JP2009157140A - Method of manufacturing liquid crystal display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of warpage of a liquid crystal display panel caused by tensile stress of a polarizing plate. <P>SOLUTION: When a pair of substrates (an array substrate 2 and a counter substrate 3) are laminated to each other, a liquid crystal material is encapsulated between the substrates 2 and 3 and then a polarizing plate 4 is laminated to at least a display surface side surface of the pair of stuck substrates 2 and 3, the pair of stuck substrates 2 and 3 (a liquid crystal display panel 1A to which the polarizing plate is not yet stuck) are bent and then the polarizing plate 4 is laminated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a liquid crystal display panel, and in particular, to an improvement in a bonding process of polarizing plates.

  In recent years, liquid crystal display devices with features such as lightweight, thin, and low power consumption are widely used as display devices for information devices such as personal computers and word processors, and display devices for video devices such as televisions, video cameras, digital cameras, and car navigation systems. It is used. The liquid crystal display device includes a liquid crystal display panel in which a liquid crystal material is sealed between two substrates (for example, an array substrate and a counter substrate). In the liquid crystal display panel, the orientation of the liquid crystal material is controlled by turning on and off the voltage. Then, image display is performed by turning on and off the transmitted light.

  In the liquid crystal display panel, it is necessary to convert the transmitted light into linearly polarized light. For this reason, polarizing plates are bonded in a crossed nicols state on both surfaces of the panel (the outer surface of the array substrate and the outer surface of the counter substrate).

  Here, after sandwiching a liquid crystal layer made of a liquid crystal material between two substrates, the polarizing plate is attached to a surface (outer surface) opposite to each liquid crystal layer of the bonded substrates. When the polarizing plate is attached, it is generally fixed by suction on a flat stage so that the attached substrate does not warp.

  However, in the liquid crystal display panel after the polarizing plate is attached as described above, a difference in shrinkage with time is generated due to the difference in hygroscopicity between the two polarizing plates. There is a phenomenon that warpage occurs due to different tensile stresses on both sides. For example, when the tensile stress due to the contraction of the polarizing plate on the display surface side is larger than the tensile stress due to the contraction of the polarizing plate on the back surface side, the warp with the display surface side concave and the back surface convex (so-called forward warpage) In the opposite case, there is a risk of warping (so-called warping in the reverse direction) in which the back surface side is concave and the display surface side is convex.

  In a liquid crystal display panel, a glass substrate is used as a substrate, and the thickness tends to be reduced. However, the above-described influence becomes more significant as the thickness of the glass substrate is reduced. In addition, in order to meet the demand for thinner and lighter liquid crystal display devices, the glass substrate constituting the liquid crystal display panel is made thinner and the frame portion holding the liquid crystal display panel is also made thinner and lighter. Further, there is a problem that the warp of the liquid crystal display panel appears as it is as a warp of the liquid crystal display device. If the liquid crystal display device is warped significantly, mechanical interference may occur in the equipment on the mounting side, which may cause mounting defects or damage due to interference with other parts after mounting. .

  Regarding the deformation of the liquid crystal display panel caused by the polarizing plate, for example, Patent Document 1 discloses a measure for improving this. The invention described in Patent Document 1 relates to suppression of a cell gap defect due to temperature expansion, and includes a first substrate, a second substrate disposed opposite to the first substrate with a predetermined gap, and both the substrates. In a liquid crystal display device comprising a liquid crystal member sealed in a gap portion of the substrate and a polarizing plate bonded to a surface opposite to the liquid crystal member side of both substrates, the polarizing plate is at least a dyeing film, and the dyeing film. Is composed of a plurality of first and second polymer films arranged so as to sandwich the film, and the temperature expansion coefficient of each polymer film is set to be different.

