JP4884027B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a method of manufacturing a liquid crystal display device including a liquid crystal display panel in which an alignment film is provided with an alignment control ability by light irradiation.

  As a method for imparting an alignment treatment, that is, an alignment control ability, to an alignment film used in a liquid crystal display device, there is a conventional method of rubbing. The alignment treatment by rubbing is performed by rubbing the alignment film with a cloth. On the other hand, there is a photo-alignment method in which alignment control ability is imparted to the alignment film without contact.

FIG. 6 is a conceptual diagram illustrating the photo-alignment method. An alignment film ORI before imparting alignment control ability is formed on the surface of the glass substrate SUB. The polarized ultraviolet light PUV from the light source SAL is irradiated from above the alignment film ORI of the glass substrate SUB. As the light source SAL, by using a short arc type discharge lamp that emits a wide range of light including ultraviolet rays, such as an ultra-high pressure mercury lamp and a metal halide lamp, it is possible to irradiate polarized ultraviolet rays PUV containing a component having a wavelength of 230 to 400 nm. Yes. The polarized ultraviolet light PUV can be irradiated more uniformly by swinging the alignment film ORI as indicated by an arrow. This polarized ultraviolet light PUV is obtained by inserting a polarizer in the optical path of the short arc light source SAL. A polarizer is a polarizing element that uses light incident on the polarizer at a predetermined angle as polarized light. The polarizer uses a Brewster angle, uses light interference, or a plurality of linear elongated electrical conductors. In general, a wire grid using a wire grid arranged in parallel on the same plane is used. However, any wavelength component having a wavelength of 230 to 400 nm may be used as polarized ultraviolet rays. Omitted.

  Then, during the photo-alignment process (alignment process) in which the alignment film ORI is irradiated with polarized ultraviolet light PUV to provide alignment control ability, heat is simultaneously applied to the alignment film ORI. This heating temperature is about 200 ° C.

FIG. 7 is a diagram for explaining a conventional process for imparting alignment control ability to an alignment film by irradiation with polarized ultraviolet rays PUV and irradiation with polarized ultraviolet rays simultaneously. As shown in FIG. 7 (a), when the alignment film is irradiated with polarized ultraviolet rays, the alignment film polymer main chain extending in the direction orthogonal to the polarization direction as shown in FIG. Disconnected. A part of the cut main chain is rearranged in the polarization direction as indicated by reference numeral CH1 in FIG. 7 (c) and cross-linked with polarized ultraviolet light on the long wavelength side. Overheating has the effect of activating the molecular chain movement of the alignment film or causing thermal crosslinking. Table 1 shows the roles of light and heat.

  However, in the conventional polarization process in which the irradiation with the polarized ultraviolet light PUV and the heat treatment are performed at the same time, as shown by the symbol CH2 in FIG. 7 (c), before the rearrangement in the main chain direction of the polarization direction, Molecules that crosslink as they occur. As described above, if the molecules of the main chain that has been cut are cross-linked in the direction perpendicular to the polarization direction, the orientation control ability is lowered, causing afterimages due to insufficient orientation regulating force.

Patent document 1 can be mentioned as what disclosed the prior art regarding optical orientation. Patent Document 1 discloses that the same light source is used for irradiation throughout the photo-alignment process, and the temperature during the photo-alignment process is constant.
JP 2004-206091 A

As I explained in FIG 6, in the process (alignment process) for imparting alignment control function of the photolytic, orientation by decomposing with polarized ultraviolet PUV a direction of the alignment film backbone becomes unnecessary on the orientation of the alignment layer Get. By simultaneously applying heat at this time, high orientation (orientation regulating force, orientation control ability) can be obtained. In this process, in the alignment film, (1) photodecomposition, (2) the alignment film main chain whose molecular chain length has been shortened by decomposition is repositioned by thermal motion (rearrangement), and (3) decomposed small molecules Three reactions are in progress: crosslinks again with a certain probability.

