JP4765962B2 - Manufacturing method of liquid crystal device - Google Patents

Description

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

  There is a liquid crystal projector as a device for displaying an image on a large screen using a liquid crystal device. Projectors are required to have high brightness and high contrast, and in that respect, a vertical alignment type liquid crystal device is capable of high-contrast display, and has recently been adopted as a liquid crystal alignment method for liquid crystal devices for projectors.

  However, in the vertical alignment method, the liquid crystal stands perpendicular to the substrate surface, and the interaction in the azimuth direction that falls when a voltage is applied is weak. Moreover, when a pixel potential is applied, a horizontal electric field is generated in a direction parallel to the substrate surface from the end of the pixel electrode. Therefore, due to the electric field in the lateral direction, the liquid crystal may fall in various directions, resulting in disclination. When disclination occurs, display defects such as light and dark unevenness, a decrease in contrast, and an afterimage are visually recognized.

For this reason, the liquid crystal is vertically aligned in the display area (pixel portion) to ensure good contrast characteristics, and the liquid crystal is horizontally aligned in the non-display area (non-pixel portion) around the pixel area mainly to align the liquid crystal. It is conceivable to prevent disclination by regulating. A liquid crystal device having such a configuration is disclosed in, for example, Patent Document 1, and in the liquid crystal device disclosed in Patent Document 1, an inorganic alignment film is formed by oblique deposition and the thickness thereof is changed. The orientation angle of the liquid crystal on the alignment film is controlled.
JP 2005-107373 A

  However, in Patent Document 1, the orientation is made different by changing the thickness of the alignment film between the display region and the non-display region. However, the method of changing the film thickness can also be realized using a metal mask or the like. Is considered difficult. In addition, since oblique deposition is almost vertical alignment and it is difficult to realize horizontal alignment, even if the orientation angle is actually reduced, it is not possible to realize an alignment regulating force that is so strong that the influence of the lateral electric field can be ignored.

  In view of such circumstances, the present inventors have proposed an invention relating to a liquid crystal device (Japanese Patent Application No. 2005-348703). According to the configuration of the present invention, the vertical alignment film is arranged on the pixel portion, and the horizontal alignment film is arranged on the non-pixel portion. The upper liquid crystal molecules are uniaxially aligned, so that high quality display is possible.

  By the way, when such an alignment film is formed, it is necessary to perform a rubbing process in order to impart a regulating force in the azimuth direction to the horizontal alignment film. However, rubbing the surface of the pixel electrode on which the vertical alignment film is not formed or rubbing the surface of the pixel electrode on which the vertical alignment film is formed leaves rubbing traces. In the state of applying stripes or voltage, stripes that match the rubbing direction with different gradations occur in the halftone solid state, resulting in deterioration of display quality.

  The present invention has been made in view of the above-described problems of the prior art, and is capable of manufacturing a liquid crystal device having good contrast characteristics and preventing display defects such as disclination with high productivity. It aims at providing the manufacturing method which can be performed.

According to the method for manufacturing a liquid crystal device of the present invention, a liquid crystal layer made of a liquid crystal having negative dielectric anisotropy is sandwiched between a pair of substrates disposed opposite to each other, and includes a plurality of pixel portions, and the liquid crystal layer of the substrate An alignment film is formed on the side, and the alignment film aligns the liquid crystal of the pixel portion with the vertical alignment film for aligning the liquid crystal of the pixel portion, and pretilts with a predetermined azimuth angle. A method of manufacturing a liquid crystal device comprising a horizontal alignment film provided with a step of forming a light shielding film so as to surround a predetermined region on a transparent substrate, and a pixel electrode using a transparent conductor in the predetermined region A positive photoresist that is solubilized by light exposure over the pixel electrode and the light-shielding film as a material for the horizontal alignment film, and an alignment film material layer is formed from the photoresist. And the alignment film material After performing the rubbing process for giving azimuth and polar angle information to the substrate and the rubbing process, the light shielding film is used as a mask from the opposite side of the substrate on which the alignment film material layer is formed. It has the process of performing the said light exposure to the said alignment film material layer, and the process of developing the said alignment film material layer after the process of performing the said light exposure .