In the liquid crystal display device, when the temperature rises, the liquid crystal display panel is distorted and warped due to the volume expansion of the liquid crystal member, which may cause a gap defect, resulting in uneven color and non-uniform response speed. In the invention described in Patent Document 1, the first and second polymer films have different coefficient of thermal expansion, thereby generating a warping stress on the polarizing plate as the temperature rises, and using this warping stress, transparent insulation is generated. A temperature expansion stress such as a liquid crystal member applied to the central portion of the substrate is dispersed to eliminate the inconvenience.
JP 2003-222849 A

  However, in the invention described in Patent Document 1, the occurrence of warpage due to the tensile stress due to the contraction of the polarizing plate cannot be eliminated, and it is necessary to bond a plurality of polymer films having different temperature expansion coefficients to the polarizing plate. There is a need to optimize the film design. Therefore, the apparatus configuration is complicated, which may increase the manufacturing cost.

  In order to eliminate the warpage of the liquid crystal display panel, for example, it is conceivable to heat-treat the polarizing plate before pasting, but even when such a method is adopted, it leads to an increase in the manufacturing process of the polarizing plate. This is also a factor that increases manufacturing costs.

  The present invention has been proposed in view of such a conventional situation, and it is possible to prevent the occurrence of warpage due to the tensile stress of the polarizing plate, and to prevent an increase in manufacturing cost. An object is to provide a method for manufacturing a display panel.

  In order to achieve the above-described object, a method for manufacturing a liquid crystal display panel according to the present invention includes a method of bonding a pair of substrates, encapsulating a liquid crystal material between the substrates, and then at least the display surface side of the bonded pair of substrates. When the polarizing plate is bonded to the surface, the polarizing plate is bonded after the pair of bonded substrates are curved in advance.

  In the present invention, the bending of the liquid crystal display panel after the contraction of the polarizing plate is suppressed by applying a bending stress to the pair of substrates in a direction opposite to the tensile stress due to the contraction of the polarizing plate in advance when the polarizing plate is attached. If the polarizing plate is attached while the substrate is curved, it becomes possible to attach the polarizing plate in a state in which a stress in a direction that cancels the tensile stress generated after the change in the hygroscopic shrinkage of the polarizing plate with time is applied in advance. Accordingly, the warpage of the liquid crystal display panel after contraction of the polarizing plate is alleviated, and the warpage generated in the liquid crystal display device combined with the frame is also suppressed.

  According to the manufacturing method of the present invention, in the liquid crystal display panel, it is possible to prevent the occurrence of warpage due to the tensile stress of the polarizing plate. For example, even when assembled to a frame, defective mounting occurs or after mounting. There is no damage caused by interference with other parts. Further, it is not necessary to change the film configuration or design of the polarizing plate itself, and it is not necessary to perform heat treatment in advance, so that the manufacturing cost does not increase.

  Hereinafter, a method of manufacturing a liquid crystal display panel to which the present invention is applied will be described with reference to the drawings.

  First, a liquid crystal display panel to which the manufacturing method of the present invention is applied and a liquid crystal display device assembled with the same will be described.

  As shown in FIG. 1, the liquid crystal display panel 1 is configured by enclosing a liquid crystal material (not shown) between an array substrate 2 and a counter substrate 3, for example. A glass substrate or the like is used as the array substrate 2 or the counter substrate 3. For example, the array substrate 2 has pixel electrodes and switching elements (thin film transistors) formed in a matrix corresponding to display pixels. In the array substrate 3, signal lines for sending electric signals to the pixel electrodes and gate lines for supplying switching signals to the thin film transistors serving as switching elements are wired perpendicular to each other.

  On the other hand, on the counter substrate 3, the counter electrode is formed on almost the entire surface with a transparent electrode material (for example, ITO), and a color filter layer is formed corresponding to each pixel. Further, polarizing plates 4 and 5 are bonded to the outer surfaces of the array substrate 2 and the counter substrate 3 in a crossed nicols state so that the polarization axes are orthogonal to each other.

  The diagonal dimension of the array substrate 2 and the counter substrate 3 is, for example, 12.1 inches, and the thickness of the glass substrate constituting the array substrate 2 and the counter substrate 3 is, for example, 0.2 mm.

