JP2008304523A - Liquid crystal display device equipped with microlens array for condensing light, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent increase of a thickness of a liquid crystal display device and to inexpensively obtain a pitch between lenses and a height of the lens with good reproducibility. <P>SOLUTION: The liquid crystal display device constituted by holding liquid crystal in a cell surrounded by two opposed substrates (TFT substrate and color filter substrate) is equipped with a plurality of condenser lenses for condensing light from a light source in the cell on the outer surface of one of the substrates. The condenser lens is formed by offset print. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device including a condensing microlens array and a manufacturing method thereof.

  Active-type small and medium-sized liquid crystal display devices using thin film transistor (TFT) substrates are strongly demanded to reduce the thickness of the module when combined with a backlight for high definition and high image quality as display performance. Therefore, coexistence with improvement of optical characteristics is a problem.

  In particular, in a transflective liquid crystal display device, a transmissive portion that displays using a backlight and a reflective portion that displays using external light are mixed in the same liquid crystal panel, so that all the light from the backlight can be used effectively. There is no problem. In high-definition liquid crystal display devices, the area occupied by the wiring on the TFT substrate increases, increasing the area that blocks the light from the backlight, making it impossible to effectively use all the light from the backlight, and increasing the brightness of the entire display device. There is a problem that it is necessary to increase the amount of light of the backlight for increasing the power consumption, and the consumption of the battery such as the mobile phone becomes intense.

  Therefore, in order to effectively use the backlight light shielded by the TFT substrate wiring and the reflecting plate over the entire panel surface, a technique for improving luminance by forming a condensing lens on the back surface of the TFT substrate is required.

  In this regard, in Patent Document 1, a light collecting plate including a line-shaped microlens is attached to the backlight side of the liquid crystal panel in order to collect the illumination light from the backlight toward the opening of the pixel electrode. A liquid crystal display device is disclosed.

In Patent Document 2, as a method of forming a microlens array, a photocurable resin film is applied on a polarizing plate, and then a lens shape is transferred by pressing a mold, and cured by exposure and baking. Is described.
JP 2003-337327 A JP 2007-25109 A

In the method of Patent Document 1,
(1) Since a light collecting plate having line-shaped microlenses is bonded to the liquid crystal cell glass substrate, it is difficult to align the microlens and the opening of the TFT substrate.
(2) Since the polarized light transmitted through the polarizing plate is condensed, the amount of light that can be collected by the lens is small,
(3) In order to bond the light collecting plate having line-shaped microlenses to the liquid crystal cell glass substrate, the thickness of the light collecting plate is larger than the height of the lens, and the total thickness of the liquid crystal display device combined with the backlight is increased.
There is a drawback.

  In addition, in the lens formation using the mold described in Patent Document 2, the pitch between lenses and the lens height cannot be formed with good reproducibility, and a high-definition liquid crystal panel cannot be manufactured with a high yield.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to prevent an increase in the thickness of a liquid crystal display device, and to realize a reproducible and low-cost pitch between lenses and a lens height.

  In order to solve the above problems, the present invention provides a liquid crystal display device in which liquid crystal is sandwiched between cells surrounded by two opposing substrates (TFT substrate and color filter substrate), A plurality of condensing lenses for condensing light from the light source in the cell are provided on the outer surface. The condensing lens is formed by offset printing.

  The lens edge interval of the condensing lens may be within 20 μm, and the lens height may be in the range of 2-25 μm.

  FIG. 1 is a plan view of a liquid crystal display device 100 to which an embodiment of the present invention is applied. The front side of the drawing is the display surface side. FIG. 2 is a cross-sectional view of the liquid crystal display device 100 and corresponds to the A-A ′ cross section of FIG. 1. FIG. 3 is an exploded perspective view of a part of the liquid crystal display device 100.

  The liquid crystal display device 100 of this embodiment has the same configuration as that of a conventional liquid crystal display device, except that it includes a microlens array 70 that efficiently condenses a backlight and enters the liquid crystal cell. Further, the liquid crystal display device of the present embodiment is a transflective type, and includes a transmissive display unit that transmits and displays a backlight and a reflective display unit that receives and reflects external light. However, the present invention can also be applied to a transmissive liquid crystal display device that does not include a reflective display portion.

  Further, the present invention can be applied to various types of liquid crystal display devices such as a TN (Twisted Nematic) method, a VA (Virtical Alignment) method, and an IPS (In-Place-Switching) method.

  As shown in the figure, the liquid crystal display device 100 includes an external optical film (polarizing plate, retardation plate, etc.) 10, a color filter substrate 20, a liquid crystal layer 40, a TFT substrate 50, an outer surface in order from the display surface side. An attached optical film (polarizing plate, retardation plate, etc.) 60, a microlens array 70, and a backlight module 80 are provided.

  The backlight module 80 generates collimated light in which light rays incident on the microlens array 70 are parallel.

  The liquid crystal layer 40 is sealed between the color filter substrate 20 and the TFT substrate 50 by the seal portion 30.