  In this way, with the pixel electrode covered with the photoresist (alignment film material layer), the alignment film material layer (photoresist) serving as a horizontal alignment film is rubbed to provide orientation. Therefore, the pixel electrode is prevented from being directly rubbed. If the pixel electrode is directly rubbed, rubbing marks are formed on the pixel electrode, which is visually recognized. In addition, rubbing marks affect the alignment of the vertical alignment film, and the liquid crystal on the horizontal alignment film cannot be aligned at a desired azimuth, resulting in a deterioration in display characteristics. However, according to the manufacturing method of the present invention, since the pixel electrode is prevented from being directly rubbed, it is possible to prevent the display characteristics of the pixel from being deteriorated.

The photoresist is preferably a positive photoresist in which the horizontal alignment film is solubilized by light exposure.
In this way, the horizontal alignment film can be self-patterned using, for example, a light shielding film or wiring provided corresponding to the peripheral portion of the pixel as a mask, and the horizontal alignment film can be formed without using a resist mask or the like. Patterning can be performed with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings, taking as an example a manufacturing method of an active matrix type transmissive liquid crystal device using TFT (Thin-Film Transistor) elements. The technical scope of the present invention is as follows. It is not limited to the following embodiment. In the drawings used for the following description, the scale of each member is appropriately changed in order to make each member a recognizable size.

  First, prior to the description of the manufacturing method of the present invention, the configuration of a liquid crystal device (transmission type liquid crystal device) 1 obtained by the manufacturing method of the present invention will be described with reference to FIGS.

FIG. 1 is an equivalent circuit diagram of switching elements, signal lines, etc. in a plurality of pixels arranged in a matrix of the transmissive liquid crystal device 1.
As shown in FIG. 1, a plurality of pixels arranged in a matrix are formed with a pixel electrode 9 and a TFT element 30 that is a switching element for controlling energization of the pixel electrode 9, respectively. A data line 6 a to which a signal is supplied is electrically connected to the source of the TFT element 30. Image signals S1, S2,..., Sn to be written to the data line 6a are supplied line-sequentially in this order, or are supplied for each group to a plurality of adjacent data lines 6a.

  In addition, the scanning line 3a is electrically connected to the gate of the TFT element 30, and scanning signals G1, G2,..., Gm are applied to the plurality of scanning lines 3a in a pulse-sequential manner at predetermined timing. The Further, the pixel electrode 9 is electrically connected to the drain of the TFT element 30, and the image signal S1, S2,... Supplied from the data line 6a is turned on by turning on the TFT element 30 as a switching element for a certain period. , Sn is written at a predetermined timing.

  A predetermined level of image signals S1, S2,..., Sn written to the liquid crystal via the pixel electrode 9 is held for a certain period with the common electrode described later. The liquid crystal modulates light by changing the orientation and order of the molecular assembly according to the applied voltage level, thereby enabling gradation display. Here, in order to prevent the held image signal from leaking, a storage capacitor 70 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9 and the common electrode.

  FIG. 2 is a diagram showing the display unit of the transmissive liquid crystal device 1, and is a schematic diagram viewed from the surface side of the first substrate on which the pixel electrode 9 is disposed, on which the alignment film (not shown) is formed. It is. The display unit of the liquid crystal device corresponds to the pixel electrode 9 (referred to as the outer periphery 9a) and a display region (pixel unit) P provided on the inner side thereof, and a position between the display regions P, that is, a position surrounded by the display region P A non-display area (non-pixel part) BM provided in the pixel electrode 9 is arranged such that the peripheral edge of the pixel electrode 9 extends over the non-display area BM. The first area A1 is formed to include at least the entire display area P, and the second area A2 is formed in the non-display area BM.

