JP2005215642A - Photomask and method for manufacturing diffusion reflector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask for manufacturing a diffusion reflector having high scattering luminance and to provide a method for manufacturing the diffusion reflector by using the photomask. <P>SOLUTION: The photomask M has a pattern region PA where a unit pattern region A is laid in a matrix. The pattern region PA has a rectangular light transmitting part T in a plurality of numbers laid in a matrix, a circular minute light transmitting part TD in a large number regularly or randomly laid to surround each light transmitting part T, and a light shielding part NT surrounding the TD. Further, a strip portion SS surrounding the light transmitting part T has no minute light transmitting part TD, and the width d of the strip portion SS is 1 μm to 5 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photomask and a method for manufacturing a diffuse reflector using the photomask.

  A small liquid crystal display element of about 2 inches to 4 inches is often used in a mobile phone or a portable information terminal. In such a small liquid crystal display element, a transflective type that can use both a backlight and external light as a light source has become the mainstream because of energy saving requirements.

  For example, in the case of a transflective liquid crystal display element using a TFD (Thin Film Diode) array substrate, a TFD array substrate is disposed on the viewer side, while a color filter is disposed on the opposite side of the viewer, and TFD Liquid crystal is sealed between the array substrate and the color filter. A backlight is placed outside the color filter. The color filter is provided with a diffuse reflection plate having a concavo-convex surface for reflecting light from the viewer side, and a colored resin region formed on the diffuse reflection plate. Has an opening for transmitting light from the backlight to the observer side.

  Such a transflective liquid crystal display element performs reflective display by reflecting external light incident from the viewer side at a portion other than the opening in the diffusive reflector during reflective display. During mold display, transmissive display is performed by emitting light from the backlight to the viewer through the opening of the diffuse reflector.

  As the above-described transflective diffuse reflection plate, for example, one having an opening at a position below the center of each colored resin region is known (see, for example, Patent Document 1).

  Further, in order to manufacture the above-described diffuse reflector, a photolithography method using a photomask is usually used, and productivity of the diffuse reflector is improved particularly in proximity exposure. In the photomask used here, a plurality of light transmitting portions for forming openings are arranged in a matrix, and a plurality of minute light transmitting portions for forming an uneven surface around the light transmitting portions. Is arranged. These minute light transmitting portions mainly transmit diffracted light.

When proximity exposure is performed on the photosensitive resin coated on the substrate through such a photomask, a latent image is formed in the photosensitive resin. And the resin layer which has an uneven | corrugated surface and an opening part is formed by developing this photosensitive resin. Thereafter, a diffuse reflection plate is obtained by forming a reflection film on the uneven surface of the resin layer.
JP 2002-287131 A

  However, when the diffuse reflector is manufactured using the photomask as described above, the opening of the obtained resin layer becomes excessively larger than the light transmission portion of the photomask corresponding to the opening. If a reflective film is formed on the uneven surface of the resin layer in this state, the opening of the diffuse reflector becomes excessively large, and the region of the uneven surface that contributes to scattering becomes small. For this reason, when the diffuse reflector is manufactured using the photomask as described above, the scattering brightness of the obtained diffuse reflector may be insufficient.

  Therefore, an object of the present invention is to provide a photomask for manufacturing a diffuse reflector having high scattering luminance and a method for manufacturing a diffuse reflector using the photomask.

  The photomask of the present invention for solving the above-described problems is a plurality of polygonal first light transmission portions arranged in a row and a plurality of first light transmission portions so as to surround each of the first light transmission portions. A second light transmission portion having a diameter smaller than the diameter of each of the first light transmission portion and each light transmission portion and a light shielding portion surrounding each second light transmission portion. The second light transmission portion includes the first light transmission portion. It is not provided in the belt-like portion extending along at least one side of the first light transmission portion outside the portion, and the width of the belt-like portion is 1 μm or more and 5 μm or less.

  When proximity exposure is performed on the photosensitive resin through the photomask, a latent image is formed in the photosensitive resin by the light transmitted through the first and second light transmission portions. When this photosensitive resin is developed, a resin layer having an opening corresponding to the first light transmission portion and an uneven surface composed of a recess corresponding to the second light transmission portion is formed.

