Apparatus for inspecting an illumination device

The present invention provides an apparatus for inspecting an illumination device where the illumination device allows light from one or more light sources to be emitted to the outside through a number of optical sheets layered on top of each other. The apparatus is provided with: a work stage on which an illumination device is placed; a work frame for fixing the position of the illumination device placed on the work stage; and a pressure reducing apparatus for making the pressure in the space inside the illumination device lower than the pressure in the space outside the apparatus for inspecting an illumination device when turned on during the inspection, wherein the work frame has an opening through which light from the illumination device is emitted and makes contact with the outer periphery of the illumination device and the work stage, respectively, through annular form during the inspection.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority over Japanese application JP 2010-278267 filed on Dec. 14, 2010, the contents of which are hereby incorporated into this application by reference.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to an apparatus for inspecting an illumination device, and in particular, to a technology that is effective when applied to an apparatus for inspecting a backlight used in a liquid crystal display device when turned on.

(2) Description of the Related Art

Some liquid crystal display devices have an illumination device, which is referred to as a backlight, provided behind the liquid crystal display panel (at the rear).

The backlights convert light emitted from a light source, such as LEDs or a fluorescent lamp, into rays emitted from an area so that the liquid crystal display panel can be illuminated, and various structures of backlights are known. In addition, backlights are usually formed of a number of optical sheets that are layered on top of each other in order to increase the degree of symmetry of the rays from an area (uniformity of the brightness in an area) or the efficiency of the use of light for illuminating the liquid crystal display panel, for example. These optical sheets include a prism sheet, a light diffusing sheet and the like, and a combination of these is determined by the type of or the way of arranging the light source, the properties required for the liquid crystal display device and the like.

The backlights used for a liquid crystal display device are usually inspected when turned on before they are combined with a liquid crystal display panel. Through this inspection when turned on, the degree of symmetry of the rays from an area (uniformity in the brightness of an area) and whether or not any foreign substance is between the optical sheets are checked. Such an inspection when turned on may be carried out on a backlight to which a light source has already been attached by turning on the light source or may be carried out on a backlight to which a light source has not yet been attached by temporarily attaching a light source for inspection.

SUMMARY OF THE INVENTION

Conventional inspection of a backlight when turned on is carried out by placing a backlight on top of a worktable for inspection, which is referred to as a work stage, and turning on the light source. In accordance with most conventional inspection methods (in most conventional inspection apparatuses), a backlight is simply fixed in a predetermined location on top of a workstation.

As described above, however, backlights have such a structure where a number of optical sheets are layered on top of each other and each optical sheet is very thin, and the thickness thereof ranges from several tens of μm to several hundreds of μm. Therefore, the optical sheets in the backlight easily bend. In addition, the bending of an optical sheet is peculiar to the optical sheet and independent, and thus does not relate to the bending of other optical sheets.

Accordingly, in the case where a backlight of which the optical sheets bend is inspected when turned on in a conventional inspection apparatus, the optical sheets that are layered on top of each other do not make close contact, which makes the outline of a foreign substance between optical sheets obscure, and thus such a problem arises that it is difficult to detect the foreign substance.

An object of the present invention is to provide an apparatus for inspecting a backlight when turned on where a foreign substance between optical sheets can be easily detected when the backlight used for a liquid crystal display device is inspected when turned on, for example.

The above-described and other objects and novel features of the present invention will be clarified by the descriptions of the present specification and the accompanying drawings.

Typical inventions disclosed in the present application can be outlined as follows.

(1) An apparatus for inspecting an illumination device, the illumination device allowing light to be emitted from one or more light sources to the outside through a number of optical sheets that are layered on top of each other, having; a work stage on which an illumination device is placed; a work frame for fixing the position of the illumination device placed on the work stage; and a pressure reducing apparatus for making the pressure in the space inside the illumination device lower than the pressure in the space outside the apparatus for inspecting an illumination device when turned on during the inspection, wherein the above-described work frame has an opening through which light from the illumination device is emitted and makes contact with the outer periphery of the illumination device and the above-described work stage, respectively, through annular form during the above-described inspection.

(2) The apparatus for inspecting an illumination device according to the above (1), wherein the illumination device does not have a light source at the time of the above-described inspection, and one or more light sources are attached to the above-described work stage.

(3) The apparatus for inspecting an illumination device according to the above (1), wherein the illumination device does not have a light source at the time of the above-described inspection, and one or more light sources are attached to the above-described work frame.

According to the present invention, a foreign substance between optical sheets can be easily detected through the inspection of the illumination device when turned on even in the case where the optical sheets that are layered on top of each other bend.

