The present invention relates to a boiled egg cooked by boiling an egg, such as an egg of a hen or duck, dipped wholly or partially in a beating medium, such as hot water, and a method for producing the boiled egg, more particularly to a boiled egg with a pattern, on its curved surface after removal of its eggshell, drawn by a yolk pattern layer coagulating in an egg white skin layer coagulating, so as to form the curved surface of the boiled egg after removal of the eggshell, or reversely, drawn by an egg white layer coagulating in a yolk skin layer, and a method for producing the boiled egg. 
A boiled egg itself is a foodstuff habitually eaten from ancient times, and even during the present it is frequently eaten as it is; the way of cutting has been improved, and a boiled egg is used only for ornamentation on the dining table as a garnish and thus generally remains as a commonplace foodstuff.  Aside from the drawing of patterns, characters and figures on the outer surface of the eggshell, in conventional attempts to draw patterns or the like on the curved surface of the boiled egg after removal of the eggshell, coloring matters are inserted under pressure or penetrated area-selectively in some form from the outside of the eggshell through the eggshell, and the coloring matters are impregnated on the curved surface of the boiled egg to draw patterns; hence, there are dangers that microorganisms may enter through minute damaged portions of the eggshell owing to the insertion under pressure and penetration treatment of the coloring matters, or that contaminants may enter because of the treatment itself; commercialization of such drawing is thus obstructed owing to concerns about food hygiene control. 
As such a prior art, Japanese Unexamined Patent Publication No.  Hei 2-249469 discloses a boiled egg, wherein numerous minute holes are provided by perforation on the surface of the eggshell, and desired patterns or characters are color-printed on the curved surface of the egg white, or seasonings are penetrated to provide a flavor, from the outside through the eggshell with the eggshell unremoved. 
Furthermore, Japanese Unexamined Patent Publication No.  Hei 2-27962 discloses a yolk/egg white reversed boiled egg having a reversed arrangement of the yolk and egg white in an eggshell without using any additives from the outside, wherein small holes are provided at both the acute end portion and the obtuse end portion of the egg, air is supplied under pressure from one small hole into the eggshell to discharge the egg white through the other small hole to the outside of the eggshell, and the yolk remaining inside the eggshell is heated together with the eggshell so that the yolk coagulates and is attached to the inner face of the eggshell to form an outside yolk layer; next, the discharged egg white is poured into the inside of the outside yolk layer through the one small hole, and the egg white is heated together with the eggshell so that the egg white coagulates at the central portion of the egg with the outside of the egg white surrounded by the yolk layer.  An egg produced in this way also has a danger in food hygiene control. 
Regarding food proceeding to be carried out for the egg white and yolk inside the eggshell without any concerns about entry of microorganisms through the minute damaged portions of the eggshell and entry of contaminants because of the coloring treatment itself in the prior art, Japanese Unexamined Patent Publication No.  Hei 2-211850 discloses a method for stirring and mixing the yolk and egg white in an eggshell by tearing the yolk film by manually swinging an egg accommodated in a cylindrical egg container made of nylon.  The egg processed and provided by this method is advantageous in food hygiene control since only the materials inside the eggshell are used; however, this egg is a strange xe2x80x9cthick omelet-likexe2x80x9d boiled egg covered with eggshell; although the advantage in food hygiene control is ensured, this egg is far inferior to a xe2x80x9cthick omelet-likexe2x80x9d fried egg in terms of seasoning, wherein the egg is commonplace as a cooked egg; in particular, the curved surface of the egg with the eggshell removed is monotonous, uniform and dull in color, whereby the egg does not provide an attractive tastefulness on the dining table. 
As desired above, in the prior art, two trade-off requests, i.e., food hygiene control and tastefulness on the dining table, are not fulfilled adequately, thereby causing a problem of incomplete satisfaction in the ornamental expression on the curved surface of the boiled egg with the eggshell removed with respect to tastefulness on the dining table. 
In view of the problem of satisfaction in tastefulness on the dining table in the above-mentioned prior art, the present invention is intended to provide ornamental patterns in two colors, white and yellow, by drawing a pattern by a yolk pattern layer formed area-selectively in an egg white skin layer on the curved surface of the boiled egg with its eggshell removed, and by drawing another pattern by an egg white pattern layer formed area-selectively in a yolk skin layer on the curved surface of the boiled egg, whereby the satisfaction of consumers with respect to tastefulness on the dining table is improved without introducing any materials inside the eggshell. 
As a first aspect of the present invention for solving the above-mentioned problems, the invention set forth in claims 1 through 3 is claimed. 