  The light irradiated on the first light transmission part in the proximity exposure is transmitted through the first light transmission part and reaches the photosensitive resin. Thereby, a latent image corresponding to the shape of the first light transmission portion is formed in the photosensitive resin. Here, since the plurality of first light transmission portions are arranged in a row, these latent images constitute a plurality of openings arranged in a row in the resin layer obtained after development. The shape of the opening substantially corresponds to the shape of the first light transmission part.

  Moreover, the light irradiated to the 2nd light transmission part permeate | transmits this 2nd light transmission part, and reaches | attains the photosensitive resin. At this time, mainly diffracted light passes through the second light transmission portion. A latent image is formed on the surface layer portion of the photosensitive resin by the diffracted light. Here, since a plurality of second light transmission portions are arranged, these latent images form a plurality of recesses in the resin layer obtained after development, and these recesses form irregularities on the surface of the resin layer. .

  Here, the belt-like portion not provided with the second light transmission part forms a light shielding part that separates the first light transmission part and the second light transmission part on at least one side of the polygonal first light transmission part. Thus, the light irradiated on the belt-shaped portion in proximity exposure is prevented from reaching the photosensitive resin.

  When the width of the band-shaped portion is less than 1 μm, the first light transmission portion and the second light transmission portion approach too much. For this reason, the diffracted lights that have passed through these light transmission parts overlap each other, so that also in the photosensitive resin between the latent image corresponding to the first light transmission part and the latent image corresponding to the second light transmission part. A latent image may be formed. If the photosensitive resin is developed in this state, the photosensitive resin between the opening and the recess may be removed in the same manner as the opening. In such a case, since the opening becomes excessively large, the region of the uneven surface contributing to scattering is reduced in the vicinity of the edge of the opening. Therefore, the scattering luminance of the obtained diffuse reflector is reduced.

  If the width of the strip portion exceeds 5 μm, the first light transmission portion and the second light transmission portion are excessively separated. For this reason, the separation distance between the latent image corresponding to the first light transmission portion and the latent image corresponding to the second light transmission portion becomes excessively large. When the photosensitive resin is developed in this state, a flat surface is formed between the opening and the recess, and an uneven surface contributing to scattering is hardly formed. For this reason, the scattering luminance of the obtained diffuse reflector is reduced.

  In contrast, in the photomask of the present invention, since the width of the band-shaped portion is 1 μm or more and 5 μm or less, the photosensitivity between the opening corresponding to the first light transmission portion and the recess corresponding to the second light transmission portion. The uneven surface contributing to scattering is easily formed on the resin. That is, since an uneven surface is formed in the vicinity of the edge of the opening of the resin layer obtained, the opening is unlikely to become excessively large. Therefore, when such a photomask is used, a diffuse reflector with high scattering luminance can be obtained.

  Moreover, it is preferable that the strip-shaped portion surrounds the entire side of the first light transmission portion.

  In this case, the belt-shaped portion forms a light shielding portion that separates the first light transmitting portion and the second light transmitting portion on all sides of the polygonal first light transmitting portion. In other words, this belt-like portion becomes a frame portion surrounding the first light transmission portion. Thereby, the light irradiated to the strip | belt-shaped part in proximity exposure is made not to reach photosensitive resin. For this reason, in the obtained resin layer, unevenness | corrugation is suitably formed in the surface of the photosensitive resin used as the frame of the opening part corresponding to a 1st light transmissive part. Therefore, when such a photomask is used, a diffuse reflector with higher scattering luminance can be obtained.

  The photomask of the present invention includes a plurality of first light transmission portions arranged in a row, and a plurality of photomasks that surround each first light transmission portion and have a diameter smaller than the diameter of the first light transmission portion. Two light transmissive portions and a light shielding portion surrounding each first light transmissive portion and each second light transmissive portion, and the second light transmissive portion surrounds the first light transmissive portion so as to surround the first light transmissive portion. It is not provided in the belt-shaped portion extending along the edge of the portion, and the width of the belt-shaped portion is 1 μm or more and 5 μm or less.

  When proximity exposure is performed on the photosensitive resin through the photomask, a latent image is formed in the photosensitive resin by the light transmitted through the first and second light transmission portions. When this photosensitive resin is developed, a resin layer having an opening corresponding to the first light transmission portion and an uneven surface composed of a recess corresponding to the second light transmission portion is formed.

