Manufacturing method of liquid crystal display device

A manufacturing method of a liquid crystal display device including a first substrate and a second substrate each including a flexible board, the manufacturing method includes a first step of forming the flexible board by forming, in a first region on a glass substrate, a first resin unit made of a first resin having a property of absorbing infrared light and forming, in a second region on the glass substrate, a second resin unit made of a second resin smaller in infrared absorptivity than the first resin; and a second step of, subsequent to the first step, irradiating the first resin unit with infrared light to cut a portion corresponding to the first region in the flexible board.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese application JP 2017-065238 filed on Mar. 29, 2017, the content of which is hereby incorporated by reference into this application.

TECHNICAL FIELD

The present invention relates to a manufacturing method of a liquid crystal display device.

BACKGROUND

Generally, a manufacturing method of a liquid crystal display device includes a step of manufacturing a thin-film transistor substrate, a step of manufacturing a color filter substrate, a step of bonding the substrates together, and a step of cutting the substrates thus bonded, into a size of a display panel. In the cutting step, generally, the thin-film transistor substrate and the color filter substrate are cut by a cutter. Also in the cutting step, a terminal portion formed on the thin-film transistor substrate to connect an electronic circuit is exposed in such a manner that a portion, overlapping the terminal portion in planar view, in the color filter substrate is cut (for example, see Unexamined Japanese Patent Publication No. 2004-118135).

In liquid crystal display devices with flexibility, which have been proposed in recent years, a thin-film transistor substrate and a color filter substrate each includes a flexible substrate made of a flexible material (for example, a polyimide-based resin material) rather than a glass substrate. In such a liquid crystal display device, since it is difficult to easily cut a flexible material by a cutter, unlike glass substrate, there is a possibility that the manufacturing process becomes complicated. When the flexible material is to be cut in such a manner that the cutter blade is stuck deeply into the flexible material, the breakage or disconnection occurs at the terminal portion disposed below the flexible material, which may result in manufacturing errors.

The present disclosure has been made in view of the above-mentioned problem, and an object thereof is to provide a manufacturing method capable of easily manufacturing a liquid crystal display device with flexibility.

SUMMARY

In one general aspect, the instant application describes a manufacturing method of a liquid crystal display device. The liquid crystal display device includes a first substrate and a second substrate each including a flexible board, the first substrate and the second substrate being disposed opposite each other, and a liquid crystal layer disposed between the first substrate and the second substrate. The manufacturing method includes a first step of forming the flexible board by forming, in a first region on a glass substrate, a first resin unit made of a first resin having a property of absorbing infrared light and forming, in a second region on the glass substrate, a second resin unit made of a second resin smaller in infrared absorptivity than the first resin; and a second step of, subsequent to the first step, irradiating the first resin unit with infrared light to cut a portion corresponding to the first region in the flexible board.

The above general aspect may include one or more of the following features. The manufacturing method may further include a third step of, subsequent to the second step, separating the glass substrate from the flexible board.

A slit is formed in the first resin unit.

The first region may be a region corresponding to an outside of an outer periphery of a display panel, and the second region may be a region located inside the outer periphery.

In the second step, the portion corresponding to the first region in the flexible board may be cut by causing volume expansion on the first resin unit due to infrared light absorption to generate a crack in the second resin unit formed on the first resin unit.

The first substrate may include a terminal to be connected to an electronic component. The first resin unit constituting a first flexible board included in the first substrate may be formed outside the terminal in planar view.

The first resin unit constituting a second flexible board included in the second substrate may be formed inside the first resin unit constituting the first flexible board in planar view.

In another general aspect, a manufacturing method of a liquid crystal display device includes a first substrate and a second substrate each including a flexible board, the first substrate and the second substrate being disposed opposite each other, and a liquid crystal layer disposed between the first substrate and the second substrate. The manufacturing method includes a first step of forming, in a first region on a glass substrate, a first separating unit having a slit and including a light absorption film having a property of absorbing ultraviolet light, and forming, in a second region on the glass substrate, a second separating unit made of a material identical to a material for the first separating unit, a second step of, subsequent to the first step, forming a flexible board made of a resin material on the first separating unit and the second separating unit; and a third step of, subsequent to the second step, irradiating the first separating unit and the second separating unit with ultraviolet light to separate the glass substrate from the flexible board, and cutting a portion corresponding to the first region in the flexible board.