The configuration of the invention set forth in claim 1 relates to a structure of a patterned boiled egg, wherein, as shown in FIG.  9, a yolk skin layer 9a is formed of a yolk coagulating along nearly one half of the curved surface of the boiled egg, an egg white pattern layer 3e is formed of an egg white coagulating so as to draw a pattern against the background of the yolk skin layer 9a while eliminating the yolk near the curved surface inside the yolk skin layer 9a, and an egg white skin layer 9b is formed of the egg white coagulating along nearly the other half of the curved surface, other than the yolk skin layer 9a.  
The configuration of the invention set forth in claims 2 and 3 relates to a method for producing the patterned boiled egg having the structure of the invention set forth in claim 1, comprising a first step, i.e., an egg white pattern layer forming step, for forming an egg white pattern layer so as to draw a pattern by heating a specific pattern area drawn on nearly one half of the curved surface of the eggshell of an egg area-selectively and concentrically, by coagulating an uncoagulated egg white on the inner face of the eggshell, and by removably attaching the uncoagulated egg white to the inner face of the eggshell; a second step, i.e., a rotating/stopping yolk film tearing step used as a yolk film tearing step, for tearing the yolk film, during the rotation of the egg around the major axis of the egg at a high speed of about 3,600 rpm, by immediately stopping the rotation and by applying a shearing force owing to the difference between the inertial force acting on the yolk at the central portion inside the eggshell and the inertial force acting on the egg white at the peripheral portion to the yolk film at the time of the immediate stop; a third step, i.e., a yolk positioning step, for positioning the uncoagulated yolk by floating the uncoagulated yolk after the tearing of the yolk film in the egg white inside the eggshell and by positioning the uncoagulated yolk so that the uncoagulated yolk surrounds the egg white pattern layer attached to the inner face of the eggshell and makes contact with the egg white pattern layer; a fourth step, i.e., a half yolk skin layer forming step, for forming a half yolk skin layer along nearly one half of the curved surface of the egg by boiling the egg, in which the uncoagulated yolk is positioned, in its stationary posture as it is in a heating medium, such as hot water, and by coagulating the uncoagulated yolk so that the uncoagulated yolk surrounds the egg white pattern layer, makes contact with the egg white pattern layer and becomes the background of the egg white pattern layer; and a simultaneously proceeding fifth step, i.e., a half egg white skin layer forming step, for forming a half egg white skin layer along nearly one half of the curved surface on the opposite side of the half yolk skin layer by boiling the egg, in which the uncoagulated yolk is positioned, in its stationary posture as it is in a heating medium, such as hot-water, and by coagulating the egg white sinking below the uncoagulated yolk floating in the eggshell. 
In accordance with the configuration of the invention set forth in claims 1 through 3 claimed as the above-mentioned first aspect, the curved surface of the boiled egg with its eggshell removed is nearly halved; a pattern is clearly drawn in two colors in the yellow half yolk skin layer disposed on nearly one half by the white egg white pattern layer, and the white half egg white skin layer is disposed on nearly the other half other than the yellow half yolk skin layer; hence, the contrast of the halves of the curved surface is intensified in ornamental expression, thereby providing a tasteful boiled egg. 
As a second aspect of the present invention for solving the above-mentioned problems, the invention set forth in claims 4 through 7 is claimed. 
The configuration of the invention set forth in claim 4 relates to a structure of a patterned boiled egg, wherein, as shown in FIG.  16, a whole yolk skin layer 3gf is formed of a yolk coagulating along the whole curved surface of the boiled egg, an egg white pattern layer 3e is formed of an egg white coagulating so as to draw a pattern against the background of the whole yolk skin layer 3gf while eliminating the yolk near the curved surface inside the whole yolk skin layer 3gf.  
The configuration of the invention set forth in claim 5 relates to a method for producing the patterned boiled egg having the structure of the invention set forth in claim 4, comprising a first step, i.e., an egg white pattern layer forming step, for forming an egg white pattern layer similar to that set forth in claim 2; a second step, i.e., a yolk film tearing step for carrying out a film tearing step similar to the yolk film tearing step set forth in claim 2; a third step, i.e., a whole yolk skin layer forming step, for forming a whole yolk skin layer along the whole curved surface of the egg so that the whole yolk skin layer becomes the background of the egg white pattern layer by sequentially exposing the whole face of the curved surface of the egg to a heating environment while rotating the egg including the uncoagulated yolk after film tearing, by floating the yolk in the egg white inside the eggshell, by attaching the yolk to the eggshell and by sequentially coagulating the uncoagulated yolk surrounding the egg white pattern layer and making contact with the egg white pattern layer near the inner face of the eggshell at the portion exposed to the heating environment during rotation and rocking or immediately after rotation and rocking. 
