JP5237625B2 - Liquid crystal display device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a liquid crystal display device and a manufacturing method thereof, and more particularly to a liquid crystal display device suitable for use in a low temperature environment and a manufacturing method thereof.

  A liquid crystal display device (LCD) has a problem that the response of the liquid crystal display becomes extremely slow because the viscosity of the liquid crystal increases in a low temperature environment. If the response is slow, the moving image may be blurred or the previous image may remain, and the display quality will be significantly impaired. In particular, in liquid crystal display devices used for in-vehicle, outdoor display boards, mobile phones, mobile TVs, etc., it is desired to improve the response speed in a low-temperature environment.

  As a countermeasure, Japanese Patent Application Laid-Open No. 2004-93841 proposes a liquid crystal display device that employs a panel heater that heats the entire liquid crystal cell with a flat heat source provided on a glass substrate. Japanese Patent Laid-Open No. 2005-24866 proposes a liquid crystal display device that employs an infrared LED as a heat source and irradiates the entire cell surface with a light guide.

JP 2004-93841 A Japanese Patent Laid-Open No. 2005-24866

  In the proposal described in Japanese Patent Application Laid-Open No. 2004-93841, the liquid crystal layer to be originally heated cannot be directly heated, but is heated through a glass substrate or a polarizing plate, so that the thermal efficiency is low. Therefore, it is difficult to adopt in portable devices with limited power.

  In the proposal described in Japanese Patent Laid-Open No. 2005-24866, it is considered that absorption of irradiated infrared rays is mainly performed by a polarizing plate, and the liquid crystal layer to be heated depends on the infrared absorption characteristics of the liquid crystal material itself, It is thought that thermal efficiency is low.

  An object of the present invention is to provide a liquid crystal display device with improved response speed in a low temperature environment.

According to one aspect of the present invention, a pair of opposing substrates, a liquid crystal layer sandwiched between the pair of substrates, an electrode pattern formed on each liquid crystal layer side of the pair of substrates, and the pair of substrates A functional material film that is formed on the liquid crystal layer side of the electrode pattern on at least one of the substrates and that contains a component that absorbs infrared wavelength light, and irradiates the functional material film with infrared wavelength light. the device and the viewing containing component which absorbs light of the infrared wavelength benzodifuranone compound, or a liquid crystal display device is any one of polyaniline is provided.

According to another aspect of the present invention, (a) a step of preparing a pair of substrates each having an electrode, and (b) infrared light on the side of the substrate on which each electrode is formed. A step of forming a functional material film containing a component to be absorbed; and (c) the pair of substrates are bonded to each other so that the surfaces on which the functional material film is formed face each other and have a gap. look including the step of holding the liquid crystal, components benzodifuranone compounds that absorb light of the infrared wavelength, or a method of manufacturing a liquid crystal display device is any one of polyaniline is provided.

  In a low temperature environment, the response speed of the liquid crystal display device is improved.

  FIG. 1 is a schematic sectional view of a liquid crystal display device according to an embodiment. A liquid crystal display device according to an embodiment of the present invention mainly includes a liquid crystal display unit 101 and a light unit 102 (here, a backlight unit). The light source of the light unit 102 includes, for example, an LED used in a normal backlight and an IR (infrared) LED that irradiates near infrared rays. A diffusion plate 103 is provided between the liquid crystal display unit 101 and the light unit 102.

  A normal LCD has a liquid crystal sandwiched between glass substrates. The infrared transmittance of the glass substrate having a wavelength of about 3 μm or more is low. When the alignment film is heated using infrared rays, it is desirable that the alignment film is not absorbed by the glass substrate.

  The inventors use near infrared rays having a wavelength of 3 μm or less in order to reduce absorption on the glass substrate, and further add a material that absorbs near infrared rays to the alignment film, so that near infrared rays of about 3 μm or less are applied to the alignment film. It was intended to improve the response speed of the liquid crystal display part by absorbing. By irradiating near-infrared rays, the near-infrared rays that have passed through the glass substrate are directly absorbed by the alignment film, and the alignment film in contact with the liquid crystal layer is heated by the energy of the absorbed light, and the liquid crystal layer is heated by the heat. The aim is. Therefore, the light unit 102 includes at least one kind of near-infrared light emitting device. As a general near infrared light emitting device, a near infrared LED (light emitting layer: GaAs compound semiconductor or the like) having a wavelength of 780 nm to 960 nm is used. Here, an infrared LED having an output of 50 mW and a peak wavelength of 880 nm is used.