  Here, the band-shaped portion where the second light transmission portion is not provided forms a light shielding portion that separates the first light transmission portion and the second light transmission portion over the entire circumference of the first light transmission portion, and the proxy. The light irradiated to the band-like portion in the Mitie exposure is prevented from reaching the photosensitive resin. And since the width | variety of this strip | belt-shaped part is 1 micrometer or more and 5 micrometers or less, in the resin layer obtained, the unevenness | corrugation which contributes to scattering is formed in the surface of the photosensitive resin used as the frame of the opening part corresponding to a 1st light transmissive part. It becomes easy to form. In other words, an uneven surface is preferably formed over the entire periphery near the edge of the opening of the resin layer to be obtained. Therefore, when such a photomask is used, a diffuse reflector with high scattering luminance can be obtained.

  Moreover, the manufacturing method of the diffuse reflection plate of the present invention includes an exposure step of exposing the photosensitive resin through the photomask of the present invention, and developing the exposed photosensitive resin, thereby providing an uneven surface and A development step of forming a resin layer having an opening, and a reflection film formation step of forming a reflection film on the uneven surface of the resin layer.

  According to such a manufacturing method, a diffuse reflector with high scattering luminance is preferably manufactured.

  According to the present invention, it is possible to provide a photomask for producing a diffuse reflector having high scattering luminance and a method for producing a diffuse reflector using the photomask.

  A photomask according to an embodiment of the present invention and a method of manufacturing a diffuse reflector using the photomask will be described below with reference to the drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate descriptions are omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.

  First, the photomask according to the present embodiment will be described with reference to FIGS.

(Photomask)
FIG. 1 is a plan view schematically showing a photomask M according to this embodiment. The photomask M is used for proximity exposure and is used to manufacture a transflective diffuse reflector. The photomask M includes a pattern area PA in which unit pattern areas A are arranged in a matrix. FIG. 2 is an enlarged view showing the unit pattern region A in the photomask M of FIG.

  The pattern area PA includes a plurality of rectangular light transmission portions T (first light transmission portions) arranged in a matrix, and a large number of regularly and randomly arranged circular microtransmission portions T so as to surround each light transmission portion T. It has a light transmission part TD (second light transmission part) and a light shielding part NT surrounding them.

  The light shielding portion NT is made of a metal or the like that shields light, and the light transmitting portion T and the minute light transmitting portion TD are made of glass or the like that transmits light. Such a photomask M is formed, for example, by forming a patterned metal film MM on a glass substrate MG.

  The light transmitting portion T is, for example, a rectangle of 60 μm × 150 μm, but may be a polygon, a circle, or an ellipse. In any case, the diameter of the light transmission portion T may be twice the average distance from the center of gravity position to the outer periphery. The diameter of the light transmission part T is preferably 10 μm or more. When the diameter of the light transmitting portion T is less than 10 μm, light diffraction becomes significant. In this case, it tends to be difficult to manage the shape and size of the opening formed by irradiating the photosensitive resin with light that passes through the light transmitting portion T. On the other hand, the minute light transmission part TD mainly transmits diffracted light, and has a diameter D smaller than the diameter of the light transmission part T. The diameter D of the minute light transmission part TD is the diameter of a circle.

  The diameter D of the minute light transmission part TD is preferably 3 μm or more and 20 μm or less, more preferably 3 μm or more and 15 μm or less. When the diameter D exceeds 20 μm, there is a tendency that it is difficult to form a latent image having a continuous energy distribution in the photosensitive resin because light diffraction is small when light is transmitted. On the other hand, when the diameter D is less than 3 μm, light diffuses at the minimum exposure gap required in proximity exposure, and it is difficult to form a stable latent image on the surface of the photosensitive resin. .

  Further, in the photomask M, the minute light transmission portion TD is not provided in the band-shaped portion SS surrounding the light transmission portion T. Here, the belt-like portion SS is a belt-like region extending along the entire side of the light transmission portion T outside the light transmission portion T. The width d of the strip portion SS is 1 μm or more and 5 μm or less, and preferably 3 μm or less.

  Note that the unit pattern region A of the photomask M corresponds to one pixel (pixel) of a color filter including a diffuse reflector manufactured using the photomask M. The unit pattern area A is composed of sub unit pattern areas A1, A2, and A3 corresponding to RGB (subpixels) in one pixel. The above-described light transmission portion T is provided at the center of each of the sub unit pattern areas A1, A2, and A3.

  Next, with reference to FIGS. 3A to 3D, a method for manufacturing the diffuse reflector according to the present embodiment will be described. The diffuse reflector is manufactured using the photomask according to the present embodiment.

