Patent Publication Number: US-9833965-B2

Title: Sealed letter producing device and envelope sheet

Description:
RELATED APPLICATIONS 
     The present application is National Phase of International Application No. PCT/JP2011/074667 filed Oct. 26, 2011, and claims priority from Japanese Application No. 2010-239789, filed Oct. 26, 2010 and Japanese Application No. 2011-212814, filed Sept. 28, 2011. 
     TECHNICAL FIELD 
     The present invention relates to a sealed letter producing device which is capable of printing on a paper sheet which serves as an envelope a paper sheet of a content, and performing the operation of enclosing and sealing a content in the envelope by folding the paper sheet which becomes the envelope with a simple configuration, and such a device suitable for an envelope sheet (a paper sheet which forms an envelope when folded). 
     BACKGROUND ART 
     Patent document 1 described below discloses an invention relating to a method for producing a sealed letter by folding in three. An envelope sheet which is substantially similar to a sealed letter form used in this invention is shown in  FIGS. 31 and 32 . As shown in  FIG. 31 , this envelope sheet  300  includes three paper pieces: an upper paper piece  301 , a middle paper piece  302 , and a lower paper piece  303 , connected by perforations. Name and address are written on the front side of the upper paper piece  301 , contents are written on the front sides the middle paper piece  302  and lower paper piece  303 . On the front side of the middle paper piece  302  and lower paper piece  303 , a pressure-sensitive adhesive  305  is formed in an approximate square U-shape and in a band-shaped pattern along the external forms of two paper piece other than perforations. No pressure-sensitive adhesive is present on the front side of the upper paper piece  301  which will finally be the other surface. Moreover, nothing is written on the back sides of the upper paper piece  301 , the middle paper piece  302  and lower paper piece  303 , or a printing pattern is formed to prevent the content from being seen through. On the back sides of the upper paper piece  301  and middle paper piece  302 , the pressure-sensitive adhesive  305  is formed in a band-shaped pattern along the outer edge other than perforations and part of the sides. No pressure-sensitive adhesive is present on the back side of the lower paper piece  303  which will be the outer back side finally. 
     After name, address, contents and other information are printed, in the case where the envelope sheet  300  is formed into the shape of the envelope, the front side of the middle paper piece  302  and the front side of the lower paper side  303  are placed together as shown in  FIG. 19  and the pressure-sensitive adhesives  305  on both paper pieces are brought into contact with eachother. Furthermore, as shown in  FIG. 32 , the back side of the upper paper side  301  and the back side of the middle paper side  302  are placed together to bring the pressure-sensitive adhesives  305  on both paper pieces into contact with each other. The envelope sheet  300  is in the form of a folded-in-three envelope in this state, but the pressure-sensitive adhesives  305  are not adhered yet. 
     Thereafter, as shown in  FIG. 4  of the above patent document 1, the envelope is nipped by a pair of rollers whose size in the axial direction is greater than their length in the width direction of the envelope, and is transferred while applying a high pressure on the entire surface of the envelope. In  FIG. 4  of the above patent document 1, a pressure is applied to the entire surface of the envelope by two pairs of rollers which are longer than the width of the envelope. Accordingly, the pressure-sensitive adhesives which are in contact with each other between the paper pieces facing each other develops tackiness, and a sealed envelope, that is, a sealed letter is produced. 
     In the technique described above, a sealed letter is produced by folding the envelope sheet, a pressure-sensitive adhesive which requires pressure has been used for the adhesion of the paper pieces of the envelope sheet. In addition, other adhesion sections include a method of applying an adhesive such as hot melts immediately before folding the envelope sheet.
     Patent document 1: Japanese Patent Publication No. 2521498   

     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     When an adhesive such as a hot melt is used as an adhesion section in the case where a sealed letter is produced by folding an envelope sheet, its application device is complicated and expensive, a heating section is also necessary, the whole system becomes a large-scale device such as a factory, therefore the limitation of the installation site is significant, and maintenance operation is also necessary. For these reasons, it is difficult to employ such an adhesive as the adhesion section of the sealed letter producing device. 
     Moreover, in the sealed letter producing device using the pressure-sensitive adhesive described with reference to the above patent document 1 and  FIGS. 31 and 32 , the adhered portion only needs to be pressurized, and therefore maintenance is unnecessary. Since the sealed letter producing device is simpler than a device using adhesives such as hot melts, it can be a relatively small device. 
     However, in the sealed letter producing device using a pressure-sensitive adhesive, the pressure applied on the adhered portion of the envelope is as high as about 1 ton/square centimeter, and the adhered portion in the example described above is present on three to four sides of the rectangular envelope, and therefore rollers longer than the width of the envelope have been necessary so that a pressure can be applied the entire surface of the envelope having a predetermined area (refer to  FIG. 4  of patent document 1 mentioned above). If such pressure rollers are to be provided, the mechanical structure of the entire device must be robust. Such a device is a costly device consequently, and it has not been spread as an office installation device accordingly. 
     The present invention has been made in view of the objects as described above, and its object is to provide a sealed letter producing device for performing printing on the envelope sheet and content, and enclosing and sealing of the folded envelope sheet, in which sealing using a pressure-sensitive adhesive can be performed with a simple configuration using pressure rollers smaller than conventional ones. 
     Means for Solving the Problems 
     The inventors of the present invention obtained the above objects and examined various solutions to the objects, and considered using other adhesives than pressure-sensitive adhesives during the examination. In the present circumstances, some of few possible examples of adhesives cheaper than pressure-sensitive adhesives are remoistening pastes such as mucilage. In the case of remoistening pastes, application of water is necessary to develop adhesive strength. However, since the material forming an envelope is paper, when the paper contains water, a considerable reduction in rigidity and deformation of the paper occur due to swelling. Accordingly, adhesion using a remoistening paste such as mucilage can be used for simple adhesion between two sheets, but in the adhesion of three or four sheets such as production of a sealed letter performed by folding the envelope sheet to which the present invention is directed, swelling is markedly increased, which likely leads to the occurrence of the problems such as a significant reduction in rigidity and breakage. Moreover, since deformation of the paper sheet remains after drying, using a remoistening paste such as mucilage in an adhered portion of parts of the folded envelope sheet stacked in a plurality of layers is considered impossible as it is. 
     To this end, a sealed letter producing device according to the first aspect is 
     a sealed letter producing device including: a printing unit which prints an envelope sheet which becomes an envelope and a content for each sealed letter to be produced; a first paper path which transfers the envelope sheet printed in the printing unit, a second paper path which transfers the content printed in the printing unit; and an enclosing and sealing unit which is disposed in a position where the first paper path and the second paper path merge, and produces a sealed letter by enclosing and sealing a content by folding the envelope sheet in a manner of containing the content, in which 
     the enclosing and sealing unit includes a pressure bonding section which performs sealing by applying pressure on both edge portions in a width direction of the envelope intersecting its transfer direction provided therein. 
     The sealed letter producing device according to the second aspect is a sealed letter producing device according to the first aspect, 
     wherein the enclosing and sealing unit includes an adhesion section which adheres the envelope sheet to the inside from both edge portions in the width direction of the envelope. 
     The sealed letter producing device according to the third aspect is the sealed letter producing device according to the second aspect, 
     wherein each of the pressure bonding sections 
     has a width smaller than an application width of pressure sensitive adhesives provided in both edge portions in the width direction of the envelope sheet and facing each other in both edge portions of the envelope, and has a pair of pressure rollers disposed at an interval greater than the size of the content in its width direction enclosed in the envelope, and smaller than the size of the envelope in its width direction. 
     The sealed letter producing device according to the fourth aspect is the sealed letter producing device according to the second or third aspect, wherein 
     the adhesion section 
     is a moistening section which moistens a remoistening paste provided inwardly of both edge portions in the width direction of the envelope sheet, 
     in the enclosing and sealing unit, adheres the envelope sheet with the remoistening paste by folding the envelope sheet after the remoistening paste is moistened by the moistening section. 
     The sealed letter producing device according to the fifth aspect is the sealed letter producing device according to the fourth aspect, wherein 
     in the enclosing and sealing unit, sealing is performed by applying pressure on both edge portions of the envelope in its width direction by the pair of pressure rollers after the envelope sheet is adhered with the remoistening paste by folding the envelope sheet after the remoistening paste is moistened by the moistening section. 
     An envelope sheet according to the sixth aspect is 
     an envelope sheet applied to a sealed letter producing device including an enclosing and sealing unit which produces a sealed letter by enclosing and sealing a content by folding an envelope sheet in a manner of containing the content, wherein the envelope sheet has 
     pressure sensitive adhesives which do not face each other when provided in its both edge portions in the width direction stacked in the same orientation, and which face each other in both edge portions of the envelope when formed on the envelope by folding, and 
     another adhesive provided inwardly of the both edge portions in the width direction. 
     An envelope sheet according to the seventh aspect is 
     an envelope sheet applied to a sealed letter producing device including an enclosing and sealing unit which produces a sealed letter by enclosing and sealing a content by folding an envelope sheet in a manner of containing the content, wherein the envelope sheet has 
     a pressure sensitive adhesive provided only on one side in both edge portions in its width direction, 
     notches provided in both edge portions of a side which becomes an inner side when bent, and 
     another adhesive provided inwardly of the both edge portions in the width direction. 
     An envelope sheet according to the eighth aspect 
     an envelope sheet applied to a sealed letter producing device including an enclosing and sealing unit which produces a sealed letter by enclosing and sealing a content by folding an envelope in a manner of containing a content, wherein the envelope sheet has 
     an adhesive for adhering the envelope sheet which is bent and formed into the shape of an envelope, and 
     an adhesive strength adjustment layer which is formed of an adhesion resistant material in a position corresponding to the adhesive in a predetermined pattern and adjusts adhesive strength of the adhesive for the envelope sheet. 
     An envelope sheet according to the ninth aspect is the envelope sheet according to the eighth aspect, 
     wherein the adhesive strength adjustment layer has adhesion resistant portions where a front side of the envelope sheet is covered with the adhesion resistant materials, and adhered portions where the front side of the envelope sheet is not covered with the adhesion resistant materials, and the adhered portions are provided in a predetermined shape and in a plurality of portions. 
     An envelope sheet according to the tenth aspect is the envelope sheet according to the ninth aspect, 
     wherein the adhesives and the adhesive strength adjustment layer are formed in different positions on the envelope sheet, and are configured to face each other when the envelope sheet is bent and formed into an envelope. 
     An envelope sheet according to the eleventh aspect is the envelope sheet according to the ninth aspect, 
     wherein the other adhesive is provided on the adhesive strength adjustment layer, and the other adhesive is adhered to the front side of the envelope sheet via the adhered portion. 
     A sealed letter producing device according to the twelfth aspect is the sealed letter producing device according to the second aspect, 
     wherein in the printing unit, a printing section which performs printing by an adhesion resistant material on the envelope sheet in a desired pattern is provided. 
     Effects of the Invention 
     According to the sealed letter producing device of the present invention, a common printing unit which performs printing on the envelope sheet and content prints and discharges an envelope sheet and a content alternately for each sealed letter to be produced. The printed envelope sheet is transferred through a dedicated first paper path, the printed content is transferred through a dedicated second paper path, the envelope sheet and content are precisely combined by an enclosing and sealing unit provided in a position where both paper paths merge, and the content is enclosed and sealed by folding the envelope sheet in a manner of containing a content, whereby a sealed letter can be produced. 