  FIG. 2 is a cross-sectional view of the liquid crystal display unit 101, and a method for creating the same will be described. Here, an embodiment of the liquid crystal display unit 101 in which the liquid crystal cell is a TN (twisted nematic) liquid crystal cell will be described.

  A transparent ITO film is formed on each of the two glass substrates 1A and 1B by CVD, vapor deposition, sputtering, or the like, and a desired ITO electrode pattern 2 and external extraction wiring 21 are formed by photolithography. An insulating film 4 is formed on the glass substrate with the ITO electrode pattern 2 by flexographic printing. The insulating film 4 is not essential, but is desirably formed to prevent a short circuit between the upper and lower substrates. As a method for forming the insulating film, a method such as vapor deposition or sputtering may be performed using a metal mask in addition to flexographic printing.

  Next, an alignment film 5 having substantially the same pattern as the insulating film 4 is formed on the insulating film 4 by spin coating. At the time of forming the alignment film 5, a near-infrared absorbing material is added to the alignment film material before solidification with stirring by 5 wt%. The near infrared absorbing material will be described later. Here, spin coating is performed at a spinner rotational speed of 2000 rpm for 30 seconds to form an alignment film 5 having a thickness of about 700 mm. The alignment film 5 may be formed by flexographic printing, ink jet printing, or the like. In Example 1, SE-410 (manufactured by Nissan Chemical Industries) is used as the alignment film material.

  Next, a rubbing process is performed. The rubbing is a process in which a cylindrical roll wound with a cloth is rotated at high speed and rubbed on the alignment film 5. The rubbing is performed so that the twist angle of the liquid crystal 3 between the upper and lower substrates becomes 90 ° (left twist). In the case of TN-LCD, it is preferable that the pretilt angle is low (2 ° or less with respect to the substrate plane).

  The sealing material 6 is screen-printed in a predetermined pattern. A dispenser may be used for forming the sealing material 6 instead of screen printing. A thermosetting ES-7500 (manufactured by Mitsui Chemicals) is used as the sealing material, but a photo-curing material or a combined light / heat sealing material may be used. This sealing material 6 contains several percent of glass fibers having a diameter of 6 μm.

  The conductive material 7 is printed at a predetermined position. Here, screen material is printed at a predetermined position as a conductive material 7 containing a sealant ES-7500 containing several percent of styrene balls plated with 6.5 μm Au.

  The sealing material pattern 6 and the conductive material pattern 7 are formed only on the upper substrate 1B, and a gap control material is sprayed on the lower substrate 1A by a dry spraying method. A plastic ball of 6 μm is used as the gap control material, but a true sphere made of silica may be used.

  The two substrates 1A and 1B are stacked into cells at predetermined positions so that the alignment film 5 is on the inside, and the sealing material 6 is cured by heat treatment in a pressed state.

  Next, the glass substrate is scratched with a scriber device, and is divided into a predetermined size and shape by breaking to create empty cells.

  The liquid crystal 3 is injected into the empty cell by an injection method utilizing capillary action, and then the injection port is sealed with an end seal material. Thereafter, the glass substrate is chamfered and cleaned to form a liquid crystal cell 101c. When a polarizing plate 8 in parallel Nicol or crossed Nicol arrangement is disposed outside the upper and lower glass substrates, an LCD 101 is obtained.

  The near-infrared absorbing material added to the alignment film will be described. The inventors have prepared a sample SA (the alignment film added with the material A) of the liquid crystal display device in which a benzodifuranone compound (referred to as a material A) and polyaniline (referred to as a material B) are respectively added to the alignment film as near-infrared absorbing materials. Liquid crystal cell) and SB (liquid crystal cell having an alignment film to which material B is added). A polarizing plate is not arranged.

  With respect to the samples SA and SB of the liquid crystal cell 101c, the spectral transmittance was measured.

  FIG. 3A shows a measurement system. As shown in the figure, a projector 9 with a spectroscopic function is disposed on the lower (rear) substrate side of the liquid crystal cell 101c, and an analyzer 10 is disposed on the upper (front) substrate side. The intensity of light detected by the analyzer 10 when the light intensity from the projector 9 before passing through the liquid crystal display unit 101 when no voltage is applied is defined as 100% was measured as transmittance (%).