(Diffusion reflector manufacturing method)
3A to 3D are process cross-sectional views illustrating a method for manufacturing the diffuse reflector R according to the present embodiment. Although only the regions corresponding to the subpixels are shown in the drawing, the regions corresponding to the pixels composed of three subpixels are actually arranged in a matrix.

Application process (a)
First, as shown in FIG. 3A, a photosensitive resin layer 20 is formed on the transparent substrate 1.

  Here, as the photosensitive resin layer 20, for example, a positive resist whose absorptivity is set so that an extinction coefficient indicating a transmittance in the photosensitive region is 0.01 / μm or more and 0.3 / μm or less. Can be used. When the light absorption coefficient in the photosensitive region of the photosensitive resin layer 20 is less than 0.01 / μm, the processability is poor and a lot of exposure energy tends to be required to form unevenness. On the other hand, when the extinction coefficient exceeds 0.3 / μm, the processing depth changes sharply with respect to exposure and development conditions, so that it tends to be difficult to form a stable uneven structure.

Exposure step (b)
Next, as shown in FIG. 3B, proximity exposure (collective exposure) is performed on the photosensitive resin through the photomask M of the present embodiment.

  As a result, a latent image 2c is formed in the photosensitive resin by the light transmitted through the light transmitting portion T and the minute light transmitting portion TD of the photomask M. The latent image 2c includes a latent image 2a and a latent image 2b.

  The light applied to the light transmission part T passes through the light transmission part T and reaches the photosensitive resin. Thereby, the latent image 2b corresponding to the shape of the light transmission part T is formed in the photosensitive resin. The latent image 2b reaches the surface of the transparent substrate 1.

  On the other hand, the light irradiated to the minute light transmission part TD passes through the minute light transmission part TD and reaches the photosensitive resin. At this time, the diameter D of the minute light transmitting portion TD is large enough to mainly transmit diffracted light. The diffracted light forms a hemispherical latent image 2a on the surface layer portion of the photosensitive resin. The latent image 2a does not reach the surface of the transparent substrate 1.

  Further, the belt-like portion SS of the photomask M forms a light-shielding portion that separates the light transmitting portion T and the minute light transmitting portion TD, so that the light irradiated to the belt-like portion SS does not reach the photosensitive resin. (See FIG. 2). For this reason, it is difficult to form a latent image between the latent image 2a and the latent image 2b.

Development step (c)
Next, as shown in FIG. 3C, the exposed photosensitive resin is developed. Here, a developer corresponding to the photosensitive resin may be appropriately selected and used. For example, a hydroxide such as sodium or potassium, an inorganic alkali such as carbonate or bicarbonate, an organic alkali such as organic ammonium, or the like. The solution can be used as a developer. Specifically, the photosensitive resin may be immersed in the developing solution or showered on the photosensitive resin under conditions of 20 ° C. to 40 ° C.

  Then, the developed photosensitive resin is sufficiently washed with pure water and then subjected to heat treatment. In the heat treatment step, the photosensitive resin is melted and softened prior to curing, and a smooth uneven surface is formed. As heat processing temperature, 120-250 degreeC is preferable and 150-230 degreeC is more preferable. Further, the heat treatment time is preferably 10 to 60 minutes.

  As a result, a resin layer 2 having an opening 2T corresponding to the latent image 2b and a concavo-convex surface composed of a recess 2TD corresponding to the latent image 2a is formed. At this time, since the opening 2T and the uneven surface are formed in the same process, the resin layer 2 can be formed easily and stably.

  The arrangement and shape of the opening 2T correspond to the arrangement and shape of the light transmission part T of the photomask M. As shown in FIGS. 1 and 2, the light transmitting portions T have a rectangular shape, and a plurality of light transmitting portions T are arranged in a matrix. Therefore, the openings 2T also have a rectangular shape and are arranged in a matrix.

  The arrangement of the recess 2TD and the shape of the opening surface thereof correspond to the arrangement and shape of the minute light transmission part TD. As shown in FIGS. 1 and 2, the minute light transmission portions TD have a circular shape and are regularly or randomly arranged in a large number. Therefore, the opening surface of the recess 2TD also has a circular shape, and a large number of the recesses 2TD are regularly or randomly arranged on the surface layer of the resin layer 2. By arranging such a recess 2TD, gentle irregularities are formed on the surface of the resin layer 2.

