JP2006235057A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element with which occurrence of malfunctions such as defective alignment of liquid crystal molecules and disconnection of an electrode, caused by an elevation change due to thickness of a black mask are suppressed, and which is suitable for downsizing and thickness reduction. <P>SOLUTION: On respective mutually opposing inside surfaces of glass substrates 1, 2 placed opposite to each other, a first black mask 4 and a second black mask 8 are arranged by making respective openings 4a, 8a respectively provided on the black masks consistent with each other. Stripe filters 5R, 5G, 5B of respective colors of red, green, blue are arranged on the opening 4a of the first black mask 4 so as to cover it, and a scanning electrode 6 and an alignment layer 7 are laminated thereon. A signal electrode 9 is arranged on the opening 8a of the second black mask 8 so as to cover it, and an alignment layer 10 is attached thereto. On surfaces of the respective alignment layers 7, 10, elevation changes G1, G3 are produced, which are reduced in heights owing to division of the black mask into the first black mask 4 and the second black mask 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display element in which a black mask is provided between pixels.

  In a liquid crystal display element in which liquid crystal is sealed in a pair of opposed substrates and a plurality of pixels for controlling light transmission are disposed, a black mask for blocking light transmission is usually disposed between the pixels. Yes. Therefore, a step due to the thickness of the black mask is formed on the inner surface of the opposing substrate in the vicinity of the boundary between the pixel region and the surrounding non-pixel region.

  The step on the inner surface of the substrate due to the thickness of the black mask described above causes problems such as poor alignment of liquid crystal molecules and disconnection of electrodes, which cause display unevenness. In order to prevent the occurrence of such defects, conventionally, as shown in Patent Document 1, a flattening film is laminated on a black mask, and the surface on which an electrode is formed by absorbing a step due to the black mask is formed. A method of flattening the surface of the alignment film that contacts is adopted.

  However, in the case of the above conventional method, the number of manufacturing steps and material costs for forming the flattening film increase, leading to an increase in cost, and the thickness of the liquid crystal display element itself increases. This is disadvantageous in promoting the reduction in size and thickness of the liquid crystal display module.

In particular, in the case of a black mask made of a resin material that is often used in recent years because a black mask having a complicated pattern can be easily manufactured, the thickness is larger than that of a metal black mask in order to obtain a required light shielding function. As a result, the level difference caused by the black mask is greatly expressed, and the thickness of the planarizing film for absorbing the level difference is also increased. As a result, the thickness of the liquid crystal display element increases, which is further disadvantageous for promoting the reduction in size and thickness of the liquid crystal display module.
JP 2000-155336 A

  The object of the present invention is to suppress the occurrence of defects such as poor alignment of liquid crystal molecules and disconnection of electrodes caused by steps on the inner surface of the substrate due to the thickness of the black mask, and is suitable for reducing the size and thickness of products to be mounted. Another object of the present invention is to provide a liquid crystal display element.

  In the liquid crystal display element of the present invention, a plurality of liquid crystals are sandwiched between a first substrate and a second substrate which are arranged to face each other, and a plurality of black masks made of a light shielding member provided between the first and second substrates. A liquid crystal display element in which a pixel unit is set and performs display by controlling light transmission for each pixel unit, the liquid crystal display element on the inner surface of the first substrate facing the second substrate A first black mask formed in a portion excluding the pixel portion and restricting transmission of light from the portion excluding the pixel portion; and an inner surface of the second substrate facing the first substrate; The second black mask is provided corresponding to the first black mask and restricts the transmission of light.

  According to the liquid crystal display element of the present invention, since the black mask is divided and disposed on the inner surfaces of the pair of substrates sandwiching the liquid crystal, the steps due to the thickness of the black mask are also dispersed and the individual steps. As a result, the occurrence of defects such as poor alignment due to a step is suppressed, and the liquid crystal display element can be reduced in size and thickness.

  The present invention is suitable for a liquid crystal display element in which a color filter that selectively transmits light of a specific wavelength is disposed in an area corresponding to a pixel portion of a substrate on which a first black mask is formed. Even if the edge of the color filter is superimposed on the black mask so that no gap is generated between the black mask and the black mask, the size of the step generated at the boundary is reduced by the amount of the black mask divided on the counter substrate side. As a result, it is possible to provide a color liquid crystal display element suitable for reducing the thickness of the mounted product as well as providing high-quality color display without light leakage and suppressing occurrence of alignment defects.