     According to the sealed letter producing device according to the first aspect, when a sealed letter is produced by folding an envelope sheet on which pressure-sensitive adhesives are provided only in both edge portions in the width direction, the entire surface of the envelope need not be pressurized in a step in the enclosing and sealing unit, and a pressure bonding section applies pressure only to both edge portions of the envelope in the width direction intersecting its transfer direction, whereby the pressure-sensitive adhesives in both edge portions of the envelope sheet in the width direction are pressurized to develop adhesive strength, so that sealing can be performed. 
     According to the sealed letter producing device according to the second aspect, in the sealed letter producing device according to the first aspect, in the enclosing and sealing unit, a portion inwardly of both edge portions in the width direction of the envelope can be adhered to the envelope sheet with an adhesion section which requires a pressure smaller than that required by than the pressure bonding section. 
     According to the sealed letter producing device according to the third aspect, in the sealed letter producing device according to the second aspect, the envelope sheet on which the pressure sensitive adhesives are provided in both edge portions in the width direction is folded, and when an envelope on which the pressure sensitive adhesives face each other in both edge portions is sealed, both edge portions of the envelope are pressurized and transferred using a pair of pressure rollers as the pressure bonding section, whereby only the pressure-sensitive adhesives on the envelope sheet can be pressurized and adhered surely without adhering the content in the envelope to the envelope, so that the envelope can be sealed. 
     According to the sealed letter producing device according to the fourth aspect, in the sealed letter producing device according to the second or third aspect, when the envelope sheet on which the remoistening paste is provided inwardly of both edge portions in its width direction is folded and sealed, the envelope can be sealed by using a moistening section as the adhesion section, applying water to the remoistening paste water to develop adhesive strength, then folding the envelope sheet, and adhering the envelope sheet securely with remoistening paste. 
     According to the sealed letter producing device according to the fifth aspect, in the sealed letter producing device according to the third or fourth aspect, in the enclosing and sealing unit, sealing can be performed by folding the envelope sheet after water is applied to the remoistening paste by the moistening section and applying pressure on both edge portions in the width direction of the envelope by a pair of pressure rollers after the envelope sheet is adhered with the remoistening paste. 
     According to the envelope sheet according to the sixth aspect, pressure sensitive adhesives are provided in such a pattern that they do not face each other when stacked in the same orientation in both edge portions in its width direction, but they face each other in both edge portions of the envelope when formed on the envelope by folding, and a pattern of another adhesive different from the pressure-sensitive adhesives provided on both edges is provided inwardly of both edge portions in the width direction of the envelope sheet, and it is therefore possible to perform sealing using the pressure-sensitive adhesives with a simple configuration using pressure rollers smaller than conventional ones by, for example, the sealed letter producing device according to the first to the fifth aspects. 
     According to the envelope sheet according to the seventh aspect, the pressure sensitive adhesives are provided only on one side of both edge portions in its width direction. Accordingly, the pressure sensitive adhesives do not face each other and are not adhered when stacked in the same orientation. Moreover, when formed on the envelope by folding, the pressure sensitive adhesives face each other directly in both edge portions of the envelope, or the pressure sensitive adhesives provided in both edge portions of one of the outer sides face the pressure sensitive adhesives provided in both edge portions of the other outer side via the notches provided in both edge portions bent to be an inside face. Moreover, inwardly of both edge portions in the width direction, another adhesive different from the pressure-sensitive adhesives is provided. It is therefore possible to perform sealing using the pressure-sensitive adhesives with a simple configuration using pressure rollers smaller than conventional ones by, for example, the sealed letter producing device according to the first to fifth aspects. 
     According to the envelope sheet according to the eighth aspect, an adhesive for adhering and sealing the envelope sheet which is bent and formed into the shape of an envelope is provided, and an adhesive strength adjustment layer made of an adhesion resistant material is provided in a position corresponding to this adhesive in a predetermined pattern. Since this adhesive adheres to the envelope sheet via the adhesive strength adjustment layer of a predetermined pattern, the adhesion area for the envelope sheet is restricted, and as a result, the adhesive strength for the envelope sheet can be set to a desired state. Therefore, ease of peeling required for opening and durability under the stress of handling required for mailing can be both achieved. Moreover, with the pressure sensitive adhesives provided in both edge portions in the width direction of the envelope, it is possible to perform sealing with a simple configuration using pressure rollers smaller than conventional ones. 
     According to the envelope sheet according to the ninth aspect, when the envelope sheet is bent and formed into the shape of an envelope, the adhesive forms an insufficient adhesion state which allows easy peeling for adhesion resistant portions of the adhesive strength adjustment layer, but forms adhesion with predetermined adhesive strength of the adhesive for the front side of the envelope sheet not covered with the adhesion resistant materials in the adhered portions. Since the adhered portions are provided in a predetermined shape and in a plurality of portions, they produce predetermined adhesive strength depending on their shape and area in the individual adhered portions, but the plurality of portions collectively develops the total adhesive strength of the individual portions. 
     According to the envelope sheet according to the tenth aspect, since it is so configured that the adhesive and adhesive strength adjustment layer are provided in different positions of the envelope sheet, the accuracy of positioning need not be set to a high level compared to the case where the adhesive and adhesive strength adjustment layer are stacked and formed and in the position on the envelope sheet, which allow easy production. 
     According to the envelope sheet according to the eleventh aspect, the adhesive is provided on the adhesive strength adjustment layer, and therefore it is possible to reserve a greater area of a region where the printed information can be read more easily in the entire area of the envelope sheet. Moreover, in the case of a configuration in which the adhesive is provided directly on the envelope sheet, the paper sheet may be possibly deformed in the process of developing adhesive strength depending on the type of the adhesive, but in this envelope sheet, the adhesive is provided on the adhesive strength adjustment layer, and therefore the force applied on the paper sheet is reduced in the process of developing the adhesive strength, so that the effects in reducing deformation of the paper sheet is obtained. 
     According to the sealed letter producing device according to the twelfth aspect, a common printing unit which performs printing on the envelope sheet and content prints and discharges an envelope sheet and a content alternately for each sealed letter to be produced. The printed envelope sheet is transferred through a dedicated first paper path, the printed content is transferred through a dedicated second paper path, the envelope sheet and content are precisely combined by an enclosing and sealing unit provided in a position where both paper paths merge, and the content is enclosed and sealed by folding the envelope sheet in a manner of containing a content, whereby a sealed letter can be produced. 
     According to the sealed letter producing device, the entire surface of the envelope need not be pressurized in a step in the enclosing and sealing unit, and the pressure bonding section applies pressure only to both edge portions of the envelope in the width direction intersecting its transfer direction, whereby the pressure-sensitive adhesives in both edge portions of the envelope sheet in the width direction are pressurized to develop adhesive strength, so that sealing can be performed. 
     Moreover, in enclosing and sealing unit, a portion inwardly of both edge portions in the width direction of the envelope can be adhered to the envelope sheet with an adhesion section which requires a pressure smaller than that required by than the pressure bonding section. In addition, the printing section provided in the printing unit allows printing on the envelope sheet with the adhesion resistant materials in a desired pattern, and therefore it can be used for production of the envelope sheet having the adhesive strength adjustment layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  A drawing of the surface of an envelope sheet according to the first embodiment. 
         FIG. 2  A drawing of the back side of the envelope sheet according to the first embodiment 
         FIG. 3  A drawing showing a folding step ( 1 ) of the envelope sheet according to the first embodiment. 
         FIG. 4  A drawing showing a folding step ( 2 ) of the envelope sheet according to the first embodiment. 
         FIG. 5  A schematic perspective view showing a portion of the configuration of an enclosing and sealing unit in the sealed letter producing device of the first embodiment and the action of the same. 
         FIG. 6  A schematic cross-sectional view showing the structure of the sealed letter producing device according to the first embodiment, and the flow of an envelope in the device by arrows. 
         FIG. 7  A schematic cross-sectional view showing the structure of the sealed letter producing device according to the first embodiment, and the flow of a content in the device by arrows. 
         FIG. 8  A schematic cross-sectional view showing the structure of the sealed letter producing device according to the first embodiment, a sealing operation and a discharge step of the envelope after the sealing in the device. 
         FIG. 9  A schematic front view showing the configuration of the enclosing and sealing unit in the sealed letter producing device of the first embodiment. 
         FIG. 10  A schematic front view showing a moistening step of a remoistening paste in the enclosing and sealing unit of the sealed letter producing device of the first embodiment. 
         FIG. 11  A schematic front view showing an adhesion step with the remoistening paste in the enclosing and sealing unit of the sealed letter producing device of the first embodiment. 
         FIG. 12  A schematic perspective view showing especially a positioning mechanism of the envelope in the enclosing and sealing unit of the sealed letter producing device of the first embodiment. 
         FIG. 13  A schematic perspective view showing the action of the positioning mechanism of the envelope in the enclosing and sealing unit of the sealed letter producing device of the first embodiment. 
         FIG. 14  A drawing of the surface of the envelope sheet according to the second embodiment. 
         FIG. 15  A drawing of the back side of the envelope sheet according to the second embodiment  FIG. 16  A drawing showing a folding step ( 1 ) of the envelope sheet according to the second embodiment. 
         FIG. 17  A drawing showing a folding step ( 2 ) of the envelope sheet according to the second embodiment. 
         FIG. 18  A drawing of the surface of an envelope sheet according to a third embodiment. 
         FIG. 19  A drawing of the back side of the envelope sheet according to the third embodiment. 
         FIG. 20  A drawing showing a structural example of an adhesive strength adjustment layer provided on the envelope sheet according to the third embodiment. 
         FIG. 21  A drawing showing a folding step ( 1 ) of the envelope sheet according to the third embodiment. 
         FIG. 22  A drawing showing a folding step ( 2 ) of the envelope sheet according to the third embodiment. 
         FIG. 23  A cross-sectional view showing the state after the folding step of the envelope sheet and immediately before other adhesives are adhered in the third embodiment. 
         FIG. 24  A schematic cross-sectional view showing the structure of a sealed letter producing device according to the third embodiment, and the flow of an envelope in the device by arrows. 
         FIG. 25  A schematic cross-sectional view showing the structure of the sealed letter producing device according to the third embodiment, and the flow of the content in the device by arrows. 
         FIG. 26  A schematic cross-sectional view showing the structure of the sealed letter producing device according to the third embodiment, and a sealing operation and a discharge step of the envelope after the sealing in the device. 
         FIG. 27  A schematic front view showing a moistening step onto the remoistening paste in the enclosing and sealing unit of the sealed letter producing device of the third embodiment. 
         FIG. 28  A schematic front view showing the adhesion step with the remoistening paste in the enclosing and sealing unit of the sealed letter producing device of the third embodiment. 
         FIG. 29  A cross-sectional view showing the state after the folding step of the envelope sheet and immediately before other adhesives are adhered in the fourth embodiment. 
         FIG. 30  A cross-sectional view showing the state after the folding step of the envelope sheet and immediately before other adhesives are adhered in the fifth embodiment. 
         FIG. 31  A drawing showing the structure and a folding step ( 1 ) of a conventional envelope sheet. 
         FIG. 32  A drawing showing the structure and a folding step ( 2 ) of a conventional envelope sheet. 