The configuration of the invention set forth in claim 6 relates to the execution of the whole yolk skin layer forming step in the method of producing the patterned boiled egg set forth in claim 5, comprising a first sub-step, i.e., a central portion yolk skin layer forming step, for forming a central portion yolk skin layer along the curved surface of a portion corresponding to the central portion along the major axis of the curved surface of the egg by sequentially exposing the portion corresponding to the central portion along the major axis of the curved surface of the egg to an upper heating environment while rotating the egg around the major axis of the egg used as its horizontal rotation center axis, and by sequentially coagulating the uncoagulated yolk floating in the egg white inside the eggshell and attached to the eggshell near the inner face of the upper portion of the eggshell exposed to the overheating environment during the rotation; a second sub-step, i.e., an acute end portion yolk skin layer forming step, for forming an acute end portion yolk skin layer along the curved surface of the acute end portion by exposing the acute end portion of the egg to the upper heating environment while rotating the egg around the major axis of the egg used as its inclined vertical rotation center axis, and by coagulating the uncoagulated yolk floating in the egg white inside the eggshell at the acute end portion and attached to the eggshell; and a third sub-step, i.e., an obtuse end portion yolk skin layer forming step, for forming an obtuse end portion yolk skin layer along the curved surface of the obtuse end portion by boiling the egg in a heating medium, such as hot water, in a stationary posture wherein the major axis of the egg extends vertically and the obtuse end portion is positioned upward, and by coagulating the uncoagulated yolk floating in the egg white inside the eggshell at the obtuse end portion and attached to the eggshell. 
The configuration of the invention set forth in claim 7 relates to the execution of the whole yolk skin layer forming step in the method of producing the patterned boiled egg set forth in claim 5, comprising a first sub-step, i.e., a rotating/rocking whole yolk skin layer forming step, for forming a whole yolk skin layer along the whole curved surface of the egg, by boiling the egg while rotating the egg around the major axis of the egg mainly used as its rotation center axis and while rocking the egg around the minor axis of the egg mainly used as its rocking center axis in a state wherein the egg is wholly dipped in a heating medium, such as hot water, and by coagulating the uncoagulated yolk, which is relatively easy to coagulate, floating near the inner face of the upper portion of the eggshell and attached to the eggshell, earlier than the uncoagulated egg white, which is relatively difficult to coagulate, sinking near the inner face of the lower portion of the eggshell and attached to the eggshell, during the rotation and rocking. 
In accordance with the configuration of the invention set forth in claims 4 through 7 claimed as the above-mentioned second aspect, a yellow whole yolk skin layer is formed so as to cover the whole of the curved surface of the boiled egg with its eggshell removed, and a pattern is drawn by the white egg white pattern layer against the background of the whole yolk skin layer; hence, the white pattern against the simple background of a single color, yellow, is expressed stably so as to appear clearly, thereby providing a tasteful boiled egg. 
As a third aspect of the present invention for solving the above-mentioned problems, the invention set forth in claims 8 through 10 is claimed. 
The configuration of the invention set forth in claim 8 relates to a structure of a patterned boiled egg, wherein, as shown in FIG.  22, a whole egg white skin layer 21a is formed of an egg white coagulating along the whole curved surface of the boiled egg, and a yolk pattern ,layer 19a is formed of a yolk coagulating so as to draw a pattern against the background of the whole egg white skin layer 21a while eliminating the egg white near the curved surface inside the whole egg white skin layer 21a.  