  In addition, the present invention is suitable for a liquid crystal display element in which the first and second black masks are resin black masks in which a black colorant is mixed in a resin material. In this case, the resin black mask is a metal black. Although the thickness is larger than that of the mask, the steps due to the individual black masks are reduced by dividing the arrangement on both substrates, and as a result, the liquid crystal molecules due to the steps due to the thickness of the black mask are reduced. The occurrence of orientation failure can be significantly suppressed.

Further, in the liquid crystal display element provided with the above-described color filter and resin black mask, the layer thickness of the first black mask on the substrate side where the color filter is provided is T1, and the layer thickness of the second black mask is T2. The ratio of layer thickness T1 to layer thickness T2 is
1 ≦ T2 / T1 ≦ 5
In this range, the step size generated in the vicinity of the boundary between the color filter and the black mask due to the thickness of the black mask is suppressed, and the uniformization of the liquid crystal sealing gap is promoted. Further, the light shielding effect by the black mask can be sufficiently obtained.

  FIG. 1 is a plan view showing a liquid crystal display element as an embodiment of the present invention, and FIG. 2 is a schematic partial cross-sectional view showing the liquid crystal display element taken along line II-II. In FIG. 2, for convenience of explanation, members such as a black mask and a spacer are shown larger than the actual ones.

  The liquid crystal display element of this embodiment is a simple matrix type liquid crystal display element, and as shown in FIG. 1, formed on one of the inner surfaces of the substrates facing each other and on the other inner surface. A plurality of pixels p are defined by a region corresponding to the opening of the black mask made of a light shielding member in the region where the signal electrodes face each other, and the plurality of pixels p are arranged in a matrix.

  A pair of glass substrates 1 and 2 whose planar outer shape is an elongated rectangle are joined to each other with a frame-shaped sealing material 3 with a predetermined gap. A first black mask 4 for restricting light transmission is formed on a portion of the inner surface of the pair of glass substrates 1 and 2 opposite to the other glass substrate 2 except for the pixel portion. Has been. In the first black mask 4, a plurality of openings 4a for allowing light to pass through corresponding to the pixels p are formed in a matrix.

  The first black mask 4 uses, as a material, a black resin paste prepared by mixing a black pigment in a photoresist material such as an acrylic photosensitive polymer or a polyimide photosensitive polymer, and the plurality of openings 4a are formed by photolithography. It is formed in the provided pattern. Thus, by forming the first black mask 4 by photolithography, a black in which the plurality of openings 4a correspond more accurately to the set pixel configuration than when formed by other methods such as a printing method. The mask 4 can be easily formed.

  Here, the film thickness T1 of the first black mask 4 should be optimally set based on the mutual relationship with the film thicknesses of the color filter described later and the second black mask on the opposite side, It is preferably about 0.2 μm to 0.6 μm, and is set to 0.3 μm in this embodiment.

  Color filters 5 that selectively transmit component light of a specific wavelength are respectively deposited on the inner surface of the first substrate corresponding to the openings 4 a of the first black mask 4. In the color filter 5 of the present embodiment, three types of stripe filters 5R, 5G, and 5B that transmit light of each wavelength of red, green, and blue are sequentially arranged along each row of openings 4a (perpendicular to the paper surface). Become. Each stripe filter 5R, 5G, and 5B is formed to have an appropriate width larger than the width of each opening 4a, covers each opening 4a, and has both ends in the width direction as corresponding opening edges of the first black mask 4. It is attached in a superposed state. This reliably eliminates the problem of causing gaps that cause light leakage between the openings 4a of the first black mask 4 and the stripe filters 5R, 5G, and 5B.

  Each of the red, green, and blue stripe filters 5R, 5G, and 5B is described above by a photolithography method using a photosensitive resin material obtained by dispersing and mixing red, green, and blue pigments in a polymer resin. Are precisely formed at predetermined positions. In this case, the thickness of each stripe filter 5R, 5G, 5B is set to about 1.2 μm.

  The surface of the first glass substrate 1 on which the first black mask 4 and the color filter 5 are installed is a surface on which steps corresponding to the thicknesses of the color filter 5 and the first black mask 4 are formed. On this surface, a plurality of scanning electrodes 6 are disposed so as to extend in parallel to a direction orthogonal to the stripe filters 5R, 5G, and 5B. Although not shown, the surface on which the first black mask 4 and the color filter 5 are installed is covered with a transparent protective film to prevent elution of organic components of the color filter 5 made of a resin material. You may wear it.