  At this time, if the re-arrangement of (2) is not performed and the cross-linking is performed as it is, the molecule is an unnecessary directional main chain before being decomposed in (1), and the re-decomposition cycle is caused by (1). It only returns, and the crosslinking cannot obtain the effect of improving the orientation. Therefore, changing the molecular position in (2) is essential for improving the orientation. However, when the amount of heat necessary for crosslinking is added all the time, a crosslinking reaction also occurs in parallel with the molecular chain movement, so that the amount of the crosslinking component that contributes to the improvement of the true orientation after the rearrangement is reduced.

In addition, the light source used in the alignment process does not have the same irradiation axis in the actually irradiated light beam due to the influence of the arrangement of the light source and the polarization axis unevenness of the polarization generating element such as a polarizer. Generally, the irradiation axis is continuously changed within the light beam, the angle of deviation of the irradiation axis of the peripheral portion is increased relative to the irradiation axis of the central portion of the light beam. For this reason, the area where the allowable irradiation axis necessary for the alignment treatment cannot be obtained is discarded by the light shielding slit, and light cannot be used efficiently.

  An object of the present invention is to use a liquid crystal display panel that can prevent high-quality display by preventing a decrease in alignment control ability by suppressing crosslinking of molecular chains separated by polarized light irradiation before rearrangement. Another object of the present invention is to provide a method for manufacturing a liquid crystal display device.

  The present invention provides one substrate having a first alignment film on the uppermost layer of the main surface on which an active element for pixel selection is formed, and a second alignment film on the uppermost layer of the main surface on which a color filter is formed. And a liquid crystal display panel comprising a liquid crystal sealed between the first alignment film of the one substrate and the second alignment film of the other substrate, and having at least the first This is a method for manufacturing a liquid crystal display device, in which an alignment treatment for imparting a liquid crystal alignment control ability by irradiation of polarized light is performed on one alignment film.

  The production method of the present invention is characterized in that the alignment film is subjected to a heat treatment during the polarized light irradiation treatment, and the temperature of the heat treatment is changed during the polarized light irradiation treatment. The temperature change of the heat treatment is defined as a temperature rise profile in which the temperature rises in the initial, middle, and late stages during the polarized light irradiation treatment. For example, the temperatures at the initial stage, middle stage, and late stage can be set to 100 ° C., 100 ° C. to 150 ° C., and 200 ° C. to 220 ° C., respectively.

  Further, the present invention is characterized in that the wavelength of the polarized light during the irradiation treatment is changed over time. The wavelength of this polarized light can be an increasing profile that becomes longer in the initial, middle, and late stages during the irradiation treatment of the polarized light, and can be, for example, 230 to 270 nm, 270 nm to 280 nm, and 280 to 330 nm, respectively.

  Moreover, this invention can implement a heat processing at the completion | finish of the said photo-alignment process. The treatment time of this heat treatment is 10 minutes to 60 minutes, and the heating temperature can be 150 ° C. to 250 ° C.

  In the present invention, the polarized light irradiated at the time of the photo-alignment treatment has at least two types of polarization directions and the irradiation wavelength ranges of the polarized lights are different from each other. The irradiation angle in the polarization direction with respect to the alignment axis can be set to 90 degrees for light of 230 to 270 nm in the initial stage and 85 degrees for light of 280 to 330 nm in the latter stage.

  Further, according to the present invention, irradiation can be performed so that the axial distribution angle of the light beam in the scanning direction of the polarized light is ± 100 or less and the axial distribution is symmetrical in the scanning direction.

  Note that the present invention is not limited to the above-described configuration and the configuration disclosed in the embodiments described later, and it goes without saying that various modifications can be made without departing from the technical idea of the present invention. .

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the liquid crystal display device using the liquid crystal display panel which prevented the fall of orientation control ability and enabled the display of high quality can be provided.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings of the examples.