  FIG. 3 is a schematic diagram of a cross section taken along line XX of FIG. As shown in FIG. 3, the transmissive liquid crystal device 1 includes a first substrate 10, a second substrate 20, and a liquid crystal layer 50 sandwiched between these substrates. The first substrate 10 includes a transparent substrate 10A such as glass, a pixel electrode 9 and a light shielding film 13 formed on the substrate 10A, a vertical alignment film 41, a horizontal alignment film 42, and the like. The TFT elements (not shown), wirings (not shown) and the like are formed on the light shielding film 13, and are prevented from being deteriorated by light incident from the substrate 10A side. Further, since the light shielding film 13 is formed, a non-display area BM is defined, and a display area P is defined as a pixel opening between the non-display areas BM.

  A first area A1 is formed on the first substrate 10 so as to include at least the display region P, and the non-display region BM extends at least to the non-display region of the pixel electrode 9. A second area A2 is formed including the peripheral edge 9b. As shown in FIG. 3, the first area A1 and the second area A2 are provided continuously. A vertical alignment film 41 is formed on the pixel electrode 9 corresponding to the first area A1, and a horizontal alignment film 41 is formed on the pixel electrode 9 and the light shielding film 13 corresponding to the second area A2. An alignment film 42 is formed.

The second substrate 20 includes a transparent substrate 20A made of glass or the like, a vertical alignment film 61, a common electrode 21 and the like.
The light shielding film 13 and the horizontal alignment film 42 may also be formed on the second substrate side.

  FIG. 4 is a diagram schematically showing the alignment of the liquid crystal when a voltage is applied between the pixel electrode 9 and the common electrode 21. When a voltage is applied between the pixel electrode 9 and the common electrode 21, the liquid crystal of the liquid crystal layer 50 is aligned according to the voltage, and the light transmitted in the thickness direction of the transmissive liquid crystal device 1 is modulated and transmitted. The type liquid crystal device 1 is capable of gradation display. At this time, in the transmissive liquid crystal device 1 of the present invention, the liquid crystal 52 positioned in the second area A2 is aligned at a predetermined pretilt angle in a state where no voltage is applied. It tilts in the direction it is oriented. Therefore, the liquid crystal 51 located in the first area A1 is oriented in a uniform direction with the liquid crystal 52 being restricted in the direction of tilting when a voltage is applied. That is, the liquid crystal located in the vicinity of the second area A2 in the first area A1 is greatly affected by the operation of the liquid crystal 52 on the peripheral edge portion 9b of the pixel electrode 9 serving as the outer peripheral portion of the second area A2. In particular, the direction in which the liquid crystal 52 falls is restricted to the direction in which the liquid crystal 52 on the peripheral edge 9b falls. As a result, the liquid crystals 51 in the first area A1 all fall down in a uniform direction and are uniformly aligned. Therefore, even if a lateral electric field is generated in the direction parallel to the first substrate 10 from the end of the pixel electrode 9, the liquid crystal 51 in the display region P is prevented from causing alignment failure.

  Further, since the liquid crystal 52 having an orientation different from that of the liquid crystal 51 corresponding to the display region P is disposed only in the non-display region BM, the transmittance of the pixel corresponding to the display region (pixel opening) P is the liquid crystal 51. It is specified only and becomes uniform. Therefore, the transmittance of the pixel can be set as desired. In addition, the liquid crystal 51 corresponding to the display region P can be aligned substantially vertically without applying a voltage because the alignment defect is prevented.

  Next, an embodiment of a method for manufacturing a liquid crystal device according to the present invention will be described using the method for manufacturing the transmissive liquid crystal device 1 as an example.

  5 and 6 are diagrams for explaining a method of manufacturing the liquid crystal device (transmission type liquid crystal device) 1. First, as shown in FIG. 5A, a light shielding film 13 made of Cr (chromium) or the like is formed in a lattice pattern on a transparent substrate 10A made of glass or the like, and the non-display area BM is defined by the light shielding film 13. In addition, a region surrounded by the non-display region BM is set as a display region (pixel opening) P. Subsequently, the TFT element 30, the data line 6a, the scanning line 3a, and the like shown in FIG. Next, the pixel electrode 9 is formed using a transparent conductor such as ITO (Indium Tin Oxide) so as to protrude from the display region P to the non-display region BM, and the first substrate 10 on which the pixel electrode 9 is formed. The precursor 10B is formed. A known method can be used for these steps.