The configuration of the invention set forth in claim 9 relates to a method for producing the patterned boiled egg having the structure of the invention set forth in claim 8, comprising a first step, i.e., a yolk film tearing step for tearing the yolk film of an egg; a second step, i.e., a yolk positioning step, for positioning an uncoagulated yolk after the tearing of the yolk film by floating the uncoagulated yolk in the egg white inside the eggshell and by positioning the uncoagulated yolk so that the uncoagulated yolk makes contact with the inner face of the eggshell; a third step, i.e., a yolk film layer forming step, for forming a yolk pattern layer, corresponding to the egg white pattern layer obtained by the egg white pattern layer forming step of claim 2, for the uncoagulated yolk, the film of which is torn; and a fourth step, i.e., a whole egg white skin layer forming step for forming a whole egg white skin layer along the whole curved surface of the egg by boiling the egg, in which the yolk pattern layer is formed, while rotating and rocking the egg around the major axis of the egg used as its rotating/rocking center axis in a state wherein the egg is partially dipped in a heating medium, such as hot water, and by coagulating the uncoagulated egg white, which is relatively difficult to coagulate, sinking near the inner face of the lower portion of the eggshell dipped in the heating medium and attached to the eggshell, earlier than the uncoagulated yolk, which is relatively easy to coagulate, floating near the inner face of the upper portion of the eggshell not dipped in the heating medium and attached to the eggshell, during the rotation and rocking, so that the uncoagulated egg white surrounds the yolk pattern layer attached to the inner face of the eggshell, makes contact with the yolk pattern layer and becomes the background of the yolk pattern layer. 
The configuration of the invention set forth in claim 10 relates to the execution of the yolk film tearing step in the method of producing the patterned boiled egg set forth in claim 9 by using a rotating/stopping yolk film tearing step similar to that set forth in claim 3. 
In accordance with the configuration of the invention set forth in claims 8 through 10 claimed as the above-mentioned third aspect, in comparison with the configuration of the invention set forth in claims 1 through 7 claimed as the first and second aspects the color arrangement relationship between the background and the pattern is reversed, that is, a pattern of the yellow yolk pattern layer is drawn against the background of the white whole egg white skin layer disposed to cover the whole of the curved surface, thereby providing unexpected enjoyment in the reverse expression of the color arrangement of the background and the pattern; in particular, tasteful boiled eggs are also provided in view of unexpected enjoyment from the combination of a pair of eggs identical in pattern but reverse in the color arrangement with respect to the background and the pattern, that is, an egg having the structure (FIG.  16) of the invention set forth in claim 4 as the second aspect and an egg having the structure (FIG.  22) of the invention set forth in claim 8 as this third aspect. 
As a fourth aspect of the present invention for solving the above-mentioned problems, the invention set forth in claims 11 through 13 is claimed. 
The configuration of the invention set forth in claim 11 relates to a structure of a patterned boiled egg, wherein, as shown in FIG.  26, a half egg white skin layer 9b is formed of an egg white coagulating along nearly one half of the curved surface of the boiled egg, a yolk pattern layer 19a is formed of a yolk coagulating so as to draw a pattern against the background of the half egg white skin layer 9b while eliminating the egg white near the curved surface inside the half egg white skin layer 9b, and a half yolk skin layer 9a is formed of a yolk coagulating along nearly the other half of the curved surface. 
The configuration of the invention set forth in claims 12 and 13 relates to a method for producing the patterned boiled egg having the structure of the invention set forth in claim 11, comprising a first step, i.e., a rotating/stopping yolk film tearing step for tearing the yolk film, similar to that set forth in claims 2 and 3 and used as a yolk film tearing step; a second step, i.e., a yolk positioning step for floating the yolk in the egg white, similar to that set forth in claim 9 and used as a yolk positioning step; a third step, i.e., a yolk pattern layer forming step for forming a yolk pattern layer, similar to that set forth in claim 9 and used as a yolk pattern layer forming step; a fourth step, i.e., a yolk/egg white positioning step, for positioning an uncoagulated yolk by floating the uncoagulated yolk in the egg white inside the eggshell so that the uncoagulated yolk makes contact with nearly the other half of the inner face of the eggshell of the egg after the yolk pattern layer is formed and attached, and for positioning an uncoagulated egg white by sinking the uncoagulated egg white so that the uncoagulated egg white surrounds the yolk pattern layer attached to nearly one half of the inner face of the eggshell of the egg and makes contact therewith; a fifth step, i.e., a half egg white skin layer forming step, for forming a half egg white skin layer along nearly one half of the curved surface of the egg by boiling the egg, after the positioning of the yolk and egg white, in its stationary posture as it is in a heating medium, such as hot water, and by coagulating the uncoagulated egg white so that the uncoagulated egg white sinks below the uncoagulated yolk floating inside the eggshell, surrounds the yolk pattern layer, makes contact with the yolk pattern layer and becomes the background of the yolk pattern layer; and a sixth step, i.e., a half yolk skin layer forming step, for forming a half yolk skin layer along nearly the other half of the curved surface of the egg by boiling the egg, after the positioning of the yolk and egg white, in its stationary posture as it is in a heating medium, such as hot water, and by coagulating the uncoagulated yolk floating in the egg white inside the eggshell. 