  FIG. 1 is a conceptual diagram illustrating a photo-alignment method of a method for manufacturing a liquid crystal display device according to the present invention. In the first embodiment, the alignment process is configured in the time series of the initial P1, the middle P2, and the late P3. An orientation film ORI before imparting orientation control ability is formed on the surface of the glass substrate SUB. From above the alignment film ORI of the glass substrate SUB, polarized ultraviolet light PUV is irradiated by a rod-shaped polarization source LAL including a wavelength region of 230 to 400 nm. The polarized ultraviolet light PUV obtains a polarization component mainly composed of a target wavelength component through the wavelength cut filters F1 and F2 as necessary. The rod-shaped polarization source LAL polarizes an elongated slit-shaped light beam obtained by a rod-shaped high-pressure mercury lamp (a long arc discharge lamp that emits a wide range of light including ultraviolet rays) as disclosed in JP-T-2001-512850. Although it can be obtained by being incident on the polarizer, the polarizer is not shown in the figure. A plurality of long arc polarized light sources LAL are arranged, and as indicated by the large arrows, they are moved in time series of early, middle and late periods while applying heat according to the arrangement direction of the long arc polarized light sources LAL. Further, if necessary, the glass substrate SUB can be swung back and forth as indicated by a thin arrow so that uniform irradiation can be performed. In the figure, the method of applying heat is to place the IR heater directly below the substrate transfer system in the figure, so that heat H is applied from below the substrate. However, as long as heat can be applied to the substrate, the arrangement position may be anywhere. In addition, the heating method can be any of the methods such as sealing the entire system and heating with hot air, or placing the hot plate directly under the substrate and moving the hot plate substrate in the direction of the large arrow in the figure. There is no particular problem using the method.

  The wavelength from the long arc light source LAL that has passed through the wavelength cut filter F1 is 230 to 270 nm from the initial P1 and the intermediate period P2 of the alignment process, and the heat H to be applied is 100 ° C. in the initial stage and 100 to 150 ° C. in the intermediate period. In the latter period P3, the wavelength from the long arc light source LAL that has passed through the wavelength cut filter F2 is 280 to 330 nm, and the heat H to be applied is 200 ° C. The polarized ultraviolet light PUV is obtained by inserting a polarizer in the optical path of the long arc light source LAL, but the illustration of the polarizer is omitted.

  As described above, in Example 1, during the photo-alignment process (alignment process) in which the alignment film ORI is irradiated with the polarized ultraviolet light PUV to provide the alignment control ability, the heat is applied to the alignment film ORI at the same time. Apply processing.

  FIG. 2 is a diagram for explaining a process for imparting orientation control ability in which heat treatment is performed in time series during irradiation with polarized ultraviolet light PUV. FIG. 2A to FIG. 7B show process contents in the initial P1. The main chain MMC of the polymer of the alignment film intersects as shown in FIG. The alignment film ORI is irradiated with polarized ultraviolet rays having a wavelength of 230 to 270 nm and heated (approximately 100 ° C.) to promote molecular chain movement, and the main chain in a direction orthogonal to the polarization direction as shown in FIG. Disconnected.

  A part of the cut main chain is regenerated in the direction following the main chain in the polarization direction as shown in FIG. 2C by slightly raising the heating temperature (approximately 100 to 150 ° C.) in the middle period P2. Arrange.

  Then, in the latter period P3 of FIG. 2D, the wavelength from the long arc light source LAL that has passed through the wavelength cut filter F2 is 280 to 330 nm, and by applying higher heating (approximately 200 ° C.), the rearranged cutting is performed. The main chain of the polymer is photocrosslinked with heat (recrosslinking).

  In Example 1, the photo-alignment process is divided into three stages, and a more uniform molecular arrangement is obtained by taking time for rearrangement along the main chain in the polarization direction in which the cut main chain is not cut. Thereby, the orientation regulating force is improved, the occurrence of afterimages is suppressed, and a high-quality image display can be obtained.

  In this way, the photo-alignment treatment process is divided into an initial stage, a middle stage, and a late stage, and by setting each reaction process as an optimal reaction condition for photolysis (initial stage), rearrangement (middle stage), and recrosslinking (late stage), The efficiency of the reaction can be increased. The temperature rising profile for changing the heating temperature can accelerate the photodecomposition reaction by applying heat of about 100 ° C. in addition to the polarized ultraviolet light PUV as a condition for promoting photodecomposition at the initial stage. In the rearrangement in the middle period, the temperature at which the crosslinking does not occur at a temperature close to the glass transition temperature of the molecule is about 100 to 150 ° C., and the latter period is about 200 ° C. necessary for the crosslinking. By these treatments, a more ordered molecular chain alignment state can be obtained, so that the alignment regulating force is improved and an afterimage hardly occurs.