DESCRIPTION OF THE EMBODIMENTS

In the following, the embodiments of the present invention are described in detail in reference to the drawings. Here, the same symbols are attached to the components having the same functions throughout the figures showing the embodiments, and the descriptions thereof are not repeated.

FIGS. 1A to 1Care schematic diagrams showing an example of the structure of the apparatus for inspecting an illumination device when turned on according to the first embodiment of the present invention.

FIG. 1Ais a schematic front diagram showing an example of the structure of a main portion in the apparatus for inspecting an illumination device when turned on according to the first embodiment.FIG. 1Bis a schematic cross-sectional diagram along line A-A′ inFIG. 1Ashowing an example of the structure.FIG. 1Cis a schematic cross-sectional diagram along line B-B′ inFIG. 1Ashowing an example of the structure;

An example of the structure and the working effects of an apparatus for inspecting a light guide plate type backlight (also referred to as edge light type backlight) when turned on are described according to the first embodiment. In addition, in the backlight according to the first embodiment, the light source, such as LEDs, is not yet attached during the inspection.

As shown inFIGS. 1A and 1B, the apparatus for inspecting a backlight when turned on according to the first embodiment has: a work stage2on which the backlight1to be inspected is placed; a work frame3for fixing the position of the backlight1placed on the work stage2; a pressure reducing apparatus4for making the pressure in the space within the backlight1lower than the pressure in the space outside the apparatus for inspecting a backlight when turned on during the inspection; and a light source5to be turned on for inspection and the power6for turning on the light.

The light guide plate type backlight1has a light guide plate101, a number of optical sheets (102ato102d) layered on top of each other, and a reflecting sheet103, which are integrally held by a frame member104. It is possible to change the types and the number of optical sheets, and any combination of appropriate optical sheets in a conventional backlight1may be used.FIGS. 1B and 1Cshow a case where four optical sheets are layered on top of each other as an example of a combination of a number of optical sheets, where a first light diffusing sheet102a, a first prism sheet102b, a second prism sheet102cand a second light diffusing sheet102dare layered in this order close to the light guide plate101.

In addition, a reflecting sheet103is provided on the side of the light guide plate101opposite to the side on which the optical sheets (102ato102d) are provided. Here,FIGS. 1B and 1Cshow a case where an opening is provided in a region of the bottom of the frame member104in which the light guide plate101is provided, and the reflecting sheet103is pasted to the frame member104using an adhesive material105so as to cover the opening.

Examples and the working effects of the light guide plate104, the optical sheets (102ato102d), the reflecting sheet103and the frame member104in the backlight1are known, and therefore the descriptions of these are omitted in the present specification.

The backlight1is placed on the work stage2, and a through hole201that penetrates from the side on which the backlight1is placed to the opposite side is provided in the region in which the backlight1is placed. An air suction pipe401of the pressure reducing apparatus4is connected to this through hole201. Here, the backlight1is placed on the work stage2so that the surface on which the reflecting sheet103is provided (in other words, the surface on the side opposite to the direction in which the light from the light source is emitted) faces the work stage2. In addition, the backlight1is placed in such a manner that the first cushion material7provided to the work stage2, for example, prevents the reflecting sheet103and the work stage2from making direct contact. Here, simple protrusions may be provided on the surface of the work stage2instead of the first cushion material7, for example.

The work frame3has an opening for a region through which light from the backlight1is emitted and has such a form as to make contact with the outer periphery of the backlight1and the work stage2, respectively, through an annular portion during the time of inspection when the backlight is turned on. Here, the contact between the work frame3and the backlight1as well as the contact between the work frame3and the work stage2are respectively intervened by a second cushion material8, for example. As a result, the space inside the backlight1during the time of inspection when the backlight is turned on is in such a state that it is almost shielded from the space outside the apparatus for inspecting a backlight when turned on. In addition, the work frame3and the work stage2are connected through a shaft202, as shown inFIGS. 1A and 1B, and thus the work frame3has such a structure as being movable with the shaft202as a rotational axis.

The pressure reducing apparatus4may be an apparatus that can inhale the air from the space in which the backlight1is placed through the air suction pipe401and the through hole201in the work stage2, and may be a vacuum pump, for example.

It is preferable for the light source5to have the same properties as the light source that is used when the liquid crystal display device into which the backlight1is incorporated is used.FIGS. 1A and 1Bshow a case where LEDs (light emitting diodes) are used as the light source5. At this time, the light source5is connected to the power6for turning on the light through a printed circuit board and wires (cables). In addition, the printed circuit board is installed on (fixed to) the work stage2, and the light source5is provided in such a location as to correspond to the surface of the light guide plate101through which light is introduced through the opening provided at the bottom of the frame member104in the backlight1.