Reflective film forming step (d)
Next, as shown in FIG. 3D, a reflective film 3 made of a metal or the like having a high reflectance is formed on the uneven surface of the resin layer 2. The material constituting the reflective film 3 is preferably pure aluminum, an aluminum alloy (Al—Nd alloy), a silver alloy (Ag—Pd—Cu alloy), or the like. The thickness of the reflective film 3 is preferably in the range of 0.1 to 0.3 μm, and more preferably in the range of 0.15 to 0.25 μm. Here, for example, after depositing the above-described metal over the entire surface to form a metal film, an unnecessary portion of the metal film, that is, a metal film formed in the opening 2T or the like may be removed by etching or the like. At this time, marks not shown can also be formed. Thereby, the diffuse reflector R is completed.

  In the method for manufacturing the diffuse reflector R, the width d of the strip portion SS of the photomask M shown in FIG. 3B is 1 μm or more and 5 μm or less.

  If the width d of the belt-like portion SS is less than 1 μm, the light transmitting portion T and the minute light transmitting portion TD are disposed too close to each other. For this reason, in the exposure step (b), the diffracted lights transmitted through the light transmitting portion T and the minute light transmitting portion TD overlap each other, thereby corresponding to the latent image 2b corresponding to the light transmitting portion T and the minute light transmitting portion TD. There is a possibility that a latent image is also formed in the photosensitive resin between the latent image 2a.

  If the photosensitive resin is developed in the developing step (c) in this state, the photosensitive resin between the opening 2T and the recess 2TD may be removed in the same manner as the opening 2T. In this case, since the opening 2T becomes excessively large, the flat surface of the transparent substrate 1 that functions as a regular reflection surface is exposed in the vicinity of the edge of the opening 2T. For this reason, since the area | region of the uneven | corrugated surface which contributes to scattering becomes small, the scattering brightness | luminance of the diffusion diffuser plate obtained will fall.

  On the other hand, when the width of the belt-shaped portion SS exceeds 5 μm, the light transmission portion T and the minute light transmission portion TD are disposed too far apart. For this reason, in the exposure step (b), the distance between the latent image 2b corresponding to the light transmission portion T and the latent image 2a corresponding to the minute light transmission portion TD is increased.

  In this state, if the photosensitive resin is developed in the developing step (c), a flat surface is formed on the photosensitive resin between the opening 2T and the recess 2TD, so that scattering occurs near the edge of the opening 2T. Contributing uneven surfaces are difficult to form. For this reason, the scattering luminance of the obtained diffuse reflector is reduced.

  On the other hand, in the photomask M, the width d of the band-shaped portion SS is 1 μm or more and 5 μm or less, so that the distance between the latent image 2b corresponding to the light transmission portion T and the latent image 2a corresponding to the minute light transmission portion TD. Is preferred. For this reason, an uneven surface contributing to scattering is easily formed on the photosensitive resin between the opening 2T corresponding to the light transmission portion T and the recess 2TD corresponding to the minute light transmission portion TD. That is, since the uneven surface is formed in the vicinity of the edge of the opening 2T of the resin layer 2 to be obtained, the opening 2T is unlikely to become excessively large. Therefore, if the photomask M of this embodiment is used, the diffuse reflector R with high scattering luminance can be suitably manufactured.

  Furthermore, when the width d of the band-shaped portion SS is 3 μm or less, an uneven surface is more easily formed near the edge of the opening 2T of the resin layer 2 to be obtained. In this case, the scattering brightness of the obtained diffuse reflector is further increased.

  The width d of the strip portion SS is determined in advance to a suitable value in accordance with the exposure apparatus characteristics and various material characteristics in the exposure process (b) and the development process (c). The width d of the strip portion SS is preferably 1/10 or more and 1/2 or less of the minimum resolution line width (resolution limit). For example, when the minimum resolution line width is 10 μm, the width d of the band-shaped portion SS is preferably 1 μm or more and 5 μm or less.

  Furthermore, when the above-mentioned diffuse reflection plate R is used, the color filter CF shown in FIG. 4 can be suitably manufactured. FIG. 4 is a cross-sectional view of a color filter CF including a transflective diffuse reflector R.