The conventional polarization irradiation, the wavelength range necessary for photolysis wavelength range required to photocrosslinking was also shines irradiation simultaneously. In contrast, in the present embodiment, the initial emission wavelength mainly irradiating the wavelength range necessary for photolysis, primarily to morphism shining a wavelength range necessary for photocrosslinking radiation wavelength range of late, each reaction Optimum reaction conditions can be achieved in the process. For this reason, a more ordered molecular chain alignment state can be obtained, the alignment regulating force is improved, and afterimages are less likely to occur.

  The wavelength required for the photolysis is 230 to 270 nm, which is the absorption wavelength region of phenylenediamine, when a general cyclobutanetetracarboxylic acid and polyimide based on phenylenediamine are used. It is preferable to irradiate mainly in this wavelength range. Further, the wavelength necessary for the later photocrosslinking is 280 to 330 mm, and it is desirable to mainly irradiate this wavelength region and to reduce the irradiation intensity of the photolysis wavelength as much as possible.

  In an alignment process that imparts photolytic alignment control capability, alignment is obtained by decomposing an alignment film main chain in a direction unnecessary for liquid crystal alignment with polarized ultraviolet light PUV. More specifically, in the photo-alignment treatment, the alignment regulation force of the main chain of the other molecule is relatively improved by cutting one alignment film main chain. However, even with a shortened alignment film main chain, there is an interaction with the liquid crystal, and the direction of the interaction is an unnecessary alignment direction. In addition, the short alignment film main chain moved in the alignment direction by the rearrangement by heat becomes an improvement factor of the alignment property in the initial stage.

  However, in the alignment film with a small molecular weight, when the liquid crystal is directed in a direction different from the alignment direction of the alignment film by electric field driving, the alignment film main chain is aligned before driving due to the influence of strong torque due to the interaction between the liquid crystal and the alignment film. It becomes easy to face in the direction shifted from the direction. In other words, the orientation direction is disturbed by driving the liquid crystal, which causes a decrease in orientation during use as a display device. Therefore, by applying a heat treatment at the end of the alignment treatment, it is possible to remove low molecular compounds present in the alignment film, particularly on the alignment film surface, and a relatively high molecular alignment film can be obtained. It can be made difficult to be affected by the decrease in orientation due to liquid crystal driving. The heat treatment is not necessarily performed immediately after the alignment treatment, and may be performed until the liquid crystal cell is manufactured by combining a pair of substrates. The heating method may be heating at 150 to 250 ° C. (substrate temperature) for about 10 to 60 minutes by IR heating, hot air heating or hot plate heating. The atmosphere during heating is desirably performed in an inert gas such as nitrogen, but a sufficient degassing effect can be obtained even in a normal air atmosphere.

  When a general cyclobutanetetracarboxylic acid and phenylenediamine-based polyimide is used, light absorption occurs in the molecular direction of phenylenediamine, which is a light absorption part, in the photo-cutting step of the photo-alignment film polyimide. Therefore, in the case of photo-cutting, irradiation with polarized ultraviolet light PUV in the 90 ° direction farthest from the alignment direction leaves the molecules in the alignment direction and cuts molecules unnecessary for alignment.

  In the recrosslinking step, the maleimide terminal generated by decomposition is photocrosslinked. In this photocrosslinking, a more ordered molecular orientation state can be obtained by irradiating polarized light in the direction of the transition absorption moment of maleimide. The transition moment of maleimide having no substituent is 90 ° with respect to the main chain of the alignment film and coincides with the polarization direction at the time of light cutting. In this case, it is not necessary to change the direction of the polarized ultraviolet light PUV. On the other hand, since the transition moment of the maleimide having a substituent is shifted from the direction of 90 ° with respect to the main chain of the alignment film, re-crosslinking can be promoted by applying polarized ultraviolet light PUV in accordance with the direction. The maleimide shown as an example has a direction of 85 ° with respect to the main chain of the alignment film.