  FIG. 4 shows the spectral transmittance of the sample from the visible region to the near infrared region. As a comparative example, the spectral characteristics of a liquid crystal cell having an alignment film to which no near-infrared absorbing material is added are shown. As shown in FIG. 4, the liquid crystal cells SA and SB in which a near-infrared absorbing material is added to the alignment film have lower transmittance in the near-infrared region. From this data, it can be seen that Material A and Material B absorb near infrared rays.

  Next, the polarizing plate 8 was attached to the above liquid crystal cell sample in a parallel Nicol arrangement, and a TN mode liquid crystal display unit 101 was produced. The voltage-transmittance characteristics under low temperature (−30 ° C.) of the manufactured liquid crystal display unit 101 were measured.

  FIG. 3B shows the measurement system. LCD-5000 (made by Otsuka Electronics) was used for the measurement. First, while changing the voltage applied to the liquid crystal display part 101, near infrared rays were irradiated from IR-LED (output 50mW, peak wavelength 880nm). The distance between the liquid crystal cell and the IR-LED is about 50 mm. In this state, the light emitted from the projector 9 and passed through the liquid crystal display unit 101 was measured by the analyzer 10, and the voltage-transmittance characteristics were measured.

  FIG. 5 shows voltage-transmittance characteristics. As shown in the figure, a large difference in voltage-transmittance characteristics was not observed between the liquid crystal display part (SA, SB) having an alignment film to which a near-infrared absorbing material was added and the liquid crystal display part that was not.

  Next, the optimum voltage for obtaining the maximum contrast is obtained from the above voltage-transmittance characteristics, and the near duty infrared rays are irradiated from the back side toward the liquid crystal layer of the liquid crystal display unit, and 1/4 duty driving, response characteristics at the optimum voltage. Was measured at a low temperature (−30 ° C.). Response measurements were performed before near-infrared irradiation (irradiation time 0) and 1 minute, 2 minutes, 3 minutes, 4 minutes, and 10 minutes after irradiation, respectively.

  FIG. 6 shows sample response characteristics. The vertical axis represents the rise time (msec) of the liquid crystal, and the horizontal axis represents the irradiation time (minute) of the near infrared LED. As shown in the figure, samples SA and SB have a shorter rise time than the comparative example. Moreover, it can be said that the response time is shortened in a short time after activation of the liquid crystal display device because the rise time is rapidly shortened to near-infrared LED irradiation time of about 1 minute and then saturated.

The inventors have added a near-infrared absorbing material to the alignment film, so that the near-infrared absorbing material in the alignment film absorbs near-infrared light, and the absorbed near-infrared energy becomes thermal energy, and the alignment film is aligned. It was considered that the liquid crystal layer in contact with the film was heated to shorten the response time of the liquid crystal.
(Other examples of near-infrared absorbing materials)
Note that material A has a good meltability in an organic solvent and the like, and material B has a high heat resistance (about 300 ° C.), and any substance having similar characteristics can be used as a near-infrared absorbing material. It will be possible. Examples of near-infrared absorbing materials applicable to the examples are benzodifuranone compounds, polyanilines, cyanine dyes, polymethine dyes, phthalocyanine compounds, aminium compounds, diimonium compounds, nickel-dithiol compounds, azide compounds, immonium dyes, diimmonium. Dyes, triallylmethane dyes, naphthoquinone dyes, anthraquinone dyes, squarylium dyes, phthalocyanine dyes, naphthalocyanine dyes, nickel-dithiol complex dyes.

  FIG. 7 shows a liquid crystal display device considered as an application example. The liquid crystal display device shown in FIG. 7 is an outdoor display board for roads. The outdoor display board needs to display quickly even in a low temperature environment. For example, for a car that exceeds speed regulation, if you want to display a `` slow down '' after sensing the speed excess with a sensor, if the liquid crystal operation is slow, the car will pass before the display Because there is a possibility. If the present invention is applied, the operation speed of the liquid crystal is increased, and a good display function can be maintained even in a cold region.

  Further, even when the voltage applied to the liquid crystal display unit 101 is OFF at a low temperature, if the infrared LED is turned on, the liquid crystal layer does not cool and a display signal is input to the liquid crystal display unit 101. Will be able to respond quickly.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto.