  Next, as shown in FIG. 5B, the material of the horizontal alignment film 42 to be described later is applied on the pixel electrode 9 side of the precursor 10B by using a method such as spin coating, for example. A layer (photoresist) 42a is formed. As this material, for example, UV-solubilized polyimide (positive PI) is used. The thickness of the alignment film material layer 42a is, for example, about 100 nm.

  Then, as shown in FIG. 5C, a rubbing treatment device 55 in which a rubbing cloth is wound around a roller performs rubbing treatment on the alignment film material layer 42a, thereby imparting orientation to the alignment film material layer 42a. . At this time, since the rubbing process is performed with the pixel electrode 9 covered with the alignment film material layer 42a, the pixel electrode 9 is protected from the rubbing process, and scratches such as rubbing marks are formed on the pixel electrode 9. Is prevented.

  Then, as shown in FIG. 5D, ultraviolet rays UV are irradiated from the back side of the substrate 10A (the side opposite to the positive PI coating surface) to perform a predetermined amount of exposure. At this time, since the substrate 10A and the pixel electrode 9 are made of a transparent material, the ultraviolet ray UV is transmitted through the display area P corresponding to the substrate 10A and the ultraviolet solubilizing polyimide on the display area P is exposed, and the Solubilized. On the other hand, in the non-display area BM corresponding to the light shielding film 13, since the ultraviolet ray UV is not transmitted, the photoresist (alignment film material layer) 42a at the position corresponding to the non-display area BM is not exposed.

After the steps as described above, the solubilized (exposed) portion of the photoresist (alignment film material layer) 42a is removed (developed) by wet etching and, for example, in an N ₂ atmosphere at a temperature of about 300 ° C. for about 1 hour. Imidization is performed by heat treatment and annealing. Thereby, as shown in FIG. 5E, the horizontal alignment film 42 corresponding to the non-display area BM is formed, and the second alignment area A2 is formed on the horizontal alignment film 42 by forming the horizontal alignment film 42. Can be formed. Further, the area between the second areas A2 is defined as the first area A1. In this way, the first substrate precursor 10C provided with the horizontal alignment film 42 is formed.

Next, a vertical alignment film is formed using an alignment film material selectively bonded to the pixel electrode 9 among the pixel electrode 9 and the horizontal alignment film 42.
First, the precursor 10C of the first substrate 10 on which the horizontal alignment film 42 is formed is subjected to a drying process for about 3 hours at a temperature of about 150 to 180 ° C., for example, in an N ₂ atmosphere. The container is left in a closed container together with a container having an ODS (Octadecyltrimethylsilane) solution. Then, the container is heated at, for example, 150 ° C. for about one hour, thereby bringing the vapor of the ODS solution into contact with the exposed surface of the pixel electrode 9 of the precursor 10C.

  In this case, the ODS molecule has a methoxysilane serving as an inorganic reactive group, so that it is not bonded to the organic material of the horizontal alignment film 42, and is a pixel made of ITO which is an inorganic material. It binds selectively on the electrode 9 and gives its long chain alkyl group on the pixel electrode 9. Accordingly, the vertical alignment film 41 can be selectively formed on the pixel electrodes 9 exposed between the horizontal alignment films 42. In addition, since rubbing marks or the like are prevented from being formed on the pixel electrode 9, the vertical alignment film 41 formed on the pixel electrode 9 is affected by the rubbing marks and may be given orientation. Is prevented.

  As described above, as shown in FIG. 5F, the first substrate 10 provided with the vertical alignment film 41 in the first area A1 and the horizontal alignment film 42 in the second area A2 is obtained. .

  In addition to the first substrate 10, the second substrate 20 is formed as shown in FIG. In the second substrate 20, a common electrode 21 is formed on a substrate 20 A made of a transparent material such as glass using a transparent conductor such as ITO, and a vertical alignment film 61 is formed on the common electrode 21. . A known method can be used for these steps. For example, a vapor deposition method or the like is suitably used for forming the common electrode 21, and a spin coating method or the like is suitably used for forming the vertical alignment film 61.