  In order to manufacture the color filter CF, first, the above-described diffuse reflector R is manufactured. Then, as shown in FIG. 4, a liquid crystal driving transparent electrode 5 made of a colored resin region 4 </ b> R, a transparent protective film 6, ITO, and the like is sequentially formed on the diffuse reflector R as necessary. Thereby, the color filter CF with high scattering luminance is suitably manufactured. Although only one subpixel (colored resin region 4R) is shown in the drawing, in reality, pixels in which three regions corresponding to the subpixel are adjacent to each other are arranged in a matrix.

  The colored resin region 4R transmits red light, for example, and corresponds to a subpixel. As the colored resin region 4R, dyed resin, dye-dispersed resin, pigment-dispersed resin, or the like can be used. In particular, it is preferable to use a pigment-dispersed resin for the colored resin region 4R in terms of the simplicity of the manufacturing process and weather resistance. Specifically, for example, a resin containing acrylic, polyvinyl alcohol, or polyimide can be used as the resin. Instead of the colored resin region 4R, for example, an inorganic film whose thickness is controlled so as to transmit only light having an arbitrary wavelength may be used. In short, any colorant that does not elute impurities that cause display defects in the liquid crystal described later may be used.

  The diffuse reflection plate R can be used not only for the color filter CF but also as an element substrate for forming wirings and driving elements thereon.

  Furthermore, when the above-described color filter CF is used, the liquid crystal display element LCD shown in FIG. 5 can be preferably manufactured. FIG. 5 is a cross-sectional view of a liquid crystal display element LCD including a color filter CF having a transflective diffuse reflection plate R.

  In order to manufacture the liquid crystal display element LCD, first, the above-described color filter CF is manufactured. Then, as shown in FIG. 5, the transparent pixel electrode 11 is formed on the glass substrate 10 to manufacture the TFD substrate 15. Subsequently, the TFD substrate 15 and the color filter CF are bonded to each other through the seal member 13, and the liquid crystal 9 is injected therein. Further, the polarizing plate 12 is formed on the outer surface of the TFD substrate 15 to complete a single polarizing plate type transflective color liquid crystal display element LCD. In this way, a liquid crystal display element LCD with high scattering luminance is suitably manufactured.

  As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment.

  For example, the shape of the first light transmission portion is not limited to a rectangle, and may be a shape having sides such as a polygon. Even in this case, if a photomask in which the band-like portion extends along at least one side of the polygon outside the polygon is used, a diffuse reflector with high scattering luminance can be manufactured. When the shape of the first light transmitting portion is not rectangular, the diameter of the first light transmitting portion may be twice the average distance from the center of gravity position to the outer periphery.

  In addition, the shape of the first light transmission part may be a shape having no side such as a circle or an ellipse. Even in this case, a diffuse reflector with high scattering luminance can be manufactured by using a photomask in which the band-like portion extends over the entire circumference of the circle so as to surround the circle. When the shape of the first light transmission part is not a circle, the diameter of the first light transmission part may be twice the average distance from the center of gravity position to the outer periphery.

  In addition, the first light transmission parts may be arranged in a line. Even in this case, a diffuse reflector with high scattering luminance can be manufactured.

  In addition, the outer shape of the second light transmission portion is not limited to a circle, and may be a polygon, a ring, or the like, and these shapes may be mixed. At this time, the diameter of the second light transmission part may be twice the average distance from the center of gravity of the polygonal or ring shape to the outer periphery.

  Next, in order to confirm the effect of the present invention, various diffuse reflectors were manufactured and the scattering luminance was measured.

(Example 1)
First, carbon black was added at a predetermined ratio to a positive resist (PR-13 manufactured by Tokyo Ohka Kogyo Co., Ltd.) to prepare a positive resist imparted with light absorbency. Next, this light absorbing resist was apply | coated on the glass substrate, and 100 degreeC * 90 second prebaked with the hotplate, and the light absorbing resist layer was formed. Here, the light-absorbing resist was applied so that the thickness of the light-absorbing resist layer after pre-baking was 1.2 μm. Further, the extinction coefficient indicating the transmittance at the main sensitivity wavelength (405 nm) of the light-absorbing photoresist layer after pre-baking was 0.07 / μm.

Next, the interval between the adjacent rectangular light transmission portions T is 21 μm, a large number of circular micro light transmission portions TD having a diameter of 9 μm are randomly arranged, and the width d of the band-shaped portion SS surrounding the light transmission portion T is 3 μm. A photomask M was prepared (see FIGS. 1 and 2). This photomask M has a unit region A shown in FIG. Then, the light-absorbing resist layer was irradiated with 300 mJ / cm ² of UV light through a photomask M with a proximity gap of 135 μm. Next, the exposed light-absorbing resist layer was developed in a 0.5% KOH solution for 80 seconds.