The above general aspect may include one or more of the following features. In the third step, the glass substrate may be separated from the flexible substrate by irradiating the first separating unit and the second separating unit with the ultraviolet ray to crystallize the first separating unit and the second separating unit, and the portion corresponding to the first region in the flexible board may be cut by irradiating the first separating unit with the ultraviolet light to crystallize the first separating unit and by generating a stress concentration at an end of the slit.

The manufacturing method may further include a fourth step of, prior to the third step, forming a semiconductor layer unit having a slit, the semiconductor layer unit being made of a material identical to a material for a semiconductor layer constituting a thin-film transistor and being formed to overlap the first separating unit in planar view. In the third step, the glass substrate may be separated from the flexible substrate by irradiating the first separating unit and the second separating unit with the ultraviolet ray to crystallize the first separating unit and the second separating unit. The portion corresponding to the first region in the flexible board may be cut by irradiating the first separating unit and the semiconductor layer unit with the ultraviolet light to crystallize the first separating unit and the semiconductor layer unit and by generating a stress concentration at an end of the slit of each of the first separating unit and the semiconductor layer unit.

According to the manufacturing method of the liquid crystal display device according to the present disclosure, the liquid crystal display device with flexibility can be easily manufactured.

DETAILED DESCRIPTION

One embodiment of the present disclosure will be described below with reference to the accompanying drawings. In an embodiment of the present disclosure, a liquid crystal display device by a chip on glass (COG) technique is taken as an example; however, the present disclosure is not limited thereto. For example, a liquid crystal display device by a chip on film (COF) technique or a tape carrier package (TCP) technique may be used.

FIGS. 1A and 1Bare respectively a plan view and a sectional view showing a schematic configuration of a liquid crystal display device according to the present embodiment. Liquid crystal display device1includes display panel10, source driver ICs20, gate driver ICs30, and a backlight (not shown). Display panel10includes thin-film transistor substrate100(TFT substrate) (first substrate), color filter substrate200(CF substrate) (second substrate), and liquid crystal layer300sandwiched between the two substrates. Display panel10includes display region10afor displaying an image, and non-display region10bdisposed around display region10a. Source driver ICs20and gate driver ICs30are mounted on thin-film transistor substrate100. The number of source driver ICs20and the number of gate driver ICs30are not limited.

FIG. 1Bis the sectional view taken along line A-A′ inFIG. 1A. Thin-film transistor substrate100includes flexible substrate103formed of a flexible material, TFT element layer105formed on a display surface side of flexible substrate103, and polarizing plate130formed on a back surface side of flexible substrate103. Terminal portion31as well as source driver ICs20and gate driver ICs30electrically connected to terminal portions31are disposed on non-display region10bof TFT element layer105. Color filter substrate200includes flexible substrate203formed of a flexible material, CF element layer205formed on a back surface side of flexible substrate203, and polarizing plate230formed on a display surface side of flexible substrate203. Liquid crystal layer300is disposed between thin-film transistor substrate100and color filter substrate200, and seal member310is formed at a periphery of liquid crystal layer300.

FIG. 2is a plan view (equivalent circuit diagram) showing a schematic configuration of display region10aof display panel10. On display panel10, a plurality of source lines11extending in a first direction (e.g., a column direction) and a plurality of gate lines12extending in a second direction (e.g., a row direction) are provided. Thin-film transistor13(TFT) is provided at an intersection of each source line11and each gate line12. Source lines11are electrically connected to source driver ICs20(seeFIGS. 1A, 1B), and gate lines12are electrically connected to gate driver ICs30(seeFIGS. 1A, 1B).

Display panel10includes a plurality of pixels14arranged in a matrix arrangement (row and column directions) so as to correspond to the respective intersection of source lines11and gate lines12. On thin-film transistor substrate100, a plurality of pixel electrodes15disposed for respective pixel14, and a common electrode16which is common to the plurality of pixels14are provided.

Data signal (data voltage) is supplied with source lines11from source driver ICs20, and gate signal (gate-on voltage, gate-off voltage) is supplied with gate lines12from gate driver ICs30. Common voltage Vcom is supplied with common electrode16from a common driver (not shown). When an ON voltage (gate-on voltage) of the gate signal is supplied with gate lines12, thin-film transistors13connected to gate lines12are turned on, and the data voltage is supplied with pixel electrodes15via source lines11connected to thin-film transistors13. An electric field is generated by a difference between the data voltage supplied to pixel electrodes15and common voltage Vcom supplied to common electrode16. This electric field drives a liquid crystal and controls the light transmittance of the backlight so as to display an image. Color display is operated by supplying desired data voltages with source lines11connected to pixel electrodes15of pixels14corresponding to red, green, and blue formed of stripe-shaped color filters.