  Next, as shown in FIG. 6B, the first substrate 10 and the second substrate are bonded together so that the vertical alignment films 41 and 61 and the horizontal alignment film 42 are inside, and FIG. As shown, the transmissive liquid crystal device 1 is formed by encapsulating a liquid crystal layer 50 between the first substrate 10 and the second substrate 20.

  According to the manufacturing method as described above, since the horizontal alignment film 42 is formed by self-patterning using the light-shielding film 13 as a mask, it is not necessary to separately provide a resist mask or the like for alignment film patterning, and the manufacturing process is performed. The liquid crystal device (transmission type liquid crystal device) 1 can be formed with high productivity. Further, since the vertical alignment film 41 is formed using an alignment film material that is selectively coupled to the pixel electrode 9 out of the pixel electrode 9 and the horizontal alignment film 42, the alignment film pattern of the vertical alignment film 42 is formed. The manufacturing process is simplified because the process of forming the film is omitted and it is not necessary to selectively dispose the material in the alignment film pattern. Therefore, the productivity of the liquid crystal device is improved.

  Further, in the liquid crystal device (transmission type liquid crystal device) 1 formed by the above-described manufacturing method, the alignment defect of the liquid crystal 51 in the display region P is prevented, so that display defects such as disclination are prevented, and the display Since the liquid crystal 51 in the region P is aligned substantially vertically with no voltage applied, the contrast is good, and the pixel electrode 9 is prevented from being scratched such as rubbing marks. The device 1 is capable of high-quality display.

In the present embodiment, the second area A2 is continuously formed between the peripheral portion of the pixel electrode 9 and between the pixel electrodes 9, but may be formed only on the peripheral portion 9b of each pixel electrode 9. . Further, although the light shielding film 13 is independently formed of Cr or the like, for example, a wiring electrode or the like may function as the light shielding film 13.
In this embodiment, the horizontal alignment film 42 is formed using a positive photoresist (alignment film material). However, the alignment film material layer 42a is formed using a negative photoresist, and this is rubbed. After the processing, the horizontal alignment film 42 may be formed by exposing and developing using a metal mask or the like.
Further, as a method of forming the vertical alignment film 41, after forming the horizontal alignment film 42, for example, a solvent containing polysiloxane which is an alignment material that is selectively bonded to the pixel electrode 9 is spin-coated or the like. It may be formed by applying to the surface of the first substrate on which the horizontal alignment film 42 is formed by the liquid phase method and curing at a temperature of about 200 ° C.

[Electronics]
An example of an electronic device including the liquid crystal device according to the above embodiment will be described.
FIG. 7A is a perspective view showing an example of a mobile phone. In FIG. 7A, reference numeral 500 denotes a mobile phone body, and reference numeral 501 denotes a liquid crystal display unit using the liquid crystal device of the above embodiment.

  FIG. 7B is a perspective view illustrating an example of a portable information processing apparatus such as a word processor or a personal computer. In FIG. 7B, reference numeral 600 denotes an information processing apparatus, reference numeral 601 denotes an input unit such as a keyboard, reference numeral 603 denotes an information processing apparatus body, and reference numeral 602 denotes a liquid crystal display unit using the liquid crystal device of the above embodiment. .

  FIG. 7C is a perspective view showing an example of a wristwatch type electronic device. In FIG. 7C, reference numeral 700 denotes a watch body, and reference numeral 701 denotes a liquid crystal display unit using the liquid crystal device of the above embodiment.

  As described above, the electronic apparatus illustrated in FIG. 7 is obtained by applying the above-described liquid crystal device as an example of the present invention to the display portion. Therefore, the display device can display with high contrast and high quality.

[Projection type display device]
Next, a configuration of a projection display device (projector) including the liquid crystal device of the above embodiment as a light modulation unit will be described with reference to FIG. FIG. 8 is a schematic configuration diagram showing a main part of a projection display device using the liquid crystal device of the embodiment as a light modulation device. In FIG. 8, 810 is a light source, 813 and 814 are dichroic mirrors, 815, 816 and 817 are reflection mirrors, 818 is an incident lens, 819 is a relay lens, 820 is an exit lens, 822, 823 and 824 are liquid crystal light modulators, Reference numeral 825 denotes a cross dichroic prism, and reference numeral 826 denotes a projection lens.