  Furthermore, after the light-absorbing resist layer after development was washed and dried, the light-absorbing resist layer was heat-treated in a clean oven maintained at 200 ° C. for 20 minutes. Thereby, the resin layer 2 in which the uneven surface and the opening 2T were formed was obtained (see FIG. 3D). Furthermore, an aluminum film having a thickness of 200 nm was formed on the resin layer using a sputtering apparatus to obtain a diffuse reflector. FIG. 6 shows an enlarged photomicrograph of a part of the diffuse reflector. And the diffused reflector and glass were bonded together via glycerin, and it was set as the sample for scattering luminance characteristic evaluation.

(Comparative Example 1)
In the same manner as in Example 1 except that the photomask having the unit region A1 shown in FIG. 7 is used instead of the photomask of Example 1 having the unit region A shown in FIG. An evaluation sample was obtained. As shown in FIG. 7, in the photomask of Comparative Example 1, the light transmission part T and the minute light transmission part TD are in contact with each other. Moreover, the microscope picture which expanded a part of diffuse reflection board manufactured using the photomask of the comparative example 1 is shown in FIG.

(Scattering luminance characteristics evaluation)
Subsequently, the evaluation samples of Example 1 and Comparative Example 1 were placed directly below 80 mm of a ring-shaped light source having an outer diameter of 55 mm, and the scattering luminance was measured using a luminance meter arranged at the center of the ring-shaped light source. This value of the scattering luminance is a relative value when the scattering luminance of the standard white plate is 1. As a result of the measurement, the scattering brightness value of the evaluation sample of Example 1 was 0.58, and the scattering brightness value of the evaluation sample of Comparative Example 1 was 0.54.

  Therefore, it has been shown that if the photomask of Example 1 is used, a diffuse reflector having a high scattering luminance can be manufactured as compared with the case of using the photomask of Comparative Example 1.

It is a top view which shows typically the photomask which concerns on this embodiment. It is an enlarged view which shows the unit pattern area | region in the photomask of FIG. It is process sectional drawing which shows the manufacturing method of the diffuse reflector which concerns on this embodiment. It is sectional drawing of the color filter provided with the transflective diffused reflection board. It is sectional drawing of the liquid crystal display element provided with the color filter which has a transflective diffused reflection board. 2 is an enlarged micrograph of a part of the diffuse reflector in Example 1. FIG. It is a figure which shows the unit area | region of the photomask of the comparative example 1. 4 is an enlarged micrograph of a part of the diffuse reflector in Comparative Example 1.

Explanation of symbols

  T ... light transmission part (first light transmission part), TD ... micro light transmission part (second light transmission part), NT ... light-shielding part, SS ... band-like part, 20 ... photosensitive resin layer, 2TD ... concave part, 2T ... Opening, 2 ... resin layer, 3 ... reflection film.

Claims (4)

A plurality of polygonal first light transmitting portions arranged in a row;
A plurality of second light transmission portions arranged so as to surround each of the first light transmission portions, and having a diameter smaller than the diameter of the first light transmission portion;
A light shielding portion surrounding each of the first light transmission portions and each of the second light transmission portions,
The second light transmission portion is not provided in a belt-like portion extending along at least one side of the first light transmission portion outside the first light transmission portion, and the width of the belt-like portion is 1 μm or more. A photomask that is 5 μm or less. The photomask according to claim 1, wherein the belt-shaped portion surrounds all sides of the first light transmission portion. A plurality of first light transmission portions arranged in a row;
A plurality of second light transmission portions arranged so as to surround each of the first light transmission portions, and having a diameter smaller than the diameter of the first light transmission portion;
A light shielding portion surrounding each of the first light transmission portions and each of the second light transmission portions,
The second light transmission portion is not provided in a belt-like portion extending along the edge of the first light transmission portion so as to surround the first light transmission portion, and the width of the belt-like portion is 1 μm or more and 5 μm or less. Photomask that is. An exposure step of exposing the photosensitive resin through the photomask according to any one of claims 1 to 3,
A development step of forming a resin layer having an uneven surface and an opening by developing the exposed photosensitive resin;
A reflective film forming step of forming a reflective film on the uneven surface of the resin layer;
A manufacturing method of a diffusive reflector including:

Images