     
    
    
     EXPLANATION OF REFERENCE NUMERALS 
     
         
           1 —Sealed letter producing device 
           2 —Printing unit 
           3 —Enclosing and sealing unit 
           10 —First paper path 
           11 —One path of the first paper path 
           13 —The other path of the first paper path 
           20 —Second paper path 
           21 —One path of the second paper path 
           26 —The other path of the second paper path 
           30 —Paper sheet 
           40 —Content 
           50 —Envelope 
           60 —Moistening section as an adhesion section 
           80 —Pressure roller as pressure bonding section 
           90 —Control section 
           100 ,  100   a ,  100   b ,  100   c ,  200 —Envelope sheet 
           106 ,  206 —Pressure-sensitive adhesive 
           107 ,  207 —Remoistening paste 
         A, A′—Main folding roller 
         B, B′—First folding roller 
         C—Second folding roller 
         D, D′ . . . Paper transport roller 
         A″—Main folding roller 
         B″—First folding roller 
         C″—Second folding roller 
         D″—Paper transport roller 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     1. First Embodiment ( FIGS. 1 to 13 ) 
     (1) Sealed Letter Paper Sheet Used in this Sealed Letter Producing Device ( FIGS. 1 to 5 ) 
       FIG. 1  is a drawing which shows the surface (the side on which the name and address are printed) of an envelope sheet  100  used in this embodiment, while  FIG. 2  is a drawing which shows the back side of the same. This envelope sheet  100  is a rectangular paper sheet including three paper pieces: a first paper piece  101 , a second paper piece  102 , and a third paper piece  103 , which are connected by folds. 
     As shown in  FIG. 1 , the surface of the first paper piece  101  corresponds to the front side of the envelope, on which name and address are printed. The first paper piece  101  has a band-shaped opening tape  104  along its width direction formed thereon by perforation, and two openings  105  are provided at an end thereof. When the sealed envelope is opened, the opening tape  104  is torn off along the perforation by placing a finger on the opening tape  104  from this opening  105 . The surface of the second paper piece  102  corresponds to the back side of the envelope, on which the name, address, etc. of the sender are printed. Pressure-sensitive adhesives  106  are provided in two portions along at a predetermined interval at both edge portions in the width direction on the surface of the third paper piece  103  in the form of bands. Moreover, on the surface of the third paper piece  103 , two portions of remoistening pastes  107  are provided on the inner side of both edge portions close to the fold bordering the second paper piece  102  in a band-shaped pattern along the width direction. 
     A pressure-sensitive adhesive exhibits adhesive strength by adhering pressure-sensitive adhesives provided on two sheets of paper together and applying a predetermined pressure. Its known examples include two-pack type adhesive using microcapsules and natural rubber-based adhesion materials, among others. The remoistening paste is, for example, mucilage or the like. The remoistening paste has no adhesive strength when it is applied on paper and dry, but develops adhesive strength when wetted with water, and when the paper sheet is placed together with another paper sheet in this state and a required pressure is applied thereto, the two paper sheets are adhered. The pressure required for adhesion with a remoistening paste is effective even when it is significantly lower than the pressure required for a pressure-sensitive adhesive. Since their adhesive strengths are at least both considerably higher than that of paper, using two types of adhesives in a single envelope does not cause any problem due to a variation in the adhesive strength. Moreover, in place of the remoistening paste, an adhesive which does not normally have adhesive strength but develops adhesive strength by any operation other than the pressure as for the pressure-sensitive adhesive may be used. For example, adhesives which develop adhesive strength by heat, light including ultraviolet radiation, and other physical sections, other pressure-sensitive adhesives which develop adhesive strength with a pressure lower than that applied on the pressure-sensitive adhesive may be used. 
     The remoistening paste, as previously mentioned, requires application of water to develop adhesive strength. Since the material forming an envelope is paper, when the paper contains water, a considerable reduction in rigidity and deformation of the paper occur due to swelling. Moreover, since deformation of the paper sheet remains after drying, the appearance of the finished envelope is deteriorated. Therefore, deformation is minimized by divisionally placing a plurality of small sized portions of the remoistening paste within an adhesion area where the paste is required. 
     As shown in  FIG. 2 , on the surface of each of the first to third paper pieces  101  to  103 , if necessary, the contents of the sealed letter, including the information such as text, graphics and photographs, can be printed. On the back side of each of the first to third paperpieces  101  to  103 , the pressure-sensitive adhesives  106  are provided in two portions along both edge portions in the width direction at a predetermined interval. Moreover, a content  40  is mounted on the back side of the second paper piece  102 . A width W of the content  40  is smaller than the interval between the pressure-sensitive adhesives  106  printed in both edge portions of the paper piece of the envelope sheet  100 . The arrangement pattern of these pressure-sensitive adhesives  106  is so considered that the pressure-sensitive adhesives  106  of corresponding paper pieces meet and come into contact with each other when the paper pieces are folded to be assembled in the form of an envelope. However, for example, when a plurality of the envelope sheets  100  are stacked in the same vertical positional relationship, e.g., with their front sides facing up, the pressure-sensitive adhesives  106  on the front sides and the pressure-sensitive adhesives  106  on the back sides do not face each other to avoid contact therebetween. When the pressure-sensitive adhesives  106  are brought into contact with each other and left for a longperiod of time, the problem of natural adhesion of the adhesives may be caused by a high temperature, high humidity and other circumstances conditions even without any pressure, but such a problem can be prevented from occurring in advance according to the envelope sheet  100  of the embodiment. 
     After the name, address, contents, etc. are printed, the procedure of folding and other processes when the envelope sheet  100  is formed into an envelope will be described. 
     As shown in  FIG. 3 , in a state that the content  40  is mounted on the back side of the second paper piece  102 , the back side of the third paper piece  103  is placed together with the second paper piece  102  and the content  40  to bring the pressure-sensitive adhesives  106  of both paper pieces  102 ,  103  into contact with each other. Further in  FIG. 4 , after water is applied onto the remoistening paste  107  by a section not shown, the back side of the first paper piece  101  and the front side of the third paper piece  103  of are put together to bring the remoistening paste  107  and the back side of the first paper piece  101  into contact, and the pressure-sensitive adhesives  106  of both paper pieces  101 ,  103  are brought into contact with each other. The envelope sheet  100  is in the form of an envelope folded in three in this state, but the pressure-sensitive adhesives  106  are yet adhered. 
     Thereafter, the entire surface of the envelope  50  is nipped by rollers not shown having a length equal to or greater than the width of the envelope to transfer the envelope  50 , and the remoistening paste  107  of the third paper piece  103  and the first paper piece  101  are adhered. Moreover, as shown in  FIG. 5 , the pressure-sensitive adhesives  106  placed in both edge portions in the width direction of the envelope  50  are adhered by pressure rollers  80 . A pair of these pressure rollers  80  includes upper and lower sets, and two left and right pairs of these rollers are provided. Thus, both edge portions in the width direction of the envelope  50  enclosing the content  40 , that is, the direction intersecting the transfer direction are nipped from above and below and pressurized to develop the adhesive strength the pressure-sensitive adhesive  106  and achieve sealing. This produces the pressure-sensitive adhesives  106  which are in contact with each other between the paper pieces facing each other develops tackiness, the form of the envelope  50  sealing the content is realized. 
     It should be noted that the enclosing and sealing operation of the envelope sheet  100  described above is automatically performed by a sealed letter producing device  1  of the first embodiment described below. 
     (2) Mechanism of this Sealed Letter Producing Device ( FIGS. 6 to 9 ) 
     The sealed letter producing device  1  of the first embodiment performs a process for each sealed letter to be produced. That is, required printing is performed in an appropriate order using a common printing unit  2  on the envelope sheet  100  and sheet-like paper sheet the content  40 . Then, the envelope sheet  100  and the content  40  after printing are transferred into an enclosing and sealing unit  3 , the envelope sheet  100  is folded so as to being the form of the envelope  50  while being transferred through the paper paths of different systems, and if necessary, the content  40  is also folded. Finally, both the envelope sheet  100  and the content  40  are merged at an enclosing and sealing section, and the content  40  is enclosed and sealed in the envelope  50  to be discharged in alignment as a finished sealed letter in an upper part of the device. 
     First, the sealed letter producing device  1  includes a printing unit  2  which prints and discharges the paper sheets which will be the envelope  50  and the content  40 . This printing unit  2  is provided with a plurality of paper feed racks P (P 1  to P 4 ) which can accommodate more than one types of printed bodies (sheet-like paper sheet  30  which will be the content  40  and the envelope sheet  100 ) inside, on a side or other places of a cabinet  4  accommodates components of the device. In this example, the envelope sheet  100  is accommodated in a paper feed rack P 1  attached to the side the cabinet  4 , the sheet-like paper sheets  30  which will be the contents  40  are accommodated in paper feed racks P 2  to P 4  provided inside the cabinet  4 . 
     Paper sheets and the like discharged from these paper feed racks P are transferred into a looped transfer path  5  from an introduction path to be transported, and an image is formed by printing section disposed at predetermined intervals downwardly along the lower half of the transfer path. In this example, four ink jet devices C, K, M and Y which discharge cyan, black, magenta and yellow inks, respectively, are disposed as printing section. 
     This looped transfer path  5  has a first discharge path  6  which discharges paper sheets to the outside of the loop in an approximately horizontal direction in a downstream adjacent portion of the printing section provided in a branching manner. Moreover, the upper half of the looped transfer path  5  has a second discharge path  7  which discharges paper sheets to the outside of the loop provided in a branching manner. In addition, a switchback path  8  is provided between the second discharge path  7  and the introduction path from the paper feed rack P in a branching manner. This switchback path  8  is a section which turns paper sheets upside down in the transfer path  5  by receiving the paper sheets transferred the transfer path  5  and then reverses the same to return to the transfer path  5 . By turning the paper sheet upside down and passing through the transfer path  5  twice using this switchback path  8 , full-color duplex printing for forming full-color images on both the front and back sides of on the paper sheet by the ink jet devices C, K, M and Y can be performed. 
     Next, adjacent to the printing unit  2 , the enclosing and sealing unit  3  for receiving and processing the paper sheets  30  which will be the envelope sheets  100  and the contents  40  transferred from the first discharge path  6  of the printing unit  2 , and enclosing and sealing the contents  40  in the envelope sheets  100  is provided. 
     That is, the first discharge path  6  of the printing unit  2  extends horizontally to protrude outwardly, and is introduced into a cabinet  9  of the enclosing and sealing unit  3  adjacent thereto. In the cabinet  9 , a second paper path  20  branches obliquely downward from this discharge path  6 , and extends obliquely downwardly to be one of a first paper path  10 , a path  11 , further downstream thereof. 
     The path  11 , which is one of the first paper path  10 , is disposed approximately in parallel to a path  21 , which is one of the second paper path  20 . The path  11 , which is one of the first paper paths  10 , is a guide path which transfers the envelope sheet  100  to a folding section, and as previously mentioned, and the path  21 , which is one of the second paper paths  20 , is a guide path which transfers the paper sheet of the content  40  to the folding section. The switching between the first and second paper paths  10  and  20  is performed by a switching flap not shown provided at the junction of the second paper path  20 . 
