JP5390177B2 - Liquid crystal display element, photographing apparatus, and method of manufacturing liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display element, a photographing apparatus, and a method for manufacturing a liquid crystal display element.

  In recent years, high-brightness type pseudo white LEDs are often used as light sources for portable terminals (cell phones, etc.), digital still cameras (DSC), digital video cameras (DVC), etc. Came.

  Auxiliary light, strobe light, etc., which uses an LED as a light source used in a conventional portable terminal or the like, has a phosphor color (yellow) that is noticeable to the user, and the design is remarkably impaired. In particular, there were cases where the matching with the body color was poor. In terms of performance, in order to suppress the phosphor color, measures such as reducing the appearance of the light source part or covering the light source part with a filter or the like to make it inconspicuous have been taken. The performance was significantly impaired.

  With respect to the above-described problems, the light emitting member is exposed from the window portion of the strobe light emitting unit by using a negative (light-shielding) liquid crystal to hide the color of the light emitting member, for example, the yellow color of the phosphor of the white LED. There has been proposed a camera with a strobe light emitting device that does not appear, does not disturb the design balance of the entire camera, and does not impair the aesthetic appearance (see, for example, Patent Document 1). In such a camera with a strobe light emitting device, a negative liquid crystal display element is disposed in front of the strobe light emitting unit, and the negative liquid crystal display element is driven before the strobe light emitting unit emits light.

JP 2004-37730 A

  In the method of hiding the light emitting part using the negative type liquid crystal as described above, since the polarizing plate is used, the transmittance of the light emitted from the light emitting part is 50% or less in the transmission state (ON voltage application state), and the strobe And so on.

  In addition, it is very difficult to match the color of the liquid crystal display element on the front surface of the light emitting unit with the body color of the portable terminal or the like in the non-transmissive state. When matching with a body color using a colored polarizing plate, it becomes dark because the reflectance of the polarizing plate is low, and only a low-saturated color can be produced, so it cannot be matched with a colorful body color. In addition, the color of the stroboscopic light changes, making it impossible to produce white, and the image quality is significantly reduced.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a photographing apparatus capable of improving design performance without impairing the performance of a light source by using a liquid crystal display element arranged in front of the light source, and a method for manufacturing the liquid crystal display element used in the present invention. Is to provide.

According to an aspect of the present invention, a liquid crystal display element includes a pair of transparent substrates arranged to face each other at a predetermined interval, a transparent electrode having a predetermined shape formed on the opposite surface side of the transparent substrate, and the transparent An alignment film formed on the opposite surface side of the substrate and subjected to alignment treatment; and a liquid crystal layer sandwiched between the pair of substrates. The liquid crystal layer includes a liquid crystal material having a positive Δε, a chiral agent, A pixel portion that includes a chromatic dye and a photopolymerizable monomer cured product, and switches between a colored state and a non-colored state of the liquid crystal layer by switching between OFF and ON of a driving voltage applied to the transparent electrode; A display region is formed including a non-pixel portion that is disposed outside the pixel portion and in which the liquid crystal layer is colored in a single color with two or more gradations so as to form a predetermined pattern.
According to another aspect of the present invention, a method of manufacturing a liquid crystal display element according to the above aspect includes (a) a step of preparing a pair of transparent substrates each having an electrode, and (b) the pair of substrates. A step of laminating with a gap; (c) 0.5 to 5 wt% of a photopolymerizable material, a dichroic dye and a chiral agent are added to the gap between the pair of substrates, and a liquid crystal having a positive Δε is formed. And (d) after the step (c), a step of performing ultraviolet exposure, wherein the step (d) partially applies ultraviolet rays according to the predetermined pattern while applying a voltage (d1). A step of exposing, and (d2) a step of exposing the entire surface without applying a voltage.

  According to the present invention, in a liquid crystal display element arranged in front of a light source, a photographing apparatus capable of improving design characteristics without impairing the performance of the light source, and a method for manufacturing the liquid crystal display element used in the present invention. Can be provided.