FIG. 3is a plan view showing a configuration of each pixel14.FIG. 4is a sectional view taken along line B-B′ inFIG. 3, andFIG. 5is a sectional view taken along line C-C′ inFIG. 3. With reference toFIGS. 3 to 5, a specific configuration of display panel10will be described.

InFIG. 3, a region defined by adjacent two of source lines11and adjacent two of gate lines12corresponds to one pixel14. Thin-film transistors13are respectively provided in the pixels14. As shown inFIG. 3, each of thin-film transistors13includes semiconductor layer17formed on insulating film121(seeFIG. 4), and drain electrode18and source electrode19each formed on semiconductor layer17. Drain electrodes18are electrically connected to source lines11, and source electrodes19are electrically connected to pixel electrodes15through through-holes21.

Each pixel electrode15formed of a transparent conductive film such as ITO or the like is formed in a pixel14. The pixel electrode15has a plurality of openings (slits) formed in stripe shapes. In common to respective pixels14, one common electrode16formed of a transparent conductive film such as ITO or the like is formed on entire display region. An opening in common electrode16for electrically connecting a pixel electrode15to a source electrode19is formed in a region overlapping through-holes21and source electrode19of thin-film transistors13.

As shown inFIGS. 4 and 5, display panel10includes thin-film transistor substrate100disposed on the back surface side, color filter substrate200disposed on the display surface side, and liquid crystal layer300sandwiched between thin-film transistor substrate100and color filter substrate200.

In thin-film transistor substrate100, gate lines12(FIG. 5) are formed via diffusion preventing layer104on the display surface side of flexible substrate103, and insulating film121is formed so as to cover gate lines12. Source lines11(FIG. 4) are formed on insulating film121, and insulating film122is formed so as to cover source lines11. Common electrode16is formed on insulating film122, and insulating film123is formed so as to cover common electrode16. Pixel electrodes15are formed on insulating film123, and alignment film124is formed so as to cover pixel electrodes15. Polarizing plate130is formed on the back surface side of flexible substrate103.

In color filter substrate200, black matrixes222and color filters206(e.g., red color filter206r, green color filter206g, and blue color filter206b) are formed through diffusion preventing layer204on the back surface side of flexible substrate203, and overcoat layer223is formed so as to cover black matrixes222and color filters206. Alignment film224is formed on overcoat layer223. Polarizing plate230is formed on the display surface side of flexible substrate203.

Liquid crystal301is sealed in liquid crystal layer300. Liquid crystal301may be a negative-type liquid crystal of which the dielectric anisotropy is negative, or may be a positive-type liquid crystal of which the dielectric anisotropy is positive.

Each of alignment films124and224may be subjected to a rubbing alignment treatment or an optical alignment treatment.

Stacked layer structures of the respective components constituting each pixel14are not limited to the configurations shown inFIGS. 4 and 5. And known configurations can be applied thereto. As described above, liquid crystal display device1has the configuration by an in plane switching (IPS) technique. The configuration of liquid crystal display device1is not limited to the configuration described above.

Next, a manufacturing method of liquid crystal display device1will be described. The manufacturing method of liquid crystal display device1includes a thin-film transistor substrate manufacturing step of manufacturing thin-film transistor substrate100(first substrate), a color filter substrate manufacturing step of manufacturing color filter substrate200(second substrate), a substrate bonding step of bonding thin-film transistor substrate100and color filter substrate200together, a separating step of separating the glass substrate which is underlying, and a cutting step of cutting the substrates for each display panel10(liquid crystal cell).

FIG. 6Ais a plan view showing a state after the substrate bonding step, andFIG. 6Bis a sectional view taken along line D-D′ inFIG. 6A. The example shown inFIGS. 6A and 6Bshows a process of manufacturing nine display panels10. In the following, for convenience, a description is given with reference to one display panel10surrounded by the dotted line inFIGS. 6A and 6B.FIG. 7is a sectional view showing a detailed configuration ofFIG. 6B.