     At an end of the path  11 , which is one of the first paper path  10 , a first folding section which folds the envelope sheet  100  to produce the form of the envelope  50  is provided. This first folding section is provided with a freely rotatable main folding roller A′, a paper transport roller D′ and a first folding roller B′ which are in contact with the same and are rotated are provided. These rollers are made of rubber, and their pressurizing abilities are low since they are for folding paper sheets. Their lengths in the axial direction are greater than the width of the envelope sheet  100 . 
     From between the main folding roller A′ and the first folding roller B′ in the first folding section of the first paper path  10 , a path  13 , which is the other path of the first paper path  10 , curves in a convex shape upwardly and extends in the horizontal direction. An end of the path  13 , which is the other path of the first paper path  10  which transfers the envelope sheet  100 , leads to an enclosing and sealing section as will be described later in detail. 
     Next, the second paper path  20  which transfers the paper sheet printed by the printing unit  2  is provided inside the cabinet  9  of the enclosing and sealing unit  3 . This second paper path  20  is positioned below the first paper path  10 , and has the path  21 , which is one of the paths for obliquely downwardly transferring the paper sheet transferred in the horizontal direction from the first discharge path  6  of the printing unit  2 . 
     In the course of this path  21 , a paper transport roller  22  and an alignment portion  23  which is a freely openable and closable gate are provided, so that the paper sheets can be stacked and retained in the path  21  by fixing the transferred paper sheets on the alignment portion  23  closing the path  21 . Moreover, a folding section which folds the paper sheets is provided at an end of this path  21 . This folding section is provided with a freely rotatable central main folding roller A, and furthermore, a first folding roller B, a second folding roller C and a single paper transport roller D are in contact with a main folding roller A, each of the rollers being freely rotatable. These rollers are made of rubber, their pressurizing abilities are low since they are for folding paper sheets, and their lengths in the axial direction are greater than the width of the envelope sheet  100 . In addition, although not shown, in a front position in the direction of transfer by the main folding roller A and the transport roller D, an impinging member on which the front end of the transferred paper sheet impinges is provided, so that the impinging paper sheet is warped and the warped portion of the paper sheet is led in between the main folding roller A and folding roller B to fold the paper sheet. Similarly, an impinging member is also provided in a front position in the transfer direction by the main folding roller A and folding roller B, so that the impinging paper sheet is warped the warped portion of the paper sheet is led in between the main folding roller A and folding roller C to fold the paper sheet. Therefore, according to these folding section, the paper sheet can be folded twice or more. 
     In the cabinet  9  of the enclosing and sealing unit  3 , the second paper path  20  has the other path  26  which continuously transfers the paper sheet  30  folded by the folding section obliquely upwardly, i.e., approximately perpendicularly to the path  21 . This other path  26  is positioned below the above-mentioned path  13 , i.e., the other path of the first paper path  10 , which transfers the envelope sheet  100  obliquely downward, and joins the path  13  of the first paper path  10  at the enclosing and sealing section. 
     Next, the enclosing and sealing section positioned at the junction between the first paper path  10  and the second paper path  20  will be described. This enclosing and sealing section is a second folding section which provides further folding with the envelope sheet  100 , if necessary, while, at the same time, it is an enclosing section which encloses the content  40  in the envelope by providing the envelope sheet  100  with further folding after the content  40  is aligned with the folded envelope sheet  100 , and is further provided with a sealing section which seals this envelope. 
     First, the enclosing and sealing section is provided with the second folding section, i.e., a freely rotatable main folding roller A″, a paper transport roller D″ which is in contact with and rotated by the same, and first and second folding rollers B″, C″. These rollers are made of rubber. Their pressurizing abilities are low since they are for folding paper sheets, and their lengths in the axial direction are greater than the width of the envelope sheet  100 . The envelope sheet  100  is folded, if necessary, by the main folding roller A′, first folding roller B′ and other components which are the above-mentioned first folding section, and then transferred further to the main folding roller A″ and other components, which the second folding section, where pre-enclosure folding, if necessary, is further performed. 
     However, as will be described later in detail, the envelope sheet  100  is folded in three to enclose the content  40  therein enclose in this embodiment. Therefore after the envelope sheet  100  is folded once by the main folding roller A′, first folding roller B′ and other component which are the first folding section, passes between the main folding roller A″ and paper transport roller D″, which are the second folding section, and then stands by for the alignment with the content  40  around where it has passed between the main folding roller A″ and second folding roller B″. After the envelope  50  is then aligned with the content  40  transferred through the second paper path  20 , it is provided with the second folding further between the main folding roller A″ and second folding roller C″, and enclosing of the content  40  into the envelope  50  is performed. 
     However, in this embodiment, a standby path  46  extends downwardly from between the main folding roller A″ and paper transport roller D″. Accordingly, production of sealed letters can be also performed for envelope sheets different from that in this embodiment or steps different from that in this embodiment. For example, after an envelope sheet is folded once by the main folding roller A′, the first folding roller B′ and other components which are the first folding section, the envelope sheet is passed between the main folding roller A″ and paper transport roller D″ which are the second folding section, and is caused to enter the standby path  46  in that state and put on standby. Thereafter, after a content transferred through the second paper path  20  is aligned with this envelope sheet during standby, both can be nipped between the main folding roller A″ and second folding roller B″, and transferred while being folded to enclose the content in the envelope. 
     Next, as shown in  FIGS. 6 to 8  and  FIG. 9 , a path  31  slightly inclined to the back is disposed between the main folding roller A″ and second folding roller C″ of the enclosing and sealing section. Around the rear end of this path  31 , a moistening section  60  as an adhesion section which applies water to the remoistening paste  107  of the envelope sheet  100  to develop adhesive strength, and adheres the envelope sheet  100  to form the envelope  50  is provided. 
     The moistening section  60  is a device for moistening the remoistening paste  107  provided inwardly of both edge portions of the width direction of the envelope sheet  100 . The moistening section  60  is provided with a water tank  61  which is disposed below the path  31 , a water-absorbing portion  62  which is immersed into water in the water tank  61  and is made from a felt material or the like, a swing arm  63  disposed above the path  31 , and a rotation cam  64  which drives this swing arm  63 . 
     The envelope sheet  100  which is folded once by the main folding roller A′, the first folding roller B′ and other components which are the first folding section passes between the main folding roller A″ and paper transport roller D″, which are the second folding section, and then stands by around where it has passed between the main folding roller A″ and second folding roller B″. Thereafter, the content  40  transferred along the path  26 , which is another second paper path  20  is aligned with the envelope sheet  100  during standby. 
     As shown in  FIG. 10 , the aligned envelope sheet  100  and content  40  are further forwarded by the main folding roller A″ and second folding roller B″. Herein, in the envelope sheet  100 , the front side of the third paper piece  103  faces down, and the remoistening paste  107  on the front side of the third paper piece  103  faces the water-absorbing portion  62  of the moistening section  60 . This is close to the state of the first paper piece  101  before it is folded in the direction of the arrow in  FIG. 4 . The rotation cam  64  is activated herein to swing the swing arm  63 , and the remoistening paste  107  is pressed against the water-absorbing portion  62  to be moistened. 
     As shown in  FIG. 11 , the envelope sheet  100  is forwarded by the main folding roller A″ and second folding roller C″. This causes the first paper piece  101  to be folded, overlapped with the front side of the third paper piece  103 , and adhered to the remoistening paste  107 . 
     Next, as shown in  FIGS. 6 to 8  and  FIG. 9 , a path  47  inclined obliquely forwardly is disposed between the main folding roller A″ and second folding roller C″ of the enclosing and sealing section. This path  47  is approximately parallel to the path  11  which is one of the first paper paths  10 , and the path  21 , which is one of the second paper paths  20 . 
     In the course of this path  47 , as has already been described with reference to  FIG. 5 , pressure rollers  80  as a pressure bonding section constituting a portion of the enclosing and sealing section is provided. Since the pressure rollers  80  is a section which applies a certain level of pressure the pressure-sensitive adhesive  106  of the envelope sheet  100 , it is constituted by a highly rigid metal. A set of these pressure rollers  80  includes upper and lower sets of rollers, and two left and right pairs are provided. The pressure rollers  80  nip each of the edge portions of the envelope  50  in the width direction thereof in which the content  40  is enclosed from above and below to apply pressure thereon, whereby sealing by the pressure-sensitive adhesive  106  can be performed. 
     As shown in  FIG. 9 , each of the pressure rollers  80  is attached to at the front end of a support arm  82  caused to be swingable about a fulcrum  81 . A biasing section  83  is attached to the rear end of this support arm  82 , a set of the pressure rollers  80  are configured to come into contact with each other at a predetermined pressure. Therefore, by guiding the envelope  50  to go between a set of the pressure rollers  80 ,  80 , and driving in the direction of transfer the pressure rollers  80 , the envelope  50  is forwarded under the predetermined pressure of both edge portions. It should be noted that the pressure applied to the envelope sheet  100  by the pressure rollers  80  due to the biasing section  83  depends on the type of the pressure-sensitive adhesive  106 , but may be, for example, about 700 N/cm 2 . 
     Herein, the width of the pressure rollers  80  is less than the width of application of a pressure sensitive adhesive provided in both edge portions of the width direction of the envelope sheet  100 . Moreover, the interval between the left and right pairs of the pressure rollers  80 ,  80  is greater than the width of the content  40  enclosed in the envelope  50 , and is less than the width of the envelope  50 . Therefore, in a sealing step by the pressure rollers  80  only the pressure-sensitive adhesive  106  in both edge portions of the envelope  50  in the width direction can be adhered by planned pressurizing surely with an area equivalent to the width of the pressure rollers  80 , and at that time, the content  40  is not pressurized by the pressure rollers  80 , and therefore the content  40  is not adhered to the envelope. As an example, when an envelope of a normal size is formed, the width of the pressure-sensitive adhesives  106  provided in both edge portions of the envelope sheet  100  may be about 5 mm in consideration of a positional shift of the pressure rollers  80 , while the width of the pressure rollers  80  may be about 3 mm in consideration of secured adhesion of the envelope sheet  100 . 
     As described above, the widths of the pressure rollers  80  are small, and only the portions of the pressure-sensitive adhesive  106  in both edge portions of an assembled envelope need to be nipped and pressurized by the pressure rollers  80 , and therefore positioning in the width direction of the envelope with respect to the pressure rollers  80  needs to be correctly performed. 
     To this end, as shown in  FIG. 12 , a positioning roller  65  is provided between the main folding roller A″ and second folding roller C″ and the pressure rollers  80  in the enclosing and sealing unit of this embodiment. The length of the positioning roller  65  in the axial direction of is greater than the width of the envelope sheet  100 , and therefore can move in the axial direction with the envelope sheet  100  left nipped therebetween to adjust the position. Moreover, an edge sensor  66  is provided above a portion slightly downstream of the positioning roller  65 , enabling capturing the edge portions of the envelope sheet  100  nipped by the positioning roller  65 , and obtaining the positional information of the envelope sheet  100  to correct the position of the positioning roller  65 . 
     Therefore, as shown in  FIG. 12 or 13 , by causing the edge sensor  66  to capture the edge portion of the envelope  50  which is being transferred by the positioning roller  65 , and moving the positioning roller  65  based on the position information, the position of the envelope  50  in the width direction relative to the pressure rollers  80  can be optimally adjusted. Accordingly, only the portions of the pressure-sensitive adhesives  106  in both edge portions of the assembled envelope  50  can be surely pressurized by the pressure rollers  80 . 