  FIG. 1 shows a configuration of a liquid crystal display element 101 according to an embodiment of the present invention. FIG. 1A is a schematic cross-sectional view of a liquid crystal display element 101 according to an embodiment of the present invention. FIG. 1B is a table showing the composition of the liquid crystal 3 according to the example of the present invention. The liquid crystal cell is a guest-host (GH) liquid crystal cell, and the liquid crystal display element 101 is, for example, a front panel of a digital still camera (DSC) (shooting light source such as a shooting lens, strobe, shooting sensor, etc.) Will be described.

  For example, a transparent film of indium tin oxide (ITO) is formed on each of a pair of glass substrates 1A and 1B made of blue glass having a thickness of 0.7 mm (hereinafter, both substrates are simply referred to as glass substrate 1). A film is formed to a thickness of 500 mm by CVD, vapor deposition, sputtering, or the like, and shaped into a desired ITO electrode pattern 2 and external extraction wiring 2L by photolithography. For example, as shown in FIG. 2B, the ITO electrode pattern 2 is formed so that the overlapping portion of the ITO electrode patterns 2 of both glass substrates 1 matches the shape, size, and position of the strobe or lens.

  The patterned glass substrate 1 with ITO is washed, an insulating film material (organic silicon oxide film) is printed on the surface including the ITO of the glass substrate 1 by flexographic printing, and the insulating film 4 is formed by baking to 500- It is formed with a thickness of 2000 mm. The insulating film 4 is not essential, but is desirably formed to prevent a short circuit between the upper and lower substrates. In addition to flexographic printing, an insulating film may be formed by a method such as vapor deposition or sputtering using a metal mask.

  Subsequently, a liquid crystal alignment film 5 is formed on the insulating film 4 in the same pattern as the insulating film 4 by flexographic printing or the like. For example, an alignment film material such as polyamic acid is baked after flexographic printing to form a polyimide film with a thickness of 500 to 800 mm and subjected to a rubbing treatment. Rubbing is a process in which a cylindrical roll wound with a cloth is rotated at high speed and rubbed on the liquid crystal alignment film 5. The rubbing direction is set so that the twist angle of the liquid crystal 3 between the upper and lower substrates is 0 to 360 ° (left twist).

  When the twist angle of the liquid crystal exceeds 240 °, hysteresis (a phenomenon in which the rising voltage-transmission curve and the falling voltage-transmission curve do not match) occurs in the voltage-transmittance characteristics, but only all ON and all OFF are used. If so, there will be no inconvenience. Note that the smaller the twist angle, the lighter the color of the element with respect to the same amount of added dye when the voltage is OFF, but the transmittance when the voltage is turned on (when ON) remains almost unchanged. The contrast becomes lower. Since the transmittance at ON is increased as the amount of added dye is lower, it is desirable that the twist angle is as large as possible in order to improve the optical characteristics of the device. From the above, the twist angle is preferably about 90 to 270 °. In this embodiment, the rubbing process is performed so that the twist is 240 °. The rubbing process may not be performed.

  Next, the sealing material 6 is screen-printed in a predetermined pattern on the surface of one side of the glass substrate 1 (lower substrate 1A). A dispenser may be used to form the sealing material 6 instead of screen printing. For the sealing material, for example, thermosetting ES-7500 available from Mitsui Chemicals is used. It may be a photo-curing material or a light / heat combination type sealing material. A gap control material 7 is added to the sealing material 6. The diameter of the gap control material 7 is selected so that the thickness of the liquid crystal layer 3 is 3 to 15 μm. In this embodiment, in order to set the thickness of the liquid crystal layer 3 to 5 μm, 3 wt% of the gap control material 7 having a diameter of 5 μm is added to ES-7500.

  A glass substrate 1 having the same diameter as the gap control material 7 added to the sealing material 6 of the lower substrate is sprayed on the other surface (upper substrate 1B). In the present embodiment, a plastic ball having a diameter of 5 μm is sprayed as a gap control material 7 by a dry spraying method.

  The two substrates 1A and 1B are overlapped at predetermined positions so that the liquid crystal alignment film 5 is on the inside to form a cell, and heat treatment is performed in a pressed state to cure the sealing material 6. In addition, when using a photocurable sealing material, light processing is performed and the sealing material 6 is hardened.

  Thereafter, the glass substrate is scratched in a predetermined size and shape by a scriber device, and is divided by breaking to create an empty cell.