  In this embodiment, the present invention can be used in a process of scanning and processing a light source or a substrate while irradiating polarized ultraviolet light PUV. In that case, it is realizable by dividing | segmenting arrangement | positioning of the apparatus which implements this method into decomposition | disassembly, rearrangement, and re-bridge | crosslinking. At that time, an allowable irradiation axis necessary for the alignment treatment cannot be obtained. Even in the case of a large axis deviation region, the average axis angle can be reduced by the scanning process if the axis distribution is symmetrical in the polarization scanning direction. At that time, if the axial distribution angle of the light beam in the scanning direction is ± 100 or less, it can be used without any problem.

  In the photolysis type alignment process, the alignment film main chain in a direction unnecessary for alignment is decomposed and irradiated with the irradiation axis of polarized ultraviolet light PUV in that direction to obtain alignment. However, the actual polarized ultraviolet light PUV also has light components other than the irradiation axis direction. The value obtained by dividing the light intensity in the irradiation axis direction by the light intensity orthogonal to the irradiation axis is the extinction ratio. However, if this value is small, the amount of molecules decomposed in the direction in which photodecomposition is not desired increases. This allowable value becomes stricter when the processing as described above is performed.

  When a light source having a large light beam axial distribution angle is canceled by scanning, it is strongly influenced by the light beam angle when initially irradiated. When scanning a single light source at a low speed, the contribution ratio is particularly large and the axes cannot be offset. Axes can be offset by scanning at high speed using multiple light sources.

  FIG. 3 is a diagram schematically illustrating a photo-alignment processing apparatus. Alignment controllability is imparted to an alignment film applied to a thin film transistor substrate (TFT substrate) which is one of the substrates suitable for glass of a liquid crystal display panel or a color filter substrate (CF substrate) which is also the other substrate. In FIG. 3, an alignment film ORI to which no alignment control ability is imparted is formed on the glass substrate SUB main surface (inner surface). The light source is a long arc light source LAL, and the ultraviolet light from the ultraviolet lamp LAL is selected only by a polarizer PLZ with a predetermined polarization component, and irradiates the alignment film ORI formed on the glass substrate. The glass substrate is moved in the direction of arrow A, and the alignment control ability is imparted to the alignment film over the entire area of the substrate. The movement of the substrate relative to the light source is relative, and the light source side may be moved, or both the light source and the substrate may be moved.

  FIG. 4 is a schematic cross-sectional view of the vicinity of one pixel for explaining a configuration example of a liquid crystal display panel to which the present invention is applied. This liquid crystal display panel PNL is an IPS liquid crystal display panel, and has a liquid crystal LC sealed between a TFT substrate SUB1 and a CF substrate SUB2, which are preferably made of glass. A thin film transistor TFT including a gate electrode GT, a gate insulating film GI, a silicon semiconductor layer SI, a source electrode SD1, and a drain electrode SD2 is formed on the inner surface of the TFT substrate SUB1. An insulating layer INS is formed to cover the thin film transistor TFT, and the counter electrode CT is patterned on the insulating layer INS.

  A passivation film (pass film) PAS is formed to cover the counter electrode CT. On the pass film PAS, the pixel electrode PX is patterned and connected to the source electrode SD1 through a contact hole formed in the insulating layer INS and the pass film PAS. The pixel electrode PX and the counter electrode CT are arranged so as to mesh with each other in a comb shape when viewed from the display surface side. One alignment film ORI1 is formed on the uppermost layer.

  A black matrix BM and a color filter CF partitioned by the black matrix BM are formed on the inner surface of the CF substrate SUB2. On the color filter CF, the other alignment film ORI2 is formed via an overcoat layer (smooth layer) OC.

  In this liquid crystal display panel, the liquid crystal alignment control ability is imparted to both the one alignment film ORI1 and the other alignment film ORI2 by the optical alignment process. In addition, at least the alignment film ORI1 on the TFT substrate SUB1 side has a rough surface due to the presence of the thin film transistor TFT on the inner surface of the TFT substrate SUB1, and therefore alignment stability can be obtained by providing a liquid crystal alignment control ability by a photo-alignment process. Thus, a liquid crystal display device capable of displaying a high-quality image can be configured.

  Note that polarizing plates POL1 and POL2 are laminated on the outer surfaces of the TFT substrate SUB1 and the CF substrate SUB2, respectively, to form a liquid crystal display panel PNL.