  The color filter substrate 20 is formed with a black matrix and colored resists (R (red), G (green), and B (blue)). Further, the common electrode 21 is formed on the main surface side (the liquid crystal layer 40 side), and an alignment film for aligning the liquid crystal layer 40 is formed on the common electrode 21. The common electrode 21 is a transparent electrode such as an ITO film.

  As shown in FIG. 1, pixel electrodes 54 that are transparent electrodes are arranged on the TFT substrate 50 in a matrix. Each pixel electrode 54 corresponds to one of R, G, and B of the color filter substrate 20 and becomes a pixel region (sub-pixel region). Between the pixel electrodes 54, a wiring layer 53 including a scanning line 51 and a signal line 52 intersecting each other is formed. Each pixel electrode 54 is connected to a TFT (thin film transistor) formed at a portion where the scanning line 51 and the signal line 52 intersect. The scanning line 51 is connected to the gate electrode of the TFT. The signal line 52 is connected to the source / drain electrodes of the TFT.

  A reflection member 55 for reflecting external light incident from the display surface side is disposed in a part of the pixel region formed of the pixel electrode 54. A portion where the reflection member 55 is disposed serves as a reflection display portion. The wiring layer 53 and the reflection member 55 block transmission of light (backlight) from the backlight module 80 side to the liquid crystal layer 40. Therefore, the area of the pixel area where the reflective display portion 55 is not disposed becomes an opening that transmits the backlight and becomes a transmissive display portion.

  Note that, in the case of the IPS system that generates lateral charges, the common electrode 21 is formed below the pixel electrode 54 provided on the TFT substrate 50 side with an insulating film interposed therebetween. In such a case, the pixel electrode 54 includes, for example, a slit-shaped opening.

  The microlens array 70 is directly formed on the external optical film (for example, a polarizing plate) 60 on the backlight module 80 side. The microlens array 70 is provided for condensing the light from the backlight module 80 toward the transmissive display unit that is the opening of the TFT substrate 50. The microlens array 70 includes a plurality of cylindrical lenses that are convex in the backlight direction.

  As shown in FIG. 3, the cylindrical lenses constituting the microlens array 70 can be arranged so that the longitudinal direction of the cylinder coincides with the longitudinal direction of the rectangular pixel region (pixel electrode 54). In addition, one cylindrical lens is arranged for the longitudinal column of the pixel region. That is, as indicated by an arrow P in the figure, the center of the convex portion of each cylinder is made to coincide with the center line of the pixel column.

Moreover, it is preferable that the lens end pitch d is within 20 μm, and the lens height h is 2 to 25 μm. Further, the width wl of each cylindrical lens is made wider than the width wd of the opening pattern in the pixel region.
Such a microlens array 70 can be formed by an offset printing technique described later.

  By arranging the microlens array 70 in this way, as shown in FIG. 2, the light enters the wiring layer 53 (scanning line 51 in the example of FIG. 1) parallel to the longitudinal direction of the pixel region (pixel electrode 54). The light that should have been can be collected in the pixel region. Then, the backlight can be effectively used.

  Note that the shape of the microlens array 70 is not limited as long as the light is efficiently condensed with respect to the transmission region. For example, as shown in FIG. 4, the microlens array 70 may be formed so that the length direction of the cylindrical lens cylinder coincides with the short direction of the pixel region (pixel electrode 54). In such a case, one cylindrical lens is arranged for the “row” in the short direction of the pixel region. That is, as indicated by an arrow P in the figure, the center of the convex portion of each cylinder is made to coincide with the center line of each row. By arranging the microlens array 70 in this way, the light that should have been incident on the wiring layer 53 (in the example of FIG. 1, the signal line 52) parallel to the short direction of the pixel region (pixel electrode 54). , It can be focused on the pixel area. Further, if the shape of the lens is appropriately selected and the center of the convex portion of each cylinder is made to coincide with the center line of the transmissive display portion, the light that should have been incident on the reflection member 54 is condensed on the transmissive display portion. It can also be made. Then, the backlight can be effectively used.

  The microlens array 70 is not limited to a cylindrical lens. Any shape may be used as long as the light is condensed on the transmissive display portion of the pixel. For example, a spherical lens may be used.

  5 to 10 are diagrams showing a process of forming the microlens array 70. FIG. In the present embodiment, the microlens array 70 is formed using an offset printing method. By using the offset printing method, a microlens array 70 having a desired pitch edge interval d (0 to 20 μm) and a lens height h (2 to 25 μm) can be realized.

  As shown in FIGS. 5 and 6, first, the lens material 203 is imprinted by the doctor blade 204 onto the intaglio 201 in which the depression 202 is formed corresponding to the pattern (lens pattern) of the microlens array 70. Here, the height of the lens to be formed can be adjusted by adjusting the depth of the recess 202.

  As the lens material 203, a UV (ultraviolet) curable polymer material or a thermosetting polymer material that is cured by heating at 100 ° C. or less can be used. As the entire polymer, an acrylic polymer, an epoxy polymer, an acrylic epoxy polymer, or the like can be used.

  Next, as shown in FIG. 7, a transfer roller 301 having a blanket 302 around it is rolled on the intaglio 201, and as shown in FIG. 8, a lens material 203 is attached to the blanket 302 to transfer the lens pattern. .

