, the temperature was almost constant throughout the measurement period.

Example 2 (Comparison: 1 direction)
A life measuring tray was mounted in the center two stages of the shelf as shown in FIG. 2 in a life measuring apparatus placed at an environmental temperature of 25 ° C. and a humidity of 50% RH, and was driven at a constant current with an initial luminance of 4000 cd / m ² .

  Fans are placed on a pair of opposing sides of the life span device, and one fan sends wind to the tray and the other works in a coordinated manner to blow the wind, but the wind direction is constant and switching is not performed. . The fan was blown at a wind speed of 0.4 m / s.

  The luminance was measured using CA2000 (manufactured by Konica Minolta), the average luminance of the light emitting surface of each device was measured at regular time intervals, and the time when the luminance remaining rate reached 50% was defined as the lifetime of the device. The temperature of the device surface was measured and observed using a thermocouple.

Example 3 (Invention: Two-way case)
As shown in Fig. 2, a life measuring tray is installed in the center two stages of the shelf in a life measuring device placed at an environmental temperature of 25 ° C and humidity of 50% RH, and it is driven at a constant current with an initial luminance of 4000 cd / m ^2. did.

  Fans were placed on a pair of opposing sides of the lifespan device, one fan sent the wind to the tray and the other operated in a coordinated manner, and the wind direction was reversed every minute. The fan wind speed was about 0.4 m / s.

  The luminance was measured using CA2000 (manufactured by Konica Minolta), the average luminance of the light emitting surface of each device was measured at regular time intervals, and the time when the luminance remaining rate reached 50% was defined as the lifetime of the device. The temperature of the device surface was measured and observed using a thermocouple.

Example 4 (Invention: 4 directions)
As shown in FIG. 2, a lifetime measuring tray was mounted in the center two stages of the shelf in a lifetime apparatus placed at an environmental temperature of 25 ° C. and a humidity of 50% RH, and was driven at a constant current with an initial luminance of 4000 cd / m ² .

  As the life measuring device, all the fans are installed on the four sides of the life measuring device shown in FIG. 2, and the wind is sent from the three fans to the tray and the wind (air) is drawn from the other fan. Driven. The wind direction was switched every minute, and the wind flow was changed in order (FIG. 3 (2)).

  With regard to the wind speed (air volume) of the fans, all the fans for blowing were performed at a wind speed of about 0.4 m / s, and the fans for blowing the air were 1.2 m / s.

  The luminance was measured using CA2000 (manufactured by Konica Minolta), the average luminance of the light emitting surface of each device was measured at regular time intervals, and the time when the luminance remaining rate reached 50% was defined as the lifetime of the device. Further, the temperature of the surface of the device was measured using a thermocouple.

  The evaluated devices were numbered as shown in FIG. 4 with reference to the case where the wind was in one direction (Example 2).

  In the upper tray, on the windward side, the right device as viewed from the leeward is (1) the left device is (2), and on the leeward side the right is (3) and the left is (4). Similarly, the devices on the lower tray were set to (5) to (8).

Moreover, the value of the obtained lifetime (luminance half-life time: L ₅₀ ) was expressed as a relative value with the value of the surface temperature of 40 ° C. under each condition as 100.

  When measured without wind, the temperature distribution is as great as 8 ° C. in the tray and 21 ° C. between the upper and lower trays, and the life obtained therewith also varies up to 41%.

  When the wind is sent from one direction, the temperature difference is slightly suppressed at 4 ° C at the same place between the upper and lower trays compared to the case without wind, but on the other hand, compared to the windward device, It can be seen that the temperature of the device is increased by 3 to 4 ° C. and the life span is still as large as 10% at maximum.

  On the other hand, when the direction of the wind is changed and the air is blown alternately from two directions (the present invention), it can be seen that the temperature distribution between the upper and lower sides of the tray decreases with 2 ° C. or less. Along with this, it was found that the variation in lifetime was suppressed to about 4% at the maximum.

  Also, it can be seen that even when the wind is sent from four directions, the temperature distribution is suppressed and the variation in life is further suppressed to 3% at the maximum.

2 Life measuring device P Organic EL device f Fan p Punch plate T Tray s Shelf

Claims (4)

  An organic electroluminescence device driving lifetime measuring method, wherein the driving lifetime of an organic electroluminescence device is measured while applying a constant temperature wind to one or a plurality of organic electroluminescence devices while changing the wind direction. The constant temperature wind,
(1) Move or swing the blower,
(2) moving or rotating the organic electroluminescence device;
Or
(3) Individually adjust the air volume of multiple fans.
The driving life measurement method for an organic electroluminescence device according to claim 1, wherein the wind direction is changed by at least one method selected from the group consisting of:   3. The organic electroluminescent device according to claim 2, wherein the plurality of blowers are individually turned on and off from at least two directions to alternately change the direction of the wind so as to apply the wind to the organic electroluminescent device. Driving life measurement method.   The driving life measurement method for an organic electroluminescence device according to any one of claims 1 to 3, wherein the wind at the constant temperature is a constant wind speed on a surface of the organic electroluminescence device.

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