  A guest-host type liquid crystal 3 is vacuum injected into the empty cell. Here, for example, nematic liquid crystal having a positive Δε (mixture: Δn = 0.210 (20 ° C.)) manufactured by Dainippon Ink and Chemicals, Inc. is used. As shown in FIG. 1B, the pigment to be added is added so that the total amount is 0.5 to 10 wt%. As the pigment, it is desirable to mix a plurality of pigments for fine color adjustment. As the dichroic dye, for example, G-472 manufactured by Hayashibara Biochemical Laboratories, Inc. can be used as a blue dye. In this embodiment, various dyes including G-472 described above are mixed and added to the liquid crystal 3 so as to be 3 wt%. Further, a chiral agent is added to the liquid crystal 3 so that d / p = 0 to 1. In this example, S-811 (Merck) is used as the chiral agent so that d / p = 0.55. The pigment concentration needs to be changed according to the desired color.

  In this embodiment, the above-mentioned G-472 is selected as the dichroic dye. However, various other dichroic dyes can be selected, and thus liquid crystal display elements having various colors can be manufactured. is there. Therefore, the liquid crystal display element 101 according to the present embodiment can be used by matching colors to various colors of DSCs, mobile phones, and the like by appropriately selecting a dichroic dye.

  Further, as shown in FIG. 1 (B), 0.5 to 5 wt% of a photosensitive monomer and about 1 wt% of a reaction initiator are added to the liquid crystal 3. In this embodiment, 3 wt% of acrylate liquid crystalline monomer UCL-001 manufactured by DIC Corporation is added.

  As described above, the addition amount of the photosensitive monomer is set to about 0.5 to 5 wt%. If the addition amount is 0.5 wt% or less, the writing state by ultraviolet exposure may not be maintained. This is because the responsiveness of the liquid crystal 3 may be deteriorated. Although it is possible to increase the amount of addition to about 15 wt%, in this case, when the entire surface is made transparent by applying voltage, the part where the pattern is written and the other part can be visually confirmed, and this is implemented in DSC etc. When the example is applied, the function of the strobe or lens may be impaired.

  Thereafter, the inlet is sealed with an end seal material, and the glass substrate is chamfered and cleaned. Thus, a liquid crystal cell is completed.

Next, the liquid crystal cell is irradiated with ultraviolet rays to photopolymerize the photosensitive monomer. At this time, a desired pattern (characters, numbers, symbols, patterns, patterns, etc.) can be written by performing pattern exposure with the liquid crystal 3 standing in the cell thickness direction instead of exposing the entire surface. Specifically, with 15 V applied to the entire surface of the liquid crystal cell, a 1/3 wavelength (third harmonic) (about 355 nm) light of a YAG laser (wavelength 1064 nm) is spotted to 100 μmφ and scanned using a galvanometer mirror. Exposure. The scan speed of the galvanometer mirror is adjusted so that the amount of irradiation at the exposed location is about 1 J / cm ² . When writing is completed, the entire surface of the liquid crystal cell is exposed to ultraviolet light (irradiation amount of about 1 J / cm ² ) without applying a voltage. Thus, the liquid crystal display element 101 is completed.

  By devising the above-described ultraviolet pattern exposure method, it is possible to write a pattern or the like that requires halftone display such as a photograph. In this case, the voltage applied to the entire cell surface may be synchronized with the pattern exposure written by the galvanometer mirror. For example, the intermediate voltage is 1.5V, 1.7V, 2V, 2.5V, 3V, 5V, 15V. Is selected, the image is classified into eight gradation states, and writing is performed in synchronization with the exposure pattern while increasing the voltage sequentially except for the darkest part. In addition, the lowest voltage (1.5V in this example) is applied to the darkest part (the second darkest part as a whole), and the voltage is increased in order, and the lightest part (transparent part). ) Is applied with the highest voltage (15 V in this example). Finally, UV exposure is performed on the entire surface of the liquid crystal cell without applying a voltage.

  FIG. 2 is a schematic plan view showing an example when the liquid crystal display element 101 according to the embodiment of the present invention is used in a front panel of a digital still camera (DSC). In addition, the part which gave the hatching of the solid line in a figure represents a semi-transparent state, and the part which gave the hatching of the dashed-dotted line represents a transparent state. The portion without hatching represents the darkest portion (the portion exposed to ultraviolet light without application of voltage). In the semi-transparent state (intermediate gradation) portion, it is assumed that the color of the portion in the state where no voltage is applied becomes darker as the hatching interval becomes closer.