  8A and 8B show other forms of the light unit 102. FIG. As shown in FIG. 8A, as the light unit 102, the light of the side light unit (a unit in which a cold cathode tube or the like and an infrared light source are mixed) 102 is irradiated from the lateral direction to the light guide plate 103b, and the liquid crystal display unit 101 is provided. A form in which light is guided in a direction may be used.

  Further, as shown in FIG. 8B, light from a light unit (a unit arranged with a cold cathode tube and an infrared light source) 102 is emitted from the front surface of the liquid crystal display unit 101 through a light guide plate 103b. It may be in the form of a front light unit in which the liquid crystal display unit 101 is irradiated by bending and irradiating and placing the reflector 104 on the back surface to reflect light. Usually, in the liquid crystal display device in the reflection mode, the liquid crystal layer does not warm because there is no backlight such as an incandescent lamp. However, if an infrared LED is incorporated in the light unit as in this application example, the functional material film is heated by infrared light and the liquid crystal layer is heated by the warmed functional material film, so use another heating device. It can be heated with low power consumption and response performance can be maintained.

  The injection method of the liquid crystal into the liquid crystal cell may be a vacuum injection method or a drop injection method (ODF). When the vacuum injection method is used, one injection port is sufficient. In the case of the dropping injection method, the injection port is not provided, and the liquid crystal is dropped and injected before the upper and lower substrates are bonded together.

  In addition, the light from the infrared light source is converted into linearly polarized light parallel to the polarizing plate transmission axis using a polarization splitter or the like, so that a decrease in thermal efficiency due to absorption by the polarizing plate can be suppressed.

  In the specification, a near-infrared absorbing material is added to the alignment film, but a film for absorbing near infrared (this film can be said to be a functional material film as well as the alignment film and insulating film) is separated from the alignment film by liquid crystal. You may form in a cell.

  Furthermore, although the case where the mode of the liquid crystal cell is TN has been described, S (super) TN, vertical alignment, IPS (In-Plane Switching), OCB (Optical Compensated Bend), PN (Polymer Network), GH (Guest Host) The embodiments will be applicable to all other liquid crystal cell modes.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.

FIG. 1 is a schematic cross-sectional view of a liquid crystal display device. FIG. 2 is a cross-sectional view of the liquid crystal display unit. 3A and 3B are schematic diagrams of the measurement system. FIG. 4 is a graph of spectral transmittance versus wavelength. FIG. 5 shows the voltage-transmittance characteristics of the sample. FIG. 6 is a graph showing the response characteristics of the sample. FIG. 7 shows an outdoor display panel to which a liquid crystal display device is applied. 8A and 8B are examples of the light unit.

Explanation of symbols

1A, 1B Substrate 2 Electrode 2l Wiring 3 Liquid crystal 4 Insulating film 5 Alignment film 6 Sealing material 7 Conductive material 8 Polarizing plate 9 Projector 10 Analyzer 101 Liquid crystal display unit 101c Liquid crystal cell 102 Light unit 103 Diffusion plate 103b Light guide plate

Claims (4)

A pair of opposing substrates;
A liquid crystal layer sandwiched between the pair of substrates;
An electrode pattern formed on the liquid crystal layer side of each of the pair of substrates;
A functional material film that includes a component that absorbs light of an infrared wavelength, and is formed closer to the liquid crystal layer than the electrode pattern in at least one of the pair of substrates;
A device for irradiating a light in the infrared wavelength to the functional material film seen including,
A liquid crystal display device, wherein the component that absorbs light of the infrared wavelength is either a benzodifuranone compound or polyaniline . The functional material films, the liquid crystal display device according to claim 1, wherein the alignment layer formed on both of the pair of substrates. (A) preparing a pair of substrates each having an electrode;
(B) forming a functional material film containing a component that absorbs light of infrared wavelengths on the side of the substrate on which each electrode is formed;
(C) said pair of substrates, said with functional material film face each other surfaces to each other which are formed, bonded together with a gap, it viewed including the step of sandwiching a liquid crystal in the gap,
A method for producing a liquid crystal display device, wherein the component that absorbs light of the infrared wavelength is either a benzodifuranone compound or polyaniline . The method for manufacturing a liquid crystal display device according to claim 3 , wherein the functional material film is an alignment film formed on both of the pair of substrates.

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