  The scanning electrode 6 is accurately formed in a predetermined pattern by a photolithography method using a transparent conductive material such as ITO (Indium Tin Oxide). In this case, the scanning electrode 6 made of ITO or the like has a thin film thickness of about 0.03 to 0.06 μm and is formed with respective steps corresponding to the thicknesses of the color filter 5 and the first black mask 4. It is formed so as to follow the surface.

  An alignment film 7 for covering the exposed surfaces of the scanning electrode 6, the color filter 5 and the black mask 4 to regulate the alignment of liquid crystal molecules is uniformly deposited with a uniform film thickness. ing. On the surface of the alignment film 7, a step G1 corresponding to the thickness of the first black mask 4 and a step G2 corresponding to the thickness of the color filter 5 are generated.

  On the other hand, a second black mask 8 is formed on the inner surface of the opposite glass substrate 2. In the second black mask 8, openings 8a are formed in a matrix so as to correspond to the openings 4a formed in the first black mask 4 on the glass substrate 1 side. The opening 8a is formed in a size that is larger than the corresponding opening 4a by a width d over the entire edge. The enlarged width d is preferably set smaller than the overlapping width s obtained by superimposing the color filter 5 on the first black mask 4. As described above, the opening 8a of the second black mask 8 is enlarged by the width d more than the opening 4a of the first black mask 4, so that the positional deviation within the enlarged width d when the glass substrate 1 and the glass substrate 2 are joined together. And an expected area equal to the opening 4a of the pixel p (see FIG. 1) is stably secured.

  Similarly to the first black mask 4, the second black mask 8 is also formed by photolithography using a black resin paste as a material. The film thickness T2 of the second black mask 8 is preferably about 0.8 μm to 1.0 μm, and is set to 0.9 μm in this embodiment.

  Here, the sum (T1 + T2) of the film thickness T1 of the first black mask 4 and the film thickness T2 of the second black mask 8 is the minimum necessary size to ensure the light shielding effect required for the liquid crystal display element. In this embodiment, the thickness of the color filter 5 is substantially equal to 1.2 μm in order to make the liquid crystal sealing gap (gap) uniform even within this range, for example, about 1.0 μm to 2.0 μm. It is preferably set.

And within the preferred range, the ratio of each film thickness T1, T2 (T2 / T1) is:
1 ≦ (T2 / T1) ≦ 5
Even in that,
2 ≦ (T2 / T1) ≦ 4
It is preferable to set to. This is because the film thickness T1 of the first black mask 4 is preferably as thin as possible in order to keep the step height of the color filter 5 on the first black mask 4 small, but if it is too thin, light leakage will occur. This is because there is a possibility that the display quality may be deteriorated due to the occurrence of color purity.

  A signal electrode 9 is provided in each opening 8 a of the second black mask 8. In this embodiment, a plurality of stripe-shaped signal electrodes 9 corresponding to the stripe filters 5R, 5G, and 5B provided on the opposite glass substrate 1 are parallel to the stripe filters 5R, 5G, and 5B. That is, they are installed so as to extend in parallel to each other in a direction perpendicular to the scanning electrode 6 (perpendicular to the paper surface). Similarly to the scanning electrode 6, the signal electrode 9 is accurately formed in a predetermined pattern with a thin film thickness of about 0.03 to 0.06 μm by a photolithography method using a transparent conductive material such as ITO. Yes.

  An alignment film 10 for covering the exposed surfaces of the signal electrode 9 and the second black mask 8 and for regulating the alignment of liquid crystal molecules is uniformly deposited with a uniform film thickness. On the surface of the alignment film 10, a step G3 due to the film thickness T2 of the second black mask 8 is generated. A step due to the film thickness of the signal electrode 9 also occurs, but since the signal electrode 9 is thin, the resulting step is slight and affects the display quality of the liquid crystal display element. is not.

  Each assembly of the glass substrate 1 and the glass substrate 2 configured as described above is joined by a frame-shaped sealing material 3 (see FIG. 1) via a spacer 11. In this embodiment, as shown in FIG. 1, a pair of glass substrates 1 and 2 having different sizes are used, and one end portion 1 a of one large glass substrate 1 is connected to the corresponding end surface of the other small glass substrate 2. It is made to protrude by a predetermined length and is joined.