  When the entire surface exposure is performed without applying a voltage, as shown in FIG. 2A, the entire surface becomes a dark color and the entire surface is filled. By applying a voltage to the electrodes (pixel portions in the display area) corresponding to the strobes, lenses, and sensor portions of such a liquid crystal display element, the liquid crystal layer 3 corresponding to the electrodes becomes transparent, and FIG. ), The strobe part 11, the lens part 12, and the sensor part 13 become visible. In this case, it is preferable to use a white LED for the strobe (light emitting portion) disposed on the rear surface of the strobe portion 11.

  Note that as described above, when a voltage is applied and ultraviolet exposure is performed in a predetermined pattern, writing is performed even when no voltage is applied to the liquid crystal display element 101 as shown in FIG. Depending on the voltage at the time of writing, the pattern 14H such as letters and symbols is transparent (in the embodiment, a part to which 15V is applied), and the strobe part 11, the lens part 12, the sensor part 13 and the pattern parts 14A to 14G are And translucent (intermediate voltage (1.5 V, 1.7 V, 2 V, 2.5 V, 3 V, 5 V applied, respectively)). In the figure, it is assumed that the pattern portions 14A to 14G have the darkest color of the pattern portion 14A and gradually become lighter and the lightest color of the pattern portion 14G.

  Further, as shown in FIG. 2C, even if predetermined patterns 14A to 14G are written on the entire surface with intermediate gradations, ITO electrodes corresponding to the strobe portion 11, the lens portion 12, and the sensor portion 13 of the liquid crystal display element. By applying a voltage to 2, the liquid crystal layer 3 corresponding to the electrode becomes transparent, and the strobe part 11, the lens part 12, and the sensor part 13 become transparent as shown in FIG. The other non-pixel portions remain in a state where the predetermined patterns 14A to 14G are present. In addition, the pattern 14H, such as a character and a symbol which applied 15V and was exposed to ultraviolet rays, is always in a transparent state. Although not shown, the entire surface can be made transparent by applying a voltage to the entire surface.

  As described above, according to the embodiment of the present invention, when no voltage is applied, the liquid crystal cell of the liquid crystal display element 101 is in a state where the liquid crystal molecules and the dichroic dye are perpendicular to the substrate plane. Becomes transparent. The other part (the part exposed by no voltage application) is colored because the liquid crystal molecules and the dichroic dye are aligned in a horizontal twisted state with respect to the substrate plane when no voltage is applied. When a voltage is applied to the liquid crystal display element 101, as the voltage is increased, as the liquid crystal molecules in the portion exposed without voltage application first stand vertically, the color of the dichroic dye becomes invisible and the portion of the portion is exposed. The coloring state becomes lighter, and eventually the entire surface becomes transparent.

  By using the GH liquid crystal, a polarizing plate is not required, so that a loss of transmitted light is small and a bright reflected color can be expressed. When a color reflector is used, the color becomes dark and dull, but according to this embodiment, a very vivid color can be expressed.

  In addition, the design can be superior without impairing the performance of the light source. That is, according to the present embodiment, the loss of transmitted light can be suppressed, various patterns can be written according to the user's preference, and images that require gradation display such as photographs can also be written. Can do. In addition, since various colors can be expressed, it can be matched with the body color of the apparatus using the liquid crystal display element according to this embodiment.

  In this embodiment, a galvanometer mirror is used, but another method such as using a digital micromirror device (DMD) is also possible. Further, when the same pattern is mass-produced, pattern exposure may be performed using a photomask.

  In addition, the transparent state of the liquid crystal display element 101 can be improved by using an antireflection film. For example, a general antireflection technique such as forming one or a plurality of transparent layers having different refractive indexes with a predetermined thickness can be used.

  In addition, since the patterns (characters, numbers, symbols, patterns, patterns, images, etc.) written as described above cannot be rewritten thereafter, the user name and identification information, and the identification of the device to which this embodiment is applied. It can be used for writing information and the like, and the owner can be confirmed even in the case of theft.