  The liquid crystal display panel 1 configured as described above is held by the frame 6 together with the backlight unit, and is incorporated in the liquid crystal display device. FIG. 2 shows a holding structure by the frame 6 of the liquid crystal display panel 1. The liquid crystal display panel 1 is held by a frame 6 having an outer peripheral portion formed of a metal material, a resin material, or the like. The backlight unit for irradiating the plane light is disposed on the back side of the liquid crystal display panel 1 and is accommodated in the frame 6 in the case of the present embodiment, but the illustration is omitted.

  The frame 6 has an outer frame portion substantially perpendicular to the main surface of the liquid crystal display panel 1, and the outer periphery of the liquid crystal display panel 1 is held by the outer frame portion. The frame 6 only needs to have a function of holding the outer periphery, and its constituent material is arbitrary. For example, resin materials such as ABS resin, polyethylene resin, polypropylene resin, polystyrene resin, and various plastics may be used, stainless steel, galvanized steel, aluminum (including alloys and surface treatment materials), iron, steel, and the like. It may be a metal material. Alternatively, other materials may be used.

  A fixing adhesive tape 7 is affixed to the outer periphery of the frame 6, and this fixing adhesive tape 7 partially extends to the outer peripheral edge of the liquid crystal display panel 1. Are bonded and fixed.

  In the liquid crystal display device configured as described above, the display surface side of the liquid crystal display panel 1 is directly exposed to the outside air, but the back surface side is covered with the frame 6 and the backlight unit. Therefore, the display surface side of the liquid crystal display panel 1 is more susceptible to the humidity of the outside air than the back surface side, and therefore the contraction rate due to the change over time of the humidity of the polarizing plate 4 that is directly exposed to the outside air is also smaller than the back surface side. large. For this reason, for example, when left at room temperature and humidity for several days, warping of about 2 mm occurs in the forward direction.

  Therefore, in the present embodiment, the surface shape of the panel fixing stage (suction stage) in the polarizing plate pasting apparatus is a convex shape or a concave shape, and the stress in a direction that cancels the tensile stress generated after the change with time is applied to the polarizing plate. By applying the polarizing plate while applying it, the warpage generated in the liquid crystal display panel 1 after contraction of the polarizing plate is alleviated.

  Hereinafter, the polarizing plate attaching step will be described. First, a conventional polarizing plate attaching step will be described for comparison. In the conventional polarizing plate attaching step, as shown in FIG. 3A, liquid crystal before attaching a polarizing plate on a flat adsorption stage 11 is obtained. The display panel 1A (the one in which the array substrate 2 and the counter substrate 3 are bonded together) is sucked and fixed.

  Next, as shown in FIG. 3B, the polarizing plate 4 is set on the polarizing plate mounting jig 12, and the polarizing plate 4 is placed on the display surface (here, the outer surface of the counter substrate 3) of the liquid crystal display panel 1A. to paste together. After the attachment of the polarizing plate 4 to the display surface side, the liquid crystal display panel 1A is reversed upside down as shown in FIG. 3 (c) and fixed on the suction stage 11 as shown in FIG. 3 (d). The polarizing plate 5 is set on the polarizing plate mounting jig 12, and the polarizing plate 5 is bonded to the back surface (here, the outer surface of the array substrate 2) of the liquid crystal display panel 1A.

  When the polarizing plates 4 and 5 are attached using the flat suction stage 11 as described above, stress is not applied to the polarizing plates 4 and 5 in advance, and tensile stress generated due to change over time This causes warping of the liquid crystal display panel 1 after the polarizing plates 4 and 5 are attached.

  On the other hand, in this embodiment, as shown in FIGS. 4A to 4D, the polarizing plate 4 is used in a state where the liquid crystal display panel 1A is curved using a suction stage having a curved suction surface. , 5 are pasted.

  Specifically, first, as shown in FIG. 4A, an adsorption stage 21 whose upper surface is curved in a convex shape is prepared, on which a liquid crystal display panel 1A (which is opposite to the array substrate 2) before the polarizing plate is attached. Adhering and fixing the substrate 3). The liquid crystal display panel 1 </ b> A that has been transported is brought into close contact with the suction stage 21 by being pressed from the display surface side with the display surface as the upper surface, and is fixed by suction. Therefore, the liquid crystal display panel 1A is suction fixed on the suction stage 21 in a curved state so that the display surface side is convex and the back surface side is concave.