The procedure for carrying out the inspection on the backlight1when turned on using the apparatus for inspecting a backlight when turned on according to the first embodiment is as follows.

First, the work frame3is rotated and the backlight1is mounted on the work stage2. Next, the work frame3is returned so that the work frame3and the work stage2fix the position of the backlight1.

Next, the pressure reducing apparatus4is operated. At this time, there is a gap between the bottom of the frame member104in the backlight1and the reflecting sheet103as shown inFIG. 1C, for example. Therefore, when the pressure reducing apparatus4is operated to start sucking air, the air in the space inside the backlight1is sucked through the gap between the frame member104and the reflecting sheet103. In addition, the contact between the outer periphery of the backlight1and the work frame3as well as the contact between the work stage2and the work frame3are respectively intervened with the second cushion material8, and therefore almost no air flows into the space inside the backlight1from the outside of the apparatus for inspecting a backlight when turned on through these contacts. Accordingly, when the pressure reducing apparatus4is operated, the pressure in the space inside the backlight1is lower than the pressure in the space outside the apparatus for inspecting a backlight when turned on (usually the air pressure).

Next, the power supplied from the power source6for turning on the light makes the light source5emit light, and the state of the light that has been emitted through the light guide plate101and the optical sheets (102ato102d) is inspected (observed).

When the inspection is completed, the light source5is turned on and the pressure reducing apparatus4is stopped, and after that, the backlight1is taken out.

FIGS. 2A and 2Bare schematic diagrams for illustrating the working effects of the apparatus for inspecting an illumination device when turned on according to the first embodiment.

FIG. 2Ais a schematic cross-sectional diagram showing an example of the structure of optical sheets before the pressure reducing apparatus4is operated.FIG. 2Bis a schematic cross-sectional diagram showing an example of the structure of optical sheets when the pressure reducing apparatus4is operated.

As described above, the optical sheets (102ato102d) used in the backlight1are very thin and have a thickness ranging from several tens of μm to several hundreds of μm, and thus are easily bent. In addition, the bending of an optical sheet is peculiar to the optical sheet and independent, and thus does not relate to the bending of other optical sheets. That is to say, in many cases, the optical sheets (102ato102d) in the backlight1before the inspection when the backlight is turned on are bent irregularly, as shown inFIG. 2Afor example. In addition, before the inspection when the backlight is turned on and during the inspection when the backlight is turned on using a conventional apparatus for inspecting a backlight when turned on, the pressure9A applied from the first light diffusing sheet102aside and the pressure9B applied from the second light diffusing sheet102dside are approximately the same. Accordingly, the inspection when the backlight is turned on using a conventional apparatus for inspecting a backlight when turned on is carried out in such a state where the optical sheets (102ato102d) are bent irregularly, as shown inFIG. 2A.

In the case where the backlight1, where the optical sheets (102ato102d) are irregularly bent, is inspected when turned on using a conventional apparatus for inspecting a backlight when turned on, the optical sheets that are layered on top of each other do not make close contact, which makes the outline of a foreign substance between optical sheets obscure. Therefore, the inspection using a conventional apparatus for inspecting a backlight when turned on has such a problem that it is difficult to detect such a foreign substance.

In contrast, the apparatus for inspecting a backlight when turned on according to the first embodiment uses a pressure reducing apparatus4that makes the pressure in the space inside the backlight1lower than the pressure in the space outside the apparatus for inspecting a backlight when turned on. That is to say, when the inspection is carried out when the backlight is turned on using the apparatus for inspecting a backlight when turned on according to the first embodiment, as shown inFIG. 2Bfor example, the pressure9A applied from the first light diffusing sheet102aside is lower than the pressure9B applied from the second light diffusing sheet102dside. At this time, due to the difference in the pressure applied to the respective optical sheets (102ato102d), it is possible for a change to occur such that the optical sheets are bent towards the first light diffusing sheet102aside. Therefore, even in the case where the respective optical sheets are irregularly bent and do not make close contact with each other before the inspection when the backlight is turned on, the optical sheets can make close contact by orienting the direction of the bending during the time of inspection when the backlight is turned on. Accordingly, the outline of a foreign substance between optical sheets can be made less obscure, and thus it becomes easier to detect the foreign substance.