     It should be noted that as shown in  FIGS. 6 to 8 , the sealed letter producing device  1  of this embodiment is provided with a control section  90  which controls each mechanism of the printing unit  2  and enclosing and sealing unit  3  described above. It should be noted that in the example illustrated, the control section  90  is disposed in the printing unit  2 , but it may be disposed in the enclosing and sealing unit  3 , or may be separately disposed outside the printing unit  2  and the enclosing and sealing unit  3 . 
     (3) Operation of this Sealed Letter Producing Device ( FIGS. 6 to 8 ,  FIGS. 10 to 13 ) 
     Next, in the sealed letter producing device  1  of this embodiment described above, the overall procedure including printing of name and address and other information on the envelope sheet  100 , performing required printing on a plurality of sheets of the content  40  and folding the same, enclosing the content  40  in the envelope  50  which is the folded and formed envelope sheet  100  and sealing the envelope  50  will be described. 
     As shown in  FIG. 6 , in the printing unit  2 , the envelope sheet  100  is transferred from the paper feed rack P 1 . In this embodiment, the envelope sheet  100  may be on any of the paper feed racks P 1  to P 4  of the printing unit  2 . This envelope sheet  100  is printed on it both sides by the ink jet devices C, K, M, Y during a single pass around the looped transfer path  5 . Not only duplex printing but also simplex printing can be selected. In general, name, address and other information are printed on the face which serves as the outer face of the envelope  50 , while any information to be sent to the address, if necessary, is printed on the face which serves as the inner face of the envelope  50 , along with particulars of the enclosed content  40 . The information printed on the inner face of the envelope  50  can be read by a receiver by cutting and opening the envelope  50 . 
     The envelope sheet  100  is transferred from the path  11 , which is one of the first paper paths  10 , by switching of a switching flap not shown to the folding section. The envelope sheet  100  is forwarded by the main folding roller A′ and the paper transport roller D′, impinges on an impinging member not shown to be warped, enters in between the main folding roller A′ and the first folding roller B′ from the warped portion, and further nipped and transferred to be provided with a fold in a portion of the front end portion thereof in the paper feed direction. The unfinished envelope which is partially folded passes between the main folding roller A″ and paper transport roller D″ of the enclosing and sealing section, further simply passes between the main folding roller A″ and second folding roller B″ along the path, and then stands by for the alignment with the content  40 . 
     As shown in  FIG. 7 , following the envelope sheet  100 , the required paper sheet  30  is transferred as the content  40  from any of the paper feed racks P 2  to P 4  into the looped transfer path  5  at a certain determined interval, both sides of the paper sheet  30  are printed by the ink jet devices C, K, M and Y during a single pass through this transfer path. Not only duplex printing but also simplex printing can be selected. The paper sheet  30  of the content  40  is transferred to the path  21 , which is one of the second paper paths  20 , by switching of a switching flap not shown. The paper sheet  30  is retained at an alignment portion  23  on the path  21 , which is one of the second paper paths  20  until a required number of sheets are accumulated, the alignment portion  23  opens when the required number is accumulated and the sheets are transferred into the folding section (main folding roller A, etc.). A plurality of folding performed by the folding section, the paper sheet  30  folded in a desired state is transferred into the enclosing and sealing unit (main folding roller A″, etc.) via the path  26 , which is the other path of the second paper paths  20 . In this embodiment, the content  40  is folded inwardly in three. This content  40  is forwarded by the main folding roller A″ and second folding roller B″, and is aligned with the envelope sheet  100  which is on standby near these rollers. 
     As shown in  FIG. 8 , an operation to bend the envelope sheet  100  is performed in a manner of wrapping up the content  40  with the envelope sheet  100  being outside by the main folding roller A″ and second folding roller C″ in the enclosing and sealing unit, and whereby an enclosing step for wrapping up the paper sheet  30  within the envelope  50  is performed. 
     As shown in  FIG. 10 , the aligned envelope sheet  100  and content  40  are further forwarded by the main folding roller A″ and second folding roller B″. Herein, the rotation cam  64  of the moistening section  60  is activated to swing the swing arm  63 , and the remoistening paste  107  of the envelope sheet  100  is pressed against the water-absorbing portion  62  to be moistened. 
     As shown in  FIG. 11 , the envelope sheet  100  is forwarded by the main folding roller A″ second folding roller C″, the first paper piece  101  is folded and is adhered to the front side of the third paper piece  103  with the remoistening paste  107  to be in the shape of the envelope  50 , and enters in between the positioning rollers  65 . 
     As shown in  FIG. 13 , the positioning rollers  65  nipping the envelope  50  adjusts the position of the envelope  50  in the axial direction based on the position of the envelope  50  grasped by the edge sensor  66  shown in  FIG. 12 , and the envelope  50  is moved to bring the pressure-sensitive adhesives  106  on the envelope  50  to a position overlapping the pressure rollers  80 . In addition, both edge portions of the envelope  50  are stuck together as it passes through the pressure rollers  80 , whereby sealing of the envelope  50  is performed. 
     According to this embodiment, in the process of folding the envelope sheet  100  aligned with the content  40  to form into the envelope  50 , paper pieces are adhered to each other with the remoistening paste  107  first, the positioning of the envelope  50  in the width direction is accurately performed and is then transferred in between the pressure rollers  80 , the pressure-sensitive adhesives  106  are pressurized securely by the pressure rollers  80  having a small width. Therefore, the pressure-sensitive adhesives  106  can be securely adhered with a width sufficient for adhesion by the pressure rollers  80  which have a small width and can produce high pressure with a small force. 
     Then, the finished sealed letter after the completion of enclosing and sealing is discharged into a discharge tray  48  provided on the top surface of the cabinet  9 , where it is sequentially stacked up to be taken out later. 
     2. Second Embodiment ( FIGS. 14 to 17 ) 
       FIG. 14  is a drawing which shows the front side (the side on which the name and address are printed) of an envelope sheet  200  used in this embodiment, while  FIG. 2  is a drawing which shows the back side of the same. This envelope sheet  200  is a rectangular paper sheet including three paper pieces: a first paper piece  201 , a second paper piece  202 , and a third paper piece  203 , which are connected by folds. 
     As shown in  FIG. 14 , the front side of the first paper piece  201  corresponds to the back side of the envelope, on which the name, address, etc. of the sender are printed. On the first paper piece  201 , two perforations  204  are formed from a long side parallel to the folds to reach both edge portions in the width direction. When the sealed envelope is opened, the central portion of the first paper piece  201  may be torn off along these perforations  204 . The surface of the second paper piece  202  corresponds to the front side of the envelope, on which the name and address are printed. On the surface of the third paper piece  203 , two portions of remoistening pastes  307  are provided on the inner side of both edge portions close to the fold bordering the second paper piece  202  in a band-shaped pattern along the width direction. Among both edge portions of the third paper piece  203 , a notch  205  is provided in the portion closer to the second paper piece  202 . 
     As shown in  FIG. 15 , on the back side of each of the first to third paper pieces  201  to  203 , if necessary, the contents of the sealed letter, including the information such as text, graphics, and photographs, can be printed. Moreover, the content  40  is placed on the back side of the second paper piece  202 . The width of the content  40  is smaller than the interval between pressure-sensitive adhesives  306  printed in both edge portions of the paper piece of the envelope sheet  200 . On the back side of each of the first to third paper pieces  201  to  203 , the pressure-sensitive adhesives  306  are provided along both edge portions in the width direction in a predetermined pattern of a band shape. The arrangement pattern of these pressure-sensitive adhesives  306  is considered so that when the paper pieces are folded to be assembled in the form of an envelope, the pressure-sensitive adhesives  306  of corresponding paper pieces coincide to abut with each other. However, when a number of the envelope sheets  200  are stacked on the same sides, for example, with their surfaces facing up, the pressure-sensitive adhesives  306  of the back sides do not face each other since no pressure-sensitive adhesive is present on the front sides to avoid contact. Accordingly, as in the envelope sheet  200  shown in  FIG. 1  and other drawings, the problem that the stacked envelope sheets  200  are stuck to each other does not occur. 
     After the name, address, contents, etc. are printed, the procedure of folding and other processes when the envelope sheet  200  is formed into an envelope will be described. 
     As shown in  FIG. 16 , in a state that the content  40  is placed on the back side of the second paper piece  202 , the back side of the third paper piece  203  is placed together with the second paper piece  202  and the content  40  to bring the pressure-sensitive adhesives  306 ,  306  of both paper pieces  202 ,  203  into contact with each other. At this time, a portion of the pressure-sensitive adhesives  306  of the second paper piece  202  is exposed from the notches  205  in the third paper piece  203 . 
     In  FIG. 17 , after water is applied to a remoistening paste  307  by a section not shown, the back side of the first paper piece  201  and the front side of the third paper piece  203  are placed together to bring the remoistening pastes  307  and the back side of the first paper piece  201  into contact, while the pressure-sensitive adhesives  306  of both paper pieces  201  and  203  are brought into contact with each other. At this time, a portion of the pressure-sensitive adhesives  306  of the second paper piece  202  exposed from the notches  205  in the third paper piece  203  is in contact with a portion of the pressure-sensitive adhesives  306  of the back side of the first paper piece  201 . In this state, the envelope sheet  200  is in the form of a folded-in-three envelope, but the remoistening pastes  207  or the pressure-sensitive adhesives  306  are not adhered yet. 
     Thereafter, as in the case of the envelope sheet  100  shown in  FIG. 1  and other drawings, the entire surface of the envelope is nipped and transferred by a roller not shown having a length equal to or greater than the width of the envelope to adhere the remoistening pastes  307  of the third paper piece  203  and the first paper piece  201 . Moreover, as shown in  FIG. 5 , the pressure-sensitive adhesives  206  are adhered by the pressure rollers  80 . Accordingly, the pressure-sensitive adhesives  306  which are in contact between the paper pieces facing each other develops tackiness, and the form of an envelope having its contents sealed is realized. 
     It should be noted that the enclosing and sealing operation of the envelope sheet  200  described above can be automatically performed by the above-mentioned sealed letter producing device  1  of the first embodiment. 
     3. Third Embodiment ( FIGS. 18 to 28 ,  FIGS. 5, 9, 12 and 13  of the First Embodiment are Referred to) 
     The third embodiment relates to a sheet-like envelope sheet which is capable of processing into a sealed letter by wrapping up and folding a content at the same time, and especially to relates to an envelope sheet which has the strength required for mailing and delivery in a sealing portion, while it can be easily developed into the original sheet-like envelope sheet from the state of the enclosed and sealed envelope without providing a special structure such as a perforation to open the envelope. Moreover, this embodiment relates to a sealed letter producing device which is capable of producing such an envelope sheet, printing on a paper sheet which serves as an envelope a paper sheet of a content, and enclosing and sealing the content in the envelope by folding these. 