  Here, the liquid crystal cell 110 (see FIG. 2) is prepared in a state where the color filter substrate 20 and the TFT substrate 50 are bonded together by sealing the liquid crystal layer 40 and the external optical films 10 and 60 are bonded together.

  Then, as shown in FIG. 9, the liquid crystal cell 110 is fixed to the surface plate of the offset printing machine with the external optical film 60 on the TFT substrate 50 side as the upper surface. Further, as shown in FIGS. 9 and 10, the transfer roller 301 to which the lens material 203 is attached is rolled on the upper surface of the external optical film 60. Thereby, the lens material 203 can be attached to the external film 60, and the lens pattern transferred to the transfer roller 301 can be transferred to the external film 60. When the lens material 203 is separated from the transfer roller 301, the surface thereof is rounded. This roundness causes the lens action of the cylindrical lens.

  Finally, the lens material 302 transferred to the external film 60 is subjected to a UV light irradiation process, a heating process, or a combination process according to the material to cure the lens material 302. As a result, the microlens array 70 having a desired pitch interval and height is formed.

  Note that printing may be performed in a plurality of times. For example, a lens pattern is further formed by offset printing between the lens patterns formed on the external film 60 in the first printing. In this way, the lens density can be further increased.

  After the microlens array 70 is formed, the backlight module 80 is fixed to the microlens array 70 side, and the liquid crystal display device 100 with a backlight is completed.

  The liquid crystal display device to which the present invention is applied and the characteristic manufacturing process thereof have been described above.

According to this embodiment, a liquid crystal display device capable of sufficiently effectively using a backlight is provided. Moreover, since the condensing lens is directly formed on the external film, the thickness of the entire liquid crystal display device is reduced. When the microlens array 70 is directly formed on the external optical film 60, when the outermost member is a polarizing plate, it is formed directly on the polarizing plate. In the case of a retardation plate, it is formed directly on the retardation plate.
In addition, since the microlens array is formed using the offset printing technique, the pitch interval between the lenses can be sufficiently narrowed, and the lens height can be easily controlled. Therefore, a high-definition liquid crystal display device can be obtained at a low cost and with a high yield.

1 is a plan view of a liquid crystal display device to which an embodiment of the present invention is applied. A-A 'sectional view of a liquid crystal display. The disassembled perspective view of a liquid crystal display device. The disassembled perspective view of a liquid crystal display device. The figure explaining the formation process of a micro lens array. The figure explaining the formation process of a micro lens array. The figure explaining the formation process of a micro lens array. The figure explaining the formation process of a micro lens array. The figure explaining the formation process of a micro lens array. The figure explaining the formation process of a micro lens array.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... External optical film 20 ... Color filter substrate, 21 ... Common electrode 30 ... Sealing material 40 ... Liquid crystal 50 ... TFT substrate, 53 ... Wiring layer, 54 ...・ Pixel electrode 60 ... External optical film 70 ... Micro lens array 80 ... Backlight module

Claims (12)

A liquid crystal display device in which liquid crystal is sandwiched between cells surrounded by two opposing substrates,
A plurality of condensing lenses for condensing light from a light source in the cell on one outer surface of the substrate,
The liquid crystal display device, wherein the condenser lens is formed by offset printing. In claim 1,
2. A liquid crystal display device, wherein a distance between lens ends of the condensing lens is 20 μm or less. In claim 1,
The height of the said condensing lens is the range of 2-25 micrometers, The liquid crystal display device characterized by the above-mentioned. In claim 1,
A transmissive display unit that displays the light from the light source through the liquid crystal layer;
The condenser lens is
A liquid crystal display device, wherein the liquid crystal display device is disposed corresponding to the transmissive display portion. In claim 1,
The liquid crystal display device
A transflective liquid crystal display device including a transmissive display unit that displays light from a light source through the liquid crystal layer and a reflective display unit that reflects and displays incident external light;
The condenser lens is
A liquid crystal display device, wherein the liquid crystal display device is arranged corresponding to an opening pattern of the transmissive display portion. In claim 5,
The width of the condenser lens is
A liquid crystal display device having a larger opening pattern width than the transmissive display portion. In claim 1,
The condenser lens is
A liquid crystal display device characterized by being a cylindrical lens. In claim 7,
The cylindrical lens constituting the condenser lens is
A liquid crystal display device, characterized in that the center of the convex portion is arranged along a row of pixel regions. In claim 7,
The cylindrical lens constituting the condenser lens is
A liquid crystal display device, wherein the length direction of the cylinder is formed so as to coincide with the longitudinal direction of the rectangular pixel region. In claim 1,
The cylindrical lens constituting the condenser lens is
A liquid crystal display device, characterized in that the length direction of the cylinder is formed to coincide with the short direction of the rectangular pixel region. In claim 1,
The plurality of condensing lenses are
A liquid crystal display device characterized by being microlenses independent of each other. In claim 1,
A liquid crystal display device comprising: a backlight unit that generates collimated light in which light rays incident on the condenser lens are parallel as a light source.

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