In the thin-film transistor substrate manufacturing step and the color filter substrate manufacturing step, first, as shown inFIG. 8, a light absorbing film having a property of absorbing ultraviolet rays or near-ultraviolet rays, such as a-Si or a-Ge, is formed on a glass substrate (mother glass) by any of a CVD method, a sputtering method, a coating and baking method and the like, to form a separating layer. The separating layer is made of a-Si, a-Ge, or the like, and has a property of absorbing ultraviolet rays or near-ultraviolet rays to cause a volume change or a structural change rapidly. Next, a first resin pattern (first resin portion) in a band shape or a grid pattern is formed by a resin (first resin) containing an acrylic resin as a main component so as to surround a region corresponding to the outer periphery of liquid crystal display device1(display panel10). The first resin has a property of absorbing infrared rays such as an organic material, for example. The method for forming the first resin pattern is not particularly limited. For example, a method by a photolithography process using a photosensitive resin and a predetermined mask or a method of directly drawing a non-photosensitive resin by an ink jet, a dispenser, or the like may be employed. After baking the first resin pattern, a second resin portion is formed on the glass substrate on which the separating layer is formed, by coating and baking a resin (second resin) containing a polyimide resin as a main component which would result in a resin substrate (flexible substrate) at the time of completion. The second resin portion absorbs smaller infrared ray than the first resin. Since the glass substrate serves for supporting the resin substrate, a glass substrate having a thickness of 0.5 mm to 1.0 mm is used. The thickness of the separating layer is set to 50 nm to 400 nm, the thickness of the first resin pattern is set to 2 μm to 10 μm, and the thickness of the second resin portion is set to 50 μm to 200 μm. As described above, the first resin pattern has a slit and is embedded in the second resin portion.

Next, a diffusion preventing layer such as SiN film is formed on a surface of the second resin portion to prevent moisture, ionic impurities and the like from entering TFT element layer105and CF element layer205.

In the thin-film transistor substrate manufacturing step, subsequent to the step shown inFIG. 8, as shown inFIG. 9A, TFT element layer105is formed on the substrate shown inFIG. 8. TFT element layer105includes the structural members (source lines11, gate lines12, thin-film transistors13, pixel electrodes15, common electrode16, and the like) shown in, for example,FIGS. 4 and 5. Thin-film transistors13are formed by, for example, a vacuum process or a coating process using an organic material. Terminal portion31is formed on the non-display region10B (seeFIG. 1A) on TFT element layer105. Terminal portion31overlaps lead wire107in planar view, and is electrically connected to lead wire107through a through-hole (not shown). First resin pattern103A is formed on a region located outside ends (shown by dotted lines L1inFIG. 9A) of terminal portion31and lead wire107in planar view. Through the steps described above, thin-film transistor substrate100is manufactured.

In the color filter substrate manufacturing step, subsequent to the step shown inFIG. 8, as shown inFIG. 9B, CF element layer205is formed on the substrate shown inFIG. 8. CF element layer205includes the structural members (color filters206, black matrixes222, and the like) shown in, for example,FIGS. 4 and 5. First resin pattern203A is formed at a position (inward) closer to display region10athan first resin pattern103A such that a region (region W inFIG. 9B) is exposed, the region overlapping terminal portion31in planar view, when thin-film transistor substrate100and CF element layer205are bonded together. Through the steps described above, color filter substrate200is manufactured.

In the substrate bonding step, first, an alignment film (seeFIGS. 4, 5) is coated to each of a surface of thin-film transistor substrate100manufactured through the thin-film transistor substrate manufacturing step and a surface of color filter substrate200manufactured through the color filter substrate manufacturing step. After being coated, the alignment are then baked. Thereafter, seal member310is provided to a predetermined position of thin-film transistor substrate100(FIG. 10B), and liquid crystal301is dropped onto display region10aon color filter substrate200(seeFIGS. 1A, 1B) (FIG. 10A). Next, thin-film transistor substrate100and color filter substrate200are bonded together, and seal member310is irradiated with ultraviolet rays and is thus cured (FIG. 10C).

In the cutting step, as shown inFIG. 11, first resin pattern103A of thin-film transistor substrate100and first resin pattern203A of color filter substrate200are irradiated with infrared rays. The process of irradiating infrared rays may be performed by an infrared lamp or an infrared laser. Infrared ray absorption of first resin patterns103A and203A causes volume expansion or embrittlement, and eventually cracks are generated in second resin portions103B and203B on first resin patterns103A and203A. Accordingly, each of thin-film transistor substrate100and color filter substrate200is easily cut and separated at portions corresponding to the cracks.