  Note that writing of patterns (characters, numbers, symbols, patterns, patterns, images, etc.) to the liquid crystal display element 101 according to the embodiment of the present invention is performed at the shipping destination after the liquid crystal display element 101 is shipped (corresponding to custom production). can do. An arbitrary pattern is written by applying a voltage, and subsequent writing cannot be performed by whole-surface exposure. For example, when applied to DSC, in order to confirm the strobe light emitting unit or the like before shipment, writing may be performed on only a part, and writing on other parts may be performed at the shipping destination. It should be noted that a part written before shipment cannot be changed, and an arbitrary pattern cannot be written to the part. In order to perform writing at the shipping destination, it is desirable to ship in a light-shielded state.

  In addition, it is desirable to apply a proper voltage, but it may be applied by applying static electricity from the outside. In this case, a liquid crystal response phenomenon can be obtained regardless of the presence or absence of the display electrode. By performing writing while maintaining this response state, a transmissive portion having a desired shape can be formed at an arbitrary position of the liquid crystal display element.

  For writing, in addition to the combination of the YAG laser, galvanometer mirror, DMD, and photomask, UV sources such as UV lamps, UV LEDs, and discharge lamps that can emit UV light, and photomasks, templates, etc. It is possible to use a member that combines openings.

  In addition, the liquid crystal display element 101 according to the embodiment of the present invention can be formed into a film using a flexible transparent plastic film instead of the glass substrate.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

It is the schematic sectional drawing and table | surface showing the structure of the liquid crystal display element 101 by the Example of this invention. It is a schematic plan view which shows an example at the time of using the liquid crystal display element 101 by the Example of this invention for the full surface panel of a digital still camera (DSC).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A, 1B ... Glass substrate, 2 ... ITO electrode, 2L ... Wiring, 3 ... Liquid crystal layer, 4 ... Insulating film, 5 ... Alignment film, 6 ... Sealing material, 7 ... Gap control material, 14 ... Ultraviolet exposure pattern, 101 ... Liquid crystal display element

Claims (7)

A pair of transparent substrates arranged to face each other at a predetermined interval;
A transparent electrode having a predetermined shape formed on the opposite surface side of the transparent substrate;
An alignment film formed on the opposite surface side of the transparent substrate and subjected to an alignment treatment;
A liquid crystal layer sandwiched between the pair of substrates,
The liquid crystal layer includes a liquid crystal material having a positive Δε, a chiral agent, a dichroic dye, and a photopolymerizable monomer cured product,
A pixel unit that switches between a colored state and a non-colored state of the liquid crystal layer by switching between OFF and ON of a driving voltage applied to the transparent electrode;
A liquid crystal display in which a display region is formed including a non-pixel portion that is arranged outside the pixel portion and in which the liquid crystal layer is monochromatic and colored with two or more gradations so as to form a predetermined pattern element. The liquid crystal display element according to claim 1, wherein in the pixel portion, the liquid crystal layer is colored with a single color having two or more gradations when the driving voltage is OFF.   3. The photographing with the liquid crystal display element disposed on the surface according to claim 1, wherein the non-colored portion of the pixel portion or the non-pixel portion is disposed in front of the photographing lens or / and in front of the photographing light source. apparatus.   4. The photographing apparatus according to claim 3, wherein the photographing apparatus is a digital still camera or a mobile phone, and the liquid crystal display element is disposed so as to cover a surface including the photographing lens and / or the photographing light source of the photographing apparatus. The imaging device described. A method for producing the liquid crystal display element according to claim 1, comprising:
(A) preparing a pair of transparent substrates each having an electrode;
(B) bonding the pair of substrates with a gap;
(C) a step of injecting a liquid crystal having a positive Δε by adding 0.5 to 5 wt% of a photopolymerizable material, a dichroic dye and a chiral agent into the gap between the pair of substrates; and (d) the step (C), and a step of performing ultraviolet exposure,
The step (d)
(D1) a step of partially exposing ultraviolet rays according to the predetermined pattern while applying a voltage;
(D2) A method for manufacturing a liquid crystal display element, including a step of exposing the entire surface without applying a voltage.   6. The method for manufacturing a liquid crystal display element according to claim 5, wherein the step (d1) is performed a plurality of times with different voltages to be applied. The method for manufacturing a liquid crystal display element according to claim 5, wherein the predetermined pattern is at least one of a character, a number, a symbol, a design, and an image.

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