     In an envelope produced using the envelope sheet as shown in  FIGS. 31 and 32 , the envelope sometimes needs to be opened orderly to put it back to an original sheet state from the envelope shape, rather than being irregularly opened by tearing of adhered portion by the receiver. When, for example, text is printed inside envelope sheet, or a portion of the envelope sheet forms a return postcard, in opening the envelope by peeling off four sides of a sealed letter sealed with a pressure-sensitive adhesive, reading of the content and its use as a postcard are prevented if the envelope sheet is damaged. However, in order to open the envelope produced using the envelope sheet shown in  FIGS. 31 and 32 , adhered portions positioned in both edge portions of the envelope are cut off along perforations provided along both edge portions of the envelope, and then adhered portions provided in its width direction need to be opened along the other edge portions of the envelope, but it has not been an easy operation to peel off only adhered portions without damaging the envelope sheet. If other adhesives than a pressure-sensitive adhesive as an adhesive for these portions is used, the difficulty of the operation is the same. Moreover, it is possible to increase ease of opening by providing perforations referred to zippers for opening which can be easily cut open in the edge portions of the envelope along its width direction, and so that the envelope can be opened without damaging the paper sheet by cutting this off or tearing this apart, but providing such an opening structure entails the following problem: such a zipper must have both ease of tearing required for opening and durability under the stress of handling required for mailing, but this involves technical difficulties. Moreover, a special perforation processing blade is necessary to produce such complicated perforations, while it involves the problems that the production costs are high, and that the area which is assigned to the cut off portion of the zipper compresses the area for placing information of as a sealed letter. 
     This embodiment has been made in view of the problems as described above, and its object is to provide a sheet-like envelope sheet for producing a sealed letter by being bent in a manner of wrapping up a content, in which the strength required for mailing and delivery in a sealing portion can be obtained, while it can be easily developed into an original sheet-like envelope sheet from the state of the enclosed and sealed envelope without providing a special structure such as a perforation to open the envelope. 
     (1) Sealed Letter Paper Sheet Used in this Sealed Letter Producing Device ( FIGS. 18 to 23  and  FIG. 5 ) 
       FIG. 18  is a drawing which shows the front face (the side on which the name and address are printed) of the envelope sheet  100   a  used in this embodiment, while  FIG. 19  is a drawing which shows the back side of the same. This envelope sheet  100   a  is a rectangular paper sheet including four paper pieces: a first paper piece  101 , a second paper piece  102 , a third paper piece  103 , a fourth paper piece  104 , which are connected by folds, and is formed into an envelope folded in four having the same shape as the external form of a sheet of the paper piece by folding in three portions. The front sides of the each piece of the envelope paper are denoted by the names A, B, C and D, respectively, while the back sides of the each piece of the envelope paper are denoted by the names E, F, G and H, respectively, for the convenience of explanation. 
     As shown in  FIGS. 18 and 19 , the first paper piece  101  (A, E) is a portion which is folded inside of the envelope and becomes a content. In this embodiment, the first paper piece  101  is provided with a perforation  220 , and forms a return postcard by cutting off the perforation  220  after opening the envelope. Moreover, the second paper piece  102  (B, F) is a portion which is folded inside of the envelope and becomes a content. Text, images and other objects can be printed, if necessary, on the front side and back side B, F of the second paper piece  102 . Moreover, the front side C of the third paper piece  103  corresponds to the front side of the envelope, on which the name and address are printed. Text, images and other objects can be printed, if necessary, on the back side G of the third paper piece  103 , and the folded first paper piece  101  and the second paper piece  102  are stacked in the order stated thereon. Moreover, the front side D of the fourth paper piece  104  corresponds to the back side of the envelope, on which the name, address, etc. of the sender, if necessary, are printed. Text, images and other objects can be printed on the back side H of the fourth paper piece  104 , and this back side H is stacked on the front side B of the folded second paper piece  102 . As will be described later, the content enclosed in the envelope is nipped between the back side G of the third paper piece  103  and the first paper piece  101  stacked thereon. As shown in  FIG. 18 , the width of the content  40  is smaller than the interval between the pressure-sensitive adhesives  106  printed in both edge portions of the paper piece of the envelope sheet  100   a . Moreover, the length in the direction perpendicular to the width of the content  40  is slightly less than the size of the same direction of the piece of the envelope sheet  100   a , and by folding this for an appropriate number of times, a size which allows accommodation in the envelope formed from this envelope sheet  100   a.    
     As shown in  FIG. 18 , the front side A of the first paper piece  101  and the front side B of the second paper piece  102  are provided with more than one portions of the pressure-sensitive adhesives  106  at a predetermined interval along both edge portions in the width direction. It should be noted that the front sides C and D of third paper side  103  and fourth paper side  104 , respectively, are provided with no pressure-sensitive adhesive. Moreover, as shown in  FIG. 19 , the back side E of the first paper piece  101  and the back side F of the second paper piece  102  are provided with the pressure-sensitive adhesives  106  along both edge portions in the width direction in a plurality of portion at predetermined intervals so as to be in positions different from those of the pressure-sensitive adhesives  106  of the front sides A and B. Moreover, as shown in  FIG. 19 , the back side G of the third paper piece  101  and the back side H of the fourth paper piece  102  are provided with the pressure-sensitive adhesives  106  along both edge portions in the width direction in the form of a continuous band. These pressure-sensitive adhesives  106  in the form of the continuous band are formed slightly beyond the back side F of the second paper piece  102 . 
     A pressure-sensitive adhesive exhibits adhesive strength by adhering pressure-sensitive adhesives provided on two sheets of paper together and applying a predetermined pressure. Its known examples include two-pack type adhesive using microcapsules and natural rubber-based adhesion materials, among others. The arrangement pattern of these pressure-sensitive adhesives  106  the pressure-sensitive adhesives  106  of corresponding paper pieces are considered to be in the same position and in contact with each other when the paper pieces are folded to be assembled in the form of an envelope. However, when the envelope sheet  100   a , for example, are stacked in the same vertical positional relationship, e.g., with their front sides facing up, the pressure-sensitive adhesives  106  on the front sides and the pressure-sensitive adhesives  106  on the back sides do not face each other to avoid contact therebetween. When the pressure-sensitive adhesives  106  are brought into contact with each other and left for a long period of time, the problem of natural adhesion due to a high temperature, high humidity and other environmental conditions even without any pressure may be caused, such a problem can be prevented from occurring in advance according to the envelope sheet  100   a  of the embodiment. 
     As shown in  FIG. 18 , on the surface of B the second paper piece  102 , in the positions of two portions to the inside from both edge portions in the width direction of the envelope and close to the folding bordering the third paper piece  103 , remoistening pastes  107  are provided as another adhesive different from the pressure-sensitive adhesives in a band-shaped pattern along the width direction. Moreover, as shown in  FIG. 19 , the back side H of the fourth paper piece  104  is provided with an adhesive strength adjustment layer  400  inwardly of both edge portions in the width direction of the envelope and close to the side opposite to the fold of the third paper piece  103 , in a band-shaped pattern along the width direction. The position in which the adhesive strength adjustment layer  400  is provided is a position facing the remoistening pastes  107  when this envelope sheet  100   a  is formed into an envelope. That is, when this envelope sheet  100   a  is formed into an envelope, the remoistening paste  107  is adhered to the fourth paper piece  104  via the adhesive strength adjustment layer  400 . 
     The remoistening paste is, for example, mucilage or the like, and has no adhesive strength when it is applied on paper and dried, but develops adhesive strength when wetted with water, and when the paper sheet is placed together with another paper sheet in this state and a required pressure is applied thereto, the two paper sheets are adhered. The pressure as in the case of adhering with a remoistening paste is effective even when it is significantly lower than the pressure required for a pressure-sensitive adhesive. Since their adhesive strengths are at least both considerably higher than that of paper, using two types of adhesives in a single envelope does not cause any problem due to a variation in the adhesive strength. Moreover, in place of the remoistening paste, an adhesive which does not normally have adhesive strength but develops adhesive strength by any operation other than the pressure as for the pressure-sensitive adhesive may be used. Examples include adhesives which develop adhesive strength by heat, light including ultraviolet radiation, and other physical sections, other pressure-sensitive adhesives which develop adhesive strength with a pressure lower than that applied on the pressure-sensitive adhesive or double-faced adhesive tape and the like. 
     The adhesive strength adjustment layer  400  may be silicon inks, waxes used for coating paper sheets, varnishes release properties, and other layers prepared from substances having low adhesiveness for various adhesives and having release properties. Herein, these substances and materials are collectively referred to as adhesion resistant materials. The formation pattern of the adhesion resistant materials is, for example, as shown in  FIG. 20 , that has adhesion resistant portions  402  in which the front side of the envelope sheet is covered with the adhesion resistant materials, and adhered portions  401  in which the front side of the envelope sheet is not covered with the adhesion resistant materials, and a plurality of adhered portions  401  in which the front side of the envelope sheet  100   a  is not covered with the adhesion resistant material is distributed predetermined shape and predetermined arrangement. More specifically,  FIG. 20( a )  show a pattern in which the circular adhered portions  401  are disposed in two upper and lower rows at regular intervals;  FIG. 20( b )  shows a checker pattern in which square adhered portions are disposed in three rows alternately in the vertical direction; and  FIG. 20( c )  shows a pattern in which adhered portions in the form of circles larger than those in  FIG. 20( a )  are disposed at regular intervals in a row. 
     In the examples of  FIGS. 20 ( a ) to ( c )  above, the adhered portions are surrounded by the adhesion resistant materials, but as in  FIG. 20( d ) , the following structure may also be employed: the adhesion resistant materials are formed of rectangular patterns disposed at predetermined intervals, the gaps between the rectangular patterns of the adhesion resistant materials form the adhered portions  401  where the front side of the envelope sheet  100   a  is exposed. Even if such a structure is employed, when the remoistening pastes  107  in the form of the continuous band exemplified in the figure are adhered, the remoistening paste  107  is adhered to the paper sheet in the adhered portions  401  which expose the paper sheet at constant intervals with a constant area. 
     In any case of  FIGS. 20 ( a ) to ( d ) , this adhesive strength adjustment layer  400  is a section which restricts the adhesion between the remoistening paste  107  and the envelope sheet  100   a  to a predetermined state and stabilizes the same, and therefore when both are caused to face and brought into contact, it is preferable that the formation area of the adhesive strength adjustment layer  400  includes the formation area of the remoistening paste  107 , and is greater than this. That is, it is preferable that the remoistening paste  107  is adhered to the envelope sheet  100   a  only in the adhered portions of the adhesive strength adjustment layer  400 , and is not adhered to the envelope sheet  100   a  irregularly outside the adhesive strength adjustment layer  400 . 
     In such a manner, in the adhesive strength adjustment layer  400  the shapes, areas and arrangement patterns of the adhered portions  401  which are holes or gaps provided in the adhesion resistant materials where the front side of the envelope sheet  100   a  appears are determined to certain ones. The remoistening paste  107  is adhered to the envelope sheet  100   a  only through the adhered portions  401  of such patterns, and exerts almost no adhesive strength on the adhesion resistant materials of the adhesive strength adjustment layer  400 . The above patterns of the adhered portions  401  in the adhesive strength adjustment layer  400  are determined as follows to simultaneously achieve two purposes which would be generally thought to contradict, that is, ease of opening of the envelope and ensuring the strength to withstand the external force applied during mailing or delivery. 