  The light source 810 includes a lamp 811 such as a metal halide and a reflector 812 that reflects the light of the lamp. The dichroic mirror 813 that reflects blue light and green light transmits red light out of the light flux from the light source 810 and reflects blue light and green light. The transmitted red light is reflected by the reflection mirror 817 and is incident on the red light liquid crystal light modulation device 822 including the liquid crystal device as an example of the present invention.

  On the other hand, of the color light reflected by the dichroic mirror 813, the green light is reflected by the dichroic mirror 814 that reflects green light, and enters the liquid crystal light modulator 823 for green light that includes the above-described liquid crystal device according to the present invention. . Note that the blue light also passes through the second dichroic mirror 814. For blue light, light guide means 821 comprising a relay lens system including an incident lens 818, a relay lens 819, and an exit lens 820 is provided in order to compensate for the difference in optical path length from green light and red light. Through this, the blue light is incident on the liquid crystal light modulation device 824 for blue light provided with the liquid crystal device as an example of the present invention.

  The three color lights modulated by the respective light modulation devices are incident on the cross dichroic prism 825. In this prism, four right-angle prisms are bonded together, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a cross shape on the inner surface. These dielectric multilayer films combine the three color lights to form light representing a color image. The synthesized light is projected onto the screen 827 by the projection lens 826 which is a projection optical system, and the image is enlarged and displayed.

  Since the projection display device having the above-described structure includes the liquid crystal device as an example of the present invention described above, there is no problem of displaying rubbing streaks, for example, when a rubbing process is performed, and high contrast. And a display device capable of high-quality display.

1 is an equivalent circuit diagram of a liquid crystal device 1 according to the present invention. FIG. 3 is a schematic view of a main part of a display unit of the liquid crystal device 1 as viewed from above. XX sectional drawing of FIG. The figure which shows typically the orientation of a liquid crystal when a voltage is applied. Explanatory drawing of the manufacturing method of the liquid crystal device 1 which concerns on this invention. Explanatory drawing of the manufacturing method of the liquid crystal device 1 which concerns on this invention. FIG. 14 is a perspective view illustrating some examples of the electronic apparatus according to the invention. The figure which shows an example about the projection type display apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transmission-type liquid crystal device (liquid crystal device), 9 ... Pixel electrode, 10 ... 1st board | substrate, 13 ... Light shielding film, 20 ... 2nd board | substrate, 21 ... Common electrode, 41, 61 ... vertical alignment film, 42 ... horizontal alignment film, 42a ... photoresist (alignment film material layer), 55 ... rubbing apparatus, A1 ... first area, A2 ... 2nd area, P ... display area (pixel part), BM ... non-display area (non-pixel part).

Claims (1)

A liquid crystal layer made of a liquid crystal having negative dielectric anisotropy is sandwiched between a pair of substrates arranged opposite to each other, and includes a plurality of pixel portions, and an alignment film is formed on the liquid crystal layer side of the substrate. A liquid crystal device in which the alignment film includes a vertical alignment film for aligning the liquid crystal in the pixel portion, and a horizontal alignment film for aligning the liquid crystal in the peripheral portion of the pixel portion and having a pretilt having a predetermined azimuth angle. A manufacturing method of
Forming a light shielding film so as to surround a predetermined region on a transparent substrate;
Forming a pixel electrode using a transparent conductor in the predetermined region;
Using a positive photoresist that is solubilized by light exposure over the pixel electrode and the light-shielding film as a material of the horizontal alignment film, and forming an alignment film material layer with the photoresist;
Performing a rubbing treatment to give azimuth and polar angle information to the alignment film material layer;
After the step of performing the rubbing process, from the opposite side of the surface on which the alignment film material layer is formed on the substrate, performing the light exposure on the alignment film material layer using the light shielding film as a mask;
And a step of developing the alignment film material layer after the step of performing the light exposure .

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