  FIG. 5 is a developed perspective view illustrating an example of the entire structure of a liquid crystal display device manufactured according to the present invention. The same reference numerals as those in FIG. 4 correspond to the same functional parts. The liquid crystal display panel PNL has a drive circuit mounted on the periphery (here, the upper side and the left side). A data line driving circuit chip is mounted on the upper side, and a scanning line driving circuit chip is mounted on the left side. Here, the description has been made that the drive circuit chip is mounted, but instead of this, a drive circuit formed directly on the TFT substrate may be used.

  The drive circuit is connected to a signal source (not shown) by a flexible printed circuit board FPC. A backlight unit BL is installed on the back surface of the liquid crystal display panel PNL. The backlight unit BL includes a light guide plate GLB, a light source, an optical compensation member made of a prism sheet or a diffusion sheet, a mold frame MDL that houses a reflection sheet (not shown) installed on the back surface of the light guide plate GLB.

  Then, an upper frame SHD of a metal material is placed on the liquid crystal display panel PNL, and is connected to and integrated with the lower frame MFL of the metal material provided on the back surface of the mold frame MDL. The electronic latent image formed on the liquid crystal display panel PNL is visualized with illumination light from the backlight unit BL.

It is a conceptual diagram explaining the photo-alignment method of the manufacturing method of the liquid crystal display device by this invention. It is a figure explaining the provision process of the orientation control ability which heat-processes in time series during irradiation of polarized ultraviolet rays PUV. It is a figure which illustrates the processing apparatus of photo-alignment typically. It is a cross-sectional schematic diagram of one pixel vicinity explaining the structural example of the liquid crystal display panel to which this invention is applied. It is an expansion | deployment perspective view explaining the example of the whole structure of the liquid crystal display device manufactured by this invention. It is a conceptual diagram explaining the photo-alignment method. It is a figure explaining the provision process of the alignment control ability with respect to the alignment film by the irradiation of the conventional polarized ultraviolet rays which performs irradiation of polarized ultraviolet rays PUV, and heat processing simultaneously.

Explanation of symbols

SUB ... Substrate, SUB1 ... TFT substrate, SUB2 ... CF substrate, PX ... Pixel electrode, ORI ... Alignment film, ORI1 ... Alignment film on TFT substrate side, ORI2 ... CF Alignment film on substrate side, CT ... counter electrode (common electrode), CF ... color filter, LC ... liquid crystal, BM ... black matrix, POL1, POL2 ... polarizing plate, PUV ... Polarized ultraviolet light, LAL ... Long arc light source.

Claims (4)

One substrate having the first alignment film on the uppermost layer of the main surface on which the active element for pixel selection is formed, and the other substrate having the second alignment film on the uppermost layer of the main surface on which the color filter is formed And a liquid crystal display panel comprising a liquid crystal sealed between the first alignment film of the one substrate and the second alignment film of the other substrate, and at least the first alignment film A method of manufacturing a liquid crystal display device that performs an alignment treatment for imparting liquid crystal alignment control ability by irradiation of polarized light,
The alignment film is subjected to a heat treatment during the irradiation treatment of the polarized light ,
The heat treatment includes a first step performed at 100 ° C., a second step performed at 100 ° C. to 150 ° C. after the first step, and a second step performed at 200 ° C. to 220 ° C. after the second step. A process for producing a liquid crystal display device. In claim 1,
The temperature of the heat treatment during the irradiation treatment of the polarized light rises from a temperature capable of promoting the photodecomposition reaction of the first alignment film to a temperature necessary for the first alignment film to crosslink. A manufacturing method of a liquid crystal display device characterized by comprising: In claim 1 or 2 ,
A method for manufacturing a liquid crystal display device, wherein the wavelength of the polarized light is lengthened during the irradiation treatment of the polarized light . In any one of Claims 1 thru | or 3 ,
The wavelength of the polarized light irradiated in the first step is 230 to 270 nm, the wavelength of the polarized light irradiated in the second step is 270 nm to 280 nm, and the wavelength of the polarized light irradiated in the third step Is 280-330 nm, The manufacturing method of the liquid crystal display device characterized by the above-mentioned.

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