     First, the adhesive strength of the remoistening paste  107  in each adhered portion  401  is set to a predetermined value lower than the strength of the envelope sheet  100   a . Accordingly, in opening the sealing portion of the envelope sheet  100   a  by means of the remoistening paste  107  and adhered portions  401 , if the paper sheet is opened in the width direction sequentially from the edge, the remoistening paste  107  adhered to the paper sheet through the adhered portions  401  is peeled off from the paper sheet without damaging the paper sheet, or even if a part of the front side of the paper sheet is peeled off, can be peeled off from the paper sheet without creating such damage that a hole is made in the paper sheet. Therefore, the envelope sheet  100   a  can be opened clearly with a small force without tearing. The adhesive strength of the remoistening paste  107  in the adhered portions  401  is determined by the shape, size, disposition intervals and other conditions of the adhered portions  401  formed in the adhesive strength adjustment layer  400  when the type of the remoistening paste  107  is the same. Moreover, by performing the operation of peeling a number of dot-like adhered portions  401  having a constant adhesive strength sequentially and successively from the edge, the opener of the letter hears successive peeling sound of the adhered portions  401 , and feels successive pleasing sense of opening at the fingertip, and therefore and he/she can confirm the certainty of opening by touch and ear. Accordingly, it is preferable that the arrangement pattern of the adhered portions  401  is regular since the above-described continuous peeling sound and the sense of opening can be obtained. 
     Next, the total adhesive strength of the remoistening paste  107  in all adhered portions  401  provided in the adhesive strength adjustment layer  400  is set to be greater than the external force possibly applied to the sealing portion of the envelope during mailing or delivery. This reduces the occurrence of the problem that the sealing portion of the envelope sheet  100   a  sealed by the remoistening paste  107  is opened by the external force applied during mailing or delivery. 
     According to this envelope sheet  100   a , when the sealed envelope is opened, it can be opened without any significant damage the paper sheet with a small force, the information printed on the opened envelope sheet  100   a  is easy to read. Moreover, when the envelope has a return postcard or other object using a part of the envelope sheet  100   a , no difficulty is found in its use. In addition, since the strength of the sealed portion by the remoistening paste  107  is set to be sufficient as a whole, accidental opening of the sealing portion sealed by the remoistening paste  107  by the external force during mailing and delivery of the envelope is unlikely to occur. 
     Moreover, in this embodiment, the remoistening paste  107  is formed in the shape of two bands, and the adhesive strength adjustment layer  400  is formed in the shape of a single continuous band. Therefore, when opening the sealing portion of the envelope by these, the finger can be inserted from the gap of the paper sheet corresponding to the gap between the two bands of the remoistening paste  107  to open the adhered remoistening paste  107 . However, as described above, the remoistening paste  107  can be peeled off successively and clearly from the edge with a small force due to the adhesive strength adjustment layer  400 , and therefore the remoistening paste  107  is not necessarily formed in the form of two bands, and may be formed in the form of a single band as the adhesive strength adjustment layer  400 . 
     Moreover, as shown in  FIGS. 18 and 19 , in positions on both sides of the envelope sheet  100   a  and in the width direction on the inside from the pressure-sensitive adhesive  106 , continuous perforations  220  are formed in the direction perpendicular to the width direction, so that the envelope is easy to open. However, according to this embodiment, in opening the envelope, the remoistening paste  107  of the adhered portions  401  can be clearly peeled off without damaging the paper sheet with a small force as described above first, and therefore if the portions of the pressure-sensitive adhesives  106  placed on both edges are then opened and peeled in the width direction, the operation of developing the envelope into the form of the original paper sheet can be easily performed. Therefore, the perforations on both sides in the width direction are not considered essential. 
     As shown in  FIG. 19 , on the back side F of the second paper side  102 , a peeling layer  405  is provided in a band-shaped pattern along the width direction in a position to the inside from both edge portions in the width direction of the envelope and close to the folding bordering the third paper piece  103 . This peeling layer  405  is formed of the adhesion resistant materials the adhesive strength adjustment layer  400 , but their functions and purposes are different. This peeling layer  405  has a positional relationship which faces the remoistening paste  107  on the other envelope sheet  100   a  when the envelope sheets  100   a  are stacked in the same vertical relationship. Without this peeling layer  405 , when a number of sheets of the envelope paper  100   a  are stacked the envelope sheet  100   a  in the same vertical relationship, the remoistening paste  107  may be possibly adhered to the other the envelope sheet  100   a  depending on the conditions humidity and others. However, providing the peeling layer  405  if the remoistening paste  107  develops adhesiveness when a large number of the envelope sheets  100   a  are stacked, the paper sheets are not adhered to each other, and even if they are adhered, they can be easily peeled off without damaging the envelope sheet  100   a.    
     After the name, address, contents, etc. are printed, the process procedure of folds and other components in the case where the envelope sheet  100   a  is formed in the shape of the envelope will be described. 
     As shown in  FIG. 21 , the first paper side  101  is bent to the back side of the envelope sheet  100   a . The back side E of the first paper side  101  is stacked on the back side F of the second paper side  102 , and the front side A of the first paper side  101  appears on the back side of the envelope sheet  100   a . Although not illustrated, the content formed by folding is disposed on the front side A of the first paper side  101 , and as shown by the arrow in  FIG. 21 , the first paper side  101 , second paper side  102  and content, are further bent onto the back side G of the third paper side  103 . As a result, the state shown in  FIG. 22  is formed. Herein, after water is applied to the remoistening paste  107  provided on the front side B of the second paper side  102  by a section not shown, the fourth paper side  104  is bend to the back side of the envelope sheet  100   a  as shown the arrow in  FIG. 22 . The cross-sectional view of  FIG. 23  schematically shows this state. The back side H of the fourth paper side  104  is stacked on the front side B of the second paper side  102 , and the remoistening paste  107  of the second paper side  102  faces the adhesive strength adjustment layer  400  of the fourth paper side  104 . Moreover, the pressure-sensitive adhesives  106  on the paper pieces  101  to  104  face each other or come into contact with each other. The envelope sheet  100   a  is formed in the shape of an envelope folded in four in this state, but the pressure-sensitive adhesives  106  are not adhered yet. It should be noted that in  FIG. 23 , the content  40  which is not illustrated in  FIGS. 21 and 22  is enclosed in the state of being folded in two. 
     Thereafter, the entire surface of the envelope  50  is nipped by rollers not shown having a length equal to or greater than the width of the envelope to transfer the envelope  50 , and the remoistening paste  107  of the second paper side  102  and the adhesive strength adjustment layer  400  of the fourth paper side  104  are adhered. Moreover, as shown in  FIG. 5 , the pressure-sensitive adhesives  106  placed in both edge portions in the width direction of the envelope  50  are adhered by the pressure rollers  80 . A set of these pressure rollers  80  includes a set of upper and lower rollers, and two left and right pairs are provided. Both edge portions in the width direction of the envelope  50  enclosing the content  40 , that is, the direction intersecting the transfer direction are nipped from above and below and pressurized to develop the adhesive strength of the pressure-sensitive adhesives  106  and achieve sealing. This causes the pressure-sensitive adhesives  106  which are in contact with each other between the paper pieces facing each other to develop tackiness, whereby the form of the envelope  50  sealing the content is realized. 
     It should be noted that the enclosing and sealing operation of the envelope sheet  100   a  described above is automatically performed by the sealed letter producing device  1  of the first embodiment described below. 
     (2) Mechanism of this Sealed Letter Producing Device ( FIGS. 24 to 26  and  FIG. 9 ) 
     In this paragraph, differences in configuration of the sealed letter producing device  1  of this embodiment from that of the first embodiment will be described. For the components substantially identical to those in the first embodiment, explanation is omitted by citing the description of the first embodiment. 
     As shown in  FIGS. 24 to 26 , in the printing unit  2  of this embodiment, in order to form the adhesive strength adjustment layer  400  on the envelope sheet, a fifth ink jet device S which is a printing section capable of discharging silicon ink which is an adhesion resistant material is provided next to the four ink jet devices C, K, M and Y. Using this ink jet device S, it is possible to print the adhesive strength adjustment layer  400  on the envelope sheet in a desired pattern, and print the peeling layer  405  thereon. 
     Next, the enclosing and sealing section of this embodiment has substantially the same mechanical configuration as the enclosing and sealing section of the first embodiment, but has a different action or control by the control section  90  provided in the printing unit  2 . The outline of the actions or controls different from those in the first embodiment will be also described in this paragraph for describing the configuration. It should be noted that the detail of the actions or controls will be described later. 
     According to the control section  90  of the sealed letter producing device of this embodiment, the envelope sheet  100   a  which is folded once by the main folding roller A′, the first folding roller B′ and other components which are the first folding section stands by where it has passed between the main folding roller A″ and paper transport roller D″, which are the second folding section, the content  40  transferred along the path  26 , which is another second paper path  20  is aligned with the envelope sheet  100  a during standby, and further passes between the main folding roller A″ and second folding roller B″ to be provided with the second folding. 
     As shown in  FIG. 27 , the aligned envelope sheet  100   a  and content  40  are further forwarded by the main folding roller A″ and second folding roller B″. Herein, the envelope sheet  100   a  is in such a state that the front side B of the second paper piece  102  faces down, and the remoistening paste  107  faces the water-absorbing portion  62  of the moistening section  60 . This state is close to, in  FIG. 22 , the state that the fourth paper piece  104  is not yet folded in the direction of the arrow, and the surface B of the second paper side  102  is faced down. Herein, the rotation cam  64  operates to swing the swing arm  63 , so that the remoistening paste  107  is pressed against the water-absorbing portion  62  to be moistened. 
     As shown in  FIG. 28 , the envelope sheet  100   a  is forwarded by the main folding roller A″ and second folding roller C″. Accordingly, the fourth paper piece  104  is folded, and the back side H of the fourth paper piece  104  is stacked on the front side B of the second paper piece  102 , so that the remoistening paste  107  and adhesive strength adjustment layer  400  are adhered. 
     (3) Operation of this Sealed Letter Producing Device ( FIGS. 24 to 28  is Referred to, while  FIGS. 12 and 13  of the First Embodiment are Cited) 
     Next, the overall procedure of printing name, address and other information on the envelope sheet  100   a  in the sealed letter producing device  1  of this embodiment described above, performing required printing on a plurality of sheets of the content  40  and folding the same, and enclosing and sealing the content  40  in the envelope  50  formed by folding the envelope sheet  100   a  will be described. 
     As shown in  FIG. 24 , in the printing unit  2 , the envelope sheet  100   a  is transferred from a paper feed rack P 1 . In this embodiment, the envelope sheet  100   a  may be on any of the paper feed racks P 1  to P 4  of the printing unit  2 . This envelope sheet  100   a  is printed on both sides by the ink jet devices C, K, M and Y during a single pass around the looped transfer path  5 . Not only duplex printing but also simplex printing can be selected. In general, name, address and other information are printed on the face which serves as the outer face of the envelope  50 , while any information to be sent to the address, if necessary, is printed on the face which serves as the inner face of the envelope  50 , along with particulars of the enclosed content  40 . The information printed on the inner face of the envelope  50  can be read by a receiver by cutting and opening the envelope  50 . Moreover, printing on the adhesive strength adjustment layer  400  and the peeling layer  405  by silicon ink using the ink jet device S may be performed before or after the printing step by the ink jet devices C, K, M and Y. 