In accordance with the configuration of the invention set forth in claims 11 through 13 claimed as the above-mentioned fourth aspect, in comparison with the configuration of the invention set forth in claims 1 through 7 claimed as the first and second aspects, the color arrangement relationship between the background and the pattern is reversed, and the curved surface is divided into nearly equal halves; that is, in the white half egg white skin layer disposed on nearly one half, a pattern is drawn clearly by the yellow yolk pattern layer in two colors, and in nearly the other half other than the white half egg white skin layer, the yellow half yolk skin layer is disposed, thereby providing unexpected enjoyment in the reverse expression of the color arrangement of the background and the pattern; in particular, tasteful boiled eggs are also provided in view of unexpected enjoyment from the combination of a pair of eggs identical in pattern but reverse in the color arrangement of the background and the pattern, that is, an egg having the structure (FIG.  9) of the invention set forth in claim 1 as the first aspect and an egg (FIG.  26) having the structure of the invention set forth in claim 11 as this fourth aspect. 
As a fifth aspect of the present invention for solving the above-mentioned problems, the invention set forth in claims 14 through 16 is claimed. 
The configuration of the invention set forth in claim 14 relates to a structure of a patterned boiled egg, wherein, as shown in FIG.  30, a half egg white skin layer 9b is formed of an egg white coagulating along nearly one half of the curved surface of the boiled egg, a yolk pattern layer 19a is formed of a yolk coagulating so as to draw a pattern against the background of the half egg white skin layer 9b while eliminating the egg white near the curved surface inside the half egg white skin layer 9b, a half yolk skin layer 9a is formed of a yolk coagulating along nearly the other half of the curved surface of the boiled egg, and an egg white pattern layer 3e is formed of an egg white coagulating so as to draw a pattern against the background of the half yolk skin layer while eliminating the yolk near the curved surface inside the half yolk skin layer 9a.  
The configuration of the invention set forth in claims 15 and 16 relates to a method for producing the patterned boiled egg having the structure of the invention set forth in claim 14, comprising a first step, i.e., a rotating/stopping yolk film tearing step, similar to that of the invention set forth in claims 12 and 13 and used as a yolk film tearing step; a second step, i.e., a yolk positioning step, similar to that of the invention set forth in claim 12; a third step, i.e., a yolk pattern layer forming step, similar to that of the invention set forth in claim 12; a fourth step, i.e., an egg white pattern layer forming step, carried out simultaneously with or before or after this, for forming an egg white pattern layer by heating a specific pattern area drawn on nearly the other half of the curved surface area-selectively and concentrically, and by coagulating the uncoagulated egg white on the inner face of the eggshell so that the uncoagulated egg white removably attaches to the inner face of the eggshell and draws a pattern; and a fifth step, i.e., a yolk/egg white positioning step; and a sixth step, i.e., a half egg white skin layer forming step and a seventh step, i.e., a half yolk skin layer forming step, similar to those of the invention set forth in claim 12, respectively; the production method is completed by these subsequent steps. 
In accordance with the configuration of the invention set forth in claims 14 through 16 claimed as the above-mentioned fifth aspect, the curved surface is divided into nearly equal halves, and in the white half egg white skin layer disposed on nearly one half, a pattern is drawn clearly by the yellow yolk pattern layer in two colors, and in the half yellow yolk skin layer disposed in nearly the other half other than the white half egg white skin layer, another pattern is drawn clearly by the white egg white pattern layer in two colors, reversed in color arrangement with respect to the egg white pattern layer; hence, regarding the background and the pattern evaluated in accordance with the relationship between an egg (FIG.  26) of the invention set forth in claim 11 as the fourth aspect and an egg (FIG.  9) of the invention set forth in claim 1 as the first aspect, the unexpected enjoyment in the combination of patterns, identical in patterns but reverse in color arrangement, is united on the curved surface of one boiled egg, thereby providing a tasteful boiled egg. 
Generally, the configuration of the invention set forth in all the claims as the above-mentioned first to fifth aspects provides an ornamental expression by forming patterns in two colors, white and yellow, on the curved surface of a boiled egg in a state with its eggshell removed, by using only the yolk and egg white, the original contents inside the eggshell, as materials and by only selectively applying heat and acceleration, without providing any mechanical process for the eggshell and without introducing any materials into the eggshell from outside the eggshell; hence, two trade-off requests, i.e., the removal of anxiety in food hygiene control and the improvement in tastefulness on the dining table, are fulfilled, whereby the satisfaction of consumers with respect to tastefulness on the dining table is improved.