  In this joining operation, the glass substrates 1 and 2 are accurately recognized by recognizing images of the alignment marks 12, 12 and 13, 13 as position references, which are previously installed in pairs on the glass substrates 1 and 2, with a camera or the like. And it can be positioned and joined easily. Here, the alignment marks 12 and 12 of the glass substrate 1 are respectively arranged at the diagonal corner portions thereof, and the alignment marks 13 and 13 of the glass substrate 2 are the alignment marks 12 and 12 that can obtain the bonding state shown in the figure. It is arranged at each corresponding position.

  These alignment marks 12, 12 and 13, 13 are simultaneously formed of the same material as the first and second black masks 4, 8 provided on the glass substrates 1, 2, respectively. That is, the alignment marks 12, 12 and 13, 13 are formed simultaneously by photolithography using the same black resin paste as that of the first and second black masks 4, 8 as a material. Therefore, both the alignment marks 12 and 13 are formed in the same material as the transparent electrode material, or compared with the case where only one is black because the black mask is provided only on one substrate. 12 and 13 are black and the thickness is moderately thin and the outline is sharply formed so that their visibility is remarkably improved. As a result, the alignment of the glass substrates 1 and 2 can be more accurately and easily performed. Can be implemented.

  Returning to FIG. 2, the spacer 11 is used to regulate the size of the gap between the glass substrates 1 and 2 in which the liquid crystal 14 is sealed. In this embodiment, the spacer 11 is a resin-based granular material. After the spacers are randomly dispersed on the alignment film 7 of one glass substrate 1 assembly, for example, the other glass substrate 2 is bonded with a frame-shaped sealing material 3 so as to be sandwiched between the glass substrates 1 and 2. The size of the gap is regulated within a predetermined range.

  Here, the spacer 11 is provided with the opening 4a of the first black mask 4 so that the gap between the glass substrates 1 and 2 on which the liquid crystal 14 is sealed is uniformly maintained over the entire liquid crystal sealing region. Not only the pixel area Ap but also the non-pixel area An between the pixel areas Ap where the first black mask 4 exists is required to be held equally. In this embodiment, by setting the sum (T1 + T2) of the thicknesses of the first and second black masks 4 and 8 to be substantially equal to the thickness of the color filter 5, the spacer 11 is in the all liquid crystal sealing region. It is held almost evenly.

  As shown in FIG. 1, in a space surrounded by both glass substrates 1 and 2 and a frame-shaped sealing material 3 in a liquid crystal display cell obtained by joining each assembly of a glass substrate 1 and a glass substrate 2. The liquid crystal 14 (see FIG. 2) is injected from a liquid crystal injection port 3 a provided in the frame-shaped sealing material 3 by, for example, a vacuum injection method or the like, and the liquid crystal injection port 3 a is sealed with a sealing material 15. .

  Note that wiring (not shown) drawn from a plurality of signal electrodes 9 (see FIG. 2) and scanning electrodes 6 (see FIG. 2) is routed in a predetermined pattern on the protruding portion 1a of the large glass substrate 1. Connection terminals (not shown) for these wirings are installed in a predetermined arrangement.

  In the liquid crystal display element of the present embodiment configured as described above, the pixel area Ap is defined by the opening 4a of the first black mask 4, as shown in FIG. In this pixel area Ap, there are steps G1 and G3 generated corresponding to the film thicknesses T1 and T2 of the first and second black masks 4 and 8, but the black mask is the first and second black masks. Since the film is divided into 4 and 8, the individual film thicknesses T1 and T2 are reduced, and accordingly, the individual steps G1 and G3 generated on the surfaces of the alignment films 7 and 10 are also reduced. As a result, the occurrence of misalignment of the liquid crystal molecules caused by the step is remarkably suppressed, and the display quality such as display unevenness caused by the misalignment of the liquid crystal molecules is suppressed and the good display quality is stabilized. Can be obtained.

  Incidentally, a case where the black mask is arranged on one substrate without being divided and a flattening film is not provided is shown as a comparative example with respect to the present embodiment as shown in FIG. As is apparent from FIG. 3, in this comparative example, the size of the step G4 generated corresponding to the black mask 31 increases correspondingly because the black mask 31 is thick. Therefore, the alignment difference of the liquid crystal molecules is remarkably generated at the large step G4, and as a result, display defects such as color unevenness are caused and display quality is deteriorated.