     The envelope sheet  100   a  is transferred from the path  11 , which is one of the first paper paths  10 , by switching of a switching flap not shown to the folding section. The envelope sheet  100   a  is forwarded by the main folding roller A′ and the paper transport roller D′, impinges on an impinging member not shown to be warped, enters in between the main folding roller A′ and the first folding roller B′ from the warped portion, and further nipped and transferred to be provided with a fold in a portion of the front end portion thereof in the paper feed direction. The unfinished envelope which is partially folded stands by for the alignment with the content  40  in a position where it has passed between the main folding roller A″ and paper transport roller D″ of the enclosing and sealing section. After the alignment of the content  40 , the envelope is further passed between the main folding roller A″ and second folding roller B″ and provided with the second folding while wrapping up the content  40 , the state shown in  FIG. 22  is almost formed, although the content is not shown. 
     As shown in  FIG. 25 , following the envelope sheet  100   a , a required paper sheet  30  is transferred as the content  40  from any of the paper feed racks P 2  to P 4  into the looped transfer path  5  at a certain determined interval, and both sides of the paper sheet  30  are printed by the ink jet devices C, K, M and Y during a single pass through this transfer path. Not only duplex printing but also simplex printing can be selected. The paper sheet  30  of the content  40  is transferred to the path  21 , which is one of the second paper paths  20  by switching of a switching flap not shown. The paper sheet  30  is retained at an alignment portion  23  on the path  21 , which is one of the second paper paths  20  until a required number of sheets are accumulated, and the alignment portion  23  opens when the required number is accumulated and the sheets are transferred into the folding section (main folding roller A, etc.). By a plurality of folding performed by the folding section, the paper sheet  30  folded in a desired state is transferred into the enclosing and sealing unit (main folding roller A″, etc.) via the path  26 , which is the other path of the second paper paths  20 . In this embodiment, the content  40  is folded inwardly in three (in the example shown in  FIG. 23 , a content folded in two is shown as another example). This content  40  is aligned with the envelope sheet  100   a  in the process of being folded standing by in a position where it has passed between the main folding roller A″ and paper transport roller D″. 
     As shown in  FIG. 26 , the aligned envelope sheet  100   a  and content  40  are further forwarded by the main folding roller A″ and second folding roller B″ to be provided with the second folding, whereby the content  40  is wrapped up in the envelope sheet  100   a . Herein, as shown in  FIG. 27 , the rotation cam  64  of the moistening section  60  is activated to swing the swing arm  63 , and the remoistening paste  107  of the envelope sheet  100   a  is pressed against the water-absorbing portion  62  to be moistened. 
     As shown in  FIG. 28 , the envelope sheet  100   a  is forwarded by the main folding roller A″ and second folding roller C″, the fourth paper piece  104  is folded, the adhesive strength adjustment layer  400  on the back side H of the fourth paper piece  104  is adhered with the remoistening paste  107  on the front side B of the second paper piece  102  to be in the shape of the envelope  50 , and the envelope enters in between the positioning rollers  65 . 
     As shown in  FIG. 13 , the positioning rollers  65  nipping the envelope  50  adjusts the position of the envelope  50  in the axial direction based on the position of the envelope  50  captured by the edge sensor  66  shown in  FIG. 12 , and the envelope  50  is moved to bring the pressure-sensitive adhesives  106  on the envelope  50  to a position overlapping the pressure rollers  80 . In addition, both edge portions of the envelope  50  are stuck together as it passes through the pressure rollers  80 , whereby sealing of the envelope  50  is performed. 
     According to this embodiment, in the process of folding the envelope sheet  100   a  aligned with the content  40  to form into the envelope  50 , the paper pieces are adhered to each other with the remoistening paste  107  first, the positioning of the envelope  50  in the width direction is accurately performed and is then transferred in between the pressure rollers  80 , so that the pressure-sensitive adhesives  106  are pressurized securely by the pressure rollers  80  having a small width. Therefore, the pressure-sensitive adhesives  106  can be securely adhered by the pressure rollers  80  which can produce a high pressure with a small force having a small width and with a width sufficient for adhesion. 
     Then, the finished sealed letter after the completion of enclosing and sealing is discharged into a discharge tray  48  provided on the top surface of the cabinet  9 , where it is sequentially stacked up to be taken out later. 
     As described above, the envelope sheet  100   a  of this embodiment for producing an envelope by folding is designed to allow adhesion of both edges in the direction the width of the envelope with the pressure-sensitive adhesive  106 , and the adhesion of a portion inside the pressure-sensitive adhesive  106  with the remoistening paste  107 , but the adhesive strength adjustment layer  400  including a number of adhesion portions  401  from which the surface of the paper sheet are exposed regularly is configured of the adhesion resistant materials on the surface of the target paper sheet adhered by the remoistening paste  107 . The adhesive strength at each point of these adhered portions  401  is set to a certain value which is lower than the breakage strength of the paper sheet, and therefore if the adhered portions are peeled off sequentially from one side, the envelope can be easily opened with a certain force. Moreover, the response felt on the hand in opening the envelope is constant, and therefore a stable and favorable sense can be obtained. Moreover, even if the adhesive strength for each point of the adhered portions  401  is small, a necessary number of adhered portions  401  are provided to set the adhesive strength as a whole as high as necessary as a whole, and therefore accidental peeling of the sealing portion of the remoistening paste  107  by a load applied during mailing or delivery can be surely prevented. 
     Since the remoistening paste  107  is generally formed by a step of applying in a stamping manner using a sponge-like projection component, it is difficult to form the same in the form of small dots, and even if it can be formed in the form of dots, it is even more difficult to form a paste having high viscosity in the form of dots with stable diameter, and therefore it has been actually impossible to adjust the adhesive strength in controlling of the application pattern of the remoistening paste  107 . However, in this embodiment, the remoistening paste  107  is formed in the shape of a uniform band, and a pattern in which a number of holes in the form of dots is formed is printed using the adhesion resistant materials on the surface of the paper sheet facing this, point adhesion with a stable small diameter by the remoistening paste  107  can be realized, and ease of opening and unlikeliness of accidental opening during mailing and the like can be both realized. 
     Moreover, the envelope sheet  100   a  of this embodiment has such a configuration that the adhesive  107  and the adhesive strength adjustment layer  400  are provided in different positions of the envelope sheet  100   a , and it therefore has such effects that it is not necessary to set the accuracy of positioning to a high level compared to the case where the adhesive  107  and adhesive strength adjustment layer  400  are formed to be stacked in the same position on the envelope sheet  100 , and that the production is easy. 
     4. Fourth Embodiment ( FIG. 29 ) 
     In the third embodiment, as shown in  FIG. 23 , there is such a configuration that the remoistening paste  107  is provided on the front side B of the second paper side  102 , the adhesive strength adjustment layer  400  is provided on the back side H of the fourth paper side  104 , and the remoistening paste  107  and adhesive strength adjustment layer  400  face each other to be adhered to each other when the envelope sheet  100   a  is folded into the shape of the envelope  50 . 
     However, the remoistening paste  107  and adhesive strength adjustment layer  400  are not necessarily formed separately on different paper sheets, but can be configured as in the fourth embodiment shown in  FIG. 29 . That is, in this example, the adhesive strength adjustment layer  400  having a number of adhered portions  401  (holes) is provided on the front side B of the second paper side  102 , the remoistening paste  107  is provided in a range smaller than the adhesive strength adjustment layer  400  thereon, and the remoistening paste  107  is adhered to the second paper side  102  in advance by causing the remoistening paste  107  to enter the adhered portions  401 . If the envelope sheet  100   b  is folded to be in the shape of an envelope in this state, the fourth paper piece  104  is adhered to the remoistening paste  107  in a large area, but the adhesive strength between the remoistening paste  107  and the second paper side  102  is as defined by the adhesive strength adjustment layer  400 , and is lower than the adhesive strength between the fourth paper piece  104  and the remoistening paste  107 . Therefore, in opening the envelope, the fourth paper side  104  on which the remoistening paste  107  is deposited can be peeled off from the second paper piece  102  with a small constant force. 
     In the third embodiment, it is possible to provide such a configuration that the remoistening paste  107  and adhesive strength adjustment layer  400  are caused to be substantially clear so that printing of the underlayer paper sheet can be visually confirmed, but the conditions for reading the information printed on the paper sheet are not considered the same as in the case where nothing exists on the paper sheet. Therefore, the smaller the areas of the remoistening paste  107  and the adhesive strength adjustment layer  400  printed on the paper sheet, the more convenient to read the information printed thereon. In this embodiment, both the remoistening paste  107  and adhesive strength adjustment layer  400  can be stacked and formed in an approximately identical position on the same paper piece, and therefore it is possible to reserve a greater area of a region where the printed information can be read more easily. Moreover, the remoistening paste  107  is moistened when used, and develops the adhesive strength by drying and shrinking after being adhered to the paper sheet, but the influence of this drying and shrinking may deform the paper in some cases. In this embodiment, the remoistening paste  107  is provided on of the adhesive strength adjustment layer  400  even partially, and therefore the remoistening paste  107  slides on the adhesive strength adjustment layer  400  when it dries and shrinks. This reduces the force applied to the paper sheet, whereby the effect in reducing the deformation of the paper sheet can be obtained. 
     5. Fifth Embodiment ( FIG. 30 ) 
     In this example, the remoistening paste  107  is provided on the front side B of the second paper side  102 , and the adhesive strength adjustment layer  400  having a number of adhered portions  401  (holes) is provided thereon to cover the remoistening paste  107 . The envelope sheet  100   c  is folded and formed into the shape of an envelope in this state, and the fourth paper piece  104  is adhered to the remoistening paste  107  through the adhered portions  401  of the adhesive strength adjustment layer  400 . Therefore, in opening, the fourth paper side  104  can be peeled off with a small constant force from the second paper piece  102  on which the remoistening paste  107  covered with the adhesive strength adjustment layer  400  is provided. 
     According to this embodiment, as in the second embodiment, both the remoistening paste  107  and the adhesive strength adjustment layer  400  can be formed on the same paper piece, and therefore the area of a region where the printed information can be read more easily can be increased. Moreover, by using the sealed letter producing device of the first embodiment including the ink jet device S which discharges the silicon ink, silicon ink is printed on the remoistening paste  107  which has been applied to the envelope sheet  100   c  in necessary positions in advance to form the adhesive strength adjustment layer  400  by printing the silicon ink on the remoistening paste  107 , whereby the envelope sheet of this embodiment can be formed. 
     6. Variants of the Embodiments 
     The sealed letter producing device  1  of each of the embodiments described above is provided with the printing unit  2 , but this printing unit  2  may be an existing image forming device. That is, the sealed letter producing device  1  of the present invention can be formed by using a normal image forming device already installed in places of business and other places as the printing unit  2  in the present invention, and connecting the enclosing and sealing unit  3  to this. Accordingly, printing of the envelope sheets  100 ,  100   a ,  100   b ,  100   c ,  200  and the content  40  can be performed by using a single existing image forming device, which would save the installation cost of the automatic sealed letter producing device. 
     Moreover, the paper sheet  30  of the content  40  is not necessarily folded, and may be enclosed in the envelope in its original size without being folded depending on its relationship with the size of the envelope. Moreover, in the embodiment s, the sheet-like paper sheet is used as the paper sheet  30  of the envelope paper sheets  100 ,  100   a ,  100   b ,  100   c ,  200  and the content  40 , but, for example, a paper roll may be used, and may be cut and provided in a required length when it is used.