DESCRIPTION TITLE OF THE INVENTION: LIQUID CRYSTAL DISPLAY DEVICE TECHNICAL FIELD [0001] The present invention relates to liquid crystal display devices each having liquid crystal sealed between a color filter and a thin film transistor (TFT) substrate. BACKGROUND ART [0002] A color filter for use in a liquid crystal display device includes, on a substrate, colored layers of three colors, that is, red, green, and blue, and black matrixes, and the colored layers form pixels, and the black matrixes are provided between each pixel for blocking light. A TFT substrate having a plurality of thin film transistors (including pixel electrodes, switching elements formed of a semiconductor, and insulating film layers), and a source wiring and a gate wiring, is provided so as to oppose the color filter. Liquid crystal is sealed between the color filter and the TFT substrate. [0003] In a process of producing the color filter, patterning is performed in a photolithography method to form the colored layers and the black matrixes. At this time, an exposure method (hereinafter, referred to as a "small mask continuous exposure method") using a plurality of small photomasks may be used. [0004] FIG. 6 is a schematic diagram illustrating an exposure method used in the process of producing a color filter, and illustrating the small mask continuous exposure method. [0005] In an exposure device for use in the small mask exposure method, a plurality of exposure heads 90 each having a mask smaller than a substrate 94 are positioned so as to be aligned in a plurality of rows. The exposure heads 90 in a row are positioned between adjacent exposure heads 90 in another row without space such that pitches between the mask patterns formed on each photomask become uniform. [0006] An exposure process is repeated multiple times, while the substrate 94 having the photoresist applied thereto is being conveyed in the Y-axis positive direction (the direction indicated by an arrow in the drawings) relative to the plurality of exposure heads 90 aligned as described above, so that pattern can be formed over the entire surface of the substrate 94 through baking. CITATION LIST PATENT LITERATURE [0007] Patent Literature 1: Japanese Laid-Open Patent Publication No. 2007-121344 Patent Literature 2: Japanese Laid-Open Patent Publication No. 2008-216593 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION [0008] In a case where colored patterns are formed on the color filter by using the small mask continuous exposure method as described above, a problem arises that variations of the formed colored patterns occur, due to misalignment of the exposure heads 90 including joining portions thereamong, in portions (near portions indicated by the alternate long and two short dashes lines in FIG. 6. Hereinafter, these portions may be also referred to as "joining portions") which are exposed to light in the joining portions of the exposure heads 90 [0009] FIG. 7 is a cross-sectional view of an exemplary schematic structure of a conventional liquid crystal display device. The alternate long and two short dashes line in FIG. 7 corresponds to any one of the alternate long and two short dashes lines indicated in FIG. 6, and represents a position of the joining portion on the substrate. A portion of the color filter indicated to the left of the alternate long and two short dashes line, and a portion of the color filter indicated to the right of the alternate long and two short dashes line are exposed to light by different exposure heads, respectively. [0010] A conventional liquid crystal display device 91 includes a color filter 92 and a TFT substrate 93 which are positioned so as to oppose each other. On a substrate 94 of the color filter 92, black matrixes 95a and 95b, and colored layers 96a, 96b, 97a, and 97b are formed. On a substrate 99 forming the TFT substrate 93, light shielding sections 100a and 100b are formed so as to oppose the black matrixes 95a and 95b, respectively. The light shielding sections 100a and 100b are each a region in which metal wiring connected to the thin film transistor provided on the TFT substrate 93 is formed. [0011 ] In pixel areas to the left of the joining portion (the alternate long and two short dashes line), the colored layers 96a and 97a formed on pixel positions, respectively, on the substrate 94 partially overlap the black matrix 95a. Since the colored layer 96a overlaps the black matrix 95a, a ridge 118a (the thick line portion in the drawings) having an upper edge 119a as a vertex is formed, and since the colored layer 97a overlaps the black matrix 95a, a ridge 128a having an upper edge 129a as a vertex is formed. It is to be noted that each of the upper edges 119a and 129a continues linearly in the Y-axis direction. Further, an overlap width of an overlap portion in which the colored layer 96a overlaps the black matrix 95a is represented as W91, and an overlap width of an overlap portion in which the colored layer 97a overlaps the black matrix 95a is represented as W92. [0012] Next, also in pixel areas to the right of the joining portion (the alternate long and two short dashes line), the colored layers 96b and 97b formed on pixel positions, respectively, on the substrate 94 partially overlap the black matrix 95b. Similarly, since the colored layer 96b overlaps the black matrix 95b, a ridge 118b having an upperedge 119b as a vertex is formed, and since the colored layer 97b overlaps the black matrix having an upper edge 129b as a vertex is formed. An overlap width of an overlap portion in which the colored layer 96b overlaps the black matrix 95b is represented as W91, which is the same as the overlap width in the pixel areas to the left of the joining portion. However, in a case where misalignment of positions of the exposure heads occurs when the colored layer 97b is exposed to light, an, overlap width of an overlap portion in which the colored layer 9aoverlaps the black matrix 9a is represented as W93(