  As is apparent from FIG. 2, the step G 2 occurring in the non-pixel area An where the black mask 4 is provided, other than the pixel area Ap, is a comparison that occurs corresponding to the thickness of the color filter 5. However, since the non-pixel area An, even if the alignment defect of the liquid crystal molecules occurs, the display quality is hardly adversely affected.

  As described above, in the present embodiment, the black mask is divided into the first black mask 4 and the second black mask 8 on both of the pair of glass substrates 1 and 2 holding the liquid crystal. The thickness of the black masks 4 and 8 is reduced, and accordingly, the step G1 generated in the pixel area Ap because the color filter 5 and the signal electrode 9 are superposed on the edge thereof is also reduced. As a result, the alignment failure of the liquid crystal molecules caused by the step G1 is suppressed to the extent that display defects such as display unevenness do not occur. Further, since the color filter 5 and the signal electrode 9 are superimposed on the edge portions of the first and second black masks 4 and 8, light leakage between them is reliably prevented, and the first and second black masks are also prevented. Although the individual light shielding effect is reduced by dividing the image into 4 and 8, the necessary light shielding effect is sufficiently ensured by combining these individual light shielding effects, so that a good contrast display can be obtained. As a result, according to the liquid crystal display element of this embodiment, even if a flattening film that is disadvantageous for promoting the reduction in size and thickness is not provided, display unevenness due to a step due to the thickness of the black mask and reduction in contrast are caused. Good display quality in which is eliminated can be stably obtained.

  In addition, since both the glass substrates 1 and 2 are provided with alignment marks 12 and 13 having high visibility made of the same black resin material as the first and second black masks 4 and 8, respectively, the black mask is used as the glass substrate 1. Since the two glass substrates 1 and 2 are divided into two, their joining operations requiring high accuracy for the alignment of the glass substrates 1 and 2 can be easily performed.

  In addition, this invention is not limited to said embodiment. For example, the present invention is effectively applied not only to a liquid crystal display element not provided with a flattening film for eliminating a step, but also to a liquid crystal display element provided with a flattening film. In this case, the thickness of the flattening film can be reduced as much as possible by dividing the black mask on both substrates, and the occurrence of steps due to the thickness of the black mask is substantially eliminated and the thickness is reduced. A high-quality liquid crystal display element in which is promoted can be obtained.

  The present invention is not limited to the simple matrix type color liquid crystal display element as in the above embodiment, but can be widely applied to various liquid crystal display elements such as an active matrix type liquid crystal display element and a monochrome display liquid crystal display element.

It is a top view which shows the liquid crystal display element as embodiment of this invention. It is the fragmentary sectional view which cut | disconnected the said liquid crystal display element by the II-II line | wire of FIG. It is a fragmentary sectional view corresponding to FIG. 2 which shows the liquid crystal display element as a comparative example with respect to the liquid crystal display element of the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st glass substrate 2 2nd glass substrate 3 Frame-shaped sealing material 4 1st black mask 5 Color filter 5R, 5G, 5B Stripe filter (red, green, blue)
6 Scan electrode 7, 10 Alignment film 8 Second black mask 9 Signal electrode 11 Spacer 12, 13 Alignment mark 14 Liquid crystal 15 Sealing material 31 Black mask

Claims (4)

The liquid crystal is sandwiched between the first substrate and the second substrate which are arranged to face each other, and a plurality of pixel portions are partitioned by a black mask made of a light shielding member provided between the first and second substrates. , A liquid crystal display element that performs display by controlling the transmission of light for each pixel unit,
A first black mask formed in a portion excluding the pixel portion on the inner surface of the first substrate opposed to the second substrate and restricting light transmission from the portion excluding the pixel portion;
A liquid crystal comprising: a second black mask provided on the inner surface of the second substrate facing the first substrate so as to correspond to the first black mask and restricting light transmission. Display element.   The color filter that selectively transmits light of a specific wavelength is disposed in an area corresponding to the pixel portion of the first substrate on which the first black mask is formed. Liquid crystal display element.   The liquid crystal display element according to claim 2, wherein the first and second black masks are formed by mixing a black colorant in a resin material. When the layer thickness of the first black mask is T1, and the layer thickness of the second black mask is T2, the ratio of the layer thickness T1 to the layer thickness T2 is
1 ≦ T2 / T1 ≦ 5
The liquid crystal display element according to claim 3, wherein the liquid crystal display element is in a range of