In the separating step, as shown inFIG. 12, line-shaped light (e.g., ultraviolet rays) is scanned from glass substrate101of thin-film transistor substrate100and glass substrate201of color filter substrate200, so that separating layers102and202(light absorption films) formed between glass substrates101and201and flexible substrates103and203are crystallized. The line-shaped light is light (coherent light) with high light directivity like a laser beam and with high energy density preferably, and is light having a wavelength in a range from 250 nm to 350 nm preferably. Since the light absorbing film causes a structural change (contraction) upon crystallization to generate an internal strain, separating layers102and202are respectively separated from flexible substrates103and203. Glass substrates101and201are thus separated. Terminal portion31is exposed on thin-film transistor substrate100. Electronic components (e.g., gate driver ICs30) are mounted on terminal portion31.

Through the steps described above, liquid crystal display device1(liquid crystal cell) with flexibility is completed as shown inFIG. 13. Liquid crystal display device1includes second resin portions103B and203B as base members (flexible substrates).

As described above, in the manufacturing method described above, the resins (first resin patterns103A,203A) which has larger absorbency of infrared ray than the resins (second resin portions103B,203B) constituting the base members (flexible substrates103,203) are formed in advance in the portions along which thin-film transistor substrate100and color filter substrate200would be cut. Thereafter, when first resin patterns103A and203A are irradiated with infrared rays, first resin patterns103A and203A heated by absorption of infrared rays cause a structural change. As a result, cracks are generated in second resin portion103B and TFT element layer105on first resin pattern103A and in second resin portion203B and CF element layer205on first resin pattern203A. Thus, a part of thin-film transistor substrate100and color filter substrate200is easily cut and separated. Therefore, liquid crystal display device1with flexibility can be manufactured easily, and it is possible to prevent manufacturing errors.

The present disclosure is not limited to the manufacturing method described above.FIG. 14is a diagram showing another manufacturing method of liquid crystal display device1. In the manufacturing method shown inFIG. 14, separating layer patterns102A and202A (first separating portions) are formed at a position (separation portion) where thin-film transistor substrate100and color filter substrate200are cut and separated, and second separating portions102B and202B are formed in a region corresponding to a panel portion inside the separation portion. Separating layer patterns102A and202A are formed in an island shape or a line shape. Each of separating layer patterns102A and202A has a slit. Each flexible substrate103or203does not include first resin pattern103A203A (seeFIG. 7). In the manufacturing method shown inFIG. 14, for example, ultraviolet rays is irradiated from back surface sides of thin-film transistor substrate100and color filter substrate200, so that the separating layers (second separating portions102B,202B) made of a-Si, for example, are crystallized. Second separating portions102B and202B causes a rapid structural change in order to generate an internal strain, so that the resin substrates (flexible substrates103,203) are respectively separated from glass substrates101and201at the panel portion. On the other hand, in the separation portion where separating layer patterns102A,202A are formed, stress concentration occurs at ends (edges) of the slits in the separating layer patterns102A,202A, and cracks are generated in the resin substrates (flexible substrates103,203) upon crystallization. A part of thin-film transistor substrate100and color filter substrate200is thus cut and separated.

FIG. 15is a diagram showing another manufacturing method of liquid crystal display device1. In the manufacturing method shown inFIG. 15, in thin-film transistor substrate100shown inFIG. 14, semiconductor layer pattern120(semiconductor layer portion) is further formed at a position (separation portion) where thin-film transistor substrate100and color filter substrate200are cut and separated. Semiconductor layer pattern120is formed in an island shape or a line shape. Semiconductor layer pattern120has a slit. Semiconductor layer pattern120is made of a material having a property of absorbing ultraviolet rays or near-ultraviolet rays to rapidly cause a volume change or a structural change. For example, the material is the same as a material of which semiconductor layer17(seeFIG. 3) included in thin-film transistor13is made. According to the manufacturing method shown inFIG. 15, particularly in thin-film transistor substrate100, semiconductor layer pattern120on separating layer pattern102A is also crystallized. As compared with the manufacturing method shown inFIG. 14, therefore, cracks are easily generated in the resin substrate (flexible substrate103), so that a part of thin-film transistor substrate100can be easily cut and separated.