  In this state, as shown in FIG. 4B, the polarizing plate 4 is set on the polarizing plate mounting jig 22, and the polarizing plate is placed on the display surface (here, the outer surface of the counter substrate 3) side of the liquid crystal display panel 1A. 4 is pasted together. At this time, the polarizing plate mounting jig 22 is also curved following the shape of the suction stage 21, and a predetermined stress is applied to the polarizing plate 4.

  Next, as shown in FIG. 4 (c), a suction stage 23 whose upper surface is curved in a concave shape is prepared opposite to the suction stage 21, and the liquid crystal display panel 1A having the polarizing plate 4 attached thereon is turned upside down. And fix it by suction. The liquid crystal display panel 1 </ b> A has the back side as an upper surface and is pressed and fixed from the back side by being stuck to the suction stage 23. Therefore, the liquid crystal display panel 1A is suction fixed on the suction stage 23 in a curved state so that the back side is concave and the display side is convex.

  In this state, as shown in FIG. 4D, the polarizing plate 5 is set on the polarizing plate mounting jig 24, and the polarizing plate 5 is placed on the back surface (here, the outer surface of the array substrate 2) of the liquid crystal display panel 1A. Paste together. At this time, the polarizing plate mounting jig 24 is also curved following the shape of the suction stage 23, and a predetermined stress is applied to the polarizing plate 5.

  In addition, the sticking of the polarizing plate on the curved adsorption stage is applied only to the polarizing plate on the side having a large tensile stress (the polarizing plate 4 on the display surface side), and the polarizing plate on the side having a small tensile stress. About a board (polarizing plate 5 on the back side), you may carry out using a flat suction stage as usual.

  As described above, when the polarizing plates 4 and 5 are bonded together, the curved adsorption stages 21 and 23 are used, and the liquid crystal display panel 1A before the polarizing plates 4 and 5 are bonded together is at least a polarizing plate 4 having a large shrinkage rate. A predetermined stress can be applied to the polarizing plates 4 and 5 in advance by performing the bonding process of the polarizing plates 4 and 5 while being curved in advance so as to be in a direction opposite to the shrinking direction of the film. The warp of the subsequent liquid crystal display panel 1 can be suppressed.

It is a schematic sectional drawing which shows the structural example of a liquid crystal display panel. It is a schematic sectional drawing which shows the structural example of the liquid crystal display device which assembled | attached the liquid crystal display panel shown in FIG. It is typical drawing which shows an example of the conventional polarizing plate sticking process, (a) is an adsorption fixing process, (b) is the sticking process of the polarizing plate to a display surface, (c) is a front-back inversion process, ( d) shows a step of attaching the polarizing plate to the back surface. It is typical drawing which shows the polarizing plate affixing process in embodiment to which this invention is applied, (a) is an adsorption fixing process, (b) is the affixing process of the polarizing plate to a display surface, (c) is front and back. Inversion step, (d) shows a step of attaching the polarizing plate to the back surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel, 2 Array substrate, 3 Opposite substrate, 4,5 Polarizing plate, 6 frame, 7 Fixing adhesive tape, 21,23 Adsorption stage, 22, 24 Polarizing plate attachment jig

Claims (3)

After laminating a pair of substrates and encapsulating a liquid crystal material between these substrates, when laminating a polarizing plate on at least the display surface side of the pair of substrates laminated,
A method of manufacturing a liquid crystal display panel, wherein the polarizing plate is pasted after the pair of pasted substrates are curved in advance.   The method for manufacturing a liquid crystal display panel according to claim 1, wherein the polarizing plate is attached to the convex surfaces of a pair of curved substrates.   3. The liquid crystal display panel according to claim 2, wherein when the polarizing plate is bonded to the surface opposite to the display surface side, the polarizing plate is bonded to the concave surfaces of the curved pair of substrates. Manufacturing method.

Images