As described above, the apparatus for inspecting a backlight when turned on according to the first embodiment can correct the irregular bending of each optical sheet due to the difference in the pressure, and thus can easily detect a foreign substance between optical sheets. Therefore, the time it takes to inspect one backlight can be shortened, and at the same time, the load during the time of inspection can be reduced. In addition, the yield can be prevented from lowering due to the oversight of a foreign substance.

FIGS. 3A and 3Bare schematic diagrams showing an example of the structure of the apparatus for inspecting an illumination device when turned on according to the second embodiment of the present invention.

FIG. 3Ais a schematic front diagram showing an example of the structure of a main portion in the apparatus for inspecting an illumination device when turned on according to the second embodiment.FIG. 3Bis a schematic cross-sectional diagram along line C-C′ inFIG. 3Ashowing an example of the structure.

In the second embodiment as well, the backlight to be inspected is a light guide plate type backlight1having four optical sheets (first light diffusing sheet102a, first prism sheet102b, second prism sheet102cand second light diffusing sheet102d) as in the first embodiment. In addition, when this backlight1is inspected when turned on, no light source, such as LEDs, has yet been attached.

As shown inFIGS. 3A and 3B, for example, the apparatus for inspecting a backlight when turned on according to the second embodiment has a work stage2on which the backlight1to be inspected is mounted, a work frame3to which the position of the backlight1mounted on the work stage2is secured, a pressure reducing apparatus4that makes the pressure in the space inside the backlight1lower than the pressure in the space outside the apparatus for inspecting a backlight when turned on, the light source5for the inspection when it is turned on, and the power6for turning on the light.

The apparatus for inspecting a backlight when turned on according to the second embodiment is different from the one in the first embodiment in that the light source5for inspection is installed on the work frame3. In addition, the work frame3in the apparatus for inspecting a backlight when turned on in the second embodiment has such a structure that it uses a shaft203that extends vertically from the surface of the work stage2on which the backlight is mounted and moves upwards and downwards along the shaft203. The mechanism for supporting the work frame3so that it is movable and the mechanism for fixing the work frame3can be modified if necessary, and therefore the descriptions of examples of concrete mechanisms are omitted.

The apparatus for inspecting a backlight when turned on according to the second embodiment is different from the one in the first embodiment in the mechanism for allowing the work frame3to be movable, but the two have the same structure in that the work frame3makes contact with the outer periphery of the backlight1and the work stage2, respectively, through an annular form during the time of inspection when the backlight is turned on. In the second embodiment as well, the contact between the work frame3and the backlight1as well as the contact between the work frame3and the work stage2are respectively intervened with a second cushion material8, for example, so as to provide such a state that the space inside the backlight1during the time of inspection when the backlight is turned on is almost shielded from the space outside the apparatus for inspecting a backlight when turned on. As a result, when the pressure reducing apparatus4is operated during the time of the inspection when the backlight is turned on, the pressure in the space inside the backlight1is lower than the pressure in the space outside the apparatus for inspecting a backlight when turned on (usually the air pressure). Accordingly, even in the case where the optical sheets (102ato102d) are irregularly bent and do not make close contact with each other before the inspection when the backlight is turned on, the outline of a foreign substance between optical sheets can be made less obscure, and thus the foreign substance can be easily detected.

As described above, the apparatus for inspecting a backlight when turned on according to the second embodiment can correct the irregular bending of each optical sheet due to the difference in the pressure, and thus can easily detect a foreign substance between optical sheets. Therefore, the time it takes to inspect one backlight can be shortened, and at the same time, the load during the time of inspection can be reduced. In addition, the yield can be prevented from lowering due to the oversight of a foreign substance.

Though the present invention is described on the basis of the above-described embodiments, the present invention is not limited to these embodiments and can of course be modified in various ways as long as the gist of the invention is not deviated from.

For example, the structure of the backlight to be inspected is not limited to those shown inFIGS. 1B and 1Cas long as a number of optical sheets are provided and layered on top of each other, and thus the backlight may naturally have another structure.

In addition, the mechanism for allowing the work frame3to be movable is not limited to the rotary system as described in the first embodiment or to the upward and downward sliding system as described in the second embodiment, and thus can of course be modified if necessary.

Though in the present specification the light source has not yet been attached to the backlight to be inspected during the time of inspection when the backlight is turned on, the present invention is not limited to this and can of course be applicable to an apparatus for inspecting a backlight when turned on, on which the light source has been installed.

The present specification lists a backlight used in a liquid crystal display device as an example to which the present invention is applied. However, the present invention is not limited to this and can of course be applicable to an inspection apparatus, such as of an illumination device, having the same structure as the backlight.